5,214 research outputs found

    Evaluation of River Health and Water Quantity at the Anseong River, Changwon City, Korea

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    The paper aims to analyse the degree of river naturality according to the river morphology and the flora at raparian regions on the Anseong River during four seasons. Number of flexion was one at upper and low regions. That of middle region was absent. Bed materials were boulders and gravel in upper region and sand, silt, and clay in middle and low regions. Material of river shore at low channel width was the state of nature without protecting materials at upper region, but that was concreted impervious. Those of middle and upper regions were many artificial levees. The flora on the Anseong River was a total of 61 taxa, including 25 families, 54 species, and 7 varieties. The oxygen demand parameters COD, and BOD were within unacceptable levels at middle and low regions. Many cement blocks were creating instead river grasslands by the Direct stream Rivers Project and wide road construction. This artificial action reduced the waters natural filtration action

    River Morphology and Riparian Vegetation at the Tributary of Seongdong, Korea

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    The purpose of this study is to investigate river morphology, riparian vegetation, and water quality on the tributary of Seongdong River in Korea during four seasons. There were not significant differences for river structure according to the river morphology and river naturality according to the environment of river at three regions (upper, middle and low areas). The portion of BOD and COD in the river increased exponentially along the upper-down gradient. The surveyed region was a total of 57 taxa, including 23 families, 50pecies, and 7varieties. Naturalized plants were 18species

    Efficient Coil Design by Electromagnetic Topology Optimization for Electromagnetic Sharp Edge Forming of DP980 Steel Sheet

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    This paper proposes a design method of the tool coil by topology optimization for the electromagnetic sharp edge forming process. Topology optimization is an approach that optimizes material configuration in a given domain to meet the design requirements. The design problem for the tool coil is defined as enhancing efficiency of the forming process and optimization problem is set to be maximization of the Lorentz force induced on the tool coil. A new topology optimization formulation based on the numerical methods for electromagnetism using FEM and BEM is developed for maximization of the Lorentz force. Optimum design of the tool coil is obtained by the topology optimization using the element density approach. The optimized result is compared with other coils which have different configurations to show the effectiveness of the proposed method. The idea of applying topology optimization to the design of the tool coil is successful and this formulation deals effectively for the optimization problems

    Vortex fluctuations in superconducting La-Sr-Cu-O

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    Vortex fluctuations in the La2−xSrxCuO4+δLa_{2-x}Sr_{x}CuO_{4+\delta} system have been studied as a function of magnetic field, temperature and carrier concentration in order to determine the dimensionality of the fluctuations. For a x=0.10x=0.10 sample, there is a unique crossing-temperature on the magnetization vs. temperature plots for all magnetic fields up to 7 T, and the data scale very well with 2D fluctuation theory. At lower x-values where Hc2H_{c2} is much smaller, there are two well defined crossing points, one at low fields (typically less than 1 T) and another at high fields (typically 3-7 T). A fit of the data to fluctuation theory shows that the low field crossing data scale as 2D fluctuations and the high field crossing data scale as 3D fluctuations. It would appear that as the magnetic field approaches Hc2H_{c2}, there is a 2D to 3D cross-over where the low field 2D pancake vortex structure transforms into a 3D vortex structure

    Electronic density of states derived from thermodynamic critical field curves for underdoped La-Sr-Cu-O

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    Thermodynamic critical field curves have been measured for La2−xSrxCuO4+δLa_{2-x}Sr_{x}CuO_{4+\delta} over the full range of carrier concentrations where superconductivity occurs in order to determine changes in the normal state density of states with carrier concentration. There is a substantial window in the H−TH-T plane where the measurements are possible because the samples are both thermodynamically reversible and the temperature is low enough that vortex fluctuations are not important. In this window, the data fit Hao-Clem rather well, so this model is used to determine HcH_c and κc\kappa_c for each temperature and carrier concentration. Using N(0) and the ratio of the energy gap to transition temperature, Δ(0)/kBTc\Delta (0)/k_BT_c, as fitting parameters, the HcvsTH_c vs T curves give Δ(0)/kBTc∼2.0\Delta (0)/k_BT_c \sim 2.0 over the whole range of xx. Values of N(0) remain rather constant in the optimum-doped and overdoped regime, but drops quickly toward zero in the underdoped regime.

    Complements of hypersurfaces, variation maps and minimal models of arrangements

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    We prove the minimality of the CW-complex structure for complements of hyperplane arrangements in Cn\mathbb C^n by using the theory of Lefschetz pencils and results on the variation maps within a pencil of hyperplanes. This also provides a method to compute the Betti numbers of complements of arrangements via global polar invariants

    Classical generalized constant coupling model for geometrically frustrated antiferromagnets

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    A generalized constant coupling approximation for classical geometrically frustrated antiferromagnets is presented. Starting from a frustrated unit we introduce the interactions with the surrounding units in terms of an internal effective field which is fixed by a self consistency condition. Results for the magnetic susceptibility and specific heat are compared with Monte Carlo data for the classical Heisenberg model for the pyrochlore and kagome lattices. The predictions for the susceptibility are found to be essentially exact, and the corresponding predictions for the specific heat are found to be in very good agreement with the Monte Carlo results.Comment: 4 pages, 3 figures, 2 columns. Discussion about the zero T value of the pyrochlore specific heat correcte

    Therapeutic embolization of the dural arteriovenous malformation involving the jugular bulb.

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    Pulsatile tinnitus is a rarely occurring symptom of vascular origin. Most frequently, the symptoms are due to an arteriovenous malformation, to a tumor of the jugular glomus or to a local arterial stenosis. A 39-yr-old Korean male suffering from pulsatile tinnitus of the left ear was diagnosed to have dural arteriovenous malformation of the jugular bulb. Magnetic resonance imaging and angiography revealed a high-velocity vascular lesion encroaching the internal jugular vein and sigmoid sinuses. Digital subtraction angiography demonstrated a dural arteriovenous malformation involving the jugular bulb. The arterial supply was from the neuromeningeal branch of the left ascending pharyngeal artery and inferior tympanic artery. Stenosis of the left jugular vein caused retrograde venous drainage through the contralateral transverse sinus. Superselective embolization of these feeding arteries was successfully performed using 25% mixture of N-butylcyanoacrylate and lipiodol. In postembolization period, his complaints of pulsatile tinnitus and buzzing noise behind his left ear disappeared
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