Tube Density Research Articles

Honeycomb worm bioconstructions persist under combined human and wave-related disturbances

Marine bioconstructions and their ecological functions are increasingly threatened by compounded natural disturbances and direct and indirect impacts of anthropogenic activities. Through a manipulative experiment in the field, we assessed the response of intertidal biogenic patches built by the honeycomb worm, Sabellaria alveolata, to combined disturbances. Repeated battering events, simulating those associated with waves, were applied on intact or previously damaged bioconstructions, mimicking those impacted by harvesting of infaunal organisms. Descriptors of reef status, including the total patch size, the percentage cover of intact bioconstruction, tube density and diameter were examined as response variables to test two hypotheses: i) multiple disturbances would result in disproportionate effects on S. alveolata structures compared to isolate perturbations; ii) the structural stability of bioconstruction would be increasingly undermined by physical impacts with the increasing degree of reef damage from previous harvesting disturbance. When applied separately, intermediate intensity of harvesting and battering were associated with a larger size of S. alveolata patches compared to the unmanipulated control, while the cover of intact bioconstruction tended to decline over time in all experimental conditions. Such a reduction was particularly small under the high level of harvesting. The density and the diameter of sabellariid tubes were not significantly affected by any treatment. The difference between the effect of battering combined with each level of harvesting and the cumulative effect of each disturbance applied separately did not deviate from what would be expected by chance. Our findings highlight the ability of the examined bioconstructions to withstand and potentially thrive under compound disturbances, offering crucial insights for the implementation of sustainable conservation strategies in a threatened biogenic habitat.

Double-sided semitransparent titania photoelectrode with enhanced light harvesting

In this work, unique semitransparent electrodes were prepared by the anodization of titanium layers (540 nm thick) initially deposited on the both sides of glass substrates employing indium-tin oxide interface layers serving as a current collector for the induced photocurrent. The anodization strategy used in this study enables fabrication of semitransparent titanium dioxide nanotube arrays with either aligned or spaced architecture on the two sides of the planar substrate. This study aims to perform a detailed investigation of this novel photoelectrode system (crystal structure, morphology and optical properties) to reveal their photoelectrochemical features. It was found that the photoelectrode exhibits enhanced photocurrent density about 1.9 times higher (4.6 μAcm−2 at +0.5 V) for aligned nanotubes compared to a substrate overgrown symmetrically by separated nanotubes (2.4 μAcm−2 at +0.5 V). This can be effectively explained by the higher tube density in the case of aligned nanostructures, which provide more channels for charge percolation. In addition, both the high donor concentration (6.4 × 1020 cm−3) together with the low charge transfer resistance of the semitransparent electrode of the aligned nanotubes make the material promising for application in photoelectrochemical systems and smart light management.

P[formula omitted]T measurements of Glycols (Mono-, Di- and Triethylene glycol) up to 423.15 K and 140.0 MPa and their aqueous solutions at atmospheric pressure

The density of three glycols, namely Monoethylene glycol (MEG), Diethylene glycol (DEG), and Triethylene glycol (TEG) was measured in the temperature range from 298.15 K to 423.15 K and pressures up to 140.0 MPa using a vibrating tube density meter Anton Paar DMA-HPM, coupled with a high-pressure mPDS 5 unit. The modified Tait-Tammann equation was used to correlate the experimental density, which gave an absolute average relative deviation (AARD) of less than 0.2 %. Derived properties such as isobaric thermal expansion and isothermal compressibility coefficients were estimated and discussed. Furthermore, the density of the binary systems composed by the aforementioned glycols (1) + water (2) was also measured in the (273.15, 373.15) K temperature range at atmospheric pressure. The Cubic-Plus-Association (CPA) and the simplified version of the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state were used to correlate the newly measured data, with deviations less than 3.7 % for pure component and 12.0 % for the binary systems.

Modal analysis of concrete filled steel tubular structure under lateral impact loading

In this paper, deformation mode and the large deflection of the concrete filled steel tubular (CFST) structural member with fixed ends under lateral impact loading was studied by rigid-plastic modal approximation method and finite element analysis by ABAQUS. Using the yield criterion and beam-on-foundation model, the modal analytical solution for plastic behavior of CFST member under lateral impact is obtained considering the interaction of bending and axial stretching. The rigid-plastic modal solution captures the FE results and the deformation mode is accordance with the available experimental results. It shows that lateral deformation of CFST member can be effective predicted by the modal solution consisting of geometric and physical parameters variations. The influence of steel tube thickness, cross-section diameter, effective length, strength and density of concrete and steel, and initial impulsive are discussed in detail. The results show that deflection of the CFST member increase with the increase of the length to diameter ratio, initial impulse and smaller thickness to diameter ratio. Finally, the relationship between lateral deformation and geometric variations are established by optimal sets of modal solution.

Density, Excess Molar Volume and Vapor–Liquid Equilibrium Measurements at 101.3 kPa for Binary Mixtures Containing Ethyl Acetate and a Branched Alkane: Experimental Data and Modeling

Vapor–liquid equilibrium (VLE) and density data for binary systems of branched alkanes + ethyl acetate are scarce in the literature. In this study, the binary mixtures 3-methylpentane + ethyl acetate and 2,3-dimethylbutane + ethyl acetate were investigated. Density measurements at atmospheric pressure were performed using a vibrating tube density meter at 293.15, 298.15 and 303.15 K. Large and positive excess molar volumes were calculated and correlated using a Redlich–Kister-type equation. Isobaric VLE data at 101.3 kPa were obtained using a Gillespie-type recirculation ebulliometer. Equilibrium compositions were determined indirectly from density measurements. The experimental data were checked for consistency by means of the Fredenslund test and the Wisniak (L-W) test and were then successfully correlated using the NRTL model. The newly studied binary systems display high deviations from ideality and minimum boiling azeotropes, the coordinates of which are reported in this work.

Structure optimization: Configuring optimum performance of randomly distributed mixed carbon nanotube bundle interconnects

SummaryThis paper presents an efficient optimization strategy based on the Stoyan and Yaskov algorithm to maximize the tube density of randomly distributed mixed carbon nanotube bundles (RMCBs) for configuring optimum performance of on‐chip interconnects. Optimizing tube density has proposed eight different RMCB (RMCB1–RMCB8) structures of a varying number of carbon nanotubes (CNTs), where RMCB1 has the maximum CNTs. Moreover, the ABCD technique adequately analyzes the temperature‐dependent frequency and stability characteristics of a three‐line RMCB interconnect placed on smooth and rough substrates (SiC, BN, and SiO2). The smooth substrate material has the best 3‐dB bandwidth compared with rough SiC substrate, followed by BN and SiO2 for all RMCB structures, and among all structures, the RMCB8 has the best 3‐dB bandwidth. The relative stability of RMCB1 is improved by 134.2% and 22.7% w.r.t. RMCB8 placed on a smooth and rough SiC substrate, respectively. Whereas bandwidth of the RMCB1 is reduced by 26% and 88.5% w.r.t. RMCB8 placed on a smooth and rough substrate, respectively. Hence, there is a tradeoff between the bandwidth and the relative stability as the number of CNT increases. Therefore, RMCB3 placed on a smooth substrate and RMCB4 placed on a rough SiC substrate are considered the best‐optimized RMCB interconnects to maintain a balance between the two.

An investigation on the thermophysical properties of glycerol

A vibrating tube density meter (VTD) was used to measure density of pure glycerol at different isotherms between 298.16 and 423.12 K, and a pressure range up to 55 MPa. The VTD was calibrated based on the measurements conducted for water and nitrogen. Speed of sound in glycerol was also obtained by mean of a double path acoustic technique in a high pressure acoustic cell. Speed of sound measurements were conducted at five isotherms between 298.14 and 398.16 K with pressures limited to 55 MPa. The acoustic cell was calibrated with distilled water. Validation tests were performed by measuring the density and sound velocity in pure toluene using the VTD and acoustic cell, respectively. The maximum uncertainty (with 95 % level of confidence, k = 2) of the measured densities and sound velocities were found to be 1.27 kg.m−3 and 4.07 m.s−1, respectively.In addition, the measured sound velocities combined with some reliable literature data for density, heat capacity and sound velocity at atmospheric pressure were utilised to determine density, isobaric, and isochoric heat capacities and the Joule-Thomson coefficient using a numerical integration method. Finally, the calculated densities were compared with measured densities from this work and literature, and a good agreement was observed.

Compressive constitutive models of bamboo and fiber-reinforced phosphogypsum and axial compression properties of composite short columns

Bamboo is an ideal building material with green, fast growing and good mechanical properties. Phosphogypsum is a kind of solid waste residue with low resource utilization and has been used as building material. Finite element analysis is an important means of structural research. In this paper, the stress-strain constitutive models of bamboo and phosphogypsum were explored based on material tests, and axial compression tests of three bamboo-phosphogypsum composite short columns were carried out. Based on the constitutive models, the simulation and test results of composite short columns were compared by finite element analysis. The results show that the finite element analysis has high accuracy. The finite element analysis of 32 models was carried out considering the influence of bamboo tube wall thickness, bamboo tube density, phosphogypsum fiber ratio, bamboo tube longitudinal reinforcement and stirrup. The results show that the bearing capacity of composite short columns increases with the increase of bamboo tube wall thickness, bamboo tube density, phosphogypsum fiber ratio, longitudinal reinforcement diameter and density, and stirrup diameter and density. The thickness of bamboo tube wall and density of bamboo tube have a significant effect on the bearing capacity of composite short columns. A method for calculating the bearing capacity of composite short columns was presented, which has high accuracy. • The constitutive models of bamboo and phosphogypsum were proposed. • A kind of bamboo-phosphogypsum composite short column was proposed. • A theoretical calculation method for the bearing capacity of bamboo-phosphogypsum composite short columns was established.

Device design and optimization of CNTFETs for high-frequency applications

Carbon nanotube (CNT) field-effect transistors (FETs) have recently reached high-frequency (HF) performance similar to that of silicon RF-CMOS at the same gate length despite a tube density and current per tube that are far from the physical limits and suboptimal device architecture. This work reports on an investigation of the optimal device design for practical HF applications in terms of cut-off frequencies, power gain, and linearity. Different fundamental designs in the gate contact arrangement are considered based on a 3D device simulation of both CNTs and contacts. First, unit cells with a single CNT and minimal contact sizes are compared. The resulting simulation data are then extended toward a structure with two gate fingers and realistic contact sizes. Corresponding parasitic capacitances, as well as series and contact resistances, have been included for obtaining realistic characteristics and figures of merit that can be used for comparison with corresponding silicon RF MOSFETs. Finally, a sensitivity analysis of the device architecture with the highest performance is performed in order to find the optimal device design space.

Density and sound velocity measurement by an Anton Paar DSA 5000 density meter: Precision and long-time stability

Vibrating tube density meters are frequently used in routine measurements. The instruments are often equiped with a cell for sound velocity measurement. The methodology of measurement is described in the operation manual and many papers contain recommedations how to achieve data with higher precision. This work is aimed to the study of importance of each aspect of the measurement procedures, effects of neglection of a viscosity correction as well as the magnitude of induced errors. Numerical values of all effects are presented. As a result of thorough analysis not yet published recommendations for best practice of density and sound velocity measurements are summarized.

Structure Fortification of Mixed CNT Bundle Interconnects for Nano Integrated Circuits Using Constraint-Based Particle Swarm Optimization

The emerging VLSI technology and simultaneously highly dense packaging of devices and interconnects in nano-scale chips have prosperously enabled realization of system-on-chip designs and advanced high-performance computing applications. Concurrently, these have aggravated inevitable challenges in miniaturized integrated circuits (ICs). One of the main limiters in the performance of high-speed VLSI designs is the on-chip interconnects. The emerging graphene based mixed carbon nanotube bundle (MCNTB) interconnects have been investigated as one of the most suited and physically realizable on-chip structure. The present work focuses on utilization of MCNTB as nano-interconnects in the optimized way. Determining optimized placement of CNTs in MCNTB configuration is tedious, skilful task and meagerly explored till date. This has been innovatively taken-up in the current work. In the present paper, novel and efficient particle swarm optimization (PSO) technique is explored and innovatively incorporated to obtain optimal distribution of CNTs in a given rectangular area. The objective function considered for the design is to maximize the tube density. Several signal integrity analyses have been executed. The proposed optimized mixed CNT bundle structure is compared with other different configurations of CNT bundle structures. It is analyzed that the proposed optimized MCNTB configuration produces highly favorable results and is apt suitable for futuristic nano IC designs. The different modelling and performance analyses are performed using MATLAB, SPICE and ADS EDA tools.

Synthesis of Vertical Carbon Nanotube Interconnect Structures Using CMOS-Compatible Catalysts.

Synthesis of the vertically aligned carbon nanotubes (CNTs) using complementary metal-oxide-semiconductor (CMOS)-compatible methods is essential to integrate the CNT contact and interconnect to nanoscale devices and ultra-dense integrated nanoelectronics. However, the synthesis of high-density CNT array at low-temperature remains a challenging task. The advances in the low-temperature synthesis of high-density vertical CNT structures using CMOS-compatible methods are reviewed. Primarily, recent works on theoretical simulations and experimental characterizations of CNT growth emphasized the critical roles of catalyst design in reducing synthesis temperature and increasing CNT density. In particular, the approach of using multilayer catalyst film to generate the alloyed catalyst nanoparticle was found competent to improve the active catalyst nanoparticle formation and reduce the CNT growth temperature. With the multilayer catalyst, CNT arrays were directly grown on metals, oxides, and 2D materials. Moreover, the relations among the catalyst film thickness, CNT diameter, and wall number were surveyed, which provided potential strategies to control the tube density and the wall density of synthesized CNT array.

Insight into solute-solute and solute-solvent interactions of l-proline in aqueous-D-xylose/L-arabinose solutions by using physicochemical methods at temperatures from 293.15 to 318.15 K

The interactions of l-proline with carbohydrates are investigated by using volumetric, viscometric and acoustic properties. The measurements of the densities, ρ, ultrasonic speeds, u and viscosities, η of the l-proline in water and in aqueous-D-xylose/L-arabinose (2.5% and 5% D-xylose/L-arabinose in water) solvents were carried out at temperatures (293.15–318.15) K and at atmospheric pressure of 101 kPa by using digital vibrating tube density and sound analyzer and microviscometer. The experimental data have been used to evaluate the apparent molar volumes, Vϕ, limiting apparent molar volumes, Vϕ°, apparent molar compressibilities, Ks, ϕ, limiting apparent molar compressibilities, Ks,ϕ°, transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr°. The viscosity A and B coefficients, Gibbs free energies of activation of viscous flow per mole of solvent, Δμ1°# and of solute, Δμ2°#, enthalpies, ΔH∘# and entropies, ΔS∘# of viscous flow, were obtained using the viscosity data. The effect of concentration, temperature and solute structure were discussed in terms of solute-solvent and solute-solute interactions prevailing in these systems. The structure making/breaking ability of l-proline is examined in from the sign of temperature derivative of B-coefficient, dB/dT. The thermodynamic parameters of viscous flow for the solutions are also calculated and discussed using transition state theory.

Nonperturbative and Thermal Dynamics of Confined Fields in Dual QCD

In order to study the detailed dynamics and associated nonperturbative features of QCD, a dual version of the color gauge theory based on a topologically viable homogeneous fibre bundle approach has been analysed taking into account its magnetic symmetry structure. In the dynamically broken phase of magnetic symmetry, the associated flux tube structure on a S2 sphere in the magnetically condensed state of the dual QCD vacuum has been analyzed for the profiles of the color electric field using flux quantization and stability conditions. The color electric field has its intimate association with the vector mode of the magnetically condensed QCD vacuum, and such field configurations have been analyzed to show that the color electric flux gets localized towards the poles for a large sphere case while it gets uniformly distributed for the small sphere case in the infrared sector of QCD. The critical flux tube densities have been computed for various couplings and are shown to be in agreement with that for lead-ion central collisions in the near infrared sector of QCD. The possible annihilation/unification of flux tubes under some typical flux tube density and temperature conditions in the magnetic symmetry broken phase of QCD has also been analyzed and shown to play an important role in the process of QGP formation. The thermal variation of the profiles of the color electic field is further investigated which indicates the survival of flux tubes even in the thermal domain that leads the possibility of the formation of some exotic states like QGP in the intermediate regime during the quark-hadron phase transition.

Quality metrology of carbon nanotube thin films and its application for carbon nanotube-based electronics

Large area, highly uniform, and density controllable carbon nanotube (CNT) films, either well-aligned or random network, are required for practical application of CNT-based electronics. Mass production methods for such CNT films and corresponding quality metrology, which are critical for pushing the CNT-based transistor technology to manufacturing, should be developed in advance. Much progress has been made on fabrication of CNT films; however, there still lacks a metrology for thoroughly quantifying their quality until now. In this paper, through comparing study of CNT films fabricated by dip-coating (DC) and direct deposition (DD) methods, local anisotropy in the film is revealed to impact the performance uniformity of devices so fabricated in a spatial scale dependent manner. The anisotropy effect should be taken into account for the quality characterization of CNT films, which was not noticed in previous studies. Based on these findings, we propose a four-parameter metrology to quantify the overall quality of the CNT films, which includes the local tube density (DL), global density uniformity (Cv), local degree of order (OL), and the relative tube proportion in a certain orientation (Pθ) at a location. The four-parameter characterization and corresponding device performance confirm DC films are superior to DD films for practical application. The four-parameter metrology is not only powerful for overall quality evaluation of CNT films, but also able to predict the fluctuation of devices’ performance. Therefore, this material metrology is important for devices and circuits design and valuable for pushing the CNT-based transistor technology forward.

Development of laid-in knitted fabric for buoyant swimwear

As the use of buoyant swimwear by children in residential swimming becomes more common, the investigation of the effects of buoyant textiles is crucial for the optimisation of functional buoyant clothing design. This study investigated buoyant knitted fabrics developed using an inlaid knitting technique for buoyant swimwear application. The impact of the inner diameter, outer diameter, and the linear density of the inlaid tube on the buoyant ability of the buoyant fabrics was analyzed using multiple linear regression. The result demonstrated that the fabric’s net buoyant force was significantly affected by all three parameters, with inner diameter having the greatest effect, followed by the outer diameter and linear density of the inlaid tube. The increase in the net buoyant force of the fabric can be predicted by the increase in the inner diameter of its inlaid tube and linear density and decrease in the outer diameter. The divergence of the results for specimens inlaid with Silicon tube and from the result predicted by multiple linear regression indicates that the net buoyant force is also affected by the linear density and the wall thickness of the inlaid tube. The new knowledge of this study can contribute to the production of buoyant layers inside the buoyant swimwear in replace of air chambers to improve the limitation of non-distributed buoyancy, accidental punctuation and bulkiness in conventional buoyant swimwear.

Study of solvation behaviour and interactions of drug betaine hydrochloride in aqueous-D-xylose/L-arabinose solutions at different temperatures by using volumetric, acoustic and viscometric methods

The densities, ρ, ultrasonic speeds, u and viscosities, η of the drug betaine hydrochloride in water and in aqueous−D-xylose/L-arabinose (5 wt% and 10 wt% D-xylose/L-arabinose in water) solvents at various temperatures (293.15–318.15) K and at atmospheric pressure of 101 kPa have been measured by using digital vibrating tube density and sound analyser and micro viscometer. The experimental data have been used to evaluate the apparent molar volumes, Vϕ, limiting apparent molar volumes, Vϕo, apparent molar compressibilities, Ks,ϕ, limiting apparent molar compressibilities, Ks,ϕo, apparent specific volume, Vϕ,sp, transfer volumes, Vϕ,tro and transfer compressibilities, Ks,ϕ,tro. The viscosity A and B coefficients, Gibbs free energies of activation of viscous flow per mole of solvent, Δμ1o# and of solute, Δμ2o#, enthalpies, ΔHo# and entropies, ΔSo# of viscous flow, were obtained using the viscosity data. The effect of concentration, temperature, taste behaviour and solute structure were discussed in terms of solute–solvent and solute–solute interactions prevailing in these systems.

The impact of intercellular communication for the generation of complex multicellular prevascularized tissue equivalents.

In reconstructive surgery the use of prevascularized soft tissue equivalents is a promising approach for wound coverage of defects after tumor resection or trauma. However, in previous studies to generate soft tissue equivalents on collagen membranes, microcapillaries were restricted to superficial areas. In this study, to understand which factors were involved in the formation of these microcapillaries, the levels of the angiogenic factors vascular endothelial growth factor (VEGF), Interleukin-8 (IL-8), and basic fibroblast growth factor (bFGF) in the supernatants of the tissue equivalents were examined at various time points and conditions. Additionally, the influence of these factors on viability, proliferation, migration, and tube formation in monocultures compared to cocultures of fibroblast and endothelial cells was examined. The results showed that VEGF production was decreased in cocultures compared to fibroblast monocultures and the lowest VEGF levels were observed in endothelial cell monocultures. Additionally, the highest levels of IL-8 were observed in cocultures compared to monocultures. Similar results were observed for bFGF with lowest levels seen within the first 24 hr and highest levels in cocultures. VEGF and IL-8 were shown to promote endothelial cell viability, proliferation and migration and angiogenic parameters such as tube density, total tube length, and number of tube branches. Addition of VEGF and IL-8 to cocultures resulted in accelerated and denser formation of capillary-like structures. The results indicate that VEGF, IL-8, and bFGF strongly influence cellular behavior of endothelial cells and this information should be useful in promoting the formation of microcapillary-like structures in complex tissue equivalents.

Simulation studies on effect of CNT physical parameters on carbon nanotube thin-film transistors (CN-TFTS)

Limitations faced in scaling of silicon-based transistors were expelled using carbon nanotube as channel material. The Carbon nanotube-based thin-film transistor (CN-TFTs) is one of the most promising devices to become successor of silicon devices in near future because of its enhanced device performance in all aspects in nano-regime. The carbon nanotube parameters such as tube length, orientation of tubes between the source and drain terminals, tube density along with channel width and length decide the drain current and device temperature primarily. Therefore, the authors had studied the influence of CNT physical parameters on the CN-TFT device performance in this work. The studies clearly bring out the influence of these parameters on device performance and temperature in addition to suggesting the need to optimize these parameters of the device.

Recoverable impacts of ocean acidification on the tubeworm, Hydroides elegans: implication for biofouling in future coastal oceans

Ocean uptake of anthropogenic CO2 causes ocean acidification (OA), which not only decreases the calcification rate, but also impairs the formation of calcareous shells or tubes in marine invertebrates such as the dominant biofouling tubeworm species, Hydroides elegans. This study examined the ability of tubeworms to resume normal tube calcification when returned to ambient pH 8.1 from a projected near-future OA level of pH 7.8. Tubeworms produced structurally impaired and mechanically weaker calcareous tubes at pH 7.8 compared to at pH 8.1, but were able to recover when the pH was restored to ambient levels. This suggests that tubeworms can physiologically recover from the impacts of OA on tube calcification, composition, density, hardness and stiffness when returned to optimal conditions. These results help understanding of the progression of biofouling communities dominated by tubeworms in future oceans with low pH induced by OA.