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Effect of Streamwise Fences on Secondary Flows and Losses in a Twodimensional Turbine Rotor Cascade

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Journal of Thermal Science 2006年第4期15卷 296-305页

作者： m.Govardhan A.Rajender J.P.Umang Thermal Turbomachines Laboratory Department of Mechanical EngineeringIndian Institute of Technology MadrasChennai 600036India

To control secondary flows, streamwise fences were attached to end wall of a linear turbine rotor cascade. The cascade had 8 blades of 400 mm long and 175 mm chord. The blades deflected the flow by 120°. The fences were made out of 0.7 mm thick brass sheet and the heights of the fences were 14 mm, 18 mm respectively. The curvature of the fences was the same as that of the blade camber line. The fences were fixed normal to the end wall and at half pitch away from the blades. The experimental program consists of total pressure, static pressure measurements at the inlet and outlet of the cascade, by using five-hole probe. In addition, static pressure on the blade suction surface and pressure surface was also obtained. Fences are effective in preventing the movement of the pressure side leg of the horseshoe vortex. Consequently the accumulation of low energy fluid on the suction surface is minimised. End wall losses are reduced by the fences due to weakening of the end wall cross flow.

关键词： Turbine cascade streamwise fences loss core lift coefficient

Nanosized complex fluorides based on Eu^(3+) doped Sr_2LnF_7(Ln=La, Gd)

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Journal of Rare Earths 2014年第3期32卷 242-247页

作者： m.Runowski S.Balabhadra S.Lis Department of Rare Earths Faculty of Chemistry Adam Mickiewicz University

A simple co-precipitation approach taking place between Ln3＋, Sr2＋ cations and F anions, led to the formation of nanocrystalline Eu3＋ doped Sr2LnF7 （Ln-La and Gd） complex fluorides. The reaction was carried out in the presence of polyeth- ylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu3＋ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd3＋ ions to Eu3＋ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction （XRD） and transmission electron microscopy （TEm） measurements were performed. Also FT-IR spectra of the products were re- corded, revealing the presence of PEG molecules on the nanoparticles suN＇ace. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu3＋ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu3＋ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

关键词： luminescence Eu3+ doping complex strontium lanthanide fluorides nanoparticles Sr2LnF7 Sr0.69La0.31F2.31 rare earths

Indica rice spread to the Tibetan Plateau in the 700s CE

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Science China Earth Sciences 2022年第12期65卷 2297-2307页

作者： Qingli SUN Qi yang Yu GAO Zhengquan GU Jishuai yang Shuzhi WANG Zhikun mA Yan TONG Xiaoyan yang Group of Alpine Paleoecology and Human Adaptation(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemResources and Environment(TPESRE)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Western China’s Environmental Systems Ministry of EducationCollege of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China The Center for Scientific Archaeology Institute of ArchaeologyChinese Academy of Social SciencesBeijing 100101China School of Cultural Heritage Northwest UniversityXi’an 710069China Tibet Autonomous Regional Institute of Cultural Relics Preservation Lhasa 850008China

Asian cultivated rice(Oryza sativa)has two main subspecies,indica(*** ***)and japonica(*** ***).Japonica rice was domesticated in the middle and lower reaches of the yangtze River in China,while indica appeared around 4000 a BP in northern south Asia after hybridization between introduced japonica and indigenous *** and how indica rice spread into China is still barely understood,although it is cultivated widely in southern China *** we report on the earliest,definite indica rice remains in China,including charred seeds,phytoliths,and ancient DNA,from the newly investigated Kongsangqiao site at an elevation of 2676 m above sea level in Tibet,along with a charcoal study that reveals the vegetation and climate during of human *** radiocarbon dating of charred indica rice grains suggests the remains are from the 8th century(700s CE).The dominant identified charcoal fragments are Himalayan pine(Pinus wallichiana),from which a rather cold climate is inferred where indica rice could not be grown in situ,suggesting it was likely brought to the *** archaeological and literature records thus support that indica rice,fully domesticated in northern south Asia,had spread to the southern margin of the Tibetan Plateau via parts of the ancient Tang-Tubo Road,Tubo-Nepal Road,by at least the 8th century CE.

关键词： Kongsangqiao site Sedimentary ancient DNA Charcoal analysis Indica rice spread Gyirong Valley

Effect of substrate temperature on the physical properties of SnS_2:Cu thin films deposited by spray pyrolysis

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Journal of Semiconductors 2018年第12期39卷 46-51页

作者： m.R.Fadavieslam School of Physics Damghan University

The main impetus of the present study is to investigate thin films of tin disulfide that have been doped with copper impurities and prepared on glass substrates by using the spray pyrolysis technique. Also, the influence of the substrate temperature on the structural, optical, and electrical properties of these films are *** thin films have been characterized by X-ray diffraction(XRD), scanning electron microscopy(SEm), and optical absorption(UV-vis) analyses. The XRD patterns clarify that the thin films possess polycrystalline structures,having a peak associated with the(001) plane of the SnS2 phase. The average crystalline grain sizes were estimated to be within the range 5.7-7.1 nm. The SEm images indicate that the grain size increases from 53 to 114 nm with an increment in the substrate temperature, resulting in an increasing-decreasing trend in the band gap of the thin films. However, the films’ resistance decreases from 92.5 to 0.174 Ω·cm as the substrate temperature increases from 400 to 450 ℃. Also, their optical energy band gap depicts an increasing-decreasing trend with the estimated values of 2.81,3.21, and 3.06 eV at 400, 425, and 450℃, respectively. The thin films exhibit n-type conductivity.

关键词： spray pyrolysis thin film polycrystalline

Evaluation of the wind energy potential of two south west sites in Nigeria

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Frontiers in Energy 2012年第3期6卷 237-246页

作者： Olaleye m.AmOO Aeromechanics-Fan Blades Cold Section Engineering(CSE)United Technologies Corporation(UTC)-Pratt&WhimeyEast HartfordCT06108USA

Wind resource assessment is a crucial first step in gauging the potential of a site to produce energy from wind turbines. In this paper, the wind energy potential of Abeokuta （07°03＇N, 03°19＇E） and Ijebu-Ode （06°47＇N, 03°58＇E）, two south west sites in Nigeria were examined. Twenty years （1990-2010） of monthly mean wind data from a 10m height were subjected to two-parameter Weibull analysis and other statistical analyses. The results show that the average annual mean wind speed variation for Abeokuta ranges from 2.2 to 5.0 m/s. For Ijebu-Ode, it ranges from 2.0 to 5.0m/s. The wind power density variation based on the Weibull analysis ranges from 4.26 to 24.51 W/m2 for Abeokuta and from 8.54 to 76.46 W/m2 for Ijebu-Ode. Ijebu-Ode was found to be the better of the two sites in terms of annual variation of mean wind speed.

关键词： wind potential wind speed wind power density wind gust turbulence intensity Nigeria

Asphericity in the Fermi Surface and Fermi Energy of Na－K,Na－Rb and Na－Cs Binary Alloys

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Communications in Theoretical Physics 2002年第9期37卷 365-369页

作者： minalH.Patel A.m.Vora 等 DepartmentofPhysics SardarPatelUniversityVallabhVidyanagar388120GujaratIndia

Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior ofthe K, Rb, and Cs with the Na generates the Fermi surface distortion (FSD) of bce simple metals. The FS of Na-K,Na-Rb, and Na-Cs solid solution is a distorted sphere with the largest deviation along [110]. We have found that theimpact of local-field correction function on FSD is maximun at [100] point and minimum at [111] point. The exchangeand correlation effect is found to suppress the value of FE.

关键词：双金属合金费米表面费米能

Combustion and NO_(x)Emission Characteristics of Coal Slime Solid Waste at Different Feeding Positions

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Journal of Thermal Science 2023年第6期32卷 2351-2360页

作者： yang Xueting SONG Guoliang yang Zhao WANG Chao JI Zengcai ZHANG Xingshun Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China Dalian National Laboratory for Clean Energy Dalian116023China School of Engineering Science University of Science&Technology of ChinaHefei230026China Shandong Huaju Energy Co.Ltd Jining273500China

The NO_(x)emission of coal slime burned in circulating fluidized bed(CFB)boilers could hardly meet the increasingly strict standards in *** coal slime from the top of furnace led to uneven combustion in furnace and cyclones,short residence time and overheated tail heating *** effects of feeding positions on the combustion uniformity and pollutant emission characteristics of coal slime were *** experimental results showed that the coal slime combustion was more uniform when feeding from the front wall and longer residence time was conducive to the control of NO_(x)*** the boiler temperature and excess air ratio were almost identical,the initial NO_(x)emissions were 45.0 mg·m^(−3)and 70.7 mg·m^(−3)when feeding from the front wall and the top of furnace,respectively;the NO_(x)emission was cut down 36.35%when feeding from the front wall,successfully meeting the ultra-low NO_(x)emission standard of *** adoption of feeding from the front wall greatly reduced the original emission of NO_(x);the operation costs in the practical applications were saved to a large extent.

关键词： solid waste coal slime CFB boiler ultra-low NO_(x)emission feeding positions combustion uniformity

基于表面平整度控制的超大型环件轧制曲线自优化方法研究

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塑性工程学报 2025年第1期32卷 92-99页

作者：羊冠立钱东升田汉邓加东王丰武汉理工大学材料科学与工程学院湖北武汉430070 武汉理工大学现代汽车零部件技术湖北省重点实验室湖北武汉430070 武汉理工大学湖北省材料绿色精密成形工程技术研究中心湖北武汉430070

针对超大型环件轧制过程中出现的环件外表面不平整缺陷,基于ABAQUS有限元软件建立超大型环件径轴向轧制热-力耦合有限元模型,研究了轧制过程中环件外表面平整性演变规律,进一步揭示了轴向与径向变形速率比对环件外表面不平整度变化的影... 详细信息

针对超大型环件轧制过程中出现的环件外表面不平整缺陷,基于ABAQUS有限元软件建立超大型环件径轴向轧制热-力耦合有限元模型,研究了轧制过程中环件外表面平整性演变规律,进一步揭示了轴向与径向变形速率比对环件外表面不平整度变化的影响规律。提出了一种两段式轧制曲线设计方法,进而建立了一种基于环件外表面平整状态反馈的轧制曲线自优化控制模型,将自优化过程中环件外表面不平整度与预设S型轧制曲线所得不平整度进行了比较,结果表明,自优化控制方法得到的轧制曲线提升了环件外表面的平整度,轧制结束时环件中间高度与下端面处不平整度分别降低了36.6%和25.5%。

关键词：超大型环件径-轴向轧制平整度数值模拟

Chitosan/Nanocrystalline Cellulose Biocomposites Based on Date Palm (Phoenix Dactylifera L.) Sheath Fibers

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Journal of Renewable materials 2019年第6期7卷 567-582页

作者： Abeer m.Adel Amira m.El-Shafei Atef A.Ibrahim mona T.Al-Shemy Cellulose and Paper Department National Research Center33El-Bohouth St.(Former El-Tahrir St.)DokkiP.O.12622GizaEgypt Textile Research Division National Research Center33El-Bohouth St.(Former El-Tahrir St.)DokkiP.O.12622GizaEgypt

In this study,nanocrystalline celluloses were used to enhance physical,mechanical and water vapor barrier properties of chitosan films for potential food packaging *** different mineral acids(sulfuric and phosphoric)were used to extract nanocrystalline cellulose from date palm sheath *** influence of cellulose I and cellulose II on the properties of the isolated nanocrystalline celluloses(e.g.,yield,energy and length of intra-and intermolecular hydrogen bonds,and degree of substitution)were studied *** characteristics of chitosan biocomposite film with phosphorylated nanocrystalline cellulose were compared to those with sulfated nanocrystalline *** showed that besides cellulose polymorphism,the ionic ester groups on the surface of nanocrystalline cellulose is one of the factors influencing the physical,chemical,mechanical,and water vapor barrier properties in chitosan/nanocrystalline cellulose biocomposites.

关键词： Biocomposite Cellulose I Cellulose II Nanocrystalline cellulose(NCC) physico-mechanical properties Thermal stability