• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.65-76
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• 2015

Objective : The purpose of this study was to analyse the differences in core stability and muscle balance of the pilates Teaser motion according to the surfaces and skills. Methods : There were 10 subjects in this study with 5 being skilled and 5 that were not skilled. The independent variables were surfaces (high elastic & aluminum) and skills (skilled & unskilled). Dependent variables were core stability and muscle balance. Core stability was measured by Force Platform (9872, Switzerland), 3D Imagery (IBS-2000, EXYMA) was used to understand the muscle balance. In order to do the Teaser movement subjects had to lay flat on their back and then lean forward as much as possible and hold the position for 10 seconds. Afterwards, they would lay back down again. A camera (MHS-PM5K, SONY) was used to make 4 phases (take off, recoil forward, holding, recoil backward) during the teaser exercise to analyze movement. In this study quantitative and qualitative analysis was used. For the statistical analysis, 2X2 ANOVA was used to analyze the differences in movement time, X,Y,Z maximum force, center of pressure and angles according to different phases. 2X3 ANOVA was used to analyze the differences in muscle balance via SPSS 18.0. Results : Soft. Elastic mat had a longer holding time, lower Fx/ Fy/ Fz, shorter Fx trajectory, larger angle and shorter gaps in muscle balance than a hard surface in skilled subjects. This was because the mat can help to recruit and then sustain core fine muscles during holding time in the Teaser movement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.323-336
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• 2003

Recently, the development of tunnel reinforcement method has been required relating to the shallow tunnelling in soft ground. In this study, the improvement method on tunnel stability is proposed by evaluating the efficiency of face reinforcement which enables to control extrusion of advance core, however, it is often neglected in urban tunnelling under the poor ground conditions. Systematic pre-confinement ahead of the face improves the tunnel stability, subsequently, displacement of the crown and surface settlement can be restrained by proper method. 3-dimensional numerical analysis including horizontal reinforcement modelling on a face is applied to estimate the behaviour of a tunnel in relation to the ground and reinforcement conditions. Consequently, extrusion at the face decreases significantly after using the horizontal reinforcement and the effect of reinforcement is much increased in case of applying the supplemental reinforcement ahead of the face together. Especially, confinement effect around the tunnel and the core is proved by means of the core reinforcement in poor ground conditions.

• Journal of the Korean GEO-environmental Society
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• v.2 no.4
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• pp.5-14
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• 2001

The NDT(Non-Destructive Testing) technique, detecting defects without damaging foundations, has, lately, been a matter of concern. In this study, the applicability of the borehole methods(CSL, CT, PS) and the surface reflection methods(SE, IR) to the evaluation of integrity of drilled shaft was investigated through field test. Ten drilled shafts, 0.4 m in diameter and 7.0 m long each, were constructed, one shaft with no defect and nine shafts intentionally with the combination of the common defects such as soft bottom, necking, bulging, cave-in, and/or weak concrete. Analysing each NDP test result on the constructed drilled shafts, an optimum combination of the NDP methods as well as the applicability of each NDP method to detecting defects of drilled shaft have been investigated.

• Journal of Korean Foot and Ankle Society
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• v.8 no.1
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• pp.86-91
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• 2004

Purpose: To evaluate the methods and results of the surgical treatment in the trimalleolar fracture of the ankle. Materials and Methods: We analysed the results of the ankle trimalleolar fracture which were treated with open reduction and internal fixation from January 1999 till September 2003. There were 45 patients who had at least six months follow up, 16 men, and 29 women. We have analysed the mechanism of injury, methods of operation and postoperative complications. Results: The results were assessed on ankle AP, lateral and mortise X-rays and retrospective chart review. There were 30 supination-external rotation, 13 pronation-external rotation, 2 pronation-abduction in the mechanism of injury by Lauge-Hansen classification. Cases of the posterior malleolar fracture which involved more than 25% of the weight bearing surface were 7 (15.6%). Medial malleolar mono-fixation was done in 5 cases, fibular mono-fixation in 2 cases, bimalleolar fixation in 32 cases, trimalleolar fixation in 6 cases. 38 cases (84.4%) were good or excellent in clincal assessment and 39 cases (86.7%) were good or excellent in radiological assessment according to the criteria of the Meyer. There was no difference of results among the surgical treatment methods. Conclusion: The results of our study indicate that the rigid fixation with early ankle motion and weight bearing is needed in ankle trimalleolar fracture. But minimal fixation is not bad in slight displaced fracture. Both anterior approach and posterior approach were useful methods to stabilization the posterior malleolar fracture. And pre-operative evaluation to detect the hidden soft tissue injuries and fracture mechanism is very important to avoid the failure.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.1
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• pp.23-33
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• 1994

Liquefaction characteristics of the reclaimed marine sand deposits is studied by means of the dynamic response analysis and the cyclic triaxial compression test. 1) From the result of the dynamic response analysis. it was found that the amplification of ground surface maximum acceleration varied with input earthquake motions and soil data, and earthquake coefficients were proposed to be applicable in evaluating liquefaction potential by simplified prediction methods. 2) For upper and soft sand deposits with small N-value, liquefaction strengths estimated by Seed and Idriss's simplified method were lower than those by the cyclic triaxial test while those by Iwasaki & Tatsuoka's or Vs-method were not lower. 3) Simplified methods were inclined to overestimate liquefaction potential in comparison with the dynamic response analysis and the cyclic triaxial compression test Allowable depths of liquefaction(safety factor 1) were estimated to be 7-14m for 0.1 -0.2g of input maximum acceleration.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.260-266
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• 2002

DLC films were deposited on Si wafer by RF plasma assisted CVD using CH4 gas. Tribological tests were conducted using rotating type ball on disk friction tester in dry air. Four kinds of mating balls were used. The mating balls were made with stainless steel but apply different annealing conditions to achieve different hardness conditions. Testing results in all load conditions showed that the harder the mating materials, the lower the friction coefficient among the three kind of martensite mating balls. In case of austenite balls, the friction coefficients were lower than fully annealed martensite ball. The high friction coefficient in soft martensite balls seems to be caused by the larger contact area between DLC film and ball. The wear tracks of DLC films and mating balls could have proven that effect. Measuring the wear track of both DLC films and mating balls have similar tendency comparing to the results of friction coefficients. Wear rate of austenite balls were also smaller than that of fully annealed martensite ball. The results of effect of applying load showed, the friction coefficients were become decrease when the applying loads exceed critical load conditions. The wear track of mating balls showed that some material transfer occurs from DLC film to mating ball during the high friction process. Raman spectra analysis showed that transferred material was a kind of graphite and contact surface of DLC film seems to undergo phase transition from carbon to graphite during the high friction process.

• Transactions of the KSME C: Technology and Education
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• v.2 no.2
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• pp.73-80
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• 2014

Drug delivery in human upper airway was studied by the numerical simulation of oral airflow. We created an anatomically accurate upper airway model from CT scan data by using a medical image processing software (Mimics). The upper airway was composed of oral cavity, pharynx, larynx, trachea, and second generations of branches. Thin sliced CT data and meticulous refinement of model surface under the ENT doctor's advice provided more sophisticated nasal cavity models. With this 3D upper airway models, numerical simulation was conducted by ANSYS/FLUENT. The steady inspiratory airflows in that model was solved numerically for the case of flow rate of 250 mL/s with drug-laden spray(Q= 20, 40, 60 mL/s). Optimal parameters for mechanical drug aerosol targeting of predetermined areas was to be computed, for a given representative upper airways. From numerical flow visualization results, as flow-rate of drug-laden spray increases, the drag spray residue in oral cavity was increased and the distribution of drug spray in trachea and branches became more homogeneous.

• Archives of Reconstructive Microsurgery
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• v.8 no.1
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• pp.56-63
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• 1999

We report two patients whose acute soft tissue and tendon defects in the hand were treated by the dorsalis pedis tendocutaneous delayed arterialized venous flap between 1994 and 1997. The surviving surface area was 100% in both patients. The flap size was $10{\times}10cm\;and\;6{\times}6cm$. At two weeks postoperatively, active flextion and passive extension commenced, and progressive resistance exercises were performed for an additional 5 weeks. Flaps showed a similar color match and skin texture compared with the normal skin of the hand. Advantages of the tendocutaneous delayed arterialized venous flap are developing a larger flap than can be obtained with pure venous flap or arterialized venous flap, increasing survival rate of the arterialized venous flap which permits using a composite flap, preservation of main artery of the donor site, taking thin non-bulky tissue and easy elevation without deep dissection. The disadvantages are the requirement of a two stage operation, donor site scarring and weak extension of the toe.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.369-372
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• 2002

In this research, a vision system for detecting tool breakage which is hardly detected by such indirect in-process measurement method as acoustic emission, cutting torque and motor current was developed and embedded into a PC-NC system. The vision system consists of CMOS image sensors, a slit beam laser generator and an image grabber board. Slit beam laser was emitted on the tool surface to separate the tool geometry well from the various obstacles surrounding the tool. An image of tool is captured through two steps of signal processing, that is, median filtering and thresholding and then the tool is estimated normal or broken by use of change of the centroid of the captured image. An air curtain made by the jetting high-pressure air in front of the lens was devised to prevent the vision system from being contaminated by scattered coolant, cutting chips in cutting process. To embed the vision system to a Siemens PC-NC controller 840D NC, an HMI(Human Machine Interface) program was developed under the Windows 95 operating system of MMC103. The developed HMI is placed in a sub window of the main window of 840D and this program can be activated or deactivated either by a soft key on the operating panel or M codes in the NC part program. As the tool breakage is detected, the HMI program emit a command for automatic tool change or send alarm to the NC kernel. Evaluation test in a high speed tapping center showed the developed system was successful in detection of the small-radius tool breakage.

• Tribology and Lubricants
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• v.31 no.1
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• pp.6-12
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• 2015

This paper investigates the stick-slip characteristic of magnetorheological elastomer (MRE) between an aluminum plate and the surface of the MRE. MRE is a smart material and it can change its mechanical behavior with the interior iron particles under the influence of an applied magnetic field. Stick-slip is a movement of two surfaces relative to each other that proceeds as a series of jerks caused by alternate sticking from friction and sliding when the friction is overcome by an applied force. This special tribology phenomenon can lead to unnecessary wear, vibration, noise, and reduced service life of work piece. The stick-slip phenomenon is avoided as far as possible in the field of mechanical engineering. As this phenomenon is a function of material property, applied load, and velocity, it can be controlled using the characteristics of MRE. MRE as a soft smart material, whose mechanical properties such as modulus and stiffness can be changed via the strength of an external magnetic field, has been widely studied as a prospective replacement for general rubber in the mechanical domain. In this study, friction force is measured under different loads, speed, and magnetic field strength. From the test results, it is confirmed that the stick-slip phenomenon can be minimized under optimum conditions and can be applied in various mechanical components.