Medium Layer Thickness Research Articles

Numerical Simulation Research on Characteristics of Underwater Explosive Bubble Jet in Offshore Water

Underwater explosions have always been a hot topic in the field of ship protection. When explosives explode in offshore waters, the influence of seabed and structural boundaries on shock wave propagation and bubble pulsation will become more complicated. In this paper, a numerical simulation study of the underwater explosion between a deformable seabed and a rigid boundary is carried out. Firstly, the ABAQUS software was used to establish a numerical model by using the CEL method. The seabed was regarded as a heavier fluid, and the density ratio of the seabed and water was used to describe the characteristics of the seabed. The validity of the model was verified by comparison with experiments. Then, a series of numerical simulations were carried out by adjust the position of the explosive, the thickness of water medium layer, and the density of the seabed. The results show that: when the position of the explosive is close to the seabed and the rigid boundary, the bubble pulsation period is longer. The water jet and the pulsating pressure of the bubbles have a strong impact on the structure when the explosive is located near to 1 times the theoretical maximum radius of the bubble. As the depth of the water decreases, it can be observed that the bubbles transform from “ellipsoid” to “nipple-like”, and finally tear into upper and lower halves. When the thickness of water medium layer is 1 times the theoretical maximum radius of the bubble, the incident pressure waveforms of the bubble pulsation and the water jet near the structure are chaotic, which is caused by the “tear” phenomenon of the bubble. As the density of the seabed increases, the depth of the intrusion of the bubbles into the seabed becomes smaller and the shape of the bubbles becomes flatter. The research results of this paper can provide reference for the protection design of ships.

High flexible additively manufactured nanocomposite textiles with desirable thermoelectric properties

Abstract3D printing can be a promising approach for depositing polymers onto textiles. Printable materials with good mechanical flexibility; can be used for wearable thermoelectric devices that convert body heat energy into electricity. In this research, first, polypropylene filament was produced. The produced polypropylene filament was printed on polypropylene fabric with different parameters of printing speed, the number of layers, layer thickness, deposition angle, and extruder temperature. A peeling test evaluated the adhesion strength of polymer layers printed on polypropylene fabric. The results showed that a single layer printed with the average printing speed (50 mm/min), the highest extruder temperature (194°C), the medium layer thickness (0.3 mm), and the deposition angle Equal to a Zero degree had a higher peeling force. The cross‐sectional morphology of the printed layer on the fabric; was also investigated by Field emission scanning electron microscopy (FE‐SEM). To achieve thermoelectric properties, multi‐walled carbon nanotubes/copper oxide nanoparticles/polypropylene nanocomposite filament were produced and printed on the fabric by a 3D printer using FDM technology. The mechanical properties of the filaments; were investigated, and filaments were characterized by FE‐SEM, X‐ray diffraction, thermogravimetric analysis, and differential scanning calorimeter. Then the electrical conductivity and Seebeck coefficient of nanocomposite filaments and printed layer on the fabric were measured. The electrical conductivity of the masterbatch, the nanocomposite filament, and the printed layer; was 1.667 × 5−10 s/cm, 2.586 × 6−10 s/cm, and 3.42 × 7−10 s/cm, respectively. Also, the Seebeck coefficient of masterbatch, the filament, and the polymer layer printed on the fabric; were 489, 430, and 220 μv/k, respectively.

Effect of Printing Orientation and Layer Thickness on Microstructure and Mechanical Properties of PLA Parts

Due to the layer-by-layer printing process, additively manufactured objects frequently display directional dependencies in their structure. It affects the material properties of the fabricated parts concerning various process parameters of the machine. This paper presents the effect of layer thickness and printing orientation on the mechanical properties and microstructure of polylactic acid (PLA)3D printed parts fabricated by Fused Deposition Modeling (FDM). Computer-aided design models of a tensile and compression test specimen were created, conforming to the ASTM: D638 (Type 1 and Type IV) and ASTM D695, respectively. The microstructure was evaluated using a Scanning Electron Microscope (SEM) on the fracture surface during the tensile test and optical microscopy on the compression specimens. The finding shows that a low layer thickness setting contributes to the highest tensile strength in the 0° printing orientation, while a medium and high layer thickness results in a better tensile strength for a 45° and 90° printing orientation. Therefore, printing orientation is more influential than layer thickness in the tensile test. As for the compressive strength, the stress decreases when the layer thickness increases and the low layer thickness setting offers the highest compressive strength at all printing orientations. The microstructure shows more significant interlayer gaps, incomplete filling, and weak bonding on the cross-sectional samples of the fractured tensile surface with lower strength. The 0° printing orientation offers better tensile strength for all layer thicknesses, minimum build time, and good compressive strength compared to other printing orientations.

Investigation of the process of cooking chicken fillet using sous-vide technology

To determine the duration of the heat treatment process on the heating medium (water)To determine the duration of the heat treatment process on the heating medium (water) temperature and layer thickness of the original sample using sous-vide technology, a chicken fillet was selected. The following diagrams were plotted and analyzed: temperature in the chicken fillet specimen as a function of duration of heat treatment process at heating medium (water) temperatures of 60, 70 and 80?C; temperature in the chicken fillet specimen as a function of duration of heat treatment process at thickness of 0.5; 1; 2 cm. Recommendations are given for choosing the optimum temperature regime and thickness of the layer of chicken fillets for cooking by sous-vide technology. At a temperature of water in the thermostat working chamber of 60? C can not be reached inside the sample of product to a temperature of 68-70 ? C, even after 5 minutes of exposure, so there is a possibility of harmful micro-organisms in the finished product. At a temperature of water in the thermostat working chamber of 80 ? C is intense heating of chicken fillets to a temperature of readiness, but the product remains raw because of the short duration of the process, with a further curing the product is heated to a higher temperature of 78-79 ? C, which reduces the quality of the finished product. Optimal selected heating medium temperature (water) in the working chamber of thermostat-70 ?C, which is in the range of recommended regulatory documentation temperatures. At this temperature, the product achieves the necessary cooking temperature of 68-70 ?C, and the duration of heat treatment is reduced by 2.9 times, energy consumption is reduced by 2 times and a high degree of readiness of the product is cooked.

Design of a Surface Plasmon Resonance-Enhanced ZnO Ultraviolet Photodetector Based on a Sub-wavelength Metal Grating Covered with a High-Refractive-Index Medium

To realize a surface plasmon resonance-enhanced zinc oxide (ZnO) ultraviolet photodetector based on a sub-wavelength metal grating, we take advantage of the sensitivity of the resonance condition of a sub-wavelength metal grating to the refractive index of the surrounding medium. We theoretically design a sub-wavelength Ag grating covered with a high-refractive-index medium layer and apply it to a ZnO ultraviolet photodetector. By optimizing the parameters (angle of incidence, grating period, grating spacing, grating thickness, high-refractive-index medium layer thickness, refractive index of the covering), the optical field is localized at the interface of the sub-wavelength Ag grating and the ZnO thin film; that is, surface plasmon resonance is realized within the device. Compared with the device without a high-refractive-index medium layer, the maximum absorption enhancement factor of the designed device can reach up to 108. This work will provide theoretical guidance to realize a surface plasmon resonance-enhanced ZnO ultraviolet photodetector with a sub-wavelength metal grating.

Heat Transfer Behavior of Green Roof Systems under Fire Condition: A Numerical Study

Currently, green roof fire risks are not clearly defined. This is because the problem is still not well understood, which raises concerns. The possibility of plants catching fire, especially during drought periods, is one of the reasons for necessary protection measures. The potential fire hazard for roof decks covered with vegetation has not yet been fully explored. The present study analyzes the performance of green roofs in extreme heat conditions by simulating a heat transfer process through the assembly. The main objective of this study was to determine the conditions and time required for the roof deck to reach a critical temperature. The effects of growing medium layer thickness (between 3 and 10 cm), porosity (0.5 to 0.7), and heating intensity (50, 100, 150, and 200 kW/m2) were examined. It was found that a green roof can protect a wooden roof deck from igniting with only 3 cm of soil coverage when exposed to severe heat fluxes for at least 25 minutes. The dependency of failure time on substrate thickness decreases with increasing heating load. It was also found that substrate porosity has a low impact on time to failure, and only at high heating loads.

Medium-thickness-dependent proton dosimetry for radiobiological experiments

A calibration method was proposed in the present work to determine the medium-thickness-dependent proton doses absorbed in cellular components (i.e., cellular cytoplasm and nucleus) in radiobiological experiments. Consideration of the dependency on medium thickness was crucial as the linear energy transfer (LET) of protons could rise to a sharp peak (known as the Bragg peak) towards the end of their ranges. Relationships between the calibration coefficient R vs medium-layer thickness were obtained for incident proton energies of 10, 15, 20, 25, 30 and 35 MeV, and for various medium thicknesses up to 5000 μm, where R was defined as the ratio DA/DE, DA was the absorbed proton dose in cellular components, and DE was the absorbed proton dose in a separate radiation detector. In the present work, DA and DE were determined using the MCNPX (Monte Carlo N-Particle eXtended) code version 2.4.0. For lower incident proton energies (i.e., 10, 15 and 20 MeV), formation of Bragg-peak-like features were noticed in their R-vs-medium-layer-thickness relationships, and large R values of >7 and >6 were obtained for cytoplasm and nucleus of cells, respectively, which highlighted the importance of careful consideration of the medium thickness in radiobiological experiments.

Evaluation of Choroidal Layer Thickness in Central Serous Chorioretinopathy.

Purpose:To evaluate medium and large choroidal vessel layer thickness (MCVT and LCVT, respectively) in eyes with acute and chronic central serous chorioretinopathy (CSC) in comparison with age-matched controls.Methods:The study included 96 eyes of 96 patients with CSC, including 53 eyes with acute CSC, 43 eyes with chronic CSC, and 30 eyes of 30 age-matched normal subjects. Manual measurements of subfoveal choroidal thickness (SFCT), MCVT, and LCVT at subfoveal and 750 μm nasal and temporal to the fovea locations were made on enhanced depth imaging optical coherence tomography (EDI-OCT) of the macula in all subjects using ImageJ software (National Institutes of Health, Bethesda, MD, USA).Results:SFCT in acute CSC was significantly larger than that in healthy eyes (P = 0.0001). SFCT in acute CSC did not differ significantly from that in chronic CSC eyes. Subfoveal LCVT and MCVT in acute CSC eyes were greater than those in healthy eyes (P = 0.02 and P = 0.03, respectively). Mean SFCT and MCVT in chronic CSC eyes were significantly larger than those in control eyes (P = 0.01 and P = 0.04, respectively). No significant difference in LCVT was observed between chronic and control eyes.Conclusion:Choroidal vasculature is altered in both acute and chronic CSC. SFCT, MCVT, and LCVT are higher in eyes with acute CSC. The thickening of medium choroidal vessels is still detectable in chronic CSC compared to control eyes.

Mesostructured Hybrid based-Perovskite Solar Cell Optical and Electrical Modeling: Influence of the Incident Light Wavelength

Analytical model is developed to give insight into the influence of the incident wavelength of the incoming light illumination on optical and electrical properties mesostructured hybrid perovskite-based solar cell for different photoactive layer thickness. Bruggeman theory and T-matrix are used to compute the analytical expressions of optical parameters such as absorption coefficient and generation rate. Then, the short-circuit current density is deduced from the continuity equation. The absorption coefficient of the photoactive layer decreases with high incident wavelength of the incoming light of the visible spectrum (400-800 nm) while the absorbance and generation rate grow up with the phototactive layer thickness. The current density increases with illuminated wavelength ranging 400-520 nm while it decreases with higher active medium (TiO2 +Perovskite) layer thickness ranging from 500 nm to 1.7 µm. Beyond to 520 nm of the wavelength of the incoming light, the current density decreases to vanish at 800 nm. As finding in the literature, it can be noticed high absorption, charge carriers generation and current density for low wavelength in the visible spectrum which correspond to high energies.

Atomic simulations of plastic deformation mechanism of MgAl/Mg nanoscale amorphous/crystalline multilayers

The deformation behavior of MgAl/Mg nanoscale amorphous/crystalline multilayers (NACMs) with equal layer thicknesses of amorphous and crystalline phases under tension loading is investigated by molecular dynamics simulation method. The results show that the plastic deformation mode of NACMs changes from cross generalized shear bands dominated deformation to finally single shear band plastic deformation with the increase of layer thickness, and the plastic deformation of NACMs with medium layer thickness is realized through cooperative interactions among crystalline layer, amorphous layer and amorphous/crystalline interfaces (ACIs), which could be treated as a transition progress. The results indicate that the peak stresses of the NACMs are greater than that of monolithic amorphous regardless of layer thickness, which is likely to result from the increase of the strong crystalline phase and the strengthening effect of the ACIs. The results also reveal that the ductility and strength of NACMs could be improved effectively by choosing the appropriate layer thickness. In addition, the deformation behavior of NACMs is also quantificationally disclosed and analyzed in current study.

Competition between Metallic and Vacancy Defect Conductive Filaments in a CH3NH3PbI3-Based Memory Device

Ion migration, which can be classified into cation migration and anion migration, is at the heart of redox-based resistive random access memory. However, the coexistence of these two types of ion migration and the resultant conductive filaments (CFs) have not been experimentally demonstrated in a single memory cell. Here we investigate the competition between metallic and vacancy defect CFs in a Ag/CH3NH3PbI3/Pt structure, where Ag and CH3NH3PbI3 serve as the top electrode and memory medium, respectively. When the medium layer thickness is hundreds of nanometers, the formation/diffusion of iodine vacancy (VI) CFs dominates the resistive switching behaviors. The VI-based CFs provide a unique opportunity for the electrical-write and optical-erase operation in a memory cell. The Ag CFs emerge and coexist with VI ones as the medium layer thickness is reduced to ∼90 nm. Our work not only enriches the mechanisms of the resistive switching but also would advance the multifunctionalization of resistive random acc...

Modulation of the Acher’s limit by medium thickness in [FeCoB/ZnO]50 multilayers

This work investigates the high frequency characteristics of [FeCoB/ZnO]50 multilayers with different ZnO thickness. The results reveal that the Acher’s limit of [FeCoB/ZnO]50 multilayers can be modulated by medium thickness. Increasing medium layer thickness is favorable for breaking through the Acher’s limit. It is found that the differences of Acher’s limit between multilayers and single layers are caused by magnetic interface anisotropy related to interface roughness and some unknown factor.

Experimental study of the possibility of 3D localization of the compact gamma-sources in soft tissues

To determine the depth of the area of radiopharmaceutical accumulation a method of simultaneous recording of two lines of gamma rays of different energies and quantitative comparison of the intensity of these lines on the surface of the patient's body is provided. Since the coefficient of linear absorption of gamma radiation in the medium depends not only on the characteristics of the medium, but also on the gamma radiation energy, the intensity of gammas of different energies is attenuated differently after passing through the same absorber layer (soft tissues). Thus, the quantitative comparison of the relative intensities of gamma lines on the surface of the patient's body allows to determine the depth of area of the accumulation of the radiopharmaceutical. The result is achieved by analyzing the energy spectrum of the source, obtained with a semiconductor spectrometer, by measuring the ratio of areas of the absorption peaks of the radioisotope and defining the depth of gamma source using the calibration dependence between the areas ratio and the medium layer thickness. The most widely used medical radioisotope technetium-99m has two gamma-lines - 140 keV and 18.5keV, which allows one to apply the proposed method to search for the sentinel lymph nodes and non-palpable malignant tumors in the soft tissues.

Research on one-dimensional function photonic crystals

In the paper, we present a new kind of function photonic crystal of which the refractive index is a function of space position. According to Fermat principle, we give the motion equations of light in one-dimensional, two-dimensional and three-dimensional function photonic crystals. For one-dimensional function photonic crystal, we give the dispersion relation, the band gap structure and the transmissivity, and we obtain wider or narrower band gap structure than that of conventional photonic crystal. We study the effects of the refractive index, the number of period, the incidence angle and the thickness of medium layer on photonic crystal band gap, and obtain some valuable laws. Our results give the theoretical support designing the photonic crystals of different band gap structures.

Mechanical and corrosion resistance of a new nanostructured Ti–Zr–Ta–Nb alloy

In this work, a multi-elementary Ti–10Zr–5Nb–5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 μm. The ARB processed alloy has a low Young’s modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained.

Amplified spontaneous emission from an Ag-backed red-fluorescent-dye-doped polymer film

We demonstrate that the amplified spontaneous emission (ASE) in an Ag-backed red-fluorescent-dye-doped polymer film can be controlled by the effect of the film thickness. Optical losses associated with the metallic contacts necessary for charge injection, an obstacle to the development of an electrically pumped organic solid-state laser, may be possible to be reduced by increasing the gain medium layer thickness. The study of ASE characteristics of Ag-backed 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)-doped polystyrene (PS) films with different thicknesses shows that increasing the film thickness can reduce the influence of the Ag layer. The threshold, gain, and loss of the device with a thickness of 800 nm are comparable to those of a metal-free device. Our findings demonstrate that the Ag-backed DCJTB:PS film can still be a good organic gain medium material for the fabrication of solid-state lasers, when the thickness of the DCJTB:PS layer increases to an appropriate value.

SANDWICH-STRUCTURE WAVEGUIDES FOR VERY HIGH-POWER GENERATION AND TRANSMISSION USING LEFT-HANDED MATERIALS

The high power generation and transmission for TM modes in a parallel-plate waveguide filled with three-layered medium called sandwich structure are investigated. The transmission power could never exceed the input power of the source in a conventional parallel-plate waveguide filled with homogeneous or inhomogeneous right-handed material (RHM) or homogenous left-handed material (LHM). Based on the stratified medium theory, extremely high power can be generated and transmitted if the waveguide is composed of RHM-LHM-RHM or LHM-RHM-LHM sandwich structure with the medium parameters and layer thickness being properly chosen. Different from the TE case, the dominant mode exists in such a structure is TM0 mode which can be always supported despite the size of the waveguide. From our numerical results, we find that the high power generation and transmission can be easily realized even in the more realistic case where the LHM is described by the Lorentz medium model.

Layer thickness-induced lens distortions during thermal nanoimprint

Arrays of convex spherical lenses with heights in the micrometer range and diameters of 100 and 200μm⁠, respectively, were imprinted into thin layers of polystyrene by thermal imprint. The masters were prepared by gray tone lithography and dry etching. They feature three distinct lens heights, so that during imprint into medium layer thickness three different situations prevail: imprint into thick layers, imprint into thin/adequate layers, and imprint into highly thinned layers. Only during imprint in such highly thinned layers slight recovery was detected combined with stretching-induced polymer layer breakup. For all other cases the replication quality was good and did not show recovery effects. This is in contrast to the imprint of flat stamps into layer thickness of similar sizes. Differences detected in height of the replicated lenses compared to the master are due to thermal expansion in the thermal nanoimprint lithography process. Negligible residual layers were obtained at only slightly changed curvature radius.

Wood moisture content of coated wood/aluminium windows during three years of natural weathering

Wood/aluminium windows of a standard construction with different coating systems were installed in a facade facing south-east on a building in Vienna. Over a period of three years the moisture content of the wooden frames and the climatic conditions under the aluminium layers of the windows were measured. The results showed that humidity stress on the wooden frames of the windows was very low. Condensation of water vapour underneath the aluminium layers occurred very seldom and the reactions in wood moisture content were only small. Highly permeable wood coatings with medium or low dry film layer thickness can provide a sufficient protection of the wooden frames of wood/aluminium windows against weathering impacts to obtain high durability.

Atomic structures of dislocations in BaF2/CaF2 strained multilayers

The atomic structures of dislocations in BaF2/CaF2 (111) multilayers grown on Al2O3 were studied by high-resolution transmission electron microscopy on ( ) and ( ) cross-sections. It was found that dislocations generated in these multilayers have structures significantly different from those observed in bulk materials, and that the dislocation structure depends on the morphology of the multilayer. Most dislocations are misfit dislocations along and have Burgers vectors of a/2 on the (111) interfaces. Interface dislocations with a Burgers vector of a/2⟨ 110 ⟩ on (11 ) planes are also observed in multilayers of medium layer thickness l with wavy interfaces. Occasionally, edge dislocations with Burgers vectors a/2⟨ 110 ⟩ and a/2⟨ 001 ⟩ are observed along [1 0]. Edge dislocations with Burgers vectors a/2[ 10] are found dissociated into two partials with an in-plane Burgers vector component of a/4[ 10], and form low-angle boundaries. The influence of these crystal defects on the chemistry of point defects in these multilayers must be taken into account when the ionic conductivity of the multilayer is predicted by space charge theory.