A potential electrolyte (Ce1-x CaxO2-δ) for fuel cells:Theoretical and experimental study

First-principles calculations are performed using density function theory to explore the effects of dopant Ca in ceria (Ce_1-xCa_xO_2-δ). The impact of oxygen vacancy on band gap and density of states is examined in doped ceria using generalized gradient approximations. Vacancy association and vacancy formation energies of the doped ceria are calculated to reveal the effect of dopant on ion conduction. The experimental study of the sample (Ce_0.875Ca_0.125O_2-δ) was performed to compare with the theoretical results. The obtained results from theoretical calculation and experimental techniques show that oxygen vacancy increases the volume, lattice constant (5.47315?Å) but decrease the band gap (1.72?eV) and bulk modulus. The dopant radius (1.173?Å) and lattice constant (5.4718?Å) are also calculated by equations which is close to the DFT lattice parameter. The result shows that oxygen vacancy shifts the density of states to lower energy region. Band gap is decreased due to shifting of valence states to conduction band. Vacancy formation shows a significance increase in density of states near the Fermi level. Density of states at Fermi level is proportional to the conductivity, so an increase in density of states near the Fermi level increases the conductivity. The experimental measured ionic conductivity is found to 0.095?S?cm^?1 at 600?°C. The microstructural studies is also reported in this work.     

Mathematical model and process for the production of granulated fuel wood

The results of a mathematical simulation of the process of wood flour granulation in the channels of flat dies are reported and a comparative analysis of currently available and developed mathematical models is performed in this work. A test bench based on a hand-power press and a bench for studying the compression of wood granules are described, and the results of full-scale experiments and the most significant results of the complex thermotechnical analysis of wood granules are presented. The effect of cooling conditions on the mechanical durability of granules is determined, and the dependences of the mechanical durability of the granules on the moisture content and temperature of a die are obtained.     

U.S. EPA Great Lakes National Program Office monitoring of the Laurentian Great Lakes: Insights from 40 years of data collection

The U.S. EPA Great Lakes National Program Office (GLNPO) implements long-term monitoring programs to assess Great Lakes ecosystem status and trends for many interrelated ecosystem components, including offshore water quality as well as offshore phytoplankton, zooplankton and benthos; chemical contaminants in air, sediments, and predator fish; hypoxia in Lake Erie's central basin; and coastal wetland health. These programs are conducted in fulfillment of Clean Water Act mandates and Great Lakes Water Quality Agreement commitments. This special issue presents findings from GLNPO's Great Lakes Biology Monitoring Program, Great Lakes Water Quality Monitoring Program, Lake Erie Dissolved Oxygen Monitoring Program, Integrated Atmospheric Deposition Network, Great Lakes Fish Monitoring and Surveillance Program, and Great Lakes Sediment Surveillance Program. These GLNPO programs have generated temporal and spatial datasets for all five Great Lakes that form the basis for assessment of the state of these lakes, including trends in nutrients, key biological indicators, and contaminants in air, sediments and fish. These datasets are used by researchers and managers across the Great Lakes basin for investigating physical, chemical and biological drivers of ongoing ecosystem changes; some of these analyses are presented in this special issue, along with discussion of new methods and approaches for monitoring.     

Thermal decomposition and combustion of coals,fuel wood,and hydrolytic lignin,as studied by thermal analysis

Different biofuel woods (spruce, pine, and spruce and pine bark), hydrolytic lignin, and coals from different deposits [D coal from Inta, Zh coal from Vorkuta, and D coal from Khakassia] were studied on a synchronous thermal analyzer at heating rates of 5, 10, and 20 K/min in inert and air atmospheres. Classical thermogravimetric and differential thermogravimetric curves were obtained to describe the thermal decomposition of hemicellulose, cellulose, and lignin and the combustion of a carbon residue as the main components of the biofuel woods. The decomposition of the coal fuels from different deposits was studied, and the temperature ranges of drying, the release of volatile substances, and the combustion of carbon residues were obtained. The results of thermal analyses were processed with the use of an isoconversional method based on the Friedman and Ozawa–Flynn–Wall models and with the aid of an extended independent parallel reaction (EIPR) model. A satisfactory repeatability of the results was obtained to indicate the applicability of both of these methods. The subsequent study of wood, hydrolytic lignin and, coals from different deposits was carried out with the aid of the EIPR model. The activation energies of biofuel woods varied in a range from 62 to 93 kJ/mol, which are much lower than those of coals (104–116 kJ/mol).     

The isothermal degradation of wood

The results of a study of spruce (whitewood) and its organic components (cellulose, hemicellulose, and lignin) by isothermal thermogravimetric analysis in air and inert atmospheres are presented. Data on the thermal decomposition of fuel wood in a temperature range from 200 to 450°C were acquired. The porous structure of biocoal and the process of its evolution were examined by scanning electron microscopy. The porous structure of the whitewood thermally treated at 200 and 300°C had pore sizes from 4 to 15 μm. The stratification of tracheids occurred in the above temperature range. At higher temperatures of 350°C or above, thermal pores with sizes of about 100 nm appeared. As the temperature was increased to 400°C, the pore size increased to 200–300 nm.     

Heat transfer during sheet rolling

An analytical solution to the heat conduction problem with a moving boundary is derived for the determination of principal temperatures in a metal during sheet rolling.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 2, pp. 321–328, February, 1971.     

Magnetization of Manganese Perovskites

Temperature dependence of spontaneous magnetization at a separate site in the compounds La_1-xCa_xMnO₃ (0 ⩽ x ⩽ 1) is investigated in the molecular field approximation using a homogeneous model for the magnetic sub-lattice with allowance for the Heisenberg superexchange and double exchange between nearest neighbors. Unlike with the usual magnets having one type of magnetic ions, in this case there appears a system of equations with two unknowns, mean spins of ions Mn³⁺ and Mn⁴⁺. In the vicinity of the ordering temperature, this system can be solved analytically and the expression for the ordering temperature can be obtained as well. To find the temperature dependence of magnetization in the whole temperature range, we used the exact expression for the double exchange operator containing spin operators under the square root. The numerical solutions were found in this case.     

Land use change in a biofuels hotspot: The case of Iowa, USA

This study looks at the land use impact of the biofuels expansion on both the intensive and extensive margin, and its environmental consequences. We link economic, geographical and environmental models by using spatially explicit common units of analysis and use remote sensing crop cover maps and digitized soils data as inputs. Land use changes are predicted via economic analysis of crop rotation choice and tillage under alternative crop prices, and the Environmental Policy Integrated Climate (EPIC) model is used to predict corresponding environmental impacts. The study focuses on Iowa, which is the leading biofuels hotspot in the U.S. due to intensive corn production and the high concentration of ethanol plants that comprise 28% of total U.S. production. We consider the impact of the biofuels industry both on current cropland and on land in the Conservation Reserve Program (CRP), a land set-aside program. We find that substantial shifts in rotations favoring continuous corn rotations are likely if high corn prices are sustained. This is consistent with larger scale analyses which show a shift of the current soybean production out of the Corn Belt. We find that sediment losses increase substantially on the intensive margin, while nitrogen losses increase less. Returning CRP land into production has a vastly disproportionate environmental impact, as non-cropped land shows much higher negative marginal environmental effects when brought back to row crop production. This illustrates the importance of differentiating between the intensive and extensive margin when assessing the expansion of biofuel production.     

Effects of the kinetics of fusion of the surface layer of metal by a concentrated energy flux

A study is made of the fusion of a thin layer of metal by a powerful heat flux and the subsequent crystallization of the melt as a result of heat removal into the body of the material, with allowance for the kinematics of the process.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 3, pp. 373–379, September, 1988.     

Editorial

Editorial Introduction

Editorial