An Accurate and Efficient Methodology to Obtain Surges for Risk Analyses for the Coast of Bangladesh

Bangladesh is one of the worst affected countries in the world in terms of tropical cyclone and storm surge effects. Until now, most of the research on annual exceedance of flood elevation for the coast of Bangladesh was based upon historical cyclone tracks along the coast. One of the major constraints of using historical tracks or tide gauge data to determine the annual exceedance of surge elevation is that the available sample size is often inadequate to capture the broad range of storm characteristics over the geographic region of interest. Over the years, several methods have been developed to increase these sample sizes. The Joint Probability Method (JPM) is one such method. It utilizes combinations of storm parameters to produce a large set of synthetic storms, but its downside is that it tends to be computationally expensive. To reduce this computational burden while maintaining accuracy, several optimal sampling methods (JPM-OS) have been introduced. While these methods effectively reduce the computational burden, they have their own limitations on ensuring a specific minimum error efficiently. This Manuscript introduces a new optimal sampling method named Response Surface Iteration for JPM analysis (JPM-OS-RSI). This iterative method incorporates the natural structure of smoothly varying surge response into results including the effect of bypassing storms within a certain error band. This new method was applied to the Bangladeshi coast where it was observed that surge response along the coast for a cyclone could be interpolated from two adjacent tracks through iterations. The number of tracks obtained through JMP-OS-RSI method was sufficient to produce surge response for interpolation using various parametric combinations. Results from these computations represent a comprehensive data set of surge height for all the possible combinations of storm surge parameters. These datasets may be further be used for JPM analysis in the coastal region of Bangladesh

Annealing effect on structural and electrical properties of AgGaSe2 thin films

180-185Structural, thermo-electrical and electrical properties of AgGaSe2 (AGS) thin films prepared in vacuum onto glass substrates by stacked elemental layer (SEL) deposition technique have been studied. The films were annealed at 100 to 350°C for 15 min. The atomic composition of the films has been measured by energy dispersive analysis of X-ray (EDAX) method. The structural and thermo-electrical properties of the films have been ascertained by X-ray diffraction (XRD) and the hot-probe method, respectively. The electrical properties of the films are measured by standard dc method using a liquid nitrogen cryostat. The structural, thermo-electrical and electrical properties have been investigated as a function of different annealing temperature. The X-ray diffraction (XRD) reveals that the films were polycrystalline in nature. The lattice parameters, grain size, strain and dislocation densities of the films have been calculated. The thermoelectric power indicates the presence of p-type majority carriers. The electrical conductivity of the films has been found to vary from 1.40 10−5 to 2.18 10−2 (-cm)−1 as temperature varies between -173 and 100°C. The activation energies vary from 43.60 to 94.70 meV as annealing temperatures vary between 350 and 100°C. Probable identities of the origin of AGS films have been obtained by using these activation energies. The dominance of grain boundary effect has been ascertained by applying the Seto’s model

Impact of Tidal Phase on Inundation and Thrust Force Due to Storm Surge

Impact of storm surge largely varies depending on the tidal phase during the landfall of a tropical cyclone. This study investigates comparative variance in inundation condition and thrust force for an identical cyclone during low tide and high tide by applying a numerical model (Delft3D) and a semi-analytical model (DFM). A moderate strength cyclone, Mora, which made landfall on Bangladesh coast in May 2017 is selected to study its impact on land during low tide and high tide. Actual landfall time of Mora was during low tide. To study the impact of storm surge during high tide, a synthetic cyclone is created which has similar strength and track to that of Mora but makes landfall during high tide. The results show that inundation depth, inundation extent, and thrust force increase when a cyclone makes landfall during high tide compared to the condition when the cyclone makes landfall during low tide. But the relation between storm surge impact and tidal phase is not linear. It depends on the land topography of the location, direction of cyclone movement, direction and magnitude of water velocity and wind velocity, gradients of water surface and wind velocity, and proximity and position of the location with respect to cyclone track