共查询到20条相似文献,搜索用时 0 毫秒
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V. Gorelik 《Vacuum》2012,86(12):2064-2066
A new energy analyzer compatible with high spatial resolution spectrometers is proposed. The analyzer accepts electrons emitted with polar angles from 90.5° to 98.5° in the full azimuth range. A position-sensitive detector collects these electrons in the parallel mode of registration by 30 virtual channels; each channel has the resolution of 0.2% and the entrance solid angle of 0.87 steradians. The proposed analyzer provides high lateral resolution due to its compatibility with extremely short-focused microscope lenses, and, at the same time, the system offers high spatial resolution in the normal direction due to its ability to register electrons emitted with grazing angles. 相似文献
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AbstractAn acousto-optic tunable filter (AOTF) causes the diffracted angle and wavelength to spread, leading to loss of resolution. The light intensity detected by a CCD pixel equals the true intensity plus the stray light caused by the spread of the wavelength and diffraction angle. Here, the true intensity is obtained using neighbourhood estimate recursive correction iteration, improving the spectral and spatial resolution. The spread of acoustic wave angles caused by diffraction is analysed. The reason for the spreads is analysed and derived. A method is reported for measuring the correspondence between the wavelength and diffraction angle spread, using an AOTF, an angle measurement spectrometer and a fibre spectrometer. The iterations’ stop condition is analysed. The improved theory is verified by an AOTF spectral imaging experiment. 相似文献
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Nitric oxide microsensor for high spatial resolution measurements in biofilms and sediments 总被引:3,自引:0,他引:3
Nitric oxide (NO) is a ubiquitous biomolecule that is known as a signaling compound in eukaryotes and prokaryotes. In addition, NO is involved in all conversions of the biogeochemical nitrogen cycle: denitrification, nitrification, and the anaerobic oxidation of ammonium (Anammox). Until now, NO has not been measured with high spatial resolution within microbial communities, such as biofilms, sediments, aggregates, or microbial mats, because the available sensors are not robust enough and their spatial resolution is insufficient. Here we describe the fabrication and application of a novel Clark-type NO microsensor with an internal reference electrode and a guard anode. The NO microsensor has a spatial resolution of 60-80 microm, a sensitivity of 2 pA microM-1, and a detection limit of approximately 30 nM. Hydrogen sulfide (H2S) was found to be a major interfering compound for the electrochemical detection of NO. The application of the novel NO microsensor to nitrifying biofilms and marine sediments revealed dynamic NO concentration profiles with peaks in the oxic parts of the samples. The local concentrations suggested that NO may be an important bioactive compound in natural environments. The consumption and production of NO occurs in separate regions of stratified microbial communities and indicates that it is linked to distinct biogeochemical cycles. 相似文献
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《成像科学杂志》2013,61(5):296-302
AbstractThis research work demonstrates an image quality assessment meter (IQAM) in reduced reference (RR) mode for discrete cosine transform (DCT) based compressed images. The DCT based image compression technique is lossy. As a result, it introduces blockiness and blurriness artefacts in the coded image. To send the image in image transmission systems, the system bandwidth is limited, and image data need to be adapted accordingly. To determine the quality of image at the recipient end, fewer image parameters are sent rather than the complete reference image. The aim of this paper is to suggest a method for the receiver to evaluate the objective received image quality. The presented RR quality meter operates in the frequency domain for the estimation of artefacts in the compressed image. The quality meter takes the image, performs edge detection, transforms it into the frequency domain and estimates the harmonics. The estimated strength of harmonics in the compressed image is compared with the received RR parameter for blockiness and blurriness distortions. For improved quality judgment, the combined effect of both these artefacts is measured as well. Peak signal to noise ratio (PSNR) is another most familiar method of image quality assessment. The received image quality is also observed by measuring the PSNR. The objective values of the artefacts obtained by the designed RR IQAM algorithm are correlated with the subjective differential mean opinion scores (DMOS) blockiness and blurriness values of Laboratory for Image and Video Engineering (LIVE) image database2. The results obtained are well matched and give 93–94% correlation with the LIVE database values, whereas the correlation obtained by PSNR values with LIVE DMOS values is only around 70%. This proves the practical application of the designed IQAM in RR. 相似文献
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Semiconductor nanowires and other semiconducting nanoscale materials configured as field-effect transistors have been studied extensively as biological/chemical (bio/chem) sensors. These nanomaterials have demonstrated high-sensitivity from one- and two-dimensional sensors, although the realization of the ultimate pointlike detector has not been achieved. In this regard, nanoscale p-n diodes are attractive since the device element is naturally localized near the junction, and while nanowire p-n diodes have been widely studied as photovoltaic devices, their applications as bio/chem sensors have not been explored. Here we demonstrate that p-n diode devices can serve as a new and powerful family of highly localized biosensor probes. Designed nanoscale axial p-n junctions were synthetically introduced at the joints of kinked silicon nanowires. Scanning electron microscopy images showed that the kinked nanowire structures were achieved, and electrical transport measurements exhibited rectifying behavior with well-defined turn-on in forward bias as expected for a p-n diode. In addition, scanning gate microscopy demonstrated that the most sensitive region of these nanowires was localized near the kinked region at the p-n junction. High spatial resolution sensing using these p-n diode probes was carried out in aqueous solution using fluorescent charged polystyrene nanobeads. Multiplexed electrical measurements show well-defined single-nanoparticle detection, and experiments with simultaneous confocal imaging correlate directly the motion of the nanobeads with the electrical signals recorded from the p-n devices. In addition, kinked p-n junction nanowires configured as three-dimensional probes demonstrate the capability of intracellular recording of action potentials from electrogenic cells. These p-n junction kinked nanowire devices, which represent a new way of constructing nanoscale probes with highly localized sensing regions, provide substantial opportunity in areas ranging from bio/chem sensing and nanoscale photon detection to three-dimensional recording from within living cells and tissue. 相似文献
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Image processing and transmission systems may introduce some amount of distortion or artefacts in a digital image. This fact usually leads to a visual or statistical image quality assessment (IQA) required in many applications and research studies in order to analyse a product image in terms of deteriorations as well as effects of the processing. There are numerous IQA criteria presented in the literature separately that makes it really difficult both for use in comparative analyses and for educational purposes. In this presented work, a user friendly web-based digital educational interface for full-reference or no-reference image quality assessment using MATLAB builder NE has been developed. In addition to this, developed system performs user-defined optional deteriorations (median noise, Gaussian blur, motion blur, high-pass filter and jpeg compression) on the image and assesses deterioration of the image. It is an extremely easy, fast and economical way of analysing digital images, especially designed for researchers, graduate and postgraduate students who work on digital image processing. Using this web-based tool well contributes to teaching all of the IQA methods and quality effects of systematic distortions on the image as well as establishes a scientific benchmark for researchers. 相似文献
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像移和采样共同作用下的TDICCD探测器像质 总被引:1,自引:0,他引:1
CCD探测器的像元尺寸一般来说是光学系统弥散斑的几倍,因此以CCD探测器为接收器的光学成像系统在理论上可以近似看作是空间移不变系统。采用计算机仿真的方法来研究在空间移变条件下的TDICCD遥感相机的影像分辨力和像质问题,结果是:在目标条带宽度一定时,像元尺寸为a,像移量为a/3,a/2,a,MTF分别下降为0.918,0.876,0.753;当MTF基本相等时,像移量为a/3,a/2,a,条带宽度为36,38,44。通过模拟,认识到在像移大于a/3时,Angle=0和Angle≠0的肘阡相差小于1%;并在像移量大于a/3的条件下得到了适用于工程应用的像元尺寸、像移量、分辨力、MTF的一个简洁函数。 相似文献
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Slaney TR Nie J Hershey ND Thwar PK Linderman J Burns MA Kennedy RT 《Analytical chemistry》2011,83(13):5207-5213
Low-flow push-pull perfusion is a sampling method that yields better spatial resolution than competitive methods like microdialysis. Because of the low flow rates used (50 nL/min), it is challenging to use this technique at high temporal resolution which requires methods of collecting, manipulating, and analyzing nanoliter samples. High temporal resolution also requires control of Taylor dispersion during sampling. To meet these challenges, push-pull perfusion was coupled with segmented flow to achieve in vivo sampling at 7 s temporal resolution at 50 nL/min flow rates. By further miniaturizing the probe inlet, sampling with 200 ms resolution at 30 nL/min (pull only) was demonstrated in vitro. Using this method, L-glutamate was monitored in the striatum of anesthetized rats. Up to 500 samples of 6 nL each were collected at 7 s intervals, segmented by an immiscible oil and stored in a capillary tube. The samples were assayed offline for L-glutamate at a rate of 15 samples/min by pumping them into a reagent addition tee fabricated from Teflon where reagents were added for a fluorescent enzyme assay. Fluorescence of the resulting plugs was monitored downstream. Microinjection of 70 mM potassium in physiological buffered saline evoked l-glutamate concentration transients that had an average maxima of 4.5 ± 1.1 μM (n = 6 animals, 3-4 injections each) and rise times of 22 ± 2 s. These results demonstrate that low-flow push-pull perfusion with segmented flow can be used for high temporal resolution chemical monitoring and in complex biological environments. 相似文献
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目的研制一种透明的用于高强度聚焦超声热消融的PAA模块,并对其声学参数进行测量。方法观察模块浓度的不同所致颜色与透明度的变化,并对PAA模块的声学特性包括密度、声速及声衰减进行测量。结果(1)PAA模块为透明的琥珀色,蛋白浓度越高,颜色越深,透明度越低。(2)PAA模块的密度与水相近,为1.0250g/cm3至1.0617g/cm3。声速与模块浓度之间有明显的相关性。声衰减从0.125dB/cm至0.329dB/cm,随着模块密度与探头频率的增加而增加。结论PAA模块是一种较好的用于高强度聚焦超声热消融的均质仿体,实验结果有较好的重复性。 相似文献
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A method is considered for measuring object quality parameters that can arise through indirect parameters, and in particular
electrophysical signals acting on the object. Methods are given for obtaining a mathematical model for the measurement procedure
and examples are quoted of the method applied with the use of spectrometric characteristics of the object.
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Translated from Izmeritel'naya Tekhnika, No. 8, pp. 13–16, August, 2008. 相似文献
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Perceptual image quality assessment (IQA) is one of the most indispensable yet challenging problems in image processing and computer vision. It is quite necessary to develop automatic and efficient approaches that can accurately predict perceptual image quality consistently with human subjective evaluation. To further improve the prediction accuracy for the distortion of color images, in this paper, we propose a novel effective and efficient IQA model, called perceptual gradient similarity deviation (PGSD). Based on the gradient magnitude similarity, we proposed a gradient direction selection method to automatically determine the pixel-wise perceptual gradient. The luminance and chrominance channels are both took into account to characterize the quality degradation caused by intensity and color distortions. Finally, a multi-scale strategy is utilized and pooled with different weights to incorporate image details at different resolutions. Experimental results on LIVE, CSIQ and TID2013 databases demonstrate the superior performances of the proposed algorithm 相似文献
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Dongqi Li Yang Wei Jin Zhang Jiangtao Wang Yinghong Lin Peng Liu Shoushan Fan Kaili Jiang 《Nano Research》2017,10(6):1896-1902
Single-walled carbon nanotube (SWCNT) films with a high density exhibit broad functionality and great potential in nanodevices,as SWCNTs can be either metallic or semiconducting in behavior.The films greatly benefit from characterization technologies that can efficiently identify and group SWCNTs based on metallic or semiconducting natures with high spatial resolution.Here,we developed a facile imaging technique using scanning electron microscopy (SEM) to discriminate between semiconducting and metallic SWCNTs based on black and white colors.The average width of the single-SWCNT image was reduced to ~9 nm,~1/5 of previous imaging results.These achievements were attributed to reduced surface charging on the SiO2/Si substrate under enhanced accelerating voltages.With this identification technique,a CNT transistor with an on/off ratio of >105 was fabricated by identifying and etching out the white metallic SWCNTs.This improved SEM imaging technique can be widely applied in evaluating the selective growth and sorting of SWCNTs. 相似文献
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Coffey JP Woywodt A Hill JC 《Hemodialysis international. International Symposium on Home Hemodialysis》2011,15(3):320-325
To compare cardiac output (CO) and cardiac index (CI) and left ventricular ejection fraction (LVEF) in end-stage renal disease (ESRD) with a control group using gated single photon emission computed tomography (SPECT)/computed tomography (CT) imaging. Altered cardiovascular function with increased CO secondary to arterio-venous fistulas (AVF) for dialysis has been reported in patients with ESRD. Thirty-two patients (18 with AVF or graft) referred for pre-renal transplant cardiac assessment using SPECT/CT were studied with 2 comparison groups, 42 normal weight (body mass index<30) and 46 obese (body mass index>30) patients. End-stage renal disease patients had overall reduced mean hemoglobin 11.6 mg/dL and elevated mean parathyroid hormone of 396 pg/mL. Gated SPECT using MIBI was performed after Bruce protocol apart from 4 renal patients who underwent cardiac stressing with adenosine. Cardiac output was calculated by product of stroke volume and resting heart rate and CI determined. Mean CI was 2.6 L/min/m(2) for renal disease group compared with 2.2 and 2.3 L/min/m(2) for the normal weight and obese groups, P=0.005 and 0.005 respectively (Wilcoxon's rank test). Cardiac output was increased for the renal group; 4.9 L/min, equal to the obese group but greater than normal weight group at 4.3 L/min. No significant difference in LVEF was seen between the 3 patient groups. No significant difference in CI or output was seen between the renal disease patients with AVF and those without fistulas. Cardiac ouput and CI, assessed using SPECT/CT, are increased in patients with ESRD. This may be independent of the presence of AVF or grafts and other factors such as anemia and hyperparathyroidism may contribute to this high output cardiac function. As LVEF is not increased for these patients, increased heart rate, may also contribute to elevated CO. 相似文献
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本文以燃料电池轿车( fuel cell vehicle, FCV )为研究对象,采集其怠速工况不同位置的声音信号作为试验样本,采用成对比较法对其中的24个样本信号进行了主观评价试验,同时计算了可以描述其声音特性的6个客观评价参量,并引入BP神经网络建立了FCV声品质预测模型。通过所建立的模型计算FCV声品质客观评价参量对主观评价结果的影响权重,文中首次提出使用BP神经网络的方法来确定声品质评价中客观评价参量对主观评价结果的影响权重,研究结果表明,FCV声品质主要受响度、粗糙度和A声级三个客观参量的影响。此次分析,不仅适用于燃料电池轿车对其它领域的声品质分析与评价都起到了指导性的意义。 相似文献
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In this paper, an efficient image deblurring algorithm is proposed. This algorithm restores the blurred image by incorporating a curvelet-based empirical Wiener filter with a spatial-based joint non-local means filter. Curvelets provide a multidirectional and multiscale decomposition that has been mathematically shown to represent distributed discontinuities such as edges better than traditional wavelets. Our method restores the image in the frequency domain to obtain a noisy result with minimal loss of image components, followed by an empirical Wiener filter in the curvelet domain to attenuate the leaked noise. Although the curvelet-based methods are efficient in edge-preserving image denoising, they are prone to producing edge ringing which relates to the structure of the underlying curvelet. In order to reduce the ringing, we develop an efficient joint non-local means filter by using the curvelet deblurring result. This filter could suppress the leaked noise while preserving image details. We compare our deblurring algorithm with a few competitive deblurring techniques in terms of improvement in signal-to-noise-ratio (ISNR) and visual quality. 相似文献
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提出一种彩色目标高维检测和空间分集检测技术,它利用 RGB 颜色的均值趋同性校正色偏,减少光照强度和光源颜色对目标检测的影响;采用检测门限自适应变化的彩色目标高维检测算法检测出疑似目标,进一步避免了传统方法受环境光照影响大的缺点;使用基于区域关联性的彩色信号自适应空间分集检测技术,提高目标检测效果。试验证明,检测并降噪以后,97.5%以上的图像的提取结果可以达到 30db 以上的信噪比。 相似文献