AW-6016-T4板材的低温成形行为（英文）

研究析出强化AW-6016-T4金属板材的低温成形行为。利用拉伸和Nakazima测试方法获得材料在-196至25°C范围内的流变曲线和成形极限曲线。结果表明,材料的强度和伸长率随温度的降低而增大。背散射电子衍射(EBSD)研究表明变形材料在室温和低温下显微组织有细微区别。但连续加热差热分析表明析出动力学之间无明显区别。本研究结果表明低温变形可用于制造8 mm深的B柱,而常温变形只能制造6 mm深的B柱。

Reflection and refraction of attenuated waves at boundary of elastic solid and porous solid saturated with two immiscible viscous fluids

The propagation of elastic waves is studied in a porous solid saturated with two immiscible viscous fluids. The propagation of three longitudinal waves is represented through three scalar potential functions. The lone transverse wave is presented by a vector potential function. The displacements of particles in different phases of the aggregate are defined in terms of these potential functions. It is shown that there exist three longitudinal waves and one transverse wave. The phenomena of reflection and refraction due to longitudinal and transverse waves at a plane interface between an elastic solid half-space and a porous solid half-space saturated with two immiscible viscous fluids are investigated. For the presence of viscosity in pore-fluids, the waves refracted to the porous medium attenuate in the direction normal to the interface. The ratios of the amplitudes of the reflected and refracted waves to that of the incident wave are calculated as a non- singular system of linear algebraic equations. These amplitude ratios are used to further calculate the shares of different scattered waves in the energy of the incident wave. The modulus of the amplitude and the energy ratios with the angle of incidence are computed for a particular numerical model. The conservation of the energy across the interface is verified. The effects of variations in non-wet saturation of pores and frequencies on the energy partition are depicted graphically and discussed,

Reflection and refraction of plane waves at the boundary of an elastic solid and double-porosity dual-permeability materials

Phenomena of reflection and refraction of plane harmonic waves at a plane interface between an elastic solid and doubleporosity dual-permeability material are investigated. The elastic solid behaves non-dissipatively, while double-porosity dual-permeability materials behave dissipatively to wave propagation due to the presence of viscosity in pore fluids. All the waves(i.e., incident and reflected) in an elastic medium are considered as homogeneous(i.e., having the same directions of propagation and attenuation), while all the refracted waves in double-porosity dual-permeability materials are inhomogeneous(i.e., having different directions of propagation and attenuation). The coefficients of reflection and refraction for a given incident wave are obtained as a non-singular system of linear equations. The energy shares of reflected and refracted waves are obtained in the form of an energy matrix. A numerical example is considered to calculate the partition of incident energy among various reflected and refracted waves. The effect of incident direction on the partition of the incident energy is analyzed with a change in wave frequency, wave-induced fluid-flow, pore-fluid viscosity and double-porosity structure.It has been confirmed from numerical interpretation that during the reflection/refraction process, conservation of incident energy is obtained at each angle of incidence.

非时变海洋测深——新概念的定义与概述

目前,全世界在陆地和海洋上应用了几百个高器基准。我们生活在陆地上,则往往优先考虑陆地基准。而适时修正一些基准的工作已经开始,这基准包括已建立的北美基准(NAD)1983、欧洲基准(ED)1979和EURFF1989以及将要建立的象南美的SIRGAS和韩国的KRF1994。 值得注意的是,在海洋上仍没有定义一个完整的精密水平基准,一般是将陆地基准外推至海洋上来绘制海图。对海图垂直基准而言,各国在顾及航行安全而进行定义时缺乏共识而使之变得复杂化。 另外,将潮汐海面作为垂直基准来确定高程和深度,其值是时变的,并且没有共同的零点。这使得海岸之间和沿岸产生倾斜,并提供不了适用于全球统一的垂直基准。 本文讨论了海图垂直基准问题,并提出用高精度大地水准面作为非时变海洋测深0参考面的新概念,详细论述了如何获得0参考面和在实时导航中如何使用这个基准。为保证0基准面的一致性,避免采用局部或不同的全球大地水准面很有必要。

Estimation of carbon pools in secondary tropical deciduous forests of Odisha,India

Secondary tropical forests sequester atmospheric CO 2 at relatively faster rates in vegetation and in soil than old-growth primary forests.Spatial understanding of biomass and carbon stocks in different plant functional types of these forests is important.Structure,diversity,composition,soil features and carbon stocks in six distinct plant functional types,namely:Moist Mixed-Deciduous Forest,Peninsular Sal Forest(PSF),Semi-Evergreen Forest(SEF),Planted Teak Forest,Bamboo Brakes(BB),and Degraded Thorny Shrubby Forest were quantified as secondary tropical deciduous forests of the Chandaka Wildlife Sanctuary,Eastern Ghats of Odisha,India.Seventy-one species≥10 cm Girth at breast height(GBH)were recorded,belonging to 38 families and 65 genera.Above-ground biomass carbon and soil organic carbon ranged from 2.1–72.7 Mg C ha^(−1) and 20.6–67.1 Mg C ha^(−1),respectively,among all plant functional types.Soil organic carbon and important value index were positively correlated with above-ground biomass carbon.Maximum carbon allocation was in SOC pool(51–91%),followed by the above-ground biomass pool(9–52%),indicating SOC is one of the major carbon sinks in secondary dry forests.The results highlight the importance of secondary tropical deciduous forests in biodiversity conservation and ecological importance in reducing greenhouse gases.

冲击热处理AW-7075-T6板材的成形过程（英文）

研究AW-7075-T6板材在200～480℃进行冲击热处理的成形行为。采用室温拉伸和深拉拔试验表征冲击热处理后样品的可成形性;采用差示扫描量热法(DSC)分析AW-7075板材冲击热处理前后的相沉积状态。结果表明,从300℃起,随着冲击热处理温度的升高,板材的成形性开始提高;由η′析出物溶解导致的应变硬化以及剩余析出物的粗化有助于板材室温成形性能的提高;沉淀物的再析出和粗化是冲击热处理试样强度提高的主要原因。

1984世界大地测量系统(WGS84)

自1960年以来,美国国防制图局(DMA)已建立了四个世界大地测量系统(WGS);WGS60、WGS66、WGS72和WGS84。最新的WGS84与前三者相比,是最为精确的大地参考框架,它是利用了广泛的、最新的大地测量数据全球确定的。WGS84提供了精确的参照框架、地球重力场模型、正常重力公式、大地水准面和包括全部大陆和主要海洋岛屿在内的105个局部(和区域)大地测量基准的转换参数。这些成果使测绘(MC&G)的复杂性明显地简化,并使国防制图局(DMA)的全球性成果在质量扣精度方面普遍得到提高。本文介绍对庞大数据组的研究和费时的计算,这些科研成果是令人感兴趣的,还给出应用WGS84去改善全球性测绘成果的方法和优点。

Measurement of the integrated luminosity of the Phase 2 data of the Belle Ⅱ experiment

From April to July 2018,a data sample at the peak energy of the T(4 S) resonance was collected with the Belle Ⅱ detector at the SuperKEKB electron-positron collider.This is the first data sample of the Belle Ⅱ experiment.Using Bhabha and digamma events,we measure the integrated luminosity of the data sample to be(496.3±0.3±3.0) pb-1,where the first uncertainty is statistical and the second is systematic.This work provides a basis for future luminosity measurements at Belle Ⅱ.

Effect of various physical properties on the reflection coefficients of inhomogeneous waves at the stress-free surface of partially saturated soils induced by obliquely incident fast P-wave

Ghasemzadeh and Abounouri[1]developed a mathematical model of partially saturated soils that is solved using the potential method,which decomposes elastodynamics equations into two standard wave equations,a scalar wave equation for scalar potential and a vector wave equation for vector potential.In such a medium,four waves exist three longitudinal and one shear.Each fluid phase tortuous path is taken into account in this model.The inertial coupling between solid and fluid particles is consid-ered.Furthermore,both open-pore and sealed-pore boundaries are explored to investigate the reflection phenomenon at the surface of partially saturated soils.For both boundaries,the reflection coefficients of inhomogeneous waves at a partially saturated soil surface are found as a non-singular set of linear equations.All waves(both reflected and incident)in partially saturated soils are pronounced as inhomogeneous due to viscosity in pore fluids(i.e.,distinct directions of attenuation and propagation).The energy shares of reflected waves are determined using an energy matrix.A numerical example is used to determine the reflection coefficients and the distribution of incident energy among the various reflected waves.The effect of different physical features on reflection coefficients and incident energy partitioning is illustrated graphically.The conservation of incident energy at the surface of partially saturated soils is mathematically confirmed at all angles of incidence.