共查询到20条相似文献,搜索用时 15 毫秒
1.
Quantitative high-resolution on-line NMR spectroscopy in reaction and process monitoring 总被引:1,自引:0,他引:1
Maiwald M Fischer HH Kim YK Albert K Hasse H 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,166(2):135-146
On-line nuclear magnetic resonance spectroscopy (on-line NMR) is a powerful technique for reaction and process monitoring. Different set-ups for direct coupling of reaction and separation equipment with on-line NMR spectroscopy are described. NMR spectroscopy can be used to obtain both qualitative and quantitative information from complex reacting multicomponent mixtures for equilibrium or reaction kinetic studies. Commercial NMR probes can be used at pressures up to 35 MPa and temperatures up to 400 K. Applications are presented for studies of equilibria and kinetics of complex formaldehyde-containing mixtures as well as homogeneously and heterogeneously catalyzed esterification kinetics. Direct coupling of a thin-film evaporator is described as an example for the benefits of on-line NMR spectroscopy in process monitoring. 相似文献
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Optical waveguide sensor for on-line monitoring of bacteria 总被引:2,自引:0,他引:2
A grating-coupled planar optical waveguide sensor is presented for sensing of bacteria by evanescent waves. The waveguide design results in increased depth of penetration into the sample volume, which makes it suitable for detecting micrometer-sized biological objects. We tested the sensor's performance by monitoring the adhesion of Escherichia coli K12 cells to the sensor surface. 相似文献
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Surface quality monitoring for process control by on-line vibration analysis using an adaptive spline wavelet algorithm 总被引:1,自引:0,他引:1
The dynamic behaviour of wood machining processes affects the surface finish quality of machined workpieces. In order to meet the requirements of increased production efficiency and improved product quality, surface quality information is needed for enhanced process control. However, current methods using high price devices or sophisticated designs, may not be suitable for industrial real-time application. This paper presents a novel approach of surface quality evaluation by on-line vibration analysis using an adaptive spline wavelet algorithm, which is based on the excellent time-frequency localization of B-spline wavelets. A series of experiments have been performed to extract the feature, which is the correlation between the relevant frequency band(s) of vibration with the change of the amplitude and the surface quality. The graphs of the experimental results demonstrate that the change of the amplitude in the selective frequency bands with variable resolution (linear and non-linear) reflects the quality of surface finish, and the root sum square of wavelet power spectrum is a good indication of surface quality. Thus, surface quality can be estimated and quantified at an average level in real time. The results can be used to regulate and optimize the machine's feed speed, maintaining a constant spindle motor speed during cutting. This will lead to higher level control and machining rates while keeping dimensional integrity and surface finish within specification. 相似文献
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Ultrasonic guided wave becomes one of promising tool for monitoring various types of structures such as large steel plates, vessels, and pipes in oil, chemical or nuclear industry, because guided waves have ability to travel wide range of the target structure in a single position. However, analysis of guided wave signals acquired from structure is difficult on account of low S/N ratio and its dispersive nature. To improve S/N ratio and overcome dispersion effect, focusing techniques for guided waves are needed. Thus, in this study, focusing techniques for guided waves were developed in order to improve long range inspection ability, and performance of the developed techniques was verified by experiments. 相似文献
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J.M. Hale 《Ultrasonics》1988,26(6):356-357
A method has been devised for determining the density of a fluid by measuring the velocity and amplitude of an ultrasonic pulse passed through it. The theory of the method is presented, together with the results of an experimental verification. 相似文献
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The supervised learning method and quality capability of process used in an on-line optical transmission inspection system of the basis weight for nonwoven material are investigated. A near-infrared light transmission inspection is applied in the production machine of a nonwoven fabric to detect the basis weight and support the producing quality. Using least squares method, the parameter transfer equations of the piecewise ploynomials functions between the measured voltage and the nonwoven basis weight are found. Supervised learning method is adopted to improve the producing capability. It is shown that the capability index of process Cp and Cpk is testing samples when the supervised learning algorithm is used. Obvious, the supervised learning method is effective to improve the producing capability and support the producing quality. 相似文献
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Photoacoustic system for on-line process monitoring of hydrogen sulfide (H2S) concentration in natural gas streams 总被引:1,自引:0,他引:1
A dual-channel hydrogen sulfide (H2S) concentration measuring system based on photoacoustic spectroscopy is described. The system uses a single-mode, fiber-coupled, room-temperature-operated, telecommunication-type diode laser with a wavelength of 1574.5 nm and an output optical power of 40 mW and two identical resonant photoacoustic cells to achieve minimum detectable H2S concentration at 0.5 ppm (3σ) in both measured natural gas streams. The instrument features excellent long-term stability and unattended automatic on-line monitoring even when operated in harsh industrial environments. The potentially deteriorating effect of temporal variation in the natural gas composition was successfully suppressed by applying a spectral baseline correction method and by introducing an additional measurement phase with measurement of a reference gas from which the H2S has been removed. Various tests of the instrument demonstrate its reliable performance and suitability for process-control application. PACS 82.80.Kq; 42.62.Fi; 07.07.Df 相似文献
10.
A. V. Dubrov V. D. Dubrov Y. N. Zavalov V. Y. Panchenko 《Applied physics. B, Lasers and optics》2011,105(3):537-543
The results of measurement of fluctuations of brightness temperature T in the region of exposure to laser radiation of a 3 mm-thick steel plate are presented. The local luminosity along the cut-front
was measured using two-color multichannel pyrometer. Cutting trials were carried out with CO2 laser (10.6 μm, 1200 W) and fiber laser (1.07 μm, 1800 W). Special attention was given to the frequency range of temperature
fluctuations above frequency of melt overflight, aiming on on-line monitoring applications. It is shown that local fluctuations
of T are related to local melt’s surface deformations due to unequal radiation absorption; thus the noise spectrum of T fluctuations reflects turbulent surface deformation, caused by gas jet and capillary waves. It is also shown that the thermo-capillary
effect with capillary-wave turbulence generation can be observed in case of exposure to 10.6 μm radiation with a laser intensity
of about 1 MW/cm2. The power law of “−7/6” describes the spectrum of the T fluctuation variance in this case of anomalous absorption of radiation, and the standard deviation of T is in excess of 10 K for a frequency of 14 kHz. There is no such effect in case of fiber-laser radiation applying, and the
source of the capillary waves is only forced low-frequency deformations of the melt surface. The standard deviation of T does not exceed 3 K on the frequency of 14 kHz, and above, and a power law of the spectrum fluctuation is described by about
“−3” in that range. 相似文献
11.
B. Kopec 《Ultrasonics》1975,13(6):267-274
This work outlines the present theory of attenuation of the ultrasonic waves, particularly the theory of scattering, and describes the measurement of attenuation in metals. Experiments were carried out to measure the attenuation of samples with different grain size taken from materials for railway wheel sets; in these experiments the pulse echo method, with elimination of the effect of the reflexion factor, was applied. The article presents the relation between the overall attenuation coefficient and its scattering component, the grain size and frequency.
On the basis of our measurements and an analysis of the obtained results, two methods of evaluation of the structure of railway materials by ultrasonic inspection were derived. 相似文献
12.
The use of the signal processing techniques based on the principle of quasi-frequency diversity can be a suitable solution for the ultrasonic inspection of liquid hydrogen tanks manufactured out of composite materials. Nevertheless, the algorithms developed up to now suffer from limitations that restrict their large-scale use. The split-spectrum processing requires preliminary adjustments that are not always accessible to the user, while the cut-spectrum processing is not sensitive enough to eliminate the noise. We have thus developed an interesting alternative to these two filters. Based on the use of progressive low-pass filters, this algorithm, called low-spectrum processing, takes into account the physical characteristics of the ultrasonic wave propagation in a composite material. Its use in the inspection of tanks made in composites showed better performances. 相似文献
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The film condensation of vapor on a cooled, downward-facing surface is a complex dynamic fluid phenomenon. This paper will describe the theoretical basis, instrumentation approach, and experimental results for a method for ultrasonic monitoring of film condensation. The ultrasound measurement system utilizes a 10 MHz broadband contact transducer, operating in pulse-echo mode. By appropriate signal processing, condensation layers over a wide thickness range, from much less than a wavelength to several wavelengths, can readily be measured. 相似文献
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《光学技术》2013,(4):304-308
研究了一种基于视觉检测的管路流量监控系统。将玻璃浮子流量计连接到管路中,采用LED光源对其进行照明,采用视觉检测系统拍摄玻璃浮子流量计图像,计算机软件对图像进行显示和处理,得出流量计的流量读数,并进一步对流量数据进行存储、显示和统计。系统既实现了管路工作状况和流量的现场目视观测,同时在主控中心还可通过由系统软件提供的流量计图像和流量数据实现管路工作状况和流量的监控。论述了系统的工作原理,分析了系统的硬件组成,在实验室条件下搭建了实验系统。对标定算法、浮子位置的亚像素定位算法进行了论述,并进行了实验测试和分析。结果表明,该系统能够满足工业现场的工作需求。 相似文献
18.
Metal oxide thin films, suitable for use on solar
energy converters and photocatalitic applications, have been
characterized on-line by ellipsometric monitoring system. Ellipsometry
is a powerful and non-invasive technique of film analysis but it is
indirect tool. The most interesting parameters such as film thickness
and complex refractive indices can be determined only by computer sample
modelling. The complex reflection coefficients obtained from model
calculation were compared with ellipsometric measurements. We discuss
composition of multilayer film structure using various models and
fittings method. The implementation of effective medium approximation
procedure enables to interpret multilayer oxides structure formation
during passivation process. It is shown that an accurate model fitting
was obtained using Levenberg-Marquardt optimization algorithm and
multidimensional mean square error. 相似文献
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Attenuation and velocity of bulk longitudinal ultrasonic waves were measured during the commercial suspension polymerization of vinyl chloride in the frequency range of a few hundred kHz to one MHz. The reproducibility of ultrasonic measurements is determined mainly by the reproducibility of polymerization technology. Measurements of attenuation during the polymerization process indicate such effects as local cavitation, boiling or foaming of the vinyl chloride polymerization system. The ultrasonic attenuation against polymerization time curve predicts morphological properties of the final polyvinyl chloride product. It was found that the magnitude of the ultrasonic velocity is in close correlation with the degree of conversion of vinyl chloride, and ultrasonic velocimetry can effectively be used for continuous monitoring of conversion degree during polymerization. 相似文献
20.
Schmachtl M Kim TJ Grill W Herrmann R Scharf O Schwieger W Schertlen R Stenzel C 《Ultrasonics》2000,38(1-8):809-812
Variations of the phase and amplitude of a transmitted ultrasonic wave package were monitored in real time during the synthesis of zeolite A and zeolite X. For both materials, characteristic changes of the measured attenuation and the sound velocity of ultrasonic waves traveling in the reaction fluid were observed, correlating with the processes of gel formation and zeolite crystallization, respectively. Aging effects of the reaction fluids are demonstrated. The observation of the onset of the zeolite crystallization was verified with ex-situ X-ray diffraction (XRD) measurements. 相似文献