The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
David Vuilleumier - One of the best experts on this subject based on the ideXlab platform.
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intermediate temperature heat release in an hcci Engine fueled by ethanol n heptane mixtures an experimental and modeling study
Combustion and Flame, 2014Co-Authors: David Vuilleumier, Darko Kozarac, Samveg Saxena, Jyhyuan Chen, Marco Mehl, Robert W. Dibble, William J Pitz, Mani S SarathyAbstract:This study examines intermediate temperature heat release (ITHR) in homogeneous charge compression ignition (HCCI) Engines using blends of ethanol and n-heptane. Experiments were performed over the range of 0–50% n-heptane liquid volume fractions, at equivalence ratios 0.4 and 0.5, and intake pressures from 1.4 bar to 2.2 bar. ITHR was induced in the mixtures containing predominantly ethanol through the addition of small amounts of n-heptane. After a critical threshold, additional n-heptane content yielded low temperature heat release (LTHR). A method for quantifying the amount of heat released during ITHR was developed by examining the second derivative of heat release, and this method was then used to identify trends in the Engine Data. The combustion process inside the Engine was modeled using a single-zone HCCI model, and good qualitative agreement of pre-ignition pressure rise and heat release rate was found between experimental and modeling results using a detailed n-heptane/ethanol chemical kinetic model. The simulation results were used to identify the dominant reaction pathways contributing to ITHR, as well as to verify the chemical basis behind the quantification of the amount of ITHR in the experimental analysis. The dominant reaction pathways contributing to ITHR were found to be H-atom abstraction from n-heptane by OH and the addition of fuel radicals to O2.
Mani S Sarathy - One of the best experts on this subject based on the ideXlab platform.
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intermediate temperature heat release in an hcci Engine fueled by ethanol n heptane mixtures an experimental and modeling study
Combustion and Flame, 2014Co-Authors: David Vuilleumier, Darko Kozarac, Samveg Saxena, Jyhyuan Chen, Marco Mehl, Robert W. Dibble, William J Pitz, Mani S SarathyAbstract:This study examines intermediate temperature heat release (ITHR) in homogeneous charge compression ignition (HCCI) Engines using blends of ethanol and n-heptane. Experiments were performed over the range of 0–50% n-heptane liquid volume fractions, at equivalence ratios 0.4 and 0.5, and intake pressures from 1.4 bar to 2.2 bar. ITHR was induced in the mixtures containing predominantly ethanol through the addition of small amounts of n-heptane. After a critical threshold, additional n-heptane content yielded low temperature heat release (LTHR). A method for quantifying the amount of heat released during ITHR was developed by examining the second derivative of heat release, and this method was then used to identify trends in the Engine Data. The combustion process inside the Engine was modeled using a single-zone HCCI model, and good qualitative agreement of pre-ignition pressure rise and heat release rate was found between experimental and modeling results using a detailed n-heptane/ethanol chemical kinetic model. The simulation results were used to identify the dominant reaction pathways contributing to ITHR, as well as to verify the chemical basis behind the quantification of the amount of ITHR in the experimental analysis. The dominant reaction pathways contributing to ITHR were found to be H-atom abstraction from n-heptane by OH and the addition of fuel radicals to O2.
Sean D Young - One of the best experts on this subject based on the ideXlab platform.
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using search Engine big Data for predicting new hiv diagnoses
PLOS ONE, 2018Co-Authors: Sean D Young, Qingpeng ZhangAbstract:Author(s): Young, Sean D; Zhang, Qingpeng | Abstract: BackgroundA large and growing body of "big Data" is generated by internet search Engines, such as Google. Because people often search for information about public health and medical issues, researchers may be able to use search Engine Data to monitor and predict public health problems, such as HIV. We sought to assess the feasibility of using Google search Data to analyze and predict new HIV diagnoses cases in the United States.Methods and findingsFrom 2007 to 2014, we collected search volume Data on HIV-related Google search keywords across the United States. State-level new HIV diagnoses Data were collected from the Centers for Disease Control and Prevention (CDC) and AIDSVu.org. We developed a negative binomial model to predict HIV cases using a subset of significant predictor keywords identified by LASSO. The Google search Data were combined with state-level HIV case reports provided by the CDC. We use historical Data to train the model and predict new HIV diagnoses from 2011 to 2014, with an average R2 value of 0.99 between predicted versus actual cases, and average root-mean-square error (RMSE) of 108.75.ConclusionsResults indicate that Google Trends is a feasible tool to predict new cases of HIV at the state level. We discuss the implications of integrating visualization maps and tools based on these models into public health and HIV monitoring and surveillance.
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using search Engine Data as a tool to predict syphilis
Epidemiology, 2018Co-Authors: Sean D Young, Elizabeth Torrone, John Urata, Sevgi O AralAbstract:Background:Researchers have suggested that social media and online search Data might be used to monitor and predict syphilis and other sexually transmitted diseases. Because people at risk for syphilis might seek sexual health and risk-related information on the internet, we investigated association
C Olm - One of the best experts on this subject based on the ideXlab platform.
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aqueous ethanol laminar burning velocity measurements using constant volume bomb methods
Fuel, 2018Co-Authors: Nathan Hinton, Richard Stone, Roger Cracknell, C OlmAbstract:Abstract Ethanol is attractive as a renewable fuel for spark ignition Engines, and can also be used as an extender in gasoline (up to about 20% by volume) or as a major component (say above 70% by volume). There are three reasons for wanting to know the laminar burning velocity of water/ethanol/air mixtures. The first reason is that a significant fraction of the fuel calorific value is required to remove the last 10 per cent or so by volume of water from bio-ethanol, and in some applications it might not be necessary to remove all the water. The second reason is to provide extended Data for model validation. The third reason is that in turbocharged Engines the knock-free operating range can be extended through water addition so as to improve both output and efficiency. Laminar burning velocity measurements with up to 40% water by volume have been made with a constant volume combustion vessel using two distinct techniques: a) imaging of the flame front during the constant pressure period and b) analyzing the pressure rise Data. When the pressure rises the adiabatic core is compressed isentropically, so if a combustion model is used, a single experiment generates a sequence of measurements that include Data at high temperatures (up to 600 K) and high pressures (up to 12 bar) that are relevant to spark ignition Engine combustion. Data from the two methods is shown here to be consistent and in-line with published Data for ethanol, and satisfactory comparisons have also been found with predictions from kinetic mechanisms for the ethanol/water/air mixtures. The constant volume combustion vessel also generates Data on the Markstein length and the pressure at the onset of cellularity, with both being increased by the presence of water. The laminar burning velocity has a direct influence on the early flame growth in a spark ignition Engine, and unless the ignition timing is adjusted for slow burning mixtures there will be a significant loss of efficiency. Engine Data show that even with 40% water by volume in the ethanol, combustion performance is still acceptable if the ignition timing is advanced.
Andre L Oehma - One of the best experts on this subject based on the ideXlab platform.
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influence of intermediate temperature heat release on autoignition reactivity of single stage ignition fuels with varying octane sensitivity
Proceedings of the Combustion Institute, 2020Co-Authors: Kwang Hee Yoo, Alexander K. Voice, Andre L OehmaAbstract:Abstract This study investigates the effects of intermediate temperature heat release (ITHR) on autoignition reactivity of full boiling range gasolines with different octane sensitivity through intake temperature and simulated exhaust gas recirculation (EGR) sweeps in a homogenous charge compression ignition (HCCI) Engine. To isolate the ITHR effects, low temperature reactivity was suppressed through the use of high intake temperature and low intake oxygen mole fraction. For quantification of ITHR, a new method was applied to the Engine Data by examining the maximum value of the second derivative of heat release rate. Combustion phasing comparisons of fuels with octane sensitivity showed that fuel with less octane sensitivity became more reactive as intake temperature and simulated EGR ratio decreased, while fuel with higher octane sensitivity had a reverse trend. For all of the fuels that were tested, the amount of ITHR increased as the intake temperature and oxygen mole fraction increased. These ITHR trends, depending on octane sensitivity, were almost identical with the trends of combustion phasing, showing that ITHR significantly affects fuel autoignition reactivity and determines octane sensitivity.