多通道辐射剂量仪的研制

研制了一种可同时测定6个点辐射剂量的智能化仪器.该仪器采用微型半导体探头作为辐射探测器,具有信号采集、数据处理及显示、储存、打印等功能,测量精确度为±0.071%(SD),稳定度为±0.18%(SD),剂量率探测上限达到80Gy/min,可用于各种60Co源的辐照实验、辐照加工及放射治疗.     

PIC simulation of plasma properties in the discharge channel of a pulsed plasma thruster with flared electrodes

Plasma in the discharge channel of a pulsed plasma thruster (PPT) with flared electrodes is simulated by a self-developed two-dimensional code. The fully particle-in-cell method with Monte Carlo collision is employed to model the particle movement and collisions and investigate the plasma properties and acceleration process. Temporal and spatial variations of the electron density distribution and the ion velocity between electrodes are calculated and analyzed in detail. The computational results of the electron number density, which is in the order of 10²³ m⁻³, show good agreements with experimental results of a PPT named ADD SIMP-LEX. The ion velocity distributions along the center line of the channel lead to a comprehensive understanding of ions accelerated by electromagnetic field. The electron distributions of PPT with discharge voltages varying from 1300 to 2000 V are compared. The diffusion of electrons presents strong dependency on discharge voltage and implies higher degree of ionization for higher voltage.     

激光诱导荧光技术对棒束通道内定位格架搅浑特性研究

基于激光诱导荧光（LIF）技术开展了5×5棒束通道内定位格架搅浑特性的可视化研究。常温常压下,通过示踪染色剂（RhB）浓度分布表征流体微团的搅浑行为,清晰展现染色剂溶液在定位格架作用下的搅浑扩散过程,获取格架下游流场的搅浑信息。采用自验证方法分析验证LIF技术测量的准确性,重构棒束通道内径向与轴向染色剂浓度分布,对比带定位格架与不带定位格架的实验结果,得到定位格架对其下游流场的影响范围及不同棒束子通道所受搅浑程度的差异,并以变异系数量化格架对流场搅浑性能的强弱。实验结果表明：定位格架能快速搅浑流动工质,其搅浑翼片分布形式的差异是造成不同子通道交叉搅浑强弱及各向异性的主要原因。本实验工况（Re＝10 478）下,格架对其下游流场的作用范围约为8倍当量直径(D_h),流动工质在格架下游5D_h附近所受搅浑最为剧烈。     

Evolution simulation of lightning discharge based on a magnetohydrodynamics method

In order to solve the load problem for aircraft lightning strikes,lightning channel evolution is simulated under the key physical parameters for aircraft lightning current component C.A numerical model of the discharge channel is established,based on magnetohydrodynamics (MHD) and performed by FLUENT software.With the aid of user-defined functions and a userdefined scalar,the Lorentz force,Joule heating and material parameters of an air thermal plasma are added.A three-dimensional lightning arc channel is simulated and the arc evolution in space is obtained.The results show that the temperature distribution of the lightning channel is symmetrical and that the hottest region occurs at the center of the lightning channel.The distributions of potential and current density are obtained,showing that the difference in electric potential or energy between two points tends to make the arc channel develop downwards.The arc channel comes into expansion on the anode surface due to stagnation of the thermal plasma and there exists impingement on the copper plate when the arc channel comes into contact with the anode plate.     

河道水环境治理中多方位生态修复技术应用的探讨

近年来,水体污染已成为我国社会所广泛关注的重点污染问题,据悉许多重工业工厂为了节省成本将不经任何处理的工业污水排入河道,造成严重的河道水污染。多方位生态修复技术是近年来新兴的环境污染治理措施,它在治理环境污染中发挥着重要作用。本文主要研究多方位生态修复技术在河道水环境治理中的应用,为改善水体污染提供参考。     

规整填料干塔压降与波纹齿角的关系

研究了规整填料压降和波纹齿角的关系,以期探索强化传统规整填料性能的新途径。干填料层压降可分解为3部分：气流在交叉单元碰撞所产生的压降,气流在填料层间改变方向所产生的压降以及塔壁区摩擦力所产生的压降。用计算流体力学（CFD）计算了这3部分压降。结果表明,当波纹齿角从90°减小到20°时,干填料层压降大幅度下降。实验数据也验证了CFD模拟计算结果。     

基于FPGA的双通道旋转变压器测角系统设计

设计了用于星载设备的双通道多对极旋转变压器的角度测量系统.以获取高精度的电机旋转角度值为目的,在旋转变压器测角工作原理、误差分析以及双通道数据组合算法和测角系统软硬件设计等方面进行了研究,并选用FPGA对步进电机的角位移量进行探测与解算.为验证所设计的双通道旋变角度测量系统的精度,采用了分辨率更高的海德汉光电编码器进行...     

提高引黄保证率的微差爆破开槽方法研究

小浪底水库运用后,由于上游水沙条件的改变,黄河下游的河型处于剧烈变化之中,常导致引水口脱溜,引黄取水保证率常处于较低水平。采用微差爆破开槽的方法,可以保证河道主流和闸门之间的引水渠畅通,是提高游荡性河段的引水闸门引水保证率的一种有效方法。该方法首先用爆破形成可以冲开的最小引槽,然后引水冲刷,形成需要的闸前引水渠。试验表明,用最大一次起爆药量,可以控制爆破影响范围,爆破使土体液化的单向水平距离,约为爆破深度的10倍。用爆破方法可以快速形成成型的引槽。爆破不仅不会把成型槽周围泥沙压实,还会通过细沙的回填分选效应,使成型槽周围泥沙更易起动。     

Cation Permeability of Voltage-Gated Hair Cell Ca2+ Channels of the Vertebrate Labyrinth

Some hearing, vestibular, and vision disorders are imputable to voltage-gated Ca²⁺ channels of the sensory cells. These channels convey a large Ca²⁺ influx despite extracellular Na⁺ being 70-fold more concentrated than Ca²⁺; such high selectivity is lost in low Ca²⁺, and Na⁺ can permeate. Since the permeation properties and molecular identity of sensory Ca²⁺ channels are debated, in this paper, we examine the Na⁺ current flowing through the L- and R-type Ca²⁺ channels of labyrinth hair cells. Ion currents and cytosolic free Ca²⁺ concentrations were simultaneously monitored in whole-cell recording synchronous to fast fluorescence imaging. L-type and R-type channels were present with different densities at selected sites. In 10 nM Ca²⁺, the activation and deactivation time constants of the L-type Na⁺ current were accelerated and its maximal amplitude increased by 6-fold compared to physiological Ca²⁺. The deactivation of the R-type Na⁺ current was not accelerated, and its current amplitude increased by 2.3-fold in low Ca²⁺; moreover, it was partially blocked by nifedipine in a voltage- and time-dependent manner. In conclusion, L channel gating is affected by the ion species permeating the channel, and its selectivity filter binds Ca²⁺ more strongly than that of R channel; furthermore, external Ca²⁺ prevents nifedipine from perturbing the R selectivity filter.     

改进的IRS辅助毫米波MIMO级联信道估计

为改善智能反射表面（Intelligent reflective surface,IRS）辅助的毫米波多输入多输出（Multiple-input multiple-output,MIMO）级联信道的估计精度和收敛速度,基于平行因子（Parallel factor,PARAFAC）分解模型,把常规的双线性交替最小二乘（Bilinear alternating least squares,BALS）算法改进为带松弛因子的ω-BALS算法和正则化的T-BALS,加快了收敛速度和算法稳定性。当基站、IRS元件或用户侧的阵列天线数目较大时,提出改进的奇异值（Singular value decomposition,svd）-BALS算法。该算法通过奇异值分解压缩张量,再利用低维度的核心张量来重构模式n矩阵。仿真结果表明,该算法的归一化均方误差性能有所提高,并且加快了收敛速度。