• 한국도로학회논문집
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• 제10권4호
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• pp.31-40
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• 2008

아스팔트 콘크리트의 동탄성계수는 아스팔트 포장 해석 및 설계에 매우 중요하다. 동탄성계수의 메스터 곡선은 일반적으로 시그모이달 함수로 표현된다. Ramberg-Osgood 모델은 지반동역학분야에서 변형률 크기에 따른 정규화 탄성계수 감소 곡선에 대한 피팅모델로 널리 사용되고 있다. 동일한 동탄성계수 시험자료에 대하여 시그모이달 함수와 수정 Rambeyg-osgood 모델 모두를 사용하여 메스터 곡선을 획득하였으며, 두 피팅모델 모두 적용성이 우수함을 확인하였다. 시그모이달 함수의 계수들은 서로 연관되어 있어서 메스터 곡선의 절대값과 형상 특성을 서로 분리하는 것이 불가능하다. 그러나 Ramberg-Osgood 모델의 계수는 물리적 의미가 명확할 뿐 아니라 서로 분리되어 있어서 메스터 곡선에 대한 영향요소를 서로 분리하여 평가할 수 있음을 확인하였다.

• Advances in materials Research
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• 제12권1호
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• pp.43-65
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• 2023

Free vibration analysis of power law and sigmoidal sandwich plates made up of functionally graded materials (FGMs) has been carried out using finite element based higher-order zigzag theory. The present model satisfies all-important conditions such as transverse shear stress-free conditions at the plate's top and bottom surface along with continuity condition for transverse stresses at the interface. A Nine-noded C0 finite element having eleven degrees of freedom per node is used during the study. The present model is free from the requirement of any penalty function or post-processing technique and hence is computationally efficient. The present model's effectiveness is demonstrated by comparing the present results with available results in the literature. Several new results have been proposed in the present work, which will serve as a benchmark for future works. It has been observed that the material variation law, power-law exponent, skew angle, and boundary condition of the plate widely determines the free vibration behavior of sandwich functionally graded (FG) plate.

• Steel and Composite Structures
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• 제49권5호
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• pp.547-570
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• 2023

In the present work, a comparative study has been carried out between power, exponential, and sigmoidal sandwich FGM plates for free vibration conditions under hygro-thermal conditions. Rules of mixture is used to determine effective material properties across the thickness for power-law and sigmoid sandwich FGM plates. Exponential law is used to plot effective material properties for exponentially graded sandwich FGM plates. Temperature and moisture dependent material properties were used during the analysis. Free vibration analysis is carried out using recently proposed finite element based HOZT. Present formulation satisfies interlayer transverse stress continuity conditions at interfaces and transverse shear stress-free conditions at the plate's top and bottom surfaces. The present model is free from any penalty or post-processing requirements. Several new results are reported in the present work, especially for unsymmetric sandwich FGM plates and exponential and sigmoidal sandwich FGM plates.

• Structural Engineering and Mechanics
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• 제66권1호
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• pp.85-96
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• 2018

This study investigates the response of functionally graded (FG) gas pipe under unsteady internal pressure and temperature. The pipe is proposed to be manufactured from FGMs rather than custom carbon steel, to reduce the erosion, corrosion, pressure surge and temperature variation effects caused by conveying of gases. The distribution of material graduations are obeying power and sigmoidal functions varying with the pipe thickness. The sigmoidal distribution is proposed for the 1st time in analysis of FG pipe structure. A Two-dimensional (2D) plane strain problem is proposed to model the pipe cross-section. The Fourier law is applied to describe the heat flux and temperature variation through the pipe thickness. The time variation of internal pressure is described by using exponential-harmonic function. The proposed problem is solved numerically by a two-dimensional (2D) plane strain finite element ABAQUS software. Nine-node isoparametric element is selected. The proposed model is verified with published results. The effects of material graduation, material function, temperature and internal pressures on the response of FG gas pipe are investigated. The coupled temperature and displacement FEM solution is used to find a solution for the stress displacement and temperature fields simultaneously because the thermal and mechanical solutions affected greatly by each other. The obtained results present the applicability of alternative FGM materials rather than classical A106Gr.B steel. According to proposed model and numerical results, the FGM pipe is more effective in natural gas application, especially in eliminating the corrosion, erosion and reduction of stresses.

• Parasites, Hosts and Diseases
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• 제53권6호
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• pp.755-757
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• 2015

Mouse models of chronic toxoplasmosis and atopic dermatitis (AD) were combined to clarify the effect of opportunistic Toxoplasma gondii infection on the development of AD. AD was induced as a chronic contact hypersensitivity (CHS) with repeated challenge of 2,4,6-trinitro-1-chlorobenzene (TNCB) on the dorsal skin of mice. TNCB induced skin thickness increases in both normal and toxoplasmic mice. The changing patterns were different from the sigmoidal which saturated at 20 days in normal mice to the convex saturated at 12 days in toxoplasmic mice with the crossing at 18 days. Compared to normal mice, toxoplasmic mice presented CHS more severely in earlier times and then moderately in later times. These data suggest that host immune modification by T. gondii infection enhances CHS in early times of atopic stimulation but soothes the reaction of CHS in later times in mouse model.

• 한국축산식품학회지
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• 제18권4호
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• pp.285-291
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• 1998

Adsorption isotherms of water vapour for infant formula milk powders manufactured by P. M. and N company in Korea were measured at temperatures between 20, 30 and 40$^{\circ}C$ using COST-90 modified method. Results showed that the isotherms were sigmoidal in shape. The adsorption isotherms of milk powder were depending on the temperature and products. The BET-model were applied and analyzed to compare the experimental value. It was found that the BET-model is fitted with measuring data. Sample P showed the lowest monolayer value and sample N showed the highest. Isosteric heat obtained upon application of BET-model was calculated in this field of temperature using the Clausius-Clapeyron equation. It is suggested that the usage of the BET-model to estimate the heat of water sorption in infant formula milk powder should be in agreement with the results from COST-90 project.

• 한국산림과학회지
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• 제100권1호
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• pp.62-69
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• 2011

본 연구는 5차 국가산림자원조사(National Forest Inventory, NFI) 표본점 자료를 이용하여 충청도 지역에 분포하는 주요 수종에 대한 수고-흉고직경 생장모델을 개발하고자 하였다. 충청도 지역 고정표본지 내에서 수고와 흉고직경이 측정된 주요 수종의 총 임목 본수는 2,681본이었으며, 무작위로 생장모델의 개발을 위해 90% 자료와 모델 타당성 검정을 위해 10% 자료로 나누어서 분석하였고, 본 연구에서 제시된 최종모형의 추정된 계수는 100% 자료를 이용하였다. 8개 주요 수종에 대한 생장모델들의 적합성 검정은 결정계수($R^2$), 추정치의 오차인 평균제곱근오차(RMSE), 평균편의(MD), 절대평균편의(AMD)와 직경급별로 평균편의(MD)를 비교 분석하였다. 본 연구 결과에 의하면, 6개 주요 생장식의 결정계수는 모두 94% 이상의 높은 설명력을 나타냈으며, 특히 C-R 생장모델과 Weibull 생장모델은 다른 모델에 비해 좋은 결과를 나타냈다. 직경급 30 cm 이하에서는 소나무, 리기다소나무, 굴참나무, 신갈나무가 상대적으로 가장 작은 평균편의를 나타낸 반면, 직경급 30 cm 이상에서는 신갈나무, 상수리나무, 졸참나무가 큰 평균편의를 나타냈다. 또한 본 연구의 결과로 제시된 6개 주요 생장식에서 추정한 수고를 임목자원평가 프로그램에 적용하여 간재적을 분석한 결과, 직경급 30 cm까지는 큰 차이를 보이지 않지만, 30 cm 이상인 대경목의 경우 추정된 간재적은 큰 차이를 보이므로, 생장모델 선정에 주의를 기울여야 한다.

• 원예과학기술지
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• 제28권5호
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• pp.768-776
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• 2010

본 실험은 thermal units을 이용하여 single-stemmed rose($Rosa$ $hybrida$ L.) 'Vital'의 초장, 생체중 및 총엽면적과 각 생육단계에 도달하는 시간을 예측하고, 장미의 신초발달 모델을 개발하기 위해 수행하였다. 기저온도($T_b$), 적정온도($T_{opt}$), 및 최대온도($T_{max}$)는 신초의 발달율과 평균온도의 회귀를 통해 예측하였다. 삽목에서 정식(CT-TP)까지의 생육단계에 대한 신초의 발달율은 linear 함수인 $R_b(d^{-1})$ = -0.0089 + $0.0016{\cdot}Temp$으로 나타났다. 정식에서 수확(TP-HV)까지의 생육단계에서 신초의 발달율은 parabolic 함수인 $R_h(d^{-1})$ = $-0.0001{\cdot}Temp^2$ + $0.0054{\cdot}Temp$ - 0.0484으로 나타낼 수 있었다. $T_b$, $T_{opt}$ 및 $T_{max}$는 각각 5.56, 27.0, 및 $42.7^{\circ}C$으로 나타났다. Tb값 $5.56^{\circ}C$은 single-stemmed rose의 신초발달에 대한 온도함수인 thermal units 계산에 이용되었다. 엽수, 엽면적 및 엽중은 삽목시기에 상관없이 sigmoid curve를 나타내었다. 엽면적(LA) 모델은 thermal units를 사용하여 sigmoid 함수, LA = 578.7 $[1+(thermal units/956.1)^{-8.54}]^{-1}$로 기술할 수 있었다. 삽목에서 정식(CT-TP)과 정식에서 수확(TP-HV)까지의 생육단계에 있어서 요구되는 평균 thermal units($^{\circ}C{\cdot}d$)는 각각 $426{\pm}42(^{\circ}C{\cdot}d)$과 $783{\pm}24(^{\circ}C{\cdot}d$)였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1991년도 춘계학술대회
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• pp.82-85
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• 1991

Cell kinetics and the chemical mass action principle formulate the basis of immune system dynamics which may be synthesized mathematically as cascades of bilinear systems which are connected by nonlinear nondynamical terms. In this manner, a model for cell-mediated immune response (CMI) to tumor antigens and debris is developed. We also consider parametric control variables relevant to the latest experimental data, i.e., sigmoidal dose-response relationship and Michaelis-Menten dynamics. The preliminary results show that the parametric control variable is important in the destruction of tumors. As well as that, the exacerbation theory is a good method for tumor treatment. Finally, tumor control as an application of immunotherapy is analyzed from the basis established above.

• 음성과학
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• 제15권4호
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• pp.85-96
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• 2008

Automatic speech recognition has severe performance degradation under noisy environments. To cope with the noise problem, many methods have been proposed. Most of them focused on noise-robust features or model adaptation. However, researchers have overlooked utterance verification (UV) under noisy environments. In this paper we discuss UV problems based on the normalized confidence measure. First, we show that UV performance is also degraded in noisy environments with the experiments of an isolated word recognition. Then we observe how the degradation of UV performances is suffered. Based on the UV experiments we propose a modeling method of the statistics of phone confidences using sigmoid functions. For obtaining the parameters of the sigmoidal models, the particle swarm optimization (PSO) is adopted. The proposed method improves 20% rejection performance. Our experimental results show that the PSO-NCM can apply noise speech recognition successfully.