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961.
Q.-H. Qin 《Archive of Applied Mechanics (Ingenieur Archiv)》1999,69(2):133-144
Summary For a two-dimensional piezoelectric plate subjected to mechanical and electric load, a Green function satisfying traction
free and exact electric boundary conditions along a hole is developed using Lekhnitskii's formalism and the technique of conformal
mapping. The critical points for the mapping function used is investigated numerically, and the study indicates that the transformation
of a polygonal hole in a piezoelectric plate into a unit circle is nonsingle-valued. A simple approach is presented to treat
such a situation. Based on the Green function developed in this paper, a system of singular integral equations for the unknown
dislocation defined on crack faces is presented to study the interaction between cracks and holes. Numerical results are presented
to elucidate the effects of crack orientation on stress and electric displacement (SED) intensity factors and to illustrate
the application of the proposed formulation.
Received 4 June 1998, accepted for publication 15 July 1988 相似文献
962.
963.
A new method for biochemical oxygen demand (BOD) determination, which combines the series piezoelectric quartz crystal (SPQC) technique with the growth of a microorganism is presented in this paper. This method needs no immobilization of bacteria and is simple and convenient. When a calibration technique was used for BOD analysis, the detection time was 2.5 h at 37°C. There was a good linear relationship between the frequency shift and BOD value in the range 2.2–11 mg/L and the regression equation was ΔF = 64.10 + 11.23[BOD]. The proposed method was compared with the conventional BOD5 method. This method was more rapid than the BOD5 method and the results obtained by the former were in good agreement with those obtained by the latter. The experimental conditions are also discussed in detail. 相似文献
964.
Tobias Werner Ingo Klimant Christian Huber Christian Krause Otto S. Wolfbeis 《Mikrochimica acta》1999,131(1-2):25-28
Fiber optic ion-microsensors based on luminescence decay time have been developed for chloride and potassium. The fiber tip
coatings consist of the respective ion-selective lipophilic ion carrier, plasticized PVC, and the ruthenium(II) tris-4,4′-diphenyl-2,2′-bipyridyl
ion-pair with Bromothymol Blue [Ru(dibipy)3(BTB)2] as a proton donor. The efficacy of radiationless fluorescence energy transfer from the donor (the ruthenium complex) to
the acceptor (BTB) is mediated by the ion concentration within the samples. The chloride response is based on the co-extraction
of chloride along with protons from the aqueous sample into a plastiziced PVC membrane, whereas in the presence of potassium
ions in the sample, the neutral BTB becomes deprotonated on extraction of potassium ions, with the release of protons. Both
processes result in a change in BTB absorbance. The absorption band of deprotonated BTB overlaps significantly with the emission
band of the ruthenium complex, allowing radiationless energy transfer to take place.
Received July 8, 1998. Revision November 10, 1998. 相似文献
965.
Gold electrodes were chemically modified with a phosphate ester monolayer designed to mimic biological ion-channel membranes.
Cyclic voltammograms of Fe(CN)6
3− as electroactive marker were measured in the presence of various types of analyte cations. Whereas in the absence of analyte
cations the marker reduction was hindered by electrostatic repulsion between the marker anions and phosphate groups of the
receptor monolayer, binding of di-and trications to the monolayer resulted in large increases of the reduction current. Trivalent
cations could be detected down to the submicromolar concentration range with excellent selectivities over alkali metal ions.
Also divalent cations were well discriminated and similar responses as to trivalent cations were only observed if their concentration
exceeded that of the trivalent cations by about two orders of magnitudes.
Received August 24, 1998. Revision March 10, 1999. 相似文献
966.
967.
Multiplexed piezoresistive sensor arrays hold great potential for measuring contact stress distributions for orthopedic research
applications. However, their acceptance has been handicapped by output drift and the fact that their dynamic response has
not been well characterized. In this report, the static and dynamic responses of one device of this class (the K-Scan piezoresistive
contact stress sensor) are formally characterized using a specially made pressure vessel that provides spatially homogeneous
contact stress. Drift was predominant early in static loading, reaching relationtive errors of approximately 30 percent over
a 10-min period. During loading, first-order dynamic analysis showed that the time constant (and time lag) was nearly zero
and there was little attenuation of the output up to 20 Hz. A deconvolution algorithm proved capable of compensating for the
great majority of static drift. 相似文献
968.
Motoaki Kimura Steve Tung James Lew Chih-Ming Ho Fukang Jiang Yu-Chong Tai 《Fluid Dynamics Research》1999,24(6):679-342
Measurements of wall shear-stress streaks of a turbulent boundary layer in the channel flow were carried out using a MEMS-based micro-shear-stress imaging chip, which contains about 100 sensors. The chip is designed and fabricated by surface micromachining technology. One arrray of 25 micro-shear-stress sensors in the chip that covers a length of 7.5 mm is used to measure the instantaneous spanwise distribution of the surface shear stress. The statistics of high shear-stress streaks were established. Based on the measurement, the physical quantities associated with the high shear-stress streaks, such as their length, width and peak shear-stress level, were obtained. We found out that a high correlation exists between the peak shear-stress level and front-end shear-stress slope of a high shear-stress streak. This important property is currently being applied to the deisgn of a real-time flow control logic. 相似文献
969.
Je-Kyun Park Hee-Jin Yee Kang Shin Lee Won-Yong Lee Min-Chol Shin Tae-Han Kim Seung-Ryeol Kim 《Analytica chimica acta》1999,390(1-3):83-91
A differential-type amperometric biosensor based on conventional thick-film technology has been developed for breath alcohol measurement. The amperometric breath alcohol biosensor utilizes the alcohol dehydrogenase (ADH) and nicotinamide adenine dinucleotide (NAD+) cofactor which produce reduced NADH as a product of the oxidation of alcohol. The biosensor was designed in a differential format consisting of a common Ag/AgCl reference electrode, an active working electrode containing the ADH, and the inactive working electrode containing only bovine serum albumin instead of the ADH. The differential signal between the active working electrode and the inactive working electrode minimized the interference from a large number of oxidizable species present in a person's breath. Prior to the amperometric measurement the biosensor was hydrated simply by dipping it into a phosphate buffer solution at pH 7.4. The NADH produced from the enzymatic reaction was oxidized at the working electrode biased at a potential of 470 mV vs. an on-board Ag/AgCl reference electrode. The biosensor can measure a person's breath alcohol over the concentration range 20–800 ppm routinely required in a test of drunken driving. 相似文献
970.