• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.893-897
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• 2006

Structures with additional frictional damping system have strong nonlinearity that the dynamic behavior is highly affected. by the relative magnitude between frictional force and excitation load. In this study, normalized response spectra of the structures with non-dimensional friction force are obtained through nonlinear time history analyses of the mass-normalized single degree of freedom systems using 20 ground motion data recorded on rock site. The variation of the control performance of frictional damping system is investigated in terms of the dynamic load and the structural natural period, of which effects were not considered in the previous studies. Least square curve fitting equations are presented for describing those normalized response spectrum and optimal non-dimensional friction forces are obtained for controlling the peak displacement and absolute acceleration of the structure based on the derivative of the curve fitted design spectrum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.85-90
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• 2003

To control spacecraft including satellite, we should understand precisely the performance of propulsion system and the program logic with appropriate format for satellite operations. In this study, the thruster performance functions was generated by using the best curve fitting for performance data from bi-propellant thrusters. Detailed thruster performance data are, in general, company proprietary information, therefore real firing tests were performed to understand the basic characteristics of the performance curve. Experimental rocket motor utilize liquid oxygen and kerosine as propellant and designed average thrust was 100 pound.

• Journal of Welding and Joining
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• v.10 no.4
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• pp.190-198
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• 1992

Among the variety of welding processes available, the flux cored arc welding is one of the most frequently used process, because of its wide range of application and high productivity. The weld joint tracking is indispensable to improve the flexibility of the arc welding robot application for the flux cored arc welding (FCAW) process. In this study, an arc sensor which utilizes the electrical signal obtained from the welding arc itself was developed for weld joint tracking in FCAW. Because a model of the welding arc in flux cored arc welding was required to develop the arc sensor, a mathematical model was proposed by analysing the welding arc behaviour, and also an experimental model by using the factorial experiment and least square method. For overcoming the fluctuation in the welding current signal during tracking the weld joint, it was fitted to a curve which is inversely proportional to a trace of tip-to-workpiece distance by using the quadratic curve-fitting method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.1 s.118
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• pp.88-94
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• 2007

Structures with additional frictional damping system have strong nonlinearity that the dynamic behavior is highly affected by the relative magnitude between frictional force and excitation load. In this study, normalized response spectra of the structures with non-dimensional friction force are obtained through nonlinear time history analyses of the mass-normalized single degree of freedom systems using 20 ground motion data recorded on rock site. The variation of the control performance of frictional damping system is investigated in terms of the dynamic load and the structural natural period, of which effects were not considered in the previous studies. Least square curve fitting equations are presented for describing those normalized response spectrum and optimal non-dimensional friction forces are obtained for controlling the peak displacement and absolute acceleration of the structure based on the derivative of the curve-fitted design spectrum.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.4
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• pp.115-123
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• 2000

This study compared the degree of consolidation by hyperbolic, curve fitting , Asaoka's and methods using values measured with a theoretical curve in consideration of smear effect and well resistance. The degree of consolidation by the Hyperboilc method was underestimated than the degree of consolidation by Curve fitting. Asaoka's , and Monden's methods. The typical range of the coefficient of horizontal consolidation was Ch=(2-3)Cv in the case considering smear effect and well resistance, and Ch =(0.5-2.1) Cv in the case disregarding smear effect and well resistance. The degree of consolidation obtained by ground settlement monitoring was nearly the same value when the coefficient of smear zone permeability by back analysis was shown to be half that of in-situ and the diameter of the smear zone was shown to be double that of mandrel. By increasing the diameter reduction ratio of the drain, the time of consolidation was delayed. The effect of well resistance showed that the case of a small coefficient of permeability was much more than in the case of a large coefficient of permeability . It was recommended that when designing diameter reduction of a drain, well resistance should be considered.

• Geomechanics and Engineering
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• v.23 no.5
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• pp.431-439
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• 2020

Soil-water retention curve (SWRC) contains key information for the application of unsaturated soil mechanics principles to engineering practice. The SWRC variables are commonly used to describe the hydro-mechanics of soils. Generally, these parameters are determined using the graphical method which can be time consuming. The SWRC is highly dependent on the pore size distribution (PSD). Theoretically, the PSD obtained by mercury intrusion porosimetry test can be used to determine some SWRC variables. Moreover, the relationship between SWRC and shrinkage curve has been investigated. A new method to determine total SWRC variables directly without curve-fitting procedure is proposed. Substituting the variables into linear SWRC equations construct SWRC. A good agreement was obtained between predicted and measured SWRCs, indicating the validity of the proposed method for unimodal SWRC.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.48-53
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• 1999

In this paper, a practical method for design and machining of cycloid gear was investigated. Based on the proposed method, a systematic program was developed for automatically designing the tooth profiles of epicycloid and hypocycloid gears for the case fo one difference between the number of teeth of cycloid gear and the number coordinates of tooth profiles and pressure angles. The error analysis between cycloid curve and Biarc curve was performed to show the effective method of equidistant partitioning of cycloid curve so that efficient method of Biarc curve fitting was also proposed for the partitioned curve.

• The KIPS Transactions:PartB
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• v.19B no.3
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• pp.201-208
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• 2012

Accurately segmenting lumen border in intravascular ultrasound images (IVUS) is very important to study vascular wall architecture for diagnosis of the cardiovascular diseases. After each of IVUS image is transformed to a polar coordinated image, initial points are detected using wavelet transform. Then, lumen border is initialized as the set of important points using non parametric probability density function and smoothing function by removing outlier initial points occurred by noises and artifacts. Finally, polynomial curve fitting is applied to obtain real lumen border using filtered important points. The evaluation of proposed method was performed with related method and the proposed method produced accurate lumen contour detection when compared to another method in most types of IVUS images.

• Journal of Digital Contents Society
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• v.18 no.1
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• pp.159-165
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• 2017

In order to solve problems in automatic quality inspection of tablet capsules, computation-efficient image processing technique, appropriate threshold setting, edge detection and segmentation methods are required. And since existing automatic system for quality inspection of tablet capsules is of very high cost, it needs to be reduced through the realization of low-price hardware system. This study suggests a technique that uses low-cost camera module to obtain image and inspects dents on tablet capsules and sorting them by applying TLS curve fitting technique and edge-based image segmentation. In order to assess the performance, the major classifications algorithm of PCA, ICA and SVM are used to evaluate training time, test time and accuracy for capsule image area and curve fitting edge data sets.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.440-449
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• 1988

Small vibration displacements may be measured by optical interferometers, based on the Michelson method. The standard Michelson interferometer works well when the mirror displacements are relatively large compared to the optical wavelength. But it does not work for displacements less than approximately a quater of optical wavelength. Several multiple reflection laser interferometers, simply modified standard Michelson interferometer, have been developed to decrease the minimum detectable limits. Among these a relatively simple and easy multiple reflection system is used to measure the small vibration displacements. This multiple reflection system is constructed with a right angle prism and a convex lens. Therefore this system makes it possible to measure a vibration displacement of the small area on the vibrating structure. The fringe interpolation method and curve fitting method are used to determine accurately the small vibration displacements from the measured interference fringe patterns. Also computer simulation technique is used to check the accuracies of these method. According to the results of the computer simulation technique, the curve fitting method is more accurate than the fringe interpolation method. The optically measured results are in good agreement with those of the standard accelerometer with high accuracy and it is possible to measure the peak vibration displacement as small as 9.01nm using multiple reflection system and curve fitting method.