• 한국환경과학회지
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• 제28권11호
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• pp.951-958
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• 2019

Seoullo7017, an elevated linear park, was created to redevelop obsolete road infrastructure as public space, which provides unique landscapes. This study was aimed to evaluate and suggest proper planting design for improving psychological benefits in Seoullo7017. Field survey and simulation experiment were carried out to investigate the user's perception on the landscapes. Many users had negative feelings of the present landscapes in Seoullo7017, due to concrete pavement and simple planting design using big concrete pots. Landscape simulation experiment showed this perception could change depending on planting design. In especial, herb species played an important role in improving the quality of landscape in a linear park and providing positive feelings such as refreshment, warmth and naturalness. This study suggested that planting design in a linear space needs to be focused rather on the planting style and species than the volume of greens.

• Journal of information and communication convergence engineering
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• 제19권4호
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• pp.263-268
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• 2021

Although the compact capacitance model of point tunneling types of tunneling field-effect transistors (TFET) has been proposed, those of line tunneling types of TFETs have not been reported. In this study, a compact capacitance model of an L-shaped TFET (LTFET), a line tunneling type of TFET, is proposed using the previously developed surface potentials and current models of P- and L-type LTFETs. The Verilog-A LTFET model for simulation program with integrated circuit emphasis (SPICE) was also developed to verify the validation of the compact LTFET model including the capacitance model. The SPICE simulation results using the Verilog-A LTFET were compared to those obtained using a technology computer-aided-design (TCAD) device simulator. The current-voltage characteristics and capacitance-voltage characteristics of N and P-LTFETs were consistent for all operational bias. The voltage transfer characteristics and transient response of the inverter circuit comprising N and P-LTFETs in series were verified with the TCAD mixed-mode simulation results.

• 한국환경과학회지
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• 제18권8호
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• pp.833-839
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• 2009

The calculation of the wind field for resource assessment is done by using CFD Reynolds-Averaged Navier-Stokes simulations performed with the commercial software WindSim. A new interface has been created to use mesoscale simulation data from a meteorological model as driving data for the simulations. This method makes it necessary to take into account thermal effects on the wind field to exploit the full potential of this method. The procedure for considering thermal effects in CFD wind field simulations as well as the impact of thermal effects on the wind field simulations is presented. Simulations for non-neutral atmospheric conditions with the developed method are consistent with expected behavior and show an improvement of simulation results compared with observations.

• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.46-50
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• 2011

The electrical insulation design of high voltage superconducting fault current limiters (SFCLs) should be confirmed to be applied for the stabilization of the power grid. This paper describes numerical analysis and AC dielectric experiments for developing high voltage SFCLs. The electric field distributions between applied high voltage part and ground were calculated by finite element method (FEM) simulation tool and AC criterion of liquid nitrogen at 200 kPa was calculated from correlation between the field utilization factor and FEM simulation results. This paper deals with ceonceptual insulation design of a 154 kV class single-phase no-inductively wound solenoid type SFCL which was focused on gap distance between the cryostat and superconducting coils. Furthermore, the shield ring effect was confirmed to reduce maximum electric field at applied high voltage part.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.115.1-115.1
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• 2011

최근 기본적인 pin 구조의 박막 cell 에서 i layer를 최적화 시키는 방안으로 double layer 구조가 많이 연구되고 있다. 본 연구에서는 ASA(Advanced Semicon ductor Analysis) simulation을 이용하여 i-double layer 최적화에 대한 연구를 진행해 보았다. 두께 150/150nm의 i double layer의 band gap 가변을 한 simulation 결과를 보았을 때, p쪽의 band gap이 상승하면서 intrinsic layer 내의 field가 증가하여 recombination center가 감소하였으나 FF의 감소가 있었다. n쪽의 band gap을 상승 시켰을때 n/i 쪽 field 증가로 Voc가 상승되어 초기 효율이 증가하였으나 intrinsic layer내의 field가 감소하여 recombination center가 오히려 증가하였다. 결과적으로 electric field와 효율을 동시에 고려했을 때 두께 300nm, 1.75의 band gap을 가지는 single layer 보다 150/150nm두께에 1.8/1.7 또는 1.8/1.75의 bandgap을 가지는 double layer를 사용하였을 때 보다 높은 효율을 얻을 수 있었다.

• 한국대기환경학회지
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• 제17권2호
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• pp.223-231
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• 2001

In order to provide some insights into the influence of electric field, gas composition, and gas temperature on electron energy distribution and electron transport characteristics, the Boltzmann equation was solved by using cross section data for electron collisions, Critical electric fields for the corona development in dry air and flue gas are 150 and 80 Td, respectively. It was seen that the decrease of critical electric field in flue gas is mainly caused by the $H_2O$ addition through the comparison of ionization and attachment coefficients of gas components. Increase of $O_2$, $H_2O$, and $CO_2$ contents in gas affected discharge characteristics according to their reciprocal characteristics between lowering the ionization threshold and increasing the electro-negativity. As electric field increases, electrons with higher energies in the electron energy distribution also increase. The mean and characteristic electron energies also linearly increase with electric field. The variation of flue gas temperature did rarely affect on the electron energy distribution function and electron transport characteristics, because the gas temperature is several hundreds or thousands times lower than the electron temperature.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1807-1816
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• 2020

In this work, a Gaussian Process (Kriging) approach is proposed to provide efficient dose mapping for complex radiation fields using limited number of responses. Given a few response measurements (or simulation data points), the proposed approach can help the analyst in completing a map of the radiation dose field with a 95% confidence interval, efficiently. Two case studies are used to validate the proposed approach. The First case study is based on experimental dose measurements to build the dose map in a radiation field induced by a D-D neutron generator. The second, is a simulation case study where the proposed approach is used to mimic Monte Carlo dose predictions in the radiation field using a limited number of MCNP simulations. Given the low computational cost of constructing Gaussian Process (GP) models, results indicate that the GP model can reasonably map the dose in the radiation field given a limited number of data measurements. Both case studies are performed on the nuclear engineering radiation laboratories at the University of Sharjah.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.492-495
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• 1997

This paper aims to derive a mathematical model of the dynamics of handling task in field robot which stable grasping and manipulates a rigid object with some dexterity. Firstly, a set of differential equation describing dynamics of the manipulators and object together with geometric constraints of tight area-contacts on motion of the overall system is analyzed and a method of computer simulation for overall system of differential-algebraic equations is presented. Thirdly, simulation results are shown and the effects of geometric constraints of contact-area are discussed. Finally, it is shown that even in the simplest case of dual single D.O.F. manipulators there exists a sensory feedback from sensing data of he rotational angle of the object to command inputs to joint actuators and this feedback connection from sensing to action eventually realizes secure grasping of the object, provided that he object is of rectangular shape and motion is confined to a horizontal

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.662-664
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• 1997

3-dimensional finite element method(FEM) electrical field analysis was performed to obtain electric fields on a field emission device tip in an array form. The simulation was performed by applying the Neumann boundary condition to the intermediate plane between tips. To verify our algorithm, comparison between simulation results and experimental data from another paper was made and the difference was discussed. Finally, analysis on triode structure was performed.

• Wind and Structures
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• 제25권6호
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• pp.589-608
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• 2017

A novel probabilistic approach is presented for estimating the equivalent static wind loads that produce a static response of the structure, which is "equivalent" in a probabilistic sense, to the extreme dynamic responses due to the unsteady pressure random field induced by the wind. This approach has especially been developed for complex structures (such as stadium roofs) for which the unsteady pressure field is measured in a boundary layer wind tunnel with a turbulent incident flow. The proposed method deals with the non-Gaussian nature of the unsteady pressure random field and presents a model that yields a good representation of both the quasi-static part and the dynamical part of the structural responses. The proposed approach is experimentally validated with a relatively simple application and is then applied to a stadium roof structure for which experimental measurements of unsteady pressures have been performed in boundary layer wind tunnel.