• Journal of KSNVE
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• v.7 no.3
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• pp.511-519
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• 1997

For a number of years it has been known that flexural vibration in a beam and plate can be damped by the application of layer of damping (viscoelastic) material that is in turn constrained by a backing layer or foil. In this study, a quantitative analysis of damping of the sandwich beam has been performed by using impact test. The damping is characterized by the loss factor .etha. in which the damping is normalized by imaginary part of the complex bending stiffiness of the beam. Results show that the relative thickness of the sandwich beam gives more effect on the riatural-frequencies and loss factor than the variation of width does. It is also shown that the Ross-Kerwin-Ungar equation and impact test can be effectively used to identify the damping characteristic of the sandwich beam and viscoelastic material.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.228-234
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• 2002

The CO$_2$ laser beam irradiation strengthening of 35kgf/mm$_2$ grade steel sheet is investigated to reduce the weight of bumper beam. The increase of tensile strength is dominated by the number of fully penetrated melting lines. The optimal laser irradiation pattern is obtained by 3-point bending test of hat-type specimens. Laser should be irradiated not only on the center specimen densely in the width direction, but also on the edge densely in the longitudinal direction. Local laser strengthening may be effective for the weight reduction of automobile bumper beam.

• Architectural research
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• v.1 no.1
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• pp.55-61
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• 1999

In reinforced concrete design, structural member sizes and amount of reinforcing steel areas are usually selected based on the structural designers' experience. Most existing charts provided for the design of reinforced concrete structural members were developed mainly based on force equilibrium conditions and some serviceability criteria. Sections selected from these charts may not result in an economic solution in terms of material costs as well as construction costs. Practical design aids are developed and suggested in this study for the economical design of reinforced concrete beam under flexural loading. With the beam width fixed, the depth of a beam, positive steel areas and negative steel areas are found from Khun-Tucker necessary conditions with Lagrangian multipliers to minimize the sectional cost of a beam. The developed design aids might be useful in selecting optimum reinforced concrete beam sections. Theoretical derivations and use of the developed design aids are described in this paper.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3127-3135
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• 1994

An approach to the simultaneous optimal design of structure and control system for large free-free flexible beam is presented. The flexible beam is modeled by the finite element method. And the reduced model of small degree of freedom is constructed by use of modal analysis. The tapered beam is considered so that the number of design variables is not dependent on the increasing number of finite elements. The width of several points of tapered beam and control gain are taken as design variables. The shape of beam and control gain are optimized simultaneously for the minimum weight of total structure including control system subject to the constraints of the magnitude of displacement of beam. It is shown that the simultaneous optimal design of structure and control systems is indeed useful.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.496-502
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• 2001

We generated a nondiffracting beam and investigated its intensity profile on propagation. We first obtained an annular output beam from Nd:YAG laser with a negative branch unstable ring resonator and, using a 1m focal length lens, we generated a Bessel- Gauss beam. The inner radius of the annular output beam was 2.57 mm and the ring width was 0.145 mm. The intensity profile of the nondiffracting beam did not show any appreciable diffraction up to 33 m distance from the focal lens. This result was compared with the theory.

• International journal of advanced smart convergence
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• v.13 no.3
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• pp.59-65
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• 2024

Non-orthogonal multiple access (NOMA) is a technique that forms a NOMA group composed of two or more users and transmits the superimposed signals of all users in the group through a single beam. In case all users in a NOMA group fall within the main lobe, a high data rate is guaranteed. However, in case not all users in the group fall within the main lobe due to the narrow beam width, the sum data rate decreases, and the data rate disparity between users inside and outside the main lobe widens significantly, leading to reduced fairness. On the other hand, an excessively wide beam might reduce the channel gain which lowers the sum data rate. This paper discusses the effects of beam configuration on the throughput and fairness performances of the NOMA system in the millimeter wave channel environments with simulation results for various channel parameters including the number of antennas and beam directions.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.135-143
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• 1998

The wheel load distribution width for lane load is not specified in current Korea bridge design code(KD code), not like in current AASHTO and AASHTO LRFD specifications which specity it as twice of wheel load distribution width for wheel load. In this study, the wheel load distribution width in continuous reinforced concrete slab bridge is investigated. The major variables affecting the wheel load distribution of a reinforced concrete continuous slab bridge are the span length, bridge width, existence edge beam and boundary condition. From a series of comprehensive parametric study on each variable, the formula for wheel load distribution in continuous reinforced concrete slab bridge is proposed from the nonlinear regression analysis of finite element analysis results. The proposed formulas can be used efficiently in the accurate design of continuous reinforced concrete slab bridges.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.217-217
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with 60 ~ 100 ${\mu}m$ lengths, $10\;{\mu}m$ width, and $0.4\;{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the 60 ~ 100 ${\mu}m$ long cantilevers, the fundamental frequency appeared at 373.4 ~ 908.1 kHz. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• Structural Engineering and Mechanics
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• v.4 no.3
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• pp.243-255
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• 1996

This paper presents a model of a layered, delaminated composite beam. The beam is modelled by beam finite elements, and the delamination is modelled by additional boundary conditions. In the present study, the laminated beam contains only one delaminated region through the thickness direction which extends to the full width of the beam. It is also assumed that the delamination is open. The influence of the delamination length and position upon changes in the bending natural frequencies of the composite laminated cantilever beam is investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.303-306
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with $60{\sim}100{\mu}m$ lengths, $10{\mu}m$ width, and $0.4{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the $60{\sim}100{\mu}m$ long cantilevers, the fundamental frequency appeared at $373.4{\sim}908.1\;kHz$. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.