• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.319-322
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• 2003

For the analysis of leveling process by the 3-dimensional elastic-plastic finite element method, a finite element analysis program modeling large deformation of shell has been developed. This program fur analyzing large deformation of sheet during leveling includes spring-back analysis as well as efficient contact treatment between sheet and rolls of leveler. This is verified by the simple leveling experiment with 5 rolls at laboratory. Besides the leveling examples, problems within the category of large strain and rotation, such as 3-dimensional roll-up and gutter occurrence at continuous bending-unbending process are also tested for verification of the program. The residual curvatures of strip predicted by finite element analysis are within 20% error range of the experiment. The formation and direction of anticlastic curvature or gutter during bending-unbending under tension is predicted and this agrees with the experimental results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.5
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• pp.222-230
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• 2005

This paper deals with the reduction of cogging torque of a outer-rotor type BLDC motor mainly used for washing machines. The motor comprises permanent magnet outer-rotor and stator with coils and core. This structure inherently produces vibration and cogging torque because of uneven reluctance according to rotation of the rotor. Up to now, adopted a type of 24 magnet pole and 36 slot-stator. This generates high main torque but accompanies comparatively large cogging torque. This paper proposes a 32-pole 36-slot type motor which reduces cogging torque remarkably. The influence of cogging torque is varied according to pole-slot combinations. The characteristic of the motor was obtained by a two-dimensional finite element method coupled with a drive circuit. The performance of the proposed model is superior to that of the existing model because of the reduction of torque ripple and the improvement of back ernf wave form.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1172-1175
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• 1992

The conventional adaptive hysteresis band current control technique has disadvantages such that on-line calculation of the hysteresis band is very complex, therefore, the adaptive hysteresis band must be stored in the look-up table. In this paper, a new simplified adaptive hysteresis band current control technique with phase decoupling is presented. The adaptive band is independent of the back EMFs. Using this adaptive band and the phase decoupled current error, the modulation frequency is fixed at nearly constant and the PWM inverter has optimal switching pattern.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.5
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• pp.628-636
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• 1994

One vertical (medianus) and six horizontal (chest, bust, below bust, waist, abdomen and hip) sections of nine healthy pregnant women were examined every month by siliding gauge method during the period from 3rd to loth monthes of pregnancy. In the body changes along the passing months of pregnancy, which were observed by a follow·up measurement, there was little change on the posterior line when viewed using a vertical cross section. On the contrary, there was a great deal of increase on the anterior median line. Particularly, the degree of protrusion was great in the waist and ubilicus area due to pregnancy. At early pregnancy the distance from front to back is much shorter than side to side, however, as pregnancy progressed the front to back distance, on a horizontal cross section, is almost equal to the side to side distance.

• Steel and Composite Structures
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• v.24 no.3
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• pp.351-358
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• 2017

Due to the increasing competition, automotive manufacturers have to manufacture highly safe and light vehicles. The parts which make up the body of the vehicle and absorb the energy in case of a crash, are usually manufactured with sheet metal forming methods such as deep drawing, bending, trimming and spinning. The part may get thinner, thicker, folded, teared, wrinkled and spring back based on the manufacturing conditions during manufacturing and the type of application methods. Transferring these effects which originate from the forming process to the crash simulations that are performed for vehicle safety simulations, makes accurate and reliable results possible. As a part of this study, firstly, the one-step and incremental sheet metal forming analysis (deep drawing + trimming + spring back) of vehicle front bumper beam and crash boxes were conducted. Then, crash performances for cases with and without the effects of sheet metal forming were assessed in the crash analysis of vehicle front bumper beam and crash box. It was detected that the parts absorbed 12.89% more energy in total in cases where the effect of the forming process was included. It was revealed that forming history has a significant effect on the crash performance of the vehicle parts.

• The Korean Journal of Pain
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• v.28 no.4
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• pp.275-279
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• 2015

Facet joint synovial cysts are usually associated with osteoarthritis of the adjacent facet joint and/or spondylolisthesis. In between the conservative and operative ends of the treatment spectrum lie minimally invasive techniques such as cyst rupture using epiduroscopy. In this report, we describe an 82-year-old male patient presenting with low back pain radiating to his lower left extremity and associated paresthesia. Magnetic resonance imaging of the lumbar spine revealed a synovial cyst at left L4/5 facet joint. Using epiduroscopy, the cyst was mechanically ruptured by popping it with the tip of the scope. The patient remained symptom-free at his successive visits until 12 months after the procedure, and was opened for desired follow up.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.59-64
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• 2001

The objectives of the thesis are to propose a pattern classification method for remote sensing data using artificial neural network. First, we apply the error back propagation algorithm to classify the remote sensing data. In this case, the classification performance depends on a training data set. Using the training data set and the error back propagation algorithm, a layered neural network is trained such that the training pattern are classified with a specified accuracy. After training the neural network, some pixels are deleted from the original training data set if they are incorrectly classified and a new training data set is built up. Once training is complete, a testing data set is classified by using the trained neural network. The classification results of Landsat TM data show that this approach produces excellent results which are more realistic and noiseless compared with a conventional Bayesian method.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.853-858
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• 1993

The error back-propagation(BP) algorithm is widely used for finding optimum weights of multi-layer neural networks. However, the critical drawback of the BP algorithm is its slow convergence of error. The major reason for this slow convergence is the premature saturation which is a phenomenon that the error of a neural network stays almost constant for some period time during learning. An inappropriate selections of initial weights cause each neuron to be trapped in the premature saturation state, which brings in slow convergence speed of the multi-layer neural network. In this paper, to overcome the above problem, Micro-Genetic algorithms(.mu.-GAs) which can allow to find the near-optimal values, are used to select the proper weights and slopes of activation function of neurons. The effectiveness of the proposed algorithms will be demonstrated by some computer simulations of two d.o.f planar robot manipulator.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4E
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• pp.9-13
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• 1996

We developed an iterative algorithm which could improve the resolution of reconstructed tomograms having random attenuation patterns and analyzed the limitation of this algorithm. The simple back-and forth propagation algorithm has depth resolution about four wavelengths. An iterative algorithm, based on back-and-forth propagation, can be used to improve the resolution of reconstructed tomograms. We analyzed the wavefield for multi-layered specimen and programmed iterative algorithm using Clanguage. Simulation results show that the images get clearer as the number of iterations increases. Also, unambiguous images can be reconstructed using this algorithm even when the layer separation is only two wavelengths. However, this iteration algorithm comes up with an incorrect solution for the number of projections less than five.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.235-242
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• 2001

Hydraulic performance of LCH4 fuel inducer in turbopump system was predicted by 3-D Wavier-stokes calculation. The inducer was designed initially using 1-D method. Different parameters with blade angle and flow coefficient were set from the initial design one, md computation was fulfilled to assess the redesigned models. Especially, influence of inlet back flow on inducer performance and its effective control were explored. The numerical results showed that through reducing inlet back flow strength., the hydraulic efficiency of inducer could be improved up to about $20\%$ compared to that of the initial design one.