The framework of the virtual laser tracker - A systematic approach to the assessment of error sources and uncertainty in laser tracker measurement

Laser trackers have been widely used in many industries to meet increasingly high accuracy requirements. In laser tracker measurement, it is complex and difficult to perform an accurate error analysis and uncertainty evaluation. This paper firstly reviews the working principle of single beam laser trackers and state-of- The- Art of key technologies from both industrial and academic efforts, followed by a comprehensive analysis of uncertainty sources. A generic laser tracker modelling method is formulated and the framework of the virtual tracker is proposed. The VLS can be used for measurement planning, measurement accuracy optimization and uncertainty evaluation. The completed virtual laser tracking system should take all the uncertainty sources affecting coordinate measurement into consideration and establish an uncertainty model which will behave in an identical way to the real system. © Springer-Verlag Berlin Heidelberg 2010.

Load–frequency control : a GA-based multi-agent reinforcement learning

The load–frequency control (LFC) problem has been one of the major subjects in a power system. In practice, LFC systems use proportional–integral (PI) controllers. However since these controllers are designed using a linear model, the non-linearities of the system are not accounted for and they are incapable of gaining good dynamical performance for a wide range of operating conditions in a multi-area power system. A strategy for solving this problem because of the distributed nature of a multi-area power system is presented by using a multi-agent reinforcement learning (MARL) approach. It consists of two agents in each power area; the estimator agent provides the area control error (ACE) signal based on the frequency bias estimation and the controller agent uses reinforcement learning to control the power system in which genetic algorithm optimisation is used to tune its parameters. This method does not depend on any knowledge of the system and it admits considerable flexibility in defining the control objective. Also, by finding the ACE signal based on the frequency bias estimation the LFC performance is improved and by using the MARL parallel, computation is realised, leading to a high degree of scalability. Here, to illustrate the accuracy of the proposed approach, a three-area power system example is given with two scenarios.

Interpreting regional frequencies from synchronized phasor measurement in multi-area power systems

In this paper a new approach is proposed for interpreting of regional frequencies in multi machine power systems. The method uses generator aggregation and system reduction based on coherent generators in each area. The reduced system structure is able to be identified and a kalman estimator is designed for the reduced system to estimate the inter-area modes using the synchronized phasor measurement data. The proposed method is tested on a six machine, three area test system and the obtained results show the estimation of inter-area oscillations in the system with a high accuracy.

Variable structure control for power systems stabilization

The application of variable structure control (VSC) for power systems stabilization is studied in this paper. It is the application, aspects and constraints of VSC which are of particular interest. A variable structure control methodology has been proposed for power systems stabilization. The method is implemented using thyristor controlled series compensators. A three machine power system is stabilized using a switching line control for large disturbances which becomes a sliding control as the disturbance becomes smaller. The results demonstrate the effectiveness of the methodology proposed as an useful tool to suppress the oscillations in power systems.

Critical success elements for the design and implementation of organisational e-learning

Organisations are engaging in e-learning as a mechanism for delivering flexible learning to meet the needs of individuals and organisations. In light of the increasing use and organisational investment in e-learning, the need for methods to evaluate the success of its design and implementation seems more important than ever. To date, developing a standard for the evaluation of e-learning appears to have eluded both academics and practitioners. The currently accepted evaluation methods for e-learning are traditional learning and development models, such as Kirkpatrick’s model (1976). Due to the technical nature of e-learning it is important to broaden the scope and consider other evaluation models or techniques, such as the DeLone and McLean Information Success Model, that may be applicable to the e-learning domain. Research into the use of e-learning courses has largely avoided considering the applicability of information systems research. Given this observation, it is reasonable to conclude that e-learning implementation decisions and practice could be overlooking useful or additional viewpoints. This research investigated how existing evaluation models apply in the context of organisational e-learning, and resulted in an Organisational E-learning success Framework, which identifies the critical elements for success in an e-learning environment. In particular this thesis highlights the critical importance of three e-learning system creation elements; system quality, information quality, and support quality. These elements were explored in depth and the nature of each element is described in detail. In addition, two further elements were identified as factors integral to the success of an e-learning system; learner preferences and change management. Overall, this research has demonstrated the need for a holistic approach to e-learning evaluation. Furthermore, it has shown that the application of both traditional training evaluation approaches and the D&M IS Success Model are appropriate to the organisational e-learning context, and when combined can provide this holistic approach. Practically, this thesis has reported the need for organisations to consider evaluation at all stages of e-learning from design through to implementation.

Resistance fluctuation at the mobility edge

Following a Migdal-Kadanoff-type bond moving procedure, we derive the renormalisation-group equations for the characteristic function of the full probability distribution of resistance (conductance) of a three-dimensional disordered system. The resulting recursion relations for the first two cumulants, K, the mean resistance and K ~ t,he meansquare deviation of resistance exhibit a mobility edge dominated by large dispersion, i.e., K $ ’/ K=, 1, suggesting inadequacy of the one-parameter scaling ansatz.

Understanding the organic chain : The framework of the interaction between the actors in organic chains in relation to ecological modernisation of food production

The sustainability of food production has increasingly attracted the attention of consumers, farmers, food and retailing companies, and politicians. One manifestation of such attention is the growing interest in organic foods. Organic agriculture has the potential to enhance the ecological modernisation of food production by implementing the organic method as a preventative innovation that simultaneously produces environmental and economic benefits. However, in addition to the challenges to organic farming, the small market share of organic products in many countries today and Finland in particular risks undermining the achievement of such benefits. The problems identified as hindrances to the increased consumption of organic food are the poor availability, limited variety and high prices of organic products, the complicated buying decisions and the difficulties in delivering the intangible value of organic foods. Small volumes and sporadic markets, high costs, lack of market information, as well as poor supply reliability are obstacles to increasing the volume of organic production and processing. These problems shift the focus from a single actor to the entire supply chain and require solutions that involve more interaction among the actors within the organic chain. As an entity, the organic food chain has received very little scholarly attention. Researchers have mainly approached the organic chain from the perspective of a single actor, or they have described its structure rather than the interaction between the actors. Consequently, interaction among the primary actors in organic chains, i.e. farmers, manufacturers, retailers and consumers, has largely gone unexamined. The purpose of this study is to shed light on the interaction of the primary actors within a whole organic chain in relation to the ecological modernisation of food production. This information is organised into a conceptual framework to help illuminate this complex field. This thesis integrates the theories and concepts of three approaches: food system studies, supply chain management and ecological modernisation. Through a case study, a conceptual system framework will be developed and applied to a real life-situation. The thesis is supported by research published in four articles. All examine the same organic chains through case studies, but each approaches the problem from a different, complementary perspective. The findings indicated that regardless of the coherent values emphasising responsibility, the organic chains were loosely integrated to operate as a system. The focus was on product flow, leaving other aspects of value creation largely aside. Communication with consumers was rare, and none of the actors had taken a leading role in enhancing the market for organic products. Such a situation presents unsuitable conditions for ecological modernisation of food production through organic food and calls for contributions from stakeholders other than those directly involved in the product chain. The findings inspired a revision of the original conceptual framework. The revised framework, the three-layer framework , distinguishes the different layers of interaction. By gradually enlarging the chain orientation the different but interrelated layers become visible. A framework is thus provided for further research and for understanding practical implications of the performance of organic food chains. The revised framework provides both an ideal model for organic chains in relation to ecological modernisation and demonstrates a situation consistent with the empirical evidence.

REHTORIT PORTINVARTIJOINA : sekä miten rehtoreiden kertomuksista muodostuu pääkaupunkiseudun Tehostetun ja erityisen tuen kehittämisverkoston tarina

Research objectives. The Special Education Strategy, the legislative change based on it, and the change in the Finnish National Core Curriculum for Pre-primary and Basic Education build the background for this study. An improvement initiative called KELPO was founded in 2008 to implement a new three-level support system in municipalities. To support this initiative, the Network of Intensified and Special Support in the Metropolitan Area was founded in 2010. The Network consists of 22 pilot schools from four metropolitan municipalities and the Centre for Educational Assessment at the University of Helsinki that carries out the developmental assessment of the initiative. The objective of my study was to form an overall view of the functioning of the Network. The data included interviews of 20 principals of the schools belonging to the Network. The interviews were conducted by the Centre for Educational Assessment in the autumn of 2010. The research question is: What do principals speak about the networking done inside and between the municipalities? Methods. I received the data as already transcribed for my use. I researched it using a narrative research approach. As a method I used both thematic reading and classifying narratives by the holistic-content. These methods belong under the analyze of narratives. I collected the narratives from the principals under themes that arose from the data delimited by my research question. The narrative analysis materialized by writing the research story, as a new story was built by the principals stories theme by theme. The classification of the narratives by the holistic-content method was realized according to what kind of a gatekeeper s role each principal had. With a gatekeeper I here mean the intermediary role of a principal between the school and outside world. In addition, I used the analysis of interactive production of the narrative when applicable. Results and conclusions. Explicit features in the story of the Network were the principals at least partial uncertainty of the purpose of the networking, lack of time and resources, changing of initiatives, and lack of continuity. Positive narratives about ownership and empowerment could also be found. Nonetheless, many of the preconditions for success described by the school reform and school networking theories were not fulfilled. According to the collective story, there was no shared goal or purpose, and nor were the needs of autonomy, competence, and relatedness fulfilled. Three different kinds of gatekeepers were found in the data: The Exemplary ones, The Survivors and The Losers. The distinguishing factor turned out to be sharing of information at school. Based on the narratives, the schools with principals taking care of sharing information were the most active in partaking in networking.

Oxidation of aqueous sulphur dioxide catalysed by poly-4-vinylpyridine-Cu(II) complex .2. Combined homogeneous and heterogeneous phase oxidation

Aqueous phase oxidation of sulphur dioxide at low concentrations catalysed by a PVP-Cu complex in the solid phase and dissolved Cu(II) in the liquid phase is studied in a rotating catalyst basket reactor (RCBR). The equilibrium adsorption of Cu(II) and S(VI) on PVP particles is found to be of the Langmuir-type. The diffusional effects of S(IV) species in PVP-Cu resin are found to be insignificant whereas that of product S(VI) are found to be significant. The intraparticle diffusivity of S(VI) is obtained from independent tracer experiments. In the oxidation reaction HSO3- is the reactive species. Both the S(IV) species in the solution, namely SO2(aq) and HSO3- get adsorbed onto the active PVP-Cu sites of the catalyst, but only HSO3- undergoes oxidation. A kinetic mechanism is proposed based on this feature which shows that SO2(aq) has a deactivating effect on the catalyst. A rate model is developed for the three-phase reaction system incorporating these factors along with the effect of concentration of H2SO4 on the solubility of SO2 in the dilute aqueous solutions of Cu(II). Transient oxidation experiments are conducted at different conditions of concentration of SO2 and O-2 in the gas phase and catalyst concentration, and the rate parameters are estimated from the data. The observed and calculated profiles are in very good agreement. This confirms the deactivating effect of nonreactive SO2(aq) on the heterogeneous catalysis.

COMPARISON AND CROSS-VALIDATION OF OPTICAL TECHNIQUES IN DIFFERENT SWIRL SPRAY REGIMES

This paper deals with an experimental study of pressure-swirl hydraulic injector nozzles using non-intrusive optical techniques. Experiments were conducted to study atomization characteristics using two nozzles with different orifice diameters, 0.3 mm and 0.5 mm, and injection pressures, 0.3-3.5 Mpa, which correspond to Reynolds number (Re-p) = 7,000-45,000, depending on nozzle utilized. Three laser diagnostic techniques were utilized: Shadowgraph, PIV (Particle Image Velocimetry), and PDPA (Phase Doppler Particle Anemometry). Measurements made in the spray in both axial and radial directions indicate that velocity, average droplet diameter profiles, and spray dynamics are highly dependent on the nozzle characteristics and injection pressure. Limitations of these techniques in the different flow regimes, related to the primary and secondary breakups as well as coalescence, are provided. Results indicate that all three techniques provide similar results throughout the different regimes. Shadowgraph and PDPA were possible in the secondary atomization and coalescence regimes while PIV measurements could be made only at the end of secondary atomization and coalescence.

五轴框架式机器人激光加工系统 轨迹算法研究

在集成化智能激光加工系统工作原理的基础上提出了五轴机器人的激光加工轨迹算法。将三维离散数据点集拟合为空间参数曲面，在此参数曲面上规划五轴激光加工的等距轨迹。给出了冲压模具激光强化加工实例。取得了理想的加工效果。

集成化激光制造系统的轴件焊接控制工艺

针对轴形零件实际焊接加工中遇到的困难，利用现场总线、串口通信和GALIL运动控制卡实现了上位计算机对激光器、机器人以及旋转台等系统的同步控制，提出了集成化激光制造系统的多种控制工艺焊接方法。对轴形零件进行了各种激光焊接控制工艺的实验研究，证明了此控制系统可实现多种焊接控制工艺，可以满足轴形零件激光焊接中变速度、变功率、偏角度等各种工艺条件焊接的需求，为轴形零件实际激光焊接中遇到的焊接过程不稳定、首尾衔接处凹坑缺陷等难题的解决提供了新的方法。编程采用VC＋＋面向对象工具加以实现。

集成激光制造系统的开放式控制研究

针对激光制造系统的发展要求,提出了一种开放式集成激光制造系统,该系统将激光器控制模块、测量模块、机器人模块和计算机控制模块等进行集成,采用模块化设计方法,各模块功能独立,实现了主控计算机对各控制模块的协调控制.其中激光器由PROFIBUS-DP现场总线控制,机器人由运动控制器控制.解决了传统激光制造系统结构封闭,专用性强,难于实现柔性化制造的难题.通过实际应用,进一步证明了该系统的开放性和可控性.

五轴框架式机器人激光加工系统轨迹算法研究

在集成化智能激光加工系统工作原理的基础上提出了五轴机器人的激光加工轨迹算法。将三维离散数据点集拟合为空间参数曲面，在此参数曲面上规划五轴激光加工的等距轨迹。给出了冲压模具激光强化加工实例，取得了理想的加工效果。

集成激光制造系统加工过程计算机模拟

激光制造是一种有别于传统方式的先进制造系统.针对集成激光制造系统,在分析其结构组成及激光加工特点的基础上,得到了机器人运动学逆解表达式,提出了一种基于碰撞检测的三角网格简化算法,设计并建立了模拟系统的模块化结构.基于VC开发环境并使用OpenGL图形接口技术开发了集成化激光制造系统加工过程计算机模拟系统,为工艺规划和优化提供有效支持,并实现了系统的通用性、易维护性和可扩展性.