수열합성법을 이용하여 우선 배향된 ZnO 나노와이어 성장 및 발광 특성

김종현,임연수,김성현,조진우,정대용,Kim, Jong-Hyun,Lim, Yun-Soo,Kim, Sung-Hyun,Jo, Jin-Woo,Jeong, Dae-Yong 한국재료학회 2011 한국재료학회지 Vol.21 No.12

1-D ZnO nanowires have been attractive for their peculiar properties and easy growth at relatively low temperature. The length, diameter, and density of ZnO nanowires were determined by the several synthetic parameters, such as PEI concentration, growth time, temperature, and zinc salt concentration. The ZnO nanowires were grown on the <001> oriented seed layer using the hydrothermal process with zinc nitrate and HMTA (hexamethylenetetramine) and their structure and optical properties were characterized. The morphology, length and diameter of the nanowires were strongly affected by the relative and/or absolute concentration of $Zn^{2+}$ and $OH^{-1}$ and the hydrothermal temperature. When the concentrations of the zinc nitrate HMTA were the same as 0.015 M, the length and diameter of the nanowires were $1.97{\mu}m$ and $0.07{\mu}m$, respectively, and the aspect ratio was 28.1 with the preferred orientation along the <001> direction. XRD and TEM results showed a high crystallinity of the ZnO nanowires. Optical measurement revealed that ZnO nanowires emitted intensive stimulated UV at 376 nm without showing visible emission related to oxygen defects.

용융시 수반되는 4가지 다른 잠열 모델의 비교 연구

김종현,임인철,김성식 ( Jong Hyun Kim,In Cheol Kim,Sung Sik Kim ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.1

상변환시 수반되는 경계면에서의 잡열의 방출(또는 흡수)의 정확한 해석은 용접, 주조, 결정 생성, 일기 예보 등의 응용에 필수적인 것이다. 특히 주조의 경우 캐스팅 온도와 고체 용적분율의 관계를 앎으로서 잠열 방출의 해석이 가능하다. 본 연구는 상변환시 수반되는 잠열의 방출 형태를 4개의 다른 모델을 사용하여 비정상 온도분포, 용융형태, 자연대류가 미치는 영향을 수치적으로 구하였다. 2개의 서로 다른 물성치를 가진 합금을 선택하였는데 하나는 넓은 mushy 영역을 가진 알루미늄 합금이고 다른 하나는 좁은 mushy 영역을 가진 철금속계 합금이다. 알루미늄 합금의 경우 온도 분포와 시간에 따른 온도의 변화가 모델에 따라 상당한 차이가 있는 반면 철금속계 합금의 경우 상이한 모델일지라도 거의 차이가 없음을 알 수 있었다. 결론으로 용융시 정확한 온도 분포와 상변화 형태를 예측하기 위해서는, 알루미늄 합금(넓은 mushy영역)의 경우 적절한 잠열 방출 모델의 채택이 필요 불가급한 것으로 사료된다. N/A

중국어 초급과정 교육 방안

김종현 동아대학교 어학연구소 1998 언어와 언어교육 Vol.13 No.-

이진 가중치 신경망의 하드웨어 구현을 위한 고정소수점 연산 정확도 분석

김종현,윤상균,Kim, Jong-Hyun,Yun, SangKyun 한국전기전자학회 2018 전기전자학회논문지 Vol.22 No.3

본 연구에서는 이진 가중치 신경망(BWN)을 부동소수점 데이터를 사용하여 학습시킨 후에, 학습된 파라미터와 주요연산을 고정소수점으로 근사화시키는 과정에서 정확도의 변화를 분석하였다. 신경망을 이루고 있는 각 계층의 입력 데이터와 컨볼루션 연산의 계산에 고정소수점 수를 사용했으며, 이때 고정소수점 수의 전체 bit 수와 소수점 이하 bit 수에 변화를 주면서 정확도 변화를 관찰하였다. 각 계층의 입력 값과 중간 계산값의 정수 부분의 손실이 발생하지 않으면 고정소수점 연산을 사용해도 부동소수점 연산에 비해 큰 정확도 감소가 없었다. 그리고 오버플로가 발생하는 경우에 고정소수점 수의 최대 또는 최소값으로 근사시켜서 정확도 감소를 줄일 수 있었다. 이 연구결과는 FPGA 기반의 BWN 가속기를 구현할 때에 필요한 메모리와 하드웨어 요구량을 줄이는 데 사용될 수 있다. In this paper, we analyze the change of accuracy when fixed point arithmetic is used instead of floating point arithmetic in binary weight network(BWN). We observed the change of accuracy by varying total bit size and fraction bit size. If the integer part is not changed after fixed point approximation, there is no significant decrease in accuracy compared to the floating-point operation. When overflow occurs in the integer part, the approximation to the maximum or minimum of the fixed point representation minimizes the decrease in accuracy. The results of this paper can be applied to the minimization of memory and hardware resource requirement in the implementation of FPGA-based BWN accelerator.

청신경 초종 수술에서 골미로를 통한 접근법의 유용성

김종현,조태구,박관,박익성,남도현,이정일,조양선,홍성화,홍승철,신형진,어환,Kim, Jong Hyun,Cho, Tae Goo,Park, Kwan,Park, Ik Seong,Nam, Do-Hyun,Lee, Jung-Il,Cho, Yang-Sun,Hong, Sung Hwa,Hong, Seung-Chyul,Shin, Hyung-Jin,Eoh, Whan 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.6

Objective : To determine the feasibility of translabyrinthine approach in the vestibular schwannoma patients, the authors reviewed eighteen consecutive cases, focusing at their functional outcome and operative complications. Materials and Method : To evaluate the functional outcome, we reviewed preoperative radiological findings such as size of tumors and location of jugular bulb as well as the preoperative neurological status including audiometric analysis and cranial nerve function in 18 patients, diagnosed as vestibular schwannoma. Also the surgical outcome was evaluated according to the functional preservation of facial nerve and incidence of the surgical complication as well as the extent of surgical resection. Results : The age of patients ranged from 21 to 62 years, with a mean of 50 years. Of 18 patients operated in our center by the translabyrinthine approach, wide exposure with total removal of the mass was possible in 16 cases (88.8%). The facial nerve was anatomically preserved in 88.8%. At six-month follow-up, facial nerve function was good(Grade I-II) in 15 patients(83%) and acceptable(I-IV) in all patients. Although the jugular bulb was highly placed is five patients, gross total resection was possible without facial nerve injury in all patients by the translabyrinthine approach. One patient experienced CSF leakage after surgery, but there was no patient with disabling deficit. Conclusion : Use of the translabyrinthine approach for removal of vestibular schwannomas resulted in good anatomical and functional preservation of the facial nerve, with minimal incidence of morbidity and no mortality. In cases of high jugular bulb impacted into mastoid bone, total removal was possible by displacing the jugular bulb with Surgicel cellulose and placement of bone wax.

인터리브드 멀티홉 인증을 적용한 무선 센서네트워크에서 퍼지로직을 이용한 서비스 거부 공격에 대한 방어 기법

김종현,조대호,Kim, Jong-Hyun,Cho, Tac-Ho 한국시뮬레이션학회 2009 한국시뮬레이션학회 논문지 Vol.18 No.3

When sensor networks are deployed in open environments, an adversary may compromise some sensor nodes and use them to inject false sensing reports. False report attack can lead to not only false alarms but also the depletion of limited energy resources in battery powered networks. The Interleaved hop-by-hop authentication (IHA) scheme detects such false reports through interleaved authentication. In IHA, when a report is forwarded to the base station, all nodes on the path must spend energies on receiving, authenticating, and transmitting it. An dversary can spend energies in nodes by using the methods as a relaying attack which uses macro. The Adversary aim to drain the finite amount of energies in sensor nodes without sending false reports to BS, the result paralyzing sensor network. In this paper, we propose a countermeasure using fuzzy logic from the Denial of Service(DoS) attack and show an efficiency of energy through the simulataion result.

직무분석에 의한 화학공학 교과과정 개발 - 동서대학교 사례연구 -

김종현,Kim Jong-Hyun 한국공학교육학회 2000 공학교육연구 Vol.3 No.2

Possible directions of chemical engineering education have been proposed in many studies. However, new curriculum is demanded to accommodate the special needs of our students' level and community industrial characteristics. We can think of two reasons. One is that various kinds of chemical engineering industry are found in every community. The other is that students' educational standards are different in every university. We have surveyed and analyzed jobs of our university graduates who are working in chemical company of our community Pusan and Kyoung-Nam. This study aims to develop the new curriculum with an emphasis on practical education and to propose the new direction for our major characteristic based on the survey. 여러 보고서를 통하여 미래의 화학공학 교육의 방향이 제시되어 있지만 각 지역마다 분포되어 있는 화학산업의 종류가 다르고 대학별로 지원하는 학생들의 학습능력이 다르므로 학습자의 능력과 지역산업에 부합하는 교과과정이 요구된다. 따라서 본 연구에서는 부산, 경남 지역의 화학회사에 취업하고 있는 졸업생을 대상으로 직무분석을 하여 실무중심의 교과과정을 개발하고 전공의 특성화를 위한 방향을 제시하고자 한다.

CH₄-공기 동축 제트화염의 NOx 배출특성에 관한 수치 및 실험적 연구

김종현,오창보,이창언,Kim, Jong-Hyun,Oh, Chang-Bo,Lee, Chang-Eon 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.11

The NOx emission characteristics of C$H_4$-Air coflow jet flames were numerically and experimentally investigated. NOx was measured using a chemiluminescent detection and calculated by the parabolic -type equation solver with a detatiled NOx chemistry. The fuel flow rate( $Q_{F}$), the diameter of mixture nozzle and the equivalence rate(Ф) were varied to discuss the EINOx of each flames at the various combustion conditions. The NOx emission index(EINOx) was introduced to quantify the NOx emission from the parametrically varied flames. The results show that Prompt EINOx increases on a logarithmic profile with increasing ${\Phi}$ and keeps nearly constant for the variation of $Q_{F}$. Thermal EINOx reaches the maximum value at around ${\Phi}$ =1.5 and then slowly decrease for ${\Phi}$ >1.5. In addition, Thermal EINOx increases with increasing $Q_{F}$, but nearly indifferent to the variation of the mixture nozzle diameter. Total EINOx also shows a peak at around ${\Phi}$ =1.5, followed by a relatively sharp decrease for 1.5< ${\Phi}$ <2.5 and increase slowly for 2.5 < ${\Phi}$ < $\infty$ The present Total EINOx trend is well explained by a combination of above Thermal and Prompt EINOx trend with the variation of ${\Phi}$ n of ${\Phi}$.

H₂/Air 비예혼합화염의 화염신장율에 따른 NO 생성경로의 상세해석

김종현,황철홍,이창언,Kim, Jong-Hyun,Hwang, Cheol-Hong,Lee, Chang-Eon 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.8

Detailed analysis of NO formation routes and its contributions with strain rate in hydrogen/air flames were numerically investigated. LiG detailed reaction mechanism has been used for calculation, which is compared with experimental data in literature. It shows good agreement with experiment for both temperature and NO mole fraction. Three routes have been found important for NO formation in hydrogen flames. These are the Thermal route, NNH route and $N_2O$ route. Strain rate were varied to discuss the $EI_{NO}$ reduction trend in hydrogen nonpremixed flames, which are analyzed by each NO formation routes. As a result, as the strain rate increase, $EI_{NO}$ decrease sharply until strain rate $100s^{-1}$ and decrease slowly until strain rate $310s^{-1}$ again, after that $EI_{NO}$ keeps nearly constant. It can be identified that $EI_{NO}$ trend with the strain rate is well explained by a combination of variation of production rate of above Thermal, NNH and $N_2O$ route. Also result of Thermal-Mech. that includes only thermal NO reaction is compared with those of Full-Mech. As a result, It can be identified that there was difference between the two results of calculation. It is attributed to result that Thermal-mech did not consider contributions of NNH and $N_2O$ route. From these result, we can conclude that NOx emission characteristics of hydrogen nonpremixed flames should consider contributions of above three routes simultaneously.

CAN기반 시스템의 통신 신뢰성 검증

김종현,정기현,최경희,Kim, Jong-Hyun,Chung, Ki-Hyun,Choi, Kyung-Hee 한국정보처리학회 2008 정보처리학회논문지 C : 정보통신,정보보안 Vol.15 No.3

CAN은 처음에는 차량 네트워크에서의 사용을 위해 고안되었으나 잡음에 강하고 신뢰성이 높아 공장자동화 등에서도 많이 사용되고 있다. 그러나 1:1통신에서 네트워크 기반의 통신방식으로 변화되면서 각 장치의 기계적인 동작뿐만 아니라 전자, 소프트웨어적인 동작에 대해서도 철저한 검증이 필요하게 되었다. 본 논문은 CAN 기반 시스템에서 통신의 신뢰성을 데이터의 정확성에 대한 부분과 시간상의 정확성에 대한 부분을 검증하는 방법을 제시하고 있다. Controller Area Network was developed originally for in-vehicle communication network. But it is now widely used for factory automation because of its properties such as strong noise resistance and high reliabilities. With changing communication environments from peer to peer topology to bus topology, we should check each devices about not only mechanical operations but also electronic or software operations. In this paper, we suggest reliability test environment for CAN based system, which is divided two parts, data correctness and timely delivery.