Design Of Protection Devices Research Articles

Analysis of damage to ship personnel in different seated postures by near-field underwater explosions

With the frequent occurrence of ship explosion accidents at sea, the safety of ships and crews has attracted much attention. At present, the research on crew injury is relatively weak. Consequently, the current study constructs a numerical model of the ship structure-crew-blast flow field to investigate the discrepancies in injury response of crew members across different sitting postures. LS-DYNA software is used for simulation and direct analysis to evaluate the damage of crew members in different positions under 100 kg TNT equivalent and 2 m blast distance conditions, and the relationship between different explosive equivalents and crew damage is analyzed. The results demonstrate that for crew members situated in working compartment, the injuries incurred across different sitting postures also differed. The lower leg and foot sections were at greater injury risks, while the head area was associated with minimal damage risks. Altering upper body postures of the crew human body had only a very small impact on lower extremity injuries. Moreover, positive correlations were exhibited between explosive equivalents and crew injury values. The research findings may offer references for injury analysis and protective device design of naval personnel.

6DOF knee kinematic alterations due to increased load levels.

Whether load carriage leads to six-degrees-of-freedom (6DOF) knee kinematic alterations remains unclear. Exploring this mechanism may reveal meaningful knee kinematic information that can be used to improve load carriage conditions, the design of protective devices, and the knowledge of the effects of load carriage on knees. We recruited 44 subjects to explore kinematic alterations from an unloaded state to 60% bodyweight (BW) load carriage. A three-dimensional gait analysis system was used to collect the knee kinematic data. One-way repeated analysis of variance (ANOVA) was used to explore the effects of load levels on knee kinematics. The effects of increasing load levels on knee kinematics were smooth with decreased or increased trends. We found that knees significantly exhibited increased lateral tibial translation (up to 1.2 mm), knee flexion angle (up to 1.4°), internal tibial rotation (up to 1.3°), and tibial proximal translation (up to 1.0 mm) when they went from an unloaded state to 60%BW load carriage during the stance phase (p < 0.05). Significant small knee adduction/abduction angle and posterior tibial translation alterations (<1°/mm) were also identified (p < 0.05). Load carriage can cause significant 6DOF knee kinematic alterations. The results showed that knee kinematic environments are challenging during increased load. Our results contain kinematic information that could be helpful for knee-protection-related activities, such as target muscle training to reduce abnormal knee kinematics and knee brace design.

Breaking the Symmetry of Cable Structures as an Instrument for Improving Modal Decomposition to Protect Critical Equipment against UWB Pulses

This work presents a detailed, comprehensive study of a new structural design of protective devices with a circular cross-section (CS) (protective cables) for protecting equipment against ultra-wideband (UWB) pulses. Multiconductor structures with 2–5 conductors with and without a protective shield are considered. The disadvantages of using symmetric configurations of protective cables are shown. Their simulation, multivariate analysis, and optimization through heuristic search, as well as evolutionary strategies, were carried out. Optimization was carried out according to the amplitude (to minimize the maximum voltage level at the output of the structures) and time (to maximize the duration of the exciting signal) criteria. The optimization results allowed for increasing the duration and overall attenuation of the exciting UWB pulse. The article shows the possibility of improving the characteristics of such structures through their cascade connection, both among themselves and with strip protective structures. The results of parametric optimization of such structures are presented in the range of real (used in practice) geometric and electrophysical parameters in terms of amplitude and time criteria, as well as the matching criterion. The article also presents the developed prototypes of protective structures with a circular CS of three types: circular 3-conductor cable, flat 3-conductor cable, and circular 4-conductor cable. The experimental results describe how these prototypes were developed and created and confirm the feasibility of these protective structures to decompose the exciting pulse signal, which was previously shown only in simulation. Finally, it is shown that the use of asymmetry in the proposed cable structures can improve their protective characteristics.

Моделирование защитных устройств для обеспечения безопасности технологических процессов с использованием взрывоопасных газов

The article presents a calculation algorithm for the theoretical substantiation of the design of protective devices used for the safe operation of explosive equipment and supply lines. Mathematical modeling is applied. The development of protective devices providing explosion and fire safety of gas-flame equipment used in construction is considered. The design of protective devices providing explosive and fire hazardous gases from deflagration to detonation combustion modes and devices developed on the principle of cutting off the flame by means of mechanical actuation of locking elements: a membrane and a conical valve are presented.

The biomechanics of injury and prevention

The biomechanics of injury and prevention is an important branch of modern biomechanics and a multi-disciplinary subject that is applied to the analysis of the mechanism of biological tissue or organ damage and its prevention. The goal of it is to prevent the human body from damage or minimize injury for tissue or organ when subjected to loads. It covers the study of the response of tissue subjected load, the mechanism and the tolerance of injury, and the methods and effective devices to reduce injury. Higher loads have high lethality due to its short-term action and explosiveness. Therefore, the ability to anti-injury under overload has been a severe constraint for the development of aircraft, the improvement of automobile performance and the enhancement of athletes' competitive ability. In particular, the emergence of the modern faster and more flexible fighter, the life-saving of supersonic ejection and the protective of maneuver flight of high load and load has presented new challenges for the subject of injury and prevention biomechanics but also provided enormous opportunities for the development of it. In recent years, the impact injury involved in aerospace, traffic accidents, sports and falls of the elder has presented the features of high incidence and low protection efficiency. However, it is difficult to obtain the actual data due to the damage caused by experiments to humans. Meanwhile, since the biological tissue has the characteristics of nonlinearity, viscoelasticity, regeneration and reconstruction, it involves how to describe the constitutive relations of biological tissue or organs, and the correlation between the anatomical features and its mechanical properties accurately. It also involves how to establish the mechanism and tolerance of tissue injury at multi-scales, the methods and the principle to design protective devices. The present paper focuses on the summarization of the major research contents and its methods to the biomechanics of injury and prevention. The types, mechanisms (including the response of the biomechanics and mechanobiology), tolerance, and the protective method of injury under complex loading for the human body are summarized, and the primary advancement and the possible tendency of development in these fields are introduced. The study on the biomechanics of injury and prevention is of great significance to protect and improve human safety under complex load. It could guide the establishment of standards and evaluation methods of musculoskeletal injuries involved in aerospace, transportation, and sports. This research is vital to guide the optimization design of protective devices and has great potential to the development and application of bionic engineering materials and protective devices.

Investigation on the transient stability of hydro generator working with power grid

Huge hydro-generator is the inevitable development trend of hydro-generator for utilization of water resources. It is very necessary to research the technical issues for 1000MW hydro-generator. Whether the short-circuit faults locate at the generator terminal or the end of transmission line, the transient stability of hydro-generator is calculated and analyzed based on the field-circuit coupling model. Short-circuit fault must be cleared immediately in order that the power system and generator can maintain stable operation, in this paper, fault clearing time limit under different conditions is obtained by mass of simulation. The results obtained in this paper can provide valuable reference for the actual operation of 1000MW hydro-generator, and it is also useful and valuable for the design of protection devices, the dispatching of power grid and the debugging of generator when be connected to power grid.

Response of 10-kV Metal-Oxide Surge Arresters Excited by Nanosecond-Level Transient Electromagnetic Disturbances

Nanosecond-level transient electromagnetic disturbance (TED), including very fast transient overvoltage caused by operation of disconnectors, high-altitude electromagnetic pulse, and many other fast transients may interfere or even damage the electrical equipment. As one of the main overvoltage protective equipment, the protective performance of metal-oxide surge arresters (MOAs) under nanosecond-level TED should be investigated and then compared with that under microsecond-level TED, especially the lightning impulse. Based on a testing platform containing a 400-kV pulse generator with adjustable rise time from 5 to 100 ns, the behaviors of nonlinearity, fast impulse response, and converting impedances of three types of 10-kV MOAs under TED with different rise time were explored experimentally in this article. The peak residual voltages of 10-kV MOAs under TED with the rise time of 5 ns at 5 kA are 50.2-60.7% higher than those under the lightning impulse. The rise time of TED has significant influence on the peak voltage and impedance converting behaviors of MOAs. A circuit model of 10-kV MOAs under nanosecond-level TED is built and validated by experimental results, which can be applied in insulation coordination and design of protective devices against TED.

Kurşun Asit Aküler İçin Kalıcı Sülfatlaşmayı Ortadan Kaldıran Yenilikçi Bir Akü Koruma Cihazı Tasarımı

Akülerde çalışma kalitesini belirleyen en temel ölçüt kutuplar arasındaki gerilim seviyesinin kararlılığı olup bu kararlılığı bozan temel sebep akü elektrolizinde meydana gelen "sülfatlaşma" olayıdır. Sülfatlaşma aküde plakalar arasında kısa devre oluşumu gibi akü açısından kritik arızalara sebebiyet verebilecek ve akünün servis süresinden daha kısa sürede değiştirilmesi ile sonuçlanacaktır. Bu çalışmada akülerde sülfatlaşma probleminin akü vazife görürken ve beklerken elektrokimyasal tepkime kontrolü yapılarak azaltılması veya kurşun asit akülerde kalıcı sülfatlaşmanın oluşumunun engellenmesi maksadıyla akü kutuplarından genliği ve frekansı ayarlanabilen sinyaller ile akünün uyarılarak elektrokimyasal tepkime kontrolü sağlayabilen bir akü koruma cihazı tasarımı yapılmıştır.

Cyber Physical Security Analytics for Anomalies in Transmission Protection Systems

Protection systems are one of the most critical components in the transmission system and are becoming more digital with ongoing automation. These digital systems are prone to vulnerabilities/attacks, and exploitation of these vulnerabilities may cause major impacts on the electric grid performance. Multiple alarms reported in the control center could be a result of the faults (expected operations) or failures in the protection system (anomalies/ unexpected operation). Situational awareness gained through sensors such as a phasor measurement unit (PMU) and data acquired through the cyber system provide an opportunity to develop continuous cyber-physical monitoring of the system. Note that relay data are not reported in the control center continuously. This paper presents a cyber-physical data analytics based technique to monitor transmission protection system and detect malicious activity. Initially, continuous monitoring of PMU data is utilized for data anomaly detection, which includes bad or missing data using long short-term memory (LSTM). Then, PMU data of interest are utilized for failure diagnosis, using a semisupervised deep autoencoder model. In this research, cyber anomalies are modeled by manipulating the setting/logic design of protective devices, and a ridge regression based classifier with a feature engineering pipeline is used to detect cyber anomalies. The results from the deep autoencoder model and ridge regression based classifier are then utilized for detailed investigation to find the root causes of the observed events assisted by the cyber log data from the protection devices. The algorithm is validated using a real-time simulation of the IEEE test system with industrial hardware relays and PMUs in the loop. Data analytics algorithm running on server utilizes these real-time data continuously for anomaly detection and classification for the developed use cases.

Rocking response of inverted pendulum structures under blast loading

We investigate the dynamics of inverted pendulum structures under fast-dynamic excitations arising from an explosion. We model blast actions using established empirical models and best-fit interpolations of existing experimental tests. We focus attention on pure rocking response mechanisms. We present moment balance equations and overturning conditions. Inspired by previous works in the frame of earthquake engineering, we derive new analytical, closed-form solutions for the rocking response and the overturning domain of slender blocks due to explosions.The analytical findings and assumptions are validated through existing experimental tests and detailed three-dimensional numerical simulations, which consider the full interaction between the blast waves and the structure. We show that unilateral rocking response and overturning are predominant mechanisms compared to sliding and up-lifting.Finally, we develop design charts to be used as a straightforward decision making tool for determining the critical stand-off distance between the explosive source and the target in order to prevent overturning. Our model can be easily applied for the design of protective devices to preserve artefacts, secure buildings and humans, as well as for devising energy absorbing systems based on rocking.

A fully nonlinear viscohyperelastic model for the brain tissue applicable to dynamic rates

Understanding the mechanical response of the brain to external loadings is of critical importance in investigating the pathological conditions of this tissue during injurious conditions. Such injurious loadings may occur at high rates, for example among others, during road traffic or sport accidents, falls, or due to explosions. Hence, investigating the injury mechanism and design of protective devices for the brain requires constitutive modeling of this tissue at such rates. Accordingly, this paper is aimed at critically investigating the physical background for viscohyperelastic modeling of the brain tissue with scrutinizing the elastic fields pertinent to large, time dependent deformations, and developing a fully nonlinear multimode Maxwell model that can mathematically explain such deformations. The proposed model can be calibrated using the simple monotonic uniaxial deformation of the sample extracted from the tissue, and does not require additional information from relaxation or creep experiments. The performance of the proposed model is examined using the experimental results of two different studies, which reveals a desirable agreement. The usefulness, limitations, and future developments of the proposed model are discussed in this paper.

Cognition based bTBI mechanistic criteria; a tool for preventive and therapeutic innovations

Blast-induced traumatic brain injury has been associated with neurodegenerative and neuropsychiatric disorders. To date, although damage due to oxidative stress appears to be important, the specific mechanistic causes of such disorders remain elusive. Here, to determine the mechanical variables governing the tissue damage eventually cascading into cognitive deficits, we performed a study on the mechanics of rat brain under blast conditions. To this end, experiments were carried out to analyse and correlate post-injury oxidative stress distribution with cognitive deficits on a live rat exposed to blast. A computational model of the rat head was developed from imaging data and validated against in vivo brain displacement measurements. The blast event was reconstructed in silico to provide mechanistic thresholds that best correlate with cognitive damage at the regional neuronal tissue level, irrespectively of the shape or size of the brain tissue types. This approach was leveraged on a human head model where the prediction of cognitive deficits was shown to correlate with literature findings. The mechanistic insights from this work were finally used to propose a novel protective device design roadmap and potential avenues for therapeutic innovations against blast traumatic brain injury.

Identifying Electric Shock in the Human Body via $\alpha$ Dispersion

The ability to identify electric shock in the human body is a crucial consideration in the design of touch/leakage protective devices. In this paper, the $\alpha$ -dispersion characteristics of electrical impedance in the human body are investigated based on the Cole–Cole model. An improved electric shock identification method is proposed accordingly. The effects of various factors (e.g., transition resistance and feeder reactance) on the accuracy and reliability are analyzed. Feasibility and effectiveness of the method are verified via numerical simulation. The results indicate that 1) $\alpha$ -dispersion is an effective feature for distinguishing living or nonliving organisms; 2) the proposed method is robust and unaffected by transition resistance; and 3) the computational cost is low to satisfy standard leakage current protective device requirements. This paper provides a solution to the dead-zone problem as well as a set of workable guidelines for protective device design.

Measuring the External Ear for Hearing Protection Device Design

In this study we aimed to obtain anthropometric measurements of external ear dimensions for designing hearing protection devices (HPDs). We measured 3 dimensions of left and right ears of 153 operational workers and compared the measured data with earplugs (Eps) and earmuffs (Ems). The mean (± SD) earhole length, pinna length, and pinna width for the subjects were 14.6 (± 2.5), 62.8 (± 5.0), and 34.8 (± 4.2) mm, respectively. The mean longitudinal and transverse diameters of the Ems for the ear were close to the 95th and 97.5th percentile, respectively. The Ems met the optimal threshold of ergonomic design; however, the Eps required a better design.

Rheological characterization of human brain tissue.

While recent experiments have shaped our understanding of the time-independent, hyperelastic response of human brain tissue, its time-dependent behavior at finite strains and under various loading conditions remains insufficiently understood. In this manuscript, we characterize the rheology of human brain tissue through a family of finite viscoelastic Ogdentype models and identify their parameters for multiple loading modes in four different regions of the brain. We show that even the simplest model of this family, with only one viscoelastic mode and five material parameters, naturally captures the essential features of brain tissue: its characteristic nonlinearity, pre-conditioning, hysteresis, and tension-compression asymmetry. For the first time, we simultaneously identify a single parameter set for shear, compression, tension, shear relaxation, and compression relaxation loading. This parameter set is significant for computational simulations under physiological conditions, where loading is naturally of mixed mode nature. Understanding the rheology of the human brain will help us predict neurosurgical procedures, inform brain injury criteria, and improve the design of protective devices.

Methodology of Automated Protection Analysis for Large Distribution Feeders With High Penetration of Photovoltaic Systems

This paper presents highly automated methods to study the protective device coordination in large distribution systems with high penetration of distributed photovoltaic (PV) generation. A real distribution feeder with large-scale distributed PV generation has been modeled and verified using the analysis tool OpenDSS and utilizing extensive field measurements. With the accurate and validated feeder model, thorough protection coordination of the system is investigated by applying all the possible phase and ground faults under various scenarios. Under varying PV penetration levels and with different PV interface transformer connections, settings for the phase and ground relay and recloser are verified/defined, such that proper coordination is achieved for the entire feeder under all operating conditions, corresponding to both fuse-clearing and fuse-saving schemes. An optimization-based design of protective devices is introduced that ensures proper protection coordination under thousands of possible fault cases. The automated protection analysis has been implemented using OpenDSS with the MATLAB COM interface, and this approach and these tools can be extended to analyze and design protection coordination of any large distribution feeder, as well as to use as a screening tool while evaluating large scale PV on distribution feeders.

Enhanced stress wave attenuation of single-walled carbon nanotube lattice via mass mismatch-induced resonance

Nanoscale homogeneous single-walled carbon nanotube lattice exhibits extraordinary attenuation performance and ultrahigh specific energy absorption upon high-velocity impact. However, upon relatively low impact velocity (for example, < 1000 m/s), this system does not possess a good stress wave attenuation performance where severe damage may still occur. To overcome this disadvantage, a new attenuation mechanism is introduced to carbon nanotube lattice via the creation of mass mismatch, i.e. carbon nanotube dimer lattice. Under specific mass ratio, a strong inherent resonance happens, resulting in an evident attenuation of the propagating pulse. The joint effect of mass mismatch-induced resonance and dissipative nature of carbon nanotube lattice make it ideal for both high and low-velocity impacts. Additionally, specific energy absorption is improved due to the mass reduction. This work reveals the possibility to achieve much higher energy dissipation by exploiting the system's inherent dynamics, suggesting a new strategy of lightweight design of protective devices and the potential of technological applications of nanoscale nonlinear granular crystals.

Optimal Design of Seismic Protective Devices for Highway Bridges Using Performance-Based Methodology and Multiobjective Genetic Optimization

AbstractThis study investigates the effectiveness and optimal design of protective devices for the seismic protection of highway bridges. The Painter Street Overcrossing is seismically redesigned with protective devices. Component-level fragility functions are first derived by probabilistic seismic demand analysis using nonlinear time history analyses that include soil–structure interaction effects and ground motion uncertainties. The bridge repair cost ratios are then derived using a performance-based methodology and the associated component failure probability. Results of the comparison of two initial protection designs show that the bridge repair cost ratios provided an efficient evaluation of the protective devices. Subsequently, a multiobjective genetic optimization method utilizing the Pareto optimal concept is employed to identify the optimal design parameters of protective devices for six design cases with various combinations of isolation bearings and fluid dampers. Finally, the repair cost ratio...

Research Update: Strategies for improving the stability of perovskite solar cells

The power-conversion efficiency of perovskite solar cells has soared up to 22.1% earlier this year. Within merely five years, the perovskite solar cell can now compete on efficiency with inorganic thin-film technologies, making it the most promising of the new, emerging photovoltaic solar cell technologies. The next grand challenge is now the aspect of stability. The hydrophilicity and volatility of the organic methylammonium makes the work-horse material methylammonium lead iodide vulnerable to degradation through humidity and heat. Additionally, ultraviolet radiation and oxygen constitute stressors which can deteriorate the device performance. There are two fundamental strategies to increasing the device stability: developing protective layers around the vulnerable perovskite absorber and developing a more resilient perovskite absorber. The most important reports in literature are summarized and analyzed here, letting us conclude that any long-term stability, on par with that of inorganic thin-film technologies, is only possible with a more resilient perovskite incorporated in a highly protective device design.

Stress-strain response analysis and protective device design for buried pipeline impacted by perilous rock

Collapse of perilous rocks is one of the most severe geological disasters for pipeline security. Stress-strain response of a buried pressure pipeline impacted by a perilous rock was simulated. Effects of impact velocity, rock’s radius, pipeline’s wall thickness, surrounding soil’s elastic modulus and Poisson’s ratio on stress, strain and deformation of the buried pipeline were investigated. The results show that the buried pipeline’s upper part is prone to instability under the rock impact. Plastic area of the buried pipeline becomes from oval to bat type with the impact load increases. Strain of the impact dent center is a compressive strain, while it is a tensile strain on the two sides of the dent. High stress area, axial strain and plastic strain of the buried pipeline increase with the increasing of impact velocity and rock’s radius, but they decrease with the increasing of wall thickness and soil’s elasticity modulus. Surrounding soil’s Poisson’s ratio has a small effect on the stress and strain of the pipeline. Impact dent’s size increases with the increasing of impact velocity and rock’s radius. Dent depth decreases with the surrounding soil’s elasticity modulus increases. With the wall thickness increases, impact dent depth first increases and then decreases. Finally, a protective device of buried pipeline is designed for preventing perilous rock impact. It can reduce the failure probability and improve the service life of buried pipeline for its simple structure and convenient installation.