•Computer vision technology will improve the agricultural automation systems.•Agricultural automation systems will be developed in an intelligent direction.•Computer vision technology will provide ...suggestions and insights to farmers.
Computer vision is a field that involves making a machine “see”. This technology uses a camera and computer instead of the human eye to identify, track and measure targets for further image processing. With the development of computer vision, such technology has been widely used in the field of agricultural automation and plays a key role in its development. This review systematically summarizes and analyzes the technologies and challenges over the past three years and explores future opportunities and prospects to form the latest reference for researchers. Through the analyses, it is found that the existing technology can help the development of agricultural automation for small field farming to achieve the advantages of low cost, high efficiency and high precision. However, there are still major challenges. First, the technology will continue to expand into new application areas in the future, and there will be more technological issues that need to be overcome. It is essential to build large-scale data sets. Second, with the rapid development of agricultural automation, the demand for professionals will continue to grow. Finally, the robust performance of related technologies in various complex environments will also face challenges. Through analysis and discussion, we believe that in the future, computer vision technology will be combined with intelligent technology such as deep learning technology, be applied to every aspect of agricultural production management based on large-scale datasets, be more widely used to solve the current agricultural problems, and better improve the economic, general and robust performance of agricultural automation systems, thus promoting the development of agricultural automation equipment and systems in a more intelligent direction.
A diketopyrrolopyrrole‐based conjugated polymer, PDPP‐4FTVT, which exhibits ambipolar transport behavior in air with hole and electron mobilities up to 3.40 and 5.86 cm2 V−1 s−1, respectively, is ...synthesized via direct arylation polycondensation. Incorporation of F‐atoms in β‐positions of thiophene rings dramatically improves the efficiency of direct arylation polycondensation.
n‐Type Azaacenes Containing B←N Units Min, Yang; Dou, Chuandong; Tian, Hongkun ...
Angewandte Chemie International Edition,
February 12, 2018, Volume:
57, Issue:
7
Journal Article
Peer reviewed
We disclose a novel strategy to design n‐type acenes through the introduction of boron–nitrogen coordination bonds (B←N). We synthesized two azaacenes composed of two B←N units and six/eight linearly ...annelated rings. The B←N unit significantly perturbed the electronic structures of the azaacenes: Unique LUMOs delocalized over the entire acene skeletons and decreased aromaticity of the B←N‐adjacent rings. Most importantly, these B←N‐containing azaacenes exhibited low‐lying LUMO energy levels and high electron affinities, thus leading to n‐type character. The solution‐processed organic field‐effect transistor based on one such azaacene exhibited unipolar n‐type characteristics with an electron mobility of 0.21 cm2 V−1 s−1.
BN there makes all the difference: The introduction of B←N units into azaacenes causes significant perturbations of their electronic structures and properties: Unique LUMOs delocalized over the acene skeletons (see picture) decrease aromaticity of the B←N‐adjacent rings and n‐type character. A solution‐processed organic field‐effect transistor based on one of the azaacenes exhibited unipolar n‐type characteristics and high electron mobility.
High‐performance unipolar n‐type conjugated polymers (CPs) are critical for the development of organic electronics. In the current paper, four “weak donor–strong acceptor” n‐type CPs based on ...pyridine flanked diketopyrrolopyrrole (PyDPP), namely PPyDPP1‐4FBT, PPyDPP2‐4FBT, PPyDPP1‐4FTVT, and PPyDPP2‐4FTVT, are synthesized via direct arylation polycondensation by using 3,3′,4,4′‐tetrafluoro‐2,2′‐bithiophene (4FBT) or (E)‐1,2‐bis(3,4‐difluorothien‐2‐yl)ethene (4FTVT) as weak donor unit. All four polymers exhibit low‐lying highest occupied molecular orbital (≈ −5.90 eV) and lowest unoccupied molecular orbital energy levels (≈ −3.70 eV). Top‐gate/bottom‐contact organic field‐effect transistors based on all four polymers display unipolar n‐channel characteristics with electron mobility (µe) above 1 cm2 V−1 s−1 in air, and presented linear |ISD|1/2 −VGS plots and weak dependence of the extracted moblity on gate voltage (VGS), indicative of the reliability of the extracted mobility values. Importantly, the devices based on PPyDPP1‐4FBT and PPyDPP2‐4FBT show a pure unipolar n‐channel transistor behavior as revealed by the typical unipolar n‐channel output characteristics and clear off‐regimes in transfer characteristics. Attributed to its high crystallinity and favorable thin film morphology, PPyDPP2‐4FBT shows the highest µe of 2.45 cm2 V−1 s−1, which is among the highest for unipolar n‐type CPs reported to date. This is also the first report for DPP based pure n‐type CPs with µe greater than 1 cm2 V−1 s−1.
The “weak donor–strong acceptor” strategy is adopted to synthesize unipolar n‐type conjugated polymers via direct arylation polycondensation by using fluorinated thiophene moieties as the weak donors and pyridine flanked diketopyrrolopyrrole as the strong acceptor. Pure unipolar n‐channel organic field effect transistors (OFETs) with an electron mobility of 2.45 cm2 V−1 s−1 and a current on/off ratio of ≈105 in the air are fabricated.
Three highly rigid and planar low‐bandgap conjugated polymers comprising alternate isoindigo and dithienocarbazole groups are synthesized for the fabrication of high performance polymer solar cells. ...Power conversion efficiencies of up to 7.2% for conventional devices and 8.2% for inverted devices are demonstrated.
Herein, we report the synthesis and characterization of a series of 1benzothieno3,2-b1benzothiophene (BTBT)-based asymmetric conjugated molecules, that is, ...2-(5-alkylthiophen-2-yl)1benzothieno3,2-b1benzothiophene (BTBT-Tn, in which T and n represent thiophene and the number of carbons in the alkyl group, respectively). All of the molecules with n ≥ 4 show mesomorphism and display smectic A, smectic B (n = 4), or smectic E (n > 4) phases and then crystalline phases in succession upon cooling from the isotropic state. Alkyl chain length has a noticeable influence on the microstructures of vacuum-deposited films and therefore on the performance of the organic thin-film transistors (OTFTs). All molecules except for 2-(thiophen-2-yl)1benzothieno3,2-b1benzothiophene and 2-(5-ethylthiophen-2-yl)1benzothieno3,2-b1benzothiophene showed OTFT mobilities above 5 cm2 V–1 s–1. 2-(5-Hexylthiophen-2-yl)1benzothieno3,2-b1benzothiophene and 2-(5-heptylthiophen-2-yl)1benzothieno3,2-b1benzothiophene showed the greatest OTFT performance with reliable hole mobilities (μ) up to 10.5 cm2 V–1 s–1 because they formed highly ordered and homogeneous films with diminished grain boundaries.
Biomass is an important indicator for evaluating crops. The rapid, accurate and nondestructive monitoring of biomass is the key to smart agriculture and precision agriculture. Traditional detection ...methods are based on destructive measurements. Although satellite remote sensing, manned airborne equipment, and vehicle-mounted equipment can nondestructively collect measurements, they are limited by low accuracy, poor flexibility, and high cost. As nondestructive remote sensing equipment with high precision, high flexibility, and low-cost, unmanned aerial systems (UAS) have been widely used to monitor crop biomass. In this review, UAS platforms and sensors, biomass indices, and data analysis methods are presented. The improvements of UAS in monitoring crop biomass in recent years are introduced, and multisensor fusion, multi-index fusion, the consideration of features not directly related to monitoring biomass, the adoption of advanced algorithms and the use of low-cost sensors are reviewed to highlight the potential for monitoring crop biomass with UAS. Considering the progress made to solve this type of problem, we also suggest some directions for future research. Furthermore, it is expected that the challenge of UAS promotion will be overcome in the future, which is conducive to the realization of smart agriculture and precision agriculture.
Seven diketopyrrolopyrrole (DPP)-based donor–acceptor (D–A) conjugated polymers, i.e., ...poly2,5-bis(4-octadecyldocosyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-3,3′,4,4′-tetrafluoro-2,2′-bithiophene (P4F2T-C40), poly2,5-bis(4-octadecyldocosyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-1,2-bis(3,4-difluorothiophen-2-yl)ethyne (P4FTAT-C40), poly2,5-bis(4-octadecyldocosyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C40), poly2,5-bis(4-tetradecyloctadecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C32), poly2,5-bis(4-decyltetradecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C24), poly2,5-bis(2-decyldodecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C22), and poly2,5-bis(2-decyltetradecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C10C12), were synthesized by direct arylation polycondensation (DArP) with multi-fluorinated thiophene derivatives 3,3′,4,4′-tetrafluoro-2,2′-bithiophene (4F2T), (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT), or 1,2-bis(3,4-difluorothiophen-2-yl) acetylene (4FTAT) as the comonomer. The structures of the multi-fluorinated thiophene derivatives have a noticeable influence on the optical properties and self-assembly properties of the polymers. Compared to P4F2T-C40, P4FTVT-C40 showed an ∼30 nm red-shift while P4FTAT-C40 exhibited an ∼60 nm blue-shift of the absorption spectrum. Top-gate and bottom-contact (TGBC) organic field-effect transistors (OFETs) of all the polymers exhibited ambipolar transport behavior. The devices based on P4FTAT-C40 displayed poor device performance since its film was almost amorphous. In contrast, the polymer based on 4FTVT with the same alkyl side chains delivered much better device performance due to its crystalline nature, favorable molecular orientations, and appropriate film morphology. With optimized side chains, P4FTVT-C32 exhibited the highest hole (μh) and electron mobilities (μe) of ca. 2.6 and ca. 8.0 cm2 V–1 s–1 in air, respectively.
Boron (B)- and sulfur (S)-doped polycyclic aromatic hydrocarbons (PAHs) are developed as a novel kind of multiple resonance emitters for ultrapure blue thermally activated delayed fluorescence (TADF) ...polymers with narrowband electroluminescence. The combination of electron-deficient B atom and electron-rich S atom in PAH can form an intramolecular push-pull electronic system in a rigid aromatic framework, leading to reduced singlet-triplet energy splitting and limited structure relaxation of excited states. The critical roles of S atom in determining emission properties with respect to the oxygen analogues are in two aspects: (i) reducing energy bandgap to shift emission from human-eye-insensitive ultraviolet zone to blue region, and (ii) promoting reverse intersystem crossing process by heavy-atom effect to activate TADF effect. The resulting polymer containing B,S-doped PAH as emitter and acridan as host exhibits efficient blue electroluminescence at 458 nm with small full-width at half-maximum of 31 nm, representing the first example for ultrapure TADF polymer with narrowband electroluminescence.
Sensing and recognizing invisible ultraviolet (UV) light is vital for exploiting advanced artificial visual perception system. However, due to the uncertainty of the natural environment, the UV ...signal is very hard to be detected and perceived. Here, inspired by the tetrachromatic visual system, we report a controllable UV-ultrasensitive neuromorphic vision sensor (NeuVS) that uses organic phototransistors (OPTs) as the working unit to integrate sensing, memory and processing functions. Benefiting from asymmetric molecular structure and unique UV absorption of the active layer, the as fabricated UV-ultrasensitive NeuVS can detect 370 nm UV-light with the illumination intensity as low as 31 nW cm
, exhibiting one of the best optical figures of merit in UV-sensitive neuromorphic vision sensors. Furthermore, the NeuVS array exbibits good image sensing and memorization capability due to its ultrasensitive optical detection and large density of charge trapping states. In addition, the wavelength-selective response and multi-level optical memory properties are utilized to construct an artificial neural network for extract and identify the invisible UV information. The NeuVS array can perform static and dynamic image recognition from the original color image by filtering red, green and blue noise, and significantly improve the recognition accuracy from 46 to 90%.
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