RTLinux调度策略的研究

RTLinux是Linux的嵌入式实时内核，本文首先分析了RTLinux的工作原理和两种典型的实时调度算法(RMS和EDF)，然后深入分析了RTLinux下的动态调度器EDF和它的实现方法，并通过编程实现了EDF在SRP协议下的调度。     

基于Linux2．6进程调度系统的实时性研究

针对Linux 2.6进程调度系统在实时性方面存在的不足,首先对Linux 2.6进程调度系统的优先级计算以及调度策略进行详细的分析.然后,根据优先级计算和调度策略实时性方面存在的缺陷,引入基于进程截止期的EDF进程调度算法,并介绍EDF算法在Ljnux 2.6内核代码中的具体实现.最后,以进程截止期满足率为标准的实验数据对比FIFO、RR和EDF调度策略在实时进程调度性能上的差异,证明EDF调度策略在处理实时进程方面具有更强的调度能力.     

EDF调度算法的实时性改进

在实时调度算法中,常用的EDF调度算法是非抢占式的,针对这个问题,研究应用SLAD算法和BACK-SLASH算法来改善EDF调度算法的实时性.对过载情况下的截止期错失率DMR的测试,结果表明其实时性确有所改进.     

Design and fabrication of erbium doped photosensitive fibers

A kind of erbium doped photosensitive fiber (EDPF) was proposed and fabricated, whose core was made of double layers named photosensitive layer and erbium doped layer. The double-layer core design can overcome difficulties in fabrication of EDPF with single core design, i.e. the conflict between the high consistency rare earth doping and high consistency germanium doping. A sample was fabricated through the modified chemical vapor deposition method combined with solution doping technique. The peak absorption coefficient was 48.80 dB/m at 1.53 μm, the background loss was lower than 0.1 dB/m, and the reflectivity of the fiber Brag gratings (FBG) written directly on the sample fiber was up to 97.3% by UV-writing technology. Moreover, a C band tunable fiber laser was fabricated using the sample fiber, in which a uniform FBG was written directly on EDPFs as a reflector. A single wavelength lasing with a maximum wavelength tuning range of 1555.2–1558.0 nm was achieved experimentally. Within this tuning range, the full-width at half maximum (FWHM) of the laser output was smaller than 0.015 nm and the side mode suppression ratio (SMSR) was better than 50 dB. Supported by the National High Technology Research and Development Program of China (863 Project) (Grant No. 2007AA01Z258), the National Natural Science Foundation of China (Grant No. 60771008), Program for New Century Excellent Talents in University (Grant No. NCET-06-0076), Beijing Natural Science Foundation (Grant No. 4052023), and the Beijing Jiaotong University Foundation (Grant No. 2006XM003)     

EDF phytolith analysis from Heying site, southeast China, Shang-Zhou dynasties

In this article, we propose to make morphotypological phytolith analysis of Heying site during Shang-Zhou Period by two methods: measuring based on extended depth of focus (EDF) image and measuring directly under microscope, and then compare their results. The comparison shows that the results by these two methods match each other for paleoenvironmental and agricultural analysis. Results of two methods show that Heying site's environment should be warm and moist based on the predominance of some specific phytolith assemblages. The phytolith morpho-types originated from crop plants also indicates that rice planting was the mainstay agricultural economy. In comparison, the morphotypological analysis method based on EDF image took only about 1/10 the time as the original method by directly measuring under microscope. Thus, we can process more samples and make a more thorough and systematic morphotypological phytolith analysis with the same amount of time. Furthermore, the constructed EDF image can also be archived for future examination and for education. The above experiments indicate that the morphotypological analysis method based on EDF image is very promising for phytolith analysis.     

基于ISM的动态优先级调度算法

在嵌入式Linux操作系统的实时调度算法中,EDF调度算法不能解决负载过载问题。为此,引进对系统负载有着良好表现的SLAD算法和BACKSLASH算法。基于ISM算法思路,提出一种动态优先级调度算法。该算法能根据一段时间内负载过载的情况,灵活地调度EDF算法和SLAD算法,从而提高系统在正常负载和过载情况下的调度效率。对实时任务截止期错失率DMR指标的测试结果证明了其改进效果。     

基于RM与EDF的实时混合调度算法研究

通过对实时系统中静态调度算法RM和动态调度算法EDF的研究与分析,针对两种调度算法在实际应用中的问题,提出了一种基于阈值δ的混合调度算法,将RM与EDF调度算法相结合,并从数学角度描述了混合调度算法的可调度性与实时任务的周期、执行时间等属性之间的关系,给出了混合调度算法可调度性的充分必要条件。最后用实验验证了混合调度算法的有效性。     

端到端时间约束的实时任务动态调度算法

在单处理机系统中,由于计算高优先级任务抢占的时间相对比较简单,所以单处理机调度理论取得了长足的进步.提出一个端到端时间约束的实时任务调度算法,当实时任务到达系统时,算法为任务的每个子任务在相应的处理机上预约一定的计算资源,把端到端的多处理机调度问题转换成单处理机调度问题,从而可以利用单处理机调度理论判定实时任务的可调度性.实验表明,该算法明显地提高了CPU利用率和任务接收率.     

光纤光栅传感器用的高功率宽带光源

运用单程后向结构,通过优化掺Er光纤结构,从实验上实现了一种功率达29.4mW,平均波长为1544.336nm的高功率宽带掺Er超荧光光源,3dB带宽为31.2nm,在C波段1525～1565nm之间可实现功率高于27.8mW,在1532.1～1560.6nm之间的平坦度可达±0.5dB(不加任何滤波器的条件下),可以较好地满足光纤Bragg光栅在传感领域的研究和实用化的应用要求,作为单独的光源也适用于光纤陀螺等场合.     

一种新的异构实时分布式系统的容错调度算法

一般来说,异构分布式实时系统中任务的周期并不完全相同且任务的时限不等于它们的周期,同时系统中还有一些无容错需求的任务.因此现有的任务调度算法一般不能满足这些要求.针对这类系统,在结合基版本/副版本技术和EDF算法的基础上,给出了一种新的容错调度算法.该算法由两部分组成：任务分配调度算法和单处理器调度算法.对于单处理器调度算法,本文采用了EDF算法;在此基础上,给出一种启发式静态任务分配算法.分析了系统的可调度性,给出了任务可调度条件和基版本/副版本时限的设置方法.仿真结果表明,这种算法是有效的.