Fiber Migration and Distribution of Twist at Different Radial Positions of Rotor Yarn-by Hi-Scope Video Microscope System

This paper describes systematic measurement of fiber migration and distribution pattern of twist at different radial positions of rotor spun yarn mixed tracer fiber by Hi-Scope Video Microscope System. The positions of tracer fibers were measured in three dimensions accurately, and the migration index and the twist distribution at different radial positions of rotor yarn were calculated and analyzed. This research result serves to provide useful references for further study on the structural mechanics of rotor spun yarn.

A study on the characterization of smoke movement in shafts with different fire source positions

In this study,experimental and numerical simulation methods were combined to simulate the changing course of the temperature and velocity fields in nine different fire scenes. The characteristics of smoke movement in shafts with different fire source position factors(h/H) were quantitatively investigated,and the non-dimensional fitting function between the fire source position factors and the maximum temperature was deduced. The results showed that the location of the neutral plane moved upward as the fire source rose,and all the generated smoke spread to the upper areas;however,there was barely any smoke in the lower areas. The maximum temperature was inversely proportional to the fire source position factor;the higher the source position is,i.e. the higher the ratio factor is,the lower the maximum temperature is in the shaft. The experimental verification of the fire dynamics simulator(FDS) showed good results.

On the Existence of Positive Solutions of Neutral Differential Equations

Consider the first order neutral delay differential equation with positive and negative coefficients:[x(t)-c(t)x(t-γ)]+p(t)x(t-τ)-Q(t)x(t-δ)=0,t≥t 0,(1)where c,p,Q∈C((t 0,∞),R +),R +=(0,∞),γ】0,t】δ≥0. We obtain the sufficient condition for the existence of positive solutions of Eq.(1). As a corollary, we improve the correspondent result in by removing the condition∫ ∞ c 0 (t) d t=∞,where (t)=p(t)-Q(t-τ+δ)≥0.

Cone beam computed tomography-guided differences among registration methods for lung cancer and the effects of tumor position,treatment model,and tumor size on positioning errors

Objective To explore the differences in three different registration methods of cone beam computed tomography(CBCT)-guided down-regulated intense radiation therapy for lung cancer as well as the effects of tumor location,treatment mode,and tumor size on registration.Methods This retrospective analysis included 80 lung cancer patients undergoing radiotherapy in our hospital from November 2017 to October 2019 and compared automatic bone registration,automatic grayscale(t+r)registration,and automatic grayscale(t)positioning error on the X-,Y-,and Z-axes under three types of registration methods.The patients were also grouped according to tumor position,treatment mode,and tumor size to compare positioning errors.Results On the X-,Y-,and Z-axes,automatic grayscale(t+r)and automatic grayscale(t)registration showed a better trend.Analysis of the different treatment modes showed differences in the three registration methods;however,these were not statistically significant.Analysis according to tumor sizes showed significant differences between the three registration methods(P<0.05).Analysis according to tumor positions showed differences in the X-and Y-axes that were not significant(P>0.05),while the autopsy registration in the Z-axis showed the largest difference in the mediastinal and hilar lymph nodes(P<0.05).Conclusion The treatment mode was not the main factor affecting registration error in lung cancer.Three registration methods are available for tumors in the upper and lower lungs measuring<3 cm;among these,automatic gray registration is recommended,while any gray registration method is recommended for tumors located in the mediastinal hilar site measuring<3 cm and in the upper and lower lungs≥3 cm.

Distributed adaptive direct position determination based on diffusion framework

The conventional direct position determination（DPD） algorithm processes all received signals on a single sensor.When sensors have limited computational capabilities or energy storage,it is desirable to distribute the computation among other sensors.A distributed adaptive DPD（DADPD）algorithm based on diffusion framework is proposed for emitter localization.Unlike the corresponding centralized adaptive DPD（CADPD） algorithm,all but one sensor in the proposed algorithm participate in processing the received signals and estimating the common emitter position,respectively.The computational load and energy consumption on a single sensor in the CADPD algorithm is distributed among other computing sensors in a balanced manner.Exactly the same iterative localization algorithm is carried out in each computing sensor,respectively,and the algorithm in each computing sensor exhibits quite similar convergence behavior.The difference of the localization and tracking performance between the proposed distributed algorithm and the corresponding CADPD algorithm is negligible through simulation evaluations.

Study on the effect of focal position change on the expansion velocity and propagation mechanism of plasma generated by millisecond pulsed laser-induced fused silica

In this work, by controlling the positional relationship between the target and the focal point, the surface damage, shock wave phenomenon and propagation mechanism involved in the plasma generation of fused silica by millisecond pulsed laser irradiation at different focal positions were studied. Laser energy is an important experimental variable. The dynamic process of plasma was detected by optical shadow method, and the influence of surface film damage on plasma propagation and the propagation mechanism at different focal positions were discussed. The study found that the plasma induced by the pulsed laser at the focus position within 0–20 μs exploded, the micro-droplets formed around 20 μs. At the same time, a shock wave is formed by the compressed air, the micro-droplets are compressed under the action of the shock wave recoil pressure, and the micro-droplets channel phenomenon is observed in the micro-droplets. The peak velocities of plasma and combustion wave appear earlier in the pre-focus position than in the post-focus position. This research provides a reference for the field of laser processing using fused silica as the substrate.

Accuracy Analysis of Position Estimation Based on Measurements of Received Signal Strength Difference

The performance of a cellular location system based on received signal strength difference （RSSD） is investigated. In the cellular location system, each mobile station needs to measure the signal strength transmitted by surrounding base stations, and sends its measurements to the service base station. Using the strength difference between the service base station and neighboring base stations, the position of a mobile station is estimated. The related Cramer-Rao lower bound （CRLB） on the location error of this method was derived, and numerical simulations are made to discuss the influences of the number of base stations, correlation coefficient of shadowing attenuation, and cell radius on CRLB. The results show that the CRLB is positively correlated with the standard deviation of shadowing attenuation and cell radius, but negatively correlated with the number of base stations and the correlation coefficient of shadowing attenuation. In addition, the CRLB results obtained in this paper were compared with those of the cellular location system based on received signal strength （RSS） measurements, which reveals that the former is more tight.

Performance Evaluation of Three-Dimensional UWB Real-Time Locating Auto-Positioning System for Fire Rescue

Fire rescue challenges and solutions have evolved from straightfor-ward plane rescue to encompass 3D space due to the rise of high-rise city buildings.Hence,this study facilitates a system with quick and simplified on-site launching and generates real-time location data,enabling fire rescuers to arrive at the intended spot faster and correctly for effective and precise rescue.Auto-positioning with step-by-step instructions is proposed when launching the locating system,while no extra measuring instrument like Total Station(TS)is needed.Real-time location tracking is provided via a 3D space real-time locating system(RTLS)constructed using Ultra-wide Bandwidth technology(UWB),which requires electromagnetic waves to pass through concrete walls.A hybrid weighted least squares with a time difference of arrival(WLS/TDOA)positioning method is proposed to address real path-tracking issues in 3D space and to meet RTLS requirements for quick computing in real-world applications.The 3D WLS/TDOA algorithm is theoretically constructed with the Cramer-Rao lower bound(CRLB).The computing complexity is reduced to the lower bound for embedded hardware to directly compute the time differential of the arriving signals using the time-to-digital converter(TDC).The results of the experiments show that the errors are controlled when the positioning algorithm is applied in various complicated situations to fulfill the requirements of engineering applications.The statistical analysis of the data reveals that the proposed UWB RTLS auto-positioning system can track target tags with an accuracy of 0.20 m.

Endemic error correction model and quantitative analysis of precise point positioning

To identify the endemic error of the precise point positioning which cannot be weakened or eliminated in precise point positioning (PPP) zero-difference model, the 24 h observation data acquired from CHAN station on Oct 31st, 2010, were adopted for analyses, different correction models of various errors were discussed and their influences on traditional zero-difference model were analyzed. The results show that the errors cannot be ignored. They must be corrected with suitable models and estimated with auxiliary parameters. The influence magnitudes of all errors are defined, and the results have guiding significance to improve the accuracy of precise point positioning zero-difference model.

基于北斗定位的铁路现场安全防护系统定位技术研究

为了解决传统铁路现场作业人员安全防护系统所暴露出的作业人员及列车位置信息不能及时实时获知、防护状态交互性缺乏等问题,提出一种基于北斗卫星定位技术的安全防护方案,通过卫星定位技术实时定位现场作业人员及列车的位置信息,传送给车站管理系统,经系统分析将相关信息传送至现场作业人员手持终端设备,根据实际情况发出列车预警信息,从而实现安全防护的目的。聚焦防护系统高精度定位技术,分析卫星定位原理、分类及高精度卫星定位算法原理,基于STC15W4K56S4单片机搭建定位数据采集系统,为验证定位算法的精度,借助串口调试工具在上位机对比2种高精度定位算法:载波相位差分和伪距差分的定位精度。试验结果表明,载波相位差分定位算法具有更高的定位精度,可达厘米级,完全满足铁路现场作业人员安全防护的定位需求。

非组合精密单点定位模型参数估计

为了进一步发挥非组合精密单点定位具有的数据利用率高、未放大观测噪声和可估计电离层延迟等优势,提出一种可估计电离层延迟和接收机差分码偏差(DCB)的改进非组合精密单点定位模型:与传统非组合精密单点定位模型估计的接收机钟差参数和DCB进行组合计算,估计出接收机钟差与参与计算的第一频点和第二频点的硬件延迟;利用北京某监测站采集的北斗三号全球卫星导航系统(BDS-3)观测数据,对B1I+B3I、B1C+B2a等2种频点组合分别进行2种非组合精密单点定位计算,估计电离层延迟、接收机钟差、第一频点和第二频点的硬件延迟。结果表明:传统非组合精密单点定位模型定位精度和收敛时间略优于改进的非组合精密单点定位模型;改进非组合精密单点定位模型估计的电离层延迟的平均修正百分比为85.54%,比传统非组合精密单点定位模型估计的电离层延迟高6.43%;B1I+B3I和与B1C+B2a频点组合估计的接收机钟差的RMS分别为0.19和0.21 ns,均值相差0.09 ns,钟差估计精度相当;接收机B1I、B3I、B1C和B2a硬件延迟与标定值都在0.14 ns以内。

大规模风电接入场景下的失步振荡中心定位方法

振荡中心的准确定位是失步保护正确动作的基础,大规模风电并网导致系统阻抗参数发生变化,使得传统基于阻抗轨迹的失步定位方法的适应性严重下降。针对该问题,提出基于节点频差的失步振荡中心定位方法。首先分析大规模风电并网对系统总阻抗的影响。进一步根据发电机功角,计算其曼哈顿距离相似度并构建启动判据。最后,通过移动平均法对广域测量频率进行平滑处理,提出基于节点频差的失步振荡中心定位方法。仿真验证表明,所提基于节点频差的失步振荡中心定位方法受噪声影响较小,不受风电渗透率的影响,能够准确定位失步振荡中心位置。

基于MLE的靶场光电经纬仪高精度定位方法研究

为解决靶场光电经纬仪现用交会定位解算模型作用范围小、与目标实际位置偏差大等问题,提高目标航迹解算精度和模型的适应范围,根据目标跟踪距离和测角误差分量关系,建立了经纬仪空间测量误差模型,优化了异面交会定位加权系数。基于最大似然估计(Maximum Likelihood Estimate,MLE)理论,提出了一种新的更高精度的定位方法,并推导了精度估算公式。详细分析了交会角度、跟踪距离和测角精度对定位误差的影响。试验证明,该方法较现用定位方法适用测量区域增加一倍以上,定位精度提高20%,更适合多测站、不等精度、远距离跟踪等工程场景,具有推广价值。

不同角度俯卧位通气在急性呼吸窘迫综合征患者中的应用效果

目的评估不同角度俯卧位通气在急性呼吸窘迫综合征(ARDS)患者中的应用效果。方法本研究为一项前瞻性、随机、对照临床试验,纳入2021年7月至2023年6月广东省第二中医院重症医学科(ICU)收治的ARDS患者共96例,随机分为A组(0°俯卧位通气)、B组(30°俯卧位通气)、C组(45°俯卧位通气),每组32例。A组男19例,女13例;年龄(50.25±11.31)岁;体重指数(BMI)(23.42±3.16)kg/m^(2)。B组男17例,女15例;年龄(51.93±12.48)岁;BMI(22.72±4.15)kg/m^(2)。C组男20例,女12例;年龄(52.39±12.82)岁;BMI(24.76±4.31)kg/m^(2)。观察时间为5 d。A组患者每天持续0°俯卧位通气16 h,每2 h将其托起一次防止压力性损伤。B组:维持0°俯卧位2 h后,使用30°翻身垫将患者身体向左倾斜30°,维持2 h;然后向右倾斜30°,同样维持2 h;最后恢复至0°俯卧位,如此循环,直至完成16 h俯卧位通气。C组:维持0°俯卧位2 h后,使用45°翻身垫将患者身体向左倾斜45°,维持2 h;然后向右倾斜45°,同样维持2 h;最后恢复至0°俯卧位,如此循环,直至完成16 h俯卧位通气。比较3组氧合指标[氧合指数(PaO_(2)/FiO_(2))、动脉血氧饱和度(SaO_(2))、动脉血氧分压(PaO_(2))、动脉血二氧化碳分压(PaCO_(2))]、血流动力学指标[心率(HR)、平均动脉压(MAP)、中心静脉压(CVP)]、Murray肺损伤评分(MLIS)、急性生理学及慢性健康状况评价Ⅱ(APACHEⅡ)评分、多器官功能障碍综合征(MODS)评分的变化,观察压力性损伤发生率。采用单因素方差分析、LSD法、配对t检验、χ^(2)检验。结果俯卧位通气5 d后,3组PaO_(2)/FiO_(2)、SaO_(2)、PaO_(2)、PaCO_(2)均较通气前改善,且A组、B组改善幅度均优于C组(均P<0.05);俯卧位通气前和通气5 d后,3组HR、MAP、CVP差异均无统计学意义(均P>0.05);俯卧位通气5 d后,3组MLIS、APACHEⅡ、MODS评分均较通气前降低,且A组、B组均低于C组[(1.72±0.37)分比(1.54±0.16)分比(1.89±0.26)分、(11.02±2.69)分比(11.01±2.01)分比(12.87±2.06)分、(5.64±0.37)分比(5.34±0.67)分比(6.19±0.43)分](均P<0.05);B组和C组压力性损伤发生率低于A组[15.63%(5/32)比18.75%(6/32)比40.63%(13/32)](P<0.05)。结论不同角度俯卧位通气均可以改善ARDS患者氧合和减轻病情,其中30°俯卧位通气改善最明显,并且可以降低压力性损伤发生率。

基于北斗定位的铁路现场安全防护系统定位技术研究

为解决传统铁路现场作业人员安全防护系统所暴露出的作业人员及列车位置信息不能及时实时获知,防护状态交互性缺乏等问题,本文提出一种基于北斗卫星定位技术的安全防护方案,通过卫星定位技术实时定位现场作业人员及列车的位置信息,传送给车站管理系统,经系统分析将相关信息传送至现场作业人员手持终端设备,根据实际情况发出列车预警信息,从而实现安全防护的目的。文章聚焦防护系统高精度定位技术,分析了卫星定位原理、分类及高精度卫星定位算法原理,基于STC15W4K56S4单片机搭建了定位数据采集系统,为验证定位算法的精度,借助串口调试工具在上位机对比了两种高精度定位算法一载波相位差分和伪距差分的定位精度,试验结果表明,载波相位差分定位算法具有更高的定位精度,可达厘米级,完全满足铁路现场作业人员安全防护的定位需求。

北斗系统多频载波相位整周模糊度解算方法研究

研究利用LAMBDA方法来解算三频载波相位BDS系统和GPS系统整周模糊度并分析其固定精度情况。通过采用2 km、5 km、8 km、10 km和12 km五条基线进行单系统解算对比,实验结果表明,无论是BDS还是GPS,在进行单系统RTK解算中,N方向坐标偏差变化幅度较其他两个方向变化都是最大的;在进行5 km的基线解算中,BDS三个坐标方向偏差基本保持在-0.2~0.4 m之间,相对于GPS系统较好;5 km的基线解算中,GPS系统三个方向坐标偏差值基本在-0.1~0.1 m之间,较BDS系统稳定且精度高。2 km基线的时候在200历元左右GPS固定精度明显优于BDS,5 km的时候GPS在1 000历元左右模糊度固定精度明显要比BDS高,但是随着基线长度的增加,GPS系统模糊度固定精度逐渐趋近,直至小于BDS系统。

中国人的积极理想情绪:近几十年来的变迁

理想情绪是人们理想中想体验的情绪,和文化密切相关。在当今社会快速变迁的背景下,已有大量研究探讨了人们日常体验的实际情绪的变迁,但是尚未有研究关注理想情绪的变迁。本研究第一次在中国对积极理想情绪的变迁进行研究。研究1让1966年之前出生的被试根据自己的判断,评估1980年代初、2000年代初和2020年前后中国人理想中想体验的积极情绪。结果发现,从1980年代初到2020年前后中国人对高唤醒积极情绪、低唤醒积极情绪、一般积极情绪的偏好都在上升。研究2让大学生被试根据自己的判断,评估祖辈、子辈和孙辈理想中想体验的积极情绪。结果表明,大学生知觉到的祖辈、子辈和孙辈这三代人对高唤醒积极情绪、低唤醒积极情绪、一般积极情绪的偏好也都在上升。研究3利用全国性大学生调查数据,通过横断对比分析发现,来自城市的大学生比来自农村的大学生更偏好高唤醒积极情绪、低唤醒积极情绪、一般积极情绪。总起来,3个研究一致启示,近几十年来,中国人对高唤醒积极情绪、低唤醒积极情绪和一般积极情绪的偏好都在上升。这些发现不仅拓展了对社会变迁的心理影响的认识,更加深了对理想情绪本身特性的认识。

正高程差下边坡爆破对X70钢管振速的影响

为了探究正高程差边坡爆炸施工对邻近埋地管道振速的影响,基于商用有限元软件ANSYS/LS-DYNA采用数值模拟方法研究了炸药量相同(30 kg),正高程差不同(2.1、2.6、3.1、3.6、4.1、4.6和5.1 m)时,边坡爆破振动对既有X70管道振速的影响,并与平面地形结果作对比分析。研究表明:相较于平面地形,在水平距离不变的条件下,管道Y方向上会出现振速放大现象,且随着高程增大,振速加快衰减。管道振速放大系数随着高程差的增大呈现先增大后减小的趋势。当高程差为3.1 m时,管道迎爆面测点的振速放大系数最大,为1.998;当高程差为3.6 m时,管道背爆面测点的放大系数最大,为1.622。爆炸地震波在不同的介质界面发生折射和反射所形成的叠加效应以及在坡脚发生绕射,是产生高程放大效应的主要原因。

基于时间差法的位置灵敏3He正比计数管位置分辨性能研究

中子定位技术可用于乏燃料后处理流程监测,以避免发生核临界安全事故。利用蒙特卡罗(Monte Carlo,MC)算法模拟了不同中子发射方式、^(3)He气压、管径、慢化体厚度等对位置灵敏^(3)He正比计数管位置分辨能力和探测效率的影响。对于管径为2.54 cm、灵敏区长80 cm、^(3)He气压为405300 Pa的位置灵敏^(3)He正比计数管,MC模拟结果表明:轴向各处位置分辨能力相同,对热中子点源的位置分辨极限为0.17 cm;慢化体厚5 cm且^(244)Cm源紧贴慢化体外壁时中子探测效率为3.0%,位置分辨为9.25 cm。用时间差法测试了^(244)Cm源在灵敏区不同位置、源管距、慢化体厚度等情况下此位置灵敏^(3)He正比计数管对^(244)Cm源的位置分辨能力与探测效率,测试结果表明:实验装置的理论位置分辨极限可达2.64 cm,当慢化体厚5 cm且^(244)Cm源紧贴慢化体外壁时位置分辨为18.50 cm,为理论值的一半。

2006-2022年中国科学院环江喀斯特生态系统观测站农田长期观测样地土壤养分数据集

中国科学院环江喀斯特生态系统观测研究站(本文中简称“环江站”)是我国西南喀斯特地区重要的农业生态系统长期野外定位观测研究站,是依照中国生态系统研究网络(Chinese Ecosystem Research Network,简称CERN)联网监测规范布置的试验样地。自2005年以来,环江站依照国家生态系统观测研究网络(National Ecosystem Research Network of China,简称CNERN)和CERN农田生态系统观测指标要求,逐一开展针对喀斯特峰丛洼地农田生态系统水分、土壤、生物、气象等环境要素的监测活动。本数据集收集、整理了环江站2006–2022年8个长期联网监测样地的土壤养分数据,包括土壤有机质、全氮、全磷、全钾、碱解氮、有效磷、速效钾、缓效钾、pH值等9项指标,均进行了严格的数据质量控制与评估,并附有完整的样地背景信息和分析方法记录。本数据集反映了桂西北喀斯特峰丛洼地农业区传统代表性作物早晚稻、玉米、大豆、桑叶、柑橘等农作地土壤常规养分含量动态变化,对指导喀斯特峰丛洼地农业生产、培育土壤地力具有参考依据。