• 한국군사과학기술학회지
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• 제23권1호
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• pp.59-65
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• 2020

Many technologies are being studied to reduce the RCS(Radar Cross Section) of stealth aircraft. Most RCS-reduction technlogies correspond to platforms. It is important to identify factors that RCS performance through simulation analysis of aircraft Mounted equipment. In particular, there are no studies of RCS performance in the radar frequency band when antenna transmit signals are applied. In this paper, the RCS performance variation on the transmit signal on/off of antennas mounted on a stealth aircraft was verified. Antennas were selected for each frequency band and simulated analysis to the RCS performance changes during antenna transmitting signal. Finally, to verify the characteristics of the change in RCS performance, RCS test measurements on the low-profile antenna transmit signal on/off were performed. In addintion, antenna RCS test measurement was performed according to the change of transmit signal power output. As a result, it was confirmed that there is no change in RCS performance when an antenna transmit signal is applied.

• 한국지반신소재학회논문집
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• 제17권1호
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• pp.111-118
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• 2018

단층 등 취약지반 조건에서의 터널굴착 시 터널천단 및 측벽변위의 억제를 목적으로 하는 각부보강공이 일반적으로 적용되고 있으며, 터널 단면증가 변화율에 따른 각부보강공 설치각도 및 길이를 고려한 지보안전성 확인을 위한 주요 인자로서 내공변위 천단침하 각부침하 각부축력 등의 여러 응력변위 특성 변수들이 있다. 이러한 굴착중 안전성확인을 위한 변수들에 대한 검토 결과, 우각부 침하영향성이 단면증가율 보다 더 큰 변위경향을 보이는 가장 중요한 중점관리 지배요소로 분석되었으며, 터널단면 증가 변화율에 대한 각 보강공 길이별 축력의 변화관점에서는 큰 연관성을 보여주지 못하는 터널단면 증가율 대비 작은 증가율을 나타냈다. 또한, 각부 보강공 축력의 발생경향은 터널 단면증가율보다 보강공 마찰지지 개념 메커니즘에 따른 거동 영향성을 보여주는 것으로 분석되었다. 본 연구결과, 일정한 길이의 각부 보강공이 선정될 경우 지반불량 구간에서의 터널 단면이 다소 대단면화하여도 무리하게 각부보강공의 길이를 연장시키지 않는 것이 시공성 및 경제성을 고려한 보다 더 합리적인 방법으로 판단된다.

• Korean Journal of Acupuncture
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• 제27권4호
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• pp.59-72
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• 2010

Objectives : In the study on the waveform analysis of radial artery pulse diagnosis, we need to establish fundaments of contemporary pulse diagnosis research, and to find the change of pulse waveform parameter with applied variation pf pressure. Methods : As we will to do experimental research on the difference of pulse waveform on the radial artery with applied variations of pressure(5 stage-pressure) and measuring position(left KWAN). In this research, we analyzed the change of the waveform according to five stage pressure. Results : The results were as follows; When we analyzed the change of the waveform according to pressure in the left KWAN, E, hl, h2 and A were the difference between 8ths pressure grades in 95% trust section. And t2, t4 were the difference between 8ths pressure grades in 95% trust section. W was the difference between 8ths pressure grades in 95% trust section. And h2/h1 was the difference between 6ths pressure grades in 95% trust section. There is the difference between 1st and 2nd grade & between 2nd and 5th grade in the case of t4/t2 in 95% trust section. And there is the difference between 1st and 5th grade, between 3rd and 4th grade, between 3rd and 5th grade & between 4th and 5th grade in the case of W/A in 95% trust section. And there is the difference between 1st and 2nd grade, between 2nd and 3rd grade, between 2nd and 4th grade, between 3rd and 4th grade, between 3rd and 5th grade & between 4th and 5th grade in the case of A/E in 95% trust section. Conclusions : We found the statistically resonable differences between each pulse depending on the applied pressure. And Analysing the radial pulse(left KWAN) at 5 applied pressure levels may be useful to study on the pulse waveform diagnosis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.7-8
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• 2010

비대칭 H형강이 콘크리트에 매립되어 화재에 노출되는 일반 합성 보에 비하여 내화성능이 높은 슬림플로어 공법에 대한 화재거동특성을 분석하고, 이를 기반으로 내화성능을 향상시킬 수 있는 최적 단면형상조건을 도출하고자 연구를 수행하였다. 단면형상은 휨 성능을 증진시킬 수 있는 웹 보강과 화재에 직접 노출되는 하부플렌지의 보강 방안에 대하여 화재실험을 진행하였으며, 무 보강조건과 형상변화시에 발생하는 합성플로어의 처짐을 비교 분석하여 최적 단면형상설계 조건을 도출하고자 하였다. 실험결과 웹보강방안에 비해 하부플렌지 보강시 내화성능 향상효율이 더 높은 것으로 나타났으며, 이는 화재에 직접적으로 노출되는 하부플렌지 부분에 보강을 하는 것이 급격한 온도상승으로 인한 강도저하로 인해 발생하는 변형을 보다 효율적으로 제어하기 때문으로 판단된다.

• Journal of Welding and Joining
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• 제20권6호
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• pp.78-78
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• 2002

Front-side members are structures with the greatest energy absorbing capability in a front-end collision of vehicles. This paper was performed to analyze initial collapse characteristics of spot welded hat and double hat-shaped section members, which are basic shape of side members, on the shift of flange weld pitches. The impact collapse tests were carried out by using home-made vertical air compression impact testing machine, and impact velocity of hat-shaped section members is 4.17m/sec and that of double hat-shaped section members is 6.54m/sec. In impact collapse tests, the collapsed length of hat-shaped section members was about 45mm and that of double hat-shaped section members was about 50mm. In consideration of these condition, axial static collapse tests(0.00017m/sec) of hat and double hat-shaped section members were carried out by using UTM which was limited displacement, about 50mm. As the experimental results, to obtain the best initial collapse characteristics, it is important that stiffness of vehicle members increases as section shapes change and the progressively folding mode induces by flange welding pitch.

• Journal of Welding and Joining
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• 제20권6호
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• pp.802-808
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• 2002

Front-side members are structures with the greatest energy absorbing capability in a front-end collision of vehicles. This paper was performed to analyze initial collapse characteristics of spot welded hat and double hat-shaped section members, which are basic shape of side members, on the shift of flange weld pitches. The impact collapse tests were carried out by using home-made vertical air compression impact testing machine, and impact velocity of hat-shaped section members is 4.17m/sec and that of double hat-shaped section members is 6.54m/sec. In impact collapse tests, the collapsed length of hat-shaped section members was about 45mm and that of double hat-shaped section members was about 50mm. In consideration of these condition, axial static collapse tests(0.00017m/sec) of hat and double hat-shaped section members were carried out by using UTM which was limited displacement, about 50mm. As the experimental results, to obtain the best initial collapse characteristics, it is important that stiffness of vehicle members increases as section shapes change and the progressively folding mode induces by flange welding pitch.

• Structural Engineering and Mechanics
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• 제22권5호
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• pp.631-645
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• 2006

Buckling capacity of compression members may change due to inadvertent changes in the member section dimensions or material properties. This may be the result of repair, modification of section properties or degradation of the material properties. In some occasions, enhancement of buckling capacity of compression members may be achieved through splicing of plates or utilization of composite materials. It is very important for a designer to predict the buckling resistance of the compression member and the important parameters that affect its buckling strength once changes in section and/or material properties took place. This paper presents an analytical approach for determining the buckling capacity of a compression member whose geometric and/or material properties has been altered resulting in a multi-step non-uniform section. This analytical solution accommodates the changes and modifications to the material and/or section properties of the compression member due to the factors mentioned. The analytical solution provides adequate information and a methodology that is useful during the design stage as well as the repair stage of compression members. Three case studies are presented to show that the proposed analytical solution is an efficient method for predicting the buckling strength of compression members that their section and/or material properties have been altered due to splicing, coping, notching, ducting and corrosion.

• Geomechanics and Engineering
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• 제17권2호
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• pp.133-143
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• 2019

An optimal hydraulic section is critical for irrigated water conservancy in seasonal frozen ground due to a large proportion of water leakage, as investigated by in-situ surveys. This is highly correlated with the frost heave of underlain soils in cold season. This paper firstly derived a practical model for frost heave of clayey soils, with temperature dependent thermal indexes incorporating phase change effect. A model test carried out on clay was used to verify the rationality of the model. A novel approach for optimizing the cross-section of irrigation canals in cold regions was suggested with live updated geometry characterized by three unique geometric constraints including slope of canal, ratio of practical flow section to the optimal and lining thickness. Allowable frost heave deformation and tensile stress in canal lining are utilized as standard in computation iterating with geometry updating while the construction cost per unit length is regarded as the eventual target in optimization. A typical section along the Jinghui irrigation canal was selected to be optimized with the above requirements satisfied. Results prove that the optimized hydraulic section exhibits smaller frost heave deformation, lower tensile stress and lower construction cost.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.261-262
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• 2010

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권3호
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• pp.354-362
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• 2017

We investigated the improvement in electrical characteristics of large AlGaN/GaN on Si Schottky barrier diode (SBD) induced by structural change to achieve a better trade-off between the forward and reverse performance to obtain high power conversion efficiency in PFC converter. Using an optimized dry etch condition for a large device, we fabricated three-types of SBD with 63 mm channel width: conventional, recessed, recessed dual-anode-metal SBD. The recessed dual-anode-metal SBD exhibited a very low turn-on voltage of 0.34 V, a high forward current of 1.63 A at 1.5 V, a leakage current of $114{\mu}A$ at -15 V, a breakdown voltage of 794 V.