• Journal of Korean Port Research
• /
• 제9권2호
• /
• pp.1-8
• /
• 1995

Generally, berth assignment problem has conflicting factors according to the interested parties. In the view of shipping company, it is desirable that berth assignment is made according to the order of arrival. But in the view of port operator, it is better to be assigned regardless the order of arrival to promote the efficiency of berth operation. Thus, it is necessary to establish berth assignment planning which reflects both of interests in a practical situation. This paper aims to develop a reasonable berth assignment algorithm in a container terminal by considering the prescribed factors, and suggests three types of models minimizing the objective functions such as total port staying time, total mooring time and total maximum mooring time by using MPS concept. These models are formulated by 0-1 integer programming and min-max type function, but as the number of variables increases, an optimal solution cannot be achieved easily within a desired computational time. Thus, to tackle this problem this paper proposes a heuristic algorithm, and also the heuristic algorithm proposed in this paper is verified through the several examples.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 한국해양정보통신학회 2009년도 추계학술대회
• /
• pp.245-248
• /
• 2009

Recently, Many studies have been progressing to path-finding with dynamic information on the Terminal Based Navigation System(TBNS). However, the most of existing algorithms are based on $A{\ast}$ algorithm. Path-finding algorithms which use heuristic function may occur a problem of the increase of exploring cost in case of that there is no way determined by heuristic function or there are 2 way more which have almost same cost. In this paper, two abstract graph(AG) that are different method of construction, Homogeneous Node merging($AG^H$) and Connected Node Merging($AG^C$), are implemented. The abstract graph is a simple graph of real road network. The method of using the abstract graph is proposed for reducing dependency of heuristic and exploring cost. In result of evaluation of performance, $AG^C$ has better performance than $AG^H$ at construction cost but $AG^C$ has worse performance than $AG^H$ exploring cost.

• Journal for History of Mathematics
• /
• 제22권3호
• /
• pp.45-60
• /
• 2009

Mathematical thinking can be symbolized by the external signs, and these signs determine in reverse the form of mathematical thinking. Each symbol - a symbol in algebra, a symbol in analysis, and a diagram which verifies syllogism - reflects the diverse characteristic of cogitation in mathematics and perfirms a heuristic function.

• Proceedings of the KOR-KST Conference
• /
• 대한교통학회 2007년도 제56회 학술발표회논문집
• /
• pp.89-97
• /
• 2007

본 연구에서는 통행배정 모형이 갖는 여러 가지 가정 중 대칭적 통행비용 함수를 갖는 가정을 극복할 수 있는 방법에 대해 살펴보았다. 통행배정 문제에 있어서 대칭적 비용함수 가정이라는 것은 링크의 통행비용은 다른 링크의 교통량에 전혀 영향을 받지 않는 않으면서, 동시에 해당 링크를 통과하는 단하나의 수단에 의해서만 결정된다는 의미이다. 본 연구에서는 이러한 가정을 극복할 수 있는 비대칭 통행배정모형의 특성을 살펴보고, 그 해석 모형에 대해 고찰하였다. 이 때 대표적 비대칭 통행배정 문제인 다수단 통행배정 모형을 중심으로 문제를 정의하여 검토하였다. 대각화(Diagonalized) 알고리즘과 Column Generation에 기반한 heuristic 모형을 다수단 통행배정 모형에 적용하여 그 결과를 분석하였다. 그 과정을 통해 대각화 알고리즘은 초기해의 수단과 수렴기준 수단에 따라 서로다른 해를 갖는 복수의 평형해(Equilibria)특성을 가지고 있었다. 그에 비해 Column Generation에 기반한 heuristic 모형은 Euclidean Norm을 이용한 부분최적화를 통해 복수의 평형해(Equilibria)에 관한 문제점을 개선할 수 있었다.

• The KIPS Transactions:PartB
• /
• 제17B권5호
• /
• pp.389-398
• /
• 2010

The Vehicle Routing and Scheduling Problem with Time Windows(VRSPTW) is to establish a delivery route of minimum cost satisfying the time constraints and capacity demands of many customers. The VRSPTW takes a long time to generate a solution because this is a NP-hard problem. To generate the nearest optimal solution within a reasonable time, we propose the heuristic by using an ACO(Ant Colony Optimization) with multi-cost functions. The multi-cost functions can generate a feasible initial-route by applying various weight values, such as distance, demand, angle and time window, to the cost factors when each ant evaluates the cost to move to the next customer node. Our experimental results show that our heuristic can generate the nearest optimal solution more efficiently than Solomon I1 heuristic or Hybrid heuristic applied by the opportunity time.

• Journal of Korean Society of Transportation
• /
• 제25권6호
• /
• pp.161-170
• /
• 2007

The purpose of this study is to find the solution that overcomes the existing assumption of symmetric cost functions in multi-class assignment. In the assignment problem, the assumption of a symmetric cost function means that the link cost is determined by each unique mode and is not affected by any other modes. In this study, the authors have applied a diagonalized algorithm and a heuristic model based on column generation to a multi-class assignment model and analyzed the result. Through the study, the authors found that the diagonalized algorithm produces equilibrium solutions by the initial convergence condition. In contrast to the diagonalized algorithm, the column generation algorithm has improved the solution model to overcome the problem of equilibrium solutions in the diagonalized algorithm.

• Journal of Korea Multimedia Society
• /
• 제12권9호
• /
• pp.1333-1341
• /
• 2009

Tactical path-finding in computer games is path-finding where a path is selected by considering not only basic elements such as the shortest distance or the minimum time spend but also tactical information of surroundings when deciding character's moving trajectory. One way to include tactical information in path-finding is to represent a heuristic function as a sum of tactical quality multiplied by a weighting factor which is.. determined based on the degree of its importance. The choice of weighting factors for tactics is very important because it controls search performance and the characteristic of paths found. In this paper. we propose a method for improving a heuristic function by adjusting weights based on the difference between paths on examples given by a level designer and paths found during the search process based on the CUITent weighting factors. The proposed method includes the search algorithm modified to detect search errors and learn heuristics and the perceptron-like weight updating formular. Through simulations it is demonstrated how different paths found by tactical path-finding are from those by traditional path-finding. We analyze the factors that affect the performance of learning and show the example applied to the real game environments.

• Structural Engineering and Mechanics
• /
• 제66권4호
• /
• pp.465-476
• /
• 2018

In this paper, a new meta-heuristic optimization method is presented. This new method is named "Numbers Cup Optimization" (NCO). The NCO algorithm is inspired by the sport competitions. In this method, the objective function and the design variables are defined as the team and the team members, respectively. Similar to all cups, teams are arranged in groups and the competitions are performed in each group, separately. The best team in each group is determined by the minimum or maximum value of the objective function. The best teams would be allowed to the next round of the cup, by accomplishing minor changes. These teams get grouped again. This process continues until two teams arrive the final and the champion of the Numbers Cup would be identified. In this algorithm, the next cups (same iterations) will be repeated by the improvement of players' performance. To illustrate the capabilities of the proposed method, some standard functions were selected to optimize. Also, size optimization of three benchmark trusses is performed to test the efficiency of the NCO approach. The results obtained from this study, well illustrate the ability of the NCO in solving the optimization problems.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권10호
• /
• pp.4640-4661
• /
• 2018

To cope with the explosive growth of Internet services, Service Function Chaining (SFC) based on Software-defined Networking (SDN) is an emerging and promising technology that has been suggested to meet this challenge. Determining the placement of Virtual Network Functions (VNFs) and routing paths that optimize the network utilization and resource consumption is a challenging problem, particularly without violating service level agreements (SLAs). This problem is called the optimal SFC placement problem and an Integer Linear Programming (ILP) formulation is provided. A greedy heuristic solution is also provided based on an improved two-step mapping algorithm. The obtained experimental results show that the proposed algorithm can automatically place VNFs at the optimal locations and find the optimal routing paths for each online request. This algorithm can increase the average request acceptance rate by about 17.6% and provide more than 20-fold reduction of the computational complexity compared to the Greedy algorithm. The feasibility of this approach is demonstrated via NetFPGA-10G prototype implementation.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 한국해양공학회 2004년도 학술대회지
• /
• pp.62-67
• /
• 2004

Many ships in voyage experience weight and buoyancy distribution change by various reasons such as change of sea water density and waves, weather condition, and consumption of fuel, provisions, etc . The weight and buoyancy distribution change can bring the ships out of allowable trim, heeling angle. In these case, the ships should adjust trim and heeling angle by shifting of liquid cargo or ballasting, deballasting of ballast tanks for recovery of initial state or for a stable voyage. But, if the adjustment is performed incorrectly, ship's safety such as longitudinal strength, intact stability, propeller immersion, wide visibility, minimum forward draft cannot be secured correctly. So it is required that the adjustment of trim and heeling angle should be planned not by human operators but by optimization computer algorithm. To make an optimized plan to adjust trim and heeling angle guaranteeing the ship's safety and quickness of process, Uk! combined mechanical analysis and optimization algorithm. The candidate algorithms for the study were heuristic algorithm, meta-heuristic algorithm and uninformed searching algorithm. These are widely used in various kinds of optimization problems. Among them, heuristic algorithm $A^\ast$ was chosen for its optimality. The $A^\ast$ algorithm is then applied for the study. Three core elements of $A^\ast$ Algorithm consists of node, operator, evaluation function were modified and redefined. And we analyzed the $A^\ast$ algorithm by considering cooperation with loading instrument installed in most ships. Finally, the algorithm has been applied to tanker ship's various conditions such as Normal Ballast Condition, Homo Design Condition, Alternate Loading Condition, Also the test results are compared and discussed to confirm the efficiency and the usefulness of the methodology developed the system.