Frequency and time domain comparison of selective polynomial filters with corrected phase characteristics

Two solutions to the polynomial filter’s transfer function synthesis problem are considered for comparison in the frequency and time domain: the broad class of filters with a critical monotonic amplitude characteristic (CMAC) in the passband and filters which use Chebyshev (C) polynomials. To complete the synthesis procedure for linear phase applications, group delay correctors are considered, for which a convenient approximation procedure is proposed here. Comparisons of the original functions and the corrected ones are performed in the frequency and time domain. It is shown that when CMAC and C are compared as such, the latter is by no means preferable from the selectivity point of view, while the opposite stands when the comparison is based on passband amplitude distortions. When phase-corrected filtering functions are compared, based on circuit complexity and time domain performance, the CMAC are shown to be preferable.     

全面实施携号转网对我国移动通信市场影响

以我国移动用户为研究对象,采用随机抽样的调查方法,通过电话外呼的调查方式,对我国移动业务携号转网后移动通信市场格局及影响进行研究,运用“马尔可夫概率转移矩阵”对实施携号转网后全国及南北方移动电话市场份额进行了预测,并创新地提出“携号转网流向路径模型”。此外,重点围绕“区域特征、在网时长、ARPU值和携号转网人数”等对3家通信运营商携号转网用户的关注点及转出和转入原因进行深入剖析。结果表明：网龄越长、ARPU值越高,携号转网意愿越强;北方用户携号转网意愿高于南方。本文结论将为通信企业经营决策提供参考。     

蓝宝石衬底上槽栅型X波段增强型AlGaN/GaN HEMT

研制了一款X波段增强型AlGaN/GaN高电子迁移率晶体管(HEMT)。在3英寸(1英寸=2.54 cm)蓝宝石衬底上采用低损伤栅凹槽刻蚀技术制备了栅长为0.3μm的增强型AlGaN/GaN HEMT。所制备的增强型器件的阈值电压为0.42 V,最大跨导为401 mS/mm,导通电阻为2.7Ω·mm。器件的电流增益截止频率和最高振荡频率分别为36.1和65.2 GHz。在10 GHz下进行微波测试,增强型AlGaN/GaN HEMT的最大输出功率密度达到5.76 W/mm,最大功率附加效率为49.1%。在同一材料上制备的耗尽型器件最大输出功率密度和最大功率附加效率分别为6.16 W/mm和50.2%。增强型器件的射频特性可与在同一晶圆上制备的耗尽型器件相比拟。     

基于RPIM 法的圆极化天线特性参数快速测试

为提高圆极化天线特性参数的测试精度,线极化分量法往往需要对线分量场进行多次测量。文中在天线测试系统中引入插值算法,减少采样点,提高圆极化天线测试效率。将径向基函数的点插值无网格(RPIM)法引入圆极化天线参数合成算法中,首先使用RPIM 拟合出测试场的幅值和相位,然后再使用解析的方式合成圆极化天线的轴比和方向图,算法性能与基于分段线性插值技术的模型参数估计法(MBPE)和基于三次样条插值的移动最小二乘法(MLS)进行比较,数值实验显示,当采样点数仅为测试点数的4%时,MLS 失效,MBPE 和RPIM 误差均为10-3量级;而当采样点数减少为测试点数的2%时,MBPE 和MLS 均失效,RPIM 的误差虽然增大到10-1 量级,但仍能保持稳定。数值实验证明,在采样点数较少情况下,RPIM 性能优于其它两种算法。     

面向NB-IoT的核心网业务模型和组网方案

窄带物联网(NB-IoT)的市场空间巨大,是未来重点的发展方向,全球主流电信运营商均开始积极布局.为更好地确定网络部署的建设方案和资源配置,从NB-IoT的业务场景出发,对NB-IoT业务特性进行分析,给出面向NB-IoT的核心网业务模型参数和组网方案,对后续NB-IoT核心网资源配置和规划方案有重要指导意义.     

Local conformation of poly(1-adamantyl methacrylate) evaluated from intrinsic viscosity

The dilute-solution properties of poly(1-adamantyl methacrylate), which was prepared by radical polymerization in benzene at 60 °C and fractionated with benzene and ethanol as solvent and nonsolvent, respectively, were examined by the measurement of intrinsic viscosities in benzene, tetrahydrofuran, and cyclohexanone at 30°C. The Mark-Houwink-Sakurada equations were established for each solvent-polymer system. From the viscosity data in these three solvents by means of the Burchard-Stockmayer-Fixman plot, the characteristic ratio and steric factor of the chain were determined to be 16.7 and 2.9, respectively, which are higher than the values reported for other methacrylate polymers bearing cycloalkyl esters.     

Theory on the molecular characteristic contou(II)

The molecular intrinsic characteristic contour (MlCC) is defined based on the classical turning point of electron movement in a molecule. Three typical organic molecules, i.e. methane, methanol and formic acid, were employed as examples for detailed introduction of our method. Investigations on the cross-sections of MlCC provide important information about atomic size changing in the process of forming molecules. The electron density distributions on the MlCCs of these molecules were calculated and shown for the first time. Results showed that the electron density distribution on the MlCC correlates closely with molecular chemical properties, and it provides a new insight into molecular boundary.     

On unicyclic conjugated molecules with minimal energies

The energy of a graph is defined as the sum of the absolute values of all the eigenvalues of the graph. Let U(k) be the set of all unicyclic graphs with a perfect matching. Let C _g(G) be the unique cycle of G with length g(G), and M(G) be a perfect matching of G. Let U ⁰(k) be the subset of U(k) such that g(G)≡ 0 (mod 4), there are just g/2 independence edges of M(G) in C _g(G) and there are some edges of E(G)\ M(G) in G\ C _g(G) for any G∈U ⁰(k). In this paper, we discuss the graphs with minimal and second minimal energies in U ^*(k) = U(k)\ U ⁰(k), the graph with minimal energy in U ⁰(k), and propose a conjecture on the graph with minimal energy in U(k).      

Characteristic parameter method for studying kinetics of opposing reactions in calorimeter

According to the theoretical basis of thermokinetics, the integral and differential thermokinetic equations of opposing reactions have been derived, and a novel thermokinetic research method, the characteristic parameter method for opposing reactions which taking place in a batch conduction calorimeter under isothermal condition, has been proposed in this paper. Only needing the characteristic thermoanalytical data corresponding to t_m and 2t_m from the same curve, the rate constants of forward and backward reactions and equilibrium constant can be calculated simultaneously with this method. In order to test the validity of this method, the proton-transfer reactions of nitroethane with ammonia at 15 and 25°C, and with trihydroxymethyl aminomethane (Tris) at 15 and 30°C have been studied, respectively. The results of rate constants and equilibrium constants calculated with this method are in agreement with those in the literature. Therefore, the characteristic parameter method for opposing reaction is believed to be correct.This revised version was published online in November 2005 with corrections to the Cover Date.     

1-乙基-4-氧-7-甲基-1,8-萘啶-3-羧酸的合成

乙基氧甲基萘啶羧酸;缩合反应;成环反应;乙基化反应;水解反应;光谱特征