• Journal of Mechanical Science and Technology
• /
• v.16 no.6
• /
• pp.810-818
• /
• 2002

When the contribution of lightweight components to the total energy of a system is small, tole inertia effects are sometimes ignored by replacing them to massless links. For example, a revolute-spherical massless link generates two kinematic constraint equations between adjacent bodies and allows four relative degrees of freedom. In this paper, to implement a massless link systematically in a computer program using the velocity transformation technique, the velocity transformation matrix of massless links is derived and numerically implemented. The velocity transformation matrix for a revolute-spherical massless link and a revolute-universal massless link are appeared as a 6$\times$4 matrix and a 6$\times$3 matrix, respectively. A massless link model in a suspension composite joint transmitting external forces is also developed and the numerical efficiency of the proposed model is compared to a conventional multibody model. For a massless link transmitting external forces, forces acting on links are resolved and transmitted to the attached points with a quasi-static assumption. Numerical examples are presented to verify the formulation.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.1
• /
• pp.89-96
• /
• 2005

This paper is concerned with a balancing motion formulation and control of the ZMP (Zero Moment Point) for a biped-walking robot that has a prismatic balancing weight or a revolute balancing weight. The dynamic stability equation of a walking robot which have a prismatic balancing weight is conditionally linear but a walking robot's stability equation with a revolute balancing weight is nonlinear. For a stable gait, stabilization equations of a biped-walking robot are modeled as non-homogeneous second order differential equations for each balancing weight type, and a trajectory of balancing weight can be directly calculated with the FDM (Finite Difference Method) solution of the linearized differential equation. In this paper, the 3dimensional graphic simulator is developed to get and calculate the desired ZMP and the actual ZMP. The operating program is developed for a real biped-walking robot IWRⅢ. Walking of 4 steps will be simulated and experimented with a real biped-walking robot. This balancing system will be applied to a biped humanoid robot, which consist legs and upper body, as a future work.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.6
• /
• pp.111-121
• /
• 2000

Generally, the hydraulic pressures are used for transmitting the force. Therefore, a highly reliable and inexpensive control system has been required for a passenger car. The control-ability of active suspension system is strongly affected by the performance of pressure control valve in the view of dynamic response and energy consumption. In this study, we suggested main design parameters for the optimum design of proportional pressure control valve. The mathematical simulation model was derived from the quarter type model which consisted a valve and hydraulic damper for the purpose of analyzing the valve characteristics. Experiments were performed to confirm the performance of the valve and computations were carried out to ascertain the usefulness of the developed program. The results from computations fairly coincide with those from experiments. This has been achieved by developing the servomechanism valve which comprises the simple combination of a solenoid, a spool valve and a poppet valve. The results from experiments and computations show the development process of optimum proportional pressure control valve in the hydraulics system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.17 no.1
• /
• pp.69-78
• /
• 1999

Recently, with a rapid industry development, the recognition of environmental pollution is being increased. And the technique of pollution-prevention is also being studied. In the past, management direction for environmental pollution was limited only to concentration reduction and technique for treatment. But ,in these day, its direction is moved to a high level study such as a management and estimation of pollution material. In this study we establish a conception about EIS(Environmental Information System) building and present its building method. And we present a method for a database building, searching, analysis and printing. Also we produced the landuse map processing LANDSAT TM image. Using DDE(Dynamic Data Exchange) between Excel and ArcView on PC platform, we are enable to write and/or update a Report - waste discharge facility approval management leader - and to recover weakness about the report management of exsiting GSIS program.

• Journal of the Korean Society of Industry Convergence
• /
• v.3 no.2
• /
• pp.131-139
• /
• 2000

Gear train in the automobile to be used for controlling gas flow in automobiles consists of spur gears with involute tooth type in multiple stages. This spur gear is designed considering to the high power transfer efficiency, bending stress and contact stress in the static and dynamic analysis. The torque has been increased simultaneously the angular velocity has been decreased through the stages after being supplied by AC synchronous motor. This apparatus is controlled by electrical devices such as the PIC microprocessor, hall sensor and other electric components. By comparing the preset data of PIC microcomputer which is supplied by external DC electric power with the value set of hall sensor which detects the rotation angle position, PIC microcomputer thus controls AC motor and gear train according to the program algorithm which includes the on-off control and PWM motor driving method. As the result of the experiment such as performance, fatigue, torque test, we can conclude that this system is superior to the same and familiar foreign systems.

• Journal of Applied Reliability
• /
• v.18 no.1
• /
• pp.72-79
• /
• 2018

Purpose: Numerical and experimental study was performed to evaluate the effect of peening temperature on the residual compressive stress distribution and magnitude of residual compressive stress at the material surface. Methods: A compressive air-propelled warm peening equipment was designed and manufactured for warm peening test. Results: 3D dynamic finite element (FE) model of the warm peening test was proposed and validity of the proposed FE model was verified by comparing the predicted residual stresses with the measured residual stresses in the open literature. Maximum warm peening temperature and a proper peening time were investigated with the proposed FE model. Conclusion: Compressive residual stress increased remarkably with peening temperature increased. But, peening temperature is greater than $350^{\circ}C$, the effect of peening temperature disappeared. Therefore, maximum peening temperature possibly applicable for warm peening industry might be $350^{\circ}C$ and peening time is 45s.

• Hwankyungkyoyuk
• /
• v.9 no.1
• /
• pp.30-38
• /
• 1996

The purpose of this study was to survey on the awareness of teachers and students to mass media as a source for school environmental education. This study was performed with the questionnaire to 179 teachers who participated in certificate in-service training for $\ulcorner$Environment$\lrcorner$subject and to 635 students(primary: 177, middle: 179, high school students: 279). The results derived from this study were as follows: First, most teachers(86.6%) evaluated that mass media's effects on students were high and positive in terms of school environmental education, thus they thought that the application necessity and possibility of mass media for environmental education were so too. Second, many teachers evaluated that more program related with environment had to be produced(57.0%) and disseminated, and information on them had to be apprised teachers to activate school environmental education(44.1%). Third, both teachers(87.1%) and students(70.4%) evaluated that audio-visual media such as television, video, movie was better than others for environmental education because audio-visual media could be more realistic and dynamic(T: 48.0%, S: 41.7%). Fourth, we found that as the result of statistical analysis, students's friendliness. credibility and preference on media were different to school classes. But we could not analize the relationship between factors for the limit of sample.

• Journal of Agricultural Extension & Community Development
• /
• v.24 no.1
• /
• pp.9-19
• /
• 2017

This paper analyses the interrelationship among wholesale price, trading volumes, import volumes and demand for three agricultural products (cabbage, onions, and garlic) by using the consumer panel and the data from the Korea Rural Economic Institute and the Korea Customs Service with a VAR model. The results are summarized as below. (1) The prices of three agricultural products decrease when trading volumes increase while the price of cabbage and onions decreases when import volumes increase. But the prices of three agricultural products have little effects on trading volumes. (2) The demand of three agricultural products increases when trading volumes increase while the demand of cabbage and onions increases when import volumes increase. (3) when demand of garlic and cabbage increases by 10%, their price increases by 2.5% and 1.3% respectively. And the demand of garlic has positive effects on import volumes of garlic.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.10
• /
• pp.718-723
• /
• 2012

The purpose of this study is to propose modeling method of Underfloor Air Distribution System with reliability and validity by comparing characteristics of modeling methods. For this, the modeling methods of UFAD were selected by investigating various modeling methods of previous researches. Then, simulations were conducted by using EnergyPlus which is dynamic analysis program of building energy. Annual energy consumption for each method was compared with a wide range of indoor thermal loads. As a result, the methodology of reducing internal gains can cause under sizing of the system. It suggests modeling methods to reflect occupied zone air-conditioning, temperature stratification and supply plenum which are the main characteristics of UFAD.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.587-598
• /
• 2008

In the trackbed design using elastic multi-layer model, the stress-dependent resilient modulus is an important input parameter, which reflects substructure performance under repeated traffic loading. The resilient moduli of crushed stone and weathered granite soil were developed using nonlinear dynamic stiffness, which can be measured by in-situ and laboratory seismic tests. The prediction models of resilient modulus varying with the deviatoric or bulk stress were proposed (Park et al., 2008). To investigate the performance of the prediction models proposed herein, the elastic response of the test trackbed near PyeongTaek, Korea was evaluated using a 3-D nonlinear elastic computer program (GEOTRACK) and compared with measured elastic vertical displacement during the passages of freight and passenger trains. The material types of the test sub-ballasts are crushed stone and weathered granite soil, respectively. The calculated vertical displacements within the sub-ballasts are within the order of 1mm, and agree well with measured values with the reasonable margin. The prediction models are thus concluded to work properly in the preliminary investigation. The prediction models proposed for resilient modulus were verified by the comparison of the calculated vertical displacements with measured ones during train passages.