• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.311-317
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• 2015

It is difficulty to calculate velocity circulation in centrifugal pump impeller outlet accurately. Velocity circulations of a double-blade pump impeller outlet were calculated with Stodola formula, Weisner formula and Stechkin formula. Simultaneously, the internal flow of impeller for the double-blade pump were measured with PIV technology and average velocity circulations at the 0.8, 1.0 and 1.2 times of design flow were obtained. All the experimental values were compared with the above calculation values at the three conditions. The results show that calculation values of velocity circulations with Weisner formula is close to the experimental values. On the basis of the above, velocity circulations of impeller outlet were corrected. The results of experimental verification show that the corrected calculation errors, whose maximum error is 3.65%, are greatly reduced than the uncorrected calculation errors. The research results could provide good references for establishment of theoretical head and multi-condition hydraulic optimization of double-blade pumps.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.3
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• pp.211-217
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• 2000

A main contribution of this paper is the development of a Hopfield network-based algorithm for the fault diagnosis of the actuators in linear system with uncertainties. An unknown input decoupling approach is introduced to the design of an adaptive observer so that the observer is insensitive to uncertainties. As a result, the output observation error equation does not depend on the effect of uncertainties. Simultaneous energy minimization by the Hopfield network is used to minimize the least mean square of errors of errors of estimates of output variables. The Hopfield network provides an estimate of the gains of the actuators. When the system dynamics changes, identified gains go through a transient period and this period is used to detect faults. The proposed scheme is demonstrated through its application to a simulated second-order system.

• Structural Engineering and Mechanics
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• v.40 no.2
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• pp.245-256
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• 2011

In this paper, the use of universal serendipity elements (USE) to eliminate node mapping distortions for dynamic problem is presented. Rectangular shaped elements for USE are being introduced by using a flexible master element with an adjustable edge node location. The shape functions of the universal serendipity formulation are used to derive the mass and damping matrices for the dynamic analyses. These matrices eliminate the node mapping distortion errors that occurs incase of the standard shape function formulations. The verification of new formulation will be tested and the errors encountered in the standard formulation will be studied for a dynamically loaded deep cantilever.

• International Journal of Control, Automation, and Systems
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• v.4 no.2
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• pp.146-154
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• 2006

In this paper, we propose direct and indirect adaptive fuzzy sliding mode control approaches for a class of nonaffine nonlinear systems. In the direct case, we use the implicit function theory to prove the existence of an ideal implicit feedback linearization controller, and hence approximate it to attain the desired performances. In the indirect case, we exploit the linear structure of a Takagi-Sugeno fuzzy system with constant conclusion to establish an affine-in-control model, and therefore design an indirect adaptive fuzzy controller. In both cases, the adaptation laws of the adjustable parameters are deduced from the stability analysis, in the sense of Lyapunov, to get a more accurate approximation level. In addition to their robustness, the design of the proposed approaches does not require the upper bounds of both external disturbances and approximation errors. To show the efficiency of the proposed controllers, a simulation example is presented.

• Journal of the Korean Professional Engineers Association
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• v.43 no.6
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• pp.23-26
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• 2010

The first high speed railway in Korea was opened to traffic on April 1, 2004 and the second phase will be opened on November 1. 2010. Many technical problems that occurred during construction have been solved. In its early period of project, difficulties were encountered in design, construction of high speed line. because most of Korean railway engineers were familiar only with conventional railway. Now they understand the various phenomena occuring during operation of the KTX and have accumulated extensive technical knowhow. Valuable experiences and knowledges that have been obtained from frials and errors will lead to further improvement for the future project.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.79-83
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• 1999

A cationic demand(CD) is a very useful indication for determining the optimum dosage rate of retention aids to the papermaking stock at the wet end. Polyelectrolyte titration has been most often used to determine a CD. Highly accurate results can be obtained by this method when the ionic strength of sample is low. But this is accompanied by the serious errors when the ionic strength is higher than that corresponding to 20 milli molar(mM) monovalent, 2 mM divalent or 0.2 mM trivalent ions because of no occurrence of the end point of titration. Therefore, it is very difficult or almost impossible for the conventional method to be applied to the industrial suspensions such as papermaking stock and industrial waste water. Then a novel method using chromophoric labeled cationic polymer which can be applicable to the sample with high ionic strength has been developed.

• Journal of Dental Anesthesia and Pain Medicine
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• v.19 no.3
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• pp.125-134
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• 2019

Successful local anesthesia in dental treatment is the most important prerequisite for pain control of patients. However, unlike that in the maxilla, it is difficult to administer local anesthesia in the mandible, and the success rate of conventional inferior alveolar nerve block (IANB) is only 80-85%. It is attributed to various causes such as anatomical variations, extreme anxiety, and technical errors; thus, various alternatives have been devised to improve this. We will analyze the causes of failure in conventional IANB and examine various alternatives that can be applied in these cases.

• Bulletin of the Korean Mathematical Society
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• v.39 no.1
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• pp.23-31
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• 2002

A scale parameter is the principal parameter to be estimated, since it corresponds to one of the main reliability characteristics, namely the average time to failure. To provide robustness of scale estimators to gross errors in the data, we apply the Huber minimax approach in time to failure models of the statistical reliability theory. The minimax valiance estimator of scale is obtained in the important particular case of the exponential distribution.

• 한국기계연구소 소보
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• s.15
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• pp.25-35
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• 1985

During one revolution of a gear, the intensity of the gear-meshing noise or vibration will vary, depending upon the run-out in the pitch diameter of the gear. Here noise can be produced bu excentricity of the shaft with respect to the base circle and by pitch errors. According to the noise generated is clearly dependent on the force and the amount of energy expended in elastically straining the machine member. The purpose of this paper is to discuss the analysis of the noise and technical reduction of gear noise for machine tool.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.586-593
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• 2017

Modeling busbar distribution system as a transmission line is an important subject of power line communication in the smart grid concept. This requires extraction of busbar RLGC parameters, accurately. In this study, a comparison is made between conventional and modified method for the aspect of optimum RLGC parameters extraction in the 1 MHz to 50 MHz frequency band. The usefulness of these methods is shown both in time and frequency-domain analysis. The frequency-domain analyzes show that the inherent power of modified method can eliminate the errors especially due to the discontinuities arise in conventional method. This makes the modeling approach of modified method more advantageous for the busbars due to its robustness against disturbances in the S-parameters measurements which cannot be eliminated with the calibration procedure. On the other hand, time-domain simulations show that the transmission line representation of the modified method is closer to physical reality by handling causality issues.