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Numerical simulation of triaxial compression test for brittle rock sample using a modified constitutive law considering degradation and dilation behavior

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Journal of Central South University 2015年第8期22卷 3097-3107页

作者：谭鑫 KONIEtZKY H FRüHWIRt t College of Civil Engineering Hunan University Geotechnical Institute TU Bergakademie Freiberg

the understanding of the rock deformation and failure process and the development of appropriate constitutive models are the basis for solving problems in rock engineering. In order to investigate progressive failure behavior in brittle rocks, a modified constitutive model was developed which follows the principles of the continuum damage mechanics method. It incorporates non-linear Hoek-Brown failure criterion, confining pressure-dependent strength degradation and volume dilation laws, and is able to represent the nonlinear degradation and dilation behaviors of brittle rocks in the post-failure region. A series of triaxial compression tests were carried out on Eibenstock(Germany) granite samples. Based on a lab data fitting procedure, a consistent parameter set for the modified constitutive model was deduced and implemented into the numerical code FLAC3 D. the good agreement between numerical and laboratory results indicates that the modified constitutive law is well suited to represent the nonlinear mechanical behavior of brittle rock especially in the post-failure region.

关键词： progress failure strength degradation dilation Hoek-Brown criterion numerical simulation brittle rock

Evaluation of natural goethite on the removal of arsenate and selenite from water

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Journal of Environmental Sciences 2019年第2期31卷 133-141页

作者： Andrew t.Jacobson Maohong Fan Department of Chemical Engineering University of Wyoming

Elevated arsenic and selenium concentrations in water cause health problems to both humans and wildlife. Natural and anthropogenic activities have caused contamination of these elements in waters worldwide, making the development of efficient cost-effective methods in their removal essential. In this work, removal of arsenate and selenite from water by adsorption onto a natural goethite(α-FeO OH) sample was studied at varying conditions. the data was then compared with other arsenate, selenite/goethite adsorption systems as much of literature shows discrepancies due to varying adsorption conditions. Characterization of the goethite was completed using inductively coupled plasma mass spectrometry, X-ray diffraction, Fouriertransform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–teller surface area analysis. Pseudo-first order(PFO) and pseudo-second order(PSO) kinetic models were applied; including comparisons of different regression methods. Various adsorption isotherm models were applied to determine the best.fitting model and to compare adsorption capacitates with other works. Desorption/leaching of arsenate and selenite was studied though the addition of phosphate and hydroxyl ions. Langmuir isotherm modeling resulted in maximum adsorption capacities of 6.204 and 7.740 mg/g for arsenate and selenite adsorption,respectively. the PSO model applied with a non-linear regression resulted in the best kinetic fits for both adsorption and desorption of arsenate and selenite. Adsorption decreased with increasing pH. Phosphate induced desorption resulted in the highest percentage of arsenate and selenite desorbed, while hydroxide induced resulted in the fastest desorption kinetics.

关键词： Arsenic Selenium Adsorption Desorption FeOOH Water treatment

Mitigation of EDFA transient effects in variable duty cycle pulsed signals

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Defence technology（防务技术） 2019年第3期15卷 276-281页

作者： D. Meena K.t. Sarath Fredy Francis E. Dipin t. Srinivas Electronics and Radar Development Establishment (LRDE) DRDO Bangalore Karnataka 560093 India Model Engineering College Thrikkakara Cochin Kerala 682021 India Indian Institute of technology Madras Chennai Tamil Nadu 600036 India

We report the transient effects in Erbium Doped Fiber Amplifier (EDFA) systems for pulsed signals with different duty-cycles. the work includes the analysis using three different duty-cycles, 10%, 20% and 50%. A curve fitting technique is also proposed to predict the transients of any lesser duty-cycled pulse, once the transients of a larger duty-cycled pulse is known. Mathematical evaluation confirms the double exponential shape of transient distorted signal. Further, EDFA transient effect is experimentally verified on a Wavelength Division Multiplexed (WDM) link by multiplexing high and low bitrate modulated optical signals. We conclude the paper by proposing a transient suppression technique for variable dutycycle signals and analyzing its effectiveness with different wavelength spacing.

关键词： EDFA transients WDM Variable duty cycle Suppression

HⅠ emission from the red giant Y CVn with the VLA and FASt

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Research in Astronomy and Astrophysics 2017年第7期17卷 39-46页

作者： Do t.Hoai Pham t.Nhung Lynn D.Matthews Eric Grard thibaut Le Bertre Department of Astrophysics Vietnam National Satellite CenterVAST LERMA CNRSObservatoire de Paris/PSLSorbonne Universite's Department of Astrophysics Vietnam National Satellite Center MIt Haystack Observatory GEPI CNRSObservatoire de Paris/PSL

Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the Asymptotic Giant Branch. the H I line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar *** reproduce the spectral map by introducing a distortion along a direction corresponding to the star＇s motion in space. We then use this fitting to simulate observations expected from the Five-hundred-meter Aperture Spherical radio telescope（FASt）, and discuss its potential for improving our description of the outer regions of circumstellar shells.

关键词： stars AGB and post-AGB-- stars carbon - stars individual Y CVn - radio lines stars

Constraining the temperature-density Relation of the Inter-galactic Medium from Analytically Modeling LyαForest Absorbers

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Research in Astronomy and Astrophysics 2023年第4期23卷 72-84页

作者： Li Yang Zheng Zheng t.-S.Kim Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Physics and Astronomy University of Utah115 S 1400 ESalt Lake CityUT 84112USA Department of Astronomy University of Wisconsin475 North Charter StreetMadisonWI 53706USA

the absorption by neutral hydrogen in the intergalactic medium(IGM)produces the Lya forest in the spectra of *** Lya forest absorbers have a broad distribution of neutral hydrogen column density N_(HⅠ) and Doppler b *** narrowest Lya absorption lines(of lowest b)with neutral hydrogen column density above~10^(13)cm^(-2) are dominated by thermal broadening,which can be used to constrain the thermal state of the *** we constrain the temperature-density relation t=t0(ρ/■)γ^(-1) of the IGM at 1.6ters measured from 24 high-resolution and high-signal-to-noise quasar spectra and by employing an analytic model to model the N_(HⅠ) -dependent low-b cutoff in the b *** each N_(HⅠ) bin,the b cutoff is estimated using two methods,one non-parametric method from computing the cumulative b distribution and a parametric method from fitting the full b *** find that the IGM temperature t0 at the mean gas densityρshows a peak of~1.5×10^(4) K at z~*** redshift higher than this,the indexγapproximately remains constant,and it starts to increase toward lower *** evolution in both parameters is in good agreement with constraints from completely different approaches,which signals that HeⅡreionization completes around z~3.

关键词： (galaxies:)intergalactic medium-(galaxies:)quasars absorption lines-radiation mechanisms thermal

Factorizations of fitting classes

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Frontiers of Mathematics in China 2012年第5期7卷 943-954页

作者： Nanying YANG Wenbin GUO N.t. VOROB'EV School of Mathematics University of Science and Technology of China Hefei 230026 China Department of Mathematics Vitebsk State University Vitebsk 210038 Belarus

In this paper, we prove that there exists a infinite set of non-trivial local fitting classes every element in which is decomposable as a non-trivial product of fitting classes such that every factor in the product is neither local nor a formation. In particular, this gives a positive answer to Problem 11.25 a） in the Kourovka Notebook.

关键词： fitting class Normal fitting class semilocal fitting class Lockett class

Bayesian data analysis to quantify the uncertainty of intact rock strength

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第1期10卷 11-31页

作者： Luis Fernando Contreras Edwin t.Brown Marc Ruest the University of Queensland St Lucia CampusBrisbaneQLD 4072Australia Golder Associates Pty.Ltd. BrisbaneAustralia

One of the main difficulties in the geotechnical design process lies in dealing with uncertainty. Uncertainty is associated with natural variation of properties, and the imprecision and unpredictability caused by insufficient information on parameters or models. Probabilistic methods are normally used to quantify uncertainty. However, the frequentist approach commonly used for this purpose has some ***, it lacks a formal framework for incorporating knowledge not represented by data. Second, it has limitations in providing a proper measure of the confidence of parameters inferred from data. the Bayesian approach offers a better framework for treating uncertainty in geotechnical design. the advantages of the Bayesian approach for uncertainty quantification are highlighted in this paper with the Bayesian regression analysis of laboratory test data to infer the intact rock strength parameters σand mused in the Hoek-Brown strength criterion. two case examples are used to illustrate different aspects of the Bayesian methodology and to contrast the approach with a frequentist approach represented by the nonlinear least squares(NLLS) method. the paper discusses the use of a Student’s t-distribution versus a normal distribution to handle outliers, the consideration of absolute versus relative residuals, and the comparison of quality of fitting results based on standard errors and Bayes factors. Uncertainty quantification with confidence and prediction intervals of the frequentist approach is compared with that based on scatter plots and bands of fitted envelopes of the Bayesian approach. Finally, the Bayesian method is extended to consider two improvements of the fitting analysis. the first is the case in which the Hoek-Brown parameter, a, is treated as a variable to improve the fitting in the triaxial region. the second is the incorporation of the uncertainty in the estimation of the direct tensile strength from Brazilian test results within the overall evaluati

关键词： Uncertainty Intact rock strength Bayesian analysis Hoek-Brown criterion

A compact charge-based model to study the nanoscale undoped double gate MOSFEts for nanoelectronic circuit design using genetic algorithms

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Journal of Semiconductors 2013年第4期34卷 30-36页

作者： t.Bendib F.Djeffal D.Arar LEA Department of ElectronicsUniversity of Batna05000Algeria

the analytical modeling of nanoscale devices is an important area of computer-aided design for fast and accurate nanoelectronic design and optimization. In the present paper, a new approach for modeling semicon- ductor devices, nanoscale double gate DG MOSFEts, by use of the gradual channel approximation （GC） approach and genetic algorithm optimization technique （GA） is presented. the proposed approach combines the universal optimization and fitting capability of GA and the cost-effective optimization concept of quantum correction, to achieve reliable, accurate and simple compact models for nanoelectronic circuit simulations. Our compact models give good predictions of the quantum capacitance, threshold voltage shift, quantum inversion charge density and drain current. these models have been verified with 2D self-consistent results from numerical calculations of the coupled Poisson-Schrrdinger equations. the developed models can also be incorporated into nanoelectronic cir- cuit simulators to study the nanoscale CMOS-based devices without impact on the computational time and data storage.

关键词： nanoscale quantum genetic algorithm analytical model

Low velocity impact studies of E-glass/epoxy composite laminates at different thicknesses and temperatures

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Defence technology（防务技术） 2019年第6期15卷 897-904页

作者： t.Sreekantha Reddy P.Rama Subba Reddy Vemuri Madhu Defence Metallurgical Research Laboratory

Low velocity impact experiments were carried out on E-glass/epoxy composite laminates having varying thicknesses at sub zero and elevated temperatures using hemi spherical steel impactor of 16 mm diameter with impact energies in the rage of 50-150 *** performance of the laminates was assessed in terms of energy absorption,maximum displacement,peak force and failure *** indicated that the effect of temperature on energy absorption of the laminate is negligible although the laminates are embrittling at sub zero *** it has influence on failure behaviour and *** force has increased linearly with increase in laminate thickness from 5 to 10 *** it got reduced by 25% when temperature was increased from-20℃ to 100℃,Based on experimental results,laminate perforation energies were predicted using curve fitting *** analysis was carried out using taguchi method to identify the global effects of various parameters on laminate performance and confirmed that the laminate thickness has significant influence as compared to temperature,for the studied range.

关键词： Laminates Glass fibres Impact behaviour Delamination