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排序方式: 共有126条查询结果,搜索用时 93 毫秒
121.
Auger Depth Profiling of Carbonized SiC/Si Samples 总被引:1,自引:0,他引:1
Silicon carbide (SiC) has been prepared by passing natural gas over (100) oriented hot Si substrate at different temperatures in the range 930~1000℃. Reaction times of 60 and 90 min are used.Depth profile, using Auger Electron Spectroscopy, shows the formation of SiC under a thin coating of carbon for the samples prepared at 930 and 950℃. Annealing, at 1050℃ for 12 h,results in a more pronounced formation of SiC. It is found that at the temperature of 1000℃and reaction times of 60 and 90 min, a hard diamond-like coating is formed. 相似文献
122.
Tuuli Toivonen Risto Kalliola Kalle Ruokolainen Riffat Naseem Malik 《Remote sensing of environment》2006,100(4):550-562
An analysis of tropical rain forest covering Amazonian lowlands has highlighted a systematic across-path, east–west radiometric gradient within Landsat TM imagery. Visual assessment of 45 and quantitative analysis of 20 Amazonian Landsat-4 and -5 TM scenes show that the gradient is band dependent and pronounced in visible light bands 1 to 3 but significant also in IR bands 4 to 7. The results show that the scan line location of a pixel explains a considerable amount of the DN variation of forests in the width of the entire scene (B1: 70%, B2: 52%, B3: 44%, B4: 34%, B5: 46%, B7: 39%). In digital numbers, the difference between east and west side of a scene may be small (9, 4, 3, 10, 9, 3, respectively) but these differences become significant if the images are to be mosaicked, or the data are used for mapping relatively subtle differences of natural forests. Apparently, the gradient is a result of at least three factors: 1) shadows caused by the undulating terrain, 2) anisotropic reflectance of the varying surfaces, and 3) atmospheric scattering. The phenomenon becomes more significant when the sun is high and the scanning line is close to solar azimuth direction—a condition more easily encountered in lower latitudes of the earth. 相似文献
123.
Naseem Uddin Sven Olaf Neumann Bernhard Weigand Bassam A. Younis 《Numerical Heat Transfer, Part A: Applications》2013,63(10):906-930
This article documents the results of an investigation into aspects of the simulation and modeling of turbulent jets that impinge orthogonally on a target surface. The focus is on the case of a jet which issues from a circular pipe into stagnant surrounding at the relatively high value of Reynolds number of 23,000 (based on nozzle diameter and bulk velocity) for which experimental data are available. Large-eddy simulations were performed to obtain details of the mean flows and the turbulence fields including distributions of all components of the turbulent heat fluxes. The outcome of these simulations were used to assess three alternative models for the turbulent heat fluxes which differ from the conventional Fourier's Law by not being based on the assumption of proportionality between the eddy and thermal diffusivities via a constant Prandtl number. It was found that only one of the models considered succeeds in representing the effects on the heat fluxes of the complex strain field associated with the stagnation region and the subsequent development into the wall-jet region. The reasons for this outcome are discussed. 相似文献
124.
Usman Allauddin Rafay Mohiuddin Hafiz Mohammad Usman Khan Naseem Uddin Waqar A. Khan 《亚洲传热研究》2021,50(1):81-104
In the current numerical study, the thermal and flow field performance of an array of confined multiple jets with air, water, and water‐Al2O3 nanofluid in the maximum crossflow configuration over the target plate with and without pin fins is investigated. The numerical results are validated with the experimental data; it is found that a reasonable prediction related to heat transfer can be made. For this study, steady‐state Reynolds‐averaged Navier‐Stokes simulations with the shear‐stress transport turbulence model in ANSYS Fluent were performed. The simulations are performed with volumetric concentration to 3% and the jet's Reynolds number Re = 15 000 to 35 000. In all cases, the jet outlet‐to‐target plate distance is 3. It is found that the increase in values of the volumetric concentration of nanoparticles results in a decrease of the Nusselt number and an increase of the convective heat transfer coefficient. This is because there is an increase in thermal conductivity of the working fluid with the increase in the volumetric concentration of nanoparticles for the same Reynolds number. About 81.5% and 89.1% enhancement in the average heat transfer flux values is observed for flat and pin fin‐roughened target plates, respectively, for . 相似文献
125.
Henriksen SS Ding M Juhl MV Theilgaard N Overgaard S 《Journal of materials science. Materials in medicine》2011,22(5):1111-1118
Eight groups of calcium-phosphate scaffolds for bone implantation were prepared of which seven were reinforced with biopolymers,
poly lactic acid (PLA) or hyaluronic acid in different concentrations in order to increase the mechanical strength, without
significantly impairing the microarchitecture. Controls were un-reinforced calcium-phosphate scaffolds. Microarchitectural
properties were quantified using micro-CT scanning. Mechanical properties were evaluated by destructive compression testing.
Results showed that adding 10 or 15% PLA to the scaffold significantly increased the mechanical strength. The increase in
mechanical strength was seen as a result of increased scaffold thickness and changes to plate-like structure. However, the
porosity was significantly lowered as a consequence of adding 15% PLA, whereas adding 10% PLA had no significant effect on
porosity. Hyaluronic acid had no significant effect on mechanical strength. The novel composite scaffold is comparable to
that of human bone which may be suitable for transplantation in specific weight-bearing situations, such as long bone repair. 相似文献
126.
Jamal Uddin Rozaida Ghazali Mustafa Mat Deris Rashid Naseem Habib Shah 《Artificial Intelligence Review》2017,47(2):145-180
Daily large number of bug reports are received in large open and close source bug tracking systems. Dealing with these reports manually utilizes time and resources which leads to delaying the resolution of important bugs. As an important process in software maintenance, bug triaging process carefully analyze these bug reports to determine, for example, whether the bugs are duplicate or unique, important or unimportant, and who will resolve them. Assigning bug reports based on their priority or importance may play an important role in enhancing the bug triaging process. The accurate and timely prioritization and hence resolution of these bug reports not only improves the quality of software maintenance task but also provides the basis to keep particular software alive. In the past decade, various studies have been conducted to prioritize bug reports using data mining techniques like classification, information retrieval and clustering that can overcome incorrect prioritization. Due to their popularity and importance, we survey the automated bug prioritization processes in a systematic way. In particular, this paper gives a small theoretical study for bug reports to motivate the necessity for work on bug prioritization. The existing work on bug prioritization and some possible problems in working with bug prioritization are summarized. 相似文献