A Method for Rapid Determination of Polymer Dissolution Time

In view of the limited space of offshore platform and the large amount of polymer injection, the dissolution time method, solution viscosity method, conductivity method, undissolved filtration method and falling ball method are used as the rapid detection methods of polymer dissolution. The results show that the error of conductivity method is the largest, and that of dissolution time method is the second, and both methods are time-consuming. Solution viscosity method and insolubles filtration method have small error, but they are time-consuming, especially for offshore platforms, which makes detection inconvenient. The drop ball method is simple in operation and has a small error, so it is a promising method for rapid determination of polymer dissolution time.

Thermodynamic performance modeling,optimization and numerical simulation of RBCC ejector mode

Ejector mode is a unique and critical phase of wide-range rocket-based combined cycle(RBCC)engine.In this paper,a quasi-one-dimensional thermodynamic performance modeling method,with more detailed model treatments for the inlet-diffuser system,pri-mary/secondaryflow interaction,and pressure feedback matching,was developed for operating characteristics studies and multi-objective optimization analysis of the ejector mode of an actual RBCC engine.A series of three-dimensional simulations of separate inlet and fullflowpath was completed to validate the modeling study and provide further insight into the operating charac-teristics.The primary/secondary equilibrium pressure ratio functions a significant effect on ejector mode performance,a higher performance augmentation can be obtained by lower rocket pressure ratio,larger mixing section area ratio,smaller throttling throat and higher equivalence ratio,within an appropriate range.The positive performance augmentation can be realized at lowflight Mach conditions,the coordination and trade-off relationships between specific im-pulse,performance augmentation ratio and thrust-to-area ratio during ejector mode are present by the Pareto-front from MOP analysis.It is further verified by CFD simulation that,the operating back-pressure at the exit of inlet-diffuser system functions a decisive influence on the airbreathing characteristics,the pressure feedback and matching should be well-controlled for secondaryflowrate and performance augmentation.The thermodynamic modeling analysis re-sults are basically consistent with those of numerical simulation,to validate the rationality and effectiveness of the modeling method.

Harmonic analysis based on time domain mutual-multiplication window

The signal spectral leakage and fence effect are prone to take place during the power harmonic analysis by fast fourier transform(FFT) under asynchronous sampling.The inhibiting ability of classical window functions is restricted by side-lobe behaviors. A new type window function called time domain mutual-multiplication window, is obtained by multiplication operation of several window functions. A novel approach of harmonic analysis is developed through analyzing performances of main-lobe and side-lobe of the new window. Simulation results show that the time domain mutual-multiplication window can significantly suppress frequency spectral leakage and improve the accuracy of harmonic parameter estimation.

Design of multidimensional nanocomposite material to realize the application both in energy storage and electrocatalysis

The development of clean,sustainable and renewable energy storage systems is in urgent need with the fast-growing energy demand in the areas of electric vehicles and mobile electronics etc.Lithium-ion batteries(LIBs)have been deemed to be the most promising energy storage devices for their high power density,long cycle life and fast charge-discharge rates[1].Transition

Toxoplasma gondii infection in children after allogeneic hematopoietic stem cell transplantation: A case report and literature review

Introduction:Toxoplasmosis is a life-threatening complication after hematopoietic stem cell transplantation(HSCT).However,for several reasons,clinicians know little about Toxoplasma infection.Case presentation:We report a case of toxoplasmosis that was diagnosed by bone marrow smear and metagenomic next-generation sequencing(mNGS)after HSCT in a boy.Additionally,we summarize the characteristics of toxoplasmosis after pediatric HSCT reported in the literature published in PubMed.Conclusion:Clinicians should increase their awareness of toxoplasmosis in children after HSCT and implement pre-transplant screening and post-transplant monitoring and prevention in future according to the national conditions of our country.

Effect of inlet-valve structures on thrust of airbreathing pulse detonation engines

Experimental studies were conducted in order to improve the understanding of the thrust generation and the pressure/flame reverse propagation of the air-breathing pulse detonation engines(APDEs)with self-designed inlets and valves structures.The present experimental research utilized a gasoline/air APDE(with 68 mm inner-diameter,2050 mm length and maximum operating frequency not less than 40 Hz which was as a benchmark structure)at different operating frequencies,with freestream air inflow of 1.1 atm and 0℃.The theoretical equivalence ratio of gasoline/air was 1.Two kinds of inlets with centerbody or without were considered and combined with two kinds of self-designed valves(the elastic-valve and the convergent aero-valve)specially designed for comparative experiments.During the test,the inflow parameters,the pressure along the longitudinal direction inside the engine and the thrust force were measured for the APDE operating characteristic analysis,including the detonation combustion,the aerodynamic drag,the pressure/flame reverse propagation and the thrust generation.The research results indicate that:The inlet centerbody does not increase drag but plays a positive effect on airflow stability and operation matching.The elastic-valve and the convergent aero-valve,though increase the inlet aerodynamic drag,have obvious effects on suppressing the detonation wave and pressure forward propagation,resulting in effective thrust increase.Effects of the convergent aero-valve are the best when the flow choked,while the effects of elastic-valve are better and continuously stable in a wider range of frequency.The wmaximum nondimensional thrust increases with the elastic-valve is reached about 1.12 at the frequency of 8-9 Hz,and about 0.97 with the convergent aero-valve at the frequency of 7 Hz.The maximum fuel specific impulse is 2514.6 s when using the convergent aerovalve.And this study provides technical reserve for the APDE optimization design.

Response of spatial structure of cotton root to soil-wetting patterns under mulched drip irrigation

The matching relationship between the spatial structure of cotton cluster root systems and soil-wetting patterns under mulched drip irrigation forms the theoretical basis for the technical design of mulched drip irrigation.A 2-year field experiment was conducted,in which different soil-wetting patterns were produced by setting different emitter discharge rates.The envelopes of cotton cluster root length densities were derived using the topological methodology and used to examine the effects of different soil-wetting patterns on the spatial structure of root systems and water uptake capacity within row spaces.The results showed that the root systems in rows of cotton grown under narrower and deeper soil-wetting patterns exhibited a single-peak distribution,while those under wider and shallower soil-wetting patterns exhibited a two-peak distribution.Furthermore,cotton rows grown near mulch edges experienced lower moisture stress,and wider and shallower soil-wetting patterns contributed to greater root growth rates in the vertical direction and resulted in more even potential water uptake capacities.The findings of this study revealed that wider and shallower soil-wetting patterns were more desirable for mulched drip irrigation of cotton and should be considered in the technical design of drip irrigation systems.

Meta-analysis of the effect of statin use and pancreatic cancer risk

Statin has been proposed to have a capacity to reduce the risk of pancreatic cancer,while the obtained results are not consistent.To gain a clearer picture of the relationship between statin use and pancreatic cancer,the present meta-analysis took into consideration data from eight cohort studies,ten case-control studies and three RCTs.We searched all relevant studies on the effect of statin use on the risk of pancreatic cancer using PubMed,Embase and the Cochrane library database from inception to July 30,2018.The following search terms were used:(1)statin("statins","statin","3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibitors","atorvastatin","cerivastatin","fluvastatin","lovastatin","pravastatin","rosuvastatin","simvastatin");(2)pancreatic cancer("cancer","neoplasm","malignancy").We manually examined the references of the relevant articles and reviews to identify additional studies.A total of 21 studies,published between 2001 and July 2018 and involving 1148680 cases and 2177842 controls,fulfilled the selection criteria.The pooled results revealed a significant relationship between statin use and pancreatic cancer risk(OR=0.84,95%CI 0.72-0.98,P=0.000,I^2=84.30).However,lipophilic statins(OR=1.07,95%CI 0.97-1.18,P=0.651,I^2=0.0%)had no significant effect on the risk of pancreatic cancer.In contrast,short-term statin use(OR=0.72,95%CI 0.54-0.96,P=0.000,I^2=80.1%)and long-term statin use(OR=0.70,95%CI 0.54-0.92,P=0.000,12=79.8%)significantly reduced pancreatic cancer risk.Notably,the high heterogeneity among the selected studies was eliminated by excluding the three studies that focused on restricted populations.Statin could significantly reduce the risk of pancreatic cancer.