Phase separation of an asymmetric binary fluid mixture confined in a nanoscopic slit pore: Molecular-dynamics simulations

As a generic model system of an asymmetric binary fluid mixture, hexadecane dissolved in carbon dioxide is considered, using a coarse-grained bead-spring model for the short polymer, and a simple spherical particle with Lennard-Jones interactions for the carbon dioxide molecules. In previous work, it has been shown that this model reproduces the real phase diagram reasonable well, and also the initial stages of spinodal decomposition in the bulk following a sudden expansion of the system could be studied. Using the parallelized simulation package ESPResSo on a multiprocessor supercomputer, phase separation of thin fluid films confined between parallel walls that are repulsive for both types of molecules are simulated in a rather large system (1356 x 1356 x 67.8 A^3, corresponding to about 3.2 million atoms). Following the sudden system expansion, a complicated interplay between phase separation in the directions perpendicular and parallel to the walls is found: in the early stages the hexadecane molecules accumulate mostly in the center of the slit pore, but as the coarsening of the structure in the parallel direction proceeds, the inhomogeneity in the perpendicular direction gets much reduced. Studying then the structure factors and correlation functions at fixed distances from the wall, the densities are essentially not conserved at these distances, and hence the behavior differs strongly from spinodal decomposition in the bulk. Some of the characteristic lengths show a nonmonotonic variation with time, and simple coarsening described by power-law growth is only observed if the domain sizes are much larger than the film thickness.Comment: accepted for publication in PR

Modelling the Influence of Slide Burnishing Parameters on the Surface Roughness of Shafts Made of 42CrMo4 Heat-Treatable Steel

This article presents the results of tests aimed at determining the effect of slide burnishing parameters on the surface roughness of shafts made of 42CrMo4 heat-treatable steel. The burnishing process was carried out using tools with polycrystalline diamond and cemented carbide tips. Before burnishing, the samples were turned on a turning lathe to produce samples with an average surface roughness Ra = 2.6 µm. The investigations were carried out according to three-leveled Hartley’s poly selective quasi D (PS/DS-P: Ha3) plan, which enables a regression equation in the form of a second-order polynomial to be defined. Artificial neural network models were also used to predict the roughness of the surface of the shafts after slide burnishing. The input parameters of the process that were taken into account included the values of pressure, burnishing speed and feed rate. Overall, the burnishing process examined leads to a reduction in the value of the surface roughness described by the Ra parameter. The artificial neural networks with the best regression statistics predicted an average surface roughness of the shafts with R2 = 0.987. The lowest root-mean-square error and mean absolute error were obtained with all the network structures analysed that were trained with the quasi Newton algorithm

Modelowanie wpływu parametrów obróbki nagniataniem na chropowatość powierzchni wałków ze stali 42CRMO4

W artykule przedstawiono wyniki badań mających na celu określenie wpływu parametrów nagniatania ślizgowego na chropowatość powierzchni wałków wykonanych ze stali 42CrMo4. Proces nagniatania wykonano przy użyciu narzędzi z końcówką z polikrystalicznego diamentu. Przed nagniataniem próbki poddano toczeniu na tokarce narzędziowej. Badania prowadzono według planu Hartleya PS/DS-P:Ha3, który umożliwia zdefiniowanie równania regresji w postaci wielomianu drugiego stopnia. Wykorzystano również modele sztucznej sieci neuronowej do przewidywania chropowatości powierzchni wałków po procesie nagniatania. Rozważane parametry wejściowe procesu obejmowały wartości nacisku, prędkości nagniatania i prędkości posuwu. We wszystkich analizowanych przypadkach nagniatania wartość chropowatości powierzchni określonej parametrem Ra uległa zmniejszeniu. Różnice między danymi eksperymentalnymi a modelem Hartleya nie przekraczały 24%. Najlepszą reprezentację modelu Hartleya uzyskano dla parametrów nagniatania: posuw f = 0,32 mm/obr, nacisk P = 130 N i prędkość nagniatania v = 180 obr/min. Perceptrony wielowarstwowe były najlepszymi predyktorami chropowatości powierzchni wałków. Przy współczynniku korelacji Pearsona R2 powyżej 0,998 wartość średniego błędu bezwzględnego nie przekroczyła 0,005

Effect of Nanofillers on the Mechanical Properties of Vinyl Ester Resin Used as a Carbon Fiber Reinforced Polymer Matrix

This article presents the results of research aimed at determining the influence of selected nanofillers of vinyl ester resin on the mechanical properties of the cured resin. The influence of the resin with nanofillers as a matrix on the properties of the unidirectional CFRP composite was also investigated. Graphite, silicon oxide and titanium dioxide nanopowders were used as resin nanofillers. Each of the fillers was considered in two different contents, i.e. 1 wt.% and 2 wt.%. The variants with such nanofillers content were compared with the unfilled reference variant. The uniaxial tensile strength tests of the resin samples were carried out, showing the possibility of increasing the strength by 19.35% for the variant 1 wt.% of silica nanopowder content. For CFRP composites, the possibility of increasing the strength in the three-point bending test by 25.57% due to the use of a matrix reinforced with graphite nanopowder with a content of 1 wt.% was demonstrated. Based on the analysis of fracture surfaces performed using SEM microscopy, it was shown that the fillers used lead to a significant improvement in the adhesion of the matrix to the composite fibers

Effect of Diamond Burnishing on the Properties of FSW Joints of EN AW-2024 Aluminum Alloys

The article presents the results of an analysis of the surface roughness parameters, microhardness, and the stresses of the surface layer ofFSW butt joints subjected to the burnishing process with a diamond tip. This can be useful in selecting the optimal parameters of the burnishing process, ensuring the best properties of the surface layer of the FSW joint. Burnishing force and feed rate influence were analyzed according to the two-factor three-level full factorial statistical completed plan PS/DC 32. The tested material was 2024-T3 aluminum alloy sheets with a thickness of 2 mm. The results show that burnishing significantly reduced the surface roughness from Sa = 6.46 μm to Sa in the range of 0.33 μm–1.7 μm. This treatment provides high compressive residual stresses σx from −86 to −130 MPa and σy from −158 to −242 MPa. Microhardness increased from 84.19% to 174.53% compared to butt joints. Based on the obtained results, multi-criteria optimization was carried out. This optimization allows us to obtain a compromise solution ensuring compressive stresses in the surface layer (σx=−123 MPa and σy=−202 MPa) and microhardness HV=362.56 mm/mm2 with the roughness of the weld surface Sa = 0.28 µm, Sku = 3.93 and Spc = 35.88 1/mm

Serum amino acid profile in patients with Parkinson's disease.

Amino acids play numerous roles in the central nervous system, serving as neurotransmitters, neuromodulators and regulators of energy metabolism. The free amino acid profile in serum of Parkinson's disease (PD) patients may be influenced by neurodegeneration, mitochondrial dysfunction, malabsorption in the gastroenteric tract and received treatment. The aim of our study was the evaluation of the profile of amino acid concentrations against disease progression. We assessed the amino acid profile in the serum of 73 patients divided into groups with early PD, late PD with dyskinesia and late PD without dyskinesia. Serum amino acid analysis was performed by high-pressure liquid chromatography with fluorescence detection. We observed some significant differences amongst the groups with respect to concentrations of alanine, arginine, phenylalanine and threonine, although no significant differences were observed between patients with advanced PD with and without dyskinesia. We conclude that this specific amino acid profile could serve as biochemical marker of PD progression

Correlations between concentrations of selected amino acids (μmol/l) and levodopa equivalent dose (LED) taken daily.

<p>Correlations between concentrations of selected amino acids (μmol/l) and levodopa equivalent dose (LED) taken daily.</p

General characteristic of the study groups.

<p>General characteristic of the study groups.</p