Shape Control Effect Research Articles

Shuttle-like core-shell gold nanorod@Ag-Au nanostructures: Shape control and electrocatalytic activity for formaldehyde oxidation

Bimetallic nanostructures have attracted much attention due to their special properties in optics, surface plasmon and catalysis. In this work, two synthesis routes of core/shell gold nanorod/silver (AuNR@Ag) nanostructures were revisited to pursue the control factor of shuttle-like shapes, which demonstrated the key role of residual Au precursor in the formation of shuttle-like shapes. A novel route was adopted to verify the shape control effect of Au and fabricate shuttle-like AuNR@Ag-Au nanostructures. The presence of gold in the shell growth solution leads to shuttle-like shapes of bimetallic nanostructures, and the Au/Ag molar ratio controls shape details of the shuttle-like nanostructures. Then, the electrocatalytic activity of these core-shell nanostructures in the electrochemical oxidation of formaldehyde in alkaline solutions was investigated. In the forward scan the peaks at +0.22–0.3 V for all samples correspond to the electrochemical oxidation catalyzed by monometallic Ag or Au atoms, but the low potential peak at about −0.1 V for AuNR@Ag-Au sample with less Au alloy shell displays the oxidation reaction catalyzed by the adjacent Ag and Au atoms. The sample with less Au alloy shell also shows higher catalytic activity. Additionally, the surface reaction mechanism is proposed for the electrocatalytic oxidation of formaldehyde in alkaline conditions.

Molecule‐Driven Shape Control of Metal Co‐Catalysts for Selective CO2 Conversion Photocatalysis

AbstractIn photocatalysis of CO2 conversion, metal co‐catalysts draw photo‐generated electrons from semiconductor components and act as reaction sites by adsorbing CO2 and its intermediates. Optimization of the metal co‐catalyst structure is indispensable to improving the efficiency of the photocatalyst, which is currently not meeting performance requirements. By performing a series of experiments and simulations, we demonstrate the effect of selective particle shape control of metal co‐catalysts (Au, Ag, Cu and Pt) by the CO2 induced gas ligands (CO2 and CO) on photocatalytic CO2 conversion activity and selectivity. Indeed, facet formation for adsorption of CO2 and CO proves to be an effective way to improve the CO2 conversion activity. In particular, proper interaction between the gas ligand and the metal co‐catalyst surface, realized by strengthening the metal‐CO2 adsorption and weakening the metal‐CO adsorption, is identified as essential factor for increasing the CO2 conversion activity. Pt and Cu, which exhibit relatively strong interaction with gas molecules, have the improved photocatalytic CO2 conversion activity when grown under CO2. In contrast, Au and Ag, which exhibit relatively weak interaction with gas molecules, have the enhanced photocatalytic CO2 conversion activity when grown under CO. This systematic understanding can be a guideline for controlling the metal co‐catalyst surface structure and will maximize the photocatalytic selectivity of the CO2 conversion.

Optimization of shape control of a cantilever beam using dielectric elastomer actuators

Dielectric elastomer (DE) is a kind of smart soft material that has many advantages such as large deformation, fast response, lightweight and easy synthesis. These features make dielectric elastomer a suitable material for actuators. This article focuses on the shape control of a cantilever beam by using dielectric elastomer actuators. The shape control equation in finite element formulation of the cantilever beam partially covered with dielectric elastomer actuators is derived based on the constitutive equation of dielectric elastomer material by using Hamilton principle. The actuating forces produced by dielectric elastomer actuators depend on the number of layers, the position and the actuation voltage of dielectric elastomer actuators. First, effects of these factors on the shape control accuracy when one pair or multiple pairs of actuators are employed are simulated, respectively. The simulation results demonstrate that increasing the number of actuators or the number of layers can improve the control effect and reduce the actuation voltages effectively. Second, to achieve the optimal shape control effect, the position of the actuators and the drive voltages are all determined using a genetic algorithm. The robustness of the genetic algorithm is analyzed. Moreover, the implications of using one pair and multiple pairs of actuators to drive the cantilever beam to the expected shape are investigated. The results demonstrate that a small number of actuators with optimal placement and optimal voltage values can achieve the shape control of the beam effectively. Finally, a preliminary experimental verification of the control effect is carried out, which shows the correctness of the theoretical method.

Effects of Tapered-Cuff Shape and Continuous Control of Cuff Pressure on Microaspiration: Against All Odds!

Jaillette, Emmanuelle MD; Voisin, Benoit MD; Rouzé, Anahita MD; Nseir, Saad MD, PhD Author Information

Intelligent Shape Regulation Cooperative Model of Cold Rolling Strip and Its Application

A new strip shape control model is established to achieve the synchronizing control of complex shape defects, which can not only takes advantage of the mechanism model's strong analysis ability, but also combines with the fast online calculation function of intelligent model to reduce the poor efficiency regulation. Firstly, the dynamic target strip shape is expressed with the Legendre polynomial contained various components to describe all kinds of online shape targets, so it is easier to compare the shape control effect. Secondly, with the dynamic influence matrix and the efficiency function, some different control methods can be tightly combined in one regulation cycle to carry out the synchronous parallel control and the serial relay regulation, respectively. At the same time, by the DE-ELM method, the intelligent shape control model can play an important role to improve the regulation efficiency of the online strip shape. On the other hand, the collaboration regulation model can make full use of all the effectiveness of each control methods according to their respective characteristics, so that the high precision of the strip shape control is able to be obtained.

Synthesis of Cuboctahedral CeO2 Nanoclusters and Their Assembly into Cuboid Nanoparticles by Oriented Attachment

AbstractHere, we describe a simple approach to control the oriented attachment process through selective ligand scavenging from the {100} facets of CeO2 nanoclusters. Aggregates of these nanoclusters smaller than 10 nm with controlled shapes and exposed facets were obtained. For the synthesis of the cuboctahedral CeO2 nanoclusters, we developed a solvent‐controlled synthesis approach based on a non‐hydrolytic sol–gel process and used an ester aminolysis reaction to control ligand scavenging from the {100} facets. First‐principle calculations allowed us to understand and interpret, at the atomic level, the effects of shape control on the synthesis. Fine‐tuning of the desired morphologies can be achieved by controlling the values of the surface energies, which leads to the formation of morphologies that the classic growth process does not allow.

Detection and evaluation mechanism of cold rolling strip edge shape

ABSTRACTThe edge shape problem of strip has great influence on the shape control precision, so it is extremely necessary to establish the high-precision strip edge shape model. Based on the theoretical analysis and the practical engineering, a new high-precision shape detection model, which consists of wide channels in the middle of detection roll and narrow channels on both sides, is established to analyse the problem of strip edge shape. Instance data showed that the strip lateral thickness difference was directly related with the shape state of strip, and the strip edge coverage rate and the strip deviation amount had important influences on the shape detection precision, the pattern recognition accuracy and the shape control effect, so the strip edge shape model has become one of the key factors to improve industrial application effect of the shape closed-loop control system in the present situation.

Optimal shape control of CNT reinforced functionally graded composite plates using piezoelectric patches

This paper presents a first known study of the optimal shape control of carbon nanotube (CNT) reinforced functionally graded composite plates. Piezoelectric patches are bonded to the top and bottom surfaces to act as actuators and sensors. The genetic algorithm (GA) is used to search the optimal actuator voltages and displacement feedback control gains for the shape control of the CNT reinforced functionally graded composite plates. Three types of CNT distributions are researched in this investigation. A higher-order shear deformation theory is applied to evaluate the displacement fields of the plate. The governing equation of the structural system is formulated with the use of Hamilton's principle and the assumed mode method. The effects of shape control on CNT reinforced functionally graded composite plates, by optimizing the voltage distribution for the open-loop control and the displacement feedback control gain for the closed-loop control, are presented. The effects of CNT distributions and plate aspect ratios on optimal shape control results are also investigated.

The effects of plasma shape control on the edge collisionless ion orbit loss

Double null magnetic configurations with different elongation κ and triangularity δ are constructed by using an analytical solution of the Grad–Shafranov equation. The ion orbit losses in plasma edge region are calculated by solving the ion guiding center orbit equation for different values of κ and δ. It is found that the ion orbit loss is larger for a smaller value of κ or δ. The variation of the ion orbit loss fraction on the magnetic surface is also studied.

Micro-Modelling Approach to Predict the Influence of Hydrogen Pressure on Short Crack Behaviour

A micromechanical model, based on the FEA (finite element analysis), was developed to estimate the influence of hydrogen pressure on short crack behaviour. Morphology of voids has important connotations in the development of the model. Stress intensity factor was calculated for different crack geometries under hydrogen pressure. The analysis indicates that the form factor of a crack emerging from a round void will be less affected by trapped hydrogen pressure-compared to an elongated void. This analysis reinforces the beneficial effect of inclusion shape control in reducing significantly the detrimental effect of hydrogen.

The effects of pattern shape, subliminal stimulation, and voluntary control on multistable visual perception

Spontaneous figure reversal of ambiguous patterns was analyzed in humans. A) With Necker-“cube”-like, or “drum”-like figures, having square or round shaped “front” and “rear” surfaces, and either large or small “depth”, the perceptual intervals corresponding to both interpretations of “drum” were longer than those of “cube”; the perceived “depth” of the figures was less relevant for reversal timing (inter-reversal intervals were only slightly longer for the “deeper” figures). Although the shape of “front” and “rear” surfaces is not a crucial geometrical feature for figure reversal, it did influence its timing. More, or longer information-processing steps should probably be needed for perceptual representations of curvilinear patterns in comparison with rectangular ones. The underlying neural mechanisms are probably located at a relatively peripheral level in the visual system. B) With a modified Necker “cube”-like figure, having the two internal vertices coincident, and the long axis of the figure aligned horizontally, the effect of voluntary control on perception-reversal timing overcomes opposite effects due to either fixation-attention to pattern's focal zones, or subliminal stimulation by the pattern's biased versions, suggesting one or the other perception's possibility, while it is enhanced by concordant imagery. Voluntary control should intervene downward at a high-level processing, and should probably affect both a decision-making and a perception-stabilizing mechanism in the process of the pattern's unconscious interpretation. Results A and B are confronted with other results on both perceptual and binocular rivalry of up-to-date literature, in the frame of discussions on low-level bottom-up automatic stimulus-driven processing vs high-level top-down covert attention-driven processing.

Freezing of Supercooling Water Using Magnetic Fluid.

To improve the performance of ice thermal storage systems, the problem of freezing on the cooling surface must be addressed. One of the authors has proposed a new ice making method in which a magnetic fluid prevents water from freezing on the cooling surface. Thus, we investigated experimentally the effect of shape control of magnetic fluid using a magnet of freezing of supercooling water. The shape changes and motion of magnetic fluid, which are controlled by controlling the magnetic field, have a slight effect on the supercooling phenomenon. However, the exposure of the cooling surface covered by a film of magnetic fluid reduces the time from controlling the magnetic field until freezing to a few seconds. Therefore, it is possible to use an electric magnet.

On the formability of sheet steels

Formability of sheet steel in stamping operation primarily depends on strain hardening exponent (n), average plastic strain ratio (\(\bar r\)) and the maximum strain the material can undergo before the onset of localized necking. The formability parameters (n and\(\bar r\)) and the forming limit diagrams have been evaluated for a variety of sheet steel products, extensively used for press forming of components of diverse shapes e.g. extra deep drawing quality auto-body sheets, high strength cold rolled sheets, LPG steel for gas cylinders, austenitic and ferritic stainless steels, etc. The effect of sulphide shape control on formability of hot rolled HSLA steel has also been studied. Additionally, the press performance of auto-body sheets and austenitic stainless steels have been monitored and evaluated at customer’s end for complete information on the formability.

Effects of processing on the transverse fatigue properties of low-sulfur AISI 4140 steel

The effects of inclusions due to steelmaking processes on the fatigue life of AISI 4140 have been investigated. The test matrix consisted of three commercially produced heats of AISI 4140 of comparable cleanliness: one was conventionally cast (CC), and two were inert gas-shielded/ bottom-poured (IGS). One of the IGS heats was calcium-treated to explore the effects of inclusion shape control (IGS/SC). All heats were hot-rolled and reduced over 95 pct to produce bar stock of 127 to 152 mm (5 to 6 in.) in diameter. Transverse axial specimens conforming to ASTM E466 were machined, quenched, and tempered to approximately 40 HRC, and they were fatigue tested in tension-tension cycling (R = 0.1). Test results and statistical analyses of the stress-life data show that the IGS grade has several times the fatigue strength of the CC grade at 107 cycles. Lower-limit fatigue strengths calculated at a 99.9 pct probability were 518.5 MPa (75.2 ksi) for IGSvs 55.6 MPa (8.1 ksi) for the CC grade. The IGS/SC grade had the best performance at all stress and life levels. The results obtained indicate that fatigue performance can be improved by choosing a processing method that reduces the incidence of exogenous oxides and by controlling the shape of the sulfides.

Hydrogen sulphide resistance of high sulphur microalloyed steels

Sulphide stress cracking (SSC) and hydrogen-induced blister cracking (HIBC) studies were conducted on a set of seven microalloyed steels to determine the effects of alloy additions and sulphide shape control on their H 2S resistance. Two commercial steels with a sulphur level of 0.025% exhibited poor SSC and HIBC resistance when tested in H 2S-containing acidic environments. A laboratory steel with 0.006% S (sulphide shape controlled) gave good SSC and HIBC resistance. High sulphur (0.025%) laboratory steels alloyed with copper, chromium, nickel, aluminium and molybdenum, and rare earth metal (REM) treated for sulphide shape control, gave an H 2S resistance equal to or better than the low sulphur steel. Addition of copper, chromium and nickel lowered the corrosion rate and improved both the SSC and HIBC resistance. Further addition of 0.5% Al improved the SSC resistance, while addition of 0.3% Mo improved both the SSC and HIBC properties. The low sulphur steel had the lowest hydrogen concentration after exposure to H 2S environments, while alloy additions and REM treatment lowered the amount of hydrogen absorbed by the high sulphur steels. Molybdenum addition seems to be a suitable method to make high sulphur microalloyed steels resistant to H 2S environments.