基于电磁环境效应的无人机系统级电磁辐射指标制定

分析了实际电磁环境对无人机的影响,通过在实际飞行环境中对各地面发射机的辐射和场地电磁环境的测试,得到对无人机造成伤害的电磁环境场强极限值在0.1~8×103MHz频段中为60~200 V/m.将不同频段下传导干扰与辐射干扰进行结合分析,并根据无人机中存在的辐射干扰和传导干扰的共性特征,得到无人机系统级电磁辐射极限场强在0.1~2×103MHz频段中为10~60 V/m.依照国军标GJB3567-99《军用飞机雷电防护鉴定试验方法》,以及在实际飞行场地中采用410 A敏感度测试系统进行测试,结果显示:采用该指标的无人机各机载设备工作正常,未出现设备失灵或降级情况,说明该指标的制定为无人机系统的电磁兼容设计提供了一个有效的评估准则.     

Impact‐specific essential work of fracture of maleic anhydride‐compatibilized polypropylene/elastomer blends and their composites

Charpy drop‐weight‐impact and essential work of fracture (EWF) characteristics of maleic anhydride (MA)‐compatibilized styrene–ethylene butylene–styrene (SEBS)/polypropylene (PP) blends and their composites reinforced with short glass fibers (SGFs) were investigated. MA was grafted to either SEBS copolymer (SEBS‐g‐MA) or PP (PP‐g‐MA). The mPP blend was prepared by the compounding of 95% PP and 5% PP‐g‐MA. Drop‐weight‐impact results revealed that the mPP specimen had an extremely low impact strength. The incorporation of SEBS or SEBS‐g‐MA elastomers into mPP improved its impact strength dramatically. Similarly, the addition of SEBS was beneficial for enhancing the impact strength of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids. A scanning electron microscopy examination of the fractured surfaces of impact specimens revealed that the glass‐fiber surfaces of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids were sheathed completely with deformed matrix material. This was due to strong interfacial bonding between the phase components of the hybrids associated with the MA addition. Impact EWF tests were carried out on single‐edge‐notched‐bending specimens at 3 m s^?1. The results showed that pure PP, mPP, and the composites only exhibited specific essential work. The nonessential work was absent in these specimens under a high‐impact‐rate loading condition. The addition of SEBS or SEBS‐g‐MA elastomer to mPP increased both the specific essential and nonessential work of fracture. This implied that elastomer particles contributed to the dissipation of energy at the fracture surface and in the outer plastic zone at a high impact speed of 3 m s^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1881–1892, 2002     

Machines Over the Reals and Non-Uniformity

We survey the research performed in the last few years on a specific topic: the power of real machines over binary inputs. This research attempts to characterize the classes of decision problems over a finite alphabet - say {0,1} - which can be decided by real machines working under several resource restrictions. Non-uniformity appears here in a natural way. However, since this is a technical concept which is not widely known, we summarize in Section 2 some of the intuitive notions, as well as a few basic theorems related to it. In Section 3 we do this for the subject of real machines and then, in Section 4 we present the state of the art of the surveyed topic. We devote Section 1 to introduce the main concepts of complexity theory. Proofs in this article are quite sketchy and are included more to convey intuitive ideas than to completely prove the claimed statements. Bibliographical references to the original literature are supplied for the latter purpose.     

N—酰化壳聚糖膜性能的研究

讨论了一系列N-酰化壳聚糖膜的抗张强度、透水性、VB_(12)的透过性、透氧性以及血液相容性。N-已酰化壳聚糖膜具有良好的血液相容性。在制膜过程中,加入分子量为1500的聚乙二醇为致孔剂,则可使N-己酰化壳聚糖膜的渗透性有较大提高。同时保持较好的血液相容性和强度。     

壳聚糖-明胶共混膜

用溶液共混法成功地制备了壳聚糖与明胶共混膜,并用红外光谱, Ｘ 射线衍射,扫描电镜,透光率,吸水率及力学性能测试对共混膜进行了表征结果表明,共混膜中壳聚糖分子与明胶分子间存在强的相互作用及良好的相容性,壳聚糖的引入有利于减小明胶的吸水率,改善其力学性能     

物理老化对PEK-C、PES-C及其复合材料的玻璃化转变热焓松弛特征的影响

本文用DSC技术研究了物理老化对PEK-C、PES-C及其共混物和复合材料玻璃化转变的影响.老化时间(t)延长,玻璃化转变温度(T_g)、热焓松弛峰温(T_(max))、峰高(△C_(pmax))和热焓(△H)提高;△H与lgt成线性关系.碳黑或碳纤维对PES-C的物理老化行为无影响,而反应性乙炔端基砜(ATS)固化物能限制PEK-C和PES-C在T_g以下温度的物理老化过程.利用物理老化能更为方便地判断多相体系的相容性,结果表明PEK-C/PSF为相容体系,而PEK-C/PES-C相容性较差.     

海藻酸钠-硫酸软骨素共混膜的结构及性能研究

利用溶液共混法成功制备了新型生物膜材料-硫酸软骨素共混膜,通过红外光谱、X-射线衍射、原子吸收光谱和扫描电镜对共混膜的结构进行了表征,并测定了不同配比共混膜的抗张强度、断裂伸长率,吸水率,同时考察了介质pH值和离子强度对共混膜吸水率的影响。结果表明:共混膜中海藻酸钠、软骨素之间具有较强的相互作用和良好的相容性,共混膜具有良好的力学性能。作为一种潜在的生物材料可望在生物医学领域得到应用。     

抗凝血聚氨酯材料的研究进展

聚氨酯由于其优良的抗凝血性能和良好的物理机械性能而成为目前研究和应用最广的一种生物医用高分子材料。本文就嵌段型聚氨酯、拦枝型聚氨酯、离子型聚氨酯及其它具有良好发展前景的聚氨酯抗凝血材料的研究进展作扼要综述。     

Dual-phase polymer electrolyte with enhanced phase compatibility based on Poly(MMA-g-PVC)/PMMA

A new plasticized dual-phase polymer electrolyte (DPE) with enhanced phase compatibility based on Poly(MMA-g-PVC)/PMMA blends has been studied. For the DPE, PMMA is selectively impregnated with the lithium salt solution forming an ion-conducting network, while Poly(MMA-g-PVC) produces good mechanical strength. Their chemical characters, thermal behavior, morphology, ionic conductivity and interfacial compatibility with lithium metal electrode were characterized by using of infrared spectroscopy (IR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), optical microscopic images, alternating current impedance (AC impedance) and linear sweep voltammetry (LSV), respectively. The ionic conductivity of DPE increases with the ratio of PMMA/Poly(MMA-g-PVC) (by weight), and the absorbed liquid electrolyte in the polymer blends plays the first important way in this behavior. Room-temperature ionic conductivity of the order of 10⁻³ S cm⁻¹ has been achieved for DPE, in addition, the DPE also shows good compatibility with Li electrodes and sufficient electrochemical stability for safe operation in Li batteries.     

PVC/ABS共混塑料结构与性能的研究

本文利用透射电镜观察PVC/ABS共混塑料的结构,结合其流变性能,机械性能,探讨结构与性能之间的关系。结果表明,PVC/ABS共混望料的热性能,抗冲击强度介于纯PVC和ABS之间,而缺口冲击强度则优于PVC和ABS,且当ABS含量为30％时有个最大值,这是由于PVC/ABS共混塑料的微观结构造成的。PVC/ABS共混塑料随着ABS含量的减少,“橡胶”粒子变小,当ABS含量为30％时,二组分相容性最好。