PF用低收缩添加剂的研究

通过调整物料配比合成了端羟基封端和端羧基封端的聚氨酯 (PU)预聚物 ,并分别与酚醛树脂 (PF)固化 ,制备了两种低收缩体系的复合物 ,利用红外光谱对其结构进行表征。通过测试固化物的体系收缩率表明 :随着聚氨酯预聚物加入量的增加 ,PF/PU共混物的体积收缩率明显变小 ,并能达到负值。端羧基PU的低收缩性能更为显著 ,当其加入量在 5 相似文献   

Homogeneous Fluidization Characteristics of Vibrating Fluidized Beds

The effects of vibration parameters, operating conditions and material properties on fluidization quality were investigated by the measurement and analysis of voidage fluctuation signals in a vibrating fluidized bed with a diameter of 148 mm. The fluctuation deviation of the bed voidage and the enhancement index of the bed derived can describe bed homogeneity and its extension. A new criterion of homogeneity, consisting of the material parameter (Ar), operating parameters (H₀, u/u_mf) and vibration parameters (a, ω), is proposed to predict a suitable range of homogeneous fluidization. Experimental results on eight kinds of solids, five static bed heights and different vibration parameters were used to propose guidelines for the reasonable selection of operating conditions for vibrating fluidization and better operating conditions.     

一种CMOS1／2Mbps3．3V1553B收发器的设计与实现

1553B总线是一种广泛用于航天、航空以及军事领域内的通用数字总线。但随着应用系统的技术发展,原有1Mb—ps传输速率的收发器已经不能满足使用需求,因此文中提出一种2Mbps的收发器系统结构,并兼容1Mbps的传输速率。该收发器采用0．35μmsingle—polyCMOS工艺实现,流片测试结果表明,在1Mbps速率下,该收发器完全满足1553B总线协议要求。在2Mbps速率下,收发器的传输误码率小于10^-12在3．3V工作电压下,收发器静态功耗为17mA。     

改进型LOG算子在偏振片绝对角度中的应用

光学成像系统自身通常都具有一定的偏振效应,严重影响仪器偏振测量精度,而提高仪器中偏振片绝对角度精度能提高偏振定标精度,对校正光学系统自身的偏振特性具有重要的意义。对偏振片直线透光轴Raw图像高精度边缘定位和直线检测是偏振片绝对角度计算的关键步骤。针对传统LOG算子各向同性及虚假边缘与边缘定位精度相矛盾的缺陷,提出改进型一阶导阈值旋转式椭圆对称LOG算子。该算子不仅保留了经典LOG算子的优点,还具有对不同角度的边缘更加有效地进行检测,在保持边缘定位精度下,减少虚假边缘的特点。在处理得到的边缘二值图像上,进行直线检测求出偏振片绝对角度,通过对比分析最小二乘法线性拟合和霍夫变换的直线检测效果,得出霍夫变换能精确计算出偏振片绝对角度。实验证明改进型LOG算子与霍夫变换相结合提高了偏振片绝对角度测量精度,对偏振定标精度具有很大的提高。     

决策粗糙集属性约简算法与属性核研究

属性约简是粗糙集理论的重要研究内容之一。在Pawlak粗糙集模型中,正区域大小随着属性增多而变大,呈现单调性。然而,在决策粗糙集模型中,概率正区域与属性集之间不具有单调性,从而产生各种属性约简定义。为此,深入研究了决策粗糙集属性约简问题,阐述了几种约简定义之间的关系,证明了保持局部最大概率正区域的约简具有较大的代价,指出了保持所有对象的正决策不变的约简呈现稳定性和存在属性核。     

HTTP-SoLDiER: An HTTP-flooding attack detection scheme with the large deviation principle

HTTP-flooding attack is a much stealthier distributed denial of service （DDoS） attack, challenging the survivability of the web services seriously. Observing the web access behavior, we find that the surfing preference of normal users is much more consistent with the webpage popularity than that of malicious users. Based on this observation, this paper proposes a novel detection scheme for HTTP-flooding （HTTP-SoLDiER）. Specifically, HTTP-SoLDiER first quantifies the consistency between web users surfing preference and the web- page popularity with large-deviation principle. Then HTTP-SoLDiER distinguishes the malicious users from normal ones according to the large-deviation probability. In practice, the webpage popularity plays a key role in attack detection of HTTP-SoLDiER. Due to the never-ending updating of the webpage content and the disturbance induced by attackers, the webpage popularity often varies over time. Thus, it is critical for HTTP-SoLDiER to dynamically update the webpage popularity. We design a reversible exponentially weighted moving average （EWMA） algorithm to solve the problem. Finally, we evaluate the effectiveness of this scheme in terms of true positive （TF） and false positive （FP） probabilities with NS-3 simulations. The simulation results show that HTTP-SoLDiER can detect all random HTTP-flooding attackers and most of the perfect-knowledge HTTP-flooding attackers at little false positive.     

Interfacial adhesion reaction of polyethylene and starch blends using maleated polyethylene reactive compatibilizer

The interfacial reaction of the polyethylene (PE)/starch blend system containing the reactive compatibilizer maleated polyethylene (m‐PE) was directly characterized by Fourier transform infrared (FTIR) spectroscopy. A significant amount of anhydride groups on m‐PE existed as hydrolyzed forms, resulting in a large amount of carboxyl groups. Using a vacuum‐heating‐cell designed in the laboratory, the carboxyl groups were successfully transformed into the dehydrolyzed state (i.e., anhydride group). This result enabled the direct spectroscopic observation of chemical reaction occurring at the interface. For the PE/starch blend system containing m‐PE, the chemical reaction at the interface was verified by the evolution of ester and carboxyl groups in the FTIR spectra. The effect of the reactive compatibilizer on the interfacial morphology was also examined by scanning electron micrography (SEM). Enhanced interfacial adhesion was clearly observed for the blend system containing reactive compatibilizer. Tensile strengths of blend systems containing m‐PE also increased noticeably compared with the corresponding system without compatibilizer. A similar observation was made for the breaking elongation data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 767–776, 2002     

莱钢2#竖炉自控系统的应 用

针对莱钢2#竖炉存在的问题,对其自控系统进行升级改造,以确保系统稳定运行,提高生产效率。     

定向井技术在白庙气田产能建设中的应用

东濮凹陷白庙气田构造破碎、储层相变快、储量分布不均匀。如何以较少的钻井投资，尽量多地钻遇气层层数，以较少的钻井数最大限度地控制气田地质储量，是高效开发白质气田的难点。通过气田地质研究及气藏工程论证，提出定向井设计思路，并根据不同的地质条件，研究设计出不同类型的定向井，应用于白庙气田产能建设中，效果显著。