A global collisionless PIC code in magnetic coordinates

A global plasma turbulence simulation code, ORB5, is presented. It solves the gyrokinetic electrostatic equations including zonal flows in axisymmetric magnetic geometry. The present version of the code assumes a Boltzmann electron response on magnetic surfaces. It uses a Particle-In-Cell (PIC), δf scheme, 3D cubic B-splines finite elements for the field solver and several numerical noise reduction techniques. A particular feature is the use of straight-field-line magnetic coordinates and a field-aligned Fourier filtering technique that dramatically improves the performance of the code in terms of both the numerical noise reduction and the maximum time step allowed. Another feature is the capability to treat arbitrary axisymmetric ideal MHD equilibrium configurations. The code is heavily parallelized, with scalability demonstrated up to 4096 processors and 10⁹ marker particles. Various numerical convergence tests are performed. The code is validated against an analytical theory of zonal flow residual, geodesic acoustic oscillations and damping, and against other codes for a selection of linear and nonlinear tests.     

结核菌H37Ra在小鼠体内诱导的免疫应答

目的检测结核菌H37Ra免疫小鼠后产生的特异性细胞免疫和体液免疫应答水平。方法将BALB/c小鼠随机分为H37Ra组、BCG组和生理盐水(NS)组,分别进行免疫,免疫8周后处死小鼠,分离血清,ELISA间接法测定血清特异性抗PPDIgG抗体的水平,流式细胞分析仪检测脾脏T淋巴细胞亚群的变化。脾淋巴细胞经体外培养、PPD刺激后,MTT法检测脾淋巴细胞的刺激指数,ELISA法检测培养上清液中IFN-γ和IL-4的水平。结果H37Ra免疫小鼠血清中抗PPDIgG抗体、脾脏CD3+T细胞和CD4+T细胞的百分率、脾淋巴细胞刺激指数、IFN-γ和IL-4水平均显著高于NS对照组,但与BCG组差异无显著意义。各组间脾脏CD8+T细胞、CD4+T/CD8+T比值差异均无显著意义。结论H37Ra免疫小鼠后,可以产生特异性的细胞免疫和体液免疫应答,有望成为结核疫苗的候选抗原。     

Variations in radioactivity of phosphate rocks from different sites in Central Eastern Desert of Upper Egypt

Natural radionuclides in the phosphate rock samples collected from Wadi Batur, Wadi Hegaza and Gabal Abu Had at Eastern Desert were determined using a high resolution 7-ray spectrometer. The experimental results concerning 226Ra, 232Th and their daughters are presented. Analyses of the measured spectra show that 226Ra is distinguished with remarkable activities with average values ranging from 22.4 to 558 Bq/kg, while 232Th activity concentration is in the range of 9.7 to 92.8 Bq/kg. The results of the analyses were found to be in a good agreement with the data obtained by others.     

基于LoRa无线技术的地震应急救援坍塌信息获取

为准确获取到地震坍塌信息,提高救援抗灾能力,提出了基于LoRa无线技术的地震应急救援坍塌信息获取方法。首先分析LoRa无线技术传输系统工作流程,考虑受灾环境多径效应,在LoRa无线系统中使用三边定位锚点,估算坍塌位置节点,得到与实际位置的距离间隔;其次选用三轴高分辨率加速度传感器作为信息获取模块,以无线振动的形式完成信息采集,建立信息获取性能评估函数,提高获取性能,并对获取到的信息幅值采用相位差值算法较正,对得到的坍塌信号频率及相位完成修正,确保可准确的得到受灾区域相关信息数值;最后通过与支持向量机对比获取到的信息数量与准确率、地震区域坍塌类型、及加入其它地形作为干扰因素进行仿真,仿真结果显示,所提方法具有更高的准确率与稳定性。     

尾矿库中U、Th和226Ra在亚粘土层的垂向迁移

在某铀尾矿库运行了31年后,取库底下方的亚粘土样,测量了从库底迁移的U、Th和226Ra的比活度分布.为研究其迁移规律,还测量了尾矿的颗粒分布、不同颗粒尾矿中核素的比活度和浸出因子、核素在亚粘土层的分配系数等参数,并采用一维对流弥散模式拟合得到核素在亚粘土层中比活度分布曲线.结果表明,矿泥是尾矿中的主要成分,其中的核素比活度高于矿砂;而浸出因子则低于矿砂.库底下方天然的和建库时人工铺垫的亚粘土层对三种核素具有较强的吸附滞留能力,从而有效地减少了核素的垂向迁移;U、Th和226Ra在亚粘土中的分配系数分别为62、1.3×103和9.8×102 mL/g,在库底下方核素比活度降到本底水平的距离,U为1.2 m,Th和226Ra为0.2 m.     

基于数值模拟的冷拉钢丝表面精度Ra的优化

为研究拉拔参数对冷拉钢丝表面精度Ra的影响,采用有限元软件MARC建立了钢丝表面微观形态的分析模型,对钢丝拉拔过程进行了模拟仿真,利用正交试验设计法研究了主要拉拔参数(拉拔速度v、过渡圆弧半径R、模具定径带长度L、模具入模角α、摩擦系数μ)对钢丝成形表面精度Ra的影响,并对模拟结果进行了极差分析和方差分析.结果表明:冷拉钢丝在一定断面缩减率的条件下Ra最佳的拉拔参数组合为v=30 mm/s、R=1 mm、L=3 mm、α=11°、μ=0.4);各因素对Ra的影响程度次序为B(R)C(L)E(μ)A(v)D(α);随v和L的增大Ra先减少后增大,α、R及μ对Ra的影响并无明显规律.在此基础上对优化方案进行模拟仿真,发现钢丝表面粗糙度有了显著改善,这表明正交试验设计对冷拉钢丝表面精度优化的有效性.     

环境样品中镭分析的基本知识与实践经验

就环境样品中镭分析的基本知识与实践中存在的问题和经验教训进行讨论,主要内容包括:镭的化学性质及其辐射特性,²²⁶Ra和²²⁸Ra的分析方法,镭的α放射性核素的测定以及分析结果不确定度的估计。     

基于Fe(OH)3-CaCO3载带的水中228Ra的γ能谱分析方法

建立了一种基于Fe(OH)₃-CaCO₃载带的水中²²⁸Ra的γ能谱分析方法,适用于环境水中²²⁸Ra的分析。采用Fe(OH)₃-CaCO₃共沉淀法富集水中的²²⁸Ra,将富集后的²²⁸Ra采用Ba(Ra)SO₄共沉淀法进一步载带,¹³³Ba示踪法确定²²⁸Ra的全程回收率,使用高纯锗γ谱仪测量与²²⁸Ra达到放射性平衡的衰变子体²²⁸Ac的特征γ能量,从而获得²²⁸Ra的分析结果。通过对5 L水样的加标验证可知,²²⁸Ra回收率为81.8%~87.5%,加标水样测量结果与添加量的相对偏差为1.7%~5.3%,此方法的探测限为57.2 mBq/L。     

Friction Drilling of IN-713LC Cast Superalloy

Friction drilling utilizes the heat generated from the friction between the rotating conical tool and the workpiece for hole-making. The process produces no chips and incurs less tool wear, thus lengthening the service life of the drill. In this study, IN-713LC, a nickel-based superalloy, was friction-drilled under different rotation speeds and feed rates. Material properties including hardness, roundness, and surface roughness (Ra) were examined after machining. Experimental results reveal that hardness is greater near the hole's wall and decreases with increasing distance from hole's edge. Moreover, higher rotation speed and faster feed rate can yield better roundness and smoother Ra.