水冷塔空气涡流导引装置的数值模拟

使用FLUENT软件, 对水冷火电厂的水冷塔换热进行了数值模拟, 解决了物模实验难以模拟热力因素的困难. 同时还对采用"空气涡流导引装置技术"的水冷塔和传统水冷塔, 在不同环境风影响下的换热效率进行了对比. 结果表明, 采用"空气涡流导引装置技术"的水冷塔换热效果优于传统水冷塔, 抵抗大风的能力更强

脉冲管制冷机的整机二维数值模拟

利用FLUENT软件对脉冲管制冷机进行了二维轴对称数值模拟.和文献中实验的对比结果表明,模拟计算使用的数理模型是合理的,能够准确预报脉冲管制冷机的最低制冷温度.进而,对中科院自主开发的脉冲管制冷系统进行了数值研究,探讨了频率,充气压力以及振幅对脉冲管制冷机性能的影响.结果显示,对于一定尺寸的脉冲管制冷机有一个最佳运行频率,大振幅和相对较小的充气压力可以取得较好的制冷效果

两栖机器人足板驱动装置研究

两栖机器人是一种既可以在陆地、滩涂上行走，又可以在水中浮游的特种机器人，具有陆上步行机器人的行走能力和水下机器人的水中航行能力。足板驱动两栖机器人的研究是在轮桨腿一体化两栖机器人的研究背景下展开的，论文针对 足板驱动两栖机器人运动和作业环境的特点从水下和陆地两个部分展开研究。机器人在水下运动的时候，由摆动足板提供前进、后退的推进力并控制机器人的运动方向。定量计算产生在摆动足板上的推进力和推进力矩是研究的难点。 首先建立了刚性足板的数学模型，利用基于求解雷诺平均的纳维——斯托克斯方程的 Fluent 软件，进行了无界流场中二维足板定常绕流的流体动力特性计算。接着采用动网格技术以及强大的后处理系统，详细计算了摆动足板在粘性流场中的非定常水动力性能；探讨了摆动的幅度、频率等对足板非定常水动力性能的影响。最后建立了足板驱动两栖机器人在水中的空间运动方程。机器人在陆地爬行的时候，在分析陆地爬行机理和特性的基础上，理论推导出足板陆地运动状态下的数学模型，为了更加接近真实情况，应用动态接触碰撞模型，考虑了足板与地面的冲击、摩擦、滑动和变形，建立了足板驱动两栖机器人运动的全局动力学仿真模型。对运动的全过程进行仿真，仿真研究包括支撑相与摆动相转换时的动态性能，以期对其进行合理的运动规划和控制，实现不同步态间的平滑转换，进行高精度的姿态调整，达到在复杂自然表面平稳行走的应用要求。同时获得足板实现预定运动要求的驱动力矩以便于进行驱动器性能指标的确定，并指导器件选型和结构强度设计。最终研究设计出既能实现陆地爬行，又能实现水下浮游的足板驱动装置，实现机器人的不同模式运动。

A Study of Qualitative and Geometric Knowledge in Reasoning about Motion

Reasoning about motion is an important part of our commonsense knowledge, involving fluent spatial reasoning. This work studies the qualitative and geometric knowledge required to reason in a world that consists of balls moving through space constrained by collisions with surfaces, including dissipative forces and multiple moving objects. An analog geometry representation serves the program as a diagram, allowing many spatial questions to be answered by numeric calculation. It also provides the foundation for the construction and use of place vocabulary, the symbolic descriptions of space required to do qualitative reasoning about motion in the domain. The actual motion of a ball is described as a network consisting of descriptions of qualitatively distinct types of motion. Implementing the elements of these networks in a constraint language allows the same elements to be used for both analysis and simulation of motion. A qualitative description of the actual motion is also used to check the consistency of assumptions about motion. A process of qualitative simulation is used to describe the kinds of motion possible from some state. The ambiguity inherent in such a description can be reduced by assumptions about physical properties of the ball or assumptions about its motion. Each assumption directly rules out some kinds of motion, but other knowledge is required to determine the indirect consequences of making these assumptions. Some of this knowledge is domain dependent and relies heavily on spatial descriptions.

Isoperimetric Partitioning: A New Algorithm for Graph Partitioning

Temporal structure is skilled, fluent action exists at several nested levels. At the largest scale considered here, short sequences of actions that are planned collectively in prefronatal cortex appear to be queued for performance by a cyclic competitive process that operates in concert with a parallel analog representation that implicitly specifies the relative priority of elements of the sequence. At an intermediate scale, single acts, like reaching to grasp, depend on coordinated scaling of the rates at which many muscles shorten or lengthen in parallel. To ensure success of acts such as catching an approaching ball, such parallel rate scaling, which appears to be one function of the basal ganglia, must be coupled to perceptual variables such as time-to-contact. At a finer scale, within each act, desired rate scaling can be realized only if precisely timed muscle activations first accelerate and then decelerate the limbs, to ensure that muscle length changes do not under- or over- shoot the amounts needed for precise acts. Each context of action may require a different timed muscle activation pattern than similar contexts. Because context differences that require different treatment cannot be known in advance, a formidable adaptive engine-the cerebellum-is needed to amplify differences within, and continuosly search, a vast parallel signal flow, in order to discover contextual "leading indicators" of when to generate distinctive patterns of analog signals. From some parts of the cerebellum, such signals control muscles. But a recent model shows how the lateral cerebellum may serve the competitive queuing system (frontal cortex) as a repository of quickly accessed long-term sequence memories. Thus different parts of the cerebellum may use the same adaptive engine design to serve the lowest and highest of the three levels of temporal structure treated. If so, no one-to-one mapping exists between leveels of temporal structure and major parts of the brain. Finally, recent data cast doubt on network-delay models of cerebellar adaptive timing.

ION, OPERA IN SEVEN SCENES, BASED ON EURIPIDES ORIGINAL PLAY

The opera ION serves as my Doctoral Dissertation at the University of Maryland School of Music. The librettist of the opera is Nick Olcott, Opera Assistant Director at the University. My interest in this little-known play of Euripides began with my work with Professor Lillian Doherty of the University's Classics Department. Since I am fluent in Greek, I was able to read the play in original, becoming aware of nuances of meaning absent in the standard English translations. Professor Leon Major, Artistic Director of the University's Opera Studio, was enthusiastic about the choice of this play as the basis for an opera, and has been very generous of his time in showing me what must be done to turn a play into an opera. ION is my first complete stage work for voices and constitutes an ambitious project. The opera is scored for a small chamber orchestra, consisting of Saxophone, Percussion (many types), Piano, a Small Chorus of six singers, as well as five Soloists. An orchestra of this size is adequate for the plot, and also provides support for various new vocal techniques, alternating between singing and speaking, as well as traditional arias. In ION, I incorporate Greek folk elements, which I know first-hand from my Balkan background, as well as contemporary techniques which I have absorbed during my graduate work at Boston University and the University of Maryland. Euripides' ION has fascinated me for two reasons in particular: its connection with founding myth of Athens, and the suggestiveness of its plot, which turns on the relationship of parents to children. In my interpretation, the leading character Ion is seen as emblematic for today's teenagers. Using the setting of the classic play, I hope to create a modern transformation of a myth, not to simply retell it. To this end, hopefully a new opera form will rise, as valid for our times as Verdi and Wagner were for theirs.

Requirements and design of an integrated European environmental information communication system, (IEEICS)

The needs for various forms of information systems relating to the European environment and ecosystem are reviewed, and limitations indicated. Existing information systems are reviewed and compared in terms of aims and functionalities. We consider TWO technical challenges involved in attempting to develop an IEEICS. First, there is the challenge of developing an Internet-based communication system which allows fluent access to information stored in a range of distributed databases. Some of the currently available solutions are considered, i.e. Web service federations. The second main challenge arises from the fact that there is general intra-national heterogeneity in the definitions adopted, and the measurement systems used throughout the nations of Europe. Integrated strategies are needed.

Using set operations to deal with the frame problem

This paper presents a simple approach to the so-called frame problem based on some ordinary set operations, which does not require non-monotonic reasoning. Following the notion of the situation calculus, we shall represent a state of the world as a set of fluents, where a fluent is simply a Boolean-valued property whose truth-value is dependent on the time. High-level causal laws are characterised in terms of relationships between actions and the involved world states. An effect completion axiom is imposed on each causal law, which guarantees that all the fluents that can be affected by the performance of the corresponding action are always totally governed. It is shown that, compared with other techniques, such a set operation based approach provides a simpler and more effective treatment to the frame problem.

What students can tell about lecturers when they are teaching: manifestations of confident and under-confident lecturers

Delivering a lecture requires confidence, a sound knowledge and well developed teaching skills (Cooper and Simonds, 2007, Quinn and Hughes, 2007). However, practitioners who are new to lecturing large groups in higher education may initially lack the confidence to do so which can manifest itself in their verbal and non-verbal cues and the fluency of their teaching skills. This results in the perception that students can identify the confident and non-confident teacher during a lecture (Street, 2007) and so potentially contributing to a lecturer’s level of anxiety prior to, and during, a lecture. Therefore, in the current educational climate of consumerisation, with the increased evaluation of teaching by students, having the ability to deliver high-quality, informed, and interesting lectures assumes greater significance for both lecturers and universities (Carr, 2007; Higher Education Founding Council 2008, Glass et al., 2006). This paper will present both the quantitative and qualitative data from a two-phase mixed method study with 75 nurse lecturers and 62 nursing students in one university in the United Kingdom. The study investigated the notion that lecturing has similarities to acting (Street, 2007). The findings presented here are concerned with how students perceived lecturers’ level of confidence and how lecturers believed they demonstrated confidence. In phase one a specifically designed questionnaire was distributed to both lecturers and students and a response rate of 91% (n=125) was achieved, while in phase two 12 in-depth semi-structured interviews were conducted with lecturers. Results suggested that students in a lecture could identify if the lecturer was confident or not by the way they performed a lecture. Students identified 57 manifestations of non-confidence and lecturers identified 85, while 57 manifestations of confidence were identified by students and 88 by lecturers. Overall, these fell into 12 main converse categories, ranging from body language to the use of space within the room. Both students and lecturers ranked body language, vocal qualities, delivery skills, involving the students and the ability to share knowledge as the most evident manifestations of confidence. Elements like good eye contact, smiling, speaking clearly and being fluent in the use of media recourses where all seen as manifestations confidence, conversely if these were poorly executed then a presentation of under confidence was evident. Furthermore, if the lecturer appeared enthusiastic it was clearly underpinned by the manifestation of a highly confidence lecturer who was secure in their knowledge base and teaching abilities: Some lecturers do appear enthusiastic but others don’t. I think the ones that do know what they are talking about, you can see it in their voice and in their lively body language. I think they are also good at involving the students even. I think the good ones are able to turn boring subjects into lively and interesting ones. (Student 50) Significantly more lecturers than students felt the lecturer should appear confident when lecturing. The lecturers stated it was particularly important to do so when they did not feel confident, because they were concerned with appearing capable. It seems that these students and lecturers perceived that expressive and apparently confident lecturers can make a positive impact on student groups in terms of involvement in lectures; the data also suggested the reverse, for the under confident lecturer. Findings from phase two indicated that these lecturers assumed a persona when lecturing, particularly, but not exclusively, when they were nervous. These lecturers went through a process of assuming and maintaining this persona before and during a lecture as a way of promoting their internal perceptions of confidence but also their outward manifestation of confidence. Although assuming a convincing persona may have a degree of deception about it, providing the knowledge communicated is accurate, the deception may aid rather than hinder learning, because enhances the delivery of a lecture. Therefore, the deception of acting a little more confidently than one feels might be justified when the lecturer knows the knowledge they are communicating is correct, unlike the Dr Fox Effect where the person delivering a lecture is an actor and does not know the subject in any detail or depth and where the deception to be justified (Naftulin, et al., 1973). In conclusion, these students and lecturers perceive that confident and enthusiastic lecturers communicate their passion for the subject in an interesting and meaningful manner through the use of their voice, body, space and interactions in such a way that shows confidence in their knowledge as well as their teaching abilities. If lecturers, therefore, can take a step back to consider how they deliver lectures in apparently confident ways this may increase their ability to engage their students and not only help them being perceived as good lecturers, but also contribute to the genuine act of education.

What a performance! Developing nurse teachers lecturing persona and identity: a performing arts perspective

Delivering lectures to large groups of students can provoke high levels of anxiety, particularly for new lecturers (Exley and Dennick, 2009). Further, to provide an informative and engaging lecture requires a teacher who is confident, has a sound knowledge and well developed teaching skills (Bentley-Davies, 2010). Thus, new lecturers often need experience and supervision to develop the tacit knowledge and insight into their own style and persona when teaching in order to feel confident when delivering a lecture (Quinn and Hughes, 2007). Considering this model, therefore, may potentially contribute to a lecturers’ development and performance in the classroom. This paper will present the results of the second phase of a two-stage mixed method study that investigated the similarities between lecturing and acting. Twelve in-depth interviews where undertaken with lecturers within one School of Nursing in The United Kingdom. Findings, established a model of ‘persona adoption’ that represents a series of stages that lecturers may go through to both develop and take on a persona when lecturing. This persona is often different from the way they lecturers present themselves in other parts of their working life. The first stage of this model of persona adoption is when the lecturer is subjected to a range of ‘influencing factors’ that provide not only the basic information about a lecture, but also the perceptual stimuli about giving a lecture on a specific subject, to a particular number of students, at a certain academic level. These influencing factors then inter-play with the ‘facets of the individual’, which represent the lecturer’s self-concept, subject knowledge base and philosophy of teaching. This may result in a cognitive dissonance between these ‘facets’ and the ‘influencing factors’, so affecting the lecturers’ perceptions, thoughts and feelings about having to give that particular lecture. This results in the lecturer undertaking specific ‘back stage preparation’ during which they decide on the content and modes of delivery to prepare in light of that discourse. It may result in delivering the information via single or multiple methods, which during the lecture will require various levels of interaction and participation from the students. Just prior to the lecture, the lecturer builds or ‘puts on their persona’ and gets into role, making their initial impact with the group. They use the ‘elements of acting’ as proposed by Tauber and Mester’s (1994) e.g. animated voice and body, space, props humour and suspense and surprise to portray and maintain their persona. This leads the to lecturer demonstrating either positive or negative ‘persona characteristics’ in terms of appearing confident, knowledgeable, fluent in the technical skills of delivering the lecture, being interesting and engendering interaction with the students, or not. These characteristics, may or may not, potentially heighten student interest, attention and attitudes to learning as suggested by Tauber and Mester (1994). This depends on whether the lecturer has successfully used the persona and if the lecturer has been able to engage students in the lecture, in competition with other factors that may be taking the students’ attention. Although the model suggests a linear process, to a great extent, the elements might be more interdependent and interrelated. This might suggest that depending on the lecturer’s perception of their effectiveness during the lecture, that they may decide to continue or adapt their persona and methods to appear more confident. Furthermore, depending on how successful the lecturer perceived the session to be, both their reflections ‘in’ and ‘on’ practice could influence how they teach in the future (Zwozdiak, 2011). Therefore, these reflections become part of the facets of the individual, via the ‘reflective feedback loop’, in the model, which then in turn influences progression through the model in subsequent lectures. This study concluded that these lecturers went through a process whereby they compare the demands of the lecture with their own knowledge base and skill, this resulted in them undertaking specific preparation in terms of content and delivery style, then they adopted their persona immediately prior to entering the lecture, maintain it throughout the lecture via the use of the elements of acting to achieve an informative interactive lecture. The results of which then feedback into their self-concept as a lecturer and consequently may affect the persona they project in future lectures. If lecturers, therefore, can take a step back to consider how they deliver lectures and the way they can deliberately, yet apparently naturally, use their voices, bodies, space and humour in meaningfully, they engage their students in lecture, it will not just result in them being perceived as a good lecturer, but also be a genuine act of education.

N1, P2 and T-complex of the auditory brain event-related potentials to tones with varying rise times in adults with and without dyslexia

Dyslexia is a learning difficulty affecting the acquisition of fluent reading and spelling skills due to poor phonological processing. Underlying deficits in processing sound rise time have also been found in children and adults with dyslexia. However, the neural basis for these deficits is unknown. In the present study event-related potentials were used to index neural processing and examine the effect of rise time manipulation on the obligatory N1. T-complex and P2 responses in English speaking adults with and without dyslexia. The Tb wave of the T-complex showed differences between groups, with the amplitudes for Tb becoming less negative with increased rise time for the participants with dyslexia only. Frontocentral N1 and P2 did not show group effects. Enhanced Tb amplitude that is modulated by rise time could indicate altered neural networks at the lateral surface of the superior temporal gyrus in adults with dyslexia. (C) 2011 Elsevier B.V. All rights reserved.

A Theoretical and Experimental Study of Resonance in a High Performance Engine Intake System: Part 1

The unsteady gas dynamic phenomena in engine intake systems of the type found in racecars have been examined. In particular, the resonant tuning effects, including cylinder-to-cylinder power variations, which can occur as a result of the interaction between an engine and its airbox have been considered. Frequency analysis of the output from a Virtual 4-Stroke 1D engine simulation was used to characterise the forcing function applied by an engine to an airbox. A separate computational frequency sweeping technique, which employed the CFD package FLUENT, was used to determine the natural frequencies of virtual airboxes in isolation from an engine. Using this technique, an airbox with a natural frequency at 75 Hz was designed for a Yamaha R6 4-cylinder motorcycle engine. The existence of an airbox natural frequency at 75 Hz was subsequently confirmed by an experimental frequency sweeping technique carried out on the engine test bed. A coupled 1D/3D analysis which employed the engine simulation package Virtual 4-Stroke and the CFD package FLUENT, was used to model the combined engine and airbox system. The coupled 1D/3D analysis predicted a 75 Hz resonance of the airbox at an engine speed of 9000 rpm. This frequency was the induction frequency for a single cylinder. An airbox was fabricated and tested on the engine. Static pressure was recorded at a grid of points in the airbox as the engine was swept through a speed range of 3000 to 10000 rpm. The measured engine speed corresponding to resonance in the airbox agreed well with the predicted values. There was also good correlation between the amplitude and phase of the pressure traces recorded within the airbox and the 1D/3D predictions.

An effective method for comparing the turbulence intensity from LDA measurements and CFD predictions within a ship propeller jet

The mean velocity and turbulence intensity are the two main inputs to investigate the ship propeller induced seabed scouring resulting from a vessel is manoeuvring within a port where the underkeel clearances are low. More accurate data including the turbulence intensity is now available by using the laser doppler anemometry (LDA) measurement system and computational fluid dynamics (CFD) approach. Turbulence intensity has a loose definition, which is the velocity fluctuation as the root mean square (RMS) referenced to a mean flow velocity. However, the velocity fluctuation and mean velocity can be the overall value includingx, y and z directions or the value of a single component. LDA and CFD results were obtained from two different acquisition systems (Dantec LDA system and Fluent CFD package) and therefore the outputs cannot be compared directly. An effective method is proposed for comparing the turbulence intensity between the experimental measurements and the computational predictions within a ship propeller jet. The flow patterns of turbulence intensity within a ship propeller jet are presented by using the LDA measurements and CFD results from turbulence models of standard k-e, RNG k-e, realizable k–e, standard k–?, SST k–?and Reynolds stresses.

Numerically Investigating the Effects of Cross-Links in Scaled Microchannel Heat Sinks

Thermal management as a method of heightening performance in miniaturized electronic devices using microchannel heat sinks has recently become of interest to researchers and the industry. One of the current challenges is to design heat sinks with uniform flow distribution. A number of experimental studies have been conducted to seek appropriate designs for microchannel heat sinks. However, pursuing this goal experimentally can be an expensive endeavor. The present work investigates the effect of cross-links on adiabatic two-phase flow in an array of parallel channels. It is carried out using the three dimensional mixture model from the computational fluid dynamics software, FLUENT 6.3. A straight channel and two cross-linked channel models were simulated. The cross-links were located at 1/3 and 2/3 of the channel length, and their widths were one and two times larger than the channel width. All test models had 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm. The results showed that the trend of flow distribution agrees with experimental results. A new design, with cross-links incorporated, was proposed and the results showed a significant improvement of up to 55% on flow distribution compared with the standard straight channel configuration without a penalty in the pressure drop. Further discussion about the effect of cross-links on flow distribution, flow structure, and pressure drop was also documented.

A Theoretical and Experimental Study of Resonance in a High Performance Engine Intake System: Part 2

The unsteady gas dynamic phenomena in a racecar airbox have been examined, and resonant tuning effects have been considered. A coupled 1D/3D analysis, using the engine simulation package Virtual 4-Stroke and the CFD package FLUENT, was used to model the engine and airbox. The models were experimentally validated. An airbox was designed with a natural frequency in the region of 75 Hz. A coupled 1D/3D analysis of the airbox and a Yamaha R6 4 cylinder engine predicted resonance at the single-cylinder induction frequency; 75 Hz at an engine speed of 9000 rpm.