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

https://opus.lib.uts.edu.au/bitstream/10453/114834/4/OCC-90253_AM.pdf

A review of clustering techniques and developments

Time--frequency feature representation using energy concentration: An overview of recent advances

Requirement of green supply with higher quality has been consumers’ demand around the globe The electrical power system is expected to deliver undistorted sinusoidal rated voltage and current continuously at rated frequency to the consumers This paper presents a comprehensive review of signal processing and intelligent techniques for automatic classification of the power quality (PQ) events and an effect of noise on detection and classification of disturbances It is intended to provide a wide spectrum on the status of detection and classification of PQ disturbances as well as an effect of noise on detection and classification of PQ events to the researchers, designers and engineers working on power quality More than 150 research publications on detection and classification techniques of PQ disturbances have been critically examined, classified and listed for quick reference

A critical review of detection and classification of power quality events

Lissajous pattern-based technique can be effectively used for condition assessment of oil-paper insulation. However, such methods are reported for a specific measurement temperature. It is not always possible to record data at a pre-determined temperature, especially during field measurement. In such cases, temperature compensation needs to be made. The present paper reports a methodology and a few preliminary research findings that can be used for achieving this temperature compensation for Lissajous pattern-based condition assessment techniques.

Effect of Measurement Temperature on Lissajous Pattern Parameters obtained using Frequency Domain Response of Oil-paper Insulation

Numerical Computation of Electric Field in High-Voltage System – Case Studies

Failure of paper insulation is the end of design life of a transformer. Researchers have already stated that paper itself is the storehouse of moisture. Different operating variations over the service life in a transformer initiate degradation and breaking down of cellulosic chain of the paper. Degradation not only weakens the dielectric strength of solid insulation electrically but also produces different carboxylic acids. Organic acids that are produced as by product play a major role in insulation degradation. Among the organic acids produced, low molecular weight acids are found to be absorbed by paper. Over the past few years, attention has been focused to look into the causes of the detrimental effects of insulation ageing, but no such serious efforts have been made to look for the detrimental effects and to understand the influence on insulation ageing due to acid formation. Hence, an attempt has been made to look into the degrading effects caused by the acids by analyzing the dielectric response data obtained in time domain. To understand the physical behavior going on inside the dielectric material due to the influence of acid, time domain data is converted to frequency domain. The frequency domain parameters obtained are used to construct the Cole-Cole diagram to draw conclusions about the condition of ageing status of transformer oil-paper insulation.

Influence of Presence of Acids in Transformer Insulation: A study using Cole-Cole Plots

This paper proposes a novel method to analyze the relaxation behavior of epoxy mica insulation under accelerated thermal ageing conditions using Havriliak-Negami (H-N) relaxation model. The epoxy mica composite insulation was subjected to thermal ageing for 200 hours, 400 hours and 600 hours, respectively, at 150°C. Then, frequency domain spectroscopy (FDS) measurement was performed on the insulation samples from 0.1 mHz to 1 kHz to record the real part ε′(ω) and imaginary part ε″(ω) of complex permittivity ε*(ω), respectively. From the recorded FDS data, real part M′(ω) and imaginary part M″(ω) of complex dielectric modulus spectrum M*(ω) was computed to unmask the dielectric relaxation, which is suppressed due to conductivity effect at very low frequencies. Then M′(ω) and M″(ω) computed at each measurement frequency were plotted and their variation was modelled using H-N relaxation model. Investigations revealed that parameters of H-N model are sensitive to thermal ageing. Finally, two empirical relationships have been developed between the H-N model parameters with ageing duration to estimate the ageing state of the epoxy-mica insulation quantitatively.

Estimation of Epoxy-Mica Insulation Ageing Through Havriliak-Negami Relaxation Model on Dielectric Modulus Spectrum

In order to use de-trapped interfacial charge as a performance parameter for diagnosis, it is necessary to reduce the influence of insulation geometry. Available literature shows that this can be done by considering dc insulation resistance $\pmb{R}_{0}$ as the normalization factor. Such normalization may not be always practically feasible as information regarding $\pmb{R}_{0}$ requires measurement of temperature sensitive low amplitude current. In this paper it is shown that geometric capacitance $\pmb{C}_{0}$ (instead of $\pmb{R}_{0})$ ) can be used as an effective normalization parameter to reduce effect of insulation geometry. Effect of normalizing freed interfacial charge using $\pmb{C}_{0}$ and $\pmb{R}_{0}$ and its subsequent effect on insulation diagnosis are presented in this paper.

Sivaji Chakravorti

Papers

Effect of Measurement Temperature on Lissajous Pattern Parameters obtained using Frequency Domain Response of Oil-paper Insulation

Numerical Computation of Electric Field in High-Voltage System – Case Studies

Influence of Presence of Acids in Transformer Insulation: A study using Cole-Cole Plots

Estimation of Epoxy-Mica Insulation Ageing Through Havriliak-Negami Relaxation Model on Dielectric Modulus Spectrum

Feasibility of using Normalized De-trapped Charge for Diagnosis of Power Transformer Insulation