ZnO微／纳米纤维的静电纺丝及其表征

以聚乙烯吡咯烷酮(PVP)为络合剂与醋酸锌[Zn(CH3COO)2]反应制得前驱体溶液,用静电纺丝法制备了PVP／Zn(CH3COO)2纤维,经煅烧得到具有微孔结构的氧化锌(ZnO)微／纳米纤维。对所制备纤维分别采用差热-热重分析、红外光谱分析、X射线衍射分析、扫描电镜等手段进行了表征。结果表明: PVP/Zn(CH3COO)纤维表面光滑,直径约300-700 nm,经700℃煅烧后,可得到ZnO微／纳米纤维。     

分子筛生产工艺中的节能新技术——固相转化法的创新和应用

先就固相法合成沸石分子筛的合成机理及演绎发展进行了综述;着重介绍了本课题组开发的干粉法(固相原位转化法)及湿胶法(超高浓度体系法)两种固相法节能新技术在合成 MOR、ZSM-5等沸石分子筛生产中的应用情况,并阐述了两种创新方法的本质及其工艺特点;最后就干粉法及湿胶法的应用前景进行了展望.     

Stabilizing bit-rates in networked control systems with decentralized event-triggered communication

In a decentralized event-triggered networked control system (NCS), an agent samples and transmits its local state information to the controller when some local event occurs. Such event-triggered NCSs were expected to be more efficient than traditional periodically sampled system in terms of communication channel usage. This paper studies the stability of decentralized event-triggered NCS in the presence of quantization and delays. We point out some potential issues in decentralized event-triggered design and propose an alternative decentralized event with a linear-affine threshold, which avoids infinitely fast data transmission. Conditions on quantizer and communication channel are derived, which, when satisfied, can guarantee stability of the resulting NCS. Based on these conditions, finite stabilizing bit-rates are provided.     

Effect of Acceptor and Donor Dopants on the Dielectric and Tunable Properties of Barium Strontium Titanate

The effects of different concentrations of Mn²⁺, Mg²⁺, Al³⁺, Fe³⁺, La³⁺, and Nb⁵⁺ on the dielectric and tunable properties of Ba_0.6Sr_0.4TiO₃ ceramics were investigated. It was found that doping in small amounts with acceptor ions such as Mg²⁺, Fe³⁺, and Al³⁺ could meliorate the dielectric properties clearly. Decrease of dielectric loss was attributed to the formation of compensating defects originating from acceptor substitution. It was concluded that the tunability was linked to both the dielectric constant and the grain size. A higher figure of merit was obtained by doping the ceramics with smaller ions of Al and Fe, compared to Ti.     

PET工程塑料概况

综述了PET工程塑料合金化方面的主要研究开发情况，就PET／PBT、PET／PC、PET／聚酯聚醚、PET／尼龙、PET／PE等合金的研究及应用情况作了简单介绍。     

Effects of the electrospray ionization parameters on the formation and morphology of colloidal microspheres of polyacrylonitrile

Polyacrylonitrile colloidal microspheres have been successfully prepared with different concentrations of electrospraying polyacrylonitrile solutions. The morphology of the colloidal spheres has two kinds of structures and is strongly affected by electrospray‐ionization parameters, such as the polymer concentration, applied voltage, and distance between the electrodes. The solvent can also affect the morphology of polyacrylonitrile. The optimum conditions for preparing colloidal spheres have been found, and differential scanning calorimetry results indicate that polyacrylonitrile colloid spheres are amorphous. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2889–2893, 2006     

塑料挤出成型模具流道优化设计

本文依据流变学理论，采用优化方法进行挤出成型模具（即机头）流道设计，探讨了建立流道优化数学模型的有关问题。     

Typhoon eye extraction with an automatic SAR image segmentation method

Spaceborne microwave synthetic aperture radar (SAR), with its high spatial resolution (10–100 m), large area coverage, and day/night imaging capability, has been used as an important tool for typhoon monitoring. Since the microwave signal can penetrate through clouds, SAR images reveal typhoon morphology at the sea surface. Within the region of a typhoon eye, wind speed and the associated sea surface roughness are usually low. Therefore, the typhoon eye can be well distinguished as dark areas in SAR images. However, automatic typhoon eye extraction from SAR images is hampered by SAR image speckle noise and other false-alarm dark features contained in an image. In this study, we propose an image processing approach to extract typhoon eyes from SAR images. The three-step image processing includes: (1) applying an extended non-local means image denoizing algorithm to reduce image speckle noise; (2) applying a top-hat transform to denoized imagery to enhance the contrast; and (3) using a labelled watershed to segment the typhoon eye. Experimental results from analysing three Environmental Satellite SAR typhoon images show that our approach provides fast and efficient SAR image segmentation for typhoon eye extraction. Typhoon eyes are segmented correctly, and their edges are well detected. Our experimental results are comparable to manually extracted typhoon eye information. Fine-tuning of this approach will provide an automatic tool for typhoon eye information extraction from SAR images.     

精制胸腺活性肽药效学研究

目的 考察精制胸腺活性肽免疫学活性。方法 建立BALB/c小鼠肝细胞肿瘤(腹水型)模型,经腹腔连续注射肝肿瘤细胞15d,检测各种生命指标,以观察抗肿瘤效果。同时用E-玫瑰花环实验及淋巴细胞转化实验评价其生物学活性。结果 抗肿瘤实验表明,生命各项指标均优于盐水对照组,用药组10d、15d的存活率明显高于对照组;E-玫瑰花环及淋巴细胞转化实验均显示精制胸腺活性肽组明显高于对照组。结论 精制胸腺活性肽具有明显的免疫增强作用。     

Association-Based Active Access Control models with balanced scalability and flexibility

In existing Active Access Control (AAC) models, the scalability and flexibility of security policy specification should be well balanced, especially: (1) authorizations to plenty of tasks should be simplified; (2) team workflows should be enabled; (3) fine-grained constraints should be enforced. To address this issue, a family of Association-Based Active Access Control (ABAAC) models is proposed. In the minimal model ABAAC₀, users are assigned to roles while permissions are assigned to task-role associations. In a workflow case, to execute such an association some users assigned to its component role will be allocated. The association's assigned permissions can be performed by them during the task is running in the case. In ABAAC₁, a generalized association is employed to extract common authorizations from multiple associations. In ABAAC₂, a fine-grained separation of duty (SoD) is enforced among associations. In the maximal model ABAAC₃, all these features are integrated, and similar constraints can be specified more concisely. Using a software workflow, case validation is performed. Comparison with a representative association based AAC model and the most scalable AAC model so far indicates that: (1) enough scalability is achieved; (2) without decomposition of a task, different permissions can be authorized to multiple roles in it; (3) separation of more fine-grained duties than roles and tasks can be enforced.