• Journal of the Korean Institute of Intelligent Systems
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• v.7 no.4
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• pp.74-81
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• 1997

This paper proposes an evolutionary learning algorithm to discipline the projection neural nctworks (PNNs) with special type of hidden nodes which can activate radial basis functions as well as sigmoid functions. The proposed algorithm not only trains the parameters and the connection weights hut also c~ptimizes the network structure. Through the structure optimization, the number of hidden node:; necessary to represent a given target function is determined and the role of each hidden node is decided whether it activates a radial basis function or a sigmoid function. To apply the algorithm, PNN is realized by a self-organizing genotype representation with a linked list data structure. Simulations show that the algorithm can build the PNN with less hidden nodes than thc existing learning algorithm using error hack propagation(EE3P) and network growing strategy.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.6
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• pp.1777-1783
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• 2004

This study was conducted to determine the effects Wonjiseokchangpo-san on brain damage in transient focal cerebral ischemia. Rats were used for testing in the following three models: Morris Water Maze, Eight-Arm Radial Maze, and Histochemistry. In the Morris Water Maze Model, the Wonjiseokchangpo-san group showed significant decrease in the 3rd and 6th training session compared with the ischemia group. A retention test, in the Morris Water Maze Model, was performed on the 7th day without the escape platform. The Wonjiseokchangpo-san group showed significant increase compared to the ischemia group. In the Eight-Arm radial Maze model, the Wonjiseokchangpo-san group showed significant decrease in the error rate compared to the ischemia group. In the density of hippocampal CA1 cell of the cresyl violet-stained section, the Wonjiseokahangpo-san group showed significant increase compared to the ischemia group. These results suggest that Wonjiseokchangpo-san may have a significant protective effect on brain damage and cognitive dysfunction in transient focal cerebral ischemia.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.2
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• pp.17-23
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• 2002

A cylindrical capacitance-type spindle displacement sensor was developed and its effectiveness as a system to monitor cutting forces during hard turning was tested in this research. The sensor was installed between the face of spindle cover and the chucking element and measured pure radial motion of the spindle under the condition with presence of roundness error at measured surface. To prove the effectiveness of the developed system hard aiming tests using ceramic inserts and tool steel as workpiece were conducted. The workpiece was hardened up to 65 Rc. The variations of pure radial motion of the spindle ware measured during the cutting tests. The signals from the sensor showed the same pattern of cutting force variations from the tool dynamometer due to the progress of tool wear. As the flank wear of the ceramic tool increased both static component of cutting forces and the amount of center shift of spindle orbit increased, Results from the research showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to monitor cutting conditions and tool performance in the un-manned machining center.

• The Journal of Korean Medicine
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• v.26 no.2 s.62
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• pp.52-62
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• 2005

Objectives: This study was conducted to determine the effects of Geupunggibodan on brain damage in transient focal cerebral ischemia in rats. Methods: Rats were used for testing in the following three models: Morris water maze, eight-ann radial maze, and histochemistry. Results: In the Morris water maze model, the Geupunggibodan group showed significant decrease in the 3rd, 4th and 6th training sessions compared with the ischemia, group. A retention test in the Morris water maze model was performed on the 7th day without the escape platform. The Geupunggibodan group showed significant increase compared to the ischemia group. In the eight-ann radial maze model, the Geupunggibodan group showed significant decrease in the error rate compared to the ischemia group. In the density of hippocampal CA1 cell of the cresyl violet-stained section, the Geupunggibodan group showed significant increase compared to the ischemia group. Conclusions: These results suggest that Geupunggibodan may have a significant protective effect on brain damage and cognitive dysfunction in transient focal cerebral ischemia.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.546-558
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• 2013

The research performed in this paper was carried out to investigate the numerical analysis of the sheet cavitation on marine propeller. The method is boundary element method (BEM). Using the Green's theorem, the velocity potential is expressed as an integral equation on the surface of the propeller by hyperboloid-shaped elements. Employing the boundary conditions, the potential is determined via solving the resulting system of equations. For the case study, a DTMB4119 propeller is analyzed with and without cavitating conditions. The pressure distribution and hydrodynamic performance curves of the propellers as well as cavity thickness obtained by numerical method are calculated and compared by the experimental results. Specifically in this article cavitation changes are investigate in both the radial and chord direction. Thus, cross flow variation has been studied in the formation and growth of sheet cavitation. According to the data obtained it can be seen that there is a better agreement and less error between the numerical results gained from the present method and Fluent results than Hong Sun method. This confirms the accurate estimation of the detachment point and the cavity change in radial direction.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.145-150
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• 2000

Out-of-sphericity is degree of deformation of an air bearing sphere deviated from a perfect sphere. This paper investigates numerically the effect of out-of-sphericity error on the radial stiffness of an air bearing Three types of out-of-sphericity modes are considered. in this study the stiffness is calculated from pressure distribution at the bearing surface which is obtained by solving th Reynolds equation. in some cases large out-of-sphericity errors are found to improve the stiffnesses of air bearings. This implies that an air bearing of perfect hemispheres is not necessarily of the best performance. Thus much labor and cost in manufacturing air bearings can be saved, In addition the radial stiffness of an air bearing depends greatly on the application direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.351-358
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• 1994

A probabilistic model and analysis methods to determine the means and variances of the velocity and acceleration in stochastically-defined planar pin jointed kinematic chains are presented. The presented model considers the effect of tolerances on link length and radial clearance and uncertainty of pin location as a net effect on the link's effective length. The determination of the mean values and variances of the output variables requires the calculation of sensitivities of secondary variables with respect to the random variables. It is shown that this computation is straightforward and can be accomplished by a conventional kinematic analysis package with minor modification. Thus, the concepts of tolerance and clearance have been captured by the model and analysis. The only input data are the nominal linkage model and statistical information. The "effective link length" model is shown to be applicable to both analytical solution and Monte Carlo simulation. The results from both methods are compared. This paper Ksolves the higher-order kinematic problems for the probabilistic design analysis of stochastically-defined mechanisms.echanisms.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.132-139
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• 1992

We have designed a magnetic field gradient useful for cylindrical imaging in NMR-CT. The direc¬tion of the designed field is parallel to the axis and the gradient in the radial direction of cylindrical coordinate is monotonically increasing. The ratio of the gradient in the radial and axial direction is greater than 10 near the center of coordinate. This ratio depends on solenoid length, the number of reverse current turns at center, and the amount of the reverse current. We built a gradient coil based on the numerical simulation and tested the field generated by NMR-CT. The resulting image matches with the theoretical expectation within 10% error. Since the data acquisition time of 1-D imaging is significantly shorter than 2-D imaging, it becomes possible to image much more dynamic objects by the use of this gradient field.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.131-137
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• 2023

In this paper, a phase comparison direction finding method of circular array composed of 8 antennas considering polarization characteristics is analyzed. A broadband cavity-backed patch antenna operating in 6 ~ 12 GHz is used, and the antennas are arranged in radial direction to receive various polarization signals. For the phase comparison, widely spaced elements are used to obtain precise DOA(Direction of Arrival), and narrowly spaced elements are used to resolve ambiguity. Two dimensional direction finding is performed for ±20° in both azimuth and elevation, and the DOA error is less than 0.5° and 1.6° near the boresight and the ±15° region, respectively.

• Computers and Concrete
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• v.29 no.6
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• pp.433-444
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• 2022

Concrete's compressive strength is widely studied in order to understand many qualities and the grade of the concrete mixture. Conventional civil engineering tests involve time and resources consuming laboratory operations which results in the deterioration of concrete samples. Proposing efficient non-destructive models for the prediction of concrete compressive strength will certainly yield advancements in concrete studies. In this study, the efficiency of using radial basis function neural network (RBFNN) which is not common in this field, is studied for the concrete compressive strength prediction. Complementary studies with back propagation neural network (BPNN), which is commonly used in this field, have also been carried out in order to verify the efficiency of RBFNN for compressive strength prediction. A total of 13 input parameters, including novel ones such as cement's and fly ash's compositional information, have been employed in the prediction models with RBFNN and BPNN since all these parameters are known to influence concrete strength. Three different train: test ratios were tested with both models, while different hidden neurons, epochs, and spread values were introduced to determine the optimum parameters for yielding the best prediction results. Prediction results obtained by RBFNN are observed to yield satisfactory high correlation coefficients and satisfactory low mean square error values when compared to the results in the previous studies, indicating the efficiency of the proposed model.