Local Well-Posedness of the Anisotropic Lagrangian Averaged Navier–Stokes Equations with Stokes Projector Viscosity

The anisotropic Lagrangian averaged Navier–Stokes (LANS-α) equations are a coupled system of nonlinear partial differential equations designed to capture both the large scale motion of an incompressible fluid and the covariance tensor. There are two choices for the divergence-free projection of the viscosity term. One choice is the classical L ²-orthogonal Leray projector. In this case, Marsden and Shkoller (2003 Marsden , J. , Shkoller , S. ( 2003 ). The anisotropic Lagrangian averaged Euler and Navier–Stokes equations . Arch. Ration. Mech. Anal. 166 : 27 – 46 . [CSA] [CROSSREF] [Crossref], [Web of Science ®] , [Google Scholar]) show that strong solutions exist and are unique in the three-dimensional periodic box for a finite time interval. We extend this result by considering the second choice of projector, the generalized Stokes projector.     

Optimizing amplifier spacing to improve performance in RZ-rectangular pulse based 10 Gb/s single channel dispersion managed optical communication system

In this paper, we optimize the inter-amplifier spacing in combination with duty cycle of RZ data format and EDFAs power so that link length of system can be maximized. The results for EDFA amplifier placement in 10 Gbps single channel dispersion managed optical communication system have been presented. By increasing the length of standard single mode fiber of dispersion 16 ps/nm/km in proportion to the increase in length of compensating fiber of dispersion −80 ps/nm/km, the pre-, post- and symmetrical-dispersion compensation schemes of the system have been compared. Further, schemes are observed at 8, 10 and 12 dBm values of EDFA power in the link with different duty cycle values of RZ optical pulse in the range of 0.2-0.8 with step size of 0.2 in relation to amplifier spacing to get lower value of bit error rate and timing jitter. The graphical results obtained show strong relationship among duty cycle of RZ optical pulse, EDFA power and, dispersion compensation scheme.     

Investigation on modified FWM suppression methods in DWDM optical communication system

The focus of this paper is to investigate the methods for Four Wave Mixing (FWM) suppression. Modified techniques equal and unequal-channel spacing with polarization, equal channel spacing with alternate channel delay, optical coupling and varied laser power have been proposed to reduce the impact of FWM on Dense Wave Length Division Multiplexing (DWDM) optical communication system. Further the comparison of reduction of FWM for existing and proposed techniques has been discussed by varying the dispersion of fiber from 0 to 16 ps/nm/km. It has been observed that the suggested techniques are simpler to design optical communication system and superior to the existing methods.     

Self-Organization,Entropy Generation Rate,and Boundary Defects: A Control Volume Approach

Self-organization that leads to the discontinuous emergence of optimized new patterns is related to entropy generation and the export of entropy. Compared to the original pattern that the new, self-organized pattern replaces, the new features could involve an abrupt change in the pattern-volume. There is no clear principle of pathway selection for self-organization that is known for triggering a particular new self-organization pattern. The new pattern displays different types of boundary-defects necessary for stabilizing the new order. Boundary-defects can contain high entropy regions of concentrated chemical species. On the other hand, the reorganization (or refinement) of an established pattern is a more kinetically tractable process, where the entropy generation rate varies continuously with the imposed variables that enable and sustain the pattern features. The maximum entropy production rate (MEPR) principle is one possibility that may have predictive capability for self-organization. The scale of shapes that form or evolve during self-organization and reorganization are influenced by the export of specific defects from the control volume of study. The control volume (CV) approach must include the texture patterns to be located inside the CV for the MEPR analysis to be applicable. These hypotheses were examined for patterns that are well-characterized for solidification and wear processes. We tested the governing equations for bifurcations (the onset of new patterns) and for reorganization (the fine tuning of existing patterns) with published experimental data, across the range of solidification morphologies and nonequilibrium phases, for metallic glass and featureless crystalline solids. The self-assembling features of surface-texture patterns for friction and wear conditions were also modeled with the entropy generation (MEPR) principle, including defect production (wear debris). We found that surface texture and entropy generation in the control volume could be predictive for self-organization. The main results of this study provide support to the hypothesis that self-organized patterns are a consequence of the maximum entropy production rate per volume principle. Patterns at any scale optimize a certain outcome and have utility. We discuss some similarities between the self-organization behavior of both inanimate and living systems, with ideas regarding the optimizing features of self-organized pattern features that impact functionality, beauty, and consciousness.     

采用发射极非均匀指间距技术改善功率异质结双极晶体管热稳定性的研究

为了提高多发射极功率异质结双极晶体管的热稳定性,本文利用耦合热阻表征发射极指间距变化对发射极指间热耦合作用的影响,得到了耦合热阻与发射极指间距之间的变化关系,提出了发射极非均匀指间距技术.通过热电反馈模型对采用发射极非均匀指间距技术的功率HBT进行热稳定性分析,得到了多发射极指上的温度分布.结果表明,多发射极HBT在采用非均匀发射极指间距技术后,峰值温度明显下降,温度变化幅度更加平缓,有效地提高了器件的热稳定性. 关键词： 异质结双极晶体管 耦合热阻 指间距     

Averaging for retarded functional differential equations

We consider retarded functional differential equations in the setting of Kurzweil-Henstock integrable functions and we state an averaging result for these equations. Our result generalizes previous ones.     

弗兰克—赫兹实验中的峰间距问题

运用吸收峰形成与变化判断准则解释了管温和阴－栅极距离对峰间距的影响。     

Improving the performance of three level code division multiplexing using the optimization of signal level spacing

In order to optimize the performance of three level code division multiplexing (3LCDM) at 2×20 Gb/s data rate, signal level spacing technique is investigated in this paper. The 3LCDM performance is improved considerably using both electrical and optical level spacing optimization configurations. The results demonstrate that by optimization, in conditions of the optical signal-to-noise ratio, an improvement of around 4.5 dB can be achieved in both approaches as well as 3.3 dB in the electrical configuration and 3.5 dB in the optical configuration can be accomplished for the 3LCDM in terms of the receiver sensitivity.     

Dense wavelength division demultiplexing using photonic crystal waveguides based on cavity resonance

We demonstrated a photonic crystal waveguide based dense wavelength division multiplexing device using the resonances in the cavities. The demultiplexing is achieved through filtering. This filtering is achieved by varying the radii of the surrounding holes of the cavity, which in turn changes the resonant wavelength of the cavity. The four wavelengths demultiplexed in the design are 0.8 nm apart in the optical region centered on 1.55 and 1.56 μm. The device designed and simulated has easy to realize structure as well as high quality factor. Two-dimensional Finite Difference Time Domain (FDTD) is chosen to do the simulation of this work.     

基于改进的统计信道模型与多天线系统性能分析

为提高电磁信号的到达角度以及多普勒效应等信道参数估计的准确性,在散射体非均匀分布下引入了散射概率和有效散射体两个物理概念,提出一种合理的改进型空间信道模型,该模型能准确地描述宏小区(macrocell)和微小区(microcell)等各种移动通信环境下的重要空时信道参数,并应用于多入多出系统(multiple input multiple output,MIMO)信道性能仿真中.数值仿真结果与早期多径衰落信道模型对比,表明本模型的信道参数估计结果符合理论和经验,拓展了空间统计信道模型的研究和应用,对评估多天线MIMO系统空时处理算法和仿真无线通信系统提供有力的工具.