• Smart Structures and Systems
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• v.14 no.5
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• pp.811-830
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• 2014

A numerical study has been carried out to simulate an innovative monitoring procedure to detect and localize damage in reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) unidirectional laminates. The main novelty of the present simulation is its ability to conduct the electromechanical admittance monitoring technique by considerably compressing the amount of data required for damage detection and localization. A FEM simulation of electromechanical admittance-based sensing technique was employed by applying lead zirconate titanate (PZT) transducers to acquire impedance spectrum signatures. Response surface methodology (RSM) is finally adopted as a tool for solving inverse problems to estimate the location and size of damaged areas from the relationship between damage and electromechanical admittance changes computed at PZT transducer surfaces. This statistical metamodel technique allows polynomial models to be produced without requiring complicated modeling or numerous data sets after the generation of damage, leading to considerably lower cost of creating diagnostic database. Finally, a numerical example is carried out regarding a steel-reinforced concrete (RC) beam model monotonically loaded up to its failure which is also retrofitted by a CFRP laminate to verify the validity of the present metamodeling monitoring technique. The load-carrying capacity of concrete is predicted in the present paper by utilizing an Ottosen-type failure surface in order to better take into account the passive confinement behavior of retrofitted concrete material under the application of FRP laminate.

• The Korean Journal of Air & Space Law and Policy
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• v.21 no.1
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• pp.65-95
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• 2006

It is essential that the liability for damage on the surface caused by aircraft be regulated at international level. However, the Rome Convention on Damage Caused by Foreign Aircraft to Third Parties on the Surface of 1952 and the Montreal Protocol of 1978 did not have significant worldwide repercussions since few countries have ratified them. So the Secretariat ofthe ICAO has produced the draft Convention for the modernization of the Rome Convention in 2002 and the Special group has considered the text of the draft Convention so far. The draft Convention contains main issues with regard to the liability system of the operator and the insurability of the risks for damage to third parties on the ground. In order to protect the air transport sector of a country as well as to facilitate speedy recoveries by victims, Work on modernizing the Rome Convention should be continued and the new Convention should be finalized in the near future.

• Korea Journal of Cosmetic Science
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• v.2 no.1
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• pp.1-10
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• 2020

Protection mechanisms for skin damage of ultraviolet (UV) absorbers in personal care products for protection against UV are well studied, but not for hair protection. The purpose of this study is to describe and compare the changes of physical property produced in human hair by doses of the UV-B exposure causing protein degradation. To observe the change of physical properties in hair, the experimental intensity of UV-B exposure has been established on the basis of statistical data from official meterological administration as daily one hour sunlight exposure for two weeks. Polysilicone-15, ethylhexyl methoxycinnamate (OMC), and octocrylene were employed for UV-B absorber, and those were treated to hair swatch by rubbing wash through shampoo and conditioner. Bending rigidity displayed kinetically successive reduction at high doses of UV exposure up to the 8,000 s, and exhibited different level at each sample of UV-B absorber. However, the values of Bossa Nova Technologies (BNT) for shinning factor were already saturable at the 2,000 s exposure except that treated with polysilicone-15. The differential scanning calorimetry (DSC) to measure a strength of inner protein produces a successive reduction of enthalpy as like a reduction of bending rigidity upon UV exposure. Surface roughness from lateral force microscope (LFM) acquired immediately after UV exposure show a saturable frictional voltage which has been also found in a saturable BNT data as the time of UV exposure increases. Through researching the DSC and the LFM, shinning of hair was much correlated to the protein damage at the surface, and bending rigidity could be regulated by the protein structural damage inside hair. Therefore, the optimization of efficient strategy for simultaneous prevention of hair protein on the surface and internal hair was required to maintain physical properties against UV.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.136-141
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• 2004

The gear in various mechanical components easily occurs at damages by the external torque. The main failure modes of the gear are surface pitting with the tooth surface and breakage with tooth root by caused fatigue. Therefore, the gear is very important role in the reliability research since it may cause fatal damage of entire system such as the gear box in automobile transmission. In this study, the failure mode of the gear was analyzed and accelerated durability analysis was employed for the life estimation of spur gears. In the case of assumed load spectrums, the reliability of spur gears was evaluated by inverse power law-Weibull accelerated life test model with cumulative damage exposure.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.423-430
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• 2005

Fire accidents in underground space may bring much loss of lives as well as properties and result in catastrophic disasters. This study aimed to manufacture the high-temperature furnace capable of simulating fire scenarios (RABT and RWS) and carry out the preliminary fire tests to evaluate fire-induced damage in underground structures. Specimens used in the fire tests were the concrete segments generally used in shield TBM tunnels. The simulated fire scenario was set to the RABT curve that is the most representative fire scenario in underground space. From the fire tests, the spalling was estimated to reach approximately 20cm from the surface exposed to fire. In addition, from the observation of core specimens obtained after fire tests, the deteriorated zone of unspalled specimens amounted to approximately 10cm from the surface of spalling.

• New & Renewable Energy
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• v.5 no.1
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• pp.26-31
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• 2009

The surface etching characteristics of single crystalline silicon wafer were investigated using potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH). The saw damage layer was removed after 10min by KOH 45wt% solution at $80^{\circ}C$. The wafer etched at high temperature ($90^{\circ}C$) and in low concentration (4wt%) of TMAH solution showed an increased etch rate of silicon wafer and wavy patterns on the surface. Especially, pyramidal textures were formed in 4wt% TMAH solution without alcohol additives.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.272-277
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• 1994

The damage of a thin film of Rd6G dye was probed by Surface Second-Harmonic Generation(SSHG) method. A portion of the Rd6G thin film on glass substrate was damaged by 532 nm laser beam, and the damage was probed by detecting intensity variation of SSHG. The result was confirmed through direct observation with optical microscope.oscope.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.3
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• pp.302-309
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• 1996

Cavitation erosion-corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. If the liquids corrosive to the material, a condition typically encountered in industry, the component materials may suffer serious damage by a combination of mechanical and electrochemical attack. To suppress cavitation erosion as well as cavitation erosion-corrosion to hydraulic equipments, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. This study was tested by using the piezoelectric vibrator with 20kHz, 24${\mu}$m for cavitation generation. And also, the vibratory cavitation erosion-corrosion tests on commercial mild steel SS41were carried out. We carefully observed the erosion pattern and surface photography. The geometrical mechanism of pit growth, which is to be likely these processing; shallow typelongrightarrowundercut typelongrightarrowwide shallow type.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.482-496
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• 1993

Radiation damage and contamination of silicons etched in the $CF_4+H_2$ and $CHF_3$ magnetron discharges have been characterized using Schottky diode characteristics, TEM, AES, and SIMS as a function of applied magnetic field strength. It turned out that, as the magnetic field strength increased, the radiation damage measured by cross sectional TEM and by leakage current of Schottky diodes decreased colse to that of wet dtched samples especially for $CF_4$ plasma etched samples, For $CF_4+H_2$and $CHF_3$ etched samples, hydrogen from the plasmas introduced extended defects to the silicon and this caused increased leakage current to the samples etched at low magnetic field strength conditions by hydrogen passivation. The thickness of polymer with the increasing magnetic field strength and showed the minimum polymer residue thickness near the 100Gauss where the silicon etch rate was maximum. Also, other contaminants such as target material were found to be minimum on the etched silicon surface near the highest etch rate condition.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.215-222
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• 2007

Coating of Hot-dip galvannealed steel consists of various Fe-Zn intermetallic compounds. Since the coating is hard and there for is very brittle, the surface of steel sheet is easy to be ruptured during second manufacturing processing. This is called as powdering. In addition, forming equipment might be polluted with debris by powdering. Therefore, various research have been carried out to prohibit powdering fur improving the quality of GA steel. This paper carried out finite element analysis combined with damage model which simulate the failure of local layer of hot-dip galvannealed steel surface during v-bending test. Since the mechanical property of intermetallic compound was unknown exactly, we used the properties calculated from measurements. The specimen was divided into substrate, coating layer and interface layer. Local failure at coating layer or interface layer was simulated when elemental strain reached a prescribed strain.