• Journal of the Ergonomics Society of Korea
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• v.30 no.6
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• pp.715-725
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• 2011

Objective: This study is aimed at developing Articulated Human Models(AHM) using superquadrics to improve the geometric accuracy of the body shape. Background: The previous work presents the AHM with geometrical simplification such as ellipsoids to improve analysis efficiency. However, because of the simplicity, their physical properties such as a center of mass and moment of inertia are computed with errors compared to their actual values. Method: This paper introduces a three steps method to present the AHM with superquadrics. First, a 3D whole body scan data are divided into 17 body segments according to body joints. Second, superquadric fitting is employed to minimize the Euclidean distance between body segments and superquadrics. Finally, Fee-Form Deformation is used to improve accuracy over superquadric fitting. Results: Our computational experiment shows that the superquadric models give better accuracy of dynamic analysis than that of ellipsoid ones. Conclusion: We generate the AHM composed of 17 superquadrics and 16 joints using superquadric fitting. Application: The AHM using superquadrics can be used as the base model for dynamics and ergonomics applications with better accuracy because it presents the human motion effectively.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.68-76
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• 2009

The sloshing tank causes the instability of the fluid flows and the fluctuation of the impact pressure by the liquid on the tank. These flow characteristics inside the sloshing tank can generate the uncomfortable sloshing noise. In the present study, a numerical analysis for the reduction of a fuel tank sloshing noise was performed. To simulate the flow characteristics in a sloshing tank with partially filled liquid, a VOF method was used for interfacial flows by applying a momentum source term for the sloshing motion in a non-inertial reference frame. This numerical method was verified by comparing its results with the available experimental data. For the reduction of the sloshing noise, the horizontal and vertical baffles and porous media inside a sloshing tank were considered and numerically analyzed in the present study. For various installations of these baffles and porous media, the characteristics of the liquid behavior in the sloshing tank were obtained along with the impact pressure on the wall and the height of the free surface along the wall. These basic results can be used for the design of the actual vehicular fuel tank with the reduced sloshing noise.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.381-388
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• 2001

Presented are heat data which describe the effect of interaction between bulk flow pulsations and a vortex embedded in a turbulent boundary layer. The pulsation frequencies are 3 Hz, 15 Hz and 30 Hz. A half delta wing with the same height as the boundary layer thickness is used to generate the vortex flow. The convection heat transfer coefficients on a constant heat-flux surface are measured by embedded 77 T-type thermocouples. Spanwise profiles of convection heat transfer coefficients show that upwash region of vortex flow is influenced by bulk flow pulsations. The local heat transfer coefficient increases approximately by 7 percent. The increase in the local change of convection heat transfer coefficient is attributed to the spanwise oscillatory motion of vortex flow especially at the low Strouhal number and to the periodic change of vortex size.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.164-169
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• 2001

The active magnetic bearing has many advantages - an active positioning, no contact and lubrication free motion - and is widely used in high precision motion stages. But, the conventional magnetic bearings composed of electromagnets only are power consuming due to their bias current and have the excessive heat generation, which can make the repeatability of the positioning system worse. To overcome this drawback, we developed a novel permanent magnet (PM) biased linear magnetic bearing for a high precision magnetically levitated stage. The permanent magnets provide a bias flux and generate a bias force, and the electromagnet increases or reduces a flux of the permanent magnets and gives a levitation force. This paper presents a theoretical magnetic circuit analysis, FEM analysis and experimental data from the 1-DOF tests, and compares the theoretical power consumption of the electromagnetic bearings and the PM biased linear magnetic bearings. The PM biased linear magnetic bearing presented in this paper gives better load capacity but lower power consumption than a conventional electromagnetic bearing and will be adopted in our 6-DOF high precision linear positioning maglev stage.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.52-57
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• 2008

Most of the electrons emitted from the filament, are captured by the anode. The portion of the electron current that leaves the gun through the hole in the anode is called the beam current. Electron beam probe is called the focused beam on the specimen. Because of the lenes and aperture, the probe current becomes smaller than the beam current. It generate various signals(backscattered electron, secondary electron) in an interaction with the specimen atoms. Backscattered electron provide an useful signal for composition and local specimen surface inclination. Secondary electron is used far the formation of surface imagination. The steady electron beam probe is very important for the imagination formation and the brightness. In this paper, we show the results of developed elements that create electron beam probe and the measured beam probe in various acceleration voltages by Faraday cup. These data are used to analysis and improve the performance of the system in the development.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.474-479
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• 1998

In this paper, we present a mathematical model of the piezoelectric pump and its application to the automobile brake system. The piezoelectric pump consists of a multi-layered piezoelectric element a diaphragm, pumping values, resonant pipes and accumulators, and the maximum pumping power of 62W nab obtained in the previous experiments by using the piezoelectric element of 22mm diameter and 55.5mm length. A detailed mathematical model of the pump is derived here by considering the compressibility of the working oil, nonlinear characteristics of piezoelectric element, the time delay of pumping values' action and be on. The validity of the model is illustrated by comparing the experimental data and the simulation results. Using the mathematical model of the piezoelectric pump, a brake system for automobile disk brake is also simulated in this paper. The brake system consists of a piezoelectric pump as a power source, calipers and its piston to generate brake force, and a three position solenoid value to change the brake situation. It is shown that 15mm/sec of piston speed and 20kN of piston force are obtained by using the piezoelectric element of 33mm diameter and 55.5mm length.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.12
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• pp.1046-1052
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• 2016

For the safe driving of autonomous vehicles, accurate position estimation is required. Generally, position error must be less than 1m because of lane keeping. However, GPS positioning error is more than 1m. Therefore, we must correct this error and a map matching algorithm is generally used. Especially, road marking intensity map have been used in many studies. In previous work, 3D LIDAR with many vertical layers was used to generate a local intensity map. Because it can be obtained sufficient longitudinal information for map matching. However, it is expensive and sufficient road marking information cannot be obtained in rush hour situations. In this paper, we propose a localization algorithm using an accumulated intensity local map. An accumulated intensity local map can be generated with sufficient longitudinal information using 3D LIDAR with a few vertical layers. Using this algorithm, we can also obtain sufficient intensity information in rush hour situations. Thus, it is possible to increase the reliability of the map matching and get accurate position estimation result. In the experimental result, the lateral RMS position error is about 0.12m and the longitudinal RMS error is about 0.19m.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.5
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• pp.281-296
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• 2015

This paper describes a novel disaster evacuation system using embedded systems such as smart devices for crisis and emergency management. In indoor environments deployed with the Bluetooth Low Energy(BLE) beacons, smart devices detect their indoor positions from beacon messages and interact with Map Server(MS) and Route Server(RS) in the Internet over the LTE and/or Wi-Fi functions. The MS and RS generate an optimal path to the nearest emergency exit based on a novel graph generation method for less route computation, called the Disaster Evacuation Graph(DEG), for each smart device. The DEG also enables efficient processing of some constraints in the computation of route, such as load balancing in situation of different capacities of paths or exits. All data interfaces among three system components, the MS, RS, smart devices, have been defined for modular implementation of our disaster evacuation system. Our experimental system has been deployed and tested in our building thoroughly and gives a good evidence that the modular design of the system and a novel approach to compute emergency route based on the DEG is competitive and viable.

• Management & Information Systems Review
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• v.4
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• pp.469-500
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• 2000

Over the past decades the concept of Third-Party Logistics(TPL) has generated considerable interest in American and European industries. It involves outsourcing logistics activities that have traditionally been performed within an organization. The functions performed by the third-party logistics can encompass the entire logistics process or, more commonly, selected activities with that process. Increasing corporate emphasis on such concepts as reengineering and supply chain management has led many companies to consider the use of such third-party logistics. This study examines the possibility of applying existing American research of the third-party logistics to Korean companies and investigates the criteria for the use of third-party logistics in Korea. To design the model and generate the hypotheses, this study conducted a comprehensive literature survey on the third-party logistics. To test the hypotheses, this study collected data from 229 companies from the public companies in Korea through a questionnaire survey and conducted descriptive analysis, correlation analysis, factor analysis, and multiple regression analysis using the SPSS for Windows Ver. 7.5 package. This study is hoped that it may contribute to the understanding and introducing of the third-party logistics in the fields of the firms. But there were some restrictions that the respondents were not covered all kinds of firms. These and other major findings from this study imply that existing American studies may be applicable the Korean companies and that this study may complement the deficiencies of the existing studies. Thus, the summary of the literature review, the research model and hypotheses, and empirical findings in this study will provide useful ideas for future research and deep insights for successful logistics management.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.177-187
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• 2003

Active galactic nuclei (AGNs) are distant, powerful sources of radiation over the entire electromagnetic spectrum, from radio waves to gamma-rays. There is much evidence that they are driven by gravitational accretion of stars, dust, and gas, onto central massive black holes (MBHs) imprisoning anywhere from $\~$1 to $\~$10,000 million solar masses; such objects may naturally form in the centers of galaxies during their normal dynamical evolution. A small fraction of AGNs, of the radio-loud type (RLAGNs), are somehow able to generate powerful synchrotron-emitting structures (cores, jets, lobes) with sizes ranging from pc to Mpc. A brief summary of AGN observations and theories is given, with an emphasis on RLAGNs. Preliminary results from the imaging of 10000 extragalactic radio sources observed in the MITVLA snapshot survey, and from a new analytic theory of the time-variable power output from Kerr black hole magnetospheres, are presented. To better understand the complex physical processes within the central engines of AGNs, it is important to confront the observations with theories, from the viewpoint of analyzing the time-variable behaviours of AGNs - which have been recorded over both 'short' human ($10^0-10^9\;s$) and 'long' cosmic ($10^{13} - 10^{17}\;s$) timescales. Some key ingredients of a basic mathematical formalism are outlined, which may help in building detailed Monte-Carlo models of evolving AGN populations; such numerical calculations should be potentially important tools for useful interpretation of the large amounts of statistical data now publicly available for both AGNs and RLAGNs.