ANSWERS-2000: Non-Point-Source Nutrient Planning Model

ANSWERS-2000, a non-point-source planning model was modified to simulate long-term nitrogen (N) and phosphorus (P) transport from rural watersheds. The model simulates infiltration, evapotranspiration, percolation, and runoff and losses of nitrate, adsorbed and dissolved ammonium, adsorbed total Kjeldahl N, and adsorbed and dissolved P losses. Eight soil nutrient pools are modeled: stable organic N, active organic N, nitrate, ammonium, and stable mineral P, active mineral P, organic P, and exchangeable P. The model was validated on two small watersheds without calibration and on a large watershed with calibration of only the sediment detachment parameters. Predicted cumulative runoff, sediment, nitrate, dissolved ammonium, adsorbed total Kjeldahl N, and orthophosphorus P losses were within a factor of 2 of observed values (?40 to +44% of observed values). Predictions of individual runoff event losses were not as accurate (?98 to +250%). The model seriously underpredicted adsorbed ammonium losses by up to 97%, and additional work is recommended on this submodel. In a practical application, the use of the model in evaluating the cost-effectiveness of alternative management scenarios was demonstrated.     

Half-metallic ferromagnetism in ZnCrTe and CdCrTe: Ab initio study

Using the first-principles method, we investigate the structural, electronic and magnetic properties of the diluted magnetic semiconductors ZnCrTe and CdCrTe in the zinc blende phase with 25% of Cr. We have treated the ferromagnetic and antiferromagnetic phases. The calculations are performed by a developed full-potential augmented plane wave plus local orbitals (FP-L/APW + lo) method within the spin density functional theory. As exchange–correlation potential we used the new generalized gradient approximation GGA form and GGA + U. Structural properties are determined from the total energy calculations and we found that these compounds are stable in the ferromagnetic phase. We discuss the electronic structures, total and partial densities of states and local moments. Furthermore, we predict the values of spin-exchange splitting energies Δ_x(d) and Δ_x(pd) and exchange constants N_0α and N_0β produced by the Cr 3d states. Finally, we demonstrate that the half-metallicity is robust with respect to lattice contraction.     

Multi-objective sustainable process plan generation in a reconfigurable manufacturing environment: exact and adapted evolutionary approaches

Achieving competitiveness in nowadays manufacturing market goes through being cost and time-efficient as well as environmentally harmless. Reconfigurable manufacturing system (RMS) is a paradigm that is able to meet these challenges due to its scalability and integrability. In this paper, we aim to solve the multi-objective sustainable process plan generation problem in a reconfigurable environment. In addition to the total production cost and the completion time, we use the amount of greenhouse gases (GHG) emitted during the manufacturing process as a sustainability criterion. We propose an iterative multi-objective integer linear programming (I-MOILP) approach and its comparison with adapted versions of the two well-known evolutionary algorithms, respectively, the Archived Multi-Objective Simulated Annealing (AMOSA) and the Non-dominated Sorting Genetic Algorithm (NSGA-II). Moreover, we study the influence of the probabilities of genetic operators on the convergence of the adapted NSGA-II. To illustrate the applicability of the three approaches, an example is presented and obtained numerical results analysed.     

Spin-Polarized Calculations of Magnetic and Thermodynamic Properties of the Full-Heusler \mathrm{{Co}}_{2}MnZ (Z = Al, Ga)

The purpose of this study is to further understanding of the structural, electronic, magnetic, and thermal properties of the full-Heusler compounds, ${\mathrm{{Co}}}_{2}$ Co 2 MnAl and ${\mathrm{{Co}}}_{2}$ Co 2 MnGa, using density functional theory. Electronic structure calculations will be performed using the full potential linear augmented plane wave. The electronic structures and magnetic properties of ${\mathrm{{Co}}}_{2}$ Co 2 MnZ (Z = Al, Ga) compounds with ${\mathrm{L}}2_{1 }$ L 2 1 structure are studied. It is shown that the calculated lattice constants and spin magnetic moments are in good agreement with experimental values using the general gradient approximation method. Thermal effects on some macroscopic properties of ${\mathrm{{Co}}}_{2}$ Co 2 MnZ (Z = Al, Ga) compounds are predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variations of the lattice constant, volume expansion coefficient, heat capacities, and Debye temperature with pressure and temperature in the ranges of 0 GPa to 18 GPa and 0 K to700 K have been obtained.     

Effect of tin content on the electrical and optical properties of sprayed silver sulfide semiconductor thin films

Silver sulfide (Ag₂S) thin films have been deposited on glass substrates by t spray pyrolysis using an aqueous solution which contains silver acetate and thiourea as precursors. The depositions were carried out at a substrate temperature of 250 °C. Structural studies by means of X-ray diffraction show that all tin (Sn)-doped Ag₂S thin films crystallized in a monoclinic space group with noticeable changes in the crystallites' orientation. The discussion of some structural calculated constants has been made with Sn doping in terms of microhardness measurements. Moreover, the optical analysis via the transmittance, reflectance as well as the photocurrent reveals that the direct band gap energy (E_gd) decreases (E_gd varies from 2.34 to 2.16 eV) and the indirect band gap energy (E_gi) increases (E_gi varies from 0.98 to 1.09 eV) slightly as a function of Sn content. Electrical study shows that Sn doping changes the electrical conductivity and proves the thermal activation of electrical conduction.     

Stability and electronic properties of ZnxCd1−xO alloys

We investigated the structural and electronic properties of Zn_xCd_1−xO alloys, with Zn concentrations varying from 0% up to 100%. The calculations are based on the total energy calculations within the hybrid full potential augmented plane-wave plus local orbitals (APW+lo) method. We have used the local density approximation for the exchange and correlation potential. In particular we have studied the relative stability of several configurations of Zn_xCd_1−xO in rocksalt (B1) structure (the ground state configuration of CdO compound), or wurtzite (B4) structure (the ground state configuration of ZnO compound). The ground state properties, equilibrium lattice constants, bulk moduli, cohesive energies, and band structures for all Zn concentrations are presented. The densities of electron states are also determined for both the binary and their related ternary alloys. It is found that for Zn concentration lower than that of x = 0.625, the favored structure is a NaCl phase, while for Zn concentration x ≥ 0.625; the favored structure is a wurtzite phase. A model structure of 16-atom supercell is used.     

Regional averaged controllability for hyperbolic parameter dependent systems

The purpose of this paper is to extend the notion of regional controllability for hyperbolic parameter dependent systems. The key idea is the characterization of the \textit{averaged regional control} with minimal energy. This control steers the state average (with respect to such a parameter) towards the desired state only on a given part of the system evolution domain. In this paper, we give the precis definition and the properties of this new concept. Then, we use an approach based on an extension of the Hilbert uniqueness method devoted to the calculation of the control in two different cases: zone control and pointwise control.     

Structural and elastic properties of TiN and AlN compounds: first-principles study

First-principles calculations of the lattice constants, bulk modulus, pressure derivatives of the bulk modulus and elastic constants of AlN and TiN compounds in rock-salt (B1) and wurtzite (B4) structures are presented. We have used the fullpotential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the generalized gradient approximation (GGA) for the exchange-correlation functional. Moreover, the elastic properties of cubic TiN and hexagonal AlN, including elastic constants, bulk and shear moduli are determined and compared with previous experimental and theoretical data. Our results show that the structural transition at 0 K from wurtzite to rock-salt phase occurs at 10 GPa and ?26 GPa for AlN and TiN, respectively. These results are consistent with those of other studies found in the literature.