一种新的适用于水声信道的常模类盲均衡算法

为了缓解常数模盲均衡算法收敛速度缓慢、稳态误差大的问题,考虑到初始化权值对CMA算法的重要影响,本文利用遗传算法对CMA算法进行了有效改进,引入了小样本重用的思想,给出了一种新的适用于水声信道的常模类盲均衡算法。计算机仿真研究证明,该算法不仅大大加快了收敛速度,而且有效地降低了稳态误差。     

高速相干光通信系统中的自适应步长恒模算法

对于高速光通信系统中的相干检测来说,盲均衡是一项常用的恢复传输符号的技术。目前应用最广泛的盲均衡算法是恒模算法,但是一方面它不能兼顾收敛速度和收敛精度,另一方面在偏分复用系统中很容易陷入奇异性。因此提出了一种改进型的恒模算法———自适应步长恒模算法,并在112Gb/s偏分复用16进制正交幅度调制系统中对提出的算法进行了测试。与传统的恒模算法相比,改进后的算法收敛速度仅为恒模算法的1/20;收敛稳定后误差函数的方差比恒模算法降低了0.7dB;对偏分复用系统中的奇异性有很好的抵抗能力;在不考虑奇异性问题时,光信噪比代价与恒模算法相比降低了1.5dB。     

An improvement on constant modulus algorithm for polarization demultiplexing in optical coherent receivers

In order to solve the problem of ill-convergence for constant modulus algorithm (CMA) in polarization division multiplexing system with optical coherent receivers, a modified CMA based on bit error rate (BER) aiding to control initial tap setup, named as BER-Aiding CMA (BA-CMA), is proposed in this paper. By analyzing the principle of CMA for adaptive digital equalization and polarization demultiplexing, the convergence behavior that leads to undesirable result is evaluated and therefore BA-CMA is proposed. Simulation results show that the proposed algorithm is able to overcome the undesirable convergence effectively and keep inherent advantages of CMA at the same time.     

Spatial and Temporal CM Equalization for Broadband Wireless Indoor Networks at Millimeter Waves

Based on a new multipath channel model, a spatial-temporal combined CM equalization approach is derived at millimeter waves. Computer simulations are presented to testify the theoretical analysis. It is shown that this method can compensate the signal degradation caused by indoor multipath propagation. The convergence behavior of the spatial-temporal CMA is also analyzed.     

超高速相干光通信两步步长优化CMA算法

在超高速相干光通信中，对偏振解复用损伤和偏振模色散的补偿一般采用恒模算法(constant modulus algorithm, CMA)。标准的CMA算法具有自适应动态均衡的功能，加权信号根据输入信号进行不断更新，是一种目前流行的盲均衡算法。通常在CMA算法中，步长系数的取值严重影响着算法收敛、误差矢量幅度(error vector magnitude, EVM)和误码率(bit error ratio, BER)性能评价。提出了一种优化的CMA算法，具有两步步长系数，可标记误差矢量函数曲线稳定时的区间。经过计算验证表明，优化的CMA算法具有不同程度的解调性能改善，能够降低X、Y偏振态的EVM，具备较好的应用性。     

语音通信降噪研究

语音通信系统中,语音通过信道传输将不可避免地引入码间串扰和信号畸变,同时受到噪声污染。本文在分析自适应盲均衡算法CMA(constant modulus algorithm）和改进盲均衡算法的基础上,考虑到自适应盲均衡技术在语音噪声控制方面能力有限,将自适应盲均衡技术与小波包掩蔽阈值降噪算法联合使用,形成一种基带语音增强新方法。仿真试验结果显示自适应盲均衡技术可以使星座图变得清晰而紧凑,有效减小误码率。研究证实该方法在语音信号ISI和畸变严重情况下,在白噪及有色噪声不同的噪声环境中都具有稳定的降噪能力,消噪同时可获得汉语普通话良好的听觉效果。     

Different chromatin fractions of tomato (Solanum lycopersicum L.) and related species

Conventional chromosome staining has suggested that more than 75% of the tomato chromosomes are constituted by heterochromatin. In order to determine whether more deeply stained proximal regions are classic heterochromatin, the distributions of C-bands and chromomycin A₃ (CMA) bands, and the prophase condensation patterns, were analysed in tomato. In this and most other species of the tomato clade, the 5S and 45S rDNA sites were also localised. In tomato, CMA banding was similar to C-banding. After conventional staining, all species displayed large condensed heteropycnotic regions that did not correspond to C-bands or CMA bands. Analyses of the CMA banded karyotypes revealed a low heterochromatin content. Around 12–17% of the chromatin of tomato was CMA⁺ and 1/4 to 1/5 of this heterochromatin corresponded to 45S rDNA. In other species, the CMA⁺ heterochromatin showed extensive variation (8–35%), but was never near the values found in the literature for tomato. These data suggest the existence of three principal fractions of chromatin in tomato and related species: the late condensed euchromatin corresponding to the terminal regions of the chromosomes, the precocious condensed euchromatin that occupies the major part of the chromosomes and the constitutive heterochromatin that represents those regions revealed by C-bands.     

Carbon nanotubes supported Pt-Ni catalysts and their properties for the liquid phase hydrogenation of cinnamaldehyde to hydrocinnamaldehyde

The Pt-Ni catalysts supported on CNTs have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding hydrocinnamaldehyde (HCMA) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.34 wt% Ni/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 70 °C under a pressure of around 2.0 MPa, and 98.6% for the conversion of CMA and 88.2% for the selectivity of CMA to HCMA, respectively. The selective hydrogenation for the CC bond in CMA would be improved as increasing the reaction temperature, and the hydrogenation for the CO bond in CMA is enhanced as increasing the H₂ pressure. In addition, these catalysts have also been characterized using TEM-EDS, XPS, H₂-TPR and H₂-TPD techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Ni would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to HCMA.     

One-body potential theory of molecules and solids modified semiempirically for electron correlation

The study of Cordero, March and Alonso (CMA) for four spherical atoms, Be, Ne, Mg and Ar, semiempirically fine-tunes the Hartree-Fock (HF) ground-state electron density by inserting the experimentally determined ionization potentials. The present Letter, first of all, relates this approach to the very recent work of Bartlett ‘towards an exact correlated orbital theory for electrons’. Both methods relax the requirement of standard DFT that a one-body potential shall generate the exact ground-state density, though both work with high quality approximations. Unlike DFT, the CMA theory uses a modified HF non-local potential. It is finally stressed that this potential generates also an idempotent Dirac density matrix. The CMA approach is thereby demonstrated to relate, albeit approximately, to the DFT exchange-correlation potential.     

Comparison of the measured and theoretical performance of a broadband circular microphone array

The design and construction of a circular microphone array (CMA) that has a wide frequency range suitable for human hearing is presented. The design of the CMA was achieved using a technique based on simulated directivity index (DI) curves. The simulated DI curves encapsulate the critical microphone array performance limitations: spatial aliasing, measurement noise, and microphone placement errors. This paper demonstrates how the non-regularized DI curves for a given beamforming order clearly define the bandwidth of operation, in other words, the frequency band for which the beamformer has relatively constant and maximum directivity. Detailed and comprehensive experimental data that characterizes the CMA beamformer are also presented.     

Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with carbon nanotubes supported Pt-Co catalysts

The Pt-Co catalysts supported on carbon nanotubes (CNTs) have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding cinnamyl alcohol (CMO) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.17 wt%Co/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 60 °C under a pressure of around 2.5 MPa, and 92.4% for the conversion of CMA and 93.6% for the selectivity of CMA to CMO, respectively. The selective hydrogenation for the CO double bond in CMA would be improved as increasing the H₂ pressure, and the selective hydrogenation for the CC double bond in CMA is enhanced as increasing the reaction temperature. In addition, these catalysts have also been characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR) and H₂-temperature programmed desorption (H₂-TPD) techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Co would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to CMO.     

Enhanced direct sunlight photocatalytic oxidation of methanol using nanocrystalline TiO2 calcined at different temperature

The pharmacokinetics (PK) of carrier-mediated agents (CMA) is dependent upon the carrier system. As a result, CMA PK differs greatly from the PK of small molecule (SM) drugs. Advantages of CMAs over SMs include prolonged circulation time in plasma, increased delivery to tumors, increased antitumor response, and decreased toxicity. In theory, CMAs provide greater tumor drug delivery than SMs due to their prolonged plasma circulation time. We sought to create a novel PK metric to evaluate the efficiency of tumor and tissue delivery of CMAs and SMs. We conducted a study evaluating the plasma, tumor, liver, and spleen PK of CMAs and SMs in mice bearing subcutaneous flank tumors using standard PK parameters and a novel PK metric entitled relative distribution over time (RDI-OT), which measures efficiency of delivery. RDI-OT is defined as the ratio of tissue drug concentration to plasma drug concentration at each time point. The standard concentration versus time area under the curve values (AUC) of CMAs were higher in all tissues and plasma compared with SMs. However, 8 of 17 SMs had greater tumor RDI-OT AUC_0–last values than their CMA comparators and all SMs had greater tumor RDI-OT AUC_0–6 h values than their CMA comparators. Our results indicate that in mice bearing flank tumor xenografts, SMs distribute into tumor more efficiently than CMAs. Further research in additional tumor models that may more closely resemble tumors seen in patients is needed to determine if our results are consistent in different model systems.     

Comparison of detrending methods for fluctuation analysis

We examine several recently suggested methods for the detection of long-range correlations in data series based on similar ideas as the well-established Detrended Fluctuation Analysis (DFA). In particular, we present a detailed comparison between the regular DFA and two recently suggested methods: the Centered Moving Average (CMA) Method and a Modified Detrended Fluctuation Analysis (MDFA). We find that CMA performs the same as DFA in long data with weak trends and is slightly superior to DFA in short data with weak trends. When comparing standard DFA to MDFA we observe that DFA performs slightly better in almost all examples we studied. We also discuss how several types of trends affect different types of DFA. For weak trends in the data, the new methods are comparable with DFA in these respects. However, if the functional form of the trend in data is not a-priori known, DFA remains the method of choice. Only a comparison of DFA results, using different detrending polynomials, yields full recognition of the trends. A comparison with independent methods is recommended for proving long-range correlations.     

Algorithm for a microfluidic assembly line

Microfluidic technology has revolutionized the control of flows at small scales giving rise to new possibilities for assembling complex structures on the microscale. We analyze different possible algorithms for assembling arbitrary structures, and demonstrate that a sequential assembly algorithm can manufacture arbitrary 3D structures from identical constituents. We illustrate the algorithm by showing that a modified Hele-Shaw cell with 7 controlled flow rates can be designed to construct the entire English alphabet from particles that irreversibly stick to each other.     

Optical pump-probe scanning tunneling microscopy for probing ultrafast dynamics on the nanoscale

The development of a method for exploring the ultrafast transient dynamics in small organized structures with high spatial resolution is expected to be a basis for further advances in current science and technology. Recently, we have developed a new microscopy technique by combining scanning tunneling microscopy (STM) with ultrashort-pulse laser technology, which enables the visualization of ultrafast carrier dynamics even on the single-atomic level. A nonequilibrium carrier distribution is generated using ultrashort laser pulses and its relaxation processes are probed by STM using the optical pump-probe method realized in STM by the pulse-picking technique. In this paper, the fundamentals of the new microscopy technique are overviewed.     

Synthesis of carbon planar structures with specified properties

A new method is proposed that allows an integrated technology to be used for the synthesis of carbon planar structures with predetermined properties. The method is based on the avalanche annealing of amorphous short-period superlattices. The synthesized samples are investigated by Raman spectroscopy and photoluminescence. The possibility of synthesizing carbon layers with diamond-like, graphite-like, graphene, or other structures is demonstrated experimentally using the example of a C/SiC superlattice.     

Modeling of the crystal structure growth process of GaAs

Current needs of the industry require new results, and current possibilities of computer technology allow solving problems at a completely new level. This article briefly describes the algorithms of obtaining the structures and appearance of discontinuities while crystals grow.     

A new approach to formation of the topology of planar structures on the basis of a YBCO high-temperature superconductor

The paper presents a new etching-free technology for the formation of planar superconductor structures based on YBCO films with metal contacts. The required topology of superconducting elements from YBCO film is created by the proposed “preliminary topology mask” method. The ohmic contacts to the superconducting structure are produced by lift-off photolithography. In order to study the capabilities of this technology, measurements of superconducting bridges with a width of 3, 10, and 50 μm and test structures for measuring the contact resistance are performed.     

Turning the world vertical: MOSFETs with current flow perpendicular to the wafer surface

Tremendous progress in information technology has been made possible by the development and optimization of metal oxide semiconductor field effect transistor (MOSFET) devices. For the last three decades, the dimensions of the devices have been scaled down and the complexity of the integrated circuits increased according to Moore’s law. Further scaling of the devices has been predicted by the international technology roadmap for semiconductors (ITRS). To meet the future technological requirements, much effort has been expended on increasing the capabilities of MOSFETs. Both new materials and new designs have been introduced to maintain device scaling. Most new designs were improvements of the normal planar design of the device, such as SOI and ultrathin body devices. In so-called FinFET structures, current flows through a thin silicon fin and is controlled by two gates in parallel on both sides of the fin. Vertical MOSFET devices represent a new category. In these structures the planar arrangement of the source gate and drain is turned through 90° so that they are positioned on top of each other and the current flow is perpendicular to the surface. By utilizing the 3rd dimension, the channel length can be adjusted by layer deposition and thus dispensing with advanced (and expensive) lithography. Furthermore, depending on the application, the vertical designs require less space than planar ones so that it is possible to increase integration density. The present paper gives a review of vertical MOSFET devices with current flow perpendicular to the surface. PACS 85.30     

超声速混合层MHz级超高频流动可视化实验

研究发展了超高频基于纳米示踪的平面激光散射（nano-tracer planar laser scattering,NPLS）技术。基于多腔并联脉冲激光器技术、棱锥分光与短曝光相机集成技术以及高精度同步控制技术,实现了MHz级流场可视化和精细测量。采用超高频NPLS技术研究了对流Mach数Ma_c=0.17,0.26混合层流场,获得了时间序列的混合层高分辨率NPLS图像。采用阵列型涡流发生器开展流动控制研究,分析涡流发生器对混合层发展的影响特性。通过选取典型涡结构,分析了超声速混合层不同发展阶段的涡运动和发展演化规律。发现混合层中段的不稳定性发展阶段,涡结构以平移和旋转为主,伴随一定的拉伸;混合层后段以变形和破碎为主,有大量小尺度结构产生。并且小尺度结构会受到剪切、大尺度结构以及小激波的影响,发生明显的非定常运动。