Determination of the seismic performance factors for post‐tensioned rocking timber wall systems

Post‐tensioned technologies for concrete seismic resistant buildings were first developed in the 1990s during the PREcast Seismic Structural Systems program. Among different solutions, the hybrid system proved to be the most resilient solution providing a combination of re‐centering and energy dissipative contributions respectively by using post‐tensioned tendons and mild steel reinforcement. The system, while providing significant strength and energy dissipation, reduces structural element damage and limits post‐earthquake residual displacements. More recently, the technology was extended to laminated veneer lumber (LVL) structural members, and extensive experimental and numerical work was carried out and allowed the development of reliable analytical and numerical models as well as design guidelines. On the basis of the experimental and numerical outcomes, this paper presents the evaluation of the seismic performance factors for post‐tensioned rocking LVL walls using the FEMA P‐695 procedure. Several archetype buildings were designed considering different parameters such as the building and story height, the type of seismic resistant system, the magnitude of gravity loads and the seismic design category. Lumped plasticity models were developed for each index archetype to simulate the behavioral aspects and collapse mechanisms. Non‐linear quasi‐static analyses were carried out to evaluate the system over‐strength factor; moreover, non‐linear time history analyses were performed using the incremental dynamic analysis concept to assess the collapse of each building. From the results of quasi‐static and dynamic analyses the response modification factor, R, system over‐strength factor, Ω₀, and deflection amplification factor, C_d, values of, respectively, 7, 3.5 and 7.5 are recommended. Copyright © 2016 John Wiley & Sons, Ltd.     

平均经圈环流在大气角动量和感热收支中的作用

本文研究相对座标系中近地表角动量的制造和自由大气中角动量的辐散之间的平衡机制,并与绝对参考系中的机制进行比较。 对1982年元月全球角动量和感热的收支分析证明,被激发的平均经圈环流具有下述特征:其下部水平支施加于大气的惯性矩与近地表角动量的制造相平衡,上部水平支反号的惯性矩与涡动角动量通量的辐合(散)相平衡;而其垂直支的绝热加热效应则平衡着自由大气中热通量的辐散和/或大气的非绝热加热。因而,无论动力上还是热力上,平均经圈环流在大气总环流中都起着重要的作用。     

Behavior of epidote at high pressure and high temperature: a powder diffraction study up to 10 GPa and 1,200 K

The thermo-elastic behavior of a natural epidote [Ca_1.925 Fe_0.745Al_2.265Ti_0.004Si_3.037O₁₂(OH)] has been investigated up to 1,200 K (at 0.0001 GPa) and 10 GPa (at 298 K) by means of in situ synchrotron powder diffraction. No phase transition has been observed within the temperature and pressure range investigated. P–V data fitted with a third-order Birch–Murnaghan equation of state (BM-EoS) give V ₀ = 458.8(1)ų, K _T0 = 111(3) GPa, and K′ = 7.6(7). The confidence ellipse from the variance–covariance matrix of K _T0 and K′ from the least-square procedure is strongly elongated with negative slope. The evolution of the “Eulerian finite strain” vs “normalized stress” yields Fe(0) = 114(1) GPa as intercept values, and the slope of the regression line gives K′ = 7.0(4). The evolution of the lattice parameters with pressure is slightly anisotropic. The elastic parameters calculated with a linearized BM-EoS are: a ₀ = 8.8877(7) Å, K _T0(a) = 117(2) GPa, and K′(a) = 3.7(4) for the a-axis; b ₀ = 5.6271(7) Å, K _T0(b) = 126(3) GPa, and K′(b) = 12(1) for the b-axis; and c ₀ = 10.1527(7) Å, K _T0(c) = 90(1) GPa, and K’(c) = 8.1(4) for the c-axis [K _T0(a):K _T0(b):K _T0(c) = 1.30:1.40:1]. The β angle decreases with pressure, β_P(°) = β_P0 −0.0286(9)P +0.00134(9)P ² (P in GPa). The evolution of axial and volume thermal expansion coefficient, α, with T was described by the polynomial function: α(T) = α₀ + α₁ T ^−1/2. The refined parameters for epidote are: α₀ = 5.1(2) × 10⁻⁵ K⁻¹ and α₁ = −5.1(6) × 10⁻⁴ K^1/2 for the unit-cell volume, α₀(a) = 1.21(7) × 10⁻⁵ K⁻¹ and α₁(a) = −1.2(2) × 10⁻⁴ K^1/2 for the a-axis, α₀(b) = 1.88(7) × 10⁻⁵ K⁻¹ and α₁(b) = −1.7(2) × 10⁻⁴ K^1/2 for the b-axis, and α₀(c) = 2.14(9) × 10⁻⁵ K⁻¹ and α₁(c) = −2.0(2) × 10⁻⁴ K^1/2 for the c-axis. The thermo-elastic anisotropy can be described, at a first approximation, by α₀(a): α₀(b): α₀(c) = 1 : 1.55 : 1.77. The β angle increases continuously with T, with β_T(°) = β_T0 + 2.5(1) × 10⁻⁴ T + 1.3(7) × 10⁻⁸ T ². A comparison between the thermo-elastic parameters of epidote and clinozoisite is carried out.     

Global photometric properties of Asteroid (4) Vesta observed with Dawn Framing Camera

Dawn spacecraft orbited Vesta for more than one year and collected a huge volume of multispectral, high-resolution data in the visible wavelengths with the Framing Camera. We present a detailed disk-integrated and disk-resolved photometric analysis using the Framing Camera images with the Minnaert model and the Hapke model, and report our results about the global photometric properties of Vesta. The photometric properties of Vesta show weak or no dependence on wavelengths, except for the albedo. At 554 nm, the global average geometric albedo of Vesta is 0.38 ± 0.04, and the Bond albedo range is 0.20 ± 0.02. The bolometric Bond albedo is 0.18 ± 0.01. The phase function of Vesta is similar to those of S-type asteroids. Vesta’s surface shows a single-peaked albedo distribution with a full-width-half-max ∼17% relative to the global average. This width is much smaller than the full range of albedos (from ∼0.55× to >2× global average) in localized bright and dark areas of a few tens of km in sizes, and is probably a consequence of significant regolith mixing on the global scale. Rheasilvia basin is ∼10% brighter than the global average. The phase reddening of Vesta measured from Dawn Framing Camera images is comparable or slightly stronger than that of Eros as measured by the Near Earth Asteroid Rendezvous mission, but weaker than previous measurements based on ground-based observations of Vesta and laboratory measurements of HED meteorites. The photometric behaviors of Vesta are best described by the Hapke model and the Akimov disk-function, when compared with the Minnaert model, Lommel–Seeliger model, and Lommel–Seeliger–Lambertian model. The traditional approach for photometric correction is validated for Vesta for >99% of its surface where reflectance is within ±30% of global average.     

Carbon dioxide degassing and thermal energy release in the Monte Amiata volcanic-geothermal area (Italy)

The quaternary volcanic complex of Mount Amiata is located in southern Tuscany (Italy) and represents the most recent manifestation of the Tuscan Magmatic Province. The region is characterised by a large thermal anomaly and by the presence of numerous CO₂-rich gas emissions and geothermal features, mainly located at the periphery of the volcanic complex. Two geothermal systems are located, at increasing depths, in the carbonate and metamorphic formations beneath the volcanic complex. The shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit (Ligurian Unit). A measured CO₂ discharge through soils of 1.8 × 10⁹ mol a⁻¹ shows that large amounts of CO₂ move from the deep reservoir to the surface. A large range in δ¹³C_TDIC (−21.07 to +3.65) characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of TDIC allows distinguishing a discharge of 0.3 × 10⁹ mol a⁻¹ of deeply sourced CO₂ in spring waters. The total natural CO₂ discharge (2.1 × 10⁹ mol a⁻¹) is slightly less than minimum CO₂ output estimated by an indirect method (2.8 × 10⁹ mol a⁻¹), but present-day release of 5.8 × 10⁹ mol a⁻¹ CO₂ from deep geothermal wells may have reduced natural CO₂ discharge. The heat transported by groundwater, computed considering the increase in temperature from the infiltration area to the discharge from springs, is of the same order of magnitude, or higher, than the regional conductive heat flow (>200 mW m⁻²) and reaches extremely high values (up to 2700 mW m⁻²) in the north-eastern part of the study area. Heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking. The comparison of CO₂ flux, heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining CO₂ degassing and heat transfer patterns.     

Detecting recent changes in the demographic parameters of drosophilid populations from western and central Africa

Previous genetic studies showing evidence of past demographic changes in African drosophilids suggested that these populations had strongly responded to Quaternary climate changes. We surveyed nine species of Zaprionus, a drosophilid genus mostly present in Africa, in forests located between southern Senegal and Gabon. The mitochondrial COI gene showed contrasted levels of sequence variation across species. Populations of the only cosmopolitan species of the genus, Z. indianus, and of its closely related sibling species, Z. africanus, are highly polymorphic and appear to have undergone a continuous population expansion beginning about 130,000 years ago. Five less variable species probably underwent a population expansion beginning only about 20,000–30,000 years ago. One of them, Z. taronus, was significantly structured between forest blocks. The last two species were nearly monomorphic, probably due to infection by Wolbachia. These results are similar to those obtained in three species from the melanogaster subgroup, and may be typical of the responses of African drosophilid populations to glacial cycles.     

A Block-Based Theoretical Model Suited to Gravitational Sliding

An original theoretical model has been devised to simulate mass flow over hill slopes due to gravitational sliding. The sliding mass is discretized into a sequence of contiguous blocks which are subjected to gravitational forces, to bottom friction and to surface resistance stresses that are generally negligible for subaerial flows, but are relevant for submarine slides. The blocks interact with each other while sliding down the hill flanks because of internal forces that dissipate mechanical energy and produce a momentum exchange between the individual blocks, yet conserving the total momentum of the mass. Internal forces are expressed in terms of interaction coefficients depending on the instantaneous distance between the block centers of mass, which is a measure of the deformation experienced by the blocks: the functional dependence includes three parameters, namely the interaction intensity ¯, the deformability parameter and the shape parameter , by means of which a wide range of interaction types can be fully accounted for. The time integration is performed numerically by solving the equations for the block velocities and positions at any time ti by means of the block accelerations at the previous time t_i-1, and by subsequently updating the block accelerations, which allows to proceed iteratively to the following times. The model has been tested against laboratory results available from literature and by means of several numerical experiments involving a simplified geometry both for the sliding body and the basal surface, with the purpose of clarifying the influence of the model parameters on the slide dynamics. The model improves the performance of the existing kinematic models for slides, moreover preserving an equivalent numerical simplicity. Future applications and possible improvements of this model are suggested.     

Recharge estimation for transient ground water modeling

Reliable ground water models require both an accurate physical representation of the system and appropriate boundary conditions. While physical attributes are generally considered static, boundary conditions, such as ground water recharge rates, can be highly variable in both space and time. A practical methodology incorporating the hydrologic model HELP3 in conjunction with a geographic information system was developed to generate a physically based and highly detailed recharge boundary condition for ground water modeling. The approach uses daily precipitation and temperature records in addition to land use/land cover and soils data. The importance of the method in transient ground water modeling is demonstrated by applying it to a MODFLOW modeling study in New Jersey. In addition to improved model calibration, the results from the study clearly indicate the importance of using a physically based and highly detailed recharge boundary condition in ground water quality modeling, where the detailed knowledge of the evolution of the ground water flowpaths is imperative. The simulated water table is within 0.5 m of the observed values using the method, while the water levels can differ by as much as 2 m using uniform recharge conditions. The results also show that the combination of temperature and precipitation plays an important role in the amount and timing of recharge in cooler climates. A sensitivity analysis further reveals that increasing the leaf area index, the evaporative zone depth, or the curve number in the model will result in decreased recharge rates over time, with the curve number having the greatest impact.     

All-sky Data Assimilation of MWTS-2 and MWHS-2 in the Met Office Global NWP System.

Microwave radiances from passive polar-orbiting radiometers have been, until recently, assimilated in the Met Office global numerical weather prediction system after the scenes significantly affected by atmospheric scattering are discarded.Recent system upgrades have seen the introduction of a scattering-permitting observation operator and the development of a variable observation error using both liquid and ice water paths as proxies of scattering-induced bias. Applied to the Fengyun 3 Microwave Temperature Sounder 2(MWTS-2) and the Microwave Humidity Sounder 2(MWHS-2), this methodology increases the data usage by up to 8% at 183 GHz. It also allows for the investigation into the assimilation of MWHS-2 118 GHz channels, sensitive to temperature and lower tropospheric humidity, but whose large sensitivity to ice cloud have prevented their use thus far. While the impact on the forecast is mostly neutral with small but significant shortrange improvements, 0.3% in terms of root mean square error, for southern winds and low-level temperature, balanced by 0.2% degradations of short-range northern and tropical low-level temperature, benefits are observed in the background fit of independent instruments used in the system. The lower tropospheric temperature sounding Infrared Atmospheric Sounding Interferometer(IASI) channels see a reduction of the standard deviation in the background departure of up to 1.2%. The Advanced Microwave Sounding Unit A(AMSU-A) stratospheric sounding channels improve by up to 0.5% and the Microwave Humidity Sounder(MHS) humidity sounding channels improve by up to 0.4%.