热线风速仪微风速(0.1～1m/s)下的校准实验研究

热线风速仪在微风速(0. 1～1m/s)的测量中有广泛的应用,为了获得准确的测量结果,需要对热线风速仪进行校准。本文基于激光多普勒测速仪对热线风速仪的校准方法进行了研究,并在实验的基础上对恒温型热线风速仪的静态特性进行了分析。为了避免热线探针干扰流场对校准结果的影响,校准时需要找到激光多普勒测速仪合理的测量位置;实验段流场轴线上速度分布偏差带来的影响可通过激光多普勒测速仪的测量实现修正;采用防污染罩的方式可以避免粒子污染探针;此外,确定了2支热线风速仪的静态特性方程参数,计算结果表明实验与理论获得了良好的一致性。不确定度分析表明:在0. 1～1m/s的范围内,探针热线校准结果的不确定度为18mm/s左右。     

风速校准中激光多普勒测速仪激光器的选择

正0引言激光多普勒测速仪(以下简称LDV)是测量通过激光探头的示踪粒子的多普勒信号[1],再根据速度与多普勒频率的关系得到速度。LDV是目前世界上测速准确度最高的在线实时测速仪器。由于是激光测量,测速范围宽,而且多普勒频率与速度是线性关系,与该点的温度、压力无关,其还具有非接触测量、不干扰流场的特点,因此LDV系统极其适合速度仪器校准。LDA系统包括电路和光路两部分。光路部分包     

对向测量皮托管的国际比对

为验证现场烟道流量测量使用的对向测量S型皮托管、球形三维皮托管和棱形三维皮托管校准系数的一致性,中国计量科学研究院(NIM)主导开展了包括美国国家标准与技术研究院(NIST)和韩国标准科学研究院(KRISS)参加的皮托管校准比对。比对结果表明:S型皮托管在不同实验室间比对结果吻合度相对较差,不适合作为比对标准器;球形三维皮托管在不同实验室间比对结果吻合度高于棱形三维皮托管,流速校准系数差异对测量轴向流速的影响高于偏航角参考位置偏差与俯仰角校准系数差异造成的影响;皮托管的偏航角参考位置偏差和俯仰角校准系数差异造成的轴向流速差异在0.03%~0.9%,由于流速校准系数差异造成的轴向流速差异在1.9%~12.2%。     

皮托管系数校准影响因素的实验研究及分析

在皮托管系数校准过程中，空气密度计算公式以及绝对静压测量方法的选择对校准结果有很大的影响。为评估这些影响进行了实验研究，实验结果表明：利用三通接头直接从皮托管静压接头处测量绝对静压以及使用CIPM-2007密度计算公式能够有效提高皮托管系数校准的准确度。     

EDE14 A2型风洞中皮托管安装方式对风速测量的影响

EDE14A2型风洞中皮托管的安装方式对风速测量的准确度存在影响。在对该风洞进行一系列的性能测试时发现,皮托管头部平行于风洞管道轴线时,皮托管测得的风速值明显小于皮托管头部偏离风洞管道轴线一定角度时测得的风速值。本文通过理论分析与实验验证,提出对提高EDE14A2型风洞在风速计量工作中提高风速测量准确度的方法。     

环形低速风洞在微风风速仪计量检测中存在的问题

环形低速风洞虽然能产生0. 1m/s以上的风速,但由于采用的皮托管-微压计标准装置只适合测量2m/s以上的风速,所以不适合用于1m/s以下微风的计量检测。要建立微风风速校准装置,可通过两个途径改进:采用测量准确度和灵敏度更高的激光多普勒测速仪作为标准测速装置;采用直型风洞,提高风速测试断截面与皮托管所在截面的面积比S,得到的最小风速为2/S。     

移动式机动车激光测速仪的校准

针对移动式红外机动车激光测速仪的测量原理,详细描述了一种基于时间延迟的校准方法.采用虚拟仪器技术的机动车激光测速仪校准系统,能够将激光测速仪发射的905nm测量脉冲激光光束进行特定时间量的延迟以模拟其在空气中对应的传播距离,完成机动车激光测速仪在(20～250)km/h时速范围内任意速度值的实验室准确校准,模拟速度不确定度优于0.5%(k=2).     

基于激光多普勒原理风速校准中的示踪粒子

正0引言基于激光多普勒原理风速校准是一种光学非接触测量技术[1]。采用示踪粒子测速技术表征风速,即以风洞测量段中示踪粒子的运动来表征校准过程中的标准风速。要求示踪粒子必须能够悬浮于风洞流场中,并完美地伴随均匀的速度场流动,那么测量得到的粒子运动速度也就可以认为是粒子所在位置的气流速度。所以,基于激光多普勒原理风速校准过程中,示踪粒子需要满足一定的要求:能够很好地跟随空气流动、易于生成、无磨蚀、无腐蚀、     

烟道流量计量标准装置

为了解决我国烟道流量计的量值溯源问题,中国计量科学研究院建立了烟道流量计量标准装置。装置使用可溯源至标准转盘的激光多普勒测速仪作为原级标准器,采用激光多普勒流速剖面扫描和超声流量计波动修正的方式测量标准流量,经校准的8声道超声流量计为工作级标准表,具备了908~104840m3/h的测量能力,扩展不确定度为0.62%(k=2),可对最大口径为1m的流量计进行校准。装置下游测试段包括圆形管段和矩形管段,能够开展烟道流量计测量性能的研究。     

移动式机动车激光测速仪的校准

针对移动式红外机动车激光测速仪的测量原理,详细描述了一种基于时间延迟的校准方法。采用虚拟仪器技术的机动车激光测速仪校准系统,能够将激光测速仪发射的905nm测量脉冲激光光束进行特定时间量的延迟以模拟其在空气中对应的传播距离,完成机动车激光测速仪在(20~250)km/h时速范围内任意速度值的实验室准确校准,模拟速度不确定度优于0.5%(k=2)。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.