Throughput analysis of production systems: recent advances and future topics

Throughput analysis is important for the design, operation and management of production systems. A substantial amount of research has been devoted to developing analytical methods to estimate the throughput of production systems with unreliable machines and finite buffers. In this paper we summarise the recent studies in this area. In addition to the performance evaluation of serial lines, approximation methods for more complex systems, such as assembly/disassembly systems, parallel lines, split and merge, closed-loop systems, etc., are discussed. Moreover, we propose future research topics from the automotive manufacturing systems perspective.     

Flash pyrolysis of biomass: a review of recent advances

Clean Technologies and Environmental Policy - To assuage global consumer demand for energy, there is a need for increased biofuel production. Flash pyrolysis is an important technique for biomass...     

Sustainability: ecological, social, economic, technological, and systems perspectives

Sustainability is generally associated with a definition by the World Commission on Environment and Development, 1987: "... development that meets the needs of the present without compromising the ability of future generations to meet their own needs ..." However, there is no mathematical theory embodying these concepts, although one would be immensely valuable in humanity's efforts to manage the environment. The concept of sustainability applies to integrated systems comprising humans and the rest of nature; the structures and operation of the human component (society, economy, law, etc.) must be such that they reinforce the persistence of the structures and operation of the natural component (ecosystem trophic linkages, biodiversity, biogeochemical cycles, etc.). One of the challenges of sustainability research lies in linking measures of ecosystem functioning to the structure and operation of the associated social system. We review the nature of this complex system including its ecological, social, economic, and technological aspects, and propose an approach to assessing sustainability based on Information Theory that bridges the natural and human systems. These principles are then illustrated using a model system with an ecological food web linked to a rudimentary social system. This work is part of the efforts of a larger multidisciplinary group at the U.S. Environmental Protection Agency's National Risk Management Research Laboratory.     

Review of silicon photonics: history and recent advances

Silicon photonics has attracted tremendous attention and research effort as a promising technology in optoelectronic integration for computing, communications, sensing, and solar harvesting. Mainly due to the combination of its excellent material properties and the complementary metal–oxide semiconductor (CMOS) fabrication processing technology, silicon has becoming the material choice for photonic and optoelectronic circuits with low cost, ultra-compact device footprint, and high-density integration. This review paper provides an overview on silicon photonics, by highlighting the early work from the mid-1980s on the fundamental building blocks such as silicon platforms and waveguides, and the main milestones that have been achieved so far in the field. A summary of reported work on functional elements in both passive and active devices, as well as the applications of the technology in interconnect, sensing, and solar cells, is identified.     

Science and engineering of electrospun nanofibers for advances in clean energy,water filtration,and regenerative medicine

Nanostructured materials with high aspect ratio and one-dimensional (ID) morphology are nature’s choices when high degree of functional performances and flexible properties are concerned. Two examples are extracellular matrices in tissues of living organism, and light harvesting rods of the retina and chlorophyll. Electrospinning (E-spinning) is a simple processing technique that allows fabrication of high aspect ratio nanofibers (NFs) in a commercial scale. Electrospun nanofibers (E-spun NFs) combine a number of physical properties such as guided electron transport, strain-induced electronic properties, high mechanical strength, high degree of flexibility, large specific surface area, high electron and thermal diffusivity, and tailorable pore distribution. Our laboratory has been involved in fabrication of E-spun polymeric, inorganic, and polymer-nanocomposite fibers in random, aligned, cross-aligned, sheaths, tubes, yarns, core/shell, and trilayer morphologies. This article focuses on application of the E-spun fibers in the areas of clean energy, water treatment, and regenerative medicine in the authors’ laboratory. In addition, the article briefly reviews the progress made in these areas using E-spun NFs.     

Inorganic solid state optical materials:: Major recent advances

Major advances have recently been made concerning the optical properties of solid-state materials. Four notable areas of research are: upconversion and downconversion luminescence, new high-efficiency scintillator materials, and photonic band gap materials or photonic crystals. Each of these research fields has contributed greatly to our basic understanding of solid-state optical materials as well as contributing to applied research.     

Recent advances in visible light-driven water oxidation and reduction in suspension systems

In order to solve the shortage of sustainable energy and the related concern about combustion of fossil fuels, converting the most abundant solar energy into chemical fuels becomes one of the most promising choices to provide the everlasting and environmentally friendly energy vector along with the minimum impact on environment. Among the methods of converting solar energy into chemical fuels, there is a significant interest in the renewable hydrogen production by photocatalysts from abundant water under visible light irradiation. Therefore, the development of efficient photocatalysts for water reduction and oxidation in a suspension system is the footstone for the development of solar energy conversion. In this review, the fundamental theory of photocatalysis and key factors affecting photocatalysis will be introduced first. Then the new materials development covering inorganic materials (oxides, nitrides and sulfides), carbon-based photocatalysts, and semiconductor-coordination compound photocatalysts developed over the past 10?years will be addressed with discussion about dominating factors in the photochemical process. This review would provide a comprehensive reference to exploring the efficient and novel materials working for the solar energy conversion to affordable and sustainable fuels. Finally, the perspective of the technology is also discussed.     

Sustainability evaluation framework for building cooling systems: a comparative study of snow storage and conventional chiller systems

In Canada, the residential building sector consumes 17 % of the total energy and 15 % of the total greenhouse gas emissions. In particular, the energy demand for cooling in the residential sector is increasing due to the large occupancy floor area and high usage of air conditioning. Minimizing energy use and greenhouse gas emissions is one of the highest priority goals set for national energy management strategies in developed countries including Canada. In this study, a framework based on the life cycle assessment approach is developed to assess the environmental impacts of different building cooling systems, namely conventional snow storage system, watertight snow storage system, high-density snow storage system, and the conventional chiller cooling system. Moreover, all these systems have varying energy requirements and associated environmental impacts during different phases (extraction and construction, utilization, and end of life) of the life cycle of a building. A low-rise residential building in Kelowna (BC, Canada) has been selected for the pragmatic application of the proposed framework. The annual cooling energy demand for the building is estimated for different phases. Subsequently, the life cycle impact assessment has been carried out using SimaPro 8.1 software and TRACI 2.1 method. For sustainability evaluation of different cooling systems over their life cycle, multi-criteria decision analysis has been employed using the ‘Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE II).’ The results showed that the snow storage systems tend to reduce greenhouse gas emissions and associated environmental impacts more than the conventional system.     

Dark energy: recent observations and future prospects

Dark energy presents us with a challenging puzzle: understanding the new physics seen in the acceleration of the expansion of the Universe. Measurements using type-Ia supernovae (SNe) first detected this acceleration, and this approach remains the most direct route to studying the details of the Universe's expansion history that can teach us more about the nature of the dark energy. Such measurements are, however, extremely demanding in both precision and accuracy, since the different dark-energy models predict very small differences in the expansion history. While several cosmological probes may reach the required statistical uncertainties, the key measurement limit will be the systematic uncertainty. The supernova-measurement approach has the advantage of well-studied systematic uncertainties, allowing a next-generation experiment to be pursued. We briefly review the progress to date and examine the promise of future surveys with large numbers of SNe and well-bounded systematics.     

室内环境参数对空调能耗的影响

综述室内环境舒适性参数变化对空调系统能耗的影响,主要涉及室内CO2浓度、新风量、室内温度设定值和室内风速等4个环境参数。此外,分析空调系统运行最佳工况,为空调设计者或使用者提供参考。     

Renewable energy transition: a market-driven solution for the energy and environmental concerns in Chile

Chile is undergoing a remarkable energy matrix transition to renewable energy. Renewable energies are expanding extraordinarily fast, exceeding earlier predictions. As a result, the country is expected to meet its 2025 goal of generating 20% of its electricity from renewable energy sources quite before. Chile has become one of the first countries in the world with subsidy-free markets, where renewable projects compete directly with other conventional sources. Favorable market conditions and successful policy reforms were keys to fostering this renewable energy development. Although the country has achieved a substantial growth in renewable energy investment in a relatively short period of time, this optimism should be treated with caution. A successful transition requires a combination of a clear decision making, persistent and consistent government policies, and a clear commitment to tackling challenges to accommodate renewable energy in the power system. In this context, this paper analyses the Chilean renewable industry and the required government policies to succeed in this transition. For this purpose, we identify several critical factors that have attracted and that could attract investment to the renewable energy sector and propose key recommendations to effectively address the major challenges faced for the future development of the industry.     

Challenges and recent advances in photodiodes-based organic photodetectors

Organic photodetectors (OPDs) have drawn extensive research efforts due to their tailorable spectral response, ease of processing, compatibility with flexible devices and cooling-free operations. In this review, we outline the promising strategies for constructing high-performance and highly stable photodiodes-based OPDs from the perspectives of molecular engineering, morphology control, and device structure design. Firstly, the impact of molecular design and morphology control on OPD performance is clearly underlined and the molecular design rules and quantitative analysis methods are presented for high-performance OPDs. Subsequently, some striking device designs for multifunctional applications are discussed to elucidate the corresponding mechanism for various responses. What follows are the research efforts of boosting OPD stability for commercial applications. This review not only presents the detailed discussion on various OPD strategies aiming at simultaneously enhancing performance and stability but also provides some insights for the remaining challenges to make further breakthrough of OPDs.     

超声强化超临界流体萃取技术及其最新进展

文章较系统地介绍了超声强化超临界CO2萃取装置的设计,讨论了超声强化超临界CO2萃取技术的应用、萃取模型及其超声强化机理。超声强化与其他强化方法相比较,具有无污染、强化效率高等优点,超声波加入不仅降低了萃取系统的压力、萃取温度以及夹带剂用量和萃取时间,而且提高了萃取率,同时萃取对象的结构并没有发生变化。文章还提出了以后研究的重点。     

Review of recent progress on in situ TEM shear deformation: a retrospective and perspective view

Journal of Materials Science - Advances in the use of in situ transmission electron microscopy (TEM) to study mechanical deformation have enabled a direct correlation of mechanical properties with...     

Nanostructure engineering in porous columnar thin films: recent advances

Glancing angle deposition (GLAD) is a physical vapour deposition method used to fabricate highly functional thin films with an engineerable columnar morphology. Recent developments in GLAD technology have produced columnar nanostructures of increased complexity, including periodic, nanofibrous, perforated, and graded porosity thin films for use in applications ranging from sensors and actuators to optical filters, microfluidics, and catalysis. A brief review of GLAD methodology and historical developments is followed by a discussion of the latest developments in this field.     

Antennas for wireless communication: recent advances using dielectric resonators

Over the last few years, developments in wireless communications have presented many challenges to the antenna and microwave communities in terms of special requirements for antenna design, fabrication and integration. These requirements include new characterisation in terms of antenna performance, miniaturised size and shape and new suitable fabrication and implementation techniques to fit with the devices. These aspects are addressed with a focus on recent developments in dielectric resonator antenna research to meet some of the new challenges. A few recent representative designs, which outline new innovations and improved antenna features, as well as directions for future research, are briefly described.