La0.85−xSmxAg0.15MnO3 (x=0−0.2) ceramics were prepared using the conventional solid-state synthesis method to investigate the effect of Sm3+ substitution on magnetic and electrical transport properties. Magnetic susceptibility versus temperature measurements showed all samples exhibit ferromagnetic to paramagnetic transition with Curie temperature, Tc decreasing from 283 K (x=0) to 164 K (x=0.2) with increasing Sm3+. The observed slope in susceptibility, χ′ versus temperature curves below Tc indicates the possible presence of FM and AFM phases in the metallic region. In addition, a deviation from the Curie-Weiss law above Tc in 1/χ′ versus T curves indicates the existence of a Griffith's phase in the x=0.05−0.2 samples due to the Sm3+ ion substitution. The Griffith temperature, TG was found to decrease from 295 K (x=0.05) to 229 K (x=0.2). Electrical resistivity measurements of the samples in zero field showed transition from metallic behavior to insulating behavior as the temperature was increased. For x=0, two metal-insulator, MI transition peaks were observed at Tp1=282 K and at Tp2=250 K. Both peaks shifted to lower temperatures with the increase in Sm3+. The relative resistivity of the first peak to the second peak decreases with increasing Sm3+ for x>0.05 while at x=0.2 the Tp1 peak was strongly suppressed. Magnetoresistance, MR was observed to weaken with Sm3+ substitution. The metallic region of the ρ(T) curve of the x=0−0.15 samples was fitted to the model of electron-electron and electron-magnon scattering while the insulating region was fitted to the variable range hopping, VRH model. The resistivity behavior indicated that the substitution of Sm3+ weakened the double exchange process and enhanced the Jahn-Teller effect. Our results indicated that the Tp1 peak is strongly related to the double-exchange mechanism while the Tp2 peak is suggested to originate from magnetic inhomogeneity. 相似文献
A series of conducting thin-film solid electrolytes based on poly (vinyl alcohol)/ poly (vinyl pyrrolidone) (PVA/PVP) polymer
blend was prepared by the solution casting technique. PVA and PVP were mixed in various weight percent ratios and dissolved
in 20 ml of distilled water. The samples were analyzed by using impedance spectroscopy in the frequency range between 100
Hz and 1 MHz. The PVA/PVP system with a composition of 80% PVA and 20 wt.% PVP exhibits the highest conductivity of (2.2±1.4)
× 10−7 Scm−1. The highest conducting PVA/PVP blend was then further studied by adding different amounts of potassium hydroxide (KOH) ionic
dopant. Water has been used as solvent to prepare PVA/PVP-KOH based alkaline solid polymer blend electrolyte films. The conductivity
was enhanced to (1.5 ± 1.1) × 10−4 Scm−1 when 40 wt.% KOH was added.
Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 –
8, 2005. 相似文献
MG30 is natural rubber grafted with 30% poly(methyl methacrylate). Gel polymer electrolytes containing MG30–LiCF3SO3–X (X = propylene carbonate, ethylene carbonate) are prepared by solution casting technique. The polymer–salt complexes were investigated using Fourier-transformed infrared. The ionic conductivity of the electrolytes are determined by the ac impedance studies over the temperature range of 303–383 K and is observed to obey the Vogel–Tamman–Fulcher (VTF) rule. The Li+ transference number obtained using the Bruce and Vincent method is <0.3. The Li/Li+ interface stability is established and the electrolytes were found to be able to withstand a voltage of more than 4.2 V. 相似文献
In this paper, an attempt has been made to develop a feasible procedure for the prediction of quality parameters of motor gasoline and to discriminate between the different adulterated motor gasoline samples using density values, distillation temperatures and Fourier transform infrared (FTIR) analyses along with multivariate calibrations without the need for using chromatographic separation or other expensive instruments such as an octane number analyser. Ten blend mixtures of regular and super motor gasoline were prepared in order to study density, distillation temperatures and FTIR spectra characteristics for each blend. Distillation temperatures for the pure and blend mixtures of regular and super motor gasoline at initial boiling point (IBP) to final boling point (FBP) at 5%Vol. interval were obtained. Accurate and complete distillation data on the uncontaminated fuel would be essential for comparison. Thirteen peaks of the absorbance at the wavenumbers: 434, 461, 484, 673, 694, 1030, 1086, 1217, 1231, 1460, 1497, 1606 and 3028 cm(-1) were chosen to perform the multivariate calibration. The results obtained were expected to be useful in determination and differentiation purposes, providing information on whether the density values, distillation temperatures and FTIR analyses along with multivariate method could be an appropriate feature for differentiating a particular pure motor gasoline sample from the others. The observed differences in the specific spectral bands are investigated and discussed. They have proven to be an effective combination in the pursuit of management's differentiation goals. 相似文献
We report on the synthesis of cobalt dihydroxide [Co(OH)2] nanorods and their deposition on a 3-dimensional graphene network via chemical bath deposition. The structural characterization reveals deposited Co(OH)2 to consist of flower-like nanorods on a 3-dimensional graphene foam. The nanocomposite was used for glucose sensing by electrocatalytic oxidation of glucose in 1 M KOH solution. Cyclic voltammetry and amperometric studies revealed a high sensitivity for glucose (3.69 mA mM?1 cm?2) and a 16 nM detection limit. The nanocomposite offers a large effective surface (11.4 cm2) and is very selective for glucose over potentially interfering materials such as dopamine, ascorbic acid, lactose, fructose and urea, not the least due to a relatively low working potential of 0.6 V (vs. Ag/AgCl). The high sensitivity, low detection limit and very good selectivity of free-standing nanocomposite electrodes are attributed to the synergistic effect of (a) the good electrocatalytic activity of the NRs, and (b) the large surface area with high conductivity offered by the 3D graphene foam.
Purity is one of the essential properties of biodiesel. Since the purity parameter depends on different operating conditions, its direct measurement is too hard and can only be obtained for specific ranges of conditions. Therefore, this work considers the least-squares support vector machines (LS-SVMs) that transform operating conditions to a multi-dimensional space to simulate biodiesel purity in wide ranges of operating conditions. Indeed, we develop a reliable LS-SVM approach for modeling the biodiesel purity as a function of catalyst type and its concentration, reaction time, temperature, methanol-to-oil volume ratio, frequency, and amplitude of ultrasonic waves. The designed LS-SVM’s predictive performance is compared with four available artificial intelligence (AI) techniques in reliable literature. The obtained results confirm that the LS-SVM paradigm outperforms other considered AI-based techniques regarding five different statistical criteria. Our LS-SVM model provides AARD?=?2.2%, RMSE?=?3.46, and R2?=?0.9868 for the prediction of 267 experimental data points, which includes 267 data points. This model is finally employed for investigating the effect of different influential variables on biodiesel purity.
A tensor method is used to formulate the on-axis scintillation index for an elliptical Gaussian beam (EGB; astigmatic Gaussian beam) propagating in a weak turbulent atmosphere. Variations of the on-axis scintillation of an EGB are studied. It is interesting to find that the scintillation index of an EGB can be smaller than that of a circular Gaussian beam in a weakly turbulent atmosphere under certain conditions and is closely related to the ratio of the beam waist size along the long axis to that along the short axis of the EGB, the wavelength, and the structure constant of the turbulent atmosphere. 相似文献
The focus of the present study was on the influence of season on yield, chemical composition, antioxidant and antifungal activities of Omani basil (Ocimum basilicum) oil. The present study involved only one of the eight Omani basil varieties. The hydro-distilled essential oil yields were computed to be 0.1%, 0.3% and 0.1% in the winter, spring and summer seasons, respectively. The major components identified were L- linalool (26.5-56.3%), geraniol (12.1-16.5%), 1,8-cineole (2.5-15.1%), p-allylanisole (0.2-13.8%) and DL-limonene (0.2-10.4%). A noteworthy extra component was beta- farnesene, which was exclusively detected in the oil extracted during winter and spring at 6.3% and 5.8%, respectively. The essential oil composition over the different seasons was quite idiosyncratic, in which the principal components of one season were either trivial or totally absent in another. The essential oil extracted in spring exhibited the highest antioxidant activity (except DPPH scavenging ability) in comparison with the oils from other seasons. The basil oil was tested against pathogenic fungi viz. Aspergillus niger, A. fumigatus, Penicillium italicum and Rhizopus stolonifer using a disc diffusion method, and by determination of minimum inhibitory concentration. Surprisingly high antifungal values were found highlighting the potential of Omani basil as a preservative in the food and medical industries. 相似文献
In this work, we investigate two groundwater inventory management schemes with multiple users in a dynamic game-theoretic structure: (i) under the centralized management scheme, users are allowed to pump water from a common aquifer with the supervision of a social planner, and (ii) under the decentralized management scheme, each user is allowed to pump water from a common aquifer making usage decisions individually in a non-cooperative fashion. This work is motivated by the work of Saak and Peterson [14], which considers a model with two identical users sharing a common aquifer over a two-period planning horizon. In our work, the model and results of Saak and Peterson [14] are generalized in several directions. We first build on and extend their work to the case of n non-identical users distributed over a common aquifer region. Furthermore, we consider two different geometric configurations overlying the aquifer, namely, the strip and the ring configurations. In each configuration, general analytical results of the optimal groundwater usage are obtained and numerical examples are discussed for both centralized and decentralized problems. 相似文献