数论中切比雪夫不等式的一点补充

利用Wallis不等式,得到素数计算函数的一个下界估计.     

相似椭圆系的一组性质

在几何图形中,相似图形是几何中较为神奇的一族,给人以视觉上的美感.众所周知,椭圆的形状是由该椭圆的离心率决定的.笔者给出相似椭圆系的定义并研究它的一组性质.定义:对于中心相同,离心率也相同的"个椭圆,其方程分别为:C₁:x²/a²+y²/λ²a²=1（0〈λ〈1,a〉0）,C₂:x²/λ²a²     

The quasi-reversibility method to solve the Cauchy problems for parabolic equations

In this paper, on the one hand, we take the conventional quasi-reversibility method to obtain the error estimates of approximate solutions of the Cauchy problems for parabolic equations in a sub-domain of QT with strong restrictions to the measured boundary data. On the other hand, weakening the conditions on the measured data, then combining the duality method in optimization with the quasi-reversibility method, we solve the Cauchy problems for parabolic equations in the presence of noisy data. Using this method, we can get the proper regularization parameter ε that we need in the quasi-reversibility method and obtain the convergence rate of approximate solutions as the noise of amplitude δ tends to zero.     

工薪类个税征收标准对调节居民收入分配作用的统计分析

个人所得税一直是中国老百姓最关注的话题之一,2011年个税征收标准改革的问题再次引起大家的关注,主要焦点集中在工资、薪金类的个税征收的起征点和累进税率。本文选择2001至2010年31个省份的19行业的平均工资为基础数据,运用SPSS统计分析软件分别按省份和行业作为因子对税前和税后的平均工资做方差分析,利用假设检验的P值构造统计量,定义了调节比和调节得分两个评价指标,用这两个指标衡量个人所得税征收标准对缩小工资差距的效用。本文中该模型把个税征收标准对调节居民收入分配的效果数量化,通过得分指标的变动说明过去两次个税征收标准调整的必要性以及今年审议的第四套个人所得税征收标准草案的优劣。还可以通过该模型构建的指标对某套个人所得税的征收标准是否适应当前经济发展需要起到参考作用。     

人造金刚石与硬质合金复合材料的研制

 本实验选用TiH₂及其它微量元素做粘结剂，在DS-029B型六面顶压机上烧结人造金刚石与硬质合金复合材料。实验中，采取TiH₂脱氢与金刚石净化同时进行的工艺，在高真空和一定温度下脱氢，得到高活性的新鲜钛，使其具有更强的粘结作用，以获得高磨耗比的金刚石复合材料。实验中比较了不同净化温度对磨耗比的影响；同一种粘结剂不同含量与磨耗比之间的关系；同时还测试了其耐热性及时间极限。结果表明，这种复合材料在850 ℃下，加热3 min，磨耗比没有明显改变。     

All-optical broadcast and multicast technologies based on PPLN waveguide

All-optical 1 ×4 broadcast and 1 ×3 multicast experiments of a 40-Gb/s return-to-zero on-off keying （RZ- OOK） signal based on a periodically poled lithium niobate （PPLN） waveguide are demonstrated in this letter. Clear opened eye diagrams and error-free performance are achieved for the broadcast signals at 1541.3, 1543.7, 1548.5, and 1550.9 nm. Multicast technology uses cascaded second-harmonic generation and difference-frequency generation in a Ti：PPLN waveguide. An error-free operation with a negligible power penalty is achieved for the three wavelength-division multiplexing multicast signals at 1533, 1537, and 1541 nm.     

Analysis of atom detection via the magnetic optical effect

We demonstrated a new method of atom detection by means of the magnetic optical effect. The number density of the atom cloud was measured by detecting the rotation angle of the polarization plane of linearly polarized probe light when propagating inside the atomic cloud. Detuning, the magnetic field and light intensity dependencies of the rotation angle were studied theoretically and experimentally to find the best parameter for atom detection. In this way, we managed to achieve a rotation angle of 0.22 rad with a signal to noise ratio (SNR) of 75 and a contrast of 87.5%.     

Four distributed feedback laser array integrated with multimode-interference and semiconductor optical amplifier

Monolithic integration of four 1.55-μm-range InGaAsP/InP distributed feedback (DFB) lasers using varied ridge width with a 4×1-multimode-interference (MMI) optical combiner and a semiconductor optical amplifier (SOA) is demonstrated. The average output power and the threshold current are 1.8 mW and 35 mA, respectively, when the injection current of the SOA is 100 mA, with a side mode suppression ratio (SMSR) exceeding 40 dB. The four channels have a 1-nm average channel spacing and can operate separately or simultaneously.     

Measuring causality by taking the directional symbolic mutual information approach

We propose a novel measure to assess causality through the comparison of symbolic mutual information between the future of one random quantity and the past of the other.This provides a new perspective that is different from the conventional conceptions.Based on this point of view,a new causality index is derived that uses the definition of directional symbolic mutual information.This measure presents properties that are different from the time delayed mutual information since the symbolization captures the dynamic features of the analyzed time series.In addition to characterizing the direction and the amplitude of the information flow,it can also detect coupling delays.This method has the property of robustness,conceptual simplicity,and fast computational speed.