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101.
The novelty of the controlled diffusion solidification (CDS) process is the mixing of two precursor alloys with different
thermal masses to obtain the resultant desired alloy, which is subsequently cast into a near-net-shaped product. The critical
event in the CDS process is the ability to generate a favorable environment during the mixing of the two precursor alloys
to enable a well-distributed and copious nucleation event of the primary Al phase leading to a nondendritic morphology in
the cast part. The turbulence dissipation energy coupled with the undercooling of the precursor alloy with the higher temperature
enables the copious nucleation events, which are well distributed in the resultant mixture. 相似文献
102.
Vani Shankar M. Valsan K. Bhanu Sankara Rao S. D. Pathak 《Transactions of the Indian Institute of Metals》2010,63(2-3):622-627
The aim of the present paper is to study the low cycle fatigue and creep-fatigue interaction behavior of modified 9Cr-1Mo ferritic steel weld joint. Total axial strain controlled continuous cycling tests were conducted between 773 K and 873 K and at strain amplitudes ±0.25%, ±0.4%, ±0.6% and ±1%. Hold tests were also conducted at +0.6% and 823 K and 873 K temperatures to study the creep-fatigue interaction behavior of the weld joint. The alloy exhibited cyclic softening from first cycle onwards irrespective of the loading conditions. Failure location in the weld joint was correlated to the test parameters. Detailed replica study conducted on all the failed specimens revealed that most of the failures occurred in one side of the heat affected zone (HAZ) of the weld joint. Strain localization in the soft zone of the HAZ and subsurface creep cavity formation in this region and their linkage had caused enhanced crack propagation that translated into lower fatigue life of the weld joint at high temperatures. Type IV mode of failure was identified to be operative under tensile hold and high temperatures. The alloy was also found to be compressive dwell sensitive and it was ascertained that the lower life under compression hold compared to tension hold was due to the deleterious effect of oxidation. 相似文献
103.
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105.
Sumanth Shankar Diran Apelian 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):47-54
This work provides a comprehensive understanding of the reactions at the ferrous die/molten metal interface in a metal mold
casting operation. The literature has shown that several important factors influence reactions at the ferrous die/molten aluminum
interface, including temperature of the melt, temperature of the die, alloy chemistry of the melt and die, die surface engineering,
topographical features, and coatings. This article discusses the effect of the more critical factors on soldering, based on
the authors’ investigations. Inaddition, based on a mechanistic understanding of the interface reactions between ferrous die
and molten aluminum, recommendations are given for specific processing issues to alleviate soldering during die casting of
aluminum alloys. 相似文献
106.
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108.
Time-dependent Maxwell's equations in differential and conservation form are solved numerically, and field components are computed for scattering and penetration involving arbitrary 2-D objects using upwind computational fluid dynamics (CFD) based techniques. The Lax-Wendroff explicit scheme, which is second-order accurate in time and space, is used. The object and surrounding space are divided into a number of zones, and the Cartesian coordinate system is converted to local body-fitted coordinate systems in those zones, to handle more conveniently arbitrary geometry cross sections as well as to facilitate implementation of the boundary conditions. The method of characteristic subpath integration, better known as the Riemann solver in CFD, is then applied to the transformed Maxwell's equations, yielding the solution for the field components in the time domain. Both steady-state and transient fields can be computed. A fast Fourier transform is used to obtain frequency-domain information. Both radar cross sections and near field distributions are presented for some canonical geometries 相似文献
109.
Dr. Alexander A. Aksenov Christian E. Sandrock Dr. Weixiang Zhao Shankar Sankaran Michael Schivo Richart Harper Dr. Carol J. Cardona Dr. Zheng Xing Dr. Cristina E. Davis 《Chembiochem : a European journal of chemical biology》2014,15(7):1040-1048
Volatile organic compounds (VOCs) emanating from humans have the potential to revolutionize non‐invasive diagnostics. Yet, little is known about how these compounds are generated by complex biological systems, and even less is known about how these compounds are reflective of a particular physiological state. In this proof‐of‐concept study, we examined VOCs produced directly at the cellular level from B lymphoblastoid cells upon infection with three live influenza virus subtypes: H9N2 (avian), H6N2 (avian), and H1N1 (human). Using a single cell line helped to alleviate some of the complexity and variability when studying VOC production by an entire organism, and it allowed us to discern marked differences in VOC production upon infection of the cells. The patterns of VOCs produced in response to infection were unique for each virus subtype, while several other non‐specific VOCs were produced after infections with all three strains. Also, there was a specific time course of VOC release post infection. Among emitted VOCs, production of esters and other oxygenated compounds was particularly notable, and these may be attributed to increased oxidative stress resulting from infection. Elucidating VOC signatures that result from the host cells response to infection may yield an avenue for non‐invasive diagnostics and therapy of influenza and other viral infections. 相似文献
110.
S. Shankar Manish Kumar Anup K. Ghosh O. P. Thakur 《Journal of Materials Science: Materials in Electronics》2014,25(11):4896-4901
The first measurements are reported for the frequency-dependent conductivity of (1?x)BiFeO3–xBaTiO3 (x = 0.10, 0.15 and 0.30) solid solutions in the frequency range of 100–106 Hz and in the temperature range of 50–300 °C. Powder X-ray diffraction confirms the formation of solid solutions. The dielectric properties were seen to improve with increasing BaTiO3 (BT) content. The conductivity (AC and DC) measurements reveal an inverse variation of the frequency exponent ‘s’ with temperature, high density of states and thermally activated process. The calculated density of states was found to be N(Ef) = 80.2 × 1032 eV?1 cm?1 at 1 kHz and 50 °C for BiFeO3–10 % BaTiO3 (BFO–10 % BT) solid solution. The impedance spectroscopy analysis confirms the presence of grain and grain boundary affecting the conductivity. Our results provide the first unambiguous evidence of conduction in crystallite BFO–BT solid solutions through correlated-barrier-hopping model. 相似文献