• Tunnel and Underground Space
• /
• v.20 no.3
• /
• pp.169-182
• /
• 2010

H-beam and lattice-girder are the two most commonly used steel supports in domestic tunnels. Reinforced Ribs of Shotcrete(R.R.S.), which is frequently used in Scandinavian countries, is yet to be employed in Korea despite its advantages over H-beam or lattice girder in terms of economy and constructional efficiency. In this study, laboratory tests were conducted to determine the most suitable design of R.R.S in domestic tunnels. Various configuration of steel reinforcements including double layer of steel rebars were tested and compared. Reinforcement with H-beam and lattice girder were also analyzed. Results of this study can be of great use in selecting and designing of tunnel supports when the tunnel is excavated by NATM or Norwegian Method of Tunnelling(NMT).

• Korean Journal of Optics and Photonics
• /
• v.33 no.6
• /
• pp.245-251
• /
• 2022

We have developed a multi-channel fiber laser for tiled laser beam combining and a laser output array system for multi-beam alignment. The fiber laser is a master oscillator power amplifier configuration that has a common seed, a preamplifier, and a 7-channel amplifier. The output power of each channel is more than 10 W. The laser output array system is a packed cylindrical configuration for a high fill-factor, and it has capabilities for collimation and tilt control with built-in PZT. Multi-beam alignment to a target is successfully implemented using PZT controlled with a stochastic parallel gradient descent (SPGD) algorithm.

• Advances in concrete construction
• /
• v.2 no.1
• /
• pp.57-75
• /
• 2014

This paper presents an analysis of the results of an experimental program on the performance of a novel configuration of a hybrid FRP-concrete beam. The beam section consists of a GFRP pultruded profile, a CFRP laminate, and a concrete block all wrapped up using filament winding. It was found that the thickness of the concrete block and the confinement by the filament-wound wrapping had a profound effect on the energy dissipation behaviour of the beam. Using a shear punching model, and comparing the predicted results with the experimental ones, it was found that beyond a given value of the concrete block thickness, the deformational behaviour of the beam shifts from brittle to ductile. It was also found that the filament-wound wrap had many benefits such as providing a composite action between the concrete block and the GFRP box, improving the stiffness of the beam, and most importantly, enhancing the load carrying ability through induced confinement of the concrete.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.147-150
• /
• 2001

In the present work, a linear static analysis is presented for thin-walled prismatic box-beams made of generally anisotropic materials. A mixed beam theory has been used to model and carry out the analysis. Three different constitutive relations are assessed into the beam formulation. Simple layup cases having symmetric or anti-symmetric configuration have been chosen and tested to clearly show the effects of elastic couplings of the beam. Both 2D and 3D finite element structural analysis using the MSC/NASTRAN has been performed to validate the current analytical results. Results show that appropriate assumptions for the constitutive equations are important and prerequisite for the accurate prediction of beam stiffness constants and also for the beam behavior.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.10 s.253
• /
• pp.1187-1193
• /
• 2006

Traditionally, the continuum-based topology optimization methods employing the SIMP technique have been used to design compliant mechanisms. Although they have been successful, the optimized mechanisms by the methods are usually difficult to manufacture because of their geometrical complexities. The objective of this study is to develop a topology optimization method that can produce easy-to-fabricate mechanism structure. The proposed method is a ground beam method where beam connectivity is controlled by the beam joint stiffness. In this approach, beam joint stiffness determines the mechanism configuration. Because b the ground structure beams have uniform thicknesses varying only discretely, the resulting mechanism topologies become easily manufacturable.

• Steel and Composite Structures
• /
• v.43 no.3
• /
• pp.311-325
• /
• 2022

For multi-story structural systems, Korean steel industry has fostered development of a steel-concrete composite beam. Configuration of the composite beam is characterized by steel angle shear connectors welded to a U-shaped cold formed-steel beam. Effects of shear connector orientation and spacing were studied to evaluate current application of the angle shear connector design equation in AC495. For the study, interfacial shear resistance behavior was investigated by conducting 24 push-out tests and attuned using unreinforced push-out specimens. Interfacial shear to horizontal slip response was reported along with corresponding failure patterns. Pure shear connector strength was also evaluated by excluding concrete shear contribution, which was estimated in relation to steel beam-slab interface separation or interfacial crack width.

• Current Optics and Photonics
• /
• v.7 no.6
• /
• pp.665-672
• /
• 2023

This study focuses on investigating the impact of the spectral linewidth of a seed laser in a master-oscillator power amplifier (MOPA) configuration on stimulated Brillouin scattering and the beam quality of the output diffracted by a grating. To conduct the study, a distributed feedback (DFB) laser is modulated in a pseudorandom binary sequence (PRBS) and amplified by a two-stage Yb-doped fiber amplifier to achieve an output power of over 1 kW. The spectral linewidth of the seed laser is systematically varied from 1 to 12 GHz in the frequency domain by varying the PRBS modulation parameters. The experimental results reveal a tradeoff between suppressing stimulated Brillouin scattering and enhancing beam quality with increased spectral linewidth. Therefore, the study provides valuable insights into optimizing spectral beam combining to achieve high beam quality and scalable power upgrade in fiber lasers.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.13 no.6
• /
• pp.1199-1206
• /
• 2018

The hybrid phase shifting device is consist of general phase shifter in sub-array and the true time delay inter sub-array. This configuration for phased shifting can efficiently improve the beam squint according to frequencies. However, when an appropriate array configuration is not selected, a gain variation of main lobe for a phased array antenna is occurred. In order to solve these problems, a simplified formula for constructing efficient array based on the system design requirements, such as the fractional bandwidth, the maximum beam steering angle, and limit criterion of the gain variation, was presented.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.4
• /
• pp.795-800
• /
• 2009

Surface plasmon resonance (SPR) has been widely used for biological and chemical sensing applications. The present study investigates numerically the optical characteristics for the single Au film and bimetallic Ag/Au film SPR configurations by using the multiple beam interference matrix (MBIM) method. We use the prism coupling method, especially Kretschmann configuration for excitation of surface plasmon wave (SPW). The estimated results of reflectance, phase shift and magnetic field intensity enhancement factor are provided for finding out the optimum configuration with high sensitivity for SPR measurement. As a result, the optimum thicknesses are found to be 52 nm for a single Au film and 5 nm to 36 nm for bimetallic Ag-Au film. From the comparison of full width half maximum (FWHM) values for reflectance, phase shift, and enhancement of magnetic field intensity, it is concluded that the highest sensitivity can be obtained when using the phase shift for SPR sensor.

• The Korean Journal of Ceramics
• /
• v.5 no.4
• /
• pp.409-413
• /
• 1999

A two-beam polarization (TBP) interfermeter with a reflection configuration for measuring the linear electroptic coefficient is described and investigated experimentally and theoretically. It is shown that a TBP interferometer can be used for measuring the Pockels coefficient of thin film with a strong Fabry-Perot effect. The TBP interferometer technique is used to measure the effective differential linear electro-optic coefficient $re=r_{33}-(n_0/n_0)^3r_{13}$of lead zirconate titanate (PZT) thin film. The results are in agreement with known data.