• Structural Engineering and Mechanics
• /
• 제84권6호
• /
• pp.723-731
• /
• 2022

Functionally graded materials (FGMs) have been spotlighted as an advanced composite material, accordingly the intensive studies have focused on FGMs to examine their mechanical behaviors. Among them is thermal buckling which has been a challenging subject, because its behavior is connected directly to the safety of structural system. In this context, this paper presents the numerical analysis of thermal buckling of metal-ceramic functionally graded (FG) plates. For an accurate and effective buckling analysis, a new numerical method is developed by making use of (1,1,0) hierarchical model and 2-D natural element method (NEM). Based on 3-D elasticity theory, the displacement field is expressed by a product of 1-D assumed thickness monomials and 2-D in-plane functions which are approximated by NEM. The numerical method is compared with the reference solutions through the benchmark test, from which its numerical accuracy has been verified. Using the developed numerical method, the critical buckling temperatures of metal-ceramic FG plates are parametrically investigated with respect to the major design parameters.

• 한국지반공학회논문집
• /
• 제27권8호
• /
• pp.39-50
• /
• 2011

본 논문에서는 지열을 이용한 PHC 말뚝형 에너지 파일의 계절별 유속변화에 따른 열교환율과 단독말뚝의 열교환율을 100시간 운용 시 포화지반 조건에 한정하여 수치해석을 수행하였다. 해석결과 동절기 및 하절기일 때 100시간 운용 시 평균 열교환율은 약 55 W/m, 47 W/m로 나타났으며, 순환수 유속이 증가할수록 전체적인 열교환율이 상승하였다. 동절기에 말뚝간격 3D 및 5D(D:말뚝직경) 배치 시 0.6m/s의 순환수 유속에 따른 열적거동을 분석결과 지반과의 열적 자유면이 많은 외곽부일수록 열효율이 증가하였다. 또한, 3D 및 5D 간격의 평균 열교환율은 약 48.5 W/m, 51 W/m로 말뚝간격이 증가할수록 열교환율이 향상되는 것으로 나타났으며, 단독말뚝의 열교환율 대비 상대적으로 3D 및 5D 간격의 군말뚝은 각각 89% 및 93%보 떨어지는 것을 알 수 있었다.

• 한국생산제조학회지
• /
• 제24권2호
• /
• pp.251-255
• /
• 2015

Thermal deformation, such as bending and twisting, occurs among the polymer parts of air-conditioner indoor units because of repetitive temperature change during heating operation. In this study, a numerical method employing finite-element analysis to efficiently simulate the thermal deformation of an assembly is proposed. Firstly, the displacement of an actual assembly produced by thermal deformation was measured using a 3D optical measurement system. The measurement results indicated a general downward sag of the assembly, and the maximum displacement value was approximately 1 mm. The temperature distribution was measured using a thermographic camera, and the results were used as initial-temperature boundary conditions to perform temperature-displacement analysis. The simulation results agreed well with the measured data. To reduce the thermal deformation, the stiffness increased 100%. As the results, the maximum displacement decreased by approximately 5.4% and the twisting deformation of the holder improved significantly.

• 한국전산유체공학회지
• /
• 제20권1호
• /
• pp.65-76
• /
• 2015

In this study, the natural convection phenomenon of the air side and the forced convection phenomenon of the oil side were simulated in the radiator through a 3-D numerical analysis, and the total heat released by the oil side into the radiator heating plate and then to the air side was evaluated. Also, a quantitative analysis was carried out on the effect of each thermal resistance on the overall heat transfer coefficient through a 1-D thermal circuit analysis on the heat transfer mechanisms of the radiators considered in this study. In addition, for the diverse shapes of the heating plates considered in this study, the pressure drops of the oil side were quantitatively compared and evaluated. The temperatures at the air side and the oil side outlets of the radiators with 8 different fin shapes considered in this study had almost similar values showing a difference of +/-3% and, accordingly, the total heat transfer also showed similar heat dissipation performance in all the models. As a result of the 1-D thermal circuit analysis, in all the models considered in this study, while the thermal resistance of the air side accounted for 92% to 96% of the total, that of the oil side was 5 to 7%, and that of the heating plate showed a very small value of 0.02%.

• KIEAE Journal
• /
• 제17권1호
• /
• pp.83-89
• /
• 2017

Purpose: Thermal sensation or thermal comfort was randomly used in many studies which focused on combined effects of thermal and acoustic environments on human perception. However, thermal sensation and thermal comfort are not synonyms. Thermal comfort is more complex human perception on thermal environment than thermal sensation. This study aims to investigate effects of noise on thermal sensation and thermal comfort separately, and also to investigate effects of temperature on acoustic sensation and comfort. Method: Combined thermal and acoustic configurations were simulated in an indoor environmental chamber. Twenty four participants were exposed to two types of noise (fan and babble) with two noise levels (45 dBA and 60 dBA) for an hour in each thermal condition of PMV-1.53, 0.03, 1.53, 1.83, respectively. Temperature sensation, temperature preference, thermal comfort, noisiness, loudness, annoyance, acoustic comfort, indoor environmental comfort were evaluated in each combined environmental condition. Result: Noise did not affected thermal sensation, but thermal comfort significantly. Temperature had an effect on acoustic comfort significantly, but no effect on noisiness and loudness in overall data analysis. More explicit interactions between thermal condition and noise perception showed only with the noise level of 60 dBA. Impacts of both thermal comfort and acoustic comfort on the indoor environmental comfort were analyzed. In adverse thermal environments, thermal comfort had more impact than acoustic comfort on indoor environmental comfort, and in neutral thermal environments, acoustic comfort had more important than thermal comfort.

• 대한약침학회지
• /
• 제4권1호
• /
• pp.103-104
• /
• 2001

This study was done to observe the effect on the local thermal changes of herbal acupuncture on D.I.T.I.. The objects of this study are as follows; If there are remarkable local thermal changes between pre and post herbal acupuncture therapy on D.I.T.I.or not. If there are those, We examine how long that changes are maintained, what the adequate interval is on herbal acupuncture therapy, and what the reaction in a .local or whole body are on that therapy Materials and Methods : To study the local thermal changes in herbal acupuncture therapy, D.I.T.I. was used. Determination of this analysis periods are pre and post-therapy(1 hour, 24hours, 48hours and 7days later). The study group was divided into three groups(comprised 23 students in oriental medical college, Woosuk University). One was NS(Normal Saline) group, another was CF(CARTHAMI SEMEN) group and the other was BU(FEL URSI + BENZOAR BOVIS) group. The Herbal Acupunture solution was injected 0.2ml divide into 0.05ml at tile P'ungmun(B12), P'yesu(B13), Pubun(B41), Paek'o(B42) 4 points. Then, in order to analyze the clinical form, we have observed response of 23 students whenever we checked the thermal changes of their after perfoming Results : The results were obtained as follows ; 1. There is no significant dermatothermal changes at NS group and CF group, but BU group have remarkable changes in 24, 48, 72 hours. 2. From post-therapy 1 hour to 48 hours, there is a significant change (P<0.01) at NS-BU group and CF-BU group, But there is none 7 days later. 3. In the analysis of whole or local body reaction, local pain appears at NS group(22%), CF group(11%), BU group(91%), discomfort reaction appears at CF group(14%), BU group(30%). BU groilp has feel vertigo(13%), drowsy (70%) and pain in action(52%). 4. In the analysis of the duration of physic진 reaction, BU group is most lately maintained. Conclusions : These results suggest that in the physical reaction of herbal acupuncture solutions, BU solution is more sensitive than CF solution or NS.

• 한국추진공학회지
• /
• 제22권1호
• /
• pp.36-44
• /
• 2018

고체 로켓 추진기관 노즐의 내열재로 사용되는 탄소/페놀릭 복합재료의 열반응 수치해석을 수행하였다. 본 논문에서 탄소/페놀릭 재료의 열반응 해석은 (1) 로켓 노즐벽에서 대류열전달계수를 구하기 위한 연소가스의 경계층 적분방정식 수치해석과 (2) 삭마두께, 숯깊이 및 온도를 계산하기 위한 탄소/페놀릭의 열반응(열분해, 삭마)을 고려한 1차원 열전도 해석으로 구성된다. 시험결과와 해석결과를 비교 분석하였으며, 목삽입재 좌우 인접 부위를 제외하고 잘 일치하는 것을 확인 할 수 있었다.

• 국제학술발표논문집
• /
• The 5th International Conference on Construction Engineering and Project Management
• /
• pp.279-286
• /
• 2013

This paper introduces a new method for identification of building energy performance problems. The presented method is based on automated analysis and visualization of deviations between actual and expected energy performance of the building using EPAR (Energy Performance Augmented Reality) models. For generating EPAR models, during building inspections, energy auditors collect a large number of digital and thermal imagery using a consumer-level single thermal camera that has a built-in digital lens. Based on a pipeline of image-based 3D reconstruction algorithms built on GPU and multi-core CPU architecture, 3D geometrical and thermal point cloud models of the building under inspection are automatically generated and integrated. Then, the resulting actual 3D spatio-thermal model and the expected energy performance model simulated using computational fluid dynamics (CFD) analysis are superimposed within an augmented reality environment. Based on the resulting EPAR models which jointly visualize the actual and expected energy performance of the building under inspection, two new algorithms are introduced for quick and reliable identification of potential performance problems: 1) 3D thermal mesh modeling using k-d trees and nearest neighbor searching to automate calculation of temperature deviations; and 2) automated visualization of performance deviations using a metaphor based on traffic light colors. The proposed EPAR v2.0 modeling method is validated on several interior locations of a residential building and an instructional facility. Our empirical observations show that the automated energy performance analysis using EPAR models enables performance deviations to be rapidly and accurately identified. The visualization of performance deviations in 3D enables auditors to easily identify potential building performance problems. Rather than manually analyzing thermal imagery, auditors can focus on other important tasks such as evaluating possible remedial alternatives.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2002년도 추계 학술대회논문집
• /
• pp.109-113
• /
• 2002

Numerical analysis of aerodynamic heating for KPSAM is performed using aerodynamic heating model suitable to KPSAM, which has complex flow field resulting from the spike attached to the dome, such as large separation area and the strong shock/boundary layer interaction region around reattachment point on the dome. The aerodynamic heating model is validated and modified through the comparison between the flight test measurement and the thermal analysis results. TFD temperature sensors are installed on the dome to measure surface temperature during the flight. Computation results, obtained from the heat transfer analysis on the sensors, agree well with flight test data. The aerodynamic heating model provides heat transfer rate into surface as a boundary condition of unsteady 1D/axisymmetric thermal analysis on the missile structure. The axisymmetric thermal analysis using FLUENT is more versatile than the 1D analysis and can be applied to the heating problem related with complex structures and multi-dimensional heat transfer problems such as prediction of temperature rise at contact surface of different materials.

• Asian-Australasian Journal of Animal Sciences
• /
• 제33권5호
• /
• pp.722-731
• /
• 2020

Objective: Two experiments were conducted using 28 healthy multiparous sows to evaluate the oxidative stress status and reproductive performance of sows during gestation and lactation under different thermal environments. Methods: Fourteen multiparous sows were used in Exp. 1 under a high thermal environment, and the other 14 multiparous sows were used in Exp. 2 under a moderate thermal environment. In both experiments, reproductive performances of sows were recorded. Plasma samples were collected on d 35, 60, 90, and 109 of gestation, and d 1 and 18 of lactation for malondialdehyde, protein carbonyls, 8-hydroxy-deoxyguanosine, immunoglobulin g (IgG), and IgM analysis. Results: For sows in Exp. 1, plasma malondialdehyde concentration on d 109 of gestation tended to be greater (p<0.05) than it on d 18 of lactation. Plasma concentration of protein carbonyl on d 109 of gestation was the greatest (p<0.05) compared with all the other days. Plasma concentrations of 8-hydroxy-deoxyguanosine on d 109 of gestation was greater (p<0.05) than d 18 of lactation in Exp. 1. For sows in Exp. 2, there was no difference of malondialdehyde and protein carbonyl concentration during gestation and lactation. In both Exp. 1 and 2, litter size and litter weight were found to be negatively correlated with oxidative stress indicators. Conclusion: Sows under a high thermal environment had increased oxidative stress during late gestation indicating that increased oxidative damage to lipid, protein, and DNA could be one of the contributing factors for reduced reproductive performance of sows in this environment. This study indicates the importance of providing a moderate thermal environment to gestating and lactating sows to minimize the increase of oxidative stress during late gestation which can impair reproductive outcomes.