• ETRI Journal
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• 제30권1호
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• pp.129-140
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• 2008

In this paper, we propose a novel ant colony optimization (ACO)-based test scheduling method for testing network-on-chip (NoC)-based systems-on-chip (SoCs), on the assumption that the test platform, including specific methods and configurations such as test packet routing, generation, and absorption, is installed. The ACO metaheuristic model, inspired by the ant's foraging behavior, can autonomously find better results by exploring more solution space. The proposed method efficiently combines the rectangle packing method with ACO and improves the scheduling results by dynamically choosing the test-access-mechanism widths for cores and changing the testing orders. The power dissipation and variable test clock mode are also considered. Experimental results using ITC'02 benchmark circuits show that the proposed algorithm can efficiently reduce overall test time. Moreover, the computation time of the algorithm is less than a few seconds in most cases.

• Smart Structures and Systems
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• 제30권6호
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• pp.557-569
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• 2022

Vibration-based structural health monitoring (SHM) is crucial for the dynamic maintenance of civil building structures to protect property security and the lives of the public. Analyzing these vibrations with modern artificial intelligence and deep learning (DL) methods is a new trend. This paper proposed an unsupervised deep learning method based on a convolutional autoencoder (CAE), which can overcome the limitations of conventional supervised deep learning. With the convolutional core applied to the DL network, the method can extract features self-adaptively and efficiently. The effectiveness of the method in detecting damage is then tested using a benchmark model. Thereafter, this method is used to detect damage and instant disaster events in a rubber bearing-isolated gymnasium structure. The results indicate that the method enables the CAE network to learn the intact vibrations, so as to distinguish between different damage states of the benchmark model, and the outcome meets the high-dimensional data distribution characteristics visualized by the t-SNE method. Besides, the CAE-based network trained with daily vibrations of the isolating layer in the gymnasium can precisely recover newly collected vibration and detect the occurrence of the ground motion. The proposed method is effective at identifying nonlinear variations in the dynamic responses and has the potential to be used for structural condition assessment and safety warning.

• Membrane and Water Treatment
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• 제3권2호
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• pp.77-98
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• 2012

A two-dimensional (2D) steady state numerical model of concentration polarisation (CP) phenomena in a membrane channel has been developed using the commercially available computational fluid dynamics (CFD) package CFX (Ansys, Inc., USA). The model incorporates the transmembrane pressure (TMP), axially variable permeate flux, variable diffusivity and viscosity, and osmotic pressure effects. The model has been verified against several benchmark analytical and empirical solutions from the membrane literature. Additionally, the model is able to predict the rejection of an arbitrary solute by the membrane using a pore model, given some basic knowledge of the geometry of the solute molecule or particle, and the membrane pore geometry. This allows for predictive design of membrane systems without experimental determination of the membrane rejection for the specified operating conditions. A demonstration of the model is presented against experimental results for two uncharged test compounds (sucrose and PEG1000) from the literature. The model will be extended to incorporate charge effects, transient simulations, three-dimensional (3D) geometry and turbulent effects in future work.

• 한국측량학회지
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• 제27권2호
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• pp.213-223
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• 2009

지오이드 모델개발에 있어서 GPS/leveling 자료는 중력지오이드의 검증이나 합성지오이드의 계산에 있어서 매우 중요한 역할을 한다. 본 연구에서는 우리나라 GPS/leveling 자료의 배점밀도를 개선하기 위하여 산악지역을 포함하는 연구대상지역에서 직접 GPS측량을 실시하고, 이를 처리하여 산정된 기하학적 지오이드 고의 정확도를 분석하였다. 이를 위해 경북지역 내의 1등 및 2등 수준노선을 대상으로 총 211개소의 GPS/leveling 자료를 취득하고, 기선해석 및 망조정을 통해 198개소의 GPS/leveling 자료를 결정하였다. 이 198개소의 자료에 의한 기하학적 지오이드고는 EGM2008 모델에 의한 지오이드고와의 교차분석을 통해 그 정확도를 분석하였다. 그 결과 정규분포에 따른 과대오차 소거 후 190개소 자료에 대한 정확도는 -0.185$\pm$ 0.079m로 나타났고, 이를 이용하여 수준점 등급, 기선길이, 그리고 표고에 따른 정확도를 분석하였다.

• 대한토목학회논문집
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• 제37권6호
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• pp.973-980
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• 2017

본 연구는 해수침투를 모의하는 연산의 바탕이 되는 밀도 결합 방정식을 2차원으로 유한차분한 VDFT (Visual Basic based Density-coupled Flow and Transport) 기법을 개발한 것이다. VDFT 코드는 직관적이고 간단하게 사용할 수 있다는 장점을 가지고 있으며 일반 업무용으로 널리 사용되고 있는 EXCEL Visual Basic 플랫폼을 활용할 수 있다는 장점이 있다. 일반적으로 수치모의를 위해 개발한 코드는 벤치마크 라는 대표적인 수치예제를 통하여 검증을 할 수 있다. 본 연구에서는 2가지 실내실험 결과로서 얻어진 데이터와 Henry Problem 및 Modified Henry Problem을 수치예제로 활용하여 VDFT 기법을 검증하였다. 마지막으로 결론에서는 VDFT 코드의 활용가능성을 진단하고 향후 연구의 방향성을 제시하였다.

• ETRI Journal
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• 제38권3호
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• pp.487-493
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• 2016

Two new methods are proposed for an unsupervised adaptation of a language model (LM) with a single sentence for automatic transcription tasks. At the training phase, training documents are clustered by a method known as Latent Dirichlet allocation (LDA), and then a domain-specific LM is trained for each cluster. At the test phase, an adapted LM is presented as a linear mixture of the now trained domain-specific LMs. Unlike previous adaptation methods, the proposed methods fully utilize a trained LDA model for the estimation of weight values, which are then to be assigned to the now trained domain-specific LMs; therefore, the clustering and weight-estimation algorithms of the trained LDA model are reliable. For the continuous speech recognition benchmark tests, the proposed methods outperform other unsupervised LM adaptation methods based on latent semantic analysis, non-negative matrix factorization, and LDA with n-gram counting.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1400-1409
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• 2023

In this study, three condensation models of the CUPID code, i.e., the resolved boundary layer approach (RBLA), heat and mass transfer analogy (HMTA) model, and an empirical correlation, were tested and validated against the COPAIN and CAU tests. An improvement on HMTA model was also made to use well-known heat transfer correlations and to take geometrical effect into consideration. The RBLA was a best option for simulating the COPAIN test, having mean relative error (MRE) about 0.072, followed by the modified HMTA model (MRE about 0.18). On the other hand, benchmark against CAU test (under natural convection and occurred on a slender tube) indicated that the modified HMTA model had better accuracy (MRE about 0.149) than the RBLA (MRE about 0.314). The HMTA model with wall function and the empirical correlation underestimated significantly, having MRE about 0.787 and 0.55 respectively. When using the HMTA model, consideration of geometrical effect such as tube curvature was essential; ignoring such effect leads to significant underestimation. The HMTA and the empirical correlation required significantly less computational resources than the RBLA model. Considering that the HMTA model was reasonable accurate, it may be preferable for large-scale simulations of containment.

• 전자공학회논문지S
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• 제34S권9호
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• pp.84-90
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• 1997

We proposed a new bit-rate control algorithm to improve MPEG-2 video software encoder. Bit-rate Control plays an improtant role in picture quality of MPEG-2 encoder. To achieve better encoding performance such as controlling picture quality and using bity properly, we proposed a MPEG-2 bit-rate control algorithm using linear average Step-Size. Using a benchmark Program, we compared our algorithm with MPEG-2 Test Model 5. Our proposed algorithm showed better Bit-Rate Control with respect to used bits, picture quality.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.172-175
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• 2002

This paper presents perceptual model with a stochastic rnultiresolution characteristic that can be applied with watermark embedding in the biorthogonal wavelet domain. The perceptual model with adaptive watermarking algorithm embed at the texture and edge region for more strongly embedded watermark by the SSQ(successive subband quantization). The watermark embedding is based on the computation of a NVF(noise visibility function) that have local image properties. This method uses non-stationary Gaussian model stationary Generalized Gaussian model because watermark has noise properties. In order to determine the optimal NVF, we consider the watermark as noise. The particularities of embedding in the stationary GG model use shape parameter and variance of each subband regions in multiresolution. To estimate the shape parameter, we use a moment matching method. Non-stationary Gaussian model use the local mean and variance of each subband. The experiment results of simulation were found to be excellent invisibility and robustness. Experiments of such distortion are executed by Stirmark benchmark test.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1488-1502
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• 2005

A three dimensional model was developed to analyze the mold filling and solidification in the casting processes. The model uses the VOF method for the calculation of the free surface and the modified Equivalent Specific Heat method for the treatment of the latent heat evolution. The solution procedure is based on the SIMPLER algorithm. The complete model has been validated using the exact solutions for phase change heat transfer and the experimental results of broken water column. The three-dimensional model has been applied to the benchmark test and the results were compared to those from experiment, a two-dimensional analysis, and another three dimensional numerical model.