Reformatted method for two-dimensional detector arrays measurement data in proton pencil beam scanning

The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with areas of steep dose gradients,inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements.This may introduce significant errors,particularly in proton spot scanning radiotherapy.In this study,by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method,a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution.Meanwhile,the similarity between the measured original data and the downsampled logfilebased reconstructed dose is regarded as the confidence of the reformatted dose distribution.Furthermore,we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements.The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements.The reformatted dose distributions generally yield a confidence exceeding 95%.

Identification of key residues in protein functional movements by using molecular dynamics simulations combined with a perturbation-response scanning method

The realization of protein functional movement is usually accompanied by specific conformational changes,and there exist some key residues that mediate and control the functional motions of proteins in the allosteric process.In the present work,the perturbation-response scanning method developed by our group was combined with the molecular dynamics(MD)simulation to identify the key residues controlling the functional movement of proteins.In our method,a physical quantity that is directly related to protein specific function was introduced,and then based on the MD simulation trajectories,the perturbation-response scanning method was used to identify the key residues for functional motions,in which the residues that highly correlated with the fluctuation of the function-related quantity were identified as the key residues controlling the specific functional motions of the protein.Two protein systems,i.e.,the heat shock protein 70 and glutamine binding protein,were selected as case studies to validate the effectiveness of our method.Our calculated results are in good agreement with the experimental results.The location of the key residues in the two proteins are similar,indicating the similar mechanisms behind the performance of their biological functions.

ANALYSIS OF HUMAN PLACENTA BY ^(31)P NUCLEAR MAGNETIC RESONANCE AND THIN-LAYER CHROMATOGRAPHY SCANNING COMBINED WITH THE CORRECTIVE METHOD OF ABSORBANCE PROPORTIONAL COEFFICIENT

Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance proportional coefficient. The NMR spectrometer used this investigation was a Bruker AM-500 spectrometer operating at 202.4 MHz for ^(31)P chemical shifts are relative to 85% phosphoric acid. TIC was carried out by silica gel H plate developed in chloroform-methanol-glacial acetic acid-ethanol-water(25:4:6:2:0.5),with Vaskovsky reagent as colour -developing agent of phospholipids.

Tip-Nanoparticle Near-Field Coupling in Scanning Near-Field Microscopy by Coupled Dipole Method

We use the couple dipole method to investigate the scanning near-field optical microscopy metallic tip-nanoparticle near-field interaction. Dependences of the local field intensity inside the nanoparticle on the nanosized tip shape,the tip open angle and the illumination angle are revealed. In combination with the previous results, we establish a complete model to understand the tip-nanoparticle near-field coupling mechanism.

Image reconstruction based on total-variation minimization and alternating direction method in linear scan computed tomography

Linear scan computed tomography （LCT） is of great benefit to online industrial scanning and security inspection due to its characteristics of straight-line source trajectory and high scanning speed. However, in practical applications of LCT, there are challenges to image reconstruction due to limited-angle and insufficient data. In this paper, a new reconstruction algorithm based on total-variation （TV） minimization is developed to reconstruct images from limited-angle and insufficient data in LCT. The main idea of our approach is to reformulate a TV problem as a linear equality constrained problem where the objective function is separable, and then minimize its augmented Lagrangian function by using alternating direction method （ADM） to solve subproblems. The proposed method is robust and efficient in the task of reconstruction by showing the convergence of ADM. The numerical simulations and real data reconstructions show that the proposed reconstruction method brings reasonable performance and outperforms some previous ones when applied to an LCT imaging problem.

Automatic identification of rock discontinuity and stability analysis of tunnel rock blocks using terrestrial laser scanning

Local geometric information and discontinuity features are key aspects of the analysis of the evolution and failure mechanisms of unstable rock blocks in rock tunnels.This study demonstrates the integration of terrestrial laser scanning(TLS)with distinct element method for rock mass characterization and stability analysis in tunnels.TLS records detailed geometric information of the surrounding rock mass by scanning and collecting the positions of millions of rock surface points without contact.By conducting a fuzzy K-means method,a discontinuity automatic identification algorithm was developed,and a method for obtaining the geometric parameters of discontinuities was proposed.This method permits the user to visually identify each discontinuity and acquire its spatial distribution features(e.g.occurrences,spac-ings,trace lengths)in great detail.Compared with hand mapping in conventional geotechnical surveys,the geometric information of discontinuities obtained by this approach is more accurate and the iden-tification is more efficient.Then,a discrete fracture network with the same statistical characteristics as the actual discontinuities was generated with the distinct element method,and a representative nu-merical model of the jointed surrounding rock mass was established.By means of numerical simulation,potential unstable rock blocks were assessed,and failure mechanisms were analyzed.This method was applied to detection and assessment of unstable rock blocks in the spillway and sand flushing tunnel of the Hongshiyan hydropower project after a collapse.The results show that the noncontact detection of blocks was more labor-saving with lower safety risks compared with manual surveys,and the stability assessment was more reliable since the numerical model built by this method was more consistent with the distribution characteristics of actual joints.This study can provide a reference for geological survey and unstable rock block hazard mitigation in tunnels subjected to complex geology and active rockfalls.

Fault Diagnosis and Separation for a Distributed Rotary-laser Scanning System

The wMPS is a laser-based measurement system used for large scale metrology.However,it is susceptible to external factors such as vibrations,which can lead to unreliable measurements.This paper presents a fault diagnosis and separation method which can counter this problem.To begin with,the paper uses simple models to explain the fault diagnosis and separation methods.These methods are then mathematically derived using statistical analysis and the principles of the wMPS.A comprehensive solution for fault diagnosis and separation is proposed,considering the characteristics of the wMPS.The effectiveness of this solution is verified through experimental observations.It can be concluded that this approach can detect and separate false observations,thereby enhancing the reliability of the wMPS.

Numerical Investigation of Laser Surface Hardening of AISI 4340 Using 3D FEM Model for Thermal Analysis of Different Laser Scanning Patterns

Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the heating system parameters and the material properties have important effects on the achieved hardened surface characteristics. The control of these variables using predictive modeling strategies leads to the desired surface properties without following the fastidious trial and error method. However, when the dimensions of the surface to be treated are larger than the cross section of the laser beam, various laser scanning patterns can be used. Due to their effects on the hardened surface properties, the attributes of the selected scanning patterns become significant variables in the process. This paper presents numerical and experimental investigations of four scanning patterns for laser surface hardening of AISI 4340 steel. The investigations are based on exhaustive modelling and simulation efforts carried out using a 3D finite element thermal analysis and structured experimental study according to Taguchi method. The temperature distribution and the hardness profile attributes are used to evaluate the effects of heating parameters and patterns design parameters on the hardened surface characteristics. This is very useful for integrating the scanning patterns’ features in an efficient predictive modeling approach. A structured experimental design combined to improved statistical analysis tools is used to assess the 3D model performance. The experiments are performed on a 3 kW Nd:Yag laser system. The modeling results exhibit a great agreement between the predicted and measured values for the hardened surface characteristics. The model evaluation reveals also its ability to provide not only accurate and robust predictions of the temperature distribution and the hardness profile as well an in-depth analysis of the effects of the process parameters.

Optimized air-ground data fusion method for mine slope modeling

Refined 3D modeling of mine slopes is pivotal for precise prediction of geological hazards.Aiming at the inadequacy of existing single modeling methods in comprehensively representing the overall and localized characteristics of mining slopes,this study introduces a new method that fuses model data from Unmanned aerial vehicles(UAV)tilt photogrammetry and 3D laser scanning through a data alignment algorithm based on control points.First,the mini batch K-Medoids algorithm is utilized to cluster the point cloud data from ground 3D laser scanning.Then,the elbow rule is applied to determine the optimal cluster number(K0),and the feature points are extracted.Next,the nearest neighbor point algorithm is employed to match the feature points obtained from UAV tilt photogrammetry,and the internal point coordinates are adjusted through the distanceweighted average to construct a 3D model.Finally,by integrating an engineering case study,the K0 value is determined to be 8,with a matching accuracy between the two model datasets ranging from 0.0669 to 1.0373 mm.Therefore,compared with the modeling method utilizing K-medoids clustering algorithm,the new modeling method significantly enhances the computational efficiency,the accuracy of selecting the optimal number of feature points in 3D laser scanning,and the precision of the 3D model derived from UAV tilt photogrammetry.This method provides a research foundation for constructing mine slope model.

Estimation of IFOV of Rosette Scan System

The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new method which uses the maximum distance between two neighboring petals as the estimated value of IFOV is developed and a comparison between the common method and the new method is given. It is concluded that the minimum allowed value of IFOV of rosette scanning is over estimated by the common method while this value can be calculated accurately with the new method.

基于3D Scan的木地板锁扣有限元模型静力学分析

木地板连接中锁扣起到了关键作用,为探索不同锁扣形式对木地板力学性能的影响,以强化地板锁扣为研究对象,以锁扣有限元模型的静力学特性为研究目标,利用三维扫描仪获取嵌入锁定和本体锁定两类强化地板12种典型锁扣的三维点云数据、逆向重构锁扣的三维实体模型,分析其结构特点,确定影响锁扣力学性能的结构特征值;采用有限元软件ANSYS对锁扣有限元模型进行弯曲和拉伸载荷作用下的整体变形、等效应力、等效应变的仿真分析,研究强化地板锁扣的静力学特性。结果表明:两类锁扣结构中,锁扣结合面长度、榫头(槽)凸(凹)出长度等参数与结合面形状是影响锁扣力学性能的主要因素;嵌入锁定锁扣具有更加优越的整体性能,受锁扣自身结构形状影响小,受锁定元件形状影响较大;本体锁定锁扣结构中,大的弧形锁扣截面形状更有利于提高锁扣的力学性能。通过三维扫描逆向重构锁扣模型以及对木地板锁扣结构和功能相关性的分析,为锁扣的设计、优化和检测提供了新的思路。

Grid-Scan定位算法的虚拟锚节点策略改进

针对无线传感器网络中Grid-Scan算法定位精度较低的问题,提出了一种基于虚拟锚节点策略的Grid-Scan定位算法。具体做了三个方面的工作:对未知节点设置可定位阈值,邻居锚节点数大于可定位阈值的未知节点使用Grid-Scan算法进行定位,定位后的节点升级为虚拟锚节点;邻居锚节点数小于可定位阈值的未知节点利用极大似然法完成定位,定位后的节点升级为虚拟锚节点;锚节点及虚拟锚节点共同参与对剩余未知节点的定位。仿真结果表明,改进算法在不同锚节点密度、不同通信半径和不同栅格大小的网络中以及通过不规则传播模型后都具有较好的定位精度。

干燥方式对山楂总黄酮含量及抗氧化性质的影响

本研究采用热风干燥、真空冷冻干燥及热风联合液氮干燥对山楂进行处理,利用亚硝酸钠-硝酸铝-氢氧化钠显色法、高效液相色谱法和自由基清除能力实验研究不同干燥方式对山楂粉样品的总黄酮得率、总黄酮组分和含量及抗氧化活性的影响。结果表明,热风干燥、真空冷冻干燥和热风联合液氮干燥的山楂粉样品色差值分别为20.60、17.70、20.05;山楂总黄酮得率分别为64.59、71.48、60.77 mg/g;对DPPH自由基清除率分别是19.56%、30.14%、18.50%;对ABTS+自由基清除率分别是51.81%、75.08%、48.68%;以及对羟自由基清除率分别是48.98%、55.77%、36.04%;真空冷冻干燥处理的山楂粉样品中总黄酮得率较高,具有较强的抗氧化活性,且与其它样品具有显著性差异(P<0.05);同时高效液相色谱对山楂总黄酮进行定性和定量分析结果表明,三种干燥方式得到的黄酮类物质均包含芦丁、金丝桃苷、杨梅素、槲皮素、芹菜素、异鼠李素,但其含量不同,真空冷冻干燥样品中总黄酮总含量达到了308.65 mg/g,与其他样品具有显著性差异(P<0.05)。除此以外,三种抗氧化方式和六种组分含量之间也存在线性关系。综上考虑,真空冷冻干燥处理山楂,是提取山楂总黄酮的推荐方法,可以有效减少对山楂的总黄酮含量及抗氧化活性的影响。

非线性相移对Z-scan曲线对称性的影响

基于由光束传输的ABCD矩阵得出的Z-scan透过率的解析结果,分析了Z-scan实验曲线随非线性相移的变化规律。发现随着相移的增加,折射非线性相移比吸收非线性相移对Z-scan曲线对称性的影响更大。对于具有强饱和吸收和弱自聚焦特性的非线性介质,其Z-scan曲线随非线性折射相移的变小将失去典型的类色散特点。对于1μm厚的ZnCdSe-ZnSe多量子阱,扫描光源采用532 nm的基模高斯光束,采用透过率表达式来拟合所得的实验数据,在吸收非线性相移为0.9与耦合因子为-10条件下,推算出三阶非线性吸收系数为2×10-3cm/W,三阶非线性折射系数为8.0×10-8cm2/W,这与J.Ma等人的结果吻合。最后对曲线特征参数随非线性相移变化进行了数值计算,得到的曲线所对应的非线性相移与曲线谷位置的乘积近似为一常量,值为0.166。

基于三维激光点云的复杂建筑结构检测方法

针对大型复杂结构建筑施工质量检测难度大的问题,该文提出一种高效的三维激光扫描及建筑结构检测分析方案。以某地铁车辆段施工建筑质量检测为例,针对规模巨大且实体空间不规则等特性,创新性地将分层联合的控制测量方法运用在多层复杂建筑结构施工检测中;后依据构件结构特点编写批量标注建筑构件尺寸等的工具,结合GIS将线面数据与设计图对比分析,实现检测的自动化分析。检测结果表明,该方法相较传统方法,全面高效地展现了复杂结构建筑的施工现状,检测精度高,具有广阔的应用前景,为相关工程提供了有益的借鉴和参考。

DMPC工法可视化泥面扫测技术应用

着重介绍了数字化微扰动压入式沉井(DMPC工法)可视化泥面扫测关键技术应用,主要包括声呐测量技术原理及核心设备参数、数据采集技术、测深系统校正及测深线布设、多波束换能器校准、可视化处理等方面,并结合实际工程案例应用情况总结了技术实施流程及扫测误差,可为DMPC工法可视化泥面扫测技术提供经验借鉴。

针对基于三维激光扫描技术岩体结构面调查方法的评述

以三维激光扫描技术为研究对象,对岩体结构面非接触调查法的作业原理、设备分类、算法优化进行了详细介绍,同时通过应用实例对该技术的实用性进行了评述。该项技术较好的符合了现场实际条件,操作速度快,操作形式多样,工作适应性强,可使现场工作人员安全得到保障,能够满足矿山企业快速评价岩体质量的需求,能够作为选择工程结构参数、科学管理生产以及评价经济效益的重要依据。

Deformation Field around the Stress Induced Crack Area in Sandstone by the Digital Speckle Correlation Method

The deformation field around sub-cracks was calculated using the digital speckle correlation method. First, the uni-axial compression tests on sandstone samples containing a pre- fabricated fracture were made. Photomicrographs showing the characteristics of the sub-crack development were taken using a scanning electron microscope （SEM）. From these photomicrographs, the real-time images showing the initiation, growth and coalescence of sub-cracks and micro-cracks in the sandstone specimens were obtained and the effects of loading level as well as grain boundaries on the development of cracks were analyzed. Second, the intensity images of the sandstone specimen surface were captured from the observations of the SEM corresponding to different loading levels. Then correlation computation was carried out for the sequential pairs of intensity images to evaluate the displacement components, as well as the strain field. The results show that the deformation varies in different areas separated by sub-cracks during rock damage processes.

Prediction Technology of Buried Water-Bearing Structures in Coal Mines Using Transient Electromagnetic Method

Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and timely forecast about water bursts. Based on the smoke ring effect of transient electromagnetic fields,the principle of transient electro-magnetic method used in detecting buried water-bearing structures in coal mines in advance,is discussed. Small multi-turn loop configurations used in coal mines are proposed and a field procedure of semicircular sector scanning is presented. The application of this method in one coal mine indicates that the technology has many advantages compared with others. The method is inexpensive,highly accurate and efficient. Suggestions are presented for future solutions to some remaining problems.

多线激光雷达转镜扫描系统

为解决传统多线激光雷达以固定角度分辨率扫描导致远距目标探测空间分辨率变低的问题,文中提出一种双光源对称布置的8线激光雷达扫描系统。运用光线矢量法系统研究了旋转反射镜和光源参数与光束扫描轨迹的规律,结合激光雷达方程优化设计8线激光雷达整机参数。通过严格计算激光经不同倾角的反射镜旋转扫描的光束轨迹,在八面反射镜两侧特定位置对称布置两个光源进行分时发光探测实现具有高空间分辨率的八面反射镜旋转扫描系统。矢量计算结果表明,对距离100 m的人体在正前方有两条扫描探测光束,人体在侧向和边缘处仍有3条扫描探测光束,说明所提八面反射镜旋转扫描系统能更有效利用扫描光束探测远距离目标,优于Velodyne 64线激光雷达。