In this study, a Trefftz collocation method (TCM) is proposed for modeling multiple interacting cylindrical nanofibers with the Steigmann-Ogden interface model. The Trefftz trial displacement fields are assumed in terms of the Papkovich-Neuber (P-N) solutions with the cylindrical harmonics as P-N potentials. The non-singular and singular harmonic functions from multiple source points are included for investigating multiple interacting nanofibers. The displacement continuity and the stress jump across the matrix/nanofiber interfaces and the boundary conditions are satisfied by the collocation method. To avoid the ill-conditioning of the resulting system of equations, a two-step scaling method is implemented: first, three characteristic lengths are introduced to scale the Trefftz trial functions; and second, a multi-scale characteristic length is adopted to scale each column of the coefficient matrix to equalize the norm. The good agreements between the numerical results and analytical solutions demonstrate the accuracy of the proposed method in simulating the interface effects of nanofiber composites. The numerical results reveal that the stress distributions in nanofibers are significantly size-dependent, which are influenced by interface elasticity parameters. Besides, the interactions of multiple nanofibers are also studied. The TCM developed in this work can be contributed to the design of advanced nanofiber composites.

For the integrated design of composite material and structures, it is essential to have an effective micromechanical numerical tool to link macroscopic material properties to microstructural configurations. In this paper, 3D computational grains (CGs) with embedded fibers are proposed for the first time, for the direct micromechanical modeling of fiber composites. The microstructure of a unidirectional lamina with random fibers can be assembled by many CGs, and the stiffness matrix of each CG with an embedded fiber can be directly computed by combining two new algorithms. On one hand, a new kind of Trefftz trial displacement field based on scaled cylindrical harmonics is independently assumed, in addition to inter-elemental displacement interpolations with surface nodal degrees of freedom (DoFs). On the other hand, a new kind of multi-field boundary variational principle is proposed to relate independently assumed Trefftz fields to nodal DoFs and to derive the stiffness matrix. Numerical examples demonstrate that without the traditional fine meshing, accurate distribution of micro-stresses in a representative volume element (RVE) with thousands of fibers can be directly computed, and the equivalent orthotropic properties of fiber composites can be predicted. This is also the first time that a three-dimensional finite element with an embedded fiber is developed.

BACKGROUND Bactrocera dorsalis is a devastating pest on fruits and vegetables because the adult female is the key factor that determines the population density of offspring and the degree of host damage. Unfortunately, there is still a lack of effective female attractants for behavioral control. Males of B. dorsalis fed on methyl eugenol (ME) were shown to be more sexually attracted to females and, therefore, were more successful in mating over ME-deprived males. RESULTS In the current study, we demonstrated that (E)-coniferyl alcohol (E-CF), one of the ME metabolites in males, was highly attractive to sexually-mature females in laboratory bioassays. During the dusk courtship period, mature females showed the highest response to E-CF. However, there were no significant differences in olfactory responses to E-CF between virgin and mated mature females. Moreover, no obvious signs and symptoms of toxicity or death were observed in mice during a 14-day acute oral toxicity test. Toxicologically, no significant changes were observed in body weight, water intake, food consumption and absolute and relative organ weights between control and treated groups of healthy-looking mice, implying that E-CF could be regarded as non-toxic. Furthermore, cytotoxicity assessment revealed that E-CF was non-toxic against human fetal lung fibroblast 1 (HFL1), human breast cancer (MDA-MB-231), mouse embryonic hepatocytes (BNL-CL.2) and Spodoptera frugiperda ovary (SF-9) cell lines. CONCLUSIONS E-CF proved to be an effective, promising and eco-friendly lure to B. dorsalis females. Therefore, this study may facilitate the development of novel control strategies against B. dorsalis in the field.

In this study, analytical micromechanical models are developed for nanocomposites with both interface stretching and bending effects. First, the interior and exterior Eshelby tensors for a spherical nano-inclusion, with an interface defined by the Steigmann–Ogden (S–O) model, subjected to an arbitrary uniform eigenstrain are derived. Correspondingly, the stress/strain concentration tensors for a spherical nano-inhomogeneity subjected to arbitrary uniform far-field stress/strain loadings are also derived. Using the obtained concentration tensors, the effective bulk and shear moduli are derived by employing the dilute approximation and the Mori–Tanaka method, respectively, which can be used for both nano-composites and nano-porous materials. An equivalent interface curvature parameter reflecting the influence of the interface bending resistance is found, which can significantly simplify the complex expressions of the effective properties. In addition to size-dependency, the closed form expressions show that the effective bulk modulus is invariant to interface bending resistance parameters, in contrast to the effective shear modulus. We also put forward a characteristic interface curvature parameter, near which the effective shear modulus is affected significantly. Numerical results show that the effective shear moduli of nano-composites and nano-porous materials can be greatly improved by an appropriate surface modification. Finally, the derived effective modulus with the S–O interface model is provided in the supplemental MATLAB code, which can be easily executed, and used as a benchmark for semi-analytical solutions and numerical solutions in future studies.

Males of the Oriental fruit fly Bactrocera dorsalis (Hendel) are highly attracted to, and compulsively feed, on methyl eugenol (ME). ME is converted into 2-allyl-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (E-CF), which are temporarily sequestered in the fly’s rectal gland prior to being released at dusk. Previous research initially confirmed that DMP is a relatively strong lure to B. dorsalis males. However, the characteristics of males’ response to DMP and toxicology of DMP remains largely unclear. In our study, we demonstrated that DMP was more attractive to sexually mature males than E-CF tested in laboratory bioassays. Interestingly, the responsiveness of mature males to DMP was not uniform throughout the day, eliciting the highest response during the day and dropping to a low level at night. Furthermore, there were no significant differences between the olfactory responses of virgin and mated mature males to DMP. No obvious signs of toxic symptom and deaths were observed in mice during a 14-day acute oral toxicity testing. Further, toxicologically significant changes were not observed in body weight, water intake, food consumption, and absolute and relative organ weights between control and treated groups, implying DMP could be regarded as nontoxic. Lastly, the cytotoxicity data of DMP on cells showed that it exhibited no significant cytotoxicity to normal human and mouse cells. Taken together, results from both the acute and cellular toxicity experiments demonstrated the nontoxic nature of DMP. In conclusion, DMP shows promise as an effective and eco-friendly lure for B. dorsalis males, and may contribute to controlling B. dorsalis in the flied.

Building footprints data is of importance in several urban applications and natural disaster management. In contrast to traditional surveying and mapping, using high spatial resolution aerial images, deep learning-based building footprints extraction methods can extract building footprints accurately and efficiently. With rapidly development of deep learning methods, it is hard for novice to harness the powerful tools in building footprints extraction. The paper aims at providing the whole process of building footprints extraction from high spatial resolution images using deep learning-based methods. In addition, we also compare the commonly used methods, including Fully Convolutional Networks (FCN)-8s, U-Net and DeepLabv3+. At the end of the work, we change the data size used in models training to explore the influence of data size to the performance of the algorithms. The experiments show that, in different data size, DeepLabv3+ is the best algorithm among them with the highest accuracy and moderate efficiency; FCN-8s has the worst accuracy and highest efficiency; U-Net shows the moderate accuracy and lowest efficiency. In addition, with more training data, algorithms converged faster with higher accuracy in extraction results.

Building rooftop data are of importance in several urban applications and in natural disaster management. In contrast to traditional surveying and mapping, by using high spatial resolution aerial images, deep learning-based building rooftops extraction methods are efficient and accurate. Although more training data is preferred in deep learning-based tasks, the effect of data volume on building extraction models is underexplored. Therefore, the paper explores the impact of data volume on the performance of building rooftop extraction from very-high-spatial-resolution (VHSR) images using deep learning-based methods. To do so, we manually labelled 0.12m spatial resolution aerial images and perform a comparative analysis of models trained on datasets of different sizes using popular deep learning architectures for segmentation tasks, including Fully Convolutional Networks (FCN)-8s, U-Net and DeepLabv3+. The experiments showed that with more training data, algorithms converged faster and achieved higher accuracy, while better algorithms were able to better mitigate the lack of training data.

Driven by the promising applications of nano-composites, the Steigmann-Ogden (S-O) interface stress model is used together with the classical Elasticity theory to model the effective mechanical properties of nano-composites, considering both interface stretching and bending effects. However, no literature has been reported on analytical or numerical solutions for composites containing multiple three-dimensional nano-inclusions with S-O interfaces. In order to overcome this difficulty, a new type of computational grain (CG) is developed with an embedded spherical inclusion and S-O matrix/inclusion interface. The stiffness matrix of each CG is computed by a new boundary-type multifield variational principle together with Papkovich-Neuber potentials. By evaluating and assembling stiffness matrices of CGs along with parallel computations, very efficient direct numerical simulations of complex nano-composites with a large number of inclusions in a Representative Volume Element of the nanocomposite are essentially realized. Numerical examples demonstrate the validity and the power of the currently developed CGs. Especially, material models with 10,000 nano-inclusions are simulated in around 50 min on the 16-core workstation. The influence of interface elastic bending parameters and spatial distributions of the nano-inclusions on the overall properties of nano-composites is also investigated in this study.

This paper introduces the design and implementation of multi-channel high speed transceiver system for P-L band radar.The system adopts high speed AD/DA chips to realize the RF direct generation and sampling of arbitrary waveform signals in the range of 2GHz. By adjusting the relative trigger relationship between the system clock and the control logic, the synchronization design of each channel's ...

In this study, computational grains (CGs) are developed for micromechanical modelling of heterogeneous materials with nanoscale inhomogeneities, considering the interface stress effect. Each two-dimensional CG, which is a virtual or mathematically defined finite-sized geometrical domain of a polygonal shape, can include a circular elastic nano inclusion. In the present model, along the outer-boundary of each CG an inter-CG compatible displacement field is assumed, while independent Trefftz trial functions are assumed as displacement fields inside the matrix and the inclusion within each CG. Complex potentials scaled by characteristic lengths are used to derive the Trefftz trial displacement fields in the matrix as well as the inclusion. The stress jump across the matrix/inclusion interface is described by the generalized Young–Laplace equation, which is enforced in a weak sense by Lagrange multipliers in a newly-developed boundary-only-type multi-field boundary variational principle. A parallel algorithm is introduced to further accelerate the computation when modelling an RVE containing a large number of nano-inclusions. Numerical examples for problems of a single, multiple, and a large number of nanoscale inhomogeneities are given to demonstrate the validity and the power of the currently developed CG model for nanomechanics.

An explicit solution, considering the interface bending resistance as described by the Steigmann–Ogden interface model, is derived for the problem of a spherical nano-inhomogeneity (nanoscale void/inclusion) embedded in an infinite linear-elastic matrix under a general uniform far-field-stress (including tensile and shear stresses). The Papkovich-Neuber (P-N) general solutions, which are expressed in terms of spherical harmonics, are used to derive the analytical solution. A superposition technique is used to overcome the mathematical complexity brought on by the assumed interfacial residual stress in the Steigmann-Ogden interface model. Numerical examples show that the stress field, considering the interface bending resistance as with the Steigmann–Ogden interface model, differs significantly from that considering only the interface stretching resistance as with the Gurtin–Murdoch interface model. In addition to the size-dependency, another interesting phenomenon is observed: some stress components are invariant to interface bending stiffness parameters along a certain circle in the inclusion/matrix. Moreover, a characteristic line for the interface bending stiffness parameters is presented, near which the stress concentration becomes quite severe. Finally, the derived analytical solution with the Steigmann–Ogden interface model is provided in the supplemental MATLAB code, which can be easily executed, and used as a benchmark for semi-analytical solutions and numerical solutions in future studies.

Two-dimensional code plays an important role in the tobacco industry. In this study, the recognition and correlation detection of two-dimensional code spray printing information were studied, and a two-dimensional code association detection device was designed, which could realize the recognition of two-dimensional code on the cigarette packet and the detection of packet-bar association. The device was tested. After two tests, it was found that the recognition rate of cigarette packet reached 99.46% and 99.97%, respectively; most of the unrecognized cases were caused by operation errors; the correct rate of packet-bar association reached 100%; the correct packet-bar association could also be realized under three artificial abnormal conditions. The test results show that the device has excellent accuracy and stability and can be further applied in practice.

In this study, the fundamental framework of analytical micromechanics is generalized to consider nano-composites with both interface stretching and bending effects. The interior and exterior Eshelby tensors for a spherical nano-inclusion, with an interface defined by the Steigmann-Ogden model, subjected to an arbitrary uniform eigenstrain are derived for the first time. Correspondingly, the stress/strain concentration tensors for a spherical nano-inhomogeneity subjected to arbitrary uniform far-field stress/strain loadings are also derived. Using the obtained concentration tensors, the effective bulk and shear moduli are derived by employing the dilute approximation and the Mori-Tanaka method, respectively, which can be used for both nano-composites and nano-porous materials. An equivalent interface curvature parameter reflecting the influence of the interface bending resistance is found, which can significantly simplify the complex expressions of the effective properties. In addition to size-dependency, the closed form expressions show that the effective bulk modulus is invariant to interface bending resistance parameters, in contrast to the effective shear modulus. We also put forward for the first time a characteristic interface curvature parameter, near which the effective shear modulus is affected significantly. Numerical results show that the effective shear moduli of nano-composites and nano-porous materials can be greatly improved by an appropriate surface modification. Finally, the derived effective modulus with the Steigmann-Ogden interface model is provided in the supplemental MATLAB code, which can be easily executed, and used as a benchmark for semi-analytical solutions and numerical solutions in future studies.

Design and synthesis of efficient bifunctional electrocatalysts for both oxygen reduction reaction and oxygen evolution reactions are of great significant for metal-air batteries. In this work, bifunctional catalysts consisting of Co3O4 nanocrystals and nitrogen-doped hollow carbon nanospheres are synthesized through in situ growth of Co3O4 nanocrystals on the surface of nitrogen-doped hollow carbon nanospheres. The observed Co-N bond formation is an indication of the nucleation of Co3O4 nanocrystals starting from N-sites in nitrogen-doped hollow carbon nanospheres. The resulted hybrids exhibit improved activity towards oxygen reduction reaction compared to pristine nitrogen-doped hollow carbon nanospheres in terms of the 42 mV positive shift of half-wave potential and comparable activity towards oxygen evolution reactions with commercial RuO2 and IrO2 catalysts. The thus-assembled Li-O-2 battery delivers an initial discharge capacity of 3325 mAhg(-1) at 100 mAg(-1) using mixed gas of O-2 and Ar (20% of O-2 in volume). The battery fails after 27 discharge/charge cycles due to the accumulation of discharge products on electrode. (C) 2018 Elsevier B.V. All rights reserved.

In digital image correlation (DIC), iterative spatial-domain cross-correlation algorithms have been routinely used to extract displacement fields from the recorded images. Then, strain fields are computed from the noisy displacement fields by a proper numerical different approach, like pointwise least squares fitting, which is tricky in choosing optimal calculation parameters. This work proposes an alternative weak-form framework to calculate strain fields from noisy displacement measurements by DIC. While direct numerical differentiation may amplify the noise in the displacement fields, the proposed method transfers differentiation into integration by employing the idea of the weak-form, which is the foundation of modern computational mechanics. By selecting cosine series as trial/test functions and employing their orthogonality, a semi-analytical formula for calculating the strain field is given. Moreover, the Filon's method is used in this study to improve the accuracy of numerical integration as sinusoidal terms are involved. The effectiveness of the proposed method is verified by numerical examples. It is found that the proposed method is comparable to the famous PLS algorithm when it is for simple strain fields, while it is better in accuracy and its insensitivity to noise when large-gradient or highly-oscillating strain fields are to be measured.

In this study, two/three-dimensional computational grains are developed for micromechanical modeling of heterogeneous materials with nanoscale inhomogeneities, considering the interface stress effect. Two types of computational grains are developed, depending on the types of inhomogeneity in each element. Each computational grain can include alternatively a spherical void or a spherical elastic inclusion. In these computational grains, an inter-element compatible displacement field is assumed along the element outer-boundary, and interior displacement fields in the matrix as well as in the inclusion are independently assumed as T-Trefftz trial functions. For planar problems, complex potentials are used to derive the Trefftz trial displacement fields, and for 3D problems spherical harmonics are used as the Papkovich-Neuber potentials to derive the Trefftz trial displacement fields. Characteristic lengths are used to scale the Trefftz trial functions, to avoid ill-conditioning of the derived system of linear equations. The compatibility between the independently assumed displacement fields and the stress jump across the matrix/inclusion interface, described by the generalized Young鈥揕aplace equation, are enforced by Lagrange multipliers in multi-field boundary variational principles. Numerical results by the computational grains with interface stress effects are consistent with available analytical solutions in the literature, demonstrating the high accuracy of the present method. Computational grains for nanocomposites with interface stress effects with ellipsoidal, and arbitrary shaped voids/inclusions will be presented in future studies.

Three-dimensional computational grains based on the Trefftz method (TCGs) are developed to directly model the micromechanical behavior of heterogeneous materials with coated spherical inclusions. Each TCG is polyhedral in geometry and contains three phases: an inclusion, the surrounded coating (or interphase) and the matrix. By satisfying the 3D Navier's equations exactly, the internal displacement and stress fields within the TCGs are expressed in terms of the Papkovich-Neuber (P-N) solutions, in which spherical harmonics are employed to further express the P-N potentials. Further, the Wachspress coordinates are adopted to represent the polyhedral-surface displacements that are considered as nodal shape functions, in order to enforce the compatibility of deformations between two TCGs. Two techniques are developed to derive the local stiffness matrix of the TCGs: one is directly using the multi-field boundary variational principle (MFBVP) while the other is first applying the collocation technique for the continuity conditions within and among the grains and then employing a primal-field boundary variational principle (PFBVP). The local stress distributions at the interfaces between the 3 phases, as well as the effective homogenized material properties generated by the direct micromechanical simulations using the TCGs, are compared to other available analytical and numerical results in the literature, and good agreement is always obtained. The material and geometrical parameters of the coatings/interphases are varied to test their influence on the homogenized and localized responses of the heterogeneous media. Finally, the periodic boundary conditions are applied to the representative volume elements (RVEs) that contain one or more TCGs to model the heterogeneous materials directly.

In this study, a Trefftz collocation method (TCM) is proposed for modeling multiple interacting nano-scale spherical inhomogeneities considering the interface stress effect. The Papkovich–Neuber (P–N) general solutions are used as Trefftz trial functions, which are expressed in terms of spherical harmonics. Non-singular harmonic functions, and singular harmonics from multiple source points are included, facilitating the study of multiple inclusions. Characteristic lengths are used to scale the Trefftz trial functions, to avoid ill-conditioning of the derived system of linear equations. The collocation method is used to enforce boundary conditions. The displacement continuity and the stress jump across the matrix/inclusion interface, which is described by the generalized Young–Laplace equation for solids, are also enforced by the collocation method. Numerical results by the proposed Trefftz method agree well with the available analytical solutions in the literature. The stress distributions of solids containing nano-inhomogeneities show significant size-dependency, in contrast to those for composites without considering the interface stress effect. Interactions of multiple nano-inclusions are also studied, which can be used as benchmark solutions in future studies.

A new chemotype of ghrelin inverse agonists was discovered through chimeric design based on molecular scaffolds known as growth-hormone secretagogue receptor (GHSR) modulators but with divergent pharmacodynamic and pharmacokinetic properties. The structure-activities/properties exploration led to compound 47, which displayed potent human GHSR antagonism and inverse agonism in cellular assays (IC50 = 68 nM, EC50 = 29 nM), moderate oral bioavailability, and notable brain penetration in rat ( F = 27%, B/ P ratio = 1.9). First in vivo studies demonstrated effective reduction of food intake after oral or parenteral administration to mouse (78% at 1 h and 38% at 8 h, respectively). Further preclinical studies are needed to evaluate the most suited mode of administration with the aim of promoting a first central-acting ghrelin inverse agonist molecule to development, which would represent a significant step toward therapeutic agents to treat metabolic disorders related to obesity, such as type 2 diabetes mellitus.

A method of using MEMS supercapacitor as the secondary electric power supply of initiation control module was proposed. In allusion of the shortcoming that using ordinary capacitor as the secondary electric power of the penetration fuze has short discharge time, which restricts the signal processing function of the fuze. As supercapacitor has characteristics of large capacity and high overload resistance, six 33 mu F tantalum capacitors in parallel is replaced by The 20 mF supercapacitor as the secondary electric power supply. Test results show that the size greatly decreases and the discharge time of 0.2s increase to more than 3s, and the supercapacitor can be discharged stably under the condition of 90 thousand G to meet the requirements of the secondary power supply for the penetration fuze.