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The propensity for roll instability in automobiles, particularly trucks, often arises during high‐speed maneuvers and emergency scenarios. The active roll control (ARC) system presents a promising solution for enhancing truck roll stability. This study delves into designing a controller for the ARC system adapted to high‐speed truck operations. It entails formulating a cost function for the linear quadratic regulator (LQR) optimal controller, incorporating variables directly pertinent to truck roll stability: vehicle body's roll angle, unsprung masses' roll angle, and normalized load transfer at the two axles. To streamline sensor usage and prioritize cost‐effectiveness, the Luenberger observer is integrated with the full‐state feedback LQR controller. The investigation involves executing double lane change maneuvers, simulating overtaking and obstacle avoidance, at speeds of 70, 100, 130, and 160 km/h. The maximum absolute value of the normalized load transfer coefficient at the axles is assessed up to speeds of 200 km/h. Research findings underscore the efficacy of the ARC system in enhancing truck safety by reducing the normalized load transfer of all axles over 30% compared to the passive system, particularly during high‐speed operations. [ABSTRACT FROM AUTHOR]

In this paper, to improve the small signal stability of the power system, the optimal coordination of multi‐band power system stabilizers (MB‐PSSs) and static synchronous compensator (STATCOM) has been done. The study is conducted on a standard four machines and two areas power system. To create coordination, a modified version of the particle swarm algorithm as well as the integral time absolute error (ITAE) criterion are proposed. To evaluate the proposed stability method in different operating conditions and in the form of two scenarios, a three‐phase fault with a duration of 200 ms has been applied in the communication line between the two areas. After the simulation, the values of overshoot, undershoot, settling time, and ITAE criteria for the proposed stability method have been calculated and their values have been compared with the results of power system stabilizer (PSS) and MB‐PSS stabilization methods. The results indicate that the proposed combined method of MB‐PSS and STATCOM performed better than the other two methods in improving the dynamic stability of the power system and has the lowest value of the criteria. The values of ITAE for the PSS, MB‐PSS stabilization methods and the proposed MB‐PSS and STATCOM combined method in the first scenario are equal to 0.002354, 0.0.001496, and 0.001242 p.u. and in the second scenario it is equal to 0.0.007418, 0.004015, and 0.003435 p.u., respectively. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of the filler are intricately linked to the stability of the subgrade. In this investigation, relying on Haoji (Haolebaoji-Ji'an, China) heavy-haul railway engineering, cyclic triaxial tests were executed to scrutinize the dynamic attributes exhibited by the 3%–5% cement-stabilized expansive soil (CSES) across a series of diverse cyclic stress, confining pressures, and frequencies. Concurrently, in situ vibration trials were undertaken to dissect the dynamic characteristics inherent to the CSES subgrade. The outcomes of cyclic triaxial tests indicate that the augmentation in both the dynamic shear strength and modulus of CSES by a factor of 2–3, coupled with an escalation of the critical dynamic stress threshold by five tosix times, is attributed to the heightened internal structural density within the CSES compared to virgin expansive soil. In identical settings, it is noteworthy that the mean critical dynamic stress threshold observed for CSES surpasses that of Group A filling by a factor of 1.5–1.7. Furthermore, the maximum critical dynamic stress exhibited by CSES achieves a 1.2-fold superiority over its lime-stabilized expansive soil (LSES). The outcomes gleaned from the in situ vibration tests elucidate that, when subjected to the passage of a high-velocity train traveling at 120 km/hr, bearing the load of 25–30 tons per axle, the subgrade surface exhibits dynamic stress ranging from 98.57 to 116.07 kPa. Meanwhile, the dynamic stress undergoes a notable escalation due to rainfall infiltration, intensifying by a factor of 1.02–1.28 times its original magnitude. The influence depth of dynamic stress extends 1.4–1.6 times beyond the designed subgrade bed thickness of 2.5 m. Notably, the critical dynamic stress of the filler surpasses the dynamic stress at the same position, underscoreing the capacity of 3%–5% CSES filling for heavy-haul railways to ensure long-term dynamic stability. [ABSTRACT FROM AUTHOR]

Objective. This study aimed to compare the impacts of different dual-task paradigms on the postural control ability and dynamic stability of the youth during stair descent. Method. Twenty young adults without regular exercise habits were randomly recruited to perform stair descent tasks with three different paradigms: single-task, cognitive dual-task, and manual dual-task. Kinematic and dynamic data were collected using an 8 Vicon motion analysis system and a Kistler force plate to evaluate postural control ability and dynamic stability during stair descent. Results. The variation trends of lower limb joint moment were similar under the three task models. Compared with a single-task, both dual-task paradigms significantly reduced the mechanical parameters and dynamic stability during stair descent. Conclusion. The dual-task paradigm increases the risk of stair-related falls. Both cognitive and manual tasks have similar impacts on postural control ability and dynamic stability during stair walking. It is recommended that people avoid performing dual tasks during stair descent. [ABSTRACT FROM AUTHOR]

The dynamic stability of slopes is the key to ensure the safety of a large open-pit mine during and after a strong earthquake. This study was mainly focused on the identification of optimal intensity measures (IMs) for the probabilistic seismic stability assessment of large open-pit mine slopes within the framework of performance-based earthquake engineering (PBEE). To this end, four open-pit slopes with different mining depths were constructed as the reference cases for the numerical investigation. The randomness of input ground motions and the uncertainty of material properties of the slopes were also considered. A total of 96 ground-motion records and 29 common IMs were selected for testing. By a series of nonlinear time-history analyses, the probabilistic seismic demand models (PSDMs) between the minimum factor of safety (FOS) of slopes and all considered IMs were developed. The optimal IMs with respect to FOS were identified based on the evaluation of five criteria: correlation, efficiency, practicality, proficiency, and sufficiency. The impacts on seismic fragility and FOS response hazard of the slopes were discussed when using different IMs. The results reveal that sustained maximum velocity (SMV) and velocity spectrum intensity (VSI) are recognized as the optimal IM for a mining depth of 50 m and 100 m, respectively. However, Housner intensity (HI) is observed to have the best predictability for both the mining depths of 200 m and 300 m. Moreover, for the three most commonly used IMs, peak ground velocity (PGV) is superior to peak ground acceleration (PGA) and spectral acceleration at first mode period (Sa (T1)) for different mining depths. Finally, based on the evaluations of seismic fragility and FOS response hazard, the uncertainty of seismic stability prediction of open-pit slopes can be greatly reduced when using a more appropriate or optimal IM. [ABSTRACT FROM AUTHOR]

This research article describes a novel optimization technique called simulink design optimization (SDO) to compute the optimal PID coefficients for an automatic voltage regulator (AVR). The time-domain performance of the proposed controller was analyzed using MATLAB/Simulation, and its performance was compared with that of water cycle algorithm, genetic algorithm, and local unimodal sampling algorithm-based PID controllers. The robustness of the proposed controller was verified by applying the disturbances to the generator field voltage and the amplifier parameter uncertainty. The studies presented in literature were discussed the AVR loop stability using the Bode plot which will not give the minimum stability margins. This study proposes a novel stability analysis called disk-based stability analysis to authenticate the stability of the AVR loop which is obtained by the classical analysis. This stability was compared with the proposed stability analysis. The MATLAB results reveal that the SDO-PID controller regulates the terminal voltage of the generator precisely, is more robust to parameter uncertainty, and is more stable than the other controllers. The maximum allowable parameter uncertainty of the amplifier model was identified as 102% of its nominal parameters. The stability margins are recognized as DGM = 10.40 dB and DPM = 56.50° for the AVR stability. [ABSTRACT FROM AUTHOR]

Selecting high-yielding and stable genotypes is the main goal of black soybean breeding. Testing new lines in multiple environments is one of the development processes in black soybean breeding. The aims of the research were (i) to identify the effects of genotype, environment, and their interactions (GEIs) on the grain yield of soybean lines in Java Island; (ii) to select stable and high-yielding soybean lines; (iii) to determine the discriminative environments; and (iv) to determine the concept of stability measurements on black soybean grain yields. Field trials of 10 new F8 promising lines and three check varieties were conducted under eight different environments during four years (2016–2019). The measurement results showed that the grain yield was influenced by genotype (8.35%), environment (59.49%), and GEIs (32.16%). Grain yield stability measurements showed that the four newly identified lines had high yields and were stable in eight environments; they were A-5A-PSJ (S2), DB-96-CTY (S5), UP 161 (S6), and UP 162 (S7). The Ngawi (2017), followed by Bogor (2019) and Banyuwangi (2016), has the strongest interactive capabilities and is suitable for use as a trial environment. Grain yield (Y) was identified as having a positive and significant correlation (p < 0.05) with S(3), S(6), NP(2), NP(3), NP(4), KR, and YSI stability measurements, which indicated that they were included in the concept of dynamic stability measurement. The selected genotypes can be proposed for the release of new high-yielding black soybean varieties in Indonesia. [ABSTRACT FROM AUTHOR]

In this study, we show that adding halloysite nanotubes (HNT) to carbon black (CB)-packed acrylic rubber (ACM) composites improves their thermal properties. The thermo-oxidative stability, thermal stability, and dynamic mechanical properties of ACM composites (filled simply with 70 phr CB) and ACM hybrid composites comprising a fixed amount of CB (60 phr) and a variable amount of halloysite nanotubes (HNT) (2, 4, 6, 8, and 10 phr) were investigated. As evidenced by the oxidation induction time analysis, hybrid structures support a higher degree of antioxidation in composites reinforced with twin fillers than composites reinforced just with CB. ACM composites with dual fillers had greater breakdown temperatures (temperatures at 10% weight loss (T10) and 50% weight loss (T50)) and char residue concentration at 600°C than ACM conventional composites, according to thermogravimetric tests. The activation energy of the thermal disintegration of ACM composites, as determined by the Kissinger and Flynn–Wall–Ozawa techniques, shows that the addition of HNT improves the thermal stability of ACM composites. The storage modulus of ACM composites was increased by 79 percent at 30°C when 10 phr of black filler was replaced with 6 phr of tubular HNT, according to additional viscoelastic experiments. [ABSTRACT FROM AUTHOR]

A novel method based on the unknown input observer is proposed to reconstruct sensor attacks and estimate system states for fruit and vegetable picking robot cyber-physical systems. By fully considering the nonlinear characteristics of the articulated fruit and vegetable picking robot system as well as the influences of external disturbances, the generalized system model is established and the unknown input observer is designed to reduce false positives and false negatives in the agricultural cyber-physical system. In view of the agricultural production environment, a digital prototype model is established for manipulators of picking robot with three joints. Following the Lagrange method, dynamic equations of the manipulator system are established and transformed into a corresponding state-space model, where the nonlinearity and unknown input information are taken into account. Then, the original system is converted into a generalized system through state augmentations based on the generalized system theory. Furthermore, an H ∞ unknown input observer is designed to estimate the system state and reconstruct sensor attacks, accommodating nonlinear characteristics and external disturbance effects of the system. The asymptotic stability of the dynamic error system is proved via the Lyapunov function. By simulation and comparison with an existing method, the results demonstrate that the proposed method reconstructs sensor attacks and estimates system states effectively. [ABSTRACT FROM AUTHOR]

To investigate the small-strain stiffness characteristics of highly weathered granite (HWG), a resonance column test system was used to conduct resonance column tests on highly weathered granite taken from the Lincang City, Yunnan Province, China. The effects of effective consolidation stress and structural changes is caused by remodeling process and initial dry density on the small-strain stiffness of HWG. Furthermore, the difference between the test data and other geotechnical materials were compared and analyzed. The test results show that the maximum dynamic shear modulus G max of remodeled highly weathered granite samples is greater than that of undisturbed samples once the effective consolidation stress is smaller than 300 kPa, but the opposite result is observed once the effective consolidation stress exceeds 300 kPa, and the phenomenon was also explained from a microscopic perspective based on the scanning electron microscopy (SEM). The G max of remodeled highly weathered granite gradually increases with the increase in dry density and effective consolidation stress. At an identical effective consolidation stress, the dynamic shear modulus ratio G / G max − γ curves of remodeled highly weathered granites at different initial dry densities are nearly consistent. Additionally, according to the test data, the mathematical model of G max for remodeled highly weathered granite considering effective consolidation pressure and initial dry density was established and agrees well with the test results of practical engineering cases. The range of variation in G / G max was given by the research results, which were compared with the G / G max of weathered granite obtained from the existing research, and the results in this work can provide a valuable reference for analyzing dynamic stability of buildings in the engineering construction of weathered granite sites. [ABSTRACT FROM AUTHOR]

In this article, we carry out the structural analysis of an IS-LM-AS macroeconomic model with adaptive inflation expectations, exploring the presence of a possible local bifurcation. We prove that the model is structurally unstable when the speed with which economic agents adjust their expectations about future inflation is equal to the inverse of the semi-elasticity of real money demand with respect to the nominal interest rate since the periodic solutions are lost when the adaptive expectations parameter suffer any small change, ceteris paribus. Additionally, the phase portraits of the instantaneous rate of change of the real interest rate, the inflation rate, and the instantaneous rate of change of the inflation rate are numerically simulated in ℝ 3 with MATLAB for three asymptotically and locally stable cases and for the degenerate Hopf bifurcation. Finally, our results show that, specifically, in the case of pure conjugate complex eigenvalues, the economy could enter periods of an inflationary/deflationary spiral when the adaptive expectations parameter is of greater magnitude to the inverse of the semi-elasticity of real money demand balances with respect to the nominal interest rate, regardless of its initial state. [ABSTRACT FROM AUTHOR]

In recent years, intelligent vehicles with cutting-edge vehicular applications have grown in popularity, enabling the growth of Vehicular Ad hoc Networks (VANETs). Vehicular Ad hoc Networks (VANETs) are a network of vehicles that share and analyze real-time data and require a well-organized and efficient data delivery method. The stability of clusters and dynamic topology change in VANETs are the major issues in finding an optimal route amongst the vehicles. The cooperative approach and surprise pounce chasing technique of Harris Hawks in nature serve as the main sources of inspiration for Harris Hawks Optimization. In this technique, several hawks work together to attack a victim from various angles to surprise it. Due to the unpredictable nature of situations and the prey's fleeing movements, Harris Hawks can exhibit a variety of intelligent strategies. This study proposes a novel route clustering optimization technique that takes into account communication range, the number of nodes, velocity, orientations, and grid size. To create and evaluate ideal cluster head (CH), the proposed method is based on Harris Hawks Intelligent Optimization Algorithm for route Clustering (iCHHO) which finds optimal and reliable routes amongst the vehicles. Other state-of-the-art methods, such as the Grasshopper Optimization Algorithm (GOA), Gray Wolf Optimization (GWO), and Whale Optimization Algorithm (WOACNET), are utilized to evaluate and validate the proposed method. Our findings show that the developed method outperforms other current methods in terms of number of clusters, variable communication ranges, network size, and the number of vehicles. Furthermore, the statistical analysis concludes that the proposed method improves cluster optimization by 79% and increases cluster stability by an adjusted R -squared of 91.22. [ABSTRACT FROM AUTHOR]

Activating the natural fracture (NF) during hydraulic fracture (HF) propagation is a dominant factor for forming the complex fracture network in shale reservoirs. On basis of Renshaw and Pollard's criterion for fracture intersection, we simulate the NF stability under dynamic disturbance of HF propagation in shale reservoirs with the cohesive zone model in ABAQUS and analyze the effects of various factors on the NF stability. The results show that activation of the NFs in shale hydraulic fracturing is controlled by NF length, NF density, intersection angle between the NF and the HF, horizontal principal stress difference, frac fluid viscosity, and injection rate. During HF propagation, the NF shorter than 0.2 m is less likely to be activated, and those longer than 0.5 m are more likely to be activated. As the NF density increases, not all NFs are activated. The NF at an approach angle larger than 10° is more likely to be activated. The NF is more likely to be activated under the low stress difference, and the NF cannot be activated when the stress difference is higher than 10 MPa. Both frac fluid viscosity and injection rate have effects on activation of NFs, and the NF is more likely to be activated by higher viscosity frac fluid and under higher injection rate. The results provide reference for fracture network stimulation in shale reservoirs. [ABSTRACT FROM AUTHOR]

Vertical takeoff and landing (VTOL) capability has extended the application of unmanned aerial vehicle (UAV) significantly. In this paper, simulation modeling and flight test were employed to investigate the hovering stability of a tail-sitter UAV named Egretta. The hovering stability simulation model was developed based on a simplified rigid body flight dynamic and the time-averaged propeller slipstream flow distribution. Meanwhile, a testing vehicle with PID controllers was built and tested to verify the hovering stability model. It was found that the Egretta UAV can achieve stable hovering in the roll, pitch, and yaw directions. The simulation model has demonstrated accuracy in predicting the hovering stability and dynamic responses with large perturbations in both trend and magnitude. Moreover, the simulation model can be extended to analyze the hovering stability of tail-sitter UAVs with different sizes. The simulation model will be very useful for initial stability sizing and PID optimization investigation. [ABSTRACT FROM AUTHOR]

The state-estimation and optimal control of multigeneration systems are challenging for wide-area systems having numerous distributed automatic voltage regulators (AVR). This paper proposes a modified Q-learning method and algorithm that aim to improve the convergence of the approach and enhance the dynamic response and stability of the terminal voltage of multiple generators in the experimental Western System Coordinating Council (WSCC) and large-scale IEEE 39-bus test systems. The large-scale experimental testbed consists of a six-area, 39-bus system having ten generators that are connected to ten AVRs. The implementation shows promising results in providing stable terminal voltage profiles and other system parameters across a wide range of AVR systems under different test scenarios including N-1 contingency and fault conditions. The approach could provide significant stability improvement for wide-area systems as compared to the implementation of conventional methods such as using standalone AVR and/or power system stabilizers (PSS) for the wide-area control of power systems. [ABSTRACT FROM AUTHOR]

The buildup of tailings in China has expanded dramatically with economic development and industrial demand, and the safety of tailings reservoirs has become increasingly serious. Due to the difficulty in finding a new reservoir site, the expansion approach of building a new tailings dam downstream of the original reservoir area was investigated. The stability of the tailings reservoir after expansion was calculated using the traditional dynamic and static stability solution method and taking into account the unpredictability of dam construction materials and tailings material parameters in the reservoir area. The results reveal that throughout the tailings accumulation process in the new reservoir, the tailings will build a back pressure slope at the original reservoir's initial dam, which can considerably improve the original reservoir's dynamic and static stability. The Monte Carlo method clearly outperforms older methods for tailing pond stability analysis. The results of this paper's calculations will give a theoretical foundation and practical reference for the later management and maintenance of such tailings reservoirs, as well as fresh ideas and insights for comparable projects due to limited site selection. [ABSTRACT FROM AUTHOR]

This paper addresses the asynchronous control problem for power systems subject to abrupt variations and cyber-attacks. In the sequel, the transient faults of circuit breakers can be described as the Markov process. In light of these situations, the power systems are transmitted to discrete-time Markov switching systems. Meanwhile, the deception attacks with time-varying delays in dispatchers are regulated by a Markov process. The controller and dispatcher are mode-dependent and their modes are nonsynchronous with those of power systems, which are modeled by the hidden Markov models. On the basis of the deception attacks, sufficient conditions are presented to guarantee the stochastic mean-square stability of the closed-loop dynamic. Finally, the proposed control design strategy is testified via a simulation result. [ABSTRACT FROM AUTHOR]

The stability of the slope along the middle section of Tibet controls the safety and smoothness of the Sichuan-Tibet highway, which is affected by multiple and uncertain factors such as rainfall. The slope dynamic stability is evaluated to the benefit of that salvager can prepare in advance and preserve timely and accurately. Therefore, engineering treatment scheme in different batches, stages, and grades can be proposed prospectively. Random Forest algorithm was used to rank 10 primary factors: precipitation, earthquake, human factors, groundwater, slope height, slope gradient, dense degree, weathering depth, vegetation, and slope shape. Considering precipitation and earthquake as dynamic factors, a wavelet and NARX dynamic neural network were used to predict the trend and quantity of precipitation and earthquake, followed by developing a dynamic stability evaluation model by combining a fuzzy neural network model with other indexes. Results show that (1) the superposition error in rainfall and earthquake prediction is 0.21%, proving that the ranking of influencing factors is reasonable, and (2) the back-judgment and test accuracy of the dynamic evaluation model are 93.98% and 91.67%, respectively, indicating that the model is accurate and applicable. The model can evaluate the dynamic stability of slopes and provide more reasonable engineering protection countermeasures so that Highway Public Works Department can deal with emergencies and disasters timely and precisely. [ABSTRACT FROM AUTHOR]

Rutting is one of the major asphalt pavement distresses that could cause hydroplaning and lead to roadway safety concerns on a rainy day. However, there is still no theoretical methodology with simulation to evaluate and predict the driving safety caused by rut-induced hydroplaning using vehicle dynamics. This paper proposes a methodology, based on a new developed "vehicle-water-filled rutting" open-loop vehicle dynamics model analyzed by CarSim (a professional vehicle dynamic software), to simulate and compute the impact of unbalanced water-filled rutting on driving stability/safety with a special focus on the vehicle's lateral dynamic stability, including lateral offset and lateral acceleration. Analysis results show the following: (1) The unbalanced water depths in left rutting and right rutting lead to the different friction between left rutting and right rutting and make the vehicle wander left and right uncontrollably along the roadway. (2) When the vehicle speed is greater than 80 km/h and the rutting width exceeds 0.7 m, the unbalanced water-filled rutting begins to affect the vehicle's lateral stability apparently and very likely threaten the driver's life. (3) By computing the vehicle's lateral offset and acceleration in different water widths and lengths in the hydroplaning situation, this paper proposes the rutting width and length thresholds for vehicle oversteer and instability, based on which the vehicle risk level is proposed, RISK I is the situation where vehicle's lateral offset exceeds 1.025 mm which likely causes vehicle running into the adjacent lane (the danger can be avoided if there is no vehicle in the adjacent lane), RISK II is the situation where the vehicle's tires begin to work into the nonlinear zone (the vehicle's lateral acceleration exceeds 0.4 g) with the increase of rutting width and length, which makes the vehicle lose controls irreversibly for drivers, and this situation should arouse more concerns for transportation agencies. The proposed methodology would enable transportation agencies to predict the security risk of rutting and play a vital role for transportation agencies to scientifically establish the relevant specifications (e.g., rutting maintenance) that proactively trigger the maintenance and rehabilitation to prevent potential safety concerns from happening. Recommendations on future researches, including taking braking stability and real rutting conditions of the proposed model into consideration, are also continued in the future study. [ABSTRACT FROM AUTHOR]

To study the variation in the high-temperature stability of asphalt mixtures under extreme high temperature and heavy load, rut tests and analyses were carried out with both the APA (asphalt pavement analyzer) test and CLWT (Chinese wheel load test). In this paper, the relationship model between the dynamic stability of asphalt mixtures and the temperature, load, and binder viscosity is established; this model provides a method for evaluating the temperature stability of asphalt mixtures under nonstandard temperature conditions. The results revealed that the dynamic viscosity of an SBS-modified asphalt binder showed an exponential relationship with temperatures varying from 55°C to 70°C. Under a temperature condition from 55°C to 70°C and a pressure of 0.7 MPa, the dynamic stability of the asphalt mixture increased linearly with increasing temperature. The dynamic stability of the asphalt mixture exhibited a temperature inflection point at 65°C, and the decay rate was increased. The APA test results, which were used to evaluate the anti-rutting performance of the asphalt mixture on the basis of the ratio of the rutting depth difference to action times from 6000 to 8000, showed a good correlation with the CLWT test results. With a high temperature of 65°C and the pressure increasing from 0.7 MPa to 1.3 MPa, the dynamic stability of the asphalt mixture exhibited exponential decay. The variation laws of dynamic stability with temperature, load, and asphalt binder viscosity were revealed by complex logarithmic variation. [ABSTRACT FROM AUTHOR]

The quadruped robot is subject to self and external interference during the running process. In this paper, in order to improve the stability of the quadruped robot, a disturbance suppression strategy based on the kinematic model and the virtual model is proposed. Through the whole-body kinematics modeling of the body, the cause of the disturbance is analyzed. At the same time, two spring-damping virtual elements are introduced on the body. The virtual force generated by the spring-damping model is according to the displacement and speed of the CoM (center of mass) when the robot is moving. By simulating the tort gait of the robot, sorting out the data obtained from the experiment, and drawing a comparison curve with the experiment results of the no spring-damping virtual element under the same conditions, it is proved that the method proposed in this paper has a significant effect on maintaining the dynamic stability of the body, and the actual trajectory is not different from the theoretical trajectory. [ABSTRACT FROM AUTHOR]

Objectives: To clarify a characteristic of dynamic stability during gait in idiopathic normal pressure hydrocephalus (iNPH) and Parkinson's disease (PD), and to explore the association between dynamic stability and disease severity in each disease. Materials and Methods: The 5‐m gait of 36 iNPH (precerebrospinal fluid drainage), 20 PD (medicated state), and 25 healthy controls (HC) were evaluated using three‐dimensional motion analysis. Ambulatory dynamic stability was defined as the ability to maintain the extrapolated center of mass within the base of support at heel contact, with the distance between the two referred to as the margin of stability (MOS). Results: Anteroposterior direction (AP) MOS was significantly larger in the iNPH and PD groups than in the HC group; no significant difference was found between the iNPH and PD groups. Mediolateral direction (ML) MOS was significantly larger in the iNPH and PD groups than in the HC group and significantly larger in the iNPH group than in the PD group. In the iNPH group, the disease severity was positively correlated with only ML MOS. In the PD group, the disease severity was positively correlated with the AP MOS and ML MOS. Conclusions: Dynamic stability in iNPH increases in AP and ML, and it may be associated with not only iNPH‐associated gait disturbance but also with a voluntarily cautious gait strategy. Dynamic stability in PD only increased in AP, and this may be associated with PD symptoms. These findings will help physicians understand the difference in pathological gait including dynamic stability between patients with iNPH and PD. [ABSTRACT FROM AUTHOR]

Summary: The linear stability of a cantilever beam subject to a follower force is investigated. A system of distributed piezoelectric devices is attached to the beam with the purpose of improving the dynamic stability of the structure. They are connected to a second‐order network and second‐order analog electrical circuit. The assembly of the mechanical and piezoelectric subsystems constitutes a coupled Piezo‐Electro‐Mechanical (PEM) system, whose equations of motion, derived within a variational approach, are discretized via the Galerkin weighted residual method and the stability of the trivial equilibrium is addressed by numerically solving the associated eigenvalue problem. A sensitivity analysis, carried out on a numerical ground, is thus conducted on a wide range of the electrical parameters to investigate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

This article presents an enhanced control strategy for voltage source converters (VSCs) based on virtual inertia concept. Considering the significant share of renewable‐based generations, frequency stability is noted as one of the most significant challenges of modern low‐inertia power systems. Therefore, as the first contribution of this article, dynamic equations of the converter are utilized in order to study its proficient active and reactive power compensation capabilities. Then, this effective power factor correction of the proposed VSC is improved by adding inertia emulation characteristics in order to provide a more synchronous generator (SG) like behavior, which is beneficial from the frequency stability point of view. In addition to that, the impacts of changes in the main control parameters such as inertia and damping on dynamic performance are analyzed using the root locus method. This applied eigenvalue analysis has then been used to support a proper selection of parameter values, which is considered as another novelty of this article. In this regard, the designed algorithm providing auto adjustment capability of controller parameters based on a desired frequency response characteristic can improve the dynamic frequency stability of the system. The functionality of the proposed controller is validated through state‐space analysis and simulations with MATLAB/Simulink. The superior performance of the proposed algorithm demonstrated through simulation results confirms that the proposed control method can be considered as a simple yet effective solution for the challenges of a reduced inertia power system. [ABSTRACT FROM AUTHOR]

The continual increase in the power network topological structure and long distances between load‐generation sources lead to modern powers systems are operated near theirs stability margins. For this issue, reliable and secure operations of electric devices through inter‐area oscillations remain an essential issue in the system dynamic stability. In the case of improper actions of controlling devices, the severe inter‐area interactions may lead to wide‐area instabilities and large blackouts. Using wide‐area measurement system (WAMS), remote signals are transferred through communications links with different inherent time latencies. In the case of large time delays, the main controllers cannot work appropriately which leads to improper performance of damping controllers through severe inter‐area fault event scenarios. For this issue, this paper presents an adaptive wide‐area damping controller (AWADC) for damping inter‐area oscillations in large power systems equipped with WAMS technology consisting of various time latencies. In this case, based on the IEEE C37.118.1 protocol, the generator buses are equipped with phasor measurement unit devices. Also, owing to the different communication links, the measured global signals (GSs) are involved within different time latencies. In this case, at each time window, considering time delay compensator (TDC) technology provided through Simevents discrete event tool, the overall time delay is evaluated and compensated. For identifying the best controlling GSs, considering two observability and controllability concepts, the system dynamic signals are evaluated which the best input decisioning signals and corresponding output controlling signals are provided. The proposed AWADC scheme consists of different compensating blocks which are adjusted through simple and well‐known Jaya optimization algorithm (JOA) through online evaluations. The structure of the proposed AWADC controlling scheme is carried out on a modified 39‐bus New England test system consisting of large synchronous generators whose damping performances are evaluated through severe fault events with the potential of unstable inter‐area oscillations. Simulation results indicate the effectiveness of developed TDC and JOA techniques to provide proper controlling signals through the AWADC controller in the presence of different time latencies. [ABSTRACT FROM AUTHOR]

Summary: Grid‐forming converters are designed to be capable of operating without a main grid. It is known that grid‐following converters operating in weak grid conditions may experience dynamic voltage stability issues. Low‐frequency oscillations have been observed in the real world. The objective of this paper is to examine grid‐forming converters' weak grid operating characteristics. To this end, two types of grid‐forming converters are examined for weak grid operation. Firstly, the steady‐state operation limits are identified relying on optimization problem formulation and solving. It is found that both grid‐forming converters may reduce the steady‐state operation limit, compared to a grid‐following converter. Secondly, dynamic stability limits are identified through electromagnetic transient (EMT) simulations. Furthermore, each converter's frequency‐domain admittance and impedance characteristics are characterized using a data‐driven system identification method. s‐domain admittance‐base eigenvalue analysis confirms the dynamic stability limit for each converter. It is found that low‐frequency oscillations appear in one type of converters while do not appear in another type of converters. The two grid‐forming converters can enhance dynamic stability comparing to the specific grid‐following converter. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to numerically study the effect of texture bottom profile on static, dynamic, and stability performance parameters of hydrodynamic journal bearings. The different performance parameters of square textured journal bearings with different bottom profiles are numerically investigated and compared with those of smooth journal bearing. There are five bottom profiles of this square texture: flat, curved, isosceles triangle (T1), oblique triangle (T2), and oblique triangle (T3). The static and dynamic coefficients are calculated by solving the steady-state Reynolds equation and the perturbation equations with FDM numerical technique. The performance characteristics under different texture distribution, depth, and bottom profiles are studied, and the current numerical results show that the selection of texture parameters is crucial to improve the static, dynamic, and stability performances of hydrodynamic journal bearing. Meanwhile, it is also found that the square texture with a flat bottom profile has a higher improvement in the values of static performance parameters in comparison to those other bottom profiles. Moreover, the simulation results indicate that the dynamic and stability performances improvement of textured journal bearing is also significant, especially when the eccentricity ratio is smaller. [ABSTRACT FROM AUTHOR]

Summary: This paper introduces an optimal voltage control (OVC) framework for islanded microgrids (MGs) as a unified hierarchical control scheme, started from bus voltage set‐points optimization at tertiary level, then effectively followed by secondary control, which controls the distributed energy resources via their primary level controllers. The distributed control structure is proposed here for both tertiary and secondary levels to benefit from higher reliability, avoidance of a single point of failure, and a relatively simple communication system. At the tertiary level, a new distributed voltage protocol, based on the Lyapunov theory, is proposed to optimize power losses and voltage profile deviations in the MG. The obtained optimal voltage references are passed to the secondary level, in which a modified distributed protocol (MDP) is utilized to ensure the OVC and dynamic stability. In addition, the proposed MDP can maintain the critical bus voltage against load changes until the next optimal set‐point updates. The performance of the MDP is examined for different scenarios such as load changes and DGs plug and play operation in the MATLAB/Simulink environment. [ABSTRACT FROM AUTHOR]

The dynamic response and its stability of a blade rotor with coupled rubbing in the labyrinth seal and tip seal are investigated. The dynamic equations are established based on the Hertz contact rubbing force at the labyrinth seal and the tip rubbing force considering both the contact deformation of the tip seal and the bending deformation of the blade. Numerical simulations show that the coupled rubbing response includes periodic motions, almost periodic motions, and chaotic motions. Compared with the single rubbing fault, coupled rubbing increases the range of rotation velocity of contact. A new continuation shooting method is used in the solution and stability analysis of the periodic response to give the bifurcation diagrams. The paths of the system for entering and exiting chaos are analyzed. [ABSTRACT FROM AUTHOR]

Summary: This article mainly focuses on the analysis and design of a dynamic hybrid optimized controllers for unbalanced DC microgrid. Small‐signal model analysis of unidirectional boost converter (UBC) and bidirectional converter (BDC) is discussed to get the efficient performance not discussed earlier. The hybrid controller manages the power between BDC and solar with UBC during the unequal loading. The problem associated with nonlinear solar I‐V curve effect is expressed by dynamic resistance. It is affected by parametric variation as the operation point of I‐V curve, temperature, and solar irradiance. The slower transient response of PI voltage and the current controller is not an effective solution for parametric variations. To address this, a simple hybrid genetic algorithms (GA) based closed current and voltage‐controlled loop is designed using proportional‐integral (PI) controller. Small‐signal model with consideration of dynamic resistance in solar model with UBC connected to BDC fed DC microgrid is described for nonlinear structure. The closed‐loop stability of GA‐based voltage and the current PI controller are verified under the deviation of load parameters using a bode plot. It covers the overshoot, time response, oscillation, and dynamic stability under the parametric variations. GA PI controller has fast response comparison to Ziegler Nichol's method as settling time, peak overshoot, rise time, and more stable. The comparison of these two methods is described under fixed and variable loading for microgrid by MATLAB/Simulink. Detailed case study for dynamic operation is verified for unequal loading between the system and dc load. [ABSTRACT FROM AUTHOR]

With the increasing depth of coal mining and expanding mining scale, the rocks surrounding deep roadways are in a complex mechanical condition of frequent dynamic disturbance. The heterogeneity has an important influence on rock mass failure under dynamic loads. Therefore, it is necessary to study the deformation and failure of heterogeneous roadway under dynamic load. In this paper, the effect of heterogeneity on stability of roadway under static and different dynamic loads is studied. According to the results, the effect of rock mass heterogeneity on the deformation and failure of surrounding rock varies with different degrees of heterogeneity. Under static loading conditions, the stability of roadway is negatively correlated with the degree of heterogeneity of the rock mass. Under dynamic loading conditions, the change of heterogeneity degree has significant influence on the stability of surrounding rock. With the increase in dynamic load strength, the change in variation difference in the average value of roof sag, stress distribution, and plastic zone caused by variations in heterogeneity will increase. This study contributes to understanding the deformation and failure characteristics of heterogeneous roadways under dynamic loads and can be used to analyze heterogeneous roadways under dynamic loads. [ABSTRACT FROM AUTHOR]

The influence of temperature on the shear performance of asphalt mixtures and the feasibility of using the deformation strength as an index of the high-temperature shear performance of these mixtures were explored in this study. Taking AC-13C and AC-20C asphalt mixtures as the research objects, uniaxial compression, rutting, deformation strength, and uniaxial static load creep tests were carried out at temperatures 40°C, 45°C, 50°C, 55°C, and 60°C. The correlations between the deformation strength and modulus of resilience, compressive strength, dynamic stability, and stiffness of the asphalt mixtures were studied. The test results show that the influence of temperature on the compressive strength, resilience modulus, and deformation strength of the asphalt mixtures decreases significantly as the temperature increased, and the rutting deformation of the two kinds of asphalt mixtures increased as the temperature increased. Strong correlations exist between the deformation strength and the modulus of resilience, the compressive strength, and the dynamic stability of asphalt mixtures, so the deformation strength can be used as an evaluation index of the high-temperature shear performance of asphalt mixtures. [ABSTRACT FROM AUTHOR]

To further reveal the road performance and noise reduction performance of open-graded friction course (OGFC), the crumb rubber prepared by adding waste tires were considered, and the performance requirements of the material were put forward. To avoid the influence of rubber particle swelling on aggregate, the special gradation and mix proportion of OGFC mixture were designed, and the particle size of 4.75 mm was proposed as the control size. The test results show that the aggregate forms a good embedded structure. The resilient modulus, deformation performance, and fatigue performance of R-OGFC asphalt mixture with different crumb rubber contents were studied. According to the test results, the rubber particle content under the best road performance and noise reduction effect was proposed. The results show that, after adding a certain amount of crumb rubber, the performance of asphalt mixture has been greatly improved, especially the dynamic stability has been improved by 84%. Although the resilient modulus has decreased by 10%, the creep performance has decreased by 37%, and the fatigue life has decreased by 31% (2% rubber content), the noise reduction can reach 3.6–8.6 dB, and the noise reduction performance is significant. This shows that the best content of rubber particles is between 1.5% and 2%, and the R-OGFC mixture modified by rubber has a good application prospect. [ABSTRACT FROM AUTHOR]

In this paper, a pseudostatic seismic coefficient evaluation method for slope dynamic stability analysis was explored with Yushu Airport Road 3# landslide as a typical engineering case, and the shaking table test and numerical calculation were performed during the exploration. The loading waveform was selected as Yushu wave, and the acceleration time-history of seismic waves was measured and analyzed, revealing the failure mode of slopes. Based on the rigid-body limit equilibrium theory, the instantaneous additional seismic forces of each block and the time-history landslide stability coefficient were calculated. According to the time-history of the landslide, dynamic stability coefficients were calculated. Subsequently, we proposed a pseudostatic seismic coefficient evaluation method and discussed the seismic coefficient slope dynamic stability analysis. The results showed that as the vibration frequency rose, the average acceleration and the residual displacement of the slope decreased, but the slope grew more dynamically stable. With the proposed method, we calculated the period of slope seismic action to be 0.126 s and the average maximum acceleration to be 0.156 g, which was close to the designed ground motion acceleration of 0.15 g. Besides, we calculated the safety factor of landslides under earthquake to be 0.93∼0.97, which was close to that obtained from the building code method and in accordance with the present seismic deformation and failure mode of landslides. Moreover, the results obtained from the method of nuclear power plant specification were relatively small compared to other specification methods. The research is significant because it provides a new idea for the evaluation of seismic landslide stability in practical engineering. [ABSTRACT FROM AUTHOR]

Nanoparticles have been widely adopted to improve the high-temperature performance of asphalt binder. However, the influence of moisture on high-temperature performance is not clear. Hence, the water absorption performance of the nano-SiO2-modified asphalt concrete is investigated. Based on this, to further analyze the pavement performance of the nano-SiO2-modified asphalt concrete, the coupled effects of high-temperature, moisture content, and nanoparticles content on the rutting resistance of the nano-SiO2-modified asphalt concrete are tested and revealed in this study. Results show that temperature has the most significant influence on the water absorption performance of the nano-SiO2-modified asphalt concrete. The rutting resistance of the nano-SiO2-modified asphalt concrete decreases as temperature and moisture content increase, especially for the temperature. The dynamic stability at the same temperature condition decreases approximately linearly as moisture content increases. The effect of the nano-SiO2 content is the most nonobvious. [ABSTRACT FROM AUTHOR]

The construction and long-term operation stage of the rock slope with argillaceous interlayer will be subjected to intermittent dynamic loads, such as blasting and earthquake. For the argillaceous interlayer in the rock slope, its rheological properties are not only related to the initial stress state caused by the gravity of the overlying rock mass but also affected by intermittent dynamic loads. In order to investigate the rheological properties of argillaceous intercalation under the combination of static and intermittent dynamic shear loads, the rheological tests of argillic intercalated soil samples under static shear, static and cyclic dynamic shear, and static and intermittent dynamic shear were carried out, and the rheological deformation characteristics of soil samples under different shear conditions were analyzed. The results show that when the soil specimens in the static shear rheological process are disturbed by intermittent dynamic shearing load, the intermittent dynamic disturbances might have no remarkable influence on the rheological deformation of the specimens if the initial static shearing stress and intermittent dynamic shearing stress were comparatively low. However, low-intensity intermittent dynamic disturbances might accelerate the rheological deformation process of the specimens remarkably if the initial static shearing stress state was close to their shearing strength. There was a stress threshold when the soil specimens failed under the static and cycling dynamic shear and static and intermittent dynamic shear, which is determined by the sum of static shear stress and dynamic shear stress peak. For rock slopes controlled by rheological weak structural planes and influenced by long-term blasting vibrations, the transient and long-term dynamic stability should be comprehensively analyzed. [ABSTRACT FROM AUTHOR]

The uneven stacking of waste rock materials caused by the dynamic instability of rock spreaders cannot be ignored for geological subsidence and local collapse in reclamation areas. Based on the dynamic stability of the existing rock spreader, combined with the actual application conditions, the load conditions of the rock spreader are analyzed. The static and dynamic analysis and optimization of the key structures such as the receiving arm, the discharging arm, and the main tower are carried out by using the topology optimization method. The optimized virtual prototype of the whole machine is established to verify its rationality. The research results show that the total weight of key parts such as receiving boom, discharging boom, and the main tower is reduced by about 4.5% (4650 kg), the lower-order vibration frequencies below the fifth order of those parts are not within the resonance range, and the stability of the whole machine is greatly improved, which fundamentally solves the problem of uneven rock stacking caused by impact stability. And, the maximum stress and deflection of the whole machine under the worst working conditions meet the actual requirements. The research ideas and conclusions can provide solutions to prevent the subsidence or local collapse of reclamation areas caused by uneven stacking materials. [ABSTRACT FROM AUTHOR]

Earthquakes are vibrations induced by the rapid releases of large quantities of energy from the crustal movements. During seismic excitation, there are kinetic energy, damping energy, and strain energy acting on the tunnel structure. Based on the indexes of the total energy, releasable elastic strain energy, and dissipated energy, this paper proposes three energy evaluation criteria for the tunnel structure, which are applied to the optimization of the aseismic design of the cross-sectional shape and material property of the tunnel structure. It can be concluded that the peak values and accumulated values of elastic strain energy at the spandrel and arch springing are significantly larger than other positions, which indicates that the strengths of the spandrel and arch springing are the most influential factor for the seismic damage of the tunnel structure. Considering this factor, the width-to-height ratio of 1.33 and Poisson's ratio of 0.3 are determined as the most optimal cross-sectional shape and material property, respectively. Furthermore, by analyzing the relationship between the internal energy and the input energy of the tunnel structure with seismic excitation and proposing an equation for the evaluation of the dynamic stability of tunnel structure, the stabilities of the tunnel structure with different PGAs are analyzed; it can be concluded that the larger the peak value of seismic wave acceleration, the longer the instable period and the greater the degree of dynamic instability. The derived equations can be used as references for the seismic analysis of the tunnel structure, and the conclusions of this paper can contribute to the aseismic design of tunnel lining. [ABSTRACT FROM AUTHOR]

Tip-over stability analysis is critical for the success of mobile manipulation of the dual arm, especially in the cases that the dual arm or the mobile platform moves rapidly. Due to strong dynamics coupling between the dual arm and mobile platform, online evaluation of dynamic stability of the mobile dual-arm robot still remains challenging. This paper presents an improved tip-over moment stability criterion dealing with the dual arm and mobile platform interaction and proposes an algorithm for calculating the tip-over stability margin of the arm end in the workspace to analyze the dynamic stability of the wheeled mobile dual-arm robot. The simulations on a four-wheeled mobile dual-arm robot validate the correctness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Summary: This work analyzes the feasibility of integrating a modified commercial Capstone C30 microturbine unit into a non‐nuclear testbed developed for performance evaluation of microreactor design concepts. Testing will be conducted to provide detailed reactor core and heat removal section thermal hydraulic performance data for prototypical geometries and operating conditions and demonstrate integration with relevant power conversion units. The modified C30 power conversion unit (PCU) uses external electrical heating, rather than fossil fuel combustion, to provide a maximum power output of ~30 kWe in a closed Brayton cycle (CBC) loop using nitrogen as the working fluid. A 75 kWt electrically heated test article was evaluated as the heat source to provide a turbine inlet temperature of 600°C to the modified C30 PCU. The operation of a test article supplying a maximum thermal power of 250 kWt was also considered. The analyses performed here indicate that the CBC PCU will be capable of operating over a range of steady state and transient conditions to evaluate test article heat transfer performance in representative operational scenarios. Normal, off‐design operation and dynamic stability of the PCU are analyzed, and a proposed set of tests of the power control schemes and heat source‐PCU coupling are outlined. This study supports the timely development of microreactors intended for deployment by the end of this decade. [ABSTRACT FROM AUTHOR]

Dynamic stability is significantly important for flying quality evaluation and control system design of the advanced aircraft, and it should be considered in the initial aerodynamic design process. However, most of the conventional aerodynamic optimizations only focus on static performances and the dynamic motion has never been included. In this study, a new optimization method considering both dynamic stability and general lift-to-drag ratio performance has been developed. First, the longitudinal combined dynamic derivative based on the small amplitude oscillation method is calculated. Then, combined with the PSO (particle swarm optimization) algorithm, a dynamic stability derivative that must not be decreased is added to the constraints of optimization and the lift-drag ratio is chosen as the optimization objective. Finally, a new aerodynamic optimization method can be built. We take NACA0012 as an example to validate this method. The results show that the dynamic derivative calculation method is effective and conventional optimization design can significantly improve the lift-drag ratio. However, the dynamic stability is enormously changed at the same time. By contrast, the new optimization method can improve the lift-drag performance while maintaining the dynamic stability. [ABSTRACT FROM AUTHOR]

Hallux valgus (HV), which is mainly caused by the wearing of narrow-width and high-heeled shoes, disrupts gait behavior because it deforms lower limb joints. There is limited information regarding the relationship between the foot disease HV and lower limb joints. Previous studies evaluating abnormal gait patterns caused by deformity used spatiotemporal parameters; however, they failed to characterize the overall gait dynamics. To address this issue, this study is aimed at characterizing the gait stability of patients with HV and examining the joints that are critically affected by HV. To assess complex gait dynamics, we quantified the potential changes in gait stability by using the maximum Lyapunov exponent (MLE). Angular displacements of the ankle, knee, and hip in the sagittal plane during walking were investigated to calculate the MLE for gait stability based on foot conditions (i.e., barefoot, flat shoes, and high heels). During walking, a large MLE (P < 0.05) was noted for the knee joints of subjects with HV, relative to the other lower limb joints. HV appears to have the most critical effect on the knee joints during walking. Ankle movement exhibited higher dynamic stability than the other joint movements of the lower limb (P < 0.05). The type of shoe used in the experiment showed no significant dependence with gait stability and joint movement (P > 0.05). Quantitative assessments of dynamic stability using the MLE may help clinicians assess the overall gait dynamics of HV patients and other people suffering from gait disturbances. [ABSTRACT FROM AUTHOR]

Summary: In this paper, an adaptive concept of virtual generator (VG)‐based controller is presented for dynamic stability of stochastically‐modeled microgrids consisting of low inertia resources. For this purpose, considering a set of energy storage systems (ESSs) dispatched in the network, a controlled islanding scheme (CIS) is provided to dynamically control the microgrid frequency. In this context, based on the concept of center of inertia (COI), the proposed VG scheme is developed through mathematical formulation. Inter‐area torques evaluated by microgrid control areas in the COI frame are used as input signals of the developed VG‐based controller. Also, for the ESSs, an equivalent dispatch model is provided and developed through the microgrid dynamic model for improving frequency stability during inter‐area oscillations. The proposed VG‐based controller is an online and non‐model‐based scheme which controls several microgrid systems together as an integrated network connected to the upstream network. In order to evaluate the ability of the proposed scheme, real‐time simulations are carried out on two different test systems consisting of several microgrids. The system dynamic performances are evaluated in time‐domain simulations. Numerical results demonstrate the effectiveness of the proposed scheme in increasing system inertia constant resulting in a proper dynamic performance with a high damping ratio in facing severe inter‐area oscillations. [ABSTRACT FROM AUTHOR]

Summary: In the islanded micro‐grids the power cannot be exchanged by the upstream network and the system inertia level is low. Therefore, the network sensitivity to disturbances and load changes is more than the connected mode. In such situation, the system states can behave with more degree of freedom and have less dependency to total system dynamic. The variety of equipment with different dynamics and the load level uncertainty leads to continuous changes in the islanded micro‐grid operating point. These changes are more considerable in the islanded micro‐grid due to lack of inertia and limited stability margins. Therefore, the determination of appropriate model order for system in such way that the reduced order model keeps the essential dynamic behavior and neglects the less effective modes, is critical. Therefore, in this paper a three‐step method based on multi‐time scale theory and singular perturbation method is proposed for optimum model order reduction in islanded micro‐grid. The proposed method is applied to a typical micro‐grid with different types of DGs and loads. The load level uncertainty is modeled by probability density function (PDF) and reduced order model of system is validated in different operating scenarios by sensitivity analysis, participation factor investigation and time domain simulation. [ABSTRACT FROM AUTHOR]

To increase the robustness and control precision of a hydraulic quadruped robot and simultaneously enhance the dynamic and steady characteristic of the hydraulic system, an active disturbance rejection controller (ADRC) tuned using the Lévy-flight beetle antennae search algorithm (LBAS) was proposed. Moreover, the designed controller was used in the hydraulic quadruped robot to enhance the control performance and restrain the disturbances. The use of the Lévy-flight trajectory in the advanced algorithm can help increase the search speed and iteration accuracy. In the LBAS-ADRC, the parameter tuning method is adopted to develop the active disturbance rejection controller enhanced using the beetle antennae search algorithm. When implemented in the hydraulic quadruped robot, the LBAS-ADRC can ensure satisfactory dynamic characteristics and stability in the presence of external interference. In particular, in the proposed method, the ADRC parameter search problem is transformed to a sixteen-dimensional search problem, the solution of which is identified using the Lévy-flight beetle antennae search algorithm. Moreover, three different algorithms are implemented in the active disturbance rejection controller tuning problem to demonstrate the control performance of the proposed controller. The analysis results show that the proposed controller can achieve a small amplitude overshoot under complex and changeable environments. [ABSTRACT FROM AUTHOR]

To study the mechanical characteristics of ballasted bed under dynamic stability, a three-dimensional discrete element model of ballasted bed with 1000 mm × 700 mm × 550 mm is established based on the discrete element method. Meanwhile, a simulation test bench with the same size is built for simulation analysis and experimental research. The variation law and trend of settlement, lateral resistance, and compactness of ballasted bed under different excitation frequencies are analyzed comprehensively. The results show that when the excitation frequency is constant, the lateral resistance of sleeper, the settlement of sleeper, and the compactness of track bed under sleeper increase first and then tend to be stable. With the increase in horizontal excitation frequency, lateral resistance of ballast bed, sleeper settlement, and compactness first increase and then decrease after stable operation. The values of these parameters are maximized when the excitation frequency is 36 Hz which is the relative optimal horizontal excitation frequency of this model. [ABSTRACT FROM AUTHOR]

Summary: The low voltage ride through (LVRT) capability is an important aspect of the microgrid system, dominated by renewable energy sources (RES). Earlier studies investigate the LVRT capabilities of microgrids but ignore their frequency stability during and after the fault scenario. This paper fills this gap by investigating the frequency fault ride through (FFRT) capability of photovoltaic (PV) based microgrid model and suggests a novel PI‐based virtual damping (PIVD) controller for enhancing the dynamic performance. This controller tracks the frequency error and de‐loads the solar power in the same proportion. This de‐loading creates useful virtual inertia reserve (VIR), which replaces the role of battery storage by stabilizing the grid during the contingency period. To validate the effectiveness, a microgrid assisted with the PIVD controller is simulated in MATLAB and its frequency performance is compared with pre‐existing conventional and ESS models. The comparative results confirm that the proposed model is capable of riding through the severe fault scenario, with the least possible frequency deviation. [ABSTRACT FROM AUTHOR]

The aim of the present study was to explore the effect of basalt fibers on the cracking resistance of microbond asphalt macadam and reduce the occurrence of cracks in asphalt pavements with semirigid base. To this end, compressive resilient modulus tests, rutting tests, and semicircular bending tests were conducted on microbond asphalt macadam with different fiber contents, and the change trends of the compressive resilient modulus, dynamic stability, and flexibility index (FI) with fiber content were revealed. According to the results of this study, the addition of basalt fibers affected the compressive resilient modulus, dynamic stability, and FI of microbond asphalt macadam significantly. With the increase of fiber content, the compressive resilient modulus, dynamic stability, and FI presented a uniform trend of increasing first and decreasing afterwards. When the fiber content was 0.4%, various indices reached their maximum values, suggesting that the cracking resistance of the basalt fiber-reinforced microbond asphalt macadam was optimal under this content. This study is of great significance for the application and promotion of basalt fiber-reinforced microbond asphalt macadam. [ABSTRACT FROM AUTHOR]

Ash storage sites are a commonly used method of disposing fly ash, a byproduct of coal combustion, in China today, and when it accumulates to a certain height, serious geological hazards may occur as a result of seismic activity. In this study, an in situ standard penetration test was carried out on a constructed ash storage site in Northwest China to evaluate the potential for liquefaction of alluvial fly ash within the site, and the results show that dynamic liquefaction can occur within a newly constructed three-stage subdam. A numerical analysis of the influence of dry beach length on the dynamic response of the primary dams and subdams and an assessment of the extent of dynamic liquefaction in the ash storage field were carried out using the Wenchuan seismic waves as input ground motion. Numerical results prove that the acceleration within the ash storage field is relatively low in the original breccias layer and gradually increases with height, with the peak acceleration occurring in the vicinity of the third subdam and a decreasing trend from the subdams towards the ash storage field. As the length of the dry beach increases, the Peak accelerations in the ash storage area occur near the third subdams at larger dry beach length. Meanwhile, the acceleration in the ash storage area close to the surface gradually increases, and, significantly, the range where higher accelerations occur also becomes larger. The maximum horizontal displacements at different dry beach lengths occur at the crest of the third subdam and in the adjacent ash storage area. As the length of the dry beach increases, the maximum horizontal displacements show a certain decrease, but they occur progressively further away from the third subdam, so that, under dynamic action, the dams become safer. The extent of liquefaction decreases at larger dry beach length and extends further away from the third subdam into the ash storage area. It is, therefore, recommended that the length of the dry beach should not be less than 150 m for this ash storage site. [ABSTRACT FROM AUTHOR]

In this paper, we put an investigation into the nonlinear vibration mechanism of the marine rotating machinery with an airbag isolation device under heaving motion. First, we consider the effects of mass unbalance and heaving motion and propose a mathematical model of the marine rotating mechanical system with airbag vibration isolation. Then, the multiple-scale method is conducted to analyze the nonlinear dynamic characteristics of the mechanical system; the frequency-response curves are mainly studied under different parameters, such as the heave excitation, rotor speed, and damping; and the numerical method is also introduced to analyze its dynamic behaviors, such as the steady-state response and its corresponding phase diagram, Poincaré section. The dynamic stability of the system is investigated based on the bifurcations and the largest Lyapunov exponent about rotor speed and heaving frequency. The obtained results indicate complex nonlinear characteristics of the system compared to the system without heaving excitation, which can help us fully understand the dynamic characteristics and parametric optimization as well as structural design of the marine mechanical isolation system. [ABSTRACT FROM AUTHOR]