Multiply Charged Conjugated Polyelectrolytes as a Multifunctional Interlayer for Efficient and Scalable Perovskite Solar Cells

A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm²) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s.     

Scalable and Structured Scheduling

Scheduling a program (i.e. constructing a timetable for the execution of its operations) is one of the most powerful methods for automatic parallelization. A schedule gives a blueprint for constructing a synchronous program, suitable for an ASIC or VLIW processor. However, constructing a schedule entails solving a large linear program. Even if one accepts the (experimental) fact that the Simplex is almost always polynomial, the scheduling time is of the order of a large power of the program size. Hence, the method does not scale well. The present paper proposes two methods for improving the situation. First, a large program can be divided into smaller units (processes), which can be scheduled separately. This is structured scheduling. Second, one can use projection methods for solving linear programs incrementally. This is specially efficient if the dependence graph is sparse.     

Quality Control for Scalable Media Processing Applications

Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load situation, deadline misses are likely to occur. This problem can be dealt with by designing media processing applications in a scalable fashion. A scalable media processing application can run in multiple qualities, leading to correspondingly different resource demands. The problem we consider is to find an accompanying quality control strategy, which minimizes both the number of deadline misses and the number of quality changes, while maximizing the quality of processing. We present an initial approach to the above problem by modeling it as a Markov decision process (MDP). Our model is based on measuring relative progress at milestones. Solving the MDP results in a quality control strategy that can be applied during runtime with only little overhead. We evaluate our approach by means of a practical example, which concerns a scalable MPEG-2 decoder.     

分布式无线传感器网络通信协议研究

在归纳分布式无线传感器网络研究进展的基础上，给出了综合分布式无线传感器网络技术各个方面的协议体系结构，并在新的体系结构下，系统地阐述了分布式无线传感器网络通信协议研究的进展，介绍了典型的应用案例和国外相关计划的研究情况。最后，指明了这一处于发展初期的研究领域的未来发展方向。     

Layered Video and Differentiated Coding for Adaptive QoS in Mixed Wired-Satellite Networks

Mobile networks are becoming nothing but a way to allow ubiquitous access to multimedia services. To allow efficient use of resources, new systems provide flexible bandwidth and different error protection techniques to match channel behavior. As the backbone network is increasingly becoming based on packet techniques and in particular on IP and related transport protocols, end to end service quality must be analyzed considering both the fixed and the mobile part. Source scalability may help in coping with a mixed and heterogeneous environment. In this work we present some results of a transmission chain comprising a scalable MPEG-2 coder, an IP network and a radio access exploiting the availability of satellites. It is shown that for a given target rate, differentiated coding can be exploited to achieve decodability and good quality at a channel SNR much lower that single layer streams. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于P2P的云计算模型及其安全性分析

文章通过将P2P技术和云计算相结合,提出了一种可靠的、可扩展的、低成本的文件共享模型PA-Cloud。该文介绍了PA-Cloud的文件下载和更新过程,并对系统的安全性进行了分析。通过对PA-Cloud进行对比实验表明,PA-Cloud可以有效提高系统的可扩展性,降低服务提供商的成本。     

极大规模并行计算系统趋势分析

高性能计算技术以加速度迅猛发展,继千万亿次系统研制成功以后,超级计算机的性能又快速提升至数万万亿次,国际学术界与工业界普遍预期在2018年左右将出现极大规模并行的百万万亿次系统(Exascale Computing,简称E级系统)。本文从最新一届TOP500榜单入手分析了超级计算领域的技术动态,在此基础上,探讨了未来E级系统的发展趋势及其所面临的能耗、可扩展、可靠性和可编程性等关键技术问题。     

基于Web的重点建设项目管理系统

为提高重点建设项目的管理水平和工作效率,在详细分析重点建设项目的业务流程和用户需求的基础上,提出基于Web的重点建设项目信息管理系统。该系统采用典型的三层体系架构,具有较强的可扩展性和灵活性。通过该系统对重点建设项目信息科学管理,可以有效克服传统管理方式的弊端,极大地提高重点建设项目信息管理工作的效率。     

基于变色龙hash的区块链可扩展存储方案

区块链中的节点以副本形式保存数据,随着时间的推移,区块链中的区块数不断增加,导致节点承受的存储压力随之增大,存储压力成为区块链应用落地的瓶颈之一。为了解决区块链中存储压力问题,提出了基于变色龙hash的区块链可扩展存储方案,该方案利用节点被攻击成功的概率和改进的温度模型,将区块分为高低安全性的冷热区块;基于变色龙hash算法和改进的Merkle tree,对高安全性的冷区块进行部分节点存储。在存储过程中,除高安全性冷区块的区块体信息被重构外,其余数据保持不变。仿真实验表明,在不改变区块链结构和安全性能的情况下,所提出的方案可减少区块链中数据的存储总量,减少存储节点的存储压力;且区块数量越多,其优势越明显。     

面向图计算的运行时系统的消息聚合技术

图计算应用的通信模式以时空随机的点对点细粒度通信为主,但现有高性能计算机的网络系统应对大量细粒度通信时表现不佳,进而影响整体性能。虽然在应用层进行通信优化可以有效提升图计算应用性能,但这会给应用开发人员带来很大的负担,因此提出并实现结构动态的消息聚合技术,通过构建虚拟拓扑的方法在通信路径上增加中间点从而提升消息聚合的效果。传统的消息聚合策略一般仅在通信源或者目的地上进行,聚合机会有限,而所提技术通过灵活调整虚拟拓扑的结构和配置适应了不同硬件条件和应用特征。同时,还提出并实现了面向图计算的有消息聚合的运行时系统,这使得在程序迭代执行时可以动态选择参数,从而减少开发人员负担。在256节点规模的系统上实验的结果显示,使用所提消息聚合技术优化后的典型图计算应用的性能可得到100%以上的提升。