• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.668-676
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• 2010

Optimal net residual dispersions (NRDs) of inline dispersion management (DM) for compensating the signal distortion of $24{\times}40$ Gbps WDM channels in optical transmission links, in which optical phase conjugator (OPC) is placed from 250 km to 750 km by spacing 50 km in 1,000 km total transmission length of single mode fiber (SMF), are induced as a function of various ope positions. And, performance improvement of WDM channels in transmission links with the induced optimal NRD is investigated by comparing with that in transmission links with NRD = 0 ps/nm. It is confirmed that optimal NRDs are decided by displacement of OPC from mid-way of total transmission length, i.e. 500 km, and the determinating and applying of optimal NRD in case of ope displacement into transmitters is more stable and effective than that in case of ope displacement into receivers from 500 km. Also, it is shown that eye opening penalties (EOPs) of WDM channels in transmission links with optimal NRD are improved by 1.5 dB to 3 dB, which are related with OPC position, from that obtained in transmission links with fixed NRD of 0 ps/nm.

• The Journal of Aerospace Industry
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• s.66
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• pp.1-16
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• 2003

전 세계적으로 항공시간 전략적 제휴가 확대되고 있는 가운데 우리나라의 국적항공사들도 2001년 대한항공이 SkyTeam에 가입하였고, 2003년 아시아나 항공이 Star에 가입하였다. 그러나 국내에서 독점금지예외조항이 없어 양 항공사가 전략적 제휴 그룹 내에서 일부 활동에 제약을 받고 있는 것으로 추정된다. 미국은 항공자유화 정책의 확대 추진 전략에 따라 미국 항공사들이 외국항공사들과 전략적 제휴를 맺는 경우, 자국의 시장에서 독점금지법 조항을 면제시켜주는 제도를 실시하고 있다. 이제도로 인하여 외국 항공사들과 폭 넓은 협력 관계를 유도하고 경쟁력 있는 항공운송산업을 이끌어 가고 있다. 본 연구는 미국의 독점금지예외(ATI ; Anti-Trust Immunity)에 대한 분석을 통해 국내환경에 적용 가능한지를 살펴보고자 한다. 과거 우리 정부는 경제성장을 위해 소비자로부터 생산자에게로 경제 잉여를 집중시키는 정책을 취하였다. 개발연대 동안 우리 기업은 정부의 정책 및 제도의 도움으로 또는 묵인 하에 국내시장에서 독과점적 지위를 유지하곤 하였다. 그러나 80년대에 접어들면서 “독점규제 및 공정거래에 관한 법률”과 공정거래위원회의 발족으로 시장구조를 경쟁적으로 만들고, 소비자 후생을 증대 시키는 정책목표가 보다 중요시 되고 있다. 그러나 미국에서도 소비자 후생을 증대 시키는 정책목표가 보다 중요시 되고 있다. 그러나 미국에서도 소비자 후생과 시장구조를 경쟁적으로 만들기 위해 제정된 독점금지법의 과도한 적용이 오히려 소비자 후생을 희생시킨다는 지적이 제기되고 있다. 또한 최근의 마이크로소프트사의 판례를 통해서도 나타났듯이 우월한 효율성과 규모의 경제에 의한 독점력은 인정되어야 한다는 추세이다. 이러한 관점에서 국내항공사가 외국의 항공사와 전략적 제휴를 맺어 효율성을 유지하고 규모의 경제성을 가지므로 인하여 지닐 수 있는 경쟁력은 국내의 항공운송삼업의 육성차원에서 지원이 되어야 할 것으로 판단된다. 향후 정부는 국제항공정책에 대한 장기적인 비젼과 함께 국내 항공법에 독점금지예외조항을 도입할 필요가 있다고 본다.

• Journal of Korea Multimedia Society
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• v.9 no.2
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• pp.215-225
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• 2006

Binary images, such as cartoon character images, text images and signature images, which consist of two values with black and white have more difficulties inserting imperceptible secret data than color images. Steganography using binary cover images is not easy to satisfy requirements for both the imperceptibility of stego images and a high embedding rate of secret data at the same time. In this paper, we propose a scheme that can get both the high quality of stego images and a high embedding rate by supplementing the advantages of previous research. In addition, the insertion of the proposed method changes only existing pixels of the imperceptible position and can embed the secret data of [$log_2(mn+1)-2$] bits in a block with size of $m{\times}n$.

• Journal of Advanced Navigation Technology
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• v.22 no.3
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• pp.240-245
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• 2018

A flexible dispersion-managed link configuration is proposed by using single-mode fibers (SMFs) and dispersion-compensating fibers (DCFs) with irregular dispersion coefficients and lengths over all fiber spans for compensating of WDM channels distortion due to the group velocity dispersion and nonlinear effects of optical fibers. The flexibility of link is enabled by artificially distributing of these fibers based on the dispersion coefficients of DCFs in each half transmission section. The simultaneous ascending and descending (AD) distribution of the DCF's coefficients before and after the optical phase conjugator, respectively, best compensates the distorted wavelength division multiplexed signals in the optical link. Therefore, to improve the compensation effect of the distorted WDM channels, AD distribution is needed to choice regardless of fiber lengths and the residual dispersion per span and fiber's dispersion coefficients.

• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.570-576
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• 2019

The configuration of dispersion-managed optical link with optical phase conjugator, which is placed at the non-midway of total transmission length, is proposed for implementing of the flexible optical network. The optical phase conjugator is located between the former half transmission section and the latter half transmission section, which are consisted of 6 fiber spans and 14 fiber spans respectively, and the averaged RDPS of each half transmission section are inconsistence. And, the artificial distribution of each fiber span's RDPS, which are gradually increased/decreased as the span numbers are increased, is adopted to compensate for the distorted wavelength division multiplexed channels. From the simulation results, it is confirmed that the compensation in dispersion-managed link configured by a special distribution pattern among 16 proposed patterns, in which the RDPS of each fiber spans are gradually decreased/increased in the former/latter half section with the small deviation, is suitable to compensate for the distorted wavelength division multiplexed channels.

• Journal of the Korean Institute of Landscape Architecture
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• v.41 no.6
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• pp.117-128
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• 2013

This study aims to examine various discourses of the urban landscape discussed in the fields of new cultural geography, spatial political economy, and landscape architecture in order to propose a theoretical framework for the interpretation of a contemporary urban landscape. The notion of landscape is a modern idea that separates humans, especially the bourgeois subject, from nature, and then achieves the visual possession of nature. New cultural geographers have studied the political aspects of landscape. According to them, landscape as materialized discourse is "a way of seeing" which includes the vision of the upper class, the imperialistic view, and the masculine and voyeuristic gaze. In addition, spatial political economists have paid attention to the economic aspects of landscape. They have emphasized that the material production of landscape is indispensable in the production of surplus values in the capitalistic system. Thus, we insist focusing dialectically on both the materiality and ideology of landscape.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1395-1401
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• 2005

Mobile manipulator is a robot that has mobility and manipulability with the combination of the task robot and mobile robot. One of the most important feature of the Mobile Manipulator is redundant freedom. Using the redundant freedom, Mobile Manipulator can move various mode, perform dexterous motion. It can have the wider workspace and better performance in avoidance of singularity and obstacle than the fixed base structured robot. Cooperation control using the Mobile Manipulator improves the performance of the robot with redundant freedom in workspace. In this paper, configuration control of the Mobile Manipulator has been studied using Task Segment and TOMM(Task-Oriented Manipulability Measure). For verifying the proposed algorithm, we implemented a mobile manipulator, PURL-II, which is composed of a mobile robot with 3DOF and a task robot with SDOF.

• Journal of Korea Water Resources Association
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• v.42 no.5
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• pp.415-424
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• 2009

Artificial injection of surplus surface water during wet seasons and recovery is one of possible solutions for conjunctive uses of surface water and groundwater. The methodology is especially attractive for regions of monsoon type weather. In this work a simulation-optimization model is developed to identify an optimal injection system to sustain an over-exploiting freshwater pumping well. The injection well is to be operated during wet seasons only while the pumping well is to be operated throughout an entire year. The objective function is the minimization of injected volume of freshwater. Saltwater intrusion and dry wells are considered as constraints. An example application is made on a small hypothetical island with poor hydrogeologic conditions. The optimization model is successful in determining optimal injection locations and rates for various cases.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.1
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• pp.58-64
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• 2004

This paper proposes a novel control scheme for the harmonic reduction of DC power regenerating systems, which can regenerate the excessive DC power from DC bus line to AC supply in subway systems. In the developed regenerating systems controlled by MAC(Modified a-Conduction) method, the order of remaining harmonics are 12k$\pm$1. In SHE(Selected Harmonic Elimination) method proposed in this paper, however, the l1th and 13th harmonics are additionally eliminated. And moreover 23rd harmonics, lowest order harmonics among the remaining harmonics, is eliminated by 23rd AC filter furnished at the output terminals of regenerating systems. To verify the validity of the proposed SHE-based harmonic reduction technique, computer simulations are carried out. Simulation results show that the THDs of output voltages are lower than that of the MAC method and the THDs in the control range are in the range of 0.53-0.68 percents.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.6
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• pp.469-475
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• 2008

In this paper, control of small PEM(Proton Exchange Membrane) fuel cell stack by a microprocessor is introduced. The water management of fuel cell stack inside, a key technique in fuel cell control, can be achieved by adjusting the required air flow for fuel and cooling, and by purging the excessive water from the stack. It is very important to precisely control the BOS(Balance of Stack) since the stable operation of the fuel cell system mainly depends on it. In this study the fuel efficiency of the system is improved by the control of the system based on the measured air flow and purge cycle during the optimal operation and its effectiveness is proved by the experiments. The operating stability of the system is improved by the developed controller using a microprocessor and it is expected to be widely used for the control of small PEM fuel cell stack.