News and Reports: Staff Relocate to SNS Site

In June 2004, the Spallation Neutron Source staff relocated to the Central Laboratory &Office (CLO) Building at the construction site on Chestnut Ridge at Oak Ridge National Laboratory. The CLO contains 23,000 m2 of space for more than 400 staff and users. In addition to office space, the CLO will contain large shop areas, conference and training rooms, a receiving department, the central control room, and large spaces for laboratories-all dedicated to the scientific mission of the SNS. Complete occupancy will occur in fall 2004.     

Function of liquid and tool wear in ultrasonic bound-abrasive polishing of fused silica with different polishing tools

The recently proposed fixed-abrasive polishing process was revisited, but this paper focuses mainly on the potential influence of various liquids and the different kinds of pellets on the polishing process as well as the wear of pellet in ultrasonic assisted and conventional processes. The results show that using liquids is helpful in improving surface quality and lowering surface roughness. In particular, the surface roughness is improved sharply for pore-free pellet, from >80 nm to <1 nm (avg.) and the polishing process smoothly proceed that otherwise will hardly progress without liquids. However, the liquids do not necessarily always improve polishing process. There is an optimal volume for a specific polishing process. Moreover, the wear of pellet was also evaluated as well. The results suggest that applying ultrasonics can effectively alleviate the wear loss of pellet and increase the “G-ratio” of polishing process.     

Studies on pore morphology of titanium and its oxide by small angle neutron scattering

Titanium metal bodies have been prepared from the sintered powder compacts of TiO₂ by a novel molten salt electrochemical approach, known as FFC Cambridge process. The phase and compositional characterizations of both Ti and TiO₂ have been carried out by X-ray diffraction. The pore morphologies of sintered TiO₂ pellet and the metallic Ti pellet, obtained after electrochemical reduction have been studied by SANS over a scattering wave vector q range of 0.003–3.5 nm⁻¹ using a double crystal diffractometer and a pin-hole collimated SANS instrument. In the case of reduced metal pellet, average pore size was found to be larger than that of the oxide pellet as the voids left behind after the oxygen atoms left the oxide matrix, could not coalesce.      

改善ITER 弹丸注入芯部加料的研究

研究了五种不同组合的固态氢同位素靶丸H₂、HD、D₂、DT 和T₂ 在聚变等离子体中的消融率。结果表明, 燃料靶丸的同位素效应, 可导致更深的靶丸消融物质沉积。在同样的本底等离子体条件和弹丸初始参数下, 注入氚丸比氢丸的穿透深度增加约40%。适度减轻一些ITER 的加料困难。进一步的研究表明从中平面高场侧注入靶丸对芯部加料有显著改善。考虑托卡马克非均匀磁场的影响, 被电离的消融云内的垂直漂移电流产生极化, 引起带电消融物沿大半径方向朝外漂移。数值模拟计算表明, 只要用初始速度为每秒几百米的低速弹丸, 便能使靶丸的消融物质沉积到ITER 等离子体中心。     

Synthesis of micro-FeTi powders by direct electrochemical reduction of ilmenite in CaCl2-NaCl molten salt

Micro-ferrotitanium powders have been prepared by molten salt electrolysis via directly electrochemical reduction of solid ilmenite in eutectic CaCl₂-NaCl melt at 973 K. In the direct electrochemical reduction process, the reduction of FeTiO₃ first gives rise to the formation of Fe and CaTiO₃, which as intermediates will be further deoxidized at the interface of iron metals, solid CaTiO₃ matrix, and electrolyte to directly form ferrotitanium alloy powders in porous structure. Furthering the electrolytic time can promote the dense structure of ilmenite pellet turn to be more porous, indicating pores inside the pellet are sufficient for the diffusion of oxygen ions. Based on the reduction behavior of partially reduced powders in metallic cavity electrode during the cathodic potentiostatic electrolysis, it shows that the slow deoxidization rate is mainly caused by the more and more difficult reduction of CaTiO₃ than that of FeTiO₃.

     

提高道路交通系统的驾驶安全

道路交通系统是一个复杂的系统，其中包含了人的直接参与。在该系统中，人的因素起了重要的作用。本文中，在道路系统路面的某一点设计了一种类型控制信号，该点被称为信号点。在控制信号的作用下，当车辆经过信号点的时候，车辆需要降低速度。其目的在于能够通过控制信号控制交通流的状态，使其由无序变为有序，从而提高道路系统的交通安全。应用双车道的确定性NaSch模型进行仿真模拟，结果表明不仅交通流的状态能够由无序变为有序，而且交通流的状态是安全的。     

基于智能视觉和BIM的建筑装配过程的高精度控制

为了确保建筑装配过程能实现开发商定义的工业化标准,需要进行建筑装配过程高精度控制。使用当前方法在建筑装配的过程中对建筑装配成本、质量的控制效果达不到开发商的要求。为此,提出一种基于智能视觉和BIM的建筑装配过程高精度控制方法。首先采用BIM技术通过计算机虚拟建筑装配场地布置,建立BIM建筑装配模型,并在BIM建筑装配模型中输入建筑配件以及施工项目相关的所有信息,其次,在BIM建筑装配模型的各个施工构件上加上时间参数和成本计划,构成5D BIM建筑装配模型,对优化完成的5D BIM建筑装配模型进行虚拟建造,调整进度和成本计划,进而将BIM和智能视觉技术相结合,实现整个建筑装配过程的三维可视化指导操作。实验结果表明,所提方法能够有效提高施工效率,且建筑装配成本控制精度较高。     

粒径均匀散体导热系数的分形描述

本文以分形理论为工具,采用填充率、散体颗粒直径等宏观易等测参数较准确地描述了颗粒散体的几何结构;运用导热与逾渗的类比,建立了均匀散体导热系数的逾渗模型,模型的预测值与实验测量结果基本一致。     

The Influence of Film Coating on the Surface Roughness and Specific Surface Area of Pellets

The aim of this paper was to study the surface roughness of pellets after the application of a film coat. In total eight batches of pellets were examined of which four were considered to be round, whereas the other four deviated from the spherical shape by various degrees. The determination of the specific surface area of the coated pellets suggested that, although the film appeared to have filled the pores, the final film structure still mirrored the original surface structure of the pellets. However, profilometry was able to evaluate these gross results in more detail. From the latter measurements it appeared as though the pellet shape was another major influence factor on the final surface texture of the film coating. Pellets with a more elongated and irregular shape such as dumbbells provided more possibilities for interparticulate contact during the coating process, whereby film forming material was ripped off the pellet surfaces making these appear more rough due to surface defects. The use of alcoholic binder solutions during the pellet production might have resulted in surfaces with slightly changed surface free energy, which allowed a better spreading and adhesion of the polymer film and resulted in less textured film surfaces.     

EAST中加热功率对弹丸注入加料效率的影响

介绍了 EAST 装置气动加速氘弹丸注入加料系统和不同加热功率条件下弹丸加料效率的实验结果。 当等离子体加热功率从 1MW 逐渐增加到 10MW 时,弹丸加料效率从 60%降低到 10%。加热功率的升高导致弹 丸粒子的沉积深度 λp/a 降低达 50%左右,从而导致大量的弹丸粒子沉积在等离子体边界。     

Determination of q=1 surface by the variation of pellet ablation rate on the HL-1M

Strong drop of Hα emission has been observed on the HL-1M tokamak by means of a detector array while a pellet crosses the q=1 surface. In this article, the q=1 surface has been determined precisely by the interval and the shape of the Hα emission striations on the pellet trajectory due to the variation of pellet ablation rate. The q-profile and current density distribution at the plasma centre region have been calculated according to the pellet ablation rate and the magnetic shear feature.     

A pellet tracking system for the PANDA experiment

Frozen microspheres of hydrogen (pellets) will be one of the target types for the future hadron physics experiment PANDA at FAIR (GSI, Darmstadt, Germany) [1]. Pellets with a diameter of 25– μm are generated about 3 meters above the interaction region, to which they travel with a velocity around 80 m/s inside a narrow pipe. The interaction region is defined by the overlap of the pellet stream and the accelerator beam and has a size of a few millimeters. One would like to know the interaction point more precisely, to have better possibilities to reconstruct particle tracks and events e.g. in charmonium decay studies. One would also like to suppress background events that do not originate in a pellet, but e.g. may occur in rest gas, that is present in the beam pipe. A solution is provided by the presented pellet tracking system together with a target operation mode that provides one and only one pellet in the interaction region most of the time. The goal is to track individual pellets in order to know their position with a resolution of a few tenths of a millimeter at the time of an interaction. The system must also be highly efficient and provide tracking information for essentially all pellets that pass the interaction region. Presented results from the design studies show that the goals can be fulfilled by this solution.     

CSNS加速器真空控制系统的设计与实现

中国散裂中子源(CSNS)加速器真空控制系统负责真空数据采集、设备监控和闸板阀控制与联锁,是设备运行和故障诊断以及超高真空保持的重要保障。本文介绍了加速器真空需求,基于实验物理及工业控制系统EPICS软件框架的真空控制系统设计与实现,使用横河可编程逻辑控制器PLC控制与联锁设备,摩莎MOXA工控机监测真空状态,EPICS PV数据直接进入声音报警系统和历史数据库系统,为工作人员及时发现和处理问题、进行后续数据分析和机器研究等提供了便捷途径和可靠保障。目前,该系统已完成现场安装和调试,并已正式投入运行。运行结果表明,该系统具有稳定性好、可靠性高、人机交互友好的特点,很好地满足了加速器真空控制系统运行的需要。     

开放仪器管理

中国科学院上海有机化学研究所通过开放上机提高Varian公司Mercury-plus 300 MHz超导核磁共振仪器的使用效率，使用该公司的氘梯度匀场方法及软件的Glide用户接口简化仪器操作步骤，使用网络传递谱图，使用身份识别系统控制仪器使用.     

Fractal patterns of fluid domains for displacement processes in porous media

Percolation invasion displacement of a compressible defender is examined for two cases: when only the smallest accessible site is entered at each step and when all accessible sites less than the size given by a reducing back pressure are entered at each time step. Although the fractions of invading fluid are different, their scaling properties are equivalent. The effect of limited control of a back pressure in a real displacement and the effect of viscosity in a real time displacement are examined. In these cases the scaling properties of a percolation process at breakthrough are removed. As a result, one should expect that realistic displacement models will not have the singular properties usually attributed to percolation processes.     

中国SONG项目高分辨光谱仪与高精度恒星震动视向速度测量

中国SONG项目(Stellar Observations Network Group)是中国天文界参与的一个国际合作的天文学研究计划。其核心是利用高分辩光谱仪获取恒星的时序光谱。光谱仪的分辨率根据科学目标的要求,用不同的狭缝宽度实现R=60 000～120 000。利用碘蒸汽发射线定标的方法,实现高达1 m·s-1的视向速度测量精度,以此测量恒星表面由于恒星震动产生的多普勒运动,并实现项目的科学目标。SONG光谱仪是项目的核心设备,将介绍光谱仪的性能和天体物理应用的参数,并给出实际测量结果。作为一个测量恒星表面多普勒运动时序数据的仪器,整个系统的长期稳定性是项目取得成功的关键,在此也将展示仪器稳定性方面的工作。     

SFC引出静电偏转板运动控制系统设计实现

SFC（扇聚焦回旋加速器）是兰州重离子加速器HIRFL重要组成部分,其束流引出效率直接关系到整个加速器的运行效率。原SFC引出静电偏转板运动控制系统由于其设备陈旧,控制方式及控制精度都已不能满足调束的需求,加之位置检测功能的缺失,给调束带来极大不方便。基于此状态,本项目在有限的检修时间内,分两期实现了偏转板的位置检测和运动控制功能。在设计过程中,使用实际位置拟合测量数据的方法,提高了位置检测的精度,特别是用了特定的软件补偿算法消除机械传动回程差,大大提高了电机控制精度,目前整体控制精度在0.2mm左右。用户界面能够显示每个电机的相对位置、模拟动画、限位开关状态指示等信息。界面简洁直观,操作方便。系统自2014年夏季运行以来,稳定可靠,提高了供束效率,减少了故障时间,得到调束人员一致好评。SFC (Sector Focusing Cyclotron) is an important part of the Heavy Ion Research Facility in Lanzhou.The beam extraction efficiency of SFC is directly related to the efficiency of the whole accelerator. Because of the old equipment and control mode, as well as the low control accuracy of the SFC electrostatic deflection plate motor control, the motion control system was not able to meet the demand of beam tuning staff. In addition, there were no position detection function for this deflection plate; the beam tuning staff cannot get the current position of the deflection plate when they move these motors. Based on this situation, we designed and realized SFC motor control and position detection system in the summer maintain period in 2014 and 2015. In the design, we used the actual position to fit the measured voltage signal to improve the accuracy of position detection. Meanwhile, a specific compensation algorithm was designed to eliminate the mechanical transmission return difference, which greatly improved the motor control accuracy. At present, the overall control accuracy is about 0.2 mm. The user interface has numbers to shows the relative position of each motor and related animation, indicator led to show the status of each limit switches, easy operate buttons to control the motor moving. The system has been running stably and reliably since 2014. It has improved the efficiency of the beam tuning and reduced the fault time, so it is well praised by the beam tuning staff.     

Persistent currents in one-dimensional aperiodic mesoscopic rings

In the tight-binding approximation, we have investigated the behaviour of persistent currents in a one-dimensional Thue-Morse mesoscopic ring threaded by a magnetic flux. By applying a transfer-matrix technique, the energy spectra and the persistent currents in the system have been numerically calculated. It is shown that the flux-dependent eigenenergies form “band” structures and the energy gaps will enlarge if the site energy increases. Actually, the site energy and the filling-up number of electrons are two important factors which have much influence upon the persistent current. Increment of the site energy in the system will lead to a dramatic suppression of the currents. When the highest-occupied energy level is on the top of the band, the total current is limited; otherwise, the persistent current increases by several orders of magnitude. Generally, this kind of large scale change in the magnitude of the current can easily be observed in the vicinity of band gaps. The parity effect in the Thue-Morse ring is also discussed. Received 22 January 2001 and Received in final form 25 October 2001     

托卡马克装置弹丸加料系统中一种新的低温制丸技术的探索

提出了一种新的低温制丸技术磁制冷技术 ,并探索其在托卡马克装置弹丸加料系统中的应用     

一种能量比调控的有源噪声控制算法*

在前馈有源噪声控制系统中,建模信号与控制信号相互影响,建模信号的引入会导致系统降噪性能变差。为了减小建模信号的影响,提出一种基于能量比调控的次级通道在线建模有源噪声控制算法。利用控制过程与建模过程的误差能量比构造步长调控函数,分别调节控制过程与建模过程的步长值,从而减弱两者的相互影响。在次级通道建模过程中,对建模步长值采取分段调控的方法,并通过建模步长值的变化来调节建模信号,从而提升系统降噪性能。仿真结果表明,对于低频噪声信号的有源噪声控制,相比已有算法,提出的算法能获得较快的建模收敛速度和较高的降噪量。