基于信息素质培养的高校计算机基础教学改革探讨

应用型普通高校计算机基础教学应以学生信息素质培养为目标,为此对计算机基础课程体系构建、教学内容选择、教学模式优化等方面进行了深入分析、探讨和改革实践,实践证明该教学改革有效地提升了学生的信息素质。     

Optimization of Geoscience Laser Altimeter System waveform metrics to support vegetation measurements

The Geoscience Laser Altimeter System (GLAS) has collected over 250 million measurements of vegetation height over forests globally. Accurate vegetation heights can be determined using waveform metrics that include vertical extent and extent of the waveform's trailing and leading edges. All three indices are highly dependent upon the signal strength, background noise and signal-to-noise ratio of the waveform, as the background noise contribution to the waveforms has to be removed before their calculation. Over the last six years, GLAS has collected data during thirteen observation periods using illumination from three different lasers. The power levels of these lasers have changed over time, resulting in variable signal power and noise characteristics. Atmospheric conditions vary continuously, also influencing signal power and noise.To minimize these effects, we optimized a noise coefficient which could be constant or vary according to observation period or noise metric. This parameter is used with the mean and standard deviation of the background noise to determine a noise level threshold that is removed from each waveform. An optimization analysis was used with a global dataset of waveforms that are near-coincident with waveforms from other observation periods; the goal of the optimization was to minimize the difference in vertical extent between spatially overlapping GLAS observations. Optimizations based on absolute difference in height led to situations in which the total extent was minimized as well; further optimizations reduced a normalized difference in height extent. The simplest optimizations were based on a constant value to be applied to all observations; noise coefficients of 2.7, 3.2, 3.4 and 4.0 were determined for datasets consisting of global forests, global vegetation, forest in the legal Amazon basin and boreal forests respectively. Optimizations based on the power level or the signal-to-noise ratio of waveforms best minimized differences in waveform extent, decreasing the percent root mean squared height difference by 25-54% over the constant value approach. Further development of methods to ensure temporal consistency of waveform indices will be necessary to support long-term satellite lidar missions and will result in more accurate and precise estimates of canopy height.     

Extended specifications and test data sets for data levelcomparisons of direct volume rendering algorithms

Direct volume rendering (DVR) algorithms do not generate intermediate geometry to create a visualization, yet they produce countless variations in the resulting images. Therefore, comparative studies are essential for objective interpretation. Even though image and data level comparison metrics are available, it is still difficult to compare results because of the numerous rendering parameters and algorithm specifications involved. Most of the previous comparison methods use information from the final rendered images only. We overcome limitations of image level comparisons with our data level approach using intermediate rendering information. We provide a list of rendering parameters and algorithm specifications to guide comparison studies. We extend Williams and Uselton's rendering parameter list with algorithm specification items and provide guidance on how to compare algorithms. Real data are often too complex to study algorithm variations with confidence. Most of the analytic test data sets reported are often useful only for a limited feature of DVR algorithms. We provide simple and easily reproducible test data sets, a checkerboard and a ramp, that can make clear differences in a wide range of algorithm variations. With data level metrics, our test data sets make it possible to perform detailed comparison studies. A number of examples illustrate how to use these tools     

一种组合电路内建自测试的改进方法

对组合电路的测试提出了一种将确定性测试生成方法与内建自测试相结合的设计方案;设计实现了利用D算法生成的测试矢量和伪随机测试序列生成电路共同构成测试矢量生成模块,利用内建自测试方法完成可测性设计,并将两者结合得出组合电路内建自测试的改进方法;分析与实验结果表明,该方法能减少系统硬件占用,同时具有测试向量少、故障覆盖率高的特点。     

Analysis of control interval for foundation fieldbus-based control systems

Fieldbus-based control systems (FCS) have been increasingly used in process automation. Some processes and dynamic specifications need higher control frequencies to avoid instability. The aim of this paper is to analyze the temporal characteristics of communication and computation tasks and the configuration of the function blocks in a FCS and to allow the control interval to be shortened. An FCS for a water tank process is used as a case study. The experimental results show that the execution time of function blocks and the margin time are dominant over communication delays, and optimizing configuration by reducing the number of external links can contribute to increasing the control frequency.     

PLC在组合机床控制中的应用

本文介绍了PLC对组合机床的控制,分析了其工作原理,详细介绍了其硬件配置和软件设计.     

复合材料层板+θ/-θ层间断裂韧性研究

本文讨论了纤维增强复合材料层板沿+θ/-θ层间断裂韧性的研究方法;提出在满足一定力学条件时,可沿用机械载荷实验方法测得G_C中“纯机械部分”G_m;结合数值方法计算得出“纯温度部分”G_T,从而得到G_C.给出一个针对DCB试验的充分条件,据此设计铺层并对T300/648和T300/QY8911进行试验和分析(θ=0～30°)、讨论了大变形的影响并提出一个新的修正系数.结合θ对G_C的影响及断口微观形貌作了进一步讨论.     

Distribution of ground stress on Puhe Coal Mine

Puhe Coal Mine is a typical Tertiary coal in Shenbei mining area. With an increase in mining depth, tectonic stress field becomes more complex, leading to increased deformation and failure of the soft rock roadway. Stress becomes an important factor of mine safety and stability. This paper analyzes the distribution of the regional tectonic field, and determines the distribution of situ stress measurement through measuring the ground stress field in the main mining area level of Puhe Coal Mine using stress relief method. The acquired in situ stress data at different locations and depths provide a reference for the rational arrangement of the stop and mine roadway supporting design, which are of great significance for the efficient safety production of the mine.     

玻璃幕墙传热系数计算方法及工程应用

在研究玻璃幕墙热传递特点的基础上,基于一维稳态热传导理论,以中空玻璃为例建立了玻璃系统传热系数计算模型;基于二维稳态热传导理论和有限单元法,采用三节点三角形单元对二维温度场进行了离散,推导了单元热传导矩阵和温度载荷列阵,并推导了热对流、热流密度、辐射以及各种边界条件耦合作用下对单元热传导矩阵和温度载荷列阵的修正公式,建立了玻璃幕墙框及附加线传热系数计算模型。利用Visual C++和ObjectARX对AutoCAD进行了二次开发,研发了玻璃幕墙传热系数计算软件TJCW,并通过算例与LBNL系列软件计算结果进行比较,验证了所编软件的正确性和有效性。最后对某工程实例中玻璃幕墙传热系数进行了节能验算。研究结果表明:建立的传热系数计算模型能够正确的计算玻璃幕墙传热系数,基于该计算模型开发出的软件能够应用于实际工程的节能分析和计算中。     

Self healing capacity of asphalt binders

To test self healing capability of asphalt binders,three asphalt specimens(pure asphalt,modified asphalt and aged asphalt) were prepared.Every specimen was tested by dynamic shear rheometer(DSR).The temperature sweeps result indicates that both aging and SBS modifying influence the self healing capability of asphalt binder.The fatigue-heal-fatigue test was introduced to study the self healing capability of asphalt in its serving periods.Furthermore,three different periods(0.5 h,1 h,3 h) were set up to study the influence of rest time on fatigue time.It is concluded that longer rest time,less load will delay the appearance of cracks and extend the service life of asphalt binders.