• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.8
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• pp.663-671
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• 2007

In this work, shape optimization of a wire-wrapped fuel assembly in a liquid metal reactor has been carried out by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the radial basis neural network method, a well known surrogate modeling technique for optimization. Sequential Quadratic Programming is used to search the optimal point from the constructed surrogate. Two geometric design variables are selected for the optimization and design space is sampled using Latin Hypercube Sampling. The optimization problem has been defined as a maximization of the objective function, which is as a linear combination of heat transfer and friction loss related terms with a weighing factor. The objective function value is more sensitive to the ratio of the wire spacer diameter to the fuel rod diameter than to the ratio of the wire wrap pitch to the fuel rod diameter. The optimal values of the design variables are obtained by varying the weighting factor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.35-39
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• 1994

One of the important characteristics of the response of nonlinear systems is the existence of subharmonic resonances. When some conditions in parameter space are satisfied. It is possible even in the presence of damping for a periodically excited nonlinear system to possess a response which is the combination of a contribution at the excitation frequency and a component at the system natural frequency. The system natural frequency being a submultiple of the excitation frequency implies that the resulting response is a subharmonic oscillation. In general, there also co-exists, for the system, a response at the excitation frequency, and initial conditions determine which of the steady-state responses is achieved in an experiment or a numerical simulation. In single-degree-of-freedom systems with harmonic excitation, depending on the type of the nonlinearity, e.g., cubic or quadratic the frequency of subharmonic response is respectively, one-third or one-half of that of the excitation frequency. Although subharmonic resonance is one of the principal characteristics of a nonlinear system the subharmonic responses of structures in the presence of internal resonances have been studied very rarely. In this work, we consider subharmonic responses in the two-mode approximation of the plate equations. It is assumed that the two modes are in one-to-one internal resonance. Constant and periodic steady-state solutions of the averaged equations are studied. Finally, the results of direct time integration of the original equations of motion are presented and compared with those obtained from the averaged equations.

• Journal of the Korean Institute of Rural Architecture
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• v.14 no.1
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• pp.9-19
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• 2012

The object of this study is to investigate the satisfaction level of group homes for the elderly living alone in rural areas. Sixty-four elderly people, living alone, were selected from ten regions operated by the Gimje city council in Jeonlabuk-do, and then a survey was conducted during January 17 to 26 in 2011. The results of the investigation are as follows: first, roughly 90.6 percent of the participants responded that they were satisfied with cohabitation. Second, average point of satisfaction was going to bed together, which is 4.39, also each unit in all the ten regions was recorded above 4.00. Third, the satisfaction of eating together averaged highly at 4.37. Fourth, 95 percent of them were satisfied with the conditions of the residential space. Fifth, the satisfaction with the amenities, such as electricity, phone, heating and sanitation, averaged 96.9 and 98.4 percent each, which was rated highest. Through analytical research, elderly people who live in 'group homes' are satisfied with their lives. It is thought that this 'group home' can play the role of an alternative family better than existing 'senior citizen centers' and 'welfare centers for the elderly'. The study means that 'group homes' in rural areas could be established successfully.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.520-529
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• 1998

Heat and mass transfer behaviors of metal hydride beds were predicted by solving a set of volume-averaged equations numerically both for the gas (hydrogen) and the solid(metal hydride) phases. Time variations of temperature and hydrogen concentration ratio distributions were obtained for internally cooled, cylindrical-shaped beds with metal(aluminum) fins imbedded in them. Also, time variations of the space-averaged hydrogen concentration ratio were obtained. Temperature and velocity of the coolant, hydrogen pressure at the gas inlet, and the fin spacing were taken as the parameters. The hydrogen absorption rate increases with the higher velocity and the lower temperature of the coolant, and with the decrease of the fin spacing. Increasing of the hydrogen pressure at the gas inlet also promotes the rate of absorption though the increasing rate gradually slows down. The amount of the hydrogen storage per unit volume of the bed decreases with the tighter fin spacing despite of the higher absorption rate ; therefore, there should be an optimum fin spacing for a given volume of the system and the amount of the hydrogen storage, in which the absorption rate is the highest.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.11
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• pp.32-41
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• 2000

A new anatomical head model was implemented based on the MR and CT images of the head of a volunteer whose head shape is close to the domestic standard. In order to compare SARs (specific absorption rates) of heads with different shapes, we calculated SARs in the two anatomical head models. The one is the new model and the other is that of the black race and was made at National Library Medicine in USA. The head model and a phone model were arranged in the computational space to be the touch or cheek position of CENELEC (European Committee for Electrotechnical Standardisation) and FCC guidelines. From the obtained results, we can see that the smaller head produces the higher whole head-averaged SAR. However, it seems that the localized SAR averaged over 1 g or 10 g is more dependent on the shape of the auricle rather than that of the head size.

• Journal of Korean Foot and Ankle Society
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• v.10 no.1
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• pp.80-83
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• 2006

Purpose: To compare ultrasonographic size of morton's neuroma measured to actual size. Materials and Methods: Thirty-two (twenty-eight patients) of symptomic Morton's neuroma were measured by ultrasonography preoperatively and by manual method that designed by authors intraoperatively from January, 2002 to May, 2003. Two results were stastically compared by paired T-test. Results: Except one, all of cases were women and the mean age of patients was 50.6 years (32-62 years). The most common associated disease was hallux valgus deformity (17 cases). Six of Morton's neuromas located on second intermetatarsal space, sixteen of them did third intemetatarsal space and ten of neuromas located simultaneously second and third intermetatarsal space. The ultrasonographic size of neuroma averaged 3.48 mm and real size was 3.99 mm. The size checked by manual method was larger than by ultrasound with statical meaning. Conclusion: The size of Morton's interdigital neuroma checked by ultrasonography on plantar aspect is smaller than real size. If you checked Morton's interdigital neuroma size by ultrasonography, you can suspect that real size of Morton's interdigital neuroma is larger than that size.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.523-532
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• 2001

A simultaneous measurement of wall vorticity and near-wall streamwise velocity fluctuations has been performed using a V-type wall vorticity probe and an I-type velocity probe to investigate the relation between them. Long-time averaged space-time correlations show that the wall vorticity is highly correlated with a turbulence structure which is tilted from the wall in the streamwise direction and that there is a streamwise vortex pair near the wall. It is shown that a structure correlated with the streamwise wall vorticity is smaller than and prior to a structure correlated with the spanwise wall vorticity. Tilting angles are obtained from the phase shift between the wall vorticity and streamwise velocity fluctuations. The tilting angle of the structure correlated with the streamwise wall vorticity is larger than that of the structure correlated with the spanwise wall vorticity. The convection velocity of the near-wall streamwise velocity fluctuations obtained from the space-time correlation is in good agreement with previous results.

• Korean Institute of Interior Design Journal
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• no.39
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• pp.100-107
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• 2003

The purpose of this study is to help create environments for early childhood education according to the principles of Constructivism. Generally, preschools in Ulsan Metropolitan City were used as samples for this study More particularly, 116 kindergartens were surveyed by telephone to evaluate their education programs. Four kindergartens that completely or partially used Constructivism in their programs were chosen as primary subjects for this study The results of this study were as follows: First, it was discovered that preschool education in Ulsan uses an integrated education model based on activities and Montessorie. Constructivist programs were also present using Project Approach, Reggio Emilia and Piaget. Second, the number of infants per class averaged 29.3. The average infants per playroom was 2.38$m^2$. It seems, therefore, that there is a lack of sufficient space for activities. Playroom furniture is primarily used for storage and it lacks variety and flexibility of use. The interior of preschools in related to materials, color and images also showed little difference among schools. Third, it was found that virtually every play space did not have adequate water playing and sand playing sections. Instead, the space for the large-muscle activities of big groups was used for this purpose. Fourth, kindergartens that use the principles of Constructivism plan to specialize their activities. Those only partially using Constructivism showed conventional tendencies and small play spaces that would be defined as inadequate according to Constructivism. This study, therefore, demonstrates that preschool education based on Constructivism are not being well-implemented in concert with other programs.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.339-348
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• 2007

KASINICS (Korea Astronomy and Space Science Institute Near Infrared Camera System) is equipped with a InSb array which can observe $1-5\;{\mu}m$ bands in near-infrared. The absorption and emission by telluric water vapor becomes serious in the bands longer than $3\;{\mu}m$. We measured PWV (precipitable Water Vapor) levels above Bohyusan Optical Astronomy Observatory and Sobaeksan Optical Astronomy Observatory from July 2006 to August 2007 using the GPS PWV measurement system of KASI. We found that monthly averaged PWVs are lower than the prediction using dew-point temperature and as low as above Kitt Peak from September to February.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.269-274
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• 2007

We established a regional ionospheric model for investigating ionospheric TEC (Total Electron Contents) variations over the Korean Peninsula during major geomagnetic storms. In order to monitor the ionospheric TEC variations, we used nine permanent GPS reference stations uniformly distributed in South Korea operated by the Korea Astronomy and Space Science Institute (KASI). The cubic spline smoothing (CSS) interpolation method was used to analyze the characteristics of the ionospheric TEC variations. It has been found that variations of TEC over the Korean Peninsula increase when a major geomagnetic storm occurred on November 20, 2003. The TEC has increased about one and a half of those averaged quite days at the specific time during a geomagnetic storm. It has been indicated that the KASI GPS-derived TEC has a correlation with the geomagnetic storm indices (eq. Kp and Dst indices).