Thermal Stability Test of Sugar Alcohols as Phase Change Materials for Medium Temperature Energy Storage Application

OpenAIRE

Solé, Aran; Neumann, Hannah; Niedermaier, Sophia; Cabeza, Luisa F.; Palomo, Elena

2014-01-01

Sugar alcohols are potential phase change materials candidates as they present high phase change enthalpy values, are non-toxic and low cost products. Three promising sugar-alcohols were selected: D-mannitol, myo-inositol and dulcitol under high melting enthalpy and temperature criterion. Thermal cycling tests were performed to study its cycling stability which can be determining when selecting the suitable phase change material. D-mannitol and dulcitol present poor thermal stability...

A solid criterion based on strict LMI without invoking equality constraint for stabilization of continuous singular systems.

Science.gov (United States)

Zhang, Xuefeng; Chen, YangQuan

2017-11-01

The paper considers the stabilization issue of linear continuous singular systems by dealing with strict linear matrix inequalities (LMIs) without invoking equality constraint and proposes a complete and effective solved LMIs formulation. The criterion is necessary and sufficient condition and can be directly solved the feasible solutions with LMI toolbox and is much more tractable and reliable in numerical simulation than existing results, which involve positive semi-definite LMIs with equality constraints. The most important property of the criterion proposed in the paper is that it can overcome the drawbacks of the invalidity caused by the singularity of Ω=PE T +SQ for stabilization of singular systems. Two counterexamples are presented to avoid the disadvantages of the existing condition of stabilization of continuous singular systems. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Concerning a criterion for stability in the neighbourhood of the magnetic axis of revolution symmetry with an anisotropic pressure

International Nuclear Information System (INIS)

Cairo, L.

1963-01-01

A stability criterion is developed which is given by local m.h.d. CGL [2] displacements in the neighbourhood of the magnetic axis of revolution symmetry. As opposed to the case of anisotropic pressure, the criterion is found to be always valid on the magnetic axis. (author) [fr

TEMPERATURE-DEFORMATION CRITERION OF OPTIMIZATION OF FINE DRAWING HIGH CARBON WIRE ROUTE

Directory of Open Access Journals (Sweden)

Y. L. Bobarikin

2012-01-01

Full Text Available The temperature-deformation criterion of assessment and optimization of routes of the thin high-carbon wire drawing enabling to increase plastic properties of wire at retaining of its durability is offered.

Time to Criterion: An Experimental Study.

Science.gov (United States)

Anderson, Lorin W.

The purpose of the study was to investigate the magnitude of individual differences in time-to-criterion and the stability of these differences. Time-to-criterion was defined in two ways: the amount of elapsed time required to attain the criterion level and the amount of on-task time required to attain the criterion level. Ninety students were…

Towards chaos criterion in quantum field theory

OpenAIRE

Kuvshinov, V. I.; Kuzmin, A. V.

2002-01-01

Chaos criterion for quantum field theory is proposed. Its correspondence with classical chaos criterion in semi-classical regime is shown. It is demonstrated for real scalar field that proposed chaos criterion can be used to investigate stability of classical solutions of field equations.

Seismic stability analysis of rock slopes by yield design theory using the generalized Hoek-Brown criterion

Directory of Open Access Journals (Sweden)

Belghali Mounir

2018-01-01

Full Text Available The stability of rock slope is studied using the kinematic approach of yield design theory, under the condition of plane strain and by considering the last version of the Hoek-Brown failure criterion. This criterion, which is suitable to intact rock or rock mass highly fractured regarded as isotropic and homogeneous, is widely accepted by the rock mechanics community and has been applied in numerous projects around the world. The failure mechanism used to implement the kinematic approach is a log-spiral rotational mechanism. The stability analysis is carried out under the effects of gravity forces and a surcharge applied along the upper plateau of the slope. To take account of the effects of forces developed in the rock mass during the passage of a seismic wave, the conventional pseudo-static method is adopted. This method is often used in slope stability study for its simplicity and efficiency to simulate the seismic forces. The results found are compared with published numerical solutions obtained from other approaches. The comparison showed that the results are almost equal. The maximum error found is less than 1%, indicating that this approach is effective for analyzing the stability of rock slopes. The relevance of the approach demonstrated, investigations are undertaken to study the influence of some parameters on the stability of the slope. These parameters relate to the mechanical strength of the rock, slope geometry and loading.

Stability Criterion of Linear Stochastic Systems Subject to Mixed H2/Passivity Performance

Directory of Open Access Journals (Sweden)

Cheung-Chieh Ku

2015-01-01

Full Text Available The H2 control scheme and passivity theory are applied to investigate the stability criterion of continuous-time linear stochastic system subject to mixed performance. Based on the stochastic differential equation, the stochastic behaviors can be described as multiplicative noise terms. For the considered system, the H2 control scheme is applied to deal with the problem on minimizing output energy. And the asymptotical stability of the system can be guaranteed under desired initial conditions. Besides, the passivity theory is employed to constrain the effect of external disturbance on the system. Moreover, the Itô formula and Lyapunov function are used to derive the sufficient conditions which are converted into linear matrix inequality (LMI form for applying convex optimization algorithm. Via solving the sufficient conditions, the state feedback controller can be established such that the asymptotical stability and mixed performance of the system are achieved in the mean square. Finally, the synchronous generator system is used to verify the effectiveness and applicability of the proposed design method.

A novel delay-dependent criterion for delayed neural networks of neutral type

International Nuclear Information System (INIS)

Lee, S.M.; Kwon, O.M.; Park, Ju H.

2010-01-01

This Letter considers a robust stability analysis method for delayed neural networks of neutral type. By constructing a new Lyapunov functional, a novel delay-dependent criterion for the stability is derived in terms of LMIs (linear matrix inequalities). A less conservative stability criterion is derived by using nonlinear properties of the activation function of the neural networks. Two numerical examples are illustrated to show the effectiveness of the proposed method.

Stability Analysis of a Type of Takagi-Sugeno PI Fuzzy Control Systems Using Circle Criterion

Directory of Open Access Journals (Sweden)

Kairui Cao

2011-04-01

Full Text Available A type of Takagi-Sugeno (T-S Proportional-Integral (PI fuzzy controllers is studied. The T-S PI fuzzy controller is formed by a T-S Proportional-Derivative (PD fuzzy controller connected with an integrator. In this particular structure, the T-S PD fuzzy controller is a weighted sum of some linear PD sub-controllers. The mathematical properties of our T-S PI fuzzy controller are also investigated. Based on these properties, the global asymptotic stability of the fuzzy control systems, in which the T-S PI fuzzy controllers are employed, are analyzed by using the well-known circle criterion. A sufficient condition with an elegant graphical interpretation in the frequency domain is further derived to guarantee the global asymptotic stability of the above fuzzy control systems. Finally, two numerical examples are provided to demonstrate how to deploy this method in analyzing the T-S PI fuzzy control systems in the frequency domain with the aid of some simple graphs.

Borehole Stability in High-Temperature Formations

Science.gov (United States)

Yan, Chuanliang; Deng, Jingen; Yu, Baohua; Li, Wenliang; Chen, Zijian; Hu, Lianbo; Li, Yang

2014-11-01

In oil and gas drilling or geothermal well drilling, the temperature difference between the drilling fluid and formation will lead to an apparent temperature change around the borehole, which will influence the stress state around the borehole and tend to cause borehole instability in high geothermal gradient formations. The thermal effect is usually not considered as a factor in most of the conventional borehole stability models. In this research, in order to solve the borehole instability in high-temperature formations, a calculation model of the temperature field around the borehole during drilling is established. The effects of drilling fluid circulation, drilling fluid density, and mud displacement on the temperature field are analyzed. Besides these effects, the effect of temperature change on the stress around the borehole is analyzed based on thermoelasticity theory. In addition, the relationships between temperature and strength of four types of rocks are respectively established based on experimental results, and thermal expansion coefficients are also tested. On this basis, a borehole stability model is established considering thermal effects and the effect of temperature change on borehole stability is also analyzed. The results show that the fracture pressure and collapse pressure will both increase as the temperature of borehole rises, and vice versa. The fracture pressure is more sensitive to temperature. Temperature has different effects on collapse pressures due to different lithological characters; however, the variation of fracture pressure is unrelated to lithology. The research results can provide a reference for the design of drilling fluid density in high-temperature wells.

Diagonal recurrent neural network based adaptive control of nonlinear dynamical systems using lyapunov stability criterion.

Science.gov (United States)

Kumar, Rajesh; Srivastava, Smriti; Gupta, J R P

2017-03-01

In this paper adaptive control of nonlinear dynamical systems using diagonal recurrent neural network (DRNN) is proposed. The structure of DRNN is a modification of fully connected recurrent neural network (FCRNN). Presence of self-recurrent neurons in the hidden layer of DRNN gives it an ability to capture the dynamic behaviour of the nonlinear plant under consideration (to be controlled). To ensure stability, update rules are developed using lyapunov stability criterion. These rules are then used for adjusting the various parameters of DRNN. The responses of plants obtained with DRNN are compared with those obtained when multi-layer feed forward neural network (MLFFNN) is used as a controller. Also, in example 4, FCRNN is also investigated and compared with DRNN and MLFFNN. Robustness of the proposed control scheme is also tested against parameter variations and disturbance signals. Four simulation examples including one-link robotic manipulator and inverted pendulum are considered on which the proposed controller is applied. The results so obtained show the superiority of DRNN over MLFFNN as a controller. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

On the stability of critical state in hard superconductors with nonhomogeneous temperature profile

CERN Document Server

Tajlanov, N A

2002-01-01

One studied the problem on thermal and magnetic breaking of critical state in hard superconductors. One assumes that initial distribution of temperature and of electrical field is very nonhomogeneous one. In quasi-stationary approximation one determined the limit of occurrence of thermal and magnetic instability in a superconductor. The derived integral criterion is shown to take account of the effect of each segment of a superconductor on the threshold of occurrence of critical state instability on contrast to similar criterion for homogeneous temperature profile

Construction of the Courant-Snyder invariants for the non-linear equations of motion and criterion for the long-term stability of the beam in a storage ring

International Nuclear Information System (INIS)

Garczynski, V.

1993-01-01

The Courant-Snyder invariants become Lyapunov functions when the β-functions admit non-zero lower, and finite upper bounds. The long-term stability of motion then follows. This alternative criterion for the long-term stability of motion can be generalized to the nonlinear case. A single particle subjected to an arbitrary static magnetic field is considered in some detail, as an example

Elliptically Bent X-ray Mirrors with Active Temperature Stabilization

International Nuclear Information System (INIS)

Yuan, Sheng; Church, Matthew; Yashchuk, Valeriy V.; Goldberg, Kenneth A.; Celestre, Rich; McKinney, Wayne R.; Kirschman, Jonathan; Morrison, Greg; Noll, Tino; Warwick, Tony; Padmore, Howard A.

2010-01-01

We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the Advanced Light Source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3K does not noticeably affect the mirror figure. Without temperature stabilization, the surface slope changes by approximately 1.5 ?mu rad rms (primarily defocus) under the same conditions.

Elliptically Bent X-Ray Mirrors with Active Temperature Stabilization

International Nuclear Information System (INIS)

Yuan, S.; Church, M.; Yashchuk, V.V.; Celestre, R.S.; McKinney, W.R.; Morrison, G.; Warwick, T.; Padmore, H.A.; Goldberg, K.A.; Kirschman, J.; Noll, T.

2010-01-01

We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the advanced light source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3 K does not noticeably affect the mirror figure. Without temperature stabilization, the rms slope error is changed by approximately 1.5 μrad (primarily defocus) under the same conditions

Criterion for the onset of quench for low-flow reflood

International Nuclear Information System (INIS)

Hsu, Y.Y.; Young, M.W.

1982-07-01

This study provides a criterion for the onset of quench for low flow reflood. The criterion is a combination of two conditions: T/sub clad/ < T/sub limiting quench/ where T = Temperature, and α < 0.95 where α = void fraction. This criterion was obtained by examining temperature data from tests simulating PWR reflood, such as FLECHT, THTF, PBF, CCTF, and FEBA tests, with void fraction data from CCTF, FEBA, and FLECHT low flood tests. The data show that quenching initiated at α = 0.95 and that the majority of quench occurred at void fractions near 0.85. The results show that rods can be completely quenched by entrained droplets even if the collapsed liquid level does not advance. A thorough discussion of the analysis which supports this quench criterion is given in the text of this report

Vibrational stability of graphene

Directory of Open Access Journals (Sweden)

Yangfan Hu

2013-05-01

Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.

Synchronization criterion for Lur'e type complex dynamical networks with time-varying delay

International Nuclear Information System (INIS)

Ji, D.H.; Park, Ju H.; Yoo, W.J.; Won, S.C.; Lee, S.M.

2010-01-01

In this Letter, the synchronization problem for a class of complex dynamical networks in which every identical node is a Lur'e system with time-varying delay is considered. A delay-dependent synchronization criterion is derived for the synchronization of complex dynamical network that represented by Lur'e system with sector restricted nonlinearities. The derived criterion is a sufficient condition for absolute stability of error dynamics between the each nodes and the isolated node. Using a convex representation of the nonlinearity for error dynamics, the stability condition based on the discretized Lyapunov-Krasovskii functional is obtained via LMI formulation. The proposed delay-dependent synchronization criterion is less conservative than the existing ones. The effectiveness of our work is verified through numerical examples.

Temperature Control of Gas Chromatograph Based on Switched Delayed System Techniques

Directory of Open Access Journals (Sweden)

Xiao-Liang Wang

2014-01-01

Full Text Available We address the temperature control problem of the gas chromatograph. We model the temperature control system of the gas chromatograph into a switched delayed system and analyze the stability by common Lyapunov functional technique. The PI controller parameters can be given based on the proposed linear matrix inequalities (LMIs condition and the designed controller can make the temperature of gas chromatograph track the reference signal asymptotically. An experiment is given to illustrate the effectiveness of the stability criterion.

Temperature stabilization of injection lasers

International Nuclear Information System (INIS)

Albanese, A.

1987-01-01

Apparatus which stabilizes the temperature, and thereby the output wavelength, of an injection laser. Means monitor the laser terminal voltage across a laser and derive a voltage therefrom which is proportional to the junction voltage of the laser. Means compares the voltage to a reference value from source and a temperature controller adjusts the laser temperature in response to the results of the comparison. Further embodiments of the present invention vary the output wavelength of the laser by varying the reference value from source against which the laser junction voltage is compared. (author)

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

OpenAIRE

Y. A. ABDELAZIZ; F. M. MEGAHED

2010-01-01

An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω) from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 0C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the...

Ignition criterion for heterogeneous energetic materials based on hotspot size-temperature threshold

Science.gov (United States)

Barua, A.; Kim, S.; Horie, Y.; Zhou, M.

2013-02-01

A criterion for the ignition of granular explosives (GXs) and polymer-bonded explosives (PBXs) under shock and non-shock loading is developed. The formulation is based on integration of a quantification of the distributions of the sizes and locations of hotspots in loading events using a cohesive finite element method (CFEM) developed recently and the characterization by Tarver et al. [C. M. Tarver et al., "Critical conditions for impact- and shock-induced hot spots in solid explosives," J. Phys. Chem. 100, 5794-5799 (1996)] of the critical size-temperature threshold of hotspots required for chemical ignition of solid explosives. The criterion, along with the CFEM capability to quantify the thermal-mechanical behavior of GXs and PBXs, allows the critical impact velocity for ignition, time to ignition, and critical input energy at ignition to be determined as functions of material composition, microstructure, and loading conditions. The applicability of the relation between the critical input energy (E) and impact velocity of James [H. R. James, "An extension to the critical energy criterion used to predict shock initiation thresholds," Propellants, Explos., Pyrotech. 21, 8-13 (1996)] for shock loading is examined, leading to a modified interpretation, which is sensitive to microstructure and loading condition. As an application, numerical studies are undertaken to evaluate the ignition threshold of granular high melting point eXplosive, octahydro-1,3,5,7-tetranitro-1,2,3,5-tetrazocine (HMX) and HMX/Estane PBX under loading with impact velocities up to 350 ms-1 and strain rates up to 105 s-1. Results show that, for the GX, the time to criticality (tc) is strongly influenced by initial porosity, but is insensitive to grain size. Analyses also lead to a quantification of the differences between the responses of the GXs and PBXs in terms of critical impact velocity for ignition, time to ignition, and critical input energy at ignition. Since the framework permits

Synthesis of high-temperature viscosity stabilizer used in drilling fluid

Science.gov (United States)

Zhang, Yanna; Luo, Huaidong; Shi, Libao; Huang, Hongjun

2018-02-01

Abstract For a well performance drilling fluid, when it operates in deep wells under high temperature, the most important property required is the thermal stability. The drilling fluid properties under high temperature can be controlled by proper selection of viscosity stabilizer, which can capture oxygen to protect polymer agent in the drilling fluid. In this paper a viscosity stabilizer PB-854 is described, which was synthesized by 4-phenoxybutyl bromide, paraformaldehyde, and phloroglucinol using etherification method and condensation reaction. We studied the effect of catalyst dosage, temperature, time, and stirring rate on the synthetic yield. Under this condition: molar ratio of 2-tert-Butylphenol, paraformaldehyde and phloroglucinol of 2:1:2.5, reacting temperature of 100 °C, stirring rate of 100 r min-1, and mass content of catalyst of 15 %, char yield of 5-bromine-3-tert-butyl salicylaldehyde reached 86 %. Under this condition: molar ratio of 5-bromine-3-tert-butyl salicylaldehyde and phloroglucinol of 4, reacting temperature of 60 °C, reacting time of 30 min, volume content of sulphuric acid of 80 %, char yield of the target product viscosity stabilizer PB-854 is 86%. Finally, in this paper, infrared spectroscopy is adopted to analyse the structure of the synthetic product PB-854.The improvement in the stability of drilling fluid was further shown after adding the viscosity stabilizer in the common polymer drilling fluid under high temperature conditions of 120 °C ˜ 180 °C. The results show significant change in terms of fluid stability in the presence of this new stabilizer as it provides better stability.

The validity and reliability of a dynamic neuromuscular stabilization-heel sliding test for core stability.

Science.gov (United States)

Cha, Young Joo; Lee, Jae Jin; Kim, Do Hyun; You, Joshua Sung H

2017-10-23

Core stabilization plays an important role in the regulation of postural stability. To overcome shortcomings associated with pain and severe core instability during conventional core stabilization tests, we recently developed the dynamic neuromuscular stabilization-based heel sliding (DNS-HS) test. The purpose of this study was to establish the criterion validity and test-retest reliability of the novel DNS-HS test. Twenty young adults with core instability completed both the bilateral straight leg lowering test (BSLLT) and DNS-HS test for the criterion validity study and repeated the DNS-HS test for the test-retest reliability study. Criterion validity was determined by comparing hip joint angle data that were obtained from BSLLT and DNS-HS measures. The test-retest reliability was determined by comparing hip joint angle data. Criterion validity was (ICC2,3) = 0.700 (preliability was (ICC3,3) = 0.953 (pvalidity data demonstrated a good relationship between the gold standard BSLLT and DNS-HS core stability measures. Test-retest reliability data suggests that DNS-HS core stability was a reliable test for core stability. Clinically, the DNS-HS test is useful to objectively quantify core instability and allow early detection and evaluation.

Characterization of the austenitic stability of metastable austenitic stainless steel with regard to its formability

Science.gov (United States)

Schneider, Matthias; Liewald, Mathias

2018-05-01

During the last decade, the stainless steel market showed a growing volume of 3-5% p.a.. The austenitic grades are losing market shares to ferritic or 200-series grades due to the high nickel price, but still playing the most important role within the stainless steel market. Austenitic stainless steel is characterized by the strain-induced martensite formation, causing the TRIP-effect (Transformation Induced Plasticity) which is responsible for good formability and high strength. The TRIP-effect itself is highly dependent on the forming temperature, the strain as well as the chemical composition which has a direct influence on the stability of the austenite. Today the austenitic stability is usually characterized by the so called Md30-temperature, which was introduced by Angel and enhanced by several researches, particularly Nohara. It is an empirical formula based on the chemical composition and the grain size of a given material, calculating the temperature which is necessary to gain a 50 % martensite formation after 30 % of elongation in a tensile test. A higher Md30-temperature indicates a lower stability and therefore a higher tendency towards martensite formation. The main disadvantage of Md30 -temperature is the fact that it is not based on forming parameters and only describes a single point instead of the whole forming process. In this paper, an experimental set up for measuring martensite and temperature evolution in a non-isothermal tensile test is presented, which is based on works of Hänsel and Schmid. With this set up, the martensite formation rate for different steels of the steel grade EN 1.4301 and EN 1.4310 is measured. Based on these results a new austenitic stability criterion is defined. This criterion and the determined Md30-temperatures are related to the stretch formability of the materials. The results show that the new IFU criterion is with regard to the formability a much more useful characteristic number for metastable austenitic steels

Analytical Solution of Tunnel Surrounding Rock for Stress and Displacement Based on Lade–Duncan Criterion

Directory of Open Access Journals (Sweden)

MingZheng Zhu

2018-01-01

Full Text Available The deformation and failure of tunnel surrounding rock is the result of tunnel excavation disturbance and rock stress release. When the local stress of surrounding rock exceeds the elastic limit of rock mass, the plastic analysis of surrounding rock must be carried out to judge the stability of tunnel. In this study, the Lade–Duncan yield criterion is used to calculate the analytic solutions for the surrounding rock in a tunnel, and the radius and displacement of the plastic zone are deduced using an equilibrium equation. The plastic zone radius and displacement based on Lade–Duncan criterion and Mohr–Coulomb criterion were compared by using single-factor analysis method under the different internal friction angles, in situ stresses, and support resistances. The results show that the solutions of the radius and displacement of plastic zone calculated by the Lade–Duncan criterion are close to those of Mohr–Coulomb criterion under the high internal friction angle and support resistance or low in situ rock stress; however, the radius and displacement of the plastic zone calculated by the Lade–Duncan criterion are larger under normal circumstances, and the Lade–Duncan criterion is more applicable to the stability analysis of the surrounding rock in a tunnel.

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

Directory of Open Access Journals (Sweden)

Y. A. ABDELAZIZ

2010-05-01

Full Text Available An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 0C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the relative resistance W(Ga at the melting point of gallium. The thermometers showed a correlation between the drift note and the values of W(Ga. It was found also that the HTSPRT which has a sensor with strip shaped support and low nominal resistance is more stable than the HTSPRT which has a sensor in the form of a coil wound on silica cross. The 0.25 Ω thermometer has better stability @ 7x10-6 0C (at TPW after 40 hour. Factors affecting the stability and accuracy of HTSPRT also will be discussed.

A criterion for heated pipe design by linear electric resistances

International Nuclear Information System (INIS)

Bloch, M.; Cruz, J.R.B.

1984-01-01

A criterion for linear eletrical elements instalation on horizontal tubes is obtainned in this work. This criterion is based upon the calculation of the thermal stresses caused by the non uniform temperature distribution in the tube cross section. The finite difference method and the SAP IV computer code are both used in the calculations. The criterion is applied to the thermal circuits of the IEN which has tube diameter varying from φ 1/2 in till φ 8 in. (author) [pt

Low beta rigid mode stability criterion for an arbitrary Larmor radius plasma

International Nuclear Information System (INIS)

Berk, H.L.; Wong, H.V.

1987-05-01

The low beta flute interchange dispersion relation for rigid displacement perturbation of axisymmetric plasma equilibria with arbitrary Larmor radius particles and field line curvature, large compared to the plasma radius, is derived. The equilibrium particle orbits are characterized by two constants of motion, energy and angular momentum, and a third adiabatic invariant derived from the rapid radial motion. The Vlasov equation is integrated, assuming that the mode frequency, axial ''bounce'' frequency, and particle drift frequency are small compared to the cyclotron frequency, and it is demonstrated that the plasma response to a rigid perturbation has a universal character independent of Larmor radius. As a result the interchange instability is the same as that predicted from conventional MHD theory. However, a new prediction, more optimistic than earlier work, is found for the low density threshold of systems like Migma, which are disc-shaped, that is, the axial extent Δz is less than the radial extent r 0 . For Δz/sub r 0 / much less than 1, the stability criterion is determined by the total particle number. Whereas the older theory (Δz/sub r 0 / much greater than 1) predicted instability at about the densities achieved in actual Migma experiments, the present theory (Δz/sub r 0 / much less than 1) indicates that the experimental results were for plasmas with particle number below the interchange threshold

Evaluation test on stability of high temperature strain gage

Energy Technology Data Exchange (ETDEWEB)

Sato, Toshimi (Kyowa Electronic Instruments Co. Ltd., Tokyo (Japan)); Ito, Haruhiko; Tanaka, Isao; Komori, Yoshihiro

1983-08-01

This report deals with the results on a stability test of high temperature strain gage which is utilized for development of the Stethoscope for OGL - 1 Components in Elevated Temperature Services (ab. SOCETS). The test has proved that the weldable strain gage (KHC - 20 - G5) exhibits excellent stability at 500/sup 0/C during 3000 to 4000 hours service and can be applied sufficiently to evaluate integrity of OGL - 1 high temperature pipings and others.

Evaluation test on stability of high temperature strain gage

International Nuclear Information System (INIS)

Sato, Toshimi; Ito, Haruhiko; Tanaka, Isao; Komori, Yoshihiro.

1983-01-01

This report deals with the results on a stability test of high temperature strain gage which is utilized for development of the Stethoscope for OGL - 1 Components in Elevated Temperature Services (ab. SOCETS). The test has proved that the weldable strain gage (KHC - 20 - G5) exhibits excellent stability at 500 0 C during 3000 to 4000 hours service and can be applied sufficiently to evaluate integrity of OGL - 1 high temperature pipings and others. (author)

Is the Mercier criterion relevant to stellarator stability?

International Nuclear Information System (INIS)

Carreras, B.A.; Lynch, V.E.; Ichiguchi, K.; Wakatani, M.; Tatsuno, T.

2001-01-01

Local flattening of the pressure profile at the resonant surfaces may significantly change the stellarator stability properties. This flattening may be an intrinsic consequence of the three-dimensional nature of the equilibrium and may invalidate the local stability criteria often used in stellarator design. (author)

Cluster temperature. Methods for its measurement and stabilization

International Nuclear Information System (INIS)

Makarov, G N

2008-01-01

Cluster temperature is an important material parameter essential to many physical and chemical processes involving clusters and cluster beams. Because of the diverse methods by which clusters can be produced, excited, and stabilized, and also because of the widely ranging values of atomic and molecular binding energies (approximately from 10 -5 to 10 eV) and numerous energy relaxation channels in clusters, cluster temperature (internal energy) ranges from 10 -3 to about 10 8 K. This paper reviews research on cluster temperature and describes methods for its measurement and stabilization. The role of cluster temperature in and its influence on physical and chemical processes is discussed. Results on the temperature dependence of cluster properties are presented. The way in which cluster temperature relates to cluster structure and to atomic and molecular interaction potentials in clusters is addressed. Methods for strong excitation of clusters and channels for their energy relaxation are discussed. Some applications of clusters and cluster beams are considered. (reviews of topical problems)

GEOINFORMATION ANALYSIS OF THE INDEX OF BIOLOGICAL EFFICIENCY OF CLIMATE AS CRITERION FOR EVALUATION OF POTENTIAL STABILITY OF THE LANDSCAPE

Directory of Open Access Journals (Sweden)

A. N. Ogurtsov

2017-01-01

Full Text Available The article considers indicator approach to assessment of potential stability of landscapes. As an example of integrated criterion the index of climate biological efficiency (TK has been used. Calculations of TK index for assessment of stability of landscapes have been executed for the territory of Tver Region. Cartograms of TK index and its components have been made. Geospatial analysis has been carried out and estimates of potential stability of landscapes are given. The example of mapping and calculation of the TK index serves as a starting point for using it in multi-criteria assessment of the state and emergent properties of geosystems built on the principles of ASPID-methodology. This example reflects the possibility of using the indicator approach in the first stage of the study of resistance to changes in the parameters of natural regime for the subsequent multicriteria and integral assessment of resistance to changes in the parameters of natural and anthropogenic regimes of geosystems functioning. The use of the index of climate biological efficiency as an indicator of sustainability will make it possible to actively use it in future in geoecological research.

Interfacial stability with mass and heat transfer

International Nuclear Information System (INIS)

Hsieh, D.Y.

1977-07-01

A simplified formulation is presented to deal with interfacial stability problems with mass and heat transfer. For Rayleigh-Taylor stability problems of a liquid-vapor system, it was found that the effect of mass and heat transfer tends to enhance the stability of the system when the vapor is hotter than the liquid, although the classical stability criterion is still valid. For Kelvin-Holmholtz stability problems, however, the classical stability criterion was found to be modified substantially due to the effect of mass and heat transfer

Protein stability and enzyme activity at extreme biological temperatures

International Nuclear Information System (INIS)

Feller, Georges

2010-01-01

Psychrophilic microorganisms thrive in permanently cold environments, even at subzero temperatures. To maintain metabolic rates compatible with sustained life, they have improved the dynamics of their protein structures, thereby enabling appropriate molecular motions required for biological activity at low temperatures. As a consequence of this structural flexibility, psychrophilic proteins are unstable and heat-labile. In the upper range of biological temperatures, thermophiles and hyperthermophiles grow at temperatures > 100 0 C and synthesize ultra-stable proteins. However, thermophilic enzymes are nearly inactive at room temperature as a result of their compactness and rigidity. At the molecular level, both types of extremophilic proteins have adapted the same structural factors, but in opposite directions, to address either activity at low temperatures or stability in hot environments. A model based on folding funnels is proposed accounting for the stability-activity relationships in extremophilic proteins. (topical review)

Introduction to the theory and application of a unified Bohm criterion for arbitrary-ion-temperature collision-free plasmas with finite Debye lengths

Science.gov (United States)

Kos, L.; Jelić, N.; Kuhn, S.; Tskhakaya, D. D.

2018-04-01

At present, identifying and characterizing the common plasma-sheath edge (PSE) in the conventional fluid approach leads to intrinsic oversimplifications, while the kinetic one results in unusable over-generalizations. In addition, none of these approaches can be justified in realistic plasmas, i.e., those which are characterized by non-negligible Debye lengths and a well-defined non-negligible ion temperature. In an attempt to resolve this problem, we propose a new formulation of the Bohm criterion [D. Bohm, The Characteristics of Electrical Discharges in Magnetic Fields (McGraw-Hill, New York, 1949)], which is here expressed in terms of fluid, kinetic, and electrostatic-pressure contributions. This "unified" Bohm criterion consists of a set of two equations for calculating the ion directional energy (i.e., the mean directional velocity) and the plasma potential at the common PSE, and is valid for arbitrary ion-to-electron temperature ratios. It turns out to be exact at any point of the quasi-neutral plasma provided that the ion differential polytropic coefficient function (DPCF) of Kuhn et al. [Phys. Plasmas 13, 013503 (2006)] is employed, with the advantage that the DPCF is an easily measurable fluid quantity. Moreover, our unified Bohm criterion holds in plasmas with finite Debye lengths, for which the famous kinetic criterion formulated by Harrison and Thompson [Proc. Phys. Soc. 74, 145 (1959)] fails. Unlike the kinetic criterion in the case of negligible Debye length, the kinetic contribution to the unified Bohm criterion, arising due to the presence of negative and zero velocities in the ion velocity distribution function, can be calculated separately from the fluid term. This kinetic contribution disappears identically at the PSE, yielding strict equality of the ion directional velocity there and the ion sound speed, provided that the latter is formulated in terms of the present definition of DPCFs. The numerical values of these velocities are found for the

Effect of triethanolamine on the stability of furfurol at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Baiburskaya, E.L.; Kalenik, G.S.; Levchenko, E.S.; Martynenko, A.G.; Okhrimenko, N.V.; Shiryaeva, G.P.

1982-01-01

The effect of triethanolamine (I) on the stability of furfurol under the conditions of oil purification was studied. It was shown that (I) shows a stabilizing effect at a temperature of 200/sup 0/, which is considerably weakened on heating the furfurol in the presence of air (at atmospheric pressure). At a temperature of 230/sup 0/ (I) is not a stabilizer for furfurol.

A geometric criterion for the stability of forced oscillations in non-linear mechanics (1961); Un critere geometrique de stabilite des oscillations forcees en mecanique non lineaire (1961)

Energy Technology Data Exchange (ETDEWEB)

Blaquiere, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

The author completes the two-parameter diagram theory which he has previously explained, by giving a geometric criterion of stability for a non-linear system under forced conditions. After two simple geometric transformations of the diagram he obtains the separators which are the boundary conditions for the zones of stability. (author) [French] L'auteur complete la theorie du diagramme a deux parametres, qu'il a anterieurement exposee, par l'enonce d'un critere geometrique de stabilite, relatif aux regimes forces d'un systeme non lineaire. Il obtient, par deux transformations geometriques simples du diagramme, les separatrices qui delimitent les zones de stabilite. (auteur)

Generalized melting criterion for beam-induced amorphization

International Nuclear Information System (INIS)

Lam, N. Q.; Okamoto, Paul R.

1993-09-01

Recent studies have shown that the mean-square static atomic displacements provide a generic measure of the enthalpy stored in the lattice in the form of chemical and topological disorder, and that the effect of the displacements on the softening of shear elastic constants is identical to that of heating. This finding lends support to a generalized form of the Lindemann phenomenological melting criterion and leads to a natural interpretion of crystalline-to-amorphous transformations as defect-induced melting of metastable crystals driven beyond a critical state of disorder where the melting temperature falls below the glass-transition temperature. Application of the generalized Lindemann criterion to both the crystalline and amorphous phases indicates that the enthalpies of the two phases become identical when their shear moduli become equal. This thermo-elastic rule provides a basis for predicting the relative susceptibility of compounds to amorphization in terms of their elastic properties as measured by Debye temperatures. The present approach can explain many of the basic findings on beam-induced amorphization of intermetallic compounds as well as amorphous phase formation associated with ion implantation, ion-beam mixing and other solid-state processes

The Distributed Criterion Design

Science.gov (United States)

McDougall, Dennis

2006-01-01

This article describes and illustrates a novel form of the changing criterion design called the distributed criterion design, which represents perhaps the first advance in the changing criterion design in four decades. The distributed criterion design incorporates elements of the multiple baseline and A-B-A-B designs and is well suited to applied…

Extended equal areas criterion: foundations and applications

Energy Technology Data Exchange (ETDEWEB)

Yusheng, Xue [Nanjim Automation Research Institute, Nanjim (China)

1994-12-31

The extended equal area criterion (EEAC) provides analytical expressions for ultra fast transient stability assessment, flexible sensitivity analysis, and means to preventive and emergency controls. Its outstanding performances have been demonstrated by thousands upon thousands simulations on more than 50 real power systems and by on-line operation records in an EMS environment of Northeast China Power System since September 1992. However, the researchers have mainly based on heuristics and simulations. This paper lays a theoretical foundation of EEAC and brings to light the mechanism of transient stability. It proves true that the dynamic EEAC furnishes a necessary and sufficient condition for stability of multi machine systems with any detailed models, in the sense of the integration accuracy. This establishes a new platform for further advancing EEAC and better understanding of problems. An overview of EEAC applications in China is also given in this paper. (author) 30 refs.

Clay facial masks: physicochemical stability at different storage temperatures.

Science.gov (United States)

Zague, Vivian; de Almeida Silva, Diego; Baby, André Rolim; Kaneko, Telma Mary; Velasco, Maria Valéria Robles

2007-01-01

Clay facial masks--formulations that contain a high percentage of solids dispersed in a liquid vehicle--have become of special interest due to specific properties presented by clays, such as particle size, cooling index, high adsorption capacity, and plasticity. Although most of the physicochemical properties of clay dispersions have been studied, specific aspects concerning the physicochemical stability of clay mask products remain unclear. This work aimed at investigating the accelerated physicochemical stability of clay mask formulations stored at different temperatures. Formulations were subjected to centrifuge testing and to thermal treatment for 15 days, during which temperature was varied from -5.0 degrees to 45.0 degrees C. The apparent viscosity and visual aspect (homogeneity) of all formulations were affected by temperature variation, whereas color, odor, and pH value remained unaltered. These results, besides the estimation of physicochemical stability under aging, can be useful in determining the best storage conditions for clay-based formulations.

Temperature Stabilized Characterization of High Voltage Power Supplies

CERN Document Server

Krarup, Ole

2017-01-01

High precision measurements of the masses of nuclear ions in the ISOLTRAP experiment relies on an MR-ToF. A major source of noise and drift is the instability of the high voltage power supplies employed. Electrical noise and temperature changes can broaden peaks in time-of-flight spectra and shift the position of peaks between runs. In this report we investigate how the noise and drift of high-voltage power supplies can be characterized. Results indicate that analog power supplies generally have better relative stability than digitally controlled ones, and that the high temperature coefficients of all power supplies merit efforts to stabilize them.

Low-temperature technique for thick film resist stabilization and curing

Science.gov (United States)

Minter, Jason P.; Wong, Selmer S.; Marlowe, Trey; Ross, Matthew F.; Narcy, Mark E.; Livesay, William R.

1999-06-01

For a range of thick film photoresist applications, including MeV ion implant processing, thin film head manufacturing, and microelectromechanical systems processing, there is a need for a low-temperature method for resist stabilization and curing. Traditional methods of stabilizing or curing resist films have relied on thermal cycling, which may not be desirable due to device temperature limitations or thermally-induced distortion of the resist features.

An analytic expression for the sheath criterion in magnetized plasmas with multi-charged ion species

International Nuclear Information System (INIS)

Hatami, M. M.

2015-01-01

The generalized Bohm criterion in magnetized multi-component plasmas consisting of multi-charged positive and negative ion species and electrons is analytically investigated by using the hydrodynamic model. It is assumed that the electrons and negative ion density distributions are the Boltzmann distribution with different temperatures and the positive ions enter into the sheath region obliquely. Our results show that the positive and negative ion temperatures, the orientation of the applied magnetic field and the charge number of positive and negative ions strongly affect the Bohm criterion in these multi-component plasmas. To determine the validity of our derived generalized Bohm criterion, it reduced to some familiar physical condition and it is shown that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when entrance velocity of ion into the sheath satisfies the obtained Bohm criterion. Also, as a practical application of the obtained Bohm criterion, effects of the ionic temperature and concentration as well as magnetic field on the behavior of the charged particle density distributions and so the sheath thickness of a magnetized plasma consisting of electrons and singly charged positive and negative ion species are studied numerically

On the Jeans criterion

International Nuclear Information System (INIS)

Whitworth, A.P.

1980-01-01

The Jeans criterion is first stated and distinguished from the Virial Theorem. Then it is discussed how the Jeans criterion can be derived from the Virial Theorem and the inherent shortcomings in this derivation. Finally, it is indicated how these shortcomings might be overcome. The Jeans criterion is a fragmentation - or condensation -criterion. An expression is given, connecting the fragmentation of an unstable extended medium into masses Msub(J). Rather than picturing the background medium fragmenting, it is probably more appropriate to envisage these masses Msub(J) 'condensing' out of the background medium. On the condensation picture some fraction of the background material separates out into coherent bound nodules under the pull of its self-gravity. For this reason the Jeans criterion is discussed as a condensation condition, reserving the term fragmentation for a different process. The Virial Theorem provides a contraction criterion. This is described with reference to a spherical cloud and is developed to derive the Jeans criterion. (U.K.)

Stability of the Hartree-Fock model with temperature

OpenAIRE

Dolbeault, Jean; Felmer, Patricio; Lewin, Mathieu

2008-01-01

This paper is devoted to the Hartree-Fock model with temperature in the euclidean space. For large classes of free energy functionals, minimizers are obtained as long as the total charge of the system does not exceed a threshold which depends on the temperature. The usual Hartree-Fock model is recovered in the zero temperature limit. An orbital stability result for the Cauchy problem is deduced from the variational approach.

Temperature stabilization near Tsub(lambda) in liquid helium

International Nuclear Information System (INIS)

Francois, M.; Lhuillier, D.

1975-01-01

The study of He I and II equilibrium properties near the lambda transition requires a very performant temperature stabilisation. A system using second or fourth sound and which offers a stability better than 10 -8 0 K/hour in the temperature range 1.8 0 K-2.2 0 K is presented. (Auth.)

Low temperature stabilization process for production of carbon fiber having structural order

Science.gov (United States)

Rios, Orlando; McGuire, Michael Alan; More, Karren Leslie; Tenhaeff, Wyatt Evan; Menchhofer, Paul A.; Paulauskas, Felix Leonard

2017-08-15

A method for producing a carbon fiber, the method comprising: (i) subjecting a continuous carbon fiber precursor having a polymeric matrix in which strength-enhancing particles are incorporated to a stabilization process during which the carbon fiber precursor is heated to within a temperature range ranging from the glass transition temperature to no less than 20.degree. C. below the glass transition temperature of the polymeric matrix, wherein the maximum temperature employed in the stabilization process is below 400.degree. C., for a processing time within said temperature range of at least 1 hour in the presence of oxygen and in the presence of a magnetic field of at least 1 Tesla, while said carbon fiber precursor is held under an applied axial tension; and (ii) subjecting the stabilized carbon fiber precursor, following step (i), to a carbonization process. The stabilized carbon fiber precursor, resulting carbon fiber, and articles made thereof are also described.

Laboratory-performance criteria for in situ waste-stabilization materials

International Nuclear Information System (INIS)

Shaw, P.; Weidner, J.

1996-01-01

The Department of Energy (DOE) Landfill Stabilization Focus Area is investigating a variety of in situ placement methods, grout materials, and characterization techniques for the stabilization of buried low-level transuranic-contaminated waste at Department of Energy sites. In situ stabilization involves underground injection or placement of substances to isolate, treat, or contain buried contaminants. Performance criteria were developed to evaluate various candidate stabilization materials for both long-term stabilization and interim stabilization or retrieval. The criteria are go/no-go, ready, and preliminary. The criterion go/no-go eliminates technologies that are not applicable for in situ treatment of buried waste. The criterion ready indicates that the technology is sufficiently developed and proven to be field demonstrated full-scale. The criterion preliminary indicates the prospective technologies to be potentially applicable to in situ buried waste stabilization, but further development is needed before the technology is ready for field-scale demonstration

Watt steam governor stability

Science.gov (United States)

Denny, Mark

2002-05-01

The physics of the fly-ball governor, introduced to regulate the speed of steam engines, is here analysed anew. The original analysis is generalized to arbitrary governor geometry. The well-known stability criterion for the linearized system breaks down for large excursions from equilibrium; we show approximately how this criterion changes.

Aerobic stability of distillers wet grains as influenced by temperature.

Science.gov (United States)

Lehman, R Michael; Rosentrater, Kurt A

2013-02-01

The storability of distillers wet grains (DWG) influences the economic, energetic, and carbon balances of fuel ethanol production, yet there are limited published data on the deterioration of DWG following its production. We used biogenic CO(2) production to assess the aerobic stability of DWG incubated at three temperatures (12 °C, 22 °C, 32 °C) and compared CO(2) production over time to the appearance of mold and changes in DWG color parameters. CO(2) production and mold colonization indicate that at temperatures near 12 °C, the aerobic stability of DWG was high and that it can be stored for at least a 10-day period. At temperatures close to 22 °C, the onset of increased microbial activity and visible mold colonization occurred between 4 and 7 days and both activity and mold ratings were very high by the ninth day in all three experiments. At 32 °C, 2 days may be a more appropriate limit for storage. Temperature and time interact in a nonlinear fashion that permits the prediction of DWG stability boundaries. The simple visual appearance of mold appears to be a reasonable indicator that correlates well (r = 0.694) with CO(2) production, a measure of the aerobic stability of DWG. Published 2012 by John Wiley & Sons, Ltd.

Robust stability of bidirectional associative memory neural networks with time delays

Science.gov (United States)

Park, Ju H.

2006-01-01

Based on the Lyapunov Krasovskii functionals combined with linear matrix inequality approach, a novel stability criterion is proposed for asymptotic stability of bidirectional associative memory neural networks with time delays. A novel delay-dependent stability criterion is given in terms of linear matrix inequalities, which can be solved easily by various optimization algorithms.

Robust stability of bidirectional associative memory neural networks with time delays

International Nuclear Information System (INIS)

Park, Ju H.

2006-01-01

Based on the Lyapunov-Krasovskii functionals combined with linear matrix inequality approach, a novel stability criterion is proposed for asymptotic stability of bidirectional associative memory neural networks with time delays. A novel delay-dependent stability criterion is given in terms of linear matrix inequalities, which can be solved easily by various optimization algorithms

Influence of temperature on the anaerobic stabilization of organic ...

African Journals Online (AJOL)

This study was aimed at determining the effect of temperature on the stabilization of organic solid waste conjugated with sewage sludge in anaerobic batch ... It is concluded that anaerobic digestion at ambient temperature represents an economical and environmentally viable strategy for the disposal of municipal solid ...

AMD-stability in the presence of first-order mean motion resonances

Science.gov (United States)

Petit, A. C.; Laskar, J.; Boué, G.

2017-11-01

The angular momentum deficit (AMD)-stability criterion allows to discriminate between a priori stable planetary systems and systems for which the stability is not granted and needs further investigations. AMD-stability is based on the conservation of the AMD in the averaged system at all orders of averaging. While the AMD criterion is rigorous, the conservation of the AMD is only granted in absence of mean-motion resonances (MMR). Here we extend the AMD-stability criterion to take into account mean-motion resonances, and more specifically the overlap of first-order MMR. If the MMR islands overlap, the system will experience generalized chaos leading to instability. The Hamiltonian of two massive planets on coplanar quasi-circular orbits can be reduced to an integrable one degree of freedom problem for period ratios close to a first-order MMR. We use the reduced Hamiltonian to derive a new overlap criterion for first-order MMR. This stability criterion unifies the previous criteria proposed in the literature and admits the criteria obtained for initially circular and eccentric orbits as limit cases. We then improve the definition of AMD-stability to take into account the short term chaos generated by MMR overlap. We analyze the outcome of this improved definition of AMD-stability on selected multi-planet systems from the Extrasolar Planets Encyclopædia.

Stability analysis of high temperature superconducting coil in liquid hydrogen

International Nuclear Information System (INIS)

Nakayama, T.; Yagai, T.; Tsuda, M.; Hamajima, T.

2007-01-01

Recently, it is expected that hydrogen plays an important role in energy source including electric power in near future. Liquid hydrogen has high potential for cooling down superconducting coil wound with high temperature superconductors (HTS), such as BSCCO, YBCO. In this paper, we study stabilities of the coils wound with BSCCO tapes, which are immersed in the liquid hydrogen, and compare stability results with those cooled by liquid helium. We treat a minimum propagation zone (MPZ) theory to evaluate the coil stability considering boiling heat flux of the liquid hydrogen, and specific heat, heat conduction and resistivity of HTS materials as a function of temperature. It is found that the coil cooled by the liquid hydrogen has higher stability margin than that cooled by the liquid helium. We compare the stability margins of both coils wound with Bi-2223/Ag tape and Bi-2212/Ag tape in liquid hydrogen. As a result, it is found that the stability of Bi-2212 coil is equivalent to that of Bi-2223 coil in low and high magnetic field, while the maximum current of Bi-2212 coil exceeds a little bit that of Bi-2223 coil in both magnetic fields

Frequency scanning-based stability analysis method for grid-connected inverter system

DEFF Research Database (Denmark)

Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

2017-01-01

This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion with conside......This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion...... with consideration of the inverter nonlinearities. Small current disturbance is injected into grid-connected inverter system in a particular frequency range, and the impedance is computed according to the harmonic-frequency response using Fourier analysis, and then the stability is predicted on the basis...... of the impedance stability criterion. The stability issues of grid-connected inverters with grid-current feedback and the converter-current feedback are addressed using the proposed method. The results obtained from simulation and experiments validate the effectiveness of the method. The frequency scanning...

Microstructure and elevated temperature stability of 9-12% Cr steels

Energy Technology Data Exchange (ETDEWEB)

Dogan, Omer N.; Hawk, Jeffrey A.

2005-02-01

Medium Cr steels have been used in fossil fired power plants for many years because of their excellent high temperature stability and mechanical properties. As the desire to increase the efficiency of power plants continues, the operating temperature (>650C) continues to go up. Currently available low and medium Cr containing steels will not withstand the new operating temperature and must be reassessed in terms of their solid-solution and precipitation strengthening schemes. Three medium Cr steels were developed to investigate high temperature alloy strengthening strategies: 0.08C-(9-12)Cr-1.2Ni-0.7Mo-3.0Cu-3.0Co-0.5Ti. The microstructure of the alloy will be described in the as-cast and thermo-mechanically worked states. In addition, the effect on microstructure from long-term high temperature exposure will also be discussed. Finally, the overall stability of these steels will be compared against currently available power plant steels.

TOPICAL REVIEW: Protein stability and enzyme activity at extreme biological temperatures

Science.gov (United States)

Feller, Georges

2010-08-01

Psychrophilic microorganisms thrive in permanently cold environments, even at subzero temperatures. To maintain metabolic rates compatible with sustained life, they have improved the dynamics of their protein structures, thereby enabling appropriate molecular motions required for biological activity at low temperatures. As a consequence of this structural flexibility, psychrophilic proteins are unstable and heat-labile. In the upper range of biological temperatures, thermophiles and hyperthermophiles grow at temperatures > 100 °C and synthesize ultra-stable proteins. However, thermophilic enzymes are nearly inactive at room temperature as a result of their compactness and rigidity. At the molecular level, both types of extremophilic proteins have adapted the same structural factors, but in opposite directions, to address either activity at low temperatures or stability in hot environments. A model based on folding funnels is proposed accounting for the stability-activity relationships in extremophilic proteins.

Phase stability of TiH{sub 2} under high pressure and temperatures

Energy Technology Data Exchange (ETDEWEB)

Selva Vennila, R.; Durygin, A.; Saxena, S.K. [Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, VH-150, University Park, Miami, FL 33199 (United States); Merlini, Marco [European Synchrotron Radiation Facility (ESRF), Grenoble 38043 (France); Wang, Zhongwu [Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States)

2008-11-15

Phase stability of titanium hydride (TiH{sub 2}) was studied at high pressure-high temperature conditions using synchrotron radiation under non-hydrostatic conditions. Resistive heating method was used to heat the sample to a maximum temperature of 873 K in a diamond anvil cell (DAC) under pressure up to 12 GPa. Pressure-temperature behavior was studied by varying the temperature upto 823 K in steps of 50 K with pressure variations within 3 GPa. Structural phase transformation from tetragonal (I4/mmm) to cubic (Fm-3 m) was observed with increase in temperature. Tetragonal phase was found to be stabilized when the sample was subjected to pressure and temperature cycle. (author)

Unit rupture work as a criterion for quantitative estimation of hardenability in steel

International Nuclear Information System (INIS)

Kramarov, M.A.; Orlov, E.D.; Rybakov, A.B.

1980-01-01

Shown is possible utilization of high sensitivity of resistance to fracture of structural steel to the hardenability degree in the course of hardening to find the quantitative estimation of the latter one. Proposed is a criterion kappa, the ratio of the unit rupture work in the case of incomplete hardenability (asub(Tsub(ih))) under investigation, and the analoguc value obtained in the case of complete hardenability Asub(Tsub(Ch)) at the testing temperature corresponding to the critical temperature Tsub(100(M). Confirmed is high criterion sensitivity of the hardened steel structure on the basis of experimental investigation of the 40Kh, 38KhNM and 38KhNMFA steels after isothermal hold-up at different temperatures, corresponding to production of various products of austenite decomposition

Selection for Protein Kinetic Stability Connects Denaturation Temperatures to Organismal Temperatures and Provides Clues to Archaean Life.

Directory of Open Access Journals (Sweden)

M Luisa Romero-Romero

Full Text Available The relationship between the denaturation temperatures of proteins (Tm values and the living temperatures of their host organisms (environmental temperatures: TENV values is poorly understood. Since different proteins in the same organism may show widely different Tm's, no simple universal relationship between Tm and TENV should hold, other than Tm≥TENV. Yet, when analyzing a set of homologous proteins from different hosts, Tm's are oftentimes found to correlate with TENV's but this correlation is shifted upward on the Tm axis. Supporting this trend, we recently reported Tm's for resurrected Precambrian thioredoxins that mirror a proposed environmental cooling over long geological time, while remaining a shocking ~50°C above the proposed ancestral ocean temperatures. Here, we show that natural selection for protein kinetic stability (denaturation rate can produce a Tm↔TENV correlation with a large upward shift in Tm. A model for protein stability evolution suggests a link between the Tm shift and the in vivo lifetime of a protein and, more specifically, allows us to estimate ancestral environmental temperatures from experimental denaturation rates for resurrected Precambrian thioredoxins. The TENV values thus obtained match the proposed ancestral ocean cooling, support comparatively high Archaean temperatures, and are consistent with a recent proposal for the environmental temperature (above 75°C that hosted the last universal common ancestor. More generally, this work provides a framework for understanding how features of protein stability reflect the environmental temperatures of the host organisms.

Temperature stability and electrical properties in La-doped KNN-based ceramics

KAUST Repository

Lv, Xiang; Wu, Jiagang; Zhu, Jianguo; Xiao, Dingquan; Zhang, Xixiang

2018-01-01

To improve the temperature stability and electrical properties of KNN‐based ceramics, we simultaneously consider the phase boundary and the addition of rare earth element (La), 0.96K0.5Na0.5Nb0.96Sb0.04O3‐0.04(Bi1‐xLax)0.5Na0.5ZrO3 (0 ≤ x ≤ 1.0) ceramics. More specifically, we investigate how the phase boundary and the addition of La3+ affect the phase structure, electrical properties, and temperature stability of the ceramic. We show that increasing the La3+ content leads to a change in phase structure, from a rhombohedral‐tetragonal (R‐T) phase coexistence to a cubic phase. More importantly, we show that the appropriate addition of La3+ (x = 0.2) can simultaneously improve the unipolar strain (from 0.127% to 0.147%) and the temperature stability (i.e., the unipolar strain of 0.147% remains unchanged when T is increased from 25 to 80°C). In addition, we find that the ceramics with x = 0.2 exhibit a large piezoelectric constant (d33) of ~430 pC/N, a high Curie temperature (TC) of ~240°C and a fatigue‐free behavior (after 106 electric cycles). The enhanced electrical properties mostly originate from the easy domain switching, whereas the improved temperature stability can be attributed to the R‐T phase boundary and the appropriate addition of La3+.

Temperature stability and electrical properties in La-doped KNN-based ceramics

KAUST Repository

Lv, Xiang

2018-04-16

To improve the temperature stability and electrical properties of KNN‐based ceramics, we simultaneously consider the phase boundary and the addition of rare earth element (La), 0.96K0.5Na0.5Nb0.96Sb0.04O3‐0.04(Bi1‐xLax)0.5Na0.5ZrO3 (0 ≤ x ≤ 1.0) ceramics. More specifically, we investigate how the phase boundary and the addition of La3+ affect the phase structure, electrical properties, and temperature stability of the ceramic. We show that increasing the La3+ content leads to a change in phase structure, from a rhombohedral‐tetragonal (R‐T) phase coexistence to a cubic phase. More importantly, we show that the appropriate addition of La3+ (x = 0.2) can simultaneously improve the unipolar strain (from 0.127% to 0.147%) and the temperature stability (i.e., the unipolar strain of 0.147% remains unchanged when T is increased from 25 to 80°C). In addition, we find that the ceramics with x = 0.2 exhibit a large piezoelectric constant (d33) of ~430 pC/N, a high Curie temperature (TC) of ~240°C and a fatigue‐free behavior (after 106 electric cycles). The enhanced electrical properties mostly originate from the easy domain switching, whereas the improved temperature stability can be attributed to the R‐T phase boundary and the appropriate addition of La3+.

Thermodynamical stability for a perfect fluid

Energy Technology Data Exchange (ETDEWEB)

Fang, Xiongjun; Jing, Jiliang [Hunan Normal University, Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Synergetic Innovation Center for Quantum Effects and Applications, Changsha, Hunan (China); He, Xiaokai [Hunan Normal University, Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Synergetic Innovation Center for Quantum Effects and Applications, Changsha, Hunan (China); Hunan First Normal University, School of Mathematics and Computational Science, Changsha (China)

2017-12-15

According to the maximum entropy principle, it has been proved that the gravitational field equations could be derived by the extrema of the total entropy for a perfect fluid, which implies that thermodynamic relations contain information as regards gravity. In this manuscript, we obtain a criterion for the thermodynamical stability of an adiabatic, self-gravitating perfect fluid system by the second variation of the total entropy. We show, for Einstein's gravity with spherical symmetry spacetime, that the criterion is consistent with that for the dynamical stability derived by Chandrasekhar and Wald. We also find that the criterion could be applied to cases without spherical symmetry, or under general perturbations. The result further establishes the connection between thermodynamics and gravity. (orig.)

Intervention criterion and control research for active front steering with consideration of road adhesion

Science.gov (United States)

Wu, Xiaojian; Zhou, Bing; Wen, Guilin; Long, Lefei; Cui, Qingjia

2018-04-01

A multi-objective active front steering (AFS) control system considering the road adhesion constraint on vehicle stability is developed using the sliding mode control (SMC) method. First, an identification function combined with the relationship between the yaw rate and the steering angle is developed to determine whether the tyre state is linear or nonlinear. On this basis, an intervention criterion for the AFS system is proposed to improve vehicle handling and stability in emergent conditions. A sideslip angle stability domain enveloped by the upper, lower, left, and right boundaries, as well as the constraint of road adhesion coefficient, is constructed based on the ? phase-plane method. A dynamic weighting coefficient to coordinate the control of yaw rate and sideslip angle, and a control strategy that considers changing control objectives based on the desired yaw rate, the desired sideslip angle, and their proportional weights, are proposed for the SMC controller. Because road adhesion has a significant effect on vehicle stability and to meet the control algorithm's requirement of real-time access to vehicle states, a unscented Kalman filter-based state observer is proposed to estimate the adhesion coefficient and the required states. Finally, simulations are performed using high and low road adhesion conditions in a Matlab/Simulink environment, and the results show that the proposed AFS control system promptly intervenes according to the intervention criterion, effectively improving vehicle handling and stability.

A stability criterion for HNFDE with non-uniform delays

International Nuclear Information System (INIS)

Liu Xingwen; Zhong Shouming; Zhang Fengli

2005-01-01

Stability of functional differential equations (FDE) is an increasingly important problem in both science and engineering. Delays, whether uniform or non-uniform, play an important role in the dynamics of a system. Since non-uniform delay is more general and less focused than uniform delay, this paper concentrates on the stability of high-order neutral functional differential equations (HNFDE) with non-uniform delay, and proposes a sufficient condition for it. This result may be widely helpful, thanks to the frequent emergence of a HNFDE with non-uniform delay in various fields. Its effectiveness is illustrated by some examples

Improvements in X-band transmitter phase stability through Klystron body temperature regulation

Science.gov (United States)

Perez, R. M.

1992-01-01

This article describes the techniques used and experimental results obtained in improving transmitter stability by control of the klystron body temperature. Related work in the measurement of klystron phase control parameters (pushing factors) is also discussed. The contribution of wave guide temperature excursions to uplink phase stability is presented. Suggestions are made as to the direction of future work in this area.

Sensing disks for slug-type calorimeters have higher temperature stability

Science.gov (United States)

1967-01-01

Graphite sensing disk for slug-type radiation calorimeters exhibits better performance at high temperatures than copper and nickel disks. The graphite is heat-soaked to stabilize its emittance and the thermocouple is protected from the graphite so repeated temperature cycling does not change its sensitivity.

Microprocessor system for temperature regulation and stabilization

International Nuclear Information System (INIS)

Nguyen Nhi Dien; Rodionov, K.G.

1989-01-01

Microprocessor based system for temperature regulation and stabilization of an operation external object is described. The system has the direct current amplifier working according to modulator-demodulator principle. The overal gain is 100, 1000, 2000. The maximum output signal is ±10 V. The power amplifier is a thyristor one and its line voltage is 220 V, 50 Hz. The output power is 0-2 kVA. The microcontroller has a remote display terminal. Data input is 8 and data output is one. Input and output voltage is ±(0-10) V. The preselection time for stabilization is within 1 s - 18 h. The program algorithm is given. 5 figs.; 1 tab

Wavelength selection in injection-driven Hele-Shaw flows: A maximum amplitude criterion

Science.gov (United States)

Dias, Eduardo; Miranda, Jose

2013-11-01

As in most interfacial flow problems, the standard theoretical procedure to establish wavelength selection in the viscous fingering instability is to maximize the linear growth rate. However, there are important discrepancies between previous theoretical predictions and existing experimental data. In this work we perform a linear stability analysis of the radial Hele-Shaw flow system that takes into account the combined action of viscous normal stresses and wetting effects. Most importantly, we introduce an alternative selection criterion for which the selected wavelength is determined by the maximum of the interfacial perturbation amplitude. The effectiveness of such a criterion is substantiated by the significantly improved agreement between theory and experiments. We thank CNPq (Brazilian Sponsor) for financial support.

Correlation of high-temperature stability of alpha-chymotrypsin with 'salting-in' properties of solution.

Science.gov (United States)

Levitsky VYu; Panova, A A; Mozhaev, V V

1994-01-15

A correlation between the stability of alpha-chymotrypsin against irreversible thermal inactivation at high temperatures (long-term stability) and the coefficient of Setchenov equation as a measure of salting-in/out efficiency of solutes in the Hofmeister series has been found. An increase in the concentration of salting-in solutes (KSCN, urea, guanidinium chloride, formamide) leads to a many-fold decrease of the inactivation rate of the enzyme. In contrast, addition of salting-out solutes has a small effect on the long-term stability of alpha-chymotrypsin at high temperatures. The effects of solutes are additive with respect to their salting-in/out capacities; the stabilizing action of the solutes is determined by the calculated Setchenov coefficient of solution. The correlation is explained by a solute-driven shift of the conformational equilibrium between the 'low-temperature' native and the 'high-temperature' denatured forms of the enzyme within the range of the kinetic scheme put forward in the preceding paper in this journal: irreversible inactivation of the high-temperature form proceeds much more slowly compared with the low-temperature form.

On the stability of non-linear systems

International Nuclear Information System (INIS)

Guelman, M.

1968-09-01

A study is made of the absolute stability of nonlinear systems, using Liapounov's second method and taking into account the results obtained from V.M. Popov's work. The results already established are first presented, in particular concerning the frequency domain criterions for absolute stability of automatic control systems containing one single non linearity. The results have been extended to show the existence of a limiting parabola. New use is then made of the methods studied for deriving absolute stability criterions for a system containing a different type of non linearity. Finally, the results obtained are considered from the point of view of Aizerman's conjecture. (author) [fr

Enhanced Stability of a Protein with Increasing Temperature

DEFF Research Database (Denmark)

Vinther, Joachim Møllesøe; Kristensen, Søren M; Led, Jens J

2010-01-01

The unusual stability of a structured but locally flexible protein, human growth hormone (hGH) at pH 2.7, was investigated using the temperature dependence of the nanosecond-picosecond dynamics of the backbone amide groups obtained from (15)N NMR relaxation data. It is found that the flexibility ...

Stability of Randomly Switched Diffusions

DEFF Research Database (Denmark)

Schiøler, Henrik; Leth, John-Josef; Gholami, Mehdi

2012-01-01

This paper provides a sufficient criterion for ε-moment stability (boundedness) and ergodicity for a class of systems comprising a finite set of diffusions among which switching is governed by a continuous time Markov chain. Stability/instability properties for each separate subsystem are assumed...

Discriminant Validity Assessment: Use of Fornell & Larcker criterion versus HTMT Criterion

Science.gov (United States)

Hamid, M. R. Ab; Sami, W.; Mohmad Sidek, M. H.

2017-09-01

Assessment of discriminant validity is a must in any research that involves latent variables for the prevention of multicollinearity issues. Fornell and Larcker criterion is the most widely used method for this purpose. However, a new method has emerged for establishing the discriminant validity assessment through heterotrait-monotrait (HTMT) ratio of correlations method. Therefore, this article presents the results of discriminant validity assessment using these methods. Data from previous study was used that involved 429 respondents for empirical validation of value-based excellence model in higher education institutions (HEI) in Malaysia. From the analysis, the convergent, divergent and discriminant validity were established and admissible using Fornell and Larcker criterion. However, the discriminant validity is an issue when employing the HTMT criterion. This shows that the latent variables under study faced the issue of multicollinearity and should be looked into for further details. This also implied that the HTMT criterion is a stringent measure that could detect the possible indiscriminant among the latent variables. In conclusion, the instrument which consisted of six latent variables was still lacking in terms of discriminant validity and should be explored further.

STABILIZATION OF TEMPERATURE REGIMES WHILE SYNTHESIZING DIAMOND POWDERS

Directory of Open Access Journals (Sweden)

A. I. Dudiak

2012-01-01

Full Text Available The paper considers peculiar features of artificial diamond powder synthesis process and also direct and indirect methods for temperature measurement in a reaction cell of high-pressure apparatus. Differences in temperature regimes of diamond synthesis associated with time fixation of strain and heating power have been analyzed in the paper. The paper  reveals their impracticability.Theoretical methodology for temperature correction in the reaction cell has been proposed in the paper. An algorithm controlling cell material heating has been developed on the basis of a microcontroller and it makes it possible to stabilize temperature in the reaction mixture that permits to improve quality and strength characteristics of the obtained diamond powders. The paper contains a graphic interpretation of calculation results with the help of the proposed algorithm. 

Thermal stability and high temperature polymorphism of topochemically-prepared Dion–Jacobson triple-layered perovskites

Energy Technology Data Exchange (ETDEWEB)

Guertin, Stephen L.; Josepha, Elisha A.; Montasserasadi, Dariush; Wiley, John B., E-mail: jwiley@uno.edu

2015-10-25

The thermal stability of six Dion–Jacobson-related triple layered perovskites, ACa{sub 2}Nb{sub 3}O{sub 10} (A = H, NH{sub 4}, Li, Na, K, CuCl), was explored to 1000 °C. Each compound was produced topochemically by low-temperature (<500 °C) ion exchange from RbCa{sub 2}Nb{sub 3}O{sub 10}. The thermal behavior of the series was examined by variable temperature X-ray powder diffraction experiments in tandem with thermogravimetric analysis and differential scanning calorimetry. Five of the species were found to be low temperature/metastable phases, decomposing below 900 °C, where the stability of the series decreased with decreasing interlayer cation size. The compounds, A = Li, Na, K, exhibited high temperature polymorphism, with a completely reversible transition evident for KCa{sub 2}Nb{sub 3}O{sub 10}. - Highlights: • Thermal stability of topochemically prepared triple-layered perovskites studied. • Clear correlation seen between stability and identity of interlayer cation. • Several in ACa{sub 2}Nb{sub 3}O{sub 10} series (A = Li, Na, K) exhibit high temperature polymorphism.

Effect of dialysate temperature on hemodynamic stability among hemodialysis patients

International Nuclear Information System (INIS)

Azar, Ahmad Taher

2009-01-01

Cooling the dialysate below 36.5 degree C is an important factor that contributes to hemody-namic stability in patients during hemodialysis (HD). In this study, the effect of dialysate tempe-rature on hemodynamic stability, patients' perception of dialysis discomfort and post dialysis fatigue were assessed in a group of patients on HD. A total of 50 patients, all of whom were on 3-times-perweek dialysis regimen, were studied. Patients were assessed during six dialysis sessions; in three sessions, the dialysate temperature was normal (37 degree C) and in three other sessions, the dialysate temperature was low (35 degree C). Specific scale questionnaires were used in each dialysis session, to evaluate the symptoms during the dialysis procedure as well as post-dialysis fatigue, and respective scores were noted. The results showed that usage of low dialysate temperature was associated with the following: higher post dialysis systolic blood pressure (P< 0.05) and lower post dialysis heart rate (P<0.01), with similar ultrafiltration rates, better intra-dialysis symptoms score and post-dialysis fatigue scores (P< 0.001, and P<0.001, respectively), shorter post-dialysis fatigue period (P<0.001) as well as higher urea removal (P< 00001) and Kt/V (P< 0.0001). Patients' perceptions were measured by a questionnaire, which showed that 76% of them felt more energetic after dialysis with cool dialysate and requested to be always dialyzed with cool dialysate. Low temperature dialysate is particularly beneficial for highly symptomatic patients, improves tolerance to dialysis in hypotensive patients and helps increase ultrafiltration while maintaining hemodynamic stability during and after dialysis. (author)

Criterion of cleavage crack propagation and arrest in a nuclear PWR vessel steel

International Nuclear Information System (INIS)

Bousquet, Amaury

2013-01-01

The purpose of this PhD thesis is to understand physical mechanisms of cleavage crack propagation and arrest in the 16MND5 PWR vessel steel and to propose a robust predicting model based on a brittle fracture experimental campaign of finely instrumented laboratory specimens associated with numerical computations. First, experiments were carried out on thin CT25 specimens at five temperatures (-150 C, -125 C, -100 C, -7 C, -50 C). Two kinds of crack path, straight or branching path, have been observed. To characterize crack propagation and to measure crack speed, a high-speed framing camera system was used, combined with the development of an experimental protocol which allowed to observe CT surface without icing inside the thermal chamber and on the specimen. The framing camera (520 000 fps) has allowed to have a very accurate estimation of crack speed on the complete ligament of CT (∼ 25 mm). Besides, to analyse experiments and to study the impact of viscosity on the mechanical response around the crack tip, the elastic-viscoplastic behavior of the ferritic steel has been studied up to a strain rate of 104 s -1 for the tested temperatures.The extended Finite Element Method (X-FEM) was used in CAST3M FE software to model crack propagation. Numerical computations combine a local non linear dynamic approach with a RKR type fracture stress criterion to a characteristic distance. The work carried out has confirmed the form of the criterion proposed by Prabel at -125 C, and has identified the dependencies of the criterion on temperature and strain rate. From numerical analyzes in 2D and 3D, a multi-temperature fracture stress criterion, increasing function of the strain rate, was proposed. Predictive modeling were used to confirm the identified criterion on two specimen geometries (CT and compressive ring) in mode I at different temperatures. SEM observations and 3D analyzes made with optical microscope showed that the fracture mechanism was the cleavage associated

TEMPERATURE INFLUENCE ON PHASE STABILITY OF ETHANOL-GASOLINE MIXTURES

Directory of Open Access Journals (Sweden)

Valerian Cerempei

2011-06-01

Full Text Available The article investigates phase stability of ethanol-gasoline mixtures depending on their composition, water concentration in ethanol and ethanol-gasoline mixture and temperature. There have been determined the perfect functioning conditions of spark ignition engines fueled with ethanol-gasoline mixtures.

Stability of two-dimensional vorticity filaments

International Nuclear Information System (INIS)

Elhmaidi, D.; Provenzale, A.; Lili, T.; Babiano, A.

2004-01-01

We discuss the results of a numerical study on the stability of two-dimensional vorticity filaments around a circular vortex. We illustrate how the stability of the filaments depends on the balance between the strain associated with the far field of the vortex and the local vorticity of the filament, and we discuss an empirical criterion for filament stability

Stability of molecular dynamics simulations of classical systems

DEFF Research Database (Denmark)

Toxværd, Søren

2012-01-01

The existence of a shadow Hamiltonian for discrete classical dynamics, obtained by an asymptotic expansion for a discrete symplectic algorithm, is employed to determine the limit of stability for molecular dynamics (MD) simulations with respect to the time-increment h of the discrete dynamics....... The investigation is based on the stability of the shadow energy, obtained by including the first term in the asymptotic expansion, and on the exact solution of discrete dynamics for a single harmonic mode. The exact solution of discrete dynamics for a harmonic potential with frequency ω gives a criterion...... for the limit of stability h ⩽ 2/ω. Simulations of the Lennard-Jones system and the viscous Kob-Andersen system show that one can use the limit of stability of the shadow energy or the stability criterion for a harmonic mode on the spectrum of instantaneous frequencies to determine the limit of stability of MD...

Intensity and frequency stabilization of a laser diode by simultaneously controlling its temperature and current

Science.gov (United States)

Mu, Weiwei; Hu, Zhaohui; Wang, Jing; Zhou, Binquan

2017-10-01

Nuclear magnetic resonance gyroscope (NMRG) detects the angular velocity of the vehicle utilizing the interaction between the laser beam and the alkali metal atoms along with the noble gas atoms in the alkali vapor cell. In order to reach high precision inertial measurement target, semiconductor laser in NMRG should have good intensity and frequency stability. Generally, laser intensity and frequency are stabilized separately. In this paper, a new method to stabilize laser intensity and frequency simultaneously with double-loop feedback control is presented. Laser intensity is stabilized to the setpoint value by feedback control of laser diode's temperature. Laser frequency is stabilized to the Doppler absorption peak by feedback control of laser diode's current. The feedback control of current is a quick loop, hence the laser frequency stabilize quickly. The feedback control of temperature is a slow loop, hence the laser intensity stabilize slowly. With the feedback control of current and temperature, the laser intensity and frequency are stabilized finally. Additionally, the dependence of laser intensity and frequency on laser diode's current and temperature are analyzed, which contributes to choose suitable operating range for the laser diode. The advantage of our method is that the alkali vapor cell used for stabilizing laser frequency is the same one as the cell used for NMRG to operate, which helps to miniaturize the size of NMRG prototype. In an 8-hour continuous measurement, the long-term stability of laser intensity and frequency increased by two orders of magnitude and one order of magnitude respectively.

Assessment of structural integrity of Monju steel liner against sodium leakage and combustion. Strain criterion of the liner material

Energy Technology Data Exchange (ETDEWEB)

Asayama, T.; Koi, M. [Japan Nuclear Cycle Development Institute, Ibaraki (Japan)

2001-07-01

In a postulated condition of sodium leakage and combustion in the secondary heat transfer system of the prototype Japanese fast breeder reactor Monju, thermal stresses raise in steel liners installed to prevent sodium from contacting to concrete. Excessive strain due to the thermal stresses leads to failure of the liner. This paper proposes a strain criterion below that the mechanical integrity of liner is assured. In-plane thermal expansion causes membrane strain and out-of-plane expansion causes bending strain. Therefore, failure modes to be taken into account are tensile fracture and bending fracture. The strain criterion can be determined based on tensile and bending tests. Tensile tests and three-point bending tests were performed at the temperature range from room temperature to 1000 C. Fracture elongation was measured in both tests. Uniform elongation was also measured in tensile tests. Various factors that can affect the above experimental results, multi-axiality, environmental effects, and creep were examined. Based on the above results, the strain criterion was determined. The criterion is 10% for membrane strain and 30% for membrane plus bending strain in the temperature range of 350 C to 1000 C. For the temperatures less than 350 C, the half of those values is used. (author)

Statistical evaluation of accelerated stability data obtained at a single temperature. I. Effect of experimental errors in evaluation of stability data obtained.

Science.gov (United States)

Yoshioka, S; Aso, Y; Takeda, Y

1990-06-01

Accelerated stability data obtained at a single temperature is statistically evaluated, and the utility of such data for assessment of stability is discussed focussing on the chemical stability of solution-state dosage forms. The probability that the drug content of a product is observed to be within the lower specification limit in the accelerated test is interpreted graphically. This probability depends on experimental errors in the assay and temperature control, as well as the true degradation rate and activation energy. Therefore, the observation that the drug content meets the specification in the accelerated testing can provide only limited information on the shelf-life of the drug, without the knowledge of the activation energy and the accuracy and precision of the assay and temperature control.

Temperature stability limits for an isothermal demagnetization refrigerator

Science.gov (United States)

Kittel, P.

1984-01-01

It is pointed out that magnetic refrigeration can provide additional cooling for infrared detectors on space missions, taking into account the Shuttle Infrared Telescope Facility (SIRTF) and the Large Deployable Reflector (LDR). From a temperature of 2 K provided by the primary cryogens, magnetic refrigerators could cool bolometers or pumped photoconductors to 0.1 K or below. Such a reduction in operating temperature would increase the sensitivity for bolometers, while the response at longer wavelengths for pumped photoconductors would be improved. Two types of magnetic refrigeration cycles have been proposed. One type uses a complete demagnetization. The present investigation is concerned with the second type, which uses a feedback-controlled isothermal demagnetization, taking into account the temperature stability limits. Attention is given to control system resolution, thermometer noise, reaction time, and thermal time constants.

Stability of cannabinoids in urine in three storage temperatures.

Science.gov (United States)

Golding Fraga, S; Díaz-Flores Estévez, J; Díaz Romero, C

1998-01-01

Stability of cannabinoid compounds in urine samples were evaluated using several storage temperatures. Appreciable losses (> 22.4 percent) were observed in some urine samples, after being stored at room temperature for 10 days. Lower losses (8.1 percent) were observed when the urine samples were refrigerated for 4 weeks. The behavior of urine samples depended on the analyzed urine. This could be due to the different stability of the cannabinoids present in each urine sample. Important losses of 8.0 +/- 10.6, 15.8 +/- 4.2, and 19.6 +/- 6.7 percent were found when the urine samples were frozen during 40 days, 1 year, and 3 years, respectively. Average losses (> > 5 percent) can be observed after one day which could mainly be due to the decrease of the solubility of 11-nor-U9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) or adsorption process of cannabinoid molecules to the plastic storage containers.

Local unitary versus local Clifford equivalence of stabilizer and graph states

International Nuclear Information System (INIS)

Zeng, Bei; Chung, Hyeyoun; Cross, Andrew W.; Chuang, Isaac L.

2007-01-01

The equivalence of stabilizer states under local transformations is of fundamental interest in understanding properties and uses of entanglement. Two stabilizer states are equivalent under the usual stochastic local operations and classical communication criterion if and only if they are equivalent under local unitary (LU) operations. More surprisingly, under certain conditions, two LU-equivalent stabilizer states are also equivalent under local Clifford (LC) operations, as was shown by Van den Nest et al. [Phys. Rev. A 71, 062323 (2005)]. Here, we broaden the class of stabilizer states for which LU equivalence implies LC equivalence (LU LC) to include all stabilizer states represented by graphs with cycles of length neither 3 nor 4. To compare our result with Van den Nest et al.'s, we show that any stabilizer state of distance δ=2 is beyond their criterion. We then further prove that LU LC holds for a more general class of stabilizer states of δ=2. We also explicitly construct graphs representing δ>2 stabilizer states which are beyond their criterion: we identify all 58 graphs with up to 11 vertices and construct graphs with 2 m -1 (m≥4) vertices using quantum error-correcting codes which have non-Clifford transversal gates

Fuel-pin cladding transient failure strain criterion

International Nuclear Information System (INIS)

Bard, F.E.; Duncan, D.R.; Hunter, C.W.

1983-01-01

A criterion for cladding failure based on accumulated strain was developed for mixed uranium-plutonium oxide fuel pins and used to interpret the calculated strain results from failed transient fuel pin experiments conducted in the Transient Reactor Test (TREAT) facility. The new STRAIN criterion replaced a stress-based criterion that depends on the DORN parameter and that incorrectly predicted fuel pin failure for transient tested fuel pins. This paper describes the STRAIN criterion and compares its prediction with those of the stress-based criterion

Extreme temperature stability of thermally insulating graphene-mesoporous-silicon nanocomposite

Science.gov (United States)

Kolhatkar, Gitanjali; Boucherif, Abderraouf; Rahim Boucherif, Abderrahim; Dupuy, Arthur; Fréchette, Luc G.; Arès, Richard; Ruediger, Andreas

2018-04-01

We demonstrate the thermal stability and thermal insulation of graphene-mesoporous-silicon nanocomposites (GPSNC). By comparing the morphology of GPSNC carbonized at 650 °C as-formed to that after annealing, we show that this nanocomposite remains stable at temperatures as high as 1050 °C due to the presence of a few monolayers of graphene coating on the pore walls. This does not only make this material compatible with most thermal processes but also suggests applications in harsh high temperature environments. The thermal conductivity of GPSNCs carbonized at temperatures in the 500 °C-800 °C range is determined through Raman spectroscopy measurements. They indicate that the thermal conductivity of the composite is lower than that of silicon, with a value of 13 ± 1 W mK-1 at room temperature, and not affected by the thin graphene layer, suggesting a role of the high concentration of carbon related-defects as indicated by the high intensity of the D-band compared to G-band of the Raman spectra. This morphological stability at high temperature combined with a high thermal insulation make GPSNC a promising candidate for a broad range of applications including microelectromechanical systems and thermal effect microsystems such as flow sensors or IR detectors. Finally, at 120 °C, the thermal conductivity remains equal to that at room temperature, attesting to the potential of using our nanocomposite in devices that operate at high temperatures such as microreactors for distributed chemical conversion, solid oxide fuel cells, thermoelectric devices or thermal micromotors.

Low-Temperature Bainite: A Thermal Stability Study

Science.gov (United States)

Santajuana, Miguel A.; Rementeria, Rosalia; Kuntz, Matthias; Jimenez, Jose A.; Caballero, Francisca G.; Garcia-Mateo, Carlos

2018-06-01

The thermal stability of nanobainitic structures obtained by heat treating two different high-carbon high-silicon steels at temperatures between 200 °C and 600 °C has been investigated by means of three complementary techniques, i.e., field emission gun-scanning electron microscopy, X-ray diffraction, and high-resolution dilatometry. Three main stages have been established, each of them characterized by a distinctive microstructure. Furthermore, the nanocrystalline structure generated by the bainite reaction confers the steel with an extraordinary tempering resistance.

Global temperature stability by rule induction: An interdisciplinary bridge

International Nuclear Information System (INIS)

Gunn, J.D.; Grzymala-Busse, J.W.

1994-01-01

Rules incorporating influences on global temperature, an estimate of radiation balance, were induced from astronomical, geophysical, and anthropogenic variables. During periods of intermediate global temperatures (generally like the present century), the influences assume canceling roles; influences cancel the effects of extreme states potentially imposed by other influences because they are, in aggregate, most likely to be assuming opposite values. This imparts an overall stability to the global temperature. To achieve cold or hot global temperature, influences assume reinforcing roles. CO 2 is an active influence on global temperature. By virtue of its constancy in the atmosphere, it can be expected to sponsor frequent hot years in combination with the other influences as they cycle through their periods. If measures were implemented to maintain warm or cool global temperatures, it could retain the status quo of present global agricultural regions. They are probably more productive than hot world regions would be because of narrow storm tracks

Intact stability analysis of dead ship conditions using FORM

DEFF Research Database (Denmark)

Choi, Ju Hyuck; Jensen, Jørgen Juncher; Kristensen, Hans Otto Holmegaard

2017-01-01

The IMO Weather Criterion has proven to be the governing stability criteria regarding minimum GM for e.g. small ferries and large passenger ships. The formulation of the Weather Criterion is based on some empirical relations derived many years ago for vessels not necessarily representative for cu...

Critical machine cluster identification using the equal area criterion

DEFF Research Database (Denmark)

Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob

2015-01-01

The paper introduces a new method to early identify the critical machine cluster (CMC) after a transient disturbance. For transient stability assessment with methods based on the equal area criterion it is necessary to split the generators into a group of critical and non-critical machines....... The generators in the CMC are those likely to lose synchronism. The early and reliable identification of the CMC is crucial and one of the major challenges. The proposed new approach is based on the assessment of the rotor dynamics between two machines and the evaluation of their coupling strength. A novel...

Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

International Nuclear Information System (INIS)

Ren, Y.; Kaye, S.M.; Mazzucato, E.; Guttenfelder, W.; Bell, R.E.; Domier, C.W.; LeBlanc, B.P.; Lee, K.C.; Luhmann, N.C. Jr.; Smith, D.R.; Yuh, H.

2011-01-01

In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k (perpendicular) ρ s ∼< 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

Effects of temperature distribution on boundary layer stability for a circular cone at Mach 10

Science.gov (United States)

Rigney, Jeffrey M.

A CFD analysis was conducted on a circular cone at 3 degrees angle of attack at Mach 10 using US3D and STABL 3D to determine the effect of wall temperature on the stability characteristics that lead to laminar-to-turbulent transition. Wall temperature distributions were manipulated while all other flow inputs and geometric qualities were held constant. Laminar-to-turbulent transition was analyzed for isothermal and adiabatic wall conditions, a simulated short-duration wind tunnel case, and several hot-nose temperature distributions. For this study, stability characteristics include maximum N-factor growth and the corresponding frequency range, disturbance spatial amplification rate and the corresponding modal frequency, and stability neutral point location. STABL 3D analysis indicates that temperature distributions typical of those in short-duration hypersonic wind tunnels do not result in any significant difference on the stability characteristics, as compared to an isothermal wall boundary condition. Hypothetical distributions of much greater temperatures at and past the nose tip do show a trend of dampening of second-mode disturbances, most notably on the leeward ray. The most pronounced differences existed between the isothermal and adiabatic cases.

Magnetic susceptibility of MnZn and NiZn soft ferrites using Laplace transform and the Routh-Hurwitz criterion

International Nuclear Information System (INIS)

Fano, Walter Gustavo; Boggi, Silvina; Razzitte, Adrian Cesar

2011-01-01

This paper is devoted to study the Routh-Hurwitz stability criterion from the MnZn and NiZn soft ferrites using a phenomenological model with the gyromagnetic spin contribution and domain wall contribution. The magnetodynamic equation and the harmonic oscillator equation have been used to obtain the domain walls and the spin contribution of the magnetic susceptibility. The ferrite materials have been considered as linear, time invariant, isotropic and homogeneous, and the magnetization vector is proportional to the magnetic field vector. The resulting expression of the magnetization in time domain of both ferrites under study has been obtained by mean of the inverse Laplace transformation applying the residue method. The poles of the magnetic susceptibility have negative real parts, which ensures that the response decays exponentially to zero as the time increase. The degree of the numerator's polynomial of the magnetic susceptibility is less than the degree of denominator's polynomial in the magnetic susceptibility function: and the poles are located in the half left s-plane. Then the system is bounded-input, bounded-output (BIBO), and the results agree with the Routh-Hurwitz stability criterion for the MnZn and NiZn soft ferrites. - Research Highlights: → Laplace transform of the magnetic susceptibility of the MnZn and NiZn soft ferrites. → Routh-Hurwitz stability criterion of magnetic materials. → Bode plot of magnetic susceptibility. → Inverse Laplace transform using residue theorem.

Phase Stability Diagrams for High Temperature Corrosion Processes

Directory of Open Access Journals (Sweden)

J. J. Ramos-Hernandez

2013-01-01

Full Text Available Corrosion phenomena of metals by fused salts depend on chemical composition of the melt and environmental conditions of the system. Detail knowledge of chemistry and thermodynamic of aggressive species formed during the corrosion process is essential for a better understanding of materials degradation exposed to high temperature. When there is a lack of kinetic data for the corrosion processes, an alternative to understand the thermodynamic behavior of chemical species is to utilize phase stability diagrams. Nowadays, there are several specialized software programs to calculate phase stability diagrams. These programs are based on thermodynamics of chemical reactions. Using a thermodynamic data base allows the calculation of different types of phase diagrams. However, sometimes it is difficult to have access to such data bases. In this work, an alternative way to calculate phase stability diagrams is presented. The work is exemplified in the Na-V-S-O and Al-Na-V-S-O systems. This system was chosen because vanadium salts is one of the more aggressive system for all engineering alloys, especially in those processes where fossil fuels are used.

The Bohm criterion for rf discharges

International Nuclear Information System (INIS)

Meijer, P.M.; Goedheer, W.J.

1991-01-01

The well-known dc Bohm criterion is extended to rf discharges. Both low- (ω rf much-lt ω pi ) and high-(ω pi much-lt ω rf ) frequency regimes are considered. For low frequencies, the dc Bohm criterion holds. This criterion states that the initial energy of the ions entering the sheath must exceed a limit in order to obtain a stable sheath. For high frequencies, a modified limit is derived, which is somewhat lower than that of the dc Bohm criterion. The resulting ion current density in a high-frequency sheath is only a few percent lower than that for the dc case

A self-adaptive thermal switch array for rapid temperature stabilization under various thermal power inputs

International Nuclear Information System (INIS)

Geng, Xiaobao; Patel, Pragnesh; Narain, Amitabh; Meng, Dennis Desheng

2011-01-01

A self-adaptive thermal switch array (TSA) based on actuation by low-melting-point alloy droplets is reported to stabilize the temperature of a heat-generating microelectromechanical system (MEMS) device at a predetermined range (i.e. the optimal working temperature of the device) with neither a control circuit nor electrical power consumption. When the temperature is below this range, the TSA stays off and works as a thermal insulator. Therefore, the MEMS device can quickly heat itself up to its optimal working temperature during startup. Once this temperature is reached, TSA is automatically turned on to increase the thermal conductance, working as an effective thermal spreader. As a result, the MEMS device tends to stay at its optimal working temperature without complex thermal management components and the associated parasitic power loss. A prototype TSA was fabricated and characterized to prove the concept. The stabilization temperatures under various power inputs have been studied both experimentally and theoretically. Under the increment of power input from 3.8 to 5.8 W, the temperature of the device increased only by 2.5 °C due to the stabilization effect of TSA

Stability analysis of the Ghana Research Reactor-1 (GHARR-1)

International Nuclear Information System (INIS)

Della, R.; Alhassan, E.; Adoo, N.A.; Bansah, C.Y.; Nyarko, B.J.B.; Akaho, E.H.K.

2013-01-01

Highlights: • We developed a theoretical model to study the stability of the Ghana Research Reactor-1. • The neutronics transfer function was described by the point kinetics model for a single group of delayed neutrons. • The thermal hydraulics transfer function was based on the modified lumped parameter concept. • A computer code, RESA (REactor Stability Analysis) was developed. • Results show that the closed-loop transfer function was stable and well damped for variable operating power levels. - Abstract: A theoretical model has been developed to study the stability of the Ghana Research Reactor one (GHARR-1). The closed-loop transfer function of GHARR-1 was established based on the model, which involved the neutronics and the thermal hydraulics transfer functions. The reactor kinetics was described by the point kinetics model for a single group of delayed neutrons, whilst the thermal hydraulics transfer function was based on the modified lumped parameter concept. The inherent internal feedback effect due to the fuel and the coolant was represented by the fuel temperature coefficient and the moderator temperature coefficient respectively. A computer code, RESA (REactor Stability Analysis), entirely in Java was developed based on the model for systems analysis. Stability analysis of the open-loop transfer function of GHARR-1 based on the Nyquist criterion and Bode diagrams using RESA, has shown that the closed-loop transfer function was marginally stable for variable operating power levels. The relative stability margins of GHARR-1 were also identified

High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions

Energy Technology Data Exchange (ETDEWEB)

Li, Lulu, E-mail: lli18@ncsu.edu; Saber, Mostafa; Xu, Weizong; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

2014-09-08

The influence of 1–4 at% Hf additions on the thermal stability of mechanically alloyed nanocrystalline Fe–14Cr alloys was studied in this work. XRD-calculated grain size and microhardness results were reported versus isochronal annealing treatments up to 1100 °C. Microstructural evolution was investigated using channeling contrast FIB imaging and TEM. Grain size of samples with 4 at% Hf was found to be maintained in the nanoscale range at temperatures up to 1000 °C. Zener pinning was considered as a major source of high temperature grain size stabilization. By comparing the Orowan strengthening contribution to the total hardness, the deviation of grain size predictions from the actual grain size in Fe–14Cr–4Hf suggests the presence of thermodynamic stabilization by the solute segregation to grain boundaries (GBs). A predictive thermodynamic model indicates that the thermodynamic stabilization can be expected.

Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals

Directory of Open Access Journals (Sweden)

Joanna Ptasinski

2014-03-01

Full Text Available In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths.

Assessment of potential solder candidates for high temperature applications

DEFF Research Database (Denmark)

pressure to eliminate lead containing materials despite the fact that materials for high Pb containing alloys are currently not affected by any legislations. A tentative assessment was carried out to determine the potential solder candidates for high temperature applications based on the solidification...... criterion, phases predicted in the bulk solder and the thermodynamic stability of chlorides. These promising solder candidates were precisely produced using the hot stage microscope and its respective anodic and cathodic polarization curves were investigated using a micro-electrochemical set up...

Energy principles for linear dissipative systems with application to resistive MHD stability

International Nuclear Information System (INIS)

Pletzer, A.

1997-04-01

A formalism for the construction of energy principles for dissipative systems is presented. It is shown that dissipative systems satisfy a conservation law for the bilinear Hamiltonian provided the Lagrangian is time invariant. The energy on the other hand, differs from the Hamiltonian by being quadratic and by having a negative definite time derivative (positive power dissipation). The energy is a Lyapunov functional whose definiteness yields necessary and sufficient stability criteria. The stability problem of resistive magnetohydrodynamic (MHD) is addressed: the energy principle for ideal MHD is generalized and the stability criterion by Tasso is shown to be necessary in addition to sufficient for real growth rates. An energy principle is found for the inner layer equations that yields the resistive stability criterion D R <0 in the incompressible limit, whereas the tearing mode criterion Δ'<0 is shown to result from the conservation law of the bilinear concomitant in the resistive layer. (author) 1 fig., 25 refs

An analysis of global robust stability of uncertain cellular neural networks with discrete and distributed delays

International Nuclear Information System (INIS)

Park, Ju H.

2007-01-01

This paper considers the robust stability analysis of cellular neural networks with discrete and distributed delays. Based on the Lyapunov stability theory and linear matrix inequality (LMI) technique, a novel stability criterion guaranteeing the global robust convergence of the equilibrium point is derived. The criterion can be solved easily by various convex optimization algorithms. An example is given to illustrate the usefulness of our results

Quicklime (CaO) Stabilization of fine-grained marine sediments in low temperature areas

DEFF Research Database (Denmark)

Skels, Peteris; Ingeman-Nielsen, Thomas; Jørgensen, Anders Stuhr

2011-01-01

This study presents laboratory testing on quicklime (CaO) stabilization of fine-grained marine sediments in low temperature areas. The soil was sampled on the Fossil Plain in Kangerlussuaq, Greenland, and analyzed in the laboratory at Technical University of Denmark (DTU). The optimum CaO content...... curing temperatures, comparing stabilization effectiveness between low and normal soil temperature conditions....... in a soil-CaO mixture was determined using a number of laboratory methods, such as pH test, consistency limit analysis, degree of compaction, and short term California Bearing Ratio (CBR) values. The study also numerically demonstrates a long term strength development of the soil-CaO mixture at 1°C and 10°C...

Evaluation of the effect of temperature on the stability of metal soaps ...

African Journals Online (AJOL)

The thermal stability of calcium and zinc dicarboxylates was studied. The kinetics of the decomposition was studied thermogravimetrically at various temperatures. The rates of the first stage decomposition were used to assess the effect of temperature on the susceptibility of the metal soaps of dicarboxylic acids to ...

[On the problems of the evolutionary optimization of life history. II. To justification of optimization criterion for nonlinear Leslie model].

Science.gov (United States)

Pasekov, V P

2013-03-01

The paper considers the problems in the adaptive evolution of life-history traits for individuals in the nonlinear Leslie model of age-structured population. The possibility to predict adaptation results as the values of organism's traits (properties) that provide for the maximum of a certain function of traits (optimization criterion) is studied. An ideal criterion of this type is Darwinian fitness as a characteristic of success of an individual's life history. Criticism of the optimization approach is associated with the fact that it does not take into account the changes in the environmental conditions (in a broad sense) caused by evolution, thereby leading to losses in the adequacy of the criterion. In addition, the justification for this criterion under stationary conditions is not usually rigorous. It has been suggested to overcome these objections in terms of the adaptive dynamics theory using the concept of invasive fitness. The reasons are given that favor the application of the average number of offspring for an individual, R(L), as an optimization criterion in the nonlinear Leslie model. According to the theory of quantitative genetics, the selection for fertility (that is, for a set of correlated quantitative traits determined by both multiple loci and the environment) leads to an increase in R(L). In terms of adaptive dynamics, the maximum R(L) corresponds to the evolutionary stability and, in certain cases, convergent stability of the values for traits. The search for evolutionarily stable values on the background of limited resources for reproduction is a problem of linear programming.

Stability of plasma in static equilibrium

Energy Technology Data Exchange (ETDEWEB)

Krusiial, M D; Oberman, N R [Project Matterhorn, Princeton University, Princeton, NJ (United States)

1958-07-01

Our purpose is to derive from the Boltzmann equation in the small m/e limit, criteria useful in the discussion of stability of plasmas in static equilibrium. At first we ignore collisions but later show their effects may be taken into account. Our approach yields a generalization of the usual energy principles for investigating the stability of hydromagnetic systems to situations where the effect of heat flow along magnetic lines is not negligible, and hence to situations where the strictly hydrodynamic approach is inapplicable. In the first two sections we characterize our general method of approach and delineate the properties of the small m/e limit which we use to determine the constants of the motion and the condition for static equilibrium. In the next two sections we calculate the first and second variations of the energy and conclude with a statement of the general stability criterion. In the final three sections we state several theorems which relate our stability criterion to those of ordinary hydromagnetic theory, we show how to take into account the effect of collisions, and briefly discuss the remaining problem of incorporating the charge neutrality condition into the present stability theory. (author)

Micelle-stabilized room-temperature phosphorescence with synchronous scanning

International Nuclear Information System (INIS)

Femia, R.A.; Love, L.J.C.

1984-01-01

The experimental requirements for synchronous wavelength scanning micelle-stabilized room temperature phosphorescence and the factors affecting peak resolution are presented and compared with those for synchronous wavelength scanning fluorescence. Identification of individual compounds in a four-component mixture is illustrated, and criteria to identify and minimize triplet state energy transfer are given. Considerable improvement in resolution of the synchronous peaks is obtained via second derivative spectra. 20 references, 7 figures, 2 tables

Stochastic stability assessment of a semi-free piston engine generator concept

Science.gov (United States)

Kigezi, T. N.; Gonzalez Anaya, J. A.; Dunne, J. F.

2016-09-01

Small engines, as power generators with low-noise and vibration characteristics, are needed in two niche application areas: as electric vehicle range extenders and as domestic micro Combined Heat and Power systems. A recent semi-free piston design known as the AMOCATIC generator fully meets this requirement. The engine potentially allows for high energy conversion efficiencies at resonance derived from having a mass and spring assembly. As with free-piston engines in general, stability and control of piston motion has been cited as the prime challenge limiting the technology's widespread application. Using physical principles, we derive in this paper two important results: an energy balance criterion and a related general stability criterion for a semi-free piston engine. Control is achieved by systematically designing a Proportional Integral (PI) controller using a control-oriented engine model for which a specific stability condition is stated. All results are presented in closed form throughout the paper. Simulation results under stochastic pressure conditions show that the proposed energy balance, stability criterion, and PI controller, operate as predicted to yield stable engine operation at fixed compression ratio.

A theoretical derivation of the Hoek–Brown failure criterion for rock materials

Directory of Open Access Journals (Sweden)

Jianping Zuo

2015-08-01

Full Text Available This study uses a three-dimensional crack model to theoretically derive the Hoek–Brown rock failure criterion based on the linear elastic fracture theory. Specifically, we argue that a failure characteristic factor needs to exceed a critical value when macro-failure occurs. This factor is a product of the micro-failure orientation angle (characterizing the density and orientation of damaged micro-cracks and the changing rate of the angle with respect to the major principal stress (characterizing the microscopic stability of damaged cracks. We further demonstrate that the factor mathematically leads to the empirical Hoek–Brown rock failure criterion. Thus, the proposed factor is able to successfully relate the evolution of microscopic damaged crack characteristics to macro-failure. Based on this theoretical development, we also propose a quantitative relationship between the brittle–ductile transition point and confining pressure, which is consistent with experimental observations.

Multiaxial fatigue criterion for 2-1/4 Cr-1 Mo steel for use in high-temperature structural design

International Nuclear Information System (INIS)

Blass, J.J.

1990-01-01

An improved multiaxial fatigue failure criterion is described that is based on a definition of equivalent inelastic strain range incorporating the shear and normal components of inelastic strain range on the planes of maximum inelastic shear strain range. Optimum values of certain parameters contained in the formulation were obtained by the method of least squares from the results of combined axial-torsional strain cycling test of 2--1/4 Cr-1 Mo steel conducted at 538 degrees C (1000 degrees F). The ability of this criterion to correlate the test results was compared with that of the Mises equivalent inelastic strain range criterion and was found to be superior. A procedure is described for calculating the required shear and normal components of strain range under general multiaxial strain cycling conditions. An improved definition of equivalent total strain range based on these considerations is directly applicable to the method of estimating fatigue damage in ASME Code Case N-47. 17 refs., 5 figs., 1 tab

A new method to determine oxidative stability of vegetable fats and oils at simulated frying temperature

Directory of Open Access Journals (Sweden)

Gertz Christian

2001-01-01

Full Text Available A new procedure at simulated frying conditions in our laboratory was developed to monitor frying stability of fats and oils. Water-conditioned silica was prepared and added to the fresh vegetable oil, which was heated for two hours at 170°C. The oil stability at frying temperature was then evaluated by determining the amount of formed dimeric triglycerides The results obtained showed that the stability of the vegetable oils at frying temperature could not be explained by the fatty acid composition alone. Corn oil was observed to be more stable than soybean oil, and rapeseed oil was better than olive oil. It was also observed that crude, non-refined oils were found to have a better heat stability than refin-ed oils. To estimate the effectiveness of synthetic and naturally occurring antioxidants, namely various tocopherols, tocopherol acetate and phytosterol fractions, phenolic compounds like quercetin, oryzanol, ferulic acid, gallates, BHT, BHA and other compounds like ascorbic acid 6-palmitate and squalene were added to refined sunflower and rape seed oil, and their oxidative stability at elevated temperature (OSET values determined. Both linoleic and oleic rich oils gave comparable results for the activity of the various compounds. alpha-tocopherol, tocopherol esters and BHA had low effects on oil stability at frying temperature, while ascorbyl palmitate and some phytosterol fractions were found to have the most stabilizing activity under frying conditions.

Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

Energy Technology Data Exchange (ETDEWEB)

Rahman, Md Taibur; McCloy, John; Panat, Rahul, E-mail: rahul.panat@wsu.edu, E-mail: rvchintalapalle@utep.edu [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99163 (United States); Ramana, C. V., E-mail: rahul.panat@wsu.edu, E-mail: rvchintalapalle@utep.edu [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

2016-08-21

Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24–500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

International Nuclear Information System (INIS)

Rahman, Md Taibur; McCloy, John; Panat, Rahul; Ramana, C. V.

2016-01-01

Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24–500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

Science.gov (United States)

Rahman, Md Taibur; McCloy, John; Ramana, C. V.; Panat, Rahul

2016-08-01

Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24-500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

Suboptimal Criterion Learning in Static and Dynamic Environments.

Directory of Open Access Journals (Sweden)

Elyse H Norton

2017-01-01

Full Text Available Humans often make decisions based on uncertain sensory information. Signal detection theory (SDT describes detection and discrimination decisions as a comparison of stimulus "strength" to a fixed decision criterion. However, recent research suggests that current responses depend on the recent history of stimuli and previous responses, suggesting that the decision criterion is updated trial-by-trial. The mechanisms underpinning criterion setting remain unknown. Here, we examine how observers learn to set a decision criterion in an orientation-discrimination task under both static and dynamic conditions. To investigate mechanisms underlying trial-by-trial criterion placement, we introduce a novel task in which participants explicitly set the criterion, and compare it to a more traditional discrimination task, allowing us to model this explicit indication of criterion dynamics. In each task, stimuli were ellipses with principal orientations drawn from two categories: Gaussian distributions with different means and equal variance. In the covert-criterion task, observers categorized a displayed ellipse. In the overt-criterion task, observers adjusted the orientation of a line that served as the discrimination criterion for a subsequently presented ellipse. We compared performance to the ideal Bayesian learner and several suboptimal models that varied in both computational and memory demands. Under static and dynamic conditions, we found that, in both tasks, observers used suboptimal learning rules. In most conditions, a model in which the recent history of past samples determines a belief about category means fit the data best for most observers and on average. Our results reveal dynamic adjustment of discrimination criterion, even after prolonged training, and indicate how decision criteria are updated over time.

Time and Temperature Test Results for PFP Thermal Stabilization Furnaces

International Nuclear Information System (INIS)

COMPTON, J.A.

2000-01-01

The national standard for plutonium storage acceptability (standard DOE-STD-3013-99, generally known as ''the 3013 standard'') has been revised to clarify the requirement for processes that will produce acceptable storage materials. The 3013 standard (Reference 1) now states that ''Oxides shall be stabilized by heating the material in an oxidizing atmosphere to a Material Temperature of at least 950 C (1742 F) for not less than 2 hours.'' The process currently in use for producing stable oxides for storage at the Plutonium Finishing Plant (PFP) heats a furnace atmosphere to 1000 C and holds it there for 2 hours. The temperature of the material being stabilized is not measured directly during this process. The Plutonium Process Support Laboratories (PPSL) were requested to demonstrate that the process currently in use at PFP is an acceptable method of producing stable plutonium dioxide consistently. A spare furnace identical to the production furnaces was set up and tested under varying conditions with non-radioactive surrogate materials. Reference 2 was issued to guide the testing program. The process currently in use at the PFP for stabilizing plutonium-bearing powders was shown to heat all the material in the furnace to at least 950 C for at least 2 hours. The current process will work for (1) relatively pure plutonium dioxide, (2) dioxide powders mixed with up to 20 weight percent magnesium oxide, and (3) dioxide powders with up to 11 weight percent magnesium oxide and 20 weight percent magnesium nitrate hexahydrate. Time and temperature data were also consistent with a successful demonstration for a mixture containing 10 weight percent each of sodium and potassium chloride; however, the molten chloride salts destroyed the thermocouples in the powder and temperature data were unavailable for part of that run. These results assume that the current operating limits of no more than 2500 grams per furnace charge and a powder height of no more than 1.5 inches remain

Basin-Wide Temperature Constraints On Gas Hydrate Stability In The Gulf Of Mexico

Science.gov (United States)

MacDonald, I. R.; Reagan, M. T.; Guinasso, N. L.; Garcia-Pineda, O. G.

2012-12-01

Gas hydrate deposits commonly occur at the seafloor-water interface on marine margins. They are especially prevalent in the Gulf of Mexico where they are associated with natural oil seeps. The stability of these deposits is potentially challenged by fluctuations in bottom water temperature, on an annual time-scale, and under the long-term influence of climate change. We mapped the locations of natural oil seeps where shallow gas hydrate deposits are known to occur across the entire Gulf of Mexico basin based on a comprehensive review of synthetic aperture radar (SAR) data (~200 images). We prepared a bottom water temperature map based on the archive of CTD casts from the Gulf (~6000 records). Comparing the distribution of gas hydrate deposits with predicted bottom water temperature, we find that a broad area of the upper slope lies above the theoretical stability horizon for structure 1 gas hydrate, while all sites where gas hydrate deposits occur are within the stability horizon for structure 2 gas hydrate. This is consistent with analytical results that structure 2 gas hydrates predominate on the upper slope (Klapp et al., 2010), where bottom water temperatures fluctuate over a 7 to 10 C range (approx. 600 m depth), while pure structure 1 hydrates are found at greater depths (approx. 3000 m). Where higher hydrocarbon gases are available, formation of structure 2 gas hydrate should significantly increase the resistance of shallow gas hydrate deposits to destabilizing effects variable or increasing bottom water temperature. Klapp, S.A., Bohrmann, G., Kuhs, W.F., Murshed, M.M., Pape, T., Klein, H., Techmer, K.S., Heeschen, K.U., and Abegg, F., 2010, Microstructures of structure I and II gas hydrates from the Gulf of Mexico: Marine and Petroleum Geology, v. 27, p. 116-125.Bottom temperature and pressure for Gulf of Mexico gas hydrate outcrops and stability horizons for sI and sII hydrate.

Current sharing effect on the current instability and allowable temperature rise of composite high-TC superconductors

International Nuclear Information System (INIS)

Romanovskii, V.R.; Watanabe, K.; Awaji, S.; Nishijima, G.; Takahashi, Ken-ichiro

2004-01-01

To understand the basic mechanisms of the thermal runaway phenomenon, the limiting margin of the current instability, which may spontaneously occur in composite high-T C superconductors like multifilament Bi-based wire or tape, is derived under DC magnetic field. The current sharing and allowable temperature rise effects were considered. A static zero-dimensional model was utilized to describe the basic formulae dealing with the peculiarities of the non-isothermal change of superconducting composite voltage-current characteristic. The boundary of allowable stable values of the temperature, electric field and current are derived analytically. It was shown that permissible values of the current and electric field might be higher than those determined by use of the standard critical current criterion. In consequence of this feature, the noticeable allowable temperature rise of the composite superconductor before its transition to the normal state may be seen. The criterion for complete thermal stability condition is written describing the state when temperature of the composite equals critical temperature of a superconductor and the transport current flows stably only in matrix. The performed analysis also proves the existence of value of the volume fraction of a superconductor in composite at which its current-carrying capacity has minimum. These peculiarities are due to the stable current redistribution between superconductor and stabilizing matrix. Therefore, the current sharing not only leads to the matrix/superconductor ratio effect on the stable operating characteristics of the composite high-T C superconductors but also becomes important in the adequate description of quench process in the high-T C superconducting magnets

Application of a new criterion for assessing the susceptibility to internal erosion

Energy Technology Data Exchange (ETDEWEB)

Li, M.; Garner, S.J. [BC Hydro, Burnaby, BC (Canada); Fannin, R.J. [British Columbia Univ., Vancouver, BC (Canada)

2009-07-01

Occasionally, internal erosion can occur in internally unstable soils that are subject to seepage flow. This paper presented a modification to the Kenney-Lau criterion for assessing susceptibility to internal erosion in widely-graded cohesionless soils. The original Kenney-Lau criterion and the newly-proposed Li-Fannin criteria were both used to evaluate the grading stability of filter and core materials from two zoned earthfill dams in British Columbia. Using a statistical approach, the criteria were applied to construction data to account for the many gradation curves available within the specification envelope for materials used in construction. The paper discussed the implications of the findings within the context of laboratory permeameter tests on the same soils, and also based on a sinkhole incident at one of the dams. It was concluded that the Kenney-Lau method appears to be less conservative for predicting the internal instability of widely graded materials. 16 refs., 5 figs.

A new criterion of photostimulated luminescence (PSL) method to detect irradiated traditional Chinese medicinal herbs

International Nuclear Information System (INIS)

Zhang, Liwen; Lin, Tong; Jiang, Yingqiao; Bi, Fujun

2013-01-01

This work used a new criterion to analyze 162 varieties (222 batches) of traditional Chinese medicinal herbs based on the European Standard EN 13751 (2009. Foodstuffs—Detection of Irradiated Food Using Photostimulated Luminescence. European Committee for Standardization, Brussels, Belgium). The characteristics of PSL signals are described, and a new criterion is established. Compared to EN 13751, the new criterion uses clearer definition to evaluate instead of the ambiguous descriptions in EN Standard, such as “much greater than” and “within the same order of magnitude”. Moreover, the accuracy of the new criterion is as good as or better than EN Standard in regard to classifying irradiated and non-irradiated traditional Chinese medicinal herbs. It can help to avoid false positive result when a non-irradiated herb got a screening PSL measurement above 5000 counts/60 s. This new criterion of photostimulated luminescence method can be applied to identify the irradiation status of traditional Chinese medicinal herbs, even if the medicinal herbs were irradiated at a low dose (0.3 kGy) or stored in the dark at room temperature for 24 months after the irradiation treatment. - Highlights: • Clearer evaluation criterion instead of the ambiguous descriptions in EN 13751. • Accuracy satisfied. • Large sample size provides outstanding representativeness. • Systematical evaluation on PSL method

Revisiting the Glansdorff–Prigogine criterion for stability within irreversible thermodynamics

Czech Academy of Sciences Publication Activity Database

Maes, C.; Netočný, Karel

2015-01-01

Roč. 159, č. 6 (2015), s. 1286-1299 ISSN 0022-4715 R&D Projects: GA ČR GAP204/12/0897 Institutional support: RVO:68378271 Keywords : irreversible processes * thermodynamic stability * excess entropy production * nonequilibrium free energy * Clausius heat theorem Subject RIV: BE - Theoretical Physics Impact factor: 1.537, year: 2015

Temperature measurements in a wall stabilized steady flame using CARS

KAUST Repository

Sesha Giri, Krishna

2017-01-05

Flame quenching by heat loss to a surface continues to be an active area of combustion research. Close wall temperature measurements in an isothermal wall-stabilized flame are reported in this work. Conventional N-vibrational Coherent Anti-Stokes Raman Scattering (CARS) thermometry as close as 275 μm to a convex wall cooled with water has been carried out. The standard deviation of mean temperatures is observed to be ~6.5% for high temperatures (>2000K) and ~14% in the lower range (<500K). Methane/air and ethylene/air stoichiometric flames for various global strain rates based on exit bulk velocities are plotted and compared. CH* chemiluminescence is employed to determine the flame location relative to the wall. Flame locations are shown to move closer to the wall with increasing strain rates in addition to higher near-wall temperatures. Peak temperatures for ethylene are considerably higher (~250-300K) than peak temperatures for methane. Preheat zone profiles are similar for different strain rates across fuels. This work demonstrates close wall precise temperature measurments using CARS.

Reconsideration of the m=0 Z-pinch stability

International Nuclear Information System (INIS)

Scheffel, J.; Coppins, M.

1993-01-01

Possible paths for obtaining linear stability against the m=0 mode in the Z-pinch are studied. Using a generalized energy principle, the necessary and sufficient Chew-Goldberger-Low (CGL) m=0 stability criterion is derived. This criterion is less restrictive than that of ideal MHD, although it also requires the boundary plasma pressure to be finite. It is shown that the edge pressure cannot be stably upheld by a surface current. By instead assuming a finite pressure external gas, it is found that an edge pressure to on-axis pressure ratio of 0.5 is required for stability of a constant current density profile. A parabolic current density profile lowers the limit to the value 0.17. The growth rates are shown to be monotonically decreasing as a function of the external gas pressure. Detailed derivations of the boundary conditions are also given. The results aid in clarifying the experimental stability of four major Z-pinch experiments. Finite Larmor radius stabilization is hence required to maintain stability in future fibre pinch experiments in vacuum, implying line densities less than 10 19 m -1 . (author). 28 refs, 10 figs

Stabilization of temperature during magnetic hyperthermia by Ce substituted magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Shaw, S.K.; Alla, S.K. [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Meena, S.S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mandal, R.K. [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Prasad, N.K., E-mail: nandkp.met@iitbhu.ac.in [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2017-07-15

Highlights: • Ce{sub x}Fe{sub 3−x}O{sub 4} (0.01 ≤ x ≤ 0.5) nanoparticles below 15 nm were synthesized by microwave refluxing method. • The saturation magnetization decreased with increased Ce concentration. • The sample displayed stabilization of temperature near 42 °C during magnetic hyperthermia. - Abstract: We report here magnetic hyperthermia using nanoparticles of Ce{sub x}Fe{sub 3−x}O{sub 4} (x = 0.01, 0.05, 0.1, 0.3 and 0.5) during which temperature was found to be stabilizing near 42 °C. This happens despite of their high saturation magnetization (M{sub S}) and Curie temperature (T{sub C}) values. It was observed that by selecting an appropriate magnetic field the temperature can be rose exactly near the therapeutic temperature and thus it will help to selectively kill the cancerous cells leaving normal cells unaffected. These nanoparticles (size around 8–15 nm) were produced by single step microwave refluxing technique. X-ray diffraction (XRD) analysis demonstrates that samples were essentially single phase except for x = 0.5 sample. The X-ray photoelectron spectroscopy (XPS) study for the samples demonstrated that Ce was present in both Ce{sup 3+} and Ce{sup 4+} states. The saturation magnetization value of the samples decreased sharply from 62 Am{sup 2}/kg for x = 0.01 to 19 Am{sup 2}/kg for x = 0.1. This value further decreased with increased Ce doping.

Stochastic stability assessment of a semi-free piston engine generator concept

International Nuclear Information System (INIS)

Kigezi, T N; Anaya, J A Gonzalez; Dunne, J F

2016-01-01

Small engines, as power generators with low-noise and vibration characteristics, are needed in two niche application areas: as electric vehicle range extenders and as domestic micro Combined Heat and Power systems. A recent semi-free piston design known as the AMOCATIC generator fully meets this requirement. The engine potentially allows for high energy conversion efficiencies at resonance derived from having a mass and spring assembly. As with free-piston engines in general, stability and control of piston motion has been cited as the prime challenge limiting the technology's widespread application. Using physical principles, we derive in this paper two important results: an energy balance criterion and a related general stability criterion for a semi-free piston engine. Control is achieved by systematically designing a Proportional Integral (PI) controller using a control-oriented engine model for which a specific stability condition is stated. All results are presented in closed form throughout the paper. Simulation results under stochastic pressure conditions show that the proposed energy balance, stability criterion, and PI controller, operate as predicted to yield stable engine operation at fixed compression ratio. (paper)

Stability and instability of axisymmetric droplets in thermocapillary-driven thin films

Science.gov (United States)

Nicolaou, Zachary G.

2018-03-01

The stability of compactly supported, axisymmetric droplet states is considered for driven thin viscous films evolving on two-dimensional surfaces. Stability is assessed using Lyapunov energy methods afforded by the Cahn-Hilliard variational form of the governing equation. For general driving forces, a criterion on the gradient of profiles at the boundary of their support (their contact slope) is shown to be a necessary condition for stability. Additional necessary and sufficient conditions for stability are established for a specific driving force corresponding to a thermocapillary-driven film. It is found that only droplets of sufficiently short height that satisfy the contact slope criterion are stable. This destabilization of droplets with increasing height is characterized as a saddle-node bifurcation between a branch of tall, unstable droplets and a branch of short, stable droplets.

A method to stabilize the temperature dependent performance of G-APD arrays

Energy Technology Data Exchange (ETDEWEB)

Huh, Yoonsuk [Molecular Imaging Research and Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Sungkyunkwan University, School of Medicine, Seoul (Korea, Republic of); Choi, Yong; Ho Jung, Jin; Jung, Jiwoong [Molecular Imaging Research and Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of)

2015-02-01

This paper presents a compensation method to stabilize the temperature dependent performance of Geiger-mode Avalanche Photodiode (G-APD) arrays for Positron Emission Tomography (PET). The compensation method is used to identify the bias voltage range that provides stable performance even at different temperatures using the G-APD’s characteristics, and to control the photo-peak variation as a function of temperature using the preamplifier gain within the identified bias voltage range. A pair of G-APD detectors and temperature sensors were located in the temperature chamber and the preamplifiers which can control the gain of the detectors using the digital potentiometer were positioned outside the chamber. The performance of the G-APD detector, especially energy resolution and coincidence timing resolution, was characterized as a function of bias voltage at different temperatures from 20 °C to 40 °C at 5 °C increments; the energy resolution, coincidence timing resolution, and photo-peak position of all channels of G-APD PET detectors before and after the preamplifier gain correction were then measured and compared. The results of this study demonstrated that the optimal bias voltage range providing the good energy and coincidence timing resolution, 12.1±1.2% and 1.30±0.09 ns, respectively, could be identified at the temperature range and the photo-peak variation and the performance at different temperatures could be stabilized by adjusting the preamplifier gain within the identified bias voltage range. We concluded the proposed method to be reliable and useful for the development of the PET system using G-APD arrays.

A work criterion for plastic collapse

International Nuclear Information System (INIS)

Muscat, Martin; Mackenzie, Donald; Hamilton, Robert

2003-01-01

A new criterion for evaluating limit and plastic loads in pressure vessel design by analysis is presented. The proposed criterion is based on the plastic work dissipated in the structure as loading progresses and may be used for structures subject to a single load or a combination of multiple loads. Example analyses show that limit and plastic loads given by the plastic work criterion are robust and consistent. The limit and plastic loads are determined purely by the inelastic response of the structure and are not influenced by the initial elastic response: a problem with some established plastic criteria

Silicon photomultiplier's gain stabilization by bias correction for compensation of the temperature fluctuations

International Nuclear Information System (INIS)

Dorosz, P.; Baszczyk, M.; Glab, S.; Kucewicz, W.; Mik, L.; Sapor, M.

2013-01-01

Gain of the silicon photomultiplier is strongly dependent on the value of bias voltage and temperature. This paper proposes a method for gain stabilization just by compensation of temperature fluctuations by bias correction. It has been confirmed that this approach gives good results and the gain can be kept very stable

Some properties of the computable cross-norm criterion for separability

International Nuclear Information System (INIS)

Rudolph, Oliver

2003-01-01

The computable cross-norm (CCN) criterion is a powerful analytical and computable separability criterion for bipartite quantum states, which is also known to systematically detect bound entanglement. In certain aspects this criterion complements the well-known Peres positive partial transpose (PPT) criterion. In the present paper we study important analytical properties of the CCN criterion. We show that in contrast to the PPT criterion it is not sufficient in dimension 2x2. In higher dimensions, theorems connecting the fidelity of a quantum state with the CCN criterion are proved. We also analyze the behavior of the CCN criterion under local operations and identify the operations that leave it invariant. It turns out that the CCN criterion is in general not invariant under local operations

A graphical criterion for working fluid selection and thermodynamic system comparison in waste heat recovery

International Nuclear Information System (INIS)

Xi, Huan; Li, Ming-Jia; He, Ya-Ling; Tao, Wen-Quan

2015-01-01

In the present study, we proposed a graphical criterion called CE diagram by achieving the Pareto optimal solutions of the annual cash flow and exergy efficiency. This new graphical criterion enables both working fluid selection and thermodynamic system comparison for waste heat recovery. It's better than the existing criterion based on single objective optimization because it is graphical and intuitionistic in the form of diagram. The features of CE diagram were illustrated by studying 5 examples with different heat-source temperatures (ranging between 100 °C to 260 °C), 26 chlorine-free working fluids and two typical ORC systems including basic organic Rankine cycle(BORC) and recuperative organic Rankine cycle (RORC). It is found that the proposed graphical criterion is feasible and can be applied to any closed loop waste heat recovery thermodynamic systems and working fluids. - Highlights: • A graphical method for ORC system comparison/working fluid selection was proposed. • Multi-objectives genetic algorithm (MOGA) was applied for optimizing ORC systems. • Application cases were performed to demonstrate the usage of the proposed method.

Structural stability of high entropy alloys under pressure and temperature

DEFF Research Database (Denmark)

Ahmad, Azkar S.; Su, Y.; Liu, S. Y.

2017-01-01

The stability of high-entropy alloys (HEAs) is a key issue before their selection for industrial applications. In this study, in-situ high-pressure and high-temperature synchrotron radiation X-ray diffraction experiments have been performed on three typical HEAs Ni20Co20Fe20Mn20Cr20, Hf25Nb25Zr25Ti...

Development of a brittle fracture acceptance criterion for the International Atomic Energy Agency (IAEA)

International Nuclear Information System (INIS)

Sorenson, K.B.; Salzbrenner, R.; Nickell, R.E.

1992-01-01

An effort has been undertaken to develop a brittle fracture acceptance criterion for structural components of nuclear material transportation casks. The need for such a criterion was twofold. First, new generation cask designs have proposed the use of ferritic steels and other materials to replace the austenitic stainless steel commonly used for structural components in transport casks. Unlike austenitic stainless steel which fails in a high-energy absorbing, ductile tearing mode, it is possible for these candidate materials to fail via brittle fracture when subjected to certain combinations of elevated loading rates and low temperatures. Second, there is no established brittle fracture criterion accepted by the regulatory community that covers a broad range of structural materials. Although the existing IAEA Safety Series number-sign 37 addressed brittle fracture, its the guidance was dated and pertained only to ferritic steels. Consultant's Services Meetings held under the auspices of the IAEA have resulted in a recommended brittle fracture criterion. The brittle fracture criterion is based on linear elastic fracture mechanics, and is the result of a consensus of experts from six participating IAEA-member countries. The brittle fracture criterion allows three approaches to determine the fracture toughness of the structural material. The three approaches present the opportunity to balance material testing requirements and the conservatism of the material's fracture toughness which must be used to demonstrate resistance to brittle fracture. This work has resulted in a revised Appendix IX to Safety Series number-sign 37 which will be released as an IAEA Technical Document within the coming year

Transient stability analysis with equal-area criterion for out of step ...

African Journals Online (AJOL)

user

*Corresponding Author: e-mail: almoatazabdelaziz@hotmail.com, Tel. ...... Transient stability of power systems: theory and Practice, John Wiley and Sons. ... and protection and new optimization techniques in power systems operation and.

Microstructure and high temperature stability of age hardenable AA2219 aluminium alloy modified by Sc, Mg and Zr additions

Energy Technology Data Exchange (ETDEWEB)

Naga Raju, P. [Metallurgical and Materials Engineering Department, IIT-Madras, Chennai 600036 (India)], E-mail: puvvala_nagaraju@yahoo.com; Srinivasa Rao, K. [Metallurgical Engineering Department, Andhra University, Visakapatnam 530003 (India); Reddy, G.M. [Defence Metallurgical Research Laboratory, Hyderabad 500258 (India); Kamaraj, M.; Prasad Rao, K. [Metallurgical and Materials Engineering Department, IIT-Madras, Chennai 600036 (India)

2007-08-25

The present work pertains to the improvement of high temperature stability of age hardenable AA2219 aluminium-copper (6.3%) alloy. Addition of scandium, magnesium and zirconium to the base metal AA2219 was adopted to improve this high temperature stability. These additions were systematically varied by preparing alloys of different composition using gas tungsten arc melting. Long time ageing studies and impression creep technique were used to study the high temperature stability of the alloys. These modified compositions of the alloy resulted in fine equiaxed grains, refined eutectics, large number of high temperature stable and finer precipitates. Among all the compositions, 0.8% Sc + 0.45% Mg + 0.2% Zr addition was found to be significant in improving the high temperature stability of AA2219 alloy. This may be attributed to the possible microstructural changes, solute enrichment of the matrix and pinning of the grain boundaries by the finer precipitates.

Angle Stability Analysis for Voltage-Controlled Converters

DEFF Research Database (Denmark)

Lin, Hengwei; Jia, Chenxi; Guerrero, Josep M.

2017-01-01

a criterion to analyze the quasi-steady angle stability and the direct current (DC) side stability for VSCs. The operating limit and the angle instability mechanism are revealed, which is generally applicable to the voltage-controlled converters. During the analysis, the influence of the parameters on angle...... stability is studied. Further, the difference on instability mechanism between power electronic converters and synchronous generators are explained in detail. Finally, experiment results with corrective actions verify the analysis....

Method for stabilizing low-level mixed wastes at room temperature

Science.gov (United States)

Wagh, Arun S.; Singh, Dileep

1997-01-01

A method to stabilize solid and liquid waste at room temperature is provided comprising combining solid waste with a starter oxide to obtain a powder, contacting the powder with an acid solution to create a slurry, said acid solution containing the liquid waste, shaping the now-mixed slurry into a predetermined form, and allowing the now-formed slurry to set. The invention also provides for a method to encapsulate and stabilize waste containing cesium comprising combining the waste with Zr(OH).sub.4 to create a solid-phase mixture, mixing phosphoric acid with the solid-phase mixture to create a slurry, subjecting the slurry to pressure; and allowing the now pressurized slurry to set. Lastly, the invention provides for a method to stabilize liquid waste, comprising supplying a powder containing magnesium, sodium and phosphate in predetermined proportions, mixing said powder with the liquid waste, such as tritium, and allowing the resulting slurry to set.

Long-Term Stability Evaluation and Pillar Design Criterion for Room-and-Pillar Mines

Directory of Open Access Journals (Sweden)

Yang Yu

2017-10-01

Full Text Available The collapse of abandoned room-and-pillar mines is often violent and unpredictable. Safety concerns often resulted in mine closures with no post-mining stability evaluations. As a result, large amounts of land resources over room-and-pillar mines are wasted. This paper attempts to establish an understanding of the long-term stability issues of goafs (abandoned mines. Considering progressive pillar failures and the effect of single pillar failure on surrounding pillars, this paper proposes a pillar peeling model to evaluate the long-term stability of coal mines and the associated criteria for evaluating the long-term stability of room-and-pillar mines. The validity of the peeling model was verified by numerical simulation, and field data from 500 pillar cases from China, South Africa, and India. It is found that the damage level of pillar peeling is affected by the peel angle and pillar height and is controlled by the pillar width–height ratio.

Negative feedback mechanism for the long-term stabilization of earth's surface temperature

International Nuclear Information System (INIS)

Walker, J.C.G.; Hays, P.B.; Kasting, J.F.

1981-01-01

We suggest that the partial pressure of carbon dioxide in the atmosphere is buffered, over geological time scales, by a negative feedback mechanism in which the rate of weathering of silicate minerals (followed by deposition of carbonate minerals) depends on surface temperature, and surface temperature, in turn, depends on carbon dioxide partial pressure through the green effect. Although the quantitative details of this mechanism are speculative, it appears able partially to stabilize earth's surface temperature against the steady increase of solar luminosity believed to have occured since the origin of the solar system

On the C(R) stability of uncertain singularly perturbed systems

International Nuclear Information System (INIS)

Sun, Y.-J.

2009-01-01

In this paper, a simple criterion for the C(R) stability of uncertain singularly perturbed systems is proposed. Such a criterion can be easily checked by some algebraic inequality. The upper bound of the singular perturbation parameter ε is also given by estimating the unique positive zero of specific function. Finally, a numerical example is provided to illustrate the main result

Developing industries in cooperative interaction: equilibrium and stability in processes with lag

Directory of Open Access Journals (Sweden)

Aleksandr Kirjanen

2017-11-01

Full Text Available A mathematical model of dynamic interaction between mining and processing industries is formalized and studied in the paper. The process of interaction is described by a system of two delay dierential equations. The criterion for asymptotic stability of nontrivial equilibrium point is obtained when both industries co-work steadily. The problem is reduced to nding stability criterion for quasi-polynomial of second order. Time intervals between deliveries of raw materials which make it possible to preserve stable interaction between the two industries are found.

Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature.

Science.gov (United States)

Barani, Hossein; Montazer, Majid; Braun, Hans-Georg; Dutschk, Victoria

2014-12-01

The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a simple and safe method by using lecithin as a stabilising agent and their stability was examined at various temperatures. The effect of the lecithin concentrations on the stability of the synthesised silver nanoparticles was examined from 25 to 80°C at 5°C intervals, by recording the changes in the UV-vis absorption spectra, the hydrodynamic diameter and the light scattering intensity of the silver nanoparticles. In addition, the morphology of the synthesised silver nanoparticles was investigated with the low-voltage scanning electron microscopy and transmission electron microscopy. The results indicated that increasing temperature caused different changes in the size of the stabilised and the unstabilised silver nanoparticles. The size of the stabilised silver nanoparticles reduced from 38 to 36 nm during increasing temperature, which confirmed good stability.

Modeling and Simulation of Swirl Stabilized Turbulent Non-Premixed Flames

Science.gov (United States)

Badillo-Rios, Salvador; Karagozian, Ann

2017-11-01

Flame stabilization is an important design criterion for many combustion chambers, especially at lean conditions and/or high power output, where insufficient stabilization can result in dangerous oscillations and noisy or damaged combustors. At high flow rates, swirling flow can offer a suitable stabilization mechanism, although understanding the dynamics of swirl-stabilized turbulent flames remains a significant challenge. Utilizing the General Equation and Mesh Solver (GEMS) code, which solves the Navier-Stokes equations along with the energy equation and five species equations, 2D axisymmetric and full 3D parametric studies and simulations are performed to guide the design and development of an experimental swirl combustor configuration and to study the effects of swirl on statistically stationary combustion. Results show that as the momentum of air is directed into the inner air inlet rather than the outer inlet of the swirl combustor, the central recirculating region becomes stronger and more unsteady, improving mixing and burning efficiency in that region. A high temperature region is found to occur as a result of burning of the trapped fuel from the central toroidal vortex. The effects of other parameters on flowfield and flame-stabilization dynamics are explored. Supported by ERC, Inc. (PS150006) and AFOSR (Dr. Chiping Li).

QV modal distance displacement - a criterion for contingency ranking

Energy Technology Data Exchange (ETDEWEB)

Rios, M.A.; Sanchez, J.L.; Zapata, C.J. [Universidad de Los Andes (Colombia). Dept. of Electrical Engineering], Emails: mrios@uniandes.edu.co, josesan@uniandes.edu.co, cjzapata@utp.edu.co

2009-07-01

This paper proposes a new methodology using concepts of fast decoupled load flow, modal analysis and ranking of contingencies, where the impact of each contingency is measured hourly taking into account the influence of each contingency over the mathematical model of the system, i.e. the Jacobian Matrix. This method computes the displacement of the reduced Jacobian Matrix eigenvalues used in voltage stability analysis, as a criterion of contingency ranking, considering the fact that the lowest eigenvalue in the normal operation condition is not the same lowest eigenvalue in N-1 contingency condition. It is made using all branches in the system and specific branches according to the IBPF index. The test system used is the IEEE 118 nodes. (author)

Transducer-based fiber Bragg grating high-temperature sensor with enhanced range and stability

Science.gov (United States)

Mamidi, Venkata Reddy; Kamineni, Srimannarayana; Ravinuthala, Lakshmi Narayana Sai Prasad; Tumu, Venkatappa Rao

2017-09-01

Fiber Bragg grating (FBG)-based high-temperature sensor with enhanced-temperature range and stability has been developed and tested. The sensor consists of an FBG and a mechanical transducer, which furnishes a linear temperature-dependent tensile strain on FBG by means of differential linear thermal expansion of two different ceramic materials. The designed sensor is tested over a range: 20°C to 1160°C and is expected to measure up to 1500°C.

Stability of retained austenite arising at low temperatures in low carbon steels with copper using TRIP effect

International Nuclear Information System (INIS)

Michta, G.; Pietrzyk, J.; Osuch, W.; Kruk, A.

2003-01-01

The magnetometric measurement results of decomposition of retained austenite arising during low temperature bainite transformation, obtained structure and mechanical properties are presented. Presented results demonstrate that the low temperature bainite transformation leads to formation of two kinds of retained austenite with different stability. Decomposition of low stability retained austenite was observed during cooling to -196 o C, the second with high stability was decomposed only during heating up to 560 o C. The first one was observed in microstructure as big grains and the second more refinement in structure was localised between bainitic regions. (author)

A measurable Lawson criterion and hydro-equivalent curves for inertial confinement fusion

International Nuclear Information System (INIS)

Zhou, C. D.; Betti, R.

2008-01-01

It is shown that the ignition condition (Lawson criterion) for inertial confinement fusion (ICF) can be cast in a form dependent on the only two parameters of the compressed fuel assembly that can be measured with existing techniques: the hot spot ion temperature (T i h ) and the total areal density (ρR tot ), which includes the cold shell contribution. A marginal ignition curve is derived in the ρR tot , T i h plane and current implosion experiments are compared with the ignition curve. On this plane, hydrodynamic equivalent curves show how a given implosion would perform with respect to the ignition condition when scaled up in the laser-driver energy. For 3 i h > n i h > n 2.6 · tot > n >50 keV 2.6 · g/cm 2 , where tot > n and i h > n are the burn-averaged total areal density and hot spot ion temperature, respectively. Both quantities are calculated without accounting for the alpha-particle energy deposition. Such a criterion can be used to determine how surrogate D 2 and subignited DT target implosions perform with respect to the one-dimensional ignition threshold.

Stability of gold cages (Au16 and Au17) at finite temperature

Indian Academy of Sciences (India)

We have employed ab initio molecular dynamics to investigate the stability of the smallest ... total simulation time is of the order of 2.4 ns for each cluster. .... energies are relevant to the finite temperature analysis, we have analysed about 50.

LMI optimization approach to stabilization of time-delay chaotic systems

International Nuclear Information System (INIS)

Park, Ju H.; Kwon, O.M.

2005-01-01

Based on the Lyapunov stability theory and linear matrix inequality (LMI) technique, this paper proposes a novel control method for stabilization of a class of time-delay chaotic systems. A stabilization criterion is derived in terms of LMIs which can be easily solved by efficient convex optimization algorithms. A numerical example is included to show the advantage of the result derived

A new kind of shape-stabilized PCMs with positive temperature coefficient (PTC) effect

International Nuclear Information System (INIS)

Cheng, Wen-long; Wu, Wan-fan; Song, Jia-liang; Liu, Yi; Yuan, Shuai; Liu, Na

2014-01-01

Highlights: • A new kind of shape-stabilized PCMs with PTC effect is first prepared. • It provides a potential means for the thermal control of the electronic devices. • The switching temperature of the materials is about 25 °C. • The most appropriate component of the material is found out by experimental study. • The NTC effect of the new PCMs is eliminated effectively by heat treatment. - Abstract: A new kind of shape-stabilized phase change materials (PCMs) with positive temperature coefficient (PTC) effect was prepared in this paper. The materials were prepared by adding graphite powder (GP) to the paraffin/low density polyethylene (LDPE) composite and the PTC characteristic was found by adjusting the component ratio of the material. Then the physical structures and thermal properties of the materials were investigated and the effect of various GP mass fractions and paraffin/LDPE mass proportions on the PTC behavior of the materials was studied experimentally. The results showed that the switching temperature of the materials was about 25 °C (room temperature) which approached to the first phase change temperature of paraffin dispersed in the materials. The PTC behavior of the materials was the best when the GP mass fraction and the mass proportion of LDPE/paraffin were 40 wt% and 30:70, respectively. Furthermore, the negative temperature coefficient (NTC) effect of the materials could be eliminated effectively with heat treatment. This new kind of materials is different from the former PTC materials which the switching temperatures focus on high temperature ranges. It makes up for the defect of previous materials that the switching temperatures only range in high temperature rather than room temperature and provides a potential means for the thermal control of the electronic devices or other room temperature thermal control applications

A machine learns to predict the stability of circumbinary planets

Science.gov (United States)

Lam, Christopher; Kipping, David

2018-01-01

Long-period circumbinary planets appear to be as common as those orbiting single stars and have been found to frequently have orbital radii just beyond the critical distance for dynamical stability. Assessing the stability is typically done either through N-body simulations or using the classic Holman-Wiegert stability criterion: a second-order polynomial calibrated to broadly match numerical simulations. However, the polynomial is unable to capture islands of instability introduced by mean motion resonances, causing the accuracy of the criterion to approach that of a random coin-toss when close to the boundary. We show how a deep neural network (DNN) trained on N-body simulations generated with REBOUND is able to significantly improve stability predictions for circumbinary planets on initially coplanar, circular orbits. Specifically, we find that the accuracy of our DNN never drops below 86%, even when tightly surrounding the boundary of instability, and is fast enough to be practical for on-the-fly calls during likelihood evaluations typical of modern Bayesian inference. Our binary classifier DNN is made publicly available at https://github.com/CoolWorlds/orbital-stability.

Failure Criterion for Brick Masonry: A Micro-Mechanics Approach

Directory of Open Access Journals (Sweden)

Kawa Marek

2015-02-01

Full Text Available The paper deals with the formulation of failure criterion for an in-plane loaded masonry. Using micro-mechanics approach the strength estimation for masonry microstructure with constituents obeying the Drucker-Prager criterion is determined numerically. The procedure invokes lower bound analysis: for assumed stress fields constructed within masonry periodic cell critical load is obtained as a solution of constrained optimization problem. The analysis is carried out for many different loading conditions at different orientations of bed joints. The performance of the approach is verified against solutions obtained for corresponding layered and block microstructures, which provides the upper and lower strength bounds for masonry microstructure, respectively. Subsequently, a phenomenological anisotropic strength criterion for masonry microstructure is proposed. The criterion has a form of conjunction of Jaeger critical plane condition and Tsai-Wu criterion. The model proposed is identified based on the fitting of numerical results obtained from the microstructural analysis. Identified criterion is then verified against results obtained for different loading orientations. It appears that strength of masonry microstructure can be satisfactorily described by the criterion proposed.

A comprehensive study of temperature stability of Silicon PhotoMultiplier

International Nuclear Information System (INIS)

Ferri, A; Acerbi, F; Gola, A; Paternoster, G; Piemonte, C; Zorzi, N

2014-01-01

The temperature stability of the SiPM signal output can be a crucial aspect in many applications. In a typical scenario where the detector is biased at a constant voltage, a temperature fluctuation determines a change in the breakdown voltage and consequently in the applied over-voltage. The latter impacts on all the parameters that determine the output signal such as gain, PDE and correlated noise probability. In this paper we show a detailed analysis of the dependence of these parameters versus the temperature. In particular, we analyze two cases in which the quantity of interest is the integrated charge or the signal amplitude, respectively. The model is applied to a 1 × 1 mm 2 FBK RGB SiPM with 50 × 50 μm 2 cells showing a good agreement with the experimental data

Heat experiment design to estimate temperature dependent thermal properties

International Nuclear Information System (INIS)

Romanovski, M

2008-01-01

Experimental conditions are studied to optimize transient experiments for estimating temperature dependent thermal conductivity and volumetric heat capacity. A mathematical model of a specimen is the one-dimensional heat equation with boundary conditions of the second kind. Thermal properties are assumed to vary nonlinearly with temperature. Experimental conditions refer to the thermal loading scheme, sampling times and sensor location. A numerical model of experimental configurations is studied to elicit the optimal conditions. The numerical solution of the design problem is formulated on a regularization scheme with a stabilizer minimization without a regularization parameter. An explicit design criterion is used to reveal the optimal sensor location, heating duration and flux magnitude. Results obtained indicate that even the strongly nonlinear experimental design problem admits the aggregation of its solution and has a strictly defined optimal measurement scheme. Additional region of temperature measurements with allowable identification error is revealed.

Finite-β stabilization of a diffuse helical l = MHD equilibrium

International Nuclear Information System (INIS)

Herrnegger, F.; Nuehrenberg, J.

1975-04-01

The stability of helically symmetric finite-β, l = 1 magnetohydrostatic equilibria with arbitrary pressure profile and vanishing longitudinal current is investigated by means of Mercier's criterion, a sufficient criterion by Lortz, Rebhan and Spies, and Shafranov's condition for a high-β magnetic well. The new finite-β effects are that 1) a magnetic well is created throughout the plasma region for 0.2 approximately [de

Heat Sinking, Cross Talk, and Temperature Stability for Large, Close-Packed Arrays of Microcalorimeters

Science.gov (United States)

Imoto, Naoko; Bandler, SImon; Brekosky, Regis; Chervenak, James; Figueroa-Felicano, Enectali; Finkbeiner, Frederick; Kelley, Richard; Kilbourne, Caroline; Porter, Frederick; Sadleir, Jack;

Determination of the potentiostatic stability of PEMFC electro catalysts at elevated temperatures

NARCIS (Netherlands)

Dam, V.A.T.; Jayasayee, K.; Bruijn, de F.A.

2009-01-01

The electrochemical stability of platinum on carbon catalyst (Hispec TM 4000, Johnson Matthey) has been investigated predominantly at constant potentials ranging from 0.95 to 1.25 V at elevated temperatures. By combining a quartz crystal microbalance (QCM) with electrochemical techniques, dynamic

Global stability of discrete-time recurrent neural networks with impulse effects

International Nuclear Information System (INIS)

Zhou, L; Li, C; Wan, J

2008-01-01

This paper formulates and studies a class of discrete-time recurrent neural networks with impulse effects. A stability criterion, which characterizes the effects of impulse and stability property of the corresponding impulse-free networks on the stability of the impulsive networks in an aggregate form, is established. Two simplified and numerically tractable criteria are also provided

Temperature-dependent spectroscopic evidences of curcumin in aqueous medium: a mechanistic study of its solubility and stability.

Science.gov (United States)

Jagannathan, Ramya; Abraham, Priya Mary; Poddar, Pankaj

2012-12-20

In curcumin, keto-enol-enolate equilibrium of the heptadiene-dione moiety determines its physiochemical and antioxidant properties. However, its poor solubility in water at neutral pH and room temperature decreases its bioavailability. Potential therapeutic applications have triggered an interest in manipulating the solubility of curcumin in water as its stability and solubility in water remains poorly understood. Here, the mechanism behind its solubility at various temperatures and the influence of interplay of temperature, intramolecular H-bonding, and intermolecular forces is reported, which leads to aggregation-disaggregation at various temperatures. Remarkable change is observed in temperature-dependent electronic transition behavior of curcumin, however, the absorption spectra after cooling and heating cycles remain unchanged, hinting much better thermal stability of curcumin in water than previously thought. This study indicates that it is perhaps the breaking of intramolecular hydrogen bonding which leads to exposure of polar groups and hence responsible for the dissolution of curcumin at higher temperature. The formation of intermolecular aggregates might be responsible behind a better room temperature stability of the molecules after cooling its aqueous suspension from 90 to 25 °C. These curcumin solubility studies have great application in biological research with reference to bioavailability and to understand target oriented mode of action of curcumin.

A Failure Criterion for Concrete

DEFF Research Database (Denmark)

Ottosen, N. S.

1977-01-01

A four-parameter failure criterion containing all the three stress invariants explicitly is proposed for short-time loading of concrete. It corresponds to a smooth convex failure surface with curved meridians, which open in the negative direction of the hydrostatic axis, and the trace in the devi......A four-parameter failure criterion containing all the three stress invariants explicitly is proposed for short-time loading of concrete. It corresponds to a smooth convex failure surface with curved meridians, which open in the negative direction of the hydrostatic axis, and the trace...

BWR stability: analysis of cladding temperature for high amplitude oscillations - 146

International Nuclear Information System (INIS)

Pohl, P.; Wehle, F.

2010-01-01

Power oscillations associated with density waves in boiling water reactors (BWRs) have been studied widely. Industrial research in this area is active since the invention of the first BWR. Stability measurements have been performed in various plants during commissioning phase but especially the magnitude and divergent nature of the oscillations during the LaSalle Unit 2 nuclear power plant event on March 9, 1988, renewed concern about the state of knowledge on BWR instabilities and possible consequences to fuel rod integrity. The objective of this paper is to present a simplified stability tool, applicable for stability analysis in the non-linear regime, which extends to high amplitude oscillations where inlet reverse flow occurs. In case of high amplitude oscillations a cyclical dryout and rewetting process at the fuel rod may take place, which leads in turn to rapid changes of the heat transfer from the fuel rod to the coolant. The application of this stability tool allows for a conservative determination of the fuel rod cladding temperature in case of high amplitude oscillations during the dryout / re-wet phase. Moreover, it reveals in good agreement to experimental findings the stabilizing effect of the reverse bundle inlet flow, which might be obtained for large oscillation amplitudes. (authors)

Mathematical modeling of photoinitiated coating degradation: Effects of coating glass transition temperature and light stabilizers

DEFF Research Database (Denmark)

Kiil, Søren; G.de With, R.A.T.M.Van Benthem

2013-01-01

A mathematical model, describing coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature, was extended to simulate the behavior of a coating with a low glass transition temperature. The effects of adding light stabilizers (a UV...

Effects of Hall current and electrical resistivity on the stability of gravitating anisotropic quantum plasma

Science.gov (United States)

Bhakta, S.; Prajapati, R. P.

2018-02-01

The effects of Hall current and finite electrical resistivity are studied on the stability of uniformly rotating and self-gravitating anisotropic quantum plasma. The generalized Ohm's law modified by Hall current and electrical resistivity is used along with the quantum magnetohydrodynamic fluid equations. The general dispersion relation is derived using normal mode analysis and discussed in the parallel and perpendicular propagations. In the parallel propagation, the Jeans instability criterion, expression of critical Jeans wavenumber, and Jeans length are found to be independent of non-ideal effects and uniform rotation but in perpendicular propagation only rotation affects the Jeans instability criterion. The unstable gravitating mode modified by Bohm potential and the stable Alfven mode modified by non-ideal effects are obtained separately. The criterion of firehose instability remains unaffected due to the presence of non-ideal effects. In the perpendicular propagation, finite electrical resistivity and quantum pressure anisotropy modify the dispersion relation, whereas no effect of Hall current was observed in the dispersion characteristics. The Hall current, finite electrical resistivity, rotation, and quantum corrections stabilize the growth rate. The stability of the dynamical system is analyzed using the Routh-Hurwitz criterion.

Electrical properties and temperature stability of a new kind of lead-free piezoelectric ceramics

International Nuclear Information System (INIS)

Wang Yuanyu; Wu Jiagang; Xiao Dingquan; Zhang Bin; Wu Wenjuan; Shi Wei; Zhu Jianguo

2008-01-01

0.995[(K 0.50 Na 0.50 ) 0.94 Li 0.06 ]NbO 3 -0.005AETiO 3 (AE=Ca, Sr, Mg, Ba) lead-free piezoelectric ceramics were prepared by normal sintering. The effects of the AETiO 3 and poling temperature on the electrical properties of the ceramics were carefully studied, and the temperature stability of the electrical properties of the ceramics was also investigated. The experimental results show that the ceramics with Li and CaTiO 3 possess the pure phase, Li and AETiO 3 improves the electrical properties of the pure (K 0.50 Na 0.50 )NbO 3 ceramics, the poling temperature near tetragonal and orthorhombic phase transition will enhance the piezoelectric properties of the ceramics and the KNLN-CT ceramics exhibit good temperature stability of electrical properties for tetragonal and orthorhombic phase transition below room temperature. The KNLN-CT ceramics exhibit relatively good properties: d 33 = 172 pC N -1 , k p = 0.43, tan δ = 0.032, ε r = 771 and T c = 465 deg. C. As a result, the KNLN-CT ceramic is promising candidate material for piezoelectric devices.

The EMU debt criterion: an interpretation

Directory of Open Access Journals (Sweden)

R. BERNDSEN

1997-12-01

Full Text Available The convergence criteria specified in the Maastricht Treaty on government deficit and debt, inflation, the exchange rate and the long-term interest rate will play an important, if not decisive, role in determining which countries move on to the third stage of the Economic and Monetary Union (EMU. The aim of this work is to provide a possible interpretation of the EMU debt criterion. The author investigates the government debt criterion which, as Article 104c(2b of the Treaty shows, has a considerable scope for interpretation. Although this subject has been discussed extensively, relatively little work has been done to develop a clear interpretation of the EMU debt criterion. A flexible approach is adopted in which parts of the relevant Treaty text are characterised using two parameters.

Zirconium phosphate waste forms for low-temperature stabilization of cesium-137-containing waste streams

International Nuclear Information System (INIS)

Singh, D.; Wagh, A.S.; Tlustochowicz.

1996-04-01

Novel chemically bonded phosphate ceramics are being developed and fabricated for low-temperature stabilization and solidification of waste streams that are not amenable to conventional high-temperature stabilization processes because volatiles are present in the wastes. A composite of zirconium-magnesium phosphate has been developed and shown to stabilize ash waste contaminated with a radioactive surrogate of 137 Cs. Excellent retainment of cesium in the phosphate matrix system was observed in Toxicity Characteristic Leaching Procedure tests. This was attributed to the capture of cesium in the layered zirconium phosphate structure by intercalation ion-exchange reaction. But because zirconium phosphate has low strength, a novel zirconium/magnesium phosphate composite waste form system was developed. The performance of these final waste forms, as indicated by compression strength and durability in aqueous environments, satisfy the regulatory criteria. Test results indicate that zirconium-magnesium-phosphate-based final waste forms present a viable technology for treatment and solidification of cesium-contaminated wastes

Chemical stability of high-temperature superconductors

Science.gov (United States)

Bansal, Narottam P.

1992-01-01

A review of the available studies on the chemical stability of the high temperature superconductors (HTS) in various environments was made. The La(1.8)Ba(0.2)CuO4 HTS is unstable in the presence of H2O, CO2, and CO. The YBa2Cu3O(7-x) superconductor is highly susceptible to degradation in different environments, especially water. The La(2-x)Ba(x)CuO4 and Bi-Sr-Ca-Cu-O HTS are relatively less reactive than the YBa2Cu3O(7-x). Processing of YBa2Cu3O(7-x) HTS in purified oxygen, rather than in air, using high purity noncarbon containing starting materials is recommended. Exposure of this HTS to the ambient atmosphere should also be avoided at all stages during processing and storage. Devices and components made out of these oxide superconductors would have to be protected with an impermeable coating of a polymer, glass, or metal to avoid deterioration during use.

Inviscid criterion for decomposing scales

Science.gov (United States)

Zhao, Dongxiao; Aluie, Hussein

2018-05-01

The proper scale decomposition in flows with significant density variations is not as straightforward as in incompressible flows, with many possible ways to define a "length scale." A choice can be made according to the so-called inviscid criterion [Aluie, Physica D 24, 54 (2013), 10.1016/j.physd.2012.12.009]. It is a kinematic requirement that a scale decomposition yield negligible viscous effects at large enough length scales. It has been proved [Aluie, Physica D 24, 54 (2013), 10.1016/j.physd.2012.12.009] recently that a Favre decomposition satisfies the inviscid criterion, which is necessary to unravel inertial-range dynamics and the cascade. Here we present numerical demonstrations of those results. We also show that two other commonly used decompositions can violate the inviscid criterion and, therefore, are not suitable to study inertial-range dynamics in variable-density and compressible turbulence. Our results have practical modeling implication in showing that viscous terms in Large Eddy Simulations do not need to be modeled and can be neglected.

Kinetic stability of internal kink mode

International Nuclear Information System (INIS)

Romanelli, F.; Fogaccia, G.

1993-01-01

With reference to studies of the attainment of ignited operations on devices like ITER (International Thermonuclear Experimental Reactor), the stability of the internal kink mode is re-investigated by taking into account the contribution of perpendicular compressibility, obtained by solving the drift kinetic equation. The resulting stability condition yields threshold values typically larger than the conventional Bussac criterion. For the case of ultra-flat safety factor profiles, the mode can be stable also in the absence of line-bending

Physical stability of API/polymer-blend amorphous solid dispersions.

Science.gov (United States)

Lehmkemper, Kristin; Kyeremateng, Samuel O; Bartels, Mareike; Degenhardt, Matthias; Sadowski, Gabriele

2018-03-01

The preparation of amorphous solid dispersions (ASDs) is a well-established strategy for formulating active pharmaceutical ingredients by embedding them in excipients, usually amorphous polymers. Different polymers can be combined for designing ASDs with desired properties like an optimized dissolution behavior. One important criterion for the development of ASD compositions is the physical stability. In this work, the physical stability of API/polymer-blend ASDs was investigated by thermodynamic modeling and stability studies. Amorphous naproxen (NAP) and acetaminophen (APAP) were embedded in blends of hydroxypropyl methylcellulose acetate succinate (HPMCAS) and either poly(vinylpyrrolidone) (PVP) or poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA64). Parameters for modeling the API solubility in the blends and the glass-transition temperature curves of the water-free systems with Perturbed-Chain Statistical Associating Fluid Theory and Kwei equation, respectively, were correlated to experimental data. The phase behavior for standardized storage conditions (0%, 60% and 75% relative humidity (RH)) was predicted and compared to six months-long stability studies. According to modeling and experimental results, the physical stability was reduced with increasing HPMCAS content and increasing RH. This trend was observed for all investigated systems, with both APIs (NAP and APAP) and both polymer blends (PVP/HPMCAS and PVPVA64/HPMCAS). PC-SAFT and the Kwei equation turned out to be suitable tools for modeling and predicting the physical stability of the investigated API/polymer-blends ASDs. Copyright © 2017 Elsevier B.V. All rights reserved.

[Evaluation of the influence of humidity and temperature on the drug stability by initial average rate experiment].

Science.gov (United States)

He, Ning; Sun, Hechun; Dai, Miaomiao

2014-05-01

To evaluate the influence of temperature and humidity on the drug stability by initial average rate experiment, and to obtained the kinetic parameters. The effect of concentration error, drug degradation extent, humidity and temperature numbers, humidity and temperature range, and average humidity and temperature on the accuracy and precision of kinetic parameters in the initial average rate experiment was explored. The stability of vitamin C, as a solid state model, was investigated by an initial average rate experiment. Under the same experimental conditions, the kinetic parameters obtained from this proposed method were comparable to those from classical isothermal experiment at constant humidity. The estimates were more accurate and precise by controlling the extent of drug degradation, changing humidity and temperature range, or by setting the average temperature closer to room temperature. Compared with isothermal experiments at constant humidity, our proposed method saves time, labor, and materials.

Stability analysis of the high temperature thermal pebble bed nuclear reactor concept

International Nuclear Information System (INIS)

Vondy, D.R.

1981-02-01

A study was made of the stability of the high temperature gas-cooled pebble bed core against xenon-driven oscillation. This generic study indicated that a core as large as 3000 MW(t) could be stable. Several aspects present a challenge to analysis including the void space above the pebble bed, the effects of possible control rod configurations, and the temperature feedback contribution. Special methods of analysis were developed in this effort. Of considerable utility was the scheme of including an azimuthal buckling loss term in the neturon balance equations admitting direct solution of the first azimuthal harmonic for a core having azimuthal symmetry. This technique allows the linear stability analysis to be done solving two-dimensional (RZ) problems instead of three-dimensional problems. A scheme for removing the fundamental source contribution was also implemented to allow direct iteration toward the dominant harmonic solution, treating up to three dimensions with diffusion theory

Stability of one-step methods in transient nonlinear heat conduction

International Nuclear Information System (INIS)

Hughes, J.R.

1977-01-01

The purpose of the present work is to ascertain practical stability conditions for one-step methods commonly used in transient nonlinear heat conduction analyses. The class of problems considered is governed by a temporally continuous, spatially discrete system involving the capacity matrix C, conductivity matrix K, heat supply vector, temperature vector and time differenciation. In the linear case, in which K and C are constant, the stability behavior of one-step methods is well known. But in this paper the concepts of stability, appropriate to the nonlinear problem, are thoroughly discussed. They of course reduce to the usual stability criterion for the linear, constant coefficient case. However, for nonlinear problems there are differences and these ideas are of key importance in obtaining practical stability conditions. Of particular importance is a recent result which indicates that, in a sense, the trapezoidal and midpoint families are quivalent. Thus, stability results for one family may be translated into a result for the other. The main results obtained are summarized as follows. The stability behavior of the explicit Euler method in the nonlinear regime is analogous to that for linear problems. In particular, an a priori step size restriction may be determined for each time step. The precise time step restriction on implicit conditionally stable members of the trapezoidal and midpoint families is shown not to be determinable a priori. Of considerable practical significance, unconditionally stable members of the trapezoidal and midpoint families are identified

Plasma sheath criterion in thermal electronegative plasmas

International Nuclear Information System (INIS)

Ghomi, Hamid; Khoramabadi, Mansour; Ghorannevis, Mahmod; Shukla, Padma Kant

2010-01-01

The sheath formation criterion in electronegative plasma is examined. By using a multifluid model, it is shown that in a collisional sheath there will be upper as well as lower limits for the sheath velocity criterion. However, the parameters of the negative ions only affect the lower limit.

Effect of Pouring Time and Storage Temperature on Dimensional Stability of Casts Made from Irreversible Hydrocolloid

Directory of Open Access Journals (Sweden)

M. Farzin

2010-12-01

Full Text Available Objective: The aim of this study was to evaluate the dimensional stability of casts made from an alginate impression material poured immediately and stored after specific periods.Materials and Methods: The common alginate used in Iran (Super; Iralgin, Golchai Co.,Tehran, Iran was tested. A master model was mounted on a special device and used to obtain the impressions. These impressions were stored at 23°C (SD=1 and 4°C (SD=1 in100% relative humidity, then poured with gypsum immediately and again after 12, 25, 45 and 60 minutes. The casts were measured with a traveling microscope with the precision of 0.5 micrometer.Results: The dimensional stability of the alginate and impressions were both significantly time and temperature dependent. The impressions were dimensionally stable significantly until 12 minutes of storage at room temperature and until 45 minutes of storage at 4°C(SD=1.Conclusion: The dimensional stability of the alginate impressions was influenced by the storage time and environment temperature, but a humid environment and 4°C (SD=1temperature may delay the pouring.

A pellet-clad interaction failure criterion

International Nuclear Information System (INIS)

Howl, D.A.; Coucill, D.N.; Marechal, A.J.C.

1983-01-01

A Pellet-Clad Interaction (PCI) failure criterion, enabling the number of fuel rod failures in a reactor core to be determined for a variety of normal and fault conditions, is required for safety analysis. The criterion currently being used for the safety analysis of the Pressurized Water Reactor planned for Sizewell in the UK is defined and justified in this paper. The criterion is based upon a threshold clad stress which diminishes with increasing fast neutron dose. This concept is consistent with the mechanism of clad failure being stress corrosion cracking (SCC); providing excess corrodant is always present, the dominant parameter determining the propagation of SCC defects is stress. In applying the criterion, the SLEUTH-SEER 77 fuel performance computer code is used to calculate the peak clad stress, allowing for concentrations due to pellet hourglassing and the effect of radial cracks in the fuel. The method has been validated by analysis of PCI failures in various in-reactor experiments, particularly in the well-characterised power ramp tests in the Steam Generating Heavy Water Reactor (SGHWR) at Winfrith. It is also in accord with out-of-reactor tests with iodine and irradiated Zircaloy clad, such as those carried out at Kjeller in Norway. (author)

Low-Temperature Superionic Conductivity in Strained Yttria-Stabilized Zirconia

DEFF Research Database (Denmark)

Sillassen, Michael; Eklund, Per; Pryds, Nini

2010-01-01

Very high lateral ionic conductivities in epitaxial cubic yttria-stabilized zirconia (YSZ) synthesized on single-crystal SrTiO3 and MgO substrates by reactive direct current magnetron sputtering are reported. Superionic conductivities (i.e., ionic conductivities of the order 1 -1cm-1) are observed...... at 500 °C for 58-nm-thick films on MgO. The results indicate a superposition of two parallel contributions - one due to bulk conductivity and one attributable to conduction along the film-substrate interface. Interfacial effects dominate the conductivity at low temperatures (...

A multipole acceptability criterion for electronic structure theory

International Nuclear Information System (INIS)

Schwegler, E.; Challacombe, M.; Head-Gordon, M.

1998-01-01

Accurate and computationally inexpensive estimates of multipole expansion errors are crucial to the success of several fast electronic structure methods. In this paper, a new nonempirical multipole acceptability criterion is described that is directly applicable to expansions of high order moments. Several model calculations typical of electronic structure theory are presented to demonstrate its performance. For cases involving small translation distances, accuracies are increased by up to five orders of magnitude over an empirical criterion. The new multipole acceptance criterion is on average within an order of magnitude of the exact expansion error. Use of the multipole acceptance criterion in hierarchical multipole based methods as well as in traditional electronic structure methods is discussed. copyright 1998 American Institute of Physics

The development of a burst criterion for Zircaloy fuel cladding under LOCA conditions

International Nuclear Information System (INIS)

Neitzel, H.J.; Rosinger, H.E.

1980-10-01

A burst criterion model, which assumes that deformation is controlled by steady-state creep, has been developed for a thin-walled cladding, in this case Zircaloy-4, subjected to a differential pressure and high temperature. The creep equation is integrated to obtain a burst time at the singularity of the strain. Once that urst time is known, the burst temperature and burst pressure can be calculated from the known temperature and pressure histories. A further relationship between burst stress and burst temperature is used to calculate the burst strain. Comparison with measured burst data shows good agreement between theory and experiment. It was found that, if the heating rate is constant, the burst temperature increases with decreasing stress, and that, if the stress level is constant, the burst temperature increases with increasing heating rate. It was also found that anisotropy alters the burst temperature and burst strain, and that thest conditions in the α-Zr temperature range have no influence on the burst data. (orig.) [de

The development of a burst criterion for zircaloy fuel cladding under LOCA conditions

International Nuclear Information System (INIS)

Neitzel, H.J.; Rossinger, H.E.

1980-02-01

A burst criterion model, which assumes that deformation is controlled by steady-state creep, has been developed for a thin-walled cladding, in this case Zircaloy-4, subjected to a differential pressure and high temperature. The creep equation is integrated to obtain a burst time at the singularity of the strain. Once the burst time is known, the burst temperature and burst pressure can be calculated from the known temperature and pressure histories. A further relationship between burst stress and burst temperature is used to calculate the burst strain. Comparison with measured burst data shows good agreement between theory and experiment was found that, if the heating rate is constant, the burst temperature increases with decreasing stress, and that, if the stress level is constant, the burst temperature increases with increasing heating rate. It was also found that anisotropy alters the burst temperature and burst strain, and that test conditions in the α-Zr temperature range have no influence on the burst data. (auth)

Nonparametric adaptive age replacement with a one-cycle criterion

International Nuclear Information System (INIS)

Coolen-Schrijner, P.; Coolen, F.P.A.

2007-01-01

Age replacement of technical units has received much attention in the reliability literature over the last four decades. Mostly, the failure time distribution for the units is assumed to be known, and minimal costs per unit of time is used as optimality criterion, where renewal reward theory simplifies the mathematics involved but requires the assumption that the same process and replacement strategy continues over a very large ('infinite') period of time. Recently, there has been increasing attention to adaptive strategies for age replacement, taking into account the information from the process. Although renewal reward theory can still be used to provide an intuitively and mathematically attractive optimality criterion, it is more logical to use minimal costs per unit of time over a single cycle as optimality criterion for adaptive age replacement. In this paper, we first show that in the classical age replacement setting, with known failure time distribution with increasing hazard rate, the one-cycle criterion leads to earlier replacement than the renewal reward criterion. Thereafter, we present adaptive age replacement with a one-cycle criterion within the nonparametric predictive inferential framework. We study the performance of this approach via simulations, which are also used for comparisons with the use of the renewal reward criterion within the same statistical framework

Effects of ion temperature fluctuations on the stability of resistive ballooning modes

International Nuclear Information System (INIS)

Singh, R.; Nordman, H.; Jarmen, A.; Weiland, J.

1996-01-01

The influence of ion temperature fluctuations on the stability of resistive drift- and ballooning-modes is investigated using a two-fluid model. The Eigenmode equations are derived and solved analytically in a low beta model equilibrium. Parameters relevant to L-mode edge plasmas from the Texas Experimental Tokamak are used. The resistive modes are found to be destabilized by ion temperature fluctuations over a broad range of mode numbers. The scaling of the growth rate with magnetic shear and mode number is elucidated. 13 refs, 4 figs

Unified Bohm criterion

Energy Technology Data Exchange (ETDEWEB)

Kos, L. [LECAD Laboratory, Faculty of Mechanical Engineering, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Tskhakaya, D. D.; Jelić, N. [Institute for Theoretical Physics, Fusion@ÖAW, University of Innsbruck, A-6020 Innsbruck (Austria)

2015-09-15

Recent decades have seen research into the conditions necessary for the formation of the monotonic potential shape in the sheath, appearing at the plasma boundaries like walls, in fluid, and kinetic approximations separately. Although either of these approaches yields a formulation commonly known as the much-acclaimed Bohm criterion (BC), the respective results involve essentially different physical quantities that describe the ion gas behavior. In the fluid approach, such a quantity is clearly identified as the ion directional velocity. In the kinetic approach, the ion behavior is formulated via a quantity (the squared inverse velocity averaged by the ion distribution function) without any clear physical significance, which is, moreover, impractical. In the present paper, we try to explain this difference by deriving a condition called here the Unified Bohm Criterion, which combines an advanced fluid model with an upgraded explicit kinetic formula in a new form of the BC. By introducing a generalized polytropic coefficient function, the unified BC can be interpreted in a form that holds, irrespective of whether the ions are described kinetically or in the fluid approximation.

Spatial and temporal stability of temperature in the first-level basins of China during 1951-2013

Science.gov (United States)

Cheng, Yuting; Li, Peng; Xu, Guoce; Li, Zhanbin; Cheng, Shengdong; Wang, Bin; Zhao, Binhua

2018-05-01

In recent years, global warming has attracted great attention around the world. Temperature change is not only involved in global climate change but also closely linked to economic development, the ecological environment, and agricultural production. In this study, based on temperature data recorded by 756 meteorological stations in China during 1951-2013, the spatial and temporal stability characteristics of annual temperature in China and its first-level basins were investigated using the rank correlation coefficient method, the relative difference method, rescaled range (R/S) analysis, and wavelet transforms. The results showed that during 1951-2013, the spatial variation of annual temperature belonged to moderate variability in the national level. Among the first-level basins, the largest variation coefficient was 114% in the Songhuajiang basin and the smallest variation coefficient was 10% in the Huaihe basin. During 1951-2013, the spatial distribution pattern of annual temperature presented extremely strong spatial and temporal stability characteristics in the national level. The variation range of Spearman's rank correlation coefficient was 0.97-0.99, and the spatial distribution pattern of annual temperature showed an increasing trend. In the national level, the Liaohe basin, the rivers in the southwestern region, the Haihe basin, the Yellow River basin, the Yangtze River basin, the Huaihe basin, the rivers in the southeastern region, and the Pearl River basin all had representative meteorological stations for annual temperature. In the Songhuajiang basin and the rivers in the northwestern region, there was no representative meteorological station. R/S analysis, the Mann-Kendall test, and the Morlet wavelet analysis of annual temperature showed that the best representative meteorological station could reflect the variation trend and the main periodic changes of annual temperature in the region. Therefore, strong temporal stability characteristics exist for

Direct numerical simulations of non-premixed ethylene-air flames: Local flame extinction criterion

KAUST Repository

Lecoustre, Vivien R.

2014-11-01

Direct Numerical Simulations (DNS) of ethylene/air diffusion flame extinctions in decaying two-dimensional turbulence were performed. A Damköhler-number-based flame extinction criterion as provided by classical large activation energy asymptotic (AEA) theory is assessed for its validity in predicting flame extinction and compared to one based on Chemical Explosive Mode Analysis (CEMA) of the detailed chemistry. The DNS code solves compressible flow conservation equations using high order finite difference and explicit time integration schemes. The ethylene/air chemistry is simulated with a reduced mechanism that is generated based on the directed relation graph (DRG) based methods along with stiffness removal. The numerical configuration is an ethylene fuel strip embedded in ambient air and exposed to a prescribed decaying turbulent flow field. The emphasis of this study is on the several flame extinction events observed in contrived parametric simulations. A modified viscosity and changing pressure (MVCP) scheme was adopted in order to artificially manipulate the probability of flame extinction. Using MVCP, pressure was changed from the baseline case of 1 atm to 0.1 and 10 atm. In the high pressure MVCP case, the simulated flame is extinction-free, whereas in the low pressure MVCP case, the simulated flame features frequent extinction events and is close to global extinction. Results show that, despite its relative simplicity and provided that the global flame activation temperature is correctly calibrated, the AEA-based flame extinction criterion can accurately predict the simulated flame extinction events. It is also found that the AEA-based criterion provides predictions of flame extinction that are consistent with those provided by a CEMA-based criterion. This study supports the validity of a simple Damköhler-number-based criterion to predict flame extinction in engineering-level CFD models. © 2014 The Combustion Institute.

Reactor instrumentation. Definition of the single failure criterion

International Nuclear Information System (INIS)

1980-12-01

The standard defines the single failure criterion which is used in other IEC publications on reactor safety systems. The purpose of the single failure criterion is the assurance of minimum redundancy. (orig./HP) [de

High temperature stability of surfactant capped CoFe2O4 nanoparticles

International Nuclear Information System (INIS)

Ayyappan, S.; Panneerselvam, G.; Antony, M.P.; Philip, John

2011-01-01

Highlights: → Self-assembled molecular layers of surfactant on nanoparticles are often used to modify surface properties. → We demonstrate that a surfactant nanolayer on CoFe 2 O 4 nanoparticles can act as a strong reducing agent under high temperature vacuum annealing. → We propose a possible reduction mechanism of CoFe 2 O 4 nanoparticles under air and vacuum annealing. → Our results are important in the understanding of the stability of nanoparticles at high temperatures. - Abstract: We investigate the effect of adsorbed surfactant on the structural stability of CoFe 2 O 4 nanoparticles during vacuum thermal annealing. In-situ high temperature X-ray diffraction studies show a reduction of oleic acid coated CoFe 2 O 4 nanoparticles into α-Fe and CoO under annealing at 800 deg. C. On the contrary, the uncoated CoFe 2 O 4 nanoparticles remains stable, with its cubic phase intact, even at 1000 deg. C. Thermo-gravimetric analysis coupled mass spectra reveals that the evolved carbon from the surfactant aids the removal of oxygen atom from CoFe 2 O 4 lattice thereby reducing it to α-Fe and CoO phases. These results are important in tailoring stable CoFe 2 O 4 nanostructures for various applications.

A machine learns to predict the stability of circumbinary planets

Science.gov (United States)

Lam, Christopher; Kipping, David

2018-06-01

Long-period circumbinary planets appear to be as common as those orbiting single stars and have been found to frequently have orbital radii just beyond the critical distance for dynamical stability. Assessing the stability is typically done either through N-body simulations or using the classic stability criterion first considered by Dvorak and later developed by Holman and Wiegert: a second-order polynomial calibrated to broadly match numerical simulations. However, the polynomial is unable to capture islands of instability introduced by mean motion resonances, causing the accuracy of the criterion to approach that of a random coin-toss when close to the boundary. We show how a deep neural network (DNN) trained on N-body simulations generated with REBOUND is able to significantly improve stability predictions for circumbinary planets on initially coplanar, circular orbits. Specifically, we find that the accuracy of our DNN never drops below 86 per cent, even when tightly surrounding the boundary of instability, and is fast enough to be practical for on-the-fly calls during likelihood evaluations typical of modern Bayesian inference. Our binary classifier DNN is made publicly available at https://github.com/CoolWorlds/orbital-stability.

Composite cathode based on yttria stabilized bismuth oxide for low-temperature solid oxide fuel cells

International Nuclear Information System (INIS)

Xia Changrong; Zhang Yuelan; Liu Meilin

2003-01-01

Composites consisting of silver and yttria stabilized bismuth oxide (YSB) have been investigated as cathodes for low-temperature honeycomb solid oxide fuel cells with stabilized zirconia as electrolytes. At 600 deg. C, the interfacial polarization resistances of a porous YSB-Ag cathode is about 0.3 Ω cm 2 , more than one order of magnitude smaller than those of other reported cathodes on stabilized zirconia. For example, the interfacial resistances of a traditional YSZ-lanthanum maganites composite cathode is about 11.4 Ω cm 2 at 600 deg. C. Impedance analysis indicated that the performance of an YSB-Ag composite cathode fired at 850 deg. C for 2 h is severely limited by gas transport due to insufficient porosity. The high performance of the YSB-Ag cathodes is very encouraging for developing honeycomb fuel cells to be operated at temperatures below 600 deg. C

Silicon photomultiplier's gain stabilization by bias correction for compensation of the temperature fluctuations

Energy Technology Data Exchange (ETDEWEB)

Dorosz, P., E-mail: pdorosz@agh.edu.pl [AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Electronics, Department of Electronics, 30-059 Krakow (Poland); Baszczyk, M.; Glab, S. [AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Electronics, Department of Electronics, 30-059 Krakow (Poland); Kucewicz, W., E-mail: kucewicz@agh.edu.pl [AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Electronics, Department of Electronics, 30-059 Krakow (Poland); Mik, L.; Sapor, M. [AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Electronics, Department of Electronics, 30-059 Krakow (Poland)

2013-08-01

Gain of the silicon photomultiplier is strongly dependent on the value of bias voltage and temperature. This paper proposes a method for gain stabilization just by compensation of temperature fluctuations by bias correction. It has been confirmed that this approach gives good results and the gain can be kept very stable.

The exploration of stability of two-dimensional nanocrystalline metallic composites depending on temperature

International Nuclear Information System (INIS)

Poletayev, G.M.; Starostenkov, M.D.; Popova, G.V.; Skakov, M.K.

2004-01-01

Full text: In nanocrystalline compositional materials the borders of phase separation play special role. The detection of stability of the borders of phase separation depending on external conditions, such pressure, temperature of alloying is the important task in the case of nanocrystalline materials. In the current paper the stability of two-dimensional nanocrystal, composite on the basis of Ni-Al system, depending on the structure of compositional material and vacancy availability is studied. Atomic packing in two-dimensional crystal corresponds to the plane (111) of fee crystal structure, or the plane (111) of superstructure L1 2 of intermetallide system Ni-Al. The interaction between atoms is set by pair potential functions of Morse, that consider interatomic bonding in the first six coordinate spheres. The calculated block was expressed in atomic packing in the cell 40x40. Beyond the bounds of the calculated block crystal is repeated with the help of periodical border conditions. Computer modeling is performed according to the method of molecular dynamics, when speeds of atom dislocations depending on temperature are set in accidental way, according to Boltzmann allocation. Two-dimensional material was represented by different packs of phases, clean Ni, Al and intermetallic superstructure NiAl in accordance with concentrations, structures and forms. It was understood that when the concentration in composite of phase of clean Al increases, or when the number of Al atoms in intermetallide rises, the initial temperature of thermo activated diffusing destruction of interphase borders turns out to be very low. On the other hand, when the part of clean nickel increases or when the concentration of clean Ni atoms in the structure (L1 2 ) rises, diffusion stability of interphase borders is observes right up to high temperatures. According to the results, basic diffusion processes take place right on interphase borders

Process for stabilizing dimensions of duplex stainless steels for service at elevated temperatures

Science.gov (United States)

Hull, Frederick C.; Tobin, John C.

1981-01-01

Duplex stainless steel materials containing austenite plus delta ferrite, are dimensionally stabilized by heating the material to a reaction temperature between about 1050.degree.-1450.degree. F. (566.degree.-788.degree. C.), holding it at this temperature during transformation of delta ferrite to austenite plus sigma phase, and subsequently heating to a reversion temperature between about 1625.degree.-1750.degree. F. (885.degree.-954.degree. C.), whereby the sigma phase transforms back to ferrite, but the austenite remains dispersed in the ferrite phase. Final controlled cooling permits transformation of ferrite to austenite plus sigma and, later, precipitation of carbides.

Effect of copper additions in tin molten pool on stability temperature and critical current of Nb3Sn

International Nuclear Information System (INIS)

Kruzliak, J.; Hutka, P.; Tomasich, M.

1979-01-01

Tested is the effect of 55 at% copper addition into the tin bath on the stability temperature and crytical current of Nb 3 Sn, prepared by the diffusion method. It is shown that copper presence in the tin bath transfers the stability temperature of NbSn 2 and Nb 6 Sn 5 phases below the annealing temperature of 700 deg C. It results in Nb 3 Sn appearance at the annealing temperatures above 600 deg C. The critical current increase is explained as follows: lower Nb 3 Sn appearance temperatures provide fine-grained structure of superconducting Nb 3 Sn layer with greater density of binning centers and with higher critical current in accordance with NbSn prepared by the diffusion of pure tin into niobium

Ceramic stabilization of hazardous wastes: a high performance room temperature process

International Nuclear Information System (INIS)

Maloney, M.D.

1996-01-01

ANL has developed a room-temperature process for converting hazardous materials to a ceramic structure. It is similar to vitrification but is achieved at low cost, similar to conventional cement stabilization. The waste constituents are both chemically stabilized and physically encapsulated, producing very low leaching levels and the potential for delisting. The process, which is pH-insensitive, is ideal for inorganic sludges and liquids, as well as mixed chemical-radioactive wastes, but can also handle significant percentages of salts and even halogenated organics. High waste loadings are possible and densification occurs,so that volumes are only slightly increased and in some cases (eg, incinerator ash) are reduced. The ceramic product has strength and weathering properties far superior to cement products

Dynamics and Stability of Permanent-Magnet Synchronous Motor

OpenAIRE

He, Ren; Han, Qingzhen

2017-01-01

The aim of this article is to explore the dynamic characteristics and stability of the permanent-magnet synchronous motor (PMSM). PMSM equilibrium local stability condition and Hopf  bifurcation condition, pitchfork bifurcation condition, and fold bifurcation condition have been derived by using the Routh-Hurwitz criterion and the bifurcation theory, respectively. Bifurcation curves of the equilibrium with single and double parameters are obtained by continuation method. Numerical simulations...

Magnetogravitational stability of resistive plasma through porous medium with thermal conduction and FLR corrections

International Nuclear Information System (INIS)

Vaghela, D.S.; Chhajlani, R.K.

1989-01-01

The problem of stability of self gravitating magnetized plasma in porous medium is studied incorporating electrical resistivity, thermal conduction and FLR corrections. Normal mode analysis is applied to derive the dispersion relation. Wave propagation is discussed for parallel and perpendicular directions to the magnetic field. Applying Routh Hurwitz Criterion the stability of the medium is discussed and it is found that Jeans' criterion determines the stability of the medium. Magnetic field, porosity and resistivity of the medium have no effect on Jeans' Criterion in longitudinal direction. For perpendicular direction, in case of resistive medium Jeans' expression remains unaffected by magnetic field but for perfectly conducting medium magnetic field modifies the Jeans' expression to show the stabilizing effect. Thermal conductivity affects the sonic mode by making the process isothermal instead of adiabatic. Porosity of the medium is effective only in case of perpendicular direction to magnetic field for perfectly conducting plasma as it reduces the stabilizing effect of magnetic field. For longitudinal wave propagation, though Finite Larmor Radius (FLR) corrections have no effect on sonic mode but it changes the growth rate for Alfven mode. For transverse wave propagation FLR corrections and porosity affect the Jeans' expression in case of non-viscous medium but viscosity of the medium removes the effect of FLR and porosity on Jeans' condition. (author)

Size and temperature dependent stability and phase transformation in single-crystal zirconium nanowire

International Nuclear Information System (INIS)

Sutrakar, Vijay Kumar; Roy Mahapatra, D.

2011-01-01

A novel size dependent FCC (face-centered-cubic) → HCP (hexagonally-closed-pack) phase transformation and stability of an initial FCC zirconium nanowire are studied. FCC zirconium nanowires with cross-sectional dimensions 20 Å, in which surface stresses are not enough to drive the phase transformation, show meta-stability. In such a case, an external kinetic energy in the form of thermal heating is required to overcome the energy barrier and achieve FCC → HCP phase transformation. The FCC-HCP transition pathway is also studied using Nudged Elastic Band (NEB) method, to further confirm the size dependent stability/metastability of Zr nanowires. We also show size dependent critical temperature, which is required for complete phase transformation of a metastable-FCC nanowire.

FFTBM and primary pressure acceptance criterion

International Nuclear Information System (INIS)

Prosek, A.

2004-01-01

When thermalhydraulic computer codes are used for simulation in the area of nuclear engineering the question is how to conduct an objective comparison between the code calculation and measured data. To answer this the fast Fourier transform based method (FFTBM) was developed. When the FFTBM method was developed the acceptance criteria for primary pressure and total accuracy were set. In the recent study the FFTBM method was used for accuracy quantification of RD-14M large LOCA test B9401 calculations. The blind accuracy analysis indicated good total accuracy while the primary pressure criterion was not fulfilled. The objective of the study was therefore to investigate the reasons for not fulfilling the primary pressure acceptance criterion and the applicability of the criterion to experimental facilities simulating heavy water reactor. The results of the open quantitative analysis showed that sensitivity analysis for influence parameters provide sufficient information to judge in which calculation the accuracy of primary pressure is acceptable. (author)

Does the Lowest Bid Price Evaluation Criterion Make for a More Efficient Public Procurement Selection Criterion? (Case of the Czech Republic

Directory of Open Access Journals (Sweden)

Ochrana František

2015-06-01

Full Text Available Through the institute of public procurement a considerable volume of financial resources is allocated. It is therefore in the interest of contracting entities to seek ways of how to achieve an efficient allocation of resources. Some public contract-awarding entities, along with some public-administration authorities in the Czech Republic, believe that the use of a single evaluation criterion (the lowest bid price results in a more efficient tender for a public contract. It was found that contracting entities in the Czech Republic strongly prefer to use the lowest bid price criterion. Within the examined sample, 86.5 % of public procurements were evaluated this way. The analysis of the examined sample of public contracts proved that the choice of an evaluation criterion, even the preference of the lowest bid price criterion, does not have any obvious impact on the final cost of a public contract. The study concludes that it is inappropriate to prefer the criterion of the lowest bid price within the evaluation of public contracts that are characterised by their complexity (including public contracts for construction works and public service contracts. The findings of the Supreme Audit Office related to the inspection of public contracts indicate that when using the lowest bid price as an evaluation criterion, a public contract may indeed be tendered with the lowest bid price, but not necessarily the best offer in terms of supplied quality. It is therefore not appropriate to use the lowest bid price evaluation criterion to such an extent for the purpose of evaluating work and services. Any improvement to this situation requires a corresponding amendment to the Law on Public Contracts and mainly a radical change in the attitude of the Office for the Protection of Competition towards proposed changes, as indicated within the conclusions and recommendations proposed by this study.

A ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum sheet in thermal forming

Directory of Open Access Journals (Sweden)

Wang Chu

2015-01-01

Full Text Available Formability of pure molybdenum in thermal forming process has been greatly improved, but it is still hard to avoid the generation of rupture and other quality defects. In this paper, a ductile fracture criterion of pure molybdenum sheet in thermal forming was established by considering the plastic deformation capacity of material and stress states, which can be used to describe fracture behaviour and critical rupture prediction of pure molybdenum sheet during hot forming process. Based on the isothermal uniaxial tensile tests which performed at 993 to 1143 K with strain rate range from 0.0005 to 0.2 s−1, the material parameters are calculated by the combination method of experiment with FEsimulation. Based on the observation, new fracture criteria can be expressed as a function of Zener-Hollomon parameter. The critical fracture value that calculated by Oyane-Sato criterion increases with increasing temperature and decreasing strain rate. The ductile fracture criterion with Zener-Hollomon parameter of pure molybdenum in thermal forming is proposed.

Effect of Static Soaking Under Different Temperatures on the Lime Stabilized Gypseous Soil

Directory of Open Access Journals (Sweden)

Abdulrahman Al-Zubaydi

2013-04-01

Full Text Available This study concerns with the effect of long-term soaking on the unconfined compressive strength, loss in weight and gypsum dissolution of gypseous soil stabilized with (4% lime, take into account the following variables: initial water content, water temperature, soaking duration. The results reveals that, the unconfined compressive strength was dropped, and the reduction in values was different according to the initial water content and water temperature, so that the reduction of the unconfined compressive strength of samples soaked in water at low temperatures (50 and 250 C was greater than those soaked in water temperatures  at (490 and 600 C. The results obtained shows that the increase in soaking period decreases the percentage amount of gypsum and loss in weight for all water temperatures and soaking durations.

Bio-lubricants derived from waste cooking oil with improved oxidation stability and low-temperature properties.

Science.gov (United States)

Li, Weimin; Wang, Xiaobo

2015-01-01

Waste cooking oil (WCO) was chemically modified via epoxidation using H2O2 followed by transesterification with methanol and branched alcohols (isooctanol, isotridecanol and isooctadecanol) to produce bio-lubricants with improved oxidative stability and low temperature properties. Physicochemical properties of synthesized bio-lubricants such as pour point (PP), cloud point (CP), viscosity, viscosity index (VI), oxidative stability, and corrosion resistant property were determined according to standard methods. The synthesized bio-lubricants showed improved low temperature flow performances compared with WCO, which can be attributing to the introduction of branched chains in their molecular structures. What's more, the oxidation stability of the WCO showed more than 10 folds improvement due to the elimination of -C=C-bonds in the WCO molecule. Tribological performances of these bio-lubricants were also investigated using four-ball friction and wear tester. Experimental results showed that derivatives of WCO exhibited favorable physicochemical properties and tribological performances which making them good candidates in formulating eco-friendly lubricants.

Effect of aluminum doping on the high-temperature stability and piezoresistive response of indium tin oxide strain sensors

International Nuclear Information System (INIS)

Gregory, Otto J.; You, Tao; Crisman, Everett E.

2005-01-01

Ceramic strain sensors based on reactively sputtered indium tin oxide (ITO) thin films doped with aluminum are being considered to improve the high-temperature stability and response. Ceramic strain sensors were developed to monitor the structural integrity of components employed in aerospace propulsion systems operating at temperatures in excess of 1500 deg C. Earlier studies using electron spectroscopy for chemical analysis (ESCA) studies indicated that interfacial reactions between ITO and aluminum oxide increase the stability of ITO at elevated temperature. The resulting ESCA depth files showed the presence of two new indium-indium peaks at 448.85 and 456.40 eV, corresponding to the indium 3d5 and 3d3 binding energies. These binding energies are significantly higher than those associated with stoichiometric indium oxide. Based on these studies, a combinatorial chemistry approach was used to screen large numbers of possible concentrations to optimize the stability and performance of Al-doped ceramic strain sensors. Scanning electron microscopy was used to analyze the combinatorial libraries in which varying amounts of aluminum were incorporated into ITO films formed by cosputtering from multiple targets. Electrical stability and piezoresistive response of these films were compared to undoped ITO films over the same temperature range

Improvement of temperature-stability in a quantum well laser with asymmetric barrier layers

DEFF Research Database (Denmark)

Zhukov, Alexey E.; Kryzhanovskaya, Natalia V.; Zubov, Fedor I.

2012-01-01

We fabricated and tested a quantum well laser with asymmetric barrier layers. Such a laser has been proposed earlier to suppress bipolar carrier population in the optical confinement layer and thus to improve temperature-stability of the threshold current. As compared to the conventional reference...

Covariance-Based Measurement Selection Criterion for Gaussian-Based Algorithms

Directory of Open Access Journals (Sweden)

Fernando A. Auat Cheein

2013-01-01

Full Text Available Process modeling by means of Gaussian-based algorithms often suffers from redundant information which usually increases the estimation computational complexity without significantly improving the estimation performance. In this article, a non-arbitrary measurement selection criterion for Gaussian-based algorithms is proposed. The measurement selection criterion is based on the determination of the most significant measurement from both an estimation convergence perspective and the covariance matrix associated with the measurement. The selection criterion is independent from the nature of the measured variable. This criterion is used in conjunction with three Gaussian-based algorithms: the EIF (Extended Information Filter, the EKF (Extended Kalman Filter and the UKF (Unscented Kalman Filter. Nevertheless, the measurement selection criterion shown herein can also be applied to other Gaussian-based algorithms. Although this work is focused on environment modeling, the results shown herein can be applied to other Gaussian-based algorithm implementations. Mathematical descriptions and implementation results that validate the proposal are also included in this work.

Unifying the criteria of elastic stability of solids

International Nuclear Information System (INIS)

Wang Hao; Li Mo

2012-01-01

The elastic stability criterion formulated by Born is based on the convexity requirement of the equilibrium free energy F of a stress-free crystal under small strain fluctuation, that demands the elastic constant tensor C to be positive definite, |C| > 0. For a crystal subject to an external stress, Hill specifies that for the crystal to be stable, the difference between its internal energy change δE and the work done to the system δW must be positive, i.e. δE - δW > 0. Polanyi, Frenkel, and Orowan proposed a different stability criterion based on stress increment for a loaded system, τ(ε + Δε) - τ(ε) > 0 until the limit is reached at dτ/dε = 0. Although known empirically, the formal connection between the different criteria has not been established rigorously. Using finite deformation theory, we show quite simply that the different formulations of the stability criteria originate from the same necessary condition for the convexity of the free energy of the system subject to external loading, f = F - W. However, in practice caution must be taken in implementation of the different criteria; they may lead to quite different results, especially when stability bifurcation occurs. (paper)

Temporal stability of diagnostic criteria for antisocial personality disorder in male alcohol dependent patients

NARCIS (Netherlands)

Verheul, R.; van den Brink, W.; Koeter, M. W.

1998-01-01

We evaluated the temporal stability of diagnostic criteria for antisocial personality disorder in 432 male alcohol dependent patients. Indicators for temporal stability were criterion continuation (i.e., the proportion of current or recent diagnoses among those with a lifetime diagnosis) and

Elevated-temperature mechanical stability and transformation behavior of retained austenite in a quenching and partitioning steel

Energy Technology Data Exchange (ETDEWEB)

Min, Junying, E-mail: junying.min@gmail.com [Chair of Production Systems, Ruhr-University Bochum, Bochum 44780 (Germany); Hector, Louis G. [General Motors Research & Development, Warren, MI 48095-9055 (United States); Zhang, Ling; Lin, Jianping [School of Mechanical Engineering, Tongji University, Shanghai 201804 (China); Carsley, John E. [General Motors Research & Development, Warren, MI 48095-9055 (United States); Sun, Li [General Motors China Science Lab, Shanghai 201206 (China)

2016-09-15

The mechanical stability and transformation behavior of both film and blocky retained austenite (RA) in a quenching and partitioning steel are investigated at 293 K, 423 K and 573 K with X-ray diffraction measurements and transmission electron microscopy. Blocky RA both completely and incompletely transforms to twinned martensite during deformation at 293 K and 423 K, respectively, and completely transforms to lath martensite during deformation at 573 K. At 293 K and 423 K, only the film RA with widths larger than ~70 nm transforms to twinned martensite. However, film RA incompletely transforms to lath martensite at 573 K. Hence, RA transformation is non-monotonic with temperature. Significant carbide formation at 573 K, and therefore less carbon to stabilize RA, overcomes the increase in austenite stability due to the decrease in the temperature-dependent chemical driving force for the martensite transformation.

High speed machining of aluminium gear box without temperature stabilization

Directory of Open Access Journals (Sweden)

Abilio P. SILVA

2010-01-01

Full Text Available At the present time both clutch and mechanism housings, which are the main components from automotive gear boxes, are made of special aluminium alloys. These alloys are extremely light when compared with steel, making them a perfect choice to mitigate the cars weight and machining costs. Nonetheless they possess a high thermal expansion coefficient, which can be considered a major disadvantage since it makes necessary to pay extraordinary attention to dimensional variations during the production cycle due to temperature deviations. High speed machining of precision components made of aluminium requests thus their temperature to become previously stable. This procedure is the only way to force dimensions to stay inside its tolerance intervals. The main purpose of the present work was to assess the possibility to avoid the use of special ovens to make the clutch housing temperature become stable prior to machining. The dimensional stabilization of 40 sample parts, pre-heated at three temperature levels, was accomplished through the use of this system. The achieved results were made possible by analysing the part’s temperature at the machine’s entrance, the machine’s interior temperature, 35 measured dimensions and their tolerance intervals as well as the average temperature deviations of each of the five considered batches. By analysing the obtained results in detail it was possible to determine which dimensions show high sensitiveness to temperature (high correlation between dimension’s variation and temperature. Among these dimensions we can point out the ones related with depth, since they display the highest deviations due to temperature. Being a work with practical application it was possible to confirm the benefit of using this methodology by achieving significant enhancements on production efficiency, energy savings and reduction on maintenance costs, through the application of small adjustments to the machining sequence and by

Stability with temperature of mixed uranium plutonium monocarbides

International Nuclear Information System (INIS)

Riglet-Martial, Ch.; Dumas, J.C.; Piron, J.P.; Gueneau, Ch.

2008-01-01

Full text: Among the different advanced fuel materials of concern for Generation IV systems, the mixed carbide of uranium and plutonium fuel is considered as one of the key materials for Gas Fast Reactors (GFR) systems. For purposes of optimising its fabrication process as well as its performances in various operating conditions, the losses of gaseous plutonium specially at elevated temperatures have to be controlled and minimized. The paper is therefore concerned with a parametric analysis of the stability with temperature of mixed carbides of uranium and plutonium. Previous published experimental studies have shown that mixed (U ,Pu) carbides undergo a highly incongruent sublimation at high temperatures: the vapour phase in equilibrium with the solid is mainly composed of gaseous plutonium (P Pu /P total > 99 % ) while the contribution of gaseous U and C remains very low. The composition of the system U 1-z Pu z C 1+x ' (z =Pu/(U+Pu) and x C/(U+Pu)), the temperature (T) and the expansion volume (V) of the gas are the main parameters in the loss of gaseous Pu. The calculations are carried out using the SAGE (Solgasmix Advanced Gibbs Energy) software, by assuming ideal solid solutions between UC and PuC, as well as between U 2 C 3 and Pu 2 C 3 . The validity of the model is previously tested using published equilibrium vapour pressure data. This work gives rise to a large description of the variations of Pu losses from mixed uranium plutonium carbides and leads to some basic recommendations in connection with the use of this advanced fuel materials

Angular criterion for distinguishing between Fraunhofer and Fresnel diffraction

International Nuclear Information System (INIS)

Medina, Francisco F.; Garcia-Sucerquia, Jorge; Castaneda, Roman; Matteucci, Giorgio

2003-03-01

The distinction between Fresnel and Fraunhofer diffraction is a crucial condition for the accurate analysis of diffracting structures. In this paper we propose a criterion based on the angle subtended by the first zero of the diffraction pattern from the center of the diffracting aperture. The determination of the zero of the diffraction pattern is the crucial point for assuring the precision of the criterion. It mainly depends on the dynamical range of the detector. Therefore, the applicability of adequate thresholds for different detector types is discussed. The criterion is also generalized by expressing it in terms of the number of Fresnel zones delimited by the aperture. Simulations are reported for illustrating the feasibility of the criterion. (author)

Novel room-temperature-setting phosphate ceramics for stabilizing combustion products and low-level mixed wastes

International Nuclear Information System (INIS)

Wagh, A.S.; Singh, D.

1994-01-01

Argonne National Laboratory, with support from the Office of Technology in the US Department of Energy (DOE), has developed a new process employing novel, chemically bonded ceramic materials to stabilize secondary waste streams. Such waste streams result from the thermal processes used to stabilize low-level, mixed wastes. The process will help the electric power industry treat its combustion and low-level mixed wastes. The ceramic materials are strong, dense, leach-resistant, and inexpensive to fabricate. The room-temperature-setting process allows stabilization of volatile components containing lead, mercury, cadmium, chromium, and nickel. The process also provides effective stabilization of fossil fuel combustion products. It is most suitable for treating fly and bottom ashes

Analysis of the structural stability of the smectite submitted to high pressures and temperatures

International Nuclear Information System (INIS)

Alabarse, Frederico Gil

2009-10-01

The thermal stability of bentonite is of particular interest for containment barrier in nuclear waste disposal facilities. However, very little is known about the stability of smectite (principal component of bentonite) under high-pressure and high-temperature conditions (HPHT). The objective of this work was to investigate the stability of the smectite structure under HP-HT conditions. The HP-HT experiments were performed on toroidal chambers (TC) with pressure up 7.7 GPa and temperatures of 1000 deg C. The samples were characterized by X-ray diffraction after the HP-HT processing. Furthermore, one sample from the original material was analyzed using Fourier transformed infra-red (FTIR) in situ measurements on a diamond anvil cell (DAC) in experiments up to 12 GPa. The original sample of bentonite, calcium dioctahedral montmorillonite with small fraction of quartz, was characterized by FTIR, XRD, X-ray fluorescence (XRF), scanning electron microscopy (SEM), surface area, thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In the experiment performed using the DAC up to 12 GPa, the FTIR in situ measurements analysis showed that the smectite structure is stable with a reversible deformation in the Si-O bond and that the smectite did not loose water. Experiments performed in TC at 7.7 GPa of pressure and 250 deg C of temperature, during 3.5 h showed, after analysis by XRD and FTIR, that the smectite structure is stable and did not loose water. Experiments performed in TC at 7.7 GPa of pressure and 1000 deg C of temperature, during 3.5 h showed, after analysis by XRD and SEM, the transformation of bentonite to the mineral assemblage: Coesite, Quartz, Kyanite and Pyrope. (author)

Shear effect on the plasma stability in a tokamak

International Nuclear Information System (INIS)

Pogutse, O.P.; Yurchenko, Eh.I.

1979-01-01

An analytical criterion of stability of balloon modes is obtained, taking into consideration two new physical effects: destabilization caused by intersection of branches of U-shaped oscillations and the balloon effect related to shear. An asymptotic variational method of solving differential equations having both periodical and non-periodical coefficients has been developed to determine the criterion. This method is a generalization of the sensitive method of asymptotic expansion, but unlike the latter, it allows one to take account of potential effects of the reflection type and wave penetration through the barrier. It is this fact that allows to describe the intersection of branch oscillations. The criterion obtained shows that plasma may be unstable even with configuration with circular magnetic surfaces

Effect of Storage Time and Temperature on Dimensional Stability of Impressions Made with Zinc Oxide Impression Paste

Directory of Open Access Journals (Sweden)

Sareh Habibzadeh

2016-10-01

Full Text Available Objectives: This study aimed to assess the effect of storage time and temperature on dimensional stability of impressions made with Cavex Outline zinc oxide impression paste.Materials and Methods: A round stainless steel mold with five grooves (three horizontal and two vertical was used in this in-vitro experimental study. Cavex Outline impression paste was prepared according to the manufacturer’s instructions and applied to the mold. The mold was placed on a block and stored at 35°C and 100% humidity for setting. The impressions were poured with stone immediately and also after 30, 120, 240 and 420 minutes and 24 hours. The distance between the vertical lines on the casts was measured and compared with that in the immediately poured cast.Results: Storage in a refrigerator and at room temperature for zero to seven hours had no significant effect on dimensional stability of the impressions; however, 24 hours of storage in a refrigerator or at room temperature decreased the dimensional stability of Cavex Outline (P=0.001. Also, a significant association was found between dimensional changes following 24 hours of storage in a refrigerator (4°C and at room temperature (23°C; P<0.01.Conclusions: The optimal pouring time of Cavex Outline impressions with stone is between zero to seven hours, and 24 hours of storage significantly decreases the dimensional stability.Keywords: Dental Impression Materials; Zinc Oxide; Cavex

Criterion for burn-up conditions in gas-cooled cryogenic current leads

International Nuclear Information System (INIS)

Bejan, A.; Cluss, E.M. Jr.

1976-01-01

Superconducting magnets are energized through helium vapour-cooled cryogenic current leads operating at high ratios of current to mass flow. The high current operation where lead temperature, runaway, and eventual burn-up are likely to occur is investigated. A simple criterion for estimating the burn-up operation conditions (current, mass flow) for a given lead geometry (cross-sectional area, length, heat exchanger area) is presented. This article stresses the role played by the available heat exchanger area in avoiding burn-up at high ratios of current to mass flow. (author)

Using high thermal stability flexible thin film thermoelectric generator at moderate temperature

Science.gov (United States)

Zheng, Zhuang-Hao; Luo, Jing-Ting; Chen, Tian-Bao; Zhang, Xiang-Hua; Liang, Guang-Xing; Fan, Ping

2018-04-01

Flexible thin film thermoelectric devices are extensively used in the microscale industry for powering wearable electronics. In this study, comprehensive optimization was conducted in materials and connection design for fabricating a high thermal stability flexible thin film thermoelectric generator. First, the thin films in the generator, including the electrodes, were prepared by magnetron sputtering deposition. The "NiCu-Cu-NiCu" multilayer electrode structure was applied to ensure the thermal stability of the device used at moderate temperature in an air atmosphere. A design with metal layer bonding and series accordant connection was then employed. The maximum efficiency of a single PN thermocouple generator is >11%, and the output power loss of the generator is <10% after integration.

Temperature and coverage effects on the stability of epitaxial silicene on Ag(111) surfaces

Energy Technology Data Exchange (ETDEWEB)

Liu, Hongsheng; Han, Nannan; Zhao, Jijun, E-mail: zhao_jijun@hotmail.com

2017-07-01

Highlights: • Chemical potential phase diagrams of silicene/Ag(111) at varied temperatures. • The priorities of various silicene phases in experiments are explained. • A proper experimental condition to obtain homogeneous 4 × 4 silicene is recommended. - Abstract: Silicene, the single layer of silicon atoms arranged in a honeycomb lattice, has been synthesized in recent experiments and attracted significant attentions. Silicene is promising in future nanoelectronic devices due to its outstanding electronic properties. In experiments, however, different silicene superstructures coexist on Ag(111) substrate. For the device applications, homogenous silicene sheet with large scale and high quality is highly desired. Here, for the first time, we investigate both the temperature and the coverage effects on the thermal stability of epitaxial silicene on Ag(111) surface by ab initio molecular dynamics simulations. The relationship between the stability of various silicene superstructures and the growth conditions, including temperature and coverage of silicon atoms, is revealed by plotting the chemical potential phase diagram of silicene on Ag(111) surfaces at different temperatures. Our results are helpful for understanding the observed diversity of silicene phases on Ag(111) surfaces and provide some useful guidance for the synthesis of homogenous silicene phase in experiments.

Criterion for testing multiparticle negative-partial-transpose entanglement

International Nuclear Information System (INIS)

Zeng, B.; Zhou, D.L.; Zhang, P.; Xu, Z.; You, L.

2003-01-01

We revisit the criterion of multiparticle entanglement based on the overlaps of a given quantum state ρ with maximally entangled states. For a system of m particles, each with N distinct states, we prove that ρ is m-particle negative partial transpose entangled, if there exists a maximally entangled state vertical bar MES>, such that >1/N. While this sufficiency condition is weaker than the Peres-Horodecki criterion in all cases, it applies to multi-particle systems, and becomes especially useful when the number of particles (m) is large. We also consider the converse of this criterion and illustrate its invalidity with counter examples

Magnetohydodynamics stability of compact stellarators

International Nuclear Information System (INIS)

Fu, G.Y.; Ku, L.P.; Cooper, W.A.; Hirshman, S.H.

2000-01-01

Recent stability results of external kink modes and vertical modes in compact stellarators are presented. The vertical mode is found to be stabilized by externally generated poloidal flux. A simple stability criterion is derived in the limit of large aspect ratio and constant current density. For a wall at infinite distance from the plasma, the amount of external flux needed for stabilization is given by Fi = (k2 minus k)=(k2 + 1), where k is the axisymmetric elongation and Fi is the fraction of the external rotational transform. A systematic parameter study shows that the external kink mode in QAS can be stabilized at high beta (approximately 5%) without a conducting wall by magnetic shear via 3D shaping. It is found that external kinks are driven by both parallel current and pressure gradient. The pressure contributes significantly to the overall drive through the curvature term and the Pfirsch-Schluter current

Thermal Stability of Hexamethyldisiloxane (MM for High-Temperature Organic Rankine Cycle (ORC

Directory of Open Access Journals (Sweden)

Markus Preißinger

2016-03-01

Full Text Available The design of efficient Organic Rankine Cycle (ORC units for the usage of industrial waste heat at high temperatures requires direct contact evaporators without intermediate thermal oil circuits. Therefore, the thermal stability of high-temperature working fluids gains importance. In this study, the thermal degradation of hexamethyldisiloxane (MM is investigated in an electrically heated tube. Qualitative results concerning remarks on degradation products as well as quantitative results like the annual degradation rate are presented. It is shown that MM is stable up to a temperature of 300 °C with annual degradation rates of less than 3.5%. Furthermore, the break of a silicon–carbon bond can be a main chemical reaction that influences the thermal degradation. Finally, it is discussed how the results may impact the future design of ORC units.

A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

Energy Technology Data Exchange (ETDEWEB)

Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland [Institute of Materials Physics, Graz University of Technology, A-8010 Graz (Austria)

2016-07-15

Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

Temperature stability of static and dynamic properties of 1.55 µm quantum dot lasers.

Science.gov (United States)

Abdollahinia, A; Banyoudeh, S; Rippien, A; Schnabel, F; Eyal, O; Cestier, I; Kalifa, I; Mentovich, E; Eisenstein, G; Reithmaier, J P

2018-03-05

Static and dynamic properties of InP-based 1.55 µm quantum dot (QD) lasers were investigated. Due to the reduced size inhomogeneity and a high dot density of the newest generation of 1.55 µm QD gain materials, ridge waveguide lasers (RWG) exhibit improved temperature stability and record-high modulation characteristics. Detailed results are shown for the temperature dependence of static properties including threshold current, voltage-current characteristics, external differential efficiency and emission wavelength. Similarly, small and large signal modulations were found to have only minor dependences on temperature. Moreover, we show the impact of the active region design and the cavity length on the temperature stability. Measurements were performed in pulsed and continuous wave operation. High characteristic temperatures for the threshold current were obtained with T 0 values of 144 K (15 - 60 °C), 101 K (60 - 110 °C) and 70 K up to 180 °C for a 900-µm-long RWG laser comprising 8 QD layers. The slope efficiency in these lasers is nearly independent of temperature showing a T 1 value of more than 900 K up to 110 °C. Due to the high modal gain, lasers with a cavity length of 340 µm reached new record modulation bandwidths of 17.5 GHz at 20 °C and 9 GHz at 80 °C, respectively. These lasers were modulated at 26 GBit/s in the non-return to zero format at 80 °C and at 25 GBaud using a four-level pulse amplitude format at 21 °C.

Influence of scandium addition on the high-temperature grain size stabilization of oxide-dispersion-strengthened (ODS) ferritic alloy

Energy Technology Data Exchange (ETDEWEB)

Li, Lulu, E-mail: lli18@ncsu.edu; Xu, Weizong; Saber, Mostafa; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

2015-06-11

The influence of 1–4 at% Sc addition on the thermal stability of mechanically alloyed ODS ferritic alloy was studied in this work. Sc addition was found to significantly stabilize grain size and microhardness at high temperatures. Grain sizes of samples with 1 and 4 at% Sc was found maintained in the nanoscale range at temperatures up to 1000 °C with hardness maintained at 5.6 and 6.7 GPa, respectively. The detailed microstructure was also investigated from EDS elemental mapping, where nanofeatures [ScTiO] were observed, while nanosized [YTiO] particles were rarely seen. This is probably due to the concentration difference between Sc and Y, leading to the formation of [ScTiO] favoring that of [YTiO]. Precipitation was considered as the major source for the observed high temperature stabilization. In addition, 14YT–Sc alloys without large second phases such as Ti-oxide can exhibit better performance compared to conventional ODS materials.

Network structure and thermal stability study of high temperature seal glass

Science.gov (United States)

Lu, K.; Mahapatra, M. K.

2008-10-01

High temperature seal glass has stringent requirement on glass thermal stability, which is dictated by glass network structures. In this study, a SrO-La2O3-Al2O3-B2O3-SiO2 based glass system was studied using nuclear magnetic resonance, Raman spectroscopy, and x-ray diffraction for solid oxide cell application purpose. Glass structural unit neighboring environment and local ordering were evaluated. Glass network connectivity as well as silicon and boron glass former coordination were calculated for different B2O3:SiO2 ratios. Thermal stability of the borosilicate glasses was studied after thermal treatment at 850 °C. The study shows that high B2O3 content induces BO4 and SiO4 structural unit ordering, increases glass localized inhomogeneity, decreases glass network connectivity, and causes devitrification. Glass modifiers interact with either silicon- or boron-containing structural units and form different devitrified phases at different B2O3:SiO2 ratios. B2O3-free glass shows the best thermal stability among the studied compositions, remaining stable after thermal treatment for 200 h at 850 °C.

Ionic liquids and ionic liquid acids with high temperature stability for fuel cell and other high temperature applications, method of making and cell employing same

Science.gov (United States)

Angell, C Austen [Mesa, AZ; Xu, Wu [Broadview Heights, OH; Belieres, Jean-Philippe [Chandler, AZ; Yoshizawa, Masahiro [Tokyo, JP

2011-01-11

Disclosed are developments in high temperature fuel cells including ionic liquids with high temperature stability and the storage of inorganic acids as di-anion salts of low volatility. The formation of ionically conducting liquids of this type having conductivities of unprecedented magnitude for non-aqueous systems is described. The stability of the di-anion configuration is shown to play a role in the high performance of the non-corrosive proton-transfer ionic liquids as high temperature fuel cell electrolytes. Performance of simple H.sub.2(g) electrolyte/O.sub.2(g) fuel cells with the new electrolytes is described. Superior performance both at ambient temperature and temperatures up to and above 200.degree. C. are achieved. Both neutral proton transfer salts and the acid salts with HSO.sup.-.sub.4 anions, give good results, the bisulphate case being particularly good at low temperatures and very high temperatures. The performance of all electrolytes is improved by the addition of a small amount of involatile base of pK.sub.a value intermediate between those of the acid and base that make the bulk electrolyte. The preferred case is the imidazole-doped ethylammonium hydrogensulfate which yields behavior superior in all respects to that of the industry standard phosphoric acid electrolyte.

Fractional-Order Discrete-Time Laguerre Filters: A New Tool for Modeling and Stability Analysis of Fractional-Order LTI SISO Systems

Directory of Open Access Journals (Sweden)

Rafał Stanisławski

2016-01-01

Full Text Available This paper presents new results on modeling and analysis of dynamics of fractional-order discrete-time linear time-invariant single-input single-output (LTI SISO systems by means of new, two-layer, “fractional-order discrete-time Laguerre filters.” It is interesting that the fractionality of the filters at the upper system dynamics layer is directly projected from the lower Laguerre-based approximation layer for the Grünwald-Letnikov difference. A new stability criterion for discrete-time fractional-order Laguerre-based LTI SISO systems is introduced and supplemented with a stability preservation analysis. Both the stability criterion and the stability preservation analysis bring up rather surprising results, which is illustrated with simulation examples.

Flow stress, subgrain size, and subgrain stability at elevated temperature

International Nuclear Information System (INIS)

Sherby, O.D.; Klundt, R.H.; Miller, A.K.

1977-01-01

Well defined subgrain boundaries dominate the microstructural changes occurring during plastic flow of polycrystalline metals at elevated temperature. The quantitative influence of subgrain size on elevated-temperature plastic flow is considered. Based on the results of tests under constant-stress and constant-structure conditions, and equation is developed which predicts the creep rate as a function of subgrain size, stress, diffusion coefficient, and elastic modulus. In general, the subgrain size is a unique function of the current modulus-compensated flow stress, but if fine subgrains can be introduced and stabilized, large increases in creep strength may result. The applicability of the phenomenological relation developed to the behavior of dispersion-strengthened materials (where the second-phase particles may predetermine the effective subgrain size) is discussed. When subgrain effects are included, it is shown that the creep rate is less dependent on stacking fault energy than has been previously thought

Error sensitivity to refinement: a criterion for optimal grid adaptation

Science.gov (United States)

Luchini, Paolo; Giannetti, Flavio; Citro, Vincenzo

2017-12-01

Most indicators used for automatic grid refinement are suboptimal, in the sense that they do not really minimize the global solution error. This paper concerns with a new indicator, related to the sensitivity map of global stability problems, suitable for an optimal grid refinement that minimizes the global solution error. The new criterion is derived from the properties of the adjoint operator and provides a map of the sensitivity of the global error (or its estimate) to a local mesh refinement. Examples are presented for both a scalar partial differential equation and for the system of Navier-Stokes equations. In the last case, we also present a grid-adaptation algorithm based on the new estimator and on the FreeFem++ software that improves the accuracy of the solution of almost two order of magnitude by redistributing the nodes of the initial computational mesh.

Low-temperature setting phosphate ceramics for stabilization of DOE problem low level mixed-waste: I. Material and waste form development

International Nuclear Information System (INIS)

Singh, D.; Wagh, A.; Knox, L.; Mayberry, J.

1994-03-01

Chemically bonded phosphate ceramics are proposed as candidates for solidification and stabilization of some of the open-quotes problemclose quotes DOE low-level mixed wastes at low-temperatures. Development of these materials is crucial for stabilization of waste streams which have volatile species and any use of high-temperature technology leads to generation of off-gas secondary waste streams. Several phosphates of Mg, Al, and Zr have been investigated as candidate materials. Monoliths of these phosphates were synthesized using chemical routes at room or slightly elevated temperatures. Detailed physical and chemical characterizations have been conducted on some of these phosphates to establish their durability. Magnesium ammonium phosphate has shown to possess excellent mechanical and as well chemical properties. These phosphates were also used to stabilize a surrogate ash waste with a loading ranging from 25-35 wt.%. Characterization of the final waste forms show that waste immobilization is due to both chemical stabilization and physical encapsulation of the surrogate waste which is desirable for waste immobilization

The use of lightweight aggregate saturated with PCM as a temperature stabilizing material for road surfaces

International Nuclear Information System (INIS)

Ryms, Michał; Lewandowski, Witold M.; Klugmann-Radziemska, Ewa; Denda, Hubert; Wcisło, Patrycja

2015-01-01

This paper presents the possibility of adding lightweight building aggregates to increase the stability – mechanical as well as thermal – of constructions and road objects. This stability can be achieved through saturating the porous granules of aggregate with a phase-change material (PCM) that allows the accumulation of solar heat. Intense solar radiation, especially during the summer, can cause the asphalt on road surfaces, bridges and parking lots to melt, thus protecting the structure from further overheating. The absence of asphalt layers results in thermal stress and strain conditions causes accelerated wear of road surface. Lightweight aggregate, previously used to reduce the weight of the structures, while maintaining the bearing capacity similar to that offered by conventional concrete structures, thereby gains a new functionality, as a temperature stabilizing material. The paper contains a review of several phase-change materials as well as a study justifying the choice of ceresin, a product of crude oil distillation, as a suitable material for such applications. Information about the aggregate and its possible applications, and a proposed method of saturating the aggregate with ceresin has also been collected and presented. With the help of quantitative research conducted through the use of differential scanning calorimetry, the characteristic of thermodynamic parameters of pure ceresin and expanded clay aggregate (Pollytag) saturated with ceresin was determined. Simulation tests conducted under real conditions on two asphalt surfaces (0.32 × 0.22 × 0.15 m), one of which contained the PCM while the other did not, have shown that even a small addition of ceresin (3% mass relative to the weight of the ground) causes a reduction in surface temperature of about 5 K within the tested temperature range of 318.15–338.15 K. - Highlights: • Road surface overheating on summer days may reach up to 344 K. • Solution against overheating through

Homogenization Pressure and Temperature Affect Protein Partitioning and Oxidative Stability of Emulsions

DEFF Research Database (Denmark)

Horn, Anna Frisenfeldt; Barouh, Nathalie; Nielsen, Nina Skall

2013-01-01

The oxidative stability of 10 % fish oil-in-water emulsions was investigated for emulsions prepared under different homogenization conditions. Homogenization was conducted at two different pressures (5 or 22.5 MPa), and at two different temperatures (22 and 72 °C). Milk proteins were used...... prior to homogenization did not have any clear effect on lipid oxidation in either of the two types of emulsions....

SOCIO-PSYCHOLOGICAL CRITERIONS OF FAMILY LIFESTYLE TYPOLOGY

Directory of Open Access Journals (Sweden)

Yekaterina Anatolievna Yumkina

2015-02-01

Full Text Available The purpose of this article is to present socio-psychological criterions of family lifestyle typology, which were found during theoretical modelling and empirical research work. It is important in fundamental and practical aspects. St-Petersburg students (n = 116, from 19 to 21 years old were examined by special questionnaire «Family relationship and home» (Kunitsi-na V.N., Yumkina Ye.A., 2012 which measures different aspects of family lifestyle. We also used complex of methods that gave us information about personal values, self-rating and parent-child relationships. Dates were divided into six groups according to three main criterions of family lifestyle typology: social environment of family life, family activity, and family interpersonal relationships. There were found statistically significant differences between pairs of group from every criterions. The results can be useful in spheres dealing with family crisis, family development, family traditions etc.

Thermal and stability considerations for a supercritical water-cooled fast reactor during power-raising phase of plant startup

International Nuclear Information System (INIS)

Cai, Jiejin; Ishiwatari, Yuki; Oka, Yoshiaki; Ikejiri, Satoshi

2009-01-01

This paper describes thermal analyses and linear stability analyses of the Supercritical Water-cooled Fast Reactor with 'two-path' flow scheme during the power-raising phase of plant startup. For thermal consideration, the same criterion of the maximum cladding surface temperature (MCST) as applied to the normal operating condition is used. For thermal-hydraulic stability consideration, the decay ratio of 0.5 is applied, which is taken from BWRs. Firstly, we calculated the flow rate distribution among the parallel flow paths from the reactor vessel inlet nozzles to the mixing plenum below the core using a system analysis code. The parallel flow paths consist of the seed fuel assemblies cooled by downward flow, the blanket fuel assemblies cooled by downward flow and the downcomer. Then, the MCSTs are estimated for various reactor powers and feedwater flow rates with system analyses. The decay ratios are estimated with linear stability analyses. The available range of the reactor power and feedwater flow rate to satisfy the thermal and stability criteria is obtained. (author)

Stresses and Temperature Stability of Dense Wavelength Division Multiplexing Filters Prepared by Reactive Ion-Assisted E-Gun Evaporation

Science.gov (United States)

Wei, Chao-Tsang; Shieh, Han-Ping D.

2005-10-01

In this paper, we report the in situ measurement of the temperature stability of narrow-band-pass filters on different types of substrate, for dense wavelength division multiplexing (DWDM) filters in optical-fiber transmission systems. The DWDM filters were designed as all-dielectric Fabry-Perot filters and fabricated by reactive ion-assisted deposition. Ta2O5 and SiO2 were used as high- and low-refractive-index layers, respectively, for constructing the DWDM filters. The accuracy and stability of the coating process were evaluated for fabricating the DWDM filters for the temperature stability of the center wavelength. The center wavelength shift was determined to be greatly dependent on the coefficient of thermal expansion of the substrate on which the filter is deposited.

Stabilization of a magnetic island by localized heating in a tokamak with stiff temperature profile

Science.gov (United States)

Maget, Patrick; Widmer, Fabien; Février, Olivier; Garbet, Xavier; Lütjens, Hinrich

2018-02-01

In tokamaks plasmas, turbulent transport is triggered above a threshold in the temperature gradient and leads to stiff profiles. This particularity, neglected so far in the problem of magnetic island stabilization by a localized heat source, is investigated analytically in this paper. We show that the efficiency of the stabilization is deeply modified compared to the previous estimates due to the strong dependence of the turbulence level on the additional heat source amplitude inside the island.

Industry Software Trustworthiness Criterion Research Based on Business Trustworthiness

Science.gov (United States)

Zhang, Jin; Liu, Jun-fei; Jiao, Hai-xing; Shen, Yi; Liu, Shu-yuan

To industry software Trustworthiness problem, an idea aiming to business to construct industry software trustworthiness criterion is proposed. Based on the triangle model of "trustworthy grade definition-trustworthy evidence model-trustworthy evaluating", the idea of business trustworthiness is incarnated from different aspects of trustworthy triangle model for special industry software, power producing management system (PPMS). Business trustworthiness is the center in the constructed industry trustworthy software criterion. Fusing the international standard and industry rules, the constructed trustworthy criterion strengthens the maneuverability and reliability. Quantitive evaluating method makes the evaluating results be intuitionistic and comparable.

Two novel synchronization criterions for a unified chaotic system

International Nuclear Information System (INIS)

Tao Chaohai; Xiong Hongxia; Hu Feng

2006-01-01

Two novel synchronization criterions are proposed in this paper. It includes drive-response synchronization and adaptive synchronization schemes. Moreover, these synchronization criterions can be applied to a large class of chaotic systems and are very useful for secure communication

1.5 μm InAs/InGaAsP/InP quantum dot laser with improved temperature stability

DEFF Research Database (Denmark)

Zubov, F. I.; Gladii, S. P.; Shernyakov, Yu M.

2016-01-01

Temperature characteristics of InAs/InGaAsP quantum dot (QD) lasers synthesized on InP (001) substrate are presented. The lasers demonstrate high temperature stability: a threshold current characteristic temperature as high as 205 K in the temperature range between 20 to 50°C was measured. Lasing...

Stabilized sulfur as cathodes for room temperature sodium-ion batteries.

Energy Technology Data Exchange (ETDEWEB)

Xu, Yunhua [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical and Biomolecular Engineering; Liu, Yang [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies; Zhu, Yujie [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical and Biomolecular Engineering; Zheng, Shiyou [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical and Biomolecular Engineering; Liu, Yihang [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical and Biomolecular Engineering; Luo, Chao [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical and Biomolecular Engineering; Gaskell, Karen [Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry and Biochemistry; Eichhorn, Bryan [Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry and Biochemistry; Wang, Chunsheng [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical and Biomolecular Engineering

2013-05-01

Sodium-sulfur batteries, offering high capacity and low cost, are promising alternative to lithium-ion batteries for large-scale energy storage applications. The conventional sodium-sulfur batteries, operating at a high temperature of 300–350°C in a molten state, could lead to severe safety problems. However, the room temperature sodium-sulfur batteries using common organic liuid electrolytes still face a significant challenge due to the dissolution of intermediate sodium polysulfides. For this study, we developed room temperatue sodium-sulfur batteries using a unique porous carbon/sulfur (C/S) composite cathode, which was synthesized by infusing sulfur vapor into porous carbon sphere particles at a high temperatrure of 600°C. The porous C/S composites delivered a reversible capacity of ~860 mAh/g and retained 83% after 300 cycles. The Coulombic efficiency of as high as 97% was observed over 300 cycles. The superior electrochemical performance is attrbuted to the super sulfur stability as evidenced by its lower sensitivity to probe beam irradiation in TEM, XPS and Raman charaterization and high evaperation temperature in TGA. The results make it promising for large-scale grid energy storage and electric vehicles.

Global exponential stability of uncertain fuzzy BAM neural networks with time-varying delays

International Nuclear Information System (INIS)

Syed Ali, M.; Balasubramaniam, P.

2009-01-01

In this paper, the Takagi-Sugeno (TS) fuzzy model representation is extended to the stability analysis for uncertain Bidirectional Associative Memory (BAM) neural networks with time-varying delays using linear matrix inequality (LMI) theory. A novel LMI-based stability criterion is obtained by LMI optimization algorithms to guarantee the exponential stability of uncertain BAM neural networks with time-varying delays which are represented by TS fuzzy models. Finally, the proposed stability conditions are demonstrated with numerical examples.

A scale invariance criterion for LES parametrizations

Directory of Open Access Journals (Sweden)

Urs Schaefer-Rolffs

2015-01-01

Full Text Available Turbulent kinetic energy cascades in fluid dynamical systems are usually characterized by scale invariance. However, representations of subgrid scales in large eddy simulations do not necessarily fulfill this constraint. So far, scale invariance has been considered in the context of isotropic, incompressible, and three-dimensional turbulence. In the present paper, the theory is extended to compressible flows that obey the hydrostatic approximation, as well as to corresponding subgrid-scale parametrizations. A criterion is presented to check if the symmetries of the governing equations are correctly translated into the equations used in numerical models. By applying scaling transformations to the model equations, relations between the scaling factors are obtained by demanding that the mathematical structure of the equations does not change.The criterion is validated by recovering the breakdown of scale invariance in the classical Smagorinsky model and confirming scale invariance for the Dynamic Smagorinsky Model. The criterion also shows that the compressible continuity equation is intrinsically scale-invariant. The criterion also proves that a scale-invariant turbulent kinetic energy equation or a scale-invariant equation of motion for a passive tracer is obtained only with a dynamic mixing length. For large-scale atmospheric flows governed by the hydrostatic balance the energy cascade is due to horizontal advection and the vertical length scale exhibits a scaling behaviour that is different from that derived for horizontal length scales.

Exponential stability in a scalar functional differential equation

Directory of Open Access Journals (Sweden)

Pituk Mihály

2006-01-01

Full Text Available We establish a criterion for the global exponential stability of the zero solution of the scalar retarded functional differential equation whose linear part generates a monotone semiflow on the phase space with respect to the exponential ordering, and the nonlinearity has at most linear growth.

Stability of operation versus temperature of a three-phase clock-driven chaotic circuit

International Nuclear Information System (INIS)

Zhou Ji-Chao; Son Hyunsik; Song Han Jung; Kim Namtae

2013-01-01

We evaluate the influence of temperature on the behavior of a three-phase clock-driven metal—oxide—semiconductor (MOS) chaotic circuit. The chaotic circuit consists of two nonlinear functions, a level shifter, and three sample and hold blocks. It is necessary to analyze a CMOS-based chaotic circuit with respect to variation in temperature for stability because the circuit is sensitive to the behavior of the circuit design parameters. The temperature dependence of the proposed chaotic circuit is investigated via the simulation program with integrated circuit emphasis (SPICE) using 0.6-μm CMOS process technology with a 5-V power supply and a 20-kHz clock frequency. The simulation results demonstrate the effects of temperature on the chaotic dynamics of the proposed chaotic circuit. The time series, frequency spectra, bifurcation phenomena, and Lyapunov exponent results are provided. (general)

Optimization of ultrasound-assisted extraction of pectinase enzyme from guava (Psidium guajava) peel: Enzyme recovery, specific activity, temperature, and storage stability.

Science.gov (United States)

Amid, Mehrnoush; Murshid, Fara Syazana; Manap, Mohd Yazid; Islam Sarker, Zaidul

2016-01-01

This study aimed to investigate the effects of the ultrasound-assisted extraction conditions on the yield, specific activity, temperature, and storage stability of the pectinase enzyme from guava peel. The ultrasound variables studied were sonication time (10-30 min), ultrasound temperature (30-50 °C), pH (2.0-8.0), and solvent-to-sample ratio (2:1 mL/g to 6:1 mL/g). The main goal was to optimize the ultrasound-assisted extraction conditions to maximize the recovery of pectinase from guava peel with the most desirable enzyme-specific activity and stability. Under the optimum conditions, a high yield (96.2%), good specific activity (18.2 U/mg), temperature stability (88.3%), and storage stability (90.3%) of the extracted enzyme were achieved. The optimal conditions were 20 min sonication time, 40 °C temperature, at pH 5.0, using a 4:1 mL/g solvent-to-sample ratio. The study demonstrated that optimization of ultrasound-assisted process conditions for the enzyme extraction could improve the enzymatic characteristics and yield of the enzyme.

Studies on Foam Decay Trend and Influence of Temperature Jump on Foam Stability in Sclerotherapy.

Science.gov (United States)

Bai, Taoping; Chen, Yu; Jiang, Wentao; Yan, Fei; Fan, Yubo

2018-02-01

This study investigated the influence of temperature jump and liquid-gas ratio on foam stability to derive the foam-decay law. The experimental group conditions were as follows: mutation temperatures (10°C, 16°C, 20°C, 23°C, 25°C, and 27°C to >37°C) and liquid-gas ratios (1:1, 1:2, 1:3, and 1:4). The control group conditions were as follows: temperatures (10°C, 16°C, 20°C, 23°C, 25°C and 27°C) and liquid-gas ratios (1:1, 1:2, 1:3, and 1:4). A homemade device manufactured using the Tessari DSS method was used to prepare the foam. The decay process was videotape recorded. In the drainage rate curve, the temperature rose, and the liquid-gas ratio varied from 1:1 to 1:4, causing faster decay. In the entire process, the foam volume decreased with increasing drainage rate. The relationships were almost linear. Comparison of the experimental and control groups shows that the temperature jump results in a drainage time range of 1 to 15 seconds. The half-life ranges from 10 to 30 seconds. The maximum rate is 18.85%. Changes in the preparation temperature yields a drainage time range of 3 to 30 seconds. The half-life varies from 20 to 60 seconds. Decreasing the temperature jump range and liquid-gas ratio gradually enhances the foam stability. The foam decay time and drainage rate exhibit an exponential function distribution.

A temperature-dependent gain control system for improving the stability of Si-PM-based PET systems

International Nuclear Information System (INIS)

Yamamoto, Seiichi; Satomi, Junkichi; Watabe, Tadashi; Imaizumi, Masao; Shimosegawa, Eku; Hatazawa, Jun; Watabe, Hiroshi; Kanai, Yasukazu

2011-01-01

The silicon-photomultiplier (Si-PM) is a promising photodetector for the development of new PET systems due to its small size, high gain and relatively low sensitivity to the static magnetic field. One drawback of the Si-PM is that it has significant temperature-dependent gain that poses a problem for the stability of the Si-PM-based PET system. To reduce this problem, we developed and tested a temperature-dependent gain control system for the Si-PM-based PET system. The system consists of a thermometer, analog-to-digital converter, personal computer, digital-to-analog converter and variable gain amplifiers in the weight summing board of the PET system. Temperature characteristics of the Si-PM array are measured and the calculated correction factor is sent to the variable gain amplifier. Without this correction, the temperature-dependent peak channel shifts of the block detector were -55% from 20 deg. C to 35 deg.C. With the correction, the peak channel variations were corrected within ±8%. The coincidence count rate of the Si-PM-based PET system was measured using a Na-22 point source while monitoring the room temperature. Without the correction, the count rate inversely changed with the room temperature by 10% for 1.5 deg. C temperature changes. With the correction, the count rate variation was reduced to within 3.7%. These results indicate that the developed temperature-dependent gain control system can contribute to improving the stability of Si-PM-based PET systems.

Influence of Temperature and Mechanical Scratch on the Recorded Magnetization Stability of Longitudinal and Perpendicular Recording Media

International Nuclear Information System (INIS)

Nagano, Katsumasa; Tobari, Kousuke; Futamoto, Masaaki

2011-01-01

Stability of recorded magnetization of hard disk drive (HDD) is influenced by external environments, such as temperature and magnetic field. Small scratches are frequently formed on HDD medium surface upon contacts with the magnetic head. The influences of temperature and mechanical scratch on the magnetization structure stability are investigated for longitudinal and perpendicular recording media by using a magnetic force microscope. PMR media remained almost unchanged up to about 300 deg. C for the area with no scratches, whereas the areas near and under mechanical scratches started to change around 250 deg. C. The magnetization structure of LMR media started to change at about 100 degrees lower temperature under mechanical scratches when compared with no scratch areas. A quantitative analysis of magnetization structure variation is carried out by measuring the recorded magnetization strength difference estimated from the MFM images observed for a same sample area before and after exposing the sample to different temperatures.

Failure criterion for graphene in biaxial loading—a molecular dynamics study

International Nuclear Information System (INIS)

Yazdani, Hessam; Hatami, Kianoosh

2015-01-01

Molecular dynamics simulations are carried out in order to develop a failure criterion for infinite/bulk graphene in biaxial tension. Stresses along the principal edge configurations of graphene (i.e. armchair and zigzag directions) are normalized to the corresponding uniaxial ultimate strength values. The combinations of normalized stresses resulting in the failure of graphene are used to define failure envelopes (limiting stress ratio surfaces). Results indicate that a bilinear failure envelope can be used to represent the tensile strength of graphene in biaxial loading at different temperatures with reasonable accuracy. A circular failure envelope is also introduced for practical applications. Both failure envelopes define temperature-independent upper limits for the feasible combinations of normalized stresses for a graphene sheet in biaxial loading. Predicted failure modes of graphene under biaxial loading are also shown and discussed. (paper)

Stability of poly(N-isopropylacrylamide-co-acrylic acid polymer microgels under various conditions of temperature, pH and salt concentration

Directory of Open Access Journals (Sweden)

Zahoor H. Farooqi

2017-03-01

Full Text Available This research article describes the colloidal stability of poly(N-isopropylacrylamide-co-acrylic acid [P(NIPAM-co-AAc] polymer microgels with different acrylic acid contents in aqueous medium under various conditions of temperature, pH and sodium chloride concentrations. Three samples of multi-responsive P(NIPAM-co-AAc polymer microgels were synthesized using different amounts of acrylic acid by free radical emulsion polymerization. Dynamic laser light scattering was used to investigate the responsive behavior and stability of the prepared microgels under various conditions of pH, temperature and ionic strength. The microgels were found to be stable at all pH values above the pKa value of acrylic acid moiety in the temperature range from 15 to 60 °C in the presence and absence of sodium chloride. Increase in temperature, salt concentration and decrease in pH causes aggregation and decreases the stability of microgels due to the decrease in hydrophilicity.

Decision criterion dynamics in animals performing an auditory detection task.

Directory of Open Access Journals (Sweden)

Robert W Mill

Full Text Available Classical signal detection theory attributes bias in perceptual decisions to a threshold criterion, against which sensory excitation is compared. The optimal criterion setting depends on the signal level, which may vary over time, and about which the subject is naïve. Consequently, the subject must optimise its threshold by responding appropriately to feedback. Here a series of experiments was conducted, and a computational model applied, to determine how the decision bias of the ferret in an auditory signal detection task tracks changes in the stimulus level. The time scales of criterion dynamics were investigated by means of a yes-no signal-in-noise detection task, in which trials were grouped into blocks that alternately contained easy- and hard-to-detect signals. The responses of the ferrets implied both long- and short-term criterion dynamics. The animals exhibited a bias in favour of responding "yes" during blocks of harder trials, and vice versa. Moreover, the outcome of each single trial had a strong influence on the decision at the next trial. We demonstrate that the single-trial and block-level changes in bias are a manifestation of the same criterion update policy by fitting a model, in which the criterion is shifted by fixed amounts according to the outcome of the previous trial and decays strongly towards a resting value. The apparent block-level stabilisation of bias arises as the probabilities of outcomes and shifts on single trials mutually interact to establish equilibrium. To gain an intuition into how stable criterion distributions arise from specific parameter sets we develop a Markov model which accounts for the dynamic effects of criterion shifts. Our approach provides a framework for investigating the dynamics of decisions at different timescales in other species (e.g., humans and in other psychological domains (e.g., vision, memory.

Measurements of Coastal Winds and Temperature. Sensor Evaluation, Data Quality, and Wind Structures

Energy Technology Data Exchange (ETDEWEB)

Heggem, Tore

1997-12-31

The long Norwegian coastline has excellent sites for wind power production. This thesis contains a documentation of a measurement station for maritime meteorological data at the coast of Mid-Norway, and analysis of temperature and wind data. It discusses experience with different types of wind speed and wind direction sensors. Accurate air temperature measurements are essential to obtain information about the stability of the atmosphere, and a sensor based on separately calibrated thermistors is described. The quality of the calibrations and the measurements is discussed. A database built up from measurements from 1982 to 1995 has been available. The data acquisition systems and the programs used to read the data are described, as well as data control and gap-filling methods. Then basic statistics from the data like mean values and distributions are given. Quality control of the measurements with emphasis on shade effects from the masts and direction alignment is discussed. The concept of atmospheric stability is discussed. The temperature profile tends to change from unstable to slightly stable as maritime winds passes land. Temperature spectra based on two-year time series are presented. Finally, there is a discussion of long-term turbulence spectra calculated from 14 years of measurements. The lack of a gap in the one-hour region of the spectra is explained from the overweight of unstable atmospheric conditions in the dominating maritime wind. Examples of time series with regular 40-minute cycles, and corresponding effect spectra are given. The validity of local lapse rate as a criterion of atmospheric stability is discussed. 34 refs., 86 figs., 11 tabs.

Measurements of Coastal Winds and Temperature. Sensor Evaluation, Data Quality, and Wind Structures

Energy Technology Data Exchange (ETDEWEB)

Heggem, Tore

1998-12-31

The long Norwegian coastline has excellent sites for wind power production. This thesis contains a documentation of a measurement station for maritime meteorological data at the coast of Mid-Norway, and analysis of temperature and wind data. It discusses experience with different types of wind speed and wind direction sensors. Accurate air temperature measurements are essential to obtain information about the stability of the atmosphere, and a sensor based on separately calibrated thermistors is described. The quality of the calibrations and the measurements is discussed. A database built up from measurements from 1982 to 1995 has been available. The data acquisition systems and the programs used to read the data are described, as well as data control and gap-filling methods. Then basic statistics from the data like mean values and distributions are given. Quality control of the measurements with emphasis on shade effects from the masts and direction alignment is discussed. The concept of atmospheric stability is discussed. The temperature profile tends to change from unstable to slightly stable as maritime winds passes land. Temperature spectra based on two-year time series are presented. Finally, there is a discussion of long-term turbulence spectra calculated from 14 years of measurements. The lack of a gap in the one-hour region of the spectra is explained from the overweight of unstable atmospheric conditions in the dominating maritime wind. Examples of time series with regular 40-minute cycles, and corresponding effect spectra are given. The validity of local lapse rate as a criterion of atmospheric stability is discussed. 34 refs., 86 figs., 11 tabs.

Blind equalization with criterion with memory nonlinearity

Science.gov (United States)

Chen, Yuanjie; Nikias, Chrysostomos L.; Proakis, John G.

1992-06-01

Blind equalization methods usually combat the linear distortion caused by a nonideal channel via a transversal filter, without resorting to the a priori known training sequences. We introduce a new criterion with memory nonlinearity (CRIMNO) for the blind equalization problem. The basic idea of this criterion is to augment the Godard [or constant modulus algorithm (CMA)] cost function with additional terms that penalize the autocorrelations of the equalizer outputs. Several variations of the CRIMNO algorithms are derived, with the variations dependent on (1) whether the empirical averages or the single point estimates are used to approximate the expectations, (2) whether the recent or the delayed equalizer coefficients are used, and (3) whether the weights applied to the autocorrelation terms are fixed or are allowed to adapt. Simulation experiments show that the CRIMNO algorithm, and especially its adaptive weight version, exhibits faster convergence speed than the Godard (or CMA) algorithm. Extensions of the CRIMNO criterion to accommodate the case of correlated inputs to the channel are also presented.

Importance biasing quality criterion based on contribution response theory

International Nuclear Information System (INIS)

Borisov, N.M.; Panin, M.P.

2001-01-01

The report proposes a visual criterion of importance biasing both of forward and adjoint simulation. The similarity of contribution Monte Carlo and importance biasing random collision event distribution is proved. The conservation of total number of random trajectory crossings of surfaces, which separate the source and the detector is proposed as importance biasing quality criterion. The use of this criterion is demonstrated on the example of forward vs. adjoint importance biasing in gamma ray deep penetration problem. The larger amount of published data on forward field characteristics than on adjoint leads to the more accurate approximation of adjoint importance function in comparison to forward, for it adjoint importance simulation is more effective than forward. The proposed criterion indicates it visually, showing the most uniform distribution of random trajectory crossing events for the most effective importance biasing parameters and pointing to the direction of tuning importance biasing parameters. (orig.)

Improved result on stability analysis of discrete stochastic neural networks with time delay

International Nuclear Information System (INIS)

Wu Zhengguang; Su Hongye; Chu Jian; Zhou Wuneng

2009-01-01

This Letter investigates the problem of exponential stability for discrete stochastic time-delay neural networks. By defining a novel Lyapunov functional, an improved delay-dependent exponential stability criterion is established in terms of linear matrix inequality (LMI) approach. Meanwhile, the computational complexity of the newly established stability condition is reduced because less variables are involved. Numerical example is given to illustrate the effectiveness and the benefits of the proposed method.

Evaluation of pharmacokinetics and the stability of daptomycin in serum at various temperatures.

Science.gov (United States)

Ogami, Chika; Tsuji, Yasuhiro; Kasai, Hidefumi; Hiraki, Yoichi; Yamamoto, Yoshihiro; Matsunaga, Kazuhisa; Karube, Yoshiharu; To, Hideto

2017-04-01

Daptomycin exhibits concentration-dependent antibacterial activity. By monitoring daptomycin serum concentrations, clinicians may be able to predict the effectiveness of treatments for infections more accurately. However, it has been reported that daptomycin concentrations in plasma samples stored at -20°C decrease approximately 25% after 4 weeks. The aim of this study was to evaluate the stability of daptomycin in serum at various temperatures. Daptomycin serum samples were prepared and stored at different temperatures. The stability of daptomycin under various conditions was evaluated by sequential measurements of concentration. Although the loss of concentration of daptomycin in serum samples stored in freezers (-80°C and -20°C) was less than 10% after 168days (6 months), the concentrations in samples stored in a refrigerator (4°C) decreased by more than 70% over the same period. Furthermore, daptomycin concentrations in serum samples stored at close to body temperature (35°C, 37°C, and 39°C) decreased by more than 50% after only 24h. The results of the present study demonstrate that the measurement of serum concentrations of daptomycin needs to be performed rapidly. Furthermore, the degradation of daptomycin in serum may be involved in its elimination from the living body. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Phycocyanin stability in microcapsules processed by spray drying method using different inlet temperature

Science.gov (United States)

Purnamayati, L.; Dewi, EN; Kurniasih, R. A.

2018-02-01

Phycocyanin is natural blue colorant which easily damages by heat. The inlet temperature of spray dryer is an important parameter representing the feature of the microcapsules.The aim of this study was to investigate the phycocyanin stability of microcapsules made from Spirulina sp with maltodextrin and κ-Carrageenan as the coating material, processed by spray drying method in different inlet temperature. Microcapsules were processed in three various inlet temperaturei.e. 90°C, 110°C, and 130°C, respectively. The results indicated that phycocyanin microcapsule with 90°C of inlet temperature produced the highest moisture content, phycocyanin concentration and encapsulation efficiency of 3,5%, 1,729% and 29,623%, respectively. On the other hand, the highest encapsulation yield was produced by 130°C of theinlet temperature of 29,48% and not significantly different with 110°C. The results of Scanning Electron Microscopy (SEM) showed that phycocyanin microcapsules with 110°C of inlet temperature produced the most rounded shape. To sum up, 110°C was the best inlet temperature to phycocyanin microencapsulation by the spray dryer.

Morphological stability of Sm123 superconductor during peritectic solidification from Sm211 + L mixture

International Nuclear Information System (INIS)

Sumida, Masaki; Shiohara, Yuh; Umeda, Takateru

2000-01-01

The interface stability of the Sm 123 superconductor was analyzed in accordance with the constitutional undercooling criterion. As the single-crystal growth of the 123 phase is largely dependent on the growth-interface stability, a quantitative analysis was very much required. From this analysis, it was clarified that the constitutional undercooling must exist in the liquid when the 123 growth interface comes close to a 211 particle during the peritectic solidification. It was also predicted that the larger 211 particle radius, smaller volume fraction of the 211 particles, larger growth rate, or smaller imposed temperature gradient would cause easy occurrence of the constitutional undercooling ahead of the 123 growth interface. Taking into account the nucleation at the L/211 interface just ahead of the 123 growth front due to the constitutional undercooling, the transition of 123 growth from a planar-interface morphology to an equiaxed blocky morphology was investigated quantitatively and qualitatively

Elimination of casting heterogeneities by high temperature heat treatment on a titanium stabilized austenitic alloy. Effect on the microstructure

International Nuclear Information System (INIS)

Decours, Jacques; Cadalbert, Robert; Sidhom, Habib.

1982-06-01

Microstructural observation on a longitudinal section of stainless steels often reveals the presence of a ''veined'' structure showing a segregation remainder due to the setting of the ingot. This casting heterogeneity can be eliminated by high temperature treatments. This study shows the change in the structure and the state of solubilization produced by these high temperature treatments and the effect of a stabilizing element such as titanium on Z6CNDT17.13 and Z10CNDT15.15B alloys compared with the Z6CND17.13 alloy. It is also shown that a high temperature treatment applied to these stabilized alloys deeply modifies the recrystallization kinetics [fr

Criterion of damage beginning: experimental identification for laminate composite

International Nuclear Information System (INIS)

Thiebaud, F.; Perreux, D.; Varchon, D.; Lebras, J.

1996-01-01

The aim of this study is to propose a criterion of damage beginning for laminate composite. The materials is a glass-epoxy laminate [+55 deg.,-55 deg.[ n performed by winding filament process. First of all a description of the damage is performed and allows to define a damage variable. Thanks to the potential of free energy, an associated variable is defined. The damage criterion is written by using this last one. The parameter of the criterion is identified using mechanical and acoustical methods. The result is compared and exhibit a good agreement. (authors). 13 refs., 5 figs

The free growth criterion for grain initiation in TiB 2 inoculated γ-titanium aluminide based alloys

Science.gov (United States)

Gosslar, D.; Günther, R.

2014-02-01

γ-titanium aluminide (γ-TiAl) based alloys enable for the design of light-weight and high-temperature resistant engine components. This work centers on a numerical study of the condition for grain initiation during solidification of TiB2 inoculated γ-TiAl based alloys. Grain initiation is treated according to the so-called free growth criterion. This means that the free growth barrier for grain initiation is determined by the maximum interfacial mean curvature between a nucleus and the melt. The strategy presented in this paper relies on iteratively increasing the volume of a nucleus, which partially wets a hexagonal TiB2 crystal, minimizing the interfacial energy and calculating the corresponding interfacial curvature. The hereby obtained maximum curvature yields a scaling relation between the size of TiB2 crystals and the free growth barrier. Comparison to a prototypical TiB2 crystal in an as cast γ-TiAl based alloy allowed then to predict the free growth barrier prevailing under experimental conditions. The validity of the free growth criterion is discussed by an interfacial energy criterion.

Effect of pasteurization temperature on stability of an acidified sugarcane juice beverage

Directory of Open Access Journals (Sweden)

Mariana Kunitake

2014-12-01

Full Text Available The shelf life of fresh sugarcane juice is quite limited due to the high rates of microbiological and enzymatic reactions which take place after extraction. In order to evaluate the impact of pasteurization temperature on quality and stability of sugarcane juice with passion fruit pulp, nine batches of sugarcane juice with 4g/100g passion fruit pulp were processed at 85, 90 and 95 °C for 30 s, in triplicate. The pasteurized beverage was aseptically packaged in polyethylene terephthalate (PET bottles and stored at 7 °C in the dark. The beverage was characterized by physicochemical tests. Activities of polyphenol oxidase (PPO and peroxidase (POD were determined before and after processing. Coliforms and Salmonella tests were carried out to assure the beverage´s microbiological safety. Color parameters were measured in the processed juice throughout the storage period. Fifty panelists evaluated the beverage's appearance, aroma, flavor, and overall impression using seven-point hedonic scale tests. Sensory stability was estimated by considering score averages above four and percentages of acceptance above 60%. The pH, soluble solids and titratable acidity of end product ranged from 3.96 to 4.19, 19.7 to 20.1 ºBrix, and 0.163 to 0.175 g/100g citric acid, respectively. The three processing binomials were effective for PPO inactivation; however, complete POD inactivation was reached at 95 °C/30 s only. The estimated sensory shelf-lives for sugarcane juice with passion fruit pulp processed at 85, 90 and 95 °C/30 s were 30, 40 and 50 days, respectively. Thus, the increase of pasteurization temperature had a positive effect on product's stability.

Effect of temperature on studtite stability: Thermogravimetry and differential scanning calorimetry investigations

International Nuclear Information System (INIS)

Rey, A.; Casas, I.; Gimenez, J.; Quinones, J.; Pablo, J. de

2009-01-01

The main objective of this work is the study of the influence of temperature on the stability of the uranyl peroxide tetrahydrate (UO 2 O 2 . 4H 2 O) studtite, which may form on the spent nuclear fuel surface as a secondary solid phase. Preliminary results on the synthesis of studtite in the laboratory at different temperatures have shown that the solid phases formed when mixing hydrogen peroxide and uranyl nitrate depends on temperature. Studtite is obtained at 298 K, meta-studtite (UO 2 O 2 . 2H 2 O) at 373 K, and meta-schoepite (UO 3 . nH 2 O, with n 3 O 8 . By means of the differential scanning calorimetry the molar enthalpies of the transformations occurring at 403 and 504 K have been determined to be -42 ± 10 and -46 ± 2 kJ mol -1 , respectively

ESBWR - Robust design for natural circulation and stability performance effectiveness

Energy Technology Data Exchange (ETDEWEB)

Alamgir, M. D.; Marquino, W.; Yang, J.; Saha, P.; Fennern, L.; Colby, M. [GE-Hitachi Nuclear Energy, M/C A65, 3901Castle Hayne Road, Wilmington, NC 28401 (United States)

2012-07-01

ESBWR is a 4500 MWt Generation III+ natural circulation reactor with an array of robust design features and passive safety systems to deliver highly effective plant performance during normal operation and to keep the reactor safe during postulated transients and accidents. With the submittal of the latest revision of the Design Control Document (DCD) to US Nuclear Regulatory Commission, ESBWR is nearing the completion of the US design certification process. This paper focuses on the natural circulation-driven plant performance aspects during normal operation, and stability evaluation of the robust ESBWR design. The TRACG computer code is used for the analysis of ESBWR plant performance, safety analysis, and stability margins. The paper describes the evaluation of ESBWR stability performance during normal power operation including operation in the Core Power-Feed Water Temperature Operating Domain. For ESBWR the normal power operation condition has the highest power/flow ratio and is limiting from the perspective of stability. The paper includes results from detailed evaluation of the most limiting decay ratio for out-of-phase regional oscillations calculated by perturbing the core inlet flow rate in this out-of-phase mode about the line of symmetry for the azimuthal harmonic mode. The paper also summarizes the ESBWR regional mode stability evaluations during a limiting transient (Loss of Feedwater Heating), and during ATWS (Anticipated Transient without Scram). Nominal decay ratios of limiting Channel oscillation, Core wide oscillation and Regional oscillation are within the maximum acceptance criterion of 0.8, at 95% content and 95% confidence. These stability evaluation results indicate decay ratio is within design limits. The paper also describes the evaluation of ESBWR stability performance during plant startup, and summarizes the defense-in-depth stability solution for ESBWR. (authors)

ESBWR - Robust design for natural circulation and stability performance effectiveness

International Nuclear Information System (INIS)

Alamgir, M. D.; Marquino, W.; Yang, J.; Saha, P.; Fennern, L.; Colby, M.

2012-01-01

ESBWR is a 4500 MWt Generation III+ natural circulation reactor with an array of robust design features and passive safety systems to deliver highly effective plant performance during normal operation and to keep the reactor safe during postulated transients and accidents. With the submittal of the latest revision of the Design Control Document (DCD) to US Nuclear Regulatory Commission, ESBWR is nearing the completion of the US design certification process. This paper focuses on the natural circulation-driven plant performance aspects during normal operation, and stability evaluation of the robust ESBWR design. The TRACG computer code is used for the analysis of ESBWR plant performance, safety analysis, and stability margins. The paper describes the evaluation of ESBWR stability performance during normal power operation including operation in the Core Power-Feed Water Temperature Operating Domain. For ESBWR the normal power operation condition has the highest power/flow ratio and is limiting from the perspective of stability. The paper includes results from detailed evaluation of the most limiting decay ratio for out-of-phase regional oscillations calculated by perturbing the core inlet flow rate in this out-of-phase mode about the line of symmetry for the azimuthal harmonic mode. The paper also summarizes the ESBWR regional mode stability evaluations during a limiting transient (Loss of Feedwater Heating), and during ATWS (Anticipated Transient without Scram). Nominal decay ratios of limiting Channel oscillation, Core wide oscillation and Regional oscillation are within the maximum acceptance criterion of 0.8, at 95% content and 95% confidence. These stability evaluation results indicate decay ratio is within design limits. The paper also describes the evaluation of ESBWR stability performance during plant startup, and summarizes the defense-in-depth stability solution for ESBWR. (authors)

The Concept of Performance Levels in Criterion-Referenced Assessment.

Science.gov (United States)

Hewitson, Mal

The concept of performance levels in criterion-referenced assessment is explored by applying the idea to different types of tests commonly used in schools, mastery tests (including diagnostic tests) and achievement tests. In mastery tests, a threshold performance standard must be established for each criterion. Attainment of this threshold…

Thermophysical and Mechanical Properties of Granite and Its Effects on Borehole Stability in High Temperature and Three-Dimensional Stress

Directory of Open Access Journals (Sweden)

Wang Yu

2014-01-01

Full Text Available When exploiting the deep resources, the surrounding rock readily undergoes the hole shrinkage, borehole collapse, and loss of circulation under high temperature and high pressure. A series of experiments were conducted to discuss the compressional wave velocity, triaxial strength, and permeability of granite cored from 3500 meters borehole under high temperature and three-dimensional stress. In light of the coupling of temperature, fluid, and stress, we get the thermo-fluid-solid model and governing equation. ANSYS-APDL was also used to stimulate the temperature influence on elastic modulus, Poisson ratio, uniaxial compressive strength, and permeability. In light of the results, we establish a temperature-fluid-stress model to illustrate the granite’s stability. The compressional wave velocity and elastic modulus, decrease as the temperature rises, while poisson ratio and permeability of granite increase. The threshold pressure and temperature are 15 MPa and 200°C, respectively. The temperature affects the fracture pressure more than the collapse pressure, but both parameters rise with the increase of temperature. The coupling of thermo-fluid-solid, greatly impacting the borehole stability, proves to be a good method to analyze similar problems of other formations.

Thermophysical and mechanical properties of granite and its effects on borehole stability in high temperature and three-dimensional stress.

Science.gov (United States)

Wang, Yu; Liu, Bao-lin; Zhu, Hai-yan; Yan, Chuan-liang; Li, Zhi-jun; Wang, Zhi-qiao

2014-01-01

When exploiting the deep resources, the surrounding rock readily undergoes the hole shrinkage, borehole collapse, and loss of circulation under high temperature and high pressure. A series of experiments were conducted to discuss the compressional wave velocity, triaxial strength, and permeability of granite cored from 3500 meters borehole under high temperature and three-dimensional stress. In light of the coupling of temperature, fluid, and stress, we get the thermo-fluid-solid model and governing equation. ANSYS-APDL was also used to stimulate the temperature influence on elastic modulus, Poisson ratio, uniaxial compressive strength, and permeability. In light of the results, we establish a temperature-fluid-stress model to illustrate the granite's stability. The compressional wave velocity and elastic modulus, decrease as the temperature rises, while poisson ratio and permeability of granite increase. The threshold pressure and temperature are 15 MPa and 200 °C, respectively. The temperature affects the fracture pressure more than the collapse pressure, but both parameters rise with the increase of temperature. The coupling of thermo-fluid-solid, greatly impacting the borehole stability, proves to be a good method to analyze similar problems of other formations.

Linear Stability of Binary Alloy Solidification for Unsteady Growth Rates

Science.gov (United States)

Mazuruk, K.; Volz, M. P.

2010-01-01

An extension of the Mullins and Sekerka (MS) linear stability analysis to the unsteady growth rate case is considered for dilute binary alloys. In particular, the stability of the planar interface during the initial solidification transient is studied in detail numerically. The rapid solidification case, when the system is traversing through the unstable region defined by the MS criterion, has also been treated. It has been observed that the onset of instability is quite accurately defined by the "quasi-stationary MS criterion", when the growth rate and other process parameters are taken as constants at a particular time of the growth process. A singular behavior of the governing equations for the perturbed quantities at the constitutional supercooling demarcation line has been observed. However, when the solidification process, during its transient, crosses this demarcation line, a planar interface is stable according to the linear analysis performed.

Techniques for Liquid Rocket Combustion Spontaneous Stability and Rough Combustion Assessments

Science.gov (United States)

Kenny, R. J.; Giacomoni, C.; Casiano, M. J.; Fischbach, S. R.

2016-01-01

This work presents techniques for liquid rocket engine combustion stability assessments with respect to spontaneous stability and rough combustion. Techniques covering empirical parameter extraction, which were established in prior works, are applied for three additional programs: the F-1 Gas Generator (F1GG) component test program, the RS-84 preburner component test program, and the Marshall Integrated Test Rig (MITR) program. Stability assessment parameters from these programs are compared against prior established spontaneous stability metrics and updates are identified. Also, a procedure for comparing measured with predicted mode shapes is presented, based on an extension of the Modal Assurance Criterion (MAC).

Numerical and Experimental Validation of a New Damage Initiation Criterion

Science.gov (United States)

Sadhinoch, M.; Atzema, E. H.; Perdahcioglu, E. S.; van den Boogaard, A. H.

2017-09-01

Most commercial finite element software packages, like Abaqus, have a built-in coupled damage model where a damage evolution needs to be defined in terms of a single fracture energy value for all stress states. The Johnson-Cook criterion has been modified to be Lode parameter dependent and this Modified Johnson-Cook (MJC) criterion is used as a Damage Initiation Surface (DIS) in combination with the built-in Abaqus ductile damage model. An exponential damage evolution law has been used with a single fracture energy value. Ultimately, the simulated force-displacement curves are compared with experiments to validate the MJC criterion. 7 out of 9 fracture experiments were predicted accurately. The limitations and accuracy of the failure predictions of the newly developed damage initiation criterion will be discussed shortly.

Prediction of Hot Tearing Using a Dimensionless Niyama Criterion

Science.gov (United States)

Monroe, Charles; Beckermann, Christoph

2014-08-01

The dimensionless form of the well-known Niyama criterion is extended to include the effect of applied strain. Under applied tensile strain, the pressure drop in the mushy zone is enhanced and pores grow beyond typical shrinkage porosity without deformation. This porosity growth can be expected to align perpendicular to the applied strain and to contribute to hot tearing. A model to capture this coupled effect of solidification shrinkage and applied strain on the mushy zone is derived. The dimensionless Niyama criterion can be used to determine the critical liquid fraction value below which porosity forms. This critical value is a function of alloy properties, solidification conditions, and strain rate. Once a dimensionless Niyama criterion value is obtained from thermal and mechanical simulation results, the corresponding shrinkage and deformation pore volume fractions can be calculated. The novelty of the proposed method lies in using the critical liquid fraction at the critical pressure drop within the mushy zone to determine the onset of hot tearing. The magnitude of pore growth due to shrinkage and deformation is plotted as a function of the dimensionless Niyama criterion for an Al-Cu alloy as an example. Furthermore, a typical hot tear "lambda"-shaped curve showing deformation pore volume as a function of alloy content is produced for two Niyama criterion values.

Adaptive and freeze-tolerant heteronetwork organohydrogels with enhanced mechanical stability over a wide temperature range

Science.gov (United States)

Gao, Hainan; Zhao, Ziguang; Cai, Yudong; Zhou, Jiajia; Hua, Wenda; Chen, Lie; Wang, Li; Zhang, Jianqi; Han, Dong; Liu, Mingjie; Jiang, Lei

2017-06-01

Many biological organisms with exceptional freezing tolerance can resist the damages to cells from extra-/intracellular ice crystals and thus maintain their mechanical stability at subzero temperatures. Inspired by the freezing tolerance mechanisms found in nature, here we report a strategy of combining hydrophilic/oleophilic heteronetworks to produce self-adaptive, freeze-tolerant and mechanically stable organohydrogels. The organohydrogels can simultaneously use water and oil as a dispersion medium, and quickly switch between hydrogel- and organogel-like behaviours in response to the nature of the surrounding phase. Accordingly, their surfaces display unusual adaptive dual superlyophobic in oil/water system (that is, they are superhydrophobic under oil and superoleophobic under water). Moreover, the organogel component can inhibit the ice crystallization of the hydrogel component, thus enhancing the mechanical stability of organohydrogel over a wide temperature range (-78 to 80 °C). The organohydrogels may have promising applications in complex and harsh environments.

The Impact of Temperatures on the Stability of Rocks Surrounding a Single Fracture

Science.gov (United States)

Zhang, Yan; Li, Ning; Dai, Jun

2018-05-01

Research on the influence of temperature and the accompanying stress on the stability of the rocks surrounding an underground tunnel has become ever more important. This paper constructs a geometric model of a single-fracture tunnel by combining a high-temperature underground tunnel as the object of study with an example that uses a high-temperature tunnel segment in the water diversion tunnel of a hydropower station in Xinjiang. Based on the relevant theoretical analysis, with the consideration of different working conditions, a numerical experimental analysis was conducted to determine the two-dimensional transient temperature field distribution of the tunnel rock mass by using a numerical analysis software. The experimental data was consistent with the measured data. The calculated results show the following: a. when the temperature difference is greater, the stress concentration is higher near the fracture of the surrounding rock; b. the degree of the stress concentration in the crack tip region is not positively correlated to the distance, and there is a sensitive region where the stress varies.

The determination of temperature stability of silver nanotubes by the molecular dynamics simulation

Science.gov (United States)

Filatov, O.; Soldatenko, S.; Soldatenko, O.

2018-04-01

Molecular dynamics simulation using the embedded-atom method is applied to study thermal stability of silver nanotubes and its coefficient of linear thermal expansion. The correspondence of face centered cubic structure potential for this task is tested. Three types of nanotubes are modelled: scrolled from graphene-like plane, scrolled from plane with cubic structure and cut from cylinder. It is established that only the last two of them are stable. The last one describes in details. There is critical temperature when free ends of the nanotube close but the interior surface retains. At higher temperatures, the interior surface collapses and the nanotube is unstable.

Joined application of a multiaxial critical plane criterion and a strain energy density criterion in low-cycle fatigue

Directory of Open Access Journals (Sweden)

Andrea Carpinteri

2017-07-01

Full Text Available In the present paper, the multiaxial fatigue life assessment of notched structural components is performed by employing a strain-based multiaxial fatigue criterion. Such a criterion, depending on the critical plane concept, is extended by implementing the control volume concept reated to the Strain Energy Density (SED approach: a material point located at a certain distance from the notch tip is assumed to be the verification point where to perform the above assessment. Such a distance, measured along the notch bisector, is a function of both the biaxiality ratio (defined as the ratio between the applied shear stress amplitude and the normal stress amplitude and the control volume radii under Mode I and Mode III. Once the position of the verification point is determined, the fatigue lifetime is assessed through an equivalent strain amplitude, acting on the critical plane, together with a unique material reference curve (i.e. the Manson-Coffin curve. Some uniaxial and multiaxial fatigue data related to V-notched round bars made of titanium grade 5 alloy (Ti-6Al-4V are examined to validate the present criterion.

Distance criterion for hydrogen bond

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Distance criterion for hydrogen bond. In a D-H ...A contact, the D...A distance must be less than the sum of van der Waals Radii of the D and A atoms, for it to be a hydrogen bond.

Longitudinal Absolute Stability of a BWB Aircraft-Pilot System with Saturated Actuator Model

Directory of Open Access Journals (Sweden)

Claudia Alice STATE

2013-09-01

Full Text Available This paper deals with the analysis of the P(ilot I(n-the-Loop O(scillations of the second category (with rate and position liming in the closed loop pilot-vehicle system, caused by the dynamic coupling between the human pilot and the aircraft. The analysis is made in the context of the longitudinal motion and the theoretical model of the airplane presented in this article is a (Blended(Wing (Body tailless configuration. In what concerns the human operator, this is expressed by the Synchronous Pilot Model, which is represented by a simple gain, without a specific delay. The Routh-Hurwitz criterion is used in order to analyze the longitudinal stability of the low-order pilot-airplane system without the influence of actuator nonlinearity (this means that the unsaturated actuator model is employed for the mentioned algebraic criterion. Most emphasis is put on the frequency Popov criterion, which is used to investigate the absolute stability property of the short-period model in the presence of the actuator rate saturation, in the condition of the Lurie problem. The transfer function of the longitudinal BWB model, obtained from open-loop analysis, has a double pole at the origin and, for the absolute stability feedback structure that contains the nonlinearity of the saturation type, the Popov frequency-domain inequalities are applied to the PIO II problem in this critical case.

Stability and uniformity of extemporaneous preparations of voriconazole in two liquid suspension vehicles at two storage temperatures.

Science.gov (United States)

Nguyen, Kyvan Q; Hawkins, Michelle G; Taylor, Ian T; Wiebe, Valerie J; Tell, Lisa A

2009-07-01

To determine the stability and distribution of voriconazole in 2 extemporaneously prepared (compounded) suspensions stored for 30 days at 2 temperatures. Voriconazole suspensions (40 mg/mL) compounded from commercially available 200-mg tablets suspended in 1 of 2 vehicles. One vehicle contained a commercially available suspending agent and a sweetening syrup in a 1:1 mixture (SASS). The other vehicle contained the suspending agent with deionized water in a 3:1 mixture (SADI). Voriconazole suspensions (40 mg/mL in 40-mL volumes) were compounded on day 0 and stored at room temperature (approx 21 degrees C) or refrigerated (approx 5 degrees C). To evaluate distribution, room-temperature aliquots of voriconazole were measured immediately after preparation. Refrigerated aliquots were measured after 3 hours of refrigeration. To evaluate stability, aliquots from each suspension were measured at approximately 7-day intervals for up to 30 days. Voriconazole concentration, color, odor, opacity, and pH were measured, and aerobic and anaerobic bacterial cultures were performed at various points. Drug distribution was uniform (coefficient of variation, suspensions. On day 0, 87.8% to 93.0% of voriconazole was recovered; percentage recovery increased to between 95.1% and 100.8% by day 7. On subsequent days, up to day 30, percentage recovery was stable (> 90%) for all suspensions. The pH of each suspension did not differ significantly throughout the 30-day period. Storage temperature did not affect drug concentrations at any time, nor was bacterial growth obtained. Extemporaneously prepared voriconazole in SASS and SADI resulted in suspensions that remained stable for at least 30 days. Refrigerated versus room-temperature storage of the suspensions had no effect on drug stability.

Effect of thermal stabilization on the low-temperature stress-corrosion cracking of Inconel 600

International Nuclear Information System (INIS)

Bandy, R.; van Rooyen, D.

1983-01-01

The propensity to low-temperature stress-corrosion cracking (SCC) of thermally stabilized Inconel 600 in sulfur-bearing environments has been investigated using U-bends and slow-strain-rate testing. The results have been compared with those of sensitized Inconel 600. The potential dependence of crack-propagation rate has been established in a single test by using several U-bends held at different potentials, by choosing an appropriate electrical circuitry. The difference in SCC susceptibility of the sensitized and stabilized materials is discussed in terms of the grain-boundary chromium depletion and resulting intergranular attack in boiling ferric sulfate-sulfuric acid tests, and electrochemical potentiokinetic reactivation (EPR) tests. 10 figures

Influence of the spacers on the stability of channel cooled superconducting coils

International Nuclear Information System (INIS)

Meuris, C.

1980-10-01

In a previous paper, the thermal stability of channel cooled superconducting magnets was experimentally studied. Stable normal zones were observed within a range of currents and local disturbance energies. Usual theories fail to fully explain these results, owing to the fact that they take into account a heat transfer to liquid helium only function of the temperature of the conductor, whatever the position is. In a simplified theoretical analysis, it is shown that in a locally uncooled superconducting wire several stationary normal zones can exist. A criterion is derived that yields the recovery current as a function of the length of the uncooled region. Besides, a detailed numerical analysis determines the evolution of a normal zone in a channel cooled magnet. Theoretical calculations are compared with experimental results

P2-17: Individual Differences in Dynamic Criterion Shifts during Perceptual Decision Making

Directory of Open Access Journals (Sweden)

Issac Rhim

2012-10-01

Full Text Available Perceptual decision-making involves placing an optimal criterion on the axis of encoded sensory evidence to maximize outcomes for choices. Optimal criterion setting becomes critical particularly when neural representations of sensory inputs are noisy and feedbacks for perceptual choices vary over time in an unpredictable manner. Here we monitored time courses of decision criteria that are adopted by human subjects while abruptly shifting the criterion of stochastic feedback to perceptual choices with certain amounts in an unpredictable direction and at an unpredictable point of time. Subjects viewed a brief (0.3 s, thin (.07 deg annulus around the fixation and were forced to judge whether the annulus was smaller or larger than an unknown boundary. We estimated moment-to-moment criteria by fitting a cumulative Gaussian function to the data within a sliding window of trials that are locked to a shift in feedback criterion. Unpredictable shifts in feedback criterion successfully induced shifts in actual decision criterion towards an optimal criterion for many of subjects, but with time delay and amount of shifts varying across individual subjects. There were disproportionately more numbers of overshooters (reaching and then surpassing the optimal criterion required than undershooters (subpar reach, with a significant anti-correlation with sensory sensitivity. To find a mechanism that generates these individual differences, we developed a dynamic criterion learning model by modifying a reinforcement learning model, which assumes that a criterion is adjusted every trial by a weighted discrepancy between actual and expected rewards.

Antibiotic stability related to temperature variations in elastomeric pumps used for outpatient parenteral antimicrobial therapy (OPAT).

Science.gov (United States)

Voumard, Rachel; Van Neyghem, Niklas; Cochet, Camille; Gardiol, Céline; Decosterd, Laurent; Buclin, Thierry; de Valliere, Serge

2017-05-01

Elastomeric pumps can be used for the continuous administration of antimicrobials in the outpatient setting. A potentially limiting factor in their use is the stability of antimicrobials. To investigate under real-life conditions the temperature variations of antibiotic solutions contained in elastomeric pumps, and to examine under such conditions the stability of five antibiotics. Healthy volunteers carried the elastomeric pumps in carry pouches during their daily activities. A thermologger measured the temperatures every 15 min over 24 h. Antibiotic concentrations were measured by HPLC coupled to tandem MS. During daytime, the temperature of solutions in the pumps increased steadily, warming to >30°C. During the night, when the pumps were kept attached to the waist, the temperatures reached up to 33°C. The use of white carry pouches avoided excessive temperature increases. Over seven experiments, cefazolin, cefepime, piperacillin and tazobactam were found to be stable over 24 h. Flucloxacillin showed a mean decrease in concentration of 11% ( P  = 0.001). Real-life situations can cause significant temperature rises in elastomeric pumps, thereby potentially increasing the risk of antibiotic degradation. Patients should be instructed to avoid situations causing excessive temperature increases. Despite these temperature variations, cefazolin, cefepime, piperacillin and tazobactam were found to be stable over 24 h. A moderate degradation was noticed for flucloxacillin, albeit most probably not to an extent that might impair anti-infective efficacy. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Self-Adjointness Criterion for Operators in Fock Spaces

International Nuclear Information System (INIS)

Falconi, Marco

2015-01-01

In this paper we provide a criterion of essential self-adjointness for operators in the tensor product of a separable Hilbert space and a Fock space. The class of operators we consider may contain a self-adjoint part, a part that preserves the number of Fock space particles and a non-diagonal part that is at most quadratic with respect to the creation and annihilation operators. The hypotheses of the criterion are satisfied in several interesting applications

Criterion-based laparoscopic training reduces total training time

OpenAIRE

Brinkman, Willem M.; Buzink, Sonja N.; Alevizos, Leonidas; de Hingh, Ignace H. J. T.; Jakimowicz, Jack J.

2011-01-01

Introduction The benefits of criterion-based laparoscopic training over time-oriented training are unclear. The purpose of this study is to compare these types of training based on training outcome and time efficiency. Methods During four training sessions within 1 week (one session per day) 34 medical interns (no laparoscopic experience) practiced on two basic tasks on the Simbionix LAP Mentor virtual-reality (VR) simulator: ‘clipping and grasping’ and ‘cutting’. Group C (criterion-based) (N...

The precautionary principle as a rational decision criterion

International Nuclear Information System (INIS)

Hovi, Jon

2001-12-01

The paper asks if the precautionary principle may be seen as a rational decision criterion. Six main questions are discussed. 1. Does the principle basically represent a particular set of political options or is it a genuine decision criterion? 2. If it is the latter, can it be reduced to any of the existing criteria for decision making under uncertainty? 3. In what kinds of situation is the principle applicable? 4. What is the relation between the precautionary principle and other principles for environmental regulation? 5. How plausible is the principle's claim that the burden of proof should be reversed? 6. Do the proponents of environmental regulation carry no burden of proof at all? A main conclusion is that, for now at least, the principle contains too many unclear elements to satisfy the requirements of precision and consistency that should reasonably be satisfied by a rational decision criterion. (author)

Probabilistic interpretation of the reduction criterion for entanglement

International Nuclear Information System (INIS)

Zhang, Zhengmin; Luo, Shunlong

2007-01-01

Inspired by the idea of conditional probabilities, we introduce a variant of conditional density operators. But unlike the conditional probabilities which are bounded by 1, the conditional density operators may have eigenvalues exceeding 1 for entangled states. This has the consequence that although any bivariate classical probability distribution has a natural separable decomposition in terms of conditional probabilities, we do not have a quantum analogue of this separable decomposition in general. The 'nonclassical' eigenvalues of conditional density operators are indications of entanglement. The resulting separability criterion turns out to be equivalent to the reduction criterion introduced by Horodecki [Phys. Rev. A 59, 4206 (1999)] and Cerf et al. [Phys. Rev. A 60, 898 (1999)]. This supplies an intuitive probabilistic interpretation for the reduction criterion. The conditional density operators are also used to define a form of quantum conditional entropy which provides an alternative mechanism to reveal quantum discord

Slope Safety Factor Calculations With Non-Linear Yield Criterion Using Finite Elements

DEFF Research Database (Denmark)

Clausen, Johan; Damkilde, Lars

2006-01-01

The factor of safety for a slope is calculated with the finite element method using a non-linear yield criterion of the Hoek-Brown type. The parameters of the Hoek-Brown criterion are found from triaxial test data. Parameters of the linear Mohr-Coulomb criterion are calibrated to the same triaxial...... are carried out at much higher stress levels than present in a slope failure, this leads to the conclusion that the use of the non-linear criterion leads to a safer slope design...

Thermal Stability of Austempered Ductile Iron Evaluated in a Temperature Range of 20-300K

Directory of Open Access Journals (Sweden)

Dawid MYSZKA

2016-05-01

Full Text Available The aim of this article was to determine through changes in magnetic properties the stability of the austempered ductile iron (ADI microstructure during temperature changes in a range of 20 – 300 K. The measurements were taken in a vibrating sample magnetometer (VSM using Fe27Ni2TiMoAlNb austenitic stainless steel and four types of austempered ductile iron obtained under various heat treatment conditions. The plotted curves showing changes in the magnetisation degree as a function of temperature had a number of characteristic points illustrating changes taking place in the microstructure. For each of the materials examined, the martensite start temperature Ms and the temperature range within which the martensitic transformation takes place were identified.

The Interdependence between Rainfall and Temperature: Copula Analyses

DEFF Research Database (Denmark)

Cong, Ronggang; Brady, Mark

2012-01-01

possible approach to this problem, five families of copula models are employed to model the interdependence between rainfall and temperature. Scania is a leading agricultural province in Sweden and is affected by a maritime climate. Historical climatic data for Scania is used to demonstrate the modeling...... process. Heteroscedasticity and autocorrelation of sample data are also considered to eliminate the possibility of observation error. The results indicate that for Scania there are negative correlations between rainfall and temperature for the months from April to July and September. The student copula...... is found to be most suitable to model the bivariate distribution of rainfall and temperature based on the Akaike information criterion (AIC) and Bayesian information criterion (BIC). Using the student copula, we simulate temperature and rainfall simultaneously. The resulting models can be integrated...

Nonparallel linear stability analysis of unconfined vortices

Science.gov (United States)

Herrada, M. A.; Barrero, A.

2004-10-01

Parabolized stability equations [F. P. Bertolotti, Th. Herbert, and P. R. Spalart, J. Fluid. Mech. 242, 441 (1992)] have been used to study the stability of a family of swirling jets at high Reynolds numbers whose velocity and pressure fields decay far from the axis as rm-2 and r2(m-2), respectively [M. Pérez-Saborid, M. A. Herrada, A. Gómez-Barea, and A. Barrero, J. Fluid. Mech. 471, 51 (2002)]; r is the radial distance and m is a real number in the interval 0criterion based on the transition from convective to absolute instabilities cannot be applied to predict the vortex breakdown of this kind of swirling jets. On the contrary, the failure of the quasicylindrical approximation used to compute the downstream evolution of the basic flow gives a clear breakdown criterion based on the catastrophic transition between slender and nonslender flows.

Short communication: Stability and integrity of classical swine fever virus RNA stored at room temperature

Directory of Open Access Journals (Sweden)

Damarys Relova

2017-12-01

Full Text Available Worldwide cooperation between laboratories working with classical swine fever virus (CSFV requires exchange of virus isolates. For this purpose, shipment of CSFV RNA is a safe alternative to the exchange of infectious material. New techniques using desiccation have been developed to store RNA at room temperature and are reported as effective means of preserving RNA integrity. In this study, we evaluated the stability and integrity of dried CSFV RNA stored at room temperature. First, we determined the stability of CSFV RNA covering CSFV genome regions used typically for the detection of viral RNA in diagnostic samples by reverse transcription-polymerase chain reaction (RT-PCR. To this end, different concentrations of in vitro-transcribed RNAs of the 5’-untranslated region and of the NS5B gene were stored as dried RNA at 4, 20, and 37oC for two months. Aliquots were analyzed every week by CSFV-specific quantitative real-time RT-PCR. Neither the RNA concentration nor the storage temperature did affect CSFV RNA yields at any of the time evaluated until the end of the experiment. Furthermore, it was possible to recover infectious CSFV after transfection of SK-6 cells with dried viral RNA stored at room temperature for one week. The full-length E2 of CSFV was amplified from all the recovered viruses, and nucleotide sequence analysis revealed 100% identity with the corresponding sequence obtained from RNA of the original material. These results show that CSFV RNA stored as dried RNA at room temperature is stable, maintaining its integrity for downstream analyses and applications.

A Criterion to Identify Maximally Entangled Four-Qubit State

International Nuclear Information System (INIS)

Zha Xinwei; Song Haiyang; Feng Feng

2011-01-01

Paolo Facchi, et al. [Phys. Rev. A 77 (2008) 060304(R)] presented a maximally multipartite entangled state (MMES). Here, we give a criterion for the identification of maximally entangled four-qubit states. Using this criterion, we not only identify some existing maximally entangled four-qubit states in the literature, but also find several new maximally entangled four-qubit states as well. (general)

A Joint Optimization Criterion for Blind DS-CDMA Detection

Directory of Open Access Journals (Sweden)

Sergio A. Cruces-Alvarez

2007-01-01

Full Text Available This paper addresses the problem of the blind detection of a desired user in an asynchronous DS-CDMA communications system with multipath propagation channels. Starting from the inverse filter criterion introduced by Tugnait and Li in 2001, we propose to tackle the problem in the context of the blind signal extraction methods for ICA. In order to improve the performance of the detector, we present a criterion based on the joint optimization of several higher-order statistics of the outputs. An algorithm that optimizes the proposed criterion is described, and its improved performance and robustness with respect to the near-far problem are corroborated through simulations. Additionally, a simulation using measurements on a real software-radio platform at 5 GHz has also been performed.

A Joint Optimization Criterion for Blind DS-CDMA Detection

Science.gov (United States)

Durán-Díaz, Iván; Cruces-Alvarez, Sergio A.

2006-12-01

This paper addresses the problem of the blind detection of a desired user in an asynchronous DS-CDMA communications system with multipath propagation channels. Starting from the inverse filter criterion introduced by Tugnait and Li in 2001, we propose to tackle the problem in the context of the blind signal extraction methods for ICA. In order to improve the performance of the detector, we present a criterion based on the joint optimization of several higher-order statistics of the outputs. An algorithm that optimizes the proposed criterion is described, and its improved performance and robustness with respect to the near-far problem are corroborated through simulations. Additionally, a simulation using measurements on a real software-radio platform at 5 GHz has also been performed.

Three-Dimensional Dynamic Rupture in Brittle Solids and the Volumetric Strain Criterion

Science.gov (United States)

Uenishi, K.; Yamachi, H.

2017-12-01

As pointed out by Uenishi (2016 AGU Fall Meeting), source dynamics of ordinary earthquakes is often studied in the framework of 3D rupture in brittle solids but our knowledge of mechanics of actual 3D rupture is limited. Typically, criteria derived from 1D frictional observations of sliding materials or post-failure behavior of solids are applied in seismic simulations, and although mode-I cracks are frequently encountered in earthquake-induced ground failures, rupture in tension is in most cases ignored. Even when it is included in analyses, the classical maximum principal tensile stress rupture criterion is repeatedly used. Our recent basic experiments of dynamic rupture of spherical or cylindrical monolithic brittle solids by applying high-voltage electric discharge impulses or impact loads have indicated generation of surprisingly simple and often flat rupture surfaces in 3D specimens even without the initial existence of planes of weakness. However, at the same time, the snapshots taken by a high-speed digital video camera have shown rather complicated histories of rupture development in these 3D solid materials, which seem to be difficult to be explained by, for example, the maximum principal stress criterion. Instead, a (tensile) volumetric strain criterion where the volumetric strain (dilatation or the first invariant of the strain tensor) is a decisive parameter for rupture seems more effective in computationally reproducing the multi-directionally propagating waves and rupture. In this study, we try to show the connection between this volumetric strain criterion and other classical rupture criteria or physical parameters employed in continuum mechanics, and indicate that the criterion has, to some degree, physical meanings. First, we mathematically illustrate that the criterion is equivalent to a criterion based on the mean normal stress, a crucial parameter in plasticity. Then, we mention the relation between the volumetric strain criterion and the

An Elasto-Plastic Damage Model for Rocks Based on a New Nonlinear Strength Criterion

Science.gov (United States)

Huang, Jingqi; Zhao, Mi; Du, Xiuli; Dai, Feng; Ma, Chao; Liu, Jingbo

2018-05-01

The strength and deformation characteristics of rocks are the most important mechanical properties for rock engineering constructions. A new nonlinear strength criterion is developed for rocks by combining the Hoek-Brown (HB) criterion and the nonlinear unified strength criterion (NUSC). The proposed criterion takes account of the intermediate principal stress effect against HB criterion, as well as being nonlinear in the meridian plane against NUSC. Only three parameters are required to be determined by experiments, including the two HB parameters σ c and m i . The failure surface of the proposed criterion is continuous, smooth and convex. The proposed criterion fits the true triaxial test data well and performs better than the other three existing criteria. Then, by introducing the Geological Strength Index, the proposed criterion is extended to rock masses and predicts the test data well. Finally, based on the proposed criterion, a triaxial elasto-plastic damage model for intact rock is developed. The plastic part is based on the effective stress, whose yield function is developed by the proposed criterion. For the damage part, the evolution function is assumed to have an exponential form. The performance of the constitutive model shows good agreement with the results of experimental tests.

Stability of low-temperature Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} cubic phase: The role of temperature and atmosphere

Energy Technology Data Exchange (ETDEWEB)

Quinzeni, Irene; Capsoni, Doretta; Berbenni, Vittorio; Mustarelli, Piercarlo [Chemistry Department, Physical-Chemistry Section, University of Pavia, Viale Taramelli 16, 27100 Pavia (Italy); Sturini, Michela [Chemistry Department, Analytical Section, University of Pavia, Viale Taramelli 12, 27100 Pavia (Italy); Bini, Marcella, E-mail: bini@unipv.it [Chemistry Department, Physical-Chemistry Section, University of Pavia, Viale Taramelli 16, 27100 Pavia (Italy)

2017-01-01

Rechargeable all solid-state lithium batteries are a promising technology for the next generation of safer batteries. In this context, strict requirements are placed on the electrolytes, among which is emerging the Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} garnet, chiefly for the relationships among synthesis conditions and phase stability. Here, the structural modifications of the low temperature (LT) Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} cubic form were investigated by using in situ X-Rays diffraction analysis. In particular, we studied the role of both temperature and atmosphere (air or argon) on phase stabilization. In argon flow, the LT phase is stable under 750 °C, and it transforms into the tetragonal one at lower temperature. In air, it partially decomposes to La{sub 2}Zr{sub 2}O{sub 7} due to Li loss above 250 °C. ICP-OES analysis confirmed that garnet stoichiometry was maintained in argon, whereas in air lithium loss occurred. The structural transformations are driven by the CO{sub 2} absorbed in the LT structure that can form Li{sub 2}CO{sub 3} and/or La{sub 2}(CO{sub 3}){sub 3} so causing stoichiometry changes responsible of the structural evolution. - Highlights: • Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} is a promising electrolyte for rechargeable all solid state batteries. • The stability of low temperature cubic phase of garnet in argon and air was determined. • The garnet stoichiometry was maintained in argon while in air lithium loss occurred. • The influence of CO{sub 2} adsorption on the structural modifications of garnet was proved.

Quantum electrodynamics at finite temperatures in presence of an external field violating the vacuum stability

International Nuclear Information System (INIS)

Gavrilov, S.P.; Gitman, D.M.; Fradkin, E.S.

1987-01-01

A functional generating expectation values is obtained for QED at a finite temperature in presence of an external field violating the vacuum stability. Equations for connected Green's functions and the effective action for the mean field are derived. The Green function is obtained as an integral with respect of the proper time; the representation takes into account temperature effects in a constant homogeneous field. The polarization operator for the mean field in an external constant homogeneous field is calculated by means of the integral representation

Sampling Criterion for EMC Near Field Measurements

DEFF Research Database (Denmark)

Franek, Ondrej; Sørensen, Morten; Ebert, Hans

2012-01-01

An alternative, quasi-empirical sampling criterion for EMC near field measurements intended for close coupling investigations is proposed. The criterion is based on maximum error caused by sub-optimal sampling of near fields in the vicinity of an elementary dipole, which is suggested as a worst......-case representative of a signal trace on a typical printed circuit board. It has been found that the sampling density derived in this way is in fact very similar to that given by the antenna near field sampling theorem, if an error less than 1 dB is required. The principal advantage of the proposed formulation is its...

A new objective criterion for IRIS localization

International Nuclear Information System (INIS)

Basit, A.

2010-01-01

Iris localization is the most important step in iris recognition systems. For commonly used databases, exact data is not given which describe the true results of localization. To cope with this problem a new objective criterion for iris localization is proposed in this paper based on our visual system. A specific number of points are selected on pupil boundary, iris boundary, upper eyelid and lower eyelid using the original image and then distance from these points to the result of complete iris localization has been calculated. If the determined distance is below a certain threshold then iris localization is considered correct. Experimental results show that proposed criterion is very effective. (author)

In-Flight Suppressant Deployment Temperatures

National Research Council Canada - National Science Library

Bein, Donald

2006-01-01

.... An assessment is made of the model output versus some aircraft measurement data, fire suppressant boiling point criterion, as well as the history of altitude/temperature at which fire suppressants have been deployed...

Nolinear stability analysis of nuclear reactors : expansion methods for stability domains

International Nuclear Information System (INIS)

Yang, Chae Yong

1992-02-01

Two constructive methods for estimating asymptotic stability domains of nonlinear reactor models are developed in this study: an improved Chang and Thorp's method based on expansion of a Lyapunov function and a new method based on expansion of any positive definite function. The methods are established on the concept of stability definitions of Lyapunov itself. The first method provides a sequence of stability regions that eventually approaches the exact stability domain, but requires many expansions in order to obtain the entire stability region because the starting Lyapunov function usually corresponds to a small stability region and because most dynamic systems are stiff. The second method (new method) requires only a positive definite function and thus it is easy to come up with a starting region. From a large starting region, the entire stability region is estimated effectively after sufficient iterations. It is particularly useful for stiff systems. The methods are applied to several nonlinear reactor models known in the literature: one-temperature feedback model, two-temperature feedback model, and xenon dynamics model, and the results are compared. A reactor feedback model for a pressurized water reactor (PWR) considering fuel and moderator temperature effects is developed and the nonlinear stability regions are estimated for the various values of design parameters by using the new method. The steady-state properties of the nonlinear reactor system are analyzed via bifurcation theory. The analysis of nonlinear phenomena is carried out for the various forms of reactivity feedback coefficients that are both temperature- (or power-) independent and dependent. If one of two temperature coefficients is positive, unstable limit cycles or multiplicity of the steady-state solutions appear when the other temperature coefficient exceeds a certain critical value. As an example, even though the fuel temperature coefficient is negative, if the moderator temperature

Effect of changes in seafloor temperature and sea-level on gas hydrate stability

Energy Technology Data Exchange (ETDEWEB)

Garg, S.K.; Pritchett, W. [Science Applications International Corp., San Diego, CA (United States)

2008-07-01

Natural gas hydrates occur in oceanic sediments and in permafrost regions around the world. As a greenhouse gas, large amounts of methane released from the global hydrate reservoir would have a significant impact on Earth's climate. The role of methane released by hydrate dissociation in climate change is uncertain. However, changes in global climate such as glaciation and warming can destabilize the hydrates. During the last glacial maximum, the sea level dropped about 100 meters. It has been suggested that the sea-level fall was associated with gas hydrate instability and seafloor slumping. This paper investigated the effect of changes in seafloor temperature and sea level on gas hydrate stability and on gas venting at the seafloor. A one-dimensional numerical computer model (simulator) was developed to describe methane hydrate formation, decomposition, reformation, and distribution with depth below the seafloor in the marine environment. The simulator was utilized to model hydrate distributions at two sites, notably Blake Ridge, located offshore South Carolina and Hydrate Ridge, located off the coast of Oregon. The numerical models for the two sites were conditioned by matching the sulfate, chlorinity, and hydrate distribution measurements. The effect of changes in seafloor temperature and sea-level on gas hydrate stability were then investigated. It was concluded that for Blake Ridge, changes in hydrate concentration were small. Both the changes in seafloor temperature and sea-level led to a substantial increase in gas venting at the seafloor for Hydrate Ridge. 17 refs., 8 figs.

Stability evaluation of quality parameters for palm oil products at low temperature storage.

Science.gov (United States)

Ramli, Nur Aainaa Syahirah; Mohd Noor, Mohd Azmil; Musa, Hajar; Ghazali, Razmah

2018-07-01

Palm oil is one of the major oils and fats produced and traded worldwide. The value of palm oil products is mainly influenced by their quality. According to ISO 17025:2005, accredited laboratories require a quality control procedure with respect to monitoring the validity of tests for determination of quality parameters. This includes the regular use of internal quality control using secondary reference materials. Unfortunately, palm oil reference materials are not currently available. To establish internal quality control samples, the stability of quality parameters needs to be evaluated. In the present study, the stability of quality parameters for palm oil products was examined over 10 months at low temperature storage (6 ± 2 °C). The palm oil products tested included crude palm oil (CPO); refined, bleached and deodorized (RBD) palm oil (RBDPO); RBD palm olein (RBDPOo); and RBD palm stearin (RBDPS). The quality parameters of the oils [i.e. moisture content, free fatty acid content (FFA), iodine value (IV), fatty acids composition (FAC) and slip melting point (SMP)] were determined prior to and throughout the storage period. The moisture, FFA, IV, FAC and SMP for palm oil products changed significantly (P  0.05). The stability study indicated that the quality of the palm oil products was stable within the specified limits throughout the storage period at low temperature. The storage conditions preserved the quality of palm oil products throughout the storage period. These findings qualify the use of the palm oil products CPO, RBDPO, RBDPOo and RBDPS as control samples in the validation of test results. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

On exponential stability of bidirectional associative memory neural networks with time-varying delays

International Nuclear Information System (INIS)

Park, Ju H.; Lee, S.M.; Kwon, O.M.

2009-01-01

For bidirectional associate memory neural networks with time-varying delays, the problems of determining the exponential stability and estimating the exponential convergence rate are investigated by employing the Lyapunov functional method and linear matrix inequality (LMI) technique. A novel criterion for the stability, which give information on the delay-dependent property, is derived. A numerical example is given to demonstrate the effectiveness of the obtained results.

High-temperature stability of electron transport in semiconductors with strong spin-orbital interaction

Science.gov (United States)

Tomaka, G.; Grendysa, J.; ŚliŻ, P.; Becker, C. R.; Polit, J.; Wojnarowska, R.; Stadler, A.; Sheregii, E. M.

2016-05-01

Experimental results of the magnetotransport measurements (longitudinal magnetoresistance Rx x and the Hall resistance Rx y) are presented over a wide interval of temperatures for several samples of Hg1 -xCdxTe (x ≈0.13 -0.15 ) grown by MBE—thin layers (thickness about 100 nm) strained and not strained and thick ones with thickness about 1 μ m . An amazing temperature stability of the SdH-oscillation period and amplitude is observed in the entire temperature interval of measurements up to 50 K. Moreover, the quantum Hall effect (QHE) behavior of the Hall resistance is registered in the same temperature interval. These peculiarities of the Rx x and Rx y for strained thin layers are interpreted using quantum Hall conductivity (QHC) on topologically protected surface states (TPSS) [C. Brüne et al., Phys. Rev. Lett. 106, 126803 (2011), 10.1103/PhysRevLett.106.126803]. In the case of not strained layers it is assumed that the QHC on the TPSS (or on the resonant interface states) contributes also to the conductance of the bulk samples.

Stabilization of apoglobin by low temperature increases yield of soluble recombinant hemoglobin in Escherichia coli.

Science.gov (United States)

Weickert, M J; Pagratis, M; Curry, S R; Blackmore, R

1997-01-01

Accumulation of soluble recombinant hemoglobin (rHb1.1) in Escherichia coli requires proper protein folding, prosthetic group (heme) addition, and subunit assembly. This served as a new model system for the study of the effects of temperature, protein synthesis rates, and protein accumulation rates on protein solubility in E. coli. Fermentation expression of rHb1.1 at 30 degrees C from cultures containing a medium or high globin gene dosage (pBR-based or pUC-based plasmids with rHb1.1 genes under the control of the tac promoter) was compared. A medium gene dosage resulted in rHb1.1 accumulating to approximately 7% of the soluble cell protein, of which 78% was soluble. A high globin gene dosage resulted in a > or = 3-fold increase in total globin to 23 to 24% of the soluble cell protein, but 70% was insoluble. Accumulation of insoluble rHb1.1 began immediately upon induction. The proportion of rHb1.1 from the high globin gene dosage that accumulated as insoluble globin was affected by reducing (i) the inducer concentration and (ii) the temperature. Reducing the inducer concentration reduced globin synthesis up to eightfold but increased the proportion of soluble rHb1.1 to 93%. In contrast, total globin protein synthesis was barely affected by reducing the temperature from 30 to 26 degrees C, while soluble globin accumulation increased > 2-fold to approximately 15% of the soluble cell protein. The contrast between the effects of reducing rates of protein synthesis and accumulation and those of reducing temperature suggests that lower temperature stabilizes one or more folding intermediates. We propose a simplified physical model which integrates protein synthesis, folding, and heme association. This model shows that temperature-dependent apoglobin stability is the most critical factor in soluble rHb1.1 accumulation. PMID:9361418

Evaluation of the stability of uranyl peroxo-carbonato complex ions in carbonate media at different temperatures

International Nuclear Information System (INIS)

Kim, Kwang-Wook; Lee, Keun-Young; Chung, Dong-Yong; Lee, Eil-Hee; Moon, Jei-Kwon; Shin, Dong-Woo

2012-01-01

Highlights: ► The stability of peroxide in uranyl peroxo carbonato complex solutions with different temperatures was characterized. ► The decomposition rate of uranyl peroxo carbonato complex ion to uranyl tris-carbonato complex ion was observed to increase with temperature ► The decomposition kinetics of uranyl peroxo carbonato complex ions was evaluated by absorption and Raman spectroscopies. ► A precipitate of uranyl peroxo carbonato complex solution was evaluated with XRD. - Abstract: This work studied the stability of peroxide in uranyl peroxo carbonato complex ions in a carbonate solution with hydrogen peroxide using absorption and Raman spectroscopies, and evaluated the temperature dependence of the decomposition characteristics of uranyl peroxo carbonato complex ions in the solution. The uranyl peroxo carbonato complex ions self-decomposed more rapidly into uranyl tris-carbonato complex ions in higher temperature carbonate solutions. The concentration of peroxide in the solution without free hydrogen peroxide represents the concentration of uranyl peroxo carbonato complex ions in a mixture of uranyl peroxo carbonato complex and uranyl tris-carbonato complex ions. The self-decomposition of the uranyl peroxo carbonato complex ions was a first order reaction, and its activation energy was evaluated to be 7.144 × 10 3 J mol −1 . The precipitation of sodium uranium oxide hydroxide occurred when the amount of uranyl tris-carbonato complex ions generated from the decomposition of the uranyl peroxo carbonato complex ions exceeded the solubility of uranyl tris-carbonato ions in the solution at the solution temperature.

Creation of Single Chain of Nanoscale Skyrmion Bubbles with Record-high Temperature Stability in a Geometrically Confined Nanostripe

KAUST Repository

Hou, Zhipeng; Zhang, Qiang; Xu, Guizhou; Gong, Chen; Ding, Bei; Wang, Yue; Li, Hang; Liu, Enke; Xu, Feng; Zhang, Hongwei; Yao, Yuan; Wu, Guangheng; Zhang, Xixiang; Wang, Wenhong

2018-01-01

Nanoscale topologically nontrivial spin textures, such as magnetic skyrmions, have been identified as promising candidates for the transport and storage of information for spintronic applications, notably magnetic racetrack memory devices. The design and realization of a single skyrmion chain at room temperature (RT) and above in the low-dimensional nanostructures are of great importance for future practical applications. Here, we report the creation of a single skyrmion bubble chain in a geometrically confined Fe3Sn2 nanostripe with a width comparable to the featured size of a skyrmion bubble. Systematic investigations on the thermal stability have revealed that the single chain of skyrmion bubbles can keep stable at temperatures varying from RT up to a record-high temperature of 630 K. This extreme stability can be ascribed to the weak temperature-dependent magnetic anisotropy and the formation of edge states at the boundaries of the nanostripes. The realization of the highly stable skyrmion bubble chain in a geometrically confined nanostructure is a very important step toward the application of skyrmion-based spintronic devices.

Creation of Single Chain of Nanoscale Skyrmion Bubbles with Record-high Temperature Stability in a Geometrically Confined Nanostripe

KAUST Repository

Hou, Zhipeng

2018-01-04

Nanoscale topologically nontrivial spin textures, such as magnetic skyrmions, have been identified as promising candidates for the transport and storage of information for spintronic applications, notably magnetic racetrack memory devices. The design and realization of a single skyrmion chain at room temperature (RT) and above in the low-dimensional nanostructures are of great importance for future practical applications. Here, we report the creation of a single skyrmion bubble chain in a geometrically confined Fe3Sn2 nanostripe with a width comparable to the featured size of a skyrmion bubble. Systematic investigations on the thermal stability have revealed that the single chain of skyrmion bubbles can keep stable at temperatures varying from RT up to a record-high temperature of 630 K. This extreme stability can be ascribed to the weak temperature-dependent magnetic anisotropy and the formation of edge states at the boundaries of the nanostripes. The realization of the highly stable skyrmion bubble chain in a geometrically confined nanostructure is a very important step toward the application of skyrmion-based spintronic devices.

Development of failure criterion for Kevlar-epoxy fabric laminates

Science.gov (United States)

Tennyson, R. C.; Elliott, W. G.

1984-01-01

The development of the tensor polynomial failure criterion for composite laminate analysis is discussed. In particular, emphasis is given to the fabrication and testing of Kevlar-49 fabric (Style 285)/Narmco 5208 Epoxy. The quadratic-failure criterion with F(12)=0 provides accurate estimates of failure stresses for the Kevlar/Epoxy investigated. The cubic failure criterion was re-cast into an operationally easier form, providing the engineer with design curves that can be applied to laminates fabricated from unidirectional prepregs. In the form presented no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exists at present to generalize this approach for all undirectional prepregs and its use must be restricted to the generic materials investigated to-date.

Assessing stress-related treatment needs among girls at risk for poor functional outcomes: The impact of cumulative adversity, criterion traumas, and non-criterion events.

Science.gov (United States)

Lansing, Amy E; Plante, Wendy Y; Beck, Audrey N

2017-05-01

Despite growing recognition that cumulative adversity (total stressor exposure, including complex trauma), increases the risk for psychopathology and impacts development, assessment strategies lag behind: Adversity-related mental health needs (symptoms, functional impairment, maladaptive coping) are typically assessed in response to only one qualifying Criterion-A traumatic event. This is especially problematic for youth at-risk for health and academic disparities who experience cumulative adversity, including non-qualifying events (separation from caregivers) which may produce more impairing symptomatology. Data from 118 delinquent girls demonstrate: (1) an average of 14 adverse Criterion-A and non-Criterion event exposures; (2) serious maladaptive coping strategies (self-injury) directly in response to cumulative adversity; (3) more cumulative adversity-related than worst-event related symptomatology and functional impairment; and (4) comparable symptomatology, but greater functional impairment, in response to non-Criterion events. These data support the evaluation of mental health needs in response to cumulative adversity for optimal identification and tailoring of services in high-risk populations to reduce disparities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Linear stability analysis of heated parallel channels

International Nuclear Information System (INIS)

Nourbakhsh, H.P.; Isbin, H.S.

1982-01-01

An analyis is presented of thermal hydraulic stability of flow in parallel channels covering the range from inlet subcooling to exit superheat. The model is based on a one-dimensional drift velocity formulation of the two phase flow conservation equations. The system of equations is linearized by assuming small disturbances about the steady state. The dynamic response of the system to an inlet flow perturbation is derived yielding the characteristic equation which predicts the onset of instabilities. A specific application is carried out for homogeneous and regional uniformly heated systems. The particular case of equal characteristic frequencies of two-phase and single phase vapor region is studied in detail. The D-partition method and the Mikhailov stability criterion are used for determining the marginal stability boundary. Stability predictions from the present analysis are compared with the experimental data from the solar test facility. 8 references

Novel stability criteria for uncertain delayed Cohen-Grossberg neural networks using discretized Lyapunov functional

International Nuclear Information System (INIS)

Souza, Fernando O.; Palhares, Reinaldo M.; Ekel, Petr Ya.

2009-01-01

This paper deals with the stability analysis of delayed uncertain Cohen-Grossberg neural networks (CGNN). The proposed methodology consists in obtaining new robust stability criteria formulated as linear matrix inequalities (LMIs) via the Lyapunov-Krasovskii theory. Particularly one stability criterion is derived from the selection of a parameter-dependent Lyapunov-Krasovskii functional, which allied with the Gu's discretization technique and a simple strategy that decouples the system matrices from the functional matrices, assures a less conservative stability condition. Two computer simulations are presented to support the improved theoretical results.

Criterion for the engineering performance of carbon materials under neutron irradiation

International Nuclear Information System (INIS)

Virgil'ev, Yu.S.

2002-01-01

The criterion for the engineering performance and substation of its applicability to the reactor graphite are proposed. The complex indicator, representing the ratio of strength limits by compression and bending is proposed as the above criterion, characterizing the graphite quality. The growth of this criterion indicates the accumulation of large heterogeneities microcracks of technological or radiation character. The decrease in this indicator testifies to the growth of small heterogeneities, and consequently to the increase in the graphite engineering performance [ru

The thermal stability of magnetically exchange coupled MnBi/FeCo composites at electric motor working temperature

Science.gov (United States)

Cheng, Ye; Wang, Hongying; Li, Zhigang; Liu, Wanhui; Bao, Ilian

2018-04-01

The magnetically exchange coupled MnBi/FeCo composites were synthesized through a magnetic self-assembly process. The MnBi/FeCo composites were then hot pressed in a magnetic field to form magnets. The thermal stability of the magnets were tested by annealing at electric motor working temperature of 200 °C for 20, 40 and 60 h, respectively. It was found that after heating for 20 h, there was negligible change in its hysteresis loop. However, when the heating time was increased 40 and 60 h, the magnetic hysteresis loops presented two-phase magnetic behaviors, and the maximum energy products of the magnet were decreased. This research showed that the magnetically exchange coupled MnBi/FeCo composites had low thermal stability at electric motor working temperature.

Performance and stability of a liquid anode high-temperature metal-air battery

Science.gov (United States)

Otaegui, L.; Rodriguez-Martinez, L. M.; Wang, L.; Laresgoiti, A.; Tsukamoto, H.; Han, M. H.; Tsai, C.-L.; Laresgoiti, I.; López, C. M.; Rojo, T.

2014-02-01

A High-Temperature Metal-Air Battery (HTMAB) that operates based on a simple redox reaction between molten metal and atmospheric oxygen at 600-1000 °C is presented. This innovative HTMAB concept combines the technology of conventional metal-air batteries with that of solid oxide fuel cells to provide a high energy density system for many applications. Electrochemical reversibility is demonstrated with 95% coulomb efficiency. Cell sealing has been identified as a key issue in order to determine the end-of-charge voltage, enhance coulomb efficiency and ensure long term stability. In this work, molten Sn is selected as anode material. Low utilization of the stored material due to precipitation of the SnO2 on the electrochemically active area limits the expected capacity, which should theoretically approach 903 mAh g-1. Nevertheless, more than 1000 charge/discharge cycles are performed during more than 1000 h at 800 °C, showing highly promising results of stability, reversibility and cyclability.

Entanglement criterion for tripartite systems based on local sum uncertainty relations

Science.gov (United States)

Akbari-Kourbolagh, Y.; Azhdargalam, M.

2018-04-01

We propose a sufficient criterion for the entanglement of tripartite systems based on local sum uncertainty relations for arbitrarily chosen observables of subsystems. This criterion generalizes the tighter criterion for bipartite systems introduced by Zhang et al. [C.-J. Zhang, H. Nha, Y.-S. Zhang, and G.-C. Guo, Phys. Rev. A 81, 012324 (2010), 10.1103/PhysRevA.81.012324] and can be used for both discrete- and continuous-variable systems. It enables us to detect the entanglement of quantum states without having a complete knowledge of them. Its utility is illustrated by some examples of three-qubit, qutrit-qutrit-qubit, and three-mode Gaussian states. It is found that, in comparison with other criteria, this criterion is able to detect some three-qubit bound entangled states more efficiently.

Stability of people exposed to water flows

Directory of Open Access Journals (Sweden)

E. Martínez-Gomariz

2016-01-01

Full Text Available Our cities are formed by several elements which are exposed to floods of a magnitude according to the importance of the rainfall event and the design of the urban drainage system. The most important components in the cities are the pedestrians who develop various activities during rain events. Focusing on pedestrians, the research on their stability when they are exposed to water flows provides the necessary knowledge to understand and manage the associated hazard for them. In this research, several experiments with humans were carried out in order to determine the stability limits to pedestrians crossing through a water flow in a real scale platform. The results obtained and by comparing those with human stability criteria proposed by other authors and guidelines provide a more restrictive criterion.

Microscopic Superconductivity and Room Temperature Electronics of High-Tc Cuprates

International Nuclear Information System (INIS)

Liu Fusui; Chen Wanfang

2008-01-01

This paper points out that the Landau criterion for macroscopic superfluidity of He II is only a criterion for microscopic superfluidity of 4 He, extends the Landau criterion to microscopic superconductivity in fermions (electron and hole) system and system with Cooper pairs without long-range phase coherence. This paper gives another three non-superconductive systems that are of microscopic superconductivity. This paper demonstrates that one application of microscopic superconductivity is to establish room temperature electronics of the high-T c cuprates

Mercier criterion for high-β tokamaks

International Nuclear Information System (INIS)

Galvao, R.M.O.

1984-01-01

An expression, for the application of the Mercier criterion to numerical studies of diffuse high-β tokamaks (β approximatelly Σ,q approximatelly 1), which contains only leading order contributions in the high-β tokamak approximation is derived. (L.C.) [pt

Stability of 2-Alkylcyclobutanones in irradiated retort pouch Gyudon topping during room temperature storage

International Nuclear Information System (INIS)

Kitagawa, Yoko; Okihashi, Masahiro; Takatori, Satoshi; Fukui, Naoki; Kajimura, Keiji; Obana, Hirotaka; Furuta, Masakazu

2016-01-01

2-Alkylcyclobutanones (ACBs), such as 2-dodecylcyclobutanone (DCB) and 2-tetradecylcylobutanone (TCB) are specific products in the irradiated liquid. Thus, DCB and TCB are suitable for indicators of the irradiation history of food. We previously reported DCB and TCB concentrations in irradiated retort pouch Gyudon topping (instant Gyudon mixes which were made from a beef, onion and soy sauce and could be preserved for a long term at room temperature) after storage for one year. Here, we have evaluated the stability of ACBs preserved in irradiated retort pouch Gyudon topping at room temperature for three years. Although interfering peaks were detected frequently after the storage at room temperature, it was possible for the detection of the irradiation history and there was no apparent decrease of ACBs concentrations in comparison with the one year storage after irradiation. These results concluded that DCB and TCB formed in retort pouch would be stable at room temperature for three years. (author)

The Absolute Stability Analysis in Fuzzy Control Systems with Parametric Uncertainties and Reference Inputs

Science.gov (United States)

Wu, Bing-Fei; Ma, Li-Shan; Perng, Jau-Woei

This study analyzes the absolute stability in P and PD type fuzzy logic control systems with both certain and uncertain linear plants. Stability analysis includes the reference input, actuator gain and interval plant parameters. For certain linear plants, the stability (i.e. the stable equilibriums of error) in P and PD types is analyzed with the Popov or linearization methods under various reference inputs and actuator gains. The steady state errors of fuzzy control systems are also addressed in the parameter plane. The parametric robust Popov criterion for parametric absolute stability based on Lur'e systems is also applied to the stability analysis of P type fuzzy control systems with uncertain plants. The PD type fuzzy logic controller in our approach is a single-input fuzzy logic controller and is transformed into the P type for analysis. In our work, the absolute stability analysis of fuzzy control systems is given with respect to a non-zero reference input and an uncertain linear plant with the parametric robust Popov criterion unlike previous works. Moreover, a fuzzy current controlled RC circuit is designed with PSPICE models. Both numerical and PSPICE simulations are provided to verify the analytical results. Furthermore, the oscillation mechanism in fuzzy control systems is specified with various equilibrium points of view in the simulation example. Finally, the comparisons are also given to show the effectiveness of the analysis method.

Electricity Consumption Forecasting Scheme via Improved LSSVM with Maximum Correntropy Criterion

Directory of Open Access Journals (Sweden)

Jiandong Duan

2018-02-01

Full Text Available In recent years, with the deepening of China’s electricity sales side reform and electricity market opening up gradually, the forecasting of electricity consumption (FoEC becomes an extremely important technique for the electricity market. At present, how to forecast the electricity accurately and make an evaluation of results scientifically are still key research topics. In this paper, we propose a novel prediction scheme based on the least-square support vector machine (LSSVM model with a maximum correntropy criterion (MCC to forecast the electricity consumption (EC. Firstly, the electricity characteristics of various industries are analyzed to determine the factors that mainly affect the changes in electricity, such as the gross domestic product (GDP, temperature, and so on. Secondly, according to the statistics of the status quo of the small sample data, the LSSVM model is employed as the prediction model. In order to optimize the parameters of the LSSVM model, we further use the local similarity function MCC as the evaluation criterion. Thirdly, we employ the K-fold cross-validation and grid searching methods to improve the learning ability. In the experiments, we have used the EC data of Shaanxi Province in China to evaluate the proposed prediction scheme, and the results show that the proposed prediction scheme outperforms the method based on the traditional LSSVM model.

Subgrade stabilization alternatives to lime and cement.

Science.gov (United States)

2010-04-15

This project involved four distinct research activities, (1) the influence of temperature on lime-stabilized soils, (2) the influence of temperature on cement-stabilized soils (3) temperature modeling of stabilized subgrade and (4) use of calcium chl...

Extrap interchange stability

International Nuclear Information System (INIS)

Scheffel, J.

1989-05-01

This is a non-linear MHD study of Extrap interchange stability. The closed-line stability criterion d(pgγ)/dψ ≥ 0 is used for fully 2-D numerical calculations of marginally stable equilibria. It is found that Extrap has a stabilzing effect on these modes. The reason for this is that q = Ιdl/B diverges towards the separatrix, which forms a boundary for the pinch. Consequently, in comparison with the 1-D Z-pinch, the Extrap octupole field allows steeper pressure profile in the boundary region. This stabilizing effect is shown to diminish in equilibria with an externally imposed axial magnetic field. It is also shown how the shape of the plasma cross-section depends on the relative direction of plasma current and external rod currents, when the current density j is finite on the boundary. Unfavourable curvature and higher values of j at the boundary are obtained in the case of parallel currents. Only when j vanishes at the separatrix, the cross-section can be truly square-shaped. The type of singularity of q at the separatrix is derived, as well as criteria for j to become singular

Study on the quantitative rod internal pressure design criterion

International Nuclear Information System (INIS)

Kim, Kyu Tae; Kim, Oh Hwan; Han, Hee Tak

1991-01-01

The current rod internal pressure criterion permits fuel rods to operate with internal pressures in excess of system pressure only if internal overpressure does not cause the diametral gap enlargement. In this study, the generic allowable internal gas pressure not violating this criterion is estimated as a function of rod power. The results show that the generic allowable internal gas pressure decreases linearly with the increase of rod power. Application of the generic allowable internal gas pressure for the rod internal pressure design criterion will result in the simplication of the current design procedure for checking the diametral gap enlargement caused by internal overpressure because according to the current design procedure the cladding creepout rate should be compared with the fuel swelling rate at each axial node at each time step whenever internal pressure exceeds the system pressure. (Author)

An experimental study on the effects of temperature and magnetic field strength on the magnetorheological fluid stability and MR effect.

Science.gov (United States)

Rabbani, Yahya; Ashtiani, Mahshid; Hashemabadi, Seyed Hassan

2015-06-14

In this study, the stability and rheological properties of a suspension of carbonyl iron microparticles (CIMs) in silicone oil were investigated within a temperature range of 10 to 85 °C. The effect of adding two hydrophobic (stearic and palmitic) acids on the stability and magnetorheological effect of a suspension of CIMs in silicone oil was studied. According to the results, for preparing a stable and efficient magnetorheological (MR) fluid, additives should be utilized. Therefore, 3 wt% of stearic acid was added to the MR fluid which led to an enhancement of the fluid stability over 92% at 25 °C. By investigating shear stress variation due to the changes in the shear rate for acid-based MR fluids, the maximum yield stress was obtained by fitting the Bingham plastic rheological model at high shear rates. Based on the existing correlations of yield stress and either temperature or magnetic field strength, a new model was fitted to the experimental data to monitor the simultaneous effect of magnetic field strength and temperature on the maximum yield stress. The results demonstrated that as the magnetic field intensified or the temperature decreased, the maximum yield stress increased dramatically. In addition, when the MR fluid reached its magnetic saturation, the viscosity of fluid depended only on the shear rate.

Factors that impact the stability of vitamin C at intermediate temperatures in a food matrix.

Science.gov (United States)

Herbig, Anna-Lena; Renard, Catherine M G C

2017-04-01

The study comprises a systematic and quantitative evaluation of potential intrinsic and extrinsic factors that impact vitamin C degradation in a real food matrix. The supernatant of centrifuged apple purée was fortified in vitamin C, and degradation was followed without stirring. Model discrimination indicated better fit for the zero order model than the first order model which was hence chosen for determination of rate constants. pH influenced strongly vitamin C degradation in citrate-phosphate buffer but not in the apple purée serum. To get an idea of the impact of the food matrix, stability in apple purée serum was compared with that in carrot purée. In the latter, stability was slightly higher. Vitamin C degradation rates were not influenced by its initial concentration. The temperature effect was only marked in the temperature range 40-60°C. In the range 60-80°C, filling height of tubes had the greatest impact. Copyright © 2016 Elsevier Ltd. All rights reserved.

Generalized Majority Logic Criterion to Analyze the Statistical Strength of S-Boxes

Science.gov (United States)

Hussain, Iqtadar; Shah, Tariq; Gondal, Muhammad Asif; Mahmood, Hasan

2012-05-01

The majority logic criterion is applicable in the evaluation process of substitution boxes used in the advanced encryption standard (AES). The performance of modified or advanced substitution boxes is predicted by processing the results of statistical analysis by the majority logic criteria. In this paper, we use the majority logic criteria to analyze some popular and prevailing substitution boxes used in encryption processes. In particular, the majority logic criterion is applied to AES, affine power affine (APA), Gray, Lui J, residue prime, S8 AES, Skipjack, and Xyi substitution boxes. The majority logic criterion is further extended into a generalized majority logic criterion which has a broader spectrum of analyzing the effectiveness of substitution boxes in image encryption applications. The integral components of the statistical analyses used for the generalized majority logic criterion are derived from results of entropy analysis, contrast analysis, correlation analysis, homogeneity analysis, energy analysis, and mean of absolute deviation (MAD) analysis.

Conflicting views on a neutrality criterion for radioactive-waste management

International Nuclear Information System (INIS)

Cochran, T.B.; Bodde, D.L.

1983-01-01

Two essays are presented by authors who agree that risks imposed on future generations through the management of radioactive waste are acceptable if they meet a criterion of neutrality, but who disagree on the interpretation of the neutrality criterion. The first viewpoint argues that acceptable isolation of high-level radioactive waste is yet to be accomplished and that a fundamental criterion for radioactive waste disposal must include consideration of the intergenerational radiation effects. The second essay promotes balanced resource allocation, technological progress, and adequate problem-solving institutions as the solution to the problem. The debate illustrates the complexities involved in applying philosophical principles to public policy, even when the principles have been agreed upon. 23 references, 1 figure

Study on the influences of reduction temperature on nickel-yttria-stabilized zirconia solid oxide fuel cell anode using nickel oxide-film electrode

Science.gov (United States)

Jiao, Zhenjun; Ueno, Ai; Suzuki, Yuji; Shikazono, Naoki

2016-10-01

In this study, the reduction processes of nickel oxide at different temperatures were investigated using nickel-film anode to study the influences of reduction temperature on the initial performances and stability of nickel-yttria-stabilized zirconia anode. Compared to conventional nickel-yttria-stabilized zirconia composite cermet anode, nickel-film anode has the advantage of direct observation at nickel-yttria-stabilized zirconia interface. The microstructural changes were characterized by scanning electron microscopy. The reduction process of nickel oxide is considered to be determined by the competition between the mechanisms of volume reduction in nickel oxide-nickel reaction and nickel sintering. Electrochemical impedance spectroscopy was applied to analyze the time variation of the nickel-film anode electrochemical characteristics. The anode performances and microstructural changes before and after 100 hours discharging and open circuit operations were analyzed. The degradation of nickel-film anode is considered to be determined by the co-effect between the nickel sintering and the change of nickel-yttria-stabilized zirconia interface bonding condition.

Global Exponential Stability of Periodic Oscillation for Nonautonomous BAM Neural Networks with Distributed Delay

Directory of Open Access Journals (Sweden)

Hongli Liu

2009-01-01

Full Text Available We derive a new criterion for checking the global stability of periodic oscillation of bidirectional associative memory (BAM neural networks with periodic coefficients and distributed delay, and find that the criterion relies on the Lipschitz constants of the signal transmission functions, weights of the neural network, and delay kernels. The proposed model transforms the original interacting network into matrix analysis problem which is easy to check, thereby significantly reducing the computational complexity and making analysis of periodic oscillation for even large-scale networks.

Elitism, Sharing and Ranking Choices in Evolutionary Multi-Criterion Optimisation

OpenAIRE

Pursehouse, R.C.; Fleming, P.J.

2002-01-01

Elitism and sharing are two mechanisms that are believed to improve the performance of an evolutionary multi-criterion optimiser. The relative performance of of the two most popular ranking strategies is largely unknown. Using a new empirical inquiry framework, this report studies the effect of elitism, sharing and ranking design choices using a benchmark suite of two-criterion problems.........

Evaluation of the stability of uranyl peroxo-carbonato complex ions in carbonate media at different temperatures

Energy Technology Data Exchange (ETDEWEB)

Kim, Kwang-Wook, E-mail: nkwkim@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Lee, Keun-Young; Chung, Dong-Yong; Lee, Eil-Hee; Moon, Jei-Kwon [Korea Atomic Energy Research Institute, 1045 Daedeok daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Shin, Dong-Woo [Gyeongsang National University, 900 Gajwa, Jinju 660-701 (Korea, Republic of)

2012-09-30

Highlights: Black-Right-Pointing-Pointer The stability of peroxide in uranyl peroxo carbonato complex solutions with different temperatures was characterized. Black-Right-Pointing-Pointer The decomposition rate of uranyl peroxo carbonato complex ion to uranyl tris-carbonato complex ion was observed to increase with temperature Black-Right-Pointing-Pointer The decomposition kinetics of uranyl peroxo carbonato complex ions was evaluated by absorption and Raman spectroscopies. Black-Right-Pointing-Pointer A precipitate of uranyl peroxo carbonato complex solution was evaluated with XRD. - Abstract: This work studied the stability of peroxide in uranyl peroxo carbonato complex ions in a carbonate solution with hydrogen peroxide using absorption and Raman spectroscopies, and evaluated the temperature dependence of the decomposition characteristics of uranyl peroxo carbonato complex ions in the solution. The uranyl peroxo carbonato complex ions self-decomposed more rapidly into uranyl tris-carbonato complex ions in higher temperature carbonate solutions. The concentration of peroxide in the solution without free hydrogen peroxide represents the concentration of uranyl peroxo carbonato complex ions in a mixture of uranyl peroxo carbonato complex and uranyl tris-carbonato complex ions. The self-decomposition of the uranyl peroxo carbonato complex ions was a first order reaction, and its activation energy was evaluated to be 7.144 Multiplication-Sign 10{sup 3} J mol{sup -1}. The precipitation of sodium uranium oxide hydroxide occurred when the amount of uranyl tris-carbonato complex ions generated from the decomposition of the uranyl peroxo carbonato complex ions exceeded the solubility of uranyl tris-carbonato ions in the solution at the solution temperature.

Formation and stability of sputtered clusters

International Nuclear Information System (INIS)

Andersen, H.H.

1989-01-01

Current theory for the formation of sputtered clusters states that either atoms are sputtered individually and aggregate after having left the surface or they are sputtered as complete clusters. There is no totally sharp boundary between the two interpretations, but experimental evidence is mainly thought to favour the latter model. Both theories demand a criterion for the stability of the clusters. In computer simulations of sputtering, the idea has been to use the same interaction potential as in the lattice computations to judge the stability. More qualitatively, simple geometrical shapes have also been looked for. It is found here, that evidence for 'magic numbers' and electron parity effects in clusters have existed in the sputtering literature for a long time, making more sophisticated stability criteria necessary. The breakdown of originally sputtered metastable clusters into stable clusters gives strong support to the 'sputtered as clusters' hypothesis. (author)

Evaluation of stability of allergen extracts for sublingual immunotherapy during transport under unfavourable temperature conditions with an innovative thermal insulating packaging.

Science.gov (United States)

Puccinelli, P; Natoli, V; Dell'albani, I; Scurati, S; Incorvaia, C; Barbieri, S; Masieri, S; Frati, F

2013-10-01

Many pharmaceutical and biotechnological products are temperature-sensitive and should normally be kept at a controlled temperature, particularly during transport, in order to prevent the loss of their stability and activity. Therefore, stability studies should be performed for temperature-sensitive products, considering product characteristics, typical environmental conditions, and anticipating environmental extremes that may occur during product transport in a specific country. Staloral products for sublingual immunotherapy are temperature sensitive and are labelled for maintenance under refrigerated conditions (2-8°C). Given the peculiar climatic context of Italy and the great temperature fluctuations that may occur during transport, this study was aimed at evaluating the impact of a new engineered thermal insulating packaging for Staloral. In particular, the purpose was to assess whether the new packaging could create a container condition able to preserve the stability and immunological activity of the product during the transport phase throughout Italy. The results showed that the range of temperatures that can affect the product, in the area surrounding the product packaging, may reach a peak of 63°C during transport under the most unfavourable climatic conditions, i.e. in a non-refrigerated van during the summer season, from the site of production in France to the patient's house in Catania, the city with the highest temperatures in Italy. However, the highest temperature reached inside the vaccine did not exceed 45°C over a period of about 2 h. The ELISA inhibition test on samples subjected to the extreme temperature conditions previously defined (45°C) showed an immunological activity higher than 75% of that initially measured and was comparable to those obtained with samples stored at controlled temperature (5°C). This means that, even in the worst case scenario, the structure of the allergen extracts is not influenced and the vaccine potency is

Validation of a Criterion for Cam Mechanisms Optimization Using Constraints upon Cam’s Curvature

Directory of Open Access Journals (Sweden)

Stelian Alaci

2016-06-01

Full Text Available For the mechanism with rotating cam and knife-edge follower, an optimization criterion by means of imposed constraints upon cam’s curvature is expressed in a special coordinate system. Thus, stating the optimization criterion in the coordinate system defined by the mechanisms constructive parameters -eccentricity and minimum follower’s stroke, a contour is obtained for any position of the mechanism. The optimization criterion assumes establishing the position of the characteristic point of the mechanism with respect to this contour. Fulfillment of optimization criterion assumes that the characteristic point is positioned in the same manner with respect to all contours. The optimization criterion is simplified when considering the envelope of the contours. The method is exemplified using two mechanisms, with the cams priori satisfying the criterion.

Relativistic stability of interacting Fermi gas in a strong magnetic field

International Nuclear Information System (INIS)

Wang Lilin; Tian Jincheng; Men Fudian; Zhang Yipeng

2013-01-01

By means of the single particle energy spectrum of weak interaction between fermions and Poisson formula, the thermodynamic potential function of relativistic Fermi gas in a strong magnetic field is derived. Based on this, we obtained the criterion of stability for the system. The results show that the mechanics stability of a Fermi gas with weak interacting is influenced by the interacting. While the magnetic field is able to regulate the influence and the relativistic effect has almost no effect on it. (authors)

Variation and design criterion of heat load ratio of generator for air cooled lithium bromide–water double effect absorption chiller

International Nuclear Information System (INIS)

Li, Zeyu; Liu, Liming; Liu, Jinping

2016-01-01

Highlights: • Design criterion of heat load ratio of generator is vital to system performance. • Heat load ratio of generator changes with working condition. • Change of heat load ratio of generator for four systems was obtained and compared. • Design criterion of heat load ratio of generator was presented. - Abstract: The heat load ratio of generator (HLRG) is a special system parameter because it is not fixed at the design value but changes with the working condition. For the air cooled chiller, the deviation from the design working condition occurs easily due to the variation of the surrounding temperature. The system is likely to suffer from crystallization when the working condition is different from the designed one if the HLRG is designed improperly. Consequently, the design criterion of HLRG based on a broad range of working condition is essential and urgent to the development of air cooled lithium bromide–water double effect absorption chiller. This paper mainly deals with the variation of HLRG with the working condition as well as corresponding design criterion. Four types of double effect chillers named series, pre-parallel, rear parallel and reverse parallel flow system were considered. The parametric model was developed by the introduction of a new thermodynamic relationship of generator. The change of HLRG for different types of chillers with the working condition was analyzed and compared. The corresponding design criterion of HLRG was presented. This paper is helpful for further improvement of the performance and reliability of air cooled lithium bromide–water double effect absorption chiller.

Room temperature synthesis of PbSe quantum dots in aqueous solution: Stabilization by interactions with ligands

Science.gov (United States)

Primera-Pedrozo, Oliva M.; Arslan, Zikri; Rasulev, Bakhtiyor; Leszczynski, Jerzy

2011-01-01

An aqueous route of synthesis is described for rapid synthesis of lead selenide quantum dots (PbSe QDs) at room temperature in an attempt to produce water-soluble and stable nanocrystals. Several thiol-ligands, including thioglycolic acid (TGA), thioglycerol (TGC), 3-mercaptopropionic acid (MPA), 2-mercaptoethyleamine hydrochloride (MEA), 6-mercaptohexanoic acid (MHA), and L-cysteine (L-cys), were used for capping/stabilization of PbSe QDs. The effects of the ligands on the stability of PbSe QDs were evaluated for a period of two months at room temperature under normal light conditions and at 4 °C in dark. The TGA- and MEA-capped QDs exhibited the highest stability prior to purification, almost two months when kept in dark at 4 °C. However, the stability of TGA-capped QDs was reduced substantially after purification to about 5 days under same conditions, while MEA-capped QDs did not show any significant instability. The stabilization energies of Pb-thiolate complexes determined by theoretical DFT simulations supported the experimental results. The PbSe QDs capped with TGA, MPA and MEA were successfully purified and re-dispersed in water, while those stabilized with TGC, MHA and L-cys aggregated during purification attempts. The purified PbSe QDs possess very susceptible surface resulting in poor stability for about 30 – 45 min after re-dispersion in water. In the presence of an excess of free ligand, the stability increased up to 5 days for TGA-capped QDs at pH 7.19, 9 –12 days for MPA-capped QDs at pH 7.3–7.5 and 45–47 days for MEA-capped QDs at pH 7.35. X-Ray Diffraction (XRD) results showed that the QDs possess a cubic rock salt structure with the most intense peaks located at 2θ = 25.3° (200) and 2θ = 29.2° (100). TEM images showed that the size of the QDs ranges between 5 and 10 nm. ICP-MS results revealed that Pb:Se ratio was 1.26, 1.28, 3.85, 1.18, and 1.31 for the QDs capped with TGA, MPA, MEA, L-Cys, and TGC, respectively. The proposed method

Unifying perspective: Solitary traveling waves as discrete breathers in Hamiltonian lattices and energy criteria for their stability

Science.gov (United States)

Cuevas-Maraver, Jesús; Kevrekidis, Panayotis G.; Vainchtein, Anna; Xu, Haitao

2017-09-01

In this work, we provide two complementary perspectives for the (spectral) stability of solitary traveling waves in Hamiltonian nonlinear dynamical lattices, of which the Fermi-Pasta-Ulam and the Toda lattice are prototypical examples. One is as an eigenvalue problem for a stationary solution in a cotraveling frame, while the other is as a periodic orbit modulo shifts. We connect the eigenvalues of the former with the Floquet multipliers of the latter and using this formulation derive an energy-based spectral stability criterion. It states that a sufficient (but not necessary) condition for a change in the wave stability occurs when the functional dependence of the energy (Hamiltonian) H of the model on the wave velocity c changes its monotonicity. Moreover, near the critical velocity where the change of stability occurs, we provide an explicit leading-order computation of the unstable eigenvalues, based on the second derivative of the Hamiltonian H''(c0) evaluated at the critical velocity c0. We corroborate this conclusion with a series of analytically and numerically tractable examples and discuss its parallels with a recent energy-based criterion for the stability of discrete breathers.

Shrinkage Porosity Criterion and Its Application to A 5.5 Ton Steel Ingot

Directory of Open Access Journals (Sweden)

Zhang C.

2016-06-01

Full Text Available In order to predict the distribution of shrinkage porosity in steel ingot efficiently and accurately, a criterion R√L and a method to obtain its threshold value were proposed. The criterion R√L was derived based on the solidification characteristics of steel ingot and pressure gradient in the mushy zone, in which the physical properties, the thermal parameters, the structure of the mushy zone and the secondary dendrite arm spacing were all taken into consideration. The threshold value of the criterion R√L was obtained with combination of numerical simulation of ingot solidification and total solidification shrinkage rate. Prediction of the shrinkage porosity in a 5.5 ton ingot of 2Cr13 steel with criterion R√L>0.21 m · °C1/2 · s−3/2 agreed well with the results of experimental sectioning. Based on this criterion, optimization of the ingot was carried out by decreasing the height-to-diameter ratio and increasing the taper, which successfully eliminated the centreline porosity and further proved the applicability of this criterion.

Stability Analysis of a Run-of-River Diversion Hydropower Plant with Surge Tank and Spillway in the Head Pond

Directory of Open Access Journals (Sweden)

José Ignacio Sarasúa

2014-01-01

Full Text Available Run-of-river hydropower plants usually lack significant storage capacity; therefore, the more adequate control strategy would consist of keeping a constant water level at the intake pond in order to harness the maximum amount of energy from the river flow or to reduce the surface flooded in the head pond. In this paper, a standard PI control system of a run-of-river diversion hydropower plant with surge tank and a spillway in the head pond that evacuates part of the river flow plant is studied. A stability analysis based on the Routh-Hurwitz criterion is carried out and a practical criterion for tuning the gains of the PI controller is proposed. Conclusions about the head pond and surge tank areas are drawn from the stability analysis. Finally, this criterion is applied to a real hydropower plant in design state; the importance of considering the spillway dimensions and turbine characteristic curves for adequate tuning of the controller gains is highlighted.

A new criterion on the global exponential stability for cellular neural networks with multiple time-varying delays

International Nuclear Information System (INIS)

Jiang Haijun; Teng Zhidong

2005-01-01

In this Letter, based on the Lyapunov stability theorem as well as some facts about the positive definiteness and inequality of matrices, a new sufficient condition to ensure the global exponential stability of equilibrium point for autonomous delayed CNNs is obtained. This condition is less restrictive than given in the earlier references

Properties of plasma sheath with ion temperature in magnetic fusion devices

International Nuclear Information System (INIS)

Liu Jinyuan; Wang Feng; Sun Jizhong

2011-01-01

The plasma sheath properties in a strong magnetic field are investigated in this work using a steady state two-fluid model. The motion of ions is affected heavily by the strong magnetic field in fusion devices; meanwhile, the effect of ion temperature cannot be neglected for the plasma in such devices. A criterion for the plasma sheath in a strong magnetic field, which differs from the well-known Bohm criterion for low temperature plasma sheath, is established theoretically with a fluid model. The fluid model is then solved numerically to obtain detailed sheath information under different ion temperatures, plasma densities, and magnetic field strengths.

Updated Drainable Interstitial Liquid Volume Estimates for 119 Single Shell Tanks (SST) Declared Stabilized

International Nuclear Information System (INIS)

FIELD, J.G.

2000-01-01

This document assesses the volume of drainable interstitial liquid (DIL) and pumpable liquid remaining in 119 single-shell tanks (SSTs) that were previously stabilized. Based on the methodology and assumptions presented, the DIL exceeded the stabilization criterion of less than 50,000 gal in two of the 119 SSTs. Tank 241-C-102 had an estimated DIL of 62,000 gal, and the estimated DIL for tank 241-BY-103 was 58,000 gal. In addition, tanks 241-BX-103, 241-T-102, and 241-T-112 appear to exceed the stabilization criterion of 5,000 gal supernatant. An assessment of the source of the supernatant in these tanks is beyond the scope of this document. The actual DIL and pumpable liquid remaining volumes for each tank may vary significantly from estimated volumes as a result of specific tank waste characteristics that are not currently measured or defined. Further refinement to the pumpable liquid and DIL volume estimates may be needed as additional tank waste information is obtained

High-temperature stability of laser-joined silicon carbide components

Energy Technology Data Exchange (ETDEWEB)

Herrmann, Marion, E-mail: marion.herrmann@tu-dresden.de; Lippmann, Wolfgang; Hurtado, Antonio

2013-11-15

Silicon carbide is recommended for applications in energy technology due to its good high-temperature corrosion resistance, mechanical durability, and abrasion resistance. The prerequisite for use is often the availability of suitable technologies for joining or sealing the components. A laser-induced process using fillers and local heating of the components represents a possible low-cost option. Investigations in which yttrium aluminosilicate glass was used for laser-induced brazing of SiC components of varying geometry are presented. A four-point bending strength of 112 MPa was found for these joints. In burst tests, laser-joined components were found to withstand internal pressures of up to 54 MPa. Helium leak tests yielded leak rates of less than 10{sup –8} mbar l s{sup −1}, even after 300 h at 900 °C. In contrast, the assemblies showed an increased leak rate after annealing at 1050 °C. The short process time of the laser technique – in the range of a few seconds to a few minutes – results in high temperature gradients and transients. SEM analysis showed that the filler in the seam predominantly solidifies in a glassy state. Crystallization occurred during later thermal loading of the joined components, with chemical equilibrium being established. Differences in seam structures yielded from different cooling rates in the laser process could not be equalized by annealing. The results demonstrated the long-term stability of laser-brazed SiC assemblies to temperatures in the range of glass transformation (900 °C) of the yttrium aluminosilicate filler. In technological investigations, the suitability of the laser joining technique for sealing of SiC components with a geometry approximating that of a fuel element sleeve pin (pin) in a gas-cooled fast reactor was proven.

Judging Criterion of Controlled Structures with Closely Spaced Natural Frequencies

International Nuclear Information System (INIS)

Xie Faxiang; Sun Limin

2010-01-01

The structures with closely spaced natural frequencies widely exist in civil engineering; however, the judging criterion of the density of closely spaced frequencies is in dispute. This paper suggests a judging criterion for structures with closely spaced natural frequencies based on the analysis on a controlled 2-DOF structure. The analysis results indicate that the optimal control gain of the structure with velocity feedback is dependent on the frequency density parameter of structure and the maximum attainable additional modal damping ratio is 1.72 times of the frequency density parameter when state feedback is applied. Based on a brief review on the previous researches, a judging criterion related the minimum frequency density parameter and the required mode damping ratio was proposed.

Stability of test environments for performance evaluation of materials for the modular high-temperature gas-cooled reactor

International Nuclear Information System (INIS)

Edgemon, G.L.; Wilson, D.F.; Bell, G.E.C.

1993-01-01

Stability of the primary helium-based coolant test gas for use in performance ests of materials for the Modular High-Temperature Gas-Cooled Reactor (MHTGR) was determined. Results of tests of the initial gas chemistry from General Atomics (GA) at elevated temperatures, and the associated results predicted by the SOLGASMIX trademark modelling package are presented. Results indicated that for this gas composition and at flow rates obtainable in the test loop, 466 ± 24C is the highest temperature that can be maintained without significantly altering the specified gas chemistry. Four additional gas chemistries were modelled using SOLGASMIX trademark

A New Criterion for Prediction of Hot Tearing Susceptibility of Cast Alloys

Science.gov (United States)

Nasresfahani, Mohamad Reza; Niroumand, Behzad

2014-08-01

A new criterion for prediction of hot tearing susceptibility of cast alloys is suggested which takes into account the effects of both important mechanical and metallurgical factors and is believed to be less sensitive to the presence of volume defects such as bifilms and inclusions. The criterion was validated by studying the hot tearing tendency of Al-Cu alloy. In conformity with the experimental results, the new criterion predicted reduction of hot tearing tendency with increasing the copper content.

Concurrent Increases and Decreases in Local Stability and Conformational Heterogeneity in Cu, Zn Superoxide Dismutase Variants Revealed by Temperature-Dependence of Amide Chemical Shifts.

Science.gov (United States)

Doyle, Colleen M; Rumfeldt, Jessica A; Broom, Helen R; Sekhar, Ashok; Kay, Lewis E; Meiering, Elizabeth M

2016-03-08

The chemical shifts of backbone amide protons in proteins are sensitive reporters of local structural stability and conformational heterogeneity, which can be determined from their readily measured linear and nonlinear temperature-dependences, respectively. Here we report analyses of amide proton temperature-dependences for native dimeric Cu, Zn superoxide dismutase (holo pWT SOD1) and structurally diverse mutant SOD1s associated with amyotrophic lateral sclerosis (ALS). Holo pWT SOD1 loses structure with temperature first at its periphery and, while having extremely high global stability, nevertheless exhibits extensive conformational heterogeneity, with ∼1 in 5 residues showing evidence for population of low energy alternative states. The holo G93A and E100G ALS mutants have moderately decreased global stability, whereas V148I is slightly stabilized. Comparison of the holo mutants as well as the marginally stable immature monomeric unmetalated and disulfide-reduced (apo(2SH)) pWT with holo pWT shows that changes in the local structural stability of individual amides vary greatly, with average changes corresponding to differences in global protein stability measured by differential scanning calorimetry. Mutants also exhibit altered conformational heterogeneity compared to pWT. Strikingly, substantial increases as well as decreases in local stability and conformational heterogeneity occur, in particular upon maturation and for G93A. Thus, the temperature-dependence of amide shifts for SOD1 variants is a rich source of information on the location and extent of perturbation of structure upon covalent changes and ligand binding. The implications for potential mechanisms of toxic misfolding of SOD1 in disease and for general aspects of protein energetics, including entropy-enthalpy compensation, are discussed.

Quantum electrodynamics at a finite temperature with an external field destroying the stability of the vacuum

International Nuclear Information System (INIS)

Gavrilov, S.P.; Gitman, D.M.; Fradkin, E.S.

1987-01-01

A generating functional for expectation values is found for QED at a finite temperature with an external field which destroys the stability of the vacuum. The equations for connected Green functions and the effective action for the mean field are written out. Their representation is obtained in the form of an integral over the proper time for the Green function taking into account temperature effects in a constant uniform field. By means of this representation the polarization operator for the mean field in an external constant uniform field has been calculated

General Criterion for Harmonicity

Science.gov (United States)

Proesmans, Karel; Vandebroek, Hans; Van den Broeck, Christian

2017-10-01

Inspired by Kubo-Anderson Markov processes, we introduce a new class of transfer matrices whose largest eigenvalue is determined by a simple explicit algebraic equation. Applications include the free energy calculation for various equilibrium systems and a general criterion for perfect harmonicity, i.e., a free energy that is exactly quadratic in the external field. As an illustration, we construct a "perfect spring," namely, a polymer with non-Gaussian, exponentially distributed subunits which, nevertheless, remains harmonic until it is fully stretched. This surprising discovery is confirmed by Monte Carlo and Langevin simulations.

The effect of irradiation temperature on the quality improvement of Kimchi, Korean fermented vegetables, for its shelf stability

Energy Technology Data Exchange (ETDEWEB)

Park, Jin-Gyu [Team for Radiation Food Science and Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of); Department of Food and Biotechnology, Korea University, Chungnam 339-700 (Korea, Republic of); Kim, Jae-Hun; Park, Jae-Nam [Team for Radiation Food Science and Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of); Kim, Young-Duk [CJ Food Research and Development, CJ Corp., Seoul 152-050 (Korea, Republic of); Kim, Wang-Geun [Department of Application Science and Technology, Chosun University, Gwangju 501-759 (Korea, Republic of); Lee, Ju-Woon [Team for Radiation Food Science and Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of); Hwang, Han-Joon [Department of Food and Biotechnology, Korea University, Chungnam 339-700 (Korea, Republic of); Byun, Myung-Woo [Team for Radiation Food Science and Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of)], E-mail: mwbyun@kaeri.re.kr

2008-04-15

The present study was conducted to evaluate the effect of irradiation temperature on the shelf stability and quality of Kimchi during storage at 35 deg. C for 30 days. Kimchi samples were N{sub 2}-packaged and heated at 60 deg. C and then gamma irradiated at 20 kGy under various temperatures (room temperature, ice, dry ice, and liquid nitrogen). In the results of microbial, pH, and acidity analysis, combination treatment of heating and irradiation was able to sterilize microbes in Kimchi regardless of irradiation temperature. When Kimchi was irradiated under frozen temperatures, especially dry ice, the softening of texture and the deterioration of sensory quality of Kimchi were reduced. Also, ESR signal intensities were weakened due to the decrease of irradiation dose and temperature.

The effect of irradiation temperature on the quality improvement of Kimchi, Korean fermented vegetables, for its shelf stability

International Nuclear Information System (INIS)

Park, Jin-Gyu; Kim, Jae-Hun; Park, Jae-Nam; Kim, Young-Duk; Kim, Wang-Geun; Lee, Ju-Woon; Hwang, Han-Joon; Byun, Myung-Woo

2008-01-01

The present study was conducted to evaluate the effect of irradiation temperature on the shelf stability and quality of Kimchi during storage at 35 deg. C for 30 days. Kimchi samples were N 2 -packaged and heated at 60 deg. C and then gamma irradiated at 20 kGy under various temperatures (room temperature, ice, dry ice, and liquid nitrogen). In the results of microbial, pH, and acidity analysis, combination treatment of heating and irradiation was able to sterilize microbes in Kimchi regardless of irradiation temperature. When Kimchi was irradiated under frozen temperatures, especially dry ice, the softening of texture and the deterioration of sensory quality of Kimchi were reduced. Also, ESR signal intensities were weakened due to the decrease of irradiation dose and temperature

Stochastic Learning and the Intuitive Criterion in Simple Signaling Games

DEFF Research Database (Denmark)

Sloth, Birgitte; Whitta-Jacobsen, Hans Jørgen

A stochastic learning process for signaling games with two types, two signals, and two responses gives rise to equilibrium selection which is in remarkable accordance with the selection obtained by the intuitive criterion......A stochastic learning process for signaling games with two types, two signals, and two responses gives rise to equilibrium selection which is in remarkable accordance with the selection obtained by the intuitive criterion...

A spectral criterion for stability of a steady viscous incompressible flow past an obstacle

Czech Academy of Sciences Publication Activity Database

Neustupa, Jiří

2016-01-01

Roč. 18, č. 1 (2016), s. 133-156 ISSN 1422-6928 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : Navier - Stokes equations * Oseen equation * stability Subject RIV: BA - General Mathematics Impact factor: 1.106, year: 2016 http://link.springer.com/article/10.1007/s00021-015-0239-0

Effects of Temperature on the Performance and Stability of Recent COTS Silicon Oscillators

Science.gov (United States)

Patterson, Richard L.; Hammoud, Ahmad

2010-01-01

Silicon oscillators have lately emerged to serve as potential replacement for crystal and ceramic resonators to provide timing and clock signals in electronic systems. These semiconductor-based devices, including those that are based on MEMS technology, are reported to be resistant to vibration and shock (an important criteria for systems to be deployed in space), immune to EMI, consume very low current, require few or no external components, and cover a wide range of frequency for analog and digital circuits. In this work, the performance of five recently-developed COTS silicon oscillator chips from different manufacturers was determined within a temperature range that extended beyond the individual specified range of operation. In addition, restart capability at extreme temperatures, i.e. power switched on while the device was soaking at extreme (hot or cold) temperature, and the effects of thermal cycling under a wide temperature range on the operation of these silicon oscillators were also investigated. Performance characterization of each oscillator was obtained in terms of its output frequency, duty cycle, rise and fall times, and supply current at specific test temperatures. The five different oscillators tested operated beyond their specified temperature region, with some displaying excellent stability throughout the whole test temperature range. Others experienced some instability at certain temperature test points as evidenced by fluctuation in the output frequency. Recovery from temperature-induced changes took place when excessive temperatures were removed. It should also be pointed out that all oscillators were able to restart at the extreme test temperatures and to withstand the limited thermal cycling without undergoing any significant changes in their characteristics. In addition, no physical damage was observed in the packaging material of any of these silicon oscillators due to extreme temperature exposure and thermal cycling. It is recommended

Selecting Items for Criterion-Referenced Tests.

Science.gov (United States)

Mellenbergh, Gideon J.; van der Linden, Wim J.

1982-01-01

Three item selection methods for criterion-referenced tests are examined: the classical theory of item difficulty and item-test correlation; the latent trait theory of item characteristic curves; and a decision-theoretic approach for optimal item selection. Item contribution to the standardized expected utility of mastery testing is discussed. (CM)

Investigation of the Adaptability of Transient Stability Assessment Methods to Real-Time Operation

DEFF Research Database (Denmark)

Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Sommer, Stefan

2012-01-01

In this paper, an investigation of the adaptability of available transient stability assessment methods to real-time operation and their real-time performance is carried out. Two approaches based on Lyapunov’s method and the equal area criterion are analyzed. The results allow to determine...

The stability of PEMFC electrodes : platinum dissolution vs potential and temperature investigated by quartz crystal microbalance

NARCIS (Netherlands)

Dam, V.A.T.; Bruijn, de F.A.

2007-01-01

The stability of platinum in proton exchange membrane fuel cell (PEMFC) electrodes has been investigated by determining the dissolution of platinum from a thin platinum film deposited on a gold substrate in 1 M HClO4 at different temperatures ranging between 40 and 80°C and potentials between 0.85

Multiaxial fatigue criterion based on parameters from torsion and axial S-N curve

Directory of Open Access Journals (Sweden)

M. Margetin

2016-07-01

Full Text Available Multiaxial high cycle fatigue is a topic that concerns nearly all industrial domains. In recent years, a great deal of recommendations how to address problems with multiaxial fatigue life time estimation have been made and a huge progress in the field has been achieved. Until now, however, no universal criterion for multiaxial fatigue has been proposed. Addressing this situation, this paper offers a design of a new multiaxial criterion for high cycle fatigue. This criterion is based on critical plane search. Damage parameter consists of a combination of normal and shear stresses on a critical plane (which is a plane with maximal shear stress amplitude. Material parameters used in proposed criterion are obtained from torsion and axial S-N curves. Proposed criterion correctly calculates life time for boundary loading condition (pure torsion and pure axial loading. Application of proposed model is demonstrated on biaxial loading and the results are verified with testing program using specimens made from S355 steel. Fatigue material parameters for proposed criterion and multiple sets of data for different combination of axial and torsional loading have been obtained during the experiment.

The role of word choice and criterion on intentional memory.

Science.gov (United States)

Toyota, Hiroshi

2015-02-01

The relationship between the criterion for choosing and the self-choice effects (greater recall in a self-choice compared to a forced-choice condition) on intentional memory was examined. Thirty-three female nursing school volunteers were administered 24 word pairs in a 2 × 2 design to assess the influence of motivation upon free recall. When word pairs were presented to participants, they were asked to choose a word to-be-remembered, either in a self-choice condition or a forced-choice condition. Words chosen by the participants were recalled more often than those chosen by the experimenter (forced choice). Thus, the self-choice effect was greater for words chosen with a self-reference criterion compared to a metamemory criterion, supporting the integration hypothesis as the origin of the self-choice effect.

STABILITY OF BETACYANIN PIGMENTS FROM RED PURPLE PITAYA FRUIT (Hylocereus polyrhizus : INFLUENCE OF PH, TEMPERATURE, METAL IONS AND ASCORBIC ACID

Directory of Open Access Journals (Sweden)

Tang, C.S Tang, C.S

2010-06-01

Full Text Available Betacyanin pigments from red-purple pitaya fruit (Hylocereus polyrhizus could be an attractive source of red colourant for food application. This paper presents results on the extraction of betacyanin pigments from pitaya fruits grown locally in Malaysia. Both the flesh of the fruit and its mesocarp were investigated and it was found that the flesh had higher pigment contents compared to its peel component. The concentration of betacyanins expressed as betanin equivalents per 100 g of flesh and peel were 10.1 ± 0.6 mg and 6.7 ± 0.2 mg, respectively when 80% methanol was used.  The stability of betacyanin pigments were investigated at different pH, temperature and in presence of different concentrations of metal ions (Cu2+ and Fe2+ and ascorbic acid. The results showed that the pigment was most stable at pH range between 5 and 6. However, it forfeited its stability to the heat induced at elevated temperatures. Metal ions (Cu2+ and Fe2+ proved to be capable of accelerating betacyanin degradation, with Cu2+ exhibiting the greatest effect. By contrast, supplementation with ascorbic acid could enhance the pigment stability against the detrimental effects caused by pH, temperature and metal ions. Nevertheless, if the concentration of ascorbic acid exceeds 0.7 %, it may change its role from pigment stabilizer to become a pro-oxidant.    Keywords: Betacyanin, pigments, pitaya fruit, Hylocereus polyrhizus, ascorbic acid

Development of Predictor and Criterion Measures for the NCO21 Research Program

National Research Council Canada - National Science Library

Knapp, Deidre

2002-01-01

... incorporated into an NCO performance management system geared to 21st century job demands. This report documents the design and development of predictor and criterion measures that will be used in a criterion-related validation data collection...

A Controlled Evaluation of the Distress Criterion for Binge Eating Disorder

Science.gov (United States)

Grilo, Carlos M.; White, Marney A.

2011-01-01

Objective: Research has examined various aspects of the validity of the research criteria for binge eating disorder (BED) but has yet to evaluate the utility of Criterion C, "marked distress about binge eating." This study examined the significance of the marked distress criterion for BED using 2 complementary comparison groups. Method:…

Effects of Mastery Criterion on the Emergence of Derived Equivalence Relations

Science.gov (United States)

Fienup, Daniel M.; Brodsky, Julia

2017-01-01

In this study, we manipulated mastery criterion form (rolling or block) and stringency (across 6 or 12 trials) and measured the emergence of derived relations. College students learned neuroanatomy equivalence classes and experienced one of two rolling mastery criteria (6 or 12 consecutive correct responses) or a block mastery criterion (12 trials…

DETERMINING OF THERMAL STABILITY OF EXPLOSIVES FOR CIVIL USES MODERN EQUIPMENT EQUIPPED WITH AUTOMATIC TEMPERATURE AND PRESSURE

Directory of Open Access Journals (Sweden)

Gabriel VASILESCU

2015-07-01

Full Text Available Thermal stability of explosives for civil use is a key security parameter. When the explosive is exposed to high tempera-tures in a given period of time can lead to undesirable phenomena such as decomposing or even very dangerous as un-controlled detonation.

Fulfillment of the kinetic Bohm criterion in a quasineutral particle-in-cell model

International Nuclear Information System (INIS)

Ahedo, Eduardo; Santos, Robert; Parra, Felix I.

2010-01-01

Quasineutral particle-in-cell models of ions must fulfill the kinetic Bohm criterion, in its inequality form, at the domain boundary in order to match correctly with solutions of the Debye sheaths tied to the walls. The simple, fluid form of the Bohm criterion is shown to be a bad approximation of the exact, kinetic form when the ion velocity distribution function has a significant dispersion and involves different charge numbers. The fulfillment of the Bohm criterion is measured by a weighting algorithm at the boundary, but linear weighting algorithms have difficulties to reproduce the nonlinear behavior around the sheath edge. A surface weighting algorithm with an extended temporal weighting is proposed and shown to behave better than the standard volumetric weighting. Still, this must be supplemented by a forcing algorithm of the kinetic Bohm criterion. This postulates a small potential fall in a supplementary, thin, transition layer. The electron-wall interaction is shown to be of little relevance in the fulfillment of the Bohm criterion.

Stress envelope of silicon carbide composites at elevated temperatures

International Nuclear Information System (INIS)

Nozawa, Takashi; Kim, Sunghun; Ozawa, Kazumi; Tanigawa, Hiroyasu

2014-01-01

To identify a comprehensive stress envelope, i.e., strength anisotropy map, of silicon carbide fiber-reinforced silicon carbide matrix composite (SiC/SiC composite) for practical component design, tensile and compressive tests were conducted using the small specimen test technique specifically tailored for high-temperature use. In-plane shear properties were, however, estimated using the off-axial tensile method and assuming that the mixed mode failure criterion, i.e., Tsai–Wu criterion, is valid for the composites. The preliminary test results indicate no significant degradation to either proportional limit stress (PLS) or fracture strength by tensile loading at temperatures below 1000 °C. A similarly good tolerance of compressive properties was identified at elevated temperatures, except for a slight degradation in PLS. With the high-temperature test data of tensile, compressive and in-plane shear properties, the stress envelopes at elevated temperatures were finally obtained. A slight reduction in the design limit was obvious at elevated temperatures when the compressive mode is dominant, whereas a negligibly small impact on the design is expected by considering the tensile loading case

Stress envelope of silicon carbide composites at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Nozawa, Takashi, E-mail: nozawa.takashi67@jaea.go.jp [Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan); Kim, Sunghun [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Ozawa, Kazumi; Tanigawa, Hiroyasu [Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan)

2014-10-15

To identify a comprehensive stress envelope, i.e., strength anisotropy map, of silicon carbide fiber-reinforced silicon carbide matrix composite (SiC/SiC composite) for practical component design, tensile and compressive tests were conducted using the small specimen test technique specifically tailored for high-temperature use. In-plane shear properties were, however, estimated using the off-axial tensile method and assuming that the mixed mode failure criterion, i.e., Tsai–Wu criterion, is valid for the composites. The preliminary test results indicate no significant degradation to either proportional limit stress (PLS) or fracture strength by tensile loading at temperatures below 1000 °C. A similarly good tolerance of compressive properties was identified at elevated temperatures, except for a slight degradation in PLS. With the high-temperature test data of tensile, compressive and in-plane shear properties, the stress envelopes at elevated temperatures were finally obtained. A slight reduction in the design limit was obvious at elevated temperatures when the compressive mode is dominant, whereas a negligibly small impact on the design is expected by considering the tensile loading case.

Dimethylacetamide as a film-forming additive for improving the cyclic stability of high voltage lithium-rich cathode at room and elevated temperature

International Nuclear Information System (INIS)

Tu, Wenqiang; Xing, Lidan; Xia, Pan; Xu, Mengqing; Liao, Youhao; Li, Weishan

2016-01-01

Highlights: • Addition of 1% DMAc improves the cyclic performances of LLO at room and elevated temperature. • DMAc oxidizes previously to the STD electrolyte and generates a protective film on the LLO surface. • The protective film is thin and uniform. - Abstract: In this work, dimethylacetamide (DMAc) was investigated as an electrolyte film-forming additive to improve the cyclic stability of high voltage Lithium-rich layered nickel manganese cobalt oxide (LLO) cathode at room (25 °C) and elevated (55 °C) temperature. At 0.5C rate, addition of 1% DMAc slightly decreases the initial discharge capacity of LLO from 187 to 179 mAh g −1 at room temperature and 255 to 246 mAh g −1 at elevated temperature, while significantly improves the capacity retention of LLO from 65.8% to 80.2% after 200 cycles at room temperature and from 21.1% to 66.7% after 150 cycles at elevated temperature. The mechanism of DMAc improving the cyclic stability of LLO was investigated via theoretical calculation and experimental characterizations, which demonstrated that DMAc oxidized preferential to the STD (1.0 M LiPF 6 in a mixed solvent of ethylene carbonate/ethyl methyl carbonate/diethyl carbonate) electrolyte, generating a thin and uniform film on the LLO surface. This film effectively suppresses the subsequent decomposition of STD electrolyte and further degradation of spinel phase converted from the layered structure of LLO, resulting in improved cyclic stability of LLO at room and elevated temperature.

Elevated Temperature Photophysical Properties and Morphological Stability of CdSe and CdSe/CdS Nanoplatelets

Energy Technology Data Exchange (ETDEWEB)

Rowland, Clare E. [Department; Center; Fedin, Igor [Department; Diroll, Benjamin T. [Center; Liu, Yuzi [Center; Talapin, Dmitri V. [Center; Department; Schaller, Richard D. [Department; Center

2018-01-03

Elevated temperature optoelectronic performance of semiconductor nanomaterials remains an important issue for applications. Here we examine two-dimensional CdSe nanoplatelets (NPs) and CdS/CdSe/CdS shell/core/shell sandwich NPs at temperatures ranging from 300-700 K using static and transient spectroscopies as well as in-situ transmission electron microscopy. NPs exhibit reversible changes in PL intensity, spectral position, and emission linewidth with temperature elevation up to ~500 K, losing a factor of ~8 to 10 in PL intensity at 400 K relative to ambient. Temperature elevation above ~500 K yields thickness dependent, irreversible degradation in optical properties. Electron microscopy relates stability of the NP morphology up to near 600 K followed by sintering and evaporation at still higher temperatures. The mechanism of reversible PL loss, based on differences in decay dynamics between time-resolved photoluminescence and transient absorption, arise primarily from hole trapping in both NPs and sandwich NPs.

Analytical criterion for shock ignition of fusion reaction in hot spot

International Nuclear Information System (INIS)

Ribeyre, X.; Tikhonchuk, V. T.; Breil, J.; Lafon, M.; Vallet, A.; Bel, E. L.

2013-01-01

Shock ignition of DT capsules involves two major steps. First, the fuel is assembled by means of a low velocity conventional implosion. At stagnation, the central core has a temperature lower than the one needed for ignition. Then a second, strong spherical converging shock, launched from a high intensity laser spike, arrives to the core. This shock crosses the core, rebounds at the target center and increases the central pressure to the ignition conditions. In this work we consider this latter phase by using the Guderley self-similar solution for converging flows. Our model accounts for the fusion reaction energy deposition, thermal and radiation losses thus describing the basic physics of hot spot ignition. The ignition criterion derived from the analytical model is successfully compared with full scale hydrodynamic simulations. (authors)

Delay-Dependent Exponential Stability for Discrete-Time BAM Neural Networks with Time-Varying Delays

Directory of Open Access Journals (Sweden)

Yonggang Chen

2008-01-01

Full Text Available This paper considers the delay-dependent exponential stability for discrete-time BAM neural networks with time-varying delays. By constructing the new Lyapunov functional, the improved delay-dependent exponential stability criterion is derived in terms of linear matrix inequality (LMI. Moreover, in order to reduce the conservativeness, some slack matrices are introduced in this paper. Two numerical examples are presented to show the effectiveness and less conservativeness of the proposed method.

A study on stability of rotating magnets

International Nuclear Information System (INIS)

Higuchi, N.; Kaiho, K.; Ishii, I.

1996-01-01

Superconducting power generators are being developed in Japan, as a part of a R and D program on energy technology, the New Sunshine Project. In this development, national laboratories are taking a role of fundamental studies to contribute to the R and D being carried out mainly by the manufacturers involved in a research association, Super-GM. Stabilities of magnets in a high gravitational field up to 2,000 G are discussed, based upon the experimental results of forced quench tests in a set of rotating magnets, in order to establish the stability design criterion of field windings of superconducting generators. Relations of propagation velocities, recovery currents, minimum quench energy and heat transfer characteristics are studied, a good agreement between the experimental results and a theory confirmed the improvement of magnet stability in a high gravitational field because of the enhanced heat transfer characteristics

The Leadership Criterion in Technological Institute

International Nuclear Information System (INIS)

Carvalho, Marcelo Souza de; Cussa, Adriana Lourenco d'Avila; Suita, Julio Cezar

2005-01-01

This paper introduces the Direction's 'Decision Making Practice'. It has recently been reviewed with the merging of the beddings of the Leadership Criterion (CE-PNQ). These changes improved the control of institutional plans of action which are the result of the global performance critical analysis and other information associated with the Decision Making Practice. (author)

Evaluation of non-volatile metabolites in beer stored at high temperature and utility as an accelerated method to predict flavour stability.

Science.gov (United States)

Heuberger, Adam L; Broeckling, Corey D; Sedin, Dana; Holbrook, Christian; Barr, Lindsay; Kirkpatrick, Kaylyn; Prenni, Jessica E

2016-06-01

Flavour stability is vital to the brewing industry as beer is often stored for an extended time under variable conditions. Developing an accelerated model to evaluate brewing techniques that affect flavour stability is an important area of research. Here, we performed metabolomics on non-volatile compounds in beer stored at 37 °C between 1 and 14 days for two beer types: an amber ale and an India pale ale. The experiment determined high temperature to influence non-volatile metabolites, including the purine 5-methylthioadenosine (5-MTA). In a second experiment, three brewing techniques were evaluated for improved flavour stability: use of antioxidant crowns, chelation of pro-oxidants, and varying plant content in hops. Sensory analysis determined the hop method was associated with improved flavour stability, and this was consistent with reduced 5-MTA at both regular and high temperature storage. Future studies are warranted to understand the influence of 5-MTA on flavour and aging within different beer types. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spatial frequency discrimination: visual long-term memory or criterion setting?

Science.gov (United States)

Lages, M; Treisman, M

1998-02-01

A long-term sensory memory is believed to account for spatial frequency discrimination when reference and test stimuli are separated by long intervals. We test an alternative proposal: that discrimination is determined by the range of test stimuli, through their entrainment of criterion-setting processes. Experiments 1 and 2 show that the 50% point of the psychometric function is largely determined by the midpoint of the stimulus range, not by the reference stimulus. Experiment 3 shows that discrimination of spatial frequencies is similarly affected by orthogonal contextual stimuli and parallel contextual stimuli and that these effects can be explained by criterion-setting processes. These findings support the hypothesis that discrimination over long intervals is explained by the operation of criterion-setting processes rather than by long-term sensory retention of a neural representation of the stimulus.

LSSVM-Based Rock Failure Criterion and Its Application in Numerical Simulation

Directory of Open Access Journals (Sweden)

Changxing Zhu

2015-01-01

Full Text Available A rock failure criterion is very important for the prediction of the failure of rocks or rock masses in rock mechanics and engineering. Least squares support vector machines (LSSVM are a powerful tool for addressing complex nonlinear problems. This paper describes a LSSVM-based rock failure criterion for analyzing the deformation of a circular tunnel under different in situ stresses without assuming a function form. First, LSSVM was used to represent the nonlinear relationship between the mechanical properties of rock and the failure behavior of the rock in order to construct a rock failure criterion based on experimental data. Then, this was used in a hypothetical numerical analysis of a circular tunnel to analyze the mechanical behavior of the rock mass surrounding the tunnel. The Mohr-Coulomb and Hoek-Brown failure criteria were also used to analyze the same case, and the results were compared; these clearly indicate that LSSVM can be used to establish a rock failure criterion and to predict the failure of a rock mass during excavation of a circular tunnel.

Robust stability analysis of Takagi—Sugeno uncertain stochastic fuzzy recurrent neural networks with mixed time-varying delays

International Nuclear Information System (INIS)

Ali, M. Syed

2011-01-01

In this paper, the global stability of Takagi—Sugeno (TS) uncertain stochastic fuzzy recurrent neural networks with discrete and distributed time-varying delays (TSUSFRNNs) is considered. A novel LMI-based stability criterion is obtained by using Lyapunov functional theory to guarantee the asymptotic stability of TSUSFRNNs. The proposed stability conditions are demonstrated through numerical examples. Furthermore, the supplementary requirement that the time derivative of time-varying delays must be smaller than one is removed. Comparison results are demonstrated to show that the proposed method is more able to guarantee the widest stability region than the other methods available in the existing literature. (general)

Free-boundary stability of straight stellarators

International Nuclear Information System (INIS)

Barnes, D.C.; Cary, J.R.

1984-02-01

The sharp-boundary model is used to investigate the stability of straight stellarators to free-boundary, long-wavelength modes. To correctly analyze the heliac configuration, previous theory is generalized to the case of arbitrary helical aspect ratio (ratio of plasma radius to periodicity lengths). A simple low-β criterion involving the vacuum field and the normalized axial current is derived and used to investigate a large variety of configurations. The predictions of this low-β theory are verified by numerical minimization of deltaW at arbitrary β. The heliac configuration is found to be remarkably stable, with a critical β of over 15% determined by the lack of equilibrium rather than the onset of instability. In addition, other previously studied systems are found to be stabilized by net axial plasma current

Stability analysis of Markovian jumping stochastic Cohen—Grossberg neural networks with discrete and distributed time varying delays

International Nuclear Information System (INIS)

Ali, M. Syed

2014-01-01

In this paper, the global asymptotic stability problem of Markovian jumping stochastic Cohen—Grossberg neural networks with discrete and distributed time-varying delays (MJSCGNNs) is considered. A novel LMI-based stability criterion is obtained by constructing a new Lyapunov functional to guarantee the asymptotic stability of MJSCGNNs. Our results can be easily verified and they are also less restrictive than previously known criteria and can be applied to Cohen—Grossberg neural networks, recurrent neural networks, and cellular neural networks. Finally, the proposed stability conditions are demonstrated with numerical examples

On the upper bound in the Bohm sheath criterion

Energy Technology Data Exchange (ETDEWEB)

Kotelnikov, I. A., E-mail: I.A.Kotelnikov@inp.nsk.su; Skovorodin, D. I., E-mail: D.I.Skovorodin@inp.nsk.su [Russian Academy of Sciences, Budker Institute of Nuclear Physics, Siberian Branch (Russian Federation)

2016-02-15

The question is discussed about the existence of an upper bound in the Bohm sheath criterion, according to which the Debye sheath at the interface between plasma and a negatively charged electrode is stable only if the ion flow velocity in plasma exceeds the ion sound velocity. It is stated that, with an exception of some artificial ionization models, the Bohm sheath criterion is satisfied as an equality at the lower bound and the ion flow velocity is equal to the speed of sound. In the one-dimensional theory, a supersonic flow appears in an unrealistic model of a localized ion source the size of which is less than the Debye length; however, supersonic flows seem to be possible in the two- and three-dimensional cases. In the available numerical codes used to simulate charged particle sources with a plasma emitter, the presence of the upper bound in the Bohm sheath criterion is not supposed; however, the correspondence with experimental data is usually achieved if the ion flow velocity in plasma is close to the ion sound velocity.

Criterion learning in rule-based categorization: simulation of neural mechanism and new data.

Science.gov (United States)

Helie, Sebastien; Ell, Shawn W; Filoteo, J Vincent; Maddox, W Todd

2015-04-01

In perceptual categorization, rule selection consists of selecting one or several stimulus-dimensions to be used to categorize the stimuli (e.g., categorize lines according to their length). Once a rule has been selected, criterion learning consists of defining how stimuli will be grouped using the selected dimension(s) (e.g., if the selected rule is line length, define 'long' and 'short'). Very little is known about the neuroscience of criterion learning, and most existing computational models do not provide a biological mechanism for this process. In this article, we introduce a new model of rule learning called Heterosynaptic Inhibitory Criterion Learning (HICL). HICL includes a biologically-based explanation of criterion learning, and we use new category-learning data to test key aspects of the model. In HICL, rule selective cells in prefrontal cortex modulate stimulus-response associations using pre-synaptic inhibition. Criterion learning is implemented by a new type of heterosynaptic error-driven Hebbian learning at inhibitory synapses that uses feedback to drive cell activation above/below thresholds representing ionic gating mechanisms. The model is used to account for new human categorization data from two experiments showing that: (1) changing rule criterion on a given dimension is easier if irrelevant dimensions are also changing (Experiment 1), and (2) showing that changing the relevant rule dimension and learning a new criterion is more difficult, but also facilitated by a change in the irrelevant dimension (Experiment 2). We conclude with a discussion of some of HICL's implications for future research on rule learning. Copyright © 2015 Elsevier Inc. All rights reserved.

Optimal Parameter Selection of Power System Stabilizer using Genetic Algorithm

Energy Technology Data Exchange (ETDEWEB)

Chung, Hyeng Hwan; Chung, Dong Il; Chung, Mun Kyu [Dong-AUniversity (Korea); Wang, Yong Peel [Canterbury Univeristy (New Zealand)

1999-06-01

In this paper, it is suggested that the selection method of optimal parameter of power system stabilizer (PSS) with robustness in low frequency oscillation for power system using real variable elitism genetic algorithm (RVEGA). The optimal parameters were selected in the case of power system stabilizer with one lead compensator, and two lead compensator. Also, the frequency responses characteristics of PSS, the system eigenvalues criterion and the dynamic characteristics were considered in the normal load and the heavy load, which proved usefulness of RVEGA compare with Yu's compensator design theory. (author). 20 refs., 15 figs., 8 tabs.

Stability of equilibrium states in finite samples of smectic C* liquid crystals

International Nuclear Information System (INIS)

Stewart, I W

2005-01-01

Equilibrium solutions for a sample of ferroelectric smectic C (SmC*) liquid crystal in the 'bookshelf' geometry under the influence of a tilted electric field will be presented. A linear stability criterion is identified and used to confirm stability for typical materials possessing either positive or negative dielectric anisotropy. The theoretical response times for perturbations to the equilibrium solutions are calculated numerically and found to be consistent with estimates for response times in ferroelectric smectic C liquid crystals reported elsewhere in the literature for non-tilted fields

Stability of Closed Loop Controlled Repetitive Periodic System applied to control of CD-Player

DEFF Research Database (Denmark)

Odgaard, Peter Fogh; Stoustrup, Jakob; Andersen, Palle

2005-01-01

In this paper a criterion for stability of specific control scheme for handling linear dynamic control systems with repetitive periodic sensor faults is derived. The given system and control scheme are described and defined. By combining these with the lifting technique a necessary and sufficient...

Stability of Hyperthermophilic Proteins

DEFF Research Database (Denmark)

Stiefler-Jensen, Daniel

stability by randomly generate mutants and lengthy screening processes to identify the best new mutants. However, with the increase in available genomic sequences of thermophilic or hyperthermophilic organisms a world of enzymes with intrinsic high stability are now available. As these organisms are adapted...... to life at high temperatures so are their enzymes, as a result the high stability is accompanied by low activity at moderate temperatures. Thus, much effort had been put into decoding the mechanisms behind the high stability of the thermophilic enzymes. The hope is to enable scientist to design enzymes...... in the high stability of hyperthermophilic enzymes. The thesis starts with an introduction to the field of protein and enzyme stability with special focus on the thermophilic and hyperthermophilic enzymes and proteins. After the introduction three original research manuscripts present the experimental data...

Stability of 2-Alkylcyclobutanones in irradiated retort pouch Gyudon topping during room temperature storage

International Nuclear Information System (INIS)

Kitagawa, Yoko; Okihashi, Masahiro; Takatori, Satoshi; Fukui, Naoki; Kajimura, Keiji; Obana, Hirotaka; Furuta, Masakazu

2014-01-01

2-Alkylcyclobutanones (ACBs), such as 2-dodecylcyclobutanone (DCB) and 2-tetradecylcylobutanone (TCB) are specific products from irradiated lipid. Thus, DCB and TCB are suitable for indicators of the irradiation history of food. The purpose of this study was to clarify the stability of ACBs in food, kept at room temperature for a long period. We evaluated DCB and TCB in irradiated retort pouch Gyudon topping (instant Gyudon mixes which were made from a beef, onion and soy sauce), which could be preserved for a long term at room temperature, after storage for one year. DCB and TCB were detected at doses of 0.6-4.5 kGy in irradiated retort pouch Gyudon topping. The peaks of DCB and TCB were separated from other peaks on the chromatogram with GC-MS. The concentration of DCB and TCB were periodically determined till 12 months later of irradiation. The dose-response curves of DCB and TCB were almost identical with those obtained from the samples after the 12 months storage at room temperature. These results concluded that DCB and TCB formed in retort pouch would stable at room temperature at least 12 months. (author)

Temperature, heat content, mixing and stability in Lake Orta: a pluriannual investigation

Directory of Open Access Journals (Sweden)

Luigi BARBANTI

2001-02-01

Full Text Available This paper describes the overall state of some physical phenomena occurring in Lake Orta, such as thermal stratification and destratification, accumulation and release of heat, vertical winter mixing, and stability of the water mass. The historical series of temperature distribution along the water column in the period 1984-1999, from which the holo-oligomictic character of Lake Orta emerges, is analysed. The monthly evaluation of the heat contents metre by metre from 0 to 143 m depth reveals how the complete winter mixing occurs only when the energy present within the whole column is less than 1,675 MJ m-2; above this value the circulation is only partial, as in the other deep subalpine lakes. A water layer in the deep hypolimnion has been shown to contain a climatic memory, which has generally increased since 1981. Walker’s stability analysis has revealed that when at a depth below 90 metres there is a level where 0.07 J m-2 are exceeded, total mixing cannot take place. In contrast, the Birgean work identifies, during the heating phase, the layers of the lake where energy is stored or lost.

The stressor criterion for posttraumatic stress disorder: Does it matter?

Science.gov (United States)

Roberts, Andrea L.; Dohrenwend, Bruce P.; Aiello, Allison; Wright, Rosalind J.; Maercker, Andreas; Galea, Sandro; Koenen, Karestan C.

2013-01-01

Objective The definition of the stressor criterion for posttraumatic stress disorder (“Criterion A1”) is hotly debated with major revisions being considered for DSM-V. We examine whether symptoms, course, and consequences of PTSD vary predictably with the type of stressful event that precipitates symptoms. Method We used data from the 2009 PTSD diagnostic subsample (N=3,013) of the Nurses Health Study II. We asked respondents about exposure to stressful events qualifying under 1) DSM-III, 2) DSM-IV, or 3) not qualifying under DSM Criterion A1. Respondents selected the event they considered worst and reported subsequent PTSD symptoms. Among participants who met all other DSM-IV PTSD criteria, we compared distress, symptom severity, duration, impairment, receipt of professional help, and nine physical, behavioral, and psychiatric sequelae (e.g. physical functioning, unemployment, depression) by precipitating event group. Various assessment tools were used to determine fulfillment of PTSD Criteria B through F and to assess these 14 outcomes. Results Participants with PTSD from DSM-III events reported on average 1 more symptom (DSM-III mean=11.8 symptoms, DSM-IV=10.7, non-DSM=10.9) and more often reported symptoms lasted one year or longer compared to participants with PTSD from other groups. However, sequelae of PTSD did not vary systematically with precipitating event type. Conclusions Results indicate the stressor criterion as defined by the DSM may not be informative in characterizing PTSD symptoms and sequelae. In the context of ongoing DSM-V revision, these results suggest that Criterion A1 could be expanded in DSM-V without much consequence for our understanding of PTSD phenomenology. Events not considered qualifying stressors under the DSM produced PTSD as consequential as PTSD following DSM-III events, suggesting PTSD may be an aberrantly severe but nonspecific stress response syndrome. PMID:22401487

The Mercier Criterion in Reversed Shear Tokamak Plasmas

International Nuclear Information System (INIS)

Kessel, C.; Chance, M.S.; Jardin, S.C.

1999-01-01

A recent numerical study has found that, contrary to conventional theoretical and experimental expectations, reversed shear plasmas are unstable primarily because the term proportional to the shear in the Mercier criterion is destabilizing. In the present study, the role of the magnetic shear, both local and global, is examined for various tokamak configurations with monotonic and non-monotonic safety factor profiles. The enhancement of the local shear due to the outward shift of the magnetic axis suggests that the latter are less susceptible to interchanges. Furthermore, by regrouping the terms in the criterion, the V'' term when differentiated instead with respect to the toroidal flux, is shown to absorb the dominant shear term. No Mercier instability is found for similar profiles as in the previous study

Stabilization of a locally minimal forest

Science.gov (United States)

Ivanov, A. O.; Mel'nikova, A. E.; Tuzhilin, A. A.

2014-03-01

The method of partial stabilization of locally minimal networks, which was invented by Ivanov and Tuzhilin to construct examples of shortest trees with given topology, is developed. According to this method, boundary vertices of degree 2 are not added to all edges of the original locally minimal tree, but only to some of them. The problem of partial stabilization of locally minimal trees in a finite-dimensional Euclidean space is solved completely in the paper, that is, without any restrictions imposed on the number of edges remaining free of subdivision. A criterion for the realizability of such stabilization is established. In addition, the general problem of searching for the shortest forest connecting a finite family of boundary compact sets in an arbitrary metric space is formalized; it is shown that such forests exist for any family of compact sets if and only if for any finite subset of the ambient space there exists a shortest tree connecting it. The theory developed here allows us to establish further generalizations of the stabilization theorem both for arbitrary metric spaces and for metric spaces with some special properties. Bibliography: 10 titles.

The effective complex permittivity stability in filled polymer nanocomposites studied above the glass transition temperature

Directory of Open Access Journals (Sweden)

Elhaouzi F.

2018-01-01

Full Text Available The temperature effecton the dielectric response of nanocomposite at low frequencies range is reported. The investigated samples are formed by a semi-crystalline ethylene-co-butyl acrylate (EBA polymer filled with three concentrations of the dispersed conducting carbon black (CB nanoparticles. The temperature dependence of the complex permittivity has been analyzedabove the glass transition temperature of the neat polymer matrix Tg=-75°C. For all CB concentrations, the dielectric spectra follow a same trend in frequency range 100-106Hz. More interestingly, the stability of the effective complex permittivity ɛ=ɛ' -iɛ'' with the temperature range of 10-70°C is explored. While the imaginary part of the complex permittivity ɛ'' exhibits a slight decreasewith temperature, the real part ɛ' shows a significant reduction especially for high loading samples. The observed dielectric response may be related to the breakup of the three-dimensional structurenetwork formed by the aggregation of CB particles causing change at the interfaceEBA-CB.This interface is estimated bythe volume fraction of constrained polymer chain according to loss tangent data of dynamic mechanical analysis.

Effect of long term exposure at elevated temperature on the microstructural stability and micromechanics of fatigue crack growth of Ti-24Al-11Nb

International Nuclear Information System (INIS)

Aswath, P.B.

1994-01-01

Titanium intermetallics are being developed for long term applications at elevated temperatures. Typical approaches include the design of appropriate microstructure for room and elevated temperature fatigue resistance. However, a little explored area is the stability of these microstructures at elevated temperature and its effect on fatigue crack growth. A coarse two phase α 2 +β Widmanstaetten microstructure was studied. Microstructural stability and elemental segregation were studied as a function of exposure time for up to 500 hours at 800 C using transmission electron microscopy. Results indicate that the Widmanstaetten microstructure is metastable and the β phase breaks up into particles. The absence of a continuous β phase surrounding the α 2 phase reduces the resistance of the microstructure to fatigue crack growth at room temperature

Room temperature d (0) ferromagnetism in hole doped Y2O3: widening the choice of host to tailor DMS.

Science.gov (United States)

Chakraborty, Brahmananda; Ramaniah, Lavanya M

2016-08-24

Transition metal-free-ferromagnetism in diluted magnetic semiconductors (DMS) is of much current interest in view of the search for more efficient DMS materials for spintronics applications. Our DFT results predict for the first time, that impurities from group1A (Li(+), Na(+), K(+)) doped on Y2O3 can induce a magnetic signature with a magnetic moment around 2.0 μ B per defect at hole concentrations around 1.63  ×  10(21) cm(-3), which is one order less than the critical hole density of ZnO with ferromagnetic coupling large enough to promote room temperature ferromagnetism. The induction of room temperature ferromagnetism by hole doping with an impurity atom from group 1A, which injects two holes per defect in the system, implies that the recommendation of three holes per defect given in the literature, which puts a restriction on the choice of host material and the impurity, is not a necessary criterion for hole induced room temperature ferromagnetism. DFT simulations with the generalized gradient approximation (GGA), confirmed by the more sophisticated hybrid functional, Heyd-Scuseria-Ernzerhof (HSE06), predict that the magnetic moment is mostly contributed by O atoms surrounding the impurity atom and the magnetic moment scale up with impurity concentration which is a positive indicator for practical applications. We quantitatively and extensively demonstrate through the analysis of the density of states and ferromagnetic coupling that the Stoner criterion is satisfied by pushing the Fermi level inside the valence band to activate room temperature ferromagnetism. The stability of the structure and the persistence of ferromagnetism at room temperature were demonstrated by ab initio MD simulations and computation of Curie temperature through the mean field approximation. This study widens the choice of host oxides to tailor DMS for spintronics applications.

The Criterion A problem revisited: controversies and challenges in defining and measuring psychological trauma.

Science.gov (United States)

Weathers, Frank W; Keane, Terence M

2007-04-01

The Criterion A problem in the field of traumatic stress refers to the stressor criterion for posttraumatic stress disorder (PTSD) and involves a number of fundamental issues regarding the definition and measurement of psychological trauma. These issues first emerged with the introduction of PTSD as a diagnostic category in the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III; American Psychiatric Association, 1980) and continue to generate considerable controversy. In this article, the authors provide an update on the Criterion A problem, with particular emphasis on the evolution of the DSM definition of the stressor criterion and the ongoing debate regarding broad versus narrow conceptualizations of traumatic events.

A new criterion to global exponential periodicity for discrete-time BAM neural network with infinite delays

International Nuclear Information System (INIS)

Zhou Tiejun; Liu Yuehua; Li Xiaoping; Liu Yirong

2009-01-01

The discrete-time bidirectional associative memory neural network with periodic coefficients and infinite delays is studied. And not by employing the continuation theorem of coincidence degree theory as other literatures, but by constructing suitable Liapunov function, using fixed point theorem and some analysis techniques, a sufficient criterion is obtained which ensures the existence and global exponential stability of periodic solution for the type of discrete-time BAM neural network. The obtained result is less restrictive to the BAM neural networks than previously known criteria. Furthermore, it can be applied to the BAM neural network which signal transfer functions are neither bounded nor differentiable. In addition, an example and its numerical simulation are given to illustrate the effectiveness of the obtained result

A novel high pressure, high temperature vessel used to conduct long-term stability measurements of silicon MEMS pressure transducers

Science.gov (United States)

Wisniewiski, David

2014-03-01

The need to quantify and to improve long-term stability of pressure transducers is a persistent requirement from the aerospace sector. Specifically, the incorporation of real-time pressure monitoring in aircraft landing gear, as exemplified in Tire Pressure Monitoring Systems (TPMS), has placed greater demand on the pressure transducer for improved performance and increased reliability which is manifested in low lifecycle cost and minimal maintenance downtime through fuel savings and increased life of the tire. Piezoresistive (PR) silicon MEMS pressure transducers are the primary choice as a transduction method for this measurement owing to their ability to be designed for the harsh environment seen in aircraft landing gear. However, these pressure transducers are only as valuable as the long-term stability they possess to ensure reliable, real-time monitoring over tens of years. The "heart" of the pressure transducer is the silicon MEMS element, and it is at this basic level where the long-term stability is established and needs to be quantified. A novel High Pressure, High Temperature (HPHT) vessel has been designed and constructed to facilitate this critical measurement of the silicon MEMS element directly through a process of mechanically "floating" the silicon MEMS element while being subjected to the extreme environments of pressure and temperature, simultaneously. Furthermore, the HPHT vessel is scalable to permit up to fifty specimens to be tested at one time to provide a statistically significant data population on which to draw reasonable conclusions on long-term stability. With the knowledge gained on the silicon MEMS element, higher level assembly to the pressure transducer envelope package can also be quantified as to the build-effects contribution to long-term stability in the same HPHT vessel due to its accommodating size. Accordingly, a HPHT vessel offering multiple levels of configurability and robustness in data measurement is presented, along

Stability of equilibrium states in finite samples of smectic C* liquid crystals

Energy Technology Data Exchange (ETDEWEB)

Stewart, I W [Department of Mathematics, University of Strathclyde, Livingstone Tower, 26 Richmond Street, Glasgow G1 1XH (United Kingdom)

2005-03-04

Equilibrium solutions for a sample of ferroelectric smectic C (SmC*) liquid crystal in the 'bookshelf' geometry under the influence of a tilted electric field will be presented. A linear stability criterion is identified and used to confirm stability for typical materials possessing either positive or negative dielectric anisotropy. The theoretical response times for perturbations to the equilibrium solutions are calculated numerically and found to be consistent with estimates for response times in ferroelectric smectic C liquid crystals reported elsewhere in the literature for non-tilted fields.

Furnace System Testing to Support Lower-Temperature Stabilization of High Chloride Plutonium Oxide Items at the Hanford Plutonium Finishing Plant

International Nuclear Information System (INIS)

Schmidt, Andrew J.; Gerber, Mark A.; Fischer, Christopher M.; Elmore, Monte R.

2003-01-01

High chloride content plutonium (HCP) oxides are impure plutonium oxide scrap which contains NaCl, KCl, MgCl2 and/or CaCl2 salts at potentially high concentrations and must be stabilized at 950 C per the DOE Standard, DOE-STD-3013-2000. The chlorides pose challenges to stabilization because volatile chloride salts and decomposition products can corrode furnace heating elements and downstream ventilation components. Thermal stabilization of HCP items at 750 C (without water washing) is being investigated as an alternative method for meeting the intent of DOE STD 3013-2000. This report presents the results from a series of furnace tests conducted to develop material balance and system operability data for supporting the evaluation of lower-temperature thermal stabilization

The role of decision criterion in the Deese-Roediger-McDermott (DRM) false recognition memory: False memory falls and rises as a function of restriction on criterion setting.

Science.gov (United States)

Jou, Jerwen; Escamilla, Eric E; Arredondo, Mario L; Pena, Liann; Zuniga, Richard; Perez, Martin; Garcia, Clarissa

2018-02-01

How much of the Deese-Roediger-McDermott (DRM) false memory is attributable to decision criterion is so far a controversial issue. Previous studies typically used explicit warnings against accepting the critical lure to investigate this issue. The assumption is that if the false memory results from using a liberally biased criterion, it should be greatly reduced or eliminated by an explicit warning against accepting the critical lure. Results showed that warning was generally ineffective. We asked the question of whether subjects can substantially reduce false recognition without being warned when the test forces them to make a distinction between true and false memories. Using a two-alternative forced choice in which criterion plays a relatively smaller role, we showed that subjects could indeed greatly reduce the rate of false recognition. However, when the forced-choice restriction was removed from the two-item choice test, the rate of false recognition rebounded to that of the hit for studied list words, indicating the role of criterion in false recognition.

Sharp conditions for global stability of Lotka-Volterra systems with distributed delays

Science.gov (United States)

Faria, Teresa

We give a criterion for the global attractivity of a positive equilibrium of n-dimensional non-autonomous Lotka-Volterra systems with distributed delays. For a class of autonomous Lotka-Volterra systems, we show that such a criterion is sharp, in the sense that it provides necessary and sufficient conditions for the global asymptotic stability independently of the choice of the delay functions. The global attractivity of positive equilibria is established by imposing a diagonal dominance of the instantaneous negative feedback terms, and relies on auxiliary results showing the boundedness of all positive solutions. The paper improves and generalizes known results in the literature, namely by considering systems with distributed delays rather than discrete delays.

Effect of stabilization temperature during pyrolysis process of P84 co-polyimide-based tubular carbon membrane for H2/N2 and He/N2 separations

Science.gov (United States)

Sazali, N.; Salleh, W. N. W.; Ismail, A. F.; Ismail, N. H.; Aziz, F.; Yusof, N.; Hasbullah, H.

2018-04-01

In this study, the effect of stabilization temperature on the performance of tubular carbon membrane was being investigated. P84 co-polyimide-based tubular carbon membrane will be fabricated through the dip-coating technique. The tubular carbon membrane performance can be controlled by manipulating the pyrolysis conditions which was conducted at different stabilization temperatures of 250, 300, 350, 400, and 450°C under N2 environment (200 ml/min). The prepared membranes were characterized by using scanning electron microscopy (SEM), x-ray diffraction (XRD), and pure gas permeation system. The pure gas of H2, He, and N2 were used to determine the permeation properties of the carbon membrane. The P84 co-polyimide-based tubular carbon membrane stabilized at 300°C demonstrated an excellent permeation property with H2, He, and N2 gas permeance of 1134.51±2.87, 1287.22±2.86 and 2.98±1.28GPU, respectively. The highest H2/N2 and He/N2 selectivity of 380.71±2.34 and 431.95±2.61 was obtained when the stabilization temperature of 450°C was applied. It is concluded that the stabilization temperatures have protrusive effect on the carbon membrane properties specifically their pore structure, and eventually their gas separation properties.

A criterion for selecting renewable energy processes

International Nuclear Information System (INIS)

Searcy, Erin; Flynn, Peter C.

2010-01-01

We propose that minimum incremental cost per unit of greenhouse gas (GHG) reduction, in essence the carbon credit required to economically sustain a renewable energy plant, is the most appropriate social criterion for choosing from a myriad of alternatives. The application of this criterion is illustrated for four processing alternatives for straw/corn stover: production of power by direct combustion and biomass integrated gasification and combined cycle (BIGCC), and production of transportation fuel via lignocellulosic ethanol and Fischer Tropsch (FT) syndiesel. Ethanol requires a lower carbon credit than FT, and direct combustion a lower credit than BIGCC. For comparing processes that make a different form of end use energy, in this study ethanol vs. electrical power via direct combustion, the lowest carbon credit depends on the relative values of the two energy forms. When power is 70$ MW h -1 , ethanol production has a lower required carbon credit at oil prices greater than 600$ t -1 (80$ bbl -1 ). (author)

Evaluation of Nucleic Acid Stabilization Products for Ambient Temperature Shipping and Storage of Viral RNA and Antibody in a Dried Whole Blood Format

Science.gov (United States)

Dauner, Allison L.; Gilliland, Theron C.; Mitra, Indrani; Pal, Subhamoy; Morrison, Amy C.; Hontz, Robert D.; Wu, Shuenn-Jue L.

2015-01-01

Loss of sample integrity during specimen transport can lead to false-negative diagnostic results. In an effort to improve upon the status quo, we used dengue as a model RNA virus to evaluate the stabilization of RNA and antibodies in three commercially available sample stabilization products: Whatman FTA Micro Cards (GE Healthcare Life Sciences, Pittsburgh, PA), DNAstāble Blood tubes (Biomātrica, San Diego, CA), and ViveST tubes (ViveBio, Alpharetta, GA). Both contrived and clinical dengue-positive specimens were stored on these products at ambient temperature or 37°C for up to 1 month. Antibody and viral RNA levels were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays, respectively, and compared with frozen unloaded controls. We observed reduced RNA and antibody levels between stabilized contrived samples and frozen controls at our earliest time point, and this was particularly pronounced for the FTA cards. However, despite some time and temperature dependent loss, a 94.6–97.3% agreement was observed between stabilized clinical specimens and their frozen controls for all products. Additional considerations such as cost, sample volume, matrix, and ease of use should inform any decision to incorporate sample stabilization products into a diagnostic testing workflow. We conclude that DNAstāble Blood and ViveST tubes are useful alternatives to traditional filter paper for ambient temperature shipment of clinical specimens for downstream molecular and serological testing. PMID:25940193

Is Oral Temperature an Accurate Measurement of Deep Body Temperature? A Systematic Review

Science.gov (United States)

Mazerolle, Stephanie M.; Ganio, Matthew S.; Casa, Douglas J.; Vingren, Jakob; Klau, Jennifer

2011-01-01

Context: Oral temperature might not be a valid method to assess core body temperature. However, many clinicians, including athletic trainers, use it rather than criterion standard methods, such as rectal thermometry. Objective: To critically evaluate original research addressing the validity of using oral temperature as a measurement of core body temperature during periods of rest and changing core temperature. Data Sources: In July 2010, we searched the electronic databases PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), SPORTDiscus, Academic Search Premier, and the Cochrane Library for the following concepts: core body temperature, oral, and thermometers. Controlled vocabulary was used, when available, as well as key words and variations of those key words. The search was limited to articles focusing on temperature readings and studies involving human participants. Data Synthesis: Original research was reviewed using the Physiotherapy Evidence Database (PEDro). Sixteen studies met the inclusion criteria and subsequently were evaluated by 2 independent reviewers. All 16 were included in the review because they met the minimal PEDro score of 4 points (of 10 possible points), with all but 2 scoring 5 points. A critical review of these studies indicated a disparity between oral and criterion standard temperature methods (eg, rectal and esophageal) specifically as the temperature increased. The difference was −0.50°C ± 0.31°C at rest and −0.58°C ± 0.75°C during a nonsteady state. Conclusions: Evidence suggests that, regardless of whether the assessment is recorded at rest or during periods of changing core temperature, oral temperature is an unsuitable diagnostic tool for determining body temperature because many measures demonstrated differences greater than the predetermined validity threshold of 0.27°C (0.5°F). In addition, the differences were greatest at the highest rectal temperatures. Oral temperature cannot

Thermal characteristics of shape-stabilized phase change material wallboard with periodical outside temperature waves

International Nuclear Information System (INIS)

Zhou, Guobing; Yang, Yongping; Wang, Xin; Cheng, Jinming

2010-01-01

Thermal characteristics of shape-stabilized phase change material (SSPCM) wallboard with sinusoidal temperature wave on the outer surface were investigated numerically and compared with traditional building materials such as brick, foam concrete and expanded polystyrene (EPS). One-dimensional enthalpy equation under convective boundary conditions was solved using fully implicit finite-difference scheme. The simulation results showed that the SSPCM wallboard presents distinct characteristics from other ordinary building materials. Phase transition keeping time of inner surface and decrement factor were applied to analyze the effects of PCM thermophysical properties (melting temperature, heat of fusion, phase transition zone and thermal conductivity), inner surface convective heat transfer coefficient and thickness of SSPCM wallboard. It was found that melting temperature is one important factor which influences both the phase transition keeping time and the decrement factor; for a certain outside temperature wave, there exist critical values of latent heat of fusion and thickness of SSPCM above which the phase transition keeping time or the decrement factor are scarcely influenced; thermal conductivity of PCM and inner surface convective coefficient have little effect on the phase transition keeping time but significantly influence the decrement factor; and the phase transition zone leads to small fluctuations of the original flat segment of inner surface temperature line. The results aim to be useful for the selection of SSPCMs and their applications in passive solar buildings.

PWR clad ballooning: The effect of circumferential clad temperature variations on the burst strain/burst temperature relationship

International Nuclear Information System (INIS)

Barlow, P.

1983-01-01

By experiment, it has been shown by other workers that there is a reduction in the creep ductility of Zircaloy 4 in the α+β phase transition region. Results from single rod burst tests also show a reduction in burst strain in the α+β phase region. In this report it is shown theoretically that for single rod burst tests in the presence of circumferential temperature gradients, the temperature dependence of the mean burst strain is not determined by temperature variations in creep ductility, but is governed by the temperature sensitivity of the creep strain rate, which is shown to be a maximum in the α+β phase transition region. To demonstrate this effect, the mean clad strain at burst was calculated for creep straining at different temperature levels in the α, α+β and β phase regions. Cross-pin temperature gradients were applied which produced strain variations around the clad which were greatest in the α+β phase region. The mean strain at burst was determined using a maximum local burst strain (i.e. a creep ductility) which is independent of temperature. By assuming cross-pin temperature gradients which are typical of those observed during burst tests, then the calculated mean burst strain/burst temperature relationship gave good agreement with experiment. The calculations also show that when circumferential temperature differences are present, the calculated mean strain at burst is not sensitive to variations in the magnitude of the assumed creep ductility. This reduces the importance of the assumed burst criterion in the calculations. Hence a temperature independent creep ductility (e.g. 100% local strain) is adequate as a burst criterion for calculations under PWR LOCA conditions. (author)

Heat pump control method based on direct measurement of evaporation pressure to improve energy efficiency and indoor air temperature stability at a low cooling load condition

International Nuclear Information System (INIS)

Park, Young Sung; Jeong, Ji Hwan; Ahn, Byoung Ha

2014-01-01

Highlights: • New heat pump control method was developed. • Experimental investigation on performance of heat pump with various control method. • New control method appeared to improve the stability of indoor air temperature. • New control method appeared to have a potential to reduce power consumption. - Abstract: The control systems of conventional heat pumps have an input of refrigerant temperature at the evaporator outlet to maintain superheat at proper level. In order to develop a control method that can be used to achieve better indoor thermal comfort and energy efficiency at a low cooling load condition than the current control method, a new method of the evaporation pressure control based on the evaporator outlet pressure reading (EPCP) was developed. The changes in the stability of indoor air temperature and power consumption were measured while changing the compressor frequency in accordance with the new control method. Compared with the evaporation pressure control based on the evaporator outlet temperature reading, the EPCP control method appeared to improve the stability of room air temperature or occupant thermal comfort significantly

Effect of churning temperature on water content, rheology, microstructure and stability of butter during four weeks of storage

DEFF Research Database (Denmark)

Rønholt, Stine; Madsen, Ann Sophie; Kirkensgaard, Jacob Judas Kain

2014-01-01

The effect of churning temperature (10 °C vs. 22 °C) is evaluated with respect to water content, rheology, microstructure and stability of butter produced using the batch churning method with a temperature ramp of 4 °C/min. Using pulsed-nuclear magnetic resonance, an increase in relative solid fat...... content from 44% to 49.5% was observed when decreasing the churning temperature. Due to lower solid fat content formed upon churning at high temperatures, average water droplet size significantly increased from 5.5 μm to 18.5 μm and less water could be incorporated into the butter during mixing. Using...... differential scanning calorimetry, it was observed that water addition as well as churning at low temperatures induced a transition toward more stable crystal structures, as the melting point in the high melting fraction was slightly lower for butter churned at high temperature. This did, however, not reflect...

Dihydrogen Phosphate Stabilized Ruthenium(0 Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature

Directory of Open Access Journals (Sweden)

Feyyaz Durap

2015-07-01

Full Text Available Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0 nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF value of 80 min−1 in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0 nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature.

Dihydrogen Phosphate Stabilized Ruthenium(0) Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature

Science.gov (United States)

Durap, Feyyaz; Caliskan, Salim; Özkar, Saim; Karakas, Kadir; Zahmakiran, Mehmet

2015-01-01

Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0) nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF) value of 80 min−1 in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0) nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature. PMID:28793435

Thermal stability and electrochemical properties of PVP-protected Ru nanoparticles synthesized at room temperature

Science.gov (United States)

Kumar, Manish; Devi, Pooja; Shivling, V. D.

2017-08-01

Stable ruthenium nanoparticles (RuNPs) have been synthesized by the chemical reduction of ruthenium trichloride trihydrate (RuCl3 · 3H2O) using sodium borohydride (NaBH4) as a reductant and polyvinylpyrrolidone (PVP) as a protecting agent in the aqueous medium at room temperature. The nanoparticles thus prepared were characterized by their morphology and structural analysis from transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis spectroscopy, Fourier transformation infrared and thermogravimetric analysis (TGA) techniques. The TEM image suggested a homogeneous distribution of PVP-protected RuNPs having a small average diameter of 2-4 nm with a chain-like network structure. The XRD pattern also confirmed that a crystallite size is around 2 nm of PVP-protected RuNPs having a single broad peak. The thermal stability studied using TGA, indicated good stability and the electrochemical properties of these nanoparticles revealed that saturation current increases for PVP-protected RuNPs/GC.

The use of a DNA stabilizer in human dental tissues stored under different temperature conditions and time intervals

Science.gov (United States)

TERADA, Andrea Sayuri Silveira Dias; da SILVA, Luiz Antonio Ferreira; GALO, Rodrigo; de AZEVEDO, Aline; GERLACH, Raquel Fernanda; da SILVA, Ricardo Henrique Alves

2014-01-01

Objective The present study evaluated the use of a reagent to stabilize the DNA extracted from human dental tissues stored under different temperature conditions and time intervals. Material and Methods A total of 161 teeth were divided into two distinct groups: intact teeth and isolated dental pulp tissue. The samples were stored with or without the product at different time intervals and temperature. After storage, DNA extraction and genomic DNA quantification were performed using real-time PCR; the fragments of the 32 samples that represented each possible condition were analyzed to find the four pre-selected markers in STR analysis. Results The results of the quantification showed values ranging from 0.01 to 10,246.88 ng/μL of DNA. The statistical difference in the quantity of DNA was observed when the factors related to the time and temperature of storage were analyzed. In relation to the use of the specific reagent, its use was relevant in the group of intact teeth when they were at room temperature for 30 and 180 days. The analysis of the fragments in the 32 selected samples was possible irrespective of the amount of DNA, confirming that the STR analysis using an automated method yields good results. Conclusions The use of a specific reagent showed a significant difference in stabilizing DNA in samples of intact human teeth stored at room temperature for 30 and 180 days, while the results showed no justification for using the product under the other conditions tested. PMID:25141206

A study of offshore wind HVDC system stability and control

Energy Technology Data Exchange (ETDEWEB)

Liu, Hanchao; Sun, Jian [Rensselaer Polytechnic Institute, Troy, NY (United States). Dept. of Electrical, Computer and Systems Engineering