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Investigating the stability of stationary motions is a highly relevant aspect when characterizing dynamical systems. For equilibria and periodic motions, well established theories and approaches exist to assess their stability: in both cases stability may be assessed using eigenvalue analyses of small perturbations. When it comes to quasi-periodic motions, such eigenvalue analyses are not applicable, since these motions can not be parameterized on finite time intervals. However, quasi-periodic motions can be densely embedded on finite invariant manifolds with periodic boundaries. In this contribution, a new approach is presented, which exploits this embedding in order to derive a sequence of finite mappings. Based on these mappings, the spectrum of 1st order Lyapunov-exponents is efficiently calculated. If the linearization of the problem is regular in the sense of Lyapunov, these exponents may be used to assess stability of the investigated solution. Beyond the numerical calculation of Lyapunov-exponents, an approach is presented which allows to check Lyapunov-regularity numerically. Together, both methods allow for an efficient numerical stability assessment of quasi-periodic motions. To demonstrate, verify and validate the developed approach, it is applied to quasi-periodic motions of two coupled van-der-Pol oscillators as well as a quasi-periodically forced Duffing equation. Additionally, a "step-by-step application instruction" is provided to increase comprehensibility and to discuss the required implementation steps in an applied context. [ABSTRACT FROM AUTHOR]

Copyright of Firat University Journal of Experimental & Computational Engineering (FUJECE) is the property of Firat University Journal of Experimental & Computational Engineering (FUJECE) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The islanded micro-grid is playing a more and more significant role to absorb more wind and solar energy because of its advantages such as flexibility, cleanliness and environmental friendliness. However, the randomness and transient of renewable energy result in many challenges for the economic operation of the islanded micro-grid. The load frequency control is the core influencing factor for the economic operation. A modified active disturbance rejection control (MADRC), combined with a compensation part and an amplitude limiter, is proposed for the load frequency control with high-proportional renewable energy. The convergence of the extended state observer is analyzed theoretically. Then a pragmatic tuning procedure is provided by examining the influence of MADRC’s parameters on the control performance. Finally, the proposed control strategy is applied to the load frequency control of the islanded micro-grid and simulations under different conditions are carried out. The simulation results compared with other comparative controller strategies show that MADRC can obtain the best control performance with good robustness. Quantitative data demonstrates the improvement of the proposed method in terms of economic operation and the proposed method also shows promising engineering application potential.

Previous investigations in the High Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Center (DLR) show that carbon fiber reinforced carbon ceramic (C/C) surfaces can be utilized to damp hypersonic boundary layer instabilities resulting in a delay of boundary layer transition onset. Numerical stability analyses confirmed these experimental results. However, C/C has some disadvantages, especially the limited oxidation resistance and its low mechanical strength, which could be critical during hypersonic flights. Thus, an ultrasonically absorptive fiber reinforced ceramic material based on a silicon carbide (C/C-SiC) was developed in the past years to fulfill this need. The present paper addresses the numerical rebuilding of the C/C-SiC absorber properties using impedance boundary conditions together with linear stability analysis. The focus of this paper is on the numerical comparison of the original C/C material and the improved C/C-SiC material, referred to as OCTRA in the literature. The influence on the second modes and the transition itself is investigated. The numerical results are compared with HEG wind tunnel tests. The wind tunnel model tested in HEG is a 7 ∘ half-angle blunted cone with an overall model length of about 1.1 m and a nose tip radius of 2.5 mm. These experiments were performed at Mach 7.5 and at different freestream unit Reynolds numbers. [ABSTRACT FROM AUTHOR]

Copyright of Revue Française de Géotechnique is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize is an essential staple food crop and is vulnerable to diseases. Maize streak disease is one of the serious illnesses that affect maize, especially in sub-Saharan Africa where the disease is endemic. We developed a stochastic epidemic model with three control measure types (mechanical, chemical and preventative) that mitigate the disease. A dynamical system analysis of the deterministic version of the model is provided. The probability of maize streak disease extinction or persistence is determined using the theory of a multi-type branching process. Using these results, the degrees to which these control measures are effective in reducing maize streak disease are considered. It is shown that chemical and mechanical control measures, preferably together, are better than preventive controls in reducing disease prevalence. However, considering the possible negative effects of a chemical control, it is shown that sufficient mechanical control combined with a small degree of each of preventative and chemical control could be the most viable strategy to limit maize streak disease.

Malaria is a life-threatening disease endemic in many African countries especially Nigeria. A mathematical model is used to study the dynamics of malaria in Nigeria. The model incorporates drug resistance, treatment, and the use of mosquito nets as preventive strategies. By fitting the model to data on the incidence of malaria in Nigeria, important parameters associated with the disease dynamics are estimated. Using these estimated parameters, the basic reproduction number is calculated, future dynamics simulated, and those parameters with a large impact on Nigerian malaria determined. Overall, the results indicate that the disease is likely to remain endemic in Nigeria unless better control measures are focused on the dominant resistant strain, treatment is improved and the use of mosquito nets become widespread.

The Malogne Phosphatic chalk quarry was developed by the rooms and pillars mining method within an area of 67 ha. The site is partially flooded and located in close proximity to important infrastructure as railway, highway, and residential houses. During and after its exploitation several significant ground collapses were registered. The last one, with an area of 1.2 ha and 3 m amplitude occurred in 2015 nearby the railway line. To assess the behavior of the underground openings a combination of in situ structural measurements and laboratory mechanical characterisation in dry and saturated state of the main lithology type in the quarry – white and phosphatic chalk, hard ground and calcarenites, are performed. The UCS of the chalk ranges from 4 to 10 MPa while its tensile strength is between 0.75 and 2.1 MPa. For the hardground, these values are over ten times higher. The results reveal significant influence of the water on the chalk properties by reduction of almost twice its strength. The data obtained was implemented in a conceptual geomechanical model, using the 2D FEM. Numerical results show a failure pattern that was confirmed from the in situ observations. [ABSTRACT FROM AUTHOR]

Lassa fever is a deadly viral illness that is endemic in some parts of West Africa, including Nigeria. A deterministic model in the form of a non-linear system of differential equations is developed to analyse the dynamics and possible control of the disease. The model is tested by fitting it to data from Nigeria's Lassa fever outbreak using a least-squares fitting routine and the model is shown to provide a reasonable fit to the data. Parameters representing various control measures in the model are estimated using the model fitting. Important epidemiological features of the model such as the basic reproduction number (R 0) , the disease-free equilibrium, and the endemic equilibrium are determined and analysed. The disease-free equilibrium is shown to be asymptotically stable when R 0 < 1 . A bifurcation about R 0 = 1 was determined using the Center Manifold Theorem. Using numerical simulations of the model future dynamics of Lassa fever disease in Nigeria are predicted and the impact of control measures on the disease determined. The use of approved rodenticides is shown to be the most effective control followed by reducing person-to-person and rodent-to-person contacts, respectively. Isolation and treatment of infected individuals are shown to be less effective when compared with the other control measures. [ABSTRACT FROM AUTHOR]

Malaria is a life-threatening disease endemic in many African countries especially Nigeria. A mathematical model is used to study the dynamics of malaria in Nigeria. The model incorporates drug resistance, treatment, and the use of mosquito nets as preventive strategies. By fitting the model to data on the incidence of malaria in Nigeria, important parameters associated with the disease dynamics are estimated. Using these estimated parameters, the basic reproduction number is calculated, future dynamics simulated, and those parameters with a large impact on Nigerian malaria determined. Overall, the results indicate that the disease is likely to remain endemic in Nigeria unless better control measures are focused on the dominant resistant strain, treatment is improved and the use of mosquito nets become widespread. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide new insight into the catastrophic mobility of the earthquake-induced flow-type Takanodai landslide that occurred on 16 April 2016, which had fatal consequences. A geological and geotechnical interpretation of the site conditions and experimental investigations of the mechanical behavior of weathered Kusasenrigahama (Kpfa) pumice are used to characterize the landslide failure mechanism. The results of large-strain undrained torsional shear tests indicate that Kpfa pumice has the potential to rapidly develop very large shear strains upon mobilization of its cyclic resistance. To evaluate the actual field performance, a series of new liquefaction triggering analyses are carried out. The liquefaction triggering analyses indicate that Kpfa pumice did not liquefy during the Mw6.2 foreshock event, and the hillslope remained stable. Instead, it liquefied during the Mw7.0 mainshock event, when the exceedance of the cyclic resistance of the Kpfa pumice deposit and subsequent flow-failure type of response can be considered the main cause of the landslide. Moreover, the combination of large cyclic stress ratios (CSR = 0.21–0.35)—significantly exceeding the cyclic resistance ratio CRR = 0.09–0.13)—and static shear stress ratios (α = 0.15–0.25) were critical factors responsible for the observed flow-type landslide that traveled more than 0.6 km over a gentle sloping surface (6°–10°). [ABSTRACT FROM AUTHOR]

Convection induced by internal heating and adverse temperature gradient in a porous medium has various real-world applications, such as solar energy collectors, solar-based drying and cooking. Thus, it is crucial to analyze such flows to understand the physics behind the flow and analyze heat transfer through the system. We assume that volumetric heating occurs within the fluid phase due to radiation exposure from an overhead source or a stratified arrangement of heat-generating materials. For modeling convenience, we further assume that internal heating diminishes exponentially with the depth of the porous layer and fluctuates sinusoidally over time, affecting the mean value. Solid and fluid phases of the porous layer are considered out of thermal equilibrium. Floquet theory is employed to determine the linear instability bound of the system. By analyzing the eigenvalue spectrum, we identify the critical Rayleigh number that marks the onset of instability. Subsequently, a weakly nonlinear analysis is carried out using a truncated Fourier series expansion of the physical quantities to analyze the heat transfer within the system. The effect of governing nondimensional parameters on the system's stability and heat transport is graphically illustrated and thoroughly discussed. The effect of modulation amplitude and volumetric heat is to enhance heat transfer, whereas depth coefficient and modulation frequency suppress heat transfer. • Effect of a non-uniform time-dependent volumetric heat source on the thermoconvective flow in a porous layer is studied. • Solid and fluid phases of a porous layer are considered out of thermal equilibrium. • Heat source diminishes exponentially with the depth of the porous layer and fluctuates sinusoidally over time. • Modulation amplitude affects the onset of convection significantly for different values of LTNE parameters in comparison to modulation frequency. • The effect of volumetric heating is to enhance heat transfer, whereas depth coefficient suppresses heat transfer. [ABSTRACT FROM AUTHOR]

Graph edit distance (GED) is a powerful tool to model the dissimilarity between graphs. However, evaluating the exact GED is NP-hard. To tackle this problem, estimation methods of GED were introduced, e.g., bipartite and IPFP, during which heuristics were employed. The stochastic nature of these methods induces the stability issue. In this paper, we propose the first formal study of stability of GED heuristics, starting with defining a measure of these (in)stabilities, namely the relative error. Then, the effects of two critical factors on stability are examined, namely, the number of solutions and the ratio between edit costs. The ratios are computed on five datasets of various properties. General suggestions are provided to properly choose these factors, which can reduce the relative error by more than an order of magnitude. Finally, we verify the relevance of stability to predict performance of GED heuristics, by taking advantage of an edit cost learning algorithm to optimize the performance and the k-nearest neighbor regression for prediction. Experiments show that the optimized costs correspond to much higher ratios and an order of magnitude lower relative errors than the expert cost. [ABSTRACT FROM AUTHOR]

The islanded micro-grid is playing a more and more significant role to absorb more wind and solar energy because of its advantages such as flexibility, cleanliness and environmental friendliness. However, the randomness and transient of renewable energy result in many challenges for the economic operation of the islanded micro-grid. The load frequency control is the core influencing factor for the economic operation. A modified active disturbance rejection control (MADRC), combined with a compensation part and an amplitude limiter, is proposed for the load frequency control with high-proportional renewable energy. The convergence of the extended state observer is analyzed theoretically. Then a pragmatic tuning procedure is provided by examining the influence of MADRC's parameters on the control performance. Finally, the proposed control strategy is applied to the load frequency control of the islanded micro-grid and simulations under different conditions are carried out. The simulation results compared with other comparative controller strategies show that MADRC can obtain the best control performance with good robustness. Quantitative data demonstrates the improvement of the proposed method in terms of economic operation and the proposed method also shows promising engineering application potential. • A MADRC scheme is restructured for the load frequency control to enhance the economic operation of the islanded micro-grid. • The convergence of the proposed extended state observer is analyzed theoretically. • A pragmatic tuning procedure is provided for MADRC. • The effectiveness of the proposed MADRC is illustrated under different conditions. [ABSTRACT FROM AUTHOR]

Lassa fever is a deadly viral illness that is endemic in some parts of West Africa, including Nigeria. A deterministic model in the form of a non-linear system of differential equations is developed to analyse the dynamics and possible control of the disease. The model is tested by fitting it to data from Nigeria’s Lassa fever outbreak using a least-squares fitting routine and the model is shown to provide a reasonable fit to the data. Parameters representing various control measures in the model are estimated using the model fitting. Important epidemiological features of the model such as the basic reproduction number (R0), the disease-free equilibrium, and the endemic equilibrium are determined and analysed. The disease-free equilibrium is shown to be asymptotically stable when R0<1. A bifurcation about R0=1 was determined using the Center Manifold Theorem. Using numerical simulations of the model future dynamics of Lassa fever disease in Nigeria are predicted and the impact of control measures on the disease determined. The use of approved rodenticides is shown to be the most effective control followed by reducing person-to-person and rodent-to-person contacts, respectively. Isolation and treatment of infected individuals are shown to be less effective when compared with the other control measures.

Copyright of Journal of Plant Production is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revue Française de Géotechnique is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize is an essential staple food crop and is vulnerable to diseases. Maize streak disease is one of the serious illnesses that affect maize, especially in sub-Saharan Africa where the disease is endemic. We developed a stochastic epidemic model with three control measure types (mechanical, chemical and preventative) that mitigate the disease. A dynamical system analysis of the deterministic version of the model is provided. The probability of maize streak disease extinction or persistence is determined using the theory of a multi-type branching process. Using these results, the degrees to which these control measures are effective in reducing maize streak disease are considered. It is shown that chemical and mechanical control measures, preferably together, are better than preventive controls in reducing disease prevalence. However, considering the possible negative effects of a chemical control, it is shown that sufficient mechanical control combined with a small degree of each of preventative and chemical control could be the most viable strategy to limit maize streak disease. [ABSTRACT FROM AUTHOR]

With the rapid development of inverter-based generators (IGs), power grid is faced with critical frequency stability challenges because the existing IGs have no inertia. To equip IGs with inertial response, researchers have proposed several virtual inertia control methods, which can be classified into two categories: virtual synchronous generator (VSG) control and droop control based on rate of change of frequency (ROCOF-droop control). In this paper, the comparison between both virtual inertia control methods is conducted from three perspectives: mathematical model, output characteristic and small-signal stability. State-space models are firstly built to analyze the control mechanism of VSG control and ROCOF-droop control methods. Simulation and eigenvalue analysis are conducted to study the transient responses and oscillation characteristics of both methods, which is helpful to understand the advantages and limitations of existing virtual inertia control methods. Finally, the obtained theoretical results are validated through realtime laboratory (RT-LAB) hardware-in-loop simulation platform.

In recent years, the virtual synchronous generator (VSG) concept has been widely studied to integrate renewable energy sources. However, instability occurs due to the implementation of the dc-link voltage controllers under the weak grid, and its mechanism remains unclear, which is investigated in this article. At first, the wideband dq-frame impedance models of the VSGs with the dc-link voltage controllers for two cases are established. Then, the stability analyses of the VSGs are compared based on these impedance models. It is revealed that the interaction dynamics between the dc-link voltage loop and the active loop lead to the negative resistor behavior of the q–q channel impedances for both VSGs, which induces the emerging oscillations of the system in a weak grid. Besides, as a useful design guideline, the parameter design of the VSGs is proposed to enhance the system stability. Finally, the experimental results obtained from a 100-kW prototype system show good agreement with simulated results, validating the impedance models and theoretical analysis. [ABSTRACT FROM AUTHOR]

On March 20, 1941, more than 110,000 yd³ (84,000 m³) of rock slumped from Brilliant Cut in Pittsburgh, Pennsylvania. Failure was triggered by water pressure buildup due to ice blockage of drainage outlets on the slope face. I investigated this slide as part of my Ph.D. research at the University of Pittsburgh in 1968-1969 and have continued to study it. Historical photographs discovered in 1997 provided new insights on the construction and failure of Brilliant Cut and led to this re-evaluation. In this paper, my 1968-1969 work is summarized and then additional geological and historical information is presented along with key observations from the historical photographs. These photographs reveal that slope excavation at Brilliant Cut in 1930-1931 removed lateral support, in turn initiating stress release and progressive failure that loosened or broke bedrock adjacent to the cut. This fractured rock mass remained marginally stable for a decade but then collapsed in March 1941. The 1941 failure was triggered by water held back in rock fractures by a frozen crust over talus and fractured rock on the slope face. A progressive failure mechanism by Brooker and Peck explains the behavior of Brilliant Cut from 1931 to 1941. Sliding Block stability analyses demonstrate the mechanism of progressive failure and suggest that friction angles were reduced gradually to near-residual values along the failure surface, with low water levels in the slope.With drainage blocked in 1941, a water level developed about 30 ft (9 m) above the basal failure surface to initiate the catastrophic failure. This water level is below that previously inferred to have existed at the time of failure. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide new insight into the catastrophic mobility of the earthquake-induced flow-type Takanodai landslide that occurred on 16 April 2016, which had fatal consequences. A geological and geotechnical interpretation of the site conditions and experimental investigations of the mechanical behavior of weathered Kusasenrigahama (Kpfa) pumice are used to characterize the landslide failure mechanism. The results of large-strain undrained torsional shear tests indicate that Kpfa pumice has the potential to rapidly develop very large shear strains upon mobilization of its cyclic resistance. To evaluate the actual field performance, a series of new liquefaction triggering analyses are carried out. The liquefaction triggering analyses indicate that Kpfa pumice did not liquefy during the Mw6.2 foreshock event, and the hillslope remained stable. Instead, it liquefied during the Mw7.0 mainshock event, when the exceedance of the cyclic resistance of the Kpfa pumice deposit and subsequent flow-failure type of response can be considered the main cause of the landslide. Moreover, the combination of large cyclic stress ratios (CSR = 0.21–0.35)—significantly exceeding the cyclic resistance ratio CRR = 0.09–0.13)—and static shear stress ratios (α = 0.15–0.25) were critical factors responsible for the observed flow-type landslide that traveled more than 0.6 km over a gentle sloping surface (6°–10°).

In the second half of the Ist century BC seismogenic landslide/rockfall tore off the front part of the Chirakman Cape in the western part of the Kavarna Bay. The rich quarters of the Roman city of Bisone slid down into the sea. According to data from underwater archaeology artifacts and walls of the settlement are found up to 80 m inside the sea. The paper considers the tectonic conditions, the geological-geomorphological structure of the landslide, the paleogeography of the coastal shelf during the Holocene and the hydrogeological and engineering geological conditions in the area. A reconstruction of the coastline and sea-level position during the catastrophic landslide has been developed. Stability analyses have been performed too. [ABSTRACT FROM AUTHOR]

Maize is a very important food crop world-wide and is vulnerable to diseases. Maize varieties that have high disease resistance are highly recommended for economic and health reasons. We consider a maize field with multiply varieties and develop a mathematical model to investigate the impact of foliar disease on the population dynamics. The possible benefit of considering control measures in reducing the spread of foliar diseases are evaluated. Results show that farmers must be aware of the disease dynamics of each variety as the dynamics vary. Also, in controlling diseases some methods are more effective than others. For the example given here controlling susceptibility of seeds to disease was the most effective method. As controlling diseases can be costly, optimal methods are important. Our results show that the most effective controls are those introduced at the outset of an outbreak and this can reduce the spread of diseases with the least cost.

Stability analysis of free convection in a liquid-saturated sparsely-packed porous medium with local-thermal-non-equilibrium (LTNE) effect is presented. For the vertical boundaries free–free, adiabatic and rigid–rigid, adiabatic are considered while for horizontal boundaries it is the stress-free, isothermal and rigid–rigid, isothermal boundary combinations we consider. From the linear theory, it is apparent that there is advanced onset of convection in a shallow enclosure followed by that in square and tall enclosures. Asymptotic analysis of the thermal Rayleigh number for small and large values of the inter-phase heat transfer coefficient is reported. Results of Darcy–Bénard convection (DBC) and Rayleigh–Bénard convection can be obtained as limiting cases of the study. LTNE effect is prominent in the case of Brinkman–Bénard convection compared to that in DBC. Using a multi-scale method and by performing a non-linear stability analysis the Ginzburg–Landau equation is derived from the five-mode Lorenz modal. Heat transport is estimated at the lower plate of the channel. The effect of the Brinkman number, the porous parameter and the inter-phase heat transfer coefficient is to favour delayed onset of convection and thereby enhanced heat transport while the porosity-modified ratio of thermal conductivities shows the opposite effect. [ABSTRACT FROM AUTHOR]

Nickel-base superalloys display cuboidal precipitates aligned along the cubic directions, which are the elastic soft directions. At high precipitate volume fraction, the microstructure is often described as a regular array of precipitates organized on a simple cubic macro-lattice. In the present work, we use a stability analysis and 3D phase field simulations to show that such a regular array is in fact unstable whatever the volume fraction of precipitates. The two main instability modes are the longitudinal [100] mode and the transverse [110] mode along the [ 1 1 ¯ 0 ] eigenvector. We argue that these instabilities lead to formation of configurational defects closely related to experimentally observed branches and herringbone patterns. The rôles of elastic anisotropy and elastic homogeneity are also discussed. [ABSTRACT FROM AUTHOR]

Recent interpretations of wetting-induced compaction revealed that water sensitivity can cause a loss of controllability in samples subjected to fluid injection. This paper elaborates these findings by focusing on fabric anisotropy, i.e., a feature of unsaturated clays not encompassed by previous studies. For this purpose, a hydromechanical elastoplastic model with rotational hardening is developed to capture fabric effects. The model performance has been validated under both saturated and unsaturated conditions with reference to laboratory tests on Lower Cromer Till (LCT). To inspect the role of the material properties, parametric analyses have been conducted, thus identifying the parameters which govern the transition from stable to unstable conditions upon wetting. The results show that fabric anisotropy affects only the deformations prior to wetting-collapse, without changing the value of suction at the onset of volumetric instability. By contrast, it is found that the model parameter governing the intensity of suction-hardening is able to alter the value of critical suction at the loss of control regardless of the intensity of fabric evolution. These results corroborate previous findings obtained through isotropic constitutive laws and emphasize the crucial role of hydromechanical constitutive couplings on the inelasticity of unsaturated porous media. [ABSTRACT FROM AUTHOR]

In the design of truss structures, stability verifications are often decisive. Especially flexural buckling is of relevant issue. Structural systems are therefore usually stabilised by means of constructional members and components. Depending on the stiffening system and loading, the torsional behaviour and lateral torsional buckling of members can be of importance as well. However, all conventional structures for stabilisation have in common that they in general provide a shear stiffness (by bracings or sheeting) as well as an elastic rotational support. The influence of different structural truss details are analysed with regard to the girder stability. In this context, the stiffness of bracing systems and its position as well as the influence of rotational stiffness provided by purlins are investigated. In doing so, individual truss girders are analysed as well as systems of several girders based on full three‐dimensional beam models. The investigations provide information on the global stability behaviour with respect to different girder quantities stabilized by one bracing system. Additionally, a subset of structural systems are modelled in more detail using shell elements in regions of connections/joints to account for structural detailing influences. Overall, the aim is to identify and focus different effects of structural details on the stability behaviour of lattice girders to promote an economic and safe design. [ABSTRACT FROM AUTHOR]

Proposing realistic hybrid traffic flow model is a promising and hot topic in the area of fluid mechanics and nonlinear dynamics, since they can take advantages of combining dynamical properties of each individual vehicle and macroscopic characteristics of the global system. In this paper, different from the previous work, we propose a hybrid traffic flow model considering the dynamical competition between ramps and main roads. Afterwards, the dynamical control equations of the proposed system are established. Then, by means of performing finite difference analyses, nonlinear dynamical characteristics and specific properties of the proposed system are investigated. Evolvement laws of characteristic order parameters of the proposed traffic flow system are obtained by analyzing the change of density, velocity and current in various circumstances. Moreover, matrices of partition coefficient are employed into the proposed traffic network composed of a main road and varied ramps. Additionally, linear and nonlinear stability analyses are considered in different phase spaces. Therefore, the robustness of the proposed system is tested by both linear and nonlinear dynamics. Our work will be helpful to understand mesoscopic dynamical behaviors of each individual vehicle and inner interactions between them. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) exhibit significant potential applications as soft robots. Due to complicated electromechanical coupling behavior, DEs generate a strong nonlinear oscillation, which may induce the undesired failure and other instabilities. Based on the DE slide actuators (DESAs), we deduce a viscoelastic dynamic model by incorporating the inertial forces and viscous dampings in all three principal directions. Numerically, calculations are utilized to detect the dynamic properties of the DESA. By employing the established model, the special phenomenon of pinnacle elimination in nonlinear oscillation is achieved. The dynamic loss of tension instability in both two DE membranes of the DESA is also analyzed. Effects of the voltage amplitude, the mass bar, the length ratio between two membranes, and the prestretches of DEs are considered and discussed, respectively. [ABSTRACT FROM AUTHOR]

Understanding three-dimensional (3D) slope deformation and failure mechanism and corresponding stability analyses are crucially important issues in geotechnical engineering. In this paper, the mechanisms of progressive failure with thrust-type and pull-type landslides are described in detail. It is considered that the post-failure stress state and the pre-peak stress state may occur at different regions of a landslide body with deformation development, and a critical stress state element (or the soil slice block) exists between the post-failure stress state and the pre-peak stress state regions. In this regard, two sorts of failure modes are suggested for the thrust-type and three sorts for pull-type landslides, based on the characteristics of shear stress and strain (or tensile stress and strain). Accordingly, a new joint constitutive model (JCM) is proposed based on the current stability analytical theories, and it can be used to describe the mechanical behaviors of geo-materials with softening properties. Five methods, i.e. CSRM (comprehensive sliding resistance method), MTM (main thrust method), CDM (comprehensive displacement method), SDM (surplus displacement method), and MPM (main pull method), for slope stability calculation are proposed. The S-shaped curve of monitored displacement vs. time is presented for different points on the sliding surface during progressive failure process of landslide, and the relationship between the displacement of different points on the sliding surface and height of landslide body is regarded as the parabolic curve. The comparisons between the predicted and observed load–displacement and displacement–time relations of the points on the sliding surface are conducted. The classification of stable/unstable displacement–time curves is proposed. The definition of the main sliding direction of a landslide is also suggested in such a way that the failure body of landslide (simplified as “collapse body”) is only involved in the main sliding direction, and the strike and the dip are the same as the collapse body. The rake angle is taken as the direction of the sum of sliding forces or the sum of displacements in collapse body, in which the main slip direction is dependent on progressive deformation. The reason of non-convergence with finite element method (FEM) in calculating the stability of slope is also numerically analyzed, in which a new method considering the slip surface associated with the boundary condition is proposed. It is known that the boundary condition of sliding surface can be described by perfect elasto-plastic model (PEPM) and JCM, and that the stress and strain of a landslide can be described properly with the JCM.

This paper presents a sliding mode controller for the deployment of two-body tethered satellite system. A sliding surface design for underactuated system is employed to reconcile pure-tension control scheme with non-linear coupled deployment dynamics. The proposed sliding surface is strictly non-linear. Hence, the control scheme does not require linearization operation of tethered satellite system and can guarantee that all the system states converge to zero with arbitrary small errors. To deal with input constraint of pure-tension control, an adaption is introduced into the controller design to remove the negative effect caused by input constraint in stability analyses and ensures the feasibility of the proposed controller even though command input overtakes the tolerance of tension actuator. To avoid the chattering phenomena, the trivial sign function is removed from the switching input and replaced by the disturbance observer. Numerical results demonstrate the effectiveness of the proposed controller for the deployment of the tethered satellite system. [ABSTRACT FROM AUTHOR]

Maize is a very important food crop world-wide and is vulnerable to diseases. Maize varieties that have high disease resistance are highly recommended for economic and health reasons. We consider a maize field with multiply varieties and develop a mathematical model to investigate the impact of foliar disease on the population dynamics. The possible benefit of considering control measures in reducing the spread of foliar diseases are evaluated. Results show that farmers must be aware of the disease dynamics of each variety as the dynamics vary. Also, in controlling diseases some methods are more effective than others. For the example given here controlling susceptibility of seeds to disease was the most effective method. As controlling diseases can be costly, optimal methods are important. Our results show that the most effective controls are those introduced at the outset of an outbreak and this can reduce the spread of diseases with the least cost. [ABSTRACT FROM AUTHOR]

A field test was conducted in Jinpingyan tunnel located in the area influenced by the 2008 Wenchuan Earthquake. The settlement of the surrounding rock, the internal displacement of the surrounding rock, the pressure between the surrounding rock and the primary support, the internal force of the support arch, the axial force of rock bolts, the pressure between the primary support and the secondary lining, and the strain of the secondary lining were measured to analyze the stability and health of the surrounding rock under the traditional supporting structure. For the phyllite tunnel located in the Wenchuan Earthquake seismic effect area, the traditional I-shape steel arch was used to control the deformation because of its large stiffness during the earlier stage of deformation of the surrounding rock. Over time, the deformation rapidly increased in the later period. The crown settlement increased quickly in a three-stage growth pattern until the values exceeded the deformation allowance. Shotcrete layer cracking and slabbing occurred at the crown and the shoulder. It can be concluded that the traditional supporting structure did not satisfy the stability requirement of tunnel, especially for the sections with extreme risk of large deformation in this seismic area. [ABSTRACT FROM AUTHOR]

Abstract: The construction of the Gotthard and Ceneri Base Tunnels through the Alps resulted in large quantities of excavated material. Selecting appropriate storage sites for the excavated material is a very important step that is often determined not only by technical criteria but also by external circumstances, a fact that may lead to sites that are not optimally suitable. Managing geotechnically difficult conditions in a professional manner is a decisive prerequisite to make a success of the planning and design process. Applying profound experience furthermore permits optimizations which lead to more efficient utilization of the available storage areas while at the same time maintaining the required structural stability. Such optimizations require detailed geotechnical investigation, careful planning and design, and thorough observation during construction. Furthermore, experience and specialist knowledge of comparable structures are helpful. The Chalchofen storage site at the Gotthard and the Sigirino site at the Ceneri Base Tunnel are used as examples to present a target‐oriented approach. The observations and measurements made the projects a success. To ensure a favorable outcome of such construction projects, it is of vital importance that all the parties involved (owner, consultant and checking engineer) work together effectively and efficiently. [ABSTRACT FROM AUTHOR]

Hot pepper cultivars developed for capsaicinoid production may not perform the same in different growing environments causing a problem to control a quality product for food and pharmaceutical industries. The aim of this study was to investigate the effect of genotype-by-environment interaction on capsaicinoid production of hot pepper hybrids ( C . chinense ) under controlled environment. Across six growing environments under protected cultivation, seven hot pepper hybrid cultivars and two commercial cultivars were evaluated for capsaicinoid production. The results showed significant differences among cultivars, environments, and cultivar-by-environment interactions for all characteristics studied. A large proportion of variation on fruit number (80.1%), dry fruit yield (78.1%) and capsaicinoid yield (67.7%) was contributed from environment while variations due to genotype were 42.4% for capsaicinoid content trait. Higher relative humidity and lower light intensity gave higher capsaicinoid production. Phet Mordindang had high dry fruit yield, capsaicinoid content and capsaicinoid yield, however it was very sensitive to environmental changes, and therefore best for specific location adaptation. Variation in capsaicinoid production in high pungent hot pepper cultivars can be exploited by selecting hot pepper hybrids with high pungency for growing in a suitable environment or a controlled environment. [ABSTRACT FROM AUTHOR]

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Abstract: In order to implement nonlinear control, nonlinear system identification must be performed, however, there are open questions concerning this field of process control, for example, experimental planning, model structure selection, parameter estimation, and validation. Therefore, the study of nonlinear model identification is a relevant unsolved problem that needs to be handled for nonlinear control synthesis. This paper presents the use of bifurcation theory, dynamic and stability analysis for nonlinear identification, and control of polymerization reactors. Peroxide‐initiated styrene‐solution polymerization reactors (lumped‐distributed) are investigated: batch, continuous stirred‐tank reactor (CSTR), and tubular reactors. Open and closed loop analyses are carried out using jacket temperature and weight average molecular weight setpoints as the bifurcation parameters. Phenomenological mathematical models, neural network nonlinear models, and an experimental data from a polymerization unit are employed for validating the proposed methodology in order to implement confident nonlinear controllers. [ABSTRACT FROM AUTHOR]

• Methodology to early consider safety requirement in the undergoing design process. • Fast-running tool platform based on reduced order models and carefully validated. • Assessment of sodium fast reactors flow stability maps. • Characterization of the main transient bifurcations in consequences and probability. Within the framework of the Generation IV Sodium-cooled Fast Reactor (SFR) R&D program of CEA (French Alternative Energies and Atomic Energy Commission), a methodology is proposed to early consider safety requirement in the undergoing reactor design process. Before the use of mechanistic tools (CATHARE, SIMMER, EUROPLEXUS, etc.) whose input deck elaboration requires an advanced knowledge of the reactor design, the methodology proposed in this article involves several physical tools simulating phenomena likely to govern the choice of design parameters. These tools are mostly based on reduced order models (ROM), meaning that they mainly involve low-dimensional modelings (mostly 0D and 1D) that are validated versus experimental results. They are gathered in a platform that covers all kind of accidental phenomenology, from the initiator (pump trip, reactivity insertion, local flow blockages, etc.) until the reach of a stable and coolable state after corium relocation. Thus, enabling a large number of simulations in a reasonable computational time, this fast-running platform makes possible the characterization of some major accident transient bifurcations (such as boiling onset, boiling stabilization, primary power excursion, molten fuel vaporization, corium axial relocation in transfer tubes, etc.), in terms of probability of occurrence and of consequences on the transient evolution. It also enables to identify the main physical parameters causing the bifurcations in order to allow a straight feedback on the core design and to give some orientations for future R&D studies. In this article, a focus is firstly made on some scenario bifurcations to illustrate the platform capabilities. The boiling onset and possible reactor state stabilization are studied. The possibility of primary power excursion depending on the core design and the fuel vaporization possibilities are assessed. This platform is also of great help in order to rapidly compare several core designs when facing accidental transients. An example is given by comparing a CADOR core design to an ASTRID-like core design through flow stability maps in natural circulation conditions obtained by the fast-running tool platform. These applications demonstrate the efficiency of the presented methodology integrating safety at the very first design stages, and at facilitating the safety-oriented design of SFRs. [ABSTRACT FROM AUTHOR]