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排序方式: 共有555条查询结果,搜索用时 15 毫秒
11.
Fred N. Tebbe Patricia A. Morris Roger H. French Uma Chowdhry Robert L. Coble 《Journal of the American Ceramic Society》1988,71(4):204-C
Aluminum hydroxide obtained by hydrolysis of triethylaluminum is free of uranium and thorium at detection limits of 1 to 9 parts per billion (ppb). Other impurities commonly associated with aluminum oxides are present at low levels (Fe, ∼ 1 ppm; Si, 3 to 6 ppm). When the organoaluminum is intentionally contaminated with an iron salt, purity is restored by a simple distillation. 相似文献
12.
This experimental study evaluated the water absorption characteristics of pineapple leaf fiber (PALF)–polyester composites of different fiber content. The degree of water absorption was found to increase with fiber loading. The mechanism of diffusion was analyzed and the effect of fiber loading on the sorption kinetics was studied. The diffusion coefficient was calculated and found to increase with fiber content. Studies were also made to correlate water absorption with the cross‐sectional areas of the specimens. The effects of ageing on the tensile properties and dimensional stability of PALF polyester composites were studied under two different ageing conditions. Ageing studies showed a decrease in tensile strength of the composites. The composite specimens subjected to thermal ageing showed only a slight deterioration in strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 503–510, 2004 相似文献
13.
14.
Drilling is a most important and crucial operation in the excavation industries.With the objective of looking into the enhancement of diamond drilling performance detailed laboratory investigations were carried out on phosphate rock.The effect of Poly (Ethylene Oxide) (PEO) added to the drilling water was studied by varying machine parameters and PEO concentration.The responses were rate of penetration and torque at the bit rock interface.Slake durability tests were also performed to understand the slaking behavior of phosphate rock in PEO solutions. 相似文献
15.
Uma Batra S. Ray S. R. Prabhakar 《Journal of Materials Engineering and Performance》2003,12(5):597-601
A ductile iron containing 0.6% copper as the main alloying element was austempered at a fixed austempering temperature of
330 °C for a fixed austempering time of 60 min after austenitization at 850 °C for different austenitization periods of 60,
90, and 120 min. The austempering process was repeated after changing austenitization temperature to 900 °C. The effect of
austenitization temperature and time was studied on the carbon content and its distribution in the austenite after austenitization.
The effect of austenitization parameters was also studied on austempered microstructure, structural parameters like volume
fraction of austenite, X
γ
, carbon content C
γ
, and X
γ
C
γ
, and bainitic ferrite needle size, d
α
after austempering. The average carbon content of austenite increases linearly with austenitization time and reaches a saturation
level. Higher austenitization temperature results in higher carbon content of austenite. As regards the austempered structure,
the lowering austenitization temperature causes significant refinement and more uniform distribution of austempered structure,
and a decrease in the volume fraction of retained austenite. 相似文献
16.
Tunable Thermal‐Sensitive Polymer–Graphene Oxide Composite for Efficient Capture and Release of Viable Circulating Tumor Cells 下载免费PDF全文
17.
Ravi Shanker Vidyarthy Dheerendra Kumar Dwivedi Vasudevan Muthukumaran 《Materials and Manufacturing Processes》2018,33(7):709-717
In the present work, the influence of process parameters such as welding current (I), welding speed (S), and flux coating density (F) on different aspects of weld bead geometry for example depth of penetration (DOP), bead width (BW), depth to width ratio (D/W), and weld fusion zone area (WA) were investigated by using the central composite design (CCD). 9–12% Cr ferritic stainless steel (FSS) plates were welded using A-TIG welding. It was observed that all input variables have a direct influence on the DOP, BW, and D/W. However, flux coating density has no significant effect on WA. Mathematical models were generated from the obtained responses to predict the weld bead geometry. An optimized DOP, BW, D/W, and WA of 6.95?mm, 8.76?mm, 0.80, and 41.99?mm2, respectively, were predicted at the welding current of 213.78 A, the welding speed of 96.22?mm/min, and the flux coating density of 1.99?mg/cm2. Conformity test was done to check the practicability of the developed models. The conformity test results were in good agreement with the predicted values. Arc constriction and reversal in Marangoni convection were considered as major mechanisms for the deep and narrow weld bead during A-TIG welding. 相似文献
18.
Identifying some important success factors in adopting agile software development practices 总被引:3,自引:0,他引:3
Agile software development (ASD) is an emerging approach in software engineering, initially advocated by a group of 17 software professionals who practice a set of “lightweight” methods, and share a common set of values of software development. In this paper, we advance the state-of-the-art of the research in this area by conducting a survey-based ex-post-facto study for identifying factors from the perspective of the ASD practitioners that will influence the success of projects that adopt ASD practices. In this paper, we describe a hypothetical success factors framework we developed to address our research question, the hypotheses we conjectured, the research methodology, the data analysis techniques we used to validate the hypotheses, and the results we obtained from data analysis. The study was conducted using an unprecedentedly large-scale survey-based methodology, consisting of respondents who practice ASD and who had experience practicing plan-driven software development in the past. The study indicates that nine of the 14 hypothesized factors have statistically significant relationship with “Success”. The important success factors that were found are: customer satisfaction, customer collaboration, customer commitment, decision time, corporate culture, control, personal characteristics, societal culture, and training and learning. 相似文献
19.
Thermal conductivity of doped polysilicon layers 总被引:7,自引:0,他引:7
The thermal conductivities of doped polysilicon layers depend on grain size and on the concentration and type of dopant atoms. Previous studies showed that layer processing conditions strongly influence the thermal conductivity, but the effects of grain size and dopant concentration were not investigated in detail. The current study provides thermal conductivity measurements for low-pressure chemical-vapor deposition (LPCVD) polysilicon layers of thickness near 1 μm doped with boron and phosphorus at concentrations between 2.0×1018 cm-3 and 4.1×1019 cm-3 for temperatures from 20 K to 320 K. The data show strongly reduced thermal conductivity values at all temperatures compared to similarly doped single-crystal silicon layers, which indicates that grain boundary scattering dominates the thermal resistance. A thermal conductivity model based on the Boltzmann transport equation reveals that phonon transmission through the grains is high, which accounts for the large phonon mean free paths at low temperatures. Algebraic expressions relating thermal conductivity to grain size and dopant concentration are provided for room temperature. The present results are important for the design of MEMS devices in which heat transfer in polysilicon is important 相似文献
20.