• 한국음향학회지
• /
• 제15권1호
• /
• pp.71-80
• /
• 1996

해양조사선 온누리호에 장착되어 있는 슬리브건 배열의 특성을 분석하였으며, 탐사 자료와 비교하였다. 주파수 영역엣 빔폭의 변화는 송이 배열인 경우, 814Hz가지는 $179.5^{\circ}$로 일정하며 814-1631Hz 주파수 범위에서는 급격히 빔폭이 좁아진다. 반면에 길이 및 폭배열인 경우, 고주파수대로 갈수록 빔폭이 좁아지며 이때의 최적 주파수는 69Hz이다. 수직면 방향성에서 주엽은 위상 각도 $0^{\circ}$에서 최대 진폭 0dB를 나타낸다. 부엽이 생성되지 않는 최적주파수 범위는 송이배열인 경우 1631Hz 미만이며, 길이 및 폭배열인 경우 108Hz 미만이다. 따라서 송이배열은 천부 지층의 고분해능 탐사에 적합하며, 길이 및 폭배열은 저주파수대 심부지질구조 탐사에 적합함을 나타낸다. 송이배열을 이용한 탄성파 단면도를 동일 측선에서 폭배열을 이용하여 획득한 탄성파 단면도와 비교하였다.

• Restorative Dentistry and Endodontics
• /
• 제24권4호
• /
• pp.604-613
• /
• 1999

This study was performed to evaluate the effect of resin and filler type on the fracture toughness of light-activated composites. Experimental composites were prepared using urethane tetramethacrylate(UTMA) and bisphenol glycidylmethacrylate(Bis-GMA) monomers and five different types of silica fillers. Fracture toughness was measured by a single edge V-notched beam(SEVNB) method, which was discussed from ASTM E399-78. Rectangular bars of $2.5{\times}5{\times}26mm$ were prepared with experimental composites and a notch about 2.25mm deep was carved at the center of the long axis of the specimen using a dental diamond disk driven by a dental micro engine. The flexural test was carried out at a crosshead speed of 0.05mm/min and fracture surfaces were observed under scanning electron microscope. The results obtained were summarized as follows: 1. The fracture toughness values of UTMA-based composites were relatively higher than those of Bis-GMA-based composites. 2. The highest fracture toughness value was observed in the UTMA-based composite containing the $1.5{\mu}m$-spherical fillers. 3 Aging in the distilled water at $37^{\circ}C$ for 10 days showed the increase of fracture toughness, which was severer in the Bis-GMA-based composites than those of UTMA-based composites. 4. The AE amplitude occurring during the fracture toughness tests was the highest at the point of macroscopic fracture.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제4권2호
• /
• pp.117-123
• /
• 2004

A 30 nm $In_{0.7}GaAs$ High Electron Mobility Transistor (HEMT) with triple-gate has been successfully fabricated using the $SiO_2/SiN_x$ sidewall process and BCB planarization. The sidewall gate process was used to obtain finer lines, and the width of the initial line could be lessened to half by this process. To fill the Schottky metal effectively to a narrow gate line after applying the developed sidewall process, the sputtered tungsten (W) metal was utilized instead of conventional e-beam evaporated metal. To reduce the parasitic capacitance through dielectric layers and the gate metal resistance ($R_g$), the etchedback BCB with a low dielectric constant was used as the supporting layer of a wide gate head, which also offered extremely low Rg of 1.7 Ohm for a total gate width ($W_g$) of 2x100m. The fabricated 30nm $In_{0.7}GaAs$ HEMTs showed $V_{th}$of -0.4V, $G_{m,max}$ of 1.7S/mm, and $f_T$ of 421GHz. These results indicate that InGaAs nano-HEMT with excellent device performance could be successfully fabricated through a reproducible and damage-free sidewall process without the aid of state-of-the-art lithography equipment. We also believe that the developed process will be directly applicable to the fabrication of deep sub-50nm InGaAs HEMTs if the initial line length can be reduced to below 50nm order.

• 한국지구과학회지
• /
• 제26권8호
• /
• pp.836-843
• /
• 2005

서해 배타적경제수역내 해사채취구역에서 해저지형 변화를 규명하기 위하여 2회에 걸쳐 단일빔음향측심기를 이용한 측심자료를 획득하였다. 교차점 분석에 의한 측심자료의 정확도는 IHO 표준의 2등급에 해당하였다. 지형도는 폭 300 m, 깊이 10 m의 구덩이 형태를 나타내었으며, 이러한 지형의 변화 과정이 두 지형도 수심차의 분포에서 표현되었다. 그러나 해사채취량을 정량화하기 위해서는 더욱 정확하고 정밀한 자료가 요구된다. 이러한 지형변화는 퇴적환경 및 저서생태 환경에 영향을 미칠 수 있으므로 한정된 모래자원을 관리하고 지속가능한 개발을 위해서는 과학적인 조사자료에 근거한 환경영향평가가 요구된다.

• 전기전자학회논문지
• /
• 제9권1호
• /
• pp.57-64
• /
• 2005

본 논문에서는 전류 테스팅을 이용하여 CMOS 집적회로에 존재하는 결함을 검출하는 내장형 전류 감지회로를 설계하였다. 이 회로는 일반적인 CMOS 공정으로 구현하였으며 결함전류와 기준전류를 전압으로 변환시켜 시험대상 회로의 결함을 고속으로 검출하며, 미세공정에도 적용가능한 회로이다 제안한 전류 감지회로는 전류원 내장으로 인한 추가적인 전력소모를 문제를 해결하였다. 제안한 회로의 정당성 및 효율성은 HSPICE를 이용한 시뮬레이션으로 그 타당성을 입증하였다. 제안한 전류 감지회로가 칩의 전체 면적에서 차지하는 면적소모는 시험대상회로에서 약 9.2%로, 내장형 전류 감지회로에 의한 면적소모는 무시할 만 하다. 제안한 회로는 Hynix O.35um 2-poly 4-metal N-Well 표준 CMOS 공정으로 제작하였다.

• 건축역사연구
• /
• 제19권6호
• /
• pp.233-250
• /
• 2010

Jukseoru as an official pavilion of the government, one of the eight sceneries in Gwndong Area, is located on the cliff over Osipcheon River. This paper interprets form and space of the pavilion with restored old life by analyzing pictures of official party in 18th century in Chosun Dynasty. Every part of the space is occupied by persons by the class and duty: the pricipal guest, nobles, subordinates, gisaengs, court musicians, and guards from the high to the low and from the inside to the outside. Applying the analysis to the Jukseoru pavilion, the noblest lord takes sit on the platform in front of folded screen at main bay under checked ceiling, enclosed by low timber beam. The next northern end bay is a place for subordinates' and servants' waiting for preparation for rice wine. Southern end entrance bay is not a result of later addition but deliberately and originally made for lower place outside the railing of wooden floor: for a waiting woman gisaeng, and subordinates. Outside under the eaves on the platform with bedrock, artificial stone and soil is a place for court musicians, subordinates, and guards. The yard in front of the building is a place for preparing meals by cookers. Every detailed ornamental form is different each other by the place for the occupied class. Existing theory tells that the building, 7 bays gable-and-hipped roof, is a result of structural extention of 2 bays at the 5 bays gabled-roof. However, through the interpretation of old pictures and application to the pavilion, the present Juseoru is not a result of later structural addition, but deliberately designed creation suited to life in hierarchical traditional society.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2009년도 춘계학술발표대회
• /
• pp.29.1-29.1
• /
• 2009

Fabrication of good quality P-type GaN remained as a challenge for many years which hindered the III-V nitrides from yielding visible light emitting devices. Firstly Amano et al succeeded in obtaining P-type GaN films using Mg doping and post Low Energy Electron Beam Irradiation (LEEBI) treatment. However only few region of the P-GaN was activated by LEEBI treatment. Later Nakamura et al succeeded in producing good quality P-GaN by thermal annealing method in which the as deposited P-GaN samples were annealed in N2 ambient at temperatures above $600^{\circ}C$. The carrier concentration of N type and P-type GaN differs by one order which have a major effect in AlGaN based deep UV-LED fabrication. So increasing the P-type GaN concentration becomes necessary. In this study we have proposed a novel method of activating P-type GaN by electrochemical potentiostatic method. Hydrogen bond in the Mg-H complexes of the P-type GaN is removed by electrochemical reaction using KOH solution as an electrolyte solution. Full structure LED sample grown by MOCVD serves as anode and platinum electrode serves as cathode. Experiments are performed by varying KOH concentration, process time and applied voltage. Secondary Ion Mass Spectroscopy (SIMS) analysis is performed to determine the hydrogen concentration in the P-GaN sample activated by annealing and electrochemical method. Results suggest that the hydrogen concentration is lesser in P-GaN sample activated by electrochemical method than conventional annealing method. The output power of the LED is also enhanced for full structure samples with electrochemical activated P-GaN. Thus we propose an efficient method for P-GaN activation by electrochemical reaction. 30% improvement in light output is obtained by electrochemical activation method.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2009년도 춘계학술발표대회
• /
• pp.28.1-28.1
• /
• 2009

The superior properties of ZnO such as high exciton binding energy, high thermal and chemical stability, low growth temperature and possibility of wet etching process in ZnO have great interest for applications ranging from optoelectronics to chemical sensor. Particularly, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. Currently, low-dimensional ZnO is synthesized by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), thermal evaporation, and sol.gel growth. Recently, our group has been reported about achievement the growth of Ga-doped ZnO nanorods using ZnO seed layer on p-type Si substrate by RF magnetron sputtering system at high rf power and high growth temperature. However, the crystallinity of nanorods deteriorates due to lattice mismatch between nanorods and Si substrate. Also, in the growth of oxide using sputtering, the oxygen flow ratio relative to argon gas flow is an important growth parameter and significantly affects the structural properties. In this study, Phosphorus (P) doped ZnO nanorods were grown on c-sapphire substrates without seed layer by radio frequency magnetron sputtering with various argon/oxygen gas ratios. The layer change films into nanorods with decreasing oxygen partial pressure. The diameter and length of vertically well-aligned on the c-sapphire substrate are in the range of 51-103 nm and about 725 nm, respectively. The photoluminescence spectra of the nanorods are dominated by intense near band-edge emission with weak deep-level emission.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제5권1호
• /
• pp.161-177
• /
• 2013

High-speed vessels require good resistance and seakeeping performance for safe operations in rough seas. The resistance and seakeeping performance of high-speed vessels varies significantly depending on their hull forms. In this study, three planing hulls that have almost the same displacement and principal dimension are designed and the hydrodynamic characteristics of those hulls are estimated by high-speed model tests. All model ships are deep-V type planing hulls. The bows of no.2 and no.3 model ships are designed to be advantageous for wave-piercing in rough water. No.2 and no.3 model ships have concave and straight forebody cross-sections, respectively. And length-to-beam ratios of no.2 and no.3 models are larger than that of no.1 model. In calm water tests, running attitude and resistance of model ships are measured at various speeds. And motion tests in regular waves are performed to measure the heave and pitch motion responses of the model ships. The required power of no.1 (VPS) model is smallest, but its vertical motion amplitudes in waves are the largest. No.2 (VWC) model shows the smallest motion amplitudes in waves, but needs the greatest power at high speed. The resistance and seakeeping performance of no.3 (VWS) model ship are the middle of three model ships, respectively. And in regular waves, no.1 model ship experiences 'fly over' phenomena around its resonant frequency. Vertical accelerations at specific locations such as F.P., center of gravity of model ships are measured at their resonant frequency. It is necessary to measure accelerations by accelerometers or other devices in model tests for the accurate prediction of vertical accelerations in real ships.

• 방사선산업학회지
• /
• 제11권1호
• /
• pp.39-45
• /
• 2017

A cyclotron is a kind of particle accelerator that produces a beam of charged particles for the production of medical, industrial, and research radioisotopes. More than 30 cyclotrons are operated in Korea to produce $^{18}F$, an FDG synthesis at hospitals. A 30-MeV cyclotron was installed at ARTI (Advanced Radiation Technology Institute, KAERI) mainly for research regarding isotope production. In this study, we analyze and estimate the items of risk such as the problems in the main components of the cyclotron, the loss of radioactive materials, the leakage of coolant, and the malfunction of utilities, fires and earthquakes. To estimate the occurrence frequency in an accident risk assessment, five levels, i.e., Almost certain, Likely, Possible, Unlikely, and Rare, are applied. The accident consequence level is classified under four grades based on the annual permissible dose for radiation workers and the public in the nuclear safety law. The analysis of the accident effect is focused on the radioactive contamination caused by radioisotope leakage and radioactive material leakage of a ventilation filter due to a fire. To analyze the risks, Occupation Safety and Health Acts is applied. In addition, action plans against an accident were prepared after a deep discussion among relevant researchers. In this acts, we will search for hazard and introduce the risk assessment for the research 30-MeV cyclotron facilities of ARTI.