被动型氢原子钟吸气剂泵的应用研究

描述了上海天文台在2008年为提高被动型氢原子钟真空系统的可靠性所研制的由非蒸散型吸气剂泵和小离子泵组成的复合泵的实验过程,吸气剂泵在室温下吸收2.1MPa.l的H2气后仍可达到3.2×10-5Pa的真空度,2l/s的离子泵电流工作在0.30μA,证明了复合泵可以维持氢钟13年以上的正常工作。经过再激活固定了激活工艺,吸气剂最终吸氢6.0 MPa.l仍没有饱和,证明了吸气剂的强大吸氢能力。至今复合泵已成功应用在4台被动型氢钟上。     

NIM的微波-光学频率基准研究——复现米和秒定义

报道中国计量科学研究院(NIM)在微波-光学频率计量研究的新进展:用NIM4激光冷却-铯原子喷泉钟复现国际单位制(SI)时间单位秒(s),用飞秒(FS)光学频率梳间接复现长度单位米(m)并标定稳频激光波长实际实施米定义.NIM4铯原子喷泉钟的不确定度达到5×10-15,飞秒(FS)光梳锁定到NIM4钟控制的氢钟后,其频率不确定度为2.2×10-14.在此基础上讨论铯原子喷泉钟、稳频激光、FS光梳的作用、意义和相互关系.最后简要介绍NIM5铯原子喷泉钟的研究进展和2006年起NIM立题研制锶原子存储光钟.     

蓝宝石主动型氢原子频标

研制了采用蓝宝石加载微波腔的蓝宝石主动型氢原子频标,腔体外径18 cm,高度20 cm,重量约2.5 kg。由于微波腔体积的减小,整钟体积较传统大氢钟明显减小。经中国计量科学研究院测试,该蓝宝石主动型氢原子频标的技术指标为3.0×10-13@1 s、3.8×10-15@1 d,是目前国内体积最小的高指标、高可靠主动型氢原子频标,可在实验室、车载等环境下使用。     

环境温度对氢原子钟性能的影响

本文探讨了被动型氢原子钟在宽温度环境下的频率特性,为小型、易搬运、高可靠、环境适应性强、高性能氢原子钟的研制提供了参考.将被动性氢原子钟置于温箱,测量其在不同温度下的开机特性、频率稳定度、频率准确度等参量.本文在10℃~35℃的宽温度范围内进行测试分析,研究了环境温度对氢原子钟开机特性、频率准确度及频率稳定度的影响.对于被动型氢原子钟在恶劣环境下的研制和应用提供可靠的依据和参考,也可为研究其它类型原子钟受温度的影响提供借鉴.     

热老化316L不锈钢在模拟核电溶解氧/氢高温高压水中应力腐蚀裂纹扩展行为

利用直流电位降(DCPD)和高温高压腐蚀测试系统,开展了热老化2 000 h的316L不锈钢(SS)样品在320℃、13 MPa的模拟核电—回路含1.5×10~(-3) B和2.3×10~(-6) Li的高温高压水中的应力腐蚀裂纹扩展速率(CGR)测试。结果表明,当溶液中的溶解氧(DO)含量从2×10~(-6)逐步降低至10~(-6)、5×10~(-7)、10~(-7)以及5×10~(-9)时,热老化316L SS的CGR逐渐降低,其中DO降低至5×10~(-7)以及更低时,CGR降低明显。当溶液由DO转为溶解氢(DH)时,CGR进一步降低。利用扫描电子显微镜(SEM)以及电子背散射衍射(EBSD),对测试后样品的断口形貌以及裂纹扩展路径进行了观察,断口呈现典型的沿晶应力腐蚀开裂(IGSCC)形貌。DO/DH的改变主要影响了裂纹尖端的传质过程以及裂纹尖端新鲜表面的再钝化过程,进而影响CGR。热老化2 000 h对316L SS的微观结构以及在高温高压水中的应力腐蚀CGR影响较小。     

铯原子喷泉钟驾驭氢钟的预估算法研究

由于铯原子喷泉钟准确度和稳定度极高,故若用喷泉钟去校准或驾驭氢钟组,可以提高原子时标的准确度和稳定度。但因铯原子喷泉钟运行是不连续的,所以给校准或驾驭工作增加难度。设法对当前的预估算法进行了改进,即根据喷泉钟与氢钟频差数据值的即时特性的走势,用SVM技术预估喷泉钟停运时的数据,以提供连续数据去驾驭原子钟组,最终使得钟组频率与铯原子喷泉钟趋于一致,同时保证了时间尺度的准确性和连续性。特编制了具体的SVM预测算法,并用NIM的铯原子喷泉钟实测数据检验了该算法,结果表明TA(NIM)很逼近铯原子喷泉钟,其相对频率稳定度达到1. 99×10~(-15)/天。     

主动型氢原子钟吸气剂泵的实验研究

为提高上海天文台的主动型氢原子钟真空维持系统——240 L/s钛溅射离子泵3～4年就可能出现的可靠性问题,研制了非蒸散型吸气剂泵和2 L/s小离子泵组成的复合泵。描述了复合泵的实验过程,吸气剂在450℃激活,在室温下吸收6.3 MPa.L的氢气后仍可达到5.9×10-5 Pa的真空度,2 L/s的离子泵电流工作在0.7μA,证明了复合泵可以维持主动型氢钟10年以上的正常工作。     

PEEK基底上厚度为6.4 nm的金薄膜导热导电性能研究

运用高真空溅射镀膜仪在聚醚醚酮(PEEK)薄膜和纤维表面分别制备了厚度为6. 4 nm的金薄膜,并通过瞬态电热技术(TET)测量了该金薄膜的导热性和导电性。PEEK薄膜基底上厚度为6. 4 nm的金薄膜的导热系数、导电系数和洛伦兹数分别为283. 97 W·m~(-1)·K~(-1)、2. 46×10~7Ω~(-1)·m~(-1)和3. 49×10~(-8)W·Ω·K~(-2)。PEEK纤维基底上厚度为6. 4 nm的金薄膜的导热系数、导电系数和洛伦兹数分别为81. 11 W·m~(-1)·K~(-1)、1. 20×10~7Ω~(-1)·m~(-1)和2. 17×10~(-8)W·Ω·K~(-2)。研究发现,在不同基底材料上制备的金薄膜的导热系数、导电系数和洛伦兹数均不同。这种差异可以归因于以下两点:一方面,不同基底材料上制备的金薄膜的晶粒尺寸不同;另一方面,不同的基底材料会引起基底与金薄膜结合界面的平整度不同。金薄膜晶粒尺寸越小,其电子的导热系数、导电系数越小;金薄膜与基底的结合界面平整度越差,其声子的导热系数越小。     

双核钴化合物分子催化剂光催化分解水析氢性能及机理研究

通过[Co(dmgH)(dmgH_2)Cl_2]与4,4′-联吡啶反应合成了一种新的非贵金属双核钴化合物分子催化剂[Co_2(dmgH)_4(μ-4,4′-bpy)Cl_2](1),并通过IR、~1H NMR、CV、荧光等表征了其结构和性能。以1为光催化剂,曙红Y(EY~(2-))为光敏剂,三乙醇胺(TEOA)为牺牲剂,在可见光(λ420 nm)照射下,构建了一种有效的均相光催化体系。在目标催化剂1的浓度为3.7×10~(-4)mol·L~(-1),EY~(2-)为4×10~(-4)mol·L~(-1),TEOA为20%(v/v),pH为10的最佳析氢条件下,光照2 h后,该体系的最大H_2产量为(1 488.3±34.5)μmol((160.0±3.7) TON vs.1),析氢速率为(744.2±17.3)μmol·h~(-1)。此外,本工作还简要地讨论了当前体系的光解水析氢机理,在所构建的析氢体系中,从激发态的~(1*)EY~(2-)到Co催化中心的电子转移也被证实是热力学可行的过程。     

脉冲微波式氢原子钟的研究进展

在传统被动型氢原子钟基础上,利用复杂可编程逻辑器件(CPLD)控制数字衰减器产生两个相干脉冲微波,激励氢原子发生Ramsey干涉,从而压缩原子跃迁谱线宽度,提高被动型氢原子钟稳定度性能。利用单片机控制直接数字频率合成器(DDS)产生扫频信号,可以得到完整的Ramsey条纹。目前已观测到Ramsey条纹并成功将原子跃迁谱线宽度压缩至1.2 Hz,仅为传统被动型氢原子钟线宽的40%。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

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 Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

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.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

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.