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排序方式: 共有243条查询结果,搜索用时 12 毫秒
91.
Suleyman Bilgin Omer Halil Çolak Ovunc Polat Etem Koklukaya 《Expert systems with applications》2009,36(6):10078-10084
Heart Rate Variability (HRV) is an efficient tool for assessment of Sympathovagal Balance (SB) and classification of cardiac disturbances. However, its index may be not enough for classification and evaluation of some disease. This study presents 32 new sub-bands over LF and HF base-bands that are accepted in the literature. Moreover, it determines dominant sub-bands over both base-bands in VTA database. These sub-bands are obtained using Wavelet Packet Transform (WPT) and evaluated using Multilayer Perceptron Neural Networks (MLPNN). Results are compared with obtained results from normal datasets. The domination effects of these sub-bands are assessed according to comparison of each other related to MLPNN training and test accuracy percentages by selecting different width of windows. As a result, obtained results showed that the LF zone including LF1, LF2 and LF3 sub-bands on 0.0390625–0.0859375 Hz frequency range is the most dominant over the LF base-band and, the HF zone including HF1, HF2 and HF3 on 0.1953125–0.28125 Hz frequency range is the most dominant over the HF base-band. In normal datasets, distinctive domination effect has not been determined. 相似文献
92.
Aylin Şakar-Deliormanlı Erdal Çelik Mehmet Polat 《Journal of the European Ceramic Society》2009,29(1):115-123
Lead magnesium niobate (PMN) is a relaxor ferroelectric material. Because of its high dielectric constant and superior electrostrictive properties it is commonly used in the manufacture of multilayer electronic devices which is typically produced by tape casting. However, preparation of PMN slurry formulations to use in aqueous tape casting process is not investigated in detail yet. Therefore, in this study aqueous PMN formulations were developed for tape casting and its relation with the final properties of PMN films were investigated. The slurries were prepared using poly(acrylic acid)-based comb polymer as the dispersant, nonionic acrylic latex as the binder and the hydroxypropyl methyl cellulose as the wetting agent. The results showed that it is possible to prepare flexible, crack-free PMN films using highly concentrated suspensions without using any plasticizer. The study gives guidelines for the aqueous tape casting of PMN and can be adapted to processing of other multi-component metal oxides. 相似文献
93.
This paper describes an approach for pattern recognition using genetic algorithm and general regression neural network (GRNN). The designed system can be used for both 3D object recognition from 2D poses of the object and handwritten digit recognition applications. The system does not require any preprocessing and feature extraction stage before the recognition. In GRNN, placement of centers has significant effect on the performance of the network. The centers and widths of the hidden layer neuron basis functions are coded in a chromosome and these two critical parameters are determined by the optimization using genetic algorithms. Experimental results show that the optimized GRNN provides higher recognition ability compared with that of unoptimized GRNN. 相似文献
94.
Obaid Saad Al‐Sobiei David Arditi Corresponding author Gul Polat 《Construction Management & Economics》2013,31(4):423-430
The construction project is subject to several risks, one of the most important of which is contractor default because contractor default may increase the final project cost considerably. In the US construction industry, owners commonly shield themselves from the risk of contractor default by transferring this risk to the contractor, who in turn transfers this risk to a surety company. On the other hand, the General Directorate of Military Works (GDMW) of the Kingdom of Saudi Arabia retains the risk of contractor default rather than transferring it to a third party. An artificial neural network (ANN) and a genetic algorithm (GA) are used in this study to predict the risk of contractor default in construction projects undertaken for the Saudi armed forces. Based on this prediction, the Saudi GDMW can make a decision to engage or not to engage the services of a contractor. In case the models are not able to generate reliable predictions (or generate contradictory outcomes), the GDMW will have to augment its budget with contingency funds to be used in the event of contractor default. The outcome of this study is of particular relevance to construction owners because it proposes an approach that can allow them to replace an indiscriminate blanket policy by a policy that is rational, effective, prudent and economical. 相似文献
95.
Ferhat ErdalErkan Do?an Mehmet Polat Saka 《Journal of Constructional Steel Research》2011,67(2):237-247
Cellular beams became increasingly popular as an efficient structural form since their introduction. Their sophisticated design and profiling process provide greater flexibility in beam proportioning for strength, depth, size and location of circular holes. The main goal of manufacturing these beams is to increase the moment of inertia and section modulus, which results in greater strength and rigidity. Cellular beams are used as primary or secondary floor beams in order to achieve long spans and service integration. In this study, the design problem of cellular beams is formulated as optimum design problem. The minimum weight is taken as the design objective while the design constraints are implemented from The Steel Construction Institute Publication Number 100. The design methods adopted in this publication are consistent with BS5950 parts 1 and 3. The formulation of the design problem considering the limitations of the above mentioned turns out to be a discrete programming problem. Harmony search and particle swarm optimization methods are used for obtaining the solution of the design problem. The design algorithms based on these two techniques select the optimum UB section to be used in the production of a cellular beam subjected to a general loading, the optimum hole diameter and the optimum number of holes in the cellular beam. Furthermore, this selection is also carried out such that the design limitations are satisfied and the weight of the cellular beam is the minimum. A number of design examples are considered to demonstrate the efficiency of the algorithm presented. 相似文献
96.
A parametric study is conducted to investigate the dynamic shear amplification factor (DAF) in low‐to‐mid‐rise frame–wall systems in which the reinforcement curtailment along the height matches the required code strength. The level of frame–wall interaction is varied by changing the wall index, defined as the ratio of the total wall area to the floor plan area, in a generic frame–wall system, and its correlation with the DAF is investigated. Wall index values ranging in the 0.2% to 2% interval are selected. Walls with lengths of 3m , 5 m and 8 m are used in the design of model buildings of 4, 8 and 12 stories. Shear–flexure beam continuum formulation is used in design and modeling. The global behavior is analyzed using nonlinear response history procedure using spectrum compatible ground motions. It is found that the primary source of amplification is the level of inelastic demand on the system. Walls designed for code‐specified force reduction factor R = 6 experienced an average base shear force amplification in the order of 1.64 with standard deviation of 0.19 with respect to design shear force. Amplification diminishes with decreasing R. An expression for the dynamic amplification factor as a function of the number of stories and force reduction factor R is proposed. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
97.
Infrared thermography (IRT) absorbs infrared radiation and generates images based on the amount of heat generated. It has been used in human medicine for diagnosis of various cancers. This experiment was conducted to determine if IRT had merit for early detection of subclinical mastitis in dairy cows. Milk sample and skin surface temperature (SST) were simultaneously evaluated using the California Mastitis Test (CMT) and IRT for each quarter in 94 dairy cows (49 Brown Swiss and 45 Holstein). Average days in milk (DIM) and milk production were 93 ± 37 d and 16 ± 2.2 kg (mean ± SD) and their ages ranged from 4 to 8 yr. There was a strong correlation between SST and CMT score (r = 0.92). Average SST was 33.19, 34.08, 34.99, and 36.15°C for quarters with the CMT score of 0 (n = 156), +1 (n = 116), +2 (n = 80), and +3 (n = 24), respectively. This association was best described by a linear model as follows: y = 0.94x + 33.17, R2 = 0.85, where y = SST and x = CMT score. Changes in rectal temperature (RT) due to the CMT score were minor (y = 0.09x + 38.39, R2 = 0.07, where y = RT and x = average CMT score). In conclusion, RT may not confirm mastitis. However, IRT is sensitive enough to perceive changes in SST in response to varying degrees of severity of the mammary gland infection as reflected by the CMT score, suggesting that as a noninvasive tool, IRT can be employed for screening dairy cows for mastitis. 相似文献
98.
O. Polat 《International Journal of Heat and Mass Transfer》2003,46(9):1563-1573
Conjugate heat transfer in inclined open shallow cavities has been numerically studied. A thick wall facing the opening is heated by a constant heat flux, sides perpendicular to the heated wall are insulated and the opening is in contact with a fluid at constant temperature and pressure. Conjugate heat transfer by conduction and natural convection is studied by numerically solving equations of mass, momentum and energy. The governing parameters were: Rayleigh numbers, Ra from 106 to 1012, conductivity ratio, kr from 1 to 60, cavity aspect ratio, A=H/L from 1 to 0.125, dimensionless wall thickness, ?/L from 0.05 to 0.20 and the inclination angle, ? from 0° to 45° from the horizontal. Isotherms and streamlines are produced, heat and mass transfer is calculated. It is found that volume flow rate, is an increasing function of Ra, A, ?/L, ?, and a decreasing function of kr. Heat transfer, Nu is an increasing function of Ra, ?/L, and a decreasing function of kr. A mixed pattern is found with respect to A and ?. In the former, Nu is an increasing function of the aspect ratio up to a critical Rayleigh number, above which the relationship changes and it becomes a decreasing function of A. In the latter case, Nu is a decreasing function at low Raleigh numbers and an increasing one at high Rayleigh numbers. 相似文献
99.
100.
MeasurementandtheoreticalevaluationofcrossectionforNa(4D)+Na(3S)→Na(4F)+Na(3S)ShenYiFan,LiWanXing,PolatAhmatandLuoLan(Depa... 相似文献