60 research outputs found
Realistic design of a floating breakwater design with moonpools
No full textIn an attempt to obtain a 2D floating breakwater model with high performance in wave reflection, genetic algorithm (GA) was combined with boundary element method (BEM) in the previous study. The performance of the obtained model was verified with numerical relations as well as an experiment in towing tank. Moreover, its performance and characteristics in 3D case were also evaluated in the subsequent study. However, because the 3D model is formed by simply extruding the 2D shape in longitudinal direction, it only produces a model with uniform transversal shape which is considered to be less effective and efficient in terms of technical and economical points of view. Consequently, it is needed to modify the model to obtain a more realistic and efficient design without reducing significantly the high performance obtained previously. In the present study, several modifications of the original 3D model are performed which include placing moonpools inside the body. The performance and characteristics of the modified models in terms of wave elevations on the free surface are evaluated at various wavelengths by using higher order boundary element method (HOBEM). The accuracy of the computed results is confirmed with Haskind-Newman and energy conservation relations. From the modifications and evaluations of the models, it could be realized that the moonpools inside the body could be used to obtain a more realistic model without reducing the optimum performance of the original model shape
ANALYSIS OF WIND ENERGY POTENTIAL WITH A MOBILE FLOATING STRUCTURE AROUND SULAWESI AND MALUKU ISLANDS OF INDONESIA
No full textThe present study uses Quikscat data to assess the offshore wind energy potential at the Eastern part of Indonesia, around the Sulawesi and Maluku Islands. Weibull distribution with two parameters is used to represent the characteristics and distribution of the wind model. In order to confirm the accuracy of computations, statistical and numerical methods are used to compute the Weibull parameters which are regression analysis, maximum likelihood method and moment method. The obtained power density is used to draw monthly wind power maps for the sea areas around the islands. The maps are used to determine the most suitable location of a mobile conversion system every month. Moreover, by assuming that a NM72/2000 NEG Micon is installed, Monte Carlo Simulation is performed to determine the expected power percentage produced by the system every month
On the use of an Arduino-based controller to control the charging process of a wind turbine
No full textComparison of Remotely Sensed Wind Data over Sulawesi and Maluku Islands Sea Areas
No full textIn order to obtain accurate prediction of ocean wind energy, long term data are needed. However, one data sources might not able to provide long duration data. Therefore, the data need to be combined with other sources of data. However, before combining the data, it is important to compare and validate them to confirm their accuracy. In the present study, wind speed data collected by QuikScat and SSM/I (SSMIS) missions are compared and analyzed. QuikScat data were collected by a satellite with the same name, while Special Sensor Microwave Imager (SSM/I) and Special Sensor Microwave Imager Sounder (SSMIS) data are processed and offered by Remote Sensing System (RSS). SSM/I (SSMIS) are passive microwave radiometers carried onboard Defense Meteorological Satellite Program (DMSP). For the comparison, 5 (five) arbitrary positions over Sulawesi and Maluku islands sea areas are chosen for the analyses. For the evaluation purposes, beside time series of daily data from several chosen positions in research location, several statistical parameters are also computed and compared such as mean, standard deviation, root mean square (RMS), correlation coefficient.
PENERAPAN MODEL PEMBELAJARAN KOOPERATIF TIPE COMPLETE SENTENCE UNTUK MENINGKATKAN KETERAMPILAN MENULIS PARAGRAF DALAM PEMBELAJARAN BAHASA INDONESIA SISWA KELAS IV B SD NEGERI BARA-BARAYA II KECAMATAN MAKASSAR KOTA MAKASSAR
No full textThe Effect of Flat Plate Theory Assumption in Post-Stall Lift and Drag Coefficients Extrapolation with Viterna Method
No full textIn employing blade element momentum (BEM) method to compute the performance of a turbine propeller, the lift and drag coefficients of propeller element/airfoil are needed. The coefficients are usually obtained from model experiment. Unfortunately, the model experiment can only be conducted for small angle of attack until stall mode. Beyond stall mode, Viterna extrapolation method is commonly used. The method is used to predict the lift and drag coefficients from stall angle to 90o. Beyond that range, besides Viterna method, original flat plate theory assumption can also be adopted. The present study compares the lift and drag coefficients extrapolation using Viterna method and flat plat theory. NACA2415 airfoil shape is used for computation. The computation formulas and procedures are presented and important parameter effect to the coefficients are shown and explained
Design Optimization and Performance Evaluation of a Floating Breakwater
No full textIn order to design an optimal floating breakwater with a high performance in a wide range of frequencies, its characteristics and performance in 2D and 3D cases are analyzed. For obtaining an optimal 2D model shape, an optimization method called Genetic Algorithm (GA) combined with Boundary Element Method (BEM) is employed. The accuracy of BEM analysis is confirmed using numerical relations such as Haskind-Newman and energy conservation relations. Moreover, since the investigated model will be an asymmetric shape, an experiment is also conducted to confirm that the present analysis could treat asymmetric body case correctly. However, because the performance of the obtained 2D model is expected to be different for some extent from real application, the performance of the corresponding model in 3D case is also analyzed using Higher Order Boundary Element Method (HOBEM). 3D Wave effect and its effect to the floating breakwater performance are analyzed and discussed. It is shown from this study that the combination of GA and BEM is effective in obtaining an optimal performance model. Moreover, it is also shown that the 3D wave effect is small on motion amplitudes while the wave elevations are found to be in 3D pattern even for a longer body length
Comparison of the Performance-Degrading Near-Interface Traps in Commercial SiC MOSFETs
No full textThis paper presents a comparison of the density of performance-degrading near-interface traps (NITs) in the most commonly available 1200 V commercial N-channel SiC power metal–oxide–semiconductor field-effect transistors (MOSFETs). A recently developed integrated-charge technique was used to measure the density of NITs with energy levels aligned to the conduction band, which degrade MOSFET’s performance by capturing and releasing electrons from the channel biased in the strong-inversion condition. Trench MOSFETs of one manufacturer have lower densities of these NITs in comparison to MOSFETs with the planar gate structure, corresponding to observed higher channel-carrier mobility in trench MOSFETs. Different response-time distributions were also observed, corresponding to different spatial location of the measured NITs.Full Tex
Numerical study of a permanent magnet linear generator for ship motion energy conversion
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