A Scalable Asynchronous Cache Consistency Scheme (SACCS) for mobile environments

In the literature, there exit two types of cache consistency maintenance algorithms for mobile computing environments: stateless and stateful. In a stateless approach, the server is unaware of the cache contents at a mobile user (MU). Even though stateless approaches employ simple database management schemes, they lack scalability and ability to support user disconnectedness and mobility. On the other hand, a stateful approach is scalable for large database systems at the cost of nontrivial overhead due to server database management. We propose a novel algorithm, called Scalable Asynchronous Cache Consistency Scheme (SACCS), which inherits the positive features of both stateless and stateful approaches. SACCS provides a weak cache consistency for unreliable communication (e.g., wireless mobile) environments with small stale cache hit probability. It is also a highly scalable algorithm with minimum database management overhead. The properties are accomplished through the use of flag bits at the server cache (SC) and MU cache (MUC), an identifier (ID) in MUC for each entry after its invalidation, and estimated time-to-live (TTL) for each cached entry, as well as rendering of all valid entries of MUC to uncertain state when an MU wakes up. The stale cache hit probability is analyzed and also simulated under the Rayleigh fading model of error-prone wireless channels. Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments.     

Computational models of a nano probe tip for static behaviors

It is difficult to predict the measurement bias arising from the compliance of the atomic force microscope (AFM) probe. The issue becomes particularly important in this situation where nanometer uncertainties are sought for measurements with dimensional probes composed of flexible carbon nanotubes mounted on AFM cantilevers. We have developed a finite element model for simulating the mechanical behavior of AFM cantilevers with carbon nanotubes attached. Spring constants of both the nanotube and cantilever in two directions are calculated using the finite element method with known Young's moduli of both silicon and multiwall nanotube as input data. Compliance of the nanotube-attached AFM probe tip may be calculated from the set of spring constants. This paper presents static models that together provide a basis to estimate uncertainties in linewidth measurement using nanotubes. In particular, the interaction between a multiwall nanotube tip and a silicon sample is modeled using the Lennard-Jones theory. Snap-in and snap-out of the probe tip in a scanning mode are calculated by integrating the compliance of the probe and the sample-tip interacting force model. Cantilever and probe tip deflections and points of contact are derived for both horizontal scanning of a plateau and vertically scanning of a wall. The finite element method and the Lennard-Jones model provide a means to analyze the interaction of the probe and sample and measurement uncertainty, including actual deflection and the gap between the probe tip and the measured sample surface.     

Germline stem cell lineage tracing by free-floating immunofluorescent assay of mouse seminiferous tubule

Whole-mount immunohistochemistry (whole-mount IH) of the seminiferous tubule is widely used to investigate the self-renewal and differentiation of spermatogonial stem cells (SSCs). Examination of the length of spermatogonial cysts is critical for tracing SSCs lineage by using Whole-mount IH. However, it is difficult for antibody molecules to penetrate into the depth of seminiferous epithelium because its thickness and the tight peritubular myoid and basement membrane outside. Here, we developed a free-floating immunofluorescent procedure of mouse seminiferous tubules using regular incubation time and normal antibody concentration. Microscopic results showed that undifferentiated spermatogonia were positively labeled by promyelocytic leukemia zinc finger protein, E-cadherin, and glial cell line-derived neurotrophic factor family receptor alpha 1, respectively. Spermatogonial cysts in varied length were revealed clearly and spermatogonia subpopulations including A(single) (A(s)), A(paired) (A(pr)), and A(aligned) (A(al)) were distinguished in lower background images. This method provides us an alternate simple way to trace the lineage of individual SSCs and show their three-dimensional locations and distributions within their niches anatomically in next step.     

基于Matlab的虚拟信号发生器设计

Matlab是一个数据分析和处理功能十分强大的工程实用软件。为输出提供了十分方便的函数和命令并且Matlab简单直观的图形用户接口易于掌握和使用。本文介绍了一种使用GUI工具箱。用Matlab实现应报信号发生器的设计。文章设计的信号发生器可以加深对信号处理概念的理解,具有一定的借鉴应用价值。     

鞍钢无料钟布料数学模型研制与应用

阐述了鞍钢无料钟布料模型的开发与应用,重点分析了模型对料流阀开口度、料面形状和矿／焦比分布应用的结果。选择料流阀开口度采用三种方法,一是理论计算方法;二是利用实际测量数据对理论模型进行修正后,采用体积流速计算方法;三是利用实际测量数据对理论模型进行修正后,采用重量流速计算方法。通过对比三种方法结果,认为采用体积流速计算方法最能够保证布料过程料层均匀,无料钟布料模型可以实现对各种布料制度、料面形状的计算。     

基于S3C44B0的图像数据采集方法

简要介绍SAMSUNG公司的嵌入式处理器芯片S3C44B0和Omnivision公司的CMOS图像传感器芯片OV7620,着重阐述以S3C44B0为核心的一种图像采集方案。文中主要描述了这种图像采集系统的基本原理以及相应的软、硬件设计以及与其它采集系统的区别。     

一种不定长水尺图像水位测量方法

针对水尺图像水位识别中存在的多根水尺拼接、水尺拍摄不完整以及环境适应性差等问题,从摄影测量学角度提出一种复杂光照条件下不定长水尺图像水位测量方法。首先通过人工选取的标识点构建水尺在像素坐标系和世界坐标系之间的透视投影关系;然后利用水尺的颜色特性将水尺与背景分割并二值化;再根据二值化图像使用方差均值阈值法检测水位线位置;最终通过投影关系计算出水尺图像中水尺中线的表达式,并结合水位线位置计算出水面上水尺中线的真实长度,获得水位值。本文对水文站真实水尺图像进行了测量实验,将检测结果与遥测水位值进行对比,结果表明本方法提高了不定长水尺图像水位检测的可靠性,测量精度达到1 cm,检测分辨率为1 pixel,基本满足水文站水位监测要求。     

陀螺仪辅助星敏感器星跟踪算法设计

针对星敏感器在大机动场景下跟踪预测误差较大和星点补充频率较高的问题,提出一种陀螺仪辅助星敏感器的星跟踪算法.在载体角加速度发生剧烈变化的大机动场景下,利用陀螺仪测量得到的角速度信息,对星点运动轨迹进行估计,得到相邻两帧星图中间时刻的星点位置信息.进一步建立星点运动模型,利用卡尔曼滤波器对星点位置进行跟踪预测,从而提前预...     

方截面CFRP-钢管混凝土压弯构件抗震性能试验

为研究方截面CFRP-钢管混凝土的动力性能,在试验研究的基础上,进行理论分析,得到方截面CFRP-钢管混凝土动力情况下的极限承载力.试验表明,方截面CFRP-钢管混凝土构件的动力性能更优于钢管混凝土.它的刚度退化缓慢,延性略好于钢管混凝土.且由于CFRP的作用,方截面CFRP-钢管混凝土构件耗能更多.     

一种削弱振荡管内反射激波能量的方法

激波吸收腔是影响热分离机效率的重要结构,采用数值模拟和实验的方法对其进行研究,结果表明：数值模拟能够捕捉振荡管内激波和接触面两个间断;反射激波压力最大值随吸收腔直径比D/d增加而减小,随吸收腔长径比L/d增加而降低。提出一种实用的吸收腔结构——串联吸收腔,对比2个和3个吸收腔串联结构后,证明在膨胀比α＜6范围内2个吸收腔串联结构是最佳选择。