Latent Tuberculosis Infection among Household Contacts of Pulmonary Tuberculosis Cases in Central State, Sudan: Prevalence and Associated Factors

Introduction: Tuberculosis is a major health problem in developing countries including Sudan. Screening for TB cases through Household contacts (HHCs) investigation is an appropriate strategy to interrupt transmission of TB. Objectives: To determine the prevalence tuberculosis infection and risk factors for tuberculosis infection among household contacts in Wadimadani locality, Central State, Sudan, between November 2015 and April 2016. Methods: An analytical cross-sectional study conducted. During study period, to confirm TB diagnosis, all suspect contacts were tested through sputum samples, tuberculin skin test or chest X-ray. Structured questionnaire was used to collect socio-demographic and environmental factors. Results: One hundred forty six patients of smear-positive pulmonary tuberculosis were included in the study, 657 household contacts were identified and screened. Forty three new TB cases were detected from household contacts, yielding a prevalence of 6.5% (95% confidence interval = 0.05, 0.09) of latent tuberculosis infection (LTBI). Two factors were significantly associated with LTBI among HHCs: duration of contact with a TB patient ≤ 4 months (P = 0.03) and the educational status (P = 0.02). Conclusion: Screening of HHCs of index case of TB will contribute in early detection and treatment of new cases, and considered as a forward step towards eliminating TB.

Numerical Computation of Stress Intensity Factors for Bolt-hole Corner Crack in Mechanical Joints

The three-dimensional finite element method is used to solve the problem of the quarter-elliptical comer crack of the bolt-hole in mechanical joints being subjected to remote tension. The square-root stress singularity around the corner crack front is simulated using the collapsed 20-node quarter point singular elements. The contact interaction between the bolt and the hole boundary is considered in the finite element analysis. The stress intensity factors （SIFs） along the crack front are evaluated by using the displacement correlation technique. The effects of the amount of clearance between the hole and the bolt on the SIFs are investigated. The numerical results indicate that the SIF for mode I decrease with the decreases in clearance, and in the cases of clearance being present, the corner crack is in a mix-mode, even if mode I loading is dominant.

On the reverse leakage current of Schottky contacts on free-standing GaN at high reverse biases

In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage（I–V –T） characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.

Thermal annealing behaviour of Al/Ni/Au multilayer on n-GaN Schottky contacts

Recently GaN-based high electron mobility transistors （HEMTs） have revealed the superior properties of a high breakdown field and high electron saturation velocity. Reduction of the gate leakage current is one of the key issues to be solved for their further improvement. This paper reports that an Al layer as thin as 3 nm was inserted between the conventional Ni/Au Schottky contact and n-GaN epilayers, and the Schottky behaviour of Al/Ni/Au contact was investigated under various annealing conditions by current-voltage （I-V） measurements. A non-linear fitting method was used to extract the contact parameters from the I-V characteristic curves. Experimental results indicate that reduction of the gate leakage current by as much as four orders of magnitude was successfully recorded by thermal annealing. And high quality Schottky contact with a barrier height of 0.875 eV and the lowest reverse-bias leakage current, respectively, can be obtained under 12 min annealing at 450 ℃ in N2 ambience.

THE CRACK-INCLUSION INTERACTION AND THE ANALYSIS OF SINGULARITY FOR THE HORIZONTAL CONTACT

Using the basic solutions of a single crack and a single inclusion, and making use of the principle of linear superposition of elastic mechanics, the interaction problem between a planar crack and a flat inclusion in an elastic solid is studied. The problem is reduced to solve a set of standard Cauchy-type singular equations. And the stress intensity factors at points of crack and inclusion were obtained. Besides, the singularity for the horizontal contact of crack and inclusion was analyzed. The calculating model put forward can be regarded as a new technique for studying the crack and its expanding caused by inclusion lip. Then several numerical examples are given.

ANALYSIS OF THE SINGULARITY FOR THE VERTICAL CONTACT PROBLEM OF LINE CRACK-INCLUSION

Taking the short-fiber composite materials as engineering back-ground, utilizing the existing basic solutions of single inclusion and single crack, the plane problem of vertical contact interactions between line crack and rigid line inclusion in infinite plane (matrix) from the viewpoint of crack fracture mechanics is studied. According to boundary conditions, a set of standard Cauchy-type singular integral equations of the problem is obtainable. Besides, singular indexes, stresses and stress intensity factors around the contact point are expressed. Numerical examples are given to provide references to engineering.

550kV气体绝缘母线大电流工况下温升特性分析

探究气体绝缘母线在超高压大电流工况下的温升特性对设备的正常运行以及监测维护意义重大。然而,在长期大电流负荷运行下,因接触异常等原因导致母线在较小封闭空间内产生大量热量,极易造成局部过热严重威胁设备安全运行。针对这一问题,本文以550kV气体绝缘母线为研究对象,构建了考虑接触电阻的3维电磁-温度-流体多场耦合模型,计算其在1.1倍额定电流(8800A)、气压0.3MPa条件下的母线温度分布,并搭建了大电流温升试验平台进行验证,试验测量结果与仿真结果吻合度高。基于验证后的可靠模型,进一步探究了通流水平、SF_(6)气压及接触状态对母线温度分布的影响规律。结果表明:母线最高温度位于盆子凹面处电接触部位顶部(约为54℃),该端触头上方SF_(6)温度比导杆上方高近15℃,凹面处触头径向温度梯度明显低于凸面处触头径向温度梯度;在非等温自然对流的情况下,母线温度整体呈径向上高下低、轴向端部高中间低的规律分布;母线温度随通流水平提高呈非线性上升、随SF_(6)气压增大呈近似线性下降,可在一定范围内提高设备绝缘气体压强以降低设备运行温度;异常电接触处温度随阻值增大近似线性增加,而电接触异常往往是母线过热的主要风险点。研究结果可为超高压大电流气体绝缘设备产品设计及状态监测提供参考。

Modeling Stress Intensity Factor of Rail Steel under Situation of Growing Fatigue Crack—A Novel Technique

Simulation of stress intensity factor as function of rolling contact fatigue cracks of railway tracks and the vehicle load is made with the help of COMSOL Multiphysics software. It is found that the critical stress intensity factor i.e. 41.6 MPa. m1/2 is reached at a stress level of 32 MPa and at the crack size 11.5 × 10-2 m.Noting the power law variation of acoustic emission count with increase in crack size (analogous to Paris Law), the simulation was further carried out to model the dependence of measured AE count with the stress intensity factor ahead of a growing RCF crack tip. It is demonstrated that AE measurement can be effective to trigger a control loop for avoidance of fatigue failure of railway track. In view of potential difference in the intensity of back scattered light from surface irregularities, a model is developed to find out the threshold intensity of scattered light that insures safety in the railway system against fatigue failure.

Factors influencing the performance of paintable carbon-based perovskite solar cells fabricated in ambient air

To date, many efforts have been made to improve the performance of paintable carbon-based （PC-based） perovskite solar cells （PSCs）. Though great progress has been achieved, their power conversion efficiencies are still relatively low compared with hole-transport-materials-based PSCs. General research on influencing factors of performance in PC-based PSCs is still insufficient. In this work, PC-based PSCs were fabricated in ambient air and four groups of controlled experi- ments were performed in which the PbI2 layers were prepared with or without antisolvent extraction treatment. These four groups of experiments were designed to find out the effect of different influencing factors on PC-based PSCs performance, for example, PbI2 residual, the surface morphology of the perovskite film, the surface roughness of the perovskite film, and the contact status of the perovskite/carbon electrode interface. With a systematic analysis, we demonstrated that the contact status of the perovskite/carbon electrode interface played a vital role in PC-based PSCs, and a fiat, smooth perovskite surface could help to improve this contact status significantly. Besides, on the precondition of a poor contact interface, no PbI2 residual and a good surface morphology only brought limited benefits to the performances of PC-based PSCs.

耐药肺结核患者密切接触者结核分枝杆菌潜伏感染危险因素分析

目的:探究耐药肺结核患者密切接触者结核分枝杆菌潜伏感染(latent tuberculosis infection,LTBI)情况及危险因素。方法:采用前瞻性研究方法,选取2020年7月至2022年1月于温州市中心医院收治的154例耐药肺结核(包括单耐利福平肺结核、耐多药肺结核)患者的306名密切接触者作为研究对象。收集研究对象社会人口学特征、卡介苗接种史、疾病史,以及与指示病例的接触情况等信息;并进行HIV抗体筛查、胸部CT扫描、结核感染T细胞斑点试验和(或)结核菌素皮肤试验(PPD试验)等。调查研究对象LTBI情况,并采用logistic回归模型分析其发生LTBI的影响因素。结果:研究对象结核分枝杆菌潜伏感染率为18.6%(57/306)。多因素分析结果表明,年龄≥40岁、女性、体力劳动者、指示病例为复治患者,以及指示病例有咳嗽、咳痰等临床症状的密切接触者发生LTBI的风险更高[OR(95%CI)值分别为6.501(1.371~30.827)、2.961(1.472~5.956)、2.716(1.368~5.391)、3.100(1.278~7.521)、3.065(1.336~7.031)];而家庭月收入≥5000元是密切接触者发生LTBI的保护因素[OR(95%CI)=0.308(0.156~0.607)]。结论:耐药肺结核患者密切接触者结核分枝杆菌潜伏感染率较高,高龄、女性、体力劳动者、低收入,以及与复治耐药肺结核患者和具有咳嗽、咳痰等临床症状耐药肺结核患者的密切接触者是发生LTBI的高危人群。

东天山维权银铜多金属矿控矿因素及成因分析

维权银铜多金属矿床位于新疆东天山地区,是具有典型特征的大型银铜多金属矿,大地构造划属觉罗塔格沟弧带中的雅满苏岛弧带。该矿床的地质特征、控矿因素、矿床成因长期存在争议。本次研究建立在多年野外地质勘查的基础上,对矿床的地质特征、控矿因素、矿床成因等进行了系统研究,认为银铜、铅锌矿体均分布于火山碎屑岩中,受地层控制的铅锌矿体被断裂构造控制的银铜矿体所切穿;铅锌矿成矿严格受地层层位控制,主要的蚀变类型为矽卡岩化,为接触交代成因类型,成矿时代为早石炭世晚期;银铜矿体形成于晚石炭世中晚期,矿体就位空间为断裂构造,矿体形态明显受断裂形态和性质所控制,有着明显的矿化边界,即断层面,认为其属岩浆期后远程中低温热液成因,成矿晚于铅锌成矿。

Analysis of composite material interface crack face contact and friction effects using a new node-pairs contact algorithm

A new node-pairs contact algorithm is proposed to deal with a composite material or bi-material interface crack face contact and friction problem （e.g., resistant coating and thermal barrier coatings） subjected to complicated load conditions. To decrease the calculation scale and calculation errors, the local Lagrange multipliers are solved only on a pair of contact nodes using the Jacobi iteration method, and the constraint modification of the tangential multipliers are required. After the calculation of the present node-pairs Lagrange multiplier, it is turned to next contact node-pairs until all node-pairs have finished. Compared with an ordinary contact algorithm, the new local node-pairs contact algorithm is allowed a more precise element on the contact face without the stiffness matrix singularity. The stress intensity factors （SIFs） and the contact region of an infinite plate central crack are calculated and show good agreement with those in the literature. The contact zone near the crack tip as well as its influence on singularity of stress fields are studied. Furthermore, the frictional contacts are also considered and found to have a significant influence on the SIFs. The normalized mode-II stress intensity factors KII for the friction coefficient decrease by 16% when f changes from 1 to 0.

2018—2021年新疆维吾尔自治区喀什地区肺结核患者家庭内密切接触者发病情况及影响因素分析

目的:分析结核病高负担环境中肺结核患者家庭内密切接触者发病风险及影响因素。方法:从“中国疾病预防控制信息系统”子系统“结核病管理信息系统”中收集2018年1月1日至2021年12月31日新疆维吾尔自治区喀什地区12个县(市)确诊的肺结核患者作为指示病例,通过接触者筛查建立家庭内密切接触者队列,跟踪随访观察其发病情况。采用泊松回归模型分析指示病例的病原学特征、治疗状态、暴露情况,以及家庭内密切接触者既往肺结核病史等对其肺结核发病的影响因素。结果:截至2021年12月31日,共计调查了40182例肺结核指示病例、57142名家庭内密切接触者。在4年的随访期间,随访时间中位数(四分位数)为3.2(2.7,3.3)年,共计发现了3585例家庭内密切接触者肺结核续发患者,续发率为6.27%,共计观察180543人年,平均发病密度为1985.68/10万人年。其中,指示病例确诊后的第1年,其家庭内密切接触者肺结核发病率最高,约为3317.62/10万人年。泊松回归分析显示,指示病例病原学检测为涂阴、初治,家庭内密切接触者为男性、≥55岁、既往有肺结核接触史和肺结核病史均是家庭内密切接触者肺结核发病的危险因素[RR(95%CI)值分别为2.491(2.347~2.562)、1.221(1.102~1.354)、1.449(1.306~1.607)、8.451(6.388~11.179)、2.680(2.314~3.104)、4.479(3.852~5.207)]。结论:家庭内密切接触者是肺结核指示病例传播的高危人群,应加强家庭内密切接触者的筛查和宣传教育工作,尤其是其中的老年、男性、既往有肺结核接触史和肺结核病史者;也有必要在结核病高负担地区系统地扩大和加强家庭内密切接触者的追踪和预防性治疗策略。同时,建议在当前策略基础上纳入全部肺结核患者的密切接触者进行筛查,尤其是涂阴和仅分子生物学检测阳性患者。

肺结核患者家庭内学生密切接触者结核分枝杆菌感染状况调查

目的:分析肺结核患者家庭内学生密切接触者结核分枝杆菌感染状况及其影响因素。方法:以2021年1月1日至12月31日在江苏省宝应县和张家港市、湖北省宜都市、重庆市彭水苗族土家族自治县和云南省昭通市昭阳区5个县(区)登记的活动性肺结核患者家庭内学生密切接触者为研究对象,开展结核菌素皮肤试验(tuberculin skin test,TST),调查人口学特征,并通过全民健康保障信息化工程疾病预防控制信息系统收集其指示病例的基本信息和诊断信息,分析结核分枝杆菌感染的相关因素。结果:477例指示病例共有686名家庭内学生密切接触者,TST检测总体接受率为92.27%(633/686),各县(区)之间的接受率差异有统计学意义(χ^(2)=57.781,P<0.001),以宝应县为最高(100.00%,35/35)。家庭内学生密切接触者总体感染率为14.85%(94/633,95%CI:11.85%~17.85%),强阳性率为5.06%(32/633),各县(区)之间的差异均有统计学意义(χ^(2)=35.800,P<0.001;Fisher确切概率法,P=0.029)。单因素分析结果显示,≥15岁年龄组[23.47%(23/98);95%CI:13.88%~33.06%]、就读于高中及以上学校[26.09%(18/69);95%CI:14.04%~38.14%]、住在宜都市[33.33%(28/84);95%CI:20.99%~45.68%]、指示病例诊断延迟[18.37%(52/283);95%CI:13.38%~23.37%]的家庭内学生密切接触者感染率更高;多因素logistic回归分析显示,在调整混杂因素后,指示病例诊断延迟的家庭内学生密切接触者的感染风险是指示病例无诊断延迟者的1.586倍(95%CI:1.016~2.476)。结论:活动性肺结核患者家庭内学生密切接触者的结核分枝杆菌感染率较高,尤其是指示病例诊断延迟的家庭内学生密切接触者,应及时开展筛查并采取后续干预措施。

人车碰撞事故中人地碰撞损伤研究进展

为了解人车碰撞事故中人地碰撞损伤的研究进展,并对可行的人地碰撞损伤防护方法做出展望。本文从人车碰撞事故特征、人体损伤评价指标、人体损伤来源、人地碰撞损伤影响因素及人地碰撞损伤防护方法5个方面回顾了已有研究成果,并对已有研究中存在的问题进行讨论,就人地碰撞防护方法的发展作出展望。人地碰撞损伤研究仍然存在许多不成熟的地方,特别是人地碰撞损伤的致伤机理和影响因素方面仍须开展深入的研究。通过回顾现有的人地碰撞损伤防护技术指出,未来可从优化车辆前部形状、安装行人安全装置以及控制车辆制动等方面来降低行人损伤风险。大部分事故中碰撞速度为中低速,而在低车速下的人地碰撞损伤不容忽视,可通过控制车辆制动降低人地碰撞损伤。此外,人地碰撞损害评价指标仍存在不足。本文可为后续更好地开展人地碰撞损伤致伤机理及防护方法的研究提供参考。

基于圆锥微凸体的结合面法向刚度改进模型

为了使结合面接触特性模型更具准确性,将粗糙接触表面微凸体等效为圆锥形微凸体,运用改进的W-M函数模拟粗糙表面三维形貌,修正了微凸体接触半径,且考虑域扩展因子对截面积分布函数的影响,建立了结合面法向接触刚度模型,并对模型进行仿真,分析了结合面形貌参数对法向接触刚度的影响。最后,将模型与真实试验数据以及以往模型做对比,证明了所建模型运用于实际结合面法向刚度数值计算的精确性,进一步证实了所建模型的可行性。所建模型有助于对结合面接触刚度进行更精确的预测,并为相关机械结构改进提供了依据。

面向机器人打磨陶瓷洁具工艺的参数优化

针对卫浴陶瓷洁具进行抛光工艺,引入新松打磨机器人作为自动化设备实现自动化抛光打磨。结合Preston方程以及赫兹接触理论,确定了海绵轮与工件之间的相对速度,正压力是对陶瓷洁具表面质量的影响的两个工艺参数,以此建立了陶瓷洁具的材料去除理论模型;后续搭建了机器人恒力抛光平台,设计了陶瓷洁具的抛光打磨抛光工序,以其主要的两个参数为变量设计了单因素实验,得到各参数对抛光效率的关系,并为提出最佳抛光工艺参数组合做好铺垫。

387名结核分枝杆菌潜伏感染者预防性治疗服药完成情况及影响因素分析

目的:研究肺结核患者密切接触者中的结核分枝杆菌潜伏感染(latent tuberculosis infection,LTBI)者对3个月每周服用2次异烟肼和利福喷丁联合间歇(3H-P)预防性治疗方案的服药完成情况及影响服药完成的因素,为进一步推广预防性治疗措施提供参考依据。方法:收集2023年1月1日至12月31日期间,新疆维吾尔自治区(简称“新疆”)阿克苏地区乌什县经知情同意纳入的387名与肺结核患者密切接触的接受预防性治疗的LTBI者作为研究对象。通过问卷调查,了解预防性治疗服药完成情况及其影响因素。问卷主要内容包括基本人口学信息、结核病防治核心知识知晓情况及预防性治疗服药情况等。采用单因素和多因素logistic回归分析与预防性服药完成情况相关的影响因素。结果:387名LTBI者中,有355名完成3H-P方案服药,服药完成率为91.73%;不良反应发生率为14.21%(55/387),因不良反应停药率为4.39%(17/387)。多因素logistic回归分析结果显示,规律运动(OR=5.337,95%CI:2.309~12.337)、参与结核病防治相关培训(OR=4.406,95%CI:1.942~9.994)是肺结核患者密切接触者中的LTBI者完成服药的保护因素;有饮酒史(OR=0.279,95%CI:0.108~0.720)、年龄在50~64岁(OR=0.254,95%CI:0.092~0.698)是肺结核患者密切接触者中的LTBI者中断服药的危险因素。结论:肺结核患者密切接触者中的LTBI者预防性治疗的服药完成情况总体良好,不良反应为中断服药的原因之一,服药完成率还会受到未规律运动、有饮酒史、未参与过结核病防治相关培训、年龄50~64岁等因素的影响。

产后持续性母子早接触减少产后出血的效果分析

目的探讨产后持续性母子早接触减少产后出血的效果。方法选取2022年3088例自然分娩产妇为对照组、2023年2199例自然分娩产妇为试验组,对照组新生儿娩出后采取常规新生儿护理,试验组在常规新生儿护理的基础上采取产后持续性母子早接触,比较两组的产后出血率,并分析影响因素。结果对照组产妇产后出血发生率为6.3%,高于试验组的2.9%(P<0.05)。Logistic回归分析结果发现,年龄、第三产程用时、麻醉镇痛分娩、产钳助产、会阴侧切、并发症是产后出血的影响因素(P<0.05)。结论产后出血的影响因素较多,产后实施持续性母子早接触能有效降低产后出血发生率,值得推广应用。