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Bearing vibration characteristic analysis based on dynamic analytical model is of importance for identifying faults of bearing in mechanical systems. However, on one hand, the relationship between the raceway-ball contact pairs in bearing dynamic models are often considered as a simplified cascade; on the other hand, the evolving law of bearing fault characteristics of the early fault (wear) and severe fault (pitting) has not been fully revealed, which confines the development of bearing fault feature extraction and severity assessment methods. This paper, therefore, constructs a dynamic analytical model considering time-varying contact pairs and parameterized defects of deep groove ball bearings (DGBB) to illustrate the dynamic vibration characteristics of DGBB under different health conditions. The degrees of freedom of balls and flexible cage, multi-parameter defect excitation, mixed-elastohydrodynamic lubrication (mix-EHL), and relative slippage are all considered in the proposed model. Positions of multiple rigid bodies and contact points are dynamically expressed by coordinate systems, from which system physical parameters and geometrical relationship can be obtained. The bearing early and severe fault excitations are described by multi-parameters. The early fault which is embodied as surface roughness yields the indirect displacement excitation and the severe fault yields the direct displacement excitation. The surface roughness and indirect displacement excitation affect the mix-EHL, the radial force and friction force of contact pairs, thereby affecting the vibration response of DGBB. The evolving mechanism analysis of bearing fault characteristics are then revealed based on the established dynamic model, indicating the coupling and nonlinear relationship between the characteristic frequency amplitude and the fault severity of DGBB. [ABSTRACT FROM AUTHOR]

With the increasing application of flexible pipes in deep-sea operations, higher processing accuracy is required for the individual metal layers of these pipes to withstand greater service loads. In the helical winding production of the tensile armour layer, the accuracy of tension control significantly affects the uniformity of the steel strip after winding. To ensure tensile stability during the processing of steel strips, a tensile model for the manufacturing process is proposed. This model can be used to predict the magnitude and trend of tension fluctuations caused by the unwinding device, facilitating the design of a constant tension control system for steel strips based on an integral separation fuzzy PID algorithm. This system can achieve rapid convergence of tension during large tension fluctuations. The experimental results confirm the accuracy of the prediction model and the reliability and effectiveness of the designed tension control system. With this system, the tension fluctuation range is reduced by nearly 40%, and the average value of the standard deviation of the spacing after steel strip winding is decreased by 0.21 mm, demonstrating the potential of this approach for improving the manufacturing quality of the tensile armour layer of flexible pipes. [ABSTRACT FROM AUTHOR]

Flexible links possess numerous advantages over rigid links which impose the research attention towards employing flexible links in robotics. However, flexible links have a tip vibration that has the difficulty of being presented in dynamic models. Furthermore, the tip vibration leads to the control difficulty as a controller must control a system for the position and the tip elastic vibration. This research proposes a dynamic model and an intelligent hybrid optimal controller of a hybrid manipulator, the hybrid manipulator has a rigid link, a flexible link, and a variable payload. The proposed dynamic model is obtained using a combined technique of the finite element method and the Lagrangian method. The proposed dynamic model is compared with a SimMechanics model in terms of their open-loop responses, and both models have close match responses which indicates that the novel dynamic model is accurate. The intelligent hybrid optimal controller is also proposed based on the integration of an optimal linear quadratic regulator and a fuzzy logic controller. The integration of the fuzzy control and the linear quadratic regulator controller achieves 39.5% reduction of the fuzzy rules which assists to solve the explosion of the fuzzy rules problem since the hybrid manipulator is a multi-input system. The proposed intelligent optimal controller demonstrates improved position control, effective tip vibration suppression, better tip trajectory tracking, and better robustness to overcome the impact of the payload uncertainty compared to the linear quadratic regulator controller based on the simulation validation of the Simulink in MATLAB. [ABSTRACT FROM AUTHOR]

The magnet-less switched reluctance motor (SRM) speed-torque characteristics are ideally suited for traction motor drive characteristics and its advantage to minimize the overall cost of on-road EVs. The main drawbacks are torque and flux ripple, which have produced high in low-speed operation. However, the emerging direct torque control (DTC) operated magnitude flux and torque estimation with voltage vectors (VVs) gives high torque ripples due to the selection of effective switching states and sector partition accuracy. On the other hand, the existing model predictive control (MPC) with multiple objective and optimization weighting factors produces high torque ripples due to the system dynamics and constraints. Therefore, existing DTC and MPC can result in high torque ripples. This paper proposed a finite set (FS)-MPC with a single cost function objective without weighting factor: the predicted torque considered to evaluate VVs to minimize the ripples further. The selected optimal VV minimizes the SRM drive torque and flux ripples in steady and dynamic state behaviour. The classical DTC and proposed model were developed, and simulation results were verified using MATLAB/Simulink. The proposed model operated in SRM drives experimental results to prove the effective minimization of torque and flux ripples compared to the existing DTC. [ABSTRACT FROM AUTHOR]

Bolted spigot joints are widely used connection types in rotating machines, such as the rotor system of aero-engines and combustion gas turbines. Due to the nonlinearity of stiffness and damping caused by the bolted joint and mating interface friction, the dynamic performance of such a connection is too complicated to model. Therefore, the modelling and analysis of bolted spigot joints considering mating interface friction have become of interest in relevant investigations at present, which are of significance for predictions focusing on vibration performance. In this paper, the stick–slip behaviour and hysteresis characteristics of bolted spigot joints caused by mating interface friction are clarified by performing a study with a finite contact element model. Then, a new Iwan-based numerical model of bolted joints is proposed and an effective discretized parameter identification method is developed using the force–displacement results corresponding to the loading process obtained from finite element (FE) simulation results. A comparison study of the established numerical model and the FE simulation results demonstrates the potential of this numerical model to capture the static hysteresis behaviour and vibration performance. Then, the influences of the preload and loading amplitude of bolted joints on the static hysteresis behaviour and vibration performance of the system are examined using the numerical model. Finally, utilizing the results of bolted joint vibration response experiments performed with the established vibration test platform, the results of the numerical simulation are verified. The present study provides a theoretical basis for the design of the joint structure and assembly technology, which further enhances its prediction accuracy of dynamic performance. [ABSTRACT FROM AUTHOR]

Produced water (PW) is the largest by-product that comes out of the oil wells during oil and gas (O&G) field exploration. PW contains high-salt concentration along with other organic and inorganic components; therefore, PW must be treated before disposal. Electrocoagulation (EC) is an effective treatment method to remove pollutants from PW which has been the focus of many experimental studies; however, a mathematical model specifically for PW treatment by EC has not been developed yet. In this work, a comprehensive mathematical model has been developed to elucidate the role of EC operating parameters on the PW treatment performance and determine the mechanism for COD (Chemical Oxygen Demand) removal. The present model considers and identifies the dominant Al-hydroxy complex species and their contribution to the COD removal from synthetic PW samples by estimating their rate constants and comparing their magnitudes and investigates multi-scale modelling of the EC reactor. The influence of working parameters such as current density, initial pH, interelectrode distance, mixing speed and solution volume of PW on Al coagulant production and COD removal was investigated and modelled. The study estimates the rate constants of the reactions taking place for COD removal by EC process and by comparing their magnitudes identifies the dominant reactions and coagulant species involved in the process. The mathematical model prediction of COD removal fits well with the experimental data at 10 mA cm−2, 15 mA cm−2 and 20 mA cm−2 current density with R2 value of 0.96, 0.97 and 0.92, respectively and for dissolved Al concentration R2 value of 0.96, 0.99, and 0.97, respectively. The simulated results reproduced a good fit at initial pH of 6.1, 7.3 and 8.6 with R2 value of 0.92, 0.96 and 0.98, respectively for COD removal. The mathematical model and the experimental results showed the role of dominant Al-hydroxy complex species such as Al OH 2 + , Al OH 2 + , Al OH 3 , Al 2 OH 2 + 4 and Al OH 4 - in controlling the COD removal process. Under different operating conditions considered in the study, the model also predicted the COD removal performance of the EC reactors at different reactor volumes with R2 value of 0.96 for higher solution volume and larger reactor. The model presented and rate constants determined in the study will provide a theoretical basis for designing, scaling up and operating the EC reactor for oil-field PW treatment. [ABSTRACT FROM AUTHOR]

This paper presents a new method for the dynamics of multibody systems based on unknown constraint force. The method can uniformly solve multibody systems with typical configurations, including the system with rigid-flexible coupling, the system in tree topology, and the system with loop constraints. Unlike common methods, the proposed method can model the loop system without "cutting off" loop constraints, leading to the exact same modelling process as the tree-like system performs. Based on graph theory, a topological record matrix Mrec is proposed to capture the arbitrary system configuration. Moreover, constraint forces are selected as the key variables in semi-recursive framework. With the recursive kinematics relationship between adjacent bodies, the constraint force equation is further assembled to achieve the full-state system solution. The numerical simulations demonstrate the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Purpose: Inertial amplification of an oscillating mass has been considered by various researchers as a means to introduce enhanced vibration control properties to a dynamic system. In this paper an experimental prototype of a novel inertial amplifier, namely the Dynamic Directional Amplification mechanism (DDA), is developed and its dynamic response is subsequently evaluated. The DDA is realized by imposing kinematic constraints to the degrees of freedom (DoFs) of a simple oscillator, hence inertia is increased by coupling the horizontal and vertical motion of the model. Methods: The concept and mathematical framework of the amplifier are introduced and then validated with experimental measurements conducted on the vertical shaking table, located in the Dynamics & Acoustics Laboratory, National Technical University of Athens. Results: Analysis indicates the beneficial effect of the DDA to the dynamic response of the oscillator when compared to the initial structure, showcasing a decrease in the acceleration values and shift of the resonating frequency in the derived transfer functions. Conclusions: The key novelty of the DDA lies in its inertial amplification properties, introduced by a simple geometry and easy-to-apply structure. The proposed framework may be incorporated in applications such as sound and vibration isolators, acoustic panels, acoustic and seismic metamaterials and other vibration control devices that aim to explore the DDA's dynamic amplification properties. The mechanism has been previously applied by the authors to phononic and locally resonant metamaterials aiming to introduce bandgaps within the low-frequency domain. [ABSTRACT FROM AUTHOR]

Cantilever parts are extensively used in aerospace applications. However, machining vibrations readily arise under the action of cutting forces due to the poor fixed stiffness of cantilever parts mounted on large structures, compromising working accuracy and efficiency. To address the shortcomings of traditional special vibration suppression fixtures including lengthy development cycles, high costs and limited universality, a mobile robot-assisted clamping system was proposed to fulfill the vibration suppression requirements of diverse cantilever parts on large structures. Furthermore, to analyze the vibration responses under different clamping states, a workpiece-fixture dynamics model incorporating the mobile robot-assisted clamping system is established using the transfer matrix method for multibody systems (MSTMM). Then, the effects of different clamping states on cantilevered part vibration are explored using acceleration responses as the metric. Finally, the effectiveness of the vibration suppression method and the accuracy of the dynamics model are validated through experiment and simulation. This work provides a solution for vibration suppression and optimal clamping states selection of different cantilever parts. [ABSTRACT FROM AUTHOR]

PTFE and filled PTFE are used in sealing applications such as rotary valves, quarter-turn ball valves and pipeline gaskets, among others. Many times, these seals are designed to operate below their yield point such that plastic effects are negligible and viscoelastic effects dominate. This may lead to leakage since these devices are placed in service environments that are subjected to vibration. In seals made of viscoelastic materials, this vibration can lead to separation of the seal faces due to the delayed recovery of the material. In this paper, the isothermal viscoelastic dynamic response of a PTFE seal subjected to a harmonic input and static preload from an ideally rigid opposing face is examined. The model is a hybrid that combines the Golla–Hughes–McTavish finite element approach, a delayed recovery creep model and a penalty method contact model. Parameters for the models are taken from experimental data using a Dynamic Mechanical Analyzer test for pure PTFE material. Results for a simple application show face separation magnitude as a function of frequency and harmonic displacement amplitude. Results show that face separation occurs in PTFE seals even for small amplitude harmonic vibrations and that this is due to delayed recovery at low frequencies and to the viscoelastic damping at higher frequencies. A threshold of static preload is also found above which there is no separation and a leakage estimation is presented. [ABSTRACT FROM AUTHOR]

Modelling the fate of micropollutants in different wastewater treatment processes is of present concern. Moreover, during the last few years, there has been an increasing interest in the development of hybrid reactors which contain both suspended biomass and biofilm. Here, a new model developed which tries to determine the fate of micropollutants in hybrid reactors such as moving bed biofilm reactor (MBBR) and called the ASM-biofilm-MPs model considered the main mechanisms leading to the micropollutant removal (sorption/desorption, biodegradation, cometabolism) in hybrid reactors. This dynamic model describes the fate of micropollutants in a hybrid reactor using first-order kinetics for biotransformation and sorption/desorption equations. Also, it considered the reactions for carbon oxidation, nitrification, and denitrification in attached and suspended biomass under aerobic conditions. The mathematical model consists of three connected models for the simulation of micropollutants, suspended biomass, and biofilm. Biochemical conversions are evaluated according to the Activated Sludge Model No. 1 (ASM1) for both attached and suspended biomass. The model is applied for a laboratory MBBR, which fed with synthetic wastewater containing 4-nonylphenol (4-NP) as micropollutant, and accurately describes the experimental concentrations of COD, attached and suspended biomass, nitrogen, and 4-NP micropollutant obtained during 180 days working at different loadings. The differences between simulations and experiments in all operational periods for sCOD, NH4–N, NO3–N, and attached and suspended biomass concentrations were less than 15%, 10%, 10%, 5% and 5%, respectively. Finally, the contribution of adsorption and biodegradation mechanisms in the fate of 4-NP was calculated, when 4-NP concentration is set to 1 µg/L (biodegradation = 86.5%, sorption = 5%) and 50 µg/L (biodegradation = 55.9%, sorption = 34.7%). [ABSTRACT FROM AUTHOR]

Over the past decade, unmanned aerial vehicles (UAVs) have received a significant attention due to their diverse capabilities for non-combatant and military applications. The primary aim of this study is to unveil a clear categorization overview for more than a decade worth of substantial progress in UAVs. The paper will begin with a general overview of the advancements, followed by an up-to-date explanation of the different mechanical structures and technical elements that have been included. The paper will then explore and examine various vertical take-off and landing (VTOL) configurations, followed by expressing the dynamics, applicable simulation tools and control strategies for a Quadrotor. In conclusion to this review, the dynamic system presented will always face limitations such as internal and/or external disturbances. Hence, this can be minimised by the choice of introducing appropriate control techniques or mechanical enhancements. [ABSTRACT FROM AUTHOR]

In this work, we present a new mathematic model for the flight of a bird-scale flapping-wing aerial vehicle, in which the impacts of the wing inertia and its deformations are considered. Based on this model, the longitudinal and later-directional orbit stability of the vehicle at uncontrolled condition are proved to be steady via Floquet Theory combined with the untethered flight experiment. However, both simulation and experiment show that the vehicle presents a periodical motion state which is similar to spiral flight at uncontrolled condition. At this spiral-like flight state, the yaw angle of the vehicle varies constantly, which makes it difficult to meet the requirements of the general flight mission. In this case, two independent PID controllers are designed to stabilize the vehicle attitude based on the approximate linear model in the vicinity of the equilibrium flight condition. And the controlled flight of the vehicle prototype is also proved to be stable through numerical calculation and physical experiment. [ABSTRACT FROM AUTHOR]

There is much need for autonomous underwater vehicles (AUVs) for inspection and mapping purposes. Most conventional AUVs use torpedo-shaped single-rigid hull, because of which their manoeuvrability is limited. Moreover, any increase in payload results in a larger hull size and the turning diameter, limiting its operation in constrained areas. As a solution to this problem, we develop M-Hull, a subsurface mapping AUV with a modular-split hull design that provides better manoeuvrability than a conventional torpedo-shaped vehicle. At the same time, it has more agility than an unconventional bio-inspired snake-like vehicle though their designs look similar. This approach makes it a hybrid solution between conventional torpedo-shaped AUVs and unconventional bio-inspired vehicles. We focus on improving the turning diameter during the mapping operation, and hence this paper concentrates on the dynamic aspects of the 2D turning motion of the vehicle. It will provide the relationship between turning speed, thrust, and joint torque requirements for the multi-hull underwater vehicle. Different turning modes are compared to choose an optimum turning configuration, and the critical speed is calculated for the vehicle's safe operation. In the end, the modelling is verified using the experimental data. One can follow the method followed here for the 2D motion analysis of similar underwater vehicles. [ABSTRACT FROM AUTHOR]

A structured-segregated dynamic model for biomass growth, sucrose utilization and flavonoid production in Ocimum tenuiflorum suspension culture is proposed, considering a dynamic heterogeneous population of viable active, viable nonactive and dead cell. The sucrose hydrolysis (into glucose and fructose), substrate uptake by biomass and intracellular flavonoid production are modelled using Contois kinetics, a competitive double-substrate Monod, and Luedeking–Piret model, respectively. The conversion of active to viable-nonactive biomass has been formulated as a function of the total substrate and biomass concentrations. Parameters for the dynamic model are evaluated while minimizing the sum of square errors between modelled and measured biomass, cell viability, glucose, fructose and intracellular flavonoid contents. Bootstrap confidence intervals and dynamic relative sensitivity analysis of these model parameters are presented. The knowledge gained from the population-based model in plant suspension culture can provide the basic framework for prediction and optimization of the bioprocess system for phytochemical production. [ABSTRACT FROM AUTHOR]

Soft robotic manipulator, which has advantages of low-weight, flexibility, safe physical interaction, shows a wide prospect in both industry and family application. In this paper, a design of pneumatic soft manipulator, in which the modularization concept is adopted, is presented. The soft manipulator is made up of three pneumatic soft actuators stacked in series. The soft actuator is composed of three inflatable bellows, which are connected and constrained by a series of thin rigid plates. The bellows is stretched by the actuation of pressured gas. The cooperation of the bellows and the rigid constraints effect the soft actuator's directional move. The stacking connection of several soft actuators can have a large coverage in space. Based on this design, the kinematic models of the soft actuator as well as the soft manipulator are proposed using piecewise constant curvature method. The elastic coefficient of the actuator, which is necessary in the numerical calculation of the proposed model, is determined experimentally. Finally, the prototype and experimental set up of the soft manipulator are designed and developed. The correctness of the proposed model and the end-repeat positioning accuracy are validated experimentally. [ABSTRACT FROM AUTHOR]

In this paper, a passive damping network between two stages of a cascaded DC–DC boost/buck interleaved converter was proposed to enhance the dynamic behavior. By this damping network, the right-half plane zeros in converter's transfer function are sufficiently departed from the left half-plane, which leads to more damped transient behavior. A frequency analysis illustrated the dynamic enhancement in the proposed converter. To validate the theoretical model under different related circumstances, experimental results are presented through implementing a prototype setup. [ABSTRACT FROM AUTHOR]

This paper demonstrates a methodology for flexible, dynamic systems modelling relevant to urban rail decarbonisation. Decarbonisation of urban rail is a vital component of policy and strategy to minimize anthropogenic emissions. Decarbonisation is a systems problem, however, that needs to reflect the interaction between components and processes. Dynamic computer modelling of systems for decarbonisation involves interfacing multiple models together and running them in parallel in order to observe and predict systems-level effects. This is challenging due to the diverse nature of models, achieving parallel model integration and concerns around intellectual property (IP). One solution is the multi-modelling paradigm, which supports integrated, diverse, secure interfacing of models. This paper demonstrates the application of the multi-modelling approach, using the INTO-CPS tool chain. A multi-model was developed comprising key components required for urban rail decarbonisation problems. This multi-model was tested for power consumption in four different scenarios with an example drawn from the Tyne and Wear Metro in Newcastle-upon-Tyne in the United Kingdom. These scenarios compared combinations of decarbonisation intervention (baseline rolling stock versus lightweight, regenerative braking rolling stock and baseline driving style versus energy-efficient defensive driving style), generating different power consumption profiles for each. As such, this serves as a proof of the application of the multi-modelling approach and demonstrates a number of benefits for flexible and rapid systems modelling. This paper fills a knowledge gap by demonstrating a potentially valuable tool for future systems-level decarbonisation challenges in urban rail. [ABSTRACT FROM AUTHOR]

Climate change will bring about a consistent increase in temperatures. Annual precipitation rates are also expected to increase in boreal countries, but the seasonal distribution will be uneven, and several areas in the boreal zone will experience wetter winters and drier summers. This study uses the dynamic forest ecosystem model ForSAFE to estimate the combined effect of changes in temperature and precipitation on forest carbon stocks in Sweden. The model is used to simulate carbon stock changes in 544 productive forest sites from the Swedish National Forest Inventory. Forest carbon stocks under two alternative climate scenarios are compared to stocks under a hypothetical scenario of no climate change (baseline). Results show that lower water availability in the future can cause a significant reduction in tree carbon compared to a baseline scenario, particularly expressed in the southern and eastern parts of Sweden. In contrast, the north-western parts will experience an increase in tree carbon stocks. Results show also that summer precipitation is a better predictor of tree carbon reduction than annual precipitation. Finally, the change in soil carbon stock is less conspicuous than in tree carbon stock, showing no significant change in the north and a relatively small but consistent decline in the south. The study indicates that the prospect of higher water deficit caused by climate change cannot be ignored in future forest management planning. [ABSTRACT FROM AUTHOR]

Rolling element bearings (REBs) play a most critical role in various industrial machinery. A clearly and in-depth understanding of vibration characteristics of REBs is very helpful for condition monitoring and diagnosis applications for the machinery. This work presented a comprehensive review of dynamic modelling and analysis methods for predicting the vibration characteristics of REBs with and without localized and distributed faults. Main capabilities and limitations of those methods for both the localized and distributed faults have been described. Explanations for the generations of the bearing vibrations were also reviewed. A summary of the literature was given followed by the recommendations of current and future research works. Moreover, recent challenges, directions and implications in research works on the dynamic modelling and analysis methods of the localized and distributed faults in REBs have also been conducted. [ABSTRACT FROM AUTHOR]

In this work, modelling of the photocatalytic degradation of para-nitrophenol (PNP) using synthesized electrospun TiO2 nanofibers under UV light illumination is reported. A dynamic model was developed in order to understand the behaviour of operating parameters, i.e. light intensity and catalyst loading on the photocatalytic activity. This model was simulated and analysed for both TiO2 solid nanofibers and TiO2 hollow nanofibers, applied as photocatalysts in the Langmuir-Hinshelwood kinetic framework. The entire photocatalytic degradation rate follows pseudo-first-order kinetics. The simulated results obtained from the developed model are in good agreement with the experimental results. At a catalyst loading of 1.0 mg mL−1, better respective degradation rates were achieved at UV light irradiance of 4 mW cm−2, for both the TiO2 solid and hollow nanofibers. However, it was also observed that TiO2 hollow nanofibers have a higher adsorption rate than that of TiO2 solid nanofibers resulting in a higher photocatalytic degradation rate of PNP. [ABSTRACT FROM AUTHOR]

A dynamic modelling approach for a multi-beam structure connected with nonlinear joints is presented and subsequently used to obtain its reduced-order analytical model. Firstly, by applying the matching and boundary conditions, the natural frequencies and global mode shapes of the system are derived. According to the nonlinear transmitted torque formulations of the joints, the joints nonlinearities are introduced into the system by using the equilibrium conditions between the beams and the joints. Then, the global mode shapes and their orthogonality relations are used to obtain an explicit set of reduced-order nonlinear ordinary differential equations(ODEs) of motion for the flexible structure with nonlinear joints. A flexible structure composed of 4 beams and nonlinear joints is given as an example to illustrate the application of the modelling approach proposed. And a comparison between the natural frequencies obtained by the proposed approach and those from the finite element method is given to verify the validity of the derived model. Through the nonlinear ODEs obtained by the Galerkin truncation of the original dynamic model, a study on the variation in dynamic responses of the system with different numbers of modes is performed. The results are used to determine the number of modes taken in nonlinear vibration analysis for certain range of the vibration amplitude of the external excitation. The dynamic responses of the system with various joint parameters are worked out, which show that the transmission characteristics of the joints can strongly affect the dynamic behavior of the whole structure. [ABSTRACT FROM AUTHOR]

A systems-based classroom intervention on environmental education was designed for seventh grade students; the results were evaluated to see its impact on the development of systems thinking skills and standard science achievement and whether the systems approach is a more effective way to teach environmental issues that are dynamic and complex. A quasi-experimental methodology was used to compare performances of the participants in various dimensions, including systems thinking skills, competence in dynamic environmental problem solving and success in science achievement tests. The same pre-, post- and delayed tests were used with both the comparison and experimental groups in the same public middle school in Istanbul. Classroom activities designed for the comparison group (N = 20) followed the directives of the Science and Technology Curriculum, while the experimental group (N = 22) covered the same subject matter through activities benefiting from systems tools and representations such as behaviour over time graphs, causal loop diagrams, stock-flow structures and hands-on dynamic modelling. After a one-month systems-based instruction, the experimental group demonstrated significantly better systems thinking and dynamic environmental problem solving skills. Achievement in dynamic problem solving was found to be relatively stable over time. However, standard science achievement did not improve at all. This paper focuses on the quantitative analysis of the results, the weaknesses of the curriculum and educational implications. [ABSTRACT FROM AUTHOR]

An important issue in the field of motion control of wheeled mobile robots is that the design of most controllers is based only on the robot's kinematics. However, when high-speed movements and/or heavy load transportation are required, it becomes essential to consider the robot dynamics as well. The control signals generated by most dynamic controllers reported in the literature are torques or voltages for the robot motors, while commercial robots usually accept velocity commands. In this context, we present a velocity-based dynamic model for differential drive mobile robots that also includes the dynamics of the robot actuators. Such model has linear and angular velocities as inputs and has been included in Peter Corke's Robotics Toolbox for MATLAB, therefore it can be easily integrated into simulation systems that have been built for the unicycle kinematics. We demonstrate that the proposed dynamic model has useful mathematical properties. We also present an application of such model on the design of an adaptive dynamic controller and the stability analysis of the complete system, while applying the proposed model properties. Finally, we show some simulation and experimental results and discuss the advantages and limitations of the proposed model. [ABSTRACT FROM AUTHOR]

Dynamic modelling and simulation of a nanofiltration-forward osmosis integrated complete system was done along with economic evaluation to pave the way for scale up of such a system for treating hazardous pharmaceutical wastes. The system operated in a closed loop not only protects surface water from the onslaught of hazardous industrial wastewater but also saves on cost of fresh water by turning wastewater recyclable at affordable price. The success of dynamic modelling in capturing the relevant transport phenomena is well reflected in high overall correlation coefficient value ( R > 0.98), low relative error (<0.1) and Willmott d-index (<0.95). The system could remove more than 97.5 % chemical oxygen demand (COD) from real pharmaceutical wastewater having initial COD value as high as 3500 mg/L while ensuring operation of the forward osmosis loop at a reasonably high flux of 56-58 l per square meter per hour. [ABSTRACT FROM AUTHOR]

Grinding is a critical machining process because it produces parts of high precision and high surface quality. Due to the semi-artisan production of the wheel, it is not possible to know in advance the performance of the wheel. One of the most useful parameters to characterize the grinding process is the specific grinding energy, which varies with the wear of the grinding wheel during its lifecycle. Thus, it would be useful to model the specific grinding energy in order to get information about the performance of the wheel before buying it. Unlike the typical applications of time series forecasting, in this work, a totally different issue is presented: the prediction of new and complete time series bounded in time without initial or historic values. In this context, an analysis of the effect of the time characteristics and the number of points of the time series on the prediction capabilities of the ANN is presented. The results of the analysis show that 200 points are enough to predict a complete time series up to 2000 mm/mm of specific volume of material removed. Actually, it is shown that modelling the evolution of the grinding specific energy up to 2000 mm/mm is possible. The net shows good capability to generalize to new grinding conditions, with errors below 23.65 %, and to new wheel characteristics, with errors below 20.01 %, which are satisfactory from the grinding process perspective. [ABSTRACT FROM AUTHOR]

A mathematical model is developed to simulate a pilot Shell entrained-flow coal gasifier. Submodels of specific structures of the gasifier are established to simulate the complicated gasification process. The model includes the total energy conservation equation and mass conservation equations for the gas components, solid flow, and gas flow. It simulates the influence of the gasifier structure and dimensions and can calculate the effects of changing almost every important operation parameter, e.g., the syngas composition, gasification temperature, carbon conversion ratio, walllayer temperature, and slag mass flow rate. The model can predict the syngas composition under a limited residence time condition. Furthermore, it considers the heat transfer coefficient of each layer of the water wall to calculate its heat loss and temperature. Thus, the model also reflects the influence of performance parameters of the gasifier's water wall. The slag mass flow rate on the wall is calculated using a slag submodel. [ABSTRACT FROM AUTHOR]

Large yellow croaker (LYC) cage farming is a rapidly developing industry in the coastal areas of the East China Sea. However, little is known about the environmental nutrient loadings resulting from the current aquaculture practices for this species. In this study, a nitrogenous waste model was developed for LYC based on thermal growth and bioenergetic theories. The growth model produced a good fit with the measured data of the growth trajectory of the fish. The total, dissolved and particulate nitrogen outputs were estimated to be 133, 51 and 82 kg N tonne of fish production, respectively, with daily dissolved and particulate nitrogen outputs varying from 69 to 104 and 106 to 181 mg N fish, respectively, during the 2012 operational cycle. Greater than 80 % of the nitrogen input from feed was predicted to be lost to the environment, resulting in low nitrogen retention (<20 %) in the fish tissues. Ammonia contributed the greatest proportion (>85 %) of the dissolved nitrogen generated from cage farming. This nitrogen loading assessment model is the first to address nitrogenous output from LYC farming and could be a valuable tool to examine the effects of management and feeding practices on waste from cage farming. The application of this model could help improve the scientific understanding of offshore fish farming systems. Furthermore, the model predicts that a 63 % reduction in nitrogenous waste production could be achieved by switching from the use of trash fish for feed to the use of pelleted feed. [ABSTRACT FROM AUTHOR]

The design of vibratory feeders ensuring effective product feeding is particularly demanding since the flexibility of the device components severely affects the dynamic response. Traditional design approaches are based on expensive and time-consuming trial and error iterations, which include building and testing tentative devices. In order to overcome these limitations, this paper proposes a novel systematic approach for designing linear vibratory feeders, based on an inverse dynamic structural modification approach. After synthesising a reduced-order model, the design is cast as an inverse eigenvalue problem and solved numerically through the minimization of a convex quadratic function. Constraints on the design variables, i.e. inertial and elastic parameters, are represented through a convex domain and included in the optimization problem. The numerical and experimental results obtained prove the effectiveness of the method and its ease of application, that make is suitable for both the design of new feeders and the optimization of existing ones. [ABSTRACT FROM AUTHOR]

The complexity of electromechanical coupling drive system (ECDS)s, specifically electrical drive systems, makes studying them in their entirety challenging since they consist of elements of diverse nature, i.e. electric, electronics and mechanics. This presents a real struggle to the engineers who want to design and implement such systems with high performance, efficiency and reliability. For this purpose, engineers need a tool capable of modelling and/or simulating components of diverse nature within the ECDS. However, a majority of the available tools are limited in their capacity to describe the characteristics of such components sufficiently. To overcome this difficulty, this paper first proposes an improved methodology of modelling and simulation for ECDS. The approach is based on using domain-based simulators individually, namely electric and mechanic part simulators and also integrating them with a co-simulation. As for the modelling of the drive machine, a finely tuned dynamic model is developed by taking the saturation effect into account. In order to validate the developed model as well as the proposed methodology, an industrial ECDS is tested experimentally. Later, both the experimental and simulation results are compared to prove the accuracy of the developed model and the relevance of the proposed methodology. [ABSTRACT FROM AUTHOR]

Inorganic nitrogen supplementation is commonly used to boost fermentation metabolism in yeast cultures. However, an excessive addition can induce an opposite effect. Hence, it is important to ensure that the ammonia supplemented to the culture leads to an improvement of the ethanol production while avoiding undesirable inhibition effects. To this end, a macroscopic model describing the influence of ammonia addition on Saccharomyces cerevisiae metabolism during bioethanol production from potato peel wastes has been developed. The model parameters are obtained by a simplified identification methodology in five steps. It is validated with experimental data and successfully predicts the dynamics of growth, substrate consumption (ammonia and fermentable sugar sources) and bioethanol production, even in cross validation. The model is used to determine the optimal quantity of supplemented ammonia required for maximizing bioethanol production from potato peel wastes in batch cultures. [ABSTRACT FROM AUTHOR]

Solar photo-Fenton process has been extensively reported to be highly efficient in the remediation of complex industrial wastewater containing several families of pollutants such as pharmaceuticals, dyes, pesticides, derivatives of wine, etc. Moreover, solar photo-Fenton mathematical modelling regarded as a powerful tool for scaling-up and process control purposes is hindered by the complexity and variability of its reaction mechanism which depends on the particular wastewater under study. In this work, non-biodegradable cork boiling wastewater has been selected as a case study for solar photo-Fenton dynamic modelling by using MATLAB® software. First of all physic-chemical pretreatment was applied attaining chemical oxygen demand (COD) reductions between 43 and 70 % and total suspended solid (TSS) reductions between 23 % and 59 %. After solar photo-Fenton treatment, COD decreased between 45 and 90 % after consumptions of HO varying around 1.9 and 2.4 g/L. Individual calibration of the semi-empirical model by using experimental results made it possible to perfectly predict hydrogen peroxide variations throughout the treatment. It must be highlighted that slight deviations between predictions and experimental data must be attributed to important changes in wastewater characteristics. [ABSTRACT FROM AUTHOR]

After being accidentally introduced from the USA at the end of the 19 century, downy mildew caused by Plasmopara viticola (Berk. et Curt.) Berlese et De Toni became one of the most damaging diseases affecting Vitis vinifera in Europe. Downy mildew causes both direct and indirect losses and can lead to severe reduction of yield. Our understanding of the life cycle and epidemiology of P. viticola has been recently altered by molecular studies that revealed that the overwintering inoculum (i.e., the oospores) does more than initiate disease, as was previously thought. A mechanistic model was developed for predicting the entire chain of processes leading to primary infections, and this primary infection model was linked to other models of secondary infection cycles. The model for primary infections defines the length of the primary inoculum season and a seasonal oospore dose consisting of several cohorts of oospores that progressively mature. The model was evaluated by means of Bayesian analysis in both Italy and eastern Canada, and showed high sensitivity, specificity, and accuracy both for potted plants and vineyards. Fungicide applications are necessary to control downy mildew because preventive agronomic practices are not very effective, including host resistance. The use of warning systems based on weather-driven models leads to a reduction in the use and cost of chemicals and a reduction in their environmental impact. [ABSTRACT FROM AUTHOR]

Using dynamic finite simulations, we investigate how the friction coefficient of ZrO/polymer nanocomposite depends on the sliding speed. The load-dependent model we developed corresponds to common friction systems, where the friction couples are sliding under fixed load for various speeds. Here, we study the effect of the sliding speed on the contact distance between two contacting bodies. In accordance with experimental observations and theoretical arguments, we find the contact distance increased with the sliding speed. We show that the dependence of the reaction force on sliding speed can be rationalized by assuming that the frequency dependence of the polymer chains relaxation times is affected by the damping effects of contact stress. By investigating the energy dissipation, we show how the friction coefficient is affected by the sliding speed. The deformation volume and relaxation times decreased with the increasing sliding speed, which result in the decreasing of energy dissipation. Then, the work in pushing the top cylinder across the bottom plateau decreases, results in a reduction of the mean horizontal reaction force and friction coefficient. [ABSTRACT FROM AUTHOR]

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The dynamic initiation of sliding at planar interfaces between deformable and rigid solids is studied with particular focus on the speed of the slip front. Recent experimental results showed a close relation between this speed and the local ratio of shear to normal stress measured before slip occurs (static stress ratio). Using a two-dimensional finite element model, we demonstrate, however, that fronts propagating in different directions do not have the same dynamics under similar stress conditions. A lack of correlation is also observed between accelerating and decelerating slip fronts. These effects cannot be entirely associated with static local stresses but call for a dynamic description. Considering a dynamic stress ratio (measured in front of the slip tip) instead of a static one reduces the above-mentioned inconsistencies. However, the effects of the direction and acceleration are still present. To overcome this, we propose an energetic criterion that uniquely associates, independently on the direction of propagation and its acceleration, the slip front velocity with the relative rise of the energy density at the slip tip. [ABSTRACT FROM AUTHOR]

Non-equilibrium molecular dynamics simulations, of crucial importance in sliding friction, are hampered by arbitrariness and uncertainties in the removal of the frictionally generated Joule heat. Building upon general pre-existing formulation, we implement a fully microscopic dissipation approach which, based on a parameter-free, non-Markovian, stochastic dynamics, absorbs Joule heat equivalently to a semi-infinite solid, and harmonic substrate. As a test case, we investigate the stick-slip friction of a slider over a two-dimensional Lennard-Jones solid, comparing our virtually exact frictional results with approximate ones from commonly adopted dissipation schemes. Remarkably, the exact results can be closely reproduced by a standard Langevin dissipation scheme, once its parameters are determined according to a general and self-standing variational procedure. [ABSTRACT FROM AUTHOR]

In the next years, air-source heat pumps may become an important renewable-energy heating system in the temperate countries. These machines may be subject to changes in the operation conditions in order to maintain their performance in the face of variations in the outdoor climate and these changes may impact on the heat pump at the cycle level. In order to optimize the control of such machines, a dynamic model is mandatory. Therefore we illustrate the potentialities of a dynamic, lumped-parameter model, which is composed of moving-boundary exchanger sub-models and static compressor and expansion valve sub-models. Firstly, it is seen that the model succeeds in designing the installation as well as in controlling the superheating. Secondly, simulation results illustrate how a change of system parameters could affect the transient behaviour of the machine, thus requiring some adaptation of the controller parameters. Future developments will be devoted to model validation through experience, to design of a robust superheating controller and to model utilization towards fault diagnosis. [ABSTRACT FROM AUTHOR]

In this paper a modular model of the GnRH neuron is presented. For the aim of simplicity, the currents corresponding to fast time scales and action potential generation are described by an impulsive system, while the slower currents and calcium dynamics are described by usual ordinary differential equations (ODEs). The model is able to reproduce the depolarizing afterpotentials, afterhyperpolarization, periodic bursting behavior and the corresponding calcium transients observed in the case of GnRH neurons. [ABSTRACT FROM AUTHOR]

This paper presents an efficient modelling of autonomous flexible airships. These flying objects lighter than air (L.T.A.) are assumed to undergo large rigid-body motion and small elastic deformation. The formalism used is based on the Euler-Lagrange approach. The airship considered in this study is represented by a flexible ellipsoid of revolution. The coupling between the added masses issued from the overall body motion and those issued from the elasticity was determined by means of the velocity potential flow theory. We develop a fully analytical methodology with some assumptions. This feature distinguishes the current work from earlier treatments of the coupling, it allows one to minimise the number of degrees of freedom of the dynamical model, and renders the model suitable for use in the algorithms of stabilisation and trajectory generation. Numerical simulations are presented at the end of this paper. They underline the interest of the developed theoretical results. [ABSTRACT FROM AUTHOR]

The atomic-scale processes taking place during the sliding of diamond and diamond-like carbon surfaces are investigated using classical molecular dynamics simulations. During the initial sliding stage, diamond surfaces undergo an amorphization process, while an sp to sp conversion takes place in tetrahedral amorphous carbon (ta-C) and amorphous hydrocarbon (a-C:H) surface layers. Upon separation of the sliding samples, the interface fails. A rather smooth failure occurs for a-C:H, where the hydrogen atoms present in the bulk passivate the chemically active carbon dangling bonds. Conversely, sp-hybridized carbon chains are observed to form on diamond and ta-C surfaces. These carbynoid structures are known to undergo a fast degradation process when in contact with oxygen. Using quantum-accurate density functional theory simulations, we present a possible mechanism for the oxygen-induced degradation of the carbon chains, leading to oxidative wear of the sp phase on diamond and ta-C surfaces upon exposure to air. Oxygen molecules chemisorb on C-C bonds of the chains, triggering the cleavage of the chains through concerted O-O and C-C bond-breaking reactions. A similar reaction caused by adsorption of water molecules on the carbon chains is ruled out on energetic grounds. Further O adsorption causes the progressive shortening of the resulting, O-terminated, chain fragments through the same O-O and C-C bond breaking mechanism accompanied by the formation of CO molecules. [ABSTRACT FROM AUTHOR]

Next-generation sequencing provides technologies which sequence whole prokaryotic and eukaryotic genomes in days, perform genome-wide association studies, chromatin immunoprecipitation followed by sequencing and RNA sequencing for transcriptome studies. An exponentially growing volume of sequence data can be anticipated, yet functional interpretation does not keep pace with the amount of data produced. In principle, these data contain all the secrets of living systems, the genotype-phenotype relationship. Firstly, it is possible to derive the structure and connectivity of the metabolic network from the genotype of an organism in the form of the stoichiometric matrix N. This is, however, static information. Strategies for genome-scale measurement, modelling and predicting of dynamic metabolic networks need to be applied. Consequently, metabolomics science-the quantitative measurement of metabolism in conjunction with metabolic modelling-is a key discipline for the functional interpretation of whole genomes and especially for testing the numerical predictions of metabolism based on genome-scale metabolic network models. In this context, a systematic equation is derived based on metabolomics covariance data and the genome-scale stoichiometric matrix which describes the genotype-phenotype relationship. [ABSTRACT FROM AUTHOR]

Molecular simulations are used to explore kinetic-friction modification in nanoscale fluid layers of oil and additive confined between sheared parallel walls. The molecules are represented by coarse-grained bead-spring models that reflect the essential solvophilic and solvophobic natures of the chemical groups. The degree of friction modification is surveyed as a function of wall separation, sliding velocity, additive molecular weight and architecture, and oil-additive composition. As a rule, the kinetic-friction coefficient is found to increase first linearly and then logarithmically with increasing sliding velocity. From the results for different additive molecules, some subtle but systematic effects are found that point towards an optimum molecular weight and architecture. [ABSTRACT FROM AUTHOR]

The Morris water maze is an experimental procedure in which animals learn to escape swimming in a pool using environmental cues. Despite its success in neuroscience and psychology for studying spatial learning and memory, the exact mnemonic and navigational demands of the task are not well understood. Here, we provide a mathematical model of rat swimming dynamics on a behavioural level. The model consists of a random walk, a heading change and a feedback control component in which learning is reflected in parameter changes of the feedback mechanism. The simplicity of the model renders it accessible and useful for analysis of experiments in which swimming paths are recorded. Here, we used the model to analyse an experiment in which rats were trained to find the platform with either three or one extramaze cue. Results indicate that the 3-cues group employs stronger feedback relying only on the actual visual input, whereas the 1-cue group employs weaker feedback relying to some extent on memory. Because the model parameters are linked to neurological processes, identifying different parameter values suggests the activation of different neuronal pathways. [ABSTRACT FROM AUTHOR]

Despite considerable research effort, the use of physics-based modelling to predict frictional behaviour is still a debatable question in modern tribological research. This article presents a dry-friction model, based on physical phenomena such as adhesion, elastic–plastic contact and deformation. This contribution offers a means to simulate all kinds of frictional behaviour that is observed in experimental research. The contact of two bodies through their surfaces is transformed into the contact of a body that is provided with asperities and containing material and geometrical information of both of the mating surfaces, and a counter profile, holding solely geometrical information. The local adhesion between the asperity tips and the counter profile, together with the elastic–plastic behaviour of the asperities themselves, form the basis for this model. The simulation results show qualitatively good agreement with experimental study. Friction and contact phenomena such as normal creep, increasing static coefficient of friction with increasing dwell time, pre-sliding hysteresis with nonlocal memory, Stribeck and viscous effect, frictional lag, stick–slip and dynamical oscillations are revealed by this model. Furthermore, future improvement and refinement of the model is possible (and ongoing) so as to incorporate lubrication and asperity wear. [ABSTRACT FROM AUTHOR]

The dynamics of frictional motion have been studied for hundreds of years, yet many key aspects of these important processes are not understood. The main challenge in predicting frictional response is the complexity of highly non-equilibrium processes going on in any tribological contact. This includes the continuous detachment and reattachment of multiple microscopic junctions at the sliding interface, the kinetics of which are controlled by the interface temperature. Our experiments reveal a non-monotonic enhancement of dry nanoscale friction at cryogenic temperatures for different material classes. We propose a model that reproduces the experimental observations and shows that the peak in temperature dependence of friction emerges from two competing processes acting at the interface: the thermally activated formation as well as the rupturing of an ensemble of atomic contacts. Our experiments and simulations provide a direct link between the temperature and velocity dependencies of friction, thus offering a new conceptual framework to describe the dynamics of dry nanoscale friction. [ABSTRACT FROM AUTHOR]