Variation of gamma radiation shielding properties with incident photon energy and penetration depth for WC/Al composites

In this work, we examined the usefulness of the WC_x/Al_100?x composites (x?=?10, 20, 50, 80 wt. %) for gamma-ray shielding materials. The mass attenuation coefficient (μ/ρ), effective atomic number (Z_eff), electron density (N_e) and energy absorption buildup factor (EABF) and exposure buildup factor (EBF) for WC_x/Al_100?x composites have been calculated by theoretical approach using XCOM program within the energy range 1?keV–100?GeV, 10 keV–1?GeV, 10 keV–1?GeV and 0.015?MeV–15?MeV, respectively. The results showed that both the values of mass attenuation coefficient and Z_eff of the WC_x/Al_100?x composites tend to increase with the increase of the WC concentration. For the energy region below 3?MeV, the WC₈₀/Al₂₀ composite was found to possess superior gamma-ray shielding effectiveness due to its higher values of both mass attenuation coefficient and effective atomic number, and lower values of both EABF and EBF values. However, for the energy region above 3?MeV, the EBF and EABF values of the WC/Al composites are directly proportional to their Z_eff values, leading to the lowest EBF and EABF values of the WC₁₀/Al₉₀ composites.     

椭圆偏振法数据处理软件设计

以C^ Builder 6．0为开发工具,成功设计和编制了一套椭偏法数据处理软件．它具有求解透明膜厚度、折射率和金属复折射率以及绘制(n,d)～(Ψ,△)列线图的功能,求解膜厚和折射率精度分别达到0．01nn、和0001．实验表明该软件的求解结果是准确和可靠的．     

Study of gamma ray energy absorption and exposure buildup factors for ferrites by geometric progression fitting method

The gamma ray energy absorption and exposure buildup factors (EABF and EBF) were calculated for ferrites such as cobalt ferrite (CoFe₂O₄), zinc ferrite (ZnFe₂O₄), nickel ferrite (NiFe₂O₄) and magnesium ferrite (MgFe₂O₄) using five parametric geometric progression (G-P fitting) formula in the energy range 0.015–15.00?MeV up to the penetration depth 40 mean free path (mfp). The obtained data of absorption and exposure buildup factors have been studied as a function of incident photon energy and penetration depth. The obtained EABF and EBF data are useful for radiation dosimetry and radiation therapy.     

A piezoelectric array for sensing radiation modes

With an example of simply supported beam, this paper presents new experimental wok that is to sense radiation modes by a piezoelectric array. An array of rectangular segments of PVDF film attached on the surface of the beam are taken as sensor. The output signals of the PVDF films are multiplied by appropriate weights so that the weighted combinations of the outputs directly lead to the radiation mode amplitudes of the beam. The weight of every PVDF film sensor is independent of the type, magnitude and position of the external excitation. Experimental results are also presented to show the feasibility of this new type radiation mode sensor.     

物理电学实验仿真软件的设计

基于探究式学习的物理电学仿真软件以探究式学习的理论为软件设计的指导理念,利用仿真技术和统一的建模语言(UML)等一些软件工程的方法,以C 作为编程语言,运用VC 开发平台作为开发工具,编程开发了物理电学实验仿真软件.     

Multifractal analysis of the software evolution in software networks

As the scale and complexity have been increased in software systems, developers place more emphases on software engineering and system designs. Software architecture is evolved with update of softwares, and it plays a fundamental role in determining quality of software systems. Multifractal characteristics of software networks can reflect software quality. In this paper, we construct a software network from the dependencies between object classes, and gain a deep understanding of software through network analysis. To be specific, multifractal analysis of the software network is performed based on a modified box-covering algorithm that yields fewer boxes. We verify that software with different functions and dependencies is multifractal. Further, different versions of the software are compared to discover the evolution of the software architecture. The results show that the singularity of class dependencies decreases as the software is updated. This trend leads to a more specific division of functions between software modules. One of the visible advantages of our work is that it allows the characterization of software structures at the code level. The methodology and results of this paper provide new insights into the evaluation and design of large-scale software systems.     

构建跨平台、易维护的物理CAI演示软件开发环境(PCAIDE)的设想

提出了一个构建“跨平台、易维护的物理CAI演示软件开发环境(PCAIDE)”的设计方案．该方案不仅使得软件的升级和维护更易实现,而且还提供给物理教学人员和普通学生一个专业计算机水准的、具有二次开发功能的物理CAI演示软件开发平台．     

红外光电立靶测试系统软件设计

介绍了红外光电立靶射击密集度的计算方法,设计了一种高效率的靶场测试软件。应用结果表明,该软件能够实时精确测量弹丸射击密集度,可提供多种射击密集度的数据。     

辐射波电磁脉冲模拟器笼形天线辐射特性的并行计算

考虑到辐射波电磁脉冲模拟器笼形天线尺寸过大、在单个微机上计算其辐射特性的时间过长及内存受限制,使用基于消息传递接口（MPI）平台的用于同轴线馈电的时域有限差分并行算法,并结合天线理论模拟分析了同轴线馈电的辐射波电磁脉冲模拟器双锥笼形天线在双指数脉冲电压激励下的脉冲辐射特性。并行时域有限差分计算时,整个时域有限差分计算区域的网格总数约为20亿。由计算结果分析可知：当锥半径大于3.5 m后,笼形天线的半径大小对电场的上升沿和峰值的影响不大;对地面上方0.5 m处的几个测试时,其上升沿、半高宽及脉冲峰值受地面反射及地面损耗的影响比较大,而对于地面上方6 m处的几个测试点,除半高宽外,几个测试点的辐射场脉冲峰值及上升沿受地面影响较小;离地面越近的点,峰值减小得越快。     

辐射波电磁脉冲模拟器笼形天线辐射特性的并行计算

 考虑到辐射波电磁脉冲模拟器笼形天线尺寸过大、在单个微机上计算其辐射特性的时间过长及内存受限制,使用基于消息传递接口（MPI）平台的用于同轴线馈电的时域有限差分并行算法,并结合天线理论模拟分析了同轴线馈电的辐射波电磁脉冲模拟器双锥笼形天线在双指数脉冲电压激励下的脉冲辐射特性。并行时域有限差分计算时,整个时域有限差分计算区域的网格总数约为20亿。由计算结果分析可知：当锥半径大于3.5 m后,笼形天线的半径大小对电场的上升沿和峰值的影响不大;对地面上方0.5 m处的几个测试时,其上升沿、半高宽及脉冲峰值受地面反射及地面损耗的影响比较大,而对于地面上方6 m处的几个测试点,除半高宽外,几个测试点的辐射场脉冲峰值及上升沿受地面影响较小;离地面越近的点,峰值减小得越快。     

A numerical method for computation of sound radiation from an unflanged duct

Some issues involved in establishing a numerical model for sound radiation from a straight duct are addressed in this paper. The main ingredient of the numerical method is solutions of linearized Euler equations using a high order compact scheme. Farfield directivity is estimated through an integral solution of Ffowcs-Williams Hawkings equations. A generic test case of planar wave radiation from an unflanged duct is studied. The sound pressure level and wave propagation in the nearfield are analyzed, together with the farfield directivity. Comparison with analytical solutions shows good agreement. The effect of grid resolution on the sound radiation pattern and the construction of integration surface on the farfield directivity are discussed.     

分布式计算机软件数据整合平台设计

为实现当前经济市场中各应用软件的整合,提高我国各行业间个性化软件的开发能力,加强企业间的科学化系统软件设立,保证企业的高效运行,以及质量和系统维护能力;根据较为常用的分布式计算机系统,提出一种软件数据整合平台的设计;以商用软件整合平台设计为例,以开发模式、服务、技术结构、功能为研究方向,在企业正常运行时,可以实现业务系统功能开发以及门户单点登录,提高企业的个性化系统应用和经济效益;本文根据以上基本需求提出该功能软件平台进行设计,并在实际应用中分析出对于当前企业发展所提供的助力;结果显示,在当前经济发展状况下,有效地使用软件数据整合平台可以很大程度上提高企业的科学化管理和有效的资源分配,使企业在市场竞争中提高经济效益和社会效益。     

Evaluation of the radiation dose to a phantom for various X-ray exposure factors performed using the dose area product in digital radiography

The aim of this study is to measure the dose area product (DAP) in digital radiography by using a DAP meter to determine the X-ray exposure. Pediatric X-ray examinations can be obtained for any radiographic examinations using the selected radiographic examination parameters (kVp and mAs), the DAP information recorded. The best peak signal-to-noise ratio (PSNR) at a fixed tube voltage of 70 kVp was obtained at tube currents of 20 and 32 mA, whereas the best PSNR at a fixed tube current of 25 mA was obtained at a tube voltage of 73 kVp. The fixed tube voltage of 70 kVp and the fixed tube current of 25 mA could help to obtain the best image quality and depict the spatial resolution of an anthropomorphic torso phantom radiographic examination. The normalized data over the DAP were provided to determine the patient dose from radiography.     

Initial flight test results of differential absorption barometric radar for remote sensing of sea surface air pressure

The accuracy of numerical weather model predictions of the intensity and track of tropical storms may be significantly improved by large spatial coverage and frequent sampling of sea surface barometry. The availability of a radar operating at moderate-to-strong O₂ absorption bands in the frequency range 50∼56 GHz to remotely measure surface barometric pressure may provide such capability. At these frequencies, the strength of radar echoes from water surfaces has a strong gradient with frequencies owing to the absorption of atmospheric O₂. Our recent research has developed a technique based on the use of a dual-frequency, O₂-band radar to estimate surface barometric pressure from the measured attenuation due to O₂. The ratio of reflected radar signals at multiple wavelengths is used to minimize the effect of microwave absorption by liquid water and water vapor in the atmosphere, and the influences of sea surface reflection over the frequency of operation. A demonstration instrument has been developed to verify the differential O₂ absorption measurement approach. Recent test flights to evaluate the in-flight performance of the demonstration instrument have been completed. The measured radar return and differential O₂ absorption show good agreement with the modeled results. These flight test results are consistent with our instrumentation goal of ±5 mb uncertainty and indicate that our proposed differential absorption measurement approach may provide a useful measurement of sea surface pressure. Future test flights will provide higher altitude data and assess the precision of the sea surface pressure measurement for the existing demonstration radar.     

组态软件在冷水机组实时监视与故障诊断方面的应用

先进行冷水机组监测参数的选择和数据采集的硬件配置,然后在MCGS组态软件的组态环境下进行组态工程的开发,组成冷水机组实时监视与故障诊断系统。该系统实现对冷水机组的运行参数实时监视、参数超限报警和故障人工智能诊断的功能;便于严密监视设备的运行工况,减少故障发生;也便于在设备发生故障后分析和判断故障产生的原因。     

Anomalous absorption of intense electromagnetic radiation in a non-uniform overdense plasma

In this work, we present numerical computation of anomalous absorption of a powerful electromagnetic wave incident normally, on an isothermal plasma with a linear density gradient. We consider first, the “intensity” dependence of anomalous absorption treating two important cases: one that of a typical high temperature, high density fusion plasma occurring in a laser-pellet application and the other that of an ionospheric (F-layer) plasma. It is found that for low incident powers, reflection is almost constant, corresponding essentially, to classical electronion collisions. As we increase the incident power, however, we find that the reflection starts dropping and the absorption takes over. This result is interpreted in terms of the instability generated anomalous absorption of the incident wave. Next, we consider the “wavelength” dependence of anomalous absorption, wherein we observe that the effect of anomalous absorption is increasing for longer wavelengths of the incident laser radiation.     

Saturation absorption studies of intersubband relaxation rates in a p-GaAs/AlGaAs QW using a free electron laser

We present saturation absorption studies of the HH1→LH1 intersubband transition in a 70 Å p-type GaAs/AlGaAs multi-quantum well. The subband separation in this sample, with strongly non-parabolic bands, varies from 26 meV at k=0 to 16 meV at the Fermi wave vector. The absorption behaviour of this transition is studied over a range of four orders of magnitude of intensity of incident THz radiation. The results are analysed within the contexts of a simple two-level model and an instantaneous thermalization model. The results indicate that the lifetime obtained with these models is limited by the pulsewidth, i.e. is greater than 1.7 ps. This places a lower limit on the energy relaxation time for transitions below the LO-phonon energy.     

基于Windows XPE的水下航行器航行操纵系统多任务软件设计

航行操纵系统是水下航行器控制系统的重要组成部分。为了保证航行操纵系统的实时性与可靠性,鉴于其硬件板卡驱动支持Windows平台,故软件采用了一种基于Windows XPE实时嵌入式系统的设计方法,根据操纵要求对航行操纵系统实时多任务进行了划分,诸如手柄信息处理任务、自动控制任务和网络通信任务等,介绍了多任务执行实体—线程(thread)的优先级的设置和线程同步工具的选取,并分析了Windows的多线程调度策略,然后详细阐述了航行操纵系统各任务的执行流程以及实现方法。最后,对航行操纵系统进行了实验室仿真测试,结果表明该系统实时性和控制精度达到了设计要求,操纵系统性能良好。     

Internal distribution of radiation absorption in a semitransparent spherical particle

The internal distribution of spectral radiation absorption in a semitransparent spherical particle irradiated uniformly and isotropically is determined by the ray tracing method, and the detailed computation formulae for the internal spectral radiation absorption are deduced. The computed results show that the peak of internal volumetric spectral radiation absorption may locate at the interior shell of the particle. The dimensionless volumetric spectral radiation absorption is higher near the center for weakly absorbing or small spheres, but the dimensionless volumetric spectral radiation absorption is higher near the surface for strongly absorbing or large spheres. The corresponding physical interpretations of the internal spectral absorption distribution are given.