scholarly journals A NOx conversion model for estimating NO2 concentration near highways.

1999 ◽  
Vol 27 ◽  
pp. 649-654
Author(s):  
Toshiya Yamada ◽  
Hirofumi Ohnishi ◽  
Nodoka Oshiro ◽  
Hiroyuki Oneyama ◽  
Seiichi Momose
Keyword(s):  
Conversion Model ◽  
Nox Conversion

scholarly journals Thermogravimetry of the Steam Gasification of Calluna vulgaris: Kinetic Study

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 657
Author(s):  
José María Encinar ◽  
Juan Félix González ◽  
Sergio Nogales-Delgado
Keyword(s):  
Kinetic Study ◽  
Raw Materials ◽  
Biomass Conversion ◽  
Calluna Vulgaris ◽  
Thermal Conversion ◽  
Positive Influence ◽  
Steam Gasification ◽  
Conversion Model ◽  
Oil Reserves ◽  
Shrinking Core

On account of the continuous decrease in oil reserves, as well as the promotion of sustainable policies, there is an increasing interest in biomass conversion processes, which imply the search for new raw materials as energy sources, like forestry and agricultural wastes. On the other hand, gasification seems to be a suitable thermal conversion process for this purpose. This work studied the thermogravimetry of the steam gasification of charcoal from heather (Calluna vulgaris) in order to determine the kinetics of the process under controlled reaction conditions. The variables studied were temperature (from 750 to 900 °C), steam partial pressure (from 0.26 to 0.82 atm), initial charcoal mass (from 50 to 106 mg), particle size (from 0.4 to 2.0 mm), N2 and steam volumetric flows (from 142 to 446 mL·min−1) and catalyst (K2CO3) concentration (from 0 to 10% w/w). The use of the shrinking core model and uniform conversion model allowed us to determine the kinetic parameters of the process. As a result, a positive influence of catalyst concentration was found up to 7.5% w/w. The kinetic study of the catalytic steam gasification showed activation energies of 99.5 and 114.8 kJ·mol−1 and order of reactions (for steam) of 1/2 and 2/3.

scholarly journals Applying MRI Intensity Normalization on Non-Bone Tissues to Facilitate Pseudo-CT Synthesis from MRI

Diagnostics ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 816
Author(s):  
Kuei-Yuan Hou ◽  
Hao-Yuan Lu ◽  
Ching-Ching Yang
Keyword(s):  
Mean Value ◽  
Tissue Type ◽  
Routine Practice ◽  
Intensity Level ◽  
Mean Values ◽  
Conversion Model ◽  
Ratio Image ◽  
Abdominal Mri ◽  
High Level ◽  
Intensity Normalization

This study aimed to facilitate pseudo-CT synthesis from MRI by normalizing MRI intensity of the same tissue type to a similar intensity level. MRI intensity normalization was conducted through dividing MRI by a shading map, which is a smoothed ratio image between MRI and a three-intensity mask. Regarding pseudo-CT synthesis from MRI, a conversion model based on a three-layer convolutional neural network was trained and validated. Before MRI intensity normalization, the mean value ± standard deviation of fat tissue in 0.35 T chest MRI was 297 ± 73 (coefficient of variation (CV) = 24.58%), which was 533 ± 91 (CV = 17.07%) in 1.5 T abdominal MRI. The corresponding results were 149 ± 32 (CV = 21.48%) and 148 ± 28 (CV = 18.92%) after intensity normalization. With regards to pseudo-CT synthesis from MRI, the differences in mean values between pseudo-CT and real CT were 3, 15, and 12 HU for soft tissue, fat, and lung/air in 0.35 T chest imaging, respectively, while the corresponding results were 3, 14, and 15 HU in 1.5 T abdominal imaging. Overall, the proposed workflow is reliable in pseudo-CT synthesis from MRI and is more practicable in clinical routine practice compared with deep learning methods, which demand a high level of resources for building a conversion model.

scholarly journals What Does Neuroscience Tell Us About the Conversion Model of Functional Neurological Disorders?

2020 ◽  
Vol 32 (1) ◽  
pp. 24-32 ◽  
Author(s):  
Alexandre Cretton ◽  
Richard J. Brown ◽  
W. Curt LaFrance ◽  
Selma Aybek
Keyword(s):  
Neurological Disorders ◽  
Conversion Model ◽  
Functional Neurological Disorders

TWC-SCR Aftertreatment System Evaluation for a Lean Burn Gasoline Engine Operating in HCCI, SACI, and SI Combustion Modes

2016 ◽  
Author(s):  
Jordan Easter ◽  
Stanislav V. Bohac
Keyword(s):  
Conversion Efficiency ◽  
Gasoline Engine ◽  
Fuel Efficiency ◽  
Compression Ignition ◽  
Scr Catalyst ◽  
Advanced Combustion ◽  
Nox Conversion ◽  
Combustion Modes ◽  
Scr System ◽  
Nox Conversion Efficiency

Low temperature and dilute Homogenous Charge Compression Ignition (HCCI) and Spark Assisted Compression Ignition (SACI) can improve fuel economy and reduce engine-out NOx emissions to very low values, often less than 30 ppm. However, these combustion modes are unable to achieve stringent future regulations such as SULEV 30 without the use of lean aftertreatment. Though active selective catalytic reduction (SCR) with urea injection and lean NOx traps (LNT) have been investigated as options for lean gasoline engines, a passive TWC-SCR system is investigated in this work because it avoids the urea storage and dosing hardware of a urea SCR system, and the high precious metal cost of an LNT. The TWC-SCR concept uses periodic rich operation to produce NH3 over a TWC to be stored on an SCR catalyst for subsequent NOx conversion during lean operation. In this work a laboratory study was performed with a modified 2.0 L gasoline engine that was cycled between lean HCCI and rich SACI operation, or between lean and rich SI (spark ignited) combustion, to evaluate NOx conversion and reduced fuel consumption. Different lambda values during rich operation and different times held in rich operation were investigated. Results are compared to a baseline case in which the engine is always operated at stoichiometric conditions. SCR system simulations are also presented that compare system performance for different levels of stored NH3. With the configuration used in this study, lean/rich HCCI/SACI operation showed a maximum NOx conversion efficiency of 10%, while lean/rich SI operation showed a maximum NOx conversion efficiency of 60%. However, if the low conversion efficiency of lean/rich HCCI/SACI operation could be improved through higher brick temperatures or additional SCR bricks, simulation results indicate TWC-SCR aftertreatment has the potential to provide near-zero SCR-out NOx concentration and increased system fuel efficiency. In these simulations, fuel efficiency improvement relative to stoichiometric SI were 7 to15% for lean/rich HCCI/SACI with zero tailpipe NOx and −1 to 5% for lean/rich SI with zero tailpipe NOx emissions. Although previous work indicated increased time for NH3 to start forming over the TWC during rich operation, less NH3 production over the TWC per fuel amount, and increased NH3 slip over the SCR catalyst for advanced combustion systems, if NOx conversion efficiency could be enhanced, improvements in fuel economy and low engine-out NOx from advanced combustion modes would more than make up for these disadvantages.

Investigations of Tail and Defect States in a-Si0.6Ge0.4:H Alloys by PDS and ESR - Implications for the Interaction of Weak and Dangling Bonds

1995 ◽  
Vol 377 ◽  
Author(s):  
Tilo P. Drüsedau ◽  
Andreas N. Panckow ◽  
Bernd Schröder
Keyword(s):  
Silicon Germanium ◽  
Defect Density ◽  
State Density ◽  
Model Parameters ◽  
Defect States ◽  
Conversion Model ◽  
Order Of Magnitude ◽  
Underlying Mechanisms ◽  
Amorphous Silicon Germanium ◽  
Excess Absorption

ABSTRACTInvestigations on the gap state density were performed on a variety of samples of hydrogenated amorphous silicon germanium alloys (Ge fraction around 40 at%) containing different amounts of hydrogen. From subgap absorption measurements the values of the “integrated excess absorption” and the “defect absorption” were determined. Using a calibration constant, which is well established for the determination of the defect density from the integrated excess absorption of a-Si:H and a-Ge:H, it was found that the defect density is underestimated by nearly one order of magnitude. The underlying mechanisms for this discrepancy are discussed. The calibration constants for the present alloys are determined to 8.3×1016 eV−1 cnr2 and 1.7×1016 cm−2 for the excess and defect absorption, respectively. The defect density of the films was found to depend on the Urbach energy according to the law derived from Stutzmann's dangling bond - weak bond conversion model for a-Si:H. However, the model parameters - the density of states at the onset of the exponential tails N*=27×1020 eV−1 cm−3 and the position of the demarcation energy Edb-E*=0.1 eV are considerably smaller than in a-Si:H.

Research Results on Processes and Catalyst Materials for Lean NOx Conversion

1996 ◽  
Author(s):  
Axel König ◽  
Thomas Richter ◽  
Edward Jobson ◽  
Michael Preis ◽  
Emanuele Leveroni ◽  
...  
Keyword(s):  
Research Results ◽  
Nox Conversion ◽  
Lean Nox

Runoff Forecast and Analysis of the Probability of Dry and Wet Transition in the Hanjiang River Basin

2021 ◽  
Author(s):  
Haoyu Jin ◽  
Xiaohong Chen ◽  
Ruida Zhong
Keyword(s):  
Water Resources ◽  
River Basin ◽  
Transition Probability ◽  
Conversion Model ◽  
Drought And Flood ◽  
Runoff Prediction ◽  
Runoff Forecast ◽  
Hanjiang River ◽  
Basin Area ◽  
Regional Water

Abstract Runoff prediction has an important guiding role in the planning and management of regional water resources, flood prevention and drought resistance, and can effectively predict the risk of changes in regional water resources. This study used 12 runoff prediction methods to predict the runoff of four hydrological stations in the Hanjiang River Basin (HRB). Through the MCMC method, the HRB runoff probability conversion model from low to high (high to low) is constructed. The study found that the runoff of the HRB had a decreasing trend. In the mid-1980s, the runoff had a significant decreasing trend. The smoother the runoff changes, the easier it is to make accurate prediction. On the whole, the QS-MFM, MFM, MA-MFM, CES and DNN methods have strong generalization ability and can more accurately predict the runoff of the HRB. The Logistic model can accurately simulate the change of runoff status in the HRB. Among them, the HLT station has the fastest conversion rate of drought and flood, and the flow that generates floods is 6 times that of drought. The smaller the basin area, the larger the gap between drought and flood discharge. Overall, this research provides important technical support for the prediction of change in water resources and the transition probability from drought to flood in the HRB.

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