微波暴露人体比吸收率(SAR)的分布研究

本文采用时域有限差分法和仿真人体电磁模型,计算并比较了E、H二种极化方向和前向、后向、左侧向、右侧向四种照射几何条件下,3GHz微波人体暴露的全身平均比吸收率(SAR)、器官平均SAR和最大峰值SAR。结果表明,H极化、前向照射几何条件下人体的平均SAR较高,其中眼睛和睾丸的器官剂量最高。上述结果为3GHz微波生物效应的实验设计提供了科学依据。     

静电放电人体电磁暴露安全评估的数值模拟

基于电磁剂量学数值计算方法和国际电工委员会(IEC)规定的典型静电放电(ESD)电流波形,将经傅里叶变换后频域中能量最强的一次谐波分量和全部谐波分量分别作为电磁辐射源,仿真分析了位于辐射源不同位置处人体生物组织的电磁效应,并将COMSOL Multiphysics软件数值仿真的结果与国际非电离辐射防护委员会(ICNIRP)推荐的公众暴露限值进行对比。结果表明：离辐射源越远感应电场强度(E)、磁场强度(H)、比吸收率(SAR)越小,体内电场线分布越均匀;电场强度进入头部后迅速衰减,脑部对空间电磁场有一定的屏蔽作用;不同位置处人体头部冠状面和矢状面SAR峰值和分布几乎相同,矢状面和冠状面SAR峰值为轴状面的15.7倍;不同位置处头部SAR峰值均出现在颅骨处,大脑中的SAR最小且关于x轴和y轴成对称分布;多频率暴露条件下,辐射源位于人体右侧面1 m(位置A)时全身SAR值超过了ICNIRP基本限值,而辐射源位于人体右侧面5 m(位置B)及更远位置时人体全身SAR均未超过ICNIRP基本限值。总之,离辐射源越远,安全裕度越大,人体需位于辐射源5 m以外,以降低暴露风险。此研究结果可为人体ESD...     

低水平电离辐射对雄性大鼠 LRH-LH-睾丸酮系统功能影响的研究

本文报道了小剂量 X 射线分次全身照射和低剂量率~(60)Coγ射线持续全身照射对雄性大鼠下丘脑组织中 LRH 含量,血清及尿中 LH 和睾丸酮含量影响的实验结果。接受 X 射线照射的大鼠,全身累积吸收剂量为1.5Gy 和3.0Gy,下丘脑组织中 LRH 含量均于停照后1周显著高于对照组;血清 LH含量在3.0Gy 组于停照后4周高于对照组;尿中睾丸酮含量1.5Gy 组在停照后2和4周及3.0Gy 组在停照后2周均显著高于对照组。接受~(60)Coγ射线照射的大鼠,于照射结束后24小时血清 LH 含量在全身累积吸收剂量为1.76Gy 组显著低于对照组;血清中睾丸酮含量在1.37和1。76Gy 组、尿中睾丸酮含量在0.98Gy 组均显著高于相应对照组。     

1～6 GHz射频暴露平台的设计及剂量特征

研制一套宽频谱生物电磁暴露平台,开展了相应暴露条件下的剂量仿真研究。射频暴露平台的频段为1～6 GHz,其基本原理是天线暴露型电磁场,额定功率下目标处的功率密度为63.3～149.0 W/m²。生物电磁剂量仿真研究表明：相对于大鼠,小鼠在1～6 GHz内可以获得更高的全身平均比吸收率,高出约一个数量级;顶部照射和侧向照射对全身平均比吸收率的影响较小,大鼠的差异值最大为0.731 dB,小鼠的差异值最大为0.276 dB,实验动物的全身平均比吸收率存在着频率相关性,对照射方向的改变不敏感;组织比吸收率对照射方向的改变较敏感,峰值频率点略大于全身平均比吸收率的共振频率点;在最大暴露值条件下,对实验动物的最大剂量值进行了评估,大鼠和小鼠的全身平均比吸收率均超过职业标准值0.4 W/kg,其中小鼠的全身平均比吸收率超过损伤阈值4 W/kg。该实验装置可用于通讯和雷达等作业常见频率的在体效应研究。     

电磁辐射防护材料人体防护性能评价研究

本文采用高分辨率人体电磁辐射模型和非均匀网络时域有限差分法(FDTD),通过比较人体模型在防护前后全身平均比吸收率SAR的变化,建立了防护材料对人体防护性能的评价方法。利用此方法,针对不同频率、不同入射角度的电磁辐射,对不同防护材料的防护性能进行了评价。结果表明,防护材料的防护性能并不仅仅取决于其屏蔽性能,还与防护方式、照射方式等密切相关。局部防护方式对被防护的器官有良好的防护效果。相对于水平照射,斜向上照射时,防护效果较差;斜向下照射时,防护效果较好。     

局部照射和全身照射诱发小鼠精原细胞染色体畸变的比较

本文对X线照射小鼠睾丸组织和全身均匀照射诱发精原细胞染色体易位率进行了比较。两种不同照射方式所诱发的易位率都随剂量增加而增高,其剂量效应关系均符合y=a+bD关系式。全身照射明显高于局部受照,从而提示用全身均匀照射的遗传风险来估价睾丸组织受照的遗传效应是不适宜的,它过高的估价了遗传危险度。因此对常见的生殖器官局部受照的遗传危害,应该用局部照射的资料来评估,更接近实际。     

凝溶胶蛋白在C57BL／6小鼠急性放射肺损伤中的表达

为研究小鼠辐射诱导肺损伤后凝溶胶蛋白（Gelsolin,GSN）在血浆和肺组织中的表达,分别采用4Gy和20Gy剂量的X射线对C57BL／6小鼠进行全身及胸部单次照射。且在照射后取不同时间点ELISAKit检测小鼠血浆型Gelsolin（Plasma GSN,pGSN）蛋白含量和Westernblot法检测小鼠肺组织胞浆型Gelsolin（Cytoplasmic GSN,cGSN）蛋白含量。同时,检测20GyX射线胸部照射后不同时间点小鼠右肺肺泡灌洗液（Bronchoalveolar lavage fluid, BALF）中的细胞总数和总蛋白的含量。结果表明,全身照射组小鼠在照射后24h时,pGSN水平降低,而胸部照射组pGSN水平在24—48h持续降低,下降速度慢于全身照射组,之后两组pGSN均逐渐上升。在照射后24h时小鼠肺组织cGSN含量低于正常水平,照射后48h时则高于正常水平,48-96h持续下降。但在照射后96h时全身照射组cGSN含量恢复到正常,胸部照射组仍高于正常水平。小鼠胸部照射后在24h时,右肺BALF中细胞总数和总蛋白浓度显著高于正常水平,约达正常值的16倍,24—96h持续下降,与肺组织cGSN含量变化存在一定程度的负相关。推测GSN可能促进急性放射肺损伤的修复。     

射频电磁辐射对大鼠脑组织胆碱能标志物的影响

将24只成年雄性SD大鼠按体重随机分成1组假辐照组和3组辐照组。辐照组给予全身射频电磁辐射,频率1.84 GHz、脑组织比吸收率(Specific absorption rate,SAR)分别为0.2、0.5、1.5 W/kg,连续辐照2周(5 d/周,30 min/d),照后立取SD大鼠大脑皮层和海马组织制备组织匀浆,采用化学比色法检测其胆碱能标志物水平、抗氧化物酶活性和氧化应激产物含量。结果显示:与假辐照组相比,1.5 W/kg辐照组大鼠大脑皮层内乙酰胆碱(ACh)含量和乙酰胆碱转移酶(Ch AT)活性明显降低(p0.05),各辐照组胆碱酯酶(ACh E)的活性没有差异;各辐照组大鼠大脑皮层内超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPX)、过氧化氢酶(CAT)的活性及丙二醛(MDA)的含量也没有明显差异;各辐照组大鼠海马组织内胆碱能标志物水平、抗氧化物酶活性和氧化应激产物均没有明显差异。结果提示,在本研究照射条件下的射频电磁辐射没有对雄性SD大鼠脑组织造成明显的氧化应激损伤,但是当SAR为1.5 W/kg时辐照能引起大鼠大脑皮层内部分胆碱能标志物水平降低。     

椭圆极化波对大鼠电磁暴露的数值模拟计算

以椭圆极化波作为波源进行大鼠电磁暴露数值模拟,比较了多个入射方向上大鼠电磁暴露的全身平均比吸收率(WBASAR)。结果发现,椭圆极化波的WBASAR随椭偏率的改变而变化,同时受到入射方向和旋向的影响。将此结果与同方向上线极化波的辐照结果比较发现:在入射功率相同的条件下,椭圆极化波和线极化波电磁暴露的WBASAR结果存在差异,且这种差异随着波源入射方向与大鼠体态的相对位置变化呈现出不同的特点。此外,波源的极化性质、辐照方式以及大鼠本身等因素,同样会使得大鼠重要组织的SAR分布规律产生较大的差异。因此,综合考虑线极化波与非线极化波的电磁暴露结果,可以对电磁暴露剂量进行更加全面的评估。本文的计算为动物电磁暴露剂量的评估提供了方法和数据上的补充。     

5G手机天线辐照特性及其在人体头部中温度场分布

为了研究5G手机天线电磁辐照对人体头部比吸收率(SAR)和温度场分布的影响,在COMSOL仿真软件中建立多频段5G手机模型以及代表人体头部组织皮肤层、颅骨层和大脑层的三层球形人体头部模型,对两种常用的手机天线输入功率和4种工作频率情况下,手机电磁辐照对人体头部各层SAR值和温度场分布进行仿真计算。仿真结果表明:两种输入功率中,1 900 MHz时皮肤层SAR值最大,为0.715 W/kg,其对应的表面温度最高,达37.209°C;当手机离人体头部的距离由5 mm增大到30 mm时,皮肤层SAR值最大减小50.20%,但温度场最大减小仅为0.180%。所有仿真计算结果所得SAR值和温度场的分布均低于国际非电离辐射防护委员会(Intemational Commission on Non-Ionizing Radiation Protection,ICNIRP)的规定限值。说明5G手机天线所致人体头部的电磁辐照和温度场的分布是安全的。     

中药知母有效组分——知母皂甙元“滋阴”作用的研究

本工作以~(123)I-心得静结合分析法及环核苷酸RIA法观察了知母中提取得到的知母皂甙元对甲亢模型(模拟“阴虚”)βAR-cAMP系统的作和,结果表现,知母皂甙元明显降低甲亢小鼠脑β受体的RT值,显著降低甲亢小鼠β受体-cAMP系统的反应性,重现了知母水煎剂的下调作用。体外竞争抑制实验表明,知母皂甙元和知母皂甙元半琥珀酸都不能抑制~(125)I-心得静与β受体的结合。     

Numerical simulations of the IPPE target geometry flows

A high speed water and liquid lithium (Li) flow is computed over the IPPE geometry to evaluate the performance of different turbulence models in 2D and 3D simulations. Results reported are the thickness of the liquid jet, irregularities in the surface, transient phenomena at the wall which can affect fluid surface and effect of the variation in bulk velocity on these quantities. All models show good near wall resolution of the boundary layer and expected profiles for the free surface flow. Predicted turbulent kinetic energy compare well with published data. Fluctuations of the flow surface at the control location (center of the curved section) and elsewhere are well within 1 mm for all models. However it was observed that the predictions are strongly dependent on the model used. Overall, the predictions of RANS models are close to each other whereas predictions of laminar simulations are close to those obtained with LES models.     

沙漠黄土边界带风成沙再生法单片技术等效剂量分布

应用再生法单片技术对一个沉积前被充分晒退的沙漠黄土边界带的风成沙样品进行石英绿光释光等效剂量（ED）测量,共测得125个数值,等效剂量范围为2．7－4．4Gy,呈一偏正态分布,其中,等效剂量为3．1Gy的数目最多,为30个,125个等效剂量的加权平均值为3．26Gy,沉积前被充分晒退的风成沙不同样片的等效量颇有差异,但其加权平均值是接近真实等效剂量的可靠值。     

Vapor Shield Models for Fusion Reactors Plasma-Facing Components

Radiant heat flux is a dominant mechanism by which energy transfers from the high-temperature core plasma to the interior critical components of the fusion reactor, which result in surface ablation and sever damage to the components. A vapor layer develops at the surface and provides a self-shielding mechanism at the plasma-material interface. Two models for the energy transmission factor through the boundary layer were developed and incorporated in the electrothermal plasma capillary code to predict the effectiveness of these models in surface self-protection. The electrothermal plasma capillary discharge simulates the typical conditions of fusion reactors disruption and quench phase and has been shown to be an adequate technique to evaluate the erosion of plasma-facing component. First model treats the radiant heat transport as it is affected by the variation of the plasma opacity, in which the vapor shield efficiency depends on the plasma optical thickness and the mean plasma opacity. The second model defines the vapor shield by the ratio of the energy reaching the surface to the total radiant energy emitted by the plasma with the inclusion of the plasma kinetic energy. The code can predict the axial and temporal variation of the transmission factor at each time step and mesh point, and predicts the plasma parameters with the effectiveness of the vapor shield at the boundary layer. The code prediction with implementation of both models has been used to compare the results with earlier ones and with some experimental data. Code results are in good correlation with experimentally measured ablation data.     

Momentum losses and convective heat transfer in rod bundles — An overview

A critical survey is made of the prediction methods available for analysing the momentum and heat transfer characteristics of axial flow in a clustered rod bundle. The Navier-Stokes and energy equations are presented, their solution procedure is outlined and the boundary layer approximation discussed. Four levels of approximation to these equations, namely, slug flow, integral methods, eddy diffusivity and turbulence energy models are examined and their limitations presented for a simple situation. Consideration is then given to the problem of extending these models to more complex situations such as, variable property flows, rough surfaces and flow blockages.     

平均共振参数的估算

通过评述矩方法和最大似然法后指出,对同一实验数据,已往给出平均共振参数的估值存在较大差异的原因,主要是由于这些方法本身的局限性和取值方法的不同引起的。只要联合使用这些方法,按本文新的取值方法和规则取值,由相关系数选出最后值,可获得比较满意的结果。     

Helium elastic scattering from carbon for 30° to 150° in the energy region from 2 to 4.8 MeV

The differential cross-sections for elastic scattering of ⁴He ions by carbon atoms were measured at scattering angles of 30°, 45°, 60°, 135° and 150° in the energy range from 2 to 4.8 MeV. Up to now mostly data for angles larger than 150° were published in the literature. A thick carbon target with a thin evaporated Cu layer on the surface was used for the measurement. The number of impinging projectiles was obtained from the He ions scattered by the Cu layer assuming Rutherford cross-sections. The carbon scattering cross-sections were then obtained from comparison of measured He energy spectra with the simulated ones. Above 2 MeV all evaluated cross-sections become non-Rutherford. Deviations from Rutherford cross-sections are about 50% for 30° scattering angle and amount up to a factor 30 for 150° scattering angle. The measured experimental cross-sections were compared with the calculated theoretical cross-sections and already published data. Satisfactory agreement was obtained for all measured scattering angles and energies.     

Statistical evaluation of pin gaps in fuel clusters for fugen

The computer program STGAP has been developed to estimate pin gaps in a fuel assembly for FUGEN. The program optionally computes the probable distribution of the pin gap between any adjacent pair of fuel pins, either at a desired location in an assembly or longitudinally averaged over the total effective length of a pin, based on the measured manufacturing and assembling tolerances in geometrical dimensions and mechanical properties of all the independent elements composing a fuel assembly. It also correlates the computed fuel gap distribution with the minimum critical heat flux ratio in the corresponding local subchannel. Sample calculations were performed for the probable distributions of the pin gaps between pairs of adjacent fuel pins in the outermost layer of a FUGEN fuel assembly using the program and satisfactory agreement was obtained with the corresponding measured distributions.     

Soft X-ray Images of Krypton Gas-Puff Z-Pinches

A series of experiments has been carried out on Qiang-guang I generator to study the dynamics of krypton gas-puff Z-pinches. The generator was operated at a peak current of 1.5 MA with a rise-time of 80 ns. The specific linear mass of gas liner was about 20 *g/cm in these experiments. In the diagnostic system, a four-frame x-ray framing camera and a pinhole camera were employed. A novel feature of this camera is that it can give time-resolved x-ray images with four frames and energy-resolved x-ray images with two different filters and an array of 8 pinholes integrated into one compact assemble. As a typical experimental result, an averaged radial imploding velocity of 157 km/s over 14 ns near the late phase of implosion was measured from the time-resolved x-ray images. From the time-integrated x-ray image an averaged radial convergence of 0.072 times of the original size was measured. An averaged radial expansion velocity was 130 km/s and the maximum radial convergence of 0.04 times of the original size