SUCTION MEASUREMENTS AND WATER RETENTION IN UNSATURATED SOILS

Techniques for testing unsaturated soils have been investigated by the author where the measurement and control of parameters were undertaken directly. Suction was measured and controlled with a new high suction tensiometer and water content through mass measurements with a balance. These techniques have been used for the determination of soil water retention curves and for the development of a suction . control system using air circulation and water injection. The techniques allow the soil to be subject to the same drying and wetting conditions that occur in nature and avoid the need for elevated air pressures, as are traditionally involved in testing using the axis translation technique. The performance of the new high suction tensiometer was evaluated, followed by its applications to soil testing. The tensiometer performance focused on the factors controlling cavitation, calibration in the negative pressure range and measurement. It was found that isotropic unloading is the most accurate technique for calibration in the negative range and that axis translation techniques can lead to errors. The research confirms high suction tensiometers are easy to use and versatile devices. Techniques were developed to measure and control suction and water content in unconfined and confined samples. Research on the unconfined samples focused on the procedures to obtain the soil water retention curve: discrete (soil dried or wetted in stages) and continuous (soil drying continuously). While both procedures were found not to influence the curves significantly, it is demonstrated that the continuous procedure is sensitive to factors such as the exposed surface area to drying or wetting and so should be used carefully. For confined conditions, wetting, drying, and water content measurement systems were developed. Wetting was based on the injection of water; drying was based on air circulation through a desiccant within a closed loop system. Water content was determined from the. difference between water injected and that adsorbed by the desiccant. This has been applied as part of a· double cell triaxial testing system that allows continuous determination of suction, water content and volume change. A challenge of such a system was imposing an air tight environment. The suitability of environmental scanning electron microscopy to observe unsaturated soils at the particle level was explored. The imaging of micron-sized materials at different relative humidities allowed a series of observations previously undocumented, among them: water menisci were visible, including their shape and interaction with surfaces; the contact angle between the air-water and water-solid interfaces was measurable.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An optimized conflict-free replicated set

Eventual consistency of replicated data supports concurrent updates, reduces latency and improves fault tolerance, but forgoes strong consistency. Accordingly, several cloud computing platforms implement eventually-consistent data types. The set is a widespread and useful abstraction, and many replicated set designs have been proposed. We present a reasoning abstraction, permutation equivalence, that systematizes the characterization of the expected concurrency semantics of concurrent types. Under this framework we present one of the existing conflict-free replicated data types, Observed-Remove Set. Furthermore, in order to decrease the size of meta-data, we propose a new optimization to avoid tombstones. This approach that can be transposed to other data types, such as maps, graphs or sequences.Comment: No. RR-8083 (2012

Post-acquisition Changes Beyond the Dyad: Power at the Net Level in Cross-Border Acquisitions(1)

A common feature of the literature on post-acquisition changes is its dyadic feature, i.e. the emphasis is placed on the actors directly involved in the acquisition, often represented by the acquiree and the acquirer. Accordingly, actors outside the dyad, such as suppliers and buyers, are usually disregarded. There is, however, a relevant exception in this literature. Recently, some Nordic authors have claimed that if actors other than the acquiree and the acquirer are not taken into account, the existing literature may only present a partial view of changes following acquisitions. Consequently, they have suggested that changes following this type of operation can be analysed fruitfully at the network level. Our article adds to the efforts of these scholars to understand post-acquisition changes at a broader level by bringing to the fore two issues that have received scarce attention in the literature: i) nets rather than the network level appears to be the locus where post-acquisition changes beyond the dyad take place; ii) relational power can be regarded as an independent variable in post-acquisitionchanges beyond the dyad. These arguments are illustrated by three brief case studies of cross-border acquisitions

Carro de Combate Leopard 2 A6 - Formação Inicial e Manutenção das qualificações. O caso do Exército Português

O tema deste trabalho, prende-se com a formação inicial e manutenção das qualificações da guarnição do Carro de Combate Leopard 2 A6. O Carro de Combate Leopard 2 A6 é um sistema de armas com elevada complexidade tecnológica. O presente estudo visa verificar se a formação inicial e a manutenção das qualificações, sem o recurso à simulação, se encontram apropriadas para manter a eficácia da guarnição do Carro de Combate. Para tal, os métodos de investigação científica utilizados, basearam-se num inquérito por questionário e em entrevistas. Os resultados mais relevantes do estudo, possibilitam verificar as dificuldades/problemas existentes na formação inicial e a importância da simulação para a manutenção das qualificações. No final, detectam-se insuficiências e deficiências na formação, afectando o bom nível de operacionalidade das guarnições.Abstract The theme of this work relates to the initial training and maintenance of skills of the crew in Main Battle Tank Leopard 2 A6. The Main Battle Tank Leopard 2 A6 is a weapon system with high technological complexity. The present study aims to verify if the initial formation and maintenance skills, without resorting to simulation, are appropriate to maintain the effectiveness of the crew in tanks. For this purpose, the methods used for scientific research,were based on a survey made by questionnaire and interviews. The most relevant results of the study, are enable to verify the difficulties/problems in training and the importance of the simulation for the maintenance of skills. At the end, are detected weaknesses and deficiencies in training, affecting the proper level of operational ability of the crews

A simple thought experiment to discuss the mass–energy equivalence in the special theory of relativity

Einstein’s relation between mass and energy is perhaps the most famous equation of Physics. Despite its simplicity, the meaning of E0 = mc2 is not easy to grasp. Furthermore, its traditional derivations rely either on the integral of momentum, on properties of electromagnetic radiation, or even on the expression for transformation of energy. In the present work, we provide a simple thought experiment with an inelastic collision between two particles observed from two inertial reference frames. We show that for the conservation of relativistic momentum to hold, the mass of the system must increase after the collision. We also show that the increase of mass relates to the loss of kinetic energy according to the equation ∆K = −∆mc2 , which enables us to define the equation for relativistic energy (E = mc2/ p 1 − v 2/c 2 ), rest energy (E0 = mc2 ) and relativistic kinetic energy (K = E − E0). There are two main advantages in this presentation: first, it relies only on simple algebra, not depending on differential calculus and on any property of radiation; second, it leads directly to a comprehensible physical meaning of the relation of equivalence, which can sometimes be too obscure in more formal derivations

Special relativity from classical gedanken experiments involving electromagnetic forces : a contribution to relativity without light

Our goal is to present a derivation of Lorentz’s transformations from gedanken experiments with electromagnetic forces without having to assume Einstein’s postulate of the constancy of the speed of light. Instead, we propose a different second postulate, namely that electric charge is independent of the state of motion of the system, and we restrict the first postulate in order to state the relativity of electromagnetic forces only. We argue that assuming that charge is invariant is much more intuitive than assuming that light speed is constant. In this derivation, furthermore, the constancy of a limit speed c is obtained as a result of the velocity addition rule. Finally, we discuss the epistemological and didactic implications of this formulation

Extending Eventually Consistent Cloud Databases for Enforcing Numeric Invariants

Geo-replicated databases often operate under the principle of eventual consistency to offer high-availability with low latency on a simple key/value store abstraction. Recently, some have adopted commutative data types to provide seamless reconciliation for special purpose data types, such as counters. Despite this, the inability to enforce numeric invariants across all replicas still remains a key shortcoming of relying on the limited guarantees of eventual consistency storage. We present a new replicated data type, called bounded counter, which adds support for numeric invariants to eventually consistent geo-replicated databases. We describe how this can be implemented on top of existing cloud stores without modifying them, using Riak as an example. Our approach adapts ideas from escrow transactions to devise a solution that is decentralized, fault-tolerant and fast. Our evaluation shows much lower latency and better scalability than the traditional approach of using strong consistency to enforce numeric invariants, thus alleviating the tension between consistency and availability

Definition of MV Load Diagrams via Weighted Evidence Accumulation Clustering using Subsampling

A definition of medium voltage (MV) load diagrams was made, based on the data base knowledge discovery process. Clustering techniques were used as support for the agents of the electric power retail markets to obtain specific knowledge of their customers’ consumption habits. Each customer class resulting from the clustering operation is represented by its load diagram. The Two-step clustering algorithm and the WEACS approach based on evidence accumulation (EAC) were applied to an electricity consumption data from a utility client’s database in order to form the customer’s classes and to find a set of representative consumption patterns. The WEACS approach is a clustering ensemble combination approach that uses subsampling and that weights differently the partitions in the co-association matrix. As a complementary step to the WEACS approach, all the final data partitions produced by the different variations of the method are combined and the Ward Link algorithm is used to obtain the final data partition. Experiment results showed that WEACS approach led to better accuracy than many other clustering approaches. In this paper the WEACS approach separates better the customer’s population than Two-step clustering algorithm

Determination of electricity consumers’ load profiles via weighted evidence accumulation clustering using subsampling

With the electricity market liberalization, the distribution and retail companies are looking for better market strategies based on adequate information upon the consumption patterns of its electricity consumers. A fair insight on the consumers’ behavior will permit the definition of specific contract aspects based on the different consumption patterns. In order to form the different consumers’ classes, and find a set of representative consumption patterns we use electricity consumption data from a utility client’s database and two approaches: Two-step clustering algorithm and the WEACS approach based on evidence accumulation (EAC) for combining partitions in a clustering ensemble. While EAC uses a voting mechanism to produce a co-association matrix based on the pairwise associations obtained from N partitions and where each partition has equal weight in the combination process, the WEACS approach uses subsampling and weights differently the partitions. As a complementary step to the WEACS approach, we combine the partitions obtained in the WEACS approach with the ALL clustering ensemble construction method and we use the Ward Link algorithm to obtain the final data partition. The characterization of the obtained consumers’ clusters was performed using the C5.0 classification algorithm. Experiment results showed that the WEACS approach leads to better results than many other clustering approaches