• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.148-162
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• 1996

Bonding wires for high frequency device packaging have dominant parasitic inductances which limit the performance of semiconductor lasers. In this paper, the inductance sof bonding wires are claculated by the method of moments with incorporation of ohmic loss, and the wideband modulation characteristics are analyzed for ddifferent wire lengths and structures. We observed the modulation bandwidth for 1mm-length bonding wire lengths and structures. We observed the modulation bandwidth for 1mm-length bonding wire is 7 GHz wider than that for 2mm-length bonding wire. We also observed th estatic inductance calculation results in dispersive deviation of the parasitic inductance and the modulation characteristics from the wideband moment methods calculations. The angled bonding wire has much less parasitic inductance and improves the modulation bandwidth more than 6 GHz. This calculation resutls an be widely used for designing and packaging of high-speed semiconductor device.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1009-1011
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• 2009

Nano-structured conducting polypyrroles were synthesized in the ionic liquids (ILs) based on 1-alkyl-3-methylimidazolium family with tetrachloroferrate as an anion ($C_n\;mim\;[FeCl_4]\;with\;n\;=\;4,\;8,\;and\;12$). The polypyrrole nanostructures synthesized in ILs were formed as spherical shapes. For ionic liquids with alkyl side chain length $C_4,\;C_4\;mim\;[FeCl_4]$, the size of particles was ranged around 60-nm with a relatively narrow size distribution. As the length of alkyl chain increases, the particle sizes become larger and their distributions become wider. The self-assembled local structures in the solvent ionic liquids are likely to serve as templates of highly organized nano-structured polymers. The length of the alkyl chain in ionic liquids seems to affect these local structures.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.688-693
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• 2007

Most frame structures cannot be manufactured in a single-piece form. Ideally, when a structure is built up by assembling multi pieces, assembly at the joints should be rigidly performed enough to have almost full stiffness, which is difficult for practical reasons such as manufacturing cost and time. In this research, we aim to develop a manufacturability-oriented compliance-minimizing topology optimization using a ground beam model incorporating additional zero-length elastic joint elements. In the present formulation, design variables control the stiffness of zero-length elastic joints, not the stiffness of beams. Because joint stiffness values at the converged state can be utilized to select candidate assembly locations and their strengths, the technique is extremely useful to design multi-piece frame structures. An optimal layout is also extracted based on the stiffness values.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.694-697
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• 2003

Materials with specific micro-structural shape can exhibit negative Poisson's ratio. These materials can be widely used in structural applications because of their high resilience and resistance to impact. Specially, in the field of artificial implant's material, they have many potential applications. In this study, we investigated the Poisson's ratio and the ratio(E$_{e}$/E) of the elastic modulus of rotational particle structures based on structural design variables using finite element method. As the ratio of fibril's length to particle's diameter increased and the ratio of fibril's diameter to fibril's length decreased fixing the fibril's angle with 45 degree. the negative Poisson effect of rotational particle structures increased. The ratio of elastic modulus of these structures decreased with Poisson's ratio. The results show the reasonable values as compared with the previous analytical results.s.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.631-641
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• 1988

Computational procedures associated with finite element nonlinear analysis of plane frame structures were examined and new solution schemes were suggested. Element stiffness matrix was derived from the principle of virtual displacements. Geometric and material nonlinearities were considered in the formulation. Solution method was based upon the constant displacement length method in conjunction with the Newton-Raphson method. New solution schemes were introduced in determining the initial load increment and the sign of load increments and predicting the length of displacement increment to improve user convenience, efficiency and stability. Numerical experiments were performed for several typical problems and suggested schemes were found efficient and convenient for analyzing nonlinear frame structures.

• Architectural research
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• v.16 no.1
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• pp.27-35
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• 2014

Nonlinear analysis of reinforced concrete structures is carried out by using Reissner-Mindlin (RM) shell finite element (FE). The brittle inelastic characteristic of concrete material is represented by using the elasto-plastic fracture (EPF) material model with the relevant material models such as cracking criteria, shear transfer model and tension stiffening model. In particular, assumed strains are introduced in the formulation of the present shell FE in order to avoid element deficiencies inherited in the standard RM shell FE. The arc-length control method is used to trace the full load-displacement path of reinforced concrete structures. Finally, four benchmark tests are carried out and numerical results are provided as future reference solutions produced by RM shell element with assumed strains.

• Steel and Composite Structures
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• v.50 no.4
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• pp.459-474
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• 2024

Classical and first-order nonlocal beam theory are employed in this study to assess the thermal buckling performance of a small-scale conical, cylindrical beam. The beam is constructed from functionally graded (FG) porosity-dependent material and operates under the thermal conditions of the environment. Imperfections within the non-uniform beam vary along both the radius and length direction, with continuous changes in thickness throughout its length. The resulting structure is functionally graded in both radial and axial directions, forming a bi-directional configuration. Utilizing the energy method, governing equations are derived to analyze the thermal stability and buckling characteristics of a nanobeam across different beam theories. Subsequently, the extracted partial differential equations (PDE) are numerically solved using the generalized differential quadratic method (GDQM), providing a comprehensive exploration of the thermal behavior of the system. The detailed discussion of the produced results is based on various applied effective parameters, with a focus on the potential application of nanotubes in enhancing sports bikes performance.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.3-11
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• 2000

In pretensioned concrete structures, bond between prestressing steel and concrete is an essential component to ensure the integrity of a pretensioned member. The anchorage and development of the prestressing force depend exclusively on bond. The purpose of this study is to investigate the characteristics of bond and development length between pretensioned steel and concrete. To resolve the controversy over the adequacy of the current code provision on development length of prestressing strands, a comprehensive test program has been scheduled and twenty four rectangular prestressed concrete beams have been tested to determine development length. Major test variables include diameter of strands (12.7mm, 15.2mm) and concrete covers (3cm, 4cm, 5cm). The test results indicate that the development length based on the bond stress-slip relation. The proposed model can evaluate realistically the development length of pretensioned prestressed concrete members and can be the good basis for the future basis of code equations on development length of PSC members.

• Journal of Veterinary Clinics
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• v.21 no.2
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• pp.143-148
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• 2004

Serial ultrasonographic examination was daily performed on 12 pregnant Shih-tzu bitches from day 15 until parturition to determine the size of gestational structures. Gestational age was timed from the day of ovulation (day 0), which was estimated to occur when plasma progesterone concentration was first increased above 4.0 ng/ml. Extra-fetal structures were measurable from days 17 to 46. Outer uterine diameter increased from $9.9{\pm}0.4$ mm (Mean${\pm}$SD) at day 20 to $44.3{\pm}0.8$ mm at day 46 and inner chorionic cavity diameter increased from $7.2{\pm}0.2$ mm at day 17 to $36.9{\pm}1.5$mm at day 41. Length of chorionic cavity or zonary placenta increased from $6.6{\pm}0.4$ mm at day 21 to $46.4{\pm}0.9$ mm at day 44. Of the extra-fetal structures, inner chorionic cavity diameter was the most accurate for estimation of gestational age until day 38. Fetal structures were measurable from days 23 to 60. Crown-rump length increased from $3.9{\pm}0.3$ mm at day 23 to $55.2{\pm}3.3$ mm at day 41, fetal body diameter increased from $7.9{\pm}0.6$ mm at day 32 to $47.8{\pm}2$ mm at day 60, and fetal head diameter increased from $6.3{\pm}1.1$ mm at day 29 to $25.6{\pm}0.2$ mm at day 60. Of the fetal structures, fetal head diameter was the most accurate for estimation of gestational age from day 38 until day 60.

• Proceeding of KASS Symposium
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• 2005.05a
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• pp.89-98
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• 2005

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. Therefore membrane structures arc unstable structures initially. These soft structures need to be introduced initial stresses first because of its initial unstable state, and it happens large deformation phenomenon. To find the structural shape after large deformation caused by initial stiffness introduced, we need the shape analysis considering geometric nonlinearity in structural design procedure. In this study, we investigate into the stress concentration at crack of membrane structures. Therefore, using the nonlinear analysis program that NASS (Nonlinear Analysis for Spatial Structures) perform nonlinear analysis, and stress distribution for creak length investigate for using linear elastic fracture mechanics.