First experimental demonstration of temporal hypertelescope operation with a laboratory prototype

In this paper, we report the first experimental demonstration of a Temporal HyperTelescope (THT). Our breadboard including 8 telescopes is firstly tested in a manual cophasing configuration on a 1D object. The Point Spread Function (PSF) is measured and exhibits a dynamics in the range of 300. A quantitative analysis of the potential biases demonstrates that this limitation is related to the residual phase fluctuation on each interferometric arm. Secondly, an unbalanced binary star is imaged demonstrating the imaging capability of THT. In addition, 2D PSF is recorded even if the telescope array is not optimized for this purpose.Comment: Accepted for publication in MNRAS. 11 pages, 25 figure

A Laboratory Investigation on Thermal Properties of the Opalinus Claystone

Some aspects of the thermal behavior of the Opalinus claystone are investigated through laboratory tests conducted on a new hollow cylinder triaxial apparatus specially designed for studying the thermo-hydro-mechanical behavior of very low permeable materials. Two hollow cylinder samples are first resaturated under isotropic stress state equal to the mean effective in situ one in order to minimize swelling and induced damage during the resaturation phase. Two drained heating-cooling cycles are performed on the first sample of Opalinus claystone. During the first cycle, a thermo-elasto-plastic response similar to that of plastic clays with low overconsolidation ratio is obtained. The thermal hardening of the sample is demonstrated by the quasi-reversible behavior of the sample during the second heating-cooling cycle. An undrained heating test performed on the second sample of Opalinus claystone induces an excess pore pressure in this sample. This induced pore pressure is attributed to the higher thermal expansion coefficient of pore water compared to that of the solid phase. It is shown that the excess pore pressure generated in the sample by undrained heating cannot be modeled by considering the free water thermal expansion coefficient. The thermal expansion coefficient of the Opalinus claystone water is back-analyzed from the experimental results which show a higher value than free wate

Determining the unsaturated hydraulic conductivity of a compacted sand-bentonite mixture under constant volume and free-swell conditions

Highly compacted sand-bentonite mixtures are often considered as possible engineered barriers in deep high-level radioactive waste disposals. In-situ, the saturation of these barriers from their initially unsaturated state is a complex hydro-mechanical coupled process in which temperature effects also play a role. The key parameter of this process is the unsaturated hydraulic conductivity of the barrier. In this paper, isothermal infiltration experiments were conducted to determine the unsaturated hydraulic conductivity according to the instantaneous profile method. To do so, total suction changes were monitored at different locations along the soil specimen by using resistivity relative humidity probes. Three constant volume infiltration tests were conducted showing, unexpectedly, a decrease of the hydraulic conductivity during infiltration. One test performed under free-swell conditions showed the opposite and standard trend. These observations were interpreted in terms of microstructure changes during wetting, both under constant volume and free swell conditions

Controlling suction by vapour equilibrium technique at different temperatures, application to the determination of the water retention properties of MX80 clay

Problems related to unsaturated soils are frequently encountered in geotechnical or environmental engineering works. In most cases, for the purpose of simplicity, the problems are studied by considering the suction effects on volume change or shear strength under isothermal conditions. Under isothermal condition, very often, a temperature independent water retention curve is considered in the analysis, which is obviously a simplification. When the temperature changes are too significant to be neglected, it is necessary to account for the thermal effects. In this paper, a method for controlling suction using the vapour equilibrium technique at different temperatures is presented. First, calibration of various saturated saline solutions was carried out from temperature of 20 degrees C to 60 degrees C. A mirror psychrometer was used for the measurement of relative humidity generated by saturated saline solutions at different temperatures. The results obtained are in good agreement with the data from the literature. This information was then used to determine the water retention properties of MX80 clay, which showed that the retention curve is shifting down with increasing of temperature

LHCb Preshower Front-End Electronics Board

This note describes the digital part of the fully synchronous solution developped for the lhcb preshower detector Front-End electronics. The general design and the main features of this board are given including trigger part

LHCb Preshower Front-End Electronics Board. Qualification of the final prototype

This note describes the tests performed on the final prototypes of the SPD/Preshower Front-End electronics boards

Models for Minimax Stochastic Linear Optimization Problems with Risk Aversion

We propose a semidefinite optimization (SDP) model for the class of minimax two-stage stochastic linear optimization problems with risk aversion. The distribution of second-stage random variables belongs to a set of multivariate distributions with known first and second moments. For the minimax stochastic problem with random objective, we provide a tight SDP formulation. The problem with random right-hand side is NP-hard in general. In a special case, the problem can be solved in polynomial time. Explicit constructions of the worst-case distributions are provided. Applications in a production-transportation problem and a single facility minimax distance problem are provided to demonstrate our approach. In our experiments, the performance of minimax solutions is close to that of data-driven solutions under the multivariate normal distribution and better under extremal distributions. The minimax solutions thus guarantee to hedge against these worst possible distributions and provide a natural distribution to stress test stochastic optimization problems under distributional ambiguity.Singapore-MIT Alliance for Research and TechnologyNational University of Singapore. Dept. of Mathematic

Effect of particle size on the measurement of the apparent contact angle in sand of varying wettability under air-dried conditions

Session: Advances in Experimental Methods: Mechanical PropertiesChanges in the wettability of soil are known to affect several processes such as infiltration and the shear strength of soil. In this study, the wettability of a medium to fine sand was chemically modified by using different concentrations of dimethyldichlorosilane (DMDCS). The sessile drop method (SDM) was used for the assessment of wettability of hydrophobised Leighton Buzzard Sand (LBS). The results demonstrate that beyond a concentration of 2 g per kg of LBS, the finer fraction had its apparent contact angle (ACA) increased up to 115° while the maximum ACA attained by the coarser fractions was 100°. At such high concentration of DMDCS, the effect of trapped air, which is known to increase the ACA, was found to be either small or insignificant. The standard deviations of the ACAs agreed well with past studies. The most important factors contributing to the water-repellent behaviour of chemically synthesised sand were attributed to the characteristics of the particles; these include surface area and particle shape.published_or_final_versio

Defect study of GaInP/GaAs based heterojunction bipolar transistor emitter layer

Defects in the emitter region of Ga0.51In0.49P/GaAs heterojunction bipolar transistors (HBTs) were investigated by means of deep-level transient spectroscopy. Both annealed (635 degreesC, 5 min) and as grown metalorganic chemical vapor deposition epitaxial wafers were investigated in this study, with an electron trap observed in the HBT emitter space-charge region from both wafers. The deep-level activation energy was determined to be 0.87+/-0.05 eV below the conduction band, the capture cross section 3x10(-14) cm(2) and the defect density of the order of 10(14) cm(-3). This defect was also found to be localized at the emitter-base interface