LTE双层网中MIMO技术性能分析*

Femtocell技术以其较好的热点覆盖、较高的传输速率以及较大的网络容量,成为LTE网络中补充覆盖的重要途径之一。但同时,也造成了网络中复杂的CCI,严重影响了异构网络的性能。为了减少LTE双层网络中的CCI,提高网路容量,本文将基于MIMO的本征波束赋形、正交空时编码、天线选择技术应用于LTE双层网络,详细给出了无Femtocell覆盖半径、Femtocell最优密度以及Macrocell覆盖半径的精确数学表达形式,并对其所带来的干扰抑制效果进行了分析。通过仿真我们发现,相对于SISO来说,本征波束赋形的干扰抑制效果最好,可以使网络性能有个很大的提高,天线选择次之,正交空时编码所带来的增益最小,而当综合考虑性能增益以及复杂度的情况下,选择分集是一种比较合适的选择。     

土壤宏电池腐蚀的实验室研究

提出了几种土壤宏电池腐蚀的室内模拟试验方法,实验表明,金属在土壤中的宏电池腐蚀作用确实相当严重。     

原油埋地传输线腐蚀穿孔原因分析及对策

本文针对原油埋地传输线局部腐蚀穿孔的情况，进行了分析，并提出了相应的解决方法。     

Investigation of steel corrosion in cracked concrete: Evaluation of macrocell and microcell rates using Tafel polarization response

Inhomogeneous corrosion in reinforced concrete is investigated using a beam with a flexural crack intersecting the reinforcement. An Evans diagram representation of the macrocell corrosion system is developed. The relationship between the current density and the potentials relative to the crack obtained from the Tafel polarization responses of active and passive steel in concrete compares favorably with the experimental values. When both microcell and macrocell mechanisms contribute to metal loss at the crack, the Evans diagram representation indicates that an increase in the macrocell current density results in a decreasing contribution from the local microcell at the macrocell anode.     

Location management in mobile network: A survey

Location management is an important area of mobile computing. Location management in mobile network deals with location registration and tracking of mobile terminals. The location registration process is called location update and the searching process is called paging. Various types of location management methods exist such as mobility based location management, data replication based location management, signal attenuation based location tracking, time, zone and distance based location update etc. In this paper, existing location management schemes are discussed and compared with respect to their cost consumption in terms of bytes. Finally the key issues are addressed in the context of location management for future generation mobile network.     

Macrocell and microcell corrosion of steel in ordinary Portland cement and high performance concretes

Microcell corrosion is the term given to the situation where active corrosion and the corresponding cathodic half-cell reaction take place at adjacent parts of the same metal. Macrocell corrosion can occur when the actively corroding bar is coupled to another bar which is passive, either because of its different composition or because of different environment. The present study was undertaken to determine the influence of concrete type and properties on the relative microcell and macrocell corrosion rates. The samples were monitored for more than 3 years and the results confirm that microcell corrosion is the major mechanism in corrosion of steel reinforcing bars in concrete. Furthermore, results show that, for high performance concrete, the difference between microcell and macrocell corrosion is far more significant than for ordinary Portland cement concrete because of its high resistance to ionic flow.     

Interference Avoidance through Pilot‐Based Spectrum Sensing Algorithm in Overlaid Femtocell Networks

Co‐channel interference between macro–femtocell networks is an unresolved problem, due to the frequency reuse phenomenon. To mitigate such interference, a secondary femtocell must acquire channel‐state knowledge about a co‐channel macrocell user and accordingly condition the maximum transmit power of femtocell user. This paper proposes a pilot‐based spectrum sensing (PSS) algorithm for overlaid femtocell networks to sense the presence of a macrocell user over a channel of interest. The PSS algorithm senses the pilot tones in the received signal through the power level and the correlation metric comparisons between the received signal and the local reference pilots. On ensuring the existence of a co‐channel macrocell user, the maximum transmit power of the corresponding femtocell user is optimized so as to avoid interference. Time and frequency offsets are carefully handled in our proposal. Simulation results show that the PSS algorithm outperforms existing sensing techniques, even at poor received signal quality. It requires less sensing time and provides better detection probability over existing techniques.     

Q235钢在土壤中宏电池腐蚀行为的研究

在实验室中通过模拟装置对Ｑ２３５钢在土壤中的宏电池腐蚀行为进行了研究。结果表明,饱和／非饱和土壤环境的差异对金属的宏电池腐蚀具有决定性的作用,土壤的电阻率可以影响宏电池的电流分布。     

碳钢的土壤盐浓差宏电池腐蚀研究

以潮湿砂土作为模拟土壤,把失重法与电化学方法相结合,研究了盐浓差（２．０％Ｃｌ＾－及０．２％Ｃｌ＾－）宏电池对Ｑ２３５钢腐蚀的影响规律。结果表明,位于较高盐浓度土壤中的试样为宏电池的阳极而加速腐蚀,宏电池作用强度达到２．２倍。     

关于土壤中宏电池腐蚀的研究

概述了土壤中宏电池腐蚀的研究历程、现状、以及存在的问题,提出应用多种电化学测试技术研究影响土壤宏电池腐蚀的因素及条件;并指出,随着应用于地下的金属材料种类越来越多,地下金属构件多为异金属连接件,当异金属连接件经过土壤性质差异比较明显区段时,两种金属构件分别位于不同的土壤中,这种情况下就会有异金属接触腐蚀与土壤宏电池腐蚀的综合作用,因此,应该加强这方面的研究。