Large Scale Probabilistic Drought Characterization Over Europe

A reliable assessment of drought return periods is essential to help decision makers in setting effective drought preparedness and mitigation measures. However, often an inferential approach is unsuitable to model the marginal or joint probability distributions of drought characteristics, such as drought duration and accumulated deficit, due to the relatively limited number of drought events that can be observed in the historical records of the hydrological variables of interest. As an alternative, the marginal and multivariate probability cdf’s of drought characteristics can be derived as functions of the parameters of the cdf of the underlying variable (e.g. precipitation), whose sample series is usually long enough to obtain trustworthy estimates in a statistical sense. In this study, the latter methodology is applied to investigate space-time variability of drought occurrences over Europe by using the CRU TS3.10.01 precipitation dataset for the period 1901–2009. In particular, a methodology able to take into account autocorrelation in the underlying precipitation series is adopted. First, a spatial analysis of historical droughts at European level is carried out. Then, the joint probability distributions of drought duration and accumulated deficit are derived for each cell, with reference to both historical and design drought events. Finally, the corresponding bivariate drought return periods are computed, as the expected values of the interarrival time between consecutive critical droughts.Results show that several heavy drought episodes have widely affected the continent. Among the most recent events, drought occurred during the period 1985–1995 was the worst in terms of extent of the regions characterized by return periods greater than 250 years. Besides Euro-Mediterranean regions, North Western and Central Eastern regions appear more drought prone than the rest of Europe, in terms of low values of return periods.     

Numerical optimisation of a two-stage ejector refrigeration plant

Jet-refrigeration cycles seem to provide an interesting solution to the increasing interest in environment protection and the need for energy saving due to their low plant costs, reliability and possibility to use water as operating fluid. A steam/steam ejector cycle refrigerator is investigated introducing a two-stage ejector with annular primary at the second stage. The steady_state refrigerator, exchanging heat with the water streams at inlet fixed temperatures at the three shell and tube heat exchangers, evaporator, condenser and generator, is considered as an open system. Heat transfer irreversibilities in the heat exchangers and external friction losses in the water streams are considered, ignoring the internal pressure drop of the vapor. A simulation program numerically searches the maximum COP at given external inlet fluid temperatures as a function of mass flows, dimensions and temperature differences in the heat exchangers. The code gives the ejector and heat exchangers design parameters.     

Super-resolution reconstruction in a computational compound-eye imaging system

From consumer electronics to biomedical applications, device miniaturization has shown to be highly desirable. This often includes reducing the size of some optical systems. However, diffraction effects impose a constraint on image quality when we simply scale down the imaging parameters. Over the past few years, compound-eye imaging system has emerged as a promising architecture in the development of compact visual systems. Because multiple low-resolution (LR) sub-images are captured, post-processing algorithms for the reconstruction of a high-resolution (HR) final image from the LR images play a critical role in affecting the image quality. In this paper, we describe and investigate the performance of a compound-eye system recently reported in the literature. We discuss both the physical construction and the mathematical model of the imaging components, followed by an application of our super-resolution algorithm in reconstructing the image. We then explore several variations of the imaging system, such as the incorporation of a phase mask in extending the depth of field, which are not possible with a traditional camera. Simulations with a versatile virtual camera system that we have built verify the feasibility of these additions, and we also report the tolerance of the compound-eye system to variations in physical parameters, such as optical aberrations, that are inevitable in actual systems.     

Emission modeling of styrene from vinyl ester resins

The use of vinyl ester (VE) resins in the composites industry has increased in the last decade, and the trend is projected to continue. Styrene is a commonly used co-monomer in VE resins, which acts as a reactive diluent and is required in many liquid molding methods to reduce viscosity and increase gel time. The emission rate of styrene from VE resins is affected by various parameters, including styrene content, temperature, and resin surface-to-volume ratio. This study experimentally measured the effect of these parameters on styrene emission rates from VE resins. It was observed that the emission rate and amount of styrene decreased with decreasing surface-to-volume ratio, temperature, and styrene content. It is also shown that diffusion coefficient and evaporation coefficient of styrene have an exponential relationship with temperature, while they remained constant with initial styrene concentration and aspect ratio. Emission rate and amount decreased with increasing resin initial depth to radius ratio. The emission profiles were self-similar for different aspect ratios and were scaled by the ratio of the instantaneous sample depth to radius. Overall, the effect of these various parameters on the emission profile can be accurately modeled using a modification of a simple one-dimensional diffusion model based on the Crank solution to diffusion through a planar sheet.     

Flexible and Scalable Automation Solutions For Scoring Single Nucleotide Polymorphisms Using Rolling Circle Amplification

A single nucleotide polymorphism (SNP) scoring assay that uses ligation-dependent Rolling Circle Amplification (RCA)† was transferred to a series of automated protocols addressing a range of throughput levels. The systems utilised various automation modules consisting of custom-made and offthe-shelf devices. Several system parameters were evaluated to ensure assay integrity and homogeneity. These included reagent carry over, liquid evaporation rates, thermal regulation of reactions and fluorescence reading capabilities.Data analysis software was developed in order to rapidly allocate SNP calls from data generated by the automated system. A modified fuzzy c -means clustering algorithm was employed to separate data points into groups associated with specific genotypes. Data were then presented graphically and within a summary table, which allowed easy and rapid organization and interpretation of data.     

Temporal Evolution of Clear-Water Pier and Abutment Scour

Scour related to bridge hydraulics received much attention in the past decade, including its relation to flood hydrology and hydraulic processes in addition to steady flow. This paper presents new research on bridge pier and abutment scour based on a large data set collected at ETH Zurich, Switzerland. In total six different sediments were tested, of which three were uniform. Also a large variety of scour elements were considered, from 1 to 60% of the channel width, and flow depths ranging from 1 to about 40% of the channel width. Using similarity arguments and the analogy to flow resistance, an equation for temporal scour evolution is proposed and verified with the available literature data. The agreement of the present scour equation with both the VAW data and the literature data were considered sufficient in terms of river engineering accuracy, provided limitations relating to hydraulic, granulometric, and geometrical parameters are satisfied. These limitations are discussed and refer particularly to effects of viscosity, which were excluded in the present scour equation.     

Influence of molecular weight on some properties of poly(vinyl chloride)

Several fractions obtained from a large-scale fractionation and several unfractionated PVC polymers and blends have been processed both as rigid and plasticized compounds. The latter have been studied by stress–strain, creep, and recovery tests. The recoverable character of the creep results show that a relatively stable network must be present in the samples. The crosslink density is little influenced by molecular weight, as shown by the modulus and compliance results. On the contrary, the ultimate tensile properties depend strongly on molecular weight, which is interpreted as evidence that the stability of the crosslinks increases with increasing chain length of the polymers.     

Health risk of coplanar polychlorinated biphenyl congeners in edible fish from the Mediterranean Sea

The muscle tissue of different species of fish was analyzed for polychlorinated biphenyls (PCBs) in order to estimate the daily intake of these contaminants. Contamination levels among the different species varied between 108 and 678 ng/g lipid weight. Isomer-specific analysis in the muscle tissue of the various fish revealed a profile dominated by hexa- and pentachlorobiphenyls, followed by hepta- and tetrachlorobiphenyls. Other congeners, including those with fewer than four or more than nine chlorine atoms, were below the instrumental limit of detection in all samples. PCB dietary intake was below the range of 1 to 4 pg 2,3,7,8-tetrachloro-p-dioxin equivalents per kg body weight per day set by the World Health Organization. From a public health point of view, there is no indication of important risks associated with the consumption of these seafoods.     

Diffusion boundaries behaviour during a parabolic flight

The behaviour of a diffusion boundary between distilled water and a 1% sodium chloride solution during a parabolic flight has been observed. The presence of a few percent of Earth gravity pulses during the micro gravity conditions is sufficient to largely perturb the diffusion boundary that stabilises again during the subsequent normal gravity conditions present inside the aircraft at the end of each parabola. A numerical simulation of the boundary behaviour agrees with the experimental observation. Student flying team     

Simple portable lens meter

A device measuring the optical power of simple lenses by means of moiré phenomena is described. The relevant equations are derived, and a working instrument is presented. A power measuring accuracy better than 0.25 m(-1) in the range of +/- 10 m(-1) is demonstrated.