Parametric study of turbine NGV blade lean and vortex design

The effects of blade lean and vortex design on the aerodynamics of a turbine entry nozzle guide vane (NGV) are considered using computational fluid dynamics. The aim of the work is to address some of the uncertainties which have arisen from previous studies where conflicting results have been reported for the effect on the NGV. The configuration was initially based on the energy efficient engine turbine which also served as the validation case for the computational method. A total of 17 NGV configurations were evaluated to study the effects of lean and vortex design on row efficiency and secondary kinetic energy. The distribution of mass flow ratio is introduced as an additional factor in the assessment of blade lean effects. The results show that in the turbine entry NGV, the secondary flow strength is not a dominant factor that determines NGV losses and therefore the changes of loading distribution due to blade lean and the associated loss mechanisms should be regarded as a key factor. Radial mass flow redistribution under different NGV lean and twist is demonstrated as an addition key factor influencing row efficiency

A gauge-invariant and current-continuous microscopic ac quantum transport theory

There had been consensus on what the accurate ac quantum transport theory was until some recent works challenged the conventional wisdom. Basing on the non-equilibrium Green's function formalism for time-dependent quantum transport, we derive an expression for the dynamic admittance that satisfies gauge invariance and current continuity, and clarify the key concept in the field. The validity of our now formalism is verified by first-principles calculation of the transient current through a carbon-nanotube-based device under the time-dependent bias voltage. Moreover, the previously well-accepted expression for dynamic admittance is recovered only when the device is a perfect conductor at a specific potential

Electro-mechanical dynamics of spiral waves in a discrete 2D model of human atrial tissue

We investigate the effect of mechano-electrical feedback and atrial fibrillation induced electrical remodelling (AFER) of cellular ion channel properties on the dynamics of spiral waves in a discrete 2D model of human atrial tissue. The tissue electro-mechanics are modelled using the discrete element method (DEM). Millions of bonded DEM particles form a network of coupled atrial cells representing 2D cardiac tissue, allowing simulations of the dynamic behaviour of electrical excitation waves and mechanical contraction in the tissue. In the tissue model, each cell is modelled by nine particles, accounting for the features of individual cellular geometry; and discrete inter-cellular spatial arrangement of cells is also considered. The electro-mechanical model of a human atrial single-cell was constructed by strongly coupling the electrophysiological model of Colman et al. to the mechanicalmyofilament model of Rice et al., with parameters modified based on experimental data. A stretch-activated channel was incorporated into the model to simulate the mechano-electrical feedback. In order to investigate the effect of mechano-electrical feedback on the dynamics of spiral waves, simulations of spiral waves were conducted in both the electromechanical model and the electrical-only model in normal and AFER conditions, to allow direct comparison of the results between the models. Dynamics of spiral waves were characterized by tracing their tip trajectories, stability, excitation frequencies and meandering range of tip trajectories. It was shown that the developed DEM method provides a stable and efficient model of human atrial tissue with considerations of the intrinsically discrete and anisotropic properties of the atrial tissue, which are challenges to handle in traditional continuum mechanics models. This study provides mechanistic insights into the complex behaviours of spiral waves and the genesis of atrial fibrillation by showing an important role of the mechano-electrical feedback in facilitating and promoting atrial fibrillation

Soil Liquid Limit and Plastic Limit Treating System Based on Analytic Method

AbstractAccording to two present China national standards, a software as Soil Liquid Limit and Plastic Limit Data Treating System, with analytic method, was developed using object-oriented visual programming tool. The analytic method used in the developed system was different to traditional method of treating soil liquid limit and plastic limit data. N-S algorithm flowchart demonstrated that switch statement and condition statement were taken as main algorithm and second level select nested structure was taken as main frame for the developed system. Three kinds of soil specimens were tested with liquid and plastic limit combined test and the test data was treated with graphic method, Excel software and Soil Liquid Limit and Plastic Limit Data Treating System. The comparative conclusion indicated that Soil Liquid Limit and Plastic Limit Data Treating System improved efficiency and accuracy evidently for treating soil liquid and plastic limit data and had advantages of easy operation and high reliability

Comparison of State-owned and Private-owned Emerging Market Enterprises’ Internationalization: Case Studies of Chinese State-owned SAIC Motor’s and Private-owned Geely’s Cross-border Acquisitions.

This research examines the internationalisation activities of firms from emerging economies. By integrating traditional theories with institutional-based view and its three pillars, this study allow us to examine how the government influence international expansion of firms with different ownership structure (state-owned and private-owned) vertically (with government level) and horizontally (with regional specific marketization). The study also highlights different motives of internationalisation for state-owned and private-owned enterprises. Using case study as research method, this study has a close examination of state-owned firm SAIC Motor’s acquisition of SsangYong Motor Company and private-owned firm Geely Holding Group’s acquisition of Volvo Car Corporation. This study finds out that while the improvement of regional marketization facilitates private firm Geely’s performance of internationalisation, it has a negative influence on SAIC’s international activities. In addition, it is found in this study that based on high development of regional marketization, both state-owned and private-owned firms are now motivated by strategic assets seeking. Different from SAIC’s consistency, Geely experienced transforming of motives from efficiency seeking to strategic assets seeking as the marketization improving. Last but not least, the study points out that both SAIC’s and Geely’s internationalisation are strongly affected by their affiliation with different levels of government. However, even though both two firms are facilitated by central government, they faced contrasting treatments from lower level of government: SAIC was encouraged to internationalise while Geely was constrained

Development of a Vacuum Ultra-Violet Laser-Based Angle-Resolved Photoemission System with a Super-High Energy Resolution Better Than 1 meV

The design and performance of the first vacuum ultra-violet (VUV) laser-based angle-resolved photoemission (ARPES) system are described. The VUV laser with a photon energy of 6.994 eV and bandwidth of 0.26 meV is achieved from the second harmonic generation using a novel non-linear optical crystal KBe2BO3F2 (KBBF). The new VUV laser-based ARPES system exhibits superior performance, including super-high energy resolution better than 1 meV, high momentum resolution, super-high photon flux and much enhanced bulk sensitivity, which are demonstrated from measurements on a typical Bi2Sr2CaCu2O8 high temperature superconductor. Issues and further development related to the VUV laser-based photoemission technique are discussed.Comment: 29 pages, 10 figures, submitted to Review of Scientific Instrument