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Comparison between oxide-reduced and water-atomized copper powders used in making sintered wicks of heat pipe

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China Particuology 2007年第3期5卷 220-224页

作者： Liu-ho Chiu Chang-Hui Wu Pee-yew Lee Department of Materials Engineering Tatung University Taipei 10451 Taiwan China Institute of Materials Engineering Taiwan Ocean University Keelung Taiwan China

Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced （OR） powders were compared with one from water-atomized （WA） powder. The green specimens were sintered at temperatures from 800 to 1000 ℃ in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR - 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.

关键词： Sintered wick Copper powder Porous property Oxide-reduced powder

Meeting the communicative demands in academic and professional training curricula: An overview of ELT in tertiary institutions in Singapore

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外语教学与研究 2001年第4期33卷 258-267页

作者： ho Wah kam TheSingaporeTeachers'Union

This paper focuses on the upper end of the formal Singapore educational spectrum,providing an overview of ELT in polytechnics and universities. It is in four *** order to show continuity between ELT in schools and tertiary institutions,Part 1 explains briefly the nation’s language policy in *** Part 2,an attempt is made to delineate the main trends in ELT in universities and polytechnics and the approaches to ELT generally adopted for mature learners. Part 3 draws attention to the changing emphases in tertiary education in Singapore and to how students are being prepared in innovative ways in ELT for a globalised world and a knowledge based economy. Part 4 provides a summary of the paper.

关键词：英语教学高等院校教学方法语言交际能力

Multi-element analysis by ArF laser excited atomic fluorescence of laser ablated plumes： Mechanism and applications

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Frontiers of physics 2012年第6期7卷 670-678页

作者： Yue Cai Po-Chun Chu Sut kam ho Nai-ho Cheung Department of Physics Hong Kong Baptist University Kowloon Tong Hong Kong China Faculty of Science and Technology University of Macao Macao China

A new multi-element analysis technique based on laser-excited atomic fluorescence was reviewed. however, the one-wavelength-one-transition constraint was overcome. Numerous elements were induced to fluoresce at a single excitation wavelength of 193 nm. This was possible provided that the analytes were imbedded in dense plumes, such as those produced by pulsed laser ablation. The underlying mechanism of the technique was explained and corroborated. Analytical applications to metals, plastics, ceramics and their composites were discribed. Detection limits in the ng/g range and mass limits of atto moles were demonstrated. Several real-world problems, including the analysis of paint coating for trace lead, the non-destructive analysis of potteries and ink, the chemical profiling of electrode plastic interfaces, and the analysis of ingestible lead colloids were discussed.

关键词： laser-excited atomic fluorescence (LEAF) argon fluoride laser laser plume spectroscopy multi-element analysis

Luminescent cyclometalated iridium(Ⅲ) dipyridoquinoxaline indole complexes as biological probes

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Science China Chemistry 2010年第10期53卷 2091-2098页

作者： LO Kenneth kam-Wing LEUNG Arthur ho-hon Department of Biology and Chemistry City University of Hong Kong

Four luminescent cyclometalated iridium(Ⅲ) dipyridoquinoxaline complexes appended with an indole moiety [Ir(N^C)2(N^N)] (PF6) (HN^C = 2-phenylpyridine, Hppy; N^N = 2-(N-(2-(indole-3-acetamido)ethyl)aminocarbonyl)dipyrido[3,2-f:2′,3′-h]quinox- aline, dpqC2indole (1a), N^N = 2-(N-(6-(indole-3-acetamido)hexyl)aminocarbonyl)dipyrido[3,2-f:2′,3′-h]quinoxaline, dpqC6indole (1b); HN^C = 7,8-benzoquinoline, Hbzq, N^N = dpqC2indole (2a), N^N = dpqC6indole (2b)) have been synthesized and characterized. Upon irradiation, all the complexes displayed moderately intense and long-lived luminescence under ambient condi-tions and in 77 K glass. On the basis of the photophysical data, the emission of the complexes has been assigned to an excited state of triplet metal-to-ligand charge-transfer (3MLCT) ((dπ(Ir)→π*(N^N)) character. Cyclic voltammetric studies revealed indole-based and iridium-based oxidations at ca. +1.10 V and +1.24 V vs. SCE, respectively, and ligand-based reductions at ca. -1.07 to-2.29 V vs. SCE. The interactions of the complexes with an indole-binding protein, bovine serum albumin (BSA), have been examined by emission titrations.

关键词： binding indole iridium luminescence probes

On the first negative Hecke eigenvalue of an automorphic representation of GL_(2)(A_(Q))

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Science China Mathematics 2021年第11期64卷 2381-2394页

作者： Yuk-kam Lau Ming ho Ng Hengcai Tang Yingnan Wang Department of Mathematics The University of Hong KongHong KongChina Department of Mathematics The Chinese University of Hong KongHong KongChina Institute of Modern Mathematics School of Mathematics and StatisticsHenan UniversityKaifeng 475004China Shenzhen Key Laboratory of Advanced Machine Learning and Applications College of Mathematics and StatisticsShenzhen UniversityShenzhen 518060China

Letπbe a self-dual irreducible cuspidal automorphic representation of GL_(2)(A_(Q))with trivial central *** Hecke eigenvalue λπ(n)is a real multiplicative function in *** show that λπ(n)<0 for some n< 详细信息

关键词： automorphic representation Hecke eigenvalue Maass cusp form sign change

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Investigation of pressure drop in flexible ventilation ducts under different compression ratios and bending angles

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Building Simulation 2021年第4期14卷 1251-1261页

作者： ho kam Dai Wenjie Huang Liye Fu Chao-Hsin Lin Daniel Wei Zhongzhe Dong Ruoyu You Chun Chen Department of Mechanical and Automation Engineering The Chinese University of Hong KongShatinN.T.999077Hong KongChina Department of Building Services Engineering The Hong Kong Polytechnic UniversityKowloon999077Hong KongChina Environmental Control Systems Boeing Commercial AirplanesEverettWA98203USA Boeing Research&Technology Beijing100027China Shenzhen Research Institute The Chinese University of Hong KongShenzhen518057China

Due to the large degree of freedom in terms of design and installation, flexible ventilation ducts are commonly used in ventilation systems. however, excessive use of flexible ducts may lead to greater pressure drop and higher energy consumption. This study conducted experimental measurements to characterize the pressure drop in flexible ventilation ducts with different compression ratios and bending angles. This investigation first measured the pressure drop in straight flexible ducts with four compression ratios under various airflow rates. The calculated friction factor for the straight flexible ducts was negatively associated with the compression ratio. Next, the pressure drops in single-bend flexible ducts with various bending angles from 30° to 150° were measured under various airflow rates. The calculated loss coefficient of the bend increased with the bending angle for single-bend flexible ducts. Finally, the influence of the intermediate duct length on the pressure drop across two bends was experimentally investigated. When the length of the intermediate duct was greater than eight times the inner diameter, the pressure drop across a double-bend flexible duct could be calculated from the friction factors and loss coefficients with a relative error less than 1%. The data obtained in this study can be used to calculate the total pressure loss in flexible ventilation ducting systems in buildings.

关键词： ventilation pressure loss flex duct fan energy friction factor loss coefficient

A newly discovered active contact binary in the field of NGC 1348

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Research in Astronomy and Astrophysics 2012年第1期12卷 93-103页

作者： Xiang-Song Fang Sheng-hong Gu ho-Keung Hui Chi-Tai Kwok Bill Yeung kam-Cheung Leung National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China hokoon Nature Education cum Astronomical Centre Sik Sik-Yuen Hong Kong China hong Kong Astronomical Society Hong Kong China

We present a CCD photometry study of a newly discovered active eclipsing binary in the field of open cluster NGC 1348 based on the first time-series photometric observation. From the minimum times, we determined an orbital period of P = 0.691363 d. Among our datasets, the BV（.RI）c light curves obtained in November 2008 were analyzed using the Wilson-Devinney light curve modeling tech- nique. Because of the uncertainty of the membership of this binary in open cluster NGC 1348, we have analyzed the photometric data in two cases with different primary effective temperatures： Case A （T1 = 7750K） and Case B （T1 = 5250K）. Our anal- yses reveal that, for Case A, it is a deep （f 〉 70%）, very low mass ratio （q - 0.096） binary system, indicating that it is now in the late evolution stage of a contact binary; while for Case B, it is a red system with extraordinarily long orbital period with respect to the period-color relation for normal contact binaries, which suggests that this binary has evolved off the main sequence. The well known O＇Connell effect （e.g., AB 0.03 mag） was found in the dataset obtained in November 2008, which could be due to the existence of starspots on the components, therefore the corresponding spot properties （for Case A： hot spot; for Case B： dark spot） were determined using the Wilson-Devinney code. With the purpose of analyzing the dark spot activity for Case B, we compared the light curves derived in different observing runs, and found that a slight change appeared from November to December, 2008, which indicates the evolution of spot activity on at least one component over a time scale of about one month.

关键词： stars: binaries: close -- stars: binaries: eclipsing -- stars: spots

Effects of ethanol on the tonicity of corporal tissue and the intracellular Ca^2＋ concentration of human corporal smooth muscle cells

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Asian Journal of Andrology 2010年第6期12卷 890-898页

作者： Sung Chul kam Mee Ree Chae Ji Young Kim Seol ho Choo Deok Hyun Han Sung Won Lee Department of Urology Samsung Medical Center Sungkyunkwan University School of Medicine Seoul 135-710 Korea

Heavy alcohol consumption is associated with an increased risk of erectile dysfunction （ED）; however, the acute effects of ethanol （EtOH） on penile tissue are not fully understood. We sought to investigate the effects of EtOH on corporal tissue tonicity, as well as the intracellular Ca^2＋ concentration （[Ca^2＋]i） and potassium channel activity of corporal smooth muscle. Strips of corpus cavernosum （CC） from rabbits were mounted in organ baths for isometric tension studies. Electrical field stimulation （EFS） was applied to strips precontracted with 10 μmol L^-1 phenylephrine as a control. EtOH was then added to the organ bath and incubated before EFS. The [Ca^2＋]i levels were monitored by the ratio of fura-2 fluorescence intensities using the fura-2 loading method. Single-channel and whole-cell currents were recorded by the conventional patch-clamp technique in short-term cultured smooth muscle cells from human CC tissue. The corpus cavernosal relaxant response of EFS was decreased in proportion to the concentration of EtOH. EtOH induced a sustained increase in [Ca^2＋]i in a dose-dependent manner, Extracellular application of EtOH significantly increased whole-cell K^＋ currents in a concentration-dependent manner （P 〈 0.05）. EtOH also increased the open probability in cell-attached patches; however, in inside-out patches, the application of EtOH to the intracellular aspect of the patches induced slight inhibition of Ca^2＋-activated potassium channel （KCa） activity. EtOH caused a dose-dependent increase in cavemosal tension by alterations to [Ca^2＋]i. Although EtOH did not affect KCa channels directly, it increased the channel activity by increasing [Ca^2＋]i. The increased corpus cavemosal tone caused by EtOH might be one of the mechanisms of ED after heavy drinking.

关键词： alcohol Ca^2+-activated potassium channel corporal smooth muscle penile erection

Magnetic activity of the spotted dwarf AP149 in the α Persei open cluster

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Research in Astronomy and Astrophysics 2010年第3期10卷 253-265页

作者： Xiang-Song Fang Sheng-hong Gu Sze-Leung Cheung ho-Keung Hui Chi-Tai Kwok kam-Cheung Leung National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China ho Koon Nature Education cum Astronomical Centre Sik Sik Yuen Hong Kong China hong Kong Astronomical Society Hong Kong China

The simultaneous photometric and spectroscopic observations of the spotted G dwarf AP149 in the young open cluster α Persei are analyzed here. We reconstruct the observed light curves with a two-starspot model by means of a light curve modeling technique, and find that the active regions shift oppositely along longitude on a time scale of one day. Combining with the observational data obtained by other groups, we discuss the evolution of spotted regions in the photosphere, and find that its starspots evolve not only on a short time scale but also on a long time scale. The pure chromospheric emissions for Ca IIHK and Hβ lines are derived by using the spectral subtraction technique. The variation of Ca IIHK lines＇ excess emission is spatially correlated to the starspot regions. There is no clear rotational modulation for the Hβ line＇s excess emission, probably due to the contamination of prominence emission.

关键词： stars: activity -- stars: late-type -- stars: spots -- stars: individual AP149