• Journal of Radiation Protection and Research
• /
• v.9 no.1
• /
• pp.26-32
• /
• 1984

The exposure doses by the radioactive gaseous effluents from nuclear power plants are investigated in the two cases of normal operation and hypothetical accident. Gaussian equation is adapted in the normal operation as the diffusion model of effluents for long period, which uses annual average meteorological data. But the real time models have been used in the case of accidents which analyze the changes of wind direction and speed. In this study the annual exposure doses by the normal operation of Kori unit 1 during $1977{\sim}1982$ were calculated on the basis of the atmospheric diffusion factor by the Gaussian straight line model. And the image processing technique was suggested as the effective method through the wind tunnel experiments to get the characteristic value of atmospheric diffusion coefficient required especially in the accidents of nuclear power plants.

• Journal of Biosystems Engineering
• /
• v.22 no.3
• /
• pp.311-316
• /
• 1997

Two methods were used to detrermine the net photosynthetic rate(NPR) in the plug stand using a wind tunnel for plug seedlings Production. One is called as the integration method in which NPR calculated by the use of air current speed and $CO^2$ concentration measured at any heights above the medium surface in a wind tunnel were summed. It was assumed that the air flow at any layer did not mix with the lower or upper air layer. The other is called as the diffusion method in which eddy diffusivities above the plug stand were used to determine the NPR in the plug stand. In this method, $CO^2$ above or inside the plug stand was assumed to be absorbed vertically. NPR determined by the diffusion method was 28~45% of the NPR calculated by the integration method. Considering the magnitude of NPR and the effects of the air current speed on NPR, the integration method would be adequate for the calculation of NPR in the plug stand. Maximum NPR determined using the integration method appeared at the air current speed of 0.7m $s^{-1}$. It was ascribed to the decreased diffusion resistances of $CO^2$ with the increasing air current speed. NPR at the rear region in plug stand was 20~34% lower than that at the front region. NPR sharply decreased with the increase of an elapsed time after the beginning of photoperiod. Therefore $CO^2$ enrichment would be effective to force the growth of plug seedlings in a semi-closed ecological system under artificial lighting.

• Journal of the Korean Society of Combustion
• /
• v.17 no.3
• /
• pp.17-29
• /
• 2012

The effects of strain rate and preferential diffusion of $H_2$ on flame extinction are numerically studied in interacting premixed syngas-air flames with fuel compositions of 50% $H_2$ + 50% CO and 30% $H_2$ + 70% CO. Flame stability diagrams mapping lower and upper limit fuel concentrations at flame extinction as a function of strain rate are examined. Increasing strain rate reduces the boundaries of both flammable lean and rich fuel concentrations and produces a flammable island and subsequently even a point, implying that there exists a limit strain rate over which interacting flame cannot be sustained anymore. Even if effective Lewis numbers are slightly larger than unity on extinction boundaries, the shape of the lean extinction boundary is slanted even at low strain rate, i.e. $a_g=30s^{-1}$ and is more slanted in further increase of strain rate, implying that flame interaction on lean extinction boundary is strong and thus hydrogen (as a deficient reactant) Lewis number much less than unity plays an important role of flame interaction. It is also shown that effects of preferential diffusion of $H_2$ cause flame interaction to be stronger on lean extinction boundaries and weaker on rich extinction boundaries. Detailed analyses are made through the comparison between flame structures with and without the restriction of the diffusivities of $H_2$ and H in symmetric and asymmetric fuel compositions. The reduction of flammable fuel compositions in increase of strain rate suggests that the mechanism of flame extinction is significant conductive heat loss from the stronger flame to ambience.

• Archives of design research
• /
• v.16 no.2
• /
• pp.121-130
• /
• 2003

The diffusion expressive power means the flexibility of which creative power test spheres(fluency, originality) by Torrance is ability making the considerations, thoughts and concepts to the meaningful symbolic change. This study is willing to develop and improve program toward the diffusion expressive power and is to testify training effect of the students are majoring design with the object. The training programs composed of six levels which is based on the theory of Eskild Tjalve. And the parameters of each levels are element, function, number, arrangement, form geometric, size and have to practice 2 weeks at once by 12 weeks. For successful measuring the effective results of this study, 40 undergraduate junior students in the department of design are grouped to excercise with experimental pilot group and regulated group. The standard type of creative paper is used to evaluate the results of student's training. This study give proof that creative power of the experimental pilot and under training group is higher than the regulated and under comparison group at in the conclusion.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.7
• /
• pp.36-41
• /
• 2018

An image intensifying device is equipment that makes weak objects visible in a dark environment, such as making nighttime bright enough to let objects be visually observed. It is possible to obtain a clear image by amplifying the light in the presence of a certain amount of weak light. However, in an extremely low-light environment, where even moonlight is not present, there is not enough light to amplify anything, and the sharpness of the screen deteriorates. In this paper, a method is proposed to improve image quality by using multiple filters and anisotropic diffusion for output noise of the image-intensifying device in extreme low-light environments. For the experiment, the output of the image-intensifying device was obtained under extremely low-light conditions, and signal processing for improving the image quality was performed. The configuration of the filters for signal processing uses anisotropic diffusion after applying a median filter and a Wiener filter for effective removal of salt-and-pepper noise and Gaussian noise, which constitute the main noise appearing in the image. Experimental results show that the improvement visually enhanced image quality. Both peak signal-to-noise ratio (PSNR) and SSIM, which are quantitative indicators, show improved values.

• Journal of KIISE:Databases
• /
• v.37 no.2
• /
• pp.82-91
• /
• 2010

Data compression technique is traditional and effective to reduce network traffic. Generally, sensor data exhibit strong correlation in both space and time. Many algorithms have been proposed to utilize these characteristics. However, each sensor just utilizes neighboring information, because its communication range is restrained. Information that includes the distribution and characteristics of whole sensor data provide other opportunities to enhance the compression technique. In this paper, we propose an orthogonal approach for compression algorithm based on a novel feedback diffusion algorithm in sensor networks. The base station or a super node generates the Huffman code for compression of sensor data and broadcasts it into sensor networks. Every sensor that receives the information compresses their sensor data and transmits them to the base station. We define this approach as feedback-diffusion. In order to show the superiority of our approach, we compare it with the existing aggregation algorithms in terms of the lifetime of the sensor network. As a result, our experimental results show that the whole network lifetime was prolonged by about 30%.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.2
• /
• pp.104-110
• /
• 1997

Increase of marine transpotation in coastal area frequently yields oil spill accidents due to collision or grounding of oil tankers, which affects great deal of damages on ocean environments. Exact prediction of oil pollution area in time domain, which is called oil map, is very important for effective and efficient oil recovery and minimization of environmental damage. The prediction is carried out by considering the two distinct processes which are initial diffusion on the still water surface and advection due to tide, wind wave induced surface currents. In the present paper, only the initial diffusion is dealt with. Somewhat new simulation model and its numerical scheme are proposed to predict it. Simple diffusion experiment is also carried out to check the validity of the present method. Furthermore, some example simulations are performed for virtual oil spill accident. Quite realistic oil map including oil thickness distributions can be obtained by the present model.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.4 no.3 s.14
• /
• pp.73-81
• /
• 2004

On this study, durability decreasing element caused by salt damage was analyzed elementally and studied with the data of the inside and outside in the country. The design strength and water-cement ratio according to diffusion coefficients of chloride were applied to Fick's diffusion equation. The required over depended on environmental conditions is estimated with endurance period, and the influences on cover according to the transformation of the each parameter were investigated. In consequence, if water-cement ratio decreases and design strength increases, it shows that slowing infiltration velocity of chloride ion can decrease required cover. Especially, it is more effective to use Portland blast-furnace slag cement into high strength concrete in the splash zone environmental conditions in blocking the diffusion of chloride ion. As the result, in the case of the offshore concrete structure needed high durability, it is needed to increase cover($3cm{\sim}8cm$) than minimum standard cover(8cm) according to environmental conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.8
• /
• pp.3005-3027
• /
• 2015

Spam has become one of the top threats of micro-blogging networks as the representations of rumor spreading, advertisement abusing and malware distribution. With the increasing popularity of micro-blogging, the problems will exacerbate. Prior detection tools are either designed for specific types of spams or not robust enough. Spammers may escape easily from being detected by adjusting their behaviors. In this paper, we present a novel model to quantitatively evaluate information diffusion in micro-blogging networks. Under this model, we found that spam posts differ wildly from the non-spam ones. First, the propagations of non-spam posts mostly result from their followers, but those of spam posts are mainly from strangers. Second, the non-spam posts relatively last longer than the spam posts. Besides, the non-spam posts always get their first reposts/comments much sooner than the spam posts. With the features defined in our model, we propose an RBF-based approach to detect spams. Different from the previous works, in which the features are extracted from individual profiles or contents, the diffusion features are not determined by any single user but the crowd. Thus, our method is more robust because any single user's behavior changes will not affect the effectiveness. Besides, although the spams vary in types and forms, they're propagated in the same way, so our method is effective for all types of spams. With the real data crawled from the leading micro-blogging services of China, we are able to evaluate the effectiveness of our model. The experiment results show that our model can achieve high accuracy both in precision and recall.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.3
• /
• pp.5-11
• /
• 2004

Characteristics of advective-diffusive transport of inorganic chemicals in clayey soils as well as in two hardened barrier materials of silica and lime are analyzed from the laboratory column test and compared with those of pure diffusive column test. The results show that the average dispersion coefficients of three materials are $4.39\times l0^{-10}\textrm{m}^2 /s,\; 1.98\times l0^{-10}\textrm{m}^2 /s,\; 1.99\times l0^{-10}\textrm{m}^2 /s$, respectively, and the value of clay is higher than that of hardened barrier materials. There was no significant difference between the dispersion coefficients of advective-diffusive column tests and the effective diffusion coefficients from the pure diffusive column tests, if advective velocity was lower than l0$^{-7}$$m^2$/s. The range of dispersion coefficients of advective-diffusive column tests was narrower than that of diffusion coefficients of pure diffusion tests.