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排序方式: 共有205条查询结果,搜索用时 27 毫秒
1.
Indium separation using ion exchange resins from acidic polymetallic and very diluted solutions are investigated. Since the selectivity of commercial ion exchange resins have proven to be too low for an effective separation from solutions with high content of other metals, Lewatit® TP 208 was impregnated with common extractants to enhance its properties. By resin impregnation with D2EHPA and Cyanex 272, not only the selective indium recovery was reached but also the resin capacity was increased approx. two times. The best loading and elution performance were shown by Cyanex 272-impregnated Lewatit® TP 208, increasing the indium purity in the eluate from 0.75 % to 85 %. 相似文献
2.
In 12 men aged 20-25 men who had minor craniocerebral trauma the profiles of daily secretion of ACTH, beta-endorphin and cortisol were studied. The studies were carried out on the second day after the trauma. Plasma concentrations of the hormones were determined on 8.00, 12.00, 17.00 and 22.00 hours. Statistically significantly increased, in relation to healthy persons, (p < 0.01) values of plasma hormone concentration were found at all time points. In 50% of the patients (six cases) a disturbance was found of the profile of daily secretion of ACTH and beta-endorphin. The disturbance of the profile of cortisol secretion was found only in one patient. 相似文献
3.
Radovan Novotný Radek Vlach Jaroslav Kadlec Radek Kuchta 《Microsystem Technologies》2014,20(4-5):719-728
Ceramics joints are applied for producing products that should be made in a general shapes and dimensions for more advantageous usage. The article presents the research work related to ceramic joint quality evaluation, the thermal-structural analysis of ceramic joining and ceramic bond design and implementation. The role of ceramic material in the electronics industry and motivation for joining ceramics is described in the introduction. The requirements and methods for improving the quality of joints are summarized. Also, the results of simulations of pressure sensor cooling after removal from the oven during joining are discussed. The experimental results are evaluated by using a t-test before and after process cooling modification. Important directions for future research are summarized, with emphasis on the statistical determination of poor connection, and how the interface of modification of joint technology and process setting affects results and parameters that have been achieved. 相似文献
4.
ABSTRACTUnderstanding the cut and chip (CC) effect in rubber is important for successful product development for tires used in off-road or poor road conditions and for other demanding applications of rubber. This research describes a laboratory testing method for characterising the CC fracture behaviour of rubber using a device that controls and records multiple applied loads and displacements during cyclic impact to the surface of a solid rubber specimen to mimic and quantify the CC damage experienced by tire tread compounds. To study the capabilities of the instrument, three model compounds were studied that are based on carbon black reinforced compounds of common elastomers used in tire treads: natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). These polymers have well-established CC tendencies in field performance of tire treads, with NR exhibiting the best CC resistance followed by SBR and finally BR. The same trend was found with the rubber impact testing approach that allowed the CC behaviour to be quantified using a new physical parameter which is the CC propensity (P). The relative ranking for CC resistance for the three compounds followed the fatigue crack growth resistances of the materials but was exactly opposite to the ranking of DIN abrasion resistance. This provides evidence that CC damage from impact by mm-scale asperities and abrasion of rubber against μm-scale asperities exhibit distinct characteristics in rubber. 相似文献
5.
Charbel Farhat Radek Tezaur Paul Weidemann‐Goiran 《International journal for numerical methods in engineering》2004,61(11):1938-1956
Recently, a discontinuous Galerkin method with plane wave basis functions and Lagrange multiplier degrees of freedom was proposed for the efficient solution of Helmholtz problems in the mid‐frequency regime. In this paper, this method is extended to higher‐order elements. Performance results obtained for various two‐dimensional problems highlight the advantages of these elements over classical higher‐order Galerkin elements such as Q2 and Q4 for the discretization of interior and exterior Helmholtz problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
Jan Louzil Jana Stikarova Dana Provaznikova Ingrid Hrachovinova Tereza Fenclova Jan Musil Martin Radek Jirina Kaufmanova Vera Geierova Eliska Ceznerova Peter Salaj Roman Kotlin 《International journal of molecular sciences》2022,23(22)
A single-center study was conducted on 120 patients with inherited disorders of primary hemostasis followed at our hematological center. These patients presented a variety of bleeding symptoms; however, they had no definitive diagnosis. Establishing a diagnosis has consequences for the investigation of probands in families and for treatment management; therefore, we aimed to improve the diagnosis rate in these patients by implementing advanced diagnostic methods. According to the accepted international guidelines at the time of study, we investigated platelet morphology, platelet function assay, light-transmission aggregometry, and flow cytometry. Using only these methods, we were unable to make a definitive diagnosis for most of our patients. However, next-generation sequencing (NGS), which was applied in 31 patients, allowed us to establish definitive diagnoses in six cases (variants in ANKRD26, ITGA2B, and F8) and helped us to identify suspected variants (NBEAL2, F2, BLOC1S6, AP3D1, GP1BB, ANO6, CD36, and ITGB3) and new suspected variants (GFI1B, FGA, GP1BA, and ITGA2B) in 11 patients. The role of NGS in patients with suspicious bleeding symptoms is growing and it changes the diagnostic algorithm. The greatest disadvantage of NGS, aside from the cost, is the occurrence of gene variants of uncertain significance. 相似文献
7.
Radek Pelánek 《User Modeling and User-Adapted Interaction》2018,28(3):207-235
The core of student modeling research is about capturing the complex learning processes into an abstract mathematical model. The student modeling research, however, also involves important methodological aspects. Some of these aspects may seem like technical details not worth significant attention. However, the details matter. We discuss three important methodological issues in student modeling: the impact of data collection, the splitting of data into a training set and a test set, and the details concerning averaging in the computation of predictive accuracy metrics. We explicitly identify decisions involved in these steps, illustrate how these decisions can influence results of experiments, and discuss consequences for future research in student modeling. 相似文献
8.
Mark B. Flegg S. Jonathan Chapman Radek Erban 《Journal of the Royal Society Interface》2012,9(70):859-868
Spatial organization and noise play an important role in molecular systems biology. In recent years, a number of software packages have been developed for stochastic spatio-temporal simulation, ranging from detailed molecular-based approaches to less detailed compartment-based simulations. Compartment-based approaches yield quick and accurate mesoscopic results, but lack the level of detail that is characteristic of the computationally intensive molecular-based models. Often microscopic detail is only required in a small region (e.g. close to the cell membrane). Currently, the best way to achieve microscopic detail is to use a resource-intensive simulation over the whole domain. We develop the two-regime method (TRM) in which a molecular-based algorithm is used where desired and a compartment-based approach is used elsewhere. We present easy-to-implement coupling conditions which ensure that the TRM results have the same accuracy as a detailed molecular-based model in the whole simulation domain. Therefore, the TRM combines strengths of previously developed stochastic reaction–diffusion software to efficiently explore the behaviour of biological models. Illustrative examples and the mathematical justification of the TRM are also presented. 相似文献
9.
10.
Ji?í Nohava Petr Hau?ild ?árka Houdková Radek En?l 《Journal of Thermal Spray Technology》2012,21(3-4):651-658
This paper compares the results of two approaches of instrumented indentation for characterization of mechanical properties of HVOF coatings. Three types of HVOF sprayed coatings (Cr3C2-NiCr, WC-Co, (Ti, Mo)(C,N)-NiCo) were investigated by the means of isolated nanoindentation and grid indentation methods. The results of the isolated indentation revealed hardness and elastic modulus of the individual phases in very good agreement with the corresponding bulk material. The grid indentation method, based on statistical evaluation of a large number of indentations, was influenced by the carbide-matrix interface, which gave rise to a third peak apart from the two peaks corresponding to the carbides and metallic matrix. As a consequence, the bimodal Gaussian fit was insufficient and a trimodal fit had to be used. The results extracted from low load grid nanoindentations were quite close to the results of isolated indentations whereas higher load grid nanoindentation revealed overall properties of the coating. 相似文献