Temperature dependence of indentation size effect,dislocation pile‐ups,and lattice friction in (001) strontium titanate

Nanoindentations with a Berkovich type indenter were performed on (001) strontium titanate (STO) single crystal at 25°C and 350°C, analyzing the influence of temperature on the indentation size effect (ISE) and dislocation structure around the residual impression. It is found that the STO exhibits an ISE, which is strongly reduced at 350°C compared to 25°C. The dislocation structure around the residual impression has been resolved using an etch‐pit technique. At 25°C, the extension of the dislocation pile‐ups were found to be shorter as compared to 350°C. This also correlates with the smaller size effects at 350°C. Peach‐Koehler forces and the elastic‐plastic indentation stress field were used to model the influence of the lattice frictional stress on the dislocation pile‐ups. Based on an equilibrium position of the outermost dislocations, the average lattice frictional stresses were calculated to be 89 MPa and 46 MPa at 25°C and 350°C, respectively.     

Production of high purity rare earth mixture from iron-rich spent fluid catalytic cracking (FCC) catalyst using acid leaching and two-step solvent extraction process

Acid leaching and a two-step solvent extraction procedure were developed to produce high purity mixture of La and Ce from iron-rich spent FCC catalyst discharged from Dzung Quat refinery (Vietnam). Acid leaching of the spent catalyst with 2M HNO₃ and a solid-to-liquid ratio of 1/3 at 80 °C in 1 h dissolved almost 90% of La while 12% of Al and 25% of Fe were transferred to the leachate. The extraction of RE metals and main impurities such as Al and Fe by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) was investigated. Experiments showed that it was necessary to remove Fe before extracting RE and the optimum extraction conditions for a high recovery of RE while 0% of Al extraction were pH-1, contact time=10min, and D2EHPA/TBP volume ratio= 4: 1. At these conditions, the extraction yields of La(III) and Ce(III) were 72% and 89%, respectively. A two-step solvent extraction was developed to achieve a high purity of RE mixture, which included (1) the removal of impurity Fe by 25% (v/v) diisooctyl phosphinic acid (DiOPA) in n-octane for 140 min, (2) the extraction of rare earths by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) in n-octane for 10 min without the need for adjusting the pH of the leaching solution.     

DC‐sputtered ZnO:Al as transparent conductive oxide for silicon heterojunction solar cells with µc‐Si:H emitter

Silicon heterojunction (SHJ) solar cells are highly interesting, because of their high efficiency and low cost fabrication. So far, the most applied transparent conductive oxide (TCO) is indium tin oxide (ITO). The replacement of ITO with cheaper, more abundant and environmental friendly material with texturing capability is a promising way to reduce the production cost of the future SHJ solar cells. Here, we report on the fabrication of the SHJ solar cells with direct current‐sputtered aluminum‐doped zinc oxide (ZnO:Al) as an alternative TCO. Furthermore, we address several important differences between ITO and the ZnO:Al layers including a high Schottky barrier at the emitter/ZnO:Al interface and a high intrinsic resistivity of the ZnO:Al layers. To overcome the high Schottky barrier, we suggest employing micro‐crystalline silicon (µc‐Si:H) emitter, which also improves temperature threshold and passivation of the solar cell precursor. In addition, we report on the extensive studies of the effect of the ZnO:Al deposition parameters including layer thickness, oxygen flow, power density and temperature on the electrical properties of the fabricated SHJ solar cells. Finally, the results of our study indicate that the ZnO:Al deposition parameters significantly affect the electrical properties of the obtained solar cell. By understanding and fine‐tuning all these parameters, a high conversion efficiency of 19.2% on flat wafer (small area (5 × 5 mm²) and without any front metal grid) is achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Toward efficient Cu(In,Ga)Se2 solar cells prepared by reactive magnetron co‐sputtering from metallic targets in an Ar:H2Se atmosphere

In this paper, we show that a reactive co‐sputtering process using metallic CuGa and In targets; an Ar:H₂Se atmosphere is well suited for the deposition of photoactive Cu(In,Ga)Se₂ (CIGSe) absorber layers for thin‐film solar cells in a single process step. The achievement of single‐phase and well‐crystallized layers is thereby no major problem if a sufficiently high H₂Se content and substrate temperatures in the range of 400–500 °C are used. However, in order to achieve the desired Cu‐poor film stoichiometry, which is crucial for the device performance, it has to be considered already that, at moderate substrate temperatures in the range of 400–500 °C, indium has a strong tendency to re‐evaporate from the film surface if the film composition is Cu‐poor. If excess indium is supplied, this effect can lead to a self‐adjustment of the film composition. This allows a very wide process window in a one‐stage process concerning the supply ratio from the two targets of [Cu]/([In] + [Ga])_supply ≈ 0.35–0.8. However, the maximum efficiencies achievable with such a process are limited to 11.7% because an adequate Cu‐poor composition can only be achieved with significant Cu‐poor conditions, which allow only a low material quality. By using an improved process with an intermediate Cu‐rich composition and a final Cu‐poor stage, the absorber quality could be significantly improved; efficiencies of up to 14.3% have been achieved with CIGSe films prepared on Na‐doped Mo back contacts. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of a fluid versus a powder pepsin formulation to detect Trichinella spiralis larvae in meat samples by a digestion technique

Pepsin powder constitutes a health risk, potentially causing severe allergic reactions to those handling the chemical. A fluid pepsin formulation was produced and tested, first in a preliminary study and then in a ring trial encompassing four European National Reference Laboratories (NRLs). The purpose of each trial was to ascertain and compare the action of pepsin powder with that of the pepsin fluid for digesting meat and liberating encapsulated Trichinella spiralis larvae for subsequent counting. The quality of digestion was furthermore evaluated by assessing the visibility through the digestion fluid and the amount of debris remaining after digestion. For the ring trial, at each laboratory 20 blinded replicate 100-g samples of pork meat containing a known number of encapsulated T. spiralis larvae (0 to 30) were digested by the magnetic stirrer method using either the standard pepsin powder (10 samples) or the pepsin fluid (10 samples). With an average recovery rate of 70 to 80%, all NRLs found the pepsin fluid and pepsin powder to be equally effective. The NRLs also found no difference between the two pepsin formulations with regard to debris remnants or visibility through the digestion fluid. The use of pepsin fluid may therefore constitute an improvement of the digestion procedure for the analysts involved.     

Estimation of the mass-balance of selected metals in four sanitary landfills in Western Norway, with emphasis on the heavy metal content of the deposited waste and the leachate

A worst-case simulation of the mass-balance for metals in the waste deposited during 1 year and the levels of cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr) and iron (Fe) in the leachate was calculated for four sanitary landfills in Western Norway. Estimates of the levels of metal content in mixed municipal solid waste (MSW) were found by using recent literature values calculated in a mass-balance study at a Norwegian waste incinerator plant. Leachate from the landfills were sampled and analyzed monthly during 1 year, and from these measurements the total annual discharge of the selected metals through the leachate was determined. The levels of the measured heavy metals in the leachate were low. For Cd less than 0.06%, for Pb less than 0.01% and for Hg less than 0.02% of the estimated year's deposited mass of metals were leached from the landfills during the year of investigation. The high retention of these metals are most likely due to sulfide precipitation, but also due to the immobile condition of the metals in their original deposited solid state (plastics, ceramics, etc.). The percentage of Cr leached was relatively higher, but less than 1.0% per year. The mass balance of Fe suggests that this element is more mobile under the prevailing conditions. The percentage of Fe leached varied and was estimated to be between 1.9% and 18%. The present study clearly supports the theory that MSW only to a small extent will lead to discharge of metals if deposited at well-constructed sanitary landfills with top layers.     

Hello ADIOS: the challenges and lessons of developing leadership class I/O frameworks

Applications running on leadership platforms are more and more bottlenecked by storage input/output (I/O). In an effort to combat the increasing disparity between I/O throughput and compute capability, we created Adaptable IO System (ADIOS) in 2005. Focusing on putting users first with a service oriented architecture, we combined cutting edge research into new I/O techniques with a design effort to create near optimal I/O methods. As a result, ADIOS provides the highest level of synchronous I/O performance for a number of mission critical applications at various Department of Energy Leadership Computing Facilities. Meanwhile ADIOS is leading the push for next generation techniques including staging and data processing pipelines. In this paper, we describe the startling observations we have made in the last half decade of I/O research and development, and elaborate the lessons we have learned along this journey. We also detail some of the challenges that remain as we look toward the coming Exascale era. Copyright © 2013 John Wiley & Sons, Ltd.     

Gaseous and particulate emissions from prescribed burning in Georgia

Prescribed burning is a significant source of fine particulate matter (PM2.5) in the southeastern United States. However, limited data exist on the emission characteristics from this source. Various organic and inorganic compounds both in the gas and particle phase were measured in the emissions of prescribed burnings conducted at two pine-dominated forest areas in Georgia. The measurements of volatile organic compounds (VOCs) and PM2.5 allowed the determination of emission factors for the flaming and smoldering stages of prescribed burnings. The VOC emission factors from smoldering were distinctly higher than those from flaming except for ethene, ethyne, and organic nitrate compounds. VOC emission factors show that emissions of certain aromatic compounds and terpenes such as alpha and beta-pinenes, which are important precursors for secondary organic aerosol (SOA), are much higher from active prescribed burnings than from fireplace wood and laboratory open burning studies. Levoglucosan is the major particulate organic compound (POC) emitted for all these studies, though its emission relative to total organic carbon (mg/g OC) differs significantly. Furthermore, cholesterol, an important fingerprint for meat cooking, was observed only in our in situ study indicating a significant release from the soil and soil organisms during open burning. Source apportionment of ambient primary fine particulate OC measured at two urban receptor locations 20-25 km downwind yields 74 +/- 11% during and immediately after the burns using our new in situ profile. In comparison with the previous source profile from laboratory simulations, however, this OC contribution is on average 27 +/- 5% lower.     

Pound-Drever-Hall error signals for the length control of three-port grating coupled cavities

Gratings enable light coupling into an optical cavity without transmission through any substrate. This concept reduces light absorption and substrate heating and was suggested for light coupling into the arm cavities of future gravitational wave detectors. One particularly interesting approach is based on all-reflective gratings with low diffraction efficiencies and three diffraction orders (three ports). However, it was discovered that, generally, three-port grating coupled cavities show an asymmetric resonance profile that results in asymmetric and low quality Pound-Drever-Hall error signals for cavity length control. We experimentally demonstrate that this problem is solved by the detection of light at both reflection ports of the cavity and the postprocessing of the two demodulated electronic signals.     

Some effects of non-condensible gas in geothermal reservoirs with steam-water counterflow

A mathematical model is developed for one-dimensional fluid and heat flow in two-phase geothermal reservoirs containing non-condensible gas (CO₂). Vertical profiles of temperature, pressures and phase saturations in steady-state conditions are obtained by numerically integrating the coupled ordinary differential equations describing conservation of water, CO₂ and energy. Solutions, including binary diffusion effects in the gas phase, are generated for cases with net mass throughflow as well as for balanced liquid—vapor counterflow. Calculated examples illustrate some fundamental characteristics of two-phase heat transmission systems with non-condensible gas.