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排序方式: 共有336条查询结果,搜索用时 15 毫秒
21.
Ten Philosophical Problems in Belief Revision 总被引:4,自引:0,他引:4
22.
A systematic study of the influence of a glass-water interface on the on-axis trapping of micrometer-sized spherical objects by optical tweezers is presented. The ways in which the escape force and the trapping position, as well as the stiffness of the trap, depend on the focusing depth, the numerical aperture, and the degree of overfilling of the objective entrance pupil are investigated. It is concluded, among other things, that objectives with the highest numerical aperture and the use of large degrees of overfilling do not always provide the optimum trapping conditions at finite depths. 相似文献
23.
Oil Spill Detection in Radarsat and Envisat SAR Images 总被引:8,自引:0,他引:8
Anne H. S. Solberg Camilla Brekke Per Ove Husoy 《Geoscience and Remote Sensing, IEEE Transactions on》2007,45(3):746-755
We present algorithms for automatic detection of oil spills in synthetic aperture radar (SAR) images. The algorithms consist of three main parts, namely: 1) detection of dark spots; 2) feature extraction from the dark spot candidates; and 3) classification of dark spots as oil spills or look-alikes. The algorithms have been trained on a large number of Radarsat and Envisat Advanced Synthetic Aperture Radar (ASAR) images. The performance of the algorithm is compared to manual and semiautomatic approaches in a benchmark study using 59 Radarsat and Envisat images. The algorithms can be considered to be a good alternative to manual inspection when large ocean areas are to be inspected 相似文献
24.
Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes. 相似文献
25.
熔盐电解精炼提纯金属硅(英文) 总被引:1,自引:0,他引:1
蔡靖 罗学涛 卢成浩 Geir Martin HAARBERG Annabelle LAURENT Ole Edvard KONGSTEIN 王淑兰 《中国有色金属学会会刊》2012,22(12):3103-3107
对熔盐电解质中硅的沉积过程进行电化学研究。在 973~223K,在硅氯化物熔盐中采用电解精炼提纯金属硅。结果表明,液态硅铜合金阳极有利于 CaCl2-NaCl-CaO-Si 熔盐体系的电解精炼。ICP-AES 分析结果显示,通过电解精炼可有效去除原料中大量的钛、铝、铁等金属杂质,硅中的硼和磷含量分别由 36×106和 25×106降低至 4.6×10 6和 2.8×10 6,电解能耗约为 9.3 kW·h/kg。 相似文献
26.
An 8-bit, 200 MSPS Folding and Interpolating ADC 总被引:1,自引:0,他引:1
An 8-bit, 200 MSPS folding and interpolating analog-to-digitalconverter, ADC, has been implemented in a 1.2 µmBiCMOS-process. It achieves 7.5 effective bits with a power dissipationof 575mW. The active area is 4mm2. The implementationand measured results are presented. A simple analytical modelfor the interpolation-induced nonlinearity in a folding and interpolatingADC using sinusoidal folding is presented. The bowing of thereference ladder due to interaction with the input stages isanalyzed, and analytical models are derived. 相似文献
27.
The exact distribution of the duration of a visit of a stationary Gaussian process to an interval is not known except for processes with certain simple auto-dependence properties of Markov type. However, the exact mean is known without any restrictive dependence assumptions.Since the duration distribution, or, equivalently, the first outpassage time distribution, is needed in several engineering applications, there is an interest in making the necessary simplifying assumptions concerning the auto-dependence properties of the process. For smooth wide band processes comparisons with simulated results show that it improves the accuracy of the results considerably if a Markov type property, called 0-lag dependence of the first passage time, is imposed on the Slepian model process rather than if it is imposed directly on the original stationary process. The Slepian model process describes the distributional behaviour of the original stationary and ergodic Gaussian process after a crossing into the interval.The resulting duration distribution formulas involve multiple integrals and are therefore numerically complicated. For practical applications a simple three-parameter distribution family is suggested such that it possesses the exact mean. The three parameters may be estimated by fit to some few points obtained by numerical calculation of the multiple integrals. 相似文献
28.
Trond E. Jentoftsen Odd-Arne Lorentsen Ernest W. Dewing Geir M. Haarberg Jomar Thonstad 《Metallurgical and Materials Transactions B》2002,33(6):909-913
The solubility of TiO2 in cryolite-alumina melts at 1020 °C was measured; it decreased with increasing alumina concentration up to ∼3.5 wt pct total
oxide and then increased at higher alumina concentrations. The solubility was found to be 3.1 wt pct Ti in cryolite, and 2.7
wt pct Ti in an alumina-saturated melt. Modeling indicated that the most probable titanium species are TiOF2 and Na2TiO3, which coexist in the solution; the former dominates at low alumina concentrations and the latter at high alumina concentrations.
Additional unknown amounts of fluoride may also be associated with these species. Determination of the solubility of TiO2 in alumina-saturated melts as a function of temperature showed that the solubility increased from 1.9 wt pct Ti at 975 °C
to 2.8 wt pct Ti at 1035 °C, the apparent partial molar enthalpy of dissolution of TiO2 being 88±4 kJ mol−1. 相似文献
29.
Principles of engineering safety: Risk and uncertainty reduction 总被引:1,自引:0,他引:1
This article provides a systematised account of safety engineering practices that clarifies their relation to the goal of safety engineering, namely to increase safety. We list 24 principles referred to in the literature of safety engineering, dividing them into four major categories: Inherently safe design, Safety reserves, Safe fail and Procedural safeguards. It emerges from this systematisation that important aspects of these methods can be better understood with the help of the distinction between risk and uncertainty. 相似文献
30.
Iulian Riposan Mihai Chisamera Stelian Stan Pavel Toboc Geir Grasmo Douglas White Chris Ecob Cathrine Hartung 《Journal of Materials Engineering and Performance》2011,20(1):57-64
Two main chemistry systems of micro-inclusions can be identified in ductile iron: Ca-S-X and Mg-Si-O-X with the majority of
the inclusions regardless of treatment type and location being of the second type, silicates. Laboratory investigations have
shown that simple silicates were present in the matrix, while more complex silicates were present in conjunction with graphite,
probably acting as graphite nucleation sites. In these more complex silicates, elevated levels of Al, Ca, Ce and La were typical.
Comparing micro-particles embedded in iron matrix and graphite nodules of iron treated with pure Mg-metal and iron treated
with MgFeSi alloy showed a higher amount of complex silicates with elevated Al-levels in the iron treated with MgFeSi. Further
laboratory investigation was undertaken to explore which source of Al and which range of residual Al would have a favorable
impact on the graphite nucleation in ductile iron. The work showed that a residual aluminum of 0.005 to 0.020 wt.% appears
to be beneficial for improving ductile iron solidification characteristics without the incidence of pinholes. Greatest benefits
were achieved when introducing the Al into the iron via an inoculant late during processing or via a pre-conditioner to the
base iron. Al added via the MgFeSi provided less benefit. Some case studies illustrating the effect of Al in ductile iron
are also presented, as Al-containing pre-conditioner or/and Al-bearing, FeSi inoculant application. 相似文献