• 한국공작기계학회논문집
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• 제11권3호
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• pp.80-85
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• 2002

The free curve gear is a non-circular gear without any relating center, which can perform free curve motion for complicated mechanisms, and minimize the work area. In this study, an algorithms for tooth profile generation of free curve involute gear is developed. The algorithm uses the involute gear creating principle in which a gear can be generated by rolling with another standard involute one. Cycloid me and third polynomial curve gears were designed and verified by computer graphics. These gears are manufactured in the wire-cut EDM and examined in engagement with a standard spur gear. The results showed that the proposed algorithm is successful to design and to manufacture the free curve gear with concave and convex profiles.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.31-35
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• 1996

The cross section of the circular rod type workpiece to be cut in the band saw machine is variable at every moment in the sawing process. When the cutting feed rate is fixed to the constant speed, the cutting edges of the band saw teeth are also variabl eat any moment, so this causes the wear of the land saw teeth and the deterioration of the quality in the surface roughness. In this study, to work out this kind of problem basically, the mean cutting force of a tooth in the band saw was estimated by using the workpiece which was smaller than the interval of each tooth, i.e. band saw pitch, in the thickness. Then the static cutting forces were predicted by appling the mean cutting forces referred above to the mechanistic cutting force model which were analyzed through the geometric profile of a band saw tooth.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.530-532
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• 2002

This paper presents an optimum design of herringbone grooved journal bearing for spindle motor of hard disk drive (HDD) system. In addition to the conventional “rectangular” groove, various groove profiles are designed. The stiffness and damping coefficients of the oil film and frictional torque are calculated and compared for tile various groove profiles. The “circular”, “valley”, and “reversed saw tooth” grooves do not produce high direct stiffness, since they partly increase the groove depths in the direction of lubricant flow, causing to reduce the pumping action of the bearing. The maximum direct stiffness can be obtained by the “rectangular”, “saw tooth”, and “step” grooves. With the same cross sectional area of the grooves, these three grooves have the same maximum stiffness, damping coefficients, and frictional torque. Among these recommendable grooves, the saw tooth groove may keep its original profile for long, enduring metal-to-metal contact during startup and shutdown.

• 유공압시스템학회:학술대회논문집
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• 유공압시스템학회 2010년도 춘계학술대회
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• pp.25-32
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• 2010

A geortor type pump is widely used in lubrication and actuator systems. Especially the pump is an essential machine element of an automotive engine to feed lubrication oil and power source of automatic transmission. A gerotor is a planar mechanism consist of a pair of rotor and circular tooth of stator assembly which forms a closed space. However, related industries do not have necessary technology to design and optimize the pump and paid royalties of gerotor profile on an advanced company. Also, gerotor profiles with setting design parameter have not been sufficiently analyzed from a theoretical view. Therefore, it is very difficult for designer to decide the specifications of the gerotor profiles, and calculation and fluctuation of flow rate is not yet confirmed. In this study, theoretical analyses and optimal design of the gerotor profiles have been performed numerical method by mathematical base. An automated design system of the tooth profile has been developed through MATLAB GUI Program considering various design parameters.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.434-439
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• 2013

PURPOSE. The aim of the present study was to evaluate the effects of posts with different morphologies on stress distribution in an endodontically treated mandibular premolar by using finite element models (FEMs). MATERIALS AND METHODS. A mandibular premolar was modeled using the ANSYS software program. Two models were created to represent circular and oval fiber posts in this tooth model. An oblique force of 300 N was applied at an angle of $45^{\circ}$ to the occlusal plane and oriented toward the buccal side. von Mises stress was measured in three regions each for oval and circular fiber posts. RESULTS. FEM analysis showed that the von Mises stress of the circular fiber post (426.81 MPa) was greater than that of the oval fiber post (346.34 MPa). The maximum distribution of von Mises stress was in the luting agent in both groups. Additionally, von Mises stresses accumulated in the coronal third of root dentin, close to the post space in both groups. CONCLUSION. Oval fiber posts are preferable to circular fiber posts in oval-shaped canals given the stress distribution at the postdentin interface.

• 한국정밀공학회지
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• 제19권2호
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• pp.228-236
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• 2002

In this study, the carbon steels, SM20C were machined with the tungsten carbide tipped circular saw to clarify the cutting-off characteristics in terms of tool wear. The results show that an improved performance in view of both the tool wear and the cutting efficiency was obtained by using oil base cutting fluid at the cutting speed of 100m/min with the feed of 0.06mm/tooth. The rake angle of 10$^{\circ}$ , clearance angle of 8$^{\circ}$ , nose radius of R0.1mm, and end cutting edge champer of 0.1mm$\times$25$^{\circ}$ are believed as the best tool geometries. The tool wear decreases due to using the saw of the disk of STS5 and the tool material of P30.

• 대한치과의사협회지
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• 제50권7호
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• pp.384-393
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• 2012

Successful treatment of a badly broken down tooth with pulpal disease depends not only on good endodontic therapy, but also on good prosthetic reconstruction of the tooth after endodontic therapy is completed. The ideal treatment of endodontically treated teeth has been widely and controversially discussed. Endocrown is a restorative option for endodontically treated teeth. Endocrown design incorporates the core and short post into the crown as a single restoration. The preparation of endocrown consists of a circular equigingival butt-joint margin and central retention cavity of the entire pulp chamber instead of employing intraradicular posts. This design significantly increases the surface area of the preparation available for cementation. It is particularly useful in young patient teeth for long-term provisional restoration and in teeth with short clinical crowns. This technique represents a promising and conservative method for the treatment of endodontically treated teeth that require long-term protection and stability. Endocrown can be considered as a feasible alternative to full crowns or composite overlays for the restoration of non vital teeth.

• Tribology and Lubricants
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• 제23권4호
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• pp.149-155
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• 2007

The CAD model of a elliptical gear for wire cutting has been developed. The rolling contact of pitch ellipses whose rotation axes coincide with their focus has been analyzed, and the perimeter of the pitch ellipse has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. The elliptical gear has been designed by imposing the master tooth on the divided points of the pitch ellipse, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of an elliptical gear is a composite curve of arcs only, and consequently NC codes for wire cutting can be easily generated. Furthermore, a computer simulation program is developed to verify the mesh of the elliptical gear.

• 복식문화연구
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• 제9권5호
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• pp.712-722
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• 2001

The purpose of this study is to classify of the Hair ornaments in old tombs of the Three Kingdom States. Hair ornaments was divided into Combs, Rod-like hairpins, Chae[;釵], Boyo[;步搖] Combs were 2 type in according to the tooth's space, wide-tooth comb[;梳] and fine-tooth comb(;比). The general name of two type was called Jeul(;櫛). Combs were excavated from the only ancient Silla tombs. Rod-like hairpins were called Gha(叉) or Jam(:簪). They were found in most of the old tombs in Goauryeo, Baekje, ancient Silla tombs. The style was L-type and embellished circular head-type. Chae(;釵) was understand Cha(:叉) that had two tongs. Chae(:釵) was generally U-type and rarely hairtweezers -type. Jakchae(;爵釵) was understand distinctive Chae(;釵) hanged with phoenix. This type was excavated from the only Baekje tombs of King of Muryeong. Boyo(;步搖) was originally a hair decoration of the northern nomadic tribes which had been introduced to the Wijin period. Boyo gained its popularity by the women in Dang Dynasty, hair ornaments were considered indicators of status and wealth. Boyo(;步搖) hair accessory features of which are suspended from a elaborate hairpin structure. Such pieces were designed to sway as their wearer walked. The bequest was not found, but we catch the Boyo(; 步搖) that was women'head decoration in painting of old tombs in Goguryeo.

• Tribology and Lubricants
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• 제1권1호
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• pp.69-79
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• 1985

Planocentric gears 장치에서 내치차에 pin type의 치형을 사용하고 휠의 치형을 원호로 구성하였을 경우 치의 접촉특성을 탄성유역학적 윤활이론을 도입하여 해석 하였다. 윤활 특성을 개선하기 위하여 물림 위치(meshing position)에 의거한 설계 방법과 치의 모서리 부분 형상을 만곡되게 하는 치형 설계 방법을 제시하고 기존 설계에 의한 장치와 수치적으로 특성을 비교 하였다.