Search

The performance analysis of mixed-exhaust turbofan engine with multi-annular rotating detonation duct burner (RDDB) is conducted for the first time, considering that the flow path of the bypass duct is ideal for a rotating detonation combustor (RDC). The configuration of the multi-annular rotating detonation combustor is constructed aiming at the advantages of a wider operation range and uniform outlet parameters over the single-annular one. Then, a parametric analysis model of the mixed-exhaust turbofan engine with a rotating detonation duct burner is developed. Thereafter, the effects of duct burner parameters on the engine performance and operating characteristics are investigated. The mixed-exhaust turbofan engine with a rotating detonation duct burner shows superior overall performance to that of one with an isobaric afterburner (ICAB) over a wide operation range. The separate-exhaust rotating detonation duct burner can hold characteristics that are higher than those of the mixed-exhaust one at lower values of fan pressure ratio, while the mixed-exhaust one corresponds to lower values of turbine inlet temperature. When the rotating detonation duct burner is "on," the low-pressure rotor operating line moves toward the surge line on the low corrected shaft speed side but away from the surge line on the high corrected shaft speed side. [ABSTRACT FROM AUTHOR]

Abstract Nitrous oxide fuel blend propellants have great potential to be used in rocket engine, and investigations on the fundamental combustion characteristics of such propellants are therefore necessary to control flashback and develop their chemical kinetics mechanism. Laminar burning velocities (LBVs) of C 2 H 4 /N 2 O flames are measured by using spherical expansion flames in this paper at 0.5–2.0 atm and 280 K. The present method for upper and lower limits of effective flame radius is reasonable for the experimental stretched flame speeds can be fitted very well with the flame stretch rates. The LBVs of C 2 H 4 /N 2 O flames are smaller than those of C 2 H 4 /N 2 /O 2 flames (same N/O ratio as N 2 O) at conditions near stoichiometric ratio, while they are larger than those at other conditions especially at fuel-rich side. The LBVs of C 2 H 4 /N 2 O flames are not sensitive to the pressure in the measured range. Two kinds of sub-mechanisms are applied for detailed chemical kinetics mechanisms of C 2 H 4 /N 2 O reactions, which are USC Mech II-2 for hydrocarbon reactions as well as GRI 3.0 mechanism and San Diego mechanism for nitrogen oxide reactions respectively. Eight key elementary reactions are chosen based on the sensitivity analysis, and the effects of their available rate constants from literatures on the LBVs are tested. Modified mechanisms for C 2 H 4 /N 2 O reactions are therefore proposed by replacing the rate constants of these key elementary reactions, which predicts well for LBVs of hydrocarbon/N 2 O flames. Sensitivity analyses are performed for C 2 H 4 /N 2 O flames at different equivalence ratios, it is found that the N 2 O decomposition is a dominant reaction in conditions near stoichiometric ratio, while it is the codominant and nondominant reaction in fuel-lean and fuel-rich conditions respectively. Furthermore, the reaction pathways of oxidizers consumption in C 2 H 4 /N 2 O flames and C 2 H 4 /N 2 /O 2 flames are analyzed, and the observations on the LBVs of these two flames in the experiment can be well explained through the reaction pathways and their relative changes under fuel-lean, stoichiometric and fuel-rich conditions. [ABSTRACT FROM AUTHOR]

Combustion instabilities of diluted hydrogen and air driven by the large scale vortex in supersonic reacting mixing layer flows have been numerically studied using detailed chemical reaction kinetics and accurate transport properties. The overall unburned, unstable and stable combustion modes are then observed under different air temperature conditions, corresponding to 925, 1100, and 1600 K. Very large pressure oscillations are observed for the reacting flow with the medium-temperature air, the amplitudes of which are several times larger than those of the unreactive flow or stable combustion case. The analyses show that the auto-ignition of fuel and oxidizer premixed mixtures are formed inside the turbulent shedding vortexes and causes the extremely high local pressures; hence, large amplitude pressure oscillations occur. The mixing layer is ignited very close to the inlet and in advance of the vortex shedding of the flow with the high-temperature air, and the diffusion combustion moves downstream. It is concluded that the auto-ignition of the fuel and oxidizer premixed mixtures induced by the turbulent coherent structures could lead to combustion instability and drive the transition from the partially premixed quasi-constant-volume combustion to the diffusion combustion depending on the increasing air stream temperature. [ABSTRACT FROM AUTHOR]

Apolipoprotein E (ApoE) gene polymorphism has been implicated in predisposition to diabetes and dementia in old population, but the results from the different studies were inconclusive. A cross-sectional study was carried out to explore the relationship among ApoE gene polymorphism, diabetes and cognition in non-demented aging Chinese adults. A total number of 1000 community dwellers aged 55 years and above were randomly recruited. Demographic information of the participants was collected using well designed selfadministered questionnaires. The Montreal Cognitive Assessment (MoCA) test was employed to evaluate the cognitive status of the participants. Semi-quantitative food frequency questionnaire was used to obtain the dietary intake information. Fasting venous blood samples were taken for ApoE genotyping and serum lipid measurements. 238 participants were type 2 diabetes mellitus (T2DM) patients and 145 participants were ApoE4 carriers. ApoE 4-T2DM subjects had higher serum triglyceride (TG) concentration than E2 and E3 carriers (P < 0.05). T2DM subjects carrying ApoE4 had lower cognition than subjects with E2 or E3 carriers (P < 0.05). Comparing to non-type 2 diabetic mild cognitive impaired (nT2DM-MCI) subjects, the type 2 diabetic mild cognitive impaired (T2DM-MCI) subjects have higher serum glucose (Glu) level and lower high-density lipoprotein (HDL-C) level (P < 0.05). The T2DM-MCI subjects carrying ApoE4 have lower cognition than E2 and E3 carriers (P <0.05); and the interaction of ApoE genotype with T2DM was detected (P < 0.05). Our results indicated the association among ApoE gene polymorphism, T2DM and cognitive performance in non-demented aging population. The carrying of ApoE4 predisposed the T2DM subjects and the T2DM-MCI subjects to have poor cognitive performance. Additional experimental studies are required to explore the mechanism that ApoE genotype modifies the risk for cognitive impairment in aging subjects with T2DM. [ABSTRACT FROM AUTHOR]

[Objective] This study aimed to develop a PCR assay for detecting Xanthomonas campestris pv. mangiferaeindicae (Xcm) in culture and in planta. [Method] Primers (XcmHF and XcmHR) were designed based on the partial sequence of hrpB gene from xanthomonads to develop a PCR assay for Xcm. Furthermore, specificity and sensitivity of the primer pairs were analyzed in detection of genomic DNA and cell from Xcm. [Result] Amplication was positive only with genomic DNA from positive control ATCC11637 and 12 Xcm strains; no PCR products were amplified with genomic DNA from ten other xanthomonads and seven other bacterial species. The sensitivity of detection was 2.4 pg/μl genomic DNA, and 1.8 × 104 CFU/ml cells. The primers also worked well for pathogen detection in direct PCR assays of Xcm colonies grown on liquid medium and in PCR assays of total DNA from leaf, branch and fruit lesions. [Conclusion] A PCR assay was successfully established for rapid detection of Xcm in culture and in planta. [ABSTRACT FROM AUTHOR]

Background: Multi-drug resistance (MDR) has been a cause of concern for tuberculosis (TB) control in both developed and developing countries. This study described the characteristics and risk factors associated with MDR-TB among 287 cases and 291 controls in Henan province, China.Methods: A hospital-based case-control study was conducted between June 2012 and December 2013. The study subjects were selected using multistage probability sampling. Multivariate conditional logistic regression models were used to determine the risk factors associated with MDR-TB.Results: The following risk factors for MDR-TB were identified: previous TB treatment (AOR = 4.51, 95% CI: 3.55-5.56), male sex (AOR = 1.09, 95% CI: 0.24-1.88), high school or lower education degree (AOR = 1.87, 95% CI: 1.27-2.69), unemployment (AOR = 1.30, 95% CI: 0.78-2.52), long distance of residence from the health facility (AOR = 6.66,95% CI: 5.92-7.72), smoking (AOR = 2.07, 95% CI: 1.66-3.19), poor knowledge regarding MDR-TB (AOR = 2.06, 95% CI: 1.66-2.92), traveling by foot to reach the health facility (AOR = 1.85, 95% CI: 1.12-3.09), estimated amount of time to reach the health facility was greater than 3 h (AOR = 1.42, 95% CI: 0.51-2.35), social stigma (AOR = 1.17, 95% CI: 0.27-2.03), having an opportunistic infection (AOR = 1.45, 95% CI: 0.58-2.4), more than 3 TB foci in the lungs (AOR = 1.98, 95% CI: 1.49-3.25), total time of first treatment was more than 8 months (AOR = 1.39, 95% CI: 0.65-2.54), adverse effects of anti-TB medication (AOR = 2.39, 95% CI: 1.40-3.26), and more than 3 prior episodes of anti-TB treatment (AOR = 1.83, 95% CI: 1.26-2.80).Conclusion: The identified risk factors should be given priority in TB control programs. Additionally, there is a compelling need for better management and control of MDR-TB, particularly through increasing laboratory capacity, regular screening, enhancing drug sensitivity testing, novel MDR-TB drug regimens, and adherence to medication. [ABSTRACT FROM AUTHOR]