Sample records for stressed tlm measurement

  1. Numerical analysis in electromagnetics the TLM method

    Saguet, Pierre


    The aim of this book is to give a broad overview of the TLM (Transmission Line Matrix) method, which is one of the "time-domain numerical methods". These methods are reputed for their significant reliance on computer resources. However, they have the advantage of being highly general.The TLM method has acquired a reputation for being a powerful and effective tool by numerous teams and still benefits today from significant theoretical developments. In particular, in recent years, its ability to simulate various situations with excellent precision, including complex materials, has been

  2. Effectiveness of E-TLM in Learning Vocabulary in English

    Singaravelu, G.


    The study enlightens the effectiveness of e-TLM in Learning Vocabulary in English at standard VI. Objectives of the study: 1. To find out the problems of conventional TLM in learning vocabulary in English. 2. To find out the significant difference in achievement mean score between the pre test of control group and the post test of control group.…

  3. TLM modeling and system identification of optimized antenna structures

    N. Fichtner


    Full Text Available The transmission line matrix (TLM method in conjunction with the genetic algorithm (GA is presented for the bandwidth optimization of a low profile patch antenna. The optimization routine is supplemented by a system identification (SI procedure. By the SI the model parameters of the structure are estimated which is used for a reduction of the total TLM simulation time. The SI utilizes a new stability criterion of the physical poles for the parameter extraction.

  4. Fs-laser micro machining for μ-TLM resistivity test structures in photovoltaic TCO multilayers

    Krause, Stephan; Kaufmann, Kai; Lancaster, Kevin; Naumann, Volker; Großer, Stephan; Hagendorf, Christian


    In this work we developed a new approach for resistivity measurements based on fs laser micro machining of μ-TLM test structures. This method is applied to highly resistive interfacial and conductive bulk multilayer systems in photovoltaic TCO thin film devices. Resistivity data has been acquired by a new TLM based method at μm-dimensions (μ-TLM, patent pending, DE 102014211352.0). For this approach, isolating trenches are prepared in the µm range with reasonable effort using fs laser processing. The application of ultrashort pulses with a laser wavelength in the IR range (λ = 1.03 μm) allows selective removal of the top SnO2 layer of the TCO multilayer stack by a reduced thermal influence on the layers beneath and in the adjacent region of the laser trenches. Small effective optical penetration and ablation depth was achieved by an ultrafast thermal ablation mechanism via free carrier absorption at the interface of the SnO2/ITO layers. Therefore the risk of laser induced modification of the electric layer properties is negligible. The μ-TLM test structure results in highly accurate and reproducible resistivity data. Applied to SnO2/ITO/glass double layer stacks, the obtained resistivity values for the SnO2 interfacial layer (ρTO = 40.5 kΩμm) and for the indium tin oxide thin film (ρITO = 1.3 Ωμm) agree with reference data from four-point-probing and from literature.

  5. Residual-stress measurements

    Ezeilo, A.N.; Webster, G.A. [Imperial College, London (United Kingdom); Webster, P.J. [Salford Univ. (United Kingdom)


    Because neutrons can penetrate distances of up to 50 mm in most engineering materials, this makes them unique for establishing residual-stress distributions non-destructively. D1A is particularly suited for through-surface measurements as it does not suffer from instrumental surface aberrations commonly found on multidetector instruments, while D20 is best for fast internal-strain scanning. Two examples for residual-stress measurements in a shot-peened material, and in a weld are presented to demonstrate the attractive features of both instruments. (author).

  6. Preparation and activation of micro-arc oxidation films on a TLM titanium alloy

    Yu, S; Yu, Z T [Northwest Institute for Non-Ferrous Metal Research, Xi' an, 710016 (China)], E-mail:


    In order to improve the biocompatibility and surface activity of a TLM alloy, a layer of a porous TiO{sub 2} film was prepared by the micro-arc oxidation method on the surface, and then the NH{sup -}{sub 2} active group was introduced on the film by an activation treatment in an aminated solution. The phase identification and surface characteristics of the micro-arc oxidation films were characterized by XRD, XPS, SEM and EDS. The in vitro blood compatibility of the TLM alloy samples with and without surface modification was evaluated by contact angle tests, hemolysis tests and electrochemical tests. The results indicate that the biocompatibility and surface activity of the TLM alloy could be remarkably improved by surface modification of micro-arc oxidation and activation treatment.

  7. Preparation and activation of micro-arc oxidation films on a TLM titanium alloy

    Yu, S.; Yu, Z. T.


    In order to improve the biocompatibility and surface activity of a TLM alloy, a layer of a porous TiO2 film was prepared by the micro-arc oxidation method on the surface, and then the NH-2 active group was introduced on the film by an activation treatment in an aminated solution. The phase identification and surface characteristics of the micro-arc oxidation films were characterized by XRD, XPS, SEM and EDS. The in vitro blood compatibility of the TLM alloy samples with and without surface modification was evaluated by contact angle tests, hemolysis tests and electrochemical tests. The results indicate that the biocompatibility and surface activity of the TLM alloy could be remarkably improved by surface modification of micro-arc oxidation and activation treatment.

  8. Interferometric Measurement Of Residual Stress

    Danyluk, Steven; Andonian, A. T.


    Stress averaged through thickness of plate measured nondestructively. Theory of elasticity combined with laser interferometric technique into technique for measurement of residual stresses in solid objects - usually in thin, nominally-flat plates. Measurements particularly useful in inspection of wafers of single-crystal silicon for making solar cells or integrated circuits, because stresses remaining after crystal-growing process cause buckling or fracture. Used to predict deflections of plates caused by known applied loads under specified boundary condition, or to infer applied loads that cause known deflections. Also used to relate known deflections to residual stresses equivalent to stresses produced by fictitious applied loads.

  9. Electromechanical Apparatus Measures Residual Stress

    Chern, Engmin J.; Flom, Yury


    Nondestructive test exploits relationship between stress and eddy-current-probe resistance. Yields data on residual stress or strain in metal tension/compression specimen (stress or strain remaining in specimen when no stress applied from without). Apparatus is assembly of commercial equipment: tension-or-compression testing machine, eddy-current probe, impedance gain-and-phase analyzer measuring impedance of probe coil, and desktop computer, which controls other equipment and processes data received from impedance gain-and-phase analyzer.

  10. Triangular node for Transmission-Line Modeling (TLM) applied to bio-heat transfer.

    Milan, Hugo F M; Gebremedhin, Kifle G


    Transmission-Line Modeling (TLM) is a numerical method used to solve complex and time-domain bio-heat transfer problems. In TLM, rectangles are used to discretize two-dimensional problems. The drawback in using rectangular shapes is that instead of refining only the domain of interest, a large additional domain will also be refined in the x and y axes, which results in increased computational time and memory space. In this paper, we developed a triangular node for TLM applied to bio-heat transfer that does not have the drawback associated with the rectangular nodes. The model includes heat source, blood perfusion (advection), boundary conditions and initial conditions. The boundary conditions could be adiabatic, temperature, heat flux, or convection. A matrix equation for TLM, which simplifies the solution of time-domain problems or solves steady-state problems, was also developed. The predicted results were compared against results obtained from the solution of a simplified two-dimensional problem, and they agreed within 1% for a mesh length of triangular faces of 59µm±9µm (mean±standard deviation) and a time step of 1ms. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Protein fold recognition with a two-layer method based on SVM-SA, WP-NN and C4.5 (TLM-SNC).

    Zangooei, Mohammad Hossein; Jalili, Saeed


    The structural knowledge of protein is crucial in understanding its biological role. An effort is made to assign a fold to a given protein in a protein fold recognition problem. A computational Two-Layer Method (TLM) based on the Support Vector Machine (SVM), the Neural Network (NN) and the Decision Tree (C4.5) has been developed in this study for the assignment of a protein sequence to a folding class in SCOP. Prediction accuracy is measured on a dataset and the accuracy of the proposed method is very promising in comparison with other classification methods.

  12. Man-machine Integration Design and Analysis System (MIDAS) Task Loading Model (TLM) experimental and software detailed design report

    Staveland, Lowell


    This is the experimental and software detailed design report for the prototype task loading model (TLM) developed as part of the man-machine integration design and analysis system (MIDAS), as implemented and tested in phase 6 of the Army-NASA Aircrew/Aircraft Integration (A3I) Program. The A3I program is an exploratory development effort to advance the capabilities and use of computational representations of human performance and behavior in the design, synthesis, and analysis of manned systems. The MIDAS TLM computationally models the demands designs impose on operators to aide engineers in the conceptual design of aircraft crewstations. This report describes TLM and the results of a series of experiments which were run this phase to test its capabilities as a predictive task demand modeling tool. Specifically, it includes discussions of: the inputs and outputs of TLM, the theories underlying it, the results of the test experiments, the use of the TLM as both stand alone tool and part of a complete human operator simulation, and a brief introduction to the TLM software design.

  13. Neutron residual stress measurements in linepipe

    Law, Michael [ANTSO, PMB1 Menai, NSW, 2234 (Australia)]. E-mail:; Gnaepel-Herold, Thomas [Department of Materials Science and Engineering, NCNR and University of Maryland (United States); Luzin, Vladimir [Department of Materials Science and Engineering, NCNR and University of Maryland (United States); Bowie, Graham [cNCNR and State University of New York at Stoneybrook (United States): Blue Scope Steel (Australia)


    Residual stresses in gas pipelines are generated by manufacturing and construction processes and may affect the subsequent pipe integrity. In the present work, the residual stresses in eight samples of linepipe were measured by neutron diffraction. Residual stresses changed with some coating processes. This has special implications in understanding and mitigating stress corrosion cracking, a major safety and economic problem in some gas pipelines.

  14. Residual stress measurements in carbon steel

    Heyman, J. S.; Min, N.


    External dc magnetic field-induced changes in natural velocity of Rayleigh surface waves were measured in steel specimens under various stress conditions. The low field slopes of curves representing the fractional changes of natural velocity were proved to provide correct stress information in steels with different metallurgical properties. The slopes of curves under uniaxial compression, exceeding about one third of the yield stress, fell below zero in all the specimens when magnetized along the stress axis. The slopes under tension varied among different steels but remained positive in any circumstances. The stress effect was observed for both applied and residual stress. A physical interpretation of these results is given based on the stress-induced domain structure changes and the delta epsilon effect. Most importantly, it is found that the influence of detailed metallurgical properties cause only secondary effects on the obtained stress information.

  15. Experimental Measurement of In Situ Stress

    Tibbo, Maria; Milkereit, Bernd; Nasseri, Farzine; Schmitt, Douglas; Young, Paul


    The World Stress Map data is determined by stress indicators including earthquake focal mechanisms, in situ measurement in mining, oil and gas boreholes as well as the borehole cores, and geologic data. Unfortunately, these measurements are not only infrequent but sometimes infeasible, and do not provide nearly enough data points with high accuracy to correctly infer stress fields in deep mines around the world. Improvements in stress measurements of Earth's crust is fundamental to several industries such as oil and gas, mining, nuclear waste management, and enhanced geothermal systems. Quantifying the state of stress and the geophysical properties of different rock types is a major complication in geophysical monitoring of deep mines. Most stress measurement techniques involve either the boreholes or their cores, however these measurements usually only give stress along one axis, not the complete stress tensor. The goal of this project is to investigate a new method of acquiring a complete stress tensor of the in situ stress in the Earth's crust. This project is part of a comprehensive, exploration geophysical study in a deep, highly stressed mine located in Sudbury, Ontario, Canada, and focuses on two boreholes located in this mine. These boreholes are approximately 400 m long with NQ diameters and are located at depths of about 1300 - 1600 m and 1700 - 2000 m. Two borehole logging surveys were performed on both boreholes, October 2013 and July 2015, in order to perform a time-lapse analysis of the geophysical changes in the mine. These multi-parameter surveys include caliper, full waveform sonic, televiewer, chargeability (IP), and resistivity. Laboratory experiments have been performed on borehole core samples of varying geologies from each borehole. These experiments have measured the geophysical properties including elastic modulus, bulk modulus, P- and S-wave velocities, and density. The apparatus' used for this project are geophysical imaging cells capable

  16. Measurements for stresses in machine components

    Yakovlev, V F


    Measurements for Stresses in Machine Components focuses on the state of stress and strain of components and members, which determines the service life and strength of machines and structures. This book is divided into four chapters. Chapter I describes the physical basis of several methods of measuring strains, which includes strain gauges, photoelasticity, X-ray diffraction, brittle coatings, and dividing grids. The basic concepts of the electric strain gauge method for measuring stresses inside machine components are covered in Chapter II. Chapter III elaborates on the results of experim

  17. Bottom stress measurements on the inner shelf

    Sherwood, Christopher R.; Scully, Malcolm; Trowbridge, John


    Bottom stress shapes the mean circulation patterns, controls sediment transport, and influences benthic habitat in the coastal ocean. Accurate and precise measurements of bottom stress have proved elusive, in part because of the difficulty in separating the turbulent eddies that transport momentum from inviscid wave-induced motions. Direct covariance measurements from a pair of acoustic Doppler velocimeters has proved capable of providing robust estimates, so we designed a mobile platform coined the NIMBBLE for these measurements, and deployed two of them and two more conventional quadpods at seven sites on the inner shelf over a period of seven months. The resulting covariance estimates of stress and bottom roughness were lower than log-fit estimates, especially during calmer periods. Analyses of these data suggest the NIMBBLEs may provide an accurate and practical method for measuring bottom stress.

  18. Runtime Instrumentation of SystemC/TLM2 Interfaces for Fault Tolerance Requirements Verification in Software Cosimulation

    Antonio da Silva


    Full Text Available This paper presents the design of a SystemC transaction level modelling wrapping library that can be used for the assertion of system properties, protocol compliance, or fault injection. The library uses C++ virtual table hooks as a dynamic binary instrumentation technique to inline wrappers in the TLM2 transaction path. This technique can be applied after the elaboration phase and needs neither source code modifications nor recompilation of the top level SystemC modules. The proposed technique has been successfully applied to the robustness verification of the on-board boot software of the Instrument Control Unit of the Solar Orbiter’s Energetic Particle Detector.

  19. BlmB and TlmB provide resistance to the bleomycin family of antitumor antibiotics by N-acetylating metal-free bleomycin, tallysomycin, phleomycin, and zorbamycin.

    Coughlin, Jane M; Rudolf, Jeffrey D; Wendt-Pienkowski, Evelyn; Wang, Liyan; Unsin, Claudia; Galm, Ute; Yang, Dong; Tao, Meifeng; Shen, Ben


    The bleomycin (BLM) family of glycopeptide-derived antitumor antibiotics consists of BLMs, tallysomycins (TLMs), phleomycins (PLMs), and zorbamycin (ZBM). The self-resistant elements BlmB and TlmB, discovered from the BLM- and TLM-producing organisms Streptomyces verticillus ATCC15003 and Streptoalloteichus hindustanus E465-94 ATCC31158, respectively, are N-acetyltransferases that provide resistance to the producers by disrupting the metal-binding domain of the antibiotics required for activity. Although each member of the BLM family of antibiotics possesses a conserved metal-binding domain, the structural differences between each member, namely, the bithiazole moiety and C-terminal amine of BLMs, have been suggested to instill substrate specificity within BlmB. Here we report that BlmB and TlmB readily accept and acetylate BLMs, TLMs, PLMs, and ZBM in vitro but only in the metal-free forms. Kinetic analysis of BlmB and TlmB reveals there is no strong preference or rate enhancement for specific substrates, indicating that the structural differences between each member of the BLM family play a negligible role in substrate recognition, binding, or catalysis. Intriguingly, the zbm gene cluster from Streptomyces flavoviridis ATCC21892 does not contain an N-acetyltransferase, yet ZBM is readily acetylated by BlmB and TlmB. We subsequently established that S. flavoviridis lacks the homologue of BlmB and TlmB, and ZbmA, the ZBM-binding protein, alone is sufficient to provide ZBM resistance. We further confirmed that BlmB can indeed confer resistance to ZBM in vivo in S. flavoviridis, introduction of which into wild-type S. flavoviridis further increases the level of resistance.

  20. Flexible Micropost Arrays for Shear Stress Measurement

    Wohl, Christopher J.; Palmieri, Frank L.; Hopkins, John W.; Jackson, Allen M.; Connell, John W.; Lin, Yi; Cisotto, Alexxandra A.


    Increased fuel costs, heightened environmental protection requirements, and noise abatement continue to place drag reduction at the forefront of aerospace research priorities. Unfortunately, shortfalls still exist in the fundamental understanding of boundary-layer airflow over aerodynamic surfaces, especially regarding drag arising from skin friction. For example, there is insufficient availability of instrumentation to adequately characterize complex flows with strong pressure gradients, heat transfer, wall mass flux, three-dimensionality, separation, shock waves, and transient phenomena. One example is the acoustic liner efficacy on aircraft engine nacelle walls. Active measurement of shear stress in boundary layer airflow would enable a better understanding of how aircraft structure and flight dynamics affect skin friction. Current shear stress measurement techniques suffer from reliability, complexity, and airflow disruption, thereby compromising resultant shear stress data. The state-of-the-art for shear stress sensing uses indirect or direct measurement techniques. Indirect measurements (e.g., hot-wire, heat flux gages, oil interferometry, laser Doppler anemometry, small scale pressure drag surfaces, i.e., fences) require intricate knowledge of the studied flow, restrictive instrument arrangements, large surface areas, flow disruption, or seeding material; with smaller, higher bandwidth probes under development. Direct measurements involve strain displacement of a sensor element and require no prior knowledge of the flow. Unfortunately, conventional "floating" recessed components for direct measurements are mm to cm in size. Whispering gallery mode devices and Fiber Bragg Gratings are examples of recent additions to this type of sensor with much smaller (?m) sensor components. Direct detection techniques are often single point measurements and difficult to calibrate and implement in wind tunnel experiments. In addition, the wiring, packaging, and installation

  1. Measuring Interlayer Shear Stress in Bilayer Graphene

    Wang, Guorui; Dai, Zhaohe; Wang, Yanlei; Tan, PingHeng; Liu, Luqi; Xu, Zhiping; Wei, Yueguang; Huang, Rui; Zhang, Zhong


    Monolayer two-dimensional (2D) crystals exhibit a host of intriguing properties, but the most exciting applications may come from stacking them into multilayer structures. Interlayer and interfacial shear interactions could play a crucial role in the performance and reliability of these applications, but little is known about the key parameters controlling shear deformation across the layers and interfaces between 2D materials. Herein, we report the first measurement of the interlayer shear stress of bilayer graphene based on pressurized microscale bubble loading devices. We demonstrate continuous growth of an interlayer shear zone outside the bubble edge and extract an interlayer shear stress of 40 kPa based on a membrane analysis for bilayer graphene bubbles. Meanwhile, a much higher interfacial shear stress of 1.64 MPa was determined for monolayer graphene on a silicon oxide substrate. Our results not only provide insights into the interfacial shear responses of the thinnest structures possible, but also establish an experimental method for characterizing the fundamental interlayer shear properties of the emerging 2D materials for potential applications in multilayer systems.

  2. Neutron stress measurement of W-fiber reinforced Cu composite

    Nishida, M; Ikeuchi, Y; Minakawa, N


    Stress measurement methods using neutron and X-ray diffraction were examined by comparing the surface stresses with internal stresses in the continuous tungsten-fiber reinforced copper-matrix composite. Surface stresses were measured by X-ray stress measurement with the sin sup 2 psi method. Furthermore, the sin sup 2 psi method and the most common triaxal measurement method using Hooke's equation were employed for internal stress measurement by neutron diffraction. On the other hand, microstress distributions developed by the difference in the thermal expansion coefficients between these two phases were calculated by FEM. The weighted average strains and stresses were compared with the experimental results. The FEM results agreed with the experimental results qualitatively and confirmed the importance of the triaxial stress analysis in the neutron stress measurement. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  3. Towards ambulatory mental stress measurement from physiological parameters

    Wijsman, J.L.P; Vullers, Ruud; Polito, Salvatore; Agell, Carlos; Penders, Julien; Hermens, Hermanus J.

    Ambulatory mental stress monitoring requires longterm physiological measurements. This paper presents a data collection protocol for ambulatory recording of physiological parameters for stress measurement purposes. We present a wearable sensor system for ambulatory recording of ECG, EMG, respiration

  4. Towards ambulatory mental stress measurement from physiological parameters

    Wijsman, Jacqueline; Vullers, Ruud; Polito, Salvatore; Agell, Carlos; Penders, Julien; Hermens, Hermie


    Ambulatory mental stress monitoring requires longterm physiological measurements. This paper presents a data collection protocol for ambulatory recording of physiological parameters for stress measurement purposes. We present a wearable sensor system for ambulatory recording of ECG, EMG, respiration

  5. Residual Stress Determination from a Laser-Based Curvature Measurement

    Swank, William David; Gavalya, Rick Allen; Wright, Julie Knibloe; Wright, Richard Neil


    Thermally sprayed coating characteristics and mechanical properties are in part a result of the residual stress developed during the fabrication process. The total stress state in a coating/substrate is comprised of the quench stress and the coefficient of thermal expansion (CTE) mismatch stress. The quench stress is developed when molten particles impact the substrate and rapidly cool and solidify. The CTE mismatch stress results from a large difference in the thermal expansion coefficients of the coating and substrate material. It comes into effect when the substrate/coating combination cools from the equilibrated deposit temperature to room temperature. This paper describes a laser-based technique for measuring the curvature of a coated substrate and the analysis required to determine residual stress from curvature measurements. Quench stresses were determined by heating the specimen back to the deposit temperature thus removing the CTE mismatch stress. By subtracting the quench stress from the total residual stress at room temperature, the CTE mismatch stress was estimated. Residual stress measurements for thick (>1mm) spinel coatings with a Ni-Al bond coat on 304 stainless steel substrates were made. It was determined that a significant portion of the residual stress results from the quenching stress of the bond coat and that the spinel coating produces a larger CTE mismatch stress than quench stress.

  6. Measurement of residual stresses using fracture mechanics weight functions

    Fan, Y. [Bettis Atomic Power Laboratory, West Mifflin, PA (United States)


    A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed. (author)

  7. Analytical Investigation for In Situ Stress Measurement with Rheological Stress Recovery Method and Its Application

    Quansheng Liu


    Full Text Available In situ stress is one of the most important parameters in underground engineering. Due to the difficulty and weakness of current stress measurement methods in deep soft rock, a new one, rheological stress recovery (RSR method, to determine three-dimensional stress tensor is developed. It is supposed that rock stresses will recover gradually with time and can be measured by embedding transducers into the borehole. In order to explore the relationship between the measured recovery stress and the initial stress, analytical solutions are developed for the stress measurement process with RSR method in a viscoelastic surrounding rock. The results showed that the measured recovery stress would be more close to the initial stress if the rock mass has a better rheological property, and the property of grouting material should be close to that of rock mass. Then, the RSR method, as well as overcoring technique, was carried out to measure the in situ stresses in Pingdingshan Number 1 coal mines in Henan Province, China. The stress measurement results are basically in the same order, and the major principal stresses are approximately in the direction of NW-SE, which correlates well with the stress regime of Pingdingshan zone known from the tectonic movement history.

  8. Realtime 3D stress measurement in curing epoxy packaging

    Richter, Jacob; Hyldgård, A.; Birkelund, Karen;


    This paper presents a novel method to characterize stress in microsystem packaging. A circular p-type piezoresistor is implemented on a (001) silicon chip. We use the circular stress sensor to determine the packaging induced stress in a polystyrene tube filled with epoxy. The epoxy curing process...... is monitored by stress measurements. From the stress measurements we conclude that the epoxy cures in 8 hours at room temperature. We find the difference in in-plane normal stresses to be sigmaxx-sigmayy=6.7 MPa and (sigmaxx+sigmayy-0.4sigmazz)=232 MPa....

  9. Early Development of UVM based Verification Environment of Image Signal Processing Designs using TLM Reference Model of RTL

    Abhishek Jain


    Full Text Available With semiconductor industry trend of “smaller the better”, from an idea to a final product, more innovation on product portfolio and yet remaining competitive and profitable are few criteria which are culminating into pressure and need for more and more innovation for CAD flow, process management and project execution cycle. Project schedules are very tight and to achieve first silicon success is key for projects. This necessitates quicker verification with better coverage matrix. Quicker Verification requires early development of the verification environment with wider test vectors without waiting for RTL to be available. In this paper, we are presenting a novel approach of early development of reusable multi-language verification flow, by addressing four major activities of verification – 1. Early creation of Executable Specification 2. Early creation of Verification Environment 3. Early development of test vectors and 4. Better and increased Re-use of blocks Although this paper focuses on early development of UVM based Verification Environment of Image Signal Processing designs using TLM Reference Model of RTL, same concept can be extended for non-image signal processing designs.

  10. Measurements of residual stress in fracture mechanics coupons

    Prime, Michael B [Los Alamos National Laboratory; Hill, Michael R [U.C. DAVIS; Nav Dalen, John E [HILL ENGINEERING


    This paper describes measurements of residual stress in coupons used for fracture mechanics testing. The primary objective of the measurements is to quantify the distribution of residual stress acting to open (and/or close) the crack across the crack plane. The slitting method and the contour method are two destructive residual stress measurement methods particularly capable of addressing that objective, and these were applied to measure residual stress in a set of identically prepared compact tension (C(T)) coupons. Comparison of the results of the two measurement methods provides some useful observations. Results from fracture mechanics tests of residual stress bearing coupons and fracture analysis, based on linear superposition of applied and residual stresses, show consistent behavior of coupons having various levels of residual stress.

  11. Measuring type II stresses using 3DXRD

    Oddershede, Jette; Schmidt, Søren; Poulsen, Henning Friis;


    An algorithm is presented for characterization of the grain resolved (type II) stress states in a polycrystalline sample based on monochromatic X-ray diffraction data. The algorithm is a robust 12-parameter-per-grain fit of the centre-of-mass grain positions, orientations and stress tensors...

  12. Galvanic Skin Response as a Measure of Soldier Stress


    in the body have been used as an effective measure of stress, including social stress such as performance in front of an audience (Nater, La Marca ...Lake, CA, 1992. Nater, U. M.; La Marca , R.; Florin, L.; Moses, A.; Langhans, W.; Koller, M. M.; Ehlert, U. Stress-Induced Changes in Human

  13. Axillary temperature measurement: a less stressful alternative for hospitalised cats?

    Girod, M; Vandenheede, M; Farnir, F; Gommeren, K


    Rectal temperature measurement (RTM) can promote stress and defensive behaviour in hospitalised cats. The aim of this study was to assess if axillary temperature measurement (ATM) could be a reliable and less stressful alternative for these animals. In this prospective study, paired rectal and axillary temperatures were measured in 42 cats, either by a veterinarian or a student. To assess the impact of these procedures on the cat's stress state, their heart rate was checked and a cat stress score (CSS) was defined and graded from 1 (relaxed) to 5 (terrified). A moderate correlation was found between RTM and ATM (r=0.52; Pcats.

  14. Experimental Development of a Novel Stress Sensor for in situ Stress Measurement

    Polsky, Yarom [ORNL; Lance, Michael J [ORNL; Mattus, Catherine H [ORNL; Daniels, Ryan J [ORNL


    This paper will describe ongoing work to adapt a previously demonstrated method for measuring stress in ceramics to develop a borehole deployed in situ stress sensor. The method involves the use of a cementitious material which exhibits a strong piezo-spectroscopic stress response as a downhole stress gage. A description of the conceptual approach will be provided along with preliminary analysis and proof-of-concept laboratory results.

  15. The measurement of in situ stress using NQR/NMR

    Schempp, E.; Murdoch, J. B.; Klainer, S. M.


    The measurement of stress in rocks underground is a difficult but very important problem in mining engineering and in the design of underground waste repositories. The structural stability of any excavation is critically dependent on the stress distribution in the surrounding rock and its capability to bear the stress, which can build up to hundreds of atmospheres in deep mines. Because existing methods for the determination of stress have limitations, Lawrence Berkeley Laboratory (LBL) has been investigating the use of spectroscopic techniques - nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) - for rapid in situ measurements of three-dimensional stress in both salt and hard rock. Efforts in the past year have been directed toward computer simulation of boreholes stress patterns and NQR lineshapes, laboratory measurements on salt and aluminosilicates, and construction of a state-of-the-art pulsed NQR spectrometer.

  16. Measurment Of Residual Stress In Ferromagnetic Materials

    Namkung, Min; Yost, William T.; Kushnick, Peter W.; Grainger, John L.


    Magnetoacoustic (MAC) and magnetoacoustic emission (MAE) techniques combined to provide complete characterization of residual stresses in ferromagnetic structural materials. Combination of MAC and MAE techniques makes it possible to characterize residual tension and compression without being limited by surface conditions and unavailability of calibration standards. Significant in field of characterization of materials as well as detection of fatigue failure.

  17. Local residual stress measurements on nitride layers

    Mansilla, C.; Ocelik, V.; De Hosson, J. Th. M.


    In this work, local stresses in different nitrided maraging steel samples of high practical interest for industrial applications were studied through the so-called micro-slit milling method using a focused ion beam. The nitrogen concentration profiles were acquired by glow discharge optical emission

  18. Measurment Of Residual Stress In Ferromagnetic Materials

    Namkung, Min; Yost, William T.; Kushnick, Peter W.; Grainger, John L.


    Magnetoacoustic (MAC) and magnetoacoustic emission (MAE) techniques combined to provide complete characterization of residual stresses in ferromagnetic structural materials. Combination of MAC and MAE techniques makes it possible to characterize residual tension and compression without being limited by surface conditions and unavailability of calibration standards. Significant in field of characterization of materials as well as detection of fatigue failure.

  19. Investigations of some rock stress measuring techniques and the stress field in Norway

    Hanssen, Tor Harald


    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  20. Phase stress measurements in composite materials

    Akiniwa, Yoshiaki; Tanaka, Keisuke [Nagoya Univ. (Japan). School of Engineering


    Using an aluminum alloy composite containing 20 wt.% of SiC powder and an aluminum alloy itself, a phase stress under monoaxial tensile load was tested using x-ray and neutron methods, to compare both of them. For specimens, a 20 vol.% SiC powder reinforced aluminum alloy and an aluminum alloy itself were used. As a result, the following results could be obtained. Young`s modulus and Poisson ratio of the aluminum alloy itself using x-ray method were E=74.5 GPa and {nu}=0.312, respectively, and those using neutron method were E=75.3 GPa and {nu}=0.384, respectively. A relationship between loading stress and lattice strain of the aluminum alloy itself using neutron method was possible to approximate linearly by containing macroscopic plastic deformation region. The lattice strain of each phase in the composite increased proportionally with loading stress in its elastic region, but when remarkably increasing plastic deformation, the lattice strain decreased proportionally in aluminum phase and increased in SiC phase. (G.K.)

  1. Measuring depth profiles of residual stress with Raman spectroscopy

    Enloe, W.S.; Sparks, R.G.; Paesler, M.A.


    Knowledge of the variation of residual stress is a very important factor in understanding the properties of machined surfaces. The nature of the residual stress can determine a part`s susceptibility to wear deformation, and cracking. Raman spectroscopy is known to be a very useful technique for measuring residual stress in many materials. These measurements are routinely made with a lateral resolution of 1{mu}m and an accuracy of 0.1 kbar. The variation of stress with depth; however, has not received much attention in the past. A novel technique has been developed that allows quantitative measurement of the variation of the residual stress with depth with an accuracy of 10nm in the z direction. Qualitative techniques for determining whether the stress is varying with depth are presented. It is also demonstrated that when the stress is changing over the volume sampled, errors can be introduced if the variation of the stress with depth is ignored. Computer aided data analysis is used to determine the depth dependence of the residual stress.

  2. Stress measurement in thick plates using nonlinear ultrasonics

    Abbasi, Zeynab, E-mail:, E-mail:; Ozevin, Didem, E-mail:, E-mail: [University of Illinois at Chicago, Civil and Materials Engineering, 842 W Taylor Street ERF 2095, Chicago, IL 60607 (United States)


    In this paper the interaction between nonlinear ultrasonic characteristics and stress state of complex loaded thick steel plates using fundamental theory of nonlinear ultrasonics is investigated in order to measure the stress state at a given cross section. The measurement concept is based on phased array placement of ultrasonic transmitter-receiver to scan three angles of a given cross section using Rayleigh waves. The change in the ultrasonic data in thick steel plates is influenced by normal and shear stresses; therefore, three measurements are needed to solve the equations simultaneously. Different thickness plates are studied in order to understand the interaction of Rayleigh wave penetration depth and shear stress. The purpose is that as the thickness becomes smaller, the shear stress becomes negligible at the angled measurement. For thicker cross section, shear stress becomes influential if the depth of penetration of Rayleigh wave is greater than the half of the thickness. The influences of plate thickness and ultrasonic frequency on the identification of stress tensor are numerically studied in 3D structural geometry and Murnaghan material model. The experimental component of this study includes uniaxial loading of the plate while measuring ultrasonic wave at three directions (perpendicular, parallel and angled to the loading direction). Instead of rotating transmitter-receiver pair for each test, a device capable of measuring the three angles is designed.

  3. Stress measurement in thick plates using nonlinear ultrasonics

    Abbasi, Zeynab; Ozevin, Didem


    In this paper the interaction between nonlinear ultrasonic characteristics and stress state of complex loaded thick steel plates using fundamental theory of nonlinear ultrasonics is investigated in order to measure the stress state at a given cross section. The measurement concept is based on phased array placement of ultrasonic transmitter-receiver to scan three angles of a given cross section using Rayleigh waves. The change in the ultrasonic data in thick steel plates is influenced by normal and shear stresses; therefore, three measurements are needed to solve the equations simultaneously. Different thickness plates are studied in order to understand the interaction of Rayleigh wave penetration depth and shear stress. The purpose is that as the thickness becomes smaller, the shear stress becomes negligible at the angled measurement. For thicker cross section, shear stress becomes influential if the depth of penetration of Rayleigh wave is greater than the half of the thickness. The influences of plate thickness and ultrasonic frequency on the identification of stress tensor are numerically studied in 3D structural geometry and Murnaghan material model. The experimental component of this study includes uniaxial loading of the plate while measuring ultrasonic wave at three directions (perpendicular, parallel and angled to the loading direction). Instead of rotating transmitter-receiver pair for each test, a device capable of measuring the three angles is designed.

  4. Comparing measured with simulated vertical soil stress under vehicle load

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan;

    in the soil profile at 0.3, 0.5 and 0.7 m depth was measured during wheeling at field capacity on five soils (13-66% clay). Stress propagation was then simulated with the semi-analytical model, using vertical stress at 0.1 m depth estimated from tyre characteristics as upper boundary condition, and v...

  5. Comparing measured with simulated vertical soil stress under vehicle load

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan

    in the soil profile at 0.3, 0.5 and 0.7 m depth was measured during wheeling at field capacity on five soils (13-66% clay). Stress propagation was then simulated with the semi-analytical model, using vertical stress at 0.1 m depth estimated from tyre characteristics as upper boundary condition, and v...

  6. Transient water stress in a vegetation canopy - Simulations and measurements

    Carlson, Toby N.; Belles, James E.; Gillies, Robert R.


    Consideration is given to observational and modeling evidence of transient water stress, the effects of the transpiration plateau on the canopy radiometric temperature, and the factors responsible for the onset of the transpiration plateau, such as soil moisture. Attention is also given to the point at which the transient stress can be detected by remote measurement of surface temperature.

  7. Measurement of spatial stress gradients near grain boundaries

    Basu, Indranil; Ocelík, Vaclav; De Hosson, Jeff Th M.


    A correlative method based on electron back scattered diffraction and focused ion-beam–digital image correlation slit milling technique was used to quantitatively determine spatially resolved stress profiles in the vicinity of grain boundaries in pure titanium. Measured local stress gradients were

  8. 3D Tyre/Road pavement contact stress measurements

    De Beer, Morris


    Full Text Available The CSIR’s proprietary Stress-in-Motion (SIM) measurements provide rational descriptions of 1D, 2D and 3D tyre/road pavement stresses for: Road pavement design testing and evaluation, as well as tyre design, testing and evaluation....

  9. Measuring Stress and Ability to Recover from Stress with Salivary Alpha-Amylase Levels


    to be resilient. So what is salivary alpha amylase ? To start, an amylase is enzyme in the body that hydrolyzes starch (breaks it down) into...Ability to Recover from Stress with Salivary α- Amylase Levels Authors Brandon L. Mulrine Michael F. Sheehan Lolita M. Burrell Michael...TITLE AND SUBTITLE Measuring Stress and Ability to Recover from Stress with Salivary Alpha Amylase Levels 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  10. High precision stress measurements in semiconductor structures by Raman microscopy

    Uhlig, Benjamin


    Stress in silicon structures plays an essential role in modern semiconductor technology. This stress has to be measured and due to the ongoing miniaturization in today's semiconductor industry, the measuring method has to meet certain requirements. The present thesis deals with the question how Raman spectroscopy can be used to measure the state of stress in semiconductor structures. In the first chapter the relation between Raman peakshift and stress in the material is explained. It is shown that detailed stress maps with a spatial resolution close to the diffraction limit can be obtained in structured semiconductor samples. Furthermore a novel procedure, the so called Stokes-AntiStokes-Difference method is introduced. With this method, topography, tool or drift effects can be distinguished from stress related influences in the sample. In the next chapter Tip-enhanced Raman Scattering (TERS) and its application for an improvement in lateral resolution is discussed. For this, a study is presented, which shows the influence of metal particles on the intensity and localization of the Raman signal. A method to attach metal particles to scannable tips is successfully applied. First TERS scans are shown and their impact on and challenges for high resolution stress measurements on semiconductor structures is explained. (orig.)

  11. Ultrasonic measurement of residual stress in shot peened aluminum alloy

    Lavrentyev, Anton I.; Veronesi, William A.


    Shot peening is a well-known method for extending the fatigue life of metal components by introducing compressive residual stresses near their surfaces. The capability to non-destructively evaluate the near surface residual stress would greatly aid the assurance of proper fatigue life in shot-peened components. This paper addresses issues encountered in near-surface residual stress measurement by an ultrasonic surface wave method. In this method, a variation of ultrasonic surface wave speed with shot peening intensity is measured. Since the effective wave penetration depth inversely related to the excitation frequency, by making measurements at different frequencies, the method has the potential to provide the stress-depth profile. Experiments were conducted on aluminum specimens (alloy 7075-T7351) peened within the Almen peening intensity from 4A-16A. Several factors were found to contribute to the measured responses: surface roughness, near surface texture change, dislocation density increase and residual stress. In this paper, the contributions of residual stress, dislocation density and surface roughness to the overall effect are separately estimated. It is shown that the experimentally observed velocity change in shot peened samples is dominated by the effect of surface roughness while the role of residual stress is much smaller.

  12. Measuring stress variation with depth using Barkhausen signals

    Kypris, O.; Nlebedim, I. C.; Jiles, D. C.


    Magnetic Barkhausen noise analysis (BNA) is an established technique for the characterization of stress in ferromagnetic materials. An important application is the evaluation of residual stress in aerospace components, where shot-peening is used to strengthen the part by inducing compressive residual stresses on its surface. However, the evaluation of the resulting stress-depth gradients cannot be achieved by conventional BNA methods, where signals are interpreted in the time domain. The immediate alternative of using x-ray diffraction stress analysis is less than ideal, as the use of electropolishing to remove surface layers renders the part useless after inspection. Thus, a need for advancing the current BNA techniques prevails. In this work, it is shown how a parametric model for the frequency spectrum of Barkhausen emissions can be used to detect variations of stress along depth in ferromagnetic materials. Proof of concept is demonstrated by inducing linear stress-depth gradients using four-point bending, and fitting the model to the frequency spectra of measured Barkhausen signals, using a simulated annealing algorithm to extract the model parameters. Validation of our model suggests that in bulk samples the Barkhausen frequency spectrum can be expressed by a multi-exponential function with a dependence on stress and depth. One practical application of this spectroscopy method is the non-destructive evaluation of residual stress-depth profiles in aerospace components, thus helping to prevent catastrophic failures.

  13. An ultrasonic technique for measuring stress in fasteners

    Stevens, K. J.; Day, P.; Byron, D.


    High temperature bolting alloys are extensively used in the thermal power generation industry as for example, reheat ESV and Governor valve studs. Remnant life assessment methodologies and plant maintenance procedures require the monitoring of the operational stress levels in these fasteners. Some conventional ultrasonic techniques require longitudinal wave measurements to be undertaken when the nut on the bolt is loosened and then re-tightened. Other techniques use a combination of shear waves and longitudinal waves. In this paper, the problems and pitfalls associated with various ultrasonic techniques for measuring stress in bolts, is discussed. An ultrasonic technique developed for measuring the stress in Durehete 1055 bolts is presented. Material from a textured rolled bar has been used as a test bed in the development work. The technique uses shear wave birefringence and compression waves at several frequencies to measure texture, fastener length and the average stress. The technique was developed by making ultrasonic measurements on bolts tensioned in universal testing machines and a hydraulic nut. The ultrasonic measurements of residual stress have been checked against strain gauge measurements. The Durehete bolts have a hollow cylinder geometry of restricted dimensions, which significantly alters compression and shear wave velocities from bulk values and introduces hoop stresses which can be measured by rotating the polarization of the shear wave probe. Modelling of the experimental results has been undertaken using theories for the elastic wave propagation through waveguides. The dispersion equations allow the velocity and length of the fastener to be measured ultrasonically in some situations where the length of the fastener can not be measured directly with a vernier caliper or micrometer and/or where it is undesirable to loosen nuts to take calibration readings of the shear and compression wave velocities.

  14. Buried wire gage for wall shear stress measurements

    Murthy, V. S.; Rose, W. C.


    A buried wire gage for measuring wall shear stress in fluid flow was studied and further developed. Several methods of making this relatively new type of gage were examined to arrive at a successful technique that is well-suited for wind-tunnel testing. A series of measurements was made to demonstrate the adequacy of a two-point calibration procedure for these gages. The buried wire gage is also demonstrated to be ideally suited for quantitative measurement of wall shear stress in wind-tunnel testing.

  15. Measuring occupational stress: development of the pressure management indicator.

    Williams, S; Cooper, C L


    The study of occupational stress is hindered by the lack of compact and comprehensive standardized measurement tools. The Pressure Management Indicator (PMI) is a 120-item self-report questionnaire developed from the Occupational Stress Indicator (OSI). The PMI is more reliable, more comprehensive, and shorter than the OSI. It provides an integrated measure of the major dimensions of occupational stress. The outcome scales measure job satisfaction, organizational satisfaction, organizational security, organizational commitment, anxiety--depression, resilience, worry, physical symptoms, and exhaustion. The stressor scales cover pressure from workload, relationships, career development, managerial responsibility, personal responsibility, home demands, and daily hassles. The moderator variables measure drive, impatience, control, decision latitude, and the coping strategies of problem focus, life work balance, and social support.

  16. Measuring wind and stress under tropical cyclones with scatterometer

    Liu, W. Timothy


    Ocean surface stress, the turbulent transport of momentum, is largely derived from wind through a drag coefficient. In tropical cyclones (TC), scatterometers have difficulty in measuring strong wind and there is large uncertainty in the drag coefficient. We postulate that the microwave backscatter from ocean surface roughness, which is in equilibrium with local stress, does not distinguish weather systems. The reduced sensitivity of scatterometer wind retrieval algorithm under the strong wind is an air-sea interaction problem that is caused by a change in the behavior of the drag coefficient and not a sensor problem. Under this assumption, we applied a stress retrieval algorithm developed over a moderate wind range to retrieve stress under the strong winds of TCs. Over a moderate wind range, the abundant wind measurements and more established drag coefficient value allow sufficient stress data to be computed from wind to develop a stress retrieval algorithm for the scatterometer. Using unprecedented large amount of stress retrieved from the scatterometer coincident with strong winds in TC, we showed that the drag coefficient decreases with wind speed at a much steeper rate than previously revealed, for wind speeds over 25 m/s. The result implies that the ocean applies less drag to inhibit TC intensification and the TC causes less ocean mixing and surface cooling than previous studies indicated. With continuous and extensive coverage from constellations of scatterometers for several decades, the impact of tropical cyclones on the ocean and the feedback from the ocean are examined.

  17. Residual stress measurement in silicon sheet by shadow moire interferometry

    Kwon, Y.; Danyluk, S.; Bucciarelli, L.; Kalejs, J. P.


    A shadow moire interferometry technique has been developed to measure residual strain in thin silicon sheet. The curvature of a segment of sheet undergoing four-point bending is analyzed to include the applied bending moments, the in-plane residual stresses, and the 'end effect' of the sheet since it is of finite length. The technique is applied to obtain residual stress distributions for silicon sheet grown by the edge-defined film-fed growth technique.

  18. Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer


    P. N., Singh, P. P., and Bhattacharya, B., “Determination of Activation Energy of Relaxation Events in Composite Solid Propellants by Dynamic...Article 3. DATES COVERED (From - To) 04 August 2016 – 29 March 2017 4. TITLE AND SUBTITLE Measuring Propellant Stress Relaxation Modulus Using Dynamic...ERC 14. ABSTRACT A method for determining the stress relaxation master curve of solid rocket propellants was developed. The propellant was tested in

  19. Molecular force sensors to measure stress in cells

    Prabhune, Meenakshi; Rehfeldt, Florian; Schmidt, Christoph F.


    Molecularly generated forces are essential for most activities of biological cells, but also for the maintenance of steady state or homeostasis. To quantitatively understand cellular dynamics in migration, division, or mechanically guided differentiation, it will be important to exactly measure stress fields within the cell and the extracellular matrix. Traction force microscopy and related techniques have been established to determine the stress transmitted from adherent cells to their substrates. However, different approaches are needed to directly assess the stress generated inside the cell. This has recently led to the development of novel molecular force sensors. In this topical review, we briefly mention methods used to measure cell-external forces, and then summarize and explain different designs for the measurement of cell-internal forces with their respective advantages and disadvantages.

  20. Normal stress measurement via image analysis of interfacial deformation

    Lowry, Brian; Höpfl, Wolfgang


    The first coefficient of normal stress in polymer solutions is determined via image analysis. The method measures pointwise normal stresses along a sheared liquid-liquid interface. In the case of a steady rotating liquid bridge, the deformation of the interface is strictly due to normal stress swelling effects. In our experiments, a cylindrical liquid bridge of polystyrene solution rotates in a cylindrical bath filled with a glycerol-water solution of similar density. The shape of the interface and the jump in normal stress across the interface are determined using pressure-stress image analysis (P-SIA) from high resolution digital images. The stress resolution is better than 0.1 Pa at the free interface. The polystyrene solution exhibits a normal stress at the interface which grows with the square of the rotation rate. This effect is absent for Newtonian liquids, and is in excellent agreement with the ideal low shear behaviour of polymer solutions. Small density differences between the liquids are taken into consideration, showing that centrifugal effects are negligible. This method is potentially an excellent alternative to classical rheometry at low shear rates.

  1. Measurement of probability distributions for internal stresses in dislocated crystals

    Wilkinson, Angus J.; Tarleton, Edmund; Vilalta-Clemente, Arantxa; Collins, David M. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Jiang, Jun; Britton, T. Benjamin [Department of Materials, Imperial College London, Royal School of Mines, Exhibition Road, London SW7 2AZ (United Kingdom)


    Here, we analyse residual stress distributions obtained from various crystal systems using high resolution electron backscatter diffraction (EBSD) measurements. Histograms showing stress probability distributions exhibit tails extending to very high stress levels. We demonstrate that these extreme stress values are consistent with the functional form that should be expected for dislocated crystals. Analysis initially developed by Groma and co-workers for X-ray line profile analysis and based on the so-called “restricted second moment of the probability distribution” can be used to estimate the total dislocation density. The generality of the results are illustrated by application to three quite different systems, namely, face centred cubic Cu deformed in uniaxial tension, a body centred cubic steel deformed to larger strain by cold rolling, and hexagonal InAlN layers grown on misfitting sapphire and silicon carbide substrates.

  2. Neutron diffraction facility for internal stress measurements at JAERI

    Tsuchiya, Yoshinori; Minakawa, Nobuaki; Morii, Yukio [Japan Atomic Energy Research Inst., Tokyo (Japan)


    The Neutron Diffractometer for Residual Stress Analysis (RESA) is a two axis type neutron diffractometer with a goniometer controllable to specimen position in high precision for spatial distribution measurement of residual stress and with one- and zero-dimensional detectors, and has a characteristics of providing a pin-hole type neutron ray diaphragm to obtain local informations of the specimen. It is elucidated from the reported examples that the RESA in JAERI has a capacity of sufficient detection to a local strain with 10{sup -3} to 10{sup -4}. The residual stress measurement in JAERI is just in beginning state, and has many necessities to do a lot of trial measurements on various materials in future. And, when finishing the construction of pulsed neutron source under planning in JAERI, it can be expected to realize a neutron intensity of more than one hundred for the residual stress measurement and to construct a powerful measurement instrument in combination with introduction of testing method for TOF. (G.K.)

  3. Improving Earthquake Stress Drop Measurements - What can we Really Resolve?

    Abercrombie, R. E.; Bannister, S. C.; Fry, B.; Ruhl, C. J.; Kozlowska, M.


    Earthquake stress drop is fundamental to understanding the physics of the rupture process. Although it is superficially simple to calculate an estimate of stress drop from the corner frequency of the radiated spectrum, it is much harder to be certain that measurements are reliable and accurate. The same is true of other measurements of stress drop and radiated energy. The large number of studies of earthquake stress drop, the high variability in results (~0.1-100 MPa), the large uncertainties, and the ongoing scaling controversy are evidence for this. We investigate the resolution and uncertainties of stress drops calculated using an empirical Green's function (EGF) approach. Earthquakes in 3 sequences at Parkfield, California are recorded by multiple borehole stations and have abundant smaller earthquakes to use as EGFs (Abercrombie, 2014). The earthquakes in the largest magnitude cluster (M~2.1) exhibit clear temporal variation of stress drop. Independent studies obtained a similar pattern implying that it is resolvable for these well-recorded, simple sources. The borehole data reveal a similar temporal pattern for another sequence, not resolvable in an earlier study using surface recordings. The earthquakes in the third sequence have complex sources; corner frequency measurements for this sequence are highly variable and poorly resolved. We use the earthquakes in the first cluster to quantify the uncertainties likely to arise in less optimal settings. The limited signal bandwidth and the quality of the EGF assumption are major sources of error. Averaging across multiple stations improves the resolution, as does using multiple good EGFs (Abercrombie, 2015). We adapt the approach to apply to larger data sets. We focus on New Zealand, with the aim of resolving stress drop variability in a variety of tectonic settings. We investigate stacking over stations and multiple EGFs, and compare earthquakes (M~3-6) from both the overlying and the subducting plates.

  4. The Acute Effect of Aerobic Exercise on Measures of Stress.

    Fort, Inza L.; And Others

    The immediate response of stress to aerobic exercise was measured by utilizing the Palmar Sweat Index (PSI) and the State-Trait Anxiety Inventory (STAI). Forty subjects (20 male and 20 female) from the ages of 18-30 sustained a single bout of aerobic activity for 30 minutes at 60 percent of their maximum heart rate. Pre-treatment procedures…

  5. Principles of the measurement of residual stress by neutron diffraction

    Webster, G.A.; Ezeilo, A.N. [Imperial Coll. of Science and Technology, London (United Kingdom). Dept. of Mechanical Engineering


    The presence of residual stresses in engineering components can significantly affect their load carrying capacity and resistance to fracture. In order to quantify their effect it is necessary to know their magnitude and distribution. Neutron diffraction is the most suitable method of obtaining these stresses non-destructively in the interior of components. In this paper the principles of the technique are described. A monochromatic beam of neutrons, or time of flight measurements, can be employed. In each case, components of strain are determined directly from changes in the lattice spacings between crystals. Residual stresses can then be calculated from these strains. The experimental procedures for making the measurements are described and precautions for achieving reliable results discussed. These include choice of crystal planes on which to make measurements, extent of masking needed to identify a suitable sampling volume, type of detector and alignment procedure. Methods of achieving a stress free reference are also considered. A selection of practical examples is included to demonstrate the success of the technique. (author) 14 figs., 1 tab., 18 refs.

  6. A Hydraulic Stress Measurement System for Deep Borehole Investigations

    Ask, Maria; Ask, Daniel; Cornet, Francois; Nilsson, Tommy


    Luleå University of Technology (LTU) is developing and building a wire-line system for hydraulic rock stress measurements, with funding from the Swedish Research Council and Luleå University of Technology. In this project, LTU is collaborating with University of Strasbourg and Geosigma AB. The stress state influences drilling and drillability, as well as rock mass stability and permeability. Therefore, knowledge about the state of in-situ stress (stress magnitudes, and orientations) and its spatial variation with depth is essential for many underground rock engineering projects, for example for underground storage of hazardous material (e.g. nuclear waste, carbon dioxide), deep geothermal exploration, and underground infrastructure (e.g. tunneling, hydropower dams). The system is designed to conduct hydraulic stress testing in slim boreholes. There are three types of test methods: (1) hydraulic fracturing, (2) sleeve fracturing and (3) hydraulic testing of pre-existing fractures. These are robust methods for determining in situ stresses from boreholes. Integration of the three methods allows determination of the three-dimensional stress tensor and its spatial variation with depth in a scientific unambiguously way. The stress system is composed of a downhole and a surface unit. The downhole unit consists of hydraulic fracturing equipment (straddle packers and downhole imaging tool) and their associated data acquisition systems. The testing system is state of the art in several aspects including: (1) Large depth range (3 km), (2) Ability to test three borehole dimensions (N=76 mm, H=96 mm, and P=122 mm), (3) Resistivity imager maps the orientation of tested fracture; (4) Highly stiff and resistive to corrosion downhole testing equipment; and (5) Very detailed control on the injection flow rate and cumulative volume is obtained by a hydraulic injection pump with variable piston rate, and a highly sensitive flow-meter. At EGU General Assembly 2017, we would like to

  7. Linear and nonlinear modulus surfaces in stress space, from stress-strain measurements on Berea sandstone

    M. Boudjema


    Full Text Available The elastic response of many rocks to quasistatic stress changes is highly nonlinear and hysteretic, displaying discrete memory. Rocks also display unusual nonlinear response to dynamic stress changes. A model to describe the elastic behavior of rocks and other consolidated materials is called the Preisach-Mayergoyz (PM space model. In contrast to the traditional analytic approach to stress-strain, the PM space picture establishes a relationship between the quasistatic data and a number density of hysteretic mesoscopic elastic elements in the rock. The number density allows us to make quantitative predictions of dynamic elastic properties. Using the PM space model, we analyze a complex suite of quasistatic stress-strain data taken on Berea sandstone. We predict a dynamic bulk modulus and a dynamic shear modulus surface as a function of mean stress and shear stress. Our predictions for the dynamic moduli compare favorably to moduli derived from time of flight measurements. We derive a set of nonlinear elastic constants and a set of constants that describe the hysteretic behavior of the sandstone.

  8. Raman microprobe measurements of stress in ion implanted materials

    Nugent, K.W.; Prawer, S.; Weiser, P.S.; Dooley, S.P. [Melbourne Univ., Parkville, VIC (Australia). School of Physics


    Raman microprobe measurements of ion implanted diamond and silicon have shown significant shifts in the Raman line due to stresses in the materials. The Raman line shifts to higher energy if the stress is compressive and to lower energy for tensile stress{sup 1}. The silicon sample was implanted in a 60 {mu}m square with 2.56 x 10{sup 17} ions per square centimeter of 2 MeV Helium. This led to the formation of raised squares with the top 370mm above the original surface. In Raman studies of silicon using visible light, the depth of penetration of the laser beam into the sample is much less than one micron. It was found that the Raman line is due to the silicon overlying the damage region. The diamond sample was implanted with 2 x 10{sup 15} ions per square centimeter of 2.8 MeV carbon. It was concluded that the Raman spectrum could provide information concerning both the magnitude and the direction of stress in an ion implanted sample. It was possible in some cases to determine whether the stress direction is parallel or perpendicular to the sample surface. 1 refs., 2 figs.

  9. Stress Rupture Life Reliability Measures for Composite Overwrapped Pressure Vessels

    Murthy, Pappu L. N.; Thesken, John C.; Phoenix, S. Leigh; Grimes-Ledesma, Lorie


    Composite Overwrapped Pressure Vessels (COPVs) are often used for storing pressurant gases onboard spacecraft. Kevlar (DuPont), glass, carbon and other more recent fibers have all been used as overwraps. Due to the fact that overwraps are subjected to sustained loads for an extended period during a mission, stress rupture failure is a major concern. It is therefore important to ascertain the reliability of these vessels by analysis, since the testing of each flight design cannot be completed on a practical time scale. The present paper examines specifically a Weibull statistics based stress rupture model and considers the various uncertainties associated with the model parameters. The paper also examines several reliability estimate measures that would be of use for the purpose of recertification and for qualifying flight worthiness of these vessels. Specifically, deterministic values for a point estimate, mean estimate and 90/95 percent confidence estimates of the reliability are all examined for a typical flight quality vessel under constant stress. The mean and the 90/95 percent confidence estimates are computed using Monte-Carlo simulation techniques by assuming distribution statistics of model parameters based also on simulation and on the available data, especially the sample sizes represented in the data. The data for the stress rupture model are obtained from the Lawrence Livermore National Laboratories (LLNL) stress rupture testing program, carried out for the past 35 years. Deterministic as well as probabilistic sensitivities are examined.

  10. Wall shear stress measurements using a new transducer

    Vakili, A. D.; Wu, J. M.; Lawing, P. L.


    A new instrument has been developed for direct measurement of wall shear stress. This instrument is simple and symmetric in design with small moving mass and no internal friction. Features employed in the design of this instrument eliminate most of the difficulties associated with the traditional floating element balances. Vibration problems associated with the floating element skin friction balances have been found to be minimized by the design features and optional damping provided. The unique design of this instrument eliminates or reduces the errors associated with conventional floating-element devices: such as errors due to gaps, pressure gradient, acceleration, heat transfer and temperature change. The instrument is equipped with various sensing systems and the output signal is a linear function of the wall shear stress. Measurement made in three different tunnels show good agreement with theory and data obtained by the floating element devices.

  11. Mechanical Stress Measurement During Thin-Film Fabrication

    Broadway, David M. (Inventor)


    A method and system are provided for determining mechanical stress experienced by a film during fabrication thereof on a substrate positioned in a vacuum deposition chamber. The substrate's first surface is disposed to have the film deposited thereon and the substrate's opposing second surface is a specular reflective surface. A portion of the substrate is supported. An optical displacement sensor is positioned in the vacuum deposition chamber in a spaced-apart relationship with respect to a portion of the substrate's second surface. During film deposition on the substrate's first surface, displacement of the portion of the substrate's second surface is measured using the optical displacement sensor. The measured displacement is indicative of a radius of curvature of the substrate, and the radius of curvature is indicative of mechanical stress being experienced by the film.

  12. The Difficult Patient Stress Scale: a new instrument to measure interpersonal stress in nursing.

    Santamaria, N


    This study describes the development of the Difficult Patient Stress Scale, an instrument designed to investigate the stress that nurses experience when they are involved in interpersonal conflict with patients. The DPSS is based on the theoretical conceptualization of stress proposed by DeLongis, Lazarus and Folkman and on the personality theory of Individual Psychology. The DPSS utilises visual analog scales to measure nurses' responses to hypothetical scenarios that present typical, difficult nurse-patient situations. The DPSS has been tested over a period of two years with 228 nurses and the results to date indicate that it is valid, reliable and suitable for use in the clinical environment. It is proposed that it may provide a useful instrument for exploring the impact and frequency of interpersonal stressors in nursing and may assist in the development of educational programs to better equip nurses to deal with interpersonal nurse-patient conflict.

  13. Developments in wireline in-situ rock stress measurement

    Pedroso, Carlos [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Canas, Jesus A.; Holzberg, Bruno; Gmach, Helmut [Schlumberger Servicos de Petroleo Ltda., Rio de Janeiro, RJ (Brazil)


    This paper presents recent developments of in-situ stress measurements with wireline tools. The stress measurements are based on the micro hydraulic techniques that can be initialized when an interval is pressurized by pumping fluid until a tensile fracture begins or by packers fracturing (sleeve fracturing). Ultrasonic and Micro-resistivity borehole image logs (before and after the testes) are used as a complement, in order to observe the fractures created by the tests, evaluating the mechanical behavior of the formation. An offshore case study is presented, where shales and tight sandstones at depths deeper than 4500 meters depth were successfully evaluated. A workflow to succeed on stress measurements on such environments is proposed, what includes a planning phase: where breakdown pressures ranges are estimated and compared with the capacity of the tools, a Real Time Monitoring phase, where a decision tree is proposed to help on quick decisions while testing, and an interpretation phase, where appropriate techniques are indicated to evaluate the results. Also, the paper presents the main operational needs to succeed on such environments. Basically, such tests require an entirely software controlled, motorized and modular design tool consisting of dual packer (DP), pump out and flow control modules (Figure 1). These modules were upgraded for the present environment: conditions such as temperatures above 300 deg F, formation pressures above 10,000 psia, very low formation permeability, high pressure differential need and oil based mud (OBM) environment. (author)

  14. Comet assay as an indirect measure of systemic oxidative stress.

    Fang, Lei; Neutzner, Albert; Turtschi, Stephanie; Flammer, Josef; Mozaffarieh, Maneli


    Higher eukaryotic organisms cannot live without oxygen; yet, paradoxically, oxygen can be harmful to them. The oxygen molecule is chemically relatively inert because it has two unpaired electrons located in different pi * anti-bonding orbitals. These two electrons have parallel spins, meaning they rotate in the same direction about their own axes. This is why the oxygen molecule is not very reactive. Activation of oxygen may occur by two different mechanisms; either through reduction via one electron at a time (monovalent reduction), or through the absorption of sufficient energy to reverse the spin of one of the unpaired electrons. This results in the production of reactive oxidative species (ROS). There are a number of ways in which the human body eliminates ROS in its physiological state. If ROS production exceeds the repair capacity, oxidative stress results and damages different molecules. There are many different methods by which oxidative stress can be measured. This manuscript focuses on one of the methods named cell gel electrophoresis, also known as "comet assay" which allows measurement of DNA breaks. If all factors known to cause DNA damage, other than oxidative stress are kept constant, the amount of DNA damage measured by comet assay is a good parameter of oxidative stress. The principle is simple and relies upon the fact that DNA molecules are negatively charged. An intact DNA molecule has such a large size that it does not migrate during electrophoresis. DNA breaks, however, if present result in smaller fragments which move in the electrical field towards the anode. Smaller fragments migrate faster. As the fragments have different sizes the final result of the electrophoresis is not a distinct line but rather a continuum with the shape of a comet. The system allows a quantification of the resulting "comet" and thus of the DNA breaks in the cell.

  15. Residual Stress Measurements After Proof and Flight: ETP-0403

    Webster, Ronald L..


    The intent of this testing was to evaluate the residual stresses that occur in and around the attachment details of a case stiffener segment that has been subjected to flight/recovery followed by proof loading. Not measured in this test were stresses relieved at joint disassembly due to out-of-round and interference effects, and those released by cutting the specimens out of the case segment. The test article was lightweight case stiffener segment 1U50715, S/N L023 which was flown in the forward stiffener position on flight SRM 14A and in the aft position on flight SRM24A. Both of these flights were flown with the 3 stiffener ring configuration. Stiffener L023 had a stiffener ring installed only on the aft stub in its first flight, and it had both rings installed on its second flight. No significant post flight damage was found on either flight. Finally, the segment was used on the DM-8 static test motor in the forward position. No stiffener rings were installed. It had only one proof pressurization prior to assignment to its first use, and it was cleaned and proof tested after each flight. Thus, the segment had seen 3 proof tests, two flight pressurizations, and two low intensity water impacts prior to manufacturing for use on DM-8. On DM-8 it received one static firing pressurization in the horizontal configuration. Residual stresses at the surface and in depth were evaluated by both the x-ray diffraction and neutron beam diffraction methods. The x-ray diffraction evaluations were conducted by Technology for Energy Corporation (TEC) at their facilities in Knoxville, TN. The neutron beam evaluations were done by Atomic Energy of Canada Limited (AECL) at the Chalk River Nuclear Laboratories in Ontario. The results showed general agreement with relatively high compressive residual stresses on the surface and moderate to low subsurface tensile residual stresses.

  16. A Study on Reynolds Shear Stress Measurement by LDV

    Mizue Munekata; Hideki Ohba; Kazuyoshi Matsuzaki


    The measurement results by Laser Doppler Velocimetry (LDV) are compared with the direct numerical simulation result by Eggels et al.[1] for a cylindrical pipe flow. In the case of a pipe flow, the bias error for mean velocity is very small, because the local turbulent intensity is very small all over the pipe cross section. However the difference of the combination of u' and v' have considerable effects on Reynolds shear stress. From our investigation, it is found that the selection of coincidence time that is a necessary parameter for combination of u' and v' is more important in obtaining the accurate Reynolds shear stress. The suitable coincidence time is selected for a jet flow and the effectiveness of coincident time method or equal time interval method with coincidence data is shown.

  17. Effects of cutting and specimen size on neutron measurement of residual stresses

    Law, M.; Luzin, V.; Kirstein, O.


    To perform neutron residual stress measurements it is often necessary to cut samples to a manageable size. The effects of cutting a girth welded pipe were investigated with analytical methods and finite element analysis. The effect of cutting on measured stresses was calculated. A simplified method of modelling residual stresses in welds, "chill modelling", is introduced. In ring slitting a cut is made in the axial direction and the deformation is maeesured. The change in elastic stress can be calculated and added to neutron diffraction measurements made on a cut ring to calculate the original stresses. Residual stress measurements were performed to validate the ring slitting correction using ANSTO's residual stress diffractometer Kowari.

  18. StressPhone: smartphone based platform for measurement of cortisol for stress detection (Conference Presentation)

    Jain, Aadhar; Rey, Elizabeth; Lee, Seoho; O'Dell, Dakota; Erickson, David


    Anxiety disorders are estimated to be the most common mental illness in US affecting around 40 million people and related job stress is estimated to cost US industry up to $300 billion due to lower productivity and absenteeism. A personal diagnostic device which could help identify stressed individuals would therefore be a huge boost for workforce productivity. We are therefore developing a point of care diagnostic device that can be integrated with smartphones or tablets for the measurement of cortisol - a stress related salivary biomarker, which is known to be strongly involved in body's fight-or-flight response to a stressor (physical or mental). The device is based around a competitive lateral flow assay whose results can then be read and quantified through an accessory compatible with the smartphone. In this presentation, we report the development and results of such an assay and the integrated device. We then present the results of a study relating the diurnal patterns of cortisol levels and the alertness of an individual based on the circadian rhythm and sleep patterns of the individual. We hope to use the insight provided by combining the information provided by levels of stress related to chemical biomarkers of the individual with the physical biomarkers to lead to a better informed and optimized activity schedule for maximized work output.

  19. Stress effects in prism coupling measurements of thin polymer films

    Agan, S.; Ay, F.; Kocabas, A.; Aydinli, A.


    Due to the increasingly important role of some polymers in optical waveguide technologies, precise measurement of their optical properties has become important. Typically, prism coupling to slab waveguides made of materials of interest is used to measure the relevant optical parameters. However, such measurements are often complicated by the softness of the polymer films when stress is applied to the prism to couple light into the waveguides. In this work, we have investigated the optical properties of three different polymers, polystyrene (PS), polymethyl-methacrylate (PMMA), and benzocyclobutane (BCB). For the first time, the dependence of the refractive index, film thickness, and birefringence on applied stress in these thin polymer films was determined by means of the prism coupling technique. Both symmetric trapezoid shaped and right-angle prisms were used to couple the light into the waveguides. It was found that trapezoid shaped prism coupling gives better results in these thin polymer films. The refractive index of PMMA was found to be in the range of 1.4869 up to 1.4876 for both TE and TM polarizations under the applied force, which causes a small decrease in the film thickness of up to 0.06 μm. PMMA waveguide films were found not to be birefringent. In contrast, both BCB and PS films exhibit birefringence albeit of opposing signs.

  20. Quantifying Stress in Marine Mammals: Measuring Biologically Active Cortisol in Cetaceans and Pinnipeds


    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Quantifying Stress in Marine Mammals : Measuring...boonstra/ LONG-TERM GOALS This research will improve our ability to measure stress in marine mammals . Stress hormones (glucocorticoids... mammal researchers to measure free glucocorticoid levels. OBJECTIVES This project has two main objectives, both related to improving our

  1. Measuring Stress Distributions of Orthotropic Composite Material in Plane Stress State by the Lock-in Infrared Thermography Technique

    LI Xu-Dong; WANG Wei-Bo; LI Yong-Sheng; WU Dong-Liu


    Feasibility of measuring stress distributions of orthotropic composite materials and structures in plane stress state by the lock-in infrared thermography technique is analyzed and stress distributions of a lap joint structure made of a kind of glass reinforced plastic composite lamination plates under tensile loadings are obtained by the lock-in infrared thermography technique. Feasibility and credibility of using this technique to measure stress distributions of orthotropic composite materials and structures in plane stress state are proved by comparing the results with the data given by the digital speckle correlation method.%@@ Feasibility of measuring stress distributions of orthotropic composite materials and structures in plane stress state by the lock-in infrared thermography technique is analyzed and stress distributions of a lap joint structure made of a kind of glass reinforced plastic composite lamination plates under tensile loadings axe obtained by the lock-in infrared thermography technique.Feasibility and credibility of using this technique to measure stress distributions of orthotropic composite materials and structures in plane stress state axe proved by comparing the results with the data given by the digital speckle correlation method.

  2. Properties of Swedish posttraumatic stress measures after a disaster.

    Arnberg, Filip K; Michel, Per-Olof; Johannesson, Kerstin Bergh


    This study evaluated the properties of Swedish versions of self-report measures of posttraumatic stress disorder (PTSD), with emphasis on the Impact of Event Scale-Revised (IES-R). Survey data from adult survivors 1, 3, and 6 years after the 2004 Indian Ocean tsunami (n=1506) included the IES-R (from which the IES-6 was derived) and the 12-item General Health Questionnaire (GHQ-12). The PTSD Checklist (PCL) was included in one survey. A structured clinical interview was performed after 6 years (n=142). Factor analyses of the IES-R and PCL indicated that a dysphoric-arousal model provided good fit invariant across assessments. Both measures were accurate in excluding PTSD while all measures provided poorer positive predictive values. The IES-R, but not the IES-6 and GHQ-12, evidenced stability across assessments. In conclusion, the Swedish IES-R and PCL are sound measures of chronic PTSD, and the findings illustrate important temporal aspects of PTSD assessment.

  3. Stress-Related Growth in Racial/Ethnic Minority Adolescents: Measurement Structure and Validity

    Vaughn, Allison A.; Roesch, Scott C.; Aldridge, Arianna A.


    Stress-related growth is defined as the perception or experience of deriving benefits from encountering stressful circumstances and, thus, has been identified as a protective factor against stress. The current study revised and subsequently validated scores on an existing measure of stress-related growth in a sample of racial/ethnic minority…

  4. Eo-1 Hyperion Measures Canopy Drought Stress In Amazonia

    Asner, Gregory P.; Nepstad, Daniel; Cardinot, Gina; Moutinho, Paulo; Harris, Thomas; Ray, David


    The central, south and southeast portions of the Amazon Basin experience a period of decreased cloud cover and precipitation from June through November. There are likely important effects of seasonal and interannual rainfall variation on forest leaf area index, canopy water stress, productivity and regional carbon cycling in the Amazon. While both ground and spaceborne studies of precipitation continue to improve, there has been almost no progress made in observing forest canopy responses to rainfall variability in the humid tropics. This shortfall stems from the large stature of the vegetation and great spatial extent of tropical forests, both of which strongly impede field studies of forest responses to water availability. Those few studies employing satellite measures of canopy responses to seasonal and interannual drought (e.g., Bohlman et al. 1998, Asner et al. 2000) have been limited by the spectral resolution and sampling available from Landsat and AVHRR sensors. We report on a study combining the first landscape-level, managed drought experiment in Amazon tropical forest with the first spaceborne imaging spectrometer observations of this experimental area. Using extensive field data on rainfall inputs, soil water content, and both leaf and canopy responses, we test the hypothesis that spectroscopic signatures unique to hyperspectral observations can be used to quantify relative differences in canopy stress resulting from water availability.

  5. An Estimation Method of Stress in Soft Rock Based on In-situ Measured Stress in Hard Rock

    LI Wen-ping; LI Xiao-qin; SUN Ru-hua


    The law of variation of deep rock stress in gravitational and tectonic stress fields is analyzed based on the Hoek-Brown strength criterion. In the gravitational stress field, the rocks in the shallow area are in an elastic state and the deep, relatively soft rock may be in a plastic state. However, in the tectonic stress field, the relatively soft rock in the shallow area is in a plastic state and the deep rock in an elastic state. A method is proposed to estimate stress values in coal and soft rock based on in-situ measurements of hard rock. Our estimation method relates to the type of stress field and stress state. The equations of rock stress in various stress states are presented for the elastic, plastic and critical states. The critical state is a special stress state, which indicates the conversion of the elastic to the plastic state in the gravitational stress field and the conversion of the plastic to the elastic state in the tectonic stress field. Two cases studies show that the estimation method is feasible.

  6. Using of abrasive water jet for measurement of residual stress in railway wheels

    Hlaváček, P. (Petr); Brumek, J.; Horsák, L.


    The paper provides a general introduction to methods of measurement of residual stresses on railway wheels. Determination of residual stress distribution is necessary for the prediction of wheel service life and possible catastrophic failure. Therefore experimental section is devoted to residual stress measurement using strain gauges according to standard EN 13262 + A1. During measurement, several segments of tested wheel were cut by abrasive water jet to detect changes of residual stresses o...

  7. Soil Stress-Strain Behavior: Measurement, Modeling and Analysis

    Ling, Hoe I; Leshchinsky, Dov; Koseki, Junichi; A Collection of Papers of the Geotechnical Symposium in Rome


    This book is an outgrowth of the proceedings for the Geotechnical Symposium in Roma, which was held on March 16 and 17, 2006 in Rome, Italy. The Symposium was organized to celebrate the 60th birthday of Prof. Tatsuoka as well as honoring his research achievement. The publications are focused on the recent developments in the stress-strain behavior of geomaterials, with an emphasis on laboratory measurements, soil constitutive modeling and behavior of soil structures (such as reinforced soils, piles and slopes). The latest advancement in the field, such as the rate effect and dynamic behavior of both clay and sand, behavior of modified soils and soil mixtures, and soil liquefaction are addressed. A special keynote paper by Prof. Tatsuoka is included with three other keynote papers (presented by Prof. Lo Presti, Prof. Di Benedetto, and Prof. Shibuya).

  8. Measuring Bus Drivers' Occupational Stress Under Changing Working Conditions

    Hlotova, Y.; Cats, O.; Meijer, S.A.


    Stress is an immense problem in modern society; approximately half of all occupational illnesses are directly or indirectly related to stress. The work of a bus driver is typically associated with high stress levels that negatively influence individual well-being as well as workforce management. The

  9. Measuring Bus Drivers' Occupational Stress Under Changing Working Conditions

    Hlotova, Y.; Cats, O.; Meijer, S.A.


    Stress is an immense problem in modern society; approximately half of all occupational illnesses are directly or indirectly related to stress. The work of a bus driver is typically associated with high stress levels that negatively influence individual well-being as well as workforce management. The

  10. Measurements of Creep Internal Stress Based on Constant Strain Rate and Its Application to Engineering

    TAO Wen-liang; WEI Tao


    This research is carried out on the basis of Constant Strain Rate(CSR) to measure creep internal stress. Measurements of creep internal stress are conducted on the material test machine by using the CSR method. A mathematical model of creep internal stress is also proposed and its application is presented in this paper.

  11. How to measure prenatal stress? A systematic review of psychometric instruments to assess psychosocial stress during pregnancy.

    Nast, Irina; Bolten, Margarete; Meinlschmidt, Gunther; Hellhammer, Dirk H


    A growing body of literature documents associations of maternal psychosocial stress during pregnancy with fetal, infant and child behaviour and development. However, findings across studies are often inconsistent, which may in part be due to differences in stress definitions and assessments. We systematically reviewed methods applied to assess maternal psychosocial stress during pregnancy in studies looking at associations with biobehavioural outcomes in the offspring. A systematic literature search was performed on Web of Science and PubMed for the time period between January 1999 and October 2009. Psychometric instruments assessing maternal psychosocial stress during pregnancy were identified and described if data on psychometric properties were available. We identified 115 publications that assessed psychosocial stress during pregnancy with validated methods. These publications applied overall 43 different instruments assessing constructs falling under seven categories, ordered according to their frequency of use: anxiety, depression, daily hassles, aspects of psychological symptomatology (not reduced to anxiety or depression), life events, specific socio-environmental stressors and stress related to pregnancy and parenting. If available, we provide information on validity and reliability of the instruments for samples of pregnant women. Within the 'prenatal stress' research, a broad range of instruments is applied to assess psychosocial stress during pregnancy. Prenatal stress research should take into consideration that the variety of methods in use might hamper the comparability of stress research results. In each category of stress constructs, one instrument with good psychometric properties in pregnant women is highlighted as the best currently available measure. © 2013 John Wiley & Sons Ltd.

  12. In-situ stress measurements and stress change monitoring to monitor overburden caving behaviour and hydraulic fracture pre-conditioning

    Puller Jesse W.; Mills Ken W.; Jeffrey Rob G.; Walker Rick J.


    A coal mine in New South Wales is longwall mining 300 m wide panels at a depth of 160–180 m directly below a 16–20 m thick conglomerate strata. As part of a strategy to use hydraulic fracturing to manage potential windblast and periodic caving hazards associated with these conglomerate strata, the in-situ stresses in the conglomerate were measured using ANZI strain cells and the overcoring method of stress relief. Changes in stress associated with abutment loading and placement of hydraulic fractures were also measured using ANZI strain cells installed from the surface and from underground. Overcore stress mea-surements have indicated that the vertical stress is the lowest principal stress so that hydraulic fractures placed ahead of mining form horizontally and so provide effective pre-conditioning to promote caving of the conglomerate strata. Monitoring of stress changes in the overburden strata during longwall retreat was undertaken at two different locations at the mine. The monitoring indicated stress changes were evi-dent 150 m ahead of the longwall face and abutment loading reached a maximum increase of about 7.5 MPa. The stresses ahead of mining change gradually with distance to the approaching longwall and in a direction consistent with the horizontal in-situ stresses. There was no evidence in the stress change monitoring results to indicate significant cyclical forward abutment loading ahead of the face. The for-ward abutment load determined from the stress change monitoring is consistent with the weight of over-burden strata overhanging the goaf indicated by subsidence monitoring.

  13. Reliable practical technique for in-situ rock stress measurements in deep gold mines.

    Stacey, TR


    Full Text Available The proposed primary output of this research project is the development of a set of equipment and method of in situ stress measurements in a high stress environment typical of the deep level gold mines....

  14. Parallel Simulation of Loosely Timed SystemC/TLM Programs: Challenges Raised by an Industrial Case Study

    Denis Becker


    Full Text Available Transaction level models of systems-on-chip in SystemC are commonly used in the industry to provide an early simulation environment. The SystemC standard imposes coroutine semantics for the scheduling of simulated processes, to ensure determinism and reproducibility of simulations. However, because of this, sequential implementations have, for a long time, been the only option available, and still now the reference implementation is sequential. With the increasing size and complexity of models, and the multiplication of computation cores on recent machines, the parallelization of SystemC simulations is a major research concern. There have been several proposals for SystemC parallelization, but most of them are limited to cycle-accurate models. In this paper we focus on loosely timed models, which are commonly used in the industry. We present an industrial context and show that, unfortunately, most of the existing approaches for SystemC parallelization can fundamentally not apply in this context. We support this claim with a set of measurements performed on a platform used in production at STMicroelectronics. This paper surveys existing techniques, presents a visualization and profiling tool and identifies unsolved challenges in the parallelization of SystemC models at transaction level.

  15. A Comparison between Deep and Shallow Stress Fields in Korea Using Earthquake Focal Mechanism Inversions and Hydraulic Fracturing Stress Measurements

    Lee, Rayeon; Chang, Chandong; Hong, Tae-kyung; Lee, Junhyung; Bae, Seong-Ho; Park, Eui-Seob; Park, Chan


    We are characterizing stress fields in Korea using two types of stress data: earthquake focal mechanism inversions (FMF) and hydraulic fracturing stress measurements (HF). The earthquake focal mechanism inversion data represent stress conditions at 2-20 km depths, whereas the hydraulic fracturing stress measurements, mostly conducted for geotechnical purposes, have been carried out at depths shallower than 1 km. We classified individual stress data based on the World Stress Map quality ranking scheme. A total of 20 FMF data were classified into A-B quality, possibly representing tectonic stress fields. A total of 83 HF data out of compiled 226 data were classified into B-C quality, which we use for shallow stress field characterization. The tectonic stress, revealed from the FMF data, is characterized by a remarkable consistency in its maximum stress (σ1) directions in and around Korea (N79±2° E), indicating a quite uniform deep stress field throughout. On the other hand, the shallow stress field, represented by HF data, exhibits local variations in σ1 directions, possibly due to effects of topography and geologic structures such as faults. Nonetheless, there is a general similarity in σ1 directions between deep and shallow stress fields. To investigate the shallow stress field statistically, we follow 'the mean orientation and wavelength analysis' suggested by Reiter et al. (2014). After the stress pattern analysis, the resulting stress points distribute sporadically over the country, not covering the entire region evenly. In the western part of Korea, the shallow σ1directions are generally uniform with their search radius reaching 100 km, where the average stress direction agrees well with those of the deep tectonic stress. We note two noticeable differences between shallow and deep stresses in the eastern part of Korea. First, the shallow σ1 orientations are markedly non-uniform in the southeastern part of Korea with their search radius less than 25 km

  16. Repeated swim stress alters brain benzodiazepine receptors measured in vivo

    Weizman, R.; Weizman, A.; Kook, K.A.; Vocci, F.; Deutsch, S.I.; Paul, S.M.


    The effects of repeated swim stress on brain benzodiazepine receptors were examined in the mouse using both an in vivo and in vitro binding method. Specific in vivo binding of (/sup 3/H)Ro15-1788 to benzodiazepine receptors was decreased in the hippocampus, cerebral cortex, hypothalamus, midbrain and striatum after repeated swim stress (7 consecutive days of daily swim stress) when compared to nonstressed mice. In vivo benzodiazepine receptor binding was unaltered after repeated swim stress in the cerebellum and pons medulla. The stress-induced reduction in in vivo benzodiazepine receptor binding did not appear to be due to altered cerebral blood flow or to an alteration in benzodiazepine metabolism or biodistribution because there was no difference in (14C)iodoantipyrine distribution or whole brain concentrations of clonazepam after repeated swim stress. Saturation binding experiments revealed a change in both apparent maximal binding capacity and affinity after repeated swim stress. Moreover, a reduction in clonazepam's anticonvulsant potency was also observed after repeated swim stress (an increase in the ED50 dose for protection against pentylenetetrazol-induced seizures), although there was no difference in pentylenetetrazol-induced seizure threshold between the two groups. In contrast to the results obtained in vivo, no change in benzodiazepine receptor binding kinetics was observed using the in vitro binding method. These data suggest that environmental stress can alter the binding parameters of the benzodiazepine receptor and that the in vivo and in vitro binding methods can yield substantially different results.

  17. Measuring mechanical stresses on inserts during injection molding

    Martina Heinle


    Full Text Available Assembly molding presents an interesting approach to innovative product solutions. Here, individual components can be simultaneously positioned, affixed, and provided with a casing. However, while overmolding elements in the mold cavity with hot polymer melt, high mechanical loads occur on, in some cases, very sensitive components such as electronic devices. For the design of such systems, it is important to know these stresses, the influences on their quantities, and mathematical options for their prediction. In this article, a new measurement method for determining the forces acting on a small element in the cavity during the injection molding process in three dimensions is presented. Therefore, a new installation method for a force sensor was developed. The results in this article concentrate on force changes during one molding cycle. Our research shows that there are different mechanical load spectra in the different phases of the molding process. For example, the force component in flow direction on an element in the cavity is positive in the direction of the flow during filling. However, after the filling step, the force becomes negative due to the contraction of the injected material and results in a continuously increasing permanent force.

  18. Measuring nonlinear stresses generated by defects in 3D colloidal crystals

    Lin, Neil Y C; Schall, Peter; Sethna, James P; Cohen, Itai


    The mechanical, structural and functional properties of crystals are determined by their defects and the distribution of stresses surrounding these defects has broad implications for the understanding of transport phenomena. When the defect density rises to levels routinely found in real-world materials, transport is governed by local stresses that are predominantly nonlinear. Such stress fields however, cannot be measured using conventional bulk and local measurement techniques. Here, we report direct and spatially resolved experimental measurements of the nonlinear stresses surrounding colloidal crystalline defect cores, and show that the stresses at vacancy cores generate attractive interactions between them. We also directly visualize the softening of crystalline regions surrounding dislocation cores, and find that stress fluctuations in quiescent polycrystals are uniformly distributed rather than localized at grain boundaries, as is the case in strained atomic polycrystals. Nonlinear stress measurements ...

  19. Pulsed eddy current and ultrasonic data fusion applied to stress measurement

    Habibalahi, A.; Safizadeh, M. S.


    Stress measurement and its variation are key problems in the operating performance of materials. Stress can affect the material properties and the life of components. There are several destructive and nondestructive techniques that are used to measure stress. However, no single nondestructive testing (NDT) technique or method is satisfactory to fully assess stress. This paper presents an NDT data fusion method to improve stress measurement. An aluminum alloy 2024 specimen subjected to stress simulation is nondestructively inspected using pulsed eddy current and ultrasonic techniques. Following these nondestructive examinations, the information gathered from these two NDT methods has been fused using a suitable fuzzy combination operator. The results obtained with these processes are presented in this paper and their efficiency is discussed. It is shown that the fusion of NDT data with a suitable fuzzy operator can be adequate to improve the reliability of stress measurements.

  20. Assessing College Student-Athletes' Life Stress: Initial Measurement Development and Validation

    Lu, Frank Jing-Horng; Hsu, Ya-Wen; Chan, Yuan-Shuo; Cheen, Jang-Rong; Kao, Kuei-Tsu


    College student-athletes have unique life stress that warrants close attention. The purpose of this study was to develop a reliable and valid measurement assessing college student-athletes' life stress. In Study 1, a focus group discussion and Delphi method produced a questionnaire draft, termed the College Student-Athletes' Life Stress Scale. In…

  1. Assessing College Student-Athletes' Life Stress: Initial Measurement Development and Validation

    Lu, Frank Jing-Horng; Hsu, Ya-Wen; Chan, Yuan-Shuo; Cheen, Jang-Rong; Kao, Kuei-Tsu


    College student-athletes have unique life stress that warrants close attention. The purpose of this study was to develop a reliable and valid measurement assessing college student-athletes' life stress. In Study 1, a focus group discussion and Delphi method produced a questionnaire draft, termed the College Student-Athletes' Life Stress Scale. In…

  2. Measurement of Residual Stress in a Welded Branch Connection and Effects on Fracture Behaviour

    Law, M.; Luzin, V.; Kirstein, O.


    The branch analysed in this paper was not post weld heat treated, resulting in significant residual stresses. Assessment codes assume these to be at, or close to, yield. An integrity assessment of a welded branch connection was carried out using these high assumed residual stresses. The weld then had residual stresses determined by neutron diffraction, performed using ANSTO's residual stress diffractometer, Kowari. The maximum measured residual stress (290 MPa or 60% of yield) was much lower than the yield value assumed by assessment codes. Reanalysing with the actual residual stresses almost doubled the critical crack size, increasing the safety of the connection.

  3. Survey of horizontal stresses in coal mines from available measurements and mapping.

    Frith, R


    Full Text Available OF HORIZONTAL STRESS IN THE WITBANK AND HIGHVELD COALFIELDS 21 4.1 Is Horizontal Stress at Work in Roadway Roof Behaviour? 21 4.2 Summary of Measured Horizontal Stresses 24 4.3 Proposed Model for the Origin of Horizontal Stress Within the Coalfields 27 4... effects of horizontal stress could be further mitigated within the practicalities of the mining methods in use. Based on the work undertaken, the following project findings have been arrived at: (a) Horizontal stresses are clearly evident within both...

  4. Measurement of lattice rotations and internal stresses in over one hundred individual grains during a stress-induced martensitic transformation

    Hachi Younes El


    Full Text Available To better understand the properties of polycrystals at a microscopic scale during cyclic mechanical loading we have measured the relationship between grain orientations, their positions inside the sample and their internal stresses. In this work, in-situ 3DXRD technique was performed on over hundred grains during the stress-induced martensitic transformation in a Cu-Al-Be shape memory alloy. Information about the position, orientation, and stress field was obtained for each austenitic grain. These results have been used to develop a procedure that allows automatic processing for a large number of grains, matching them during loading and leads to a quantitative stress field. A strong heterogeneity of stress state between the grains at the surface and in the volume is evident.

  5. Stress Measurement with an Improved Hollow Inclusion Technique In Jinchuan Nickel Mine


    Borehole overcoring stress measurement with an improved hollow inclusion technique was carried out at 10 points on 3 levels in Jinchuan nickel mine which is situated in north-west of China. Through the measurement, 3-D in situ stress state at the measuring points and distribution characteristics of the stress field in the mine were obtained. The stress state in Jinchuan mine is dominated by the horizontal tectonic stress field. The maximum principal stress is horizontal which is about twice the weight of the overburden and its orientation is approximately vertical to the regional tectonic line. The difference between two horizontal principal stresses is quite large which is an important reason to cause failure of underground excavations.

  6. Numerical and experimental demonstration of shear stress measurement at thick steel plates using acoustoelasticity

    Abbasi, Zeynab; Ozevin, Didem


    The purpose of this article is to numerically quantify the stress state of complex loaded thick steel plates using the fundamental theory of acoustoelasticity, which is the relationship with stress and ultrasonic velocity in the nonlinear regime. The normal and shear stresses of a thick plate can be measured using a phased array placement of ultrasonic sensors and Rayleigh ultrasonic waves. Three measurement angles (i.e., 0 45 and 90 degrees) are selected since three measurements are needed to solve the stress tensor in an isotropic plate. The ultrasonic data is influenced significantly by the frequency of the Rayleigh waves as well as the thickness of the plate being examined; consequently the overall experimental process is influenced by the measurement parameters. In this study, a numerical demonstration is implemented to extract the nonlinearity coefficients using a 3D structural geometry and Murnaghan material model capable of examining the effects of various plate thicknesses and ultrasonic frequencies on the shear stress measurement. The purpose is that as the thickness becomes smaller, the shear stress becomes negligible at the angled measurement. For thicker cross section, shear stress becomes influential if the depth of penetration of Rayleigh wave is greater than the half of the thickness. The correlation between the depth of penetration and shear stress is then obtained. The numerical results are compared with 1 MHz ultrasonic frequency and a 3/8 inch thick steel plate loaded uniaxially while the measurement direction is angled to have the presence of shear stress in the measurement direction.

  7. Measurement and modeling of bed shear stress under solitary waves

    Jayakumar, S.; Guard, P.A.; Baldock, T.E.

    convolution integration methods forced with the free stream velocity and incorporating a range of eddy viscosity models. Wave friction factors were estimated from skin shear stress at different instances over the wave (viz., time of maximum positive total...

  8. A photoelastic measurement system for residual stress analysis in scintillating crystals by conoscopic imaging.

    Montalto, L; Paone, N; Scalise, L; Rinaldi, D


    The assessment of the stress state of scintillating crystals is an important issue for producers as well as users of such materials, because residual stress may arise during growth process. In this paper, a measurement system, based on the use of a photoelastic, conoscopic optical setup, is proposed for the assessment of stress state in scintillating crystals. Local stress values can be measured on the crystal in order to observe their spatial distribution. With the proposed system, it is possible to vary the dimensions of the inspected measurement volume. It has been validated with reference to a known stress state induced in a birefringent crystal sample and it has been tested for the case of loaded and unloaded samples, showing sub-millimetric spatial resolution and stress uncertainty ≤0.25 MPa. The proposed measurement system is a valid method for the inspection of scintillating crystals required by producers and users of such materials.



    In this article, a shear plate was mounted on the bottom in a wave flume and direct measurements of the smooth and rough bed shear stress under regular and irregular waves were conducted with the horizontal force exerted on the shear plates by the bottom shear stress in the wave boundary layer. Under immobile bed condition, grains of sand were glued uniformly and tightly onto the shear plate, being prevented from motion with the fluid flow and generation of sand ripples. The distribution of the bottom mean shear stress varying with time was measured by examining the interaction between the shear plate and shear transducers. The relation between the force measured by the shear transducers and its voltage is a linear one. Simultaneous measurements of the bottom velocity were carried out by an Acoustic Doppler Velocimeter (ADV), while the whole process was completely controlled by computers, bottom shear stress and velocity were synchronously measured. Based on the experimental results, it can be concluded that (1) the friction coefficient groews considerably with the increase of the Reynolds number, (2) the shear stress is a function varying with time and linearly proportional to the velocity. Compared with theoretical results and previous experimental data, it is shown that the experimental method is feasible and effective, A further study on the bed shear stress under regular or irregular waves can be carried out. And applicability to the laboratory studies on the initiation of sediments and the measurement of the shear stress after sediment imigration.

  10. Strain Measurement Using FBG on COPV in Stress Rupture Test

    Banks, Curtis; Grant, Joseph


    White Sands Test Facility (WSTF) was requested to perform ambient temperature hydrostatic pressurization testing of a Space Transportation System (STS) 40-in. Kevlar Composite Overwrapped Pressure Vessel (COPV). The 40-in. vessel was of the same design and approximate age as the STS Main Propulsion System (MPS) and Orbiter Maneuvering System (OMS) vessels. The NASA Engineering Safety Center (NESC) assembled a team of experts and conducted an assessment that involved a review of national Kevlar COPY data. During the review, the STS COPVs were found to be beyond their original certification of ten years. The team observed that the likelihood of STS COPV Stress rupture, a catastrophic burst before leak failure mode, was greater than previously believed. Consequently, a detailed assessment of remaining stress rupture life became necessary. Prior to STS-114, a certification deviation was written for two flights of OV-103 (Discovery) and OV-104 (Atlantis) per rationale that was based on an extensive review of the Lawrence Livermore National Laboratories, COPV data, and revisions to the STS COPV stress levels. In order to obtain flight rationale to extend the certification deviation through the end of the Program, the Orbiter Project Office has directed an interagency COPV team to conduct further testing and analysis to investigate conservatism in the stress rupture model and evaluate material age degradation. Additional analysis of stress rupture life requires understanding the fiber stresses including stress that occurs due to thru-wall composite compression in COPV components. Data must be obtained at both zero gauge pressure (pre-stress) and at the component operating pressure so that this phenomenon can be properly evaluated. The zero gauge pressure stresses are predominantly a result of the autofrettage process used during vessel manufacture. Determining these pre-stresses and the constitutive behavior of the overwrap at pressure will provide necessary information

  11. Residual stress measurement in a metal microdevice by micro Raman spectroscopy

    Song, Chang; Du, Liqun; Qi, Leijie; Li, Yu; Li, Xiaojun; Li, Yuanqi


    Large residual stress induced during the electroforming process cannot be ignored to fabricate reliable metal microdevices. Accurate measurement is the basis for studying the residual stress. Influenced by the topological feature size of micron scale in the metal microdevice, residual stress in it can hardly be measured by common methods. In this manuscript, a methodology is proposed to measure the residual stress in the metal microdevice using micro Raman spectroscopy (MRS). To estimate the residual stress in metal materials, micron sized β-SiC particles were mixed in the electroforming solution for codeposition. First, the calculated expression relating the Raman shifts to the induced biaxial stress for β-SiC was derived based on the theory of phonon deformation potentials and Hooke’s law. Corresponding micro electroforming experiments were performed and the residual stress in Ni–SiC composite layer was both measured by x-ray diffraction (XRD) and MRS methods. Then, the validity of the MRS measurements was verified by comparing with the residual stress measured by XRD method. The reliability of the MRS method was further validated by the statistical student’s t-test. The MRS measurements were found to have no systematic error in comparison with the XRD measurements, which confirm that the residual stresses measured by the MRS method are reliable. Besides that, the MRS method, by which the residual stress in a micro inertial switch was measured, has been confirmed to be a convincing experiment tool for estimating the residual stress in metal microdevice with micron order topological feature size.

  12. Residual stress measurements of 2-phase sprayed coating layer

    Nishida, Masayuki [Kagawa Polytechnic College, Kagawa (Japan); Hanabusa, Takao


    In a series of the already reported single phase metal and ceramic melt sprayed films, on two phase melt sprayed films, their stress and thermal stress changes due to their bending load are tried to test. In order to prepare two phase state, austenitic stainless steel wire is used by a laser melt spraying method. In this method, CO{sub 2} laser is used for a thermal source, and proceeding direction of its laser is selected to cross melt spraying direction. As a result, the following facts can be elucidated. The stress values at {alpha}- and {gamma}-phase in the stainless steel film are linearly responsive to the bending load, and the stress change in {alpha}-phase is smaller than that in {gamma}-phase. In a heat and cool cycle, {alpha}-phase shows a trend of extension with increasing temperature but {gamma}-phase shows a trend of compression inversely. And, stress behavior at {alpha}- and {gamma}-phases in the stainless steel film does not agree with a mixing rule in common two-phase materials. (G.K.)

  13. Study to evaluate the effectiveness of stress management workshops on response to general and occupational measures of stress.

    Heron, R J; McKeown, S; Tomenson, J A; Teasdale, E L


    This study was designed to evaluate the effectiveness of stress management training workshops within Zeneca Pharmaceuticals. The study was of cross-sectional design, comparing groups of workshop attendees and non-attendees. In addition, self-rated well-being scores of attendees were compared with results obtained pre-workshop and 2-3 months after the workshop. Employees participating in the study were drawn from the Manufacturing, Research and Development, Sales and Marketing sites of Zeneca Pharmaceuticals located in Cheshire, United Kingdom. Three hundred and ninety persons who had participated in stress management workshops since 1988 were matched for age, gender and department with an equal number of employees who had not attended stress management workshops. Outcome measures included self-rated well-being (as measured by the 30-question General Health Questionnaire), knowledge of company guidance on the management of stress in staff, and an assessment of coping strategies. Subjects who had not attended a stress management workshop were much more likely to have a poor understanding of the principles of management of stress in staff [odds ratio (OR) = 8.3; 95% confidence interval (CI) = 3.3-21.3] and more likely to have poor coping skills (OR = 2.8; CI = 1.3-6.1). However, mean scores for the two measures were similar in attendees and non-attendees. Self-rating of current well-being was strongly associated with the life-events score, but not related to workshop attendance. The study indicates that stress management training workshops reduce the prevalence of employees with a poor understanding of the principles of the management of stress in staff and with poor coping strategies. An improvement in the self-rated well-being observed shortly after the workshop was not sustained.

  14. Physiologic Measures of Animal Stress during Transitional States of Consciousness

    Robert E. Meyer


    Full Text Available Determination of the humaneness of methods used to produce unconsciousness in animals, whether for anesthesia, euthanasia, humane slaughter, or depopulation, relies on our ability to assess stress, pain, and consciousness within the contexts of method and application. Determining the subjective experience of animals during transitional states of consciousness, however, can be quite difficult; further, loss of consciousness with different agents or methods may occur at substantially different rates. Stress and distress may manifest behaviorally (e.g., overt escape behaviors, approach-avoidance preferences [aversion] or physiologically (e.g., movement, vocalization, changes in electroencephalographic activity, heart rate, sympathetic nervous system [SNS] activity, hypothalamic-pituitary axis [HPA] activity, such that a one-size-fits-all approach cannot be easily applied to evaluate methods or determine specific species applications. The purpose of this review is to discuss methods of evaluating stress in animals using physiologic methods, with emphasis on the transition between the conscious and unconscious states.

  15. Final Report: Geothermal dual acoustic tool for measurement of rock stress

    Normann, Randy A. [Perma Works LLC, Pattonville, TX (United States)


    This paper outlines the technology need for a rock formation stress measurement in future EGS wells. This paper reports on the results of work undertaken under a Phase I, DOE/SBIR on the feasibility to build an acoustic well logging tool for measuring rock formation stress.

  16. Final Report. Geothermal Dual Acoustic Tool for Measurement of Rock Stress

    Normann, Randy A [Perma Works LLC, Pattonville, TX (United States)


    This paper outlines the technology need for a rock formation stress measurement in future EGS wells. This paper reports on the results of work undertaken under a Phase I, DOE/SBIR on the feasibility to build an acoustic well logging tool for measuring rock formation stress.

  17. Accuracy of soil stress measurements as affected by transducer dimensions and shape

    Lamandé, Mathieu; Keller, Thomas; Berisso, Feto Esimo


    Accurate measurements of soil stress are needed to evaluate the impact of traffic on soil properties and prevent soil compaction. Four types of transducer commonly used to measure vertical stress were calibrated in realistic traffic conditions in the field. The four transducer types differed in s...

  18. Instruction manual for the use of CSIR triaxial rock stress measuring equipment

    Coetzer, SJ


    Full Text Available This is an updated version of CSIR Report no ME 1763 entitled "Instruction manual for the use for the CSIR triaxial rock stress measuring equipment" by F A Vreede. The manual contains a detailed description of CSIR Triaxial rock stress measuring...

  19. Final Report: Geothermal Dual Acoustic Tool for Measurement of Rock Stress

    Normann, Randy A.


    This paper outlines the technology need for a rock formation stress measurement in future EGS wells. This paper reports on the results of work undertaken under a Phase I, DOE/SBIR on the feasibility to build an acoustic well logging tool for measuring rock formation stress.



    Traditional methods of residual stress measurement are generally destructive or semi-destructive, as well as expensive, time-consuming and complex to implement. With the new development of welded structure, traditional methods can not satisfy the need of full life task management. So the acoustical theory is introduced, since the ultrasonic technique provides a useful nondestructive tool in the evaluation of stresses. In this study an ultrasonic stress measurement experimental installation is established, which consists of a special transducer, a signal emission unit and a signal recipient processing unit. Longitudinal critically refracted wave is selected as the measurement wave mode. The supporting software is programmed by Labview software. The longitudinal residual stress and transverse residual stress of twin wire welded plate are measured by this installment, in which the measuring process is real-time, quick and nondestructive. The experiment results indicate that the system can satisfy the need of life evaluation for welded structure. The system is light and portable.

  1. Perceived stress, recurrent pain, and aggregate salivary cortisol measures in mid-adolescent girls and boys.

    Lindfors, Petra; Folkesson Hellstadius, Lisa; Östberg, Viveca


    Measures of perceived stress have been criticized for theoretical inconsistency. However, the validated pressure activation stress scale has been suggested as a theoretically sound alternative. But it is unclear how pressure and activation stress relate to objective and subjective measures including commonly used aggregate cortisol measures and health complaints respectively. Specifically, this study aimed at investigating how pressure and activation stress were related to aggregate salivary cortisol measures and recurrent pain in mid-adolescent girls and boys. Mid-adolescents (119 girls and 56 boys) provided self-reports in questionnaires on activation and pressure stress and recurrent pain (headache, stomach ache, neck/shoulder and back pain). Additionally, adolescents sampled saliva during an ordinary school day: (1) immediately at awakening; (2) 30 minutes after waking up; (3) 60 minutes after waking up, and (4) at 8 p.m. These samples were analyzed for cortisol. Hierarchical regressions showed no statistically significant associations between activation and pressure stress and cortisol, neither for girls nor for boys. However, activation and pressure stress were significantly associated with recurrent pain but only for girls. The findings may relate to subjective and objective measures reflecting distinct aspects of stress-related functioning. However, the study participants included mid-adolescents whose bodily systems are flexible and still relatively unaffected by the strain of their daily stress perceptions. To conclude, the non-significant relationships between activation and pressure stress and commonly used aggregate measures of cortisol adds to the understanding of how perceived stress may relate to physiological functioning in the daily life of adolescents when using such aggregate measures.

  2. Remarks on residual stress measurement by hole-drilling and electronic speckle pattern interferometry.

    Barile, Claudia; Casavola, Caterina; Pappalettera, Giovanni; Pappalettere, Carmine


    Hole drilling is the most widespread method for measuring residual stress. It is based on the principle that drilling a hole in the material causes a local stress relaxation; the initial residual stress can be calculated by measuring strain in correspondence with each drill depth. Recently optical techniques were introduced to measure strain; in this case, the accuracy of the final results depends, among other factors, on the proper choice of the area of analysis. Deformations are in fact analyzed within an annulus determined by two parameters: the internal and the external radius. In this paper, the influence of the choice of the area of analysis was analysed. A known stress field was introduced on a Ti grade 5 sample and then the stress was measured in correspondence with different values of the internal and the external radius of analysis; results were finally compared with the expected theoretical value.

  3. Methods of Measuring Stress Relaxation in Composite Tape Springs


    additional analysis done in SOLIDWORKS . For the first method of analysis, PolyWorks is used to cut out the unnecessary portions of the raw scan data. Then...each tape spring is exported as a ‘.stl’ file. This file is imported as a surface into a SOLIDWORKS part file. The SOLIDWORKS parts are combined into...analyzed using MATLAB, PolyWorks, and SOLIDWORKS . These data provide a greater insight into the stress relaxation of tape springs when deformed

  4. Workshop on industrial application of neutron diffraction. Stress measurement by neutron diffraction

    Minakawa, N; Morii, Y; Oyama, Y


    This workshop was planned to make use of the neutron from the reactor and the pulse neutron source JSNS for the industrial world. Especially, this workshop focused on the stress measurement by the neutron diffraction and it was held on the Tokai JAERI from October 15 to 16, 2001. The participant total was 93 and 40 participated from the industrial world. The introduction of the residual stress development of measurement technique by the neutron diffraction method and a research of the measurement of the residual stress such as the nuclear reactor material, the ordinary structure material, the composite material, the quenching steel, the high strength material were presented and discussed in this workshop. Moreover, it was introduced for the industrial world that an internal stress measurement is important for development of new product or an improvement of a manufacturing process. The question from the industrial world about which can be measured the product form, the size, the measurement precision, the reso...

  5. Measurements of thermal residual stresses in SiC/Ti-15-3 composites

    Bobet, J.-L.; Masuda, C. [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan)


    Residual stresses present in an as received and thermally cycled SCS-6/Ti-15-3 metal matrix composite (MMC) have been approached via X-ray diffraction (sin{sup 2}{psi}) experiments. Determination of stress profiles have been achieved by successive removal of the matrix from the composite surface by electropolishing. Axial and hoop stresses in the matrix were tensile (higher on the surface) and those measured in the fiber were compressive (about -500 to -600 MPa). A stress gradient normal to the surface of the composite was found. Measurement of residual stress levels in the composite subjected to thermal cycling from 400degC to 800degC in an inert atmosphere or in vacuum revealed a huge stress relaxation after only 200 cycles. (author)

  6. Measuring stress before and during pregnancy: a review of population-based studies of obstetric outcomes.

    Witt, Whitney P; Litzelman, Kristin; Cheng, Erika R; Wakeel, Fathima; Barker, Emily S


    Mounting evidence from clinic and convenience samples suggests that stress is an important predictor of adverse obstetric outcomes. Using a proposed theoretical framework, this review identified and synthesized the population-based literature on the measurement of stress prior to and during pregnancy in relation to obstetric outcomes. Population-based, peer-reviewed empirical articles that examined stress prior to or during pregnancy in relation to obstetric outcomes were identified in the PubMed and PsycInfo databases. Articles were evaluated to determine the domain(s) of stress (environmental, psychological, and/or biological), period(s) of stress (preconception and/or pregnancy), and strength of the association between stress and obstetric outcomes. Thirteen studies were evaluated. The identified studies were all conducted in developed countries. The majority of studies examined stress only during pregnancy (n = 10); three examined stress during both the preconception and pregnancy periods (n = 3). Most studies examined the environmental domain (e.g. life events) only (n = 9), two studies examined the psychological domain only, and two studies examined both. No study incorporated a biological measure of stress. Environmental stressors before and during pregnancy were associated with worse obstetric outcomes, although some conflicting findings exist. Few population-based studies have examined stress before or during pregnancy in relation to obstetric outcomes. Although considerable variation exists in the measurement of stress across studies, environmental stress increased the risk for poor obstetric outcomes. Additional work using a lifecourse approach is needed to fill the existing gaps in the literature and to develop a more comprehensive understanding of the mechanisms by which stress impacts obstetric outcomes.

  7. Stress Measurement in Coal Seam Ahead of Longwall Face - Case Study

    Kukutsch, R. (Radovan); P. Koníček; Waclawik, P. (Petr); Ptáček, J.; Staš, L. (Lubomír); M. Vavro; Hastíková, A. (Alice)


    Stress measurement and stress monitoring is an important task in mining geomechanics, because knowledge of the stress - strain state in a rock mass is the determining factor for the proper planning of roadway support and for the correct design of underground mining. This strategy is useful for ensuring mining safety, because increasing depth causes several issues, especially in areas with rockbur st hazard, when roadways are loaded by the pressure ahead...

  8. Study on in-situ stress measurement around coastal marginal land in Fujian

    LI Hong; AN Qi-mei; XIE Fu-ren


    The in-situ hydraulic fracturing stress measurements have been carried out around the coastal marginal land in Fujian Province. And the characteristics of magnitude, direction and distribution of tectonic stress have been obtained.Based on the observed stress data, the characteristics and activities of fault zones are analyzed and studied in the paper according to the Coulomb friction criteria. ① The maximum horizontal principal compressive stress is in the NW-WNW direction from the north to the south along the coastline verge, which is parallel to the strike of the NW-trending fault zone, consistent with the direction of principal compressive stress obtained from geological structure and across-fault deformation data, and different from that reflected by focal mechanism solution by about 20°. ② The horizontal principal stress increases with depth, the relation among three stresses is SH>Sv>Sh or SH≈Sv>Sh, and the stress state is liable to normal fault and strike-slip fault activities. ③ According to Coulomb friction criteria and taking the friction strength μ as 0.6~1.0 for analysis, the stress state reaching or exceeding the threshold for normal-fault frictional sliding near the fault implies that the current tectonic activity in the measuring area is mainly normal faulting. ④ The force source of current tectonic stress field comes mainly from the westward and northwestward horizontal extrusions from the Pacific and Philippine Plates respectively to the Eurasian Plate.

  9. Measuring residual stress in ceramic zirconia-porcelain dental crowns by nanoindentation.

    Zhang, Y; Allahkarami, M; Hanan, J C


    Residual stress plays a critical role in failure of ceramic dental crowns. The magnitude and distribution of residual stress in the crown system are largely unknown. Determining the residual stress quantitatively is challenging since the crown has such complex contours and shapes. This work explored the feasibility and validity of measuring residual stress of zirconia and porcelain in ceramic crowns by nanoindentation. Nanoindentation tests were performed on the cross-section of a crown for both porcelain and zirconia along four critical locations: the thickest, thinnest and medium porcelain thicknesses. Zirconia and porcelain pieces, chipped off from the crown and annealed at 400 °C, were used as reference samples. The residual stress was determined by comparing the measured hardness of the stressed sample with that of the reference sample. Nanoindentation impression images were acquired through a scanning probe microscope (SPM) equipped with a Hysitron Triboindenter. Zirconia showed large pile-up. Residual stress is determined along the thickness of crowns at the chosen locations for both porcelain and zirconia. The measured results were compared with the results from X-ray diffraction (XRD) and finite element modeling (FEM). Results show there are large amounts of residual stresses in the dental crown and their magnitude differs between locations due to the complex shape of the crown. The average residual stress readings were as high as -637 MPa and 323 MPa for zirconia and porcelain respectively.

  10. Measurement of the residual stress in hot rolled strip using strain gauge method

    Kumar, Lokendra; Majumdar, Shrabani; Sahu, Raj Kumar


    Measurement of the surface residual stress in a flat hot rolled steel strip using strain gauge method is considered in this paper. Residual stresses arise in the flat strips when the shear cut and laser cut is applied. Bending, twisting, central buckled and edge waviness is the common defects occur during the cutting and uncoiling process. These defects arise due to the non-uniform elastic-plastic deformation, phase transformation occurring during cooling and coiling-uncoiling process. The residual stress analysis is very important because with early detection it is possible to prevent an object from failure. The goal of this paper is to measure the surface residual stress in flat hot rolled strip using strain gauge method. The residual stress was measured in the head and tail end of hot rolled strip considering as a critical part of the strip.

  11. Research on Measurements for Temperature and Stress of Pistons in Internal Combustion Engine

    DONG Xiao-rui; TAN Jian-song


    In both numerical simulation and experimental research for the piston of internal combustion engine, the verification foundations are always insufficient. The reason is the measurements for its transient temperature and stress under actual operation conditions are very difficult. A multi-channel measurement-storage technology is used in the engine bench experiment to measure the piston temperature and stress in real time. The temperature and stress changes in the engine operation process are obtained. They provide reliable instructive criteria for numerical analysis and experiment of the piston working state.

  12. Residual stress measurements with barkhausen noise in power plant creep failure analysis

    Karvonen, I. [CoMoTest Oy, Maentsaelae (Finland)] Suominen, L. [Stresstech Oy, Jyvaeskylae (Finland)


    Continuously developing power and process industry needs predictive maintenance inspection methods in order to prevent failures with correctly timed and properly specified measures. Materials` monitoring has traditionally been non-destructive inspection to detect growing cracks or other deficiencies. Recently, after the development of portable stress measurement systems, some advances has been reached. Based on stress anomalies due to creep, fatigue or corrosion, new applications have been found in the use of Barkhausen noise inspection. When the Barkhausen noise findings have been simultaneously confirmed with other stress measuring methods, a wider acceptance of the application of the method can be proposed. (orig.) 7 refs.

  13. Measuring short-term stress in birds: Comparing different endpoints of the endocrine-immune interface.

    Huber, Nikolaus; Fusani, Leonida; Ferretti, Andrea; Mahr, Katharina; Canoine, Virginie


    Stress is a collective term for certain conditions and sequences of physiological events enabling living organisms to overcome unpredictable and uncontrollable situations. The context-dependent nature, multidimensional course and large individual variability make stress responses difficult to measure. In avian species, a plethora of studies on short-term stress responses have been conducted by measuring the corticosteroid response to a standardized stress protocol. Here we aimed to test the viability of the Leukocyte Coping Capacity (LCC), measuring oxygen radical production by leukocytes, to assess short-term stress in birds. We collected blood samples from captive house sparrows (Passer domesticus) in the two seasons of winter and spring, right after capture and 30min thereafter. In order to assess the overall physiological stress response to a standardized stressor, i.e. handling and temporary constraint, we measured LCC and additionally combined it with measures of total circulating glucocorticoids (GCs) and oxidative stress. All three methodologies detected significant changes due to the stressor albeit they were not correlated with each other and revealed different information. There was no significant change in oxidative stress levels between the two time points although the amount of relative oxidative damage as well as the anti-oxidative capacity changed significantly. We observed a significant seasonal difference in GC stress response with no difference between sexes. On the contrary, LCC measures revealed with a high individual consistency, that individuals experienced a similar magnitude of stress in both seasons with a significant difference between sexes. Total GC-levels have to be interpreted with caution regarding the assessment of short-term stress reactions. We therefore suggest to supplementary combine classical approaches for measuring stress with the immunological tool of LCC. Our results reveal LCC as a strong and reliable tool to assess short

  14. Measurement techniques for in situ stresses around underground constructions in a deep clay formation

    Li X.L.


    Full Text Available Disposal in deep underground geological formations is internationally recognized as the most viable option for the long-term management of high-level radioactive waste. In Belgium, the Boom clay formation is extensively studied in this context, in particular at the 225 m deep HADES Underground Research Facility in Mol. A cost-effective design of deep underground structures requires an accurate assessment of the in situ stresses; a good estimation of these stresses is also essential when interpreting in situ experiments regarding the hydro-mechanical behaviour of the host formation. Different measurement techniques are available to provide data on the stress evolution and other mechanical properties of the geological formation. The measurement can be direct (measurement of total pressure, or it can be an indirect technique, deriving the stress from related quantities such as strain (changes in structural members. Most total stress measurements are performed through permanently installed sensors; also once-only measurements are performed through specific methods (e.g. pressuremeter. Direct measurement of the stress state is challenging due to the complex mechanical behaviour of the clay, and the fact that the sensor installation inevitably disturbs the original stress field. This paper describes ways to deal with these problems and presents the results obtained using different techniques at HADES.

  15. Research on Measurement of Bed Shear Stress Under WaveCurrent Interaction

    徐华; 夏云峰; 张世钊马炳和; 郝思禹; 杜德军


    The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to research the theory of sediment movement. However, there is not a measuring and computing method to measure the bed shear stress under a complicated dynamic effect like wave and current. This paper describes the measurement and test research on the bed shear stress in a long launder of direct current by the new instrument named thermal shearometer based on micro-nanotechnology. As shown by the research results, the thermal shearometer has a high response frequency and strong stability. The measured results can reflect the basic change of the bed shear stress under wave and wave-current effect, and confirm that the method of measuring bed shear stress under wave-current effect with thermal shearometer is feasible. Meanwhile, a preliminary method to compute the shear stress compounded by wave-current is put forward according to the tested and measured results, and then a reference for further study on the basic theory of sediment movement under a complicated dynamic effect is provided.

  16. Method for contact resistivity measurements on photovoltaic cells and cell adapted for such measurement

    Burger, Dale R. (Inventor)


    A method is disclosed for scribing at least three grid contacts of a photovoltaic cell to electrically isolate them from the grid contact pattern used to collect solar current generated by the cell, and using the scribed segments for determining parameters of the cell by a combination of contact end resistance (CER) measurements using a minimum of three equally or unequally spaced lines, and transmission line modal (TLM) measurements using a minimum of four unequally spaced lines. TLM measurements may be used to determine sheet resistance under the contact,, while CER measurements are used to determine contact resistivity, .rho..sub.c, from a nomograph of contact resistivity as a function of contact end resistance and sheet resistivity under the contact. In some cases, such as the case of silicon photovoltaic cells, sheet resistivity under the contact may be assumed to be equal to the known sheet resistance, R.sub.s, of the semiconductor material, thereby obviating the need for TLM measurements to determine

  17. Effect of reference point selection on microscopic stress measurement using EBSD

    Mikami, Yoshiki, E-mail: [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Oda, Kazuo [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kamaya, Masayuki [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Mochizuki, Masahito [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)


    It is important to evaluate microscopic stress distributions on the order of the grain size to clarify the deformation and fracture behavior of structural materials. In this study, the microscopic stress distribution of coarse-grained austenitic stainless steel during tensile testing was measured using a method that employs cross-correlation of the electron backscatter diffraction (EBSD) pattern, and the effect of the reference point selection on the measured stress was investigated. First, parameters that characterize the quality of the EBSD pattern measurement—namely, the image quality (IQ), confidence index (CI), and Fit—and the parameter that corresponds to the extent of the plastic deformation—the kernel average misorientation (KAM)—were used to determine the reference point. It was confirmed that the value of the microscopic stress measured using the EBSD-based approach is relative to the value of the stress state of the reference point. Second, multiple reference points were determined within a grain by considering only the location, and the stress distribution in the grain was evaluated using each of the reference points. The deviation of the measured stress was calculated from the averaged value for all the measured results using a certain reference point, and its relationship to parameters such as the IQ, CI, Fit, and KAM of the reference point used was investigated. It was demonstrated that the choice of parameters did not significantly affect the evaluation of the relative stress distribution within a grain. The results of this study therefore show that the selection of the reference point does not affect the measured stress distribution, as long as the evaluation is limited to the relative stress within a grain for the selected reference point.

  18. Measurement invariance of the perceived stress scale and latent mean differences across gender and time.

    Barbosa-Leiker, Celestina; Kostick, Marylynne; Lei, Ming; McPherson, Sterling; Roper, Virginia; Hoekstra, Trynke; Wright, Bruce


    Measurement invariance of the 2-factor model of the Perceived Stress Scale--10-item version (Cohen & Williamson, 1988) was tested across men and women at two time points and in the combined total sample over a 2-year time frame (n = 871). Measurement invariance results indicated that the scale measured the latent factors, stress and counter-stress, equivalently in men and women and over time. With measurement invariance demonstrated, differences in latent means were tested. Results indicated that men had lower levels of frequencies of stressors, and at one time point, higher levels of counter-stress, when compared with women. When examining change in frequencies of stressors and counter-stress over 2 years with the combined male and female sample, stressors remained stable, yet counter-stress increased over time. These findings may aid in the interpretation of results when examining stressors and counter-stress in clinical samples where one would expect stress to increase, whereas positive psychological states decrease.

  19. Instruction manual for the use of the CSIR triaxial rock stress measuring equipment

    Vreede, F. A.


    A guide is presented for users of an instrument designed to measure the state of stress at any one point in a rock mass. The overscoring technique used to determine the absolute stress is described as well as equipment components. A computer program for processing the data is discussed and the equations on which the program is based are given.

  20. Demonstration of over core stress measurement from surface using the Sigra IST tool

    Gray, I


    Full Text Available 7 Core Sample Mechanical Properties Page 8 Stress Measurement Results Page 8 Principal and Tectonic Stresses and Tectonic Strains Page 9 Conclusions Page 11 Acknowledgments Page 11 Table 1 Sample Descriptions... Solutions Page 26 Appendix D Directional Survey Information Page 39 Appendix E Photographs of Each Test Core Page 41 4 5 TABLES Table 1- Sample Descriptions and Material...

  1. Detection of stress concentrations around a defect by magnetic Barkhausen noise measurements

    Mandal, K.; Dufour, D.; Sabet-Sharghi, R.; Sijgers, B.; Micke, D.; Krause, T.W.; Clapham, L.; Atherton, D.L. [Applied Magnetics Group, Department of Physics, Queen`s University, Kingston, K7L 3N6, Ontario (Canada)


    The stress distribution around a 50{percent} blind-hole pit in a steel pipe with a 9 mm wall has been studied using high-resolution magnetic Barkhausen noise (MBN) measurements. A magnetic disk read-head is used as the pick up coil in the MBN probe. The study shows a stress concentration factor of {approximately}2 at the defect edge perpendicular to the direction of applied stress and {approximately}{minus}0.6 at the edge parallel to the same. The experimental results are consistent with the analytical solutions obtained by the Airy{close_quote}s stress function approach. {copyright} {ital 1996 American Institute of Physics.}

  2. 热处理对医用TLM钛合金硬度及成形性能的影响%Effect of heat treatment on hardness and formability of biomedical TLM titanium alloy

    麻西群; 于振涛; 牛金龙; 刘汉源; 张亚峰


    对TLM钛合金进行了不同热处理条件下的室温硬度测试、杯突试验和弯曲试验. 结果表明,固溶处理后合金板材的杯突值IE为4.7~5.8 mm,最大弯曲角为180°,显微硬度为226~236 HV0.1. 时效处理后板材的杯突值IE为1.9~3.1 mm,最大弯曲角为77 °~153 °,显微硬度为240~403 HV0 .1. 同时,结合文献还定性地得到了相组织对板材硬度及成形性能的影响关系.%Hardness test , cupping test and bending test were carried out on TLM alloy sheet under different heat treatment conditions . Results show that under solution treatment conditions , the cupping test value (IE) is 4.7-5.8 mm, the max bending angle is up to 180°, and the hardness is 226-236 HV0.1, however, under aging conditions , the IE value of the sheet is 1.9-3.1 mm, the maximum bending angle is only 77°-153°and the hardness is 240-403 HV0.1.Moreover, effect of microstructure on the hardness and formability of the TLM alloy were analyzed qualitatively to reference the literatures .

  3. Measuring multiple residual-stress components using the contour method and multiple cuts

    Prime, Michael B [Los Alamos National Laboratory; Swenson, Hunter [Los Alamos National Laboratory; Pagliaro, Pierluigi [U. PALERMO; Zuccarello, Bernardo [U. PALERMO


    The conventional contour method determines one component of stress over the cross section of a part. The part is cut into two, the contour of the exposed surface is measured, and Bueckner's superposition principle is analytically applied to calculate stresses. In this paper, the contour method is extended to the measurement of multiple stress components by making multiple cuts with subsequent applications of superposition. The theory and limitations are described. The theory is experimentally tested on a 316L stainless steel disk with residual stresses induced by plastically indenting the central portion of the disk. The stress results are validated against independent measurements using neutron diffraction. The theory has implications beyond just multiple cuts. The contour method measurements and calculations for the first cut reveal how the residual stresses have changed throughout the part. Subsequent measurements of partially relaxed stresses by other techniques, such as laboratory x-rays, hole drilling, or neutron or synchrotron diffraction, can be superimposed back to the original state of the body.

  4. A Steel Wire Stress Measuring Sensor Based on the Static Magnetization by Permanent Magnets.

    Deng, Dongge; Wu, Xinjun; Zuo, Su


    A new stress measuring sensor is proposed to evaluate the axial stress in steel wires. Without using excitation and induction coils, the sensor mainly consists of a static magnetization unit made of permanent magnets and a magnetic field measurement unit containing Hall element arrays. Firstly, the principle is illustrated in detail. Under the excitation of the magnetization unit, a spatially varying magnetized region in the steel wire is utilized as the measurement region. Radial and axial magnetic flux densities at different lift-offs in this region are measured by the measurement unit to calculate the differential permeability curve and magnetization curve. Feature parameters extracted from the curves are used to evaluate the axial stress. Secondly, the special stress sensor for Φ5 and Φ7 steel wires is developed accordingly. At last, the performance of the sensor is tested experimentally. Experimental results show that the sensor can measure the magnetization curve accurately with the error in the range of ±6%. Furthermore, the obtained differential permeability at working points 1200 A/m and 10000 A/m change almost linearly with the stress in steel wires, the goodness of linear fits are all higher than 0.987. Thus, the proposed steel wire stress measuring sensor is feasible.

  5. A Steel Wire Stress Measuring Sensor Based on the Static Magnetization by Permanent Magnets

    Dongge Deng


    Full Text Available A new stress measuring sensor is proposed to evaluate the axial stress in steel wires. Without using excitation and induction coils, the sensor mainly consists of a static magnetization unit made of permanent magnets and a magnetic field measurement unit containing Hall element arrays. Firstly, the principle is illustrated in detail. Under the excitation of the magnetization unit, a spatially varying magnetized region in the steel wire is utilized as the measurement region. Radial and axial magnetic flux densities at different lift-offs in this region are measured by the measurement unit to calculate the differential permeability curve and magnetization curve. Feature parameters extracted from the curves are used to evaluate the axial stress. Secondly, the special stress sensor for Φ5 and Φ7 steel wires is developed accordingly. At last, the performance of the sensor is tested experimentally. Experimental results show that the sensor can measure the magnetization curve accurately with the error in the range of ±6%. Furthermore, the obtained differential permeability at working points 1200 A/m and 10000 A/m change almost linearly with the stress in steel wires, the goodness of linear fits are all higher than 0.987. Thus, the proposed steel wire stress measuring sensor is feasible.

  6. Bond strength and stress measurements in thermal barrier coatings

    Gell, M.; Jordan, E. [Univ. of Connecticut, Storrs, CT (United States)


    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. To meet the aggressive Advanced Turbine Systems goals for efficiency, durability and the environment, it will be necessary to employ thermal barrier coatings on turbine airfoils and other hot section components. For The successful application of TBCs to ATS engines with 2600{degrees}F turbine inlet temperatures and required component lives 10 times greater than those for aircraft gas turbine engines, it is necessary to develop quantitative assessment techniques for TBC coating integrity with time and cycles in ATS engines. Thermal barrier coatings in production today consist of a metallic bond coat, such as an MCrAlY overlay coating or a platinum aluminide (Pt-Al) diffusion coating. During heat treatment, both these coatings form a thin, tightly adherent alumina (Al{sub 2}O{sub 3}) film. Failure of TBC coatings in engine service occurs by spallation of the ceramic coating at or near the bond coat to alumina or the alumina to zirconia bonds. Thus, it is the initial strength of these bonds and the stresses at the bond plane, and their changes with engine exposure, that determines coating durability. The purpose of this program is to provide, for the first time, a quantitative assessment of TBC bond strength and bond plane stresses as a function of engine time and cycles.

  7. Genetic influence on blood pressure measured in the office, under laboratory stress and during real life

    Wang, Xiaoling; Ding, Xiuhua; Su, Shaoyong; Harshfield, Gregory; Treiber, Frank; Snieder, Harold

    To determine to what extent the genetic influences on blood pressure (BP) measured in the office, under psychologically stressful conditions in the laboratory and during real life are different from each other...

  8. Research on a system and method of automated whole-field measurement of optical glass stress

    Zhang, Li-jun; Tang, Yi; Bai, Ting-zhu


    On the basis of the principle of single quarter wave plate method, a model of automatic whole-field measuring optical glass stress is presented, which is called "4+1steps phase shifting method" including the model for the isoclinic parameter and the stress birefringence. According to this model, an automatic whole-field measuring system is established. The correctness of the model was testified by numeric emulation experiments under the preset conditions of isoclinic angle and stress birefringence. Practical measurement obtained a result coincident with the actual distribution of the isoclinic angle and the birefringence. The automatic whole-field measuring model and system can achieve the whole process intelligently and automatically, and dispose the disadvantages of tradition method about interpreting the stress level by subjective judging birefringence of some selected spots.

  9. A novel concept of measuring mass flow rates using flow induced stresses

    P I Jagad; B P Puranik; A W Date


    Measurement of mass flow rate is important for automatic control of the mass flow rate in many industries such as semiconductor manufacturing and chemical industry (for supply of catalyst to a reaction). In the present work, a new concept for direct measurement of mass flow rates which does not depend on the volumetric flow rate measurement and obviates the need for the knowledge of density is proposed from the measurement of the flow induced stresses in a substrate. The concept is formulated by establishing the relationship between the mass flow rate and the stress in the substrate. To this end, the flow field and the stress field in the substrate are evaluated simultaneously using a numerical procedure and the necessary correlations are derived. A least squares based procedure is used to derive the mass flow rate from the correlations as a function of the stress in the substrate.

  10. Measurement of stress-strain behaviour of human hair fibres using optical techniques.

    Lee, J; Kwon, H J


    Many studies have presented stress-strain relationship of human hair, but most of them have been based on an engineering stress-strain curve, which is not a true representation of stress-strain behaviour. In this study, a more accurate 'true' stress-strain curve of human hair was determined by applying optical techniques to the images of the hair deformed under tension. This was achieved by applying digital image cross-correlation (DIC) to 10× magnified images of hair fibres taken under increasing tension to estimate the strain increments. True strain was calculated by summation of the strain increments according to the theoretical definition of 'true' strain. The variation in diameter with the increase in longitudinal elongation was also measured from the 40× magnified images to estimate the Poisson's ratio and true stress. By combining the true strain and the true stress, a true stress-strain curve could be determined, which demonstrated much higher stress values than the conventional engineering stress-strain curve at the same degree of deformation. Four regions were identified in the true stress-strain relationship and empirical constitutive equations were proposed for each region. Theoretical analysis on the necking condition using the constitutive equations provided the insight into the failure mechanism of human hair. This analysis indicated that local thinning caused by necking does not occur in the hair fibres, but, rather, relatively uniform deformation takes place until final failure (fracture) eventually occurs.

  11. A New Method to Identify Quaternary Moraine:Acoustic Emission Stress Measurement

    ZHAO Zhizhong; QIAO Yansong; TIAN Jiaorong; WANG Min; LI Mingze; HE Peiyuan; QIAN Fang


    How to effectively identify glacial sediments, especially Quaternary moraine, has been in dispute for decades. The traditional methods, e.g., sedimentary and geomorphologic ones, are facing challenge in eastern China where controversial moraine deposits are dominatingly distributed. Here,for the first time, we introduce the acoustic emission (AE) stress measurement, a kind of historical stress measurement, to identify Quaternary moraine. The results demonstrate that it can be employed to reconstruct stress information of glaciation remaining in gravels, and may shed light on the identification of Quaternary moraine in eastern China. First, we measured the AE stress of gravels of glacial origin that are underlying the Xidatan Glacier, eastern Kunlun Mountains in western China.Second, we calculated the stress according to the actual thickness of the glacier. The almost identical stress values suggest that the glacial gravels can memorize and preserve the overlying glacier-derived aplomb stress. And then we introduce this new approach to the controversial moraine in Mount Lushan, eastern China. The results indicate that the stress is attributed to the Quaternary glacier, and the muddy gravels in the controversial moraine in Mount Lushan are moraine deposits but not others.

  12. A new sensor for stress measurement based on blood flow fluctuations

    Fine, I.; Kaminsky, A. V.; Shenkman, L.


    It is widely recognized that effective stress management could have a dramatic impact on health care and preventive medicine. In order to meet this need, efficient and seamless sensing and analytic tools for the non-invasive stress monitoring during daily life are required. The existing sensors still do not meet the needs in terms of specificity and robustness. We utilized a miniaturized dynamic light scattering sensor (mDLS) which is specially adjusted to measure skin blood flow fluctuations and provides multi- parametric capabilities. Based on the measured dynamic light scattering signal from the red blood cells flowing in skin, a new concept of hemodynamic indexes (HI) and oscillatory hemodynamic indexes (OHI) have been developed. This approach was utilized for stress level assessment for a few usecase scenario. The new stress index was generated through the HI and OHI parameters. In order to validate this new non-invasive stress index, a group of 19 healthy volunteers was studied by measuring the mDLS sensor located on the wrist. Mental stress was induced by using the cognitive dissonance test of Stroop. We found that OHIs indexes have high sensitivity to the mental stress response for most of the tested subjects. In addition, we examined the capability of using this new stress index for the individual monitoring of the diurnal stress level. We found that the new stress index exhibits similar trends as reported for to the well-known diurnal behavior of cortisol levels. Finally, we demonstrated that this new marker provides good sensitivity and specificity to the stress response to sound and musical emotional arousal.

  13. Systematic Review of Uit Parameters on Residual Stresses of Sensitized AA5456 and Field Based Residual Stress Measurements for Predicting and Mitigating Stress Corrosion Cracking


    significant amount of grinding and other sorts of damage marks that may have influenced the measurements. These measurements will be repeated on non...Mech. Eng., Naval Postgraduate School, Monterey, CA, 2012. 107 [24] M. Pourbaix, Atlas of Electrochemical Equilibria, Houston, TX: National...Journal of Electrochemical Science and Technology, vol. 129, no. 12, pp. 2660–2665, Dec. 1982. [26] H. L. Logan, "Film rupture mechanism of stress

  14. Wall shear stress measurement in blade end-wall corner region

    Bhargava, R.; Raj, R.; Boldman, D. R.


    The magnitude and the direction of wall shear stress and surface pressure in the blade end-wall corner region were investigated. The measurements were obtained on a specially designed Preston tube, the tip of which could be concentrically rotated about its axis of rotation at the measurement location. The magnitude of wall shear stress in the vicinity of the corner was observed to increase significantly (170 percent) compared to its far-upstream value; the increase was consistently higher on the blade surface compared to the value on the plate surface of the blade end-wall corner. On both surfaces in the blade end-wall corner, the variation of the wall shear stress direction was found to be more predominant in the vicinity of the blade leading-edge location. The trend of the measured wall shear stress direction showed good agreement with the limiting streamline directions obtained from the flow visualization studies.

  15. Comparison of surface wind stress measurements - Airborne radar scatterometer versus sonic anemometer

    Brucks, J. T.; Leming, T. D.; Jones, W. L.


    Sea surface wind stress measurements recorded by a sonic anemometer are correlated with airborne scatterometer measurements of ocean roughness (cross section of radar backscatter) to establish the accuracy of remotely sensed data and assist in the definition of geophysical algorithms for the scatterometer sensor aboard Seasat A. Results of this investigation are as follows: Comparison of scatterometer and sonic anemometer wind stress measurements are good for the majority of cases; however, a tendency exists for scatterometer wind stress to be somewhat high for higher wind conditions experienced in this experiment (6-9 m/s). The scatterometer wind speed algorithm tends to overcompute the higher wind speeds by approximately 0.5 m/s. This is a direct result of the scatterometer overestimate of wind stress from which wind speeds are derived. Algorithmic derivations of wind speed and direction are, in most comparisons, within accuracies defined by Seasat A scatterometer sensor specifications.


    Henningsen, Poul; Arentoft, Mogens; Lagergren, Jonas;


    A load transducer has been developed to measure the contact forces in the deformation zone during rolling. The transducer consists of a strain gauge equipped insert, embedded in the surface of the roll. The length of the insert exceeds the contact length between material and roll. By analyzing...

  17. In Situ Measurement of Voltage-Induced Stress in Conducting Polymers with Redox-Active Dopants.

    Sen, Sujat; Kim, Sung Yeol; Palmore, Lia R; Jin, Shenghua; Jadhav, Nitin; Chason, Eric; Palmore, G Tayhas R


    Minimization of stress-induced mechanical rupture and delamination of conducting polymer (CP) films is desirable to prevent failure of devices based on these materials. Thus, precise in situ measurement of voltage-induced stress within these films should provide insight into the cause of these failure mechanisms. The evolution of stress in films of polypyrrole (pPy), doped with indigo carmine (IC), was measured in different electrochemical environments using the multibeam optical stress sensor (MOSS) technique. The stress in these films gradually increases to a constant value during voltage cycling, revealing an initial break-in period for CP films. The nature of the ions involved in charge compensation of pPy[IC] during voltage cycling was determined from electrochemical quartz crystal microbalance (EQCM) data. The magnitude of the voltage-induced stress within pPy[IC] at neutral pH correlated with the radius of the hydrated mobile ion in the order Li(+) > Na(+) > K(+). At acidic pH, the IC dopant in pPy[IC] undergoes reversible oxidation and reduction within the range of potentials investigated, providing a secondary contribution to the observed voltage-induced stress. We report on the novel stress response of these polymers due to the presence of pH-dependent redox-active dopants and how it can affect material performance.

  18. Evaluation of Pressure Pain Threshold as a Measure of Perceived Stress and High Job Strain.

    Hven, Lisbeth; Frost, Poul; Bonde, Jens Peter Ellekilde


    To investigate whether pressure pain threshold (PPT), determined by pressure algometry, can be used as an objective measure of perceived stress and job strain. We used cross-sectional base line data collected during 1994 to 1995 within the Project on Research and Intervention in Monotonous work (PRIM), which included 3123 employees from a variety of Danish companies. Questionnaire data included 18 items on stress symptoms, 23 items from the Karasek scale on job strain, and information on discomfort in specified anatomical regions was also collected. Clinical examinations included pressure pain algometry measurements of PPT on the trapezius and supraspinatus muscles and the tibia. Associations of stress symptoms and job strain with PPT of each site was analyzed for men and women separately with adjustment for age body mass index, and discomfort in the anatomical region closest to the point of pressure algometry using multivariable linear regression. We found significant inverse associations between perceived stress and PPT in both genders in models adjusting for age and body mass index: the higher level of perceived stress, the lower the threshold. For job strain, associations were weaker and only present in men. In men all associations were attenuated when adjusting for reported discomfort in regions close to the site of pressure algometry. The distributions of PPT among stressed and non-stressed persons were strongly overlapping. Despite significant associations between perceived stress and PPT, the discriminative capability of PPT to distinguish individuals with and without stress is low. PPT measured by pressure algometry seems not applicable as a diagnostic tool of a state of mental stress.

  19. Measurement of in-situ stress in salt and rock using NQR techniques

    Schempp, E.; Hirschfeld, T.; Klainer, S.


    A discussion of how stress and strain affect the quantities which can be measured in an NQR experiment shows that, for stresses of the magnitude to be expected at depths up to about 10,000 feet, quadrupole coupling constants will fall in the range of 1 to 10 kHz for both the sodium and chloride ions in NaCl. The most promising system involves pulsed nuclear double resonance detection; and alterative is to observe the quadrupolar splitting of the NMR signal. Choices to be made in the measurement and mapping techniques are discussed. The well-known perturbation of the homogenous stress field in the neighborhood of a borehole is shown to be advantageous from the point of view of obtaining directional information on the stress. Construction and operation of a borehole stress sensor are considered. The NQR technique seems feasible for measuring the magnitude and direction of underground stress with a resolution of about 25 psi, or 2.5% at 1000 psi. Downhole instrumentation suitable for in-situ determinations of stress appears within the state of the art. Additional tasks required on the project are identified.

  20. Test with different stress measurement methods in two orthogonal bore holes in Aespoe HRL

    Janson, Thomas; Stigsson, Martin [Golder Associates AB, Stockholm (Sweden)


    Within the scope of work, to provide the necessary rock mechanics support for the site investigations, SKB has studied some available pieces of equipment for in situ stress measurements in deep boreholes. A project with the objective to compare three different pieces of equipment for in situ stress measurements under similar conditions has been carried out. The main objective for the project is to compare the three different pieces of equipment for in situ stress measurements and find a strategy for SKB's Site Investigations to determine the state of stress in the rock mass. Two units of equipment use the overcoring method while the third uses the hydraulic fracturing method. The overcoring was performed by AECL, using Deep Door stopper Gauge System (DDGS), and SwedPower, using their triaxial strain measuring instrument (Borre Probe). MeSy Geo Systeme GmbH performed the hydraulic fracturing. The DDGS system is a new method to SKB while the experience of the SwedPower overcoring and the hydraulic fracturing methods are long. The tests were performed in the same orthogonal boreholes at Aespoe Hard Rock Laboratory (HRL), Oskarshamn, Sweden. The measured results have been verified against known conditions at the Aespoe HRL. The results from the three in situ stress measurement methods rose more questions than answers. Which illustrate the complexity to determine the in situ stresses in a rock mass. To understand the difference in results and answer the questions, it was necessary to do deeper investigations such as laboratory tests and theoretical calculations such as geological structure model, analysis of the influence of a nearby fracture, P-wave measurements, uniaxial tests on small cores from the HQ-3 core, theoretical and numerical analyses of the hole bottom (theoretical strains, stress concentrations and microcracking), auditing of DDGS measurements results and assumptions in the DDGS analyse and microscopy investigations on the cores. The following

  1. Acoustic Measurements of Residual Stresses and Grain Sizes in Aluminum Alloys

    Fisher, Martin John

    The theory of acoustoelasticity relates the velocity of an acoustic wave in a solid to the elastic stress state in that solid. This thesis presents new theories, measurement techniques, and methodologies related to the use of longitudinal wave acoustoelasticity in aluminum alloys. A one-dimensional model has been developed to provide a simple understanding of the acoustoelastic effect. A new acoustic device for accurately measuring relative thickness variations has been designed and built. This device is used--in conjunction with a pulse-echo phase measurement device and a computer controlled scanning system--to measure acoustic velocity variations in plastically deformed and non-flat-and-parallel samples. Acoustic velocity variations from point to point in an unstressed sample can sometimes be on the same order as velocity changes due to applied or residual stresses, and this can make stress measurements difficult. A statistical theory has been developed to relate these unstressed velocity variations to the average grain size in the sample and to the active area of the acoustic transducer used. Large transducers and small grain sizes will minimize these variations. This relationship has been verified by tests on a number of aluminum alloys and a new method for non-destructive grain size determination has been suggested. A systematic methodology has been developed and tested for studying the influence of uniaxial plastic deformation on the acoustoelastic response. Samples have been plastically deformed in four-point bending to produce elastic-plastic and residual stress states. Acoustic measurements of these stresses have then been compared directly to theoretical predictions based on the materials' stress-strain curves and simple beam theory. In the aluminum alloys tested (2024-T351 and 7075-T651), the acoustoelastic constants are shown to be virtually unchanged by uniaxial plastic strains of less than 2.5%. Thus, the acoustoelastic technique can be reliably

  2. Measurement of Residual Stress Field of Hardfacing Metal with RE Oxide and Its Numerical Simulation

    杨庆祥; 姚枚


    The temperature and residual stress fields of a medium-high carbon steel, welded by a cracking resistance electrode with rare earth (RE) oxide, were measured by thermo-vision analyzer and X-ray stress analyzer respectively. Meanwhile, the martensitic transformation temperatures of matrix, hard-face welding (hardfacing) metal welded by conventional hardfacing electrode and that welded by cracking resistance electrode with RE oxide were determined. According to the expe rimental data and the thermo-physical, mechanical parameters of materials, finite element method (FEM) of temperature and stress fields was established. In this FEM, the effect of martensitic transformation on residual stress of hardfacing metal of medium-high carbon steel was taken into account. The results show that, by adding RE oxide in the coat of hardfacing electrode, the martensitic trans formation temperature can be decreased, so that the residual tensile stress on the dangerous position can be decreased. Therefore, the cracking resistance of hardfacing metal can be improved.

  3. Coupled stress-strain and electrical resistivity measurements on copper based shape memory single crystals

    Gonzalez Cezar Henrique


    Full Text Available Recently, electrical resistivity (ER measurements have been done during some thermomechanical tests in copper based shape memory alloys (SMA's. In this work, single crystals of Cu-based SMA's have been studied at different temperatures to analyse the relationship between stress (s and ER changes as a function of the strain (e. A good consistency between ER change values is observed in different experiments: thermal martensitic transformation, stress induced martensitic transformation and stress induced reorientation of martensite variants. During stress induced martensitic transformation (superelastic behaviour and stress induced reorientation of martensite variants, a linear relationship is obtained between ER and strain as well as the absence of hys teresis. In conclusion, the present results show a direct evidence of martensite electrical resistivity anisotropy.

  4. Rolling Mill Work Roll Stress Analysis and Strain Measurement

    R. K. Jones


    This study of a rolling mill work roll failure consisted of (a) a review of related published materials, (b) measuring strain on the spindles with strain gages, (c) performing finite element analyses (FEA) modeling of the work roll thrust groove section (using the measured spindle loading), (d) fabricating and testing an physical model of the work roll, using the good end of a broken work roll, (e) recording motor voltage and current, and (f) processing, analyzing, and comparing the results. A methodical approach was taken to determine the causes of the failures. The actual loading to which the work rolls were subjected was determined, then these loads were used in a FEA of the thrust groove sections of three work roll designs: failed, current, and proposed. To verify the FEA results, a physical model was fabricated, built, and subjected to instrumented tests. The study offered the following recommendations: remove the undercut groove in the thrust groove section on future procurements; investigate possible methods of removing the transverse keyway; forego the larger drive train upgrades proposed by the mill manufacturer; continue frequent thrust groove inspections; require chemical and mechanical property certifications on all future procurements; and immediately scrap any work rolls that exhibit surface cracking.

  5. Residual stress measurement with high energy x-rays at the Advanced Photon Source.

    Winholtz, R. A.; Haeffner, D. R.; Green, R.E.L.; Varma, R.; Hammond, D.


    Preliminary measurements with high energy x-rays from the SRI CAT 1-ID beam line at the Advanced Photon show great promise for the measurement of stress and strain using diffraction. Comparisons are made with neutron measurements. Measurements of strains in a 2 mm thick 304 stainless steel weld show that excellent strain and spatial resolutions are possible. With 200 {micro}m slits, strain resolutions of 1 x 10{sup {minus}5} were achieved.

  6. Measurement of heat treatment induced residual stresses by using ESPI combined with hole-drilling method

    Jie Cheng; Si-Young Kwak; Ho-Young Hwang


    In this study,residual stresses in heat treated specimen were measured by using ESPI(Electronic Speckle-Pattern Interferometry)combined with the hole-drilling method.The specimen,made of SUS 304austenitic stainless steel,was quenched and water cooled to room temperature.Numerical simulation using a hybrid FDM/FEM package was also carried out to simulate the heat treatment process.As a result,the thermal stress fields were obtained from both the experiment and the numerical simulation.By comparision of stress fields,results from the experimental method and numerical simulation well agreed to each other,therefore,it is proved that the presented experimental method is applicable and reliable for heat treatment induced residual stress measurement.

  7. Self-oscillation acoustic system destined to measurement of stresses in mass rocks

    Kwasniewski, Janusz; Dominik, Ireneusz; Dorobczynski, Lech


    The paper presents an electronic self-oscillation acoustic system (SAS) destined to measure of stresses variations in the elastic media. The system consists of piezoelectric detector, amplifier-limiter, pass-band filter, piezoelectric exciter and the frequency meter. The mass rock plays a role of delaying element, in which variations in stresses causing the variations of acoustic wave velocity of propagation, and successive variation in frequency of oscillations generated by system. The laboratory test permitted to estimate variations in frequency caused by variations in stresses of elastic medium. The principles of selection of frequency and other parameters of the electronic system in application to stresses measurement in condition of the mine were presented.

  8. Measurement and tailoring of residual stress in expanded austenite on austenitic stainless steel

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Winther, Grethe


    Expanded austenite on stainless steel with a high interstitial nitrogen content is characterized by elasto-plastic accommodation of the large composition-induced lattice expansion leading to huge compressive residual stress. The elasto-plastic accommodation as well as the (steep) concentration...... profile has implications for the measurement strategy to determine lattice strains and associated residual stresses with X-ray diffraction. Lattice strain measurements were performed on nitrided as well as subsequently de-nitrided expanded austenite on AISI 316L stainless steel, for various grazing...... stresses in expanded austenite can be tailored by de-nitriding after nitriding, such that a condition of virtually zero stress at the surface is obtained....

  9. Laser Treatment of HVOF Coating: Modeling and Measurement of Residual Stress in Coating

    Arif, A. F. M.; Yilbas, B. S.


    High-velocity oxy-fuel (HVOF) coating of diamalloy 1005 (similar to Inconel 625 alloy) onto the Ti-6Al-4V alloy is considered and laser-controlled melting of the coating is examined. The residual stress developed after the laser treatment process is modeled using the finite element method (FEM). The experiment is conducted to melt the coating using a laser beam. The residual stress measurement in the coating after the laser treatment process is realized using the XRD technique. The morphological and metallurgical changes in the coating are examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is found that the residual stress reduces at the coating-base material interface and the residual stress predicted agrees with the XRD measurements. A compact and crack-free coating is resulted after the laser treatment process.

  10. Stress

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  11. Stress

    ... sudden negative change, such as losing a job, divorce, or illness Traumatic stress, which happens when you ... stress, so you can avoid more serious health effects. NIH: National Institute of Mental Health

  12. Spatial Resolution Correction for Electrochemical Wall-shear Stress Measurements using Rectangular Sensors

    Fethi Aloui


    Full Text Available This article is mainly motivated by the growing needs for highly resolved measurements for wall-bounded turbulent flows and aims to proposes a spatial correction coefficient in order to increase the wall-shear stress sensors accuracy. As it well known for the hot wire anemometry, the fluctuating streamwise velocity measurement attenuation is mainly due to the spatial resolution and the frequency response of the sensing element. The present work agrees well with this conclusion and expands it to the wall-shear stress fluctuations measurements using electrochemical sensors and suggested a correction method based on the spanwise correlation coefficient to take into account the spatial filtering effects on unresolved wall-shear stress measurements due to too large sensor spanwise size.

  13. Turbulent stress measurements with phase-contrast magnetic resonance through tilted slices

    MacKenzie, Jordan; Soederberg, Daniel; Lundell, Fredrik [Linne FLOW Centre, KTH Mechanics, Stockholm (Sweden); Swerin, Agne [SP Technical Research Institute of Sweden-Chemistry, Materials and Surfaces, Stockholm (Sweden); KTH Royal Institute of Technology, Surface and Corrosion Science, Stockholm (Sweden)


    Aiming at turbulent measurements in opaque suspensions, a simplistic methodology for measuring the turbulent stresses with phase-contrast magnetic resonance velocimetry is described. The method relies on flow-compensated and flow-encoding protocols with the flow encoding gradient normal to the slice. The experimental data is compared with direct numerical simulations (DNS), both directly but also, more importantly, after spatial averaging of the DNS data that resembles the measurement and data treatment of the experimental data. The results show that the most important MRI data (streamwise velocity, streamwise variance and Reynolds shear stress) is reliable up to at least anti r = 0.75 without any correction, paving the way for dearly needed turbulence and stress measurements in opaque suspensions. (orig.)

  14. An accelerometer based system to measure myocardial performance index during stress testing.

    Anh Dinh; Bui, Francis M; Tam Nguyen


    Stress testing is used to measure the performance of the heart in an elevated stress state, in order to monitor or diagnose certain heart problems. Many measurements can be used to determine the performance of the heart, with the Tei index being the measurement of interest in this work. The Tei index has been used as a reliable method to evaluate systolic and diastolic performance, as it overcomes some limitations of the classical echocardiographic indices. It is calculated based on the time intervals derived from echocardiography. This paper presents an exploratory study, which uses an accelerometer to record mechanical events occurring in each cardiac cycle, also known as the seismocardiogram (SCG). From timing measurements corresponding to various events in the heart, a metric for myocardial performance is calculated based on the Tei index. The use of SCG in addition to ECG has the potential to provide further insights about the heart during stress testing, since the SCG quantifies mechanical actions of the heart.

  15. Mental stress assessment using simultaneous measurement of EEG and fNIRS.

    Al-Shargie, Fares; Kiguchi, Masashi; Badruddin, Nasreen; Dass, Sarat C; Hani, Ahmad Fadzil Mohammad; Tang, Tong Boon


    Previous studies reported mental stress as one of the major contributing factors leading to various diseases such as heart attack, depression and stroke. An accurate stress assessment method may thus be of importance to clinical intervention and disease prevention. We propose a joint independent component analysis (jICA) based approach to fuse simultaneous measurement of electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) on the prefrontal cortex (PFC) as a means of stress assessment. For the purpose of this study, stress was induced by using an established mental arithmetic task under time pressure with negative feedback. The induction of mental stress was confirmed by salivary alpha amylase test. Experiment results showed that the proposed fusion of EEG and fNIRS measurements improves the classification accuracy of mental stress by +3.4% compared to EEG alone and +11% compared to fNIRS alone. Similar improvements were also observed in sensitivity and specificity of proposed approach over unimodal EEG/fNIRS. Our study suggests that combination of EEG (frontal alpha rhythm) and fNIRS (concentration change of oxygenated hemoglobin) could be a potential means to assess mental stress objectively.

  16. In situ stress and nanogravimetric measurements during underpotential deposition of bismuth on (111)-textured Au.

    Stafford, G R; Bertocci, U


    The surface stress associated with the underpotential deposition (upd) of bismuth on (111)-textured Au is examined, using the wafer curvature method, in acidic perchlorate and nitrate supporting electrolyte. The surface stress is correlated to Bi coverage by independent nanogravimetric measurements using an electrochemical quartz crystal nanobalance. The mass increase measured in the presence of perchlorate is consistent with the (2 x 2) and (p x square root 3)-2Bi adlayers reported in the literature. ClO(4)(-) does not play a significant role in the upd process. The complete Bi monolayer causes an overall surface stress change of about -1.4 N m(-1). We attribute this compressive stress to the formation of Bi-Au bonds which partially satisfy the bonding requirements of the Au surface atoms, thereby reducing the tensile surface stress inherent to the clean Au surface. At higher Bi coverage, an additional contribution to the compressive stress is due to the electrocompression of the (p x square root 3)-2Bi adlayer. In nitric acid electrolyte, NO(3)(-) coadsorbs with Bi over the entire upd region but has little fundamental impact on adlayer structure and stress.

  17. Residual stress measurements in the dissimilar metal weld in pressurizer safety nozzle of nuclear power plant

    Campos, Wagner R.C.; Rabello, Emerson G.; Mansur, Tanius R.; Scaldaferri, Denis H.B.; Paula, Raphael G., E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Souto, Joao P.R.S.; Carvalho Junior, Ideir T., E-mail:, E-mail: [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Metalurgica


    Weld residual stresses have a large influence on the behavior of cracking that could possibly occur under normal operation of components. In case of an unfavorable environment, both stainless steel and nickel-based weld materials can be susceptible to stress-corrosion cracking (SCC). Stress corrosion cracks were found in dissimilar metal welds of some pressurized water reactor (PWR) nuclear plants. In the nuclear reactor primary circuit the presence of tensile residual stress and corrosive environment leads to so-called Primary Water Stress Corrosion Cracking (PWSCC). The PWSCC is a major safety concern in the nuclear power industry worldwide. PWSCC usually occurs on the inner surface of weld regions which come into contact with pressurized high temperature water coolant. However, it is very difficult to measure the residual stress on the inner surfaces of pipes or nozzles because of inaccessibility. A mock-up of weld parts of a pressurizer safety nozzle was fabricated. The mock-up was composed of three parts: an ASTM A508 C13 nozzle, an ASTM A276 F316L stainless steel safe-end, an AISI 316L stainless steel pipe and different filler metals of nickel alloy 82/182 and AISI 316L. This work presents the results of measurements of residual strain from the outer surface of the mock-up welded in base metals and filler metals by hole-drilling strain-gage method of stress relaxation. (author)

  18. Transducer for measuring normal and friction stress in contact zone during rolling

    Henningsen, Poul; Wanheim, Tarras; Arentoft, Mogens


    by the friction conditions. To achieve this important information, measurements of the normal pressure and friction stresses in the deformation zone are requested. The interface conditions are analyzed by several authors [1-8] The direction of the friction stress is changing during the rolling gap....... At the entrance of the deformation zone, the peripherical velocity of the roll is higher than for the incoming material, which causes frictional stresses at the material acting in the rolling direction. At the outlet of the rolling gap, the velocity of the deformed material exceeds the velocity of the roll...

  19. X-ray residual stress measurement of laminated coating layers produced by plasma spraying

    Nishida, Masayuki (Faculty of Engineering, Tokushima Univ. (Japan)); Hanabusa, Takao (Faculty of Engineering, Tokushima Univ. (Japan)); Fujiwara, Haruo (Faculty of Engineering, Tokushima Univ. (Japan))


    The present paper describes residual stress in laminated layers deposited by thermal spraying on a low carbon steel substrate. Laminated layers were made of Al[sub 2]O[sub 3]-NiCr or Al[sub 2]O[sub 3]-NiAl with various combinations of mixing ratios. X-Ray diffraction was used to measure residual stress in the outermost surface layer. The results of finite-element method (FEM) thermal stress analysis were compared with the experimental results of X-ray measurements. From the X-ray stress measurements, tensile residual stress (100-300 MPa) was measured in the as-coated surface layers of all specimens. The effect of annealing on residual stress variation was also examined. In the case of the Al[sub 2]O[sub 3] (100%) layer of the Al[sub 2]O[sub 3]-NiCr system, residual stress of surface layers was not greatly affected by the method of lamination and did not change significantly upon annealing. In contrast, in the layer with mixed Al[sub 2]O[sub 3] and NiAl, residual stress in the as-coated layer was influenced by the mixing ratio of Al[sub 2]O[sub 3] and NiAl. Furthermore, residual stresses were gradually reduced in both the Al[sub 2]O[sub 3] and Ni phase following annealing. FEM calculation revealed that large compressive residual stress (about -2 GPa) was produced in the 100% Al[sub 2]O[sub 3] layer after a full annealing treatment. The value of residual stress depends on the difference between the thermal expansion coefficients of the laminated layers and the substrate. This result was exactly opposite to the experimental results for the fully annealed Al[sub 2]O[sub 3]-NiCr system. However, residual stresses in the mixed layer (Al[sub 2]O[sub 3]-NiAl) depended on the mixing ration of Al[sub 2]O[sub 3] and NiAl. This agrees qualitatively with the experimental results. (orig.)

  20. The distorting effect of varying diets on fecal glucocorticoid measurements as indicators of stress

    Kalliokoski, Otto; Teilmann, A. Charlotte; Abelson, Klas S. P.


    The physiological stress response is frequently gauged in animals, non-invasively, through measuring glucocorticoids in excreta. A concern with this method is, however, the unknown effect of variations in diets on the measurements. With an energy dense diet, leading to reduced defecation, will low...

  1. Measuring Thermal Stress of Dairy Cattle Based on Temperature Humidity Index (THI) in Tropical Climate

    Sugiono; Dewi Hardiningtyas; Rudy Soenoko


    Thermal comfort for workers is very important factor to increase their performance, as well as the comfort level of dairy cattle will influence in milk productivity. The purposes of the paper is to measure the level of heat stress and then use the information to design the dairy cattle house for increasing thermal comfort. The research is started with literature review of heat stress and early survey of environment condition e.g. temperature, wind speed and relative humidity. The next step is...

  2. Green space and stress: evidence from cortisol measures in deprived urban communities.

    Roe, Jenny J; Thompson, Catharine Ward; Aspinall, Peter A; Brewer, Mark J; Duff, Elizabeth I; Miller, David; Mitchell, Richard; Clow, Angela


    Contact with green space in the environment has been associated with mental health benefits, but the mechanism underpinning this association is not clear. This study extends an earlier exploratory study showing that more green space in deprived urban neighbourhoods in Scotland is linked to lower levels of perceived stress and improved physiological stress as measured by diurnal patterns of cortisol secretion. Salivary cortisol concentrations were measured at 3, 6 and 9 h post awakening over two consecutive weekdays, together with measures of perceived stress. Participants (n = 106) were men and women not in work aged between 35-55 years, resident in socially disadvantaged districts from the same Scottish, UK, urban context as the earlier study. Results from linear regression analyses showed a significant and negative relationship between higher green space levels and stress levels, indicating living in areas with a higher percentage of green space is associated with lower stress, confirming the earlier study findings. This study further extends the findings by showing significant gender differences in stress patterns by levels of green space, with women in lower green space areas showing higher levels of stress. A significant interaction effect between gender and percentage green space on mean cortisol concentrations showed a positive effect of higher green space in relation to cortisol measures in women, but not in men. Higher levels of neighbourhood green space were associated with healthier mean cortisol levels in women whilst also attenuating higher cortisol levels in men. We conclude that higher levels of green space in residential neighbourhoods, for this deprived urban population of middle-aged men and women not in work, are linked with lower perceived stress and a steeper (healthier) diurnal cortisol decline. However, overall patterns and levels of cortisol secretion in men and women were differentially related to neighbourhood green space and warrant

  3. Feasibility of using a biowatch to monitor GSR as a measure of radiologists' stress and fatigue

    Krupinski, Elizabeth A.; MacKinnon, Lea; Reiner, Bruce I.


    We have been investigating the impact of fatigue on diagnostic performance of radiologists interpreting medical images. In previous studies we found evidence that eye strain could be objectively measured and that it correlates highly with degradations in diagnostic accuracy as radiologists work long hours. Eye strain however can be difficult to measure in a non-invasive and continuous manner over the work day so we have been investigating other ways to measure physiological stress and fatigue. In this study we evaluated the feasibility of using a commercially available biowatch to measure galvanic skin response (GSR), a well known indicator of stress. 10 radiology residents wore the biowatch for about 8 hours during their normal work day and data were automatically collected at 10 Hz. They completed the Swedish Occupational Fatigue Inventory (SOFI) at the start and finish of the day. GSR values (microsiemens) ranged from 0.14 to 38.27 with an average of 0.50 (0.28 median). Overall GSR tended to be fairly constant as the day progressed, but there were definite spikes indicating higher levels of stress. SOFI scores indicated greater levels of fatigue and stress at the end of the work day. Although further work is needed, GSR measurements obtained via an easy to wear watch may provide a means to monitor stress/fatigue and alert radiologists when to take a break from interpreting images to avoid making errors.

  4. Diffraction plane dependence of elastic constants in residual stress measurement by neutron diffraction

    Okido, Shinobu; Hayashi, Makoto [Hitachi Ltd., Tokyo (Japan); Morii, Yukio; Minakawa, Nobuaki; Tsuchiya, Yoshinori


    In a residual stress measurement by x-ray diffraction method and a neutron diffraction method, strictly speaking, the strain measurement of various diffracted surface was conducted and it is necessary to use its elastic modulus to convert from the strain to the stress. Then, in order to establish the residual stress measuring technique using neutron diffraction, it is an aim at first to make clear a diffraction surface dependency of elastic modulus for the stress conversion in various alloys. As a result of investigations the diffraction surface dependency of elastic module on SUS304 and STS410 steels by using RESA (Neutron diffractometer for residual stress analysis) installed at JRR-3M in Tokai Establishment of JAERI, following results are obtained. The elastic modulus of each diffraction surface considering till plastic region could be confirmed to be in a region of {+-}20% of that calculated by Kroner`s model and to be useful for that used on conversion to the stress. And, error of this elastic modulus was thought to cause the transition and defect formed at inner portion of the materials due to a plastic deformation. (G.K.)

  5. Residual stress measurement on propellant tank of 2219 aluminum alloy and study on its weak spot

    Huang, Chaoqun; Li, Huan; Li, Jianxiong; Luo, Chuanguang; Ni, Yanbing [Tianjin University, Tianjin (China)


    This paper presented residual stress measurement on two circumferential Variable polarity plasma arc welding (VPPAW) joints and one circular closed Friction stir welding (FSW) joint on the propellant tank of 2219 aluminum alloy using the indentation strain-gauge method. Quite large tensile residual stresses were attached to the center and inner areas of the circular closed FSW joint. There were very large tensile stresses in some points of the two circumferential VPPAW joints, among these points, the maximum value was +253 MPa, which was about 63 % of the yield strength of 410 MPa measured in the base material. In addition, the peak of compressive residual stress was about -160 MPa. Above all, there were two typical peaks of residual stress in the circumferential VPPAW joints, one was located in the middle part while the other one was near the start/end position of the joints. Combining the result of residual stress measurement with the characteristics of the tank structure, it can be concluded that circular closed FSW joint around the flange was a weak spot on the propellant tank. And the most vulnerable point on the circular closed FSW joint has also been found.

  6. Review of Stress and the Measurement of Stress in Marine Mammals


    et al., 2006). Hair shaft cortisol will be determined using a technique recently validated for use in free-ranging terrestrial mammals ( Macbeth et...extracted into methanol, reconstituted in phosphate buffer, and measured using a commercially available enzyme- linked immunosorbent assay ( Macbeth ...species of delphinids. Marine Mammal Science 22, 1-16. Macbeth , B. J., Cattet, M. R. L., Stenhouse, G. B., Gibeau, M. L., and Janz, D. M. 2010. Hair

  7. Comparison of stress-measuring techniques at the DNA-UTP site, Rodgers Hollow, Kentucky

    Finley, R.E.


    The Defense Nuclear Agency (DNA) is developing explosives technology through its Underground Technology Program (UTP). Sandia National Laboratories (SNL) has supported the DNA by conducting research to characterize the in situ stress and rock mass deformability at one of the UTP underground sites at Rodgers Hollow, near Louisville, Kentucky on the Fort Knox Military Reservation. The purpose of SNL`s testing was to determine the in situ stress using three different measurement techniques and, if possible, to estimate the rock mass modulus near the underground opening. The three stress-measuring techniques are (1) borehole deformation measurements using overcoring, (2) Anelastic Strain Recovery (ASR) complemented by laboratory ultrasonic and mechanical properties testing, and (3) the in situ flatjack technique using cancellation pressure. Rock mass modulus around the underground opening was estimated using the load deformation history of the flatjack and surrounding rock. Borehole deformation measurements using the overcoring technique probably represent the most reliable method for in situ stress determination in boreholes up to 50 ft (15 m) deep in competent rock around an isolated excavation. The technique is used extensively by the tunneling and mining industries. The ASR technique is also a core-based technique and is used in the petroleum and natural gas industries for characterization of in situ stress from deep boreholes. The flatjack technique has also been used in the tunneling and mining industries, and until recently has been limited to measurement of the stress immediately around the excavation. Results from the flatjack technique must be further analyzed to calculate the in situ stress in the far field.

  8. A new nondestructive instrument for bulk residual stress measurement using tungsten kα1 X-ray

    Ma, Ce; Dou, Zuo-yong; Chen, Li; Li, Yun; Tan, Xiao; Dong, Ping; Zhang, Jin; Zheng, Lin; Zhang, Peng-cheng


    We describe an experimental instrument used for measuring nondestructively the residual stress using short wavelength X-ray, tungsten kα1. By introducing a photon energy screening technology, the monochromatic X-ray diffraction of tungsten kα1 was realized using a CdTe detector. A high precision Huber goniometer is utilized in order to reduce the error in residual stress measurement. This paper summarizes the main performance of this instrument, measurement depth, stress error, as opposed to the neutron diffraction measurements of residual stress. Here, we demonstrate an application on the determination of residual stress in an aluminum alloy welded by the friction stir welding.

  9. Uncertainty Quantification and Comparison of Weld Residual Stress Measurements and Predictions.

    Lewis, John R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brooks, Dusty Marie [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    In pressurized water reactors, the prevention, detection, and repair of cracks within dissimilar metal welds is essential to ensure proper plant functionality and safety. Weld residual stresses, which are difficult to model and cannot be directly measured, contribute to the formation and growth of cracks due to primary water stress corrosion cracking. Additionally, the uncertainty in weld residual stress measurements and modeling predictions is not well understood, further complicating the prediction of crack evolution. The purpose of this document is to develop methodology to quantify the uncertainty associated with weld residual stress that can be applied to modeling predictions and experimental measurements. Ultimately, the results can be used to assess the current state of uncertainty and to build confidence in both modeling and experimental procedures. The methodology consists of statistically modeling the variation in the weld residual stress profiles using functional data analysis techniques. Uncertainty is quantified using statistical bounds (e.g. confidence and tolerance bounds) constructed with a semi-parametric bootstrap procedure. Such bounds describe the range in which quantities of interest, such as means, are expected to lie as evidenced by the data. The methodology is extended to provide direct comparisons between experimental measurements and modeling predictions by constructing statistical confidence bounds for the average difference between the two quantities. The statistical bounds on the average difference can be used to assess the level of agreement between measurements and predictions. The methodology is applied to experimental measurements of residual stress obtained using two strain relief measurement methods and predictions from seven finite element models developed by different organizations during a round robin study.

  10. Standard test method for calibration of surface/stress measuring devices

    American Society for Testing and Materials. Philadelphia


    Return to Contents page 1.1 This test method covers calibration or verification of calibration, or both, of surface-stress measuring devices used to measure stress in annealed and heat-strengthened or tempered glass using polariscopic or refractometry based principles. 1.2 This test method is nondestructive. 1.3 This test method uses transmitted light, and therefore, is applicable to light-transmitting glasses. 1.4 This test method is not applicable to chemically tempered glass. 1.5 Using the procedure described, surface stresses can be measured only on the “tin” side of float glass. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  11. Residual stress measurement by successive extension of a slot: A literature review

    Prime, M.B.


    This report reviews the technical literature on techniques that employ successive extension of a slot and the resulting deformations to measure residual stress. Such techniques are known variously in the literature as the compliance or crack compliance method, the successive cracking method, the slotting method, and a fracture mechanics based approach. The report introduces the field and describes the basic aspects of these methods. The report then reviews all literature on the theoretical developments of the method. The theory portion first considers forward method solutions including fracture mechanics, finite element, analytical, and body force methods. Then it examines inverse solutions, including incremental inverses and series expansions. Next, the report reviews all experimental applications of slotting methods. Aspects reviewed include the specimen geometry and material, the details of making the slot, the method used to measure deformation, and the theoretical solutions used to solve for stress. Finally, the report makes a brief qualitative comparison between slotting methods and other residual stress measurement methods.

  12. A test case of the deformation rate analysis (DRA) stress measurement method

    Dight, P.; Hsieh, A. [Australian Centre for Geomechanics, Univ. of WA, Crawley (Australia); Johansson, E. [Saanio and Riekkola Oy, Helsinki (Finland); Hudson, J.A. [Rock Engineering Consultants (United Kingdom); Kemppainen, K.


    As part of Posiva's site and ONKALO investigations, the in situ rock stress has been measured by a variety of techniques, including hydraulic fracturing, overcoring, and convergence measurements. All these techniques involve direct measurements in a drillhole or at the rock surface. An alternative method is to test drillhole core in a way that enables estimation of the magnitudes and orientations of the in situ rock stress. The Kaiser Effect (KE) and Deformation Rate Analysis (DRA) are two ways to do this. In the work reported here, a 'blind' DRA test was conducted on core obtained from the POSE (Posiva's Olkiluoto Spalling Experiment) niche in the ONKALO. The term 'blind' means that the two first authors of this report, who conducted the tests at the Australian Centre for Geomechanics, did not know the depths below surface at which the cores had been obtained. The results of this DRA Test Case are presented, together with an explanation of the DRA procedure. Also, additional information that would help in such DRA testing and associated analysis is explained. One of the problems in comparing the DRA results with the known Olkiluoto stress field is that the latter is highly variable across the site, as experienced by the previous in situ stress measurements and as predicted by numerical analysis. The variability is mainly caused by the presence of the large brittle deformation zones which perturb the local stress state. However, this variability reduces with depth and the stress field becomes more stable at the {approx} 350 m at which the drillhole cores were obtained. Another compounding difficulty is that the stress quantity, being a second order tensor, requires six independent components for its specification. In other words, comparison of the DRA results and the known stress field requires comparison of six different quantities. In terms of the major principal stress orientation, the DRA results predict an orientation completely

  13. A new device designed for direct yield stress measurements of cement spacer

    Gordon, C.L.; Tonmukayakul, P.; Morgan, R.L. [Halliburton Energy Services, Houston, TX (United States)


    The rheological properties of spacer fluids and cement slurries have a significant impact on the hydraulic shear stress of well casing walls. This paper described experimental studies and numerical models of a device designed to measure the yield stress and rheological properties of spacer and cement samples. The device was designed using the Couette principle for rheological measurements, and measured the yield stress of particle-laden samples between 4 and 150 degrees C. A sample contained in a gap between a stator and a blade located along the inside wall of a steel cup was analyzed using the device. A stator was attached to a torque device and remained static during the rheological measurement. Yield stress was measured by rotating the device at a low speed at 3 rpm and at steady state torque. Torque was recorded when the rotation stopped. Two aqueous mixtures of titanium oxide (TiO{sub 2}) particles were used for the experiment. A cement spacer comprised of a blend of barite, citric acid and water was also measured. A volume-averaged shear method was used to calculate shear rate and shear stress. Key dimensionless variables were the impeller Reynolds number; the Froude number; the Weber number; and the Weissenberg number. Accuracy was assessed by examining the data obtained with a model fluid where yield stress data was already determined. Results of the comparison showed that values obtained using the device were consistent and comparable with results obtained using other techniques. It was concluded that further research is needed to characterize the elastic fluids in the device. 13 refs., 2 tabs., 3 figs.

  14. Rock stress measurements. Preparatory stage of the equipment development project; Kallioperaen jaennitystilan mittaaminen. Laitekehityshankkeen valmisteluvaihe

    Mononen, S.; Hakala, M.; Mikkola, P


    In recent years the rock stress measurement methods used in Finland have been overcoring and hydraulic fracturing. There have been mainly two companies involved in these measurements, namely Suomen Malmi Oy (Smoy) and SwedPower AB. Smoy has done measurements for mines and for rock engineering projects, whereas SwedPower AB has mainly been involved in nuclear waste disposal investigations and conducted hydraulic fracturing measurements in deep boreholes. Smoy together with its partners started in February 2001 a project named JTM, which was a preliminary stage for a future project, which aims to develop a device most suitable for rock stress measurements in Finland. The partners in the project were HUT Rock Engineering, Posiva Oy, Saanio and Riekkola Oy, Gridpoint Finland Oy and Geopros Oy. Tekes, the National Technology Agency, provided almost half of the project funding. In the management group of the project were Pekka Mikkola (chairman) and Tero Laurila from Smoy, Pekka Saerkkae and Sakari Mononen (full-time researcher) from HUT, Aimo Hautojaervi (Posiva Oy), Erik Johansson (Saanio and Riekkola Oy), Matti Hakala (Gridpoint Finland Oy) and Heikki Haemaelaeinen (Geopros Oy). The aim of the JTM-project was to find out the needs for the development of a device most suitable for rock stress measurements in Finnish mines and rock engineering projects. During the project work was done to find out the range of rock stress measurement devices available, to find out the needs for measurements, and to get acquainted to the measurements done in Scandinavia. Also a report of the most suitable methods for Finnish rock conditions was done based on literature and on interviews of rock stress experts. Based on all the information collected during the project a clear picture of the needs for rock stress measurements in Finland could be formed and a preliminary plan of a future project was done. The aim of the suggested project is to build a device based on hydraulic fracturing

  15. A Method Using Optical Contactless Displacement Sensors to Measure Vibration Stress of Small-Bore Piping.

    Maekawa, Akira; Tsuji, Takashi; Takahashi, Tsuneo; Noda, Michiyasu


    In nuclear power plants, vibration stress of piping is frequently evaluated to prevent fatigue failure. A simple and fast measurement method is attractive to evaluate many piping systems efficiently. In this study, a method to measure the vibration stress using optical contactless displacement sensors was proposed, the prototype instrument was developed, and the instrument practicality for the method was verified. In the proposed method, light emitting diodes (LEDs) were used as measurement sensors and the vibration stress was estimated by measuring the deformation geometry of the piping caused by oscillation, which was measured as the piping curvature radius. The method provided fast and simple vibration estimates for small-bore piping. Its verification and practicality were confirmed by vibration tests using a test pipe and mock-up piping. The stress measured by both the proposed method and an accurate conventional method using strain gauges were in agreement, and it was concluded that the proposed method could be used for actual plant piping systems.

  16. Studies of residual stress measurement and analysis techniques for a PWR dissimilar weld joint

    Ogawa, Naoki, E-mail: [Mitsubishi Heavy Industries, Ltd., 2-1-1, Shinhama, Arai-cho, Takasago 676-8686 (Japan); Muroya, Itaru; Iwamoto, Youichi; Ohta, Takahiro; Ochi, Mayumi; Hojo, Kiminobu [Mitsubishi Heavy Industries, Ltd., 2-1-1, Shinhama, Arai-cho, Takasago 676-8686 (Japan); Ogawa, Kazuo [Japan Nuclear Energy Safety Organization, 3-17-1, Toranomon, Minato-ku, Tokyo 105-0001 (Japan)


    For evaluation of the PWSCC crack propagation behavior, a test model was produced using the same fabrication process of Japanese PWR plants and the stress distribution change was measured during a fabrication process such as a hydrostatic test, welding a main coolant pipe to the stainless steel safe end and an operation condition test. For confirmation of validity of the numerical estimation method of the stress distribution, FE analysis was performed to calculate the stress distributions for each fabrication process. From the validation procedure, a standard residual stress evaluation method was established. Furthermore for consideration of characteristics of PWSCC's propagation behavior of the dissimilar welding joint of the safe end nozzles, the influence coefficients at the deepest point for the stress intensity factors of axial cracks with large aspect ratio a/c (crack depth/half of surface crack length) was prepared. The crack shape was assumed a rectangular shape and the stress intensity factors at the deepest point of the crack were calculated with change of crack depth using FE analysis. By using these stress distribution and influence coefficients, a behavior of a PWSCC crack propagation at the safe end nozzles can be estimated easily and rationally.

  17. Residual stresses in a quenched superalloy turbine disc: Measurements and modeling

    Rist, M. A.; James, J. A.; Tin, S.; Roder, B. A.; Daymond, M. R.


    A series of neutron diffraction measurements have been carried out to determine the elastic residual strains deep within a large, 40-cm-diameter, forged and water-quenched IN718 aeroengine compressor disc. Neutron path lengths of up to 6 cm were necessary to probe the thickest parts of the forging, and three-dimensional strain and stress components have been derived for the first time in such a large superalloy specimen. Measurements have been compared with the results from a coupled thermal-mechanical finite-element model of the quenching process, based upon appropriate temperature-dependent material properties, with some success. The general residual stress state in the disc is one of near-surface compression, balanced by tension within the disc interior. The steepest stress and strain gradients occur in the transition region from compression to tension, about 1 cm below the surface all around the disc. The largest stress component is in the disc tangential direction and reaches a magnitude of 400 to 500 MPa near the disc surface and at its core. This exceeds the effective yield stress because of the presence of significant hydrostatic stress.

  18. Measurement of 3-D hydraulic conductivity in aquifer cores at in situ effective stresses.

    Wright, Martin; Dillon, Peter; Pavelic, Paul; Peter, Paul; Nefiodovas, Andrew


    An innovative and nondestructive method to measure the hydraulic conductivity of drill core samples in horizontal and vertical directions within a triaxial cell has been developed. This has been applied to characterizing anisotropy and heterogeneity of a confined consolidated limestone aquifer. Most of the cores tested were isotropic, but hydraulic conductivity varied considerably and the core samples with lowest values were also the most anisotropic. Hydraulic conductivity decreased with increasing effective stress due to closure of microfractures caused by sampling for all core samples. This demonstrates the importance of replicating in situ effective stresses when measuring hydraulic conductivity of cores of deep aquifers in the laboratory.

  19. Neutron measurements of stresses in a test artifact produced by laser-based additive manufacturing

    Gnäupel-Herold, Thomas; Slotwinski, John; Moylan, Shawn


    A stainless steel test artifact produced by Direct Metal Laser Sintering and similar to a proposed standardized test artifact was examined using neutron diffraction. The artifact contained a number of structures with different aspect ratios pertaining to wall thickness, height above base plate, and side length. Through spatial resolutions of the order of one millimeter the volumetric distribution of stresses in several was measured. It was found that the stresses peak in the tensile region around 500 MPa near the top surface, with balancing compressive stresses in the interior. The presence of a support structure (a one millimeter high, thin walled, hence weaker, lattice structure deposited on the base plate, followed by a fully dense AM structure) has only minor effects on the stresses.

  20. The measurement of shear stress and total heat flux in a nonadiabatic turbulent hypersonic boundary layer

    Mikulla, V.; Horstman, C. C.


    Turbulent shear stress and direct turbulent total heat-flux measurements have been made across a nonadiabatic, zero pressure gradient, hypersonic boundary layer by using specially designed hot-wire probes free of strain-gauging and wire oscillation. Heat-flux measurements were in reasonably good agreement with values obtained by integrating the energy equation using measured profiles of velocity and temperature. The shear-stress values deduced from the measurements, by assuming zero correlation of velocity and pressure fluctuations, were lower than the values obtained by integrating the momentum equation. Statistical properties of the cross-correlations are similar to corresponding incompressible measurements at approximately the same momentum-thickness Reynolds number.

  1. Measurement and prediction of residual stress in a bead-on-plate weld benchmark specimen

    Ficquet, X.; Smith, D.J. [Department of Mechanical Engineering, University of Bristol, Queen' s Building, University Walk, Bristol BS8 1TR (United Kingdom); Truman, C.E. [Department of Mechanical Engineering, University of Bristol, Queen' s Building, University Walk, Bristol BS8 1TR (United Kingdom)], E-mail:; Kingston, E.J. [Veqter Ltd, University Gate East, Park Row, Bristol BS1 5UB (United Kingdom); Dennis, R.J. [Frazer-Nash Consultancy Limited, 1 Trinity Street, College Green, Bristol BS1 5TE (United Kingdom)


    This paper presents measurements and predictions of the residual stresses generated by laying a single weld bead on a flat, austenitic stainless steel plate. The residual stress field that is created is strongly three-dimensional and is considered representative of that found in a repair weld. Through-thickness measurements are made using the deep hole drilling technique, and near-surface measurements are made using incremental centre hole drilling. Measurements are compared to predictions at the same locations made using finite element analysis incorporating an advanced, non-linear kinematic hardening model. The work was conducted as part of an European round robin exercise, coordinated as part of the NeT network. Overall, there was broad agreement between measurements and predictions, but there were notable differences.

  2. Measurement and Modeling of Job Stress of Electric Overhead Traveling Crane Operators

    Krishna, Obilisetty B.; Maiti, Jhareswar; Ray, Pradip K.; Samanta, Biswajit; Mandal, Saptarshi; Sarkar, Sobhan


    Background In this study, the measurement of job stress of electric overhead traveling crane operators and quantification of the effects of operator and workplace characteristics on job stress were assessed. Methods Job stress was measured on five subscales: employee empowerment, role overload, role ambiguity, rule violation, and job hazard. The characteristics of the operators that were studied were age, experience, body weight, and body height. The workplace characteristics considered were hours of exposure, cabin type, cabin feature, and crane height. The proposed methodology included administration of a questionnaire survey to 76 electric overhead traveling crane operators followed by analysis using analysis of variance and a classification and regression tree. Results The key findings were: (1) the five subscales can be used to measure job stress; (2) employee empowerment was the most significant factor followed by the role overload; (3) workplace characteristics contributed more towards job stress than operator's characteristics; and (4) of the workplace characteristics, crane height was the major contributor. Conclusion The issues related to crane height and cabin feature can be fixed by providing engineering or foolproof solutions than relying on interventions related to the demographic factors. PMID:26929839

  3. Measurement of the state of stress in silicon with micro-Raman spectroscopy

    Harris, Stephen J.; O'Neill, Ann E.; Yang, Wen; Gustafson, Peter; Boileau, James; Weber, W. H.; Majumdar, Bhaskar; Ghosh, Somnath


    Micro-Raman spectroscopy has been widely used to measure local stresses in silicon and other cubic materials. However, a single (scalar) line position measurement cannot determine the complete stress state unless it has a very simple form such as uniaxial. Previously published micro-Raman strategies designed to determine additional elements of the stress tensor take advantage of the polarization and intensity of the Raman-scattered light, but these strategies have not been validated experimentally. In this work, we test one such stategy [S. Narayanan, S. Kalidindi, and L. Schadler, J. Appl. Phys. 82, 2595 (1997)] for rectangular (110)- and (111)-orientated silicon wafers. The wafers are subjected to a bending stress using a custom-designed apparatus, and the state of (plane) stress is modeled with ABAQUS. The Raman shifts are calculated using previously published values for silicon phonon deformation potentials. The experimentally measured values for σxx, σyy, and τxy at the silicon surface are in good agreement with those calculated with the ABAQUS model.

  4. Measurement of the Full State of Stress of Silicon with Micro-Raman Spectroscopy

    Harris, Stephen; Weber, W. H.; Majumdar, Bhaskar; Ghosh, Somnath


    Micro-Raman spectroscopy has been widely used to measure local stresses in silicon and other cubic materials. However, a single (scalar) line position measurement cannot determine the complete stress state unless it is has a very simple form, such as uniaxial. Previously published micro-Raman strategies designed to determine additional elements of the stress tensor take advantage of the polarization and intensity of the Raman scattered light, but these strategies have not been validated experimentally. In this work we test one such stategy [S. Narayanan, S. Kalidindi, and L. Schadler, JAP. 82, 2595 (1997)] for rectangular (110)- and (111)-orientated silicon wafers. The wafers are subjected to a bending stress, and the state of (plane) stress is modeled with ABAQUS. The Raman shifts, intensities, and polarizations are calculated using previously published values for silicon phonon deformation potentials. The experimentally measured values for σxx, σyy, and τxy at the silicon surface are in good agreement with those calculated with the ABAQUS model.

  5. The advising alliance for international and domestic graduate students: Measurement invariance and implications for academic stress.

    Rice, Kenneth G; Suh, Hanna; Yang, Xiaohui; Choe, Elise; Davis, Don E


    We expanded the focus of a prior study of international graduate student advising relationships (Rice et al., 2009) to examine advising experiences of both international and domestic students. International (n = 434) and domestic (n = 387) students completed the Advisory Working Alliance Inventory (AWAI-S; Schlosser & Gelso, 2001) and measures of advising experiences, perceived academic stress, and desire to change advisor. Measurement invariance analyses suggested that a 23-item AWAI-S showed support for scalar invariance. A bifactor structure showed superior fit to the 3-factor model or a second-order factor model for the AWAI-S. International and domestic graduate students did not differ in ratings of general alliance, academic stress, or desire to change advisors. General alliance was strongly related to less academic stress and less desire to change advisors. International students who felt disrespected by their advisors were more likely to be academically stressed than domestic students. Structured mentoring experiences were associated with lower stress and less desire to change, and this effect was similar in both international and domestic students. Overall, results suggested that the current level of measurement, and possibly theory development, regarding the advisory alliance is good at identifying generic satisfaction but weaker at differentiating components of the alliance. (c) 2016 APA, all rights reserved).

  6. Method of stress and measurement modes for research of thin dielectric films of MIS structures

    Andreev, Vladimir V.; Maslovsky, Vladimir M.; Andreev, Dmitrii V.; Stolyarov, Alexander A.


    The paper proposes a new method of stress and measurement modes for research of thin dielectric films of MIS structures. The method realizes injection of the most part of charge into gate dielectric in one of stress modes: either current owing through dielectric is constant or voltage applied to gate is constant. In order to acquire an additional information about changing of charge state of MIS structure, the stress condition is interrupted in certain time ranges and during these time ranges the mode, in which structure is, is the mode of measurement. In measurement mode, changing of electric fields at interfaces between dielectric and semiconductor is monitored. By using these data, density of charge, which is accumulated in gate dielectric, and its centroid are calculated. Besides, by using these data, one studies processes of generation and relaxation of charge in dielectric. In order to raise precision of the method and reduce an influence of switching effects in measurement mode, density of measurement current should be much lower than density of stress current.

  7. Measurement invariance of the Depression Anxiety Stress Scales-21 across medical student genders.

    Jafari, Peyman; Nozari, Farnoosh; Ahrari, Forooghosadat; Bagheri, Zahra


    This study aimed to assess whether male and female Iranian medical students perceived the meaning of the items in the Depression Anxiety Stress Scales-21 consistently. A convenience sample of 783 preclinical medical students from the first to sixth semester was invited to this cross-sectional study. Of the 477 respondents, 238 were male and 239 were female. All participants completed the Persian version of the Depression Anxiety Stress Scales-21. The graded response model was used to assess measurement invariance of the instrument across the gender groups. Categorical confirmatory factor analysis was used to evaluate the construct validity of the measure. Moreover, internal consistency was assessed via Cronbach's Alpha. Statistically significant differential item functioning was flagged for just item 6 in the depression subscales (c(2)=6.5, df=1, p=0.011). However, removing or retaining the item 6 in the stress subscale did not change our findings significantly, when we compared stress scores across two genders. The results of categorical confirmatory factor analysis supported the fit of the three-factor model of Depression Anxiety Stress Scales-21. Moreover, Cronbach's alpha was greater than 0.7 in depression, anxiety and stress subscales. This study revealed that Depression Anxiety Stress Scales-21 is an invariant measure across male and female medical students. Hence, this reliable and valid instrument can be used for meaningful comparison of distress scores between medical student genders. Gender comparisons of medical students' psychological profiles provide a better insight into gender influences on the outcome of medical education and medical practice.

  8. Measurement and modelling of residual stresses in straightened commercial eutectoid steel rods

    Martinez-Perez, M.L. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Borlado, C.R. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Open University, Faculty of Technology, Milton Keynes, MK7 6AL (United Kingdom); Mompean, F.J. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Garcia-Hernandez, M. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Gil-Sevillano, J. [CEIT, Paseo de Manuel Lardizabal 15, E-20018 San Sebastian (Spain); Ruiz-Hervias, J. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, c/ Profesor Aranguren s/n, E-28040 Madrid (Spain); Atienza, J.M. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, c/ Profesor Aranguren s/n, E-28040 Madrid (Spain)]. E-mail:; Elices, M. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, c/ Profesor Aranguren s/n, E-28040 Madrid (Spain); Peng, Ru Lin [NFL Studsvik, Uppsala University, S-61182 Nykoeping (Sweden); Daymond, M.R. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, K7L 3N6 (Canada)


    Neutron strain scanning measurements on a eutectoid steel rod that has been subjected to standard industrial coiling and straightening operations are presented. Strains were determined non-destructively using two different diffractometers, one at a steady-state neutron source and the other at a pulsed spallation neutron source, with measurements made in both the ferrite and cementite components of the pearlitic microstructure. The residual stress state is explained in terms of a simplified analytical model for a two-phase material, which takes into account the successive loading operations contributing to residual stress. The results show that residual stresses generated by bending-straightening operations are significant and are likely to play an important role in the mechanical properties of the final wires.

  9. Confocal detection of Rayleigh scattering for residual stress measurement in chemically tempered glass

    Hödemann, S.; Möls, P.; Kiisk, V.; Murata, T.; Saar, R.; Kikas, J.


    A new optical method is presented for evaluation of the stress profile in chemically tempered (chemically strengthened) glass based on confocal detection of scattered laser beam. Theoretically, a lateral resolution of 0.2 μm and a depth resolution of 0.6 μm could be achieved by using a confocal microscope with high-NA immersion objective. The stress profile in the 250 μm thick surface layer of chemically tempered lithium aluminosilicate glass was measured with a high spatial resolution to illustrate the capability of the method. The confocal method is validated using transmission photoelastic and Na+ ion concentration profile measurement. Compositional influence on the stress-optic coefficient is calculated and discussed. Our method opens up new possibilities for three-dimensional scattered light tomography of mechanical imaging in birefringent materials.

  10. Confocal detection of Rayleigh scattering for residual stress measurement in chemically tempered glass

    Hödemann, S., E-mail:; Möls, P.; Kiisk, V.; Saar, R.; Kikas, J. [Institute of Physics, University of Tartu, Wilhelm Ostwald st., Tartu 50411 (Estonia); Murata, T. [Nippon Electric Glass Co., 7-1 Seiran 2-chome, Otsu-shi, Shiga 520-8639 (Japan)


    A new optical method is presented for evaluation of the stress profile in chemically tempered (chemically strengthened) glass based on confocal detection of scattered laser beam. Theoretically, a lateral resolution of 0.2 μm and a depth resolution of 0.6 μm could be achieved by using a confocal microscope with high-NA immersion objective. The stress profile in the 250 μm thick surface layer of chemically tempered lithium aluminosilicate glass was measured with a high spatial resolution to illustrate the capability of the method. The confocal method is validated using transmission photoelastic and Na{sup +} ion concentration profile measurement. Compositional influence on the stress-optic coefficient is calculated and discussed. Our method opens up new possibilities for three-dimensional scattered light tomography of mechanical imaging in birefringent materials.

  11. Numerical analysis of drilling hole work-hardening effects in hole-drilling residual stress measurement

    Li, H.; Liu, Y. H.


    The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.

  12. Measured Resolved Shear Stresses and Bishop Hill Stress States in Individual Grains of Austenitic Stainless Steel (Postprint)


    Activation of a slip system requires that it is critically stressed , i.e. that the shear stress resolved on the slip system exceeds a threshold...increment. A direct way of investigating which slip systemsmay be active in each grain is to investigate the stress state of the grain. From...correlation (DIC) system [29] and a load cell. The stress - strain curve in Fig. 1b) presents the maximum stress reading after each loading step. Relaxation

  13. A new quantitative approach to measure perceived work-related stress in Italian employees.

    Cevenini, Gabriele; Fratini, Ilaria; Gambassi, Roberto


    We propose a method for a reliable quantitative measure of subjectively perceived occupational stress applicable in any company to enhance occupational safety and psychosocial health, to enable precise prevention policies and intervention and to improve work quality and efficiency. A suitable questionnaire was telephonically administered to a stratified sample of the whole Italian population of employees. Combined multivariate statistical methods, including principal component, cluster and discriminant analyses, were used to identify risk factors and to design a causal model for understanding work-related stress. The model explained the causal links of stress through employee perception of imbalance between job demands and resources for responding appropriately, by supplying a reliable U-shaped nonlinear stress index, expressed in terms of values of human systolic arterial pressure. Low, intermediate and high values indicated demotivation (or inefficiency), well-being and distress, respectively. Costs for stress-dependent productivity shortcomings were estimated to about 3.7% of national income from employment. The method identified useful structured information able to supply a simple and precise interpretation of employees' well-being and stress risk. Results could be compared with estimated national benchmarks to enable targeted intervention strategies to protect the health and safety of workers, and to reduce unproductive costs for firms.

  14. FEM Analysis and Measurement of Residual Stress by Neutron Diffraction on the Dissimilar Overlay Weld Pipe

    Kim, Kang Soo; Lee, Ho Jin; Woo, Wan Chuck; Seong, Baek Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Byeon, Jin Gwi; Park, Kwang Soo; Jung, In Chul [Doosan Heavy Industries and Construction Co., Changwon (Korea, Republic of)


    Much research has been done to estimate the residual stress on a dissimilar metal weld. There are many methods to estimate the weld residual stress and FEM (Finite Element Method) is generally used due to the advantage of the parametric study. And the X-ray method and a Hole Drilling technique for an experimental method are also usually used. The aim of this paper is to develop the appropriate FEM model to estimate the residual stresses of the dissimilar overlay weld pipe. For this, firstly, the specimen of the dissimilar overlay weld pipe was manufactured. The SA 508 Gr3 nozzle, the SA 182 safe end and SA376 pipe were welded by the Alloy 182. And the overlay weld by the Alloy 52M was performed. The residual stress of this specimen was measured by using the Neutron Diffraction device in the HANARO (High-flux Advanced Neutron Application ReactOr) research reactor, KAERI (Korea Atomic Energy Research Institute). Secondly, FEM Model on the dissimilar overlay weld pipe was made and analyzed by the ABAQUS Code (ABAQUS, 2004). Thermal analysis and stress analysis were performed, and the residual stress was calculated. Thirdly, the results of the FEM analysis were compared with those of the experimental methods

  15. Computer-assisted measurement of perceived stress: an application for a community-based survey.

    Kimura, Tomoaki; Uchida, Seiya; Tsuda, Yasutami; Eboshida, Akira


    The assessment of stress is a key issue in health promotion policies as well as in treatment strategies for patients. The aim of this study was to confirm the accessibility and reliability of computer-assisted data collection for perceived stress measurement, using the Japanese version of the Perceived Stress Scale (JPSS), within the setting of a community-based survey. There were two groups of participants in this survey. One group responded to a Web-based application, and the other to the VBA of a spreadsheet software. The total scores of JPSS were almost normally distributed. The means of total scores of JPSS were 23.6 and 23.1. These results were lower than the previous study of JPSS. Since Cronbach's alpha coefficients in both surveys were more than 0.8, high reliability was demonstrated despite a number of computer-illiterate and/or aged participants. They felt that the spreadsheet form was easier to respond to. Two components were extracted with the Varimax rotation of principal component analysis, and these were named "perception of stress and stressors" and "behavior to stress". This finding suggests that it is possible to determine sub-scales. From the viewpoint of preventive medicine, it is expected that the JPSS applications will be utilized to investigate the relationship between stress and other factors such as lifestyle, environment and quality of life.

  16. Orientation on quantitative IR-thermografy in wall-shear stress measurements

    Mayer, R.


    Wall-shear stresses are highly important in the aerodynamic design of aircraft, because they determine the drag and thus the fuel consumption of an airplane. Due to this importance many different measurement techniques have been developed. Most of these techniques are intrusive, which means that the

  17. Association between objectively measured physical activity, chronic stress and leukocyte telomere length.

    von Känel, Roland; Bruwer, Erna J; Hamer, Mark; de Ridder, J Hans; Malan, Leoné


    Physical activity (PA) attenuates chronic stress and age-related and cardiovascular disease risks, whereby potentially slowing telomere shortening. We aimed to study the association between seven-day objectively measured habitual PA, chronic stress and leukocyte telomere length. Study participants were African (N.=96) and Caucasian (N.=107) school teachers of the Sympathetic activity and Ambulatory Blood Pressure in Africans study. All lifestyle characteristics (including PA) were objectively measured. The general health questionnaire and serum cortisol were assessed as psychological and physical measures of chronic stress. Leukocyte telomere length was measured using the quantitative real-time polymerase chain reaction. Africans had significantly shorter telomeres (Pstress or telomere length. However, more time spent with light intensity PA time was significantly and independently correlated with lower waist circumference (r=-0.21, P=0.004); in turn, greater waist circumference was significantly associated shorter telomeres (β=-0.17 [-0.30, -0.03], P=0.017). Habitual PA of different intensity was not directly associated with markers of chronic stress and leukocyte telomere length in this biethnic cohort. However, our findings suggest that light intensity PA could contribute to lowered age-related disease risk and healthy ageing by facilitating maintenance of a normal waist circumference.

  18. Enhancing Maritime Education and Training: Measuring a Ship Navigator's Stress Based on Salivary Amylase Activity

    Murai, Koji; Wakida, Shin-Ichi; Miyado, Takashi; Fukushi, Keiichi; Hayashi, Yuji; Stone, Laurie C.


    Purpose: The purpose of this paper is to propose that the measurement of salivary amylase activity is an effective index to evaluate the stress of a ship navigator for safe navigation training and education. Design/methodology/approach: Evaluation comes from the simulator and actual on-board experiments. The subjects are real captains who have…

  19. Obtaining Heat Stress Measurements. Module 15. Vocational Education Training in Environmental Health Sciences.

    Consumer Dynamics Inc., Rockville, MD.

    This module, one of 25 on vocational education training for careers in environmental health occupations, contains self-instructional materials on obtaining heat stress measurements. Following guidelines for students and instructors and an introduction that explains what the student will learn are three lessons: (1) naming and describing the…

  20. Biotechnology Predictors of Physical Security Personnel Performance: Cerebral Potential Measures Related to Stress.


    Rosenman, 1983), are oriented primarily toward matching personalities with certain patterns of clinical responses to stress. Other, more general schemes...measured for the medio -basal region of the frontal lobes or for the limbic formations. Factual information relevant to problems of this kind will

  1. Application of x-ray stress measurement to practical materials for plastic work

    Sekiguchi, Haruo; Kiriyama, Sadao


    X-ray diffraction stress measurement is achieved commonly from calculating elastic strain of crystal lattice. Therefore, the accuracy of the measurement is apt to be influenced from plastic zone or preferred orientation of surface layer for the measurement of practical materials with strong plastic work. It was found that the Two-Axis Oscillation Method was suitable to improve the accuracy of measurement on those materials. This papar discussed on the mechanism of residual stress mode during the process of plastic work, and described the application results on the plastic worked materials, such as spring steel surface treated by shot peening, titanium alloy with preferred orientation and mechanically worked surface of SUS 304 materials.

  2. Psychological Stress Measure (PSM-9): integration of an evidence-based approach to assessment, monitoring, and evaluation of stress in physical therapy practice.

    Lemyre, Louise; Lalande-Markon, Marie-Pierre


    Stress can be a primary or secondary contributor to ill health via excessive and sustained sympathetic arousal leading to ischemic heart disease, hypertension, stroke, obesity, and mental ill health, or through related behaviors such as smoking, substance abuse, and over or inappropriate eating; or as a contextual variable in terms of risk factor and lifestyle outcome. In addition, psychosocial stress can impair recovery from any pathological insult or injury. Most assessments of stress relate to life events, and both past and current life stressors, acute and chronic, play a major role. However, beyond the impact of stressors, it is the reported state of feeling stressed that is the critical predictor of ill health. This article describes stress and its correlates, discusses models of stress, and presents the nine-item Psychological Stress Measure (PSM-9). This tool is aimed directly at the state of feeling stressed, is suited for assessing stress clinically in the general population and serving as an outcome measure. The tool is valid and reliable and easy to administer in health care settings; it has a normal distribution, which makes it a very sensitive-to-change instrument in repeated measures to document progress.

  3. Blood Contamination in Saliva: Impact on the Measurement of Salivary Oxidative Stress Markers

    Natália Kamodyová


    Full Text Available Salivary oxidative stress markers represent a promising tool for monitoring of oral diseases. Saliva can often be contaminated by blood, especially in patients with periodontitis. The aim of our study was to examine the impact of blood contamination on the measurement of salivary oxidative stress markers. Saliva samples were collected from 10 healthy volunteers and were artificially contaminated with blood (final concentration 0.001–10%. Next, saliva was collected from 12 gingivitis and 10 control patients before and after dental hygiene treatment. Markers of oxidative stress were measured in all collected saliva samples. Advanced oxidation protein products (AOPP, advanced glycation end products (AGEs, and antioxidant status were changed in 1% blood-contaminated saliva. Salivary AOPP were increased in control and patients after dental treatment (by 45.7% and 34.1%, p<0.01. Salivary AGEs were decreased in patients after microinjury (by 69.3%, p<0.001. Salivary antioxidant status markers were decreased in both control and patients after dental treatment (p<0.05 and p<0.01. One % blood contamination biased concentrations of salivary oxidative stress markers. Saliva samples with 1% blood contamination are visibly discolored and can be excluded from analyses without any specific biochemic detection of blood constituents. Salivary markers of oxidative stress were significantly altered in blood-contaminated saliva in control and patients with gingivitis after dental hygiene treatment.

  4. The revised Stress Measurement of Female Marriage Immigrants in Korea: Evaluation of the psychometric properties.

    Park, Min Hee; Yang, Sook Ja; Chee, Yeon Kyung


    The twenty-one item Stress Measurement of Female Marriage Immigrants (SMFMI) was developed to assess stress of female marriage immigrants in Korea. This study reports the psychometric properties of a revised SMFMI (SMFMI-R) for application with female marriage immigrants to Korea who were raising children. Participants were 190 female marriage immigrants from China, Vietnam, the Philippines, and other Asian countries, who were recruited using convenience sampling between November 2013 and December 2013. Survey questionnaires were translated into study participants' native languages (Chinese, Vietnamese, and English). Principal component analysis yielded nineteen items in four factors (family, parenting, cultural, and economic stress), explaining 63.5% of the variance, which was slightly better than the original scale. Confirmatory factor analysis indicated adequate fit for the four-factor model. Based on classic test theory and item response theory, strong support was provided for item discrimination, item difficulty, and internal consistency (Cronbach's alpha = 0.923). SMFMI-R scores were negatively associated with Korean proficiency and subjective economic status. The SMFMI-R is a valid, reliable, and comprehensive measure of stress for female marriage immigrants and can provide useful information to develop intervention programs for those who may be at risk for emotional stress.

  5. Children's stress during a restorative dental treatment: assessment using salivary cortisol measurements.

    Akyuz, S; Pince, S; Hekin, N


    Dental environment may be a source of stress for the young patient. Such stressful conditions may provoke fear in anxious children. It is well known that stress produces an activation adrenal steroid secretion. Among the methods for assessing child dental fear, measurement of salivary cortisol level is a simple method, because especially in children, sampling of saliva is easy, and cortisol levels in saliva closely mirror serum free cortisol levels, independent of salivary flow rate. For this study, the salivary cortisol levels of 8 children (mean age 5.6 yr) were measured receiving initial dental treatment. Saliva samples were collected via cotton rolls placed to the floor of the mouth at four stages; prior to treatment, during cavitation, placement of the liner and the restoration. Statistical comparison of the results were done by Student-t test. The increase in salivary cortisol levels during cavitation at the first and secondary appointments were significant (p0.05). The results of this study suggest that in restorative procedures, mostly it is the cavitation step that creates stress and anxiety in children. Knowledge of the most stressful condition may be helpful for the dentist to prepare the child to treatment steps.

  6. Towards an automatic early stress recognition system for office environments based on multimodal measurements: A review.

    Alberdi, Ane; Aztiria, Asier; Basarab, Adrian


    Stress is a major problem of our society, as it is the cause of many health problems and huge economic losses in companies. Continuous high mental workloads and non-stop technological development, which leads to constant change and need for adaptation, makes the problem increasingly serious for office workers. To prevent stress from becoming chronic and provoking irreversible damages, it is necessary to detect it in its early stages. Unfortunately, an automatic, continuous and unobtrusive early stress detection method does not exist yet. The multimodal nature of stress and the research conducted in this area suggest that the developed method will depend on several modalities. Thus, this work reviews and brings together the recent works carried out in the automatic stress detection looking over the measurements executed along the three main modalities, namely, psychological, physiological and behavioural modalities, along with contextual measurements, in order to give hints about the most appropriate techniques to be used and thereby, to facilitate the development of such a holistic system.

  7. Measurement of urethral closure function in women with stress urinary incontinence

    Klarskov, N; Scholfield, D; Soma, K;


    , double-blind, placebo controlled, crossover study 17 women with stress urinary incontinence or mixed urinary incontinence received 4 mg esreboxetine or placebo for 7 to 9 days followed by a washout period before crossing over treatments. Urethral pressure reflectometry and urethral pressure profilometry...... esreboxetine patients had significantly fewer incontinence episodes and reported a treatment benefit (global impression of change) compared to placebo. CONCLUSIONS: The opening pressure measured with urethral pressure reflectometry was less variable compared to the parameters measured with urethral pressure...

  8. New measurement technology for diagnostic evaluation of stress and deformation states in building objects

    Kollataj, Robert; Kollataj, Jerzy


    This paper presents a new wireless measurement method for static and dynamic examination of buildings, bridges, masts, towers, steel structures, silos etc. by using new generation telemetric modules operating in intelligent radio network. The system provides a possibility of steel and reinforced concrete structures evaluation by measurement of mechanical stresses, deformation and temperature - depending on used sensor. Developed and built prototype system can be used for the on line monitoring, quality assessment and the usefulness of the building objects over long time periods.

  9. Internal tibial torsion correction study. [measurements of strain for corrective rotation of stressed tibia

    Cantu, J. M.; Madigan, C. M.


    A quantitative study of internal torsion in the entire tibial bone was performed by using strain gauges to measure the amount of deformation occuring at different locations. Comparison of strain measurements with physical dimensions of the bone produced the modulus of rigidity and its behavior under increased torque. Computerized analysis of the stress distribution shows that more strain occurs near the torqued ends of the bones where also most of the twisting and fracturing takes place.

  10. A comparison of X-ray stress measurement methods \\\\based on the fundamental equation

    Miyazaki, Toshiyuki; Sasaki, Toshihiko


    Stress measurement methods using X-ray diffraction (XRD methods) are based on so-called fundamental equations. The fundamental equation is described in the coordinate system that best suites the measurement situation, and, thus, making a comparison between different XRD methods is not straightforward. However, by using the diffraction vector representation, the fundamental equations of different methods become identical. Furthermore, the differences between the various XRD methods are in the ...

  11. Optical measurements on overhead optical fiber cables for stresses and damage identification

    Ravet, Fabien L.; Heens, Bernard; Daniaux, D.; Froidure, Jean-Christophe; Blondel, Michel; Dascotte, M.; Lots, P.


    This paper concerns the characterization of various trunks of an OPGW based network. No strong fiber aging has been observed but combined OTDR and PMD measurements have pointed out strong cable clamping at suspension pylon. Large local losses have been measured at both 1.55 micrometers and 1.6 micrometers and stress induced birefringent behavior have been experienced. PMD temporal evolution has also been studied. A correlation between temperature variation and PMD evolution has been observed.

  12. In situ stress measurement with the new LVDT - Cell - method description and verification

    Hakala, M. [KMS Hakala Oy, Nokia (Finland); Christiansson, R. [Svensk Kaernbraenslehantering AB, Stockholm (Sweden); Martin, D. [Univ. of Alberta, Edmonton (Canada); Siren, T.; Kemppainen, K.


    Posiva Oy and SKB (Svensk Kaernbraenslehantering AB) tested the suitability a new LVDT-cell (Linear Variable Differential Transducer cell) to measure the induced stresses in the vicinity of an excavated surface and further to use these results to interpret the in situ state of stress. It utilises the overcoring methodology, measuring the radial convergence of four diameters using eight LVDTs, and is similar in concept to the USBM-gauge. A 127 mm diameter pilot-hole is required and the overcore diameter is 200 mm. The minimum overcoring length is 350 mm, and hence a compact drill can be utilised. Extensive testing of the LVDT-cell shows it to be robust and suitable for use in an underground environment. Sensitivity tests also show that the cell can withstand a range of operating conditions and still provide acceptable results. The in situ stress at the measurement location can be solved by numerical inversion using the results of at least three overcoring measurements around the three-dimensional tunnel section. The large dimensions of the measurement tool and the ability to utilise multiple measurements at various locations in a tunnel section, provides flexibility in selecting an appropriate rock mass volume. Because the inversion technique relies on knowing the exact location of the measurements and the geometry profile of the tunnel, modern survey techniques such as Lidar or photogrammetric technology should be used. Checks using traditional surveying techniques should also be used to ensure adequate survey resolution, specially in case of sidecoring measurements. To evaluate the suitability of the LVDT-cell to provide the in situ state of stress, tests were carried out in the drill-and-blast TASS tunnel and TBM tunnel at the Aespoe Hard Rock Laboratory in Sweden. The state of stress established using the LVDT-cell was in agreement with the state of stress established previously using traditional overcoring and hydraulic fracturing methods. In this study, the

  13. New methods to directly measure adhesive stress and movement on glass

    Watts, David C.; Marouf, A. S.; Heindl, Detlef


    Practical scientific methods have been devised to measure cure-shrinkage phenomena for a small-volume disk geometry of adhesive agents, in liquid or paste form. These can be conducted simply, reproducibly and quickly, typically 5-120 min, once the apparati are set up. Originally utilised to measure shrinkage behavior in photocuring dental adhesives and biomaterials, the measurements may be applied as well to adhesives for fiber optic and optical applications. They are especially suitable for UV and visible-light curing adhesives. The 'bonded-disk' method is used for the measurement of shrinkage-strain kinetics and the Bioman method for shrinkage-stress of adhesives.

  14. Comparison of local stress values obtained by two measuring methods on blast furnace shell

    P. Bigoš


    Full Text Available This paper describes measuring of time behaviour specified for local stress increments on the blast furnace shell that were performed using strain gauge sensors. These results are compared with values obtained by means of the second specific measuring method. There is also presented in this paper a commentary and discussion concerning the measured time behaviour obtained from the both measuring methods. This article presents results from another of experimental analysis series concerning the blast furnace shell in one concrete metallurgical plant.

  15. Static and dynamic stress analyses of the prototype high head Francis runner based on site measurement

    Huang, X.; Oram, C.; Sick, M.


    More efforts are put on hydro-power to balance voltage and frequency within seconds for primary control in modern smart grids. This requires hydraulic turbines to run at off-design conditions. especially at low load or speed-no load. Besides. the tendency of increasing power output and decreasing weight of the turbine runners has also led to the high level vibration problem of the runners. especially high head Francis runners. Therefore. it is important to carry out the static and dynamic stress analyses of prototype high head Francis runners. This paper investigates the static and dynamic stresses on the prototype high head Francis runner based on site measurements and numerical simulations. The site measurements are performed with pressure transducers and strain gauges. Based on the measured results. computational fluid dynamics (CFD) simulations for the flow channel from stay vane to draft tube cone are performed. Static pressure distributions and dynamic pressure pulsations caused by rotor-stator interaction (RSI) are obtained under various operating conditions. With the CFD results. static and dynamic stresses on the runner at different operating points are calculated by means of the finite element method (FEM). The agreement between simulation and measurement is analysed with linear regression method. which indicates that the numerical result agrees well with that of measurement. Furthermore. the maximum static and dynamic stresses on the runner blade are obtained at various operating points. The relations of the maximum stresses and the power output are discussed in detail. The influences of the boundary conditions on the structural behaviour of the runner are also discussed.

  16. Effects of perch access and age on physiological measures of stress in caged White Leghorn pullets.

    Yan, F F; Hester, P Y; Enneking, S A; Cheng, H W


    The neuroendocrine system controls animals' adaptability to their environments by releasing psychotropic compounds such as catecholamines [epinephrine (EP), norepinephrine (NE), and dopamine (DA)], corticosterone (CORT), and serotonin (5-hydroxytryptamine or 5-HT). Changes of these neuroendocrine compounds have been used as biomarkers of animals' stress responses associated with their well-being. Assuming that pullets, like laying hens, are highly motivated to perch, we hypothesize that pullets with access to perches will experience less stress than pullets that never have access to perches. The objective of this study was to examine the effects of perch access and age on physiological measurements of stress in White Leghorn pullets housed in conventional cages. Hatchlings (n = 1,064) were randomly assigned to 28 cages. Two parallel metal round perches were installed in each of 14 cages assigned the perch treatment, whereas control cages were without perches. Two birds per cage were bled at wk 4, 6, and 12 wk of age. Plasma levels of CORT, DA, EP, and NE, blood concentrations of 5-HT and Trp, and heterophil to lymphocyte ratios were measured. Data were analyzed using a 2-way ANOVA. The perch treatment or its interaction with age did not affect any parameter measured in the study. The increase in the concentrations of circulating EP, NE, 5-HT (numerical increase at 4 wk), and Trp in 4- and 6-wk-old pullets compared with 12-wk-old pullets is unclear, but may have been due to acute handling stress at younger ages. In contrast, concentrations of DA were less at 4 wk compared with levels at 6 and 12 wk of age. Plasma CORT levels and the heterophil to lymphocyte ratio, indicators of long-term stress, were unaffected by age (P = 0.07 and 0.49, respectively). These results indicated that age, but not perch access, affects neuroendocrine homeostasis in White Leghorn pullets. Pullets that were never exposed to perches showed no evidence of eliciting a stress response.


    WANGShu-hong; ZUODun-wen; WANGMin; WANGZong-rong


    The integrated structure parts are widely used in aircraft. The distortion caused by residual stresses in thick pre-stretched aluminum plates during machining integrated parts is a common and serious problem. To predict and control the machining distortion, the residual stress distribution in the thick plate must be measured firstly. The modified removal method for measuring residual stress in thick pre-stretched aluminum plates is proposed and the stress-strain relation matrix is deduced by elasticity theory. The residual stress distribution in specimen of 7050T7451 plate is measured by using the method, and measurement results are analyzed and compared with data obtained by other methods. The method is effective to measure the residual stress.

  18. A Novel Deflection Method for Measuring the Growth Stress of Thermally Growing Oxide Scales


    A kind of new deflection technique has been developed for measuring the growth stress of thermally growing oxide scales duringhigh temperature oxidation of alloys. The average growth stresses in oxide scales such as Al2O3, NiO and Cr2O3 formed onthe surface of the superalloys can be investigated by this technique. Unlike the comventional deflection method, the novelmethod does not need to apply a coating for preventing one main face of thin strip specimen from oxidizing and can be usedunaer tne condition of longer time and higher temperature.

  19. First Measurement of the Magnetic Turbulence Induced Reynolds Stress in a Tokamak

    徐国盛; 万宝年; 宋梅


    Reynolds stress component due to magnetic turbulence was first measured in the plasma edge region of the HT- 7 superconducting tokamak using an insertable magnetic probe. A radial gradient of magnetic Reynolds stress was observed to be dose to the velocity shear layer location; however, in this experiment its contribution to driving the poloidal flows is small compared to the electrostatic component. The electron heat transport driven by magnetic turbulence is quite small and cannot account for the total energy transport at the plasma edge.

  20. Through-Thickness Measurements of Residual Stresses in an Overlay Dissimilar Weld Pipe using Neutron Diffraction

    Woo, Wan Chuck; EM, Vyacheslav; Lee, Ho Jin; Kim, Kang Soo; Kang, Mi Hyun; Joo, Jong Dae; Seong, Baek Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Byeon, Jin Gwi; Park, Kwang Soo [Doosan Heavy Industries and Construction Co., Changwon (Korea, Republic of)


    The distribution of residual stresses in dissimilar material joints has been extensively studied because of the wide applications of the dissimilar welds in many inevitable complex design structures. Especially the cracking of dissimilar welding has been a long standing issue of importance in many components of the power generation industries such as nuclear power plant, boiling pressure system, and steam generators. In particular, several failure analysis and direct observations have shown that critical fractures have frequently occurred in one side of the dissimilar welded parts. For example, the heat-affected zone on the ferrite steel side is known to critical in many dissimilar welding pipes when ferrite (low carbon steel) and austenite (stainless) steels are joined. The main cause of the residual stresses can be attributed to the mismatch in the coefficient of thermal expansion between the dissimilar metals (ferrite and austenite). Additional cladding over circumferential welds is known to reinforce the mechanical property due to the beneficial compressive residual stress imposed on the weld and heat-affected zone. However, science-based quantitative measurement of the through thickness residual stress distribution is very limited in literature. The deep penetration capability of neutrons into most metallic materials makes neutron diffraction a powerful tool to investigate and map the residual stresses of materials throughout the thickness and across the weld. Furthermore, the unique volume averaged bulk characteristic of materials and mapping capability in three dimensions are suitable for the engineering purpose. Thus, the neutron-diffraction measurement method has been selected as the most useful method for the study of the residual stresses in various dissimilar metal welded structures. The purpose of this study is to measure the distribution of the residual stresses in a complex dissimilar joining with overlay in the weld pipe. Specifically, we measured

  1. The Measurement of Wall Shear Stress in the Low-Viscosity Liquids

    Adamec J.


    Full Text Available The paper is focused on quantitative evaluation of the value of the wall shear stress in liquids with low viscosity by means of the method of the hot film anemometry in a laminar and turbulent flow. Two systems for calibration of probes are described in the paper. The first of these uses an innovative method of probe calibration using a known flow in a cylindrical gap between two concentric cylinders where the inner cylinder is rotated and a known velocity profile and shear rate, or shear stress profile, is calculated from the Navier-Stokes equations. This method is usable for lower values of the wall shear stress, particularly in the areas of laminar flow. The second method is based on direct calibration of the probes using a floating element. This element, with a size of 120x80 mm, is part of a rectangular channel. This method of calibration enables the probe calibration at higher shear rates and is applicable also to turbulent flow. Values obtained from both calibration methods are also compared with results of measurements of the wall shear stress in a straight smooth channel for a certain range of Reynolds numbers and compared with analytical calculations. The accuracy of the method and the influence of various parasitic phenomena on the accuracy of the measured results were discussed. The paper describes in particular the influence of geometric purity of the probe location, the impact of various transfer phenomena, requirements for the measured liquid and layout of the experiment.

  2. Transactional stress and coping theory in accounting for psychological states measures

    V. Buško


    Full Text Available The paper examines a relative predictive value of some stable individual attributes and the processes of cognitive appraisals and coping with stress in accounting for specific components of anxiety state measures. Self-report instruments for the measurement of selected psychological constructs, i.e. perceived incompetence, externality, stress intensity and duration, situation-specific coping strategies, and the two anxiety state components, were taken in a sample of 449 male military basics trainees, ranging in age from 18-27. Hierarchical multiple regression analyses showed that the set of predictors employed could account for statistically, as well as theoretically and practically a significant part of variance in cognitive anxiety component (45,5%, and in visceral-emotional component (32,2% of the anxiety state. The extent of anxiety reactions assessed by both scales could primarily be explained by general perception of personal incompetence, as a relatively stable dimension of general self-concept. Of the ways of coping examined, reinterpretation of stressful events was the only strategy contributing to low level, whereas passivization, wishful thinking, and seeking social support contributed to higher levels of anxiety measured by both scales. The results give partial support to the basic hypotheses on the mediating role of coping in the relationships among particular components of the stress and coping models.

  3. Characterization of Residual Stresses in Ferrous Components by Magnetic Anisotropy Measurements Using a Hall Effect Sensor Array Probe

    Lo, C. C. H.


    A new surface sensor probe comprising an angular array of Hall effect sensors has been developed for characterization of residual stresses in ferrous materials by means of stress-induced magnetic anisotropy measurements. The sensor probe applies a radially spreading ac magnetic field to a test sample, and detects stray fields in different directions simultaneously to determine the principal stress axes. In situ measurements were conducted on a annealed steel plate under four-point bending stresses to evaluate the probe performance. The ratio of stray field signals measured along and perpendicular to the stress axis varies linearly with the surface stress, indicating the possibility of characterizing residual stresses in ferrous components using the sensor array probe.

  4. Stress

    Keller, Hanne Dauer


    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  5. Stress

    Keller, Hanne Dauer


    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  6. Acoustical and optical backscatter measurements of sediment transport in the 1988 1989 STRESS experiment

    Lynch, J. F.; Gross, T. F.; Sherwood, C. R.; Irish, J. D.; Brumley, B. H.


    During the 1988-1989 Sediment Transport Events on Shelves and Slopes (STRESS) experiment, a 1-MHz acoustic backscatter system (ABSS), deployed in 90 m of water off the California coast measured vertical profiles of suspended sediment concentration from 1.5 to (nominally) 26 meters above bottom (m.a.b.). An 8-week-long time series was obtained, showing major sediment transport events (storms) in late December and early January. Comparison of the acoustics measurements from 1.5 m.a.b. are made with optical backscatter system (OBS) concentration estimates lower in the boundary layer (0.25 m.a.b.). Correlations between ABSS and OBS concentration measurements and the boundary layer forcing functions (waves, currents, and their non-linear interaction) provided a variety of insights into the nature of the sediment transport of the STRESS site. Transport rates and integrated transport are seen to be dominated by the largest storm events.

  7. Enhancement to Non-Contacting Stress Measurement of Blade Vibration Frequency

    Platt, Michael; Jagodnik, John


    A system for turbo machinery blade vibration has been developed that combines time-of-arrival sensors for blade vibration amplitude measurement and radar sensors for vibration frequency and mode identification. The enabling technology for this continuous blade monitoring system is the radar sensor, which provides a continuous time series of blade displacement over a portion of a revolution. This allows the data reduction algorithms to directly calculate the blade vibration frequency and to correctly identify the active modes of vibration. The work in this project represents a significant enhancement in the mode identification and stress calculation accuracy in non-contacting stress measurement system (NSMS) technology when compared to time-of-arrival measurements alone.

  8. H/L ratio as a measurement of stress in laying hens - methodology and reliability.

    Lentfer, T L; Pendl, H; Gebhardt-Henrich, S G; Fröhlich, E K F; Von Borell, E


    Measuring the ratio of heterophils and lymphocytes (H/L) in response to different stressors is a standard tool for assessing long-term stress in laying hens but detailed information on the reliability of measurements, measurement techniques and methods, and absolute cell counts is often lacking. Laying hens offered different sites of the nest boxes at different ages were compared in a two-treatment crossover experiment to provide detailed information on the procedure for measuring and the difficulties in the interpretation of H/L ratios in commercial conditions. H/L ratios were pen-specific and depended on the age and aviary system. There was no effect for the position of the nest. Heterophiles and lymphocytes were not correlated within individuals. Absolute cell counts differed in the number of heterophiles and lymphocytes and H/L ratios, whereas absolute leucocyte counts between individuals were similar. The reliability of the method using relative cell counts was good, yielding a correlation coefficient between double counts of r > 0.9. It was concluded that population-based reference values may not be sensitive enough to detect individual stress reactions and that the H/L ratio as an indicator of stress under commercial conditions may not be useful because of confounding factors and that other, non-invasive, measurements should be adopted.

  9. Wall shear stress measurement method based on parallel flow model near vascular wall in echography

    Shimizu, Motochika; Tanaka, Tomohiko; Okada, Takashi; Seki, Yoshinori; Nishiyama, Tomohide


    A high-risk vessel of arteriosclerosis is detected by assessing wall shear stress (WSS), which is calculated from the distribution of velocity in a blood flow. A novel echographic method for measuring WSS, which aims to distinguish a normal vessel from a high-risk vessel, is proposed. To achieve this aim, the measurement error should be less than 28.8%. The proposed method is based on a flow model for the area near a vascular wall under a parallel-flow assumption to avoid the influences of error factors. This was verified by an in vitro experiment in which the WSS of a carotid artery phantom was measured. According to the experimental results, the WSS measured by the proposed method correlated with the ground truth measured by particle image velocimetry; in particular, the correlation coefficient and measurement error between them were respectively 0.70 and 27.4%. The proposed method achieved the target measurement performance.

  10. Neutron diffraction measurements for the determination of residual stresses in MMC tensile and fatigue specimens

    Fiori, F.; Girardin, E.; Giuliani, A.;


    , residual stresses are present in both the matrix and the particles microstructure, prior to any macroscopic loading. They vary with the temperature and with the type and level of loading imposed to the material, having a strong influence on the mechanical behaviour of MMCs. Neutron diffraction measurements...... have been performed at RISO (Roskilde, DK) and HMI-BENSC (Berlin, D), for the determination of residual stress in AA2124 + 17% SiCp and AA359 + 20% SiCp specimens, submitted to tensile and fatigue tests. For each of the investigated samples, the macrostress has been separated from the elastic...... and thermal mismatch microstresses. The results show that, in general, the main contribution to the stress state of both matrix and reinforcement is given by the thermal microstresses, already existing due to heat treatment prior to mechanical tests. (C) 2000 Elsevier Science B.V. All rights reserved....

  11. Transducer for measuring normal and friction stress in contact zone during rolling

    Henningsen, Poul; Wanheim, Tarras; Arentoft, Mogens


    For the cold rolling process, knowledge about interface conditions is important since it directly influences the maximum reduction ratio and thereby the number of steps required for a given reduction. The mechanical properties of the produced sheet and the surface quality are also influenced...... by the friction conditions. To achieve this important information, measurements of the normal pressure and friction stresses in the deformation zone are requested. The interface conditions are analyzed by several authors [1-8] The direction of the friction stress is changing during the rolling gap....... At the entrance of the deformation zone, the peripherical velocity of the roll is higher than for the incoming material, which causes frictional stresses at the material acting in the rolling direction. At the outlet of the rolling gap, the velocity of the deformed material exceeds the velocity of the roll...

  12. Basic Study on Estimating Water Stress of a Plant Using Vibration Measurement of Leaf

    Sano, Motoaki; Sugimoto, Tsuneyoshi; Hosoya, Hiroshi; Ohaba, Motoyoshi; Shibusawa, Sakae


    A new noninvasive method for estimating the water stress of a plant was proposed. In order to investigate this method, we first examined the characteristic frequency of an individual leaf picked from the plant, and obtained the result that its characteristic frequency decreased in proportion to the reduction in the water content of the leaf. Next, we applied this method to a leaf on a branch and confirmed the same tendency when the water stress was increased by stopping the water supply of a plant cultured in water. From these results, it was suggested that the water stress of the plant could be estimated from the vibration measurement of the leaf. Lastly, the relationship between the water potential of the leaf and its elastic constant was discussed with the soil-plant-atmosphere-continuum model (SPAC model), and Young's modulus of a tomato leaf was roughly estimated.

  13. [Changes in Kinetics of Chemiluminescence of Plasma as a Measure of Systemic Oxidative Stress in Humans].

    Sozarukova, M M; Polimova, A M; Proskurnina, E V; Vladimirov, Yu A


    Oxidative stress is a pathogenetic factor of many diseases. The control of its level is important for early diagnosis and therapy adjustment. In this work, antioxidant status was estimated in blood plasma. In the system of 2,2'-azo-bis(2-amidinopropane)dihydrochloride-luminol a set of chemiluminescence kinetic curve parameters is proposed for oxidative stress level estimation (the latent period τ(lat) and the increasing of analytical signal ΔI(CL)). Uric acid and albumin were shown as the main components that responsible for changes in chemiluminescence kinetic curve of plasma. Serum albumin undergoes oxidative modification in dose-depend manner under the action of UV irradiation, it causes the enhancement of antioxidant properties. Changes in plasma chemiluminescence kinetics are proposed as a measure of oxidative stress in human body.

  14. Stresses and residual stresses optical measurements systems evaluation; Avaliacao de sistemas opticos de medicao de tensoes e tensoes residuais em dutos

    Peixoto Filho, Flavio Tito; Goncalves Junior, Armando Albertazzi [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Lab. de Metrologia e Automatizacao (LABMETRO)


    There is always a constant concern about the pipelines' integrity. An important control parameter is the level of total mechanical stresses acting over the pipeline. However, the loading and residual stresses acting on a pipeline are not measured in the field as much as necessary. Technical difficulties and the high cost of the nowadays techniques and the hostile measurement conditions are the main reason for that. An alternative method has been developed at the Universidade Federal de Santa Catarina (UFSC) since 1992. A new optical measurement device is used to measure strains, mechanical stresses and residual stresses acting over the structure. A metrological and functional evaluation of this system is the main focus of this paper. (author)

  15. Bed shear stress estimation on an open intertidal flat using in situ measurements

    Zhu, Q.; van Prooijen, B. C.; Wang, Z. B.; Ma, Y. X.; Yang, S. L.


    Accurate estimations for the bed shear stress are essential to predict the erosion and deposition processes in estuaries and coasts. This study used high-frequency in situ measurements of water depths and near-bed velocities to estimate bed shear stress on an open intertidal flat in the Yangtze Delta, China. To determine the current-induced bed shear stress (τc) the in situ near-bed velocities were first decomposed from the turbulent velocity into separate wave orbital velocities using two approaches: a moving average (MA) and energy spectrum analysis (ESA). τc was then calculated and evaluated using the log-profile (LP), turbulent kinetic energy (TKE), modified TKE (TKEw), Reynolds stress (RS), and inertial dissipation (ID) methods. Wave-induced bed shear stress (τw) was estimated using classic linear wave theory. The total bed shear stress (τcw) was determined based on the Grant-Madsen wave-current interaction model (WCI). The results demonstrate that when the ratio of significant wave height to water depth (Hs/h) is greater than 0.25, τcw is significantly overestimated because the vertical velocity fluctuations are contaminated by the surface waves generated by high winds. In addition, wind enhances the total bed shear stress as a result of the increases in both τw and τc generated by the greater wave height and reinforcing of vertical turbulence, respectively. From a comparison of these various methods, the TKEw method associated with ESA decomposition was found to be the best approach because: (1) this method generates the highest mean index of agreement; (2) it uses vertical velocities that are less affected by Doppler noise; and (3) it is less sensitive to the near-bed stratification structure and uncertainty in bed location and roughness.

  16. Perceived and measured physical activity and mental stress levels in obstetricians.

    Martinez de Tejada, Begoña; Jastrow, Nicole; Poncet, Antoine; Le Scouezec, Iona; Irion, Olivier; Kayser, Bengt


    Obstetric work generates important subjective and objective mental stress and is perceived as a physically demanding activity by obstetricians. The aim of this study was to quantify physical and mental stress levels in obstetricians at work and during leisure activities to investigate their association with overall physical activity levels and professional experience. 18 obstetricians at the maternity unit of the University of Geneva Hospitals were enrolled in a prospective observational study. Physical activity and stress levels were measured in two different activity sectors (delivery room and outpatient clinic) and outside work. Physical activity was assessed by questionnaire, visual analogue scale (VAS), and accelerometer. Mental stress levels were assessed by validated questionnaires, VAS, measurement of urine catecholamines and salivary cortisol, and night-time heart rate variability indices. Daily stress levels were higher at work compared to outside work (all, P = 0.002). Adrenalin (P = 0.002) and dopamine (P = 0.09) levels were elevated after a labour suite shift and a trend was observed for reduced heart rate variability during the night after this shift. The median average daily number of steps was 7132 (range, 5283-8649). Subjects reached a median of 32 min (range, 19-49 min) of moderate or higher intensity (≥ 1952 counts/min) daily physical activity. Contrary to perception, obstetrics work is not physically demanding. It is, however, accompanied by important subjective and objective mental stress that may have a negative impact on health when combined with a lack of regular daily physical activity. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  17. Measuring bed shear stress along vegetated river beds using FST-hemispheres.

    Bockelmann-Evans, B N; Davies, R; Falconer, R A


    The measurement of the bed shear stress along vegetated river beds is essential for accurately predicting the water level, velocity and solute and sediment transport fluxes in computational hydroenvironmental models. Details are given herein of an experimental and theoretical study to determine the bed boundary shear stress along vegetated river beds introducing a novel field measuring method, namely the FliessWasserStammtisch (FST)-hemispheres. Although investigations have been conducted previously for sedimentary channels using the FST-hemispheres, this preliminary study is thought to be the first time that such hemispheres have been used to investigate the bed shear stresses in vegetated channels. FST-hemispheres were first developed by Statzner and Müller [1989. Standard hemispheres as indicators of flow characteristics in lotic benthos research. Freshwater Biology 21, 445-459] to act as an integrated indicator of the gross hydrodynamic stresses present near the bed. Test and validation data were found to be at least of the same order of magnitude for the stresses predicted from literature for sedimentary channels, with this study establishing the commencement of a database of calibrated FST-hemisphere laboratory data for vegetated channel beds. In a series of experiments, depths ranging from 0.1 to 0.28 m were considered, equating directly to comparable conditions in small rivers or streams. The results of this study provide a basis for enabling the FST-hemispheres to be used to evaluate the boundary shear stress for a wider range of applications in the future, including vegetated river beds.

  18. Measuring Thermal Stress of Dairy Cattle Based on Temperature Humidity Index (THI in Tropical Climate



    Full Text Available Thermal comfort for workers is very important factor to increase their performance, as well as the comfort level of dairy cattle will influence in milk productivity. The purposes of the paper is to measure the level of heat stress and then use the information to design the dairy cattle house for increasing thermal comfort. The research is started with literature review of heat stress and early survey of environment condition e.g. temperature, wind speed and relative humidity. The next step is using the information to determine the temperature humidity index (THI level for dairy cattle with maximum THI = 86 and 84 (moderate stress. The 3D CAD model and Computational Fluid Dynamic (CFD simulation are employed to looking for solution for reducing the discomfort thermal of dairy cattle. A scenario (fan air conditioning to get better condition of thermal comfort have been successfully presented with final THI index = 76 and 78 (mild stress. Finally, the paper shows how to reduce heat stress of cattle house by installation 3 exhaust fans in tropical climate.

  19. General job stress: a unidimensional measure and its non-linear relations with outcome variables.

    Yankelevich, Maya; Broadfoot, Alison; Gillespie, Jennifer Z; Gillespie, Michael A; Guidroz, Ashley


    This article aims to examine the non-linear relations between a general measure of job stress [Stress in General (SIG)] and two outcome variables: intentions to quit and job satisfaction. In so doing, we also re-examine the factor structure of the SIG and determine that, as a two-factor scale, it obscures non-linear relations with outcomes. Thus, in this research, we not only test for non-linear relations between stress and outcome variables but also present an updated version of the SIG scale. Using two distinct samples of working adults (sample 1, N = 589; sample 2, N = 4322), results indicate that a more parsimonious eight-item SIG has better model-data fit than the 15-item two-factor SIG and that the eight-item SIG has non-linear relations with job satisfaction and intentions to quit. Specifically, the revised SIG has an inverted curvilinear J-shaped relation with job satisfaction such that job satisfaction drops precipitously after a certain level of stress; the SIG has a J-shaped curvilinear relation with intentions to quit such that turnover intentions increase exponentially after a certain level of stress.

  20. PIV Measurement of Wall Shear Stress and Flow Structures within an Intracranial Aneurysm Model

    Chow, Ricky; Sparrow, Eph; Campbell, Gary; Divani, Afshin; Sheng, Jian


    The formation and rupture of an intracranial aneurysm (IA) is a debilitating and often lethal event. Geometric features of the aneurysm bulb and upstream artery, such as bulb size, bulb shape, and curvature of the artery, are two groups of factors that define the flow and stresses within an IA. Abnormal flow stresses are related to rupture. This presentation discusses the development of a quasi-3D PIV technique and its application in various glass models at Re = 275 and 550 to experimentally assess at a preliminary level the impact of geometry and flow rate. Some conclusions are to be drawn linking geometry of the flow domain to rupture risk. The extracted results also serve as the baseline case and as a precursor to a companion presentation by the authors discussing the impact of flow diverters, a new class of medical devices. The PIV experiments were performed in a fully index-matched flow facility, allowing for unobstructed observations over complex geometry. A reconstruction and analysis method was devised to obtain 3D mean wall stress distributions and flow fields. The quasi 3D measurements were reconstructed from orthogonal planes encompassing the entire glass model, spaced 0.4mm apart. Wall shear stresses were evaluated from the near-wall flow viscous stresses.

  1. Modified Layer-Removal Method for Measurement of Residual Stress in Pre-stretched Aluminium Alloy Plate

    Liangbao Liu; Jianfei Sun; Wuyi Chen; Pengfei Sun


    Residual stress is one of the factors affecting the machining deformation of monolithic structure parts in the aviation industry. Thus, the studies on machining deformation rules induced by residual stresses largely depend on correctly and efficiently measuring the residual stresses of workpieces. A modified layer⁃removal method is proposed to measure residual stress by analysing the characteristics of a traditional layer⁃removal method. The coefficients of strain release are then deduced according to the simulation results using the finite element method ( FEM) . Moreover, the residual stress in a 7075T651 aluminium alloy plate is measured using the proposed method, and the results are then analyzed and compared with the data obtained by the traditional methods. The analysis indicates that the modified layer⁃removal method is effective and practical for measuring the residual stress distribution in pre⁃stretched aluminium alloy plates.

  2. Dry fracture method for simultaneous measurement of in-situ stress state and material properties

    Serata, S. [Serata Geomechanics, Inc., Richmond, CA (United States); Oka, S.; Kikuchi, S. [JDC Corp., Tokyo (Japan)


    Based on the dry fracture principle, a computerized borehole probe has been developed to measure stress state and material properties, simultaneously. The probe is designed to obtain a series of measurements in a continuing sequence along a borehole length, without any interruptive measures, such as resetting packers, taking indentation of borehole wall, overcoming, etc. The new dry fracture probe for the single fracture method is designed to overcome the difficulties posed by its ancestor which was based on the double fracture method. The accuracy of the single fracture method is confirmed by a close agreement with the theory, FE modeling and laboratory testing.

  3. Combined full field stress and strain measurement methods for granular materials

    Broere W.


    Full Text Available The current paper re-introduces the photoelastic measurement method in experimental geomechanics. A full-field phase stepping polariscope suitable for geomechanical model tests has been developed. Additional constraints on the measurement and mechanical setup arising from geomechanical test conditions are outlined as well as the opportunity to measure the displacement fields in the sample with digital image correlation. The capability of the current setup in retrieving the stress and strain field in a granular material is demonstrated.

  4. Measuring Stress-dependent Fluid Flow Behavior in Fractured Porous Media

    Huo, Da; Benson, Sally


    Maintaining long-term storage of CO2 is one of the most important factors for selecting the site for a geological CO2 storage project. Nevertheless, it is important to be prepared for possible leakage due to leaking wells or leakage pathways through the seal of a storage reservoir. This research project is motivated by the need to understand unexpected CO2 leakage. The goal of this research is to investigate stress-dependent fracture permeability and relative permeability of CO2/brine systems. Laboratory measurements of fracture permeability and fracture apertures have been made as a function of effective stress. The phenomenon that permeability decreases with effective pressure increase is observed. Due to deformation of the fracture surface during periods with high effective stress, hysteretic behavior of fractured rock permeability is also observed in core flood experiments. A series of experiments are conducted to investigate permeability hysteresis. A single saw-cut fracture is created in the rock sample to simplify the problem and to focus on the fracture itself. Permeability is measured using a high pressure core flood apparatus with X-Ray CT scanning to measure the fracture aperture distributions. Two permeability data sets, including a high permeability fractured Berea Sandstone and a low permeability fractured Israeli Zenifim Formation sandstone, show clear hysteretic behavior in both permeability and fracture aperture in repeated cycles of compression and decompression. Due to closure of the fracture aperture, when a fractured rock is compressed axially, the permeability has an exponential decline with effective pressure, as expected from stress-dependent permeability theory. When the fractured rock is decompressed afterwards, permeability increases, but not along the compression pathway and never returns to the original value. Depending on the nature of the fracture and host rock, permeability can decrease from a factor of 2 to 40. After one or more

  5. Physiological Adjustments to Stress Measures Following Massage Therapy: A Review of the Literature

    Albert Moraska


    Full Text Available Use of massage therapy by the general public has increased substantially in recent years. In light of the popularity of massage therapy for stress reduction, a comprehensive review of the peer-reviewed literature is important to summarize the effectiveness of this modality on stress-reactive physiological measures. On-line databases were searched for articles relevant to both massage therapy and stress. Articles were included in this review if (i the massage therapy account consisted of manipulation of soft tissues and was conducted by a trained therapist, and (ii a dependent measure to evaluate physiological stress was reported. Hormonal and physical parameters are reviewed. A total of 25 studies met all inclusion criteria. A majority of studies employed a 20–30 min massage administered twice-weekly over 5 weeks with evaluations conducted pre-post an individual session (single treatment or following a series of sessions (multiple treatments. Single treatment reductions in salivary cortisol and heart rate were consistently noted. A sustained reduction for these measures was not supported in the literature, although the single-treatment effect was repeatable within a study. To date, the research data is insufficient to make definitive statements regarding the multiple treatment effect of massage therapy on urinary cortisol or catecholamines, but some evidence for a positive effect on diastolic blood pressure has been documented. While significant improvement has been demonstrated following massage therapy, the general research body on this topic lacks the necessary scientific rigor to provide a definitive understanding of the effect massage therapy has on many physiological variables associated with stress.

  6. Physiological adjustments to stress measures following massage therapy: a review of the literature.

    Moraska, Albert; Pollini, Robin A; Boulanger, Karen; Brooks, Marissa Z; Teitlebaum, Lesley


    Use of massage therapy by the general public has increased substantially in recent years. In light of the popularity of massage therapy for stress reduction, a comprehensive review of the peer-reviewed literature is important to summarize the effectiveness of this modality on stress-reactive physiological measures. On-line databases were searched for articles relevant to both massage therapy and stress. Articles were included in this review if (i) the massage therapy account consisted of manipulation of soft tissues and was conducted by a trained therapist, and (ii) a dependent measure to evaluate physiological stress was reported. Hormonal and physical parameters are reviewed. A total of 25 studies met all inclusion criteria. A majority of studies employed a 20-30 min massage administered twice-weekly over 5 weeks with evaluations conducted pre-post an individual session (single treatment) or following a series of sessions (multiple treatments). Single treatment reductions in salivary cortisol and heart rate were consistently noted. A sustained reduction for these measures was not supported in the literature, although the single-treatment effect was repeatable within a study. To date, the research data is insufficient to make definitive statements regarding the multiple treatment effect of massage therapy on urinary cortisol or catecholamines, but some evidence for a positive effect on diastolic blood pressure has been documented. While significant improvement has been demonstrated following massage therapy, the general research body on this topic lacks the necessary scientific rigor to provide a definitive understanding of the effect massage therapy has on many physiological variables associated with stress.

  7. Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

    Dadfarnia, Mohsen (University of Illinois at Urbana-Champaign, Urbana, IL); Nibur, Kevin A.; San Marchi, Christopher W.; Sofronis, Petros (University of Illinois at Urbana-Champaign, Urbana, IL); Somerday, Brian P.; Foulk, James W., III; Hayden, Gary A. (CP Industries, McKeesport, PA)


    Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.

  8. Blood Contamination in Saliva: Impact on the Measurement of Salivary Oxidative Stress Markers.

    Kamodyová, Natália; Baňasová, Lenka; Janšáková, Katarína; Koborová, Ivana; Tóthová, Ľubomíra; Stanko, Peter; Celec, Peter


    Salivary oxidative stress markers represent a promising tool for monitoring of oral diseases. Saliva can often be contaminated by blood, especially in patients with periodontitis. The aim of our study was to examine the impact of blood contamination on the measurement of salivary oxidative stress markers. Saliva samples were collected from 10 healthy volunteers and were artificially contaminated with blood (final concentration 0.001-10%). Next, saliva was collected from 12 gingivitis and 10 control patients before and after dental hygiene treatment. Markers of oxidative stress were measured in all collected saliva samples. Advanced oxidation protein products (AOPP), advanced glycation end products (AGEs), and antioxidant status were changed in 1% blood-contaminated saliva. Salivary AOPP were increased in control and patients after dental treatment (by 45.7% and 34.1%, p Saliva samples with 1% blood contamination are visibly discolored and can be excluded from analyses without any specific biochemic detection of blood constituents. Salivary markers of oxidative stress were significantly altered in blood-contaminated saliva in control and patients with gingivitis after dental hygiene treatment.

  9. Racial/ethnic differences in self-reported and biologic measures of chronic stress in pregnancy.

    Borders, A E B; Wolfe, K; Qadir, S; Kim, K-Y; Holl, J; Grobman, W


    Racial differences in chronic maternal stress may contribute to disparities in pregnancy outcomes. The objective is to identify racial and ethnic differences in self-reported and biologic measures of stress between non-Hispanic black (NHB) and non-Hispanic white (NHW) pregnant women. NHB and NHW pregnant women were enrolled before 23 weeks of gestation in this prospective cohort study. Equal numbers of women were recruited with public vs private insurance in each racial group. Self-reported stress was measured and blood samples collected in the second and third trimesters were analyzed for serum Epstein-Barr virus antibody, C-reactive protein (CRP), corticotropin-releasing hormone (CRH) and adenocorticotropic hormone (ACTH). One hundred and twelve women were enrolled. NHW women reported more buffers against stress (P=0.04) and neighborhood satisfaction (P=0.02). NHB women reported more discrimination (Pstress were identified between NHB and NHW pregnant women with similar economic characteristics. Future studies should investigate mechanisms underlying these differences and their relationship to pregnancy outcomes.

  10. Residual stress in hydroxyapatite coating: nonlinear analysis and high-energy synchrotron measurements.

    Fogarassy, Paul; Cofino, Bruno; Millet, Pierre; Lodini, Alain


    The thermal deposition of hydroxyapatite (HA) on titanium alloy substrate (Ti-6A1-4V) leads to a structure that has very good osseointegration properties. However, clinical failures have been occasionally reported at the interface between substrate and coating. Lifetime is the main parameter in such prostheses; therefore, in order to improve their quality, it is necessary to evaluate the level of stresses near the interface. The high-energy synchrotron radiation combines the advantages of a bulk analysis and reduced volume of the gauge. The objective of our study was to calculate the residual stress using a nonlinear finite-element model and to measure residual stress level near the interface, in the hydroxyapatite coating and in titanium alloy substrate with a nondestructive and high-resolution experiment. The high-energy synchrotron radiation of the BM16 beam-line at ESRF (Grenoble-France) was used with a resolution of down to 10 micrometers. The experimental measurements validate the results found by means of nonlinear finite-element analysis of the plasma spraying induced stress.

  11. Cross-Sectional Residual Stresses in Thermal Spray Coatings Measured by Moiré Interferometry and Nanoindentation Technique

    Zhu, Jianguo; Xie, Huimin; Hu, Zhenxing; Chen, Pengwan; Zhang, Qingming


    A plasma-sprayed thermal barrier coating (TBC) was deposited on a stainless steel substrate. The residual stresses were firstly measured by moiré interferometry combined with a cutting relaxation method. The fringe patterns in the cross-section of the specimen clearly demonstrate the deformation caused by the residual stress in thermal spray coatings. However, restricted by the sensitivity of moiré interferometry, there are few fringes in the top coat, and large errors may exist in evaluating the residual stress in the top coat. Then, the nanoindentation technique was used to estimate the residual stresses across the coating thickness. The stress/depth profile shows that the process-induced stresses after thermal spray are compressive in the top coat and a tendency to a more compressive state toward the interface. In addition, the stress gradient in the substrate is nonlinear, and tensile and compressive stresses appear simultaneously for self-equilibrium in the cross-section.

  12. Design and analysis of a toroidal tester for the measurement of core losses under axial compressive stress

    Alatawneh, Natheer; Rahman, Tanvir; Lowther, David A.; Chromik, Richard


    Electric machine cores are subjected to mechanical stresses due to manufacturing processes. These stresses include radial, circumferential and axial components that may have significant influences on the magnetic properties of the electrical steel and hence, on the output and efficiencies of electrical machines. Previously, most studies of iron losses due to mechanical stress have considered only radial and circumferential components. In this work, an improved toroidal tester has been designed and developed to measure the core losses and the magnetic properties of electrical steel under a compressive axial stress. The shape of the toroidal ring has been verified using 3D stress analysis. Also, 3D electromagnetic simulations show a uniform flux density distribution in the specimen with a variation of 0.03 T and a maximum average induction level of 1.5 T. The developed design has been prototyped, and measurements were carried out using a steel sample of grade 35WW300. Measurements show that applying small mechanical stresses normal to the sample thickness rises the delivered core losses, then the losses decrease continuously as the stress increases. However, the drop in core losses at high stresses does not go lower than the free-stress condition. Physical explanations for the observed trend of core losses as a function of stress are provided based on core loss separation to the hysteresis and eddy current loss components. The experimental results show that the effect of axial compressive stress on magnetic properties of electrical steel at high level of inductions becomes less pronounced.

  13. Stress

    Jensen, Line Skov; Lova, Lotte; Hansen, Zandra Kulikovsky; Schønemann, Emilie; Larsen, Line Lyngby; Colberg Olsen, Maria Sophia; Juhl, Nadja; Magnussen, Bogi Roin


    Stress er en tilstand som er meget omdiskuteret i samfundet, og dette besværliggør i en vis grad konkretiseringen af mulige løsningsforslag i bestræbelsen på at forebygge den såkaldte folkesygdom. Hovedkonklusionen er, at selv om der bliver gjort meget for at forebygge, er der ikke meget der aktivt kan sættes i værk for at reducere antallet af stressramte, før en fælles forståelse af stressårsager og effektiv stresshåndtering er fremlagt. Problemformuleringen er besvaret gennem en undersø...

  14. Repeated measures of inflammation and oxidative stress biomarkers in preeclamptic and normotensive pregnancies.

    Ferguson, Kelly K; Meeker, John D; McElrath, Thomas F; Mukherjee, Bhramar; Cantonwine, David E


    Preeclampsia is a prevalent and enigmatic disease, in part characterized by poor remodeling of the spiral arteries. However, preeclampsia does not always clinically present when remodeling has failed to occur. Hypotheses surrounding the "second hit" that is necessary for the clinical presentation of the disease focus on maternal inflammation and oxidative stress. Yet, the studies to date that have investigated these factors have used cross-sectional study designs or small study populations. In the present study, we sought to explore longitudinal trajectories, beginning early in gestation, of a panel of inflammation and oxidative stress markers in women who went on to have preeclamptic or normotensive pregnancies. We examined 441 subjects from the ongoing LIFECODES prospective birth cohort, which included 50 mothers who experienced preeclampsia and 391 mothers with normotensive pregnancies. Participants provided urine and plasma samples at 4 time points during gestation (median, 10, 18, 26, and 35 weeks) that were analyzed for a panel of oxidative stress and inflammation markers. Oxidative stress biomarkers included 8-isoprostane and 8-hydroxydeoxyguanosine. Inflammation biomarkers included C-reactive protein, the cytokines interleukin-1β, -6, and -10, and tumor necrosis factor-α. We created Cox proportional hazard models to calculate hazard ratios based on time of preeclampsia diagnosis in association with biomarker concentrations at each of the 4 study visits. In adjusted models, hazard ratios of preeclampsia were significantly (Pinflammation biomarkers that were measured at visit 2 (median, 18 weeks; hazard ratios, 1.31-1.83, in association with an interquartile range increase in biomarker). Hazard ratios at this time point were the most elevated for C-reactive protein, for interleukin-1β, -6, and -10, and for the oxidative stress biomarker 8-isoprostane (hazard ratio, 1.68; 95% confidence interval, 1.14-2.48) compared to other time points. Hazard ratios for

  15. In-situ neutron diffraction measurement of stress redistribution in a dissimilar joint during heat treatment

    Dodge, M.F., E-mail: [TWI Ltd., Great Abington, Cambridge CB21 6AL (United Kingdom); Gittos, M.F. [TWI Ltd., Great Abington, Cambridge CB21 6AL (United Kingdom); Dong, H. [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Zhang, S.Y.; Kabra, S.; Kelleher, J.F. [ISIS, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom)


    Neutron diffraction is routinely used to monitor stress redistribution before and after heat treatment in dissimilar joints. However there remains a paucity of information concerning the evolution of strain throughout the process of heat treatment itself. Due to different mechanical properties between opposing sides, a competitive strain redistribution process occurs. Consequently, a novel in-situ measurement approach has been developed: strains at multiple points in a dissimilar joint have been measured during heat treatment. Thus, the described work elucidates areas within the thermal cycle in which competitive strain redistribution occurs, and where high residual stresses remain, following PWHT. The method may be used to characterise comparable material combinations, with a view to optimising the thermal cycles, and ultimately, the structural integrity of dissimilar joints.

  16. Development of procedures for the measurement of residual stress by neutron diffraction

    Webster, G A


    Neutron diffraction is a non-destructive method for determining residual stresses in crystalline materials. It is a relatively new technique and no standard is currently available for making these measurements. This paper gives the background to research that has been carried out to develop a standard. It outlines the main findings and indicates the precautions that are required to achieve accurate positioning and alignment of specimens (and components) in a neutron beam and the analysis required to obtain reliable results. It also shows that special attention is needed in dealing with near-surface measurements because of surface aberration. It is demonstrated that, provided the recommended procedures are followed, a positional tolerance of +-0.1 mm can be achieved with an accuracy in strain of propor to 10 sup - sup 4 , to give a resolution in residual stress of propor to 7 to 20 MPa in most materials of practical interest. (orig.)

  17. A system for remote measurements of the wind stress over the ocean

    Large, William G.; Businger, J. A.


    The DISSTRESS system for remote measurements of the surface wind stress over the ocean from ships and buoys is described. It is fully digital, utilizing the inertial dissipation technique. Parallel processing allows anemometer data to be filtered in natural frequency space; that is, the filter cutoffs shift linearly with the mean wind speed of the data to be filtered. The construction of the digital Butterworth bandpass filters is presented in detail. The performance of the system is evaluated by analyzing the results from 28 days of operation during the Frontal Air-Sea Interaction Experiment. The mean wind speed is checked, the anemometer response function is established, and drag coefficients are compared to previous studies. The capability of the system is demonstrated by continuous time series of the friction velocity computed every 20 min. The conclusion is that the surface wind stress can be measured more reliably and accurately (20 percent) with this system than from anemometer wind speeds and a bulk formula.

  18. Measuring Mechanical Properties by Staring: Using Stress Assessment from Local Structural Anisotropy (SALSA) to Probe Viscosity and Visualize Stress Networks in Colloidal Suspensions

    Cohen, Itai; Bierbaum, Matthew; Sethna, James; Lin, Neil


    Measurement of stress induced thermal fluctuations in materials can be used to determine macroscopic mechanical properties including viscosity in fluids, as well as bulk and shear moduli in solids. When extended to the single particle scale, such measurements also reveal underlying spatially inhomogeneous response mechanisms in systems such as glasses, gels, and polycrystals. Unfortunately, it is not possible to experimentally measure these temporal and spatial stress fluctuations in a colloidal suspension using conventional rheometers. Here however, we show that using fast confocal microscopy it is possible conduct a Stress Assessment from Local Structural Anisotropy (SALSA) to measure such spatio-temporal stress fluctuations. We directly image the microstructure of a nearly hard-sphere suspension using a high-speed confocal microscope and determine particle positions. We compute the structure anisotropy of the suspension and building on the Brady formalism, calculate particle-level stresses. In conjunction with the fluctuation-dissipation theorem, we then determine the bulk viscosity of a colloidal liquid. Furthermore, we show our local measurements allow direct visualization of the complex stress networks in a 3D supercooled liquid under compression. Our method provides an experimental approach that applies to a broad range of processes arising in sheared glasses, compressed gels, and even indented crystals.

  19. Evaluation of metal-nanowire electrical contacts by measuring contact end resistance.

    Park, Hongsik; Beresford, Roderic; Ha, Ryong; Choi, Heon-Jin; Shin, Hyunjung; Xu, Jimmy


    It is known, but often unappreciated, that the performance of nanowire (NW)-based electrical devices can be significantly affected by electrical contacts between electrodes and NWs, sometimes to the extent that it is really the contacts that determine the performance. To correctly understand and design NW device operation, it is thus important to carefully measure the contact resistance and evaluate the contact parameters, specific contact resistance and transfer length. A four-terminal pattern or a transmission line model (TLM) pattern has been widely used to measure contact resistance of NW devices and the TLM has been typically used to extract contact parameters of NW devices. However, the conventional method assumes that the electrical properties of semiconducting NW regions covered by a metal are not changed after electrode formation. In this study, we report that the conventional methods for contact evaluation can give rise to considerable errors because of an altered property of the NW under the electrodes. We demonstrate that more correct contact resistance can be measured from the TLM pattern rather than the four-terminal pattern and correct contact parameters including the effects of changed NW properties under electrodes can be evaluated by using the contact end resistance measurement method.

  20. Relationship between the onset of depression and stress response measured by the Brief Job Stress Questionnaire among Japanese employees: a cohort study.

    Keiko Wada

    Full Text Available BACKGROUND: The proportion of Japanese workers experiencing intense worry or stress during working life is in excess of 60%, and the incidence of psychiatric disorders and suicide due to psychological burden from work duties is increasing. To confirm whether the stress response measured by the Brief Job Stress Questionnaire (BJSQ can identify risk for depression, a cohort study was conducted to evaluate whether the stress response measured by BJSQ was associated with the onset of depression. METHODS: A total of 1,810 participants aged 20-70 years in 2005 completed the stress response of the BJSQ and were followed-up until August, 2007 by examining sick pay records. Depression was defined by a description in sick pay records that included "depression" or "depressive symptoms" as a reason for sick leave according to a physician's medical certificate. The participants were divided into quartiles (Ql, Q2, Q3, and Q4 according to the total stress response score of BJSQ at baseline. Furthermore, the participants were divided into a higher score category (Q4 and a lower score category (Q1-Q3. Risk ratios of the stress response of the BJSQ for onset of depression were calculated using a multivariable Cox proportional hazard model. RESULTS: Among 1,810 participants, 14 developed depression during a mean of 1.8 years of follow-up. The risk ratio was 2.96 (95% confidence interval [CI], 1.04-8.42, p for trend = 0.002 when the higher stress response score category of BJSQ was compared with the low stress response score category for sick leave due to depression. After adjusting for gender, age, marital status, and having children, the risk ratios were similar to no adjustment. CONCLUSIONS: These findings suggest that the stress response measured by the BJSQ can demonstrate risk for the onset of depression.

  1. Measurement of heart rate variability and stress evaluation by using microwave reflectometric vital signal sensing

    Nagae, Daisuke; Mase, Atsushi


    In this paper, we present two robust signal processing techniques for stress evaluation using a microwave reflectometric cardiopulmonary sensing instrument. These techniques enable the heart rate variability (HRV) to be recovered from measurements of body-surface dynamic motion, which is subsequently used for the stress evaluation. Specifically, two novel elements are introduced: one is a reconfiguration of the HRV from the cross-correlation function between a measurement signal and a template signal which is constructed by averaging periodic component over a measurement time. The other is a reconstruction of the HRV from the time variation of the heartbeat frequency; this is evaluated by a repetition of the maximum entropy method. These two signal processing techniques accomplish the reconstruction of the HRV, though they are completely different algorithms. For validations of our model, an experimental setup is presented and several sets of experimental data are analyzed using the two proposed signal processing techniques, which are subsequently used for the stress evaluation. The results presented herein are consistent with electrocardiogram data.

  2. Measurements of gap pressure and wall shear stress of a blood pump model.

    Chua, L P; Akamatsu, T


    The centrifugal blood pump with a magnetically suspended impeller has shown its superiority as compared to other artificial hearts. However, there is still insufficient understanding of fluid mechanics related issues in the clearance gap. The design nature of the pump requires sufficient washout in the clearance between the impeller and stationary surfaces. As the gap is only 0.2 mm in width, it is very difficult to conduct measurements with present instrumentation. An enlarged model with 5:1 ratio of the pump has been designed and constructed according to specifications. Dimensionless gap pressure measurements of the model are very close to the prototype. The measurements of wall shear stress of the fluid flow in the clearance gap between the impeller face and inlet casing of a blood pump model were accomplished through hot-wire anemometry and rotating disk apparatus. Regions of relatively high and low shear stresses are identified. These correspond to spots where the likelihood of hemolysis and thrombus formation is high. With the use of dimensional analysis, it is found that the highest wall shear stress is equivalent to 146 Pa which is much lower than the threshold value of 400 Pa for hemolysis reported in the literature.

  3. Measurement and modeling of residual stress in a welded Haynes[reg] 25 cylinder

    Larsson, C. [Div. of Eng. Mat., Department of Mech. Eng., Linkoeping University, 58183 Linkoeping (Sweden)]. E-mail:; Holden, T.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bourke, M.A.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stout, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Teague, J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lindgren, L.-E. [Div. Comp. Aided Design, Lulea University of Technology and Dalarna University, 97187 Lulea (Sweden)


    An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld, used to join a hemispherical end cap to a cylinder. The capped cylinder is used in a satellite application and was fabricated from a Co-based Haynes[reg] 25 alloy. The cylinder was 34.7 mm in outer diameter and 3.3 mm in thickness. The experimental measurements were made by neutron diffraction and the simulation used the implicit Marc finite element code. The experimental resolution was limited to approximately 3 mm parallel to the axis of the cylinder (the weld was 6 mm in the same direction) and comparison over the same volume of the finite element prediction showed general agreement. Subject to the limited spatial resolution, the largest experimentally measured tensile residual stress was 180 MPa, located at the middle of the weld. However, the predictions suggest that there are regions in the weld where average tensile residual stresses as much as 400 MPa exist. One qualitative disparity between the model and the experiments was that the measurement included a larger degree of asymmetry on either side of the weld than predicted by the model.

  4. Accounting for posttraumatic stress disorder symptom severity with pre- and posttrauma measures

    Ogle, Christin M.; Rubin, David C.; Siegler, Ilene C.


    Using data from a longitudinal study of community-dwelling older adults, we analyzed the most extensive set of known correlates of posttraumatic stress disorder (PTSD) symptoms obtained from a single sample to examine the measures’ independent and combined utility in accounting for PTSD symptom...... attachment and factors related to the current trauma memory, such as self-rated severity, event centrality, frequency of involuntary recall, and physical reactions to the memory, accounted for symptom severity better than did measures of pretrauma factors. In an analysis restricted to prospective measures...... severity. Fifteen measures identified as PTSD risk factors in published meta-analyses as well as 12 theoretically and empirically supported individual difference and health-related measures were included in our analysis. Individual difference measures assessed after the trauma, including insecure...

  5. Structural integrity assessment and stress measurement of CHASNUPP-1 fuel assembly

    Waseem,, E-mail:; Murtaza, Ghulam; Elahi, Nadeem


    Highlights: • Finite element model of CHASNUPP-1 fuel assembly produced, using Shell181 elements. • Non-linear contact and buckling analysis have been performed. • Structural integrity and stress measurement of fuel assembly is calculated. • Calculated stresses and deformations, are compared with test results. • Results of both studies are comparable, which validate finite element methodology. - Abstract: Fuel assembly of the PWR nuclear power plant is a long and flexible structure. This study has been made in an attempt to find the structural integrity of the fuel assembly (FA) of Chashma Nuclear Power Plant-1 (CHASNUPP-1) at room temperature in air. Non-linear contact and buckling analyses have been performed using ANSYS 13.0, in-order to determine the FA's deformation behaviour as well as the location/values of the maximum stress intensity and stresses developed in axial direction under applied compression load of 7350 N or 1.6 g being the FA's handling load (Zhang et al., 1994). The finite element (FE) model comprises spacer grids, fuel rods, flexible contact between the fuel rods and grids’ supports system (springs and dimples) and guide thimbles with dash-pots and flow holes, in addition to the spot welds between spacer grids and guide thimbles, has been developed using Shell181, Conta174 and Targe170 elements. FA is a non-straight structure. The actual behaviour of the geometry is non-linear. The value of the perturbation force is related to the geometry of the model and/or the tolerance defined for the geometry. Therefore, a sensitivity study has been made to determine the appropriate value of an arbitrary perturbation load. It has been observed that FA deformation values obtained through FE analysis and experiment (SNERDI Tech Doc, 1994) under applied compression load are comparable and show linear behaviours. Therefore, it is confirmed that buckling of FA will not occur at the specified load. Moreover, the values of stresses obtained

  6. Association of CD4+ T cell subpopulations and psychological stress measures in women living with HIV.

    Rehm, Kristina E; Konkle-Parker, Deborah


    Psychological stress is a known immunomodulator. In individuals with HIV, depression, the most common manifestation of increased psychological stress, can affect immune function with lower CD4+ T cell counts correlating with higher levels of depression. It is unknown how other forms of psychological stress can impact immune markers in people living with HIV. We conducted a cross-sectional study to determine how CD4+ T cell subpopulations correlated with different forms of psychological stress. We recruited 50 HIV-positive women as part of the Women's Interagency HIV Study. We assessed perceived stress, worry, acute anxiety, trait anxiety, and depression through self-report questionnaires and CD4+ T cell subpopulations using flow cytometry. Our sample was 96% African-American with a mean ± SD age and body mass index of 42 ± 8.8 years and 36.6 ± 11.5 kg/m(2), respectively. The mean ± SD scores on the psychological measures were as follows: Perceived Stress Scale (PSS), 16.5 ± 6.4; Penn State Worry Questionnaire (PSWQ), 47.7 ± 13.8; State-Trait Anxiety Inventory - State (STAIS), 39.1 ± 12.3; State-Trait Anxiety Inventory - Trait (STAIT), 40.2 ± 11.4; Center for Epidemiological Studies Depression Scale (CES-D), 15.6 ± 11.4. The mean + SD values for the immune parameters were as follows: regulatory T cells (Treg), 1.25% ± 0.7; T helper 1 (Th1), 14.9% ± 6.1; T helper 2 (Th2), 3.8% ± 2; Th1/Th2 ratio, 4.6 ± 3; and CD4+ T cell count (cells/mm(3)), 493 ± 251. Treg levels positively correlated with PSS, STAIS, and STAIT. CD4+ T cell count negatively correlated with PSS, PSWQ, STAIS, STAIT, and CES-D. These data suggest that immune function may be impacted by various forms of psychological stress in HIV-positive women. Interventions that target stress reduction may be useful in improving immune parameters and quality of life.

  7. On the reliability of neutron diffraction for residual stress measurement in cold-drawn steels

    Ruiz-Hervias, J.; Mompean, F.; Hofmann, M.; Atienza, J. M.


    Residual strains were measured in the ferrite phase of pearlitic steel rods along the radial, axial and hoop directions. Two samples with different initial diameters were subjected to one drawing pass (using same drawing parameters) with 20% section reduction and measured in two different neutron diffraction instruments. The results show that the residual strain state is very similar in both cases, regardless of the diameter of the initial rod. This means that the final residual strain-stress state is unique and it is related to the cold-drawing process parameters. In addition, the results show the reliability of strain scanning with different neutron instruments and experimental conditions.

  8. Reliable cost effective technique for in situ ground stress measurements in deep gold mines.

    Stacey, TR


    Full Text Available percussion boreholes drilled with a conventional jackhammer • creating the enlargement, or stress/strain change, not by overcoring,but by drilling parallel, overlapping holes • control of the direction of adjacent holes, and prevention of movement... of drill chips into the measuring hole, by means of a special borehole guide • measurement of deformation changes in the first borehole, as a result of the drilling of the third borehole, by means of a borehole deformation meter • sequential deformation...

  9. Effect of acute stresses on zebra fish (Danio rerio) metabolome measured by NMR-based metabolomics.

    Mushtaq, Mian Yahya; Marçal, Rosilene Moretti; Champagne, Danielle L; van der Kooy, Frank; Verpoorte, Robert; Choi, Young Hae


    We applied an acute stress model to zebra fish in order to measure the changes in the metabolome due to biological stress. This was done by submitting the fish to fifteen minutes of acute confinement (netting) stress, and then five minutes for the open field and light/dark field tests. A polar extract of the zebra fish was then subjected to (1)H nuclear magnetic spectroscopy. Multivariate data analysis of the spectra showed a clear separation associated to a wide range of metabolites between zebra fish that were submitted to open field and light/dark field tests. Alanine, taurine, adenosine, creatine, lactate, and histidine were high in zebra fish to which the light/dark field test was applied, regardless of stress, while acetate and isoleucine/lipids appeared to be higher in zebra fish exposed to the open field test. These results show that any change in the environment, even for a small period of time, has a noticeable physiological impact. This research provides an insight of how different mechanisms are activated under different environments to maintain the homeostasis of the body. It should also contribute to establish zebra fish as a model for metabolomics studies.

  10. The comparison of methods for measuring oxidative stress in zebrafish brains.

    Moussavi Nik, Seyyed Hani; Croft, Kevin; Mori, Trevor A; Lardelli, Michael


    The zebrafish is a versatile model organism with the potential to contribute to our understanding of the molecular pathological mechanisms underlying Alzheimer's disease (AD). An early characteristic of AD brain pathology is lipid peroxidation resulting from oxidative stress. However, changes in lipid peroxidation have not yet been assessed in zebrafish brains, and an earlier attempt to observe changes in F₂-isoprostane levels in the brains of zebrafish exposed to hypoxia was unsuccessful. In this article, we examine the utility of various assays of lipid peroxidation and more general assays of intracellular oxidative stress to detect the changes in oxidative stress in the brains of adult zebrafish exposed to hypoxia or explanted into a sodium azide solution for chemical mimicry of hypoxia. Levels of F₂-isoprostanes and F₄-neuroprostanes were low and variable in zebrafish brains such that statistically significant changes due to hypoxia or chemical mimicry of hypoxia could not be observed. However, measurement of lipid hydroperoxides did reveal significant changes in lipid peroxidation under these conditions, while analyses of catalase gene expression and an assay based on 2',7'-dicholorofluorescein oxidation also revealed changes in oxidative stress levels.

  11. Piezospectroscopic measurements capturing the evolution of plasma spray-coating stresses with substrate loads.

    Freihofer, Gregory; Fugon-Dessources, Daniela; Ergin, Emrecan; Van Newkirk, Amy; Gupta, Ankur; Seal, Sudipta; Schülzgen, Axel; Raghavan, Seetha


    Plasma-spray coatings have a unique microstructure composed of various types of microcracks and weakly bonded interfaces which dictate their nonlinear mechanical properties. The intrinsic photo-luminescence (PL) characteristics of alpha-alumina (α-Al2O3) within these coatings offer a diagnostic functionality, enabling these properties to be probed experimentally at the microscale, under substrate loading. The piezospectroscopic (PS) measurements from the coatings are capable of revealing microstructural stress at high spatial resolution. Here, for the first time, the evolution of stresses within air plasma spray (APS) coatings under increasing substrate loads were captured using piezospectroscopy. With mechanical cycling of the substrate, the PS properties revealed anelastic and inelastic behavior and a relaxation of residual tensile stress within the APS coatings. With decreasing substrate thickness, the coating was observed to sustain more stress, as the substrate's influence on the mechanical behavior decreased. The findings provide an insight into the microstructural response that can serve as the basis for model validation and subsequently drive the design process for these coatings.

  12. Measurement of residual stresses in the dissimilar metal weld joint of a safe-end nozzle mock-up

    Ogawa, Kazuo (Japan Nuclear Energy Safety Organisation, Tokyo (Japan)); Kingston, E.; Chidwick, L. (VEQTER Ltd., Bristol (United Kingdom)); Smith, D. (Univ. of Bristol (United Kingdom))


    Knowledge of the origin, magnitude and distribution of residual stresses generated during the manufacture of nuclear power plants is of vital importance to their structural integrity assessment. The overall aim of this work was to measure welding residual stresses in components prone to primary water stress corrosion cracking in nuclear reactor pressure vessels. This paper describes the on-site application of the Deep-Hole Drilling (DHD) technique to measure the through-thickness residual stress distributions through a safe-end nozzle component containing a dissimilar metal weld joint at different stages of manufacture

  13. Repeated measures of urinary oxidative stress biomarkers during pregnancy and preterm birth.

    Ferguson, Kelly K; McElrath, Thomas F; Chen, Yin-Hsiu; Loch-Caruso, Rita; Mukherjee, Bhramar; Meeker, John D


    The purpose of this study was to investigate oxidative stress as a mechanism of preterm birth in human subjects; we examined associations between urinary biomarkers of oxidative stress that were measured at multiple time points during pregnancy and preterm birth. This nested case-control study included 130 mothers who delivered preterm and 352 mothers who delivered term who were originally recruited as part of an ongoing prospective birth cohort at Brigham and Women's Hospital. Two biomarkers that included 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane were measured in urine samples that were collected at up to 4 time points (median 10, 18, 26, and 35 weeks) during gestation. Urinary concentrations of 8-isoprostane and 8-OHdG decreased and increased, respectively, as pregnancy progressed. Average levels of 8-isoprostane across pregnancy were associated with increased odds of spontaneous preterm birth (adjusted odds ratio, 6.25; 95% confidence interval, 2.86-13.7), and associations were strongest with levels measured later in pregnancy. Average levels of 8-OHdG were protective against overall preterm birth (adjusted odds ratio, 0.19; 95% confidence interval, 0.10-0.34), and there were no apparent differences in the protective effect in cases of spontaneous preterm birth compared with cases of placental origin. Odds ratios for overall preterm birth were more protective in association with urinary 8-OHdG concentrations that were measured early in pregnancy. Maternal oxidative stress may be an important contributor to preterm birth, regardless of subtype and timing of exposure during pregnancy. The 2 biomarkers that were measured in the present study had opposite associations with preterm birth; an improved understanding of what each represents may help to identify more precisely important mechanisms in the pathway to preterm birth. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Field measurement of critical shear stress for erosion and deposition of fine muddy sediments

    Salehi, M.; Strom, K. B.; Field Study


    The movement of muddy sediment from one region to another is linked to the fate and transport of pollutants that can be attached to this sediment. Important in understanding this movement is the need to know the critical conditions for erosion and deposition of the fine muddy sediment. For non-cohesion sediment, such as sands and gravels, reasonable estimates for the critical conditions can often be made theoretically without in situ measurements of the critical fluid condition or sediment transport rate. However, the shear stress needed for the incipient motion of the mud (cohesive sediments) is inherently difficult to calculate theoretically or in research flumes due to the influence of (1) flow history; (2) local sediment composition; (3) biological activity within the bed; (4) water content of the bed; and (5) salinity of the water column. The complexity of the combination of these factors makes the field measurement necessary. A field experiment was conducted under tidal flow in the region surrounding the Houston Ship Channel (near Houston, TX) to determine these conditions. Observations were made using single point, simultaneous, in situ measurement of turbulent flow and suspended sediment concentration within bottom boundary layer. Measurements were primarily made with a 6 MHz Nortek Vector velocimeter (ADV). The ADV was programmed to record 3-minute turbulent velocity with 32 Hz frequency every 10 minute. The suspended sediment concentration (SSC) was measured using the calibration of acoustic backscatter recorded by ADV against sample derived SSC. Different methods such as turbulent kinetic energy (TKE), TKEw and direct covariance method (COV) are compared together. TKE showed much more reasonable estimation on bed shear stress. Combination of time varying SSC, distance from the bed to the sampling volume recorded by ADV and calculation of shear stress made the determination of critical conditions for erosion and deposition possible.

  15. Direct measurement of cell wall stress-stiffening and turgor pressure in live bacterial cells

    Deng, Yi; Shaevitz, Joshua W


    The mechanical properties of gram-negative bacteria are governed by a rigid peptidoglycan (PG) cell wall and the turgor pressure generated by the large concentration of solutes in the cytoplasm. The elasticity of the PG has been measured in bulk and in isolated sacculi and shown to be compliant compared to the overall stiffness of the cell itself. However, the stiffness of the cell wall in live cells has not been measured. In particular, the effects that pressure-induced stress might have on the stiffness of the mesh-like PG network have not been addressed even though polymeric materials often exhibit large amounts of stress-stiffening. We study bulging Escherichia coli cells using atomic force microscopy to separate the contributions of the cell wall and turgor pressure to the overall cell stiffness. We find strong evidence of power-law stress-stiffening in the E. coli cell wall, with an exponent of $1.07 \\pm 0.25$, such that the wall is significantly stiffer in live cells ($E\\sim32\\pm10$ MPa) than in unpres...

  16. Creation of a questionnaire to measure stress among nurses engaged in palliative care on general wards.

    Terakado, Ako; Watanabe, Takako


    This study was conducted to create a questionnaire that measures stress among nurses engaged in palliative care on general wards. Nurses with at least 3 years of experience involved in palliative care on a general ward in six facilities in Japan were the subjects from September 7 to October 4, 2004. A draft questionnaire on stress factors and conditions of stress in nurses engaged in end-of-life care was created, and question items and content meaning were revised to produce 32 question items, with a four-point Likert scale for the responses. Two pretests were conducted. Internal validity was investigated and resulted in 31 question items. Factor analysis using the principal factor method (Varimax rotation) was performed, and Cronbach's coefficient alpha was used to evaluate internal consistency and check reliability. The survey response rate was 94%, with a valid response rate of 98%. Analysis was conducted using responses from 269 participants, of whom 98.9% were female, with a mean age of 35.4 years. The mean length of experience as a nurse was 13.6 years, and the mean length of experience in cancer nursing was 8 years. Results of factor analysis produced eigenvalues of 5.260-1.558 and a cumulative proportion of 58.032%. After two items were deleted, six stress-related factors were identified; their alpha coefficients were 0.753 to 0.912, ensuring high reliability. The questionnaire developed had high internal validity and high reliability, and it can thus serve as a first stage in elucidating stress among nurses engaged in palliative care on general wards.

  17. Phenotypic flexibility as a measure of health: the optimal nutritional stress response test.

    Stroeve, Johanna H M; van Wietmarschen, Herman; Kremer, Bas H A; van Ommen, Ben; Wopereis, Suzan


    Nutrition research is struggling to demonstrate beneficial health effects, since nutritional effects are often subtle and long term. Health has been redefined as the ability of our body to cope with daily-life challenges. Physiology acts as a well-orchestrated machinery to adapt to the continuously changing environment. We term this adaptive capacity "phenotypic flexibility." The phenotypic flexibility concept implies that health can be measured by the ability to adapt to conditions of temporary stress, such as physical exercise, infections or mental stress, in a healthy manner. This may offer a more sensitive way to assess changes in health status of healthy subjects. Here, we performed a systematic review of 61 studies applying different nutritional stress tests to quantify health and nutritional health effects, with the objective to define an optimal nutritional stress test that has the potential to be adopted as the golden standard in nutrition research. To acknowledge the multi-target role of nutrition, a relevant subset of 50 processes that govern optimal health, with high relevance to diet, was used to define phenotypic flexibility. Subsequently, we assessed the response of biomarkers related to this subset of processes to the different challenge tests. Based on the obtained insights, we propose a nutritional stress test composed of a high-fat, high-caloric drink, containing 60 g palm olein, 75 g glucose and 20 g dairy protein in a total volume of 400 ml. The use of such a standardized nutritional challenge test in intervention studies is expected to demonstrate subtle improvements of phenotypic flexibility, thereby enabling substantiation of nutritional health effects.

  18. Laser deposition of YBaCuO thin films: stress measurements and microstructure investigations

    Gaboriaud, R. J.; Pailloux, F.


    Superconducting thin films of YBaCuO have been deposited by laser ablation at 750°C on MgO (001) single crystals. X-ray pole figures indicate a high crystalline quality of c-axis oriented films. A four-circle X-ray goniometer has been used for the measurements of the internal stress in the films by means of the fundamental metric tensor method generally used in the field of continuum mechanics. Microstructural investigation has been done by HRTEM on plan-view samples in order to study the film-substrate epitaxy relations from the observation of the moiré pattern brought about by the superimposition of both YBaCuO and MgO lattices (9% misfit). The results are discussed in terms of crystallographic accommodation and stress relaxation between the film and the substrate.

  19. Bias stress instability in organic transistors investigated by ac admittance measurements

    Di Girolamo, F. V.; Barra, M.; Capello, V.; Oronzio, M.; Romano, C.; Cassinese, A.


    In this paper, the bias stress effect (BSE) in organic field-effect transistors has been analyzed by an alternative experimental approach based on ac admittance (Y=G+jωC) measurements. conductance (C) and capacitance (G) curves have been recorded as a function of frequency at different times of the bias stress experiments and simultaneously fitted through a transmission line circuit, able to separately model the conducting properties of the channel and contact regions. The determination of the time behavior of the model fitting parameters is assumed as the starting point for a quantitative analysis of the BSE occurrence. This experimental procedure clarifies that both channel resistance (Rch) and contact resistance (Rc) are largely affected by the BSE, while the channel capacitance (Cch), related to the charge accumulation sheet, and the contact capacitance (Cc) result almost unchanged.

  20. Neutron scattering instruments for residual stress/strain measurements at KUR

    Ono, Masayoshi [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.


    A Kyoto University Reactor project research finished on March, 1997 is a first trial in Japan. In this research, some residual stress measurement in accompany with thermal and processing deformation history of various superconductive composite wires and so on were conducted to obtain a lot of research results. At TOF system, simultaneous measurement of the direction dependent collective texture using a multi point detector was useful, and at PSD system the strain measurement in a region under 10{sup -4} became possible to conduct. In addition, it is intending now to establish high performance instruments such as a two-stage type disc chopper at the TOF system and a high resolution vent type Si monocrystal monochromator at the PSD system. In particular, it is expected a the TOF system that a direction dependent collective texture and a stress distribution state in various kinds of functional materials can be measured simultaneously and without destruction. The mechanical property research of the metallic materials using low speed neutron scattering method is now a big interest in and out of Japan. This research contains a lot of contents coinciding to the industrial fields in an application research field of nuclear basic research and is expected in future to powerfully promote international cooperative research and to deeply recognize its usefulness and importance. (G.K.)

  1. Plant-Stress Measurements Using Laser-Induced Fluorescence Excitation: Poland Experiment

    Gene Capelle; Steve Jones


    Bechtel Nevada's Special Technologies Laboratory (STL) has been involved in remote sensing for many years, and in April 1995 STL began to study the use of active remote sensing for detecting plant stress. This work was motivated by the need to detect subsurface contamination, with the supposition that this could be accomplished by remote measurement of optical signatures from the overgrowing vegetation. The project has been a cooperative DOE/Disney effort, in which basic optical signature measurements (primarily fluorescence) were done at the Disney greenhouse facilities at Epcot Center in Florida, using instrumentation developed by STL on DOE funding. The primary instrument is a LIFI system, which had originally been developed for detection of surface uranium contamination at DOE sites. To deal specifically with the plant stress measurements, a LIFS system was built that utilizes the same laser, but captures the complete fluorescence spectrum from blue to red wavelengths. This system had continued to evolve, and the version in existence in September 1997 was sent to Poland, accompanied by two people from STL, for the purpose of making the measurements described in this report.

  2. Caregivers’ hair cortisol: a possible biomarker of chronic stress is associated with obesity measures among children with disabilities

    Chen, Xiaoli; Gelaye, Bizu; Velez, Juan Carlos; Barbosa,Clarita; Pepper, Micah; Andrade, Asterio; Gao, Wei; Kirschbaum, Clemens; Williams, Michelle A.


    Background: The stress of caring for a loved one with chronic illness has been associated with childhood obesity. Hair cortisol has been proposed as a novel biomarker of chronic psychological stress. This study aimed to evaluate the associations between caregivers’ chronic stress evaluated by hair cortisol concentrations (HCC) and obesity measures among children with disabilities such as autism. Methods: Eighty-five dyads of children with disabilities and their primary caregivers participated...

  3. Laue-DIC: a new method for improved stress field measurements at the micrometer scale

    Petit, J., E-mail: [LEME, Université Paris Ouest, 50 rue de Sèvres, F-92410 Ville d’Avray (France); Castelnau, O. [PIMM, CNRS, Arts and Métiers ParisTech, 151 Bd de l’Hopital, F-75013 Paris (France); Bornert, M. [Laboratoire Navier, Université Paris-Est, École des Ponts ParisTech, F-77455 Marne-la-Vallée (France); Zhang, F. G. [PIMM, CNRS, Arts and Métiers ParisTech, 151 Bd de l’Hopital, F-75013 Paris (France); Hofmann, F.; Korsunsky, A. M. [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom); Faurie, D. [LSPM, CNRS, Université Paris 13, 93430 Villetaneuse (France); Le Bourlot, C. [INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Micha, J. S. [Université Grenoble Alpes, INAC-SPrAM, F-38000 Grenoble (France); CNRS, SPrAM, F-38000 Grenoble (France); CRG-IF BM32 at ESRF, 71 Avenue des Martyrs, F-38000 Grenoble (France); Robach, O.; Ulrich, O. [Université Grenoble Alpes, INAC-SPrAM, F-38000 Grenoble (France); CRG-IF BM32 at ESRF, 71 Avenue des Martyrs, F-38000 Grenoble (France); CEA, INAC-SP2M, F-38000 Grenoble (France)


    The increment of elastic strain distribution, with a micrometer spatial resolution, is obtained by the correlation of successive Laue images. Application to a bent Si crystal allows evaluation of the accuracy of this new Laue-DIC method, which is about 10{sup −5}. A better understanding of the effective mechanical behavior of polycrystalline materials requires an accurate knowledge of the behavior at a scale smaller than the grain size. The X-ray Laue microdiffraction technique available at beamline BM32 at the European Synchrotron Radiation Facility is ideally suited for probing elastic strains (and associated stresses) in deformed polycrystalline materials with a spatial resolution smaller than a micrometer. However, the standard technique used to evaluate local stresses from the distortion of Laue patterns lacks accuracy for many micromechanical applications, mostly due to (i) the fitting of Laue spots by analytical functions, and (ii) the necessary comparison of the measured pattern with the theoretical one from an unstrained reference specimen. In the present paper, a new method for the analysis of Laue images is presented. A Digital Image Correlation (DIC) technique, which is essentially insensitive to the shape of Laue spots, is applied to measure the relative distortion of Laue patterns acquired at two different positions on the specimen. The new method is tested on an in situ deformed Si single-crystal, for which the prescribed stress distribution has been calculated by finite-element analysis. It is shown that the new Laue-DIC method allows determination of local stresses with a strain resolution of the order of 10{sup −5}.

  4. Stress release model and proxy measures of earthquake size. Application to Italian seismogenic sources

    Varini, Elisa; Rotondi, Renata; Basili, Roberto; Barba, Salvatore


    This study presents a series of self-correcting models that are obtained by integrating information about seismicity and fault sources in Italy. Four versions of the stress release model are analyzed, in which the evolution of the system over time is represented by the level of strain, moment, seismic energy, or energy scaled by the moment. We carry out the analysis on a regional basis by subdividing the study area into eight tectonically coherent regions. In each region, we reconstruct the seismic history and statistically evaluate the completeness of the resulting seismic catalog. Following the Bayesian paradigm, we apply Markov chain Monte Carlo methods to obtain parameter estimates and a measure of their uncertainty expressed by the simulated posterior distribution. The comparison of the four models through the Bayes factor and an information criterion provides evidence (to different degrees depending on the region) in favor of the stress release model based on the energy and the scaled energy. Therefore, among the quantities considered, this turns out to be the measure of the size of an earthquake to use in stress release models. At any instant, the time to the next event turns out to follow a Gompertz distribution, with a shape parameter that depends on time through the value of the conditional intensity at that instant. In light of this result, the issue of forecasting is tackled through both retrospective and prospective approaches. Retrospectively, the forecasting procedure is carried out on the occurrence times of the events recorded in each region, to determine whether the stress release model reproduces the observations used in the estimation procedure. Prospectively, the estimates of the time to the next event are compared with the dates of the earthquakes that occurred after the end of the learning catalog, in the 2003-2012 decade.

  5. Glass-modified stress waves for adhesion measurement of ultra thin films for device applications

    Gupta, Vijay; Kireev, Vassili; Tian, Jun; Yoshida, Hiroshi; Akahoshi, Haruo


    Laser-generated stress wave profiles with rarefaction shocks (almost zero post-peak decay times) have been uncovered in different types of glasses and presented in this communication. The rise time of the pulses was found to increase with their amplitude, with values reaching as high as 50 ns. This is in contrast to measurements in other brittle crystalline solids where pulses with rise times of 1 -2 ns and post-peak decay times of 16 -20 ns were recorded. The formation of rarefaction shock is attributed to the increased compressibility of glasses with increasing pressures. This was demonstrated using a one-dimensional nonlinear elastic wave propagation model in which the wave speed was taken as a function of particle velocity. The technological importance of these pulses in measuring the tensile strength of very thin film interfaces is demonstrated by using a previously developed laser spallation experiment in which a laser-generated compressive stress pulse in the substrate reflects into a tensile wave from the free surface of the film and pries off its interface at a threshold amplitude. Because of the rarefaction shock, glass-modified waves allow generation of substantially higher interfacial tensile stress amplitudes compared with those with finite post-peak decay profiles. Thus, for the first time, tensile strengths of very strong and ultra thin film interfaces can be measured. Results presented here indicate that interfaces of 185-nm-thick films, and with strengths as high as 2.7 GPa, can be measured. Thus, an important advance has been made that should allow material optimization of ultra thin layer systems that may form the basis of future MEMS-based microelectronic, mechanical and clinical devices.

  6. Propagation of Nonlinear Waves in Waveguides and Application to Nondestructive Stress Measurement

    Nucera, Claudio

    Propagation of nonlinear waves in waveguides is a field that has received an ever increasing interest in the last few decades. Nonlinear guided waves are excellent candidates for interrogating long waveguide like structures because they combine high sensitivity to structural conditions, typical of nonlinear parameters, with large inspection ranges, characteristic of wave propagation in bounded media. The primary topic of this dissertation is the analysis of ultrasonic waves, including ultrasonic guided waves, propagating in their nonlinear regime and their application to structural health monitoring problems, particularly the measurement of thermal stress in Continuous Welded Rail (CWR). Following an overview of basic physical principles generating nonlinearities in ultrasonic wave propagation, the case of higher-harmonic generation in multi-mode and dispersive guided waves is examined in more detail. A numerical framework is developed in order to predict favorable higher-order generation conditions (i.e. specific guided modes and frequencies) for waveguides of arbitrary cross-sections. This model is applied to various benchmark cases of complex structures. The nonlinear wave propagation model is then applied to the case of a constrained railroad track (CWR) subjected to thermal variations. This study is a direct response to the key need within the railroad transportation community to develop a technique able to measure thermal stresses in CWR, or determine the rail temperature corresponding to a null thermal stress (Neutral Temperature -- NT). The numerical simulation phase concludes with a numerical study performed using ABAQUS commercial finite element package. These analyses were crucial in predicting the evolution of the nonlinear parameter beta with thermal stress level acting in the rail. A novel physical model, based on interatomic potential, was developed to explain the origin of nonlinear wave propagation under constrained thermal expansion. In fact

  7. Measurement of residual stress for ITO/PET substrates by the double beam shadow moiré interferometer.

    Chen, Hsi-Chao; Huang, Kuo-Ting; Lo, Yen-Ming


    This study constructed a measurement system that can quickly and accurately analyze the residual stress of flexible electronics. A double beam shadow moiré interferometer was set up to measure and evaluate the residual stress of tin-doped indium oxide films on a polyethylene terephthalate substrate. However, this system required only two symmetrical fringes to evaluate the residual stress of transparent conductive oxide films on flexible substrate. Applying the grating translation techniques to the double beam shadow moiré interferometer greatly improved the measurement resolution and accuracy, and the relative error was reduced to 1.2%.

  8. Measurement of the stressed state of welded joints in the NPP process components and circulation pipelines based on acoustoelasticity theory

    A.I. Trofimov


    Full Text Available The paper presents the results of a theoretical justification and an experimental research for a method to measure the stressed state of welded joints in the nuclear power plant (NPP process components and circulation pipelines based on acoustoelasticity theory, as well as for ways to implement them technically. Devices for measuring the stressed state of welded joints in the NPP process components and circulation pipelines based on acoustoelasticity theory allow online measurement of residual stresses along the weld height and detection of crack formation points. The use of such devices will enable early crack detection in welded joints for an increased safety of the NPP operation.

  9. Residual stress measurement in carbon coatings of optical fibers from the fiber bending curvature and coating thickness difference

    Shiue, Sham-Tsong; Lin, Hung-Chien; Shen, Ting-Ying; Ouyang, Hao


    The residual stress measurement in carbon coatings of optical fibers is theoretically and experimentally investigated. A simple formula used to measure the residual stresses in the thin film deposited on a cylindrical substrate with the bending curvature is proposed. During a temperature drop, the carbon-coated optical fiber is bent due to the nonuniform deposition of coating materials. The axial residual stresses in carbon coatings of optical fibers can be measured from the fiber bending curvature and coating thickness difference. Furthermore, if Young's modulus of carbon coatings is known, the thermal expansion coefficient of carbon coatings can be determined.

  10. Hall coefficient measurement for residual stress assessment in precipitation hardened IN718 nickel-base superalloy

    Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled


    We investigated the feasibility of residual stress assessment based on Hall coefficient measurements in precipitation hardened IN718 nickel-base superalloy. As a first step, we studied the influence of microstructural variations on the galvanomagnetic properties of IN718 nickel-base superalloy. We found that the Hall coefficient of IN718 increases from ≈ 8.0×10-11 m3/C in its fully annealed state of 15 HRC Rockwell hardness to ≈ 9.4×10-11 m3/C in its fully hardened state of 45 HRC. We also studied the influence of cold work, i.e., plastic deformation, at room temperature and found that cold work had negligible effect on the Hall coefficient of fully annealed IN718, but significantly reduced it in hardened states of the material. For example, measurements conducted on fully hardened IN718 specimens showed that the Hall coefficient decreased more or less linearly with cold work from its peak value of ≈ 9.4×10-11 m3/C in its intact state to ≈ 9.0×10-11 m3/C in its most deformed state of 22% plastic strain. We also studied the influence of applied stress and found that elastic strain significantly increases the Hall coefficient of IN718 regardless of the state of hardening. The relative sensitivity of the Hall coefficient to elastic strain was measured as a unitless gauge factor K that is defined as the ratio of the relative change of the Hall coefficient ΔRH/RH divided by the axial strain ɛ = σ/E, where σ is the applied uniaxial stress and E is the Young's modulus of the material. We determined that the galvanomagnetic gauge factor of IN718 is κ ≈ 2.6 - 2.9 depending on the hardness level. Besides the fairly high value of the gauge factor, it is important that it is positive, which means that compressive stress in surface-treated components decreases the Hall coefficient in a similar way as plastic deformation does, therefore the unfortunate cancellation that occurs in fully hardened IN718 in the case of electric conductivity measurements will not

  11. How integrated are behavioral and endocrine stress response traits? A repeated measures approach to testing the stress-coping style model.

    Boulton, Kay; Couto, Elsa; Grimmer, Andrew J; Earley, Ryan L; Canario, Adelino V M; Wilson, Alastair J; Walling, Craig A


    It is widely expected that physiological and behavioral stress responses will be integrated within divergent stress-coping styles (SCS) and that these may represent opposite ends of a continuously varying reactive-proactive axis. If such a model is valid, then stress response traits should be repeatable and physiological and behavioral responses should also change in an integrated manner along a major axis of among-individual variation. While there is some evidence of association between endocrine and behavioral stress response traits, few studies incorporate repeated observations of both. To test this model, we use a multivariate, repeated measures approach in a captive-bred population of Xiphophorus birchmanni. We quantify among-individual variation in behavioral stress response to an open field trial (OFT) with simulated predator attack (SPA) and measure waterborne steroid hormone levels (cortisol, 11-ketotestosterone) before and after exposure. Under the mild stress stimulus (OFT), (multivariate) behavioral variation among individuals was consistent with a strong axis of personality (shy-bold) or coping style (reactive-proactive) variation. However, behavioral responses to a moderate stressor (SPA) were less repeatable, and robust statistical support for repeatable endocrine state over the full sampling period was limited to 11-ketotestosterone. Although post hoc analysis suggested cortisol expression was repeatable over short time periods, qualitative relationships between behavior and glucocorticoid levels were counter to our a priori expectations. Thus, while our results clearly show among-individual differences in behavioral and endocrine traits associated with stress response, the correlation structure between these is not consistent with a simple proactive-reactive axis of integrated stress-coping style. Additionally, the low repeatability of cortisol suggests caution is warranted if single observations (or indeed repeat measures over short sampling

  12. Measurement of stress-induced birefringence in glasses based on reflective laser feedback effect

    Haisha, Niu; YanXiong, Niu; Jiyang, Li


    A glass birefringence measurement system utilizing the reflective laser feedback (RLF) effect is presented. The measurement principle is analyzed based on the equivalent cavity of a Fabry-Perot interferometer, and the experiments are conducted with a piece of quartz glass with applied extrusion force. In the feedback system, aluminum film used as a feedback mirror is affixed to the back of the sample. When the light is reflected back into the cavity, as the reinjected light is imprinted with the birefringence information in the sample, the gain and polarization states of the laser are modulated. The variation of optical power and polarization states hopping is monitored to obtain the magnitude of the stress. The system has advantages such as simplicity and low-cost with a precision of 1.9 nm. Moreover, by adjusting the position of the aluminum, large-area samples can be measured anywhere at any place.

  13. Development of Simple Dip-Stick-Type Uniaxial Stress Actuator for Alternating-Current Susceptibility Measurements

    MYDEEN Kamal; YU Yong; JIN Chang-Qing


    A simple dip-stick type uniaxial stress actuator for ac-susceptibility measurement is designed. Target pressure can be achieved by smooth and continues work carried out using a combination of light weight micrometer and spring.The magnitude of the pressure is directly calculated from the force constant of the spring and the surface area of the sample. Benchmark on the quality of the data under uniaxial pressure is confirmed by the Piezo resistance measurements on [100] oriented n-type Si. The system is examined and calibrated with the standard paramagnetic Gd2O3. Further, the device performance, generation of constant uniaxial pressure against temperature variations,is assured by investigating the ac-magnetic susceptibility measurements on highly anisotropic La1.25 Sr1.75Mn2 O7bilayer single crystal.

  14. The effect of consignment to broodmare Sales on physiological stress measured by faecal glucocorticoid metabolites in pregnant Thoroughbred mares.

    Schulman, Martin; Becker, Annet; Ganswindt, Stefanie; Guthrie, Alan; Stout, Tom; Ganswindt, Andre


    BACKGROUND: Validation of a method for the minimally-invasive measurement of physiological stress will help understanding of risk factors that may contribute to stress-associated events including recrudescence of Equid herpesvirus (EHV), which is anecdotally associated with sales consignment of preg

  15. Patient Characteristics Impacting Health State Index Scores, Measured by the EQ-5D of Females with Stress Urinary Incontinence Symptoms

    Tincello, Douglas; Sculpher, Mark; Tunn, Ralf; Quail, Deborah; van der Vaart, Huub; Falconer, Christian; Manning, Martina; Timlin, Louise


    Objective: To describe the characteristics of women seeking treatment for symptoms of stress urinary incontinence (SUI) and to investigate the association of SUI symptoms with generic health-related quality of life (HRQoL) as measured by the EuroQol (EQ-5D) instrument. Methods: The Stress Urinary In

  16. Patient Characteristics Impacting Health State Index Scores, Measured by the EQ-5D of Females with Stress Urinary Incontinence Symptoms

    Tincello, Douglas; Sculpher, Mark; Tunn, Ralf; Quail, Deborah; van der Vaart, Huub; Falconer, Christian; Manning, Martina; Timlin, Louise


    Objective: To describe the characteristics of women seeking treatment for symptoms of stress urinary incontinence (SUI) and to investigate the association of SUI symptoms with generic health-related quality of life (HRQoL) as measured by the EuroQol (EQ-5D) instrument. Methods: The Stress Urinary In

  17. Caffeine intake inverts the effect of adenosine on myocardial perfusion during stress as measured by T1 mapping

    Kuijpers, Dirkjan; Prakken, Niek H.; Vliegenthart, Rozemarijn; van Dijkman, Paul R. M.; van der Harst, Pim; Oudkerk, Matthijs


    Caffeine intake before adenosine stress myocardial perfusion imaging may cause false negative findings. We hypothesized that the antagonistic effect of caffeine can be measured by T1 relaxation times in rest and adenosine stress cardiac magnetic resonance imaging (CMR), as T1 mapping techniques are

  18. The effect of consignment to broodmare Sales on physiological stress measured by faecal glucocorticoid metabolites in pregnant Thoroughbred mares.

    Schulman, Martin; Becker, Annet; Ganswindt, Stefanie; Guthrie, Alan; Stout, Tom|info:eu-repo/dai/nl/304828831; Ganswindt, Andre


    BACKGROUND: Validation of a method for the minimally-invasive measurement of physiological stress will help understanding of risk factors that may contribute to stress-associated events including recrudescence of Equid herpesvirus (EHV), which is anecdotally associated with sales consignment of

  19. Wearable Biomedical Measurement Systems for Assessment of Mental Stress of Combatants in Real Time

    Fernando Seoane


    Full Text Available The Spanish Ministry of Defense, through its Future Combatant program, has sought to develop technology aids with the aim of extending combatants’ operational capabilities. Within this framework the ATREC project funded by the “Coincidente” program aims at analyzing diverse biometrics to assess by real time monitoring the stress levels of combatants. This project combines multidisciplinary disciplines and fields, including wearable instrumentation, textile technology, signal processing, pattern recognition and psychological analysis of the obtained information. In this work the ATREC project is described, including the different execution phases, the wearable biomedical measurement systems, the experimental setup, the biomedical signal analysis and speech processing performed. The preliminary results obtained from the data analysis collected during the first phase of the project are presented, indicating the good classification performance exhibited when using features obtained from electrocardiographic recordings and electrical bioimpedance measurements from the thorax. These results suggest that cardiac and respiration activity offer better biomarkers for assessment of stress than speech, galvanic skin response or skin temperature when recorded with wearable biomedical measurement systems.

  20. Core based stress measurements: A guide to their application. Topical report, July 1991--June 1993

    Warpinski, N.R.; Teufel, L.W.; Lorenz, J.C.; Holcomb, D.J. [Sandia National Labs., Albuquerque, NM (United States)


    This report is a summary and a guide to core-based stress measurements. It covers anelastic strain recovery, circumferential velocity anistropy, differential strain curve analysis, differential wave velocity analysis, petrographic examination of microcracks, overcoring of archieved core, measurements of the Kaiser effect, strength anisotropy tests, and analysis of coring-induced fractures. The report begins with a discussion of the stored energy within rocks, its release during coring, and the subsequent formation of relaxation microcracks. The interogation or monitoring of these microcracks form the basis for most of the core-based techniques (except for the coring induced fractures). Problems that can arise due to coring or fabric are also presented, Coring induced fractures are discussed in some detail, with the emphasis placed on petal (and petal-centerline) fractures and scribe-knife fractures. For each technique, a short description of the physics and the analysis procedures is given. In addition, several example applications have also been selected (where available) to illustrate pertinent effects. This report is intended to be a guide to the proper application and diagnosis of core-based stress measurement procedures.

  1. Measuring water-borne cortisol in Poecilia latipinna:is the process stressful, can stress be minimized and is cortisol correlated with sex steroid release rates?

    Gabor, C R; Contreras, A


    The stress of water-borne hormone collection process was examined in sailfin mollies Poecilia latipinna. Baseline release rates of the stress hormone cortisol were measured and minimum confinement time for water sampling was evaluated for a standard 60 min v. a 30 min protocol. A 30 min hormone collection period reflects release rates over 60 min. Potential stress response to confinement in the beaker for the water-borne collection process was tested over 4 days. There was no evidence of stress due to the collection methods, as cortisol release rates did not differ significantly across four sequential days of handling for P. latipinna. Males and females did not differ significantly in baseline cortisol release rates. Baseline cortisol release rates from fish immediately after being collected in the field were also not significantly different than those in the 4 day confinement experiment. After exposure to a novel environment, however, P. latipinna mounted a stress response. Stress may also affect sex steroids and behaviour but cortisol release rates were not significantly correlated with sex steroids [11-ketotestosterone (KT), testosterone, or oestradiol], or mating attempts. The correlation between water-borne release rates and plasma steroid levels was validated for both cortisol and KT. Finally, normalizing cortisol release rates using standard length in lieu of mass is viable and accurate. Water-borne hormone assays are a valuable tool for investigating questions concerning the role of hormones in mediating stress responses and reproductive behaviours in P. latipinna and other livebearing fishes.

  2. Attention-Affect Check List: A self-report measure of acute mental stress.

    Sawada, YUKIHIRO; Tanaka, GOHICHI


    Given a hint from Lang, Bradley, and Cutbert's (1997) defense cascade, two cognitive processes, instead of passive versus active behavioral coping, which seem to have differential effects on the provocation of vascular- versus cardiac-dominant reaction pattern during mental stress were advocated: attention (Attent) versus unpleasant affect (UnplAff). Based on this notion the Attention-Affect Check List (AACL) was developed as a self-report measure. In addition, items on uncontrollability (Uncontr) were prepared for the purpose of checking whether heightened Attent and UnplAff are accompanied by alterations in Uncontr. Two hundred and eighty-four students underwent two kinds of mental stress, which seemed to specifically heighten Attent and UnplAff. Four factors with four items each were extracted from the AACL item pool: concentrated and allocated Attent, UnplAff, and pleasant affect. Also, one factor with four items was extracted from the Uncontr item pool. For both the mental stresses, each scale, although very brief, had quite reasonable alpha reliability. Accountability of each scale for the total variance was reasonably high. Some problems are discussed in relation to the validity of AACL.

  3. A new dynamical diffraction-based technique of residual stress measurements in thin films

    Agamalian, M; Kaiser, H; Rehm, C; Werner, S A


    The recently discovered dynamical diffraction effect 'neutron camel' was used for residual stress measurements in a thick Si (111) crystal coated with a 2000 A-thick Ni film. The observed asymmetry of the back-face rocking curve corresponds to the bending radius of propor to 19 km and the tension force applied to the Ni film is propor to 90 N/m. Relative deformation of the Si crystallographic cells in the vicinity of diffractive surfaces is vertical stroke partial deriv u sub z /partial deriv z vertical stroke approx 1.6 x 10 sup - sup 6. (orig.)

  4. Reynolds and Maxwell stress measurements in the reversed field pinch experiment Extrap-T2R

    Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Cavazzana, R.; Bergsåker, H.; Cecconello, M.; Drake, J. R.


    The complete Reynolds stress (RS) has been measured in the edge region of the Extrap-T2R reversed field pinch experiment. The RS exhibits a strong gradient in the region where a high E × B shear takes place. Experimental results show this gradient to be almost entirely due to the electrostatic contribution. This has been interpreted as experimental evidence of flow generation via turbulence mechanism. The scales involved in flow generation are deduced from the frequency decomposition of RS tensor. They are found related to magnetohydrodynamic activity but are different with respect to the scales responsible for turbulent transport.

  5. Inversion of calcite twin data for stress (2) : EBSD as a tool for data measurements

    Parlangeau, Camille; Lacombe, Olivier; Brisset, Francois; Kohler, Eric; Daniel, Jean-Marc; Schueller, Sylvie


    Inversion of calcite twin data are known to be a powerful tool to reconstruct the past state(s) of stress in carbonate rocks of the crust, especially in fold-and-thrust belts and sedimentary basins. Twin data measurements have been for long carried out optically using a Universal-Stage. This data collection is time-consuming and suffers from limitations and bias related to measurements of twin planes oblique at low angle or parallel to the thin section, or the unambiguous evaluation of the twinned/untwinned character of collected twin data. EBSD (electron backscatter diffraction) is a well-known technique applied to characterize textures and microstructures of metals or deformed fine-grained rocks. The challenge is to define a strategy for measuring calcite-twin orientations that should be fast, without any loss of information, and which must reconcile (1) the need for a large amount of calcite twin data (3 mutually perpendicular thin sections and at least 30 crystals per thin section), (2) the spacing between EBSD spots, that should take into account (3) the small width of twin lamellae within grains deformed at low pressure and temperature and (4) the large size (usually several hundreds of microns) of twinned calcite grains used for stress analysis. To date, these multiple requirements preclude any (classical) automatic twin data acquisition but instead imply a preliminary definition of the areas of the thin section to be scanned by the EBSD spots, including grain boundaries, because the stress inversion technique requires to know for each grain the orientations of the C axis and of the 3 potential e twin planes. In order to reconcile a perfectly polished surface as required by EBSD and the recognition of grain boundaries, we adopted the double etching technique (Herwegh, 2000) to first reveal grain and twin boundaries. Then, with a SEM and a very fine coating sample, the section is scanned using secondary electrons bin; each spot of interest is visually defined

  6. Measuring permeability, Young's modulus, and stress relaxation by the beam-bending technique

    Vichit-Vadakan, Wilasa

    Recent interest in the permeability of cement paste, mortars, and concrete lies in the need to gain further understanding of mechanisms affecting the durability of these materials. Conventional techniques for measuring permeability are cumbersome and often take days to complete just one measurement. This thesis proposes a new technique for measuring the permeability. The advantage of this technique is that the results are obtained in a few minutes to a few hours; moreover, there is no problem with leaks or need for high pressures. The method is particularly well suited for examining the changes in permeability and viscoelastic properties of young cement paste samples. When a saturated rod of a porous material is instantaneously deflected under three-point bending, two types of relaxation processes occur simultaneously: hydrodynamic relaxation, caused by the flow of liquid in the porous body to restore ambient pressure, and viscoelastic relaxation of the solid network. By measuring the decrease in the force required to sustain a constant deflection, it is possible to obtain the permeability and Young's modulus from the hydrodynamic relaxation function, in addition to the stress relaxation function of the sample. The exact viscoelastic solution is developed and the total relaxation is shown to be very closely approximated as the product of the hydrodynamic and stress relaxation functions. The analytical results are verified on porous VycorRTM glass saturated in various solvents, including normal alcohols, water, and glycerol. The results show excellent agreement with the theory. Consistent with observations of previous workers, the permeability is found to be influenced by the size of the solvent molecule; by assuming that the pore surfaces are covered with a monolayer of immobile solvent, the observed variation can be explained. The evolution of the permeability, Young's modulus, and stress relaxation function are reported for Type III Portland cement paste with

  7. Measurement of Perceived Stress Among Pregnant Women: A Comparison of Two Different Instruments.

    Solivan, Amber E; Xiong, Xu; Harville, Emily W; Buekens, Pierre


    Assess the amount of agreement between the classification of stress from the Perceived Stress Scale (PSS) and the Assessment of Stress portion of the Prenatal Psychosocial Profile (PPP) among pregnant women. A secondary data analysis on a cross-sectional study of 301 pregnant women from the New Orleans and Baton Rouge areas who were exposed to Hurricane Katrina was conducted. Women with complete data (219) were analyzed. Women scoring in the third tertile of each instrument were compared. The kappa statistic was used to assess agreement between instruments. Additional comparisons were made with three instruments that measure other important psychosocial constructs that could be related to stress: the Edinburgh Depression Scale (EDS) and the Assessments of Support (partner and other support) and Self-Esteem from the PPP. No significant difference was found between the two tests. The PSS and the PPP were both statistically significantly correlated to each other (ρ = 0.71, p < 0.01). Thirty-five women were classified discordantly resulting in a Kappa Coefficient of 0.61 (95% CI 0.50-0.72, p < 0.01). No significant differences were found between these two instruments in correlation with the EDS (PPP, r = 0.76; PSS, r = 0.72; p < 0.01 for each), partner support (PPP, r = -0.47; PSS r = -0.46; p < 0.01 for each), other support (PPP, r = -0.31; PSS r = -0.32; p < 0.01 for each) and self-esteem (PPP, r = -0.41; PSS, r = -0.52; p < 0.01 for each), respectively. Given the similarities between the PSS and PPP, researchers are encouraged to choose and administer one instrument to participants, or to use the instruments in combination as an external reliability check.

  8. Evaluation of Various Pulse-Decay Laboratory Permeability Measurement Techniques for Highly Stressed Coals

    Feng, Ruimin; Harpalani, Satya; Pandey, Rohit


    The transient technique for laboratory permeability measurement, proposed by Brace et al. (J Geophys Res 73:2225-2236, 1968) and widely used for conventional gas reservoir rocks, is the preferred method when testing low-permeability rocks in the laboratory. However, Brace et al.'s solution leads to considerable errors since it does not take into account compressive storage and sorption effect when applied to sorptive rocks, such as, coals and shales. To verify the applicability of this solution when used to characterize fluid flow behavior of coal, an in-depth investigation of permeability evolution for flow of helium and methane depletion was conducted for San Juan coals using the pressure pulse-decay method under best replicated in situ conditions. Three permeability solutions, Brace et al.'s (1968), Dicker and Smits's (International meeting on petroleum engineering, Society of Petroleum Engineers, 1988) and Cui et al.'s (Geofluids 9:208-223, 2009), were utilized to establish the permeability trends. Both helium and methane permeability results exhibited very small difference between the Brace et al.'s solution and Dicker and Smits's solution, indicating that the effect of compressive storage is negligible. However, methane permeability enhancement at low pressures due to coal matrix shrinkage resulting from gas desorption can be significant and this was observed in pressure response plots and the estimated permeability values using Cui et al.'s solution only. Therefore, it is recommended that Cui et al.'s solution be employed to correctly include the sorption effect when testing coal permeability using the transient technique. A series of experiments were also carried out to establish the stress-dependent permeability trend under constant effective stress condition, and then quantify the sole contribution of the sorption effect on permeability variation. By comparison with the laboratory data obtained under in situ stress/strain condition, it was verified that

  9. GSTM1 and APE1 genotypes affect arsenic-induced oxidative stress: a repeated measures study

    Breton, Carrie V; Kile, Molly L; Catalano, Paul J; Hoffman, Elaine; Quamruzzaman, Quazi; Rahman, Mahmuder; Mahiuddin, Golam; Christiani, David C


    .... Generation of oxidative stress may contribute to arsenic carcinogenesis. To investigate the association between arsenic exposure and oxidative stress, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG...

  10. Direct measurements of wall shear stress by buried wire gages in a shock-wave boundary-layer interaction region

    Murthy, V. S.; Rose, W. C.


    Detailed measurements of wall shear stress (skin friction) were made with specially developed buried wire gages in the interaction regions of a Mach 2.9 turbulent boundary layer with externally generated shocks. Separation and reattachment points inferred by these measurements support the findings of earlier experiments which used a surface oil flow technique and pitot profile measurements. The measurements further indicate that the boundary layer tends to attain significantly higher skin-friction values downstream of the interaction region as compared to upstream. Comparisons between measured wall shear stress and published results of some theoretical calculation schemes show that the general, but not detailed, behavior is predicted well by such schemes.

  11. Residual stress measurement inside a dissimilar metal weld mock-up of the pressurizer safety and relief nozzle

    Campos, Wagner R.C.; Rabello, Emerson G.; Silva, Luiz L.; Mansur, Tanius R., E-mail:, E-mail:, E-mail:, E-mail: [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte (Brazil). Servico de Integridade Estrutural; Martins, Ketsia S., E-mail: [Universidade Federal de Minas Gerais (UFMG), Nelo Horizonte (Brazil). Departamento de Engenharia Metalurgica


    Residual stresses are present in materials or structural component in the absence of external loads or changes in temperatures. The most common causes of residual stresses being present are the manufacturing or assembling processes. All manufacturing processes, such as casting, welding, machining, molding, heat treatment, among others, introduces residual stresses into the manufactured object. The residual stresses effects could be beneficial or detrimental, depending on its distribution related to the component or structure, its load service and if it is compressive or tensile. In this work, the residual strains and stresses inside a mock-up that simulates the safety and relief nozzle of Angra 1 Nuclear Power Plant pressurizer were studied. The current paper presents a blind hole-drilling method residual stress measurements both at the inner surface of dissimilar metal welds of dissimilar metal weld nozzle mock-up. (author)

  12. Correlation of predicted and measured thermal stresses on an advanced aircraft structure with dissimilar materials. [hypersonic heating simulation

    Jenkins, J. M.


    Additional information was added to a growing data base from which estimates of finite element model complexities can be made with respect to thermal stress analysis. The manner in which temperatures were smeared to the finite element grid points was examined from the point of view of the impact on thermal stress calculations. The general comparison of calculated and measured thermal stresses is guite good and there is little doubt that the finite element approach provided by NASTRAN results in correct thermal stress calculations. Discrepancies did exist between measured and calculated values in the skin and the skin/frame junctures. The problems with predicting skin thermal stress were attributed to inadequate temperature inputs to the structural model rather than modeling insufficiencies. The discrepancies occurring at the skin/frame juncture were most likely due to insufficient modeling elements rather than temperature problems.

  13. Self-reported and measured stress related responses associated with exposure to wind turbine noise.

    Michaud, David S; Feder, Katya; Keith, Stephen E; Voicescu, Sonia A; Marro, Leonora; Than, John; Guay, Mireille; Denning, Allison; Bower, Tara; Villeneuve, Paul J; Russell, Evan; Koren, Gideon; van den Berg, Frits


    The current study was the first to assess stress reactions associated with wind turbine noise (WTN) exposure using self-reported and objective measures. Randomly selected participants, aged 18-79 yr (606 males; 632 females), living between 0.25 and 11.22 km from wind turbines, were exposed to outdoor calculated WTN levels up to 46 dBA (response rate 78.9%). Multiple regression modeling left the great majority (77%-89%) of the variance in perceived stress scale (PSS) scores, hair cortisol concentrations, resting blood pressure, and heart rate unaccounted for, and WTN exposure had no apparent influence on any of these endpoints. PSS scores were positively, but weakly, related to cortisol concentrations and resting heart rate (Pearson r = 0.13 and r = 0.08, respectively). Across WTN categories, modeled mean PSS scores ranged from 13.15 to 13.84 (p = 0.8614). Modeled geometric means for hair cortisol concentrations, resting mean systolic, diastolic blood pressure, and heart rate were 150.54-191.12 ng/g (p = 0.5416), 113.38-116.82 mmHg (p = 0.4990), 67.98-70.34 mmHg (p = 0.5006), and 68.24-70.71 bpm (p = 0.5223), respectively. Irrespective of WTN levels, diastolic blood pressure appeared to be slightly (2.90 mmHg 95% CI: 0.75,5.05) higher among participants highly annoyed by blinking lights on turbines (p = 0.0081). Collectively, the findings do not support an association between exposure to WTN up to 46 dBA and elevated self-reported and objectively defined measures of stress.

  14. Turbulence measurements in hypersonic boundary layers using constant-temperature anemometry and Reynolds stress measurements in hypersonic boundary layers

    Spina, Eric F.


    The primary objective in the two research investigations performed under NASA Langley sponsorship (Turbulence measurements in hypersonic boundary layers using constant temperature anemometry and Reynolds stress measurements in hypersonic boundary layers) has been to increase the understanding of the physics of hypersonic turbulent boundary layers. The study began with an extension of constant-temperature thermal anemometry techniques to a Mach 11 helium flow, including careful examinations of hot-wire construction techniques, system response, and system calibration. This was followed by the application of these techniques to the exploration of a Mach 11 helium turbulent boundary layer (To approximately 290 K). The data that was acquired over the course of more than two years consists of instantaneous streamwise mass flux measurements at a frequency response of about 500 kHz. The data are of exceptional quality in both the time and frequency domain and possess a high degree of repeatability. The data analysis that has been performed to date has added significantly to the body of knowledge on hypersonic turbulence, and the data reduction is continuing. An attempt was then made to extend these thermal anemometry techniques to higher enthalpy flows, starting with a Mach 6 air flow with a stagnation temperature just above that needed to prevent liquefaction (To approximately 475 F). Conventional hot-wire anemometry proved to be inadequate for the selected high-temperature, high dynamic pressure flow, with frequent wire breakage and poor system frequency response. The use of hot-film anemometry has since been investigated for these higher-enthalpy, severe environment flows. The difficulty with using hot-film probes for dynamic (turbulence) measurements is associated with construction limitations and conduction of heat into the film substrate. Work continues under a NASA GSRP grant on the development of a hot film probe that overcomes these shortcomings for hypersonic

  15. Drought stress and carbon uptake in an Amazon forest measured with spaceborne imaging spectroscopy.

    Asner, Gregory P; Nepstad, Daniel; Cardinot, Gina; Ray, David


    Amazônia contains vast stores of carbon in high-diversity ecosystems, yet this region undergoes major changes in precipitation affecting land use, carbon dynamics, and climate. The extent and structural complexity of Amazon forests impedes ground studies of ecosystem functions such as net primary production (NPP), water cycling, and carbon sequestration. Traditional modeling and remote-sensing approaches are not well suited to tropical forest studies, because (i) biophysical mechanisms determining drought effects on canopy water and carbon dynamics are poorly known, and (ii) remote-sensing metrics of canopy greenness may be insensitive to small changes in leaf area accompanying drought. New spaceborne imaging spectroscopy may detect drought stress in tropical forests, helping to monitor forest physiology and constrain carbon models. We combined a forest drought experiment in Amazônia with spaceborne imaging spectrometer measurements of this area. With field data on rainfall, soil water, and leaf and canopy responses, we tested whether spaceborne hyperspectral observations quantify differences in canopy water and NPP resulting from drought stress. We found that hyperspectral metrics of canopy water content and light-use efficiency are highly sensitive to drought. Using these observations, forest NPP was estimated with greater sensitivity to drought conditions than with traditional combinations of modeling, remote-sensing, and field measurements. Spaceborne imaging spectroscopy will increase the accuracy of ecological studies in humid tropical forests.

  16. Comparison of computational analysis with clinical measurement of stresses on below-knee residual limb in a prosthetic socket.

    Zhang, M; Roberts, C


    Interface pressures and shear stresses between a below-knee residual limb and prosthetic socket predicted using finite element analyses were compared with experimental measurements. A three-dimensional nonlinear finite element model, based on actual residual geometry and incorporating PTB socket rectification and interfacial friction/slip conditions, was developed to predict the stress distribution. A system for measuring pressures and bi-axial shear stresses was used to measure the stresses in the PTB socket of a trans-tibial amputee. The FE-predicted results indicated that the peak pressure of 226 kPa occurred at the patellar tendon area and the peak shear stress of 50 kPa at the anterolateral tibia area. Quantitatively, FE-predicted pressures were 11%, on average, lower than those measured by triaxial transducers placed at all the measurement sites. Because friction/slip conditions between the residual limb and socket liner were taken into consideration by using interface elements in the FE model, the directions and magnitudes of shear stresses match well between the FE prediction and clinical measurements. The results suggest that the nonlinear mechanical properties of soft tissues and dynamic effects during gait should be addressed in future work.

  17. Techniques for Interface Stress Measurements within Prosthetic Sockets of Transtibial Amputees: A Review of the Past 50 Years of Research.

    Al-Fakih, Ebrahim A; Abu Osman, Noor Azuan; Mahmad Adikan, Faisal Rafiq


    The distribution of interface stresses between the residual limb and prosthetic socket of a transtibial amputee has been considered as a direct indicator of the socket quality fit and comfort. Therefore, researchers have been very interested in quantifying these interface stresses in order to evaluate the extent of any potential damage caused by the socket to the residual limb tissues. During the past 50 years a variety of measurement techniques have been employed in an effort to identify sites of excessive stresses which may lead to skin breakdown, compare stress distributions in various socket designs, and evaluate interface cushioning and suspension systems, among others. The outcomes of such measurement techniques have contributed to improving the design and fitting of transtibial sockets. This article aims to review the operating principles, advantages, and disadvantages of conventional and emerging techniques used for interface stress measurements inside transtibial sockets. It also reviews and discusses the evolution of different socket concepts and interface stress investigations conducted in the past five decades, providing valuable insights into the latest trends in socket designs and the crucial considerations for effective stress measurement tools that lead to a functional prosthetic socket.

  18. Techniques for Interface Stress Measurements within Prosthetic Sockets of Transtibial Amputees: A Review of the Past 50 Years of Research

    Ebrahim A. Al-Fakih


    Full Text Available The distribution of interface stresses between the residual limb and prosthetic socket of a transtibial amputee has been considered as a direct indicator of the socket quality fit and comfort. Therefore, researchers have been very interested in quantifying these interface stresses in order to evaluate the extent of any potential damage caused by the socket to the residual limb tissues. During the past 50 years a variety of measurement techniques have been employed in an effort to identify sites of excessive stresses which may lead to skin breakdown, compare stress distributions in various socket designs, and evaluate interface cushioning and suspension systems, among others. The outcomes of such measurement techniques have contributed to improving the design and fitting of transtibial sockets. This article aims to review the operating principles, advantages, and disadvantages of conventional and emerging techniques used for interface stress measurements inside transtibial sockets. It also reviews and discusses the evolution of different socket concepts and interface stress investigations conducted in the past five decades, providing valuable insights into the latest trends in socket designs and the crucial considerations for effective stress measurement tools that lead to a functional prosthetic socket.

  19. High-resolution compact shear stress sensor for direct measurement of skin friction in fluid flow

    Xu, Muchen; Kim, Chang-Jin ``Cj''


    The high-resolution measurement of skin friction in complex flows has long been of great interest but also a challenge in fluid mechanics. Compared with indirect measurement methods (e.g., laser Doppler velocimetry), direct measurement methods (e.g., floating element) do not involve any analogy and assumption but tend to suffer from instrumentation challenges, such as low sensing resolution or misalignments. Recently, silicon micromachined floating plates showed good resolution and perfect alignment but were too small for general purposes and too fragile to attach other surface samples repeatedly. In this work, we report a skin friction sensor consisting of a monolithic floating plate and a high-resolution optical encoder to measure its displacement. The key for the high resolution is in the suspension beams, which are very narrow (e.g., 0.25 mm) to sense small frictions along the flow direction but thick (e.g., 5 mm) to be robust along all other directions. This compact, low profile, and complete sensor is easy to use and allows repeated attachment and detachment of surface samples. The sheer-stress sensor has been tested in water tunnel and towing tank at different flow conditions, showing high sensing resolution for skin friction measurement. Supported by National Science Foundation (NSF) (No. 1336966) and Defense Advanced Research Projects Agency (DARPA) (No. HR0011-15-2-0021).

  20. The measurement of thermal stress distributions along the flow path in injection-molded flat plates

    Hastenberg, C.H.V.; Wildervanck, P.C.; Leenen, A.J.H.; Schennink, G.G.J.


    Internal stresses in injection-molded parts are the result of thermal, flow, and pressure histories. Internal stresses can be roughly divided into thermal and flow-induced stresses. In this paper, a modified layer-removal method is presented to determine thermal stress distributions in injection-mol

  1. The Perceived Stress Reactivity Scale: Measurement Invariance, Stability, and Validity in Three Countries

    Schlotz, Wolff; Yim, Ilona S.; Zoccola, Peggy M.; Jansen, Lars; Schulz, Peter


    There is accumulating evidence that individual differences in stress reactivity contribute to the risk for stress-related disease. However, the assessment of stress reactivity remains challenging, and there is a relative lack of questionnaires reliably assessing this construct. We here present the Perceived Stress Reactivity Scale (PSRS), a…

  2. GSTM1 and APE1 genotypes affect arsenic-induced oxidative stress: a repeated measures study

    Quamruzzaman Quazi


    Full Text Available Abstract Background Chronic arsenic exposure is associated with an increased risk of skin, bladder and lung cancers. Generation of oxidative stress may contribute to arsenic carcinogenesis. Methods To investigate the association between arsenic exposure and oxidative stress, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG was evaluated in a cohort of 97 women recruited from an arsenic-endemic region of Bangladesh in 2003. Arsenic exposure was measured in urine, toenails, and drinking water. Drinking water and urine samples were collected on three consecutive days. Susceptibility to oxidative stress was evaluated by genotyping relevant polymorphisms in glutathione-s transferase mu (GSTM1, human 8-oxoguanine glycosylase (hOGG1 and apurinic/apyrimidinic endonuclease (APE1 genes using the Taqman method. Data were analyzed using random effects Tobit regression to account for repeated measures and 8-OHdG values below the detection limit. Results A consistent negative effect for APE1 was observed across water, toenail and urinary arsenic models. APE1 148 glu/glu + asp/glu genotype was associated with a decrease in logged 8-OHdG of 0.40 (95%CI -0.73, -0.07 compared to APE1 148 asp/asp. An association between total urinary arsenic and 8-OHdG was observed among women with the GSTM1 null genotype but not in women with GSTM1 positive. Among women with GSTM1 null, a comparison of the second, third, and fourth quartiles of total urinary arsenic to the first quartile resulted in a 0.84 increase (95% CI 0.27, 1.42, a 0.98 increase (95% CI 033, 1.66 and a 0.85 increase (95% CI 0.27, 1.44 in logged 8-OHdG, respectively. No effects between 8-OHdG and toenail arsenic or drinking water arsenic were observed. Conclusion These results suggest the APE1 variant genotype decreases repair of 8-OHdG and that arsenic exposure is associated with oxidative stress in women who lack a functional GSTM1 detoxification enzyme.

  3. Finite element analysis and measurement for residual stress of dissimilar metal weld in pressurizer safety nozzle mockup

    Lee, Kyoung Soo; Kim, W.; Lee, Jeong Geun; Park, Chi Yong; Yang, Jun Seok; Kim, Tae Ryong [Korea Electric Power Research Institute, Daejeon (Korea, Republic of); Park, Jai Hak [Chungbuk University, Cheongju (Korea, Republic of)


    Finite element (FE) analysis and experiment for weld residual stress (WRS) in the pressurizer safety nozzle mockup is described in various processes and results. Foremost of which is the dissimilar simulation metal welding (DMW) between carbon steel and austenitic stainless steel. Thermal and structural analyses were compared with actual residual stress, and actual measurements of. Magnitude and distribution of WRS in the nozzle mockup were assessed. Two measurement methods were used: hole-drilling method (HDM) with strain gauge for residual stress on the surface of the mockup, and block removal and splitting layer (BRSL) method for through-thickness. FE analysis and measurement data showed good agreement. In conclusion, the characteristics of weld residual stress of DMW could be well understood and the simplified FE analysis was verified as acceptable for estimating WRS

  4. New development of hydraulic fracturing technique for in-situ stress measurement at great depth of mines


    In-situ stress measurement using the hydraulic fracturing technique was made at Wanfu Coal Mine in Shandong Province,China.To solve problems caused by great measuring depth and extra thick overburden soil layers in the mine,a series of improved techniques were developed for the traditional hydraulic fracturing technique and equipment to increase their pressure-enduring ability and to ensure safe and flexible removal of the sealing packers with other experimental apparatus.Successful in-situ stress measurement at 37 points within 7 boreholes,which were mostly over 1000 m deep,was completed.Through the measurement,detailed in

  5. Application of indirect stress measurement techniques (non strain gauge based technology) to quantify stress environments in mines

    Stacey, TR


    Full Text Available Reliable values of in situ stress are essential for the valid modelling of mine layouts. Available non-strain gauge methods are reviewed as potential practical techniques for South African mines. From this review it is concluded that the most...

  6. Development of methodology for measurements of residual stresses in welded joint based on displacement of points in a coordinated table

    Aníbal Veras Siqueira Filho


    Full Text Available Residual stresses in a welded joint of ASTM A131 grade AH32 steel was measured either by the X-ray diffraction or by displacements of referenced points measured on a coordinate measuring machine before and after heat treatment. For all tests, the welding was performed with Shielded Metal Arc Welding, vertical-up position, by a certified welder. After welding, some specimens were subjected to marking, made through small holes evenly spaced and mapped on a coordinate measuring machine. After labeling, the samples were subjected to heat treatment at temperatures nearby recrystallization. After heat treatment, the samples were subjected to new measurements by coordinate measuring machine to evaluate the displacements of the points produced by the recrystallization. In parallel, residual stress measurements were made by XRD for validation of this new methodology. The results obtained either by X-ray or by coordinate measuring machine showed a good correlation between the two measurement methodologies employed.

  7. Sensing of damage and substrate stress in concrete using electro-mechanical impedance measurements of bonded PZT patches

    Narayanan, Arun; Subramaniam, Kolluru V. L.


    The influence of stress and induced damage in concrete on the electro-mechanical (EM) impedance response of bonded PZT patches is evaluated for applied compressive loading. Full field displacements obtained from digital image correlation are used to evaluate the level of stress-induced damage in concrete. Stress in the substrate produces an imposed strain on the PZT. A change in the imposed strain produces a rightward frequency shift and an increase in the amplitude of the resonant peak in the EM conductance spectrum of the PZT. An increase in the substrate compliance produces a decrease in the resonant frequency and an increase in the amplitude of the resonant peak. Changes in the resonant peak in the conductance spectrum induced by increasing substrate stress are of a significant magnitude when compared with the changes induced by damage. In the early stages of damage associated with distributed microcracking, the counteracting influences of increasing level of damage and increasing stress on the resonant peak result in no shift in frequency for measurements under applied load. There is however an increase in the amplitude of the resonance peak. When the applied stress is removed, there is a net decrease in frequency resulting from damage in the form of distributed microcracks. Measures of changes in the resonant peak based on root mean square deviation (RMSD), do not show any observable change when measurements are performed under applied loading. There is a consistent increase in RMSD values and frequency shift with increasing damage when the applied stress is removed. The centroidal measure of the normalized frequency spectrum reflects changes in substrate stress. At higher applied stress levels, there is a nonlinear increase in damage, leading to localization and cracking. The influence of damage is dominant in this region and significant changes are obtained in the RMSD values in both loaded and unloaded conditions.

  8. On-Chip Quantitative Measurement of Mechanical Stresses During Cell Migration with Emulsion Droplets

    Molino, D.; Quignard, S.; Gruget, C.; Pincet, F.; Chen, Y.; Piel, M.; Fattaccioli, J.


    The ability of immune cells to migrate within narrow and crowded spaces is a critical feature involved in various physiological processes from immune response to metastasis. Several in-vitro techniques have been developed so far to study the behaviour of migrating cells, the most recent being based on the fabrication of microchannels within which cells move. To address the question of the mechanical stress a cell is able to produce during the encounter of an obstacle while migrating, we developed a hybrid microchip made of parallel PDMS channels in which oil droplets are sparsely distributed and serve as deformable obstacles. We thus show that cells strongly deform droplets while passing them. Then, we show that the microdevice can be used to study the influence of drugs on migration at the population level. Finally, we describe a quantitative analysis method of the droplet deformation that allows measuring in real-time the mechanical stress exerted by a single cell. The method presented herein thus constitutes a powerful analytical tool for cell migration studies under confinement.

  9. On-Chip Quantitative Measurement of Mechanical Stresses During Cell Migration with Emulsion Droplets

    Molino, D.; Quignard, S.; Gruget, C.; Pincet, F.; Chen, Y.; Piel, M.; Fattaccioli, J.


    The ability of immune cells to migrate within narrow and crowded spaces is a critical feature involved in various physiological processes from immune response to metastasis. Several in-vitro techniques have been developed so far to study the behaviour of migrating cells, the most recent being based on the fabrication of microchannels within which cells move. To address the question of the mechanical stress a cell is able to produce during the encounter of an obstacle while migrating, we developed a hybrid microchip made of parallel PDMS channels in which oil droplets are sparsely distributed and serve as deformable obstacles. We thus show that cells strongly deform droplets while passing them. Then, we show that the microdevice can be used to study the influence of drugs on migration at the population level. Finally, we describe a quantitative analysis method of the droplet deformation that allows measuring in real-time the mechanical stress exerted by a single cell. The method presented herein thus constitutes a powerful analytical tool for cell migration studies under confinement. PMID:27373558

  10. Flexural Capability of Patterned Transparent Conductive Substrate by Performing Electrical Measurements and Stress Simulations

    Chang-Chun Lee


    Full Text Available The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation conditions is a major concern regarding the mechanical reliability of indium–tin–oxide (ITO films deposited on polyethylene terephthalate (PET substrates; mechanical reliability is commonly used to estimate the flexibility of displays. However, the pattern effect is rarely investigated to estimate the mechanical reliability of ITO/PET films. Thus, this study examined the flexible content of patterned ITO/PET films with two different line widths by conducting bending tests and sheet resistance measurements. Moreover, a stress–strain simulation enabled by finite element analysis was performed on the patterned ITO/PET to explore the stress impact of stacked film structures under various levels of flexural load. Results show that the design of the ITO/PET film can be applied in developing mechanically reliable flexible electronics.

  11. Measurement and study of the distributing law of in-situ stresses in rock mass at great depth


    To solve the technical cruxes of the conventional system in deep rock mass, an automatic testing system for hydraulic fracturing that includes a single tube for hydraulic loop, a pressure-relief valve, central-tubeless packers, and a multichannel real-time data acquisition system was used for in-situ stresses measurement at great depths (over 1000 m) in a coalfield in Juye of Northern China.The values and orientations of horizontal principal stresses were determined by the new system. The virgin stress field and its distributing law were decided by the linear regression from the logged 37 points in seven boreholes. Besides, the typical boreholes arranged in both the adjacent zone and far away zone of the faults were analyzed, respectively. The results show that a stress concentration phenomenon and a deflection in the orientation of the maximal horizontal stress exist in the adjacent zone of the faults, which further provides theoretical basis for design and optimization of mining.

  12. Evaluation of stress-related anterior lower leg pain with magnetic resonance imaging and intracompartmental pressure measurement.

    Kiuru, Martti J; Mantysaari, Matti J; Pihlajamaki, Harri K; Ahovuo, Juhani A


    The purpose of this work was to evaluate stress-related anterior lower leg pain with clinical examination, magnetic resonance imaging, and measurement of anterior tibial compartment pressure findings. All medical data were gathered from 24 conscripts with stress-related anterior lower leg pain. Twenty exhibited bilateral symptoms. In 22 of the 44 cases, the intracompartmental pressure was pathological. Symptoms were exhibited for longer periods by patients with chronic exertional compartment syndrome (CECS) than by other patients (p periostitis. On magnetic resonance imaging, there was no difference in bone findings between patients with and without CECS (p > 0.05). Stress-related anterior lower leg pain can be related to CECS, bone stress injury, and traction periostitis. Clinical diagnosis is unreliable. CECS and bone stress injury or traction periostitis can occur separately or together.

  13. Minimization and Mitigation of Wire EDM Cutting Errors in the Application of the Contour Method of Residual Stress Measurement

    Ahmad, Bilal; Fitzpatrick, Michael E.


    The contour method of residual stress measurement relies on the careful application of wire electro-discharge machining (WEDM) for the cutting stage. Changes in material removal rates during the cut lead to errors in the final calculated values of residual stress. In this study, WEDM cutting parameters have been explored to identify the optimum conditions for contour method residual stress measurements. The influence of machine parameters on the surface roughness and cutting artifacts in the contour cut is discussed. It has been identified that the critical parameter in improving the surface finish is the spark pulse duration. A typical cutting artifact and its impact on measured stress values have been identified and demonstrated for a contour cut in a welded marine steel. A procedure is presented to correct contour displacement data from the influence of WEDM cutting artifacts, and is demonstrated on the correction of a measured weld residual stress. The corrected contour method improved the residual stress magnitude up to 150 MPa. The corrected contour method results were validated by X-ray diffraction, incremental center hole drilling, and neutron diffraction.

  14. Performance Improvement of Membrane Stress Measurement Equipment through Evaluation of Added Mass of Membrane and Error Correction

    Sang-Wook Jin


    Full Text Available One of the most important issues in keeping membrane structures in stable condition is to maintain the proper stress distribution over the membrane. However, it is difficult to determine the quantitative real stress level in the membrane after the completion of the structure. The stress relaxation phenomenon of the membrane and the fluttering effect due to strong wind or ponding caused by precipitation may cause severe damage to the membrane structure itself. Therefore, it is very important to know the magnitude of the existing stress in membrane structures for their maintenance. The authors have proposed a new method for separately estimating the membrane stress in two different directions using sound waves instead of directly measuring the membrane stress. The new method utilizes the resonance phenomenon of the membrane, which is induced by sound excitations given through an audio speaker. During such experiment, the effect of the surrounding air on the vibrating membrane cannot be overlooked in order to assure high measurement precision. In this paper, an evaluation scheme for the added mass of membrane with the effect of air on the vibrating membrane and the correction of measurement error is discussed. In addition, three types of membrane materials are used in the experiment in order to verify the expandability and accuracy of the membrane measurement equipment.

  15. Generation of biocompatible droplets for in vivo and in vitro measurement of cell-generated mechanical stresses.

    Lucio, Adam A; Ingber, Donald E; Campàs, Otger


    Here we describe a detailed protocol to produce biocompatible droplets that permit the measurement of mechanical stresses at cell and tissue scales. The droplets can be used as force transducers in vivo, ex vivo, and in vitro, to measure mechanical stresses in situ, in three dimensions and time. Versatile and modular droplet coatings using biotinylated molecules, such as ligands for specific adhesion receptors, enable the targeting of specific tissues or cells. Droplet sizes can be varied to measure forces at different scales (tissue and cell scales) and the range of measurable mechanical stresses ranges within approximately 0.3-100 kPa. The protocol described in this chapter is divided in three sections. First, we describe the generation and stabilization of biocompatible droplets. Next, we explain the steps necessary to functionalize the droplet surface. Finally, we describe how to characterize the mechanical properties of the droplets, so that they can be used as calibrated mechanical probes. The procedure to generate, stabilize, and functionalize the droplets is straightforward and can be completed in about 3h with basic laboratory resources. The calibration of the droplet's mechanical properties to perform quantitative stress measurements is also straightforward, but requires the proper equipment to measure interfacial tension (such as a tensiometer). Calibrated droplets can be used to quantify cell-generated mechanical stresses by analyzing the tridimensional shape of the droplet. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Standard test method for verifying the alignment of X-Ray diffraction instrumentation for residual stress measurement

    American Society for Testing and Materials. Philadelphia


    1.1 This test method covers the preparation and use of a flat stress-free test specimen for the purpose of checking the systematic error caused by instrument misalignment or sample positioning in X-ray diffraction residual stress measurement, or both. 1.2 This test method is applicable to apparatus intended for X-ray diffraction macroscopic residual stress measurement in polycrystalline samples employing measurement of a diffraction peak position in the high-back reflection region, and in which the θ, 2θ, and ψ rotation axes can be made to coincide (see Fig. 1). 1.3 This test method describes the use of iron powder which has been investigated in round-robin studies for the purpose of verifying the alignment of instrumentation intended for stress measurement in ferritic or martensitic steels. To verify instrument alignment prior to stress measurement in other metallic alloys and ceramics, powder having the same or lower diffraction angle as the material to be measured should be prepared in similar fashion...

  17. Measuring soft measures within a stated preference survey: The effect of pollution and traffic stress on mode choice

    Sottile, Eleonora; Cherchi, Elisabetta; Meloni, Italo


    The objective of this research is to study the extent to which information on pollution and individual stress has on the choice to shift from private car to Park and Ride. A Stated Preference experiment was built where the reduction of CO2 and stress are attributes of the experimental design. Res...

  18. Laser sheet scattered light method for industrial measurement of thickness residual stress distribution in flat tempered glass

    Castellini, P.; Stroppa, L.; Paone, N.


    The paper presents the laser sheet scattered light technique, a fast optical non contact method for measuring internal stress distribution over a cross section of flat glass specimens, designed for closed loop control of glass tempering furnaces. The technique is an evolution of the scattered light method for flat glass residual stress analysis and allows a full thickness stress profile to be measured with a single shot acquisition across a glass plate without any contact. A linearly polarized laser sheet, shaped into a thin plane of parallel light beams, enters orthogonally to the side of the flat glass illuminating its full thickness. Light sheet is orthogonal to the glass surface and travels parallel to it. Stress induced birefringence through the glass affects light polarization, thus scattered light intensity detected at 90° with respect to the polarization of the incident light appears spatially modulated in intensity. A camera aligned orthogonal to the laser light polarization collects an image of fringes whose shape is digitally analyzed to measure the thickness stress state. The paper describes the development of this technique by recalling the scattered light method, then describing its automation by scanning a collimated beam across the glass thickness and finally by showing that the scan method can be substituted by the light sheet method. Light sheet method provides a full field non contact stress measurement across the glass thickness, thus allowing for a fast inspection method, suitable for industrial use. Flat glass items for industrial use have bevelled edges; this does not allow measurements close to glass surface. To solve this limit, experimental data are extrapolated by a symmetrical polynomial fitting and imposing a zero integral to the stress profile. Results on surface stress measured by the laser sheet scattered method are in agreement with those of the automated light scattered method and show a fair agreement with measurement by an

  19. Crustal Stress Measurement for Significant Project Construction and Its Application in Design


    The hydrofracturing technique has developed into a reliable and practical method for determining the original three-dimensional crustal stress state of underground caverns, the load-bearing capacity of a high pressure cavern itself, and the high pressure hydraulic permeability of rock masses, and has also been extensively used in disposal of nuclear waste,long and deeply-buried traffic channels and high-pressure cavern engineering for hydraulic power plants. The practice shows that the comprehensive measurement of the physical parameters of the rock mass and taking full use of the wall rock load-bearing capacity to optimize the engineering design hold are very useful in ensuring the engineering safety and improving the design level.

  20. Development of buried wire gages for measurement of wall shear stress in Blastane experiments

    Murthy, S. V.; Steinle, F. W.


    Buried Wire Gages operated from a Constant Temperature Anemometer System are among the special types of instrumentation to be used in the Boundary Layer Apparatus for Subsonic and Transonic flow Affected by Noise Environment (BLASTANE). These Gages are of a new type and need to be adapted for specific applications. Methods were developed to fabricate Gage inserts and mount those in the BLASTANE Instrumentation Plugs. A large number of Gages were prepared and operated from a Constant Temperature Anemometer System to derive some of the calibration constants for application to fluid-flow wall shear-stress measurements. The final stage of the calibration was defined, but could not be accomplished because of non-availability of a suitable flow simulating apparatus. This report provides a description of the Buried Wire Gage technique, an explanation of the method evolved for making proper Gages and the calibration constants, namely Temperature Coefficient of Resistance and Conduction Loss Factor.

  1. Serial measurements of exercise performance in pediatric heart transplant patients using stress echocardiography.

    Yeung, Joanne P; Human, Derek G; Sandor, George G S; De Souza, Astrid M; Potts, James E


    Heart transplantation is an increasingly acceptable therapeutic option for children with end-stage and complex congenital heart disease. With advances in surgery, immunosuppression, and follow-up care, functional outcomes need to be evaluated. We report the results of serial exercise testing performed using stress echocardiography in a cohort of pediatric HTP. HTP (n = 7) exercised on a semi-recumbent ergometer to volitional fatigue. Echocardiography-Doppler measurements, HR, and blood pressure were taken at rest and during staged exercise. Results were compared with healthy CON (n = 12). HTP did significantly less work during exercise (940 vs. 1218 J/kg, p HTP had a lower SF at peak exercise (48% vs. 52%, p HTP. HTP are able to exercise safely; however, their exercise tolerance is reduced, and hemodynamics and contractility are diminished. Over time, their hemodynamics and left ventricular function have remained relatively constant.

  2. Residual stress measurements via neutron diffraction of additive manufactured stainless steel 17-4 PH.

    Masoomi, Mohammad; Shamsaei, Nima; Winholtz, Robert A; Milner, Justin L; Gnäupel-Herold, Thomas; Elwany, Alaa; Mahmoudi, Mohamad; Thompson, Scott M


    Neutron diffraction was employed to measure internal residual stresses at various locations along stainless steel (SS) 17-4 PH specimens additively manufactured via laser-powder bed fusion (L-PBF). Of these specimens, two were rods (diameter=8 mm, length=80 mm) built vertically upward and one a parallelepiped (8×80×9 mm(3)) built with its longest edge parallel to ground. One rod and the parallelepiped were left in their as-built condition, while the other rod was heat treated. Data presented provide insight into the microstructural characteristics of typical L-PBF SS 17-4 PH specimens and their dependence on build orientation and post-processing procedures such as heat treatment. Data have been deposited in the Data in Brief Dataverse repository (doi:10.7910/DVN/T41S3V).

  3. Residual stress measurements via neutron diffraction of additive manufactured stainless steel 17-4 PH

    Mohammad Masoomi


    Full Text Available Neutron diffraction was employed to measure internal residual stresses at various locations along stainless steel (SS 17-4 PH specimens additively manufactured via laser-powder bed fusion (L-PBF. Of these specimens, two were rods (diameter=8 mm, length=80 mm built vertically upward and one a parallelepiped (8×80×9 mm3 built with its longest edge parallel to ground. One rod and the parallelepiped were left in their as-built condition, while the other rod was heat treated. Data presented provide insight into the microstructural characteristics of typical L-PBF SS 17-4 PH specimens and their dependence on build orientation and post-processing procedures such as heat treatment. Data have been deposited in the Data in Brief Dataverse repository (doi:10.7910/DVN/T41S3V.

  4. Field measurements, simulation modeling and development of analysis for moisture stressed corn and soybeans, 1982 studies

    Blad, B. L.; Norman, J. M.; Gardner, B. R.


    The experimental design, data acquisition and analysis procedures for agronomic and reflectance data acquired over corn and soybeans at the Sandhills Agricultural Laboratory of the University of Nebraska are described. The following conclusions were reached: (1) predictive leaf area estimation models can be defined which appear valid over a wide range of soils; (2) relative grain yield estimates over moisture stressed corn were improved by combining reflectance and thermal data; (3) corn phenology estimates using the model of Badhwar and Henderson (1981) exhibited systematic bias but were reasonably accurate; (4) canopy reflectance can be modelled to within approximately 10% of measured values; and (5) soybean pubescence significantly affects canopy reflectance, energy balance and water use relationships.

  5. Measurement and analysis of flow wall shear stress in an interior subchannel of triangular array rods. [LMFBR

    Fakori-Monazah, M.R.; Todreas, N.E.


    A simulated model of triangular array rods with pitch to diameter ratio of 1.10 (as a test section) and air as the fluid flow was used to study the LMFBR hydraulic parameters. The wall shear stress distribution around the rod periphery, friction factors, static pressure distributions and turbulence intensity corresponding to various Reynolds numbers ranging from 4140 to 36170 in the central subchannel were measured. Various approaches for measurement of wall shear stress were compared. The measurement was performed using the Preston tube technique with the probe outside diameter equal to 0.014 in.

  6. In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing

    Spataru, Sergiu; Hacke, Peter; Sera, Dezso

    We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity-freeze stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. We analyze dark I-V curves measured...... due to cell fractures, and the additional series resistance losses observed under illumination. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test and initial and final module flash testing...

  7. Urinary oxidative stress biomarkers among local residents measured 6years after the Hebei Spirit oil spill.

    Kim, Jung-Ah; Noh, Su Ryeon; Cheong, Hae-Kwan; Ha, Mina; Eom, Sang-Yong; Kim, Heon; Park, Myung-Sook; Chu, Yeonhee; Lee, Seung-Hwa; Choi, Kyungho


    In December 2007, the Hebei Spirit oil spill occurred on the west coast of South Korea. Association between crude oil exposure and the levels of urinary oxidative stress biomarkers was reported among the local residents, 1.5years after the accident. The aim of this study was to follow-up possible longer-term effects of the oil spill among the residents near the oil spill. Six years after the accident, urinary oxidative stress biomarkers of the residents were associated with surrogates of oil exposure. The target subjects were divided into two groups based on the distance of their residence to the spill site, i.e., those near the spill site ('Near' group, n=476), and those far from the spill ('Far' group, n=152). A questionnaire was administered by trained interviewers or self-reporting, and demographic information and other parameters of the participants, such as socioeconomic status, smoking and drinking behaviors, disease history, and duration of clean-up activities after the spill, were collected. The participants' levels of 8-hydroxy-2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) in 12 h urine samples were measured as indicators of oxidative DNA damage and lipid peroxidation, respectively. A general linear model was used for statistical analysis. Urinary MDA and 8-OHdG levels measured from 'Near' group, i.e., geometric mean of 2.19μmol/g creatinine, and 5.41μg/g creatinine, respectively, were higher than those of 'Far' group. Especially, urinary 8-OHdG levels in the 'Near' group were significantly higher than those of 'Far' after adjusting relevant covariates. In addition, the duration of clean-up activities showed a significant association with both urinary 8-OHdG and MDA levels. Even 6years after the oil spill, positive associations between oxidative stress biomarkers and surrogates of oil exposure were evident. While the present study design lacks biomarkers of exposure, the results of this study suggest that the consequences of oil pollution may last

  8. Racial discrimination is associated with a measure of red blood cell oxidative stress: a potential pathway for racial health disparities.

    Szanton, Sarah L; Rifkind, Joseph M; Mohanty, Joy G; Miller, Edgar R; Thorpe, Roland J; Nagababu, Eneka; Epel, Elissa S; Zonderman, Alan B; Evans, Michele K


    There are racial health disparities in many conditions for which oxidative stress is hypothesized to be a precursor. These include cardiovascular disease, diabetes, and premature aging. Small clinical studies suggest that psychological stress may increase oxidative stress. However, confirmation of this association in epidemiological studies has been limited by homogenous populations and unmeasured potential confounders. We tested the cross-sectional association between self-reported racial discrimination and red blood cell (RBC) oxidative stress in a biracial, socioeconomically heterogeneous population with well-measured confounders. We performed a cross-sectional analysis of a consecutive series of 629 participants enrolled in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Conducted by the National Institute on Aging Intramural Research Program, HANDLS is a prospective epidemiological study of a socioeconomically diverse cohort of 3,721 Whites and African Americans aged 30-64 years. Racial discrimination was based on self-report. RBC oxidative stress was measured by fluorescent heme degradation products. Potential confounders were age, smoking status, obesity, and C-reactive protein. Participants had a mean age of 49 years (SD = 9.27). In multivariable linear regression models, racial discrimination was significantly associated with RBC oxidative stress (Beta = 0.55, P discrimination was not associated with RBC oxidative stress in Whites but was associated significantly for African Americans (Beta = 0.36, P racial discrimination amplifies cardiovascular and other age-related disease risks.

  9. Instantaneous strain measurements during high-temperature stress cycling of a dispersion-strengthened niobium alloy

    Farkas, D.M.; Mishra, R.S.; Mukherjee, A.K. [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science


    Experimental results obtained from stress cycling tests performed during high-temperature creep of a dispersion strengthened niobium alloy indicate that the instantaneous strain following the stress change decreases with accumulated strain. The true work-hardening rate was shown to be a small fraction of the elastic modulus which remained fairly constant throughout the strain history. The instantaneous strain change from a stress addition was typically greater than the strain from the corresponding stress reduction. This effect is quite pronounced for small stress changes and diminishes as the magnitude of the stress change increases. This implies that the mobility of dislocations is impeded in the reverse direction unless the magnitude of stress reduction exceeds the value of the internal stress.


    D. A. Stepanenko


    Full Text Available Problems of design, fabrication and application of sensors for measurement of mechanical stresses in ultrasonic waveguide systems based on Villari effect and providing spatial resolution of measurements are considered. Results of experimental studies of spatial distribution of vibration parameters in waveguide systems for ultrasonic thrombolysis are presented. Technique of calibration and potential applications of the sensors are described.

  11. In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing

    Spataru, Sergiu; Hacke, Peter; Sera, Dezso

    We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity-freeze stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. We analyze dark I-V curves measured...

  12. Oceanic Wind Speed and Wind Stress Estimation from Ambient Noise Measurements.


    it was found that noise records may be used to monitor wind speed and wind stress over the ocean. Time series of wind speeds can be produced from...wind direction, the wind stress has also been estimated and vector-averaged. The monthly mean stress from the authors’ data is higher than values

  13. Investigation of PACE™ software and VeriFax's Impairoscope device for quantitatively measuring the effects of stress

    Morgenthaler, George W.; Nuñez, German R.; Botello, Aaron M.; Soto, Jose; Shrairman, Ruth; Landau, Alexander


    Many reaction time experiments have been conducted over the years to observe human responses. However, most of the experiments that were performed did not have quantitatively accurate instruments for measuring change in reaction time under stress. There is a great need for quantitative instruments to measure neuromuscular reaction responses under stressful conditions such as distraction, disorientation, disease, alcohol, drugs, etc. The two instruments used in the experiments reported in this paper are such devices. Their accuracy, portability, ease of use, and biometric character are what makes them very special. PACE™ is a software model used to measure reaction time. VeriFax's Impairoscope measures the deterioration of neuromuscular responses. During the 1997 Summer Semester, various reaction time experiments were conducted on University of Colorado faculty, staff, and students using the PACE™ system. The tests included both two-eye and one-eye unstressed trials and trials with various stresses such as fatigue, distractions in which subjects were asked to perform simple arithmetic during the PACE™ tests, and stress due to rotating-chair dizziness. Various VeriFax Impairoscope tests, both stressed and unstressed, were conducted to determine the Impairoscope's ability to quantitatively measure this impairment. In the 1997 Fall Semester, a Phase II effort was undertaken to increase test sample sizes in order to provide statistical precision and stability. More sophisticated statistical methods remain to be applied to better interpret the data.

  14. Spatio-temporal characteristics of large scale motions in a turbulent boundary layer from direct wall shear stress measurement

    Pabon, Rommel; Barnard, Casey; Ukeiley, Lawrence; Sheplak, Mark


    Particle image velocimetry (PIV) and fluctuating wall shear stress experiments were performed on a flat plate turbulent boundary layer (TBL) under zero pressure gradient conditions. The fluctuating wall shear stress was measured using a microelectromechanical 1mm × 1mm floating element capacitive shear stress sensor (CSSS) developed at the University of Florida. The experiments elucidated the imprint of the organized motions in a TBL on the wall shear stress through its direct measurement. Spatial autocorrelation of the streamwise velocity from the PIV snapshots revealed large scale motions that scale on the order of boundary layer thickness. However, the captured inclination angle was lower than that determined using the classic method by means of wall shear stress and hot-wire anemometry (HWA) temporal cross-correlations and a frozen field hypothesis using a convection velocity. The current study suggests the large size of these motions begins to degrade the applicability of the frozen field hypothesis for the time resolved HWA experiments. The simultaneous PIV and CSSS measurements are also used for spatial reconstruction of the velocity field during conditionally sampled intense wall shear stress events. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1315138.

  15. Prediction and measurement of relieved residual stress by the cryogenic heat treatment for Al6061 alloy: mechanical properties and microstructure

    Ko, Dae Hoon; Ko, Dae Cheol; Kim, Byung Min [Pusan National University, Busan (Korea, Republic of); Lim, Hak Jin; Lee, Jung Min [Poongsan Co., Gyungju (Korea, Republic of)


    The purpose of this study is to predict the residual stress resulting from the cryogenic heat treatment (CHT) which affects the mechanical properties and microstructure for Al6061 alloy. The CHT is very effective method to reduce the residual stress by quenching media such as liquid nitrogen, boiling water and steam. In this study, experimental T6 and CHT are carried out to measure the temperature of Al parts and to determine the convective heat transfer coefficient. This coefficient is used to predict the residual stress during FE-simulation. In order to consider the relaxation of residual stress during artificial ageing, the Zener-Wert-Avrami function with elasto-plastic nonlinear analysis is used in this study. The predicted residual stress is compared with the measured one by X-ray diffraction (XRD) and is found to be in good agreement with results of the FE-simulation. Further, after T6 and CHT, the electrical conductivity and hardness of the Al6061 alloy are measured to estimate the mechanical properties and its microstructure such as precipitates is observed by Transmission electron microscopy (TEM). Also, the creation of precipitates during T6 and CHT are verified by XRD with component analysis. It is found that CHT affects the residual stress, mechanical properties, and precipitation of the Al 6061 alloy.

  16. In-situ measure to internal stress of shotcrete layer in soft-rock roadway

    Shulin Fang; Jian Zhang


    In order to solve the difficult conditions of soft rock, water-trickling and hard-maintain of main air-return roadway in Tarangaole Colliery, high pretensioned stress and intensive bolt-shotcrete support program was designed and mechanical property of shotcrete layer was specially monitored through utilizing a type of concrete stress meter with oscillating chord after the program was carried out. It was indicated that, due to rock pressure and support resistance, the interior of shotcrete layer would emerge diverse stresses in axial, radial and tangential directions. With time passing internal stresses in three directions, whose average values were-0.061, 0.043 and 0.517 MPa respectively, fluctuated first and then tended to stability slowly. The axial and radial stresses were relatively smaller than tangential stress which was 11, 12 times the two formers respectively. Along the section of roadway, axial and tangential stresses distributed symmetri-cally and increased gradually from the top of arch to the waist of wall, but reduced at the foot of wall. Radial stresses reduced from the top of arch to the waist of arch first, and then increased in the waist of wall. Axial stresses were tensile substantially, except for stresses in arch vault tending to compressive, but all the radial stresses were compressive. Nevertheless, tangential stresses in the wall were compressive and tangential stresses in the arch were tensile. During the period of roadway excavating, the stress of shotcrete layer was less than its ultimate bearing capacity, with no significant stress concentration. At the end of this article, some suggests are given to shotcrete support design.

  17. Rock stress orientation measurements using induced thermal spalling in slim boreholes

    Hakami, Eva [Geosigma AB, Uppsala (Sweden)


    In the planning and design of a future underground storage for nuclear waste based on the KBS-3 method, one of the aims is to optimize the layout of deposition tunnels such that the rock stresses on the boundaries of deposition holes are minimized. Previous experiences from heating of larger scale boreholes at the Aespoe Hard Rock Laboratory (AHRL) gave rise to the idea that induced borehole breakouts using thermal loading in smaller diameter boreholes, could be a possible way of determining the stress orientation. Two pilot experiments were performed, one at the Aespoe Hard Rock Laboratory and one at ONKALO research site in Finland. An acoustic televiewer logger was used to measure the detailed geometrical condition of the borehole before and after heating periods. The acoustic televiewer gives a value for each 0.7 mm large pixel size around the borehole periphery. The results from the loggers are presented as images of the borehole wall, and as curves for the maximum, mean and minimum values at each depth. Any changes in the borehole wall geometry may thus be easily detected by comparisons of the logging result images. In addition, using an optical borehole televiewer a good and detailed realistic colour picture of the borehole wall is obtained. From these images the character of the spalls identified may be evaluated further. The heating was performed in a 4 m long section, using a heating cable centred in an 8 m deep vertical borehole, drilled from the floor of the tunnels. For the borehole in the Q-tunnel of AHRL the results from the loggings of the borehole before the heating revealed that breakouts existed even before this pilot test due to previous heating experiments at the site (CAPS). Quite consistent orientation and the typical shape of small breakouts were observed. After the heating the spalling increased slightly at the same locations and a new spalling location also developed at a deeper location in the borehole. At ONKALO three very small changes

  18. Measuring stress level of dairy cows during milking using by geometric indices of heart rate variability

    Levente Kovács


    Full Text Available AbstractHeart rate (HR and heart rate variability (HRV were investigated in cows (n=32, age: 3.86 years, milk production: 35±2.5 kg, DIM: 150±15 milked in a parallel milking parlour. Geometric parameters of HRV (SD1 and SD2 were calculated using Poincare graphs. HRV indices of resting 1 h after midday milking (reference period were compared to those measured during the different phases of the evening milking (driving; in the holding pen; udder preparation; milking; after milking in the milking stall. There was no difference between the reference period and the different phases of milking in animal welfare terms. During the reference period SD2 (198.5 ms was significantly higher (p<0.05 than every other measured period suggesting an increasing parasympathetic tone after milking. This parasympathetic predominance decreased with time of the day (1.5 h after milking. SD2 was significantly affected by parity, by the breeding bull (p<0.01 and by milk production (p<0.05. SD2 was notably higher (102.8 ms in multiparous cows than in primiparous cows (p<0.017; α=0.005 during resting and milking. Results suggested that a conventional milking process is not really stressful for cows. Primiparous cows were more susceptible of milking process than multiparous ones. SD2 is a good marker of vagus activity and affected by several independent factors.

  19. Stress-Release Seismic Source for Seismic Velocity Measurement in Mines

    Swanson, P. L.; Clark, C.; Richardson, J.; Martin, L.; Zahl, E.; Etter, A.


    Accurate seismic event locations are needed to delineate roles of mine geometry, stress and geologic structures in developing rockburst conditions. Accurate absolute locations are challenging in mine environments with rapid changes in seismic velocity due to sharp contrasts between individual layers and large time-dependent velocity gradients attending excavations. Periodic use of controlled seismic sources can help constrain the velocity in this continually evolving propagation medium comprising the miners' workplace. With a view to constructing realistic velocity models in environments in which use of explosives is problematic, a seismic source was developed subject to the following design constraints: (i) suitable for use in highly disturbed zones surrounding mine openings, (ii) able to produce usable signals over km-scale distances in the frequency range of typical coal mine seismic events (~10-100 Hz), (iii) repeatable, (iv) portable, (v) non-disruptive to mining operations, and (vi) safe for use in potentially explosive gaseous environments. Designs of the compressed load column seismic source (CLCSS), which generates a stress, or load, drop normal to the surface of mine openings, and the fiber-optic based source-initiation timer are presented. Tests were conducted in a coal mine at a depth of 500 m (1700 ft) and signals were recorded on the surface with a 72-ch (14 Hz) exploration seismograph for load drops of 150-470 kN (16-48 tons). Signal-to-noise ratios of unfiltered signals ranged from ~200 immediately above the source (500 m (1700 ft)) to ~8 at the farthest extent of the array (slant distance of ~800 m (2600 ft)), suggesting the potential for use over longer range. Results are compared with signals produced by weight drop and sledge hammer sources, indicating the superior waveform quality for first-arrival measurements with the CLCSS seismic source.

  20. Healthy Dietary Patterns and Oxidative Stress as Measured by Fluorescent Oxidation Products in Nurses’ Health Study

    Seungyoun Jung


    Full Text Available Healthy diets may lower oxidative stress and risk of chronic diseases. However, no previous studies examined associations between diet and fluorescent oxidation products (FlOP, a global marker of oxidative stress. We evaluated associations between healthy eating patterns (Alternative Healthy Eating Index (AHEI, Dietary Approach to Stop Hypertension (DASH, and Alternate Mediterranean Diet (aMED and FlOP, measured at three excitation/emission wavelengths (FlOP_360, FlOP_320, FlOP_400 from 2021 blood samples collected from 1688 women within the Nurses’ Health Study. AHEI, DASH, and aMED scores were significantly positively associated with FlOP_360 and FlOP_320 concentrations (p-trend ≤ 0.04, but not associated with FlOP_400. Among specific food groups that contribute to these diet scores, significantly positive associations were observed with legumes and vegetables for FlOP_360, vegetables and fruits for FlOP_320, and legumes and alcohol for FlOP_400. Inverse associations were observed with nuts, sweets or desserts, and olive oil for FlOP_360, nuts for FlOP_320 and sweets or desserts for FlOP_400 (all p-trend ≤ 0.05. However, FlOP variation due to diet was small compared to overall FlOP variation. In conclusion, AHEI, DASH, and aMED scores were unexpectedly positively, but weakly, associated with FlOP_360 and FlOP_320. However, these findings should be interpreted cautiously as the determinants of FlOP concentrations are not fully understood.

  1. Measuring stress responses in female Geoffroy's spider monkeys: Validation and the influence of reproductive state.

    Rodrigues, Michelle A; Wittwer, Dan; Kitchen, Dawn M


    broadly, we conclude that future studies using fecal glucocorticoid metabolites to index stress should consider that reproductive state might confound glucocorticoid measurements. Am. J. Primatol. © 2015 Wiley Periodicals, Inc.

  2. Instrumented sphere method for measuring thermal pressure in fluids and isotropic stresses and reaction kinetics in thermosetting resins

    Merzlyakov, Mikhail; Meng, Yan; Simon, Sindee L.; McKenna, Gregory B.


    A novel technique is described for measuring thermal pressure in fluids and for measuring isotropic stress development and reaction kinetics in thermosetting resins during cure and thermal cycling. The method uses a 12.7-mm-diam sealed stainless steel spherical pressure vessel to impose three-dimensional isotropic constraints. The vessel is instrumented with strain gauges and thermocouples. Both isotropic stresses and reaction kinetics during cure at cure temperatures as high as 300 °C can be measured. In addition, measurement of the isotropic stress as a function of temperature yields the thermal pressure coefficient in both the glassy and rubbery (or liquid) states. Experimental results are presented for sucrose benzoate, a pressure-transmitting oil di-2-ethylhexylsebacate and an epoxy resin. The method provides reproducible estimates for the thermal pressure coefficient and the stresses are highly isotropic. A suggestion for improved versions of the device is: thicker walled vessels can be used to increase the upper stress limit (currently at 30 MPa). Also if a lower temperature range is to be studied, then aluminum can be used as a vessel material. Since epoxy resins have better adhesion to aluminum than to stainless steel, there may be an advantage to this.

  3. Measurements of internal stresses in bond coating using high energy x-rays from synchrotron radiation source

    Suzuki, K; Akiniwa, Y; Nishio, K; Kawamura, M; Okado, H


    Thermal barrier coating (TBC) techniques enable high temperature combustion of turbines made of Ni-base alloy. TBC is made of zirconia top coating on NiCoCrAlY bond coating. The internal stresses in the bond coating play essential role in the delamination or fracture of TBC in service. With the X-rays from laboratory equipments, it is impossible to measure nondestructively the internal stress in the bond coating under the top coating. synchrotron radiations with a high energy and high brightness have a large penetration depth as compared with laboratory X-rays. Using the high energy X-rays from the synchrotron radiation, it is possible to measure the internal stress in the bond coating through the top coating. In this study, the furnace, which can heat a specimen to 1473 K, was developed for the stress measurement of the thermal barrier coatings. The internal stresses in the bond coating were measured at the room temperature, 773 K, 1073 K and 1373 K by using the 311 diffraction from Ni sub 3 Al with about 73...

  4. Residual Stress Measurement and Calibration for A7N01 Aluminum Alloy Welded Joints by Using Longitudinal Critically Refracted ( LCR) Wave Transmission Method

    Zhu, Qimeng; Chen, Jia; Gou, Guoqing; Chen, Hui; Li, Peng; Gao, W.


    Residual stress measurement and control are highly important for the safety of structures of high-speed trains, which is critical for the structure design. The longitudinal critically refracted wave technology is the most widely used method in measuring residual stress with ultrasonic method, but its accuracy is strongly related to the test parameters, namely the flight time at the free-stress condition ( t 0), stress coefficient ( K), and initial stress (σ0) of the measured materials. The difference of microstructure in the weld zone, heat affected zone, and base metal (BM) results in the divergence of experimental parameters. However, the majority of researchers use the BM parameters to determine the residual stress in other zones and ignore the initial stress (σ0) in calibration samples. Therefore, the measured residual stress in different zones is often high in errors and may result in the miscalculation of the safe design of important structures. A serious problem in the ultrasonic estimation of residual stresses requires separation between the microstructure and the acoustoelastic effects. In this paper, the effects of initial stress and microstructure on stress coefficient K and flight time t 0 at free-stress conditions have been studied. The residual stress with or without different corrections was investigated. The results indicated that the residual stresses obtained with correction are more accurate for structure design.

  5. Measuring animal welfare within a reintroduction: an assessment of different indices of stress in water voles Arvicola amphibius.

    Merryl Gelling

    Full Text Available Reintroductions are an increasingly common conservation restoration tool; however, little attention has hitherto been given to different methods for monitoring the stress encountered by reintroduced individuals. We compared ten potential measures of stress within four different categories (neuroendocrine, cell function, body condition and immune system function as proxies for animal welfare in water voles being reintroduced to the Upper Thames region, Oxfordshire, UK. Captive-bred voles were assessed pre-release, and each month post-release for up to five months. Wild-born voles were captured in the field and assessed from two months post-release. Plasma corticosteroid, hydration and body condition of captive-bred voles differed between their pre-release measures and both their first ("short-term" recapture, and their final recapture ("long-term" release, however only body condition and immunocompetence measured using the Nitroblue Tetrazolium (NBT test were significantly different post-release between the first and last recaptures. Captive-bred animals had lower fat reserves, higher weight/length ratios and better immunocompetence (NBT than did wild-born voles. Captive-bred males had higher ectoparasite burdens compared to wild-born males and, as reintroduction site quality decreased, became less hydrated. These observations indicate that some methods can identify changes in the stress response in individuals, highlighting areas of risk in a reintroduction programme. In addition, a single measure may not provide a full picture of the stress experienced; instead, a combination of measures of different physiological systems may give a more complete indication of stress during the reintroduction process. We highlight the need to monitor stress in reintroductions using measures from different physiological systems to inform on possible animal welfare improvements and thus the overall success rate of reintroductions.

  6. Two-component laser Doppler anemometer for measurement of velocity and turbulent shear stress near prosthetic heart valves.

    Woo, Y R; Yoganathan, A P


    The velocity and turbulent shear stress measured in the immediate vicinity of prosthetic heart valves play a vital role in the design and evaluation of these devices. In the past hot wire/film and one-component laser Doppler anemometer (LDA) systems were used extensively to obtain these measurements. Hot wire/film anemometers, however, have some serious disadvantages, including the inability to measure the direction of the flow, the disturbance of the flow field caused by the probe, and the need for frequent calibration. One-component LDA systems do not have these problems, but they cannot measure turbulent shear stresses directly. Since these measurements are essential and are not available in the open literature, a two-component LDA system for measuring velocity and turbulent shear stress fields under pulsatile flow conditions was assembled under an FDA contract. The experimental methods used to create an in vitro data base of velocity and turbulent shear stress fields in the immediate vicinity of prosthetic heart valves of various designs in current clinical use are also discussed.

  7. Measurement of the stress field of a tunnel through its rock EMR

    Qiu, Liming; Wang, Enyuan; Song, Dazhao; Liu, Zhentang; Shen, Rongxi; Lv, Ganggang; Xu, Zhaoyong


    In order to quantitatively study the relationship between the disturbance stress of coal mine roadways and the electromagnetic radiation (EMR) of rocks, and further evaluate their internal stress distributions, we first examined the characteristics of EMR signals emitted from rock mass under uniaxial compression, analyzed the relationship between the stress inside the rock mass and its emitted EMR intensity, and put forward a new disturbance stress testing method by monitoring the EMR from the rock mass to retrieve its surrounding stress field. Then, we applied the method to monitor EMR intensity from the no.11803 rock roadway of the Nuodong coal mine, China, and inversely retrieved its stress field. Lastly, we analyzed the causes of local stress anomalies in the Nuodong area by testing the EMR intensity of its nearby areas, and we examined the geology of the whole region. The results showed that: (1) in the rock roadway and the surrounding area of the Nuodong coal mine, the disturbance stress was in the range of 4.8 ∼ 9.1 MPa, the angle between the direction of the stress field and the horizontal plane of the roadway was 35 ± 2.5°, the lateral pressure coefficient was 1.30 ∼ 1.57 (2) the Laoguishan and Yulong anticlines in the vicinity of the Nuodong coal mine caused great horizontal tectonic stress in the region, and the existence of the auxiliary roadway and F12 normal fault resulted in the formation of two high stress zones in the no.11803 rock roadway. Overall, monitoring the EMR from rock mass could ascertain the state, direction, size and distribution of disturbance stress in a roadway and further obtain the distribution of the stress field of an underground structure.

  8. Analysis of faults stability with dynamic phenomena in the mine based on slide criterion and in-situ stress measurement

    SONG Wei-hua; WANG Yu-feng; WANG Xin-hua


    For the study on the relationship between the dynamic phenomena in the mining such as mine earthquakes,outburst and faults slide,firstly,double shear friction experiments of sandstone were made,and its slide criterion was suggested considering the viewing of engineering.Secondly,in order to study the stability of underground rock and zone of tectonic stress field,based on the analysis on distribution characteristic of initial rock stress measurements,the geology structural model was built and tectonic stress field was made a back-analysis by applying finite element method.The calculating results fit with the analysis result of earthquakes mechanism and the distribution characteristic of the measurements.The high stress regional centers station locates discontinuous zone of I level faults and is corresponding to underground earthquakes scene.From then it is certain that tectonic stress is the major origin and necessary condition of mine earthquakes.The instability slide of the faults is the main manifest and the mining activity is the leading factor.Beipiao fault has a dominate effect on other sub faults and tectonic stress area and is dynamical fountain of dynamic phenomena in the Beipiao Mines.

  9. Analysis of faults stability with dynamic phenomena in the mine based on slide criterion and in-situ stress measurement

    SONG Wei-hua; WANG Yu-feng; WANG Xin-hua


    For the study on the relationshfp between the dynamic phenomena in the min-ing such as mine earthquakes, outburst and faults slide, firstly, double shear friction ex-periments of sandstone were made, and its slide criterion was suggested considering the viewing of engineering. Secondly, in order to study the stability of underground rock and zone of tectonic stress field, based on the analysis on distribution characteristic of initial rock stress measurements, the geology structural model was built and tectonic stress field was made a back-analysis by applying finite element method. The calculating results fit with the analysis result of earthquakes mechanism and the distribution characteristic of the measurements. The high stress regional centers station locates discontinuous zone of I level faults and is corresponding to underground earthquakes scene. From then it is cer-tain that tectonic stress is the major origin and necessary condition of mine earthquakes. The instability slide of the faults is the main manifest and the mining activity is the leading factor. Beipiao fault has a dominate effect on other sub faults and tectonic stress area and is dynamical fountain of dynamic phenomena in the Beipiao Mines.

  10. Measurement of wall shear stress in chick embryonic heart using optical coherence tomography

    Ma, Zhenhe; Dou, Shidan; Zhao, Yuqian; Wang, Yi; Suo, Yanyan; Wang, Fengwen


    The cardiac development is a complicated process affected by genetic and environmental factors. Wall shear stress (WSS) is one of the components which have been proved to influence the morphogenesis during early stages of cardiac development. To study the mechanism, WSS measurement is a step with significant importance. WSS is caused by blood flow imposed on the inner surface of the heart wall and it can be determined by calculating velocity gradients of blood flow in a direction perpendicular to the wall. However, the WSS of the early stage embryonic heart is difficult to measure since the embryonic heart is tiny and beating fast. Optical coherence tomography (OCT) is a non-invasive imaging modality with high spatial and temporal resolution, which is uniquely suitable for the study of early stage embryonic heart development. In this paper, we introduce a method to measure the WSS of early stage chick embryonic heart based on high speed spectral domain optical coherence tomography (SDOCT). 4D (x,y,z,t) scan was performed on the outflow tract (OFT) of HH18 (~3 days of incubation) chick embryonic heart. After phase synchronization, OFT boundary segmentation, and OFT center line calculation, Doppler angle of the blood flow in the OFT can be achieved (This method has been described in previous publications). Combining with the Doppler OCT results, we calculate absolute blood flow velocity distribution in the OFT. The boundary of the OFT was segmented at each cross-sectional structural image, then geometrical center of the OFT can be calculated. Thus, the gradients of blood flow in radial direction can be calculated. This velocity gradient near the wall is termed wall shear rate and the WSS value is proportional to the wall shear rate. Based on this method, the WSS at different heart beating phase are compare. The result demonstrates that OCT is capable of early stage chicken embryonic heart WSS study.

  11. Time evolving bed shear stress due the passage of gravity currents estimated with ADVP velocity measurements

    Zordan, Jessica; Schleiss, Anton J.; Franca, Mário J.


    Density or gravity currents are geophysical flows driven by density gradients between two contacting fluids. The physical trigger mechanism of these phenomena lays in the density differences which may be caused by differences in the temperature, dissolved substances or concentration of suspended sediments. Saline density currents are capable to entrain bed sediments inducing signatures in the bottom of sedimentary basins. Herein, saline density currents are reproduced in laboratory over a movable bed. The experimental channel is of the lock-exchange type, it is 7.5 m long and 0.3 m wide, divided into two sections of comparable volumes by a sliding gate. An upstream reach serves as a head tank for the dense mixture; the current propagates through a downstream reach where the main measurements are made. Downstream of the channel a tank exist to absorb the reflection of the current and thus artifacts due to the limited length of the channel. High performance thermoplastic polyurethane simulating fine sediments forms the movable bed. Measures of 3D instantaneous velocities will be made with the use of the non-intrusive technique of the ADV (Acoustic Doppler Current Profiler). With the velocity measurements, the evolution in time of the channel-bed shear stress due the passage of gravity currents is estimated. This is in turn related to the observed erosion and to such parameters determinant for the dynamics of the current as initial density difference, lock length and channel slope. This work was funded by the ITN-Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7-PEOPLE-2013-ITN under REA grant agreement n_607394-SEDITRANS.

  12. Sex differences in objective measures of sleep in post-traumatic stress disorder and healthy control subjects.

    Richards, Anne; Metzler, Thomas J; Ruoff, Leslie M; Inslicht, Sabra S; Rao, Madhu; Talbot, Lisa S; Neylan, Thomas C


    A growing literature shows prominent sex effects for risk for post-traumatic stress disorder and associated medical comorbid burden. Previous research indicates that post-traumatic stress disorder is associated with reduced slow wave sleep, which may have implications for overall health, and abnormalities in rapid eye movement sleep, which have been implicated in specific post-traumatic stress disorder symptoms, but most research has been conducted in male subjects. We therefore sought to compare objective measures of sleep in male and female post-traumatic stress disorder subjects with age- and sex-matched control subjects. We used a cross-sectional, 2 × 2 design (post-traumatic stress disorder/control × female/male) involving83 medically healthy, non-medicated adults aged 19-39 years in the inpatient sleep laboratory. Visual electroencephalographic analysis demonstrated that post-traumatic stress disorder was associated with lower slow wave sleep duration (F(3,82)  = 7.63, P = 0.007) and slow wave sleep percentage (F(3,82)  = 6.11, P = 0.016). There was also a group × sex interaction effect for rapid eye movement sleep duration (F(3,82)  = 4.08, P = 0.047) and rapid eye movement sleep percentage (F(3,82)  = 4.30, P = 0.041), explained by greater rapid eye movement sleep in post-traumatic stress disorder females compared to control females, a difference not seen in male subjects. Quantitative electroencephalography analysis demonstrated that post-traumatic stress disorder was associated with lower energy in the delta spectrum (F(3,82)  = 6.79, P = 0.011) in non-rapid eye movement sleep. Slow wave sleep and delta findings were more pronounced in males. Removal of post-traumatic stress disorder subjects with comorbid major depressive disorder, who had greater post-traumatic stress disorder severity, strengthened delta effects but reduced rapid eye movement effects to non-significance. These findings support previous evidence that post

  13. Development and validation of an instrument to measure occupational stress in speech-language pathologists.

    Fimian, M J; Lieberman, R J; Fastenau, P S


    The Speech-Language Pathologist Stress Inventory (SLPSI) is a 48-item questionnaire adapted from the Teacher Stress Inventory (Fimian, 1988). Factor analyses of the responses of 626 speech-language pathologists revealed four stress source factors (Bureaucratic Restrictions, Time and Workload Management, Lack of Professional Supports, and Instructional Limitations) and two stress manifestation factors (Emotional-Fatigue Manifestations and Biobehavioral Manifestations). The internal consistency reliability of scales based on these factors ranged from .71 to .87, with .93 for the entire scale. Evidence for construct validity was found in moderate positive correlations between the scales of the SLPSI and the scales of the Maslach Burnout Inventory (MBI) (Maslach & Jackson, 1986). Stress and burnout subscale intercorrelations ranged from .10 to .82 (p less than .01), and the correlation between stress strength and burnout frequency was .66 (p less than .001).

  14. Consistency and validity of self-reporting scores in stress measurement surveys.

    Masood, Khalid; Ahmed, Beena; Choi, Jongyong; Gutierrez-Osuna, Ricardo


    Stress has been attributed to physiological and psychological demands that exceed the natural regulatory capacity of a person. Chronic stress is not only a catalyst for diseases such as hypertension, diabetes, insomnia but may also lead to social problems such as marriage breakups, suicide and violence. Objective assessment of stress is difficult so self-reports are commonly used to indicate the severity of stress. However, empirical information on the validity of self-reports is limited. The present study investigated the authenticity and validity of different self-report surveys. An analysis, based on a three-pronged strategy, was performed on these surveys. It was concluded that although subjects are prone to systematic error in reporting, self-reports can provide a useful substitute for data modeling specifically in stress evaluation where other objective assessments such as determination of stress using only physiological response are difficult.

  15. Several methods applied to measuring residual stress in a known specimen

    Prime, M.B.; Rangaswamy, P.; Daymond, M.R.; Abelin, T.G.


    In this study, a beam with a precisely known residual stress distribution provided a unique experimental opportunity. A plastically bent beam was carefully prepared in order to provide a specimen with a known residual stress profile. 21Cr-6Ni-9Mn austenitic stainless steel was obtained as 43 mm square forged stock. Several methods were used to determine the residual stresses, and the results were compared to the known values. Some subtleties of applying the various methods were exposed.

  16. Measurement and Analysis on Hardness and Residual Stress of Heavy Forging after Heat Treatment


    The hardness and residual stress in the forging for cold roller during low temperature tempering, and the relationship of residual stress and cooling temperature of high temperature tempering for heavy forgings were studied. The stress relaxation constant at low temperature tempering and the elasto-plastisity inversion temperature at high temperature tempering were found. The results are of great importance to determine rational tempering cooling process of heavy forgings.

  17. Synchrotron strain scanning for residual stress measurement in cold-drawn steel rods

    Ruiz Hervías, Jesús; Atienza Riera, José Miguel; Elices Calafat, Manuel


    Cold-drawn steel rods and wires retain significant residual stresses as a consequence of the manufacturing process. These residual stresses are known to be detrimental for the mechanical properties of the wires and their durability in aggressive environments. Steel makers are aware of the problem and have developed post-drawing processes to try and reduce the residual stresses on the wires. The present authors have studied this problem for a number of years and have performed a detailed chara...

  18. A preliminary investigation of workplace stress in platinum miners using subjective and objective measures

    Edwards, A


    Full Text Available conditions -TB and high blood pressure To inform decisions about Safer workplaces Healthier workers Knowledge on workplace stress is one of the missing links in mining Slide 4 ? CSIR 2011 Aim of the study... of accidents and injuries. Slide 5 ? CSIR 2010 Definitions Work place Stress ? Work place stress can be defined as the harmful physical and emotional responses that occur when the psychological and/or physiological...

  19. Neutron diffraction measurements for the determination of heat treatment effectiveness in generating compressive residual stress in an automotive crown gear

    Albertini, G.; Bruno, G.; Fiori, F.; Girardin, E.; Giuliani, A.; Quadrini, E.; Romani, F.


    Thermal austenitizing and tempering treatments are being developed in automotive industry to prevent crack initiation and propagation, especially in components where stress intensity factors influence the stress field and ultimately the fatigue life of the component. This is the case of crown gears, where the tooth root typically undergoes impulsive and very high loads which frequently cause cracking if tensile residual stresses are present at the surface. The sign reversal of these stresses is the aim of austenitizing and tempering treatments. In this work neutron diffraction measurements of residual stress (RS) on a UNI55Cr3 steel crown gear, carried out at HMI-BENSC , are presented. The sample was submitted to a new multi-frequency induction technique whose effectiveness was checked. Comparisons with X-ray measurements are shown, and RS measured by X-rays on a similar shot-peened sample are also mentioned. Experiments at HMI-BENSC have received financial support by the European Commission under the TMR/LSF Access Programme (contract no. ERBFMGE CT950060).

  20. Analytical methods for the measurement of polymerization kinetics and stresses of dental resin-based composites: A review

    Ghavami-Lahiji, Mehrsima; Hooshmand, Tabassom


    Resin-based composites are commonly used restorative materials in dentistry. Such tooth-colored restorations can adhere to the dental tissues. One drawback is that the polymerization shrinkage and induced stresses during the curing procedure is an inherent property of resin composite materials that might impair their performance. This review focuses on the significant developments of laboratory tools in the measurement of polymerization shrinkage and stresses of dental resin-based materials during polymerization. An electronic search of publications from January 1977 to July 2016 was made using ScienceDirect, PubMed, Medline, and Google Scholar databases. The search included only English-language articles. Only studies that performed laboratory methods to evaluate the amount of the polymerization shrinkage and/or stresses of dental resin-based materials during polymerization were selected. The results indicated that various techniques have been introduced with different mechanical/physical bases. Besides, there are factors that may contribute the differences between the various methods in measuring the amount of shrinkages and stresses of resin composites. The search for an ideal and standard apparatus for measuring shrinkage stress and volumetric polymerization shrinkage of resin-based materials in dentistry is still required. Researchers and clinicians must be aware of differences between analytical methods to make proper interpretation and indications of each technique relevant to a clinical situation. PMID:28928776

  1. Surface preparation for XRD residual stress measurements; Preparacao de superficie para medicao de tensoes residuais em soldagem por DRX

    Mishchenko, Andrii; Oliveira, Bruno Jose de; Scotti, Americo, E-mail:, E-mail:, E-mail: [Universidade Federal de Uberlandia (UFU), MG (Brazil)


    A characteristic feature of the X Ray Diffraction (XRD) method for stress determination is that measurements occur at a thin surface layer. Steel sheets come with surfaces modified by lamination, cleaning (sandblasting, grinding) and even corrosion, which induce residual stresses or roughness inherent to the material. Therefore, surface preparation prior to the residual stress measurement is essential, although no standard procedure seems to be available. A general recommendation is to remove a thin layer so that only residual stresses related to the welding process will be measured. In this study, the use of portable electrolytic equipment was evaluated for mechanized surface material removal. Chemical compositions of electrolytic solutions and the influence of current on the removed material, removal time and temperature during the process were studied. As a result, a suitable chemical solution for electro etching of low carbon steel was developed and a set of “soft” parameters that allowed the removal of about 300 um in a reasonable time was found. Higher currents reduce the removal time, yet increasing the consumption of the solution and plate temperature (which could adversely alter the microstructure or generate thermal stresses). Furthermore, the influence of these parameters on the operability of the process was demonstrated. (author)

  2. In-situ stress from hydraulic fracture measurements in G Tunnel, Nevada Test Site

    Smith, C.; Vollendorf, W. C.; Warren, W. E.


    Hydraulic fracture work in G Tunnel, Nevada Test Site, performed to obtain the in-situ stress state is discussed. Field equipment and procedures are described; analysis is developed to relate the hydraulic fracture pressures to the in-situ stress state. Pressure data are analyzed to provide estimates of the stress state at a number of locations in the tunnel complex. A unique feature of the work is the mineback - a mining process in which the rock is cut away to reveal the actual plane of the fracture. Advantages, limitations, and problem areas associated with extracting in-situ stress fields from hydraulic fracture pressure records are discussed in detail.

  3. Swept frequency eddy current (SFEC) measurements of Inconel 718 as a function of microstructure and residual stress

    Chandrasekar, Ramya

    The goal of this thesis was to determine the dependency of swept frequency eddy current (SFEC) measurements on the microstructure of the Ni-based alloy, Inconel 718 as a function of heat treatment and shot peening. This involved extensive characterization of the sample using SEM and TEM coupled with measurements and analysis of the eddy current response of the various sample conditions using SFEC data. Specific objectives included determining the eddy current response at varying depths within the sample, and this was accomplished by taking SFEC measurements in frequencies ranging from 100 kHz to 50 MHz. Conductivity profile fitting of the resulting SFEC signals was obtained by considering influencing factors (such as surface damage). The problems associated with surface roughness and near surface damage produced by shot peening were overcome by using an inversion model. Differences in signal were seen as a result of precipitation produced by heat treatment and by residual stresses induced due to the shot peening. Hardness of the material, which is related both to precipitation and shot peening, was seen to correlate with the measured SFEC signal. Surface stress measurement was carried out using XRD giving stress in the near surface regions, but not included in the calculations due to shallow depth information provided by the technique compared to SFEC. By comparing theoretical SFEC signal computed using the microstructural values (precipitate fraction) and experimental SFEC data, dependency of the SFEC signals on microstructure and residual stress was obtained.

  4. Focused ultrasonic beam behavior at a stress-free boundary and applicability for measuring nonlinear parameter in a reflection mode

    Jeong, Hyunjo; Zhang, Shuzeng; Li, Xiongbing


    In this work, we employ a focused beam theory to modify the phase reversal at the stress-free boundary, and consequently enhance the second harmonic generation during its back-propagation toward the initial source position. We first confirmed this concept through experiment by using a spherically focused beam at the water-air interface, and measuring the reflected second harmonic and comparing with a planar wave reflected from the same stress-free or a rigid boundary. In order to test the feasibility of this idea for measuring the nonlinearity parameter of solids in a reflection mode, a focused nonlinear ultrasonic beam is modeled for focusing at and reflection from a stress-free boundary. A nonlinearity parameter expression is then defined together with diffraction and attenuation corrections.

  5. Influence of acoustoelastic coefficient on wave time of flight in stress measurement in piezoelectric self-excited system

    Kwaśniewki, Janusz; Dominik, Ireneusz; Lalik, Krzysztof; Holewa, Karolina


    This paper presents the Self-excited Acoustical System (SAS) in elastic construction stress change measurement. The system is based on the acoustical autoresonance phenomena and enables an indirect measurement of the construction effort level. The essence of the SAS system is to use a piezoelectric vibration emitter and a piezoelectric vibration receiver placed at a distance, which are coupled with a proper power amplifier, and which are operating in a closed loop with a positive feedback. This causes the excitation of the system. The change of the velocity of wave propagation, which is associated with the change of the resonance frequency in the system is caused by the stress change in the examined material. A variable, which determines the change of the acoustic wave velocity, is called an acoustoelastic coefficient β. Such a coefficient allows to determine the absolute stress value in the tested material.

  6. The Border Community & Immigration Stress Scale: A Preliminary Examination of a Community Responsive Measure in Two Southwest Samples

    Carvajal, Scott C.; Rosales, Cecilia; Rubio-Goldsmith, Raquel; Sabo, Samantha; Ingram, Maia; McClelland, Debra Jean; Redondo, Floribella; Torres, Emma; Romero, Andrea J.; Oleary, Anna Ochoa; Sanchez, Zoila; de Zapien, Jill Guernsey


    Background Understanding contemporary socio-cultural stressors may assist educational, clinical and policy-level health promotion efforts. This study presents descriptive findings on a new measure, the Border Community & Immigration Stress Scale (BCISS). Methods The data were from two community surveys as part of community based participatory projects conducted in the Southwestern US border region. This scale includes stressful experiences reflected in extant measures, with new items reflecting heightened local migration pressures and health care barriers. Results Stressors representing each main domain, including novel ones, were reported with frequency and at high intensity in the predominantly Mexican-descent samples. Total stress was also significantly associated with mental and physical health indicators. Discussion The study suggests particularly high health burdens tied to the experience of stressors in the US border region. Further, many of the stressors are also likely relevant for other communities within developed nations also experiencing high levels of migration. PMID:22430894

  7. Effect of Young's modulus evolution on residual stress measurement of thermal barrier coatings by X-ray diffraction

    Chen, Q.; Mao, W. G.; Zhou, Y. C.; Lu, C.


    Subjected to thermal cycling, the apparent Young's modulus of air plasma-sprayed (APS) 8 wt.% Y 2O 3-stabilized ZrO 2 (8YSZ) thermal barrier coatings (TBCs) was measured by nanoindentation. Owing to the effects of sintering and porous microstructure, the apparent Young's modulus follows a Weibull distribution and changes from 50 to 93 GPa with an increase of thermal cycling. The evolution of residual stresses in the top coating of an 8YSZ TBC system was determined by X-ray diffraction (XRD). The residual stresses derived from the XRD data are well consistent with that obtained by the Vickers indention. It is shown that the evolution of Young's modulus plays an important role in improving the measurement precision of residual stresses in TBCs by XRD.

  8. [Measurement method of arterial shear stress of rats model based on ultrasonic particle imaging velocimetry].

    Xhu, Yiheng; Qian, Ming; Niu, Lili; Zheng, Hairong; Lu, Guangwen


    The development and progression of atherosclerosis and thrombosis are closely related to changes of hemodynamics parameters. Ultrasonic pulse wave Doppler technique is normally used for noninvasively blood flow imaging. However, this technique only provides one-dimensional velocity and depends on the angle between the ultrasound beam and the local velocity vector. In this study, ultrasonic particle image velocimetry method was used to assess whole field hemodynamic changes in normal blood vessels. By using the polynomial fitting method, we investigated the velocity gradient and assessed the shear in different blood flow velocity of 10 healthy rats. It was found that using four polynomial fitting could result in optimal measurement results. The results obtained by ultrasonic particle image velocimetry accorded with the results obtained using Doppler technique. The statistical average of cyclical vessel wall shear stress was positively related to the locational mean velocity. It is proven that ultrasonic particle image velocimetry method could be used to assess directly the real-time whole field hemodynamic changes in blood vessels and was non-invasively, and should be a good prosperous technique for monitoring complex blood flow in stenotic ar- teries.

  9. High temperature gradient micro-sensor for wall shear stress and flow direction measurements

    Ghouila-Houri, C.; Claudel, J.; Gerbedoen, J.-C.; Gallas, Q.; Garnier, E.; Merlen, A.; Viard, R.; Talbi, A.; Pernod, P.


    We present an efficient and high-sensitive thermal micro-sensor for near wall flow parameters measurements. By combining substrate-free wire structure and mechanical support using silicon oxide micro-bridges, the sensor achieves a high temperature gradient, with wires reaching 1 mm long for only 3 μm wide over a 20 μm deep cavity. Elaborated to reach a compromise solution between conventional hot-films and hot-wire sensors, the sensor presents a high sensitivity to the wall shear stress and to the flow direction. The sensor can be mounted flush to the wall for research studies such as turbulence and near wall shear flow analysis, and for technical applications, such as flow control and separation detection. The fabrication process is CMOS-compatible and allows on-chip integration. The present letter describes the sensor elaboration, design, and micro-fabrication, then the electrical and thermal characterizations, and finally the calibration experiments in a turbulent boundary layer wind tunnel.

  10. Direct bed stress measurements under solitary tsunami-type waves and breaking tsunami wave fronts

    JayaKumar, S.; Baldock, T.E.

    in the stability of submarine sediments. Laboratory experiments were performed to obtain total shear stresses under tsunami-type breaking and non-breaking solitary waves. The total stress comprises arises from a pressure gradient force and a skin friction shear...

  11. Measurement and Interpretation of Flow Stress Data for the Simulation of Metal-Forming Processes


    fitting constants that differ in each equation): Ludwik Equation: c)εb(aσ += , (29) Voce Equation: )]εcexp([1*a][baσ −−−+= (30) Swift...stress at low strains (ɘ.2) and to overestimate the stress for high strains. For heavily prestrained materials, c ~ 1. The Voce and Swift equations tend

  12. Measures of Model Uncertainty in the Assessment of Primary Stresses in Ship Structures

    Östergaard, Carsten; Dogliani, Mario; Guedes Soares, Carlos;


    The paper considers various models and methods commonly used for linear elastic stress analysis and assesses the uncertainty involved in their application to the analysis of the distribution of primary stresses in the hull of a containership example, through statistical evaluations of the results...

  13. An automated system for the measurement of magnetostriction in electrical steel sheet under applied stress

    Anderson, P I; Stanbury, H J


    The design of an automated system for the rapid assessment of the AC magnetostriction in electrical steel sheet under linear applied stress in the range +-10 MPa is described in detail. Typical results are presented showing the effect of induction on the unstressed material together with plots of the harmonics of magnetostriction and specific total loss versus applied stress.

  14. The Use of Neuropeptide Y as a Measurement of the Effectiveness of Stress Inoculation


    Sarinopoulos, Mackiewicz, Schaefer, & Davidson (2006) demonstrated that, when stress is certain to occur, emotional reactions mimic the responses...corresponding increase in emotional response, so the body experiences a greater stress reaction than if it had been prepared through expectation of... Ekman , & Heilig, 1998; Thorsell, Michalkiewicz, Dumont, Quirion, Caberlotto, Rimondini, Mathe, & Heilig, 2000). Since this research, similar effects

  15. A Novel Instrument and Methodology for the In-Situ Measurement of the Stress in Thin Films

    Broadway, David M.; Omokanwaye, Mayowa O.; Ramsey, Brian D.


    We introduce a novel methodology for the in-situ measurement of mechanical stress during thin film growth utilizing a highly sensitive non-contact variation of the classic spherometer. By exploiting the known spherical deformation of the substrate the value of the stress induced curvature is inferred by measurement of only one point on the substrate's surface-the sagittal. From the known curvature the stress can be calculated using the well-known Stoney equation. Based on this methodology, a stress sensor has been designed which is simple, highly sensitive, compact, and low cost. As a result of its compact nature, the sensor can be mounted in any orientation to accommodate a given deposition geometry without the need for extensive modification to an already existing deposition system. The technique employs the use of a double side polished substrate that offers good specular reflectivity and is isotropic in its mechanical properties, such as oriented crystalline silicon or amorphous soda lime glass, for example. The measurement of the displacement of the uncoated side during deposition is performed with a high resolution (i.e. 5nm), commercially available, inexpensive, fiber optic sensor which can be used in both high vacuum and high temperature environments (i.e. 10(exp-7) Torr and 480oC, respectively). A key attribute of this instrument lies in its potential to achieve sensitivity that rivals other measurement techniques such as the micro cantilever method but, due to the comparatively larger substrate area, offers a more robust and practical alternative for subsequent measurement of additional characteristics of the film that can might be correlated to film stress. We present measurement results of nickel films deposited by magnetron sputtering which show good qualitative agreement to the know behavior of polycrystalline films previously reported by Hoffman.

  16. The Emotional Stress Reaction Questionnaire (ESRQ): Measurement of Stress Reaction Level in Field Conditions in 60 Seconds


    Woods & Hampson, 2005) designed to measure the five dimensions/factors in the Big Five model of personality ( Costa & McCrae , 1992): Extraversion...National Defense University Press. Costa , P. T. Jr, & McCrae , R. R. (1992). NEO PI-R: Professional manual. Odessa, FL: Psychological Assessment

  17. Simulation and in situ measurement of stress distribution in a polymer electrolyte membrane fuel cell stack

    de la Cruz, Javier; Cano, Ulises; Romero, Tatiana


    A critical parameter for PEM fuel cell's electric contact is the nominal clamping pressure. Predicting the mechanical behavior of all components in a fuel cell stack is a very complex task due to the diversity of materials properties. Prior to the integration of a 3 kW PEMFC power plant, a numerical simulation was performed in order to obtain the mechanical stress distribution for two of the most pressure sensitive components of the stack: the membrane, and the graphite plates. The stress distribution of the above mentioned components was numerically simulated by finite element analysis and the stress magnitude for the membrane was confirmed using pressure films. Stress values were found within the elastic zone which guarantees mechanical integrity of fuel cell components. These low stress levels particularly for the membrane will allow prolonging the life and integrity of the fuel cell stack according to its design specifications.

  18. Measurement of specific medical school stress: translation of the "Perceived Medical School Stress Instrument" to the German language.

    Kötter, Thomas; Voltmer, Edgar


    Zielsetzung: Medizinstudierende sind spezifischen Stressoren ausgesetzt. Als Folge der Stressbelastung kommt es bei Medizinstudierenden im Vergleich zu gleichaltrigen Berufstätigen häufiger zu Ängsten, Depressionen und Burn-out. Vitaliano et al. haben bereits 1984 ein 13 Items umfassendes Instrument zur Messung der spezifischen Stressbelastung von Medizinstudierenden, das „Perceived Medical School Stress Instrument“ (PMSS), vorgestellt. Es wurde seitdem im englischsprachigen Bereich breit eingesetzt und validiert. Bislang liegt jedoch keine deutschsprachige Version des Instrumentes vor. Ziel des Projektes war die Übersetzung des PMSS in die deutsche Sprache, um es im Rahmen von Studien im deutschsprachigen Raum einzusetzen.Methodik: Die englischsprachigen Items des PMSS wurden von drei Untersuchern in die deutsche Sprache übersetzt. Die Versionen wurden synoptisch gegenübergestellt und auf dieser Basis wurde für jedes Item eine deutschsprachige Version formuliert. Diese Versionen wurden von Muttersprachlerinnen in die englische Sprache zurückübersetzt. Auf der Basis dieser Rückübersetzungen, eines kognitiven Debriefings an 19 deutschen Medizinstudierenden und einer testtheoretischen Evaluation an 169 deutschen Medizinstudierenden wurden dann die endgültigen deutschsprachigen Formulierungen festgelegt. Ergebnisse: Das PMSS konnte ohne größere Schwierigkeiten in die deutsche Sprache übersetzt werden. Sowohl zwischen den Übersetzungen in die deutsche Sprache als auch zwischen beiden Rückübersetzungen waren die Übereinstimmungen groß. Bei Diskrepanzen erfolgte die Einigung schnell und unkompliziert. Der Einsatz der deutschsprachigen Version erbrachte einen guten Wert für die Reliabilität (Cronbachs Alpha 0,81).Schlussfolgerung: Es steht nun auch für deutschsprachigen Raum ein spezifisches Instrument zur Messung der Stressbelastung von Medizinstudierenden zur Verfügung.

  19. Skin autofluorescence, a measure of cumulative metabolic stress and advanced glycation end products, predicts mortality in hemodialysis patients

    Meerwaldt, R; Hartog, JWL; Graaff, R; Huisman, RJ; Links, TP; den Hollander, NC; Thorpe, [No Value; Baynes, JW; Navis, G; Gans, ROB; Smit, AJ


    Tissue advanced glycation end products (AGE) are a measure of cumulative metabolic stress and trigger cytokines driven inflammatory reactions. AGE are thought to contribute to the chronic complications of diabetes and ESRD. Tissue autofluorescence is related to the accumulation of AGE. Therefore,

  20. The Effect of Meditation on Self-Reported Measures of Stress, Anxiety, Depression, and Perfectionism in a College Population

    Burns, Jaimie L.; Lee, Randolph M.; Brown, Lauren J.


    The effects of meditation, specifically Transcendental Meditation (TM), on college students' experience of stress, anxiety, depression, and perfectionistic thoughts was investigated using 43 undergraduate students. Self-report measures of the variables were completed prior to the start of the study. Student groups were trained in TM and practiced…

  1. Measuring cortisol in the water as an indicator of stress caused by increased loading density in common carp (Cyprinus carpio)

    Ruane, N.M.; Komen, J.


    The influence of a high loading density for a period of 28 days on growth, water quality and stress parameters in common carp (Cyprinus carpio) was investigated. In addition, cortisol levels in the water were measured during the experiment to investigate if a relationship exists between loading

  2. The Effect of Meditation on Self-Reported Measures of Stress, Anxiety, Depression, and Perfectionism in a College Population

    Burns, Jaimie L.; Lee, Randolph M.; Brown, Lauren J.


    The effects of meditation, specifically Transcendental Meditation (TM), on college students' experience of stress, anxiety, depression, and perfectionistic thoughts was investigated using 43 undergraduate students. Self-report measures of the variables were completed prior to the start of the study. Student groups were trained in TM and practiced…

  3. Skin autofluorescence, a measure of cumulative metabolic stress and advanced glycation end products, predicts mortality in hemodialysis patients

    Meerwaldt, R; Hartog, JWL; Graaff, R; Huisman, RJ; Links, TP; den Hollander, NC; Thorpe, [No Value; Baynes, JW; Navis, G; Gans, ROB; Smit, AJ


    Tissue advanced glycation end products (AGE) are a measure of cumulative metabolic stress and trigger cytokines driven inflammatory reactions. AGE are thought to contribute to the chronic complications of diabetes and ESRD. Tissue autofluorescence is related to the accumulation of AGE. Therefore, sk


    Smaranda CIMPOERU


    Full Text Available Measuring financial stress is a key research issue that has gained a lot of interest in the years following the extreme events from 2007. Although a lot of models were used for assessing and measuring financial stress, none of the managed to forecast the global crisis from 2007. We can identify three generation of models plus the approach of measuring the probability of a crisis with financial stress indexes. In our paper, we review briefly the most important approaches in measuring financial stress from the specialty literature and we propose a case study for European countries. We apply a logistic regression model for panel data, using macroeconomic indicators with the goal of finding the most important triggers for a financial crisis or otherwise said, the early warning signals of a crisis. We obtain very good accuracy of the proposed model (85% and the results are of great importance for policy makers and also for researchers. The study highly contributes to the specialty literature, considering that it is the first early warning system developed on macroeconomic indicators only for European advanced and emerging economies. Moreover, it includes in the analysis a period of five year following 2007.

  5. Full elastic strain and stress tensor measurements from individual dislocation cells in copper through-Si vias.

    Levine, Lyle E; Okoro, Chukwudi; Xu, Ruqing


    Nondestructive measurements of the full elastic strain and stress tensors from individual dislocation cells distributed along the full extent of a 50 µm-long polycrystalline copper via in Si is reported. Determining all of the components of these tensors from sub-micrometre regions within deformed metals presents considerable challenges. The primary issues are ensuring that different diffraction peaks originate from the same sample volume and that accurate determination is made of the peak positions from plastically deformed samples. For these measurements, three widely separated reflections were examined from selected, individual grains along the via. The lattice spacings and peak positions were measured for multiple dislocation cell interiors within each grain and the cell-interior peaks were sorted out using the measured included angles. A comprehensive uncertainty analysis using a Monte Carlo uncertainty algorithm provided uncertainties for the elastic strain tensor and stress tensor components.

  6. Time-Resolved Particle Image Velocimetry Measurements with Wall Shear Stress and Uncertainty Quantification for the FDA Nozzle Model.

    Raben, Jaime S; Hariharan, Prasanna; Robinson, Ronald; Malinauskas, Richard; Vlachos, Pavlos P


    We present advanced particle image velocimetry (PIV) processing, post-processing, and uncertainty estimation techniques to support the validation of computational fluid dynamics analyses of medical devices. This work is an extension of a previous FDA-sponsored multi-laboratory study, which used a medical device mimicking geometry referred to as the FDA benchmark nozzle model. Experimental measurements were performed using time-resolved PIV at five overlapping regions of the model for Reynolds numbers in the nozzle throat of 500, 2000, 5000, and 8000. Images included a twofold increase in spatial resolution in comparison to the previous study. Data was processed using ensemble correlation, dynamic range enhancement, and phase correlations to increase signal-to-noise ratios and measurement accuracy, and to resolve flow regions with large velocity ranges and gradients, which is typical of many blood-contacting medical devices. Parameters relevant to device safety, including shear stress at the wall and in bulk flow, were computed using radial basis functions. In addition, in-field spatially resolved pressure distributions, Reynolds stresses, and energy dissipation rates were computed from PIV measurements. Velocity measurement uncertainty was estimated directly from the PIV correlation plane, and uncertainty analysis for wall shear stress at each measurement location was performed using a Monte Carlo model. Local velocity uncertainty varied greatly and depended largely on local conditions such as particle seeding, velocity gradients, and particle displacements. Uncertainty in low velocity regions in the sudden expansion section of the nozzle was greatly reduced by over an order of magnitude when dynamic range enhancement was applied. Wall shear stress uncertainty was dominated by uncertainty contributions from velocity estimations, which were shown to account for 90-99% of the total uncertainty. This study provides advancements in the PIV processing methodologies over

  7. Measuring lifetime stress exposure and protective factors in life course research on racial inequality and birth outcomes.

    Malat, Jennifer; Jacquez, Farrah; Slavich, George M


    There has been a long-standing interest in better understanding how social factors contribute to racial disparities in health, including birth outcomes. A recent emphasis in this context has been on identifying the effects of stress exposure and protective factors experienced over the entire lifetime. Yet despite repeated calls for a life course approach to research on this topic, very few studies have actually assessed how stressors and protective factors occurring over women's lives relate to birth outcomes. We discuss this issue here by describing how challenges in the measurement of lifetime stress exposure and protective factors have prevented researchers from developing an empirically-based life course perspective on health. First, we summarize prevailing views on racial inequality and birth outcomes; second, we discuss measurement challenges that exist in this context; and finally, we describe both new tools and needed tools for assessing lifetime stress exposure and suggest opportunities for integrating information on stress exposure and psychosocial protective factors. We conclude that more studies are needed that integrate information about lifetime stress exposures and the protective factors that promote resilience against such exposures to inform policy and practice recommendations to reduce racial disparities in birth outcomes.

  8. Contraction stresses in dental composites adjacent to and at the bonded interface as measured by crack analysis.

    Yamamoto, Takatsugu; Nishide, Akihito; Swain, Michael V; Ferracane, Jack L; Sakaguchi, Ronald L; Momoi, Yasuko


    The objective of this study was to calculate stresses produced by polymerization contraction in regions surrounding a dental resin composite restoration. Initial cracks were made with a Vickers indenter at various distances from the edge of a cylindrical hole in a soda-lime glass disk. Indentation crack lengths were measured parallel to tangents to the hole edge. Resin composites (three brands) were placed in the hole and polymerized (two light irradiation protocols) at equal radiation exposures. The crack lengths were re-measured at 2 and 10 min after irradiation. Radial tensile stresses due to polymerization contraction at the location of the cracks (σ(crack)) were calculated from the incremental crack lengths and the fracture toughness K(c) of the glass. Contraction stresses at the composite-glass bonded interface (σ(interface)) were calculated from σ(crack) on the basis of the simple mechanics of an internally pressurized thick-walled cylinder. The greater the distance or the shorter the time following polymerization, the smaller was σ(crack). Distance, material, irradiation protocol and time significantly affected σ(crack). Two-step irradiation resulted in a significant reduction in the magnitude of σ(interface) for all resin composites. The contraction stress in soda-lime glass propagated indentation cracks at various distances from the cavity, enabling calculation of the contraction stresses.

  9. Relation between Coda-Q and stress loaded to an elastic body. -parameters of material conditions derived by stochastic measurement-

    Okamoto, K.; Mikada, H.; Goto, T.; Takekawa, J.


    Seismic coda is formed by superposed signals caused by scatterers. When heterogeneous condition is changed due to crustal deformations, coda-Q should vary reflecting the physical state if the materials. When the spatial scale of scatters in a medium becomes comparable with or smaller then the wavelength of seismic waves traveling through, it becomes very difficult to analyze the coda-wave quantitatively in terms of the location of scatterers, scattering mechanisms, etc. For inhomogeneous medium, it is natural to deal with stochastic methodologies to interpret seismic data. In this regard coda-Q has been frequently used as a stochastic measure of the medium in which seismic waves propagate. Since objectives of recent structural surveys include spatiotemporal or time-lapse variation of physical properties of underground medium, we propose a new geophysical monitoring method using the stochastic parameters if these parameters reflect changes of physical state of the medium. Several observed examples are reported that the relationship between the coda-Q and the number of earthquakes (e.g., Aki,2004). Aki (2004) said that the interrelation between the coda-Q and the number of earthquakes might be a key to understand the change in the state of crustal stress field. Here, we hypothesize that the change of the coda- Q reflects that of the stress magnitude and direction and try to focus on the relationship between the coda-Q and loaded stress which could cause earthquakes. The purpose of this study is to relate this relationship to non-stochastic quantity of the underground physical state, i.e., the stress to test our hypothesis. We employ two methods to achieve our objectives. One is Finite Difference Method (FDM), and the other is Boundary Integral Equation Method (BIEM). FDM is superior in the calculation of large field and saving calculation time. BIEM is superior in the free shape of boundaries. These two methods are applied to a numerical model of elastic body

  10. A robust method to measure residual stress in micro-structure

    KANG Yi-lan; QIU Wei; LEI Zhen-kun


    An experimental investigation on the residual stress in porous silicon micro-structure by means of micro-Raman spectroscopy is presented. It is shown by detecting the Raman peak shifts on the surfaces and cross-sections of electrochemical etched porous silicon samples with different porosities that serious residual stresses distribute complicatedly within the whole porous silicon structure. It is proved that micro-Raman spectroscopy is an effective method for residual stress testing on the micro-structures applied in optoelectronics and microelectronics.

  11. Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: Lack of concordance between mortality and physiological measures of stress

    Davis, M.W.; Olla, B.L.; Schreck, C.B.


    In a series of laboratory studies designed to simulate bycatch processes, sablefish Anoplopoma fimbria were either hooked for up to 24 h or towed in a net for 4 h and then subjected to an abrupt transfer to elevated sea water temperature and air. Mortality did not result from hooking or net towing followed by exposure to air, but increased for both capture methods as fish were exposed to elevated temperatures, reflecting the magnifying effect of elevated temperature on mortality. Hooking and exposure to air resulted in increased plasma cortisol and lactate concentrations, while the combination of hooking and exposure to elevated temperature and air resulted in increased lactate and potassium concentrations. In fish that were towed in a net and exposed to air, cortisol, lactate, potassium and sodium concentrations increased, but when subjected to elevated temperature and air, no further increases occurred above the concentrations induced by net towing and air, suggesting a possible maximum of the physiological stress response. The results suggest that caution should be exercised when using physiological measures to quantify stress induced by capture and exposure to elevated temperature and air, that ultimately result in mortality, since the connections between physiological stress and mortality in bycatch processes remain to be fully understood.

  12. Bioimpedance-Based Wearable Measurement Instrumentation for Studying the Autonomic Nerve System Response to Stressful Working Conditions

    Ferreira, J.; Álvarez, L.; Buendía, R.; Ayllón, D.; Llerena, C.; Gil-Pita, R.; Seoane, F.


    The assessment of mental stress on workers under hard and stressful conditions is critical to identify which workers are not ready to undertake a mission that might put in risk their own life and the life of others. The ATREC project aims to enable Real Time Assessment of Mental Stress of the Spanish Armed Forces during military activities. Integrating sensors with garments and using wearable measurement devices, the following physiological measurements were recorded: heart and respiration rate, skin galvanic response as well as peripheral temperature. The measuring garments are the following: a sensorized glove, an upper-arm strap and a repositionable textrode chest strap system with 6 textrodes. The implemented textile-enabled instrumentation contains: one skin galvanometer, two temperature sensors, for skin and environmental, and an Impedance Cardiographer/Pneumographer containing a 1 channel ECG amplifier to record cardiogenic biopotentials. The implemented wearable systems operated accordingly to the specifications and are ready to be used for the mental stress experiments that will be executed in the coming phases of the project in healthy volunteers.

  13. Measurement of residual stresses in a multi-pass low alloy ferritic steel weld using X-ray diffraction

    McDonald, E.J.; Exworthy, L.F.; Flewitt, P.E.J. [Magnox Generation, Berkeley (United Kingdom); Hallam, K. [Interface Analysis Centre, Univ. of Bristol (United Kingdom); Bell, W. [Mitsui Babcock Energy Ltd, Renfrew (United Kingdom)


    A trial part through-section excavation manual metal arc repair weld, designed with a view to minimising residual stresses, was prepared by using a critical combination of weld metal strength, bead size and deposition pattern. The repair was in a low alloy ferritic CrMoV steel plate, and the weldment was made using a lower strength C-Mn steel weld metal. Residual stresses have been measured to a high spatial resolution, 1.5 mm, across the weldment using the X-ray diffraction technique with Cr K{alpha} X-radiation. Peak tensile stresses have been identified in the heat affected zone in the parent plate adjacent to the weld metal. Further measurements have been made using the rosette strain gauge centre hole relaxation and deep hole drilling techniques. Results from the experimental techniques are compared and the measured residual stress profiles are discussed with respect to the predictions of a finite element model for this particular multi-pass repair weld. (orig.)

  14. X-ray residual stress measurement of alumina detonation coating. Bakuhatsu yosha alumina himaku no X sen zanryu oryoku sokutei

    Tanaka, K.; Mine, N. (Kyoto University, Kyoto (Japan). Faculty of Engineering); Suzuki, K. (Niigata University, Niigata (Japan). Faculty of Engineering); Kawase, R. (Ariake Institute of Technology, Fukuoka (Japan))


    Alumina ceramics were coated on mild steel by a detonation gun with different amounts of detonation gas, and residual stresses in coated films were measured by X-ray diffraction from the (844) plane of {gamma}-alumina by Cu-K {alpha} radiation. Cracks and pores were observed on the film surface and cross section. The pore increased and the film bulk density decreased with a decrease in amount of detonation gas, and the mechanical Young {prime} s modulus decreased with an increase in pore. Since strains measured mechanically were those in the film bulk with pores while strains measured by X-ray were average values in only crystalline phases, the X-ray Young {prime} s modulus was larger than the mechanical one. The residual stress in films was a large tensile stress and distributed uniformly in films. The residual tensile stress decreased with an increase in amount of detonation gas, however, it was rather insensitive to the film thickness and surface grinding after coating. 10 refs., 8 figs., 2 tabs.


    亚敏; 戴福隆; 谢惠民; 吕坚


    Hole-drilling method is one of the most convenient methods for engineering residual ment data, hole-drilling technique can be used to solve non-uniform residual stress problems, both (MIIHD) for non-uniform residual stress measurement is introduced. Three dimensional finite element model is constructed by ABAQUS to obtain the coefficients for the residual stress calculation.An experimental system including real-time measurement, automatic data processing and residual stresses calculation is established. Two applications for non-uniform in-depth residual stress of surface nanocrystalline material and non-uniform in-plane residual stress of friction stir welding are presented.Experimental results show that MIIHD is effective for both non-uniform in-depth and in-plane residual stress measurements.

  16. Cortisol Variability and Self-reports in the Measurement of Work-related Stress

    Karlson, Björn; Eek, Frida; Hansen, Åse Marie


    We examined whether a high cortisol awakening response (CAR) and low cortisol decline over the day (CDD) are related to self-reported work stress and well-being, and whether there are gender differences in these relationships. Three hundred eighty-three working men and women responded to a survey...... was associated only with higher job demands, but the self-report scores showed a number of interactions between cortisol group and gender. Among women, those showing a low CDD, compared with those with a higher CDD, had more favourable scores on a number of job stress factors and symptom load. In contrast, among...... men, a similar comparison showed those with low CDD to have poorer scores on job stress factors and symptom load. We conclude that individuals displaying high CAR or low CDD differ from those not displaying these cortisol profi les in self-report of work stress and well-being, and that gender...


    Knowles, C. R.


    Full Text Available Selective laser melting (SLM of Ti-6Al-4V has significant potential in the aerospace and biotechnology industries. SLM employs a focused laser beam to melt successive layers of metallic powder into complex components. This process can result in the generation of high thermally-induced residual stresses. These residual stresses, together with micro-flaws/ pores from the inherent fabrication process, may lead to premature fatigue crack initiation and propagation at relatively low cyclic stresses. The hole-drilling strain gauge method was used to evaluate residual stresses within SLM Ti-6Al-4V specimens, with the intention of understanding the associated mechanisms for the successful application of SLM Ti-6Al-4V in industry.

  18. Measuring Shear Stress with a Microfluidic Sensor to improve Aerodynamic Efficiency Project

    National Aeronautics and Space Administration — Skin friction drag is directly proportional to the local shear stress of a surface and can be the largest factor in an aerodynamic body's total parasitic drag. The...

  19. Experimental measurements of surface damage and residual stresses in micro-engineered plasma facing materials

    Rivera, David; Wirz, Richard E.; Ghoniem, Nasr M.


    The thermomechanical damage and residual stresses in plasma-facing materials operating at high heat flux are experimentally investigated. Materials with micro-surfaces are found to be more resilient, when exposed to cyclic high heat flux generated by an arc-jet plasma. An experimental facility, dedicated to High Energy Flux Testing (HEFTY), is developed for testing cyclic heat flux in excess of 10 MW/m2. We show that plastic deformation and subsequent fracture of the surface can be controlled by sample cooling. We demonstrate that W surfaces with micro-pillar type surface architecture have significantly reduced residual thermal stresses after plasma exposure, as compared to those with flat surfaces. X-ray diffraction (XRD) spectra of the W-(110) peak reveal that broadening of the Full Width at Half Maximum (FWHM) for micro-engineered samples is substantially smaller than corresponding flat surfaces. Spectral shifts of XRD signals indicate that residual stresses due to plasma exposure of micro-engineered surfaces build up in the first few cycles of exposure. Subsequent cyclic plasma heat loading is shown to anneal out most of the built-up residual stresses in micro-engineered surfaces. These findings are consistent with relaxation of residual thermal stresses in surfaces with micro-engineered features. The initial residual stress state of highly polished flat W samples is compressive (≈ -1.3 GPa). After exposure to 50 plasma cycles, the surface stress relaxes to -1.0 GPa. Micro-engineered samples exposed to the same thermal cycling show that the initial residual stress state is compressive at (- 250 MPa), and remains largely unchanged after plasma exposure.

  20. Review of magnetoacoustic residual stress measurement technique for iron-like ferromagnetic alloys

    Namkung, M.; Utrata, D.; Langlois, P.; Kushnick, P. W.; Grainger, J. L.


    It is shown that the elastic moduli of ironlike ferromagnetics depends explicitly on the state of 90 deg domain walls: the more 90 deg domain wall area available, the lower the elastic modulus. New experimental results obtained for three types of carbon and pure iron samples are presented. The magnetoacoustic response due to magnetization perpendicular to the uniaxial stress axis is considered as well as the magnetoacoustic response due to magnetization parallel to the uniaxial stress axis.

  1. New Computer Automated Holo-Photoelastic Method For Measuring Planar Principal Stress Magnitudes And Orientation

    Brown, G. M.; Sullivan, J. L.


    A complete experimental determination of the stress and strain fields in an arbitrary deformed structure is generally unavailable. However, for two dimensional elasticity problems, such determinations are possible since in those cases one needs only to solve for three stresses (two normal and one shear). In fact, such determinations have been conducted quite often. By using isochromatic and isoclinic photoelastic data, the shear difference and numerical iteration techniques (1) and the least squares techniques (2) have been successfully used for complete stress field determinations of two dimensional elasticity problems. Though the shear difference technique can be particularly sensitive to cumulative errors resulting from numerical integration, the least squares technique is not affected by this and appears to yield better accuracy. The methods just cited use both experimental data and one or more mechanics conditions(e.g., the equations of equilibrium) to determine the stress field. However, the stress field can also be obtained from experimental data alone for planar elasticity problems, if there is enough of it to solve for the three stresses. For example, the Moire* technique or the combination of isochromatic, isoclinic, and isopachic data (for transparent models) can be used for such determinations. Further, with the marriage of advanced image processing equipment to computers, such analyses using this type of data can be conveniently conducted. It is even possible that such analyses could be more accurate than those using the combined experimental/numerical techniques cited above. The purposes of this report are two fold: i) to describe a single apparatus for obtaining isochromatic, isopachic, and isoclinic results for complete stress field determinations of two dimensional transparent models, and ii) to compare experimental and theoretical stress field values for an antisymmetrically loaded beam obtained using that apparatus.

  2. Thermal stress measurement in continuous welded rails using the hole-drilling method

    Zhu, Xuan; Lanza di Scalea, Francesco; Fateh, Mahmood


    The absence of expansion joints in Continuous Welded Rail (CWR) has created the need for the railroad industry to determine the in-situ level of thermal stresses so as to prevent train accidents caused by rail buckling in hot weather and by rail breakage in cold weather. The development of non-destructive or semi-destructive methods for determining the level of thermal stresses in rails is today a high research priority. This study explores the known hole-drilling method as a possible solution to this problem. A new set of calibration coefficients to compute the relieved stress field with the finer hole depth increments was determined by a 3D Finite Element Analysis that modeled the entire hole geometry, including the mechanics of the hole bottom and walls. To compensate the residual stress components, a linear relationship was experimentally established between the longitudinal and the vertical residual stresses of two common sizes of rails, the 136RE and the 141RE, with statistical significance. This result was then utilized to isolate the longitudinal thermal stress component in hole-drilling tests conducted on the 136RE and 141RE thermally-loaded rails at the Large-scale CWR Test-bed of UCSD's Powell Research Laboratories. The results from the Test-bed showed that the hole-drilling procedure, with the appropriate residual stress compensation, can indeed estimate the in-situ thermal stresses to achieve a +/-5°F accuracy of Neutral Temperature determination with a 90% statistical confidence, which is the desired industry gold standard.

  3. Impact of Ramadan Intermittent Fasting on Oxidative Stress Measured by Urinary 15-F2t-Isoprostane

    Mo'ez Al-Islam Ezzat Faris


    fast Ramadan were recruited. Urine and serum sampling and anthropometric and dietary assessments were conducted one week before Ramadan (T0, at the end of the third week of Ramadan (T1, and one month after Ramadan (T2. Biochemical measurements included urinary 15FIP, creatinine, and hematological indices. Results revealed that the urinary level of 15FIP measured at T0 was normal, while they showed a significantly (P<0.05 higher level when measured at T1 concomitant with a significant (P<0.05 increase in the body weight and total body fat percent. In conclusion, results suggest that increased body weight is associated with increased lipid peroxidation and oxidative stress, and the impact of RIF on oxidative stress is mediated by the changes in body weight at the end of the month.

  4. Finite Element Modeling of the Bulk Magnitization of Railroad Wheels to Improve Test Conditions for Magnetoacoustic Residual Stress Measurements

    Fulton, J. P.; Wincheski, B.; Namkung, M.; Utrata, D.


    The magnetoacoustic measurement technique has been used successfully for residual stress measurements in laboratory samples. However, when used to field test samples with complex geometries, such as railroad wheels, the sensitivity of the method declines dramatically. It has been suggested that the decrease in performance may be due, in part, to an insufficient or nonuniform magnetic induction in the test sample. The purpose of this paper is to optimize the test conditions by using finite element modeling to predict the distribution of the induced bulk magnetization of railroad wheels. The results suggest that it is possible to obtain a sufficiently large and uniform bulk magnetization by altering the shape of the electromagnet used in the tests. Consequently, problems associated with bulk magnetization can be overcome, and should not prohibit the magnetoacoustic technique from being used to make residual stress measurements in railroad wheels. We begin by giving a brief overview of the magnetoacoustic technique as it applies to residual stress measurements of railroad wheels. We then define the finite element model used to predict the behavior of the current test configuration along with the nonlinear constitutive relations which we obtained experimentally through measurements on materials typically used to construct both railroad wheels and electromagnets. Finally, we show that by modifying the pole of the electromagnet it is possible to obtain a significantly more uniform bulk magnetization in the region of interest.

  5. Considerations on the choice of experimental parameters in residual stress measurements by hole-drilling and ESPI

    C. Barile


    Full Text Available Residual stresses occur in many manufactured structures and components. Great number of investigations have been carried out to study this phenomenon. Over the years, different techniques have been developed to measure residual stresses; nowadays the combination of Hole Drilling method (HD with Electronic Speckle Pattern Interferometry (ESPI has encountered great interest. The use of a high sensitivity optical technique instead of the strain gage rosette has the advantage to provide full field information without any contact with the sample by consequently reducing the cost and the time required for the measurement. The accuracy of the measurement, however, is influenced by the proper choice of several parameters: geometrical, analysis and experimental. In this paper, in particular, the effects of some of those parameters are investigated: misknowledgment in illumination and detection angles, the influence of the relative angle between the sensitivity vector of the system and the principal stress directions, the extension of the area of analysis and the adopted drilling rotation speed. In conclusion indications are provided to the scope of optimizing the measurement process together with the identification of the major sources of errors that can arise during the measuring and the analysis stages.

  6. The effect of early weaning on feedlot performance and measures of stress in beef calves.

    Arthington, J D; Spears, J W; Miller, D C


    Forty crossbred steers (Brahman x English) were categorized into two groups: 1) early weaned (EW; n = 20); and 2) normal weaned (NW; n = 20). Calves were 89 and 300 d of age at the time of EW and NW, respectively; SEM = 4.4. Early-weaned calves were kept on-site (University of Florida, Ona), provided supplement (1% of BW), and grazed on annual and perennial pastures until NW. At the time of normal weaning, all calves were loaded on a commercial livestock trailer and transported to the North Carolina State University Research Feedlot in Butner (approximately 1,200 km). Upon arrival, calves were stratified by BW and randomly allotted to four pens per weaning age treatment. Individual calf BW and blood samples were collected at the time of normal weaning, on arrival at the feedlot (d 1; 24 h following weaning), and on d 3, 7, 14, 21, and 28 of the receiving period. Individual BW was collected at the start and end of the growing and finishing periods, and feed intake by pen was measured daily. As an estimate of stress during the receiving period, plasma was collected and analyzed for the acute-phase proteins, haptoglobin and ceruloplasmin. Early-weaned calves were lighter (P = 0.03) at normal weaning than NW calves (221 vs. 269 kg; SEM = 10.6). By d 28, EW calves tended (P = 0.12) to be lighter than NW calves (242 vs. 282 kg, respectively). Gain:feed was improved for EW compared with NW calves during both the receiving (G:F = 0.157 vs. 0.081) and growing (0.159 vs. 0.136) periods. There tended (P Carcass measures, including backfat thickness, USDA yield grade, marbling score, and LM area, did not differ between treatments. These data imply that EW calves, which are maintained onsite before shipping, may be more tolerant to the stressors associated with transportation and feed yard entry. Early weaned calves, managed within the system described in this study, may have improved G:F.

  7. Combined heart rate variability and dynamic measures for quantitatively characterizing the cardiac stress status during cycling exercise.

    Chen, Szi-Wen; Liaw, Jiunn-Woei; Chang, Ya-Ju; Chuang, Li-Ling; Chien, Chun-Tse


    In this study, we aimed to seek for different ways of measuring cardiac stress in terms of heart rate variability (HRV) and heart rate (HR) dynamics, and to develop a novel index that can effectively summarize the information reflected by these measures to continuously and quantitatively characterize the cardiac stress status during physical exercise. Standard deviation, spectral measure of HRV as well as a nonlinear detrended fluctuation analysis (DFA) based fractal-like behavior measure of HR dynamics were all evaluated on the RR time series derived from windowed electrocardiogram (ECG) data for the subjects undergoing cycling exercise. We recruited eleven young healthy subjects in our tests. Each subject was asked to maintain a fixed speed under a constant load during the pedaling test. We obtained the running estimates of the standard deviation of the normal-to-normal interval (SDNN), the high-fidelity power spectral density (PSD) of HRV, and the DFA scaling exponent α, respectively. A trend analysis and a multivariate linear regression analysis of these measures were then performed. Numerical experimental results produced by our analyses showed that a decrease in both SDNN and α was seen during the cycling exercise, while there was no significant correlation between the standard lower frequency to higher frequency (LF-to-HF) spectral power ratio of HRV and the exercise intensity. In addition, while the SDNN and α were both negatively correlated with the Borg rating of perceived exertion (RPE) scale value, it seemed that the LF-to-HF power ratio might not have substantial impact on the Borg value, suggesting that the SDNN and α may be further used as features to detect the cardiac stress status during the physical exercise. We further approached this detection problem by applying a linear discriminant analysis (LDA) to both feature candidates for the task of cardiac stress stratification. As a result, a time-varying parameter, referred to as the cardiac

  8. Critical study of the method of calculating virgin rock stresses from measurement results of the CSIR triaxial strain cell

    Vreede, F. A.


    The manual of instructions for the user of the CSIR triaxial rock stress measuring equipment is critically examined. It is shown that the values of the rock stresses can be obtained from the strain gauge records by means of explicit formulae, which makes the manual's computer program obsolete. Furthermore statistical methods are proposed to check for faulty data and inhomogeneity in rock properties and virgin stress. The possibility of non-elastic behavior of the rock during the test is also checked. A new computer program based on the explicit functions and including the check calculations is presented. It is much more efficient than the one in the manual since it does not require computer sub-routines, allowing it to be used directly on any modern computer. The output of the new program is in a format suitable for direct inclusion in the report of an investigation using strain cell results.

  9. Local wall shear stress measurements with a thin plate submerged in the sublayer in wall turbulent flows

    Hua, Dan; Suzuki, Hiroki; Mochizuki, Shinsuke


    A local wall shear stress measurement technique has been developed using a thin plate, referred to as a sublayer plate which is attached to the wall in the sublayer of a near-wall turbulent flow. The pressure difference between the leading and trailing edges of the plate is correlated to the known wall shear stress obtained in the fully developed turbulent channel flow. The universal calibration curve can be well represented in dimensionless form, and the sensitivity of the proposed method is as high as that of the sublayer fence, even if the sublayer fence is enveloped by the linear sublayer. The results of additional experiments prove that the sublayer plate has fairly good angular resolution in detecting the direction of the local wall shear stress vector.

  10. Comparison of estimated core body temperature measured with the BioHarness and rectal temperature under several heat stress conditions.

    Seo, Yongsuk; DiLeo, Travis; Powell, Jeffrey B; Kim, Jung-Hyun; Roberge, Raymond J; Coca, Aitor


    Monitoring and measuring core body temperature is important to prevent or minimize physiological strain and cognitive dysfunction for workers such as first responders (e.g., firefighters) and military personnel. The purpose of this study is to compare estimated core body temperature (Tco-est), determined by heart rate (HR) data from a wearable chest strap physiology monitor, to standard rectal thermometry (Tre) under different conditions.  Tco-est and Tre measurements were obtained in thermoneutral and heat stress conditions (high temperature and relative humidity) during four different experiments including treadmill exercise, cycling exercise, passive heat stress, and treadmill exercise while wearing personal protective equipment (PPE).  Overall, the mean Tco-est did not differ significantly from Tre across the four conditions. During exercise at low-moderate work rates under heat stress conditions, Tco-est was consistently higher than Tre at all-time points. Tco-est underestimated temperature compared to Tre at rest in heat stress conditions and at a low work rate under heat stress while wearing PPE. The mean differences between the two measurements ranged from -0.1 ± 0.4 to 0.3 ± 0.4°C and Tco-est correlated well with HR (r = 0.795 - 0.849) and mean body temperature (r = 0.637 - 0.861).  These results indicate that, the comparison of Tco-est to Tre may result in over- or underestimation which could possibly lead to heat-related illness during monitoring in certain conditions. Modifications to the current algorithm should be considered to address such issues.

  11. Instrumented thick-walled tube method for measuring thermal pressure in fluids and isotropic stresses in thermosetting resins

    Merzlyakov, Mikhail; Simon, Sindee L.; McKenna, Gregory B.


    We have developed a method for measuring the thermal pressure coefficient and cure-induced and thermally induced stresses based on an instrumented thick-walled tube vessel. The device has been demonstrated at pressures up to 330 MPa and temperatures to 300 °C. The method uses a sealed stainless steel thick-walled tube to impose three-dimensional isotropic constraints. The tube is instrumented with strain gauges in hoop and in axial directions and can be used in open or closed configurations. By making measurements of the isotropic stresses as a function of temperature, the method allows determination of the thermal pressure coefficient in both the glassy and rubbery (or liquid) states. The method also can be used to measure isotropic stress development in thermosetting resins during cure and subsequent thermal cycling. Experimental results are presented for sucrose benzoate, di-2-ethylhexylsebacate, and an epoxy resin. The current report shows that the method provides reliable estimates for the thermal pressure coefficient. The thermal pressure coefficient is determined with resolution on the order of 10kPa/K. Among advantages of the method is that the tubes are reusable, even when measurements are made for cure response of thermosetting resins.

  12. In situ stress measurements during electrochemical cycling of lithium-rich cathodes

    Nation, Leah; Li, Juchuan; James, Christine; Qi, Yue; Dudney, Nancy; Sheldon, Brian W.


    Layered lithium transition metal oxides (Li1+xM1-xO2, M = Ni, Mn, Co) are attractive cathode materials for lithium-ion batteries due to their high reversible capacity. However, they suffer from structural changes that lead to substantial voltage fade. In this study, we use stress as a novel way to track irreversible changes in Li1.2Mn0.55Ni0.125Co0.125O2 (LR-NMC) cathodes. A unique and unpredicted stress signature is observed during the first delithiation. Initially, a tensile stress is observed, consistent with volume contraction from lithium removal, however, the stress reverses and becomes compressive with continued charging beyond 4 V vs Li/Li+, indicating volume expansion; this phenomenon is present in the first cycle only. This irreversible stress during delithiation is likely to be at least partially due to oxygen loss and the resulting cation rearrangement. Raman spectroscopy provides evidence of the layered-to-spinel phase transition after cycling in the LR-NMC films, as well as recovery of the original spectra upon re-annealing in an oxygen environment.

  13. Measuring Social Capital Investment: Scale Development and Examination of Links to Social Capital and Perceived Stress.

    Chen, Xinguang; Wang, Peigang; Wegner, Rhiana; Gong, Jie; Fang, Xiaoyi; Kaljee, Linda


    Individuals with greater social capital have better health outcomes. Investment in social capital likely increases one's own social capital, bearing great implications for disease prevention and health promotion. In this study, the authors developed and validated the Social Capital Investment Inventory (SCII). Direct effects of social capital investment on perceived stress, and indirect effects through social capital were examined. 397 Participants from Beijing and Wuhan, China completed surveys. Analyses demonstrated that the SCII has a single factor structure and strong internal consistency. Structural equation modeling showed that individuals who invested more in social capital had greater bonding social capital, and subsequently less perceived stress. Results suggest that disease prevention and health promotion programs should consider approaches to encourage social capital investment; individuals may be able to reduce stress by increasing their investment in social capital. Future research is needed to provide additional empirical support for the SCII and observed structural relationships.

  14. Measuring Social Capital Investment: Scale Development and Examination of Links to Social Capital and Perceived Stress

    Wegner, Rhiana; Gong, Jie; Fang, Xiaoyi; Kaljee, Linda


    Individuals with greater social capital have better health outcomes. Investment in social capital likely increases one’s own social capital, bearing great implications for disease prevention and health promotion. In this study, the authors developed and validated the Social Capital Investment Inventory (SCII). Direct effects of social capital investment on perceived stress, and indirect effects through social capital were examined. 397 Participants from Beijing and Wuhan, China completed surveys. Analyses demonstrated that the SCII has a single factor structure and strong internal consistency. Structural equation modeling showed that individuals who invested more in social capital had greater bonding social capital, and subsequently less perceived stress. Results suggest that disease prevention and health promotion programs should consider approaches to encourage social capital investment; individuals may be able to reduce stress by increasing their investment in social capital. Future research is needed to provide additional empirical support for the SCII and observed structural relationships. PMID:25648725

  15. Measurement of residual stresses in deposited films of SOFC component materials

    Kato, T.; Momma, A.; Nagata, S.; Kasuga, Y. [Electrotechnical Lab., Ibaraki (Japan)


    The stress induced in Solid oxide fuel cells (SOFC)s has important influence on the lifetime of SOFC. But the data on stress in SOFC and mechanical properties of SOW component materials have not been accumulated enough to manufacture SOFC. Especially, the data of La{sub 1-x}Sr{sub x}MnO{sub 3} cathode and La{sub 1-x}Sr{sub x}CrO{sub 3} interconnection have been extremely limited. We have estimated numerically the dependences of residual stress in SOFC on the material properties, the cell structure and the fabrication temperatures of the components, but these unknown factors have caused obstruction to simulate the accurate behavior of residual stress. Therefore, the residual stresses in deposited La{sub 1-x}Sr{sub x}MnO{sub 3} and La{sub 1-x}Sr{sub x}CrO{sub 3} films are researched by the observation of the bending behavior of the substrate strips. The films of SOFC component materials were prepared by the RF sputtering method, because: (1) It can fabricate dense films of poor sinterable material such as La{sub 1-x}Sr{sub x}CrO{sub 3} compared with sintering or plasma spray method. (2) For the complicated material such as perovskite materials, the difference between the composition of a film and that of a target material is generally small. (3) It can fabricate a thick ceramics film by improving of the deposition rate. For example, Al{sub 2}O{sub 3} thick films of 50{mu}m can be fabricated with the deposition rate of approximately 5{mu}m/h industrially. In this paper, the dependence of residual stress on the deposition conditions is defined and mechanical properties of these materials are estimated from the results of the experiments.

  16. Creep measurements confirm steady flow after stress maximum in extension of branched polymer melts

    Javier Alvarez, Nicolas; Román Marín, José Manuel; Huang, Qian;


    We provide conclusive evidence of nonmonotonic mechanical behavior in the extension of long-chain branched polymer melts. While nonmonotonic behavior is known to occur for solids, for the case of polymeric melts, this phenomenon is in direct contrast with current theoretical models. We rule out...... the possibility of the overshoot being an experimental artifact by confirming the existence of steady flow after a maximum in the ratio of stress to strain rate versus strain under both constant stress and constant strain-rate kinematics. This observation indicates the omission of important physics from current...

  17. Measurement of stress relaxation on strips of copper materials. Spannungsrelaxationsmessungen an Baendern aus Kupferwerkstoffen

    Helmenkamp, T.; Steinkamp, W. (Kabel- und Metallwerke Gutehoffnungshuette AG, Osnabrueck (Germany, F.R.). Zentralbereich Technik); Schleicher, K. (Stolberger Metallwerke GmbH und Co. KG, Stolberg (Germany, F.R.))


    The stress relaxation behaviour has been investigated for strips of copper alloys that are commonly used for electromechanical elements like contacts and springs. Among the materials examined, i.e. CuSnMg, CuMg0,7, CuSn6, CuFe2P, CuFe2Mg, CuNi18Zn20, CuNi9Sn2 as well as the age-hardenable alloys CuNi1,5Si0,3 and CuCrZr, the copper-chromium-zirconium alloy proves to have the best stress relaxation properties. (orig.).

  18. X-ray measurements of the depth dependence of stress in gold films

    Brennan, S.; Munkholm, A.; Leung, O. S.; Nix, W. D.


    X-rays are used to determine the stress as a function of depth for five evaporated gold films of 0.8--2.5 microns thickness. The depth dependence is achieved by varying the incident angle of the x-rays, which effects the penetration depth of the x-rays into the film. The films, which have a different thermal expansion coefficient than the silicon substrate, are strained as a result of thermal cycling after deposition. The authors find essentially no variation with stress as a function of depth for these films.

  19. In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing: Preprint

    Spataru, Sergiu; Hacke, Pater; Sera, Dezso


    We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. From the analysis we determine three main categories of failure modes associated with the module degradation consisting of: shunting, recombination losses, increased series resistance losses, and current mismatch losses associated with a decrease in photo-current generation by removal of some cell areas due to cell fractures. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test, and initial and final module flash testing, to determine the power degradation characteristic of the module.

  20. In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing: Preprint

    Spataru, Sergiu; Hacke, Pater; Sera, Dezso


    We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. From the analysis we determine three main categories of failure modes associated with the module degradation consisting of: shunting, recombination losses, increased series resistance losses, and current mismatch losses associated with a decrease in photo-current generation by removal of some cell areas due to cell fractures. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test, and initial and final module flash testing, to determine the power degradation characteristic of the module.

  1. Salutary effects of an attention bias modification mobile application on biobehavioral measures of stress and anxiety during pregnancy.

    Dennis-Tiwary, Tracy A; Denefrio, Samantha; Gelber, Shari


    Stress and anxiety during pregnancy are associated with a range of adverse health outcomes, but there is an unmet need for low-barrier treatments that target stress and anxiety. One such treatment approach, attention bias modification training (ABMT), targets the anxiety-related threat bias, a disruption in attention to and neural processing of threat-related information. It remains unclear, however, whether reducing treatment barriers via mobile delivery of ABMT is effective and whether ABMT efficacy varies depending on individual differences in neural processing of threat. The present study tested whether mobile, gamified ABMT reduced prenatal threat bias, anxiety and stress, and whether ABMT efficacy varied with individual differences in neural responses to threat. Participants were 29 women in their 19th-29th week of pregnancy, randomized to four weeks of an ABMT or placebo training (PT) version of the mobile app using a double-blind design. Self-report of anxiety, depression, and stress were obtained; salivary cortisol was collected at home and in lab in response to stressors to index biological stress reactivity. Threat bias was measured using a computerized attention assay during which EEG was recorded to generate event-related potentials (ERPs) to threat cues. Results showed lower levels of lab cortisol following ABMT versus PT. Although the main effect of ABMT on subjective anxiety was not significant, the magnitude of cortisol reduction was correlated with lower levels of subjective anxiety and threat bias. Those receiving ABMT also reported less anxiety when showing smaller ERPs to threat (P1, P2) prior to training, but, conversely reported more anxiety when showing larger ERPs to threat. Use of gamified, mobile ABMT reduced biobehavioral indices of prenatal stress and anxiety, but effects on anxiety varied with individual differences in cortisol response and neurocognitive indices of early attention to threat. Copyright © 2017 Elsevier B.V. All rights

  2. Tag-based Heart Rate Measurements of Harbor Porpoises During Normal and Noise-exposed Dives to Study Stress Responses


    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Tag-based Heart Rate Measurements of Harbor Porpoises...The typical mammalian startle or stress response to an acoustic stressor is increased heart rate, cardiac output and ventilation rate (Graham 1979...routinely experience. Here we propose to examine the dive heart rate, ventilation rate and activity in both captive and wild porpoise to better understand

  3. Tag-based Heart Rate Measurements of Harbor Porpoises During Normal and Noise-exposed Dives to Study Stress Responses


    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Tag-based Heart Rate Measurements of Harbor Porpoises...acoustic stressor is increased heart rate , cardiac output and ventilation rate (Graham 1979), all which are contrary to the typical marine mammal dive...nitrogen management and can provide information on the level of stress the animals routinely experience. Here we examine the dive heart rate

  4. Using energetic budgets to assess the effects of environmental stress on corals: are we measuring the right things?

    Lesser, M. P.


    Historically, the response of marine invertebrates to their environment, and environmentally induced stress, has included some measurement of their physiology or metabolism. Eventually, this approach developed into comparative energetics and the construction of energetic budgets. More recently, coral reefs, and scleractinian corals in particular, have suffered significant declines due to climate change-related environmental stress. In addition to a number of physiological, biophysical and molecular measurements to assess "coral health," there has been increased use of energetic approaches that have included the measurement of specific biochemical constituents (i.e., lipid concentrations) as a proxy for energy available to assess the potential outcomes of environmental stress on corals. In reading these studies, there appears to be some confusion between energy budgets and carbon budgets. Additionally, many assumptions regarding proximate biochemical composition, metabolic fuel preferences and metabolic quotients have been made, all of which are essential to construct accurate energy budgets and to convert elemental composition (i.e., carbon) to energy equivalents. Additionally, models of energetics such as the metabolic theory of ecology or dynamic energy budgets are being applied to coral physiology and include several assumptions that are not appropriate for scleractinian corals. As we assess the independent and interactive effects of multiple stressors on corals, efforts to construct quantitative energetic budgets should be a priority component of realistic multifactor experiments that would then improve the use of models as predictors of outcomes related to the effects of environmental change on corals.

  5. High pressure measurement of the uniaxial stress of host layers on intercalants and staging transformation of intercalation compounds

    Park, T R; Kim, H; Min, P


    A layered double-hydroxide intercalation compound was synthesized to measure the uniaxial stress the host layers exert on the intercalants. To measure the uniaxial stress, we employed the photoluminescence (PL) from the intercalated species, the Sm ion complex, as it is sensitive to the deformation of the intercalants. Of the many PL peaks the Sm ion complex produces, the one that is independent of the counter-cation environment was chosen for the measurement since the Sm ion complexes are placed under a different electrostatic environment after intercalation. The peak position of the PL was redshifted linearly with increasing hydrostatic pressure on the intercalated sample. Using this pressure-induced redshifting rate and the PL difference at ambient pressure between the pre-intercalation and the intercalated ions, we found that, in the absence of external pressure, the uniaxial stress exerted on the samarium ion complexes by the host layers was about 13.9 GPa at room temperature. Time-resolved PL data also ...

  6. Valsalva ratio: a measure of stress in first year medical students

    Shamshad Begum Abdul Razak Loni


    Conclusion: We conclude that VR is affected by the academic stress in the first year medical students and that among them females are more affected which may be due to the new environment and new protocol of the education system. [Int J Res Med Sci 2015; 3(7.000: 1599-1604

  7. Stress Levels of Agricultural Science Cooperating Teachers and Student Teachers: A Repeated Measures Comparative Assessment

    McKim, Billy R.; Rayfield, John; Harlin, Julie; Adams, Andy


    This study compared job stress levels of Texas agricultural science cooperating teachers and Texas agricultural science student teachers across a semester. The research objectives included describing secondary agricultural science cooperating teachers and student teachers perceptions of stressors, by time of semester (beginning, middle, and end),…

  8. A biological measure of stress levels in patients with functional movement disorders.

    Maurer, Carine W; LaFaver, Kathrin; Ameli, Rezvan; Toledo, Ryan; Hallett, Mark


    While the presence of co-existing psychological stressors has historically been used as a supportive factor in the diagnosis of functional neurological disorders, many patients with functional neurological disorders deny the presence of these stressors. The stress response circuitry in these patients remains largely unexplored. We performed an observational study examining biological stress levels in patients with functional movement disorders as compared with matched healthy controls. Specifically, we compared levels of circulating cortisol, the end-product of the hypothalamic-pituitary-adrenal axis. Salivary cortisol samples were collected from patients with "clinically definite" functional movement disorders (n = 33) and their age- and sex-matched controls (n = 33). Collections were performed at five standardized time points, reflecting participants' diurnal cortisol cycles. To rule out confounders, participants also underwent extensive psychological assessment including Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Hamilton Anxiety Rating Scale, and Hamilton Rating Scale for Depression. Patients with functional movement disorders did not differ from matched controls with respect to levels of circulating cortisol. We demonstrate that current stress levels are not altered in patients with functional movement disorders. Our results warrant careful review of current management of patients with functional neurological symptoms, and suggest that the insistence on heightened stress levels in these patients is unjustified. Published by Elsevier Ltd.

  9. Residual stress measurements in an SiC continuous fiber reinforced Ti matrix composite

    Willemse, P.F.; Mulder, F.M.; Wei, W.; Rekveldt, M.Th.; Knight, K.S.


    During the fabrication of ceramic fiber reinforced metal matrix composites mismatch stresses will be introduced due to differences in thermal expansion coefficients between the matrix and the fibers. Calculations, based on a coaxial cylinder model, [1 and 2] predict that, for a Ti matrix SiC

  10. Measuring stress and cognitive load effects on the perceived quality of a multimodal dialogue system

    Niculescu, A.I.; van Dijk, Elisabeth M.A.G.; Cao, Y.; Nijholt, Antinus; Spink, A.J.; Grieco, F; Krips, O.E.; Loyens, L.W.S.; Noldus, L.P.J.J.; Zimmerman, P.H.


    In this paper we present the results of a pilot study investigating the impact of stress and cognitive load on the perceived interaction quality of a multimodal dialogue system for crisis management. Four test subjects interacted with the system in four differently configured trials aiming to induce

  11. Measurement of Family-centered care perception and parental stress in a neonatal unit

    Flávia Simphronio Balbino

    Full Text Available ABSTRACT Objective: to evaluate the effects of the implementation of the Patient and Family-Centered Care Model on parents and healthcare perceptions and parental stress. Method: a quasi-experimental study developed in a neonatal unit of a university hospital in the municipality of São Paulo, Brazil, with the implementation of this model of care. Data collection were performed by two sample groups, one using non-equivalent groups of parents, and another using equivalent groups of healthcare professionals. The instruments Perceptions of Family-Centered Care-Parent Brazilian Version, Perceptions of Family-Centered Care-Staff Brazilian Version and Parental Stress Scale: Neonatal Intensive Care Unit, were applied to 132 parents of newborns hospitalized and to 57 professionals. Results: there was a statistically significant improvement in the perceptions of the parents in most items assessed (p ≤0,05 and for the staff in relation to the family welcome in the neonatal unit (p = 0.041 and to the comprehension of the family's experience with the infant´s hospitalization (p = 0,050. There was a reduction in the average scores of parental stress, with a greater decrease in the Alteration in Parental Role from 4,2 to 3,8 (p = 0,048. Conclusion: the interventions improved the perceptions of parents and healthcare team related to patient and family-centered care and contributed to reducing parental stress.

  12. Measuring stress and cognitive load effects on the perceived quality of a multimodal dialogue system

    Niculescu, Andreea; Dijk, van Betsy; Cao, Yujia; Nijholt, Anton; Spink, A.J.; Grieco, F.; Krips, O.E.; Loyens, L.W.S.; Noldus, L.P.J.J.; Zimmerman, P.H.


    In this paper we present the results of a pilot study investigating the impact of stress and cognitive load on the perceived interaction quality of a multimodal dialogue system for crisis management. Four test subjects interacted with the system in four differently configured trials aiming to induce

  13. Guide to the measurement and assessment of heat stress in Gold Mines

    Stewart, JM


    Full Text Available This report is intended primarily for ventilation staff on mines, but is also of importance to management. In the gold mining industry the assessment of heat stress is likely to be for one of three purposes: to assess either the average or the worst...

  14. Accounting for posttraumatic stress disorder symptom severity with pre- and posttrauma measures

    Ogle, Christin M.; Rubin, David C.; Siegler, Ilene C.


    Using data from a longitudinal study of community-dwelling older adults, we analyzed the most extensive set of known correlates of posttraumatic stress disorder (PTSD) symptoms obtained from a single sample to examine the measures’ independent and combined utility in accounting for PTSD symptom...

  15. Structural integrity assessment and stress measurement of CHASNUPP-1 fuel assembly



    Full Text Available Fuel assembly of the PWR nuclear power plant is a long and flexible structure. This study has been made in an attempt to find the structural integrity of the fuel assembly (FA of Chashma Nuclear Power Plant-1 (CHASNUPP-1 at room temperature in air. The non-linear contact and structural tensile analysis have been performed using ANSYS 13.0, in order to determine the fuel assembly (FA elongation behaviour as well as the location and values of the stress intensity and stresses developed in axial direction under applied tensile load of 9800 N or 2 g being the fuel assembly handling or lifting load [Y. Zhang et al., Fuel assembly design report, SNERDI, China, 1994]. The finite element (FE model comprises spacer grids, fuel rods, flexible contacts between the fuel rods and grid's supports system and guide thimbles with dash-pots and flow holes, in addition to the spot welds between spacer grids and guide thimbles, has been developed using Shell181, Conta174 and Targe170 elements. FA is a non-straight structure. The actual behavior of the geometry is non-linear due to its curvature or design tolerance. It has been observed that fuel assembly elongation values obtained through FE analysis and experiment [SNERDI Tech. Doc., Mechanical strength and calculation for fuel assembly, Technical Report, F3.2.1, China, 1994] under applied tensile load are comparable and show approximately linear behaviors. Therefore, it seems that the permanent elongation of fuel assembly may not occur at the specified load. Moreover, the values of stresses obtained at different locations of the fuel assembly are also comparable with the stress values of the experiment determined at the same locations through strain gauges. Since the results of both studies (analytical and experimental are comparable, therefore, validation of the FE methodology is confirmed. The stress intensity of the FE model and maximum stresses developed along the guide thimbles in axial direction are

  16. Direct measurements of bed sediment entrainment and basal stress from the headwaters of a natural debris-flow basin

    McCoy, S. W.; Kean, J. W.; Coe, J. A.; Tucker, G. E.; Staley, D. M.; Wasklewicz, T. A.


    When mixtures of soil, rock and water flow down slope as a debris flow they can entrain and transport large amounts of bed sediment and erode underlying bedrock. Although sediment entrainment and bedrock scour by debris flows are commonplace in steep terrain, there are few measurements to constrain key terms in event-scale debris-flow routing models or longer-term landscape evolution models that include the effects of bedrock erosion by debris-flows. Particularly conspicuous are the lack of bed sediment entrainment measurements and measurements of the evolving stress state at the flow-bedrock interface as the shielding layer of sediment is removed and sediment entrainment gives way to bedrock erosion. Here we present data from the headwaters of a debris-flow basin at Chalk Cliffs, Colorado, where we directly measured entrainment of channel sediment and the evolving stress state at the bedrock interface during three debris-flow events. We made these measurements through the combined the use of a novel sediment entrainment sensor and a force plate with more commonly used video imagery and instrumentation, to measure pore-fluid pressure, flow stage, soil moisture, and rainfall during the three debris-flow events. We extended these at-a-point process measurements to evaluate the reach-scale response using pre- and post-event terrestrial laser scans. During the three separate debris-flow events approximately 1.1 m, 0.5 m, and 0.4 m of unconsolidated bed sediment were entrained. Following entrainment of the sediment, bedrock was scoured by flows that ranged from water-poor coarse-grained surge fronts to water-rich turbulent flows with vigorous bedload transport. In all cases, entrainment of bed sediment was progressive, rather than by a single en masse failure of the sediment at the sediment-bedrock interface. The measured rates were dependent on bed sediment water content. When the bed sediment was unsaturated, entrainment was relatively slow, generally taking several

  17. Ultrasonic Measurement of Transient Change in Stress-Strain Property of Radial Arterial Wall Caused by Endothelium-Dependent Vasodilation

    Ikeshita, Kazuki; Hasegawa, Hideyuki; Kanai, Hiroshi


    The endothelial dysfunction is considered to be an initial step of atherosclerosis. Additionally, it was reported that the smooth muscle, which constructs the media of the artery, changes its characteristics owing to atherosclerosis. Therefore, it is essential to develop a method for assessing the regional endothelial function and mechanical property of the arterial wall. There is a conventional technique of measuring the transient change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) after the release of avascularization. For more sensitive and regional evaluation, we developed a method of measuring the change in the elasticity of the radial artery due to FMD. In this study, the transient change in the mechanical property of the arterial wall was further revealed by measuring the stress-strain relationship during each heartbeat. The minute change in the thickness (strain) of the radial arterial wall during a cardiac cycle was measured by the phased tracking method, together with the waveform of blood pressure which was continuously measured with a sphygmometer at the radial artery. The transient change in stress-strain relationship during a cardiac cycle was obtained from the measured changes in wall thickness and blood pressure to show the transient change in instantaneous viscoelasticity. From the in vivo experimental results, the stress-strain relationship shows the hysteresis loop. The slope of the loop decreased owing to FMD, which shows that the elastic modulus decreased, and the increasing area of the loop depends on the ratio of the loss modulus (depends on viscosity) to the elastic modulus when the Voigt model is assumed. These results show a potential of the proposed method for the thorough analysis of the transient change in viscoelasticity due to FMD.

  18. Nondestructive and Localized Measurements of Stress-Strain Curves and Fracture Toughness of Ferritic Steels at Various Temperatures Using Innovative Stress-Strain Microprobe Technology. Final Report for Period 8/13/1996--06/16/1999

    Fahmy M. Haggag


    The results presented in this report demonstrate the capabilities of Advanced Technology Corporation's patented Portable/In Situ Stress-Strain Microprobe (TM) (SSM) System and its Automated Ball Indentation (ABI) test techniques to nondestructively measure the yield strength, the stress-strain curve, and the fracture toughness of ferritic steel samples and components in a reliable and accurate manner.

  19. Comparison between Neutron Diffraction measurements and numerical simulation of residual stresses of a Wire-Drawing process

    Tomaz Fantin de Souza


    Full Text Available In this work, a drawing processed was simulated to calculate forces and the resulting residual stresses in the material. The calculated residual stresses were compared with experimentally measured residual stresses by the Neutron Diffraction Method. The modeled process was the Wire Drawing. The necessary parameters to model the process were taken from an industrial currently used process. Rods of an AISI 1045 steel with nominal diameters of 21.46 mm were reduced to 20.25 mm by drawing with an drawing angle of 15°. Compression tests were used to determinate flow curves of the real material an used in the simulation models. The possibility to estimate drawing forces by numerical simulation was evaluated by comparing simulated results with values from empirical equations given by the literature. The results have shown a sufficient accuracy for the calculation of forces, but the comparison of residual stresses has shown differences to the experimentally determined ones that can be minimized by the consideration of high strain rates in the compression tests, anisotropy of the material and kinematic hardening.

  20. Computing a Synthetic Chronic Psychosocial Stress Measurement in Multiple Datasets and its Application in the Replication of G × E Interactions of the EBF1 Gene.

    Singh, Abanish; Babyak, Michael A; Brummett, Beverly H; Jiang, Rong; Watkins, Lana L; Barefoot, John C; Kraus, William E; Shah, Svati H; Siegler, Ilene C; Hauser, Elizabeth R; Williams, Redford B


    Chronic psychosocial stress adversely affects health and is associated with the development of disease [Williams, 2008]. Systematic epidemiological and genetic studies are needed to uncover genetic variants that interact with stress to modify metabolic responses across the life cycle that are the proximal contributors to the development of cardiovascular disease and precipitation of acute clinical events. Among the central challenges in the field are to perform and replicate gene-by-environment (G × E) studies. The challenge of measurement of individual experience of psychosocial stress is magnified in this context. Although many research datasets exist that contain genotyping and disease-related data, measures of psychosocial stress are often either absent or vary substantially across studies. In this paper, we provide an algorithm to create a synthetic measure of chronic psychosocial stress across multiple datasets, applying a consistent criterion that uses proxy indicators of stress components. We validated the computed scores of chronic psychosocial stress by observing moderately strong and significant correlations with the self-rated chronic psychosocial stress in the Multi-Ethnic Study of Atherosclerosis Cohort (Rho = 0.23, P psychosocial stress variable by providing three additional replications of our previous finding of gene-by-stress interaction with central obesity traits [Singh et al., 2015].

  1. Psychometric properties of the Perceived Stress Scale (PSS): measurement invariance between athletes and non-athletes and construct validity.

    Chiu, Yi-Hsiang; Lu, Frank Jing-Horng; Lin, Ju-Han; Nien, Chiao-Lin; Hsu, Ya-Wen; Liu, Hong-Yu


    Although Perceived Stress Scale (PSS, Cohen, Kamarack & Mermelstein, 1983) has been validated and widely used in many domains, there is still no validation in sports by comparing athletes and non-athletes and examining related psychometric indices. The purpose of this study was to examine the measurement invariance of PSS between athletes and non-athletes, and examine construct validity and reliability in the sports contexts. Study 1 sampled 359 college student-athletes (males = 233; females = 126) and 242 non-athletes (males = 124; females = 118) and examined factorial structure, measurement invariance and internal consistency. Study 2 sampled 196 student-athletes (males = 139, females = 57, Mage = 19.88 yrs, SD = 1.35) and examined discriminant validity and convergent validity of PSS. Study 3 sampled 37 student-athletes to assess test-retest reliability of PSS. Results found that 2-factor PSS-10 fitted the model the best and had appropriate reliability. Also, there was a measurement invariance between athletes and non-athletes; and PSS positively correlated with athletic burnout and life stress but negatively correlated with coping efficacy provided evidence of discriminant validity and convergent validity. Further, the test-retest reliability for PSS subscales was significant (r = .66 and r = .50). It is suggested that 2-factor PSS-10 can be a useful tool in assessing perceived stress either in sports or non-sports settings. We suggest future study may use 2-factor PSS-10 in examining the effects of stress on the athletic injury, burnout, and psychiatry disorders.

  2. Psychometric properties of the Perceived Stress Scale (PSS: measurement invariance between athletes and non-athletes and construct validity

    Yi-Hsiang Chiu


    Full Text Available Background Although Perceived Stress Scale (PSS, Cohen, Kamarack & Mermelstein, 1983 has been validated and widely used in many domains, there is still no validation in sports by comparing athletes and non-athletes and examining related psychometric indices. Purpose The purpose of this study was to examine the measurement invariance of PSS between athletes and non-athletes, and examine construct validity and reliability in the sports contexts. Methods Study 1 sampled 359 college student-athletes (males = 233; females = 126 and 242 non-athletes (males = 124; females = 118 and examined factorial structure, measurement invariance and internal consistency. Study 2 sampled 196 student-athletes (males = 139, females = 57, Mage = 19.88 yrs, SD = 1.35 and examined discriminant validity and convergent validity of PSS. Study 3 sampled 37 student-athletes to assess test-retest reliability of PSS. Results Results found that 2-factor PSS-10 fitted the model the best and had appropriate reliability. Also, there was a measurement invariance between athletes and non-athletes; and PSS positively correlated with athletic burnout and life stress but negatively correlated with coping efficacy provided evidence of discriminant validity and convergent validity. Further, the test-retest reliability for PSS subscales was significant (r = .66 and r = .50. Discussion It is suggested that 2-factor PSS-10 can be a useful tool in assessing perceived stress either in sports or non-sports settings. We suggest future study may use 2-factor PSS-10 in examining the effects of stress on the athletic injury, burnout, and psychiatry disorders.

  3. Measurement of heat stress conditions at cow level and comparison to climate conditions at stationary locations inside a dairy barn.

    Schüller, Laura K; Heuwieser, Wolfgang


    The objectives of this study were to examine heat stress conditions at cow level and to investigate the relationship to the climate conditions at 5 different stationary locations inside a dairy barn. In addition, we compared the climate conditions at cow level between primiparous and multiparous cows for a period of 1 week after regrouping. The temperature-humidity index (THI) differed significantly between all stationary loggers. The lowest THI was measured at the window logger in the experimental stall and the highest THI was measured at the central logger in the experimental stall. The THI at the mobile cow loggers was 2·33 THI points higher than at the stationary loggers. Furthermore, the mean daily THI was higher at the mobile cow loggers than at the stationary loggers on all experimental days. The THI in the experimental pen was 0·44 THI points lower when the experimental cow group was located inside the milking parlour. The THI measured at the mobile cow loggers was 1·63 THI points higher when the experimental cow group was located inside the milking parlour. However, there was no significant difference for all climate variables between primiparous and multiparous cows. These results indicate, there is a wide range of climate conditions inside a dairy barn and especially areas with a great distance to a fresh air supply have an increased risk for the occurrence of heat stress conditions. Furthermore, the heat stress conditions are even higher at cow level and cows not only influence their climatic environment, but also generate microclimates within different locations inside the barn. Therefore climate conditions should be obtained at cow level to evaluate the heat stress conditions that dairy cows are actually exposed to.

  4. A comparison and measurement standardisation of four in situ devices for determining the erosion shear stress of intertidal sediments

    Tolhurst, T. J.; Black, K. S.; Paterson, D. M.; Mitchener, H. J.; Termaat, G. R.; Shayler, S. A.


    Predictive modelling of estuarine sediment erosion and transport requires a description of the erosional properties of the bed. The two main variables of interest are the critical erosion shear stress ( τcr) and the erosion rate ( ɛ). A number of different erosion devices exist to measure the erosion shear stress of intertidal sediments in situ. These devices apply different strategies to induce and measure erosion, and the area over which erosion is integrated varies greatly. In addition, the definition of erosion threshold differs between workers. This makes comparison of data collected from different devices very difficult. Four different types of erosion device, Microcosm system, In Situ Erosion Flume (ISEF), SedErode and cohesive strength meter (CSM) were used during the July 1997 EC INTRMUD Humber estuary (UK) field campaign. These devices were deployed simultaneously on the Skeffling intertidal mudflat to allow comparison of the data generated. This involved the comparison of suspended particulate matter (SPM) time series, the nature of the applied shear stress ( τo) and the area over which erosion was integrated. The initial goal was to develop a standard analysis procedure for comparison of stability measurements. The erosion threshold calculated from area normalised suspended particulate matter (SPM n) time series was relatively comparable between devices especially between the Microcosm and ISEF. However, device size and natural sediment spatial heterogeneity affected the results. The erosion rate varied by orders of magnitude between the different devices. This variation seemed to be due to the considerable differences in device deployment time. In conclusion, SPM data from different devices are broadly comparable, whilst erosion rates are only comparable if the shear stress steps are of the same duration.

  5. Differential effect of severe and moderate social stress on blood immune and endocrine measures and susceptibility to collagen type II arthritis in male rats.

    Stefanski, Volker; Hemschemeier, Susanne K; Schunke, Kerstin; Hahnel, Anja; Wolff, Christine; Straub, Rainer H


    The effects of social stress on several blood immune measures and collagen-induced arthritis (CIA) were investigated in Wistar rats using the resident-intruder confrontation paradigm to induce stress of different intensity. Male intruders were exposed for one week to a dominant opponent either repeatedly for 4h daily (moderate stress) or continuously (severe stress). Arthritis was induced by intradermal injection of collagen type II (CII) into the tail skin at the end of day 3 of confrontation. Only severe stress was associated with decreased CD4 and CD8 T cells, and the increase in granulocyte numbers and body mass loss was more pronounced under these conditions. Only severe stress reduced the susceptibility to arthritis by about 50%. Severity scores did not differ in the first five days after disease onset between all groups. Subsequent experiments focused on severely stressed rats indicated that disease progressed until day 10 only in control animals, but not in severely stressed males. Stressor exposure resulted in increased blood monocyte numbers, but these males failed to accumulate macrophages into the skin at the site of CII injection. High numbers of attacks experienced by intruders correlated with delayed disease onset in severely stressed rats. We hypothesize that severe stress persisting after disease induction exhibits beneficial effects on the susceptibility of CIA and propose that the specific endocrine and immunological profile associated with severe stress is an important factor for disease outcome--a factor which probably explains many of the conflicting data of previous stress studies on CIA.

  6. A Comparison of Residual Stress Measuring Techniques: Their Strengths and Weaknesses


    1 i OJ 1 ll CM 1 t~- VD CO OJ V* -J iv 1 a. viJ b * r-l .J" _J -^r -a- r^ a; ON 00 cn m OJ «.>. u o rH CM CO a.i (H 3 irv OT ^f pi r i...components of stress are given by the Kirsch (ref 7) equations, namely: CTrr = a (1 - a 2) + a (1 + 3a.k - 4a2) cos 20 (4) rr 2 T2" 2...G. E. Bowie, "Residual Stress by Blind-Hole Method with 0££-Center Hole," Exp. Mech., lg. No. 5, (May 1978), pp 173-179. 7. G. Kirsch , "Die Theorie

  7. Numerical predictions and measurements of Reynolds normal stresses in turbulent pipe flow of polymers

    Resende, P.R. [Centro de Estudos de Fenomenos de Transporte, DEMEGI, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal)]. E-mail:; Escudier, M.P. [Department of Engineering, University of Liverpool, Brownlow Street, Liverpool L69 3GH (United Kingdom)]. E-mail:; Presti, F [Department of Engineering, University of Liverpool, Brownlow Street, Liverpool L69 3GH (United Kingdom); Pinho, F.T. [Centro de Estudos de Fenomenos de Transporte, DEM, Universidade do Minho Campus de Azurem, 4800-058 Guimaraes (Portugal)]. E-mail:; Cruz, D.O.A. [Departamento de Engenharia Mecanica, Universidade Federal do Para-UFPa Campus Universitario do Guama, 66075-900 Belem, Para (Brazil)]. E-mail:


    An anisotropic low Reynolds number k-{epsilon} turbulence model has been developed and its performance compared with experimental data for fully-developed turbulent pipe flow of four different polymer solutions. Although the predictions of friction factor, mean velocity and turbulent kinetic energy show only slight improvements over those of a previous isotropic model [Cruz, D.O.A., Pinho, F.T., Resende, P.R., 2004. Modeling the new stress for improved drag reduction predictions of viscoelastic pipe flow. J. Non-Newt. Fluid Mech. 121, 127-141], the new turbulence model is capable of predicting the enhanced anisotropy of the Reynolds normal stresses that accompanies polymer drag reduction in turbulent flow.

  8. Preliminary Results of Stress Measurement Using Drill Cores of TCDP Hole-A: an Application of Anelastic Strain Recovery Method to Three-Dimensional In-Situ Stress Determination

    Weiren Lin En-Chao Yeh1


    Full Text Available In order to understand the feature of rock stress change at different depths above, within, and beneath the Chelungpu fault after the Chi-Chi earthquake, we employed a core-based stress measurement method, anelastic strain recovery (ASR technique to determine both the orientations and magnitudes of present three-dimensional principal rock stresses using drill core samples retrieved from Taiwan Chelungpu-fault Drilling Project (TCDP main Hole-A. The core samples used were taken from three depths; and their lithology were sandstone at depths of 592 and 1755 m and siltstone at 1112 m. The anelastic strains of the specimens in nine directions, including six independent directions, were measured after its in-situ stress was released. Acquired anelastic strains were of high quality and reached several hundred microstrains, which is sufficiently high for the accuracy of the measurement system used. Thus, the strain data could be used for three dimensional analysis resulting in the determination of orientations and the estimation of magnitudes of the principal in-situ stresses. Preliminary stress measurement results showed that the orientations of principal stresses changed between the shallower depth above the fault and the deeper depth beneath it, that is, the present stress distribution in the TCDP hole might be influenced by the Chelungpu fault rupture. At the same time, anelastic strain recovery measurement is well suited for the task of directly determining the orientations of principal in-situ stresses and to estimate the magnitude of stresses at large/great depth.

  9. A systematic review of randomised control trials on the effects of yoga on stress measures and mood.

    Pascoe, Michaela C; Bauer, Isabelle E


    Stress related disorders such as depression and anxiety are leading sources of disability worldwide, and current treatment methods such as conventional antidepressant medications are not beneficial for all individuals. There is evidence that yoga has mood-enhancing properties possibly related to its inhibitory effects on physiological stress and inflammation, which are frequently associated with affective disorders. However the biological mechanisms via which yoga exerts its therapeutic mood-modulating effects are largely unknown. This systematic review investigates the effects of yoga on sympathetic nervous system and hypothalamic pituitary adrenal axis regulation measures. It focuses on studies collecting physiological parameters such as blood pressure, heart rate, cortisol, peripheral cytokine expression and/or structural and functional brain measures in regions involved in stress and mood regulation. Overall the 25 randomised control studies discussed provide preliminary evidence to suggest that yoga practice leads to better regulation of the sympathetic nervous system and hypothalamic-pituitary-adrenal system, as well as a decrease in depressive and anxious symptoms in a range of populations. Further research is warranted to confirm these preliminary findings and facilitate implementation in clinical settings.

  10. Implementation and Development of the Incremental Hole Drilling Method for the Measurement of Residual Stress in Thermal Spray Coatings

    Valente, T.; Bartuli, C.; Sebastiani, M.; Loreto, A.


    The experimental measurement of residual stresses originating within thick coatings deposited by thermal spray on solid substrates plays a role of fundamental relevance in the preliminary stages of coating design and process parameters optimization. The hole-drilling method is a versatile and widely used technique for the experimental determination of residual stress in the most superficial layers of a solid body. The consolidated procedure, however, can only be implemented for metallic bulk materials or for homogeneous, linear elastic, and isotropic materials. The main objective of the present investigation was to adapt the experimental method to the measurement of stress fields built up in ceramic coatings/metallic bonding layers structures manufactured by plasma spray deposition. A finite element calculation procedure was implemented to identify the calibration coefficients necessary to take into account the elastic modulus discontinuities that characterize the layered structure through its thickness. Experimental adjustments were then proposed to overcome problems related to the low thermal conductivity of the coatings. The number of calculation steps and experimental drilling steps were finally optimized.

  11. In situ measurements of shear stress, erosion and deposition in man-made tidal channels within a tidal saltmarsh

    Pieterse, Aline; Puleo, Jack A.; McKenna, Thomas E.; Figlus, Jens


    A field study was conducted in man-made ditches in a tidal saltmarsh in Lewes, Delaware, USA. Ditches are prevalent throughout tidal marshes along the Atlantic US coast, and influence hydrodynamics and sediment transport. The field study focused on measuring near-bed velocity, shear stress, sediment concentration, and bed level variability at 5 stations over a 3-week period. Velocities in the ditch (2-5 m wide, 1 m deep) peaked between 0.4 and 0.6 m/s and were slightly ebb dominated. Velocity and shear stress were maximum during a storm event, with peak shear stresses of 2 N/m2. Bed levels were estimated from acoustic amplitude return of a downward-looking velocity profiler. The bed level in the ditch at the landward locations increased ∼ 0.03 m over 3 weeks, while there was ∼ 0.01 m bed level decrease at the most seaward site suggesting a net import of sediment into the channel. At all sites, erosion (∼ 0.005-0.015 m) occurred during the accelerating phase of the flood tide, and accretion of a similar magnitude occurred during the decelerating phase of the ebb tide. This erosion-deposition sequence resulted in small net changes in bed level at the end of each tidal cycle. The intratidal behavior of the bed level was simulated using erosion and deposition flux equations based on shear stress, critical shear stress, and suspended sediment concentration. Erosion was predicted well with RMS errors on the order of 2 ṡ10-3 m. The bed level during the deposition phase could not be reproduced using the simple approach. Model inaccuracies for deposition were attributed to advection and variations in fall velocity due to flocculation that were not modeled due to lack of ground-truth observations.

  12. Hair Measurements of Cortisol, DHEA, and DHEA to Cortisol Ratio as Biomarkers of Chronic Stress among People Living with HIV in China: Known-Group Validation

    Li, Xiaoming; Zilioli, Samuele; Chen, Zheng; Deng, Huihua; Pan, Juxian


    Background Existing literature suggests that endocrine measures, including the steroid hormones of cortisol and Dehydroepiandrosterone (DHEA), as well as the DHEA to cortisol ratio in the human hair can be used as promising biomarkers of chronic stress among humans. However, data are limited regarding the validity of these measures as biomarkers of chronic stress among people living with HIV (PLWH), whose endocrine system or hypothalamic pituitary adrenal (HPA) axis may be affected by HIV infection and/or antiretroviral therapy (ART) medications. Method Using hair sample data and self-reported survey from 60 PLWH in China, we examined the validity of three endocrine measures among Chinese PLWH using a known-groups validation strategy. High-stress group (n = 30) and low-stress group (n = 30) of PLWH were recruited through individual assessment interviews by a local licensed psychologist. The endocrine measures in hair were extracted and assessed by LC-APCI-MS/MS method. Both bivariate and multivariate analyses were conducted to examine the associations between the endocrine measures and the stress level, and to investigate if the associations differ by ART status. Results The levels of endocrine measures among Chinese PLWH were consistent with existing studies among PLWH. Generally, this pilot study confirmed the association between endocrine measures and chronic stress. The high stress group showed higher level hair cortisol and lower DHEA to cortisol ratio. The higher stress group also reported higher scores of stressful life events, perceived stress, anxiety and depression. Hair cortisol level was positively related to anxiety; DHEA was negatively associated with stressful life events; and the DHEA to cortisol ratio was positively related to stressful life events and perceived stress. ART did not affect the associations between the endocrine measures and stress level. Conclusions Our findings suggest that hair cortisol and DHEA to cortisol ratio can be used as

  13. Effects of grain, fructose, and histidine feeding on endotoxin and oxidative stress measures in dairy heifers.

    Golder, H M; Lean, I J; Rabiee, A R; King, R; Celi, P


    Ruminal endotoxin and plasma oxidative stress biomarker concentrations were studied in dairy heifers challenged with grain, fructose, and histidine in a partial factorial study. Holstein-Friesian heifers [n=30; average body weight (BW) of 359.3±47.3 kg] were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [crushed triticale at 1.2% of BW dry matter intake (DMI)]; (3) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI) + histidine (6g/head); and (5) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI) + histidine (6 g/head). Rumen samples were collected by stomach tube 5, 65, 115, 165, and 215 min after diet consumption and blood samples at 5 and 215 min after consumption. Rumen fluid was analyzed for endotoxin concentrations. Plasma was analyzed for concentrations of the following oxidative stress biomarkers: reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), advanced oxidation protein products, and ceruloplasmin, and activity of glutathione peroxidase. Dietary treatment had no effect on concentrations of endotoxin or oxidative stress biomarkers. We observed no interactions of treatment by time. Ruminal concentrations of endotoxin decreased during the sampling period from 1.12×10(5) ± 0.06 to 0.92×10(5) endotoxin units/mL ± 0.05 (5 and 215 min after diet consumption, respectively). Concentrations of dROM and the oxidative stress index (dROM/BAP × 100) increased over the sampling period, from 108.7 to 123.5 Carratelli units (Carr U), and from 4.1 to 4.8, respectively. Ceruloplasmin concentrations markedly declined 5 min after the consumption of diets, from 190 to 90 mg/L over the 215-min sampling period. Overall, a single feeding challenge for dairy cattle with grain, fructose, and histidine, and combinations thereof, may not be sufficient to induce marked changes in endotoxin or oxidative stress biomarker concentrations.

  14. [Adaptability of Helianthus annuus seedlings to crude oil pollution in soil and its improvement measures under salinization stress].

    Zhang, Jing-lei; Ci, Hua-cong; He, Xing-dong; Liang, Yu-ting; Zhao, Xuan; Sun, Hui-ting; Xie, Hong-tao


    To explore the adaptability of plant under salt stress to crude oil pollution of soil and improvement measures, a pot experiment of Helianthus annuus seedlings was conducted using orthogonal experiment method with crude oil-sodium chloride-desulfurization gypsum and cinder-zeolite-desulfurization gypsum-sawdust. The results showed that, with the increase of soil crude oil concentration, the relative growth rate (RGR) of plant height, RGR of aboveground biomass and root N: P ratios of H. annuus seedlings decreased significantly, while the activity of SOD and CAT increased at first and then decreased significantly. The RGR of plant height and aboveground biomass significantly increased (P cinder, zeolite, desulfurization gypsum under salinization condition. The crude oil pollution of soil could decrease the relative growth rate of H. annuus seedling, and sawdust could reduce the influence of crude oil pollution on plant growth under salt stress.

  15. Mediation of the Relationship between Maternal Phthalate Exposure and Preterm Birth by Oxidative Stress with Repeated Measurements across Pregnancy.

    Ferguson, Kelly K; Chen, Yin-Hsiu; VanderWeele, Tyler J; McElrath, Thomas F; Meeker, John D; Mukherjee, Bhramar


    Mediation analysis is useful for understanding mechanisms and has been used minimally in the study of the environment and disease. We examined mediation of the association between phthalate exposure during pregnancy and preterm birth by oxidative stress. This nested case-control study of preterm birth (n = 130 cases, 352 controls) included women who delivered in Boston, Massachusestts, from 2006 through 2008. Phthalate metabolites and 8-isoprostane, an oxidative stress biomarker, were measured in urine from three visits in pregnancy. We applied four counterfactual mediation methods: method 1, utilizing exposure and mediator averages; method 2, using averages but allowing for an exposure-mediator interaction; method 3, incorporating longitudinal measurements of the exposure and mediator; and method 4, using longitudinal measurements and allowing for an exposure-mediator interaction. We observed mediation of the associations between phthalate metabolites and all preterm birth by 8-isoprostane, with the greatest estimated proportion mediated observed for spontaneous preterm births specifically. Fully utilizing repeated measures of the exposure and mediator improved precision of indirect (i.e., mediated) effect estimates, and including an exposure-mediator interaction increased the estimated proportion mediated. For example, for mono(2-ethyl-carboxy-propyl) phthalate (MECPP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), the percent of the total effect mediated by 8-isoprostane increased from 47% to 60% with inclusion of an exposure-mediator interaction term, in reference to a total adjusted odds ratio of 1.67 or 1.48, respectively. This demonstrates mediation of the phthalate-preterm birth relationship by oxidative stress, and the utility of complex regression models in capturing mediated associations when repeated measures of exposure and mediator are available and an exposure-mediator interaction may exist. Citation: Ferguson KK, Chen YH, VanderWeele TJ, Mc

  16. Numerical analysis of stress distribution in the upper arm tissues under an inflatable cuff: Implications for noninvasive blood pressure measurement

    Deng, Zhipeng; Liang, Fuyou


    An inflatable cuff wrapped around the upper arm is widely used in noninvasive blood pressure measurement. However, the mechanical interaction between cuff and arm tissues, a factor that potentially affects the accuracy of noninvasive blood pressure measurement, remains rarely addressed. In the present study, finite element (FE) models were constructed to quantify intra-arm stresses generated by cuff compression, aiming to provide some theoretical evidence for identifying factors of importance for blood pressure measurement or explaining clinical observations. Obtained results showed that the simulated tissue stresses were highly sensitive to the distribution of cuff pressure on the arm surface and the contact condition between muscle and bone. In contrast, the magnitude of cuff pressure and small variations in elastic properties of arm soft tissues had little influence on the efficiency of pressure transmission in arm tissues. In particular, it was found that a thickened subcutaneous fat layer in obese subjects significantly reduced the effective pressure transmitted to the brachial artery, which may explain why blood pressure overestimation occurs more frequently in obese subjects in noninvasive blood pressure measurement.

  17. Numerical analysis of stress distribution in the upper arm tissues under an inflatable cuff: Implications for noninvasive blood pressure measurement

    Deng, Zhipeng; Liang, Fuyou


    An inflatable cuff wrapped around the upper arm is widely used in noninvasive blood pressure measurement. However, the mechanical interaction between cuff and arm tissues, a factor that potentially affects the accuracy of noninvasive blood pressure measurement, remains rarely addressed. In the present study, finite element (FE) models were constructed to quantify intra-arm stresses generated by cuff compression, aiming to provide some theoretical evidence for identifying factors of importance for blood pressure measurement or explaining clinical observations. Obtained results showed that the simulated tissue stresses were highly sensitive to the distribution of cuff pressure on the arm surface and the contact condition between muscle and bone. In contrast, the magnitude of cuff pressure and small variations in elastic properties of arm soft tissues had little influence on the efficiency of pressure transmission in arm tissues. In particular, it was found that a thickened subcutaneous fat layer in obese subjects significantly reduced the effective pressure transmitted to the brachial artery, which may explain why blood pressure overestimation occurs more frequently in obese subjects in noninvasive blood pressure measurement.

  18. Investigation of Bucket Wheel Excavator Lattice Structure Internal Stress in Harsh Environment through a Remote Measurement System

    Risteiu, M.; Dobra, R.; Andras, I.; Roventa, M.; Lorincz, A.


    The paper shows the results of a lab model for strain gauges based measuring system for multiple measuring heads of the mechanical stress in lattice structures of the bucket wheel excavator for open pit mines-harsh environment. The system is designed around a microcontroller system. Because of specific working conditions, the measuring system sends data to a processing system (a PC with Matlab software), we have implemented a secure communication solution based on ISM standard, by using NRF24L01 module. The transceiver contains a fully integrated frequency synthesizer based on crystal oscillator, and a Enhanced ShockBurst™ protocol engine. The proposed solution has a current consumption around 9.0 mA at an output power of -6dBm and 12.3mA in RX mode. Built-in Power Down and Standby modes makes power saving easily realizable for our solution battery powered. The stress from structures is taken by specific strain gauges adapted to low frequency vibrations. We are using a precision 24-bit analog-to-digital converter (ADC) designed for weigh scales and industrial control applications to interface directly with a bridge sensor-instrumentation device, with low drift voltage, low noise, common mode rejection signal, frequency and temperature stability. As backup implementation for measurements a high speed storage implementation is used.

  19. Value of the pudendal nerves terminal motor latency measurements in the diagnosis of occult stress urinary incontinence

    ZHU Lan; HAI Ning; LANG Jing-he; YU Shi-yun; LI Bin; WONG Felix


    Background Occult stress urinary incontinence may lead to de novo stress urinary incontinence after pelvic floor repair surgery.A measurement of pudendal nerve terminal motor latency can reflect the integrity of the nerves.We aimed to explore the value of pudendal nerve terminal motor latency in the diagnosis of occult stress urinary incontinence in pelvic organ prolapse patients.Methods Ten patients with stress urinary incontinence (SUI group),10 with SUI and uterine or vaginal prolapse (POP+SUI group) and 10 with uncomplicated uterine or vaginal prolapse (POP group) were evaluated for their pudendal nerve terminal motor latency using a keypoint electromyogram.Results The amplitude of positive waves was between 0.1 and 0.2 mV.The nerve terminal motor latency was between 1.44 and 2.38 ms.There was no significant difference in the wave amplitudes of pudendal nerve evoked action potential among the three different groups (P >0.05).The pudendal nerve latency of the SUI group,POP+SUI group and POP group were (2.9±0.7) seconds,(2.8±0.7) seconds and (1.9±0.5) seconds respectively.The difference between the SUI group and POP+SUI group was not statistically significant (P >0.05),whereas the difference between the SUI and POP groups and between the POP+SUI and POP groups were statistically significant (P <0.05).There was a positive correlation between pudendal nerve latency and the severity of SUI; the correlation coefficient was 0.720 (P <0.01).Conclusions Patients with SUI may have some nerve demyelination injuries in the pudendal nerve but the damage might not involve the nerve axons.The measurement of pudendal nerve latency may be useful for the diagnosis of SUI in POP patients.

  20. Early life stress-induced alterations in rat brain structures measured with high resolution MRI.

    Sarabdjitsingh, R Angela; Loi, Manila; Joëls, Marian; Dijkhuizen, Rick M; van der Toorn, Annette


    Adverse experiences early in life impair cognitive function both in rodents and humans. In humans this increases the vulnerability to develop mental illnesses while in the rodent brain early life stress (ELS) abnormalities are associated with changes in synaptic plasticity, excitability and microstructure. Detailed information on the effects of ELS on rodent brain structural integrity at large and connectivity within the brain is currently lacking; this information is highly relevant for understanding the mechanism by which early life stress predisposes to mental illnesses. Here, we exposed rats to 24 hours of maternal deprivation (MD) at postnatal day 3, a paradigm known to increase corticosterone levels and thereby activate glucocorticoid receptors in the brain. Using structural magnetic resonance imaging we examined: i) volumetric changes and white/grey matter properties of the whole cerebrum and of specific brain areas; and ii) whether potential alterations could be normalized by blocking glucocorticoid receptors with mifepristone during the critical developmental window of early adolescence, i.e. between postnatal days 26 and 28. The results show that MD caused a volumetric reduction of the prefrontal cortex, particularly the ventromedial part, and the orbitofrontal cortex. Within the whole cerebrum, white (relative to grey) matter volume was decreased and region-specifically in prefrontal cortex and dorsomedial striatum following MD. A trend was found for the hippocampus. Grey matter fractions were not affected. Treatment with mifepristone did not normalize these changes. This study indicates that early life stress in rodents has long lasting consequences for the volume and structural integrity of the brain. However, changes were relatively modest and-unlike behavior- not mitigated by blockade of glucocorticoid receptors during a critical developmental period.