同步数据流模型调度序列的空间优化

提出了一种嵌入式DSP系统的存储优化方法。该方法基于同步数据流模型SDF(Synchronous Data Flow)。针对其他优化算法不适用于存在反馈环的同步数据流模型的问题,该方法为反馈环的空间优化设计实现了启发式的调度算法,并提出了将SAS(Single Appearance Schedules)和Non-SAS类型调度序列相结合的层次化的空间优化方案,为同步数据流模型调度序列的空间优化提供一个通用的解决方案。实验结果证实了该方案的有效性。

VarBIFT:指令级的变量冗余容错检测技术

为了解决空间辐射对嵌入式计算机系统正确性的影响越来越明显的问题,基于典型的编译级容错技术,在编译器LCC上实现了基于有向无环图的编译级容错检测方法VarBIFT。该方法可以有效的保护由于粒子效应所引起的瞬时硬件故障,并可针对不同的目标机自动生成容错代码。实验结果表明,VarBIFT使源程序的平均段错误率从32.3%降到了13.9%,平均错误输出率从28.6%降到了9.2%;而其时间开销和空间开销仅为0.7%和36%。

ARM嵌入式系统在纳米操作系统中的应用研究

近年来，随着微纳米科技的迅速发展，机电产品有望向更微观化、高性能化发展，这将促进材料、制造、电子、生物医学、信息等领域新的科学技术出现，在新的科学技术层次上为可持续发展的理论提供物质和技术保障。微纳米科技最终目标是研究和发现微纳尺度物质所具有的新颖的物理、化学和生物学现象与特性。并以此为基础来设计、制作、组装成新的材料、组件或系统，实现与之相应的特定功能，促进新的科学技术发展与变革，这无疑具有十分重要的科学意义和经济价值。而实现这个目标的使能技术便是微纳米尺度下观测、操作和装配的科学方法与相关的技术和装备，因此开展微纳米操作研究具有特别重要的意义。微纳米操作是微纳米制造科学技术的重要内容之一，使用探针模式的机器人化微纳操作方法，实现在微纳米尺度物体的可控操作，对促进我国微纳米科学技术发展具有特别重要的意义。 目前已有的基于探针的纳米技术装置如SPM (Scanning Probe Microscope)是基于探针模式的纳米观测基本装置。在此基础上研究发展的基于探针的纳米操作已成为纳米科技研究的新领域，是目前世界上各国正在大力开发的前沿研究课题。但目前市场上的SPM等纳米观测设备缺乏驱动控制与信息交互功能和开放界面，限制了用户在此基础上开发纳米操作、装配等功能的能力，因而研究具有信息交互能力的、可进行在线操作控制与宏-微-纳观信息交互的纳米操作监控系统，进而发展成具有自动化/机器人化功能的纳米作业系统队纳米科学技术发展、纳米制造的实现无疑具有重要意义。本论文的科研内容是以面向纳米制造的机器人化系统为研究背景，在自主技术的基础上，开展应用ARM嵌入式系统构成纳米作业系统的实时控制器研究。实时多任务的操作控制系统是纳米作业系统的核心技术，可以实时进行基于探针的传感信息采集、状态反馈控制、形貌观测数据生成、作业运动轨迹生成、位置反馈控制等功能的数据处理与实现。本论文重点介绍以SAMSUNG公司的ARM9处理器芯片S3C2410为嵌入式控制器系统的核心，在移植嵌入式Linux作为操作系统的基础上，开发具有实时数据采集与控制指令、通信功能的人机交互界面。基于ARM的实时控制器的研究为探针模式的纳米观测与操作系统开发提供了关键技术，可以提供开放的AFM系统，促进操作型纳米系统的研究与实现，可以保证纳米观测与操作控制的实时性，可以为纳米作业控制方法提供方便的编程、开发功能。本论文主要研究了面向纳米作业的基于ARM嵌入式实时控制器硬件结构及软件系统的研究与开发过程。首先介绍嵌入式系统的基本概念和特点；其次介绍基于SPM模式的纳米操作系统性能与技术特点；第三，根据纳米作业系统的技术功能要求，详细介绍了具有实时多任务管理功能的硬件系统的设计，重点解决核心板和扩展板各部分功能模块的设计；第四，详细介绍了嵌入式Linux操作系统下的应用程序开发模式及开发过程；最后，详细介绍了嵌入式Linux操作系统下的应用程序开发，主要工作是完成SPM纳米操作系统中的ARM开发平台的功能接口模块的调试及Linux系统下多线程技术在本系统中的应用。本次毕业设计已完成ARM开发平台在整个SPM纳米操作系统中要实现的各个功能模块，结合SPM纳米操作系统的实时性问题，进行了ARM开发平台的系统软件架构分析和利用多线程技术的以太网通信实验，在一定程度上提高了纳米操作系统中的实时性和成像质量。

Memory effect in a system of zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs

Zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs matrices are fabricated by in situ postgrowth annealing diluted magnetic semiconductor (Ga,Mn)As films with Mn concentration ranging from 2.6% to 8% at 650 degrees C. Magnetization measurements show that memory effect and slow magnetic relaxation, the typical characteristics of the spin-glass-like phase, occur below the blocking temperature of 45 K in samples with high Mn concentration, while for samples with low Mn concentration, ferromagnetic order remains up to 360 K. The behavior of low-temperature spin dynamics can be explained by the hierarchical model. (c) 2007 American Institute of Physics.

Electroluminescence from nano-crystalline Si/SiO2 structures embedded in pn junctions

Phosphorous-doped and boron-doped amorphous Si thin films as well as amorphous SiO2/Si/SiO2 sandwiched structures were prepared in a plasma enhanced chemical vapor deposition system. Then, the p-i-n structures containing nano-crystalline Si/SiO2 sandwiched structures as the intrinsic layer were prepared in situ followed by thermal annealing. Electroluminescence spectra were measured at room temperature under forward bias, and it is found that the electroluminescence intensity is strongly influenced by the types of substrate. The turn-on voltages can be reduced to 3 V for samples prepared on heavily doped p-type Si (p(+)-Si) substrates and the corresponding electroluminescence intensity is more than two orders of magnitude stronger than that on lightly doped p-type Si (p-Si) and ITO glass substrates. The improvements of light emission can be ascribed to enhanced hole injection and the consequent recombination of electron-hole pairs in the luminescent nanocrystalline Si/SiO2 system. (C) 2008 Elsevier Ltd. All rights reserved.

Spin-polarized transport of two-dimensional electron gas embedded in a diluted magnetic semiconductor

The spin-polarized transport property of a diluted magnetic semiconductor two-dimensional electron gas is investigated theoretically at low temperature. A large current polarization can be found in this system even at small magnetic fields and oscillates with increasing magnetic field while the carrier polarization is vanishingly small. The magnitude as well as the sign of the current polarization can be tuned by varying magnetic field, the electron density and the Mn concentration. (c) 2005 American Institute of Physics.

Photoluminescence mechanism of Si nanocrystals embedded in SiO2 matrix

The interface state recombination effect from the quantum confinement effect in PL signals from the SRO material system was studied. The results show that the larger the size of Si NCs, the more beneficial for the interface state recombination process to surpass the quantum confinement process, in support of Qin's model.

Performance of an embedded optical vector matrix multiplication processor architecture

An embedded architecture of optical vector matrix multiplier (OVMM) is presented. The embedded architecture is aimed at optimising the data flow of vector matrix multiplier (VMM) to promote its performance. Data dependence is discussed when the OVMM is connected to a cluster system. A simulator is built to analyse the performance according to the architecture. According to the simulation, Amdahl's law is used to analyse the hybrid opto-electronic system. It is found that the electronic part and its interaction with optical part form the bottleneck of system.

Continuous-flow polymerase chain reaction microfluidics by using spiral capillary channel embedded on copper

This paper presents a novel method for performing polymerase chain reaction (PCR) amplification by using spiral channel fabricated on copper where a transparent polytetrafluoroethylene ( PTFE) capillary tube was embedded. The channel with 25 PCR cycles was gradually developed in a spiral manner from inner to outer. The durations of PCR mixture at the denaturation, annealing and extension zones were gradually lengthened at a given flow rate, which may benefit continuous-flow PCR amplification as the synthesis ability of the Taq polymerase enzyme usually weakens with PCR time. Successful continuous-flow amplification of DNA fragments has been demonstrated. The PCR products of 249, 500 and 982 bp fragments could be obviously observed when the flow rates of PCR mixture were 7.5, 7.5 and 3.0 mm s(-1), respectively, and the required amplification times were about 25, 25, and 62 min, respectively. Besides, the successful segmented-flow PCR of three samples ( 249, 500 and 982 bp) has also been reported, which demonstrates the present continuous-flow PCR microfluidics can be developed for high-throughput genetic analysis.

Real-time counting of single electron tunneling through a T-shaped double quantum dot system

Real-time detection of single electron tunneling through a T-shaped double quantum dot is simulated, based on a Monte Carlo scheme. The double dot is embedded in a dissipative environment and the presence of electrons on the double dot is detected with a nearby quantum point contact. We demonstrate directly the bunching behavior in electron transport, which leads eventually to a super-Poissonian noise. Particularly, in the context of full counting statistics, we investigate the essential difference between the dephasing mechanisms induced by the quantum point contact detection and the coupling to the external phonon bath. A number of intriguing noise features associated with various transport mechanisms are revealed.

Architecture research and hardware implementation on simplified neural computing system for face identification

This paper describes a special-purpose neural computing system for face identification. The system architecture and hardware implementation are introduced in detail. An algorithm based on biomimetic pattern recognition has been embedded. For the total 1200 tests for face identification, the false rejection rate is 3.7% and the false acceptance rate is 0.7%.

Electrocatalytic oxidation of ascorbic acid by norepinephrine embedded in lipid cast film at glassy carbon electrode

A stable lipid cast film was made by casting a lipid in chloroform onto a glassy carbon electrode. We imbedded a new mediator norepinephrine into this lipid cast film, which was considered as a biological membrane model. Through electro catalytic oxidation of ascorbic acid by this system, the anodic overpotential was reduced by about 250 mV compared with that obtained at a bare glassy carbon electrode. The electrochemical behavior of norepinephrine in the cast film was controlled by diffusion. The obtained diffusion coefficient of ascorbic acid was 1.87 x 10(-5) cm 2 s(-1). The catalytic current increased linearly with the concentration of ascorbic acid in the range from 0.5 to 10 mM. Using cyclic voltammetry, we obtained two peaks for ascorbic acid and uric acid in the same solution. The separation between the two peaks is about 147 mV. (C) 2001 Elsevier Science Ltd. All rights reserved.

Submesoscale activity over the shelf of the northern South China Sea in summer: simulation with an embedded model

We applied a primitive equation ocean model to simulate submesoscale activities and processes over the shelf of the northern South China Sea (NSCS) with a one-way nesting technology for downscaling. The temperature and density fields showed that submesoscale activities were ubiquitous in the NSCS shelf. The vertical velocity was considerably enhanced in submesoscale processes and could reach an average of 58 m per day in the subsurface. At this point, the mixed layer depth also was deepened along the front, and the surface kinetic energy also increased with the intense vertical movement induced by submesoscale activity. Thus, submesoscale stirring/mixing is important for tracers, such as temperature, salinity, nutrients, dissolved organic, and inorganic carbon. This result may have implication for climate and biogeochemical investigations.