• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1445-1451
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• 2011

Pneumatic valves are widely used parts that have the ability to control the air supplied to automation systems. However, if failure occurs in a pneumatic valve, it may affect the entire system and could lead to huge losses, depending on the characteristics of the system at the time of failure. Because of this significant risk and the level of consumer demand for reliability, there has been much study on ensuring the reliability of products by predicting valve lifetime distributions and degradation characteristics. In this paper, in order to determine the main factors useful for predicting the lifetime of a pneumatic valve, the scale parameter and $B_{10}$ life time value of the widely used plug-in-type pneumatic manifold valves were measured using complete observational data on the valve lifetimes. And also the property of life distribution has been distribution-suitabilityreviewed by correlation coefficients, the degradation characteristics of valve has been presented by the result of analysis through dynamic response time test and leakage test.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.4
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• pp.13-22
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• 2007

The uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modeling system under uncertainty was described and demonstrated for use in watershed management and receiving-water quality prediction. A watershed model (HSPF), a receiving water quality model (WASP), and a wetland model (NPS-WET) were incorporated into an integrated modeling system (modified-BASINS) and applied to the Hwaseong Reservoir watershed. Reservoir water quality was predicted using the calibrated integrated modeling system, and the deterministic integrated modeling output was useful for estimating mean water quality given future watershed conditions and assessing the spatial distribution of pollutant loads. A Monte Carlo simulation was used to investigate the effect of various uncertainties on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorous (T-P) in the Hwaseong Reservoir, considering uncertainty, would be less than about 4.8 and 0.26 mg 4.8 and 0.26 mg $L^{-1}$, respectively, with 95% confidence. The effects of two watershed management practices, a wastewater treatment plant (WWTP) and a constructed wetland (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaseong Reservoir to less than 3.54 and 0.15 mg ${L^{-1}$, 26.7 and 42.9% improvements, respectively, with 95% confidence. Overall, the Monte Carlo simulation in the integrated modeling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on probability and level of risk, and its application is recommended.

• Journal of Biosystems Engineering
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• v.17 no.1
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• pp.65-78
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• 1992

When using a computer vision system for a measurement, the geometrically distorted input image usually restricts the site and size of the measuring window. A geometrically distorted image caused by the image sensing and processing hardware degrades the accuracy of the visual measurement and prohibits the arbitrary selection of the measuring scope. Therefore, an image calibration is inevitable to improve the measuring accuracy. A calibration process is usually done via four steps such as measurement, modeling, parameter estimation, and compensation. In this paper, the efficient error calibration technique of a geometrically distorted input image was developed using a neural network. After calibrating a unit pixel, the distorted image was compensated by training CMLAN(Cerebellar Model Linear Associator Network) without modeling the behavior of any system element. The input/output training pairs for the network was obtained by processing the image of the devised sampled pattern. The generalization property of the network successfully compensates the distortion errors of the untrained arbitrary pixel points on the image space. The error convergence of the trained network with respect to the network control parameters were also presented. The compensated image through the network was then post processed using a simple DDA(Digital Differential Analyzer) to avoid the pixel disconnectivity. The compensation effect was verified using known sized geometric primitives. A way to extract directly a real scaled geometric quantity of the object from the 8-directional chain coding was also devised and coded. Since the developed calibration algorithm does not require any knowledge of modeling system elements and estimating parameters, it can be applied simply to any image processing system. Furthermore, it efficiently enhances the measurement accuracy and allows the arbitrary sizing and locating of the measuring window. The applied and developed algorithms were coded as a menu driven way using MS-C language Ver. 6.0, PC VISION PLUS library functions, and VGA graphic functions.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.1-9
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• 2008

The current test methods are insufficient to evaluate and ensure the safety and reliability of vehicle system for all possible dynamic situation including the worst case such as rollover, spin-out and so on. Although the known NHTSA J-turn and Fish-hook steering maneuvers are applied for the vehicle performance assessment, they aren't enough to estimate other possible worst case scenarios. Therefore, it is crucial for us to verify the various worst cases including the existing severe steering maneuvers. This paper includes the procedure to search for other useful worst case based upon the existing worst case scenarios mentioned above and its application in simulation basis. The only human steering angle is selected as a design parameter here and optimized to maximize the index function to be expressed in terms of either roll angle or yaw rate. The obtained scenarios were enough to generate the worst case to meet NHTSA worst case definition (ex.2-inch wheel lift). Additionally, as an application, the worst case steering maneuver is acquired for the vehicle to operate with a simple ESP system. It has been concluded that the new procedure in this paper is adequate to create other feasible worst case scenarios for a vehicle system both with an intelligent safety control system and without it.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.105-113
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• 2002

In this study, the steady state performance analysis program was developed for a turboprop engine, and its performance was analyzed at uninstalled and installed conditions. For the purpose of evaluation the developed program was compared with the performance data provided by the engine manufacturer and analysis results of GASTURB8.0 program. It was confirmed that the developed program was reliable because the results by the developed program were well agreed with those by GASTURB8.0 within %%. The linear and non-linear GPA(Gas Path Analysis) programs for performance diagnotics were developed, and selection of optimal measurement variables was studied. Furthermore, in order to investigate effects of the number and the kind of measurement variables, the linear and non-linear GPAs were analyzed with various measurement set. If the measurement parameters were properly selected, the reliable and economic faults detection might be possible even thought the small number of measuring parameters were used.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.251-257
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• 2012

The flight controller should meet the flying qualities, stability margins, and time response requirement according to the class of a target aircraft or UAV. Classical design process of PID controller is a very time consuming process and needed trial and erros. The best way is to apply the multi-disciplinary optimization algorithm to meet the numerous constraints of controller requirements. This paper presents how multi-objective parameter optimization (CONDUIT) can be used to determine many design parameters of lateral stability and augmentation system for roll and heading controller of the small UAV. To verify the effectiveness of applying the optimization method, designed controller using optimization are compared with the baseline controller that is designed only considering the time responses.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.18-24
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• 2009

The volatile compounds of dried sancho (Zanthoxylum schinifolium), an aromatic plant were extracted by simultaneous distillation and extraction (SDE) method and identified by gas chromatograph-mass spectrometry (GC-MS). Selected chiral constituents of sancho oil were characterized by enantiodifferentiation using multidimensional gas chromatograph (MDGC)-MS. A total of 57 compounds were identified and quantified, and the major compounds were identified estragole, nonanoic acid, octanoic acid, $\beta$-phellandrenene, and limonene. Among them, estragol (63.9%) was found as the predominantly abundant component of sancho. $\alpha$-pinene and nerolidol, and $\beta$-pinene and linalool were determined to be enantiomerically pure (100%) for their (S)-form and (R)-form, respectively. The enantiomeric composition of limonene in sancho revealed 83.9% purity for the (S)-enantiomer, whereas (E)- and (Z)-rose oxides showed mixtures of both enantiomers. The enantiomeric excess (%) for citronellal was 22.6% with the (R)-enantiomer as major enantiomer. The enantiomeric composition of these compounds can be used as parameter for authenticity control of sancho.

• The Journal of the Korea Contents Association
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• v.15 no.3
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• pp.415-426
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• 2015

For a long time, evaluation of soundness and strength in concrete has been performed through ultrasonic velocity(UV), which is essential work in field assessment. Porosity in concrete is a major parameter indicating durability and strength, and UV passing concrete depends on porosity variation. In this paper, a modeling on UV through concrete is carried out considering porosity and the results are verified with those from test. Additionally UV in concrete under compression/tension loading condition is measured and UV modeling with loading condition is performed. Up to 50% of loading ratio, UV slightly increases and greatly drops at peak load in compression region, however it fluctuates in tensile region due to micro cracking in matrix. The proposed model shows a reasonable agreement with test results in control and compression region, and needs modification for tensile region considering micro cracks and local aggregate interlocking.

• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.79-88
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• 2011

A fill-drain valve is operated by provided control gas at the ground for liquid propellant feeding system of space launch vehicle, which fills or drains on-board propellant tanks with a cryogenic oxidizer. We have analyzed and modified the data of fill-drain valve designed by Yuzhnoye. The simulation model of fill-drain valve is designed by using the AMESim code to predict and evaluate the dynamic characteristics and pneumatic behavior of valve. In this study, we performed a dynamic characteristic simulation on design parameter. And we could predict opening/closing time and pressures, operating performances on design parameters. This study will serve as one of reference guides to enhance the developmental efficiency of fill-drain valves with the various operating requirements, which shall be used in the Koreanized Space Launch Vehicle.

• Journal of ILASS-Korea
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• v.25 no.1
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• pp.8-14
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• 2020

Recently, 1-D model-based engine development using virtual engine system is getting more attention than experimental-based engine development due to the advantages in time and cost. Injection rate profile is the one of the main parameters that determine the start and end of combustion. Therefore, it is essential to set up a sophisticated model to accurately predict the injection rate as starting point of virtual engine system. In this research, procedure of 1-D model setup based on AMESim is introduced to predict the dynamic behavior and injection rate of diesel injector. As a first step, detailed 3D cross-sectional drawing of the injector was achieved, which can be done with help of precision measurement system. Then an approximate AMESim model was provided based on the 3D drawing, which is composed of three part such as solenoid part, control chamber part and needle and nozzle orifice part. However, validation results in terms of total injection quantity showed some errors over the acceptable level. Therefore, experimental work including needle movement visualization, solenoid part analysis and flow characteristics of injector part was performed together to provide more accuracy of 1-D model. Finally, 1-D model with the accuracy of less than 10% of error compared with experimental result in terms of injection quantity and injection rate shape under normal temperature and single injection condition was established. Further work considering fuel temperature and multiple injection will be performed.