Development of blade profiles for low pressure turbine applications

This paper describes a program of work, largely experimental, which was undertaken with the objective of developing an improved blade profile for the low-pressure turbine in aero-engine applications. Preliminary experiments were conducted using a novel technique. An existing cascade of datum blades was modified to enable the pressure distribution on the suction surface of one of the blades to be altered. Various means, such as shaped inserts, an adjustable flap at the trailing edge, and changing stagger were employed to change the geometry of the passage. These experiments provided boundary layer and lift data for a wide range of suction surface pressure distributions. The data was then used as a guide for the development of new blade profiles. The new blade profiles were then investigated in a low-speed cascade that included a set of moving bars upstream of the cascade of blades to simulate the effect of the incoming wakes from the previous blade row in a multistage turbine environment.

The low Reynolds number aerodynamics of leading edge flaps

Within the low Reynolds number regime at which birds and small air vehicles operate (Re=15,000-500,000), flow is beset with laminar separation bubbles and bubble burst which can lead to loss of lift and early onset of stall. Recent video footage of an eagle's wings in flight reveals an inconspicuous wing feature: the sudden deployment of a row of feathers from the lower surface of the wing to create a leading edge flap. An understanding of the aerodynamic function of this flap has been developed through a series of low speed wind tunnel tests performed on an Eppler E423 aerofoil. Experiments took place at Reynolds numbers ranging from 40000 to 140000 and angles of attack up to 30°. In the lower range of tested Reynolds numbers, application of the flap was found to substantially enhance aerofoil performance by augmenting the lift and limiting the drag at certain incidences. The leading edge flap was determined to act as a transition device at low Reynolds numbers, preventing the formation of separation bubbles and consequently decreasing the speed at which stall occurs during landing and manoeuvring.

Heliconema savala n.sp. (Nematoda:Physalopteridae) from marine fish Lepturacanthus savala (Cuvier) (Trichiuridae) and Psettodes erumei (Schneider) new host (Pisces:Pettodidae) of Physalopterid Nematode, Bulbocephalus inglisi Rasheed, 1966 in Pakistan

Helicnonema savala, n.sp. obtained from the marine fish, Lepturacanthus savala in Sindh coast is distinguished from members of the genus processing in the male 10 tessellated longtitudinal ridges and a spicule ratio 1:15. Females have vulvular flap. Heliconema savala is a morphologically most closely related to Heliconema heliconema. The marine fish, Psettodes erumei is recorded as a new host of Bulbocephalus inglisi.

Genetic diversity of cattle in South China as revealed by blood protein electrophoresis

Genetic variation of 31 blood protein loci in 236 cattle from eight South China populations (including mithan, Bos frontalis) and a Holstein population was investigated by means of horizontal starch gel electrophoresis. Thirteen loci (ALB, CAR, Hb-b, Np, PGM, Amy-I, PEP-B, AKP, 6PGD, Cp, Pa, EsD, and TF) were found to be polymorphic. The comparison of average heterozygosities (H) shows that all the native cattle embrace a rich genetic diversity Our results on protein polymorphism suggest that cattle in China originated mainly from Bos indicus and Bos taurus; Xuwen, Hainan, Wenshan, and Dehong cattle and the Dehong zebu are close to zebu-type cattle, and Diqing and Zhaotong cattle are close to the taurine. The mithan was very different from other native cattle, and we suggest that its origin was complicated and may be influenced by other cattle species.

半野生大额牛的研究进展和保护利用现状

下载PDF阅读器大额牛(Bos frontalis)在我国又叫独龙牛,是一种半野生的珍稀牛种.本文较系统地介绍大额牛的起源、繁殖特点、生产性能与杂交利用、疾病调查、迁地保护、饲养管理等研究进展,提出我国独龙牛保护、利用中存在的问题及相应对策和建议.

The influence of geometry on jet plume development

Our recent efforts of using large-eddy simulation (LES) type methods to study complex and realistic geometry single stream and co-flow nozzle jets and acoustics are summarized in this paper. For the LES, since the solver being used tends towards having dissipative qualities, the subgrid scale (SGS) model is omitted, giving a numerical type LES (NLES). To overcome near wall streak resolution problems a near wall RANS (Reynolds averaged Navier-Stokes) model is smoothly blended in the LES making a hybrid RANS-NLES approach. Several complex nozzle geometries including the serrated (chevron) nozzle, realistic co-axial nozzles with eccentricity, pylon and wing-flap are discussed. The hybrid RANS-NLES simulations show encouraging predictions for the chevron jets. The chevrons are known to increase the high frequency noise at high polar angles, but decrease the low frequency noise at lower angles. The deflection effect of the potential core has an important mechanism of noise reduction. As for co-axial nozzles, the eccentricity, the pylon and the deployed wing-flap are shown to influence the flow development, especially the former to the length of potential core and the latter two having a significant impact on peak turbulence levels and spreading rates. The studies suggest that complex and real geometry effects are influential and should be taken into count when moving towards real engine simulations. © 2012 Elsevier Ltd. All rights reserved.

On the effects of turbulence modelling in design optimisation for high-lift devices

Aerodynamic shape optimisation is being increasingly utilised as a design tool in the aerospace industry. In order to provide accurate results, design optimisation methods rely on the accuracy of the underlying CFD methods applied to obtain aerodynamic forces for a given configuration. Previous studies of the authors have highlighted that the variation of the order of accuracy of the CFD solver with a fixed turbulence model affects the resulting optimised airfoil shape for a single element airfoil. The accuracy of the underlying CFD model is even more relevant in the context of high-lift configurations where an accurate prediction of flow is challenging due to the complex flow physics involving transition and flow separation phenomena. This paper explores the effect of the fidelity of CFD results for a range of turbulence models within the context of the computational design of aircraft configurations. The NLR7301 multi-element airfoil (main wing and flap) is selected as the baseline configuration, because of the wealth of experimental an computational results available for this configuration. An initial validation study is conducted in order to establish optimal mesh parameters. A bi-objective shape optimisation problem is then formulated, by trying to reveal the trade-off between lift and drag coefficients at high angles of attack. Optimisation of the airfoil shape is performed with Spalart-Allmaras, k - ω SST and k - o realisable models. The results indicate that there is consistent and complementary impact to the optimum level achieved from all the three different turbulence models considered in the presented case study. Without identifying particular superiority of any of the turbu- lence models, we can say though that each of them expressed favourable influence towards different optimality routes. These observations lead to the exploration of new avenues for future research. © 2012 AIAA.

On the effects of turbulence modelling in design optimisation for high-lift devices

Aerodynamic shape optimisation is being increasingly utilised as a design tool in the aerospace industry. In order to provide accurate results, design optimisation methods rely on the accuracy of the underlying CFD methods applied to obtain aerodynamic forces for a given configuration. Previous studies of the authors have highlighted that the variation of the order of accuracy of the CFD solver with a fixed turbulence model affects the resulting optimised airfoil shape for a single element airfoil. The accuracy of the underlying CFD model is even more relevant in the context of high-lift configurations where an accurate prediction of flow is challenging due to the complex flow physics involving transition and flow separation phenomena. This paper explores the effect of the fidelity of CFD results for a range of turbulence models within the context of the computational design of aircraft configurations. The NLR7301 multi-element airfoil (main wing and flap) is selected as the baseline configuration, because of the wealth of experimental an computational results available for this configuration. An initial validation study is conducted in order to establish optimal mesh parameters. A bi-objective shape optimisation problem is then formulated, by trying to reveal the trade-off between lift and drag coefficients at high angles of attack. Optimisation of the airfoil shape is performed with Spalart-Allmaras, k - ω SST and k - ε realisable models. The results indicate that there is consistent and complementary impact to the optimum level achieved from all the three different turbulence models considered in the presented case study. Without identifying particular superiority of any of the turbu- lence models, we can say though that each of them expressed favourable influence towards different optimality routes. These observations lead to the exploration of new avenues for future research. © 2012 by the authors.

Differential equation based length scales to improve DES and RANS simulations

Surprisingly expensive to compute wall distances are still used in a range of key turbulence and peripheral physics models. Potentially economical, accuracy improving differential equation based distance algorithms are considered. These involve elliptic Poisson and hyperbolic natured Eikonal equation approaches. Numerical issues relating to non-orthogonal curvilinear grid solution of the latter are addressed. Eikonal extension to a Hamilton-Jacobi (HJ) equation is discussed. Use of this extension to improve turbulence model accuracy and, along with the Eikonal, enhance Detached Eddy Simulation (DES) techniques is considered. Application of the distance approaches is studied for various geometries. These include a plane channel flow with a wire at the centre, a wing-flap system, a jet with co-flow and a supersonic double-delta configuration. Although less accurate than the Eikonal, Poisson method based flow solutions are extremely close to those using a search procedure. For a moving grid case the Poisson method is found especially efficient. Results show the Eikonal equation can be solved on highly stretched, non-orthogonal, curvilinear grids. A key accuracy aspect is that metrics must be upwinded in the propagating front direction. The HJ equation is found to have qualitative turbulence model improving properties. © 2003 by P. G. Tucker.

沙蜥属部分物种分类性状评价

沙蜥属Phrynocephalus Kaup，1825隶属于爬行纲（Reptilia）有鳞目（Squamata）蜥蜴亚目（Lacertilia）鬣蜥科（Agamidae），是欧亚大陆荒漠和稀疏草原常见蜥蜴。沙蜥属的分类及系统演化关系、地理分布格局与新生代第三纪以来古地中海的变迁、青藏高原的抬升及亚洲内陆干旱荒漠化的过程有密切的关系，长期以来有关沙蜥属的研究一直受到中外学者们的关注。由于沙蜥属地理分布广、形态变异大、体色和斑纹变化复杂，虽然前人使用过许多形态性状来描述和分类沙蜥属物种，但是仍然存在许多问题。性状的分类学意义不明确是造成这些问题的主要原因之一，因此本研究针对沙蜥属常用的鉴别性状进行分类意义的分析，希望能对沙蜥属物种鉴定及分类学其它研究有所裨益。 中国沙蜥属物种主要分布于西北的干旱荒漠区域及青藏高原的大部分地区，大约为18种。 本文研究了中国境内12种沙蜥：青海沙蜥（Phrynocephalus vlangalii）、西藏沙蜥（P. theobaldi）、南疆沙蜥（P. forsythii）、变色沙蜥（P. versicolor）、旱地沙蜥（P. helioscopus）、荒漠沙蜥（P. przewalskii）、乌拉尔沙蜥（P. guttatus）、草原沙蜥（P. frontalis）、叶城沙蜥（P. axillaris）、白稍沙蜥（P. koslowi）、无斑沙蜥（P. immaculatus）和白条沙蜥（P. albolineatus），对它们的65项外部形态性状进行了观察和测量，其中数量性状29项、质量性状36项。评价了这些性状的序级性、间断性和代表性，结论如下： 1. 对于数量性状，得出了适合各级分类的数值区间； 2. 给出了在不同序级上适合分类的质量性状。 并利用各性状评价的结果，给出12种沙蜥的检索表，以及对中国沙蜥物种某些尚存在争议的问题进行了探讨。 详细记录了青海沙蜥红原亚种的骨骼系统，首次发现并命名了肘骨（elbow bone）和垫骨（stepping bone），为沙蜥属系统学研究补充了骨骼方面的证据；解剖了乌拉尔沙蜥、旱地沙蜥、荒漠沙蜥的雌体和雄体的骨骼系统，并在14项骨骼形态性状上对这3种沙蜥进行了比较。 Phrynocephalus （Squamata，Agamidae） is a familiar genus of lizards inhabited desert and sparse steppes in Eurasia. The taxonomics, phylogenetics and distribution pattern of Phrynocephalus are relative intensely to these events: the vicissitudes of the archaic Mediterranean sea since the Cainozoic, the uplift of Qingzang Plateau and the expending arid areas in the inland of Asia. Owing to the wide distribution, the large variability of the morphology and the different colors in Phrynocephalus, it is difficult to identify them. Tough many morphological characters are used to describe and discriminate them，a lot of questions still exist. One of the most important reasons is the confusion in the morphological characters. In this study, we demonstrate the validity and the invalidity of the familiar characters. There are about 18 species of the genus Phrynocephalus in China, which exist in arid desert in Northwest China and Qingzang Plateau. Twelve Chinese species was analyzed in this paper. They are P. vlangalii，P. theobaldi，P. forsythia，P. versicolor，P. helioscopus，P. przewalskii，P. guttatus，P. frontalis，P. axillaris，P. koslowi，P. immaculatus，P. albolineatus. We measure 29 quantitative characters and observe 36 qualitative characters in each individual. Through analyzing these characters, we made some conclusions as follows: 1. to every quantitative character, we get a clear numeric area to discriminate the different operational taxonomic units. 2. we chose the valid qualitative characters in these operational taxonomic units. This paper is the first to describe the “elbow bone”, which is a bone in pectoral appendage equivalent to patella，and “stepping bone”, which is a bone under carpal. A detailed description of the skeletal system of female Phrynocephalus vlangalii hongyuanensis was conducted. We also anatomise the skeletal systems of three species: P. guttatus，P. przewalskii，P. helioscopus, and compare or contrast 14 skeletal characters in them. What’s more，this paper offers some suggestions to the questions of Chinese Phrynocephalus species and keys to 12 species of Phrynocephalus basing on our conclusions on the evaluation of the morphological characters.

Incisões e Suturas em Implantologia

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina Dentária

Síndrome Dolorosa Miofascial no contexto da Medicina Dentária

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina Dentária

An Online Distributed Algorithm for Inferring Policy Routing Configurations

We present an online distributed algorithm, the Causation Logging Algorithm (CLA), in which Autonomous Systems (ASes) in the Internet individually report route oscillations/flaps they experience to a central Internet Routing Registry (IRR). The IRR aggregates these reports and may observe what we call causation chains where each node on the chain caused a route flap at the next node along the chain. A chain may also have a causation cycle. The type of an observed causation chain/cycle allows the IRR to infer the underlying policy routing configuration (i.e., the system of economic relationships and constraints on route/path preferences). Our algorithm is based on a formal policy routing model that captures the propagation dynamics of route flaps under arbitrary changes in topology or path preferences. We derive invariant properties of causation chains/cycles for ASes which conform to economic relationships based on the popular Gao-Rexford model. The Gao-Rexford model is known to be safe in the sense that the system always converges to a stable set of paths under static conditions. Our CLA algorithm recovers the type/property of an observed causation chain of an underlying system and determines whether it conforms to the safe economic Gao-Rexford model. Causes for nonconformity can be diagnosed by comparing the properties of the causation chains with those predicted from different variants of the Gao-Rexford model.

Foundational Theory for Understanding Policy Routing Dynamics

In this paper we introduce a theory of policy routing dynamics based on fundamental axioms of routing update mechanisms. We develop a dynamic policy routing model (DPR) that extends the static formalism of the stable paths problem (introduced by Griffin et al.) with discrete synchronous time. DPR captures the propagation of path changes in any dynamic network irrespective of its time-varying topology. We introduce several novel structures such as causation chains, dispute fences and policy digraphs that model different aspects of routing dynamics and provide insight into how these dynamics manifest in a network. We exercise the practicality of the theoretical foundation provided by DPR with two fundamental problems: routing dynamics minimization and policy conflict detection. The dynamics minimization problem utilizes policy digraphs, that capture the dependencies in routing policies irrespective of underlying topology dynamics, to solve a graph optimization problem. This optimization problem explicitly minimizes the number of routing update messages in a dynamic network by optimally changing the path preferences of a minimal subset of nodes. The conflict detection problem, on the other hand, utilizes a theoretical result of DPR where the root cause of a causation cycle (i.e., cycle of routing update messages) can be precisely inferred as either a transient route flap or a dispute wheel (i.e., policy conflict). Using this result we develop SafetyPulse, a token-based distributed algorithm to detect policy conflicts in a dynamic network. SafetyPulse is privacy preserving, computationally efficient, and provably correct.

Principles of Safe Policy Routing Dynamics

We introduce the Dynamic Policy Routing (DPR) model that captures the propagation of route updates under arbitrary changes in topology or path preferences. DPR introduces the notion of causation chains where the route flap at one node causes a flap at the next node along the chain. Using DPR, we model the Gao-Rexford (economic) guidelines that guarantee the safety (i.e., convergence) of policy routing. We establish three principles of safe policy routing dynamics. The non-interference principle provides insight into which ASes can directly induce route changes in one another. The single cycle principle and the multi-tiered cycle principle provide insight into how cycles of routing updates can manifest in any network. We develop INTERFERENCEBEAT, a distributed algorithm that propagates a small token along causation chains to check adherence to these principles. To enhance the diagnosis power of INTERFERENCEBEAT, we model four violations of the Gao-Rexford guidelines (e.g., transiting between peers) and characterize the resulting dynamics.