There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This review focuses on inverter technologies for connecting photovoltaic (PV) modules to a single-phase grid. The inverters are categorized into four classifications: 1) the number of power processing stages in cascade; 2) the type of power decoupling between the PV module(s) and the single-phase grid; 3) whether they utilizes a transformer (either line or high frequency) or not; and 4) the type of grid-connected power stage. Various inverter topologies are presented, compared, and evaluated against demands, lifetime, component ratings, and cost. Finally, some of the topologies are pointed out as the best candidates for either single PV module or multiple PV module applications.

A review of single-phase grid-connected inverters for photovoltaic modules

Two techniques for generating-high DC voltage using a three-phase power supply are presented. The laboratory model of the converters is developed and tested. The converter system is based on a single-stage power conversion using an isolated flyback converter topology and cascaded voltage doubler circuit. The power switching devices in the controlled bridge are controlled by the three-phase pulse width modulation (PWM) switching technique. Low harmonic current distortion in the AC side is considered in this design. A field programmable gate array (FPGA) is used to generate the three-phase PWM pattern which makes the overall circuit compact and less discrete components are involved. Furthermore, the control bridge consists of three power switching devices with twelve diodes, and is thus less complicated to control. The performance of the converters are compared in terms of efficiency, voltage stress across the devices and voltage gain.

Three-phase single-stage high-voltage DC converter

A mathematical approach of modelling and analysing three-phase pulse width modulation (PWM) is presented. The three-phase flyback converter required a unique pattern of PWM to optimise the power transfer in the magnetic circuit used in the converter. The three-phase PWM is generated digitally based on uniform symmetrical sampling technique using Xilinx chip. The generated PWM pattern is able to reduce the low order of harmonic components present in the input AC supply. Although software simulation could simulate the PWM pattern, it does not represent the exact pattern as been generated digitally. The mathematical approach used is to model the PWM pattern exactly as been created digitally. The proposed mathematical technique could also be used to analyse any digital PWM. The result of the mathematical analysis on the PWM pattern could be used to study the characteristics of the pattern such as maximum and minimum value of duty cycle, pulse width, turn-on time, turn-off time and modulation index. To verify the validity of the proposed technique, the results obtained from the mathematical model, experimental and simulation using PSpice were compared.

Modelling of three-phase uniform symmetrical sampling digital PWM for power converter

This paper presents the new topology of a three-phase four-wire Dynamic Voltage restorer (DVR) for mitigating voltage disturbances in low voltage distribution system. The proposed DVR topologies are consist of filtering scheme, isolation or distribution transformer, injection transformer winding and two split DC-link capacitors. The direct-quadrature-zero transformation technique was used as a controller of the proposed DVR. The suggested topologies and its controller was verified through simulation using MATLAB/SIMULINK Sim-Power System Toolbox and implemented in a prototype of the DVR with 5 KVA of the power rating. The experimental and simulation results validate the capability in compensating of voltage disturbances.

New Configuration of a Three Phase Dynamic Voltage Restorer (DVR) for Voltage Disturbances Mitigation in Electrical Distribution System

This paper presents a practical method to study the high frequency ferrite losses in the magnetic component and the magnetic design of the core. The study of the magnetic design of the core is to ensure that the core can handle the required flux without entering saturation. Modeling of the magnetic material as a transformer or coupled inductors for high frequency power electronics application has been developed. The DC to DC flyback converter with transformer isolation was designed and the test was implemented. The transformer was build up by using a ferrite E core by placing a coil around the centre limb and setting an airgap between the two cores. Experimental test results are carried out and shown.

Ferrite core analysis for DC-DC flyback converter

All humans and animals need access to clean water in their daily lives. Unfortunately, we are facing water scarcity in several places around the world, and, intentionally or unintentionally, we are contaminating the water in a number of ways. The rise in population, globalization, and industrialization has simultaneously given rise to the generation of wastewater. The pollutants in wastewater, such as organic contaminants, heavy metals, agrochemicals, radioactive pollutants, etc., can cause various ailments as well as environmental damage. In addition to the existing pollutants, a number of new pollutants are now being produced by developing industries. To address this issue, we require some emerging tools and materials to remove effluents from wastewater. Zeolites are the porous aluminosilicates that have been used for the effective pollutant removal for a long time owing to their extraordinary adsorption and ion-exchange properties, which make them available for the removal of a variety of contaminants. However, zeolite alone shows much less photocatalytic efficiency, therefore, different photoactive materials are being doped with zeolites to enhance their photocatalytic efficiency. The fabrication of zeolite-based composites is emerging due to their powerful results as adsorbents, ion-exchangers, and additional benefits as good photocatalysts. This review highlights the types, synthesis and removal mechanisms of zeolite-based materials for wastewater treatment with the basic knowledge about zeolites and wastewater along with the research gaps, which gives a quality background of worldwide research on this topic for future developments. 

/pdf/comprehensive-review-on-zeolite-based-nanocomposites-for-39jnie1y.pdf

Nasrudin Abd Rahim

Papers

Three-phase single-stage high-voltage DC converter

Modelling of three-phase uniform symmetrical sampling digital PWM for power converter

New Configuration of a Three Phase Dynamic Voltage Restorer (DVR) for Voltage Disturbances Mitigation in Electrical Distribution System

Ferrite core analysis for DC-DC flyback converter

Comprehensive Review on Zeolite-Based Nanocomposites for Treatment of Effluents from Wastewater