• Title/Summary/Keyword: Characteristic ratio

Search Result 2,586, Processing Time 0.045 seconds

The Prediction of Void Ratio in Unsaturated Soils (불포화토에서 공극비의 추정)

  • Lee Dal-Won
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.48 no.4
    • /
    • pp.51-57
    • /
    • 2006
  • This study was carried out to investigate the soil water characteristic curve and prediction of void ratio with net stress and matric suction using the linear elastic and volumetric deformation analysis method on unsaturated silty. The unsaturated soil tests were conducted using a modified oedometer cell and specimens were prepared at water content 2 times of liquid limit and required void ratio. The axis translation technique was used to create the desired matric suctions in the samples. It is shown that soil water characteristic curve and volumetric water content were affected significantly by preconsolidation pressure. As a matric suction increases, the reduction ratio of void ratio was shown to considerably small. Also, the predicted and measured void ratio for unsaturated soils using the linear elastic and volumetric deformation analysis showed good agreement as net stress and matric suction increases.

Development of Equation of the Soil-Water Characteristic Curve for an Unsaturated Soil (불포화의 흙-수분 특성곡선 방정식의 개발)

  • Song, Chang-Seob;Lim, Seong-Yoon;Kim, Myung-Hwan
    • Proceedings of the Korean Society of Agricultural Engineers Conference
    • /
    • 2003.10a
    • /
    • pp.191-194
    • /
    • 2003
  • The purpose of this paper was to derive soil-water characteristic curve equation for unsaturated soil. To this end, a series of suction measured test was conducted on the selected 4 kinds of soil which is located in Korea, used the modified pressure plate apparatus. From the test results, it was proved that characteristic curve changes according to grain size distribution, size of void and fine grained soil contents. Residual degree of saturation(Sr) was decreased with void ratio and changed with fine grained soil contents, parameter ${\lambda}$ and hr was increased with void ratio. Soil-water characteristic curve equation based on the test result was suggested by void ratio or grain size distribution.

  • PDF

Pin Fin Optimization Based on the Ratio of Heat Loss to the Maximum Heat Loss (최대 열손실에 대한 열손실 비에 기준한 Pin 핀의 최적화)

  • Kang, Hyung-Suk
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.32 no.11
    • /
    • pp.817-823
    • /
    • 2008
  • A pin fin with variable fin base thickness is optimized based on the ratio of heat loss to the maximum heat loss using a two-dimensional analytic method. The temperature profile along the normalized radius position in the fin is presented. For fixed fin outer radius, the optimum heat loss, fin length and efficiency as a function of fin base thickness, outer radius, convection characteristic numbers ratio and ambient convection characteristic number are presented. One of the results shows that the effect of fin outer radius and ambient convection characteristic number on the optimum fin length is remarkable.

A New Definition of Short-circuit Ratio for Multi-converter HVDC Systems

  • Liu, Dengfeng;Shi, Dongyuan;Li, Yinhong
    • Journal of Electrical Engineering and Technology
    • /
    • v.10 no.5
    • /
    • pp.1958-1968
    • /
    • 2015
  • In this paper, a new definition of short-circuit ratio concept for multi-converter HVDC systems is proposed. Analysis results of voltage interaction between converters show that the reactive power-voltage characteristic of a converter has a dominant effect on voltage interaction level compared with its active power-voltage characteristic. Such a relation between converter reactive power and voltage interaction level supports taking the former into account in the definition of short-circuit ratio concept for multi-converter systems. The proposed definition is verified by the method of maximum power curve for various system configurations. Furthermore, a formula to calculate transient overvoltage for multi-converter systems is derived based on the proposed definition, and the efficiency of the derived formula is verified.

A Geometrical Approach to the Characteristic Analysis of Parallel Mechanism for Planar Task (평면 작업용 병렬 메카니즘의 특성 해석을 위한 기하학적 접근)

  • Song, Nak-Yoon;Cho, Hwang
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.15 no.9
    • /
    • pp.158-166
    • /
    • 1998
  • This paper presents a geometrical approach to the characteristic analysis of parallel mechanism with free joints intended for use as a planar task robot. Solution of the forward and inverse kinematic problems are described. Because the mechanism has only three degree-of-freedom output, constraint equations must be generated to describe the inter-relationship between actuated joints and free joints so as to describe the position and orientation of the moving platform. Once these constraints are incorporated into the kinematics model, a constrained Jacobian matrix is obtained. and it is used for the solution of the forward kinematic equations by Newton-Raphson technique. Another Jacobian matrix was derived to describe the interrelationship between actuated joints and moving platform. The stiffness, velocity transmission ratio, force transmission ratio and dexterity of the mechanism are then determined based on this another Jacobian matrix. The geometrical construction of the mechanism for the best performance was investigated using the characteristic analysis.

  • PDF

A Study of Fuel Gauge System Matching Method Using Characteristic Chart to Fuel Consumption Ratio in Vehicles (특성 선도를 이용한 자동차용 연료 지침계의 연료 소비율에 따른 시스템 제어 방법에 관한 연구)

  • Lee, Seon-Bong;Lee, Boo-Youn
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.32 no.2
    • /
    • pp.194-201
    • /
    • 2008
  • In the present study, fuel system matching was analyzed, and a characteristic chart for common use for design-related parts is presented. Based on the characteristic chart thus presented, controlled fuel system matching was tested for a 35-liter fuel system, and actual mass product movement coils were applied to validate the test. The keynote of the present research is the use of the characteristic chart to devise a preferred fuel system matching method. Through the present study, it will be possible to design standard parts for efficient fuel system matching in the near future.

Combustion Performance of a Pintle Injector Rocket Engine with Canted Slit Shape by Characteristic Length and Total Momentum Ratio (Canted Slit 형상의 핀틀 인젝터 로켓엔진의 특성길이와 운동량비에 따른 연소성능)

  • Yu, Isang;Kim, Sunhoon;Ko, Youngsung;Kim, Sunjin;Lee, Janghwan;Kim, Hyungmo
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.21 no.1
    • /
    • pp.36-43
    • /
    • 2017
  • In this study, a pintle injector rocket engine which uses kerosene and liquid oxygen as propellants was manufactured by collecting basic design data and establishing a design procedure. Combustion performance of the liquid rocket engine was investigated by characteristic velocity efficiency with characteristic length of the combustion chamber and total momentum ratio. As a result of hot fire tests, it showed that the engine had shorter characteristic length comparing to those of other type injectors, which was known as recommended value with the propellant combination. Also, the characteristic velocity efficiency was greatly affected by total momentum ratio and almost constant within 1.0~1.5.

The Characteristic Study on Mixture Ratio Stabilizer for Gas Generator of LRE(Liquid Rocket Engine) (액체로켓엔진 가스발생기 혼합비 안정기의 특성 연구)

  • Jung, Tae-Kyu;Lee, Joong-Yeop;Han, Sang-Yeop;Kwon, Se-Jin
    • 유체기계공업학회:학술대회논문집
    • /
    • 2006.08a
    • /
    • pp.509-512
    • /
    • 2006
  • The propellant mixture ratio of gas generator changes when thrust control valve operate to change LRE thrust level. The mixture ratio change of gas generator result in gas temperature change and failure of turbine blade or deterioration of LRE specific impulse. The mixture ratio stabilizer has been developed to maintain propellant mixture ratio of gas generator. This article deals with design and static/dynamic characteristic of stabilizer. Also gas generator system simulation test has shown that the stabilizer can maintain propellant mixture ratio effectively within tolerable range.

  • PDF

Development and performance evaluation of a test particle generator for a field inspection equipment of PM-2.5 sensors (미세먼지 간이측정기 현장 검사용 시험 입자 발생기 개발 및 성능 평가)

  • Chung, Hyeok;Park, Jin-Soo
    • Particle and aerosol research
    • /
    • v.18 no.3
    • /
    • pp.61-68
    • /
    • 2022
  • In this study, a fluidized bed particle generator was developed to generate an aerosol without supply of compressed air and to increase portability. It was assumed that the mixing ratio of the test particles and beads, the input amount, and the air flow rate supplied to the generator would have effect on the aerosol generation characteristics. The product of these three parameters was set as a characteristic parameter and particle generation characteristics according to the change of the characteristic parameter were observed. As a result, it was confirmed that the input amount of test particles and beads was not suitable as a characteristic parameter and a characteristic parameter expressed as a product of the mass mixing ratio and the air flowrate was newly defined. When the new characteristic parameter is applied, it can be confirmed that the total amount of particles generated from the particle generator is a function of the characteristic parameter. As a result of measuring the amount of particle generation by adjusting the characteristic parameter, it was confirmed that the performance required for the test particle generator for the field inspection equipment of PM-2.5 sensors could be satisfied.