Static Resistance Research Articles

Dynamic behavior of concrete filled steel tubular columns internally strengthened with I-shaped CFRP against vehicular bombs

Square concrete filled steel tubular columns internally strengthened with I-shaped carbon fiber reinforced polymer (SCFST-CFRP) demonstrate promising potential for application in building structures, particularly in high-risk buildings and critical structural elements, due to their exceptional static and impact resistance. High-risk buildings may be vulnerable to vehicular bomb attacks over their lifespan, resulting in blast loading. In this study, the blast resistance of SCFST-CFRP columns is investigated through field blast tests and numerical simulation. The plastic deformation of SCFST-CFRP members is low, and they exhibit promising blast resistance in explosion tests with a scaled distance of 0.07m/kg1/3. Subsequently, SCFST-CFRP columns with varying steel ratios were designed according to specifications to investigate their deformation and damage under typical vehicular bomb scenarios. It was found that the blast resistance of SCFST-CFRP columns is superior to that of ordinary SCFST columns, particularly when the steel ratio is smaller. Additionally, a protection distance of 3.95m (1.01H) is sufficient to ensure that the composite columns do not fail under these scenarios, highlighting favorable blast resistance for SCFST-CFRP columns. Based on the parametric analysis of 115 sets of data, a prediction formula for the critical failure distance of SCFST-CFRP columns under typical vehicular bomb scenarios is proposed. This study serves as a valuable reference for designing SCFST-CFRP columns with blast resistance.

Shear behavior at the interface of rough surfaces and cohesive soils under axial loading

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens’ preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

Behavior of Polymeric Substrates and Sintered Silver Printed Hybrid Electronic Assemblies Subject to Extreme Acceleration Levels and Elevated Temperatures

Abstract This paper focuses on the response of printed hybrid electronic (PHE) assemblies with polymeric substrates and additively manufactured sintered silver electrical traces subject to extreme mechanical shocks (up to 100,000 g) and high temperatures (up to 150 °C). The substrates are hemispherical domes of injection-molded polycarbonate and polysulfone thermoplastics. Trace deposition onto the domes is accomplished by a novel process that combines conventional milling with extrusion printing to recess silver traces and dielectric insulation within the surface of the substrate. Mechanical shock testing is performed using an accelerated-fall drop tower equipped with a dual mass shock amplifier (DMSA) able to generate accelerations from 10,000 g up to 100,000 g with pulse durations of ∼0.05–0.1 ms and impact velocities of 6.5–20.5 m/s. Specimen performance is characterized by electrical and physical testing before and after testing. While polycarbonate domes survive multiple drops at all acceleration levels and temperatures, they are sensitive to heat and susceptible to warping and structural deformation at 150 °C which can compromise trace performance. Polysulfone domes can survive these temperatures without issue, but are less shock resistant and only survive 3–4 drops at 100,000 g (compared to 30+ for polycarbonate domes). Trace resistance is used as a metric to assess trace performance. All traces exhibit progressive long-term degradation over the course of multiple shocks, followed by instantaneous discontinuity during the final shock event. Trace failure (defined as the doubling of static trace resistance) occurs at ∼105–106 J/kg cumulative impact energy for all acceleration levels.

Synthesis of titanium-vanadium oxide thin films through thermal oxidation process for their use in CO gas sensing application

The thermal oxidation of evaporated titanium-vanadium thin films was carried out at different post-annealing temperatures. The structural, morphological, compositional, optical, electrical, and gas sensing properties of titanium-vanadium oxide thin films were primarily investigated. The results of the XRD study and Raman spectroscopy verified the presence of the orthorhombic V2O5, tetragonal TiO2, and monoclinic V2Ti3O9 phases. The crystallinity of TVO thin films was improved at higher annealing temperatures. The grain size (seen from SEM images) and oxygen compositions (obtained from EDS measurement) of TVO samples are also enhanced when the post-annealing temperature is increased from 500 to 575 °C. From the transmittance curves, the bandgap values for TVO samples were estimated and found in the range of 2.14–2.36 eV. The n-type conductivity of TVO films was confirmed by the negative Hall coefficient values. At last, the CO gas sensing response of TVO thin films was analyzed by monitoring the change in the surface electrical resistances at different operating temperatures and CO gas concentrations. The dynamic and static resistances were assessed at different operating temperatures varying from 100 to 300 °C. The TVO sample prepared at 550 °C showed the best conditions by examining the materials and CO sensing properties.

Investigating the Influence of Protic Ionic Liquid on the Triboelectrical Properties of Trimethylolpropane Trioleate (TMPO)

Under triboelectric conditions, where tribocharging accelerates lubrication failure, lubricants with enhanced electrical properties are essential. Trimethylolpropane Trioleate (TMPO) oil, derived from esters that possess good lubricating properties and wear performance but is lacking in terms of electrical properties which can be further improved when blended with Ionic Liquid. This study blends 1 – 5 wt% of Protic Ionic Liquid (PIL) into TMPO and evaluate the frictional and wear performances of the blends under 1 – 2 A current conditions to understand the behaviour towards the tribological properties of different blends of material. Electric currents ranging around 1 – 2 A are implemented to the custom-designed ball-on-disc tribometer, with a constant 4.5 V voltage supply and the static resistance are measured. Mechanical wear properties are observed after the tribological test with different samples. The frictional properties of all concentrations of PIL in TMPO showed significant frictional improvements with 1%wt PIL showed 53% better results indicating improvements in frictional properties and wear performance under 2A current conditions, owing to its lowest film resistivity of 0.14 mΩ.

Phase-cancellation of velocity oscillations in a flow duct using a slow-sound metamaterial

Self-sustained acoustic oscillations in industrial systems with mean flow can cause unwanted vibrations or noise pollution. Acoustic metamaterials can be engineered and integrated in such systems to prevent these limit cycles. In this study, an acoustic metamaterial is proposed for decreasing the acoustic admittance at the outlet of a contraction in a pipe. It can reduce velocity oscillations by more than 50%, without requiring an enlargement of the pipe or increasing the static resistance to the mean flow significantly. The acoustic metamaterial consists of an array of slow-sound and regular channels, which form a contraction in a pipe. The slow-sound effect shifts the resonances of the respective slow-sound channels. For the frequency of interest, the velocity oscillations of these two types of channels are out of phase, which reduces the spatially averaged velocity oscillations at the outlet of the contraction and therefore decreases its acoustic admittance. The effect is demonstrated experimentally, using impedance measurements and particle image velocimetry. A key achievement of this work is the demonstration of a device that is nearly lossless for the mean (steady) flow, i.e. having a low pressure drop, while being very stiff for the acoustic (oscillating) flow at its nominal working frequency, i.e. low admittance, which was so far a difficult challenge to address.

Experimental study on non-load bearing multi-span sandwich wall panels for blast mitigation

Sandwich wall panels are known for their ability to provide resistance over a wide deformation range, rendering them suitable for blast resistance applications. These panels consist of layers of concrete with an insulating core, offering a structural solution with enhanced performance. Quasi-static testing was conducted on multi-span sandwich wall panels with intermediate connections to evaluate their behavior under controlled loading conditions. A total of twelve two-span details were examined and selected to match the standard designs employed in the Tilt-Up Construction (TCA) and Prestressed/Precast Concrete Industry (PCI). Among these details, three belonged to the TCA type with two duplicates, while the remaining two were representative of PCI designs with three duplicates. The results obtained from the quasi-static testing indicate that insulated sandwich wall panels possess sufficient deformation capability to meet the current blast response criteria. To assess the findings of the static experiments to the prevailing response limits, the outcomes were distilled into a multi-linear static resistance analysis. The findings support the use of insulated precast concrete (PC) sandwich wall panels, highlighting their suitability for blast-resistant designs within the constraints of current blast design limitations. Specimens with Halfen connectors showed 32 % higher energy absorption and a 58 % advantage over Stud connectors, making them superior for robust blast resistance applications.

Determination of metal crack resistance on half-size Charpy specimens at cryogenic temperatures

The work consists in the manufacture of experimental equipment for fracture toughness tests at cryogenic temperatures in the range from -196 °Cto -80 °Cand the analysis of the efficiency of determining the reference temperature of a metal by the maker curve for static crack resistance in accordance with ASTM E 1921 and ASTM E399. Liquid nitrogen and its vapours were used to cool the samples to the required temperature. The temperature stability during sample loading was ensured within ±0.5°C around the required temperature. Pre-cracking of the samples was carried out at room temperature in accordance with ASTM E647. Experimental studies on static crack resistance are carried out for three-point bending using half-size Charpy specimens (55×10×5 mm) for the material - 10GN2MFA steel, which is used as the main metal for the main circulation pipelines of VVER-1000. The reference temperature is determined by processing a set of relevant experimental data.

Numerical and experimental blast response of multilayer laminated glass panels

Laminated glass is used in high-security buildings to mitigate the effects of blasts and ballistic loadings. The multi-layered composition of the laminated glass (LG) panels allows the glass panes to crack and undergo large deflections while preventing glass shards from spalling by mostly remaining attached to the polymeric interlayer. To characterize multilayer LG panels under blast loading, it is essential to develop their static resistance response under uniform loading. A full-scale water chamber was used to experimentally evaluate the quasistatic response to the failure of the multilayer LG panel systems under uniform pressure. The influence of different polymeric interlayer types on the response of multilayer LG panels was studied. Also, the glass breakage patterns and deflections exhibited by various multilayer glass configurations were investigated. The response of LG panels under blast was developed using ANSYS AUTODYN, which was verified using field experiments. LG panels with an Ethylene Vinyl Acetate (EVA) polymeric interlayer experienced the most dynamic deflections, whereas LG panels with an ionoplast SentryGlas® (SG) polymeric interlayer displayed the least dynamic deflections. The results indicated that multilayer LG systems provide higher blast resistance compared to double-layer systems; the additional layers can help reduce glass breakage and maintain structural integrity. Multilayer LG system’s SG interlayer enhanced blast protection by allowing load transfer and ensuring uniform load distribution between glass layers.

Particleboard from the residues of wooden door production as a closed material cycle

The research was aimed at verifying that waste material from the production of wooden doors can be used to produce type P2 particleboard by EN 312 standards and that the interior door leaves made from it will meet the required tests. For this purpose, particleboards consisting of wood-based panel waste material were produced using MUF resins. The mechanical, physical and hygienic properties of the particleboard produced were investigated. Based on the results, it was confirmed that the boards made from both 100 % and 50 % waste met all the requirements for type-P2 particleboards. Prototype door leaves were then manufactured using boards made from 50 % waste and tested for functional properties. The door leaves for static torsional strength and resistance to vertical loads, soft and heavy impacts and strong body impacts meet the requirements for Class 1 by EN 1192, and resistance to repeated opening and closing cycles meets the requirements for Class 3 by EN 12400. The results indicate that producing the particleboards from waste from the same production line of interior door leaves does not impair the properties of the doors and the particle boards can be used to produce them. This product fits in with the idea of a circular economy and the idea itself contributes to the sustainability of production processes by managing part of the waste generated.

Using ligand regulation, metal replacement, and ligand doping strategies on Zr-FUM to improve methane separation from coalbed gas

Developing adsorbents suitable for industrial applications that can effectively enhance the separation of methane (CH4) from nitrogen (N2) in coalbed gas is crucial to improve energy recovery and mitigate greenhouse gas emissions. In this study, three modification strategies were implemented on Zr-FUM, including ligand regulation, metal replacement, and ligand doping, to synthesize Zr-FDCA, Al-FUM, and Zr-FUM-FA, with the aim of improving the performance of CH4/N2 separation under humid conditions. The results demonstrated that the promotion of robust orbital overlap and strengthened electrovalent bonding on adsorbents can selectively enhance CH4 adsorption. As a result, Zr-FUM-FA achieved a saturated CH4 adsorption capacity of 1.37 mmol/g, a CH4 working window of 307 s, and a CH4/N2 sorbent selection parameter (Ssp) of 47.31, exceeding the performance of most reported adsorbents. Analyses of the pore structure, surface morphology, and functional groups revealed that the presence of an ultramicropore proximity to CH4, reduced static resistance, and enhanced electrovalent bond were key factors for CH4 separation. Grand Canonical Monte Carlo and Density Functional Theory studies indicated that the introduction of -C-H- in FA played a crucial role in enhancing CH4 adsorption. Optimization of adsorption parameters using the Aspen adsorption package showed that in a dual-adsorbent bed system, the recovery and purity of CH4 in Zr-FUM-FA reach 99.5% and 97.3%, respectively, providing important theoretical support for the improvement of CH4 recovery in the pressure swing adsorption process from coalbed gas.

Safety and Effectiveness of Acceleration Training as Cardiac Rehabilitation Immediately After Open Heart Surgery - A Pilot Study.

We examined the safety and efficacy of acceleration training (AT) in patients immediately after cardiac surgery. This randomized controlled study included patients who underwent open-heart surgery using cardiopulmonary bypass. Of these patients, 31 received regular cardiac rehabilitation (CR) and 39 received AT in addition to regular CR (AT group). AT was provided using a vibration platform (Power Plate®Pro7TMand Power plate®personal; Performance Health System, Chicago, IL, USA). The AT group performed 5 static resistance training sessions: squats, wide stance squats, toe stands, banded squats, and front lunges. Each vibration session lasted 30 s. We evaluated the short physical performance battery, anterior mid-thigh thickness, maximum voluntary isometric contraction of the knee extensors, and serum intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) concentrations as indicators of endothelial function. The observation period was during hospitalization and lasted approximately 20 days. No adverse events occurred during AT. Ultrasound revealed a significantly lower reduction in muscle mass at discharge in the AT group. No significant differences were observed in ICAM-1 and VCAM-1 concentrations between the 2 groups preoperatively, postoperatively, or at discharge. AT is considered safe and effective for patients immediately after open-heart surgery. AT, along with regular CR, may prevent skeletal muscle mass loss, muscle weakness, and physical function loss immediately after open-heart surgery.

Central and peripheral mechanisms underlying respiratory deficits in a mouse model of accelerated senescence.

Aging invariably decreases sensory and motor stimuli and affects several neuronal systems and their connectivity to key brain regions, including those involved in breathing. Nevertheless, further investigation is needed to fully comprehend the link between senescence and respiratory function. Here, we investigate whether a mouse model of accelerated senescence could develop central and peripheral respiratory abnormalities. Adult male Senescence Accelerated Mouse Prone 8 (SAMP8) and the control SAMR1 mice (10months old) were used. Ventilatory parameters were assessed by whole-body plethysmography, and measurements of respiratory input impedance were performed. SAMP8 mice exhibited a reduction in the density of neurokinin-1 receptor immunoreactivity in the entire ventral respiratory column. Physiological experiments showed that SAMP8 mice exhibited a decreased tachypneic response to hypoxia (FiO2 = 0.08; 10min) or hypercapnia (FiCO2 = 0.07; 10min). Additionally, the ventilatory response to hypercapnia increased further due to higher tidal volume. Measurements of respiratory mechanics in SAMP8 mice showed decreased static compliance (Cstat), inspiratory capacity (IC), resistance (Rn), and elastance (H) at different ages (3, 6, and 10months old). SAMP8 mice also have a decrease in contractile response to methacholine compared to SAMR1. In conclusion, our findings indicate that SAMP8 mice display a loss of the NK1-expressing neurons in the respiratory brainstem centers, along with impairments in both central and peripheral respiratory mechanisms. These observations suggest a potential impact on breathing in a senescence animal model.

Enhancement of mechanical and thermal properties of diamond particles via vanadium carbide coatings

Vanadium carbide coated diamonds were successfully fabricated by molten salt method. The effect of temperature (from 700 °C to 1000 °C) and molar ratio (carbon:vanadium, from 7:1 to 1:1) on the mechanical and thermal performance of vanadium carbide coatings and coated diamond particles were systematically investigated by SEM, EDS, XRD and XPS. The results showed that, compared with uncoated diamonds, the static compressive strength and oxidation resistance of the coated diamonds increased by 42.27 % and 158.82 °C, respectively. The vanadium carbide coatings were mainly composed of V2C and VC. As the temperature rose, the thickness of the coatings increased and cracks and holes appeared on the surface of the coating under thermal stress. With the increasing of the relative content of vanadium in raw materials, the crystal structure of vanadium carbide coatings changed from microcrystalline structure to reticular structure and the microcrystalline structure vanadium carbide coatings showed better performance.

Electrothermal-Assisted Photothermal Lubrication Surfaces for Continuous Anti-Icing/Deicing in Multiple Low-Temperature Environments.

Solving the problem of ice accumulation on solid surfaces is of great significance to the economic development of the country and the safety of people's lives. In this work, a coating with multifunctional photothermal/electrothermal solid-state lubrication (PEL) for anti-icing/deicing was prepared in layers based on the intrinsic properties of silicone oil and paraffin wax in combination with conductive graphite and multiwalled carbon nanotubes. Silicone oils and paraffins are used as lubricating media giving the coating excellent lubricity, which results in a water sliding angle (SA) of only 12° on the PEL surface. Meanwhile, PEL shows favorable static and dynamic ice resistance at low temperatures; at -10 °C, the freezing time of water droplets on the PEL surface is extended by at least 4 times compared to the bare substrate. Furthermore, PEL also offers highly efficient photothermal and electrothermal deicing performance, which can effectively remove the accumulated ice at a light intensity of 0.6 kW/m2 or an EPD of 0.1 W/cm2. Meanwhile, the synergistic deicing mechanism of photothermal and electrothermal was verified at -20 °C. Interestingly, the coating shows heat-assisted healing ability due to the phase change characteristic of paraffin wax, which allows the coating to regain lubricating properties after mechanical abrasion. Therefore, this work provides a reliable way for the design of stable all-weather anti-icing/deicing strategies at low temperatures.

Influence of remaining coronal tooth morphology with resin abutment and fiber post on static and dynamic fracture resistances.

This study aimed to clarify the fracture resistance of resin abutments built on endodontically treated roots with the remaining coronal teeth via static and cyclic loading tests. Endodontically treated bovine roots, which had a remaining coronal tooth covered with an occupied area for a quarter and half of the circumference at the tensile side or covered the circumference at both the tensile and compressive sides, were fabricated to build up to the resin abutment. Fracture resistance was evaluated via static and cyclic loading tests by applying a load of 30° to the tooth axis. Half of the circumference of the remaining coronal tooth showed a significantly higher static fracture load and survival rate. The remaining coronal tooth on the compressive side improved the dynamic fracture resistance associated with severe fractures. The occupied area and location of the remaining coronal tooth affected the static and dynamic fracture resistances.

Friction Investigation of Closed-Cell Aluminium Foam during Radial-Constrained Test.

The energy-absorbing capacity and friction phenomena of different closed-cell aluminium foam-filled Al tube types are investigated through experimental compression tests. Concerning the kind of investigation, free, radial-constrained and friction tests occurred. The radial-constrained compression test results confirm that the process requires significantly more compression energy than without the constrain. Pushing away different pre-compressed foams inside the aluminium tube, the static and kinematic frictional resistances can be determined and the energy required to move them can be calculated. Knowing the value of the energy required for the frictional resistance, we can obtain how much of the energy surplus in radially inhibited compression is caused by the friction phenomena. The main goal present study is to reveal the magnitude of friction between the foam and the wall of the tube during the radially constrained test. The investigation used 0.4 and 0.7 g/cm3 density closed-cell aluminium foam whilst a compressive test was applied where the force-displacement data were recorded to calculate the absorbed energy due to friction. Considering the results of the test, it can be stated that 18% of the invested energy was used to overcome friction in the case of lighter foam and almost 23% with 0.7 g/cm3 foam during the radial-constrained test.

Corrosion and tribological properties of ta-C/ta-C: Ta coatings: Analysis of the influence of Ta-O/Ta-C ratio

Multilayer ta-C/ta-C: Ta coatings with varying total thicknesses (300, 600, and 1000 nm) and layer thickness ratios (1:0.5, 1:1, and 1:2) between the ta-C layer and ta-C: Ta layer were prepared. The study investigated the static corrosion resistance and tribological properties of the coatings in the NaCl solution. The static corrosion resistance positive correlation depended on the coating surface's Ta-O/Ta-C ratio. The lowest friction coefficient of 0.05 was obtained from the coating with a total thickness of 1000 nm due to the formation of the graphitized transfer film on the counterpart surface. A decreased sp2/sp3 ratio and the formation of tantalum oxide on the wear scar contributed to the lowest corrosion current, corrosive defect density, and wear rate.

No antagonism or cross-resistance and a high barrier to the emergence of resistance in vitro for the combination of islatravir and lenacapavir.

Islatravir (ISL) is a deoxyadenosine analog that inhibits HIV-1 reverse transcription by multiple mechanisms. Lenacapavir (LEN) is a novel capsid inhibitor that inhibits HIV-1 at multiple stages throughout the viral life cycle. ISL and LEN are being investigated as once-weekly combination oral therapy for the treatment of HIV-1. Here, we characterized ISL and LEN in vitro to assess combinatorial antiviral activity, cytotoxicity, and the potential for interactions between the two compounds. Bliss analysis revealed ISL with LEN demonstrated additive inhibition of HIV-1 replication, with no evidence of antagonism across the range of concentrations tested. ISL exhibited potent antiviral activity against variants encoding known LEN resistance-associated mutations (RAMs) with or without the presence of M184V, an ISL RAM in reverse transcriptase (RT) . Static resistance selection experiments were conducted with ISL and LEN alone and in combination, initiating with either wild-type virus or virus containing the M184I RAM in RT to further assess their barrier to the emergence of resistance. The combination of ISL with LEN more effectively suppressed viral breakthrough at lower multiples of the compounds' IC50 (half-maximal inhibitory concentration) values and fewer mutations emerged with the combination compared to either compound on its own. The known pathways for development of resistance with ISL and LEN were not altered, and no novel single mutations emerged that substantially reduced susceptibility to either compound. The lack of antagonism and cross-resistance between ISL and LEN support the ongoing evaluation of the combination for treatment of HIV-1.

On Unusual Fractures Occurring under Testing Static Crack Resistance

On Unusual Fractures Occurring under Testing Static Crack Resistance