Analytical solutions for transient temperature distribution in a geothermal reservoir due to cold water injection

An analytical solution to describe the transient temperature distribution in a geothermal reservoir in response to injection of cold water is presented. The reservoir is composed of a confined aquifer, sandwiched between rocks of different thermo-geological properties. The heat transport processes considered are advection, longitudinal conduction in the geothermal aquifer, and the conductive heat transfer to the underlying and overlying rocks of different geological properties. The one-dimensional heat transfer equation has been solved using the Laplace transform with the assumption of constant density and thermal properties of both rock and fluid. Two simple solutions are derived afterwards, first neglecting the longitudinal conductive heat transport and then heat transport to confining rocks. Results show that heat loss to the confining rock layers plays a vital role in slowing down the cooling of the reservoir. The influence of some parameters, e.g. the volumetric injection rate, the longitudinal thermal conductivity and the porosity of the porous media, on the transient heat transport phenomenon is judged by observing the variation of the transient temperature distribution with different values of the parameters. The effects of injection rate and thermal conductivity have been found to be profound on the results.

Investigation on the Sr-doped ceria Ce1-xSrO2-delta (x=0.05-0.2) as an electrolyte for intermediate temperature SOFC

The effect of Sr doping in CeO2 for its use as solid electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been explored here. Ce1-xSrxO2-delta (x = 0.05-0.2) are successfully synthesized by citrate-complexation method. XRD, Raman, FT-IR, FE-SEM/EDX and electrochemical impedance spectra are used for structural and electrical characterizations. The formation of well crystalline cubic fluorite structured solid solution is observed for x = 0.05 based on XRD and Raman spectra. For compositions i.e., x > 0.05, however, a secondary phase of SrCeO3 is confirmed by the peak at 342 cm(-1) in Raman spectra. Although the oxygen ion conductivity was found to decrease with increase in x, based on ac-impedance studies, conductivity of Ce0.95Sr0.05O2-delta was found to be higher than of Ce0.95Gd0.1O2-delta and Ce0.8Gd0.2O2-delta. The decrease in conductivity of Ce1-xSrxO2-delta with increasing dopant concentration is ascribed to formation of impurity phase SrCeO3 as well as the formation of neutral associated pairs, Se `' Ce V-o. The activation energies are found to be 0.77, 0.83, 0.85 and 0.90 eV for x = 0.05, 0.1, 0.15 and 0.20, respectively. (C) 2014 Elsevier B.V. All rights reserved.

Temperature dependent magnetic, dielectric and Raman studies of partially disordered La2NiMnO6

We report a detailed magnetic, dielectric and Raman studies on partially disordered and biphasic double perovskite La2NiMnO6. DC and AC magnetic susceptibility measurements show two magnetic anomalies at T-C1 similar to 270 K and T-C2 similar to 240 K, which may indicate the ferromagnetic ordering of the monoclinic and rhombohedral phases, respectively. A broad peak at a lower temperature (T-sg similar to 70 K) is also observed indicating a spin-glass transition due to partial anti-site disorder of Ni2+ and Mn4+ ions. Unlike the pure monoclinic phase, the biphasic compound exhibits a broad but a clear dielectric anomaly around 270 K which is a signature of magneto-dielectric effect. Temperature-dependent Raman studies between the temperature range 12-300 K in a wide spectral range from 220 cm(-1) to 1530 cm(-1) reveal a strong renormalization of the first as well as second-order Raman modes associated with the (Ni/Mn)O-6 octahedra near T-C1 implying a strong spin-phonon coupling. In addition, an anomaly is seen in the vicinity of spin-glass transition temperature in the temperature dependence of the frequency of the anti-symmetric stretching vibration of the octahedra. (C) 2014 Elsevier Ltd. All rights reserved.

Low temperature and self catalytic growth of ultrafine ITO nanowires by electron beam evaporation method and their optical and electrical properties

We report the self catalytic growth of Sn-doped indium oxide (ITO) nanowires (NWs) over a large area glass and silicon substrates by electron beam evaporation method at low substrate temperatures of 250-400 degrees C. The ITO NWs growth was carried out without using an additional reactive oxygen gas and a metal catalyst particle. Ultrafine diameter (similar to 10-15 nm) and micron long ITO NWs growth was observed in a temperature window of 300-400 degrees C. Transmission electron microscope studies confirmed single crystalline nature of the NWs and energy dispersive spectroscopy studies on the NWs confirmed that the NWs growth proceeds via self catalytic vapor-liquid-solid (VLS) growth mechanism. ITO nanowire films grown on glass substrates at a substrate temperature of 300-400 degrees C have shown similar to 2-6% reflection and similar to 70-85% transmission in the visible region. Effect of deposition parameters was systematically investigated. The large area growth of ITO nanowire films would find potential applications in the optoelectronic devices. (C) 2014 Elsevier Ltd. All rights reserved.

Toward Real-Time Availability of 3D Temperature Maps Created with Temporally Constrained Reconstruction

PurposeTo extend the previously developed temporally constrained reconstruction (TCR) algorithm to allow for real-time availability of three-dimensional (3D) temperature maps capable of monitoring MR-guided high intensity focused ultrasound applications. MethodsA real-time TCR (RT-TCR) algorithm is developed that only uses current and previously acquired undersampled k-space data from a 3D segmented EPI pulse sequence, with the image reconstruction done in a graphics processing unit implementation to overcome computation burden. Simulated and experimental data sets of HIFU heating are used to evaluate the performance of the RT-TCR algorithm. ResultsThe simulation studies demonstrate that the RT-TCR algorithm has subsecond reconstruction time and can accurately measure HIFU-induced temperature rises of 20 degrees C in 15 s for 3D volumes of 16 slices (RMSE = 0.1 degrees C), 24 slices (RMSE = 0.2 degrees C), and 32 slices (RMSE = 0.3 degrees C). Experimental results in ex vivo porcine muscle demonstrate that the RT-TCR approach can reconstruct temperature maps with 192 x 162 x 66 mm 3D volume coverage, 1.5 x 1.5 x 3.0 mm resolution, and 1.2-s scan time with an accuracy of 0.5 degrees C. ConclusionThe RT-TCR algorithm offers an approach to obtaining large coverage 3D temperature maps in real-time for monitoring MR-guided high intensity focused ultrasound treatments. Magn Reson Med 71:1394-1404, 2014. (c) 2013 Wiley Periodicals, Inc.

Luminescent Molecular Sensors for Assessment of Temperature Field in Machining

A new technique based on luminescent molecular sensors is utilized in these series of experiments for measurement of temperatures in material removal processes. 2-Dimensional machining of metals at low speeds and surface grinding configurations are used as the model experimental systems to understand the efficacy of this experimental technique. The experiments were conducted with a series of luminescent sensors and binder combinations for the temperature measurement. The luminescence of the sensor was measured through a charge-coupled device imaging camera, and intensive calibration exercises were performed on these sensors. Excellent agreement in the temperature fields measured through this new experimental approach and traditional infrared thermography is seen here. This technique offers the unique capability of allowing measurement of temperatures in the presence of a lubricant, akin to manufacturing conditions in situ. Extension of the technique to measure the temperature field at the tool-chip contact is described.

Temperature dependent electrical behaviour of Cu2SnS3 films

The temperature dependent electrical properties of the dropcasted Cu2SnS3 films have been measured in the temperature range 140 K to 317 K. The log I versus root V plot shows two regions. The region at lower bias is due to electrode limited Schottky emission and the higher bias region is due to bulk limited Poole Frenkel emission. The ideality factor is calculated from the ln I versus V plot for different temperatures fitted with the thermionic emission model and is found to vary from 6.05 eV to 12.23 eV. This large value is attributed to the presence of defects or amorphous layer at the Ag / Cu2SnS3 interface. From the Richardson's plot the Richardson's constant and the barrier height were calculated. Owing to the inhomogeneity in the barrier heights, the Richardson's constant and the barrier height were also calculated from the modified Richardson's plot. The I-V-T curves were also fitted using the thermionic field emission model. The barrier heights were found to be higher than those calculated using thermionic emission model. From the fit of the I-V-T curves to the field emission model, field emission was seen to dominate in the low temperature range of 140 K to 177 K. The temperature dependent current graphs show two regions of different mechanisms. The log I versus 1000/T plot gives activation energies E-a1 = 0.367095 - 0.257682 eV and E-a2 = 0.038416 - 0.042452 eV. The log ( I/T-2) versus 1000/T graph gives trap depths Phi(o1) = 0.314159 - 0.204752 eV and Phi(o2) = 0.007425- 0.011163 eV. With increasing voltage the activation energy E-a1 and the trap depth Phi(o1) decrease. From the ln (IT1/ 2) versus 1/T-1/ 4 graph, the low temperature region is due to variable range hopping mechanism and the high temperature region is due to thermionic emission. (C) 2014 Author(s).

NaOsO3: A high Neel temperature 5d oxide

The origin of a high Neel temperature in a 5d oxide, NaOsO3, has been analyzed within the mean-field limit of a multiband Hubbard model and compared with the analogous 4d oxide, SrTcO3. Our analysis shows that there are a lot of similarities in both of these oxides on the dependence of the effective exchange interaction strength (J(0)) on the electron-electron interaction strength ( U). However, the relevant value of U in each system puts them in different portions of the parameter space. Although the Neel temperature for NaOsO3 is less than that for SrTcO3, our results suggest that there could be examples among other 5d oxides that have a higher Neel temperature. We have also examined the stability of the G-type antiferromagnetic state found in NaOsO3 as a function of electron doping within GGA + U calculations and find a robust G-type antiferromagnetic metallic state stabilized. The most surprising aspect of the doped results is the rigid bandlike evolution of the electronic structure, which indicates that the magnetism in NaOsO3 is not driven by Fermi surface nesting.

Effects of temperature on complexes I and II mediated respiration, ROS generation and oxidative stress status in isolated gill mitochondria of the mud crab Scylla serrata

Effects of fluctuations in habitat temperature (18-30 degrees) on mitochondrial respiratory behavior and oxidative metabolic responses in the euryhaline ectotherm Scylla serrate are not fully understood. In the present study, effects of different temperatures ranging from 12 to 40 degrees C on glutamate and succinate mediated mitochondrial respiration, respiratory control ratio (RCR), ATP generation rate, ratio for the utilization of phosphate molecules per atomic oxygen consumption (P/O), levels of lipid peroxidation and H2O2 in isolated gill mitochondria of S. serrata are reported. The pattern of variation in the studied parameters was similar for the two substrates at different temperatures. The values recorded for RCR ( >= 3) and P/O ratio (1.4-2.7) at the temperature range of 15-25 degrees C were within the normal range reported for other animals (3-10 for RCR and 1.5-3 for P/O). Values for P/O ratio, ATP generation rate and RCR were highest at 18 degrees C when compared to the other assay temperatures. However, at low and high extreme temperatures, i.e. at 12 and 40 degrees C, states III and IV respiration rates were not clearly distinguishable from each other indicating that mitochondria were completely uncoupled. Positive correlations were noticed between temperature and the levels of both lipid peroxidation and H2O2. It is inferred that fluctuations on either side of ambient habitat temperature may adversely influence mitochondria respiration and oxidative metabolism in S. serrata. The results provide baseline data to understand the impacts of acute changes in temperature on ectotherms inhabiting estuarine or marine environments. (C) 2014 Elsevier Ltd. All rights reserved.

An electrochemical method for the synthesis of few layer graphene sheets for high temperature applications

We demonstrate an electrochemical technique for the large scale synthesis of high quality few layer graphene sheets (FLGS) directly from graphite using oxalic acid (a weak acid) as the electrolyte. One of the interesting observations is that the FLGS are stable at least up to 800 degrees C and hence have potential application in solid oxide fuel cells as a gas diffusion layer.

Enhancing the high temperature plasticity of a Cu-containing austenitic stainless steel through grain boundary strengthening

The addition of 3 wt% Cu to heat-resistant SUS 304H austenitic steel enhances its high temperature mechanical properties. To further improve the properties, particularly the creep resistance and ductility at high temperatures, a post-solutionizing heat-treatment method that involves an intermediated annealing either at 700 or 800 degrees C after solutionizing for durations up to 180 min was employed. The purpose this heat-treatment is to precipitate planar Cr23C6 at the grain boundaries, which results in the boundaries getting serrated. Detailed microstructural analyses of these `grain boundary engineered' alloys was conducted and their mechanical performance, both at room temperature and at 750 degrees C, was evaluated. While the grain size and texture are unaffected due to the high temperature hold, the volume fraction of Sigma 3 twin boundaries was found to increase significantly. While the strength enhancement was only marginal, the ductility was found to increase significantly, especially at high temperature. A marked increase in the creep resistance was also noted, which is attributed to the reduction of the grain boundary sliding by the grain boundary serrations and the suppression of grain boundary cavitation through the optimization of the volume fraction and spacing of the Cr23C6 precipitates. The special heat-treatment performed with holding time of 3 h at 700 degrees C resulted in the optimum combination of strength, ductility and creep resistance at high temperature. (C) 2014 Elsevier B.V. All rights reserved.

Effect of Substrate Temperature on the Microstructure Variation in Sputter-deposited Hydrogenated Amorphous Silicon Thinfilms

Vacancy, void incorporation and Si-H-x configuration in hydrogenated amorphous silicon (a-Si:H) thin films was studied. Films were grown by Direct Current (DC), pulsed DC and Radio Frequency (RF) magnetron sputtering. Fourier Transform Infrared (FTIR) spectroscopic analysis has been carried out on the films and found that, the a-Si: H films grown by DC magnetron sputtering are of good quality compared to pulsed DC and RF deposited films. The effect of Substrate temperature (T-S) on the total hydrogen concentration (C-H), configuration of hydrogen bonding, density (decided by the vacancy and void incorporation) and the microstructure factor (R*) was studied. T-S is found to be an active parameter in affecting the above said properties of the films. The films contain both vacancies and voids. At low hydrogen dilutions the films are vacancy dominated and at high hydrogen dilutions they are void dominated. It is found that T-S favors monohydride (Si-H) bonding at the cost of dihydride (Si-H-2) bonding. This dividing line is at C-H=14 at.% H for DC sputter deposited films. The microstructure structure factor R* is found to be zero for as deposited DC films at T-S=773K. The threshold C-H for void dominated region is found to be C-H=23 at.% H for RF, C-H=18 at.% H for PDC and C-H similar to 14 at.%H for DC sputter deposited films.

Dynamic recovery and recrystallization during high-temperature tensile deformation of a free-standing Pt-aluminide bond coat

Free-standing Pt-aluminide (PtAl) bond coat, when subjected to tensile testing at high temperatures (T >= 900 degrees C), exhibits significant decrease in strength and increase in ductility during deformation at strains exceeding that corresponding to the ultimate tensile strength (UTS), i.e., in the post-UTS regime. The stress-strain curve is also marked by serrations in this regime. Electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM) studies suggest dynamic recovery and recrystallization (DRR) as the mechanisms for the observed tensile behavior in the coating. Activation energy values suggest vacancy diffusion assists DRR. The fine recrystallized grains formed after deformation had a strong < 110 > texture. (c) 2014 Elsevier B.V. All rights reserved.

Multi-site downscaling of maximum and minimum daily temperature using support vector machine

Climate change impact assessment studies involve downscaling large-scale atmospheric predictor variables (LSAPVs) simulated by general circulation models (GCMs) to site-scale meteorological variables. This article presents a least-square support vector machine (LS-SVM)-based methodology for multi-site downscaling of maximum and minimum daily temperature series. The methodology involves (1) delineation of sites in the study area into clusters based on correlation structure of predictands, (2) downscaling LSAPVs to monthly time series of predictands at a representative site identified in each of the clusters, (3) translation of the downscaled information in each cluster from the representative site to that at other sites using LS-SVM inter-site regression relationships, and (4) disaggregation of the information at each site from monthly to daily time scale using k-nearest neighbour disaggregation methodology. Effectiveness of the methodology is demonstrated by application to data pertaining to four sites in the catchment of Beas river basin, India. Simulations of Canadian coupled global climate model (CGCM3.1/T63) for four IPCC SRES scenarios namely A1B, A2, B1 and COMMIT were downscaled to future projections of the predictands in the study area. Comparison of results with those based on recently proposed multivariate multiple linear regression (MMLR) based downscaling method and multi-site multivariate statistical downscaling (MMSD) method indicate that the proposed method is promising and it can be considered as a feasible choice in statistical downscaling studies. The performance of the method in downscaling daily minimum temperature was found to be better when compared with that in downscaling daily maximum temperature. Results indicate an increase in annual average maximum and minimum temperatures at all the sites for A1B, A2 and B1 scenarios. The projected increment is high for A2 scenario, and it is followed by that for A1B, B1 and COMMIT scenarios. Projections, in general, indicated an increase in mean monthly maximum and minimum temperatures during January to February and October to December.

Citrate-complexation synthesized Ce0.85Gd0.15O2-delta (GDC15) as solid electrolyte for intermediate temperature SOFC

A typical Ce0.85Gd0.15O2-delta (CDC15) composition of CeO2-Gd2O3 system is synthesized by modified sol - gel technique known as citrate-complexation. TG-DTA, XRD, FT-IR, Raman, FE-SEM/EDX and ac impedance analysis are carried out for structural and electrical characterization. XRD pattern confirmed the well crystalline cubic fluorite structure of CDC15 after calcining at 873 K. Raman spectral bands at 463, 550 and 600 cm(-1) are also in agreement with these structural features. FE-SEM image shows well-defined grains separated from grain boundary and good densification. Ac impedance studies reveal that GDC15 has oxide ionic conductivity similar to that reported for Ce0.9Gd0.1O2-delta (GDC10) and Ce0.8Gd0.2O2-delta (GDC20). Ionic and electronic transference numbers at 673 K are found to be 0.95 and 0.05, respectively. This indicates the possible application of GDC15 as a potential electrolyte for IT-SOFCs. (C) 2014 Elsevier B.V. All rights reserved.