• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.724-727
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• 2000

Rapid Prototyping(RP)이란 3차원 솔리드 모델을 단면화한 뒤 하나씩 적층하는 가공방식을 총칭한다. 이때 단면화하는 방법에 따라서 uniform, adaptive slicing으로 나뉘며, 입력 모델에 따라서 direct slicing과 STL을 이용한 방식으로 나뉜다. 적층 방법에 따라서는 연속된 2D 윤곽을 기반으로 적층하는 vertical layer 방식과 인접한 두 개의 2D 윤곽들을 연결하며 만들어진 3D layer를 기반으로 가공하는 sloping layer방식으로 나뉠 수 있다. 현재 상용 RP 시스템들에서는 거의 모든 경우 vertical layer 방식이 채택되어 사용되고 있다. RP와 절삭 공정, 예를 들면 CNC 밀링의 장점을 효율적으로 결합하기 위해서는 임의의 복잡한 형상을 갖는 솔리드 모델을 정밀도에 제한이 없이 제조할 수 있어야 한다. 그러나 절삭 공정은 특별한 전문적 지식들을 필요로 한다 또한 상용 RP에서 사용하는 순차적인 적층 작업으로는 가공할 수 없는 형상들이 많다. 대표적인 것으로 지지대를 필요로 하는 형상들이 있다. 이러한 형상들을 지원하기 위해서는 복잡한 3D 형상을 절삭 가능한 형식으로 분할하는 것과 적층 가능한 순서대로 공정 계획하는 것이 필요하게 된다. 본 연구에서는 SDM에서 제시된 3D 분할 방법이 솔리드 모델을 기반으로 전개되어 STL file과 같은 삼각다면체 형식으로 근사화된 모델에 적용하기 어렵다는데 착안하여 STL file에서 읽어들인 삼각 다면체 모델을 가공 가능한 3D 형상으로 분할하는 알고리즘을 제시하고자 한다.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.2 s.13
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• pp.71-76
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• 2004

To investigate the inundation of tsunamis in the vicinity of a circular island, a numerical model has been developed based on quadtree grids. The governing equations of the model are the nonlinear shallow-water equations. The governing equations are discretized explicitly by using a finite difference leap-frog scheme on adaptive hierarchical quadtree grids. The quadtree grids are generated around a circular island where refined with rectangular or circular domain. Obtained numerical results have been verified by comparing to available laboratory measurements of run-up heights. A good agreement has been achieved.

• Journal of Korea Multimedia Society
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• v.10 no.6
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• pp.716-725
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• 2007

In this paper we describe a motion tracking algorithm for 3D human animation using stereo vision system. This allows us to extract the motion data of the end effectors of human body by following the movement through segmentation process in HIS or RGB color model, and then blob analysis is used to detect robust shape. When two hands or two foots are crossed at any position and become disjointed, an adaptive algorithm is presented to recognize whether it is left or right one. And the real motion is the 3-D coordinate motion. A mono image data is a data of 2D coordinate. This data doesn't acquire distance from a camera. By stereo vision like human vision, we can acquire a data of 3D motion such as left, right motion from bottom and distance of objects from camera. This requests a depth value including x axis and y axis coordinate in mono image for transforming 3D coordinate. This depth value(z axis) is calculated by disparity of stereo vision by using only end-effectors of images. The position of the inner joints is calculated and 3D character can be visualized using inverse kinematics.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.523-531
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• 2009

In this study, we propose a joint source/channel rate control algorithm for video encoder targeting packet erasure channel. Based on the buffer constraints of video communication systems, encoding rate constraint is presented. After defining source distortion models for coded and skipped video frames and a channel distortion model for packet errors and their propagation, an average distortion model of received video is proposed for a given encoding window. Finally, we define an optimization problem to minimize the average distortion for given channel rates and packet loss rates by controlling spatio-temporal parameters of source video and FEC block sizes. Then, we propose a window-based algorithm to solve the problem in real-time.

• Computers and Concrete
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• v.18 no.1
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• pp.1-16
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• 2016

In this study, an Artificial Neural Network (ANN) and Adaptive Network-based Fuzzy Inference Systems (ANFIS) prediction models for flexural strength of the cement mortars have been developed. For purpose of constructing this models, 12 different mixes with 144 specimens of the 2, 7, 28 and 90 days flexural strength experimental results of cement mortars containing pure Portland cement (PC), blast furnace slag (BFS), waste tire rubber powder (WTRP) and BFS+WTRP used in training and testing for ANN and ANFIS were gathered from the standard cement tests. The data used in the ANN and ANFIS models are arranged in a format of four input parameters that cover the Portland cement, BFS, WTRP and age of samples and an output parameter which is flexural strength of cement mortars. The ANN and ANFIS models have produced notable excellent outputs with higher coefficients of determination of $R^2$, RMS and MAPE. For the testing of dataset, the $R^2$, RMS and MAPE values for the ANN model were 0.9892, 0.1715 and 0.0212, respectively. Furthermore, the $R^2$, RMS and MAPE values for the ANFIS model were 0.9831, 0.1947 and 0.0270, respectively. As a result, in the models, the training and testing results indicated that experimental data can be estimated to a superior close extent by the ANN and ANFIS models.

• Journal of the Korean Operations Research and Management Science Society
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• v.33 no.1
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• pp.131-148
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• 2008

Today, it is not difficult to use information technology (IT), especially, Internet based ones. Many people can not only access IT without learning how to use it but also find and develop new techniques and usages which couldn't be expected by system engineers or designers. This is owing to social interactions among users as well as advancement of IT. Theoretically, such social interactions in using IT can be well explained by adaptive structuration theory (AST) which has been considered as one of trying to capture the change of using IT due to social interactions between users and system. This study is to analyze the relationship between social interactions and motivation in using IT which can determine attitude and intention of using IT. For this purpose we provide a research model, in which two AST related variables, faithfulness of appropriation and consensus on appropriation, are independent variables and three beliefs for using IT, usefulness, ease of use and playfulness, are dependent ones. Additionally, for reflection of changing uses, usefulness is formed as second order factor by two first order factors-usefulness of self-expression and communication. An empirical test of our model for blog users which is analyzed by Partial Least Square method shows supporting most of hypotheses except one, consensus-ease of use.

• Journal of Korea Multimedia Society
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• v.13 no.2
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• pp.225-236
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• 2010

This study proposes a method for the recognition of emergency situation according to the bimodal information of camera image sensor and gravity sensor. This method can recognize emergency condition by mutual cooperation and compensation between sensors even when one of the sensors malfunction, the user does not carry gravity sensor, or in the place like bathroom where it is hard to acquire camera images. This paper implemented HMM(Hidden Markov Model) based learning and recognition algorithm to recognize actions such as walking, sitting on floor, sitting at sofa, lying and fainting motions. Recognition rate was enhanced when image feature vectors and gravity feature vectors are combined in learning and recognition process. Also, this method maintains high recognition rate by detecting moving object through adaptive background model even in various illumination changes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.7
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• pp.15-25
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• 2011

This proposes an online loss minimization algorithm for series PI(SPI) based interior permanent magnet synchronous motor(IPMSM) drive to yield high efficiency and high dynamic performance over wide speed range. The loss minimization algorithm is developed based on the motor model. In order to minimize the controllable electrical losses of the motor and thereby maximize the operating efficiency, the d-axis armature current is controlled optimally according to the operating speed and load conditions. For vector control purpose, a SPI is used as a speed controller which enables the utilization of the reluctance torque to achieve high dynamic performance as well as to operate the motor over a wide speed range. Also, this paper proposes current control of model reference adaptive fuzzy controller(MFC), and estimation of speed using artificial neural network(ANN) controller. The proposed efficiency optimization control, SPI, MFC, ANN in this paper is applied to IPMSM drive system, the validity of this paper is proved by analyzing response characteristics in variety operating conditions.

• The Transactions of the Korea Information Processing Society
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• v.4 no.6
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• pp.1531-1540
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• 1997

In this paper, we presents automatic Korean continuous speech recognizer which is improved by the speech rate estimation and the compensation methods. Automatic continuous speech recognition is significantly more difficult than isolated word recognition because of coarticulatory effects and variations in speech rate. In order to recognize continuous speech, modeling methods of coarticulatory effects and variations in speech rate are needed. In this paper, the speech rate is measured by change of format, and the compensation is peformed by extracting relatively many feature vectors in fast speech. Coarticulatory effects are modeled by defining 514 Korean diphone set, and ETRI's 445 word DB is used for training speech material. With combining above methods, we implement automatic Korean continuous speech recognizer, which shows improved recognition rate, based on DHMM(Discrete Hidden Markov Model).

• ETRI Journal
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• v.25 no.5
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• pp.356-368
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• 2003

This paper analyzes the characteristics of packet losses in mobile computing environments based on the Gilbert model and then describes a mechanism that can recover the lost audio packets using redundant data. Using information periodically reported by a receiver, the sender dynamically adjusts the amount and offset values of redundant data with the constraint of minimizing the bandwidth consumption of wireless links. Since mobile computing environments can be often characterized by frequent and consecutive packet losses, loss recovery mechanism need to deal efficiently with both random and consecutive packet losses. To achieve this, the suggested mechanism uses relatively large, discontinuous exponential offset values. That gives the same effect as using both the sequential and interleaving redundant information. To verify the effectiveness of the mechanism, we extended and implemented RTP/RTCP and applications. The experimental results show that our mechanism, with an exponential offset, achieves a remarkably low complete packet loss rate and adapts dynamically to the fluctuation of the packet loss pattern in mobile computing environments.