Mach-Zehnder interferometers with asymmetric modulation arms in applications of high speed silicon-on-insulator based optical switches

Modulation arms with different widths are introduced to Mach-Zehnder interferometers (MZIs) to obtain improved performance. Theoretical analysis and numerical simulation have shown that when the widths of the two arms are properly designed to achieve an inherent m pi/2 (m is an odd integer) optical phase difference between the arms, the asymmetric MZI presents higher modulation speed. Furthermore, the carrier-absorption induced divergence of insertion losses in silicon-on-insulator (SOI) based MZI optical switches can be obviously improved.

Comparing the Performance of Biomimetic Pattern Recognition with W8 and SVM on Prediction of Horizontal Gene Transfers in Bacteria Genomes

National Natural Science Foundation of China 60753001

Multiple energy transfers in rare earth complex-doped SiO2 spheres

Silica spheres doped with Eu(TTFA)(3) and/or Sm(TTFA)(3) were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in the same samples co-doped with Eu (TTFA)(3) and Sm(TTFA)(3), namely between the ligand and Eu3+ ion, the ligand and Sm3+ ion, and Sm3+ ion and Eu3+, ion. Energy transfer of Sm3+-> Eu3+, in the hybrid spheres leads to fluorescence enhancement of Eu3+ emission by approximately an order of magnitude. The lifetimes of the hybrid spheres were also measured.

Synthesis and micellization of star-like hyperbranched polymer with poly(ethylene oxide) and Poly(epsilon-caprolactone) arms

Novel star-like hyperbranched polymers with amphiphilic arms were synthesized via three steps. Hyperbranched poly(amido amine)s containing secondary amine and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with feed molar ratio of 1:2. H-1, C-13, and HSQC NMR techniques were used to clarify polymerization mechanism and the structures of the resultant hyperbranched polymers

White Electroluminescence from a Star-Like Polymer with an Orange Emissive Core and Four Blue Emissive Arms

A star-like white light-emitting polymer with an orange emissive core and four blue emissive arms is designed and synthesized. White electroluminescence is observed with simultaneous orange emission from the core and blue emission from the arms. A single-layer device based on this polymer emits white light with CIE coordinates of (0.35, 0.39) and a luminous efficiency of 7.06 cd A(-1).

Laboratory Study on Sediment Diffusion and Deposition into Blind Channels

Any waterway with one end closed and the other open is generally called a blind channel. The main flow tends to expand, separate, and cause circulation at the mouth of blind channels. The main flow continuously transfers momentum and sediment into the circulation region through the turbulent mixing region (TMR) between them, thus leading to a large amount of sediment deposition in the blind channels. This paper experimentally investigated the properties of the water flow and sediment diffusion in TMR, demonstrating that both water flow and sediment motion in TMR approximately coincide with a similar structure as in the free mixing layer induced by a jet. The similarity functions of flow velocity and sediment concentration are then assumed, based on observation, and the resulting calculation of these functions is substantially facilitated. For the kind of low velocity flow system of blind channels with a finite width, a simple formula for the sediment deposition rate in blind channels is established by analyzing the gradient of crosswise velocity and sediment concentration in TMR.

Influence of the Processing Conditions on the Characteristics of the Clad Layers Produced with Laminar Plasma Technology

Laminar plasma technology was used to produce ceramic hardened layers of Al2O3-40% mass Ni composite powders on stainless steel substrates. In order to investigate the influences of processing conditions on the morphologies of the surface modified layers, two different powder-feeding methods were tested, one with carrier gas called the powder injection method, and the other without carrier gas called powder transfers method. The microscopic investigations demonstrate that the cross-section of the clad layers consists of two distinct microstructural regions, in which the Al2O3 phases exhibit different growth mechanisms. When the powder transfers method is adopted, the number density and volume fraction of the Al2O3 particles increase considerably and their distributions exhibit zonal periodical characteristics. When the powder-feeding rate increases, the microstructure of the Al2O3 phases changes from a small globular to a long needle shape. Finite element simulations show that the transient thermo-physical features of the pool substances, such as solidification rate and cooling rate, influence strongly the mechanisms of the nucleation and the directional growth of the Al2O3 phases in the thermal processing.

Numerical Analysis of LEC Growth of GaAs with an Axial Magnetic Field

A set of numerical analyses for momentum and heat transfer For a 3 in. (0.075 m) diameter Liquid Encapsulant Czochralski (LEC) growth of single-crystal GaAs with or without all axial magnetic field was carried Out using the finite-element method. The analyses assume a pseudosteady axisymmetric state with laminar floats. Convective and conductive heat transfers. radiative heat transfer between diffuse surfaces and the Navier-Stokes equations for both melt and encapsulant and electric current stream function equations Cor melt and crystal Lire considered together and solved simultaneously. The effect of the thickness of encapsulant. the imposed magnetic field strength as well as the rotation rate of crystal and crucible on the flow and heat transfer were investigated. (C) 2002 Published by Elsevier Science Ltd.

Comparative Study Of The Influence Of Natural Convection On Directional Solidification Of Al-3.5 Wt% Ni And Al-7 Wt% Si Alloys

We present numerical simulations of thermosolutal convection for directional solidification of Al-3.5 wt% Ni and Al-7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al-7 wt% Si, but not in Al-3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

A phase-shifting vectorial-shearing interferometer with wedge plate phase-shifter

We present a novel phase-shifting vectorial-shearing interferometer with a wedge plate phase-shifter. The interferometer is based on a modified Mach-Zehnder configuration; the common-path nature makes it capable of testing the wavefront of a short coherence-length light source, such as a laser diode. Vectorial shear (shearing in the x and y directions simultaneously) in an arbitrary direction is introduced by inserting two wedge plates orthogonally in two arms, respectively. One of the wedge plates is split into two parts (parallel part and wedge part); phase shift is produced by moving the wedge part in contact along the parallel part. The moving distance for a 2 pi phase shift is a few millimetres in specific conditions. The wedge plate phase-shifter increases the moving distance for phase shift and makes the control of phase shift relatively easy. We also discuss the lateral shear error and phase shift errors induced by wedge plates. The lateral shear error is small enough to be ignored; the phase shift error is determined mainly by the wedge angle error. Lastly, we give the experimental results of phase-shifting interference fringes in vectorial shear mode.

Analysis of beam-quality degradation in nonlinear frequency conversion

Based on the ripple transfers of electric-field amplitude and phase in frequency tripling, simple formulas are derived for the harmonic laser's beam-quality factor M-3omega(2), with an arbitrary fundamental incidence to ideal nonlinear crystals. Whereas the harmonic beam's quality is generally degraded, the beam's divergence is similar to that of the fundamental after nonlinear frequency conversion. For practical crystals with periodic surface ripples that are caused by their machining, a multiorder diffractive model is presented with which the focusing properties of harmonic beams can be studied. Predictions of the theories are shown to be in excellent agreement with full numerical simulations. (C) 2002 Optical Society of America.

芍药属两物种染色体结构变异杂合性研究

芍药属由大约35个灌木和多年生草本种组成，分为三个组：牡丹组(Sect. Moutan)、北美芍药组(Sect. Onaepia)和芍药组(Sect. Paeonia)。四川牡丹(Paeonia decomposita Handel-Mazzetti)和块根芍药(P. intermedia Meyer)分别隶属于牡丹组和芍药组。在该属的所有种中，染色体基数均为 x = 5，最短的五号染色体是端部着丝粒染色体，很容易辨认。 本论文研究了块根芍药三个居群22个个体和四川牡丹两个居群13个个体的减数分裂。减数分裂异常广泛发生，以至于发现所有被研究的个体都有数量不等的桥、断片和单价体。结果表明在中期I，块根芍药第一个居群平均每个小孢子母细胞有2.17个棒状二价体和2.7个环形二价体，第二个居群平均每个细胞有2.04个棒状二价体和2.86个环形二价体，第三个居群平均每个细胞有2.21个棒状二价体和2.71个环形二价体。而在四川牡丹中，第一个居群平均每个小孢子母细胞有2.09个棒状二价体和2.81个环形二价体，第二个居群平均每个细胞有1.85个棒状二价体和3.08个环形二价体。 块根芍药第一个居群的平均减数分裂染色体构型是2n = 10 = 0.25 I + 4.87 II，第二个居群是2n = 10 = 0.20 I + 4.90 II，第三个居群是2n = 10 = 0.17 I + 4.92 II，在该种的平均构型是2n = 10 = 0.21 I + 4.89 II。四川牡丹第一个居群的平均减数分裂染色体构型是2n = 10 = 0.21 I + 4.90 II，第二个居群是2n = 10 = 0.14 I + 4.93 II，在该种的平均构型是2n = 10 = 0.20 I + 4.90 II。在块根芍药中，不同个体的配对系数变化范围在69.5%和81.07%之间，在四川牡丹中在72.97%和81.37%之间。 在后期I和末期I，出现了染色体桥、断片、落后染色体、不等分离等异常现象。最明显的减数分裂异常是后期I桥/断片。尽管在不同的居群中桥/断片异常出现的频率有所变化(块根芍药居群一是26.03%，居群二是11.67%，居群三是13.39%;四川牡丹居群一是7.59%，居群二是9%)，但是这种异常出现在所有个体中(块根芍药平均为18.67%，四川牡丹平均为7.69%)。结果表明，所有的个体都是染色体臂内倒位结构杂合体，广泛存在于野生自然居群中，可能存在某些选择优势。而且，桥的出现频率和断片的大小在个体之间是变化的，这因此表明在这两个种中存在不同的倒位。然而，这两个种在野生居群中是如何维持染色体结构杂合的，其维持机制还有待于进一步阐明，还需要更进一步的证据。 该研究还揭示了块根芍药和四川牡丹这两个种具有共同的第五号染色体减数分裂异常：与长臂相比，短臂在遗传距离和物理距离之间存在巨大的背离。短臂的遗传距离，通过交叉频率计算出来，约是长臂的三十分之一（块根芍药）。然而，物理距离用臂的比率表示，大约是长臂的三分之一，物理距离是遗传距离的十倍。 在四川牡丹红心桥居群和其它居群之间，臂比存在微小的差异，而且在芍药属不同的种内也发现了存在差异。在四川牡丹中，环形二价体(两个臂形成交叉)和棒状二价体(仅一个臂形成交叉)的比率是1.94 : 98.06，而在块根芍药中是3.42 : 96.58。在这两个种中，棒状二价体大大多于环形二价体。在第五号染色体的短臂上可能存在某些“搭车效应”，这表明第五号染色体的短臂上存在高度永久杂合，导致短臂高度保守、极为稳定。这与芍药属古老的分布格局、进化历史长可能存在某些联系。四川牡丹第五号染色体的后期I倒位桥出现频率非常低，仅为0.51 - 3.47%，平均为1.43%。而且断片长度是变化的，其变化范围在1.7 - 10.8 µm之间。