间隔靶对射流侵彻影响的数值模拟和实验研究

对某聚能装药射流侵彻靶板的过程进行了数值模拟 ,得出其碰撞点附近应力分布与传统理论相符 ,侵彻深度与实验结果及工程计算结果基本相符 ;分别对该聚能装药侵彻连续靶和间隔靶的过程进行了数值模拟 ,数值模拟结果显示间隔靶的侵彻深度明显低于连续靶的侵彻深度 ,这说明侵彻开坑阶段的能耗侵深比远大于准定常阶段。为了验证间隔靶对射流侵彻的影响 ,用另一聚能装药分别对连续靶和间隔靶进行了侵彻实验 ,并排除了炸高的影响。实验结果也表明 ,间隔靶对射流侵彻的确存在着不利影响。还结合数值模拟及实验结果对传统的侵彻公式进行了修正。     

MCNP Dose Calculations in a CT Phantom for Therapeutic External Photon Beam

In this paper, we have addressed the problem of the radiation transport with the Monte Carlo N particle(MCNP) code. This is a general purpose Monte Carlo tool designed to transport neutron, photon and electron in three dimensional geometries. To examine the performance of MCNP5 code in the field of external radiotherapy, we performed the modeling of an Electron Density phantom (EDP) irradiated by photons from 60Co source. The model was used to calculate the Percent Depth Dose (PDD) at different depths in an EDP. One field size for PDD has been examined. A 60Co photons source placed at 80 cm source to surface distance (SSD). The results of calculations were compared to TPS data obtained at National Institute of Oncology of Rabat.     

杆式射流侵彻半无限靶的理论分析

 理论分析高速杆式射流侵彻半无限靶过程时,考虑速度梯度对聚能射流的影响,将射流进行分段计算,得到了射流拉伸后实际碰靶时的微元长度和直径变化。采用伯努利方程和静力学方法,通过对射流形状和速度分布作线性近似,理论分析了高速杆式射流侵彻半无限靶的过程,得到了靶体中的侵彻深度和侵彻孔径与射流长度、速度及直径之间的关系。将模拟结果与实验结果进行对比,结果表明理论分析结果与侵彻实验结果符合较好。     

808 nm大功率半导体激光器阵列的优化设计

 采用激射波长为808 nm的GaAs/AlGaAs梯度折射率波导分别限制单量子阱结构外延片,制备了沟道深度不同的半导体激光器阵列,并对载流子分布进行理论分析和模拟。理论和实验结果表明：引入脊形台面和隔离沟道后,激光器阵列的输出功率、电光转换效率、斜率效率和光谱特性均有显著提高。随着沟道的加深,对电流侧向扩散的限制作用增强,从而提高了阵列性能。     

TLD measurements and Monte Carlo simulations for glandular dose and scatter fraction assessment in mammography: A comparative study

The main purpose of this study was to validate and compare Mean Glandular Dose (MGD) values obtained using Monte Carlo simulations with experimental values obtained from Entrance Surface Dose (ESD) and depth dose measurements performed in a Hospital mammography unit. ESD and depth dose were measured using ThermoLuminescent Dosimeters (TLDs), and a tissue equivalent mammography phantom recommended by the American College of Radiology (ACR). Measurements and Monte Carlo simulations were also compared with the MGD calculated using the Automatic Exposure Control (AEC) system of the mammographic unit. In the simulations the Doppler energy broadening effect was also taken into account. The simulated ESD are about 5%–10% higher than the measured ESD values. The deviation between the measured and simulated MGD values in the phantom is of about 15%. The MGD evaluated using the AEC system is smaller both with respect to the Monte Carlo simulation and experimental result by a factor of about 15% and 25% respectively. Moreover the BackScatter Factor (BSF) estimated by Monte Carlo simulations was used for the MGD calculation according to the Wu’s method. Finally the inclusion of the energy broadening effect on MGD calculation produces negligible variations on the simulated results.     

UV dosimeter based on polyamide woven fabric and nitro blue tetrazolium chloride as an active compound

This paper reports on the preparation and features of a UV light dosimeter composed of nitro blue tetrazolium chloride (NBT) and polyamide woven fabric. This textile dosimeter is based on the conversion reaction of NBT into formazan, which was initially examined in aerated aqueous solutions through steady state UV irradiation. Irradiated solutions change their colour as a consequence of the formation of polydisperse NBT formazan particles. This was analysed in relation to the absorbed dose of UV light through UV–VIS spectrophotometry and dynamic laser light scattering measurements. When NBT substrate molecules are embedded in polyamide textile, UV irradiation leads to similar effects as in solution. However, the tinge intensity changes at much lower absorbed doses. The dependence of the tinge intensity on the absorbed dose was followed by measurements of the remission of light from the NBT-polyamide samples. Consequently, the calibration parameters were calculated such as the dose sensitivity, dose range, and quasi-linear dose range. An improvement of the NBT-polyamide samples by application of a colour levelling agent and improvement of their resistance to humidity is presented. Finally, the samples were used for estimation of absorbed UV energy distribution showing their capability as new dosimeters for in-plane high resolution radiation dose measurements.     

p型金属氧化物半导体场效应晶体管低剂量率辐射损伤增强效应模型研究

对一种非加固4007电路中p型金属氧化物半导体场效应晶体管(PMOSFET)在不同剂量率条件下的电离辐射损伤效应及高剂量率辐照后的退火效应进行了研究. 通过测量不同剂量率条件下PMOSFET的亚阈I-V特性曲线,得到阈值电压漂移量随累积剂量、退火时间的变化关系. 实验发现,此种型号的PMOSFET具有低剂量率辐射损伤增强效应. 通过描述H⁺在氧化层中的输运过程,解释了界面态的形成原因,初步探讨了非加固4007电路中PMOSFET低剂量率辐射损伤增强效应模型. 关键词： p型金属氧化物半导体场效应晶体管 60Co γ射线')" href="#">⁶⁰Co γ射线 电离辐射损伤 低剂量率辐射损伤增强效应     

Composition depth profiles of Bi3.15Nd0.85Ti3O12 thin films studied by X-ray photoelectron spectroscopy

In the present work, X-ray photoelectron spectroscopy (XPS) was used to investigate the composition depth profiles of Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) ferroelectric thin film, which was prepared on Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by chemical solution deposition (CSD). It is shown that there are three distinct regions formed in BNT film, which are surface layer, bulk film and interface layer. The surface of film is found to consist of one outermost Bi-rich region. High resolution spectra of the O 1s peak in the surface can be decomposed into two components of metallic oxide oxygen and surface adsorbed oxygen. The distribution of component elements is nearly uniform within the bulk film. In the bulk film, high resolution XPS spectra of O 1s, Bi 4f, Nd 3d, Ti 2p are in agreement with the element chemical states of the BNT system. The interfacial layer is formed through the interdiffusion between the BNT film and Pt electrode. In addition, the Ar⁺-ion sputtering changes lots of Bi³⁺ ions into Bi⁰ due to weak Bi-O bond and high etching energy.     

可调光瞳滤波器的轴向焦移及扩展焦深

光学超分辨、焦深扩展及焦移3种效应一直受到研究人员的关注,且在光学显微成像、光学校准、光学相干层析成像及光存储中有着重要的应用.提出一种可调谐光瞳滤波器来实现光学系统的轴向焦移及扩展焦深.该光瞳滤波器由两个完全相同且相互平行的λ/4波片和置于其间的λ/2波片组成,其中λ/2波片分为两个可作相对旋转的区域,并且通过推导得...     

微槽道内气体流动特性的实验研究

搭建了微槽道的单相实验台,分析了氮气在不同深／宽比、长径比及水力直径的微槽道中流动特性。层流区的摩擦常数与理论预测值吻合较好（除L=20mm工况）,层流到湍流的转捩均有不同程度的提前（转捩Re数在1000左右）;在湍流区,槽道的长径比变小、相对粗糙度的增大（或水力直径的减小）及长度的减小可使流动阻力增大;拟合出了湍流区...