scholarly journals Utilization of a Gas-Sensing System to Discriminate Smell and to Monitor Fermentation during the Manufacture of Oolong Tea Leaves

Micromachines ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 93
Author(s):  
Ting-Shiang Tseng ◽  
Mei-Hui Hsiao ◽  
Po-An Chen ◽  
Shu-Yen Lin ◽  
Shih-Wen Chiu ◽  
...  
Keyword(s):  
Gas Sensing ◽  
Critical Factor ◽  
Current Method ◽  
Sensory Function ◽  
Oxide Semiconductor ◽  
Tea Leaves ◽  
Linear Discriminant ◽  
Oolong Tea ◽  
Olfactory Sense ◽  
On Line

The operational duration of shaking tea leaves is a critical factor in the manufacture of oolong tea; this duration influences the formation of its flavor and fragrance. The current method to control the duration of fermentation relies on the olfactory sense of tea masters; they monitor the entire process through their olfactory sense, and their experience decides the duration of shaking and setting. Because of this human factor and olfactory fatigue, it is difficult to define an optimum duration of shaking and setting; an inappropriate duration of shaking and setting deteriorates the quality of the tea. In this study, we used metal-oxide-semiconductor gas sensors to establish an electronic nose (E-nose) system and tested its feasibility. This research was divided into two experiments: distinguishing samples at various stages and an on-line experiment. The samples of tea leaves at various stages exhibited large differences in the level of grassy smell. From the experience of practitioners and from previous research, the samples could be categorized into three groups: before the first shaking (BS1), before the shaking group, and after the shaking group. We input the experimental results into a linear discriminant analysis to decrease the dimensions and to classify the samples into various groups. The results show that the smell can also be categorized into three groups. After distinguishing the samples with large differences, we conducted an on-line experiment in a tea factory and tried to monitor the smell variation during the manufacturing process. The results from the E-nose were similar to those of the sense of practitioners, which means that an E-nose has the possibility to replace the sensory function of practitioners in the future.

scholarly journals Ripeness Prediction of Postharvest Kiwifruit Using a MOS E-Nose Combined with Chemometrics

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 419 ◽  
Author(s):  
Dongdong Du ◽  
Jun Wang ◽  
Bo Wang ◽  
Luyi Zhu ◽  
Xuezhen Hong
Keyword(s):  
Prediction Models ◽  
Extraction Methods ◽  
Oxide Semiconductor ◽  
Soluble Solids ◽  
Support Vector ◽  
Least Squares Regression ◽  
Accuracy Rate ◽  
Linear Discriminant ◽  
The Difference ◽  
Ripe Stage

Postharvest kiwifruit continues to ripen for a period until it reaches the optimal “eating ripe” stage. Without damaging the fruit, it is very difficult to identify the ripeness of postharvest kiwifruit by conventional means. In this study, an electronic nose (E-nose) with 10 metal oxide semiconductor (MOS) gas sensors was used to predict the ripeness of postharvest kiwifruit. Three different feature extraction methods (the max/min values, the difference values and the 70th s values) were employed to discriminate kiwifruit at different ripening times by linear discriminant analysis (LDA), and results showed that the 70th s values method had the best performance in discriminating kiwifruit at different ripening stages, obtaining a 100% original accuracy rate and a 99.4% cross-validation accuracy rate. Partial least squares regression (PLSR), support vector machine (SVM) and random forest (RF) were employed to build prediction models for overall ripeness, soluble solids content (SSC) and firmness. The regression results showed that the RF algorithm had the best performance in predicting the ripeness indexes of postharvest kiwifruit compared with PLSR and SVM, which illustrated that the E-nose data had high correlations with overall ripeness (training: R2 = 0.9928; testing: R2 = 0.9928), SSC (training: R2 = 0.9749; testing: R2 = 0.9143) and firmness (training: R2 = 0.9814; testing: R2 = 0.9290). This study demonstrated that E-nose could be a comprehensive approach to predict the ripeness of postharvest kiwifruit through aroma volatiles.

Microstructure and Gas Sensing Property of Porous SnO2 Sputtered Films

2007 ◽  
Vol 539-543 ◽  
pp. 3508-3513 ◽  
Author(s):  
Toshinari Yamazaki ◽  
Cheng Ji Jin ◽  
Yan Bai Shen ◽  
Toshio Kikuta ◽  
Noriyuki Nakatani
Keyword(s):  
Surface Area ◽  
Gas Sensing ◽  
Columnar Structure ◽  
Oxide Semiconductor ◽  
Bet Surface Area ◽  
Semiconductor Film ◽  
Effective Surface Area ◽  
Effective Surface ◽  
Discharge Gas ◽  
Film Porosity

It is often said that the sensitivity of a gas sensor made of an oxide semiconductor film is enhanced by making the film porous. However, the porosity of sensor films has not been sufficiently examined. In this study, SnO2 films were deposited using DC magnetron sputtering under various substrate temperatures and discharge gas pressures. In addition to the structural analysis by means of X-ray diffraction and scanning electron microscopy, the density and the BET surface area were measured to clarify the film porosity. The sensitivity to H2 gas of undoped and Pd-doped SnO2 films upon exposure to 1000 ppm H2 was measured at 300 . SnO2 films generally showed a columnar structure. The film deposited at a low temperature and a high pressure showed a low density and a large effective surface area. The H2 sensitivity increased as the density decreased, that is, as the effective surface area increased.

scholarly journals Silver Enhances Hematite Nanoparticles Based Ethanol Sensor Response and Selectivity at Room Temperature

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 440
Author(s):  
Daniel Garcia-Osorio ◽  
Pilar Hidalgo-Falla ◽  
Henrique E. M. Peres ◽  
Josue M. Gonçalves ◽  
Koiti Araki ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Gas Sensors ◽  
Room Temperature ◽  
Gas Sensing ◽  
Ethanol Vapor ◽  
Oxide Semiconductor ◽  
Charge Carrier Density ◽  
Ethanol Sensor ◽  
Volatile Organic

Gas sensors are fundamental for continuous online monitoring of volatile organic compounds. Gas sensors based on semiconductor materials have demonstrated to be highly competitive, but are generally made of expensive materials and operate at high temperatures, which are drawbacks of these technologies. Herein is described a novel ethanol sensor for room temperature (25 °C) measurements based on hematite (α‑Fe2O3)/silver nanoparticles. The AgNPs were shown to increase the oxide semiconductor charge carrier density, but especially to enhance the ethanol adsorption rate boosting the selectivity and sensitivity, thus allowing quantification of ethanol vapor in 2–35 mg L−1 range with an excellent linear relationship. In addition, the α-Fe2O3/Ag 3.0 wt% nanocomposite is cheap, and easy to make and process, imparting high perspectives for real applications in breath analyzers and/or sensors in food and beverage industries. This work contributes to the advance of gas sensing at ambient temperature as a competitive alternative for quantification of conventional volatile organic compounds.

Proteomic analysis of “Oriental Beauty” oolong tea leaves with different degrees of leafhopper infestation

2020 ◽  
Vol 34 (15) ◽  
Author(s):  
Han‐Ju Chien ◽  
Man‐Miao Yang ◽  
Wei‐Chen Wang ◽  
Xiang‐Gui Hong ◽  
Yi‐Feng Zheng ◽  
...  
Keyword(s):  
Proteomic Analysis ◽  
Tea Leaves ◽  
Oolong Tea

scholarly journals Extremely high-gain source-gated transistors

2019 ◽  
Vol 116 (11) ◽  
pp. 4843-4848 ◽  
Author(s):  
Jiawei Zhang ◽  
Joshua Wilson ◽  
Gregory Auton ◽  
Yiming Wang ◽  
Mingsheng Xu ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Indium Tin Oxide ◽  
High Performance ◽  
Critical Factor ◽  
High Gain ◽  
Oxide Semiconductor ◽  
Design Rule ◽  
Short Channel ◽  
Channel Effects ◽  
Channel Lengths

Despite being a fundamental electronic component for over 70 years, it is still possible to develop different transistor designs, including the addition of a diode-like Schottky source electrode to thin-film transistors. The discovery of a dependence of the source barrier height on the semiconductor thickness and derivation of an analytical theory allow us to propose a design rule to achieve extremely high voltage gain, one of the most important figures of merit for a transistor. Using an oxide semiconductor, an intrinsic gain of 29,000 was obtained, which is orders of magnitude higher than a conventional Si transistor. These same devices demonstrate almost total immunity to negative bias illumination temperature stress, the foremost bottleneck to using oxide semiconductors in major applications, such as display drivers. Furthermore, devices fabricated with channel lengths down to 360 nm display no obvious short-channel effects, another critical factor for high-density integrated circuits and display applications. Finally, although the channel material of conventional transistors must be a semiconductor, by demonstrating a high-performance transistor with a semimetal-like indium tin oxide channel, the range and versatility of materials have been significantly broadened.

Recent advances and perspectives on constructing metal oxide semiconductor gas sensing materials for efficient formaldehyde detection

2020 ◽  
Vol 8 (38) ◽  
pp. 13169-13188
Author(s):  
Zejun Han ◽  
Yuan Qi ◽  
Zhengyi Yang ◽  
Hecheng Han ◽  
Yanyan Jiang ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Gas Sensing ◽  
Metal Oxide Semiconductor ◽  
Detection Performance ◽  
Metal Oxide Semiconductors ◽  
Oxide Semiconductor ◽  
Oxide Semiconductors ◽  
Effective Strategies ◽  
Recent Advances

The sensing mechanisms and effective strategies for enhancing the formaldehyde detection performance of metal oxide semiconductors have been reviewed.

scholarly journals Discriminable Sensing Response Behavior to Homogeneous Gases Based on n-ZnO/p-NiO Composites

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 785 ◽  
Author(s):  
Wen-Dong Zhou ◽  
Davoud Dastan ◽  
Jing Li ◽  
Xi-Tao Yin ◽  
Qi Wang
Keyword(s):  
Gas Sensors ◽  
Gas Sensing ◽  
Sol Gel ◽  
High Sensitivity ◽  
Oxide Semiconductor ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
P Type ◽  
Type Response ◽  
Properties Of Composites

Metal oxide semiconductor (MOS) gas sensors have the advantages of high sensitivity, short response-recovery time and long-term stability. However, the shortcoming of poor discriminability of homogeneous gases limits their applications in gas sensors. It is well-known that the MOS materials have similar gas sensing responses to homogeneous gases such as CO and H2, so it is difficult for these gas sensors to distinguish the two gases. In this paper, simple sol–gel method was employed to obtain the ZnO–xNiO composites. Gas sensing performance results illustrated that the gas sensing properties of composites with x > 0.425 showed a p-type response to both CO and H2, while the gas sensing properties of composites with x < 0.425 showed an n-type response to both CO and H2. However, it was interesting that ZnO–0.425NiO showed a p-type response to CO but an discriminable response (n-type) to H2, which indicated that modulating the p-type or n-type semiconductor concentration in p-n composites could be an effective method with which to improve the discriminability of this type of gas sensor regarding CO and H2. The phenomenon of the special gas sensing behavior of ZnO–0.425NiO was explained based on the experimental observations and a range of characterization techniques, including XRD, HRTEM and XPS, in detail.

scholarly journals Applications of a Strong Track Filter and LDA for On-Line Identification of a Switched Reluctance Machine Stator Inter-Turn Shorted-Circuit Fault

Energies ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 134 ◽  
Author(s):  
Li Xiao ◽  
Hexu Sun ◽  
Liyi Zhang ◽  
Feng Niu ◽  
Lu Yu ◽  
...  
Keyword(s):  
Switched Reluctance Machine ◽  
Switched Reluctance ◽  
Linear Discriminant ◽  
Reluctance Machine ◽  
Before And After ◽  
Diagnosis Method ◽  
On Line ◽  
Unbalanced Status ◽  
Machine Drives ◽  
Track Filter

Reliability is pivotal significance for switched reluctance machine drives (SRD) applied to safety essential transportation and industrial fields. An inter-turn shorted-circuit fault (ISCF) could incite the machine to operate in unbalanced status, resulting in the noise increases. In the event such a fault remains untreated, the fault will further destroy the rest of the normal phases, even leading to a tragic incident for the entire drive application. To improve the reliability of SRD, an efficient on-line fault diagnosis method for ISCF should be proposed. This paper is focused on employing the strong track filter (STF) to achieve real-time phase resistance differences between before and after ISCF, which are used as features to diagnose the fault occurrence and the fault phase. Furthermore, a classification namely as linear discriminant analysis (LDA) is selected to estimate fault severity. Finally, simulation and experiments correspond to various running statuses are executed and their results can verify that the diagnosis method has accuracy and robustness.

scholarly journals A Suppression Method of Concentration Background Noise by Transductive Transfer Learning for a Metal Oxide Semiconductor-Based Electronic Nose

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1913
Author(s):  
Huixiang Liu ◽  
Qing Li ◽  
Zhiyong Li ◽  
Yu Gu
Keyword(s):  
Transfer Learning ◽  
Environmental Changes ◽  
Oxide Semiconductor ◽  
Target Domain ◽  
Fisher Linear Discriminant ◽  
Linear Discriminant ◽  
Signal Features ◽  
Changes Over Time ◽  
Independence Criterion ◽  
Better Than

Signal drift caused by sensors or environmental changes, which can be regarded as data distribution changes over time, is related to transductive transfer learning, and the data in the target domain is not labeled. We propose a method that learns a subspace with maximum independence of the concentration features (MICF) according to the Hilbert-Schmidt Independence Criterion (HSIC), which reduces the inter-concentration discrepancy of distributions. Then, we use Iterative Fisher Linear Discriminant (IFLD) to extract the signal features by reducing the divergence within classes and increasing the divergence among classes, which helps to prevent inconsistent ratios of different types of samples among the domains. The effectiveness of MICF and IFLD was verified by three sets of experiments using sensors in real world conditions, along with experiments conducted in the authors’ laboratory. The proposed method achieved an accuracy of 76.17%, which was better than any of the existing methods that publish their data on a publicly available dataset (the Gas Sensor Drift Dataset). It was found that the MICF-IFLD was simple and effective, reduced interferences, and deftly managed tasks of transfer classification.

scholarly journals Synthesis of g-C3N4-Decorated ZnO Porous Hollow Microspheres for Room-Temperature Detection of CH4 under UV-Light Illumination

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1507 ◽  
Author(s):  
Min Xiao ◽  
Yanwei Li ◽  
Bo Zhang ◽  
Guang Sun ◽  
Zhanying Zhang
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Uv Light ◽  
Response Speed ◽  
Hollow Microspheres ◽  
Oxide Semiconductor ◽  
Light Illumination ◽  
Long Term Stability ◽  
Temperature Detection ◽  
Good Repeatability

UV light-assisted gas sensors based on metal oxide semiconductor (MOS) have attracted much attention in detecting flammable and explosive gases at room temperature. In this paper, graphite-based carbon nitride (g-C3N4) nanosheets-decorated ZnO porous hollow microspheres (PHMSs) with the size about 3~5 μm in diameter were successfully synthesized by annealing the solvothermally-synthesized Zn5(CO3)2(OH)6 PHMSs together with g-C3N4. The synthesized samples were characterized by XRD, SEM, TEM, FT-IR and XPS. The results indicated that the prepared g-C3N4/ZnO PHMSs were constructed by numerous loosely stacked ZnO nanoparticles of 20~30 nm in diameter. Gas sensing tests indicated that under UV light (365~385 nm) illumination, the sensors fabricated with g-C3N4/ZnO HPMSs showed an enhanced response and faster response speed than the pure ZnO counterpart at room temperature. In addition, the g-C3N4/ZnO sensor also exhibited good repeatability and long-term stability for CH4 detection.

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