• The korean journal of orthodontics
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• v.39 no.4
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• pp.257-272
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• 2009

This case report describes the treatment of an adult patient with a Class I canine and molar relationship but a convex profile with a retrognathic mandible and marked lip protrusion, as well as an excessive lower anterior facial height and reduced transverse width on both arches due to a nasal airway obstruction. The constricted arches were expanded by surgically-assisted rapid palatal expansion and the application of a Schwarz appliance to the maxilla and mandible. Acceptable facial balance was obtained using contemporary directional force technology with microimplant anchorage (MIA), which provided horizontal and vertical anchorage in the maxillary and mandibular posterior teeth, as well as intrusion and torque control in the maxillary anterior teeth, resulting in a favorable counterclockwise mandibular response. The total treatment period was 29 months and the results were acceptable for 13 months after debonding.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.159-164
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• 1988

The directions of the principal strain increment, stress, and stress increment during rotation of the principal stress axes at any stress level was studied for $K_0$-consolidated clay using torsion shear apparatus with individual control of the vertical stress, the confining pressure, and the shear stress on hollow cylinder specimens under undrained and drained condition. The torsion shear tests were performed according to predetermined stress-paths, which were chosen to cover over the full range of rotation of principal stress axes. The test results indicated that the strain increment vectors at failure coincided with the stress vectors. That is, the direction of strain increment coincided with the direction of stress increment at small stress levels and with the direction of stress at higher stress levels, which indicated that the behavior of clay was transfered from elastic to plastic as the stress level was increased. The applicability of the elastoplastic theory for modeling of the behavior of clay during rotation of the principal stress axes was given.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.107-116
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• 2012

In this study, the trucks(2.9-liter) have been developed to use DME as fuel, and performance test of the vehicle's DME engine, power, emissions, fuel economy and vehicle aspects was conducted. For experiments, the fuel system(common-rail injectors and high-pressure pump included) and the engine control logic was developed, and ECU mapping was performed. As a result, the rail pressure from 40MPa to approximately 65% increase compared to the base injector has been confirmed that. Also, the pump discharge flow is 15.5 kg/h when the fuel rail pressure is 400rpm(40MPa), and the pump discharge flow is 92.1 kg/h when the fuel rail pressure is 2,000rpm(40MPa). The maximum value of full-load torque capability is 25.5 kgfm(based on 2,000 rpm), and more than 90% compared to the level of the diesel engine were obtained. The DME vehicle was developed in this study, 120 km/h can drive to the stable, and calculated in accordance with the carbon-balance method of fuel consumptions is 5.7 km/L.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.59-67
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• 2018

In this paper, the test facility for coaxial propellers at low Reynolds developed and validated by measured data. The test equipment was designed to measure the hovering performance of propellers according to distances between the upper/lower propellers. Thrust, torque, rotational speed, vibration, and amperage of upper and lower propellers can be measured separately. The data acquisition system was built to collect signals of sensors, and LabVIEW software was used to control the motor and collect the signal. The hover performance tests of single propellers were preceded for the facility validation, and then the performance values of coaxial propellers were measured according to distances and diameter differences between the upper/lower propellers. The results showed that the high efficiency is achieved at 20%~30% distance between the upper propeller and lower one. The configuration that the upper propeller has shorter diameter than the lower one has the highest efficiency than other configuration.

• Korean Journal of Applied Biomechanics
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• v.22 no.2
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• pp.201-208
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• 2012

The purpose of this study was to investigate the effect of leg extension exercises performed on outdoor resistance exercise machines on knee extension muscle strength and quadriceps muscle group cross sectional area (CSA) in elderly women. Two groups were recruited for this study, including an exercise group (EG: n=13, $71.38{\pm}2.79$ yrs) and a control group (CG: n=5, $73.4{\pm}5.94$), In all subjects, maximum isometric and isokinetic muscle strength of knee flexion and extension were measured using an isokinetic dynamometer (Cybex(R) Humac Norm Testing & Rehabilitation System, USA). Quadriceps muscle group CSA were measured using MRI (Philps, Intera 1.5 T, NE Netherlands). The results of this study showed that post-intervention isometric knee extension peak torque value were higher than pre-intervention measures in the EG. However, the EG did not show improvement in quadriceps muscle group CSA, Also, no differences in the shift of optimal knee joint angle were observed between pre and post-intervention exercise. Outdoor leg extension exercise showed small increases in muscle strength in comparison to other resistance training exercises. The results of this study suggest that because outdoor leg extension exercise machines lack a progressive loading mechanism, significant increases in muscle strength may not be obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.603-606
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• 2006

We present a study on the development of a practical and quantitative technique for the assessment of the structural health condition with using piezoceramic(PZT) sensors. The electro-impedance-based technique with the PZT patches is very sensitive for evaluation of the incipient and small damage in a high frequency range, and however the commonly traditional modal analysis method is effective only for considerably larger damages in low frequency range. The paper presents the technique in detecting and characterizing real-time damage on the specimen that is an aluminum plate fastened with bolts and nuts by different torques and as well a plate with a crack. By using the special arrangement of the PZT sensors, the required longitudinal wave is generated through the specimen. A large number of experiments are conducted and the different conditions of the specimens, i.e. the location and extent of loosening bolts, and the plate with a crack are simulated. respectively. Since fixing and loosening the loosened bolt is controlled by a torque wrench, we can control exactly the experiment of the different torques. Compared with the simulated healthy condition, we can find whether or not there is a damage in the specimen with using an impedance analyzer with the PZT sensors. Several indices are discussed and used for assessing the different simulated damages. As for the location of bolt loosening, the RMSD is found to be the most appropriate index for numerical assessment and as well the RMSD shows strongly linear relationship for assessing the extent of the bolt loosening, and the frequency peak shift ${\Delta}F$ is used to assess the cracked plate. The possibility of repeatability of the pristine condition signatures is also presented and the appropriate frequency range and interval are uniquely selected through large numbers of experiments.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.98-99
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• 2016

The aim of study is to develop a dual driven ship berthing/deberthing system with $360^{\circ}$ steerability. A large ship used bow thruster, side thruster and pod propulsor etc. when approaching to a pier. But as marine leisure boats become large-scaled, the number of accidents is recently increasing what caused a ship to crash into a ship and a ship to crash into mooring facilities during berthing/deberthing on a marina. To solve the problem, the control responsiveness of a joystick connected with two motors and a propeller was checked and torque was increased by the electromagnetic design of magnetic gear. A sea trial test was carried out to investigate a performance of the developed system in the real sea.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.97-103
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• 1999

The power curve during rubber mixing presents useful information for the understanding of rubber mixing process, because the power curve is determined the mixing state of rubber at the point. The time to the second peak on the power curve is known as carbon black incorporation time, BIT. This study gets the quantity relationship of BIT and viscosity of natural rubber, so by determining the mixing time of the compound on the ground of viscosity of the raw rubber. The mixing with natural rubber and carbon black is examined for various grade natural rubbers, encompassing a wide range of Mooney viscosity. Alter smoothing the mixing power curve using a polynomial, the carbon black incorporation time, BIT, was determined time to second power peak on the curve, The BIT's versus specific values on Mooney viscometer test curve show a linear relation, Especially, the peak of initial maximum torque on Mooney viscometer curve, PMT, is most relevant property relating to the BIT. PMT is useful index for determined optimum mixing time, To apply this results at the mixing, we effectively control the natural rubber mixing but can also know the grading of natural rubber upon processability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.981-988
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• 2016

Dynamometer is a device for testing the performance of the brake and it is composed of a test zone, the mechanical inertia zone, the electric motor and the control zone. Hybrid dynamometer is a way to compensate for the loss of mechanical inertia in accordance with the brake operation by using an electric motor to reduce the size of the mechanical inertia with the advantage that can be tested in the relatively small size of the mechanical inertia and low cost. In this paper, design the proper size of hybrid dynamometer in the laboratory level with the space constraints, analysed the effect of critical parameter on the braking performance of hybrid dynamometer such as changing the friction coefficient. With this study, could get the results of guideline to judge the poor friction material by measuring the torque of the electric motor to compensate the energy loss due to a reduced mechanical inertia.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.6
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• pp.411-420
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• 2000

The energy storage systems are being widely researched for the high quality of the electric power. The FES(flywheel energy system) is especially, on the center of the research because it does not make any pollution and its life is long. The FES converts the electrical energy into the mechanical kinetic energy of the flywheel and reconverts the mechanical energy into the electrical energy. In order to store as much energy as possible, the flywheel is supposed to be rotated with very high speed. The motor/generator of the FES should be high efficient at high speed, and generate constant torque with respect to the rotation. In this paper, a motor/generator employing a Halbach array of permanent magnets is designed and constructed to meet the requirements, and its characteristics are examined. The magnetic field is analysed by using the magnetic surface charge method. The armature winding is designed for the harmonic components to be minimized by using the FFT. The sinusoidal current for the motor driving are generated by the hysteresis current controller. A sample superconducting flywheel energy storage system is constructed with a duralumin flywheel which has a maximum rotating speed of 40,000[rpm] and a stored energy of 240[Wh] and its validity is examined through the experiment.