ULTRASONIC VELOCITY AND OXYGEN-RELATED ELASTIC ANOMALIES IN Zn2+-SUBSTITUTED (Dy,Ca)Ba2Cu3-yZnyO7-δ SUPERCONDUCTORS

2011 ◽  
Vol 25 (01) ◽  
pp. 63-75
Author(s):  
N. A. RASIH ◽  
A. K. YAHYA ◽  
M. I. YUSOF
Keyword(s):  
Low Temperatures ◽  
Longitudinal Velocity ◽  
Transition Process ◽  
Shear Velocity ◽  
The Other ◽  
Velocity Measurements ◽  
Oxygen Ordering ◽  
Phase Transition Process ◽  
Slope Change ◽  
Elastic Anomalies

Ultrasonic longitudinal velocity measurements between 80 K and 280 K and shear velocity measurements between 80 K and 230 K have been performed in polycrystalline superconducting DyBa 2 Cu 3-x Zn x O 7-δ (x = 0, 0.01 and 0.03) and Dy 0.9 Ca 0.1 Ba 2 Cu 3-y Zn y O 7-δ (y = 0.01) samples utilizing the pulsed-echo-overlap technique. A longitudinal anomaly characterized by a step-like slope change was observed at around 240 K for DyBa 2 Cu 3-x Zn x O 7-δ (x = 0) and at 230 K for x=0.01 and 0.03. Zn 2+ substitution suppressed critical temperature, Tc but did not suppress the step-like anomaly. On the other hand, substitution of Ca 2+ in Dy 0.9 Ca 0.1 Ba 2 Cu 3-y Zn y O 7-δ (y = 0.01) caused the step-like anomaly to disappear. The step-like anomaly was suggested due to the oxygen-ordering process in Cu – O chains during a phase transition process at low temperatures. Substitution of Zn 2+ ions in place of Cu was suggested to go into CuO 2 planes and did not interfere with oxygen-ordering in Cu – O chains. This is suggested as the reason why the step-like anomalies were not suppressed in DyBa 2 Cu 3-x Zn x O 7-δ (x = 0.01 and 0.03) samples. Disappearance of the step-like anomaly due to Ca 2+ substitution is probably related to reduction in oxygen content which depletes Cu – O chain sites.

Ultrasonic Velocity Studies on Tl2Ba2Ca2Cu3O10 Superconductor

1998 ◽  
Vol 12 (24) ◽  
pp. 1029-1037 ◽  
Author(s):  
A. K. Yahya ◽  
R. Abd-Shukor
Keyword(s):  
Ultrasonic Velocity ◽  
Longitudinal Mode ◽  
Shear Velocity ◽  
Shear Mode ◽  
Velocity Measurements ◽  
Slope Change ◽  
Slope Discontinuity

Ultrasonic longitudinal and shear velocities propagated at 7–10 MHz in bulk Tl 2 Ba 2 Ca 2 Cu 3 O 10 have been measured between 80 K and 300 K. Shear velocity measurements revealed a pronounced slope discontinuity of 421 ppm/K at around 160 K. A similar slope change was not observed in the longitudinal mode. The slope change around 160 K for the shear mode is suggested to be attributed to some form of correlated Tl and O(4) orderings in the material.

scholarly journals Catalytic Conversion of n-C7 Asphaltenes and Resins II into Hydrogen Using CeO2-Based Nanocatalysts

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1301
Author(s):  
Oscar E. Medina ◽  
Jaime Gallego ◽  
Sócrates Acevedo ◽  
Masoud Riazi ◽  
Raúl Ocampo-Pérez ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Low Temperatures ◽  
Gaseous Mixture ◽  
H2 Production ◽  
The Other ◽  
Hydrogen Release ◽  
Catalytic Gasification ◽  
Three Samples ◽  
Main Decomposition ◽  
Catalytic Capacity

This study focuses on evaluating the volumetric hydrogen content in the gaseous mixture released from the steam catalytic gasification of n-C7 asphaltenes and resins II at low temperatures (<230 °C). For this purpose, four nanocatalysts were selected: CeO2, CeO2 functionalized with Ni-Pd, Fe-Pd, and Co-Pd. The catalytic capacity was measured by non-isothermal (from 100 to 600 °C) and isothermal (220 °C) thermogravimetric analyses. The samples show the main decomposition peak between 200 and 230 °C for bi-elemental nanocatalysts and 300 °C for the CeO2 support, leading to reductions up to 50% in comparison with the samples in the absence of nanoparticles. At 220 °C, the conversion of both fractions increases in the order CeO2 < Fe-Pd < Co-Pd < Ni-Pd. Hydrogen release was quantified for the isothermal tests. The hydrogen production agrees with each material’s catalytic activity for decomposing both fractions at the evaluated conditions. CeNi1Pd1 showed the highest performance among the other three samples and led to the highest hydrogen production in the effluent gas with values of ~44 vol%. When the samples were heated at higher temperatures (i.e., 230 °C), H2 production increased up to 55 vol% during catalyzed n-C7 asphaltene and resin conversion, indicating an increase of up to 70% in comparison with the non-catalyzed systems at the same temperature conditions.

On the criteria for reverse transition in a two-dimensional boundary layer flow

1969 ◽  
Vol 35 (2) ◽  
pp. 225-241 ◽  
Author(s):  
M. A. Badri Narayanan ◽  
V. Ramjee
Keyword(s):  
Longitudinal Velocity ◽  
Outer Region ◽  
Transition Process ◽  
Velocity Profiles ◽  
Wall Region ◽  
Two Dimensional ◽  
Mean Velocity ◽  
Law Of The Wall ◽  
Reverse Transition ◽  
Turbulence Decay

Experiments on reverse transition were conducted in two-dimensional accelerated incompressible turbulent boundary layers. Mean velocity profiles, longitudinal velocity fluctuations $\tilde{u}^{\prime}(=(\overline{u^{\prime 2}})^{\frac{1}{2}})$ and the wall-shearing stress (TW) were measured. The mean velocity profiles show that the wall region adjusts itself to laminar conditions earlier than the outer region. During the reverse transition process, increases in the shape parameter (H) are accompanied by a decrease in the skin friction coefficient (Cf). Profiles of turbulent intensity (u’2) exhibit near similarity in the turbulence decay region. The breakdown of the law of the wall is characterized by the parameter \[ \Delta_p (=\nu[dP/dx]/\rho U^{*3}) = - 0.02, \] where U* is the friction velocity. Downstream of this region the decay of $\tilde{u}^{\prime}$ fluctuations occurred when the momentum thickness Reynolds number (R) decreased roughly below 400.

The effect of Argon pressure dependent V thin film on the phase transition process of (020) VO2 thin film

2018 ◽  
Vol 427 ◽  
pp. 304-311 ◽  
Author(s):  
Yifan Meng ◽  
Kang Huang ◽  
Zhou Tang ◽  
Xiaofeng Xu ◽  
Zhiyong Tan ◽  
...  
Keyword(s):  
Thin Film ◽  
Phase Transition ◽  
Transition Process ◽  
Argon Pressure ◽  
Phase Transition Process

Exploration of Doubly Thermal Phase Transition Process of PDEGA-b-PDMA-b-PVCL in Water

Langmuir ◽  
2016 ◽  
Vol 32 (26) ◽  
pp. 6691-6700 ◽  
Author(s):  
Zhangxin Ye ◽  
Youcheng Li ◽  
Zesheng An ◽  
Peiyi Wu
Keyword(s):  
Phase Transition ◽  
Transition Process ◽  
Thermal Phase Transition ◽  
Phase Transition Process ◽  
Thermal Phase

Interaction Between Low Temperatures Spacers and Source Drain Extensions and Pockets for Both NMOS and PMOS of the 65 nm Node Technology

2006 ◽  
Vol 912 ◽  
Author(s):  
Nathalie Cagnat ◽  
Cyrille Laviron ◽  
Daniel Mathiot ◽  
Pierre Morin ◽  
Frédéric Salvetti ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Hydrogen Content ◽  
Low Temperatures ◽  
Direct Contact ◽  
Fabrication Process ◽  
Experimental Results ◽  
The Other ◽  
Mos Transistors ◽  
Phosphorus Source ◽  
Activation Annealing

AbstractDuring the MOS transistors fabrication process, the source-drain extension areas are directly in contact with the oxide liner of the spacers stack. In previous works [1, 2, 3] it has been established that boron can diffuse from the source-drain extensions into the spacer oxide liner during the subsequent annealing steps, and that the amount of boron loss depends on the hydrogen content in the oxide, because it enhances B diffusivity in SiO2.In order to characterize and quantify the above phenomena, we performed test experiments on full sheet samples, which mimic either BF2 source-drain extensions over arsenic pockets implants, or BF2 pockets under arsenic or phosphorus source-drain extensions implants. Following the corresponding implants, the wafers were covered with different spacer stacks (oxide + nitride) deposited either by LPCVD, or PECVD. After appropriate activation annealing steps, SIMS measurements were used to characterize the profiles of the various dopants, and the corresponding dose loss was evaluated for each species.Our experimental results clearly evidence that LPCVD or PECVD spacer stacks have no influence on the arsenic profiles. On the other hand, phosphorus and boron profiles are affected. For boron profiles, each spacer type has a different influence. It is also shown that boron out-diffuses not only from the B doped source-drain extension in direct contact with the oxide layer, but also from the "buried" B pockets lying under n-doped source drain extension areas. All these results are discussed in term of the possible relevant mechanism.

scholarly journals Acoustic nondestructive testing and measurement of tension for steel reinforcing members

2021 ◽  
Author(s):  
Michael McInerney ◽  
Matthew Brenner ◽  
Sean Morefield ◽  
Robert Weber ◽  
John Carlyle
Keyword(s):  
Laboratory Tests ◽  
Quantitative Methods ◽  
Longitudinal Velocity ◽  
Measurement Techniques ◽  
Field Tests ◽  
Shear Velocity ◽  
Structural Members ◽  
Unstressed State ◽  
Testing And Measurement ◽  
Theory And Model

Many concrete structures contain internal post-tensioned steel structural members that are subject to fracturing and corrosion. The major problem with conventional tension measurement techniques is that they use indirect and non-quantitative methods to determine whether there has been a loss of tension. This work developed an acoustics-based technology and method for making quantitative tension measurements of an embedded, tensioned steel member. The theory and model were verified in the laboratory using a variety of steel rods as test specimens. Field tests of the method were conducted at three Corps of Engineers dams. Measurements of the longitudinal and shear velocity were done on rods up to 50 ft long. Not all rods of this length were able to be measured and the quality and consistency of the signal varied. There were fewer problems measuring the longitudinal velocity than shear velocity. While the tension predictions worked in the laboratory tests, the tension could not be accurately calculated for any of the field sites because researchers could not obtain the longitudinal or shear velocities in an unstressed state, or precise measurements of the longitudinal and shear velocities due to the unknown precise length of the rods in the tensioned state.

scholarly journals The principal magnetic susceptibilities of neodymium sulphate octahydrate at low temperatures

1939 ◽  
Vol 170 (941) ◽  
pp. 266-271 ◽  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Energy Levels ◽  
Constant Factor ◽  
The Other ◽  
Crystalline Field ◽  
Cubic Symmetry ◽  
The Subject ◽  
The Difference ◽  
The One

The magnetic and other related properties of neodymium sulphate have been the subject of numerous investigations in recent years, but there is still a remarkable conflict of evidence on all the essential points. The two available determinations of the susceptibility of the powdered salt at low temperatures, those of Gorter and de Haas (1931) from 290 to 14° K and of Selwood (1933) from 343 to 83° K both fit the expression X ( T + 45) = constant over the range of temperature common to both, but the constants are not the same and the susceptibilities at room temperature differ by 11%. The fact that the two sets of results can be converted the one into the other by multiplying throughout by a constant factor suggested that the difference in the observed susceptibilities was due to some error of calibration. It could, however, also be due to the different purity of the samples examined though the explanation of the occurrence of the constant factor is then by no means obvious. From their analysis of the absorption spectrum of crystals of neodymium sulphate octahydrate Spedding and others (1937) conclude that the crystalline field around the Nd+++ ion is predominantly cubic in character since they find three energy levels at 0, 77 and 260 cm. -1 .* Calculations of the susceptibility from these levels reproduce Selwood’s value at room temperature but give no agreement with the observations-at other temperatures. On the other hand, Penney and Schlapp (1932) have shown that Gorter and de Haas’s results fit well on the curve calculated for a crystalline field of cubic symmetry and such a strength that the resultant three levels lie at 0, 238 and 834 cm. -1 , an overall spacing almost three times as great as Spedding’s.

A New Lattice Boltzmann Model for Phase Transition Process

2009 ◽  
Author(s):  
Longjian Li ◽  
Jianbang Zeng ◽  
Quan Liao ◽  
Wenzhi Cui
Keyword(s):  
Phase Transition ◽  
Lattice Boltzmann ◽  
Equations Of State ◽  
Density Ratio ◽  
Transition Process ◽  
Lattice Boltzmann Model ◽  
New Model ◽  
Phase Transition Process ◽  
Simulation Results ◽  
Boltzmann Model

A new lattice Boltzmann model, which is based on Shan-Chen (SC) model, is proposed to describe liquid-vapor phase transitions. The new model is validated through simulation of the one-component phase transition process. Compared with the simulation results of van der Waals fluid and the Maxwell equal-area construction, the results of new model are closer to the analytical solutions than those of SC model and Zhang model. Since the range of temperature and the maximum density ratio are increased, and the value of maximum spurious current is between those of SC and Zhang models, it is believed that this new model has better stability than SC and Zhang models. Therefore, the application scope of this new model is expanded. According to the principle of corresponding states in Engineering Thermodynamics, the simulations of water and ammonia phase transition process are implemented by using this new model with different equations of state. Compared to the experimental data of water and ammonia, the results show that the Peng-Robinson equation of state is more suitable to describe the water, ammonia and other substances phase transition process. Therefore, these simulation results have great significance for the real engineering applications.

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