해상 HF대역 디지털 데이터 교환을 위한 통신시스템 분석 및 제안

최성철,소지은,박형철,Choi, Sung-Cheol,So, Ji-Eun,Park, Hyung-Chul 한국정보통신학회 2017 한국정보통신학회논문지 Vol.21 No.12

IMO (International Maritime Organization) has been providing GMDSS (Global Maritime Distress and Safety System) and mandating to install distress and safety systems according to SOLAS. Digital-HF(High-Frequency) coast station communication system maintains interoperability between ship and coast station and digital data exchange in maritime mobile service by digitizing existing analog base voice communication. In this paper, we analyze ITU-R M. 1798-1 established by ITU for digital HF communications and propose Advanced annex2 and new Annex 5 to improve the problems of the existing Annex 2 and Annex 4. The proposed OFDM protocol basically adopts ARQ (Automatic Retransmission Request) which retransmits when an error occurs in a half-duplex manner between an information transmitting side (ISS) and an information receiving side (IRS) and we propose a digital HF communication system and its operational concept which is more reliable and superior than the existing ITU-R M. 1798 by implementing technical development on implementation and performance improvement. 해상통신은 국제해사기구(International Maritime Organization, IMO)에서 세계 해상 조난 및 안전제도(Global Maritime Distress and Safety System, GMDSS)를 마련하고, SOLAS 규약에 따라 조난 및 안전 시스템을 탑재하도록 의무화하고 있다. Digital-HF(High-Frequency) 해안국 통신 시스템은 선박과 해안기지국 사이에 상호 운용성을 유지하며, 기존 아날로그 기반의 음성통신을 디지털화하여 해상이동업무에서 디지털 데이터 교환을 하기 위한 시스템이다. 본 논문은 디지털 HF통신을 위해 ITU에서 제정한 ITU-R M.1798-1을 분석하고, 기존 Annex 2와 Annex4의 문제점을 개선하여 Advanced annex2와 새로운 부속서인 Annex 5를 제안하고자 한다. 제안된 OFDM 프로토콜은 기본적으로 정보 송신측(ISS)과 정보 수신측(IRS)간의 반이중화 방식으로 에러발생시 재전송을 하는 ARQ(Automatic Retransmission Request)방식을 취하고 있으며, 이에 상응하는 구현 및 성능향상에 관한 기술적 개발을 하여 기존에 제시된 ITU-R M.1798-1보다 안정성과 우수성을 확보한 디지털 HF 통신시스템을 제안하고자 한다.

유치열기의 치아 외상에 관한 연구

최성철,박재홍,이긍호,Choi, Sung-Chul,Park, Jae-Hong,Lee, Keung-Ho 대한소아치과학회 2003 大韓小兒齒科學會誌 Vol.30 No.4

The purpose of this study was to analyze the traumatized primary teeth and investigate the occurrence, types, area, cause, place of trauma to primary teeth and seasonal variation in a hospital population, and to evaluate the interval between injury and treatment. A total 411 children with 745 traumatized teeth participated in this study from 1998 to 2000. The results were as follows : 1. There were slightly more boys than girls giving a male-to-girl ratio of 1.74:1.0. The 1-2, 2-3 year old boys and girls had the highest number of traumatic injuries to their primary dentition. 2. The most common injury was concussion. 3. The majority of traumatized teeth are the upper primary central incisors. 4. Falling down was the most common cause of injury in both sexes. The most of the injuries occurred inside home. 5. 46% of the children visited the dental office within 24 hours after traumatic injury. 6. The most common month was October(12.7%), and June(12.2%), May(11.7%) were followed. 본 연구는 경희대학교 치과대학병원 소아치과에 치아외상을 주소로 내원한 411명의 어린이를 대상으로 치아외상의 발생 연령과 남녀간의 성차, 발생의 양상, 부위, 원인, 장소 및 외상 후 내원 시기와 계절적인 발생빈도 등을 조사하여 외상의 예방, 적절한 진단과 치료 그리고 보호자의 계도 및 외상에 관한 홍보에 도움이 되고자 시행하였다. 1998년부터 2000년 사이에 치아외상을 주소로 내원한 환자 중 생후 5개월에서 6세 사이 남아 261명, 여아 150명의 외상치아 745개를 대상으로 다음과 같은 결과를 얻었다. 1.치아 외상은 남아가 여아보다 1.74배 많은 것으로 나타났으며, 남녀 모두 $1{\sim}2$세(34.1%) 및 $2{\sim}3$세(24.3%) 사이에 많이 발생하였다. 2. 치아 외상 양태는 진탕 32.2% 함입 11.9%, 측방변위 10.1%의 순으로 나타났다. 3. 상악 유중절치가 외상 치아의 75.3%로 가장 많이 발생하였다. 4. 치아 외상의 원인은 '넘어짐' 46.0%, '부딪힘' 40.3%, '떨어짐' 6.0% 순으로, 장소는 집안 48.0%, 집밖 37.7%, 유치원 9.2% 순으로 발생하였다. 5. 치아 외상 후 24시간 내에 내원하는 경우가 46.0%, 1주일내 29.5%, 1시간내가 7.5%를 보였다. 6. 월별 치아 외상은 10월(12.7%), 6월(12.2%), 5월(11.7%) 순으로 발생하였다.

Purification and Biocompatibility of Fermented Hyaluronic Acid for Its Applications to Biomaterials

최성철,Woncheol Choi,Sekweon Kim,Su Yeon Lee,노인섭,김찬화 한국생체재료학회 2014 생체재료학회지 Vol.18 No.2

Background: Hyaluronic acid (HA) is of importance due to its diverse applications in pharmaceuticals and medical devices such as dermal filler, adhesion barriers, carrier for cells and bioactive molecules as well as scaffold biomaterials for tissue engineering. Evaluations of purification and biocompatibility of HA are required for its applications to biomaterials. Methods: After synthesizing HA by fermentation of streptococcus zooepidemicus for 25 hr, extensively purification of the fermented broth was performed to remove impurities using a filtration process for insoluble components and cells, and diverse adsorbents for soluble impurities. Its in vitro biocompatibility has been evaluated by measurement of cell counting and assay of cell live and dead. Results: 60% yield of white HA powder was obtained, having 15-17 dL/g intrinsic viscosity with a molecular weight of approximately 1,000 kDa. While low molecular weight impurities and insoluble impurities were successfully removed using a ultrafiltration membrane with 50 KDa molecular weight cut, endotoxins, high molecular weight proteins and nucleic acids were removed from the broth by employing adsorbents such as alumina and activated carbons. Alumina showed the best results for the removal of endotoxins, all of the activated carbons were very effective in the removal of high molecular weight proteins and nucleic acids. The purified HA solution showed excellent cell compatibility with no cell damages as observed by both measurement of cell proliferation and observation of cell viability. Conclusions: We obtained high molecular weight HA with excellent biocompatibility as judged by both measurement of cell proliferation and viability, indicating high possibility of its applications to biomaterials.

Growth of silicon carbide nanowires on porous silicon carbide ceramics by a carbothermal reduction process

최성철,Jin-Seok Lee,Do-Mun Choi,Chang-Bum Kim,이상훈 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.2

Porous SiC ceramics with a high specific surface area are promising candidates for catalyst support applications and further fabrication of nanowire-reinforced composites. This study employed the carbothermal reduction process using a mixed powder bed consisting of low-purity SiO2 and carbon black in order to grow SiC nanowires on phenolic resin-coated porous SiC ceramics. A nanowire grown at 1400 oC in the absence of a metal catalyst additionally introduced from the outside had a diameter of 100 nm and a length of several tens of micrometres. The carbothermal reduction method for growing SiC nanowires on surfaces as well as inner pores of porous SiC substrates involves migration and liquid droplet formation of elemental Fe generated from the mixed powder bed into the surface and the pores of the SiC substrate. Subsequently, gaseous SiO and CO from the mixed powder bed as the intermediate for 1-dimensional SiC were offered to the neighborhood of the porous substrate, and then the growth of β-SiC nanowires on α-SiC substrate occurred via a VLS mechanism. Porous SiC ceramics with a high specific surface area are promising candidates for catalyst support applications and further fabrication of nanowire-reinforced composites. This study employed the carbothermal reduction process using a mixed powder bed consisting of low-purity SiO2 and carbon black in order to grow SiC nanowires on phenolic resin-coated porous SiC ceramics. A nanowire grown at 1400 oC in the absence of a metal catalyst additionally introduced from the outside had a diameter of 100 nm and a length of several tens of micrometres. The carbothermal reduction method for growing SiC nanowires on surfaces as well as inner pores of porous SiC substrates involves migration and liquid droplet formation of elemental Fe generated from the mixed powder bed into the surface and the pores of the SiC substrate. Subsequently, gaseous SiO and CO from the mixed powder bed as the intermediate for 1-dimensional SiC were offered to the neighborhood of the porous substrate, and then the growth of β-SiC nanowires on α-SiC substrate occurred via a VLS mechanism.

차동 직교 위상 편이 변조 방식의 직교주파수 분할다중 기반 단파 대역 통신 시스템

최성철,김정년,박형철,Choi, Sung-Cheol,Kim, Jeong-Nyun,Park, Hyung Chul 한국전기전자학회 2018 전기전자학회논문지 Vol.22 No.3

본 논문에서는 차동 직교 위상 편이 변조 방식 (DQPSK)의 직교주파수 분할다중 (OFDM) 기반의 단파 (HF) 대역 통신시스템을 제안한다. 제안 시스템은 약 3 kHz의 대역폭에서 약 3.6 kbps의 전송속도를 지원한다. 디지털 변복조부는 32-point 고속 푸리에 변환 프로세스를 이용한다. 한편, 각각의 부반송파 데이터가 DQPSK 변조를 이용한다. 그래서, 복조기는 반송파 위상 복구 회로와 심볼 타이밍 복구 회로를 필요로 하지 않는 장점이 있다. 또한, 각 부반송파는 개별적으로 CRC 오류 검출 코드를 사용함으로서, 다중경로 페이딩에 의한 비트 오류를 간단히 해결할 수 있다. This paper presents a novel HF band differential quadrature phase-shift keying (DQPSK) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 3.6 kbps with a bandwidth of about 3 kHz. In a digital modem, OFDM with 32-point fast Fourier transform is used. In the system, each subcarrier uses DQPSK modulation. Hence, a demodulator does not require carrier phase recovery and symbol timing recovery. And, each subcarrier employs CRC error check code individually. By using CRC code for each subcarrier, bit error caused by multipath fading can be recovered simply.

COSMOS-standard AISBL과 우리나라 유기농 화장품 기준에 관한 분석

최성철,손상목,Choi, Sung-chul,Sohn, Sang Mok 한국유기농업학회 2015 韓國有機農業學會誌 Vol.23 No.1

The purpose of this study is to examine the tendency of certified organic cosmetics market and the certification standards and regulations they are under, compare one of the most commonly used COSMOS-standard AISBL with the Korea Ministry of Food and Drug Safety (MFDS) organic cosmetic standard regulation. And then examining their differences and any potential issues is to present suggestions to be made as data for certification standard for natural & organic cosmetics in Korea regulation. This contents of study will be used as good research and development to promote the sustainable growth of the natural & organic cosmetic ingredients which have been grown by organic farmers certified. Also certified organic ingredients may help to growth the organic industry. I believe these are actual comparative for application to develop of natural and organic cosmetics in Korea as well the strengthening of the competitiveness of organic cosmetics certified in the world.

Surface treatment of Indium Tin Oxide (ITO) thin films synthesized by chemical solution deposition

최성철,윤영훈,Jin-Woo Choi 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.4

Indium tin oxide (ITO) thin films were synthesized on glass substrates by chemical solution deposition from starting materials of Indium (III) acetylacetonate and Tin (IV) iso-propoxide. The ITO films were fired in a temperature range of 400 oC to 600 oC and annealed under N2 gas at 500 oC. The effects of surface chemical treatment on the sheet resistance of ITO films were investigated with AFM surface morphology and sheet resistance. The spin-coated ITO thin films, which was etched with KOH solution for 20 seconds, exhibited a sheet resistance value of approximately 352 Ω/square. The AFM surface morphologies of ITO thin films revealed a difference of surface roughness and morphology between the as-received films and the etched films. Also, ITO thin films showed an optical transmittance of about 90% in the range of 800 nm.

펨토초 레이저를 이용한 금속 나노패턴 형성 연구

최성철,이영락,노영철,이종민,고도경,이정훈,김강윤,김창종,이웅상,허명구,Choi, Sung-Chul,Lee, Yeung-Lak,Noh, Young-Chul,Lee, Jong-Min,Ko, Do-Kyeong,Lee, Jung-Hoon,Kim, Kang-Yoon,Kim, Chang-Jong,Lee, Ung-Sang,Heo, Myeong-Koo 한국광학회 2006 한국광학회지 Vol.17 No.2

펨토초 레이저 펄스를 이용하여 Slide glass 위에 코팅된 Al 박막표면에 나노패턴 구조를 생성하였다. 생성된 나노패턴 구조의 공간적 주기는 레이저 강도와 펄스 수에 의존함을 확인하였고, 레이저 강도와 펄스 수를 미세하게 조절함으로써 Al 샘플 표면에 균일한 나노패턴을 형성 시킬 수 있다. 이와 같은 현상은 레이저 입사빔과 샘플 표면에서 산란되는 빛의 광학적 간섭에서 야기 된다. 또한, Al 박막표면 위에 형성된 산화막이 짧은 주기의 나노패턴을 형성하는데 중요한 역할을 수행하는 것을 확인하였다. Femtosecond laser-induced nano-patterning of an Al surface coated on a slide glass is reported in this paper. It was found that the period of the laser-induced nano-patterning was much dependent on the incident laser power and pulse number. Through finely adjusting the laser power and pulse number, uniform nano-patterns could be formed on the Al surface. It is based on the interference of the incident laser beam with some form of a surface scatted electromagnetic wave. It was also found that an Al oxide layer played an important role in forming the nano-patterning on the Al surface.

초기 영구 전치 파절시의 치아 재부착술의 임상 증례

최성철,이긍호,최영철,Choi, Sung-Chul,Lee, Keung-Ho,Choi, Yeong-Chul 대한소아치과학회 2002 大韓小兒齒科學會誌 Vol.29 No.1

본 증례는 경희대학교 치과대학병원 소아치과학교실에 상악 중절치의 치수노출을 동반한 외상을 주소로 내원한 아동의 치험례이다. 증례 1은 미성숙 치근을 가지는 만 8세의 남아로 치아의 치수 노출에 따른 수산화칼슘 치수절단술을 이용한 치근단 형성술을 시행한 후 치아 재부착술을 시행한 증례이며, 증례 2는 점상의 치수노출을 보이는 미성숙 영구 중절치를 직접 치수 복조 추 석회화 층을 형성하는 기간동안 레진을 이용하여 유지한 후 치아 재부착술을 시행하였고 증례 3은 치은 연하로 치경부 파절을 보이는 만 12세의 환아로 신경치료 후 골 삭제술과 골 성형술을 동반한 판막술을 시행하여 carbon fiber post를 이용한 치아 재부착술을 시행한 증례이다 이상의 증례를 통하여 치아 재부착술을 성공적으로 시행하였으며 심미적으로 양호한 결과를 얻었기에 보고하는 바이다. When a tooth is fracture with the pulp exposure, and if a fragment is large enough to save, reattachment of the fragment would be a choice of treatment and reattachment of the fragment provides several advantages over other forms of dental restoration following crown fracture. For the purpose of tooth reattachment, it is important to preserve the sound enamel around fracture area. For young patients, tooth reattachment has more advantages in the sense that they recover faster and that it enables other treatments at the same time. Through the continuous advancement in adhesion technology and the effort for aestheticism, various reattachment methods have been practiced and more efforts are considered necessary. The presented cases are that we had practiced in our department in Kyung Hee Medical center, I may address that fragmentation has been successfully done with aesthetically fine results, and no pathologic changes were found in short term follow-ups.

Research on the Difficulty of 9th Level Dan Promotion Test of Taekwondo

Seongkon Choi,Hyoungkeun Oh J-INSTITUTE 2022 International Journal of Martial Arts Vol.7 No.1

Purpose: This study aims to analyze the essential Poomsae difficulty of Taekwondo 9th level Dan promotion test with the awareness of the problem. This will help standardize the Taekwondo curriculum in order to meet the Taekwondo education goals pursued by the Kukkiwon, the headquarters of the World Taekwondo. Method: The literature research and in-depth interviews with people to be tested were performed to analyze the difficulty of essential Poomsae of Taekwondo 9th Dan promotion test. Results: As a result of questioning and analyzing the level of difficulty of the 9th level Dan promotion winner, it was concluded that the level of difficulty of Illyo Poomsae of the 9th level Dan promotion test is not appropriate. Courses to be completed for Color and Black Belts must comply with the completion time of the essential course and the selection course. Basic courses for Black Belt (Poomsae, breaking, sparring, and KTA personality) must be completed as mandatory courses, and in-depth courses (KTA self-defence techniques, KTA practical hand skills, and KTA core exercises) must be assigned. Conclusion: It is thought that Taekwondo 9th level Dan, the highest stage of the competition held at the Kuk-kiwon of the World Taekwondo Headquarters, should be educated to learn, guide, and evaluate Taekwondo ac-cording to the standard curriculum. However, the standardized Taekwondo curriculum should be distributed in consideration of the current Taekwondo training population, where the standardized Taekwondo curriculum has not been established. Taekwondo leaders will contribute to the educational use of Taekwondo by analyzing the essential Poomsae and curriculum of Taekwondo 9th level Dan promotion test and presenting the evaluation rules based on the Taekwondo standard curriculum.