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

The paper proposes and describes the design and operating principles of 5 levels voltage source inverter which acts as a link between the output of the linear generator and the load. The output frequency of the linear generator varies from 25 to 50 Hz depending on the load. Due to that, it is not suitable for many applications, which use 50 Hz ac. This inverter consists of 6 switches (two levels conventional inverter) which operate at the main line power frequency and another additional circuit consists of 3 switches which operate at double the line power frequency. A prototype has been designed and implemented. To asses the proposed inverter, it is compared with the conventional two level inverter with single switching inverter. Simulation and experimental results are presented to verify the validity of the model

Five levels voltage source inverter with line power frequency switching for linear generator applications

With Malaysia being surrounded by water bodies, tidal energy could be used for energy extraction. While several turbine designs and technologies have been used for tidal energy extraction, information on the use of vertical-axis tidal turbines (VATTs) for shallowwater applications is scarce. However, implementing horizontal-axis tidal turbines (HATTs) is not feasible due to Malaysian ocean depths. Hence, examining the wake-flow characteristics of VATTs in a shallow water-working environment in Malaysia is essential. The wake turbulence of the Savonius turbine model was compared with that of a hypothetical ‘actuator' cylinder, a VATT representation. Subsequently, the wake turbulences of a Savonius turbine model in static and dynamic simulations were compared to understand the flow distinction. Compared with that exhibited by the hypothetical actuator cylinder of 2.5 m, the hypothetical actuator cylinder of 5 m exhibits greater velocity deceleration. Additionally, the modelled Savonius turbine exhibits significantly more deceleration than that exhibited by the hypothetical actuator cylinder. Finally, the analysis of the static model of the Savonius turbine shows deceleration that is greater than that of the dynamic model.

International Journal of Renewable Energy Development

In this paper, a multilevel inverter based on cascaded half-bridge and three-phase unfolder is proposed. The proposed inverter design is simulated by using MATLAB Simulink. The converter is designed with four series-connected half-bridge cells and a three-level neutral-point-clamped inverter. The proposed converter is able to produce an output voltage of 230V and a frequency of 50 Hz. There are two modulation techniques implemented for the proposed inverter topology namely; phase-shifted modulation and phase opposition disposition modulation. The basic principle of operations using both modulation techniques including the performance analysis are presented.

Design and Analysis of Multilevel Inverter based on Cascaded Half-Bridge and Three-Phase Unfolder Circuit

In this paper, design and analysis of a multilevel converter for micro distributed generation (DG) system is presented. The design of the multilevel converter is simulated using Matlab Simulink. The power converter is designed to accept low input voltage from micro renewable energy sources such as a single solar panel or a low power wind turbine. The power converter produces an output voltage of 230V and frequency of 50Hz. Its basic principle of operation including performance analysis are presented. The system is suitable for use in micro DG system either on-grid or off-grid applications.

Nasrudin Abd Rahim

Papers

Five levels voltage source inverter with line power frequency switching for linear generator applications

International Journal of Renewable Energy Development

Design and Analysis of Multilevel Inverter based on Cascaded Half-Bridge and Three-Phase Unfolder Circuit

Design and Analysis of a Multilevel Converter for Micro Distributed Generation System