The phenomena of combustion instabilities beyond limit cycles caused by the nonlinear interaction of various instability modes have recently received much attention. This paper numerically studied ...the mode competition and cooperation phenomena in the liquid rocket engines when combustion instabilities occur. The liquid rocket engine with the single-element structure is the focus of the present work, and the numerical model is developed employing the Large Eddy Simulation technology, with the complete conservation Navier-Stokes equations taken into account. The results first reveal the relationship between the acoustic mode and the intrinsic vorticity mode: the competition and cooperation between the two will result in the complex dynamic process, such as semi-stable oscillation and intermittency. What's more, a more detailed coupling process between intrinsic vortex shedding and acoustic oscillation is analyzed, indicating existence of four stability regimes in the liquid rocket engines and an important insight into combustion instability in non-premixed dump combustors is provided.
•A numerical framework is developed to study the stability transition in a model liquid rocket engine.•The interaction of various modes is introduced to explain the phenomenon of combustion instability beyond limit cycle.•The conversion between acoustic mode and intrinsic vorticity mode leads to intermittency.
•We evaluate three parameter estimation methods for connectome generative models.•The three methods show a tradeoff between accuracy, reliability, and computational expense.•We develop a new fast, ...accurate and reliable estimation method.•We report minimum sample sizes required to detect between-group differences in model parameters.
Generative models of the human connectome enable in silico generation of brain networks based on probabilistic wiring rules. These wiring rules are governed by a small number of parameters that are typically fitted to individual connectomes and quantify the extent to which geometry and topology shape the generative process. A significant shortcoming of generative modeling in large cohort studies is that parameter estimation is computationally burdensome, and the accuracy and reliability of current estimation methods remain untested. Here, we propose a fast, reliable, and accurate parameter estimation method for connectome generative models that is scalable to large sample sizes. Our method achieves improved estimation accuracy and reliability and reduces computational cost by orders of magnitude, compared to established methods. We demonstrate an inherent tradeoff between accuracy, reliability, and computational expense in parameter estimation and provide recommendations for leveraging this tradeoff. To enable power analyses in future studies, we empirically approximate the minimum sample size required to detect between-group differences in generative model parameters. While we focus on the classic two-parameter generative model based on connection length and the topological matching index, our method can be generalized to other growth-based generative models. Our work provides a statistical and practical guide to parameter estimation for connectome generative models.
The unsteady combustion of solid propellants under oscillating environments is the key to understanding the combustion instability inside solid rocket motors. The discontinuous Galerkin–finite ...element method (DG-FEM) is introduced to provide an efficient yet flexible numerical platform to investigate the combustion dynamics of solid propellants. The algorithm is developed for the classical unsteady model, the Zel’dovich–Novozhilov model. It is then validated based on a special analytical solution. The DG-FEM algorithm is then compared with the classical spectral method based on Laguerre polynomials. It is shown that the DG-FEM works more efficiently than the traditional spectral method, providing a more accurate solution with a lower computational cost.
Solid rocket motors are prone to combustion instabilities, which may lead to various problems for the rockets, from unexpected oscillations, precision decreasing, to explosion. The unsteady ...combustion dynamics of the propellants play a crucial role in most solid rocket motors experiencing combustion instabilities. A modeling framework for the unsteady combustion of the solid propellant is constructed via the Zel’dovich-Novozhilov (ZN) phenomenological perspective. The overall unsteady combustion features of a quasi-steady homogeneous one-dimensional (QSHOD) model are investigated. The phenomenological ZN parameters are then calculated. Compared with the traditional ZN-QSHOD linear equivalence relation, the new calculated system yields better results for the pressure coupling response, especially in the non-linear regime. The proposed phenomenological modeling provides a new methodology for the model reduction of the complex flame models.
Abel. (
) is an important woody edible oil tree species in China. The quality of
oil (tea oil) is mainly determined by the contents of linoleic acid (LA) and α-linolenic acid (ALA). However, how to ...increase the contents of LA and ALA in tea oil and the corresponding regulating mechanism have not been clarified. In the present study, we found that the LA and ALA contents in
seeds were significant positively associated with the concentrations of ethephon and were decreased by ethylene inhibitor treatment. Furthermore, 1.5 g L
ethephon could receive an optimal LA and ALA contents without adverse effects to the growth of 'Huashuo' trees in this study. The ethephon treatment also increased the contents of 1-aminocyclopropane-1-carboxylic acid (ACC), sucrose, soluble sugar and reducing sugar contents in seeds. Transcriptome analysis further suggested that exogenous ethephon application enhanced the accumulation of LA and ALA
regulating genes involved in LA and ALA metabolism, plant hormone signal transduction pathways, and starch and sucrose metabolism. Our findings confirm the role of ethylene in LA and ALA regulation and provide new insights into the potential utilization of ethylene as a LA and ALA inducer in
cultivation.
In this study, we constructed a new membrane, which was prepared by free radical polymerization of a mixture containing vinyl-functionalized SiO2 nanoparticles (M-SiO2), modified cellulose acetate ...(M-CA) and poly(ethylene glycol)dimethacrylate (PEGDMA). The M-SiO2 was the SiO2 nanoparticles coupled with vinyltrimethoxysilane (VTMO), and the M-CA was the cellulose acetate modified with methacryloyl groups. The effects of M-SiO2 content on the porosity, electrolyte uptake and other properties of the membrane were studied. The results showed that the membrane with a suitable M-SiO2 content had good mechanical strength and other properties. For example, the membrane with 15 wt% of M-SiO2 (named as C-CAS15) possessed the excellent comprehensive performance. The mechanical strength of C-CAS15 membrane was up to 14.30 MPa, and it had no obvious dimension change at 200 °C. Meanwhile, the C-CAS15 membrane exhibited a relatively high ionic conductivity of 1.54 mS cm−1. The LiFePO4/GPE/Li half-cell assembled by the C-CAS15 membrane displayed excellent cycle charge-discharge performance and C-rate discharge performance, in which the discharge specific capacity retention could retain 98% after 100 cycles under 0.5 C/0.5 C and the discharge specific capacity could reach above 100 mAh g−1 under the higher C-rate of 4 C. Compared with the commercial PE membrane and the common membranes reported in previous literatures, the prepared C-CAS15 membrane presented better comprehensive performance, which indicated that the C-CAS15 membrane could be a promising separator for high performance lithium-ion batteries.
•A whole cross-linked GPE separator based on cellulose acetate is prepared.•The effects of components on the performance of membranes are studied.•The cells assembled by the GPE shows excellent cycle and C-rate performance.
Global climate change is increasingly influencing the economic system. With the frequent occurrence of extreme weather events, the influences of climate change on the economic system are no longer ...limited to the agricultural sector, but extend to the industrial system. However, there is little research on the influences of climate change on industrial economic systems. Among the different sectors of the industrial economic system, the mining industry is more sensitive to the influences of climate change. Here, taking the mining industry as an example, we analyzed the influences of extreme precipitation on the mining industry using the trans-logarithm production function. In addition, the marginal output elasticity analysis method was employed to analyze the main factors influencing the mining industry. It was found that the mining investment in fixed assets, labor input, and technical progress could promote the development of the mining economy, while the extreme precipitation suppressed the growth of the mining industry. The increase in fixed asset investment and the technical progress could enhance the resistance of the mining industry to extreme precipitation, while there was no indication that labor input can reduce the influences of extreme precipitation.
Cellulose acetate (CA) is attractive for use as a separator in lithium-ion batteries (LIBs). However, the dissolubility in the liquid electrolyte limits its applications. Herein, we would report a ...cellulose acetate (CA) cross-linked film for the separator of lithium-ion battery. First, methacrylate modified cellulose acetate (M-CA) was prepared by esterification between CA and methylacryloyl chloride. Subsequently, an insoluble polymer membrane was obtained through the UV-induced polymerization of M-CA, poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) and trihydroxymethylpropyl trimethylacrylaye (TMPTMA). The results show that these polymer membranes have good thermal and chemical stability due to the cross-linked polymer matrix. When the amount of TMPTMA is 20% of the molar amount of PEGMEMA, not only has the obtained gel polymer electrolyte (GPE) a suitable ionic conductivity of 4.17 mS cm−1 and an excellent lithium ion transfer number of 0.80, but also it has discharge capacity of the half battery composed of LiFePO4/GPE/Li 120 mAh g−1 at 2 C. This study demonstrated a great possibility that the high-performance and biodegradable GPE could be applied in LIBs. In addition, there are many other methacrylate monomers that can be polymerized with M-CA to prepare various GPEs, which will open a new avenue for the application of CA in GPEs.
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•Cellulose acetate cross-linked film was prepared by UV photopolymerization as separator for lithium ion battery.•The ionic conductivity and mechanical strength of membranes could be adjusted by the amount of TMPTMA.•The obtained separator had good electrolyte retention ability and thermal stability for the safety of lithium-ion batteries.•The assembled cells possessed good electrochemical performance.
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