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排序方式: 共有6275条查询结果,搜索用时 23 毫秒
91.
Hoh Huey Jiun Ibrahim Ahmad Azman Jalar Ghazali Omar 《Microelectronics Reliability》2006,46(5-6):836-845
This paper characterizes die damage resulting from various wafer thinning processes. Die fracture strength is measured using ball breaker test with respect to die surface finish. Further study on surface roughness and topography of each surface finish is obtained by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Stress relief process with 25 μm removal is able to strengthen 100 μm wafer by 20.4% using chemical wet etch and 75 μm wafer by 36.4% with plasma etch. Relatively, plasma etching shows higher fracture strength and flexibility compared to chemical wet etch. This is due to topography of the finished surface of plasma etch is smoother and rounded, leading to a reduced stress concentration, hence improved fracture strength. 相似文献
92.
Ahmad A. Hamid Wael W. El-Dakhakhni Zeyad H. R. Hakam Mohamed Elgaaly 《Canadian Metallurgical Quarterly》2005,9(1):73-83
An experimental investigation was conducted to study the in-plane behavior of face shell mortar bedded unreinforced masonry (URM) wall assemblages retrofitted with fiber-reinforced polymer (FRP) laminates. Forty-two URM assemblages were tested under different stress conditions present in masonry shear and infill walls. Tests included prisms loaded in compression with different bed joint orientation (on/off-axis compression), diagonal tension specimens, and specimens loaded under joint shear. The behavior of each specimen type is discussed with emphasis on modes of failure, strength and deformation characteristics. Results showed that the application of FRP laminates on URM has a great influence on strength, postpeak behavior, as well as altering failure modes and maintaining the specimen integrity. The retrofitted specimens reached compressive strength of 1.62–5.64 times that of their unretrofitted counterparts, depending on the bed joint orientation, and joint shear strength increased by eightfold. 相似文献
93.
A novel pressurised chamber was designed to construct a special purpose test rig to achieve saturated liquid state of refrigerants for lubricated rolling contact fatigue experiments. Traditional bench testing using refrigerants as the lubricant is difficult due to the gaseous phase at standard atmospheric conditions. Pressurising the concentrated contact test chamber is therefore necessary to evaluate at a liquid state and therefore simulate practical applications. The gas/liquid phase transitions have a significant influence on the lubricant properties and hence wear mechanisms. It is necessary to modify the wear test conditions for the Hydrocarbon (HC) and Hydrofluorocarbon refrigerants to obtain realistic simulation of refrigerator compressor tests. The chamber design and test rig are described in this paper. A preliminary experimental study of the influence of the HC (R600a) on rolling wear of the silicon nitride (Si3N4)/steel elements using the pressurised chamber is presented. Rolling fatigue test methods are adopted to measure the wear performance of silicon nitride/steel bearing materials. In this case the rolling wear mechanisms of Si3N4 were measured using R600a refrigerant lubrication. 相似文献
94.
Ahmad E. Valavanis A. Claydon J.S. Lu Y.X. Xu Y.B. 《IEEE transactions on magnetics》2005,41(10):2592-2594
We report experimental transport measurements of a vertical hybrid ferromagnetic (FM)/III-V semiconductor (SC)/ferromagnetic(FM) type structure, i.e., Cr(20ML)/Co(15ML)/GaAs(50 nm, n-type)/Al/sub 0.3/Ga/sub 0.7/As(200 nm, n-type)/FeNi(30 nm). The current-voltage (I-V) characteristics reveal Schottky/tunneling type behavior in the direction of FeNi/Semiconductor/Co and observed to be dependent on external magnetic field. The magnetoresistance (MR) behavior shows a strong dependence on the measured current and field. At low fields no significant change in MR has been observed with increasing current. However, at high fields the MR initially increases with increasing current and becomes stable beyond a critical current of 10 /spl mu/A. A maximum of 12% change in the MR has been observed at room temperature, which is far larger than that of the conventional AMR effect. This property of the device could be utilized as field sensors or magnetic logic devices. 相似文献
95.
On exploiting task duplication in parallel program scheduling 总被引:1,自引:0,他引:1
Ishfaq Ahmad Yu-Kwong Kwok 《Parallel and Distributed Systems, IEEE Transactions on》1998,9(9):872-892
One of the main obstacles in obtaining high performance from message-passing multicomputer systems is the inevitable communication overhead which is incurred when tasks executing on different processors exchange data. Given a task graph, duplication-based scheduling can mitigate this overhead by allocating some of the tasks redundantly on more than one processor. In this paper, we focus on the problem of using duplication in static scheduling of task graphs on parallel and distributed systems. We discuss five previously proposed algorithms and examine their merits and demerits. We describe some of the essential principles for exploiting duplication in a more useful manner and, based on these principles, propose an algorithm which outperforms the previous algorithms. The proposed algorithm generates optimal solutions for a number of task graphs. The algorithm assumes an unbounded number of processors. For scheduling on a bounded number of processors, we propose a second algorithm which controls the degree of duplication according to the number of available processors. The proposed algorithms are analytically and experimentally evaluated and are also compared with the previous algorithms 相似文献
96.
Notoriously high delays in accessing Web pages loaded with massive multimedia objects are highly undesirable. Inspired by the requirements of news agencies and other information providers to include multimedia content in their pages, this paper proposes a new solution to the problem of minimizing the Web response time. We consider an environment that consists of a central multimedia repository and various sites physically dispersed. Our approach is based on simultaneous downloading of some of the embedded multimedia objects from the repository, and the rest from the regional servers. We propose a cost model to formalize the relative benefits of the proposed scheme, and design an algorithm that replicates multimedia objects so as to take advantage of concurrency in data transferring. An extensive simulation study evaluates the performance of the proposed replication policy under storage and processing capacity constraints, as well as with various network transfer rates. Comparisons are carried out with alternative schemes. 相似文献
97.
In this study, NIMROD simulations are performed to investigate the effects of massive helium gas injection level on the induced disruption on EAST tokamak. It is demonstrated in simulations that two different scenarios of plasma cooling(complete cooling and partial cooling) take place for different amounts of injected impurities. For the impurity injection above a critical level, a single MHD activity is able to induce a complete core temperature collapse. For impurity injection below the critical level, a series of multiple minor disruptions occur before the complete thermal quench. 相似文献
98.
Alireza Shirazi Ahmad Varvani-Farahani Hua Lu 《International Journal of Fracture》2008,151(2):135-150
The present study attempts to evaluate the stress-strain hysteresis responses of SAC solder joints in Resistor and FleXBGA144
packages subjected to thermal cyclic loading using several constitutive models. The total deformation of the solder material
consists of elastic, rate-independent plastic and rate-dependent creep components. The constitutive models discussed in this
study each weighted elastic, plastic and creep deformations differently. At low stresses SAC solder alloys were found to be
creep resistant, where at higher stresses, the influence of different microstructures disappears as matrix-creep dominates
in this region. Thus, the proper constitutive model requires all the three ingredients of the elastic, the creep, and the
time-independent plastic data for different stress levels to effectively predict the hysteresis behavior of the SAC solder
alloys. The hysteresis loops predicted by constitutive models were also found in close agreement with the loops generated
by FEM for the SAC solder joint subjected to thermal cycling. 相似文献
99.
Raj Munshi Suhail Ahmad 《Hemodialysis international. International Symposium on Home Hemodialysis》2014,18(1):172-174
Rapid removal of small molecules during hemodialysis places an acutely ill patient with kidney failure at an increased risk of hemodynamic instability and for dialysis disequilibrium syndrome. The use of high‐flux, high‐efficiency (HEF) dialyzers may increase this risk despite reductions in blood and dialysate flow. We performed in vitro experiments to compare urea clearance at low dialysate flow and various blood flows using a low‐efficiency low‐flux (LEF) and a HEF membrane. Compared to LEF, there was a significant increase in the clearance of urea at all blood flows with the HEF (all P values < 0.005). HEF dialyzer (F180NR) had higher urea clearance at a blood flow of 150 mL/min than LEF dialyzer (F5) at blood flow of 300 mL/min (144.1 ± 0.99 vs. 130.1 ± 0.001 mL/min for F180 vs. F5, respectively, P < 0.002). Our data suggest that use of HEF dialyzer are not as safe as LEF in high‐risk acute dialysis patients since these are associated with more rapid removal of urea despite reduction in blood and dialysate flow as compared to LEF. 相似文献
100.
Shweta Pandey Asiya Mahtab Vijay Kumar Farhan Jalees Ahmad Anita Kamra Verma 《Drug development and industrial pharmacy》2013,39(7):1181-1192
The aim of this investigation is the management of rheumatoid arthritis (RA) by developing methotrexate-loaded calcium phosphate nanoparticles (MTX-CAP-NP) and to evaluate pharmacokinetic and pharmacodynamic behavior in adjuvant induced arthritis model. The nanoparticles were synthesized by wet precipitation method and optimized by Box-Behnken experimental design. MTX-CAP-NPs were characterized by TEM, FTIR, DSC and XRD studies. The particle size, zeta potential and entrapment efficiency of the optimized nanoparticles were found to be 204.90?±?64?nm, ?11.58?±?4.80?mV, and 88.33?±?3.74%, respectively. TEM, FTIR, DSC and XRD studies revealed that the developed nanoparticles were nearly spherical in shape and the crystalline structure of CAP-NP was not changed after MTX loading. The pharmacokinetic studies revealed that MTX-CAP-NP enhanced bioavailability of MTX by 2.6-fold when compared to marketed formulation (FOLITRAX-10). Under pharmacodynamic evaluation, arthritic assessment, radiography and histopathology studies revealed that CAP has ability to regenerate cartilage and bone therefore, together with MTX, MTX-CAP-NPs have shown significant reduction in disease progression. The overall work demonstrated that the developed nanodelivery system was well tolerated and more effective than the marketed formulation. 相似文献