ENGINEERING GEOLOGICAL CHARACTERISATION OF BLOCK-IN-MATRIX ROCKS

Οι σχηματισμοι block-in-matrix (ή «bimrocks») είναι πολύμικτοι και ετερογενείς γεωλογικοί σχηματισμοί που αποτελούνται από ανθεκτικά μπλοκ ενσωματωμένα σε ένα ασθενέστερο συνδετικό υλικό. Οι δυσκολίες που συναντώνται κατά τη δειγματοληψία και την εκτέλεση εργαστηριακών δοκιμών τους δημιουργεί σημαντικές προκλήσεις κατά το γεωτεχνικό σχεδιασμό και την αξιολόγηση της συμπεριφοράς τους. Μια προσέγγιση για τον χαρακτηρισμό αυτών των γεωυλικών είναι η χρήση της στερεολογικής ανάλυσης που οδηγεί στην εκτίμηση της ογκομετρική αναλογία των μπλοκ σε σχέση με το συνδετικό υλικό. Η παρούσα εργασία παρουσιάζει τις παραμέτρους που θεωρούνται σημαντικές για τον τεχνικο γεωλογικό χαρακτηρισμό των σχηματισμών αυτών και παρουσιάζονται σύντομα αποτελέσματα από δύο θέσεις «bimrock» στην ΒΔ Ελλάδα.Block-in-matrix rocks (“bimrocks”) are complex, mixed and heterogeneous formations of competent blocks embedded in weaker matrix. The inherent difficulty of sampling and consequently, laboratory testing of bimrocks leads to considerable challenging in geotechnical design and assessment of their engineering behaviour. An approach for the characterisation of “bimrocks” is the use of stereological analysis that extrapolates one-dimensional or two dimensional data to estimate the block volumetric proportion. This has been an established approach of dealing with bimrocks and melanges for the last two decades. This paper presents the parameters that are considered important for the engineering characterisation of such complex formations, while a case study from a bimrock in NW Greece is discussed

Practical interference mitigation for Wi-Fi systems

Wi-Fi's popularity is also its Achilles' heel since in the dense deployments of multiple Wi-Fi networks typical in urban environments, concurrent transmissions interfere. The advent of networked devices with multiple antennas allows new ways to improve Wi-Fi's performance: a host can align the phases of the signals either received at or transmitted from its antennas so as to either maximize the power of the signal of interest through beamforming or minimize the power of interference through nulling. Theory predicts that these techniques should enable concurrent transmissions by proximal sender-receiver pairs, thus improving capacity. Yet practical challenges remain. Hardware platform limitations can prevent precise measurement of the wireless channel, or limit the accuracy of beamforming and nulling. The interaction between nulling and Wi-Fi's OFDM modulation, which transmits tranches of a packet's bits on distinct subcarriers, is subtle and can sacrifice the capacity gain expected from nulling. And in deployments where Wi-Fi networks are independently administered, APs must efficiently share channel measurements and coordinate their transmissions to null effectively. In this thesis, I design and experimentally evaluate beamforming and nulling techniques for use in Wi-Fi networks that address the aforementioned practical challenges. My contributions include: - Cone of Silence (CoS): a system that allows a Wi-Fi AP equipped with a phased-array antenna but only a single 802.11g radio to mitigate interference from senders other than its intended one, thus boosting throughput; - Cooperative Power Allocation (COPA): a system that efficiently shares channel measurements and coordinates transmissions between independent APs, and cooperatively allocates power so as to render received power across OFDM subcarriers flat at each AP's receiver, thus boosting throughput; - Power Allocation for Distributed MIMO (PADM): a system that leverages intelligent power allocation to mitigate inter-stream interference in distributed MIMO wireless networks, thus boosting throughput

The basic chemistry of exercise-induced DNA oxidation:oxidative damage, redox signalling and their interplay

Acute exercise increases reactive oxygen and nitrogen species generation. This phenomenon is associated with two major outcomes: (1) redox signalling and (2) macromolecule damage. Mechanistic knowledge of how exercise-induced redox signalling and macromolecule damage are interlinked is limited. This review focuses on the interplay between exercise-induced redox signalling and DNA damage, using hydroxyl radical (·OH) and hydrogen peroxide (H2O2) as exemplars. It is postulated that the biological fate of H2O2 links the two processes and thus represents a bifurcation point between redox signalling and damage. Indeed, H2O2 can participate in two electron signalling reactions but its diffusion and chemical properties permit DNA oxidation following reaction with transition metals and ·OH generation. It is also considered that the sensing of DNA oxidation by repair proteins constitutes a non-canonical redox signalling mechanism. Further layers of interaction are provided by the redox regulation of DNA repair proteins and their capacity to modulate intracellular H2O2 levels. Overall, exercise-induced redox signalling and DNA damage may be interlinked to a greater extent than was previously thought but this requires further investigation

Passive Control of Bridges

In the design of bridges with large spans, the significant values of the moments at the main deck-structure require very heavy members, either in the case of a beam or a truss deck-structure. In order to minimize the influence of bending moments, several applications of passive control of displacements using cable nets are herein proposed. The base for all the proposed systems is the cables supported beam nets with additional prestressing control on support cables to optimize the structural behavior of the system. The passive control design problem leads to an optimal control problem for structures governed by variational inequalities. In this presentation several bridge systems are proposed and studied as applications of this method

From physiology and nutrition to biological sciences, and back again!

No abstract available

Sediment Transport in the Koiliaris River of Crete

AbstractIn this paper, a study of the sediment transport in a complex Mediterranean watershed (i.e. the Koiliaris River Basin of Crete) consisting of temporary flow tributaries and karstic springs is presented. Both daily flow data (2005-2013) and monthly sediment concentration data (2011-2013) were used to calibrate the modified Soil and Water Assessment Tool (SWAT) model, designed to simulate the hydrology, sediment yield and water quality of ungauged watersheds, and augmented with a karst flow model in order to simulate the contribution of the extended karst to the spring discharge in the basin. The results showed good agreement between observed and model values for both flow and sediment concentration. However, since no data representative of high sediment concentration conditions were available, such as during extreme flow events, an automated sediment sampling device (Sediment Trap), which allows for flow weighted sampling, has been developed and is detailed in this paper. This device is undergoing testing to ensure it can provide accurate estimates of sediment yield, especially during a flush flood event when large amounts of sediment are carried downstream. The sediment measurements will then be used to calibrate and verify the sediment transport simulations of the Koiliaris River watershed generated by the SWAT model. The sediment transport simulations and the development of the automated sampling device were part of the preliminary work for the pilot application of the “Cybersensors” infrastructure in the Koiliaris River. The Cybersensors research project aims to develop an intelligent integrated monitoring system, which will utilize electrochemical and optical sensors, and will allow for high-frequency monitoring of the physical and chemical parameters of a river flow and thus the rapid detection of environmental change during episodic events, as well as for long term monitoring

Techno economic and environmental assessment of wind assisted marine propulsion systems

In recent years, the increase in marine fuel prices coupled with stricter regulations on pollutant emissions set by the International Maritime Organization have promoted the research in new propulsion technologies and the utilisation of cleaner fuels. This paper describes a novel methodology to enable quantifying and evaluating the environmental and economic benefits that new technologies and fuels could allow in the marine sector. The proposed techno economic and environmental analysis approach enables consistent assessment of different traditional propulsion systems (diesel engine and gas turbine) when operated in conjunction with a novel environmental friendly technology, such as a vertical axis wind turbine. The techno-economic and environmental assessment is focused on the potential reduction in fuel consumption and pollutant emissions that may be accrued while operating on typical Sea Lines Of Communication (Mediterranean, North Sea, Atlantic). The study demonstrates the benefits of the installation of two vertical axis wind turbines on the deck of a ship in conjunction with conventional power plants. The analysis indicates that the performance of the wind turbines and the corresponding benefits strongly depend on the routes and environment in which they operate (therefore favourable wind conditions) allowing fuel savings from 14% (in the gas turbine case) to 16% (in the diesel engine case). The study also indicates that possible benefits may diminish for weak wind conditions. The results reported in this paper establish the economic benefits of installing vertical axis wind turbines in conjunction with conventional technology (Diesel and Gas Turbine Power plants) when installed on a ship travelling through the Atlantic Ocean. The primary purpose of this study is to introduce a methodology to demonstrate the application, performance and economic benefits of the technology at a preliminary design phase and further form a foundation for more elaborate analysis on the subject in the future

Fast ReRoute on Programmable Switches

Highly dependable communication networks usually rely on some kind of Fast Re-Route (FRR) mechanism which allows to quickly re-route traffic upon failures, entirely in the data plane. This paper studies the design of FRR mechanisms for emerging reconfigurable switches. Our main contribution is an FRR primitive for programmable data planes, PURR, which provides low failover latency and high switch throughput, by avoiding packet recirculation. PURR tolerates multiple concurrent failures and comes with minimal memory requirements, ensuring compact forwarding tables, by unveiling an intriguing connection to classic ``string theory'' (i.e., stringology), and in particular, the shortest common supersequence problem. PURR is well-suited for high-speed match-action forwarding architectures (e.g., PISA) and supports the implementation of a broad variety of FRR mechanisms. Our simulations and prototype implementation (on an FPGA and a Tofino switch) show that PURR improves TCAM memory occupancy by a factor of 1.5x-10.8x compared to a naïve encoding when implementing state-of-the-art FRR mechanisms. PURR also improves the latency and throughput of datacenter traffic up to a factor of 2.8x-5.5x and 1.2x-2x, respectively, compared to approaches based on recirculating packets