Response Of Protection System Research Articles

Evaluation of frontal occupant protection system responses to crash pulse variations

Occupant Protection System (OPS) is a key component in today's vehicle systems to reduce occupant's injuries during collisions. To assess OPS performance under a wide variety of crash conditions, vehicle barrier tests, laboratory dynamic sled tests and computer simulations are the major tools for the systems development. As the main input to the system, vehicle crash pulse controls the OPS design. Its variations have significant impact on the overall system responses. A well-correlated MADYMO model is employed to evaluate the effects on a frontal OPS. A set of crash pulses are quantitatively analyzed to assess the sled repeatability. Statistical analyses are then performed to define the corresponding dummy dynamic response corridors. The results show that small crash pulse discrepancy could result in significant variations of dummy dynamic responses and injury measurements. This study has the potential to help design a robust occupant restraint system less sensitive to crash pulse variations.

Modeling of Mechanical Ablation in Thermal Protection Systems

An integrated thermomechanical modeling of response of low-temperature ablative thermal protection system under thermal loading encountered by reentry vehicles is presented. Of the three thermal protection mechanisms, thermal, chemical, and mechanical ablations, only the latter is assumed to influence the recession in the presence of aerodynamic surface shear for materials with low shear strength at higher temperatures. A model for the mechanical ablation (erosion) is presented that is based on the matching point scheme. The degenerated doubly curved shell element is employed in the modeling. This enables consideration of the general type of aerodynamic loads, distributed and varying with surface and time coordinates, which differs from the earlier studies reported in the open literature. The finite element method uses polynomial approximation to represent the nonlinear through-thickness temperature profile and explicit-through-thickness integration in the computation of element matrices. This brings in computational efficiency without loss of numerical accuracy, particularly in the context of multilayered construction. No attempt is made to compute the incident heat flux and other aerodynamic loads. Numerical examples are presented for specified loads to bring out the influences of material properties and heating rates on surface recession and are based mostly on assumed material properties.

Serious and fatal injuries to infants with discrepant parental explanations: some assessment and case management issues

AbstractThe objective of this study was to examine the challenges faced by child protection systems in assessment and case management where babies and infants have received serious and fatal physical injuries in the context of discrepant parent/carer explanations. Thirty‐eight case files or review records of children under the age of 2 with serious or fatal physical injuries were examined. Qualitative methods were employed to identify issues relating to types of parent/carer explanations, factors of concern in addition to the injuries and child protection system responses to the families. Findings indicate that the initial safety response by child protection systems to babies with serious injuries with discrepant explanations can be inadequate. Assessment of further risks could be inconsistent, especially in cases where there are few other factors of concern apart from the injury. There is a need for the development in the UK of more systematic decision‐making processes to achieve more consistent standards of assessment and case management of high‐risk infants and to minimize false‐negative and false‐positive predictions of further risk. Copyright © 2002 John Wiley & Sons, Ltd.

Thermostructural Analysis of X-34 Wing Leading-Edge Tile Thermal Protection System

Finiteelementthermaland stressanalysesarepresentedforceramictiles,assemblies,andarcjetmodelsrelevant to the thermal protection system for the X-34 wing leading edge. The analyses are performed to verify thermal and structural models for silicone impregnated reusable ceramic ablator, to establish a failure criterion for stressed tiles, to simulate the response of the wing leading-edge thermal protection system under e ight aerothermal and mechanicalloads,andtocone rm thatthedesignhasadequatesafetymargins.Thee naldesignwith0.04-in.intertile gaps is found to meet all thermal and structural requirements.

Calculation of lightning's EM effects on surrounding structure

A high-intensity current that is drained to the soil by a lightning protection system generates electromagnetic interference in its immediate surroundings. A mathematical model is presented for evaluating the electromagnetic fields induced in a device (simulated by an open square turn) positioned in a vulnerable area. The model is based on the dynamic analysis of the protection system's response to a lightning stroke. It takes into account the complete simulation of the complex phenomenology tied to the partial discharges of the ground electrode.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Adaptive transmission relaying concepts for improved performance

Concepts for adaptive protective relaying of transmission lines are presented. These include changes in online relay settings, relay characteristics, or logic in response to power system or environmental changes, or as a result of operating experience. Such changes as line-out or generator-out contingencies, which affect fault current distributions and degrade the system's security level, initiate adaptive protection system responses. Adaptive relaying is shown to be capable of improving relaying reliability and power system security and of achieving better utilization of transmission facilities. Most of the concepts require a hierarchical computer system, involving front-line parallel processors, a substation host, and remote central processors, all linked by channels that transmit data or relaying changes prior to or after a disturbance. It is suggested that maximum value from adaptive relaying will result from integration with existing or planned substation control and data acquisition functions and interfacing with the central energy management system (EMS). Emphasis is placed on use of interim hardware approaches to allow evolutionary development. >