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排序方式: 共有525条查询结果,搜索用时 15 毫秒
91.
Martins Tde C de Camargo ED Lima RG Amato MB Tsuzuki Mde S 《IEEE transactions on bio-medical engineering》2012,59(7):1861-1870
Electrical impedance tomography (EIT) is an imaging technique that attempts to reconstruct the impedance distribution inside an object from the impedance between electrodes placed on the object surface. The EIT reconstruction problem can be approached as a nonlinear nonconvex optimization problem in which one tries to maximize the matching between a simulated impedance problem and the observed data. This nonlinear optimization problem is often ill-posed, and not very suited to methods that evaluate derivatives of the objective function. It may be approached by simulated annealing (SA), but at a large computational cost due to the expensive evaluation process of the objective function, which involves a full simulation of the impedance problem at each iteration. A variation of SA is proposed in which the objective function is evaluated only partially, while ensuring boundaries on the behavior of the modified algorithm. 相似文献
92.
93.
Perez-Rovira A Cabido R Trucco E McKenna SJ Hubschman JP 《IEEE transactions on medical imaging》2012,31(1):140-150
We present RERBEE (robust efficient registration via bifurcations and elongated elements), a novel feature-based registration algorithm able to correct local deformations in high-resolution ultra-wide field-of-view (UWFV) fluorescein angiogram (FA) sequences of the retina. The algorithm is able to cope with peripheral blurring, severe occlusions, presence of retinal pathologies and the change of image content due to the perfusion of the fluorescein dye in time. We have used the computational power of a graphics processor to increase the performance of the most computationally expensive parts of the algorithm by a factor of over × 1300, enabling the algorithm to register a pair of 3900 × 3072 UWFV FA images in 5-10 min instead of the 5-7 h required using only the CPU. We demonstrate accurate results on real data with 267 image pairs from a total of 277 (96.4%) graded as correctly registered by a clinician and 10 (3.6%) graded as correctly registered with minor errors but usable for clinical purposes. Quantitative comparison with state-of-the-art intensity-based and feature-based registration methods using synthetic data is also reported. We also show some potential usage of a correctly aligned sequence for vein/artery discrimination and automatic lesion detection. 相似文献
94.
Raul Diaz 《能源与动力工程:英文版》2014,(5):794-804
The current need to fasten the implementation of renewable energies greatly depends on the development of competitive storage devices, and while there is not a single technology which is likely capable to competitively cover the wide range of possible demands, electrochemical technologies are one of the most promising for many of them. For the realization of this promise, new materials fulfilling criteria such as high energy density, high power density, competitive cost, reliability, and environmental compatibility need to be developed in the near future. Electrochemical energy storage devices can be classified into two main technologies: supercapacitors and batteries (including redox flow batteries). Materials and applications for these technologies are discussed and compared, listing current status, technical and strategic challenges. 相似文献
95.
P.Clark Souers HenryG. Andreski Jan Batteux Brad Bratton Chris Cabacungan CharlesF. Cook Sabrina Fletcher Raul Garza Denise Grimsley Jeff Handly Andy Hernandez Pat McMaster JohnD. Molitoris Rick Palmer Jim Prindiville John Rodriguez Dan Schneberk Bradley Wong Peter Vitello 《Propellants, Explosives, Pyrotechnics》2006,31(2):89-97
Pin and X‐ray corner turning data have been taken on ambient LX‐17 and PBX 9052, and the results are listed in tables as an aid to future modeling. The results have been modeled at 4 zones/mm with a reactive flow approach that varies the burn rate as a function of pressure. A single rate format is used to simulate failure and detonation in different pressure regimes. A pressure cut‐off must also be reached to initiate the burn. Corner turning and failure are modeled using an intermediate pressure rate region, and detonation occurs at high pressure. The TATB booster is also modeled using reactive flow, and X‐ray tomography is used to partition the ram‐pressed hemisphere into five different density regions. The model reasonably fits the bare corner turning experiment but predicts a smaller dead zone with steel confinement, in contradiction with experiment. The same model also calculates the confined and unconfined cylinder detonation velocities and predicts the failure of the unconfined cylinder at 3.75 mm radius. The PBX 9502 shows a smaller dead zone than LX‐17. An old experiment that showed a large apparent dead zone in Composition B was repeated with X‐ray transmission and no dead zone was seen. This confirms the idea that a variable burn rate is the key to modeling. The model also produces initiation delays, which are shorter than those found in time‐to‐detonation. 相似文献
96.
Ftima Churruca Raul SanMartin Blanca Ins Imanol Tellitu Esther Domínguez 《Advanced Synthesis \u0026amp; Catalysis》2006,348(14):1836-1840
The Suzuki biaryl coupling of a range of electronically dissimilar arylboronic acids and aryl bromides is performed in neat water with excellent to quantitative yields by means of a new CNC‐pincer palladium catalyst that is soluble in water due to its para‐carboxy group. Extremely high turnover numbers and frequencies combined with a remarkable robustness allow an effective catalyst reuse in sustainable conditions. 相似文献
97.
Bhattacharya P Claesson M Bundschuh J Sracek O Fagerberg J Jacks G Martin RA Storniolo Adel R Thir JM 《The Science of the total environment》2006,358(1-3):97-120
Factors controlling arsenic (As) mobilization in the aquifers of the Río Dulce alluvial cone were investigated. Groundwater analyses show severe As contamination (average concentration of 743 mug/L) from geogenic sources, but spatial variability of As concentration is considerable. Sequential leaching of sediment samples from unsaturated zone using de-ionised water, bicarbonate, acetate, and oxalate extracted As to different extents. Sediment oxalate extraction showed that Al and Mn oxide and hydroxides are more abundant than Fe oxides and hydroxides, in spite of similar total Fe, Mn, and Al concentrations in the sediment. Speciation calculations performed for saturated zone samples indicated that Fe and Al oxides and hydroxides are stable in groundwater, suggesting that As adsorption processes may be to some extent controlled by the presence of Fe and Al mineral phases. Principal Component Analysis (PCA) showed that As is related to F, V, Mo, B, Si, most likely due to their common origin in volcanic ash. This suggests the volcanic ash as the probable source of groundwater As. Locally, elevated pH values linked to carbonate dissolution, cation exchange, and dissolution of silicates promote release of adsorbed As. Another factor contributing to the release of As locally may be the input of organic matter from excessive irrigation. The conceptual model of As release includes: i) As influx from dissolution of volcanic glass in volcanic ash, ii) adsorption of As on the surface of Fe and Al mineral phases in relatively low pH zones, and iii) high mobility of As in high pH zones. Future work should be focused on the determination of mineralogical forms of As in volcanic ash and on detailed investigation on factors controlling As mobility. 相似文献
98.
99.
Borges M Birkett M Aldrich JR Oliver JE Chiba M Murata Y Laumann RA Barrigossi JA Pickett JA Moraes MC 《Journal of chemical ecology》2006,32(12):2749-2761
The male-produced sex pheromone from the Brazilian rice stalk stink bug Tibraca limbativentris is reported. Olfactometer bioassays with sexually mature males and females showed that males attracted females, which suggests that males release a sex pheromone. Males were not attracted to either sex, nor were females attractive to conspecific females. Attraction of the females to males was highest at night. The headspace volatiles collected from male and female bugs were analyzed by gas chromatography (GC) and GC–mass spectrometry. Two male-specific compounds were identified as isomers of 1′S-zingiberenol, whereas a series of defensive compounds were identified in extracts from both sexes. Zingiberenol has three chiral centers, and the nonselective syntheses used produced two groups of isomers, zingiberenol I containing four isomers, namely (1RS,4RS,1′R)-4-(1′,5′-dimethylhex-4′-enyl)-1-methylcyclohex-2-en-1-ol, and zingiberenol II containing the other four isomers, namely (1RS,4RS,1′S)-4-(1′,5′-dimethylhex-4′-enyl)-1-methylcyclohex-2-en-1-ol. Both groups of stereoisomers were more attractive than hexane controls. The absolute configuration of the insect-produced pheromonal components remains to be elucidated, but the 1′S stereochemistry was established for at least one of the isomers. 相似文献
100.
Francisco Payri Jose Vicente Pastor Raul Payri Julien Manin 《Journal of Mechanical Science and Technology》2011,25(1):209-219
The optical depth is responsible of limiting the optical diagnostic using visible wavelength in the sprays. This paper proposes to measure the optical depth directly in a real Diesel spray through line-of-sight laser extinction measurements. This easily reproducible method which does not require expensive or complex optical techniques is detailed and the measurement procedure is presented in this paper. As diesel sprays are mostly optically thick, the measurements in the denser region are not reliable and a fuel concentration model has been used to derive the results to the entire spray. This work provides values of SMD at different distance from the nozzle tip depending on the specific parameters like injection pressure or discharge density. The values extracted from a combined experimental/computational approach have been compared to PDPA measurements under the same testing conditions. The results have shown that the maximum optical depth was higher than 10 and that an increase of the injection pressure led to higher τ values. The SMD values appeared to be below the results measured by the PDPA and the droplet diameter showed to be the main responsible of the optical depth of the jet under the tested conditions. 相似文献