Comparative Study of the Dynamics of Cosmic Rays for the Pakistan and China Atmospheric Regions

This paper presents an analysis of cosmic ray intensity in Pakistan air space using spatial interpolation, comparing it with Chinese cosmic ray records from 1984 to 1993. The Exploratory Data Analytic (EDA) approach was applied to compare the cosmic ray fluctuations in both countries. The time series plot of the monthly cosmic rays showed relatively flatter counts in Pakistan than in China. The cosmic ray data for the years 1984 to 1993 fell within Solar Cycle 22, which lasted from 1986 to 1996, with its maximum phase in 1989 to 1991. The cosmic radiation varies between the atmospheric regions of Pakistan and China due to modulations in intensity that are accessible accordingly. It can be explained by purely astrophysical phenomena: (1) the source of emission of cosmic radiation may be different, (2) the rate at which emanation takes place depends on bursts of deep space dynamical objects from their sources that may be affected by solar wind and other solar radiations. Therefore, modulations in intensity are not only due to different geophysical locations. This study will help government organizations to predict and forecast cosmic rays values

Use of spread spectrum time domain reflectometry to estimate state of health of power converters

pre-printA new online measurement and analysis method has been presented in this paper to identify the state of health of power converter circuits. Using spread spectrum time domain reflectometry (SSTDR), impedance in the various current paths inside the converter as well as any fault can be identified without interrupting the circuit's normal operation. Multiple sets of test data have been generated while the SSTDR process is applied to each of the components i.e. the power MOSFETs, the dc bus capacitor and the load. These obtained test data are analyzed to show how these test results are consistent with the impedances in various current paths. An impedance matrix was formed for a non-aged converter and a corresponding matrix using SSTDR data was formed as well. The matrices could be formed for any power converter, and the impedance matrix for the non-aged converter could be considered as a "Reference matrix" for comparison purpose. By comparing these two matrices, the variation in path impedances due to aging could be determined. This research aims to identify the measurable quantities to characterize the aging process, their origins of these quantities and propose convenient methods to measure them

Hybrid electric vehicle power management solutions based on isolated and nonisolated configurations of multilevel modular capacitor-clamped converter

Journal ArticleAbstract-This paper presents the various configurations of a multilevel modular capacitor-clamped converter (MMCCC), and it reveals many useful and new formations of the original MMCCC for transferring power in either an isolated or nonisolated manner. The various features of the original MMCCC circuit are best suited for a multibus system in future plug-in hybrid or fuel-cell-powered vehicles' drive train. The original MMCCC is capable of bidirectional power transfer using multilevel modular structure with capacitor-clamped topology. It has a nonisolated structure, and it offers very high efficiency even at partial loads. This circuit was modified to integrate single or multiple high-frequency transformers by using the intermediate voltage nodes of the converter. On the other hand, a special formation of the MMCCC can exhibit dc outputs offering limited isolation without using any isolation transformer. This modified version can produce a high conversion ratio from a limited number of components and has several useful applications in providing power to multiple low-voltage loads in a hybrid or electric automobile. This paper will investigate the origin of generating ac outputs from the MMCCC and shows how the transformer-free version can be modified to create limited isolation from the circuit. In addition, this paper will compare various modified forms of the MMCCC topology with existing dc-dc converter circuits from compactness and component utilization perspectives

Universal multilevel DC-DC converter with variable conversion ratio, high compactness factor and limited isolation feature

Journal ArticleA multilevel dc-dc converter with programmable conversion ratio (CR) is presented in this paper. This converter is a modified version of the MMCCC converter. A universal version of the MMCCC is developed in this paper, and the CR can be easily changed within a wide range. The MMCCC converter is based on capacitor-clamped topology, and the conversion ratio of the circuit depends on the number of active modules. However, like any other capacitor-clamped circuit, the MMCCC circuit requires a large number of transistors and capacitors to attain a high conversion ratio (CR). In this paper, a new circuit module will be introduced that can be connected in a cascade pattern to form the new converter. By using the new modular cell, it is possible to attain very high conversion ratio using a limited number of components, and thus more compactness compared to the predecessor MMCCC circuit can be achieved

Design and simulation of contour mode MEMS resonator on Si for power converters

pre-printMicroelectromechanical systems (MEMS) resonators on Si have the potential to replace the discrete passive components in a power converter. These devices not only can reduce the size and weight of the converter but also can facilitate the implementation of power converter on a chip. In this paper, a contour mode MEMS resonator has been presented that can achieve resonant frequency in the range of several MHz, and the operating principles of the device have been discussed in detail. This device was simulated in COMSOL Multiphysics, and a resonant converter has been simulated in PSIM to harvest energy from a thermo electric generator. The equivalent electrical model of the MEMS resonator was incorporated into that circuit validating the feasibility of using MEMS resonator in power conversion systems. Detailed fabrication process of the device has been presented and implemented at University of Utah's Nanofab. Initial experimental characteristics of the resonator have been included in the paper

AC solar cells: An embedded "all in one" PV power system

Journal ArticlePower converters constructed from discrete components are difficult to mass produce, and the installation involves a significant labor cost to have the proper interconnection among the panel, inverter and the grid. These facts indicate that the present PV technology may not be able to address the challenges involved in reaching the DOE target of $1/W. Therefore, a paradigm shift in the design of the entire PV power system is needed to reach this goal. In order to increase the converter reliability and watts/$, the active and passive elements of a power converter (especially capacitors and active switches such as MOSFETs, JFETs or IGBTs) could be embedded on the same substrate material used for fabricating the p-n junctions in the photovoltaic panel. To the knowledge of the author, there is no prior work in cell level power conversion, and therefore, this project idea could be considered as an "Out of the box" kind. A novel fabrication process is proposed in this paper demonstrating the integration of PV cells and two major components needed to build a power converter. Because of the cell level power conversion, PV panels constructed from these cells are likely to be immune to partial shading and hot-spot effects. The end goal of this research is to produce 120V/240V ac output directly from the panel. An extremely accurate device simulator (*Silvaco Athena/Atlas) was used to generate reasonably accurate characteristics of the proposed PV system