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71.
Arzu ?encan ?ahin 《Heat and Mass Transfer》2012,48(11):1921-1928
Thermal performance of solar air collector depends on many parameters as inlet air temperature, air velocity, collector slope and properties related to collector. In this study, the effect of the different parameters which affect the performance of the solar air collector are investigated. In order to maximize the thermal performance of a solar air collector genetic algorithm (GA) and artificial bee colony algorithm (ABC) have been used. The results obtained indicate that GA and ABC algorithms can be applied successfully for the optimization of the thermal performance of solar air collector. 相似文献
72.
73.
C. Çakır A. Gürol L. Demir Y. Şahin 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):345-348
In this study, we have prepared seven Au-Cu standards in the concentration range of 18–24 (as carat) for nondestructive control
of gold quarter liras. Some calibration curves for quantitative analysis of Au in the gold quarter liras that commercially
present in Turkey have been plotted using these standard samples. The characteristic X-rays of Au and Cu emitted from these
standard samples and the test sample with known composition are recorded by using a Ge(Li) detector. These calibration curves
provide a nondestructive analysis of gold quarter liras with the uncertainties about 1.18%. 相似文献
74.
In this work, we aim a detailed investigation of the electronic properties of a spherical multi-layer quantum dot with and without a hydrogenic impurity. The structure is introduced in the form of core/shell/well/shell layers. The core and well layers are defined by the parabolic electronic potentials. We carry out the effect of the core radius and layer thickness on the energy levels, their wave functions, binding energies of the impurity and the probability distributions. In order to determine the sublevel eigenvalues and eigenfunctions, the Schrödinger equation is solved full numerically by shooting method in the frame of the effective mass approximation. The results are analyzed in detail as a function of the layer thicknesses and their probable physical reasons are tried to be explained. It is found that the electronic properties and impurity binding energies are strongly depending on the layer thicknesses. 相似文献
75.
Şahin Yıldırım 《Nonlinear dynamics》2008,52(3):207-215
The use of a proposed recurrent neural network control system to control a four-legged walking robot is presented in this
paper. The control system consists of a neural controller, a standard PD controller, and the walking robot. The robot is a
planar four-legged walking robot. The proposed Neural Network (NN) is employed as an inverse controller of the robot. The
NN has three layers, which are input, hybrid hidden and output layers. In addition to feedforward connections from the input
layer to the hidden layer and from the hidden layer to the output layer, there is also a feedback connection from the output
layer to the hidden layer and from the hidden layer to itself. The reason to use a hybrid layer is that the robot’s dynamics
consists of linear and nonlinear parts. The results show that the neural-network controller can efficiently control the prescribed
positions of the stance and swing legs during the double stance phase of the gait cycle after sufficient training periods.
The goal of the use of this proposed neural network is to increase the robustness of the control of the dynamic walking gait
of this robot in the case of external disturbances. Also, the PD controller alone and Computed Torque Method (CTM) control
system are used to control the walking robot’s position for comparison. 相似文献
76.
A. Z. Şahin 《Heat and Mass Transfer》1998,33(5-6):425-430
Various cross sectional duct geometries were compared from the point of view of entropy generation and pumping power requirement
in order to determine the possible optimum duct geometry which minimizes the exergetic losses within the range of laminar
flow conditions and constant wall temperature. Duct geometries used are; circular, square, equilateral triangle, rectangle
with aspect ratio 1/2 and sinusoidal with aspect ratio . It is shown that the optimum duct geometry for constant thermophysical properties depends on the Reynolds number, however,
the circular duct geometry is found to be the favorable one especially when the frictional contribution of entropy generation
becomes dominant. Triangular and rectangular duct geometries are in general the worst choices for both entropy generation
and pumping power requirement.
Received on 17 June 1997 相似文献
77.
Starting from the notion of thickness of Parks we define a notion of robustness for arbitrary subsets of Rk and we investigate its relationship with the notion of positive reach of Federer. We prove that if a set M is robust, then its boundary ∂M is of positive reach and conversely (under very mild restrictions) if ∂M is of positive reach, then M is robust. We then prove that a closed non-empty robust set in Rk (different from Rk) is a codimension zero submanifold of class C1 with boundary. As a partial converse we show that any compact codimension zero submanifold with boundary of class C2 is robust. Using the notion of robustness we prove a kind of stability theorem for codimension zero compact submanifolds with boundary: two such submanifolds, whose boundaries are close enough (in the sense of Hausdorff distance), are diffeomorphic. 相似文献
78.
AzaPCs containing tetra- and octaguaiacol moieties have not been investigated up to now. In this study, an unusual method is used for the synthesis of metalloAzaPCs (M: Zn, Co, Cu) containing guaiacol moieties. All compounds are characterized by a combination of FT-IR, 1H NMR, 13C NMR, mass and UV/vis spectroscopy techniques. The molecular structure of starting pyrazine compounds 1 and 2 is also determined by the single crystal X-ray diffraction technique. The aggregation behavior of new Zn(II) AzaPCs is investigated in DMSO at different concentrations. The fluorescence properties of Zn(II) AzaPCs are investigated in different solvents. The fluorescence quantum yields of Zn(II) AzaPCs are calculated in DMSO. 相似文献
79.
The differential cross sections of the emission of M-shell fluorescence X-rays from Tl and Pb have been measured by 5.96 keV photons at seven angles ranging from 50° to 110°. The differential cross section is found to decrease with the increasing emission angle, showing an anisotropic spatial distribution of M-shell fluorescence X-rays. Furthermore, M-shell fluorescence cross sections and the average fluorescence yields were measured for Pt, Au, Hg, Tl, Pb, Bi, Th, and U at an excitation energy of 5.96 keV using a Si(Li) detector. The experimental results of the total M X-ray fluorescence cross sections and M-shell fluorescence yields were compared with the theoretical values.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
80.
Mustafa Ersin Pekdemir Mediha Kök Muhammed Sait Kanca Ecem Özen Öner Sibel Pekdemir Şule Inci Sevda Kirbağ Beyhan Tatar 《先进技术聚合物》2023,34(2):605-612
Recently, there has been a great demand for boron-containing compounds (BCCs) with unique biological properties. The demand for the use of these compounds not alone but as additives in composite materials is increasing day by day. In this study, the effect of adding B2O3 compound to the blend of PLA and PEG polymers, which is an important biocompatible shape memory polymer, was investigated. In order to examine the effect of increasing B2O3 additive on the thermal properties of PLA-PEG blend, it was determined by using a Differential Scanning Calorimetry (DSC) and thermogravimetric analyzer (TGA), and it was seen that while the melting temperature of PEG decreased, the melting temperature of PLA increased. In addition, when the thermal stability of the composites was examined, increasing of thermal stability was observed with the addition of B2O3 and a three-step degradation occurred. It was determined that the B2O3/PLA-PEG composite was homogeneous by taking X-ray measurements and SEM measurements. The antimicrobial property of the PLA-PEG blend improved with the increasing B2O3 contribution were observed from the antimicrobial activity measurements of the composite against 4 different bacteria. However, it was determined that the PLA-PEG blend preserved its shape memory effect with increasing diboron trioxide contribution. 相似文献