Large Contact Regions Research Articles

Characterization and Eddy Current Flaw Detection of Dissimilar Aluminium Butt Joint by Friction Stir Welding

Dissimilar aluminum butt joints were successfully joined using a friction stir welding machine, employing four welding speeds (50, 60, 70, 80 mm/min), four rotational speeds (900, 1000, 1100, 1200 rpm), and four different weld tool profiles (T1=12/4, T2=15/5, T3=16/4, T4=20/5 in D/d ratio). The corrosion analysis suggests that specimens 9, 10, 11, and 13 exhibit higher corrosion resistance, with a breaking potential of -0.6 eV, while specimen 8 shows the lowest corrosion resistance with a breaking potential of -2.1 eV. The results from the differential scanning calorimeter illustrate the formation of precipitation dissolution due to high heat generation at the nugget zone. An eddy current defect detector experiment was conducted to detect surface flaws in the welded samples. Few surface cracks were observed in the T2 profile specimens, which have a larger contact region or shoulder diameter, while more surface cracks were observed in the T1 profile samples.

CoMoSx@Ni-CoMoSx double-shelled cage-in-cage hollow polyhedron as enhanced Pt-free catalytic material for high-efficiency dye-sensitized solar cell

Double-shelled hollow structures possess unique properties in energy conversion/storage fields due to their higher surface area, larger contact region with the electrolyte and much shortened paths of charge transfer. In this work, CoMoSx@Ni-CoMoSx hollow polyhedron catalyst with a double-shelled cage-in-cage structure is prepared by a sequence of template-engaged synthetic processes. In the synthetic procedure, (NH4)2MoS4 is applied as a multifunctional vulcanizator, which can conveniently afford Mo and S elements at the same time. Noteworthily, by comparing with single-shelled hollow CoMoSx and Ni-CoMoSx polyhedrons, the double-shelled CoMoSx@Ni-CoMoSx polyhedron catalyst demonstrates superior catalytic properties in the reduction of triiodide in dye-sensitized solar cells. The solar cell with CoMoSx@Ni-CoMoSx based counter electrode exhibits a high power conversion efficiency of 9.30%, which is much higher than that of Pt (8.01%).

Fabrication of two-dimensional Ni2P/ZnIn2S4 heterostructures for enhanced photocatalytic hydrogen evolution

Promoting electron-hole separation and migration and lowering the overpotential of hydrogen evolution reactions are two effective solutions for improving photocatalytic hydrogen performance. Suitable co-catalyst and appropriate interfacial contacts can effectively lower overpotential and can also construct an electric field at the interface to increase the separation efficiency of the carriers. In this work, we design and fabricate a 2D-2D type of Ni2P co-catalyst modified with ZnIn2S4 for boosting the performance of photocatalytic hydrogen evolution. As a co-catalyst, the 2D Ni2P nanosheets exhibit a lower overpotential and smaller charge transfer resistance in hydrogen evolution reactions, and is much improved in both respects compared to Ni2P nanoparticles. Based on this, 2D/2D Ni2P/ZnIn2S4 nanohybrids with large contact regions and shorter transmission distances of the charges were fabricated, which effectively improve the separation of photo induced carriers and the interfacial charge transfer. By taking advantage of the above features, the fabricated 2D-2D Ni2P/ZnIn2S4hybrid exhibits a superior hydrogen evolution rate of 2066 μmol·h−1·g−1 under visible light irradiation, and the apparent quantum yield was 7.7% at 420 ± 20 nm. This activity far exceeds performance of the 0D/2D Ni2P/ZnIn2S4 hybrid, and is ascribed to better charge separation and accelerated surface reactions of the Ni2P nanosheets.

Construction of mesoporous carbon nitride/binary metal sulfide heterojunction photocatalysts for enhanced degradation of pollution under visible light

A novel binary metal sulfide fabricated with mesoporous carbon nitride (mpg-C3N4/SnCoS4) was synthesized by the simple in situ hydrothermal method. Characterizations indicate that a homogenous dispersion of SnCoS4 nanoparticles on the ordered mesoporous structure of mpg-C3N4 (248m2g−1) with average diameter of 25nm, providing more catalytic active sites and large contact regions for adsorption and degradation of pollutant. By taking advantage of this feature, the photocatalytic properties are evaluated systematically by degradation of rhodamine B (RhB) and methylene blue (MB) under visible light irradiation, and the photocatalyitc performance of MCN/SnCoS4-50 is much higher than that of pristine SnCoS4, mpg-C3N4, MCN/CoS2 and MCN/SnS2. Moreover, mpg-C3N4/SnCoS4 heterojunction exhibits excellent photostability after four recycles. The enhanced photo-induced oxidation and reduction activity of mpg-C3N4/SnCoS4 can be attributed to not only the high surface area of composite, but also the formation of n-n type heterojunction. The incorporation of binary metal sulfides into mpg-C3N4 can decrease the band gap, alter the CB and VB potential, enhance the photoinduced interfacial charge transfer, and therefore increase the charge separation efficiency during the photocatalytic reaction.

Ultrathin hexagonal SnS2 nanosheets coupled with g-C3N4 nanosheets as 2D/2D heterojunction photocatalysts toward high photocatalytic activity

In this work, we present the 2D/2D type of heterojunction photocatalysts fabricated by horizontal loading ultrathin hexagonal SnS2 nanosheets on g-C3N4 nanosheets through a facile ultrasonic dispersion method. The sheet-like structures of these two nanomaterials induce a large contact region in the heterojunction interface, as evidenced by electron microscopic analyses. By taking advantage of this feature, the as-fabricated SnS2/g-C3N4 heterojunction nanosheets exhibit considerable improvement on the photocatalytic activities for the degradation of organic dyes and phenols under visible light irradiation as compared to pure g-C3N4 and SnS2 nanosheets. In particular, the optimal heterojunction nanosheet with 5.0wt.% SnS2 shows the apparent rate constant of ∼0.2min−1 for the RhB photodegradation, which is higher than that of pure g-C3N4 and SnS2 nanosheets by a factor of 4 and 8, respectively. Further studies by steady-state and transient photoluminescence spectroscopy indicate that the photosynergistic effect of SnS2/g-C3N4 heterojunction can remarkably enhance the photoinduced interfacial charge transfer, thereby increasing the charge separation during the photocatalytic reaction.

Continuous Self‐Collision Detection for Deformable Surfaces Interacting with Solid Models

AbstractIn this paper, we propose a new continuous self‐collision detection (CSCD) method for a deformable surface that interacts with a simple solid model. The method is developed based on the radial‐view‐based culling method. Our method is suitable for the deformable surface that has large contact region with the solid model. The deformable surface may consist of small round‐shaped holes. At the pre‐processing stage, the holes of the deformable surface are filled with ghost triangles so as to make the mesh of the deformable surface watertight. An observer primitive (i.e. a point or a line segment) is computed so that it lies inside the solid model. At the runtime stage, the orientations of triangles with respect to the observer primitive are evaluated. The collision status of the deformable surface is then determined. We evaluated our method for several animations including virtual garments. Experimental results show that our method improves the process of CSCD.

On an ice failure model with a large contact region

An ice failure model with large force contact region is presented. This model is based on survey and analysis of field and experimental observations and assumes the existence of a quasiregular failure structure in the contact region, where the failure nucleus can move on the contact surface (scan it). The character of motion is determined by the conditions of the failure nucleus displacement and the failure product extrusion from the contact region. The mechanism ensuring the average stress decrease as the contact region increases is explained.

Robust continuous collision detection for interactive deformable surfaces

AbstractCollision events between 3D objects in motion in computer animations or simulations are difficult to detect due to the difficulty of accurately sampling the motion paths of objects in space and time. One approach to this problem has been continuous collision detection but because the current approaches process potentially interacting primitive pairs (PIPPs) redundantly. This is time‐expensive, especially where there are a large number of PIPPs. In this paper we propose a novel collision detection process that more accurately and robustly detects collisions on simulated meshed deformable surfaces. We embed a new layer, primitive filtering layer (PFL), to extract PIPPs. This has two results. It reduces the number of PIPPs significantly and it means that each interacting primitive pair is processed just one time. Experimental results show that this approach achieves interactive rates for complex deformable surfaces with large contact regions. This is especially practical for cloth dynamics. Our method is efficient, accurate, reliable, and robust even in the presence of objects with sharp features. We also present techniques to implement the method on programmable graphics processing units (GPUs). Copyright © 2007 John Wiley & Sons, Ltd.

Transient Thermoelastic Analysis of Composite Brake Disks

This paper presents a modeling analysis of transient thermoelastic behavior occurring in composite brake disks. A finite element code was developed which allowed an effective investigation of the transient thermoelastic analysis. The coupled heat and elastic analysis was done using the finite element method differently from other previous researches. The result of the finite element analysis presented the pressure distributions and the temperature distributions along the friction surfaces, and heat flux vectors for the present model. The thermoelastic state on any friction surface affected the other friction surfaces each other. Thus, the whole modeling of brake disks was necessary for accurate results. The orthotropic brake disks showed better characteristics as a brake friction material than the isotropic ones. Since the composite multiple brake disk system showed the larger contact region of the friction surfaces, the smoother heat flow through the contact interfaces took place. Therefore, the more uniform and lower temperatures and the milder pressure distributions along the friction surfaces than the isotropic multiple brake disk system was caused.

Intermolecular contacts in various crystal forms related to the open and closed conformational states of the catalytic subunit of cAMP-dependent protein kinase.

All hitherto solved crystal structures of the catalytic (C) subunit of cAMP-dependent protein kinase can be classified into two groups, those with a closed and those with an open conformation of the ATP-binding lobe. The molecules with the closed conformation are all related by a crystallographic 2(1) axis that connects them into an infinite-chain motif. The motif has only one large contact region that involves many residues, several of them in the ATP-binding lobe, embedded in an extensive network of water molecules. The dominant feature of this region is the hydrophobic interaction between Trp196 and Arg133, Arg134. This motif has been found so far in three different crystal forms, two correspond to ternary enzyme-inhibitor-ATP complexes with mammalian and recombinant C, and one to a binary enzyme-inhibitor complex with recombinant C. The open conformation has been found in two closely related crystal structures, both of cubic symmetry, of the apoenzyme and a binary complex of the mammalian catalytic subunit. In this cubic structure of the binary complex, the hydrogen-bonded intramolecular contacts between Arg18 of the inhibitor and the ATP-binding lobe of the binary and ternary complexes of the recombinant enzyme are missing due to a strong hydrophobic intermolecular contact involving the diiodinated Tyr7. In solution, no crystal contacts prevent these hydrogen bonds involving Arg18 from forming so that it is likely that the binary complex with Tyr7 of the peptide inhibitor iodinated or not, can assume the closed conformation in solution. While the closed structure very likely represents a stable conformation in solution, there is no evidence to suggest that the open conformation represents a unique stable conformational state of the enzyme in solution.

Effect on the adhesion and locomotion of mouse fibroblasts by their interacting with differently charged substrates: A quantitative study by ultrastructural method

Attachment of fibroblastic cells to differently charged substrates was observed by electron microscopy. Cells attached with large contact regions to less negatively charged substrates. When the negativity of the substrate charge increased, the total area of the contact regions decreased. The degree of adhesion was estimated by the ‘contact index’, which is the percentage of the contact regions in comparison with the circumference of the cells in vertical sections. The results in this paper show that the contact index has a fine correlation with both the substrate charge and cell locomotion. This indicates that electrostatic interaction at the cell surface is an important factor in controlling cell locomotion and cell adhesion.