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Sensing Applications of Fluctuations and NoiseChang, Hung-Chih 2010 December 1900 (has links)
Noise and time-dependent fluctuations are usually undesirable signals. However,
they have many applications. This dissertation deals with two kinds of sensing
applications of fluctuation and noise: soil bulk density assessment and bacterium sensing.
The measurement of Vibration-Induced Conductivity Fluctuations (VICOF)
provides information about the bulk density and other parameters of soils. Bulk density
is the physical property of soils that is important to both the agriculture and construction
industries. The traditional measurements of soil bulk density are often time-consuming,
expensive or destructive. To determine the soil bulk density without the above
drawbacks, the VICOF measurement scheme was proposed. The research of VICOF in
this dissertation includes two parts: the initial phase of study and the new methods and
their theory. In the initial phase of study, the simple experiments, theory, and simulations
of VICOF were tested for relations between the soil bulk density, wetness, salinity, and
the VICOF data. Then, new measurement arrangements and their theoretical models
were proposed to improve the weaknesses of the initial approach (such as large scattering of data due to loose and heavy contacts) and to calculate the relationship
between the measured signals and the electromechanical transport parameters of the soils.
The bacterium sensing study in this dissertation was proposed to explore simple,
practical, rapid, sensitive, specific, portable, and inexpensive ways to detect and
recognize bacteria by Fluctuation-Enhanced Sensing (FES). One such potential way of
bacterium sensing is to analyze their odor. The research of bacterium sensing also
includes two parts: the initial phase of study and the new methods and their theory. The
initial phase study was proposed to explore the possibility of detecting and identifying
bacteria by sensing their odor via FES with commercial Taguchi sensors. Then the
subsequently developed new methods and their theory provide a simple way to generate
binary patterns with perfect reproducibility based on the spectral slopes in different
frequency ranges at FES. This new type of signal processing and pattern recognition is
implemented at the block diagram level using the building elements of analog circuitries
and a few logic gates with total power consumption in the microWatts range.
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Electronic noise in nanostructures: limitations and sensing applicationsKim, Jong Un 25 April 2007 (has links)
Nanostructures are nanometer scale structures (characteristic length less than 100 nm) such as
nanowires, ultra-small junctions, etc. Since nanostructures are less stable, their characteristic
volume is much smaller compared to defect sizes and their characteristic length is close to
acoustical phonon wavelength. Moreover, because nanostructures include significantly fewer
charge carriers than microscale structures, electronic noise in nanostructures is enhanced
compared to microscale structures. Additionally, in microprocessors, due to the small gate
capacitance and reduced noise margin (due to reduced supply voltage to keep the electrical field
at a reasonable level), the electronic noise results in bit errors. On the other hand, the enhanced
noise is useful for advanced sensing applications which are called fluctuation-enhanced sensing.
In this dissertation, we first survey our earlier results about the limitation of noise posed on
specific nano processors. Here, single electron logic is considered for voltage controlled logic
with thermal excitations and generic shot noise is considered for current-controlled logic.
Secondly, we discuss our recent results on the electronic noise in nanoscale sensors for SEnsing
of Phage-Triggered Ion Cascade (SEPTIC, for instant bacterial detection) and for silicon
nanowires for viral sensing. In the sensing of the phage-triggered ion cascade sensor,
bacteriophage-infected bacteria release potassium ions and move randomly at the same time;
therefore, electronic noise (i.e., stochastic signals) are generated. As an advanced model, the
electrophoretic effect in the SEPTIC sensor is discussed. In the viral sensor, since the
combination of the analyte and a specific receptor located at the surface of the silicon nanowire
occurs randomly in space and time, a stochastic signal is obtained. A mathematical model for a
pH silicon nanowire nanosensor is developed and the size quantization effect in the nanosensor
is also discussed. The calculation results are in excellent agreement with the experimental results
in the literature.
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Využití chemirezistorů pro zlepšené snímání látek při analýze dechu / Usage of electric noise in chemiresistors for improved sensing of substances for breath analysisKřivský, Josef January 2019 (has links)
The master's thesis deals with the question of breath analysis using chemiresistors as detection elements for exhaled air analysis. Emphasis is placed on the application of fluctuation-enhanced sensing for chemiresistors for breath analysis, construction design of usable measurement system, and its calibration. Compared to the usual concept, which includes various methods ranging from DC processing in time to controlled impedance measurement, this method of signal analysis focuses on the evaluation of fluctuations and determination of indicators of its change in dependence of change in detected substance concentration.
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