• Geophysics and Geophysical Exploration
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• v.25 no.2
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• pp.85-92
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• 2022

An elongated object in one direction can be approximated as a line segment. Here, the closed-form expressions of a line segment's vector magnetic and magnetic gradient tensor are required to interpret responses by a line segment. Therefore, the analytical expressions of the vector magnetic and magnetic gradient tensor are derived. The vector magnetic is converted from the existing gravity gradient tensor using Poisson's relation where the gravity gradient tensor caused by a line segment can be transformed into a vector magnetic. Then, the magnetic gradient tensor is derived by differentiating the vector magnetic with respect to each axis in the Cartesian coordinate system. The synthetic total magnetic data simulated by an iron pile on boreholes are inverted by a nonlinear inversion process so that the physical parameters of the iron pile, including the beginning point, the length, orientation, and magnetization vector are successfully estimated.

• Journal of Korean Society of Transportation
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• v.23 no.3 s.81
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• pp.125-136
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• 2005

The current traffic accident reduction procedure in economic feasibility study does not consider the characteristics of road and V/C ratio. For solving this problem, this paper suggests methods to be able to evaluate safety of each road in construction and improvement through developing accident Prediction model in reflecting V/C ratio Per road types and traffic characters. In this paper as primary process, model is made by tke object of urban roads. Most of all, factor effecting on accident relying on road types is selected. At this point, selecting criteria chooses data obtained from road planning procedure, traffic volume, existence or non-existence of median barrier, and the number of crossing point, of connecting road. and of traffic signals. As a result of analyzing between each factor and accident. all appear to have relatives at a significant level of statistics. In this research, models are classified as 4-categorized classes according to roads and V/C ratio and each of models draws accident predicting model through Poisson regression along with verifying real situation data. The results of verifying models come out relatively satisfactory estimation against real traffic data. In this paper, traffic accident prediction is possible caused by road's physical characters by developing accident predicting model per road types resulted in V/C ratio and this result is inferred to be used on predicting accident cost when road construction and improvement are performed. Because data using this paper are limited in only province of Jeollabuk-Do, this paper has a limitation of revealing standards of all regions (nation).

• Journal of Wetlands Research
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• v.16 no.3
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• pp.327-336
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• 2014

Submerged thin walls are extreme case of submerged rectangular blocks, and could be used for many purposes in rivers or coastal zones, e.g. to tsunami. To understand flow characteristics including flow and pressure fields around a specific submerged thin wall a numerical model was applied which includes computation of hydrodynamic pressure on ${\sigma}$-coordinate. ${\sigma}$-coordinate has strong merits for simulation of subcritical flow over mild-sloped beds. On the other hand ${\sigma}$-coordinate is quite poor to treat sharp structures on the bed. There have been a few trials to incorporate dynamic pressure in ${\sigma}$-coordinate by some researchers. One of the previous approaches includes process of sloving the Poisson equation. However, the above method includes many high-order terms, and requires long cpu for simulation. Another method SOLA was developed by Hirt et al. for computation of dynamic pressure, but it was valid for straight grid system only. Previous SOLA was modified for ${\sigma}$-coordinate for the present purpose and was adopted in a model system, CST3D. Computed flow field shows reasonable behaviour including vorticity is much stronger than the upstream and downstream of the structure. The model was verified to laboratory experiments at a 2DV flume. Time-average flow vectors were measured by using one-dimensional electro-magnetic velocimeter. Computed flow field agrees well with the measured flow field within 10 % error from the speed point of view at 5 profiles. It is thought that the modified SOLA scheme is useful for ${\sigma}$-coordinate system.