• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.381-387
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• 2002

In this work, the dynamic characteristics of an oil-lubricated, short SFD with a central feeding groove are derived based on a theoretical analysis considering the effect of a groove. The validity of the analysis is investigated experimentally using an Active Magnetic Bearing (AMB) system as an exciter. For the theoretical solution, the fluid film forces of a grooved SFD are analytically derived so that the dynamic coefficients of a SFD are expressed in terms of its design parameters. For the experimental validation of the analysis, a test rig using AMB as an exciter is proposed to identify the dynamic characteristics of a short SFD with a central groove. As an exciter, the AMB represents a mechatronic device to levitate and position the test journal without any mechanical contact, to generate relative motions of the journal inside the tested SFD and to measure the generated displacements during experiments with fairly high accuracy. Using this test rig, experiments are extensively conducted with different clearance, which is one of the most important design parameters, in order to investigate its effect on the dynamic characteristics and the performance of SFDs. Damping and inertia coefficients of the SFD that are experimentally identified are compared with the analytical results to demonstrate the effectiveness of the analysis. It is also shown that AMB is an ideal device for tests of SFDs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1548-1562
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• 2003

This paper is the first of several companion papers which compare the methods of Air-fuel ratio determination. There are many methods which calculate Air-Fuel ratio from exhaust emission. Most of them are based on the simple chemical equations, which use balance of atom, and the error of the calculation is negligible as far as the instrumentation accuracy is guaranteed. They assume homogeneous mixture and complete combustion to the extent of oxygen availability. Because of these simple assumptions, they cannot offer the information about the fuel distribution state and the malfunction of instrument. For these limitations, Eltinge offered new one based on stricter mathematical model. This result coincides with the others very well and gives more information about the mixture state and instrumentation. Consequently this might be a general solution for Air-fuel ratio determination and exhaust composition. The objects of the calculation, however, were not commercial fuels except gasoline and the compensation method of unburned hydrocarbon was not appropriate to recent analyzer. Moreover he did not consider the fuel which contains oxygen, such as methanol, ethanol and blend of gasoline-alcohol. In this paper, Eltinge chart is expanded to the arbitrary fuel composition as the reference exhaust compositions for the purpose of further discussions about Air-fuel ratio determination methods and the charts fur gasoline, diesel, methanol, M85, liquefied petroleum gas(LPG), natural gas(NG), propane, butane are illustrated.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.4
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• pp.270-274
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• 2006

This study proposes a new method for automatic recording of snowfall by a mass unit which is required in weather forecast and hydrology research. In this method the weight of a buoyancy bar submerged in a liquid is measured by a strain-gauge loadcell. Field test results of the strain-gauge loadcell showed good stability as well as high accuracy. Indoor tests of the instrument using a large tank of 120 cm diameter and 25 cm height connected to a small tank measured the liquid level with a good stability, showing a measurement error of less than 0.1 mm in a 100 mm range. This method of water depth measurement is very useful in measuring snowfall because it has no limitation on the funnel size of the instrument. In addition, an antifreezing solution instead of water used in the tank makes a heating system for melting snow unnecessary.

• Journal of Astronomy and Space Sciences
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• v.2 no.1
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• pp.19-33
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• 1985

The singularities of differential Newtonian equation of motion in three body problem cause the loss of accuracy and the considerable increase of the computer time. These singularities could be eliminated during the process of regularization to transform the independent variables and the coordinate of Newtonian equations of motion. In this study, we calculated the positions and velocities of three body along the time scale to find out the unique solution of regularized Newtonian equations of motion with the $5^{th}$ order Runge-Kutta method by assuming the suitable initial velocities and positions. As the results of these calculations it is shown that the tripe stellar system eventually distintegrated, two of them formed a binary, and the last one escaped from this system with a hyperbolic orbit. This may suggest one possible explanation for the binary formation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.3
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• pp.283-292
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• 2005

After USA removed the Selective Availability (SA), Global Positioning System (GPS) has monopolized the world market and other countries have been depended on GPS, absolutely. So the other countries, Russia, European Community (EC) and Japan, which apprehend to monopolize in technical and strategic parts, are developing the next generation GNSS including GLONASS Galileo and JRANS. And the countries are planning to provide the another GNSS. This research has focused on the next generation GNSS system based on GPS and Galileo system with developing a GNSS simulation software, named as GlMS2005, which generates and analyzes satellite constellation and measurements. Based on the software, a variety of simulation tests have been carried out to recognize limits of GPS-only system and potential benefits of integrated GPS/Galileo positioning in terms of satellite geometry strength and solution accuracy.

• Journal of Pharmaceutical Investigation
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• v.35 no.1
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• pp.51-55
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• 2005

A high-performance liquid chromatographic method was employed for the determination of bumetanide in human plasma. After addition of internal standard (IS, naproxen) and acidification of the plasma with 1 M hydrochloric acid, the drug and IS were extracted into dichloromethane. The organic phase was back-extracted into 1 M sodium bicarbonate solution and 50 ${\mu}l$ of the aqueous phase was injected onto a reversed-phase C18 column with a mobile phase consisting of methanol: water: glacial acetic acid = 65 : 35 : 1. The samples were detected utilizing a fluorescence detector (excitation wavelength 235 nm, emission wavelength 405 nm). The method was specific and validated with a lower limit of 5 ng/mL. Intra- and inter-day precision and accuracy were acceptable for all quality control samples including the lower limit of quantification. The applicability of the method was demonstrated by analysis of plasma after oral administration of a single 2 mg dose to 24 healthy subjects. From the plasma bumetanide concentration vs. time curves, the mean AUC was $246.5{\pm}73.8\;ng{\cdot}hr/mL$ and $C_{max}$ of $132.1{\pm}40.9$ ng/mL reached 1.2 hr after administration. The mean biological half-life of burnet ani de was $1.1{\pm}0.2$hr. Based on the results, this simple and validated assay method could readily be used in any pharmacokinetic or bioequivalence studies using humans.

• Journal of Pharmaceutical Investigation
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• v.35 no.6
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• pp.431-436
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• 2005

A high-performance liquid chromatographic method was validated for quantitation of nadolol in human plasma. Nadolol and internal standard, pindolol, were extracted with tert-butyl methyl ether after addition of 10 M sodium hydroxide solution. The analytes were separated on a reverse phased C18 column using a mobile phase consisting of 0.05 M ammonium phosphate monobasic buffer, acetonitrile and methanol (81: 17:2 v/v/v) and detected using a fluorescence detector (excitation wavelength 230 nm, emission wavelength 294 nm). The method was specific and sensitive enough to detect as low as 3 ng/mL of nadolol in human plasma. Linear calibration range was 3-150 ng/mL with correlation coefficient greater than 0.999. The overall accuracy was in the range of 96.8 to 103% and precision C.V.(%) 7.30 to 12.2%. The recovery was approximately 100% and stability was confirmed during storage and sample preparation. The present HPLC method was successfully applied to study bioavailability after oral administration of 80 mg of nadolol in healthy Korean subjects. The mean $AUC_{t}$ was $1968{\pm}397\;ng{\cdot}hr/mL$ and $C_{max}$ of $186{\pm}79.3\;ng/mL$ was reached at $3.5{\pm}0.76\;hr$. The mean $t_{1/2}$ of nadolol was $17.3{\pm}2.59\;hr$.

• Ocean Systems Engineering
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• v.3 no.3
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• pp.219-236
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• 2013

The accurate prediction of motion in waves of a marine vehicle is essential to assess the maximum sea state vs. operational requirements. This is particularly true for small crafts, such as Autonomous Surface Vessels (ASV). Two different numerical methods to predict motions of a SWATH-ASV are considered: an inviscid strip theory initially developed at MIT for catamarans and then adapted for SWATHs and new a hybrid strip theory, based on the numerical solution of the radiation forces by an unsteady viscous, non-linear free surface flow solver. Motion predictions obtained by the viscous flow method are critically discussed against those obtained by potential flow strip theory. Effects of viscosity are analyzed by comparison of sectional added mass and damping calculated at different frequencies and for different sections, RAOs and motions response in irregular waves at zero speed. Some relevant conclusions can be drawn from this study: influence of viscosity is definitely non negligible for SWATH vessels like the one presented: amplitude of the pitch and heave motions predicted at the resonance frequency differ of 20% respectively and 50%; in this respect, the hybrid method with fully non-linear, viscous free surface calculation of the radiation forces turns out to be a very valuable tool to improve the accuracy of traditional strip theories, without the burden of long computational times requested by fully viscous time domain three dimensional simulations.

• Journal of Intelligence and Information Systems
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• v.15 no.4
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• pp.123-140
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• 2009

Fuzzy neural network is an integrated model of artificial neural network and fuzzy system and it has been successfully applied in control and forecasting area. Recently ANFIS(Adaptive Network-based Fuzzy Inference System) has been noticed widely among various fuzzy neural network models because of outstanding performance of control and forecasting accuracy. ANFIS has capability to refine its fuzzy rules interactively with human expert. In particular, when we use initial rule structure for machine learning which is generated from human expert, it is highly probable to reach global optimum solution as well as shorten time to convergence. We propose metrics to evaluate interpretability of generated rules as a means of acquiring domain knowledge and compare level of interpretability of ANFIS fuzzy rules to those of C5.0 classification rules. The proposed metrics also can be used to evaluate capability of rule generation for the various machine learning methods.

• Journal of Biomedical Engineering Research
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• v.27 no.6
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• pp.392-401
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• 2006

Image Guided Surgery (IGS) system which has variously tried in medical engineering fields is able to give a surgeon objective information of operation process like decision making and surgical planning. This information is displayed through 3D images which are acquired from image modalities like CT and MRI for pre-operation. The technique of image registration is necessary to construct IGS system. Image registration means that 3D model and the object operated by a surgeon are matched on the common frame. Major techniques of registration in IGS system have been used by recognizing fiducial markers placed on the object. However, this method has been criticized due to additional trauma, its invasive protocol inserting fiducial markers in patient's bone and generating noise data when 2D slice images are acquired by image modality because many markers are made of metal. Therefore, this paper developed shape-based registration technique to improve the limitation of fiducial marker based IGS system. Iterative Closest Points (ICP) algorithm was used to match corresponding points and quaternion based rotation and translation transformation using closed form solution applied to find the optimized cost function of transformation. we assumed that this algorithm were used in Total Knee replacement (TKR) operation. Accordingly, we have developed region-based 3D registration technique based on anatomical landmarks and this registration algorithm was evaluated in a femur model. It was found that region-based algorithm can improve the accuracy in 3D registration.