• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.107-110
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• 2003

The sheet metal shearing process is normally used in the precision elements such as semi-conductor components. In precision elements, burrs usually reduce the quality of machined parts and cause interference, jamming and misalignment during assembly procedures and because of their sharpness, they can be safety hazard to personnel. Furthermore, not only burrs are hard to predict and avoid, but also deburring, the process of removing burrs, is time-consuming and costly. In order to get the burr-free parts, therefore, we developed the precise burr measuring system using the laser. Using the X-Y precious table, we used vertical measuring method. Through the laser measurement system, we gain the minute analog signal, so this signal was amplified by the electric circuit. Finally, we gained the realtime burr data using A/D converter, PC. By introducing the novel laser measuring method which employing vertical measurement mechanism, we could get fast and precious burr data. Through the experiments, the accuracy of the developed system is proved. The burr height measured during the punching process can be used for automatic deburring and in-situ aligning.

• Interaction and multiscale mechanics
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• v.4 no.3
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• pp.187-206
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• 2011

Accurate estimations of pre-failure deformations and post-failure responses of geostructures require that the simulation tool possesses at least three main ingredients: 1) a constitutive model that is able to describe the macroscopic stress-strain-strength behavior of soils subjected to complex stress/strain paths over a wide range of confining pressures and densities, 2) an embedded length scale that accounts for the intricate physical phenomena that occur at the grain size scale in the soil, and 3) a computational platform that allows the analysis to be carried out beyond the development of an initially "contained" failure zone in the soil. In this paper, a two-scale micropolar plasticity model will be used to incorporate all these ingredients. The model is implemented in a finite element platform that is based on the mechanics of micropolar continua. Appropriate finite elements are developed to couple displacement, micro-rotations, and pore-water pressure in form of $u_n-{\phi}_m$ and $u_n-p_m-{\phi}_m$ (n > m) elements for analysis of dry and saturated soils. Performance of the model is assessed in a biaxial compression test on a slightly heterogeneous specimen of sand. The role of micropolar component of the model on capturing the post-failure response of the soil is demonstrated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1186-1190
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• 2003

In this paper, a valveless bubble-actuated fluid micropump was has been developed and its performance was tested. The valveless micropump consists of the lower plate, the middle plate, the upper plate and a resistive heater. The lower plate includes the nozzle-diffuser elements and the double-chamber. Nozzle-diffuser elements and a double-chamber are fabricated on the silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The lower plate also has inlet/outlet channels for fluid flow. The middle plate is made of glass and plays the role of the diaphragm. The chamber in the upper plate is filled with deionized water, and which contacts with the resistive heater. The resistive heater is patterned on a silicon substrate by Ti/Pt sputtering. Three plates and the resister heater are laminated by the aligner and bonded in the anodic bonder. Since the bubble is evaporated and condensed periodically in the chamber, the fluid flows from inlet to outlet with respect to the diffusion effect. In order to avoid backflow, the double chamber system is introduced. Analytical and experimental results show the validity of the developed double-chamber micropump.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.118-121
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• 2003

A new approach, using MEMS, for improving the performance of high efficiency amplifiers is proposed in this paper. The MEMS tuning element is described as a variable-length shorted CPW stub. Class-E amplifiers can be optimally tuned by these MEMS tuning elements because their operation varies with the impedance of the output tuning circuit. A MEMS tuning element was simulated using full-wave EM simulators to obtain its S-parameters. A Class-E amplifier with the MEMS was designed at 8GHz. The non-linear operation of this amplifier was simulated to explore the effect of the MEMS tuning. Comparing the initially designed amplifier without MEMS, the Power Added Efficiency (PAE) of the amplifier with MEMS is improved from 46.3% to 66.9%. For the amplifier with MEMS, the nonlinear simulation results are PAE = 66.90%, $\eta$(drain efficiency) = 75.89%, and $P_{out}$ = 23.37 dBm at 8 GHz. In this paper, the concept of the MEMS tuning element is successfully applied to the Class E amplifier designed with transmission lines.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.76-81
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• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• Ceramist
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• v.22 no.4
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• pp.357-367
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• 2019

Secondary Ion Mass Spectrometry(SIMS) is an analytical method that measures the distribution and concentration of elements or compounds by analyzing the mass of secondary ions released by irradiating ion beams with energy of hundreds eV to 20 keV on the sample surface. Unlike other similar analytical instruments, SIMS directly detect the elemental ions that constitute a sample, allowing you to accurately identify components and obtain concentration information in the depth direction. It is also a great feature for measuring isotopes and analyzing light elements, especially hydrogen. In particular, with the development of materials science, there is an increasing demand for trace concentration analysis and isotope measurements in the micro-regions of various materials. SIMS has a short history compared to other similar methods; nevertheless, SIMS is still advancing in hardware and is expected to contribute to the development of materials science through research and development of advanced analytical techniques.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.120-124
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• 2004

The protection performance and energy absorption capability are important for both MOAs for distribution lines and MOAs for high voltage systems, therefore the manufacturing technique of ZnO varistor elements with high ability against surge impacts is great important for high voltage systems. But until now ZnO varistors for low voltage class have been developed in Korea, ZnO varistors with the rate discharge current of 5, 10kA class for high voltage systems depend on an import from advanced countries, such as Japan or U.S.A, which have developed its in the late 1980s. So in the aspect of taking independent technique the development of ZnO varistors with the rate discharge current of 5, 10kA class for high voltage systems is important. In this research project ZnO varistor elements with diameters of 35mm and 70mm for the rate discharge current of 5, 10kA class for high voltage systems are manufactured, then various chemical composition and processing variables affected the electrical and the physical characteristics of these ZnO varistors are investigated.

• Earthquakes and Structures
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• v.8 no.1
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• pp.225-251
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• 2015

This paper presents a state-of-the-art review of the nonlinear modelling techniques available today for describing the structural behaviour of masonry infills and their interaction with frame structures subjected to in-plane loads. Following brief overviews on the behaviour of masonry-infilled frames and on the results of salient experimental tests, three modelling approaches are discussed in more detail: the micro, the meso and the macro approaches. The first model considers each of the infilled frame elements as separate: brick units, mortar, concrete and steel reinforcement; while the second approach treats the masonry infill as a continuum. The paper focuses on the third approach, which combines frame elements for the beams and columns with one or more equivalent struts for the infill panel. Due to its relative simplicity and computational speed, the macro model technique is more widely used today, though not all proposed models capture the main effects of the frame-infill interaction.

• Korean Institute of Interior Design Journal
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• v.22 no.6
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• pp.3-10
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• 2013

This study intends to clarify the key elements of designing low energy residential building construction by planning out residential construction in nature oriented designing method utilizing nearby environment and nature oriented energy from designing stage instead of construction of low energy residential building. Development of building technology is proportional to the development of technology that lasts already. However, what is no less important than the advancement of technology, it is the study of fundamental phenomena energy use in response to climate, reduction, such as recycling. It is possible in such a purpose, it is assumed that there is a need to study elements implementation plan in accordance with the climatic characteristics of the study. Method for controlling the condition solar radiation, sunshine, depending on the characteristics of the weather, by utilizing the convection phenomenon of nature, to maintain the air comfort in the interior space is the essence of eco-friendly construction and passive Property This is an important architectural elements to be aim. For through the analysis of this case, corresponding to the phenomenon of the features of the macro climate and micro climate due to climate change, a combination building blocks of classification placement of each, shape, structure, elevation, space, of the material appeared in various it was possible to know the construction characteristics were. As shown in each case, construction method to address climate change has been found to apply to a comprehensive analysis climatic characteristics of each region, in response to this, the construction of element each corresponding.

• Journal of the Korean Institute of Gas
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• v.24 no.5
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• pp.39-46
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• 2020

This paper is considered about centerline segregation of API 5L steel used in pipeline. Mn/S, Nb and C were known as segregated elements in the centerline of pipe thickness. The Mn usually was accompanied by S consisting of long viscous shape. Microstructure of the centerline was composed of MnS and Nb/Ti indusions including oxide. The segregation effect in centerline region was analyzed by OM, SEM/EDS and micro Vickers hardness. The Mn, Nb and C are retarded elements in transformation from austenite to ferrite or martensite. These elements could derive a bainitic microstructure as a kind of martensite, which is different from difference and element segregation between in matrix and centerline derived from steel melting and heat treatment.