Asymptotic solution of the turbulent mixing layer for velocity ratio close to unity

The equations describing the first two terms of an asymptotic expansion of the solution of the planar turbulent mixing layer for values of the velocity ratio close to one are obtained. The first term of this expansion is the solution of the well-known time-evolving problem and the second, which includes the effects of the increase of the turbulence scales in the stream-wise direction, obeys a linear system of equations. Numerical solutions of these equations for a two-dimensional reacting mixing layer show that the correction to the time-evolving solution may explain the asymmetry of the entrainment and the differences in product generation observed in flip experiments

Novel coal gasification process: Improvement of syngas yield and reduction of emissions

This article is intended to propose and model an innovative process layout for coal gasification that improves the production of syngas and also reduces the sulfur and CO2emissions. The typical coal gasification process uses Sulfur Recovery Units to convert H2S to sulfur, but these have some disadvantage, e.g low sulfur price, coal charge with low sulfur flow rate, use of Tail Gas Treatment unit. Compared to the Claus process, this solution converts H2S and CO2into syngas (economically appealing), reduces emission of H2S and CO2and allows the use of coal charge with high sulfur flow rate, e.g. 9.5% mol/mol. The novel process takes advantage of a double amine wash, a thermal regenerative furnace and considers the recycle of the acid gases coming from the catalytic reactor to further promote the H2S conversion. In particular, the double amine wash is useful to purify the H2S stream to be sent to the thermal furnace from the syngas and CO2, in order to reduce the reactor inlet flow rate. The regenerative furnace is simulated using a large detailed kinetic scheme to appropriately describe the minor species (among them, pollutants like CS2 and COS). As a result, the recycle appears to substantially reduce the pollutant emissions. In addition, the conversion of the Claus process into the novel process doesn't require any change in the main equipment, just needing for a variation in the layout and the operating conditions

Development of a front end ASIC for Dark Matter directional detection with MIMAC

A front end ASIC (BiCMOS-SiGe 0.35 \mum) has been developed within the framework of the MIMAC detector project, which aims at directional detection of non-baryonic Dark Matter. This search strategy requires 3D reconstruction of low energy (a few keV) tracks with a gaseous \muTPC. The development of this front end ASIC is a key point of the project, allowing the 3D track reconstruction. Each ASIC monitors 16 strips of pixels with charge preamplifiers and their time over threshold is provided in real time by current discriminators via two serializing LVDS links working at 320 MHz. The charge is summed over the 16 strips and provided via a shaper. These specifications have been chosen in order to build an auto triggered electronics. An acquisition board and the related software were developed in order to validate this methodology on a prototype chamber. The prototype detector presents an anode where 2 x 96 strips of pixels are monitored.Comment: 12 pages, 10 figure

Self-consistent propagation of flux ropes in realistic coronal simulations

The aim of this paper is to demonstrate the possible use of the new coronal model COCONUT to compute a detailed representation of a numerical CME at 0.1~AU, after its injection at the solar surface and propagation in a realistic solar wind, as derived from observed magnetograms. We present the implementation and propagation of modified Titov-D\'emoulin (TDm) flux ropes in the COCONUT 3D MHD coronal model. The background solar wind is reconstructed in order to model two opposite configurations representing a solar activity maximum and minimum respectively. Both were derived from magnetograms which were obtained by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory (SDO) satellite. We track the propagation of 24 flux ropes, which differ only by their initial magnetic flux. We especially investigate the geometry of the flux rope during the early stages of the propagation as well as the influence of its initial parameters and solar wind configuration on 1D profiles derived at 0.1~AU. At the beginning of the propagation, the shape of the flux ropes varies between simulations during low and high solar activity. We find dynamics that are consistent with the standard CME model, such as the pinching of the legs and the appearance of post-flare loops. Despite the differences in geometry, the synthetic density and magnetic field time profiles at 0.1~AU are very similar in both solar wind configurations. These profiles are similar to those observed further in the heliosphere and suggest the presence of a magnetic ejecta composed of the initially implemented flux rope and a sheath ahead of it. Finally, we uncover relationships between the properties of the magnetic ejecta, such as density or speed and the initial magnetic flux of our flux ropes.Comment: 20 pages, 13 figure

Statistical Analysis of a Semilinear Hyperbolic System Advected by a White in Time Random Velocity Field

We study a system of semilinear hyperbolic equations passively advected by smooth white noise in time random velocity fields. Such a system arises in modeling non-premixed isothermal turbulent flames under single-step kinetics of fuel and oxidizer. We derive closed equations for one-point and multi-point probability distribution functions (PDFs) and closed form analytical formulas for the one point PDF function, as well as the two-point PDF function under homogeneity and isotropy. Exact solution formulas allows us to analyze the ensemble averaged fuel/oxidizer concentrations and the motion of their level curves. We recover the empirical formulas of combustion in the thin reaction zone limit and show that these approximate formulas can either underestimate or overestimate average concentrations when reaction zone is not tending to zero. We show that the averaged reaction rate slows down locally in space due to random advection induced diffusion; and that the level curves of ensemble averaged concentration undergo diffusion about mean locations.Comment: 18 page

Triggers of acute attacks of gout, does age of gout onset matter?: a primary care based cross-sectional study

Objectives To determine the proportion of people with gout who self-report triggers of acute attacks; identify the commonly reported triggers, and examine the disease and demographic features associated with self-reporting any trigger(s) of acute attacks of gout. Methods Individuals with gout were asked to fill a questionnaire enquiring about triggers that precipitated their acute gout attacks. Binary logistic regression was used to compute odds ratio (OR) and 95% confidence intervals (CI) to examine the association between having ≥1 self-reported trigger of acute gout and disease and demographic risk factors and to adjust for covariates. All statistical analyses were performed using STATA. Results 550 participants returned completed questionnaires. 206 (37.5%) reported at least one trigger of acute attacks, and less than 5% reported >2 triggers. Only 28.73% participants reported that their most recent gout attack was triggered by dietary or lifestyle risk factors. The most frequently self-reported triggers were alcohol intake (14.18%), red-meat or sea-food consumption (6%), dehydration (4.91%), injury or excess activity (4.91%), and excessively warm or cold weather (4.36% and 5.45%). Patients who had onset of gout before the age of 50 years were significantly more likely to identify a trigger for precipitating their acute gout attacks (aOR (95%CI) 1.73 (1.12–2.68) after adjusting for covariates. Conclusion Most people with gout do not identify any triggers for acute attacks, and identifiable triggers are more common in those with young onset gout. Less than 20% people self-reported acute gout attacks from conventionally accepted triggers of gout e.g. alcohol, red-meat intake, while c.5% reported novel triggers such as dehydration, injury or physical activity, and weather extremes

The nutrition-based comprehensive intervention study on childhood obesity in China (NISCOC): a randomised cluster controlled trial

<p>Abstract</p> <p>Background</p> <p>Childhood obesity and its related metabolic and psychological abnormalities are becoming serious health problems in China. Effective, feasible and practical interventions should be developed in order to prevent the childhood obesity and its related early onset of clinical cardiovascular diseases. The objective of this paper is to describe the design of a multi-centred random controlled school-based clinical intervention for childhood obesity in China. The secondary objective is to compare the cost-effectiveness of the comprehensive intervention strategy with two other interventions, one only focuses on nutrition education, the other only focuses on physical activity.</p> <p>Methods/Design</p> <p>The study is designed as a multi-centred randomised controlled trial, which included 6 centres located in Beijing, Shanghai, Chongqing, Shandong province, Heilongjiang province and Guangdong province. Both nutrition education (special developed carton style nutrition education handbook) and physical activity intervention (Happy 10 program) will be applied in all intervention schools of 5 cities except Beijing. In Beijing, nutrition education intervention will be applied in 3 schools and physical activity intervention among another 3 schools. A total of 9750 primary students (grade 1 to grade 5, aged 7-13 years) will participate in baseline and intervention measurements, including weight, height, waist circumference, body composition (bioelectrical impendence device), physical fitness, 3 days dietary record, physical activity questionnaire, blood pressure, plasma glucose and plasma lipid profiles. Data concerning investments will be collected in our study, including costs in staff training, intervention materials, teachers and school input and supervising related expenditure.</p> <p>Discussion</p> <p>Present study is the first and biggest multi-center comprehensive childhood obesity intervention study in China. Should the study produce comprehensive results, the intervention strategies would justify a national school-based program to prevent childhood obesity in China.</p> <p>Trial Registration</p> <p>Chinese clinical trial registry (Primary registry in the WHO registry network) Identifier: ChiCTR-TRC-00000402</p