• 천문학회보
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• 제41권1호
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• pp.74.2-74.2
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• 2016

It is important to know how well observation errors are removed in the calibration process prior to ensuing scientific research. In mm-VLBI observations, a radio wave suffers from an atmospheric propagation delay due to the rapid change of atmospheric refraction. It makes phases of VLBI correlation output fluctuate rapidly, which essentially decreases the coherence of phases and reduces the integration time. Consequently, it is challenging to achieve a high signal-to-noise ratio and enhance the quality of scientific output. Among the causes of the atmospheric propagation delay, water vapor in the troposphere is the most decisive factor to affect phase errors in the high frequency range (> 10GHz). It is expected to have the non-dispersive characteristic that enables to introduce new calibration strategy, Frequency Phase Transfer (FPT). This new method utilizes low frequency phases to compensate phase errors in high frequency bands. In addition, Korean VLBI Network (KVN) which benefits from the simultaneous 4-channels (22/43/86/129 GHz) observations is ideal to probe FPT performance. In order to evaluate FPT performance of KVN, we present the results of FPT phase analysis and discuss its performance.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.361-365
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• 2005

Since the fuel cell uses the hydrogen for its fuel. it has no emission and higher efficiency than an internal combustion engine. Also fuel cell is much quieter than engine generator and generates heat much less than engine generator. So it has advantage of Army's 'si lent watch' capability and the ability to operate undetected by the enemy. The fuel cell hybrid system combines a fuel cell power system with an ESS. The ESS (e.g., batteries or ultracapacitors) reduces the fuel cell's peak power and transient response requirements. It allows the fuel cell to operate more efficiently and recovery of vehicle energy during deceleration. The battery has high energy density, so it has the advantage regarding driving distance. However, it has a disadvantage considering dynamic characteristic because of low power density. One other hand. the ultracapacitor has higher power density, so it can handle sudden change or discharge of required power. Yet. it has lower energy density. so it will be bigger and heavier than the battery when it has the same energy. This paper proposes the power management strategy for multi-power source fuel cell hybrid system. which is applied with the merits of both battery and ultra capacitor by using both of them simultaneous.

• 문화기술의 융합
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• 제6권3호
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• pp.105-109
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• 2020

2050년 미래 육군은 미래의 다양한 위협에 대비하고 초지능·초연결 무기체계를 효과적으로 활용하여 다영역 전장을 지배하고 승리를 달성하기 위한 새로운 개념의 싸우는 방법을 발전시켜야 한다. 미래 육군이 추구해야 할 방향은 다음과 같다. 첫째. 능력에 기초한 적극적·공세적인 군사전략의 수립이다. 둘째, 적 전투의지 마비를 위한 중심 타격 전투이다. 셋째, 다 영역을 활용한 동시 통합 모자이크 전투이다. 넷째, 시공간을 초월한 인공지능 기반의 사이버전이다. 다섯째, 복합 플랫폼 전쟁이다. 결국, 미래의 전쟁은 사이버상에서 보이지 않는 전쟁에 의해 승패가 좌우될 것이다.

• 한국해양공학회지
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• 제14권4호
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• pp.35-42
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• 2000

The sway control problem of the pendulum motion of a container hanging on the trolly, which transports containers from a container ship to trucks, is considered in the paper. In the container crane control problem, suppressing the residual swing motion of the container at the end of acceleration or the case of that the unexpected disturbance input exists is main issue. For this problem, in general, the trolley motion control strategy is introduced and applied. But in this paper, we introduce and synthesize a new type of swing motion control system. In this control system, a small auxiliary mass is installed on the spreader. And the actuator reacts against the auxiliary mass, applying intertial control forces to the container to reduce the swing motion in the desired manner. In this paper, we apply the LMI approach and simultaneous optimization design method to design the anti-swing motion control system for the controlled plant. And the simulation result shows that the proposed control strategy is shown to be robust to disturbances like winds and initial sway motion.

• 대한수혈학회지
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• 제29권3호
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• pp.240-252
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• 2018

점탄성 응고 검사법은 전혈 검사법으로 혈장성분뿐 아니라 응고 과정의 세포 기반 측면까지 동시에 볼 수 있는 방법이다. 프로트롬빈시간이나 활성화부분트롬보플라스틴시간과 같은 기존의 응고 검사법과 달리 이 검사는 현장 현시 검사로 즉시 시행할 수 있다. 점탄성 응고 검사법은 사망률 등의 예후 예측 인자이고, 응고 장애를 좀 더 예민하게 감지하여 결과적으로 출혈을 줄여주는 효과를 줄 수 있다. 점탄성 응고 검사 결과를 이용한 수혈 전략이 수혈 요구량을 줄여주었다고 보고되기도 하였다. 아직 이 방법의 정확성과 신뢰도에 대한 우려가 있기도 하지만, ROTEM 등의 점탄성 응고 검사법은 환자혈액관리에 응용하는 것은 유용할 것이다.

• 한국전자통신학회논문지
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• 제18권3호
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• pp.527-534
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• 2023

삼중구조 시스템에서는 하나의 프로세서에서 고장이 발생해도 여유도 때문에 주어진 임무를 계속 수행할 수 있다. 본 연구에서는 삼중구조 시스템에 체크포인터 기법을 도입한 후 고장 탐지와 체크포인터를 분리하는 새로운 고장 극복 방법을 제안한다. 먼저 한 개 프로세서에서 고장이 발생하면 고장 탐지와 동시에 모든 프로세서의 상태를 동기화함으로써 고장을 복구한다. 또한 두 개 이상의 프로세서에서 동시에 고장이 발생하면 직전의 체크포인터로 회귀하여 태스크를 재실행함으로써 고장을 복구한다. 본 논문에서는 태스크가 데드라인 이내에서 성공적으로 수행될 확률을 최대화하는 고장 탐지 구간과 체크포인터 구간의 선정 방법을 제안한다. 제안된 방식을 탑재한 삼중구조 시스템을 마코프 체인으로 모델링하고 실시간 태스크의 성공적 수행 확률을 도출하는 모의실험을 수행하여 최적의 해를 구하는 과정을 제시한다.

• Smart Structures and Systems
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• 제31권3호
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• pp.229-245
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• 2023

The absence of excitation measurements may pose a big challenge in the application of structural damage identification owing to the fact that substantial effort is needed to reconstruct or identify unknown input force. To address this issue, in this paper, an iterative strategy, a synergy of Tikhonov regularization method for force identification and modified Jaya algorithm (M-Jaya) for stiffness parameter identification, is developed for damage identification with partial output-only responses. On the one hand, the probabilistic clustering learning technique and nonlinear updating equation are introduced to improve the performance of standard Jaya algorithm. On the other hand, to deal with the difficulty of selection the appropriate regularization parameters in traditional Tikhonov regularization, an improved L-curve method based on B-spline interpolation function is presented. The applicability and effectiveness of the iterative strategy for simultaneous identification of structural damages and unknown input excitation is validated by numerical simulation on a 21-bar truss structure subjected to ambient excitation under noise free and contaminated measurements cases, as well as a series of experimental tests on a five-floor steel frame structure excited by sinusoidal force. The results from these numerical and experimental studies demonstrate that the proposed identification strategy can accurately and effectively identify damage locations and extents without the requirement of force measurements. The proposed M-Jaya algorithm provides more satisfactory performance than genetic algorithm, Gaussian bare-bones artificial bee colony and Jaya algorithm.

• Membrane and Water Treatment
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• 제11권1호
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• pp.79-85
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• 2020

A single-stage deammonification with a sequencing batch reactor (SBR) that simultaneous nitritation, anaerobic ammonia oxidation (anammox), and denitrification (SNAD) occur in one reactor has been widely applied for sidestream of wastewater treatment plant. For the stable and well-balanced SNAD, a feeding strategy of influent wastewater is one of the most important operating factors in the single-stage deammonification SBR. In this study, single-stage deammonification SBR (working volume 30L) was operated to treat a high-strength ammonium wastewater (1200 mg NH₄⁺-N/L) with different feeding strategies (single feeding and nine-step feeding) under the condition without COD. Each cycle of the step feeding involved 6 sub-cycles consisted of aerobic and anoxic periods for partial nitritation (PN) and anammox, respectively. Contrary to unstable performance in the single feeding, the step feeding showed better deammonification performance (0.565 kg-N/m³/day). Under the condition with COD, however, the nitrogen removal rate (NRR) decreased to 0.403 kg-N/m³/day when the Nine-step feeding strategies had an additional denitrification period before sub-cycles for PN and anammox. The NRR was recovered to 0.518 kg-N/m³/day by introducing an enhanced multiple-step feeding strategy. The strategy had 50 cycles consisted of feed, denitrification, PN, and anammox, instead of repeated sub-cycles for PN and anammox. The multiple-step feeding strategy without sub-cycle showed the most stable and excellent deammonification performance: high nitrogen removal efficiency (98.6%), COD removal rate (0.131 kg-COD/m³/day), and COD removal efficiency (78.8%). This seemed to be caused by that the elimination of the sub-cycles might reduce COD oxidation during aerobic condition but increase the COD utilization for denitrification period. In addition, among various sensor values, the ORP pattern appeared to be applicable to monitor and control each reaction step for deammonification in the multiple-step feeding strategy without sub-cycle. Further study to optimize the number of multiple-step feeding is still needed but these results show that the multiple-step feeding strategy can contribute to a well-balanced SNAD for deammonification when treating high-strength ammonium wastewater with COD in the single-stage deammonification SBR.

• Asia Marketing Journal
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• 제15권4호
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• pp.1-32
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• 2014

The purpose of this paper is to investigate upon a diversification strategy through market creation of CJ Group, which has contributed in positioning of the firm as one of the leading conglomerates in South Korea. With such objective, the background of CJ Group, followed by its business diversification strategies were explored, with reference to several case studies. The history of CJ Group began with establishment of CheilJedang Industrial Corporation in 1953, as the first domestic sugar producer and exporter of South Korea. The corporation gradually expanded its business ever since at both national and global level, to include the fields of food production, pharmaceutical, biotechnology, and life chemicals. Later, CheilJedang (CJ) Group was established as an affiliate of CheilJedang Industrial Corporation. With such independence, extension of business has been witnessed across the industries of media, entertainment, finance, information technology and distribution. Thus, the current CJ Group pursues to define itself as a progressive global living culture company with four major business categories from food and food service, biotechnology, entertainment and media, and logistics. Despite its success in today's market, CJ Group underwent hardships in its business diversification in 1990s due to indiscreet management, along with the Asian financial crisis. Here, many firms overcame the financial difficulties by taking advantage of the exchange rate for overseas expansion. Though, CJ Group tried to differentiate itself by focusing on the domestic market by creating something out of nothing. Hence, CJ Group takes a unique position among many cases of business diversification and their categorization. In an effort to identify and classify the types of growth experienced by the top 30 companies in South Korea, the firms were categorized into four groups according to their diversification strategies adapted after the Asian financial crisis. Based on the mode and time of entry, corporations were identified either as the 'Explorer', 'Invader', 'Venture Capitalist', or 'Assimilator'. Here, the majority of the firms showed the qualities of Invader, entering mature markets through large-scaled mergers and acquisitions. However, CJ Group was the only firm that was categorized as an Explorer, for its focus on the newly emerging service sector in culture-contents industry. This diversification strategy through market creation is worth examining, due to its contribution in generating simultaneous growth between the market and the company itself. Diverse brands of CJ Group have been referred to as case studies in this regard, from 'Hatban', 'Cine de Chef', 'VIPS' to 'CJ GLS'. These four businesses, each to represent processed food, film, restaurant service, and logistics industries respectively, show CJ Group's effectiveness in creating a whole new category of goods and services that are innovative. In fact, such businesses not only contributed in advancement of consumers' wellbeing, but toward generating additional value and employment. It is true that the diversification strategy of CJ Group requires long-term capital investment with high risk, compared to the other strategies mentioned in the paper. However, this model does create high employment and additional values that are positive to both the society and the firm itself. Therefore, the paper comes to a conclusion that the diversification strategy through market creation conveys the most positive impact relative to the others.

• ETRI Journal
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• 제36권5호
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• pp.808-818
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• 2014

To deal with the major challenges of embedded sensor networks, we consider the use of magnetic fields as a means of reliably transferring both information and power to embedded sensors. We focus on a power allocation strategy for an orthogonal frequency-division multiplexing system to maximize the transferred power under the required information capacity and total available power constraints. First, we consider the case of a co-receiver, where information and power can be extracted from the same signal. In this case, we find an optimal power allocation (OPA) and provide the upper bound of achievable transferred power and capacity pairs. However, the exact calculation of the OPA is computationally complex. Thus, we propose a low-complexity power reallocation algorithm. For practical consideration, we consider the case of a separated receiver (where information and power are transferred separately through different resources) and propose two heuristic power allocation algorithms. Through simulations using the Agilent Advanced Design System and Ansoft High Frequency Structure Simulator, we validate the magnetic-inductive channel characteristic. In addition, we show the performances of the proposed algorithms by providing achievable ${\eta}$-C regions.