• Title/Summary/Keyword: Dynamic Property

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A minimum energy control of a load-sensing hydraulic servo system

  • Kim, S.D.;Cho, H.S.
    • 제어로봇시스템학회:학술대회논문집
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    • 1987.10a
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    • pp.747-752
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    • 1987
  • The dynamic characteristics of a load-sensing hydraulic servo system are complex and highly unstable. Another property of the system is that the setting value of pump compensator is closely related to energy efficiency as well as control performance of the system. This necessitates the development of an effective control algorithm which guarantees good control performance, stability and energy efficiency. This paper considers a suboptimal PID control for the velocity control problem of the load-sensing hydraulic servo system. The results of simulations studies and experiments show that the proposed suboptimal controller can produce much better control performance than nonoptimal controllers and give effective energy efficiency.

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A study on the PWM type High Speed Electromagnet (PWM 방식 고속 전자석에 관한 연구)

  • Song, Chang-Seop;Yang, Hae-Jeong;Song, Sung-Bae
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.6
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    • pp.127-135
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    • 1994
  • This paper is concerned about a high speed electromagnet of Pressure control solenoid valve. Solenoid valve is controlled by means of Pulse width modulation. The magnetostatic field problem on a solenoid is numerically solved by the 2-D axisymmetric finite element method. And permeance method is adopted for analysing the static and dynamic property of solenoid part theoretically. In addition, in this study, experiments on solenoid part were performed in order to measure the magnetic force and plunger displacement. The numerical results coincided with the experimental results. As a result, the magnetic force has the linear relation with displacement of plunger and the primary factors on the performance of PWM type high speed electromagnet are coil resistance, plunger mass, and the length of air gap between plunger and core.

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A Study on the Dynamic Amplification Characteristics of the Domestic Seismic Observation Sites using Shear- and Coda-Wave (S파 및 Coda파를 이용한 국내 관측소지반의 동적 증폭특성에 관한 연구)

  • Kim, Jun-Kyoung
    • Tunnel and Underground Space
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    • v.19 no.5
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    • pp.432-439
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    • 2009
  • For more reliable estimation of seismic source, attenuation properties and dynamic ground property, site amplification function should be considered. Among various estimation methods, this study used the Nakamura's method (1989) for estimating site amplification characteristics. This method was originally applied to the surface waves of background noise and therefore there are some limitations in applying to general wave energy. However, recently this method has been extended and applied to the S wave energy successfully. This study applied the method to S wave and Coda wave energy, which is equivalent to the backscattered S wave energy. We used more than 60 observed ground motions from 5 earthquakes which were occurred recently, with magnitude range from 3.6 to 5.1. Each station showed characteristic site amplification property in low-, high- and resonance frequencies. Some of the stations showed as high as 4 times of site amplification in the range of specific frequencies, which may imply abnormal small scale geologic strata below the station or development of various trapped modes in the basin structure. Moreover, removal of site amplification can give us more reliable seismic source and attenuation parameters, addition to the seismic hazard estimation.

Mechanical and Durability Properties of Partial-Depth Patch Materials using Polymer Materials for Concrete Pavement (단면보수용 콘크리트 패치재료의 역학적 특성 및 내구성 실험)

  • Yang, Sung-Chul;Hwang, In-Dong;Han, Seong-Hwan;Kim, Seong-Min
    • International Journal of Highway Engineering
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    • v.11 no.3
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    • pp.23-32
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    • 2009
  • In this paper an experimental program was launched to determine the mechanical and durability properties of spall repair materials (RCC: 3 items, PCC: 2 items, PC: 3 items). Test items were mechanical property tests such as setting times, strengths, modulus of elasticity, plastic shrinkage, and durability tests such as dynamic modulus ratio, bond property with freeze-thaw, water absorption, chemical resistance, ultraviolet exposure. Modulus of the PC products exhibits ductile while the modulus is in the order of RCC > PCC > PC. At early ages the PC products experience higher plastic shrinkage than others, henceforth stable at 28 days. Other test results such as dynamic modulus ratio, absorption, and chemical resistance show that the PCs are superior to the PCCs and the RCCs. Except for PC-2, all patch materials had bond strength more than 1.3MPa after freeze-thaw cycles of 200~300 while the PCs and the PCCs seem to be better than the RCCs. With 500 hours of ultraviolet exposure, all patch materials showed to have no crack or deterioration at the surface.

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Study on Physical Properties of Domestic Species II: Sorption, Thermal, Electrical and Acoustic Properties of Pinus koraiensis and Larix kaempferi (국산재의 응용물성연구II: 잣나무 낙엽송의 수분흡착성 및 열적·전기적·음향적 성질)

  • Byeon, Hee-Seop;Lee, Won-Hee;Park, Byung-Soo;Chong, Sung-Ho;Kang, Ho-Yang
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.4
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    • pp.1-10
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    • 2008
  • A series of the studies on the applied physical properties of domestic species have been conducted last three years. Pinus koraiensis and Larix kaempferi were two of the three species examined for the first year. Because the same apparatus and experimental procedures were used for all species, their results can be easily comparable. The experiments for sorption property were conducted with 20- and 80-mesh wood powder and resulted in their EMCs and sorption isotherms at various RH conditions. The thermal conductivity and diffusivity, and electric resistance and volumetric electric resistivity were measured with a thermal-wire device and a high electric resistance meter. The differences in the thermal and electric properties between quarter- and flat-sawn specimens were observed, which were partially attributed to their anatomical differences. An acoustic measurement system was used to evaluate dynamic MOE and internal friction. This paper provides the useful fundamental data for designing a wood structure, correcting a portable resistance-type moisture meter, and acoustic properties of wood.

Measurement of Mechanical and Physical Properties of Pepper for Particle Behavior Analysis

  • Nam, Ju-Seok;Byun, Jun-Hee;Kim, Tae-Hyeong;Kim, Myoung-Ho;Kim, Dae-Cheol
    • Journal of Biosystems Engineering
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    • v.43 no.3
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    • pp.173-184
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    • 2018
  • Purpose: This study was conducted to investigate the mechanical and physical properties of a Korean red pepper variety for particle behavior analysis. Methods: Poisson's ratio, modulus of elasticity, shear modulus, density, coefficient of restitution, and coefficient of friction were derived for "AR Legend," which is a domestic pepper variety. The modulus of elasticity and Poisson's ratio were measured through a compression test using a texture analyzer. The shear modulus was calculated from the modulus of elasticity and Poisson's ratio. The density was measured using a water pycnometer method. The coefficient of restitution was measured using a collision test, and the static and dynamic friction coefficients were measured using a inclined plane test. Each test was repeated 3-5 times except for density measurement, and the results were analyzed using mean values. Results: Poisson's ratios for the pepper fruit and pepper stem were 0.295 and 0.291, respectively. Elastic moduli of the pepper fruit and pepper stem were $1.152{\times}10^7Pa$ and $3.295{\times}10^7Pa$, respectively, and the shear moduli of the pepper fruit and pepper stem were $4.624{\times}10^6Pa$ and $1.276{\times}10^7Pa$, respectively. The density of the pepper fruit and the pepper stem were $601.8kg/m^3$ and $980.4kg/m^3$, respectively. The restitution coefficients between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.383, 0.218, 0.277, 0.399, and 0.148, respectively. The coefficients of static friction between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.455, 0.332, 0.306, 0.364, and 0.404, respectively. The coefficients of dynamic friction between a pepper fruit and plastic and a pepper stem and plastic were 0.043 and 0.034, respectively.

Study on Physical Properties of Domestic Species I: Sorption, Thermal, Electrical and Acoustic Properties of Pinus Densiflora (국산재의 응용물성연구 I: 소나무(Pinus densiflora)의 수분흡착성 및 열적·전기적·음향적 성질)

  • Kang, Ho-Yang;Byeon, Hee-Seop;Lee, Won-Hee;Park, Byung-Soo;Park, Jung-Hwan
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.3
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    • pp.70-84
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    • 2008
  • A series of the studies on the applied physical properties of domestic species have been conducted last three years. Pinus densiflora was one of the three species examined for the first year. Because the same apparatus and experimental procedures were used for all species, their results can be easily comparable. The experiments for sorption property were conducted with 20- and 80-mesh wood powder and resulted in their EMC's and sorption isotherms at various heating conditions. The thermal conductivity and diffusivity, and electric resistance and volumetric electric resistivity were measured with a thermal-wire device and a high electric resistance meter. The differences of the thermal and electric properties between quarter- and flat-sawn specimens were observed, which was partially attributed to their anatomical differences. An acoustic measurement system was used to evaluate dynamic MOE and internal friction. This paper provides the useful fundamental data for designing a wood structure, correcting a portable resistance-type moisture meter, and nondestructive testing wood.

Analysis of Scaling Factor applied to Lab-Scale Model for Estimating Dynamic Characteristics of Real Structures (실구조물의 동특성 파악을 위한 축소모형에 적용되는 상사비 분석)

  • Park, Gun;Yoon, Hyungchul;Kim, Sung Bo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.1
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    • pp.59-66
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    • 2021
  • The earthquakes are the natural disasters that can cause the most serious damage to civil structures. Therefore, various studies are being conducted to secure the safety of structures against earthquakes. Most studies on the safety or mechanism of civil structures during earthquakes are being conducted based on lab scale test, because real structure tests are impossible when considering the scale of civil structures. The scaling factor proposed by Iai is mainly cited, but when applying the scaling factor proposed by Iai, there are many difficulties in selecting the structural members necessary for the production of the lab scale model. This is because when applying the scaling factor proposed by Iai, the scaling factor must be applied to the elastic modulus, which is the material property of the structure. Therefore, a new method based on Iai's 's similarity law for determining scale factor is applied in this study where the material property of real structure is same as that of lab-scale model. Through the results of this study, it is considered that the characteristics of the structure calculated through the lab scale model test can more accurately reflect the characteristics of the real structure.

A New Direction and Its Challenges for Linkage of Agricultural Research and Extension As a Traditional Knowledge Development in Rural Korea: Agricultural Knowledge Systems (농업지식체계 구축에 의한 전통지식개발 방법으로서의 농업연구지도 연계의 방향)

  • Park, Duk-Byeong;Kang, Kyeong-Ha;Lee, Min-Soo
    • Journal of Agricultural Extension & Community Development
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    • v.10 no.1
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    • pp.15-29
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    • 2003
  • The study uses agricultural knowledge system theory to explore how traditional knowledge applies to the linkage system of agricultural research and extension in rural Korea. By agricultural knowledge system we emphasize the dynamic networks of actors, processes of negotiation, and the diverse ways in which knowledge is constructed and performed. The knowledge systems reflect the idea that the boundaries between knowledge groups are not closed and that there could be considerable overlap between knowledge system. The results of this study are the following : First, we should know that some extension agents clearly value farmer knowledge and try to facilitate farmer-to-farmer communication. Extension plays a significant role in the knowledge-creation process and shaping communities because knowledge processes are embedded in social processes that involve aspects of power, authority, and legitimization. Third, the constructions of agricultural knowledge systems thus include social interactions, communication, and the diverse processes individuals employ create, use, and evaluate multiple types and sources of information through the linkage between agricultural colleges and Rural Development Administration (RDA), establishing the research institution of research and extension linkage, exchange research agent with extension agent, and bottom-up approach. Second, we should know that the focus of traditional knowledge development is rural community development as a community process. Nowadays the sessions of the Intergovernmental Committee of World Intellectual Property Organization (WIPO) cover two lines of inquiry, which are the use of existing standards of intellectual property for the protection of traditional knowledge and that of new legal standards, eventually in the from of sui generis mechanisms of protection.

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A Coupling Metric between Classes for Efficient System Design (효율적인 시스템 설계를 위한 클래스 간의 결합 척도)

  • Choi, Mi-Sook;Lee, Jong-Suk;Lee, Seo-Jeong
    • Journal of Internet Computing and Services
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    • v.9 no.5
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    • pp.85-97
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    • 2008
  • Recently, service-oriented systems have been issued by their properties of reducing software development time and effort by reusing functional service units. The reusability of services can effectively promote through loose coupling between services and loose coupling between services depends on component-based system. That is, the component-based system is designed by grouping the tightly coupled classes of the object-oriented system and the service-oriented system is designed by the component-based system. Therefore, to design the component-based system and service-oriented system efficiently, a metric to measure the coupling between classes accurately needs. In this paper, we propose a coupling metric between classes applying a structural property, a dynamic property, and the normalized value by 0-1. We prove the theoretical soundness of the proposed metric by the axioms of briand et al, and suggest the accuracy and practicality through a case study. We suggest the evaluation results of the proposed metric through a comparison with the conventional metrics.

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