PTC: Full and Drift Particle Orbit Tracing Code for α Particles in Tokamak Plasmas

Fusion born α particle confinement is one of the most important issues in burning plasmas,such as ITER and CFETR.However,it is extremely complex due to the nonequilibrium characteristics,and multiple temporal and spatial scales coupling with background plasma.A numerical code using particle orbit tracing method(PTC)has been developed to study energetic particle confinement in tokamak plasmas.Both full orbit and drift orbit solvers are implemented to analyze the Larmor radius effects on α particle confinement.The elastic collisions between alpha particles and thermal plasma are calculated by a Monte Carlo method.A triangle mesh in poloidal section is generated for electromagnetic fields expression.Benchmark between PTC and ORBIT has been accomplished for verification.For CFETR burning plasmas,PTC code is used for α particle source and slowing down process calculation in 2D equilibrium.In future work,3D field like toroidal field ripples,Alfven and magnetohydrodynamics instabilities perturbation inducing α particle transport will be analyzed.     

原始数据动态观察窗法在火灾特征信号融合提取中的应用研究

多源信息融合技术逐步在火灾探测中得到应用,火灾特征信号融合提取算法的优劣,对火灾探测结果影响较大。为寻找火灾特征信号提取的最优方案,利用原始数据动态观察窗法,将NIST FR系列火灾试验中试验6的原始数据作为训练样本,借助神经网络分类器进行Matlab仿真实验,发现采用10 s步长和15 s窗长算法融合提取火灾特征信号最优。同时验证了原始数据动态观察窗法在火灾特征信号融合提取中应用价值。     

Unusual Normal and Superconducting State Properties Observed in Hydrothermal Fe_(1-δ)Se Flakes

The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T. The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT) growth. No signature of the electronic nematicity, but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples. Interestingly, a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se. Moreover, the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of ~42 T, which breaks the Pauli limit by a factor of 1.8.     

基于剔除拟合的股骨头修复建模

提出了一种可以获得目标病例健康时股骨头模型的新建模方法.通过CT扫描获得髋骨部位的序列断层图像,利用一种精确的自动分割方法提取图像中的髋臼轮廓.针对髋臼的特殊结构,使用辐条式采样法得到髋臼凹面的空间坐标点集.剔除坐标点集中的误差采样点.采用闭合形式解的最小二乘法拟合原始股骨头球面模型.通过对2例不同坏死程度的男性患者进行修复实验,证明此方法可以良好地还原坏死的股骨头模型,既为骨科临床中的精确手术定位提供了理论模型,又为针对个体化制造的人工假体生产提供了新的实践方法.     

Polling Strategy for Wireless Multimedia LANs

Introduction There is an increasing demand for wireless multimedia networks to communicate using any type of media without any geographical restrictions. Therefore, wire- less networks are expected to support multimedia ser- vices with guaranteed quality …     

Interpretation of Strengthening Mechanism of Densified Wood from Supramolecular Structures

In this study, densified wood was prepared by hot pressing after partial lignin and hemicellulose were removed through alkaline solution cooking. The tensile strength and elastic modulus of densified wood were improved up to 398.5 MPa and 22.5 GPa as compared with the original wood, and the characterization of its supramolecular structures showed that the crystal plane spacing of the densified wood decreased, the crystallite size increased, and the maximum crystallinity (CI) of cellulose increased by 15.05%; outstandingly, the content of O(6)H⋯O(3′) intermolecular H-bonds increased by approximately one-fold at most. It was found that the intermolecular H-bond content was significantly positively correlated with the tensile strength and elastic modulus, and accordingly, their Pearson correlation coefficients were 0.952 (p < 0.01) and 0.822 (p < 0.05), respectively. This work provides a supramolecular explanation for the enhancement of tensile strength of densified wood.     

基于积累线性模型的证券单笔交易模型

积累线性模型是处理自变量为连续变量、因变量为离散变量时的常用方法。而单笔交易中证券价格的变动为离散变量,本文采用积累线性模型为其建模,得到了在一定的交易方向和交易量下,证券价格变动的条件概率分布。理论与实证结果均显示,积累线性模型更适合用于建立单笔交易模型;其中序次Logisic回归又比序次Prob it回归的拟合效果更好。使用积累线性模型建立的证券单笔交易模型具有良好的应用前景。     

Si掺杂介孔SO2-4/TiO2的非模板剂法合成及表征

在不使用模板剂的条件下,以工业硫酸氧钛溶液为原料合成介孔偏钛酸前驱体,再经正硅酸乙酯浸渍焙烧制备了具有良好热稳定性的Si掺杂介孔SO2-4/TiO2.采用X射线衍射、N2吸附-脱附、扫描电镜、X射线能谱和傅里叶变换红外光谱等表征方法对样品的组成和结构进行了分析,并考察了该材料在亚甲基蓝氧化降解反应中的光催化性能.结果表明,在焙烧过程中,被吸附在偏钛酸孔道内的正硅酸乙酯发生水解,并与偏钛酸孔壁上的自由羟基形成 Ti - O - Si 键;Si进入二氧化钛骨架中,对孔结构起到了支撑作用,从而提高了介孔SO2-4/TiO2的热稳定性.700 ℃焙烧 2 h 后,Si掺杂介孔SO2-4/TiO2材料的比表面积仍达到189 m2/g,平均孔径为2.8 nm.400 ℃焙烧的样品在亚甲基蓝降解反应中表现出较好的光催化活性.     

基于网络流量自相似的DDoS攻击检测方法

分布式拒绝服务攻击(DDoS)是目前黑客经常采用并极为有效的网站攻击手段。本文在验证局域网流量具有严格自相似性的同时,介绍了常用的Hurst参数计算方法。通过大量实验研究了DDoS攻击对Hurst系数产生的定量影响,并在实验数据分析的基础上,提出了攻击发生和结束的准确判据。实验结果显示,该方法性能良好。