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排序方式: 共有181条查询结果,搜索用时 15 毫秒
141.
Heimann P Krupin O Schlotter WF Turner J Krzywinski J Sorgenfrei F Messerschmidt M Bernstein D Chalupský J Hájková V Hau-Riege S Holmes M Juha L Kelez N Lüning J Nordlund D Perea MF Scherz A Soufli R Wurth W Rowen M 《The Review of scientific instruments》2011,82(9):093104
We present the x-ray optical design of the soft x-ray materials science instrument at the Linac Coherent Light Source, consisting of a varied line-spaced grating monochromator and Kirkpatrick-Baez refocusing optics. Results from the commissioning of the monochromator are shown. A resolving power of 3000 was achieved, which is within a factor of two of the design goal. 相似文献
142.
A complete understanding of the reaction kinetics for the industrial production process of expandable polystyrene 下载免费PDF全文
143.
The in vitro antifungal activity of compounds 1-3 ({[(CH3)2NCH2]2C6H3}R2SnX; (where X=Cl, R=n-Bu for 1, X=Br, R=n-Bu for 2 and x=PF6, R=n=Bu for 3)) was estimated with the help of a modified microdilution format of the M27-A guidelines and was compared with in vitro activity of their diphenyltin(IV) analogues 4 and 5 (where X=Br, R=Ph for 4 and X=PF6, R=Ph for 5), and of drugs currently in clinical use (ketoconazole, fluconazole and amphotericin B). It was found that in coordinating solvents the more soluble derivative 2 is less active than the phenyl one (4), and compounds 1 and 3 are even inactive.In this paper, the in vitro antitumour activity of ionic diphenyltin(IV) complexes 4 and 5 against seven tumoural cell lines of human origin is also reported. The preparation and characterization (H1, C13 and Sn119 NMR spectroscopy and electrospray ionization mass spectrometry) of the novel compound 3 is mentioned too. 相似文献
144.
Hexagonal mesoporous silica (HMS) catalysts post-synthetically doped with vanadia oxo-species were characterized by means
of XRD, UV-Vis spectroscopy, H2-TPR and studied in oxidative dehydrogenation of propane (ODH). The relationship between catalytic activity in ODH and the
presence of different vanadia-oxo species (monomeric, oligomeric and oxide-like species) was suggested. Monomeric VOx species
are responsible for high catalytic activity and selectivity, oligomeric species containing V-O-V bond are active but non-selective
to propene and oxide-like VOx particles are significantly less active and selective. 相似文献
145.
Darina Dostálová Vratislav Kafka David Vokoun Luděk Heller Libor Matějka Lukáš Kadeřávek Jan Pěnčík 《Journal of Materials Engineering and Performance》2017,26(11):5166-5172
A waste-based particle polymer composite (WPPCs) made of foam glass and polypropylene was developed as a low-cost construction material. Thermomechanical properties of the composite, including creep properties of WPPC and polypropylene binder, were examined. By adding a relatively small amount of polypropylene to foam glass (about 2:8 in volume parts), the maximum bearing capacity at room temperature of the composite increased from 1.9 (pure foam glass) to 15 MPa. A significant creep strain accumulated during compressive loading of WPPC (5 MPa) in the first 2000 s at elevated temperatures (40, 60 °C). In the study, Kafka’s mesomechanical model was used to simulate creep strain changes in time for various temperatures. The applicability of Kafka’s mesomechanical model for simulating creep properties of the studied composite material was demonstrated. 相似文献
146.
Milena pírkov Libor Matjka Drahomíra Hlavat Bohumil Meissner Jindich Pytela 《应用聚合物科学杂志》2000,77(2):381-389
A series of segmented polyurethanes was prepared from the new commercial product KRASOL LBH (linear liquid polybutadiene terminated with secondary hydroxy groups), aromatic diisocyanates, and an aliphatic low‐molecular‐weight diol. Three types of networks were prepared, with the nature of the crosslinks varied from purely chemical to physical, with a continuous transition to “combined” networks containing both crosslink types. Potassium 2‐ethyl hexanoate was used as a catalyst of the in situ formation of trifunctional isocyanurate groups (by cyclotrimerization of isocyanate groups). It was confirmed that mechanical, thermal, and swelling properties are considerably influenced by the ratio of chemical to physical crosslink concentration. The best balance of stress–strain properties was obtained for “combined” networks at a NCO–OH molar ratio of 1.10 when only a few chemical crosslinks are present in predominantly physically crosslinked networks. The presence of thermally stable isocyanurate groups mainly influences the storage shear modulus at elevated temperatures. Small‐angle X‐ray scattering confirmed the two‐phase structure of polyurethanes with a periodicity of 6–8 nm. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 381–389, 2000 相似文献
147.
Libor ervený Antonín Marhoul Vlastimil Ri
ka 《Advanced Synthesis \u0026amp; Catalysis》1977,319(4):601-610
Catalytic Cleavage of Substituted 1,3-Dioxane The catalytic cleavage of 4-phenyl-1,3-dioxane and 4-methyl-4-phenyl-1,3-dioxane using palladium or CuO Cr2O3 BaCrO4 catalysts was studied in this work. The hydrogenolysis of cited 1,3-dioxanes using CuO Cr2O3 BaCrO4 catalyst gives 3-phenyl-1-propanole and 3-phenyl-1-butanole, resp. in high yields. It is possible to obtain these primary alcohols also by pressureless cleavage using the palladium catalysts in a hydrogen atmosphere. The cleavage of 4-phenyl-1,3-dioxane in the inert atmosphere produced propiophenone selectivelly. The byproducts of the reactions were identified and the reaction scheme of the catalytic cleavage is suggested. 相似文献
148.
149.
David Vališ Libor Žák Ondřej Pokora 《Quality and Reliability Engineering International》2016,32(2):635-645
The aim of the paper is to estimate a system‐soft failure occurrence and residual technical life. When estimating a residual technical life statistically, usually a big amount of tribodiagnostic data is used. Data include the information about particles contained in oil that testifies to oil and system conditions. We focus here on the particles that we consider to be interesting. They are ferrum (Fe) and lead (Pb) as contact degradation product. By modelling the occurrence of particles in oil, we expect to determine the expected moment for soft failure occurrence or adequate moment to perform preventive maintenance. The way of our modelling is based on the specific characteristics of diffusion processes, namely the Wiener process with positive drift and Ornstein–Uhlenbeck process. Following the modelling results, we could judge hazard rate and set‐up principles of ‘CBM ‐ Condition Based Maintenance’ (CBM). However, the possibilities are much wider, because we can also plan operation, mission and reduce life cost. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
150.
Jozef Zrnik Reinhard Pippan Stephan Scheriau Libor Kraus Martin Fujda 《Journal of Materials Science》2010,45(17):4822-4826
Using the high pressure torsion (HPT) deformation method the medium carbon steel (AISI 1045) was the experimental material
used to conduct the deformation process. The torsion deformation experiment was performed at increased temperature of 400 °C.
The influence of deformation processing parameters, resolved shear strain γ (number of turns N = 1–6) and applied pressure p (constant pressure of 7 GPa), was evaluated by microstructure analysis and mechanical properties. The strength behaviour
was assessed by microhardness measurements across the disc to detect the positional hardening, by tensile tests and in situ
measured torque. In situ measurement of torque during deformation allows characterizing the changes in mechanical properties
due to the large shear deformation developed across the disc. To obtain absolute values of strength the ultimate tensile strength
was measured in radial direction with respect to the deformed sample. From each deformed disc two sub-sized tensile test specimens
with gauge length of 2.5 mm were machined. The tensile strength in samples increased markedly with the number of turns. The
hardness measured at disc edge gradually increases as straining increases until it saturates after 2–3 turns. However, the
hardness values at edge were different from those measured in disc centre and for applied straining no saturation was reached
across the disc. The SEM and TEM investigations were carried out to analyze the fine microstructure evolution regarding the
strain introduced. To follow the difference in strain distribution across the deformed disc the microstructure analysis was
performed at edge and central site of the disc in order to evaluate the effect of the strain distribution. TEM investigation
confirmed the increasing misorientation even in very small grains, the fragmentation and dissolution of the cementite lamellae,
(diffuse cementite/ferrite boundaries), the alignment of the fragments to the shear plane with increasing deformation. Indistinct
deformation of ferrite and preserved cementite lamellae morphology were found at the centre of the disc. 相似文献