• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.398-401
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• 2009

민간 주도형 사회간접자본 (social overhead capital :SOC) 사업은 BOT(build-operate-transfer)를 비롯하여 대상 프로젝트의 정부 정책 등의 여러 환경의 변경에 따라 다양하게 변형되어 적용되어 BTL(build-lease-transfer), BOO (build-own-operate)등의 여러 기법들을 사용된다. 민간 SOC 사업은 프로 젝트의 규모와 장기에 걸친 공사의 불확실성 때문에 프로젝트의 경제성 분석을 하는 것은 복잡하다. 일반적으로 사용하고 있는 현금흐름 할인모형(discount cash flow model; DCF)은 미래의 불확실성 변수들을 적절히 반영하지 못한다는 한계점을 가지고 있지만 현실적으로 많이 쓰이고 있는 방식이다. 본 논문은 옵션기반모형에 근거한, BOT-옵션가치평가(BOT-OV)모형을 국내 민간 SOC 사업의 경제성 분석을 위해 적용한다. BOT-OV모형을 적용하는 것이 기존 순현재가치(net present value; NPV)방식을 통하여 프로젝트 가치 평가 할 때보다 더 정밀한 경제적 타당성 평가를 할 수 있다는 것을 확인하여 기존의 NPV 평가방식의 방법을 대체할 수 있는 가능성을 확인하는데 의의가 있다고 할 수 있다.

• New & Renewable Energy
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• v.7 no.2
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• pp.18-27
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• 2011

Management flexibility to adapt its future actions in response to altered future market conditions can expand the value of an investment opportunity by improving its upside potential without the change in the downside losses. Module manufacturers in solar industry continuously have to decide how much and when its production capacity should be expanded with regards to the demand in the global markets. Either over- or under-investment can cause sunk and/or opportunity costs to the module manufacturers. Option of exercising the additional investments only on favorable opportunities can increase total value of the investment. This paper analyzes the case which shows that the expansion of production capacity with more expandibility can have more value than the rigid plan of capacity expansion. The expansion option value is equivalent to KRW 38.286 billion, thus switching the negative NPV of the initial investment opportunity into the positive value. High volatility and the high growth in the cashflows as the major business features of the renewable energy provide condition where real options can play the crucial role in increasing the investment value as well as in determining the size and timing of capacity expansion in the course of capital budgeting process.

• Proceedings of the Technology Innovation Conference
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• 2001.06a
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• pp.117-130
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• 2001

R&D is the core competence of an enterprise. Furthermore, R&D requires huge capital investment and has very risky characteristics. Therefore, to be successful in R&D process, several approaches of engineering economics are used prior to decision-making. Until now, typical approaches of engineering economics such as NPV(net present value) or DCF(Discounted cash flow) have been used. But, they cannot properly capture managerial flexibility to adapt and revise later decisions in response to unexpected market development. In a constantly changing and always uncertain marketplace, managerial operation flexibility and strategic adaptability have become vital in order to successfully capitalize on favorable future investment opportunities and limit losses from adverse market development. For the alternatives of conventional static decision-making approaches, new concept of using real options is introduced. Real option theory is based on financial option's characteristics and checks every revision interval whether situation have changed favorable to decision maker or not. In advantageous situation, the decision maker has only to go on. In contrast, with unfavorable situation, he abandons the investment immediately. In this aspect, real option model is more suitable in very uncertain and dynamic business environment in that it can provide the opportunity to cope with flexibility. This paper suggests efficient and effective R&D investment strategy by using real options model. In addition, this paper compares financial options and real options.

• Journal of Life Science
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• v.18 no.3
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• pp.311-317
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• 2008

Pathophysiological oxidative stress results in neuronal cell death mainly due to the generation reactive oxygen species (ROS). In low oxygen situation such as hypoxia and ischemia, excessive ROS is generated. Coptidis Rhizoma (CR) is a traditional medicine used for the incipient stroke. In this report we show that CR water extracts $(1\;{\mu}g/ml)$ exhibited protective effects of neuronal cell death in a hypoxic model (2% $O_2/5%\;CO_2,\;37^{\circ}C,$ 3 hr) of cultured rat cortical cells. We further show that CR water extracts significantly reduced the intensity of green fluorescence after staining with $H_2DCF-DA$ on one hour and three days after hypoxic shock and in normoxia as well. Our results indicate that CR water extracts prevent neuronal death by suppressing ROS generation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.305-326
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• 2019

Discriminative correlation filter (DCF) based tracking algorithms have recently shown impressive performance on benchmark datasets. However, amount of recent researches are vulnerable to heavy occlusions, irregular deformations and so on. In this paper, we intend to solve these problems and handle the contradiction between accuracy and real-time in the framework of tracking-by-detection. Firstly, we propose an innovative strategy to combine the template and color-based models instead of a simple linear superposition and rely on the strengths of both to promote the accuracy. Secondly, to enhance the discriminative power of the learned template model, the spatial regularization is introduced in the learning stage to penalize the objective boundary information corresponding to features in the background. Thirdly, we utilize a discriminative multi-scale estimate method to solve the problem of scale variations. Finally, we research strategies to limit the computational complexity of our tracker. Abundant experiments demonstrate that our tracker performs superiorly against several advanced algorithms on both the OTB2013 and OTB2015 datasets while maintaining the high frame rates.

• Journal of Life Science
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• v.18 no.12
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• pp.1631-1636
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• 2008

Rhei Rhizoma (RR; 大黃) consists of the underground parts (rhizome and root) of Rheum officinale Baill. and Rheum palmatum L. (Polygonaceae), and is widely used in Southeast Asian folk medicine to alleviate liver and kidney damages. In this study, we investigated into the efficacy and mechanism of RR water extract in supporting neuronal survival in a hypoxia model of cultured rat hippocampal neurons. RR exhibited no cytotoxicity up to 10 ${\mu}g$/ml and exhibited neurosupportive effects at 2.5 ${\mu}g$/ml in normoxia. When RR was added to the culture media on 10 days in vitro (DIV10) and given a hypoxic shock (2% $O_2$/5% $CO_2$, 3 hr, $37^{\circ}C$) on DIV13, RR exhibited neuroprotective effects on 5 days post-shock. $H_2DCF$ stainings indicated that RR effectively prevents ROS production in both normoxia and hypoxia. JC-1 stainings showed that RR prevents dissipation of MMP in hypoxia. These results indicate that RR protects neurons by suppressing ROS production and MMP loss.

• Journal of Communications and Networks
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• v.11 no.5
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• pp.518-528
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• 2009

IEEE 802.11 wireless local area network (WLAN) has become the prevailing solution for wireless Internet access while transport control protocol (TCP) is the dominant transport-layer protocol in the Internet. It is known that, in an infrastructure-based WLAN with multiple stations carrying long-lived TCP flows, the number of TCP stations that are actively contending to access the wireless channel remains very small. Hence, the aggregate TCP throughput is basically independent of the total number of TCP stations. This phenomenon is due to the closed-loop nature of TCP flow control and the bottleneck downlink (i.e., access point-to-station) transmissions in infrastructure-based WLANs. In this paper, we develop a comprehensive analytical model to study TCP dynamics in infrastructure-based 802.11 WLANs. We calculate the average number of active TCP stations and the aggregate TCP throughput using our model for given total number of TCP stations and the maximum TCP receive window size. We find out that the default minimum contention window sizes specified in the standards (i.e., 31 and 15 for 802.11b and 802.11a, respectively) are not optimal in terms of TCP throughput maximization. Via ns-2 simulation, we verify the correctness of our analytical model and study the effects of some of the simplifying assumptions employed in the model. Simulation results show that our model is reasonably accurate, particularly when the wireline delay is small and/or the packet loss rate is low.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.8
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• pp.797-804
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• 2011

Network coding has recently emerged as an effective solution for multicast and broadcast communications in wireless ad hoc networks. In this paper, we propose a throughput performance model for IEEE 802.11 wireless networks with network coding. Specifically, we consider IEEE 802.11 DCF protocol and linear topology in which traffic sources are located at both ends and intermediate nodes act as relays performing network coding. The proposed analytic model has the form of nonlinear equations in terms of throughput of each node. The solution of the nonliear equations thus correspond to the end-to-end throughput. Extensive simulation experiments have been performed to validate accuracy of the proposed model. Numerical results show that the results of the proposed analytic model agree fairly well with the corresponding simulation results.

• The Journal of Korean Medicine
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• v.32 no.1
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• pp.109-120
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• 2011

Objectives: The aim of this investigation was to evaluate the efficacy of KHchunggan-tang aqueous extract on the experimental nonalcoholic fatty liver disease(NAFLD) induced by palmitate. Materials and Methods: To generate a cellular model of NAFLD, we used HepG2 cells, a human hepatoma cell line, treated with 0.5 mM palmitate. By this cellular model, effects of KHchunggan-tang aqueous extract were evaluated. Intracellular lipid accumulation, free radical formation, and apoptosis were detected by Nile red staining, 2',7'-dichloroflourescin diacetate(H2DCF-DA), and 4',6-diamidino-2-phenylindole(DAPI)/propidium iodide(PI) staining, respectively. Some proteins related with NAFLD were determined by western blot. Results: Typical pathological features of NAFLD occurred in the cellular model. Palmitate increased the levels of intracellular lipid vacuoles, decreased cell viability, and increased apoptosis. Palmitate increased free radical formation and lipid peroxidation, too. However, KHchunggan-tang aqueous extract reduced palmitate-induced pathologic features, i.e. steatosis, free radical formation, and apoptosis. In addition, KHchunggan-tang aqueous extract suppressed palmitate-activated c-Jun N-terminal kinase(JNK) signaling, and SP600125, a JNK inhibitor, significantly reversed the palmitate-induced pathologic changes as KHchunggan-tang aqueous extract. It means that the signaling pathway other than JNK can be involved in the KHchunggan-tang mediated cellular protection of palmitate-treated Hep G2 cells. Conclusions: These results suggest that KHchunggan-tang aqueous extract has hepatoprotective effects on NAFLD with combined properties in cellular steatosis, ROS production, and cytoprotection, and thus may have valuable clinical applications for treatment of this chronic liver disease.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.3862-3888
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• 2017

In high diversity node situation, single-channel MAC protocols suffer from many collisions. To solve this problem, the research of multichannel MAC protocol has become a hotspot. And the cyclic quorum-based multichannel (CQM) MAC protocol outperformed others owing to its high frequency utilization. In addition, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver. To obtain the accurate performance of CQM MAC protocol, a Markov chain model, which combines the channel hopping strategy of CQM protocol and IEEE 802.11 distributed coordination function (DCF), is proposed. The metrics (throughput and average packet transmission delay) are calculated in performance analysis, with respect to node number, packet rate, channel slot length and channel number. The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm (BSA). Finally, the Markov chain model and saturation bound are verified by Qualnet platform. And the simulation results show that the analytic and simulation results match very well.