Capture Properties of the Generalized CMA in Alpha-Stable Noise Environment

Constant modulus algorithm (CMA) is an adaptive technique for correcting multipath and interference-induced degradations in constant envelope waveforms. The algorithm exploits the fact that both multipath and additive interference can disrupt the constant envelope of the received signal. By detecting the received envelope variations, the adaptive algorithm has the ability to reset the coefficients vector so as to remove the variations, and in the process, reject the various interference components from the desired signal. If both the interferer and the signal of interest have constant envelope and are spectrally non-overlapped, it is possible to find two different solutions for the coefficient vector, in which one suppresses the interferer and the other “captures” the interferer. The problem of how “capture” can occur and how it may be prevented in Gaussian noise environment has been perfectly developed in the previous work (Treichler, Larimore, IEEE Trans Acoust Speech Signal Process, 33:946–958, 1985). However, recent investigation on the physical channels in wireless communication shows that there is aggregate noise component exhibiting high amplitudes for small duration time interval. This paper proposes a GCMA (Generalized CMA) which generalizes the CMA by introducing the α-stable distribution as the noise model. Here the original CMA is only a special case of the GCMA. In order to describe the average behavior of the GCMA, a simple model consisting of only two sinusoids is presented. As assuming slow adaptation, the adaptive weight recursion is shown to compress into a two-by-two recursion in the tone output amplitudes. The simplified recursion is analyzed to determine what combination of signals power and initialization on coefficient vectors leads to “lock” and what leads to the capture of the interferer. The method to determine lock and capture zone boundaries is analyzed. These convergence properties of the GCMA are studied by computer simulations.

Mechanical spectroscopy of nanocrystalline metals: Structure and anelastic behavior

Nanocrystalline aluminum and nickel were prepared by mechanical attrition in a planetary ball-milling apparatus working under a 10⁻⁴ Pa vacuum in the 150–300 K range. A detailed investigation of the mechanical behavior in the anelastic regime was accomplished by employing different mechanical spectroscopy apparatuses in the 0.01–10³ Hz range. Measurements of the elastic energy dissipation coefficient and of the dynamic elasticity modulus as a function of temperature and frequency have shown an enhanced damping at low temperatures and an anelastic relaxation peak tentatively assigned to the short range dynamics at the interfaces. Moreover the magnetic field dependence of the dynamic elastic modulus in nickel revealed a strict correlation between the microstrains confined at the interfaces and the magnitude of the magnetoelastic coupling.     

Blind Equalization Using Coordinate Mapping for 4-PAM and 16-QAM Signals

It is well known that the famous Constant modulus algorithm （CMA） presents a large steady-state Mean square error （MSE） for nonconstant modulus sig- nals. In this paper a coordinate mapping approach for a 4-PAM nonconstant modulus signal is described which can change the signal to an Offset QPSK （OQPSK） constant modulus signal. And a new algorithm based on this ap- proach is proposed which is also suitable for a 16-QAM signal. For the 4-PAM and 16-QAM nonconstant modulus signals the proposed algorithm can achieve a zero steady- state MSE in a noiseless environment but CMA cannot, Theoretical analysis and simulations results demonstrate the high performance of the proposed algorithm.     

叉指型微电极交流电渗泵的阻抗谱分析

阻抗谱的研究对于优化交流电渗泵的结构具有重要意义。通过分析交流电渗泵的结构和工作原理,指出双电层的电容特性和电解质溶液的电阻特性,建立了用来研究交流电渗泵阻抗谱的RC等效电路。在最佳电极结构参数设置下,得到了不同频率下的阻抗谱,分析了电极周期长度以及通道高度改变对交流电渗泵阻抗模以及幅角的影响,并对电解质溶液浓度对阻抗谱的影响做了估计。结果表明,工作频率的增加总体上会造成阻抗模的增大和阻抗角的减小,而同一频率下不同因素对阻抗谱的影响又有所不同。该结论对交流电渗泵的设计和功耗研究有一定的理论指导意义。     

Property of eigenvalues and eigenfunctions for an interface V-notch in antiplane elasticity

The so-called pseudo-orthogonal property of the eigenfunction expansion form is proved to be valid for the case of an antiplane interface V-notch and the corresponding path-independent integral is derived. The relation between the path-independent integral and the stress intensity factor of the notch is found. The influence of loads on the related integral is also presented.     

新型棉/氨弹力织物的染整工艺研究

系统研究了染整加工中各工艺因素对棉/氨弹力织物各项性能的影响.研究表明,棉/氨弹力织物高温碱性条件下,损伤较为严重;双氧水漂白后织物的强力和弹性损伤较次氯酸钠漂白小;丝光碱用量以180g/L为宜;热定形以温度180℃,时间30s为宜.对含氨纶较少的棉/氨弹力织物可选择活性染料染色,染色后各项牢度较好,弹性回复率较高.     

PTT纤维小提花纬弹织物的开发

利用PTT纤维的性能优势，开发了小提花纬弹机织产品，设计并优选了染色后整理工艺参数，并进行了性能测试。     

Development of a method to measure rheological properties of carrot cell and cell-wall materials

A method for measuring the rheological properties of carrot cells and cell-wall material during typical cooking conditions has been evaluated. A Bohlin controlled-stress rheometer with a rapid heating attachment was used. Because of potential slippage and sensitivity problems with cells and cell-wall material, different geometries (parallel plate, cone and plate, and concentric cylinder) were assessed. Initial experiments were designed to determine the linear viscoelastic regions for the cell and cell-wall materials at 25°C. Samples were subjected to varying shear stresses and oscillatory frequencies. For carrot cells, linearity was observed with cone and plate geometry and with concentric cylinder geometry over a fairly wide range of stresses and frequencies. Parallel plate geometry did not give linear results. Carrot cell-wall material behaved in a linear fashion with all three geometries over similar stress and frequency ranges as carrot cells. Using the appropriate conditions of geometry, frequency and stress, the influence of heat treatments on cell and cell-wall rheology was compared. A comparison of cone and plate and concentric cylinder geometry was performed using cells and cell-wall material heated from 25 to 90°C. Cone and plate geometry showed greater changes in rheological properties during heating than concentric cylinder geometry and also allowed a greater range of heating rates. Cone and plate geometry was used in further studies. Studies on the rheological behaviour of cells during heating showed that the complex shear modulus (G^*) increased in the range 25–75°C then decreased. For cell-wall material, G^* showed a steady increase from 25 to 90°C. Further experiments demonstrated that the increase in G^* was not due to water loss during heating. The amount of cell damage during heating was measured using a conductivity meter to establish if there was a correlation between changes in G^* and cell damage.     

双向等比例加载下的混凝土动态抗压性能

为了研究混凝土试件在多轴受力、不同应力途径下的动态力学性能,采用大型静动态电液伺服试验系统,对混凝土试件进行双轴应力状态下等比例加载的动态抗压试验.双轴加载比例为1∶0、1∶05、1∶1,应变速率分别为10^-5/s、10^-4/s、10^-3/s、10^-2/s 4个量级.通过试验,研究了在不同应变速率、不同应力比情况下,混凝土抗压强度、弹性模量、峰值应变、应力应变曲线的性能.试验结果表明,随着应变速率的提高,各种应力比下混凝土的抗压强度、弹性模量均有提高.在相同应变速率下,与单轴动态受压相比,1∶0.5的应力比其抗压强度提高幅度大.     

张力条件下不同热处理对PTT纤维及毛/PTT混纺纱弹性的影响

研究了不同张力条件下,干热和湿热处理后的PTT纤维及毛/PTT混纺纱的弹性及拉伸性能.松弛条件下的干热和湿热处理导致了PTT纤维初始模量的降低、延伸性能的增加.一定张力条件下的干热和湿热处理可以防止PTT纤维初始模量的降低,且在张力小于6 cN/tex、150℃干热条件下处理PTT纤维将提高其回弹性能,这可能是由于张力作用导致了非晶区大分子链"Z"构象取向增加以及高温作用导致的结晶增加.这些现象在毛/PTT混纺纱弹性测试中也得到了验证.