SAGE 알고리즘을 이용한 MIMO 채널 파라미터 추정과 분석

김주석,여봉구,최홍락,김경석,Kim, Joo-Seok,Yeo, Bong-Gu,Choi, Hong-Rak,Kim, Kyung-Seok 한국인터넷방송통신학회 2017 한국인터넷방송통신학회 논문지 Vol.17 No.5

본 논문은 다중 경로 다중입력 (Multiple-input multiple-output : MIMO) 채널에서 space alternating generalized expectation-maximization(SAGE) 알고리즘을 이용하여 채널 파라미터 추정 성능을 확인한다. 성능을 비교하기 위해 781 대역의 제주도 측정지역에서의 채널 파라미터로부터 시변 채널 환경 채널 파라미터 추정을 SAGE 알고리즘을 통해 추정하고 원본 데이터와 비교한다. 이를 통해 SAGE 알고리즘의 성능을 확인할 수 있으며 일반적인 파라미터 계산보다 SAGE 알고리즘을 통해 추정하는 것이 지연 확산(Delay Spread), 도래각 확산(Arrive of Angular Spread)이 적어 정확 측면에서 성능이 뛰어나고 안정적이다. This paper is a multi-input multi-path (Multiple-input multiple-output: MIMO) using a space-alternating generalized expectation maximization(SAGE) algorithm in the parameter channel and determine the channel estimation performance. Estimated by the algorithm, SAGE time-varying channel environment, the channel parameters estimated from the parameters of the channel measured in the island region 781 of the band in order to compare the performance and compares the original data. This allows you to check the performance of the algorithm SAGE and is highly stable to delay spread (Delay Spread), the diffusion angle of arrival (Arrive of Angular Spread) performance in terms of accuracy down through the SAGE algorithm for estimating a more general calculation parameters.

T-DMB 대역에서 DAB 채널의 효율적인 채널 배치 방안

김주석,김경석,Kim, Joo-Seok,Kim, Kyung-Seok 한국인터넷방송통신학회 2011 한국인터넷방송통신학회 논문지 Vol.11 No.6

디지털 통신기술의 발전으로 아날로그 미디어들이 디지털로 전환되고 있다. 국내 라디오 방송은 아직 아날로그 방식을 통해 서비스되고 있고 디지털라디오를 위한 연구가 진행 중이다. 아날로그 방식의 주파수 효율이 저하되는 등의 기술적인 한계 때문에 외국에서는 이미 라디오의 디지털 전환이 보편적으로 이루어져 있다. DAB는 디지털 라디오 방식중 하나로써, 기존 AM/FM 대역을 사용하지 않고, T-DMB 대역을 이용한다. 따라서 기존 라디오 방송에 간섭없이 동시 방송을 할 수 있다는 장점이 있다. 반면에 이미 사용중인 T-DMB 방송에 간섭을 주지 않고 채널을 배치해야 하는 문제점이 있다. 본 논문에서는 T-DMB 대역에서 디지털 라디오를 위한 효율적인 DAB 채널배치 방안을 제안한다. 기존 T-DMB 방송에 간섭을 주지 않고 DAB 방송채널을 배치하였고, 모의실험을 통해 간섭영향을 도출하여 제안된 방안을 검증하였다. Analog medias are converting to digital with the development of the digital communications. The Korean radio broadcasting services yet on analog and the research for the digital radio is progressing. The digital conversion of radio broadcasting has already progressed in foreign countries because of the technical limitation of analog broadcasting(The radio-frequency efficiency is poor). DAB is one of the digital radio mode, it doesn't use on AM/FM band and uses on T-DMB frequency band. So, it has an advantage of being able to broadcast with the existing radio without interference at once. On the other hand, it has the potential to cause interference to existing T-DMB broadcasting. In this paper, we propose an efficient DAB channel allocation method for digital radio on T-DMB frequency band. This paper allocates the DAB channel without interference to existing T-DMB broadcasting and proves the proposed method through simulations for the interference analysis.

재충전이 가능한 박막전자용 $LiMn_2O_4$ 박막 전지의 전기화학 특성 분석

김주석,정헌준,김찬수,주승기,Kim Joo-Seok,Jung Hunjoon,Kim Chan-Soo,Joo Seung-Ki 한국전기화학회 2000 한국전기화학회지 Vol.3 No.3

[ $LiMn_2O_4$ ]박막전지의 충방전 사이클에 따른 용량 감소의 원인을 파악하기 위하여, $LiMn_2O_4/1M\;LiClO_4-PC/Li$전지를 구성하여 충방전 사이클에 따른 AC impedance분석을 수행하였다. 적절한 등가회로를 이용하여 비선형 최소자승 맞춤에서 얻은 값이 Impedance측정 결과와 잘 일치하였다. 충방전에 따른 정전용량은 초기의 급격한 감소를 보인 이후 완만한 감소를 보였다. 충방전 사이클이 초기 70-100사이클까지는 저항 성분 중 양극전해질 계면의 전하 전달저항 성분이 급격히 증가하다가 이후 안정된 값을 보임으로 초기 급격한 용량변화의 원인으로 파악되었다. 전하전달 저항이 안정된 이후에는 Warburg저항이 충방전에 따라 조금씩 증가하였으며, LiMn2O4박막의 화학확산 계수가 사이클에 따라 초기 $5.15\times10^{-11}cm^2/sec$에서 800사이클이 지난 후 $6.3\times10^{-12}cm^2/sec$로 점차 감소하는 것이 관찰되어 100사이클이 후의 용량감소의 지배적 원인으로 파악하였다. Warburg저항의 증가는 Jahn-Teller변형 또는 Mn용해에 의한 것으로 추정하였다. In order to investigate the origin of capacity fading with charge/discharge cycling in $LiMn_2O_4$ thin film battery, impedance studies have been performed with increasing cycling in $LiMn_2O_4/1M\;LiClO_4-PC/Li$ cells. The fitted values obtained from impedance data show good agreements with the experimental results. Especially, the element of charge transfer resistance of $LiMn_2O_4/liquid$ electrolyte interface initially increased, and then saturated with increasing the charge/discharge cycles, which could explain the cause of initial abrupt capacity fading of $LiMn_2O_4$ thin film with cycling due to interfacial reaction. The steady capacity fading is caused by the increasing of Warburg resistance. The chemical diffusion coefficient of Li ions decreased from $5.15\times10^{-11}cm^2/sec$ at 1st cycles to $6.3\times10^{-12}cm^2/sec$ at 800th cycles, which attributed to the Jahn-Teller distortion/Mn dissolution which diminishes tetra hedral sites necessary for Li diffusion in $LiMn_2O_4$.

실내 멀티홉 VLC환경에서 디밍을 적용한 파워 성능 비교

김주석,이민정,김경석,Kim, Joo-Seok,Lee, Min-Jung,Kim, Kyung-Seok 한국인터넷방송통신학회 2017 한국인터넷방송통신학회 논문지 Vol.17 No.5

본 논문에서는 멀티 홉 VLC 환경에서 디밍 제어를 이용한 각 변조 방식의 전력 성능을 분석 하였다. 성능을 분석하기 위해서 VLC기반 실내 멀티 홉 시스템을 구성하였으며, OPPM과 VPPM의 두 가지 변조 방식 기법을 적용하였다. 시뮬레이션은 송신 전력과 수신 전력을 고려하여 각 변조기법의 dimming 제어 및 홉 수에 따라서 수행하였다. 그 결과, 변조에 따른 송신 전력 및 수신 전력에서, dimming이 증가함에 따라, OPPM은 VPPM보다 적은 전력 성능을 갖으며, 수신 전력 대 홉 수 및 dimming이 50 % 일 때, 홉 수가 증가하고 거리가 길수록 VPPM 및 OPPM의 수신 전력은 급속히 감소하는 것으로 나타났다. Visible light communication (VLC) offers communication function in addition to illumination. Because the signal communication capacity per cable is 1,000 times compared to the power line communication (PLC), optical fiber is being advertised as the basis of the information and communication. Also dimming control of LED is an important component needed to provide energy savings and quality of life. This study configured multi-hop VLC system model in a building using optical fiber and analyzed the power performance of two of modulations using dimming techniques. The transmission power and received power were used to compare the power performance in multi-hop VLC environments.

IEEE 802.22 WRAN에서 Cognitive Radio를 위한 효율적인 Spectrum 할당 기법

김주석,김경석,박우구,김진업,Kim, Joo-Seok,Kim, Kyung-Seok,Park, Woo-Goo,Kim, Jin-Up 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.12b

주파수 자원 가치는 무선통신의 발전과 함께 더욱 커지고 있다. 하지만 앞으로 정보화 사회에서는 주파수 자원의 수요가 공급에 비하여 매우 많기 때문에 주파수 부족 현상이 심각하게 대두된다. 따라서 사용되지 않고 있는 주파수 자원을 효율적으로 이용하기 위한 기술로서 최근 각광을 받고 있는 Cognitive Radio 기술이 필요한 시점이다. 본 논문에서는 CR 기반의IEEE 802.22 WRAN 환경에서 효율적인 Dynamic Spectrum Allocation 기법을 제안한다. Spectrum을 좀 더 효율적으로 공유하기 위해 Variable bandwidth, Mobility의 변수를 적용한 Dynamic Spectrum Allocation 기법을 제시하고 시뮬레이션 결과들을 통해 이를 검증하였다. Frequency resource value is growing bigger more with the development of the wireless communication. But Frequency shortage phenomenon is risen seriously because the need of Frequency resource is very many compared with the supply in an information society of the future. So we need Cognitive technique Radio which is taking the attention recently to use Frequency resource not to be not using efficiently. We propose efficient Dynamic Spectrum Allocation method in IEEE a 802.22 WRAN environment of CR foundation in this paper. To share spectrum more efficiently, we presented some Dynamic Spectrum Allocation technique to apply the Variable bandwidth, Mobility and verified this through the result of the simulations.

퍼지추론을 이용한 저항 점용접부위의 품질평가 알고리듬

김주석,이재익,이상룡,Kim, Joo-Seok,Lee, Jae-Ik,Lee, Sang-ryong 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3

In resistance spot weld, the assurance of weld quality has been a long-standing problem. Since the weld nuggets if resustance spot welding form between the workpieces, visual detection of defects in usually impossible. Welding quality of resistance spot welding can be verified by non destructive and destructive inspections such as X-Ray inspection and testing of weld strength. But these tests, in addition to being time-consuming and costly, can entail risks due to sampling basis. The purpose of this study is the development of the monitoring system based on fuzzy inference, aimed at diagonosis of quality in resistance spot welding. The fuzzy inference system consists of fuzzy input variables, fuzzy membership functions and fuzzy rules. For inferring the welding quality(strength), the experimental data of the spot welding were acquired in various welding conditions with the monitoring system designed. Some fuzzy input variables-maximum, slop and difference values of electrode movement signals-were extracted from the experimental data. It was confirmed that the fuzzy inference values of strength have a .${\pm}$5% error in comparison with actual values for the selected welding conditions(9-10.5KA, 10-14 cycle, 250-300 $kg_f$). This monitoring system can be useful in improving the quality assurance and reliability of the resistance spot welding process.

펨토초 레이저 어블레이션을 이용한 Si 웨이퍼의 미세 관통 홀 가공

김주석,심형섭,이성혁,신영의,Kim, Joo-Seok,Sim, Hyung-Sub,Lee, Seong-Hyuk,Shin, Young-Eui 한국마이크로전자및패키징학회 2007 마이크로전자 및 패키징학회지 Vol.14 No.3

The main objectives of this study are to investigate the micro-scale energy transfer mechanism for silicon wafer and to find an efficient way for fabrication of silicon wafer through-hole by using the femtosecond pulse laser ablation. In addition, the electron-phonon interactions during laser irradiation are discussed and the carrier number density and temperatures are estimated. In particular, the present study observes the shapes of silicon wafer through-hole with $100\;{\mu}m$ diameter and it also measures the heat-affected area and the ablation depths fur different laser fluences by using the optic microscope and the three-dimensional profile measurement technique. First, from numerical investigation, it is found that the nonequilibrium state exists between electrons and phonons during laser irradiation. From experimental results, it should be noted that the heat-affected area increases with laser fluence, and the optimal conditions for through-hole formation with minimum heat affected zone are finally obtained. 본 논문에서는 펨토초 레이저를 사용하여 정밀하고 효과적인 레이저 어블레이션 작업이 가능한지를 확인하기위한 수치 해석 및 가공 작업을 수행하였다. 이를 위하여 Si 재료 내부의 에너지 전달 메커니즘에 대한 수치해석을 실시하였으며, Si 웨이퍼에 각각 다른 조건으로 적용된 레이저 플루언스 값으로 $100\;{\mu}m$ 직경의 미세 관통 홀을 형성한 후, 광학현미경과 3차원 표면 형상 측정 장비를 사용하여 형성된 미세 관통 홀의 가공성과 열영향부의 발생 정도를 관찰하고 분석하였다. 실험 결과를 통해 레이저 플루언스 조건에 따른 열영향부의 발생 정도를 분석하였으며, 또한 최소한의 열영향부를 가지며 우수한 홀 가공성을 보이는 최적의 미세 관통 홀 가공 조건을 도출하였다.

차량용 연료첨가제 위험성 평가 연구

김주석(Joo Seok Kim),나용운(Yong Un Na) 한국화재소방학회 2022 한국화재소방학회 학술대회 논문집 Vol.2022 No.추계

현재 차량 연료 효율을 높이기 위해서 차량용 연료첨가제를 사용한다. 차량용 연료첨가제의 경우 인화성액체로 추정되는 물질이다. 이 물질의 경우 대형쇼핑몰, 인터넷, 자동차용품 판매점, 주유소 등에서 쉽게 구할 수 있다. 따라서 주변에서 쉽게 구할 수 있는 인화성액체로 구성된 차량용 연료첨가제의 위험성을 평가할 필요가 있다. 본 연구에서는 현재 가장 많이 유통되고 사용되는 차량용 연료첨가제의 위험성 평가 및 분류 기준을 위험물안전관리법의 시험방법과 「UN 위험물 운송에 관한 권고 모델 규칙(Recommendations on the Transport of Dangerous Goods Manual Regulations)」의 시험방법으로 위험성을 평가 차량용 연료첨가제의 위험성을 확인하였다. 대부분 관련법을 만족하나, 외국산의 경우 위험성 평가가 제대로 이루어지지 않아 위험성 표기가 누락, 소량포장의 경우 위험성 표시 예외 사항에 해당하는 물질로 주의 문구가 표시되지 않은 제품도 있었다. 차량용 연료첨가제는 위험물안전관리법상 위험물로 분류, 대부분의 연료첨가제가 제4류 위험물 제2석유류, 일부 제품은 제1석유류, 제3석류유로 분류되었다. 「UN 위험물 운송에 관한 권고 모델 규칙(Recommendations on the Transport of Dangerous Goods Manual Regulations)」에서 60도 이하의 인화점을 가지는 액체는 위험물을 Packing Group으로 관리하고 있다. 따라서 화재 예방과 안전 확보를 위해서 판매 유통과정에서 안전관리가 필요하다. 대부분의 연료첨가제는 개방식 인화점 측정에서 인화가 되는 동시에 연소가 되는 현상이 확인되었다. 높은 상대 휘발도 또는 물질 고유의 증기압이 낮아 외부의 열원으로 인하여 쉽게 인화성 증기 발생하여 쉽게 점화되는 것으로 추정된다. 차량 엔진 내에서 연소를 촉진하여 미연소물질을 제거하는 것으로 추정된다.

문서감정인 자격에 관한 개선방안

김주석 ( Kim Joo-seok ),박우경,서용성 사법정책연구원 2022 연구보고서 Vol.2022 No.5

Both domestically and globally, document examination has played an important role by revealing the author of the related document in various cases. Despite the importance of document examination, controversy over the qualification of document examiners continues to date. Given the feature of the document examination expertise, which presupposes legal disputes and does not have national or official qualification system, it can be said that the management of the qualification of document examiners is virtually left to the court. Document examination is an examination on specific facts, and the examiner selection/ management process is governed by the Supreme Court Judicial Directives on the Examination (hereinafter referred to as “Examination Directives”) likewise other areas of expert examination. A person who wants to become a document examiner candidate applies for registration on the list of examiners every year in accordance with the Examination Directives, and is subject to registration on the list of examiners after undergoing qualification screenings by the National Court Administration and the courts or their branches of various levels. However, the procedure for selecting and managing document examiners as stipulated in the Examination Directives is carried out in a stereotyped manner and is focused only on ex-post evaluation, so it is hard to admit that substantial qualification management is being performed properly. For example, in the course of qualification screening for applicants, the review has customarily been done over the documents such as career or training certificates, and evaluations by judges in individual cases are left not actually conducted. Furthermore, criminal record check on the applicants for examiners is regarded as futile because the relevant agency unfailingly denies the inquiry on the ground that it has no legal basis. In order to improve the qualification management of document examiners, efforts should be made to get suggestions by comparatively scrutinizing foreign examples.  In Anglo-American Law countries, a document examiner becomes an expert witness of specific party and testifies in court according to the adversarial system. In England, as the Rule Against Comparison of Hands was abandoned, document examiners have appeared as expert witnesses in a full-fledged way. While their professional qualifications are leniently recognized by the courts, the Chartered Society of Forensic Science is managing their qualifications by operating an accreditation system for forensic practitioners, which aims to endow the qualification of expert witness in courtrooms. In the United States, some courts and scholars have raised questions about the methodologies of document examination. But currently, the qualification of a document examiner is the main issue in determining the admissibility or competency of his or her testimony in the individual case on the premise that practical expertise in document examination is generally admitted. On the other hand, standardization of the methodologies and training/education was attempted in order to increase the reliability of document examination, and with the support of public entities, authoritative certification bodies were created regarding the qualification of document examiners. In Civil Law countries, document examiner is perceived as a neutral assistant to a judge. Document examiners in France are managed within the large framework of the judicial examiner system. Several entities are involved in qualification screening for the registration on the list of examiners, including the chief prosecutor, the general meeting of judges, and the review committee composed of judges, prosecutors, and examiners. Examiner disciplinary system is a characteristic feature. Document examiners in Germany are publicly appointed and managed by Chambers of Commerce. Some German state courts have established and operated examiners quality management circles and have provided useful feedback to examiners by way of using judge questionnaires. In Austria, pursuant to the Examiner Act, an individual statute, the court officially appoints an examiner after a review by the qualification committee. In principle, document examiners must be registered on the list of examiners in order to perform an examination, and the list is made public online. Although Japan is a Civil Law country, the courts do not conduct qualification screening in every area of examination, except for the fields of medicine and architecture, where committees composed of both expert and lawyer members are involved in the selection and management of each examiner. The courts usually select examiners on the recommendation of the parties in other areas of examination, including document examination. In general, the courts strictly decide on the credibility of the document examination, and do not differentiate in the weight of the evidence between the court examination and the party’s private examination. The qualification of a document examiner should be determined to ensure both the integrity or ethics and the expertise. Specific improvement measures to secure these objectives are presented as follows. First of all, substantial qualification screening of document examiners shall be implemented. To this end, the document examiner selection and management committee should be established, and the document examiner qualification test ought to be entrusted to the National Forensic Service so that it could be properly carried out. Moreover, the factors of the evaluation standard table would have to be changed, and facilities and equipments standard needs to be reorganized as well. Judges’ evaluations of examiners in specific cases and the list adjustment system should also be activated. Next, considering the circumstances under which the courts across the country use the same list, and also the necessity to centralize the diversified affairs, the Minister of the National Court Administration, instead of chief judges in each level of courts and their branches, should be in charge of the training/education instruction for document examiners. Financial support and practical guidance for the training/education needs to be provided, and subsequent results of the training/education shall be reflected on the re-registration of the current examiners. Furthermore, to improve disqualification check, it is also proposed to provide the legal grounds for criminal record inquiry of examiner candidates. Last but not least, it is additionally suggested that (i) the norms having binding force with regard to the selection and management of the list of examiners be restructured by elevating from the level of the Supreme Court Judicial Directives to the level of the Supreme Court Rules or the Statutes, (ii) the meaning of ‘training’ as in the qualification requirement be clearly defined as indicating an apprenticeship, (iii) the list of examiners be made public, (iv) the registration period be extended, and (v) the fees be raised realistically.

에틸 알코올을 포함한 손소독제 위험성 평가 및 분류에 관한 연구

김주석(Joo-Seok Kim) 한국화재소방학회 2020 한국화재소방학회논문지 Vol.34 No.6

코로나 바이러스 감염증(COVID-19) 증가로 개인위생과 감염병 예방을 위한 손소독제의 사용이 증가하고 있다. 대부분의 손소독제는 에틸 알코올이 다량으로 함유되어 있다. 위험물로 의심되는 손소독제 14종의 위험성을 분석해본결과 7종의 손소독제가 에틸알코올의 함량이 60 wt% 이상 함유, 인화점이 22.0 ℃ 이하로 측정되었다. 위험물안전관리법은 에틸 알코올의 함량, 인화점 및 연소점으로 위험물 여부를 분류한다. 그러나 국제기준에서는 인화점, 초기끓는점 및 연소지속성으로 위험물 여부를 분류한다. 에틸알코올 수용액을 UN GHS (화학물질에 대한 분류ㆍ표시 국제조화 시스템)과 UN RTDG (유엔 위험물운송권고안)으로 분류한 결과, 표지기준에서는 모두 인화성액체로 분류,UN RTDG (유엔 위험물운송권고안)은 연소지속성 실험결과에 따라 40 wt% 에틸 알코올수용액부터 인화성액체로 분류되었다. 60 wt% 에틸 알코올 수용액의 인화점은 22 ℃, 연소점은 33 ℃로 확인되었다. The use of hand sanitizers for personal hygiene and the prevention of infectious diseases is increasing due to coronavirus(COVID-19) infections. Most hand sanitizers contain a significant amount of ethyl alcohol. This study analyzed 14 typesof hand sanitizers suspected of being dangerous and showed that seven of them contained more than 60 wt% of ethylalcohol and had a flash point of 22.0 ℃ or less. The Hazardous Substances Safety Control Act classifies hazardoussubstances by the content, flashpoint, and fire point of ethyl alcohol. However, international standards classify hazardoussubstances by the ignition point, initial boiling point, and combustion persistence. Both the United Nation GlobalHamonized System of Classification and Labelling Chemical (UN GHS) and United Nation Recommendation on theTransport Dangerous Goods (UN TRDG) classify hand sanitizers as flammable liquids. In addition, the UN RTDG classifies40 wt% ethyl alcohol receptors as flammable liquids, according to sustained combustibility experiments. Meanwhile, the 60wt% ethyl alcohol solution is found to have a flash point of 22 ℃ and a fire point of 33 ℃ for combustion.