Types Of Protection Systems Research Articles

Ballistic protection plates for military helicopters structures: Experimental and numerical research

The paper presents a combined experimental - numerical research that tries to evaluate the ballistic capabilities of three different types of protection plates having aluminum and/or steel skins and aluminum honeycomb core. Shootings with two types of bullets from a distance of 10 m were performed for each plate in an approved military training ground, which ensured the necessary safety and performance conditions. For each plate, the velocity before and after penetration was measured using an ultrafast camera, and a freeware code. The diameter of the hole made by the bullets was also measured. The experimental results were compared with the numerical ones obtained using the finite element method and a very good accuracy was noticed with differences less than 5%, validating thus the numerical models. The assessment of the degree of protection for each plate was made by evaluation of the energy absorbed by the plate from the kinetic energy of the bullet and by the reduction of the bullet velocity after penetration. The mass of each protection plate was also analyzed since it is a critical factor in the design of the ballistic protection systems. Conclusions were drawn regarding the efficiency of each of the three considered sandwich plates. The validation of the numerical models opens the path for the future assessment of other types of protection systems, made of lighter materials for the skins of the sandwich plates, namely fiber reinforced composites.

Li-Ion Battery Short-Circuit Protection by Voltage-Driven Switchable Resistance Polymer Layer

Safety issues with lithium-ion batteries prevent their widespread use in critical areas of technology. Various types of protective systems have been proposed to prevent thermal runaway and subsequent battery combustion. Among them, thermoresistive systems, representing polymer composites that sharply increase their resistance when the temperature rises, have been actively investigated. However, they are triggered only when the heating of the battery has already occurred, i.e., the system undergoes irreversible changes. This paper describes a new type of protective polymer layer based on the intrinsically conducting polymer poly[Ni(CH3OSalen)]. The response mechanism of this layer is based on an increase in resistance both when heated and when the cell voltage exceeds the permissible range. This makes it possible to stop undesirable processes at an earlier stage. The properties of the polymer itself and of the lithium-ion batteries modified by the protective layer have been studied. It is shown that the introduction of the polymer protective layer into the battery design leads to a rapid increase of the internal resistance at short circuit, which reduces the discharge current and sharply reduces the heat release. The effectiveness of the protection is confirmed by analysis of the battery components before the short circuit and after it.

Electrochemical characterization of corrosion in materials of grounding systems, simulating conditions of synthetic soils with characteristics of local soils

The integrity of structures buried in earthing becomes relevant when analysing maintenance and replacement costs of these systems, as the deterioration is mainly due to two factors, namely: the failures caused in the electrical systems, which are due to the system. Failure in earthing due to corrosion at the interface cause an alteration in the structure of the component material and generates an undesirable resistivity that cause malfunction in this type of protection systems. Two local soils were chosen that were categorized as sandy loam and clay loam type, whose chemical characteristics were simulated by means of an electrolyte corresponding to the amount of ions present determined by a soil characterization based on the CICE (effective cation exchange coefficient), which allows us to deduce the percentage of chloride and sulphate ions present for the different levels established in the experimental matrix. The interaction of these soils with grounding electrodes is a complex problem involving many factors to consider. In this study, the rates and corrosion currents of the different soils on two types of electrodes, one copper and the other AISI 304 stainless steel, were approximated by electrochemical techniques such as potentiodynamic curves and electrochemical impedance spectra. Considerably higher speeds were determined for copper-type electrodes when compared to those based on steel. However, from the Nyquist diagrams, it was noted that copper electrodes have better electrical performance than steel ones. The soil with the highest ionic activity turned out to be the sandy loam. The clay loam soil presents a tendency to water retention and this may be the reason for the different behaviour with respect to ionic mobility. The diffusion control in the steel seems to alter the ionic mobility because its corrosion rates proved to be very similar regardless of the type of soil chemistry. In general, corrosion rates fell since tenths of a millimetre every year to the hundredths of a millimetre in the case of the steel-based electrode, which are relatively small corrosion rates.

A Reliability Evaluation Method of a Protection System using Unavailability Tables and Event Trees

A reliability evaluation method of traditional Substation Automation System (SAS) has ever been well developed based on its physical configurations. However, appearance of Intelligent Electronic Devices (IED) based on IEC 61850 requires another type of evaluation with a functional viewpoint, because they integrate control and protection functions. This paper proposes a quantitative reliability evaluation method using an event tree method and unavailability of a module constituting an IED. It also states experimental results of the method applied to two types of protection systems that have a model of double bus bar and two transmission lines, and shows its effectiveness.

Early ischemic brain lesions after carotid angioplasty and stenting on diffusion-weighted magnetic resonance imaging study

Summary Aim: The aim of the paper is to evaluate the appearance of the new early ischemic lesions in the brain after carotid angioplasty and stenting on diffusion-weighted magnetic resonance imaging, and their relationship with clinical and procedural factors. Methods: Carotid artery stenting (CAS) procedures performed by a single interventional cardiologist in years November 2006 to January 2013 were evaluated retrospectively. In total, 227 procedures for 211 patients (mean age 69.8 ± 8.5 years) were performed, from which 171 (75.3%) for male and 56 (24.7%) for female patients. Seventy-two (34.1%) patients had symptomatic stenosis of carotid artery. The following protection systems to avoid the distal microembolism were used during the CAS: (1) Filters: FilterWire EZ (Boston Scientific Corporation); Emboshield NAV (Abbott Vascular); SpideRX (EV3); Defender (Medtronic); FiberNet Filter (Invatec-Medtronic); (2) Occlusion MoMa Baloon System (Invatec-Medtronic). Acute ischemic damages of the brain before and after CAS procedure were diagnosed using magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) sequences. Sixty-five (30.8%) patients underwent MRI test. Exact and asymptomatic χ2 criteria were applied for testing the hypothesis of inter-dependency of the symptoms. Results: Forty-six (70.8%) patients had new ischemic foci in the brain on MRI DWI after CAS procedures. Among those patients, focal damage of the brain was diagnosed in 36 (78.3%) cases; linear damage of the brain - in 9 (19.6%) patients; ipsilateral damage of the brain - in 37 (80.4%) patients; bilateral damage of the brain - in 16 (34.8%) patients, 38 (82.6%) patients were diagnosed with forebrain damage; 4 (8.7%) patients were diagnosed with damage of brainstem; 5 (10.9%) patients were diagnosed with cerebellum damage. Clinical symptoms of brain damage were diagnosed only for 2 (4.3%) patients. Focal damage of the brain was significantly less frequent only for aortic arch type 1, if compared with aortic arch type 2 and 3: 64.3%, 93.3% and 100.0%, respectively (p < 0.05). Focal damage of the brain occurred least in patients (28.6%) with Emboshield NAV protection type, if compared to other types of protection (71.4-100.0%). Linear >10mmbrain damage was less frequent when using FilterWire EZ, Emboshield NAV and SpideRX protection type. Ipsilateral ischemic brain damage also occurred less frequent when using Emboshield NAV protection type; bilateral damage occurred less frequent when using FilterWire EZ, Emboshield NAV and SpideRX protection type. Ischemic forebrain damage was also diagnosed less often in patients for whom protection type FilterWire EZ and Emboshield NAV was applied. Conclusions: Most frequent findings by MRI after CAS procedures were focal, ipsilateral and forebrain damage (about 80%), but less than 5% patients had clinical symptoms. In the case of aorta arch type 1 focal ischemic damage of the brain was significantly less frequent, then in aortic arch type 2 and 3. The localization and extent of brain damage was associated with the type of protection systems that have been used.

Full Depth Precast and Precast, Prestressed Concrete Bridge Deck Panels

Since 1970, there has been a dramatic increase in the use of full depth precast and precast, prestressed concrete deck panels for the rehabilitation and new construction of bridges. In order to document the various applications of bridge deck panels in North America, a questionnaire survey was sent to the departments of transportation (DOTs) of individual states and one province. Requested information in the survey included type of construction, deck dimensions, deck supporting system, panel dimensions and reinforcement, type of connecting system between panels and supporting system, type of joint between the adjacent panels, type of bonding material used to fill the joints, problems associated with the joints, reasons for adverse results, and type of protection system. The returned questionnaires were compiled and analyzed. This paper summarizes the significant results of this survey

超電導マグネットにおける常電導部の伝播と保護

A superconducting magnet, not fully stabilized, has instability that a normal zone, induced by a certain local disturbance, may lead to normal transition of the magent as a whole. Approximate evaluation of propagation of normal zones in superconducting wires is outlined and some remarks are made for anisotropic propagation in magnets. As a typical example, an analytical expression proposed by Wilson is presented and is compared with experimental results in bare and insulated wires. Basic ideas of magnet protection from mechanical and thermal damages in quench process are explained in two types of protection systems by an external resistor and “quenchback.” New aspects of magnet protection are also discussed in prospective applications of superconducting magnet.