• The Journal of Korean Academy of Prosthodontics
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• v.49 no.4
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• pp.324-332
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• 2011

Purpose: The purpose of this study was to compare the stress distribution of teeth and jaw on load by differentiating property of materials according to each layer of widely used mouthguard. Materials and methods: A Korean adult having normal cranium and mandible was selected to examine. A customized mouthguard was constructed by use of DRUFOMAT plate and DRUFOMAT-TE/-SQ of Dreve Co. according to Signature Mouthguard system. The cranium was scanned by means of computed tomography with 1mm interval. It was modeled with CANTIBio BIONIX/Body Builder program and simulated and interpreted using Alter HyperMesh program. The mouthguard was classified as follows according to the layers. (1) soft guard (Bioplast)(SG) (2) hard guard (Duran)(HG) (3) medium guard (Drufomat)(MG) (4) soft layer + hard layer (SG + HG) (5) hard layer + soft layer (HG + SG) (6) soft layer + hard layer + soft layer (SG + HG + SG) (7) hard layer + soft layer + hard layer (HG + SG + HG) The impact locations on mandible were gnathion, the center of inferior border, and the anterior edge of gonial angle. And the impact directions were oblique ($45^{\circ}$). The impact load was 800 N for 0.1 sec. The stress distribution was measured at maxillary teeth, TMJ and maxilla. The statistics were conducted using Repeated ANOVA and in case of difference, Duncan test was used as post analysis. Results: In teeth and maxilla, the mouthguard contacting soft layer of mandibular teeth presented lowest stress measure and, in contrast, in condyle, the mouthguard contacting hard layer of mandibular teeth presented lowest stress measure. Conclusion: For all impact directions, soft layer + hard layer + soft layer, the mouthguard with three layers which the hard layer is sandwiched between two soft layers, showed relatively even distribution of stress in impact.

• Journal of Korean Foot and Ankle Society
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• v.17 no.3
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• pp.225-233
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• 2013

Purpose: This study was performed to evaluate the impact of the lesser toe operation on the overall clinical outcomes, and to analyze the clinical results of concomitant surgery for hallux valgus and lesser toe deformities. Materials and Methods: Forty-six cases underwent surgery for hallux valgus with concomitant lesser toe deformities were followed up for at least 1 year. Lesser toe deformities consisted of 9 crossover toes, 10 claw toes, 12 hammer toes and 15 bunionettes. Clinical evaluation was performed according to AOFAS (American Orthopaedic Foot and Ankle Society) score, patient's satisfaction score, and pain VAS (visual analogue scale) score. Hallux valgus angle (HVA), intermetatarsal angle (IMA), and period to union were measured. Preoperative expectation about lesser toe deformities, postoperative satisfaction, complication rate, hospitalization period, medical expenses, and frequency of outpatient follow-up were analyzed. Results: AOFAS score, VAS score, HAV and IMA had improved significantly. On preoperative expectation of patients, correction of lesser toe deformities was ranked third, following the improvement of big toe(bunion) pain and the correction of hallux valgus. Patient's satisfaction score was average 92.8 points, and the importance of lesser toe operation was 30.2%. When compared to hallux valgus operation only, there were average 2.5 days of additional hospitalization, 2.4 times of additional outpatient follow-up, 386000 won of additional medical expenses. Conclusion: Combined operation for hallux valgus and concomitant lesser toe deformities showed good clinical results. When compared to hallux valgus operation only, there were longer hospitalization, more frequent follow-up, more medical expenses, more complications. However, lesser toe deformity correction in patients underwent hallux valgus operation is considerable, because of high preoperative expectation and postoperative satisfaction.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.3
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• pp.291-297
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• 2016

Direct georeferencing has become widespread in the field of digital aerial photogrammetry; as a result, the boresight calibration has become an essential component of the procedure to calculating exterior orientation parameters of aerial photographs accurately. During this procedure, a reference is used for the height of the geoid model, and the calibration results can appear different depending on the geoid model. The exterior orientation parameters calculated through direct georeferencing during boresight calibration may have varied values according to the corresponding geoid model. With that in mind, the effects of the geoid model on the boresight calibration were analyzed through three different cases. The geoid models used in the experiments were EGM96, EGM08, and KNGeoid14, and, through boresight calibration, the datum shift and boresight angle for each model was computed. After calculating the exterior orientation of each case, the GCP (Ground Control Point) was verified using the DPW (Digital Photogrammetry Workstation). In each case, results in the boresight calibration acquired through the geoid model demonstrated a difference in the Z datum, the exterior orientation heights Z, and the rotation Ω and Φ. After utilizing the DPW in each case and comparing it to the GCP, the difference in accuracy in accordance with the geoid model was found to be within 3cm, and it was concluded that the geoid model did not have a significant impact on boresight calibration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.1
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• pp.25-33
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• 2020

In this study, parametric analyses are performed using the coupled Eulerian-Lagrangian scheme for the collision behaviors of a vessel and an underwater slope that constitutes part of an artificial protective island. The vessel parameters considered in the analysis are bow angle, stem angle, draft, and impact velocity. The gradient of the slope, the friction coefficient between the bow and the slope, and soil strength are considered as parameters of the slope. For each parameter, the dissipated collision energy and the collision force are estimated from the behavior of the vessel, and the energy dissipation mechanism is identified in terms of the ground deformation. The collision force is assumed as an exponential function, and the effects of the parameters are estimated. As a result, only two parameters, the gradient of the slope and the friction coefficient between the vessel and the soil, can affect the exponential coefficient of the function. The dissipated energy by the soil can thus be estimated adequately. The relationship between the volume of the soil pushed out by the bow and the dissipated collision energy is estimated as a linear function. This relationship is independent of the magnitude of the collision energy, and affected more by the friction coefficient and the soil strength than by the parameters of the vessel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.552-561
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• 2016

In this experimental study, the dynamic stability derivatives of a tailless lambda-shape UAV are estimated from time history data of aerodynamic moments measured from the internal balance while the test model is forced to oscillate at given frequencies and amplitudes. A 3-axis forced oscillation apparatus is designed to induce decoupled roll, yaw, pitch oscillations respectively. The results show that the roll damping derivatives remain stable at the entire range of angle of attack tested, whereas the pitch damping derivatives become unstable beyond $15^{\circ}$ angle of attack. The amplitude and frequency have little impact on roll damping derivatives while the smaller amplitude and frequency of oscillation improves the pitch stability. The yaw damping derivative values are fairly small as expected for a tailless configuration. The results indicate that the proposed methodology and test apparatus area valid for estimating the dynamic stability derivatives of a tailless UAV.

• Korean Journal of Construction Engineering and Management
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• v.18 no.5
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• pp.11-19
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• 2017

The purpose of this study is to analyze the efficiency of PV according to installation condition in the complex type buildings. For this purpose, annual performance of solar power generation in a certain area was investigated and various methods were conducted including post operation evaluation. In addition, we tried to find out influencing factors that affect the efficiency and sought to identify their relative impact of degree through the data analysis and site visits together. In the middle of this process we can draw up major considerations for the efficient photovoltaic power generation installation. In the mean while, previous studies are making something new related with method for efficiency enhancement and individual influential factors based on experimental environment rather than the empirical data site based. As a result of the study, it was confirmed that even if installed in the same area, the power generation efficiency is 1.5 times as high as the installation condition. Furthermore, statistical analyses were performed on azimuth, tilted angle and shade, which are variables affecting conversion efficiency, and it was statistically confirmed that all variables are meaningful factors that affect the conversion efficiency which is a dependent variable. The most influential factor is the azimuth, followed by the tilted angle and the shade factor. From this result, we expect to be able to provide installation guidelines for the solar power generation equipments on the rooftop zone.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.95-106
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• 2021

Side-jets enable the immediate maneuver of a missile compared to control surfaces; however, they may cause adverse effects on aerodynamic coefficients, for they interfere with freestream. To find out the impact of side-jets on aerodynamic coefficients, we simulate side-jets as air gas and utilize multi-fidelity models to evaluate differences between aerodynamic coefficients obtained with and without side-jets. We computed differences in aerodynamic coefficients to investigate side-jet effects for the changes of a Mach number, a bank angle, and an angle of attack. As a result, asymmetrically developed side-jets affect the longitudinal force and moment coefficients, and the lateral force and moment coefficients drastically change in-between -30 and 30 degrees of bank angles. In contrast, side-jets hardly influence the axial force coefficients. As for the axial moment coefficient, we could not determine the side-jet effect due to a lack of aerodynamic coefficient samples in the Mach number. All in all, we confirm that side-jets lead to the change of a missile attitude as they considerably vary the longitudinal and lateral aerodynamic coefficients.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.4
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• pp.260-266
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• 2023

The concept of 'Implant Supracrestal Complex (ISC)' was introduced as a way to determine the impact of implant prosthetic design form on both short-term clinical outcomes and the long-term prognosis of bone and soft tissues around the implant. Implant-prosthesis-abutment complex design forms, such as implant-abutment design, junction, and location, can have important implications for the stable and healthy long-term maintenance of the tissues around the implant. In this case, a customized concave abutment and a prosthesis with an emergence angle of about 30 degrees were restored to a patient suffering from chronic soft tissue inflammation and pain after restoration of an implant prosthesis. It was confirmed that the new prosthesis improved complications by allowing sufficient bone and soft tissue space, achieved appropriate soft tissue sealing, and maintained the long-term stability of the implant.

• Korean Journal of Environmental Agriculture
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• v.24 no.4
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• pp.334-340
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• 2005

This experiment was conducted to evaluate the nutrient loss and to assess the eutrophication into small stream by intensive rains in the steeped cornfield during cultivation. The crop cultivated was a soiling com (DW5969), and the experimental plots were divided into two parts that were 10 and 18% of slope degrees. The amount of T-N and T-P loss was calculated by analysis of surface run-off water quality, and was investigated the effect of eutrophication to small stream as a part of life cycle assessment (LCA) methodology application. For the surface run-off water quality, EC and T-N values were highest in first runoff event as compared to the other events and maintained the stage state with litter variations at every hour during the runoff period except for EC in the slope 18%. However, T-P concentration has been a transient stage after runoff event of July 27. Total surface run-off ratio was not significantly different with slope degrees, but amount of T-N and T-P losses at 18% of slope were high as $5.96kg\;ha^{-1}\;and\;0.65kg\;ha^{-1}$ as relative to 10% of slope degree, respectively. Furthermore, T-N losses from run-off water in the sloped cornfield 10 and 18% were approximately 9.8 and 12.5% of the N applied as fertilizer when the fertilizer applied at recommended rates after soil test, respectively. For the eutrophication impact to the small stream, it was shown that $PO_4$ equivalence and Eco-indicator value at 18% of slope degree were greater as much $6.11kg\;ha^{-1}$ and 0.81 as compared to the slope angle 10%, respectively. Therefore, it was appeared that each effect of nutrient losses, eutrophication and Eco-indicator value was enhanced according with higher slope degree.

• Journal of Biosystems Engineering
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• v.7 no.1
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• pp.17-32
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• 1982

The binders introduced in Korea were originally designed to be used for Japonica-type varieties which have relatively long stem and are highly resistant to shattering. In order to use it for Tongil varieties which are short and easy to be shattered, mechanical modifications are necessary to reduce a grain loss incurred during binder operation. This study was intended to investigate analytically and experimentally the major sources of grain losses caused by three kinds of binders now introduced in Korea. Actual modification for each of three binders was done and experimentally compared to see if any improvement on grain loss was achieved. The results obtained in this study are summarized as follows; 1. It was required that the power transmission of binder should have a shifting mechanism so that velocities of pick-up and traveling units could be changed independently as desired according to the Japonica-type and Tongil varieties. In other words, the desired velocity of traveling unit should be obtained by shifting the transmission and the velocity of pick-up unit should be selected by reaping clutch according to the variety independent of the velocity of traveling unit as shown in Fig. 6. 2. To reduce grain loss it was desired that the moving parts of the pick-up unit should have the lowest possible velocities in harvesting Tongil varieties, unless the reduction of the speed be hindered the conveyance of the material. Based on the study, it was concluded that the velocities of pick-up unit be reduced by about 35% of those of the existing units. 3. It was found that the lug at the upper rotating section of pick-up case gave a severe impact on the ears of rice to increase grain loss. The optimum design of pick-up case to protect the ears from the protruding part of the lug was recommended by the result of analysis of the trajectory of the end-point of lug at the position. 4. It was proved analytically and experimentally that pick-up unit at the lower-rotating part was the other important source of grain loss in pick-up and divider assembly. In order to reduce a grain loss incurred by lugs at their lower-rotating section, it was suggested to improve it by (1) widening the space between right and left lower-rotating section, (2) shortening the length of lugs, (3) enlargement of the angle between the pick-up case and ground-level, and (4) attaching guard to right and left dividers so that the rotating lug could not give a high impact to the paddy hill. 5. Pick-up and divider assembly of the original binder of three models studied was modified according to the suggestions that were given by the preliminary study. Field test showed that the modified binders were able to reduce grain losses by about 0.4-0.7 percentage points compared to those without modification.