An Absorbed-Dose/Dose-Rate Dependence for the Alanine-EPR Dosimetry System and Its Implications in High-Dose Ionizing Radiation Metrology

NIST developed the alanine dosimetry system in the early 1990s to replace radiochromic dye film dosimeters. Later in the decade the alanine system was firmly established as a transfer service for high-dose radiation dosimetry and an integral part of the internal calibration scheme supporting these services. Over the course of the last decade, routine monitoring of the system revealed a small but significant observation that, after examination, led to the characterization of a previously unknown absorbed-dose-dependent, dose-rate effect for the alanine system. Though the potential impact of this effect is anticipated to be extremely limited for NIST’s customer-based transfer dosimetry service, much greater implications may be realized for international measurement comparisons between National Measurement Institutes.     

Recollections on Sixty Years of NBS Ionizing Radiation Programs for Energetic X Rays and Electrons

These recollections are on ionizing radiation programs at the National Bureau of Standards (NBS) that started in 1928 and ended in 1988 when NBS became the National Institute of Standards and Technology (NIST). The independent Council on Ionizing Radiation Measurements and Standards (CIRMS) was formed in 1992. This article focuses on how measurements and standards for x rays, gamma rays, and electrons with energies above 1 MeV began at NBS and how they progressed. It also suggests how the radiation processors of materials and foods, the medical radiographic and radiological industries, and the radiological protection interests of the government (including homeland security) represented in CIRMS can benefit from NIST programs.     

应用结构声强技术测量耦合损耗因子

介绍了一种新的耦合损耗因子测量方法：声强法。以点和线耦合结构为例，应用两点差分技术和单点技术测量弯曲波耦合损耗因子，将测量结果与传统方法获得的测量结果相比较：声强法能较准确地测量点耦合结构间弯曲波耦合损耗因子，其测量精度与能级差分法和直接测量方法的测量精度相似。     

声辐射模态在声场重构中的应用

基于声辐射模态,对辐射声场的重构进行仿真研究,取得了令人满意的结果。声辐射模态包含声源几何形状的影响,利用声辐射模态可实现对任意复杂形状声源的声场重构。声源相对简单时,需要较少的测点数就可以得到很好的重构效果。对于复杂的声源辐射声场,重构中结合正则化方法保证重构的高效性与精确性。同时,探讨通过重构声源表面声压的方法来识别噪声源,经过模拟计算和可视化的实现,表明方法简单可行。     

铁路钢轨垂向振动的声辐射分析

在ANSYS中建立轨道的实体模型,求出钢轨在作用力处的谐响应;与离散轨道模型中钢轨在作用力处的谐响应对比,找到合适的轨道模型,求出钢轨在50—4000Hz之间1／3倍频带中心频率处的表面谐响应;建立钢轨的边界元模型,把从ANSYS中得到的钢轨表面谐响应导入SYSNOISE作为钢轨的激励位移边界条件,得到钢轨在50-4000Hz之间1／3倍频带中心频率处的声辐射效率。与从二维轨道声辐射模型得到的结果吻合。     

环保型防氡、防辐射建筑材料研究进展

综合国内外文献介绍了氡和原子辐射的危害、致癌机理,部分建筑材料的氡和放射性情况以及防氡、防辐射的机理,并重点介绍了当前国内外防氡、防辐射建筑材料的研究进展,提出了可利用我国丰富的矿产资源如重晶石、石膏、沸石、以及各种工业废渣开发各种具有防氡、防辐射的功能微集料作为基元材料,制备能够吸收和屏蔽建筑材料所释放的氡气和辐射的环保型建筑涂料、砌筑水泥、各种瓷砖胶结剂以及墙体腻子等的建设性意见.     

多种水等效材料的医用电子束修正因子研究

针对水等效材料在医用电子束剂量测量中修正因子的测量和使用问题,通过扫描医用电子束在水中和水等效材料中的百分深度剂量(percentage depth dose, PDD)曲线,计算获得深度缩放因子cpl、注量缩放因子hpl及总修正因子kpl的实验值。结果表明,通过cpl和hpl组合或仅使用kpl均可将水等效材料测量结果转换为水吸收剂量。比较PDD曲线表明,在10~20MeV电子能量下3种水等效材料通过cpl-hpl修正后的R50,较水中测量最大偏差分别为0.19%、0.28%、0.22%;经kpl修正得到的R50,较水中测量最大偏差分别为0.23%、0.29%、0.18%。结论:研究提供了多种材料cpl-hpl、kpl的实验值,可方便用户快速完成电子束水吸收剂量的测量,相比于cpl-hpl,使用kpl更加简单高效。     

Electrode Regions of a Continuous Optical Discharge in a Thermionic Converter of Laser Radiation Energy to Electric Energy

A mathematical model is developed of nonequilibrium electrode regions of a continuous optical discharge burning in the interelectrode gap of a thermionic converter of laser radiation energy to electric energy, which is free of a number of limitations of the previously suggested analytical theory. The structure of the electrode regions is investigated. The singularities of the distribution of plasma parameters at different electron temperatures are revealed. The boundary conditions on the electrode boundaries of the equilibrium core of continuous optical discharge are obtained for equations which describe the distribution of the plasma temperature and in the discharge core.     

In-situ Attenuation Corrections for Radiation Force Measurements of High Frequency Ultrasound With a Conical Target

Radiation force balance (RFB) measurements of time-averaged, spatially-integrated ultrasound power transmitted into a reflectionless water load are based on measurements of the power received by the RFB target. When conical targets are used to intercept the output of collimated, circularly symmetric ultrasound sources operating at frequencies above a few megahertz, the correction for in-situ attenuation is significant, and differs significantly from predictions for idealized circumstances. Empirical attenuation correction factors for a 45° (half-angle) absorptive conical RFB target have been determined for 24 frequencies covering the 5 MHz to 30 MHz range. They agree well with previously unpublished attenuation calibration factors determined in 1994 for a similar target.     

电导率在确定水中总放射性检测项目取样体积的应用

在检测水中总α放射性和总β放射性的时候,对于一些蒸发残渣较少的水样,为了得到足够的固体残渣用于铺样,需要预先知道所需蒸干的水样体积。本文通过试验研究了水样的电导率数值与蒸发残渣数值之间的对应关系。试验结果表明,西江、北江水系水样的电导率数值和残渣含量之间的平均关联系数（电导率戚渣含量）为1．8,该系数不受季节变化的影响。东江水系水样的平均关联系数为2．0。通过测定水样的电导率值,再根据水样的电导率数值与蒸发残渣数值之间的对应关系计算得出取样体积,从而提高总放射性项目检测结果的准确度。     

体积源边界点法及其在声辐射计算中的应用

利用作者提出的体积源边界点法，对结构振动声辐射的计算问题进行了研究。给出了该法在全频率范围内存在唯一解的数学证明；通过诸多不同边界曲面和不同边界量分布的声辐射算例，从计算精度、计算稳定性、对振动体任意表面几何形状的适应性以及克服解的非唯一性等方面，对该方法的有效性进行了检验。     

我国超声测量技术和标准化发展的三十年

结合作者的研究经历回顾了30年来我国超声测量技术发展历程和标准化的进展,展望了未来的发展趋势.这些进展包括对辐射力天平(RFB)法测量超声功率的主要改进(例如一系列辐射力计算新公式的导出和应用并得到IEC同行的验证认同,还使RFB的适用范围由平面波束拓展到各种聚焦波束,量程从30W提高到500W)、测量水听器的研发和互...     

An Approximate Method to Measure Crack Opening Displacement of Fast Propagating Crack in Araldite B

Abstract: The method of crack opening displacement (COD) has been used to obtain the energy release rate of fast propagating cracks just before and just after crack bifurcation. In this method, COD is measured on the microscopic photographs of the cracks. But, in the case of cracks in Araldite B, the corner made of a crack surface and a specimen surface is chipped out of the specimen; then, it is often difficult to measure CODs from the photographs of the cracks. The present study proposes a method to approximately measure the COD in the region where COD is difficult to be measured directly on the photograph. The accuracy of the approximate method is good enough that the measured CODs can give the energy release rate of the crack at bifurcation with the accuracy of about 7%.     

Certified Reference Tables on Decay Characteristics and Radiations of Radionuclides Used to Calibrate Semiconductor Spectrometers for Photon Radiation in the Energy Range 5–140 keV

A draft for certifying reference data is presented as recommended values for the energies and absolute probabilities of emission for characteristic x-rays and low-energy gamma rays, together with the half-lives of the radionuclides ⁴⁴Ti + ⁴⁴Sc, ⁵⁴Mn, ⁵⁵Fe, ⁵⁷Co, ⁶⁵Zn, ¹⁰⁹Cd, ²⁰⁷Bi, and ²⁴¹Am. The recommended values have been obtained by analysis and selection from published estimated and experimental data on the basis of the information available in January 2003.