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排序方式: 共有343条查询结果,搜索用时 15 毫秒
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2.
Q. Ahsan A. S. M. A. Haseeb E. Haque J. P. Celis 《Journal of Materials Engineering and Performance》2003,12(3):304-311
This paper describes an investigation on the failure of a large leaded bronze bearing that supports a nine-ton roller of a
plastic calendering machine. At the end of the normal service life of a good bearing, which lasted for seven years, a new
bearing was installed. However the new one failed catastrophically within a few days, generating a huge amount of metallic
wear debris and causing pitting on the surface of the cast iron roller. Following the failure, samples were collected from
both good and failed bearings. The samples were analyzed chemically and their microstructures examined. Both samples were
subjected to accelerated wear tests in a laboratory type pin-on-disk apparatus. During the tests, the bearing materials acted
as pins, which were pressed against a rotating cast iron disk. The wear behaviors of both bearing materials were studied using
weight loss measurement. The worn surfaces of samples and the wear debris were examined by light optical microscope, scanning
electron microscope, and energy-dispersive x-ray microanalyzer. It was found that the laboratory pin-on-disk wear data correlated
well with the plant experience. It is suggested that the higher lead content (∼18%) of the good bearing compared with 7% lead
of the failed bearing helped to establish a protective transfer layer on the worn surface. This transfer layer reduced metal-to-metal
contact between the bearing and the roller and resulted in a lower wear rate. The lower lead content of the failed bearing
does not allow the establishment of a well-protected transfer layer and leads to rapid wear. 相似文献
3.
Memoona Malik Faraz Ahsan Sajjad Mohsin 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2016,20(3):925-938
This paper presents a novel denoising approach based on smoothing linear and nonlinear filters combined with an optimization algorithm. The optimization algorithm used was cuckoo search algorithm and is employed to determine the optimal sequence of filters for each kind of noise. Noises that would be eliminated form images using the proposed approach including Gaussian, speckle, and salt and pepper noise. The denoising behaviour of nonlinear filters and wavelet shrinkage threshold methods have also been analysed and compared with the proposed approach. Results show the robustness of the proposed filter when compared with the state-of-the-art methods in terms of peak signal-to-noise ratio and image quality index. Furthermore, a comparative analysis is provided between the said optimization algorithm and the genetic algorithm. 相似文献
4.
Klara Nahrstedt Zhenyu Yang Wanmin Wu Ahsan Arefin Raoul Rivas 《Multimedia Tools and Applications》2011,51(2):593-623
In the recent past we have seen a boom of distributed interactive multimedia environments which use multiple correlated media
sensors, multi-view displays, and advanced haptic-audio-visual user interfaces for teleimmersive gaming, business meetings
and other collaborative activities. However, when we investigate the emerging teleimmersive environments closer, we realize
that their overall session management, including end-to-end session setup, establishment and run-time management are not appropriate
for the new demands that these environments present. These environments are cyber-physical rooms that demand (a) large scale of multi-sensory devices across geographically-distributed locations and (b) interaction with each other in synchronous and real-time manner. To deal with the new teleimmersive demands, we present a new session management design with (a) session initiation protocol(s) that understand media correlations, (b) view-based multi-stream topology establishment among multiple parties, (c) efficient, light-weight and distributed session monitoring with querying and debugging capabilities, (d) flexible view-based session adaptation with efficient topology adjustments, and (e) light-weighted and consistent session tear-down protocols. The presented design of the next generation session management protocols, services, algorithms and data structures is based
on our extensive experiences with building 3D teleimmersive interactive systems, experimenting with high impact teleimmersive
applications and deploying such environments at various venues. 相似文献
5.
Mohammad M. Hailat Ahsan Mian Zariff A. Chaudhury Golam Newaz Rahul Patwa Hans J. Herfurth 《Microsystem Technologies》2012,18(1):103-112
In this paper continuous laser welding of two dissimilar materials, aluminum and copper, was investigated. The aluminum and
the copper utilized were Al3003-H14 and Cu110-H00, respectively. Two different sets of samples were laser welded; one in which
a filler material, tin foil alloy (S-bond 220), was sandwiched between the aluminum and the copper and another set in which
the aluminum and copper were directly welded without any filler. The foil alloy was utilized to enhance the compatibility
of the two metals; aluminum and copper, reducing the brittleness of the intermetallic compound that may form and, subsequently,
enhance the mechanical properties. The welding was carried out using an IPG 500 SM fiber laser. The length of the laser joint
produced was 20 mm and the width was about 200 μm. The strength of the joint was evaluated by conducting the lap shear stress
test. Samples in which filler foil was used exhibited a better performance in the lap shear stress test (an average of 780 N)
than the samples without tin foil (an average of 650 N). The improvement in the lap shear test could be attributed to the
positive effects of the filler on enhancing the compatibility of the intermetallic compound formed via diffusion. The fracture
surface of both types of joints (with and without filler) was characterized using scanning electron microscope equipped with
energy-dispersive X-ray (EDAX). To understand the failure initiation and propagation of the samples under tension, a finite
element (FE) model was developed for the samples created with no filler material. The failure mechanism predicted from the
FE model matches reasonably well with the experimental observations from EDAX analysis. 相似文献
6.
Federico Waisman Kurtis Gurley Mircea Grigoriu Ahsan Kareem 《Canadian Metallurgical Quarterly》2002,128(7):730-741
Significant interest has been shown in identifying the nonlinear mechanisms that induce a ringing type response in offshore structural systems. This high frequency transient type response has been observed in offshore systems, particularly in tension leg platforms (TLPs). Given the implications of this behavior on the fatigue life of TLP tendons, it is essential that ringing be considered in the overall response evaluation. This study presents two non-Gaussian probabilistic models of nonlinear viscous hydrodynamic wave forces that induce ringing. The response of a single-degree-of-freedom system exposed to these non-Gaussian wave force models is then evaluated using analytical and numerical studies based on the It? differentiation rule and the Monte Carlo simulation procedure, respectively. The results demonstrate that the proposed models induce ringing type response in a simplified structure. This study provides a probabilistic framework for modeling ringing type phenomenon which will serve as a building block for more refined hydrodynamic load models. 相似文献
7.
Giuditta Guerrini Sabrina Gioria Aisha V. Sauer Simone Lucchesi Francesca Montagnani Gabiria Pastore Annalisa Ciabattini Donata Medaglini Luigi Calzolai 《International journal of molecular sciences》2022,23(16)
PEGylated lipids are one of the four constituents of lipid nanoparticle mRNA COVID-19 vaccines. Therefore, various concerns have been raised on the generation of anti-PEG antibodies and their potential role in inducing hypersensitivity reactions following vaccination or in reducing vaccine efficacy due to anti-carrier immunity. Here, we assess the prevalence of anti-PEG antibodies, in a cohort of vaccinated individuals, and give an overview of their time evolution after repeated vaccine administrations. Results indicate that, in our cohort, the presence of PEG in the formulation did not influence the level of anti-Spike antibodies generated upon vaccination and was not related to any reported, serious adverse effects. The time-course analysis of anti-PEG IgG showed no significant booster effect after each dose, whereas for IgM a significant increase in antibody levels was detected after the first and third dose. Data suggest that the presence of PEG in the formulation does not affect safety or efficacy of lipid-nanoparticle-based COVID-19 vaccines. 相似文献
8.
Eslam B. Elkaeed Ibrahim H. Eissa Hazem Elkady Ahmed Abdelalim Ahmad M. Alqaisi Aisha A. Alsfouk Alaa Elwan Ahmed M. Metwaly 《International journal of molecular sciences》2022,23(15)
Among a group of 310 natural antiviral natural metabolites, our team identified three compounds as the most potent natural inhibitors against the SARS-CoV-2 main protease (PDB ID: 5R84), Mpro. The identified compounds are sattazolin and caprolactin A and B. A validated multistage in silico study was conducted using several techniques. First, the molecular structures of the selected metabolites were compared with that of GWS, the co-crystallized ligand of Mpro, in a structural similarity study. The aim of this study was to determine the thirty most similar metabolites (10%) that may bind to the Mpro similar to GWS. Then, molecular docking against Mpro and pharmacophore studies led to the choice of five metabolites that exhibited good binding modes against the Mpro and good fit values against the generated pharmacophore model. Among them, three metabolites were chosen according to ADMET studies. The most promising Mpro inhibitor was determined by toxicity and DFT studies to be caprolactin A (292). Finally, molecular dynamics (MD) simulation studies were performed for caprolactin A to confirm the obtained results and understand the thermodynamic characteristics of the binding. It is hoped that the accomplished results could represent a positive step in the battle against COVID-19 through further in vitro and in vivo studies on the selected compounds. 相似文献
9.
Habibullah Khalilullah Deepak K. Agarwal Mohamed J. Ahsan Surender S. Jadav Hamdoon A. Mohammed Masood Alam Khan Salman A. A. Mohammed Riaz Khan 《International journal of molecular sciences》2022,23(12)
Newly designed series of indole-containing pyrazole analogs, pyrazolinylindoles, were synthesized, and their structures were confirmed based on the spectral data of the 1H NMR, 13C NMR, and HR-MS analyses. Preliminary anti-cancer activity testings were carried out by the National Cancer Institute, United States of America (NCI, USA). Compounds HD02, HD05, and HD12 demonstrated remarkable cytotoxic activities against nine categories of cancer types based cell line panels which included leukemia, colon, breast, melanoma, lungs, renal, prostate, CNS, and ovarian cancer cell lines. The highest cytotoxic effects were exhibited by the compounds HD02 [1-(5-(1-H-indol-3-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)-2-phenylethanone], HD05 [1-(3-(4-chlorophenyl)-5-(1H-indol-3-yl)-4,5-dihydro-1H-pyrazol-1-yl)-2-phenoxyethanone], and HD12 [(3-(4-chlorophenyl)-5-(1H-indol-3-yl)-4,5-dihydro-1H-pyrazol-1-yl)(pyridin-4-yl)methanone] against some of the 56 types of NCI-based cell lines in different panels. Compound HD05 showed the maximum range of cancer cell growth inhibitions against all categories of the cell lines in all nine panels. On average, in comparison to the referral standard, imatinib, at a dose level of 10 µM, the HD05 showed significant activity against leukemia in the range of 78.76%, as compared to the imatinib at 9% of cancer cells’ growth inhibitions. Molecular docking simulation studies were performed in silico on the epidermal growth factor receptor (EGFR) tyrosine kinase, in order to validate the activity. 相似文献
10.
The formulation and solution of multi‐criteria healthcare decision problems is of critical importance to the health and socio‐economic betterment of developing countries. The study shows how the multi‐criteria decision‐making method could facilitate implementation of healthcare performance analysis, especially for the public healthcare system of Bangladesh, which operates mainly through thana health complexes (THCs). We include outreach services and rural facilities together with ongoing THC activities, and analyze their relative performance. The methodology uses a phase of the Delphi method and of the analytic hierarchy process (AHP) approach. The outcome of Delphi is used as input for the hierarchical processing procedure in AHP and determines performance order of the healthcare activities. Results from AHP are discussed for implementation in decision‐making and the managerial policymaking process, towards improvement of overall healthcare performance. 相似文献