倒相管内开口对系统响应的影响

通过试验和理论分析,讨论了倒相型扬声器系统的内开口状态变化对系统特性的影响,得出倒相管对系统响应的影响并不局限于低频.针对传统的结论提出新的观点,对容积为10L以下的小型系统而言,内开口对系统特性的影响不能忽视.     

Liquid‐Filling Polydimethylsiloxane Composites with Enhanced Triboelectric Performance for Flexible Nanogenerators

Material functionalization of triboelectric nanogenerators (TENG) plays an important role in TENG's electric performance for sustainable energy harvesting. In this work, a method for improving polydimethylsiloxane (PDMS) composites triboelectric performance has been proposed, via filling high dielectric constant liquid (instead of solids) into PDMS matrix. The improvement is attributed to the high dielectric constant liquid in PDMS matrix that reduced the effective thickness of PDMS and increased the dielectric constant of PDMS composite synchronously. At 50% filling ratio (PDMS‐HD50), the triboelectric performance exhibits an enhancement of 4.5‐fold in output voltage and 3.9‐fold in output current as compared to pure PDMS. The results, besides higher transparency, are superior to the results from traditional solid dielectric constant doping materials like BaTiO₃ nanoparticle in PDMS. This work has proved potentials of dielectric liquid filling materials in fabricating TENGs and could be a guidance for exploring new liquid filling materials.     

过渡区的摩擦特性研究

用GCr１５的球试样和45^#钢平面试样在200N的法向务作用下对大范围位移幅值下的往复滑动作了大量磨损试验，着重对摩擦系数、磨损系数、平面试样磨痕的表面形貌以及磨屑的尺寸和分析情况进行分析研究。结果表明，在本试验条件下，过渡区范围是75－125μm。过渡区和微动、滑动状态下的磨损系数、磨痕形貌以及磨屑的尺寸和分布均有所差异。     

Ownership-hidden group-oriented proofs of storage from pre-homomorphic signatures

In this paper, we study the problem of secure cloud storage in a multi-user setting such that the ownership of outsourced files can be hidden against the cloud server. There is a group manager for initiating the system, who is also responsible for issuing private keys for the involved group members. All authorized members are able to outsource files to the group’s storage account at some cloud server. Although the ownership of outsourced file is preserved against the cloud server, the group manager could trace the true identity of any suspicious file for liability investigation. To address this issue, we introduce and formalize a notion of ownership-hidden group-oriented proofs of storage (OPoS). We present a generic OPoS construction from pre-homomorphic signatures, and propose an OPoS instantiation by employing the Boneh–Boyen short signature. We show that the OPoS instantiation can be optimized using a polynomial commitment technique, so that the integrity auditing protocol would only take constant-size communication overheads by the cloud server. Theoretical and experimental analyses show that our OPoS instantiations are efficient and practical for enterprise-oriented cloud storage applications. Also, we show that the OPoS instantiations can be enhanced to safeguard against a dynamic set of corrupted members, as well as support batch integrity auditing mechanism.     

HSDPA与WiMAX的综合比较

1引言 目前在各大通信展与技术论坛上,两种后3G技术——HSDPA和WiMAX正在成为新的技术焦点。在蜂窝移动通信的阵营中,由于数据业务的比例不断增加,移动通信在向提供无线高速数据业务的方向演进,移动通信设备制造商也相应地优化系统结构,不断提高数据传输速率。例如GSM的演进路线,传输速率从GPRS的40kbit／s到EDGE的130kbit／s以及UMTS的384kbit／s和即将到来的HSDPA 3 Mbit／s发展,最终实现话音和数据的移动宽带。     

分子筛中碳氢化合物扩散行为的分子模拟研究进展

分子筛催化过程中反应物、产物以及中间体等分子在分子筛孔道内的扩散行为显著影响催化剂择形催化性能、限域效应、产物选择性和稳定性等.本文总结了近二十年来分子模拟技术在分子筛扩散研究中的应用进展.首先简单介绍以分子动力学模拟为代表的分子筛扩散研究方法,然后介绍了包括烷烃、烯烃和芳烃在内的单组分以及多组分碳氢化合物在分子筛中的...     

改进的R23/R134a自复叠制冷系统实验研究

为了研究R23/R134a混合工质自复叠制冷系统在变工况下的运行性能,更深入地了解系统各部件对自复叠循环的影响,在已建成的自复叠循环系统实验台上进行实验研究.在冷凝温度较高的夏季,测试该自复叠实验装置所能达到的最低蒸发温度,并研究冷凝温度、工质充注质量分数及蒸发冷凝压力对该系统的影响.     

再生器腐蚀裂纹与生产安全

近年来 ,国内一些炼油厂的催化装置相继发生了设备事故 ,尤其是重油催化裂化装置的再生器、三旋及再生烟气系统主体设备发现了大量裂纹。这些裂纹多发生在焊缝、熔合线或热影响区内 ,不少裂纹为穿透性裂纹 ,并有烟气和催化剂外泄情况发生。目前 ,已有十几套装置的再生器或三旋壳体发生了开裂事故。前郭石化分公司二催化第二再生器密相床部位也发现有 8条焊缝裂纹 ,其中一条长 1 0 0ｍｍ、深 8ｍｍ ,已达壁厚的 1 / 3。这些裂纹虽然已经进行了修复 ,但是潜在裂纹和再生裂纹将严重威胁着装置的安全生产。1　设备开裂原因分析1 .1再生器裂纹特…     

Verifiably encrypted cascade-instantiable blank signatures to secure progressive decision management

In this paper, we introduce the notion of verifiably encrypted cascade-instantiable blank signatures (CBS) in a multi-user setting. In CBS, there is a delegation chain that starts with an originator and is followed by a sequence of proxies. The originator creates and signs a template, which may comprise fixed fields and exchangeable fields. Thereafter, each proxy along the delegation chain is able to make an instantiation of the template from the choices passed down from her direct predecessor, before generating a signature for her instantiation. First, we present a non-interactive basic CBS construction that does not rely on any shared secret parameters among the users. In verifying an instantiation signature, all the preceding instantiation signatures leading back to the template signature are also verified concurrently. It is formally proved to be secure against collusion attacks by the originator and proxies. Second, we investigate verifiably encrypted CBS to provide fairness between the originator and proxies, where the security model is stricter than basic CBS in that the adversary may also collude with the arbitrator. Efficiency analysis shows that the proposed CBS schemes enjoy linear computation costs. Finally, we extend our scheme to CBS supporting designated instantiations, free instantiations, privately verifiable template signature, identity-based CBS, as well as CBS secure against proxy-key exposure.