• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.551-555
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• 2010

Electrowetting is a versatile tool to handle tiny droplets and forms a backbone of digital microfluidics. Numerical analysis is necessary to fully understand the dynamics of electrowetting, especially in designing electrowetting-based devices, such as liquid lenses and reflective displays. We developed a numerical method to analyze the general contact-line problems, incorporating dynamic contact angle models. The method is based on the conservative level set method to capture the interface of two fluids without loss of mass. We applied the method to the analysis of spreading process of a sessile droplet for step input voltages and oscillation of the droplet for alternating input voltages in electrowetting. The result was compared with experimental data. It is shown that contact line friction significantly affects the contact line motion and the oscillation amplitude. The pinning process of contact line was well represented by including the hysteresis effect in the contact angle models. In level set method, in the mean time, material properties are made to change smoothly across an interface of two materials with different properties by introducing an interpolation or smoothing scheme. So far, the weighted arithmetic mean (WAM) method has been exclusively adopted in level set method, without complete assessment for its validity. We viscosity, thermal conductivity, electrical conductivity, and permittivity, can be an alternative. I.e., the WHM gives more accurate results than the WAM method in certain circumstances. The interpolation scheme should be selected considering various characteristics including type of property, ratio of property of two fluids, geometry of interface, and so on.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.2
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• pp.160-178
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• 2023

Diagnosis and analysis of occlusal relationships are important factors in prosthetic treatment. A thorough occlusion analysis and evaluation should be performed before treatment to restore a stable interocclusal relationship. Analysis and evaluation are essential during the treatment process and at regular follow-ups. Recently, with the development of dental equipment and digital processing methods, new quantitative analysis methods that can record the patient's occlusal relationship have been introduced. Among them, the T-Scan Novus (Tekscan Inc., S. Boston, MA, USA) displays the strength of the initial contact point and the occlusal contact point of the teeth using a pressure sensor. With this, occlusal contact time of the teeth, anteroposterior and left-right balance of occlusal force can be compared. The Dental prescale II (GC Co., Tokyo, Japan) scans the occlusal contact point using a pressure-sensing film and analyzes the density of the contact point. It can measure the distribution and strength of the occlusal force of the teeth in the most natural occlusion state. Based on this, appropriate prosthetic treatment (four-unit fixed partial denture, removable partial denture, complete denture, and complete oral restoration cases) was performed according to the area and extent of the patient's tooth loss. The patient's occlusion at the first visit, treatment stage, right after treatment, and regular follow-up were compared and evaluated using a quantitative method for appropriate occlusion analysis using T-Scan Novus and Dental prescale II. This report enhances the understanding of occlusion analysis during prosthetic restoration. The results satisfied both the clinician and patients in terms of function and aesthetics.

• The Journal of the Korean dental association
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• v.50 no.1
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• pp.13-21
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• 2012

In an edentulous situation, the dentist must make several determinations when constructing artificial teeth. These include vertical and horizontal relationships of mandible with respect to the maxilla, occlusal form and position, vertical dimension, occlusal relationships during both centric closure and eccentric excursive movements. Artificial teeth are attached to a movable base resting on movable and displaceable living tissue subject to damage. They act as a unit; therefore, they must be arranged to function as a unit. Bilateral balanced occlusion is that stability of the denture is attained when bilateral contacts ex ist throughout all dynamic and static states of the denture during function. Lateral excursion in a balanced scheme implies simultaneous working side and nonworking side contact, while occlusal contacts are maintained on both anterior and posterior teeth as the mandible moves anteriorly into protrusion.

• Clinics in Shoulder and Elbow
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• v.9 no.2
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• pp.216-221
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• 2006

Avulsion of the triceps brachii is an uncommon injury. The usual mechanism of injury is fall onto an outstretched hand but can occur after direct contact injuries. Diagnosis is critical and dependent on history, physical examination, and radiological findings. Rupture of triceps brachii occurs most frequently at the tendo-osseous insertion and may be complete or partial, and could be associated with radial head fracture. Treatments include surgical repair of the complete rupture and immobilization of partial triceps rupture. We report 3 cases of triceps avulsion fractures treated by open surgical repair with literature reviews.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.9 no.1
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• pp.20-36
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• 2000

The movements of oral surrounding muscles, lips, and tongue play a very important role while masticating, swallowing, and speaking. In case of the edentulous patient wearing dentures as well, every movement of the tongue can be seen almost the same as that of the dentulous jaw. The crushed food during mastication is swallowed and sent to pharynx. At this course, the contact of the posterior portion of tongue with dentures affects the stabilization of denture. The retention and stability of the complete dentures are related with buccinator muscles of buccal parts, lips in front, and tongue of the lingual sides. Strack(1946) insisted that the arrangement of artificial teeth in the same place as that of the natural dentition is the best way to maintain the stability of denture. In this report, I would like to introduce the several advantages of a new impression method taken simultaneously, and its procedures and clinical cases.

• Coupled systems mechanics
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• v.1 no.2
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• pp.165-182
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• 2012

Macroscopic hot spots formed due to the large thermal gradients at the surface of the disc brake rotor, make the rotor to fail or wear out early. Thermo-elastic deformation results in contact concentration, leading to the non uniform distribution of temperature making the disc susceptible to hot spot formation. The formation of one hot spot event will predispose the system to future hot spotting at the same location. This leads to the complete thermo-elastic instability in the disc brakes; multitude parameters are responsible for the thermo elastic instability. The predominant factor is the sliding velocity and above a certain sliding velocity the instability of the brake system occurs and hot spots is formed in the surface of the disc brake. Commercial finite element package ABAQUS(R) is used to find the temperature distribution and the result is validated using Rowson's analytical model. A coupled analysis methodology is evolved for the automotive disc brake from the transient thermo-elastic contact analysis. Temperature variation is studied under different sliding speeds within the operation range.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2717-2720
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• 2003

A mathematical framework for deriving acceleration bounds from given joint torque limits of two cooperating robots are described in this paper. Especially when the torque limits are given in 2-norm, the resultant geometrical configuration is ellipsoid(the ellipsoid is often called manipulability ellipsoid in many works). At first, the mathematical derivation starts from the dynamics of both object and robots as well as the kinematics of the robots, and is finally arranged in a form of equation relating joint torques to object acceleration through a complete constraint contact(or “very-soft contact”). To show the usefulness of the proposed method, two examples are included, and especially the case where friction effects the ellipsoid shape is also considered In the example.

• Transactions of Materials Processing
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• v.11 no.1
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• pp.75-83
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• 2002

Recently, the hydroforming process is widely applied to the automotive industry and rapidly spreaded to other industries. In this paper, An implicit finite element formulation for simulating axisymmetric tube hydroforming processes is performed. In order to describe normal anisotropy of the tube, Hill's non-quadratic yield function is employed. The frictional contact between die and tube and the frictionless contact between tube and fluid are considered using the mesh-normal vectors computed from the finite element mesh of the tube. The complete set of the governing relations comprising equilibrium and interfacial equations is linearized for Newton-Raphson procedure. In order to verify the validity of the developed finite element formulation, the axisymmetric tube bulge test is simulated and the simulation results are compared with experimental measurements. In a simulation of stepped circular tube hydroforming processes, an optimal hydraulic pressure curve is pursued by considering simultaneously internal pressures and axial forces.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.397-401
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• 1995

ESPI(Electronic Speckle Pattern Interfermetry) is an optical technique to measure surface deforamtion of engineering components and materials in industrial ares. This optical method is capable of providing full-field results with high spatial resolution, high speed and is the non-contact technique. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The contouring method by modified dual-beam speckle pattern interferometry is proposed. We introduce a shift of the illumination beams through optical fiber in order to obtain the contour fringe patterns. The speckle pattern correlation technique is suitable for providing measurement range from millimeters to several centimeters. The complete geometric analysis of the contoretical and experimental results are obtained.