• Composites Research
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• v.33 no.1
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• pp.13-18
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• 2020

Recently, the fire rescue truck in problem proceed research it for the fast works action and for pass the small road. So we were research for weight reduction. In this study, the (NO. 5) fifth boom of the fire rescue truck have 288 mm(W) × 299 mm(D) × 3,691 mm(L) with a maximum load of 876 kg and the thickness of 3 mm of the Steel Boom. This changing of Steel (STRENX960) to CFRP was weave Carbon Fiber NCF (±45°, 2axis) and then it make the NCF Prepreg. This process was designed based on structural analysis, the effects of NCF Prepreg (±45°) on torsion were identified, and the optimal design was made with Stacking Pattern (b). Stack patterns were optimized for levels equal or higher than existing Steel Boom and CFRP Boom stacked in the UD direction, and finally, the lightening effect on weight of approximately 49.6% of the steel was identified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.773-780
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• 2015

Traditionally, additive manufacturing (AM) technology has been used to fabricate prototypes in the early development phase of a product. This technology is being applied to release manufacturing of a product because of its low cost and fast fabrication. AM technology is a process of joining materials to fabricate a product from the 3D CAD data in a layer-by-layer manner. The orientation of a layer during manufacturing can affect the mechanical properties of the product because of its anisotropy. In this paper, tensile testing of polymer-based specimens were built with a typical AM process (FDM, PolyJet and SLA) to study the mechanical properties of the AM materials. The ASTM D 638 tensile testing standard was followed for building the specimens. The mechanical properties of the specimens were determined on the basis of stress-strain curves formed by tensile tests. In addition, the fracture surfaces of the specimens were observed by SEM to analyze the results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.31-36
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• 2011

This paper investigates the ESD robustness of the stacked output driver with a 0.13um CMOS process. To represent an actual I/O system, we implemented stacked output driver circuits with pre-drivers and a rail-based power clamp. We implemented eight kinds of circuits varying pre-driver input connections and stacked driver size. The test circuits are examined with TLP measurements. It is shown that breakdown current and voltage can be increased by connecting the pre-driver input to a power supply and using stacked devices of a similar size. Based on the test results, design guideline is suggested to improve ESD robustness of the stacked output drivers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.37-42
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• 2012

LIFT (laser-induced forward transfer) is an advanced laser processing method used for selectively transferring micron-sized objects. In our study, this process was applied in order to deposit solder balls in microsystem packaging processes for electronics. Locally melted solder paste could be transferred to a rigid substrate using laser pulses. A thin glass plate with a solder cream layer was used as a donor film, and an IR laser pulse (wavelength = 1070 nm) was used to transfer a micron-sized solder ball to the receptor. Mass balance and energy balance were applied to analyze the shape and temperature profiles of the solder paste drops. The transferred solder bumps had measured diameters of 30-40 ${\mu}m$ and thicknesses of 50 ${\mu}m$ in our experiment. The limits and applications of this method are also presented.

• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.413-423
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• 2015

Exterior Insulation and Finishing System(EIFS) is recognized as a promising alternative for energy reduction as energy reduction ratio of apartment is to be increased from 40% to 60% in 2017. However, EIFS is not actively applied to apartment because additional construction costs and duration are required for the current existing construction method of EIFS. Therefore, this study proposes a conceptual framework for concurrent construction method of EIFS which can reduce construction costs and duration by working sequentially from frame work to exterior insulation finishing work, and then verify the method's feasibility by analyzing a case study. It has been proven from the analysis that concurrent construction method of EIFS reduces 6.7% of construction duration and 13% of construction costs compared with the conventional exiting method. The proposed method is expected to contribute to invigorated application of EIFS to apartment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1542-1548
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• 2009

This paper describes a size-reduced Wilkinson power divider using substrate integrated artificial dielectric(SIAD). SIAD transmission lines have increased effective refractive index, so the line width and length are reduced from those of standard transmission lines. Therefore the "size-reduction effect" is achieved if SIAD lines are applied to high frequency circuits. An efficient simulation method is proposed for SIAD lines which have an enormous number of via-holes. A 2GHz Wilkinson power divider is designed and measured using SIAD transmission line as an example of application. The size of the fabricated divider is reduced by 32% due to the increased effective refractive index of SIAD, while the performances are maintained similarly.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.237-245
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• 2003

Since the velocity is dependent on the fiber orientation in anisotropic composites, the application of traditional acoustic emission (AE) source location techniques based on the constant velocity to composite structures has been practically impossible. The anisotropy makes the source location procedure complicated and deteriorates the accuracy of the location. In this study, we have divided the region of interest(ROI) into a set of finite elements, taken each element as a virtual source, and calculated the arrival time differences between sensors by using the velocities at every degree from 0 to 90. The calculated and the experimentally measured values of the arrival time difference aye then compared to minimize the location error. The results from two different materials, namely AA6061-T6 and CFRP(uni-directional; UD, $[0]_{32}4$) laminate confirmed the practical usefulness of the proposed method.

• Composites Research
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• v.19 no.1
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• pp.1-8
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• 2006

Prediction of damage caused by low-velocity impact in laminated composite plate is an important problem faced by designers using composites. Not only the inplane stresses but also the interlaminar normal and shear stresses playa role in estimating the damage caused. But it is well known that the conventional approach based on the homogenization has the limit in description of damage. The work reported here is an effort in getting better predictions of dynamic behavior and damage in composite plate using DNS approach. In the DNS model, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. In the view of microscopic mechanics with DNS model, interlaminar stress behaviors in the inside of composite materials are investigated and compared with the results of the homogenized model which has been used in the conventional approach to impact analysis. Also the multiscale model based on DNS concept is developed in order to enhance the effectiveness of impact analysis, and we present the results of multiscale analysis considering micro and macro structures simultaneously.

• Composites Research
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• v.19 no.3
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• pp.23-28
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• 2006

Carbon nanotubes reinforced copper matrix laminated nanocomposites were developed and the mechanical properties were evaluated by using micro-tensile testing system. Sandwich-type laminated structure constituted with carbon nanotube layers as a reinforcement and electroplated copper matrix were fabricated by a new processing approach based on selective dip-coating of carbon nanotubes. The mechanical properties of nanocomposites were improved due to an enhanced load sharing capacity of carbon nanotubes homogeneously distributed within the in-plane direction, as well as a bridging effect of carbon nanotubes along the out-of-plane direction between the upper and lower matrices. The universality of the layering approach is applicable to a wide range of functional materials, and here we demonstrate its potential use in reinforcing composite materials.

• Composites Research
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• v.36 no.2
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• pp.117-125
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• 2023

This paper proposes a new finite element formulation based on enhanced first-order shear deformation theory including the transverse normal strain effect via the mixed formulation (EFSDTM-TN) for the effective thermo-mechanical analysis of laminated composite structures. The main objective of the EFSDTM-TN is to provide an accurate and efficient solution in describing the thermo-mechanical behavior of laminated composite structures by systematically establishing the relationship between two independent fields (displacement and transverse stress fields) via the mixed formulation. Another key feature is to consider the thermal strain effect without additional unknown variables by introducing a refined transverse displacement field. In the finite element formulation, an eight-node isoparametric plate element is newly developed to implement the advantage of the EFSDTM-TN. Numerical solutions for the thermo-mechanical behavior of laminated composite structures are compared with those available in the open literature to demonstrate the numerical performance of the proposed finite element model.