• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.130-137
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• 2012

The underwater glider using conception of Lagrangian method, is a new observation platform to understand the properties of the ocean vertically. In 2011 March, KORDI made a first successful autonomous trip from Hupo to west coast of Uleungdo piloting Littoral Glider of Alaska Native Technology LLC. The journey considered many environmental variables and route vigilantly selected, the glider covered 177 km horizontally and took approximately 6 days (153 hours). Despite the existence of 1 kt eddy current, Sound velocity sampling was conducted from 5 meters and reaching maximum of 200 meters depth at each dive. It successfully collected sound velocity and temperature profile at every 5 seconds totaling up to 1408 profiles using SVT&P sensor. During the flight it was also a mission to check the diverse modes of the glider i.e. spiral, waypoints, heading, drift and hover could function without a defect in a given situation. These modes were thoroughly monitored and it could be considered that the glider handled it well during the flight. As a result of this test flight, it was evident that the given underwater glider could operate under 2kt current environment with users defined heading and depth, also with the payload up to 5 kg without changing internal buoyancy.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.831-838
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• 2006

An experimental/analytic study has been conducted to understand the adverse effects of low vehicle speed, high axle load and high tire pressure on the performance of asphalt pavements. Of 33 asphalt sections at KHC test road, two sections having different base layer thickness (180 mm versus 280 mm) are adopted for rollover tests. During the test, a standard three-axle dump truck maintains a steady state condition as moving along the wheel path of a passing lane, and lateral offsets and real travel speed are measured with a laser-based wandering system. Test results suggest that vehicle speed affects both longitudinal and transverse strains at the bottom of asphalt layer (290 mm and 390 mm below the surface), and even slightly influences the measured vertical stresses at the top of subbase and subgrade due to the dynamic effect of rolling vehicle. Since the anisotropic nature of asphalt-aggregate mixtures, the difference between longitudinal and transverse strains appears prominent throughout the measurements. As the thickness of asphalt pavement increases, the measured lateral strains become larger than its corresponding longitudinal strains. Over the limited testing conditions, it is concluded that higher axle weight and higher tire pressures induce more strains and vertical stresses, leading to a premature deterioration of pavements. Finally, a layered elastic analysis overestimates the maximum strains measured under the 1st axle load, while underestimating the maximum vertical stress in both pavement sections.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.9-15
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• 2005

In this research the discharge characteristics of logic gate of the discharge logic gate plasma display panel with the NOT-AND logic function newly designed was analyzed. As for this discharge logic gate a logical output is induced by controlling the voltage between the electrodes using the discharge path. From the experimental result the discharge characteristics of logic gate is influenced by the interrelation of the voltages appling two vertical electrodes. To in the application possibility to large screen PDP, the discharge characteristics by the line resistance of the electrode was evaluated In result it has been inferred that the influence which the drop of voltage by the line resistance of two vertical electrodes exerts on the discharge of the logic gate is minute. Through the experiment, the optimized values of the pulse voltages and the current limitation resistances of each electrode which composed the discharge logic gate were obtained and maximum operation margin of 49[V] was obtained.

• Spatial Information Research
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• v.9 no.1
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• pp.1-13
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• 2001

Nowadays, SAR Interferometry is actively being studied as a new technique in topographic mapping using satellite imagery. It extracts height values using phase information derived by two SAR imageries covering same areas. Unlike when using SPOT imagery, it is not affected by atmospheric conditions and time. So to speak, we can say that SAR Interferometry is flexible in imagery acquisitions and can get height data economically over wide area. So, it is expected that SAR Interferometry will be widely using in GIS applications. But, in some area occurring geometric distortion, height data are misjudged or not extracted depending on phase unwrapping algorithms. IN the case of ERS tandem data, the accuracy of height data was worst in mountain area. It is the because of the short incidence angle resulted in layover effect. Of the phase unwrapping algorithms, path-following was better in height accuracy but could not get data in layover area. In this area, we could get height data using Height Sensitivity. In concludion, we could get DEM that maintained the accuracy of path-following method and have overall data across imagery.

• The Journal of the Acoustical Society of Korea
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• v.38 no.6
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• pp.678-686
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• 2019

Underwater communication performance is degraded by the influence of Inter-Symbol Interference (ISI) due to multipath. Passive time reversal processing is the most effective technique for mitigating multipath, and the diversity combining method can be used to improve its performance. This paper analyzed communication performance using the beam diversity combining method, which combines signals obtained through the beam steering to various angles. Directions of arrival were estimated through the beam-time migration, which, in turn, was estimated from probe signals received by a vertical line array. The performance was analyzed based on the number and type of combinations among the estimated angles. In this paper, the data obtained from the Biomimetic Long range Acoustic Communications 2018 (BLAC18) experiment, which was conducted in the East sea, ~50 km east of Pohang, in October 2018, were used for the analysis. The output Signal to Noise Ratio (SNR) was used as communication indicators.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.369-369
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• 2011

양자점 감응형 태양전지는 가시광 영역을 흡수, 이용할 수 있는 광감응 물질로 무기물 양자점을 사용하며, 이 경우 나노미터 크기의 무기물 양자점으로 인한 양자제한 효과 (quantum confinement effect)에 의해 양자점의 사이즈 조절 만으로 밴드갭을 조절할 수 있어 광학적 특성 조절이 용이하며, 하나의 광자를 흡수하여 두개 이상의 전자-정공쌍을 만들 수 있는 (multiple exciton generation) 가능성이 있어 기존 태양전지가 가지는 이론적 한계효율(Shockley-Queisser limit)을 뛰어넘을 수 있다. 본 연구에서는 양자점 및 염료 감응형 태양전지분야에서 가장 많이 사용되고 있는 TiO2 다공성 필름이 아닌, ZnO 나노선 구조를 이용하여 양자점 감응형 태양전지를 제작하였다. ZnO의 경우 TiO2보다 높은 전자이동도를 가지며, 나노선 구조가 바닥전극까지 수직 연결된 1차원의 전자전달경로를 제공하여 결과적으로 광전자 포집에 유리하다. 또한, CdS, CdSe 양자점을 동시에 사용하여 광흡수 범위를 가시광 전 영역으로 확장하였으며, 계단형 밴드구조를 통해 광전자-정공 분리 및 포집을 용이하게 하였다. 더 나아가 전해질의 조성, 나노선의 길이 등 다양한 부분을 조절하면서 각 변수가 소자의 효율에 미치는 영향을 관찰하였다.

• Journal of Advanced Navigation Technology
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• v.25 no.3
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• pp.248-255
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• 2021

The main causes of the July 2013 OZ 214 accident were poorly performed approach and the failure to recognize the autothrottle in the HOLD position which the automated speed control was not provided. The pilots late decision for go-around was also a critical factor leading to the accident. The B777 POM restricts the use of FLCH mode beyond the FAF. This research utilized the QAR data of an airline's B777 fleet in the period of two years where 44 cases were found. In many cases, the FLCH mode was used for rapid descent from an higher than normal situation. In addition, in the base turn, continuous use of FLCH mode even when the path was below the glide path were observed. Airports with elevation above 500 ft MSL had a higher rate of occurrence. In this research, the proper descent planning and vertical path monitoring, and the adherence to the limitation set in the manuals and the stabilized approach criteria were re-emphasized as mitigation to reduce event occurences.

• Communications of Mathematical Education
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• v.34 no.3
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• pp.393-419
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• 2020

Trigonometry allows us to recognize the usefulness of mathematics through connection with real life and other disciplines, and lays the foundation for the concept of higher mathematics through connection with trigonometric functions. Since international comparisons on the trigonometry area of textbooks can give implications to trigonometry teaching and learning in Korea, this study attempted to compare trigonometry in textbooks in Korea, Australia and Finland. In this study, through the horizontal and vertical analysis presented by Charalambous et al.(2010), the objectives of the curriculum, content system, achievement standards, learning timing of trigonometry content, learning paths, and context of problems were analyzed. The order of learning in which the three countries expanded size of angle was similar, and there was a difference in the introduction of trigonometric functions and the continuity of grades dealing with trigonometry. In the learning path of textbooks on the definition method of trigonometric ratios, the unit circle method was developed from the triangle method to the trigonometric function. However, in Korea, after the explanation using the quadrant in middle school, the general angle and trigonometric functions were studied without expanding the angle. As a result of analyzing the context of the problem, the proportion of problems without context was the highest in all three countries, and the rate of camouflage context problem was twice as high in Korea as in Australia or Finland. Through this, the author suggest to include the unit circle method in the learning path in Korea, to present a problem that can emphasize the real-life context, to utilize technological tools, and to reconsider the ways and areas of the curriculum that deal with trigonometry.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.287-301
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• 2022

This study aims to propose a crane-tip control method to intuitively control the end-effector vertically or horizontally for improving the crane work efficiency and to confirm the control performance. To verify the control performance based on experimental variables, a laboratory-scale crane was manufactured using an electric cylinder. Through a forward and reverse kinematics analysis, the crane was configured to output the position coordinates of the current crane-tip and the joint angle at each target point. Furthermore, a method of generating waypoints was used, and a dead band using lateral boundary offset (LBO) was set. Appropriate parameters were selected using bang-bang control, which confirmed that the number of waypoints and LBO radius were associated with positioning error, and the cylinder speed was related to the lead time. With increased number of waypoints and decreased LBO radius, the positioning error and the lead time also decreased as the cylinder speed decreased. Using the proportional control, when the cylinder velocity was changed at every control cycle, the lead time was greatly reduced; however, the actual control pattern was controlled by repeating over and undershoot in a large range. Therefore, proportional control was performed by additionally applying velocity gain that can relatively change the speed of each cylinder. Since the control performed with in a range of 10 mm, it was verified th at th e crane-tip control can be ach ieved with only th e proportional control to which the velocity gain was applied in a control cycle of 20 ms.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.137-146
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• 2006

In this paper, a numerical study on the evaluation of the redundancy according to the dimension and spacing of cross beams in the composite twin steel plate girder bridges that are generally recognized as a non-redundant load path structures, has been performed. Specifically, a two-lane three-span continuous (40+50+40m) bridge with I-section cross beams which serve as cross bracing, and without a lateral bracing were considered. The material and geometric nonlinear analyses were conducted to evaluate the ultimate loading capacity of the intact and damaged bridge in which one of the two girders is seriously fractured. Through the numerical analyses, it was recognized that there is little difference in redundancy according to the variation of the dimension and spacing of the cross beams for both intact and damaged bridges.