光纤Bragg光栅应变传感器在霍普金森压杆上的冲击试验研究

利用复合材料封装光纤Bragg光栅(FBG)设计制作了用于测量高速碰撞或爆炸与冲击作用下混凝土内部动态应变的FBG应变传感器。在霍普金森压杆上对FBG在封装前的裸光栅和封装后的FBG传感器分别进行了高速冲击试验,试验表明：设计的FBG传感器的瞬态响应上升时间小于20μs,具有良好的动态响应特性,可以用于工程中混凝土结构内高速冲击下的动态应变测试     

裸光纤Bragg光栅传感器工程特性试验研究

裸光纤Bragg光栅传感器结构纤巧,具有其它光纤光栅传感器无法比拟的结构优势。本文以等强度梁作为试验装置,通过对裸光纤Bragg光栅传感器的静态特性参数和动态响应特性进行的标定试验,验证了裸光纤光栅传感器在工程上直接应用的可能性。试验结果表明：裸光纤光栅传感器线性好,灵敏度较高,动态响应特性好,能够满足普通工程应用现场应力、应变的测量需求。     

光纤光栅传感技术在桥梁试桩中的应用

基于对光纤布拉格光栅(FBG)传感特性的理论分析,研制了可用于桥梁试桩应变监测的光纤光栅钢筋应变计,并进行了标定试验;研究了光纤光栅传感器的布设工艺,在某特大跨海大桥试桩项目中的钻孔灌注桩里成功地埋入了52支光纤光栅钢筋应变计,进行了荷载试验.研究结果表明,在桥梁试桩项目中利用光纤光栅传感技术可以方便有效地对试桩的应变进行多点实时监测,为桥梁桩基础的优化设计提供了可靠的依据.     

光纤Bragg光栅用于三维编织复合材料结构的内应变测量

本文对应用光纤Bragg光栅传感器编入三维编织复合材料结构内部的测量进行了研究.首先简要介绍了光纤光栅的编入方法和传感原理.随后进行的实验结果显示由应变计及光纤光栅所得到的载荷-应变曲线都具有良好的线性关系,实验之间的结果符合得很好,表明光纤Bragg光栅传感器可以用来精确检测编织试件复杂载荷状态下的内应变.从而将会促进光纤光栅在3-D编织复合材料结构的内部结构检测和强度失效分析中的更广泛应用.     

考虑混凝土基体蠕变的FBG传感器应变传递研究

为研究光纤光栅应变传感器在混凝土结构中的长期监测性能,需考虑混凝土基体的长期蠕变效应对传感器应变传递率的影响。以玻璃纤维增强塑料(GFRP)封装的埋入式光纤布拉格光栅(FBG)应变传感器为研究对象,引入混凝土蠕变本构,进行应变传递分析,并通过有限元计算对理论分析结果加以验证。研究表明传感器的平均应变传递率随着混凝土基体的蠕变发展而逐渐降低,蠕变的影响不可忽略,需进行误差修正。在此基础上,利用平均应变传递率公式,可对光纤光栅传感器的选型提供一定参考。     

光纤光栅传感器在CFRP冲击载荷监测中的应用研究

提出了一种用光纤光栅传感器监测CFRP结构冲击载荷的方法,构建了冲击监测系统。将FBG传感器粘贴于CFRP试件表面构成传感网络,针对不同冲击点,同一传感器监测的冲击响应信号进行分析,CFRP试件的一阶、二阶谐振频率为53 Hz、100 Hz,不同谐振频率对应的幅值随冲击点的改变而不同。冲击CFRP试件,对FBG传感网络感知的冲击响应信号进行小波包分解,获得各传感器的小波包能量谱图。结果表明传感器信号的第6阶小波包能量变化明显,能量大小与冲击点和传感器之间的距离及其夹角有关。研究结果将为CFRP结构的动态监测领域提供了实验参考。     

冲击荷载下橡胶混凝土道面应变响应研究

为阐明冲击荷载作用下橡胶混凝土道面的应变响应，基于光纤光栅应变计和重型落锤式弯沉仪(heavy weight deflectometer, HWD),设计了一种道面冲击应变响应的测试方法。通过该方法，对比分析了冲击荷载下橡胶混凝土道面与普通混凝土道面的应变响应差异，并通过监测不同尺寸的橡胶混凝土道面，研究道面板尺寸对应变响应的影响。试验结果表明：相较于普通混凝土道面，橡胶颗粒的加入改变了冲击荷载下道面的应变响应分布，使混凝土道面板中的水平应变均减小，而板边、板角的水平纵向应变增加；并且随着板长增加，橡胶混凝土道面板中、板边、板角处最不利应变响应方向的应变逐渐增加，其中板角处纵向应变增加最快，即道面板长增加将使橡胶混凝土道面冲击荷载下的最不利位置和方向从板边横向转移至板角纵向，因此在大尺寸橡胶混凝土道面设计与建造中，板角应变也应被考虑。     

埋入CFRP的FBG光纤传感器界面传递特性实验研究

埋入碳纤维复合材料（CFRP）的光纤布拉格光栅（FBG）传感器应变测量值与基体实际应变存在误差，用光纤、保护层、粘贴层和基体材料的界面传递特性来表征应变测量值可提高精度．根据弹性力学和边界条件，得出FBG应变测量值与基体材料实际应变值的关系方程，通过裸光栅直埋基体材料界面传递的特征系数，可表征和计算FBG检测应变与测点实际应变的误差及修正系数．试验结果表明：对埋入裸光栅的碳纤维复合材料同时进行电阻应变与FBG—IS波长解调试验对比，试验测量FBG应变传感灵敏系数与理论值十分接近；对埋入CFRP的FBG裸光栅，由于不存在粘贴层界面传递的影响，其应变测量值可无需修正．     

混凝土结构用智能FRP筋的试验研究

在纤维增强聚合物Fiber Reinforced Polymer (FRP)筋拉挤工艺中,将光纤布拉格光栅Optic Fiber Bragg Grating(OFBG)传感器与普通纤维束一起经过拉挤模具,为改进FRP筋与混凝土的粘结性能,在FRP筋表面螺旋缠绕纤维束,制备了智能OFBGFRP筋.对OFBG-FRP筋的力学性能和应变灵敏性能进行试验研究,试验结果表明OFBG-FRP筋的力学性能与普通FRP筋相同、OFBG-FRP筋的应变灵敏系数与普通光纤传感器相同、OFBG-FRP筋在重复荷载作用下性能良好.OFBG-FRP加筋混凝土梁受弯试验表明OFBG-FRP筋可以监测混凝土梁的开裂和FRP筋与混凝土的滑移.在OFBG-FRP筋中埋置多个光纤传感器可以监测沿FRP筋长度方向的应变分布及混凝土与FRP筋发生滑移的位置.OFBG-FRP筋在混凝土结构中可以作为受力材料和传感器.     

马赫-曾德光纤传感器应变性能实验研究

构建了基于马赫-曾德干涉原理的新型光纤传感器,配合信号采集和数据分析部件组成应变检测系统.在内部粘有光纤传感器的玻璃纤维增强混凝土梁进行弯曲试验时,应用该系统检测了试件的应力应变状态,结果与同步电测数据相符,这说明马赫-曾德光纤传感器性能稳定,测量精度高,在工程结构中的应用前景良好.     

Gender differences in publication productivity in psychology in India

An analysis of gender differences in psychology in India provides quantitative and qualitative assessment of R&D output contributed by psychologists with the indication of the trend of growth, skewness, relatedness, co-authorship pattern of productivity.     

Metrology in Chemistry in Germany

The system for Metrology in Chemistry in Germany is described. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements. A dissemination mechanism employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD). They act as “multipliers” between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. Traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described     

Natural radioactivity in drinking water in private wells in Finland

Natural radioactivity in drinking water was determined in population-based random study of 472 private wells. The mean concentrations of (222)Rn, (226)Ra, (234)U, (238)U, (210)Pb and (210)Po in drilled wells were 460, 0.05, 0.35, 0.26, 0.04 and 0.05 Bq l(-1), and in wells dug in the soil were 50, 0.016, 0.02, 0.015, 0.013 and 0.007 Bq l(-1), respectively. Approximately 10% of the drilled wells exceeded a radon concentration of 1000 Bq l(-1) and 18% a uranium concentration of 15 microg l(-1). The mean annual effective dose from natural radionuclides for a drilled well user was 0.4 mSv and 0.05 mSv for a user of a well dug in the soil. The effective dose arising from (222)Rn was 75% of the total of all natural radionuclides for drilled well users. As regards long-lived radionuclides, (210)Po and (210)Pb caused the largest portion of the effective dose. The dose arising from (238)U, (234)U and (226)Ra was only 8% of the total of all natural radionuclides.     

Natural radioactivity in drinking water in private wells in Finland

Radiation Protection Dosimetry     

Optische in situ Schichtdickenmessung in Bedampfungsanlagen. Optical in situ film thickness monitoring in coating systems

Optical film thickness monitoring is more precise than crystal monitoring. The optical measurement makes use of the fact that the intensity of a monochromatic light beam which is reflected on a film will change periodically with increasing film thickness. The measurement is performed at an exchangeable test glass that is positioned beside the substrates and is therefore coated in the same way as the substrates. The accuracy of cut‐off is achieved by a “fit” of a theoretical curve shape to the measured values. Order filters are used to ensure that, at a certain wavelength, higher deflection orders do not influence the measurement when a monochromator grating is used.     

Spanish experience in education and training in radiation protection in medicine

In most of its publications, the International Commission on Radiological Protection has highlighted the importance of education and training in radiation protection (RP) for medical exposures. Spain, like other Member States of the European Union, has implemented the Directive and the Guidelines in the medical area. The purpose of this paper is to present the Spanish experience in RP education and training in medicine, the different objectives established according to professional levels, existing regulations and feedback obtained from various RP actions.     

Differences in coagulation in clotting of vascular access in hemodialysis patients

Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F₁₊₂) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F₁₊₂ levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis.