• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.70-75
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• 2010

The aim of this study is to evaluate the axial residual stress in multi-pass drawn high carbon steel wire by using FE analysis and XRD. When FE analysis is applied to evaluate the residual stress in drawn wire of multi-pass drawing process, obtaining the reliable effective stress-strain curve at high strain is very important. In this study, a model, which can express the reliable effective stress-strain curve at high strain, is introduced based on the Bridgman correction and tensile test for multi-pass drawn high carbon steel wires. By using the introduced model, FE analysis was carried out to evaluate the axial residual stress in the drawn wires. Finally, the effectiveness of the FE analysis with the introduced stress-strain relation was verified by the measurement of residual stress in the drawn wires through XRD. As a result, the evaluated residual stress of FE analysis shows good agreement with the measured residual stress.

• Current Photovoltaic Research
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• v.8 no.4
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• pp.124-128
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• 2020

Output power of photovoltaic (PV) modules installed outdoors decreases every year due to environmental conditions such as temperature, humidity, and ultraviolet irradiations. In order to promote the installation of PV modules, the reliability must be guaranteed. One of the important factors affecting reliability is intermetallic compounds (IMC) layer formed in ribbon solder joint. For this reason, various studies on soldering properties between the ribbon and cell have been performed to solve the reliability deterioration caused by excessive growth of the IMC layer. However, the IMC layer of the PV module interconnected by multi-wires has been studied less than using the ribbon. It is necessary to study soldering characteristics of the multi-wire module for improvement of its reliability. In this study, we analyzed the growth of IMC layer of the PV module with multi-wire and the degradation of output power through damp-heat test. The fabricated modules were exposed to damp-heat conditions (85 ºC and 85 % relative humidity) for 1000 hours and the output powers of the modules before and after the damp-heat test were measured. Then, the process of dissolving ethylene vinyl acetate (EVA) as an encapsulant of the modules was performed to observe the IMC layer. The growth of IMC layer was evaluated using OM and FE-SEM for cross-sectional analysis and EDS for elemental mapping. Based on these results, we investigated the correlation between the IMC layer and output power of modules.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.320-326
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• 2011

Flat rolling of wire is an industrial process used to manufacture electrical flat wire, medical catheters, springs, piston segments and automobile parts, among other products. In a multi-step wire flat rolling process, a wire with a circular crosssection is rolled at room temperature between two flat rolls in several passes to achieve the desired thickness to width ratio. To manufacture a flat wire with a homogeneous microstructure, mechanical and metallurgical properties with an appropriate pass schedule, this study investigated the effect of each pass schedule (1stand ~ 4stand) on the microstructures, mechanical properties and widths of cold rolled high carbon steel wires using four-pass flat rolling process. The evolutions of the microstructures and mechanical properties of the widths of cold rolled wires during three different pass schedules of the flat rolling process of high carbon wires were investigated, and the results were compared with those for a conventional eight-pass schedule. In the width of cold rolled wires, three different pass schedules are clearly distinguished and discussed. The experimental conditions were the same rolling speed, rolling force, roll size, tensile strength of the material and friction coefficient. The experimental results showed that the four-pass flat cold rolling process was feasible for production of designed wire without cracks when appropriate pass schedules were applied.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.4
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• pp.524-533
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• 2017

This paper presents a novel reset scheme for mm-scale sensing systems with stringent volume and area constraints. In such systems, multi-layer structure is required to maximize the silicon area per volume and minimize the system size. The multi-layer structure requires wirebonding connections for power delivery and communication among layers, but the area overhead for wirebonding pads can be significant. The proposed reset scheme exploits already existing power wires and thus does not require additional wires for system-wide reset operation. To implement the proposed reset scheme, a power management unit is designed to impose reset condition, and a reset detector is designed to interpret the reset condition indicated by the power wires. The reset detector uses a coupling capacitor for the initial power-up and a feedback path to hold the developed supply voltage. The prototype reset detector is fabricated in a $180-{\mu}m$ CMOS process, and the measurement results with the prototype mm-scale system confirmed robust reset operation over a wide range of temperatures and voltages.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.7 s.196
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• pp.98-105
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• 2007

In modern industries, materials are required that possess multi-functional properties and at the same time flexibility in their shapes with structural stability. The major technology realizing this requirement consists of thinning metal wires and laying them with stable contact nodes. This research has dealt with a new method to manufacture thin wires by drawing without applying dies, but with introducing enforced necking, which enables to process multi-ends. Based on the new method, the process dynamics was modelled and its steady-state characteristics were analyzed. Results showed that the profiles of the material velocity in the drawing zone increased with a downward convex shape, while the cross-sectional area decreased with the shape of upward convex. The microwave heating turned out to be effective in wire drawing, but dependent on the input feeding direction. The variation in the diameters of the drawn wires was negatively affected by increasing the drawing ratio.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.245-252
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• 2007

Since the new millennium, truss PCMs(Periodic Cellular Metals) have drawn attention because of their superior specific stiffness, strength and multi-functionality. Prior studies have focused on the structural design and optimization. Kagome truss PCM has been proved to have the higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. In this study, we introduce a new idea to fabricate multi-layered Kagome truss PCM from continuous wires which can gain high strength as in piano wires and can be controlled to be defect free owing to drawing process. The relative density, the stiffness and the strength under bending and compressive load are estimated through elementary mechanics and compared with the results from experiments and FEA. The failure mechanisms are analyzed, and also mechanical performance and production are discussed.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1001-1004
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• 1998

In this paper, we present a gridless router for MCMs. Instead of the commonly employed grid a set of comer stitched tiles are used as a routing framework. The router routes variablewidth pins with wires of any width. It also a allows arbitrary location of terminals, wires, and vias. It performs faster than most grid-based MCM routers and produces the routing results which are comparable to their achievements.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.186-189
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• 2010

Reflection(R($\omega$)), transmission(T($\omega$)) and loss(L($\omega$)) characteristics of multi-layer metamaterials are investigated experimentally in free space with the incident EM waves perpendicular to the substrate plane. The sample is made of split-ring resonators(SRRs) and wires which are the typical model of metamaterials. The R($\omega$) and T($\omega$) of multi-layer metamaterials have been calculated from the measured S-parameters. In this paper, we got the impedance-matched result according to the curves of R($\omega$), meanwhile the T($\omega$) decreased with increasing number of layers. At last, we attained the result that the L($\omega$) gets to nearly 98% around 8 GHz, with R($\omega$)=T($\omega$)=0. The design presented in this paper achieves experimented loss near unity.

• Smart Structures and Systems
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• v.22 no.4
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• pp.481-493
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• 2018

Ultrasonic guided waves have attracted increasing attention for non-destructive testing (NDT) and structural health monitoring (SHM) of bridge cables. They offer advantages like single measurement, wide coverage of acoustical field, and long-range propagation capability. To design defect detection systems, it is essential to understand how guided waves propagate in cables and how to select the optimal excitation frequency and mode. However, certain cable characteristics such as multiple wires, anchorage, and polyethylene (PE) sheath increase the complexity in analyzing the guided wave propagation. In this study, guided wave modes for multi-wire bridge cables are identified by using a semi-analytical finite element (SAFE) technique to obtain relevant dispersion curves. Numerical results indicated that the number of guided wave modes increases, the length of the flat region with a low frequency of L(0,1) mode becomes shorter, and the cutoff frequency for high order longitudinal wave modes becomes lower, as the number of steel wires in a cable increases. These findings were used in design of transducers for defect detection and selection of the optimal wave mode and frequency for subsequent experiments. A magnetostrictive transducer system was used to excite and detect the guided waves. The applicability of the proposed approach for detecting and locating wire breakages was demonstrated for a cable with 37 wires. The present ultrasonic guided wave method has been found to be very responsive to the number of brokenwires and is thus capable of detecting defects with varying sizes.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.2
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• pp.9-18
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• 1991

Among the many maunfactured processes of producing multi filamentary composites, in situ process is widely used owing tv its simplicity and easyness of mass production. In this study, the mechanical and electromagnetic properties of Cu-Fe composite materials was investigated. The tensile strength of the Cu-Fe wires increased as the Fe content and reduction ratio were increased. The Cu-30 wt%Fe composites had the best properties in terms of figure merits compared to the other Cu-Fe composites made in this study or the commercially manufactured 6/1 ACSR cables of Cu cable. The coercivity was decreased by increasing Fe content, but the squareness was increased greatly. As increasing reduction ratio, the coercivity and squareness increased up to the maximum points, and then decreased. For example, the maximum values were obtained at $0.09mm{\phi}$ for Cu-30 wt%Fe composites and at $0.066mm{\phi}$ for Cu-45 wt%Fe composites. The magnetic property of Cu-Fe wires produced by precipitation treatment was higher than that of Cu-Fe wires produced by thermomechanical treatment. By annealing Cu-Fe wires after drawing process, the coercivity, remanence and squareness were improved.