Droplet-Based Manufacturing 공정에 의해 제조된 무연 솔더볼의 제조공정 변수 연구

엄호천,조경목,송인혁,한유동 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.1

Uniform droplet of lead-free solder balls was produced by using the Droplet-Based Manufacturing(DBM) process. Compositions of solder were Sn, Sn-3.6 wt.% Ag, and Sn-3.8 wt.%Ag-0.6 wt.% Zn. Effect of parameters such as orifice size, pressure difference, and frequency on the solder ball production was also investigated. Mean size, size distribution, and surface defect of solder balls were analyzed with variations of the parameters. Droplet spacing decreased with increasing frequency and decreasing pressure difference. Thus the size of solder ball decreased with increasing frequency and decreasing pressure difference. Size distribution fell within the narrow range of ±5% from the mean diameter of solder balls. The experimentally measured diameter of the solder balls fabricated by DBM process coincided quite well with the theoretically anticipated value of d_d=A d_o^2/3.

음성/데이타 통합환경에서 VoIP를 이용한 컴퓨터 네트워크 QoS 성능평가

엄기복,조경룡,여현 순천대학교 1999 순천대학교 자연과학논문집 Vol.18 No.2

Most computer networks have processed only data using TCP/IP, but recent technology of computer network makes it possible to process both voice and data service. This paper presents an analysis method of computer network which provide both voice and data service, and a result of Qos performance evaluation on the computer network using VoIP under voice and data environment. We simulate at a small office with 60 terminals, for which the major parameters include system operation rate, network protocol, network structure, CPU processing rate, inter-system delay, and the number of buffer failures. As a result, The network structure was consisted of FastEthernet. The CPU processing rates were below 15%. The average inter-system delay was 0.7ms. In FastEthernet network, the average is normal. number of buffer failures was 0. This computer network, therefore, is sufficient ofr voice service.

홍윤숙 시인의 삶과 시정신

엄경희 崇實語文學會 2001 崇實語文 Vol.17 No.-

月谷에 유배된 시인 一金宗三論

엄경희 崇實語文學會 1999 崇實語文 Vol.15 No.-

폐지의 효소 탈묵

윤경동,박성배,박용현,엄태진 慶北大學校 農業科學技術硏究所 2004 慶北大農學誌 Vol.22 No.-

Cellulolytic enzymes were prepared from alkaline resistant microorganisms which were newly screened from calcic soil. Characteristics of enzymes and enzymatic deinking efficiency of wastepaper were investigated. The results were summarized as fellows: 1. The recovery rate of crude enzyme was 93.7% in Bio-B and 57.4% in Bio-F. 2. The protein content in crude enzymes was lowest and the thermal stability of crude enzymes was highest in Bio-F. 3. The brightness gain of Bio-F deinked pulp was best in ONP and Bio-B deinked pulp was best in MOW. 4. The reject yield was increased with enzymatic deinking flotation process. 5. The residual ink area of paper was increased with enzymatic deinking and large size of ink particles were remained in paper.

변형된 신경회로망을 이용한 PID 제어 방식

정경권,김경수,엄기환 동국대학교 산업기술연구원 1999 산업기술논문집 Vol.13 No.-

본 논문에서는 산업 현장에서 일반적으로 많이 사용되고 있는 PID 제어기의 비례, 적분, 미분 파라미터를 다층 신경회로망을 이용하여 자동으로 동조하는 방법을 제안한다. 제안한 방식은 자기 궤환 뉴런을 가진 다층 신경회로망이 플랜트의 입력과 출력을 이용하여 PID 제어기의 파라미터들을 학습에 의하여 자동 동조한다. 다층 신경회로망은 자기 궤환 뉴런을 이용하여 입력층, 은닉층, 출력층의 3층으로 구성되고, 출력은 3개 값을 갖는다. 이것은 PID 제어기의 비례(P), 적분(I), 미분(D) 파라미터로 사용된다. 이 값들은 특정한 값으로 고정되는 것이 아니라 제어 수행과정 중에서도 다층 신경회로망의 학습에 의해 계속 변화된다. DC 서보 모터를 대상으로 추종 제어 시뮬레이션 및 실험을 통해서 제안한 방식의 유용성을 확인하였다. In this paper, we propose a modified neural network for the auto-tuning of proportional, integral, and derivative parameters of PID controller, which is widely used in the industries. The proposed method uses a multi-layer neural network with self-feedback neuron for the auto-tuning of the parameters of PID controller using input and output of the plant by learning. The neural network consists of three layers ; input-layer, hidden-layer, and output-layer. The output layer will have three outputs and each will be used as P, I, D parameters. Those values are not specific not fixed but being modified according to the learning of multi-layer neural network. The simulation and experiment results showed the effectiveness of proposed control method.

삼일열 말라리아에 합병된 비장 파열 1예

홍경욱,이정아,김원진,박철민,권혜리,박혜원,엄중식 대한감염학회 2007 감염과 화학요법 Vol.39 No.5

국내의 토착형 말라리아는 삼일열 말라리아로, 1993년부터 재유행이 시작되었다. 말라리아의 중요한 합병증으로 드물지만 비장 파열이 있는데, 이는 주로 삼일열 말라리아에 의해서 발생되며, 국내에서는 1999년 말라리아에 의한 비장 파열로 비장 절제술을 시행한 예가 보고된 바 있다. 현재까지는 비장 파열이 있을 때 비장 절제술이 일차적인 치료로 되어 있으나, 비장 절제술 후의 감염 위험성이 크므로, 활력 징후가 불안정하거나, 출혈이 지속되는 소견이 보이지 않으면 가급적 보존적 치료를 하는 것이 추천된다. 저자들은 비장 파열이 동반된 말라리아 환자에서 비장 절제술을 시행하지 않고 보존적 치료로 호전된 예를 경험하여 보고하는 바이다. Plasmodium vivax has been the predominant Plasmodium species in the Republic of Korea and reemerged in 1993. Spontaneous rupture of malarial spleen is a rare but important complication associated with P. vivax infection. Only one case of spontaneous rupture of malarial spleen was reported in Korea in 1999. Splenectomy is still accepted as the treatment of choice in cases of spontaneous rupture of the spleen. But, considering increased risk of postsplenectomy infecion, splenectomy should be reserved for those patients with severe rupture or those with continued or recurrent bleeding. And conservative treatment should be considered in selected, closely monitored patients. We report a patient with P. vivax malaria who developed a spontaneous splenic rupture and was improved by conservative treatment.

수정된 Elman 신경회로망을 이용한 제어방식

정경권,김주웅,엄기환 동국대학교 대학원 1998 大學院硏究論集-東國大學校 大學院 Vol.28 No.-

The neural network is a static network that consists of a number of layer: input layer, output layer and one or more hidden layer connected in a feedforward way. The popularity of neural network appear to be related to its ability of learning and approximation capability. The Elman Neural Network proposed the J.Elman, is a type of recurrent network. It has the feedback links from hidden layer to context layer. So Elman neural network is the better performance than the neural network. In this paper, we propose the Modified Elman Neural Network. The structure of a MENN is based on the basis ENN. The recurrency of the network is due to the feedback links from the output layer and the hidden layer to the context layer. In order to certify the usefulness of the proposed method, the MENN apply to the multi tracking control and the X-Y Cartesian tracking. Simulation shows that the proposed MENN method is better performance than the multi layer neural network and the ENN.

전방향 신경회로망을 이용한 블록암호화 기법

정경권,엄기환 동국대학교 산업기술연구원 1998 산업기술논문집 Vol.11 No.-

본 논문에서는 전방향 신경회로망으로 암호 함수를 구성하는 블록 암호 알고리즘 방법을 제안한다. 제안한 방법은 블록 암호 알고리즘에서 사용되는 암호화 함수 전체를 전방향 신경회로망으로 대치하는 방법과, DES 암호 알고리즘에서 S-box를 전방향 신경회로망으로 대치하는 방법이다. 신경회로망의 가중치를 키로 사용하여 암호화 및 복호화를 수행한다. 신경회로망의 비선형적인 특성과 각각의 층을 구성하고 있는 뉴런간의 방대한 연결로 복잡한 구조를 가지고 있다. 또한 은닉층의 구성에 따라 여러 형태의 설계가 가능하다. In this paper, we propose a block cipher algorithms composing cipher function using feedforward neural network. The proposed methods are that cipher function used in the block cipher algorithm is totally replaced with feedforward neural network, and also, S-box is replaced with feedforward neural network in DES algorithm. The weight of neural network is used as a key to perform an encryption and decryption. It has complex structure due to its nonlinear characteristic and the enormous connections among neurons which organize layers respectively. Also, various design shapes are applicable by different structures of hidden layers.

유전자 알고리즘을 이용한 비선형 시스템 동정

정경권,정성부,엄기환 동국대학교 산업기술환경대학원 1998 산업기술논총 Vol.4 No.-

In this paper, we propose a nonlinear system identification method using genetic algorithm. We represent the nonlinear system as a parameter vector and a measurement vector. In order to identify the nonlinear system, we find the parameter vector using genetic algorithm. The parameter vector is regarded as a chromosome of gene. The error between the desired output and estimated output every sampling period is used to calculate the fitness of one gene. The simulation results showed the effectiveness of using the genetic algorithm in the nonlinear system identification.