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排序方式: 共有116条查询结果,搜索用时 250 毫秒
71.
Chao Zhang Chenbao Lu Shuai Bi Yang Hou Fan Zhang Ming Cai Yafei He Silvia Paasch Xinliang Feng Eike Brunner Xiaodong Zhuang 《Frontiers of Chemical Science and Engineering》2018,12(3):346-357
Porous polymers have been recently recognized as one of the most important precursors for fabrication of heteroatom-doped porous carbons due to the intrinsic porous structure, easy available heteroatom-containing monomers and versatile polymerization methods. However, the heteroatom elements in as-produced porous carbons are quite relied on monomers. So far, the manipulating of heteroatom in porous polymer derived porous carbons are still very rare and challenge. In this work, a sulfur-enriched porous polymer, which was prepared from a diacetylene-linked porous polymer, was used as precursor to prepare S-doped and/or N-doped porous carbons under nitrogen and/or ammonia atmospheres. Remarkably, S content can sharply decrease from 36.3% to 0.05% after ammonia treatment. The N content and specific surface area of as-fabricated porous carbons can reach up to 1.32% and 1508 m2·g−1, respectively. As the electrode materials for electrical double-layer capacitors, as-fabricated porous carbons exhibit high specific capacitance of up to 431.6 F·g−1 at 5 mV·s−1 and excellent cycling stability of 99.74% capacitance retention after 3000 cycles at 100 mV·s−1. Furthermore, as the electrochemical catalysts for oxygen reduction reaction, as-fabricated porous carbons presented ultralow half-wave-potential of 0.78 V versus RHE. This work not only offers a new strategy for manipulating S and N doping features for the porous carbons derived from S-containing porous polymers, but also paves the way for the structure-performance interrelationship study of heteroatoms co-doped porous carbon for energy applications. 相似文献
72.
In this study we evaluated the relation between exposure of the ear canal to cold water and development of exostosis. Furthermore we wanted to evaluate the clinical outcome of surgical removal of the exostosis. The material consisted of a group of 15 winter bathers who had been exposed to cold water over a period varying from three to 45 years. All but one subject who had exposed the ear canal to cold water had developed exostoses of the ear canals. Follow-up examinations of nine patients after surgical removal of the exostosis revealed normal, well calibrated ear canals. Three winter bathers who continued the exposure to cold water developed a new exostosis. 相似文献
73.
The article reports on the current status of West German energy policy, and in a sense it is a case study of a predominantly, though not purely, market-oriented approach. It presents some interesting facts and figures on the West German energy economy, and although written in an introductory fashion, leads the reader into the heart of current energy policy issues. The short retrospective demonstrates the remarkable success of the market-oriented approach to energy policy. The main current problems are the implementation of stricter environmental standards and the structural adjustments of the domestic coal and refining industries. A short discussion on future perspectives shows that total primary energy demand up to the end of the century is likely to remain stagnant, while further marked progress in energy efficiency can be expected. 相似文献
74.
Eike Venzmer Alexander Kronenberg Martin Jourdan 《Journal of Superconductivity and Novel Magnetism》2016,29(4):897-903
Planar tunneling junctions of the presumably unconventional superconductor FeSe were prepared and investigated. The junctions consisted of rf-sputtered FeSe/AlO x /Ag multilayers patterned lithographically into mesa structures. Bias voltage-dependent differential conductivities dI/dV(V) of junctions in the tunneling, intermediate barrier strength, and metallic regimes were investigated. Depending on the barrier type between two to four features of the conductivity were obtained, which are discussed in the framework of multiple superconducting energy gaps. Specifically, we reproduced with all barrier types two established energy gaps and identified another feature as presumably originating from an additional large superconducting gap. A further conductivity feature could be associated with a resonant state. 相似文献
75.
Eike Kiltz Krzysztof Pietrzak Daniele Venturi David Cash Abhishek Jain 《Journal of Cryptology》2017,30(4):1238-1275
We construct efficient authentication protocols and message authentication codes (MACs) whose security can be reduced to the learning parity with noise (LPN) problem. Despite a large body of work—starting with the \({\mathsf {HB}}\) protocol of Hopper and Blum in 2001—until now it was not even known how to construct an efficient authentication protocol from LPN which is secure against man-in-the-middle attacks. A MAC implies such a (two-round) protocol. 相似文献
76.
Substantial Cyano‐Substituted Fully sp2‐Carbon‐Linked Framework: Metal‐Free Approach and Visible‐Light‐Driven Hydrogen Evolution 下载免费PDF全文
Shuai Bi Zhi‐An Lan Silvia Paasch Wenbei Zhang Yafei He Chao Zhang Feng Liu Dongqing Wu Xiaodong Zhuang Eike Brunner Xinchen Wang Fan Zhang 《Advanced functional materials》2017,27(39)
Polymeric semiconductors are emerging as a kind of competitive photocatalysts for hydrogen evolution due to their well‐tunable structures, versatile functionalization, and low‐cost processibility. In this work, a series of conjugated porous polymers with substantial cyano‐substituted fully sp2‐carbon frameworks are efficiently synthesized by using electron‐deficient tricyanomesitylene as a key building block to promote an organic base‐catalyzed Knoevenagel condensation with various aldehyde‐substituted arenes. The resulting porous polymers feature donor‐acceptor structures with π‐extended conjugation, rendering them with distinct semiconducting properties. They possess hierarchically porous structures, nanoscale morphologies, and intriguing wettability. These promising physical characters, finely tailorable by varying the arene units, are essentially relevant to the abundant cynao substituents over the whole frameworks. The as‐prepared porous polymers exhibit excellent visible‐light‐driven photocatalytic activity for water‐splitting hydrogen evolution with apparent quantum yield up to 2.0% at 420 nm or 1.9% at 470 nm, among the highest values yet reported for porous polymer‐based photocatalysts, also representing the first example of such kinds of catalysts formed through a metal‐free‐catalyzed carbon–carbon coupling reaction. 相似文献
77.
Sebastian Breß Felix Beier Hannes Rauhe Kai-Uwe Sattler Eike Schallehn Gunter Saake 《Information Systems》2013
Specialized processing units such as GPUs or FPGAs provide great opportunities to speed up database operations by exploiting parallelism and relieving the CPU. However, distributing a workload on suitable (co-)processors is a challenging task, because of the heterogeneous nature of a hybrid processor/co-processor system. In this paper, we present a framework that automatically learns and adapts execution models for arbitrary algorithms on any (co-)processor. Our physical optimizer uses the execution models to distribute a workload of database operators on available (co-)processing devices. We demonstrate its applicability for two common use cases in modern database systems. Additionally, we contribute an overview of GPU-co-processing approaches, an in-depth discussion of our framework's operator model, the required steps for deploying our framework in practice and the support of complex operators requiring multi-dimensional learning strategies. 相似文献
78.
Myrto Arapinis Loretta Ilaria Mancini Eike Ritter Mark Dermot Ryan 《International Journal of Information Security》2017,16(5):491-523
We present a thorough experimental and formal analysis of users’ privacy in mobile telephony systems. In particular, we experimentally analyse the use of pseudonyms and point out weak deployed policies leading to some critical scenarios which make it possible to violate a user’s privacy. We also expose some protocol’s vulnerabilities resulting in breaches of the anonymity and/or user unlinkability. We show these breaches translate in actual attacks which are feasible to implement on real networks and discuss our prototype implementation. In order to countermeasure these attacks, we propose realistic solutions. Finally, we provide the theoretical framework for the automatic verification of the unlinkability and anonymity of the fixed 2G/3G procedures and automatically verify them using the ProVerif tool. 相似文献
79.
Eike Falk Anderson Leigh McLoughlin Fotis Liarokapis Christopher Peters Panagiotis Petridis Sara de Freitas 《Virtual Reality》2010,14(4):255-275
Although the widespread use of gaming for leisure purposes has been well documented, the use of games to support cultural
heritage purposes, such as historical teaching and learning, or for enhancing museum visits, has been less well considered.
The state-of-the-art in serious game technology is identical to that of the state-of-the-art in entertainment games technology.
As a result, the field of serious heritage games concerns itself with recent advances in computer games, real-time computer
graphics, virtual and augmented reality and artificial intelligence. On the other hand, the main strengths of serious gaming
applications may be generalised as being in the areas of communication, visual expression of information, collaboration mechanisms,
interactivity and entertainment. In this report, we will focus on the state-of-the-art with respect to the theories, methods
and technologies used in serious heritage games. We provide an overview of existing literature of relevance to the domain,
discuss the strengths and weaknesses of the described methods and point out unsolved problems and challenges. In addition,
several case studies illustrating the application of methods and technologies used in cultural heritage are presented. 相似文献
80.