Bunch-by-bunch beam size measurement during injection at Shanghai Synchrotron Radiation Facility

Fast beam profile measurement is important in fast beam dynamic behavior investigations. A bunch-bybunch beam size measurement system, which is presently used to measure horizontal profile, has been developed at the Shanghai Synchrotron Radiation Facility(SSRF) and is capable of measuring bunches within a separation of 2 ns.The system is based on a direct-imaging optical system and high-speed photomultiplier array detector. A high-bandwidth linear signal amplifier and acquisition module have also been designed to process bunch-by-bunch multichannel signals from the detector. The software resampling technique and principal component analysis method were developed to obtain the synchronized data and enhance the signal-to-noise ratio. The fast injection of transients was successfully captured and analyzed. Moreover, the bunchby-bunch positions and sizes exhibited strong oscillation after the injection at the horizontal betatron oscillation frequency of the SSRF storage ring, and this demonstrated the bunch-by-bunch measurement capability of our system.

Performance of beam size monitor based on Kirkpatrick–Baez mirror at SSRF

High-energy photon source(HEPS) is a 6 GeV ultralow emittance storage ring light source to be built in Beijing, China. Both the horizontal and vertical beam sizes of the HEPS storage ring are below 10 lm. It is a challenge to measure such a small beam size in both directions. To this end, measurement by a Kirkpatrick–Baez(KB) mirror imaging system was evaluated. A test KB system for the Shanghai Synchrotron Radiation Facility storage ring was designed and tested. Two crossed cylindrical mirrors were used to image the dipole source point. Both mirrors can be moved in and out so that the monitor is interchangeable with the original X-ray pinhole monitor. The aberration and point spread function, which would cause image blur, were evaluated. A beam-based calibration scheme was used by varying the beam size with different quadrupole settings and fitting them with the corresponding theoretical values.We updated the original X-ray camera with a new camera having a 5-lm-thick LuAG/Ce scintillator, and the imaging result shows greatly decreased image blur.

Simulation of beam size multiknobs correction at the Accelerator Test Facility 2 at KEK

The ATF2 project is the final focus system prototype for the ILC and CLIC linear collider projects, with a purpose of reaching a 37 nm vertical beam size at the interaction point （IP）. During the initial commissioning, we started with larger-than-nominal β-functions at the IP in order to reduce the effects from higher-order optical aberrations and thereby simplifying the optical corrections needed. We report on the simulation studies at two different IP locations developed based on waist scan, dispersion, coupling and β function multiknobs correction in the large β optics of ATF2, in the presence of two kinds of magnet inaccuracies （quadrupole gradient and roll errors） to generate all possible linear optic distortions at the IP. A vertical beam size which is very close to the nominal beam size is obtained based on the simulation study.

The measurement of electron beam transverse sizes by synchrotron radiation interferometry for HLS Ⅱ

In order to improve accuracy of electron beam transverse sizes measurement,the vertical and horizontal synchrotron radiation light interferometers have been designed to measure beam transverse sizes for the upgrade project of Hefei Light Source(HLS II).In this paper,the light intensity distributions of the interferogram are descussed,and parameters of the interferometers are optimized.The interferograms are simulated under MATLAB. Taking integrations of two-dimensional interferogram intensity,normalized one-dimensional interference intensities distribution of the vertical and horizontal interferogram are obtained.The two curves are fitted to compare the beam transverse sizes with the designed sizes,and this verifies the feasibility of this method.Finally,several factors that affect the beam sizes measurement are discussed.

Nonlinear beam formulation incorporating surface energy and size effect:application in nano-bridges

A nonlinear beam formulation is presented based on the Gurtin-Murdoch surface elasticity and the modified couple stress theory. The developed model theoretically takes into account coupled effects of the energy of surface layer and microstructures size- dependency. The mid-plane stretching of a beam is incorporated using von-Karman nonlinear strains. Hamilton＇s principle is used to determine the nonlinear governing equation of motion and the corresponding boundary conditions. As a case study, pull-in instability of an electromechanical nano-bridge structure is studied using the proposed formulation. The nonlinear governing equation is solved by the analytical reduced order method （ROM） as well as the numerical solution. Effects of various parameters including surface layer, size dependency, dispersion forces, and structural damping on the pull- in parameters of the nano-bridges are discussed. Comparison of the results with the literature reveals capability of the present model in demonstrating the impact of nano- scale phenomena on the pull-in threshold of the nano-bridges.

The Influences of an Embedded Structure Fiber-Optic Radiation Dosimeter in Different SSD and Beam Field Size

With a rapidly increasing demand and widespread use of radiotherapy treatment, the subject area of in-vivo real time dose rate dosimeters has become a significant area of study. An embedded structure fiber-optic radiation dosimeter has proved to be a promising candidate to fulfil this role because of its high SNR (signal-to-noise ratio) and excellent light conversion efficiency. In this paper, the properties of this kind of dosimeter with respect to different SSD (Source to Surface Distance) and beam field size in a clinical Linac are studied. The characteristics of the dosimeter were evaluated by the sensor’s output intensity response in these conditions.

The influence of Laval nozzle throat size on supersonic molecular beam injection

In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.

A Pilot Survey of Odontomas for Size Constancy Using Cone-Beam Computed Tomography: Effect of Age, Sex, Lesion Location, and Histological Type: A Case Series

Objectives: Odontoma is the most common type of odontogenic tumors. Many studies have analyzed the statistical associations between odontoma location and patient age and sex, according to the histological tumor type. However, few studies have assessed odontoma morphological characteristics using cone-beam computed tomography (CBCT). We aimed to evaluate the association between odontoma location and size. Methods: We performed CBCT on patients with odontomas (19 patients;10 women, 9 men;average age, 12.6 [range, 6 - 34] years) according to the pathology type at a university hospital between April 2008 and February 2017. The locations of the lesions were noted, and their sizes were measured on CBCT images. Buccolingual, mesiodistal, and vertical diameters of the lesions were recorded on the same slice with the greatest diameters on axial, coronal, and sagittal CBCT images. Results: Altogether, 9 (47.4%) and 10 (52.6%) odontomas were located in the mandible and maxilla, respectively. There was no significant difference in the mesiodistal and vertical diameters on the CBCT image between the mandibular and maxillary groups when the odontoma size was compared with location (p < 0.05). However, the average diameters in only the buccolingual diameter were significantly greater in the maxilla. There were no significant differences between the two groups according to sex, age, or histological type. Conclusions: These data suggest that the sizes of odontomas in the maxilla are affected by bone expansion in the buccolingual direction, but they may be invariable in most settings. Three-dimensional assessment across the age groups suggests a lack of variation in size.

长江口桁拖网最小网目尺寸的选择性研究

为完善东海区桁拖网最小网目尺寸标准,2017年6月和9月分别于长江口(30°50′~31°24′N,122°12′~122°26′E)近海使用主机功率88.2 kw和总吨位30 t的渔船进行套网法25 mm和35 mm网囊网目的渔获选择性试验,供渔政主管部门制定网目尺寸标准参考。本研究利用Logistic模型分别拟合虾蟹类优势种安氏白虾(Palaemon annandalei)、三疣梭子蟹(Portunus trituberculatus)和葛氏长臂虾(Palaemon gravieri)的选择性曲线,利用极大似然法估算模型参数。结果表明,桁拖网共捕获渔获物47种,包括鱼类23种,虾类13种,蟹类6种,其他类5种;虾蟹类优势种为安氏白虾、三疣梭子蟹和葛氏长臂虾,体长范围分别为17~45 mm、13~130 mm和18~52 mm。在25 mm标准网目尺寸下,安氏白虾、三疣梭子蟹和葛氏长臂虾的选择率为50%所对应的体长或甲宽(L_(50))分别为33.784 mm、30.850 mm和32.930 mm,选择系数(SR)分别为10.100 mm、7.978 mm和9.094 mm。各优势种的平均逃逸率均低于50%,三疣梭子蟹的逃逸率显著低于其他优势种(P<0.05)。研究表明,当网囊网目尺寸由25 mm增大至35 mm时,能够有效释放本研究海域的虾蟹类,建议适当增大现行网目尺寸标准。

翼缘尺寸对地聚物混凝土T形梁抗剪性能的影响

为探究翼缘尺寸对地聚物混凝土T形梁抗剪性能的影响,对1根普通混凝土和4根不同翼缘尺寸的地聚物混凝土T形梁进行了集中荷载下的抗剪试验;试验获得了T形梁试件的承载力、挠度、钢筋应变、破坏模式及裂缝的开展等相关参数。研究结果表明:地聚物混凝土T形梁具有与普通混凝土T形梁相似的裂缝扩展、破坏模式及抗剪承载力,但其刚度和斜截面开裂荷载较低,跨中纵筋和箍筋的应变较大;将翼缘厚度与截面有效高度比值从0.24增大到0.48时,地聚物混凝土T形梁的刚度增大、跨中纵筋应变减小,抗剪承载力提高了12.7%,地聚物混凝土的归一化抗剪强度增大了25.3%;当翼缘宽度超过两倍腹板宽度时,继续增大能减小跨中纵筋应变,但地聚物混凝土T形梁的刚度、抗剪承载力及地聚物混凝土归一化抗剪强度不再增大。规范ACI 318—19和Eurocode 2的计算结果明显低估了地聚物混凝土T形梁的抗剪承载力,GB 50010—2010较接近试验值。为更好预测地聚物混凝土T形梁的计算抗剪承载力,建议在抗剪承载力计算公式中增加翼缘有效受剪面积所提供的剪力。

小提花织物双织轴织造工艺的优化

探讨在双织轴喷气织机上生产平纹小提花织物的技术措施。以一款细号高密平纹小提花织物生产为例,统计织造工序停台次数并进行原因分析。通过优化浆料配方,改进浆纱工艺,提高了经纱质量。在织造工序,重点优化了经位置线、开口时间、上机张力、织机速度等工艺参数,提高了织机效率。结果表明:工艺优化后,织机效率从69.8%提升到88.9%,百米布疵点评分从17分降低到14分。认为:优化后的工艺参数符合生产要求,并提高了双织轴喷气织机生产平纹小提花织物的织机效率。

弯剪耦合作用下大尺寸碳纤维C型梁失效损伤模式分析

为进一步探究大尺寸碳纤维C型梁结构抗弯剪屈曲的承载性能,提出了一种可同时施加弯曲和剪切载荷并任意调节弯剪比的试验装置。通过设计3种不同弯剪耦合条件进行试验载荷的加载,使用应变片监测大尺寸碳纤维C型梁结构在屈曲以及后屈曲阶段应变分布状况。通过有限元模型对基于不同损伤准则的后屈曲行为进行预测。研究结果表明:大尺寸碳纤维C型梁在抗弯和抗弯剪耦合的载荷条件下,都具有优良的后屈曲承载能力;在2种弯剪耦合条件下,试验件分别在3.28倍和2.3倍设计载荷时发生梁腹板失稳现象,试验件进入后屈曲状态,继续进行弯剪耦合载荷的加载,达到4.6倍设计载荷后,样品出现局部损伤;采用Hashin和LaRC05准则对试验件损伤情况进行预测,破坏损伤形式分别为沿45°方向开始向外扩展和上部翼缘扭曲破坏。

基于断裂能的混凝土弹塑性损伤本构模型和尺寸效应研究

为研究混凝土断裂特性与尺寸效应,引入断裂能和等效应变表示混凝土的损伤演化规律,结合混凝土塑性变形特征,提出基于断裂能的混凝土弹塑性损伤本构模型,并建立相应的数值计算模型。为验证数值计算结果的合理性,引入改进的能量尺寸效应公式进行对比分析。通过对三点弯曲梁的有限元数值模拟和断裂参数敏感性分析发现,尺寸较小的梁失效时,断裂过程区未扩展至特征长度,限制了能量耗散,从而提高了梁的抗断裂能力,增强了梁的名义强度;随着尺寸增大,失效时的断裂过程区逐渐接近特征长度,梁的名义强度逐渐减小;当断裂过程区达到特征长度后,结构名义强度不再随梁尺寸的增大而减小。

中小跨径梁桥中组合橡胶支座的减隔震性能分析

地震作用下,中小跨径梁桥所用板式橡胶支座易出现滑动,使墩梁的位移偏大,而组合橡胶支座的耗能能力及位移能力相对高。采用拟静力试验及有限元分析探讨了组合橡胶支座、板式橡胶支座各工况下的地震响应,结果表明:中小跨径梁桥采用组合橡胶支座能够有效防止支座滑动,显著降低了桥墩弯矩与支座位移。

基于ANSYS的混凝土试件成型机梁柱连接件轻量化设计

梁柱连接件是混凝土试件成型机的重要组成部件,为提高框架结构的安全性、可靠性和稳定性,针对某型号混凝土试件成型机的梁柱连接件,通过拓扑优化和尺寸优化实现轻量化设计.首先,对现有梁柱连接件进行拓扑优化设计,并根据拓扑优化结果开展二次设计;其次对二次设计后的梁柱连接件构建尺寸优化模型,采用正交试验和方差分析筛选出对性能响应影响较大的结构参数作为设计变量,以成型机连接件质量最小为优化目标构建尺寸优化模型;最后,通过建立响应面优化模型进行求解获得最优的尺寸参数组合.研究结果表明,经过拓扑优化和尺寸优化后,连接件在质量方面降低了1.472 9 kg,减重比例达27.5%.

笔形束质子放疗系统质控中束斑大小测量方法对比研究

目的 研究对比笔形束质子放疗系统质控中束斑大小的测量方法。方法 使用Matrixx One二维平面电离室矩阵、Lynx-PT平面闪烁体探测器及XRV-124锥形闪烁体探测器-三种不同种类、不同形状的探测器对质子放疗系统中不同能量的质子束斑大小进行测量,并将测量结果与加速器验收时束斑大小结果进行对比。结果 Matrixx One的束斑大小测量结果与验收结果相比偏差较大,其中230 MeV时的最大偏差达到41.25%。而Lynx-PT和XRV-124的束斑测量结果与验收结果相比,最大偏差分别为-7.35%和3.69%,Lynx-PT测量结果相较于验收结果系统性偏小。结论 Lynx-PT和XRV-124均适用于质子放疗系统束斑大小的测量,Matrixx One适用于束斑尺寸较大的质子放疗系统,相较于Lynx-PT和Matrixx One, XRV-124在旋转治疗室单能单点束斑尺寸测量中更有优势。

加腋梁加腋板楼盖工程造价分析

文中分析了加腋尺寸对梁及板的材料用量及造价成本的影响,并对加腋梁、加腋板楼盖与单向板主次梁楼盖的工程造价进行了对比分析。分析结果表明,梁加腋长度采用4倍的梁加腋高度,即可保证经济性,与未加腋梁相比,其总造价降幅达19.8%;板加腋长度采用2倍的加腋高度,即可保证经济性,与未加腋板相比,其总造价降幅达17.3%。与单向板主次梁楼盖相比,加腋梁加腋板楼盖的单位面积所用设备造价降低幅度达21.2%,所用材料造价降低幅度达8.7%,材料和设备总造价降低幅度达10.4%。

一种新型梁类机械零件夹具装置的设计与应用研究

为了开展基于声音信号对梁类机械零件损伤检测识别的实验,文章结合实际需求,设计了一种梁类机械零件的夹具装置,并结合应用实例,解释了该夹具装置的使用方法。该夹具装置对现有装置进行升级,设计了一种表面各具特点的夹紧块,使其能够快速适应不同横截面形状、不同大小机械零件的装夹,以实现高效、多功能、低成本的目的;同时采用丝杠螺母副,利用其结构简单、运动平稳的优点,实现机械零件的上下移动和装夹,为基于声音信号的结构损伤检测识别提供了有效的实验基础。

大跨无柱地下车站梁-柱节点受力性能的局部多尺度有限元方法

岗厦北综合交通枢纽核心换乘区的中庭51.2 m×48.0 m(南北长度×东西长度)范围为无柱设计范围,其跨度在全国尚属最大。梁-柱节点是该结构传力关键,但数量繁多、类型复杂,且建造过程存在多重体系转换,必须确保节点传力顺畅。基于多点约束方程法(MPC),提出一种局部多尺度有限元方法(LMFEM)。采用LMFEM方法,进一步研究梁、柱贯通方式对本文依托工程典型梁-柱节点受力性能的影响,发现柱贯通节点整体应力较低,传力顺畅,应力集中不显著,更适用于岗厦北大跨无柱地下空间结构。基于现场监测,将节点受力状态实测值与不同方法所得计算值进行对比分析。研究结果表明:相比于传统局部精细化有限元方法(LRFEM),LMFEM方法具有建模工作量小、边界条件易于满足圣维南原理、可兼顾计算精度和计算效率的特点;在同等建模规模和网格细度情况下,LRFEM2模型计算值与实测值的最大相对误差为11.8%,LMFEM模型计算值与实测值的最大相对误差为12.5%,但后者具有更少的节点数量和更短的计算时间,而LRFEM方法的计算精度受边界条件和单元网格细度影响较LMFEM方法的大;本文提出的LMFEM方法具有计算精度高、计算效率高、边界条件易明确等优势,可应用于大型复杂工程结构的节点局部受力性能分析。

A segmented conical electric lens for optimization of the beam spot of the low-energy muon facility at PSI: a Geant4 simulation analysis

The low-energy muon facility at PSI provides nearly fully polarized positive muons with tunable energies in the ke V range to carry out muon spin rotation(LE-μSR)experiments with nanometer depth resolution on thin films,heterostructures, and near-surface regions. The low-energy muon beam is focused and transported to the sample by electrostatic lenses. In order to achieve a minimum beam spot size at the sample position and to enable the steering of the beam in the horizontal and vertical direction, a special electrostatic device has been implemented close to the sample position. It consists of a cylinder at ground potential followed by four conically shaped electrodes,which can be operated at different electric potential. In LE-μSR experiments, an electric field at the sample along the beam direction can be applied to accelerate/decelerate muons to different energies(0.5–30 keV). Additionally, a horizontal or vertical magnetic field can be superimposed for transverse or longitudinal field μSR experiments. The focusing properties of the conical lens in the presence of these additional electric and magnetic fields have been investigated and optimized by Geant4 simulations. Some experimental tests were also performed and show that the simulation well describes the experimental setup.