Coating with boron nitride on SiC fiber using atomic substitution

Woo‑Seong Tak,Jin‑Uk Hwang,Young‑Keun Jeong,Woo‑Sik Kim 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.2

To increase the mechanical properties of ceramic matrix composite, it is important that formation of lubricant layer for crack deflection between matrix and fiber. Therefore, we fabricated uniform boron nitride (BN) lubricant layer using atomic substitution method. Silicon carbide (SiC) fiber surface was modified with amine groups using (3-amonipropyl)triethoxysilane to coat SiC fiber with BN as a solid lubricant. Then, surface was coated with graphene oxide (GO). Boric acid powder was supplied to the GO-coated fibers and the samples were heat-treated at 1200–1400 ℃ under N2 and NH3 atmospheres. An uniform BN layer could be coated on SiC fiber with 10 nm-1.11 μm. Crystallinity and thickness of BN layer could be controlled by reaction temperature. It was also confirmed that crystalline BN formed under process conditions of higher than 1400 ℃.

학점은행제 도입을 위한 소고

도성탁,박재원 대구보건대학 2003 대구보건대학 論文集 Vol.23 No.-

The Credit Bank System (CBS) is an open educational system which recognizes diverse learning experiences gained not only in-school but also out-of-school. When the learner accumulates the necessary CBS-approved credits, he/she can be awarded a degree. The Credit Bank, a central agency for continuing education, aims to provide all citizens with greater access to a variety of educational opportunities and to foster a lifelong learning society. Between May and December 1997, the accreditation system and standardized curriculum were developed and the first proposal for accreditation of educational institutes and curricula were evaluated. In March 1998, with effective of Enforcement Decree and Regulations of the Act on the Credit Recognition, the first stage of implementation was begun. There was a considerable increase in the number of students who took a degree from CBS year after year. Therefore it is desirable to introduce credit bank system into Daegu Health College(DHC). To operate CBS in DHC, we must get certification for standardized studying subjects from Ministry of Education & Human Resources Development. DHC can manage only 15 subjects in the first year of running CBS. So, cultural subjects is thought to have advantage over major subject. It is desirable to determine the major subjects according to students desires.

성능향상을 위한 멀티스레드 구조의 TMN Agent Platform 설계 및 구현

김성우,김영탁 嶺南大學校 工業技術硏究所 1998 工業技術硏究所論文集 Vol.26 No.2

TMN(Telecommunications Management Network) Agent manages the network element's operational status and real-resources of network elements, such as exchange, transmission systems. It performs the requested management functions from manager and maintains consistent status data of real-resource. The agent system affects directly the performance of network management operation. When the agent implements sequential processing with single process the agent processing can be blocked according to the status of real-resources. This problem can be solved by parallel and distribute processing scheme. To improve the TMN Agent, we propose TMN Agent Platform's functional architecture based on parallel processing with multi-thread and effective message transferring scheme between agent and various real-resource. We also propose CMIP(Common Management Information Protocol)-over-ATM(Asynchronous Transfer Mode). We implemented TMN Agent Platform and analyze of its performance.

저장기간에 따른 3개 수종의 종자 및 발아 특성 변화

한심희,김찬수,장석성,이현주,탁우식 한국농림기상학회 2004 한국농림기상학회지 Vol.6 No.3

This study was conducted to examine the changes in the seed physical characters and germinative properties of three tree species at three different storage times in order to determine the most suitable storage time and condition. Seed physical characters and germinative properties were examined from seeds of Fraxinus rhynchophylla, Zanthoxylum schinifolium and Staphylea bumalda that were stored at -18C for 1, 3 and 10 years, and the growth performance and physiological characters of their seedlings were analyzed. Seed physical characters and germinative properties showed significant differences between three storage times as well as three tree species. Seed moisture content of F. rhynchophylla and S. bumalda and seed fresh weight of Z. schinifolium decreased with increase of storage time. Storage time represented negative correlation with moisture content and fresh weight (r = -0.822, p < 0.01). Seed percent germination of Z. schinifolium and S. bumalda stored for 3 and 10 years decreased less than 15% and 10.7% respectively. Mean germination times for seed of F. rhynchophylla, Z. schinifolium and S. bumalda were delayed 11.9, 5.7 and 9.7 days after a storage time of 10 years, respectively. However the growth and viability of seedlings didn't show a special pattern for storage time and tree species.

Preparation and Properties of Hydroxyapatite/Methylcellulose for Bone Graft

Tak, Woo-Seong,Kim, Dong-Jun,Ryu, Su-Chak The Korean Ceramic Society 2018 한국세라믹학회지 Vol.55 No.2

Although many bone graft materials have been developed, powder graft materials are somewhat difficult to use in surgery. To solve this problem, a bone graft material in the form of a viscous paste was prepared. Hydroxyapatite was used as a bone graft material, and methyl cellulose was used to impart viscosity. Three cases of samples were prepared, and freeze-dried block type and sintered specimens were made from the paste. The recrystallization of the graft material in a simulated body fluid and the degree of graft adhesion with a tooth were observed by scanning electron microscopy (SEM). The test for cytotoxicity was carried out and the sample was grafted into the back of a mouse to confirm the presence or absence of side effects in the animal's body. Based on these investigations, composites of this type are expected to be applicable for bone grafts.

자동차 조향장치용 TAS module을 위한 Multi-track Encoder기반 신호처리보드의 구현

우승탁 ( Seong Tak Woo ),한춘수 ( Chun Soo Han ),백준병 ( Jun Byung Baek ),이상훈 ( Sang-hoon Lee ),정민우 ( Min Woo Jung ),추성중 ( Sung Joong Choo ),박재률 ( Jae Roul Park ),유종호 ( Jong-ho Yoo ),정상훈 ( Sanghun Jung ),김주영 한국센서학회 2017 센서학회지 Vol.26 No.6

As 4.0 industry has been developed, research on a self-driving car technology and related parts of an automobile has been highly investigated recently. Particularly, a TAS(Torque Angle Sensor) module on steering wheel system has been considered as a key technology because of its precise angle, torque detection and high speed signal processing. The environmental assessment is generally required on the TAS module to examine high resolution of angle/torque detection. In the case of existing TAS module, angle detection errors has been occurred by back-lash on main and sub gear in addition to complicated structure caused by gears. In this paper, a structure of the TAS module, which minimizes the numbers of components and angle detection errors on the module compared with the existing TAS module, for vehicle steering system based on a Multi-track Encoder has been proposed. Also, angle detection signal processing board, and key technology of the TAS module were fabricated and evaluated. As a result of the experiments, we confirmed an excellent performance of the fabricated signal processing board for angle detection and an applicability of the fabricated angle detection board on the TAS module of vehicles by the environmental assessment an automobile standard.

저작운동으로 인한 진동 잡음 신호의 경감을 위한 측두골 이식형 마이크로폰의 설계

우승탁 ( Seong Tak Woo ),정의성 ( Eui Sung Jung ),임형규 ( Hyung Gyu Lim ),이윤정 ( Yun Jung Lee ),성기웅 ( Ki Woong Seong ),이정현 ( Jyung Hyun Lee ),조진호 ( Jin Ho Cho ) 한국센서학회 2012 센서학회지 Vol.21 No.2

A microphone for fully implantable hearing device was generally implanted under the skin of the temporal bone. So, the implanted microphone`s characteristics can be affected by the accompanying noise due to masticatory movement. In this paper, the implantable microphone with 2-channels structure was designed for reduction of the generated noise signal by masticatory movement. And an experimental model for generation of the noise by masticatory movement was developed with considering the characteristics of human temporal bone and skin. Using the model, the speech signal by a speaker and the artificial noise by a vibrator were supplied simultaneously into the experimental model, the electrical signals were measured at the proposed microphone. The collected signals were processed using a general adaptive filter with least mean square(LMS) algorithm. To confirm performance of the proposed methods, the correlation coefficient and the signal to noise ratio(SNR) before and after the signal processing were calculated. Finally, the results were compared each other.

Study of Oxygen Additive Effect in High Aspect Ratio Contact Etching using High Polymer Forming Hydrofluorocarbon Isomers

Hyun Woo Tak,Seong Bae Kim,Chan Hyuk Choi,Seul Ki Kim,Dong Woo Kim,Geun Young Yeom 한국표면공학회 2023 한국표면공학회 학술발표회 초록집 Vol.2023 No.11-1

친환경 바이오 투수 블록의 개발

송현우(Hyun-Woo Song):이중우(Joong-Woo Lee):권성민(Seong-Min Kwon),이태형(Tae-Hyeong Le),오영탁(Yeong-Tak Oh) 한국항해항만학회 2018 한국항해항만학회 학술대회논문집 Vol.2018 No.추계

지구온난화에 따른 연안의 해수면 상승은 해안에 가해지는 파랑에너지의 상승을 유발한다. 이러한 해수면의 상승은 상대적으로 수심이 깊어지는 효과를 초래하고 이는 과거 발생하지 않았던 해안지역의 침식 및 해빈에서의 모래를 유실시킨다. 특히, 국내 연안 225개소의 연안 모니터링 결과 142개소인 62%가 침식우려 이상의 등급으로 나타났다. 일반적으로 연안침식에 대응하는 방법은 호안을 쌓아 보호하게 되는 경성공법으로 외력의 변화에 따라 현장여건에 맞는 호안의 경사, 단면형상 및 재료를 선택하게 된다. 하지만 현상에 대한 불충분한 이해에 근거한 공법 적용으로 제반국가에서 다양한 피해가 발생하고 있으며, 이는 공법신뢰도 향상을 위한 기술개발 및 융합기술 도입의 필요성을 보여 준다. 본 연구는 파랑저감에 효과적인 다공성 구조물Biocoast를 활용하여 해안침식피해억제를 위한 친환경 투수 바이오 콘크리트 블록을 개발 하였다. 특히, 자연해변 및 호안시설에 대해 자연 및 인위적 외력에 의한 침식과 세굴로부터 연안을 보호하고, 블록의 유닛화를 통해 품질관리및 공정관리의 효율성을 향상시킬 수 있을 것으로 사료된다.

A Feasibility Study on the Use of Optical Fibers for the Transfer of Scintillation Light to Silicon Photomultipliers

Seong Jong Hong,Chan Mi Kim,Sung Mook Cho,Heon Woo,Guen Bae Ko,Sun Il Kwon,June Tak Rhee,In Chan Song,Jae Sung Lee IEEE 2011 IEEE transactions on nuclear science Vol.58 No.3

<P>Integrated PET/MRI units with simultaneous acquisition capability are set to play an important role in studies of human breast and prostate imaging and brain function. However, to take advantage of existing MRI units in hospitals and institutions, minimally modified combined PET MRI is highly desirable. In addition, the current MRI trend is to utilize powerful body coils to transmit radio-frequency (RF) waves and local RF coils to receive signals. The authors propose a silicon photomultiplier (SiPM) PET equipped with optical fiber bundles that transfer photons from scintillation crystal to SiPM. To investigate the feasibility of SiPM PET using optical fiber bundles, the authors studied the performances of SiPM/scintillator couplings using single optical fibers and a fiber bundle. GEANT4 Monte-Carlo simulation was used to study scintillation photon transfer from scintillation crystals to the SiPM. This simulation showed that light loss, due to the bending of an optical fiber, is not significant for a fiber with a diameter of 2.0 mm and a bending radius of greater than 25 mm. To validate the GEANT4 Monte-Carlo simulation, several simple detectors were assembled and tested. Simulation results agreed reasonably well with experimental results. Two Hamamatsu multi-pixel photon counters (MPPCs) were tested using double clad optical fibers of 1.5 mm and 2.0 mm diameter, and 25 mm and 50 mm bending radius, respectively. When two MPPCs were directly attached to 2.0 × 2.0 × 10.0 mm<SUP>3</SUP> LYSO crystals, a ~14% energy and a ~1.3 ns coincidence timing resolution were obtained at full width half maximum (FWHM). With one of the MPPCs attached to an optical fiber of 1.5 mm diameter, 50 mm bending radius, and length 300 mm, energy and coincidence timing resolutions were 27% and 2.2 ns, respectively. With an optical fiber bundle made of bare fibers with 1.5 mm diameter and length 100 mm, an ~ 26% energy resolution was obtained. Even though the Monte-Carlo simulation showed light loss was not significant for a single 90° turn of bending, the mechanical integrity of the optical fiber, especially the absence of cracks which can be caused by sharp bending, seemed to be a far more important constraint on sharp bending. These initial results are encouraging with respect to the use of combined SiPM PET using optical fibers.</P>