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排序方式: 共有1964条查询结果,搜索用时 31 毫秒
31.
Lutz Hofmann Tobias Fischer Thomas Werner Franz Selbmann Michael Rennau Ramona Ecke Stefan E. Schulz Thomas Geßner 《Microsystem Technologies》2016,22(7):1665-1677
This paper discusses approaches for the isolation of deep high aspect ratio through silicon vias (TSV) with respect to a Via Last approach for micro-electro-mechanical systems (MEMS). Selected TSV samples have depths in the range of 170…270 µm and a diameter of 50 µm. The investigations comprise the deposition of different layer stacks by means of subatmospheric and plasma enhanced chemical vapour deposition (PECVD) of tetraethyl orthosilicate; Si(OC2H5)4 (TEOS). Moreover, an etch-back approach and the selective deposition on SiN were also included in the investigations. With respect to the Via Last approach, the contact opening at the TSV bottom by means of a specific spacer-etching method have been addressed within this paper. Step coverage values of up to 74 % were achieved for the best of those approaches. As an alternative to the SiO2-isolation liners a polymer coating based on the CVD of Parylene F was investigated, which yields even higher step coverage in the range of 80 % at the lower TSV sidewall for a surface film thickness of about 1000 nm. Leakage current measurements were performed and values below 0.1 nA/cm2 at 10 kV/cm were determined for the Parylene F films which represents a promising result for the aspired application to Via Last MEMS-TSV. 相似文献
32.
33.
In this paper, I review both mathematics education and CSCL literature and discuss how we can better take advantage of CSCL tools for developing mathematical proof skills. I introduce a model of proof in school mathematics that incorporates both empirical and deductive ways of knowing. I argue that two major forces have given rise to this conception of proving: a particular learning perspective promoted in reform documents and a genre of computer tools, namely dynamic geometry software, which affords this perspective of learning within the context of mathematical proof. Tracing the move from absolutism to fallibilism in the philosophy of mathematics, I highlight the vital role of community in the production of mathematical knowledge. This leads me to an examination of a certain CSCL tool whose design is guided by knowledge-building pedagogy. I argue that knowledge building is a suitable pedagogical approach for the proof model presented in this paper. Furthermore, I suggest software modifications that will better support learners’ participation in authentic proof tasks. 相似文献
34.
Sparse nonlinear classification and regression models in reproducing kernel Hilbert spaces (RKHSs) are considered. The use of Mercer kernels and the square loss function gives rise to an overdetermined linear least-squares problem in the corresponding RKHS. When we apply a greedy forward selection scheme, the least-squares problem may be solved by an order-recursive update of the pseudoinverse in each iteration step. The computational time is linear with respect to the number of the selected training samples. 相似文献
35.
Sevan Platin Elif Ö. Özer Ugur Akman Öner Hortaçsu 《Journal of the American Oil Chemists' Society》1994,71(8):833-837
Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve
key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO2 were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular
weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO2 are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO2 within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than
about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all
monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher
vapor pressures of these components and significantly lower solvating power of the dense-gas solvent at these particular temperatures
and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and
molecular mass of the key components. Deterpenation of spearmint oil with dense CO2 is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO2-rich phase. 相似文献
36.
37.
Ümit Sönmez 《International Journal of Mechanics and Materials in Design》2006,3(4):347-360
Buckling dynamics of a pinned-pinned flexible imperfect beam attached to a sliding mass is investigated using nonlinear Elastica
theory. Initially straight flexible buckling beam having pinned end boundary conditions loaded at one of its end with curved
imperfection is considered. Large deflection analysis of flexible beam is studied using nonlinear Elastica theory. Imperfection
analysis of the flexible beam is investigated considering the imperfection as an initial curvature. The governing differential
equations are expressed in terms of nonlinear functions that are typical of flexible beams, generally leading to highly implicit
relationships involving elliptic integrals and functions. Dynamic simulation of the flexible beam is studied using numerical
simulation procedures with various types of loading (step, ramp, and sinusoidal) assuming this member buckles in its first
mode. Dynamic response of the imperfect buckling Elastica has been obtained by using numerical Runge-Kutta methods. Load deflection
characteristics of flexible beams are presented in polynomial curve fits. The polynomial curve fits obtained from nonlinear
inextensible exact beam theory may then be used as the nonlinear lumped system stiffness. The buckling Elastica may find applications
in compliant mechanism design. The motivation behind this research is not only to present the dynamic behavior of the buckling
beam considering the magnitude of the imperfection but also to provide a tool to design new types of compliant mechanisms.
Original compliant mechanism designs are presented demonstrating where the buckling dynamics of imperfect Elastica or flexible
curved beams might be needed in mechanism design and synthesis. 相似文献
38.
C. Yürdü S. Işçi C. Ünlü O. Atici Ö. I. Ece N. Güngör 《Bulletin of Materials Science》2005,28(6):623-628
In this study, the rheologic and colloidal characterizations of sodium montmorillonite (NaMMT) were examined. Hexadecylamine
(CH3(CH2)15NH2, HDA) was added to the bentonite water dispersion (2%, w/w) in different concentrations in the range 5.6 × 10−4−9.4 × 10−3 mmol/l. The rheological and electrokinetic behaviour of aqueous montmorillonite dispersions was investigated as a function
of solid content and HDA concentration. The basal spacings of the HDA/NaMMT composites were studied by X-ray diffraction.
The FTIR spectra were obtained from the modified bentonite products, which revealed the characteristic absorbances after treatment
with HDA. 相似文献
39.
Consideration of the errors inherent in mapping historical glacier positions in Austria from the ground and space (1893-2001) 总被引:4,自引:0,他引:4
Dorothy K. Hall Klaus J. BayrWolfgang Schöner Robert A. BindschadlerJanet Y.L. Chien 《Remote sensing of environment》2003,86(4):566-577
The historical record of in situ measurements of the terminus positions of the Pasterze and Kleines Fleißkees glaciers in the eastern Alps of Austria is used to assess uncertainties in the measurement of decadal scale changes using satellite data. Topographic maps beginning in 1893, and satellite data from 1976 to 2001, were studied in concert with ground measurements to measure glacier changes. Ground measurements show that the tongue of the Pasterze Glacier receded ∼1150 m from 1893 to 2001, while satellite-derived measurements, using August 2001 Landsat Enhanced Thematic Mapper Plus (ETM+) data registered to an 1893 topographic map, show a recession of 1300-1800 m, with an unknown error. The measurement accuracy depends on the registration technique and the pixel resolution of the sensor when two satellite images are used. When using topographic maps, an additional source of error is the accuracy of the glacier position shown on the map. Between 1976 and 2001, Landsat-derived measurements show a recession of the terminus of the Pasterze Glacier of 479±136 m (at an average rate of 19.1 m a−1) while measurements from the ground showed a recession of 428 m (at an average rate of 17.1 m a−1). Four-meter resolution Ikonos satellite images from 2000 and 2001 reveal a shrinkage of 22,096±46 m2 in the Pasterze tongue. The nearby Kleines Fleißkees glacier lost 30% of its area between 1984 and 2001, and the area of exposed ice increased by 0.44±0.0023 km2, according to Landsat satellite measurements. As more recent satellite images are utilized, especially data that are geocoded, the uncertainty associated with measuring glacier changes has decreased. It is not possible to assess the uncertainty when an old topographic map and a satellite image are coregistered. 相似文献
40.
This study presents the possibility of the power flattening in the ARIES-RS breeder reactor using mixed (Th,U)C or (Th,U)N fuels. Two different types of mixing, namely, homogeneous mixing (HM) and linear mixing (LM) were used to investigate the uniformity of fission power distribution through the fuel zone. In HM, fraction of uranium content were kept constant in all rows of the fuel zone whereas, in LM the fraction of the uranium were linearly increased from the first to last fuel row in the fuel zone. Neutron transport calculations were performed with the aid of the SCALE4.3 system by solving the Boltzmann transport equation with the XSDRNPM code in 238 neutron groups and a S8–P3 approximation. Flat fission power distribution was maintained successfully for the blanket using linearly mixed fuels. However, the fission density profile was not uniform in the blanket with homogeneously mixed fuels. It decreased exponentially form the 1st to 10th fuel row. 相似文献