• Publications of The Korean Astronomical Society
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• 제30권2호
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• pp.461-462
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• 2015

Quasars are among the farthest and brightest objects known in the universe. Because quasars are mostly observed in the redshift range between 1 and 3, they can be used to study large scale structure in the universe, and its evolution over the past billion years. An important issue is the evolution of the quasar luminosity function, which has been investigated for relative small samples of the 2QZ catalog. Here we extend the study to 3 quasar samples, the most recent data of the Milliquas, Master and 2QZ quasar catalogs to determine the luminosity function of quasars and its evolution, using the Standard cosmological ${\Lambda}CDM$ model with ${\Omega}_{\Lambda}=0.73$, ${\Omega}_M=0.27$, and $H_0=70kms^{-1}Mpc^{-1}$. For the purpose of this analysis we initially used 0.25-mag bins and approximately 0.180-redshift bins, then calculated the comoving distance and comoving volume for each bin of redshift and calculated the number of objects in each bin per unit volume, in order to find the number density per absolute magnitude bin. Our analysis on the basis of these new and much more complete datasets is largely in agreement with earlier studies of the luminosity evolution of quasars.

• Korean Journal of Materials Research
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• 제18권12호
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• pp.683-688
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• 2008

For development of a human body model for electric shock, electroconductive paints with carbon black as a filler material were developed. The characteristics of the volume resistivities of thin films fabricated using the electroconductive paints were investigated as a function of the particle sizes and content of carbon black. With a carbon black particle size over $80\;{\mu}m$, agglomeration of carbon black powders was observed. The volume resistivity of the particles increased as the porosity increased and as the amount of carbon black decreased due to the agglomeration of carbon black powders. With a particle size of $4\;{\mu}m$ and $20\;{\mu}m$, agglomeration of carbon black powders was not observed and their porosities were measured as 0.86% and 1.12% with volume resistivities of $20\;{\Omega}{\cdot}cm$ and $80\;{\Omega}{\cdot}cm$ respectively. A carbon black particle size of less than $20\;{\mu}m$ is considered to be suitable as a type of electric-shock electroconductive paint for a human body model.

• Bulletin of the Korean Chemical Society
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• 제28권10호
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• pp.1709-1714
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• 2007

It is demonstrated in this study that the nanoliter reactor arrays with an inkjet printing, can be used for high throughput screen of antibiotic function. As a model antibiotic, gramicidin was used in this study. The gramicidin embedded lipid vesicles were immobilized on the surface in the nanoliter reactor structure with control of the volume in the nanoliter reactor. By dispensing acidic drops into the reactor, the gramicidin function was monitored. The technique developed in this research also has a great potential to be used for discovery of drugs.

• The Journal of Fisheries Business Administration
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• 제43권1호
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• pp.19-34
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• 2012

The purpose of the paper is to find out the trade patten and characteristics of Korea's fisheries products by figuring out the factors of affecting the volume of the export of Korean frozen fisheries products based on the data of frozen fisheries (HS0303), which make up of the large volume of Korea's fisheries export using gravity model. The paper has performed regression analysis through using 624 panel data and the statistical program, STATA 12.0. In this study, we can get two results as follows: First, the total import volume of fisheries and transportation distance of trade partners have an influence on the Korea's trade of frozen fisheries products. The time and fare of transportation have also an influence on the Korea's trade of frozen fisheries products. Second, Korea's trade of frozen fisheries products is also affected by the exchange rate of currencies and settlement of FTA which could be shown as important factors in the estimation of export function of general products.

• Computers and Concrete
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• 제23권5호
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• pp.321-327
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• 2019

Experimental isotherm compressive tests show that concrete behaviour is dependent on temperature. The aim of such tests is to reproduce how concrete will behave under environmental changes within a moderate range of temperature. In this paper, a novel constitutive elastic damage behaviour law is proposed based on a free energy with an apparent damage depending on temperature. The proposed constitutive behaviour leads to classical theory of thermo-elasticity at small strains. Fixed elastic mechanical characteristics and fixed evolution law of damage independent of temperature and the material volume element size are considered. This approach is applied to compressive tests. The model predicts compressive strength and secant modulus of elasticity decrease as temperature increases. A power scaling law is assumed for specific entropy as function of the specimen size which leads to a volume size effect on the stress-strain compressive behaviour. The proposed model reproduces theoretical and experimental results from literature for tempertaures ranging between $20^{\circ}C$ and $70^{\circ}C$. The effect of the difference in the coefficient of thermal expansion between the mortar and coarse aggregates is also considered which gives a better agreement with FIB recommendations. It is shown that this effect is of a second order in the considered moderate range of temperature.

• Journal of Korean Society of Transportation
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• 제33권1호
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• pp.14-28
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• 2015

Numerous research has been conducted using internet search data since the mid-2000s. For example, Google Inc. developed a service predicting influenza patterns using the internet search data. The main objective of this study is to prove the hypothesis that highway traffic indices are similar to the internet search patterns. In order to achieve this objective, a model to predict the number of vehicles entering the expressway and space-mean speed was developed and the goodness-of-fit of the model was assessed. The results revealed several findings. First, it was shown that the Google search traffic was a good predictor for the TCS entering traffic volume model at sites with frequent commute trips, and it had a negative correlation with the TCS entering traffic volume. Second, the Naver search traffic was utilized for the TCS entering traffic volume model at sites with numerous recreational trips, and it was positively correlated with the TCS entering traffic volume. Third, it was uncovered that the VDS speed had a negative relationship with the search traffic on the time series diagram. Lastly, it was concluded that the transfer function noise time series model showed the better goodness-of-fit compared to the other time series model. It is expected that "Big Data" from the internet search data can be extensively applied in the transportation field if the sources of search traffic, time difference and aggregation units are explored in the follow-up studies.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제27권10C호
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• pp.887-901
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• 2002

Software management model divided into the software project model and design estimation model, software matrices model, reliability growth model, process improvement model(or process maturity model) etc. Among these software management models, software complexity model make an estimated of the product software. For a practice of software managed, need to guideline of the static analysis of software. Especially, Software complexity model introduced for the estimation of software quantity and program complexity. In case of measurement the software matrices, its need for us to analysis of software quality and products. On the other hand, we known that complexity program include many defects and consuming of source cost. So, we apply to complexity model using of the program complexity, control structure and volume matrices, interface metrics, process complexity metrics method. In this paper, we represent that the analysis of fault data detected during the system test. Also, we analysis of program control structure and interface, volume matrices in various aspect of switching software. Others, their results utilized similar of project and system development.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.15-18
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• 2004

A numerical method for simulating two-phase flows including surface force is presented. The method is based on fractional step method of finite volume formulation and the interface is tracked with PLIC VOF method. In the CSF model, as color function, f, representing the location of interface varies steeply in the interface region, we need to use smoothed function f to get accurate unit normal and the curvature. Peskin kernel is used to get smoothed function f. A spherical drop in static equilibrium and three-dimensional merging of gas bubble are tested, resulting in the validation of this method

• Journal of Korean Society of Industrial and Systems Engineering
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• 제25권4호
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• pp.40-45
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• 2002

An AS/RS construction cost minimization model under throughput rate requirement constraint has been developed, whose objective function includes S/R machine cost, storage rack cost, and interrace conveyor cost. S/R machine cost is a function of the storage rack height, the unit load weight, and the control logic used by the system, while storage rack cost is a function of the storage rack height, the weight and the volume of the unit load. Since the model is a nonlinear integer programming problem which is very hard to solve exactly with large problem size, a solution procedure is developed to determine the height and the length of the storage rack with a fixed number of S/R machines, while increasing the number of S/R machines one by one to meet the throughput rate requirement.

• Composites Research
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• 제16권6호
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• pp.1-9
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• 2003

In this paper, probabilistic failure analysis based on Weibull distribution function is proposed to predict the fiber strength of composite pressure vessel. And, experimental tests were performed using fiber strand specimens, unidirectional laminate specimens and composite pressure vessels to confirm the volumetric size effect on the fiber strength. As an analytical method, the Weibull weakest link model and the sequential multi-step failure model are considered and mutually compared. The volumetric size effect shows the clearly observed tendency towards fiber strength degradation with increasing stressed volume. Good agreement of fiber strength distribution was shown between test data and predicted results for unidirectional laminate and hoop ply in pressure vessel. The site effect on fiber strength depends on material and processing factors, the reduction of fiber strength due to the stressed volume shows different values according to the variation of material and processing conditions.