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排序方式: 共有348条查询结果,搜索用时 15 毫秒
81.
Bringing useful old houses up to acceptable standards has become a recognised policy throughout Europe. In this edited article — originally a paper to CIB working group W70 at a meeting in Prague — the general approach of the Czechoslovakian authorities to this problem is explained by an architect at the country's Research Institute for Building and Architecture. There follows an article on the detailed application of modernisation measures to the old spa town of Karlovy Vary, better known perhaps as Carlsbad. 相似文献
82.
Šachlová Šárka Kuchařová Aneta Pertold Zdeněk Přikryl Richard Fridrichová Michaela 《Bulletin of Engineering Geology and the Environment》2017,76(1):133-144
Bulletin of Engineering Geology and the Environment - The alkali silica reaction (ASR), which originates in highly alkaline conditions in concrete where reactive forms of silica are available,... 相似文献
83.
Carmen C. Mayorga‐Martinez Adriano Ambrosi Alex Yong Sheng Eng Zdeněk Sofer Martin Pumera 《Advanced functional materials》2015,25(35):5611-5616
Selective gas sensing is of immense importance for industrial as well as safety purposes. Here it is shown that metallic 1T phase transition metal dichalcogenides, such as tungsten sulfide (WS2), provide sensitive and selective platform for gas sensing. Using impedance spectroscopy distinguishable alterations can be detected on the impedance phase spectrum of interdigitated gold electrode modified with chemically exfoliated 1T‐WS2 caused by different vapors. In particular, it is found that the impedance phase spectra of 1T‐WS2 device present different resonant frequencies with maximum around 1 Hz in the presence of methanol vapor and around 1 kHz in the presence of water vapor. Such a well‐distinguished signal allows their selective detection also when they are present in a mixture. The impedance phase spectra allow the selective methanol and water vapor sensing with an impedimetric device based on 1T‐WS2. This system utilizing 1T phase of WS2 for selective gas sensing based on impedance spectroscopy opens new avenues for gas sensing and shall find wide spectra of applications. 相似文献
84.
Critical evaluation of sequential extraction and sink-float methods used for the determination of Ga and Ge affinity in lignite 总被引:1,自引:0,他引:1
The affinities of Ga and Ge in lignite were determined using sequential extraction (SE) and element affinity calculation (EAC) based on sink-float data. For this study a bulk lignite sample was fractioned into two sets. The first set of samples (A) consisted of the different grain sizes fractions; the second one set (B) was prepared by density fractionation. Sequential extractions [1] were performed on both sets of fractions with very good agreement between determined organic elements affinities (OEA of Ga evaluated from A data is 32%, from B data 35%; OEA of Ge evaluated from A data is 31% and from B data 26%). The data of B lignite fractions were evaluated using two element affinity calculations: (a) EAC (I) of Klika and Kolomazník [2] and b) newly prepared subroutine EAC (II) based on quantitative contents of lignite macerals and minerals. There was also good agreement between both methods obtained (OEA of Ga calculated by EAC (I) is 83% and by EAC (II) 77%; OEA of Ge calculated by EAC (I) is 89% and by EAC (II) 97%). The significant differences of organic elements affinities of Ga and Ge evaluated by sequential extraction and by element affinity calculation based on sink-float data are discussed. 相似文献
85.
Determination of the reference temperature for the kinematic viscosity of Reynolds number is the key problem for describing the forced convection of a heated bluff-body. The heat transfer of a heated circular cylinder in laminar cross airflow is experimentally investigated in this paper. New correlation equations based on the effective temperature have been firstly derived. All experimental data collapsed excellently on the correlation curves. Moreover, the derived Nusselt and Reynolds number relations are independent of the vortex shedding patterns. The correlation equations have further been transformed to an explicit form without temperature ratio. By introducing a newly proposed representative Reynolds number concept, linear correlation equations have been successfully derived. 相似文献
86.
Alexander Andreevich Kharlamov Zdeněk Chára Pavel Vlasák 《Journal of Engineering Mathematics》2008,62(2):161-172
Simple formulae for the components of the added-mass coefficient tensor of a sphere moving near a wall with variable velocity
in an ideal fluid bounded by a solid surface are derived. The added mass is calculated numerically as a function of the dimensionless
distance between the sphere and the wall for both perpendicular and parallel motions. The calculation is performed by the
method of successive images. The velocity field is computed as the sum of the velocity fields of sequences of dipoles located
along the axis. The obtained dependences of the added-mass tensor components are fitted by simple continuous functions with
high accuracy. 相似文献
87.
Martin Pexa Tomáš Hladík Zdeněk Aleš Václav Legát Vít Havlů Miroslav Müller Petr Valášek 《Journal of Mechanical Science and Technology》2014,28(10):3963-3970
We propose a new methodology for application of well-known tools — RCM, RBI and SIFpro — with the aim to treat risks by means of suitable maintenance. The basis of the new methodology is the complex application of all three methods at the same time and not separately as is typical today. The proposed methodology suggests having just one managing team for reliability and risk treatment centred maintenance (RRTCM), employing existing RCM, RBI, and SIFpro tools concurrently. This approach allows for significant reduction of engineering activities’ duration. In the proposed methodology these activities are staged into five phases and structured to eliminate all duplication resulting from separate application of the three tools. The newly proposed methodology saves 45% to 50% of the engineering workload and adequate significant financial savings. 相似文献
88.
Zdeněk Kala 《Thin》2011
The objective of the paper is to analyse the influence of initial imperfections on the load-carrying capacity of a single storey steel plane frame comprised of two columns loaded in compression. The influence of the variance of initial imperfections on the variance of the load-carrying capacity was calculated by means of Sobol’ sensitivity analysis. Monte Carlo based procedures were used for computing full sets of first order and second order sensitivity indices of the model. The geometrical nonlinear finite element solution, which provides numerical results per run, was employed. The mutual dependence of sensitivity indices and column non-dimensional slenderness is analysed. The derivation of the statistical characteristics of system imperfections of the initial inclination of columns is described in the introduction of the present work. Material and geometrical characteristics of hot-rolled IPE members were considered to be random quantities with histograms obtained from experiments. The Sobol sensitivity analysis is used to identify the crucial input random imperfections and their higher order interaction effects. 相似文献
89.
Monitoring changes in the error distribution of autoregressive models based on Fourier methods 总被引:1,自引:1,他引:0
We develop a procedure for monitoring changes in the error distribution of autoregressive time series while controlling the overall size of the sequential test. The proposed procedure, unlike standard procedures which are also referred to, utilizes the empirical characteristic function of properly estimated residuals. The limit behavior of the test statistic is investigated under the null hypothesis as well as under alternatives. Since the asymptotic null distribution contains unknown parameters, a?bootstrap procedure is proposed in order to actually perform the test and corresponding results on the finite?Csample performance of the new method are presented. As it turns out the procedure is not only able to detect distributional changes but also changes in the regression coefficient. 相似文献
90.
Zdeněk Bouchal 《Journal of Modern Optics》2013,60(12):2437-2444
Abstract The phase-conjugate mirror realized by means of degenerate four-wave mixing in a Kerr-like medium is investigated using the angular spectrum representation of interacting fields. The analysed model is based on the nonlinear mixing of two infinite plane pump waves with the spatially limited probe and signal waves. Relations among harmonic components of the probe and signal fields are derived assuming non-depleted pumping and neglecting the evanescent waves. The influence of the injected signal field on the frequency spectrum of the generated phase-conjugate field is also examined. 相似文献