• Journal of Korean Institute of Industrial Engineers
• /
• v.30 no.4
• /
• pp.285-293
• /
• 2004

In this study, a machine grouping problem for the formation of manufacturing cells is considered. We constructed the problem as minimizing manufacturing leadtime consisting of parts' processing, moving, and waiting time. Specifically, the main objective of the defined problem is established as minimizing inter-cell traffic in order to minimize the part's moving time. In addition, to reduce the waiting time of parts, the load balance among cells is implicitly included as constraints. Since this problem is well known as NP-complete and cannot be solved in polynomial time, a genetic algorithm is implemented to obtain solutions. Also, a local optimization algorithm is applied in order to improve the solution by the genetic algorithm. Several experiments show that the suggested algorithms guarantee near optimal solutions in a few seconds.

• Journal of the Korean Society of Industry Convergence
• /
• v.11 no.2
• /
• pp.83-91
• /
• 2008

GMAW(Gas Metal Arc Welding) processes are usually used in industrial side in order to get its high productivity. But those are only adopted in the semi-automated welding equipment because of a lot of welding spatters. Many industrial robot actually percents from being engaged in the welding processes. The welding spatter problem of causes blocking them being a fully automated welding process.This study was carried out to investigate the optimal conditions for minimizing welding spatter generation at GMAW robot. The spatter can be significantly reduced below 2% of welding spatter generation at the following conditions ; First, below 18V at the wire-feed rate 2.0mm/min Second, below 23V at the wire-feed rate 3.6mm/min Third, below 24V at the wire-feed rate 5.5mm/min.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 1993.10a
• /
• pp.1395-1404
• /
• 1993

Application of water-saving self-feeders can reduce water consumption of pigs by more than 50% . so the feeding-watering system one of the most important way of the reduction of the slurry. Bioactive deep litter housing can eliminate slurry. Matured urine, faeces and litter can use for the purposes of soil conditioning and fertilizing . Water-saving slurry handling technology can halve manure dilution so it can double the nutrient content of the slurry. By using of straw bale biofilter for reducing emissions of pig houses makes fattening of pigs possible close to populated area. Developed rate control system for slurry application make avoiding over-fertilization possible , can fulfill better the demand of nutrient of plants. By means of computer aided manure utilization system area distribution of soil characteristics can determinate . The system is suitable for planning the utilization of manure and slurry in environment -friendly way.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.2
• /
• pp.334-343
• /
• 2017

The optimum design of an SAR (Synthetic Aperture Radar) satellite constellation is developed herein using a genetic algorithm. The performance of Earth observations using a satellite constellation can be improved by minimizing the maximum revisit time. Classical orbit design using analytic methods has limitations when addressing orbit dynamics due to various disturbances. To overcome this issue, an optimization technique based on a genetic algorithm is used. STK (Systems Tool Kit) is utilized to propagate the satellite orbit when considering external disturbances, and the maximum revisit time on the earth observation area is calculated. By minimizing the performance index using a genetic algorithm, the optimum orbit of the satellite constellation is designed. Numerical results are provided to demonstrate the performance of the proposed method.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1998.10a
• /
• pp.182-185
• /
• 1998

In the two-tier CDMA cellular system with microcells and overlaying macrocells, slow-moving mobile user are assigned to microcells and those who move fast are assigned to overlaying macrocells in order to minimize the total number of handoffs. With this consideration the problem is how to find the thresholds by which the system distinguishes fast-moving user from those who move slowly based on the estimated speed of users. In this paper, two methods for the mobile speed estimation are proposed and two operations schemes for micro-macro cellular CDMA system are suggested. Based on these, Optimization models to find the optimal thresholds for micro-macrocell selection, which are subject to the constrains of QoS, are developed in view of minimizing the weighted total number of handoffs. And then algorithms to find optimal solutions of the models are devised.

• Journal of Astronomy and Space Sciences
• /
• v.25 no.4
• /
• pp.361-374
• /
• 2008

Recently, satellite formation flying has been a topic of significant research interest in aerospace society because it provides potential benefits compared to a large spacecraft. Some techniques have been proposed to design optimal formation trajectories minimizing fuel consumption in the process of formation configuration or reconfiguration. In this study, a method is introduced to build fuel-optimal trajectories minimizing a cost function that combines the total fuel consumption of all satellites and assignment of fuel consumption rate for each satellite. This approach is based on collocation and nonlinear programming to solve constraints for collision avoidance and the final configuration. New constraints of nonlinear equality or inequality are derived for final configuration, and nonlinear inequality constraints are established for collision avoidance. The final configuration constraints are that three or more satellites should form a projected circular orbit and make an equilateral polygon in the horizontal plane. Example scenarios, including these constraints and the cost function, are simulated by the method to generate optimal trajectories for the formation configuration and reconfiguration of multiple satellites.

• Journal of Navigation and Port Research
• /
• v.32 no.9
• /
• pp.737-742
• /
• 2008

In this paper, we deal with an allocation model of vertical type container yard for minimizing the total ATC (Automated Transfer Crane) working time and the equivalence of ATC working load in each block on automated container terminal. Firstly, a layout of automated container terminal yard is shown The characteristic of equipment which work in the terminal and its basic assumption are given Next, an allocation model which concerns with minimizing the total working time and the equivalence of working load is proposed for effectiveness of ATC working in automated container terminal. Also, a weight values on critical function are suggested to adjust the critical values by evaluating the obtained allocation plan. For ATC allocation algorithm, we suggest a simple repeat algorithm for on-line terminal operation.

• Journal of Power Electronics
• /
• v.9 no.3
• /
• pp.335-342
• /
• 2009

The Z-source inverter (ZSI) provides unique features such as the ability to boost dc voltage with a single stage simple structure. Although the dc capacitor voltage can be boosted by a shoot-through state, the voltage stress across the switching devices is rapidly increased, so high switching device power is required at the ZSI. In this paper, algorithms for minimizing the voltage stress are suggested. The possible operating region for obtaining a desired ac output voltage according to both the shoot-through time and active state time is investigated. The reference capacitor voltages are derived for minimizing the voltage stress at any desired ac output voltage by considering the dc input voltage. The proposed methods are carried out through the simulation studies and experiments with 32-bit DSP.

• Communications for Statistical Applications and Methods
• /
• v.6 no.2
• /
• pp.443-456
• /
• 1999

The estimation of mean lifetimes in presence of interval censoring with mixed replacement procedure are examined when the distribution s of lifetimes are exponential. it is assumed that due to physical restrictions and/or economic constraints the number of failures is investigated only at several inspection times during the lifetime test; thus there is interval censoring. Comparisons of mixed replacement designs are made with those with and without replacement The maximum likelihood estimator is found in an implicit form. The Cramer-Rao lower bound which is the asymptotic variance of the estimator is derived. The test conditions for minimizing the Cramer-Rao lower bound and minimizing the test costs within a desired width of the Cramer-Rao bound have been studied.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.35 no.1
• /
• pp.79-86
• /
• 2012

This study focuses on the problem of scheduling wafer lots of several recipe(operation condition) types in the photolithography workstation in a semiconductor wafer fabrication facility, and sequence-dependent recipe set up times may be required at the photolithography machines. In addition, a lot is able to be operated at a machine when the reticle(mask) corresponding to the recipe type is set up in the photolithography machine. We suggest various heuristic algorithms, in which developed recipe selection rules and lot selection rules are used to generate reasonable schedules to minimizing the total weighted flowtime. Results of computational tests on randomly generated test problems show that the suggested algorithms outperform a scheduling method used in a real manufacturing system in terms of the total weighted flowtime of the wafer lots with ready times.