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排序方式: 共有276条查询结果,搜索用时 15 毫秒
91.
KR Meehan UN Verma R Cahill S Frankel EM Areman RA Sacher R Foelber C Rajagopal EA Gehan ME Lippman A Mazumder 《Canadian Metallurgical Quarterly》1997,20(8):643-651
Incubating hematopoietic stem cells with IL-2 in vitro for 24 h generates cytotoxic T cells. When infused into patients, these cells may stimulate a graft-versus-tumor (GVT) effect. This clinical trial was designed to assess the ability of IL-2 activated peripheral blood stem cells (PBSC) to reconstitute hematopoiesis, to investigate dose levels and dose-limiting toxicities of IL-2, and to evaluate clinical results and preliminary laboratory effects using a combination of IL-2-activated autologous PBSC followed by IL-2 after transplantation. Sixty-one women with stage II-IV breast cancer were treated. After the administration of carboplatin (200 mg/m2/day for 3 days) and cyclophosphamide (2 g/m2/day for 3 days), patients received autologous PBSC that were cultured in IL-2 for 24 h followed by parenteral administration of IL-2 beginning the day of transplantation. Three escalating doses of IL-2 were evaluated with increasing duration up to 4 weeks. Of the 57 patients receiving IL-2 after tranplantation, 19 patients (33.3%) were unable to complete the planned course of IL-2 therapy due to persistent fevers (n = 9), diarrhea (n = 2), pulmonary capillary leak syndrome (n = 3), development of a rash (n = 1), atrial fibrillation (n = 1), or patient's request (n = 3). One death occurred during hospitalization. Engraftment of neutrophils occurred on day 11.5 (mean; range 8-21 days) and platelets on day 11.7 (mean; range 7-33 days). The maximal tolerated dose of IL-2 was 6 x 10(5) IU/m2/day for 4 weeks. Disease-free survival rates for all stages were comparable to current reports in the literature. Preliminary laboratory evaluations include FACScan analysis of the IL-2 activated PBSC demonstrating an increased percentage of CD3+, CD25+, HLA-DR+ T cells. Phenotypically similar cells were present in peripheral blood samples of patients when tested 15 days after transplantation. This study demonstrates successful engraftment with IL-2-activated PBSC after high-dose chemotherapy for women with stage II-IV breast cancer. The regimen is feasible and, although toxicities are common, they are manageable and correlate with increasing dose and duration of IL-2. 相似文献
92.
Due to low content of volatile organic compounds and the ability to reclaim unused material, powder coatings present an environmentally friendly and economical means of providing protective and decorative finishes. Because the ratio of reclaimable material to virgin powder is kept low in many applications, obtaining high first pass transfer efficiency (FPTE) is a topic of current research. Theoretical models necessary to determine optimum operating conditions are very complex due to interactions of multiple parameters that determine FPTE. Frequently, a simplified approach is desirable to obtain solutions for optimization. Empirical methods can be used which can provide adequate tools for optimization in a short time. This paper describes response surface methodology and applies it to enhance the relative first pass transfer efficiency of an industrial powder coating process. 相似文献
93.
The laser surface cladding technique was used to formin situ Fe-Cr-Mn-C alloys on AISI 1016 steel substrate. In this process mixed powders containing Cr, Mn, and C with a ratio of 10:1:1
were delivered using a screw feed, gravity flow carrier gas aided system into the melt pool generated by a 10 kw CO2 laser. This technique produced ultrafine microstructure in the clad alloy. The microstructure of the laser surface clad region
was investigated by optical, scanning, and transmission electron microscopy and X-ray microanalysis techniques. Microstructural
study showed a high degree of grain refinement and an increase in solid solubility of alloying elements which, in turn, produced
a fine distribution of complex types of carbide precipitates in the ferrite matrix because of the high cooling rate. An alloy
of this composition does not show any martensitic or retained austenite phase. In preliminary wear studies the laser clad
Fe-Cr-Mn-C alloys exhibited far superior wear properties compared to Stellite 6 during block-on-cylinder tests. The improved
wear resistance is attributed to the fine distribution of metastable M6C carbides. 相似文献
94.
Non-equilibrium synthesis of Fe-Cr-C-W alloy by laser cladding 总被引:2,自引:0,他引:2
Synthesis of Fe-Cr-C-W alloy using the laser cladding technique offered an opportunity to produce a novel wear-resistant material with fine and uniform microstructure. Use of preheating during laser cladding Fe-Cr-C-W provided crack-free clads. The preheating temperature was very critical to eliminate cracks in the clad. Different complex types of carbide were observed in this research. Overall laser process parameters such as power density or specific energy as well as preheating temperature affected the characteristics of the carbide precipitates in the matrix. The increase of solid solubility and high cooling rate resulted in good metallurgical characteristics. Mostly M6C or M23C6 type carbides were observed. Usually diamond-shaped M6C carbides showed good tribological characteristics. In general, increasing the power density brought an increase of average hardness, while decreasing the power density brought a decrease of wear scar width. The laser-clad Fe-Cr-C-W alloy showed better wear properties than laser-clad Fe-Cr-Mn-C and several times smaller scar width as compared to Stellite 6 hard-facing during line-contact wear testing. 相似文献
95.
Static random-access memories (SRAMs) exhibit faults that are electrical in nature. Functional and electrical testing are performed to diagnose faulty operation. These tests are usually designed from simple fault models that describe the chip interface behavior without a thorough analysis of the chip layout and technology. However, there are certaintechnology and layout-related defects that are internal to the chip and are mostly time-dependent in nature. The resulting failures may or may not seriously degrade the input/output interface behavior. They may show up as electrical faults (such as a slow access fault) and/or functional faults (such as a pattern sensitive fault). However, these faults cannot be described properly with the functional fault models because these models do not take timing into account. Also, electrical fault models that describe merely the input/output interface behavior are inadequate to characterize every possible defect in the basic SRAM cell. Examples of faults produced by these defects are: (a) static data loss, (b) abnormally high currents drawn from the power supply, etc. Generating tests for such faults often requires a thorough understanding and analysis of the circuit technology and layout. In this article, we shall examine ways to characterize and test such faults. We shall divide such faults into two categories depending on the types of SRAMs they effect—silicon SRAMs and GaAs SRAMs. 相似文献
96.
Talmage G. Mazumder S. Brown S.H. Sondergaard N.A. 《Energy Conversion, IEEE Transaction on》1995,10(4):634-644
Designing high performance liquid-metal sliding electrical contacts for homopolar machinery requires a precise knowledge of the magnitudes of the viscous and Joulean losses under various operating conditions. The liquid metal, which is confined to a channel between a rotor and stator, is subjected to a large external magnetic induction while transporting current. Significant power losses can occur in these devices. The geometry and electrical conductivity of the channel walls have a significant effect on these losses. In past theoretical work, copper electrodes were generally treated as perfect electrical conductors as compared to liquid metals. Calculations based on this perfectly conducting electrode approximation predicted unrealistically high power losses. In the present study, the effects of electrodes with finite conductivity on both the viscous dissipation and Joulean heating are explored. Numerical results are presented for both radial and axial magnetic inductions. It is found that the magnetic induction orientation has a significant impact on the losses. The results of this type of analysis can be used to minimize the power losses in the design of liquid-metal sliding electrical contacts 相似文献
97.
Processing,microstructure, and properties of laser-clad Ni alloy FP-5 on Al alloy AA333 总被引:5,自引:0,他引:5
Y. Liu J. Koch J. Mazumder K. Shibata 《Metallurgical and Materials Transactions B》1994,25(3):425-434
This article describes the results of laser cladding Ni alloy FP-5 on Al alloy AA333, microstructure and crystal structure
characterization, and properties of the clad evaluated by Vickers hardness measurement and wear testing. Direct cladding of
Ni alloy on Al alloy creates brittle Ni
x
Al
y
compounds in the interface, which make the interface very brittle, and result in cracking at the interface. The compound
formation is avoided by introducing an intermediate layer of Cu or bronze. The cracking tendency of the clad is prevented
by preheating the substrate to 673 K. The microstructure and crystal structure of the clad and interface are investigated
by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Five phases in the clad layer (including
three new phases) and two phases in the interface are identified by convergent beam electron diffraction (CBED) and selected
area diffraction (SAD) studies. The mechanical properties of the laser-clad Ni alloy are evaluated by Vickers hardness measurements
and wear testing, which show superior results over Cu- and Fe-based alloys. 相似文献
98.
Trigwell S. Grable N. Yurteri C.U. Sharma R. Mazumder M.K. 《Industry Applications, IEEE Transactions on》2003,39(1):79-86
Experiments performed on different powders of different size distributions tribocharged with stainless-steel (SS) beads showed the charge acquired by the powder could be correlated with the actual work function difference between the powder and SS. Ultraviolet and X-ray photoelectron spectroscopy were performed on various materials involved, and showed the work function increased with surface contamination and oxidation, and the difference narrowed for metals and polymers. Such a small difference in work function may contribute to bipolar charging. Experiment data showed that while charge acquired increased with particle size, the charge distribution was generally bipolar. Both surface analysis and charge distribution studies suggest that for tribocharging, minimization of oxidation and surface contamination are needed. It also appears that the relative humidity must also be controlled to obtain reliable tribocharging. Semiempirical molecular modeling calculations of the work function of several polymers showed good agreement with experiment. Surface plasma treatment is presented as a viable method for modifying the work function. 相似文献
99.
Studies on the evaporation phenomenon of a pure ethanol droplet have been mostly confined to the semianalytical modeling in stagnant ambient. Investigation into this aspect in a convective environment by considering the Navier–Stokes equation is also minimal. Hence, in this study we analyze and investigate the evaporation characteristics of a single-component spherical-shaped isolated pure ethanol droplet under force convective air environment by considering both gas- and liquid-phase motions, nonunitary Lewis number in the interface, variable Stefan flow (blowing) effect, and the transient droplet heating. The finite difference method is utilized while solving the governing equations of the spherical polar coordinate system for species, momentum, and energy transfer. The maximum Reynolds number and ambient temperature are kept at 100 and 600 K, respectively. The present work is validated by comparing the normalized surface regression curve of the droplet with the earlier experimental and theoretical results. Using the current simulated data, flow and temperature profiles of both gas and liquid regions are visualized in streamline and isotherm contour plots at various instants of time. It is observed that at a moderate Reynolds number a detached vortex forms at the downstream location of the droplet. However, the detachment length increases with time. The temperature gradients along the droplet surface are observed at the initial stage. Moreover, the heat-up period occupies about 20% of the total lifetime of the droplet. The droplet life and heat-up period decrease with an increase in free-stream velocity. In addition, the saturation temperature increases with ambient temperature. 相似文献
100.
Lijun Song Vijayavel Bagavath-Singh Bhaskar Dutta Jyoti Mazumder 《The International Journal of Advanced Manufacturing Technology》2012,58(1-4):247-256
This paper presents a hybrid control system that is able to improve dimensional accuracy of geometrically complex parts manufactured by direct metal deposition process. The melt pool height is monitored by three high-speed charged couple device cameras in a triangulation setup. The melt pool temperature is monitored by a dual-color pyrometer. A two-input single-output hybrid control system including a master height controller and a slave temperature controller is used to control both height growth and melt pool temperature at each deposition layer. The height controller is a rule-based controller and the temperature controller uses a generalized predictive control algorithm with input constraints. When the melt pool height is above a prescribed layer thickness, the master height controller blocks control actions from the temperature controller and decreases laser power to avoid over-building. When the melt pool height is below the prescribed layer thickness, the temperature controller bypasses the height controller and dynamically adjusts laser power to control the melt pool temperature. This hybrid controller is able to achieve stable layer growth by avoiding both over-building and under-building through heat input control. A complex 3-D turbine blade with improved geometrical accuracy is demonstrated using the hybrid control system. 相似文献