Three-dimensional flow in radial turbomachinery and its impact on design

In the two papers on the 'Theory of Blade Design for Large Deflections' published in 1984, a new inverse design technique was presented for designing the shape of turbomachinery blades in three-dimensional flow. The technique involves the determination of the blade profile from the specification of a distribution of the product of the radius and the pitched averaged tangential velocity (i.e., r bar-V(sub theta), the mean swirl schedule) within the bladed region. This is in contrast to the conventional inverse design technique for turbomachinery blading in two dimensional flow in which the blade surface pressure or velocity distribution is specified and the blade profile determined as a result; this is feasible in two-dimensional flow because the streamlines along the blade surfaces are known a priori. However, in three-dimensional flow, the stream surface is free to deform within the blade passage so that the streamlines on the blade surfaces are not known a priori; thus it is difficult and not so useful to prescribe the blade surface pressure or velocity distribution and determine the resulting blade profile. It therefore seems logical to prescribe the swirl schedule within the bladed region for designing a turbomachinery blade profile in three-dimensional flow. Furthermore, specifying r bar-V(sub theta) has the following advantages: (1) it is related to the circulation around the blade (i.e., it is an aerodynamic quantity); (2) the work done or extracted is approximately proportional to the overall change in r bar-V(sub theta) across a given blade row (Euler turbine equation); and (3) the rate of change of r bar-V(sub theta) along the mean streamline at the blade is related to the pressure jump across the blade and therefore the blade loading. Since the publications of those two papers, the technique has been applied to the design of a low speed as well as a high speed radial inflow turbine (for turbocharger applications) both of which showed definite improvements in performance over that of wheels of conventional designs, the design study of a high pressure ratio radial inflow turbine with and without splitter blades

Computational study of three dimensional viscous flow through a turbine cascade using a multi-domain spectral technique

The three dimensional viscous flow through a planar turbine cascade is numerically simulated by direct solution of the incompressible Navier-Stokes equations. Flow dependence in the spanwise direction is represented by direct expansion in Chebyshev polynomials, while the discretization on planes parallel to the endwalls is accomplished using the spectral element method. Elemental mapping from the physical to the computational space uses an algebraic mapping technique. A fractional time stepping method that consists of an explicit nonlinear convective step, an implicit pressure correction step, and an implicit viscous step is used to advance the Navier-Stokes equations forward in time. Results computed at moderate Reynolds numbers show a three dimensional endwall flow separation, a midspan separation of the blade suction surface boundary layer, and other three-dimensional features such as the presence of a saddle point flow in the endwall region. In addition, the computed skin friction lines are shown to be orthogonal to the surface vorticity lines, demonstrating the accuracy achievable in the present method

The origin, functions, and nature of the tributary system in the Chou times

In this dissertation, the author, Ch’un-sik Yi, used the English version of his name, Choon S. Lee

Measuring the efficiency of capital allocation in commercial banking

Commercial banks leverage their equity capital with demandable debt that participates in the economy's payments system. The distinctive nature of this debt generates an unusual degree of liquidity risk that can, at times, threaten the payments system. To reduce this threat, insurance protects deposits; and to reduce the moral hazard problems of the debt contract and deposit insurance, bank regulation constrains risk-taking and defines standards of capital adequacy. The inherent liquidity risk of demandable debt as well as potential regulatory penalties for poor financial performance creates the potential for costly episodes of financial distress that affects banks' employment of capital. ; The existence of financial-distress costs implies that many banks are likely to take actions, such as holding additional capital, that increase bank safety at the expense of short-run returns. While such a strategy may reduce average returns in the short run, it may maximize the market value of the bank by protecting charter value and protecting against regulatory interventions. On the other hand, some banks whose charter values are low may have an incentive to follow a higher risk strategy, one that increases average return at the expense of greater risk of financial distress and regulatory intervention. ; This paper examines how banks' employment of capital in their production plans affects their "market value" efficiency. The authors develop a market-based measure of production efficiency and implement it on a sample of publicly traded bank holding companies. Our evidence indicates that banks' efficiency and, hence, the market value of their assets are influenced by the level and allocation of capital. However, even controlling for the effect of size, we find that the influence of equity capital differs markedly between banks with higher capital-to-assets ratios and those with lower ratios. For inefficient banks with higher capital-to-assets ratios, marginal increases in capitalization and asset quality boost their market-value efficiency. For inefficient banks with lower levels of capitalization, the signs of these effects are reversed. Controlling for asset size, it appears that less capitalized banks cannot afford to mimic the investment strategy of more capitalized banks, which may be using this greater capitalization to signal their safety to financial markets.Bank capital

Inferring gene regulatory networks from gene expression data by a dynamic Bayesian network-based model

Enabled by recent advances in bioinformatics, the inference of gene regulatory networks (GRNs) from gene expression data has garnered much interest from researchers. This is due to the need of researchers to understand the dynamic behavior and uncover the vast information lay hidden within the networks. In this regard, dynamic Bayesian network (DBN) is extensively used to infer GRNs due to its ability to handle time-series microarray data and modeling feedback loops. However, the efficiency of DBN in inferring GRNs is often hampered by missing values in expression data, and excessive computation time due to the large search space whereby DBN treats all genes as potential regulators for a target gene. In this paper, we proposed a DBN-based model with missing values imputation to improve inference efficiency, and potential regulators detection which aims to lessen computation time by limiting potential regulators based on expression changes. The performance of the proposed model is assessed by using time-series expression data of yeast cell cycle. The experimental results showed reduced computation time and improved efficiency in detecting gene-gene relationships

Inferring gene regulatory networks from gene expression data by a dynamic Bayesian network-based model

Enabled by recent advances in bioinformatics, the inference of gene regulatory networks (GRNs) from gene expression data has garnered much interest from researchers. This is due to the need of researchers to understand the dynamic behavior and uncover the vast information lay hidden within the networks. In this regard, dynamic Bayesian network (DBN) is extensively used to infer GRNs due to its ability to handle time-series microarray data and modeling feedback loops. However, the efficiency of DBN in inferring GRNs is often hampered by missing values in expression data, and excessive computation time due to the large search space whereby DBN treats all genes as potential regulators for a target gene. In this paper, we proposed a DBN-based model with missing values imputation to improve inference efficiency, and potential regulators detection which aims to lessen computation time by limiting potential regulators based on expression changes. The performance of the proposed model is assessed by using time-series expression data of yeast cell cycle. The experimental results showed reduced computation time and improved efficiency in detecting gene-gene relationships

Effects of Steam and Alkali Treatment on Chemical Composition and in vitro Digestibility of Oil Palm Trunks

Oil palm trunks (OPT)were sawn into planks,reduced to flakes and processed for use in feeding trials to bulls. The optimum size of flakes was found to be 2cm with three different treatment for drying , streaming and alkali treatments.Chemical analysis and in vitro dry matter digestibility were determined on materials. Steam treatment decreased the neutral detergent fiber ( NDF) but did not cause considerable change in the acid detergent fiber ( ADF)content. The acid detergent lignin (ADL ) content was increased . The optimum dry matter digestibilities at steam pressures of 7. 5, 10.0, 12.5 were obtained at steaming times of 60 , 20. 10 and 5min respectively. Treatment with sodium hydroxide also decreased the NDF content.The ADF content was only lowered at concentrations of NaOH greater than 6%. The ADL content was increased due to removal of carbohydrates.Disruption of the lignin-polysaccharide bonds led to a rise in the in vitro dry matter digestibility .The optimum digestibility was obtained by treatment with 9% NaOH 14 days

Do Bankers Sacrifice Value to Build Empires? Managerial Incentives, Industry Consolidation and Financial Performance

Bank consolidation is a global phenomenon that may enhance stakeholders' value if managers do not sacrifice value to build empires. We find strong evidence of managerial entrenchment at U.S. bank holding companies that have higher levels of managerial ownership, better growth opportunities, poorer financial performance, and smaller asset size. At banks without entrenched management, both asset acquisitions and sales are associated with improved performance. At banks with entrenched management, sales are related to smaller improvements while acquisitions are associated with worse performance. Consistent with scale economies, an increase in assets by internal growth is associated with better performance at most banks. Key Words: consolidation, acquisitions, managerial incentives, efficiency, agency problems, corporate control, stochastic frontier