• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.66.2-66
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• 2002

In this study, a novel systematic design procedure by Genetic Algorithm of a two stage relief valve is proposed. First of all, a mathematical model describing the dynamics of a balanced piston type relief valve has been derived. Governing equations such as dynamic equations for the main spool and the pilot spool and flow equations for each orifice are established. The mathematical model is verified by comparing the results of simulation with that of experiments. Furthermore, influences of the parameters on the dynamic characteristics of a relief valve have been investigated by simulation of the proposed model. Major design parameters on the valve response are determin...

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2477-2485
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• 1994

Air damper has a great advantage that is independent of temperature change. This paper presents an analysis approach and an application for designing nonviscous air damper with a piston and a cylinder. The objective functions for optimum design is damping coefficient and is maximized by changing two design variables that are length between piston and cylinder and orifice diameter. A digital computer program was developed which determines optimal air damper configuration for maximum damping coefficients. The results were applied to the automatic washer and are confirmed to be valid for the range of operating conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.645-649
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• 1997

In case of swash plate type axial piston hydraulic motor, hydrostatic bearing used to achieve the lubrication effect on the mechanical sliding contact areas between the following parirs ; sliooer-pad and swash plate,piston and cylinder bore,valve plate and cylinder block, etc. This study discussed the basic charateristic for the hydrostatic slipper-pad bearings with the capillary or orifice restrictor under static load condition. And, we also development of hydrostatic bearing tester for hydrostatic balancing test of pistion & slipper-pad assembly, and some experimental data on supply pressure step responce are reported.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.156-158
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• 2008

Along the various gap distance between shoe and swash plate and pocket diameter, lifting force of piston shoe during the compressing stage was calculated. The flow in piston, orifice, shoe, and back space was considered to be 2-dimension axisymmetric and analysed by Fluent, a commercial CFD Software. The wall boundary condition was given as nonslip and adiabatic, while the change in fluid viscosity was considered as linear along temperature. Calculated lifting force and oil leakage of shoe was used in the design of a pump to confirm the shape of the shoe.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.726-739
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• 2003

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.69-69
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• 2011

영산강 수계인 함평지역의 면적이 13.69ha인 논 유역에 건설기술연구원에서 개발된 수문모형인 CAT 모형을 적용하였다. 이 유역에서는 배수를 위해 플라스틱 파이프로 된 배수공을 쓰고 있으며, 배수공은 기존의 Weir Type의 물꼬와는 상이하게 Orifice 형식의 수리적 특성을 갖는다. 이러한 조건에 맞는 수문분석을 위해서 CAT 모형에 배수공을 위한 모듈이 추가되었으며, 현장 계측 자료를 이용한 적용성 평가가 요구되고 있다. 본 연구에서는 2008년부터 2010년까지 대상지역 논에서 모니터링 한 강우-유출 자료를 이용하여 논에서의 물수지 분석을 위한 CAT 모형의 적용성을 평가하였다.

• Journal of Korea Foundry Society
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• v.20 no.6
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• pp.368-376
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• 2000

Rheology forming technology has been accepted as a new method for fabricating near net shaped products with lightweight aluminum alloys. The rheology forming process consists of reheating process of billet, billet handling, filling into the die cavity and solidification of rheology formed part. The rheology forming experiments are performed with two different die temperatures ($T_d$ = $200^{\circ}C$, $300^{\circ}C$) and orifice gate type. The filling behavior and various defects of Al-Si materials with wear resistance (A357, A390 and ALTHIX 86S) fabricated in rheology forming process are evaluated in terms of alloying elements and surface non-uniformity. Finally, the methods to obtain the rheology formed products with high quality are described by solutions for avoiding the surface and internal defects.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.165-169
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• 1986

A total of 114 extracted human mandibular 2nd molars were used to study the configuration of the floor of the chamber. The specimens were ground and the pulp chamber was examined with a magnifier and explored with sharp explorer. The study showed the shape of the pulp chamber, number of root canals, and the type of canal orifice. The results were as follows, 1. In so far as observing the shape of the pulp chamber of the teeth, 47.4% of the teeth were square, 42.9% were triangle and 9.7% were ovoid shape. 2. 35% of the samples had 2 root canal orifices, 62% had 3 root canal orifices, 3% had 4 root canal orifices. 3. 3% of the specimens showed 'H' shape, 5% showed 'Square' shape, 51% showed 'T' shape, 1% showed 'reverse-T' shape, 35% showed 'I' shape and 5% showed the specific 'C' shape.

• The KSFM Journal of Fluid Machinery
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• v.9 no.5 s.38
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• pp.22-27
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• 2006

Sedimentation phenomenon of suspended solids occurs by the gravitational force. Pollution particles are separated from slowly flowing waste water in clarifier. Recently, the sludge suction collector is Preferred rather than the scraper type sludge collector due to the enhancement of the clarifier efficiency. The sludge suction collector is usually operated by the user's experiences without any scientific and/or technical consideration. To evaluate the performance of sludge suction collector, the three dimensional numerical simulation was conducted by the finite volume method. To analyze the performance, the velocity vectors and the suction flow rates of the orifices were investigated. The result showed that each suction flow rate through out the collector was equivalent in the sludge suction collector and the efficiency of suction collector was good to remove high concentrated sludge in clarifier.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.121-126
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• 2001

In this study, the 4-way spool valve characteristics are clearly defined and proposed new type of spool valve. This paper presents governing equations of the flow through clearances between sleeve and spool as a model of orifice flow for null characteristic analysis, and programmed analysis software of it. This software is possible to basically analysis that not only which case of open center, closed center or critical center but +,- displacement of spool, lab position, boundary region and spool opening of the valve, and to estimate the pressure variation in the spool and external leak flow variation. We are convinced that the scale of load pressure difference is changed as lab condition of spool valve, and this scale is changed with boundary point on the annular clearance. It is vary useful to designer and user of spool valve with this design data and analysis software.