Polar nephelometer based on a rotational confocal imaging setup

Rapid measurement of the angular distribution of light scattered by particles, the scattering phase function, is achieved by using a new type of polar nephelometer, a device for measuring the angular scattered-light intensity distribution, with a high angular precision and across many orders of magnitude of intensity. The design offers high-speed measurements and avoids many of the problems often associated with traditional goniometers when they are used for measurements of light scattering from small particles or biological cells in suspension. Our system relies on confocal imaging of the test space with off-axis parabolas, using a rotating mirror to scan the angular field of view at the second focus of a pair of conjugated parabolic mirrors, with the test space located at the first focus. The angular resolution of the system is limited mainly by the data-acquisition sampling frequency. In this proof-of-principle demonstration the system performs multiple scans of a 55 deg field of view in a very short time (<1 s). To significantly increase the signal-to-noise ratio, we averaged the successively acquired scans during this time. Polystyrene spheres dispersed in water at low concentrations were used to test the system. The scattering patterns obtained were found to be in good agreement with Mie theory calculations.     

Performance of high-power laser diode arrays for spaceborne lasers

The adequacy of commercial quasi-continuous high-power laser diode arrays (HPLDAs) as pump sources for spaceborne lasers has been assessed by endurance tests up to 3 x 10(9) shots under various stress conditions, vacuum operation up to 0.36 x 10(9) shots, and proton radiation tests. Observations of the evolution of the electro-optic parameters and of the near-field patterns of the HPLDAs during endurance tests have revealed that some diode bars could reach the required lifetime of a multibillion shots, suggesting how to build long lifetime HPLDAs by proper selection of the diode bars. The robustness of the HPLDAs against the proton environment experienced in a typical low Earth orbit has been checked. Finally, high-power laser diode arrays have been operated under vacuum, showing a behavior similar to that of HPLDAs operating in atmospheric conditions.     

Solutions to reduce release behavior of plasticizers out of PVC-made equipments: binary blends of plasticizers and thermal treatment

In order to reduce migration of plasticizers out of polyvinyl chloride (PVC), several techniques were attempted. First, binary blends of plasticizers were added to PVC, migration was decreased 100 or 1,000 times as compared to PVC samples containing only one plasticizer: the diffusion coefficient was of the order of 10⁻⁸ cm² s⁻¹ for the blend di-2-ethylhexylphthalate (DEHP)/di-2-ethylhexylterephthalate (TDHP) or 10⁻⁹ cm² s⁻¹ for the blend DEHP/DBP. A thermal treatment of PVC samples containing only one plasticizer leads to diffusion coefficients of the order of 10⁻¹⁰ cm² s⁻¹. This second method was also applied to PVC samples plasticized with binary blends. It lowers even more migration of both plasticizers out of PVC. But no particular phenomena were observed with ternary blends of plasticizers introduced in PVC.     

The Clarifying Reagent, or how to make the analysis of milk and dairy products easier

Difficulties with the analysis of opaque milk and dairy products can be resolved by rendering the sample transparent. This allows direct photometric measurements of the reaction mixtures, and all sample pre-treatment steps become unnecessary. For this, several reagents have been reported in literature. Among them, the 'Clarifying Reagent' is mainly described here: its composition is given because it is now released from patenting restrictions. Its main property is a low absorbance between 340 and 800 nm. So it can be used in many chemical and enzymatic colorimetric measurements for estimating the quality of milk and dairy products.     

Tolerating Radiation-Induced Transient Faults in Modern Processors

As MOS device sizes continue shrinking, lower charges, for example those charges carried by single ionizing particles of naturally occurring radiation, are sufficient to upset the functioning of complex modern microprocessors. In order to handle these inevitable errors, designs should include fault-tolerant features so that the processors can continue to correctly perform despite the occurrence of errors. The main goal of this work is to develop architecture mechanisms to protect processors against the effect of such radiation-induced transient faults. It should first be noted that, from a program execution perspective, many faults manifest themselves as control flow errors that cause processors to violate the correct sequencing of instructions. We present here at first a basic compile-time signature assignment algorithm and describe a novel approach to improve the fault detection coverage of the basic algorithm. Moreover, to allow the processor to efficiently check the run-time sequence and detect control flow errors, we introduce an on-chip assigned-signature checker which is capable of executing three additional instructions (SIC, SIJ, SIJC). Second, since the very concept of simultaneous multi-threading (SMT) provides the necessary redundancy, some proposals have been made to run two copies of the same thread on top of SMT platforms in order to detect and correct soft errors. This allows, upon detection of an error, the rolling back of the processor state to a known safe point, and then a retry of the instructions, thereby effecting a completely error-free execution. This paper has focused on two crucial implementation issues introduced by this scheme: (1) the design trade-off between the fault detection coverage versus design costs; (2) the possible occurrence of deadlock situations.     

The RAMI On-line Model Checker (ROMC): A web-based benchmarking facility for canopy reflectance models

The exploitation of global Earth Observation data hinges increasingly on physically-based radiative transfer (RT) models. These models simulate the interactions of solar radiation within a given medium (e.g., clouds, plant canopies) and are used to generate look-up-tables that are embedded into quantitative retrieval algorithms, such as those delivering the operational surface products for MODIS, MISR and MERIS. An assessment of the quality of canopy RT models thus appears essential if accurate and reliable information is to be derived from them. Until recently such an undertaking was a time consuming and labour intensive process that was made even more challenging by the general lack of absolute reference standards. Several years of benchmarking activities in the frame of the RAdiation transfer Model Intercomparison (RAMI) exercise have now led to the development of the RAMI On-line Model Checker (ROMC). The ROMC is a web-based tool allowing model developers and users to autonomously assess the performance of canopy RT models (http://romc.jrc.ec.europa.eu/). Access to the ROMC is free and enables users to obtain both statistical and graphical indications as to the performance of their canopy RT model. In addition to providing an overall indication of the skill of a given model to correctly match the reference data, the ROMC allows also for interactive comparison/evaluations of different model versions/submissions of a given user. All ROMC graphs can be downloaded in PostScript format and come with a reference number for easy usage in presentations and publications. It is hoped that the ROMC will prove useful for the RT modeling community as a whole, not only by providing a convenient means to evaluate models outside the triennial phases of RAMI but also to attract participation in future RAMI activities.     

Applying Trajectory approach with static priority queuing for improving the use of available AFDX resources

AFDX (Avionics Full Duplex Switched Ethernet) standardized as ARINC 664 is a major upgrade for avionics systems. The mandatory certification implies a worst-case delay analysis of all the flows transmitted on the AFDX network. Up to now, this analysis is done thanks to a tool based on a Network Calculus approach. The more recent Trajectory approach has been proposed for the computation of worst-case response time in distributed systems. It has been shown that the worst-case delay analysis of an AFDX network can be improved using an optimized Trajectory approach. This paper extends this optimized approach with the integration of static priority QoS policies. This extension makes possible to compute the bounds needed for deterministic avionics flows (high priority) when (lower priority) non avionics flows are added. Moreover, the paper provides an analysis of the pessimism of the obtained bounds.     

Expressing embedded systems configurations at high abstraction levels with UML MARTE profile: Advantages,limitations and alternatives

Embedded systems have become an essential aspect of our professional and personal lives. From avionics, transport and telecommunication systems to general commercial appliances such as smart phones, high definition TVs and gaming consoles; it is difficult to find a domain where these systems have not made their mark. Moreover, Systems-on-Chips (SoCs) which are considered as an integral solution for designing embedded systems, offer advantages such as run-time reconfiguration that can change system configurations during execution, depending upon Quality-of-Service (QoS) criteria such as performance and energy levels. This article deals with aspects related to modeling of these configurations, useful for describing various states of an embedded system, from both structural and operational viewpoints. Our proposal adapts a high abstraction level approach based on the principles of Model-Driven Engineering (MDE) and takes into account the UML MARTE profile for modeling of real-time and embedded systems. Elevating the design abstraction levels help to increase design productivity and achieve execution platform independence, among other advantages. The article details the current proposition of configurations in MARTE via some examples, and points out the advantages as well as some limitations, mainly concerning the semantic aspects of the defined concepts. Finally, we report our experiences on the modeling of an alternate notion of configurations and execution modes within the MARTE compliant Gaspard2 SoC Co-Design framework that has been successful for the design as well as implementation of FPGA based SoCs.