• IE interfaces
• /
• v.16 no.1
• /
• pp.27-33
• /
• 2003

The maintenance cost in K Steelworks has been continuously increased in proportion to the production cost. However, there seems to be a possibility of reducing cost through the optimization of maintenance actions. The failure types of the equipment in steelworks ate various with different failure cost. Thus the failure rate and cost of each type of failures should be considered simultaneously when the optimum maintenance period is to be determined. It is considered that the equipment undergoes periodic replacement and a specified number of incomplete preventive maintenance actions are performed during a replacement period. Assuming that the time to failure follows a Weibull distribution, the parameters of the failure rate are estimated using the maximum likelihood estimation. The optimal replacement period is determined to minimize the average cost per unit time. As the result of analysis it is suggested that the existing maintenance period for a hot-rolling equipment can be extended significantly.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.387-390
• /
• 2008

The importance of the life cycle cost analysis for construction projects of bridge has been recognized over the last decades. Accordingly, theoretical models, guidelines, and supporting softwares have been developed for the life cycle cost analysis of bridges. However, it is difficult to predict life cycle cost considering uncertainties precisely. This paper presents methodology for optimal design of substructure for a steel box bridge. Total life cycle cost for the service life is calculated as sum of initial cost, damage cost considering uncertainty, maintenance cost, repair and rehabilitation cost. The optimization method is applied to design of a bridge substructure with minimal cost, in which the objective function is set to life cycle cost and constraints are formulated on the basis of Korean Bridge Design Specification. Initial cost is calculated based on standard costs of the Korea Construction Price Index and damage cost on the damage probabilities to consider the uncertainty of load and resistance. An advanced first-order second moment method is used as a practical tool for reliability analysis using damage probability. Maintenance cost and cycle is determined by a stochastic method and user cost includes traffic operation costs and time delay costs.

• The Journal of Korea Robotics Society
• /
• v.7 no.2
• /
• pp.150-159
• /
• 2012

In this paper, we propose a cost-aware Rapidly-exploring Random Tree (RRT) path planning algorithm for mobile robots. A mobile robot is presented with a cost map of the field of interest and assigned to move from one location to another. As a robot moves, the robot is penalized by the cost at its current location according to the cost map. The overall cost of the robot is determined by the trajectory of the robot. The goal of the proposed cost-aware RRT algorithm is to find a trajectory with the minimal cost. The cost map of the field can represent environmental parameters, such as temperature, humidity, chemical concentration, wireless signal strength, and stealthiness. For example, if the cost map represents packet drop rates at different locations, the minimum cost path between two locations is the path with the best possible communication, which is desirable when a robot operates under the environment with weak wireless signals. The proposed cost-aware RRT algorithm extends the basic RRT algorithm by considering the cost map when extending a motion segment. We show that the proposed algorithm gives an outstanding performance compared to the basic RRT method. We also demonstrate that the use of rejection sampling can give better results through extensive simulation.

• Solar Energy
• /
• v.13 no.2_3
• /
• pp.151-156
• /
• 1993

The comparison of solar energy technologies with conventional technologies involves more than just comparing the costs of supplying energy and provding capacity. Solar technologies supply energy in a sustainable manner while having minimal effects on the environment. When choosing between solar energy technologies and conventional technologies, first cost is a important factor. The environmental and other social benifits of using solar energy technologies contrasts sharply with the environmental degradation and social costs resulting from the use of conventional technologies. These hidden costs, sometimes called "social cost", are not included in conventional economics. This paper is emphasized that the consideration of social costs effects comparisons between renewable and conventional energy technologies is of importance.

• Proceedings of the IEEK Conference
• /
• 2002.06e
• /
• pp.107-110
• /
• 2002

Soft masks mean that part or all of the program code for operating system or applications are located in the EEPROM or flash ROM. Since Soft masks allow errors to be corrected and programs to be modified quickly and at minimal cost, they are used primarily during testing and in the field trials. This paper introduces a hardware architecture of IC card for soft masks. We suggest a new down loading scheme for soft-mask ROM connected by an I/O interface. This scheme saves the new IC card development cost and time.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.13 no.21
• /
• pp.51-60
• /
• 1990

In this paper we deal with the miniaml cost network flow problem with uncertain arc capacity constraints. When the arc capacities are fuzzy with linear L-R type membership function, using parametric programming procedure, we reduced it to the deterministic minimal cost network flow problem which can be solved by various typical network flow algorithms. A modified Algorithm using the Out-of-kilter algorithm is developed.

• Journal of Korean Society for Quality Management
• /
• v.22 no.3
• /
• pp.54-65
• /
• 1994

A hybrid warranty policy for a repairable item is considered. Assuming that minimal repairs ar e performed for failures during warranty period, present worth of warranty cost is derived from a supplier's viewpoint. An optimal preventive periodic replacement policy for the case is also derived from a user's viewpoint Numerical examples are presented in order to explain the results.

• International Journal of Reliability and Applications
• /
• v.5 no.4
• /
• pp.147-154
• /
• 2004

This work developed and algorithm for a set covering model when the reliability of covers is a concern. This model extended the usage of the set covering model.

• Journal of the Korean Data and Information Science Society
• /
• v.14 no.2
• /
• pp.393-403
• /
• 2003

In this paper, various replacement policies for the general failure model are considered. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. In this model, when the unit fails at its age t, Type I failure occurs with probability 1-p(t) and Type II failure occurs with probability p(t), $0{\leq}p(t){\leq}1$. Under the model, optimal replacement policies for the long-run average cost rate and the limiting efficiency are considered. Also taking the cost and the efficiency into consideration at the same time, the properties of the optimal policies under the Cost-Priority-Criterion and the Efficiency-Priority-Criterion are obtained.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.10
• /
• pp.81-92
• /
• 1995

In this paper, we present a high-level synthesis system that generates area-efficient RT-level datapaths with multiport memories. The proposed scheduling algorithm assigns an operation to a specific control step such that maximal sharing of functional units can be achieved with minimal number of memory ports, while satisfying given constraints. We propose a measure of multiport memory cost, MAV (Multiple Access Variable) which is defined as a variable accessed at several control steps , and overall memory cost is reduced by equally distributing the MAVs throughout all the control steps. Experimental results show the effectiveness of the proposed algorithm. When compared with previous approaches for several benchmarks available from literature, the proposed algorithm generates the datapaths with less memory modules and interconnection structures by reflecting the memory cost in the scheduling process.