• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.753-756
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• 2005

Rapid prototyping (RP) technologies are mainly performed by layered manufacturing (LM) process which manufactures 3D physical objects by depositing 2D sections in a direction. Thus, deformations are apt to occur in overhanging area of the RP processed part. Also, excessive adhesion between part and platform of the RP apparatus is generated. In order to prevent these problems, most of the RP technologies adopt support structure. Main element to support a part in the support structure is strand. In actual field, however, the number of strand is determined by the software operating reference guide or RP system operator's experience. In this paper, a methodology to determine the optimal strand spacing is presented through experiments and measurements for the SL part deformation by change of strand spacing and part weight in the support structure of the stereolithography.

• Wind and Structures
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• v.17 no.6
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• pp.671-680
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• 2013

Static aeroelastic is investigated in a wind turbine blade. Imposed to different loadings, the very long and flexible structures of blades experience some changes in its preliminary geometry. This results in variations of aerodynamic loadings. An iterative approach is developed to study the interactions between structure and aerodynamics evaluating variations in induced stresses in presence of aeroelasticity phenomenon for a specific wind turbine blade. A 3D finite element model of the blade is constructed. Aerodynamic loading is applied to the model and deflected shape is extracted. Then, aerodynamic loadings are updated in accordance with the new geometry of the deflected blade. This process is repeated till the convergence is met. Different operational conditions consisting of stand-by, start-up, power production and normal shut-down events are investigated. It is revealed that stress components vary significantly in the event of power production at the rated wind speed; while it is less pronounced for the events of normal shut-down and stand-by.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.806-811
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• 2001

To develop design and evaluation technologies of automotive seat frames, structural analysis and fatigue tests have been performed. Under the back moment loading condition, the numerical simulation yielded the maximum stress over the yield strength at the side frame bracket. To measure the stresses under the test condition, strain gauges were attached on some weakest points of the side frames. the measured strains are in good agreements with the CAE results. On the other hand, fatigue tests have been performed using the side frame bracket specimens made of various welding types to estimate their durabilities. From the fatigue test results and the analysis ones, it was recommended that the welding position of the bracket should be moved upward.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1578-1585
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• 2018

This work investigates two different motor drive technologies, switched reluctance motor (SRM) and induction motor (IM). They are designed optimally to meet the desired performances for electric scooters. The comparison of both motors is described in terms of performances and material cost. With the similar constraint, induction motor performs slightly better than switched reluctance motor. But this must be traded-off with higher weight and cost. Both drive systems are, however, suitable for electric scooter application. Finally, the range simulations are conducted on a European urban driving cycle, ECE15 driving cycle and a more realistic cycle, Bangkok driving cycle. The e-scooter ranges are varied from 36 to 109 km depending on driving cycle, motor technology and number of passengers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1577-1586
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• 2018

The emergence of the Smart Grid is an integrated solution for the next generation power system that combines IT technology in the power system to create optimal energy utilization and various services. However, these convergence technologies (power systems and information communications) are not only improving the related technologies but also producing various problems especially exposure to cyber risk. In particular, the intelligent power grid has security vulnerabilities through real-time information sharing among various organically linked systems, and it is more complicated than the cyber risk problem in the existing IT field and is directly connected to national disaster accidents. Therefore, in order to construct and operate a more stable smart grid, this paper analyzes the system of power system control system in Korea, and proposes a cyber security element definition and a countermeasure establishment method of power monitoring & control systems based on security standards of smart grid (No. SPS-SGSF-121-1-1).

• Journal of Korea Multimedia Society
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• v.24 no.12
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• pp.1682-1692
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• 2021

Digital Twin, one of the core technologies of the Fourth Industrial Revolution, is attracting attention as a very suitable technology for disaster monitoring such as fires and earthquakes. In this paper, we implement a system equipped with UWB RTLS(Ultra-Wideband Real Time Location System), real-time remote control, and video streaming, which are element technologies for disaster monitoring digital twin. Since the proposed system structure is based on a cloud server, the actual location of the UWB indoor positioning-based client is transmitted to the user device in real time and stored on the cloud server for statistical and data analysis. In addition, we demonstrate through experiments that outliers occurs when the value of RSSI(Received Signal Strength Indicator) decreases due to communication collisions between UWB Tags, and propose an RSSI outlier correction algorithm to solve this problem.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.331-331
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• 2022

This research aims to developing new commercialization project of convergence agricultural industrial model. First, we established an inventory for the planning of convergence agricultural industrial model categorize the relevant factors identified, and then suggested three models which are the business profit model for convergence agriculture industrialization, the resource recycling complex and agricultural tourism model, and the smart agricultural model. Second, in order to investigate the feasibility of each industrial model, we investigated the willingness to participate in the project according to the pilot models such as related organizations and management agencies, and proposed the result of business feasibility analysis. Finally, we suggested the establishment of a demonstration complex through the systemization of element technologies at two models. The related systems and technologies was reviewed as a new commercialization plan through the modeling of convergence agricultural industrial types in main crop production complex presented, and set up mid- to long-term development direction. The results of this study can be applied to the design of convergence agricultural industrial model in main crop production complex.

• Journal of Korea Technology Innovation Society
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• v.19 no.3
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• pp.483-510
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• 2016

Disruptive technology is increasingly gaining attention by industries, standards development organizations (SDOs), academia, government and regulatory bodies due to its massive scope of impact on the incumbents and consumers. Companies that take a lead in new technologies intend to dominate the global market by making their technologies into an international standard. However, they tend to seek ways of by-passing the slow procedures of formal SDOs that often hinder prompt action in response to rapid changes in technology and market situations. In the area of disruptive technologies, there is a need to harmonize standardization efforts in formal SDOs for various companies and stakeholders to reap the benefits of technological development and diffusion of innovation. This paper examines the reasons why standardization is more active using market-based mechanisms than through formal SDOs for disruptive technologies. We conducted a Delphi study to investigate standardization strategies in the area of disruptive technologies. This research found that experts understood the core element of disruptive technologies as creating new markets and changing the competition basis in existing industries through the transformation of consumers' behavior. Based on these core characteristics, experts agreed that flexibility and speed are the most important factors for standardization. Results also show that the perception that standardization activities are not directly connected to companies' profit-making is the key barrier to links between research and companies' participation in standardization. This research provides implications for formal SDOs and policymakers.

• Structural Engineering and Mechanics
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• v.7 no.6
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• pp.589-599
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• 1999

This paper presents the development and applications of the software package JIFEX, a new finite element system which can be used for structural analysis and optimum design by the modern computer hardware and software technologies such as MS Windows95/NT and Pentium PC platforms. The complete system of JIFEX is programmed with $C/C^{++}$ language to make full use of advanced facilities of MS Windows95/NT. In the system, the finite element data pre-processing, based on the most popular CAD package AutoCAD (R13, R14), has been implemented, so that the finite element modeling could be integrated with geometric modeling of CAD. The system not only has interactive graphics facility for data post-processing, but also realizes the real-time computing visualization by means of the Dynamic Data Exchange (DDE) technique. Running on the Pentium computers, JIFEX can solve large-scale finite element analysis problems such as the ones with more than 60000 nodes in the finite element model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.139-142
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• 2007

This study focuses on the manufacturing process of a magnesium alloy impeller used for the fuel cell car using the hot forging technology. The impeller has the very complicated shape with sharply curved blade and thus generally produced by mechanical machining or casting process. However, since these technologies give the high manufacturing cost or poor mechanical properties, the forging technology is required to make the high-quality impeller with the lower manufacturing cost. In order for production of the impeller by forging technology, the parametric studies using finite element analyses were carried out to find the optimal perform shape of impeller made of magnesium alloy AZ 31 and finally die design was proposed based on the simulation results.