지역 서버 기능을 강화한 다중 서버 음성 수집 시스템의 개선 : CSDBWeb3.1

정경채(Kyeongchae Chung),강선미(Sunme Kang),장문수(Moonsoo Chang) 한국통신학회 2004 한국통신학회 학술대회논문집 Vol.2004 No.7

핵연료 분말제조 공정에서 발생되는 폐액으로부터 NaF 제조

정경채,정원명,김응호,박진호,황성태 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.8

BGF/PLA 복합재료를 이용한 골절치료용 고정판의 체액 노출 조건에 따른 성능평가

정경채 ( Kyung Chae Jung ),한민구 ( Min Gu Han ),( Ali Mehboob ),장승환 ( Seung Hwan Chang ) 한국복합재료학회 2017 Composites research Vol.30 No.1

본 연구에서는 일방향 생분해성 유리섬유(BGF)와 친환경 생분해성 수지인 폴리락트산(PLA)을 이용하여 골절치료용 복합재료 고정판을 제작하고 체액 노출에 따른 고정판의 성능 변화를 확인하고자 50.0°C 온도조건으로 설정된 인산완충식염수(PBS)에 제작된 생분해성 고정판을 0~3주 동안 노출시켜 질량 변화를 측정하고 4점 굽힘 실험을 수행하였다. 굽힘 강성, 수분 흡수율, 그리고 질량 감소율과 같은 기계적 특성 변화를 파악하였으며 실험 결과로부터 노출 기간이 증가함에 따라 고정판을 구성하고 있는 생분해성 재료들의 손실로 인해 기계적 물성이 서서히 저하되는 경향을 보이는 것을 확인하였다. The aim of this study is to fabricate composite bone plates consisted of unidirectional biodegradable glass fibers (BGF) and polylactic acid (PLA) and evaluate the performance of the composite bone plates according to the temperature (50.0°C) of PBS (Phosphate Buffer Saline) solution and exposure time (0~3 weeks). Mechanical characteristics, such as bending stiffness, flexural strength, water uptake and mass loss, were investigated and the results showed that mechanical properties of the plates decreased as soaking duration increased due to loss of composite material.

핵연료분말 제조에서 반응물질의 변화가 분말의 특성에 미치는 영향

정경채,박진호,황성태 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.6

The powder characteristics of UO2 via AUC prepared by precipitation from a UN with AC soiution produced from nuclear fuel powder conversion plant and that of the existing facility were compared. Mean particle size of AUC powder was decreased and agglomerates were much occured in case of using the AC solution that that of the gases but other properties such as particle size distribution and shape of particle are thought to be similarly. In compaction of UO2 powder the breaking pressur of agglomerated UO2 powder and the sintered density of final UO2 pellet from AC solution were measured 1.45$\times$108 N/m2 and 10.52 g/cc, These values could be used in nuclear fuel powder fabrication process.

액체소듐속에서 소듐-물반응에 의한 재질의 Wastage현상

정경채,정지영,김병호,김태준,최병해,최종현,김의식 한국공업화학회 2003 응용화학 Vol.7 No.1

In this study we observed and analyzed the corrosion phenomena in leak site and the effect on temperature at the target surface of heat transfer tube material by sodium-water reaction through water leakage in liquid sodium atmosphere. Surrounding of leak hole of the specimen was damaged by the wastage phenomena due to corrosion and erosion of material, and hole size by damage of leak site was extended from 150㎛ to about 200㎛. Also, the damaged size appeared in the target surface was observed to about 1000㎛ diameter. The temperature of target surface increased about 70~80℃ by the heat of sodium-water reaction even with the small leakage of 15㎖ water. From the results of EPMA and EDX analysis, damaged area are found to covered with complex compounds such as (NaOH+Na_2O) FexOy or (NaCrO_2+nA_2CrO4) mixed up with the sodium oxides by sodium-water reaction and the Fe or Cr element by matrix of tube sodium oxides by matrix of tube material.

기획사물 인터넷 : 사물 인터넷 환경에서 무선 AP의 수면 모드 운영 및 송출 전력 조절을 통한 전력 소비 절감 알고리즘

정경채 ( Kyeong Chae Jeong ),최원석 ( Won Seok Choi ),최성곤 ( Seong Gon Choi ) 한국정보처리학회 2014 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.3 No.11

최근 스마트폰을 포함한 사물 인터넷(IoT) 기술 기반의 스마트 기기의 급속한 확산에 따라 IEEE 802.11 무선 랜에서 전력 소비 또한 급격히 증가하고 있다. 특히 모바일 기기 사용자가 급격하게 증가하면서 가정이나 사무실 같은 실내 환경에서 사설 무선 AP(Access Point) 설치가 급증하고 있는 추세이다. 본 논문은 현재 무선 AP의 비효율적인 운영을 개선한 무선 AP의 전력 소비 절감 알고리즘을 제안한다. 제안한 알고리즘 동작은 STA(Station)의 무선 AP 접속 여부에 따라 구분되며, STA가 있을 경우는 STA로 전송할 데이터가 있을 때와 없을 때로 나뉜다. STA가 없는 경우, 수면 모드로 동작하여 불필요한 전력 소비를 최소화한다. 또한 추가적으로 STA가 접속을 하고 있는 경우에도 데이터를 수신하지 않을 경우에는 인증 및 결합이 유지된 상태로 수면 모드를 운영한다. STA로부터 데이터 요청이 있을 경우 STA의 거리와 전송률을 파악하여 STA의 전송률을 만족하는 최소의 송출 전력으로 패킷을 전송한다. 이때, STA와 최초로 스캔 과정을 하는 데 필요한 관리 프레임은 최대 송출 전력으로 전송한다. 본 논문에서 제시한 시나리오를 바탕으로 제안한 전력 소비 절감 알고리즘이 적용된 무선 AP에서의 전력 소비량은 기존 방안이 적용된 무선 AP와 비교하면 약 18%, 전력 소비 절감이 적용되지 않은 일반적인 무선 AP와 비교하면 약 35% 감소했다. We have experienced an explosive increase of the IoT(Internet of Things) technology based devices including smart phones and the wireless communications. Also the growing power consumption in IEEE 802.11 WLANs(Wireless LANs) driven by these dramatic increases in not only mobile users and but also wireless APs(Access Points). To reduce the power consumption, this paper proposes a wireless AP power saving algorithm, which minimizes the transmission power without decrease the transmission and carrier sense ranges. A wireless AP which is use in our algorithm checks its own original coverage periodically for whether there is a new STA(Station) or not when its transmission power is decreased. Moreover, if there are no signaling message to connect the wireless AP, it changes its operation mode Wake-up to sleep. A Result shows that the proposed AP algorithm can reduce the total power consumption of the wireless AP approximated 18% and 35% compared to the conventional wireless AP with and without the existing power saving algorithm, respectively.

고점성 모사용액 내 Carbon Black 입자의 분산특성

정경채 ( Kyung Chai Jeong ),엄성호 ( Sung Ho Eom ),김연구 ( Yeon Ku Kim ),조문성 ( Moon Sung Cho ) 한국공업화학회 2013 공업화학 Vol.24 No.2

An external gelation method in place of an internal gelation method applied to the fabrication process of an intermediated compound of Uranium Oxy-Carbide (UCO) kernel spheres for Very High Temperature Reactor (VHTR) fuel preparation is under development in Korea. For the preliminary experiments of the UCO kernel sphere preparation using an external gelation method, the carbon black dispersion experiments were carried out using a simulated broth solution. From the selection experiments of various kinds of carbon black through dispersion experiments in a viscous metal salt solution, Cabot G carbon black was selected owing to its dispersion stability, and the homogeneous dispersing state of carbon black particles in our system. For the effective dispersion of nano-size aggregated carbon black particles in a high viscous liquid, the carbon black particles in a metal salt solution were first de-aggregated with ultrasonic force. The mixed solution was then dispersed secondly by the use of the extremely high-speed agitation with a mechanical mixer of 6000 rpm after feeding the Poly Vinyl Alcohol (PVA) in the solution. This results in the broth solution with good stability and homogeneity alongside no further changes in physical properties.

나트륨-물 반응에 의한 전열관 표면에서의 부식과 반응특성에 대한 연구

정경채 ( Kyung Chai Jeong ),정지영 ( Ji Yong Jeong ),김병호 ( Byung Ho Kim ),김태준 ( Tae Joon Kim ),최종현 ( Jong Hyeun Choi ),김의식 ( Eui Sik Kim ) 한국공업화학회 2003 공업화학 Vol.14 No.1

본 연구에서는 증기발생기 전열관 재질로 예상되는 페라이트 강을 사용해서, 액체 나트륨 분위기에서 미량 물누출 실험을 수행하여, 시편의 누출 부위와 표적표면에서 발생되는 재질의 부식현상. 나트륨-물 반응에 의한 온도 상승현상 등에 대한 특성을 관찰하였다. 실험결과, 시편의 누출구멍 주변은 나트륨부위에서 나트륨-물 반응에 의해 발생되는 부식 및 침식에 의한 wastage 현상에 의해 손상을 입어 누출 구멍의 직경이 확대되었으며, 누출 부위에서의 손상은 초기 누출구멍 크기인 150㎛에서 200㎛정도로 확대되었고, 표적표면에 나타난 손상부위의 크기는 약 1000㎛ 정도로 분석되었다. 또한, 표적표면에서의 온도는 나트륨-물 반응에 의해 형성되는 반응열에 의해 약 70-80℃ 정도 상승하였으며, 손상부위 표명을 EPMA 및 EDX로 분석한 결과, 나트륨 산화물과 전열관의 모지 금속을 구성하는 Fe이나 Cr 등의 원소와 반응하여 (NaOH+Na_2O)ㆍFe_xO_y나 (NaCrO_2+Na_2Cro_4) 같은 형태의 복합산화물을 형성하는 것으로 판명되었다. In this study we observed and analyzed the corrosion phenomena in a leak site and he effect of temperature at the target surface of heat transfer tube material by sodium-water reaction through water leakage in liquid sodium atmosphere. Surrounding of the leak hole of the specimen was damaged by the wastage phenomena due to corrosion and erosion of material, and the hole size, by damage of leak site, was extended from 150㎛to about 200㎛. Also, the damaged size appeared in the target surface was observed to be about 1000㎛ diameter. The temperature of target surface increased about 70~80℃ by the heat of sodium-water reaction even with a small leakage of 15mL water. From the results of EPMA and EDX analysis, damaged areas are found to be covered with complex compounds such as (NaOH+Na_2O)·Fe_xO_y or (NaCrO_2+Na_2CrO_4) mixed up with the sodium oxides by sodium-water reaction and the Fe or Cr element by matrix of tube material.

External Gelation 방법을 이용한 구형 UO3 Gel 입자제조

정경채,조문성,이영우,장종화,김연구,오승철 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.11

HTGR (High Temperature Gas-cooled Reactor) is spotlighted to next generation nuclear power plant for producing the clean hydrogen gas and the electricity. In this study, the spherical UO3 gel particles were prepared by the external gelation process, and the characteristics of these particles were analyzed the particle shape, composition of precipitate, and thermal decomposition characteristics with the Streoscope, FT-IR, and X-ray diffractometer. Raw material of the ADUN (Acid Deficient Uranyl Nitrate) solution, which has [NO3]/[U] mole ratio=1.75, was obtained from dissolution of the U3O8 powder with concentrated HNO3, and its concentration is 3.5 M-U/ℓ. The broth solution is prepared with the ADUN, urea, PVA, and THFA solution. The droplets of the broth solution was made through a nozzle system. From this study, we obtained the following results ; 1) an externel chemical gelation process is a suitable method in the spherical UO3 particle production, 2) the particle shape are changed by an urea mixing time, THFA volume, and the viscosity of the broth solution, 3) the amorphous UO3 particles obtained from these experiments was converted to U3O8 and then UO2 by heat treatment in hydrogen atmosphere at 600℃. 차세대 수소생산을 위한 원자로로 고온가스로가 각광을 받고 있으며, 본 연구에서는 고온가스로 핵연료 중간매체로 예상되는 구형 UO3 gel 입자를 external gelation 공정을 이용해서 제조한 후, gel입자의 특성을 파악하고자하였다. 원료용액은 U3O8분말을 질산에 용해시켜 [NO3]/U mole ratio 1.75인 ADUN(Acid Deficient Uranyl Nitrate)용액을 제조한 후 우라늄 농도 3.5M/ℓ 인 초기용액에 urea 와 THFA(TetraHydroFurfurylAlcohol) 및 PVA(PolyVinylAlcohol)를 첨가하여 broth 용액을 제조하였다. 제조된 broth 용액을 미세 needle을 통해 공기, 암모니아 가스층을 통과시킨 후 암모니아 용액에서 구형 UO3 침전물을 얻었으며, Streoscope, X-ray, FT-IR 등을 이용해서 침전물의 입자모양, 구성성분 및 열분해 특성 등을 관찰하였다. 초기 broth 용액 제조과정에서 urea의 혼합시간, THFA의 적가량, PVA에 의한 점성등에 의해 입자의 모양과 크기가 다르게 나타났으며, 제조된 UO3 gel입자는 수소분위기에서 UO3→U3O8→UO2로 형태로 상변화가 진행되는 것을 알 수 있었다.

Investigation of Water-in-Sodium Leaks Self-development Using Ferrite Steel

정경채,정지영,김병호,김태준,최종현 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.3

In this study are presented the results of an investigation on the durability of 2.25Cr-1Mo steel in conditions of water-in-sodium small leaks in the range of their initial flow rates, 0.005~0.02 g/sec. Water outflow into sodium was performed through an artificial defect, having a cross section diameter of 0.1~0.2 mm in the specimen of the steel under investigation, with simulated wall thicknesses of 2.5, 3.5, and 5.0 mm. Water injection through the defects was performed at a pressure of 5~10 atm (gauge) in sodium flow, having a velocity of ~0.3 m/sec and temperature of 450℃. In six experimental runs, the overall leak quantity of water has been measured. For the walls` thickness investigated in the experiments, the injected water masses have been measured to be in the limits of 25~125 g, increasing with the walls` thicknesses. We give the results of a visual and metallographic investigation of the 2.25Cr-IMo steel specimens in the region of water outflow channel rupture and determination of the final dimensions of the channel. In the steel rupture region, no changes in the steel structure, elemental composition or traces of inter-granular corrosion have been detected.