Overcoming the Limits of Cross-Sensitivity:Pattern Recognition Methods for Chemiresistive Gas Sensor Array

As information acquisition terminals for artificial olfaction,chemiresistive gas sensors are often troubled by their cross-sensitivity,and reducing their cross-response to ambient gases has always been a difficult and important point in the gas sensing area.Pattern recognition based on sensor array is the most conspicuous way to overcome the cross-sensitivity of gas sensors.It is crucial to choose an appropriate pattern recognition method for enhancing data analysis,reducing errors and improving system reliability,obtaining better classification or gas concentration prediction results.In this review,we analyze the sensing mechanism of crosssensitivity for chemiresistive gas sensors.We further examine the types,working principles,characteristics,and applicable gas detection range of pattern recognition algorithms utilized in gas-sensing arrays.Additionally,we report,summarize,and evaluate the outstanding and novel advancements in pattern recognition methods for gas identification.At the same time,this work showcases the recent advancements in utilizing these methods for gas identification,particularly within three crucial domains:ensuring food safety,monitoring the environment,and aiding in medical diagnosis.In conclusion,this study anticipates future research prospects by considering the existing landscape and challenges.It is hoped that this work will make a positive contribution towards mitigating cross-sensitivity in gas-sensitive devices and offer valuable insights for algorithm selection in gas recognition applications.

Cross-sensitivity of Fiber Grating Solved by FFP Triangle Notch Filter

Employing a fiber Fabry-Perot (FFP) interferometer has been considered as a triangle notch filter to demodulate the wavelength of fiber Bragg grating (FBG) sensor.The single parameter of strain has been demodulated,and the cross-sensitivity influence of temperature has been eliminated.The principle of this method is simple and easy to be implemented,and has been used to design a 30 t fiber grating weightbridge successfully.The maximal temperature drift error of the weightbridge is 4 με,which means that the full scale error is 8‰. The result reveals that the accuracy is high enough to be used in measurement.

Research on dynamic characteristics of multi-sensor system in the case of cross-sensitivity

In this study, the dynamic characteristic of a multi-sensor system made up of such sensors as are sensitive to several parameters is discussed, and the effect of cross-sensitivity on the precision of a measurement system is also discussed. A multi-sensor system is looked as a serial of a linear filter and a memoryless nonlinear system, i.e. Wiener system, and the subsequent information fusion system is regarded as a Hammerstein system, i.e. a serial of a memoryless nonlinear system and a linear filter. On the basis of static calibration, it is presented to determine the inverse filter in a Hammerstein system using blind deconvolution. In order to control the uncertainty of amplitude of signals recovered by blind deconvolution well, a regulation approach to regulating the inverse linear filter coefficient matrixes is presented according to the identity between inverse filter coefficient matrixes and static calibrating matrix. So the approximate inverse dynamic model of multi-sensor system is obtained, the degree of distortion of dynamic measurement result is reduced, the measurement precision is improved, and the need of practice can be reached. Simulation example and simulation result show that the recovered error of the inputs of sensor system, the frequency of which is 1/10 of sampling frequency, is 1/20 of the measurement results without dynamic compensation, and is one half of the measurement results with sole dynamic compensation, and the rapidity is improved 2 times. The dynamic compensation results of a metal oxide semiconductor methane sensor show that the dynamic measurement error is less than one half of that without dynamic compensation. So this method expands the bandwidth of multi-sensor system.

Study of Optical Fibers Strain-Temperature Sensitivities Using Hybrid Brillouin-Rayleigh System

In this paper, the most recent progress as well as challenges of distributed optical fiber sensing （DOFS） in industrial applications is discussed. Compared to the vast market of sensors used to measure strain or temperature, the success of distributed optical fiber sensing （DOFS） at the industrial level is very limited, at best. One of the reasons for this lack of the wider acceptance is the mismatch between the commercially available systems and actual industrial requirements, especially for the spatial resolution and precision. These requirements are organized and clarified in the paper. It also describes the hybrid Brillouin-Rayleigh system, which exhibits capabilities surpassing those of strain gauges. The principles of the system are illustrated considering the fiber calibration methodology. Formulas required for determining strain, temperature, and hydro-pressure are derived and discussed. Finally, the examples of applications are presented.

A CuO/TiO_(2)Heterojunction Based CO Sensor with High Response and Selectivity

The use of heterojunctions is a promising solution to the problem of cross-sensitivity in gas sensors.In this work,a carbon monoxide sensor based on the CuO/TiO_(2)heterojunction was designed and fabricated.Due to the good adsorption properties of CuO materials to CO,and the heterojunction interface charge transfer,the CuO/TiO_(2)thin film sensor exhibits high sensitivity to CO at room temperature.The response is as high as 10.8–200 ppm CO,about 10 times its response to H_(2).Interference from H_(2)is greatly reduced by optimizing the structure of the CuO/TiO_(2)heterojunction.This reliable detection of carbon monoxide with excellent discrimination against H_(2)is of great significance for the development of CO gas sensors.

Experimental study on cross-sensitivity of temperature and vibration of embedded fiber Bragg grating sensors

In view of the principle for occurrence of cross-sensitivity, a series of calibration experiments are carried out to solve the cross-sensitivity problem of embedded fiber Bragg gratings(FBGs) using the reference grating method. Moreover, an ultrasonic-vibration-assisted grinding(UVAG) model is established, and finite element analysis(FEA) is carried out under the monitoring environment of embedded temperature measurement system. In addition, the related temperature acquisition tests are set in accordance with requirements of the reference grating method. Finally, comparative analyses of the simulation and experimental results are performed, and it may be concluded that the reference grating method may be utilized to effectively solve the cross-sensitivity of embedded FBGs.

Recognizing frequency characteristics of gas sensor array

A novel method based on independent component analyzing (ICA) in frequency domain to distinguish the frequency characteristics of multi-sensor system is presented. The conditions of this type of ICA are considered and each step of resolving the problem is discussed. For a two gas sensor array, the frequency characteristics including amplitude-frequency and phase-frequency are recognized by this method, and cross-sensitivity between them is also eliminated. From the principle of similarity, the recognition mean square error is no more than 0.085.

A High Spatial Resolution FBG Sensor Array for Measuring Ocean Temperature and Depth

Exploring and understanding the ocean is an important field of scientific study.Acquiring accurate and high-resolution temperature and depth profiles of the oceans over relatively short periods of time is an important basis for understanding ocean currents and other associated physical parameters.Traditional measuring instruments based on piezoelectric ceramics have a low spatial resolution and are not inherently waterproof.Meanwhile,sensing systems based on fiber Bragg grating(FBG)have the advantage of facilitating continuous measurements and allow multi-sensor distributed measurements.Therefore,in this paper,an all-fiber seawater temperature and depth-sensing array is used to obtain seawater temperature and depth profiles.In addition,by studying the encapsulation structure of the FBG sensors,this paper also solves the problem of the measurement error present in traditional FBG sensors when measuring seawater temperature.Through a theoretical analysis and seaborne test in the Yellow Sea of China,the sampling frequency of the all-fiber seawater temperature and depth profile measurement system is 1 Hz,the accuracy of the FBG sensors reaches 0.01℃,and the accuracy of the FBG depth sensors reaches 0.1%of the full scale.The resulting parameters for these sensors are therefore considered to be acceptable for most survey requirements in physical oceanography.

Neurotrophin signaling and visceral hypersensitivity

Neurotrophin family are traditionally recognized for their nerve growth promoting function and are recently identified as crucial factors in regulating neuronal activity in the central and peripheral nervous systems. The family members including nerve growth factor （NGF）, brain-derived neurotrophic factor （BDNF）, and neurotrophin-3 （NT-3） are reported to have distinct roles in the development and maintenance of sensory phenotypes in normal states and in the modulation of sensory activity in disease. This paper highlights receptor tyrosine kinase （Trk） -mediated signal transduction by which neurotrophins regulate neuronal activity in the visceral sensory reflex pathways with emphasis on the distinct roles of NGF and BDNF signaling in physiologic and pathophysiological processes. Viscero-visceral cross-organ sensitization exists widely in human diseases. The role of neurotrophins in mediating neural cross talk and interaction in primary afferent neurons in the dorsal root ganglia （DRG） and neurotrophin signal transduction in the context of cross-organ sensitization are also discussed.

A Micro S-Shaped Optical Fiber Temperature Sensor Based on Dislocation Fiber Splice

We fabricated a simple, compact, and stable temperature sensor based on an S-shaped dislocated optical fiber. The dislocation optical fiber has two splice points, and we obtained the optimal parameters based on the theory and our experiment, such as the dislocation amount and length of the dislocation optical fiber. According to the relationship between the temperature and the peak wavelength shift, the temperature of the environment can be obtained. Then, we made this fiber a micro bending as S-shape between the two dislocation points, and the S-shaped micro bending part could release stress with the change in temperature and reduce the effect of stress on the temperature measurement. This structure could solve the problem of sensor distortion caused by the cross response of temperature and stress. We measured the S-shaped dislocation fiber sensor and the dislocation fiber without S-shape under the same environment and conditions, and the S-shaped dislocation fiber had the advantages of the stable reliability and good linearity.