Short Time Delay Research Articles

Effect of microwave pulse parameters on energy coupling and enhancement of microwave assisted ignition

Microwave Assisted Ignition (MAI) is a promising technology to optimize the lean combustion characteristics of internal combustion engines. This research investigated the effects of microwave pulse waveform and delay time on energy coupling and ignition enhancement by using a power diagnostic with high time-resolution. The pulse width ranged from 80 to 200 μs and the corresponding peak power was adjusted between 1000 and 400 W to keep the incident energy of microwave pulse constant. Results showed that a high power and short width pulse waveform was conducive to the microwave energy absorption. The coupled energy generally decreased with delay time. There was a significant ignition enhancement with only 6∼7 mJ energy coupled into the flame kernel, which was approximately 1/5 of total spark energy. Moreover, the ignition enhancement was well correlated with the coupled energy, suggesting that ignition enhancement was determined by coupled energy via electron collision reactions. Finally, the main influencing factor of coupled energy was the energy coupling pattern which changed from none-coupling to saturated coupling. A high pulse power and short delay time facilitated this change. This study revealed the saturated coupling pattern independent of waveform and delay time, which is caused by a stable electron number density due to the cut-off effect.

Reactivity of hypergolic hybrid solid fuel with industrial grade hydrogen peroxide

Hypergolic solid fuels and hydrogen peroxide oxidizers have attracted considerable attention for the development of safe hybrid rocket propulsion systems. In this study, a new approach was explored to develop a safe hypergolic hybrid propulsion system using industrial-grade hydrogen peroxide (∼70 wt%). Initially, the propulsion performance of different hypergolic solid fuels with an industrial-grade hydrogen peroxide was calculated using the NASA CEA code to find an appropriate propellant combination. The theoretical specific impulse of the hypergolic solid fuel was 27.8 % over hydrazine and 13.4 % over LMP-103S. Based on theoretical investigations, hypergolic solid fuels, named such as HSF-1 to HSF-10, were fabricated using molding and pressing methods. The ignition delay time was measured using the drop-test method. Interestingly, HSF-3 and HSF-4 exhibited very short ignition delay times of 4.92 and 8.75 ms, respectively, with industrial-grade hydrogen peroxide. In addition, the drop test results of hypergolic solid fuel with varying compression pressure in the pressing method confirmed that a pressure above the compressive strength of the binder shortens the ignition delay times deviation. Further, HSF was also ignited even at low concentration of IGHP (>40 wt%); opens the new area of research in combustion science. Overall, low-toxicity hypergolic solid fuels and industrial-grade hydrogen peroxide are promising alternatives to conventional toxic hypergolic propellants.

TH2.8 Continuing fast-track (Expedited) pancreaticoduodenectomy service during the Covid-19 pandemic: Experience from an established pancreatic surgical centre

AimAvoiding preoperative biliary drainage (PBD) can facilitate early curative surgery for patients with periampullary tumours. However, the evidence over PBD is conflicting. This prospective re-audit aimed to assess compliance to NICE guidelines (NG85) and surgical outcomes at a well-established HPB surgery unit after achieving additional theatre sessions following prior audit.MethodsProspective data collection and analysis for all patients undergoing pancreaticoduodenectomy with curative intent was performed as re-audit at a tertiary pancreatic centre between September 2020 to August 2021.Results64 or 71 patients received curative pancreaticoduodenectomy (43 Kausch-Whipple & 23 pylorus-preserving pancreaticoduodenectomy, 7 inoperable). Of 29 patients without PBD, 10 were jaundiced with median bilirubin levels of 138 Micromole/L (range 27–357 Mmol/L). Median time (range) from diagnostic imaging to surgery with curative intent was 21 days (3–42) for patients without PBD compared to 62 days (22–305) for those with PBD (p=0.00028). No statistically significant difference in median HDU/ITU stay (4 Vs 3 days, p=0.849), postoperative complications (C-D>2) (30% Vs 27.8%, p=0.755), R0 resection rates (42.8% Vs 75%, p=0.364), and median hospital stay (17 Vs 10 days, p=0.076) was observed for patients without or with PBD respectively. Interestingly, inoperable patients had shorter time delay from diagnostic imaging to surgery (29 Vs 49 days, p=0.010)ConclusionFast-track (expedited) pancreaticoduodenectomy is feasible and safe for selected group of jaundiced patients without PBD. The constraints and challenges posed by Covid-19 pandemic are likely reflected in higher number of patients receiving PBD (42/ 71) despite clear referral pathway established following prior work at our institute.

Outcomes in pediatric patients with documented delays between ileocolic intussusception diagnosis and therapeutic enema attempt: evaluation of reduction efficacy and complication rate.

Ileocolic intussusception is considered a pediatric emergency, with concerns for risk of significant morbidity in children with a prolonged intussusception state. Emergent therapy is standard of care, as prior studies have shown poor outcomes in patients with long delays (> 24h) before intervention. Various factors can result in shorter delays, and there are limited studies evaluating outcomes in these patients. This study aimed to determine if there were differences in reduction success rates associated with short in-hospital time delays. This study is to determine enema success rate and morbidity in patients with documented time delays between intussusception diagnosis and therapeutic enema. A retrospective evaluation of pediatric patients with intussusception at a single children's hospital between 2007 and 2019 was performed. Patient's records were reviewed for time of symptom onset, radiologic diagnosis, and attempted enema. Ultrasounds and radiographs were reviewed for bowel obstruction, free peritoneal fluid, trapped fluid around the intussusceptum, and absent bowel wall perfusion. Patients were evaluated for efficacy of reduction attempt, requirement for surgical reduction, and complications including bowel resection and bowel perforation. There were 175 cases of ileocolic intussusception requiring enema reduction. Successful reduction occurred in 72.2% (13/18) of cases performed within 1h of diagnosis; 74.3% (78/105) between 1 and3 h; 73.2% (30/41) between 3 and 6h; and 81.2% (9/11) with greater than 6h. Need for bowel resection was not associated with short delays between diagnosis and reduction attempts (p = .07). There was no difference in intussusception reduction efficacy or complication rate in patients with increasing time between imaging diagnosis of ileocolic intussusception and reduction attempt, including delay intervals up to 8h.

Structural displacement estimation using accelerometer and FMCW millimeter wave radar

Structural displacement plays a crucial role in structural health monitoring. However, its measurement remains challenging for many civil infrastructure applications. This study proposes a structural displacement estimation technique that fuses measurements from a collocated accelerometer and frequency-modulated continuous-wave millimeter wave radar at displacement estimation location on a structure. Automated initial calibration was first performed using short-period (less than 1 min) radar and acceleration measurements. The best target is automatically selected from the surroundings, and a conversion factor to convert the line-of-sight displacement to the structural displacement in the actual vibration direction is automatically estimated for the target. After calibration, the displacement is estimated in real time from radar measurements using the selected best target and its estimated conversion factor. Note that an accelerometer-aided phase-unwrapping algorithm is proposed and applied to address the phase-wrapping issue when the structural displacement is larger than the radar wavelength. The radar-based displacement is further fused with the acceleration measurement using a finite impulse response filter to estimate the displacement with improved accuracy at the cost of a short time delay. Laboratory tests on a four-story building model and a field test on a pedestrian bridge were conducted to validate the proposed displacement estimation technique. The displacements estimated by the proposed technique had an error of less than 1 mm in both tests compared to the ground-truth displacements measured by laser-based displacement sensors.

Quantum trajectory theory and simulations of nonlinear spectra and multiphoton effects in waveguide-QED systems with a time-delayed coherent feedback

We study the nonlinear spectra and multi-photon correlation functions for the waveguide output of a two-level system (including realistic dissipation channels) with a time-delayed coherent feedback. We compute these observables by extending a recent quantum trajectory discretized-waveguide (QTDW) approach which exploits quantum trajectory simulations and a collisional model for the waveguide to tractably simulate the dynamics. Following a description of the general technique, we show how to calculate the first and second order quantum correlation functions, in the presence of a coherent pumping field. With a short delay time, we show how feedback can be used to filter out the central peak of the Mollow triplet or switch the output between bunched and anti-bunched photons by proper choice of round trip phase. We further show how the loop length and round trip phase effects the zero-time second order quantum correlation function, an indicator of bunching or anti-bunching. New resonances introduced through the feedback loop are also shown through their appearance in the incoherent output spectrum from the waveguide. We explain these results in the context of the waiting time distributions of the system output and individual trajectories, uniquely stochastic observables that are easily accessible with the QTDW model.

Experimental investigations of the effect of millisecond-delay time on the blast vibration reduction with electronic detonators

The error of precise initiation time controlled at the microsecond level in the electronic detonator blasting is accurate enough to realize blasting vibration reduction; however, the realization of precise control of blasting vibration using the electronic detonators remains rudimentary, researches on the precise zoning protection of buildings and field experiments are lacked. Therefore, multi-delay time of double-hole and multi-hole blasting experiments were carried out to explore the influence of different delay time on blast-induced PPV (Peak Particle Velocity). Based on the measured blasting vibration waveforms with blasting center distance of 16–200 m the reasonable delay time reducing PPV was investigated when the protective buildings at different blasting center distances and the reasonable delay time suitable for zoning protection was put forward to verify the applicability of the electronic detonators. The results show that as the initiation delay time increases, the PPV of blasting vibration first decreases then increases and finally attenuates to the single-hole PPV, with the increase of the blasting center distance, the reasonable delay time for reducing PPV gradually increases. However, a greater vibration enhancement effect will be produced when the delay time reaches at a certain value in the near area, the generated maximum PPV is about 1.8 times the single-hole PPV and there will be multiple short delay time producing enhancement effect in multi-hole blasting, the short delay time cannot be blindly adopted to reduce vibration. Therefore, the delay time of electronic detonators should be reasonably set to achieve the effect of blasting vibration reduction based on the distance between the protected buildings and the blasting zone.

Blockchain Consensus Mechanism Based on Quantum Teleportation

The consensus mechanism is the core secret of the blockchain network. However, the consensus mechanism of the classical blockchain is based on the classical cryptosystem, which is based on the problem of computational complexity. With the improvement of computing power, the security of this cryptosystem is being threatened. In addition, the consensus mechanism of classic blockchain also has the following disadvantages: serious waste of computing resources and energy; the inability to withstand a 51% attack; low system throughput and large delay. Based on quantum teleportation technology and the randomness of quantum measurement, a consensus mechanism for a quantum blockchain system is proposed. Based on the physical properties of quantum mechanics, this scheme has the unconditional security of quantum cryptography. This new consensus mechanism does not involve a great deal of computing resources and hence has a lower energy consumption, shorter time delay and higher throughput. Furthermore, the new consensus mechanism could withstand a 51% attack.

Signature whistles exhibit a ‘fade-in’ and then ‘fade-out’ pattern of relative amplitude declination

Bottlenose dolphins have individually distinct signature whistles that are characterized by a stereotyped frequency-time contour. Signature whistles are commonly exchanged with short time delays between calls. Dolphin whistles are produced by pressurized nasal sacs that increase and then decrease in pressure over emission. This study found that the relative amplitude modulation pattern over time exhibited the same fade-in and then fade-out pattern in the signature whistles of eight bottlenose dolphins at the Navy in San Diego, CA. Both the initial and final five percent of the whistle’s duration also had significantly lower mean relative amplitude than the center five percent. The current analyses of the amplitude-time relationship was then integrated to a previously reported model of the negative relationship between relative log amplitude and log peak frequency. This produced a more robust model for accounting for the predictable aspects of the more broadly non-stereotyped amplitude modulations of signature whistles. Whether dolphins can intentionally manipulate these amplitude features or they are simple by-products of the sound production system, and further whether they are perceived and utilized by receivers, is an exciting area for continued research.

Effect of microalgae biodiesel blending on diesel engine characteristics

AbstractThe current numerical work investigates the effect of using algae methyl ester (AME) blends with diesel fuel on diesel engine performance, combustion, and emission characteristics. Five volumetric blends of biodiesel drived from spirulina algae (20%, 30%, 50%, 70%, and 100% AME) have been examined numerically with help of Diesel‐RK and compared with diesel fuel. As a result of investigations, the addition of AME blends reduces the cylinder pressure and shifts it closer to Top Dead Center. The heat release rate reduced as the percentage of AME increased, whereas 30% AME reduces the heat release by 9.96%. All blends of AME to diesel decrease brake thermal efficiency (BTE) slightly and increase brake‐specific fuel consumption (BSFC), whereas using 30% AME reduces BTE 1.09% and increases BSFC 5.89% compared with diesel. The shorter delay time is observed by using the proposed AME blends recording reduction in the delay period starting from 18.23% up to 65.77%. Bosch smoke number decreases as a result of AME addition recording a 17.19% reduction in case of 30% AME while it increased after 70% AME. Promising reduction in SO2 emissions compared with diesel observed by an average of 14.08%, 21.78%, 38.41%, 56.28%, and 84.07% when using 20%, 30%, 50%, 70%, and 100% AME, respectively. Slight increase in CO2 emissions within the range of 1.17%–6.22% when using AME blends between 20% and 100%. On the basis of the main findings, the 30% AME biodiesel was noticed as the most excellent mixing proportion. The main contribution focuses on “How spirulina microalgae biodiesel can enhance the characteristics of a diesel engine.” The obtained results are compared with the findings of other studies.

0112 Classification of reconstructed depth profiles shows Global and non-Global slow oscillations differentiate in the hippocampus and thalamus

Abstract Introduction Sleep slow oscillations (SOs, 0.5-1.5 Hz) can be classified on the scalp as Global, Local or Frontal, where Global SOs are found in most electrodes within a short time delay and gate long-range information flow during NREM sleep. In this study, we estimate the current density within the brain that generates a Global SO, to evaluate which sub-cortical structures are involved in Global SO dynamics. We then train multiple machine learning algorithms to distinguish between Global SOs and other SO types, and probe variance of Global/non-Global SO profiles within and across subjects.Sleep slow oscillations (SOs, 0.5-1.5 Hz) can be classified on the scalp as Global, Local or Frontal, where Global SOs are found in most electrodes within a short time delay and gate long-range information flow during NREM sleep. In this study, we estimate the current density within the brain that generates a Global SO, to evaluate which sub-cortical structures are involved in Global SO dynamics. We then train multiple machine learning algorithms to distinguish between Global SOs and other SO types, and probe variance of Global/non-Global SO profiles within and across subjects. Methods 32 volunteers (18 females) slept in the lab with polysomnography including 24 head EEG channels; their sleep was scored according to AASM criteria. SOs were algorithmically detected at each channel and classified as Global or non-Global using our method (Malerba et al., 2019). The depth profile of each SO was reconstructed with current source estimation (in Brainstorm followed by sLORETA), with a standardized head model including 17 regions. Each depth profile was embedded in a matrix averaging current by region and in three 200ms-long time bins: before, during and after the SO trough. Thirty classifiers were applied to this dataset, leveraging Matlab’s supervised learning application. We compared accuracy within and across subjects and identified best-performing algorithms across dataset size. We then used univariate feature selection to quantify the relevance of each region-time pair to successful classification. Results Global/non-Global SOs current depth profiles have higher variance across subjects, and accuracy improves when data is sampled between rather than within individuals. Ensemble subspace methods reached highest accuracy (98.5%). Feature selectivity identified cortical, hippocampal, and thalamic currents at the trough of the SO as the most relevant for Global/non-Global SO classifications. Conclusion We introduce an analytical framework enabling the study of SO depth profiles, including their time evolution, as matrices. The predominant differentiation of Global/non-Global SOs in cortical, hippocampal, and thalamic currents supports the potential functional difference of these SO types. Support (If Any) NIH grant (R01 AG046646) to S.C.M.

Effect of shock wave formation on propellant ignition in capillary discharge

In order to study the effect of shock wave formation on propellant ignition in capillary discharge, the shock wave formation process was analyzed using experimental and theoretical methods; the plasma jet temperature was measured, and closed bomb and 30 mm gun experiments were carried out. The results show that the first shock wave has a smaller value and larger range of influence, while the second shock wave has a larger value and smaller range of influence. A plasma jet can generate a shock wave at the nozzle according to the calculated plasma pressure and velocity, which is well confirmed by experiments and calculations. The plasma jet temperature is high during the formation of a shock wave and then decreases sharply. Plasma ignition can increase the burning rate of a propellant by about 30% by increasing the burning surface area of the propellant. Compared to conventional ignition, the average maximum chamber pressure and average muzzle velocity of plasma ignition are increased by 9.1 MPa and 29.3 m·s−1 (∼3%), respectively, in a 30 mm gun. Plasma ignition has strong ignition ability and short ignition delay time due to the generation of a shock wave. By increasing the burning rate of the propellant, the muzzle velocity can be greatly improved when the maximum chamber pressure increases a little. The characteristics of the shock wave can be applied in the application of the capillary discharge plasma. For example, it can be applied in fusion, launching and combustion.

Experimental investigations of indirect noise due to modulation of axial vorticity and entropy upstream of a choked nozzle

An experimental cold-gas study of the response of a choked convergent–divergent nozzle to swirl perturbations is presented. The perturbations were obtained by means of upstream unsteady tangential injections into initially steady flows with different values of steady background swirl. The swirl perturbations induced changes in the axial mass-flow rate, due to either their ingestion or evacuation by the nozzle. This in turn caused a downstream acoustic response. For low-intensity background swirl the responses were found to be similar to those obtained without steady background swirl. Perturbations of a high-intensity background swirl led to different effects. For long injection times, the negative mass-flow rate modulation occurred in two stages. The first stage was similar to that of the background-swirl free case. The second stage occurred after a short time delay, and induced a much stronger negative acoustic response. This unexpected behavior suggests that a significant part of the tangentially injected fluid flows upstream inducing an accumulation of swirl, which is – after tangential injection is ceased – suddenly cleared out through the nozzle. A scaling rule for the amplitudes of these acoustic responses is reported. Furthermore, quasi-steady models, based on steady-state measurements are proposed. These models predict the downstream acoustic response amplitude within a factor two. Additionally, preliminary empirical evidence of the effect of swirl on the downstream acoustic response due to the interaction of entropy patches with a choked nozzle is reported. This was obtained by comparison of sound produced by abrupt radial or tangential sonic injection, upstream from the choked nozzle, of air from a reservoir at room temperature to that from a reservoir with a higher stagnation temperature. Because the mass flow through the nozzle does not increase instantaneously, the injected higher-enthalpy air accumulates upstream of the injection-port position in the main flow. This eventually induces a large downstream acoustic pulse when tangential injection is interrupted. The magnitude of the resulting sound pulse can reach that of a quasi-steady response of the nozzle to a large air patch with a uniform stagnation temperature equal to that of the upstream-injected heated air. This hypothesis is consistent with the fact that the initial indirect-sound pulse is identical to one obtained with unheated air injection. The authors posit that – given all of the insight gleaned from them in this case – acoustic measurements of indirect sound appear to be a potentially useful diagnostic tool.

Pseudo-continuous arterial spin labeling with short post-labeling delay time sensitively reflects the hemodynamics of symptomatic patients with permanent large vessel occlusion before and after revascularization.

This study evaluated the feasibility of arterial spin labeling (ASL) for diagnosing hemodynamic stroke due to permanent anterior circulation large vessel occlusion. Three-dimensional pseudo-continuous ASL data at two post-labeling delay (PLD) times (1.5 and 2.5s) in patients with unilateral permanent middle cerebral artery (MCA) segment 1 (M1) or internal cerebral artery (ICA) occlusion were acquired during routine magnetic resonance angiography. Sixty-one patients with symptomatic occlusion (M1, 24; ICA, 37) and 69 patients with asymptomatic occlusion (M1, 21; ICA, 48) were enrolled. Regions of interest were automatically placed in the MCA region using a template. The respective scans were compared with asymptomatic M1 or ICA occlusion scans. The ratio of signal intensity (occlusion side/non-occlusion side) in the perfusion area of MCA (asymmetry index [AI]) was compared between both groups. In both PLD groups, AI was significantly lower in symptomatic patients than in asymptomatic patients. The receiver operating characteristic curve showed moderate capacity for the prediction of symptomatic AI in both groups (area under the curve, 0.739 and 0.712, respectively). As a result of extracranial-intracranial bypass operation in 28 symptomatic (M1, eight; ICA, 20) patients, AI was significantly higher postoperatively in the PLD 1.5s group than in the PLD 2.5s group. In symptomatic patients with permanent large vessel occlusion, the signal intensity ratio of pseudo-continuous ASL with short PLD sensitively reflects the hemodynamics before and after revascularization; therefore, this technique may be an alternative method in situations where PET or SPECT cannot be performed.

The Redshift Evolution of the Binary Black Hole Merger Rate: A Weighty Matter

Gravitational-wave detectors are starting to reveal the redshift evolution of the binary black hole (BBH) merger rate, R BBH(z). We make predictions for R BBH(z) as a function of black hole mass for systems originating from isolated binaries. To this end, we investigate correlations between the delay time and black hole mass by means of the suite of binary population synthesis simulations, COMPAS. We distinguish two channels: the common envelope (CE), and the stable Roche-lobe overflow (RLOF) channel, characterized by whether the system has experienced a common envelope or not. We find that the CE channel preferentially produces BHs with masses below about 30 M ⊙ and short delay times (t delay ≲ 1 Gyr), while the stable RLOF channel primarily forms systems with BH masses above 30 M ⊙ and long delay times (t delay ≳ 1 Gyr). We provide a new fit for the metallicity-dependent specific star formation rate density based on the Illustris TNG simulations, and use this to convert the delay time distributions into a prediction of R BBH(z). This leads to a distinct redshift evolution of R BBH(z) for high and low primary BH masses. We furthermore find that, at high redshift, R BBH(z) is dominated by the CE channel, while at low redshift, it contains a large contribution (∼40%) from the stable RLOF channel. Our results predict that, for increasing redshifts, BBHs with component masses above 30 M ⊙ will become increasingly scarce relative to less massive BBH systems. Evidence of this distinct evolution of R BBH(z) for different BH masses can be tested with future detectors.

A Three-Sample Filter for Fast Arbitrary Harmonic Elimination

When suffering the grid voltage distortion, the phase-locked loop (PLL) should equip with the fast response filter to precisely extract the fundamental voltage information for proper grid integration. To shorten the time delay induced by filters, this article proposes a new three-sample filter (TSF) to fast eliminate the harmonics of sampled grid voltage. Theoretically, it can filter out arbitrary individual harmonic with short time delay which could be as small as only two sampling periods. Moreover, TSF can reject a group of harmonics simultaneously within the specifically set time interval. The implementation issues of TSF as in-loop filter or prefilter for both three- and single-phase applications are demonstrated in synchronous reference frame PLL (SRF-PLL) SRF-PLL. Simulation and experimental results verified its advanced performance.

Estimating transient rates from cosmological simulations and BPASS

ABSTRACT The detection rate of electromagnetic (EM) and gravitational wave (GW) transients is growing exponentially. As the accuracy of the transient rates will significantly improve over the coming decades, so will our understanding of their evolution through cosmic history. To this end, we present predicted rates for EM and GW transients over the age of the universe using Binary Population and Spectral Synthesis (bpass) results combined with four cosmic star formation histories (SFHs). These include a widely used empirical SFH of Madau & Dickinson and those from three cosmological simulations: MilliMillennium, EAGLE, and IllustrisTNG. We find that the choice of SFH changes our predictions: transients with short delay times are most affected by the star formation rate and change up to a factor of 2, while long delay time events tend to depend on the metallicity evolution of star formation and can change the predicted rate up to an order of magnitude. Importantly, we find that the cosmological simulations have very different metallicity evolution that cannot be reproduced by the widely used metallicity model of Langer & Norman, which impacts the binary black hole merger, stripped-envelope supernovae, and LGRBs in the local Universe most acutely. We recommend against using simple prescriptions for the metallicity evolution of the universe when predicting the rates of events that can have long delay times and that are sensitive to metallicity evolution.

Effects of jet/flame interaction on deflagration-to-detonation transition by non-reactive gas jet in a methane-oxygen mixture

Jet-in-crossflow (JICF) is a potential and reliable technique that can promote flame acceleration and deflagration-to-detonation transition (DDT). Most of the previous researches utilized combustible mixture or oxygen as the medium of JICF, therefore the detonation enhancement effect may be partly attributed to the chemical properties of the jet, and the purely turbulent effect induced by JICF on DDT has not been fully understood. In our previous work, the non-reactive gas jet affected flame propagation indirectly by separating the injection and ignition in the control sequence. A competing mechanism between the positive combustion-enhancement effect caused by jet-induced turbulence and the negative non-reactive gas-inhibition effect on combustion has not been found, the non-reactive gas jet with high pressure and short duration time was also verified to be beneficial for precursor shock wave formation and flame acceleration. However, no detonation was observed in the work. In this paper, the non-reactive jet interacts with the flame propagation directly by overlapping the working time of the jet and ignitor partly, and the effect of jet parameters including injection pressure and time delay on DDT is investigated systematically. The results show that the flame affected by the non-reactive gas jet with a high-pressure ratio and a short time delay can transit to detonation in a short run-up distance successfully. The schlieren images of the flame evolution process illustrate that the flame interacted by the jet experiences four states: layered flame, wrinkled flame, cellular flamelets, and turbulent flame. Kelvin–Helmholtz (K-H) instability and Rayleigh-Taylor (R-T) instability dominate in the flame distortion. The characteristic timescales of the flow and reaction are computed in the four flame states, turning out that as the flame evolving, the turbulent intensity of the flame is enhanced. Damköhler number (Da) on the flame front eventually converges to [1,2] demonstrates the characteristic timescales of the turbulence and reaction are on the same order, and the turbulence dominates the flame evolution.

National and regional variations in timely adherence to recommended measles vaccination scheme in 2-years old in Switzerland, 2005–2019

BackgroundAlthough monitoring of vaccination program performance is usually evaluated by measurement of vaccine coverage, timely uptake is rarely part of this assessment. This study aims to examine the timeliness of the administration of a measles-containing-vaccine (MCV) for 2-year-old children between 2005 and 2019. MethodsWe used data from the Swiss National Vaccination Coverage Survey 2005–2019 for the study. We defined timely vaccinated as a vaccination administered within the recommended age specified in the Swiss National Vaccination Schedule, with an added tolerance period of 30.4 days for both MCV 1 and 2 doses. The median delay time was estimated by Kaplan-Meier survival curve and examined using log-rank test. A Cox hazard ratio was used to identify factors associated with delay. Results81% (95% CI:79–82%) of toddlers were timely vaccinated for MCV1 and 82% (95% CI:81–83%) for MCV2 in survey period 2017–2019. Between 2005 and 2019, the median age of vaccinated children ranged between 12.2 and 12.5 and 18.3–22.0 months for MCV1 and MCV2 with median delay of 44 and 38 days, respectively, at the national level. Children in the French-, Italian- and German-speaking regions were vaccinated earlier between 2005 and 2019 for MCV1 (vaccination coverage range before 10 months of age: 1.7–45.9%, 1.2–35.3% and 1.4–15.0%, respectively). Nationality, linguistic regions, and survey periods were the strongest predictive factors related to prolonged delay time. ConclusionOverall adherence to recommendations has improved over time, as MCV coverage has significantly increased over the years with differences across linguistic regions. Vaccinations were administered earlier and with shorter delay time.

Regional frequency analysis of drought severity and duration in Karkheh River Basin, Iran using univariate L-moments method.

Drought is one of the natural disasters that causes a great damage to human life and natural ecosystems. The main differences are in the gradual effect of drought over a relatively long period, impossibility of accurately determining time of the beginning and end of drought, and geographical extent of the associated effects. On the other hand, lack of a universally accepted definition of drought has added to the complexity of this phenomenon. In the last decade, due to increasing frequency of drought in Iran and reduction of water resources, its consequences have become apparent and have caused problems for planners and managers. So in this research, regional frequency analysis using L-moments methods was performed to investigate severity and duration of Standardized Precipitation Index (SPI), Standardized Evapotranspiration Index (SEI), Standardized Runoff Index (SRI), and Standardized Soil Moisture Index (SSI) and to study of meteorological, agricultural, and hydrological droughts in Karkheh River Basin in Iran. Using K-means clustering method, basin was divided into four homogeneous areas. Uncoordinated stations in each cluster were removed. The best regional distribution function was selected for each homogeneous region, and it was found that Pearson type (3) has the highest fit on the data set in the basin. Based on Hosking and Wallis heterogeneity test, Karkheh Basin with H1 < 1 was identified as acceptable homogeneous in all clusters. The results showed that hydrological drought occurs with a very short time delay in Karkheh River Basin after the meteorological drought, and two indicators show meteorological and hydrological drought conditions well. Agricultural drought occurs after meteorological and hydrological drought, respectively, and its severity and duration are less than the other indicators. Meteorological, hydrological, and agricultural droughts do not occur at the same time in all of the years. In general, the SPI drought index shows the most severe droughts compared with the other three indices. By this way, in 5- to 20-year return period with severity of 3SPI and in 20- to 100-year return period with severity of 7SPI, region IV or the western and northwestern areas of the basin has been affected by severe meteorological drought. By using the regional standardized quantities, it is possible to estimate the probability of drought in any part of the catchment that does not have sufficient data for hydrological studies.