Context-awareness is becoming critical for mo- bile and ubiquitous computing, where the application needs dynamically adapt its behavior to its execution environment. Context-oriented programming （COP） languages sup...Context-awareness is becoming critical for mo- bile and ubiquitous computing, where the application needs dynamically adapt its behavior to its execution environment. Context-oriented programming （COP） languages support dy- namic behavior adaptation, however, they do not support dy- namic layer addition. As a result, they provide little support for the runtime adaptation of application behavior in case that unpredictable execution environments are encountered. Furthermore, block-structured constructs for layer activation hardly support fine-grain adaptation and separate changes of contexts and execution of context-specific methods with dif- ficulty. In this paper, we propose a virtual machine （VM）- centric approach to address these issues. It incorporates ob- ject composition and delegation into the VM to implement layer activation, and extends existing VM services to sup- port dynamic layer addition. To ensure that our approach preserves the type safety properties of the program, we de- velop a calculus built on featherweight Java （FJ） to describe the approach, focus on type-checking issues, and prove type soundness of the calculus. We also present the implementa- tion and evaluation of our approach. The evaluation demon- strates that our approach has advantages over the compiler- based approach proposed by JCOP.展开更多
A series of Cu-doped La-Ni intermetallic compounds(LaN5-xCux, x = 0-4) was studied. The bulk structure and surface composition of the samples were detected before and after they were used as catalyst for nitrobenzene ...A series of Cu-doped La-Ni intermetallic compounds(LaN5-xCux, x = 0-4) was studied. The bulk structure and surface composition of the samples were detected before and after they were used as catalyst for nitrobenzene hydrogennation. The catalytic properties of the intermetallic compounds depend on the surface region composition, especially on the valence of the metal ions.展开更多
为了研究菱镁矿在不同温度轻烧后的显微结构与活性，取粒度＜0．074 mm 的菱镁矿粉分别在850、900、950、1000、1050、1100、1150和1200℃保温2 h 煅烧制备了轻烧镁粉。采用柠檬酸溶解－EDTA 络合滴定法测定了试样中活性氧化镁的含量，...为了研究菱镁矿在不同温度轻烧后的显微结构与活性，取粒度＜0．074 mm 的菱镁矿粉分别在850、900、950、1000、1050、1100、1150和1200℃保温2 h 煅烧制备了轻烧镁粉。采用柠檬酸溶解－EDTA 络合滴定法测定了试样中活性氧化镁的含量，并利用 XRD 和 SEM对试样的物相组成和显微结构进行了分析。结果表明：在850～1050℃阶段，方镁石的晶粒尺寸增加缓慢，其活性氧化镁含量变化并不明显，均高于80％（w）；在1050～1200℃阶段，方镁石的晶粒尺寸快速增加，其活性氧化镁含量快速降低。展开更多
文摘Context-awareness is becoming critical for mo- bile and ubiquitous computing, where the application needs dynamically adapt its behavior to its execution environment. Context-oriented programming （COP） languages support dy- namic behavior adaptation, however, they do not support dy- namic layer addition. As a result, they provide little support for the runtime adaptation of application behavior in case that unpredictable execution environments are encountered. Furthermore, block-structured constructs for layer activation hardly support fine-grain adaptation and separate changes of contexts and execution of context-specific methods with dif- ficulty. In this paper, we propose a virtual machine （VM）- centric approach to address these issues. It incorporates ob- ject composition and delegation into the VM to implement layer activation, and extends existing VM services to sup- port dynamic layer addition. To ensure that our approach preserves the type safety properties of the program, we de- velop a calculus built on featherweight Java （FJ） to describe the approach, focus on type-checking issues, and prove type soundness of the calculus. We also present the implementa- tion and evaluation of our approach. The evaluation demon- strates that our approach has advantages over the compiler- based approach proposed by JCOP.
文摘A series of Cu-doped La-Ni intermetallic compounds(LaN5-xCux, x = 0-4) was studied. The bulk structure and surface composition of the samples were detected before and after they were used as catalyst for nitrobenzene hydrogennation. The catalytic properties of the intermetallic compounds depend on the surface region composition, especially on the valence of the metal ions.
文摘为了研究菱镁矿在不同温度轻烧后的显微结构与活性，取粒度＜0．074 mm 的菱镁矿粉分别在850、900、950、1000、1050、1100、1150和1200℃保温2 h 煅烧制备了轻烧镁粉。采用柠檬酸溶解－EDTA 络合滴定法测定了试样中活性氧化镁的含量，并利用 XRD 和 SEM对试样的物相组成和显微结构进行了分析。结果表明：在850～1050℃阶段，方镁石的晶粒尺寸增加缓慢，其活性氧化镁含量变化并不明显，均高于80％（w）；在1050～1200℃阶段，方镁石的晶粒尺寸快速增加，其活性氧化镁含量快速降低。
