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Benjamin Hagedorn,Alan Mair,Suzanne Tillery,Aly I. El-Kadi,하규철,고기원 한국지질과학협의회 2014 Geosciences Journal Vol.18 No.4
Volcanic islands can be characterized by remarkablesurface air temperature variability. The distribution of weather stationsin these settings, however, is typically too sparse to reliably describetemperature patterns which can complicate regional-scale hydrologicanalyses. Here, a simple method is presented to estimate near surfaceair temperatures for such a setting (Jeju Island, Republic of Korea). The method utilizes temperature lapse rates (TLR; the change intemperature with elevation) which are computed for Tmin, Tave, andTmax for two distinct hemispheres: the more arid northern flanksand the more humid southern flanks of the central orographicdivide. Computed TLRs vary greatly with season and location relativeto the orographic divide and, unlike in continental mountainoussettings, are generally highest for Tmin in winter. Cross-validationresults indicate a good match between modeled and measuredvalues particularly for high altitude stations that are characterizedby highest precipitation rates. Because temporally changing TLRsperform better than the often applied theoretical constant environmentallapse rate of 6.5 °C/km, monthly mean TLRs compiled fromtemperature data from Jeju Island are presented here as proxiesfor surface air temperature simulation efforts in similar settingsfor which only limited climatic data are available.
Wind induced vibrations of long electrical overhead transmission line spans: a modified approach
Verma, Himanshu,Hagedorn, Peter Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.2
For estimating the vortex excited vibrations of overhead transmission lines, the Energy Balance Principle (EBP) is well established for spans damped near the ends. Although it involves radical simplifications, the method is known to give useful estimates of the maximum vibration levels. For very long spans, there often is the need for a large number of in-span fittings, such as in-span Stockbridge dampers, aircraft warning spheres etc. This adds complexity to the problem and makes the energy balance principle in its original form unsuitable. In this paper, a modified version of EBP is described taking into account in-span damping and in particular also aircraft warning spheres. In the first step the complex transcendental eigenvalue problem is solved for the conductor with in-span fittings. With the thus determined complex eigenvalues and eigenfunctions a modified energy balance principle is then used for scaling the amplitudes of vibrations at each resonance frequency. Bending strains are then estimated at the critical points of the conductor. The approach has been used by the authors for studying the influence of in-span Stockbridge dampers and aircraft warning spheres; and for optimizing their positions in the span. The modeling of the aircraft warning sphere is also described in some detail.
El-Kadi, A. I.,Tillery, S.,Whittier, R. B.,Hagedorn, B.,Mair, A.,Ha, K.,Koh, G. W. Springer Science + Business Media 2014 Hydrogeology journal Vol.22 No.3
Numerical groundwater models were used to assess groundwater sustainability on Jeju Island, South Korea, for various climate and groundwater withdrawal scenarios. Sustainability criteria included groundwater-level elevation, spring flows, and salinity. The latter was studied for the eastern sector of the island where saltwater intrusion is significant. Model results suggest that there is a need to revise the current estimate of sustainable yield of 1.77 x 10(6) m(3)/day. At the maximum extraction of 84 % of the sustainable yield, a 10-year drought scenario would decrease spring flows by 28 %, dry up 27 % of springs, and decrease hydraulic head by an island-wide average of 7 m. Head values are particularly sensitive to changes in recharge in the western parts of the island, due to the relatively low hydraulic conductivity of fractured volcanic aquifers and increased groundwater extraction for irrigation. Increases in salinity are highest under drought conditions around the current 2-m head contour line, with an estimated increase of up to 9 g/L under 100 % sustainable-yield use. The study lists recommendations towards improving the island's management of potable groundwater resources. However, results should be treated with caution given the available data limitations and the simplifying assumptions of the numerical modeling approaches.