| 1. |
- Davide, F., et al.
(författare)
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Chaotic chemical sensing
- 2002
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 2:6, s. 656-662
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we have examined the behavior of a chaotic circuit where one of the components has been replaced by a chemical sensor. The response of the sensor is manifested as a change in the attractor of the circuit. Furthermore, with a proper operating point, a small response of the sensor causes a change in the attractor of the circuit within a time much shorter than the normally defined response time of the sensor. This technique unites sensors and data processing as one combined unit in a unique fashion. © 2002 IEEE.
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| 2. |
- Lindgren, David, et al.
(författare)
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A Novel Feature Extraction Algorithm for Asymmetric Classification
- 2004
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Ingår i: IEEE Sensors Journal. - : IEEE Sensors Council. - 1530-437X .- 1558-1748. ; 4, s. 643-650
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Tidskriftsartikel (refereegranskat)abstract
- A linear feature extraction technique for asymmetric distributions is introduced, the asymmetric class projection (ACP). By emph {asymmetric classification} is understood discrimination among distributions with different covariance matrices. Two distributions with unequal covariance matrices do not in general have a symmetry plane, a fact that makes the analysis more difficult compared to the symmetric case. The ACP is similar to linear discriminant analysis (LDA) in the respect that both aim at extracting discriminating features (linear combinations or projections) from many variables. However, the drawback of the well known LDA is the assumption of symmetric classes with separated centroids. The ACP, incontrast, works on (two) possibly concentric distributions with unequal covariance matrices. The ACP is tested on data from anarray of semiconductor gas sensors with the purpose of distinguish bad grain from good.
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| 3. |
- Nakagomi, S., et al.
(författare)
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Electrical characterization of carbon monoxide sensitive high temperature sensor diode based on catalytic metal gate - Insulator - Silicon carbide structure
- 2002
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 2:5, s. 379-385
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Tidskriftsartikel (refereegranskat)abstract
- Field-effect gas sensors based on catalytic metal-insulator-silicon carbide (MISiC) devices are investigated. For the evaluation of the barrier height, the temperature dependence of the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of MISiC Schottky diodes were investigated in CO and O2 atmospheres. Four methods were used to evaluate how a change in gas ambient influences the barrier height of the diode: a change of the intersection current at zero voltage in the forward direction of the I-V curve, a change of the temperature dependence in the forward direction and the reverse direction, respectively, of the I-V curve, and a change of the intersection voltage of 1/C2 versus V plot. The four methods gave similar changes in the barrier height for the device in 8000 ppm CO and 4000 ppm O2. The values of barrier height obtained from the I-V curves were here normalized by the ideality factor calculated from I-V measurements. The correlation between the barrier height change obtained from the I-V and the C-V measurements, respectively, is discussed regarding the ideality factor. It is proposed that absolute value of the barrier height under flat-band condition is the most important for the evaluation of the barrier height. In the mixture of CO and O2, the change of barrier height obtained from the C-V curve had roughly the same values as that from the I-V curve when normalized by the ideality factors. © 2002 IEEE.
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| 4. |
- Wang, Guoliang, et al.
(författare)
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An optical gas sensor based on ellipsometric readout
- 2003
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Ingår i: IEEE Sensors Journal. - IEEE. - 1530-437X .- 1558-1748. ; 3:6, s. 739-743
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Tidskriftsartikel (refereegranskat)abstract
- A gas sensor system based on ellipsometric readout is presented. It includes a gas chamber and a compact null ellipsometer operated in off-null mode. Small, low-cost optical components are used to demonstrate that this advanced methodology can be implemented in simplified instrumentation. The off-null ellipsometric sensing principle and transducer mechanisms of the sensing layers, as well as the instrumentation, are described. The application of the sensor system is exampled with experimental results on low-concentration alcoholic gases (methanol, ethanol, and 2-propanol) using porous silicon as a sensing layer. Optimization of the optics of the sensor system, improvement of sensitivity or alteration of selectivity by modification of sensing layers, and multisensing by using several ellipsometric units in parallel are discussed.
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