Layers Of Equal Thickness Research Articles

The Influence of Panel Lay-Up on the Characteristic Bending and Rolling Shear Strength of CLT

The objective of this study was to characterise the behaviour of cross laminated timber (CLT) panels and the influence of the panel lay-up on the failure strength. Three different panel configurations of thickness, 60 mm, 100 mm, and 120 mm, were loaded in the out-of-plane direction. The 60 mm and 120 mm panel configuration comprised three layers of equal thickness, and the intermediate 100 mm thick panel comprised five layers of equal thickness. The mean and characteristic bending and rolling shear strength of the panels were examined. The results show that the mean bending and rolling shear strength decrease with the panel thickness. The characteristic results have shown that there is an influence because of the number of boards within the panel. The characteristic bending strength values for the five-layer 100 mm thick panel were found to be higher than that of the three-layer 60 mm panel. The characteristic rolling shear values decreased in the five-layer panels, however, the increased number of layers subjected to the rolling shear results in a reduced variability in the rolling shear strength.

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.

Unique mechanical properties of Cu/(NbMoTaW) nanolaminates

Nanostructured face-center-cubic/body-center-cubic Cu/(NbMoTaW) multilayers were prepared with equal layer thickness (h) spanning from 5 to 100 nm. The hardness was found to increase with reducing h to ~50 nm, following the Hall–Petch relation. Below this critical thickness, a hardness plateau emerged indicative of an interface barrier strengthening mechanism. The high density of misfit dislocations at interfaces facilitates the yielding of high entropy alloy NbMoTaW layers at stresses far less than the strength of Cu/(NbMoTaW) estimated by rule-of-mixture. Compared with reported multilayers, the present Cu/(NbMoTaW) samples show the size-independent hardness at a larger size-range h < 50 nm.

The effects of proteins released from silk mat layers on macrophages

BackgroundThe objective of this study was to evaluate the changes in gene expression after incubation of cells with proteins released from different silk mat layers.MethodsA silk cocoon from Bombyx mori was separated into four layers of equal thickness. The layers were numbered from 1 to 4 (from the inner to the outer layer). The proteins were released by sonication of a silk mat layer in normal saline. The concentration of proteins was determined by spectrophotometry. They were incubated with RAW264.7 cells, and changes in the expression of genes were evaluated by cDNA microarray analysis and quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR).ResultsLayer 1 and 4 groups had higher protein concentrations compared to those in layer 2 and 3 groups. The genes associated with inflammation and angiogenesis showed significantly higher expression in layer 1 and 4 groups. The results of qRT-PCR were in agreement with those of the cDNA microarray analysis.ConclusionsThe silk mat from the middle portion of the silkworm cocoon yielded a lower protein release and caused an insignificant change in the expression of genes that are associated with inflammation and angiogenesis.

Tear resistance of a square-wave joint: Experiment versus cohesive zone model

The load versus displacement response of a double-cantilever beam (DCB) adhesive joint is measured for two interface geometries: a planar interface and a non-planar “square-wave” interface. Joints with a square-wave interface are stronger and tougher than planar joints of equal adhesive layer thickness provided the square-wave amplitude is sufficiently large. Computed tomography (CT) imaging is used to examine the failure morphology of DCB specimens with planar interfaces, and optical fractography is used to observe the failure mechanisms for DCB specimens with square-wave joints of fixed wavelength and selected amplitude; in all cases, the failure mode is similar to those of tensile, square-wave, butt joints. The finite element method is used to predict the cracking response of the DCB adhesive joint. To do so, the adhesive layer is idealised as a plane of cohesive elements with a normal traction versus separation response, as measured independently from square-wave butt joint specimens. Satisfactory agreement exists between the predicted and observed DCB response for all interface geometries, provided the reduction in DCB bending stiffness, arising as a consequence of the square-wave interface geometry, is taken into account.

Improving the crack resistance and fracture toughness of Cu/Ru multilayer thin films via tailoring the individual layer thickness

The microstructure evolutions of Cu/Ru multilayered films with equal individual layer thickness h ranging from 1.5 nm to 200 nm were investigated. Based on systematic X-ray diffraction and transmission electron microscopy analyses, as h was varied, structure transition between face-centered cubic and hexagonal close-packed lattice was observed in Ru constituent layer. This structure transition was found to influence the length-scale dependent cracking behavior and fracture toughness of the Cu/Ru multilayers. In direct contrast to previous study that fracture toughness would decrease dramatically when h was reduced below 25 nm, the fracture toughness of Cu/Ru multilayer increased monotonically as h was as small as 1.5 nm. Along with the reduction of h, the coupling effects from the increased interface transparency as well as lattice structure transformation were considered as the main reasons for the enhanced toughness. In this way, the fracture toughness between fcc/hcp multilayers with structure transformation and fcc/bcc multilayers without structure transformation had been compared and discussed in detail.

Reduced cortical oxygenation predicts a progressive decline of renal function in patients with chronic kidney disease

Renal tissue hypoxia is a final pathway in the development and progression of chronic kidney disease (CKD), but whether renal oxygenation predicts renal function decline in humans has not been proven. Therefore, we performed a prospective study and measured renal tissue oxygenation by blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) in 112 patients with CKD, 47 with hypertension without CKD, and 24 healthy control individuals. Images were analyzed with the twelve-layer concentric objects method that divided the renal parenchyma in 12 layers of equal thickness and reports the mean R2* value of each layer (a high R2* corresponds to low oxygenation), along with the change in R2* between layers called the R2* slope. Serum creatinine values were collected to calculate the yearly change in estimated glomerular function rate (MDRD eGFR). Follow up was three years. The change in eGFR in CKD, hypertensive and control individuals was -2.0, 0.5 and -0.2 ml/min/1.73m2/year, respectively. In multivariable regression analysis adjusted for age, sex, diabetes, RAS-blockers, eGFR, and proteinuria the yearly eGFR change correlated negatively with baseline 24 hour proteinuria and the mean R2* value of the cortical layers, and positively with the R2* slope, but not with the other covariates. Patients with CKD and high outer R2* or a flat R2* slope were three times more likely to develop an adverse renal outcome (renal replacement therapy or over a 30% increase in serum creatinine). Thus, low cortical oxygenation is an independent predictor of renal function decline. This finding should stimulate studies exploring the therapeutic impact of improving renal oxygenation on renal disease progression.

Unraveling the discrepancies in size dependence of hardness and thermal stability in crystalline/amorphous nanostructured multilayers: Cu/Cu-Ti vs. Cu/HfO2.

Crystalline/amorphous interfaces (CAIs) confer outstanding mechanical properties on crystalline/amorphous nanostructured multilayers (C/ANMs), which are widely used in micro/nanodevices, because their unique interfacial structure possesses high strain compatibility. In this study, Cu/X (X = Cu-Ti, HfO2) C/ANMs with equal layer thicknesses (h) were comparatively investigated in terms of size-dependent hardness (H) and thermal stability to uncover the fundamental difference(s) between Cu/Cu-Ti and Cu/HfO2. It was found that both as-deposited Cu/Cu-Ti and Cu/HfO2 C/ANMs exhibited a maximum hardness at a critical thickness of h ∼30 nm, which was caused by a transition from confined dislocation gliding to dislocation transmission across the interface. Specifically, the Cu/Cu-Ti C/ANMs exhibited annealing hardening, whereas the Cu/HfO2 C/ANMs exhibited annealing softening associated with a minimum softening at h ∼ 30 nm, which was closely correlated with their thermal stability. In comparison with monolithic amorphous X thin films, the glassy X nanolayers in the present Cu/X C/ANMs exhibited reduced thermal stability and a trend that smaller sizes led to higher stability. The underlying mechanism of the size-dependent crystallization behavior of X nanolayers is discussed in terms of the constraining effects of the interface. These findings provide deep insights into the design of Cu/metallic-glass and Cu/ceramic-glass C/ANMs with optimal performance.

Water-Injection Operations and Gas-Injection Sensitivities in the Bakken Formation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 185030, “Improved Oil Recovery in Tight Oil Formations: Results of Water-Injection Operations and Gas-Injection Sensitivities in the Bakken Formation of Southeast Saskatchewan,” by S.M. Ghaderi, C.R. Clarkson, and A. Ghanizadeh, University of Calgary, and K. Barry and R. Fiorentino, Crescent Point Energy, prepared for the 2017 SPE Canada Unconventional Resources Conference, Calgary, 15–16 February. The paper has not been peer reviewed. Although improvement in hydraulic-fracture properties and infill drilling remains the focus of recovery enhancement from the Bakken, low oil recoveries and steep initial decline rates are experienced in primary-recovery operations, even after application of multifractured-horizontal-well technology. Therefore, many pilots have been executed to determine the viability of waterflooding for maintaining oil rates and improving recoveries through reservoir-pressure maintenance and sweep-efficiency enhancement. This paper presents the performance results from one of the waterflood pilots in the Viewfield Bakken. Numerical-Model Setup A section of the Bakken reservoir (the geology of which is described in detail in the complete paper) deemed to be representative of the waterflood performance in Viewfield is considered for modeling. This section has been developed by use of multifractured horizontal wells completed in the Middle Bakken (main target reservoir) with a well spacing of 200 m (eight wells per section, named A through H). All eight wells started oil production within a similar time frame, and, after approximately 1 year of production, every other well was converted to a water injector. Reservoir-Fluid Model. Conventional pressure/volume/temperature (PVT) analysis was conducted by a commercial laboratory on 12 surface-separator oil and gas samples. Recombination of fluids at reservoir temperature (156.2°F) yields a final gas/oil ratio of 810 scf/STB. Subsequently, a series of constant-composition-expansion and differential-liberation tests was conducted on the recombined fluid to determine oil-saturation pressure, oil-formation-volume factor, oil density, and oil and gas viscosity as a function of pressure. The Peng-Robinson equation of state and modified Pedersen viscosity correlation were tuned to replicate the PVT properties of oil and gas as a function of pressure. Reservoir Grid Model. On the basis of the well tops and reservoir net-pay values, reservoir structure for the study area was generated. It is known that the minimum horizontal stress is aligned in the northwest direction and at approximately 50° with respect to the east/west horizon. Therefore, reservoir gridding is rotated at this angle to mimic the hydraulic-fracture orientation along the horizontal-well laterals. Grid size in the horizontal direction is 65×65 ft, and the total thickness of the reservoir is approximately 28 ft, which is divided into nine layers of equal thickness.

МОДЕЛЮВАННЯ ЗАКОНОМІРНОСТЕЙ РОЗТАШУВАННЯ МАТЕРІАЛУ ВЗДОВЖ НИЖНЬОЇ ЧАСТИНИ ПІСКОВОГО ТІЛА МЕХАНІЧНОГО СПІРАЛЬНОГО КЛАСИФІКАТОРА

Improving the quality of automatic control of the first stage of grinding feed ore to ore-dressing plants is constrained due to disregard of regularities the location of the material along the sand body (between turns two filar spiral) mechanical spiral classifier, which are quite important information on the pre- and post-production processes. Identification and registration of the patterns can significantly improve the quality of management of the first stage of grinding the original ore, reduce energy and material costs, as a consequence, lead to an increase in the competitiveness of the final product - magnetite concentrate in the global market. Therefore, the solution of this problem, which is the subject of this article is its relevance. The aim of the article is to develop a mathematical modeling approach and to obtain the specific location of the laws of the material along the bottom of the sand body mechanical spiral classifier. Sand spiral classifier body consists of top and bottom. The upper portion has a simple shape - the shape of a truncated pyramid, and bottom - more complex - form part of the inclined cylinder. The lower part, which is dedicated to the article, is more complex and has independent significance, because at low, medium and higher average value of the circulating load in the original ore grinding circuit manufacturing process takes place in this part of sand bodies. Dividing the lower part of the sand bodies by nine horizontal layers of equal thickness, and giving each layer of material in the form of a triangle, given them the edge effects incomplete filling along the vertical and finding the projection of all the layers in the upper horizontal plane carried graph-analytical modeling of regularities arrangement of the material along the bottom of the sand body mechanical spiral classifier. It was found that the mechanical spiral classifier 1KSN-30 lower part of the sand body is the serial number of the vertical bars, the volume of material that is subject to an exponential dependence with a maximum amount in the central part of which is determined by the capacity of sand.

On the influence of Ti-Al intermetallic coating architecture on mechanical properties and wear resistance of end mills

Thin-film wear-resistant coatings are widely used to increase life and efficiency of metal cutting tools. This paper shows the results of a study on the influence of architecture (number, sequence and thickness of layers) of wear-resistant coatings on physical, mechanical and operational properties of end mills. Coatings consisting of alternating Ti-Al/Ti-Al-N layers of equal thickness demonstrated the best physical and mechanical properties. Durability of coated tools when processing materials from chromium-vanadium steel increased twice as compared to uncoated tools.

Molecular dynamics study of deformation behavior of crystalline Cu/amorphous Cu50Zr50 nanolaminates

Crystalline/amorphous (C/A) metallic nanolaminates have been increasingly studied due to its excellent mechanical behaviors. Here, the effects of layer thickness and sample size on the deformation behavior of C/A Cu/CuZr nanolaminates under tension loading are investigated using molecular dynamics simulation method. For nanolaminates with equal layer thickness of crystalline and amorphous, a transition in the plastic deformation mode takes place in the C/A nanolaminates from homogeneous plastic co-deformation between interfacial dislocation and shear transformation zones to multiple shear bands interaction. For the nanolaminates with fixed amorphous layer, the peak stress decreases with the decreasing crystalline layer thickness, consisting with the results calculated by the mixed rule. However, when crystalline layer thickness is >5nm, the peak stress reaches a plateau, which can be well-explained by the confined layer slip model. In addition, the results indicate that the plastic deformation behavior of nanolaminates transits from global plastic deformation to local plastic deformation with decreasing aspect ratio.

Comparative studies on AlGaN/GaN/Si MOS-HFETs with Al2O3/TiO2 stacked dielectrics by using an ultrasonic spray pyrolysis deposition technique

Al0.26Ga0.74N/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) grown on a Si substrate with Al2O3/TiO2 stacked gate dielectrics formed by using non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique are investigated. High permittivity (k) values of Al2O3 and TiO2 were characterized to be 9 and 46.1, respectively, with an equal layer thickness of 10 nm. The present MOS-HFET (Schottky-gate HFET) design has demonstrated enhanced device characteristics at 300 K, including maximum drain–source current density (IDS,max) of 725 (530) mA/mm, IDS at VGS = 0 V (IDSS0) of 471 (383) mA/mm, gate-voltage swing (GVS) of 2.5 (1.6) V, two-terminal gate-drain breakdown voltage (BVGD) of −182 (−121) V, turn-on voltage (Von) of 4.9 (3.2) V, three-terminal off-state drain-source breakdown voltage (BVDS) of 174 (103) V, on/off current ratio (Ion/Ioff) of 5.6 × 107 (3.7 × 103), unity-gain cut-off frequency (fT) of 10.3 (6.8) GHz, maximum oscillation frequency (fmax) of 14.8 (8.6) GHz, and power-added efficiency (P.A.E.) of 38.5% (31.7%) at 2.4 GHz. High temperature device characteristics up to 450 K are also discussed.

A multi-layer integral model for locally-heated thin film flow

Based on an approach used to model environmental flows such as rivers and estuaries, we develop a new multi-layered model for thin liquid film flow on a locally-heated inclined plane. The film is segmented into layers of equal thickness with the velocity and temperature of each governed by a momentum and energy equation integrated across each layer individually. Matching conditions applied between the layers ensure the continuity of down-plane velocity, temperature, stress and heat flux. Variation in surface tension of the liquid with temperature is considered so that local heating induces a surface shear stress which leads to variation in the film height profile (the Marangoni effect). Moderate inertia and heat convection effects are also included.In the absence of Marangoni effects, when the film height is uniform, we test the accuracy of the model by comparing it against a solution of the full heat equation using finite differences. The multi-layer model offers significant improvements over that of a single layer. Notably, with a sufficient number of layers, the solution does not exhibit local regions of negative temperature often predicted using a single-layer model.With Marangoni effects included the film height varies however we find heat convection can mitigate this variation by reducing the surface temperature gradient and hence the surface shear stress. Numerical results corresponding to the flow of water on a vertical plane show that very thin films are dominated by the Marangoni shear stress which can be sufficiently strong to overcome gravity leading to a recirculation in the velocity field. This effect reduces with increasing film thickness and the recirculation eventually disappears. In this case heating is confined entirely to the interior of the film leading to a uniform height profile.

Reduction of cortical oxygenation in chronic kidney disease: evidence obtained with a new analysis method of blood oxygenation level-dependent magnetic resonance imaging.

Determinations of renal oxygenation by blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) in chronic kidney disease (CKD) patients have given heterogeneous results, possibly due to the lack of a reproducible method to analyse BOLD-MRI. It therefore remains uncertain whether patients with CKD have a reduced renal tissue oxygenation. We developed a new method to analyse BOLD-MRI signals and applied it to CKD patients and controls. MRI was performed under standardized conditions before and 15 min after IV furosemide in 104 CKD patients, 61 hypertensives and 42 controls. MR images were analysed with the new twelve-layer concentric objects method (TLCO) that divides renal parenchyma in 12 layers of equal thickness. The mean R2* value of each layer was reported, along with the change in R2* between successive layers, as measured by the slope steepness of the relevant curve. Inter-observer variability was 2.3 ± 0.9%, 1.9 ± 0.8% and 3.0 ± 2.3% in, respectively, controls, moderate and severe CKD. The mean R2* of the outer (more cortical) layers was significantly higher in CKD, suggesting lower cortical oxygenation as compared with controls. In CKD patients, the response to furosemide was blunted in the inner (more medullary) layers, and the R2* slope was flatter. In multivariable regression analysis, the R2* slope correlated positively with estimated glomerular filtration rate (eGFR) in patients with an eGFR <90 mL/min/1.73 m2 (P < 0.001). Using the new TLCO method, we confirm the hypothesis that renal cortical oxygenation is reduced in CKD in humans, and that the level of cortical oxygenation correlates with CKD severity.

Influence of the Nb growth surface on the allotropic Ti phase transformation in Nb/Ti/Nb nanolaminates

As the thickness of a thin film is decreased, the interfacial structure becomes paramount and crystals can undergo phase transformations. Molecular dynamic simulations have been performed to capture how such transformation could occur under the growth surface of a film. An hcp to bcc transition in Ti for Ti/Nb multilayers was used as the case studies. The simulations had good agreement with experiments. The simulations further predicted a mixed phase state for Ti for particular equal layer thicknesses.

Influence of Fe underlayers on stress evolution of Ti in Ti/Fe multilayers

A series of 40–2 nm bilayer spacing Ti/Fe multilayers were sputter-deposited. As the length scale of individual Ti layers equaled to 2 nm, Ti phase transforms from a hexagonal close packed (hcp)-to-body centered cubic (bcc) crystal structures for equal layer thicknesses in Ti/Fe multilayers. Further equal reductions in bilayer spacing to less than 1 nm resulted in an additional transformation from a crystalline to amorphous structure. Atom probe tomography reveals significant intermixing between layers which contributes to the observed phase transformations. Real-time, intrinsic growth stress measurements were also performed to relate the adatom mobility to these phase transformations. For the hcp Ti/bcc Fe multilayers of equivalent volume fractions, the multilayers undergo an overall tensile stress state to a compressive stress state with decreasing bilayer thickness for the multilayers. When the above phase transformations occurred, a modest reduction in the overall compressive stress of the multilayer was noted. Depending on the Fe thickness, the Ti growth was observed to be a tensile to compressive growth change to a purely compressive growth for thinner bilayer spacing. Fe retained a tensile growth stress regardless of the bilayer spacing studied.

Unusual size dependent strengthening mechanisms of Cu/amorphous CuNb multilayers

Nanostructured crystalline/amorphous metallic multilayers have been increasingly studied due to their high strength and potential enhancement of plasticity in amorphous metals. Here we report on mechanical behaviors of Cu/amorphous CuNb multilayers that were prepared by magnetron sputtering with equal individual layer thickness (h) varying from 1 to 200 nm. A medium-range-order amorphous CuNb layer formed between Cu and amorphous CuNb layers. This intermediate layer facilitates transmission of plasticity from Cu to amorphous layers by preventing the smear of dislocation core on the interface. The maximum hardness of Cu/amorphous CuNb multilayers is achieved when h ≤ 50 nm, and is much lower than the hardness of single-layer amorphous CuNb films. Molecular dynamics simulations show that, comparing with single-layer amorphous CuNb, the pile-up of dislocations in Cu layers lowers the stress for the activation of shear transformation zones in amorphous CuNb layers in multilayers.

Vertical Profile of Leaf Nitrogen Distribution at Different Densities of Plant And Different Levels of N Fertilizer on Corn Hybrids Canopy

In this study, the distribution of leaf nitrogen of two corn hybrids during the growing season, in response to the density and N supply were studied. There were two corn hybrids (S.C. 704 and maxima (MV 524)) under three levels of nitrogen: Recommended (300 kg N/ha); RDN plus 25% (375 kg N/ha); RDN plus 50% (450 kg N/ha) and were three levels of population. Recommended (RDN) (7 plants m-2); RDN plus 10% (7.7 plants m-2); RDN plus 20% (8.4 plants m-2).Regular samplings were made from 40 days after sowing until crop maturity. Every 2 weeks, a 1 m2 sample of the canopy was cut in four successive vertical layers of equal thickness. Leaf area and N concentration (%) in each layer were measured. The vertical N gradient became more marked with ongoing vegetative development. The whole canopy photosynthetic benefit that would accrue from maintaining the N gradient is likely to be accentuated. The rate of decline in leaf N concentration in a layer was not related to either the initial concentration in the leaves within the layer.

A Brownian motion simulation for the chloride diffusivity of concrete

The purpose of this paper is to present a Brownian motion simulation for the chloride diffusivity of concrete. According to stereological theory, the probability density function and cumulative distribution function for the circular aggregates in terms of the number of aggregates are derived. By coating each aggregate with an interfacial transition zone (ITZ) layer of equal thickness, concrete is then reduced to a two-phase composite material, composed of a bulk cement paste and equivalent aggregates. The equivalent ITZ thickness and the chloride diffusivity of each equivalent aggregate are formulated in an analytical manner. The Brownian motion simulation is used to compute the chloride diffusivity of concrete. Finally, the validity of the numerical simulation is verified with two sets of experimental results and the effects of the aggregate area fraction, the chloride diffusivity of ITZ, and the ITZ thickness on the chloride diffusivity of concrete are evaluated in a quantitative manner. The paper concludes that the numerical simulation can predict the chloride diffusivity of concrete with an average relative error smaller than 6% for the two selected verification examples.