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排序方式: 共有106条查询结果,搜索用时 15 毫秒
1.
Effects of circumferential pick spacing on boom type roadheader cutting head performance 总被引:4,自引:0,他引:4
E. Mustafa Eyyuboglu Naci Bolukbasi 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2005,20(5):418-425
Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force–balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads. 相似文献
2.
Sudipta N. Sinha Jan-Michael Frahm Marc Pollefeys Yakup Genc 《Machine Vision and Applications》2011,22(1):207-217
This paper describes novel implementations of the KLT feature tracking and SIFT feature extraction algorithms that run on
the graphics processing unit (GPU) and is suitable for video analysis in real-time vision systems. While significant acceleration
over standard CPU implementations is obtained by exploiting parallelism provided by modern programmable graphics hardware,
the CPU is freed up to run other computations in parallel. Our GPU-based KLT implementation tracks about a thousand features
in real-time at 30 Hz on 1,024 × 768 resolution video which is a 20 times improvement over the CPU. The GPU-based SIFT implementation
extracts about 800 features from 640 × 480 video at 10 Hz which is approximately 10 times faster than an optimized CPU implementation. 相似文献
3.
Lines in one orthographic and two perspective views 总被引:1,自引:0,他引:1
Navab N. Genc Y. Appel M. 《IEEE transactions on pattern analysis and machine intelligence》2003,25(7):912-917
We introduce a linear algorithm to recover the Euclidean motion between an orthographic and two perspective cameras from straight line correspondences filling the gap in the analysis of motion estimation from line correspondences for various projection models. The general relationship between lines in three views is described by the trifocal tensor. Euclidean structure from motion for three perspective views is a special case in which the relationship is defined by a collection of three matrices. Here, we describe the case of two calibrated perspective views and an orthographic view. Similar to the other cases, our linear algorithm requires 13 or more line correspondences to recover 27 coefficients of the trifocal tensor. 相似文献
4.
The low temperature photoluminescence under bias (PLb) and the photoconductivity (PC) of a p-i-n GaInNAs/GaAs multiple quantum well sample have been investigated. Under optical excitation with photons of energy greater than the GaAs bandgap, PC and PLb results show a number of step-like increases when the sample is reverse biased. The nature of these steps, which depends upon the temperature, exciting wavelength and intensity and the number of quantum wells (QWs) in the device, is explained in terms of thermionic emission and negative charge accumulation due to the low confinement of holes in GaInNAs QWs. At high temperature, thermal escape from the wells becomes much more dominant and the steps smear out. 相似文献
5.
Turbidity and chemical oxygen demand (COD) removal efficiencies were analyzed depending on electrode layouts by performing electrocoagulation experiments using horizontal and vertical electrochemical cells. Multiple aluminum plate electrodes were placed into different sections of the electrochemical cells. Removal efficiencies at the horizontal electrochemical cell were always higher than the one’s obtained from the vertical electrochemical cell. But the use of vertical electrochemical cell consumed less energy during the electrocoagulation tests. The highest COD removal efficiencies were 97% and 88% in the horizontal and vertical electrochemical cells, respectively. However, the energy consumption for COD removal in the horizontal electrochemical cell was 47% higher than the energy consumed in the vertical electrochemical cell. 相似文献
6.
Sabriye Acikgoz Yakup Ulusu Seckin Akin Savas Sonmezoglu Isa Gokce Mehmet Naci Inci 《Ceramics International》2014
Green fluorescent protein (GFP) molecules are attached to titanium dioxide and cadmium oxide nanoparticles via sol–gel method and fluorescence dynamics of such a protein–metal oxide assembly is investigated with a conventional time correlated single photon counting technique. As compared to free fluorescent protein molecules, time-resolved experiments show that the fluorescence lifetime of GFP molecules bound to these metal oxide nanoparticles gets shortened dramatically. Such a decrease in the lifetime is measured to be 22 and 43 percent for cadmium oxide and titanium dioxide respectively, which is due to photoinduced electron transfer mechanism caused by the interaction of GFP molecules (donor) and metal oxide nanoparticles (acceptor). Our results yield electron transfer rates of 3.139×108 s−1 and 1.182×108 s−1 from the GFP molecules to titanium dioxide and cadmium oxide nanoparticles, respectively. The electron transfer rates show a marked decrease with increasing driving force energy. This effect represents a clear example of the Marcus inverted region electron transfer process. 相似文献
7.
2,5-dimethylfuran (DMF) is a promising compound in the production of biofuel with high-quality properties. In this study, it is aimed to develop new efficient catalysts to synthesize DMF from 5-hydroxymethylfurfural (HMF). Co, Mn/Co, and Ru/Co catalysts were prepared using the NaBH4 reduction method. The catalysts were subjected to activity tests for the hydrogenation of HMF to DMF by changing the reaction parameters, such as temperature and time. Mn/Co catalysts prepared from metal precursors at various molar ratios of Mn/Co were found to be effective in hydrogenation reactions of HMF to DMF. A 91.8% DMF yield was achieved in the presence of a Mn/Co (50/50) catalyst without noble metal at 180°C for 4 hours. The Brunauer-Emmet-Teller (BET) method, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and induction coupled plasma mass spectroscopy (ICP-MS) techniques were used to characterize the efficient Mn/Co catalyst. 相似文献
8.
Frying is a common and popular cooking method, which has been widely used in food manufacturing, though it is a very energy-intensive process. Energy analysis has been commonly used to assess the performance of fryers. In this study, we attempted to exergetically assess the performance of a potato crisp frying system, which consists of three main components, a combustor, a heat exchanger, and a fryer. In the analysis, we utilized the actual operational data obtained from the literature. We determined exergy destruction in each system component and the whole system. We calculated universal and functional exergy efficiency values for the system components and compared them with each other. We also undertook a parametric study to investigate how the overall cycle performance was affected by changing the reference environment temperature and some operating conditions. We illustrated the exergy results through the Grassmann (exergy loss and flow) diagram. We calculated the universal exergetic efficiency values of 58, 82, and 77% for the combustor, heat exchanger, and fryer, respectively, with a universal exergetic efficiency value of 4% for the whole frying system. We found that the fryer had the highest functional exergetic efficiency value of 74%, followed by the heat exchanger with 47% and the combustor with 0.08%. 相似文献
9.
The electric generating capacity of Turkey must be tripled by 2010 to meet Turkey’s electric power consumption, if the annual 8% growth in electric power consumption continues. Turkey has to make use of its renewable energy resources, such as wind and solar, not only to meet the increasing energy demand, but also for environmental reasons. Studies show that Iskenderun (36°35′N; 36°10′E) located on the Mediterranean coast of Turkey is amongst the possible wind energy generation regions. In the present study, the wind energy potential of the region is statistically analyzed based on 1-year measured hourly time-series wind speed data. The probability density distributions are derived from time-series data and distributional parameters are identified. Two probability density functions are fitted to the measured probability distributions on a monthly basis. The wind energy potential of the location is studied based on the Weibull and the Rayleigh models. 相似文献
10.
We apply absolute beta convergence techniques to cross sectional per capita income data for alternative specifications of
U.S. regions in order to detect whether U.S. regional growth rates are converging over relatively recent time periods. We
also explore whether estimates of convergence differ between economic and political region specifications. We show that convergence
of growth rates across regions of the U.S. has continued in modern times (1969–1997) for almost any regional specification
and for all time frames considered. We do find, however, some difference in convergence rates between economic and political
regions. Convergence coefficients, however, are remarkably similar across alternative economic region specifications.
An earlier version of this paper was presented in February 2003 at the 42nd annual meetings of the Western Regional Science
Association in Rio Rico, Arizona. We would like to thank our session participants in Rio Rico and three anonymous referees
for helpful comments. Any remaining errors or oversights, however, are entirely our responsibility. 相似文献