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排序方式: 共有61条查询结果,搜索用时 15 毫秒
1.
Bayesian feature and model selection for Gaussian mixture models   总被引:1,自引:0,他引:1  
We present a Bayesian method for mixture model training that simultaneously treats the feature selection and the model selection problem. The method is based on the integration of a mixture model formulation that takes into account the saliency of the features and a Bayesian approach to mixture learning that can be used to estimate the number of mixture components. The proposed learning algorithm follows the variational framework and can simultaneously optimize over the number of components, the saliency of the features, and the parameters of the mixture model. Experimental results using high-dimensional artificial and real data illustrate the effectiveness of the method.  相似文献   
2.
We present the global k-means algorithm which is an incremental approach to clustering that dynamically adds one cluster center at a time through a deterministic global search procedure consisting of N (with N being the size of the data set) executions of the k-means algorithm from suitable initial positions. We also propose modifications of the method to reduce the computational load without significantly affecting solution quality. The proposed clustering methods are tested on well-known data sets and they compare favorably to the k-means algorithm with random restarts.  相似文献   
3.
A theoretical model has been developed for simulating the laser grooving process. It takes into account the interaction among subsequent pulses, the required time for the melting temperature to be reached and the subsequent removal of a finite volume of material during each laser pulse. The model predicts the maximum groove depth that can be achieved for a specified set of process parameters, such as laser power, pulsing frequency, and scanning velocity. The theoretical predictions have been experimentally tested with a medium-power laser beam.  相似文献   
4.
This paper introduces a new stochastic control method, Extended Linear Quadratic Gaussian control, that appears to be particularly promising for the management of complex reservoir configurations such as the River Nile system. The method is introduced by means of a short case study related to the regulation of the Equatorial Lakes in the Nile basin. If the necessary data are available, the method can be easily adapted to the entire Nile system and used to investigate a variety of management issues.  相似文献   
5.
Tissue engineering (TE) may provide effective alternative treatment for challenging temporomandibular joint (TMJ) pathologies associated with disc malpositioning or degeneration and leading to severe masticatory dysfunction. Aim of this study was to evaluate the potential of chitosan/alginate (Ch/Alg) scaffolds to promote fibro/chondrogenic differentiation of dental pulp stem cells (DPSCs) and production of fibrocartilage tissue, serving as a replacement of the natural TMJ disc. Ch/Alg scaffolds were fabricated by crosslinking with CaCl2 combined or not with glutaraldehyde, resulting in two scaffold types that were physicochemically characterized, seeded with DPSCs or human nucleus pulposus cells (hNPCs) used as control and evaluated for cell attachment, viability, and proliferation. The DPSCs/scaffold constructs were incubated for up to 8 weeks and assessed for extracellular matrix production by means of histology, immunofluorescence, and thermomechanical analysis. Both Ch/Alg scaffold types with a mass ratio of 1:1 presented a gel-like structure with interconnected pores. Scaffolds supported cell adhesion and long-term viability/proliferation of DPSCs and hNPCs. DPSCs cultured into Ch/Alg scaffolds demonstrated a significant increase of gene expression of fibrocartilaginous markers (COLI, COL X, SOX9, COM, ACAN) after up to 3 weeks in culture. Dynamic thermomechanical analysis revealed that scaffolds loaded with DPSCs significantly increased storage modulus and elastic response compared to cell-free scaffolds, obtaining values similar to those of native TMJ disc. Histological data and immunochemical staining for aggrecan after 4 to 8 weeks indicated that the scaffolds support abundant fibrocartilaginous tissue formation, thus providing a promising strategy for TMJ disc TE-based replacement.  相似文献   
6.
 The geomorphic and instability conditions of the Neogene formations in Northern Peloponnesus are examined and related to the lithologies and hydrological data. Instability phenomena caused by erosion are briefly described and a qualitative analysis of the run-off conditions within the Finikas and Meganeitos catchments is presented. Received: 31 July 1997 · Accepted: 12 January 1998  相似文献   
7.
Opioids and somatostatin analogs have been implicated in the modulation of renal water handling, but whether their action is accomplished through central and/or peripheral mechanisms remains controversial. In different cell systems, on the other hand, opioids and somatostatin inhibit cell proliferation. In the present study, we have used an established cell line, derived from opossum kidney (OK) proximal tubules, in order to characterize opioid and somatostatin receptors and to investigate the action of opioids and somatostatin on tubular epithelial tissue. Our results show the presence of one class of opioid binding sites with kappa, selectivity (KD 4.6 +/- 0.9 nM, 57,250 sites/cell), whereas delta, mu, or other subtypes of the kappa site were absent. Somatostatin presents also a high affinity site on these cells (KD 24.5 nM, 330,000 sites/cell). No effect of either opioids or somatostatin on the activity of the NA+/Pi cotransporter was observed, indicating that these agents do not affect ion transport mechanisms. However, opioid agonists and somatostatin analogs decrease OK cell proliferation in a dose-dependent manner; in the same nanomolar concentration range, they displayed reversible specific binding for these agents. The addition of diprenorphine, a general opioid antagonist, reversed the effects of opioids, with the exception of morphine. Furthermore, morphine interacts with the somatostatin receptor in this cell line too, as was the case in the breast cancer T47D cell line. Our results indicate that in the proximal tubule opioids and somatostatin do not affect transport, but they might have a role in the modulation of renal cell proliferation either during ontogenesis or in kidney repair.  相似文献   
8.
In this paper, we demonstrate how the differential Earth Mover's Distance (EMD) may be used for visual tracking in synergy with Gaussian mixtures models (GMM). According to our model, motion between adjacent frames results in variations of the mixing proportions of the Gaussian components representing the object to be tracked. These variations are computed in closed form by minimizing the differential EMD between Gaussian mixtures, yielding a very fast algorithm with high accuracy, without recurring to the EM algorithm in each frame. Moreover, we also propose a framework to handle occlusions, where the prediction for the object's location is forwarded to an adaptive Kalman filter whose parameters are estimated on line by the motion model already observed. Experimental results show significant improvement in tracking performance in the presence of occlusion.  相似文献   
9.
An attempt has been made to correlate the uniaxial compressive strength and Young's modulus of gabbros and basalts with Schmidt hammer rebound number, the point load strength index, Is(50) and the degree of weathering. Sixty three samples of gabbro and thirty of basalt from the ophiolitic comlex of Pindos zone (Northern Greece) have been collected by core drilling and tested accordingly. The results have been processed using techniques from the statistical software SPSS. Some of the equations produced show relatively high correlation coefficients, all significant at a significance level higher than 95%. The equations establish reliable prediction models for the uniaxial compressive strength and modulus of elasticity of the above rock types by means of simple tests which can be carried out in the field.  相似文献   
10.
The complex-forming interaction between two direct dyes, CI Yellow 106 and CI Blue 78, and two nonionic surfactants, namely, polyoxyethylene nonyl phenyl ether (NP-12) and polyoxyethylene stearylamine (R-11), in aqueous solutions was studied. The estimation was made by measuring surface tension and critical micelle concentration (CMC) changes as a function of dye concentration. A decrease of NP-12 surface tension at low concentration and an increase of R-11 surface tension in the presence of both dyes were observed along with a significant decrease of NP-12 CMC values. A difference in the spectrophotometric absorbance of dye solutions in the presence of both surfactants, indicating a change in the environment of the dye chromophore, was also visible. These results confirm the formation of hydrophobic complexes of NP-12 and hydrophilic complexes of R-11 with both dyes.  相似文献   
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