• Transactions of Materials Processing
• /
• v.24 no.3
• /
• pp.212-217
• /
• 2015

SmartCrown is a system to control the plate crown by shifting the sine-shaped work rolls in the axial direction. The control range of the plate crown depends on a depth of sine-shaped roll profile because the roll radius varies continuously along the axial direction. When the roll profile is changed to improve the control range, the contact stress between the work roll and the back-up roll also changes. In the current study, the contact stress for various profiles and rolling conditions were analyzed using the finite element method and compared with results from Hertzian contact theory. A submodel method is used to increase the accuracy of the finite element analysis. The analysis results showed that the maximum increase in the contact stress was only 53MPa, so it is anticipated that no back-up roll spalling will occur.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.43 no.1
• /
• pp.83-88
• /
• 2010

Acoustic telemetry is a useful method to investigate fish behavior and is widely used to obtain biological information. In this study, the detection ability of a mooring-type acoustic telemetry system and the seasonal changes were studied for survey design and data analysis. The system detection range was examined with an underwater noise model, and seasonal changes were estimated with a ray-tracing program and underwater temperature profile data. The field experiment was conducted with two sets of pingers and six receivers to estimate the difference in detection rate by installation depth and to compare the model estimate. Results indicated that the long-range detection ability of the acoustic telemetry system was significantly affected by underwater temperature. The detection rate rapidly decreased near the sea surface or bottom despite that the near-range Signal to noise ratio was sufficient.

• Structural Engineering and Mechanics
• /
• v.68 no.4
• /
• pp.485-495
• /
• 2018

This paper presents the results of an experimental study on the structural performance of an innovative GFRP-concrete composite beam construction, which is reinforced with longitudinal GFRP pultruded box-profile and transverse steel stirrups. GFRP perfobond (PBL) shear connectors are employed to enhance the bonding performance between the GFRP profile and the concrete portion. To investigate the shear and flexural performance of this composite system, eight specimens were designed and tested under three-point and four-point bending. The main variables were the height of the composite beam and the shear span-to-depth ratio. The test results indicated that bonding cracks did not occur at the interface between the GFRP profile and the concrete until the final stage of the test. This shows that the specimens performed well as composite beams during the test and that the GFRP PBL connectors were reliable. Based on the test results, two calculation methods were used to determine the flexural and shear capacity of the composite beams. A comparative study of the test and theoretical results suggests that the proposed methods can reasonably predict both the flexural and shear capacities of the specimens, whereas the provisions of ACI 440 are relatively conservative on both counts.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.25 no.2
• /
• pp.118-123
• /
• 2016

Overlap cutting is a fundamental method of applying abrasive water jet (AWJ) machining to milling to produce a wider surface because the nozzle outlet is approximately 1.0 mm wide. In this study, the effects of overlap cutting on the depth profile and surface roughness are investigated. The overlapping area depends on the amount of step over, which is controlled in the pick-feed direction. If the step over is equal to or larger than the diameter of the nozzle, no overlap cut occurs but large cusps remain between the cut paths. A step over as small as one-thirds of the nozzle diameter may lead to triple-overlap cutting resulting in an extraordinary depth. By using pocket milling experiments with a step over of 0.46 (or 0.47), it is verified that AWJ can produce a milled surface of titanium, one of the hard-to-cut materials, with $76{\mu}m$ Ra.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.3
• /
• pp.193-199
• /
• 2000

As an energetic focused-ion beam(FIB) is irradiated on an inorganic amorphous thin film a majority of ions without a reflection at surface, is randomly collided with constituent atoms in thin film. but their distribution exhibits generally a systematic form of distribution. In our previous paper we reported the concentration distribution and the transmission per unit depth of Ga$^{+}$ ions penetrated int a-Se$_{75}$ /Ge$_{25}$ thin film using the LSS-based calculation. In this paper these simulated results are compared with those obtained by a conventional profile code(ISC) and a practical SIMS profile. Then the results of LSS-based calculation have only a small difference with those of code and SIMS Especially. in the case of Ga$^{+}$-FIB with an accelerating energy of 15keV. the depth of the maximum ion concentration is coincident with each other in an error range of $\pm$5$\AA$.EX>.

• Journal of Radiation Protection and Research
• /
• v.41 no.2
• /
• pp.173-178
• /
• 2016

Background: In situ gamma spectrometry has been used to measure environmental radiation, assumptions are usually made about the depth distribution of the radionuclides of interest in the soil. The main limitation of in situ gamma spectrometry lies in determining the depth distribution of radionuclides. The objective of this study is to develop a method for subsurface characterization by in situ measurement. Materials and Methods: The peak to valley method based on the ratio of counting rate between the photoelectric peak and Compton region was applied to identify the depth distribution. The peak to valley method could be applied to establish the relation between the spectrally derived coefficients (Q) with relaxation mass per unit area (${\beta}$) for various depth distribution in soil. The in situ measurement results were verified by MCNP simulation and calculated correlation equation. In order to compare the depth distributions and contamination levels in decommissioning KRR site, in situ measurement and sampling results were compared. Results and Discussion: The in situ measurement results and MCNP simulation results show a good correlation for laboratory measurement. The simulation relationship between Q and source burial for the source layers have exponential relationship for a variety depth distributions. We applied the peak to valley method to contaminated decommissioning KRR site to determine a depth distribution and initial activity without sampling. The observed results has a good correlation, relative error between in situ measurement with sampling result is around 7% for depth distribution and 4% for initial activity. Conclusion: In this study, the vertical activity distribution and initial activity of $^{137}Cs$ could be identifying directly through in situ measurement. Therefore, the peak to valley method demonstrated good potential for assessment of the residual radioactivity for site remediation in decommissioning and contaminated site.

• Journal of the Society of Naval Architects of Korea
• /
• v.51 no.1
• /
• pp.88-98
• /
• 2014

A supercavitation is modern technology that can be used to reduce the frictional resistance of the underwater vehicle. In the process of reaching the supercavity condition which cavity envelops whole vehicle body, a vehicle passes through transition phase from fully-wetted to supercaviting operation. During this phase of flight, unsteady hydrodynamic forces and moments are created by partial cavity. In this paper, analytical and numerical investigations into the dynamics of supercavitating vehicle in transition phase are presented. The ventilated cavity model is used to lead rapid supercavity condition, when the cavitation number is relatively high. Immersion depth of fins and body, which is decided by the cavity profile, is calculated to determine hydrodynamical effects on the body. Additionally, the frictional drag reduction associated by the downstream flow is considered. Numerical simulation for depth tracking control is performed to verify modeling quality using PID controller. Depth command is transformed to attitude control using double loop control structure.

• Medical Lasers
• /
• v.10 no.3
• /
• pp.146-152
• /
• 2021

Background and Objectives Although lasers have been widely applied in tissue treatment, the light penetration depth in tissues is limited by the tissue turbidity and affected by its absorption and scattering characteristics. This study investigated the effect of using an optical clearing agent (OCA) on tissue to improve the therapeutic effect of 1064 nm wavelength laser light by reducing the heat generated on the skin surface and increasing the penetration depth. Materials and Methods A diode laser (λ = 1064 nm) was applied to a porcine specimen with and without OCA to investigate the penetration depth of the laser light and temperature distribution. A numerical simulation using the finite element method was performed to investigate the temperature distribution of the specimen compared to ex-vivo experiments using a thermocouple and double-integrating sphere to measure the temperature profile and optical properties of the tissue, respectively. Results Simulation results showed a decrease in tissue surface temperature with increased penetration depth when the OCA was applied. Furthermore, both absorption and scattering coefficients decreased with the application of OCA. In ex-vivo experiments, temperatures decreased for the tissue surface and the fat layer with the OCA, but not for the muscle layer. Conclusion The use of an OCA may be helpful for reducing surface heat generation and enhance the light penetration depth in various near-infrared laser treatments.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.233-234
• /
• 2006

For the machining of freeform surface, fly cutting is one of the key technology to meet profile accuracy and surface roughness simultaneously. Fly cutting can be applied to manufacturing of optical components with complex profile. In this study aluminum alloy was machined in the process of ultra precision fly cutting and investigated optimum machining conditions in terms of feed-rate, pitch per cycle and depth of cut.

• Journal of radiological science and technology
• /
• v.45 no.5
• /
• pp.449-455
• /
• 2022

This study is to present a Geant4 code for the simulation of the absorbed dose distribution given by a medical linac for 6 MV photon beam. The dose distribution was verified by comparison with calculated beam data and beam data measured in water phantom. They were performed for percentage depth dose(PDD) and beam profile of cross-plane for two field sizes of 10 × 10 and 15 × 15 cm². Deviations of a percentage and distance were obtained. In energy spectrum, the mean energy was 1.69 MeV. Results were in agreement with PDD and beam profile of the phantom with a tolerance limit. The differences in the central beam axis data 𝜹₁ for PDD had been less than 2% and in the build up region, these differences increased up to 4.40% for 10 cm square field. The maximum differences of 𝜹₂ for beam profile were calculated with a result of 4.35% and 5.32% for 10 cm, 15 cm square fields, respectively. It can be observed that the difference was below 4% in 𝜹₃ and 𝜹₄. For two field sizes of 𝜹_50-90 and RW₅₀, the results agreed to within 2 mm. The results of the t-test showed that no statistically significant differences were found between the data for PDD of 𝜹₁, p>0.05. A significant difference on PDD was observed for field sizes of 10 × 10 cm², p=0.041. No significant differences were found in the beam profile of 𝜹₃, 𝜹₄, RW₅₀, and 𝜹_50-90. Significant differences on beam profile of 𝜹₂ were observed for field sizes of 10 × 10 cm², p=0.025 and for 15 × 15 cm², p=0.037. This work described the development and reproducibility of Geant4 code for verification of dose distribution.