Evolution of dendritic nanosheets into durable holey sheets: a lattice gas simulation study

2011 ◽  
Vol 15 (05n06) ◽  
pp. 449-458 ◽  
Author(s):  
Sivakumar R. Challa ◽  
Yujiang Song ◽  
John A. Shelnutt ◽  
James E. Miller ◽  
Frank van Swol
Keyword(s):  
Surface Area ◽  
Lattice Gas ◽  
Sheet Thickness ◽  
Stable Range ◽  
Long Duration ◽  
Double Exponential ◽  
Model Pore ◽  
Intuitive Method ◽  
The Stability ◽  
Rapid Coarsening

Monte Carlo lattice gas simulations are performed to study sintering in a realistic dendritic platinum nanosheet. The morphological and topological transformations observed in the simulations are in good agreement with sintering experiments. Employing an intuitive method of quantifying surface area, the stability of the surface area of the dendritic nanosheets is analyzed. The surface area is found to have a double exponential decay, one decay corresponding to rapid coarsening of dendritic features into pores and the other decay corresponding to a slow disappearance of unstable pores. Long duration simulations indicate that the thickness of the dendritic nanosheet remains fairly stable. Stability simulations of a single model pore in a sheet establish that there exists a narrow range of sheet thickness and pore size combinations that produces stable holey sheets. Outside this parameter range pores either rapidly close or expand without bound. The thickness of the engineered dendritic platinum nanosheet and the size of the crevices between dendritic arms put the Pt sheet into this stable range, further corroborating the detailed simulations and explaining the persistence of pores observed in actual dendritic platinum nanosheets.

scholarly journals The training schedule affects the stability, not the magnitude, of the interlimb transfer of learned dynamics

2013 ◽  
Vol 110 (4) ◽  
pp. 984-998 ◽  
Author(s):  
Wilsaan M. Joiner ◽  
Jordan B. Brayanov ◽  
Maurice A. Smith
Keyword(s):  
Short Duration ◽  
Dynamic Environment ◽  
Internal Representation ◽  
Motor Adaptation ◽  
Training Period ◽  
Visually Guided ◽  
Brief Training ◽  
Long Duration ◽  
The Stability ◽  
The Right

The way that a motor adaptation is trained, for example, the manner in which it is introduced or the duration of the training period, can influence its internal representation. However, recent studies examining the gradual versus abrupt introduction of a novel environment have produced conflicting results. Here we examined how these effects determine the effector specificity of motor adaptation during visually guided reaching. After adaptation to velocity-dependent dynamics in the right arm, we estimated the amount of adaptation transferred to the left arm, using error-clamp measurement trials to directly measure changes in learned dynamics. We found that a small but significant amount of generalization to the untrained arm occurs under three different training schedules: a short-duration (15 trials) abrupt presentation, a long-duration (160 trials) abrupt presentation, and a long-duration gradual presentation of the novel dynamic environment. Remarkably, we found essentially no difference between the amount of interlimb generalization when comparing these schedules, with 9–12% transfer of the trained adaptation for all three. However, the duration of training had a pronounced effect on the stability of the interlimb transfer: The transfer elicited from short-duration training decayed rapidly, whereas the transfer from both long-duration training schedules was considerably more persistent (<50% vs. >90% retention over the first 20 trials). These results indicate that the amount of interlimb transfer is similar for gradual versus abrupt training and that interlimb transfer of learned dynamics can occur after even a brief training period but longer training is required for an enduring effect.

Evaluation of Non-Vibrating Utility Burner/Furnace Systems for Resistance to Thermoacoustic Oscillations

2006 ◽  
Author(s):  
Frantisek L. Eisinger ◽  
Robert E. Sullivan
Keyword(s):  
Design Process ◽  
Axial Direction ◽  
Stability Diagram ◽  
Stable Range ◽  
Design Engineers ◽  
Secondary Role ◽  
The Stability ◽  
Thermoacoustic Oscillations

Six burner/furnace systems which operated successfully without vibration are evaluated for resistance to thermoacoustic oscillations. The evaluation is based on the Rijke and Sondhauss models representing the combined burner/furnace (cold/hot) thermoacoustic systems. Frequency differences between the lowest vulnerable furnace acoustic frequencies in the burner axial direction and those of the systems’ Rijke and Sondhauss frequencies are evaluated to check for resonances. Most importantly, the stability of the Rijke and Sondhauss models is checked against the published design stability diagram of Eisinger [1] and Eisinger and Sullivan [2]. It is shown that the resistance to thermoacoustic oscillations is adequately defined by the published design stability diagram to which the evaluated cases generally adhere. Once the system falls into the stable range, the frequency differences or resonances appear to play only a secondary role. It is concluded, however, that in conjunction with stability, the primary criterion, sufficient frequency separations shall also be maintained in the design process to preclude resonances. The paper provides sufficient details to aid the design engineers.

Active surface centres in vanadium pentoxide/alkali metal sulphate heterogeneous catalysts for 2-propanol decomposition

1979 ◽  
Vol 57 (18) ◽  
pp. 2464-2469 ◽  
Author(s):  
David Victor Fikis ◽  
William John Murphy ◽  
Robert Anderson Ross
Keyword(s):  
Alkali Metal ◽  
Surface Area ◽  
Vanadium Pentoxide ◽  
Heterogeneous Catalysts ◽  
Catalyst Activity ◽  
Active Surface ◽  
Hydroxyl Groups ◽  
Kinetic Measurements ◽  
The Stability ◽  
The Individual

Infrared spectra of the surfaces of vanadium pentoxide and vanadium pentoxide containing 9.09 mol% caesium and potassium, as sulphates, have been determined after exposure to 2-propanol for various times. Interpretation of the spectra leads to the proposal that the principal source of catalyst activity may be associated with surface hydrogen and hydroxyl groups on V5+ and V4+ sites. The "stability" of the catalysts towards reduction by the alcohol was consistent with the activity series derived from kinetic measurements: V2O5 (pure) < V2O5 (Cs) < V2O5 (K). The degree of sample reduction has also been assessed qualitatively by measurements of the ratio of surface area before to that after reaction and the same catalyst sequence was established. The trend in surface area ratios was similar to that shown by the surface "Tammann" temperatures of vanadium pentoxide and alkali metal sulphates which has been taken to imply that the ease and (or) extent with which the sulphates enter into inter-solid reactions with the oxide in the preparation stage may exert influence on the subsequent reducibility of the individual members of the catalyst series.

scholarly journals Adhesion state estimation based on improved tire brush model

2018 ◽  
Vol 10 (1) ◽  
pp. 168781401774770
Author(s):  
Bei Shaoyi ◽  
Li Bo ◽  
Zhu Yanyan
Keyword(s):  
Lateral Force ◽  
Longitudinal Force ◽  
Lateral Acceleration ◽  
Stable Range ◽  
The Road ◽  
Nonlinear Compensation ◽  
The Stability ◽  
Standard Calculation ◽  
Double Nonlinear ◽  
Brush Model

On the basis of calculating the longitudinal force using the original brush model, we simplify the tire structure and consider the lateral force generated by the lateral elasticity of the tread. At the same time, the boundary conditions between the adhesion area and the slip zone in the contact area of the tire are fully discussed. By establishing an improved tire brush model, the error caused by neglecting the sideslip characteristics is avoided, and the adaptability of the tire model is improved. A double nonlinear compensation method based on the lateral acceleration deviation and the yaw rate deviation is employed to estimate the road adhesion coefficient, which is closer to the actual attachment situation than the standard calculation. Based on this model, the vehicle stability coefficient k is defined and calculated to describe the stability of the vehicle during the driving process. The modeling results show that the value of k is always in the stable range of [0, 1]. Therefore, the vehicle that utilizes the improved tire brush model is always within the controllable range in the driving process, which verifies the effectiveness of the model.

Study on Alkylation of Catechol with Ethanol by Al-P-Ti-O Oxides

2012 ◽  
Vol 599 ◽  
pp. 114-117 ◽  
Author(s):  
Xiao Mei Zhu ◽  
Bing Sun ◽  
Cheng Huo
Keyword(s):  
Citric Acid ◽  
Surface Area ◽  
Vapour Phase ◽  
Cane Sugar ◽  
Precipitation Method ◽  
Title Reaction ◽  
Catalytic Activities ◽  
P Content ◽  
The Stability ◽  
Ti Content

Vapour-phase alkylation of catechol with ethanol has been investigated over Al-P-Ti-O oxides prepared by non-uniform precipitation method. The catalytic activities decrease with the increase of P content. The catalytic activities increase with increasing Ti content, while the selectivity to guathol decreases. The results of XRD characterization demonstrate that the increase of titanium and the addition of additive affects the structure of the catalysts. The addition of additive (cane sugar or citric acid) decrease the catalytic activities of the catalysts, while increase the stability of the catalyst. Both the conversion of catechol and the selectivity to guathol decrease by the addition of additive, and the C-alkylation products increase obviously. The results indicate that the appropriate pores and surface area are enough for the title reaction, lager pore and higher surface area are favorable to C-alkylation products and stability of catalyst.

The crystallography of calf rennin (chymosin)

1971 ◽  
Vol 178 (1052) ◽  
pp. 245-258 ◽  
Keyword(s):  
Degradation Products ◽  
Protein Solutions ◽  
Stable Range ◽  
X Ray Diffraction ◽  
Stable Species ◽  
Wide Range ◽  
Unit Cells ◽  
Diffraction Patterns ◽  
The Stability ◽  
Ph Range

The growth of crystals of calf rennin (chymosin, † EC 3.4.4.3) and the control of nucleation to produce crystals of desired size, are described. Only one stable species, orthorhombic rennin I, has been found, but a metastable monoclinic species, rennin II, appeared on one occasion in a solution nearly saturated with glycine. The morphology, optical characteristics and unit cells of these species are recorded. In rennin I, small differences in the properties of sectors built by deposition on the three types of crystal faces are attributed to differences in the proportions of either degradation products or of the slightly different isoenzymes known to be present in calf rennin. Rennin I crystals have been obtained only within the pH range of greatest stability of the protein, 5. 0 to 6. 2; but the crystals tolerate subsequent changes of pH down to 2. 0. The stability of crystals appears to be much greater than that of salt-free protein solutions. Rennin I may be crosslinked with glutaraldehyde with no loss of order, giving crystals stable over a wide range of solution conditions, including pH 2.0 to 10.0 and salt-free solutions. The remarkable swelling behaviour when the pH is raised beyond the stable range is described. Rennin II, though monoclinic in symmetry, shows in its X -ray diffraction patterns strong evidence of a pseudo-orthorhombic arrangement of molecules.

The Survey-Based Term Premium in Comparison to the Realized Term Premium

2019 ◽  
Keyword(s):  
Interest Rate ◽  
Interest Rates ◽  
Forecast Errors ◽  
Stable Range ◽  
Wide Margin ◽  
Term Premium ◽  
Ex Post ◽  
Daunting Task ◽  
Ex Ante ◽  
The Stability

This article constructs a 10-year realized term premium from the 10-year zero coupon Treasury yield in year 1 and the ex post three-month Treasury yields from years 1 to 10. The realized term premium swung wildly until the mid-1980s, and then fluctuated within a fairly stable range showing no trend. In comparison, the term premium derived from surveys of interest rate forecasts (survey-based term premium) was substantially lower than the realized term premium and trended downward since the early 1990s. The large and systematic forecast errors in combination with the stability of the realized term premium suggest possibilities that professional forecasters might have missed the term premium demanded by investors (ex ante term premium) by a wide margin and/or that investors forecast the future paths of interest rates more accurately than professional forecasters. It is also unclear that the survey-based term premium fairly represents the professional forecasters’ estimate of the ex ante term premium, not to mention the ex ante term premium itself. While it would be a daunting task to verify these possibilities, it is fairly clear that surveys of interest rate forecasts are of limited value as an investment guide.

scholarly journals Stability of Sheet Flow of Water Beneath Temperate Glaciers and Implications for Glacier Surging

1982 ◽  
Vol 28 (99) ◽  
pp. 273-293 ◽  
Author(s):  
Joseph S. Walder
Keyword(s):  
Mathematical Model ◽  
Pressure Gradient ◽  
Heat Dissipation ◽  
Sheet Thickness ◽  
Sheet Flow ◽  
High Speeds ◽  
Effective Roughness ◽  
Viscous Heat ◽  
Surface Slopes ◽  
The Stability

AbstractA mathematical model is presented for the stability of sheet flow of water beneath a temperate glacier. Enhanced viscous heat dissipation in thick parts of the sheet tends to make sheet flow unstable, the instability increasing as sheet thickness and pressure gradient increase. However, incipient channels may be destroyed as the glacier slides over protuberances on its bed. Quasi-stable sheet flow may be possible for sheets up to several millimeters in thickness, especially beneath glaciers that have relatively gentle surface slopes and slide at moderate to high speeds. Such water sheets may somewhat reduce the effective roughness of glacier beds, but probably not enough to allow surge initiation. Furthermore, the presence of numerous water-filled cavities at the glacier bed will tend to reduce the sheet thickness and lessen the degree of “lubrication” of the glacier bed by the water sheet.

Conformational Analysis, Solvent-Accessible Surface and Geometric Extent of Inhibitors and Substrates

2006 ◽  
Vol 71 (6) ◽  
pp. 842-858 ◽  
Author(s):  
Matheus Froeyen ◽  
Hans De Winter ◽  
Piet Herdewijn
Keyword(s):  
Conformational Analysis ◽  
Surface Area ◽  
Contact Surface ◽  
Peptide Ligands ◽  
Receptor Complex ◽  
Extended Conformation ◽  
Accessible Surface ◽  
The Stability ◽  
Solvent Accessible Surface

Peptide ligands are known to often bind in an extended conformation to maximize the contact surface with the receptor. The complementarity of shape and surface is a very important factor contributing to the stability of a ligand receptor complex. In this communication we try to answer the following questions: What is the influence of conformation on the surface area? Do ligands maximize their contact surface with the receptor to increase stability of the complex?

scholarly journals Review on the recent progress in the preparation and stability of graphene-based nanofluids

2020 ◽  
Vol 142 (3) ◽  
pp. 1145-1172 ◽  
Author(s):  
Thong Le Ba ◽  
Omid Mahian ◽  
Somchai Wongwises ◽  
Imre Miklós Szilágyi
Keyword(s):  
Physical Properties ◽  
Surface Area ◽  
Heat Conductivity ◽  
Recent Progress ◽  
Research Work ◽  
Volume Ratio ◽  
Suspension Stability ◽  
Pumping Power ◽  
Erosion Corrosion ◽  
The Stability

Abstract Graphene has attracted much attention from the science world because of its mechanical, thermal, and physical properties. Graphene nanofluid is well known for its easy synthesis, longer suspension stability, higher heat conductivity, lower erosion, corrosion, larger surface area/volume ratio, and lower demand for pumping power. This article is an audit of experimental outcome about the preparation and stability of graphene-based nanofluids. Numerous researches to prepare and stabilize graphene-based nanofluids have been developed, and it is indispensable to create a complete list of the approaches. This research work outlines the advancement on preparation and assessment methods and the techniques to enhance the stability of graphene nanofluids and outlook prospects.

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