• The korean journal of orthodontics
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• v.34 no.2 s.103
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• pp.197-203
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• 2004

Tweed-Merrifield directional force technology is a very useful concept, especially for the treatment of Glass II malocclusion. It has contributed to treating a favorable counter-clockwise skeletal change and balanced face, while head gear force using high pull J-hook (HPJH) in an appropriate direction is also essential to influence such results. Clinicians have encountered some problems concerning patients' compliance; however skeletal anchorage has been used widely of late because it does not necessitate patients' compliance, yet produces absolute anchorage. In this case, a good facial balance was obtained by Tweed-Merrifield directional force technology using HPJH together with skeletal anchorage, which provided anchorage control in the maxillary posterior area, torque control in the maxillary anterior area, and mandibular response. This indicates 4hat skeletal anchorage can be used to reinforce sagittal and vortical anchorage in the maxillary posterior area during the retraction of anterior teeth. The author used HPJH for torque control, Intrusion, and the bodily movement of maxillary anterior teeth during on masse movement. However, it is thought that such a result nay also be achieved by substituting mini- or microscrews for HPJH. Consequently, Tweed-Merrifield directional force technology using skeletal anchorage for the treatment of Class II malocclusion not only maximiaes the result of treatment but can also minimize patients' compliance.

• The korean journal of orthodontics
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• v.18 no.2
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• pp.367-385
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• 1988

In case of skeletal Class III malocclusion with underdeveloped maxilla, the extraoral orthopedic force for the stimulation of maxillary growth or anterior reposition of the maxilla has been used clinically for the improvement of facial skeletal relationship. The purpose of this investigation was to examine the initial reaction of maxillofacial complex to the maxillary protraction by using extraoral orthopedic force. The dried human skull was used and this investigation was done by means of double exposure holographic interferometry. The protraction forces placed on the canine or the first molar were parallel, $10^{\circ}$ downward, $20^{\circ}$ downward to the occlusal plane. Fringe pattern of each protraction condition was compared and analized. The results were as follows: 1. Each maxillofacial bone displaced saparately. 2. More displacement was shown at the area of the teeth and the alveolar bone. 3. A counterclockwise rotation of the maxilla wa decreased by downward protraction and especially 20 degree downward protraction from the canine showed least rotation. 4. On the zygomatic arch, outward bend was observed and this effect was decreased by downward protraction. 5. On the zygomatic bone, the counter clockwise rotation was increased by the downward protraction. 6. When maxillary expansion was applied at the same time, outward and upward displacement with counterclockwise rotation was observed on the maxilla. 7. The lateral pterygoid plate of sphenoid bone was affected by maxillary protraction.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.167-174
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• 2015

Purpose : The purpose of this study was to investigate the effects of loaded vertical jumps on the following vertical jumps and to find how long the transient effect of warm-ups would continue. Methods : Twelve healthy college male students, majoring in physical education, participated in this study voluntarily. They performed three sets of unloaded jumps (pre-jump, 5% post jump, and 10% post jump) and two sets of loaded jumps (5% and 10% loaded jumps) according to the counter-balanced order. At each set, three trials of maximal vertical jumps were performed by a 30 second interval between trials and a 3 minute break after warm-up jumps. Force platform and motion capturing system were used to record motions and ground reaction force. Results : Only 5% post-warm-up jumps ($48.29{\pm}2.06cm$) showed significant increase in the jump height compared with pre-warm-up jumps ($47.35{\pm}2.21cm$). The transient effects of loaded warm-ups disappeared 4 minutes after loaded jumps. Conclusion : Conclusively, a decent amount of loading (around 5% extra of body weight) during sport specific warm-ups would give a positive, transient effect on the performance of the vertical jump.

• KSTLE International Journal
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• v.4 no.2
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• pp.60-65
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• 2003

Tribological properties of novolac resin composites containing particulate barite (BaSO$_4$) or potassium titanate (K$_2$Oㆍ6(TiO$_2$))whiskers (two typical space fillers for commercial automotive brake linings) were investigated. The emphasis of the current investigation was given to the effect of the two fillers on the propensity of the stick-slip phenomena and formation of stable rubbing surface. A block-on-disk type tribometer was used for friction assessment. Results showed that the BaSO$_4$-filled composite produced large friction force oscillations at slow sliding speeds and created severe damage on the gray iron counter surface. On the other hand, the composite with $K_2$Oㆍ6(TiO$_2$) whiskers formed a stable rubbing surface and showed smooth sliding behavior without large friction force fluctuation. The microscopic observation of the rubbing surface revealed that the $K_2$Oㆍ6(TiO$_2$)whiskers played a key role in the formation of stable rubbing surface and smooth sliding behavior by effectively reinforcing the resin.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.760-768
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• 2000

Filter efficiency of electrically charged particle in uncharged fibrous filter was measured. In previous studies, the effect of charged particle on filter efficiency was investigated but there was difficulty in measuring of image effect that is appeared at the charged small particle. We could easily measure the image effect with charging small particles by photoelectric charging. The spark discharge aerosol generator and a differential mobility analyzer (DMA) were used to generate sub-micron monodisperse particles (${\leq}200$ nm). The generated particles were charged in photoelectric charging process using ultraviolet lamp and electric field. The filter efficiency of the charged particles, classified by another DMA, was measured in filter tester using a condensation nucleus counter (CNC) as function of particle diameter, particle charge and airflow velocity. It is shown that the filter efficiency increases with increasing charge number of the particle and is affected by particle size and flow velocity. Single fiber filter efficiency mainly depends on image force parameter and peclet number. The peclet number was not considered at previous other papers. We propose a modi fied experimental correlation as function of image force parameter and peclet number.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.24-34
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• 2014

In order to manage essential parts that are required for the repairable parts services performed at the military maintenance depots, the United States Air Force developed the Repairability Forecasting Model (RFM). In the RFM, if the requirements of the parts are assumed to follow the normal probability distribution after applying means from the past data to the replacement rate and lead times, the chance of the AWP (Awaiting Parts) occurring is 50%. In this study, to counter the uncertainties of requirements and lead times from the RFM, the safety level concept is considered. To obtain the safety level for requirements, the binomial probability distribution is applied, while the safety level for lead time is obtained by applying the normal probability distribution. After adding this concept, the improved RFM is renamed as the ARFM (Advanced RFM), and by conducting the numerical stimulation, the effectiveness of the ARFM, minimizing the occurrence of the AWP, is shown by increasing the efficiency of the maintenance process and the operating rate of the weapon system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.2
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• pp.74-83
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• 2018

It is very crucial activities that Korean army have to detect and recognize enemy's locations and types of weapon of their artillery firstly for effective operation of friendly force's artillery weapons during wartime. For these activities, one of the most critical artillery weapon systems is the anti-artillery radar (hereafter; radars) for immediate counter-fire operations against the target. So, in early wartime these radar's roles are very important for minimizing friendly force's damage because arbiters have to recognize a several enemy's artillery positions quickly and then to take an action right away. Up to date, Republic of Korea Army for tactical artillery operations only depends on individual commander's intuition and capability. Therefore, we propose these radars allocation model based on integer programming that combines ArcGIS (Geographic Information System) analysis data and each radar's performances which include allowable specific ranges of altitude, azimuth (FOV; field of view) and distances for target detection, and weapons types i.e., rocket, mortars and cannon ammo etc. And we demonstrate the effectiveness of their allocation's solution of available various types of radar asset through several experimental scenarios. The proposed model can be ensured the optimal detection coverage, the enhancement of artillery radar's operations and assisting a quick decision for commander finally.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.8
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• pp.39-47
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• 2011

The motion of a conductive spherical particle under uniform electric field is investigated in order to find a suitable method for removing the conducting solid impurities contained in liquid plastic. When the positive dc voltage applied to the upper electrode, the vertical up-and-down motion of a charged particle by electrostatic force is observed by a charge-coupled device (CCD) camera or a high-speed video camera. The experimental data of the static threshold voltage by which the particle starts to move toward the counter electrode in air or silicone oil are in good agreement with theoretical value. When the applied voltage is larger than the static threshold voltage, the particle motion pattern in silicone oil consists of four stages: upward motion, stopping at the upper electrode, downward motion and stopping at the lower electrode. The stopping motion on the electrode is thought to be caused by the liquid flow accompanied by the particle motion. The particle charge calculated by integrating the pulse current, which is generated by the charge exchange between the electrode and the particle, is approximately 0.1~0.25 times of the theoretical value. This study is expected to help understand the electric properties of microparticles in oil circuit breaker (OCB) and oil transformer and improve their performance and longevity.

• Journal of Auto-vehicle Safety Association
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• v.15 no.3
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• pp.27-33
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• 2023

Electric vehicles are widely produced from many car manufacturers around the world instead of internal combustion engine vehicle in order to respond a variety of environmental regulations. Also, they are applying for modular design method to develop plenty of the vehicles. And, both of these two issues will be an important trend to lead the future global automobile industries for a long time. In this paper, new brake architecture concept is proposed in order to respond to such a situation. First, physical interfaces between brake system like caliper, disc and other counter-parts are established for modular assembly. Second, we analyze effective factors of brake system for electric vehicles which need to reflect vehicle specifications such as total vehicle weight. Here, we consider ideal brake force by critical deceleration. Third, we simulate accumulated regenerative brake energy for two main driving modes to confirm to effectiveness for a variety of Electric Vehicle. Finally, we hope that it contributes to implement brake architecture for the development of Electric Vehicle platform through such a study.

• Tribology and Lubricants
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• v.17 no.5
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• pp.391-398
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• 2001

Two dimensional slow viscous flow around two counter-rotating equal cylinders is investigated based on Stokes'approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns around the cylinders are shown and the pressure distribution in the flow field is determined. By integrating the stress distributions on the cylinder, the force and the moment exerted on the cylinder are calculated. The flow rate through the gap between the two cylinders is also determined as the distance between two cylinders varies. Special attention is directed to the case of very small distance between two cylinders concerned with the lubrication theory and the minimum pressure is calculated to explain a possible cavitation.