Search

A model for numerical homogenization of triply periodic minimal surfaces (TPMS) based on electrostrictive composites is presented. This electrostrictive composite consists of TPMS (a three-dimensional continuous structure) implanted in a soft non-electrostrictive matrix. A representative volume element (RVE)-based approach is used to homogenize the electrostrictive composites and determine all the effective electrostrictive, mechanical, and electrical coefficients. Finite element formulation is employed to solve the nonlinear electrostrictive constitutive equations. Special attention is paid to designing the boundary conditions that permit the fast calculation based on simulations of overall deformation-induced due to mechanical and electrical loads. Interestingly, the value of the effective electrostrictive coefficient of the composite surpasses that of the inclusion Pb (mg1/3Nb2/3)O3-PbTO3-BaTiO3 (PMN-PT-BT), even though the matrix is non-electrostrictive due to the additional flexibility imparted by the matrix. This electrostrictive response of TPMS-based composite is independent of the type of TPMS structures used. It is prudent to say that these composites will find their place in practical application owing to their salient features of more flexibility and high electrostrictive coefficient.

Chemotherapy is the first choice in the treatment of cancer and is always preferred to other approaches such as radiation and surgery, but it has never met the need of patients for a safe and effective drug. Therefore, new advances in cancer treatment are now needed to reduce the side effects and burdens associated with chemotherapy for cancer patients. Targeted treatment using nanotechnology are now being actively explored as they could effectively deliver therapeutic agents to tumor cells without affecting normal cells. Dendrimers are promising nanocarriers with distinct physiochemical properties that have received considerable attention in cancer therapy studies, which is partly due to the numerous functional groups on their surface. In this review, we discuss the progress of different types of dendrimers as delivery systems in cancer therapy, focusing on the challenges, opportunities, and functionalities of the polymeric molecules. The paper also reviews the various role of dendrimers in their entry into cells via endocytosis, as well as the molecular and inflammatory pathways in cancer. In addition, various dendrimers-based drug delivery (e.g., pH-responsive, enzyme-responsive, redox-responsive, thermo-responsive, etc.) and lipid-, amino acid-, polymer- and nanoparticle-based modifications for gene delivery, as well as co-delivery of drugs and genes in cancer therapy with dendrimers, are presented. Finally, biosafety concerns and issues hindering the transition of dendrimers from research to the clinic are discussed to shed light on their clinical applications.

Coalesce of photovoltaic effect with converse piezoelectric effect will turn into a photostrictive phenomenon. The current study conceptualizes a 1-3 photostrictive composite consists of a photovoltaic polymer as matrix and fibers of piezoelectric material. The proposed artificial photostrictive composite is capable of replacing lead-based naturally occurring photostrictive material, not only opening a potential for new applications but also caters to tailor the desired properties. Present study employs poly{4,8-bis[5-(2-ethyl-hexyl)thiophen-2-yl]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the fibers. A representative volume element technique (RVE) is employed to embrace the local variation of multi-physics properties. The actuation response of cantilever and simply supported beam bonded to photostrictive composite patch is accurately predicted by finite element method, while discretizing the structure with degenerated shell element. Photostrictive composite with 60% volume fraction of fibers, arranged in square pattern have deflected the cantilever tip to 1.95 mm. Therefore, we provide 1-3 photostrictive composite as a solution for future wireless and lightweight vibration control applications.

Somewhere in the June of 2018, I happened to visit a small village called Deoliya, near Jaipur, central Rajasthan, India. I came across a huge male gathering near the temple and was drawn to it. As...

The increasing obligatory demand for clean and environment-friendly alternates for refrigeration and air-conditioning has made solid-state refrigeration more alluring for researchers of the relevant fields. The flexocaloric effect is a mechanism providing solid-state refrigeration in mechanically loaded samples. In this work, we explore the potential of functionally graded (FG) dielectric material with Ba0.67Sr0.33TiO3 (BST) and polyvinylidene fluoride (PVDF) as its constituents to impart the cooling effect via the flexocaloric effect. A theoretical analysis based on the phenomenological thermodynamic theory of caloric effects is performed. The entropy and temperature changes (adiabatic) are derived by including flexoelectricity-induced polarization in Maxwell’s relation for the electrocaloric effect. An average temperature change of 1.82 K was achieved under an applied pressure of 100 MPa, which is not possible in conventionally used homogeneous trapezoid samples. The flexocaloric effect is observed to increase sharply with increasing load due to quadratic proportionality of temperature change with strain gradient. Further, the material composition can be tailored for increased entropy and temperature change by omitting the pure BST and PVDF phases at the top and bottom.

Commercial trucks are not always transporting goods at full capacity, which means that the box-shape trailer is partially occupied or even completely empty on occasions. In this work, we explore foldable trailer design to improve truck efficiency and sustainability. To achieve the folding feature we explore active compliant hinges in origami-inspired design. Active origami engineering relies on two-dimensional smart hinges able to interact in a three-dimensional design without external forces. The truck trailer is envisioned to be able to fold itself into an aerodynamic wedge shape when the trailer is (partially) empty. This design can be made lighter and more environmentally friendly than the original trailer design and the use of such a foldable trailer can reduce fuel consumption. Smart material layered hinges made from dielectric elastomers actuate the plastic faces of the construction to achieve the folding and deploying of the adaptable trailer design. Initial studies of geometry, materials, and actuation power as well as the potential for energy savings are presented. The drag coefficient is reduced by 33.77% when folded into an aerodynamic shape which leads to an annual decrease in fuel consumption of 6.32% for the average truck that drives around empty 20% of the time and 15.8% for one way transport trucks that drive around empty 50% of the time.

The present study proposes a 3-dimensional approach for enhancing the effective piezoelectric properties by poling orientation. The governing parameters for actuation and sensing applications are $$d_{31}$$ and $$d_{31} /\varepsilon_{33}$$ , respectively. The effective magnitudes of these parameters, i.e., $$ d_{31}^{{{\text{eff}}}}$$ and $$d_{31}^{{{\text{eff}}}} /\varepsilon_{33}^{{{\text{eff}}}}$$ , change with poling angles (roll and pitch angles). The combination of poling angles corresponding to the maximum magnitude of $$ d_{31}^{{{\text{eff}}}}$$ and $$d_{31}^{{{\text{eff}}}} /\varepsilon_{33}^{{{\text{eff}}}}$$ is called the optimum poling angle for piezoelectric materials. BaTiO3 and KNN piezoelectric materials with tetragonal symmetry show an enhancement in $$d_{31}^{{{\text{eff}}}} /\varepsilon_{33}^{{{\text{eff}}}}$$ and $$ d_{31}^{{{\text{eff}}}}$$ at an optimized poling angle (roll angle). The piezoelectric material, 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-0.33PT) with rhombohedral symmetry, shows a maximum improvement of 575% in $$d_{31}^{{{\text{eff}}}} /\varepsilon_{33}^{{{\text{eff}}}}$$ at an optimum roll angle of 29° and a pitch angle of 60°. On the other hand, PMN-0.33PT shows an enhancement of 2034.44% in the $$ d_{31}^{{{\text{eff}}}}$$ coefficient at optimum roll and pitch angles of 50° and 60°. The effect of poling orientation on different piezoelectric materials with tetragonal and rhombohedral symmetry has been studied for actuation and sensing applications. The experimental approach to achieve inclination of dipoles through the placement of electrodes for different piezoelectric materials is also discussed.

Simultaneous action of photovoltaic effect and converse piezoelectric effect will induce the photostrictive effect. In contrast to the naturally occurring photostrictive material, the present study proposes a 0-3 photostrictive composite. The current photostrictive composite comprises of poly{4,8-bis[5-(2-ethyl-hexyl) thiophen-2-yl] benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethyl-hexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer matrix and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the particulates. The current study shows that the present 0-3 photostrictive composite is a suitable alternative for the most popular lead-based photostrictive material. While evaluating all the effective elastic, dielectric, piezoelectric, and pyroelectric properties of 0-3 photostrictive composite, the effect of local fluctuations was incorporated in representative volume element (RVE) using the finite element method. A finite element formulation using a degenerated shell element is derived to simulate the actuation response of the proposed 0-3 photostrictive composite. Numerical studies have been performed on cantilever and simply supported beams. The maximum tip and center deflection of cantilever beam and simply supported beam bonded with 0-3 photostrictive patch is 9.75×10−4 mm and 1.22×10−4 mm, respectively. The maximum value of the effective piezoelectric coefficient d31eff, effective thermal expansion coefficient αeff, effective Young’s modulus E1eff, and effective pyroelectric coefficient peff of proposed 0-3 photostrictive composite are −3.81×10−13 m/V, 4.59×10−4 °C−1, 1.63×109 N/m2, and 7.57×10−5 C/m2 K, respectively, obtained at 25% volume fraction of particulates. This study opens possibilities of photostrictive coupling in composites.

Photostriction is a multiphysics phenomenon comprising of both photovoltaic effect and converse piezoelectric effect. The extensively researched photostrictive material is lead lanthanum zirconate titanate, i.e., Pb0.92La0.08(Zr0.65Ti0.35)0.98O3 (PLZT) ceramic. In contrast to the traditional approaches of improving deflection response, the current study proposes a 0–3 composite model to substantially enhance the effective material properties, which in turn significantly improves the deflection response. A computational framework based on finite element analysis is employed to 0–3 photostrictive composite of PLZT as matrix and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the inclusions. The representative volume element (RVE) or unit cell technique is used to incorporate the local variation of constituent properties and to calculate photostrictive properties such as effective elastic, dielectric, piezoelectric, and pyroelectric properties. An opto-electro-thermo-mechanical finite element formulation was engaged to get the actuation response of photostrictive material bonded to cantilever and simply supported beam. The maximum deflection for cantilever beam attached to photostrictive composite patch having 25% inclusions volume fraction in 0–3 composite is found to be 38% more in comparison to pure PLZT material. It is established that the opto-electro-mechanical 0–3 composite actuators possess high potential in lightweight, compact and wireless actuation applications.

This paper presents active vibration control of smart cantilever beam using poling tuned piezoelectric actuator. The vibrating response of piezo-laminated cantilever beam is modeled using a lumped ...

The field of surgical computer vision has undergone considerable breakthroughs in recent years with the rising popularity of deep neural network-based methods. However, standard fully-supervised approaches for training such models require vast amounts of annotated data, imposing a prohibitively high cost; especially in the clinical domain. Self-Supervised Learning (SSL) methods, which have begun to gain traction in the general computer vision community, represent a potential solution to these annotation costs, allowing to learn useful representations from only unlabeled data. Still, the effectiveness of SSL methods in more complex and impactful domains, such as medicine and surgery, remains limited and unexplored. In this work, we address this critical need by investigating four state-of-the-art SSL methods (MoCo v2, SimCLR, DINO, SwAV) in the context of surgical computer vision. We present an extensive analysis of the performance of these methods on the Cholec80 dataset for two fundamental and popular tasks in surgical context understanding, phase recognition and tool presence detection. We examine their parameterization, then their behavior with respect to training data quantities in semi-supervised settings. Correct transfer of these methods to surgery, as described and conducted in this work, leads to substantial performance gains over generic uses of SSL - up to 7.4% on phase recognition and 20% on tool presence detection - as well as state-of-the-art semi-supervised phase recognition approaches by up to 14%. Further results obtained on a highly diverse selection of surgical datasets exhibit strong generalization properties. The code is available at https://github.com/CAMMA-public/SelfSupSurg.

Improvement in operating characteristics of piezoelectric materials, one of the most extensively used dielectric materials, is a major focus of research among materials scientists. Present work puts forward, a novel approach for achieving enhanced piezoelectricity in ferroelectric materials by manipulating electrode placement during poling. Three unique poling configurations, abbreviated as PC1, PC2, and PC3 are developed for exploiting the dependence of effective piezoelectric properties on spatially varying poling direction. Finite element method based numerical simulations are performed to evaluate the electric field distribution, poling direction, and their effect on effective piezoelectric coupling coefficients of PMN–0.35PT (Pb(Mg1/3Nb2/3)O3–0.35PbTiO3) piezoelectric ceramic. A two-phase solution process is developed to evaluate the local orientation of dipoles for each poling configuration and subsequently computing effective piezoelectric properties of the material in an average sense. Parametric studies are carried out to analyze the effect of aspect ratio R of sample and electrode to sample length ratio, r on effective piezoelectric properties. PC1 yields an increase of up to 135% in the magnitude of the transverse coupling coefficient $$({e}_{31}^{eff})$$ and an 8% increase in effective longitudinal coupling coefficient $$({e}_{33}^{eff})$$ while PC2 is observed to exhibit a maximum enhancement of 164% in the magnitude of $${e}_{31}^{eff}$$ and 11.2% in the magnitude of $${e}_{33}^{eff}$$ . PC3, presented as a special case, yields zero values of piezoelectric coefficients in an average sense but can result in a highly elevated net output for bending applications, owing to favorable spatial variation in stresses and associated piezoelectric coefficients.

In this article, active vibration control of a piezo laminated smart structure is presented using poling tuned piezoelectric material. To improve the performance of existing materials and utilize the actuation potential of different modes of operation ( d31, d33, and d15), simultaneously, the poling direction of the piezoelectric materials is altered and an optimum poling direction is found. Poling tuned piezoelectric patches at the top and bottom layers of the structure are mounted which act as sensors and actuators, respectively. The computational technique used for calculating the time history of the structure is a finite element method. A fuzzy logic controller is developed to compute the appropriate actuator signal as output while taking sensor voltage and its derivative as input. The controlled response due to this fuzzy logic controller is calculated for different piezoelectric materials under consideration and the performance of these materials in active vibration control is compared. Influence of poling angle on the controlled response of the structure is scrutinized and is found to vary from material to material. A large enhancement due to poling tuning is seen in the properties of Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-0.35PT), whereas other materials show very less improvement or even decay in the properties.

Only a few piezoelectric materials interact with light owing to their wide bandgap, which leaves researchers with very few options. The high piezoelectric coupling coefficient of lead lanthanum zirconate titanate, i.e., PLZT (Pb0.92La0.08(Zr0.65Ti0.35)0.98O3), makes it very popular amongst the research fraternities. In this paper, piezoelectric coupling coefficient is further improved by designing a 1–3 composite of PLZT as matrix and fibers of PMN35PT (Pb(Mg1/3Nb2/3)O3–0.35PbTiO3). First, a finite element method is applied to representative volume elements of 1–3 photostrictive composites to determine the elastic, piezoelectric, pyroelectric, and thermal expansion coefficient. Secondly, degenerated shell element-based finite element formulation is used to simulate the actuation response of host structure bonded with 1–3 photostrictive composite, while prescribed with cantilever and simply supported boundary conditions. It is observed that the 1–3 composite of PLZT and PMN-35PT has 15% higher piezoelectric coupling coefficient and its pyroelectric coefficient is 7.5 times of PLZT material. Keeping the constant geometrical and boundary conditions, the structure equipped with the proposed 1–3 photostrictive composite produces a 74.8% enhanced actuation response.

The reviews have shown that regulatory governance increases the economic growth of the country that further improves the financial stability. Weak governance promotes a weak financial sector. It is established that there are several crises took place in ancient times because of failed policy (Greco, Ishizaka, Tasiou, & Torrisi, 2019; Kuc Czarnecka, Lo Piano, & Saltelli, 2020). The purpose of the research is to find out more about how weak governance can damage the economy of nations, and that is how it leads to financial instability. Besides, how good governance leads to economic stability can also be understood. The research problem presented in terms of the objective of the research is to find out the association between financial stability and regulatory governance for the selected nations under study. This is done by taking a sample of fifteen nations of the world. By taking selective indicators for regulatory governance and financial stability and applying the causality test, the association is checked. The results indicate a less significant association between regulatory governance and financial stability for nations under study. The results are relevant in continuously expanding global financial markets wherein emphasis is strong regulations.