检索结果-南通市图书馆

Absolute cryogenic radiometer for high accuracy optical radiant power measurement in a wide spectral range

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2019年第9期17卷 50-54页

作者：甘海勇赫英威刘想靓徐楠吴厚平冯国进刘文德林延东 Division of Optics National Institute of Metrology

An absolute cryogenic radiometer(ACR) with a detachable optical window was designed and built for high accuracy optical radiant power measurement and photodetector spectral responsivity calibration. The ACR receiver is an electroplated pure copper cavity with a 50-μm-thick wall and inner surface coated with a specular black polymer material mixed with highly dispersible carbon nanotubes. The absorptivity of the cavity receivers was evaluated to be ≥0.9999 in the 250 nm–16 μm wavelength range and ≥0.99995 in 500 nm–16 μm. The cavity receiver works at the temperature of ~5.2 K with nanowatt-level noise-equivalent power. The relative standard uncertainty is 0.041% for the measurement of ~100 μW optical radiant power(250 nm–16 μm) and 0.015% for^1 m W(500 nm–16 μm).

关键词： Absolute cryogenic radiometer optical radiant power measurement

cryogenic System for PKU-FEL

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Physics 2013年第6期4卷 1-4页

作者： Lianyou Xiong Nan Peng Wenhai Lu Liqiang Liu Xiaojun Liu Jing Li Liya Ma Bing Dong Yongcheng Jiang Jiancheng Tang Liang Zhang State Key Laboratory of Technologies in Space cryogenic Propellants Beijing China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing China

PKU-FEL based on superconducting (SC) accelerator facility is under construction at PekingUniversity. It will run in IR (5 - 10 μm) and THz (100 - 3000 μm) region as an ideal experimental FEL platform for universities. The SC accelerator facility is composed of a DC-SC injector and a 1.3-GHz 2 × 9-cell SC accelerator. In order to better the performance, the injector and the accelerator are bath-cooled by 2 K super fluid helium in cryostats. A 2 K cryogenic system has been designed, constructed and assembled.

关键词： Free Electron Laser Superconducting Accelerator cryogenic System

Role of remote Coulomb scattering on the hole mobility at cryogenic temperatures in SOI p-MOSFETs

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2020年第3期29卷 473-479页

作者：张先乐常鹏鹰杜刚刘晓彦 Institute of Microelectronics Peking UniversityBeijing 100871China

The impacts of remote Coulomb scattering(RCS)on hole mobility in ultra-thin body silicon-on-insulator(UTB SOI)p-MOSFETs at cryogenic temperatures are investigated.The physical models including phonon scattering,surface roughness scattering,and remote Coulomb scatterings are considered,and the results are verified by the experimental results at different temperatures for both bulk(from 300 K to 30 K)and UTB SOI(300 K and 25 K)p-MOSFETs.The impacts of the interfacial trap charges at both front and bottom interfaces on the hole mobility are mainly evaluated for the UTB SOI p-MOSFETs at liquid helium temperature(4.2 K).The results reveal that as the temperature decreases,the RCS due to the interfacial trap charges plays an important role in the hole mobility.

关键词： remote Coulomb scattering hole mobility cryogenic temperatures UTB SOI p-MOSFETs

Analysis of Thermal Conductivity of Frost on cryogenic Finned-tube Vaporizer Using Fractal Method

在线全文

学校读者我要写书评

暂无评论

Energy and Power Engineering 2013年第4期5卷 109-115页

作者： Shuping Chen Shuting Yao Fushou Xie School of Petrochemical Engineering Lanzhou University of Technology Lanzhou China

Thermal conductivity of frost is not only related to density, but also affected by its microstructure and environmental conditions, and it will continuously change with the formation and growth of frost. Images of frost formation and growth on the cryogenic surface in various shapes at different stages were obtained by experimental measurements, and a numerical simulation of frost formation and growth was carried out based on Diffusion Limited Aggregation (DLA) model of fractal theory in this paper. Based on the frost structure obtained by experiment, the fractal dimension of pore area distribution and porosity of frost layer on the cryogenic finned-tube?vaporizer were calculated by using fractal method, and combined with heat conduction model of frost layer obtained by thermal resistance method, the thermal conductivity of frost on the cryogenic surface was calculated. The result shows that the thermal conductivity calculated by the fractal model coincides with the range of the experimental data. Additionally, comparison with other heat conduction models indicated that it is feasible to introduce the fractal dimension of pore area distribution into heat conduction model to deduce the thermal conductivity of frost.

关键词： cryogenic Finned-tube Vaporizer Thermal Conductivity Frost Layer Fractal

Influence of Deep cryogenic Treatment (DCT) on Thermo Mechanical Performance of AISI H13 Tool Steel

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science and Chemical Engineering 2017年第1期5卷 91-101页

作者： Valmik Bhawar Shreyans Khot Prakash Kattire Mohan Mehta Rajkumar Singh Kalyani Center for Technology and Innovation Bharat Forge Ltd. Pune India

Deep cryogenic treatment (DCT) is one of the most recent processes being used to treat tool steels. It is a supplementary treatment where components are treated below subzero temperatures for several cryo-soaking hours. This paper focuses on to study the effect of deep cryogenic treatment on Thermo mechanical properties of AISI H-13 tool steel. Deep cryogenic treatment at 32 hours of cryo-soaking time is applied and thermo mechanical performance of tool steel was analyzed by using pin on disk high temperature wear testing and stress rupture testings. The microstructural evolutions during DCT were evaluated by using scanning electron microscope (SEM). It was observed that microstructural modifications like increase in carbide density, fine and uniform martensitic structure during DCT had significantly improved properties.

关键词： cryogenic Treatment Wear Resistance Tool Steel H-13 Tool Steel

Influence of cryogenic Treatment on Microstructure and Properties Improvement of Die Steel

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science and Chemical Engineering 2015年第9期3卷 37-46页

作者： Shangtan Liu Xiaochun Wu Lei Shi Yiwen Wu Wei Qu Material Science and Engineering School Shanghai University Shanghai China

cryogenic treatment has been increasingly applied to enhance the hardness, antiwear ability and fatigue performance of die steel. On the basis of reading a large number of research papers and references across the world, the author makes a detailed analysis and brief summary of the influence of cryogenic treatment on microstructure after quenching process or quenching plus tempering process, on first and second carbides, on content of retained austenite, on surface hardness, on mechanical properties and antiwear ability of die steels. It’s proved that cryogenic treatment on die steel significantly improves its hardness, antiwear capacity and service life. It’s the cryogenic process to make die steel have higher hardness, better antiwear ability, better ductility and longer service life because cryogenic process actually has a good influence on die steel of its microstructure, retained austenite volume and amount and size of the second carbide.

关键词： Die Steel cryogenic Treatment Retained Austenite The Second Carbide Antiwear Ability

Finite Element Modelling of Insulation Thicknesses for cryogenic Products in Spherical Storage Pressure Vessels

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Engineering（科研） 2012年第6期4卷 324-328页

作者： Oludele Adeyefa Oluleke Oluwole Department of Mechanical Engineering University of Ibadan Ibadan Nigeria

This study investigates various insulation thicknesses requirements for double-walled spherical pressure vessels for the storage of cryogenic liquids. The inner tank is suspended from the outer tank by straps or cables and the annular space between the tanks is filled with insulation. The outer tank is not subjected to the freezing temperatures and is thus assumed to be a standard carbon steel sphere. In the Finite Element Analysis model of the system, one dimensional analysis was employed. This is due to the assumption that temperature gradient does only exist along the spherical radial direction. In the developed model, once the thickness of the inner shell has been determined based on relevant standards and codes—ASME Sec VIII Div 1 or 2, BS 5500 etc and the thickness of the outer shell is known;the required insulation material thicknesses were calculated for different insulating materials. Set of equations resulting from Finite Element Analysis were solved with computer programme code which was written in FORTRAN 90 programming language. The results obtained are validated by analytical method. The results showed no significant difference (P > 0.05) with values obtained through analytical method. The thicknesses for different insulating materials in-between inner and outer tank shells were compared. The results showed that as the insulating material thickness was increased, the heat flux into the stored product was decreasing and at a certain thickness;it started increasing. The insulating thickness at which this happens is termed as critical thickness of insulating material—the thickness of insulation at which the heat influx to the stored products is minimal;this would therefore reduce boil-off of the stored cryogenic product. High thermal conductivity insulating materials need to be thicker than lower thermal conductivity insulating materials if the system is conditioned to have the same heat flux into the stored product for all insulating materials. In the simulation, different insulating material gives di

关键词： NASA LPG LNG FEM EIA FORTRAN 90 ANOVA cryogenic ASME BS

RADIATION FROM THE cryogenic CALIBRATION LOAD FOR MICROWAVE RADIOMETERS

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Electronics(China) 1998年第2期15卷 182-186页

作者： Lu Ying Guo Wei Zhang Zuyin(Huazhong University of Science and Technology, Wuhan 430074)

A styrofoam layer is introduced to the cryogenic calibration load for microwave radiometers in order to keep the antenna at ambient temperature while calibrating. Obviously the insulation layer has nonuniform temperature profile. A novel approach based on the transmission-line theory is presented to calculate the emission from the load. According to the sample calculation through this new approach, the contribution of the insulation layer to the load radiation can not be neglected.

关键词： cryogenic calibration load Layered media Brightness temperature

Effects of cryogenic Treatment on the Thermal Physical Properties of TC4 Titanium Alloy

在线全文

学校读者我要写书评

暂无评论

材料科学与工程（中英文A版） 2018年第1期8卷 43-46页

作者： Ying Xiao Institute of Electrical Engineering Yan Shan UniversityQinhuangdao 066004China

A cryogenic treatment test was carried on TC4 titanium alloy,and the effects of cryogenic treatment on the thermal physical properties of TC4 titanium under the temperature range of 25~600°C were investigated through comparing the variation of the thermal conductivity and thermal expansion coefficient of the alloy before and after cryogenic treatment.The results show that the thermal conductivity of the cryogenic treated alloy is first less and then greater than that of the untreated alloy,however,its thermal expansion coefficient is first greater and then less than that of the untreated alloy with the increase of temperature.When the temperature is up to 600°C,the thermal conductivity and thermal expansion coefficient of the cryogenic treated alloy are 7.24 W·m-1·K-1 and 11.71×10-6°C-1,and increased and decreased by 3.18%and 1.65%than that of the untreated alloy at the same temperature,respectively.

关键词： TC4 titanium alloy cryogenic treatment thermal conductivity thermal expansion coefficient.