Papers by Keyword: PSD

Abstract: This paper proposes the correlation of absorbed energy with calculated energy using the power spectrum density (PSD) method. The total absorbed energy was obtained using the dial/encoder system may significantly vary depending on the strength and ductility of the material. In addition, according to ASTM E23, over 80% of absorbed energy is inaccurate and approximate. For this reason, we determined the energy collected from the dial/encoder Charpy impact test using the signal processing approach. Strain gauges were connected to the Charpy impact striker and the high frequency data acquisition system in order to capture the dynamic impact strain response. Specimens of an aluminium alloy of 6061-T6 and carbon steel 1050 with different velocities and thicknesses were used in the experiment. The specimens are prepared based on the ASTM E23. A collection of signal was converted from the time domain to the frequency domain by means of PSD method and the area under its plot was used to calculate strain energy. The comparison between energy absorbed during the experiment with PSD peak and the strain energy were performed using different materials, velocities and thicknesses. The total energy absorbed for both material with the PSD peak and the strain energy using the dial/encoder system can be linked by a power law equation with R² 96% and R² 94 %. Thus, the effects of the strain signal pattern and impact duration with different parameters were correlated with the PSD peak and the strain energy. This correlation using PSD can be used as an alternative for the charpy impact test and solve the problem of inaccurate absorbed energy.

Abstract: AISI 304 and 316L flat samples were exposed during 3 months in Carribean sea water.At the end of the experiment E_corr of AISI 316L reached one-half the negative potential value than that of AISI 304. The tendencies of E_corr were correlated with the pitting corrosion development. They could be considered as a consequence of the opposition between the nucleation of new pits and repassivation of active sites. The analysis of E_corr fluctuations was carried out with the potential spectral density (PSD) vs. frequency in logarithmic scale. The decrease of the PSD slopes, exponent b values, indicated a release of spontaneous energy with the advance of pits formation on the stainless steel surface. The data showed that in the range of low frequencies the process that occurs on both stainless steels surfaces could be considered as fractional Brownian motion, an anti-persistent non-stationary process, while in the range of higher frequencies as fractional Gaussian noise, an persistent stationary.

Abstract: This paper presents the interference impact of Ultra Wide-Band (UWB) sensor using frequency of 3.5 GHz on 3G mobile system in Korea. The Minimum Coupling Loss (MCL) method and Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) were used to evaluate the interference impacts of UWB sensor on 3G mobile system. The minimum allowable distance between UWB interferer and the victim receiver is required 0.09 m in indoor environment; in the case of multiple UWB interferers in outdoor environment, the maximum allowable UWB transmitting Power Spectral Density (PSD) should be-93.1 dBm/MHz below to guarantee co-existence with 3G mobile system.

Abstract: Because resistance of two-dimensional position sensitive detector's (PSD) photo surface is not absolute uniformity that its output is nonlinear. It is this feature enables the PSD difficult to measure small displacement. In order to solve this problem, BP neural network is proposed to solve the problem of PSD nonlinear correction after the study of traditional nonlinear correction method; BP neural network would have a strong ability of nonlinear mapping after training, and it can approach arbitrarily contact function by arbitrary precision, and MATLAB neural networking boxes can simulate BP neural network easily. Simulation and verification indicate that the method has a remarkable effect in solving nonlinear problems, and it can meet system requirements.

Abstract: This document conducts simulation analysis on spherical anti-seismic bearing employing the Finite Element Methods and PSD analysis of random vibration based on modal analysis, from which results as statistical parameters of random vibration of structure and demonstrates: this specific anti-seismic spherical bearing satisfies industry security demands related.

Abstract: The electronics package in a spacecraft is subjected to a variety of dynamic loads during launch phase and suitable thermal environment for the mission life. The dynamic and thermal analyses performed for a structurally reconfigured electronics package. Two different simulation models are developed to carry out the analyses. This paper discusses in two parts, in part-1, the vibration responses are determined at various critical locations, including on the Printed Circuit Board (PCB) for the vibration loads specified by launch vehicle using Finite Element Analysis (FEA). The mechanical properties of PCB are determined from the test specimens, which are then incorporated in the finite element model. In part-2, the steady-state temperature distributions on the components and on the PCB are determined, to check the effectiveness of heat transfer path from the components to the base of the package and to verify the predicted values are within the acceptable temperature limits specified. The predicted temperature values are then compared with on-orbit observations.

Abstract: The nanotechnology field has been developing strongly in recent years and ultra-precision measuring systems are nowadays required. A new two-dimensional moving platform with 50x50 mm range of travel, nanometer resolution and sub micrometer accuracy is being designed by the authors in order to be integrated with an Atomic Force Microscope (AFM). In this work the definition, design and experimental characterization of a homing sensor system for this 2D moving platform is presented. The homing sensor system will allow the generation of an absolute 2D reference for the platform (X-Y axis and θz rotation), defining an initial cero for the measuring system, which is based on laser encoders.

Abstract: A two-dimensional position sensitive detecting sensor (PSD) based on avalanche breakdown is introduced in this paper. The structure of the sensor is designed under the assumption that the breakdown of the PN junction in the sensor occurs at the bottom of the PN junction. The breakdown structure and characteristics of the sensor are simulated by Medici software and the doping structure and process conditions are calculated by Tsuprem4 software. By using COMSOL Multiphysics, we obtained current allocation of the straight and right angle type electrodes, which is corresponding to the optimal structure. In simulation, the root mean square error of the rectangular-shaped electrode and the straight line-shaped electrode are 0.198, 0.145 respectively. Experiment results show that in the 50% photosensitive area with the center as the origin, the rectangular-shaped electrode error is much smaller than a straight line-shaped electrode and fits in to linear relationship better. But the error of the angle the boundary of the electrode is significantly worse than the line-shaped electrode.

Abstract: This paper presents a new approach for obstacle avoidance of small mobile robots, which combine the position sensitive detector (PSD) with digital compass. It is important for an autonomous robot to explore its surroundings in performing the task of localization and navigation for searching. Because of the complexity of the environment, one simple kind of sensors is not sufficient for robot to accomplish these tasks. In this paper, the small mobile robots are enabled to identify barriers and distinguish surroundings by using the angle signal from the digital compass which is generally mounted on the robot. Experimental results indicate that this approach based on digital compass shows great potential in autonomous robot obstacle avoidance.

Abstract: The article deals with probability analysis for a vibration isolation system of sensitive equipment. Vibration isolation system is subjected to external base vibrations due to ambient oscillations (background noise). Considering Gauss distribution for ambient vibrations, we estimate the probability when the relative displacement of isolated mass will still be lower than the vibration criteria. The problem is solved in three-dimensional space, evolved by the system parameters damping and natural frequency. According to this probability distribution, the chance of exceeding vibration criteria for a vibration isolation system is evaluated and different vibration isolation systems are compared.