• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.1
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• pp.67-76
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• 2004

This study presents the evaluation of CSM(Capacity Spectrum Method, ATC-40) in developing fragility curves for a sample concrete bridge. The CSM is originally developed as one of the simplified procedures for building structures, while this study adopts the CSM to develop fragility curves of bridge structures. Four(4) different approaches are demonstrated and the fragility curves developed are compared those by the nonlinear time history analysis. Fragility curves in this study are represented by lognormal distribution functions with two parameters and developed as a function of PGA. The sixty(60) ground acceleration time histories for the Los Angeles area developed for the Federal Emergency Management Agency (FEMA) SAC(SEAOC-ATC-CUREe) steel project are used for the bridge analysis. The comparison of fragility curves by the CSM with those by the time history analysis indicates that the agreement is excellent for one of the methods investigated in this study. In this respect. it is recommended that the demand spectrum might be improved according to the guidelines suggested in this study. However, this observation might not always apply, depending on the details of specific bridge characteristic

• Journal of the Korean Chemical Society
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• v.29 no.6
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• pp.608-614
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• 1985

Electrical conductivities of $ZrO_2-Sm_2O_3$ systems containing 10, 20, 30, 40, and 50 mol% of $ZrO_2$ have been measured as a function of temperature and of oxygen partial pressure at temperature from 500 to 1000${\circ}C$ and oxygen partial pressures from 1 ${\times}10^{-5}to 1{\times}10^{-1}$ atm. Plots of log conductivity vs. 1/T are found to be linear with an inflection point at around 650$^{\circ}C$ and the temperature dependence of conductivity shows two different defect structures. The conductivities are increased with increasing pressure, slowing a p-type character. The electrical conductivity dependences on $Po_2$ are found to be ${\sigma}{\propto}Po_2^{1/5.3}$ at 650∼1000$^{\circ}C$ and ${\sigma}{\propto}Po_2^{1/6}$ at 500∼650$^{\circ}C$, respectively, The defect structures are Oi" at 650-1000$^{\circ}C$ and $Vs_m$"' at 500-650$^{\circ}C$. The electron hole is main carrier type, however ionic contribution is found at low temperature portion. Ionic contributions increased with the increasing amount of $ZrO_2$ dopant. In 60mol% $ZrO_2-Sm_2O_3$ system, the conductivity is increased with decreasing oxygen pressure.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.276-285
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• 2020

In this study, accelerated chloride diffusion tests were performed on OPC(Ordinary Portland Cement) and FA(Fly Ash) concrete considering three levels o f W/B(Water to Binder) ratio o n 1,095 curing days. The accelerated chloride diffusion coefficient and the passed charge were evaluated in accordance with Tang's method and ASTM C 1202, and the resistance performance to chloride attack improved over time. FA concrete showed excellent resistance performance against chloride penetration with help of pozzolanic reaction. As the result of the passed charge, FA concrete showed durability improvement, "low" grade to "very low" grade, but OPC concrete changed "moderate" grade to "low" grade at 1,095 curing days. After assuming the design variables used for durability design as normal distribution functions, the service life of each case was evaluated by the probabilistic analysis method based on MCS(Monte Carlo Simulation). In FA concrete, the increase of probability of durability failure was lower than that of OPC concrete with increasing time, because the time-dependent coefficient of FA concrete was up to 3.2 times higher than OPC concrete. In addition, the service life by probabilistic analysis was evaluated lower than the service life by deterministic analysis, since the target probability of durability failure was set to 10%. It is considered that more economical durability design will be possible if the mo re suitable target probability of durability failure is set for various structures through researches on actual conditions and indoor tests under various circumstances.

• Journal of the Korean GEO-environmental Society
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• v.16 no.8
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• pp.21-35
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• 2015

Electrical resistivity survey (2D and 3D) were employed for detection of possible weak zone of core zones of three central core earth-rockfill dams in Korea. In the 2D results, the core zones is lower resistivity zone with less than $50{\sim}400ohm{\cdot}m$, and the basement is relatively higher resistivity zone with over $1,000ohm{\cdot}m$. In the 3D results, especially, the weak zone with under $100ohm{\cdot}m$ was detected spatial distribution area in the dam. We also drilled boreholes to collect soil samples of core zones of each dam. Water was not used during boring, because water for rotary wash boring could cause structural damages in earth dams. We found that the soil samples of core zones from all of the boreholes correspond to CL (USCS), but we also found that the fluidized or water-saturated soil samples were found in lower resistivity zones. Therefore, the electrical resistivity survey and drilling method without water are a quick and efficient method for structural-health evaluation which is detection of possible weak zones in earth core rockfill dams.

• Journal of the Korean Geotechnical Society
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• v.21 no.8
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• pp.73-84
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• 2005

A three layered neural network model was developed using back propagation algorithm to estimate the UU undrained shear strength of Korean soft soil based on the database of actual undrained shear strengths and piezocone measurements compiled from 8 sites over the Korea. The developed model was validated by comparing model predictions with measured values about new piezocone data, which were not previously employed during development of model. Performance of the neural network model was also compared with conventional empirical methods. It was found that the number of neuron in hidden layer is different for the different combination of transfer functions of neural network models. However, all piezocone neural network models are successful in inferring a complex relationship between piezocone measurements and the undrained shear strength of Korean soft soils, which give relatively high coefficients of determination ranging from 0.69 to 0.72. Since neural network model has been generalized by self-learning from database of piezocone measurements and undrained shear strength over the various sites, the developed neural network models give more precise and generally reliable undrained shear strengths than empirical approaches which still need site specific calibration.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.270-274
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• 2017

Formic acid has been known as one of key sources of hydrogen. Among various monometallic catalysts, hydrogen can be efficiently produced on Pd catalyst. However, the catalytic activity of Pd is gradually reduced by the blocking of active sites by CO, which is formed from the unwanted indirect oxidation of formic acid. One of promising solutions to overcome such issue is the design of alloy catalyst by adding other metal into Pd since alloying effect (such as ligand and strain effect) can increase the chance to mitigate CO poisoning issue. In this study, we have investigated formic acid deposition on the bimetallic $Pd/Pd_3Fe$ core-shell nanocatalyst using DFT (density functional theory) calculation. In comparison to Pd catalyst, the activation energy of formic acid dehydrogenation is greatly reduced on $Pd/Pd_3Fe$ catalyst. In order to understand the importance of alloying effects in catalysis, we decoupled the strain effect from ligand effect. We found that both strain effect and ligand effect reduced the binding energy of HCOO by 0.03 eV and 0.29 eV, respectively, compared to the pure Pd case. Our DFT analysis of electronic structure suggested that such decrease of HCOO binding energy is related to the dramatic reduction of density of state near the fermi level.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.954-961
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• 2010

Stream cipher was worse than block cipher in terms of security, but faster in execution speed as an advantage. However, since so far there have been many algorithm researches about the execution speed of block cipher, these days, there is almost no difference between them in the execution speed of AES. Therefore an secure and fast stream cipher development is urgently needed. In this paper, we propose a 32bit output fast stream cipher, AA32, which is composed of ASR(Arithmetic Shifter Register) and simple logical operation. Proposed algorithm is a cipher algorithm which has been designed to be implemented by software easily. AA32 supports 128bit key and executes operations by word and byte unit. As Linear Feedback Sequencer, ASR 151bit is applied to AA32 and the reduction function is a very simple structure stream cipher, which consists of two major parts, using simple logical operations, instead of S-Box for a non-linear operation. The proposed stream cipher AA32 shows the result that it is faster than SSC2 and Salsa20 and satisfied with the security required for these days. Proposed cipher algorithm is a fast stream cipher algorithm which can be used in the field which requires wireless internet environment such as mobile phone system and real-time processing such as DRM(Digital Right Management) and limited computational environments such as WSN(Wireless Sensor Network).

• Polymer(Korea)
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• v.33 no.4
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• pp.297-306
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• 2009

A homologous series of side chain liquid crystalline polymers, poly [1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s(CAPETn, where n, the number of methylene units in the spacer, is $2{\sim}10$) were synthesized from poly(vinyl alcohol) and 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides(CAPBn, n=$2{\sim}10$), and their thermotropic liquid crystalline phase behaviors were investigated. The CAPBn with n of $2{\sim}5$ did not show any liquid crystalline behavior, while those with n of 6 and $7{\sim}10$ showed enantiotropic and monotropic nematic phases, respectively. In contrast, among the CAPETn polymers, only CAPET5 exhibited an enantiotropic nematic phase, while other polymers showed monotropic nematic phases. The isotropic-nematic transition temperatures of CAPETns and their entropy variation at the phase transition that were higher values than those of CAPBns, demonstrated a typical odd-even effect as a function of n. These phase transition behaviors were disscussed in terms of the 'virtual trimer model' by Imrie. The mesophase properties of CAPETns were largely different from those reported for the polymers in which the (cyanophenylazo) phenoxy groups are attached to polyacrylate, polymethacrylate, and polystyrene backbones through polymethylene spacers. The results indicate that the mode of chemical linkage of the side group with the main chain plays an important role in the formation, stabilization, and type of mesophase.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.342-347
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• 1999

As the waveguide width and the radius of curvature get smaller for the effort of monolithic fabrication of integrated photonic devices, the waveguide characteristics change significantly according to the change of the waveguide width or the radius of curvature. Especially, variation of the waveguide width due to fabrication process errors induces a phase error for each waveguide from the change of the propagation constant. Therefore, it is important to quantify these variation effects on the device characteristics for the design and fabrication of highly integrated photonic devices. Here, we analyze four different types of waveguides to get general characteristics in propagation constant change by utilizing the effective index method and the analytic solution method. Futhermore, the output characteristics of two AWG(Arrayed Waveguide Grating) devices are simulated by a highly-functional computer code. The simulated results have been found to be similar to the realistic device characteristics. The required fabrication error limit for the ridge-type InP-AWG device should be smaller than 0.02 ${\mu}{\textrm}{m}$ to get better channel crosstalk than-25 dB, while the required fabrication error limit for rib-type silica-AWG devices may be allowed up to 0.1 ${\mu}{\textrm}{m}$ to obtain better crosstalk than -30 dB.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.161-172
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• 2003

This study has evaluated the stream gauge network with the main emphasis on if the current stream gauge network can catch the runoff characteristics of the basin. As the evaluation of the stream gauge network in this study does not consider a special purpose of a stream gauge, nor the effect from a hydraulic structure, it becomes an optimization of current stream gauge network under the condition that each stream gauge measures the natural runoff volume. This study has been applied to the Nam-Han River Basin for the optimization of total 31 stream gauge stations using the entropy concept. Summarizing the results are as follows. (1) The unit hydrograph representing the basin response from rainfall can be transferred into a probability density function for the application of the entropy concept to optimize the stream gauge network. (2) Accurate derivation of unit hydrographs representing stream gauge sites was found the most important part for the evaluation of stream gauge network, which was assured in this research by comparing the measured and derived unit hydrographs. (3) The Nam-Han River Basin was found to need at least 28 stream gauge stations, which was derived by considering both the shape of the unit hydrograph and the runoff volume. If considering only the shape of the unit hydrograph, the number of stream gauges required decreases to 23.