DFT insight into the effect of Cu atoms on adsorption and dissociation of CO2 over a Pd8/ TiO2(101) surface

The Cu atom provides the positive polarization charge center to enhance CO2 adsorption and up-shifts its d-band center to improve the activation of CO2.

Life on Chure and Siwalik Under the Extreme Threat of Lightning

Of all the natural disasters in Nepal, lightning is the second highest killer after earthquake. According to the data available from the Disaster Risk Reduction (DRR) portal of Ministry of Home Affairs (MoFA), an average of 108 people are killed by lightning each year. As would be expected, fatalities over the high mountains are rare due to both low population and low lightning flash density. Surprisingly, most fatalities and injuries are reported over the hilly areas of the Siwalik and Chure range in the middle of Nepal, despite the southern region having both a significantly higher population and higher lightning flash density. The higher fatalities over the Chure and Siwalik can be attributed to their elevation leading to a smaller distance to the charge center in the cloud and meteorological conditions that may arise for the development of a turbulence in the lee waves at the interface of southern plains and middle hills.

Blast-induced ground motion effect on dynamic response of a cylindrical vertical water tank with piled raft foundation

This paper studies to estimate the dynamic behavior of a demineralized water tank with a piled raft foundation system considering soil-pile-structure-fluid interaction to shock-ground motion. A three-dimensional finite element model of a coupled system is constituted in ANSYS software. Interaction between pile and soil is represented with the frictional contact element. The frictionless contact elements are utilized to model between the water and tank shell to allow for displacement of the free surface adjacent to the tank wall. Shell elements are used for the tank body and its vault. The dynamic analyses of the tank including soil-pile-structure-fluid interaction are presented by using shock response spectra. Ground shock acceleration time histories, generated by using a developed computer program based on Fortran programming language, produce shock response spectra. The effects of the different charge weights and distances from the charge center are examined in the analyses. Also, the effect of the water fill level in the tank and the number of piles is also investigated. The results of the research are presented with the directional displacements and equivalent stresses. It seen from the analyses that the dynamic responses of the tank increase with the charge weight, while decreasing with the charge center distance. Moreover, the water fill level and the number of piles extremely affect the displacement and stress values of the coupled interaction system.

Latitude and Topographical Dependence of Lightning Return Stroke Peak Current in Natural and Tower-Initiated Negative Ground Flashes

Experimental data show that the peak currents of first and subsequent lightning return strokes in negative ground flashes increase with decreasing latitude. In this paper, the reason for this dependence of peak return stroke current on latitude is explained using the fact that the height of the charge centers increases with decreasing latitude. Results show that in tropical regions where the height to the negative charge center is about 8 km, the median values of the first and the subsequent return stroke peak currents are about 42 kA and 15 kA, respectively. If the height to the charge center is larger than 8 km, the peak currents will also become larger. For example, if the location of the charge center is increased to about 9 km, the median values of the first and subsequent return stroke peak currents will increase to about 45 kA and 16 kA respectively. The same reasoning shows that, even in the same geographical region, the peak return stroke current may decrease as the elevation of the ground where the lightning strikes take place increases. The results also indicate that the peak subsequent return stroke current in tower-initiated negative lightning flashes decreases as the height of the tower increases. These theoretical predictions are in general agreement with the available experimental data.

Optical Properties of Continuous and Pixelated Scintillation Crystals

The optical photon distribution produced inside continuous and pixelated scintillation crystals by the absorption of a γ-ray have been studied with the photon transport program DETECT 2000. With this program the charge signals recorded by a multi-wired anode system, like the Position Sensitive PhotoMultiplier Tube (PSPMT) of a γ-Camera, are simulated. Based on the analytical parametrization which is fitted to experimental data, a new position reconstruction method for PSPMTs is proposed in this work. Planar images have been reconstructed with the new method and compared to the traditional charge center of gravity technique. Data are obtained from a small field, high resolution γ-Camera system with a multi- wired crossed anode using the R2486 (HAMAMATSU) PSPMT. Systematic studies for continuous and pixelated inorganic scintillation crystals of CsI(Tl) have been performed for different phantom geometries using small capillaries of 99mTc. The developed method seems to drastically improve the resolution of the reconstructed planar information, even when homogeneous crystals are used.