• Journal of Korean Society for Quality Management
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• v.47 no.3
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• pp.479-496
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• 2019

Purpose: The purpose of this research is to develop defense quality evaluation model in order to improve the problem of private sector quality evaluation model and propose the total integrated defense quality management model which enables to evaluate not only large defense industry, but also small-medium industry. Methods: This paper consider the characteristics on ISO 9001 Quality Management System, single PPM, PASS and defense quality and develop defense quality maturity model and index which enables to measure the current quality management level and characteristics and to evaluate operational characteristics in each maturity level for domestic defense industry. Results: From 176 DQMS certified defense industry, the defense quality maturity level is 68,2, C grade. The large defense industry shows, 80.9, A grade; medium industry 69.7, C grade; small-medium industry shows 54.1, D grade. Through the classified types of industries, the current level of quality management of defense industries was diagnosed and the areas to be supplemented for the total quality management were identified. Conclusion: Developed DQMI can be used as the basic information for spreading quality management activities in the defense industry by diagnosing the overall quality management of existing defense industries and quantifying the ambiguity of non-metric measurements and measurement standard that were presented as the threshold of the defense quality management system certification process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.866-870
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• 2008

In this study, we designed cold gas propulsion system with minimum 0.25 mm nozzle and micro-thrust measurement system to analyze flow characteristic of micro propulsion system in ambient and vacuum condition. Argon and Nitrogen are used for propellant and the result of experiments is compared with CFD analysis and theory. But there is a point where reduced scale versions of conventional propulsion systems will no longer be practical. Therefore, a fundamentally different approach to propulsion systems was taken. That is thermal transpiration based micro propulsion system. It has no moving parts such as lubricants, pressurizing system and can pump the gaseous propellant by temperature gradient only(cold to hot). We are advancing basic research of propulsion system based on thermal transpiration in vacuum conditions and had tried experiment process and theoretical access in advance. To characterize membrane of Knudsen pump, we select Polyimide material that has low thermal conductivity(0.29 W/mK) and can stand high temperature($300^{\circ}C$) for long time. And we fabricated hole diameter 1, 0.5, 0.2, 0.1 mm using precision manufacturing. Experimental results show that pressure gradient efficiency of Knudsen pump is increased to maximum 82% according to Knudsen number and thick membranes are more effective than thin membranes in transition flow regime.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.96-99
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• 2012

The test facility for confirming performance of a propulsion system is essential infra-structure to develop launch vehicle system. Using the PSTC, cold flow and combustion tests are performed to the propulsion system of individual stage in launcher. Moreover the ground test for the total launching process is conducted. In order to construct the PSTC, we not only have surveyed technology of internal and external countries, but also actively use the case in terms of the system. The test facility consists of feeding system, test stand, control and measurement, and flame deflector.

• Smart Structures and Systems
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• v.2 no.2
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• pp.127-140
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• 2006

In this study, a wavelet-based covariance-driven system identification technique is proposed for damage assessment of structures under ambient excitation. Assuming the ambient excitation to be a white-noise process, the covariance computation is shown to be able to separate the effect of random excitation from the response measurement. Wavelet transform (WT) is then used to convert the covariance response in the time domain to the WT magnitude plot in the time-scale plane. The wavelet coefficients along the curves where energy concentrated are extracted and used to estimate the modal properties of the structure. These modal property estimations lead to the calculation of the stiffness matrix when either the spectral density of the random loading or the mass matrix is given. The predicted stiffness matrix hence provides a direct assessment on the possible location and severity of damage which results in stiffness alteration. To demonstrate the proposed wavelet-based damage assessment technique, a numerical example on a 3 degree-of-freedom (DOF) system and an experimental study on a three-story building model, which are all under a broad-band excitation, are presented. Both numerical and experimental results illustrate that the proposed technique can provide an accurate assessment on the damage location. It is however noted that the assessment of damage severity is not as accurate, which might be due to the errors associated with the mode shape estimations as well as the assumption of proportional damping adopted in the formulation.

• Structural Engineering and Mechanics
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• v.56 no.2
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• pp.257-273
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• 2015

Numerical value of correlation between effective parameters in the strength of a structure is as important as its stochastic properties in determining the safety of the structure. In this article investigation is made about the variation of coefficient of correlation between effective parameters in corrosion initiation time of reinforcement and the time of concrete cover cracking in reinforced concrete (RC) structures. Presence of many parameters and also error in measurement of these parameters results in uncertainty in determination of corrosion initiation and the time to crack initiation. In this paper, assuming diffusion process as chloride ingress mechanism in RC structures and considering random properties of effective parameters in this model, correlation between input parameters and predicted time to corrosion is calculated using the Monte Carlo (MC) random sampling. Results show the linear correlation between corrosion initiation time and effective input parameters increases with increasing uncertainty in the input parameters. Diffusion coefficient, concrete cover, surface chloride concentration and threshold chloride concentration have the highest correlation coefficient respectively. Also the uncertainty in the concrete cover has the greatest impact on the coefficient of correlation of corrosion initiation time and the time of crack initiation due to the corrosion phenomenon.

• Wind and Structures
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• v.11 no.1
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• pp.19-33
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• 2008

This research investigates the adaptive input estimation method applied to the multilayer shearing stress structure. This method is to estimate the values of wind load inputs by analyzing the active reaction of the system. The Kalman filter without the input term and the adaptive weighted recursive least square estimator are two main portions of this method. The innovation vector can be produced by the Kalman filter, and be applied to the adaptive weighted recursive least square estimator to estimate the wind load input over time. This combined method can effectively estimate the wind loads to the structure system to enhance the reliability of the system active performance analysis. The forms of the simulated inputs (loads) in this paper include the periodic sinusoidal wave, the decaying exponent, the random combination of the sinusoidal wave and the decaying exponent, etc. The active reaction computed plus the simulation error is regard as the simulated measurement and is applied to the input estimation algorithm to implement the numerical simulation of the inverse input estimation process. The availability and the precision of the input estimation method proposed in this research can be verified by comparing the actual value and the one obtained by numerical simulation.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.5 s.143
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• pp.542-549
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• 2005

Naval ships are complex weapon systems which play the integrated performance by system integration of many kinds of weapon systems and their leading ships are usually not disposed after test and evaluation but militarised. Then, strict project management is required for naval ship building projects by identifying problems early and by taking prefer measures in time against unexpected situations encountered in the process of the projects. EVMS is a project management system which can manage the schedule and the budget of a project concurrently and estimate the project's time duration and the cost at project completion. In this paper, the applicability and usefulness of WMS is studied for a assumed navai ship building project, in the environment of monetary fluctuations such as price index, wage increase rate and exchange rate.

• Solar Energy
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• v.20 no.1
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• pp.31-43
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• 2000

The Korea Institute of Energy Research(KIER) has been collecting horizontal global radiation data since May, 1982 for 16 different locations. KIER's new data is expected to be extensively used by designer and researchers of solar systems in lieu of unreliable old ones. Unfortunately, the quality of the data has not always been properly mentioned. Some of them were taken at temporary field stations where the primary goal of the measurement was quick estimation of local solar radiation. The purpose of this study is to systematically identify errors in such data set using clear-day analysis in an effort to rehabilitate error-ridden old data. Clear-day analysis successfully uncovered solar radiation data that had questionable quality. Even through the rehabilitation process not necessarily improves the quality of data for daily or monthly mean, it can be used to improve the quality of data for monthly means of several years and the processed data can be used in various applications of solar energy with more confidence. A average ETR value of 0.63 obtained in this study is in good agreement with previous results obtained by other researchers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.889-894
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• 2004

Infrared (IR) detectors are widely used for many applications, such as temperature measurement, intruder and fire detection, robotics and industrial equipment, thermoelstic stress analysis, medical diagnostics, and chemical analysis. Quantum detectors commonly need to be refrigerated below 80 K, and thus a cooling system should be equipped together with the detector system. The cooling load, which should be removed by the cooling system to maintain the nominal operating temperature of the detector, critically depends on the insulation efficiency of the cryochamber housing the detector. Thermal analysis of cryochamber includes the conduction heat transfer through a cold well, the gases conduction and gas outgassing, as well as radiation heat transfer, The transient cooling characteristics of an infrared detector cryochamber are investigated experimentally in the present study. The transient cooling load increases as the gas pressure is increased. Gas pressure becomes significant as the cooling process proceeds. Cool down time is also increased as the gas pressure is increased. It is also found that natural convection effects on cool down time become significant when the gas pressure is increased.

• Journal of the Korea Society of Computer and Information
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• v.15 no.1
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• pp.83-90
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• 2010

The number of searched nodes and the computation time in an index should be minimized for optimizing the processing cost of the nearest neighbor query. The Measurement of search distance considered a circular location property of objects is required to accurately select the nodes which will be searched in the nearest neighbor query. In this paper, we propose the processing method of the nearest neighbor query be considered a circular location property of object where the search space consists of a circular domain and show its performance by experiments. The proposed method uses the circular minimum distance and the circular optimal distance which are the search measurements for optimizing the processing cost of the nearest neighbor query.