AEROTHERMODYNAMIC INVESTIGATION OF THE TURBINE BLADE FILM COOLING WITH LARGE EDDY SIMULATION METHOD

Gas turbines have been widely used in the aviation, marine, power plant, etc., which plays an indispensable role in modern industries. Nowadays, higher efficiency and larger output power is demanded, consequently, the turbine inlet temperature (TIT) has to be increased to up to 2260K in some turbofan engines. The turbine blades or vanes operate in a harsh environment and the operating temperature significantly surpasses the melting point of the turbine blade material. Therefore, the turbine cooling technology is of vital importance aiming to guarantee the lifespan of the turbine blades and the safe operation. Apart from the internal cooling methods, the external film cooling is a necessary and effective solution to protect the outer surface of the blades against the extreme high temperature mainstream from the combustion chamber. In this thesis, the thermal performance of the laidback fan-shaped film hole structure was numerically studied, which is known as 7-7-7 laidback fan-shaped film hole proposed by Thole [1]. Large eddy simulation (LES) method was implemented to investigate the thermal performance of the shaped film hole, and the LES result was compared with the RANS simulation with various turbulent models and verified by the experimental data from Thole. Besides, a comparative study was conducted between the conventional cylindrical film hole and the 7-7-7 shaped film hole. The results show the better cooling effectiveness with sufficient spread in spanwise direction as the blowing ratio increases, and proper orthogonal decomposition (POD) method was employed to present the coherent structure in flow field. Additionally, the effects of the blowing ratios M on the shaped film hole were simulated with LES in the range of M=0.5-3.0. Three different mainstream inlet turbulence intensities included between Tu=0.5% and Tu=20% were chosen to research the effects on the cooling effectiveness. Three mainstream inlet velocity profiles were applied for the LES calculation. The convex curved bottom surface was also investigated and compared with the flat bottom wall. The results show that M=1.5 can obtain a relative better performance for the same turbulence intensity of 0.5%. The cooling effectiveness deteriorates as the mainstream turbulence intensity increases from 0.5% to 20%. The mainstream inlet velocity profile causes less effects on the effectiveness relative to the blowing ratio and inlet turbulence intensity. The effectiveness of the convex curved bottom surface decays at higher blowing ratio condition. In addition, aerothermal performance of film cooled C3X vane was analyzed, and a comparison between the cylindrical and shaped film hole cases was presented. The effects of the two different film hole structures on the pressure and temperature distributions were studied. The present work evaluated the LES accuracy through a comparison with the experimental data and presented the reason of the different predictions between the LES and RANS. The numerical research on the film cooling can be considered as a baseline for further comparison and investigation of the film cooling in turbine blades or vanes

Evaluation system of urban smart tourism competitiveness based on AHP-entropy weight method

In order to quantitatively evaluate the competitiveness of smart tourism cities efficiently and reasonably, a smart tourism city competitiveness evaluation system composed of four primary indicators such as infrastructure, economic basis, scientific and technological basis and environmental basis and 15 secondary indicators such as the number of mobile phone users at the end of the year and the number of urban Internet users is constructed, which is comprehensively weighted by hierarchical analysis method and entropy weight method. The empirical case of competitiveness evaluation of 13 cities in Jiangsu Province shows that the evaluation system can quantitatively evaluate the competitiveness of urban smart tourism comprehensively and objectively. The main factors affecting the competitiveness of urban smart tourism are urban infrastructure construction and economic foundation. Increasing investment in 5G, artificial intelligence and other information technology and enhancing urban economic strength are the key strategies to improve the competitiveness of urban tourism

Numerical simulation of sub-100 nm strained Si/SiGe MOSFETs for RF and CMOS applications

Drift-Diffusion, Hydrodynamic and Monte Carlo simulations have been used in this work to simulate strained Si/SiGe devices for RF and CMOS applications. For numerical simulations of Si/SiGe devices, strain effects on the band structure of Si have been analyzed and analytical expressions are presented for parameters related to the bandgap and band alignment of Si/SiGe heterostructure. Optimization of n-type buried strained Si channel Si/SiGe MODFETs has been carried out in order to achieve high RF performance and high linearity. The impact of both lateral and vertical device geometries and different doping strategies has been investigated. The impact of the Ge content of the SiGe buffer on the performance of p-type surface channel strained Si/SiGe MOSFETs has been studied. Hydrodynamic device simulations have been used to assess the device performance of p-type strained Si/SiGe MOSFETs down to 35 nm gate lengths. Well-tempered strained Si MOSFETs with halo implants around the source/drain regions have been simulated and compared with those devices possessing only a single retrograde channel doping. The calibrations in respect of sub-100 nm Si and strained Si MOSFETs fabricated by IBM lead to a scaling study of those devices at 65 nm, 45 nm and 35 nm gate lengths. Using Drift-Diffusion simulations, ring oscillator circuit behaviour has been evaluated. Strained Si on insulator (SSOI) circuits have also been simulated and compared with strained Si circuits, Si circuits employing conventional surface channel MOSFETs along with SOI devices. Ensemble Monte Carlo simulations have been used to evaluate the device performance of n-type strained Si MOSFETs. A non-perturbative interface roughness scattering model has been used and validated by calibrating with respect to experimental mobility behaviour and device characteristics. The impact of interface roughness on the performance enhancement of strained Si MOSFETs has been investigated and evidence for reduced interface roughness scattering is presented, i.e., a smoother interface is suggested in strained Si MOSFETs. A 35 nm gate length Toshiba Si MOSFET has been simulated and the performance enhancement of 35 nm strained Si MOSFETs over the Toshiba Si device is predicted. Monte Carlo simulations are also employed to investigate the performance degradation due to soft-optical phonon scattering, which arises with the introduction of high-K gate dielectrics. Based on the device structures of the calibrated sub-100 nm n-type conventional and strained Si IBM MOSFETs, significant current degradation has been observed in devices with high-K gate dielectrics, HfO2 and Al2O3

A centrifugal pump fault diagnosis approach based on LCD-ApEn and PNN

According to the non-stationary and nonlinear characteristics of bearing vibration signals of the centrifugal pumps, a fault diagnosis method based on local characteristic-scale decomposition (LCD)-approximate entropy (ApEn) and probabilistic Neural Network (PNN) is proposed in this paper. First, the vibration signals are decomposed into a finite number of intrinsic scale components (ICSs), after which the ApEn of each ISC is obtained to form the feature vector. Then, the feature vectors are selected as the input vectors of the PNN for fault diagnosis. The classification results achieve a fault recognition rate of 100 % for various centrifugal pump fault patterns, which verifies the effectiveness and feasibility of the proposed method

Graphene-enhanced visible-light photocatalysis of large-sized CdS particles for wastewater treatment

The hybrid composites of graphene decorated by large-sized CdS particles (G/M-CdS) were prepared by a one-pot solvothermal route in which the reduction of graphite oxide into graphene was accompanied by the generation of microsized CdS particles. The structure and composition of the obtained nanocomposites were studied by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The CdS particles with the average sizes of approximately 640 nm were formed on graphene sheets. The as-prepared composite was used as adsorbent to remove dye from wastewater using the organic dye Rhodamine B as the adsorbate. The G/M-CdS composite reveals a high photodegradation rate under visible light irradiation. Our results demonstrate that the G/M-CdS is very promising for removing organic dyes from wastewater

Identification and Characterization of the PEBP Family Genes in Moso Bamboo (Phyllostachys heterocycla).

Moso bamboo is one of the economically most important plants in China. Moso bamboo is a monocarpic perennial that exhibits poor and slow germination. Thus, the flowering often causes destruction of moso bamboo forestry. However, how control of flowering and seed germination are regulated in moso bamboo is largely unclear. In this study, we identified 5 members (PhFT1-5) of the phosphatidyl ethanolamine-binding proteins (PEBP) family from moso bamboo genome that regulate flowering, flower architecture and germination, and characterized the function of these PEBP family genes further in Arabidopsis. Phylogenetic analysis revealed that 3 (PhFT1, PhFT2 and PhFT3), 1 (PhFT4) and 1 (PhFT5) members belong to the TFL1-like clade, FT-like clade, and MFT-like clade, respectively. These PEBP family genes possess all structure necessary for PEBP gene function. The ectopic overexpression of PhFT4 and PhFT5 promotes flowering time in Arabidopsis, and that of PhFT1, PhFT2 and PhFT3 suppresses it. In addition, the overexpression of PhFT5 promotes seed germination rate. Interestingly, the overexpression of PhFT1 suppressed seed germination rate in Arabidopsis. The expression of PhFT1 and PhFT5 is significantly higher in seed than in tissues including leaf and shoot apical meristem, implying their function in seed germination. Taken together, our results suggested that the PEBP family genes play important roles as regulators of flowering and seed germination in moso bamboo and thereby are necessary for the sustainability of moso bamboo forest

Lycorine reduces mortality of human enterovirus 71-infected mice by inhibiting virus replication

Human enterovirus 71 (EV71) infection causes hand, foot and mouth disease in children under 6 years old and this infection occasionally induces severe neurological complications. No vaccines or drugs are clinical available to control EV71 epidemics. In present study, we show that treatment with lycorine reduced the viral cytopathic effect (CPE) on rhabdomyosarcoma (RD) cells by inhibiting virus replication. Analysis of this inhibitory effect of lycorine on viral proteins synthesis suggests that lycorine blocks the elongation of the viral polyprotein during translation. Lycorine treatment of mice challenged with a lethal dose of EV71 resulted in reduction of mortality, clinical scores and pathological changes in the muscles of mice, which were achieved through inhibition of viral replication. When mice were infected with a moderate dose of EV71, lycorine treatment was able to protect them from paralysis. Lycorine may be a potential drug candidate for the clinical treatment of EV71-infected patients

Direct and negative regulation of the sycO-ypkA-ypoJ operon by cyclic AMP receptor protein (CRP) in Yersinia pestis

<p>Abstract</p> <p>Background</p> <p>Pathogenic yersiniae, including <it>Y. pestis</it>, share a type III secretion system (T3SS) that is composed of a secretion machinery, a set of translocation proteins, a control system, and six Yop effector proteins including YpkA and YopJ. The cyclic AMP receptor protein (CRP), a global regulator, was recently found to regulate the laterally acquired genes (<it>pla </it>and <it>pst</it>) in <it>Y. pestis</it>. The regulation of T3SS components by CRP is unknown.</p> <p>Results</p> <p>The <it>sycO</it>, <it>ypkA </it>and <it>yopJ </it>genes constitute a single operon in <it>Y. pestis</it>. CRP specifically binds to the promoter-proximate region of <it>sycO</it>, and represses the expression of the <it>sycO-ypkA-yopJ </it>operon. A single CRP-dependent promoter is employed for the <it>sycO-ypkA-yopJ </it>operon, but two CRP binding sites (site 1 and site 2) are detected within the promoter region. A CRP box homologue is found in site 1 other than site 2. The determination of CRP-binding sites, transcription start site and core promoter element (-10 and -35 regions) promotes us to depict the structural organization of CRP-dependent promoter, giving a map of CRP-promoter DNA interaction for <it>sycO-ypkA-yopJ</it>.</p> <p>Conclusion</p> <p>The <it>sycO-ypkA-yopJ </it>operon is under the direct and negative regulation of CRP in <it>Y. pestis</it>. The <it>sycO-ypkA-yopJ </it>promoter-proximate regions are extremely conserved in <it>Y. pestis</it>, <it>Y. pseudotuberculosis </it>and <it>Y. enterocolitica</it>. Therefore, data presented here can be generally applied to the above three pathogenic yersiniae.</p

A CRY-BIC negative-feedback circuitry regulating blue light sensitivity of Arabidopsis.

Cryptochromes are blue light receptors that regulate various light responses in plants. Arabidopsis cryptochrome 1 (CRY1) and cryptochrome 2 (CRY2) mediate blue light inhibition of hypocotyl elongation and long-day (LD) promotion of floral initiation. It has been reported recently that two negative regulators of Arabidopsis cryptochromes, Blue light Inhibitors of Cryptochromes 1 and 2 (BIC1 and BIC2), inhibit cryptochrome function by blocking blue light-dependent cryptochrome dimerization. However, it remained unclear how cryptochromes regulate the BIC gene activity. Here we show that cryptochromes mediate light activation of transcription of the BIC genes, by suppressing the activity of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), resulting in activation of the transcription activator ELONGATED HYPOCOTYL 5 (HY5) that is associated with chromatins of the BIC promoters. These results demonstrate a CRY-BIC negative-feedback circuitry that regulates the activity of each other. Surprisingly, phytochromes also mediate light activation of BIC transcription, suggesting a novel photoreceptor co-action mechanism to sustain blue light sensitivity of plants under the broad spectra of solar radiation in nature

SUPPLEMENTARY INFORMATION Dislocation nucleation facilitated by atomic segregation DOI: 10.1038/NMAT5034

This is a set of supplementary data and information supporting the Journal Publication 'Dislocation nucleation facilitated by atomic segregation', DOI: 10.1038/NMAT5034, and available at Journal article in Nature Materials