Research of the Processes of Eliminating Warpage of Aviation Products Made of Polymer-Composite Materials Obtained by High-Temperature Molding

The article considers issues of identifying the causes and factors that have a significant impact on the occurring and development of the warping process in monolithic products made of polymer — composite materials (PCM) obtained by the method of multidirectional layering of uncured PCM — semi-finished product (prepreg) and subsequent high-temperature molding in an autoclave. Warping is understood as a defect of a PCM product in the form of distortion of its configuration (deformation) under stresses arising during the polymerization of the binder prepreg at a high temperature (1800C) and cooling the product to room temperature. Flat samples made of glass-based prepregs have been researched. The selecting schemes of equilibrium stacking of samples of monolithic panels has been carried out. The influence of the binder content in the prepreg on the deformations in non-equilibrium layouts of the panel samples has been evaluated. It is shown that the most significant factors influencing the occurrence of warpage of monolithic PCM panels are: the weaving pattern of the prepreg reinforcing base, the amount of binder deposited in the prepreg, the direction of stacking monolayers in the panel, the edge effect and the shape of the product surface. It was found that the warpage of the sample occurs along the direction of unbalanced shrinkage of the binder. For balanced stacking, compensation in the direction of binder shrinkage and symmetry with respect to the central layer are necessary; more binder in the prepreg reduces the amount of warpage, but only slightly. The development of constructive and technological recommendations based on the results obtained will lead to a reduction in the terms of development of PCM products.

Highly Compact Through-Wire Microstrip to Empty Substrate Integrated Coaxial Line Transition

Empty substrate integrated coaxial line (ESICL) technology preserves the many advantages of the substrate integrated technology waveguides, such as low cost, low profile, or integration in a printed circuit board (PCB); in addition, ESICL is non-dispersive and has low radiation. To date, only two transitions have been proposed in the literature that connect the ESICL to classical planar lines such as grounded coplanar and microstrip. In both transitions, the feeding planar lines and the ESICL are built in the same substrate layer and they are based on transformed structures in the planar line, which must be in the central layer of the ESICL. These transitions also combine a lot of metallized and non-metallized parts, which increases the complexity of the manufacturing process. In this work, a new through-wire microstrip-to-ESICL transition is proposed. The feeding lines and the ESICL are implemented in different layers, so that the height of the ESICL can be independently chosen. In addition, it is a highly compact transition that does not require a transformer and can be freely rotated in its plane. This simplicity provides a high degree of versatility in the design phase, where there are only four variables that control the performance of the transition.

Simultaneous Improvement of Yield Strength and Ductility at Cryogenic Temperature by Gradient Structure in 304 Stainless Steel

The tensile properties and the corresponding deformation mechanism of the graded 304 stainless steel (ss) at both room and cryogenic temperatures were investigated and compared with those of the coarse-grained (CGed) 304 ss. Gradient structures were found to have excellent synergy of strength and ductility at room temperature, and both the yield strength and the uniform elongation were found to be simultaneously improved at cryogenic temperature in the gradient structures, as compared to those for the CG sample. The hetero-deformation-induced (HDI) hardening was found to play a more important role in the gradient structures as compared to the CG sample and be more obvious at cryogenic temperature as compared to that at room temperature. The central layer in the gradient structures provides stronger strain hardening during tensile deformation at both temperatures, due to more volume fraction of martensitic transformation. The volume fraction of martensitic transformation in the gradient structures was found to be much higher at cryogenic temperature, resulting in a much stronger strain hardening at cryogenic temperature. The amount of martensitic transformation at the central layer of the gradient structures is observed to be even higher than that for the CG sample at cryogenic temperature, which is one of the origins for the simultaneous improvement of strength and ductility by the gradient structures at cryogenic temperature.

Objective Assessment of Corneal Backscattered Light in Myopic, Hyperopic, and Emmetropic Children

Purpose: To determine the corneal densitometry values by using Scheimpflug imaging in myopic, and hyperopic children and to compare the results with emmetropic children.Methods: The corneal densitometry measurements of the subject were obtained with Pentacam Scheimpflug tomography. The values were automatically measured in standardized grayscale units (GSU) over an area 12 mm in diameter, which was subdivided into 4 annular concentric zones (0-2 mm, 2-6 mm, 6-10 mm, 10-12 mm) and 3 corneal depths (anterior layer: anterior 120 µm; central layer: from 120 µm to the last 60 µm; posterior layer: last 60 µm). In addition, we evaluated the correlation between spherical equivalence and anterior corneal morphological parameters and the corneal densitometry values.Results: A total of 216 participants were included in this prospective cross-sectional study. The eyes were divided into three groups related to their spherical equivalent (SE) refractive error values as follows: 89 (41.2%) hyperopic eyes, 66 (30.6%) myopic eyes, and 61 (28.2%) emmetropic control eyes. The hyperopic eyes were found to have lower corneal densitometry values in 4 annular zones and the total diameter of all depths except the central layer. However, only the 6-10 mm annular zone of the central and posterior layers of the myopic eyes had lower corneal densitometry values than emmetropic eyes. There was also a significant correlation between spherical equivalence and corneal densitometry values in some zones of the hyperopic eyes. Conclusion: Backward scattering of light was lower in hyperopic eyes and this could affect the visual quality.

Composite Polymer Anion Exchange Membranes with Sandwich Structure and Improved Performance for Zn–Air Battery

In this study, we fabricated a composite polymer anion exchange membrane (AEM) with a sandwich structure. This prepared AEM demonstrated high ionic conductivity (0.25 Scm−1), excellent alkali resistance (8 M KOH), and good mechanical properties (tensile strength of 0.455 MPa and elongation at break of 82.13%). Here, degrease cotton (DC) treated with LiOH/urea aqueous solution was used and immersed into a coagulation bath to form a film. This film was immersed in acrylic acid (AA) monomers, and in-suit polymerization was carried out in the presence of KOH and an initiator. Finally, a composite polymer membrane with sandwich structure was achieved, in which the upper and bottom layers were mainly composed of polymerized AA (PAA) while the central layer was mainly composed of DC derived film. The central layer acted as a skeleton to improve the mechanical properties and alkali resistance. The top and bottom layers (PAA-rich layers) acted as OH- ion transport carriers, making basic cations migrate along the main chain of PAA. This newly developed composite membrane showed increased tensile strength and an elongation at break of 2.7 and 1.5 times, respectively, when compared to a control PAA/KOH AEM film. Furthermore, an electrochemical stability window of 2.0 V was measured via the cyclic voltammetry curve test, showing a wide electrochemical window and promising application in Zn–Air batteries.

Introducing the metacore concept for multi-target ligand design

Metacore hierarchy. Shown are two model series of structural analogs (bottom, right) from which series cores (central layer) are isolated that yield a metacore (top left layer).

Raman and AFM-IR chemical imaging of stratum corneum model membranes

Stratum corneum (SC), the outermost layer of the epidermis, is the primary barrier to percutaneous absorption. The diffusion of substances through the skin occurs through the SC lipid fraction, which is essentially constituted of an equimolar mixture of ceramides, free fatty acids, and cholesterol. The lipid constituents of SC are mainly forming continuous multilamellar membranes in the solid/crystalline state. However, recent findings suggest the presence of a highly disordered (liquid) phase formed by the unsaturated C18 chain of ceramide EOS, surrounded by a highly ordered lipid environment. The aim of the present work was to study the lipid spatial distribution of model SC membranes composed of ceramide EOS, ceramide NS, a mixture of free fatty acids, and cholesterol, using Raman microspectroscopy and AFM-IR spectroscopy techniques. The enhanced spatial resolution at the tens of nanometers scale of the AFM-IR technique revealed that the lipid matrix is overall homogeneous, with the presence of small, slightly enriched, and depleted regions in a lipid component. No liquid domains of ceramide EOS were observed at this scale, a result that is consistent with the model proposing that the oleate nanodrops are concentrated in the central layer of the three-layer organization of the SC membranes forming the long periodicity phase. In addition, both Raman microspectroscopy and AFM-IR techniques confirmed the fluid nature of the unsaturated chain of ceramide EOS while the rest of the lipid matrix was found highly ordered.

Evolution of microstructure, texture and inhibitor of medium temperature grain-oriented silicon steel

The medium temperature reheating and two-stage cold rolling process were adopted to produce industrialized Grain-oriented silicon steel. Results showed there were three sections (surface layer, transition layer and central layer) along the thickness direction on hot rolled sheets. Surface layer was occupied by complete recrystallization grains with average grain size 42.81 µm, while the central layer mainly consisted of fibrous microstructure. The Goss texture appeared only on surface layer with content 3.44%∼3.65%. After the first cold rolling with 72% reduction and decarburization annealing, the primary recrystallization occurred and average grains size reached 19.0 µm, simultaneously accompanied with texture rotated to λ, γ fiber texture and Goss texture dropped to 2.89%. Adopting the second cold rolling with 58% reduction, the cold rolled sheet consisted of deformed fiber microstructure and the texture maintained γ fiber texture with a peak at {111} <112>. The precipitates in hot rolled sheets comprised Cu2S and few AlN, and the average particle size was ∼14 nm. The inhibitors in the decarburization annealing sheet were mainly AlN, Cu2S, MnS and their composite precipitation, which were spherical or massive with the average particle size ∼21 nm. The single Goss oriented grains with average grain size 9.41 mm were obtained after high temperature annealing, and the intensity reached 873.30. The final magnetic properties were: B8 = 1.865 T and P1.7/50 = 1.124 W/kg, which met the requirement of 27Q120.

Свойства микрорезонатора на основе таммовского плазмона с внутрирезонаторными металлическими слоями и органической активной областью

A theoretical study of the properties of a microcavity structure with intracavity metal layers and an organic active region (material CBP(4,4′-Bis(N-carbazolyl)-1,1′-biphenyl)) was done. The structure consisted of a layer of organic material CBP, sandwiched between two silver layers, thin phase matching layers (dph=26 nm) and two quarter-wave Bragg reflectors. It was shown that hybrid modes localized in the central layer of the structure can significantly increase the decay rate of the luminescence of an organic emitter by means of the Purcell effect. A shift in the hybrid modes spectral position was shown upon their interaction with the exciton resonance in CBP. This fact may indicate the appearance of a strong coupling regime.