• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.9 s.102
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• pp.1009-1015
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• 2005

Fluid-elastic instability and turbulence excitation for an under developing steam generator are investigated numerically. The stability ratio and the amplitude of turbulence excitation are obtained by using the $PIAT^{(R)}$ (program for integrity assessment of steam generator tube) code from the information on the thermal-hydraulic data of the steam generator. The aspect ratio, the ratio between the height of U-tube from the upper most tube support Plate (h) and the width of two vertical portion of U-tube (w), is defined for geometric parameter study. Several aspect ratios with relocation of tube support plates are adopted to study the effects on the mode shapes and characteristics of flow-induced vibration. When the aspect ratio exceeds value of 1, most of the mode shapes at low frequency are generated at the top of U-tube. It makes very high value of the stability ratio and the amplitude of turbulent excitation as well. We can consider that the local mode shape at the upper side of U-tube will develop the wear phenomena between the tube and the anti-nitration bars such as vortical, horizontal, and diagonal strips. It turns out that the aspect ratio reveals very important parameter for the design stage of the steam generator. The appropriate value of the aspect ratio should be specified and applied.

• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.143-152
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• 2005

The purpose of this study was to predict the failure or success of the Snatch-lifting trial as a consequence of the stand-up phase simulated in Kane's equation of motion that was effective for the dynamic analysis of multi-segment. This experiment was a case study in which one male athlete (age: 23yrs, height: 154.4cm, weight: 64.5kg) from K University was selected The system of a simulation included a multi-segment system that had one degree of freedom and one generalized coordinate for the shank segment angle. The reference frame was fixed by the Nonlinear Trans formation (NLT) method in order to set up a fixed Cartesian coordinate system in space. A weightlifter lifted a 90kg-barbell that was 75% of subject's maximum lifting capability (120kg). For this study, six cameras (Qualisys Proreflex MCU240s) and two force-plates (Kistler 9286AAs) were used for collecting data. The motion tracks of 11 land markers were attached on the major joints of the body and barbell. The sampling rates of cameras and force-plates were set up 100Hz and 1000Hz, respectively. Data were processed via the Qualisys Track manager (QTM) software. Landmark positions and force-plate amplitudes were simultaneously integrated by Qualisys system The coordinate data were filtered using a fourth-order Butterworth low pass filtering with an estimated optimum cut-off frequency of 9Hz calculated with Andrew & Yu's formula. The input data of the model were derived from experimental data processed in Matlab6.5 and the solution of a model made in Kane's method was solved in Matematica5.0. The conclusions were as follows; 1. The torque motor of the shank with 246Nm from this experiment could lift a maximum barbell weight (158.98kg) which was about 246 times as much as subject's body weight (64.5kg). 2. The torque motor with 166.5 Nm, simulated by angular displacement of the shank matched to the experimental result, could lift a maximum barbell weight (90kg) which was about 1.4 times as much as subject's body weight (64.5kg). 3. Comparing subject's maximum barbell weight (120kg) with a modeling maximum barbell weight (155.51kg) and with an experimental maximum barbell weight (90kg), the differences between these were about +35.7kg and -30kg. These results strongly suggest that if the maximum barbell weight is decided, coaches will be able to provide further knowledge and information to weightlifters for the performance improvement and then prevent injuries from training of weightlifters. It hopes to apply Kane's method to other sports skill as well as weightlifting to simulate its motion in the future study.

• The korean journal of orthodontics
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• v.27 no.2
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• pp.197-208
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• 1997

Class III malocclusion patients can be approached with many different types of treatment methods, and thus, each patient's problems must be accurately evaluated to allow selection of the best possible treatment method. Cephalometric analysis is an essential part of diagnosis and treatment planning of orthodontic patients, and it would certainly be helpful if reliable cephalometric guidelines could be set. The author divided 482 Class III malocclusion patients(253 males and 229 females) into fourgroups according to different types of treatment methods they have received to correct imbalance between upper and lower jaws: 1) orthopedic appliance (face mask & RPE), 2) camouflage treatment with fixed appliance, 3) surgical-orthodontic treatment, 4) cross-bite correction with removable plates/ functional appliance. Cephalometric values at the time of first clinical examination were compare among the four groups. Cephalometric analysis indicates the following results: 1)the amounts of antero-posterior and vertical skeletal discrepancies and dental compensation were greatest in surgery group 2) SNB, Wits, distance from Nasion Perpendicular Plane to point a facial angle, facial convexity, and APDI were greater in orthopedic appliance group than fixed appliance(camouflage) group, but there was no statistical difference 3) removable plates/ functional appliance group showed least amounts of skeletal discrepancies and dental compensation with statistical significance.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.569-579
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• 2013

A steel-type breakwater that uses a submerged dual horizontal porous plate was originally proposed by Kweon et al. (2005), and its hydrodynamic characteristics and design methodology were investigated in a series of subsequent researches. In particular, Kweon et al. (2011) proposed a method of estimating the vertical uplift force that acts on the horizontal plate, applicable to the design of the pile uplift drag force. However, the difference between the method proposed by Kweon et al. (2011), and the wave force measured at a different time without a phase difference, have not yet been clearly analyzed. In this study, such difference according to the method of estimating the wave force was analyzed, by measuring the wave pressure acting on a breakwater model. The hydraulic model test was conducted in a two-dimensional wave flume of 60.0 m length, 1.5 m height and 1.0 m width. The steepness range of the selected waves is 0.01~0.03, with regular and random signals. 20 pressure gauges were used for the measurement. The analysis results showed that the wave force estimate in the method of Kweon et al. (2011) was smaller than the wave force calculated from the maximum pressure at individual points, under a random wave action. Meanwhile, the method of Goda (1974) that was applied to the horizontal plate produced a smaller wave force, than the method of Kweon et al. (2011). The method of Kweon (2011) was already verified in the real sea test of Kweon et al. (2012), where the safety factor of the pile uplift force was found to be greater than 2.0. Based on these results, it was concluded that the method of estimating the wave force by Kweon et al. (2011) can be satisfactorily used for estimating the uplift force of a pile.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1209-1218
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• 2001

The present paper proposes a new correlation for the flow boiling heat transfer coefficients in the low flow rate condition (Re(sub)LF$\leq$200) within horizontal rectangular channels with small gaps (heights). The gap between the upper and the lower plates of each channel ranges from 0.4 to 2mm while the channel width being fixed to 20mm. Refrigerant 113 was used as the test fluid. The mass flux ranges from 50 to 200kg/㎡s and the channel walls were uniformly heated with the heat flux range of 3-15kW/㎡. The quality range covers from 0.19 to 0.76 and the flow pattern is considered to be annular. The measured heat transfer coefficients increase with the mass flux and the local quality; however the effect of the heat flux appears to be minor. At the low mass flux condition, which is more likely with the smaller gap size, the heat transfer is primarily controlled by the liquid film thickness. The proposed F factor for the heat transfer coefficient in the range of Re(sub)LF$\leq$200 well represents the experimental data within the deviation of $\pm$20%. The Kandlikars flow boiling correlation covers the higher flow-rate range(Re(sub)LF>200) within the deviation of $\pm$20%.

• Journal of Korean Society of Forest Science
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• v.77 no.3
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• pp.283-293
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• 1988

Anatomical features of the secondary xylem were described in the branches, stems, and roots of Salix glandulosa and Quercus variavilis. In Quercus variavilis, the stem shows ring-porous wood, while the root shows diffuse-porous wood. In both species, it is found that the boundaries between the growth rings are not well defined in the roots. Both vessel elements and fibers are the longest in the roots followed by the sterns and the branches in turn and diameter of vessel elements shows the same trend. In cross section, the number of vessels per unit area are the longest in the branches followed by the stems and the roots in turn as well. Perforation plates are simple in both species and their angles are wide in the root, intermediate in the stems, and narrow in the branches. In tangential section, height of rays is taller in the roots than in the stem and branches.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.330-335
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• 2011

This paper presents estimation of average compressive strengths of three types of stiffened panels under lateral pressure and axial compression based on simplified formulas from CSRs and nonlinear FEAs. FEA scenarios are prepared based on the slenderness ratios of the stiffened panels used for in-service vessels. The seven step lateral pressures by 1bar increment are imposed on FE models assuming maximum 30m water height. The number of FEAs for FB-, AB-, and TB-stiffened panels is totally 189 times. FEA results show that existence of pressure can evolves significant reduction of ultimate strengths, meanwhile CSR formulas do not take into account the lateral pressure effect. Lateral pressure acting on the stiffened panel with higher column slenderness ratio more reduces the ultimate strengths than those with smaller column slenderness ratio. A new concept of relative average compressive strain energy instead of the ultimate strength is introduced in order to rationally compare the average compressive strength through complete compressive straining regime. The differences of the ultimate strengths between CSR formulas and FEA results are relatively small for FB- and AB-stiffened panels, but larger discrepancies of relative average compressive strain energies are shown.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.247-258
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• 2007

This paper describes the results of an experimental study on the new type of encased composite beams that use deep deck plates, which could reduce the story height of buildings by controlling the bottom flange of steel beams. The profiled steel beam was thus developed. It was advantageous to the long span of the buildings. Seven full-scale specimens were constructed, and simply supported bending tests were conducted on the encased composite beams with different steel plate thicknesses, with and without shear studs, reinforcing bars, and web openings. The test results showed that the encased composite beams that were developed in this study had sufficient composite action without additional shear connectors due to their inherent shear-bond effects between the steel beams and concrete.

• Journal of Haehwa Medicine
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• v.7 no.2
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• pp.609-620
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• 1999

Over the period between January 1997 and December 1998, herbal medicine was more than three times administered to the patients coming to Na dong gyu's Oriental Medical Clinic on account of the symptom of growth deficiency. According to radiological opinions about the patients providing cooperation for measuring their height and weight as well as their bone age every three months, it was found that the growth plates were not closed. A research was conducted for 200 children randomly selected of patients in prepuberty (they grew by less than 5cm a year before treatment at a age of 12years for female children and 14years for male children). As a result, the following conclusion was drawn: 1. The randomly selected subjects were made up of 116 male and 84 female children in terms of gender. The age direstribution was most 10 to 12 years in 86 children(34.00%), followed by 8-10 years(27.50%) and 12 to 14 years(19.50%). 2. Considering the distribution of sick children's parental height, the fathers of 141 children(70.50%) measured less than 170cm high, the subaverage height, while the mothers of 172 children(86%) measured less than 160cm high, the subaverage height. It was shown that sick childen's height was genetically influenced by their parents. 3. Children patients's weight at a time of birth was most 3.1-3.5kg for 85 children(44%) and less than 2.5kg which came under the range of growth dificiency for 19 children(9.5%). 4. The highest proportian of the children patients with growth dificiency(56.33%) had the symptom of digestive disorders, of which 77 children patients(18.78%) had anorexia, 16.59% of children patients had the high level of respiratory disorders. Both the digestive disorder and the respiratory disorder put together, they had the high rate of 72.92%. Therefore, this indicates that both the digestive disorder and the respiratory disorder have a great effect on children's growth dificiency. 10.74% of chilren patients were shown to have allergic disorders, which indicates that they also exert an effect on growth deficiency. Specifically, 7.07% of the children patients had the high level of obesity, which shows that an excessive uptake of nutrition may rather induce children to have growth dificiency though an appropriate amount of nutritional uptake is necessary. 5. Comparing their bone age and their chronological age, 58 children patients(29.00%) showed that they were the same at the highest percent. 79 children patients(39.50%) showed that thier bone age was lower than their chronological age. And 63 children patients(31.50%) showed that their bone age was higher than their chronological age. 6. As regards the prescription administered to children patients for treating their growth dificiency, Growth tang A related to the kidney, the congenital factor, of the causes for growth dificiency in traditional Oriental Medicine was administered to 108 children patients(54%), whereas the Growth tang B related to the spleen, the acquired factor, was administered to 92 children patients(46%). 7. 116 male children patients with growth dificiency had the average value of growth for one year before treatment, 4.39cm, while 84 female children patients had the average value of growth for one year before treatment, 4.24cm. A total of 200 children had the average value of growth for one year before treatment, 4.33cm. The annual average value of growth in growth curve surveyed by the Korea Pediatrics Society was 5.79cm. Compared to this value, the one year average value of growth for 108 male and female children patients taking Growth tang A was shown be 8.44cm, which indicates a greater growth by 4.12cm(95.37%) in comparison with the average value of growth before treatment, 4.32cm, and a greater growth by 2.65cm(45.77%) compared to 5.79cm, the average value of growth in growth curve surveyed by the Korea Pediatrics Society. Also, the average value of growth before treatment for 92 male and female children patients taking Growth tang B was shown to be 8.47cm, which indicates a greater increase by 4.15cm(96.06%) compared to 4.32cm, the average value of growth before treatment and a greater increase by 2.67cm(46.29%) in comparison with 5.79cm, the average value of growth in growth curve surveyed by the Korea Pediatrics Society. Considering the average value of growth for male and female children patients taking Growth tang A and B, it was shown to be 8.46cm, which indicates a greater increase by 4.14cm(95.81%) compared to 4.32cm, the average value of growth before treatment, and a greater increase by 2.67cm(46.11%) compared to 5.79cm, the average value of growth in growth curve surveyed by the Korea Pediatrics Society.

• Korean Journal of Applied Biomechanics
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• v.33 no.3
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• pp.110-117
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• 2023

Objective: The purpose of this study was to find out kinematic and kinetic differences the lower extremity joint according to the landing type during vertical jump movement after jump landing, and to present an efficient landing method to reduce the incidence of injury in youth players. Method: Total of 24 Youth players under Korean Sport and Olympic Committee, who used either heel contact landing (HCG) or toe contact landing (TCG) participated in this study (HCG (12): CG height: 168.7 ± 9.7 cm, weight: 60.9 ± 11.6 kg, age: 14.1 ± 0.9 yrs., career: 4.3 ± 2.9 yrs., TCG height: 174.8 ± 4.9 cm, weight: 66.9 ± 9.9 kg, age 13.9 ± 0.8 yrs., career: 4.7 ± 2.0 yrs.). Participants were asked to perform jump landing consecutively followed by vertical jump. A 3-dimensional motion analysis with 19 infrared cameras and 2 force plates was performed in this study. To find out the significance between two landing styles independent t-test was performed and significance level was set at .05. Results: HCG showed a significantly higher dorsi flexion, extension and flexion angle at ankle, knee and hip joints, respectively compared with those of TCG (p<.05). Also, HCG revealed reduced RoM at ankle joint while it showed increased RoM at knee joint compared to TCG (p<.05). In addition, HGC showed greater peak force, a loading rate, and impulse than those of TCG (p<.05). Finally, greater planta flexion moment was revealed in TCG compared to HCG at ankle joint. For the knee joint HCG showed extension and flexion moment in E1 and E2, respectively, while TCG showed opposite results. Conclusion: Compared to toe contact landing, the heel contact landing is not expected to have an advantage in terms of absorbing and dispersing the impact of contact with the ground to the joint. If these movements continuously used, performance may deteriorate, including injuries, so it is believed that education on safe landing methods is needed for young athletes whose musculoskeletal growth is not fully mature.