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321.
322.
王丹 《辽宁城乡环境科技》2009,(10):26-28
提出一种利用高分辨率遥感影像半自动提取建筑物边缘的方法。先对遥感影像进行预处理,对所有边缘进行边缘检测。然后进行边缘跟踪,提取建筑物的主方向线,利用模型进行线段关系判断,再进行线段关系处理、区域分割和区域生长,最后进行区域合并提取出建筑物的轮廓。用上述方法对Quick Bird卫星的高分辨率影像进行了实验,实验结果证明该方法有较高的识别率、较好的准确性,具有一定的实用价值。 相似文献
323.
324.
依据JJG1059-1999对ICP发射光谱仪锌元素检出限的不确定度进行了评估,分析了影响测量不确定度的各个因素,计算得出ICP发射光谱仪锌元素检出限的扩展不确定度为:U=0.00066(μg.mL-1),k=2。 相似文献
325.
填埋场直流电阻电路模型及分析 总被引:1,自引:0,他引:1
为研究垃圾填埋场的导电特性,建立了一种填埋场直流电阻电路模型,并对回路中的各部分电阻进行了分析.结果表明:随着供电电极直径和入土深度的增加,回路电阻减小,而随着供电电极与漏洞之间距离的增大,回路电阻缓慢增加;漏洞电阻由接触电阻和内阻组成,前者远大于后者,对一个半径为1cm的圆形漏洞来说,接触电阻可达1500Ω,而内阻只占到接触电阻的1/10;在供电电极周围浇水可明显降低回路电阻,在场内电极直径为20mm,入土深度为0.4m,电极与漏洞之间距离为20m时,浇水后的回路电阻可减小26.6%. 相似文献
326.
Based on Inverse Transient Analysis (ITA) method, a real-time leak detection method is proposed to capture leak location and the associated leak rate in oil pipe conveyance systems. In the proposed approach, location and flow rate of leak (if any), the fluid properties, as well as physical parameters of the system, are calculated in consecutive periods through minimizing the discrepancy between the calculated and measured flow parameters of the system. The method of characteristics is employed to numerically calculate the transient responses of the system and the genetic algorithm is utilized as the optimization engine. The proposed approach was applied to several real pipeline systems in which the required transient flow data are either directly collected from the field or fabricated with a third-party numerical software. Extensive numerical explorations were conducted to investigate the performance of the proposed method in real-time leak detection and to determine the extent to which field data errors, stemming from Supervisory Control and Data Acquisition (SCADA) systems and measurement equipment, affect the leak flow rate and location detectability of the proposed approach. The results show that the proposed approach provides promising results under a variety of transient and steady-state flow conditions even in the case with small leak flow rate of around 2% of the line rate. The results also reveal that the noises in the measurement data and the errors originated from SCADA systems do not significantly compromise the leak detectability of the proposed approach, confirming that the proposed approach can be utilized in practice. 相似文献
327.
Accurate detection of CO gas is crucial to the prevention of coal combustion. Tuneable diode laser absorption spectroscopy (TDLAS) is a reliable method for CO detection during coal combustion. The influences of temperature and pressure cause changes in the line strength and linewidth of the index gases’ absorption spectra, leading to sizable measurement errors. To correct the distortion of the CO absorption spectrum caused by temperature and pressure fluctuation, a compensation model based on the grey wolf optimizer–support vector machine (GWO–SVM) was proposed. The results were compared with those of the single SVM, the back propagation neural network (BPNN), and multiple regression analysis (MRA). MRA was revealed to result in the lowest accuracy, which indicated that MRA is not ideal for compensation in TDLAS. The hyperparameter selection of the SVM had the disadvantages of randomness and blindness, which led to instability and large errors. The BPNN achieved better correction in the training stage, but severe overfitting occurred in the testing stage. The modified results revealed that the GWO–SVM model had higher accuracy and stability than the other models. It effectively inhibited the effects of temperature and pressure on the measured concentration and greatly improved the measurement accuracy. The equipment is thus suitable for CO gas detection with the aim to preventing coal combustion loss, and it can be further applied to loss prevention in other process fields. 相似文献
328.
Positive polarotaxis in a mayfly that never leaves the water surface: polarotactic water detection in Palingenia longicauda (Ephemeroptera) 总被引:3,自引:2,他引:1
Tisza mayflies, Palingenia longicauda (Olivier 1791), swarm exclusively over the river Tisza (from which the name of the mayfly was derived). This river is bordered
by a high vertical wall of trees and bushes, which hinder P. longicauda to move away horizontally from the water. During swarming, Tisza mayflies fly immediately above the river in such a way that
their cerci touch the water frequently or sweep its surface. This continuous close connection with water and the vertical
wall of the shore and riparian vegetation result in that Tisza mayflies never leave the water surface; consequently, they
need not search for water. Several Ephemeroptera species move away far from water and return to it guided by the horizontal
polarization of water-reflected light. To reveal whether also P. longicauda is or is not polarotactic, we performed a field experiment during the very short swarming period of Tisza mayflies. We show
here that also P. longicauda has positive polarotaxis, which, however, can be observed only under unnatural conditions, when the animals are displaced
from the water and then released above artificial test surfaces. P. longicauda is the first species in which polarotactic water detection is demonstrated albeit it never leaves the water surface, and
thus, a polarotactic water detection seems unnecessary for it. The polarotactic behaviour of Tisza mayflies explains the earlier
observation that these insects swarm above wet asphalt roads running next to river Tisza. 相似文献
329.
Development of systems for detection, early warning, and control of pipeline leakage in drinking water distribution: A case study 总被引:1,自引:0,他引:1
Weifeng Li Wencui Ling Suoxiang Liu Jing Zhao Ruiping Liu Qiuwen Chen Zhimin Qiang Jiuhui Qu 《环境科学学报(英文版)》2011,23(11):1816-1822
The integrated system for the detection, early warning, and control of pipeline leakage has been successfully developed to manage the pipeline networks of Beijing. 相似文献
330.
An E. coli SOS-EGFP biosensor which expresses enhanced green fluorescent protein as a reporter protein under the control of recA gene promoter in SOS response was constructed for detection of DNA damage and evaluation of DNA damaging chemicals. The chemicals that may cause substantial DNA damage will trigger SOS response in the constructed bacterial biosensor, and then the reporter egfp gene under the control of recA promoter is stimulated to express as a fluorescent protein, allowing fast and sensitive fluorescence detection. Interestingly, this biosensor can be simultaneously applied for evaluation of genotoxicity and cytotoxicity. The SOS-EGFP bacterial biosensor provides a sensitive, specific and simple method for detecting known and potential DNA damaging chemicals. 相似文献