• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.81-94
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• 1997

In many solute transport studies, either flux or resident concentration has been used. Choice of the concentration mode was dependent on the monitoring device in solute displacement experiments. It has been accepted that no priority exists in the selection of concentration mode in the study of solute transport. It would be questionable, however, to accept the equivalency in the solute transport parameters between flux and resident concentrations in structured soils exhibiting preferential movement of solute. In this study, we investigate how they differ in the monitored breakthrough curves (BTCs) and transport parameters for a given boundary and flow condition by performing solute displacement experiments on a number of undisturbed soil columns. Both flux and resident concentrations have been simultaneously obtained by monitoring the effluent and resistance of the horizontally-positioned TDR probes. Two different solute transport models namely, convection-dispersion equation (CDE) and convective lognormal transfer function (CLT) models, were fitted to the observed breakthrough data in order to quantify the difference between two concentration modes. The study reveals that soil columns having relatively high flux densities exhibited great differences in the degree of peak concentration and travel time of peak between flux and resident concentrations. The peak concentration in flux mode was several times higher than that in resident one. Accordingly, the estimated parameters of flux mode differed greatly from those of resident mode and the difference was more pronounced in CDE than CLT model. Especially in CDE model, the parameters of flux mode were much higher than those of resident mode. This was mainly due to the bypassing of solute through soil macropores and failure of the equilibrium CDE model to adequate description of solute transport in studied soils. In the domain of the relationship between the ratio of hydrodynamic dispersion to molecular diffusion and the peclet number, both concentrations fall on a zone of predominant mechanical dispersion. However, it appears that more molecular diffusion contributes to the solute spreading in the matrix region than the macropore region due to the nonliearity present in the pore water velocity and dispersion coefficient relationship.

• Restorative Dentistry and Endodontics
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• v.32 no.4
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• pp.385-396
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• 2007

The aims of this study were to compare the shaping effect and safety between single length technique recommended by manufacturer and crown-down technique using Mtwo rotary file and to present a modified method in use of Mtwo file. Sixty simulated root canal resin blocks were used. The canals were divided into three groups according to instrument and the manner of using methods. Each group had 20 specimens. Group MT was instrumented with single length technique of Mtwo, group MC was instrumented with crown-down technique of Mtwo and group PT was instrumented with crown-down technique of ProTaper. All of the rotary files used in this study were operated by an electric motor. The scanned canal images of before and after preparation were superimposed. These superimposed images were evaluated at apical 1 to 8 mm levels Angle changes were calculated. The preparation time, weight loss, instrument failure and binding, canal aberrations, and centering ratio were measured. Statistical analysis of the three experimental groups was performed with ANOVA and Duncan's multiple range tests for post-hoc comparison and Fisher's exact test was done for the frequency comparison. In total preparation time, group MT and group MC were less than group PT. In the aberrations, group MT had more elbows than those of group MC and group PT. The binding of group MC was least and group MT was less than group PT (P < 0.05). Under the condition of this study, crown-down technique using Mtwo rotary file is better and safer method than single length technique recommended by the manufacturer.

• Explosives and Blasting
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• v.9 no.1
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• pp.3-13
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• 1991

The cautious blasting works had been used with emulsion explosion electric M/S delay caps. Drill depth was from 3m to 6m with Crawler Drill ${\phi}70mm$ on the calcalious sand stone (soft -modelate -semi hard Rock). The total numbers of test blast were 88. Scale distance were induced 15.52-60.32. It was applied to propagation Law in blasting vibration as follows. Propagtion Law in Blasting Vibration $V=K(\frac{D}{W^b})^n$ were V : Peak partical velocity(cm/sec) D : Distance between explosion and recording sites(m) W : Maximum charge per delay-period of eight milliseconds or more (kg) K : Ground transmission constant, empirically determind on the Rocks, Explosive and drilling pattern ets. b : Charge exponents n : Reduced exponents where the quantity $\frac{D}{W^b}$ is known as the scale distance. Above equation is worked by the U.S Bureau of Mines to determine peak particle velocity. The propagation Law can be catagorized in three groups. Cubic root Scaling charge per delay Square root Scaling of charge per delay Site-specific Scaling of charge Per delay Plots of peak particle velocity versus distoance were made on log-log coordinates. The data are grouped by test and P.P.V. The linear grouping of the data permits their representation by an equation of the form ; $V=K(\frac{D}{W^{\frac{1}{3}})^{-n}$ The value of K(41 or 124) and n(1.41 or 1.66) were determined for each set of data by the method of least squores. Statistical tests showed that a common slope, n, could be used for all data of a given components. Charge and reduction exponents carried out by multiple regressional analysis. It's divided into under loom over loom distance because the frequency is verified by the distance from blast site. Empirical equation of cautious blasting vibration is as follows. Over 30m ------- under l00m ${\cdots\cdots\cdots}{\;}41(D/sqrt[2]{W})^{-1.41}{\;}{\cdots\cdots\cdots\cdots\cdots}{\;}A$ Over 100m ${\cdots\cdots\cdots\cdots\cdots}{\;}121(D/sqrt[3]{W})^{-1.66}{\;}{\cdots\cdots\cdots\cdots\cdots}{\;}B$ where ; V is peak particle velocity In cm / sec D is distance in m and W, maximLlm charge weight per day in kg K value on the above equation has to be more specified for further understaring about the effect of explosives, Rock strength. And Drilling pattern on the vibration levels, it is necessary to carry out more tests.

• Journal of the Korean Geographical Society
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• v.38 no.2
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• pp.312-323
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• 2003

This writer absolutely agrees with the government that regional disequilibrium is severe enough to consider moving the administrative capital. Pursuing this course solely to establish a balanced development, however, is not a convincing enough reason. The capital city is directly related to not only the social and economic situation but, much more importantly, to the domestic political situation as well. In the mid-1970s, the proposal by the Third Republic to move the capital city temporarily was based completely on security reasons. At e time, the then opposition leader Kim, Dae-jung said that establishing a safe distance from the demilitarized zone(DMZ) reflected a typically military decision. His view was that retaining the capital city close to the DMZ would show more consideration for the will of the people to defend their own country. In fact, independent Pakistan moved its capital city from Karachi to Islamabad, situated dose to Kashmir the subject of hot territorial dispute with India. It is regrettable that no consideration has been given to the urgent political situation in the Korean peninsula, which is presently enveloped in a dense nuclear fog. As a person requires health to pursue his/her dream, a country must have security to implement a balanced territorial development. According to current urban theories, the fate of a country depends on its major cities. A negligently guarded capital city runs the risk of becoming hostage and bringing ruin to the whole country. In this vein, North Koreas undoubted main target of attack in the armed communist reunification of Korea is Seoul. For the preservation of our state, therefore, it is only right that Seoul must be shielded to prevent becoming hostage to North Korea. The location of the US Armed Forces to the north of the capital city is based on the judgment that defense of Seoul is of absolute importance. At the same time, regardless of their different standpoints, South and North Korea agree that division of the Korean people into two separate countries is abnormal. Reunification, which so far has defied all predictions, may be realized earlier than anyone expects. The day of reunification seems to be the best day for the relocation of the capital city. Building a proper capital city would take at least twenty years, and a capital city cannot be dragged from one place to another. On the day of a free and democratic reunification, a national agreement will be reached naturally to find a nationally symbolic city as in Brazil or Australia. Even if security does not pose a problem, the governments way of thinking would not greatly contribute to the balanced development of the country. The Chungcheon region, which is earmarked as the new location of the capital city, has been the greatest beneficiary of its proximity to the capital region. Not being a disadvantaged region, locating the capital city there would not help alleviate regional disparity. If it is absolutely necessary to find a candidate region at present, considering security, balanced regional development and post-reunification scenario of the future, Cheolwon area located in the middle of the Korean peninsula may be a plausible choice. Even if the transfer of capital is delayed in consideration of the present political conflict between the South and the North Koreas, there is a definite shortcut to realizing a balanced regional development. It can be found not in the geographical dispersal of the central government, but in the decentralization of power to the provinces. If the government has surplus money to build a new symbolic capital city, it is only right that it should improve, for instance, the quality of drinking water which now everyone eschews, and to help the regional subway authority whose chronic deficit state resoled in a recent disastrous accident. And it is proper to time the transfer of capital city to coincide with that of the reunification of Korea whenever Providence intends.