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• The dissimilar material and the crack are treated as inhomogeneities of different elastic modulus based on the EIM. • A semi-analytical model for two joined dissimilar materials with interfacial cracks is established and validated. • Parametric analysis on rupture performance of joined materials with interfacial cracks are carried out. Existing interfacial cracks in two joined dissimilar materials play a crucial role in determining the stress concentration and its further propagation, which severely affects the interfacial strength of the bi-materials, even leading to its debonding failure under external loading. This study proposes a semi-analytical method (SAM) to analyze the elastic field of two joined dissimilar materials with interfacial cracks. One of the two dissimilar materials is treated as an inhomogeneity having different material properties from the other and the crack is regarded as a line inhomogeneity whose elastic modulus equals to zero, hence the problem for the two joined dissimilar materials with an interfacial crack is converted to a homogeneous half space material problem with the assistance of the well-known Eshelby equivalent inclusion method (EIM). The results obtained with the SAM agree very well with those with the finite element method (FEM), providing a verification for the proposed method. Cases studies are conducted to explore the influences of the material mismatch, the length and the depth of the crack, the friction coefficient and the loading location on the elastic field of the two joined dissimilar materials, demonstrating that this work has potential in the analysis of joined dissimilar materials with interfacial cracks. [ABSTRACT FROM AUTHOR]

High frequency fatigue behavior of near surface of turbine disk are critical for its application and operation. High frequency indentation fatigue tests of GH4169 alloy under different load amplitudes, frequencies and mean loads at small length scale were conducted, and the dependence of load amplitude, load frequency and mean load on high frequency indentation fatigue property of GH4169 alloy are discussed in this paper. Depth amplitude (ha), mean depth (hm) and depth propagation rate (dh/dN) were employed as evaluation indicators of the indentation behavior. Results show that depth amplitude is only relevant with load amplitude, while mean depth is related to all the adopted influencing factors, ranked in an ascending order as load amplitude, mean load and frequency with a ranking relation of nm1=1.4 < nm2=1.71 < nm3=2.02. Furthermore, a modified Paris law was utilized to reveal the fatigue mechanism, and found the fatigue mechanism is dominated by intrinsic mechanism under the influence of mean load and load amplitude, while for the influence of frequency, the fatigue mechanism is governed by extrinsic mechanisms. Combined with SEM results and three-dimensional morphology analysis, it can be deduced that dislocation movement mode in high frequency indentation fatigue is dislocation slip. [ABSTRACT FROM AUTHOR]

• Elastic field for layered composite rock with excavated tunnels is predicted by a semi-analytical method. • The layer and tunnel are considered as inhomogeneities of different elastic moduli through employing the EIM. • A yield approximate index is used to evaluate safety of layered composite rock with excavated tunnels. • Effects of parameters of the layer and tunnel on the elastic field and plastic zones are discussed. Tunnels excavation in layered composite rock subjected to ground loads to make the best of underground space is an important engineering problem in more and more mega-cities. Such a three-dimensional case, layered composite rock with excavated tunnels, is usually simplified as a two-dimensional plane strain problem in mechanics. The present study reports a Semi-Analytical Method (SAM) to predict elastic field of an excavated layered composite rock with the assistance of the Equivalent Inclusion Method (EIM) that can handle elastic field of the layers and tunnels simultaneously. In the EIM, the layer and tunnel are considered as inhomogeneities of different elastic moduli from the base rock, and the inhomogeneities are further equivalent to inclusions of identical elastic modulus to the base rock but including eigenstrains. Effectiveness of the SAM is examined by the Finite Element Method (FEM) through comparing their results. Moreover, a yield approximate index (YAI) is introduced to evaluate safety of excavated layered composite rock and acoustic emission (AE) event is used to count the number of plastic yield elements. Finally influences of depth of and distance between the tunnels, thickness, elastic modulus, number of the layer, range of ground load on principal stress, YAI , plastic zones are discussed, which may have potentials to provide guidance for practical engineering applications of tunnel excavation. [ABSTRACT FROM AUTHOR]

The Niutitang Formation of the lower Cambrian (Є1n) is a target reservoir of shale gas widely developed in China's Middle-Upper Yangtze region, with the characteristics of being widely distributed, having a big thickness and highly organic carbon abundance. However, the exploration and research degree are relatively low. Based on extensive core sample, experimental test results, drilling, and field outcrop surveying, the shale gas generation capacity, gas content, and gas composition are discussed. The preservation conditions of shale gas are then systematically analyzed from the aspects of tectonic movement, fault development, structural style, and thermal evolution degree. The results show that the organic-rich shale with a thickness ranging from 40 to 150 m developed in the mid-lower part of the Є1n Formation, with the TOC content values ranging from 0.4% to 14.64%. While it has unfavorable characteristics of a high thermal evolution, with Ro values ranging from 1.92% to 5.74%, a low gas content and a high nitrogen content (70% wells). The Є1n shale gas has complex preservation conditions. The Є1n Formation has good roof-to-floor conditions, but after the main gas generating peak of the Є1n shale during the Jurassic–Cretaceous, the most intensive tectonic activity of the Yanshan movement resulted in poor preservation conditions (faults developed and cap rock fractured). The huge faults extended to the surface are formed due to tectonic movement in an extensional environment, and the structural style and development are the main factors affecting the preservation conditions of the Є1n shale gas. Additionally, the high thermal evolution of the Є1n shales also has a certain impact on the preservation conditions. Therefore, the stable area far from large faults (>2.0 km), with weak local tectonic activity and tectonic deformation, is the favorable area for shale gas preservation in the Є1n Formation. [ABSTRACT FROM AUTHOR]

Deep ensemble learning, where we combine knowledge learned from multiple individual neural networks, has been widely adopted to improve the performance of neural networks in deep learning. This field can be encompassed by committee learning, which includes the construction of neural network cascades. This study focuses on the high-dimensional low-sample-size (HDLS) domain and introduces multiple instance ensemble (MIE) as a novel stacking method for ensembles and cascades. In this study, our proposed approach reformulates the ensemble learning process as a multiple-instance learning problem. We utilise the multiple-instance learning solution of pooling operations to associate feature representations of base neural networks into joint representations as a method of stacking. This study explores various attention mechanisms and proposes two novel committee learning strategies with MIE. In addition, we utilise the capability of MIE to generate pseudo-base neural networks to provide a proof-of-concept for a "growing" neural network cascade that is unbounded by the number of base neural networks. We have shown that our approach provides (1) a class of alternative ensemble methods that performs comparably with various stacking ensemble methods and (2) a novel method for the generation of high-performing "growing" cascades. The approach has also been verified across multiple HDLS datasets, achieving high performance for binary classification tasks in the low-sample size regime. [ABSTRACT FROM AUTHOR]

Taking the HD1 well as the research target, through intensive core sampling, experimental test analysis, comprehensive logging interpretation and other methods, the fracability of shale reservoirs was discussed in this paper. The results show that the Gufeng–Dalong Formation in the HD1 well has a high organic carbon content, and the organic-rich shale developed in the lower part of the Gufeng and Dalong Formations with thicknesses of 30 m and 15 m, respectively. For the low-porosity and ultralow-permeability shale reservoir type, the natural fractures are undeveloped in the lower part of the Dalong Formation, with a lower linear density, while they are well developed in the Xiayao and Longtan Formations and the lower part of the Gufeng Formation, and the interlayer bedding fractures are relatively developed. The Gufeng–Dalong Formation shale also has a high mineral brittleness index (average of 44.5%), high static Young's modulus (20–70 GPa), low static Poisson's ratio (0.10–0.31), and high horizontal pressure difference coefficient of two phases (0.17–0.56). It is concluded that the shale reservoir is favorable for fracture development in the lower part of the Dalong Formation, with depths of 1249–1289.5 m, and the lower part of the Xiayao, Longtan and Gufeng Formations, with depths of 1300–1335.3 m. Overall, the fracable shale section with high brittleness and rock strength is beneficial to fracturing. However, the existence of a large number of shale bedding fractures increases the complexity of the fractures, and at the same time, it has a certain negative impact on fracture generation. Double wing fractures are easily formed because of the high two-phase horizontal pressure difference. Therefore, the leakage caused by shale bedding fractures and the influence on the fracture height and extension length should be considered comprehensively in fracturing design. [ABSTRACT FROM AUTHOR]

A meta‐analysis on seven large case series (>1000 cases) of chromosome microarray analysis (CMA) on products of conceptions (POC) evaluated the diagnostic yields of genomic disorders and syndromic pathogenic copy number variants (pCNVs) from a collection of 35,130 POC cases. CMA detected chromosomal abnormalities and pCNVs in approximately 50% and 2.5% of cases, respectively. The genomic disorders and syndromic pCNVs accounted for 31% of the detected pCNVs, and their incidences in POC ranged from 1/750 to 1/12,000. The newborn incidences of these genomic disorders and syndromic pCNVs were estimated in a range of 1/4000 to 1/50,000 live births from population genetic studies and diagnostic yields of a large case series of 32,587 pediatric patients. The risk of spontaneous abortion (SAB) for DiGeorge syndrome (DGS), Wolf–Hirschhorn syndrome (WHS), and William–Beuren syndrome (WBS) was 42%, 33%, and 21%, respectively. The estimated overall risk of SAB for major genomic disorders and syndromic pCNVs was approximately 38%, which was significantly lower than the 94% overall risk of SAB for chromosomal abnormalities. Further classification on levels of risk of SAB to high (>75%), intermediate (51%–75%), and low (26%–50%) for known chromosomal abnormalities, genomic disorders, and syndromic pCNVs could provide evidence‐based interpretation in prenatal diagnosis and genetic counseling. [ABSTRACT FROM AUTHOR]

Electrostatic electron cyclotron harmonic (ECH) waves which can efficiently produce scattering loss of electrons, are frequently observed in the first band. Here we present new results on the global occurrence of higher‐band ECH waves in the radiation belts from Van Allen Probes data. We develop a novel noise reduction algorithm which can be widely applied to various plasma waves to better identify naturally occurring waves during periods of instrument interference. The occurrence rate of ECH waves in higher harmonic bands is comparable to that in the first harmonic band, except in the noon‐to‐dusk sector. As the level of geomagnetic activity increases, ECH waves in all bands can be observed at lower L‐shells. The occurrence rates of weak (moderate, strong) waves in all four bands increase 3–4 (4–6, 5–10) times during disturbed periods compared to those during quiet periods. The current results may provide better understanding of ECH‐driven magnetosphere‐ionosphere coupling. Plain Language Summary: Electrostatic electron cyclotron harmonic (ECH) waves are believed to cause resonant scattering of energetic electrons. The global distribution of ECH waves in higher harmonic bands is not completely determined. Satellite observations of electric fields may be contaminated by broadband noise. Here we develop a novel noise reduction algorithm that can be widely applied to various plasma waves to better identify ECH waves. We present new results on the global occurrence of higher‐bands ECH waves in radiation belts by using 7 years of Van Allen Probes data after noise reduction processing. The first harmonic ECH waves are observed in all MLT, with the highest occurrence at L = 5.0–6.0 and MLT = 00–05 and the lowest one on the noon‐to‐dusk sector. The occurrence rate of ECH waves in higher harmonic bands is comparable to that in the first harmonic band, except on the noon‐to‐dusk sector. As the geomagnetic condition intensifies, ECH waves can extend to lower L‐shells with a higher occurrence. The current results can provide better understanding of ECH‐driven magnetosphere‐ionosphere coupling. Key Points: The global occurrence of higher‐bands electron cyclotron harmonic (ECH) waves in radiation belts based on a novel noise reduction algorithm is presentedThe occurrence rate of ECH waves in higher harmonic bands is comparable to that in the first harmonic band except on the noon‐to‐dusk sectorThe ECH wave activity extends to a broader spatial region with a higher occurrence when the geomagnetic conditions intensify [ABSTRACT FROM AUTHOR]

Phenomenons of adhesive contact are quite common in micro-electro-mechanical system devices, whose reliability is severely affected by the adhesive properties of contacting bodies. The Classical JKR model fails when the contacting body size decreases to nanoscale because of the assumption failures. This investigation reports a novel numerical model of adhesive contact between a rigid smooth sphere and an elastic multi-layered medium, in which the Hamaker summation method and Lennard–Jones intermolecular potential law are employed. Analytical expressions of adhesive contact pressure for multi-layered media are derived. The Newton–Raphson method and fast Fourier transform algorithm are introduced to enhance the computational efficiency. Further, the effectiveness of the present model is validated by comparison with results from published literature. Finally, parametric studies about the influences of layer properties, like elastic modulus, Dupré adhesion energy and layer thickness, on the adhesive mechanical behavior of multi-layered media are carried out. The analysis results are beneficial to the optimal design of an adhesive contact system to improve its comprehensive mechanical performance. [ABSTRACT FROM AUTHOR]

• A semi-analytical method to predict the elastic field for a welding repaired material is developed and validated. • The elastic modulus mismatch between the welding material and the matrix is investigated. • Effects of shape, angle of and interactions among the welding beads on elastic field are discussed. Material mismatch between the welding bead and its surrounding matrix has been known to cause stress concentration due to incompatible deformation, and/or even crack regeneration, thus greatly affecting the performance of a welding repaired material. In this paper, a semi-analytical method (SAM) is developed to tackle problems for material mismatch in a welding repaired material with free surface under remote tensile loading. The heterogeneous welding bead is modeled by a homogeneous base material containing unknown eigenstrains through the equivalent inclusion method; after which a numerical discretization is adopted and the eigenstrains within each computational element are determined by iteratively solving a set of linear equations with the assistance of conjugate gradient method. Stress field arising from the eigenstrains can be obtained by employing previously derived influence coefficients. The SAM is then examined by a simple finite element model and utilized to analyze influences of material properties, aspect ratio, angle of differently shaped welding bead and interactions among multiple welding beads on the stress distribution. The SAM may have potential applications in dealing with problems related to residual stress in welded material due to eigenstrains. [ABSTRACT FROM AUTHOR]

Anisotropic deformation behavior of single crystalline material under scratching has a significant effect on machining precision in nano-mechanical machining. In the present work, a crystal plasticity finite element model simulating the scratching process is developed, and the established model is validated by comparison with experimental results. (001)-, (101)- and (111)-oriented coppers are selected to investigate the deformation behavior including scratching depth, surface topography and subsurface deformation affected by scratching path. Further, the deformation mechanisms of (001)-, (101)- and (111)-oriented coppers are analyzed to be caused by deformation of slip systems. [ABSTRACT FROM AUTHOR]

Herein, a series of organic molecules were designed through locating different substituents on the compound (WD8-c-1) to develop their performances used as the sensitizers in the field of dye-sensitized solar cells. The geometry and relevant electronic properties of WD8-c-1 and its derivatives were simulated at the B3LYP/6–31G(d,p) level. The absorption spectra were calculated using the TD-PBE0/6–31+G(d,p) method. These calculated results show that the type and position of the substituents strongly affected the distributions of frontier molecular orbitals and the energy gaps for the WD8-c-1-derived molecules. The reorganization energies results reveal that their hole charge transfer rates are higher than that of the representative hole transport material. Moreover, the mobility of the representative WD8-c-1 derivative also has been simulated. [ABSTRACT FROM AUTHOR]

• An EHL model considering imperfect transversely isotropic coating was developed. • Imperfect of normal interfacial displacement has a great influence on lubrication. • Coating thickness under cooperative bearing capacity is recommended about 0.03 a to 4 a. Lubricated contact characteristics of transversely isotropic coating considering imperfect interface is of great importance in engineering to provide guidance on tribological design and optimization of tribo-pairs. The current investigation reports an elastohydrodynamic lubrication (EHL) contact model for transversely isotropic coating of imperfect interface. The interface is described by dislocation-like condition, i.e., displacement across it is transmitted discontinuously and such discontinuity is controlled by an imperfect index changing from 0 to 1. Based on this interfacial condition, frequency response functions (FRFs) of elastic field of imperfect transversely isotropic coating were derived, which was further used to establish the EHL contact model combined with the lubrication theory. The proposed model can be reduced to the one without coating, whose calculation results are consistent with those from literatures, providing a good verification. Finally, effects of imperfect index of interfacial displacement, coating thickness on film thickness, surface pressure, stress for transversely isotropic coating were investigated using the proposed model. [ABSTRACT FROM AUTHOR]

This paper investigates the pullback attractor of Cohen–Grossberg neural networks with multiple time-varying delays. Compared with the existing references, the networks considered here are more general and cannot be expressed in the vector-matrix form due to multiple time-varying delays. After constructing a proper Lyapunov–Krasovskii functional and eliminating the terms involving multiple time-varying delays, two sets of new sufficient criteria on the existence of the pullback attractor are derived based on the theory of pullback attractors. In the end, two examples are given to demonstrate the effectiveness of our theoretical results. [ABSTRACT FROM AUTHOR]

• A spatial heat flux model was developed to calculate the time-varying effective solar heat flux received by the antenna structure. • Constructed a thermodynamic model of antenna structure considering thermal-structural coupling effect. • The thermodynamic response of antenna structures in a realistic space time-varying thermal environment is investigated. Space truss antennas may undergo thermally induced vibration due to temperature changes caused by thermal mutations in the space environment, which will result in antenna performance degradation or even vibration failure. This paper aims to investigate the thermal-structural coupled dynamics of a space truss antenna in the orbital space thermal environment. A spatial thermal analysis model is established based on the spatial heat flux model, Fourier-temperature element, finite element method (FEM) and astrometric model to calculate temperature variation of the antenna structure during its operation in orbit. In this model, the effective solar heat flux received by the antenna structure is calculated on the basis of an astrometric model, with consideration of the Earth's shadow effect and the shading effect of the reflective surfaces. Additionally, a thermo-structural coupled dynamic model of the antenna structure is constructed considering the coupled effects of structural deformation and absorbed effective solar heat flux, which was validated using a finite element shell model. Numerical cases are arranged to comparatively analyze the thermal-structural coupling effects, light shading by reflective surfaces, and thermodynamic response during the space operation cycle, respectively. It is demonstrated that both the earth shadow effect and the shading effect of components have great effect on the temperature distribution and variation of the antenna structure. Moreover, significant vibrations will occur at certain moments especially when the thermal radiation flux to the structural components changes suddenly due to light shading from the earth shadow and reflective surfaces. The thermal-structural coupling dynamic model of the antenna structure presented in this work can provide guidance for thermal compensation and thermal-induced vibration attenuation of truss antenna structures. [ABSTRACT FROM AUTHOR]

• Based on semi-analytical method, a novel model for the elastoplastic impact-contact of materials with coatings is developed. • The validity and accuracy of the proposed model are demonstrated by a nano-impact experiment conducted on a 304 stainless steel with Cr coating. • The effects of the coatings and surface roughness of the plasticity of the material are studied. Plastic deformation resulting from high stress exceeding material yield limit widely exists in many mechanical components, especially for those subjected to impact load, which further compromises the accuracy and reliability of the affected parts. Coating technology is an effective way to provides protection for the substrate against the heavy impact load. A novel solution method for simulating the elastoplastic impact-contact of coated medium is presented in the current investigation. The second-order Newmark algorithm is introduced for impact dynamics iteration. The plastic yielding and plastic strain accumulation during impact process are determined by the von Mises yield criteria. The effectiveness of the proposed solution method is demonstrated numerically by the finite element method (FEM) via commercial software and experimentally by a nano-impact test. Impact-contact problems for a rigid spherical punch against a coated medium with either a rough or smooth surface are further studied to illustrate the elastoplastic mechanical response of materials under impact contact load. [ABSTRACT FROM AUTHOR]

We propose a dynamic combined-mode traffic network model considering transfer behaviors. We assume that travelers can be classified into two classes: one class is pure-mode travelers who complete a trip by single transportation mode, and another is combined-mode travelers who cover a journey by car, bus, and so forth. The multimode point queue model is used to model the interaction of cars and buses on the network. We present an integrated variational inequality formulation to capture the complex traveler choice behaviors such as departure time choices, transfer point, and route choices. Finally, a numerical example is given to illustrate the effectiveness of the proposed heuristic algorithm and model. [ABSTRACT FROM AUTHOR]

We propose a dynamic combined-mode traffic network model considering transfer behaviors. We assume that travelers can be classified into two classes: one class is pure-mode travelers who complete a trip by single transportation mode, and another is combined-mode travelers who cover a journey by car, bus, and so forth. The multimode point queue model is used to model the interaction of cars and buses on the network. We present an integrated variational inequality formulation to capture the complex traveler choice behaviors such as departure time choices, transfer point, and route choices. Finally, a numerical example is given to illustrate the effectiveness of the proposed heuristic algorithm and model. [ABSTRACT FROM AUTHOR]

Structural parameters, electronic and optical properties of biphenylene have been investigated using the plane-wave ultrasoft pseudo-potential technique based on the first-principles density functional theory. The non-uniform pressure dependence of the lattice parameters may also mean that the biphenylene undergoes anisotropic compression. And the bulk modulus at ambient pressure and temperature is B0 = 12.37 GPa and its derivative is B ′ 0 = 7.09. Meanwhile, the pressure dependence of the electronic band structure, density of states and partial density of states of biphenylene were presented. It is shown that biphenylene is a semiconductor with a direct gap of 2.325 eV, and a pressure induced decrease of the band gap is observed. Moreover, the complex dielectric function, absorption coefficient, reflectivity, refractive index and extinction coefficient are calculated and analysed. According to our work, we found that the optical properties of biphenylene undergo a red shift with increasing pressure. [ABSTRACT FROM AUTHOR]

• RML was efficiently expressed in Yarrowia lipolytica. • A method for constructing hybrid promoters and multi-copy genes expressing vectors was developed. • A recombinant strain with hp12d promoter and 2 copies of rml gene showed the highest lipase activity. • The fermenting conditions for recombinants were optimized and the RML activity increased 8.1 fold. Rhizomucor miehei lipase (RML), a GRAS catalyst with wide applications, was overexpressed in Yarrowia lipolytica , also a GRAS unconventional yeast, via a combined strategy, optimization for promoter, gene dosage and fermentation process. The lipase activity of the recombinant strain was first increased from 19.5 to 26.9 U/mL via codon optimization of rml gene. Subsequently, a method was developed for constructing hybrid promoters harboring different copy number of upstream activation sequences fragment (UAS1B), and the recombinant strain Po1g/hp12d- rml 25# reached 38.9 U/mL. On this basis, expression vectors with different optimized rml gene copy numbers were constructed and introduced into Y. lipolytica Po1g. The recombinant strain Po1g/hp12d-2 rml 14# carrying 12 copies of UAS1B in the upstream of pLEUmin and 2 copies of rml gene obtained the highest lipase activity of 59.6 U/mL. Moreover, in optimized shaking flask culture parameters: 5% (m / v) of d -Sorbitol, 2% (v / v) inoculation density, initial pH 7.0, and 30 mL initial culture medium, the RML activity of Po1g/hp12d-2 rml 14# further reached 157 U/mL after 84-h of incubation at 28 ℃. Overall, RML activity was enhanced about 8-fold compared with the initial recombinant strain via the combined strategy, which provides a consolidated basis for the large-scale production of RML in Y. lipolytica to match urgent demand of the market. [ABSTRACT FROM AUTHOR]

By combining the density functional theory (DFT) with the nonequilibrium Green's function, we studied the transmission properties of Si2C2 clusters (the linear form M1 and the rhombic form M2). The result shows that the I-V characteristics of the cluster are closely related to the structure of the cluster. The change in the structure of the cluster causes a change in the coupling process between the cluster and the electrode, resulting in a change in its transmission characteristics. Compared with the linear form M1 system, the rhombic form M2 system has obvious rectification and negative differential resistance (NDR) effects, which makes it more advantageous as a candidate for molecular devices. [ABSTRACT FROM AUTHOR]

In this study, we designed an improved method to construct gene-deficient strain in non-conventional yeast Pichia pastoris. This method achieved high efficiency of gene deletion without disruption of NHEJ-related genes. The disruption efficiency of Och1 reached about 80%. This simple method will be a new useful molecular tool for P. pastoris. • A novel method designed for efficient gene disruption in Pichia pastoris. • A plasmid was constructed to disrupt the Och1 gene. • The disruption efficiency of Och1 reached about 80%. [ABSTRACT FROM AUTHOR]

Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L‐shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from 1 October 2012 to 30 June 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L = 4–6 and 00–24 MLT, with a higher occurrence in the region of L = 5–6 and 06–19 MLT. The electron phase space density exhibits a distinct ring distribution (∂f/∂v⊥ > 0) with the peak energy around a few kiloelectron volts. Both ECH wave events and the electron ring distributions are closely related and tend to be more distinct with increasing geomagnetic activity. Key Points: Coordinated observation of electrostatic electron cyclotron harmonic (ECH) waves and electron ring distributions is presentedECH waves can be present over a broad region of magnetosphere, with a higher occurrence in the region of L = 5–6 and 06–19 MLTBoth ECH waves and electron ring distributions are closely related and tend to be more distinct with increasing geomagnetic activity [ABSTRACT FROM AUTHOR]

Abstract A three dimensional model for solving steady state heat conduction in a semi-infinite domain containing an elementary cuboidal inhomogeneity is established in this paper. A set of analytical formulas for steady state heat conduction in a full space with an embedded cuboidal inclusion is derived. The temperature field of a half space distributed with arbitrarily shaped inhomogeneities is then obtained via the application of numerical discretization and the method of images. Benchmark comparisons involving a cuboidal/ellipsoidal inhomogeneity and double-inhomogeneity particle with the results produced by the finite element method (FEM) are conducted. Good agreements between the results of the two methods demonstrate the effectiveness and capability of the proposed model. Further, a case of heterogeneous material containing arrayed inhomogeneities is studied to explore the disturbance and interaction of the temperature field due to distributed inhomogeneities. [ABSTRACT FROM AUTHOR]

Abstract The present study explores the thermoelastic contact behaviours of two heterogeneous bodies subjected to both contact and frictional heat loads. The equivalent inclusion method (EIM) is employed to model the steady state heat conduction in contacting materials involving spherical inhomogeneities. The explicit analytical solutions for the thermal field inside and outside an inhomogeneity embedded in an infinite medium are derived, which are utilized to solve thermal field of semi-infinite medium with the help of the method of images. Further, a thermoelastic contact model for convex bodies with distributed spherical inhomogeneities is developed. The interaction between any adjacent inhomogeneities is fully considered. A conjugate gradient method and a fast Fourier transform algorithm are introduced to enhance the computation efficiency. Finally, parametric study about the influences of inhomogeneity material properties and contact parameters on the volumetric stress integral of the contact body is conducted, demonstrating the fatigue performance of heterogeneous contact bodies under thermoelastic loads. Highlights • Derivation of the influence coefficients of temperature distribution in a full space involving a sphere inclusion. • A thermoelastic contact model considering both thermal and mechanical loads for heterogeneous materials is established. • Effects of inhomogeneity parameters on rolling contact fatigue performance of heterogeneous material are explored. [ABSTRACT FROM AUTHOR]

In this study, a novel air-assisted liquid-liquid microextraction (AALLME) method was developed for the HPLC determination of bisphenols migration from disposable plastic lunch box to contacting water. The AALLME was carried out in commercially-available medical plastic syringes with low-density extraction solvent ( n -octanol), and the reaction of NaHCO 3 and HCl was introduced to simultaneously induce the in-situ phase separation and salt effect. After the AALLME processes, the upper organic phase was pushed into the end of syringes (narrow tube) by moving the piston so that it could be readily collected for the HPLC analysis. The factors including the type and volume of extraction solvent, NaHCO 3 addition and extraction cycles were optimized. Under the optimal conditions, the limits of detection (LODs) for target bisphenols were evaluated to be 0.2–0.7 μg L −1 , and good linearities with correlation coefficients higher than 0.9955 were obtained. The recoveries for target bisphenols ranged from 80% to 106%, with the relative standard deviations (RSDs) of 4.4–14.1%. The proposed method was successfully applied to investigate the migration of bisphenols from the disposable plastic lunch boxes to the contacting water, revealing that compared to the conventional water-bath heating, the microwave heating could induce the significant migration of bisphenols in a much shorter time. [ABSTRACT FROM AUTHOR]

The magneto-electro-elastic (MEE) medium is a typical intelligent material with promising application prospects in sensors and transducers, whose thermal contact response is responsible for their sensitivity and stability. An effective thermal contact model between a moving sphere and a coated MEE medium with transverse isotropy is established via a semi-analytical method (SAM) to explore its thermal contact response. First, a group of frequency response functions for the magneto-electro-thermo-elastic field of a coated medium are derived, assuming that the coating is perfectly bonded to the substrate. Then, with the aid of the discrete convolution–fast Fourier transform algorithm and conjugate gradient method, the contact pressure and heat flux can be determined. Subsequently, the induced elastic, thermal, electric and magnetic fields in the coating and substrate can be obtained via influence coefficients relating the induced field and external loads. With the proposed method, parametric studies on the influence of the sliding velocity and coating property are conducted to investigate the thermal contact behavior and resulting field responses of the MEE material. The sliding velocity and thermal properties of the coating have a significant effect on the thermal contact response of the MEE material; the coupled multi-field response can be controlled by changing the coating thickness between ~0.1 a0 and a0. [ABSTRACT FROM AUTHOR]

Rhizopus oryzae lipase (ROL) is an important industrial enzyme limited in application due to its low production in native strains. Here, we used a new combined strategy to overexpress ROL in Pichia pastoris . An efficient method based on bio-brick was developed to construct a series of vectors harboring different copy numbers of ROL gene cassettes, which were then transformed into P. pastoris GS115 to generate a strain with specific copy numbers of ROL . An optimized gene-dosage recombinant strain of GS115/pAOα-5ROL 11# harboring five copies of ROL was screened, revealing production of the highest activity (2700 U/mL), which was 8-fold higher than that of the strain harboring one copy. The activity of GS115/pAOα-5ROL 11# was then enhanced to 3080 U/mL in a shaking flask under optimized culture conditions. Subsequently, the endoplasmic reticulum-associated protein-degradation-related genes Ubc1 or/and Hrd1 were co-expressed with ROL to further increase ROL expression. The activities of the recombinant strains, GS115/5ROL-Ubc1 22#, -Hrd1 15#, and -Hrd1-Ubc1 1#, were 4000 U/mL, 4200 U/mL, and 4750 U/mL, which was 29.9%, 36.4%, and 54.2% higher, respectively, than that observed in GS115/pAOα-5ROL 11#. Using the combined strategy, ROL expression was improved 15.8-fold, with maximum GS115/5ROL-Hrd1-Ubc1 1# activity reaching 33,900 U/mL via a sorbitol/methanol co-feeding strategy in a 3-L fermenter and resulting in a 1.65-, 1.26-, and 1.14-fold enhancement relative to the activities observed in strains GS115/pAOα-5ROL 11#, GS115/5ROL-Ubc1 22#, and GS115/5ROL-Hrd1 15#, respectively. These results indicated that heterologous overexpression of ROL in P. pastoris using this combined strategy is feasible for large-scale industrialization. [ABSTRACT FROM AUTHOR]

Posttransformational vector amplification (PTVA) is widely used to enrich the gene-copy number in Pichia pastoris . We engineered two test strains for PTVA studies and demonstrate that the PTVA process results in the amplification of a fragment with the resistant gene flanked by two homologous arms instead of the entire vector. [ABSTRACT FROM AUTHOR]

The effect of iron atom junction on transport characteristics of carbon-silicon mixed chain has been studied from an ab initio study. At zero bias, the Fe(CSi) system appears to be the decrease of the conductance as the number of the Si-C pairs in the chain increases ( n changes). When n 5, the conductance tends to zero. These changes are independent of the transferring charge of the system, depending on the coupling of the electrodes and the central region. Under bias, the higher the bias voltage, the bigger the transmission coefficient of the system, and the transmission peak moves closer to the Fermi level. The I- V curves of Fe(CSi)2 and Fe (CSi)3 are linear, showing the behavior of metal resistance. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry (IMS) opened a potential avenue for the rapid detection of organophosphorus pesticides (OPPs), though an improved selectivity of stand-alone IMS was still in high demand. In this study, a stand-alone positive photoionization ion mobility spectrometry (PP-IMS) apparatus was constructed for the rapid detection of OPPs with acetone as dopant. The photoionization of acetone molecules was induced by the ultraviolet irradiation to produce the reactant ions (Ac) 2 H + , which were employed to ionize the OPPs including fenthion, imidan, phosphamidon, dursban, dimethoate and isocarbophos via the proton transfer reaction. Due to the difference in proton affinity, the tested OPPs exhibited the different dopant-dependent manners. Based on this observation, the switching of dopant concentration was implemented to improve the selectivity of PP-IMS for OPPs detection. For instance, a mixture of fenthion, dursban and dimethoate was tested. By switching the concentration of doped acetone from 0.07 to 2.33 to 19.94 mg L −1 , the ion peaks of fenthion and dursban were inhibited in succession, achieving the selective detection of dimethoate at last. In addition, another mixture of imidan and phosphamidon was initially detected by PP-IMS with a dose of 0.07 mg L −1 acetone, indicating that their ion peaks were severely overlapped; when the concentration of doped acetone was switched to 19.94 mg L −1 , the inhibition of imidan signals promised the accurate identification of phosphamidon in mixture. Finally, the PP-IMS in combination of switching dopant concentration was applied to detect the mixed fenthion, dursban and dimethoate in Chinese cabbage, demonstrating the applicability of proposed method to real samples. [ABSTRACT FROM AUTHOR]

The submicron atmospheric particulate matters (PMs), consisting of 7 size-resolved fractions, were collected by two Dekati low pressure impactors from December 2015 to January 2016 in Hangzhou, China. The chemical analysis revealed the higher accumulation efficiency of polycyclic aromatic hydrocarbons (PAHs) in the finer submicron PMs, and 77.0% of particulate PAHs in PM 1 were associated with PM 0.4 . Moreover, the BaP equivalent concentrations (BaP eq ) were evaluated for size-fractionated submicron PMs, indicating that 77.2% of carcinogenicity of particulate PAHs in PM 1 were associated with PM 0.4 . In the cytotoxic tests, a significant size-dependent decrease of glutathione (GSH) level was observed in the PMs-exposed human pulmonary epithelial cells (A549), demonstrating the greater intracellular oxidative stress induced by the finer submicron PMs. The results also suggested that 82.4% of PM 1 -induced oxidative stress were associated with PM 0.4 , and the intracellular oxidative stress was significantly correlated with the particulate PAHs. Therefore, besides PM 10 , PM 2.5 and PM 1 , special attentions should be given to PM 0.4 as well. [ABSTRACT FROM AUTHOR]

Ni-rich layered oxides are promising cathode materials for next generation Li-ion batteries due to high energy density. However, structural instability severely constrains its application during charging/discharging. Herein, we performed first-principles calculations to study the mechanism of performance improvement by d0 transition metal doping. The results show that the d0 cation Ti4+, V5+ and Mo6+ doping is beneficial to suppress the lattice distortion of the Ni-rich cathode during delithiation process, especially in the c-direction. Moreover, d0 cation doping can deliver high intercalation potentials, thereby increasing the energy density of the Li-ion batteries. Among them, Mo6+ is considered as the most ideal dopant in improving the structural stability and energy density. However, it is disappointing that d0 cation doping accelerates the formation of O-vacancies in Ni-rich cathode materials. These theoretical findings provide a new insight for the doping strategy of Ni-rich cathode materials, which is helpful for designing high performance cathodes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • UE-AA-LLME method was simple, rapid, and efficient. • UE-AA-LLME-UPLC was validated with good sensitivity, linearity, and repeatability. • OPP levels in urban river were higher in autumn as compared to winter. • No human health risks of OPP residues in the proposed river water. Organophosphorus pesticide (OPP) residues in environment are harmful to ecosystem and human health. In this study, an ultrasound-enhanced air-assisted liquid–liquid microextraction (UE-AA-LLME) method was developed for ultra-high performance liquid chromatography (UPLC) determination of OPPs in water samples. The UE-AA-LLME was performed in a 1.5-mL centrifuge tube under ultrasound condition by sucking in and pushing out the mixture of aqueous solution and extraction solvent using a 2-mL syringe. After centrifugation, the sediment layer was collected and analyzed by UPLC. The parameters affecting the extraction efficiency including the type and volume of extraction solvent, pH, and extraction cycles were optimized. Under the optimized conditions, the limit of detection (LOD) of target OPPs ranged from 0.04 to 0.15 μg/L, and good linearities were acquired with correlation coefficients higher than 0.9927. The recoveries of target OPPs were evaluated to be 75.4–112.6 %, with relative standard deviations (RSDs) lower than 14.9 %. The proposed UE-AA-LLME method was successfully employed for the UPLC determination of OPPs in an urban river of Hangzhou, China. The results revealed that six OPPs were detected in the river waters at the levels of 0.06–0.54 μg/L, and the levels of OPP residues in autumn were higher than those in winter. The risk assessment suggested that there was no human health risk of OPP residues in the river water for adult and child by ingestion pathway. [ABSTRACT FROM AUTHOR]

Mechanical components are often subject to impact loads during service. It has been proven that application of a solid coating effectively improves contact mechanical performance of the component and prolongs its service life. The present paper proposes a semi-analytical model for elastic solid coatings subjected to impact load, which is based on numerical solution of classical contact theory, combined with a novel step-by-step iterative strategy with respect to impact time and binary search method. A conjugate gradient method (CGM) and discrete-convolution and fast Fourier transform (DC-FFT) algorithm are employed for enhancing computation efficiency of the present model. Comparative studies between results obtained by the proposed model and finite element method (FEM) show the validity of the model. Influences of impact velocities and coating parameters on impact mechanical performance and elastic stress distribution of solid coated medium are further investigated as a step towards understanding the impact contact failure mechanism of coated material or component. • A semi-analytical model of coated medium under an impact load was developed. • An impact SAM solver based on a step-by-step iterative strategy was proposed. • Impact contact mechanical performance of coated medium was investigated. [ABSTRACT FROM AUTHOR]

This work presented the microstructure variation and local plastic response of chrome molybdenum alloy steel under quasi rolling contact fatigue (quasi-RCF) testing. The quasi-RCF testing means using the similar method of actual RCF to introduce obviously local plastic deformation and microstructure variation on surface layers of materials. After quasi-RCF testing, the microstructure were observed using optical microscope and scanning electron microscope (SEM) from both the top surface and cross section. Based on microstructure analysis, the deformation volume of materials after quasi-RCF testing were calculated. The local plastic response was demonstrated by the unique local strain-stress curve and strain hardening exponent obtained via experimental measurements and simulation prediction. One hand, the increase in the hardness of plastic zones due to quasi-RCF testing was measured by a Vickers indenter. The other hand, based on the virgin hardness and elastic modulus, some possible local stress-strain curves were obtained. Then according to the possible local stress-strain curves, finite element analysis was introduced to predict the increased hardness. Comparing the increased hardness obtained by experiments and prediction, the unique local strain-stress curve and strain hardening exponent of chrome molybdenum alloy steel were determined. All results were discussed in detail. [ABSTRACT FROM AUTHOR]

Rolling contact experiments of (TiB + TiC)/Ti–6Al–4V composites reveal that inhomogeneous reinforcements reduce the materials’ rolling-contact fatigue (RCF) lives. The composite microstructures are examined and reconstructed based on the dual-beam focus ion beam scanning electron microscopy (FIB/SEM) technique. Integration of the microstructure-based stress analysis approach and Zaretsky’s RCF life prediction methodology leads to a new numerical RCF life modeling method. The newly developed mesh differential refinement scheme, together with the fast Fourier Transform techniques, is utilized to improve the efficiency and versatility of the proposed method. The RCF lives of the composites predicted by the new model are then compared with the experimental data, illustrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a numerical solution approach of solving smooth- and rough-surface contact problems involving distributed inhomogeneities with arbitrary shapes and different material properties, based on the numerical equivalent inclusion method (EIM). Full 3D FFT techniques and a mesh differential refinement scheme are incorporated into the proposed solution method to enhance the efficiency and flexibility. Comparative studies referencing the FEM and a simplified method demonstrate the efficiency and accuracy of the present method. Computations of several heterogeneous contact cases verify the capability of the method in solving complicated and rough-surface contact problems involving materials with distributed inhomogeneities. [ABSTRACT FROM AUTHOR]

This work quantitatively explores the dependence of the truncation errors on computational mesh settings for image-inclusion approaches and proposes a corresponding amendment. The new method is based on FFT algorithms and involves four individual portions. A mesh differential refinement scheme, consisting of independent and flexible selections-combinations of the surface, source, and target domains, is conceived to assist the proposed method. Comparisons of the results produced by the new and conventional mesh schemes demonstrate the significant improvements in computational performances. The new method can facilitate the numerical evaluation of local elastic characteristics caused by distributed inclusions or defects in contacting components. [ABSTRACT FROM AUTHOR]

Pullback attractor for Cohen–Grossberg neural networks with time-varying delays is investigated. By using the theory of pullback attractors and Lyapunov-Krasovskii functional, some novel criteria are established to ensure the existence of pullback attractor for Cohen–Grossberg neural networks. Finally, two examples are given to illustrate our theoretical results and indicate that two sets of criteria do not include each other. [ABSTRACT FROM AUTHOR]

In this paper, a time-delayed free boundary problem for tumor growth under the action of external inhibitors is studied. It is assumed that the process of proliferation is delayed compared with apoptosis. By Lp theory of parabolic equations, the Banach fixed point theorem and the continuation theorem, the existence and uniqueness of a global solution is proved. The asymptotic behavior of the solution is also studied. The proof uses the comparison principle and the iteration method. [ABSTRACT FROM AUTHOR]

Planetary gearboxes are widely used in helicopters, wind turbines, mining machinery, and so forth. The structure and motion type of a planetary gearbox are more complex in comparison with a fixed-shaft one, which makes condition monitoring and fault diagnosis of planetary gearbox a challenging issue in practical applications. In order to understand the fundamental nature of planetary gearbox vibration, this paper conducts an investigation on vibration characteristics of a single-stage planetary gearbox. Assuming that the gearbox and the sensor revolve inversely at the speed of planet carrier, the problem can be transformed into two easier parts: research on fixed-shaft gearbox signal model and research on influence of sensor spinning. Based on this assumption, a vibration signal model of planetary gearbox is obtained. Experimental data are used to validate the model. [ABSTRACT FROM AUTHOR]

Background and objective: The COVID-19 pandemic is a major global health crisis of this century. The use of neural networks with CT imaging can potentially improve clinicians' efficiency in diagnosis. Previous studies in this field have primarily focused on classifying the disease on CT images, while few studies targeted the localisation of disease regions. Developing neural networks for automating the latter task is impeded by limited CT images with pixel-level annotations available to the research community. Methods: This paper proposes a weakly-supervised framework named "Weak Variational Autoencoder for Localisation and Enhancement" (WVALE) to address this challenge for COVID-19 CT images. This framework includes two components: anomaly localisation with a novel WVAE model and enhancement of supervised segmentation models with WVALE. Results: The WVAE model have been shown to produce high-quality post-hoc attention maps with fine borders around infection regions, while weak supervision segmentation shows results comparable to conventional supervised segmentation models. The WVALE framework can enhance the performance of a range of supervised segmentation models, including state-of-art models for the segmentation of COVID-19 lung infection. Conclusions: Our study provides a proof-of-concept for weakly supervised segmentation and an alternative approach to alleviate the lack of annotation, while its independence from classification & segmentation frameworks makes it easily integrable with existing systems. [ABSTRACT FROM AUTHOR]

On-line monitoring of propofol in exhaled air is a potential way to evaluate the anaesthesia depth for patients during surgery. In this study, a negative Ni ionization high resolution ion mobility spectrometer with Bradbury-Nielsen-Gate-Grid structure was built to measure propofol with reactant ions Cl(HO) using dichloromethane as dopant. Instead of forming three propofol ions (M - H), M · O, and (M - H) with reactant ions O(HO), only product ion M · Cl was produced when introducing dichloromethane gas. The peak-to-peak resolution ( R) between reactant ions Cl(HO) and product ion M · Cl was 17.4, which was 1.6 times larger than that between O(HO) and product ion. Furthermore, the linear response range using reactant ions Cl(HO) was 3.5 times wider than that obtained with reactant ions O(HO). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This research explores the influence of distributed non-interpenetrating inhomogeneities on the contact of inhomogeneous materials via a new efficient numerical model based on Eshelby's Equivalent Inclusion Method. The half-space contact of a sphere with an inhomogeneous material is considered, and the solutions take into account interactions between all inhomogeneities. The efficiency and solution accuracy of the proposed method are demonstrated through comparative studies with those of an existing numerical method and the finite element method. The influence of spatial inhomogeneity orientations on the contact elastic field is investigated and parametric studies are conducted for the effect of arbitrarily distributed inhomogeneities on the stress field of the materials. The significance of the influences of inhomogeneity distribution parameters on the inverse volumetric stress integral is quantified and the corresponding data are fitted into selected several formulas as a step towards understanding the rolling contact fatigue life of the materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] The microstructure variations analyzed with SEM reveal the plastic flows. [•] The reinforcements are prone to flake off and fracture in the damaged layers. [•] The rolling pressure and cyclic stress are adverse to the RCF lives. [•] The reinforcements cause the reduction of RCF lives due to stress concentration. [•] The relative RCF lives are predicted via a new numerical method. [Copyright &y& Elsevier]

This paper deals with a mathematical model for tumor growth with angiogenesis and a necrotic core. The problem is a nonlinear problem which has two free boundaries: the external boundary of the tumor and the external boundary of the internal necrotic core. Using the implicit function theorem, the relationship between the two free boundaries is studied. The asymptotic stability of the unique steady-state solution is proved. The effect of nutrient concentration on tumor growth is studied. The relationship between the stage with a necrotic core and the stage without necrotic core is also studied. The results show that whether the steady-state of tumor growth has a necrotic core or not is determined by the concentration of external nutrients. The stage of tumor with necrotic core and the stage without necrotic core could transform into each other by adjusting the concentration of external nutrients. [ABSTRACT FROM AUTHOR]

Background Lung cancer is the leading cause of cancer-related death and has become an enormous economic burden in China. Low-dose spiral computed tomography ( LDCT) screening could reduce lung cancer mortality. The feasibility of conducting a population-based lung cancer screening with LDCT in China is uncertain. Methods In 2010, a demonstration program of lung cancer screening was initiated in China. High-risk individuals were enrolled in a cluster sampling design in different centers. Participants received baseline and annual screening with spiral CT and follow-up information was collected. The objective of this program is to evaluate the feasibility of conducting population-based LDCT lung cancer screening in the Chinese context. The rates of detection, early diagnosis and treatment are defined as indicators of program performance. The optimal management strategies for nodules are explored in the Chinese context based on experiences in other studies overseas. Results A demonstration program of ongoing prospective, multi-center, population-based lung cancer screening is being performed in China. Conclusions This demonstration program will provide opportunities to explore the feasibility of LDCT lung cancer screening in the Chinese setting. [ABSTRACT FROM AUTHOR]