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排序方式: 共有223条查询结果,搜索用时 93 毫秒
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2.
Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios
G. Muthu Kumaran Shelu Garg Kapil Soni Manoj Kumar J.K. Gupta L.D. Sharma K.S. Rama Rao G. Murali Dhar 《Microporous and mesoporous materials》2008,114(1-3):103-109
Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, 27Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH3. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH3 adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities. 相似文献
3.
Systems which have to work at or below a maximum acceptable failure rate should be maintained at predetermined points such that the failure rate does not exceed the acceptable level. As the system ages, the post-maintenance failure rate of the system drops to some newer one, unless the system has been replaced, but does not restore the system to the original state. A branching algorithm with effective dominance rules that curtail the number of nodes created is presented; this algorithm determines the number of maintenance interventions before each replacement in order to minimize the total cost over a finite time horizon. The model considers inflationary trends. A numerical example and computational experience are presented. The authors treat the maintenance cost as constant and successive simple-maintenance intervals as decreasing. Though the cost/maintenance is assumed constant, any increasing maintenance cost function could be incorporated. The optimum solutions depend on the constant improvement factor, first simple-maintenance point, rate of increase in acquisition cost, maintenance cost factor, and planning period 相似文献
4.
Kathiravan Vaiyapuri Thangavel Subramani Ashok Kumar Rajamani Muthu Lakshmi Thangavel Satheesh Kumar Ganesan Selvarajan Palanisamy Kumaresavanji Malaivelusamy 《电子科技学刊:英文版》2022,20(4):345-355
Single crystals of L-alanine cadmium iodide (LACI) were grown by the slow evaporation technique at room temperature. A single-crystal X-ray diffraction (SXRD) model was used to evaluate the crystal structure of the as-grown LACI crystal. The energy dispersive X-ray (EDX) analysis and ultraviolet-visible-near infrared (UV-vis-NIR) transmittance studies were carried out, and the results reveal the presence of elements in the title compound. From the transmittance data, the optical bandgap as a function of photon energy was estimated, and the different optical constants were calculated. A fluorescence study was performed for the LACI crystal. Thermogravimetric and differential thermal analyses have also been studied to investigate the thermal property of the LACI crystal. The efficiency of the second harmonic generation (SHG) of the title crystal was investigated. The magnetic and electrical properties were estimated by the vibrating sample magnetometer (VSM) analysis and impedance study, respectively. 相似文献
5.
Abd Elnaby Kabeel Yazan Taamneh Ravishankar Sathyamurthy Padmanabhan Naveen Kumar Athikesavan Muthu Manokar Thirugnanasambantham Arunkumar 《亚洲传热研究》2019,48(1):100-114
This study primarily focuses on comparative experimental analysis on standalone conventional solar still (CSS), inclined solar still (ISS), and integrated conventional and inclined solar still (CSS‐ISS) for different parameters that affect the freshwater yield. For enhancing the freshwater yield only a few studies are available on still‐still integration. The present novel study provides a greater improvement in improving the freshwater yield by integrating ISS with CSS. This experimental work mainly concentrates on the importance of water depth (d w) and mass flow rate of water ( m w) in the solar still. Water depth inside the conventional still varied from 0.02 to 0.06 m whereas, water is constantly flown with a mass flow rate of 8.33 kg/hour in an ISS with baffles. The experimental result shows that the accumulated freshwater yield from CSS‐ISS, ISS, and CSS were 6.2, 5.04, and 4.24 kg, respectively. CSS‐ISS and ISS produced 46.23% and 18.87% higher productivity than the CSS. From the experimental investigation, it is also identified that the water temperature is significantly improved by 20% using integration as compared with CSS without integration under the same water depth of d w = 0.02 m. The overall improvement in yield was higher in the case of CSS‐ISS. The deviations between experimental and theoretical values of yield from the conventional and modified solar still were in the range of ±7%. 相似文献
6.
Luciano C. Ramires Gabriel Silva Santos Rafaela Pereira Ramires Lucas Furtado da Fonseca Madhan Jeyaraman Sathish Muthu Anna Vitria Lana Gabriel Azzini Curtis Scott Smith Jos Fbio Lana 《International journal of molecular sciences》2022,23(3)
Some say that all diseases begin in the gut. Interestingly, this concept is actually quite old, since it is attributed to the Ancient Greek physician Hippocrates, who proposed the hypothesis nearly 2500 years ago. The continuous breakthroughs in modern medicine have transformed our classic understanding of the gastrointestinal tract (GIT) and human health. Although the gut microbiota (GMB) has proven to be a core component of human health under standard metabolic conditions, there is now also a strong link connecting the composition and function of the GMB to the development of numerous diseases, especially the ones of musculoskeletal nature. The symbiotic microbes that reside in the gastrointestinal tract are very sensitive to biochemical stimuli and may respond in many different ways depending on the nature of these biological signals. Certain variables such as nutrition and physical modulation can either enhance or disrupt the equilibrium between the various species of gut microbes. In fact, fat-rich diets can cause dysbiosis, which decreases the number of protective bacteria and compromises the integrity of the epithelial barrier in the GIT. Overgrowth of pathogenic microbes then release higher quantities of toxic metabolites into the circulatory system, especially the pro-inflammatory cytokines detected in osteoarthritis (OA), thereby promoting inflammation and the initiation of many disease processes throughout the body. Although many studies link OA with GMB perturbations, further research is still needed. 相似文献
7.
In this paper, a new approach for extracting stress intensity factors (SIFs) by the extended element-free Galerkin method, through a crack closure integral (CCI) scheme, is proposed. The CCI calculation is used in conjunction with a local smoothing technique to improve the accuracy of the computed SIFs in a number of case studies of linear elastic fracture mechanics. The cases involve problems of mixed-mode, curved crack and thermo-mechanical loading. The SIFs by CCI, displacement and stress methods are compared with those based on the M-integral technique reported in the literature. The proposed CCI method involves very simple relations, and still gives good accuracy. The convergence of the results is also examined. 相似文献
8.
The mechanics of composite materials and their “fracture behaviors” are relatively complex phenomena to analyze and establish
due to their inconsistent process stability and reliability, combined with production and related processing problems. In
this work, an attempt has been made to statistically analyze the tensile behavior of metal matrix composites. Composites of
aluminum alloy containing 5–20% volume fraction of Al2O3 particles of 15 μm size were prepared by adding alumina particles to a vigorously agitated semi-solid aluminum alloy. Prior
to this, alumina particles were subjected to preheating at 800 °C for 5 h. Particles were then added to the aluminum alloy
and further heated to 850 °C by using a mixer in a nitrogen medium. A total of 20 tension tests were performed for each volume
fraction according to ASTM Standards B557 and using these test data, the initial estimators for an empirical model were obtained.
Using this empirical model, the reliability of the composite characteristics in terms of its tensile strength was assessed.
Another significant implication of the present study is proving the ability and utility of the Weibull statistical distribution
for describing the experimentally measured data on the tensile strength of metal matrix composites, in a more appropriate
manner. 相似文献
9.
S. Muthu P. Maruthamuthu P. R. Vasudeva Rao 《Fullerenes, Nanotubes and Carbon Nanostructures》1993,1(4):481-497
The paper presents data on the photocatalytic decomposition of water and destruction of oxalic acid using the fullerene mixture as a photocatalyst. Based on the data obtained, mechanisms are proposed for the destruction of oxalic acid and splitting of water. 相似文献
10.
Ismail Omar Hababeh Muthu Ramachandran Nicholas Bowring 《The Journal of supercomputing》2007,39(1):3-18
Enhancing the performance of the DDBs (Distributed Database system) can be done by speeding up the computation of the data allocation, leading to higher speed allocation decisions and resulting
in smaller data redundancy and shorter processing time. This paper deals with an integrated method for grouping the distributed
sites into clusters and customizing the database fragments allocation to the clusters and their sites. We design a high speed
clustering and allocating method to determine which fragments would be allocated to which cluster and site so as to maintain
data availability and a constant systemic reliability, and evaluate the performance achieved by this method and demonstrate
its efficiency by means of tabular and graphical representation. We tested our method over different network sites and found
it reduces the data transferred between the sites during the execution time, minimizes the communication cost needed for processing
applications, and handles the database queries and meets their future needs. 相似文献