• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.456-466
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• 2017

This work investigated the particle morphology change to difference in milling media in a metal based composite fabrication process using a stirred ball mill with ball behavior of DEM simulation. A simulation of the three dimensional motion of grinding media in the stirred ball mill for the research of grinding mechanism to clarify the force, kinetic energy, and medium velocity of grinding media were calculated. In addition, the rotational speed of the stirred ball mill was changed to the experimental conditions for the composite fabrication, and change of the input energy was also calculated while changing the ball material, the flow velocity, and the friction coefficient under the same conditions. As the rotating speed of the stirred ball mill increased, the impact energy between the grinding media to media, media to wall, and media and the stirrer increased quantitatively. Also, we could clearly analyze the change of the particle morphology under the same experimental conditions, and it was found that the ball behavior greatly influences in the particle morphology changes.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.1-7
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• 2016

Mastication is the process to help digestion by chewing or grinding food. Masticatory system consists of maxilla, mandible, temporomandibular joints, ligaments, dentitions, and musculatures. Assessing the bite force can be one of the methods to estimate the masticatory system. Bite force is influenced by facial morphology, age, sex, periodontal status, temporomandibular joint disorder and dental condition, and so forth. In general, higher maximum bite force is seen in those who have a square-shaped face and in male rather than female. In addition, bite force tends to be increased by age 20, maintained constantly until age 40 - 50, and then decreased. Periodontal disease is known as a causative factor for decreased bite force while temporomandibular disorder (TMD) remains controversial as to whether it affects the force. The status of teeth is considered as an important factor to determine the maximum bite force.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.339-345
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• 2002

연삭 가공시 발생하는 채터는 정밀도 및 품질을 저하시킨다. 본 논문에서는 연삭가공시 작업시간에 따른 연삭 법선력 및 AE 신호의 거동을 관찰함으로써 (1) 연삭법선력의 수학적 모델은 그 진폭이 지수적으로 변하는 형태이고, (2) 그 지수가 음(minus)이 될 때가 체터 발생시점이며 (3) 이를 토대로 이론적으로 (2)를 규명할 수 있는 방법을 고찰하였다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.714-719
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• 2000

This paper describes a transfer matrix approach to analyze the dynamics of a high sped flexible rotor system supported at 2 positions by five ceramic bearings. The rotor system is modelled as lumped parameters in which many factors are considered not only lumped inertia or mass, bending moment, shear force but also gyroscopic effect and unbalance. The equation of motion is derived in the transfer matrix form, from which the eigenvalues equation is also derived. The transfer natural frequencies and modes. The eigenvalues, eigenmodes, campbell diagram, whirling critical speed, whirling modes, and the response of unbalance are calculated and discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.260-260
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• 2004

연삭 가공은 대직경 반도체 웨이퍼의 경면 가공, 산업용 정밀 부품, 광학 분야의 고정밀급 렌즈 등 여러 산업 분야의 각종 정밀 부품의 마무리 공정에 적총되어 제품의 질을 좌우하는 필수적인 공정이라 할 수 있다. 이러한 연삭 가공은 높은 치수 정밀도와 양호한 표면 거칠기 및 제품의 형상을 동시에 만족시킬 수 있는 가공 기술로서 , 대직경 웨이퍼 생산에 있어서, 고정밀ㆍ고품위의 웨이퍼를 양산하는데 적합한 기술로 인식되고 있다.(중략)

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.97-103
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• 1994

The influence of ground petroleum coke, preheat-treated at temperatures ranged of 150~35$0^{\circ}C$, was studied. It has been found that the coke powder preheat-treated at the temperature of 175$^{\circ}C$ has been spherical-shaped in grinding and have showed the highest strength and density in sintering. The coke powder was also the best for the binding force and the (H/C) values showed 0.45 at the above temperature.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.47 no.2
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• pp.149-150
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• 2021

Bruxism is defined as a parafunctional activity during sleep or while awake that includes locking and grinding of teeth and clenching. It generates excessive occlusal force that may lead to implant failure. Therefore, diagnosis of bruxism and providing specific protocols such as occlusal splint and/or injection of botulinum toxin before implant installation are important to prevent increases the risk of implant failure in bruxism patients.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.243-249
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• 2001

This paper has been presented the hydrodynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from existed investigations in the side of pressure distribution of air film because of the high speed of journal and the wedge effects by the eccentricity. These optimal chooses of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high speed spindle. In this paper, the pressure behavior in theory of air film according to the eccentricity of journal and the source positions analyzed. The theoretical analysis have been identified by experiments. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high speed milling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1768-1771
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• 2003

Hard turning replaces grinding for finishing process with expectations of higher productivity and demanded surface quality. Especially for the surface roughness as surface quality demanded in finishing process of hard turning, know-how of machining characteristics of hardened materials by cutting force analysis should be accumulated in company with achievement of precision of elements and high stiffness design technology in hard turning. Considering chip formation mechanism of hardened materials, adequate cutting conditions are selected for machining experiments and cutting forces are measured according to cutting conditions. Increase of cutting forces especially thrust force and increase of dynamic instability could occur in hard turning. Analysis of dynamic characteristics of the cutting forces is executed to investigate relation between dynamic instability and surface roughness in hard turning. Investigation on effects of relative motion of machining system generated by vibration due to dynamic instability shows that ultimate surface roughness could be predicted considering relative motion of machining system with geometrical surface roughness.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.2
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• pp.181-189
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• 2000

This paper presents the optimal redundant actuation of parallel manipulators for complicated robotic applications such as cutting grinding drilling and digging that require a high degree of operational stiffness as well as the balance between force applicability and dexterity. First by taking into account the distribution(number and location) of active joints the statics and the operational stiffness of a redundant parallel manipulator are formulated and the effects of actuation redundancy are analyzed, Second for given task requirements including joint torque limit task force maximum allowable disturbance and maximum allowable deflection the task execution conditions of a redundant parallel manipulator are derived and the efficient testing formulas are provided. Third to achieve high operational stiffness while maintaining moderate dexterity the redundant actuation of a parallel manipulator is optimized which determines the optimal distribution of active joints and the optimal internal joint torque, Finally the simulation results for the optimal redundant actuation of a planar parallel manipulator are given.