Obsevations Ofstress-Induced Structuraldisorder and Fictive Stress in Bulk Metallic Glasses

2002 ◽  
Vol 754 ◽  
Author(s):  
Ho-Sou Chen ◽  
Hidemi Kato ◽  
Akihisa Inoue
Keyword(s):  
Steady State ◽  
Viscous Flow ◽  
Glass Structure ◽  
Constant Strain Rate ◽  
Transient State ◽  
Structural Disorder ◽  
Constant Load ◽  
In Situ Observation ◽  
Flow Process ◽  
Direct Measurements

ABSTRACTThe transformation from Newtonian to non-Newtonian viscous flow at the glass transition of Pd- and Zr-based alloy glasses has been investigated in compressive tests under either a constant strain rate, or a constant load. The transition occurs at a critical stress being nearly independent of temperature. The mechanism of the transition thus has been attributed to the stress-induced structural relaxation. This paper describes the evidence of stress-induced disorder as indicated by the change in the viscosity with stress and the evolution of specific heat of the alloy glasses subjected to non-Newtonian steady-state viscous flow. Also presented in this paper is the in-situ observation of structural disorder, by direct measurements of the temperature change of sample, in particular the soften process during a constant load deformation. The heat of evolution is then calculated, and found to scale as the logarithm of the normalized viscosity during entire deformation. This result implies that the relationship between the structural disorder, as indicated by the enthalpy change and viscosity is the same in the transient state during deformation as well as in the steady-state flow process. This is conceptionally very important in that it enables us to introduce a fictive stress which indirectly represents the glass structure.

scholarly journals Heat Transport Analysis in Rectangular Shields Using the Laplace and Poisson Equations

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1714
Author(s):  
Stefan Owczarek ◽  
Mariusz Owczarek
Keyword(s):  
Temperature Field ◽  
Steady State ◽  
Heat Flow ◽  
Direct Method ◽  
Transient State ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Flow Process ◽  
Infinite Power ◽  
Building Physics

In the design of a building envelope, there is the issue of heat flow through the partitions. In the heat flow process, we distinguish steady and dynamic states in which heat fluxes need to be obtained as part of building physics calculations. This article describes the issue of determining the size of those heat fluxes. The search for the temperature field in a two-dimensional problem is common in building physics and heat exchange in general. Both numerical and analytical methods can be used to obtain a solution. Two methods were dealt with, the first of which was used to obtain the solution in the steady state and the other in the transient. In the steady state a method of initial functions, the basics of which were given by W.Z. Vlasov and A.Y. Lur’e was adopted. Originally MIF was used for analysis of the loads of a flat elastic medium. Since then it was used for solving concrete beams, plates and composite materials problems. Polynomial half-reverse solutions are used in the theory of a continuous medium. Here solutions were obtained by the direct method. As a result, polynomial forms of the considered temperature field were obtained. A Cartesian coordinate system and rectangular shape of the plate were assumed. The problem is governed by the Laplace equation in the steady state and Poisson in the transient state. Boundary conditions in the form of temperature (τ(x), t(y)) or/and flux (p(x), q(y)) can be provided. In the steady state the solution T(x, y) was assumed in the form of an infinite power series developed in relation to the variable y with coefficients Cn depending on x. The assumed solution was substituted into the Fourier equation and after expanding into the Taylor series the boundary condition for y = 0 and y = h was taken into account. From this condition the coefficient Cn can be calculated and, therefore, a closed solution for the temperature field in the plate.

Exercise slightly above the maximal lactate steady state reduces self-efficacy and increases negative affect

2019 ◽  
Author(s):  
James Graeme Wrightson ◽  
Louis Passfield
Keyword(s):  
Steady State ◽  
Negative Affect ◽  
Power Output ◽  
Self Efficacy ◽  
Repeated Measures ◽  
Physiological State ◽  
Constant Load ◽  
Peak Power Output ◽  
Time To Exhaustion ◽  
Maximal Lactate Steady State

Objectives: To examine the effect of exercise at and slightly above the maximal lactate steady state (MLSS) on self-efficacy, affect and effort, and their associations with exercise tolerance.Design: Counterbalanced, repeated measures designMethod: Participants performed two 30‐minute constant‐load cycling exercise at a power output equal to that at MLSS and 10 W above MLSS, immediately followed by a time‐to‐exhaustion test at 80% of their peak power output. Self-efficacy, affect and effort were measured before and after 30 minutes of cycling at and above MLSS.Results: Negative affect and effort higher, and self-efficacy and time to exhaustion were reduced, following cycling at MLSS + 10 W compared to cycling at the MLSS. Following exercise at the MLSS self-efficacy, affect and effort were all associated with subsequent time-to exhaustion. However, following exercise at MLSS + 10 W, only affect was associated with time-to exhaustion. Conclusions: Self efficacy, affect and effort are profoundly affected by physiological state, highlighting the influence of somatic states on perceptions and emotions during exercise. The affective response to exercise appears to be associated with exercise tolerance, indicating that the emotional, as well as physiological, responses should be considered when prescribing exercise training.

scholarly journals Multi-Machine Repairable System with One Unreliable Server and Variable Repair Rate

Mathematics ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1299
Author(s):  
Shengli Lv
Keyword(s):  
Steady State ◽  
Transient State ◽  
Repairable System ◽  
Repair Rate ◽  
Numerical Illustration ◽  
Transform Method ◽  
Unreliable Server ◽  
Busy Time ◽  
The Mean ◽  
Mean Time

This paper analyzed the multi-machine repairable system with one unreliable server and one repairman. The machines may break at any time. One server oversees servicing the machine breakdown. The server may fail at any time with different failure rates in idle time and busy time. One repairman is responsible for repairing the server failure; the repair rate is variable to adapt to whether the machines are all functioning normally or not. All the time distributions are exponential. Using the quasi-birth-death(QBD) process theory, the steady-state availability of the machines, the steady-state availability of the server, and other steady-state indices of the system are given. The transient-state indices of the system, including the reliability of the machines and the reliability of the server, are obtained by solving the transient-state probabilistic differential equations. The Laplace–Stieltjes transform method is used to ascertain the mean time to the first breakdown of the system and the mean time to the first failure of the server. The case analysis and numerical illustration are presented to visualize the effects of the system parameters on various performance indices.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Behzad ◽  
Benjamin Herrmann ◽  
Williams R. Calderón-Muñoz ◽  
José M. Cardemil ◽  
Rodrigo Barraza
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Steady State ◽  
Discrete Model ◽  
Continuum Model ◽  
Transient State ◽  
Operating Conditions ◽  
Steady State Condition ◽  
Content Type ◽  
The Continuum

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress. Design/methodology/approach The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events. Findings The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions. Originality/value Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

Faster adjustment of O2 uptake to the energy requirement of exercise in the trained state

1978 ◽  
Vol 44 (6) ◽  
pp. 877-881 ◽  
Author(s):  
R. C. Hickson ◽  
H. A. Bomze ◽  
J. O. Hollozy
Keyword(s):  
Steady State ◽  
Exercise Training ◽  
Training Program ◽  
Endurance Exercise ◽  
Time Course ◽  
Energy Requirement ◽  
Constant Load ◽  
O2 Uptake ◽  
Endurance Exercise Training

The purpose of this study was to determine the effect of endurance exercise training on the time course of the increase in VO2 toward steady state in response to submaximal constant load work. Seven men participated in a strenuous program of endurance exercise for 40 min/day, 6 days/wk for 10 wk. Their average VO2max increased from 3.29 liters before training to 4.53 liters at the end of the training program. VO2 was measured continuously on a breath-by-breath basis at work rates requiring 40%, 50%, 60%, or 70% of VO2max before training. After training the subjects were retested both at the same absolute and the same relative work rates. The increases in VO2 toward steady state occurred more rapidly in the trained than in the untrained state both at the same absolute and at the same relative work rates. The finding that O2 uptake rises to meet O2 demand more rapidly in the trained than in the untrained state provides evidence that the working muscles become less hypoxic at the onset of exercise of the same intensity after training.

scholarly journals A Mechanical Test Procedure for Avalanche Snow

1977 ◽  
Vol 19 (81) ◽  
pp. 489-497 ◽  
Author(s):  
S. L. McCabe ◽  
F. W. Smith
Keyword(s):  
Mechanical Test ◽  
Test Procedure ◽  
Testing Machine ◽  
Constant Strain Rate ◽  
Time Behavior ◽  
Stress Strain ◽  
Direct Measurements ◽  
Natural Snow ◽  
Relaxation Curves ◽  
Design Construction

AbstractThe design, construction and testing of a portable, constant strain-rate testing machine for determining the mechanical behavior of avalanche now is described. The machine is intended for use in determining the stress-strain-time behavior of low-density natural snow in the field. A technique for making direct measurements of strain in the snow sample is described and stress-strain curves are presented for strain-rates ranging from 0.5 to 5.0 × 10−5 s−1. The densities of the snow samples tested range from 186 to 335 kg m−3. Ultimate-strength data and relaxation curves are also presented.

scholarly journals Contribution of human melanopsin retinal ganglion cells to steady-state pupil responses

2010 ◽  
Vol 277 (1693) ◽  
pp. 2485-2492 ◽  
Author(s):  
Sei-ichi Tsujimura ◽  
Kazuhiko Ukai ◽  
Daisuke Ohama ◽  
Atsuo Nuruki ◽  
Kazutomo Yunokuchi
Keyword(s):  
Steady State ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Pupil Diameter ◽  
Retinal Ganglion ◽  
Silent Substitution ◽  
Conventional View ◽  
Rods And Cones ◽  
Direct Measurements ◽  
Stimulation System

The recent discovery of melanopsin-containing retinal ganglion cells (mRGCs) has led to a fundamental reassessment of non-image forming processing, such as circadian photoentrainment and the pupillary light reflex. In the conventional view of retinal physiology, rods and cones were assumed to be the only photoreceptors in the eye and were, therefore, considered responsible for non-image processing. However, signals from mRGCs contribute to this non-image forming processing along with cone-mediated luminance signals; although both signals contribute, it is unclear how these signals are summed. We designed and built a novel multi-primary stimulation system to stimulate mRGCs independently of other photoreceptors using a silent-substitution technique within a bright steady background. The system allows direct measurements of pupillary functions for mRGCs and cones. We observed a significant change in steady-state pupil diameter when we varied the excitation of mRGC alone, with no change in luminance and colour. Furthermore, the change in pupil diameter induced by mRGCs was larger than that induced by a variation in luminance alone: that is, for a bright steady background, the mRGC signals contribute to the pupillary pathway by a factor of three times more than the L- and M-cone signals.

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