Carbon nanotube (CNT), poly(ethylene-co-methacrylic acid) (EMAA) and epoxy (EP) are used to prepare a hierarchical interleaf, consisting of CNT/EP/EMAAs sandwich structure with periodic EP column ...arrays, which can act as crack self-healing interface within carbon fiber reinforced plastic (CFRP) by in-situ electrical-heating the CNTs. Results show that the introduced CNT/EP/EMAAs interleaf has little effect on the free-edge delamination initiation stress (<±3.2%) and the in-plane strength (<±1.2%) of the baseline CFRP. But, the interleaved CFRP shows high self-healing efficiencies of 99.1–111.3% to the delamination initiation stress and 97.9–99.4% to the elastic modulus, respectively, from two delamination initiation-healing circles activated by electrical-heating the embedded CNTs, as well as with a maintenance of 92.6–99.7% to the tensile ultimate strength. This study reveals that the CNT/EP/EMAAs interleaf and the electrical-heating activated self-healing method are promising to effectively restore the initial damage of CFRP without decreasing the in-plane strength, unlike the traditional pure EMAA interleaf.
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•A self-healable hierarchical interleaf, sandwich CNT/EP/EMAAs with periodic epoxy column arrays, is developed.•The self-healable interleaf shows a little effect on the tensile properties of CFRP.•The interleaved CFRP can be healed by in-situ electrical-heating.•The interleaved CFRP shows high self-healing efficiency of 99.1–111.3% to free-edge delamination initiation stress.
To date, it is still a challenge to simultaneously reinforce and well monitor the delamination of carbon fiber reinforced plastics (CFRPs) using nanocarbon-based interleaf due to the high electrical ...conductivity of CFRPs. Herein, this work prepares a novel woven grid composed of carbon nanotubes and graphenes (CG) with various grid densities and suitable resistivity. Results reveal that the CG woven grid-based interleaf could significantly reinforce the interlaminar shear properties of CFRPs, i.e. mode II interlaminar fracture toughness and interlaminar shear strength can be improved by 38–60% and 17–25%, respectively. Meanwhile, the relative resistance change (ΔR/R0%) of CFRPs at the delamination initiation stage can reach ~12% or more, which is greater than that reported by previous literatures. The results suggest that the prepared CG woven grid can not only greatly enhance the delamination resistance, but also can sensitively monitor the delamination of the highly conductive CFRPs.
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•Prepared a novel Carbon nanotube/Graphene woven grid.•Improved mode II interlaminar fracture toughness by 38–60% and interlaminar shear strength by 17–25%.•High resistance variation response to delamination initiation (12% or more).
•A chamber experiment was designed to verify the effect of personal control.•Perceived control capability alleviated occupants’ discomfort complaints.•Personal control approaches had both ...psychological and physical impacts.•Occupants should be offered opportunities to interact with thermal environment.
In this paper we explore the influence of personal control over space conditioning systems on occupants’ thermal comfort perception. It aims to identify the psychological effects of perceived control as well as the physical impacts when the controllable approaches are utilized. A chamber experiment was conducted, the results from which indicate that subjects with perceived control tended to report more positive comfort perception. The severer the thermal conditions were, the more subjects wanted to use personal control approaches, thus corresponding to stronger psychological effects. When personal control approaches were utilized appropriately, even a slight improvement in thermal conditions could significantly alleviate subjects’ thermal discomfort complaints. These findings provide support to the adaptive comfort theory and can serve as reference for the design of personal environmental control systems.
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•A carbon nanotube/graphene grid structure is proposed to be used as damage sensor.•Improved tensile strength by 27–41% and tensile-shear-strength by 28–49%•Improved ΔR/R0 of 10% for ...tension and 6% for tensile-shearing at damage initiation.
A new carbon nanotube (CNT)/graphene (GN) grid structure is prepared and used to reinforce and health-monitor the epoxy composites. Results reveal that with a 30–50% mesoscopic-porosity of the CNT/GN grid, tensile strength and single-lap-shear (SLS) strength of the CNT/GN/epoxy composites can be improved by 27–41% and 28–49%, respectively. Also, relative resistance change (ΔR/R0%) at damage initiation would sudden change more than 10% for the tensile testing and 6% for the SLS testing. Meanwhile, during the damage evolution stage, the gauge factor obtained from tensile testing reaches 10.2–24.9 improved by 23–200%, and ΔR/R0% from SLS testing achieves 47.4–60.4% increased by 69–116%, respectively, when compared to the baseline composite. Moreover, an equivalent resistance prediction mode for the CNT/GN grid composites is proposed and which can well explain the resistance response mechanism. The result reveals that the gridded CNT/GN sensor is potential in reinforcing and structural health monitoring the epoxy resin-based composites.
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•A SERS sensor was constructed to identify multiple foodborne pathogens.•Au@Ag NPs/ filter paper was used as a SERS active substrate.•SERS combined with PLS-DA can correctly classify ...various bacteria species.•S. aureus, E. coli, and L. monocytogenes were discriminated.
In this study, a surface enhanced Raman scattering (SERS) sensor based on Au@Ag NPs solid-phase substrate combined with chemometrics was constructed for the discrimination of three pathogenic bacteria (Staphylococcus aureus, Escherichia coli and Listeria monocytogenes). The Au@Ag NPs were synthesized and self-assembled on filter paper using the dip-coating method. The good absorbency of the filter paper immobilized the bacteria on the substrate, increased the interaction between the bacteria and the substrate, and enhanced the SERS signal of the bacteria. The main peaks of the bacterial spectra were close to each other, but the relative intensities of the vibrational peaks were significantly different, and each strain exhibited unique Raman peaks. The combination of partial least squared discriminant analysis (PLS-DA) method with bacterial SERS allowed the effective identification of the three bacteria. Moreover, the method was applied for the quantitative detection of Staphylococcus aureus with a minimum detection concentration of 104 cfu/mL.
Radiant heating systems are increasingly widely utilized in buildings for its energy conservation potential and enhanced thermal comfort. This paper presented an experiment to compare the thermal ...comfort performance of radiant heating system with convective heating system through objective measurement and subjective survey. Six physical parameters which might influence occupants’ thermal satisfaction, including the Mean Radiant Temperature (MRT), humidity, air movement, A-weighted sound level, temperature fluctuation and vertical temperature difference, were measured. In addition, 97 subjects participated in the subjective survey part of this experiment, experiencing all the three environments heated by air source heat pump, radiator and floor heating. And they were asked to vote in six thermal comfort related aspects, i.e. thermal sensation, humidity, draught, local discomfort, overall thermal satisfaction and overall preferences, plus the acoustic environment, since the operation noise of heating system might lead to complains of the occupants. It was found that in continuous heating, no significant difference between radiant and convective heating system was observed in the Mean Radiant Temperature (MRT), indoor humidity and noise issue. Though radiant heating systems resulted in lower draught risk and less local discomfort complains in the feet region due to the less significant temperature fluctuations and vertical temperature gradients, radiant heating did not have significantly higher overall thermal satisfaction votes and was not significantly more preferred by occupants.
•Thermal comfort of air source heat pump, radiator and floor heating, were compared.•Six physical parameters which influence occupants’ thermal comfort were measured.•97 subjects voted in seven thermal comfort related aspects.•Convective heating terminals result in higher draught and local discomfort risks.•Radiant heating terminals doesn’t have significantly higher thermal comfort votes.
Foodborne pathogens have become ongoing threats in the food industry, whereas their rapid detection and classification at an early stage are still challenging. To address early and rapid detection, ...hyperspectral microscope imaging (HMI) technology combined with convolutional neural networks (CNN) was proposed to classify foodborne bacterial species at the cellular level. HMI technology can simultaneously obtain both spatial and spectral information of different live bacterial cells, while two CNN frameworks, U-Net and one-dimensional CNN (1D-CNN), were employed to accelerate the data analysis process. U-Net was used for automating cellular regions of interest (ROI) segmentation, which generated accurate cell-ROI masks in a shorter timeframe than the conventional Otsu or Watershed methods. The 1D-CNN was employed for classifying the spectral profiles extracted from cell-ROI and resulted in a higher accuracy (90%) than
k
-nearest neighbor (81%) and support vector machine (81%). Overall, the CNN-assisted HMI technology showed potential for foodborne bacteria detection.
•Nonlinear correlation between thiabendazole (TBZ) and SERS data was diagnosed.•ACO-ELM, UVE-ELM and CARS-ELM were comparatively investigated for TBZ detection.•CARS-ELM model achieved optimum ...results when principal component was 7.•The recoveries of TBZ in spiked apple were ranged from 83.02 to 93.54%.•A robust SERS-based method for TBZ was developed with a LOD of 0.001 mg/L.
Thiabendazole (TBZ) is extensively used in agriculture to control molds; residue of TBZ may pose a threat to humans. Herein, surface-enhanced Raman spectroscopy (SERS) coupled variable selected regression methods have been proposed as simple and rapid TBZ quantification technique. The nonlinear correlation between the TBZ and SERS data was first diagnosed by augmented partial residual plots method and calculated by runs test. Au@Ag NPs with strong enhancement factor (EF = 4.07 × 106) of Raman signal was used as SERS active material to collect spectra from TBZ. Subsequently, three nonlinear regression models were comparatively investigated and the competitive adaptive reweighted sampling-extreme learning machine (CARS-ELM) achieved a higher correlation coefficient (Rp2 = 0.9406) and the lower root-mean-square-error of prediction (RMSEP = 0.5233 mg/L). Finally, recoveries of TBZ in apple samples were 83.02–93.54% with relative standard deviation (RSD) value < 10%. Therefore, SERS coupled CARS-ELM could be employed as a rapid and sensitive approach for TBZ detection in Fuji apples.
Near-infrared (NIR) spectroscopy as an emerging analytical technique was used for the first time to quantitatively detect the watercore degree and soluble solids content (SSC) in apple. To reduce the ...data processing time and meet the needs of practical application, the variable selection methods including synergy interval (SI), successive projections algorithm (SPA), genetic algorithm (GA) and competitive adaptive reweighted sampling (CARS) were used to identify the characteristic variables and simplify the models. The spectral variables closely related to the apple bioactive components were used for the establishment of the partial least squares (PLS) models. The predictive correlation coefficient (Rp), root mean square error of prediction (RMSEP), and residual predictive deviation (RPD) were used to estimate the performance of the models. The CARS-PLS models displayed the best prediction performance using 600–1000 nm spectra with Rp, RMSEP, and RPD values of 0.9562, 1.340% and 3.720 for apple watercore degree; 0.9808, 0.327 oBx and 4.845 for apple SSC, respectively. These results demonstrate the potential of the NIR transmittance spectroscopy technology for quantitative detection of SSC and watercore degree in apple fruit.
•Novel NIR transmittance spectroscopy quantitatively detected the degree of watercore in apple.•The characteristic spectral variables of apple watercore disease detection were studied.•Multiple variables selection simplified and improved the performance of models.•NIR spectroscopy is advantageous as the fast, non-destructive measurements.
In light of growing concerns about productivity, much more attention has focused on the indoor environment in offices in recent years. Standards typically address different environmental factors such ...as thermal comfort, indoor air quality, and aural and visual environments separately. In fact, these environmental factors have notable combined effects on occupants' acceptability and work performance. ASHRAE Guideline 10P emphasized the interactions among indoor environmental factors and recommended that more detailed research is conducted. In this study, a controlled field survey was carried out to investigate the acceptable range of every individual environmental factor as well as the cumulative effects of multiple factors on indoor environmental quality. In the survey, the parameters of thermal, luminous, and acoustic environments were measured and subjects' satisfaction levels with regard to the indoor environment were determined using questionnaires. The results show that the satisfaction levels of both temperature and noise have one-vote veto power over the satisfaction level of the indoor environment as a whole. In addition, the interactions among different factors were examined through chart analysis to classify indoor environmental quality.
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