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排序方式: 共有1034条查询结果,搜索用时 62 毫秒
61.
A shrinkage testimator, based on a test of hypothesis when an initial estimate of the scale parameter is available, has been proposed. The salient feature of the proposed testimator is that, being dependent on the test statistic, it removes arbitrariness in the choice of the shrinkage factor for a given level of significance. Expressions for bias, mean square error and relative efficiency with respect to the conventional estimator have been derived. Also, it has been shown that by taking the square of the shrinkage factor the relative efficiency of the testimator can be increased. 相似文献
62.
Estimation of cutting forces and surface roughness for hard turning using neural networks 总被引:5,自引:1,他引:4
Vishal S. Sharma Suresh Dhiman Rakesh Sehgal S. K. Sharma 《Journal of Intelligent Manufacturing》2008,19(4):473-483
Metal cutting mechanics is quite complicated and it is very difficult to develop a comprehensive model which involves all
cutting parameters affecting machining variables. In this study, machining variables such as cutting forces and surface roughness
are measured during turning at different cutting parameters such as approaching angle, speed, feed and depth of cut. The data
obtained by experimentation is analyzed and used to construct model using neural networks. The model obtained is then tested
with the experimental data and results are indicated. 相似文献
63.
Alexander Vasiliev Hakim Ferroukhi Martin A. Zimmermann Rakesh Chawla 《Annals of Nuclear Energy》2008
Studies in support of the assessment of aging structural materials in pressurized water reactors are being performed at the Paul Scherrer Institut. To that aim, a state-of-the-art methodology based on applying a CASMO-4/SIMULATE-3/MCNPX calculation scheme has been developed. In the frame of the methodology validation, an investigation is currently reported pertaining to the sensitivity of the calculated results, for a specific reactor pressure vessel scraping test, to the nuclear data used with the Monte Carlo code. Thus, the MCNPX-2.4.0 calculations have been carried out using three different data libraries, based on JEF-2.2, ENDF/B-VI.8 and JENDL-3.3 evaluations, respectively. 相似文献
64.
This paper considers the analysis of a single server n-similar unit system. Initially k(<n) units form an orbit which functions if one unit functions at a time and the remaining n − k units work as cold standbys. When a unit fails in the orbit it is instantaneously replaced by one of the standbys with the help of a perfect transfer switch. The system is said to fail when n − k + 1 units have failed. The distribution of time to failure and time to repair of a unit are negative exponential. Using the regenerative point technique several reliability characteristics are obtained to carry out the cost-benefit analysis. 相似文献
65.
Over the past few years, hydrogen has been recognized as a suitable substitute for present vehicular fuels. This paper covers the economic analysis of one of the most promising hydrogen production methods—using wind energy for producing hydrogen through electrolysis of seawater—with a concentration on the Indian transport sector. The analysis provides insights about several questions such as the advantages of offshore plants over coastal installations, economics of large wind-machine clusters, and comparison of cost of producing hydrogen with competing gasoline. Robustness of results has been checked by developing several scenarios such as fast/slow learning rates for wind systems for determining future trends. Results of this analysis show that use of hydrogen for transportation is not likely to be attractive before 2012, and that too with considerable learning in wind, electrolyzer and hydrogen storage technology. 相似文献
66.
A synthetic strategy based on precursor and prepolymer approaches has been adopted for preparing the functional polymeric
agents with urethane linkage and functional groups such as –CONH–, –COOH, –NH–, C–N, –COOR and C–Cl, that can interact with
the pigment surfaces. The agents were tested for their dispersion capacity. High pigment-loaded (as high as 64%) and solvent-free
stainers with potential applications in low-VOC paints were successfully prepared. The stainers were mixed with two commercial
binder resins—namely epoxy base white and polyurethane metal coat binder resins—to get first paints and their coats on various
substrates such as standard glaze paper, tin and mild steel panels. The paint-specific properties, viz. percentage opacity,
color strength, solvent resistance, adhesion, scratch hardness and salt spray resistance, were measured to adjudge the suitability
of high pigment-loaded coats in industrial applications. The properties measured in general showed improvement in spite of
the increase in the pigment loading. The paint coats resisted not only the xylene, petrol, and lubricating oil attack but
also humidity and salt spray (up to 1000 h of exposure). 相似文献
67.
Fei Chen Nikhil Gupta Rakesh K. Behera Pradeep K. Rohatgi 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(6):837-845
Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent?+?inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application. 相似文献
68.
Tract‐tracing study of the extrabulbar Olfactory projections in the brain of some teleosts 下载免费PDF全文
Biagio D'aniello Luciano Luongo Rakesh K. Rastogi Maria Di Meglio Claudia Pinelli 《Microscopy research and technique》2015,78(4):268-276
The extrabulbar olfactory projections (EBOP) is a collection of nerve fibers that originate from primary olfactory receptor neurons. These fibers penetrate into the brain, bypassing the olfactory bulbs (OBs). While the presence of an EBOP has been well established in teleosts, here we morphologically characterize the EBOP structure in four species each with a different morphological relationship of OB with the ventral telencephalic area. Tract‐tracing methods (carbocyanine DiI/DIA and biocytin) were used. FMRFamide immunoreactive nervus terminalis (NT) components were also visualized to define any neuroanatomical relationship between the NT and EBOP. Unilateral DiI/DiA application to the olfactory chamber stained the entire olfactory epithelium, olfactory nerve fibers, and ipsilateral olfactory bulb. Labeled primary olfactory fibers running ventromedially as extrabulbar primary olfactory projections reached various regions of the secondary prosencephalon. Only in Moenkhausia sanctaefilomenae (no olfactory peduncle) did lipophilic tracer‐labeled fibers reach the ipsilateral mesencephalon. The combination of tracing techniques and FMRFamide immunohistochemistry revealed a substantial overlap of the label along the olfactory pathways as well as in the anterior secondary prosencephalon. However, FMRFamide immunoreactivity was never colocalized in the same cellular or fiber component as visualized using tracer molecules. Our results showed a certain uniformity in the neuroanatomy and extension of EBOP in all four species, independent of the pedunculate feature of the OBs. The present study also provided additional evidence to support the view that EBOP and FMRFamide immunoreactive components of the NT are separate anatomical entities. Microsc. Res. Tech. 78:268–276, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
69.
Khushbu Kushwaha Balazs Pinter Syeda A. Shehzadi Chandi C. Malakar Christophe M. L. VandeVelde Frank deProft Kourosch AbbaspourTehrani 《Advanced Synthesis \u0026amp; Catalysis》2016,358(1):41-49
The metal‐free reaction of terminal arylacetylenes with α,α‐dichloroaldimines in 1,1,1,3,3,3‐hexafluoro‐2‐propanol as the sole solvent results in the rapid and selective formation of γ,γ‐dichloro‐β‐amino ketones. In this solvent the expected dichlorinated propargylamines and/or allylic amines are not formed. The dichloromethylene moiety of the aldimine acts as an activating group and is essential to accomplish this transformation. Electron‐rich acetylenes lead to the best results and work well with all imines (with or without α′‐H at the nitrogen substituent), while electron‐deficient acetylenes only reacted with N‐tert‐butylaldimines (no α′‐H). The mechanistic pathway showed 1,1,1,3,3,3‐hexafluoro‐2‐propanol to protonate the aldimine, which in the rate‐determining step will react with the arylacetylene to form a resonance‐stabilized allene cation, which is trapped by a HFIP molecule giving rise to an enol ether, which promptly hydrolyzes to furnish exclusively the β‐amino ketones. Using DFT techniques we found that the first C C bond forming step is the rate‐determining step and is associated with a barrier of about 21 kcal mol−1.
70.
Rakesh Kumar Soni Harjeet Singh Krishna Dutt Priyanka Arora 《Journal of Polymer Research》2010,17(3):411-427
The mixing torque behavior of ter blends of isotactic-polypropylene (iPP) with ethylene-propylene diene rubber (EPDM)/Nitrile
rubber (NBR) was studied with the help of Rheometer using resole type phenolic resin as a cross-linking agents. Systematic
changes with varying blend composition were observed in stress-strain behavior in the yield region viz., width of yield peak,
work of yield, yield stress and yield strain. Analysis of yield stress data was made on the basis of various mathematical
expressions of first power and two-thirds power laws of blend composition dependence and the porosity model. It led to consistent
result from the expressions about the variation of stress concentration effect in both uncross-linked and cross-linked blend
systems. With the aid of scanning electron microscopy (SEM) shapes and sizes of dispersed elastomer phase (EPDM / NBR) domains
at varying blend compositions were studied. 相似文献