平面曲线上几何MDS码的主猜想

本文用Ｌａｎｇ－Ｗｅｉｌ的一个经典结果证明了在一定维数限制下充分大域上平面代数曲线上ＭＤＳ码的主猜想成立。     

码为交换前缀码的两个充要条件与层层可扩码

本文给出码为交换前缀码的充要条件,并由此得到一类交换前缀码,所谓层层可扩码。     

因数乘积中九码毕现而不重的结构

大约在１９７０年，辗转传来一个问题，说是一本很老的像是趣味数学的书里发现的：由１，２，３，…，８，９九个数码组成Ａ，Ｂ，Ｃ三个数，他们的位数依次为二、三、四，九个数码全要用到，不许重复，而且要ＡＢ＝Ｃ，求这三个数．原书有答案而无解法．答案有七组，是１...     

游程长度受限码RLL(4,18)的研究

介绍了一种新的用于高密度光盘存储的游程长度受限码。给出RLL(4,18)码的构造方法和编解码步骤。对RLL(4,18)码的编码器和解码器进行了CPLD实现。对不同游程长度受限码的主要性能参数进行了比较。     

岛津推出高性价比紫外可见分光光度计UV-1780

紫外可见分光光度计UV-1780具有同档次最高分辨率,同时光谱带宽5档可选,满足用户各种分析需求。UV-1780标准配备3个USB接口,分别用于与PC机连接(选配UVProbe软件)直接控制主机,与打印机连接(支持PCL语言)直接打印,与市售USB储存器(U盘)存储连接传输数据。标准配备3个I/O接口,用于应用附件的连接。     

岛津推出高性价比紫外可见分光光度计UV-1780

<正>紫外可见分光光度计UV-1780具有同档次最高分辨率,同时光谱带宽5档可选,满足用户各种分析需求。UV-1780标准配备3个USB接口,分别用于与PC机连接(选配UVProbe软件)直接控制主机,与打印机连接(支持PCL语言)直接打印,与市售     

New exact solutions for free vibrations of rectangular thin plates by symplectic dual method

The separation of variables is employed to solve Hamiltonian dual form of eigenvalue problem for transverse free vibrations of thin plates, and formulation of the natural mode in closed form is performed. The closed-form natural mode satisfies the governing equation of the eigenvalue problem of thin plate exactly and is applicable for any types of boundary conditions. With all combinations of simplysupported （S） and clamped （C） boundary conditions applied to the natural mode, the mode shapes are obtained uniquely and two eigenvalue equations are derived with respect to two spatial coordinates, with the aid of which the normal modes and frequencies are solved exactly. It was believed that the exact eigensolutions for cases SSCC, SCCC and CCCC were unable to be obtained, however, they are successfully found in this paper. Comparisons between the present results and the FEM results validate the present exact solutions, which can thus be taken as the benchmark for verifying different approximate approaches.     

利用人工神经网络法预测烷烃的沸点

有机物沸点是有机物的一种非常重要的性质 .采用人工神经网络模型 ,选用结构描述码作为输入特征参数对烷烃的沸点进行预测 ,得到了很高的预测精度 .该方法还可作为对有机化合物的其他性质进行预测的一种有效手段     

环F_(p~k)+uF_(p~k)+u~2F_(p~k)上码是循环码的一个充分必要条件

记环R=F_p~k+uF_p~k+u~2F_p~k,定义了一个从R~n到F_p~k~(2np~k)的Gray映射.利用Gray映射的性质,研究了环R上任意长循环码.证明了环R上任意长码是循环码当且仅当它的Gray象是F_p~k上的准循环码.特别的,环R上的线性循环码的Gray象是F_p~k上的线性准循环码.     

Study of FSK/IM orthogonal modulation system with optical Manchester-coded payload

<正>We study the performance of an orthogonal modulation system with frequency-shift keying(FSK) label and optical Manchester-coded(MC) payload.Simulation result shows that by introducing an optical MC payload,the available extinction ratio(ER) value of a FSK and intensity modulation(IM) orthogonal modulation system can be improved from 5 to 9 dB for system optimization,exhibiting great advantages over the traditional non-return-to-zero(NRZ) payload.Besides,the bit error rate(BER) characteristics of both label and payload show a more remarkable advantage than that of NRZ coding,verifying itself as a perfect candidate for the payload coding method in orthogonal modulation systems.