Assessing sustainability of groundwater resources on Jeju Island, South Korea, under climate change, drought, and increased usage

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.

Photonic sensors for micro-damage detection: A proof of concept using numerical simulation

M. Sheyka,I. El-Kady,M. F. Su,M. M. Reda Taha 국제구조공학회 2009 Smart Structures and Systems, An International Jou Vol.5 No.4

Damage detection has been proven to be a challenging task in structural health monitoring (SHM) due to the fact that damage cannot be measured. The difficulty associated with damage detection is related to electing a feature that is sensitive to damage occurrence and evolution. This difficulty increases as the damage size decreases limiting the ability to detect damage occurrence at the micron and submicron length scale. Damage detection at this length scale is of interest for sensitive structures such as aircrafts and nuclear facilities. In this paper a new photonic sensor based on photonic crystal (PhC) technology that can be synthesized at the nanoscale is introduced. PhCs are synthetic materials that are capable of controlling light propagation by creating a photonic bandgap where light is forbidden to propagate. The interesting feature of PhC is that its photonic signature is strongly tied to its microstructure periodicity. This study demonstrates that when a PhC sensor adhered to polymer substrate experiences micron or submicron damage, it will experience changes in its microstructural periodicity thereby creating a photonic signature that can be related to damage severity. This concept is validated here using a three-dimensional integrated numerical simulation.

Photonic sensors for micro-damage detection: A proof of concept using numerical simulation

Sheyka, M.,El-Kady, I.,Su, M.F.,Taha, M.M. Reda Techno-Press 2009 Smart Structures and Systems, An International Jou Vol.5 No.4

Damage detection has been proven to be a challenging task in structural health monitoring (SHM) due to the fact that damage cannot be measured. The difficulty associated with damage detection is related to electing a feature that is sensitive to damage occurrence and evolution. This difficulty increases as the damage size decreases limiting the ability to detect damage occurrence at the micron and submicron length scale. Damage detection at this length scale is of interest for sensitive structures such as aircrafts and nuclear facilities. In this paper a new photonic sensor based on photonic crystal (PhC) technology that can be synthesized at the nanoscale is introduced. PhCs are synthetic materials that are capable of controlling light propagation by creating a photonic bandgap where light is forbidden to propagate. The interesting feature of PhC is that its photonic signature is strongly tied to its microstructure periodicity. This study demonstrates that when a PhC sensor adhered to polymer substrate experiences micron or submicron damage, it will experience changes in its microstructural periodicity thereby creating a photonic signature that can be related to damage severity. This concept is validated here using a three-dimensional integrated numerical simulation.

Temporal and spatial variability of rainfall and climate trend on Jeju Island

Alan Mair,Aly I. El-Kadi,하규철,Gi-Won Koh 한국지질과학협의회 2013 Geosciences Journal Vol.17 No.1

The temporal and spatial analyses of rainfall and temperature were conducted for understanding spatial variability and climate trend on Jeju Island. Rainfall data from 1992 to 2009 were used for the spatial analyses, and missing data were adjusted on Mt. Halla and along the northeast coast to reduce uncertainty of spatial variability. In addition, rainfall time series data of both Jeju City and Seogwipo City from 1961 to 2009 were analyzed for a long-term trend and identification of droughts. Mean annual rainfall for the period 1992–2009 shows an area of maximum rainfall centered around Mt. Halla where maximum annual rainfall reaches more than 4,300 mm and mean island rainfall is 2,082 mm. Upward trends in rainfall intensity, magnitude, and dryness conditions at the Jeju City and Seogwipo City from 1961 to 2009 suggest that rainfall has intensified with greater quantities of rainfall occurring over shorter durations, with longer dry periods between storm events. The annual cycle shows a distinct monsoon signature with peak rainfall typically occurring in August. Rainfall seasonality shows a shift in peak rainfall from June, July, and August, to July, August, and September. The most severe droughts in the period 1961–2009 were identified using a 12-month composite SPI. Three severe droughts each lasting around two years were identified over a relatively short nine-year period from 1964–1972.

Enhancing the Stability, Hydrophilicity, Mechanical and Biological Properties of Electrospun Polycaprolactone in Formic Acid/Acetic Acid Solvent System

Basma Ekram,Bothaina M. Abd El-Hady,Abeer M. El-Kady,Sherif M. Amr,Hala Gabr,Ahmed I. Waly,Osiris W. Guirguis 한국섬유공학회 2019 Fibers and polymers Vol.20 No.4

Electrospun polycaprolactone is widely used in the medical field. Formic acid/acetic acid (FA/AA) solvent systemis one of the safest solvents used for the production of nano-range polycaprolactone (PCL) fibers, although it has a very lowstability. In the present study, the stability of PCL in FA/AA system was enhanced by sodium hydrogen carbonate (NaHCO3)addition with three different concentrations (1, 5 and 10 wt%). The resultant electrospun fiber properties were compared tothat treated by alkaline hydrolysis. The viscosity and conductivity of PCL solutions were measured before the electrospinningprocess. Moreover, the obtained electrospun PCL mats were characterized by SEM, FT-IR, XRD, contact anglemeasurements, degradability, swelling, and mechanical properties, as well as their ability to enhance the proliferation andadhesion of mesenchymal stem cells (MSCs). It was found that NaHCO3 not only enhanced the fiber properties, such ashydrophilicity, degradability and mechanical properties but also had a significant effect on the stability of polycaprolactone inFA/AA solvent system, as well as an enhanced MSCs proliferation and adhesion. Although hydrolyzed PCL showed high cellviability and adhesion, it showed much lower mechanical properties (0.7 MPa) compared to neat PCL (1.3 MPa) and PCLNaHCO3(5.1 MPa). In conclusion, the addition of NaHCO3 to PCL solution prior to the electrospinning process represents anovel and an effective approach to improve the physicochemical properties and biological behavior of electrospun PCL matsfor tissue engineering application.

Simple equations for temperature simulations on mid-latitude volcanic islands: a case study from Jeju (Republic of Korea)

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.