• Structural Engineering and Mechanics
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• v.56 no.5
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• pp.767-785
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• 2015

The stochastic finite element method is employed to obtain a stochastic dynamic model of angled beams subjected to impact loads when uncertain material properties are described by random fields. Using the perturbation technique in conjunction with a precise time integration method, a random analysis approach is developed for efficient analysis of random elastic waves. Formulas for the mean, variance and covariance of displacement, strain and stress are introduced. Statistics of displacement and stress waves is analyzed and effects of bend angle and material stochasticity on wave propagation are studied. It is found that the elastic wave correlation in the angled section is the most significant. The mean, variance and covariance of the stress wave amplitude decrease with an increase in bend angle. The standard deviation of the beam material density plays an important role in longitudinal displacement wave covariance.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.334-338
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• 2001

A Fizeau interferometer without beam splitter was constructed. Single-mode optical fiber was used as a spherical wave source and the face of fiber end was polished and coated to be a reflecting surface. The reflecting surface was angled so that interference fringe could be detected by CCD camera. Beam splitter in front of a spherical wave source could distort the wave front and that was one of the component error sources. With the proposed configuration there was no need to place beam splitter in the system. Improvement of phase measuring accuracy was evaluated quantitatively by comparing the result of this setup with that of a conventional Fizeau interferometer. Wave front of the angled end-face optical fiber source was also measured to verify its sphericity by PS/PDI (Phase Shifting/Point Diffraction Interferometer). The principle of this technique was presented and the experimental results and its applications were discussed. ussed.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.142-148
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• 1996

It is shown that a simple vector analysis method can provide beam cone shapes for laser bemas non-paraxially input to dielectric boundaries with inclination. Acceptance coen shapes for angled-endface fibers are calculated by the method. Beam cone shapes inside InP substrates are also calculated by the method for the coupling of an optical fiber and an InP-based photodiode using a Si v-groove. The effectiveness and errors of the recently suggested matrix method for inclined boundaries are also studied.

• Structural Engineering and Mechanics
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• v.7 no.3
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• pp.331-344
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• 1999

This paper provides an analysis of the transient behaviour of a right-angled bent cantilever beam subjected to a suddenly applied force at its tip perpendicular to its plane. Based on a rigid, perfectly plastic material model, a double-hinge mechanism is required to complete the possible deformation under a rectangular force pulse (constant force applied for a finite duration) with a four-phase response mode. The kinematics of the various response phases are described and the partitioning of the input energy at the plastic hinges during the motion is evaluated.

• Imaging Science in Dentistry
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• v.44 no.2
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• pp.115-119
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• 2014

Purpose: The aim of this in vitro study was to determine the sensitivity and specificity of cone-beam computed tomography (CBCT) and digital periapical radiography in the detection of mesial root perforations of mandibular molars. Materials and Methods: In this in vitro study, 48 mandibular molars were divided into 4 groups. First, the mesial canals of all the 48 teeth were endodontically prepared. In 2 groups (24 teeth each), the roots were axially perforated in the mesiolingual canal 1-3 mm below the furcation region, penetrating the root surface ("root perforation"). Then, in one of these 2 groups, the mesial canals were filled with gutta-percha and AH26 sealer. Mesial canals in one of the other 2 groups without perforation (control groups) were filled with the same materials. The CBCT and periapical radiographs with 3 different angulations were evaluated by 2 oral and maxillofacial radiologists. The specificity and sensitivity of the two methods were calculated, and P<0.05 was considered significant. Results: The sensitivity and specificity of CBCT scans in the detection of obturated root canal perforations were 79% and 96%, respectively, and in the case of three-angled periapical radiographs, they were 92% and 100%, respectively. In non-obturated root canals, the sensitivity and specificity of CBCT scans in perforation detection were 92% and 100%, respectively, and for three-angled periapical radiographs, they were 50% and 96%, respectively. Conclusion: For perforation detection in filled-root canals, periapical radiography with three different horizontal angulations would be trustworthy, but it is recommended that CBCT be used for perforation detection before obturating root canals.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.500-506
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• 1999

We designed and fabricated a bidirectional optical transceiver module for low cost access network. An integrated chip forming a pin-PD on an 1.3 urn FP-LD was assembled by flip-chip bonding on a Si optical bench, a single mode fiber with an angled end facet was aligned passively with the integrated chip on V-groove of Si-optical bench. Gaussian beam theory was applied to evaluate the coupling coefficients as a function of some parameters such as alignment distance, angle of fiber end facet, vertical alignment error. The theory is also used to search the bottle-neck between transmittance and receiving coupling efficiency in the bi-directional optical system. Tn this paper, we confirmed that reduction of coupling efficiency by the vertical alignment error between laser beam and fiber core axis can be compensated by controlling the fiber facet angle. In the fabrication of sub-module, a'||'&'||' we made such that the fiber facet have a corn shape with an angled facet only core part, the reflection of transmitted laser beam from the fiber facet could be minimized below -35 dE in alignment distance of 2: 30 /J.m. In the same condition, transmitted output power of -12.1 dEm and responsivity of 0.2. AIW were obtained.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.3
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• pp.21-29
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• 2016

In this paper, optical tracking and analysis was carried out to find the optical properties with respect to various geometric design parameters of collimator lens which is very efficient when collect the light. As a result, a whole, ellipse incident part can obtain a high light efficiency and a narrow beam angle, and angled cylinder incident part is confirmed to obtain high efficiency and a narrow beam angle at a certain height or more. When Transmission part have a specific surface which can reflect the light in forward direction, a good optical properties was confirmed.

• Journal of architectural history
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• v.21 no.2
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• pp.21-36
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• 2012

As wooden construction developed, it was observed that the rafters with corners changed to angled rafters. The change from rafters to angle rafters means that the angle rafters became the most important member in supporting the roof weight as the construction scale increased and structurally developed. The specific installation methods of angle rafters were all unique in Korea, China, and Japan. In East Asia, the angle of the angle rafter gradually decreased along with the development of construction. However, in Joseon Dynasty Korea, the angle of the angle rafter was larger than that of the Gorye era because the method of fixing the corner of the roof more firmly by building the fan-shaped rafter was utilized. The changes to the angle rafter installation method is a unique characteristic of Korea, in that it was developed in a totally different way from the methods used in China and Japan.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1970-1978
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• 2021

The aim of this study was to optimize the target, moderator, and collimator (TMC) in a neutron beam generator for the accelerator-based BNCT (A-BNCT) system. The optimization employed the Monte Carlo Neutron and Photon (MCNP) simulation. The optimal geometry for the target was decided as the one with the highest neutron flux among nominates, which were called as angled, rib, and tube in this study. The moderator was optimized in terms of consisting material to produce appropriate neutron energy distribution for the treatment. The optimization of the collimator, which wrapped around the target, was carried out by deciding the material to effectively prevent the leakage radiations. As results, characteristic of the neutron beam from the optimized TMC was compared to the recommendation by the International Atomic Energy Agent (IAEA). The tube type target showed the highest neutron flux among nominates. The optimal material for the moderator and collimator were combination of Fluental (Al₂0₃+AlF₃) with ⁶⁰Ni filter and lead, respectively. The optimized TMC satisfied the IAEA recommendations such as the minimum production rate of epithermal neutrons from thermal neutrons: that was 2.5 times higher. The results can be used as source terms for shielding designs of treatment rooms.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.12-16
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• 2012

In the paper, we fabricated a Ni master with $45^{\circ}$-mirror structures for flexible waveguide fabrication. The flexible waveguide films with embedded $45^{\circ}$-angled mirrors at the waveguide ends were successfully fabricated using a UV-imprint process. Next, in order to enhance the reflectivity of the mirrors, Ni(3 nm)-Au(200 nm) bilayers were evaporated on the $45^{\circ}$-angled facets through a locally opened thin mask using an electron beam evaporator. We measured propagation loss, bending loss, mirror loss and bending reliability of the fabricated waveguide.