Acheron's rainbow: Free associations on 75 years of exploration geo-electromagnetics

Geophysics ◽  
2005 ◽  
Vol 70 (6) ◽  
pp. 25ND-31ND ◽  
Author(s):  
Alan C. Tripp
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Raw Materials ◽  
Effective Means ◽  
Modern Life ◽  
Goods And Services ◽  
The Past

Geophysics has proved to be an effective means of prospecting for the raw materials necessary for modern life. Electromagnetic techniques are the methods of choice when buried treasure has an anomalous electrical conductivity or dielectric permittivity. In the past 75 years, SEG has provided a forum for the usually rational exchange of ideas in electromagnetic prospecting as well as a bazaar for goods and services.

scholarly journals Bio-Based Alternatives to Phenol and Formaldehyde for the Production of Resins

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2237 ◽  
Author(s):  
P. R. Sarika ◽  
Paul Nancarrow ◽  
Abdulrahman Khansaheb ◽  
Taleb Ibrahim
Keyword(s):  
Raw Materials ◽  
Phenol Formaldehyde ◽  
Raw Material ◽  
Wood Industry ◽  
Suitable Material ◽  
The Past ◽  
Wide Range ◽  
Recent Developments ◽  
Sustainable Materials ◽  
Materials Used

Phenol–formaldehyde (PF) resin continues to dominate the resin industry more than 100 years after its first synthesis. Its versatile properties such as thermal stability, chemical resistance, fire resistance, and dimensional stability make it a suitable material for a wide range of applications. PF resins have been used in the wood industry as adhesives, in paints and coatings, and in the aerospace, construction, and building industries as composites and foams. Currently, petroleum is the key source of raw materials used in manufacturing PF resin. However, increasing environmental pollution and fossil fuel depletion have driven industries to seek sustainable alternatives to petroleum based raw materials. Over the past decade, researchers have replaced phenol and formaldehyde with sustainable materials such as lignin, tannin, cardanol, hydroxymethylfurfural, and glyoxal to produce bio-based PF resin. Several synthesis modifications are currently under investigation towards improving the properties of bio-based phenolic resin. This review discusses recent developments in the synthesis of PF resins, particularly those created from sustainable raw material substitutes, and modifications applied to the synthetic route in order to improve the mechanical properties.

scholarly journals Multi-Task Optimization and Multi-Task Evolutionary Computation in the Past Five Years: A Brief Review

Mathematics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 864
Author(s):  
Qingzheng Xu ◽  
Na Wang ◽  
Lei Wang ◽  
Wei Li ◽  
Qian Sun
Keyword(s):  
Evolutionary Computation ◽  
Explicit Knowledge ◽  
Optimization Problems ◽  
Effective Means ◽  
Typical Application ◽  
The Past ◽  
Current State ◽  
Evolution Algorithms ◽  
Application Fields

Traditional evolution algorithms tend to start the search from scratch. However, real-world problems seldom exist in isolation and humans effectively manage and execute multiple tasks at the same time. Inspired by this concept, the paradigm of multi-task evolutionary computation (MTEC) has recently emerged as an effective means of facilitating implicit or explicit knowledge transfer across optimization tasks, thereby potentially accelerating convergence and improving the quality of solutions for multi-task optimization problems. An increasing number of works have thus been proposed since 2016. The authors collect the abundant specialized literature related to this novel optimization paradigm that was published in the past five years. The quantity of papers, the nationality of authors, and the important professional publications are analyzed by a statistical method. As a survey on state-of-the-art of research on this topic, this review article covers basic concepts, theoretical foundation, basic implementation approaches of MTEC, related extension issues of MTEC, and typical application fields in science and engineering. In particular, several approaches of chromosome encoding and decoding, intro-population reproduction, inter-population reproduction, and evaluation and selection are reviewed when developing an effective MTEC algorithm. A number of open challenges to date, along with promising directions that can be undertaken to help move it forward in the future, are also discussed according to the current state. The principal purpose is to provide a comprehensive review and examination of MTEC for researchers in this community, as well as promote more practitioners working in the related fields to be involved in this fascinating territory.

Complex dielectric permittivity, electric modulus and electrical conductivity analysis of Au/Si3N4/p-GaAs (MOS) capacitor

2021 ◽  
Author(s):  
Sema Türkay ◽  
Adem Tataroğlu
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Electric Modulus ◽  
Arrhenius Equation ◽  
Rf Magnetron Sputtering ◽  
Oxide Semiconductor ◽  
Complex Dielectric Permittivity ◽  
Mos Capacitor ◽  
Universal Power Law ◽  
Complex Electrical Conductivity

AbstractRF magnetron sputtering was used to grow silicon nitride (Si3N4) thin film on GaAs substrate to form metal–oxide–semiconductor (MOS) capacitor. Complex dielectric permittivity (ε*), complex electric modulus (M*) and complex electrical conductivity (σ*) of the prepared Au/Si3N4/p-GaAs (MOS) capacitor were studied in detail. These parameters were calculated using admittance measurements performed in the range of 150 K-350 K and 50 kHz-1 MHz. It is found that the dielectric constant (ε′) and dielectric loss (ε″) value decrease with increasing frequency. However, as the temperature increases, the ε′ and ε″ increased. Ac conductivity (σac) was increased with increasing both temperature and frequency. The activation energy (Ea) was determined by Arrhenius equation. Besides, the frequency dependence of σac was analyzed by Jonscher’s universal power law (σac = Aωs). Thus, the value of the frequency exponent (s) were determined.

Effects of layered sediments on the guided wave in crosswell radar data

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1698-1707 ◽  
Author(s):  
Karl J. Ellefsen
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Radar Data ◽  
Guided Wave ◽  
Sand Layer ◽  
Clay Layers ◽  
The Waves

To understand how layered sediments affect the guided wave in crosswell radar data, traces are calculated for a model representing a sand layer between two clay layers. A guided wave propagates if the wavelengths in the sand layer are similar to the thickness of the sand layer. The amplitude of the guided wave but not its initial traveltime is affected by the thickness of the sand layer. In contrast, both the amplitude and the initial traveltime are affected by the locations of the transmitting and receiving antennas, the electrical conductivity of the sand layer, and the dielectric permittivity of the sand layer. This permittivity can be estimated from the initial traveltime. The effects of the layering on the waves in these calculated traces also are observed in field traces, which were collected in layered sediments.

SPECIAL ARTICLE

PEDIATRICS ◽  
1954 ◽  
Vol 14 (6) ◽  
pp. 668-672
Author(s):  
THOMAS H. LANMAN
Keyword(s):  
Effective Means ◽  
Surgical Service ◽  
Open Thoracotomy ◽  
Basic Principles ◽  
Children's Hospital ◽  
The Past ◽  
American Academy Of Pediatrics ◽  
Children’S Hospital ◽  
Surgical Field ◽  
Heavy Mortality

IT IS a great honor to be asked to present the first William E. Ladd Lecture before the American Academy of Pediatrics. This I appreciate and as this is the first lecture in my former Chief's honor, I shall devote my time more to Doctor Ladd and what he accomplished during his long and devoted service as Chief of the Surgical Service of the Boston Children's Hospital than to the presentation of anything new. In these days of great changes in the surgical field, it is very easy to overlook or even to forget the good things that were done in the past. I said "changes" rather than advances for some of the changes of today are not advances. It is easier to appreciate the extraordinary widening in the field of surgical endeavor that has been made possible by improvements in pre- and postoperative care, anesthesia, and the more effective means to combat infection than it is to remember what was done in a previous generation without such new and valuable aids. When I began my service at the Boston Children's Hospital in 1919, most of the deaths on the Surgical Service were caused by infection. Long surgical procedures involving an open thoracotomy were impossible. Prolonged operations on the gastrointestinal tract carried a heavy mortality largely because of our lack of knowledge of fluid balance. In those earlier days, an operation that exceeded an hour in length was considered to be entering a very dangerous phase. It is well, however, to review some of the types of cases done in those days and to keep in mind that the basic principles one had to follow at that time are still valid and that the good results of today are by no means entirely due to modern methods. Let me cite a few examples.

Border Trade between Regions of Russia and Provinces of China

2021 ◽  
Vol 20 (10) ◽  
pp. 103-116
Author(s):  
Natalya S. Epifanova ◽  
Vladimir N. Akulinin
Keyword(s):  
Manufacturing Industry ◽  
Raw Materials ◽  
Value Added ◽  
Raw Material ◽  
Structural Development ◽  
Regional Economies ◽  
Russian Regions ◽  
Goods And Services ◽  
Border Trade ◽  
Regions Of Russia

The purpose of this article is to study border trade in the regions of Russia and the provinces of China. It is shown that in recent years there have been negative trends in border trade, leading to its reduction. Therefore, Russian regions bordering with China should transform into separate objects of regional policy, while also forming a legislative framework for border interaction in all its main spheres: trade, humanitarian cooperation, science and education, and others. In border cooperation with China, special emphasis should be placed on cooperation in the innovation sphere, as well as on improving the quality of exported goods and services and promoting infrastructure projects. Border trade between the regions of Russia and China is built mainly on trade and export of labour resources from China to Russia, as well as China’s receipt of additional sales channels for the confidently growing sales markets for consumer goods and sources of raw materials and primary products. The interaction of Russian regions with neighbouring provinces on the border with China not only preserves the raw material orientation of these regions, but also hinders the development and strengthening of the manufacturing industry in the structure of their regional economies, since border interaction for Russian regions immobilizes those stages of value-added production observed in the very first stages. In general, for the Chinese provinces there is a similar problem associated with such exports to border regions that have common borders with Russia, which does not contribute to the diversification and structural development of the regional economies of the Chinese provinces. That is why building an effective mechanism for border interaction between Russia and China is a strategically important issue for both countries.

Statistics and Economic History

1941 ◽  
Vol 1 (1) ◽  
pp. 26-41 ◽  
Author(s):  
Simon Kuznets
Keyword(s):  
Statistical Analysis ◽  
Economic History ◽  
Raw Materials ◽  
The Other ◽  
Economic Study ◽  
Statistical Research ◽  
Historical Approach ◽  
The Past ◽  
Economic Inquiry ◽  
Analytical Tools

This paper deals with the relation between statistical analysis as applied in economic inquiry and history as written or interpreted by economic historians. Although both these branches of economic study derive from the same body of raw materials of inquiry—the recordable past and present of economic society—each has developed in comparative isolation from the other. Statistical economists have failed to utilize adequately the contributions that economic historians have made to our knowledge of the past; and historians have rarely employed either the analytical tools or the basic theoretical hypotheses of statistical research. It is the thesis of this essay that such failure to effect a close interrelation between historical approach and statistical analysis needs to be corrected in the light of the final goal of economic study.

scholarly journals Nigerian Foreign Policy in a Globalising World: The Imperative of a Paradigm Shift

2015 ◽  
Vol 1 (1) ◽  
pp. 55 ◽  
Author(s):  
EJITU N. OTA ◽  
Chinyere S. Ecoma
Keyword(s):  
Foreign Policy ◽  
International Relations ◽  
Paradigm Shift ◽  
Raw Materials ◽  
Major Objective ◽  
Goods And Services ◽  
Challenges And Opportunities ◽  
Developed World ◽  
Globalising World ◽  
East West

The end of East-West hostilities in 1991 brought to the fore of international relations, some issues that had hitherto either been ignored or trivialised. One of these is the phenomenon commonly referred to as globalisation, which is more or less a euphemism for westernisation. Like colonisation, globalisation is propelled not by any moral considerations or an abstract concept of humanitarianism, but by the more economic exigencies of finding reliable markets for the industrial goods and services of the developed world as well as ready sources of raw materials for the industries of the world’s major economic powers. For developing countries like Nigeria, where political leadership influences not only domestic policies but foreign policy as well, there is a compelling need to embrace the globalisation with cautious optimism. For one thing, globalisation is a powerful force for growth and development. For another, it is a process that presents both challenges and opportunities. Such opportunities, however, must be exploited against the background of a dynamic foreign policy that sees the welfare of Nigerians as its major objective.

Wills Lifestyle in India

2017 ◽  
pp. 1-16
Author(s):  
Sunil Chopra
Keyword(s):  
Supply Chain ◽  
Raw Materials ◽  
Supply And Demand ◽  
Third Parties ◽  
The Past ◽  
Relative Value ◽  
High Level

In 2003, ITC responded to the high level of obsolete inventory by shifting risk from finished products to manufacturing and raw materials. This required that their supply chain be much more flexible and responsive than it was in the past. By 2006, changes in the supply chain that included moving manufacturing in-house improved flexibility and responsiveness. Obsolete inventory was significantly reduced and the company was much better at matching supply and demand. Cost, however, continued to be higher than that at third parties. The company had to decide on the appropriate tradeoff between cost and responsiveness when structuring its supply chain.The case illustrates how Wills has changed its supply chain to become more flexible and responsive. This change, however, has come at a cost. The case requires the students to analyze the tradeoff between cost and responsiveness/flexibility to decide on an appropriate level of flexibility/responsiveness. The case also requires the student to understand the relative value of increased flexibility versus increased responsiveness.

LOW TEMPERATURE THERMOELECTRIC PROPERTIES AND AGING PHENOMENA OF NANOSTRUCTURED p-TYPE Bi2-XSbXTe3 (x = 1.46, 1.48, 1.52 AND 1.55)

2013 ◽  
Vol 06 (05) ◽  
pp. 1340008 ◽  
Author(s):  
DALE HITCHCOCK ◽  
YEN-LIANG LIU ◽  
YUFEI LIU ◽  
TERRY M. TRITT ◽  
JIAN HE ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Low Temperature ◽  
Thermoelectric Properties ◽  
Optimal Composition ◽  
Ambient Conditions ◽  
Bulk Materials ◽  
The Past ◽  
Aging Phenomena ◽  
P Type ◽  
Cold Pressed

Over the past decade the widely used p-type ( Bi 2-x Sb x) Te 3 bulk thermoelectric materials have been subject to various nanostructuring processes for higher thermoelectric performance. However, these nanostructuring processing were conducted on compositions optimized for bulk materials (x ~ 1.52–1.55). This leads to the question of whether the optimal composition for bulk materials is the same for their nanoscale counterparts. In this work we hydrothermally grew Bi 2-x Sb x Te 3 nanopowders (nominally, x = 1.46, 1.48, 1.52 and 1.55) and measured their thermoelectric properties on cold-pressed vacuum-sintered pellets (74–78% of the theoretical density) below 300 K. The measurements were conducted 18 months apart to probe the aging phenomena, with the samples stored in ambient conditions. We have found that (i) the peak of thermopower shifts to lower temperatures upon nanostructuring but it shifts back to higher temperatures upon aging; (ii) the electrical conductivity degrades by a factor of 1.5–2.3 upon aging while the temperature dependence is largely retained; and (iii) the ZT of freshly made samples is sensitive to the x value, a maximum ZT ~ 1.25(~ 0.62) at ~ 270 K (~ 255 K) was attained in the freshly made sample x = 1.55(x = 1.46), respectively; while the ZT of aged samples is significantly lowered by a factor of 2–4 but lesser x-dependent. These observations have been discussed in the context of charge buildup and compensation at grain boundaries.

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