Trade-offs in refrigerant selections: past, present, and future

Recent attention to depletion of stratospheric ozone, by chemicals containing bromine and chlorine, resulted in an international accord to halt their production. The most widely used refrigerants are among them. Chemical and equipment manufacturers mounted aggressive research and development programs to introduce alternative and transition refrigerants, associated lubricants and desiccants, and redesigned equipment. The already difficult criteria became even more complex, with subsequent linkage of chemical emissions from human activities to global climate change. The very successful response to protect the ozone layer has led some regulators and users to assume that ideal substitutes will be found. Such chemicals should be free of all environmental and safety concerns, be chemically and thermally stable, and perform efficiently. The analyses presented in this paper demonstrate that the outlook for discovery or synthesis of ideal refrigerants is extremely unlikely. Trade-offs among desired objectives, therefore, are necessary to achieve balanced solutions. The paper also shows that fragmented regulation of the chemicals involved, to address individual issues, jeopardizes the prospect of solving subsequently addressed problems. The paper reviews the history of refrigerants, their roles in ozone depletion and global climate change, and necessary trade-offs in refrigerant selections.     

Service multinationals: Their past,present, and future

Abstract and Key Results

Optoelectronics — past,present, and future

Considerable progress has been made in the field of optoelectronics in the last thirty years. The two principal drivers for this progress have been the invention of the laser and low-loss optical fibres. But what is optoelectronics? Optoelectronics is more than just a marriage of electronics and optics. It represents the higher order integration of technical achievements in electronics and photonics to allow one to chose what, where, when, and how to address both old and new problems and opportunities for increasing customer satisfaction in the areas of information movement and management. I will review the progress in the field and share my insights into where the future lies. The important question no longer is if optics will replace electronics in many of the technologies underlying information movement and management; it is when and to what degree. The limitation no longer arises from the technical capabilities, it comes from economics and social values provided by the increased capabilities in communications and computers.     

Interlaminar fracture studies in Portugal: past,present and future

This paper reviews the state‐of‐the‐art in interlaminar fracture testing of composite materials, with particular emphasis on the work performed in Portugal over the last 15 years. Early work, carried out within the ESIS Polymer and Composite Technical Committee, was concerned with improving test methods on unidirectional [0°]_n specimens. The focus was on the mode I double cantilever beam (DCB) test and on mode II end‐notched flexure (ENF) and end loaded split (ELS) tests. In spite of some remaining controversy on mode II testing, the main issue nowadays is fracture toughness measurement on multidirectional specimens. Remaining difficulties are discussed in the light of the most recent work. Guidelines for ongoing and future research are also presented.     

Hydrothermal processing of materials: past,present and future

The hydrothermal technique provides an excellent possibility for processing of advanced materials whether it is bulk single crystals, or fine particles, or nanoparticles. The advantages of hydrothermal technology have been discussed in comparison with the conventional methods of materials processing. The current trends in hydrothermal materials processing has been described in relation to the concept of soft solution processing, as a single-step low energy consuming fabrication technique. Also some recent developments in multi-energy processing of materials such as microwave-hydrothermal, mechanochemical-hydrothermal, electrochemical-hydrothermal, sonar-hydrothermal, etc. have been discussed. An overview of the past, present and future perspective of hydrothermal technology as a tool to fabricate advanced materials has been given with appropriate examples.     

通信声学:过去、现在和未来

通信声学的定义:通信声学是面向人与人、人与机器之间的信息交互,研究一般声学环境中音频信号的产生、传播和接收的声学分支学科。基于现代声学、信息处理和通信技术的发展,通信声学已成为一个多学科交叉的研究领域。它融合了心理生理声学、房间声学、电声学、语音和音频信号处理、通信技术、计算机技术等不同领域的研究成果,在当今的科学与技术变革中具有显著的位置。     

The past, present, and future of fracture mechanics

The science of fracture mechanics was born and came to maturity in the 20th century. Its literature is now vast. Perhaps the most successful application of fracture mechanics is to fatigue. However, this short paper is limited to a core topic of fracture, the initiation and propagation of fracture under monotonic loading at low strain rates.As the author was invited to present this paper on the occasion of his 65th birthday, it is a somewhat personal view of the development and future of fracture mechanics, but it is hoped that it will interest many, especially the young researchers at the beginning of their careers.     

Periodic mesoporous organosilicas (PMOs): past, present, and future

Periodic mesoporous organosilicas (PMOs) represent a new class of organic-inorganic hybrid materials suitable for a broad range of applications such as chromatography, catalysis, sensing and microelectronics. Unlike in organic functionalized mesoporous silica phases obtained via grafting or co-condensation procedures the organic groups in PMOs are direct parts of the 3D framework structure, thus giving raise to enormous possibilities to tune their chemical and physical properties in designated ways by varying the structure of the precursors. In this review the distinctive features of PMOs are discussed, the latest developments concerning compositions, structures, morphologies and potential applications are figured out and finally a brief outlook of future aspects is given.     

Nanorefrigerants: A comprehensive review on its past,present and future

Nanofluid as a heat transfer fluid has been gaining popularity ever since its inception. Consequently, the researchers and experimentalists from the refrigeration industry could not keep themselves away from the ever growing horizon of nanofluid applications. The research on the refrigerant based nanofluids or a nanorefrigerant is slowly but surely increasing. The boiling heat transfer coefficient data for nanofluids and nanorefrigerants have been inconsistent but, in general, researchers have observed a rise in the boiling heat transfer coefficient that encourages them to pursue their research further in this field. Numerous studies regarding nanorefrigerants have shown that the addition of nanoparticles lead to a better system performance and energy efficiency. This review paper is an attempt to summarise all the aspects of nanorefrigerants such as its preparation, thermophysical properties, pressure drop in nanorefrigerants, boiling heat transfer and performance of nanorefrigerants in various domestic refrigerators.     

A look at physical simulation of metallurgical processes,past, present and future

The year 2007 marks the 50th anniversary of the founding of Dynamic Systems Inc., the developer and manufacturer of Gleeble physical simulation systems. From the initial welding simulators in the 1950s to today's complex rolling simulators and multi-axis nano-material development tools, the evolution of equipment for physical simulation research has evolved along several paths. In each case, a need to develop or improve processes and materials has pushed the technology to new levels. This paper takes a brief look at the historical developments of physical simulation tools over the last 50 years and reviews a number of significant milestones in the evolving science of physical simulation. After a historical review, the current technologies and accomplishments are discussed. This includes a look at the most recent developing methods such as the use of laser ultrasonics to gather real-time microstructure information during the simulation. This paper also reviews recent work in simulating thin slab continuous casting. Finally a look at what may be expected in the future for physical simulation is presented.     

European patents for biotechnological inventions – past, present and future

It is now well accepted that although biotech inventions may relate to living materials it is possible to secure patent protection for all but a limited number in certain defined categories. The author traces the development of biotech patents from the early days, when decisions of the Courts and the EPO set the necessary precedents, to the adoption of the European Directive in July 1998. He then goes on to explain in more detail the key features of the Directive and refers to a number of precedent decisions which, in combination with the Directive, show how certain problem areas have been tackled. Although emphasis is placed on the key areas of plant and animal patents, the patenting of gene sequences and issues of morality the author stresses that the established principles of novelty, inventive step and industrial application are, more often than not, adequate to decide the patentability of the vast majority of biotech inventions.     

Fatigue life prediction of aircraft structures—past, present and future

An exceptional lack of correlation between the fatigue life predicted from calculations and tests and the service life actually obtained has been reported many times. This may be due to one or several of the following causes:

1. 1. Incorrect load spectra were assumed in the calculations and applied in the tests including the full scale test.

2. 2. Miner's Rule was used in the life calculations.

3. 3. Unexpected failures occurred, starting from material flaws in non redundant structure built of high strength materials.

4. 4. The load sequence in the tests including the full scale test was over simplified.

It is suggested in this paper that major improvements in the accuracy of fatigue life prediction should be possible using modern methods and modern data. These are compared to hitherto existing methods for life calculations in the design state, for component testing and for the full scale fatigue test.

Reference is also made to other work in the same area.     

Mapping past,current and future energy research trend in Pakistan: a scientometric assessment

This work describes the contribution of researchers in the field of the energy from Pakistan in the period 1990–2016. A scientometric approach was applied to analyze the scientific publications in the field using the Scopus Elsevier database. Different aspects of the publications were analyzed, such as publication type, major research areas, journals, citations, authorship pattern, affiliations as well as the keyword occurrence frequency. The present research trends are analyzed and future research directions are outlined. The impact factor, h-index and number of citations were used to investigate the strength of active institutes, authors, and journals in the field of the energy in Pakistan. From 1990 to 2016, 991 articles have been published by 2139 authors from 213 research institutes. The total number of citations and impact factor are 10,287 and 2301 respectively, corresponding to 10 citations per paper and an impact factor of 2.32 per publication. The research articles originate primarily from COMSATS, NUST, PIEAS, and PINSTECH. Pakistan has published 60% of publication with the collaboration of the foreign institutes, mainly from the United States, the United Kingdom, China and Malaysia. The core research activities in the field are mainly focused on resource assessment, energy policy, energy efficiency, feasibility study, energy economics, and performance assessment. The most productive journal, author, institution, are renewable & sustainable energy review, Shahbaz M., and COMSATS, respectively.