Evidence of beneficial role of inclined piles: observations and summary of numerical analyses

The behaviour under seismic loading of inclined piles embedded in two idealized soil profiles, a homogeneous and a non-homogenous “Gibson” soil, is analysed with 3D finite elements. Two structures, modeled as single-degree-of-freedom oscillators, are studied: (1) a tall slender superstructure (H _st = 12 m) whose crucial loading is the overturning moment, and (2) a short structure (H _st = 1 m) whose crucial loading is the shear force. Three simple two-pile group are studied: (a) one comprising a vertical pile and a pile inclined at 25°, (b) one consisting of two piles symmetrically inclined at 25°, and (c) a group of two vertical piles. The influence of key parameters is analysed and non-dimensional diagrams are presented to illustrate the role of raked piles on pile and structure response. It is shown that this role can be beneficial or detrimental depending on a number of factors, including the slenderness of the superstructure and the type of pile-to-cap connection.     

Northern Greece's industrial minerals: production and environmental technology developments

This paper reviews the use of Greek industrial minerals into developing low-cost, high-tech solutions to remediate parts of the chemical pollution environmental problem. The remediation strategy, based on the application and implementation of the Greek industrial minerals potential, became a major line of investigation in projects to develop new environmental technologies. Although past and current experiments have been successful on a lab scale in a number of applications, the results have not always been implemented on industrial scales. Greek olivine has been successfully tested as neutralizing agent for acid wastes, co-producing exploitable amounts of silica gel, magnesium sulphate and magnetite. Vermiculite is currently tested as an environmental ‘cleanser' in a variety of applications, i.e. metalliferous mine seepage and processing waters, organically contaminated waste water from the textile/dye industry and absorption material for oil spills. Wollastonite will be applied as long-term fertiliser and dolomite, as a substitute of asbestos in brake linings, as pollution controller of heavy metal concentrations in waste waters and as a binder to stabilize waste solids. Magnesite has been successfully applied for neutralization of acid mine wastes produced from active sulphide deposits. Zeolites (fly ash and perlite converted to zeolites were also considered) is an objective for several environmental applications, i.e. as floating absorbent for waste water ponds, as drinking water purificator or as smell abatement.     

Storm graded sand at 200 m water depth,Scotian Shelf,Eastern Canada

Graded sand-to-mud beds are a common shelf facies in the rock record. Similar beds were studied in nine cores from the sandmud transition at the edge of Emerald Basin to determine their frequency and mode of origin. Graded sand-to-mud beds 5 to 20 cm thick can be correlated between cores and thicken basinwards, with average sand content decreasing from 60% to 5% over 7 km. European weed pollen distribution indicates only the top bed is less than 200 years old. The graded beds were deposited from suspension during storms with a several hundred year recurrence interval.     

Geophysical investigation of tumuli by means of surface 3D Electrical Resistivity Tomography

Tumuli are artificially erected small hills that cover monumental tombs or graves. In this work, the surface three-dimensional (3D) Electrical Resistivity Tomography (ERT) method, composed of dense parallel two-dimensional (2D) tomographies, was used to investigate the properties of the tumuli filling material and to resolve buried archaeological structures inside the tumuli.The effectiveness of the method was investigated by numerical modeling and through 3D inversion of synthetic apparent resistivity data. A resistivity model that simulates the inhomogeneous tumulus material and the tombs that are buried inside the tumulus was assumed. The Dipole–Dipole (DD), Pole–Dipole (PD), Pole–Pole (PP), Gradient (GRAD), Midpoint-Potential-Referred (MPR) and Schlumberger Reciprocal (SCR) arrays, which are suitable for multichannel resistivity instruments, were tested. The tumulus topography (pyramid or capsized cup) was incorporated into the inversion procedure through a distorted finite element mesh. The inversion procedure was based on a smoothness constrained Gauss–Newton algorithm in which the Active Constraint Balancing (ACB) method was also applied in order to enhance the least-squares resolving power and stability.Synthetic modeling showed that the different tumulus layers and the horizontal contact of the artificial tumulus material with the natural background soil were reconstructed by all of the tested electrode arrays. Generally, PD and the GRAD arrays comprise the optimum choices to investigate the subsurface properties of a tumulus and locate buried tombs. The MPR model was inferior to the GRAD model, while the DD, PP and SCR models had the poorest resolution. It was also shown that the inversion models are practically independent from the survey direction and the topography shape of the tumulus.The real field data collected employing the PD array along a small tumulus from the archaeological site of Vergina in northern Greece enhanced the synthetic modeling results. The inversion model outlined a number of archaeological structures that exhibit a high possibility to correlate with graves. Overall, this work signifies that the surface 3D ERT method can provide a valuable tool in the non-destructive archaeological exploration of tumuli.     

Gamma rays from cosmic radioactivities

Abstract— Gamma rays from radioactive byproducts of cosmic nucleosynthesis are direct messengers from nuclear processes taking place in various cosmic sites, and can be measured with telescopes operated in space. Due to low detector sensitivity, up until now, only a handful of sources have been detected in that electromagnetic window. Cobalt lines from SN1987A and ⁴⁴Ti lines from the Cassiopeia A (Cas A) supernova remnant offer unique constraints on the properties of the innermost regions of core collapse supernovae. Diffuse gamma‐ray lines from the decay of radioactive ²⁶Al and the annihilation of positrons are bright enough for mapping the Milky Way in the MeV regime, and are both measured by recent spaceborne spectrometers with unprecedented precision. This constrains the sources of Al production and the state of interstellar gas in the vicinity of these sites: the total mass of ²⁶Al produced by stellar sources throughout the Galaxy is estimated to be ～3 M_⊙ per Myr, and the interstellar medium near those sources appears to be characterized by velocities of ～100 km s^?1. Positron annihilation must occur in a modestly ionized, warm phase of the interstellar medium, but at present the major positron production site(s) remain unknown. The spatial distribution of the annihilation gamma‐ray emission constrains positron production sites and positron propagation in the Galaxy. ⁶⁰Fe radioactivity has been clearly detected recently; the flux ratio relative to ²⁶Al of about 15% is on the lower side of predictions from massive star and supernova nucleosynthesis models. Those views at nuclear and astrophysical processes in and around cosmic sources by space‐based gamma‐ray telescopes offer invaluable information on cosmic nucleosynthesis.     

Efficient execution of the WRF model and other HPC applications in the cloud

There are many scientific applications that have high performance computing (HPC) demands. Such demands are traditionally supported by cluster- or Grid-based systems. Cloud computing, which has experienced a tremendous growth, emerged as an approach to provide on-demand access to computing resources. The cloud computing paradigm offers a number of advantages over other distributed platforms. For example, the access to resources is flexible and cost-effective since it is not necessary to invest a large amount of money on a computing infrastructure nor pay salaries for maintenance functions. Therefore, the possibility of using cloud computing for running high performance computing applications is attractive. However, it has been shown elsewhere that current cloud computing platforms are not suitable for running some of these kinds of applications since the performance offered is very poor. The reason is mainly the overhead from virtualisation which is extensively used by most cloud computing platforms as a means to optimise resource usage. Furthermore, running HPC applications in current cloud platforms is a complex task that in many cases requires configuring a cluster of virtual machines (VMs). In this paper, we present a lightweight virtualisation approach for efficiently running the Weather Research and Forecasting (WRF) model (a computing- and communication-intensive application) in a cloud computing environment. Our approach also provides a higher-level programming model that automates the process of configuring a cluster of VMs. We assume such a cloud environment can be shared with other types of HPC applications such as mpiBLAST (an embarrassingly parallel application), and MiniFE (a memory-intensive application). Our experimental results show that lightweight virtualisation imposes about 5 % overhead and it substantially outperforms traditional heavyweight virtualisation such as KVM.     

Evaluation of ASCE-41, ATC-40 and N2 static pushover methods based on optimally designed buildings

Alternative static pushover methods for the seismic design of new structures are assessed with the aid of advanced computational tools. The current state-of-practice static pushover methods as suggested in the provisions of European and American regulations are implemented in this comparative study. In particular the static pushover methods are: the displacement coefficient method of ASCE-41, the ATC-40 capacity spectrum method and the N2 method of Eurocode 8. Such analysis methods are typically recommended for the performance assessment of existing structures, and therefore most of the existing comparative studies are focused on the performance of one or more structures. Therefore, contrary to previous research studies, we use static pushover methods to perform design and we then compare the capacity of the outcome designs with reference to the results of nonlinear response history analysis. This alternative approach pinpoints the pros and cons of each method since the discrepancies between static and dynamic analysis are propagated to the properties of the final structure. All methods are implemented in an optimum performance-based design framework to obtain the lower-bound designs for two regular and two irregular reinforced concrete building configurations. The outcome designs are compared with respect to the maximum interstorey drift and maximum roof drift demand obtained with the Incremental Dynamic Analysis method. To allow the comparison, also the life-cycle cost of each design is calculated; i.e. a parameter that is used to measure the damage cost due to future earthquakes that will occur during the design life of the structure. The problem of finding the lower bound designs is handled with an Evolutionary type optimization algorithm.     

An analysis of the linear fixed altimetry-gravimetry boundary-value problem

In this paper the linear fixed altimetry-gravimetry boundary-value problem is analyzed with respect to the existence and uniqueness of the solution. Nowadays, it is possible to determine very precisely points on the physical surface of the Earth by 3D satellite positioning and the problem is to determine the disturbing potential in an unbounded domain representing the exterior of the Earth. In order to establish realistic boundary conditions, a Dirichlet condition is imposed at seas and an oblique derivative condition on land. Then, mathematical methods are used within the frame of functional analysis for attacking the problem under consideration. Specifically, the Stampacchia theorem is used to decide upon the existence and uniqueness of the weak solution of the problem in a weighted Sobolev space. Finally, we confirm that the condition of validity for such a theorem has a geometrical interpretation.