• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.226-231
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• 2001

The purpose of this paper is to propose the experimental method of thermal properties of Phase Change Materials (PCMs) by using T-history method. As far, in order to measure the heat of fusion and specific heat of PCMs, conventional thermal analysis methods such as DSC and DTA have been used. Because these methods test very small samples, thermal properties of samples are usually different from those of materials consisting of several components. For these reasons, T-history method, the simple measurement method of the heat of fusion and specific heat of PCMs have been performed. In this paper, we investigated the thermal properties of low temperature PCMs(below $0^{\circ}C$) under the charging process by using T-history method. The results are compared to those of DSC method. The T-history method will be useful for selection of the best PCM from lots of candidates and development of new PCMs.

• 전기학회논문지
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• 제62권4호
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• pp.489-494
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• 2013

In analysis of power transformer loss using calculation of magnetic field, Finite element method is commonly used. When using this method, calculation of magnetic field needs the very large number of elements and the performance of common work station is not sufficient to calculate the magnetic fields. In addition, the definition of boundary conditions may arise. However, When using Integral equation method, only ferromagnetic materials need to be modeled, since the domain is infinite. All the space in which the primary and secondary sources exist is regarded as free(${\mu}={\mu}_0$).

• Korean Journal of Radiology
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• 제22권8호
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• pp.1352-1368
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• 2021

Objective: For an accurate dynamic contrast-enhanced (DCE) MRI analysis, exact baseline T1 mapping is critical. The purpose of this study was to compare the pharmacokinetic parameters of DCE MRI using synthetic MRI with those using fixed baseline T1 values. Materials and Methods: This retrospective study included 102 patients who underwent both DCE and synthetic brain MRI. Two methods were set for the baseline T1: one using the fixed value and the other using the T1 map from synthetic MRI. The volume transfer constant (K^trans), volume of the vascular plasma space (v_p), and the volume of the extravascular extracellular space (v_e) were compared between the two methods. The interclass correlation coefficients and the Bland-Altman method were used to assess the reliability. Results: In normal-appearing frontal white matter (WM), the mean values of K^trans, v_e, and v_p were significantly higher in the fixed value method than in the T1 map method. In the normal-appearing occipital WM, the mean values of v_e and v_p were significantly higher in the fixed value method. In the putamen and head of the caudate nucleus, the mean values of K^trans, v_e, and v_p were significantly lower in the fixed value method. In addition, the T1 map method showed comparable interobserver agreements with the fixed baseline T1 value method. Conclusion: The T1 map method using synthetic MRI may be useful for reflecting individual differences and reliable measurements in clinical applications of DCE MRI.

• 대한기계학회논문집A
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• 제33권2호
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• pp.127-134
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• 2009

T-splines are recently proposed geometric modeling tools. A T-spline surface is a NURBS surface with T-junctions and is defined by a control grid called T-mesh. Local refinement can be performed very easily for T-splines while it is limited for B-splines or NURBS. Using T-splines, patches with unmatched boundaries can be combined easily without special technique. In this study, the analysis methodology using T-splines is proposed. In this methodology, T-splines are used both for description of geometries and for approximation of solution spaces. Two-dimensional linear elastic and dynamic problems will be solved by employing the proposed T-spline finite element method, and the effectiveness of the current analysis methodology will be verified.

• 제어로봇시스템학회논문지
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• 제8권11호
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• pp.941-947
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• 2002

Two methods of constructing T-S fuzzy model which is equivalent to a given nonlinear system are presented. The first method is to obtain an equivalent T-S fuzzy model by using the sum of linearly independent scalar functions with constant real matrix coefficients. The sum of products of linearly independent scalar functions is used in the second method. The former method is to formulate the procedures of T-S fuzzy modeling dealt in many examples of previous publications; the latter is a new method. By comparing the number of linearly independent functions used in the two methods, we can easily find out which method makes fewer rules than the other. The nonlinear dynamics of an inverted Pendulum on a cart is used as an equivalent T-5 fuzzy modeling example.

• 한국산업정보학회논문지
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• 제18권1호
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• pp.25-35
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• 2013

Automatically deriving only individual don't-care minterms that can effectively reduce a Boolean logic expressions are being investigated. Don't-care conditions play an important role in optimizing logic design. The type of unknown don't-care minterms that can always reduce the number of product terms in Boolean expression are referred as single hypothetical don't-care (S-HDC) minterms. This paper describes the Quasi Quine-McCluskey method that systematically derives S-HDC minterms. For the most part, this method is similar to the original Quine-McCluskey method in deriving the prime implicants. However, the Quasi Quine-McCluskey method further derives S-HDC minterms by applying so-called a combinatorial comparison operation. Upon completion of the procedure, the designer can review generated S-HDC minterms to test its appropriateness for a particular application.

• International journal of advanced smart convergence
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• 제12권1호
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• pp.64-69
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• 2023

We devise a collaboration construction method based on the SPRT (Sequential Probability Ratio Test) for malware detection in IoT. In our method, high-end IoT nodes having capable of detecting malware and generating malware signatures harness the SPRT to give a reward of malware signatures to low-end IoT nodes providing useful data for malware detection in IoT. We evaluate our proposed method through simulation. Our simulation results indicate that the number of malware signatures provided for collaboration is varied in accordance with the threshold for fraction of useful data.

• 한국정밀공학회지
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• 제20권10호
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• pp.208-217
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• 2003

In order to construct the extrusion die surface of T -shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the mapping concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile are determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the T-shaped section and T-shaped section with rounded corners.

• 한국융합학회논문지
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• 제9권4호
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• pp.57-63
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• 2018

IoT 장치는 클라우드 환경에서 다양한 역할과 기능을 수행할 수 있도록 여러 분야에서 사용되고 있다. 그러나, IoT 장치를 안정적으로 제어할 수 있는 접근제어에 대한 방안은 아직 구체적으로 제시되고 있지 않은 상황이다. 본 논문에서는 클라우드 환경에서 사용되고 있는 IoT 장치의 안정적인 접근을 수행할 수 있는 계층적 기반의 다단계 속성 접근제어 기법을 제안한다. 제안 방법은 IoT 장치의 원활한 접근을 돕기 위해서 IoT Hub을 두어 IoT 장치에 고유한 ID 키(보안 토큰)를 제공할 뿐만 아니라 수 있도록 하는 X.509 인증서 및 개인 키를 IoT Hub에서 인증하도록 하여 IoT 장치의 개인키를 IoT 장치 외부에서 알 수 없도록 하였다. 성능평가 결과, 제안방법은 기존 기법보다 인증 정확도가 평균 10.5% 향상되었으며 처리 시간도 14.3% 낮은 결과를 얻었다. IoT 속성 수에 따른 IoT Hub의 오버헤드는 기존 기법보다 9.1% 낮은 결과를 얻었다.

• Journal of the Korean Statistical Society
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• 제34권3호
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• pp.245-261
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• 2005

The marginal distribution of X is considered when (X, Y) has a truncated bivariate t-distribution. This paper mainly focuses on the marginal nontruncated distribution of X where Y is truncated below at its mean and its observations are not available. Several properties and applications of this distribution, including relationship with Azzalini's skew-normal distribution, are obtained. To circumvent inferential problem arises from adopting the frequentist's approach, a Bayesian method utilizing a data augmentation method is suggested. Illustrative examples demonstrate the performance of the method.