水溶性固体壳聚糖盐的制备及其性能研究

通过半湿研磨法由壳聚糖制备了多种水溶性粉末状壳聚糖盐。该产品可以溶解在酸性、中性和弱碱性介质中,溶解范围扩大;水溶液pH值在3.36—5.54之间,而且具有较强的缓冲作用;吸湿率提高30%以上。通过红外光谱、X-射线衍射、质量损失曲线及电位滴定曲线对目标产物结构进行分析,结果表明,在无溶剂条件下实现了壳聚糖氨基的质子化反应而不是简单的物理吸附,因此产品性能稳定。该方法操作简单,无污染而且经济。     

Ca-Mn co-doping LaCrO3 coating with high emissivity and good mechanical property for enhancing high-temperature radiant heat dissipation

Two techniques, including spray drying and electrostatic spray, were applied to produce feedstocks for preparing Ca-Mn co-doping LaCrO₃ ceramic coatings with two different structures on Ni-based alloy by the atmospheric plasma spraying method. The results show that coating from feedstocks produced by spray drying exhibits lower roughness and porosity than the coating from feedstocks produced by electrostatic spray due to the full melting of smaller feedstocks. Higher proportion of melting zones is beneficial to enhance the ratio of hardness to modulus to improve wear resistance. The emissivity of the coatings with roughness from 0.65 µm to 4.6 µm is all above 0.9 in the waveband of 1–14 µm at room temperature. What’s more, structure-dependent emissivity is affected by surface roughness and pore size due to the infrared scattering. The temperature-dependent thermal infrared emissivity at 1–14 µm decreases with the increasing temperature, and is still above 0.67 at 1200 °C.     

Facile synthesis of molybdenum-based layered double hydroxide nanorods for boosting water oxidation reaction

Exploiting environmentally friendly and robust oxygen evolution reaction (OER) electrodes is still a great difficulty to promote the water oxidation for electrocatalytic water splitting. In the work, molybdenum-doped nickel copper hydrotalcite (NiCuMo_x LDH) nanoarrays have been firstly in situ grown on nickel foam (NF) via a typical hydrothermal process. When NiCuMo_0.2 LDH/NF was used as a OER electrocatalyst, it displays superior electrocatalytic performance with the need of small overpotentials of only 290 mV to drive 40 mA cm⁻² and a low Tafel slope of 39.8 mV dec⁻¹, which are almost one of the best water oxidation activities reported so far. The enhanced electrocatalytic performance is attributed to unique urchin-like structure, more exposure to active sites and enhanced charge transfer rate owing to the synergistic effect of Mo doping and NiCu LDH. The work put forward a new method for the development of efficient water oxidation electrocatalysts, which will fill the gap for the exploitation of trimetal LDH-based electrodes in large-scale water splitting applications in the future.     

计算机网络攻击及解决办法

计算机网络在给人们工作和生活提供方便的同时,数据窃取、黑客侵袭、病毒感染、内部泄密等网络攻击问题无时不刻不在困扰着用户的正常使用,虽然计算机广泛的采用了各种复杂的安全技术,但网络安全问题依然给社会和个人造成了严重的危害。将对计算机网络攻击方法以及计算机网络信息安全和防护进行探讨,并提出了有效的解决方案。     

无线传感器网络中非GPS的定位算法

无线传感器网络中节点自定位一直是一个具有挑战性的研究课题。全球定位系统(GPS)是一种传统的定位技术,但是定位的准确性低且网络花费较大。通过分析现有的节点自定位算法,认为六边形节点自定位算法是比较优秀的非GPS算法,该算法基于蜂窝交叠的思想,节点仅使用简单的连接矩阵和信标帧中的定位数据就能自定位,且定位准确性高,最后提出了今后要做的工作。     

A flexible nanostructured paper of MnO NPs@MWCNTs/r-GO multilayer sandwich composite for high-performance lithium-ion batteries

Designing a high capacity and long cycle life MnO-based composite material for lithium ion batteries (LIBs) is still a great challenge because of the intrinsically low electrical conductivity and dramatic volume variations during lithiation/delithiation. In this paper, the MnO nanoparticles (MnO NPs) are recombined with multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (r-GO) to rationally construct a novel MnO NPs@MWCNTs/r-GO multilayer sandwich structure via electrostatic interaction self-assembly and vacuum filtration processes. As a result, the MnO NPs are closely attracted in the conductive MWCNTs network, and the MWCNTs adsorbed on the surface of MnO NPs can be served as a soft and flexible carbon coating layer to self-adapt the huge volume expansion. For another, the r-GO between two MnO NPs@MWCNTs layers is the cause to form a free-standing paper, enhancing the transverse conductivity of the whole electrode simultaneously. These features will contribute to achieve excellent cycling stability and improved rate capability.     

基于Logistic映射的压缩图像加密算法

大多数的图像加密算法是针对整幅图像的,加密、解密和传输效率较低.利用局部图像的特点,采用自适应的分块方法以及多种块分类技术相结合对图像进行块分解,借助Logis-tic映射产生的混沌序列分别对分解后的图像序列块进行不同密钥的加密.经实验验证,该方法不仅增加了输出密钥序列的周期性和安全性,而且提高了加密、解密速度及传输效率,加密、解密效果良好.     

A generalized Young’s equation for contact angles of droplets on homogeneous and rough substrates

Using Gibbs’ method of dividing surfaces, the contact angle of a drop on a flat homogeneous rough non-deformable solid substrate is investigated. For this system, a new generalized Young’s equation for the contact angle, including the influences of line tension and which valid for any dividing surface between liquid phase and vapor phase is derived. Under some assumptions, this generalized Young’s equation reduces to the Wenzel’s equation or Rosanov’s equation valid for the surface of tension.     

煤矿网络安全ARP攻击原理及解决方法

文章首先介绍煤矿网络安全ARP网络协议原理以及攻击原理,之后阐述ARP攻击的检测,并提出解决煤矿网络安全ARP攻击的对策建议。     

Synthesis of titanoaluminosilicates isomorphous to zeolite Beta,active as oxidation catalysts

Isomorphous replacement of Si by Ti in the low aluminum-containing zeolite Beta framework has been achieved by direct synthesis. The crystallization must be carried out in the absence of alkali cations, as they promote the precipitation of amorphous titanosilicate. The incorporation of Ti to the framework has been characterized by XRD, i.r., and thermal analysis. Ti is believed to perform a stabilizing role of the Beta framework similar to that of Al. The large pores of [Al, Ti]-Beta compared to TS-1 allow the use of this material as a catalyst in the selective oxidation of cyclododecane with hydrogen peroxide.