关于软件开发的确认过程

本刊于上期发表了林华撰写的"软件开发是否需要过程确认"一文后,不少专家认为该文提出了很好的问题,值得大家探讨,又有读者投稿阐述了自己的观点与看法,希望与林华研讨交流,本刊特选登两篇,以飨读者。     

Comparison of linear and nonlinear spectral unmixing approaches: a case study with multispectral TM imagery

Spectral unmixing has been widely used by researchers in quantitative remote sensing due to the prevalence of mixed pixels in low- or middle-resolution images. In this article, six linear and nonlinear unmixing approaches – fully constrained least squares (FCLS), bilinear-Fan model (BFM), polynomial post-nonlinear model (PPNM), supervised fuzzy c-means (SFCM), Support Vector Machine (SVM), and artificial neural network (ANN) – are applied with multispectral Landsat Thematic Mapper (TM) data in order to systematically compare their performance under different scenarios. In addition, a strategy of band selection was proposed for solving the endmember variability issue. The unmixing results were analysed in terms of the overall performance, pure and mixed data set, sub-scenes with different mixture proportions by calculating the accuracy indices: root mean square error (RMSE) and the Pearson correlation coefficient (r). Nonlinear approaches can generate a closer abundance fraction map to reference, and have a higher overall accuracy than the linear approach. Nevertheless, the performance of nonlinear approaches differed dramatically with the increased proportion of mixed pixels in different study areas. SVM, SFCM, BFM, and PPNM depicted a scenario better when the proportion of mixed pixels was high, whereas ANN worked more effectively when processing large amounts of relatively pure pixels (or mixed pixels with large/extreme proportions). The linear approach, in contrast, performed more consistently for various areas. Overall, our study indicates that nonlinear approaches are more effective than the linear one, especially for a study area consisting of different small parcels. The performance of nonlinear approaches is more sensitive to the proportion change of mixed pixels in a study area. The linear approach, however, is more appropriate for a rough estimation, particularly with little prior knowledge of the study area.     

方案设计阶段数据机房空调冷负荷的估算

本文介绍了数据机房空调冷负荷的组成，分析了数据机房冷负荷组成的特点，给出了方案设计阶段冷负荷估算的方法。     

山东省生土建筑的应用现状与发展探讨

生土建筑是一种古老的建筑形式,因其绿色、生态、节能、成本低等特点,在过去得到了广泛的应用。然而因其自身固有的不足,现在的应用越来越少。当今可持续发展的政策给生土建筑提供了很大的发展空间。论文通过对山东省的生土建筑进行实地调研,总结了现存的生土建筑形式及存在的主要问题,并提出了有针对性的改进措施。     

电除尘粉煤灰混凝土的试验研究与应用

1　试验研究的目的为进行技术创新 ,提高混凝土的科技含量 ,以质优价廉的粉煤灰取代部分水泥和砂子 ,为我公司推广使用粉煤灰提供技术保障和配比参数、降低混凝土工程成本 ,提高经济效益 ,1994年春就开展了粉煤灰混凝土的试验研究和应用 ,现将情况总结如下 :2　试验用原材料采用如下原材料 :( 1)水泥　用十七冶水泥厂 4 2 5号矿渣水泥和巢湖水泥厂 52 5号普通水泥 ,其技术性能指标见表1。　　　表 1水泥技术性能指标水泥标号生产厂家 种类 凝结时间 (h∶ min)初凝终凝安定性抗压强度 (MPa)R3、R7R2 842 5号十七治矿渣 2∶ 15 3∶ 0 0合格 …     

Palm-print recognition by matrix discriminator

In this study, the characteristic matrix is employed to generate the various discriminators, by which to identify different palm-prints. The “ring rotation invariant transform” technique can deal with image rotation problem. In this study, the transformed signals will be fed to the characteristic matrix to generate various discriminators. For dealing with image-shifting problem, one pixel in sample image is compared with the surrounding pixels in unknown image to locate the closest matching. The comparison approaching in this study is by the basis of pixel-to-pixel-comparisons.     

Directed electrochemical synthesis of ZnO/PDMcT core/shell nanorod arrays with enhanced photoelectrochemical properties

In this paper, we demonstrate a simple two-step electrochemical deposition strategy for synthesizing ZnO/Poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT) core/shell nanorod arrays. The as-synthesized ZnO/PDMcT samples are characterized by Fourier-transform infrared (FTIR), Raman spectroscopy, power X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The ZnO/PDMcT nanorod arrays are found to exhibit significantly enhanced photocurrent density in photoelectrochemical cell applications as compared to the prinstine ZnO nanorod arrays.     

选区激光熔化Inconel 718合金的熔池形态与组织

通过不同扫描速度和扫描方式的选区激光熔化(SLM)技术制备了Inconel 718合金,研究了工艺参数对熔池的形态、凝固组织、晶粒大小和晶粒取向的影响。结果表明,随着扫描速度增加,熔池的深度与宽度的比值增大,曲率增大;而扫描速度为1 450mm/s时,采用单向扫描比十字交叉扫描时深宽比值更大。在熔池内,凝固组织由熔池底部的胞晶向熔池侧面的胞枝晶转变。晶粒以<001>方向择优生长,其晶粒间的取向差角以小角度(<15°)为主。当十字交叉扫描时,随着扫描速度增加,小角度取向差角的分布分数增加。当速度一定、采用十字交叉扫描时,小角度的取向差角占比为62.57%,而采用单向扫描时为47.69%。     

1Cr13不锈钢硼-碳复合渗工艺及其性能

对1Cr13马氏体不锈钢进行950 ℃预渗碳6 h复合不同渗硼工艺处理,通过光学显微镜(OM)、扫描电镜(SEM)及配套能谱分析仪(EDS)、显微维氏硬度计、XRD、电化学工作站等研究了复合渗工艺以及最终热处理对硼碳复合渗层组织和性能的影响。结果表明,1Cr13钢最佳硼碳复合渗工艺为950 ℃固体渗碳6 h复合950 ℃固体粉末渗硼6 h,在此工艺下,渗硼层硬度高达1436 HV0.1,交界层硬度为924 HV0.1,预渗碳层硬度为630~910 HV0.1,基体心部硬度为560～590.7 HV0.1,复合渗层硬度梯度整体较为平缓。EDS检测得出交界层Cr元素含量最高,其质量分数为13.49%。XRD物相检测得出渗硼层中主要是硬度高且脆性较小的Fe₂B相,存在少量FeB和CrB相。复合渗试样与原样的腐蚀电极电位相比提升了0.104 V,硼碳复合渗工艺提高了1Cr13不锈钢的耐腐蚀性能。