Local Overload Research Articles

Effect of the Nb content on the microstructure evolution and properties of the CrFeCoNiNbx layers prepared by laser cladding

Marine engineering components, such as ship stern shafts, are often subject to local overload, wear and seawater erosion. In order to improve the performance and service life of marine engineering components, the CrFeCoNiNb x ( x = 0, 0.25, 0.5, 0.75 and 1) high-entropy alloy (HEA) coating were prepared on the 42CrMo substrate by laser cladding. The microstructure, microhardness, wear behaviour and the corrosion resistance of the prepared HEA coatings with different Nb contents were evaluated. Results show that the cladding layer of CrFeCoNiNb0 is composed of single dendrites with a small amount of short rod-shaped protrusions distributed along the dendrites. The addition of Nb promotes growing of the original dendrite structures into interdendritic structures with internal substructures retained. Apart from the variations in the microstructure, the formation of the Laves phase, which is both hard and corrosion resistant, is also an important factor in the performance of the cladding. This variation leads to the increase of the microhardness of the cladding layer, accompanying with the improvement of wear resistance property. Notably, the improvement of microhardness is ascribed to the combined contribution from the refinement strengthening, the solid-solution strengthening and the dispersion strengthening by Laves phase. The improvement of the corrosion resistance is mainly attributed to dense passivation film formed by the Cr and Nb on the surface of the cladding layer. The above results suggest that the CrFeCoNiNb x cladding layer could achieve synergistic interaction between the mechanical properties and the corrosion resistance on stern shaft surface.

Cascading failure mechanism of major drainage system in mountainous city: Taking the basin of the main urban area of Chongqing as an example, China

Failure of major drainage systems is almost always accompanied by waterlogging. Understanding the operation and failure mechanism of major drainage systems is an important prerequisite for understanding and managing waterlogging. The natural and artificial environments in mountainous cities are more complex, and the major drainage system, as an open system for excessive surface runoff discharge and storage, is more prone to local overload and cascading failure. Existing theories and methods are difficult to explain and analyze the cascading failure characteristics and principles of major drainage systems in mountainous cities. Based on the complex network technology and the principle of runoff balance, the cascade failure model of major drainage system was constructed, and the characteristics and laws of cascade failure under six kinds of terrain, six kinds of short duration rainstorm and two kinds of surface environments were quantitatively analyzed. Research has found that the cascading failure of major drainage systems and waterlogging in mountainous cities should be the same phenomenon from different perspectives, and the simulated matching degree between the two can reach 79.5%. Meanwhile, 456 potential waterlogging locations were discovered in the study area, which is much larger than the actual 73 locations. When urban construction and rainfall conditions change, these unstable potential waterlogging locations are easily apparent. Among them, terrain is the main factor restricting the cascading failure of major drainage systems. Low lying valley areas often quickly accumulate a large amount of overflow, while flat areas are prone to overflow spreading to the surrounding areas; Slope areas are not prone to overflow, but are prone to local flooding. The change of short duration rainstorm and the difference of surface environmental openness will further interfere with the cascade failure of the major drainage system. The longer the return period of the short duration rainstorm or the increase of the peak value of the rainfall pattern, the greater the discharge and storage pressure of the major drainage system per unit time, resulting in intensified waterlogging. The open and unobstructed surface environment will lead to the small-scale spread of waterlogging, but this will significantly reduce the overall degree of waterlogging in the late rainstorm. The study revealed the spatiotemporal principles and basic laws of cascading failure of major drainage systems in mountainous cities. The conclusion is helpful for mountainous cities to formulate urban construction management strategies and climate change adaptation strategies, and to cope with current and future potential waterlogging disasters.

Analysis of Failure Mode of Reinforced Embankments Overlying Voids Based on Discrete Method

The mode of the reinforced embankment overlying voids was generated based on discrete element software. By changing the vertical distance H and the horizontal distance L, the influence of the void position on the bearing capacity characteristics, displacement field, stress field and its reinforcement deformation law of the reinforced embankment was analyzed when a local overload was applied. Numerical simulation results show that the vertical displacement of the geogrid is symmetrical around the center of the loading plate, and the transverse displacement of the geogrid shows a centrosymmetric trend around the center of the loading plate at different void locations. In addition, the failure mode of the embankment at different void positions is proposed. Four different failure modes exist for the reinforced embankments overlying voids under local overloading: perforation failure, collapse perforation failure, void side failure and no impact failure. When L = 0, as H increases, the embankment failure mode changes from perforation failure to collapse perforation failure; and when L > 0, as L increases, the failure mode changes from void side failure to no impact failure.

Biomechanical Analysis of Different Footwork Foot Movements in Table Tennis.

In order to solve the problem of athletes with lower limb movement injuries in table tennis footwork, with the increasing risk of sports, the incidence of acute injury also increased. The increase in athletic training, on the one hand, improves the skill level of the athlete; on the other hand, it increases the chances of more chronic injuries. Through the investigation of the injury site of 143 table tennis players, the researchers found that the lower limb injury accounted for 32% of the total injuries and the upper limb injury rate accounted for 33.14% of the trunk, accounting for 34.29%. The injury sites are mostly concentrated in the lumbar region, followed by the shoulders and knees. Through epidemiological research on the injuries of outstanding table tennis players, the survey results show that the probability of lower extremity injuries ranks in the top three, and most of them are acute sprains and chronic strain injuries. By applying the principles of sports biomechanics, a biomechanical analysis of the asynchronous foot movement in table tennis is proposed; from three aspects of kinematics, dynamics, and plantar pressure, it is found that the injury of table tennis is closely related to technical play connect. The risk of sports injury is inevitable in a sense, due to the long-term local overload, which causes the strain of the sports system. In order to avoid or reduce the occurrence of such sports injuries, coaches should standardize the technical movements of the players and arrange the exercise load reasonably according to the characteristics of the sports.

Clinical and diagnostic features of occupational polyneuropathy in combination with damage to the locomotor apparatus in workers of harmful professions

An urgent task for the occupational pathology service of the country is the search for objective methods for the early diagnosis of occupational diseases of the peripheral nervous system, in combination with the pathology of the musculoskeletal system, often occurring among workers of hazardous industries. Based on the analysis of electroneuromyographic and radiological research methods in 60 workers performing work with the impact of local vibration and physical overload, the degree of impairment of the peripheral nervous system and the musculoskeletal system of the upper limbs was studied in comparison with persons whose labor activity excluded contact with these labor factors. A relationship has been established between the severity of clinical and instrumental data obtained with the duration of exposure to harmful factors. Identification of lesions of the peripheral nervous system and the locomotor apparatus will ensure timely prevention and adequate therapeutic measures.

Research for axial power distribution control of a space nuclear reactor based on nonlinear model

During the operating process of a space nuclear reactor, once the local overload of heat energy occurs in the core, the corresponding fuel elements would be damaged and the lifespan of the reactor would be seriously reduced. In fact, the heat flux at any point in the core is proportional to the neutron flux density. A sufficiently flat axial neutron flux density distribution can protect the fuel assembly from frequent load changes. It is so clear that the axial power distribution control is crucial for the safe and stable operation of the space nuclear reactor. However, the space nuclear reactor is a distributed parameter system, which brings great challenges to the traditional lumped parameter control methods. In this paper, a distributed parameter control method is proposed to suppress the initial neutron flux peaks and realize the exponential stability of the neutron flux distribution control system. First of all, the spatiotemporal model of the reactor core based on the neutron diffusion equation is established. Then, the stability analysis of the control law for the neutron flux distributed parameter control problem is performed by constructing the Lyapunov function. The optimization technique based on the spatial differential linear matrix inequality is used to approximate the solution of the suboptimal integral control law. The control law is implemented by rotating drum, and the flat distribution of the axial power of the core is realized by the distributed parameter control. Finally, the numerical results are provided to validate the feasibility of the proposed control scheme.

Development of a crushable foam model for human trabecular bone

Finite element (FE) simulations can be used to evaluate the mechanical behavior of human bone and allow for quantitative prediction of press-fit implant fixation. An adequate material model that captures post-yield behavior is essential for a realistic simulation. The crushable foam (CF) model is a constitutive model that has recently been proposed in this regard. Compression tests under uniaxial and confined loading conditions were performed on 59 human trabecular bone specimens. Three essential material parameters were obtained as a function of bone mineral density (BMD) to develop the isotropic CF model. The related constitutive rule was implemented in FE models and the results were compared to the experimental data. The CF model provided an accurate simulation of uniaxial compression tests and the post-yield behavior of the stress-strain was well-matched with the experimental results. The model was able to reproduce the confined response of the bone up to 15% of strain. This model allows for simulation of the mechanical behavior of the cellular structure of human bone and adequately predicts the post-yield response of trabecular bone, particularly under uniaxial loading conditions. The model can be further improved to simulate bone collapse due to local overload around orthopaedic implants.

Analysis and Prediction of Overloaded Extra-Heavy Vehicles for Highway Safety Using Machine Learning

Along with the prosperity and rapid development of the national economy, the transportation industry has rapidly developed in China. However, overloaded vehicles have been causing frequent traffic accidents. Thus, to alleviate or resolve the corresponding problems associated with highway engineering safety and the market economy, an improved technique for overload management is urgently required. In this study, to analyze the overload data on expressways and highways in China, we developed a machine learning model by comparing the performances of cluster analysis, backpropagation neural network (BPNN), generalized regression neural network (GRNN), and wavelet neural network (WNN) in analyzing global and local time series overload data. In a case study, our results revealed the trends of overloading on highways in Jiangsu Province. Given sufficient data, BPNN performed better than GRNN and WNN. As the amount of training data increased, GRNN performed better, but the runtime increased. WNN had the shortest runtime among the three methods and could reflect the future trends of the overload rate in the monthly data prediction of overload. Our model provides information with potential value for expressway network management departments through data mining. This information could help management departments allocate resources reasonably and optimize the information utilization rate.

Development of an Efficient Tool for Solar Charging Station Management for Electric Vehicles

One important goal of the climate commitment in the European Union (EU) is to reduce primary energy demand in the transport sector and increase the use of renewables, since around 33% of primary energy is consumed in this sector. Therefore, the EU ordered its member states to raise the number of electric vehicles (EVs) within Europe. Consequently, the energy demand for electricity will rise as a function of the number of EVs. To avoid local grid overload and guarantee a higher percentage of clean energy, EV charging stations can be supported by a combined system of grid-connected photovoltaic modules and battery storage. In this paper, the focus lies on the feasibility and economic aspects of such systems. To provide an overview of the different e-charging station combinations, a support tool was modelled and developed, making it possible to size and manage EVs charging stations with only a few input parameters. Thanks to its easy handling, the tool suits a wide spectrum of users. Due to enhanced optional settings, this tool is suitable for detailed input parameters for professionals as well. Input categories are basically divided into the photovoltaic (PV) system, battery storage, the charging station itself, and investment analysis. The tool supports decisions for solar charging stations designed for different parking locations like offices, schools, and public and private places.

THE RESEARCH OF THE RAILWAY RAIL FOR ANALYSIS OF SURFACE INITIATED ROLLING CONTACT FATIGUE CRACKS

Problems. Under the influence of dynamic loading from trains and natural conditions, the railway track deteriorates, characterized by the appearance of defects and residual deformations of the railway track, which lead to accelerated wear and malfunction of other elements of the rail. The appearance of the specified defects, failures and destructions of the elements of the rail grating is associated with the action of additional local stresses arising in the rails of the railway track. On a low-quality track grating with deviations of the parameters of the rail track, when the train is moving, there is an unaccounted interaction of the track and rolling stock with local overload of the interaction elements along the path. As a rule, the unaccounted interaction of track and rolling stock is accompanied by the impact of the wheel and the rail with overloading the contact area. When the impact of the wheel and rail strikes, stresses exceeding the endurance limit occur in the rail head. In this case, the rails are born in the head and begin to develop defects of contact-fatigue origin in the form of horizontal vertical and transverse cracks.The aim of the study. Conducting practical studies of the origin and development of contact-fatigue cracks by wear of the rails in the laboratory.Methods of implementation. An experimental unit was designed and manufactured to investigate the rails for contact damage. The unit is mounted on a mechanical single-cylinder press of the K 2322 model with a nominal force of 16 tons at a nominal stroke frequency of 120 per minute. The bulk of the experimental setup contains a wheel-rail friction unit. The force of clamping the rail to the wheel. Provides a hydraulic system. For testing, a test program was developed, which provides for two-hour tests, after which tests for the presence of defects (micro cracks) on the rail are conducted. Research on the presence of defects is carried out by the method of magnetic powder non-destructive testing.Research results. Studies have shown that contact-fatigue cracks in the rail head occurred after approximately 200 thousand load cycles. This generally coincides with the results presented in other papers, which show the occurrence of similar damage after 190-290 thousand cycles, depending on the properties of rail steel (hardness, surface roughness, etc.).Conclusions. The main cause of the origin and development of contact fatigue defects in the rail head is insufficient contact fatigue strength of the rail steel. For carrying out practical researches in laboratory conditions the methodology was developed, the experimental unit was constructed and made. Experimental studies have shown that the occurrence of defects on the surface of the rail is observed after 200-250 thousand load cycles. With the further increase in the number of load cycles, there is a rapid development of existing contact-fatigue cracks and the formation of new cracks in the contact zone.

Development of the method of distribution of memory in nonstationary loaded information processing systems

The trend of growing capacity of modern infrastructures and popularity of network services raises the requirements for multi-server information processing systems they work with. The occurrence of events on a regional and global scale affects the activity of processed data streams, which can lead to losses of processed information and decrease in the quality of services for end users. The dependence of the variation coefficient of time intervals between adjacent requests and the probability of loss of the request processed by the software module is found. The two-level control scheme of the shared memory resource of all modules and the functioning algorithm of managers are proposed. The experiment proves the efficiency of the developed method and algorithm for abnormal situations. This method is applicable and effective for various information processing systems and will allow the rational use of computing resources. The application of the method will allow preserving the efficiency of information processing systems for cases of local overload of nodes. Practical implementation of the method will reduce losses of processed information to 10 %. This is especially important for systems that process user-defined data streams based on the concept of software-defined networks.

СОЕДИНЕНИЕ АВТОМОБИЛЬНЫХ ПРОВОДНИКОВ МЕТОДОМ УЛЬТРАЗВУКОВОЙ СВАРКИ. ПОЖАРНАЯ ОПАСНОСТЬ

Introduction. Nowadays ultrasonic welding of metals including conductors is widely used. The con­nection of copper conductors by ultrasound is based on high-frequency oscillations. Materials and methods. Copper stranded conductors interconnected by ultrasonic welding were chosen as the materials for the study. The study of these samples was carried out in the laboratory by metallographic analysis. Results and discussion. In case of a poor contact at the connection point, a large transient resistance may occur when an electric current passes through a given point and cause fire. To establish the involvement of a poor adhesion to the occurrence of a fire, it is necessary to conduct metallographic studies of the compound. With qualitatively performed welding, fusion of individual sections of wires at the junction site is observed, while in the case of a “poor” connection, clearly defined boundaries are observed. A very long exposure to ultrasound in the welding process on the connected conductors leads to a de­crease in the plasticity of the conductor, which in turn leads to the fracture of the veins near the junction and, as a consequence, to the emergence of local current overload. Where the places of rupture after the fire are melted and smoked, indicates that the test conductor was damaged even before the ignition of the vehicle. Conclusion. Thus, the possibility of vehicle combustion as a result of a poorly executed connection of conductors by ultrasonic welding is shown. It is noted that the fire can be caused by uncompleted welding (“non-fusion” of the conductors), or vice versa when an impact of ultrasonic waves on the conductors to be connected has been too long. It is necessary to withdraw this connection directly at the seat of fire for further laboratory metallo­graphic research.

Multilayer collaborative traceback technique based on net-flow fingerprint

Aimed at loop fallacy, indeterminate serialisation of suspicious nodes and local overload problems of suspicious information source traceback in net-flow exchange, this paper proposes a multilayer collaborative traceback technique based on net-flow fingerprint. The traceback is divided into controllable inter-AS layer, intra-AS routing layer and controllable subnet layer. Based on the characteristics of each layer, it achieves efficient suspicious path extraction in controllable inter-AS layer by BGP protocol properties. In intra-AS routing layer, it solves loop fallacy by directed graph transformation and indeterminate serialisation of suspicious nodes by local time relationship approach. In controllable subnet layer, it achieves precise location by using forwarding tables. What is more, by proposing multilayer collaborative approach, it improves the efficiency of suspicious path extraction and reduces local overload of traceback servers without compromising the accuracy of traceback. Finally, the correctness and computational complexity of NFCMT are proved, and the feasibility and correctness of this scheme are discussed by experiments.

Dynamic Load Balancing With Handover in Hybrid Li-Fi and Wi-Fi Networks

In this paper, a hybrid network combining light fidelity (Li-Fi) with a radio frequency (RF) wireless fidelity (Wi-Fi) network is considered. An additional tier of very small Li-Fi attocells which utilize the visible light spectrum, offers a significant increase in the wireless data throughput in an indoor environment, while at the same time providing room illumination. Importantly, there is no interference between Li-Fi and Wi-Fi. A Li-Fi attocell covers a significantly smaller area than a Wi-Fi access point (AP). This means that even with a moderate user movement a large number of handover between Li-Fi attocells can occur, and this compromises the system throughput. Dynamic load balancing (LB) can mitigate this issue so that the quasi-static users are served by Li-Fi attocells, while moving users are served by a Wi-Fi AP. However, due to the user movement, local overload situations may occur which prevent handover, leading to a lower throughput. This research studies LB in a hybrid Li-Fi/Wi-Fi network by taking into account user mobility and handover signalling overheads. Furthermore, a dynamic LB scheme is proposed, where the utility function considers system throughput and fairness. In order to better understand the handover effect on the LB, the service areas of different APs are studied, and the throughput of each AP by employing the proposed LB scheme is analyzed.

Contact damage of hard and brittle thin films on ductile metallic substrates: an analysis of diamond-like carbon on titanium substrates

Friction and wear minimizing coatings are crucial for applications in combustion engines and medical implants. Their performance is typically limited by mechanical failure especially due to local overload. In this work, the contact damage creation, evolution, and final morphology of hydrogenated diamond-like carbon (DLC)-coated titanium (Ti) substrates are investigated. The influence of the DLC film thickness and the elastic–plastic deformation of the Ti on the contact damage are studied by microindentation and static finite-element analysis. Film thickness, indenter radius, and applied load as well as the elastic–plastic deformation of the Ti are shown to significantly affect contact damage. A failure plot is presented with the location of first failure in the DLC and compared to the experimental observation. In addition, a case study with variable fracture toughness of the DLC and its influence on the failure plot is shown. The stress distribution in the DLC follows a transition from a membrane-like to a plate-like deformation behavior upon increasing the DLC film thickness. Thin DLC films reveal increased cracking in the inner zone of the indent, while thicker DLC films reveal pronounced edge cracking. These edge cracks were correlated to pop-ins in force–displacement curves upon microindentation. Finally, a film thickness optimization process is presented for hard and brittle films on soft and ductile metallic substrates.

Critical phenomena in communication/computation networks with various topologies and suboptimal to optimal resource allocation

We generalize previous studies on critical phenomena in communication networks [1,2] by adding computational capabilities to the nodes. In our model, a set of tasks with random origin, destination and computational structure is distributed on a computational network, modeled as a graph. By varying the temperature of a Metropolis Montecarlo, we explore the global latency for an optimal to suboptimal resource assignment at a given time instant. By computing the two-point correlation function for the local overload, we study the behavior of the correlation distance (both for links and nodes) while approaching the congested phase: a transition from peaked to spread g(r) is seen above a critical (Montecarlo) temperature Tc. The average latency trend of the system is predicted by averaging over several network traffic realizations while maintaining a spatially detailed information for each node: a sharp decrease of performance is found over Tc independently of the workload. The globally optimized computational resource allocation and network routing defines a baseline for a future comparison of the transition behavior with respect to existing routing strategies [3,4] for different network topologies.

Research on the optimal initial shunt strategy of Jiuzhaigou based on the optimization model

Tourism load imbalance is a serious problem in Jiuzhaigou, which may destroy the environment and reduce the feeling of tourists. A reasonable initial shunt strategy is the key factor in making the scenic become balance. So, this paper considers this problem by finding an optimal initial shunt strategy. An optimization model containing two flow models is built, which takes the total overload balance as objective. In order to solve this model and find the optimal initial shunt strategy, a hGA is proposed as solution method. Finally, a comparison analysis is conducted to show the efficiency of this model in remitting the local overload problem.

A Dynamic Replication Algorithm Based on Access Popularity in Cloud Storage Environment

Replication technology is a very important data management in cloud storage. Traditional replication control methods cannot usefully solve the load imbalance caused by the hotspot access. This paper proposed a dynamic replication algorithm based on access popularity called APDRA. Replicas were created and deleted dynamically according to the popularity of data, situation of the system and the load of nodes, effectively solving the problem of local overload caused by hot spot access and the recovery of idle replicas. In the end, the superiority of APDRA was verified by experiment.

Study on Structure and Performance Optimization for Spherical Stern Bearing Based on ANSYS

Spherical stern bearing is kind of new bearing, which combines ordinary water lubricated stern bearing with sphere bearing. It has function to adjust contact situation of stern bearing and stern shaft automatically, decreases pressure peak, leads to pressure distribution on the bearing being more uniform, helps to overcome the problem of local overload to avoid edge effect and improves damping performance. On the base of the ANSYS software, the contact deformation and pressure calculation of spherical stern bearing are carried out to compare with ordinary stern bearing and analyse the effectiveness of reducing pressure on bearing, optimization problems of the sphere position and sphere diameter are discussed, which shows that the contact pressure achieves a minimum when the sphere is located at intermediate position of bearing bush and the maximum contact pressure decreases with the increase of sphere diameter, and they have linear relation.

Rheumatic Diseases and Obesity: Adipocytokines as Potential Comorbidity Biomarkers for Cardiovascular Diseases

Inflammation has been recognized as a common trait in the pathogenesis of multifactorial diseases including obesity, where a low-grade inflammation has been established and may be responsible for the cardiovascular risk related to the disease. Obesity has also been associated with the increased incidence and a worse outcome of rheumatoid arthritis (RA) and osteoarthritis (OA). RA is characterized by systemic inflammation, which is thought to play a key role in accelerated atherosclerosis and in the increased incidence of cardiovascular disease, an important comorbidity in patients with RA. The inflammatory process underlying the cardiovascular risk both in obesity and RA may be mediated by adipocytokines, a heterogeneous group of soluble proteins mainly secreted by the adipocytes. Many adipocytokines are mainly produced by white adipose tissue. Adipocytokines may also be involved in the pathogenesis of OA since a positive association with obesity has been found for weight-bearing and nonweight-bearing joints, suggesting that, in addition to local overload, systemic factors may contribute to joint damage. In this review we summarize the current knowledge on experimental models and clinical studies in which adipocytokines were examined in obesity, RA, and OA and discuss the potential of adipocytokines as comorbidity biomarkers for cardiovascular risk.