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131.
132.
For Al-11.6 % Si alloy, the influence of the addition of Sr on the morphology of the dendrite α phase was investigated, and the characteristic parameters of the dendrite α phase, the primary dendrite spacing and the secondary dendrite arm spacing, were also measured. The addition of strontium promotes the columnar dendrite growth and leads to a decrease of both the primary dendrite spacing and secondary dendrite arm spacing with the increase of the content of strontium in the modified near-eutectic Al-Si alloys. It is thought that the addition of Sr leads to a reduction of the solid-liquid interfacial energy of the dendrite α phase, consequently resulting in a decrease of the growth undercooling of dendrite tips. And hence, the nucleation of the equiaxed grains in the liquid in front of the columnar dendrite tips is restrained, thus the addition of strontium in Al-Si alloys promotes the growth of the columnar dendrites. The reduction of the solid-liquid interfacial energy also leads to the decreases in the primary dendrite spacing and the secondary dendrite arm spacing. 相似文献
133.
过共晶铝硅自生梯度复合材料的组织与性能 总被引:20,自引:0,他引:20
用电磁分离工艺成功制备了初生Si相体积分数、材料显微硬度和耐磨性沿径向呈梯度分布的棒状复合材料 ,讨论了梯度层的形成过程。微观组织观察和力学性能测试结果表明 :在近外壁区域形成了体积分数高达16 %的细小初生Si相偏聚区 ,此区硬度高 ,耐磨性好 ,中心区为细小和均匀的共晶组织 ,两部分之间为颗粒体积分数渐变的过渡区 ,可使耐磨层与基体的结合强度得到保证 相似文献
134.
R. Hunter J. Rios J.M. Perez A. Vizan 《International Journal of Machine Tools and Manufacture》2006,46(6):683-697
The design of machining fixtures is a highly complex process that relies on designer experience and his/her implicit knowledge to achieve a good design. In order to facilitate its automation by the development of a knowledge-based application, the explicit definition of the fixture design process and the knowledge involved is a prior and a fundamental task to undertake. Additionally, a fundamental and well-known engineering principle should be considered: the functional requirements and their associated constraints should be the first input to any design process. Considering these two main ideas, this paper presents the development undertaken to facilitate the automation of the fixture design process based on a functional approach.In this context, the MOKA methodology has been used to elicit fixtures knowledge. IDEF0 and UML have been used to represent the fixture design process. A methodology based on the function concept and aiming to formalize such design process is proposed. Fixture functional requirements have been defined and formalized. Functional fixtures elements have been used to create a functional design solution, the link of these elements with the functional requirements and with typical commercial fixture components has been defined via tables and rules mapping. And finally, a prototype knowledge-based application has been developed in order to make an initial validation of the proposed methodology. 相似文献
135.
136.
针对锦屏二级水电站引水隧洞长,机组容量大、运行水头高,导致调压室水位波动稳定性以及机组间的水力干扰等较为突出的问题,对一次调频进行了深入分析研究,在满足电网安全的前提下,通过对机组一次调频进行仿真计算,得到了各种模拟工况下的机组开度、功率和转速的变化情况,为机组正常投入运行提供了可靠保证。 相似文献
137.
Architectural design decisions (ADDs) have been used in recent years for capturing design rationale and documenting architectural knowledge (AK). However, various architectural design views still provide the most common means for describing and communicating architectural design. The evolution of software systems requires that both ADDs and architectural design views are documented and maintained, which is a tedious and time-consuming task in the long run. Also, in lack of a systematic and automated support for bridging between ADDs and architectural design views, decisions and designs tend to become inconsistent over time. In our proposal, we introduce a reusable AK transformation language for supporting the automated transformation of reusable AK knowledge to component-and-connector models, the architectural design view used most commonly today. In addition, reusable consistency checking rules verify the consistency between decisions and designs. We evaluate our approach in an industrial case study and show that it offers high reusability, provides automation, and can, in principle, deal with large numbers of recurring decisions. 相似文献
138.
We present a flexible initial framework for defining self‐motivated, self‐aware agents in simulated worlds, planning continuously so as to maximize long‐term rewards. While such agents employ reasoned exploration of feasible sequences of actions and corresponding states, they also behave opportunistically and recover from failure, thanks to their continual plan updates and quest for rewards. Our framework allows for both specific and general (quantified) knowledge and for epistemic predicates such as knowing‐that and knowing‐whether. Because realistic agents have only partial knowledge of their world, the reasoning of the proposed agents uses a weakened closed‐world assumption; this has consequences for epistemic reasoning, in particular introspection. The planning operators allow for quantitative, gradual change and side effects such as the passage of time, changes in distances and rewards, and language production, using a uniform procedural attachment method. Question answering (involving introspection) and experimental runs are shown for our particular agent ME in a simple world, demonstrating the value of continual deliberate, reward‐driven planning. Though the primary merit of agents definable in our framework is that they combine all of the aforementioned features, they can also be configured as single or multiple goal‐seeking agents and as such perform comparably with some recent experimental agents. 相似文献
139.
Jean-Gabriel Ganascia 《人工智能实验与理论杂志》2015,27(1):23-35
The notion of level of abstraction (LoA) is one of the foundations of the Floridi's Philosophy of Information. It also serves for many practical purposes as in information ethics. But the notion of abstraction is not new; it has been given many different meanings in various fields, especially in scientific disciplines and, in particular, in computer science. Our purpose here is to examine the use of abstraction in Floridi's works in conjunction with some of the meanings of abstraction in computer science. The article is divided into five sections. After a general introduction to the Floridi's method of abstraction (MoA) in Section 1, Section 2 revisits Floridi's definition of abstraction and Section 3 gives the different senses of abstraction in computer science. The Section 4 compares them with the Floridi's LoAs and proposes to generalise the Floridi's approach to abstraction using an abstraction of the LoAs, while Section 5 concludes on what we think to be some new arguments in favour of MoA and LoA. 相似文献
140.
针对融合识别领域中不同框架下多源异类传感器的不确定证据信息无法有效融合的问题, 提出一种基于条件证据网络的多源异类知识融合识别方法. 该方法将战场协同作战中不同框架下多源异类传感器的领域知识统一在证据网络的结构下, 形成多源异类知识融合识别模型, 对多源异类传感器的不确定性证据信息进行基于条件证据网络的融合推理, 得到识别结果. 仿真实例验证了所提出方法的优越性.
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