• Korean Journal of Weed Science
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• v.30 no.4
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• pp.429-436
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• 2010

Herbicidal activity and characteristics of chrysophanic acid were investigated in semi-field condition. At early and middle post-emergence, Trifolium repens appeared to be very susceptible to chrysophanic acid of $2,000{\mu}g\;mL^{-1}$. However, herbicidal activity of chrysophanic acid of $2,000{\mu}g\;mL^{-1}$ estimated by visual injury to Artemisia princeps was not caused considerable phytotoxicity. Also by foliar application, the concentration of crysophanic acid for effectively control to Polygonum aviculare was much higher than $2,000{\mu}g\;mL^{-1}$. Herbicidal activity of chrysophanic acid to Echinochloa crus-galli, Cypres difformis, Setaria viridis, Digitaria sangguinalis, Bidens tripartita by foliar application was more effective at concentration ranges from 4,000 to $6,000{\mu}g\;mL^{-1}$. These results suggest that chrysophanic acid demanded for higher than $2,000{\mu}g\;mL^{-1}$ to successful weed control in the field condition.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.720-731
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• 2002

Flow with moving free surfaces is analyzed with an the Eulerian coordinate system. This study proposes a semi-implicit filling algorithm using VOF in which the PLIC (Piecewise Linear Interface Calculation) -type interface reconstruction method and the donor-acceptor-type front advancing scheme are adopted. Also, a new scheme using extrapolation of the stream function is proposed to find the velocity of the node that newly enters the computational domain. The effect of wall boundary conditions on the flow field and temperature field is examined by numerically solving a two-dimensional casting process.

• Korean Journal of Mathematics
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• v.25 no.1
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• pp.127-135
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• 2017

The manifold $^*g-ESX_n$ is a generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by the unified field tensor $^*g^{{\lambda}{\nu}}$ through the ES-connection which is both Einstein and semi-symmetric. The purpose of the present paper is to prove a necessary and sufficient condition for a unique Einstein's connection to exist in 5-dimensional $^*g-ESX_5$ and to display a surveyable tnesorial representation of 5-dimensional Einstein's connection in terms of the unified field tensor, employing the powerful recurrence relations in the first class.

• Korean Journal of Mathematics
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• v.23 no.2
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• pp.313-321
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• 2015

The manifold $^*g-ESX_n$ is a generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by the unified field tensor $^*g^{{\lambda}{\nu}}$ through the ES-connection which is both Einstein and semi-symmetric. The purpose of the present paper is to prove a necessary and sufficient condition for a unique Einstein's connection to exist in 3-dimensional $^*g-ESX_3$ and to display a surveyable tnesorial representation of 3-dimensional Einstein's connection in terms of the unified field tensor, employing the powerful recurrence relations in the first class.

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.27-36
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• 1988

For the purposes of drilling oil field and extracting oil deep water in more rough weather, the size of drilling rigs must be estimated. In this paper, the three dimensional source distribution method is used and we assume 10 deg. heeling and trimming condition of the drilling rig(SR-192). Also, the effects of the hydrodynamic forces which include the drift forces for field method, and the motion responses are studied with changing the incident wave direction in the assumed inclining condition. The theory and numerical codes used in this thesis appeared to be very useful for the preliminary design of drilling rigs.

• KSTLE International Journal
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• v.1 no.1
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• pp.8-11
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• 2000

A surface crack in a semi-infinite body under Hertzian contact was considered. The simplified method used to estimate stress intensity factor K for specimen was extended to the model which is chosen in this paper. Very satisfactory results are obtained comparing with those known and it is proved that the method is more convenient than other methods. The results of the analysis show that due to the presence of $K_I$ for unlubricated condition, mode I fracture is active in the field below the surface and the maximum $K_{I}$ is obtained when the trailing edge of Hertzian contact reaches a position over the crack. The magnitudes of stress intensity factors $K_I$ and $K_Il$ increase with increasing friction forces. For a surface crack perpendicular to the contact surface, the stress intensity factor $K_I$ reaches its maximum value at a depth very close to the surface. Driving forve fer crack initiation and propagation is $K_I$ for unlubricated condition and $K_Il$ for both fluid and boundary lubricated condition.n.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.109-114
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• 2000

The purpose of the present study is to develope the estimation scheme for sensible heat flux by semi-empirical approach using routine meteorological data such as solar radiation and air temperature. To compare observed sensible heat flux with estimated sensible heat flux, the sensible heat fluxes were measured by three dimensional sonic anemometer-thermometer. The field observation was performed during 1 year from December 1, 1995 to November 30, 1996 on a rice paddy field in Chunchon basin. The heat fluxes were measured at a heights of 5m and mean meteorological variables were obtained at two levels, 2.5m(or 1.5m) and 10m. Since condition of rice paddy field such as, wetness of the field, roughness length, vary widely, we devided annual data to 5 periods. Comparing with two sensible heat fluxes, the results showed that the correlation coefficients were more than 0.86. Thus, we can conclude that the estimation method of sensible heat fluxes using routine meteorological data is practical and reliable enough.

• Bulletin of the Korean Mathematical Society
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• v.35 no.4
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• pp.641-652
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• 1998

Chung and et al. ([2].1991) introduced a new concept of a manifold, denoted by $^{\ast}g-SEX_n$, in Einstein's n-dimensional $^{\ast}g$-unified field theory. The manifold $^{\ast}g-SEX_n$ is a generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by the unified field tensor $^{\ast}g^{\lambda \nu}$ through the SE-connection which is both Einstein and semi-symmetric. In this paper, they proved a necessary and sufficient condition for the unique existence of SE-connection and sufficient condition for the unique existence of SE-connection and presented a beautiful and surveyable tensorial representation of the SE-connection in terms of the tensor $^{\ast}g^{\lambda \nu}$. Recently, Chung and et al.([3],1998) obtained a concise tensorial representation of SE-curvature tensor defined by the SE-connection of $^{\ast}g-SEX_n$ and proved deveral identities involving it. This paper is a direct continuations of [3]. In this paper we derive surveyable tensorial representations of constracted curvature tensors of $^{\ast}g-SEX_n$ and prove several generalized identities involving them. In particular, the first variation of the generalized Bianchi's identity in $^{\ast}g-SEX_n$, proved in theorem (2.10a), has a great deal of useful physical applications.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.969-974
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• 2007

In this paper, a beamforming technique is introduced to measure the acoustic impedance at both normal and oblique incidence in a free field. The acoustic impedance is obtained by separating incident and reflected signals using the adaptive nulling method which is one of the various beamforming algorithms. To obtain better results, pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone and the white Gaussian noise is suppressed by a wavelet shrinkage technique. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the acoustic impedance of sound absorbing materials under a free field condition.

• Korean Journal of Mathematics
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• v.26 no.1
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• pp.43-51
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• 2018

The manifold $^{\ast}g-ESX_n$ is a generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by the unified field tensor $^{\ast}g^{{\lambda}{\nu}}$ through the ES-connection which is both Einstein and semi-symmetric. The purpose of the present paper is to derive a new set of powerful recurrence relations and to prove a necessary and sufficient condition for a unique Einstein's connection to exist in 5-dimensional $^{\ast}g-ESX_5$ and to display a surveyable tnesorial representation of 5-dimensional Einstein's connection in terms of the unified field tensor, employing the powerful recurrence relations in the second class.