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2021 ◽  
pp. 1-10
Author(s):  
Omid Samimi Abianeh

Abstract Autoignition of an n-heptane/air mixture was simulated in non-uniform temperature environments of a Rapid Compression Machine (RCM) and Shock-Tube (ST) with and without the presence of a cold-spot. The simulations were performed to investigate how the presence of a cold-spot and the cold boundary layer of the chamber wall may affect the ignition delay of the hydrocarbon mixture with NTC behavior. The simulations were performed using three models, (1) 3-Dimensional (3D) Computational Fluid Dynamics (CFD) model, (2) Zero-Dimensional (0D) homogenous batch reactor model by including the heat transfer model, and (3) 0D adiabatic homogenous batch reactor model. A detailed n-heptane mechanism was reduced in this work and used for 3D combustion modeling. A cold-spot critical radius of 7 mm was determined, which affects the ignition delay by more than 9%. In addition, two combustion modes were observed in the combustion chamber with a non-uniform temperature environment. With the first combustion mode, combustion starts at the high gas temperature region of the combustion chamber and quickly propagates towards the periphery of the chamber. In this combustion mode, the location of the maximum concentration of hydroxyl radical and the maximum temperature are the same. With the second combustion mode, the combustion starts at the periphery of the chamber, where the temperature is lower than the center of the chamber due to heat transfer to the cold chamber wall. The location of maximum concentration of the hydroxyl radical and maximum temperature are different with this combustion mode. The two observed combustion modes are due to the NTC behavior of the n-heptane mixture. The 0D homogenous batch reactor model (with and without heat transfer models) failed to mimic the ignition delay accurately when the second combustion mode was present. In addition, a propagating combustion has been observed in the simulation which is in agreement with some of the optical autoignition diagnostics of these hydrocarbons. This propagating combustion leads to a gradual pressure rise during autoignition, rather than a sharp pressure rise. The results of this work show that 0D homogenous batch reactor models are unable to simulate autoignition of mixtures with NTC behavior.


Heart Rhythm ◽  
2021 ◽  
Vol 18 (8) ◽  
pp. S227-S228
Author(s):  
Irum Kotadia ◽  
Iain Sim Michelle Williams ◽  
Caroline H. Roney ◽  
Jose Solis-Lemus ◽  
Orod Razeghi ◽  
...  

2021 ◽  
Author(s):  
Graeme Richards

This study investigates the influence of cavity ventilation on the wind driven rain (WDR) performance of brick veneer walls. Two types of walls (type C and D) both bonded with N-type mortar were studied. The volume and frequency of WDR was based on weather station data from York University. Cavity conditions were mocked with a cavity chamber and ventilation was simulated with a fan providing air suction out of the cavity. Ventilation rates were simulated at 0, 5 and 10 ACH. Higher ventilation rates resulted in more efficient drying and lower RH within the cavity chamber. Wall type C exhibited more absorption with increased ventilation rates. Moisture content readings were generally irrelevant due to failure of the prescribed method. Measuring the influence of cavity ventilation on the amount of penetrated water should be further investigated by applying different ventilation rates to the same wall specimens to reduce the impact of physical variations within the same brick type.


2021 ◽  
Author(s):  
Graeme Richards

This study investigates the influence of cavity ventilation on the wind driven rain (WDR) performance of brick veneer walls. Two types of walls (type C and D) both bonded with N-type mortar were studied. The volume and frequency of WDR was based on weather station data from York University. Cavity conditions were mocked with a cavity chamber and ventilation was simulated with a fan providing air suction out of the cavity. Ventilation rates were simulated at 0, 5 and 10 ACH. Higher ventilation rates resulted in more efficient drying and lower RH within the cavity chamber. Wall type C exhibited more absorption with increased ventilation rates. Moisture content readings were generally irrelevant due to failure of the prescribed method. Measuring the influence of cavity ventilation on the amount of penetrated water should be further investigated by applying different ventilation rates to the same wall specimens to reduce the impact of physical variations within the same brick type.


2021 ◽  
pp. 146808742110080
Author(s):  
Tetsuya Aizawa ◽  
Tomoki Kinoshita ◽  
Shinobu Akiyama ◽  
Kouya Shinohara ◽  
Yuusei Miyagawa

As a demonstration of a new method to examine the extremely unsteady and spatially varying wall heat transfer phenomena on diesel engine combustion chamber wall, high-speed imaging of infrared thermal radiation from the wall surface impinged by a diesel spray flame was attempted using a high-speed infrared camera. A 35 mm-diameter chromium-coated quartz window surface was impinged by a diesel spray flame with an impinging distance of 27 mm from the nozzle orifice in a constant volume combustion chamber. The infrared thermal radiation from the back surface of the 0.6 µm thick chromium layer was successfully visualized at 10 kHz frame rate and 128 × 128 pixel resolution through the quartz window. The infrared radiation exhibited coherent and streaky structure with radial stripes extending and waving from the stagnation point. The width of the radial stripes, spatial amplitude and the period of the waving movement were comparable to the ones for turbulent heat transfer on the engine cylinder wall previously measured with a heat flux sensor, suggesting that they are resulting from the turbulent structure in the wall-impinging diesel flame. The radiation intensity was calibrated to temperature and converted to heat flux via 3-D numerical analysis of transient thermal conduction in the quartz window. The peak-to-peak variation amplitudes of temperature and heat flux among the radial stripes during the diesel spray flame impingement were about 20 K and 2.3 MW/m2, corresponding to 13% of 150 K maximum temperature swing amplitude and 18 MW/m2 maximum heat flux, respectively.


2021 ◽  
Author(s):  
John J. Kelly ◽  
Dale Tranter ◽  
Els Pardon ◽  
Gamma Chi ◽  
Holger Kramer ◽  
...  

AbstractThe integrity of a cell’s proteome depends on correct folding of polypeptides by chaperonins. The TCP-1 ring chaperonin (TRiC) acts as obligate folder for >10% of cytosolic proteins, including cytoskeletal proteins actin and tubulin. While its architecture and how it recognises folding substrates is emerging from structural studies, the subsequent fate of substrates inside the TRiC chamber is not defined. We trapped endogenous human TRiC with substrates (actin, tubulin) and co-chaperone (PhLP2A) at different folding stages, for structure determination by cryogenic electron microscopy. The already-folded regions of client proteins are anchored at the chamber wall, positioning unstructured regions towards the central space to achieve their folding. Substrates engage with different sections of the chamber during the folding cycle, coupled to TRiC open-and-close transitions. Furthermore, the cochaperone PhLP2A modulates folding, acting as a molecular strut between substrate and TRiC chamber. Our structural snapshots piece together an emerging atomistic model of client protein folding through TRiC.


2021 ◽  
Author(s):  
Amir Yazdani ◽  
Satoshi Takahama ◽  
Jack K. Kodros ◽  
Marco Paglione ◽  
Mauro Masiol ◽  
...  

<p>Fine particulate matter (PM) affects visibility, climate and public health. Organic matter (OM), which is hard to characterize due to its complex chemical composition, can constitute more than half of the PM. Biomass burning from residential wood burning, wildfires, and prescribed burning is a major source of OM with an ever-increasing importance.</p><p>    Aerosol mass spectrometry (AMS) and Fourier transform infrared spectroscopy (FTIR) are two complementary methods of identifying the chemical composition of OM. AMS measures the bulk composition of OM with relatively high temporal resolution but provides limited parent compound information. FTIR, carried out on samples collected on Teflon filters, provides detailed functional groupinformation at the expense of relatively low temporal resolution.</p><p>    In this study, we used these two methods to better understand the evolution of biomass burning OM in the atmosphere with aging. For this purpose, primary emissions from wood and pellet stoves were injected into the Center for Studies of Air Qualities and Climate Change (C-STACC) environmental chamber at ICE-HT/FORTH. Primary emissions were aged using hydroxyl and nitrate radicals (with atmospherically relevant exposures) simulating atmospheric day-time and night-time oxidation.  A time-of-flight (ToF) AMS reported the composition of non-refractory PM<sub>1 </sub>every three minutes and PM<sub>1 </sub>was collected on PTFE filters over 20-minute periods before and after aging for off-line FTIR analysis.</p><p>    We found that AMS and FTIR measurements agreed well in terms of measured OM mass concentration, the OM:OC ratio, and concentration of biomass burning tracers – lignin and levoglucosan. AMS OM concentration was used to estimate chamber wall loss rates which were then used separate the contribution of primary and secondary organic aerosols (POA and SOA) to the aged OM. AMS mass spectra and FTIR spectra of biomass burning SOA and estimates of bulk composition were obtained by this procedure. FTIR and AMS spectra of SOA produced by OH oxidation of biomass burning volatile organic compounds (VOCs) were dominated by acid signatures. Organonitrates, on the other hand, appeared to be important in the SOA aged by the nitrate radical. The spectra from the two instruments also indicated that the signatures of certain compounds such as levoglucosan, lignin and hydrocarbons, which are abundant in biomass burning POA, diminish with aging significantly more than what can be attributed to chamber wall losses. The latter suggests biomass burning POA chemical composition might change noticeably due to heterogeneous reactions or partitioning in the atmosphere. Therefore, the common assumption of stable POA composition is only partially true. In addition, more stable biomass burning tracers should be used to be able to identify highly aged biomass burning aerosols in the atmosphere.</p>


2021 ◽  
pp. 50-56
Author(s):  
G.P. Glazunov ◽  
V.E. Moiseenko ◽  
S.M. Maznichenko ◽  
M.N. Bondarenko ◽  
A.L. Konotopskiy ◽  
...  

The experiments were carried out to determine the vacuum-plasma characteristics (mainly erosion and outgassing rate in a vacuum) of the stainless steel 12X18H10T before and after processing the walls of the vacuum chamber with the glow discharge and combined, glow-microwave plasma discharges in argon atmosphere. The current-voltage characteristics, the electron density and electron temperature were measured. It was observed that the discharge voltage in the combined regime is significantly lower than in glow discharges. In some modes, this voltage decrease can be up to 200 V. It was shown that erosion of stainless steel 12X18H10T in the combined discharges is 70 %, less than in the glow discharges. Measurements were made of the outgassing rate of 12X18H10T stainless steel with the thermal desorption probe in situ in the DSM-1 vacuum chamber. It was shown that cleaning the chamber wall by the glow discharge during 5 h leads to a decrease in the outgassing rate from 5.5·10-5 to 1·10-5 (Torr.l)/(s.cm2) . When the chamber wall is treated with GM discharge starting from nearly the same initial conditions the outgassing rate decreased to 3·10-6 (Torr.l)/(s.cm2). Spectral measurements of the plasma radiation of a glow and combined discharges show a decrease in the ratio of the peaks of argon ions and neutrals during the transition from a glow discharge to a combined one.


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