The Future of RICH Detectors through the Light of the LHCb RICH

The limitations in performance of the present RICH system in the LHCb experiment are given by the natural chromatic dispersion of the gaseous Cherenkov radiator, the aberrations of the optical system and the pixel size of the photon detectors. Moreover, the overall PID performance can be affected by high detector occupancy as the pattern recognition becomes more difficult with high particle multiplicities. This paper shows a way to improve performance by systematically addressing each of the previously mentioned limitations. These ideas are applied in the present and future upgrade phases of the LHCb experiment. Although applied to specific circumstances, they are used as a paradigm on what is achievable in the development and realisation of high precision RICH detectors

Diesel engines equipped with piezoelectric and solenoid injectors: hydraulic performance of the injectors and comparison of the emissions, noise and fuel consumption

A comprehensive comparison between solenoid and indirect acting piezoelectric injectors has been carried out. The working principle of these injector typologies is illustrated, and their hydraulic performance has been analysed and discussed on the basis of experimental data collected at a hydraulic test rig. The injector char- acteristics, injected fl ow-rate pro fi les, nozzle opening and closure delays, injector leakages and injected volume fl uctuations with the dwell time have been compared in order to evaluate the impact of the injector driving system. The solenoid and piezoelectric injectors have been installed on a Euro 5 diesel engine, which has been tested experimentally at a dynamometer cell. Optimized double and triple injection strategies have been considered at some representative key points of the New European Driving Cycle. Engine-out emissions, brake speci fi c fuel consumption and combustion noise are presented and discussed, with the support of a three-zone, diesel com- bustion diagnostic model. The research has focused on the cause-and-e ff ect relationships between the hydraulic performance of the injectors and the results of the engine tests. The primary goal has been to assess if the di ff erences in engine performance between the solenoidal and indirect-acting piezoelectric injector setups are due to the injector driving system or to speci fi c features that are present in the hydraulic circuit of the considered injectors and which are not closely related to the driving system. A fi nal evaluation of the potential of the piezoelectric technology for driving indirect acting injectors is provided on the basis of real engine result

Analysis of plasma formation during hypersonic flight in the earth atmosphere

In this study we investigate the formation of plasma in hypersonic flight and its impact on radio communications and radar tracking. The transfer of kinetic energy from the vehicle to the surrounding gas in the hypersonic regime leads to the formation of plasma, which can cause interference with electromagnetic waves. By conducting a numerical simulation campaign using Computational Fluid Dynamics (CFD), we are determining the critical Mach number and altitude conditions that lead to plasma formation. The plasma generated at the nose of the vehicle and its subsequent convection along the body and in the wake are the main subjects of our investigation. The simulations include physical models that account for chemical, vibrational and electronelectron energy non-equilibria, using a two-temperature approach. The results indicate the Mach numbers and altitudes at which plasma formation can significantly affect the propagation of electromagnetic waves

A Study on Plasma Formation on Hypersonic Vehicles using Computational Fluid Dynamics

This study focuses on understanding high-temperature effects and plasma formation in sub-orbital hypersonic flight using Computational Fluid Dynamics (CFD) simulations. The research compares two models with different kinetic parameters derived from shock tube experiments and state-to-state chemical kinetics. The simulations consider various Mach numbers and altitudes relevant to reentry conditions. Results show that the choice of model and the number of species composing the mixture significantly impact the flow field, with the more recent model demonstrating improved accuracy compared to experimental and numerical data

The role of chiral loops in η→π0π0γγ\eta\to\pi^0\pi^0\gamma\gamma

We consider the rare decay $\eta\to\pi^0\pi^0\gamma\gamma$ and calculate the non-resonant contribution to the amplitude to one loop in Chiral Perturbation Theory. We display our result as both a diphoton energy spectrum and a partial decay rate as a function of the photon energy cut. It turns out that the one-loop correction can be numerically very important and could be detected, at sufficiently large center-of-mass photon energies, from a measurement of the partial decay width.Comment: 10 pages, Latex. Discussion on the resonant background enlarged, sign error corrected, basic results unchanged. To appear in Phys. Lett.

Developing a framework and the construction of an understanding of place value

In an effort to make sense of prospective teacher’s views of decimal fractions, an exploration of facets of place value understanding was conducted. To move past a focus on performance as a measure of understanding, a framework for the exploration of place value ideas as they relate to prospective teachers’ understanding of decimal fractions was developed. The framework is used to analyze the work of a small collection of prospective elementary teachers who worked to share their understanding of decimals. Conclusions regarding the power of the inquiry in mathematics teacher educator’s understandings of learners and as a springboard for instruction are shared

Characterization of Hydrotreated Vegetable Oil (HVO) in a Euro 6 Diesel Engine as a Drop-In Fuel and With a Dedicated Calibration

Renewable fuels can play an important role in achieving future goals of energy sustainability and CO2 reduction. In particular, hydrotreated vegetable oil (HVO) represents one of the most promising alternatives to petroleum-derived diesel fuels. Several studies have shown that conventional diesel engines can run on 100% HVO without significant modifications to the hardware and control strategies. The current activity has experimentally evaluated the potential of HVO as a “drop-in” fuel, i.e., without changes to the original baseline calibration, comparing it to conventional diesel fuel on a 2.3-litre Euro 6 compression ignition engine. Tests revealed that HVO can significantly reduce engine-out soot (by more than 60%), HC and CO emissions (by about 40%), compared to diesel, while NOx levels and fuel conversion efficiency remain relatively unchanged under steady-state warmed-up conditions. The advantages of HVO proved to be further enhanced when the engine has not yet warmed up. Using statistical techniques of design of experiments (DoE) at three warmed-up steady-state operating points, the main engine control parameters were recalibrated to demonstrate that engine-out emissions can be further optimized with a dedicated calibration

Utilization of Hydrotreated Vegetable Oil (HVO) in a Euro 6 Dual-Loop EGR Diesel Engine: Behavior as a Drop-In Fuel and Potentialities along Calibration Parameter Sweeps

This study examines the effects on combustion, engine performance and exhaust pollutant emissions of a modern Euro 6, dual-loop EGR, compression ignition engine running on regular EN590-compliant diesel and hydrotreated vegetable oil (HVO). First, the potential of HVO as a "drop-in" fuel, i.e., without changes to the original, baseline diesel-oriented calibration, was highlighted and compared to regular diesel results. This showed how the use of HVO can reduce engine-out emissions of soot (by up to 67%), HC and CO (by up to 40%), while NOx levels remain relatively unchanged. Fuel consumption was also reduced, by about 3%, and slightly lower combustion noise levels were detected, too. HVO has a lower viscosity and a higher cetane number than diesel. Since these parameters have a significant impact on mixture formation and the subsequent combustion process, an engine pre-calibrated for regular diesel fuel could not fully exploit the potential of another sustainable fuel. Therefore, the effects of the most influential calibration parameters available on the tested engine platform, i.e., high-pressure and low-pressure EGR, fuel injection pressure, main injection timing, pilot quantity and dwell-time, were analyzed along single-parameter sweeps. The substantial reduction in engine-out soot, HC and CO levels brought about by HVO could give the possibility to implement additional measures to limit NOx emissions, combustion noise and/or fuel consumption compared to diesel. For example, higher proportion of LP EGR and/or smaller pilot quantity could be exploited with HVO, at low load, to reduce NOx emissions to a greater extent than diesel, without incurring penalties in terms of incomplete combustion species. Conversely, at higher load, delayed main injection timings and reduced rail pressure could reduce combustion noise without exceeding soot levels of the baseline diesel case

Coating thermal noise for arbitrary shaped beams

Advanced LIGO's sensitivity will be limited by coating noise. Though this noise depends on beam shape, and though nongaussian beams are being seriously considered for advanced LIGO, no published analysis exists to compare the quantitative thermal noise improvement alternate beams offer. In this paper, we derive and discuss a simple integral which completely characterizes the dependence of coating thermal noise on shape. The derivation used applies equally well, with minor modifications, to all other forms of thermal noise in the low-frequency limit.Comment: 3 pages. Originally performed in August 2004. Submitted to CQG. (v2) : Corrections from referee and other

Ponesimod, a selective S1P1 receptor modulator: a potential treatment for multiple sclerosis and other immune-mediated diseases

The first oral treatment for relapsing multiple sclerosis, the nonselective sphingosine-1-phosphate receptor (S1PR) modulator fingolimod, led to identification of a pivotal role of sphingosine-1-phosphate and one of its five known receptors, S1P(1)R, in regulation of lymphocyte trafficking in multiple sclerosis. Modulation of S1P3R, initially thought to cause some of fingolimod's side effects, prompted the search for novel compounds with high selectivity for S1P1R. Ponesimod is an orally active, selective S1P(1)R modulator that causes dose-dependent sequestration of lymphocytes in lymphoid organs. In contrast to the long half-life/slow elimination of fingolimod, ponesimod is eliminated within 1 week of discontinuation and its pharmacological effects are rapidly reversible. Clinical data in multiple sclerosis have shown a dose-dependent therapeutic effect of ponesimod and defined 20mg as a daily dose with desired efficacy, and acceptable safety and tolerability. Phase II clinical data have also shown therapeutic efficacy of ponesimod in psoriasis. These findings have increased our understanding of psoriasis pathogenesis and suggest clinical utility of S1P(1)R modulation for treatment of various immune-mediated disorders. A gradual dose titration regimen was found to minimize the cardiac effects associated with initiation of ponesimod treatment. Selectivity for S1P(1)R, rapid onset and reversibility of pharmacological effects, and an optimized titration regimen differentiate ponesimod from fingolimod, and may lead to better safety and tolerability. Ponesimod is currently in phase III clinical development to assess efficacy and safety in relapsing multiple sclerosis. A phase II study is also ongoing to investigate the potential utility of ponesimod in chronic graft versus host disease