• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.53-54
• /
• 2011

• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.5
• /
• pp.90-99
• /
• 1995

A numerical method is proposed to synthesize automotive cam profiles. An arbitrary acceleration profile for the cam follower motion is divided into several segments, each of them is described by a Hermite curve. A cam profile is defined by control point locations and control variables assigned to each segment. Closed form equations are derived for velocity and displacement constraints which should be satisfied for the curve to be a cam profile. Because the method is flexible and provide arbitrary local controllability, any types of cam acceleration profile can be reproduced by the method. The method is expecially useful for the design of roller type OHC valve trains which need precise local control in the cam profile design to avoid under-cutting problems.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.27 no.4
• /
• pp.365-371
• /
• 2005

In esthetic treatment of bimaxillary protrusion, it is important to move backward the anterior teeth segment. For the backward movement of the anterior teeth segment, orthodontic force and segmental osteotomy have been applied on the clinical treatment until recently. These methods caused long treatment time, anchorage loss, the possibility of root resorption and the complication followed by segmental osteotomy. Therefore, corticotomy has become a major concern lately. This research has been conducted to study the efficiency of corticotomy in the treatment of bimaxillary protrusion comparing the profile change, canine retraction velocity and space closing time. The research compared and analyzed space closing time, canine retraction velocity and profile change in two groups of patients. Both groups were formed out of patients over 18 years old who visited the department of dentistry in Hanyang University for treatments. The experimental group who was treated by corticotomy and Skeletal Anchorage System(SAS). The control group who received orthodontic treatment using SAS. The following results are produced after analyzing both groups. The significant statistic difference in space closing time has been observed in the experimental group as compared with the control group(p<0.05). In the experimental group, the significant statistic increase in canine retraction velocity was also observed(p<0.05). There was no significant difference in profile change between the control group and the experimental group(p<0.05). As a result, orthodontic treatment using corticotomy has a reasonable efficiency in space closing time as compared with the existing orthodontic treatment. Therefore, it is concluded that corticotomy with orthodontic treatment can be reasonably applied to dentofacial abnormality.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.4
• /
• pp.71-81
• /
• 2005

Surface wave techniques were initially based on 2-D plane waves and were later improved to the techniques based the 3-D based cylindrical waves. However, body-wave interference, near-field effect and limited technology in surface wave measurements restricted the use of 3-D cylindrical waves to the 1-D evaluation of subgrade stiffness. In this study, by the numerical simulation of SASW measurements, the dispersion properties of surface waves including vertical, horizontal Rayleigh waves and Love waves were thoroughly investigated in the 3-D domain, and a new filter criteria to minimize the near-field effect was established, which led to CAP (common-array-profiling)-SASW technique. The CAP-SASW technique enabled the evaluation of subgrade stiffness fur a specific subgrade segment, not for a whole section of measurement array. Therefore, a contour plot of subgrade stiffness with a ground-truth quality can be obtained by the CAP-SASW technique. The procedure proposed in this study was verified by comparing the shear-wave velocity profiles with the shear-wave velocity profiles of downhole testing at two geotechnical sites.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.8 no.4
• /
• pp.325-334
• /
• 2006

Understanding the airflow characteristics within the canopy structure installed between closely adjacent tunnels either for light adaptation or for protection from snow hazards is required for the normal ventilation as well as safety system design. Grade, horizontal alignment, cross-sectional area and shape are known to substantially influence the fire smoke behavior and their influences raise great concern for the safety design. This paper aims at studying the effects of tunnel geometrical characteristics and canopy installation on the ventilation and fire propagation through CFD analysis. In the case of 145m long canopy, 50% opening ratio is preferred with respect to the airflow pattern and ventilation efficiency. When a 20MW fire occurs in a 1.8km-long tunnel and four 1250mm reversible jet fans are instantly turned on, smoke concentration at 40m downstream of the fire decrease 13% for the upgrade tunnel with 2% gradient and increases 20% for -2% gradient, compared to the standard horizontal tunnel. Backlayering is observed within 45m-long segment toward the entrance in 2% down-graded tunnel. In a rectangular tunnel, there is no significant difference of smoke concentration as well as velocity profile from the standard crown tunnel. Three-laned tunnel shows lower level of both profiles and backlayering is detected up to 50m upstream of the fire, while the risky situation rapidly disappears thereafter.