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排序方式: 共有1498条查询结果,搜索用时 15 毫秒
91.
Himani Gaur Jain Hatice Karacuban David Krix Hans-Werner Becker Hermann Nienhaus Volker Buck 《Carbon》2011,49(15):4987-4995
Well aligned carbon nanowalls, a few nanometers thick, were fabricated by continuous flow of aluminum acetylacetonate (Al(acac)3) without a catalyst, and independent of substrate material. The nanowalls were grown on Si, and steel substrates using inductively coupled plasma-enhanced chemical vapor deposition. Deposition parameters like flow of argon gas and substrate temperature were correlated with the growth of carbon nanowalls. For a high flow of argon carrier gas, an increased amount of aluminum in the film and a reduced lateral size of the carbon walls were found. The aluminum is present inside the carbon nanowall matrix in the form of well crystallized nanosized Al4C3 precipitates. 相似文献
92.
I. Gavrilyuk M. Hermann V. Trotsenko Yu. Trotsenko A. Timokha 《Journal of Engineering Mathematics》2014,85(1):83-97
This paper generalizes earlier authors’ results on the analytical approximation of the singularly perturbed boundary problem describing the eigenoscillations of a thin-walled axisymmetric shell. The asymptotic behavior of the eigenmodes at the clamped ends is studied, and a set of trial functions capturing this behavior is constructed to be used in the Ritz method. Illustrative numerical examples demonstrate a fast convergence so that the eigenmodes are accurately approximated in a uniform metric together with their second-, third-, and fourth-order derivatives. The numerical results are validated by comparing them with an asymptotic eigensolution and computations done by the ANSYS codes based on the finite-element method. 相似文献
93.
Dowling N. Maritza; Hermann Bruce; La Rue Asenath; Sager Mark A. 《Canadian Metallurgical Quarterly》2010,24(6):742
Objective: To examine the latent structure of a test battery currently being used in a longitudinal study of asymptomatic middle-aged adults with a parental history of Alzheimer's disease (AD) and test the invariance of the factor solution across subgroups defined by selected demographic variables and known genetic risk factors for AD. Method: An exploratory factor analysis (EFA) and a sequence of confirmatory factor analyses (CFA) were conducted on 24 neuropsychological measures selected to provide a comprehensive estimate of cognitive abilities most likely to be affected in preclinical AD. Once the underlying latent model was defined and the structural validity established through model comparisons, a multigroup confirmatory factor analysis model was used to test for factorial invariance across groups. Results: The EFA solution revealed a factor structure consisting of five constructs: verbal ability, visuospatial ability, speed & executive function, working memory, and verbal learning & memory. The CFA models provided support for the hypothesized 5-factor structure. Results indicated factorial invariance of the model across all groups examined. Conclusions: Collectively, the results suggested a relatively strong psychometric basis for using the factor structure in clinical samples that match the characteristics of this cohort. This confirmed an invariant factor structure should prove useful in research aimed to detect the earliest cognitive signature of preclinical AD in similar middle aged cohorts. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
Hermann Vollbrecht 《国际钢铁研究》1936,9(8):397-404
Mittel zur Vermeidung des Festfressens von Schraubenverbindungen. Versuche mit unlegiertem Stahl, warmfestem Chrom-Molybdän-, austenitischem Chrom-Nickel- und nitriertem Chrom-Aluminium-Molybdän-Stahl in wechselseitiger Zusammenstellung. Messung der Oxydschichtdicke nach 12 h. Erwärmen auf 100 bis 500° sowie des Reibungswertes in Abhängigkeit vom Flächendruck und der Oxydschichtdicke. Versuche an Schraubenverbindungen mit gleichmäßig belasteten Gewindegängen und an gewöhnlichen Schraubenverbindungen. Einfluß einer Lagerzeit von 750 h auf das Festfressen. 相似文献
95.
For the transmission of flexible andhigh data rates in future mobile communicationsystems, the multicarrier transmission technique(Orthogonal Frequency Division Multiplexing, OFDM) canbe regarded as a possible alternative tosingle-carrier transmission that is used in today'ssystems. One of the advantages of OFDM is theflexibility concerning modulation and multiple accesstechniques. Since in OFDM the total bandwidth isdivided into a large number of subcarriers, it can beflexibly shared among all the users. In addition, themodulation scheme can be individually chosen for eachsubcarrier, thus granting the possibility of anadaptation to the radio channel characteristics. Inthis paper, the combination of two different multipleaccess schemes, OFDM-FDMA and OFDM-TDMA, and anappropriate adaptive modulation technique isconsidered for the downlink of a communication system.Different degrees of adaptivity are analysed andcompared to show the benefit of an ``intelligent'multiple access and modulation strategy. For thegiven parameters and assumptions, OFDM-TDMA withadaptive modulation yields an improvement of 6 dB insignal-to-noise ratio (SNR) at a bit error rate (BER)of 10-2. When OFDM-FDMA with adaptive subcarrierallocation is applied, the SNR gain amounts to 12.5 dB(BER of 10-2). 相似文献
96.
Single- and polycrystals of (Mg, Me)O (Me = Fe, Co, Ni) have been oxidized or reduced under appropriate conditions of oxygen partial pressure, at temperatures ranging from 973 to 1673 K The reaction always occurred internally and yielded a two-phase layer. The growth kinetics of this layer were measured and can be interpreted in terms of cation diffusion. The variability of the microstructures developed is emphasized and the effect of temperature, oxygen partial pressure and initial concentration in Me are discussed. 相似文献
97.
98.
99.
Hermann Gewecke 《Holz als Roh- und Werkstoff》1940,3(10):321-325
Zusammenfassung Nach Angabe eines einfachen Verfahrens, um bei der Tr?nkung nach dem Saftverdr?ngungsverfahren die aufgenommene L?sungs- und
damit Salzmenge für H?lzer verschiedenster Art und Herkunft schnell zu ermitteln, werden Ergebnisse derartiger Untersuchungen
mitgeteilt, die zeigen, da? bei der in Deutschland gebr?uchlichen Durchführung des Saftverdr?ngungsverfahrens mit chromarsenhaltigen
Salzgemischen die im Splintholz der Nadelh?lzer aufgenommene Salzmenge das 12- bis 15 fache derjenigen ist, die gerade noch
eine F?ulnis verhindert, und nach einer gründlichen Auslaugung die Sicherheit gegen F?ulnis immer noch eine 8- bis 10 fache
ist.
Mitteilung aus dem Laboratorium der Atlasmaste K.-G. 相似文献
100.