• Computers and Concrete
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• v.14 no.2
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• pp.145-161
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• 2014

The article presents the statistical method of grouping the results of the compressive strength of concrete in continuous production. It describes the method of dividing the series of compressive strength results into batches of statistically stable strength parameters at specific time intervals, based on the standardized concept of "concrete family". The article presents the examples of calculations made for two series of concrete strength results, from which sets of decreased strength parameters were separated. When assessing the quality of concrete elements and concrete road surfaces, the principal issue is the control of the compressive strength parameters of concrete. Large quantities of concrete mix manufactured in a continuous way should be subject to continuous control. Standardized approach to assessing the concrete strength proves to be insufficient because it does not allow for the detection of subsets of the decreased strength results, which in turn makes it impossible to make adjustments to the concrete manufacturing process and to identify particular product or area on site with decreased concrete strength. In this article two independent methods of grouping the test results of concrete with statistically stable strength parameters were proposed, involving verification of statistical hypothesis based on statistical tests: Student's t-test and Mann - Whitney - U test.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.405-411
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• 2013

Purpose: In this study, the mounting status of trial case lens was investigated. Methods: We measured distances between geometric center of lens mount and optical center of lens and angle deviations between axis mark on lens and real axis using arbitrary trial case lens sets distributed in Korea, and then, compared those results with international standards. Results: In some of lenses, the prismatic power on geometric center of lens mount and the angle deviations between axis mark and real axis of cylindrical lens were out of tolerance according international standards. Conclusions: The more precise control of the manufacturing process and more thorough quality control for trial case lenses will be required to offer an accurate vision test.

• Journal of the Korean Operations Research and Management Science Society
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• v.18 no.3
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• pp.151-157
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• 1993

In this paper, we investigate the effects of yield randomness for lot-sizing in a multi-stage production system. The practical importance of incorporating yield randomness into production models has been emphasized by many researchers. Yield randomness, especially in semiconductor manufacturing, poses a mojor challenge for production planning and control. The task becomes even more difficult if the demand for final product is uncertain. An attempt to meet the demand with a higher level of confidence forces one to release more input in the fabrication line. This leads to excessive work-in-process (WIP) inventories which cause jobs to spend unpredictably longer time waiting for the machines. The result is that it is more difficult to meet demand with exceptionally long cycle time and puts further pressure to increase the safety stocks. Due to this spiral effect, it is common to find that the capital tied in inventory is the msot significant factor undermining profitability. We propose a policy to determine the quantity to be processed at each stage of a multi-stage production system in which the yield at each stage may be random and may need rework.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.409-412
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• 2006

In process of reinforced concrete(RC) box structure, the heat of hydration may cause serious thermal cracking problems. In order to eliminate hydration heat of mass concrete, this paper reports results of hydration heat control in mass concrete using the OCHP(Oscillating Capillary tube Heat Pipe). Recently OCHP is drawn special attention from these points of low cost as well as short construction schedule for the manufacturing of heat exchanger, flexibility, simplification and high performance. There were three RC box molds$(1.2{\times}1.2{\times}1.2m)$ which shows a difference as compared with each other. One was not equipped with OCHP. While others were equipped with OCHP and these were cooled with air natural convection and spraying water respectively. The OCHP was composed of copper pipe with 12 turns(O.D : 4mm, I.D : 2.8mm). The working fluid was R-22 and its charging ratio was 30(Vol. %). In order to analyze the distribution of temperature and index figure of thermal crack in sequential placement of mass concrete, we used HYCON of computer program. As a result of the experiment, the peak temperature decreased about $15.6\sim23.4^{\circ}C$ than the general specimen and the probability of thermal crack generated in mass concrete decreased up to 0%.

• Korean Journal of Construction Engineering and Management
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• v.9 no.6
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• pp.185-193
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• 2008

As buildings become higher and larger, the possibility of accident also increases, and recurrent accidents and serious accidents are also increasing. However, it is not possible to control all the hazardous activities in construction site. Therefore, hazardous activities with higher possibility should be identified and prioritized in advance so engineers and managers can control the activities in safe manner. For this purpose, this research adopts FMEA technique, which has been widely utilized in manufacturing industry. In order to apply FMEA technique in construction safety management, the process of construction work is divided into sub-processes or activities. Then FMEA technique is applied to quantitatively analyze the importance of each activity from the safety perspective.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.218-220
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• 2006

Sn-3.0Ag-0.5Cu solder is widely used as micro-joining materials of flip chip package(FCP) because of the fact that it causes less dissolution and has good thermal fatigue property. However, compared with ternary electroplating in the manufacturing process, binary electroplating is still used in industrial field because of easy to make plating solution and composition control. The objective of this research is to fabricate Sn-3.0Ag-0.5Cu solder bumping having accurate composition. The ternary Sn-3.0Ag-0.5Cu solder bumping could be made on a Cu pad by sequent binary electroplating of Sn-Cu and Sn-Ag. Composition of the solder was estimated by EDS and ICP-OES. The thickness of the bump was measured using SEM and the microstructure of intermetallic-compounds(IMCs) was observed by SEM and EDS. From the results, contents of Ag and CU found to be at $2.7{\pm}0.3wt%\;and\;0.4{\pm}0.1wt%$, respectively.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.10
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• pp.847-852
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• 2016

In this paper, important design parameters for parallel kinematic robots are defined, paying special attention to machining errors which may cause kinematic errors at the end effector of a robot. The kinematic effects caused by each design parameter, as well as their upper/lower limits, are analyzed here. To do so, we have developed a novel software program to compute kinematic errors by considering its defined design parameters. With this program, roboticists designing parallel kinematic robots can understand the important design parameters for which upper/lower allowances have to be strictly controlled in the design process. This tactic can be used for the design of high-speed, parallel kinematic robots to reduce the design/manufacturing costs and increase kinematic precision.

• Journal of the Korean Society of Tobacco Science
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• v.19 no.1
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• pp.51-56
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• 1997

This experiment was conducted to reduce the cost of orient leaf using izmir, samsun and basma scraps in cigarettes manufacturing process. We manufactured rolled and paper sheet tobacco using orient scraps and substituted orient leaf in Pine tree to the rolled and paper sheet tobacco using orient scraps. Orient scraps were lower in total sugar, total sugar/nicotine and total nitrogen/nicotine, higher in nicotine and crude ash than those of orient leaves. Izmir and basma scraps were higher of 2-methyl butanoic, 3-methyl butanoic and 3-methyl pentanoic acid, but the chemical contents in samw scraps were lower than those of orient leaves. The specific gravity thickness, flness index, filling value were similar between orient scraps blended sheet tobacco and present sheet tobacco. The physical characteristics of orient scraps blended sheet tobacco were within Present sheet tobacco quality specification. The sheet tobacco using orient scraps was higher 2-metal butanoic, 3-methyl butanoic and 3-methyl pentanoic acid than those of present sheet tobacco. The rolled processed sheet tobacco using orient scraps was higher 2-methyl butanoic, 3-methyl butanoic and 3-methyl Pentanoic acid than those of paper sheet tobacco using orient scraps. The sample cigarettes using orient scraps sheet tobacco were lower 2-methyl butanoic, 3-mettwl butanoic and 3-mettwl Pentanoic acid than those of control cigarettes. The result of sensory test showed no great difference compared with sample of orient scraps and control cigarettes. This result shows that we can possible to substitute orient leaf to orient scraps to reduce the cost of orient leaf.

• Journal of the Korea Society for Simulation
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• v.14 no.3
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• pp.91-100
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• 2005

Grid computing is widely applicable to various fields of industry including process control and manufacturing, military command and control, transportation management, and so on. In a viewpoint of application area, grid computing can be classified to three aspects that are computational grid, data grid and access grid. This paper focuses on computational grid which handles complex and large-scale computing problems. Computational grid is characterized by system dynamics which handles a variety of processors and jobs on continuous time. To solve problems of system complexity and reliability due to complex system dynamics, computational grid needs scheduling policies that allocate various jobs to proper processors and decide processing orders of allocated jobs. This paper proposes a service prediction-based job scheduling model and present its scheduling algorithm that is applicable for computational grid. The service prediction-based job scheduling model can minimize overall system execution time since the model predicts the next processing time of each processing component and distributes a job to a processing component with minimum processing time. This paper implements the job scheduling model on the DEVS modeling and simulation environment and evaluates its efficiency and reliability. Empirical results, which are compared to conventional scheduling policies, show the usefulness of service prediction-based job scheduling.

• Proceedings of the Korea Society for Simulation Conference
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• 2005.05a
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• pp.29-33
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• 2005

Grid computing is widely applicable to various fields of industry including process control and manufacturing, military command and control, transportation management, and so on. In a viewpoint of application area, grid computing can be classified to three aspects that are computational grid, data grid and access grid. This paper focuses on computational grid which handles complex and large-scale computing problems. Computational grid is characterized by system dynamics which handles a variety of processors and jobs on continuous time. To solve problems of system complexity and reliability due to complex system dynamics, computational grid needs scheduling policies that allocate various jobs to proper processors and decide processing orders of allocated jobs. This paper proposes the service prediction-based job scheduling model and present its algorithm that is applicable for computational grid. The service prediction-based job scheduling model can minimize overall system execution time since the model predicts a processing time of each processing component and distributes a job to processing component with minimum processing time. This paper implements the job scheduling model on the DEVSJAVA modeling and simulation environment and simulates with a case study to evaluate its efficiency and reliability Empirical results, which are compared to the conventional scheduling policies such as the random scheduling and the round-robin scheduling, show the usefulness of service prediction-based job scheduling.