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31.
It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.This research was supported by the Highly Advanced National Project (http://www.most.go.kr), which performs some of the National R&D Program, and sponsored by the Korean Ministry of Science and Technology under the contract project code M10214000116-02B1500-02010. 相似文献
32.
Giorgio Vittadini Marco Fattore Pietro G. Lovaglio 《Computational statistics & data analysis》2007,51(12):5828-5846
A new approach for the estimation and the validation of a structural equation model with a formative-reflective scheme is presented. The basis of the paper is a proposal for overcoming a potential deficiency of PLS path modeling. In the PLS approach the reflective scheme assumed for the endogenous latent variables (LVs) is inverted; moreover, the model errors are not explicitly taken into account for the estimation of the endogenous LVs. The proposed approach utilizes all the relevant information in the formative manifest variables (MVs) providing solutions which respect the causal structure of the model. The estimation procedure is based on the optimization of the redundancy criterion. The new approach, entitled redundancy analysis approach to path modeling (RA-PM) is compared with both traditional PLS Path Modeling and LISREL methodology, on the basis of real and simulated data. 相似文献
33.
分析了连杆滚轮式水力自动翻板闸门的运动轨迹,并由此得出闸门动、静坐标系间的转换关系.结合翻板闸门的运转机理,探讨了闸门在运行过程中的瞬心轨迹线及其对闸门稳定性的影响.结果表明,通过优化闸门结构可调整“瞬心”的位置,保证闸门运转的稳定性. 相似文献
34.
We report an unexpectedly rich variety of new flow patterns on a granular heap that is centrifuged so as to simulate a reduction
in gravity. These surface patterns exhibit coexisting static and flowing regions that depend strongly on centrifugal stress,
but surprisingly not on mass flow rate. A discrete cellular automata model reproduces some of the patterning features and
indicates that subsurface jamming may precipitate the formation of localized frozen patterns on the surface. This model provides
insights into the mechanics of granular flows under controlled stress environment and jammed-to-flowing transitions in granular
media. 相似文献
35.
Maarja Kruusmaa 《Journal of Intelligent and Robotic Systems》2003,38(1):55-83
This paper presents a self-adapting approach to global level path planning in dynamic environments. The aim of this work is to minimize risk and delays in possible applications of mobile robots (e.g., in industrial processes). We introduce a hybrid system that uses case-based reasoning as well as grid-based maps for decision-making. Maps are used to suggest several alternative paths between specific start and goal point. The casebase stores these solutions and remembers their characteristics. Environment representation and casebase design are discussed. To solve the problem of exploration vs. exploitation, a decision-making strategy is proposed that is based on the irreversibility of decisions. Forgetting strategies are discussed and evaluated in the context of case-based maintenance. The adaptability of the system is evaluated in a domain based on real sensor data with simulated occupancy probabilities. Forgetting strategies and decision-making strategies are evaluated in simulated environments. Experiments show that a robot is able to adapt in dynamic environments and can learn to use paths that are less risky to follow. 相似文献
36.
ListofSymbol B———Buoyancy ,m·s- 2 ; c———Concentrationofsoluteelement ; Cμ———Turbulentconstant; D———Diffusivityofsoluteelement ,m2 ·s- 1 ; fl,fs———Liquidandsolidfraction ; fμ———Turbulentcoefficient ; h———Enthalpy ,J·kg- 1 ; k———Turbulentkineticenergy ,m2 ·s- 2 ; kp———Equilibriumpartitioncoefficient; Kp———Permeabilityofmushyzone ,m2 ; K0 ———Permeabilitycoefficient; p———Pressure ,Pa ; Pr———Prandtlnumber ;… 相似文献
37.
This paper is a summary of an extensive research program carried out by the authors on the structure of rapidly solidified aluminum alloys; and a comparison with the work of others also involved in this field. The paper discusses the changes in the dendritic and non-dendritic structure of the matrix at cooling rates from 10–3 to 1010 K/s and discusses the hetergeneity of the structure caused by interdendritic-segretion during solidification. 相似文献
38.
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40.
利用ZM定向凝固装置研究了镍基单晶高温合金DD3在高温度梯度(700~1200K/cm)定向凝固条件下的微观组织演化特征及其对工艺参数的响应函数,结果表明:该合金在高界面温度梯度条件下,柱晶生长速度范围向高速区扩展,从而使单晶亚结构细化成为可能。所得单晶棒中亚结构一次间距可比传统HRS法定向凝固籽晶中相应尺度减小5~10倍。本文还对其组织演化机制进行了分析。 相似文献