Results Of Stability Analysis Research Articles

Limit equilibrium method-based 3D slope stability analysis for wide area considering influence of rainfall

We propose a method for evaluating the risks of slope failure induced by heavy rain over a wide area by combining infiltration analysis, surface flow analysis, and slope stability analysis based on three-dimensional limit equilibrium method. The influence of the resolution of terrain data is also examined. To determine rainfall-induced water transportation, we employ an infiltration analysis, using the Green-Ampt model, and a surface flow analysis, using the diffusion wave model. For the slope stability analysis, a three-dimensional arc-slip calculation applying the Hovland method is used. The infiltration depth is obtained from the results of the infiltration analysis, whereas the simulated data are used as input data for the slope stability analysis. A region in Kamaishi City, Iwate Prefecture, Japan, where slope failures were observed during typhoon Hagibis on October 12 and 13, 2019, is selected in this study as the target area and a series of analyses are performed. The topographical survey data by an Unmanned Aerial Vehicle (UAV) observed before and after the typhoon are used to identify the actual collapse locations and compare them with the results of the slope stability analysis. In addition, high-resolution topographic data of the target area using UAV data is created and differences in the factor of safety distribution with and without the UAV data for terrain data are compared and discussed. The obtained results revealed that the proposed method can roughly represent the actual slope failure, which is useful for evaluating rainfall-induced slope failure hazards. The results derived from utilizing detailed terrain data by UAV show the importance of using a high-resolution terrain model for evaluating the stability of microtopography, such as forest roads.

Pairing-induced motion of source and inert particles driven by surface tension.

We experimentally and theoretically investigate systems with a pair of source and inert particles that interact through a concentration field. The experimental system comprises a camphor disk as the source particle and a metal washer as the inert particle. Both are floated on an aqueous solution of glycerol at various concentrations, where the glycerol modifies the viscosity of the aqueous phase. The particles form a pair owing to the attractive lateral capillary force. As the camphor disk spreads surface-active molecules at the aqueous surface, the camphor disk and metal washer move together, driven by the surface tension gradient. The washer is situated in the front of the camphor disk, keeping the distance constant during their motion, which we call a pairing-induced motion. The pairing-induced motion exhibited a transition between circular and straight motions as the glycerol concentration in the aqueous phase changed. Numerical calculations using a model that considers forces caused by the surface tension gradient and lateral capillary interaction reproduced the observed transition in the pairing-induced motion. Moreover, this transition agrees with the result of the linear stability analysis on the reduced dynamical system obtained by the expansion with respect to the particle velocity. Our results reveal that the effect of the particle velocity cannot be overlooked to describe the interaction through the concentration field.

Nonlinear localized gap modes in width-modulated Fibonacci lattices

We address the properties of nonlinear localized gap modes supported by the width-modulated Fibonacci lattices, including their existence and stability. Linear system with the width-modulated Fibonacci lattices has multiple gaps. We find the existence of different families of nonlinear localized modes in two relatively large gaps. One of the nonlinear localized gap modes originates from the upper band-edge linear mode. Such gap modes are mostly stable in their entire existence domain, except for a small region in the middle of their existence. The other two families of nonlinear modes localized in the relatively large gap are pure nonlinear modes, and they have a narrow stable region near their upper cutoff. The results of the linear stability analysis are in good agreement with that of the propagation simulations.

The sleeper group influences on lateral resistance and stability of ballast bed

ABSTRACT The sleeper group, composed of a certain number of rail sleepers, influences the characterization of lateral resistance and the stability of continuous welded rail (CWR). According to full-scale model tests and discrete element model simulation tests of ballast bed, we established a new lateral stability analysis model of CWR considering the effect of sleeper group and resistance sharing characteristics, and compared it with the traditional model. The case analysis shows that the lateral stability analysis result of CWR is safer when considering the effect of sleeper group. When the curve radius is 300 m, the safety margin of the sleeper group model is about 20.8% larger than that of the traditional model. For CWR with potential large lateral displacement in special sections (such as small-radius and large temperature difference), it is advisable to consider the effect of sleeper group for the lateral stability analysis.

Complex dynamical properties of coupled Van der Pol–Duffing oscillators with balanced loss and gain

We consider a Hamiltonian system of coupled Van der Pol–Duffing (VdPD) oscillators with balanced loss and gain. The system is analyzed perturbatively by using renormalization group (RG) techniques as well as multiple scale analysis (MSA). Both the methods produce identical results in the leading order of the perturbation. The RG flow equation is exactly solvable and the slow variation of amplitudes and phases in time can be computed analytically. The system is analyzed numerically and shown to admit periodic solutions in regions of parameter-space, confirming the results of the linear stability analysis and perturbation methods. The complex dynamical behavior of the system is studied in detail by using time-series, Poincaré-sections, power-spectra, auto-correlation function and bifurcation diagrams. The Lyapunov exponents are computed numerically. The numerical analysis reveals chaotic behaviour in the system beyond a critical value of the parameter that couples the two VdPD oscillators through linear coupling, thereby providing yet another example of Hamiltonian chaos in a system with balanced loss and gain. Further, we modify the nonlinear terms of the model to make it a non-Hamiltonian system of coupled VdPD oscillators with balanced loss and gain. The non-Hamiltonian system is analyzed perturbatively as well as numerically and shown to posses regular periodic as well as chaotic solutions. It is seen that the -symmetry is not an essential requirement for the existence of regular periodic solutions in both the Hamiltonian as well as non-Hamiltonian systems.

Commutation Overlap Characteristic Modeling and Stability Analysis of LCC-HVDC in Sending AC Grid

In recent years, the doubly fed induction generator (DFIG)-based wind power generation and high-voltage direct-current (HVDC) transmission are widely utilized in practice. The stability issues of sending AC grid, which is composed of line-commutated converter (LCC)-based HVDC and DFIG system, is worthy of attention. Commutation is an important factor in the impedance model of LCC-HVDC rectifier, due to the nonnegligible leakage inductance of transformer. However, it was overlooked in previous studies because there are many difficulties in modeling commutation overlap characteristic. In this paper, the spectral models of voltage and current mapping functions are proposed by 3-D Fourier series method, in which the commutation overlap angle is considered. Then, based on the concept of harmonic linearization, an analytical model that describes the commutation process is established and validated by simulations. The mechanism that the commutation overlap characteristic affects the impedance model of LCC-HVDC is investigated, and the simplified modeling method in different frequency bands is studied. The stability of sending AC grid is analyzed applying the Generalized Nyquist Criterion (GNC). The results of stability analysis show that the effect of commutation overlap cannot be ignored. The simulation results confirm the correctness of the obtained conclusion.

A Study of the Failure Mechanism of Braced Excavations Using 3D Finite-Element Analysis

This study aims to investigate the failure mechanism of structural support systems in braced excavations. The three-dimensional finite-element method (FEM) was used to model the complexity of real geometry by considering the elastoplastic structural support system. Because failure could occur at the connection between walls and struts, a new model of a strut–wall connection was considered in the analysis to represent the actual condition of excavation failure. Three failure case histories were studied to investigate the performance of strut–wall connections by calibrating their strength parameters until the factor of safety was close to unity. It was found that a good result of stability analysis could be obtained in the FEM by considering this model. The yielding of the strut–wall connection model initiated the collapse of the bracing system in all case histories, followed by the yield of struts and failure of soils. A robust failure mechanism was also obtained, in which the yielding of the structural support system at failure initially developed at the middle section toward the corner of excavation geometry.

A Novel Approach of Leflunomide Nanoemulgel for Topical Drug Delivery System

Objectives: This research’s primary goals are Leflunomide (LFD) nanoemulgel formulation and characterization for topical administration. Materials and Methods: A pseudo ternary phase diagram was created utilizing castor oil, Tween 20 as the surfactant, PEG 300 as a co-surfactant, and ethanol as the cosolvent. Spontaneous emulsification was used to create LFD-nanoemulgel, which is now commercially available. Gel matrix Carbopol 934 was employed to generate nanoemulgel in the prepared nanoemulsion. Studies on the LFD-globule nanoemulgel’s size, physical appearance, viscosity, spreadability, TEM, FTIR drug content, release kinetics, and stability contributed to its characterization and assessment. Optimum nanoemulgel formulation contained 6% castor oil, 36% Tween 80 and PEG 300 as Smix (surfactant and co-surfactant mixture), 46% water, and 12% w/w carbopol 934. Results: The produced nanoemulgel was translucent and had a zeta potential of 26.12 mV and a particle size of 113.55 ± 1.73 nm. The improved formulation has a drug release rate of 98.13% ± 1.20%. They were determined to be ideal for pH, viscosity, and spreadability. According to the stability analysis, the generated nanoemulgel was shown to be stable at temperatures ranging from 25 ± 45°C, according to the stability analysis results. Conclusion: An effective formulation for topical medication delivery using LFD-loaded nanoemulgel has been developed. It may be an alternative drug therapy to the topical application of drugs to treat arthritis.

ℓ₂-ℓ∞ Control of Discrete-Time State-Delay Interval Type-2 Fuzzy Systems via Dynamic Output Feedback.

This article investigates the design of the l2-l∞ dynamic output-feedback (DOF) controller for interval type-2 (IT2) T-S fuzzy systems with state delay. For nonlinear systems, the IT2 fuzzy model is an efficient modeling method which can better express uncertainties than the (type-1) fuzzy model. In addition, state delay is also a general factor that affects system performance. After analyzing the stability of the system, based on convex linearization and the projection theorem, this article proposes a delay-dependent output-feedback controller design method. The IT2 membership functions (MFs) of the fuzzy controller are chosen to be different from those of the model so as to increase the freedom of controller selection. A membership-function-dependent (MFD) method based on the staircase MFs is applied to relax the stability analysis results. Finally, a numerical simulation example is given to illustrate the effectiveness of the results.

Numerical Analysis of Boundary Layer Flow and Heat Transfer over a Shrinking Cylinder

The investigation concerning the movement of the viscous fluid and heat transfer rate when the cylinder shrinks is carried out. The role of curvature parameter and effect of cylinder parameter on skin friction and heat transfer rate were studied. The existence of a dual solution is observed and subsequently identifies which solution is stable. By using the similarity transformation, the boundary layer equations are transformed into nonlinear ordinary differential equations which are then solved numerically using bvp4c in MATLAB. The results for the skin friction coefficient, temperature gradient coefficient as well as velocity and temperature profiles are presented graphically. The effects of mass suction parameter and curvature parameter on flow and heat transfer characteristics are also presented. It is found that the dual solution existed when mass suction parameter greater or equal to 2. Cylinder surface diminished the performance of skin friction coefficient and heat transfer rate. The stability analysis result is performed to verify that the upper branch solution is stable and physically meaningful.

Power System Stability Analysis of the Sicilian Network in the 2050 OSMOSE Project Scenario

This paper summarizes the results of a power system stability analysis realized for the EU project OSMOSE. The case study is the electrical network of Sicily, one of the two main islands of Italy, in a scenario forecasted for 2050, with a large penetration of renewable generation. The objective is to establish if angle and voltage stabilities can be guaranteed despite the loss of the inertia and the regulation services provided today by traditional thermal power plants. To replace these resources, new flexibility services, potentially provided by renewable energy power plants, battery energy storage systems, and flexible loads, are taken into account. A highly detailed dynamical model of the electrical grid, provided by the same transmission system operator who manages the system, is modified to fit with the 2050 scenario and integrated with the models of the mentioned flexibility services. Thanks to this dynamic model, an extensive simulation analysis on large and small perturbation angle stability and voltage stability is carried out. Results show that stability can be guaranteed, but the use of a suitable combination of the new flexibility services is mandatory.

Cold‐Formed Steel Profiles with Multiple Stiffeners Effective Section Calculation Using Alternative Methodology of the EN1993‐1‐3 Standard

SummaryIn this article, the use of paragraph 5.5.1 (7) is applied, only for stiffeners, and the use of the numerical results of linear stability analyses (LSA) obtained by the GBT (Generalized Beam Theory) methods is tested for the section, namely the distortional modes, relating them to the formulas currently present in EC3‐1‐3. For comparison and analysis of results, studies present in the bibliography were used that show experimental and numerical results, relevant and representative, of sections with stiffeners. In the calculation of effective sections, the Class4Section application, developed by the authors, is used to run several tests combining EC3‐1‐3 specifications and LSA results.

Adaptive Cooperative Control for Human-Robot Load Manipulation

In this letter, we propose a control strategy for human-robot cooperative manipulation under the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ambiguous</i> collaboration of a human agent. To cope with this uncertainty, an adaptive update law inferring the human contribution to the system dynamics from basic perception feedback through the human arm stiffness is used. Furthermore, the robustness and accuracy of the approach is enhanced by redundantly tracking the shared load references and its associated end-effector position references. To validate the control strategy, both theoretical Lyapunov stability analysis and experimental results –employing two robot manipulators with 6 degrees of freedom under external disturbances– are provided.

ANALISIS KESTABILAN LOKAL TITIK EKUILIBRIUM MODEL EPIDEMI SEIV DENGAN PERTUMBUHAN LOGISTIK

The SEIV model uses population growth which is assumed to follow logistical growth. The model is studied then analyzed. The analysis shows that the non-endemic (disease-free) equilibrium point is locally asymptotically stable when the basic reproduction number less than one, while the endemic equilibrium point is locally asymptotically stable when the basic reproduction number greater than one. Then a numerical simulation was carried out using Maple software to support the results of the local stability analysis of the equilibrium point. Based on numerical simulations, it shows that a disease will disappear from the population when the basic reproduction number less than one and for a long time a disease will remain in the population (still an epidemic) when the basic reproduction number greater than one.Keywords: SEIV model, logistical growth, equilibrium point, basic reproduction numberMSC2020: 92C60

Biomechanical design and control of an eight DOF human lower extremity rehabilitation exoskeleton robot

Exoskeleton robot-assisted physical therapy has received a lot of research attention due to its positive impact on human upper and lower extremity rehabilitation. The exoskeleton robot attaches closely to the human limbs and facilitates natural movements at the joints. The effectiveness of the exoskeleton robot-assisted physical therapy is influenced by the mechanical design of the manipulator. An ergonomic design helps the user exercise for an extended period. In this paper, the mechanical design of an 8 degrees of freedom human lower extremity exoskeleton robot for rehabilitation is presented. Among the 8 degrees of freedom, 7 are actively actuated and 1 is passively actuated. A cam follower mechanism is developed to replicate the complex motion at the knee joint. To make the exoskeleton comfortable and easy to use for the users, ergonomic design rules are followed. A dynamic model of the human lower extremity exoskeleton robot is also developed for controlling the robot. A Sliding mode controller with super twisting algorithm is employed to simulate the dynamic model. Results for stability analysis of the developed controller are also presented.

An adaptive fast super-twisting disturbance observer-based dual closed-loop attitude control with fixed-time convergence for UAV

In this paper, a fixed-time dual closed-loop attitude control method is investigated for a quadrotor unmanned aerial vehicle. Firstly, a fixed-time adaptive fast super-twisting disturbance observer is presented for estimating the unknown external disturbance. A modified adaptive law is employed based on an equivalent control method to obtain proper observer gains. Secondly, a fixed-time controller is designed by using a universal barrier Lyapunov function to satisfy asymmetric tracking error constraints. Then, a tracking differentiator is utilised to arrange the transition process. Finally, the implementation of the developed method in a quadrotor unmanned aerial vehicle is performed. Through stability analysis and simulation results, the effectiveness and superiority of the proposed fixed-time control method are validated.

Transient growth analysis of hypersonic flow over an elliptic cone

Non-modal linear stability analysis results are presented for hypersonic flow over an elliptic cone with an aspect ratio of two at zero angle of attack, completing earlier modal instability analysis of flow around the same geometry. The theoretical framework to perform transient growth analysis of compressible flows on a generalized two-dimensional frame of reference is developed for the first time and is then applied to solve the initial-value problem governing non-modal linear instability on planes perpendicular to the cone axis, taken at successive streamwise locations along the elliptic cone. Parameter ranges examined here are chosen so as to model flight of the Hypersonic International Flight Research Experimentation 5 (HIFiRE-5) test geometry at altitudes of 21 km and 33 km, corresponding to Mach numbers 7.45 and 8.05 and unit Reynolds numbers $Re' = 1.07\times 10^7$ and $1.89\times 10^6$ , respectively. Results obtained indicate that the significance of the non-modal growth for laminar–turbulent transition increases with increasing flight altitude (decreasing Reynolds number). At a given set of flow parameters, transient growth is stronger in the vicinity of the tip of the cone and in azimuthal locations away from both of the minor (centreline) and major (attachment line) axes of the cone. Linear optimal disturbances calculated at conditions of maximal transient growth are found to peak in the crossflow region of the elliptic cone. These structures are elongated along the streamwise spatial direction, while being periodic along the spanwise direction with periodicity lengths of the same order of magnitude as the well-known structures identified as crossflow vortices in both experiments and simulations.

PERENCANAAN SABO DAM SEBAGAI BANGUNAN PENGENDALI SEDIMEN PADA SUNGAI TALANG KOTA PADANG PANJANG

Sedimentation is the process of forming sedimentary material deposits or fragments of rocks, minerals and organic materials that drift and move in the direction of the flow of river water. There are various ways of holding it, such as being pushed, carried by jumping up and down and some are dissolved. Sedimentation in the Talang River which occurred at 185,764 m³/year resulted in silting, thereby reducing the water holding capacity of the Talang River. The construction of the Sabo Dam is one solution that can be done to control sedimentation in the river. The purpose of this study is to design a sediment control weir that is safe for stability with the largest sediment storage volume. The method used in this research is to compare the hydraulic design of the Sabo building at two specified locations (STA 0+200 and STA 201+400), then stability analysis is carried out based on the forces that occur and the volume of sediment that can be accommodated. Based on the results of stability analysis at two locations, it was found that the STA 201+400 weir was safe against shearing, overturning, bearing capacity and piping. The sediment volume that can be retained is 156,206.85 m³ and Sabo will be full of sediment after 8 months. Meanwhile, at the location of STA 0+200 the sediment that can be retained is 7,913,787 m and will be full after 4 months. The construction of the Sabo Dam at STA 201+400 is expected to reduce sedimentation that occurs in the Talang River.

Rainfall Triggered Slope Instability Analysis with Changing Climate

Slope instability triggered by rainfall is common in tropical countries like India, where the soil of hill slopes are generally in unsaturated condition, having higher strength than in the saturated condition due to matric suction. This study aims to investigate the change in pore water pressure (PWP) with rainfall infiltration into the slope and the corresponding effect of the slope stability on different hill slopes from different regions of India. By applying rainfall on the surface of slope as a flux boundary condition, a transient seepage analysis is performed using SEEP/W, and the corresponding results in the form of PWP distribution within the slope are used as input for SLOPE/W program of Geostudio 2018 R2, to check the stability of slope. This study involves the use of CMIP5 (Coupled model intercomparision project phase 5) simulations for rainfall data of different regions for the duration of 2015–2050, 2051–2075 and 2076–2100; which is completely based on non-stationary approach (i.e., the statistics of extremes changes with time) rather than the conventional methods of extracting rainfall data that are based on stationary approach. The stability of different slopes is checked for 95 percentile rainfall intensity as well as for maximum rainfall intensity for a period of 2015–2100, and the analysis is performed for 5 days for which the duration of rainfall is considered to be 24 h. It is concluded that due to climate change, slopes which may be marginally stable under historical and present rainfall events can fail under projected precipitation estimates, and this can be understood by the results of Haflong slope stability analysis as the 30° slope, which is marginally stable under maximum rainfall intensity for the period 2015–2050 having factor of safety (FOS) value 1.0013, will fail under the maximum rainfall intensity for the period 2051–2075 and 2076–2100 having FOS value 0.9935 and 0.9989, respectively. A continuous decrease in FOS with increasing rainfall intensity is observed for all the study areas under consideration.

Limit cycle oscillation suppression controller design and stability analysis of the periodically time-varying flapping flight dynamics in hover

The periodically time-varying forces make the equilibrium state of Beihawk, an X-shaped flapping-wing aircraft, to be a periodic limit cycle oscillation. However, traditional controllers based on averaging theory fail to suppress this oscillation and the derived stability result may be inaccurate. In this study, a period-based method is proposed to design the oscillation suppression controller, locate the corresponding cycle and analyze its stability. A periodically time-varying wing-tail interaction model is built and Discrete Fourier Transform is applied to adapt the model for controller design. The harmonics less than quintuple flapping frequency account for more than 96 percent of the total harmonics and are reserved to present a concise model. Based on this model, active disturbance rejection controller (ADRC) is designed and its Extended State Observer can observe the disturbance to suppress the oscillation. Poincaré map is introduced to convert the stability analysis of the cycle to a fixed point. A multiple shooting method is adopted to locate several points on the cycle and the map is obtained by calculating the submaps between the adjacent points with the Floquet theory. The located points are proved to be accurate compared with the numerical solved cycle and the stability analysis result of the cycle is verified by the dynamic evolution. Compared with the State Feedback Controller, the ADRC performs better in suppressing the limit cycle oscillation and eliminating the attitude control error. The oscillation suppression is meaningful in maintaining a stable flight and capturing high quality images.