• Journal of Korean Society for Quality Management
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• v.52 no.2
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• pp.275-286
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• 2024

Purpose: The spare part cost is one of the most important cost factors with which construct Life Cycle Cost. The LCSP(Life Cycle Sustainment Plan) Guidebook issued by Korea Ministry of Defense, however, suggests a simple equation to estimate the spare part cost using maintenance task frequencies and each part cost. Therefore, following the cost estimation method in the LCSP Guidebook may lead to an improper cost estimation result since both the hierarchical structure of the weapon system and the part discard rate are not considered. The purpose of this study is to develop a new life cycle cost estimation method for spare parts of weapon system during its life cycle. Methods: In this study, the detailed cost structure of spare parts is provided. Also a new spare part cost estimation methods for the each cost element are proposed, considering the hierarchical structure of weapon system and the part discard rate. And the proposed spare cost estimation methods are applied to K system for a case study. Results: Based on the case study of K system, the spare part cost estimation method, proposed by this study, shows that it can complement the estimation method suggested by the LCSP Guidebook. It also shows that it is applicable to the weapon systems for Korea armed forces. Conclusion: The proposed life cycle cost estimation method for spare parts has an advantage of estimating the spare part cost more accurately. It is expected to be useful in analyzing the procurement alternatives objectively and making up the Korea armed forces budget effectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.6
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• pp.3208-3229
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• 2017

Rectification is an essential procedure for simplifying the disparity extraction of stereo matching algorithms by removing vertical mismatches between left and right images. To support real-time stereo matching, studies have introduced several look-up table (LUT)- and computational logic (CL)-based rectification approaches. However, to support high-resolution images, the LUT-based approach requires considerable memory resources, and the CL-based approach requires numerous hardware resources for its circuit implementation. Thus, this paper proposes a multi-level accumulation-based rectification method as a simple CL-based method and its circuit implementation. The proposed method, which includes distortion correction, reduces addition operations by 29%, and removes multiplication operations by replacing the complex matrix computations and high-degree polynomial calculations of the conventional rectification with simple multi-level accumulations. The proposed rectification circuit can rectify $1,280{\times}720$ stereo images at a frame rate of 135 fps at a clock frequency of 125 MHz. Because the circuit is fully pipelined, it continuously generates a pair of left and right rectified pixels every cycle after 13-cycle latency plus initial image buffering time. Experimental results show that the proposed method requires significantly fewer hardware resources than the conventional method while the differences between the results of the proposed and conventional full rectifications are negligible.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.3
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• pp.275-286
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• 2015

In this paper, we propose a practical method for setting up a daily production plan which can operate semiconductor fabrication factories more stably and linearly by determining work in process (WIP) targets and movement targets. We first adjust cycle times of the operations to satisfy the monthly production plan. Second, work in process (WIP) targets are determined to control the production progress of operations: earliness and tardiness. Third, movement targets are determined to reduce cumulated differences between WIP targets and actual WIPs. Finally, the determined movement targets are modified through a simulation model which considers capacities of the equipments and allocations of the WIPs in the fab. The proposed daily production planning method can be easily adapted to the memory semiconductor fabs because the method is very simple and has straightforward logics. Although the proposed method is simple and straightforward, the power of the method is very strong. Results from the shop floor in past few periods showed that the proposed methodology gives a good performance with respect to the productivity, workload balance, and machine utilization. We can expect that the proposed daily production planning method will be used as a useful tool for operating semiconductor fabrication factories more efficiently and effectively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1349-1355
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• 1990

By examining the fatigue deformation properties of 12% Cr rotor steel which has been proved to have high fatigue and creep rupture strength around 600deg. C, authors reviewed major fatigue life prediction models such as Manson, Langer and Morrow equations, and following results were obtained. (1) A simple life prediction model for 12% Cr rotor steel was obtained as follows : DELTA..epsilon.$_{t}$ =2.18+.sigma.$_{u}$ /E+ $N^{-0.065}$+ $e^{0.6}$ $N^{-0.025}$ This equation shows that fatigue life, N, can be easily determined when total strain range, DELTA..epsilon.$_{t}$ and ultimate tensile strength, .sigma.$_{u}$ are known by simple tension test on the given test conditions. (2) Life prediction equation with equivalent maximum stress, DELTA..sigma./2, corresponding maximum strain in one cycle at room temperature is as follows: DELTA..sigma./w=-7.01logN+96.69+96.69

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.5
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• pp.675-683
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• 2002

The purposes of the study were to analyze the changes in formal attires and decorative features of middle age Korean women during the last half of 20th century and to find out any significant differences in formal attires according to periods. The study was a documentary research, and data were collected from 344 family wedding photographs by convenient sampling. The statistics used were content analysis, frequency and a time series analysis, and the results were as follows : 1. Four schematic clusters of formal attires were categorized according to skirt(chima) length and width, jacket(jogori) length, motifs and decorative features; simple classic, decorative classic, fashionable, and extravagant fashionable. Simple classic attires were popular until 1960s, the decorative classics were appeared from late 1960s to 1970s, fashionable attires were introduced from the late 1970s and the attires became more luxurious and extravagant until 2000. 2. Color symbolism in couples mothers'attires according to the couples gender - pink or red for the bride's mother and blue or green for groom's mother - was introduced from the late 1970s, and reached the maximum level by the early 1980s but slowly disappeared after the late 1980s. 3. The complete fashion cycle did not exist in the formal attires'change, however, since the Period of data were ranged from 1943 to 2000, the 57 years period may not long enough to measure a complete fashion cycle.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.4
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• pp.157-164
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• 2022

The TMD has a simpler structure than other vibration control devices and shows excellent control performance for the standardized vibration occurring in the structure. However, when the vibration cycle of the structure coincides with the vibration cycle of the TMD due to the sudden external loads, the off-tuning occurs, which threatens the structure while increasing the vibration width of the TMD. Therefore, Electromagnetic Tuned Mass Damper (ETMD) was developed as a semi-active TMD that prevents off-tuning while exhibiting excellent control performance like TMD. To verify the control performance of the developed ETMD, the bending behavior control performance evaluation experiment using a simple beam bridge was performed. The experimental method compared the mutual control power by experimenting with the existing TMD method and the developed ETMD under nine excitation frequency conditions. As a result, it was confirmed that the control effect of ETMD was about 4.85% higher than that of TMD at 3.02Hz, which generates the maximum displacement in the simple beam bridge. Also, the off-tuning occurred in some excitation conditions when using TMD, although the off-tuning did not occur when using ETMD. Therefore, the excellent control performance of the ETMD developed in this study was verified.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.129-131
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• 2006

This paper presents a new ZVS-PWM high frequency inverter. The ZVS operation is achieved in the whole load range by using a simple auxiliary reverse blocking switch in parallel with series resonant capacitor. The operating principle and the operating characteristics of the new high frequency circuit treated here are illustrated and evaluated on the basis of simulation results. It was examined that the complete soft switching operation can be achieved even for low power setting ranges by introducing the high frequency dual duty cycle control scheme. In the proposed high frequency inverter treated here, the dual mode pulse modulation control strategy of the asymmetrical PWM in the higher power setting ranges and the lower power setting ones, the output power of this high frequency inverter could introduce in order to extend soft switching operation ranges. Dual duty cycle is used to provide a wide range of output power regulation that is important in many high frequency inverter applications. It is more suitable for induction heating applications the operation and control principle of the proposed high frequency inverter are described and verified through simulated results.

• 연구논문집
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• s.34
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• pp.39-46
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• 2004

The compressors in the air conditioner have the role of the pressurization and circulation of the refrigerant. The hermetic reciprocating compressors driven by rotary motor have been used for the air conditioner. The linear compressor has very simple structure and enhancement in the efficiency in comparison to that of conventional reciprocating compressor. The linear compressors are widely used for the small cryogenic refrigerator (below 1 kW), such as the Stirling refrigerator and pulse tube refrigerator. In the cryogenic application, the pressure ratio of the linear compressor is below 1.5, but the linear compressor for the air conditioner should overcome the high pressure ratio and the large pressure difference between the each sides of the piston. The resonance characteristics of the linear compressor has the significant impacts on the power consumption. To minimize the power consumption, the linear compressor should be operated at the resonance point. In the resonance characteristics, the role of the mechanical and gas spring should be considered. In present study, the cycle of the analysis of the vapor compression refrigeration cycle with the different refrigerants (R134a, R4l0a, R600a) and the designs of the linear compressor are performed. The effects of the stiffness of the mechanical spring on the electromagnetic forces would be discussed. Finally, the results show the design specification of the linear compressor for the air conditioner.

• Korean Journal of Adult Nursing
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• v.26 no.2
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• pp.139-148
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• 2014

Purpose: This study was aimed to investigate the factors influencing problem drinking of male drinkers above 19 years old according to the life cycle. Methods: The study subjects consisted of a representative community sample of 2,229 male drinkers aged 19 and older from the 2011 Korean National Health and Nutrition Examination Survey. The collected data were analyzed using descriptive statistics, Rao-Scott $x^2$-test, simple and multiple logistic regressions. Results: The problem drinking rates were 38.7% in adolescence, 44.5% in middle age, and 23.9% in senescence. In adolescence, the predictors of problem drinking included occupation, stress recognition, and smoking. In middle age, the predictors of problem drinking were education level, depression, and smoking. In senescence, the predictors of problem drinking were not identified in this study. Conclusion: The findings of this study suggested that the factors influencing problem drinking of male drinkers were different according to life cycle. Thus different intervention methods should be developed for each age group in order to intervene the problem drinking.

• Communications for Statistical Applications and Methods
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• v.25 no.3
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• pp.283-296
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• 2018

Ranked set sampling, as introduced by McIntyre (Australian Journal of Agriculture Research, 3, 385-390, 1952), dealt with the estimation of the mean of one population. To deal with two or more variables, different forms of bivariate and multivariate ranked set sampling were suggested. For a technique to be useful, it should be easy to implement in practice. Bivariate ranked set sampling, as introduced by Al-Saleh and Zheng (Australian & New Zealand Journal of Statistics, 44, 221-232, 2002), is not easy to implement in practice, because it requires the judgment ranking of each of the combination of the order statistics of the two characteristics. This paper investigates two modifications that make the method easier to use. The first modification is based on ranking one variable and noting the rank of the other variable for one cycle, and do the reverse for another cycle. The second approach is based on ranking of one variable and giving the second variable the same rank (Concomitant Order Statistic) for one cycle and do the reverse for the other cycle. The two procedures are investigated for an estimation of the means of some well-known distributions. It is show that the suggested approaches can be used in practice and can be more efficient than using SRS. A real data set is used to illustrate the procedure.