• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.49 no.6
• /
• pp.365-368
• /
• 2023

The mentum plays an important role in the aesthetics of the face, and genioplasty is performed to improve an unbalance of the mentum. Among the various surgical approaches, setback genioplasty is used to create an aesthetic jaw-end appearance by moving the mentum backward when it protrudes more than normal. However, conventional setback genioplasty may be aesthetically disadvantageous because the profile of the mentum could become flat. This case study attempted to overcome the limitations of conventional setback genioplasty by rotating the position of the menton and pogonion. We devised a new method for setback genioplasty by rotating the segment anteroinferiorly. Using virtual surgery, we were able to specify the range of surgery more accurately and easily, and the surgery time was reduced. This case report showed the difference in chin soft tissue responses between conventional setback genioplasty and setback genioplasty with rotation.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.1
• /
• pp.24-31
• /
• 2004

Recently, as the marine compressor power is increased, vibration problems on the marine vessel with V/W type reciprocating compressor have been occurred. A research on the balancing of marine V/W type reciprocating compressor has hardly been reported though a number of researches on the balancing of rotating machinery have been conducted. As a V/W type compressor has high capacity with long stroke, compact size and high center of gravity, It is easy to have a vibration problem by a little bit unbalanced force and moment. In this study, calculation methods for balance weight of the V/W type reciprocating compressors, which have different piston weight and asymmetry structure, are formulated. And their reliability were verified by comparing calculated balance weight with the experimental results of the real marine V/W type reciprocating compressors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.843-847
• /
• 2007

The unbalanced mass of a high precision rotor deteriorates mechanical performance of the rotor. The geometrical center of a rotor generally corresponds to the rotational axis of the rotor. However, this alignment carried out with a stationary rotor does not guarantee the dynamic rotor balance. There have been a number of schemes for the correction of the imbalance published for decades especially in the hard drive industry where the issues are directly affecting manufacturing costs and product performances. Realizing the significance of the problem, the present work tries to refine one of the methods that works by applying external impact during a rotor spins. A systematic way to apply the external impact to a rotating rotor has been introduced to minimize imbalance correction process time.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1998.04a
• /
• pp.51-56
• /
• 1998

This paper presents modal contribution method to reduce vehicle vibration. Normal mode analysis is performed to obtain modal vector matrix. The proposed method uses this modal vector matrix to evaluate forced response of an active mode to the applied engine forces and the rotating force due to wheel unbalance mass. Comparing the responses, of the specific active mode with one another, it can be easily done to determine most contributed mode in the interesting frequency band. Then we can find dominant bushes by the strain energy distribution of the mode. Vibration response is decrease with modification of those bushes.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.3
• /
• pp.254-259
• /
• 2009

In this paper it was attempted to treat the hydrodynamic journal bearing as a time-based nonlinear reaction source in each step of rotor rotation in order to observe the bearing effect more realistically and accurately in stead of the conventional method of simple linearized stiffness and damping. Lubrication analysis based on finite element method is employed to calculate the hydrodynamic reaction of bearing and Newmark's method was used to calculate the rotor dynamics in the time domain. Simulation for an industrial electrical motor showed remarkable results with differences compared to those by the conventional method in the dynamic behavior of the rotor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.282-287
• /
• 2004

Noise and vibrations in the pipe systems may be arisen from pumps. compressors, etc. The source mechanism is classified with the mechanical and hydraulic. Mechanical vibrations may be excited by the unbalance in rotating machinery. Hydraulic source may be generated in the turbulent flow. The vibro-acoustic behaviour of flexible, fluid-filled pipe system is a very complex and determined by two parameters: the frequency and the mass ratio of fluid and pipe wall. As the frequency increases, the mode number in the pipe increases. The mass ratio is close to one, the structure and the fluid are strongly coupled. In ease the diameter is very small to the length of pipe, the behaviour of pipe is same as a beam. The finite element formulation when the fluid and the structure are coupled is derived by using beam element. The Numerical results are compared with the package (Sysnoise) which is using the shell element.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.04a
• /
• pp.274-278
• /
• 2012

Vertical pumps are structurally weak in terms of vibration because of installed heavy motor on top of the pumps in form of cantilever. So high vibration on top of the pumps can occur with low vibration in the bottom. These vibration problems experienced very frequently. Majority of studies have been related to the unbalance of rotating parts or structural resonance. In this paper, we introduce an unusual case, vibration variation caused by VPF(Vane Passing Frequency) according to water level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.190-195
• /
• 2002

The intermittent high vibration has been occurred one or two times a day for a 500MW large steam turbine during 5 months. This abnormal vibration was caused by the rubbing between the rotor and the carbide accumulated on the seal tooth of oil deflector. It was found that the accumulated carbide was insulation material installed on the HIP casing from the examination of the chemical composition. Also, this paper presents the mechanism of the intermittent high vibration and the proper method to eliminate this vibration problem. This result would be good practice to find the solution of similar high vibration in the steam turbines for power plant as well as industrial rotating machineries.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.902-909
• /
• 2006

In this study, three-dimensional rotordynamic analyses have been conducted using equivalent beam, hybrid and fun three-dimensional models. The Present computational method is based on the general finite element method with rotating gyroscopic effects of a rotor system. General purpose commercial finite element code, SAMCEF which includes practical rotordynamics module with various types of rotor analysis methods and bearing elements is applied. For the purpose of numerical verification, comparison study for a benchmark rotor model with support bearings is performed first. Detailed finite element models based on three different modeling concepts are constructed and then computational analyses are conducted for the realistic and complex three-dimensional rotor system. The results for rotor stability and mass unbalance response are presented and compared with the experimental vibration test conducted in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.520-525
• /
• 2003

The determination of unknown parameters in rotating machinery is a difficult task and optimization techniques represent an alternative technique for parameter identification. The Simulated Annealing(SA) and Genetic Algorithm(GA) are powerful global optimization algorithm. This paper proposes new hybrid algorithm which combined GA with SA and local search algorithm for the purpose of parameter identification. Numerical examples are also presented to verify the efficiency of proposed algorithm. And, this paper presents the general methodology based on hybrid algorithm to identify unknown bearing parameters of flexible rotors using measured unbalance responses. Numerical examples are used to ilustrate the methodology used, which is then validated experimentally.