Modeling of soil penetration resistance using multiple linear regression (MLR)

In agricultural areas, the use of machinery leads to improved yields. Nevertheless, its inadequate implementation and excessive utilization can seriously affect the soil efficiency. In fact, latter can be generated by increasing the penetration resistance and subsequently, it results in the compaction phenomenon. This problem becomes considerable with the increasing report wheel/soil. The aim of this work was to evaluate the efficiency through the prediction of soil penetration resistance (Rp) using a statistical model based on moisture content, density, tractor weight, number of passes, and the wheel inflation pressure. Experimental works (211 measurements) were analyzed and the penetration resistance was modeled using multiple linear regressions (MLR). Besides, the developed model elucidates the variables affecting the accentuation of soil Rp and allows the investigation of equations for novel sampled soils. Our results showed that the parameters related to soil and tractors were significant to explain Rp. The adopted model in the MLR analysis emphasizes that the mechanical parameters of ground measurements are statistically significant in estimating and evaluating Rp. The statistical calculation of the R ² expresses 83% of the variance in Rp generated by the various parameters related to soil and tractor. In view of the importance of estimating the penetration resistance (Rp), the regression equation shows that the weight of the tractor and the number of passages contributed the most to the proposed model for the soil.     

Flow‐Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations

This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow‐through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream‐aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow‐through streams.     

An isolation system for limited seismic gaps in near‐fault zones

The ability of a recently proposed seismic isolation system, with inherent self‐stopping mechanism, to mitigate or even eliminate seismic pounding of adjacent structures is investigated under severe near‐fault earthquakes. The isolation system is referred to as roll‐in‐cage (RNC) isolator. It is a rolling‐based isolator that provides in one unit the necessary functions of vertical rigid support, horizontal flexibility with enhanced stability, hysteretic energy dissipation, and resistance to minor vibration loads. In addition, the RNC isolator is distinguished by a self‐stopping (buffer) mechanism to limit the bearing displacement under excitations stronger than a design earthquake or at limited seismic gaps, and a linear gravity‐based self‐recentering mechanism to prevent permanent bearing displacement without causing vertical fluctuation of the isolated structure. A previously developed multifeature SAP2000 model of the RNC isolator is improved in this paper to account for the inherent buffer mechanism's damping. Then, the effectiveness of the isolator's buffer mechanism in limiting peak bearing displacements is studied together with its possibly arising negative influence on the isolation efficiency. After that, the study investigates how to alleviate or even eliminate those possibly arising drawbacks, due to the developed RNC isolator's inner pounding as a result of its buffer activation, to achieve efficient seismic isolation with no direct structure‐to‐structure pounding, considering limited seismic gaps with adjacent structures and near‐fault earthquakes. The results show that the RNC isolator could be an efficient solution for aseismic design in near‐fault zones considering limited seismic gaps. Earthquake Engineering and Structural Dynamics. Copyright © 2014 John Wiley & Sons, Ltd.     

Neo-deterministic seismic hazard assessment in North Africa

North Africa is one of the most earthquake-prone areas of the Mediterranean. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss of life and considerable economic damage to the region. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using the neo-deterministic, multi-scenario methodology (NDSHA) based on the computation of synthetic seismograms, using the modal summation technique, at a regular grid of 0.2?×?0.2°. This is the first study aimed at producing NDSHA maps of North Africa including five countries: Morocco, Algeria, Tunisia, Libya, and Egypt. The key input data for the NDSHA algorithm are earthquake sources, seismotectonic zonation, and structural models. In the preparation of the input data, it has been really important to go beyond the national borders and to adopt a coherent strategy all over the area. Thanks to the collaborative efforts of the teams involved, it has been possible to properly merge the earthquake catalogues available for each country to define with homogeneous criteria the seismogenic zones, the characteristic focal mechanism associated with each of them, and the structural models used to model wave propagation from the sources to the sites. As a result, reliable seismic hazard maps are produced in terms of maximum displacement (D _max), maximum velocity (V _max), and design ground acceleration.     

组合压气机中尾迹与势流同频/异频干涉的叠加特性

为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化;当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。      

Studies on water-in-oil products from crude oils and petroleum products

Water-in-oil mixtures such as emulsions, often form and complicate oil spill countermeasures. The formation of water-in-oil mixtures was studied using more than 300 crude oils and petroleum products. Water-in-oil types were characterized by resolution of water at 1 and 7 days, and some after 1 year. Rheology measurements were carried out at the same intervals. The objective of this laboratory study was to characterize the formed water-in-oil products and relate these properties to starting oil properties. Analysis of the starting oil properties of these water-in-oil types shows that the existence of each type relates to the starting oil viscosity and its asphaltene and resin contents. This confirms that water-in-oil emulsification is a result of physical stabilization by oil viscosity and chemical stabilization by asphaltenes and resins. This stabilization is illustrated using simple graphical techniques. Four water-in-oil types exist: stable, unstable, meso-stable and entrained. Each of these has distinct physical properties.     

Bacterial and Virus‐Like Particle Abundances in Purged and Unpurged Groundwater Depth Profiles

Bacteria and viruses are ubiquitous in subterranean aquatic habitats. Bacterial abundance is known to vary with depth in aquifers; however, whether viral abundance varies with depth is less well known. Here we use flow cytometry (FCM) to enumerate bacteria and virus‐like particles (VLP) from groundwater depth profiles. Groundwater samples were obtained from a set of nested piezometers from depths of 15, 30, 45, 60, 80, and 90 m and bacteria and VLP abundances were determined in purged aquifer water and unpurged water at each slot depth. Mean bacterial abundance (cells / mL) was not significantly different in unpurged water (3.2 × 10⁵) compared to purged water (1.4 × 10⁵); however, mean VLP abundance (particles / mL) was significantly greater in unpurged water (4.4 × 10⁵) compared to purged water (2.3 × 10⁵). Purged water was used to investigate the aquifer depth profile and bacterial and VLP abundances were observed to vary significantly between depths. The virus‐bacteria ratio was determined and was observed to steadily increase with depth. Overall, our data indicate the dynamic nature of bacterial and viral abundances in subsurface environments which should be considered when designing groundwater microbial sampling methodologies.     

安徽及近邻区地震烈度衰减特征研究

利用安徽及近邻区地震烈度资料,采用椭圆衰减模型和长轴可转向与近、远场补点方法,通过多元回归方法进行拟合,建立该地区地震烈度衰减关系。该衰减关系用于安徽地震应急指挥技术系统震害快速评估模块,为地震灾害损失快速评估提供基础资料;也可用于安徽地区地震安全性评价、震害预测等防震减灾领域。