硅单电子晶体管的制造及特性

报道了采用电子束光刻、反应离子刻蚀及热氧化等工艺,在p型SIMOX(separation by implanted oxygen)硅片上成功制造的一种单电子晶体管.特别是,提供了一种制造量子线和量子点的工艺方法,在器件的电流-电压特性上观测到明显的库仑阻塞效应和单电子隧穿效应.器件的总电容约为9.16aF.在77K工作温度下,也观测到明显的电流-电压振荡特性.     

Automated post scoring: evaluating posts with topics and quoted posts in online forum

Online forumpost evaluationis an effective way for instructors to assess students’ knowledge understanding and writing mechanics. Manually evaluating massive posts costs a lot of time. Automatically grading online posts could significantly alleviate instructors’ burden. Similar text assessment tasks like Automated Text Scoring evaluate the writing quality of independent texts or relevance between text and prompt. And Automatic Short Answer Grading measures the semantic matching of short answers according to given problems and correct answers. Different from existing tasks, we propose a novel task, Automated Post Scoring (APS), which grades all online discussion posts in each thread of each student with given topics and quoted posts. APS evaluates not only the writing quality of posts automatically but also the relevance to topics. To measure the relevance, we model the semantic consistency between posts and topics. Supporting arguments are also extracted from quoted posts to enhance posts evaluation. Specifically, we propose a mixture model including a hierarchical text model to measure the writing quality, a semantic matching model to model topic relevance, and a semantic representation model to integrate quoted posts. We also construct a new dataset called Online Discussion Dataset containing 2,542 online posts from 694 students of a social science course. The proposed models are evaluated on the dataset with correlation and residual based evaluation metrics. Compared with measuring posts alone, experimental results demonstrate that incorporating topics and quoted posts could improve the performance of APS by a large margin, more than 9 percent on QWK.

     

基于协作反馈控制算法的车联网行车安全动态强化模型

针对车联网（IoV）环境下,单车的信息采集和处理能力不足以满足时间敏感的行车安全应用需求,需要通过多车协作增强车间信息共享和信道接入能力等问题,提出一种基于协作反馈控制算法的行车安全动态强化模型。首先,提出虚拟车队协作模型,提升交通信息的采集精度,扩大采集范围,建立车间的稳定协作关系,在形成协作虚拟车队的同时降低信道拥塞;然后,实现一个针对消息传输和驾驶控制的联合优化模型,通过异构交通数据的深度融合最大化IoV的安全效用;最后,在对车流量时空变化进行预测的基础上,提出自适应的反馈控制模型实时调整驾驶安全策略。仿真结果表明,所提出的行车安全动态强化模型在各种车流分布模型下,均能够取得良好的性能指标,可以有效支持驾驶辅助控制系统,在保障行车安全的同时降低信道拥塞。     

Context reasoning using extended evidence theory in pervasive computing environments

Most existing context reasoning approaches implicitly assume that contexts are precise and complete. This assumption cannot be held in pervasive computing environments, where contexts are often imprecise and incomplete due to unreliable connectivity, user mobility and resource constraints. To this end, we propose an approach called CRET: Context Reasoning using extended Evidence Theory. CRET applies the evidence theory to context reasoning in pervasive computing environments. Because evidence theory is limited by two fundamental problems–computation-intensiveness and Zadeh paradox, CRET presents evidence selection and conflict resolution strategies. Empirical study shows that CRET is desirable for pervasive applications.     

On the source switching problem of Peer-to-Peer streaming

Peer-to-Peer(P2P) streaming has been proved a popular and efficient paradigm of Internet media streaming. In some applications, such as an Internet video distance education system, there are multiple media sources which work alternately. A fundamental problem in designing such kind of P2P streaming system is how to achieve fast source switching so that the startup delay of the new source can be minimized. In this paper, we propose an efficient solution to this problem. We model the source switch process, formulate it into an optimization problem and derive its theoretical optimal solution. Then we propose a practical greedy algorithm, named fast source switch algorithm, which approximates the optimal solution by properly interleaving the data delivery of different media sources. The algorithm can adapt to the dynamics and heterogeneity of real Internet environments. We have carried out extensive simulations on various real-trace P2P overlay topologies to demonstrate the effectiveness of our model and algorithm. The simulation results show that our proposed algorithm outperforms the normal source switch algorithm by reducing the source switch time by 20%–30% without bringing extra communication overhead. The reduction in source switching time is more obvious as the network scale increases.     

自由旋转珠杆链分子模型的Brown动力学模拟

利用聚合物分子理论,推导了自由旋转珠杆链分子模型在广义坐标下的伊藤型随机微分方程(朗之万方程),构造了相应的Brown动力学模拟算法,首次研究了该模型在定常剪切流和拉伸流中的动力学行为及其流变性质,并在微机上利用MATHE-MATICA软件实现了流动中高分子微观结构形态演变的动态显示.     

布朗合成氨工艺的蒸汽平衡

针对合成装置蒸汽系统在生产过程中暴露出的问题,进行原因分析,通过优化调整和技术改造加以解决。     

宅基地价值化及其在城中村改造中的应用研究——以义乌经济开发区为例

城中村改造既是政府的难题,又是业界讨论的热点。科学定量地界定城中村改造所涉及的相关利益群体,特别是城市与城中村居民的利益分配是解决城中村改造问题的关键。综合运用产权理论、地租理论、区位理论和报酬资本化理论,对宅基地产权权能的释放、城中村住房收益来源、城中村的住房价值等进行分析,结果表明,通过宅基地价值化,实现城中村居民的"高层公寓式安置",既有利于城市的可持续发展,也有利于增加城中村居民的利益,是一种实现城市与城中村居民利益双赢的办法。     

Sensitive determination of parabens in soy sauces by capillary zone electrophoresis with amperometric detection

A high-performance capillary zone electrophoresis with amperometric detection (CZE-AD) method has been developed for the separation and sensitive determination of the preservatives methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in soy sauce samples. The effects of several factors such as the pH and concentration of running buffer, the separation voltage, the applied potential and the injection time on CZE-AD were investigated. Under the optimum conditions, four preservatives can be well separated within 16 min at the separation voltage of 16 kV in a 80 mmol/L borax running buffer (pH 9.94), and adequate extraction was obtained with ethanol for the determination of the above four parabens. Satisfactory recovery (95.0–102.0%), repeatability of the peak current (≤2.4%) and migration time (≤0.5%) of four analytes, as well as detection limits (5.7 × 10⁻⁸–4.4 × 10⁻⁸ g/mL) for the method, were achieved. This proposed procedure has been successfully used for the analysis of paraben preservatives in soy sauce samples, and the content of EP was from 0.08 to 0.14 mg/mL in the tested samples.