IJEM Vol. 10, No. 1, Feb. 2020
Cover page and Table of Contents: PDF (size: 908KB)
Optimal installation of electrical distribution transformers has always been a challenging task for distribution operator (DSO)s due to load variations, particularly for seasonal loads. Depending on the quality of distribution systems in different regions and countries, a considerable number of installed transformers may be oversized or have capacity lower than critical standard. In this study, IEC 60076-7 is used to calculate the temperature limitations for distribution transformer capacities and determine optimal transformer capacity for an electrical distribution substation based on the critical values and limitations given in the standard. A data logger is installed on the substation and the load data is recorded for one year. Additionally, the impact of different parameters like ambient temperature is investigated for optimal determination of transformer capacity.[...] Read more.
Research on thermal response of liquid helium storage tank is an important part of non-destructive storage technology for liquid helium, However there are few reports on the thermal response of liquid helium storage tanks. Taking the thermal stratification, pressure rise phenomenon and natural convection of liquid helium storage tank as research objects, based on the Lee model, the finite volume method was used for the first time to study the non-steady-state thermal response which simultaneously considering the change of liquid helium and vapor helium properties. Thus the tank pressure, temperature and flow rate distribution at different times were obtained, and the effects of evaporation rate and filling rate on the pressure rise and temperature rise of the storage tank were analyzed. The research shows that with the increase of simulation time, the liquid helium shows thermal stratification. In addition, the pressure is distributed in a stepwise manner which is lower in the upper part, and higher in the lower part, while the pressure distribution in the gas phase space is more uniform; After the liquid helium in the near-wall area is heated, it rises along the wall surface to the free liquid surface under buoyancy lift, and then flows into the main flow area of the liquid helium; As the evaporation rate increases, the temperature rise and pressure rise rate in the gas phase space of the storage tank increase, while the filling rate have less influence on the temperature rise and pressure rise rate.This work provides guidance for non-destructive storage and transportation theory of liquid helium storage tanks.[...] Read more.
The major disadvantage of a standard bus topology is the constraint of being able to realize only one communication at a time (the tasks may take place in parallel but the communications are only done in a sequential). As these communications are handled by the bus arbiter, a Bottleneck when the number of communications increases, but also when the bandwidth constraints of several communications become important.This arbitration plays a predominant role because it authorizes communications on the bus but it is also in charge of resolving the conflicts (several requests of communications at the same time). This arbitration implies therefore a limitation on the number of IP connected to the bus to a dozen elements.
This work elaborates the AMBA bus interface with four masters interacting with single memory system, using Arbiter between memory controller and other supporting peripherals. Different module of i.e., AHB MSTER, AHB SLAVE INTERFACE AND AHB ARBITER(round robin algorithm)has been developed with VHDL. Further integration with FIFO, RAM and ROM with memory controller is done. The Four AHB master initiates the operations and generates the necessary control signals on single bus to memory controller with the help of arbiter. The proposed architecture shows the area efficient management as compared to previous researches of multiple data communication in AHB BUS system. The system model is synthesized with Xilinx XC6vx75t-2ff484 and simulated with MODELSIM.
The organic compound used as corrosion inhibitor was benzaldehyde. The use of organic compounds as corrosion inhibitors is of potential interest due to their abundant availability, cost effectiveness, and environmental acceptability. However, this study investigates the inhibition effect of this organic compound (benzaldehyde) on the corrosion of aluminium in phosphoric acid solution. Experiments were performed by varying the temperature and concentration of the compound under study. The results obtained from the study shows that the organic compound (benzaldehyde) is a potential inhibitor for the corrosion of aluminium in phosphoric acid solution. The inhibition efficiency was found to increases progressively as the concentration of the inhibitor increases but decreases when the temperature rises. Activation energy values for the corrosion process was found to be 32.61 kJ/mol in uninhibited phosphoric acid solution which increased to 49.53 kJ/mol in the presence 0.1 M concentration of the inhibitor. The values of the rate constant and half live were 9.12 × 10-3 hr-1 and 75.94 hr in uninhibited phosphoric acid solution which changed to 4.56× 10-3 and 151.80 hr in the presence of 0.1 M inhibitor concentration. Kinetics of the reaction in uninhibited and in the presence of the inhibitor revealed that the process follows a first order reaction. The evaluated enthalpy (ΔH) gave positive values which indicate that the heat of adsorption process on the surface of aluminum was endothermic. The negative values of entropy (ΔS) signified that the activated complex at the rate determining step is an association, not dissociation. Evaluated values of free energy of adsorption (ΔGads) were all negative, implying spontaneity of the process and were around and less than -20 kJ/mol, indicative of physisorption of the adsorption process.[...] Read more.
With the explosive increase in the data traffic of wireless communication systems and the scarcity of spectrum, terahertz (THz) frequency band is predicted as a hopeful contender to shore up ultra- broadband for the forthcoming beyond fifth generation (5G) communication system. THz frequency band is a bridge between millimeter wave (mmWave) and optical frequency bands. The contribution of this paper is to carry out an in-depth study of the THz channel impairments using mathematical models to evaluate the requirements for designing indoor THz communication systems at 300GHz. Atmospheric absorption loss, diffraction loss and free space path loss were investigated and modeled. Finally, we discuss several potential application scenarios of THz and the essential technical challenges that will be encountered in the future THz communications. Finally, the article finds that propagating in the THz spectrum is strongly dependent on antenna gain.[...] Read more.