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A variety of lakes located in the dry steppe area of southwestern Siberia are exposed to rapid climatic changes, including intra-century cycles with alternating dry and wet phases driven by solar activity. As a result, the salt lakes of that region experience significant fluctuations in water level and salinity, which have an essential impact on the indigenous microbial communities. But there are few microbiological studies that have analyzed this impact, despite its importance for understanding the functioning of regional water ecosystems. This work is a retrospective study aimed at analyzing how solar activity-related changes in hydrological regime affect phototrophic microbial communities using the example of the shallow soda lake Tanatar VI, located in the Kulunda steppe (Altai Region, Russia, southwestern Siberia). The main approach used in this study was the comparison of hydrochemical and microscopic data obtained during annual field work with satellite and solar activity data for the 12-year observation period (2011–2022). The occurrence of 33 morphotypes of cyanobacteria, two key morphotypes of chlorophytes, and four morphotypes of anoxygenic phototrophic bacteria was analyzed due to their easily recognizable morphology. During the study period, the lake surface changed threefold and the salinity changed by more than an order of magnitude, which strongly correlated with the phases of the solar activity cycles. The periods of high (2011–2014; 100–250 g/L), medium (2015–2016; 60 g/L), extremely low (2017–2020; 13–16 g/L), and low (2021–2022; 23–34 g/L) salinity with unique biodiversity of phototrophic communities were distinguished. This study shows that solar activity cycles determine the dynamics of the total salinity of a southwestern Siberian soda lake, which in turn determines the communities and microorganisms that will occur in the lake, ultimately leading to cyclical changes in alternative states of the ecosystem (dynamic stability)., BT/Environmental Biotechnology

The IEEE 1547 Standard for the interconnection of distributed energy resources (DERs) to distribution grids provisions that smart inverters could be implementing Volt/VAR control rules among other options. Such rules enable DERs to respond autonomously in response to time-varying grid loading conditions. The rules comprise affine droop control augmented with a deadband and saturation regions. Nonetheless, selecting the shape of these rules is not an obvious task, and the default options may not be optimal or dynamically stable. To this end, this work develops a novel methodology for customizing Volt/VAR rules on a per-bus basis for a single-phase feeder. The rules are adjusted by the utility every few hours depending on anticipated demand and solar scenarios. Using a projected gradient descent-based algorithm, rules are designed to improve the feeder’s voltage profile, comply with IEEE 1547 constraints, and guarantee stability of the underlying nonlinear grid dynamics. The stability region is inner approximated by a polytope and the rules are judiciously parameterized so their feasible set is convex. Numerical tests using real-world data on the IEEE 141-bus feeder corroborate the scalability of the methodology and explore the trade-offs of Volt/VAR control with alternatives.

Compte tenu du comportement aléatoire et fluctuant des sources d'énergie renouvelable (SER), l'équilibre entre la génération et la demande ne sont pas faciles à contrôler. Par conséquent, la stabilité dynamique du flux d'énergie et le contrôle de la fréquence deviennent de plus en plus difficiles en raison des impacts de la pénétration élevée des SER dans les micro-réseau électrique. Des stratégies de contrôle des convertisseurs/onduleurs avec filtre sont nécessaires pour maintenir l'alimentation électrique appropriée dans l'ensemble du micro-réseau. L'objectif de notre travail est d'explorer les aspects critiques de la génération distribuée (GD), de l'intégration des énergies renouvelables et des systèmes de stockage de l'énergie, en mettant l'accent sur l'amélioration de l'efficacité du réseau électrique tout en minimisant la pollution atmosphérique. Cette thèse reconnaît les avantages environnementaux et économiques de la GD tout en soulignant les défis inhérents à la gestion des sources d'énergie renouvelable fluctuantes. Un algorithme de contrôle pour un système de stockage d'énergie hybride diesel-éolien à forte pénétration est conçu pour maintenir la stabilité dynamique du flux d'énergie et le contrôle de la fréquence du réseau. Les principaux résultats comprennent la réduction efficace du temps de transition dans le flux d'énergie éolienne et des fluctuations de fréquence. D'autre part, cette étude répond aux défis posés par la nature intermittente des SER et leur impact sur la stabilité dynamique et le contrôle de la fréquence. Nous avons introduit un algorithme de contrôle utilisant la logique floue pour un système de stockage d'énergie éolienne en utilisant la méthode de partage de puissance. En comparant cette approche au contrôleur conventionnel, l'algorithme proposé a démontré des améliorations substantielles dans la réduction du temps de transition dans le flux d'énergie éolienne et des fluctuations de fréquence. Dans le cadre de cette thèse, une étud

Over the last decades, the frequency on the Nordic electrical power grid has deteriorated. Therefore, new stricter requirements are developed for the hydropower delivering regulating active power on the Frequency Containment Reserve market (FCR). This thesis aims to investigate the possibility of modeling two double-regulated hydropower plants, referred to as Unit 1 and 2, to evaluate their compliance with the new FCR-requirements. By modeling the hydropower plants, the first goal was to find a model structure that captures the essential dynamics of the systems. A second goal was to evaluate whether the two units currently fulfill the new FCR-requirements, and investigate how the turbine governors’ settings could be optimized to fulfill the new requirements. Data obtained from FCR-tests was used in MATLAB to evaluate the two stations’ dynamic stability and performance requirements. Through system identification in MATLAB, grey-box modeling was used to create linear and non-linear turbine and waterways models for Unit 1 and Unit 2. The non-linear turbine and waterways models were implemented in Simulink, together with corresponding turbine governors, to find optimal parameter settings to fulfill the FCR-requirements. The evaluation of the new FCR-requirements shows that none of the two units fulfills the dynamic stability requirement. However, Unit 1 fulfills the performance requirement. The results imply that double-regulated turbines will most likely have difficulties fulfilling the new requirements, which will cause major consequences in improving the frequency regulation quality. The results from the grey-box modeling present that the linear models are not validated with the step response data, due to not capturing the system dynamics when compared with provided data from the units. On the other hand, the non-linear models are validated with step response data as the model captures the system dynamics more accurately. However, the non- linear Simulink models ca

Over the last decades, the frequency on the Nordic electrical power grid has deteriorated. Therefore, new stricter requirements are developed for the hydropower delivering regulating active power on the Frequency Containment Reserve market (FCR). This thesis aims to investigate the possibility of modeling two double-regulated hydropower plants, referred to as Unit 1 and 2, to evaluate their compliance with the new FCR-requirements. By modeling the hydropower plants, the first goal was to find a model structure that captures the essential dynamics of the systems. A second goal was to evaluate whether the two units currently fulfill the new FCR-requirements, and investigate how the turbine governors’ settings could be optimized to fulfill the new requirements. Data obtained from FCR-tests was used in MATLAB to evaluate the two stations’ dynamic stability and performance requirements. Through system identification in MATLAB, grey-box modeling was used to create linear and non-linear turbine and waterways models for Unit 1 and Unit 2. The non-linear turbine and waterways models were implemented in Simulink, together with corresponding turbine governors, to find optimal parameter settings to fulfill the FCR-requirements. The evaluation of the new FCR-requirements shows that none of the two units fulfills the dynamic stability requirement. However, Unit 1 fulfills the performance requirement. The results imply that double-regulated turbines will most likely have difficulties fulfilling the new requirements, which will cause major consequences in improving the frequency regulation quality. The results from the grey-box modeling present that the linear models are not validated with the step response data, due to not capturing the system dynamics when compared with provided data from the units. On the other hand, the non-linear models are validated with step response data as the model captures the system dynamics more accurately. However, the non- linear Simulink models ca

Stepped hull forms are hulls with a vertical step in the hull bottom to improve performance at top speed. Stepped hulls are well documented anecdotally and scientifically to improve calm water performance at high speeds, but commonly demonstrate dangerous and unexpected dynamic instabilities during initial trials. These hulls also operate practically in waves, but their performance characteristics in waves are not well understood and rarely evaluated prior to full scale trials. To expand the scientific understanding of stepped hull performance, a systematic set of experiments and Reynolds Averaged Navier Stokes (RANS) computational fluid dynamics (CFD) simulations are used to evaluate the calm water performance, dynamic stability, and regular head wave response of two stepped hull models. Calm water experiments on two stepped hull models at varying displacement, longitudinal center of gravity location and forward speed offer data which can be used in the design to interpolate hull performance throughout expected operating conditions. CFD simulations in calm water are validated using the experimental results and numerical modeling approaches for stepped hull simulations are recommended. The calm water dynamic stability of both stepped hulls is investigated experimentally and numerically and procedures to evaluate the dynamic stability using both approaches are recommended. The performance of both stepped hulls in regular head waves is studied through experiments, which are used to validate CFD simulations of the hull in regular waves. System identification is used on five calm water CFD simulations to identify a reduced order model for the prediction of stepped hull response in waves.

This article models the inherent cooperative and non-cooperative incentives of stakeholders in investment projects in a novel way by combining concepts from co operative game theory and real options theory. As stakeholders have outside options, in the sense that they may terminate negotiations with the current coalition and join another, we introduce and analyze a coalitional and dynamic stability concept. We show that investment projects, in which cooperation between stakeholders is necessary, are more prone to coalitional instability when there are insufficient synergies between the stakeholders. We characterize the proportional investment scheme as the investment scheme that maximizes the total project value and that results in the earliest investment timing. A failure to implement proportional investing leads to the formation of a smaller, less efficient, coalition. The vulnerability to fail is exacerbated in a market that is characterized by high profit growth and low profit uncertainty, or vice versa. Finally, we explicitly consider one-leader investment projects and characterize the prioritized investment scheme that maximizes the value of the leader. We show that the same market conditions govern the stability of the prioritized investment scheme, which contributes to the robustness of our results.

The dynamic stability of E-mode active-passivation p-GaN gate HEMT (AP- HEMT) is investigated, including dynamic VTH shift, dynamic RON degradation, and dynamic leakage current. The AP-HEMT features an ohmic-type gate/p-GaN contact that results in a stable dynamic VTH, as the charge storage effect associated with the floating p-GaN layer is avoided. At a 650- V VDS stress, the AP- HEMT exhibits a low dynamic RON/static RON ratio of 1.4, which can be attributed to the presence of the p-GaN active-passivation layer that screens the influence of surface traps. The hole injection in the p-GaN gate HEMT is expected to increase the dynamic OFF-state leakage current, as the holes reduce the energy barrier of the buffer layer. Despite a larger injector area, the AP-HEMT exhibits a lower dynamic leakage current increase, which is due to the relocation of the electric field peak from the gate edge towards the drain. This relocation suppresses the lowering of the energy barrier under the gate. Overall, the unique device structure of the AP-HEMT leads to a negligible dynamic VTH shift, a low dynamic RON, and a small OFF-state dynamic leakage increase. © 2023 IEEE.

This paper presents the results of the performance diagnosis of a 6-cylinder engine-generator set, originally designed to run on diesel fuel or natural gas, operating in spark ignition mode and fueled with high butane content liquefied petroleum gas (LPG). In order to assess the steady-state and transient operation of the engine-generator, an original protocol for testing and recording of operating variables was designed, based on a stepped sequence of loads, comprising cold start, idling, operation at some mean load points and at a limited full load. During the tests, the variation of crankshaft rotational speed, warm-up time, engine temperatures, block vibrations, active/reactive power and engine-generator frequency, as well as exhaust emissions were continuously logged. The results show that, during the cold starting process, the engine is slow to reach nominal rated speed, its warm-up time is lengthy and its speed response during load transients is also sluggish, the latter being reflected in the voltage and frequency deviations of the output power; also, during transients, vibration levels are intensified, though the values are within the acceptable ranges according to the regulations. The torque performance of the engine-generator set is good when operating with LPG, satisfying the requirements for class G2 engine-generator units, but during transient processes it does not meet the specifications required for class G1, in terms of frequency and voltage deviations. In light of the emission limits suggested by the Environmental Protection Agency (EPA) for stationary units, it can be concluded that, without appropriate adjustments and regulations particular to LPG, the engine-generator set does not meet the carbon monoxide emission limits., En este trabajo se presentan los resultados del diagnóstico de desempeño de un grupo motor-generador de 6 cilindros, originalmente diseñado para funcionar con combustible diésel o con gas natural, operando en modo de encendido por chispa y alimentado con gas licuado de petróleo (GLP) de alto contenido de butano. Con el fin de evaluar la operación en estados estacionarios y transitorios del motor-generador, se ha diseñado un protocolo original de prueba y registro de variables de operación, basado en una secuencia escalonada de cargas, que comprende el arranque en frío, la operación en vacío, la operación en unos puntos de carga media y a una limitada plena carga. Durante las pruebas se registraron continuamente la variación de la velocidad de rotación del cigüeñal, el tiempo de calentamiento, las temperaturas del motor, las vibraciones del bloque, la potencia activa/reactiva y frecuencia del motor-generador, así como las emisiones de escape. Los resultados evidencian que, durante el arranque en frío el motor tarda en alcanzar la velocidad nominal, su tiempo de calentamiento es largo y su respuesta de revoluciones durante los transitorios de carga también es lenta, reflejándose esto último en las desviaciones de voltaje y frecuencia de la energía de salida; también durante los transitorios se intensifican los niveles de vibración, aunque los valores se inscriben dentro de los rangos aceptables según la normativa. El desempeño del par del grupo motor-generador es bueno cuando opera con GLP, satisfaciendo las exigencias para las unidades de motor-generador de clase G2, pero durante los cambios transitorios no cumple con las especificaciones requeridas para la clase G1, en términos de desviaciones de frecuencia y voltaje. A la luz de los límites de emisiones sugeridos por la Agencia de Protección Ambiental (EPA) para las unidades estacionarias, se puede concluir que, sin ajustes y regulaciones apropiados particulares para el GLP, el conjunto motor-generador no cumple co

We report a detailed analysis of atmospheric stabilities in the mesopause region (85–100 km) based on over 2,000 hr of high-resolution temperature and horizontal wind measurements made with a Na lidar at the Andes Lidar Observatory, located in Cerro Pachón, Chile (30.25°S, 70.74°W). The square of Brunt–Väisälä frequency and the Richardson number are calculated, and occurrence probabilities of convective and dynamic instabilities are derived. An approach to assess the biases due to measurement uncertainties is used to obtain more accurate occurrence probabilities. The overall occurrence probabilities of convective and dynamic instabilities are 2.7% and 6.7%, respectively. High-, medium-, and low- frequency gravity wave (GW) contributions to these probabilities are isolated, which show that the high-frequency GWs contribute most but simultaneous presence of high- and medium frequency GWs is much more effective in increasing the probabilities. Convective and dynamic instabilities are mainly generated because of the joint effect of different-scale GWs. Isolated parts of GWs have much less contribution to the generation of both convective and dynamic instabilities. The dynamic instability is mainly contributed from less stable stratification and large wind shear together. Either factor can lead to about 15% of dynamic instability.

Low back pain (LBP) remains the most prevalent and costly work-related disability worldwide and is directly associated with "physical" risk factors prevalent in manual material handling (MMH) tasks. Back-support exoskeletons (BSEs) are a promising ergonomic intervention to mitigate LBP risk, by reducing muscular exertion and spine loading. The purpose of this work was to help better understand both the "intended" and "unintended" consequences of BSE use on physical risk factors for LBP, as an essential prerequisite for the safe and effective implementation of this technology in actual workplaces. The first study assessed the effects of using two BSEs on objective and subjective responses during repetitive lifting involving symmetric and asymmetric postures. Wearing both BSEs significantly reduced peak levels of trunk extensor muscle activity and reduced energy expenditure. Such reductions, though, were more pronounced in the symmetric conditions and differed between the two BSEs tested. The second study quantified the assistive torque profiles of two passive BSEs using a computerized dynamometer, with both human subjects and a mannequin. Clear differences in torque magnitudes were evident between the BSEs, though both generated more assistive torques during flexion than extension. The third study estimated the effects of BSE use on lumbosacral compressive and shear forces during repetitive lifting using an optimization-based model. Using both BSEs reduced peak compression and anteroposterior shear forces, but these effects differed between tasks and BSE designs. Reductions in composite measures of trunk muscle activity did not correspond consistently with changes in spine forces when using a BSE. The fourth study quantified the effects of two passive BSEs on trunk stability and movement coordination during repetitive lifting. Some adverse effects on stability were evident for pelvis and thorax movements and coupling of these body segments, suggesting that caution is

Aerospace Engineering

Due to global warming and the subsequent rise of the sea level, scarcity of land to build on, the continues increase of the world’s population and a shift in population from rural areas to the city, there is a need for innovative projects to tackle or deal with the increase of needed liveable area. One of the solutions is floating cities. A component of a modern city is high-rise buildings. High-rise is an advantageous option to deal with the limited availability of ground surface on the floating platforms. The question is whether it is possible to realise these floating high-rise structures. This research investigates whether it is possible to realise high-rise buildings on floating platforms with limited dimensions on the sea or ocean regarding stability. And if it is feasible, what the requirements are for the general dimensions of both the platform and the high-rise building. For this purpose, conditions were used from three representative locations. At these three locations, the floating high-rise is tested for four different wave situations: Tsunami, Growing waves, most extreme wave. And an Irregular wave field. The platform and building are tested whether the structure could meet the various requirements and regulations. These are divided into three forms of stability: Buoyancy, static stability and dynamic stability. In this study, for both the platform and the building a square cross-section is used and both are prismatic in the direction of the height. The platform and the core of the building are made of concrete. Apart from the four parameters: height of the building and width, height and depth of the platform all other parameters are based on these four parameters. No stability systems in the building were used (except the core), nor methods to keep the platform in place, such as mooring systems. For the buoyancy, mainly the relation between the mass and the depth of the platform is determined. This is a relationship that has been used exten, Civil Engineering | Building Engineering - Structural Design

Low back pain (LBP) remains the most prevalent and costly work-related disability worldwide and is directly associated with "physical" risk factors prevalent in manual material handling (MMH) tasks. Back-support exoskeletons (BSEs) are a promising ergonomic intervention to mitigate LBP risk, by reducing muscular exertion and spine loading. The purpose of this work was to help better understand both the "intended" and "unintended" consequences of BSE use on physical risk factors for LBP, as an essential prerequisite for the safe and effective implementation of this technology in actual workplaces. The first study assessed the effects of using two BSEs on objective and subjective responses during repetitive lifting involving symmetric and asymmetric postures. Wearing both BSEs significantly reduced peak levels of trunk extensor muscle activity and reduced energy expenditure. Such reductions, though, were more pronounced in the symmetric conditions and differed between the two BSEs tested. The second study quantified the assistive torque profiles of two passive BSEs using a computerized dynamometer, with both human subjects and a mannequin. Clear differences in torque magnitudes were evident between the BSEs, though both generated more assistive torques during flexion than extension. The third study estimated the effects of BSE use on lumbosacral compressive and shear forces during repetitive lifting using an optimization-based model. Using both BSEs reduced peak compression and anteroposterior shear forces, but these effects differed between tasks and BSE designs. Reductions in composite measures of trunk muscle activity did not correspond consistently with changes in spine forces when using a BSE. The fourth study quantified the effects of two passive BSEs on trunk stability and movement coordination during repetitive lifting. Some adverse effects on stability were evident for pelvis and thorax movements and coupling of these body segments, suggesting that caution is

Introduire des fibres dans un béton fluide à rhéologie adaptée (FCAR) permet d'améliorer ses performances mécaniques. Cependant, cela peut augmenter le risque d'hétérogénéité des mélanges SCC renforcés de fibres (FR-SCC), notamment en présence de barres de renforcement. Pour assurer une performance d'écoulement adéquate des FR-SCC, il est nécessaire d'optimiser les caractéristiques physiques et rhéologiques de ses différentes phases, y compris le squelette solide (fibre-agrégat) et la matrice du mortier. La présente recherche vise à évaluer l'effet couplé des caractéristiques des systèmes granulats-fibres et des propriétés rhéologiques du mortier sur les performances d'écoulement homogène du béton autoplaçant fibré (SCC-F). Dans la première phase, une enquête exhaustive a été entreprise pour identifier les caractéristiques des fibres et des granulats grossiers afin de concevoir 19 mélanges SCC-F. Ensuite, un nouveau dispositif de test empirique, Square-Box, a été utilisé pour évaluer les performances d'écoulement régulier de divers mélanges SCC-F en termes de passabilité et de stabilité dynamique. Enfin, dans la dernière phase, les mélanges FR-SCC étudiés dans les phases précédentes ont été coulés dans le dispositif d'essai développé pour évaluer l'effet combiné des caractéristiques des composants du mélange, et la présence de barres de renforcement sur la distribution et l'orientation des fibres (FOD). Les résultats montrent que l'optimisation des mélanges FR-SCC en termes d'effet couplé du squelette solide et de la rhéologie du mortier, en plus de l'effet des barres d'armature, est une approche prometteuse pour obtenir un FOD correct et des FR-SCC maniables., The use of highly-flowable cementitious mixtures, such as self-consolidating concrete (SCC), in concrete industry including repair application aims to facilitate the casting of highly congested reinforced elements. This is based on the various advantages of SCC mixtures in both fresh and hardened states. However, cementitious materials are generally considered as brittle, with low tensile and flexural strengths and weak strain capacity. Therefore, concrete is reinforced by rebar and fibers to improve strength-strain capacity and ductility of concrete structures. On the other hand, the addition of fiber to cementitious materials enhances their mechanical performance but can negatively impact their workability. This study deals with the homogenous performance of fiber-reinforced self-consolidating concrete (FR-SCC) as one of the most promising materials for repair applications. The performance of FR-SCC, as a diphasic suspension, depends on the characteristics of both fiber-coarse aggregate (suspended-solid skeleton) and mortar (suspending liquid) phases. The solid components play a key role in the overall performance of the concrete produced. Then, the optimization of the fiber-coarse aggregate (F-A) combination is necessary to enhance the workability design of FR-SCCs. In the first phase of this study, a comprehensive investigation was undertaken to identify the coupled effect of the characteristics of fibers and coarse aggregate on the packing density (PD) of F-A combination used without any cement paste/mortar. The F-A skeleton can be characterized in terms of particle-size distribution (PSD), volumetric content, and morphology of the coarse aggregate, as well as size, rigidity, and content of fibers. Various types of steel, polypropylene, and polyolefin fibers having different sizes and rigidities are investigated in this phase. Moreover, four combinations of three different classes of coarse aggregate were used to proportion F-A mixtures. Test results

The dynamic stability of phase change material (PCM) emulsions is a crucial factor for their practical applica-tions. So far most previous studies on PCM emulsions have been focused on the static stability in the laboratory and cooling performance in small scale systems, but few or none on the dynamic stability and cooling perfor-mance in pilot-or larger-scale systems. This study was to evaluate the dynamic stability or service life and cooling storage performance of a novel PCM nano-emulsion for room air-conditioning application in a self -designed, pilot-scale latent heat thermal energy storage unit. The pilot unit was constructed with a chiller, a storage tank, three sets of ceiling panels, circulation pumps and flow control valves in a pipeline. The PCM nano -emulsion remained stable through 45 repeated charging and discharging cycles over a period of 70 days in the pilot unit and could be well regenerated for even longer period of operation. The PCM nano-emulsion retained a stable cooling capacity, e.g. with a discharging rate of 199.6 W in the 1st-5th cycles and 196.9 W in the 35th-40th cycles at a given flow rate. The droplet size increased to a maximum of-180 nm but was still small compared with many of the previously published ranges. Therefore, it is expected that the novel PCM nano-emulsion can have a long service life. Moreover, its volumetric thermal storage capacity was about 1.45 times higher than water in the range of 5.5-20 degrees C, with the highest average charging rate of about 1.4 kW during the phase transition process, and a high efficiency of-85% in the cooling energy release with no limitation by fast dis-charging flow rate, which make it favourable for practical situations.

Due to global warming and the subsequent rise of the sea level, scarcity of land to build on, the continues increase of the world’s population and a shift in population from rural areas to the city, there is a need for innovative projects to tackle or deal with the increase of needed liveable area. One of the solutions is floating cities. A component of a modern city is high-rise buildings. High-rise is an advantageous option to deal with the limited availability of ground surface on the floating platforms. The question is whether it is possible to realise these floating high-rise structures. This research investigates whether it is possible to realise high-rise buildings on floating platforms with limited dimensions on the sea or ocean regarding stability. And if it is feasible, what the requirements are for the general dimensions of both the platform and the high-rise building. For this purpose, conditions were used from three representative locations. At these three locations, the floating high-rise is tested for four different wave situations: Tsunami, Growing waves, most extreme wave. And an Irregular wave field. The platform and building are tested whether the structure could meet the various requirements and regulations. These are divided into three forms of stability: Buoyancy, static stability and dynamic stability. In this study, for both the platform and the building a square cross-section is used and both are prismatic in the direction of the height. The platform and the core of the building are made of concrete. Apart from the four parameters: height of the building and width, height and depth of the platform all other parameters are based on these four parameters. No stability systems in the building were used (except the core), nor methods to keep the platform in place, such as mooring systems. For the buoyancy, mainly the relation between the mass and the depth of the platform is determined. This is a relationship that has been used exten, Civil Engineering | Building Engineering - Structural Design

Aerospace Engineering

Integration of accurate vestibular, visual, and proprioceptive information is crucial in managing the centre of mass in relation to the base of support during gait. Therefore, bilateral loss of peripheral vestibular function can be highly debilitating when performing activities of daily life. To further investigate the influence of an impaired peripheral vestibular system on gait stability, spatiotemporal parameters, step-to-step variability, and mechanical stability parameters were examined in 20 patients with bilateral vestibulopathy and 20 matched healthy controls during preferred overground walking. Additionally, using a partial least squares analysis the relationship between spatiotemporal parameters of gait and the margins of stability was explored in both groups. Patients with bilateral vestibulopathy showed an increased cadence compared to healthy controls (121 ± 9 vs 115 ± 8 steps/min; p = 0.02; d = 0.77). In addition, although not significant (p = 0.07), a moderate effect size (d = 0.60) was found for step width variability (Coefficient of Variation (%); Bilateral vestibulopathy: 19 ± 11%; Healthy controls: 13 ± 5%). Results of the partial least squares analysis suggest that patients with peripheral vestibular failure implement a different balance control strategy. Instead of altering the step parameters, as is the case in healthy controls, they use the single and double support phases to control the state of the centre of mass to improve the mechanical stability.

Nowadays, modern power converters installed in renewable power plants can provide flexible electromechanical characteristics that rely on the developed control technologies such as Synchronous Power Controller (SPC). Since high renewable penetrated power grids result in a low-inertia system, this electromechanical characteristic provides support to the dynamic stability of active power and frequency in the power generation area. This goal can be achieved through the proper tuning of virtual electromechanical parameters that are embedded in the control layers of power converters. In this paper, a novel mathematical pattern and strategy have been proposed to adjust dynamic parameters in Renewable Static Synchronous Generators controlled by SPC (RSSGSPC). A detailed dynamic modeling was obtained for a feasible design of virtual damping coefficient and virtual moment of inertia in the electrometrical control layer of RSSG-SPC’s power converters. Mathematical solutions, modal analysis outcomes, time-domain simulation results, and real-time validations of the test in IEEE-14B benchmark confirm that the proposed method is an effective procedure for the dynamic design of RSSG-SPC to provide these dynamic stability supports in grid connection., Intelligent Electrical Power Grids

A new form of high-speed transportation, which involves a magnetically levitated vehicle that travels through a vacuum tube, is currently under development. Those parts of the trajectory along which the tube is supported by columns---which possess both axial and bending stiffness---requires the use of a model that allows to study a form of instability that is inherent to this type of support. Specifically, the stability is studied of a point mass with a lateral and vertical degree-of-freedom that moves with constant velocity along an infinite Euler-Bernoulli beam on coupled lateral-vertical periodically inhomogeneous foundation. The beam model is able to deflect in both the lateral and vertical direction and the concentrated mass is attached to this beam by a lateral and vertical contact spring. With the help of a perturbation method it is shown that the system's vibrations can become unstable. As for the model that only exhibits degrees-of-freedom in the vertical direction, the underlying physical phenomenon is parametric resonance, which occurs because of the periodic variation of the foundation stiffnesses. For the lateral-vertical model, this form of instability is referred to as combination parametric resonance, which yields four instability domains in the velocity-mass parameter space as opposed to the one domain for the vertical-only model. The center lines of these four domains depend strongly on the period of inhomogeneity; the larger the period, the higher the velocity at which instability occurs. Vehicle-structure interaction (i.e. the maglev system) also affects the center lines considerably; including contact springs between the beam and the point mass reduces the velocity at which instability occurs. To obtain the complete instability domains and to be able to investigate the mitigating effect of foundation damping, the method from another paper is recommended to be used for follow-up research., Civil Engineering

The most of the oligopolistic models described in the existing literature analyze dynamic processes and the stability of the Nash equilibrium by introducing concrete specifications for the demand and the cost functions. This paper analyzes the dynamic stability of the Cournot-Nash equilibrium in the context of a duopoly using general functions to establish both demand and costs. The condition that guarantees the stability of the Nash equilibrium under the adjustment process implicit in the Cournot’s original model is found to be a key requirement underpinning the dynamic stability of the Cournot-Nash equilibrium regardless of the firms’ expectations scheme. Moreover, this condition is more decisive the higher the degree of rationality of firms., La mayoría de los modelos de oligopolio descritos en la literatura analizan los procesos dinámicos y la estabilidad del equilibrio de Nash mediante la introducción de especificaciones concretas para las funciones de demanda y de costes. Este trabajo analiza la estabilidad dinámica del equilibrio de Cournot-Nash en el contexto de un duopolio utilizando funciones generales para describir tanto la demanda como los costes. Se concluye que la condición que garantiza la estabilidad del equilibrio de Nash bajo el proceso de ajuste implícito en el modelo original de Cournot es un requisito clave en la estabilidad dinámica del equilibrio de Cournot-Nash independientemente del esquema de expectativas de las empresas. Además, esta condición es más decisiva cuanto mayor sea el grado de racionalidad de las empresas.

The most of the oligopolistic models described in the existing literature analyze dynamic processes and the stability of the Nash equilibrium by introducing concrete specifications for the demand and the cost functions. This paper analyzes the dynamic stability of the Cournot-Nash equilibrium in the context of a duopoly using general functions to establish both demand and costs. The condition that guarantees the stability of the Nash equilibrium under the adjustment process implicit in the Cournot’s original model is found to be a key requirement underpinning the dynamic stability of the Cournot-Nash equilibrium regardless of the firms’ expectations scheme. Moreover, this condition is more decisive the higher the degree of rationality of firms., La mayoría de los modelos de oligopolio descritos en la literatura analizan los procesos dinámicos y la estabilidad del equilibrio de Nash mediante la introducción de especificaciones concretas para las funciones de demanda y de costes. Este trabajo analiza la estabilidad dinámica del equilibrio de Cournot-Nash en el contexto de un duopolio utilizando funciones generales para describir tanto la demanda como los costes. Se concluye que la condición que garantiza la estabilidad del equilibrio de Nash bajo el proceso de ajuste implícito en el modelo original de Cournot es un requisito clave en la estabilidad dinámica del equilibrio de Cournot-Nash independientemente del esquema de expectativas de las empresas. Además, esta condición es más decisiva cuanto mayor sea el grado de racionalidad de las empresas.

Society of today is struggling with both large amounts of emissions as well as congestion on the roads. For this reason, AFRY in collaboration with Volvo GTT is working on develop and implement longer and heavier transports in traffic network. These combinations are called high capacity transport and have high performance-based demands. Dynamic stability is one demand that can be improved for the DUOCAT, which is a high capacity transport combination. The hypothesis is that a displacement backward in the direction of travel of the v-stay can improve the dynamic stability. The v-stay is a component of the rear wheel suspension and has an important function regarding dynamic stability by absorbing lateral forces. To achieve better dynamic stability, the goal is to create counter steering on the rear axle of the DUO-CAT through small design changes on the v-stay. The suggestion from Volvo is to move the v-stay backward in the direction of travel, which in this thesis has become the focus in both concept generation and design work. The thesis includes development of new concepts of the v-stay. An extensive evaluation process consisting of dynamic analysis was carried out in PTC Creo Parametric, which made it possible to compare the new concepts with the current v-stay. An important part of the thesis is to obtain a simplified model that simulate the physical conditions. The delimitations are to examine lateral acceleration with load on the axle and friction between asphalt and wheels. The maneuver in the analyses emulates a quick lane change at 80 km/h. This has resulted in a new concept that includes the current v-stay where only the position on the frame and axle is changed with the help of new fastening components. The new concept provides an increased counter steering of 6%. The conclusion is that a displacement backwards in the direction of travel of the vehicle gives an increased counter steering. Future work is required to achieve the desired improved steering an

While tremendous advances have been made in prosthesis technology, a greater understanding of amputee gait is needed, especially among amputees in developing countries. Field studies as well as prosthesis technology in developing countries are limited due to barriers associated with equipment and resources availability. Furthermore, individuals with lower limb amputation experience increased difficulty walking and a higher fall rate compared to non-amputees, which may be exacerbated by environment, terrain, or prosthesis componentry. Due to the importance of walking on various terrain for increased quality of life as well as the differences between prosthesis technology available in developing and developed countries, a better understanding of amputee gait on underdeveloped outdoor terrain is needed. We began to address these needs with three studies that explored factors that influenced and predicted amputee gait on realistic end-user outdoor terrain. First, we investigated the effects of environment (i.e. indoor laboratory or outdoor natural walking path), terrain, and amputation level on energy expenditure and dynamic stability while walking among lower limb amputees and non-amputees. We found that terrain and amputation level affected amputee energy expenditure and stability while environment and specific uneven terrain type had minimal effects. These results may guide future work investigating the effects of terrain in laboratory-based studies. Second, we investigated the ability to predict quantitative measures of amputee gait on outdoor underdeveloped terrain from laboratory-based measurements. We found individual participant characteristics and easily accessible measures of indoor gait were as or more effective at predicting energy expenditure and dynamic stability than gait measures requiring greater experimental and analytical resources. These results may offer a tool for researchers to assess performance among amputees in various settings without the need

Massive infrastructure networks such as electric power, natural gas, or water systems play a pivotal role in everyday human lives. Development and operation of these networks is extremely capital-intensive. Moreover, security and reliability of these networks is critical. This work identifies and addresses a diverse class of computationally challenging and time-critical problems pertaining to these networks. This dissertation extends the state of the art on three fronts. First, general proofs of uniqueness for network flow problems are presented, thus addressing open problems. Efficient network flow solvers based on energy function minimizations, convex relaxations, and mixed-integer programming are proposed with performance guarantees. Second, a novel approach is developed for sample-efficient training of deep neural networks (DNN) aimed at solving optimal network dispatch problems. The novel feature here is that the DNNs are trained to match not only the minimizers, but also their sensitivities with respect to the optimization problem parameters. Third, control mechanisms are designed that ensure resilient and stable network operation. These novel solutions are bolstered by mathematical guarantees and extensive simulations on benchmark power, water, and natural gas networks.

Society of today is struggling with both large amounts of emissions as well as congestion on the roads. For this reason, AFRY in collaboration with Volvo GTT is working on develop and implement longer and heavier transports in traffic network. These combinations are called high capacity transport and have high performance-based demands. Dynamic stability is one demand that can be improved for the DUOCAT, which is a high capacity transport combination. The hypothesis is that a displacement backward in the direction of travel of the v-stay can improve the dynamic stability. The v-stay is a component of the rear wheel suspension and has an important function regarding dynamic stability by absorbing lateral forces. To achieve better dynamic stability, the goal is to create counter steering on the rear axle of the DUO-CAT through small design changes on the v-stay. The suggestion from Volvo is to move the v-stay backward in the direction of travel, which in this thesis has become the focus in both concept generation and design work. The thesis includes development of new concepts of the v-stay. An extensive evaluation process consisting of dynamic analysis was carried out in PTC Creo Parametric, which made it possible to compare the new concepts with the current v-stay. An important part of the thesis is to obtain a simplified model that simulate the physical conditions. The delimitations are to examine lateral acceleration with load on the axle and friction between asphalt and wheels. The maneuver in the analyses emulates a quick lane change at 80 km/h. This has resulted in a new concept that includes the current v-stay where only the position on the frame and axle is changed with the help of new fastening components. The new concept provides an increased counter steering of 6%. The conclusion is that a displacement backwards in the direction of travel of the vehicle gives an increased counter steering. Future work is required to achieve the desired improved steering an

Nowadays, modern power converters installed in renewable power plants can provide flexible electromechanical characteristics that rely on the developed control technologies such as Synchronous Power Controller (SPC). Since high renewable penetrated power grids result in a low-inertia system, this electromechanical characteristic provides support to the dynamic stability of active power and frequency in the power generation area. This goal can be achieved through the proper tuning of virtual electromechanical parameters that are embedded in the control layers of power converters. In this paper, a novel mathematical pattern and strategy have been proposed to adjust dynamic parameters in Renewable Static Synchronous Generators controlled by SPC (RSSG-SPC). A detailed dynamic modeling was obtained for a feasible design of virtual damping coefficient and virtual moment of inertia in the electrometrical control layer of RSSG-SPC’s power converters. Mathematical solutions, modal analysis outcomes, time-domain simulation results, and real-time validations of the test in IEEE-14B benchmark confirm that the proposed method is an effective procedure for the dynamic design of RSSG-SPC to provide these dynamic stability supports in grid connection., This project has been partially funded by Spanish Ministry of Science Innovation andUniversities under the project RTI-2018-100921-B-21 and the H2020-LC-SC3-2018-ES-SCC projectInterface GA824330., Peer Reviewed, Postprint (author's final draft)

Integration of accurate vestibular, visual, and proprioceptive information is crucial in managing the centre of mass in relation to the base of support during gait. Therefore, bilateral loss of peripheral vestibular function can be highly debilitating when performing activities of daily life. To further investigate the influence of an impaired peripheral vestibular system on gait stability, spatiotemporal parameters, step-to-step variability, and mechanical stability parameters were examined in 20 patients with bilateral vestibulopathy and 20 matched healthy controls during preferred overground walking. Additionally, using a partial least squares analysis the relationship between spatiotemporal parameters of gait and the margins of stability was explored in both groups. Patients with bilateral vestibulopathy showed an increased cadence compared to healthy controls (121 ± 9 vs 115 ± 8 steps/min; p = 0.02; d = 0.77). In addition, although not significant (p = 0.07), a moderate effect size (d = 0.60) was found for step width variability (Coefficient of Variation (%); Bilateral vestibulopathy: 19 ± 11%; Healthy controls: 13 ± 5%). Results of the partial least squares analysis suggest that patients with peripheral vestibular failure implement a different balance control strategy. Instead of altering the step parameters, as is the case in healthy controls, they use the single and double support phases to control the state of the centre of mass to improve the mechanical stability.

Nowadays, modern power converters installed in renewable power plants can provide flexible electromechanical characteristics that rely on the developed control technologies such as Synchronous Power Controller (SPC). Since high renewable penetrated power grids result in a low-inertia system, this electromechanical characteristic provides support to the dynamic stability of active power and frequency in the power generation area. This goal can be achieved through the proper tuning of virtual electromechanical parameters that are embedded in the control layers of power converters. In this paper, a novel mathematical pattern and strategy have been proposed to adjust dynamic parameters in Renewable Static Synchronous Generators controlled by SPC (RSSGSPC). A detailed dynamic modeling was obtained for a feasible design of virtual damping coefficient and virtual moment of inertia in the electrometrical control layer of RSSG-SPC’s power converters. Mathematical solutions, modal analysis outcomes, time-domain simulation results, and real-time validations of the test in IEEE-14B benchmark confirm that the proposed method is an effective procedure for the dynamic design of RSSG-SPC to provide these dynamic stability supports in grid connection., Intelligent Electrical Power Grids

A new form of high-speed transportation, which involves a magnetically levitated vehicle that travels through a vacuum tube, is currently under development. Those parts of the trajectory along which the tube is supported by columns---which possess both axial and bending stiffness---requires the use of a model that allows to study a form of instability that is inherent to this type of support. Specifically, the stability is studied of a point mass with a lateral and vertical degree-of-freedom that moves with constant velocity along an infinite Euler-Bernoulli beam on coupled lateral-vertical periodically inhomogeneous foundation. The beam model is able to deflect in both the lateral and vertical direction and the concentrated mass is attached to this beam by a lateral and vertical contact spring. With the help of a perturbation method it is shown that the system's vibrations can become unstable. As for the model that only exhibits degrees-of-freedom in the vertical direction, the underlying physical phenomenon is parametric resonance, which occurs because of the periodic variation of the foundation stiffnesses. For the lateral-vertical model, this form of instability is referred to as combination parametric resonance, which yields four instability domains in the velocity-mass parameter space as opposed to the one domain for the vertical-only model. The center lines of these four domains depend strongly on the period of inhomogeneity; the larger the period, the higher the velocity at which instability occurs. Vehicle-structure interaction (i.e. the maglev system) also affects the center lines considerably; including contact springs between the beam and the point mass reduces the velocity at which instability occurs. To obtain the complete instability domains and to be able to investigate the mitigating effect of foundation damping, the method from another paper is recommended to be used for follow-up research., Civil Engineering

A physical model was constructed for a pulse mechanical seal as a system for automatically controlling the end clearance.The effect of pulse compaction parameters on static characteristics was studied. The analysis of static characteristics revealed the influence of the design parameters of pulse compaction on the size of the end clearance and the flow rate of the fluid being sealed. Conclusions were made about the influence of the load factor and the efforts of the preliminary compression of the springs on the static characteristics of pulse compaction. The static calculation helped determine the coefficient of hydrostatic stiffness, the condition of static stability, and the range of permissible sealing pressures.The factors affecting the dynamic characteristics of the seal were determined. Dimensional values of the amplitudes of the forced axial vibrations of the ring were estimated at any rotation frequency. Expressions of the amplitude and phase frequency characteristics were obtained, which made it possible to identify dangerous regions of rotational frequencies and select the sealing parameters so that the amplitudes of the forced axial vibrations of the ring could not go beyond the limits of dynamic stability. It was revealed that the stability region expands due to a decrease in the volume of the chambers and a decrease in the coefficient of hydrostatic stiffness.A method for the analytical calculation of pulse mechanical seals was proposed to make it possible to calculate the geometry of the seal at the design stage. The study offers an example of engineering calculations for a pulse mechanical seal as well as the design of a sealing assembly developed by the proposed method, Построена физическая модель импульсного торцового уплотнения как системы автоматического регулирования торцового зазора и протечек.Изучено влияние параметров импульсного уплотнения на его статические характеристики. Проведенный анализ статических характеристик позволил выявить влияние конструктивных параметров импульсного уплотнения на величину торцового зазора и расход уплотняемой жидкости. Сделаны выводы о влиянии коэффициента нагрузки и усилия предварительного сжатия пружин на статические характеристики импульсного уплотнения. Статический расчет позволяет определить коэффициент гидростатической жесткости, условие статической устойчивости, диапазон допустимых уплотняемых давлений.Определены факторы, влияющие на динамические характеристики уплотнения. Проведена оценка размерных значений амплитуд вынужденных осевых колебаний кольца на любой частоте вращения. Получены выражения амплитудных и фазовых частотных характеристик, позволяющие выявить опасные области частот вращения и подобрать параметры уплотнения так, чтобы амплитуды вынужденных осевых колебаний кольца не выходили за пределы динамической устойчивости. Выявлено, что область устойчивости расширяется за счет уменьшения объема камер и уменьшения коэффициента гидростатической жесткости.Предложена методика аналитического расчета импульсных торцовых уплотнений, позволяющая рассчитывать геометрию уплотнения на этапе его проектирования. Приведен пример инженерного расчета импульсного торцового уплотнения, а также конструкция уплотнительного узла, спроектированного по предложенной методике, Побудована фізична модель імпульсного торцевого ущільнення як системи автоматичного регулювання торцового зазору і протікання.Вивчено вплив параметрів імпульсного ущільнення на його статичні характеристики. Проведений аналіз статичних характеристик дозволив виявити вплив конструктивних параметрів імпульсного ущільнення на величину торцового зазору і витоків ущільнюваної рідини. Зроблено висновки про вплив коефіцієнта навантаження і зусилля попереднього стиснення пружин на статичні характеристики імпульсного ущільнення. Статичний розрахунок дозволяє визначити коефіцієнт гідростатичної жорсткості, умови статичної стійкості, діапазон допустимих ущільнюваних тисків.Визначено фактори, що впливають на динамічні характеристики ущільнення. Проведено оцінку розмірних значень амплітуд вимушених осьових коливань кільця на будь-якій частоті обертання. Отримані вирази амплітудних і фазових частотних характеристик, що дозволяють виявити небезпечні області частот обертання і підібрати параметри ущільнення так, щоб амплітуди вимушених осьових коливань кільця не виходили за межі динамічної стійкості. Виявлено, що область стійкості розширюється за рахунок зменшення обсягу камер і зменшення коефіцієнта гидростатичної жорсткості.Запропоновано методику аналітичного розрахунку імпульсних торцових ущільнень, що дозволяє розраховувати геометрію ущільнення на етапі його проектування. Наведено приклад інженерного розрахунку імпульсного торцового ущільнення, а також конструкцію вузла ущільнення, спроектованого за запропонованою методикою

Due to globalisation and technological advancements, the world is becoming increasingly complex. Volatile, uncertain, complex and ambiguous (VUCA) environments have called for organisations to become more agile in order to survive and compete in such changing environments. Large organisations are at particular risk for becoming stagnant due to operational inertia. In order to combat this and achieve agility, dynamic capabilities are developed. These capabilities allow an organisation to more effectively and efficiently change to incoming threats or opportunities. Such changes create uncertainty and insecurity amongst employees which translates into higher employee turnover and decreased performance. Stability therefore needs to be provided for individuals, while achieving dynamacy for organisations. This paradox of dynamic stability drives research into understanding relationships and effects caused by disruptions. Covid-19 is used as an extreme use case in order to create these understandings. After primary and secondary research conclusions were developed, a conceptual framework was developed in order to orchestrate capabilities. This aims to help speed up the time taken for opportunities/threats to be translated into outcomes. This also aims to help improve the depth, diversity and accuracy of these outcomes., Strategic Product Design

The ability to rapidly adjust gait to cope with unexpected mechanical perturbations declines with ageing. Previous studies, however, have not ensured that gait stability pre-perturbation was equivalent across participants or age groups which may have influenced the outcomes. In this study, we investigate if age-related differences in stability following gait perturbations remain when all participants walk with equivalent stability. We also examine if interlimb transfer of gait adaptations are observed in healthy older adults, by examining if adaptation to repeated perturbations of one leg can benefit stability recovery when the other leg is perturbed. During walking at their stability-normalised walking speeds (young: 1.32 +/- 0.07 m/s; older: 1.31 +/- 0.13 m/s; normalised to an average margin of stability of 0.05 m), 30 young and 28 older healthy adults experienced ten unpredictable treadmill belt accelerations (the first and last applied to the right leg, the others to the left leg). Using kinematic data, we assessed the margins of stability during unperturbed walking and the first eight post-perturbation recovery steps. Older adults required three more steps to recover during the first perturbation to each leg than the young adults. Yet, after repeated perturbations of the left leg, older adults required only one more step to recover. Interestingly, for the untrained right leg, the older adults could regain stability with three fewer steps, indicating interlimb transfer of the improvements. Age differences in reactive gait stability remain even when participants' walk with equivalent stability. Furthermore, we show that healthy older adults can transfer improvements in balance recovery made during repeated perturbations to one limb to their recovery following a perturbation to the untrained limb.

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., In this paper, three different centralized control designs that vary on complexity are presented to damp inter-area oscillations in large power systems. All the controls are based on phasor measurements. The first two proposed architectures use simple proportional gains that consider availability of measurements from different areas of the system and fulfill different optimization functions. The third controller is based on a more sophisticated Linear Quadratic Gaussian approach which requires access to the state space model of the system under investigation. The novelty of the proposed scheme resides in designing a single control to command the most influence group of machines in the system. To illustrate the effectiveness of the proposed algorithms, simulations results in the IEEE New England model are presented.

Cassava is one of the largest starch producing tuber crops in Indonesia. Tapioca from cassava starch can be used as a raw materials for a variety of foods including biscuits, instant porridge, meatball, sausage, nuggets, and flour condiment. Breeding programs to improve cassava yield and starch content by using mutagen gamma rays irradiation was tested in four cassava generations (M1V4). Cassava is propagated by stem cuttings and the new characteristic obtained from gamma irradiation mutation is stable and can be passed from one generation to the next. Cassava mutants were obtained by evaluating the performance in different environmental conditions. The testing of yield adaptability and stability through a series of multi location is an important step before a new variety can be released. The aim of this research was to compare nonparametric stability and to evaluate the stability of the starch content of 16 genotypes (14 mutants and 2 varieties) in three locations in West Java Province i.e. Tapos (Depok), Cikarawang (Bogor), and Ciseeng (Bogor). Experiments were conducted in a completely randomized block design with three replications nested in each environment. Testing of yield stability in this study used four approaches with 10 parameters of nonparametric method. Starch content was estimated using gravimetric method. Based on frequency stability ranking of starch content from gravimetric method the G63142 genotype had the highest starch content estimation (29.99%), and the top five genotypes with high starch content were G63142, G61142, “Manggu”, G62151, and G63124. G61142 was categorized as genotype with static and dynamic stability, therefore this genotype is a very potential mutant to be released, whereas G63124 is categorized as a genotype with a static stability. Genotypes G63142, G62151, and “Manggu” had variable but relatively high starch content.

The ability to rapidly adjust gait to cope with unexpected mechanical perturbations declines with ageing. Previous studies, however, have not ensured that gait stability pre-perturbation was equivalent across participants or age groups which may have influenced the outcomes. In this study, we investigate if age-related differences in stability following gait perturbations remain when all participants walk with equivalent stability. We also examine if interlimb transfer of gait adaptations are observed in healthy older adults, by examining if adaptation to repeated perturbations of one leg can benefit stability recovery when the other leg is perturbed. During walking at their stability-normalised walking speeds (young: 1.32 +/- 0.07 m/s; older: 1.31 +/- 0.13 m/s; normalised to an average margin of stability of 0.05 m), 30 young and 28 older healthy adults experienced ten unpredictable treadmill belt accelerations (the first and last applied to the right leg, the others to the left leg). Using kinematic data, we assessed the margins of stability during unperturbed walking and the first eight post-perturbation recovery steps. Older adults required three more steps to recover during the first perturbation to each leg than the young adults. Yet, after repeated perturbations of the left leg, older adults required only one more step to recover. Interestingly, for the untrained right leg, the older adults could regain stability with three fewer steps, indicating interlimb transfer of the improvements. Age differences in reactive gait stability remain even when participants' walk with equivalent stability. Furthermore, we show that healthy older adults can transfer improvements in balance recovery made during repeated perturbations to one limb to their recovery following a perturbation to the untrained limb.

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., In this paper, three different centralized control designs that vary on complexity are presented to damp inter-area oscillations in large power systems. All the controls are based on phasor measurements. The first two proposed architectures use simple proportional gains that consider availability of measurements from different areas of the system and fulfill different optimization functions. The third controller is based on a more sophisticated Linear Quadratic Gaussian approach which requires access to the state space model of the system under investigation. The novelty of the proposed scheme resides in designing a single control to command the most influence group of machines in the system. To illustrate the effectiveness of the proposed algorithms, simulations results in the IEEE New England model are presented.

Due to globalisation and technological advancements, the world is becoming increasingly complex. Volatile, uncertain, complex and ambiguous (VUCA) environments have called for organisations to become more agile in order to survive and compete in such changing environments. Large organisations are at particular risk for becoming stagnant due to operational inertia. In order to combat this and achieve agility, dynamic capabilities are developed. These capabilities allow an organisation to more effectively and efficiently change to incoming threats or opportunities. Such changes create uncertainty and insecurity amongst employees which translates into higher employee turnover and decreased performance. Stability therefore needs to be provided for individuals, while achieving dynamacy for organisations. This paradox of dynamic stability drives research into understanding relationships and effects caused by disruptions. Covid-19 is used as an extreme use case in order to create these understandings. After primary and secondary research conclusions were developed, a conceptual framework was developed in order to orchestrate capabilities. This aims to help speed up the time taken for opportunities/threats to be translated into outcomes. This also aims to help improve the depth, diversity and accuracy of these outcomes., Strategic Product Design

In gait stability research, neither self-selected walking speeds, nor the same prescribed walking speed for all participants, guarantee equivalent gait stability among participants. Furthermore, these options may differentially affect the response to different gait perturbations, which is problematic when comparing groups with different capacities. We present a method for decreasing inter-individual differences in gait stability by adjusting walking speed to equivalent margins of stability (MoS). Eighteen healthy adults walked on a split-belt treadmill for two-minute bouts at 0.4 m/s up to 1.8 m/s in 0.2 m/s intervals. The stability-normalised walking speed (MoS = 0.05 m) was calculated using the mean MoS at touchdown of the final 10 steps of each speed. Participants then walked for three minutes at this speed and were subsequently exposed to a treadmill belt acceleration perturbation. A further 12 healthy adults were exposed to the same perturbation while walking at 1.3 m/s: the average of the previous group. Large ranges in MoS were observed during the prescribed speeds (6–10 cm across speeds) and walking speed significantly (P < 0.001) affected MoS. The stability-normalised walking speeds resulted in MoS equal or very close to the desired 0.05 m and reduced between-participant variability in MoS. The second group of participants walking at 1.3 m/s had greater inter-individual variation in MoS during both unperturbed and perturbed walking compared to 12 sex, height and leg length-matched participants from the stability-normalised walking speed group. The current method decreases inter-individual differences in gait stability which may benefit gait perturbation and stability research, in particular studies on populations with different locomotor capacities. [Preprint: https://doi.org/10.1101/314757]

Visually guided weight shifting is widely employed in balance rehabilitation, but the underlying visuo-motor integration process leading to balance improvement is still unclear. In this study, we investigated the role of center of pressure (CoP) feedback on the entrainment of active voluntary sway to a moving visual target and on sway’s dynamic stability as a function of target predictability. Fifteen young and healthy adult volunteers (height 175 ± 7 cm, body mass 69 ± 12 kg, age 32 ± 5 years) tracked a vertically moving visual target by shifting their body weight antero-posteriorly under two target motion and feedback conditions, namely, predictable and less predictable target motion, with or without visual CoP feedback. Results revealed lower coherence, less gain, and longer phase lag when tracking the less predictable compared to the predictable target motion. Feedback did not affect CoP-target coherence, but feedback removal resulted in greater target overshooting and a shorter phase lag when tracking the less predictable target. These adaptations did not affect the dynamic stability of voluntary sway. It was concluded that CoP feedback improves spatial perception at the cost of time delays, particularly when tracking a less predictable moving target., Peer Reviewed

Instability training provides the nervous system with a greater challenge than traditional training, and thus can be performed with a reduced external load, potentially reducing the likelihood of injury. Unstable exercises have also been found to elicit higher levels of core muscle activity than their stable counterparts and so may increase joint loading. The degree to which instability challenges the stability of the human body likely relies on the level of instability of the movement, but the influence of experimental instability, and its effect on the level of stability of the human body, has yet to be determined. This study aims to examine how altering the available degrees of freedom of the pushup, as a means of quantifying instability, may affect the dynamic stability of the lumbar spine. The results of this study indicate that adding two available degrees of freedom to the conventional pushup significantly increases kinematic variance of the L1 vertebra through 3-dimensional space. No significant difference in kinematic variability existed between the two conditions of additional available degrees of freedom. These results may help health care professionals improve the individualization of their training programs by taking desired level of instability into account, and adjusting available degrees of freedom accordingly.

Supervised machine learning has been successfully used in the past to infer a system's security boundary by training classifiers (also referred to as security rules) on a large number of simulated operating conditions. Although significant research has been carried out on using classifiers for the detection of critical operating points, using classifiers for the subsequent identification of suitable preventive/corrective control actions remains underdeveloped. This paper focuses on addressing the challenges that arise when utilizing security rules for control purposes. Illustrative examples and case studies are used to show how even very accurate security rules can lead to prohibitively high risk exposure when used to identify optimal control actions. Subsequently, the inherent tradeoff between operating cost and security risk is explored in detail. To optimally navigate this tradeoff, a novel approach is proposed that uses an ensemble learning method (AdaBoost) to infer a probabilistic description of a system's security boundary. Bias in predictions is compensated by the Platt Calibration method. Subsequently, a general-purpose framework for building probabilistic and disjunctive security rules of a system's secure operating domain is developed that can be embedded within classic operation formulations. Through case studies on the IEEE 39-bus system, it is showcased how security rules derived from supervised learning can be efficiently utilized to optimally operate the system under multiple uncertainties while respecting a user-defined balance between cost and risk. This is a fundamental step toward embedding data-driven models within classic optimisation approaches., Intelligent Electrical Power Grids

The continuous growth and development of society have a direct correlation to the amount of energy required to satisfy its demand. As consequence, more interconnections of existing electrical networks are required, increasing the complexity on its operation. Thus, larger power systems are prone to experience inter-area oscillations, which are triggered by generators oscillating against each other from different geographic locations. Whether these so called inter-area oscillations are undamped, they could eventually lead to a system collapse. In this work, a Linear Quadratic Gaussian (LQG) control approach to damp inter-area oscillations out, which is coupled with a dynamic eigensystem realization algorithm (ERA), is proposed. Although these two concepts are well documented on the literature, the novelty presented here is its combination resulting on a fast and effective damping controller. The proposed architecture is implemented as a digital Power System Stabilizer (PSS) using the combination of the professional softwares DigSilent PowerFactory and Matlab. The presented controller is validated trough dynamic system simulations on the IEEE benchmark New England model. Additionally, a tutorial to implement the proposed controller is also presented.

In this work a state-feedback controller for pole placement is presented. In addition, a model predictive control (MPC) to minimize the magnitude of the controller input is also presented. The MPC use an observer to estimate the states of the plant and optimize a cost function to maintain the input within a pre-defined limit. The proposed approach is validate trough nonlinear simulations using the equivalent Nordic power system and where a Static Var Compensator is used as actuator. Wide-area signals from Phasor Measurement Units (PMUs) are used to improve the damping of the system.

The consortium Projectorganisatie Uitbreiding Maasvlakte (PUMA), consisting out of Van Oord and Boskalis, constructed a hard sea defence for the protection of Maasvlakte 2, which is the expansion of the Port of Rotterdam. This hard sea defence consists of a Dynamic Rock Slope (DRS) with a Block Dam (BD) situated in front of it. The BD is build up out of large concrete blocks which were recycled from Maasvlakte 1. The DRS behind it protects the hinterland through an approximate three to four meter thick layer of quarry rock. When waves travel obliquely through this Block Dam and interact with the DRS, stones are transported in alongshore direction. This process is called Longshore Transport (LT) and will have erosion and accretion of stones to effect along the DRS. In order to maintain the layer thickness of this stone layer, PUMA made a prognosis on LT for the coming 50 years after construction. From this prognosis a nourishment campaign was set-up, consisting of volumes of stone PUMA expected to nourish every 2.5 years. After a maintenance period of five years it was concluded by PUMA that the nourishment volumes were lower than expected. Therefore this thesis assessed where differences in the prognosis of PUMA on LT and the observed LT rates over the period 2013 to 2018 come from. Within their prognosis, PUMA made use of a dimensional LT relation. As this specifically calibrated Longshore Transport relation is only applicable for the computation of LT rates at a structure containing the characteristics of the DRS at Maasvlakte 2, this research looked into the possibilities of using a non-dimensional Longshore Transport relation for the computation of Longshore Transport rates at the DRS of Maasvlakte 2., Civil Engineering | Hydraulic Engineering

Instability training provides the nervous system with a greater challenge than traditional training, and thus can be performed with a reduced external load, potentially reducing the likelihood of injury. Unstable exercises have also been found to elicit higher levels of core muscle activity than their stable counterparts and so may increase joint loading. The degree to which instability challenges the stability of the human body likely relies on the level of instability of the movement, but the influence of experimental instability, and its effect on the level of stability of the human body, has yet to be determined. This study aims to examine how altering the available degrees of freedom of the pushup, as a means of quantifying instability, may affect the dynamic stability of the lumbar spine. The results of this study indicate that adding two available degrees of freedom to the conventional pushup significantly increases kinematic variance of the L1 vertebra through 3-dimensional space. No significant difference in kinematic variability existed between the two conditions of additional available degrees of freedom. These results may help health care professionals improve the individualization of their training programs by taking desired level of instability into account, and adjusting available degrees of freedom accordingly.