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61.
Clustering-Based Denoising With Locally Learned Dictionaries 总被引:4,自引:0,他引:4
In this paper, we propose K-LLD: a patch-based, locally adaptive denoising method based on clustering the given noisy image into regions of similar geometric structure. In order to effectively perform such clustering, we employ as features the local weight functions derived from our earlier work on steering kernel regression . These weights are exceedingly informative and robust in conveying reliable local structural information about the image even in the presence of significant amounts of noise. Next, we model each region (or cluster)-which may not be spatially contiguous-by ldquolearningrdquo a best basis describing the patches within that cluster using principal components analysis. This learned basis (or ldquodictionaryrdquo) is then employed to optimally estimate the underlying pixel values using a kernel regression framework. An iterated version of the proposed algorithm is also presented which leads to further performance enhancements. We also introduce a novel mechanism for optimally choosing the local patch size for each cluster using Stein's unbiased risk estimator (SURE). We illustrate the overall algorithm's capabilities with several examples. These indicate that the proposed method appears to be competitive with some of the most recently published state of the art denoising methods. 相似文献
62.
Rajamani Ganesh Kuriacose Joseph Newman D. Wilson Dipankar Raychaudhuri 《International Journal of Wireless Information Networks》1994,1(3):199-222
This paper presents a simulation-based study of cellular packet CDMA systems operating in an integrated voice/data traffic scenario. Spread-spectrum CDMA provides a suitable framework for resource-shared packet transport capable of combining isochronous (voice, ISDN) and bursty data services. In this work, a general network model for cellular packet CDMA with mixed voice/data traffic is described and used to evaluate the capacity/performance impact of several key system parameters. First, the effect of spreading factor (N) and forward error correction (FEC) rate are studied, confirming earlier work indicating a weak dependence onN and a well-defined optimum code rate in the range of 0.5–0.7 (with BCH coding). Next, the effect of propagation loss coefficient () on network capacity is investigated over a range of possible assumptions for, including both constant and distance-dependent models. The results show that system capacity depends strongly on, varying by as much as a factor of 2 over the range of parameters considered. For a given distance-dependent assumption, performance results are also obtained for different cell sizes in order to understand the overall spatial reuse efficiency achievable in different cellular and microcellular scenarios. This is followed by an investigation of traffic source model effects: first the capacity improvement from voice activity detection VAD) is presented, showing the expected 21 gains. Results for varying proportions of voice and data traffic intensities indicate that the operating efficiency does not change significantly as the proportion of bursty data relative to voice is varied. 相似文献
63.
A 2D model for the potential distribution in silicon film is derived for a symmetrical double gate MOSFET in weak inversion. This 2D potential distribution model is used to analytically derive an expression for the subthreshold slope and threshold voltage. A drain current model for lightly doped symmetrical DG MOSFETs is then presented by considering weak and strong inversion regions including short channel effects, series source to drain resistance and channel length modulation parameters. These derived models are compared with the simulation results of the SILVACO (Atlas) tool for different channel lengths and silicon film thicknesses. Lastly, the effect of the fixed oxide charge on the drain current model has been studied through simulation. It is observed that the obtained analytical models of symmetrical double gate MOSFETs are in good agreement with the simulated results for a channel length to silicon film thickness ratio greater than or equal to 2. 相似文献
64.
Chatterjee A. Volakis J.L. Kent W.J. 《Antennas and Propagation, IEEE Transactions on》1992,40(7):761-769
A traveling-wave model is used in conjunction with a Galerkin's solution of the exact integral equation to solve for the scattering by a thin perfectly conducting and a thin dielectrically coated wire. The proposed current model consists of three weighted traveling-wave components; one is associated with the current on the infinite wire whereas the other two describe the reflected traveling waves from the wire terminations. Several current distribution and scattering patterns are presented which serve to validate the accuracy of the model and the derived analytical formulas 相似文献
65.
Crystal behaviours such as crystallization temperature (amorphous to tetragonal (t) zirconia), tendency of phase transformation (tetragonal to monoclinic (m) zirconia) and lattice strain were studied with mechanical property e.g. tensile strength of sol-gel derived ZrO2-2 mol% RE2O3 (RE = La, Pr, Nd, Sm, Gd and Dy) spun fibres. Rare earth cations of varying sizes played a significant role in changing the
above mentioned properties of ZrO2-2 mol% RE2O3 fibres. It was found that with decreasing the ionic size difference between the zirconium and RE ions, crystallization temperature
(amorphous →)t-ZrO2) decreased, the probability of phase transformation (t→m) decreased, lattice strain which is related to lattice distortion decreased and tensile strength increased. 相似文献
66.
Moutusi Banerjee Abhisek Gupta Shyamal K. Saha Dipankar Chakravorty 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(28):3451-3457
Attachment of Li+ ion on graphene surface to realize Li+‐ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1‐aza‐15‐crown‐5, the cage‐like structure containing four oxygens that can bind Li+ ion through electrostatic interaction. Li+ migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye‐type relaxation behavior with β (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li+ migration arising due to cation‐π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li+‐ion battery. 相似文献
67.
An inhomogeneous thermal block model of man with 476 cubical cells has been developed. It incorporates inhomogeneous blood flow rates, metabolic heat production, specific heats, and thermal conductivities, obtained by volume-weighted averaging of the values for eleven different tissue types which constitute the human body. The transient heat conduction equation for the thermal model includes the effects of internal metabolic heat generation, electromagnetic energy deposition, heat conduction through the tissues, convective heat transfer by blood, evaporative heat dissipation by sweating and insensible perspiration, respiratory heat loss, and heat transfer to the environment by radiation and convection. The standard implicit finite difference technique has been utilized to solve the three-dimensional heat conduction equation. 相似文献
68.
Experiment conducted on a microstrip quarterwave antenna structure on a typical ferrite substrate reveals reduction in size, interesting radiation characteristics and a broadband nature over a wide range of frequencies in the lower UHF region. 相似文献
69.
Shreyas Sen Aritra Banerjee Vishwanath Natarajan Shyam Devarakond Hyun Choi Abhijit Chatterjee 《Journal of Electronic Testing》2012,28(4):405-419
Testing of Radio Frequency (RF) circuits for nonlinearity specifications generally requires the use of multiple test measurements thereby contributing to increased test cost. Prior RF test methods have suffered from significant test calibration effort (training for supervised learners) when using compact tests or from increased test time due to direct specification measurement. On the other hand, due to aggressive technology scaling, there are plenty of digital transistors available that can be used to simplify testing of Analog/Mixed-Signal (AMS) and RF devices. In this paper, an RF test methodology is developed that: (a) allows RF devices to be tested for several distortion specifications using distortion model fitting algorithms in test time comparable to what can be achieved using supervised learning techniques while retaining the accuracy of direct specification measurement, (b) allows multiple RF specifications to be determined concurrently from a single data acquisition and (c) allows digital-compatible testing/BIST to be performed using digital testers or on-chip built in self-test (BIST) circuitry. With regard to (a), a key benefit is that no training of supervised learning algorithm is necessary. The proposed method based on distortion model fitting is shown to give excellent results across common RF performance metrics while providing ~10× improvements in test time compared to previous methods. 相似文献
70.
Robert Rieger Martin Schuettler Dipankar Pal Chris Clarke Peter Langlois John Taylor Nick Donaldson 《IEEE transactions on neural systems and rehabilitation engineering》2006,14(4):427-437
In this paper, we describe the design and testing of a system for recording electroneurographic signals (ENG) from a multielectrode nerve cuff (MEC). This device, which is an extension of the conventional nerve signal recording cuff, enables ENG to be classified by action potential velocity. In addition to electrical measurements, we provide preliminary in vitro data obtained from frogs that demonstrate the validity of the technique for the first time. Since typical ENG signals are extremely small, on the order of 1 1 microV, very low-noise, high-gain amplifiers are required. The ten-channel system we describe was realized in a 0.8 microm CMOS technology and detailed measured results are presented. The overall gain is 10 000 and the total input-referred root mean square (rms) noise in a bandwidth 1 Hz-5 kHZ is 291 nV. The active area is 12 mm(2) and the power consumption is 24 mW from +/-2.5 V power supplies. 相似文献