浅析防火墙技术在校园网络安全中的应用

在如今,防火墙技术已经成为了互联网最重要的安全技术之一。防火墙技术的使用,是抵抗黑客的入侵和防止未经授权而非法访问某些信息节点最有效手段之一。文章深度剖析了防火墙技术所具备的强大功能和特性,并重点讨论了校园网安全的相关内容,指出了在校园网络环境下应如何利用防火墙技术提高校园网络的安全性。     

图像的几何运算方法

介绍了图像几何运算的两个步骤，并以按水平扫描线排列的数字图像转换为按外极线排列的图像为例，具体阐述了图像几何运算的方法。     

聚吡咯/聚砜复合膜修饰电极的制备及其对对苯二酚的电化学催化性能

采用循环伏安法电化学聚合制备了聚吡咯(PPY)/聚砜(PSF)复合膜修饰电极.结果发现:复合膜的正面(与工作电极接触的一面)是黑色的;而反面(与溶液接触的一面)是白色的.复合膜的表面形态和化学组分分别用SEM和FTIR表征,用电化学循环伏安法对PPY/PSF复合膜修饰电极的电化学催化性能进行了研究.实验结果表明:所得复合膜修饰电极电化学可逆性好并且对对苯二酚有显著的催化效果,其氧化峰电流在5～30mM的范围内与对苯二酚的浓度呈线性关系,表明该复合膜修饰电极在对苯二酚H2Q的监测方面将有潜在的用途.     

特大跨径钢管混凝土拱桥成桥荷载试验

为检验拱桥的受力状况和承载能力是否符合设计要求,对特大跨径钢管混凝土拱桥进行了成桥荷载试验。建立钢管混凝土拱桥的三维有限元模型,对桥梁在设计荷载作用下的结构变形和内力进行了验算。同时为考虑试验过程中温度对桥梁变形和应力的影响,对拱桥进行温度实时监测,获得温度变形和温度应力关系睦线,基于得到的温度修正曲线进行了桥梁在实际加载条件下的变形和应力修正。试验结果表明：桥梁的刚度满足设计要求。     

点缺陷半径变化对光子晶体直接耦合结构THz波调制器性能的影响

点缺陷构成的微腔对THz波调制器的性能起着决定性的作用,而在实际制作加工过程中,由于工艺的原因,光子晶体的结构参量会产生偏差,难以制备出孔径毫无偏差的光子晶体,且介质柱的放置位置不能达到完全精确,因此光子晶体器件的性能也因此会受到一定程度的影响。文中重点讨论了点缺陷介质柱的半径变化对直接耦合结构的THz波调制器性能的影响,为光子晶体调制器的实际制作和相应的误差分析提供了理论帮助。     

Changes in microorganism, enzyme, aroma of hami melon (Cucumis melo L.) juice treated with dense phase carbon dioxide and stored at 4 °C

The effects of dense phase carbon dioxide (DP-CO₂) treatment of 8, 15, 22, 30 and 35 MPa for 5 min, 15 min, 30 min, 45 min, 60 min at 35 °C, 45 °C, 55 °C, 65 °C on microorganism, enzyme, and aroma compounds in hami melon juice during storage at 4 °C for 4-weeks were investigated. Meanwhile, the color, browning degree, and Vitamin C were also studied. The DP-CO₂ treatment had significant effects on inactivation of microorganism and enzyme. It was indicated that higher pressure caused more inactivation of microbial total count and enzyme activity. When it reached 35 Mpa, 55 °C, 60 min, the microorganism was totally inactivated. The least residual activity of polyphenol oxidase (PPO), peroxidase (POD), and lipoxygenase (LOX) was 25.26%, 38.46 and 0.02% at 35MP, respectively. The restoration of PPO, POD and LOX residual activity after DP-CO₂ treatment was also observed, which was dependent on the pressure level. The aroma compounds were less affected after being treated with DP-CO₂, and the flavor of the melon juice was close to the fresh juice after storage at 4 °C for 4 weeks and did not produced cook off-odor. The changes of lightness L and browning degree A during storage were well fitted to a first-order kinetic model. The Vitamin C concentration decreased by DP-CO₂ processing, but this loss was lower than of the untreated sample.

Industrial relevance

Hami melon is highly appreciated for its nutritional quality and special flavor. The flesh of melon is heat sensitive, the sensitive nutrients, color and aromatic profile will be spoiled greatly or off-odour when it was produced with high temperature treatment. Dense phase carbon dioxide processing (DP-CO₂) is important to find an innovative food process to inactivate the enzyme and microorganism and protect the nutrient and unique flavor. In this study, the data proved that DP-CO₂ processing is a promising non-thermal alternative pasteurization to preserved fresh-squeezed melon juice.     

开关电流高阶滤波器的设计

开关电流电路属于电流模电路，它具有电流模电路的诸多优点。文章介绍了两种映射设计开关电流高阶滤波器的方法，通过设计实例，证明了这两种方法是正确的。