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Measurement Principle (measurement + principle)

Distribution by Scientific Domains

Engineering	42%

Selected Abstracts

Defining the moment of erosion: the principle of thermal consonance timing

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2005
D. M. LawlerArticle first published online: 9 DEC 200
Abstract Geomorphological process research demands quantitative information on erosion and deposition event timing and magnitude, in relation to fluctuations in the suspected driving forces. This paper establishes a new measurement principle , thermal consonance timing (TCT) , which delivers clearer, more continuous and quantitative information on erosion and deposition event magnitude, timing and frequency, to assist understanding of the controlling mechanisms. TCT is based on monitoring the switch from characteristically strong temperature gradients in sediment, to weaker gradients in air or water, which reveals the moment of erosion. The paper (1) derives the TCT principle from soil micrometeorological theory; (2) illustrates initial concept operationalization for field and laboratory use; (3) presents experimental data for simple soil erosion simulations; and (4) discusses initial application of TCT and perifluvial micrometeorology principles in the delivery of timing solutions for two bank erosion events on the River Wharfe, UK, in relation to the hydrograph. River bank thermal regimes respond, as soil temperature and energy balance theory predicts, with strong horizontal thermal gradients (often >1 K cm,1 over 6·8 cm). TCT fixed the timing of two erosion events, the first during inundation, the second 19 h after the discharge peak and 13 h after re-emergence from the flow. This provides rare confirmation of delayed bank retreat, quantifies the time-lag involved, and suggests mass failure processes rather than fluid entrainment. Erosion events can be virtually instantaneous, implying ,catastrophic retreat' rather than ,progressive entrainment'. Considerable potential exists to employ TCT approaches for: validating process models in several geomorphological contexts; assisting process identification and improving discrimination of competing hypotheses of process dominance through high-resolution, simultaneous analysis of erosion and deposition events and driving forces; defining shifting erodibility and erosion thresholds; refining dynamic linkages in event-based sediment budget investigations; and deriving closer approximations to ,true' erosion and deposition rates, especially in self-concealing scour-and-fill systems. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Polyaniline Film Based Amperometric pH Sensor Using A Novel Electrochemical Measurement System

ELECTROANALYSIS, Issue 8 2009
Wei Gao
Abstract A polyaniline based amperometric pH sensor has been developed using a novel electrochemical measurement system. A polyaniline film (PANI) coated pencil graphite electrode (PGE) is connected in series between the working and counter electrodes of a potentiostat, and immersed in the solution together with a reference electrode. When an external potential is applied, the resulting current varies with the solution pH, which provides the basis for the amperoemtric pH sensor. Equations describing the measurement principle are presented. Based on pH dependent emeraldine salt,emeraldine base transition of PANI film, the pH sensor exhibits high stability, accuracy, selectivity, sensitivity and a short time. [source]

Theoretical and experimental study of polarization characteristics of polarization maintaining fiber based on wavelength-sweeping modulation

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010
Zuo-Liang Duan
Abstract We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According to the dependence of the phase difference between two orthogonally polarized modes (denoted as HE and HE) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the beat length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466,1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244 [source]

Reliable hot-spot classification in 10,ms using ultra-fast lock-in thermography

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2009
Martin Kasemann
Abstract We propose and demonstrate a reliable and non-destructive spatially resolved measurement technique for ultra-fast hot-spot classification of solar cells. The method can deliver quantitative images of the local heat dissipation in hot-spots in measurement times below 10,ms. The high accuracy and sensitivity allow for reliable hot-spot testing and provide the basis for a reliable classification of solar cells into different hot-spot categories. The method can be applied to wafer-based silicon solar cells and in principle also to thin-film solar cells of all material compositions. This paper explains the measurement principle, gives a detailed step-by-step description of viable automated evaluation procedures, and assesses the sensitivity and accuracy of the method. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Wireless contact lens sensor for intraocular pressure monitoring: assessment on enucleated pig eyes

ACTA OPHTHALMOLOGICA, Issue 4 2009
Matteo Leonardi
Abstract. Purpose:, Assessment on enucleated pig eyes of a novel and minimally invasive method for the continuous monitoring of intraocular pressure (IOP), based on a novel wireless contact lens sensor (CLS). Methods:, The wireless CLS is a disposable silicone soft contact lens with a sensor embedded in it, allowing the wireless measurement of changes in corneal curvature induced by IOP variations. A CLS was adapted and tested on enucleated pig eyes. To demonstrate the measurement principle of the device, the enucleated pig eye was cannulated, allowing precise control of IOP. The CLS signal was then compared to the imposed IOP. Results:, First, the IOP of enucleated pig eyes was changed between 11 and 14 mmHg, simulating ocular pulsation. Then, IOP was changed with static steps of 1 mmHg between 20 and 30 mmHg to assess the reproducibility and linearity of the CLS. In both cases, measurements from the CLS and IOP showed very good correlation. A calibration graph shows that the CLS is capable of monitoring the IOP of each individual eye with a reproducibility of ± 0.2 mmHg (95% confidence interval). Conclusion:, The wireless CLS shows a good functionality to monitor the IOP on enucleated pig eyes. The device is placed in the same way as a soft disposable contact lens. This device would allow a minimally invasive and continuous monitoring of IOP over prolonged periods of up to 24 hr, regardless of patient activity, thus opening up new diagnostic and therapeutic methods to manage glaucoma. [source]

Comparison of Electrochemical and Surface Plasmon Resonance Immunosensor Responses on Single Thin Film

ELECTROANALYSIS, Issue 20 2008
Ryoji Kurita
Abstract This paper reports results obtained when comparing an electrochemical enzyme immunosensor and a surface plasmon resonance (SPR) based immunosensor on the same gold surface installed in an electrochemical SPR flow cell. Simultaneous electrochemical and SPR measurements were performed on a gold surface modified with multilayers of poly- L -lysine and poly-styrenesulfonate assembled with the layer-by-layer method. First, we obtained the SPR response induced by the formation of an immunocomplex from the shift in the SPR angle by injecting an anti tumor necrosis factor-, antibody solution labeled with alkaline phosphatase into the flow cell containing the multilayer modified with tumor necrosis factor-,. Then we compared this SPR result with that obtained for the electrochemical oxidation current of p -aminophenol catalyzed by alkaline phosphatase from p -aminophenolphosphate on the same gold film. We compared the two immunosensor responses obtained using the different measurement principles and found that there was a high correlation efficient of 0.973 between them. This was because we were able to immobilize the immunoreagents with good stability and without losing the transport of the enzyme product in the multilayer whose thickness we easily controlled with nanometer scale accuracy. We also report that the detection limit of our electrochemical immunosensor after optimization was around 100,pg/mL (0.4,pM), which is one of the lowest values yet reported for an electrochemical immunosensor. [source]