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1.
Distribution systems are most commonly operated in a radial configuration for a number of reasons. In order to impose radiality constraint in the optimal network reconfiguration problem, an efficient algorithm is introduced in this paper based on graph theory. The paper shows that the normally followed methods of imposing radiality constraint within a mixed-integer programming formulation of the reconfiguration problem may not be sufficient. The minimum-loss network reconfiguration problem is formulated using different ways to impose radiality constraint. It is shown, through simulations, that the formulated problem using the proposed method for representing radiality constraint can be solved more efficiently, as opposed to the previously proposed formulations. This results in up to 30% reduction in CPU time for the test systems used in this study. 相似文献
2.
In digital communication systems, typical methodologies in determining loop parameters of the digital phase-locked loop (DPLL) are based on the mapping transformation from the analog domain to the digital domain. However, such transform based algorithms are relatively complicated and not straightforward, and they also cause the problem that loop parameters are affected by the pre-detection integration time greatly. To solve these issues, an effective direct method of determining loop parameters of the second-order DPLL in the z-domain is proposed in this paper. Through ascertaining specific positions of the closed-loop system function's poles inside the right-hand side of the z-plane's unit circle, unknown parameters are calculated directly and flexibly in this method, which enables the DPLL to acquire good low-pass filtering characteristic and system stability. This novel method not only reduces the complexity of solving the parameters, but also eliminates the effect of the pre-detection integration time on loop parameters. Simulation results are provided to confirm the feasibility of the proposed method and to show that the DPLL obtained by this method achieves the similar tracking performance to the discretized PLL. 相似文献
3.
Anees A. Khadom Hongfang Liu Ahmed A. Fadhil Abdul Mun’em A. Karim 《Oxidation of Metals》2016,86(5-6):553-565
The high-temperature corrosion rate of boiler tubes was studied as a function of inhibitor concentration, time, and temperature in the absence and presence of fuel ash. Samples of steel tubes were taken from boilers that operate in Northern Baghdad Station for Electric Power Generation. Fuel ash was collected from the boiler combustion chamber, as well. Normal and nano-MgO were used as a corrosion inhibitor in different mixing ratios. A weight loss technique was used to evaluate the corrosion rates, while scanning electron microscopy was used to study the surface morphology. It was seen that corrosion rates increased with both time and temperature, and decreased with the addition of inhibitors. The maximum inhibitor efficiency was 81 %, obtained via using nano-MgO at mixing weight ratio 2:1, 600 °C, and 10 h. The Presence of fuel ash had harmful effects on the steel surface. 相似文献
4.
Wireless Networks - This paper studies enhancing non-orthogonal multiple access (NOMA) spectral efficiency (SE) through optimizing the assigned power to each NOMA user depending on their channel... 相似文献
5.
《Ceramics International》2016,42(3):3930-3937
Room-temperature multiferroic 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 solid solution ceramics have been prepared by the sol–gel method. We have discussed the annealing temperature dependence of the multiferroic properties. The samples are annealed at 1023, 1123, 1223 and 1323 K for 3 h, respectively. X-ray diffraction patterns identify that all samples are pure. Scanning electron micrographs present the increasing grain size with higher annealing temperature. Magnetic, ferroelectric and dielectric properties are enhanced obviously with the increase in annealing temperature. The coexistence of ferroelectric and ferromagnetic properties is also proved at room temperature. In addition, it reveals that the optimal annealing temperature accompanied with favorable multiferroic properties of 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 solid solution ceramics is near 1223 K. 相似文献
6.
Kazarinov I. A. Isaicheva L. A. Makhmmod Adiba A. Trepak N. M. 《Protection of Metals and Physical Chemistry of Surfaces》2019,55(4):700-705
Protection of Metals and Physical Chemistry of Surfaces - Kinetics of formation of phosphate coatings (PCs) on St3 carbon steel in zinc nitrate–phosphate solution (0.65 М Zn2+ + 0.3... 相似文献
7.
《Fuel Processing Technology》1987,17(2):107-115
Flash pyrolysis of low rank Italian coal (Sulcis coal) has been studied in a fluidized bed pyrolyser using temperatures between 460 and 900°C. The maximum yield of oils (tars) was obtained at about 600°C. Yields of C1C3 hydrocarbons increased with increasing temperature, reaching 6% at 900°C. Fractionation of tars showed that the composition was strongly dependent on pyrolysis temperature. By the behaviour of the composition of tars on temperature, a possible reaction mechanism is suggested. 相似文献
8.
Farid Jamali-Sheini Ramin Yousefi M.R. Mahmoudian Nabeel Ali Bakr Abdolhossein Sa΄aedi Nay Ming Huang 《Ceramics International》2014
Te-doped ZnO nanostructures were synthesized by an annealing (vapor–solid) process under ambient conditions, and characterized in terms of their morphological, structural, compositional and optical properties. The structural and morphological characterizations revealed that the synthesized nanostructures were well-defined multipods, needles and spherical particles, and possessed well-crystalline ZnO wurtzite hexagonal phase. Also, in the X-ray diffraction studies, the presence of a shift in the peak positions towards a lower angle, and a decrease in the intensity, with an increase in the Te concentration, as compared to the undoped ZnO, were observed. The chemical composition confirmed the presence of Te, in the case of multipod and needle morphologies. The effect of doping on the crystalline quality and optical properties was also investigated, by using photoluminescence (PL) and Raman spectrometers. The Raman results demonstrated that the doped ZnO nanostructures had a lower crystalline quality than the undoped ZnO. Moreover, the PL results showed a decrease in the band gap for the doped ZnO nanostructures, in comparison to the undoped ZnO. A possible growth mechanism was also proposed. 相似文献
9.
A. S. Yaro K. W. Hameed A. A. Khadom 《Theoretical Foundations of Chemical Engineering》2013,47(3):266-273
Corrosion of steel tube in sea water was controlled by cathodic protection. Sacrificial anode technique was used. In this technique, weight loss method was used to determine the rate of zinc consumption as a function of temperature, time, pH and solution velocity. Reaction kinetics studies showed that the rate of zinc consumption was first order. Activation parameters were obtained from Arrhenius equation and transition state equation. Two mathematical models were suggested to represent the consumption data. Statistical analysis proved that the second-order multi-terms model was better than the one-term model. 相似文献
10.
《Catalysis communications》2007,8(11):1748-1754
This work reports the mild synthesis of LaCoO3 catalyst with the interesting nanowire morphology in the presence of both carbon nanotubes (CNTs) and citrate. In comparison, LaCoO3 nanoparticles were prepared by conventional citrate method. The samples were characterized by TEM (Transmission electron microscopy), XRD (X-ray diffraction), N2 adsorption isotherm and CO-TPD (Temperature-programming desorption), etc. The results showed that the morphology of LaCoO3 catalyst was controlled effectively by the CNTs template; and that the adding of citrate not only controlled effectively the stoichiometric ratio of La to Co, but also reduced the crystallizing temperature of LaCoO3 crystal greatly. Moreover, after calcined at 750 °C for 48 h, LaCoO3 nanowires exhibited higher thermal stability and catalytic activity for CO oxidation, compared with the nanoparticles. 相似文献