基于陀螺全站仪的地铁贯通定向分析应用

地铁隧道工程的开挖掘进由于缺少可靠的检核条件,导致控制导线的精度较低,大大影响了隧道的贯通精度。本文采用高精度的陀螺全站仪通过逆转点方法对地铁隧道进行加测陀螺定向边,并对陀螺仪的定向原理进行分析利用,结合相应的计算公式进行优化分析,得到精确的导线边方位角。通过验证确保了成果的可靠性,有效提高了控制网的精度,减小了导线网的测角误差积累及地下导线测量最弱边对地铁贯通的影响,保障地铁隧道顺利贯通。

一种参考源修正的短波辐射源时差定位方法

为解决短波辐射源到达时间差(time difference of arrival,TDOA)定位(简称时差定位)方法受电离层影响导致的定位精度下降的问题,提出了一种利用参考源修正的短波辐射源目标时差定位方法。针对地球表面短波辐射源,基于电离层球面反射模型的电离层反射虚高近似方法,建立了利用参考修正的短波目标时差定位模型。考虑参考源与目标共用电离层反射区域对电离层虚高的影响,将各电离层反射点的距离相关性引入电离层虚高的协方差矩阵中,实现了目标定位精度的修正。通过推导和仿真所提模型的克拉美·罗下界,分析了参考源修正目标定位精度的可行性。进一步给出基于Armijo直线搜索Newton法的最大似然估计方法,通过仿真数据验证了所提算法的有效性,实现了良好的定位效果。

Renin-angiotensin system inhibitors prescriptions in Chinese hospitalized chronic kidney disease patients

BACKGROUND Many guidelines have recommended renin-angiotensin system inhibitors(RASI)as the first-line treatment for patients with chronic kidney disease(CKD).We studied RASI prescription trends from 2010 to 2019,and analyzed the characteristics associated with RASI prescription in Chinese hospitalized CKD patients.AIM To study the prescription of renin angiotensin system inhibitors in hospitalized patients with CKD in China.METHODS It was retrospectively,cross-sectional reviewed RASI prescriptions in hospitalized CKD patients in China from 2010 to 2019.RASI prescribing trends were analyzed from 2010 to 2019,and bivariate and multivariate logistic regression analyses were conducted to identify characteristics associated with RASI prescription.RESULTS A total of 35090 CKD patients were included,with 10043(28.6%)RASI prescriptions.Among these patients,18919(53.9%)met the criteria for RASI treatments based on the 2012 kidney disease:Improving global outcomes guidelines.Of these,7246(38.3%)patients received RASI prescriptions.RASI prescriptions showed an initial rapid increase from 2011 to 2012,reached its peak around 2015 and 2016,and then exhibited a subsequent slight decreasing trend.Both bivariate and multivariate analyses showed that several characteristics,including the male gender,age less than 60-year-old,nephrology department admission,lower CKD stage,history of hypertension or diabetes,proteinuria,glomerulonephritis as the CKD etiology,and non-acute kidney injury were associated with RASI prescriptions.CONCLUSION The frequency of RASI prescriptions showed an initial increase but a slight decreasing trend in more recent years.CKD patients with certain characteristics such as elderly age,advanced disease stage,surgery department admission,or acute kidney injury were less likely to receive RASI prescriptions.In the application of RASI in hospitalized CKD patients is insufficient.The actual clinical practice needs to be improved.The development of related research is helpful to guide the correct choice of clinical treatment strategy.

Research Progress of Assessment Tools for Peripheral Venous Access Difficulties in Children

Objective:To review the research progress of peripheral venous access difficulty assessment tools in children and to provide a reference for clinical nurses to select and develop appropriate assessment tools.Methods:Search the literature at home and abroad and summarize and analyze the existing evaluation tools.Results:There is no unified assessment tool about difficult venous access in children at home and abroad.The existing tools include the difficult venous access assessment scale and peripheral venous grading assessment tool.Conclusion:The current assessment tools for venous access difficulties in children have their own limitations,and it is necessary to develop further the assessment tools suitable for the cultural background of children's venous access difficulties.This paper summarized the current progress of research on peripheral venous access difficulty assessment tools.It also analyzed and summarized the shortcomings of existing tools to provide a reference for clinical staff to choose appropriate assessment tools.

Discussion on Influencing Factors of Water Resources Environment and Strategies for Protecting Water Ecology

At present,the major problems facing the water resource environment worldwide include water pollution,water resource shortage,and water ecosystem degradation.The discharge of industrial wastewater,agricultural non-point source pollution,and the discharge of urban sewage lead to a serious decline in water quality,which directly affects the safety of human drinking water and the living environment of aquatic organisms.Additionally,the unbalanced distribution and excessive exploitation of water resources lead to the problem of water shortage in many areas,which then leads to social and economic contradictions and ecological crises.In terms of ecosystems,the phenomena of water ecological degradation and reduction of biodiversity are increasingly obvious,and the carrying capacity of aquatic ecosystems are gradually declining.This paper aims to analyze the natural,social,and economic factors affecting the water resource environment,and propose effective strategies to protect the water ecology.To provide a theoretical basis and practical guidance for the sustainable utilization of water resources and the long-term development of the water ecosystem.

Optimal Cut-off Point of Waist to Height Ratio in Beijing and Its Association with Clusters of Metabolic Risk Factors

A host of studies found waist-to-height ratio(WHtR)having higher diagnostic value than other abdominal obesity anthropometric indicators for metabolic disorders.But the cut-off points are still not consistent.This study was aimed to explore the optimal cut-off point of WHtR in Chinese population and identify the association between WHtR and cluster of metabolic risk factors.In total,13379 Han adults(7553 men and 5726 women)from over 40 institutions who took physical examination in Xuanwu Hospital of Capital Medical University between January 2014 and January 2015 were involved in this cross-sectional study.Subjects with two or more components of metabolic syndrome(MetS)were considered to have multiple risk factors.Optimal cut-off points of WHtR for cluster of metabolic risk factors were analyzed by receiver operating characteristic(ROC)curve analysis.The optimal cut-off points of WHtR were 0.51 for men and 0.49 for women.People with elevated WHtR had higher levels of metabolic risk factors.And the prevalence of individual and clusters of 5 risk factors were all higher among WHtR-defined abdominal obesity people than in normal subjects.The optimal cut-off points of WHtR were 0.51 for men and 0.49 for women.In conclusion,people with elevated WHtR.are susceptible to cluster of metabolic risk factors.

碳纤维与扩散层厚度对Al-Mg-Ti微叠层复合材料组织性能的影响

以1060纯铝、TC4钛合金、AZ31镁合金和镀镍碳纤维编织布为原材料,使用真空热压扩散技术和“箔-纤维-箔”法制备出碳纤维增强Al-Mg-Ti微叠层复合材料。通过控制铝镁保温时间分析了铝镁扩散层厚度对材料组织性能的影响,探讨碳纤维的强化机理,采用X射线衍射仪(XRD)、能谱分析仪(EDS)和扫描电子显微镜(SEM)等分析了复合材料的相组成、元素分布与裂纹扩展形貌,测试了复合材料的抗弯强度和冲击韧性。结果表明:碳纤维增强Al-Mg-Ti微叠层复合材料扩散层厚度随着保温时间的延长而增加,力学性能呈先上升后下降的趋势,碳纤维通过纤维脱粘、纤维拔出和纤维劈裂等方式吸收了大量断裂能,起到显著的增韧效果。在铝钛热压温度640℃保温时间2 h,铝镁热压温度440℃保温时间8 h时,复合材料力学性能最优,抗弯强度为380 MPa,冲击韧度为26.2 J/cm^(2),相对于基体抗弯强度和冲击韧性分别提高了10.8%和30.3%。

Timing of surgical operation for patients with intra-abdominal infection:A systematic review and meta-analysis

BACKGROUND Intra-abdominal infections(IAIs)is the most common type of surgical infection,with high associated morbidity and mortality rates.In recent years,due to the use of antibiotics,various drug-resistant bacteria have emerged,making the treatment of abdominal infections more challenging.Early surgical exploration can reduce the mortality of patients with abdominal infection and the occurrence of complications.However,available evidence regarding the optimal timing of IAI surgery is still weak.In study,we compared the effects of operation time on patients with abdominal cavity infection and tried to confirm the best timing of surgery.AIM To assess the efficacy of early vs delayed surgical exploration in the treatment of IAI,in terms of overall mortality.METHODS A systematic literature search was performed using PubMed,EMBASE,Cochrane Central Register of Controlled Trials,Ovid,and ScienceDirect.The systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-analyses method.Based on the timing of the surgical operation,we divided the literature into two groups:Early surgery and delayed surgery.For the early and delayed surgery groups,the intervention was performed with and after 12 h of the initial surgical intervention,respectively.The main outcome measure was the mortality rate.The literature search was performed from May 5 to 20,2021.We also searched the World Health Organization International Clinical Trials Registry Platform search portal and ClinicalTrials.gov on May 20,2021,for ongoing trials.This study was registered with the International Prospective Register of Systematic Reviews.RESULTS We identified nine eligible trial comparisons.Early surgical exploration of patients with IAIs(performed within 12 h)has significantly reduced the mortality and complications of patients,improved the survival rate,and shortened the hospital stay.CONCLUSION Early surgical exploration within 12 h may be more effective for the treatment of IAIs relative to a delayed operation.

基于射频层析成像的雷达探测新技术

射频层析成像是一种新兴的目标定位技术,在军事、医疗和安全监控等领域有着十分广阔的应用前景。本文借鉴延伸射频层析成像理念,提出一种针对空中目标的雷达探测新技术。文章首先分析了射频层析成像基本原理,在此基础上论述了基于射频层析成像的雷达探测理念,构建了雷达层析成像探测模型,讨论了应用于大区域空中目标探测时的电磁射线构造方法,分析了雷达层析成像处理权重模型,并完成了仿真实验验证,最后对该雷达探测新技术进行了发展展望。

对抗条件下雷达部署优化方法研究

针对强对抗环境下雷达网面临隐身、低空突防、复杂电子干扰等威胁问题,提出了基于雷达网探测威力和重点目标跟监能力相结合的大区域组网雷达优化部署方法,建立了雷达组网优化部署的评估指标体系和综合效能计算模型,给出了基于人工蜂群算法的雷达组网优化部署求解过程。仿真实验表明,该方法能显著提高组网效能,对雷达网作战有参考价值。

浅议猫砂标准现状与发展趋势

文章主要介绍了猫砂标准现状,分析了除臭效果检测方法的不足和改进方式,探讨猫砂标准进一步发展的可行性方向。

高效液相色谱法测定纺织品中2种苯并三唑类紫外吸收剂

建立了纺织品中苯并三唑类紫外吸收剂的高效液相色谱(HPLC)分析检测方法。通过对纺织品中苯并三唑类紫外吸收剂2-(2′-羟基-3′,5′-二叔戊基苯基)苯并三唑(UV-328)和2-(2′-羟基-3′-异丁基-5′-叔丁基苯基)苯并三唑(UV-350)的测定,结果表明在一定浓度范围内线性关系良好,相关系数(R^(2))均大于0.999,方法简单快速,回收率和精密度良好,具有较好的灵敏度,适用于纺织品中紫外吸收剂的检测方法。

超高层超大构件高强混凝土防收缩开裂技术措施

为了解决超高层超大构件高强混凝土易开裂问题,消除超大构件开裂对建筑结构的影响,因而采用超高层超大构件高强混凝土防收缩开裂技术,通过配合比试验调整配合比,增设抗裂钢筋,箍筋外侧增设抗裂钢丝网的方式,有效控制超限连梁裂缝的产生,保证了工程施工质量,避免了后期超限连梁裂缝维修加固,节约了后期维修成本。

角膜塑形镜配戴不同时长对青少年近视影响的Meta分析

目的:系统评价角膜塑形镜配戴不同时长对青少年近视患者的角膜曲率、屈光度、裸眼视力及眼轴的影响。增加青少年近视患者对配戴角膜塑形镜的认识及对配戴时长的合理把握,为广大青少年近视患者提供相应的戴镜指导。方法:计算机检索PubMed、CBM、WanFang Data、VIP和CNKI等数据库,检索角膜塑形镜对控制青少年近视进展的相关文献,检索时限均为建库至2019-04。经过两名本课题参与的研究人员独立进行文献的筛选和相关数据资料的提取及方法学质量评价之后,使用RevMan软件(Ver5.3)进行Meta分析。结果:最后本课题共纳入了8个相关的研究,包含了1 136例患有近视的青少年。Meta分析结果显示:在戴镜后1wk角膜曲率变化无统计学意义[1wk:MD=0.91,95%CI(-0.01~1.83),P=0.05]。但戴镜后1、3、6、12mo时,角膜曲率有一定程度降低[1mo:MD=0.82,95%CI(0.12~1.53),P=0.02;3mo:MD=1.31,95%CI(0.63~2.00),P<0.05;6mo:MD=1.35,95%CI(0.62~2.09),P<0.05;12mo:MD=1.41,95%CI(0.68~2.14),P<0.05]。戴镜后12mo,屈光度增长得到有效控制[12mo:MD=2.61,95%CI(1.52~3.71),P<0.05]。裸眼视力也得到了提高[12mo:MD=-0.81,95%CI(-0.84^-0.79),P<0.05]。在戴镜12mo后,眼轴增长无统计学意义[12mo:MD=-0.06,95%CI(-0.21~0.09),P=0.44]。结论:角膜塑形镜不仅能够降低角膜的曲率,还可以控制眼轴的增长,然而,这些结果都是长期才会发生。

基于三维激光扫描技术的盾构隧道变形分析

为保证地铁隧道建设过程中的安全,对其进行变形监测是必不可少的工作。传统测量方法采用特征点位进行隧道断面监测,存在数据量较少、点位不够全面等缺点,且工作量较大,工作效率低。针对这一问题,本文将三维激光扫描技术应用于盾构隧道监测,利用获取的三维激光点云对盾构隧道进行监测。为验证其可靠性,将其与全站仪数据进行联合分析。实验表明,三维激光扫描系统测量断面中心坐标的点位精度为3.41 mm,横断面半轴长度与全站仪测量结果的差值小于4 mm;地铁隧道整体表现为水平外凸、竖直下沉的状态。结果显示了三维激光扫描技术的高精度、高效率等工作特点,并且能够对隧道整体变形情况进行分析,具有广阔的发展前景。

室内三维相机检校场温度改正阈值研究

室内三维相机检校场可以用于检校量测型相机或非量测型相机的内方位元素、光学畸变,以及多相机组合拼接参数。受温度变化影响,检校场观测标志载体发生热胀冷缩,观测标志发生相对位置变化,影响相机检校精度。通过采用经纬仪工业测量系统对检校场观测标志进行高精度测量,在不同温度条件下对检校场开展周期性观测,得出检校场标志点载体钢筋混凝土和金属挂杆的热膨胀系数,根据待检校相机的类型,计算出检校场需要达到的精度要求,确定检校场坐标温度改正阈值。

背包式移动测量系统传感器间数据融合研究

在开发包含两台Velodyne VLP-16小型三维激光扫描仪和一个GX5小型惯导的背包式移动测量系统过程中,为实现各传感器之间对采集数据更好的信息融合,基于Leica Axyz经纬仪工业测量系统,探索了对各传感器单体标定建立单体坐标系,对各传感器集成后进行整体标定,确定它们之间的相对位置和坐标系转换关系的方法,实验结果表明在使用室外检校场检校前,先使用工业测量系统标定出一组高精度参数作为初始参数,可以提高传感器之间数据融合精度,减少迭代次数。

基于开放式考核模式的高职生学习行为分析

分析了目前高职教学考评环节存在的问题,提出开放式教学考核模式,对该考核模式下学生的学习行为进行了分析,研究结果表明:开放式的考核模式不仅有利于高职学生知识、技能的掌握,而且对于学生职业素养和综合能力的培养与发展起到积极作用。

基于遗传优化径向基函数的梁板固有特性分析

为了提高径向基函数(RBF)的计算精度,利用遗传优化的径向基函数分析薄壁梁和板的固有特性。在静态分析的基础上,通过遗传算法(GA)优化径向基函数中的形状参数;利用改进后的径向基函数,分析薄壁梁和板的固有特性,得到了不同工况下结构的特征值和特征模态。数值计算表明:使用遗传算法优化后,径向基函数的计算精度大幅度提高,固有频率的最大误差在5%以内,远小于未优化的情况。

大实践视阈下高职实践教学考核模式探讨

分析了目前高职实践教学考评过程中存在的问题,针对高职实践教学内容的新特点,提出开放式大实践教学考核模式理论,设计实施方案,探讨建立符合高职人才培养目标的实践教学考核模式。