Ballistic and diffusive phonon transport under small time and spatial scales are important in fast-switching electronic devices and pulsed-laser processing of materials. The Fourier law represents only diffusive transport and yields an infinite speed for heat waves. Although the hyperbolic heat equation involves a finite heat wave speed, it cannot model ballistic phonon transport in short spatial scales, which under steady state follows the Casimir limit of phonon radiation. An equation of phonon radiative transfer (EPRT) is developed which shows the correct limiting behavior for both purely ballistic and diffusive transport. The solution of the EPRT for diamond thin films not only produces wall temperature jumps under ballistic transport but shows markedly different transient response from that of the Fourier law and the hyperbolic heat equation even for predominantly diffusive transport. For sudden temperature rise at one film boundary, the results show that the Fourier law and the hyperbolic heat equation can significantly over- or underpredict the boundary heat flux at time scales smaller than the phonon relaxation times.

Optical absorption and photoluminescence techniques were used to investigate the energy band gap of CdSe∕ZnS core/shell nanocrystals matrixed into a resin. The band gap is measured as a function of temperature for several samples with different nanocrystal diameters. Debye and Einstein temperatures were obtained by fitting the energy band gap using two different empirical expressions. Stokes shift was estimated by taking the difference between the first exciton and emission peaks. The Stokes shift was found to increase as the nanocrystal diameter is decreased suggesting a stronger electron-phonon coupling in smaller size nanocrystals.

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Activated carbon (AC) was modified by the coprecipitation method to induce magnetic properties for the removal of isonicotinic acid (iNA). Magnetization was done by using salts of Fe2+ and Fe3+ as precursors. The induced magnetism in magnetic activated carbon (MAC) was confirmed by Fourier transform infrared and field-emission scanning electron microscopy–electron diffraction spectroscopy analyses. Also, the stability of both AC and MAC was tested by TGA. Batch adsorption experiments were performed using both AC and MAC to see the effects of adsorption time (0–180 min), adsorbent amount (12–40 g/L for AC and 4– 80 g/L for MAC), initial iNA concentration (1.23–6.16 g/L), and temperature (298–333 K) on the removal efficiency. Steady state was reached at 120 min by using both adsorbents. Equilibrium data was best fitted by Langmuir and Temkin isotherms for AC and MAC, respectively. The maximum adsorption capacities were noted to be 0.406 g/g of AC and 0.071 g/g of MAC. Pseudo-second-order model fitted the kinetic data for both adsorbents. The magnetic property in MAC ensured easy separation of adsorbent using magnet after adsorption from the aqueous medium.

Installation layout of wind turbines plays a prominent role in the design of every wind farm. Thus, the wind farm layout optimization problem is proposed to maximize the total power output with the minimum cost. In this research, Kahrizak region in Tehran province of Iran is selected as a windy region and its real wind speed data are gleaned. Three different scenarios are also considered, with various number of generations and populations for GA parameters, effective distances, and longitude and latitude distances of turbines from each other. Among these scenarios, the best result is obtained for the one in which the longitudinal distance between turbines is greater than the latitudinal distance. By observing the wind rose of Kahrizak region, it is observed that the dominant wind direction of the region is toward the east and south-east. Therefore, by increasing the longitudinal distance of the turbines from each other, the efficiency can be improved and the turbine layout becomes more realistic. In this case, the efficiency rate and normalized cost of turbines are 89.5% and 37.4, respectively, and also 56 turbines are needed. The amounts of efficiency and power output are very convenient for real wind speed data of a region.