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

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

计量经济分析 = Econometric analysis

This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

World energy outlook

Introduction to stochastic programming

This paper proposes an Artificial Intelligence (AI) based data-driven approach to forecast heat demand for various customer types in a District Heating System (DHS). The proposed day-ahead forecasting approach is based on a hybrid model consisting of Imperialistic Competitive Algorithm (ICA) and Support Vector Machine (SVM). The model is built using two years (2015 - 2016) of hourly data from various buildings in the Otaniemi area of Espoo, Finland. Day-ahead forecast models are also developed using Persistence and four other AI based techniques. Comparative forecasting performance analysis among these techniques was performed. The proposed ICA-SVM heat demand forecasting model is tested and validated using an out-of-sample one-year (2017) hourly data of the buildings’ district heat consumption. The prediction results are presented for the out-of-sample testing days in a one-hour time interval. The validation results demonstrate that the devised model is able to predict the buildings’ heat demand with an improved accuracy and short computation time. Moreover, the proposed model demonstrates outperformed prediction accuracy improvement, compared to the other five evaluated models.

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Day-ahead Prediction of Building District Heat Demand for Smart Energy Management and Automation in Decentralized Energy Systems

Direct lightning strikes to medium voltage (MV) overhead lines cause insulation flashovers in great majority. Generally, the pole-mounted distribution transformers are protected by spark gaps and surge arresters at the MV terminals. In this paper, Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP) simulations have been performed to evaluate the performance of different lightning protection schemes for the pole-mounted distribution transformers. Both first and subsequent stroke currents were considered to estimate the lightning performance of a typical MV unearthed network. The results indicate that the effect of subsequent stroke current is more severe at the low voltage (LV) terminals of the transformer. In case of spark gap protected transformers, the operation of spark gaps produce steep-front overvoltages. As a result, high frequency overvoltages transfer from MV to LV terminals of the distribution transformer that are directly connected to the consumer premises. The steepness of the overvoltages can be mitigated by installing a series filtering element at the MV side of the distribution transformer. Furthermore, surge arrester can be employed to smoothly limit the transient overvoltage at the MV terminals of the transformer in spite of the higher protection cost. Thus, low rating surge arresters in conjunction with spark gaps can be also used to mitigate the lightning overvoltages. Finally, it is recommended that higher energy class surge arrester should be employed for this combined spark gap and surge arrester protection scheme.

Evaluation of Lightning Overvoltage Protection Schemes for Pole-Mounted Distribution Transformers

This paper presents a new framework for island formation prior to windstorms, which considers tree-caused failures of distribution networks. In the proposed framework, both direct and indirect effects of windstorms on distribution lines are quantified. Thus, a novel discrete Markov chain model is proposed for representing the failure modes of trees in each time interval of windstorm duration. This model categorizes “healthy”, “uprooted”, “stem breakage”, and “branch breakage” states of a tree. In addition, a new line-tree interaction model is presented for calculating tree-caused failure probability of overhead lines. The results of the proposed Markov model are taken as inputs by the developed line-tree interaction model. In these models, the different characteristics of windstorms are taken into account. Tree vulnerability to windstorms is characterized by different factors such as their species, height, and critical wind speeds. Windstorm duration is sectionalized into multiple time intervals, and the proposed models are applied to trees and distribution system components in each interval. Moreover, the interdependency between the intervals is captured by the Markov model. The results of the models are used by an optimization model, thereby dividing a distribution system into multiple islands before storm onset. Subsequently, the framework is extended as a two-stage stochastic optimization problem to address the uncertainties of loads. In addition, this framework considers the allocation of mobile emergency resources. The proposed models are implemented on the IEEE 33- and 123-bus test systems, as well as a practical distribution feeder, and their effectiveness is demonstrated through several case studies.

/pdf/a-novel-pre-storm-island-formation-framework-to-improve-2ufqufeu.pdf

A Novel Pre-Storm Island Formation Framework to Improve Distribution System Resilience Considering Tree-Caused Failures

Kotien reaaliaikaisen sähkönkulutuksen mittaaminen ja havainnollistaminen – HEAT'07 projektin tulokset

This paper reports an experimental investigation of locating arc sources using strategically placed antennas and the signal arrival times of first peak component of the wide-band electromagnetic signals radiated from the sources toward the antennas.  Theoretical approaches of such electromagnetic source location are first introduced and then a new approach of using the dominant frequency component of the first peak wave to clarify the source location distance is discussed. Experiments of arc generation and radiation signal measurement are conducted and, using the measured electromagnetic data, the arc source location method is applied and the results are compared against the actual location.  It is found that the first peak signal arrival method with of the captured signal works at a reasonable level of accuracy.

/pdf/power-arcing-source-location-using-first-peak-arrival-of-rf-1cx0n6xk8r.pdf

Matti Lehtonen

Papers

Day-ahead Prediction of Building District Heat Demand for Smart Energy Management and Automation in Decentralized Energy Systems

Evaluation of Lightning Overvoltage Protection Schemes for Pole-Mounted Distribution Transformers

A Novel Pre-Storm Island Formation Framework to Improve Distribution System Resilience Considering Tree-Caused Failures

Kotien reaaliaikaisen sähkönkulutuksen mittaaminen ja havainnollistaminen – HEAT'07 projektin tulokset

Power arcing source location using first peak arrival of rf-signal