Load Stability Research Articles

Multi-objective optimization of snap-through instability of helicoidal composite imperfect beams using Bernstein polynomials method

This paper deals with the multi-objective optimization problems of snap-through instability of geometrically imperfect simply supported helicoidal composite beam with nonlinear orientation schemes. The objective function is to maximize the load required to initiate snap-through and minimize the instability region. It is assumed that the curved bioinspired beam is embedded on nonlinear elastic foundation and is subjected to different types of lateral loads. The presented formulation is based on Euler-Bernoulli theory, nonlinear higher order strain, and imperfect curvature. Bernstein polynomials (BPs) method is employed to solve the nonlinear nonhomogeneous fourth order integro-differential governing equation. Developed model can considered the effect of imperfection, lamination scheme, and elastic foundation on the nonlinear deflection and snap-through behaviors of helicoidal composite structures. Analytical closed form formula of the nonlinear load-deflection relationship is developed. The analytical relation is validated by comparing it with exact solution and numerical results available in literature. Multi-objective particle swarm optimization (MOPSO) algorithm is employed to determine Pareto-optimal set for limiting load and region of instability. In these analyses, optimal lamination parameter, amplitude of imperfection and elastic foundation constants are found for helicoidal composite beam, and the results are presented as 2D Pareto-optimal design points.

Multi-Time-Scale Coordinated Optimum Scheduling Technique for a Multi-Source Complementary Power-Generating System with Uncertainty in the Source-Load

An optimal dispatching strategy for a multi-source complementary power generation system taking source–load uncertainty into account is proposed, in order to address the effects of large-scale intermittent renewable energy consumption and power load instability on power grid dispatching. The uncertainty problem is first converted into common situations for study, such as load power forecasting and solar and wind power. The backward scenario reduction and Latin hypercube sampling techniques are used to create these common situations. Based on this, a multi-timescale coordinated optimum scheduling control method for a multi-source complementary power generation system taking the demand response into account is presented, and the optimal operation of a wind–PV–thermal-pumped storage hybrid system is examined. The time-of-use power price optimizes the electrical load in the day-ahead pricing mode, and the two types of demand response loads are selected in the day-ahead scheduling. Second, the lowest system operating cost and the minimal day-ahead and intra-day adjustment of each source are established as the optimization targets in the day-ahead and intra-day phases of the multi-timescale coordinated scheduling model of the multi-source complementary system. The example study demonstrates that the scheduling strategy may increase the amount of renewable energy consumed, minimize load fluctuations, increase system stability, and further reduce operating expenses, proving the viability and efficiency of the suggested strategy.

Enhanced room temperature gas sensing performance of ZnO with atomic-level Pt catalysts facilitated by the polydopamine mediator

The poor sensitivity of metal-oxide (MO) sensing material at room temperature can be enhanced by the modification of noble metal catalysts. However, the large size and uncontrollable morphology of metal nanoparticles (NPs) compromise the catalytic activity and selectivity. Downsizing metal NPs to the atomic level is a promising solution because it offers high activity and selectivity. Nevertheless, a facile and universal approach for stable loading atomic-level metal on MO-based sensing materials is still challenging. Herein, we present a strategy to construct synergetic coordination interface for uniform loading of atomic-level metal catalysts on MO-based gas-sensing materials using a difunctional mediator layer. In this work, atomically dispersed Pt catalysts are coordinately anchored on ZnO nanorods (NRs) using polydopamine (PDA) as a mediator. As a result, compared with pristine ZnO NRs, a six-fold enhanced response of 18,489% is achieved toward 100 ppm NO2 on 0.20 wt%Pt–ZnO@PDA-1.5 nm, and the selectivity is also promoted. Such sensitivity is higher than that of most reported noble metal-modified MO NO2-sensing materials. This work provides a simple and general strategy for building highly sensitive and selective gas-sensing materials using atomic-level noble metal catalyst.

A reusable and leakage-proof immobilized laccase@UiO-66-NH2(30) for the efficient biodegradation of rifampicin and lincomycin

The enzyme leakage in physical adsorption dramatically limits the application of immobilized laccase (Lac) in environmental treatment. Therefore, a leakage-proof Zr-based metal-organic framework (MOF) carrier, UiO-66-NH2(30), was constructed for the stable loading of Lac and efficient antibiotic biodegradation, which could fix the Lac inside the carrier rather than only adsorbed on the surface. Based on the aperture modulation strategy, the pore size distribution of MOFs at about 10 nm was significantly increased to match the diameter of Lac (7.6 nm), by which Lac@UiO-66-NH2(30) was successfully prepared with a high enzyme loading amount (275.96 mg/g) and high enzyme recovery (618 %). The immobilized Lac@UiO-66-NH2(30) could nearly 100 % biodegrade rifampicin and lincomycin in 6 min and 6 h, respectively, and after 8 times reuse, the degradation rates of antibiotics remained at 81.46 % and 76.12 %, which showed excellent reusability and stability. Overall, Lac@UiO-66-NH2(30) is expected to be an ideal candidate for pollution control.

Bone-targeted bioengineered bacterial extracellular vesicles delivering siRNA to ameliorate osteoporosis

Osteoporosis (OP), characterized by decreased bone mass and destruction of bone microarchitecture, is the most common bone degenerative disease. Conventional treatments for OP have several side effects, new treatment approaches are needed. Bacterial extracellular vesicles (BEVs) carrying curative molecules have emerged as a promising alternative due to their unique nanosized structures, stable loading capacity, good biocompatibility, ease of modification, and industrialization. In this study, we modified probiotics Escherichia coli Nissle 1917 (ECN) to overexpress hCXCR4 fused with the ClyA on the membrane surface of BEVs. The bone targeted BEVs took advantage of the intrinsic anti-OP function and loaded with SOST siRNA to generate BEVs-hCXCR4-SOST siRNA (BEVs-CSs). The customized BEVs-CSs have exhibited great bone targeting ability without long-term cytotoxicity. In addition, the bioengineered BEVs-CSs can be internalized by bone marrow mesenchymal stem cell and promote their osteogenic differentiation with significant cytocompatibility. Finally, the bifunctional BEVs-CSs successfully reversed the OP in an ovariectomized mouse model. Taken together, such a bioengineered BEVs-based strategy provides an innovative, safe, efficient and promising therapeutic solution for intractable OP treatment.

A study on the dynamic instability of CFST arches with spatial curvature differences

With the rapid development of the construction technology of concrete-filled steel tube (CFST) arch bridges, the width-span and width-to-height ratios continue to increase, which cause stability problems, especially for the dynamic stability. The current Budiansky-Roth criterion (B-R criterion) and the energy criterion are hard to use and cannot be quantitatively described. Therefore, a CFST arch dynamic instability criterion by the difference in spatial curvature based on the changes in fiber strains is proposed in this paper. Firstly, the critical spatial curvature difference is derived based on the structural characteristics of CFST arches and is the threshold value of the dynamic stability discrimination. Then, the calculation format of the CFST arches’ dynamic instability criterion is established by the central difference method, and the calculation procedure is programmed. Furtherly, the accuracy of the proposed critical curvature difference method is validated by the instability-induced failure experiments. In addition, the discrimination results of instability-induced failure experiments are also obtained by B-R criterion as well as the energy criterion. The discrimination result of the proposed critical curvature difference method is consistent with those of B-R criterion and energy criterion. Moreover, the method proposed quantifies the critical load of dynamic instability into the threshold index by the critical curvature difference and has easy-to-measure parameters as well as easy to operate, which are more suitable for the engineering applications compared with other methods.

Copper(I)-Iodide Clusters as Carriers for Regulating and Visualizing Release of Aroma Molecules.

Achieving the controlled release of functional substances is indispensable in many aspects of life. Especially for the aroma molecules, their effective delivery of flavor and fragrance is challenging. Here, selected pyridines, as highly volatile odorants, were individually coordinated with copper(I) iodide (CuII) via a straightforward one-pot synthesis method, rapidly forming pure or even crystalline CuII cluster-based profragrances at room temperature. The obtained profragrances enabled the stable and high loading of volatile fragrances under ambient conditions and guaranteed their long-lasting release during heating. Furthermore, the intrinsic emission luminescence of these solid-state profragrances decayed along with the aroma release, which can serve as an additional indicator for monitoring the delivery process. This research sets a precedent for using CuII clusters as dual-purpose release agents and greatly expands their potential applications.

Efficient photothermal conversion for oxidation removal of formaldehyde using an rGO-CeO2 modified nickel foam monolithic catalyst

Photocatalysis is a feasible method for degrading indoor formaldehyde (HCHO) pollutants. To improve the purification efficiency and lower the cost of using noble metals as the primary component of the catalyst, synergistic catalysis involving two catalytic modes, such as thermocatalysis/photocatalysis, has attracted significant attention. In this study, a monolithic catalyst was prepared by loading reduced graphene oxide (rGO) and cerium dioxide (CeO2) on a nickel foam (NF) matrix. It was observed that the HCHO removal efficiency could be > 93 % under xenon light. The pre-deposited rGO on the NF matrix served as the photothermal conversion layer and contributed to the uniform and stable loading of CeO2. The surface temperature of this synthesized monolithic catalyst could rapidly rise to 170 °C. In addition, the heat was distributed evenly because of the increased near-infrared (NIR) light absorption caused by the added rGO and high electron mobility owing to the heat-conducting property of NF. At this temperature, the oxidation of HCHO was stimulated not only by the lattice oxygen of CeO2 but also by the production of O2– via oxidation by photogenerated electrons. In addition, O2– would reoxidize Ce3+ to Ce4+ on oxygen vacancies and accelerate the lattice oxygen consumption and supply cycle to reinforce the existing Mars-van Krevelen (MvK) mechanism.

Mucopenetrating Janus Nanoparticles For Field-Coverage Oral Cancer Chemoprevention

IntroductionOral squamous cell carcinoma (OSCC), is associated with high morbidity and mortality. Preemptive interventions have been postulated to provide superior therapeutic options, but their implementation has been restricted by the availability of broadly applicable local delivery systems.MethodsWe address this challenge by engineering a delivery vehicle, Janus nanoparticles (JNP), that combine the dual mucoadhesive properties of a first cationic chitosan compartment with a second hydrophobic poly(lactide-co-glycolide) release compartment. JNP are designed to avoid rapid mucus clearance while ensuring stable loading and controlled release of the IL-6 receptor antagonist, tocilizumab (TCZ).ResultsThe JNP featured defined and monodispersed sizes with an average diameter of 327 nm and a PDI of 0.245, high circularities above 0.90 and supported controlled release of TCZ and effective internalization by oral keratinocytes. TCZ released from JNP retained its biological activity and effectively reduced both, soluble and membrane-bound IL-6Rα (71% and 50%). In full-thickness oral mucosal explants, 76% of the JNP breached the stratum corneum and in 41% were observed in the basal cell layer indicating excellent mucopenetrating properties. When tested in an aggressive OSCC xenograft model, TCZ-loaded JNP showed high levels of xenograft inhibition and outperformed all control groups with respect to inhibition of tumor cell proliferation, reduction in tumor size and reduced expression of the proto-oncogene ERG.ConclusionBy combining critically required, yet orthogonal properties within the same nanoparticle design, the JNP in this study, demonstrate promise as precision delivery platforms for intraoral field-coverage chemoprevention, a vastly under-researched area of high clinical importance.

Enzyme/GSH/pH-responsive hyaluronic acid grafted porous silica nanocarriers bearing Ag2S QDs for fluorescence imaging and combined therapy

Hyaluronic acid (HA) is a naturally polysaccharide that has been used for drug delivery, but is limited by low drug loading capacity and drug leakage in circulation. To improve drug delivery efficient, HA modified porous silica (pSiO2) nanocarriers were successfully prepared for drug delivery and combining therapy. pSiO2 nanocarriers have stable porous structure and high loading capacity, and pSiO2/HA nanocarriers would possess advantages of HA-based carriers and pSiO2 nanoparticles. Herein, pSiO2 nanocarriers were prepared by two-phase process, followed by embedding Ag2S QDs in the pore walls of pSiO2 carriers, which render the carriers photothermal effect. pSiO2 nanocarriers have size of 30 nm, large channels, and high loading capacity (29.3 %). To graft HA, a sensitive linker with alkyl amine and disulfide bond was conjugated on the surface of Ag2S/pSiO2 nanocarriers by three-step reaction. After loading doxorubicin (DOX), HA was grafted via sensitive linker onto the surface of Ag2S/pSiO2 carriers via the formation of amide bonds to seal the loaded drugs. The interaction between HA and CD44 confers the carrier targeting ability to cancer cells. HA coating can be degraded by hyaluronidase resulting in the release of internal cargo. The Ag2S/pSiO2/HA nanocarriers performs responsive drug release and combining photothermal chemotherapy.

An In-Situ Low Temperature-Mechanical Coupling Test System for Battery Materials

The mechanical properties of battery materials under actual service conditions are crucial for the safety and durability of batteries, but specialized systems which are able to carry out in-situ low temperature-mechanical coupling testing of battery materials are lacking. In the present work, a low temperature-mechanical coupling test system for battery materials is developed to investigate the mechanical properties of battery materials under low-temperature conditions. A semi-enclosed stable low-temperature loading unit is built by using high-power Peltier coolers and a double circulating water cooling system, which facilitates the observation of the changes in morphology and temperature of battery materials at different low temperatures. Based on the proposed double circulating water cooling system, a target temperature of -40 °C with maximum fluctuation lower than ±0.40 °C was realized within a rapid refrigeration time of 112 seconds. Through in-situ tensile tests of typical lithium-ion battery separators at temperatures in a range from -40 °C to 20 °C, the load-displacement response and the brittleness trend of the separators with the decrease of temperature are confirmed, which verify the low-temperature loading capacity and testing function of the proposed system. Compared with the separators at 20 °C, the strain to fracture and fracture energy under -40 °C decreased by 29.3% and 15.2%, respectively.

Organoid extracellular vesicle-based therapeutic strategies for bone therapy.

With the rapid development of population ageing, bone-related diseases seriously affecting the life of the elderly. Over the past few years, organoids, cell clusters with specific functions and structures that are self-induced from stem cells after three-dimensional culture in vitro, have been widely used for bone therapy. Moreover, organoid extracellular vesicles (OEVs) have emerging as promising cell-free nanocarriers due to their vigoroso physiological effects, significant biological functions, stable loading capacity, and great biocompatibility. In this review, we first provide a comprehensive overview of biogenesis, internalisation, isolation, and characterisation of OEVs. We then comprehensively highlight the differences between OEVs and traditional EVs. Subsequently, we present the applications of natural OEVs in disease treatment. We also summarise the engineering modifications of OEVs, including engineering parental cells and engineering OEVs after isolation. Moreover, we provide an outlook on the potential of natural and engineered OEVs in bone-related diseases. Finally, we critically discuss the advantages and challenges of OEVs in the treatment of bone diseases. We believe that a comprehensive discussion of OEVs will provide more innovative and efficient solutions for complex bone diseases.

Development and Characterizations of Novel Aqueous-Based Ceramic Inks for Inkjet Printing.

Stable rheological properties of ceramic ink are a key requirement for inkjet printing (IJP), which should be satisfied in terms of the Reynolds and Weber numbers. In this paper, the reverse microemulsion was introduced for the synthesis of monodispersed nanosized ceramic powders, and the average size was less than 100 nm. A comparison of two different dispersants, i.e., polyacrylic ammonium (PAANH4) and polyacrylic aid (PAA), revealed that the former exerted a good dispersion effect on the ceramic ink. The sedimentation ratio, zeta potential, surface tension, viscosity, and density of the inks were measured, and the Reynolds and Weber numbers, as well as Z value, were calculated. A stable, homogeneous, and high solid loading (20 wt%) ceramic ink could be achieved after aging for a period of 72 h. Finally, the ceramic inks showed the desired printable property in the inkjet printing process. Combining inkjet printing technology with a sintering process, Ni-Mn-O films have the potential to monitor temperature and humidity parameters for intelligent wearable devices.

Printed, wearable e-skin force sensor array

The need to develop electronic skin (e-skin) for robotics is essential to provide a sense of touch on a large area, the same as human skin. This paper reports the design and development of printed e-skin force sensor arrays. The performance analysis of these capacitive force sensor arrays showed a resolution of 2.5 sq. mm, localization accuracy of 99% and a sensitivity of 0.53 pF/N. The sensor patches provided significant force sensitivity and stable loading and unloading for static force. A graphical user interface is developed in open-source python software. An unsupervised machine learning algorithm trains the tactile e-skin system for different user styles to distinguish the cluster of lower and higher touch angles for improving accuracy. The proposed e-skin sensor finds application in large-area sensors and gripper pads for prosthetics in biomedical devices where the sense of touch and high resolution is needed.

Fracture characteristics analysis of FRP-reinforced concrete based on acoustic emission

To study the acoustic emission (AE) characteristics of fibre-reinforced polymer (FRP)-reinforced concrete during the fracture process, three-point bending tests of FRP-reinforced concrete beams with cracks were carried out. The AE characteristics of FRP-reinforced concrete beams with different bonding lengths and different bonding layers were analysed based on the AE parameters, and the effect of the fracture parameters was studied. The test results reveal that the crack initiation load and peak load of single-layer FRP-reinforced concrete beams first increase and then decrease with the increase of bonding length. The failure mode of multi-layer FRP-reinforced concrete beams is a kind of dangerous brittle failure, which easily forms the ‘super-reinforcement failure’ mode. The ductility of single-layer FRP-reinforced concrete beams with a bonding length of 25 cm is optimal, which can effectively delay crack propagation. By combining the load–time curves, AE ringing count–time curves and AE energy–time curves, the time points of crack initiation load and instability load can be accurately determined. The analysis of RA–AF (ratio of ringing count to duration–ratio of rise time to maximum amplitude) and clearance factor index can be used to evaluate the damage state of FRP-reinforced concrete beams.

Instability load analysis of a telescopic boom for an all-terrain crane

Abstract. The instability load for the telescopic boom of an all-terrain crane is investigated in this paper. Combined with structural characteristics of the telescopic boom, each boom section is divided into several substructures, and the fixed-body coordinate system of each substructure is established based on the co-rotational method. A 3D Euler–Bernoulli eccentric beam element of the telescopic boom is derived. On the premise of considering the discretization of gravity and wind load, internal degrees of freedom of the substructure are condensed to the boundary nodes, forming a geometrical nonlinear super element. According to the nesting mode of the telescopic boom, a constraint way is established. The unstressed original length of the guy rope is calculated with a given preload so as to establish the equilibrium equations of the boom system with the external force of the guy rope and the corresponding tangent stiffness matrix. Regarding the above work, a new method for calculating the structural equilibrium path and instability load of telescopic boom structure is presented by solving the governing equations in a differential form. Finally, the method is validated by examples with different features.

Principal Component Analysis and Exploratory Factor Analysis of the Mechanical Waves Conceptual Survey

Mechanical waves conceptual survey (MWCS) is a measurement tool established by the physics education research (PER) community to evaluate conceptual physics understanding of mechanical waves. A validation study is still needed to figure out the factor structure of MWCS using two data reduction techniques, namely exploratory factor analysis (EFA) and principal component analysis (PCA). The MWCS dataset in this paper was gathered from physics students (n = 419) from nineteen Ugandan secondary schools. The findings of this research suggested the single factor of the MWCS construct that has emerged from the dataset explored in this study. Several issues involved in the calculation of inter-item correlation within the dataset are suspected as the leading cause of the missing component solution or stable loading in the data. Moreover, there might be other issues that leave open space for future exploration. The findings reported in this paper could be the subject of further discussion in evaluating the validity of the MWCS as a research-based assessment (RBA) to measure students' conceptual understanding of wave mechanics within PER studies.

Incorporating self-healing capability in temperature-sensitive hydrogels by non-covalent chitosan crosslinkers

Through the use of non-covalent chitosan (CS) crosslinkers, reversible yet strong non-covalent interactions are introduced into the poly-N-isopropylacrylamide (PNIPAM) temperature-sensitive hydrogel, which renders desirable mechanical properties, biocompatibility, and most importantly high-level self-healing capability, in combination of facile temperature response near body temperature for drug loading/release. Best overall performance is then reached by optimizing the formulation of CS, N-isopropylacrylamide (NIPAM), acrylic acid (PAA), and acrylamide (AM) in the CS-g-P(NIPAM-AM-AA) graft copolymer system. By virtue of quantum chemical calculations, the nature of a variety of non-covalent interactions within the hydrogel framework is uncovered, those of which between CS and PAM units is found to be superiorly strong, being predominately responsible for the excellent self-healing capability. Synthesis of the hydrogel system simply requires a single-step one-pot procedure, where low cost of all components and the production process is guaranteed. After a series of synthetic optimizations, we notice that hydrogel with NIPAM/AM = 7/1 have the lower critical solution temperature (LCST, 37 °C) corresponding to human body temperature, elongation at break of more than 1500%, strain recovery ratio and stress recovery ratio of 92.89% and 96.15%, remarkable biocompatibility and can provide a good and stable drug loading and release platform. In a nutshell, this study provides a low-cost yet highly viable approach for self-healable thermosensitive hydrogels with biocompatibility, which is appropriate for commercial uses.

Effects of initial stress anisotropy on the onset of undrained instability for Guamo sand

Undrained instability is a failure mode that has been observed in many sandy slopes. However, the highly anisotropic stress states caused by the geometry of the slope have not been duly considered from the experimental point of view. This article studies the influence of the initial stress anisotropy of laboratory samples on the static undrained instability of the Colombian reference sand. Forty-five consolidated undrained triaxial tests were performed, prescribing combinations of different initial void ratios, mean confining pressure, and initial stress ratios. Experimental results allow concluding that: a. the size of the instability zone on the p′ − q plane becomes smaller for larger initial anisotropic stress ratios; b. a novel undrained instability plane can be proposed in the p′ − q − e space to set a boundary between stable and unstable undrained loading conditions; c. mean confining pressure plays a vital role in the estimation of undrained instability for Guamo sand samples under low and medium confining stresses; d. despite multiple factors that influence the onset of undrained instability, a relation can be derived between the undrained instability susceptibility of sandy slopes and the initial stress ratio η0.

On the nonlinear post-critical responses of VAT sandwich beams with variable stiffness composite skins under axial compression

In this article, the nonlinear post-critical problem of Variable Angle Tow (VAT) sandwich beams with variable stiffness composite skins under axial compression is studied for the first time. The present sandwich beam model is constructed from a modified version of extended high-order sandwich panel theory (EHSAPT), in which the first-order shear deformation theory with von Kármán’s strain–displacement relation is utilized for the skin layer, whereas the high-order theory with linear strain–displacement is applied to characterize the deformation of the core layer. Based on the principal of virtual work, a system of differential equations with variable coefficients is firstly formulated for the postbuckling problem of VAT sandwich beams with variable stiffness composite skins under plane-strain state. Meanwhile, a more efficient Rayleigh–Ritz approach combined with variational formulas is employed to derive the nonlinear algebraic equations in weak forms, and thereafter a sophisticated path-tracing technique is applied to determine the postbuckling equilibrium path. Both super-critical and sub-critical postbuckling states of VAT sandwich beams can be readily captured under the present analytical model framework. The accuracy and effectiveness of the developed Rayleigh–Ritz procedure are validated by comparing against the results available in literature. Effects of variation in skin stiffness on both the critical instability and post-critical behaviours of VAT sandwich beams are discussed in numerical examples. It is found that the change in skin stiffness plays a determinative role in the formation of nonperiodic wrinkling patterns of VAT sandwich beams. In addition, the change in skin stiffness may cause global and local instability loads to be close to each other, and accordingly, the possibility of encountering interactive buckling is increased. The results presented herein may be beneficial for the design of VAT sandwich structures under compression.