Cycle performance studies on a new HFC-161/125/143a mixture as an alternative refrigerant to R404A

In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a (0.15/0.45/0.40 in mass fraction), as a promising mixed refrigerant to R404A, is presented. The ozone depletion potential (ODP) of the new refrigerant is zero and its basic thermodynamic properties are similar to those of R404A, but its global warming potential (GWP) is much smaller than those of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition I (the average evaporation temperature: −23 °C, the average condensing temperature: 43 °C, the superheat temperature: 28 °C, the subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher, respectively, than those of R404A. The coefficient of performance (COP) of the new mixture is 5.19% higher than that of R404A and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II (the average evaporation temperature: −40 °C, the average condensing temperature: 35 °C, the superheating temperature: 30 °C, the subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions (condensing temperatures: 35–45 °C, evaporation temperatures: −40–−20 °C). Experimental results show that the new mixture can obtain a higher COP, by 6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system.     

版面费难题的破解呼唤评价机制、管理体制创新--关于学术刊物版面费问题论争的述评

随着越来越多的学术刊物开始收取版面费,版面费问题引起了广泛关注。充分交锋的各种观点,主要涉及版面费是否合理合法、产生原因与破解路径等。对于版面费的存废,学术期刊本身无能为力,需要通过政府行为,以政策创新各种评价机制和考核机制,从源头上控制论文发表的非正常需求;强化对期刊的综合治理,淘汰“害群之马”;加大对期刊的经费投入,保障刊物正常运转。所以,版面费难题的破解呼唤学术评价机制和刊物管理体制创新。     

关于中职英语教学的改革与探索

由于中职学生的英语基础普遍薄弱,传统的英语教学方法已经不适应他们的现状,本文主要阐述中职英语教材的改革、课堂教学的改革和考试方法的改革,从而吸引学生兴趣,提高中职英语教学的效果。     

Effects of the shape and size of a mooring line surface buoy on the mooring load of wave energy converters

This paper describes the physical model testing of a wave energy converter (WEC) undertaken in the Henot-watt wave basin during October 2010 as part of the SUPERGEN2 project funded by the British gover...     

Using quantitative data in World Bank per-student funding reform projects: data,designs and dilemmas in transition countries

Since the late 1980s, education systems have increasingly moved to allocating funding for general education by means of a per-student formula. The trend started with developed economies and moved to transition and developing economies, where the World Bank has promoted the adoption of per-student funding (PSF). But promoting a particular reform, such as PSF, by including it in a package of sector-specific development projects funded by World Bank grants or loans, and employing local and international specialist staff do not guarantee successful implementation. This paper examines experience with implementing PSF to school level in transition countries, comparing varying degrees of success to date (2013) in Bulgaria, Moldova and Kosovo. The paper considers the dilemmas inherent in designing PSF formulae for schools, how this played out in each of the countries and the reasons for varying success in implementation.     

新时期高等院校园艺专业大学生创业教育探索与研究

近年来,大学生就业压力逐年增大,高校毕业生创业是时代对大学生的要求,部分大学毕业生开始选择自主创业,由于园艺专业毕业生有创业模式多样、创业门槛低等方面的优势再加上政府也出台了相关政策予以鼓励。在此背景下选择创业道路,对于高校园艺专业的毕业生来说并不是一种无奈的选择,因为他们有独特的创业优势。研究如何引导他们树立创业意识,提高创业能力,变就业岗位的竞争者为就业岗位的供给者,意义十分重大。     

Founders’ Continuing Roles in Schools Supporting Self-Directed Learning

What should be the continuing role of founders in schools supporting self-directed learning? To answer this, the founders’ views of two North American schools for self-directed learners will be compared. One school is exam-focused and private; the other is, test-free and public. The founders of both schools have comparable beliefs regarding the importance of self-direction in education: Dr. Able, the founder of Able School, sees the primary value of the school as constructing a cohesive “tribe” based on the Socratic method of questioning. Dr. Green, influenced by A. S. Neill’s Summerhill in founding Unschool, considers freedom to live life as one chooses as the principle value. Although both founders played a substantial role in the formative years of their schools, only the founder of Able School still holds a prominent position in the school. Why does this discrepancy exist in the continuing role of the founders? What continuing role for a founder is most compatible with democratic society? The answers to these questions provided in this paper are based on personal communications with Dr. Green after a visit this founder of Unschool made to Able School December 12, 2013 to meet with Dr. Able. The names of the founders and their schools are pseudonyms.     

Student Learning about Biomolecular Self-Assembly Using Two Different External Representations

Self-assembly is the fundamental but counterintuitive principle that explains how ordered biomolecular complexes form spontaneously in the cell. This study investigated the impact of using two external representations of virus self-assembly, an interactive tangible three-dimensional model and a static two-dimensional image, on student learning about the process of self-assembly in a group exercise. A conceptual analysis of self-assembly into a set of facets was performed to support study design and analysis. Written responses were collected in a pretest/posttest experimental design with 32 Swedish university students. A quantitative analysis of close-ended items indicated that the students improved their scores between pretest and posttest, with no significant difference between the conditions (tangible model/image). A qualitative analysis of an open-ended item indicated students were unfamiliar with self-assembly prior to the study. Students in the tangible model condition used the facets of self-assembly in their open-ended posttest responses more frequently than students in the image condition. In particular, it appears that the dynamic properties of the tangible model may support student understanding of self-assembly in terms of the random and reversible nature of molecular interactions. A tentative difference was observed in response complexity, with more multifaceted responses in the tangible model condition.     

Use of Polarised Light Microscopy to Improve Conservation of Parchment

ABSTRACT

The preservation state of parchment primarily depends on the structure of the collagen fibre network, which in turn is responsible for optical anisotropy, i.e. birefringence. Polarised light microscopy can therefore be used as a non-invasive technique that allows recording of birefringence distribution in the parchment, which directly relates to stress–strain distribution. Using samples from diverse sources (commercial parchment, parchment used by restorers for book binding, and parchment fabricated for the purpose of this study), we assessed the capability of polarised light microscopy for various diagnostics. We performed, for instance, identification of gelatinised regions, layered or ?brous regions in parchment cross section, qualitative analysis of parchment fat content (lipids), observation of stress-induced patterns resulting from tensile tests, and observation of water diffusion. These proof-of-principle experiments extend the capability of polarised light microscopy far beyond its common use and open the path to its deployment in conservation studies.