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71.
72.
Raju Sethuraman G. Siva Sankara Reddy I. Thanga Ilango 《International Journal of Pressure Vessels and Piping》2003,80(12):843-859
A finite thickness plate with two coplanar self-same shallow and deep semi-elliptical surface cracks subjected to remote tensile surface traction is considered for fracture analysis. Based on three-dimensional (3D) finite element solutions, stress intensity factors (SIFs) are evaluated along the entire crack front using a force method. The line spring model has also been used to evaluate crack depth point SIFs using shell finite element analysis. A wide range of geometric dimensions and crack configurations viz. crack shape aspect ratio (0.3≤a/c≤1.2), crack depth ratio (1.25≤t/a≤6), relative crack location (0.33≤2c/d≤0.9) and normalized location on the crack front (0≤2φ/π≤2) are considered for numerical estimation of crack interaction factors. SIFs evaluated at the depth point using the force method from the 3D finite element results are compared with SIFs evaluated using the line spring model. Finally, using finite element results, an empirical relation is proposed for the evaluation of crack interaction factors. For the ranges considered, the proposed empirical relation predicts crack interaction factors at critical locations within ±2% of the 3D finite element solutions. 相似文献
73.
Raju BI Hall CS Seip R 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(5):944-954
Ultrasound transducers designed for therapeutic purposes such as tissue ablation, histotripsy, or drug delivery require large apertures for adequate spatial localization while providing sufficient power and steerability without the presence of secondary grating lobes. In addition, it is highly preferred to minimize the total number of channels and to maintain simplicity in electrical matching network design. To this end, we propose array designs that are both space-filling and non-periodic in the placement of the elements. Such array designs can be generated using the mathematical concept of non-periodic or aperiodic tiling (tessellation) and can lead to reduced grating lobes while maintaining full surface area coverage to deliver maximum power. For illustration, we designed two 2-D space-filling therapeutic arrays with 128 elements arranged on a spherical shell. One was based on the two-shape Penrose rhombus tiling, and the other was based on a single rectangular shape arranged non-periodically. The steerability performance of these arrays was studied using acoustic field simulations. For comparison, we also studied two other arrays, one with circular elements distributed randomly, and the other a periodic array with square elements. Results showed that the two space-filling non-periodic arrays were able to steer to treat a volume of 16 x 16 x 20 mm while ensuring that the grating lobes were under -10 dB compared with the main lobe. The rectangular non-periodic array was able to generate two and half times higher power than the random circles array. The rectangular array was then fabricated by patterning the array using laser scribing methods and its steerability performance was validated using hydrophone measurements. This work demonstrates that the concept of space-filling aperiodic/non-periodic tiling can be used to generate therapy arrays that are able to provide higher power for the same total transducer area compared with random arrays while maintaining acceptable grating lobe levels. 相似文献
74.
Raju R Baddi 《电子设计技术》2011,(3):57
图1中的电路用三只NPN晶体管和三只PNP晶体管做了一个逻辑探头。两只晶体管作为驱动LED的开关;逻辑1是绿色LED,逻辑0是红色LED。Q1和Q2测试探头尖的逻辑1状况,Q3和Q4测试逻辑O的状况。Q1在Q2射极电路中用作齐纳二极管。R12和R14构成的分压 相似文献
75.
Wide‐Area Strain Sensors based upon Graphene‐Polymer Composite Coatings Probed by Raman Spectroscopy 下载免费PDF全文
Arun Prakash Aranga Raju Amanda Lewis Brian Derby Robert J. Young Ian A. Kinloch Recep Zan Kostya S. Novoselov 《Advanced functional materials》2014,24(19):2865-2874
Functional graphene optical sensors are now viable due to the recent developments in hand‐held Raman spectroscopy and the chemical vapor deposition (CVD) of graphene films. Herein, the strain in graphene/poly (methyl methacrylate) sensor coatings is followed using Raman band shifts. The performance of an “ideal” mechanically‐exfoliated single crystal graphene flake is compared to a scalable CVD graphene film. The dry‐transferred mechanically exfoliated sample has no residual stresses, whereas the CVD sample is in compression following the solvent evaporation during its transfer. The behavior of the sensors under cyclic deformation shows an initial breakdown of the graphene‐polymer interface with the interface then stabilizing after several cycles. The Raman 2D band shift rates per unit strain of the exfoliated graphene are ≈35% higher than CVD graphene making the former more strain sensitive. However, for practical wide‐area applications, CVD graphene coatings are still viable candidates as a Raman system can be used to read the strain in any 5 μm diameter spot in the coating to an absolute accuracy of ≈0.01% strain and resolution of ≈27 microstrains (μs), which compares favorably to commercial photoelastic systems. 相似文献
76.
A recent article (W. H. Stewart & P. L. Roth, 2001) in the Journal of Applied Psychology presented the conclusion from meta-analysis that entrepreneurs have a higher risk propensity than managers and that this propensity is particularly pronounced among the growth-oriented. A previously unresolved question was said to be laid to rest and a "vital component" of a theory of entrepreneurship established. The present article disagrees and cites data from 14 studies not included in the Stewart and Roth (2001) analysis, adding up to a conclusion (supported by new meta-analyses) that entrepreneurs (and those with a growth orientation) are more risk avoidant. Thus, a conservative view, retaining the position that the role of risk propensity in entrepreneurship remains unresolved, is upheld. Potential explanations for the conflicting results are explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
MF Chan A Kois EJ Verner BG Raju RS Castillo C Wu I Okun FD Stavros VN Balaji 《Canadian Metallurgical Quarterly》1998,6(12):2301-2316
The systematic modification of the ETA selective N-(5-isoxazolyl)benzene-sulfonamide endothelin antagonists to give ETB selective antagonists is reported. The reversal in selectivity was brought about by substitution of the 4-position with aryl and substituted aryl groups. Of all the aromatic substituents studied, the para-tolyl group gave rise to the most active and selective ETB antagonist. Larger substituents caused a decrease in both ETB activity and selectivity. A similar trend was observed by substitution at the 5-position of the N-(5-isoxazolyl)-2-thiophenesulfonamide ETA receptor antagonists. The para-tolyl group was again found to be optimal for the ETB activity and selectivity. The structural features that were found to be favorable for binding to the ETB receptor, that is, the presence of a linear, conjugated pi-system of definite shape and size, have been successfully incorporated into the design of ETB selective polycyclic aromatic sulfonamides antagonists. 相似文献
78.
79.
The use of a linear two-parameter approximation for determining limiting viscosity number, [η], of a polymer in the state of infinite dilution requires considerable amount of time, effort, and materials. Several workers who attempted to estimate [η] directly from single-viscosity measurement also proposed equations for this purpose. Such equations are tested and found to have good applicability to practical data within specified limits of concentration or specific viscosity. A new equation has been derived and tested for polymers of high and low molecular weights in various solvents and at different temperatures. The introduction of a constant in this equation makes it applicable over a wider range of specific viscosity. It is found to serve better for determination of [η] from a single-viscosity measurement. 相似文献
80.
UM Ohndorf JP Whitehead NL Raju SJ Lippard 《Canadian Metallurgical Quarterly》1997,36(48):14807-14815
The anticancer drug cisplatin is particularly effective against testicular tumors. Although the clinical consequences of cisplatin chemotherapy are well-known, the precise mechanism of action remains elusive. Specific recognition of cisplatin-damaged DNA by a class of proteins containing the high-mobility group (HMG) domain DNA-binding motif could play a role in mediating the cytotoxicity of the drug. This study presents a quantitative investigation of binding of the murine testis-specific high-mobility group protein tsHMG to DNA modified by cisplatin. The binding affinity and specificity of this protein to a site-specific 1,2-d(GpG) cisplatin-DNA intrastrand cross-link in a 20 bp probe were determined. A value for the apparent dissociation constant, Kd(app), of 24 +/- 5 nM was obtained by gel mobility shift assays. Binding competition assays with the corresponding unmodified 20 bp probe gave a ratio (rho) of nonspecific to specific Kd(app) values of 230. A polypeptide containing tsHMG domain A (residues 1-82) was expressed and purified to homogeneity. This domain alone was sufficient for specific recognition of cisplatin-modified DNA with a Kd(app) of 300 +/- 50 nM and a rho of 20, a comparatively high discrimination factor. DNase I interference analysis of the adduct-containing strand revealed that tsHMG binding extends over 14 nucleotides, centered around the platinated bases. The domain A polypeptide protection pattern covers a slightly smaller area of 13 nucleotides. The binding affinity and specificity of tsHMG for cisplatin-modified DNA are exceptional compared to those of other HMG-domain proteins studied previously. The possible relevance of these findings to the mechanism of action of cisplatin is discussed. 相似文献