논문 : 수산기업의 부채수용력이 자본조달순서이론에 미치는 영향

남수현 ( Soo Hyun Nam ),김성태 ( Sung Tae Kim ) 한국수산경영학회 2014 수산경영론집 Vol.45 No.3

We try to test the pecking order theory of Korean fisheries firm’s capital structure using debt capacity. Atfirst, we estimate the debt capacity as the probability of assigning corporate bond rating from credit-ratingagencies. We use logit regression model to estimate this probability as a proxy of debt capacity. The majorresults of this study are as follows. Firstly, we can confirm the fisheries firm’s financing behaviour which issues new debt securities forfinancial deficit. Empirical test of SSM model indicates that the higher probability of assigning corporatebond rating, the higher the coefficient of financial deficit. Especially, high probability group follows thisresult exactly. Therefore, the pecking order theory of fisheries firm’s capital structure applies well for highprobability group which means high debt capacity. It also applies for medium and low probability group, buttheir significances are not good. Secondly, the most of fisheries firms in high probability group issue new debt securities for their financialdeficit. Low probability group’s fisheries firms also issue new debt securities for their financial deficit withinthe limit of their debt capacity, but beyond debt capacity they use equity financing for financial deficit. Therefore, the pecking order theory on debt capacity come into existence well in high probability group.

교차로 지체를 고려한 통행시간함수 개발

오상진,박상혁,박병호 대한교통학회 2008 대한교통학회지 Vol.26 No.4

The goals of this study are to develop travel time functions based on intersection delay and to analyze the applicability of the functions to traffic assignment models. The study begins with the premise that the existing assignment models can not effectively account for intersection delay time. In pursuing the goals, this study gives particular attention to dividing the link travel time into link moving time and stopped time at node, making the models based on such variables as the travel speed, volume, geometry, and signal data of signalized intersections in Cheongju, and analyzing the applicability of these models to traffic assignment. There are several major findings. First, the study presents the revised percentage of lanes (considering type of intersection) instead of g/C for calculating intersection delay, which is analyzed to be significant in the paired t-test. Second, the assigned results of applying these models to the Cheongju network in EMME/2 are compared with the data observed from a test car survey in Cheongju. The analyses show that the BPR models do not consider the intersection delay, but the modified uniform delay model and modified Webster model are comparatively well fitted to the observed data. Finally, the assigned results of applying these models are statistically compared with the test car survey data in assigned volume, travel time, and average speed. The results show that the estimates from the divided travel time model are better fitted to observed data than those from the BPR model 본 연구는 교차로 지체를 고려한 통행시간함수를 개발하고, 이를 도시가로망에 적용하여 분석하는데 그 목적을 두고 있다. 이는 기존 통행배정 모형이 교차로 지체를 적절히 고려하지 못하고 있다는 분석에 근거하고 있다. 이를 위하여 본 연구에서는 링크의 통행시간을 구간 순행시간과 교차로 지체시간으로 구분하고, 청주시 주행속도, 교통량, 기하구조 및 신호운영 자료 등을 수집하여 계획단계에 적절한 구간 순행시간과 교차로 지체시간 산출모형을 구축하고, 이를 통행배정 단계에 적용하여 그 타당성을 분석하는데 중점을 두고 있다. 주요 연구결과는 다음과 같다. 첫째, 교차로 지체시간을 산출하기 위해 교차로의 녹색시간비 대신 접근로의 차로수비율을 교차로 유형별로 보정한 후, 이를 실제 녹색시간비율과의 t-검정을 시행하여, 평균값에 차이가 없다는 귀무가설을 기각할 수 없는 것으로 분석되어, 보정 차로수비율을 모형구축에 적용하였다. 둘째, 기존의 BPR모형과 보정 차로수비를 이용한 균일지체기반 수정모형 및 Webster기반 수정모형을 청주시 가로망에 EMME/2를 활용하여 통행배정하여 주행속도 조사자료와 비교한 결과, BPR모형은 교차로 지체의 영향을 반영하지 못하는 것으로 나타난 반면에 균일지체기반 수정모형과 Webster기반 수정모형은 관측된 조사자료에 보다 근접한 결과를 보였다. 셋째, 이들 모형의 배정결과와 실측 통행시간, 교통량, 평균통행속도간 통계검증 결과 통행시간 분리모형이 BPR모형 보다 실측치와의 통계적 오차가 감소하는 것으로 분석되었다.

소프트 링크 용량 제약 조건을 결합한 이용자 균형 통행배정 알고리즘 개발

류승규 한국도로학회 2021 한국도로학회논문집 Vol.23 No.5

PURPOSES : This study aims to develop an algorithm to solve the user equilibrium traffic assignment problem using soft link capacity constraints. This model is used to relax the hard capacity constraints model. METHODS : In the traffic assignment model that imposes the hard capacity constraints, the well-known solution algorithms used are the augmented Lagrange multiplier method and the inner penalty function method. The major drawback of using the hard-capacity constraint model is the feasible solution issue. If the capacities in the network are not sufficient to absorb the flow from the diverged flows through the hard capacity constraints, it might result in no solution; whereas, using a soft capacity constraint model guarantees a feasible solution because the soft capacity constraint model uses the penalization of constraint violation in the objective function. In this study, the gradient projection (GP) algorithm was adapted. RESULTS : Two numerical experiments were conducted to demonstrate the features of the soft capacity constraint model and the computational performance of the solution algorithm. The results revealed that imposing the soft link capacity constraints can ensure convergence. CONCLUSIONS : The proposed model can be easily extended by considering other traffic assignment models, for e.g., non-additive traffic equilibrium problem, stochastic traffic equilibrium model, and, elastic demand traffic equilibrium problem. Furthermore, the model can exist regardless of the sufficient capacity for each O-D pair to cater to their demands.

패키지 여행상품 가격결정 및 자원할당 문제 연구

윤문길 ( Moon Gil Yoon ),황명선 ( Myung Sun Hwang ),박광식 ( Kwang Sik Park ) 한국항공경영학회 2014 한국항공경영학회지 Vol.12 No.2

여행상품은 출발시점 이후에 가치가 소멸되는 소멸성 자산으로 불확실한 수요발생에 대한 체계적인 가격 및 수요관리가 절실히 요구된다. 소멸성 자산에 대한 가격설계 문제는 수익경영 연구 분야에서 많은 연구가 수행되어 왔으나, 여행상품에 대한 연구는 매우 제한적이었다. 본 연구에서는 여행상품을 구성하는 주요 공급원인 항공사의 좌석과 호텔의 객실에 대한 공급제약이 주어진 환경에서 불확실한 시장수요를 고려한 여행상품의 가격결정과 자원할당 문제를 다룬다. 본 연구에서는 여행상품의 공급제약 특성과, 고객의 해지, 일정변경, 가격정책의 변화 등을 반영하여 가격결정과 자원할당이 가능한 통합 최적화 모형을 개발한다. 모의실험 결과 본 연구에서 제시한 모형이 여행사 현장에서 효과적으로 적용될 수 있음을 확인하였다. 그러나 시장수요의 변동, 고객들의 주관적 선호도 등을 고려하여 다양한 할인가격을 결정할 수 있는 연구로 확장되어야 하고, 동적 최적가격결정 모형으로 확장될 필요가 있다. 이 같은 확장 연구에 본 연구가 효과적으로 활용될 것이다. Since tour products has been recognized as a perishable asset which has no values after the service is offered, it need to manage pricing and demand control schemes efficiently for maximizing the total revenue under uncertain demand. Pricing and capacity assignment problems have been studied as a revenue management problem in airlines and hotel industries. However, there are few researches on Revenue Management problems in the area of tourism industry. In this paper, we concentrate on pricing and capacity assignment problem for tour products to maximize the total revenue. In particular, we will focus on the air-inclusive package tour products using airlines as transport mode. The problem can be modeled as a stochastic programming problem. Applying the linear approximation technique and given the price set for each time, we suggest a mixed Integer Programming model to solve our problem efficiently. With some computational results, we can find our model makes good pricing decision and capacity control for tour companies, and can be expanded to other comprehensive problems.

Pilot Sequence Assignment for Spatially Correlated Massive MIMO Circumstances

( Pengxiang Li ),( Yuehong Gao ),( Zhidu Li ),( Dacheng Yang ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.1

For massive multiple-input multiple-output (MIMO) circumstances with time division duplex (TDD) protocol, pilot contamination becomes one of main system performance bottlenecks. This paper proposes an uplink pilot sequence assignment to alleviate this problem for spatially correlated massive MIMO circumstances. Firstly, a single-cell TDD massive MIMO model with multiple terminals in the cell is established. Then a spatial correlation between two channel response vectors is established by the large-scale fading variables and the angle of arrival (AOA) span with an infinite number of base station (BS) antennas. With this spatially correlated channel model, the expression for the achievable system capacity is derived. To optimize the achievable system capacity, a problem regarding uplink pilot assignment is proposed. In view of the exponential complexity of the exhaustive search approach, a pilot assignment algorithm corresponding to the distinct channel AOA intervals is proposed to approach the optimization solution. In addition, simulation results prove that the main pilot assignment algorithm in this paper can obtain a noticeable performance gain with limited BS antennas.

Harmony Search Algorithm for Continuous Network Design Problem with Link Capacity Expansions

Ozgur Baskan 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.1

The Continuous Network Design Problem (CNDP) deals with determining the set of link capacity expansions and the corresponding equilibrium link flows which minimizes the system performance index defined as the sum of total travel times and investment costs of link capacity expansions. In general, the CNDP is characterized by a bilevel programming model, in which the upper level problem is generally to minimize the total system cost under limited expenditure, while at the lower level problem, the User Equilibrium (UE)link flows are determined by Wardrop’s first principle. It is well known that bilevel model is nonconvex and algorithms for finding global or near global optimum solutions are preferable to be used in solving it. Furthermore, the computation time is tremendous for solving the CNDP because the algorithms implemented on real sized networks require solving traffic assignment model many times. Therefore, an efficient algorithm, which is capable of finding the global or near global optimum solution of the CNDP with less number of traffic assignments, is still needed. In this study, the Harmony Search (HS) algorithm is used to solve the upper level objective function and numerical calculations are performed on eighteen link and Sioux Falls networks. The lower level problem is formulated as user equilibrium traffic assignment model and Frank-Wolfe method is used to solve it. It has been observed that the HS algorithm is more effective than many other compared algorithms on both example networks to solve the CNDP in terms of the objective function value and UE traffic assignment number.

Capacity Assignment and Routing for Interactive Multimedia Service Networks

Byung Ha Lim,박준성 한국통신학회 2010 Journal of communications and networks Vol.12 No.3

A binary linear integer program is formulated for the problem of expanding the capacity of a fiber optic network and routing the traffic to deliver new interactive multimedia services. A two-phase Lagrangian dual search procedure and a Lagrangian heuristic are developed. Computational results show superior performance of the two-phase subgradient optimization compared with the conventional one-phase approach.

Capacity design by developed pole placement structural control

Fereidoun Amini,Kaveh Karami 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.1

To ensure safety and long term performance, structural control has rapidly matured over the past decade into a viable means of limiting structural responses to strong winds and earthquakes. Nonlinear response history analysis requires rigorous procedure to compute seismic demands. Therefore the simplified nonlinear analysis procedures are useful to determine performance of the structure. In this investigation, application of improved capacity demand diagram method in the control of structural system is presented for the first time. Developed pole assignment method (DPAM) in structural systems control is introduced. Genetic algorithm (GA) is employed as an optimization tool for minimizing a target function that defines values of coefficient matrices providing the placement of actuators and optimal control forces. The ground acceleration is modified under induced control forces. Due to this, performance of structure based on improved nonlinear demand diagram is selected to threshold of nonlinear behavior of structure. With small energy consumption characteristics, semi-active devices are especially attractive solutions for limiting earthquake effects. To illustrate the efficiency of DPAM, a 30-story steel moment frame structure employing the semi-active control devices is applied. In comparison to the widely used linear quadratic regulation (LQR), the DPAM controller was shown to be just as effective and better in the reduction of structural responses during large earthquakes.

구매유예 옵션 상품의 도입을 고려한 항공사 좌석배분 모형 연구

윤문길 ( Moon-gil Yoon ),이휘영 ( Hwi-young Lee ) 한국항공경영학회 2017 한국항공경영학회지 Vol.15 No.6

항공시장의 경쟁 심화는 비즈니스 모형의 변화를 가져왔고, 대표적인 것이 서비스 분할을 통한 부가서비스의 도입이다. 부가서비스는 항공사의 수익성 개선에 기여하여 왔고, 많은 항공사에서 다양한 형태의 부가서비스 도입을 시도하고 있다. 본 연구에서는 예약 확정 후 일정기간 구매를 유예하는 구매유예 옵션상품을 고려하는 경우 최대 수익을 위한 좌석배분 문제를 다룬다. 기존의 연구에서는 확률적 동적계획법으로 최적화 모형을 제시하고 있으나, 현실적인 적용이 어려워 본 연구에서는 기대한계수익 개념을 이용한 모형을 개발하고자 한다. 개발된 구매유예 옵션상품을 고려한 좌석배분 모형에 대하여 모의실험을 통해 본 연구에서 제시한 모형이 수익증대에 기여하고 있음을 확인한다. 모의실험을 통해 구매유예 옵션상품과 같은 부가서비스의 도입을 고려할 때, 수익경영 모형 자체의 개발 보다는 고객특성에 대한 분석이 사전적으로 이루어지는 것이 중요함을 확인할 수 있다. 본 연구 모형은 항공산업뿐만 아니라 여행, 호텔, 렌터카, 공연, 외식 등 예약기반의 비즈니스 영역으로 효과적으로 확장될 수 있다. Severe competition in the airline market has brought on changes in the business model, and a typical one is an introduction of ancillary services generated from service un-bundling. Ancillary services have contributed to improving the profitability of airlines and most airlines are trying to introduce various types of ancillary services. This study deals with the seat assignment for maximizing profits when considering commitment options for deferred purchases after a reservation is confirmed. In the previous research, stochastic dynamic programming model has been suggested for solving the problem effectively. However, due to the difficulty of estimation for real time parameters in the model, it is very hard to employ the model in practice. In this study, we will develop a model based on the concept of expected marginal revenue. The simulation with a randomly generated data show that our model makes some contribution in revenue gain. From the simulation, we can find that when introducing ancillary services such as a commitment option, more important one is to analyze customer characteristics in advance than the development of a RM model itself. Our models can be expanded to various service industries, such as concert shows, hotels, travel, and rental cars.

Capacity design by developed pole placement structural control

Amini, Fereidoun,Karami, Kaveh Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.1

To ensure safety and long term performance, structural control has rapidly matured over the past decade into a viable means of limiting structural responses to strong winds and earthquakes. Nonlinear response history analysis requires rigorous procedure to compute seismic demands. Therefore the simplified nonlinear analysis procedures are useful to determine performance of the structure. In this investigation, application of improved capacity demand diagram method in the control of structural system is presented for the first time. Developed pole assignment method (DPAM) in structural systems control is introduced. Genetic algorithm (GA) is employed as an optimization tool for minimizing a target function that defines values of coefficient matrices providing the placement of actuators and optimal control forces. The ground acceleration is modified under induced control forces. Due to this, performance of structure based on improved nonlinear demand diagram is selected to threshold of nonlinear behavior of structure. With small energy consumption characteristics, semi-active devices are especially attractive solutions for limiting earthquake effects. To illustrate the efficiency of DPAM, a 30-story steel moment frame structure employing the semi-active control devices is applied. In comparison to the widely used linear quadratic regulation (LQR), the DPAM controller was shown to be just as effective and better in the reduction of structural responses during large earthquakes.