Papers by Keyword: GaP

Abstract: There are two distinctive regions can be identified (low (LC) and high currents (HC)) of a watt-ampere (W-I) characteristic of initial LEDs based upon GaP with 590 nm wavelength. The established patterns differ in the exponent. At the same time, the LC region corresponds to an increase in the efficiency of conversion of operating current into light radiation, and the HC region is a slow decline with an increase in the operating current. As a result of irradiation with gamma-quanta in the passive power mode, the change in the shape of W-I characteristic is established, which can be characterized by an increase in the threshold current separating the LC and HC regions with an increase in the irradiation dose. The change in the emissive power of the LEDs and the shift of the threshold current occurs in two stages: in the first stage, the emissive power decreases due to radiation-stimulated rearrangement of the initial defect structure. At the same time, with an increase in the radiation dose, a partial recovery of the emissive power is observed against the background of its overall decrease. At the end of the first stage, the dependence of the damage coefficient on the operating current density in measurements of the W-I characteristics is manifested explicitly. The second stage of reducing the emissive power due to the introduction of radiation defects. In this case, the damage coefficient does not depend on the working current density, and the observed differences are due to the fact that by the end of the first stage its contribution to the overall reduction in emissive power is inversely proportional to the working current density. The established patterns can be used at the stage of designing the LEDs to substantiate the choice of the optimal value of the operating current density and to predict the resistance to irradiation with gamma rays.

Abstract: The electronic structure and optical properties of GaP were calculated using generalized gradients in density functional theory. The Bonn effective charge, optical frequency dielectric constant and the LO-TO splitting value were calculated by density functional theory perturbation method.

Abstract: The buckling-restrained brace must be able to provide the designed structural performance in actual use. In other words, the buckling-restrained brace must retain its initial quality in during the fabricating process. In this study, for the purpose of ensuring the initial quality of the buckling-restrained brace using steel mortar planks (BRBSM), quality control values at the time of fabrication are set and conduct verification testing on clearance and gap.

Abstract: This paper reports the findings from an analytical study into the influence of fiber reinforced polymer (FRP)-to-concrete interface gap and prestressed FRP tubes on strain reduction factor (k_ε) for concrete-filled FRP tube (CFFT) columns. A database that consists of a total of 45 aramid FRP- (AFRP) confined normal-and high-strength concrete (NSC and HSC) specimens with circular cross-sections is presented. All specimens were cylinders with a 152 mm diameter and 305 mm height, and their unconfined concrete strengths ranged from approximately 45 to 110 MPa. Analyses of the experimental databases that consisted of 22 specimens manufactured with FRP-to-concrete interface gap and a further 23 specimens prepared with lateral prestress is presented and discussed. Based on close examination of the hoop strain development on the FRP confining shell, expressions to predict strain reduction factors (k_ε) are proposed. The comparison of the proposed model predictions with the experimental test results of specimens prepared with an interface gap or prestressed FRP tubes shows good agreement.

Abstract: Laser cutting is a process used as an alternative of conventional machinery that works by directing the output of the laser power on the would be-cut material. Material exposed to the laser light is then melted, burned, and evaporated by the gas. Thus, this laser cutting process produces high-quality edge surface. The research aimed to determine the effects of the laser head distance and cutting speed to obtain minimum width of gap and the laser cutting process with the 3 mm-thick polymethyl methacrylate. This experiment used a 60 Watt-powered laser cutting machine to take the specimen in the form of a 30 mm-long horizontal line. The laser head distance ranged from 6 to 10 mm and cutting speed varied from 4 to 8 mm/s. A stereo zoom microscope with 30 times magnification was used to measure the gap. The research resulted in 0.582 to 0.931 mm as the value of the width gap in the cutting of 3 mm thick 60 Watts-powered polymethyl methacrylate (PMMA). The laser head distance and cutting speed contributed to the gap width of the product. The increased cutting speed and gap distance resulted in the smaller gap width.

Abstract: Roadside development plays an important role in the safety of the entire road in general and intersections in particular. Illegal and improper buildouts such as roadside kiosks, bus stops and fire stations are an accident hazard and a hindrance towards sustainable development. This paper presents the first account of analysis of safety evaluation of intersections with respect to roadside development in Malaysia. The data collected on 14 sites was analyzed. The results indicated that the bus stops and restaurants located right infront of the unsignalized intersections were the major contributory factors in decreasing the safety. Moreover it was found that facilities staggered away from the intersection such as another access point are less hazardous. It is recommended that relevant authorities should ensure the removal of such risky roadside developments.

Abstract: This paper reports on an experimental investigation on the influence of FRP-to-concrete interface gap, caused by concrete shrinkage, on axial compressive behavior of concrete-filled FRP tube (CFFT) columns. A total of 12 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were manufactured. 3 of these specimens were instrumented to monitor long term shrinkage strain development and the remaining 9 were tested under monotonic axial compression. The influence of concrete shrinkage was examined by applying a gap of up to 0.06 mm thickness at the FRP-to-concrete interface, simulating 800 microstrain of shrinkage in the radial direction. Axial strain recordings were compared on specimens instrumented with two different measurement methods: full-and mid-height linear variable displacement transformers (LVDTs). Results of the experimental study indicate that the influence of interface gap on stress-strain behavior is significant, with an increase in interface gap resulting in a decrease and increase in the compressive strength and ultimate axial strain, respectively. It was also observed that an increase in interface gap leads to a slight loss in axial stress at the transition region of the stress-strain curve. Finally, it is found that an increase in the interface gap results in a significant decrease in the ratio of the ultimate axial strains obtained from mid-section and full-height LVDTs.

Abstract: Mathematical background for static analysis of impulse gas seal is created in current paper. It includes evaluation of gap and flow rates of gas in turbocompressors. This paper consists of two parts. In the first one all logical steps of creation of the theoretical model for impulse gas seals are given. It should be mentioned, that they are valid for isothermal steady process which is observed here. The verification of derived theory is shown in the second part on a calculation example.

Abstract: Currently, there are many designs of sealing devices pumps and turbines. However, not all of them have found widespread application. Most commonly used in the industry to non-contact seal minimum positive clearance. These include gap, labyrinth, celled, grooved, screw, etc. The article describes the modeling of the working fluid in sealing gap using Ansys CFX through the gaps, grooved and screw seals, comparison values leaks.)

Abstract: When gear oil pump works, oil chamber is filled with high pressure oil, gear moves between housing and sealing devices and must maintain a certain gap between them, so that leakage is inevitable. In this paper, from structure and working principle of gear pump, the main factors influencing its leakage are spindle end gap, face clearance, radial clearance and the gap of the tooth contact surface. Taking effective measures to control the gear oil pump clearance and improve the working efficiency.