A new method of detecting interferogram in differential phase-contrast imaging system based on special structured x-ray scintillator screen

An x-ray scintillator screen with a special structure, functioning as detector and analyser grating, was proposed for collecting the interferogram of differential phase contrast imaging without absorption grating and difficulty of fabrication by a state of the art technique. On the basis of phase grating diffraction, a detecting model of the scintillator screen was built for analysing the phase and absorption information of objects. According to the analysis, a new method of phase retrievals based on two-images and the optimal structure of screen were presented.

Random phase screen influence of the inhomogeneous tissue layer on the generation of acoustic vortices

The influence of the inhomogeneous tissue layer on the generation of acoustic vortices （AV） is studied theoretically and experimentally based on the phase screen model. By considering the time-shift of a random phase screen, the formula of acoustic pressure for the AV beam generated by a circular array of eight planar piston sources is derived. With the actual correlation length of the abdominal wall, numerical simulations before and after the insertion of the inhomogeneous tissue layer are conducted, and also demonstrated by experimental measurements. It is proved that, when the thickness variation of the phase screen is less than one wavelength, no significant influence on the generation of AVs can be produced. The variations of vortex nodes and antinodes in terms of the location, shape, and size of AVs are not obvious. Although the circular pressure distribution might be deformed by the phase interference with a larger thickness variation, AVs can still be generated around the center axis with perfect phase spirals in a reduced effective radius. The favorable results provide the feasibility of AV generation inside the human body and suggest the application potential of AVs in object manipulation for biomedical engineering.

A DISCUSSION ON FRESNEL APPROXIMATION IN PHASE SCREEN MODEL

The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k】】k.The application condition for Rino’s results is obtained,and it is|▽R△Ne|/R△ne【【1.

Non-Gaussian Phase Screen Based on log-Poisson Distribution and Effect on Imaging

Gaussian models without intermittency are extensively used in estimating the effect of turbulence,but italso brings some puzzles,for example the observed pulse shape that disagrees with the result of the standard theoryof interstellar scintillations.Indeed the property of intermittency is inherent in turbulence,i.e.,all the quantities thatcharacterize it suffer from strong fluctuations.So it is necessary to consider turbulent intermittency in many applications.In this paper we propose a non-Gaussian phase screen,which obeys log-Poisson statistics,and also offers the correspondingpoint spread function(PSF).These results describe that intermittency leads to the more extent and different directionaldistribution of PSF.Theoretical analysis is made under the hypothesis of the phase difference satisfying log-Poissonstatistics,and the average point spread function,which accord qualitatively with the result of the above generated phasescreen,is derived.

The Phenomenon of High Hardness Values on the S-Phase Layer of Austenitic Stainless Steel via Screen Plasma Nitriding Process

The purpose of this study is to improve the surface properties of austenitic stainless steel using the double-folded electrode screen plasma nitriding (SPN) process. In general, the S-phase is well-known for its excellent properties such as improved hardness and wear resistance along with sustained corrosion resistance. The concentrated nitrogen via SPN process was injected to form S-phase with time at 713 K. This study was carried out under the conditions of 44 at% of nitrogen injection, which was higher than 25 at% known as the condition of no precipitation of S-phase formed by the SPN process, and 20 K higher than the maximum temperature without precipitation phase. The hardness analysis of stainless steel sample treated by the SPN process at 713 K showed a much higher value than the typical nitriding hardness at a depth of lower nitrogen than the maximum nitrogen concentration. The SPN 20 hr treated specimen showed the average value of 2339 HV while 40 hr showed the average value of 2215 HV. The result is attributed to the concentrated nitrogen formed in the SPN process reacting with the alloying elements contained in the base material to form fine precipitates, thus producing a synergy effect of the extreme hardening effect;that is, the movement of precipitates and dislocations due to the GP-zone (Guinier-Preston zone).

递进式N×N型采样方式次谐波海洋湍流相位屏模拟方法

以N×N型采样方式次谐波法为基础,引入了递进式采样,提出了一种递进式N×N型采样方式次谐波法,用于数值模拟海洋湍流相位屏。该方法利用Nikishov提出的海水折射率波动谱模拟海洋湍流相位,通过相位结构函数和补偿效果验证该方法生成相位屏的准确性。通过改变递进区域个数、补偿阶数和谐波次数,比较分析相位屏参数对改变对相位屏准确性的影响。此外,将所提方法与N×N型采样方式次谐波法、改进的次谐波补偿法和改进的次谐波法进行比较。结果表明:递进式N×N型采样方式次谐波法只需谐波次数为11时,补偿效果即可达到0.9995,并且在准确度相同的情况下具有更快的模拟速度。

弱风条件下斜程海洋湍流中涡旋光束的传输特性

光束在海洋介质中传输会极大地受到海洋湍流的影响。此外,涡旋光束轨道角动量的复用会极大地提高系统容量,因此研究涡旋光束在海洋湍流中的传输具有重要意义。在水平海洋湍流理论基础上,创新性地构建了斜程路径上海洋湍流相位屏模型,以相位结构函数为依据验证了海洋湍流相位屏的准确性,根据多相位屏法搭建准直高斯涡旋光束在海洋湍流中的上行传输链路模型。数值模拟并分析了不同天顶角、海洋湍流内外尺度及拓扑荷数等其他海洋湍流参数对准直高斯涡旋光束经海洋湍流上行传输的光强及相位分布、光束漂移、轴上闪烁指数和长曝光光斑半径的影响。结果表明:涡旋光束的拓扑荷数越小、天顶角越小,光束受到湍流的影响越大;在海洋湍流上行传输链路中,准直高斯涡旋光束的光束漂移、轴上闪烁指数及长曝光光斑半径随海洋湍流外尺度的增大而增大,且主要受传输距离的影响;理想情况下,取海洋湍流外尺度为无穷大,会高估湍流对光束的影响;由于涡旋光束的本身特性,拓扑荷数对光强及相位分布和长曝光光斑半径的影响也较为显著。

基于外差干涉的涡旋光水下传输相位测量

涡旋光束在湍流介质中传输时,光束相位会受到湍流运动的影响产生畸变。采用了一种基于外差干涉的点像元相位提取方法,通过采集各个点在一个周期内的干涉条纹获得的相对相位,重构出涡旋光束经过水下湍流传输后的相位分布。通过功率谱反演法生成随机相位屏,完成不同湍流强度下涡旋光束的传输仿真,结果表明光束相位畸变随着湍流强度的增大而增加。搭建了实验装置,实现了水下环境的涡旋光传输及相位测量。实验结果表明,当涡旋光在存在湍流的水下传输时,其复振幅分布经历了较为复杂的传输过程,强度分布及相位均存在畸变,所采用的方法能精确测量出涡旋光的复杂相位分布,有效完成涡旋光的拓扑荷数识别。

空中目标动态HRRP特征可重构模拟方法

针对目前无源模拟技术无法实现目标动态电磁特征模拟的问题,提出了一种利用相位调制表面(phase-switched screen, PSS)进行空中目标动态高分辨距离像(high resolution range profile, HRRP)特征可重构的模拟方法。以无人直升机旋翼为例,对旋翼的运动状态进行了建模,并详细分析了其动态HRRP特征。另外,通过建立PSS的周期调制信号模型,详细分析了PSS对雷达入射波的调控效果。在此基础上,提出了一种调制频率时变的PSS可重构模拟方法,该方法能够生成随时间变化的可控谐波分量,模拟产生的谐波分量与无人直升机旋翼的动态HRRP特征变化规律相似。通过仿真数据对比分析,调制频率时变的PSS可重构模拟方法能够实现无人直升机旋翼的动态HRRP特征模拟效果。

全息空间三维显示研究

本文基于计算全息、光电衍射再现及散射成像等技术,研究全息空间三维显示,利用随机相位抑制全息空间三维再现像的散斑噪声,实现高分辨率全息空间三维显示。同时,测试不同厚度的散射介质屏对三维成像的影响,探究全息空间三维显示的亮度变化规律。

离子推进器屏栅电源稳压控制方法研究

为了解决离子推进器屏栅电源在负载突变过程中产生的过压、过流等问题,对LLC谐振变换器采用移相-变频控制(PS-PFM)稳定输出电压,当采样电压低于设定值下限时,进入变频控制模式,当采样电压高于设定值上限时,进入移相控制模式。实验证明,相比于常用的调频控制,移相控制的加入能够解决轻载或空载模式下的电压飘高问题,通过PID参数的调整,可以实现负载跳变时的稳定快速调节,使输出电压保持在设定值;通过PCB布局与磁性元件优化设计,所研制的原理样机在额定情况下效率高达98.9%,功率密度可达6.47×10^(6)W/m^(3),在同等级的电源产品中具有优势。

激光在动态大气湍流中的传播特性研究

激光束在大气中传播的过程中会受到大气湍流的影响,导致光斑发生畸变,影响光束质量,并且在真实情况下湍流是随着时间变化的。本文针对这一问题,基于傅里叶变换的谱反演法建立了湍流相位屏模型,并根据湍流冻结法获得动态相位屏,开展了激光在不同强度的动态大气湍流中传输的仿真研究。仿真结果表明:对于相同的激光束,在相同时间内的光斑畸变随着大气湍流强度的增加而增加,并且接收到的功率密度整体上减小,起伏增加。

太阳电池阵基板锁相红外检测中的缺陷特征分析

针对太阳电池阵基板在制造过程中产生的脱黏缺陷产生的质量问题,开展锁相红外热成像检测研究。通过设计与电池阵基板脱黏类型一致的对比试块,分析含胶均匀性、碳纤维网格致密性对检测图像的影响,获取真实脱黏缺陷特征信息及参数,实现自动筛选缺陷。测试结果表明,锁相红外热成像能够有效检出太阳电池基板脱黏缺陷,可以有效提高产品检测效率,减少检测人员的工作强度。

Y型过滤器流动特性的数值模拟研究

过滤器作为管道中众多部件之一,其水力特性至关重要。为了准确了解某Y型过滤器内部流场特点和压降特征,采用多相流数值模拟方法对某Y型过滤器内部流场进行计算,得到了入口流速对压降和最大固相浓度的影响曲线,分析了压力、速度和固相颗粒分布规律。在过滤器内部,由于流体动能转化为压力势能和能量耗散原因,导致流体对固相颗粒的拖曳力降低,小于滤孔直径的固相颗粒主要堆积在滤网内部下端以及滤网和支管内壁之间,且颗粒直径越大,越容易出现大面积堆积,特别是粒径大于0.5 mm时。

串联质谱联合气相质谱在新生儿重症监护病房遗传代谢病筛查诊断中的应用价值

目的探讨串联质谱(tandem mass spectrometry,MS/MS)联合气相质谱(gas phase mass spectrometry,GC-MS)在新生儿重症监护病房(neonatal intensive care unit,NICU)遗传代谢病(inherited metabolic disorders,IMD)筛查诊断中的应用价值。方法选取2020年1月至2021年12月解放军总医院第七医学中心NICU收治的3682例新生儿(其中足月儿1794例,早产儿1888例)为观察对象,采集干血斑行MS/MS遗传代谢病筛查。初次筛查阳性者重新采样复查并行尿液GC-MS检测。根据患儿代谢谱结合临床表现进行生化诊断。统计学方法采用χ^(2)检验。结果3682例NICU患儿中初筛阳性率为5.65%(208/3682),复筛阳性率为1.33%(49/3682),共生化诊断IMD患儿14例,总检出率为0.38%(14/3682),其中足月儿检出率高于早产儿[0.67%(12/1794)与0.11%(2/1888),χ^(2)=7.697,P=0.006]。14例IMD中,有机酸代谢异常11例,包括甲基丙二酸血症8例(57.1%)、戊二酸血症2例(14.3%)、3-甲基戊二烯酸尿症1例(7.1%);氨基酸代谢异常3例,包括尿素循环障碍2例(14.3%)、高苯丙氨酸血症1例(7.1%)。MS/MS初筛假阳性率为5.29%(194/3668),阳性预测值为6.73%(14/208)。召回复查后,二次MS/MS复测,假阳性率为0.95%(35/3668),阳性预测值为28.57%(14/49)。在各类MS/MS指标异常中,丙酰肉碱及其比值增高、戊二酰肉碱增高的阳性预测值高于氨基酸类代谢异常。结论NICU人群IMD发病率较高,且存在早产、感染等多种非遗传因素,干扰MS/MS代谢筛查结果。及时进行MS/MS复查及尿GC-MS分析可以提高诊断效率,明确生化诊断。

基于顶空-固相微萃取的饮用水中挥发性有机物非目标性筛选方法

VOCs在饮用水中存在较为广泛,在长期、持续饮用的情况下很容易对人体健康造成不同程度的危害,基于此,对饮用水中的挥发性有机物进行筛选具有重要的现实意义。本文采取实验方法,基于顶空-固相微萃取技术,对饮用水中挥发性有机物进行非目标性筛选,并得出了相应的结论。希望本文的研究内容能够为饮用水质量检测活动提供一定理论支持。

钛系锂离子筛的制备研究

文章以二氧化钛(TiO_(2))和碳酸锂(Li_(2)CO_(3))作为钛源和锂源,通过高温固相法制备钛系锂离子筛前驱体Li_(2)TiO_(3)(LTO),用稀HCl对前驱体LTO进行酸洗,经Li^(+)与H^(+)交换后得到钛系锂离子筛H_(2)TiO_(3)(HTO)。通过XRD、SEM等手段对钛系锂离子筛结构、形貌进行表征。考察了煅烧温度、酸洗浓度、酸洗温度、酸洗时间等因素对钛系锂离子筛吸附性能的影响。实验结果表明:在850℃条件下煅烧10h,制备得到LTO。进一步将LTO在80℃的条件下用0.20mol/LHCl溶液酸洗6h,可制得HTO吸附剂。HTO吸附剂对溶液中锂离子的吸附容量(Q_e)最高达到28.83mg/g。

NUMERICAL STUDY ON EFFECT OF OPERATING TABLE PROTECTED BY HORIZONTAL LAMINAR FLOW SCREEN

Transmission of airborne bacteria is the main factor causing surgical site infection(SSI),which is harmful to patients′health and even lives.Numerical study is conducted on the effect of the operating table protected by horizontal laminar flow screen.Discrete phase model(DPM)is used.Numerical simulation is carried out to evaluate particle trajectories with the Lagrange approach.As a result,the protecting effect of horizontal laminar flow screen is established,and the protecting parameters of the air velocity supplied by the screen and the protecting distance are optimized.The optimized air velocity supplied by the screen should be at 0.4—0.6 m/s.And the protecting distance should be less than 1.3 m.This work provides references for the study on the depuration of operating table or room.

Research of Anti-Cancer Components in Traditional Chinese Medicine on Hollow Fibre Cell Fishing and Hollow Fibre Liquid Phase Microextraction

Hollow fibre cell fishing with HPLC (HFCF-HPLC) based on the human ovarian cancer cell line SKOV-3, human renal tubular cell line ACHN or hepatoma cell line HepG-2 was employed to screen active groups of coumarin and volatile oil in Radix angelicae sinensis, Radix angelicae dahuricae and Fructus citri sarcodactylis. Simultaneously, hollow fibre liquid phase microextraction with HPLC (HFLPME-HPLC) was conducted to enrich and determine the contents of active components in the same sample solution. Before application, for HFCF-HPLC, cells growth states and survival rates on the fibre, effect of ethanol concentration in the extract of samples on cell survival rates, non-specific binding between fibre active centres and the target components, positive and negative controls and repeatabilities were validated;for HFLPME, extraction solvent, sample phase pH, agitation speed, extraction time and sample phase volume were investigated. Many active components were screened from three medicines. Some of them, such as scoparone, psoralen, bergapten, oxypeucedanin, imperatorin, ligustilide, were identified by MS. The target fishing factors of active components and the cell apoptosis rates of three cells under the medicines effect were researched. The binding sites of active groups on HepG-2 cells were preliminarily determined. The results demonstrated that HFCF-HPLC, coupled with HFLPME-HPLC, is a simple and universal approach to find bioactive components at the cellular level, determine their content and research traditional Chinese medicines (TCMs) entirety effect of multi-component and multi-target. The approach may provide us a new and good solution to clarify the material basis of anti-cancer effect and conduct personalized quality control for the components associated with efficacy in TCMs.

适用于苏北地区日光温室的相变材料筛选与测试

为解决日光温室存在的问题,以苏北地区为例,根据苏北地区气候特点,筛选硬脂酸正丁酯(PCM1)、石蜡(PCM2)、石蜡与硬脂酸正丁酯按质量比5∶5配合的复合相变材料(PCM3)、90%Na_(2)SO_(4)·10H_(2)O+2%硼砂+8%膨胀石墨(PCM4)共4组材料,通过差示扫描量热试验、热物理参数测定试验、蓄放热性能试验以及经济性分析,并采用熵权法进行多指标评价,结果PCM3以0.320的相对优属度位列第一。将所筛选出的PCM3应用于无后墙日光温室中,并以普通无后墙日光温室作为对照。试验结果表明,PCM3对温室内空气温度、土壤温度均有所优化,可有效缩小日光温室的昼夜温差,提高日光温室夜间温度,优化温室内热工性能。