摘要：高效非贵金属催化剂对于推进析氢反应(HER)的大规模工业化至关重要.碳化钼(Mo_(2)C)因其类似铂的能带密度和优良的中间产物吸附特性,有望替代贵金属基材料成为具有前景的催化剂.然而,它在常规制备过程中存在严重的晶体过度生长和团聚问题,导致催化效率低.本研究利用三聚氰胺辅助法制备了含有丰富表面和界面的超细碳化钼/氮化钼(Mo_(2)C/Mo_(2)N)异质结构,并同时将其嵌入到氮掺杂碳纳米纤维(CNFs)中.Mo_(2)C/Mo_(2)N异质结构的协同作用与超细纳米晶表面暴露的丰富活性位点共同提高了电催化活性,而氮掺杂碳纳米纤维框架保证了快速的电荷转移和良好的结构稳定性.此外,原位形成的Mo_(2)C/Mo_(2)N晶体与碳基质之间存在较强的界面耦合作用,进一步提高了电子电导率和电催化活性.得益于这些优势,Mo_(2)C/Mo_(2)N@N-CNFs在碱性溶液中表现出优异的电催化析氢性能,在电流密度10 mV cm^(-2)时具有75 mV的低过电势,优于单相Mo_(2)C@N-CNFs对比样以及近期报道的Mo_(2)C/Mo_(2)N基催化剂.这个合成方法集成了异质结构、纳米化和碳修饰策略,为设计高效率电催化材料提供了新的参考.

摘要：Rapid developing information retrieval technology has become one of the most important means of obtaining useful information from massive web resources. However, traditional keyword-based information retrieval has encountered several major bottlenecks, such as theme drift, low recall and meaning lacking. Combining topic information retrieval with ontology-based semantic technology is one of those effective methods to improve above mentioned shortages. To prove the idea, this paper tries to design and implement a retrieval system based on the computer technology domain ontology, which is constructed on basis of the existing ontology theory. For better effect, this paper makes some improvements to the existing semantic similarity algorithms and designs a new query expansion algorithm. Results show that the prototype system acts efficiently on query extension and topic information search. To certain extent, it improves the recall and precision of keyword based retrieval system.

摘要：Facing on the increasing CAD product data owned by manufacturing enterprises, apparently few of contemporary document version management methods can satisfy customers" requirements. Considering the developing actuality of CAD document version management in domestic manufacturing, this paper proposes a version finalizing method based on PLM platform and employs ENOVIA as its implementing platform. After emphasizing current demand for version finalization during the entire product designing process, it introduces a detailed presentation of the constraint condition and specific implementing methods of proposed CAD document version finalization. The experimental results in PLM projects shows us that appropriate implementing method of version finalization could facilitate the identification of working version or release version, standardize the product design flow, reduce the frequency of engineering modifications, and effectively shorten the period of product design cycle.