• Journal of the Korean Society of Safety
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• v.28 no.4
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• pp.14-18
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• 2013

Blades of horizontal axis are nowadays made of composite materials. Generally, composite materials satisfy design provides lower weight and good stiffness, while laminate composites have often damages as like the delamination and cracks at the interface of laminates. The box spar and tail parts of a blade are composed of the CFRP/GFRP hybrid laminate composites. However, delamination and the interfacial crack often occur in the interface of CFRP/GFRP hybrid laminate composites under the mixed mode fracture condition, especially mode I and mode II. Therefore, there is a need for the evaluation of the mixed mode fracture behavior during the delamination of CFRP/GFRP hybrid laminates. This study shows the experimental results for the delamination fracture toughness in CFRP/GFRP hybrid laminate composites. Fracture toughness experiments and estimation are performed by using DMMB(Dissimilar mixed mode bending) specimen. The materials used in the test are a commercial woven type CFRP(Carbon fiber reinforced plastic) prepreg(CF3327) and UD type GFRP(Glass fiber reinforced plastic) prepreg(HD224A). A CFRP/GFRP hybrid laminate composite is composed by the 10 plies CFRP and GFRP prepreg for DMMB. A thickness of CFRP and GFRP layer is 2.5mm and 3.0mm, respectively. Also the fulcrum location which is a loading parameter is changed from 80 to 100mm on the specimen of length 120mm because it defines the ratio of mode I to mode II. In this study, the effects of the fulcrum location are evaluated in the viewpoint of energy release rate in mode I and mode II contribution. The results show that the delamination crack initiates at higher displacement and lower load according to the increase of the fulcrum location ratio. And the variation of the energy release rate for mode I and II contributions for the mode mixity are shown.

• Journal of Radiation Protection and Research
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• v.48 no.4
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• pp.175-183
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• 2023

Background: Recently, biological adsorbents have been developed for removing radionuclides from radioactive liquid waste due to their high selectivity, eco-friendliness, and renewability. However, since they can be damaged by radiation in radioactive waste, a method for estimating the bio-adsorbent performance as a time should consider the radiation damages in terms of their renewability. This paper aims to develop a simulation method that applies a deep learning technique to rapidly and accurately estimate the adsorption performance of bio-adsorbents when inserted into liquid radioactive waste. Materials and Methods: A model that describes various interactions between a bio-adsorbent and liquid has been constructed using numerical methods to estimate the adsorption capacity of the bio-adsorbent. To generate datasets for machine learning, Monte Carlo N-Particle (MCNP) simulations were conducted while considering radioactive concentrations in the adsorbent column. Results and Discussion: Compared with the result of the conventional method, the proposed method indicates that the accuracy is in good agreement, within 0.99% and 0.06% for the R² score and mean absolute percentage error, respectively. Furthermore, the estimation speed is improved by over 30 times. Conclusion: Note that an artificial neural network can rapidly and accurately estimate the survival rate of a bio-adsorbent from radiation ionization compared with the MCNP simulation and can determine if the bio-adsorbents are reusable.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.4
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• pp.53-63
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• 2007

Seismic design codes are developed mainly based on the observation of the behavior of structures in the high seismicity regions where structures may experience significant amount of inelastic deformations and major earthquakes may result in structural damages in a vast area. Therefore, seismic loads are reduced in current design codes for building structures using response modification factors which depend on the ductility capacity and overstrength of a structural system. However, structures in low seismicity regions, subjected to a minor earthquake, will behave almost elastically because of the larger overstrength of structures in low seismicity regions such as Korea. Structures in low seismicity regions may have longer periods since they are designed to smaller seismic loads and main target of design will be minor or moderate earthquakes occurring nearby. Ground accelerations recorded at stations near the epicenter may have somewhat different response spectra from those of distant station records. Therefore, it is necessary to verify if the seismic design methods based on high seismicity would he applicable to low seismicity regions. In this study, the adequacy of design spectra, period estimation and response modification factors are discussed for the seismic design in low seismicity regions. The response modification factors are verified based on the ductility and overstrength of building structures estimated from the farce-displacement relationship. For the same response modification factor, the ductility demand in low seismicity regions may be smaller than that of high seismicity regions because the overstrength of structures may be larger in low seismicity regions. The ductility demands in example structures designed to UBC97 for high, moderate and low seismicity regions were compared. Demands of plastic rotation in connections were much lower in low seismicity regions compared to those of high seismicity regions when the structures are designed with the same response modification factor. Therefore, in low seismicity regions, it would be not required to use connection details with large ductility capacity even for structures designed with a large response modification factor.

• Environmental Analysis Health and Toxicology
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• v.5 no.3_4
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• pp.47-56
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• 1990

Smoking damages nonsmoker's health who have been exposed to passive smoking as well as smoker's own health. Passive smoking can cause serious health damage to particular groups, such as the old aged, children and pregnant women. The purpose of this study is to investigate the relationship between nicotine concentrations in environmental tobacco smoke (ETS) and urinary cotinine concentrations of nonsmokers exposed to ETS, and to provide basic information related to health risk assessment. The results of this study were summarized as follows: 1. When 180 cigarrette were smoked during S hours (high concentrations exposure) in 132 m$^3$chamber, mean concentrations of nicotine in ETS showed 263.52 $\mu\textrm{g}$/m$^3$${\pm}$51.93. When 45 cigarretts were smoked (low concentrations exposure), it was 69.43${\pm}$8.96 $\mu\textrm{g}$/m$^3$. 2. The urinary cotinine concentrations of each times (0, 2.5, 5, 17 and 24 hours) in nonsmokers ranged from 0.27∼12.52 ng/ml in high concentrations exposure and 0.22∼2.28 ng/ml in low concentrations exposure. Mean while the total urinary cotinine concentrations during 24 hours ranged from 11.62∼31.65 ng/ml in high concentrations exposure and 3.45∼5.64 ng/ml in low concentrations exposure. 3. The correlation equation and coefficient between cotinine concentrations in nonsmokers' urine (y) and nicotine concentrations in ETS (x) was y=0.421+0.0171x and 0:875 (p<0.01) respectively, 4. The quantity of nonsmokers' smoking exposure by passive smoking can be assumed as based on the estimation of nicotine concentrations in ETS by measuring cotinine concentrations of nonsmokers' urine.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.3
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• pp.236-242
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• 2018

Damage due to ice collision is the most serious threat for the structural safety of ships operating in arctic region. Since such hull damages are usually caused by the collision of floating ice at excessive voyage speed of ships, the authorities responsible for the shipping at arctic sea are required to provide the speed limit for safe voyage, so-called safe speed. In countries near arctic ocean, such as Canada and Russia, empirical methods to determine the safe speed of ships based on their long experience of arctic voyage have been established and applied them in the real arctic navigation. However, in Korea, it is not easy to accumulate the arctic voyage experience and related technical database, so it seems to be a realistic approach to adopt a safe voyage speed estimating method in arctic sea based on the ice collision simulation technology using the nonlinear finite element analysis. The aim of this study is to develop a technique for estimating the safe voyage speed of vessels operating at arctic sea through the ice collision analysis, In order to achieve this goal, the standard procedure of the ice collision analysis is dealt with and example analysis was carried out and the results were considered. To investigate the validity of developed method, POLARIS system proposed by IMO was studied for comparison.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.30-31
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• 2009

Through the full scale ship collision response analysis of high speed passenger ship with underwater floating matters, the objective of this study is to perform the crashworthy safety assessment of its hull and passengers. For this safety assessment, diverse collision scenarios could be established through the thorough understanding of damage mechanisms due to the collision of its hydrofoil system with underwater floating matter examining the damage informations of its hull and passengers from the collision accidents, and through the estimation of the damages of its hull and passenger. The next step, crashworthy safety assessment of its hull and passengers, was carried out by the collision response analyses of high speed passenger ship with underwater floating matter using Fluid-Structure Interaction(FSI) analysis technique of LS-DYNA code in consideration of surrounding water, and using local zooming analysis technique.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.263-277
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• 1998

Recently, it is frequently reported that fatigue damages of deck slabs and floor systems of highway bridges occur under the conditions of increasing weight and traffic of heavy vehicles. These troubles are affected by dynamic wheel load of heavy vehicles running on roadway surface roughness with bump at expansion joint. It is required that this kind of traffic-induced vibration of highway bridges must be analyzed by using three-dimensional models of bridge and vehicle. In this study, the three-dimensional dynamic analysis is carried out, and dynamic responses of deck slab and wheel loads of moving vehicle are estimated according to different vehicle speeds and bump heights. Analytical responses of bridge deck slab are compared with experimental ones which were measured at Umeda entrance bridge of Hanshin Expressway in Osaka.

• Journal of the Korea Institute of Building Construction
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• v.3 no.2
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• pp.95-102
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• 2003

Financial difficulties and claims frequently stop construction works and cause subsequent contract cancellations. However, as the criteria to assess costs have not been established, many cases of legal disputes over the assessment of cancellation costs are taking place and the concerned parties are suffering the loss of time and money. Therefore, the present research aimed at developing a rational and systematic model of cancellation cost assessment following the cancellation of contracts. The research was carried out in the following methods and scopes. 1 ) The research was focused on the assessment of fair cancellation costs from constructors' side for contracts cancelled by any causes for which the owners have liability. 2) To obtain basic materials about cancellation cost assessment methods, contracts, claims, contract cancellations and construction-related laws at home and abroad were examined. 3) A cost assessment model was developed for systematization and efficient operation of cancellation cost assessment, and the reliability and efficiency of the proposed model was verified through a case study. The conclusions drawn from the research are as follows. The importance of the cancellation cost assessment model was confirmed as, using the cancellation cost assessment model, direct cancellation cost and indirect cancellation cost could be assessed systematically, the number of disputable items could be reduced because reasonable evidences of actual spending were presented, and the loss of constructors could be minimized because systematic and rational cost assessment became possible for many disputable cases of indirect cancellation cost, which the constructors had been unable to prove so far though having spent.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.3
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• pp.121-128
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• 2024

There are growing concerns that the recently implemented Earthquake Early Warning service is overestimating the rapidly provided earthquake magnitudes (M). As a result, the predicted damages unnecessarily activate earthquake protection systems for critical facilities and lifeline infrastructures that are far away. This study is conducted to improve the estimation accuracy of M by incorporating the observed S-wave seismograms in the near source region after removing the site effects of the seismograms in real time by filtering in the time domain. The ensemble of horizontal S-wave spectra from at least five seismograms without site effects is calculated and normalized to a hypocentric target distance (21.54 km) by using the distance attenuation model of Q(f)=348f^0.52 and a cross-over distance of 50 km. The natural logarithmic mean of the S-wave ensemble spectra is then fitted to Brune's source spectrum to obtain the best estimates for M and stress drop (SD) with the fitting weight of 1/standard deviation. The proposed methodology was tested on the 18 recent inland earthquakes in South Korea, and the condition of at least five records for the near-source region is sufficiently fulfilled at an epicentral distance of 30 km. The natural logarithmic standard deviation of the observed S-wave spectra of the ensemble was calculated to be 0.53 using records near the source for 1~10 Hz, compared to 0.42 using whole records. The result shows that the root-mean-square error of M and ln(SD) is approximately 0.17 and 0.6, respectively. This accuracy can provide a confidence interval of 0.4~2.3 of Peak Ground Acceleration values in the distant range.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.2
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• pp.65-75
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• 2023

Ships operated at sea for a long time are subjected to various kinds of loads, which may cause various types of damage. Such damages will eventually reduce the strength of hull structures. Therefore, it is necessary to estimate and evaluate the residual strength and remaining fatigue life of aging ships in order to secure structural safety, establish a reasonable maintenance plan, and make a judgment of life extension. For this purpose, the corrosion damage and local denting damage should be measured, fatigue damage estimation should be performed, and material properties of aged steel should be identified. For this study, in order to investigate the mechanical properties of aged steel, steel plates were obtained from a naval ship that reached the end of her life span. The specimens were manufactured from the obtained steel plates, and static and dynamic tensile tests, fatigue tests, and metallographic tests were performed. The mechanical properties obtained from the aged steel plates were compared with those of new steel plates to quantify the aging effect on the mechanical properties of marine steel materials.