The Experts below are selected from a list of 69639 Experts worldwide ranked by ideXlab platform
Chee-wee Liu - One of the best experts on this subject based on the ideXlab platform.
-
Oxide Roughness Effect on tunneling current of MOS diodes
IEEE Transactions on Electron Devices, 2002Co-Authors: B.-c. Hsu, Kuan-chao Chen, Chiu-ling Lai, Sheng-wei Lee, Chee-wee LiuAbstract:Two-dimensional (2-D) device simulation is used to investigate the tunneling current of metal ultra-thin-oxide silicon tunneling diodes with different oxide Roughness. With the conformal nature of ultrathin oxide, the tunneling current density is simulated in both direct tunneling and Fowler-Nordheim (FN) tunneling regimes with different oxide Roughness. The results show that oxide Roughness dramatically enhances the tunneling current density and the 2-D electrical Effect is responsible for this increment of tunneling current density. Furthermore, a set of devices with controlled oxide Roughness is fabricated to verify the simulation results and our model qualitatively agrees with the experiment results.
Osman Turan - One of the best experts on this subject based on the ideXlab platform.
-
validation of the cfd approach for modelling Roughness Effect on ship resistance
Ocean Engineering, 2020Co-Authors: Soonseok Song, Mehmet Atlar, Yigit Kemal Demirel, Osman TuranAbstract:Abstract Recently, there have been active efforts to investigate the Effect of hull Roughness on ship resistance using Computational Fluid Dynamics (CFD). Although, several studies demonstrated that the Roughness modelling in the CFD simulations can precisely predict the increase in frictional resistance due to the surface Roughness, the experimental validations have been made only for flat plates which have zero pressure gradient. This means that the validations cannot necessarily guarantee the validity of this method for other ship resistance components besides the frictional resistance. Therefore, it is worth demonstrating the validity of the Roughness modelling in CFD on the total resistance of a 3D hull. In this study, CFD models of a towed flat plate and a KRISO Container Ship (KCS) model were developed. In order to simulate the Roughness Effect in the turbulent boundary layer, a previously determined Roughness function of a sand-grain surface was employed in the wall-function of the CFD model. Then the result of the CFD simulations was compared with the experimental data. The result showed a good agreement suggesting that the CFD approach can precisely predict the Roughness Effect on the total resistance of the 3D hull. Finally, the Roughness Effects on the individual ship resistance components were investigated.
-
Validation of the CFD approach for modelling Roughness Effect on ship resistance
2019Co-Authors: Soonseok Song, Mehmet Atlar, Yigit Kemal Demirel, Saishuai Dai, Sandy Day, Osman TuranAbstract:Recently, there have been active efforts to investigate the Effect of hull Roughness on ship resistance using Computational Fluid Dynamics (CFD). Although, several studies demonstrated that the Roughness modelling in the CFD simulations can precisely predict the increase in frictional resistance due to the surface Roughness, the experimental validations have been made only for flat plates which have zero pressure gradient. This means that the validations cannot necessarily guarantee the validity of this method for other ship resistance components besides the frictional resistance. Therefore, it is worth to demonstrate the validity of the Roughness modelling in CFD on the total resistance of a 3D hull. In this study, CFD models of a towed flat plate and a KRISO Container Ship (KCS) model were developed. In order to simulate the Roughness Effect in the turbulent boundary layer, a previously determined Roughness function of a sand-grain surface was employed in the wall-function of the CFD model. Then the result of the CFD simulations was compared with the experimental data. The result showed a good agreement suggesting that the CFD approach can precisely predict the Roughness Effect on the total resistance of the 3D hull. Finally, the Roughness Effects on the individual ship resistance components were investigated.
-
Investigating the Roughness Effect of Biofouling on Propeller Performance
SCC2015: Shipping in Changing Climates Conference 2015, 2015Co-Authors: Pamm Kellett, K Mizzi, Yigit Kemal Demirel, Osman TuranAbstract:As a result of the increasing pressure being placed on the marine industry to address ship emissions, regulations to govern the fuel efficiency and efficient operation of ships in the form of the Energy Efficiency Design Index (EEDI) (IMO, 2014) and Energy Efficiency Operation Index (EEOI) (IMO, 2009a) have recently come into force. These have been introduced alongside regulations concerning specific emissions requirements (UNFCCC). Attention has therefore been turned to all aspects of ship design and operation which have impact on their efficiency. In turn, this paper focuses on the Effects of biofouling on propeller surfaces highlighting the benefits of reducing biofouling. This subject was the focus of a recently completed EU-Funded FP7 Project entitled FOUL-X-SPEL (2011). This paper investigates the detrimental impacts of biofouling on the performance of a real ship propeller using Computational Fluid Dynamics (CFD) simulations. Initially, the CFD approach used in this study was validated through CFD open-water tests of a propeller. A previously-developed CFD approach for approximating the surface Roughness that results from biofouling has then been applied in order to predict the Effects on propeller efficiency. The Roughness Effects of a typical coating and different fouling conditions on the propeller performance were therefore predicted for various advance coefficients Results indicated negative Effects of biofouling on the propeller efficiency and the importance of the mitigation of such Effects, supporting the importance of informing the industry about the impacts such that they are able to make informed decisions regarding regular propeller maintenance and cleaning.
-
A parametric study: hull Roughness Effect on ship frictional resistance
2013Co-Authors: Yigit Kemal Demirel, Osman Turan, Atilla Incecik, KhorasanchiAbstract:Ship resistance is very important in terms of ship performance and fuel consumption. The more resistance a ship has, the more fuel it consumes for the same range. Ship resistance can be broken into two parts; frictional resistance and residuary resistance. Especially for merchant ships which sail with normal or low velocity, frictional resistance may be 60-90% of the total resistance and it is directly affected by surface Roughness; namely physical and biological Roughness. Hull Roughness leads to frictional resistance increase which means fuel penalty. Marine coatings are widely used in order to avoid or minimise fouling and hull Roughness, hence increase in frictional resistance. This paper outlines details of a parametric numerical study which was carried out to monitor the Effect of changing surface Roughness of marine coatings on ship frictional resistance. This investigation was made by means of a computational fluid dynamics (CFD) based software (STAR-CCM+). Firstly, towing test simulations of a flat plate were conducted and the results were compared with the experimental results given in literature to validate the model. After the validation procedure, a parametric study was carried out to obtain frictional resistance and frictional drag coefficient variations depending on various hull Roughness conditions. Moreover, a simple formulation which correlates the Roughness height and frictional drag coefficient was obtained within the validated Roughness height range and speed. Finally, the results were presented in both graphical and tabular forms and discussed in details.
Georgios Palasantzas - One of the best experts on this subject based on the ideXlab platform.
-
Roughness Effect on the measurement of interface stress
Acta Materialia, 2000Co-Authors: Georgios Palasantzas, J.th.m. De HossonAbstract:Stimulated by a recent paper by Spaepen (Acta mater. 48 (2000) 31) we concentrate on the Effect of Roughness parameters on stress measurements in thin films for self-affine and mound rough interfaces. A self-affine interface is characterized by a lateral correlation length ξ, an rms Roughness amplitude σ, and a Roughness exponent H (0
-
Roughness Effect on heterojunction photovoltaics
Journal of Applied Physics, 1996Co-Authors: Georgios Palasantzas, E. KoumanakosAbstract:In this work, we present an investigation of the junction interface Roughness Effect on the open circuit voltage, Voc for thin film heterojunction photovoltaics. The Roughness Effect is studied for self‐affine rough interfaces, which are described in Fourier space by the correlation model ∼σ2ξ2(1+aq2ξ2)−1−H. σ, ξ, and H denote, respectively, the rms Roughness, the in‐plane Roughness correlation length, and the interface irregularity exponent (0
Ya-chin King - One of the best experts on this subject based on the ideXlab platform.
-
Roughness Effect on Uniformity and Reliability of Sequential Lateral Solidified Low-Temperature Polycrystalline Silicon Thin-Film Transistor
Electrochemical and Solid-State Letters, 2006Co-Authors: Hung-tse Chen, Yu-cheng Chen, Jia-xing Lin, Szu-i Hsieh, Ya-chin KingAbstract:Roughness Effect on uniformity and reliability of sequential lateral solidified low-temperature polycrystalline silicon thin-film transistors were studied by comparison of transistors made on a thin-film substrate with and without planarization process. The two-step planarization process, including the wet etching of the precursor and a fine-tuned laser annealing procedure, can reduce the average Roughness level to less than 1.4 nm. The results show that transistors without protrusion around the grain boundaries have higher threshold voltage uniformity, smaller subthreshold swing, larger breakdown voltage, and better reliability under high field stress than those made without planarization process.
B.-c. Hsu - One of the best experts on this subject based on the ideXlab platform.
-
Oxide Roughness Effect on tunneling current of MOS diodes
IEEE Transactions on Electron Devices, 2002Co-Authors: B.-c. Hsu, Kuan-chao Chen, Chiu-ling Lai, Sheng-wei Lee, Chee-wee LiuAbstract:Two-dimensional (2-D) device simulation is used to investigate the tunneling current of metal ultra-thin-oxide silicon tunneling diodes with different oxide Roughness. With the conformal nature of ultrathin oxide, the tunneling current density is simulated in both direct tunneling and Fowler-Nordheim (FN) tunneling regimes with different oxide Roughness. The results show that oxide Roughness dramatically enhances the tunneling current density and the 2-D electrical Effect is responsible for this increment of tunneling current density. Furthermore, a set of devices with controlled oxide Roughness is fabricated to verify the simulation results and our model qualitatively agrees with the experiment results.