• Wind and Structures
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• 제11권1호
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• pp.35-50
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• 2008

Wind and temperature have been shown to be the critical sources causing changes in the modal properties of large-scale bridges. While the individual effects of wind and temperature on modal variability have been widely studied, the investigation about the effects of multiple environmental factors on structural modal properties was scarcely reported. This paper addresses the modeling of the simultaneous effects of wind and temperature on the modal frequencies of an instrumented cable-stayed bridge. Making use of the long-term monitoring data from anemometers, temperature sensors and accelerometers, a neural network model is formulated to correlate the modal frequency of each vibration mode with wind speed and temperature simultaneously. Research efforts have been made on enhancing the prediction capability of the neural network model through optimal selection of the number of hidden nodes and an analysis of relative strength of effect (RSE) for input reconstruction. The generalization performance of the formulated model is verified with a set of new testing data that have not been used in formulating the model. It is shown that using the significant components of wind speeds and temperatures rather than the whole measurement components as input to neural network can enhance the prediction capability. For the fundamental mode of the bridge investigated, wind and temperature together apply an overall negative action on the modal frequency, and the change in wind condition contributes less to the modal variability than the change in temperature.

• 설비공학논문집
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• 제24권10호
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• pp.718-723
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• 2012

The purpose of this study is to propose modeling method of Underfloor Air Distribution System with reliability and validity by comparing characteristics of modeling methods. For this, the modeling methods of UFAD were selected by investigating various modeling methods of previous researches. Then, simulations were conducted by using EnergyPlus which is dynamic analysis program of building energy. Annual energy consumption for each method was compared with a wide range of indoor thermal loads. As a result, the methodology of reducing internal gains can cause under sizing of the system. It suggests modeling methods to reflect occupied zone air-conditioning, temperature stratification and supply plenum which are the main characteristics of UFAD.

• 대한기계학회논문집A
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• 제22권2호
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• pp.302-310
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• 1998

In the accompanying paper, part I, we have presented the physical modeling and the associated numerical analysis of injection molding process with a compressible viscoelastic fluid model. In part II, the effects of compression stage in the injection/compression molding process are presented. Numerical results showed that the injection/compression molding process reduced birefringence as compared with the injection molding process. In this respect, one can conclude that the injection/compression molding process is more suitable for manufacturing the precise optical products than the injection molding process. In the distribution of birefringence, the effect of packing procedure in injection/compression molding process was found to be similar to that in injection molding process. From the numerical results, we found that birefringence becomes smaller as the melt temperature gets higher and the closing velocity of the mold gets smaller with the flow rate and the mold temperature affecting the birefringence insignificantly. As far as the distribution of density is concerned, the flow rate, the melt temperature, and the closing velocity of the mold had insignificant effect on the distribution of density in comparison with the mold temperature.

• 한국항공우주학회지
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• 제35권1호
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• pp.33-39
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• 2007

본 논문은 대기층을 통한 파장별 태양복사를 고려한 3차원 지상 물체의 표면 온도 분포를 예측하는 소프트웨어를 개발하는데 도움을 줄 것이다. 다양한 가스로 구성된 대기층을 통과하는 파장별 태양복사 에너지를 계산하기 위해서 LOWTRAN7을 이용하였으며, 여기서 얻어진 결과는 파장별 흡수 또는 총괄흡수 방식으로 에너지보존방정식에 반영하였다. 원통형 물체 위의 시간별 표면온도 분포를 나타내기 위해서 준 내재적 방법을 사용하여 계산하였으며 물체의 파장별 표면 복사 특성을 이용하기 위해서 태양복사를 흡수하거나 물체의 표면 방사가 이루어지는 모델을 사용하였다. 본 논문에서는 개발된 S/W의 성능 향상을 위하여 파장별 태양복사 분석 방법과 총괄태양복사 분석 방법을 각각 적용하여 본 결과 이들 두 방법 사이에는 약 3% 이내의 차이를 나타내었으나 두 방법 모두 실용적 관점에서 충분한 결과를 나타내었음을 알 수 있었다.

• 한국환경과학회지
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• 제29권1호
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• pp.33-44
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• 2020

Recently, a variety of modeling studies have been conducted to examine the air quality over South Korea during the Korea - United States Air Quality (KORUS-AQ) campaign period (May 1 to June 10, 2016). This study investigates the impact of different meteorological initializations on atmospheric modeling results. We conduct several simulations during the KORUS-AQ period using the Weather Research and Forecasting (WRF) model with two different initial datasets, which is FNL of NCEP and ERA5 of ECMWF. Comparing the raw initial data, ERA5 showed better accuracy in the temperature, wind speed, and mixing ratio fields than those of NCEP-FNL. On the other hand, the results of WRF simulations with ERA5 showed better accuracy in the simulated temperature and mixing ratio than those with FNL, except for wind speed. Comparing the nudging efficiency of temperature and wind speed fields, the grid nudging effect on the FNL simulation was larger than that on the ERA5 simulation, but the results of mixing ratio field was the opposite. Overall, WRF simulation with ERA5 data showed a better performance for temperature and mixing ratio simulations than that with FNL data. For wind speed simulation, however, WRF simulation with FNL data indicated more accurate results compared to that with ERA5 data.

• Advances in aircraft and spacecraft science
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• 제5권1호
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• pp.141-164
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• 2018

In this paper, the thermal effect on buckling and free vibration characteristics of functionally graded (FG) size-dependent Timoshenko nanobeams subjected to an in-plane thermal loading are investigated by presenting a Navier type solution for the first time. Material properties of FG nanobeam are supposed to vary continuously along the thickness according to the power-law form and the material properties are assumed to be temperature-dependent. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on Timoshenko beam theory through Hamilton's principle and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared to some cases in the literature. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as thermal effect, material distribution profile, small scale effects, aspect ratio and mode number on the critical buckling temperature and normalized natural frequencies of the temperature-dependent FG nanobeams in detail. It is explicitly shown that the thermal buckling and vibration behaviour of a FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

• Elastomers and Composites
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• 제52권3호
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• pp.216-223
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• 2017

The additive manufacturing technology, also called 3D printing, is growing fast. There are several methods for 3D printing. Fused deposition modeling (FDM) type 3D printing is the most popular method because it is simple and inexpensive. Moreover, it can be used for printing various thermoplastic materials. However, it contains the cooling of layered road and causes thermal shrinkage. Thermal shrinkage should be controlled to obtain high-quality products. In this study, temperature distribution and cooling behavior of a layered road with cooling are studied through computer simulation. The thermal shrinkage of the layered road was simulated using the calculated temperature distribution with time. Shape variation of the layered road was predicted as cooling proceeded. Stress between the bed and the layered road was also predicted.This stress was considered as the detaching stress of the layered road from the bed. The simulations were performed for various thermal conductivities and temperatures of the layered road, bed temperature, and chamber temperature of a 3D printer. The simulation results provide detailed information about the layered road for FDM type 3D printing under operational conditions.

• 한국환경보건학회지
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• 제28권5호
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• pp.93-101
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• 2002

We have studied that the prediction of desulfurization efficiency by limestone in fluidized-bed coal combustor. The results were presented as follows : Firstly, the bed temperature had a great deal of effect on the desulfurization and the optimum temperature of limestone was 85$0^{\circ}C$~90$0^{\circ}C$. Secondly, as the velocity and temperature increased, $K_{s}$, K and the desulfurization efficiency increased. So, $k_{s}$, $k_{d}$ highly depended on the air velocity and bed temperature, and $k_{s}$, $k_{d}$ were 82.53 mm/sec, 0.0041/sec at 0.2 m/sec, 85$0^{\circ}C$, $k_{s}$, $k_{d}$ were 125.62 mm/sec. 0.00532/sec at 0.3 m/sec, 80$0^{\circ}C$ respectively. And $k_{s}$, $k_{d}$ were 143.78 mm/sec, 0.00568/sec at 0.3 m/sec, 85$0^{\circ}C$. Thirdly, as a result of desulfurization modeling, there was good agreement between theory and experiments as anthracite fraction increased. At 3.0 of optimum Ca/S molar ratio, there was very good agreement between theory and experiments.riments.riments.s.

• 한국생산제조학회지
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• 제9권5호
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• pp.105-111
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• 2000

Micronization of sensor is a trend of the silicon sensor development with regard to a piezoresistive silicon pressure sensor, the size of the pressure sensor diaphragm have become smaller year by year, and a microaccelerometer with a size less than 200~300${\mu}{\textrm}{m}$ has been realized. Over the past four or five years, numerical modeling of microsensors and microstructures has gradually been developed as a field of microelectromechanical system(MEMS) design process. In this paper, we study some of the micromachining processes of single crystal silicon(SCS) for the microaccelerometer, and their subsequent processes which might affect thermal and mechanical loads. The finite element method(FEM) has been a standard numerical modeling technique extensively utilized in structural engineering discipline for component design of microaccelerometer. Temperature rise sufficiently low at the suspended beams. Instead, larger temperature gradient can be seen at the bottom of paddle part. The center of paddle part becomes about 5~2$0^{\circ}C$ higher than the corner of paddle and suspended beam edges.

• 한국축산식품학회지
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• 제32권3호
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• pp.274-284
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• 2012

In this study, the effects of physical parameters (30-270 MPa of pressure, 3-57 min of time, and 1-$49^{\circ}C$ of temperature) on pork quality were investigated. Response surface methodology was used in order to monitor and model the changes in pork quality under varied pressure conditions. As quality characteristics, shear force, water holding capacity (WHC) and the CIE color of pork were measured, and optimum pressure conditions were evaluated by statistical modeling. Pressure improved the WHC of pork at relatively low temperature ($<25^{\circ}C$); however, the opposite occurred with increasing temperature. Although pressure and temperature affected the tenderness of the meat, interaction effects among variations were not observed. At pressure levels higher than 200 MPa, the color of pork differed markedly from that of the untreated controls. In particular, differential scanning calorimetry (DSC) revealed marked evidence of myosin denaturation. The present study demonstrates that pork quality varies depending on pressure conditions.