• The KIPS Transactions:PartD
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• v.13D no.4 s.107
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• pp.455-462
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• 2006

Recently, the filtering approach using vector approximation such as VA-file[1] or LPC-file[2] have been proposed to support similarity search in high dimensional data space. This approach filters out many irrelevant vectors by calculating the approximate distance from a query vector using the compact approximations of vectors in database. Accordingly, the total elapsed time for similarity search is reduced because the disk I/O time is eliminated by reading the compact approximations instead of original vectors. However, the search time of the VA-file or LPC-file is not much lessened compared to the brute-force search because it requires a lot of computations for calculating the approximate distance. This paper proposes a new bitmap index structure in order to minimize the calculating time. To improve the calculating speed, a specific value of an object is saved in a bit pattern that shows a spatial position of the feature vector on a data space, and the calculation for a distance between objects is performed by the XOR bit calculation that is much faster than the real vector calculation. According to the experiment, the method that this paper suggests has shortened the total searching time to the extent of about one fourth of the sequential searching time, and to the utmost two times of the existing methods by shortening the great deal of calculating time, although this method has a longer data reading time compared to the existing vector approximation based approach. Consequently, it can be confirmed that we can improve even more the searching performance by shortening the calculating time for filtering of the existing vector approximation methods when the database speed is fast enough.

• Journal of the Korean Institute of Gas
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• v.14 no.4
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• pp.31-36
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• 2010

An alternative method is presented for predicting failure probability of pipelines with corrosion defects in this paper. The failure of corroded pipeline occurs when the operating pressure is grater than the remaining strength of the pipeline, and a limit state function can be defined as the differences between the remaining strength and the operating pressure. Then, based on structural reliability theory, we can estimate the failure probability of corroded pipeline, which is dependent on elapsed time of the pipeline with active corrosion defects. In this study, a root finding (RF) method has been adopted to solve the limit state function instead of Monte-Carlo simulation (MCS) method which traditionally has been employed to solve those kinds of problems. The calculation results shows that there are only small differences between the RF and the MCS method but the RF has higher efficiency in calculation than the MCS.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2_spc
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• pp.305-315
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• 2020

For geological disposal of radioactive wastes, a method was proposed to evaluate the radionuclide transport in the biosphere by calculating the elapsed time of nuclide migration. The radionuclides were supposed to be introduced from a natural barrier and reached a large surface water body following a groundwater flow in a shallow subsurface. The biosphere was defined as a shallow subsurface environment that included aquifers on a host rock. Using the proposed method, a calculation algorithm was established, and a computer code that implemented the algorithm was developed. The developed code was verified by comparing the simulation results of the simple cases with the results of the analytical solution and a public program, which has been widely used to evaluate the radiation dose using the radionuclide transport near the surface. A case study was constructed using the previous research for radionuclide transport from the hypothetical geological disposal repository. In the case study, the code calculated the mass discharge rate of radionuclide to a stream in the biosphere. Because the previous research only demonstrated the transport of radionuclides from the hypothetical repository to the host rock, the developed code in the present study could help identify the total transport of radionuclide along the complete pathway.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.308-314
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• 1996

The crystal growth rate of benzene from benzene-cyclohexane mixtures at a cylindrical layer crystallizer was determined from the slope of the line of correlation between operating time and layer thickness. The thickness of crystal layer was obtained from the amount of crystal deposited on the cooled wall surface of the crystallizer. The crystal growth rate was related with the degree of subcooling, which was defined as the difference between temperature of melt and that of growing crystal surface. The linear crystal growth rate for binary mixtures was proportional to the second power of the degree of subcooling. Equation model which was obtained from data through the rate of heat and mass transfer in the crystallizer and thus can tell crystal thickness and surface temperature of crystal layer according to the elapsed time was presented and successfully correlated to the experimental data. For the benzene-cyclohexane mixtures contains 5wt% and 10wt% of cyclohexane, the comparison of experimental data with calculation using model equation was done for crystal thickness corresponding to the various cooling temperatures.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.57-66
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• 2017

Self-weight consolidation test and soil property of dredged soil at Incheon habour route were analyzed to determine the initial dredging reclamation amount, reclamation depth, and estimating the required time of self-weight consolidation with calculation of the final planned height of dredging reclamation site. The moisture content, void ratio and ratio of volume change with elapsed time after throwing were estimated through Yano's empirical equation. As a result, there was a less variation in elements when fine-grained soil content was low as similarly to the behavior of coefficient of sedimentation-consolidation, Cs and the highest variation was shown at the fine-grained soil content of 50%. The retention ratio according to the fine grained soil content that could reinforce the comprehensive aspect of retention ratio for each particle size presented in the standard of estimate for reclamation construction work was calculated and presented using the calculated ratio of volume change.

• Nuclear Engineering and Technology
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• v.3 no.3
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• pp.148-154
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• 1971

Some formulae have been derived for the handy calculation of the formation of radioisotope when a reactor is operated regularly on a usual on-off pattern. In particular, the case of isotope production with the present operation condition of tile Korean reactor, which is in operation for 8.2 hours from Monday to Thursday and is not operated on friday and Sunday but is back in operation on Saturday only for 3.2 hours, is discussed herein with special emphasis. Should there be no secondary nuclear reaction resulting in the transformation of produced nuclide, the formula for the calculation of its activity could be derived as follows: (equation omitted) where A: activity (dps), $\Phi$： neutron flux (n cm$^{-2}$ sec$^{-1}$ ), No : number of atoms before the irradiation, $\sigma$ : activation cross section ($\textrm{cm}^2$), λ : disintegration constant of the radioactiveisotope formed (hr$^{-1}$ ), t : elapsed time of target in the reactor (hr), n : number of elasped days of target in the reactor, m : number of days from the first day of sample irradiation to Friday, s, r, q: number of weekday of Friday, Saturday and Sunday, respectively. Since the above formula consists of many invariables on the whole, the activity of each radioisotope to be produced can he easily and conveniently made available from the chart in advance which is made of the invariable terms calculated.

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

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1719-1729
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• 1994

In this paper, an adaptive CAC(Connection Admission Control) method is proposed. The adaptive CAC uses traffic estimates derived from both traffic parameter specified by user and cell flow measurements. Traffic estimation using user-specified parameters is performed at every moment of connection request or connection release by recursive formula which makes real-time calculation possible. Traffic estimation using cell flow measurement is carried out when the number of connected calls does not change during a measurement reflection period-renewal period. The most import ant thing for the traffic estimation using cell flow measurement is the determination of the length of a renewal period to trace a real traffic flow with an allowable time lag and the measurement reflection ratio(MRR) both to reduce the portion of overestimation and to avoid underestimation of real traffic flow. To solve these problems, the adaptive CAC updates renewal period and MRR adaptively according to the number of connections and the elapsed time after last connection or release respectively. Performance analysis for the proposed method is evaluated in several aspects for the cases of both homogeneous and heterogeneous bursty traffic. Numerical examples show the adaptive CAC method has the better performance compared with conventional CAC method based on burst model from the both utilization and QOS point of view.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1077-1080
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• 2008

Material parameters such as surface chloride content, water permeability coefficient, chloride diffusivity and critical chloride content are a substantial key parameter for understanding the durability performance of concrete and its micro-structural densification. Over the past few decades, a considerable number of studies on the durability design for marine concrete structures have been carried out. However, the results are different to each other. In order to establish a consistent durability design system of concrete, it is a precondition to define material parameters, which affect deterioration of concrete due to chloride penetration. Such parameters are surface chloride content, chloride diffusivity, and critical chloride content. Usually these parameters are assumed as temporary constant values or obtained from the experimental results for short term. However, it is necessary to define these parameters reasonably, because these significantly influence the calculation of service life of concrete. In this paper, it is introduced to define material parameters of concrete for chloride diffusion, such as surface chloride content $[Cl]_s$, water permeability coefficient K, chloride diffusivity $D_{Cl}$, critical chloride content $[Cl]_{cr}$. These are expressed as time function considering hydration evolution of hardened cement paste. The definition of the material parameters is a prerequisite to simulate chloride penetration into concrete as time elapsed.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.103-115
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• 2000

The formation of brown-colored precipitates is one of the serious problems frequently encountered in the development and supply of groundwater in Korea, because by it the water exceeds the drinking water standard in terms of color. taste. turbidity and dissolved iron concentration and of often results in scaling problem within the water supplying system. In groundwaters from the Pajoo area, brown precipitates are typically formed in a few hours after pumping-out. In this paper we examine the process of the brown precipitates' formation using the equilibrium thermodynamic and kinetic approaches, in order to understand the origin and geochemical pathway of the generation of turbidity in groundwater. The results of this study are used to suggest not only the proper pumping technique to minimize the formation of precipitates but also the optimal design of water treatment methods to improve the water quality. The bed-rock groundwater in the Pajoo area belongs to the Ca-$HCO_3$type that was evolved through water/rock (gneiss) interaction. Based on SEM-EDS and XRD analyses, the precipitates are identified as an amorphous, Fe-bearing oxides or hydroxides. By the use of multi-step filtration with pore sizes of 6, 4, 1, 0.45 and 0.2 $\mu\textrm{m}$, the precipitates mostly fall in the colloidal size (1 to 0.45 $\mu\textrm{m}$) but are concentrated (about 81%) in the range of 1 to 6 $\mu\textrm{m}$in teams of mass (weight) distribution. Large amounts of dissolved iron were possibly originated from dissolution of clinochlore in cataclasite which contains high amounts of Fe (up to 3 wt.%). The calculation of saturation index (using a computer code PHREEQC), as well as the examination of pH-Eh stability relations, also indicate that the final precipitates are Fe-oxy-hydroxide that is formed by the change of water chemistry (mainly, oxidation) due to the exposure to oxygen during the pumping-out of Fe(II)-bearing, reduced groundwater. After pumping-out, the groundwater shows the progressive decreases of pH, DO and alkalinity with elapsed time. However, turbidity increases and then decreases with time. The decrease of dissolved Fe concentration as a function of elapsed time after pumping-out is expressed as a regression equation Fe(II)=10.l exp(-0.0009t). The oxidation reaction due to the influx of free oxygen during the pumping and storage of groundwater results in the formation of brown precipitates, which is dependent on time, $Po_2$and pH. In order to obtain drinkable water quality, therefore, the precipitates should be removed by filtering after the stepwise storage and aeration in tanks with sufficient volume for sufficient time. Particle size distribution data also suggest that step-wise filtration would be cost-effective. To minimize the scaling within wells, the continued (if possible) pumping within the optimum pumping rate is recommended because this technique will be most effective for minimizing the mixing between deep Fe(II)-rich water and shallow $O_2$-rich water. The simultaneous pumping of shallow $O_2$-rich water in different wells is also recommended.