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521.
Efficient use of solar radiation needs detailed knowledge of its spatial and temporal variations. Such information can be achieved using interpolating measured irradiance by ground stations. But more reliable results can be obtained by processing geostationary satellite images. Heliosat is an algorithm which has been developed to estimate global horizontal irradiance at ground level from images taken in the visible band by the Meteosat satellites.The aim of this study was to evaluate the Heliosat-II model by using daily global solar irradiation data measured at the four radiometric stations in Iran as well as Meteosat-5 images which are recorded by a spacecraft over 63°E. Mean RMSD% and MBD% for all stations were 11.7% and 1.9%, respectively. The mean values of intercept, slope and correlation coefficient were 0.82 (kWh m−2), 1.05 and 0.93, respectively. Seasonally, the maximum RMSD occurs in autumn (22.1%) and the minimum is experienced in spring (8.4%). This accuracy is a great achievement for producing a high quality solar radiation atlas in a country such as Iran with very sparse radiometric network and frequently unreliable measured irradiation data. 相似文献
522.
S. Shahab R. Mirzaeifar H. Bahai 《International Journal of Mechanical Sciences》2009,51(9-10):708-717
This paper proposes a new method for performing predefined simultaneous modification of natural frequencies and buckling loads of composite cylindrical panels. The method is based on the fact that both natural frequencies and buckling loads are eigenvalues of an algebraic system of simultaneous equations. First- and second-order derivatives of these eigenvalues are calculated and the first two terms in Taylor expansion are used for developing a modification procedure that is defined as an inverse eigenvalue problem. A four-layered composite cylindrical panel with an arbitrary angle-ply stacking sequence is considered as a case study and several simultaneous modifications for natural frequencies and buckling loads are carried out. It is shown that the proposed method can perform the predefined modification with an acceptable accuracy even for large perturbations in objective functions. 相似文献
523.
Hamed Moradi Gholamreza Vossoughi Mohammad R. Movahhedy Hassan Salarieh 《Journal of Process Control》2013,23(5):631-648
During the milling process, self-excited vibration or chatter adversely affects tool life, surface quality and productivity rate. In this paper, nonlinear cutting forces of milling process are considered as a function of chip thickness with a complete third order polynomial (instead of the common linear dependency). An optimal control strategy is developed for chatter suppression of the system described through nonlinear delay differential equations. Counterbalance forces exerted by actuators in x and y directions are the control inputs. For optimal control problem, an appropriate performance index is defined such that the regenerative chatter is suppressed while control efforts are minimized. Optimal control law is determined based on variation of extremals algorithm. Results show that under unstable machining conditions, regenerative chatter is suppressed effectively after applying the optimal control strategy. In addition, optimal controller guarantees robust performance of the process in the presence of model parametric uncertainties. 相似文献
524.
Absorption and emission spectra of three hetarylazoquinoline compounds with different substituents were examined in liquids and liquid crystalline solvents for the first time. The spectral features of the hetarylazoquinoline dyes were explained according to azo/hydrazone tautomerism in conjunction with the solvatochromic characteristic of the preferred tautomer. The nature and extent of solute-solvent interactions were described using Kamlet-Taft and Katritzky multiparameter polarity scales. It was observed that solvatochromic azo/hydrazone tautomerism depend on multiple solute-solvent interactions, in particular on specific interactions and the solvent ability to transport the hydrogen atom through the media. In addition, it was concluded that anisotropic hosts prevent shift of the tautomeric equilibrium toward the hydrazone form. 相似文献
525.
Hamid Reza Afshoun Mahdi Pourafshari Chenar Mohammad Reza Moradi Ahmad Fauzi Ismail Takeshi Matsuura 《应用聚合物科学杂志》2020,137(28):48860
Enhancing the performance of gas separation membranes is one of the major concerns of membrane researchers. Thus, in this study, poly(ether-block-amide) (Pebax)/polyetherimide (PEI) thin-film composite membranes were prepared and their CO2/CH4 gas separation performance was investigated by means of pure and mixed gases permeation tests. To improve the properties of these membranes, halloysite nanotubes (HNT) were added to Pebax layer at different loadings of 0.5, 1, 2, and 5 wt % to form Pebax-HNT/PEI membranes. Scanning electron microscopy, gas sorption, X-ray diffraction, Fourier-transform infrared, and differential scanning calorimetry tests were also performed to investigate the impact of HNT on structure and properties of prepared membranes. Results showed that both CO2/CH4 selectivity and CO2 permeance increased by adding HNT to Pebax layer up to 2 wt %. By increasing HNT loading to 5 wt %, the CO2/CH4 selectivity decreased from 32 to 18, while CO2 permeance increased from 3.25 to 4.2 GPU. Pebax/PEI and Pebax-HNT/PEI membranes containing 2 wt % of HNT were tested using CO2/CH4 gas mixtures at different feed CO2 concentrations and feed pressure of 4 bar. The results showed that with increasing CO2 concentration from 20 to 80 vol %, CO2/CH4 selectivity of Pebax/PEI composite membranes increased by 19%, while, in Pebax-HNT/PEI membrane, CO2/CH4 selectivity decreased by 40%. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48860. 相似文献
526.
This paper deals with the dynamic output feedback stabilization problem of deterministic finite automata (DFA).The static form of this problem is defined and so... 相似文献
527.
In this research study, 6, 8‐dichloro‐4‐hydroxyquinolin‐2(1H)‐one was prepared by the thermal cyclocondensation of 2‐(2, 4‐dichlorophenylcarbamoyl) acetic acid or N, N?‐bis(2,4‐dichlorophenyl)malonamide at 140‐150°C in polyphosphoric acid, resulting in a yield of 48%. This compound was then coupled with a series of diazonium salts derived from aromatic and heteroaromatic amines for synthesis of the corresponding azo dyes. The structures of the compounds were confirmed using elemental analysis as well as ultraviolet‐visible, Fourier Transform‐infrared and proton nuclear magnetic resonance spectroscopy. The effects of organic solvents with different polarities, pH values and substituents of the diazotising components on the maximum absorption wavelength of the colorants were discussed and evaluated in detail. The acidity constants (pKa) of the dyes were also determined using the spectrophotometric method in an ethanol‐water mixture (80:20, v/v) at 20‐23°C. 相似文献
528.
4–Hydroxy–1, 8–naphthalimides and the isomer mixtures of'3–and 4–hydroxy–7 H–benzimidazo–(2, l–a)–benz(d, e)–isoquinolin–7–ones were coupled with diazotised arylamines to yield orange–red to bluish–red dyes having good coloration properties and excellent fastness to light on polyester fibres. Structure–property relationships in the dyes are discussed with respect to the nature of the substituents in the imide, imidazole and arylazo moieties. 相似文献
529.
Shiva Rahmani Shahab Faghihi Ghassem Amoabediny Mehdi Shakibaie Behnam Noorani 《国际聚合物材料杂志》2018,67(1):27-35
Different ratios of poly(ε-caprolactone) (PCL) and gelatinwere used to fabricate scaffolds for regeneration of retinal pigment epithelium (RPE) layer. Physical and chemical characterizations were performed and the behavior of human RPE cells on the scaffolds was evaluated subsequently. An increase in gelatin content in the scaffold enhanced hydrophilicity, RPE cell attachment, proliferation, and spreading over PCL scaffolds. Granular and cytoplasmic expressions of RPE65 and Cytokeratin 8/18 markers confirmed the presence of RPE cells. It was believed that PCL/gelatin scaffolds could be used as substrates to replace RPE extracellular matrix to facilitate regeneration of RPE layer in retinal diseases. 相似文献
530.