超声血流向量成像技术探讨颈动脉球部壁面剪切应力的影响因素

目的：运用超声血流向量成像(Vector Flow Imaging, V Flow)技术探讨颈动脉球部自体解剖结构及血流动力学因素对壁面剪切应力(Wall Shear Stress, WSS)的影响。方法：选取颈动脉超声检查正常患者 70例,将 V Flow感兴趣区置于颈总动脉分叉部及颈内动脉起始段。测量颈动脉球部与颈总动脉间角度(θ)、测量收缩末期颈动脉球部(Carotid Bulb, CB)膨大最明显处内径(D_CB)与颈总动脉末段内径(D_CCA)的比值(D_CB/D_CCA)、测量颈动脉球部分流量(Q_CB)与颈总动脉末段流量(Q_CCA)的比值(Q_CB/Q_CCA)、描记颈动脉球部血流紊乱区可视化面积(A_CB)以及测量颈动脉球部起始段内侧平均壁面剪切应力(WSSI-CB)和外侧平均壁面剪切应力(WSS_E-CB),并对上述各项参数进行统计学分析。结果：(1)颈动脉球部起始段 WSS_I-CB值为(0.88±0.30) Pa,外侧 WSS_E-CB值为(0.32±0.15) Pa,外侧壁明显小于内侧壁,差异有统计学意义(P<0.01)。(2)颈动脉球部与颈总动脉夹角 θ值为(24.5±12.1)°,与 WSS_E-CB相关系数为r=-0.171,二者无相关性且差异无统计学意义(P>0.05);颈动脉球部膨大最明显处内径与颈总动脉末段内径比值 D_CB/D_CCA为(0.66±0.09),与 WSS_E-CB值呈负相关,相关系数为r=-0.312,差异有统计学意义(P<0.05)。(3)颈动脉球部分流量与颈总动脉末段流量比值Q_CB/Q_CCA为(0.69±0.15),与 WSS_E-CB值呈正相关,相关系数为r=0.428,差异有统计学意义(P<0.01);颈动脉球部血流紊乱区面积 A_CB为(0.27±0.17) cm²,与 WSSE-CB值呈负相关,相关系数分别为 r=-0.545,差异有统计学意义(P< 0.01)。结论：颈动脉球部血流量、血流紊乱区面积及膨大程度是影响外侧壁面剪切应力 WSS的主要因素,而与颈动脉球部发出角度的关系并不密切。     

JJF1493-2014《超短光脉冲自相关仪校准规范》解读

<正>超短脉冲光学是一门前沿的新技术,具有重要的应用前景和重大的应用价值。JJF1493-2014《超短光脉冲自相关仪校准规范》是我国、也是国际上的首个超短脉冲光学测量仪器校准规范。该规范于2014年11月17日获得批准,并于2015年2月17日实施。为更好地实施该规范,本文对该规范进行解读。一、制定背景及目的超短光脉冲是指持续时间在飞秒(fs)至皮秒(ps)量级的光辐射脉冲,也称作超短激光脉冲、超短脉冲     

微米、纳米颗粒国家标准测量装置的研究

研究的目标是建立一套可溯源至激光波长的微米、纳米颗粒国家标准测餐装置,它用扫描电子显微镜高倍数放大、对准和定位颗粒影像,采用纳米位移扫描工作台和激光干涉仪测量微米、纳米量级的标准颗粒直径,其测量标准不确定度可优于5 nm+5×10~(-3).通过文中测量认证的标准颗粒校准各类不同原理和测量范围的颗粒测量仪器,达到各型颗粒测量仪器的量值准确和统一,并溯源至激光光波波长.     

响应面分析法优化不锈钢激光切割工艺参数

为了获得良好的不锈钢激光切割质量,确定合理的切割工艺参数,本文以3 mm厚304不锈钢为研究对象,采用响应面法进行试验方案的设计和分析,利用超景深显微镜进行了试样表面切缝宽度、表面纹理最大峰值、挂渣量的测量,利用最小二乘法进行数据处理,研究了激光功率(X₁)、切割速度(X₂)、离焦量(X₃)以及辅助气体压力(X₄)对不锈钢切割表面切缝宽度、表面纹理最大峰值、挂渣量的影响规律,并基于响应面法得到了3个响应目标的预测函数.实验结果表明:X₂=2.48 m/min,X₃=-1.05 mm,X₄=1 MPa时,随着激光功率的增加,切缝宽度不断增大;X₁=300 W, X₄=1.2 MPa时,随着切割速度的加快切缝宽度逐渐减小,随着离焦量的增大切缝宽度先减小后增大;X₁=300 W,X₃=0 mm,X₄=1.40 MPa时表面纹理的最大波峰值RZ随着激光功率、离焦量以及切割速度的增大先减小后增大。以切缝宽度最窄、表面纹理最大峰值最小、挂渣量最少为响应目标确定了3 mm厚304不锈钢激光切割的最佳工艺参数为X₁=365.86 W,X₂=2.75 m/min,X₃=0 mm,X₄=1.4 MPa。试验验证发现:切缝宽度、表面纹理最大峰值、挂渣量的预测误差应分别控制在8.4%~12.7%、21%~24.9%、16.7%~19.5%。     

Preferred orientation of AlN plates prepared by chemical vapour deposition of AlCl3 + NH3 system

Aluminium nitride (AlN) plates about 1 mm thick (maximum) were prepared by chemical vapour deposition (CVD) at the maximum deposition rate of 430 nm s⁻¹ using AlCl₃, NH₃ and H₂ gases at deposition temperatures,T _dep, of 873–1473 K. The effects of deposition conditions on the preferred orientation, morphology and micro-structure were investigated. WhenT _dep was less than 1073 K, the resulting CVD AlN plates contained some impurity chlorine and the aluminium content exceed the nitrogen content. WhenT _dep exceeded 1173 K, no chlorine was detected, and the Al/N atomic ratio matched the stoichiometric value. The lattice parameters (a=0.311 nm,c=0.4979 nm) and density (3.26×10³ kgm⁻³) were in agreement with values reported previously. The crystal planes oriented parallel to the substrates changed from (1 1 ˉ2 0) to (1 0 ˉ1 0) to (0001) with increasing total gas pressure (P _tot) and decreasingT _dep. This tendency is discussed thermodynamically and is explained by the change of supersaturation in the gas phase.     

自生复合Al11La3/Al共晶材料的轴向拉伸性能及其断裂机制

本文研究了自生复合Al₁₁La₃/Al共晶材料从室温到673K时的轴向拉伸性能和轴向拉伸断裂机制.结果表明:在G=700K/cm、R=11.1μm/s的定向凝固条件下,该材料轴向拉伸性能在室温时为260MPa、在673K时为265MPa.对拉伸过程的动态观察和断口形貌的分析表明:自生复合Al₁₁La₃/Al共晶材料在室温到673K温度范围内,其轴向拉伸断裂机制相同:纤维相Al₁₁La₃的断裂是整个共晶体断裂的控制机制:其轴向拉伸的断裂模型为:弹性变形、裂纹萌生、界面脱粘、搭桥过程、宏观断裂.     

Modified sol-gel process for the preparation of BaTiO3 and PbTiO3 ferroelectric films

A modified method for preparing barium and lead titanate films is suggested, which combines precipitation from solution and elements of sol-gel processing. The ∼1-μm-thick BaTiO₃/Pt and PbTiO₃/Pt films deposited on Pt foil are transparent, show good adhesion, and have the 1 : 1 : 3 stoichiometry. The films are finegrained, with a mean grain size of 0.1–0.2 μm. The barium titanate films are characterized byt _C = 110-125°C, ε₂₀ = 167-500, tanδ₂₀ = 0.015-0.06, ε_max = 1050,P _s= 3.2 μC/cm²,E _c = 14 kV/cm, ρ = (5-7) × 10⁹ Ω cm, andV _br = 80-150 kV/cm. The lead titanate films are characterized byc/a = 1.056, ε₂₀ = 105-110, tanδ₂₀ = 0.11-0.16,P _s = 4.1 μC/cm²,E _c = 34 kV/cm, ρ = (0.8-3.0) × 10⁹ Ω cm, andV _br = 50-100 kV/cm.     

娱乐场所的噪声——香港酒吧的情况

许多城市居民喜欢在酒吧等娱乐场所享受快乐时光。但是,他们暴露在可能造成健康危害的娱乐场所环境中。这是因为人们逗留在酒吧时,会受到昏暗的灯光、二手烟和高噪声的影响。回顾了有关酒吧噪声的文献,并在香港的六家酒吧进行了噪声测量。分析结果显示,在欢乐时间即在5：00 pm和9：00 pm之间,酒吧声音水平（L_eq,10-min）介于66.5~79.9 dB （A）之间,酒吧声音水平在繁忙时间即10：00 pm至11：30 pm介于69.5~97.0 dB （A）之间。在欢乐时间,最高噪音水平（L_max）介于78.5~96.5 dB （A）之间,在繁忙时间介于80.9~107.8 dB （A）之间。分析发现,酒吧内的声音水平可以通过L_eq,10-min测量,酒吧内的背景噪音则可以通过L₉₀测量。     

基于栅格节距中心峰值检测的扫描探针显微镜校准方法

为了解决扫描探针显微镜（Scanning Probe Microscope, SPM）现有校准方法复杂程度高且存在局限性的问题,提出了一种基于二维标准微尺度正交栅格的SPM校准方法,通过对扫描获取的栅格图像进行互相关 / 卷积（Cross?correlation / Convolution, CC）滤波,实现对栅距中心坐标的峰值检测。校准的运动几何误差包括x轴和y轴位置偏差Δx和Δy、沿x轴和y轴扫描的直线度偏差δy和δx以及两轴之间的正交性偏差γ_xy。根据x轴和y轴扫描像素数、扫描范围、标准栅格计量检定节距平均值、栅距平均值计算得出校准因子C_x和C_y。采用标称节距为10 μm的正交栅格样板对原子力显微镜（Atomic Force Microscope, AFM）进行校准实验,结果显示C_x和C_y分别为0.925和1.050,γ_xy为0.015°,该台AFM的校准扩展不确定度为0.33 μm（k = 2.56）。研究成果对于推动SPM校准标准文件的具体实施和执行具有积极意义,并为SPM仪器研制及性能评估提供了技术参考。     

气相色谱内标法测定塑料制品中乙苯和苯乙烯含量的不确定度评定

目的 对气相色谱内标法测定塑料制品中乙苯和苯乙烯含量进行不确定度评定，为塑料制品中乙苯、苯乙烯含量测定的准确性提供参考。方法 依据GB 31604.16—2016采用气相色谱内标法对塑料制品中乙苯和苯乙烯含量进行测定，根据相应的测量模型，分析不确定度主要影响因素的来源，并对各影响因素引入的相对标准不确定度进行评估。结果 测量塑料制品中乙苯、苯乙烯的扩展不确定度分别为(23.83±1.50)、(23.90±1.26)mg/kg(P=95%、k=2)。结论 结果表明，混标工作液配制、试样重复测量、气相色谱仪性能是影响乙苯和苯乙烯含量测量不确定度的主要因素，应选择精度高且量程合适的量具，加强气相色谱仪的期间核查，提高实验人员操作的熟练水平，进一步减小测量不确定度，使测量结果更为准确、可靠。     

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.     

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.     

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.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.