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831.
Sarbjit Kaur Raymond A. Cutler Dinesh K. Shetty 《Journal of the American Ceramic Society》2009,92(1):179-185
The fracture toughness of four different silicon carbides was measured using single-edge precracked beam (SEPB) and indentation/strength techniques. Two were development grades with similar microstructures and chemistries, and yet exhibited different fracture modes. The grade that exhibited a predominantly intergranular fracture had an SEPB fracture toughness (6.4 MPa√m) 88% higher than the one that showed primarily a transgranular fracture (3.4 MPa√m). The higher fracture toughness was associated with a modest increase in average strength (25%), although there was a significant increase in the Weibull modulus (11–32). Fracture toughness at short crack lengths was assessed by an indentation method that used fracture strengths, crack lengths at fracture, and a new method of estimating the constant δ that characterizes the residual driving force of the plastic zones based on the stable growth of the indentation cracks from the initial ( c 0 ) to the instability ( c * ) lengths. The results showed a rising crack-growth-resistance behavior for the grade exhibiting intergranular fracture, while the grade showing transgranular fracture had a flat crack-growth resistance. Tests on two commercial grades of silicon carbide showed similar behaviors associated with the respective fracture modes. 相似文献
832.
Interactive surface decomposition for polyhedral morphing 总被引:4,自引:0,他引:4
Arthur Gregory Andrei State Ming C. Lin Dinesh Manocha Mark A. Livingston 《The Visual computer》1999,15(9):453-470
833.
Dinesh Prasad D.R. Bhaskar A.K. Singh 《AEUE-International Journal of Electronics and Communications》2009,63(6):497-501
A new universal current-mode biquad filter using current differencing transconductance amplifier (CDTA) is proposed. The proposed configuration can realize the second-order low pass, high pass, band pass, and band reject responses simultaneously. The circuit employs both grounded capacitors (ideal for integrated circuit implementation), and offers low active and passive sensitivities. The workability of the proposed configuration has been verified using SPICE simulation. 相似文献
834.
Ca0.5 Sr0.5 Zr4 P6 O24 and Ba1.25 Zr4 P5.5 Si0.5 O24 compositions, which belong to the [NZP] family of low-thermal-expansion materials, were synthesized by the combustion reaction method using urea as a fuel and NH4 NO3 as an oxidizer. The combustion method is a highly exothermic reaction often referred to as self-propagating high-temperature synthesis. The raw materials used were metal zirconates and fine ZrO2 powders. An earlier-described combustion method using metal nitrates, zirconium oxynitrate, and ammonium dihydrophosphate to synthesize [NZP] compounds was modified in the present study by replacing these costly raw materials with less-expensive oxides. The reactivity of different combinations of raw materials also is discussed. 相似文献
835.
Trends in the Molecular Pathogenesis and Clinical Therapeutics of Common Neurodegenerative Disorders
Yahya E. Choonara Viness Pillay Lisa C. du Toit Girish Modi Dinesh Naidoo Valence M.K. Ndesendo Sibongile R. Sibambo 《International journal of molecular sciences》2009,10(6):2510-2557
The term neurodegenerative disorders, encompasses a variety of underlying conditions, sporadic and/or familial and are characterized by the persistent loss of neuronal subtypes. These disorders can disrupt molecular pathways, synapses, neuronal subpopulations and local circuits in specific brain regions, as well as higher-order neural networks. Abnormal network activities may result in a vicious cycle, further impairing the integrity and functions of neurons and synapses, for example, through aberrant excitation or inhibition. The most common neurodegenerative disorders are Alzheimer’s disease, Parkinson’s disease, Amyotrophic Lateral Sclerosis and Huntington’s disease. The molecular features of these disorders have been extensively researched and various unique neurotherapeutic interventions have been developed. However, there is an enormous coercion to integrate the existing knowledge in order to intensify the reliability with which neurodegenerative disorders can be diagnosed and treated. The objective of this review article is therefore to assimilate these disorders’ in terms of their neuropathology, neurogenetics, etiology, trends in pharmacological treatment, clinical management, and the use of innovative neurotherapeutic interventions. 相似文献
836.
Three dimensional finite element models of nacre were constructed based on reported microstructural studies on the 'brick and mortar' micro-architecture of nacre. 3D eight noded isoparametric brick elements were used to design the microarchitecture of nacre. Tensile tests were simulated using this model. The tests were conducted at low stresses of 2 MPa which occur well within the elastic regime of nacre and thus effects related to locus and extent of damage were ignored. Our simulations show that using the reported values of elastic moduli of organic (0.005 GPa) and aragonitic platelets (205 GPa), the displacements observed in nacre are extremely large and correspond to a very low modulus of 0.011 GPa. The reported elastic modulus of nacre is of the order of 50 GPa. The reason for this inconsistency may arise from two possibilities. Firstly, the organic layer due to its multilayered structure is possibly composed of distinct layers of different elastic moduli. The continuously changing elastic modulus within the organic layer may approach modulus of aragonite near the organic-inorganic interface. Simulations using variable elastic moduli for the organic phase suggest that an elastic modulus of 15 GPa is consistent with the observed elastic behavior of nacre. Another explanation for the observed higher elastic modulus may arise from localized platelet-platelet contact. Since the observed modulus of nacre lies within the above two extremes (i.e. 15 GPa and 205 GPa) it is suggested that a combination of the two possibilities, i.e. a higher modulus of the organic phase near the organic-inorganic interface and localized platelet-platelet contact can result in the observed elastic properties of nacre. 相似文献
837.
Anish Sachdeva Pradeep Kumar Dinesh Kumar 《The International Journal of Advanced Manufacturing Technology》2009,45(1-2):156-169
This paper presents an approach based on Petri nets for studying the behavior of a real industrial system and evaluating its performance. Stochastic reward nets, a class of high level Petri nets, have been used to model dynamic interaction among active or standby equipment in the system, and the performance parameters have been evaluated using Markovian approach. The performance analysis of the system in long-run conditions is carried out using the data related to equipment’s operational behavior of a real industrial system. The methodology adopted in this paper provides a better understanding of the behavior of the system under varying operating conditions. Reliability analysis of a feeding system of a paper industry presented in this paper will help the management in deciding upon the maintenance strategy to be adopted to improve the performance of the system and consequently reduce the operation and maintenance cost. 相似文献
838.
Dinesh KumarSanjay K. Srivastava P.K. SinghM. Husain Vikram Kumar 《Solar Energy Materials & Solar Cells》2011,95(1):215-218
We report fabrication of solar cell (n+-p-p+ structure) on black silicon substrates consisting of silicon nanowire (SiNW) arrays prepared by Ag induced wet chemical etching process in aqueous HF-AgNO3 solution. SiNW arrays surface has low reflectivity (<5%) in the entire spectral range (400-1100 nm) of interest for solar cells. The solar cells were fabricated by conventional cell fabrication protocol. Performance of three types of cells, namely cell with SiNW over the entire front surface, cell with SiNW only in the active device area and control cell (on planar surface), has been compared. It was found that cell based on selectively grown shorter length SiNW arrays has the best cell performance. 相似文献
839.
Devendra Verma Kalpana S. Katti Dinesh R. Katti 《Materials science & engineering. C, Materials for biological applications》2009,29(7):2079-2084
In the current work, polyelectrolyte complex (PEC) fibrous scaffolds for tissue engineering have been synthesized and a mechanism of their formation has been investigated. The scaffolds are synthesized using polygalacturonic acid and chitosan using the freeze drying methodology. Highly interconnected pores of sizes in the range of 5–20 µm are observed in the scaffolds. The thickness of the fibers was found to be in the range of 1–2 µm. Individual fibers have a nanogranular structure as observed using AFM imaging. In these scaffolds, PEC nanoparticles assemble together at the interface of ice crystals during freeze drying process. Further investigation shows that the freezing temperature and concentration have a remarkable effect on structure of scaffolds. Biocompatibility studies show that scaffold containing chitosan, polygalacturonic acid and hydroxyapatite promotes cell adhesion and proliferation. On the other hand, cells on scaffolds fabricated without hydroxyapatite nanoparticles showed poor adhesion. 相似文献
840.
Dinesh Kumar C. S. Rai Shakti Kumar 《International journal of imaging systems and technology》2010,20(3):261-267
Face recognition has always been a potential research area because of its demand for reliable identification of a human being especially in government and commercial sectors, such as security systems, criminal identification, border control, etc. where a large number of people interact with each other and/or with the system. The last two decades have witnessed many supervised and unsupervised learning techniques proposed by different researchers for the face recognition system. Principal component analysis (PCA), self‐organizing map (SOM), and independent component analysis (ICA) are the most widely used unsupervised learning techniques reported by research community. This article presents an analysis and comparison of these techniques. The article also includes two SOM processing methods global SOM (GSOM) and local SOM (LSOM) for performance evaluation along with PCA and ICA. We have used two different databases for our analysis. The simulation result establishes the supremacy of GSOM in general among all the unsupervised techniques. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 261–267, 2010 相似文献