To set up a rapid real-time nondestructive detection of moisture content, this paper reported the results of a combination of LF-NMR and BP-ANN to monitor the relationship between drying parameters ...and state of water under different microwave vacuum drying conditions. Three kinds of materials, carrot (fruit), banana (vegetable) and pleurotus eryngii (edible fungus), were tested in the experiment of applicability. The resulted showed that the information of Atotal and T23 can be used to analyze the drying behavior and the information of A20, A21 and A22 can be used as the fingerprint characteristics of material discrimination. Three classic models (PLS, SVM and BP-ANN) were compared to study the prediction ability of moisture content with the inputs of A20, A21, A22, A23 and Atotal. The performance of BP-ANN model was the best. Although the BP-ANN model of mixed species was not as good as the BP-ANN model of single fruit or vegetable, it still had excellent predictive performances with R2 0.9969 and RMSE 0.0184 to meet the needs of current industry and production.
•A rapid real-time nondestructive detection method of combination of LF-NMR and BP-ANN was set up.•The information of Atotal and T23 can be used to analyze the drying behavior.•The information of A20, A21 and A22 can be used as the fingerprint characteristics of material discrimination.•The BP-ANN model of mixed species had excellent predictive performances with R2 0.9969 and RMSE 0.0184.
The feasibility of low-field nuclear magnetic resonance (LF-NMR) was investigated to predict the dielectric properties of Chinese yam slices. Changes in relaxation behaviors and dielectric properties ...(at 915 and 2450 MHz) of samples during microwave vacuum drying as well as their relationship were studied. Results showed that the total moisture content decreases gradually over drying time, and the free water was removed first, followed by the immobile water and bound water. Correspondingly, the dielectric constant (ε′) gradually decreased till to reach a relative and stable low value; while the loss factor (ε″) changed slightly first, then decreased gradually and also reached a low value finally. Univariate linear models showed that the signal intensity of free water peak (A23) and the transverse relaxation time of immobile water (T22) had good correlation with dielectric properties. Furthermore, partial least squares regression (PLSR) models with four NMR parameters as variables gave better results with R2P of 0.946, 0.936, 0.962 and 0.921 for ε′ and ε″ at 915 MHz and ε′ and ε″ at 2450 MHz, respectively. The overall results revealed that LF-NMR is suitable for predicting the dielectric properties as a rapid and noninvasive method.
•Drying caused significant changes in the T2 curves.•Moisture-dependent dielectric properties (DPs) were analyzed.•PCA analysis indicated the relation between NMR parameters and DPs.•PLSR model with 4 NMR parameters showed better prediction accuracy for DPs.
In this paper, intelligent technology of combined low field NMR (LF-NMR) and back propagation artificial neural network (BP-ANN) was used to monitor moisture content in carrot during microwave vacuum ...drying. The relationship between different drying powers (200, 300, and 400 W) and NMR signals (A
21
, A
22
, A
23
, and A
total
) was investigated. Results show that as the drying time elapsed, the NMR signals of A
total
and A
23
decrease all drying conditions, A
21
and A
22
tend to increase at high moisture content and then decrease, which is consistent with the state of water while changes during drying. NMR signals can be used as indicators for online monitoring of moisture and control of the drying process. With NMR signals as input variables, a BP-ANN model was built optimized by transfer function, training function, and the number of neurons to model the moisture content (output). Compared with a linear regression model and multiple linear regression model, the BP-ANN model with the topology of 4-25-1, transfer function of tansig and purelin, and training function of trainlm outperformed the fitting performance and accuracy. This shows that the combined approach of utilizing LF-NMR and BP-ANN has great potential in intelligent online monitoring and control applications for carrot drying.
One of the modern crop breeding techniques uses doubled haploid plants that contain an identical pair of chromosomes in order to accelerate the breeding process. Rapid haploid identification method ...is critical for large-scale selections of double haploids. The conventional methods based on the color of the endosperm and embryo seeds are slow, manual and prone to error. On the other hand, there exists a significant difference between diploid and haploid seeds generated by high oil inducer, which makes it possible to use oil content to identify the haploid. This paper describes a fully-automated high-throughput NMR screening system for maize haploid kernel identification. The system is comprised of a sampler unit to select a single kernel to feed for measurement of NMR and weight, and a kernel sorter to distribute the kernel according to the measurement result. Tests of the system show a consistent accuracy of 94% with an average screening time of 4 seconds per kernel. Field test result is described and the directions for future improvement are discussed.
Low-field nuclear magnetic resonance (LF-NMR) and electronic nose combined with Gas chromatography mass spectrometry (GC–MS) were used to collect the data of moisture state and volatile substances to ...predict the flavor change of ginger during drying. An back propagation artificial neural network (BP-ANN) model was established with the input values of LF-NMR parameters and the output values of sensors for different flavor substances obtained from electronic nose. The results showed that fresh ginger contained three water components: bound water (T21), immobilized water (T22) and free water (T23), with the corresponding peak areas of A21, A22 and A23, respectively. During drying, the changes of A21 and A22 were not significant, while A23 and ATotal decreased significantly (p < .05). Linear discriminant analysis (LDA) of electronic nose data showed that samples with different drying time can be well distinguished. Hierarchical clustering analysis (HCA) confirmed that the electronic nose characteristic sensor data S4, S5, S8 and S13 corresponded with the data measured by GC–MS. The correlation analysis between LF-NMR parameters and characteristic sensors showed that A23 and ATotal were significantly correlated with the volatile components (p < .05). The results of the BP-ANN prediction showed that the model fitted well and had strong approximation ability (R > 0.95 and error < 3.65%) and stability, which indicated that the ANN model can accurately predict the flavor change during ginger drying based on LF-NMR parameters.
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•LF-NMR and electronic nose combined with GC-MS were used to collect the data of moisture state and volatile substances.•LDA and HCA analysis confirmed the e-nose characteristic sensors.•The correlation analysis showed LF-NMR parameters and characteristic sensors were significantly correlated.•The BP-ANN prediction model fitted well and had strong approximation ability and stability.
The severe plastic deformation process induces dynamic recrystallization in the machined surface and the adiabatic shear band during high-speed machining. It is a desirable approach to directly ...improve the machined surface integrity by the ultra-fine grains generated from the finish machining. The grain size modification mechanism depends on the incorporated effects of high strain, strain rate, and temperature in machining. The Zener-Hollomon (Z-H) model has been a popular approach to predicting the dynamic recrystallization behavior in grains in processing. The model combines strain rate and temperature into a single parameter,
Z
, to achieve simplicity in prediction. However, it cannot achieve reliable prediction in high-speed machining involving large strain, high strain rate, and high temperature. Hence, based on the original Z-H model, a modified dynamic recrystallization model is proposed particularly for high-speed machining. In the modified model, the competitive roles of strain rate and temperature are emphasized since extremely high strain rate induced dynamic recrystallization and high temperature promoted dynamic recovery. Additionally, large plastic strain, neglected in the original Z-H model, is treated as a control variable to capture the behavior of grain dynamic recrystallization. Furthermore, an incremental formulation based on the modified dynamic recrystallization model is proposed to accurately explore the evolution of grain size to overcome the unpredictable abrupt changes in grain sizes generated from the original Z-H model. The results demonstrate the effective enhancement of predicted accuracy in terms of the evolution behavior of dynamic recrystallization in high-speed machining of titanium alloy.
Graphical Abstract
•Various frozen storage time of whole buckwheat extruded noodles (WBEN) were prepared.•The structural results of starch and water implied the retrogradation pronounced at first 30 days.•The changes ...in starch-gel networks due to ice growth decided noodles quality in long-term storage.•Overall, frozen storage can chronically maintain the quality of WBEN and inhibit its digestibility.
The effects of frozen storage (-18 °C, 180 days) on the quality of frozen whole buckwheat extruded noodles (FWBEN) were investigated. The water content of FWBEN decreased, while the reheating time, water absorption, and dry consumption rate increased with prolonged storage time. Cooking loss increased from 3.20% to 4.31%. Texture analysis indicated that the hardness initially increased, then decreased. Microstructure results showed that the starch gel structure was damaged to a certain extent after storage for a longer period of time, whereas the porous structure became non-uniform with the appearance of cracks. The relative crystallinity gradually increased, and the freezable water content decreased with prolonged storage. These results demonstrated that FWBEN quality was affected by starch retrogradation and ice recrystallization. In general, FWBEN quality was relatively stable during 180 days of frozen storage at −18 °C.
Water and lipid changes play important roles for the quality formation of salted duck eggs. In the present study, low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) ...were introduced to monitor water and lipid dynamics of duck egg during salting as nondestructive methods. Four proton pools with different mobilities in fresh duck egg matrix were identified by LF-NMR transverse relaxation, and salting significantly changed the proton mobility due to the gelation of egg yolk, release of lipid and watery of egg white. MRI showed high density of proton with lower mobility and higher mobility in egg yolk and white, respectively, and the brighter region of egg yolk in T1 images continuously decreased from vitelline membrane to center. The variations in the relaxation parameters and MRI images have a close relationship with other quality characteristics of duck eggs induced by salt. Therefore, LF-NMR and MRI could provide information about water and lipid dynamics of duck eggs during salting, and have great potential for quality assurance in salted duck eggs as a fast and non-destructive method.
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•Four proton pools in duck egg matrix were identified by LF-NMR transverse relaxation.•Salting changed mobilities of multilayer bound water, lipid and free water.•T1 and T2 weighted images enabled the visualization of water migration during salting.
Shale gas and oil is an increasingly important source of unconventional energy. Shale gas and oil reservoirs differ from their conventional counterparts mainly in the nanoporous structures of the ...former, which play a critical role not only for the resource estimation but also for the shale gas/oil extraction and development. However, the traditional methods for characterizing rock porosities, such as gas sorption (the Brunauer–Emmett–Teller technique, BET), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), cannot satisfactorily and adequately measure and characterize the nanoporous structures. Nuclear magnetic resonance (NMR) spectroscopy is known for its sensitivity to local environments at the atomic level and, therefore, can provide an alternative method for the investigation of nanoporous structures in gas shales. This study has refined the low field NMR cryoporometry (NMRC) method and applied it along with other methods such as NMR relaxometry (NMRR) to measure and characterize the nanoporous structures (i.e., the pore size distribution, PSD) of selected shale samples from the Sinian-Cambrian-Ordovician strata at the Low Yangzi Plateau, China. Our NMRC measurements of a controlled porous glass (CPG) and shale samples show that the organic compound octamethylcyclotetrasiloxane (OMCTS) is a superior NMR probe liquid in terms of improved spectral resolution and signal/noise (S/N) ratio. Comparisons of the NMRC shale PSD results with those from NMRR and gas sorption show that NMRC is an independent and effective method for determining the distribution of nanosized pores in gas shales. Moreover, important parameters such as porosity can also be estimated from the low field NMR cryoporometry.
Freeze-drying (FD) and cryo-milling (CM) are common methods for preparing powder gelatinized starch samples. This study investigates the structural characterization of raw/gelatinized maize starches ...and digestibility after FD/CM processes to elucidate their effect on starch digestibility determination. Results showed that FD slightly increased digestibility, while higher initial glucose content in CM samples, especially for gelatinized samples. Only FD retained the granular morphology and relative crystallinity (RC), while gelatinized-FD decreased RC by 75%. CM decreased RC by 12%, while gelatinized-CM decreased it by 97%. Combined with short-range and chain structural results, FD tended to disrupt internal connected chains through volume stress, while CM cleaved glycosidic bonds in external chain. Stretched chains in gelatinized starch promoted the breakage of chains during shearing and their efficient binding with digestive enzymes. These findings would provide a basis for pre-treatment of powder samples and processes of starch- rich foods.
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•Cryo-milling (CM) increased gelatinized starch digestibility than freeze-drying (FD).•The volume stress of ice crystal formation-sublimation acts on connected chains.•Shear degradation effect of CM caused cleavage of α-1, 6- and 1, 4-glycosidic bonds.•Stretched chain structure rose the susceptibility of starch to followed CM and FD.•It merits pre-treatment of gelatinized starch and development of starchy foods.
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