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21.
22.
R. S. Meena Anand Pal Shiva Kumar K. V. R. Rao V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2013,26(7):2383-2389
We report superconductivity in the SmFeAsO1?x F x for the x=0.2 system being synthesized using the single step solid state reaction route. Rietveld analysis of room temperature X-ray diffraction (XRD) data shows the studied samples, SmFeAsO1?x F x with x=0.0 and x=0.2, are crystallized in a single phase tetragonal structure with space group P4/nmm. The resistivity measurement shows superconductivity for the x=0.20 sample with T c (onset) ~51.7 K. The upper critical field, [H c2(0)] is estimated ~3770 kOe by Ginzburg–Landau (GL) theory. Broadening of superconducting transition in magnetotransport is studied through thermally activated flux flow in an applied field up to 130 kOe. The flux flow activation energy (U/k B ) is estimated ~1215 K for 1 kOe field. Magnetic measurements exhibited bulk superconductivity with lower critical field (H c1) of ~1.2 kOe at 2 K. In the normal state, the paramagnetic nature of compound confirms no trace of magnetic impurity, which orders ferromagnetically. AC susceptibility measurements have been carried out for SmFeAsO0.80F0.20 sample at various amplitude and frequencies of applied AC drive field. The intergranular critical current density (J c ) is estimated. Specific heat [C p (T)] measurement showed an anomaly at around 140 K due to the SDW ordering of Fe, followed by another peak at 5 K corresponding to the antiferromagnetic (AFM) ordering of Sm+3 ions in the SmFeAsO compound. Interestingly, the change in entropy (marked by the C p transition height) at 5 K for Sm+3 AFM ordering is heavily reduced in the case of the superconducting SmFeAsO0.80F0.20 sample. 相似文献
23.
Renato Alexandre C. Santana Ana Regina N. Campos Emanuelle A. Medeiros Aldrighi Luiz M. Oliveira Liana Maria F. Silva Shiva Prasad 《Journal of Materials Science》2007,42(22):9137-9144
A ternary alloy Ni–W–Co was electrodeposited and operational parameters in relation to its corrosion resistance and deposition
efficiency were optimized. A 22 full factorial design was successfully employed for experimental design analysis of the results. By means of response surface
analysis, the statistical model identified the following operating conditions for obtaining corrosion resistant alloy: 60 mA/cm2 current density, 70 °C temperature, 20 rpm cathode rotation and 8.0 pH. The alloy was deposited at 36% current efficiency,
with an average composition of 70% Ni, 8% Co, 22% W and traces of boron and with E
corr −0.508 V and R
p
4.56 × 104 Ohm. The deposit obtained under these conditions had an amorphous character and showed good adherence, high corrosion resistance
and presence of nodules on its surface. Electrochemical corrosion tests verified that the Ni–W–Co alloy had better corrosion
resistance than similarly electrodeposited Co–W amorphous alloy. 相似文献
24.
Shiva K. Madishetty Arjuna Madanayake Renato J. Cintra Vassil S. Dimitrov Dale H. Mugler 《Multidimensional Systems and Signal Processing》2014,25(4):829-845
A multiplierless architecture based on algebraic integer representation for computing the Daubechies 4-tap wavelet transform for 1-D/2-D signal processing is proposed. This architecture improves on previous designs in a sense that it minimizes the number of parallel 2-input adder circuits. The algorithm was achieved using numerical optimization based o exhaustive search over the algebraic integer representation. The proposed architecture furnishes exact computation up to the final reconstruction step, which is the operation that maps the exactly computed filtered results from algebraic integer representation to fixed-point. Compared to Madishetty et al. (IEEE Trans Circuits Syst I (Accepted, In Press), 2012a), this architecture shows a reduction of \(10\cdot n-3\) adder circuits, where \(n\) is the number of wavelet decomposition levels. Standard \(512\times 512\) images Mandrill, Lena, and Cameraman were submitted to digital realizations of both proposed algebraic integer based as well as fixed-point schemes, leading to quantifiable comparisons. The design is physically implemented for a 4-level 2-D decomposition using a Xilinx Virtex-6 vcx240t-1ff1156 FPGA device operating at up to a maximum clock frequency of 263.15 MHz. The FPGA implementation is tested using hardware co-simulation using an ML605 board with clock of 100 MHz. A 45 nm CMOS synthesis shows improved clock frequency of better than 500 MHz for a supply voltage of 1.1 V. 相似文献
25.
Reis MT Freitas OM Agarwal S Ferreira LM Ismael MR Machado R Carvalho JM 《Journal of hazardous materials》2011,192(3):986-994
The present study deals with the extraction of phenols from aqueous solutions by using the emulsion liquid membranes technique. Besides phenol, two derivatives of phenol, i.e., tyrosol (2-(4-hydroxyphenyl)ethanol) and p-coumaric acid (4-hydroxycinnamic acid), which are typical components of the effluents produced in olive oil plants, were selected as the target solutes. The effect of the composition of the organic phase on the removal of solutes was examined. The influence of pH of feed phase on the extraction of tyrosol and p-coumaric was tested for the membrane with Cyanex 923 as an extractant. The use of 2% Cyanex 923 allowed obtaining a very high extraction of phenols (97-99%) in 5-6 min of contact time for either single solute solutions or for their mixtures. The removal efficiency of phenol and p-coumaric acid attained equivalent values by using the system with 2% isodecanol, but the removal rate of tyrosol was found greatly reduced. The extraction of tyrosol and p-coumaric acid from their binary mixture was also analysed for different operating conditions like the volume ratio of feed phase to stripping phase (sodium hydroxide), the temperature and the initial concentration of solute in the feed phase. 相似文献
26.
With the increase in automotive powertrain complexity, an upfront assessment of powertrain capability in meeting its design targets is important early on in the development programs. The optimization of control policy based on powertrain simulation models can facilitate this assessment and establish limits of achievable performance for a given powertrain configuration and parameters. The paper discusses several computational optimization and user interface solutions for deploying a numerical optimal control approach in a user‐friendly software environment. 相似文献
27.
Wusi C. Nirankar N. Shiva K. Eric Brian Paul Gary K. 《Sensors and actuators. B, Chemical》2008,133(2):547-554
The development of rapid and ultra-sensitive detection technologies is a long-standing goal for researchers in the bio-detection fields. Nanowire field-effect transistor (nano-FET) devices have shown great promise in label-free and ultra sensitive detection of biological agents. However, critical application problems in using this technology have not been addressed, particularly the difficulties of FET sensing surface modification for various targets and lower detection specificity in real biological samples. A novel molecular signal transduction system reported herein overcomes such problems. With this system, various complicated bio-molecular interactions are “translated” into simple signal molecules with universal sequences. These signal molecules are captured on the sensing surface of nano-FET devices through sequence-specific recognition and generate detectable electronic signals. Using this system, nano-FET devices become universal for detecting almost any bio-agents. Staphylococcus aureus was used as the target to demonstrate the detection of DNA, RNA and protein on the same nano-FET device. Detection sensitivity was achieved at 25 fM levels in pure sample. 相似文献
28.
Nasim Shokraei Shiva Asadpour Shabnam Shokraei Mehrdad Nasrollahzadeh Sabet Reza Faridi‐Majidi Hossein Ghanbari 《Microscopy research and technique》2019,82(8):1316-1325
Conductive nanofibers have been considered as one of the most interesting and promising candidate scaffolds for cardiac patch applications with capability to improve cell–cell communication. Here, we successfully fabricated electroconductive nanofibrous patches by simultaneous electrospray of multiwalled carbon nanotubes (MWCNTs) on polyurethane nanofibers. A series of CNT/PU nanocomposites with different weight ratios (2:10, 3:10, and 6:10wt%) were obtained. Scanning electron microscopy, conductivity analysis, water contact angle measurements, and tensile tests were used to characterize the scaffolds. FESEM showed that CNTs were adhered on PU nanofibers and created an interconnected web‐like structures. The SEM images also revealed that the diameters of nanofibers were decreased by increasing CNTs. The electrical conductivity, tensile strength, Young's modulus, and hydrophilicity of CNT/PU nanocomposites also enhanced after adding CNTs. The scaffolds revealed suitable cytocompatibility for H9c2 cells and human umbilical vein endothelial cells (HUVECs). This study indicated that simultaneous electrospinning and electrospray can be used to fabricate conductive CNT/PUnanofibers, resulting in better cytocompatibility and improved interactions between the scaffold and cardiomyoblasts. 相似文献
29.
30.
Mehdi Shafiee Ardestani Alireza Salehi Fordoei Asghar Abdoli Reza Ahangari Cohan Golnaz Bahramali Seyed Mehdi Sadat Seyed Davar Siadat Hamid Moloudian Nasser Nassiri Koopaei Azam Bolhasani Pooneh Rahimi Soheila Hekmat Mehdi Davari Mohammad Reza Aghasadeghi 《Journal of materials science. Materials in medicine》2015,26(5):1-8