• Journal of Practical Engineering Education
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• v.14 no.1
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• pp.119-125
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• 2022

Materials used for education are materials such as SM20C, Al6061, and acrylic. SM20C materials are carbon steel and are often used in certification tests and functional competitions, but are also widely used in industrial sites. The Al6061 material is said to be a material that has lower hardness and stronger flexibility than carbon steel, so it is a material that generates a lot of compositional selection of tools. If students are taught practical training using acrylic materials, vibration occurs due to excessive cutting in some parts and damage to the tool occurs. In this process, we examine to what extent the impact on the 2NC head, which is a five-axis equipment, can affect precision control. The weakest part of the five-axis equipment can be said to be the weakest part of the head that controls the AC axis. When the accuracy and cumulative tolerance of this part occur, the accuracy of all products decreases. Therefore, the core part of the 2NC head, the spindle housing, was carried out using an Al7075 T6 (Alcoa, USA) material. In the process of vibration and cutting applied to this material, the analysis was conducted to find out the value applied to the finite element analysis under extreme conditions. It is hoped that this analysis data will help students see and understand the structure of 5-axis machining rather than 5-axis cutting.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.69-80
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• 2017

In or To use, manage, and preserve sustainable water resources for the current and future generations amid the threat of abnormal climate, it is necessary to establish a smart water grid system, the next-generation intelligent water management system. In this study, sensors, which make use of the five senses to watch, listen, and detect machine vibration, bearing temperature, machine operation sounds, current, voltage, and other symptoms that cannot be verified when the irrigation facilities are running, are used to establish various decision-making criteria appropriate to on-site situations. Based on such criteria, the unmanned conditions in the facilities were verified and analyzed. Existing technologies require on-site workers to check any defects caused by overloading of machines, which is the biggest constraining factor in the application of an unmanned control system for irrigation facilities. The new technology proposed in this study, on the other hand, allows for the unmanned analysis of the existence of machine vibration. This controls the decision-making process of any defect based on the analysis results, and necessary measures are taken automatically, resulting in improved reliability of the unmanned automation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.667-671
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• 2012

Low frequency noises (up to about 200 Hz) mainly occur due to particular modes, resulting in booming noises, and in general the solutions may be found based on mode controls where conventional methods such as FEM can be used. However, at higher frequencies between 0.3~ 1 kHz, as the number of modes rapidly increase, radiation characteristics from structures, performances of damping sheets and sound packages may be more crucial rather than particular modes, and consequently the conventional FEM may be less practical in dealing with this kinds of structure-borne problems. In this context, so-called 'mid-frequency simulation model' based on FE-SEA hybrid method is studied and validated. Energy Transmission loss (i.e. air borne noise) is also studied. A dash panel component is chosen for this study, which is an important path that transfers both structure-borne and air borne energies into the cavity. Design modifications including structural modifications, attachment of damping sheets and application of different sound packages are taken into account and the corresponding noise characteristics are experimentally identified. It is found that the dash member behaves as a noise path. The damping sheet or sound packages have similar influences on both sound radiation and transmission loss. The comparison between experiments and simulations shows that this model could be used to predict the tendency of noise improvement.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.346-349
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• 2013

This paper describes a triple-input energy harvesting circuit using solar, vibration and thermoelectric energy with MPPT(Maximum Power Point Tracking) control. The designed circuit employs MPPT control to harvest maximum power available from a solar cell, PZT vibration element and thermoelectric generator. The harvested energies are simultaneously combined and stored in a storage capacitor, and then managed and transferred into a sensor node by PMU(Power Management Unit). MPPT controls are implemented using the linear relation between the open-circuit voltage of an energy transducer and its MPP(Maximum Power Point) voltage. The proposed circuit is designed in a CMOS 0.18um technology and its functionality has been verified through extensive simulations. The designed chip occupies $945{\mu}m{\times}995{\mu}m$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.161-168
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• 2008

In this paper, a tuned liquid mass damper(TLMD) was proposed and experimentally investigated on its control performance, which can control bi-axial responses of building structures by using only one device. The proposed TLMD controls the structural response in a specific one direction by using a liquid sloshing of TLCD. Also, the TLMD reduces the response of structures in the other orthogonal direction by behaving as a TMD that uses mass of the container itself and liquid within container of TLCD installed on linear motion guides. Force-vibration tests on a real-sized structure installed with the TLMD were performed to verify its independent behavior in two orthogonal directions. Test results showed that the responses of a structure were considerably reduced by using the proposed TLMD and its usefulness for structural control in two orthogonal directions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.755-762
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• 2004

In our country, when the replacement for individual components of equipment in nuclear power plants is required, establishment of individual criteria i.e. Required Response Spectra(RRS) of seismic test/analysis for the component is very difficult because of the absence of Test Response Spectra(TRS) for the individual component to be replaced, from the existing qualification documents. In this case, it is required to perform the structural analysis for the nuclear equipment including the components to be replaced. After the structural analysis, Analysis Response Spectra(ARS) at the point of the component shall be generated and used for seismic test of the component. However, as of today, no standard program authorized for the response spectra generation by using the structural analysis exists in korea. Because of above reason, the STAR-Egs computer program was developed by using the method which calculates directly the expected response spectrum(frequency vs. acceleration type) of the selected points in the nuclear equipment with input spectrum(Required Response Spectra, RRS), based on the dynamic characteristics of the Finite Element(FE) model that is equivalent to the nuclear equipment. The STAR-Egs controls ANSYS/I-DEAS commercial software and automatically extract modal parameters of the FE model. The STAR-Egs calculates response spectrum using the established algorithm based on the extracted modal parameters, too. Reliance on the calculation result of the STAR-Egs was verified through comparison output with the result of MATLAB commercial software based on the identical algorithm. Moreover, actual seismic testing was performed as per IEEE344-1987 for the purpose of program verification by comparison of the FE analysis results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.923-934
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• 1987

A flexible one-link robotic manipulator is modelled as a rotating cantilever beam with a hub and tip mass. An active control law is developed with consideration of the distributed flexibility of the arm. Equation of motion is derived by Hamilton's principle and, for modal control, represented as state variable form using Galerkin's mode summation method. Feedback coefficients are chosen to minimize the linear quadratic performance index(PI). To reconstruct the complete state vector from the measurements, an observer is proposed. In order to suppress vibration of the manipulator arm to desirable extent and to obtain accuracy of the positioning, weighting factor of input in PI is adjusted. Spillover effect due to the controller which controls several important modes is examined. Experiment is also performed to validate the theoretical analysis.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.1
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• pp.90-96
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• 2011

The shock absorber base assembly is one of the parts in the shock absorber equipment that controls the vehicle movement. It absorbs the shock and vibration to guarantee riding stability and comfort. It demands strength, reliability and strict airtightness of the welded section because the shock absorber base assembly is a container which resists pressure and needs durability by being filled with gas and oil. However, the current engineering needs a lot of production time, has a high cost and shows a low production rate. These problem due to the eight production processes, four of which are spot welding, reinforcement welding like metal active welding (MAG), prior process of the base assembly cap and tube for precision and pressing. We will analyze the manufacturing processes of the base assembly and suggest an improved manufacturing method that uses frictional welding. The results will show that the new method of the frictional welding is better than the previous welding technique. Through the use of this concept of frictional welding, the welding conjunction will be strengthened, measurements will be more precise, and the cost and the number of processes will be reduced.

• Structural Engineering and Mechanics
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• v.30 no.1
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• pp.1-20
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• 2008

The dynamic characteristics of the passive, semi-active, and active tuned-liquidcolumn dampers (or TLCDs) are studied in this paper. The design of the latter two are based on the first one. A water-head difference (or simply named as water head in this paper) of a passive TLCD is pre-set to form the so-called semi-active one in this paper. The pre-set of water head is released at a proper time instant during an earthquake excitation in order to enhance the vibration reduction of a structure. Two propellers are installed along a shaft inside and at the center of a passive TLCD to form an active one. These two propellers are driven by a servo-motor controlled by a computer to provide the control force. The seismic responses of a five-story shear building with a passive, semiactive, and active TLCDs are computed for demonstration and discussion. The responses of this building with a tuned mass damper (or TMD) are also included for comparison. The small-scale shaking-table experiments of a pendulum-like system with a passive or active TLCD to harmonic and seismic excitations are conducted for verification.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.12
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• pp.671-678
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• 1999

In this study, it has been aimed that the accuracy of position control be increased by microstep drive to the 2 phase 8 pole HB type prototype of linear pulse motor of which winding are applied sine wave current and the vibration and noise in the lower speed region be decreased. The fixed off-time method which controls the exciting current bandwidth, was applied to the microstep current controller. When the LPM was driven 1/8 microstep its accuracy of position was 0.109[mm] (=tooth pitch 3.5[mm] ). Also, the elimination method of harmonics in the static thrust force is proposed. It was confirmed that the position error range of the prototype LPM was $\pm$0.2[mm].