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1.
This article studied the effects of low-velocity impact on the failure stresses and stiffness using a pendulum test. The specimens were of variable depth (20, 30, and 40 mm), a width of 50 mm, length of 650 mm, and span-length of 480 mm. The smallest specimen depth was similar to specimen sizes tested in the literature used to create the duration of load curve, while the largest specimen depth are considered structural size specimens. The impact was predicted using a numerical approach with Euler–Bernoulli beam, as well as Timoshenko beam theory, with a plastic contact law. The models were validated for impact from a low release-angle (where the beam remained elastic), but could use improvement for the force prediction at a high incidence velocity. The measured force signals were used as forcing functions to obtain the dynamic failure stresses for all of the evaluated specimens, and the Timoshenko–Goens–Hearmon Method to derive the dynamic E. The resulting strain rates ranged from 9.11?×?10?5 s?1 for the quasi-static specimens up to 25 s?1 for the greatest incidence velocity. The results from this study suggest different duration of load factors than the Madison Curve, influencing the design of structures subjected to dynamic loading. 相似文献
2.
Jinbai Yang Bohumil Volesky 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,66(4):355-364
Cadmium equilibrium sorption isotherms were determined for formaldehyde crosslinked Sargassum fluitans, establishing that an effective regeneration of the new biosorbent material is possible by an acid wash. Batch desorption kinetics were investigated at pH values of 1·0 and 2·0. By incorporating the linear and non-linear Langmuir equilibrium isotherm relationships into the rate equations, a mathematical model was proposed for modeling the metal desorption process. The model was solved numerically and a MATLAB computer program was used to curve-fit the experimental data. The model successfully predicted the Cd2+ elution concentration profile in a batch reactor. The average values of the intraparticle diffusivity of Cd2+ in the algal biosorbent calculated from the model were 3·40 × 10−6 and 1·65 × 10−6 cm2 s−1, 0·473 and 0·229 times the molecular diffusivity of Cd2+ in water, at pH values of 1·0 and 2·0, respectively. These values agreed well with theoretical predictions. 相似文献
3.
Krassimira Ilieva Sergey Belousov Antonio Ballesteros Bohumil Osmera Sergey Zaritsky 《Progress in Nuclear Energy》2009,51(1):1-13
A state of the art review of Reactor Dosimetry used for reactor pressure vessel irradiation damage assessment and lifetime evaluation of the Russian type VVER reactors is presented. The necessity of prospective studies in Reactor Dosimetry for improvements that will reduce the neutron fluence uncertainty and in this way to substantiate the extension of NPP lifetime is summarized by specialists in Reactor Dosimetry from countries operating VVER reactors such as Russia, Ukraine, Czech Republic, Finland, Hungary, and Bulgaria, together with specialists from Western European countries such as France, Spain, Germany, Belgium, The Netherlands, and UK, operating PWR and BWR type reactors. 相似文献
4.
Filip Alexandrescu Petr Klusáček Stephan Bartke Robert Osman Bohumil Frantál Stanislav Martinát Josef Kunc Lisa Pizzol Alex Zabeo Elisa Giubilato Andrea Critto Alena Bleicher 《Clean Technologies and Environmental Policy》2017,19(5):1323-1334
This article deals with experiences acquired during the process of developing the Timbre Brownfield Prioritization Tool (TBPT). Developing a decision support tool that takes into account the expectations and experiences of its potential users is similar to creating applicable knowledge by the joint action of scientists and heterogeneous actors. Actor network theory is used to explore the construction of this form of applicable knowledge as a process of actor network creation. Following the French sociologist Callon, networks are seen to be initiated and carried out by a group of scientists (tool developers) via four moments of translation, called problematization, interessement, enrolment and mobilization. Each step in the construction of the TBPT—from the initial research question to the final model—can be linked in retrospect to changing configurations of actor networks. Based on the experiences of the tool developers in the Czech Republic, Poland, Germany and Romania, we illustrate how these configurations varied across space and time. This contribution emphasizes the ability to correlate gains in knowledge with the more visible changes in the scope of actor networks in order to highlight achievements but also limitations in acquiring applicable knowledge. 相似文献
5.
The discovery of a consistent and unusual enrichment in homopolymeric alpha-L-guluronic acid G-blocks in alginates extracted from a suite of Sargassum brown algae is described in this study. 1H NMR spectroscopy was used to characterize these alginates which display homopolymeric guluronic acid block (G-block) frequency values (F(GG)) between 0.37 and 0.81. The presence of these G-blocks results in an enhanced selectivity for cadmium or calcium relative to monovalent ions such as sodium and the proton as well as smaller divalent ions such as magnesium. Results of competitive exchange experiments for the Cd-Ca-alginate system yield selectivity coefficient, K*(Cd)Ca, values between 0.43 +/- 0.10 and 1.32 +/- 0.02 for a range in F(GG) of 0.23 to 0.81. In contrast to the Cd-Ca-alginate system, the Mg-Ca-alginate and Mg-Cd-alginate systems yielded maximum values of K*(Mg)Ca (18.0 +/- 1.4) and K*(Mg)Cd (16.0 +/- 0.9) for the alginates extracted from Sargassum fluitans (F(GG) = 0.81; Cuba) and Sargassum thunbergii (F(GG) = 0.75; Korea), respectively. Selectivity studies with mixed-metal pair alginate systems highlight the importance of the specific macromolecular conformation of the alginate polymer in determining metal binding behavior in multiple-metal systems. Furthermore, they demonstrate the importance of the conformation of the alginate as it occurs within the tissue of Sargassum in determining the metal binding behavior of this algal biosorbent. The unique composition of the alginates present in species of Sargassum may represent a distinct advantage over other brown algal species when considering their implementation for the strategic removal of toxic heavy metals from contaminated and industrial wastewaters. 相似文献
6.
This paper describes the analysis of a laminated timber arch radially reinforced with composite fiber rods to arrest crack growth. A laminated arch with a through crack was instrumented with crack propagations gages to detect crack growth and was tested experimentally. A finite element model was developed, which represented the laminated timber arch and the reinforcing rods, and used two dimensional interface elements to simulate crack extension. The arch was modeled with a flaw in the form of a through crack that was assumed to be sharp. Material properties of the arch and rods were determined experimentally, and the crack dimensions in the model were taken from the experimental arch, which was measured using an X-ray emitter with 33 μm resolution. The experimental results (deformations, strains and crack growth) were compared with the analyses. The model showed reasonable agreement with the experiment but an improved model is required to capture the behavior correctly. This paper demonstrates the possibilities in reinforcing wood structural members using high-strength composites and points to some experimental and analytical challenges. 相似文献
7.
Michal Hoznedl Ladislav Tajc Jaroslav Krejcik Lukas Bednar Kamil Sedlak Jiri Linhart 《Frontiers of Energy and Power Engineering in China》2009,3(3):321-329
In the past, increased attention was given to the development of an optimal shape for the inlet part of LP turbine casings
in SKODA POWER. A double-flow design is typically used for high power output turbines. An optimized shape for the internal
diffuser has been found, which transforms the kinetic energy of steam into increased pressure, thus effectively increasing
the thermodynamic efficiency of the stage. Some conclusions have been drawn from laboratory experiments, others derived directly
from on-site measurements at power plants. The conclusions from the development of double-flow turbines form the basis for
the design of the single-flow turbine arrangement. Single-flow design is typically used for lower output turbines. There are
still some limitations in applying this arrangement. The designer needs to resolve the bearing position and how to ensure
access to them. Reinforcing the ribs and supports are used, therefore, to ensure the rigidity of the entire casing. The optimization
of the single-flow diffuser shape is therefore the subject of the study presented below. 相似文献
8.
9.
I. Bednar E. Royanian S. Bühler-Paschen E. Bauer N. Nasir A. Grytsiv N. Melnychenko-Koblyuk P. Rogl 《Journal of Electronic Materials》2010,39(9):1687-1691
In the present work we focus on cubic type I Ba-Ge-based clathrates, where Ge in
Ba8Ge43 \square3\rm Ba_8Ge_{43} \square_3 (where □ is a vacancy) is substituted by Cu, Zn, Pd, and Si. Structural investigations in all cases confirm cubic primitive
symmetry consistent with the space group type Pm[`3]nPm\bar{3}n of a typical type I clathrate structure with lattice parameter a ≈ 1.06 nm. Electronic transport has been studied in a broad temperature range from 4.2 K to about 800 K, demonstrating that
substitution allows fine-tuning of the charge carrier density, shifting the materials into the proximity of a metal-to-insulator
transition. This is evidenced from giant thermopower reaching values of 400 μV/K in the case of Ba8Cu5.2Zn0.8Ge40.0 at temperatures well below room temperature (T
max
S
≈ 150 K). 相似文献
10.
Michal Košťál František Cvachovec Jiří Cvachovec Bohumil Ošmera Wolfgang Hansen 《Annals of Nuclear Energy》2011
In this paper computational procedures and the experimental determination of the AKR-2 (Technical University Dresden) beam parameters are described. The calculations were performed using the MCNPX code (Pelowitz, 2002) and the nuclear data libraries ENDF/B VI.2., ENDF/B VII.0., JEFF 3.1., JENDL 3.3 and BROND 3. The nuclear data were processed using the NJOY code (MacFarlane and Muir, 1994). The measurements were performed with a two-parameter stilbene spectrometer (Bures et al., 2002). 相似文献