• Journal of Korean Society of Transportation
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• v.23 no.7 s.85
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• pp.99-110
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• 2005

Total travel cost of route which connects origin with destination (O-D) is consist of the total sum of link travel cost and route perception cost. If the link perception cost is different according to the origin and destination, optimal route search has limitation to reflect the actual condition by route enumeration problem. The purpose of this study is to propose optimal route searching formulation and algorithm which is enable to reflect different link perception cost by each route, not only avoid the enumeration problem between origin and destination. This method defines minimum unit of route as a link and finally compares routes using link unit costs. The proposed method considers the perception travel cost at both origin and destination in optimal route searching process, while conventional models refect the perception cost only at origin. However this two-way searching algorithm is still not able to guarantee optimum solution. To overcome this problem, this study proposed an orign based optimal route searching method which was developed based on destination based optimal perception route tree. This study investigates whether proposed numerical formulas and algorithms are able to reflect route perception behavior reflected the feature of origin and destination in a real traffic network by the example research including the diversity of route information for the surrounding area and the perception cost for the road hierarchy.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.1207-1213
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• 2006

오늘날 모바일 기기가 갖는 역할이 다양해짐과 동시에 모바일 플랫폼에서의 사용자 인터페이스(User Interface, UI)에 대한 연구 또한 활발히 이루어지고 있다. 이는 전통적인 데스크탑 플랫폼에서의 정보에 대한 일반적인 접근 방법이 모바일 기기에 적용하기에는 적절하지 않기 때문이며, 이는 모바일 기기의 제한된 스크린 크기, 부자연스러운 상호작용 방식, 그리고 기기와 관련된 기술적인 다른 요인들과 관련된다고 할 수 있다. 본 연구에서는 휴대폰, PDA, 스마트폰과 같이 작은 화면을 가진 모바일 기기에서 제시되는 메뉴를 탐색할 때 효과적인 메뉴 형식과 페이징 형식이 무엇인지 알아보고자 하였다. 메뉴 형식은 모바일 기기에서 일반적으로 많이 사용되는 열거형(list) 메뉴와 격자형(grid) 메뉴의 두 가지로 제시하였고, 페이징 형식은 한 번에 한 줄씩 화면 하단에서 위로 이동하는 스크롤(scrolling) 방식과 한 번에 한 화면 전체가 위로 이동하는 페이지 간(page-to-page) 이동 방식의 두 가지로 제시하였다. 실험 1 에서는 한 수준의 깊이를 가진 메뉴에서 메뉴 형식과 페이징 형식에 따른 탐색 과제 수행을 측정한 결과, 열거형 메뉴보다 격자형 메뉴에서 사용자들의 메뉴 탐색 수행이 유의미하게 빠르며, 사용자의 만족도 또한 높은 것으로 나타났다. 그러나 페이징 형식에 따른 메뉴 탐색 수행 시간과 선호도에는 유의미한 차이점이 없었고, 메뉴 형식과 페이징 형식간의 상호작용 또한 나타나지 않았다. 실험 2 의 결과, 두 수준의 깊이를 가진 메뉴에서는 페이징 방식이 메뉴 탐색 정확도에 미치는 유의미한 주효과가 있었다. 메뉴 탐색 수행 시간과 주관적 만족도는 실험 1 과 같게 나타났다. 이는 메뉴 형식과 페이징 방법에 따라 사용자의 수행과 선호도가 차이가 있음을 시사한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7A
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• pp.1080-1089
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• 1999

The union upper bounds to the bit error probability of maximum likelihood(ML) soft-decoding of parallel concatenated convolutional codes(PCCC) and serially concatenated convolutional codes(SCCC) can be evaluated through the weight enumerating function(WEF). This union upper bounds become the lower bounds of the BER achievable when iterative decoding is used. In this paper, to compute the WEF, an efficient error event search algorithm which is a combination of stack algorithm and bidirectional search algorithm is proposed. By computor simulation, it is shown that the union boounds obtained by using the proposed algorithm become the lower bounds to BER of concatenated convolutional codes with iterative decoding.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.3 s.8
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• pp.9-22
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• 2005

Route travel cost in transportation networks consists of actual route travel cost and route perception cost. Since the route perception cost is differently perceived according to each origin and each destination, route search has limitation to reflect the note perception cost due to route enumeration problem. Thus, currently employed advanced traveller information systems (ATIS) have considered only actual route travel cost for providing route information. This study proposes an optimal and a K-route searching algorithm which are able to reflect the route perception cost but encompass route enumeration problem. For this purpose, this research defines the minimum nit of route as a link by adopting the link label technique in route searching, therefore the comparison of two adjacent links which can be finally expanded the comparison of two routes. In order to reflect the characteristics of route perception in real situation, an optimal shortest cost path algorithm that both the forward search from the origin and the backward search from the destination can be simultaneously processed is proposed. The proposed algorithm is applied for finding K number of shortest routes with an entire-path-deletion-type of K shortest route algorithm.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.6
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• pp.1-20
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• 2022

The basic way to charge vehicles for using road and public transport networks is the entry-exit toll system. This system works by reading Hi-Pass and public transportation cards of the vehicles using card readers. However, the problems of navigating a route in consideration of entry-exit toll systems include the non-additive costs of enumerating routes. This problem is known as an NP-complete task that enumerates all paths and derives the optimal path. So far, the solution to the entry-exit toll system charging has been proposed in the form of transforming the road network. However, unlike in the public transport network where the cards are generalized, this solution has not been found in situations where network expansion is required with a transfer, multi-modes and multiple card readers. Hence, this study introduced the Link Label for a public transportation network composed of card readers in which network expansion is bypassed in selecting the optimal path by enumerating the paths through a one-to-one k-path search. Since the method proposed in this study constructs a relatively small set of paths, finding the optimal path is not burdensome in terms of computing power. In addition, the ease of comparison of sensitivity between paths indicates the possibility of using this method as a generalized means of deriving an optimal path.

• The Journal of Korean Association of Computer Education
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• v.9 no.3
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• pp.67-74
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• 2006

The purpose of this study is identifying variables that affect to learners' preference toward specific e-learning programs, using an exploratory factor analysis(EFA) method. We extract common factors that explain the correlations among variables. In the result, 8 factors were identified as main influential factors: e-learning program design(1st factor), the purpose of e-learning use(2nd factor), social and cultural issues(3rd factor), demographics(4th factor), organizational needs(5th factor), impacts of e-learning(6th factor), e-learning management(7th factor), and technical issue(8th factor).

• Journal of KIISE
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• v.44 no.9
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• pp.986-991
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• 2017

In this paper, we present a method for synthesizing imperative programs from input-output examples. Given (1) a set of input-output examples, (2) an incomplete program, and (3) variables and integer constants to be used, the synthesizer outputs a complete program that satisfies all of the given examples. The basic synthesis algorithm enumerates all possible candidate programs until the solution program is found (enumerative search). However, it is too slow for practical use due to the huge search space. To accelerate the search speed, our approach uses code optimization and avoids unnecessary search for the programs that are syntactically different but semantically equivalent. We have evaluated our synthesis algorithm on 20 introductory programming problems, and the results show that our method improves the speed of the basic algorithm by 10x on average.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.17-29
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• 2008

A volume-delay function(VDF) has been used to describe the relation between traffic volumes and delay experienced by travelers on the roads traveling from origin to destination, which has been usually adopted in traffic assignment. For the purpose of more precise description of traffic pattern, we have to estimate the parameters of VDF in advance. This paper presents a methodology for estimating the parameters, which combined with golden section method. By using the method we have estimated the parameters with real data based on KTDB(2006), and validated them. Compared to the existing values of the parameters, newly estimated values are found to be closer to real world.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.3
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• pp.60-67
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• 2016

In cumulative transfer functions, as number of transfer increase, the impact of individual transfer to transfer cost increase linearly or non linearly. This function can effectively explain various passengers's travel behavior who choose their travel routes in integrated transit line networks including bus and railway modes. Using the function, it is possible to simulate general situations such that even though more travel times are expected, less number of transfer routes are preferred. However, because travel cost with cumulative transfer function is known as non additive cost function types in route search algorithms, finding an optimal route in integrated transit networks is confronted by the insolvable enumeration of all routes in many cases. This research proposes a methodology for finding an optimal path considering cumulative transfer function. For this purpose, the reversal phenomenon of optimal path generated in route search process is explained. Also a heuristic methodology for selecting an optimal route among multiple routes predefined by the K path algorithm. The incoming link based entire path deletion method is adopted for finding K ranking path thanks to the merit of security of route optimality condition. Through case studies the proposed methodology is discussed in terms of the applicability of real situations.

• Journal of Korean Society of Transportation
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• v.23 no.2
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• pp.117-130
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• 2005

In both deteministic user Optimal Traffic Assignment Model (UOTAM) and stochastic UOTAM, travel time, which is a major ccriterion for traffic loading over transportation network, is defined by the sum of link travel time and turn delay at intersections. In this assignment method, drivers actual route perception processes and choice behaviors, which can become main explanatory factors, are not sufficiently considered: therefore may result in biased traffic loading. Even though there have been some efforts in Stochastic UOTAM for reflecting drivers' route perception cost by assuming cumulative distribution function of link travel time, it has not been fundamental fruitions, but some trials based on the unreasonable assumptions of Probit model of truncated travel time distribution function and Logit model of independency of inter-link congestion. The critical reason why deterministic UOTAM have not been able to reflect route perception cost is that the route perception cost has each different value according to each origin, destination, and path connection the origin and destination. Therefore in order to find the optimum route between OD pair, route enumeration problem that all routes connecting an OD pair must be compared is encountered, and it is the critical reason causing computational failure because uncountable number of path may be enumerated as the scale of transportation network become bigger. The purpose of this study is to propose a method to enable UOTAM to reflect route perception cost without route enumeration between an O-D pair. For this purpose, this study defines a link as a least definition of path. Thus since each link can be treated as a path, in two links searching process of the link label based optimum path algorithm, the route enumeration between OD pair can be reduced the scale of finding optimum path to all links. The computational burden of this method is no more than link label based optimum path algorithm. Each different perception cost is embedded as a quantitative value generated by comparing the sub-path from the origin to the searching link and the searched link.