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.

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.

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.

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.

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).

空间分集光密钥生成的信道相关性影响

利用无线光信道本身的特性实现光密钥生成和分发,可为高速星地保密通信提供安全和高效的保障。开展了无线光信道空间分集密钥生成系统相邻子信道相关性的研究。通过实现功率谱反演产生的Kolmogorov大气湍流相位屏,构建了无线光信道(WOC)信道中的多输入多输出(MIMO)模型,采用蒙特卡罗模拟了高斯光束经大气湍流传输特性,比较了不同湍流强度和光束传输距离对光强分布的影响,分析了大气湍流强度、相邻两接收孔径之间的距离、接收孔径、传输距离、光波波长对相邻子信道相关性的影响。结果表明,相邻两接收孔径接收到的光信号功率的相关性随相邻两接收孔径的直径和波长的增大而增加,随相邻两接收孔径之间的距离、光波的传输距离、湍流强度的增加而减小。在大气折射率结构常数C_(n)^(2)为5×10^(-14)m^(-2/3)、接收口径为0.03 m、传输距离为2000 m的近地水平链路条件下,相邻信道之间的距离在0.07 m时接收到的光信号功率的相关性近似为零,此时两个相邻信道彼此独立。该结果可为建立空间分集大气光信道密钥提取系统提供参考。

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.

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。

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.

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。

基于复合相位屏的光传输多孔径接收特性研究

多孔径接收技术可以有效抑制无线激光通信中的光强闪烁,然而接收孔径的直径、间距以及个数对于改善无线激光通信性能的作用规律目前还尚不清晰完备。因此,提出一种基于复合相位屏的光传输方法,并对多孔径接收特性进行了研究。首先,将功率谱反演法和zernike倾斜方法相结合以生成复合相位屏,并构建了光传输多孔径接收的数学模型;然后,改变接收孔径的直径、间距以及个数,统计接收端光强闪烁的变化情况;最后,在不同的大气折射率结构常数、光波波长、传输距离的实际光传输场景下,分析了多孔径接收光强闪烁的变化规律。结果表明,当大气折射率结构常数从2.231 3×10^(-16) m^(-2/3)减小至1.5 81 2×10^(-17) m^(-2/3),5个孔径直径为0.2 m,孔径间距为0.4 m的接收孔径的光强闪烁从0.2032减小到0.0524;当光波波长由532 nm变为1550 nm,5个孔径直径为0.14 m,孔径间距为0.4 m的接收孔径的光强闪烁从0.2696减小到0.1982;当传播距离从7×10^(3) m增大到7×10^(5) m,5个孔径直径为0.2 m,孔径间距为0.4m的接收孔径的光强闪烁从0.0043增大到0.3239,该项研究总结了无线激光通信的多孔径接收特性的规律。

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。

胃肠道肿瘤患者相位角及其与营养状况的相关性研究

目的:探讨胃肠道恶性肿瘤患者相位角(phase angle,PA)与营养风险及营养不良的相关性,并分析其影响因素。方法:采用随机抽样方式收集2022年10月—2023年3月在苏州大学附属第一医院肿瘤科收治的胃肠道肿瘤51例患者的临床资料,采用营养风险筛查2002量表(nutrition risk screening 2002,NRS 2002)进行营养风险筛查及患者主观整体评估量表进行营养评估;使用CAMRY便携式握力计测量非利手握力;利用生物电阻抗技术进行人体各项指标测量。结果:诊断有营养风险的PA截断值为4.85°,当PA<4.85°时,患者有营养风险的可能性较大。低PA组有营养风险患者的比例(90.9%)显著高于高PA组(27.5%);多因素分析结果显示BMI、白蛋白、非利手握力是PA的影响因素(P<0.05)。结论:PA是反映胃肠道肿瘤患者是否有营养风险的有效指标,PA的影响因素分析结果为临床营养风险筛查提供新的思路。

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。

扩展重采样次谐波大气湍流模拟相位屏研究

提出了一种扩展重采样次谐波方法生成大气湍流相位屏,扩展了低频补偿的起始区域,并设计了低频补偿区域的新型采样方式。以Kolmogorov理论进行模拟,分析了该方法设置不同次谐波级数所生成相位屏的相位结构函数与理论值的误差,搭建大气湍流模拟系统进行分析。结果表明:扩展重采样次谐波法生成相位屏的相位结构函数与理论值的相对误差为0.368%,加载此方法生成的大气湍流相位屏后,产生的湍流效应对图像调制传递函数的影响与湍流调制传递函数曲线的误差平均值为0.0336。该方法能够生成高精度的大气湍流相位屏。

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。

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。

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。

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。