Load Redistribution Research Articles

Analysis of Controllability in Cyber–Physical Power Systems under a Novel Load-Capacity Model

In cyber–physical power systems (CPPSs), system collapse can occur as a result of a failure in a particular component. In this paper, an approach is presented to build the load-capacity model of CPPSs using the concept of electrical betweenness and information entropy, which takes into account real-time node loads and the allocation of power and information flows within CPPSs. By introducing an innovative load redistribution strategy and comparing it with conventional load distribution strategies, the superior effectiveness of the proposed strategy in minimizing system failures and averting system collapses has been demonstrated. The controllability of the system after cascading failures under different coupling strategies and capacity parameters is investigated through the analysis of different information network topologies and network parameters. It was observed that CPPSs constructed using small-world networks, which couple high-degree nodes from the information network to high-betweenness nodes from the power grid, exhibit improved resilience. Furthermore, increasing the capacity parameter of the power network yields more favorable results compared to increasing the capacity parameter of the information network. In addition, our research results are validated using the IEEE 39-node system and the Chinese 132-node system.

BIOMECHANICAL SUBSTANTIATION OF THE ALGORITHM FOR CHOOSING THE OPTION OF DISTAL CORRECTIVE OSTEOTOMY OF THE II–IV METATARSAL BONES IN THE TREATMENT OF METATARSALGIA

Deformations of the front part of the foot with valgus deformity of the first toe lead to a redistribution of the body weight load during walking between the heads of the metatarsal bones. At the same time, the load on the head of II and III, and sometimes IV metatarsal bones increases significantly. Objective. To substantiate the choice of the most correct distal metatarsal osteotomy for the treatment of patients with metatarsalgia. Materials and methods. Three variants of distal metatarsal osteotomy were simulated: Weil, Helal, and distal wedge-shaped metatarsal osteotomy. Result. Weil osteotomy allows you to raise the support point of the metatarsal head above the support surface from 2 to 7 mm, depending on the amount of displacement of the head in the proximal direction and the angle of inclination of the metatarsal bone relative to the plane of the support surface, which effectively reduces the load on the metatarsal head during walking, but under conditions of magnitude the angle of inclination of the axis of the metatarsal bone is more than 20°. Helal osteotomy with the subsequent displacement of the separated part proximally, ensures the lifting of the head above the conventional plane of support from 1 to 4 mm, contributes to the effective unloading of the head while standing and while walking. They are used only for severe metatarsalgia. The range of correction of the standing height of the support surface of the metatarsal head for performing a distal wedgeshaped osteotomy is determined to be from 0.6 to 2.9 mm. Its advantage is the independence of the amount of correction from the presence or absence of a decrease in the longitudinal arch of the foot. Conclusions. Weil osteotomy has the worst corrective possibilities of raising the head of the metatarsal bone, but is very easy to perform, so its use is advisable in the absence of reduction of the longitudinal arch of the foot. A wedge-shaped distal osteotomy has a range of correction of the metatarsal headelevation up to 3 mm, but it depends on its diameter, so it is used in the case of a head diameter of at least 10 mm. Helal osteotomy provides the widest range of elevation of the metatarsal head, which does not depend on the presence of any degree of flat feet, but has some technical limitations.

Physical Model Tests of Concrete Buttress Dams with Failure Imposed by Hydrostatic Water Pressure

Although the failure of a concrete dam is a complex and highly dynamic process, the current safety assessments of concrete gravity and buttress dams rely on a simplified 2D stability analysis, which neglects the load redistribution due to 3D monolith interactions and the valley shape. In addition, the estimation of breach parameters in concrete dams is based on assumptions rather than analyses, and better prediction methods are needed. Model tests have been conducted to increase the understanding of the failure behavior of concrete dams. A scale model buttress dam, with a scale of 1:15, consisting of 5 monoliths that were 1.2 m in height and 4 m in width, was constructed and loaded to failure using water pressure. The model dam had detachable abutment supports and shear keys to permit variations in the 3D behavior. The results showed that the shear transfer was large between the monoliths and that the failure of a single dam monolith is unlikely. A greater lateral restraint gives not only a higher failure load but also a better indication of impending failure. These findings suggest that the entire dam, including its boundary conditions, should be considered during a stability assessment. The results also suggest that the common assumption in dam safety codes that a single monolith fails during flooding analysis is not conservative. The dataset obtained provides a foundation for the future development of dam-monitoring alarm limits and for predictive models of dam-breaching processes.

A mechanism to detect load redistribution attacks in interdependent gas and power systems based on deep learning

A mechanism to detect load redistribution attacks in interdependent gas and power systems based on deep learning

Walking with a Posterior Cruciate Ligament Injury: A Musculoskeletal Model Study.

The understanding of the changes induced in the knee's kinematics by a Posterior Cruciate Ligament (PCL) injury is still rather incomplete. This computational study aimed to analyze how the internal loads are redistributed among the remaining ligaments when the PCL is lesioned at different degrees and to understand if there is a possibility to compensate for a PCL lesion by changing the hamstring's contraction in the second half of the swing phase. A musculoskeletal model of the knee joint was used for simulating a progressive PCL injury by gradually reducing the ligament stiffness. Then, in the model with a PCL residual stiffness at 15%, further dynamic simulations of walking were performed by progressively reducing the hamstring's force. In each condition, the ligaments tension, contact force and knee kinematics were analyzed. In the simulated PCL-injured knee, the Medial Collateral Ligament (MCL) became the main passive stabilizer of the tibial posterior translation, with synergistic recruitment of the Lateral Collateral Ligament. This resulted in an enhancement of the tibial-femoral contact force with respect to the intact knee. The reduction in the hamstring's force limited the tibial posterior sliding and, consequently, the tension of the ligaments compensating for PCL injury decreased, as did the tibiofemoral contact force. This study does not pretend to represent any specific population, since our musculoskeletal model represents a single subject. However, the implemented model could allow the non-invasive estimation of load redistribution in cases of PCL injury. Understanding the changes in the knee joint biomechanics could help clinicians to restore patients' joint stability and prevent joint degeneration.

Failure mechanisms and load paths in a standing seam metal roof under extreme wind loads

In this paper, the failure sequence and load sharing for standing seam metal roofs (SSMR), up to the limit state, were investigated using full-scale experiments. The tested SSMR system had full-scale dimensions and boundary conditions, which provided the opportunity to investigate the performance of SSMR systems under realistic conditions. The results show that there is a linear relationship between the wind pressure and clip reaction under low wind pressure (less than 500 Pa). Load redistribution happens along with the deformation of roof panels with greater load transfer to the ridge and eaves of the roof at higher pressure. Near the corner of the roof, between 27 and 46 % of the applied load is transferred to edges of the eaves and gable end. Away from the roof corner, between 17 and 23 % of the applied load is transferred to eave edge. Global buckling of panels occurs before connection failures and the initial location of global buckling is near the seam and in the middle of two adjacent clips. Two failure modes for the connections, clip slippage and fastener failure, were observed during the tests. However, the failure modes vary with the clip arrangement and boundary conditions.

Modeling and assessing load redistribution attacks considering cyber vulnerabilities in power systems

Introduction: Load Redistribution (LR) attacks, as a common form of false data injection attack, have emerged as a significant cybersecurity threat to power system operations by manipulating load buses’ measurements at substations. Existing LR attack methods typically assume that any substation can be equally attacked, contributing to the analysis of LR attacks in power systems. However, the diversity of cyber vulnerabilities in substation communication links implies varying costs associated with falsifying load buses’ measurements. Thus, quantitatively evaluating these costs and analyzing the impact of LR attacks on power systems within cost constraints holds practical significance.Methods: In this paper, we employ a Bayesian attack graph model to characterize the intrusion process through cyber vulnerabilities. The costs of falsifying load buses’ measurements at substations are quantitatively evaluated using the mean time-to-compromise model. Subsequently, from the attacker’s perspective, we propose a bi-level optimization model for LR attacks, considering the mean time to compromise in conjunction with limited attack resources and power flow constraints.Results: Simulations conducted on the IEEE 14-bus system illustrate the influence of cyber vulnerabilities on LR attacks within power systems. Furthermore, we verify that the attack scenario of the existing LR attack model aligns with a case of the proposed bi-level LR attack model when there is sufficient attack time to compromise all communication links.Discussion: The findings of this research demonstrate that the impact of cyber vulnerabilities on LR attacks can be quantified by assessing the attack costs. Effective management of LR attacks can be achieved under cost constraints through optimization methods. These insights contribute to enhancing network security strategies for power systems, mitigating potential threats posed by LR attacks in power system operations.

Robustness of dual-layer networks considering node load redistribution

To investigate the spread of cascading failure on dual-layer networks, we propose a dual-layer network model based on eigenvector centrality and define network interactions through different connection strategies. Following the local priority reallocation rule of load and the nonlinear relationship between load and capacity, we conduct theoretical analysis of the proposed model and simulate it on the BA scale-free network. The result simulation shows that under different connection strategies, when the controllable coefficient [Formula: see text] of the initial load, the dual-layer network demonstrates better robustness regardless of attacking a node with a large initial load or a small initial load. And when [Formula: see text], the robustness of the network for attacking a node with low initial load is enhanced as the node coupling rate of the dual-layer network increases. For [Formula: see text], the variation of network robustness does not vary essentially with the node coupling rate.

An integrated section model to enable simulating composite slabs in fire simply as modelling a flat slab

Modelling slabs is vitally necessary when simulating building structures in fire. The composite action between slabs and beams and tensile membrane action after fire induced deflections significantly reshape the load redistribution mechanisms and failure patterns. Modelling slabs particularly composite slabs of ribbed sections as a common choice of modern steel structures is a challenging task. Currently, those existing modelling approaches, such as beam & shell model and strip models, require elements for ribbed and flat parts separately, which produces much complexity and ideally it can be solved using a suitable section model to appropriately represent the behaviour. This paper begins with formulating the theoretical base of state determination in the integrated composite section, which enables correct deformation distribution to ribbed and flat subsections. While being compatible to typical modelling infrastructure for slabs, the integrated section model has demonstrated excellent capability in comparison to the strip models and fire tests. Even using a coarse mesh scheme (e.g. 8 × 6 elements), the prediction error of mid-span deflection remains low (around 10%). The appealing benefit is further shown in modelling Cardington Corner fire test, which significantly reduces the efforts of determining geometric details, the number of nodes & elements, and the computation time cost.

Assessment of the kidney functional state prior and after partial nephrectomy for a unilateral tumor using mathematical processing of computed tomography data with contrast enhancement

Background. According to the contemporary data available contrast-enhanced computed tomography can be used to assess total and split kidney function. The Urology Clinic of the I.M. Sechenov First Moscow State Medical University, Ministry of Health of Russia (Sechenov University) utilizes mathematical processing of computed tomography data for the assessment of split kidney function.Aim. To evaluate the effect of main renal artery clamping (warm ischemia time) during partial nephrectomy for a unilateral tumor on the kidney function.Materials and methods. 33 patients of both sexes who underwent partial nephrectomy for unilateral kidney tumor were enrolled in the study. Prior to and 3–6 months after the surgery, 3D glomerular filtration rate (GFR), 3D perfusion, 3D volume of the renal parenchyma were evaluated by mathematical processing of computed tomography data with contrast enhancement. As well as that the dynamics of the total GFR (CKD-EPI equation) and total volume of the kidneys were assessed.Results. No significant changes were registered for both general functional renal parameters (creatinine level, total GFR, total volume of functioning renal parenchyma) and split 3D GFR. There were significant differences in 3D perfusion and kidney parenchyma volume prior and after partial nephrectomy.Conclusion. The results of the research highlight good reserve capacity the kidneys after partial nephrectomy with main renal artery clamping. The evidence that the non-operated kidney takes over the function of the resected kidney is based on the fact that there is an increase in its perfusion and volume of the kidney in the postoperative period. This state can also be regarded as a redistribution of functional loads between the kidneys, which is an adaptive mechanism in the postoperative period.

DEVELOPMENT OF A THEORETICAL MODEL OF THE ROLLER SCREW MECHANISM FOR ITS CALCULATIONS TAKING INTO ACCOUNT MANUFACTURING ERRORS

Considered promising planetary roller screw mechanisms (PRSM), which are the most promising converters of rotational motion to translational motion and are increasingly used in products of the aerospace industry because of the high load capacity with small dimensions and high reliability. PRSM are spatial mechanisms and have a number of features. They are multi-threaded, have numerous redundant links, have loading peculiarities. During operation in PRSM there is a constant redistribution of load, the reason for this phenomenon is due to manufacturing errors of numerous (measured in hundreds) mating turns of threaded parts (screws, rollers, nuts) of the mechanism. Since the manufacturing errors of the threaded parts of the PRSM are random, the research methods and models under development must have a probabilistic nature. Due to the large number of working turns of the threaded parts of the computers, the research should be carried out by numerical methods with extensive use of computers. Hence, it was proposed to carry out the computers studies by the methods of computer simulation modeling. In the development of a theoretical model that can be used for the force calculation of PRSM and other studies, it is proposed on the basis of metrological measurements of the threaded parts of the mechanism to take into account the manufacturing errors of these parts, primarily errors in the thread pitch. This will make it possible to obtain reasonable and more reliable results of force calculation and other studies. This paper describes the development of mathematical models of the threaded parts of the PRSM and the mathematical model of the mechanism as a whole. Experiments with the mathematical models of the threaded parts of the prototype PRSM and the mechanism as a whole are performed and the results obtained are analyzed. Further works will describe the continuation of this complex study with the developed models.

Data Cleansing & Overfitting Check for Interpretable ML in Concrete Design – a punching shear paradigm

AbstractEvaluation of shear capacity is crucial for existing concrete buildings and bridges. Shear failure can cause an abrupt and brittle loss of load‐carrying capacity, leading to load redistribution and progressive collapse. An internationally research and scietific discourse is actively ongoing on the best prediction model for shear, torsion, and punching shear capacity, with no clear consensus. A machine learning‐based strength model is suggested for accurate prediction of punching shear capacity, using Gaussian Process Regression and Support Vector Regression models. Data elaboration and thorough evaluation are needed to enhance the model's performance and interpretability. The paper discusses critical methodological steps based on the authors' experience of developing ML‐models for structural concrete design against punching shear failure using 544 full‐scale tests.

Determining the load on a body of the gondola car with unloading hoppers under the basic operating modes

The object of research is the processes of occurrence, perception, and redistribution of loads in the supporting structure of a gondola car with unloading hoppers. In order to increase the carrying capacity of the gondola car, and accordingly the profitability of railroad transportation, it has been proposed to improve its structure. This improvement implies the installation of unloading hoppers in its middle part. According to preliminary calculations, the use of unloading hoppers could increase the usable volume of the body by 2.82 m3. At the same time, the carrying capacity of the car would increase by 3.8 tons. Accordingly, the axial load on the wheelsets would increase. It is possible to solve this issue by using wheelsets with increased axial load in bogies. As part of the research, a mathematical modeling of the vertical dynamics of the gondola car during its movement in the empty and loaded states of the rail track was carried out. It was established that the movement of the car is evaluated as "excellent". The calculation of the strength of the gondola car body under the main operational load modes was carried out. The stability of the car's equilibrium was determined, and its modal analysis was also carried out. The peculiarity of the results within the framework of the study is that the proposed improvement could be implemented not only when designing a new car structure but also during modernization. The area of practical application of the results is the machine-building industry, in particular, railroad transport. The conditions for the practical application of the research results are compliance with the axial load within the permissible values. The research reported here will contribute to improving the technical and economic indicators of cars, as well as increasing the profitability of railroad transportation

The response of diagrid structures to fire

The diagrid structural system has seen significant uptake in medium to high rise buildings because of the architectural and resource advantages that it provides. These arise mainly as a result of flexibility in the topology that this particular structural solution provides. However, as a result of the way in which diagrids carry both horizontal and vertical loading, the diagrid structure itself may be susceptible to fire in ways which are not immediately obvious on the basis of our understanding of more traditional rectilinear construction forms. This study addresses this to improve our understanding of diagrid structures' response to fire. A comprehensive structural analysis on 45 fire load cases is conducted, considering different fire locations and sizes, using parametric design tools and finite element analysis software. The results provide valuable insights into the load redistribution and collapse mechanisms of diagrid structures in fire conditions.

Risk-constrained day-ahead planning of an energy hub integrated with the on-site hydrogen fueling station and active battery swapping infrastructure considering high level of renewable energies and load redistribution

The presence of green technologies has increased in recent years due to their efficiency and capability to mitigate environmental issues. This paper evaluates the day-ahead planning of an energy hub integrated with the on-site hydrogen fueling station and active battery swapping infrastructure considering the high level of renewable energies. According to the indeterminate nature of energy systems, the power of wind and solar units, state of vehicles in stations, local loads and price of markets are modeled by diffident scenarios and then, the conditional value-at-risk metric is utilized to measure the risk of decisions. The influence of load redistribution on electrical, heating and cooling loads is also examined and a sensitivity analysis is proposed to assess the role of various parameters on the objective function. The results indicate that the risk-averse strategy decreases profit for a specific conservatism level by 5.68 % to improve the robustness against uncertainties; however, lower risks can be achieved by changing the risk control index. The simulations demonstrate that the swapping station acts as a bulk storage, especially considering the high penetration of renewable resources. In addition, load redistribution has a positive effect, where the load profile modification equal to 10 % increases profit by 4.55 %.

The National Childcare Agenda in Cambodia: A Feminist Transformative Ethics of Care Perspective

This article critically examines Cambodia’s national childcare agenda from a feminist transformative ethics of care perspective. It employs a discourse analysis for policy texts and examines, through in-depth interviews and participant observation, the perspectives and/or lived experiences of people engaged in and/or affected by the policy. The researcher conducted 104 in-depth interviews and observed three meetings/workshops in Cambodia from February to May in 2018. This paper argues that Cambodia’s national childcare agenda is far from ‘transformative’ because it neither contributes to the redistribution of childcare loads from the family to the public sphere nor enhances women’s autonomy in a way that enables them to participate in the labour market. A primary contribution of this paper is its application of a feminist transformative ethics of care to childcare policy analysis in Cambodia, in a developing country context. This transformative tool brings together different feminist thinking to enable us to investigate and evaluate childcare policy discourses, how they are interpreted by different actors, and how they shape policy practices and people’s lives.

Analysis of the geotechnical behavior of a piled raft in tropical lateritic soil based on long-term monitoring of columns, piles, and raft–soil interface

This paper aims to analyze and describe the geotechnical behavior of a piled raft foundation of a tall building (53 floors, 172.4 m high) through the monitoring of strains in the building’s columns and piles, the stresses at the raft–soil interface, and the foundation settlements. Field and laboratory tests were performed, and associated with axisymmetric and three-dimensional finite element analysis to the assessment of the measured data. The monitoring of the pile strains suggests the occurrence of soil expansion, caused by the raft excavation process, up to approximately 6 months after the excavation was completed. The presence of different soil profiles under the raft, with different mechanical properties, affected the distribution of the foundation settlements and the pile loads. Initially, the average pile loads were concentrated in the perimeter elements, but, as the construction of the building evolved, they tended to become more uniform. The effect of the superstructure stiffness caused successive load redistributions in the columns, which contributed to the maintenance of the maximum angular distortion of the building within the allowable values and reduced the load difference between the piles positioned in opposite soil profiles.

Progressive Collapse Assessment of High-Rise Framed Structure Using ETABS Software

Abstract: The structures generally get collapse due to the failure of one or a few structural components which then progresses over the successive of other components. This process is referred as progressive collapse of the structure. Local damage that initiates progressive collapse is called initiating damage. In order to study the collapse in analytical way, loading pattern or boundary conditions are required to be changed so that other structural elements within the structure are loaded beyond their capacity. This leads to development of alternative load paths to initiate the redistribution of loads.

Percolation phase transition in the heterogeneous multi-coupled interdependent network

In previous studies, complex system models have often been set up in an oversimplified manner and the failure mechanism for nodes affected by each other is not correspond to reality. Accordingly, we develop a new model of heterogeneous multi-coupled interdependent networks and analyze the change in the giant component of the network after the attack in conjunction with the load redistribution mechanism. We first analyze the cascading failure process of the network analytically by recursive methods, estimate the critical phase transition threshold and the size of the giant component of the remaining network after network percolation, and find that the threshold of the WS sub-network is positively related to the average degree, and the BA sub-network is related to the power exponent λ of the distribution. When λ is less than or equal to 2, there is always a giant component in the network. After λ is greater than 3.4788⋯, there is no giant component. When λ is between 2 to 3.4788⋯, we found that the threshold of the sub-network is more influenced by the proportion of attacks (p1 and p2), and when p1 is larger, the sub-networks interact with each other, resulting in a smaller threshold for the BA sub-network, while the threshold of the WS sub-network is smaller in other cases. Finally, the cross-sectional comparison illustrates that as λ increases to 3.4788⋯, the robustness of the BA sub-network increases, contrary to the findings for single-layer networks. Overall, the heterogeneous multi-coupled interdependent network is more robust, and the giant component is greatly affected by the low robust sub-network, but its existence is related to the stock of nodes.

Studying the load of composite brake pads under high-temperature impact from the rolling surface of wheels

The object of the research is the processes of thermal stress, perception and redistribution of loads by the brake composite pad during braking of the car in operation. In the current conditions, wedge-dual wear of composite brake pads is observed in the braking systems of freight cars, the feature of which is the deterioration of the braking efficiency of freight trains. With this type of wear, both an increase in the load on the brake pad and an "underuse" of the amount of pressure on it can occur. A comprehensive thermal calculation was carried out for composite brake pads with uniform and wedge-dual wear. The results of the calculation showed that the amount of pressure on an abnormally worn pad is 23.3 % less than that acting on a pad with nominal values. It has been proven that the change in the pressure force on the composite pad with different values of the wear parameters during braking leads to a change in the braking force that occurs between the wheel and the rail during braking. The calculation of the strength of the composite brake pad with wedge-dual wear was carried out. The obtained results will make it possible to develop measures to modernize the elements of the brake lever transmission of freight cars. The field of practical use of the obtained results is car-building enterprises. The conditions for the practical use of the results are the brake lever transmissions of carriages of cars with a gauge of 1520 mm. The conducted studies prove the negative impact of wedge-dual wear not only on braking efficiency, but also on the strength of brake pads. This makes it necessary to create measures aimed at its elimination, which will contribute to increasing the level of train traffic safety and significantly reducing the operational costs of maintaining freight cars