环Z/p\+kZ上m阶交错矩阵的计数定理及其应用

设W\-m(R)是有限局部环R=Z/p\+kZ上所有m阶交错矩阵所构成的集合（p是素数,k>1）. 该文通过确定R上任意m阶交错矩阵的标准形,计算出W\-m(R)在线性群GL\-m(R)作用下的轨道数及n(2r,2t,\{r\-1,\:,r\-1\}[TXX}][DD(X]s\-1[DD)],\:,\{r\-l,\:,r\-l\}[TXX}][DD(X]s\-l[DD)]),其中W（2r,2t,\{r\-1,\:,r\-1\}[TXX}][DD(X]s\-1[DD)],\:,\{r\-l,\:,r\-l\}[TXX}][DD(X]s\-l[DD)])(∑[DD(]l[]i=1[DD)]s\-i=t)表示不变因子为（2r,2t,\{r\-1,\:,r\-1\}[TXX}][DD(X]s\-1[DD)],\:,\{r\-l,\:,r\-l\}[TXX}][DD(X]s\-l[DD)])的所有m阶交错矩阵构成的集合,n(2r,2t,（2r,2t,\{r\-1,\:,r\-1\}[TXX}][DD(X]s\-1[DD)],\:,\{r\-l,\:,r\-l\}[TXX}][DD(X]s\-l[DD)])表示其中的元素个数. 最后,作者利用有限局部环R上交错矩阵的标准形构作了一个Cartesian认证码,并计算出其全部参数.     

Critical evaluation of CFD codes for interfacial simulation of bubble‐train flow in a narrow channel

Computational fluid dynamics (CFD) codes that are able to describe in detail the dynamic evolution of the deformable interface in gas–liquid or liquid–liquid flows may be a valuable tool to explore the potential of multi‐fluid flow in narrow channels for process intensification. In the present paper, a computational exercise for co‐current bubble‐train flow in a square vertical mini‐channel is performed to investigate the performance of well‐known CFD codes for this type of flows. The computations are based on the volume‐of‐fluid method (VOF) where the transport equation for the liquid volumetric fraction is solved either by the methods involving a geometrical reconstruction of the interface or by the methods that use higher‐order difference schemes instead. The codes contributing to the present code‐to‐code comparison are an in‐house code and the commercial CFD packages CFX, FLUENT and STAR‐CD. Results are presented for two basic cases. In the first one, the flow is driven by buoyancy only, while in the second case the flow is additionally forced by an external pressure gradient. The results of the code‐to‐code comparison show that only the VOF method with interface reconstruction leads to physically sound and consistent results, whereas the use of difference schemes for the volume fraction equation shows some deficiencies. Copyright © 2007 John Wiley & Sons, Ltd.     

关于某些BCH码的不可检错误概率

本文研究了二元对称信道上，某些ＢＣＨ码的不可检错误概率。首先得到了几个重要的不等式。然后证明了纠正两个错误二进制本原ＢＣＨ码的扩展码是最佳检错码。     

采用光码分多址技术的高速计算机局域网

本文提出一种可行的适于高速计算机网络的光码分多址技术，该网络采用光正交码和光信号处理，以保证实时数据通信。提出的全光结构的快速可调光正交码编码器和解码器，可在光域中用电光开关和光延迟线实现，能支持超高速吞吐量且重构时间很短     

Measurement and analysis of alpha-induced reactions on Ta,Ag and Co

Excitation functions for the reaction¹⁸¹Ta (α,xn)^185−x Re,^107,109Ag (α, ypxn) and⁵⁹Co (α, ypxn) were obtained from measurements of residual activity of stacked foils from threshold to 60 MeV. The excitation functions for the production of¹⁸¹Re,¹⁸²Re,¹⁸³Re,¹⁸⁴Re,¹⁰⁵Ag,¹¹¹In,⁵⁴Mn,⁵⁶Co,⁵⁸Co, and⁶⁰Co, are being presented. The experimental data are compared with calculations considering equilibrium as well as pre-equilibrium reactions according to the hybrid model of Blann. High energy part of the excitation functions is dominated by the pre-equilibrium reaction mechanism. Calculations were done using a priori calculational method of Overlaid Alice Code of Blann. Most of the excitation functions in the energy range mentioned above could be very well fitted with the hybrid model calculation for exciton numbern=4 withn _p=2 andn _n=2. The overall agreement with theory is good. Certain discrepancies, however, indicate the necessity to revise the hybrid model with respect to emission of complex particles.     

The Generalized Delay-Locked Loop

The delay-locked loop (DLL) is a synchronization device that is widely used for PN-code tracking in spread spectrum systems. The error detector characteristic (S-curve) of the DLL has a major impact on the performance. Using more than two correlators will extend the tracking range of the S-curve. The Generalized DLL (GenDLL) theory provides a concept to analyze a large class of DLL configurations including the classical DLL. The focus of the performance criteria is on tracking jitter and the mean time to lose lock (MTLL). It is shown that the MTLL can be considerably improved by using extended S-curves. However, the tracking jitter is increased by additional correlators. The tradeoff between the two criteria is explained. With the GenDLL theory loop configurations can be designed having both low tracking jitter and high loop robustness against loss of lock.     

一种基于星座协作映射的改进P-OFDM方法

针对室内高速光无线链路设计,提出了一种新的光正交频分复用技术方案——改进极性光正交频分复用(MP-OFDM)。通过将星座协作映射技术引入到极性光OFDM(P-OFDM)系统中,在获得高效的功率和频谱利用率、较低峰均平均功率比(PAPR)及较好误码性能的同时,还可以进一步提高系统编码增益,增加系统设计自由度。仿真实验表明,与P-OFDM技术相比,该方案的PAPR性能与其接近,而平均误码块率性能则优于前者,即MP-OFDM系统可在不牺牲PAPR的同时获得更好的平均误码块率性能。同时,在功率分配方案中,系统能在平均误码块率性能与PAPR性能之间取得更好的折衷。     

SCMA codebook design based on resource block constellation

Aiming at the problems of typical sparse code multiple access codebook design scheme based on multidimensional mother constellation that the complexity is high and the minimum Euclidean distance between constellation points on resource blocks is difficult to determine,a SCMA codebook design scheme based on resource block constellation was proposed.By converting the design of multidimensional mother constellation into the design of two-dimensional resource block constellation,the design complexity of constellation was reduced.And the codebook design scheme starting from resource block constellation could maximize the minimum Euclidean distance between constellation points on resource blocks,which was better than the design method in which user codebooks were obtained from multi-dimensional mother constellation.Simulation results show that the proposed SCMA codebook design scheme based on resource block constellation can significantly improve the BER performance of system compared with the typical codebook design scheme based on multidimensional mother constellation.     

多无人机扩频测控链路的扩频码分析

在码分多址（CDMA）的多无人机扩频测控链路中,多址干扰（MAI）是多目标系统需考虑的重要因素。在此类系统中,针对抗多址干扰的要求,设计具有相应互相关性能的扩频码是首要任务。从多无人机对抗多址能力的需求入手,分析了码速率、用户个数以及码的互相关性能对抗多址干扰能力的影响,得出了Kasami码型互相关性较好、序列部分相关会降低互相关性能的结论。仿真结果验证了理论分析的正确性。     

“北斗”B2频段导航信号伪码跟踪性能分析

与传统卫星导航信号体制不同,新一代“北斗”B2频段导航信号采用了交替二进制偏移载波调制（AltBOC）体制,因此伪码跟踪性能也与传统信号体制有较大差异。首先介绍了AltBOC调制信号原理及特点,然后根据码跟踪精度理论比较了新型调制信号与传统信号体制的性能差异,分析了不同鉴相器时B2频段信号的码跟踪误差,并对不同相关器间隔、环路带宽、前端带宽、载噪比环境条件下的伪码跟踪误差进行了仿真分析。仿真结果表明,提高信号载噪比、射频前端带宽或减小相关器间隔、环路带宽均能减小码跟踪误差。研究结果对新一代“北斗”导航信号新体制性能的评估以及“北斗”导航接收机的系统设计具有一定指导意义。