• Journal of Communications and Networks
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• v.8 no.4
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• pp.451-460
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• 2006

Since low earth orbit (LEO) satellite constellations have important advantages over geosynchronous earth orbit (GEO) systems such as low propagation delay, low power requirements, and more efficient spectrum allocation due to frequency reuse between satellites and spotbeams, they are considered to be used to complement the existing terrestrial fixed and wireless networks in the evolving global mobile network. However, one of the major problems with LEO satellites is their higher speed relative to the terrestrial mobile terminals, which move at lower speeds but at more random directions. Therefore, handover management in LEO satellite networks becomes a very challenging task for supporting global mobile communication. Efficient and accurate methods are needed for LEO satellite handovers between the moving footprints. In this paper, we propose a new seamless handover management scheme for LEO satellites (SeaHO-LEO), which utilizes the handover management schemes aiming at decreasing latency, data loss, and handover blocking probability. We also present another interesting handover management model called satellite mobility pattern based handover management in LEO satellites (PatHO-LEO) which takes mobility pattern of both satellites and mobile terminals into account to minimize the handover messaging traffic. This is achieved by the newly introduced billboard manager which is used for location updates of mobile users and satellites. The billboard manager makes the proposed handover model much more flexible and easier than the current solutions, since it is a central server and supports the management of the whole system. To show the performance of the proposed algorithms, we run an extensive set of simulations both for the proposed algorithms and well known handover management methods as a baseline model. The simulation results show that the proposed algorithms are very promising for seamless handover in LEO satellites.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.972-980
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• 2010

In this study, we introduce the design methodology of an optimized type-2 fuzzy cascade controller with the aid of hierarchical fair competition-based genetic algorithm(HFCGA) for ball & beam system. The ball & beam system consists of servo motor, beam and ball, and remains mutually connected in line in itself. The ball & beam system determines the position of ball through the control of a servo motor. Consequently the displacement change of the position of the moving ball and its ensuing change of the angle of the beam results in the change of the position angle of a servo motor. The type-2 fuzzy cascade controller scheme consists of the outer controller and the inner controller as two cascaded fuzzy controllers. In type-2 fuzzy logic controller(FLC) as the expanded type of type-1 fuzzy logic controller(FLC), we can effectively improve the control characteristic by using the footprint of uncertainty(FOU) of membership function. The control parameters(scaling factors) of each fuzzy controller using HFCGA which is a kind of parallel genetic algorithms(PGAs). HFCGA helps alleviate the premature convergence being generated in conventional genetic algorithms(GAs). We estimated controller characteristic parameters of optimized type-2 fuzzy cascade controller applied ball & beam system such as maximum overshoot, delay time, rise time, settling time and steady-state error. For a detailed comparative analysis from the viewpoint of the performance results and the design methodology, the proposed method for the ball & beam system which is realized by the fuzzy cascade controller based on HFCGA, is presented in comparison with the conventional PD cascade controller based on serial genetic algorithms.

• The Journal of the Korea Contents Association
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• v.12 no.12
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• pp.93-102
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• 2012

This study started from the project that make the record of legendary actor's heritage in Korea. This research was focused on Sung Hee Beck's artistic footprint which was almost same steps as the Korean modern play of the centennial theater history by reviewing her; domestic royal actor; acting techniques which learn from real acting field by herself and her career. Her life shows constant resistance for the social negative reputation of the acting field, and her frantic effort to Korean play and actor's phase. Above all, this passionate actor's life contributes to society, and improve the Korean theater through 70 year's her experiences with countless roles in around 400 performances and her own valuable acting techniques. To look up legendary actress of our time, Sung Hee Beak's life gives us a chance to reflect art of acting which emphasizes its fundamental.

• Journal of the Korean Arthroscopy Society
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• v.15 no.2
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• pp.125-131
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• 2011

Optimal treatment of the torn posterior cruciate ligament (PCL) remains controversial. The type of tibial fixation (transtibial vs inlay), the femoral tunnel position within the femoral footprint (central, eccentric or isometric), and the number of bundles in the reconstruction (single-bundle vs double-bundle) are controversial issues. The PCL has a better chance of spontaneously healing than the anterior cruciate ligament (ACL) because of a rich blood supply (near the branch of the middle genicular artery) and coverage with a thicker synovium. In general, for easier passage of the graft and full visualization of the original ligament attachment site during the precise positioning of the tunnel, the remaining PCL fibers are usually debrided during reconstruction. However, the remaining remnant structures would significantly contribute to the posterior stability of the knee joint, the healing of the graft, preserving proprioceptive function of the mechanoreceptors in the PCL. Double bundle PCL reconstruction may result in some surgical complications because of increased complexity of making tunnel. Therefore, single bundle PCL reconstruction with remnant preservation seems to be an effective procedure.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.12
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• pp.1940-1947
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• 2020

Objective: Combination of two stressors on alteration of mineral footprints in animals needs due attention to meet maximum production and welfare, particularly in grazing sheep. This study tested whether ewes (Ovis aries) exposed to water deprivation and thermal-humidity stressors had altered mineral footprints in their wool, serum, urine, and feces. Methods: Nine ewes (age = 3 years; mean body weight = 41±3.5 kg) were divided among a control group with free access to water, and treatment groups with water deprivation lasting either 2 h (2hWD) or 3 h (3hWD) after feeding. Using a 3×3 Latin square design, animals were assigned to treatment groups for three sampling periods of 21 days each (n = 9). Blood was collected by jugular venipuncture. Wool was collected at the end of periods 2 and 3. Metabolic crates designed with metal grated floors were used for urine and feces collection. We measured sodium (Na), magnesium (Mg), phosphorus (P), chloride (Cl), calcium (Ca), manganese (Mn), copper (Cu), iron (Fe), and zinc (Zn). Results: The wool mineral levels did not differ between the treatment groups, although K was marginally lower (p = 0.10) in the 2hWD group. The serum and urine mineral levels did not differ between the treatments (p>0.05). Fecal K was significantly lower in the 2hWD group than in the other groups (p≤0.05). Conclusion: In conclusion, water deprivation and thermal-humidity exposure altered the excretion of K, but not of other minerals, in the wool, urine, feces, or serum of ewes. Thus, no additional mineral supplementation is needed for water deprived ewes during thermalhumidity exposure.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.466-466
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• 2011

가상수는 Allan에 의해 1993년 처음 도입된 개념으로 모든 재화나 서비스를 생산하기 위하여 사용된 물의 양( /kg)을 의미한다. 예를 들어 1차 농산물의 경우 생육기간동안 농산물이 필요로 하는 물의 양이 가상수로 사용되고, 가공품의 경우 가공과정을 거치며 소비되는 물의 양이 가상수에 포함된다. 이러한 가상수의 개념을 활용한 소비 기반 물사용 지표가 물발자국이며 이는 2002년 Hoekstra에 의해 도입되었다. 물발자국은 개인이나 지역, 집단 등이 소비하는 재화와 서비스를 생산하는데 필요한 물의 총량을 나타낸다. 우리나라와 같은 물 부족 국가에서는 농 축산물 관련 정책의 수립 시 정량적인 생산량뿐만 아니라 소비되는 물의 양도 동시에 고려할 필요가 있다. 특히 현 정부는 2015년 식량자급률 목표치(곡물자급률 25%, 육류자급률 71%)를 설정하여 농 축산물의 생산 및 수입량을 조정하고자 한다. 이러한 식량자급률의 목표치에 따라 국내 생산 및 수입량의 비율이 변화하게 되므로 국내 물발자국의 값도 변화하게 되며 이는 수자원 정책 수립 시 주요한 요인으로 작용할 수 있다. 그러므로 식량자급률의 변화에 대해 단순히 생산량의 관점뿐 아니라 물 소비 절약의 관점에서의 접근이 필요하다. 이에 본 연구에서는 2015년 정부의 식량자급률 목표치 달성을 위하여 각 품목별로 소비되는 가상수의 양을 정량적으로 산정하고, 국내적으로 소비 또는 절약되는 가상수의 양을 추정하고자 하였다. 추정된 결과를 바탕으로 식량자급률 목표치에 따른 생산량의 조정으로 인한 물발자국의 변화와 그 영향을 파악하고자 하였다. 본 연구를 위하여 식량 자급률 목표치 설정에 포함된 농 축산물의 단위 가상수량과 생산량 추이, 목표 생산량 등을 조사 하였다. 이중 곡물의 단위 가상수량은 국내의 실정을 적용한 국내 연구결과를 활용하였으며, 축산물의 단위가상수량은 음용, 세척을 위한 원단위 필요수량과 소비되는 사료의 재배를 위한 단위 가상수량을 활용하여 전체 축산물의 가상수량을 산정하였다. 조사, 산정된 자료를 활용하여 2015년 식량자급률 목표치 달성을 위해 필요로 하는 가상수의 변화량과 국내적으로 소비 또는 절약되는 가상수의 양을 파악하고자 하였다.

• Ocean and Polar Research
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• v.24 no.3
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• pp.255-261
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• 2002

We investigated the distribution of sea ice using Topex/Poseidon (T/P) and ERS-1 .ada. altimeter data in the northwest Weddell Sea, Antarctica, between the area $45-75^{\circ}W\;and\;55-66^{\circ}S$. Using the Geo_Bad_1 flag of the Merged GDR of the T/P, we classified the surface into ocean, land, and sea. Total 257 cycles of altimeter measurements between Oct. 1992 and Sep. 1999 (for nearly 2570 days) were used to analyze the distribution of the Antarctic sea ice. We then calculated the surface area of ice coverage using SUTM20 map projection to monitor the periodic variations. Each year, the maximum and minimum coverage of the sea ice were found in late August and February in the study area, respectively. We also studied the sea ice distribution using ERS-1 altimeter data between $45-75^{\circ}W\;and\;55-81.5^{\circ}S$ to compare with the T/P Using the Valid/Invalid flag of the Ocean Product, we analyzed the sea ice distribution between March and August of 1995, which showed very good coherence with the T/P measurements. Our preliminary results showed that the altimeter measurements can be effectively used to monitor the distribution of the sea ice in the polar region. However, the size of radar footprint, typically 2-6km depending on the roughness of the sea surface, may be too big to monitor the sharp boundary between ice and water/land. If more other altimeter mission data with dense coverage such as Geosat GM are analyzed together, this limitation can be significantly improved. If we also combine other microwave remote sensing data such as radiometer, and SSM/I, the result will be significantly enhanced.

• Ocean and Polar Research
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• v.39 no.2
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• pp.159-168
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• 2017

To evaluate the accuracy of UAV photogrammetry for Hyangho coast, eastern coast of Korea, we conducted a field experiment wherein UAV photogrammetry test was repeated three times. Since the Haygho coast is located within a military reservation zone, it was necessary to obtain permission to gain access to the beach and to have sensitive aerial photographs showing military facilities inspected and cropped. The standard deviation of the UAV shooting position between the three tests was less than 1 m, but repeatability of footprint on the ground was low due to wind-driven variability of the UAV pose. Self-calibrating bundle adjustment(SCBA) of implementing non-metric camera calibration was failed in one test. In two tests, the vertical error was twice as large as the pixel size except for those areas that were subject to security inspection and cropping. Given the problems that can arise with regard to the repeatability of the shooting area as well as the possibility of failure with regard to SCBA, we strongly recommend that UAV photogrammetry in coastal areas needs to be repeated at least twice.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.51-60
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• 2002

The Monte-Carlo simulation of statistical analysis is used to investigate the final conditions of states as well as the footprint boundaries resulting from the atmospheric re-entry dispersions. The re-entry dispersions in this paper are specified by a $7\times7$ covariance matrix of latitude, longitude, altitude, bank angle, flight path angle, heading error, and range at entry velocity. The error sources that affect these at re-entry for a deboost are the uncertainties associated with atmospheric density and temperature, initial errors, wind, and estimation error of aerodynamic coefficients. Using $3{\sigma}_n$ deviations of these errors and a nominal flight trajectory, the covariance matrix of state variables can be determined by performing a trajectory error analysis. Major considerations in the application of the Monte-Carlo method are the simulation of perturbed trajectories, bank reversal, and determination of the impact points for each of these trajectories. This paper analyzes the results of uncertainties from the viewpoint of aero-coefficients and bank reversal.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.1
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• pp.21-28
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• 2017

Eddy current array (ECA) technology provides the ability to electronically scan without mechanical scanning for a footprint of probe that consists of several eddy current coils arranged side-by-side and two dimensionally. Compared to single-coil eddy current technology, the ECA technology has a higher inspection speed and reliability because a large area can be covered in a single-probe pass and the obtained images can facilitate data interpretation. In this study, we developed an eddy current array probe with $2{\times}16$ coil arrays and a multiplexer that can select transmit-receive coils sequentially and operate in transmit-receive mode. Surface inspection was performed using this probe for specimens that had various flaws and the characteristics of transmit-receive mode ECA technology was studied through an analysis of the obtained eddy current signals and C-scan images.