Thermo-Chemo-Mechanical Model for Concrete. I: Hydration and Aging

In this work a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages is proposed. The model allows simulation of the observed phenomena of hydration, aging, damage, and creep. It is formulated within an appropriate thermodynamic framework, from which the state equations are derived. In this first part, the formulation and assessment of the thermochemical aspects of the model are presented. It is based on the reactive porous media theory, and it can accurately predict the evolution in time of the hydration degree and the hydration heat production. The evolution of the compressive and tensile strengths and elastic moduli is related to the aging degree, a concept introduced to account for the effect of the curing temperature in the evolution of the mechanical properties. The short- and long-term mechanical behavior is modeled by means of a viscoelastic damage model that accounts for the aging effects. The formulation and assessment of the mechanical part of the model are relegated to a companion paper.     

Single Mach–Zehnder Modulator Electro-Optical Harmonic Mixer for Broadband Microwave/Millimetre-Wave Applications

We investigated theoretically and experimentally amicrowave/millimetre-wave optical harmonic upconverterbased on a single Mach–Zehnder electro-opticalmodulator (MZ-EOM). Biasing at quadrature andnon-linear operating points as well as comparison withthe traditional cascaded approach is considered. Thisoptical mixing technique provides a lower opticalinsertion loss at a lower cost than the traditionalcascaded optical modulator mixing approach as well assimilar conversion loss and isolation performance.A BER of less than 10^-9is achievedusing this single MZ-EOM upconversion scheme in thequadrature and minimum transmission bias points for a50 km single mode fibre transmission of a 34 Mbits/sPRBS signal, demonstrating that this approach issuitable for broadband applications in themillimetre-wave band.     

MMALE—A Methodology for Malware Analysis in Linux Environments

In a computer environment, an operating system is prone to malware, and even the Linux operating system is not an exception. In recent years, malware has evolved, and attackers have become more qualified compared to a few years ago. Furthermore, Linux-based systems have become more attractive to cybercriminals because of the increasing use of the Linux operating system in web servers and Internet of Things (IoT) devices. Windows is the most employed OS, so most of the research efforts have been focused on its malware protection rather than on other operating systems. As a result, hundreds of research articles, documents, and methodologies dedicated to malware analysis have been reported. However, there has not been much literature concerning Linux security and protection from malware. To address all these new challenges, it is necessary to develop a methodology that can standardize the required steps to perform the malware analysis in depth. A systematic analysis process makes the difference between good and ordinary malware analyses. Additionally, a deep malware comprehension can yield a faster and much more efficient malware eradication. In order to address all mentioned challenges, this article proposed a methodology for malware analysis in the Linux operating system, which is a traditionally overlooked field compared to the other operating systems. The proposed methodology is tested by a specific Linux malware, and the obtained test results have high effectiveness in malware detection.     

Embedding Arabidopsis Plant Cell Suspensions in Low-Melting Agarose Facilitates Altered Gravity Studies

Gravity plays a role in modulating plant growth and development and its alteration induces changes in these processes. Microgravity research has recently been extended to the use of in vitro plant cell cultures which are considered as an ideal model system to study cell proliferation and growth. In general, among the ground-based facilities available for microgravity simulation, the 2D pipette clinostat had been previously considered a suitable facility to be used for unicellular biological models although studies using single plant cell cultures raised some concerns. The incompatibility comes from the standard requirement of shaking a suspension culture for assuring its viability and active proliferation status in the control samples. Moreover, a related issue applies to the use of the random positioning machine (RPM) for cell suspension experiments. Here, we demonstrate an alternative culture method based on the immobilization of the culture before the altered gravity treatment occurs, such that it behaves as a solid object. Our immobilization procedure preserved plant cell culture viability without compromising basic cell properties as viability, morphology, cell cycle phases distribution, or chromatin organization, when compared with a standard cell suspension under shaking as a control. This approach should allow the space biology community to improve the quantity and quality of plant cell results in future simulated microgravity experiments or spaceflight opportunities.     

Drop Tower Setup to Study the Diffusion-driven Growth of a Foam Ball in Supersaturated Liquids in Microgravity Conditions

The diffusion-driven growth of a foam ball is a phenomenon that appears in many manufacturing process as well as in a variety of geological phenomena. Usually these processes are greatly affected by gravity, as foam is much lighter than the surrounding liquid. However, the growth of the foam free of gravity effects is still very relevant, as it is connected to manufacturing in space and to the formation of rocks in meteorites and other small celestial bodies. The aim of this research is to investigate experimentally the growth of a bubble cloud growing in a gas-supersaturated liquid in microgravity conditions. Here, we describe the experiments carried out in the drop tower of the Center of Applied Space Technology and Microgravity (ZARM). In few words, a foam seed is formed with spark-induced cavitation in carbonated water, whose time evolution is recorded with two high-speed cameras. Our preliminary results shed some light on how the size of the foam ball scales with time, in particular at times much longer than what could be studied in normal conditions, i.e. on the surface of the Earth, where the dynamics of the foam is already dominated by gravity after several milliseconds.     

The Multiregional Core-periphery Model: The Role of the Spatial Topology

We use the multiregional core-periphery model of the new economic geography to analyze and compare the agglomeration and dispersion forces shaping the location of economic activity for a continuum of network topologies — spatial or geographic configuration — characterized by their degree of centrality, and comprised between two extremes represented by the homogenous (ring) and the heterogeneous (star) configurations. Resorting to graph theory, we systematically extend the analytical tools and graphical representations of the core-periphery model for alternative spatial configuration, and study the sustain and break points. We study new phenomena such as the infeasibility of the dispersed equilibrium in the heterogeneous space, resulting in the introduction of the concept pseudo flat-earth as a long-run equilibrium corresponding to an uneven distribution of economic activity between regions.