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51.
The molecular motions of spin probes at the interphase region of poly(methyl methacrylate) particles sterically stabilized by polyisobutylene (PIB) were studied by ESR spectroscopy. The correlation times (τ) were measured by using the methods of Freed and Kivelson. Activation energies for different modes of motion were calculated at wide temperature range between ?140 and 140°C. Viscosities were estimated in methanol saturated PIB channels in the polymer particles. © 1994 John Wiley & Sons, Inc. 相似文献
52.
A new classification algorithm, called VFI5 (for Voting Feature Intervals), is developed and applied to problem of differential diagnosis of erythemato-squamous diseases. The domain contains records of patients with known diagnosis. Given a training set of such records, the VFI5 classifier learns how to differentiate a new case in the domain. VFI5 represents a concept in the form of feature intervals on each feature dimension separately. classification in the VFI5 algorithm is based on a real-valued voting. Each feature equally participates in the voting process and the class that receives the maximum amount of votes is declared to be the predicted class. The performance of the VFI5 classifier is evaluated empirically in terms of classification accuracy and running time. 相似文献
53.
This study presents the effects of mixture fractions of nuclear fuels (mixture of fissile–fertile fuels and mixture of two different fertile fuels) and 6Li enrichment on the neutronic parameters (the tritium breeding ratio, TBR, the fission rate, FR, the energy multiplication ratio, M, the fissile breeding rate, FBR, the neutron leakage out of blanket, L, and the peak-to-average fission power density ratio, Γ) of a deuterium–tritium (D–T) fusion neutron-driven hybrid blanket. Three different fertile fuels (232Th, 238U and 244Cm), and one fissile fuel (235U) were selected as the nuclear fuel. Two different coolants (pressurized helium and natural lithium) were used for the nuclear heat transfer out of the fuel zone (FZ). The Boltzmann transport equation was solved numerically for obtaining the neutronic parameters with the help of the neutron transport code XSDRNPM/SCALE4.4a. In addition, these calculations were performed by also using the MCNP4B code. The sub-limits of the mixture fractions and 6Li enrichment were determined for the tritium self-sufficiency. The considered hybrid reactor can be operated in a self-sufficiency mode in the cases with the fuel mixtures mixed with a fraction of equal to or greater than these sub-limits. Furthermore, the numerical results show that the fissile fuel breeding and fission potentials of the blankets with the helium coolant are higher than with the lithium coolant. 相似文献
54.
A technique, based on Echo planar imaging (EPI)-based phase modulation factor maps, is described for correction of EPI distortions resulting from field inhomogeneity. In this paper, a phase modulation factor was employed to remove the distortions. The phase modulation factor was obtained experimentally by collecting EPI images with a spin-echo (TE) spacing, deltaTE, equal to the inter-echo time interval, T(i). Then, the distortions resulting from the field inhomogeneity were removed by modulating the kappa-space data with the phase modulation factor. One of the advantages of this method is that it requires only a few extra scans to collect the information on field inhomogeneity. The proposed method does not require a phase unwrapping procedure for field inhomogeneity correction and, hence, is easier to implement, compared to other techniques. In addition, it corrects geometric distortion as well as intensity distortions simultaneously, which is robust to external noise or estimation error in severely distorted images. In this work, we also compared the proposed technique with others including, a) interpolation method with EPI-based displacement maps, and b) modulation method with phase modulation factor maps generated from spin-echo images. The results suggest the proposed technique is superior in correcting severely distorted images. 相似文献
55.
We consider the component testing problem of a series system with redundant subsystems where all components fail exponentially. The main feature of our model is that the component failure rates are not constant parameters, but in fact change in a dynamic fashion with respect to time. The optimal component testing problem is formulated as a semi-infinite linear program. We present an algorithmic procedure to compute optimal test times based on the column generation technique, and illustrate it with numerical results. 相似文献
56.
This paper presents an integrated approach to solve the buffer allocation problem in unreliable production lines so as to maximize the throughput rate of the line with minimum total buffer size. The proposed integrated approach has two control loops; the inner loop and the outer loop. While the inner loop control includes an adaptive tabu search algorithm proposed by Demir et al. [8], binary search and tabu search are proposed for the outer loop. These nested loops aim at minimizing the total buffer size to achieve the desired throughput level. To improve the efficiency of the proposed tabu search, alternative neighborhood generation mechanisms are developed. The performances of the proposed algorithms are evaluated by extensive computational experimentation, and the results are reported. 相似文献
57.
One of the major activities performed in product recovery is disassembly. Disassembly line is the most suitable setting to disassemble a product. Therefore, designing and balancing efficient disassembly systems are important to optimize the product recovery process. In this study, we deal with multi-objective optimization of a stochastic disassembly line balancing problem (DLBP) with station paralleling and propose a new genetic algorithm (GA) for solving this multi-objective optimization problem. The line balance and design costs objectives are simultaneously optimized by using an AND/OR Graph (AOG) of the product. The proposed GA is designed to generate Pareto-optimal solutions considering two different fitness evaluation approaches, repair algorithms and a diversification strategy. It is tested on 96 test problems that were generated using the benchmark problem generation scheme for problems defined on AOG as developed in literature. In addition, to validate the performance of the algorithm, a goal programming approach and a heuristic approach are presented and their results are compared with those obtained by using GA. Computational results show that GA can be considered as an effective and efficient solution algorithm for solving stochastic DLBP with station paralleling in terms of the solution quality and CPU time. 相似文献
58.
Kaan Sevki Kavak Orhan Tatar John Piper Fikret Kocbulut B. Levent Mesci 《International journal of remote sensing》2013,34(17):4507-4524
The junction between the East Anatolian and the Dead Sea fault zones lies close to an unstable F: Transform fault (FFF) triple junction where the African, Eurasian and Arabian plates meet in south-eastern Turkey. The Karasu Basin is an ephemeral rifted structure located close to the junction of these plate boundaries and is expressed by a range of tectono-morphological features. This study uses remote sensing to define tectonic structures and discriminate volcanic rocks linked to rifting within the basin using Landsat Enhanced Thematic Mapper Plus (ETM+) imagery. Prior to advanced image processing stages, images were corrected to eliminate atmospheric scattering effects and determine the best band combination for multi-spectral processing techniques based on statistical methods. Following pre-processing stages, edge detection filters were applied to derive tectonic structures defining the basin. The Brovey transformation, a statistical data merging method, was used to combine reflective multi-spectral bands with the Landsat ETM+?panchromatic band. This method fuses higher spatial data with data of lower spatial value. The western margin of the Karasu Basin is defined by the left-lateral Amanos Fault Zone with a contemporary motion (c. –0.4 mm a?1) probably accommodating most of the left-lateral strike-slip motion between Arabian and African plates on the northern continuation of the Dead Sea Fault Zone. The rift zone has been the site of extensive recent volcanism concentrated within the Brunhes Chron (<0.78 Ma) and linked to fault block rotations between the intracontinental master faults. The boundaries of this activity are defined here using a regolith mapping technique. 相似文献
59.
Martin Oberringer Erhan Akman Juseok Lee Wolfgang Metzger Cagri Kaan Akkan Elif Kacar Arif Demir Hashim Abdul-Khaliq Norbert Pütz Gunther Wennemuth Tim Pohlemann Michael Veith Cenk Aktas 《Materials science & engineering. C, Materials for biological applications》2013,33(2):901-908
In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell–surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 μm. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis. 相似文献
60.
An optimal control algorithm for cryopreservation of cells using ultrarapid freezing technique is applied successfully in the present study to determine the strength of optimal laser heating based on the desired limited temperature distribution of the cell. The validity of this optimal control analysis utilizing the conjugate gradient method of minimization is examined using numerical experiments. Three different heating times are given, and the corresponding optimal control heat fluxes are determined. Results show that the optimal boundary heat fluxes can be obtained with any arbitrary initial guesses within a very short CPU time on a Pentium III 600-MHz PC. 相似文献