Artificial intelligence approach for tomato detection and mass estimation in precision agriculture

Funding: This study was carried out with the support of “Research Program for Agricultural Science & Technology Development” (Project No: PJ013891012020), National Institute of Agricultural Sciences, Rural Development Administration, Republic of Korea.Application of computer vision and robotics in agriculture requires sufficient knowledge and understanding of the physical properties of the object of interest. Yield monitoring is an example where these properties affect the quantified estimation of yield mass. In this study, we propose an image-processing and artificial intelligence-based system using multi-class detection with instance-wise segmentation of fruits in an image that can further estimate dimensions and mass. We analyze a tomato image dataset with mass and dimension values collected using a calibrated vision system and accurate measuring devices. After successful detection and instance-wise segmentation, we extract the real-world dimensions of the fruit. Our characterization results exhibited a significantly high correlation between dimensions and mass, indicating that artificial intelligence algorithms can effectively capture this complex physical relation to estimate the final mass. We also compare different artificial intelligence algorithms to show that the computed mass agrees well with the actual mass. Detection and segmentation results show an average mask intersection over union of 96.05%, mean average precision of 92.28%, detection accuracy of 99.02%, and precision of 99.7%. The mean absolute percentage error for mass estimation was 7.09 for 77 test samples using a bagged ensemble tree regressor. This approach could be applied to other computer vision and robotic applications such as sizing and packaging systems and automated harvesting or to other measuring instruments.Publisher PDFPeer reviewe

Unsaturated Drift Velocity of Monolayer Graphene

We observe that carriers in graphene can be accelerated to the Fermi velocity without heating the lattice. At large Fermi energy vertical bar E-F vertical bar > 110 meV, electrons excited by a high-power terahertz pulse E-THz relax by emitting optical phonons, resulting in heating of the graphene lattice and optical phonon generation. This is owing to enhanced electron phonon scattering at large Fermi energy, at which the large phase space is available for hot electrons. The emitted optical phonons cause carrier scattering, reducing the drift velocity or carrier mobility. However, for vertical bar E-F vertical bar < 110 meV, electron phonon scattering rate is suppressed owing to the diminishing density of states near the Dirac point. Therefore, E-THz continues to accelerate carriers without them losing energy to optical phonons, allowing the carriers to travel at the Fermi velocity. The exotic carrier dynamics does not result from the massless nature, but the electron-optical-phonon scattering rate depends on Fermi level in the graphene. Our observations provide insight into the application of graphene for high-speed electronics without degrading carrier mobility © 2018 American Chemical Society

Phase conversion of chemically exfoliated molybdenum disulfide

Multilayer MoS2 is exfoliated by Li treatment. A thin film of Li-treated MoS2 contains a large portion of 1T phases. This is attributed to the atomic structural change caused by Li insertion, which is investigated using X-ray photoelectron spectroscopy (XPS). In a phase recovery via thermal annealing at 523 K in air, we observe another phase, referred to as the relaxed 1T phase, with a slightly larger binding energy than the 1T phase. After annealing at 523 K in air, the peak intensity of the relaxed 1T phase is reduced, accompanying a strong MoOx peak and weak S 2s peak, according to XPS. This indicates that the annealing of Li-treated MoS2 in air yields sulfur vacancies that induce the oxidation of Mo. However, after annealing at 523 K in vacuum, no MoOx is observed, and the considerable peak intensity of the relaxed 1T phase remains, which starkly contrasts Raman-spectroscopy results supporting a full recovery from the 1T phase to the 2H phase. The absence of a gating effect of the Li-treated MoS2 device supports the possibility of an incomplete phase change of Li-treated MoS2 annealed in a vacuum. © 2016 Elsevier B.V. All rights reserved.1451sciescopuskc

Coaxial Fiber Supercapacitor Using All-Carbon Material Electrodes

We report a coaxial fiber supercapacitor, which consists of carbon microfiber bundles coated with multiwalled carbon nanotubes as a core electrode and carbon nanofiber paper as an outer electrode. The ratio of electrode volumes was determined by a half-cell test of each electrode. The capacitance reached 6.3 mF cm-1 (86.8 mF cm-2) at a core electrode diameter of 230 μm and the measured energy density was 0.7 μWh cm-1 (9.8 μWh cm-2) at a power density of 13.7 μW cm-1 (189.4 μW cm-2), which were much higher than the previous reports. The change in the cyclic voltammetry characteristics was negligible at 180o bending, with excellent cycling performance. The high capacitance, high energy density, and power density of the coaxial fiber supercapacitor are attributed to not only high effective surface area due to its coaxial structure and bundle of the core electrode but also all-carbon materials electrodes which have high conductivity. Our coaxial fiber supercapacitor can promote the development of textile electronic in near future.12402391sciescopu

Heterogeneous nucleation and high orientation of ZnO nanorods on graphene

We report the realization of ZnO nanostructures on a graphene/SiO2/Si substrate by using a facile precursor-template synthesis technique through catalyst-free, seed-layer-free chemical vapor deposition. Vertical growth on the graphene buffer layers resulted in highly-oriented ZnO nanorods due to heterogeneous nucleation of the bond-centered sites on graphene. This demonstrates that the morphology of the structures is sensitive to the graphene substrate owing to the strong ZnOgraphene interaction. The photoluminescence exhibited distinctive band-edge emission and defect emission. The defect emission could be largely eradicated by covering the graphene and decreasing the ZnO-graphene spacing

Electrical Transport Properties of Polymorphic MoS2

The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T&apos; phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T&apos; phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T&apos; puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over IT domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 x 10(-2) K-1 at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect © XXXX American Chemical Society118191sciescopu

Unsaturated Drift Velocity of Monolayer Graphene

We observe that carriers in graphene can be accelerated to the Fermi velocity without heating the lattice. At large Fermi energy |<i>E</i>_F| > 110 meV, electrons excited by a high-power terahertz pulse <i>E</i>_THz relax by emitting optical phonons, resulting in heating of the graphene lattice and optical-phonon generation. This is owing to enhanced electron–phonon scattering at large Fermi energy, at which the large phase space is available for hot electrons. The emitted optical phonons cause carrier scattering, reducing the drift velocity or carrier mobility. However, for |<i>E</i>_F| ≤ 110 meV, electron–phonon scattering rate is suppressed owing to the diminishing density of states near the Dirac point. Therefore, <i>E</i>_THz continues to accelerate carriers without them losing energy to optical phonons, allowing the carriers to travel at the Fermi velocity. The exotic carrier dynamics does not result from the massless nature, but the electron–optical-phonon scattering rate depends on Fermi level in the graphene. Our observations provide insight into the application of graphene for high-speed electronics without degrading carrier mobility

Thickness-dependent in-plane thermal conductivity of suspended MoS2 grown by chemical vapor deposition

The in-plane thermal conductivities of suspended monolayer, bilayer, and multilayer MoS2 films were measured in vacuum by using non-invasive Raman spectroscopy. The samples were prepared by chemical vapor deposition (CVD) and transferred onto preformed cavities on a Au-coated SiO2/Si substrate. The measured thermal conductivity (13.3 ± 1.4 W m−1 K−1) of the suspended monolayer MoS2 was below the previously reported value of 34.5 ± 4 W m−1 K−1. We demonstrate that this discrepancy arises from the experimental conditions that differ from vacuum conditions and small absorbance. The measured in-plane thermal conductivity of the suspended MoS2 films increased in proportion to the number of layers, reaching 43.4 ± 9.1 W m−1 K−1 for the multilayer MoS2, which explicitly follows the Fuchs-Sondheimer suppression function. The increase in the thermal conductivity with the number of MoS2 layers is explained by the reduced phonon boundary scattering. We also observe that the Fuchs-Sondheimer model works for the thickness-dependent thermal conductivity of MoS2 down to 10 nm in thickness at room temperature, yielding a phonon mean free path of 17 nm for bulk. © The Royal Society of Chemistry9