• Steel and Composite Structures
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• 제1권1호
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• pp.17-32
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• 2001

The Rosette-joining system is a completely new press-joining method for cold-formed steel structures. One Rosette-joint has a shear capacity equal to that of approximately four screws or rivets. The Rosette thin-walled steel truss system presents a new fully integrated prefabricated alternative to light-weight roof truss structures. The trusses are built up on special industrial production lines from modified top hat sections used as top and bottom chords and channel sections used as webs which are joined together with the Rosette press-joining technique to form a completed structure easy to transport and install. A single web section is used when sufficient but can be strengthened by double-nesting two separate sections or by using two lateral profiles where greater compressive axial forces are met. An individual joint in the truss can be strengthened by introducing a hollow bolt into the joint hole. The bolt gives the connection capacity a boost of approximately 20%. A series of laboratory tests have been carried out in order to verify the Rosette truss system in practice. In addition to compression tests on individual sections of different lengths, tests have also been done on small structural assemblies and on actual full-scale trusses of a span of 10 metres. Design calculations have been performed on selected roof truss geometries based on the test results, FE-analysis and on the Eurocode 3 and U.S.(AISI) design codes.

• 대한화학회지
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• 제43권3호
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• pp.315-320
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• 1999

고성능 전계발광(electroluminescent, EL) 소자에 사용되는 발광물질의 개발을 위하여 설계된 발광기능기의 분자구조는 비스스틸렌구조의 발광기능기에 전자주입과 수송을 위한 시안기와 정공주입과 수송을 위한 페닐아민기를 가진 구조이다. 위의 발광기능기로 구성 된 고분자물질, PU-BCN과 저분자물질, D-BCN을 합성하였다. PU-BCN과 D-BCN을 발광층으로 사용하여 만들어진 단층형 소자(SL)의 구조는 Indium-tin oxide(ITO)/발광층/MgAg이고, 적층형소자의 구조는 ITO/발광층/oxadiazole dehvative/MgAg, (DL-E)와 ITO/tri-phenylamine derivative/발광층/MgAg,(DL-H)의 두 종류이다. 동일한 발광기능기를 가진 고분자 발광물질, PU-BCN과 저분자발광물질, D-BCN은 전하주입과 수송성이 띄어난 물질로 평가되었으며, 두 발광물질들은 높은 전류밀도하에서 거의 동일한 발광특성을 보였다. 발광물질들의 최대 발광 피이크는 약 640 nm의 적색 발광영역에서 측정되었다.

• 한국광학회지
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• 제17권3호
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• pp.273-277
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• 2006

홀버닝 광메모리의 광원으로서 상용 반도체 레이저 다이오드에 Littman형 및 고정방향 Littrow형 외부공진기를 결합하여 파장가변 레이저 다이오드 시스템을 제작하고 성능을 비교 분석하였다. 두 형태의 파장가변 레이저 다이오드 시스템 모두 0차 출력광은 단일종모드로 동작하며 CFP(Confocal Fabry-Perot)의 분해능인 9MHz이내의 선폭을 예상할 수 있었으며 다이오드 구동전류 140mA 및 동작 온도 $25^{\circ}C$의 조건하에서 거울 및 회절격자를 수동나사로 회전시키는 성긴 튜닝시 Littman형은 5.375nm, 고정방향 Littrow형은 13.65 nm이상의 파장가변 범위를 보였고 PZT (Piezoelectric Transducer)에 200Hz의 톱니파 전압을 인가해서 거울을 회전시키는 미세 튜닝 시 두 형태 모두 0.042nm의 범위 내에서 연속적인 파장가변이 가능하였다. 특히 고정방향 Littrow형 외부공진기는 출력광의 방향이 바뀌는 기존의 단점을 보강하였으며, 또한 외부공진기의 길이에 따른 최대파장가변 범위를 측정하였다.

• 한국융합학회논문지
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• 제8권7호
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• pp.123-129
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• 2017

본 연구는 모발 수질의 형태적, 미세구조적 특성을 주사전자현미경과 투과전자현미경을 사용하여 관찰하였다. 수질은 모발의 중앙부위에 존재하며 모발의 장축을 따라 기부에서부터 정단부위까지 불연속적으로 존재한다. 또한, 수질은 일정한 모양으로 존재하지 않고 매우 불규칙한 모양을 하고 있다. 한 개의 모발에서 연속되는 수질의 두께는 매우 다양하게 나타났다. 모발의 가로 절단면에서 수질의 두께는 최고 $21{\mu}m$로 측정되었고 세로 절단면에서는 최고 $27{\mu}m$로 측정되었다. 수질은 모발 직경의 1/3-1/4을 차지하고 있다. 수질은 각화된 수질형성세포의 거대원섬유들이 분리되면서 빈 공간을 형성하고 있다. 수질에 형성된 빈공간은 최고 $6.5{\mu}m$의 직경을 가지고 있으며 공기로 채워져 있다.

• 한국전자파학회논문지
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• 제11권5호
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• pp.782-787
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• 2000

광대역 고출력 SP3T MMIC GaAs PIN 다이오드 스위치를 설계, 제작하고 특성을 측정하였다. 전력단속능력을 개선시키기 위하여 다이오드의 버퍼층을 저온 버퍼와 초격자 버퍼로 이루어진 2층 구조로 설계하였다. 개발된 다이오드의 항복전압은 65V이고 순방향 정압강하는 1.3V 이었다. MMIC 스위치는 마이크로스트립 라인형으로 구현되었고 인덕턴스가 낮은 via hole 공정을 이용하여 신호를 접지하였다. 평면형 구조보다 더 낮은 기생성분과 진성영역에서 고품질을 갖는 수직형 에피텍셜 PIN 구조를 사용하여 우수한 마이크로파 성능을 얻었다. 제작된 SP3T 스위치의 고출력 특성은 14.5GHz CW에서 입력전력을 8dBm부터 32dBM 까지 증가시킬 때 삽입손실은 0.6dB보다 작은, 분리도는 50dB보다 크게 측정되었다.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.65-74
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• 2009

Device quality indium tin oxide (ITO) films are deposited on glass substrates and ultra-thin diamond-like carbon films are deposited as a buffer layer on ITO by a pulsed Nd:YAG laser at 355 nm and 532 nm wavelength. ITO films deposited at room temperature are largely amorphous although their optical transmittances in the visible range are > 90%. The resistivity of their amorphous ITO films is too high to enable an efficient organic light-emitting device (OLED), in contrast to that deposited by a KrF laser. Substrate heating at $200^{\circ}C$ with laser wavelength of 355 nm, the ITO film resistivity decreases by almost an order of magnitude to $2{\times}10^{-4}\;{\Omega}\;cm$ while its optical transmittance is maintained at > 90%. The thermally induced crystallization of ITO has a preferred <111> directional orientation texture which largely accounts for the lowering of film resistivity. The background gas and deposition distance, that between the ITO target and the glass substrate, influence the thin-film microstructures. The optical and electrical properties are compared to published results using other nanosecond lasers and other fluence, as well as the use of ultra fast lasers. Molecularly doped, single-layer OLEDs of ITO/(PVK+TPD+$Alq_3$)/Al which are fabricated using pulsed-laser deposited ITO samples are compared to those fabricated using the commercial ITO. Effects such as surface texture and roughness of ITO and the insertion of DLC as a buffer layer into ITO/DLC/(PVK+TPD+$Alq_3$)/Al devices are investigated. The effects of DLC-on-ITO on OLED improvement such as better turn-on voltage and brightness are explained by a possible reduction of energy barrier to the hole injection from ITO into the light-emitting layer.

• 농업과학연구
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• 제47권3호
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• pp.415-424
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• 2020

This study investigated the effects of an ethylene scrubber (ES) with a micro-perforated polypropylene (MP-PP, 30 ㎛) or a high density polyethylene (MP-HDPE, 30 ㎛) film liner for the export carton packaging box in 'Campbell Early' grapes. Rachis browning was highest in the untreated group, followed by MP-PP and MP-HDPE for 14 days of simulated marketing at 20℃. The combination treatment of ES with the film liners showed a partial inhibition of the rachis browning regardless of the film liners. The effects of an alcohol releaser (AR) sachet or chlorine dioxide (CD) diffuser co-packaging were also investigated in the 'Campbell Early' grapes packed with the MP-HDPE (40 × 99 pin hole·m^-2) film liner. The CD 1 g treatment showed a very limited weight loss of 1.1%, which was significantly lower than the 4.7% of the untreated control after 14 days of simulation marketing at 20℃. The berry shatter was 0.7% for the MP-HDPE + CD 1 g treatment and 1.8% for the MP-HDPE + CD 5 g treatment on the 10th day of the simulated marketing, which was significantly lower than the 8.9% of the control. The stem browning was significant suppressed until the 10th day of the simulated marketing. In particular, the CD 1 g treatment in combination with the MP-HDPE showed a low rachis and pedicel browning index of 2.0, which is 50% and 40% lower than that of the untreated control and the MP-HDPE single treatment, respectively. In addition, the CD 1 g treatment group showed a higher decay reduction effect than the CD 5 g treatment group, which caused high concentration damage.

• 대한방사선기술학회지:방사선기술과학
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• 제21권1호
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• pp.29-34
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• 1998

The purpose of simple abdomen erect projection is to see the fluid level which indicates gastrointestinal ileus or free air due to perforation. we do not have to insist on low kVp technique in simple abdomen erect position as long as we can detect the fluid level and free air shadow. Therefore, the author tried to decrease patient dose by high kVp technique and to improve the image quality due to motion artifact by reduction of exposure time. [Methods] Experiment 1. * screen/film SRO1000/HRH * exposure factor : $140\;kvp{\pm}5\;kv$ with added filters, 200 mA, 0.01 sec * phantom : Acryles : 15.0 cm(equivalent to 17 cm body thickness) 17.5 cm(equivalent to 21 cm body thickness) 20.0 cm (equivalent to 25 cm body thickness) With the exposure factor for same film density($D=0.8{\pm}0.1$) and with the materials above, we tried to find out entrance skin dose and gonad dose for both male and female. Experiment 2. Burger's phantom radiography were checked to see whether there was any change of image quality according to the kVp and the added filters. Experiment 3. Using rotating meter(self made), we examined the motion artifact and the exposure time limitation. [Results and conculution] 1. Using high voltage technique of 140 kVp with added filter, Skin dose, testicle dose and ovary dose decrease to 89.3%, 47% and 71.4% respectively compare to 70 kVp technique, 2. No great changes of Burger's phantom image has detected as from 70 kVp to 140 kVp and the air hole size of Burger's phantom over 0.028 cc(Diameter 3 mm, hight 4 mm) can be distinghished. 3. 0.01 sec(1 pulse) exposure time is possible in the single phase full wave rectification that why we can quitely reduce the unsharness caused by patient's movement.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.782-787
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• 2005

The bottom structure of an instrumented capsule is a part which is joined at the receptacle of the flow tube in the reactor in-core. A geometrical change or the bottom structure has an effect on the pressure drop and the vibration of the capsule. The out-pile test to evaluate the structural Integrity of the material capsule called 04M-l7U was performed by using a single channel and a half core test loop. From the pressure drop test, the optimized diameter of the cone shape's bottom structure which satisfies HANARO's flow requirement (19 6 kg/s) is 71 mm. The maximum displacement of the capsule measured at the half core test loop is lower than 1.0 mm. From the analysis results, it is found that the test hole will not be interfered with near the flow tubes because its displacement due to the cooling water is very small at 0.072 mm. The fundamental frequency of the capsule under water is 9.64 Hz. It is expected that the resonance between the capsule and the fluid flow due to the cooling water in HANARO's In-core will not occur. Also, the new bottom structure of a solid cone shape with 71 mm in diameter will be applicable to the material and special capsules in the future.

• Journal of Korean Neurosurgical Society
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• 제37권5호
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• pp.370-374
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• 2005

Objective: We investigated the morphologic changes within 24 hours after a single ${\gamma}$-irradiation in the rat brain. Methods: Forty Sprague-Dawley rats were used. After a burr hole trephination on right parietal area, cerebral hemisphere was irradiated with 2Gy and 5Gy using iridium-192($^{192}Ir$), respectively. The effect was assessed at 4, 8, 12 and 24 hours after irradiation. The histological changes were scored following the detection of edema or disarray severity. TUNEL-positive cells exhibiting apoptotic morphology were counted in irradiated region. Results: Cortical edema and disarray were initially showed at 4 or 8 hour and almost all defined at 24 hour after irradiation. And the injury was wedge shape. TUNEL-positive cells were minimal at 8 hour after irradiation as the number of positive cells were $2.6{\pm}5.27$(n=5) after 2Gy, and $0.8{\pm}0.84$(n=5) after 5Gy. But, the number of apoptotic cells were increased markedly to $60{\pm}6.24$ at 12 hour after 2Gy and to $104{\pm}19.7$ at 24 hour after 5Gy. Conclusion: There were prominent morphologic changes immediately after ${\gamma}$-irradiation. And, apoptosis was increased according to the time period. These findings implicate that brain irradiation induces rapid apoptotic change, which may play an important role in the pathogenesis of radiation-induced pathologic conditions.