• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.117-124
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• 2007

The pressure ripple in most hydraulic systems is the root cause of their noise and vibration. This paper reduced the pressure ripple using side branch hose for an axial piston pump applied to small excavator. First, in calculating open area, a new method using groove area of valve plate is proposed. Simulation model in AMESim environment is developed to verify proposed method, find effective length and diameter of branch hose. Finally, the comparisons with experiment results show that the proposed method is more effective than previous method in reducing the pressure ripple.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.328-330
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• 2005

현재의 RSVP-TE는 VPN hose provisioning 메커니즘들을 고려하여 자원예약을 수행하지 못한다. 이 논문에서는 Provider Provisioned-Virtual Private Network(PP-VPN)에서 Quality of Service(QoS)를 제공하는 Hose 모델 기반의 provisioning 메커니즘들을 네트워크에 적용하여 자원예약을 수행하도록 하기 위해 Resource Reservation Protocol Traffic Engineering(RSVP-TE)의 확장방안에 대해 설명한다. 동일한 VPN을 서비스하는 LSP들 간 자원을 공유할 수 있게 함으로써 네트워크 상에 요구되는 자원을 최적화하였으며, VPN 고객을 서비스하기 위한 효율적이고 자동적인 자원예약이 가능하도록 하였다. 이 논문에서는 솔루션의 프로토콜 elements와 procedure에 대하여 설명한다.

• Journal of KSNVE
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• v.6 no.5
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• pp.671-677
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• 1996

This paper presents the analytical method for predicting turbulence- induced noise in the multilayered cylinder composed of an outer hose, an inner fluid and an internal core. It is assumed that an infinite axisymmetric cylinder is located horizontally in water with free stream velocity and the turbulent boundary layer (TBL) surrounding the outer hose is fully developed and homogeneous. The transfer function at the core surface due to the propagation of the pressure fluctuation within the TBL is formulated using the linearized Navier-Stockes equation for solid and fluid. In the estimation of the energy spectrum of wall pressure fluctuation, the empirical formula proposed by Strawderman based on the Corcos model is used. A general algorithm for the calculation of the pressure level at the surface of a core, that is, turbulence- induced noise, is presented. Through the detailed numerical simulation, it is found that the major noise mechanism is the propagation of the bulge wave along hose.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.22-28
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• 1998

This paper presents experimental investigations on the attenuation characteristics of pressure ripple in automotive power steering hydraulic hoses. Also, a mathematical model of hydraulic hoses is proposed to support design of the power steering hydraulic circuit and analyze the attenuation characteristics of pressure ripples. The experimental results show that the pulsation attenuation characteristics of hydraulic hoses is remarkably affected by the flexible metal tube inserted coaxially inside a hydraulic hose with a finite length as well as viscoelastic properties of hose wall. It is also shown that the predicted results by the model proposed here agree well with the measured results over a wied range of frequency.

• Journal of Applied Reliability
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• v.11 no.3
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• pp.235-244
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• 2011

Hydraulic hose assemblies deliver a fluid power in various oil pressure equipment such as construction machinery, automobile, aircraft, industrial machinery, machine tools and machinery for ships. Also, they are widely used as pipes in oil pressure circuit. When we estimate their lifetime, it is essential to conduct an accelerated life test by choosing the factor that suits the usage condition of the test object since traditional test method for estimating lifetime under the influence of various external factors incurs hardship in terms of time and expenses. The objective of this study is to propose an acceleration model that takes both temperature and pressure without flexing condition into consideration. The lifetime is estimated by applying the proposed temperature-nonthermal acceleration model to the test data. And we compare the proposed temperature-nonthermal acceleration model and the accelerated life equation suggested by John(1994).

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.886-892
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• 2013

Hydraulic hose assemblies are used as piping components for construction machinery, automobile, aircraft, industrial machinery, machine tools, and machinery for ships. Then the reliability of hose assemblies is important because total hydraulic system, which used to deliver the fluid power ($P^*Q$) needed to flexibility in the piping system, is not operated if the hose assembly failed in the system. The data of the accelerated life test estimated through the shape parameter(${\beta}$) resulting of the Weibull distribution analysis. This study has tried to reduce the test time resulting from varying impulse pressure range and the flexing diameter. Accelerated life test model for the test results was adopted the GLL(generalized log linear) and the accelerated indexes are identified as 6.64 for the pressure and 4.46 for flexing radius. Also, it found that shape parameter is 6.19, scale parameter(${\eta}$) is $1.035{\times}108$, which were adopted the pressure 35 MPa and the flexing diameter R100 mm in the used condition.

• Journal of KIISE:Information Networking
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• v.33 no.3
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• pp.247-256
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• 2006

Among the resource provisioning mechanisms for the hose based Virtual Private Network (VPN) Quality of Service (QoS ), VPN-specific state provisioning allows the service provider to obtain highest resource multiplexing gains. However, dynamic and automatic resource reservation for the VPN-specific state provisioning is difficult due to the lack of appropriate resource reservation protocol. Furthermore, users of a VPN may experience unfair usage of resources among themselves since the reserved resources of a VPN are shared by the VPN users in a similar way that the traditional LAN bandwidth is shared by the attached hosts. In this paper, we propose a resource reservation protocol and a traffic service mechanism, which not only enable dynamic and automatic resource reservation according to the VPN-specific state provisioning algorithm, but also enforce the fair usage of reserved resources among the users of a VPN in case of congestion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1697-1703
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• 2010

Hydraulic hoses are used as pipelines for transferring power from hydraulic systems in various machineries such as construction equipments, automobiles, and aircraft. Hydraulic hoses protect the system from vibration or impacts, and they are being used to transfer energy in all segments of the industry. In order to protect the system from various external environmental conditions, hydraulic hose assemblies must be able to withstand a wide range of temperatures and pressures, as well as variations in other factors. In previous studies, an acceleration model for the hydraulic hose assembly was developed by taking into account only one of the acceleration factors (temperature or pressure). Therefore, the objective of this study is to develop a comprehensive acceleration model that takes both temperature and pressure into consideration.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.11-16
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• 2010

The development of lifting pumps that lift minerals to a mining vessel are one of the vital parts of the commercial mining process. The purpose of this study is to investigate internal flow and its effect on the performance of a mixed flow pump in order to improve the pump's performance. Numerical analysis was performed by commercial code of ANSYS CFX-11 based on flow rate and length of flexible hose. The rated rotational speed of the impeller is 1750rpm. For taking into account the turbulence, k-$\omega$ SST model was selected to guarantee more accurate prediction of flow separation. The simulated results are in good agreement with the experimental results and showed that its efficiency and the head of the pump are related mainly to the flow rate and the length of flexible hose. A lesser flow rate caused more secondary flow through the guide vane passage. The length of flexible hose and flow rate exert much more influence on the pump's performance than the shape of the flexible hose.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.800-803
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• 2020

실 환경 로봇에 강화학습을 적용하기 위해서는 가상 환경 시뮬레이션이 필요하다. 그러나 가상 환경을 구축하는 플랫폼은 모두 다르고, 학습 알고리즘의 구현에 따른 성능 편차가 크다는 문제점이 있다. 또한 학습을 적용하고자 하는 대상이 실세계의 하드웨어 사양이 낮은 스마트 로봇인 경우, 계산량이 많은 학습 알고리즘을 적용하기는 쉽지 않다. 본 연구는 해당 문제를 해결하기 위해 Unity3D에서 제공하는 강화학습 프레임인 ML-Agents 모듈을 사용하여 실 환경의 저사양 스마트 로봇에 장애물을 회피하고 탐색하는 모델의 강화학습을 적용해본다. 본 연구의 유의점은 가상 환경과 실 환경의 유사함과 일정량의 노이즈 발생 처리이다. 로봇의 간단한 행동은 원만하게 학습 및 적용가능함을 확인할 수 있었다.