Popular benchmark problems for geometric nonlinear analysis of shells

In most, if not all, of the previous work on finite element formulation and nonlinear solution procedures, results of geometric nonlinear benchmark problems of shells are presented in the form of load-deflection curves. In this paper, eight sets of popularly employed benchmark problems are identified and their detailed reference solutions are obtained and tabulated. It is hoped that these solutions will form a convenient basis for subsequent comparison and that the tedious yet inaccurate task of reconstructing data points by graphical measurement of previously reported load-deflection curves can be avoided. Moreover, the relative convergent difficulty of the problems are revealed by the number of load increments and the total number of iterations required by an automatic load incrementation scheme for attaining the converged solutions under the maximum loads. © 2003 Elsevier B.V. All rights reserved.postprin

The Probability Density Function of Ocean Surface Slopes and Its Effects on Radar Backscatter

Based on Longuet-Higgins\u27s theory of the probability distribution of wave amplitude and wave period and on some observations, a new probability density function (PDF) of ocean surface slopes is derived. It is f(zeta(x), zeta(y)) = n/2 pi(n - 1)sigma(u) sigma(c) x [1 + zeta(x)(2)/(n - 1)sigma(n)(2) + zeta(y)(2)/(n - 1)sigma(c)(2)](-(n + 2)/2) + skewness, where zeta(x) and zeta(y) are the slope components in upwind and crosswind directions, respectively; sigma(u)(2) and sigma(c)(2) are the corresponding mean-square slopes. The peakedness of slopes is generated by nonlinear wave-wave interactions in the range of gravity waves. The skewness of slopes is generated by nonlinear coupling between the short waves and the underlying long waves. The peakedness coefficient n of the detectable surface slopes is determined by both the spectral width of the gravity waves, and the ratio between the gravity wave mean-square slope and the detectable short wave mean-square slope. When n equals 10, the proposed PDF fits the Gram Charlier distribution, given by Cox and Munk, very well in the range of small slopes. When n --\u3e infinity, it is very close to the Gaussian distribution. Radar backscatter cross sections (RBCS), calculated from specular reflection theory using the new PDF of the C-band radar filtered surface slopes, are in keeping with empirically based ERS-1 C-band scatterometer models. In other words, the proposed PDF can be used successfully in the specular reflection theory to predict the RBCS in the range of incidence angles away from normal incidence. This suggests that the proposed PDF can be used to describe the distribution of surface slopes over the full range of slopes. This is an improvement over the Gaussian distribution and the Gram Charlier distribution. The comparison between the calculated RBCS and the ERS-1 C-band scatterometer models indicates that the peakedness coefficient n should be 5, for wind condition of U-10 less than or equal to 10 m s(-1). It is also found that the spectral width plays an important role on radar backscatter in the range of incidence angles less than 30 degrees

Hydrostatic pressure induced Dirac semimetal in black phosphorus

Motivated by recent experimental observation of an hydrostatic pressure induced transition from semiconductor to semimetal in black phosphorus [Chen et al. in arXiv:1504.00125], we present the first principles calculation on the pressure effect of the electronic structures of black phosphorus. It is found that the band crossover and reversal at the Z point occur around the critical pressure Pc1=1.23 Gpa, and the band inversion evolves into 4 twofold-degenerate Dirac cones around the Z point, suggesting a 3D Dirac semimetal. With further increasing pressure the Dirac cones in the Gamma-Z line move toward the Gamma point and evolve into two hole-type Fermi pockets, and those in the Z-M lines move toward the M point and evolve into 2 hole-type Fermi pockets up to P=4.0 Gpa. It demonstrates clearly that the Lifshitz transition occurs at $P_{c1}$ from semiconductor to 3D Dirac semimetal protected by the nonsymmorphic space symmetry of bulk. This suggests the bright perspective of black phosphorus for optoelectronic and electronic devices due to its easy modulation by pressure.Comment: 7 pages, 9 figures, and 2 table

Stabilized conforming nodal integration: Exactness and variational justification

In most Galerkin mesh-free methods, background integration cells partitioning the problem domain are required to evaluate the weak form. It is therefore worthwhile to consider these methods using the notions of domain decomposition with the integration cells being the subdomains. Presuming that the analytical solution is admissible in the trial solution, domain and boundary integration exactness, which depend on the orders of the employed trial solution and the required solution exactness, are identified for the strict satisfaction of traction reciprocity and natural boundary condition in the weak form. Unfortunately, trial solutions constructed by many mesh-free approximants contain non-polynomial terms which cannot be exactly integrated by Gaussian quadratures. Recently, stabilized conforming (SC) nodal integration for Galerkin mesh-free methods was proposed and illustrated to be linearly exact. This paper will discuss how linear exactness is ensured and how spurious oscillation encountered by direct nodal integration is suppressed in SC nodal integration from a domain decomposition point of view. Moreover, it will be shown that SC nodal integration can be formulated by the Hellinger-Reissner Principle and thus justified in the classical variational sense. Applications of the method to straight beam, plate and curved beam problems are presented. © 2004 Elsevier B.V. All rights reserved.postprin

Green Vehicle Routing Optimization Based on Carbon Emission and Multiobjective Hybrid Quantum Immune Algorithm

© 2018 Xiao-Hong Liu et al. Green Vehicle Routing Optimization Problem (GVROP) is currently a scientific research problem that takes into account the environmental impact and resource efficiency. Therefore, the optimal allocation of resources and the carbon emission in GVROP are becoming more and more important. In order to improve the delivery efficiency and reduce the cost of distribution requirements through intelligent optimization method, a novel multiobjective hybrid quantum immune algorithm based on cloud model (C-HQIA) is put forward. Simultaneously, the computational results have proved that the C-HQIA is an efficient algorithm for the GVROP. We also found that the parameter optimization of the C-HQIA is related to the types of artificial intelligence algorithms. Consequently, the GVROP and the C-HQIA have important theoretical and practical significance

珊瑚中微量铀的ID-ICP-MS 高精度测定及其在珊瑚U/Ca 温度计研究中的应用

建立了同位素稀释技术与IC-MS 相结合的ID-ICP-MS 分析方法, 成功测量了取自南海北部的滨珊瑚样品中的微量铀, 获得0.5% 左右的精度。并以此建立南海北部近岸海域的珊瑚U/Ca 温度计, 其温度精度可达士0.5 ℃。ID-ICP-MS, an analytical method that combines isotope dilution technique and ICP-MS method had been developed in our laboratory. Trace uranium of the coral samples from the northern area of the South China Sea had been measured to an accuracy of 0.5%. Depended on these results, a high resolution coral U/Ca thermometer for thes area was established. Monthly average SSTs with a precision of ±0.5℃ were attainable by this U/Ca thermometer.published_or_final_versio

Frequency-Reconfigurable Antenna using Metasurface

A frequency-reconfigurable antenna designed using metasurface (MS) to operate at around 5 GHz is proposed and studied. The frequency-reconfigurable metasurfaced (FRMS) antenna is composed of a simple circular patch antenna and a circular MS with the same diameter of 40 mm (0.67 λ) and implemented using planar technology. The MS is placed directly atop the patch antenna, making the FRMS antenna very compact and low profile with a thickness of only 3.048 mm (0.05 λ). The MS consists of rectangular-loop unit cells placed periodically in the vertical and horizontal directions. Simulation results show that the operating frequency of the antenna can be tuned by physically rotating the MS around the center with respect to the patch antenna. The MS placed atop the patch antenna behaves like a dielectric substrate and rotating the MS changes the equivalent relative permittivity of the substrate and hence the operating frequency of the FRMS antenna. Measured results show that the antenna has a tuning range from 4.76 to 5.51 GHz, a fractional tuning range of 14.6%, radiation efficiency and a realized peak gain of more than 80% and 5 dBi, respectively, across the tuning range. © 2013 IEEE.published_or_final_versio

Precise Sm-Nd and U-Pb isotopic dating of the supergiant Shizhuyuan polymetallic deposit and its host granite, SE China

The supergiant Shizhuyuan W-Sn-Bi-Mo deposit is hosted by the Qianlishan granite, a small, highly fractionated granitic pluton (~10 km2) with multiple phases of intrusions within the Early Yanshanian granitoid province of SE China. Strong alteration of skarn and greisen that formed in the contact zone between the first and second phases of granite intrusions and Devonian limestone is responsible for the polymetallic mineralizations. SHRIMP U-Pb zircon analysis indicates that the two early phases of the Qianlishan granite formed contemporaneously at 152 ± 2 Ma. Metasomatic minerals (garnet, fluorite and wolframite) separated from the skarn and greisen yield a Sm-Nd isochron age of 149 ± 2 Ma that is interpreted as the formation age of the Shizhuyuan deposit. Therefore, the mineralization of the supergiant Shizhuyuan polymetallic deposit formed contemporaneously with, or very shortly after, the intrusion of the small, highly fractionated Qianlishan granite. © 2004 Cambridge University Press.published_or_final_versio

Bio-Inspired Aggregation Control of Carbon Nanotubes for Ultra-Strong Composites

High performance nanocomposites require well dispersion and high alignment of the nanometer-sized components, at a high mass or volume fraction as well. However, the road towards such composite structure is severely hindered due to the easy aggregation of these nanometer-sized components. Here we demonstrate a big step to approach the ideal composite structure for carbon nanotube (CNT) where all the CNTs were highly packed, aligned, and unaggregated, with the impregnated polymers acting as interfacial adhesions and mortars to build up the composite structure. The strategy was based on a bio-inspired aggregation control to limit the CNT aggregation to be sub 20--50 nm, a dimension determined by the CNT growth. After being stretched with full structural relaxation in a multi-step way, the CNT/polymer (bismaleimide) composite yielded super-high tensile strengths up to 6.27--6.94 GPa, more than 100% higher than those of carbon fiber/epoxy composites, and toughnesses up to 117--192 MPa. We anticipate that the present study can be generalized for developing multifunctional and smart nanocomposites where all the surfaces of nanometer-sized components can take part in shear transfer of mechanical, thermal, and electrical signals

Genetic loci mapping for ear axis weight using recombinant inbred line (RIL) population under different nitrogen regimes in maize

Ear axis weight (EAW) is one of the important agronomic traits in maize (Zea mays L.), related to yield. To understand its genetic basis, a recombinant inbred line (RIL) population, derived from the cross Mo17 × Huangzao4, was used for quantitative trait locus mapping (QTL) for EAW under high and low nitrogen (N) regimes. The results showed that a total of three QTLs were mapped on chromosomes 2 (two) and 4 (one) under the two N regimes, which could explain phenotypic variances from 4.76 to 7.12%. They were near to their linked markers, with mapping interval of 0.2 to 1.0 cM. The two loci on chromosome 2 (bin 2.09) made EAW increase due to positive additive effects, while the other locus on chromosome 4 (bin 4.08) made EAW decrease to some extent, owing to negative additive effects. These results are beneficial for understanding the genetic basis of KNE and developing marker-assisted selection in maize breeding project.Key words: Maize (Zea mays L.), ear axis weight, quantitative trait locus, recombinant inbred line, nitrogen