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

Optimal operating scheme of neighborhood energy storage communities to improve power grid performance in smart cities

Large number of photovoltaic (PV) installations can lead to the network constraints' violations that comprise the voltage level outside the statutory limits and equipment ampacity-limit violations. This study quantifies the hosting capacities (HCs) of the Finnish LV networks and their limiting constraints. A stochastic approach is implemented to cover all the probabilistic variables of the LV network. Geographically distinct LV networks of rural, intermediate and urban regions are studied with the balanced and unbalanced PV feed-in scenarios. Later, the HC enhancement potential of various auxiliary equipment and techniques, like the battery storage, on-load tap changer (OLTC), network reinforcement and reactive power control of inverters, is determined. Moreover, the effect of different country-specific voltage level standards' implementation and the commercially available OLTC employment are also studied with varying PV penetrations.

Probabilistic Assessment of Photovoltaic Hosting Capacity in Finnish LV Networks

This article presents a novel approach for the annual energy consumption estimation in escalator technology. The method is based on short-term energy measurements of several day types within a week. It suits best for appliances where the passenger flow is weekly recurring. This article explores the implication of the method with seasonal changes, as well as stresses the impact of various day types and holidays on annual energy consumption estimation. The performance of the proposed method was compared with the existing approaches of energy consumption estimation in the standard ISO 25745-3 and annual energy measurement results. The approach is favorable among other existing approaches because it does not require additional passenger measurements, while providing more accurate results.

https://research.aalto.fi/files/30262446/ELEC_Uimonen_etal_Predicting_the_Annual_JOBE_13_319_2017.pdf

Predicting the annual escalator energy consumption based on short-term measurements

Residential buildings energy cost optimization requires demand response (DR) scheduling when employing electric storage space heating in a market that hourly tariff electricity price is applied for customers. Thus, a suitable optimization algorithm for the thermal storage controller causes the household energy expenditure for heating purpose to be minimized. This study proposes greedy variable neighborhood algorithm (GVNA) that is composed of greedy algorithm and variable neighborhood search as the DR control algorithm. The case study outcomes illustrate that the daily heating electricity price decreases by 3,5 % to 11,4 % and monthly heating electricity cost reduces by 9 % to 20 % when employing different storage degrees from 10 % to 100 % of the total daily or monthly heat demand, respectively. Furthermore, this method enables both dayahead and realtime scheduling of a residential thermal storage. Thus, GVNA can be a feasible approach at least for residential houses energy cost minimization problem due to its simplicity and small computational burden compared to other techniques in the literature.

Demand response control of a townhouse thermal storage by greedy variable neighborhood algorithm

Summary form only given. Voltage sag distributions caused by faults at different voltage levels and experienced by low voltage customers were established for four different power system areas. The shares of different fault types at each voltage level and the sag propagation throughout the power system were taken into account. The results show that the origin of sags in urban and rural areas tends to be different. This data is needed when, for example, planning measures for sag mitigation in different parts of the power system.

Matti Lehtonen

Papers

Optimal operating scheme of neighborhood energy storage communities to improve power grid performance in smart cities

Probabilistic Assessment of Photovoltaic Hosting Capacity in Finnish LV Networks

Predicting the annual escalator energy consumption based on short-term measurements

Demand response control of a townhouse thermal storage by greedy variable neighborhood algorithm

Voltage sag distributions caused by power system faults