Papers by Keyword: Transient

Abstract: This research developed a performance improvement of power transmission system to enhance performance during line disturbance using model Predictive control (MPC) control scheme. This research work was implemented using MATLAB 2023a. However, the parameters of these controllers are usually adjusted based on a linearized model of the power system, which typically depends on the system's operating point or state. To assess the performance of the developed scheme, multiple simulation studies were carried out under conditions where the voltage magnitude of the infinite bus and the transmission line reactance changed due to faults at the infinite bus and sending terminals. The results from the waveform analyses indicate that the dynamic characteristics of the system under investigation have significantly improved. settling time, at post fault of the transmission and from fault recovery settled time to its stable state value of 1.8sec compared to 2.8sec with minimal control effort that fluctuated between faults and system stability before settling time at the shortest time value of 2. 6305s in 2.42s compared to 4.28, in 1.92s compared, and 3.32s.

Abstract: Semiconductor devices rely on the incorporation of donor and acceptor atoms into the crystal lattice to form locally doped regions. For dopant atoms incorporated into SiC by ion implantation, a high-temperature annealing step is required to achieve electrical activation. This annealing step is accompanied by redistribution of the implanted atoms. The influence of the annealing parameters on dopant redistribution is crucial when aiming for ever smaller device dimensions. In this work, we present a consistent analysis of the diffusion of Al implanted in 4H-SiC after high-temperature annealing at 1650 °C and 1800 °C for different annealing times. We identify the equilibrium diffusion coefficient at long annealing times from Al profiles obtained by SIMS analyses for both annealing temperatures. The temperature dependence is determined using an Arrhenius representation. This allows to quantify the equilibrium diffusion lengths for the actual temperature profiles, including heating and cooling rates. We find that the measured diffusion lengths for short annealing times are larger than expected from equilibrium diffusion and attribute the excess length to transient enhanced diffusion. Comparing the transient diffusion lengths of room-temperature and 500 °C-implanted samples, we conclude that the transient behavior is likely related to residual crystal damage induced during the implantation process.

Abstract: In this work a transient three-dimensional mathematical model was developed using cylindrical-elliptic coordinate system and thermo-physical properties as functions of the position or temperature. The aim is to predict heat transfer in an elliptic-cylindrical fixed bed reactor subjected to a chemical reaction of first order whose heat of reaction is given by the power law. The governing equation of the phenomenon is solved using the finite volume method, and the WUDS interpolation scheme, and the fully implicit method. Results are presented and discussed by varying reagent concentration, Arrhenius pre-exponential factor and reagent temperature at the reactor inlet. It was found that: first-order reactions at low molar concentrations have few effect in the temperature distribution and high molar concentrations, from 0.8 kmol/m³, increase the radial temperature gradients; an increase in the inlet temperature of reactor favours the increase in the heating zone in the centre of the equipment, but does not significantly alter the radial temperature gradients; the Arrehnius pre-exponential factor varying in the same order of magnitude as the concentration of reagents practically produces the same field of temperature in the reactor,

Abstract: This work aims to develop a transient three-dimensional mathematical model to predict the temperature distribution in a fixed-bed elliptical cylindrical reactor to different geometric aspect ratio (L₂/L₁=1.5, 2.0 and 3.0). The model considers variable thermo-physical properties, a flat temperature profile at the fluid inlet, as well as a variable porosity model. The governing equation is solved using the finite volume method, coupled with WUDS interpolation scheme and fully implicit method. Results of the temperature profile along the reactor are presented and discussed at different times. As results, it was found that the maximum rate of heat transfer within the reactor occurs near the minor half-axis region of the ellipse (cross-section area of the reactor) and it intensifies over time and that the dimensionless temperature profile is practically unchanged with the aspect ratio.

Abstract: This work aims to develop a transient three-dimensional mathematical model using the elliptic cylindrical coordinate system, to predict heat transfer in a elliptic cylindrical packed fixed bed reactor. The model considers variable thermo physical properties and a parabolic temperature profile at the fluid inlet. The governing equation is solved using the finite volume method. Results of temperature profile along the reactor are presented and discussed at different moments.It was verified that the maximum heat transfer rate inside the reactor occurs near the extreme region close to minor semi-axis of the ellipse; the higher temperatures at the reactor surface are also in this region, along the entire height of the bed; the steady-state regime is reached at t = 4.5 s of process, presenting after this time interval,small axial temperature gradients and high radial gradients along of the reactor bed; the parabolic temperature profile give to the bed a predominance of radial temperature gradients, and the radial porosity profile favours a higher heat transfer rate at reactor surface.

Abstract: Structural health monitoring (SHM) is an inevitable component of modern civil and aerospace structures. It essentially detects the damages in the system by evaluating the performance parameters by the integration of sensing and possibly also actuation devices into the structure. In this paper damage detection process in an aluminium cantilever plate using piezoelectric sensors and actuators is simulated. Possible root damage such as transverse crack and longitudinal crack are studied. The results are compared with undamaged case. The plate is actuated using PZT actuators and performance is evaluated using PVDF sensors. Modelling for PZT/PVDF and structural parts are carried out using coupled field finite element PLANE223 ofAnsys^(TM) finite element package. Strain response at the root of the cantilever plate is captured as the voltage output of the PVDF sensor. Strain response is directly related to the voltage generated in the PVDF sensor. The percentage variation of the fundamental frequency is found to be less than 3% in the present study and hence it is not taken as an index of damage. The transient voltage response captured with the transient coupled field analysis shows variation up to 24% as a signature between damaged and undamaged systems. Therefore, the present study suggests transient response evaluation using PVDF sensor is a suitable evaluation technique for the cases under consideration.

Abstract: A novel transducer for megasonic cleaning of photomasks presents an approach that differs from previous configurations, and appears to have unique features for cleaning while minimizing damage. As the cleaning and damage processes are determined by the presence of cavitation, a thorough acoustic analysis was performed on the device, by using a calibrated hydrophone scanned at the photomask location, and a quartz photomask with embedded sensors.

Abstract: The paper considers issues of a mathematical model development of a “deformation zone - main electric drive” concerning hot plate mills. The dependence of the calculation of rolling torque on features of high deformation zone is given. Based on the obtained expressions, the structural diagram of the deformation zone model has been developed. The paper specifies the structure of the mathematical model for electric drive speed control system based on the known equations of synchronous motor. After the comparison of the transient processes of the electric drive coordinates and rolling settings obtained at the modeling and oscillography at the mill the conformity of the developed model to the studied object has been proved. The provided mathematical model is recommended to analyze the dynamic percussion leads that occurred at hot plate mill. The model obtained allows it to improve the reliability of the electromechanical system owing to the adaptation of the rolling schedule at the real-time operation mode.

Abstract: Proliferation in the use of digital data in manufacturing led to a new industrial revolution by virtue of which user groups and researchers from multiple industrial enterprises have introduced Rapid Prototyping (RP) into their product development processes. This paper presents a coupled field thermos-structural analysis of new RP process namely, Selective Inhibition Sintering Process (SISP) for the evaluation on the effect of temperature in various polymer materials. The present study provides information of the requirement of heat source to achieve effective sintering phenomenon. The structured Finite Element (FE) model with a dimension of 30 X 30 X 1.5 mm is considered for the analysis where in different heat quantity is applied in an iterative manner to examine the sintering temperature. Based on the simulation results, for each polymer, required amount of heat to observe sintering characteristics is evaluated. The effect of applied heat on the examination of structural aspects of polymer materials including thermal stress, distortion and displacement is carried out. The simulation results affirms that the polymer materials are within in the safe structural and thermal limit and the selection of low cost heat source will be useful for the development of cost-effective SISP system.

Abstract: This work studied fluid flow in the hydroponics systems to create 4 prototypes of the hydroponics systems; horizontal (traditional), inclined-flow, vertical-droplet and vertical-bowl systems, for a household application with initial conditions as low investment cost and easy installation. Red Oak was used to plant in all prototypes to investigate the prototype productivity. Fluid in the experimental investigation was the plant nutrient solution. All variables; fluid and ambient temperatures, fluid pH and sunlight intensity were measured 2 times a day from 4 systems placed in the same area and environment during 15 days of the experimental period in July 2013,. From results, the solution temperatures affected the productivity less than the fluid flow patterns did. The vertical-droplet system could not be used to grow Red Oak because the plants died during the experiment period. The vertical-bowl system could provide the highest productivity. We noticed that the fluid in the vertical-bowl system flowed transitionally while the flow in the other systems was laminar. Therefore, the fluid flow patterns could affect the productivity in the hydroponics systems.