The induced flow field by internal solitary wave and its action on cylindrical piles in the stratified ocean

The induced flow fields by internal solitary waves and its actions on cylindrical piles in density stratified ocean with a basic density profile and a basic velocity profile are investigated. Some results, such as the time evolution of flow fields and hydrodynamic forces on the piles are yielded both by theoretical analysis and numerical calculation for general and specific cases. Several kinds of ambient sea conditions of the South China Sea are specified for numerical simulation. Moreover, the effects of relative density difference, depth ratio and wave steepness on maximal total force and total torque are analyzed.

Research progress on high-enthalpy and hypersonic flows

The research progress on high-enthalpy and hypersorlic flows having been achieved in the Institute of Mechanics, Chinese Academy of Sciences, is reported in this paper. The paper consists of three main parts: The first part is on the techniques to develop advanced hypersonic test facilities, in which the detonation-driven shock-reflected tunnel and the detonation-driven shock-expanded tube are introduced. The shock tunnel can be used for generating hypersonic flows of a Mach number ranging from 10 to 20, and the expansion tube is applicable to simulate the flows with a speed of 7 similar to 10km/s. The second part is dedicated to the shock tunnel nozzle flow diagnosis to examine properties of the hypersonic flows thus created. The third part is on experiments and numerical simulations. The experiments include measuring the aerodynamic pitching moment and heat transfer in hypersonic flows, and the numerical work reports nozzle flow simulations and flow non-equilibrium effects on the possible experiments that may be carried out on the above-mentioned hypersonic test facilities.

Stimulation discomfort comparison of asynchronous and synchronous methods with multi-field electrodes

Functional Electrical Stimulation (FES) is a technique that consists on applying electrical current pulses to artificially activate motor nerve fibers and produce muscle contractions to achieve functional movements. The main applications of FES are within the rehabilitation field, in which this technique is used to aid recovery or to restore lost motor functions. People that benefit of FES are usually patients with neurological disorders which result in motor dysfunctions; most common patients include stroke and spinal cord injury (SCI). Neuroprosthesis are devices that have their basis in FES technique, and their aim is to bridge interrupted or damaged neural paths between the brain and upper or lower limbs. One of the aims of neuroprosthesis is to artificially generate muscle contractions that produce functional movements, and therefore, assist impaired people by making them able to perform activities of daily living (ADL). FES applies current pulses and stimulates nerve fibers by means of electrodes, which can be either implanted or surface electrodes. Both of them have advantages and disadvantages. Implanted electrodes need open surgery to place them next to the nerve root, so these electrodes carry many disadvantages that are produced by the use of invasive techniques. In return, as the electrodes are attached to the nerve, they make it easier to achieve selective functional movements. On the contrary, surface electrodes are not invasive and are easily attached or detached on the skin. Main disadvantages of surface electrodes are the difficulty of selectively stimulating nerve fibers and uncomfortable feeling perceived by users due to sensory nerves located in the skin. Electrical stimulation surface electrode technology has improved significantly through the years and recently, multi-field electrodes have been suggested. This multi-field or matrix electrode approach brings many advantages to FES; among them it is the possibility of easily applying different stimulation methods and techniques. The main goal of this thesis is therefore, to test two stimulation methods, which are asynchronous and synchronous stimulation, in the upper limb with multi-field electrodes. To this end, a purpose-built wrist torque measuring system and a graphic user interface were developed to measure wrist torque produced with each of the methods and to efficiently carry out the experiments. Then, both methods were tested on 15 healthy subjects and sensitivity results were analyzed for different cases. Results show that there are significant differences between methods regarding sensation in some cases, which can affect effectiveness or success of FES.

Rarefied gas dynamics: fundamentals, simulations and micro flows

Design, Construction and Testing of a Hydraulic Power Take-Off for Wave Energy Converters

This paper presents the construction, mathematical modeling and testing of a scaled universal hydraulic Power Take-Off (PTO) device for Wave Energy Converters (WECs). A specific prototype and test bench were designed and built to carry out the tests. The results obtained from these tests were used to adjust an in-house mathematical model. The PTO was initially designed to be coupled to a scaled wave energy capture device with a low speed and high torque oscillating motion and high power fluctuations. Any Energy Capture Device (ECD) that fulfils these requirements can be coupled to this PTO, provided that its scale is adequately defined depending on the rated power of the full scale prototype. The initial calibration included estimation of the pressure drops in the different components, the pressurization time of the oil inside the hydraulic cylinders and the volumetric efficiency of the complete circuit. Since the overall efficiency measured during the tests ranged from 0.69 to 0.8 and the dynamic performance of the PTO was satisfactory, the results are really promising and it is believed that this solution might prove effective in real devices.

A robust position control for induction machines

ICEM 2010

Leistungsmessung an Bord von Fischereifahrzeugen zur Kontrolle der 300-PS-Begrenzung in der Schollenbox

For monitoring of the engine power of fishing vessels permitted for fishery in the plaice box with engine power of 300 HP or less at sea three different portable power measurement systems are developed and tested. A system measuring the twist of the propeller shaft by two divisible gearwheels mounted on the shaft worked well at shafts with roller bearing at both sides of the measured interval of 100–300 mm length. Only at a very few fishing vessels this system is applicable and therefore for monitoring purposes not suitable. The application of a commercial available system measuring the stress at the surface of the shaft was simplified for application by non experts. The torque is measured by strain gauges. The calibration of the system, measuring and recording of the power is done by a PC automatically. A small polished facet on the shaft protected against oxidation is needed for easy and quick application. In this case the system can be used by technical personnel of supervision boats for monitoring of the engine power at sea in a short time. A third power measurement system determinates the torque by measuring the displacement of two supports clamped on the shaft at a distance of 100 mm. The displacement is measured by a micrometer gauge mounted on one of the supports. Readout of the rotating gauge display is possible taking advantage of stroboscopic effect. The system needs no conditioning of the shaft and can be used by non technicians. The development is not finished until now and some additional investigations and tests are required. Additional measures for monitoring of the power on fishing vessels by self recording power measurement systems and sealed fuel racks with limited injection are reported and discussed.

Some problems in nonlinear elasticity

Two separate problems are discussed: axisymmetric equilibrium configurations of a circular membrane under pressure and subject to thrust along its edge, and the buckling of a circular cylindrical shell.

An ordinary differential equation governing the circular membrane is imbedded in a family of n-dimensional nonlinear equations. Phase plane methods are used to examine the number of solutions corresponding to a parameter which generalizes the thrust, as well as other parameters determining the shape of the nonlinearity and the undeformed shape of the membrane. It is found that in any number of dimensions there exists a value of the generalized thrust for which a countable infinity of solutions exist if some of the remaining parameters are made sufficiently large. Criteria describing the number of solutions in other cases are also given.

Donnell-type equations are used to model a circular cylindrical shell. The static problem of bifurcation of buckled modes from Poisson expansion is analyzed using an iteration scheme and pertubation methods. Analysis shows that although buckling loads are usually simple eigenvalues, they may have arbitrarily large but finite multiplicity when the ratio of the shell's length and circumference is rational. A numerical study of the critical buckling load for simple eigenvalues indicates that the number of waves along the axis of the deformed shell is roughly proportional to the length of the shell, suggesting the possibility of a "characteristic length." Further numerical work indicates that initial post-buckling curves are typically steep, although the load may increase or decrease. It is shown that either a sheet of solutions or two distinct branches bifurcate from a double eigenvalue. Furthermore, a shell may be subject to a uniform torque, even though one is not prescribed at the ends of the shell, through the interaction of two modes with the same number of circumferential waves. Finally, multiple time scale techniques are used to study the dynamic buckling of a rectangular plate as well as a circular cylindrical shell; transition to a new steady state amplitude determined by the nonlinearity is shown. The importance of damping in determining equilibrium configurations independent of initial conditions is illustrated.

Estimation and inference for grasping and manipulation tasks using vision and kinesthetic sensors

This thesis presents a novel framework for state estimation in the context of robotic grasping and manipulation. The overall estimation approach is based on fusing various visual cues for manipulator tracking, namely appearance and feature-based, shape-based, and silhouette-based visual cues. Similarly, a framework is developed to fuse the above visual cues, but also kinesthetic cues such as force-torque and tactile measurements, for in-hand object pose estimation. The cues are extracted from multiple sensor modalities and are fused in a variety of Kalman filters.

A hybrid estimator is developed to estimate both a continuous state (robot and object states) and discrete states, called contact modes, which specify how each finger contacts a particular object surface. A static multiple model estimator is used to compute and maintain this mode probability. The thesis also develops an estimation framework for estimating model parameters associated with object grasping. Dual and joint state-parameter estimation is explored for parameter estimation of a grasped object's mass and center of mass. Experimental results demonstrate simultaneous object localization and center of mass estimation.

Dual-arm estimation is developed for two arm robotic manipulation tasks. Two types of filters are explored; the first is an augmented filter that contains both arms in the state vector while the second runs two filters in parallel, one for each arm. These two frameworks and their performance is compared in a dual-arm task of removing a wheel from a hub.

This thesis also presents a new method for action selection involving touch. This next best touch method selects an available action for interacting with an object that will gain the most information. The algorithm employs information theory to compute an information gain metric that is based on a probabilistic belief suitable for the task. An estimation framework is used to maintain this belief over time. Kinesthetic measurements such as contact and tactile measurements are used to update the state belief after every interactive action. Simulation and experimental results are demonstrated using next best touch for object localization, specifically a door handle on a door. The next best touch theory is extended for model parameter determination. Since many objects within a particular object category share the same rough shape, principle component analysis may be used to parametrize the object mesh models. These parameters can be estimated using the action selection technique that selects the touching action which best both localizes and estimates these parameters. Simulation results are then presented involving localizing and determining a parameter of a screwdriver.

Lastly, the next best touch theory is further extended to model classes. Instead of estimating parameters, object class determination is incorporated into the information gain metric calculation. The best touching action is selected in order to best discern between the possible model classes. Simulation results are presented to validate the theory.

Design support for turbomachinery

From the steam turbines which provide most of our electricity to the jet engines which have shrunk our World, turbomachines undoubtedly play a major role in life today. Competition in the turbomachinery industry is fiercely strong [Wisler, 1998], hence good aerodynamic design is vital. However, with efficiency levels already close to their theoretical maxima, companies are increasingly looking to reduce costs and increase reliability through improved design practice. Computational Fluid Dynamics (CFD) can make a strong contribution to assisting this process as it has the potential to increase performance while reducing cost. The situation is, however, complicated by an ever decreasing number of engineers with sufficient design experience to reap the full benefits offered by CFD. With the large risks involved, novice designers of today are increasingly confined to refining old designs rather than gaining experience, like their forebears, through 'clean sheet' exercises. Hence it is desirable to capture the knowledge and experience of older designers, before it is lost, to assist the engineers of tomorrow. It is therefore the aim of this project to produce a design support tool which will not only store the appropriate CFD codes, but also provide a dynamic signpost (based on elicited knowledge and experience) to advise the engineer in their use. The signposting methodology developed for the aerospace industry [Clarkson and Hamilton, 1997] will provide the basic framework for the tool. This paper reviews current turbomachinery design practice (including an examination of the relevant CFD) in order to establish the important issues which a support tool must address. Current design support methodologies and their propriety are then reviewed, followed by a detailed description of the signposting concept. It then sets out a clear statement of the objectives for the research and the methods proposed to meet them. The paper concludes with a timetable of the work.

Magnetic alignment of high-aspect ratio microwires into vertical arrays

Fundamental studies of magnetic alignment of highly anisotropic mesostructures can enable the clean-room-free fabrication of flexible, array-based solar and electronic devices, in which preferential orientation of nano- or microwire-type objects is desired. In this study, ensembles of 100 micron long Si microwires with ferromagnetic Ni and Co coatings are oriented vertically in the presence of magnetic fields. The degree of vertical alignment and threshold field strength depend on geometric factors, such as microwire length and ferromagnetic coating thickness, as well as interfacial interactions, which are modulated by varying solvent and substrate surface chemistry. Microwire ensembles with vertical alignment over 97% within 10 degrees of normal, as measured by X-ray diffraction, are achieved over square cm scale areas and set into flexible polymer films. A force balance model has been developed as a predictive tool for magnetic alignment, incorporating magnetic torque and empirically derived surface adhesion parameters. As supported by these calculations, microwires are shown to detach from the surface and align vertically in the presence of magnetic fields on the order of 100 gauss. Microwires aligned in this manner are set into a polydimethylsiloxane film where they retain their vertical alignment after the field has been removed and can subsequently be used as a flexible solar absorber layer. Finally, these microwires arrays can be protected for use in electrochemical cells by the conformal deposition of a graphene layer.

Diseño de un aerogenerador de muy baja potencia para la alimentación de sistemas eléctricos aislados

[ES]En este Proyecto se desarrolla el diseño y la optimización de un aerogenerador de muy pequeña potencia enfocado a alimentar sistemas eléctricos aislados; concretamente, un sistema de iluminación. Se analizan todos los componentes del sistema aerogenerador, comparando las diversas alternativas posibles y eligiendo soluciones sencillas, baratas y eficientes para cada uno de ellos. Asimismo, se lleva a cabo un primer dimensionamiento de los mismos. El esfuerzo de diseño se ha centrado en las palas, por considerarse el componente más crítico y menos normalizado. Se han estudiado herramientas para su análisis detallado y su optimización desde el punto de vista aerodinámico, y éstas han sido implementadas en Matlab. Esto ha permitido generar un diseño óptimo ajustado a las necesidades del sistema. Asimismo, se han realizado las correspondientes tareas de planificación, analizado los múltiples beneficios de tipo técnico, económico, social y ambiental que la ejecución del presente Proyecto reportará, haciendo una programación completa del mismo y un análisis de los costes que supondrá.

Lehiaketako motor baten erditxasiaren diseinua

[EU]Proiektu honek lehiaketarako moto baten erditxasia garatzen du, baita txasira lotuta egongo den modua ere. Erditxasia pieza estruktural bat da eta nahiz eta agian beharrezkoa ez izan lehiaketako moto batean, izan ere hauetan pilotuek ipurdia oso aurrean kokatzen dute pisua txasira bideratuz, moto guztiek duten atal bat da eta pertsonaren pisua eta honek egiturari eragiten dizkion indar eta esfortzuak eusteko erabiltzen da. Kasu batzuetan txasiaren beraren barnean egoten da zati hau eta beraz dena pieza bat izaten da, baina gure kasuan biak, erditxasia eta txasia elkarri lotuta egongo dira. Hasteko erditxasi hau zein eratara fabrikatua izan daitekeen aztertuko da(hodi, txapa…), eta modu bakoitzaren abantailak eta desabantailak ikusi beharko dira azkenik nola egingo den aukeratzeko. Honela gure piezaren eboluzio bat emango da guk behar ditugun exijentzia teknikoak bete ditzan eta ekonomikoki ere bideragarria izan dadin. Amaitzeko pieza bere lekuan bermatzeko beharko diren elementu laguntzaileak ere kalkulatu edo aukeratu beharko dira, lehiaketan dugun portaera guk nahi duguna izan dadin.

Optical levitation measurements with intensity-modulated light beams

Illumination of an optically levitated particle with an intensity-modulated transverse beam induces a transverse vibration of a particle in an optical trap. Based on this, the trapping force of a trap can be measured. Using an intensity-modulated longitudinal levitating beam causes a particle to move vertically, allowing for the determination of some aerodynamic parameters of a particle in air. The principles and the experimental phenomena are described and the initial results are given. (C) 1997 Optical Society of America.

Metodologia para conversão de veículos equipados com motores a combustão interna para tração elétrica: aplicação de motor síncrono de ímã permanente com fluxo magnético radial a um furgão, Brasil. 2009.

Questões climáticas, atmosféricas e de poluição ambiental têm tornado o uso final da energia assunto de interesse mundial. Sistemas com tração elétrica oferecem a oportunidade de redução de emissões. O mix de energia caracterizado pela matriz energética brasileira viabiliza o desenvolvimento desta tecnologia. É desenvolvida aqui uma metodologia para conversão de veículos equipados com motores a combustão interna para tração elétrica. A metodologia considera fatores como o peso e tamanho, o torque de partida, transmissão e potência, entre outros. Ferramentas matemáticas e a prática corrente fornecem a base para a elaboração deste trabalho, que descreve a análise de desempenho de veículos elétricos, os componentes utilizados, as equações mecânicas e os critérios para escolha do veículo ideal para conversão. É apresentada a execução de um projeto de conversão de uma Kombi para tração elétrica, cujo objetivo tem caráter educativo, buscando assim promover os benefícios da tecnologia veicular elétrica. Para viabilização do experimento, o trabalho conclui que é necessário ampliar a demanda por nacionalização de tecnologia, o que tornaria o projeto uma realidade comercialmente viável. Além disto, há necessidade de políticas públicas para o incentivo da tecnologia veicular elétrica no Brasil. Este trabalho apresenta uma contribuição para converter veículos para tração elétrica, visto que sistematiza as etapas de projeto, a partir das quais outros poderão seguir, utilizando componentes encontrados no mercado nacional.