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21.
Linear equalities, disequalities and inequalities on fixed-width bit-vectors, collectively called linear modular constraints, form an important fragment of the theory of fixed-width bit-vectors. We present a practically efficient and bit-precise algorithm for quantifier elimination from conjunctions of linear modular constraints. Our algorithm uses a layered approach, whereby sound but incomplete and cheaper layers are invoked first, and expensive but complete layers are called only when required. We then extend this algorithm to work with arbitrary Boolean combinations of linear modular constraints as well. Experiments on an extensive set of benchmarks demonstrate that our techniques significantly outperform alternative quantifier elimination techniques based on bit-blasting and linear integer arithmetic. 相似文献
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23.
Sujit Majumdar Suraj Kumar Debasish Roy Samik Chakraborty Santanu Das 《Materials and Manufacturing Processes》2018,33(13):1459-1465
The presence of air boundary layer around a grinding wheel impedes the proper entry of cutting fluid into grinding zone and thereby lubrication and cooling are hampered. It leads to the thermal damage to the workpiece and rapid wheel wear. This experimental work is aimed at increasing the lubrication and cooling effects in grinding by a novel method of using scraper board. The experiments are conducted, using the scraper board, to find the critical region where the air pressure is zero. The coolant jet has then impinged into the grinding zone which is maintained within the critical region. The requirement of specific energy, surface texture, and mechanical properties of the ground surface are analyzed and compared with the traditional grinding and the grinding at various positions of scraper board. Results show that the grinding ratio improved by 35.6and 119%, surface roughness decreased by 36 and 54.2%, while the requirement of specific energy is reduced by 50.8 and 57.3% when scraper board is positioned at the critical distance in comparison to the 57.5° position and no scraper board, respectively. The results indicate that the introduction of fluid in the present method can improve the process efficiency and the product quality effectively. 相似文献
24.
Chakraborty B. Kaustubha R. Hegde A. Pereira A. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(12):2722-2725
A self-organizing feature map (SOFM), a kind of artificial neural network (ANN) architecture, is used in this work for continental shelf seafloor sediment classification. Echo data are acquired using an echosounding system from three types of seafloor sediment areas. Excellent classification (~100%) for an ideal output neuron grid size of 15×1 is obtained for a moving average of 35 input snapshots 相似文献
25.
Shen L. Coffie R. Buttari D. Heikman S. Chakraborty A. Chini A. Keller S. DenBaars S.P. Mishra U.K. 《Electron Device Letters, IEEE》2004,25(1):7-9
In this paper, a high-power GaN/AlGaN/GaN high electron mobility transistor (HEMT) has been demonstrated. A thick cap layer has been used to screen surface states and reduce dispersion. A deep gate recess was used to achieve the desired transconductance. A thin SiO/sub 2/ layer was deposited on the drain side of the gate recess in order to reduce gate leakage current and improve breakdown voltage. No surface passivation layer was used. A breakdown voltage of 90 V was achieved. A record output power density of 12 W/mm with an associated power-added efficiency (PAE) of 40.5% was measured at 10 GHz. These results demonstrate the potential of the technique as a controllable and repeatable solution to decrease dispersion and produce power from GaN-based HEMTs without surface passivation. 相似文献
26.
Dora Y. Chakraborty A. Heikman S. McCarthy L. Keller S. DenBaars S.P. Mishra U.K. 《Electron Device Letters, IEEE》2006,27(7):529-531
The effect of ohmic contacts on the buffer leakage of GaN transistors is presented. The buffer leakage for AlGaN/GaN high-electron mobility transistors and GaN MESFETs grown on the same underlying buffer was observed to be different. Controlled experiments show that the increased buffer leakage is due to the nature of the alloyed ohmic contacts and can be minimized if they are screened by the Si doping or by the two-dimensional electron gas. 相似文献
27.
Anjan Sarkar Anjan Banerjee Nilanjan Banerjee Siddhartha Brahma B Kartikeyan Manab Chakraborty K L Majumder 《IEEE transactions on image processing》2005,14(5):634-645
This work deals with multisensor data fusion to obtain landcover classification. The role of feature-level fusion using the Dempster-Shafer rule and that of data-level fusion in the MRF context is studied in this paper to obtain an optimally segmented image. Subsequently, segments are validated and classification accuracy for the test data is evaluated. Two examples of data fusion of optical images and a synthetic aperture radar image are presented, each set having been acquired on different dates. Classification accuracies of the technique proposed are compared with those of some recent techniques in literature for the same image data. 相似文献
28.
Carlos Zúñiga Espinoza Anura P. Rathnayake Momtanu Chakraborty Sindhuja Sankaran Pete Jacoby 《International journal of remote sensing》2013,34(23):8818-8836
ABSTRACTThis study investigates the applicability of ground-based 3D time-of-flight (ToF) imaging and small unmanned aerial system (UAS) integrated multispectral imaging as a rapid grapevine canopy vigour mapping tool for decision support during crop production management. Direct root-zone deficit irrigation was applied to grapevines with continuous and pulse irrigation techniques at 15%, 30%, and 60% rates as that of standard irrigation rate (100%) established by the grower in a commercial production. The control block was irrigated continuously at 100% standard irrigation rate. Field plots were imaged using ground platform integrated with 3D ToF imaging sensor and small UAS-integrated multispectral camera at 128 and 65 days before the harvest to estimate the canopy vigour variability associated with irrigation treatments. Customized as well as standard methods (convex hull and voxel grid) were utilized to extract canopy attributes (e.g. volume) from the 3D ToF imaging sensor data. The multispectral images were processed to extract normalized and green normalized difference vegetation index images. Resulting data were used to estimate canopy area ratio i.e. the ratio between the grapevine canopy area with respect to the total area in selected region of interest. A significant correlation (r = 0.34) between canopy volume estimated by customized algorithm and aerial canopy area ratio was observed. Custom canopy volume estimates were also highly correlated (r = 0.79) with voxel grid derived canopy volume data. Overall, 60% continuous direct root zone deficit irrigation appeared to produce canopy volume/vigour comparable with those under control treatment. Results also suggest that grower can utilize either or both (ground and aerial) grapevine canopy mapping techniques for effective management. 相似文献
29.
A new moment-modified polynomial dimensional decomposition (PDD) method is presented for stochastic multiscale fracture analysis of three-dimensional, particle-matrix, functionally graded materials (FGMs) subject to arbitrary boundary conditions. The method involves Fourier-polynomial expansions of component functions by orthonormal polynomial bases, an additive control variate in conjunction with Monte Carlo simulation for calculating the expansion coefficients, and a moment-modified random output to account for the effects of particle locations and geometry. A numerical verification conducted on a two-dimensional FGM reveals that the new method, notably the univariate PDD method, produces the same crude Monte Carlo results with a five-fold reduction in the computational effort. The numerical results from a three-dimensional, edge-cracked, FGM specimen under a mixed-mode deformation demonstrate that the statistical moments or probability distributions of crack-driving forces and the conditional probability of fracture initiation can be efficiently generated by the univariate PDD method. There exist significant variations in the probabilistic characteristics of the stress-intensity factors and fracture-initiation probability along the crack front. Furthermore, the results are insensitive to the subdomain size from concurrent multiscale analysis, which, if selected judiciously, leads to computationally efficient estimates of the probabilistic solutions. 相似文献
30.