• Journal of Korean Society for Quality Management
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• v.18 no.2
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• pp.18-24
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• 1990

The location of inspection stations is a significant component of production systems. In this paper, a prototype expert system is designed for deciding the optimal location of inspection stations. The production system is defined as a single channel of n serial operation stations. The potential inspection station can be located after any of the operation stations. Nonconforming units are generated from a compound binomial distribution with known parameters at any given operation station. Traditionally Dynamic programming, Zero-one integer programming, or Non-linear programming techniques are used to solve this problem. However a problem with these techniques is that the computation time becomes prohibitively large when t be number of potential inspection stations are fifteen or more. An expert system has the potential to solve this problem using a rule-based system to determine the near optimal location of inspection stations. This prototype expert system is divided into a static database, a dynamic database and a knowledge base. Based on defined production systems, the sophisticated rules are generated by the simulator as a part of the knowledge base. A generate-and-test inference mechanism is utilized to search the solution space by applying appropriate symbolic and quantitative rules based on input data. The goal of the system is to determine the location of inspection stations while minimizing total cost.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1453-1463
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• 1999

An electromagnetic flowmeter, based on a magnetic induction principle; provides an obstructionless flowmeter that essentially averages the velocity distribution over the pipe cross-sectional area. To predict the installation effects, the flowmeter installed near $90^{\circ}$ elbow is simulated by using a commercial code FLUENT(ver. 4.48) for the laminar flow field and a code developed through this study for magnetic field. The installation effects of the flowmeter are estimated by varying a number of the dependent parameters such as the radius of the elbow(Rc=1D, 1.5D, 2D, 3D), the location, Reynolds number and the direction of electrodes plane(${\varphi}$). It was found that all these factors affect the performance of the electromagnetic flowmeter significantly. The longer installation distance from the elbow is not always optimal to minimize the error, and also there exists an optimal location to install the EMF for a minimum error. Especially the flow signal with the electrodes plane direction of ${\varphi}=45^{\circ}$ is shown to yield smallest measurement error regardless of the Reynolds number and the curvature of elbow.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.157-164
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• 2012

When designing a multifunctional system consisting of many components performing many functions or missions, it is important to determine the reliability, availability, and maintainability (RAM) of the system and components, and we consider system availability to be the optimization criterion. For given intervals of mean time between failure (MTBF) and mean time to repair (MTTR) of the components, we want to determine the values of MTBF and MTTR for all components that satisfy the target availability. A heuristic method is proposed for finding near-optimal solutions through simulation. We also study numerical examples to check effects of model parameters on the optimal solutions.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.745-745
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• 2002

Both geophysical and geospatial data provide important information in the establishment of the optimal telecommunication systems especially in the mobile telecommunication environment. The objective of this study is to utilize geophysical properties and geospatial information in the analysis of the telecommunication environment through point-to-point wave property modeling. Geophysical properties associated with wave propagation parameters of the earth surface were analyzed based on hierarchical land classification using Landsat ETM＋ and IKONOS images. Three-dimensional geospatial information was obtained by processing stereo aerial images. The results show that the accurate geospatial information and reliable geosphysical property of the surface improve the prediction of receiving power of the receivers located near corners of the buildings where diffractions occur. The wave property model developed from accurate telecommunication environment could be applied to optimal cell planning and delay time analysis.

• Journal of the Korean Society of Safety
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• v.37 no.3
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• pp.45-51
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• 2022

This paper focuses on a recently proposed asymmetric base-isolation coupling control system (ABiCS) for the vibration control of adjacent twin buildings. The ABiCS consists of inter-story diagonal dampers, a connecting damper between the two buildings, and a seismic isolation device at the base floor of one building. To investigate the control characteristics of ABiCS, a parametric study was performed by numerically simulating the 20-story twin buildings. In the parametric study, the control capacities of the inter-story diagonal dampers, connecting damper, and seismic isolation device were considered as varying parameters. The parametric study results indicate that the connecting damper between the two buildings reduces the responses of both buildings only at optimal or near-optimal capacity. In addition, adjusting the stiffness of the base isolation is found to be the most effective method for improving seismic performance and achieving cost-effectiveness. Accordingly, we presented a scenario-based performance improvement approach in which reducing the stiffness of the base isolation device could be an effective technique to improve the seismic performance of both buildings. However, note that checking the maximum allowable displacement of the base isolation device is essential.

• Geomechanics and Engineering
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• v.38 no.6
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• pp.553-569
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• 2024

In recent tunneling projects, encounters with multi-layered strata have become more frequent as the desired scale of tunneling increases. Despite substantial practical experience, the design of large-diameter shield-driven tunnels often simplifies the surrounding ground as uniform, overlooking the complexities introduced by non-uniform geotechnical factors. This study comparatively analyzed the influence of design factors, particularly segment stiffness and joint parameters, on segmental lining behavior in layered ground conditions using numerical methods. A comprehensive parametric study revealed the significant impact of deformative interaction between the lining and the soft top soil layer on overall tunnel behavior. Permitting lining deformation in the soft soil layer effectively mitigated the induced internal forces but resulted in considerable tunnel lining convergence, adopting a peanut-shaped appearance. From a practical design perspective, application of a soft segment with lower stiffness near the stiff soil layer is an economically advantageous approach, alleviating internal forces within an acceptable convergence level. Notably, around the interfaces between soil layers with different stiffnesses, the induced internal forces in the lining were minimized based on joint rotational stiffness and location. This indicates the possibility of achieving an optimal design for segmental lining joints under layered ground conditions. Additionally, a preliminary design method was proposed, which sequentially optimizes parameters for joints located near soil layer interfaces. Subsequently, a specialized design based on the proposed method for complex multi-layered strata was compared with a conventional design. The results confirmed that the internal force was effectively relieved at an allowable lining deflection level.

• Radiation Oncology Journal
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• v.10 no.1
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• pp.95-100
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• 1992

Since LINAC-based stereotactic radiosurgery uses multiple noncoplanar arcs, three-dimensional dose evaluation and many beam parameters, a lengthy computation time is required to optimize even the simplest case by a trial and error. The basic approach presented in this paper is to show promising methods using an experimental optimization and an analytic optimization The purpose of this paper is not to describe the detailed methods, but introduce briefly, proceeding research done currently or in near future. A more detailed description will be shown in ongoing published papers. Experimental optimization is based on two approaches. One is shaping the target volumes through the use of multiple isocenters determined from dose experience and testing. The other method is conformal therapy using a beam's eye view technique and field shaping. The analytic approach is to adapt computer-aided design optimization in finding optimum irradiation parameters automatically.

• Journal of Environmental Impact Assessment
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• v.22 no.6
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• pp.713-724
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• 2013

In terms of waste load allocation, inequality of waste load discharge must be considered as well as economic aspects such as minimization of waste load abatement. The inequality of waste load discharge between areas was calculated with Gini coefficient and was included as one of the objective functions of the multi-objective waste load allocation. In the past, multi-objective functions were usually weighted and then transformed into a single objective optimization problem. Recently, however, due to the difficulties of applying weighting factors, multi-objective genetic algorithms (GA) that require only one execution for optimization is being developed. This study analyzes multi-objective waste load allocation using NSGA-II-aJG that applies Pareto-dominance theory and it's adaptation of jumping gene. A sensitivity analysis was conducted for the parameters that have significant influence on the solution of multi-objective GA such as population size, crossover probability, mutation probability, length of chromosome, jumping gene probability. Among the five aforementioned parameters, mutation probability turned out to be the most sensitive parameter towards the objective function of minimization of waste load abatement. Spacing and maximum spread are indexes that show the distribution and range of optimum solution, and these two values were the optimum or near optimal values for the selected parameter values to minimize waste load abatement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.193-214
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• 2017

In this paper, we study the problem of network utility maximization in a CSMA based multi-hop wireless network. Existing work in this aspect typically adopted continuous time Markov model for performance modelling, which fails to consider the channel conflict impact in actual CSMA networks. To maximize the utility of a CSMA based wireless network with channel conflict, in this paper, we first model its weighted network capacity (i.e., network capacity weighted by link queue length) and then propose a distributed link scheduling algorithm, called CSMA based Maximal-Weight Scheduling (C-MWS), to maximize the weighted network capacity. We derive the upper and lower bounds of network utility based on C-MWS. The derived bounds can help us to tune the C-MWS parameters for C-MWS to work in a distributed wireless network. Simulation results show that the joint optimization based on C-MWS can achieve near-optimal network utility when appropriate algorithm parameters are chosen and also show that the derived utility upper bound is very tight.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.160-164
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• 2003

Materials processing by ultrashort pulsed laser is actively being applied to micromachining technology due to its advantages with regard to non-thermal machining. In this study, materials processing with ultrashort pulses was studied by using the high repetition rate of a 800 nm Ti:sapphire regenerative amplifier. This revealed that the highly precise micromachining of metallic thin film and bulk glass with a minimal heat affected zone (HAZ) could be obtained by using near damage threshold energy. Grooves with diffraction limited sub-micrometer width were obtained with widths of 620 nm on Cr thin film and 800 nm on a soda-lime glass substrate. The machined patterns were investigated through SEM images. We also phenomenologically examined the influence of variations of parameters and proposed the optimal process conditions for microfabrication.