γ刻度室及其控制系统

本文扼要介绍了γ刻度室及其控制系统,其中包括放射源升降,载探头小车的进退,风机停启以及工业电视监视。着重介绍了车位显示仪。它以±1厘米的精度测量和显示小车位置,并在到达预定位置时,发出停车信号,实现自动停车。     

换热器传热管与支承板间碰撞力的分析和实验研究

由于流致振动而产生的传热管微振磨损,已构成核电站蒸汽发生器故障的主要原因之一。影响管子磨损的因素很多,关键参数之一是管子一支承板间的碰撞力。本文用非线性间歇碰撞的有限元模型,编制了平面横向和空间横向碰撞力计算程序。在室温空气条件下进行的单跨管微振实验表明,平面和空间横向碰撞力的计算值与实验数据二者的符合程度是满意的。     

强激励单透镜的象差特性及其在离子源能散测量中的应用

一、相空间中的等角等高曲线族对于强激励单透镜,因象差展开式中的高阶项不能忽略,故计算与分析的工作量均变大,且展开法的结果也不直观。而象面相空间中的等角等高曲线族可以反映出直至高阶的几何象差的总体作用,我们可惜此在任选的物面与接收平面之间进行任意发射图形的变换。     

基于天幕靶的弹丸过靶信息探测提取方法的研究

天幕靶是一种探测弹丸通过空间预定平面时刻的触发传感器,天幕具有一定厚度,并不是一个没有厚度的理想平面,弹丸也并不是一个规则的理想圆柱,所以弹丸穿过天幕不是一个时间点而是一个时刻段.研究弹丸穿过天幕的时间段内哪个时刻点更精确的代表弹丸穿过天幕的时刻点,从而触发计时仪,才能更精确的实现弹丸测速.通过论述弹尖、弹底和幕中触发方式的弹丸过靶信息提取方式,以天幕厚度与测试精度之间的关系为出发点,构建了弹丸穿过光幕的几何计算模型,分析了弹长与幕厚的不同关系下的弹丸过靶信息提取的方法.     

上海市核医学单光子显像报告书写要素规范

核医学单光子发射计算机断层扫描(Single Photon Emission Computed Tomography,SPECT)是目前核医学科装机最多、应用最广的设备,可以反映活体生理、生化、功能和代谢变化.SPECT示踪剂多样,但空间分辨率差,而X线计算机体层成像(X-ray Computed Tomography...     

反应堆控制棒驱动机构管座焊接坡口及密封焊焊缝三维设计

通过分析反应堆控制棒驱动机构管座焊接坡口及密封焊焊缝的平面和空间形状,定义了4条空间的相贯线,提出了管座焊接坡口及密封焊焊缝的三维设计思路与要点;利用UG软件实现了管座焊接坡口及密封焊焊缝的参数化设计,分析了影响管座密封焊焊缝截面积的主要因素.测量结果表明,使用样条法建立的管座焊接截面积误差均控制在0.8%以内.     

基于特征线方法的三维中子输运程序(Ⅰ)——边界条件的插值处理

特征线方法在处理三维中子输运问题的反射边界条件时存在空间问题和角度问题,本文提出了采用平面插值和球面插值方法来分别处理这两个问题,插值方法不仅可以有效解决空间问题和角度问题,而且三维特征线方法在采用插值方法处理边界条件后对离散求积组和射线布置没有要求。     

空间离散对弥散颗粒燃料燃耗计算的影响

单栅元燃耗计算是全堆芯燃耗计算的基础，栅元空间离散对燃耗计算的结果有显著影响。弥散颗粒燃料由于双重非均匀性的存在，空间离散的情况更为复杂。本文基于ALPHA组件程序，分析了颗粒在平源区上归类的宏观离散方案与颗粒内部细分燃耗区的微观离散方案对弥散颗粒燃料燃耗计算的影响。算例包括无毒物的UC颗粒单栅元，含Gd₂O₃层的QUADRISO颗粒单栅元和含UC颗粒与Gd₂O₃毒物颗粒的双颗粒单栅元。数值结果表明，无毒物栅元宏观需分3圈以上，含Gd₂O₃栅元宏观需分5圈以上；无毒物算例微观不需要分圈，含Gd₂O₃层的QUADRISO颗粒需在微观燃料区细分2圈，双颗粒问题的Gd₂O₃毒物颗粒微观需分12～15圈。     

松辽盆地北部砂岩型铀矿成矿有利条件分析与找矿方向探讨

松辽盆地是我国北方主要产铀盆地之一,但是盆地北部铀矿工作程度较低,近几年核工业系统在盆地北部进行系列铀矿勘查工作,由于铀成矿条件不明确,严重制约了松辽盆地北部砂岩型铀矿的勘查和预测工作。前人研究成果主要集中于研究区西部和南部,北部研究相对比较薄弱;对盆地的构造演化未进行系统性分析;目的层的砂体空间展布特征尚未明确;对目的层岩石地球化学特征未进行系统论述等。针对上述问题,通过对松辽盆地北部野外地质调查、典型钻孔岩心编录、连井剖面和铀源情况进行分析,结合研究区的构造演化,深入分析铀成矿有利条件,明确松辽盆地北部上白垩统四方台组、姚家组为主要找矿目的层。认为：目的层具备含铀性较好,砂体具有平面分布广、侧向连通性好的特点,且后生改造作用明显。在此基础上圈定了目的层有利砂体的空间展布,并明确了岩石地球化学的空间分布规律,优选了讷南—通南、林甸和拜泉—三道镇3片铀成矿有利地区,为铀矿勘查工作提供了依据。     

高分辨率小动物SPECT成像系统的设计与性能评估

为实现低成本、高分辨率的小动物单光子发射断层成像(SPECT),设计了一种基于临床探测器和针孔准直器的小动物SPECT成像系统。综合考虑视野尺寸、空间分辨率和绝对探测效率等指标,分别给出了单针孔和七针孔准直器的两种最优化设计方案,并通过对比两种设计方案在全视野范围内的平均空间分辨率和探测效率,对成像性能进行了评估。结果表明,与单孔准直器相比采用七针孔准直器设计可同时获得更高的空间分辨率和探测效率。经蒙特卡罗模拟成像实验验证,该七针孔准直器在临床探测器上可达0.5mm级的超高空间分辨率,且成本远低于采用专用探测器的现有小动物SPECT系统。     

A collocation method using B-splines for one-dimensional heat or mass-transfer-controlled moving boundary problems

A collocation method employing B-splines as approximating functions in the space variable and Gaussian quadrature points as the collocation points is developed for treating the heat or mass-transfer-controlled one-dimensional dissolution problems. It is demonstrated that this method provides an alternative technique which is considerably more accurate than the finite-difference method even at the very end of the dissolution process. The method presented here is first applied to the dissolution problem in the plane slab geometry where direct comparison has been made with the exact solution to assess the accuracy of the method. For spherical particle dissolution, the method is then compared with the existing finite-difference solution where it is shown that a more accurate solution can be obtained with considerably fewer equations.     

Investigations of the radiation purity of atmospheric air and of the river Neva in the region of berth tests of the atomic icebreaker Lenin

During the berth tests of the atomic icebreaker Lenin, we investigated the amount of radioactive substances in the air of the central section holds, in the icebreaker's mainmast, as well as in the atmospheric air, river water, and flora and fauna in the region adjoining the test location. The investigation results indicate that the nuclear power plant of the atomic icebreaker Lenin is provided with a highly efficient radiation protection system, due to which the operation of this vessel is completely safe for the servicing personnel, the berth location, and the stationing of the icebreaker and the ships following in its wake.     

非平面对称磁场的空间展开及样条函数表述

为了研究带电粒子光学系统的光学特性,需要知道系统中磁场的空间分布。实际磁场往往不具有严格的平面对称性质,一些作者曾就这类磁场的空间展开做过不少工作。但他们的工作是在柱坐标系统中进行的,适用于诸如回旋加速器、双向聚焦磁分析器、环形磁β谱仪等一类装置的磁场分析。对于大型同位素电磁分离器(calutron)那样一类装置,其磁场分布需要     

Replacement of a lattice lump near the reflector

The results of an investigation concerning the replacement of a lump in a semi-infinite plane square lattice by a lump with different physical properties are given. The lump to be replaced is located near the boundary between the semi-infinite reflector and the lattice. The lattice is considered to be active. This problem is reduced to the Riemann problem on a unit-radius circle in the plane of imaginary numbers, the solution which can be expressed in closed form. No special assumptions were made concerning the character of neutron moderation and diffusion.     

The features of band structures for woodpile three-dimensional photonic crystals with plasma and function dielectric constituents

The features of the band structures of woodpile three-dimensional (3D) photonic crystals composed of plasma and function dielectric constituents, referred to as function plasma photonic crystals (FPPCs), are theoretically studied by a modified plane wave expansion method, and the formulas for computing the band structures are derived. The arrangement for the proposed FPPCs is that the function dielectric columns are surrounded by plasma, and the embedded dielectric columns are stacked according to the woodpile lattices, which are arrayed with face- centered-tetragonal symmetry. The relative permittivity of function dielectric rods depends on the function coefficient and space coordinates. The relationships between the parameters for inserted function dielectric rods and plasma and the band structures are also investigated. The computed results illustrate that the obtained PBG can be tuned by those parameters as mentioned above. Compared to dielectric–air PCs, function dielectric PCs and plasma dielectric PCs with the same topology, a wider bandwidth of the photonic band gap can be observed in the proposed FPPCs. The calculated results also show us another alternative way to realize reconfigurable applications with 3D FPPCs.     

Elastic-plastic deformation of cylindrical pressure vessels under cyclic loading

A numerical procedure based on the finite element method and incremental solution approach is presented for analyzing cylindrical pressure vessels deformed in the state of generalized plane strain. The structures considered are subjected to internal pressure, thermal gradients and axial forces, which are cyclic in nature. The materials are assumed to obey the von Mises yield criterion with kinematic strain hardening which, during the process of plastic deformation, the yield surface is permitted to translate in the stress space and may change its size as a function of temperature. Based on Drucker's postulates for stable materials in the incremental theory of plasticity, a noniso-thermal flow rule is deduced in the cylindrical coordinates. By use of the virtual work principle, the finite element equations with displacement formulations are derived. The numerical solution is then carried out by a step-by-step approach for small loading increments and an iteration scheme is employed for each loading step. Furthermore, the analysis method is extended to the determination of limit load and shakedown load of a vessel. Several problem cases are presented.     

空间电荷透镜电子云状态研究

本文分析了新型空间电荷透镜磁镜的轴对称磁场(z,r)平面的磁感应强度的变化曲线,由电子的磁流体运动方程组,推导了处于动态平衡状态下电子云中电子密度的波尔兹曼分布。结合磁镜场的磁感应强度分布和电子的波尔兹曼分布,采用四阶龙格 库塔公式对泊松方程进行二阶微分方程数值求解,得到了理想空间透镜中电子云的电势分布。在磁镜场的磁场基础上分析了空间电荷透镜中心轴线的磁约束因子沿z轴方向变化的趋势和数值模拟中心电子密度、磁约束因子、电子温度对电子云状态的影响。磁约束因子越大,对电子云的约束能力越强,电子集中在空间电荷透镜中心轴附近区域的现象越明显;电子温度越高,电子运动越活跃,弥散空间越大,电子集中在空间电荷透镜中心轴附近区域的现象越不明显。     

Finite-element analyses of post-collapse plastic bending of thick pipes

A comparative study of the application of four different types of finite-elements namely elbow (ring), shell, solid, and generalised plane strain to model the post collapse bending behaviour and flow area reduction in an initially straight thick cylindrical pipe made of a highly non-linear material is presented to evaluate their effectiveness. Large strain-large bending FE analyses were performed in each case and the results of moment-curvature relations and pipe-section deformation predictions are compared. The study shows that although solid elements do provide a reasonably accurate and effective solution these are computationally more expensive, while the generalised plane strain finite-elements yield an equally effective and reasonably accurate solution to the problem but are less expensive.     

SOFT X-RAY IMAGES OF CHROMOSOMES WITHIN INTACT TUMOR CELLS TREATED WITH COLCHICINE

In order to avoid any possible effect of separating procedures from intact cell on morphologic structure of the chromosomes, cultivated Hep-2 tumor cells were treated with colchicine and observed by soft X-ray contact microscopy for the first time. The fine structures of chromosomes are more clear with stereo features. The thread-like and coarse granular structures twine and tangle up together within chromosome masses which can not easily be revealed in Wright's stained sample by light microscope or osmium stained sample by transmission electron microscope