光周期对穗花狐尾藻生长、开花与种子形成的影响

通过人工补光和遮光处理,初步研究了光周期对狐尾藻生长和开花的影响。研究发现:8h短日照条件不利于狐尾藻的生长和花序形成,导致狐尾藻不能正常开花和结实;与自然日照长度(平均日照14h)条件下相比,16h长光照条件可以增加植株的高度和分枝数,形成更大的生物量;但24h全光照条件对生长有抑制作用。长光照条件下,狐尾藻花序形成时间和开花时间均比自然条件下延迟,形成花序的数目也显著较自然条件下的少,但长光照条件下形成的种子比自然条件下形成的种子具有更高的萌发率。

纤细裸藻褪色突变株的残留质体及其对核基因表达的影响

用氧氟沙星(Ofl)和链霉素(Sm)分别处理纤细裸藻获得褪色突变株,电子显微镜观察显示细胞中存在残留质体,其中一个Ofl突变株质体有原初类囊体膜形成,而两个Sm突变株质体内有异常致密、发达的膜结构。用PCR方法检查了质体DNA的9个基因,显示所有突变株均有核糖体蛋白基因丢失,其中一个Sm突变株仍保留质体DNA的大部分基因,其余突变株质体DNA则基本丢失。通过差异显示和RT-PCR方法证明叶绿体的退化在完全黑暗异养条件下也可导致某些核基因转录的变化。

Unified compression model for venice lagoon natural silts

Over the last 50 years, the city of Venice, Italy, has observed a significant increase in the frequency of flooding. Numerous engineering solutions have been proposed, including the use of movable gates located at the three lagoon inlets. A key element in the prediction of performance is the estimation of settlements of the foundation system of the gates. The soils of Venice Lagoon are characterized by very erratic depositional patterns of clayey silts, resulting in an extremely heterogeneous stratigraphy with discontinuous layering. The soils are also characterized by varying contents of coarse and fine-grained particles. In contrast, the mineralogical composition of these deposits is quite uniform, which allows us to separate the influence of mineralogy from that of grain size distribution. A comprehensive geotechnical testing program was performed to assess the one-dimensional compression of Venice soils and examine the factors affecting the response in the transition from one material type to another. The compressibility of these natural silty clayey soils can be described by a single set of constitutive laws incorporating the relative fraction of granular to cohesive material. © 2007 ASCE.

MEMS-based mechanical AGC for oscillator circuits

This paper investigates a nonlinear amplitude saturation behavior in an electrostatically transduced, silicon MEMS disk resonator operating in its secondary elliptical bulk-mode (SEBM) at 3.932 MHz towards its implementation as an all-mechanical automatic gain control (AGC) element. The nonlinear vibration behavior of the SEBM mode is experimentally observed in open-loop testing such that above a threshold small signal drive voltage at a given polarization voltage, the vibration amplitude of the SEBM mode saturates. We also study this nonlinearity in an oscillator circuit designed such that the driving power level at the resonator input can be manually tuned as the circuit operates. The measurements of the voltage amplitudes show a clear transition from the linear to the nonlinear saturation region as the driving power is increased. Short-term frequency stability measurements were also conducted for different v ac and the resulting Allan deviation plots show an improvement in the short-term stability from 1.4 ppb in the linear region to 0.4 ppb in the amplitude saturation region. © 2013 IEEE.

Design of triangular lattice photonic crystals using genetic algorithms

Genetic Algorithms (GAs) were used to design triangular lattice photonic crystals with large absolute band-gap. Considering fabricating issues, the algorithms represented the unit cell with large pixels and took the largest absolute band-gap under the fifth band as the objective function. By integrating Fourier transform data storage mechanism, the algorithms ran efficiently and effectively and optimized a triangular lattice photonic crystal with scatters in the shape of 'dielectric-air rod'. It had a large absolute band gap with relative width (ratio of gap width to midgap) 23.8%.

Effects of annealing ambient on the formation of compensation defects in InP

Positron annihilation lifetime (PAL) and photoinduced current transient spectroscopies (PICTS) have been employed to study the formation of compensation defects in undoped InP under different annealing processes with pure phosphorus (PP) ambience and iron phosphide (IP) ambience, respectively. The different annealing ambiences convert the as-grown n-type undoped InP into two types of semi-insulating (SI) states. The positron average lifetimes of as-grown InP, PP SI-InP, and IP SI-InP are found to be 246, 251, and 243 ps, respectively, which are all longer than the bulk lifetime of 240 ps, indicating the existence of vacancy-type positron-trapping defects. For as-grown InP, VInH4 complexes are the dominant defects. They dissociate into VInHn(0less than or equal tonless than or equal to3) acceptor vacancies under PP ambience annealing, compensating the residual shallow donors and turning the material semi-insulating. In forming IP SI-InP, diffusion of iron into V-In complexes under IP ambience annealing produces the substitutional compensation defect Fe-In, causing a shorter positron average lifetime. The PICTS measurements show that a group of vacancy-type defects has been suppressed by iron diffusion during the annealing process, which is in good agreement with the PAL results. (C) 2003 American Institute of Physics.

Optical anisotropy of InAs monolayer in (311)-oriented GaAs matrix

In-plane optical anisotropy which comes from the heavy hole and the light hole transitions in an InAs monolayer inserted in (311)-oriented GaAs matrix is observed by reflectance difference spectroscopy. The observed steplike density of states demonstrates that the InAs layer behaves like a two-dimensional quantum well rather than isolated quantum dots. The magnitude of the anisotropy is in good agreement with the intrinsic anisotropy of (311) orientation quantum wells, indicating that there is little structural or strain anisotropy of the InAs layer grown on (311)-oriented GaAs surface.

VCSEL-based parallel optical transmission module

This paper describes the design process and performance of the optimized parallel optical transmission module. Based on 1x12 VCSEL (Vertical Cavity Surface Emitting Laser) array, we designed and fabricated the high speed parallel optical modules. Our parallel optical module contains a 1x12 VCSEL array, a 12 channel CMOS laser driver circuit, a high speed PCB (Printed Circuit Board), a MT fiber connector and a packaging housing. The L-I-V characteristics of the 850nm VCSEL was measured at the operating current 8mA, 3dB frequency bandwidth more than 3GHz and the optical output 1mW. The transmission rate of all 12 channels is 30Gbit/s, with a single channel 2.5Gbit/s. By adopting the integration of the 1x12 VCSEL array and the driver array, we make a high speed PCB (Printed Circuit Board) to provide the optoelectronic chip with the operating voltage and high speed signals current. The LVDS (Low-Voltage Differential Signals) was set as the input signal to achieve better high frequency performance. The active coupling was adopted with a MT connector (8 degrees slant fiber array). We used the Small Form Factor Pluggable (SFP) packaging. With the edge connector, the module could be inserted into the system dispense with bonding process.

A Simplified Soft-output QRD-M MIMO Detector

In this paper, a low-complexity soft-output QRD-M detection algorithm is proposed for high-throughput Multiple-input multiple-output (MIMO) systems. By employing novel expansion on demand and distributed sorting scheme, the proposed algorithm can reduce 70% and 85% foundational operations for 16-QAM and 64-QAM respectively compared to the conventional QRD-M algorithm. Furthermore, the proposed algorithm can yield soft information to improve the bit error rate (BER) performance. Simulation results show that the proposed algorithm can achieve a near-NIL detection performance with less foundational operations

遗传算法优化设计三角晶格光子晶体

将遗传算法应用于三角晶格光子晶体的禁带设计过程．考虑到可制备性，算法以第五能级下最大绝对禁带为优化目标，采用粗粒度像素表示原胞结构．通过引入傅里叶变换数据备份机制以提高禁带计算速度和算法效率，从而快速搜索到了具有较大绝对禁带的“介质空气柱”散射体形状的三角晶格光子晶体，其最大绝对禁带的相对宽度值（绝对禁带宽度和中心高度的比值）为23．8％．