The effect of casting processing and natural aging on microstructures and mechanical properties of T5-treated Al–7wt.%Si–0.5 wt.%Mg–0.01 wt.%Sr (ASTM 357) alloys has been investigated. An artificial ...aging gives fine precipitation microstructures, and the thixo-cast processing provides much finer distributions of eutectic Si phases and Al8Si6Mg3Fe phases than the gravity-cast and die-cast processing, leading to higher level of strength-ductility balance in the thixo-cast alloys than that of T6-treated Al–Si based cast alloys. Although the prolonged natural aging significantly changes the subsequent artificial age-hardening behaviors and precipitation microstructures, it is interesting to note that the cast alloys could keep their good strengths even after the T5-treatment including the long-term natural aging. This finding will open up the development of strong and ductile cast Al–7wt.%Si–Mg based alloys which can broaden the application of aluminum alloys in automotive industry.
•Thixo-casting results in uniform dispersion of fine eutectic compounds.•T5-treatment brings about fine distributions of precipitates.•Thixo-casting and subsequent T5-treatment provide good tensile property.•T5-treated alloys could keep good strengths even after prolonged natural aging.
The mineral phase of dentin is located primarily within collagen fibrils. During development, bone or dentin collagen fibrils are formed first and then water within the fibril is replaced with ...apatite crystallites. Mineralized collagen contains very little water. During dentin bonding, acid-etching of mineralized dentin solubilizes the mineral crystallites and replaces them with water. During the infiltration phase of dentin bonding, adhesive comonomers are supposed to replace all of the collagen water with adhesive monomers that are then polymerized into copolymers. The authors of a recently published review suggested that dental monomers were too large to enter and displace water from collagen fibrils. If that were true, the endogenous proteases bound to dentin collagen could be responsible for unimpeded collagen degradation that is responsible for the poor durability of resin–dentin bonds. The current work studied the size–exclusion characteristics of dentin collagen, using a gel-filtration-like column chromatography technique, using dentin powder instead of Sephadex. The elution volumes of test molecules, including adhesive monomers, revealed that adhesive monomers smaller than ∼1000Da can freely diffuse into collagen water, while molecules of 10,000Da begin to be excluded, and bovine serum albumin (66,000Da) was fully excluded. These results validate the concept that dental monomers can permeate between collagen molecules during infiltration by etch-and-rinse adhesives in water-saturated matrices.
•Dissimilar lap joining of CP-Ti/SUS304 was carried out using friction stir welding.•Fracture occurred in the CP-Ti base material at every joining speed.•A four-layer reaction layer formed along the ...interface.•The joining speed of 50mmmin−1 is optimum to obtain strong peel strength.•At the lower joining speed, the interface showed a mixed and laminated structure.
Friction stir welding was performed to accomplish dissimilar lap joining of commercially pure titanium (CP-Ti) to 304 stainless steel (SUS304). The joining speed was varied from 25 to 100mmmin−1. At a joining speed of 50mmmin−1, the morphology of the interface was a flat and simple interfacial reaction layer whose thickness was less than 1μm. The reaction layer consisted of four layers: β-Ti (+ ω-Ti), Ti2Ni, FeTi+Fe2Ti, and σ-FeCr, listed in order from the CP-Ti side to the SUS304 side. At a joining speed of 25mmmin−1, the interface consisted of a macroscopically mixed and laminated structure approximately 300μm thick consisting of multiple reaction layers. During the tensile shear test, joint fractures occurred in the CP-Ti base material at every joining speed. However, during the peel test, joint fractures occurred at the joint interface.
Now that YBCO-coated conductors have been commercialized, a number of YBCO coils have been developed. However, their basic performances have not been systematically investigated so far. Here, we ...demonstrate that of a YBCO double pancake coil. The critical current of an epoxy impregnated YBCO double pancake coil was substantially degraded, i.e. the normal voltage appears above 8A, only 18% of that for the dry coil. It was inferred that degradation occurs if the cumulative radial stress developed during cool down exceeds the critical transverse stress for the YBCO-coated conductor (typically 10MPa). Under these conditions, the conductor was debonded at the interface between the buffer layer and YBCO layers, or fractured in the YBCO layer itself, causing cracks on the YBCO layer, resulting in a significant decline of the critical current. These negative effects are suppressed if the coils are dry wound or impregnated with paraffin, as the bonding strengths between turns are negligible and therefore turns are separated if the cumulative radial stress tends to be tensile. For non-circular coils in which epoxy impregnation is inevitable, degradation due to cumulative tensile transverse stress is still the major problem.
Super‐rotation and waves are sensitive to horizontal subgrid‐scale fourth‐order diffusion in long‐term time integrations of a dynamical core under a Venus‐like condition. The rigid‐body rotation ...component of the super‐rotation intensifies as the diffusion strengthens, and the fluid dynamic similarity of the nondimensional winds is found among the different diffusions. In the experiments with weak diffusion, the super‐rotation is weak in the presence of strong poleward eddy heat flux, enhancing the downward angular momentum transport by the Eliassen–Palm (E–P) flux. In contrast, the strong super‐rotation is developed, and both the poleward eddy heat and vertical E–P fluxes are weak in the strong horizontal diffusion experiments. Because the waves with high zonal wave numbers and poleward heat fluxes are strongly dissipated, the vertical E–P fluxes become weak and the contribution of subgrid‐scale vertical diffusion becomes large in the momentum budget. As the horizontal diffusion strengthens, the phase velocities of the equatorial waves increase due to the faster background zonal flow (i.e., mean zonal flow). Although strong empirical diffusion produces strong super‐rotation, it is still unknown whether it is valid. Thus, we must carefully assess the robustness of the super‐rotation in the long‐term simulation based on the sensitivity test of horizontal diffusion.
Plain Language Summary
Large differences were observed among the general circulation models under the same Venus‐like idealized condition. We focused on horizontal subgrid‐scale diffusion as one of the factors for the differences. The atmospheric super‐rotation (which rotates at a faster rate than the planetary rotation) intensifies as the diffusion strengthens, and the fluid dynamic similarity is found among the different diffusions. In the experiments with weak diffusion, the super‐rotation is weak in the presence of the strong poleward eddy heat flux, enhancing the downward angular momentum transport. In contrast, the strong super‐rotation is developed, and both the poleward eddy heat and vertical E–P fluxes are weak in the strong horizontal diffusion experiments. Because waves with high zonal wave numbers and poleward heat fluxes are strongly dissipated, the vertical E–P fluxes become weak, and the contribution of subgrid‐scale vertical diffusion becomes large in the momentum budget. Our sensitive study clarified that the tuning up of the empirical diffusion parameter is important in Venus general circulation modeling and contributes to the assessment of the robustness of the simulated super‐rotation of Venus.
Key Points
Vertical momentum flux by zonal‐mean meridional circulation exceeds that by eddies for strong horizontal subgrid‐scale diffusion
Stronger horizontal subgrid‐scale diffusion leads to faster super‐rotation and waves in long‐term Venus‐like simulations
Nondimensional wind profiles are dynamically similar among experiments with different diffusions
Background
Splenic vein ligation may result in sinistral (left‐sided) portal hypertension and gastrointestinal haemorrhage. The aim of this study was to analyse the pathogenesis of sinistral portal ...hypertension following splenic vein ligation in pancreaticoduodenectomy.
Methods
Patients who underwent pancreaticoduodenectomy for pancreatic cancer between January 2005 and December 2012 were included in this retrospective study. The venous flow pattern from the spleen and splenic hypertrophy were examined after surgery.
Results
Of 103 patients who underwent pancreaticoduodenectomy with portal vein resection, 43 had splenic vein ligation. There were two predominant venous flow patterns from the spleen. In the varicose route (27 patients), flow from the spleen passed to colonic varices and/or other varicose veins. In the non‐varicose route, flow from the spleen passed through a splenocolonic collateral (14 patients) or a spontaneous splenorenal shunt (2 patients). The varicose route was associated with significantly greater splenic hypertrophy than the non‐varicose route (median splenic hypertrophy ratio 1·52 versus 0·94; P < 0·001). All patients with the varicose route had colonic varices, and none had a right colic marginal vein at the hepatic flexure.
Conclusion
Pancreaticoduodenectomy with splenic vein ligation may lead to sinistral portal hypertension. To avoid the development of varices, it is important to preserve the right colic marginal vein. Reconstruction of the splenic vein should be considered if the right colic marginal vein is divided.
Portal vein resection has consequences
Microstructure, mechanical and shape memory properties of homogenized Ti–55Pd–5x (x=Zr/Hf/V/Nb) (at%) ternary alloys were investigated to identify potential alloy systems for functional applications ...in the temperature range of 400–600°C. The four characteristic temperatures of these alloys were observed to be in the desired temperature range. The yield strengths of martensite and austenite phases were measured to be better than reported for binary Ti–Pd alloys. Two kinds of microstructure developed in these alloys: (i) Ti–55Pd–5Zr and Ti–55Pd–5Hf alloys had B19 martensite as their matrix phase with a significant amount of (Ti, x)2Pd3 and Pd3(Ti, x) (x=Zr or Hf) precipitates; (ii) Ti–55Pd–5V and Ti–55Pd–5Nb alloys had (Ti, x)2Pd3 (x=V or Nb) phase as their major phase along with a small amount of martensite phase. As a result, Ti–55Pd–5Zr and Ti–55Pd–5Hf alloys exhibited significant shape memory; the maximum observed shape memory strain was 1.69% for Ti–55Pd–5Hf alloy. The non-transformable nature of (Ti, x)2Pd3 phase was responsible for the poor shape memory behavior of the other two alloys.
Abstract
An improved model was proposed to reduce a computational cost for subcritical millimeter-wave discharge. The proposed model was able to reproduce the plasma-front propagation via radiation ...transport as similar to the conventional model, and the plasma-front propagation speed was in agreement with the previous simulation. An electron transport effect by neutral fluid advection, which has been introduced into the conventional model, does not affect the propagation speed. By using the presented model, a computational time was reduced by 35%, which was suitable for a multi-dimensional simulation in the future.
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