VOC reactivity in central California: comparing an air quality model to ground-based measurements

International audienceVolatile organic compound (VOC) reactivity in central California is examined using a photochemical air quality model (the Community Multiscale Air Quality model; CMAQ) and ground-based measurements to evaluate the contribution of VOC to photochemical activity. We classify VOC into four categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC. Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes and other oxygenated VOC include both primary anthropogenic emissions and secondary products from primary VOC oxidation. To evaluate the model treatment of VOC chemistry, we compare calculated and modeled OH and VOC reactivities using the following metrics: 1) cumulative distribution functions of NO_x concentration and VOC reactivity (R_OH,VOC), 2) the relationship between R_OH,VOC and NO_x, 3) total OH reactivity (R_OH,total) and speciated contributions, and 4) the relationship between speciated R_OH,VOC and NO_x. We find that the model predicts R_OH,total to within 25?40% at three sites representing urban (Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry. However in the urban area of Fresno, the model under predicts NO_x and VOC emissions by a factor of 2?3. At all locations the model is consistent with observations of the relative contributions of total VOC. In urban areas, anthropogenic and biogenic R_OH,VOC are predicted fairly well over a range of NO_x conditions. In suburban and rural locations, anthropogenic and other oxygenated R_OH,VOC relationships are reproduced, but calculated biogenic and aldehyde R_OH,VOC are often poorly characterized by measurements, making evaluation of the model with available data unreliable. In central California, 30?50% of the modeled urban VOC reactivity is due to aldehydes and other oxygenated species, and the total oxygenated R_OH,VOC is nearly equivalent to anthropogenic VOC reactivity. In rural vegetated regions, biogenic and aldehyde reactivity dominates. This indicates that more attention needs to be paid to the accuracy of models and measurements of both primary emissions of oxygenated VOC and secondary production of oxygenates, especially formaldehyde and other aldehydes, and that a more comprehensive set of oxygenated VOC measurements is required to include all of the important contributions to atmospheric reactivity

Charged Particle Production in Proton-, Deuteron-, Oxygen- and Sulphur-Nucleus Collisions at 200 GeV per Nucleon

The transverse momentum and rapidity distributions of net protons and negatively charged hadrons have been measured for minimum bias proton-nucleus and deuteron-gold interactions, as well as central oxygen-gold and sulphur-nucleus collisions at 200 GeV per nucleon. The rapidity density of net protons at midrapidity in central nucleus-nucleus collisions increases both with target mass for sulphur projectiles and with the projectile mass for a gold target. The shape of the rapidity distributions of net protons forward of midrapidity for d+Au and central S+Au collisions is similar. The average rapidity loss is larger than 2 units of rapidity for reactions with the gold target. The transverse momentum spectra of net protons for all reactions can be described by a thermal distribution with `temperatures' between 145 +- 11 MeV (p+S interactions) and 244 +- 43 MeV (central S+Au collisions). The multiplicity of negatively charged hadrons increases with the mass of the colliding system. The shape of the transverse momentum spectra of negatively charged hadrons changes from minimum bias p+p and p+S interactions to p+Au and central nucleus-nucleus collisions. The mean transverse momentum is almost constant in the vicinity of midrapidity and shows little variation with the target and projectile masses. The average number of produced negatively charged hadrons per participant baryon increases slightly from p+p, p+A to central S+S,Ag collisions.Comment: 47 pages, submitted to Z. Phys.

Microservice Transition and its Granularity Problem: A Systematic Mapping Study

Microservices have gained wide recognition and acceptance in software industries as an emerging architectural style for autonomic, scalable, and more reliable computing. The transition to microservices has been highly motivated by the need for better alignment of technical design decisions with improving value potentials of architectures. Despite microservices' popularity, research still lacks disciplined understanding of transition and consensus on the principles and activities underlying "micro-ing" architectures. In this paper, we report on a systematic mapping study that consolidates various views, approaches and activities that commonly assist in the transition to microservices. The study aims to provide a better understanding of the transition; it also contributes a working definition of the transition and technical activities underlying it. We term the transition and technical activities leading to microservice architectures as microservitization. We then shed light on a fundamental problem of microservitization: microservice granularity and reasoning about its adaptation as first-class entities. This study reviews state-of-the-art and -practice related to reasoning about microservice granularity; it reviews modelling approaches, aspects considered, guidelines and processes used to reason about microservice granularity. This study identifies opportunities for future research and development related to reasoning about microservice granularity.Comment: 36 pages including references, 6 figures, and 3 table

The PHENIX Experiment at RHIC

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix

Charged particle spectra in central S+S collisions at 200 GeV/c per nucleon

The transverse momentum and rapidity distributions of negative hadrons and participant protons have been measured for central 32S+ 32S collisions at plab=200 GeV/c per nucleon. The proton mean rapidity shift ~1.6 and mean transverse momentum ~0.6 GeV/c are much higher than in pp or peripheral AA collisions and indicate an increase in the nuclear stopping power. All pT spectra exhibit similar source temperatures. Including previous results for K0s Lambda , and Lambda -bar, we account for all important contributions to particle production.Authors: Bächler, J.; Bartke, J.; Bialkowska, H.; Bock, R.; Brockmann, R.; Buncic, P.; Chase, S. I.; Derado, I.; Eckardt, V.; Eschke, J.; Ferenc, D.; Fleischmann, B.; Foka, P.; Fuchs, M.; Gazdzicki, M.; Gladysz, E.; Harris, J. W.; Heck, W.; Hoffmann, M.; Jacobs, P. M.; Kabana, S.; Kadija, K.; Keidel, R.; Kosiec, J.; Kowalski, M.; Kühmichel, A.; Lahanas, M.; Lee, J. Y.; Ljubicic, A.; Margetis, S.; Morse, R.; Nappi, E.; Odyniec, G.; Paic, G.; Panagiotu, A. D.; Petridis, A.; Piper, A.; Posa, F.; Poskanzer, A. M.; Pugh, H. G.; Pühlhofer, F.; Rai, G.; Rauch, W.; Renfordt, R.; Röhrich, D.; Roland, G.; Rothard, H.; Runge, K.; Sandoval, A.; Schambach, J. J.; Schmitz, N.; Schmoetten, E.; Schneider, I.; Seyboth, P.; Seyerlein, J.; Skrzypczak, E.; Stefanski, P.; Stock, R.; Ströbele, H.; Teitelbaum, L.; Tincknell, M. L.; Tonse, S.; Vasileiadis, G.; Vesztergombi, G.; Vranic, D.; Wenig, S

Natural Gas Variability In California: Environmental Impacts And Device Performance Combustion Modeling of Pollutant Emissions From a Residential Cooking Range

As part of a larger study of liquefied natural gas impacts on device performance and pollutant emissions for existing equipment in California, this report describes a cmoputer modeling study of a partially premixed flame issueing from a single cooktop burner port. The model consisted of a reactive computational fluid dynamics three-dimensional spatial grid and a 71-species chemical mechanism with propane combustion capability. Simulations were conducted with a simplified fuel mixture containing methane, ethane, and propane in proportions that yield properties similar to fuels distributed throughout much of California now and in recent years (baseline fuel), as well as with two variations of simulated liquefied natural gas blends. A variety of simulations were conducted with baseline fuel to explore the effect of several key parameters on pollutant formation and other flame characteristics. Simulations started with fuel and air issuing through the burner port, igniting, and continuing until the flame was steady with time. Conditions at this point were analyzed to understand fuel, secondary air and reaction product flows, regions of pollutant formation, and exhaust concentrations of carbon monoxide, nitric oxide and formaldehyde. A sensitivity study was conducted, varying the inflow parameters of this baseline gs about real-world operating conditions. Flame properties responded as expected from reactive flow theory. In the simulation, carbon monoxide levels were influenced more by the mixture's inflow velocity than by the gas-to-air ratio in the mixture issuing from the inflow port. Additional simulations were executed at two inflow conditions - high heat release and medium heat release - to examine the impact of replacing the baseline gas with two mixtures representative of liquefied natural gas. Flame properties and pollutant generation rates were very similar among the three fuel mixtures

The PHENIX experiment at RHIC

Later this decade the Relativistic Heavy Ion Collider (RHIC) will be built at Brookhaven National Laboratory. Its goal will be to accelerate and collide Au beams at 100 GeV/c in an attempt to create a Quark Gluon Plasma (QGP). The PHENIX detector aims to detect the QGP through its leptonic and hadronic signatures. We describe here its physics capabilities and the details of the apparatus designed to pick out rare leptonic signatures from among hadronic multiplicities of up to 1500 particles per unit of rapidity

The effect of prechambers on flame propagation in a natural-gas powered engine

Large-bore two-stroke natural-gas-fueled engines commonly are located along natural gas pipelines, siphoning off a small portion of gas from the pipeline for use as a fuel, in order to pump the remaining gas along the pipeline. The KIVA-3 computational fluid dynamics program was used to simulate the compression stroke, combustion, and power stroke in a natural-gas-fueled engine by solving the full Navier-Stokes equations. These calculations include cases with and without prechambers. Prechamber stoichiometry and spark locations were independently varied with the goal of understanding how various prechamber parameters influence the ignition of the fuel-air charge in the main chamber. The goal is to allow the use of very lean main-chamber charges to minimize nitrogen oxide (NO{sub x}) production. These calculations were performed in both two and three dimensions