• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.69-75
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• 2003

In this study, his technique was applied to a GDI spray in order to investigate the mixture distribution. In addition, the homogeneity degree and diffusion effect according to ambient temperature in the high pressure chamber were analyzed by using an entropy analysis method. From this experiment, we could find that entropy analysis is very effective method for the analysis of mixture formation, and the entropy values increase with the progress of uniformity in diffusion Process. we tried to provide the fundamental data for parameter which effects on the spray macroscopic characteristics with mixture ratio of diesel and gasoline. In addition, the mixture formation was analyzed by using entropy analysis. The entropy analysis is based on the concept of statistical entropy, and it identifies the degree of homogeneity in the fuel concentration. From the entropy analysis results we could find that the direct diffusion phenomena is a dominant factor in the formation of a homogeneous mixture at downstream of GDI spray especially in vaporizing conditions. As to increasing ambient temperature and increasing gasoline rate, the entropy intensity using the statistic thermodynamics method is increased because evaporation rate is higher gasoline than diesel.

• Journal of the Semiconductor & Display Technology
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• v.12 no.1
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• pp.23-28
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• 2013

Epoxy resins are widely used in microelectronics packaging such as printed circuit board and encapsulating for semiconductor manufacturing. Water can diffuse into and through the epoxy matrix systems and moisture absorption at boarding interfaces of matrix resin systems can lead to a hydrolysis at the interfaces resulting in delamination of encapsulating materials. In the study, the changes of diffusion coefficient and moisture content ratio of epoxy resin systems with nano-sized fillers according to the change of liquid type epoxy resins were investigated. RE-304S, RE-310S, RE-810NM and HP-4032D as a epoxy resin, Kayahard AA as a hardener, and 1B2MI as a catalyst were used in these epoxy resin systems. After curing, moisture content ratios were measured with time under the 85 and 85% relative humidity condition using a thermo-hydrostat. The maximum moisture absorption ratio and diffusion coefficient of EMC decrease with the filler content. It can be seen that these decreases are due to the increase of filler surface area and the decrease of moisture through channel with the content of nano-sized filler.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.84-91
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• 2014

In this study, in order to find the improvement effect of metakaolin for using improvement of strength in concrete structures, it is investigated the diffusion coefficient of chloride ions and adiabatic temperature rise test. As a result, due to the mixing of metakaolin, it has been confirmed reducing diffusion coefficient of chloride ions and could prevent down of slump for use of adding fly ash. Therefore, ensuring resistance to chloride ion penetration into concrete, it is possible to enlarge the W/B ratio and reduce the adiabatic temperature rise by mixing of metakaolin. So, it is confirmed that the durability of concrete structures is increased.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.207-212
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• 2002

Reportedly, the use of mineral admixtures make concrete more durable and tighten against water. But, it is needed to study more about the relationship between the admixtures and the chloride ion diffusion. When concrete is mixed with fly-ash, pozzolanic reaction occur to time. So we should consider the factors that can evaluate inner structure of concrete in order to evaluate the chloride diffusion of the concrete more accurately. Therefore, in this study, we analyzed the correlation between chloride ion diffusion and physical properties such as compressive strength, void ratio, air permeability of the concrete, and tried to use them as fundamental data for analyzing chloride ion diffusion mechanism of the concrete mixed with fly-ash.

• Computers and Concrete
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• v.10 no.6
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• pp.587-607
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• 2012

The purpose of this research is to propose a design technique of concrete mix proportions satisfying service life through genetic algorithm (GA) and neural network (NN). For this, thirty mix proportions and the related diffusion coefficients in high performance concrete are analyzed and fitness function for diffusion coefficient is obtained considering mix components like w/b (water to binder ratio), cement content, mineral admixture (slag, flay ash and silica fume) content, sand and coarse aggregate content. Through averaging the results of 10 times GA simulations, relative errors to the previous data decrease lower than 5.0% and the simulated mix proportions are verified with the experimental results. Assuming the durability design parameters, intended diffusion coefficient for intended service life is derived and mix proportions satisfying the service life are obtained. Among the mix proportions, the most optimized case which satisfies required concrete strength and the lowest cost is selected through GA algorithm. The proposed technique would be improved with the enhancement of comprehensive data set including wider the range of diffusion coefficients.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.429-432
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• 2000

The studies on chloride diffusion of concrete have been done so far by many researchers. However, there are few studies on the effects of other attacks, like carbonation, on chloride diffusion properties. In this study, the experiments are carried out focusing on this by varying cement type, water to cement ratio and replacement of fly ash of concrete. The results show that carbonation attacks do not affect greatly chloride diffusion properties of plain concrete, while the different tendencies are exhibited for fly ash concrete. Therefore, it is desirable to consider the effects of carbonation attacks on the chloride diffusion model to predict accurately the penetration of chloride ion fly ash is partially replaced for cement.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.280-280
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• 2012

We examined ammonia diffusion on the surface of amorphous ice film through the measurement of decreasing residual quantity of $NH_3$ molecules compared to $H_2O$. The populations of $NH_3$ molecules on the surface of amorphous ice were monitored by using the techniques of temperature programmed reactive ion scattering (TPRIS) method. The ratio of intensity between ammonia and water was examined as a function of time at controlled temperature. When ammonia molecules were externally added onto an ice film at a temperature of 80 K, ammonia coverage with regard to ice was 0.12-0.16 ML. The intensity of ammonia molecules on the surface of ice decreased as time increased and the extent of decreased intensity of ammonia increased as controlled temperature increased. Moreover, energy barrier was estimated to be $51kJmol^{-1}$ on amorphous ice film. The results of the experiment indicate that ammonia molecules have a property of vertical diffusion into amorphous ice and the energy barrier of ammonia diffusion into bulk of ice is higher than that of hydrogen bonding.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.99-107
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• 2003

The diffusion coefficient of Xe-133 was obtained from an annealing test. The specimens were made from a UO$_2$ single crystal powder with natural enrichment. Weight and grain size were 300mg and ($23\mu\textrm{m}$, respectively. Oxygen potentials were obtained from an oxygen sensor. Released fractions were obtained from both results of gamma scans and quantitative analysis with MCNP code, The annealing test was performed at three temperatures at once. Diffusion coefficients of Xe-133 were calculated using slope of Booth theory in each O/M ratios. Activation energy and the pre-exponential factor of the diffusion coefficient were obtained. The activation energy of near stoichiomeric $UO_2$ is 310 kJ/mol. The measured values of near stoichiometric $UO_2$ are very close to other data available. Diffusion coefficients increase with hyper-stoichiometry, due to higher concentration of cation vacancies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.9-17
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• 2019

Cement hydrates and the related characteristics change with ages, and the behaviors are much related with chloride diffusion. In this work, 30% replacement ratio with FA(Fly Ash) and GGBFS(Ground Granulated Blast Furnace Slag) are considered for concrete with three levels of W/B (Water to Binder ratio) and 2 years of curing period. Chloride diffusion coefficients from accelerated condition are obtained at 5 measurement period (28days, 56days, 180days, 365days, and 730days), and the results are compared with porosity, binding capacity, and permeability from program-DUCOM. The similar changing pattern between chloride diffusion and permeability is observed since permeability is proportional to the square of porosity. Curing period is grouped into 4 periods and the changing ratios are investigated. Cement hydrate characteristics such as porosity, permeability, and diffusion coefficient are dominantly changed at the early ages (28~56 days), and diffusion coefficient in OPC concrete with low W/B continuously changes to 180days.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.120-122
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• 2015

In this paper, we proposed an algorithm of the unnecessary copied message inhibition using dynamic density what is called DDIM(Dynamic Density-based Inhibited Message diffusion) in DTNs(Delay Tolerant Networks). Existing DTN routing algorithms as Epidemic and Spray and Wait have some problems that occur large overhead in dense network due to the thoughtless message diffusion. Our proposed method, the DDIM, determines adjusted number of copied message through dynamic node density that is calculated using node's radio coverage and neighbor nodes in period time to solve message diffusion problem. It decrease overhead without losing message delivery ratio and increased latency through reducing message diffusion. In this paper, we compare delivery ratio, average latency and overhead of proposed algorithm, DDIM, and existing DTN routing algorithm and prove enhanced performance through simulation results.