Single Wall Research Articles

Small-scale airblast testing for the assessment of multiple perimeter wall barriers on shock wave propagation

Assessment of the impact of structural systems on blast wave propagation has traditionally been explored using experimental, analytical, and/or numerical methods. Though numerical modeling techniques have grown in popularity because of their lower cost and high accuracy, experimental testing remains necessary for verifying these models. Issues of scale, equipment capacity, and the availability of research funding continue to limit full-scale testing of subassemblies or complete structures under blast loads. In addition, full-scale blast testing can be time-consuming, allowing only a handful of tests to be conducted. Small-scale airblast experiments offer an economic alternative to full-scale testing, in terms of material and labor requirements. Additionally, these small-scale experiments can be performed rapidly with repeatable results. The use of a novel reusable tabletop small-scale airblast experiment framework is presented for repeatable, cost-effective, quick turnaround testing of airblast scenarios. This novel setup also allows for reflective surfaces to be included as part of the investigation of the behavior of the shockwave-interaction with structures. The goal is to understand the behavior of the blast shockwave interacting with multiple barriers and the effect of pressure due to those barriers; therefore, the scaled structure remains rigid in the experimental and numerical analysis. Three different wall configurations were used to investigate how the presence of multiple barriers affects the shockwave and subsequent observed pressures around and behind the barriers. The explosives used were hemispherical and elevated spherical C4 charges. Pressure gauges were used to read pressures in front of, between, and behind the barriers on the tabletop. The airblast effects such as pressure and impulse, from the scaled experiments are presented and compared to the analytical predictions using a hydrocode model. It was found that multiple walls are measurably effective in reducing the pressure shockwave compared to no walls. The use of single and double walls reduced the pressure by 50% and 25%, respectively, compared to having no walls at the same scaled distance. The hydrocode model results were generally in agreement with the experimental data. The results can allow engineers and decision makers to understand the impact that properly distanced multiple barriers can have on protection from blast events.

Switching Behavior of the Composite Low Dimensional Structural Hybrids of Carbon After UV Exposure

Low dimensional multi structural components of carbon are of great interest currently owing to their applications in developing flexible plastic electronics. In this work, we discuss emergence of different structural hybrids of carbon from as-prepared HiPCO SWCNTs subjecting them to oxidative acid purification and covalent functionalization process. Transmission electron microscopy (TEM) investigations reveal single wall carbon nanotubes (SWCNTs) serve as a building block to obtain multi wall carbon nanotubes (MWCNTs), graphene sheets (GS), carbon nano scrolls (CNS) structures which coexist in the sample. These structures when grafted with polymer binder and spray coated on Si substrate provide highly sustainable thin film coatings that are stable even in adverse space conditions [1]. These CNT and CNS based composite coatings are promising candidates for stray light control space applications exhibiting a low reflectance of the order of 2-3% in the visible spectral range [1]. Electrical switching behaviour of these films were investigated by capturing current(time) (I(t)) response, displaying promising switching character with distinct ON-OFF cycle. These coatings offer opportunities for the development of facile, cost-effective carbon-based devices without going into the nontrivial task of separating different the structures.

Controlling of the single domain wall propagation in magnetic microwires by magnetostatic interaction

Ultrafast magnetization switching through the single domain wall (DW) propagation has been reported in amorphous micrometric and submicrometric wires. However the performance of prospective devices utilizing DW propagation is determined by the degree to which DW propagation can be controlled. In this article, we propose a novel method for effectively controlling the single DW propagation in a specially designed array consisting of two magnetic microwires by the stray field from magnetically softer microwires. We have experimentally demonstrated that the DW velocity of magnetically harder Fe-rich microwire in such a linear array is affected by the stray field of magnetically softer Co-rich microwire. Additionally, the domain wall can be trapped in the Fe-rich microwire by the stray field produced by the Co-rich microwire in such a linear array. The observed effect of magnetostatic interaction depends on the position of the Co-rich microwire in such a linear array. Controllable domain wall propagation observed in such a linear array can be a useful tool for simple and more flexible ways of controllable trapping and braking of single DWs in Fe-rich microwires showing spontaneous magnetic bistability.

Investigation of The Failure Mechanisms of Li-Ion Pouch Cells with Si/Graphite Composite Negative Electrodes and Single Wall Carbon Nanotube Conducting Additive

Silicon-Graphite composite electrodes are a rapidly developing area of research and commercialization. Increasing the energy density of current Li-ion battery technology can be done by simply creating silicon-graphite composite electrodes. It is well known that the failure of these silicon-graphite composite electrodes stems from the expansion of the silicon during cycling that causes mechanical degradation, excessive SEI formation, and electrode shift loss. Here we explore the use and capacity loss mechanisms of a silicon-graphite composite anode employing CMC/SBR binder used in conjunction with single wall carbon nanotubes. These nanotubes are thought to be effective in increasing mechanical resiliency of the electrodes and increase the electrical connectivity between particles within the formed electrode. When the Si/graphite electrode cycles, it is believed that the SWCNTs help keep the active particles electrically connected and, hence, electrochemically active. Through dV/dQ analysis and in situ pressure monitoring, the pouch cells studied here are shown to exhibit minimal loss of active mass in the positive and negative electrodes but experience capacity loss due to continued negative electrode SEI growth leading to lithium inventory or shift loss.

Wire arc additive manufacturing of the Al-5.55Cu alloy: Insight the effect of intrinsic heat treatment on microstructure and mechanical properties

Al-5.55Cu alloy single wall sample were fabricated by cold metal transfer wire arc additive manufacturing (CMT-WAAM) technique, and the microstructure characteristics and evolution mechanism of the different deposition regions were analyzed. Under the influence of intrinsic heat treatment and remelting process caused by layer-by-layer deposition, the top region exhibits dendritic characteristics, while the middle and bottom are characterized by a non-uniform banding distribution of fine equiaxial grains alternating with columnar grains. According to the non-equilibrium solidification theory and the related nucleation mechanism, the formation of equiaxed grains in the inter-layer region is related to the elements such as Ti and Zr contained in Al-5.55Cu alloy, which can be used as nucleation particles. In addition, the morphology and quantity of the θ'-Al2Cu phase inside the grain change with the increase of deposition height due to the thermal cycling effect. After heat treatment, the tensile strength of the deposited sample is greatly improved and remains isotropic. The ultimate tensile strength of the heat-treated sample is 508.0 ± 18.9 MPa in the horizontal direction and 503.8 ± 6.2 MPa in the vertical direction.

Dynamics of a bubble-pair between two parallel rigid walls

The dynamics of two gas bubbles placed side-by-side in liquid between parallel rigid plates is studied numerically using the multiphase volume of fluid (VOF) model in OpenFOAM. This model solves a single set of Navier–Stokes equations for both the gas in the bubbles and the surrounding liquid. Being initially stationary, the bubbles first expand to their maximum volume due to the high gas pressure inside them and then collapse. Both phases are treated as viscous and immiscible without any phase change. The model is validated against available experimental data of a single bubble oscillation between parallel plates and a bubble-pair oscillation near a single rigid wall. Parametric studies are then performed, with the main variables being the initial sizes of the bubbles and their standoff distances from the rigid plates. The bubbles exhibit symmetric or asymmetric behavior depending on these two variables. Three distinct scenarios are identified in the symmetric case based on the relative influence of bubble-bubble and bubble-wall interactions. The jet strength and direction, bubble oscillation period, coalescence, and early asymmetric bubble collapse are characterized by initial distances and radii. This study provides valuable insights into intricate hydrodynamic interactions and behaviors of bubble pairs bounded by rigid surfaces.

Elastic properties of honeycombs with spline curve cell walls

In the ideal models, cell walls of honeycomb structures are perfect flat sheets or straight lines (viewed from out-of-plane projection), whereas most of the real honeycomb products contain curved cell walls due to the widely employed manufacturing processes. Moreover, some honeycomb products are made intentionally to have corrugated cell walls for an enhanced out-of-plane stability or an increase of structural stiffness. In the presented study, a relative new modeling method for the nonlinear cell walls of honeycomb structures is used. The method makes use of Bezier spline functions to describe the curved cell walls. Energy method and Castigliano's theorem are used to formulate the force-displacement relationship of a single cell wall, and the homogenized stiffness matrix is derived based on the proper boundary conditions of the cell walls. Analytical and experimental verification shows that the proposed model is very accurate and versatile in predicting the mechanical responses of different honeycomb geometries. Parametric studies are conducted, analytically and numerically, to examine the influence of the spline cell wall geometries on the honeycomb's effective in-plane properties and the out-of-plane stability. The study leads to the recommendation of a cell wall design strategy for maximizing the out-of-plane buckling resistance of honeycomb structures.

Dextran sulfate bulk and surface-modified microfiltration membrane for simultaneous blood plasma harvesting and low-density lipoprotein removal during plasmapheresis

Plasmapheresis is currently used for the harvesting of blood plasma in medical labs and plasma donation centers. This is a fast, single-step membrane process for both collection of blood plasma and simultaneous blood cell isolation. This paper presents the development of a novel membrane that can be used to simultaneously harvest blood plasma and isolate low-density lipoprotein (LDL), known as bad cholesterol, from the blood. To achieve this goal, dual surface and bulk modification by dextran sulfate (DS) was performed on a polyethersulfone (PES) membrane containing single wall carbon nanotubes (SWCNT). DS is an anionic ligand that repels negatively charged substances like red blood cells (RBCs) and adsorbs positively charged substances like Apo B100; the apoprotein of LDL. Scanning Electron Microscope (SEM), Energy Dispersive X-Ray (EDX), and Fourier Transform Infrared (FTIR) spectroscopy analyses provided evidence of the grafting of DS on single wall carbon nanotubes (DS-SWCNT). Surface studies including water contact angle, zeta potential analysis, surface morphology, Attenuated Total Reflectance-FTIR (ATR-FTIR), and EDX, confirmed the presence of DS on the PES membrane surface. The SEM cross-section results showed the formation of a two-zone morphology with an open structure on the upside and a dense structure on the downside that provide optimal conditions for efficient separation of blood cells. The complete blood count (CBC) and biochemistry analyses revealed dual bulk and surface-modified membrane, and a specific sample (DM2) showed the best performance for blood cells and LDL separation. The maximum separation of blood cells was 87% RBC, 98% white blood cells (WBCs), and 83% platelets (PLTs). Moreover, DM2 exhibited a sieving ratio for LDL of 0.33. Blood compatibility analyses confirmed that DM2 and other related samples had low hemolysis and prolonged coagulation times.

Sound transmission loss through steel-framed building partitions

Load-bearing steel-stud walls pose a unique acoustical challenge because both the spacing and the mil thickness of the studs can significantly affect the acoustical performance of these walls. A single wall type in a load-bearing steel building may actually include many acoustically distinct walls as the stud spacing and mil thickness change from floor to floor in the building due to the different loads. This can be especially challenging on delegated design projects where the final selection of the steel studs is left to the framing contractor and may not be included in the project documents supplied to the acoustical consultant, if there even is one on the project. In prior ASA presentations, Ben Shafer has clearly documented the effects of steel stud spacing and mil thickness on acoustical performance. This presentation adds to Ben’s prior work by investigating the effects of resilient sound isolation clips on wall performance. Clips are a unique application because the spacing of both the clips, and the hat channels does not change with changing stud spacing and because the low stiffness of the rubber isolators should reduce the effect of stud stiffness. This presentation will present the results of recent lab tests of walls with resilient sound isolation clips and compare the results to the data previously presented by Mr. Shafer.

Irreversibility scrutiny of SWCNT and MWCNT nanofluid convective flow using Darcy-Forchheimer rule in an upright microchannel with variable thermal conductivity and Brownian motion and thermophoresis

Carbon nanotubes are used to attain greater thermal transfer rates in a various of enormous applications in the field of microsystem, emission, conductive polymers, fibers, and fabrics. Hence the aim of this article is to explore the entropy generation analysis of single wall carbon nanotubes and multiwall carbon nanotubes flow in an upright micro channel with variable thermal conductivity. The exponential heat source and non-linear thermal radiation were considered. The micro channel retains the no slip and convective boundary conditions. The Buongiorno model was used in this study, which emphasizes the light on Brownian motion and thermophoresis phenomena that occur during the fluid flow. Darcy- Forchheimer model is also taken into account. The governing equation numerically solved by employing Runge-Kutta Fehlberg's fourth-fifth order. The repercussion of this study upholds that the inflates of variable thermal conductivity magnify the thermal field. Entropy production inflates at right wall of the channel with augmented Brownian parameter and exhibits exactly opposite behavior at left wall of the channel. One of the important tasks of the investigation was to compare SWCNT and MWCNT. The findings confirmed that multiwall carbon nanotubes exhibit more magnificent heat and mass transfer than single wall carbon nanotubes.

Design and performance investigation of CIGS/SWCNT tandem solar cell for efficiency improvement

This research work demonstrates the design and simulation of highly efficient tandem solar cell by using SCAPS-1D software. This tandem solar cell has been designed with a higher bandgap Copper Indium Gallium Diselenide (CIGS) absorber as a top cell and a lower bandgap Single Wall Carbon Nano Tube (SWCNT) absorber as a bottom cell, which are arranged in the series connection. Firstly, both top and bottom solar cells were analysed under standalone afterward, tandem configuration was developed with the top cell illumined by AM 1.5 spectrum and the bottom cell illumined by AM 1.5 filtered by top cell spectrum. The effects of absorber thickness, doping density, and bandgap on the output characteristics of the solar cell are also investigated. The current matching of both cells is attained by tuning the bandgap and thickness of Cu(In1-xGax)Se2 absorber of the upper cell. The remarkable efficiency of 38.91 % (Voc = 1.3441 V, Jsc = 37.87 mA/cm2 and FF = 76.41 %) is attained of the proposed CIGS/SWCNT tandem device at a thickness of 860 nm and 2000 nm for absorber of top and bottom cell respectively. The results of this research suggest a route for the fabrication of CIGS/SWCNT tandem solar cell with high efficiency.

High-Performance Thienothiophene and Single Wall Carbon Nanotube-Based Supercapacitor as a Free-Standing and Flexible Hybrid Energy Storage Material

High-Performance Thienothiophene and Single Wall Carbon Nanotube-Based Supercapacitor as a Free-Standing and Flexible Hybrid Energy Storage Material

Structural, acoustical, and thermal evaluation of an experimental house built with reinforced/hollow interlocking compressed stabilized earth brick-masonry

With the increasing demand on affordable construction that addresses the global challenges of the modern world, earthen construction is being reintroduced and investigated as a potential sustainable and affordable building method. Compressed stabilized earth blocks (CSEBs) are a common form of enhanced earthen building materials. Previous studies focused on the structural performance of CSEB walls and prisms consisting of one type of bricks with the same mixture, analyzed their thermal and acoustic properties as units only, or evaluated the thermal performance of solid unreinforced CSEB masonry.The present research is the first complete structural, acoustical, and thermal investigation of an experimental house built with a novel reinforced/hollow interlocking compressed stabilized earth brick-masonry (ICSEB) using varying stabilizer contents, compliant with the Egyptian code for building with stabilized soil—Part One: Building with compressed stabilized soil units (EG-SE2016). Methods depend on experimental testing, codified theoretical calculations, finite element analysis, and live measurements. According to the structural experimental testing program, reinforcement was found to triple the load bearing capacity of ICSEB columns and, although minimal rebars were used in the ICSEB walls, it has improved their load bearing capacity by 23% for single walls (125 mm) and 58% for double walls (250 mm). In addition, doubling the thickness of the unreinforced ICSEB walls increased the load bearing capability by 164%, while raising the thickness of the reinforced wall from 125 mm to 250 mm increased the load bearing capacity by more than threefold (3.38). Based on the codified theoretical calculations and findings of the finite element analysis, it is safe to recommend reinforced double ICSEB walls as a reliable construction for a two-story residential building. Acoustically, double ICSEB walls attained the noise reduction index value of 40 dB, which is required by the Egyptian code for acoustic insulation and noise control in residential buildings, to protect against the average outdoor noise levels of 65–70dBA. Thermally, reinforced double ICSEB walls kept the indoor air temperature and relative humidity values within the thermal comfort zone, 23.9–25.7 °C and 28–36%, respectively, despite the fluctuating outdoor temperatures and relative humidities (16–37 °C and 7–88%, respectively). Indoor air temperatures were 1.5–2 °C lower than those of concrete masonry walls. Additional research is required to evaluate resistance to environmental aspects, such as exposure to water, wind, and corrosion, and to further investigate their thermal and acoustical properties.

Ratiometric Imaging of Catecholamine Neurotransmitters with Nanosensors.

Neurotransmitters are important signaling molecules in the brain and are relevant in many diseases. Measuring them with high spatial and temporal resolutions in biological systems is challenging. Here, we develop a ratiometric fluorescent sensor/probe for catecholamine neurotransmitters on the basis of near-infrared (NIR) semiconducting single wall carbon nanotubes (SWCNTs). Phenylboronic acid (PBA)-based quantum defects are incorporated into them to interact selectively with catechol moieties. These PBA-SWCNTs are further modified with poly(ethylene glycol) phospholipids (PEG-PL) for biocompatibility. Catecholamines, including dopamine, do not affect the intrinsic E11 fluorescence (990 nm) of these (PEG-PL-PBA-SWCNT) sensors. In contrast, the defect-related E11* emission (1130 nm) decreases by up to 35%. Furthermore, this dual functionalization allows tuning selectivity by changing the charge of the PEG polymer. These sensors are not taken up by cells, which is beneficial for extracellular imaging, and they are functional in brain slices. In summary, we use dual functionalization of SWCNTs to create a ratiometric biosensor for dopamine.

Optimization Analysis of Partition Wall Support Scheme of Multi-Arch Tunnel

With the fast progress of infrastructure projects, super-large cross-section projects are constantly emerging, and, therefore, engineering challenges and problems are increasing. Taking the triple-arch tunnel project in the turn-back line section of Santunbei Station in Urumqi Metro Line 1# as a case study, this research applied numerical simulation software Midas GTS/NX 2022 for the analysis of tunnel force and deformation in triple-arch cross-sections under different support forms of partition wall. Following the optimization of the support design of the mixed partition wall to a single straight wall, the following analytical results were obtained: surface settlement was decreased by 21.15% at the original cross-section; maximum values of principal stress and displacement of partition wall were decreased by 6.73 and 10.64%, respectively; and corresponding values for initial support structure were decreased by 21.47% and 54.74%, respectively. Meanwhile, combined with comparative analysis of engineering measurement and numerical simulation results, surface settlement and vault deformation were found to be similar to the optimized simulation results, which not only verified the reliability of simulation results but also ensured the safe and smooth construction of the project, greatly improving construction efficiency and saving construction time and cost.

Energy matrices, enviro-economic and characteristic equation-based performance analyses of photovoltaic thermal compound parabolic concentrator (PVT-CPC) coupled solar still equipped with heat exchanger using SWCNTs and MWCNTs–water nanofluids

In this paper, effect of single wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs)- water based nanofluid have been studied to examine the performance, long-term feasibility andenviro-enviro-economic analysis of partially covered series connected N- photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collectors coupled double slope solar still (DSSS) equipped with helically coiled heat exchanger (HE). Analysis have been carried out by developing thermal modelling of the proposed system. Instantaneous gain and loss efficiencies; annual thermal energy/exergy, and productivity – is investigated for optimized parameters of the proposed system in detail. Gain efficiency of the proposed system is found to be approximately 25-30% higher using CNT-NPs as compared to the system without using NPs. Annual thermal energy and exergy of CNTs, particularly SWCNTs water-based nanofluid (thermal energy- 2491.55 kWh, thermal exergy-894.67 kWh) have been found to be greater in comparison to basefluid (thermal energy -2185.76 kWh, thermal exergy-772.18 kWh). Also, results give higher value of CO2 mitigation using CNT-NPs both on the basis of energy (SWCNT-5.082t, MWCNT-4.787t) and exergy (SWCNT-1.83t, MWCNT-1.76t) respectively. SWCNT-NPs shows better performance due to their better TPPs; also PVT-CPC collector integrated DSSS equipped with HE is more viable practically.

In-bulk polarization reversal in lithium tantalate with single charged domain wall

This paper presents the results of the first experimental observation of polarization reversal in the bulk of ferroelectric with a charged domain wall (CDW) under the action of an electric field on the example of a single crystal LiTaO3 plate. A CDW was obtained in the sample bulk at the locus of points with a sign change of the composition gradient which results from sample annealing in lithium rich atmosphere. Imaging of the domain structure in the bulk and its evolution on the surface made it possible to detect anomalous domain kinetics, which represents the growth of ledges on the CDW toward the polar surface. The main stages of the domain structure evolution on the polar surface, including the growth of isolated domains, as well as the formation and decay of the maze domain structure, were revealed. An analysis is made for the time dependence of the area fraction occupied by growing domains. We used a kinetic approach based on the analogy between the growth of domains and crystals to explain the obtained results.

Electromagnetic absorption/reflection manipulation by piezoelectric effect in PDMS/CZS/SWCNT/iron fabric hybrid composite

The development of externally controlled electromagnetic shielding materials for protecting high-end electronic devices operating in GHz frequencies in satellite, military, and other communication fields is a significant technological challenge. Previously developed foamed composites and capacitor-based shielding materials exhibit active modulation of reflection and absorption. However, the higher thickness of foamed composites and the costly complex manufacture process along with requirement of an external voltage source by capacitor-based shields constrain their direct usability in realistic electronic applications. Herein, a piezo-tuned polydimethylsiloxane (PDMS)/carbon-doped zinc stannate (CZS)/single wall carbon nanotube (SWCNT)/iron fabric-based hybrid composite is prepared which features piezo-voltage controlled shielding performance. In this composite, the electrostatic modification of iron fabric electrodes and PDMS/CZS, PDMS/SWCNT layers by piezo-voltage enables control of dynamic reflection/absorption ability of 14.5–20 GHz electromagnetic radiation (EMR). Additionally, this composite reveals a functional transition from EMR reflector to EMR absorber at higher than 14 mV piezo-voltage. At 14.5 GHz frequency, this piezo-composite (1.51 mm thick) attains an excellent total shielding (SET) performance of 87.8 dB along with >98 % EMR absorption capability at 30.6 kPa pressure tuned 243 mV piezo-voltage. Hence, this achievement not only reveals the strategies for developing shielding materials for the future of electronic applications but also boosts the advancement of self-adaptable electromagnetic shielding.

Ultrashort vertical-channel MoS2 transistor using a self-aligned contact

Two-dimensional (2D) semiconductors hold great promises for ultra-scaled transistors. In particular, the gate length of MoS2 transistor has been scaled to 1 nm and 0.3 nm using single wall carbon nanotube and graphene, respectively. However, simultaneously scaling the channel length of these short-gate transistor is still challenging, and could be largely attributed to the processing difficulties to precisely align source-drain contact with gate electrode. Here, we report a self-alignment process for realizing ultra-scaled 2D transistors. By mechanically folding a graphene/BN/MoS2 heterostructure, source-drain metals could be precisely aligned around the folded edge, and the channel length is only dictated by heterostructure thickness. Together, we could realize sub-1 nm gate length and sub-50 nm channel length for vertical MoS2 transistor simultaneously. The self-aligned device exhibits on-off ratio over 105 and on-state current of 250 μA/μm at 4 V bias, which is over 40 times higher compared to control sample without self-alignment process.

The aggregation of casein micelles induced by Ca2+ during in vitro digestion: effects on the release of loaded anthocyanins.

Colloidal calcium phosphate (CCP) confers a modifiable structure to micellar casein (MC), which endows it with potential advantages as a delivery carrier. However, it is difficult to achieve multipattern release of the core material in the intestine with MC as a single wall. In this study, we prepared an anthocyanin-casein-based delivery system utilizing MC with different freezing degrees as the wall material with the objective of achieving the controlled release of anthocyanin as the model core in the intestine. The results showed that freezing could significantly reduce the CCP level up to 50%. Static in vitro simulated digestion with the addition of exogenous Ca2+ showed that the designed delivery system exhibited low anthocyanin release (15%-35%) in the gastric tract. The pattern of release in the intestine depended on the CCP dissociation degree. High and low dissociation degrees corresponded to slow release (from 15% to 65% within 2 h) and burst release (from 35% to 90% within 5 min), respectively. WAXS/SAXS analysis revealed that exogenous serum Ca2+ inherent in simulated gastric fluid and endogenous serum Ca2+ induced by CCP dissociation was synergistically involved in the reconstitution of CCP-mediated nanoclusters and large aggregates. The freezing degree of MC determined the endogenous serum Ca2+ level, which influenced the gastric aggregation behavior of wall MC and ultimately led to a fairly different gastrointestinal release behavior of anthocyanins.