基于振幅稳定的原点反共振振动机动力学分析及其控制

利用反共振原理可有效减小振动机械对基础的作用,提高振动机械的寿命。建立了原点反共振振动机的动力学模型,阐明了其工作原理。以工作体和下质体振幅稳定为核心,分析了各系统参数一定时质量比和反共振频率比对系统振幅稳定性的影响情况,得到了作为组合参数时质量比和反共振频率比分别与上下质体动力放大因子的关系曲面,由此可得到满足工艺要求并能保证振幅稳定的参数区间,为各类反共振振动机设计提供了重要依据。研究了物料质量波动对系统振幅稳定性的影响和反共振点的漂移情况,揭示了对反共振机激振频率进行控制的必要性。在合理动力学参数组合的前提下通过引入控制技术,有效地提高了反共振振动机的工作机体和下质体的振幅稳定性。

基于超短基线的缆控水下机器人动力定位

动力定位 (DynamicPositioning(DP) )技术是水下机器人的关键技术之一。因此针对当前动力定位主要在缆控水下机器人 (ROV)中应用的情况 ,给出了ROV动力定位技术的实施方法。通过声学定位技术确定ROV的坐标 ,计算出与期望位姿的差 ,将其作为神经网络控制器的输入量来控制ROV ,从而进行动力定位。同时还重点研究了ROV动力定位中的主要研究内容即水声定位技术和定位控制技术的构建。

自动化制造系统的产生与发展

探讨了自动化与制造业的产生和互促发展过程 ,论述了自动化制造系统的形成和不同发展阶段的内涵及重大作用 ,指出自动化技术与制造技术是驱动自动化制造系统发展的两个轮子 ,不能忽视任何一个侧面 ,自动化研究与制造技术研究相结合是发展先进制造技术的必由之路

敏捷竞争的挑战与思考

在未来持续多变和不可预测的竞争环境中,保持企业的竞争地位和生存发展的重要概念就是由敏捷制造和动态联盟构成的敏捷竞争的概念。动态联盟的思想加上当今高速信息网的建立和CALS提供的支持全球合作的技术和标准,为我们确定先进制造技术的研究计划,帮助中国的广大企业顺利地进入21世纪的国际合作大环境都有着重要的意义。

河道砂油藏产能预测系统研究

Productivity prediction is a serious factor to oil reservoir management and working out economic plans so that it is paid great attention to all the time. Gudao Oil Field, which has been yielding more than 100 million tons of crude oil accumulatively since it was put into developing in 1970's as a complete set of oil field, now entering double extra high water-bearing period after productivity construction, stable production and depletion stage. It's main layer series of development is thought to be type of channel sand reservoir in east China. Form channel sand reservoir in upper Guantao Group of Shengli Oil Field, there are several large oil fields such as Gudao, Gudong and Chengdao etc. with almost one-third reserves of whole Shengli Oil Field. It is considered the common characteristics in this area would be that the layer is less developed, the sand distribution is sporadic, the connectivity is weak, the heterogeneity is strong in plane, the oil layer is unconsolidated with big porosity, high permeability and serious sanding, and the oil is heavy. Because of the restricted factors to productivity of this kind of reservoir, it is very significant to study the productivity prediction this kind of reservoir. By selecting the upstream fluvial reservoir in Guantao Group of Neogene system as researching object, the author studied the forecasting technology with heterogeneous reservoir. Firstly, the author constructed the 3D subtle geological model quantificationally through researching exploitation geology in the way of combination of dynamic and static methods. Secondly, by the aid of dynamic material obtained while producing, the author analyzed the oil distribution law and influencing factors, then finished dynamic oil reservoir description on the basis of static oil reservoir description. Thirdly, via comparing and analyzing all the forecasting methods of productivity existed, the author developed a set of method to forecast productivity of single well and oil field which fit to channel sand reservoir. At last, under the support of ORACLE database, with the advanced computer technology, the author programmed the software called 'Channel Sand Reservoir Prediction System'. Up to now, this system has been putting into use in Gudao Oil Field and very successful.

Novel processes, test structures and characterisation for future germanium technologies

In order to widely use Ge and III-V materials instead of Si in advanced CMOS technology, the process and integration of these materials has to be well established so that their high mobility benefit is not swamped by imperfect manufacturing procedures. In this dissertation number of key bottlenecks in realization of Ge devices are investigated; We address the challenge of the formation of low resistivity contacts on n-type Ge, comparing conventional and advanced rapid thermal annealing (RTA) and laser thermal annealing (LTA) techniques respectively. LTA appears to be a feasible approach for realization of low resistivity contacts with an incredibly sharp germanide-substrate interface and contact resistivity in the order of 10 -7 Ω.cm2. Furthermore the influence of RTA and LTA on dopant activation and leakage current suppression in n+/p Ge junction were compared. Providing very high active carrier concentration > 1020 cm-3, LTA resulted in higher leakage current compared to RTA which provided lower carrier concentration ~1019 cm-3. This is an indication of a trade-off between high activation level and junction leakage current. High ION/IOFF ratio ~ 107 was obtained, which to the best of our knowledge is the best reported value for n-type Ge so far. Simulations were carried out to investigate how target sputtering, dose retention, and damage formation is generated in thin-body semiconductors by means of energetic ion impacts and how they are dependent on the target physical material properties. Solid phase epitaxy studies in wide and thin Ge fins confirmed the formation of twin boundary defects and random nucleation growth, like in Si, but here 600 °C annealing temperature was found to be effective to reduce these defects. Finally, a non-destructive doping technique was successfully implemented to dope Ge nanowires, where nanowire resistivity was reduced by 5 orders of magnitude using PH3 based in-diffusion process.

Computational model for prediction of particle degradation during dilute phase pneumatic conveying: the use of a laboratory scale degradation tester for the determination of degradation propensity

The overall objective of this work is to develop a computational model of particle degradation during dilute-phasepneumatic conveying. A key feature of such a model is the prediction of particle breakage due to particle–wall collisions in pipeline bends. This paper presents a method for calculating particle impact degradation propensity under a range of particle velocities and particle sizes. It is based on interpolation on impact data obtained in a new laboratory-scale degradation tester. The method is tested and validated against experimental results for degradation at 90± impact angle of a full-size distribution sample of granulated sugar. In a subsequent work, the calculation of degradation propensity is coupled with a ow model of the solids and gas phases in the pipeline.

Computational model for prediction of particle degradation during dilute-phase pneumatic conveying: modeling of dilute-phase pneumatic conveying

A complete model of particle impact degradation during dilute-phase pneumatic conveying is developed, which combines a degradation model, based on the experimental determination of breakage matrices, and a physical model of solids and gas flow in the pipeline. The solids flow in a straight pipe element is represented by a model consisting of two zones: a strand-type flow zone immediately downstream of a bend, followed by a fully suspended flow region after dispersion of the strand. The breakage matrices constructed from data on 90° angle single-impact tests are shown to give a good representation of the degradation occurring in a pipe bend of 90° angle. Numerical results are presented for degradation of granulated sugar in a large scale pneumatic conveyor.

Analysis and modeling of heaping behavior of granular mixtures within a computational mechanics framework

This paper presents a continuum model of the flow of granular material during filling of a silo, using a viscoplastic constitutive relation based on the Drucker-Prager plasticity yield function. The performed simulations demonstrate the ability of the model to realistically represent complex features of granular flows during filling processes, such as heap formation and non-zero inclination angle of the bulk material-air interface. In addition, micro-mechanical parametrizations which account for particle size segregation are incorporated into the model. It is found that numerical predictions of segregation phenomena during filling of a binary granular mixture agree well with experimental results. Further numerical tests indicate the capability of the model to cope successfully with complex operations involving granular mixtures.

Modelling of aircraft manufacturing cost at the concept stage

The work presented is concerned with the estimation of manufacturing cost at the concept design stage, when little technical information is readily available. The work focuses on the nose cowl sections of a wide range of engine nacelles built at Bombardier Aerospace Shorts of Belfast. A core methodology is presented that: defines manufacturing cost elements that are prominent; utilises technical parameters that are highly influential in generating those costs; establishes the linkage between these two; and builds the associated cost estimating relations into models. The methodology is readily adapted to deal with both the early and more mature conceptual design phases, which thereby highlights the generic, flexible and fundamental nature of the method. The early concept cost model simplifies cost as a cumulative element that can be estimated using higher level complexity ratings, while the mature concept cost model breaks manufacturing cost down into a number of constituents that are each driven by their own specific drivers. Both methodologies have an average error of less that ten percent when correlated with actual findings, thus achieving an acceptable level of accuracy. By way of validity and application, the research is firmly based on industrial case studies and practice and addresses the integration of design and manufacture through cost. The main contribution of the paper is the cost modelling methodology. The elemental modelling of the cost breakdown structure through materials, part fabrication, assembly and their associated drivers is relevant to the analytical design procedure, as it utilises design definition and complexity that is understood by engineers.

Eyes open to stem cells: safety trial may pave the way for cell therapy to treat retinal disease in patients

A clinical trial using human embryonic stem cell (hESC) therapy for an inherited retinal degenerative disease is about to commence. The Advanced Cell Technology (ACT) trial will treat patients with Stargardt's macular dystrophy using transplanted retinal pigment epithelium derived from hESCs. Currently, no effective treatment is available for Stargardt's disease so a stem cell-based therapy that can slow progression of this blinding condition could represent a significant breakthrough. While there are some hurdles to clear, the ACT trial is a fine example of translational research that could eventually pave the way for a range of stem cell therapies for the retina and other tissues.