网络考试系统的关键技术的分析

本文主要阐述一个功能比较强大的在线考试系统的后台操作过程及一些关键技术。关键实现了考生在选择科目后进入考试窗体,考试计时,考试时间到,系统强制考生退出,及考完后对客观题的自动评分、存档。     

基于机载激光雷达数据识别单株木的新方法

在林业应用中,机载激光雷达技术较被动式遥感技术有着独特优势。以从机载激光雷达数据中分离单株木,提取单株木树高和树冠大小信息为目的,融合有标记约束的分水岭分割和流域跟踪分割两种图像分割方法,提出一种新的单株木识别思路。以美国某地区实地采集激光雷达数据为例验证本文提出方法,实验结果表明该方法通过增加边缘检测范围的约束条件,能够有效避免过分割现象,并通过使用约束条件,减少在其检测范围内的目标数量,从而避免不必要的检测干扰,较传统方法能快速准确地识别单株木。     

Dynamics of Noisy Neural Nets with Chemical Markers and Gaussian-distributed Connectivities

We have previously investigated the dynamics of probabilistic neural nets with chemical markers and Gaussian distribution of connectivities of the constituent neurons. These investigations have shown that the change from a Poisson to a Gaussian distribution may cause a net to change class. We have now generalized these studies by considering the intrinsic noise of the systems, caused by the spontaneous release of synaptic transmitter substance. A simple mathematical model is developed, the dynamics of which is compared with the Poisson model.     

Pollution situation and possible markers of different sources in the Ordos Region, Inner Mongolia, China

In order to investigate the pollution situation for a fast-developing industrial area at its first stage, a systematic study on the gaseous and particulate pollution in the Ordos Region of Inner Mongolia was performed during 9-24 September 2005. The gases SO₂, NO_x, O₃, CO, and the particulates PM₁₀ and PM_2.5 were sampled at five sites in Ordos. Species measured in aerosol were 21 elements, 10 ions, organic carbon (OC), elemental carbon (EC), and the acid-buffering capacity of particulates. Possible markers of sources for different transport directions were firstly investigated, which was a new attempt for clarification of regional transport with different directions. None of the gases exceeded the national standards of China. PM_2.5 contributed most to PM₁₀ at the background site, indicating the greatest contribution of regional transport. Organic matter, crustal material, and sulfate ion were the three dominant species of aerosol, followed by EC, NO₃⁻, NH₄⁺, trace elements, and other ions. The acidity of PM_2.5 was higher than that of PM₁₀, and the buffering capacity in PM₁₀ was higher than that in PM_2.5. Four peaks of pollution aerosol were observed during the 3-week study sampling period, separated by periods of cleaner air. Back-trajectories revealed that the peaks came from the south and the cleaner air from the north. It is the first time to find different markers for aerosols from different transport directions in Ordos. S and Pb, as well as SO₄²⁻, NO₃⁻, and NH₄⁺ appeared to be good markers of southern aerosol in the Ordos, since all showed four clear peaks on days dominated by southern direction. Extremely high peaks of Al and Ti on the 16th and 17th, especially at the dust-monitoring site, indicated good markers for soil dust. Ca and Mg showed earlier peaks on the 16th at the western site, indicating possible markers for western aerosol.     

Neural Modelling Neural Connectivities Chemical Markers

Non-isolated randomly interconnected neural nets with chemical markers are investigated, which receive steady or slowly varying excitatory or inhibitory inputs. We extend here our previous studies to include nets of Poisson and Gaussian connectivities. Our results show that the multi-hysteresis loops obtained by applying the steady-state condition for the Gaussian approximation are wider than the corresponding ones of the Poisson case, and they have been slightly shifted to larger values of the parameter sigma + (which is the fraction of external active fibres). Also, in the Gaussian nets, the stable steady states are lower than the corresponding ones of the Poisson nets, whereas the unstable states are higher.     

Monosaccharide anhydrides,new markers of toasted oak wood used for ageing wines and distillates

In order to shed light on the thermal carbohydrate transformation chemistry, the non-volatile composition of natural and toasted oak wood samples of different origins were studied. GC–MS analysis revealed the presence of monosaccharide anhydrides (MAs) only in toasted oak wood samples. They were formed by the cellulose and hemicelluloses thermal degradation produced during the toasting process, and the content was dependent on the degree of toasting. The principal MAs formed in the oak wood toasting process were 1,6-anhydro-β-d-glucopyranose (levoglucosan), 1,6-anhydro-β-d-galactosane (galactosan) and 1,6-anhydro-β-d-mannopyranose (mannosan), with levoglucosan being the dominant MAs detected. Monosaccharide anhydrides can be considered specific products formed during the thermal treatment of wood; therefore they are proposed as markers of toasted wood and could be used to monitor and determine the intensity of toasting process.     

A Strategy for Atherosclerosis Image Segmentation by Using Robust Markers

The watersheds method is a powerful segmentation tool developed in mathematical morphology, which has the drawback of producing over-segmentation. In this paper, in order to prevent its over-segmentation, we present a strategy to obtain robust markers for image segmentation of atherosclerotic lesions of the thoracic aorta. In such sense, we introduced an algorithm, which was very useful in order to obtain the markers of the atherosclerotic lesions. Images were pre-processed using the Gauss filter and a contrast enhancement. The obtained results by using our strategy were validated calculating the false negatives (FN) and false positives (FP) according to criterion of physicians, where 0% for FN and less than 11% for FP were obtained. Extensive experimentation showed that, using real image data, the proposed strategy was very suitable for our application. These images will be subject to an additional morphometrical analysis in order to study automatically the atherosclerosis and its organic-consequences.     

基于分水岭变换的高分辨率机载城区SAR图像建筑物自动检测方法

该文提出了一种从单幅高分辨率机载SAR图像上自动检测建筑物目标轮廓的方法。该方法以应用标记的分水岭变换为基础,针对建筑物的强回波特性和形状特征,主要采用CFAR检测和方向相关分析得到标记图像,然后利用最小强制技术和标记图像修改原始图像的梯度图,最后对修改后的梯度图作分水岭变换得到建筑物目标的边界轮廓。实验结果表明了该算法的有效性。     

网络考试系统的关键技术的分析

本文主要阐述一个功能比较强大的在线考试系统的后台操作过程及一些关键技术：关键实现了考生在选择科目后进入考试窗体,考试计时,考试时间到,系统强制考生退出,及考完后对客观题的自动评分、存档。