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A series of random polymers based on the donor polymer PM6 were designed from the perspective of regulating the surface electrostatic potential (ESP) distribution of the polymers and applied in organic solar cells (OSCs). Random polymers with different ESPs were obtained by introducing structural units of polymer PM6 into the polymer structure as the third unit. The simulation results showed that the random polymers feature a wider electron-donating region after the introduction of BDT units, indicating a more efficient charge generation probability. Benefiting from the optimized morphology of the active layer and the stronger interaction between the donor and the acceptor in the active layer, the device exhibited the best charge transport efficiency and lower charge recombination after the introduction of 5% BDT units, and a high power conversion efficiency (PCE) of 16.76% was achieved. In addition, OSC devices based on random polymers incorporating 5% BDT units exhibit excellent device stability. In contrast, the devices based on random polymers after the introduction of BDD units showed a much lower PCE of around 13% due to the inferior charge generation and charge transport. This work not only provides a new perspective for the molecular design of efficient random polymers, but also demonstrates that the OSC devices based on random polymers can still achieve better stability.

A star-shaped nitrogen heterocyclic-ring acceptor TF1 featuring a unique 3D skeleton was successfully utilized to inhibit excessive molecular aggregation of Y6 to improve the stability and performance of organic solar cells.

To design an automatic harvesting machine for hydroponic lettuce (Lactuca sativa L.), physical and mechanical properties of hydroponic lettuce were investigated and analyzed. Moisture content of stem, root and leaf, geometric characteristics, pulling force, and root cutting force were studied for harvesting hydroponic lettuce. The pulling force was examined by a tensile experiment, while the root cutting force was investigated by a shear experiment on the electronic universal testing machine. The moisture content of hydroponic lettuce was obtained by direct drying. Experiment data were processed using regression analysis and mathematical statistics method. A regression equation and the law of numerical distribution were obtained. The results showed that the geometric size of different hydroponic lettuce had little difference, and the distribution of physical parameters was concentrated. Moisture content was found statistically similar in stem and root (around 91%), while the highest moisture content was found in the leaf of 95.73%. The root cutting force decrease with the increase of cutting speed and decrease with the cutting position move downward. The minimum average root cutting force in the experiment was 1.41 N. The average pulling force was 13 N. This study provides adequate theoretical support for the design of the automatic harvesting machine of hydroponic lettuce.

In order to reduce the mechanical damage during the kiwifruit picking process, the fruit rate of the picked fruit should be improved. The mechanical properties of the epidermis and interior of the fruit during the harvesting process were studied, so as to analyze the damage principle of the fruit. Firstly, a three-dimensional model of kiwifruit was constructed by point cloud scanning, and the flesh and placenta were filled in order to become a complete kiwifruit model. The elastic modulus, failure stress, and density of the kiwifruit skin, flesh, and placenta were obtained experimentally, and the material properties of the kiwifruit model were endowed with properties. Secondly, the finite element method was used to analyze the epidermis and internal stress of the kiwifruit by simulating the two processes of grabbing kiwifruit and picking to fruit boxes. The results show that the relative error of the simulation and test of the simulated grasping of kiwifruit was 6.42%, and the simulation and test of picking to fruit box confirmed the existence of damage, and the reflectivity of the damaged point in the detection was 6.18% on average, and the hardness value decreased to 8.30 kg/cm2 on average. The results from this study can provide a reference for control strategies and damage avoidance during grasping.

Purpose Omnidirectional mobile platforms are still plagued by the problem of heading deviation. In four-Mecanum-wheel systems, this problem arises from the phenomena of dynamic imbalance and slip of the Mecanum wheels while driving. The purpose of this paper is to analyze the mechanism of omnidirectional motion using Mecanum wheels, with the aim of enhancing the heading precision. A proportional-integral-derivative (PID) setting control algorithm based on a radial basis function (RBF) neural network model is introduced. Design/methodology/approach In this study, the mechanism of omnidirectional motion using Mecanum wheels is analyzed, with the aim of enhancing the heading precision. A PID setting control algorithm based on an RBF neural network model is introduced. The algorithm is based on a kinematics model for an omnidirectional mobile platform and corrects the driving heading in real time. In this algorithm, the neural network RBF NN2 is used for identifying the state of the system, calculating the Jacobian information of the system and transmitting information to the neural network RBF NN1. Findings The network RBF NN1 calculates the deviations ?Kp, ?Ki and ?Kd to regulate the three coefficients Kp, Ki and Kd of the heading angle PID controller. This corrects the driving heading in real time, resolving the problems of low heading precision and unstable driving. The experimental data indicate that, for a externally imposed deviation in the heading angle of between 34º and ∼38°, the correction time for an omnidirectional mobile platform applying the algorithm during longitudinal driving is reduced by 1.4 s compared with the traditional PID control algorithm, while the overshoot angle is reduced by 7.4°; for lateral driving, the correction time is reduced by 1.4 s and the overshoot angle is reduced by 4.2°. Originality/value In this study, the mechanism of omnidirectional motion using Mecanum wheels is analyzed, with the aim of enhancing the heading precision. A PID setting control algorithm based on an RBF neural network model is introduced. The algorithm is based on a kinematics model for an omnidirectional mobile platform and corrects the driving heading in real time. In this algorithm, the neural network RBF NN2 is used for identifying the state of the system, calculating the Jacobian information of the system and transmitting information to the neural network RBF NN1. The method is innovative.

The excited state charge transfer (CT) characteristics of nonfullerene acceptors play an important role in determining the photo excited CT mechanisms and performance for organic solar cells (OSCs)...

Polymer acceptors based on extended fused ring π skeleton has been proven to be promising candidates for all-polymer solar cells (all-PSCs), due to their remarkable improved light absorption than the traditional imide-based polymer acceptors. To expand structural diversity of the polymer acceptors, herein, two polymer acceptors PSF-IDIC and PSi-IDIC with extended fused ring π skeleton are developed by copolymerization of 2,2′-((2Z,2′Z)-((4,4,9,9-tetrahexadecyl-4,9-dihydro-s-indaceno [1,2-b:5,6-b']dithiophene-2,7-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC-C16) block with sulfur (S) and fluorine (F) functionalized benzodithiophene (BDT) unit and silicon (Si) atom functionalized BDT unit, respectively. Both polymer acceptors exhibit strong light absorption. The PSF-IDIC exhibits similar energy levels and slightly higher absorption coefficient relative to the PSi-IDIC. After blended with the donor polymer PM6, the functional atoms on the polymer acceptors show quite different effect on the device performance. Both of the acceptors deliver a notably high open circuit voltage (VOC) of the devices, but PSi-IDIC achieves higher VOC than PSF-IDIC. All-PSC based on PM6:PSi-IDIC attains a power conversion efficiency (PCE) of 8.29%, while PM6:PSF-IDIC-based device achieves a much higher PCE of 10.18%, which is one of the highest values for the all-PSCs reported so far. The superior device performance of PM6:PSF-IDIC is attributed to its higher exciton dissociation and charge transport, decreased charge recombination, and optimized morphology than PM6:PSi-IDIC counterpart. These results suggest that optimizing the functional atoms of the side chain provide an effective strategy to develop high performance polymer acceptors for all-PSCs.

Purpose The purpose of this study is to investigate the influence of additive particle size on the anti-corrosion behaviors of polyurethane (PU) coating. Design/methodology/approach The graphite (Gr) and poly-graphite (PGr) were used as large size additive and small size additive, respectively. The immersion test and electrochemical test were used to study the corrosion behaviors. Findings In the immersion test, the surface of the bare steel sample was corroded uniformly. However, for the steel samples with coatings, the surfaces were corroded locally. This phenomenon showed that the coating can isolate artificial sea-water and samples and then decreased the corrosion rate. Furthermore, the most severe corrosion was observed on the sample with the Gr/PU coating compared with other anti-corrosion coatings. The results of the electrochemical measurements indicated that the corrosion rate of the sample with PGr/PU coating was approximately two times lower than that of the sample with the Gr/PU coating and the sample with PGr/PU coating was hardest to be corroded. Originality/value To have a more objective and direct recognition of the particle size effect on the coating quality.

Automatic detection of kiwifruit in the orchard is challenging because illumination varies through the day and night and because of color similarity between kiwifruit and the complex background of leaves, branches and stems. Also, kiwifruits grow in clusters, which may result in having occluded and touching fruits. A fast and accurate object detection algorithm was developed to automatically detect kiwifruits in the orchard by improving the YOLOv3-tiny model. Based on the characteristics of kiwifruit images, two convolutional kernels of 3 × 3 and 1 × 1 were added to the fifth and sixth convolution layers of the YOLOv3-tiny model, respectively, to develop a deep YOLOv3-tiny (DY3TNet) model. It takes multiple 1 × 1 convolutional layers in intermediate layers of the network to reduce the computational complexity. Testing images captured from day and night and comparing with other deep learning models, namely, Faster R-CNN with ZFNet, Faster R-CNN with VGG16, YOLOv2 and YOLOv3-tiny, the DY3TNet model achieved the highest average precision of 0.9005 with the smallest data weight of 27 MB. Furthermore, it took only 34 ms on average to process an image of a resolution of 2352 × 1568 pixels. The DY3TNet model, along with the YOLOv3-tiny model, showed better performance on images captured with flash than those without. Moreover, the experiments indicated that the image augmentation process could improve the detection performance, and a simple lighting arrangement could improve the success rate of detection in the orchard. The experimental results demonstrated that the improved DY3TNet model is small and efficient and that it would increase the applicability of real-time kiwifruit detection in the orchard even when small hardware devices are used.

Purpose The purpose of this study is to test a chassis robot on rugged road cargo handling. Design/methodology/approach Attitude solution of D-H series robot gyroscope speed and acceleration sensor. Findings In identical experimental environments, hexapodal robots experience smaller deviations when using a four-footed propulsive gait from a typical three-footed gait for forward motion; for the same distance but at different speeds, the deviation basically keeps itself within the same range when the robot advances forward with four-foot propulsive gait; because the foot slide in the three-footed gait sometimes experiences frictions, the robot exhibits a large gap in directional deviations in different courses during motion; for motion using a four-footed propulsive gait, there are minor directional deviations of hexapodal robots resulting from experimental errors, which can be reduced through optimizing mechanical structures. Originality/value Planning different gaits can solve problems existing in some typical gaits. This article has put forward a gait planning method for hexapodal robots moving forward with diverse gaits as a redundant multifreedom structure. Subsequent research can combine a multiparallel-legged structure to analyze kinematics, optimize the robot’s mechanical structure and carry out in-depth research of hexapod robot gaits.

The precise design of organic photovoltaic materials and the control of morphology in the active layer are crucial for achieving high-performance organic solar cells (OSCs). However, it still remains difficult to fully obtain the intrinsic properties of organic photovoltaic materials, as well as the details of molecular stacking in disordered films and the evolution of the specific morphology of active layers, using traditional characterization methods, which hinders the screening of organic photovoltaic materials and understanding the structure–property relationship. Accordingly, computational chemistry provides a good method and plays a vital role in current scientific research. In this review, we first introduce the theoretical methods used in the recent study of OSCs, including density functional theory (DFT), time-dependent DFT (TD-DFT), all atomic molecular dynamics (AAMD) and coarse-grained molecular dynamics (CGMD). Then, the effects of the molecular structure on its conformation, frontier molecular orbital, ultraviolet-visible (UV-Vis) absorption spectrum, dipole moment, electrostatic potential, binding energy, stacking, and morphological evolution are discussed and analyzed. In addition, the application of machine learning (ML) in materials screening is briefly summarized. Finally, the intrinsic properties of OSCs are summarized based on the molecular structure and the future development and prospects of OSCs are analyzed to accelerate the efficiency over 20% in the near future.

Fused-ring electron acceptor (FREA) based ternary organic solar cells (OSCs) have made significant progress and attracted considerable attention due to their simple device architecture and broad absorption range in devices. There are three key parameters that need to be fine-tuned in ternary OSCs including absorption, energy level and morphology in order to realize high efficiencies. Herein, a series of FREAs with diverse electron-rich cores or electron-deficient terminals are developed and rationally combined to achieve high performance ternary OSCs. The dipole moment of FREAs’ terminals has been unveiled as an important factor and its working mechanism has been thoroughly investigated by systematically studying six ternary OSCs. These ternary blends all exhibit complementary absorption and cascade energy levels, which can facilitate efficient light-harvesting and charge transfer. Additionally, the morphological effects on ternary OSCs are eliminated through comparative studies while demonstrating distinctively different performance. The preliminary results show that compatible dipole moment between two FREAs is critical in ternary blends. Specifically, the performance of the ternary system with two FREAs having quite different dipole moment terminals is worse compared to that with similar terminal dipole moments. The pair with larger difference in the dipole moment will also negatively impact device performance. This interesting phenomenon is likely due to the fact that very different dipole moments of terminals in FREAs can significantly decrease the electron mobility as well as induce unbalanced hole/electron transport. Consequently, it results in increased charge recombination and reduced charge collection efficiency. This finding demonstrates that the dipole moment of FREAs should be taken into account in designing ternary OSCs.

In this letter, we discuss the application of low pressure chemical vapor deposition (LPCVD) grown SiNx passivation-first process to improve the power density and linearity performance of a metal oxide chemical vapor deposition (MOCVD) grown AlGaN channel polarization-graded field-effect transistor (PolFET). Significantly improved dispersion behavior was observed compared to plasma enhanced chemical vapor deposition (PECVD) grown SiNx passivation. The Current collapse at 30 V drain quiescent condition for pulsed I-V was reduced to 8% (LPCVD) from 25% (PECVD). 10 GHz load-pull measurement showed a maximum output power density of 3.4 W/mm with a peak power added efficiency (PAE) of 40%. Two-tone intermodulation distortion measurement at 10 GHz for devices with $150\boldsymbol {\mu }\text{m}$ width revealed an OIP3 of 39 dBm and an excellent corresponding linearity figure of merit OIP3/ $\text{P}_{{\textit {DC}}}$ of 13.3 dB. This is the best device level OIP3/ $\text{P}_{{\textit {DC}}}$ reported to date at X-band for III-Nitride microwave transistors.

We have designed and fabricated the first self-biased circulator operating in ${C}$ -band and monolithically integrated it with Qorvo’s GaN MMIC technology by embedding a FeNi-based magnetic nanowire composite (MNC) in a $100~\mu \text{m}$ thick SiC substrate. This integrated microstrip circulator shows a circulation frequency centered at 5.7 GHz, with an insertion loss of 2.7 dB and isolation of 14 dB. The circulator also demonstrated power handling of 9.6 W with continuous wave and at least 40 W under pulsed conditions. This letter points a path in integrating miniaturized circulators into full-duplex GaN T/R MMICs with stringent form factor limits.

This research work aims at developing a machine vision system capable of distinguishing kiwifruits on plants prior to harvest. The methodology was based on developing an algorithm able to detect each fruit, even when they are clustered in a line. It segments the fruits from the background, counts the number of fruits in each cluster, and identifies the edges of each fruit. After segmentation, the algorithm initially distinguishes between the fruit skin and calyx based on colour differences using selected hue and red channels. Next, a calyx line is drawn to connect all the calyxes in one cluster together. Then, the periphery of each cluster is scanned to find the contact points between the adjacent fruits. Finally, a separating line is drawn between the two closest contact points, provided that this line intersected almost vertically the calyx line. The separating lines determine the borders of each fruit and enable singling them out. The results showed that 93.7% of the fruit calyxes were correctly detected. In night-time with flash, 92.0% of the fruits were separated and counted correctly by the algorithm.

Inorganic adhesive is widely used in the sealing and connection of electronic devices. Its insulation is highly important in the performance of installation. In this paper, the insulation resistance and tensile strength of different composite silicate samples were measured by test machines. The morphology and surface composition were analyzed by electronic microscope and energy spectrum analyzer. The results show that: In a humid environment, the resistance insulation of adhesive increases with the rising of heat treatment temperature, and decreases with the increment of wet environment. When the modulus ratio of colloidal liquid is in the range of 7.2~9.1 and the heat-treatment temperature is larger than 600°C, the effect of moisture resistant is remarkable. The tensile strength of adhesive deteriorates with the increasing of humidity. Furthermore, with ascending heat treatment temperature, the tensile strength rises when the modulus ratio of adhesive is less than 7.2, and declines when it is more than 9.1.

Correction for ‘Non-halogenated-solvent-processed highly efficient organic solar cells with a record open circuit voltage enabled by noncovalently locked novel polymer donors’ by Hui Guo et al., J. Mater. Chem. A, 2019, 7, 27394–27402.

Kiwifruit is widely planted in Shaanxi, China, accounting for approximately 70% of the local production, and 33% of the global. Harvesting kiwifruits in China relies mainly on manual picking, and it is labor-intensive. To develop a machine vision system for harvesting robot which can work all day, kiwifruit images were captured in an orchard at different timing, morning, afternoon, and night, with or without flash, respectively. Kiwifruit images of 2400 were divided into training (1440) and testing (960) groups. A Faster R-CNN model implemented by VGG16 were constructed and trained. The average precision of VGG16 model was 87.61%, and the kiwifruit images collected under different timing and lighting conditions were detected well. In the end, the performance of the proposed method was compared with ZFNet in the same image dataset. It suggested that the proposed method achieved higher detection average precision than ZFNet (72.50%). This system is able to detect different categories of fruit in the field effectively and provides strong support for the harvesting robot, which can work all day round during the busy season.

Although performance of Li S batteries with various carbon/sulfur composites has been wildly explored at room temperature, the reports studying the behaviors of Li S cathodes at low temperature are few. Herein, a novel multifunctional graphene oxide-Zn(II)-triazole complex (denoted as GO-Zn(II)-AmTZ) with excellent property at low temperature(-20 °C) is successfully prepared. In GO-Zn(II)-AmTZ, the metal ions (Zn(II)), amine groups and the N penta-heterocycle are introduced synchronously, leading improvement of Li S performance at both room and low temperature. As a result of the multifunctional arrangement, GO-Zn(II)-AmTZ cathodes could provide a discharge capacity of 315 mAh g−1 (0.5C) after 100 cycles at −20 °C. A capacity of ∼520 mAh g−1 is achieved over 300 cycles at room temperature with low capacity attenuation rate at current rate of 0.5C. The improved performance is speculated to the contribution of enhanced polysulfide immobilization of GO-Zn(II)-AmTZ modified by the Zn(II), amine groups and the N atoms.

The elements Nb and Y were simultaneously substituted to the Zr sites of an Li7La3Zr2O12 (LLZO) electrolyte to improve its Li-ion conductivity and air stability. Samples of Li7La3Zr2-2xNbxYxO12 were fabricated using a solid-state reaction method. The results show that the introduction of Nb and Y can stabilise cubic-phase LLZO. The total conductivity of Li7La3ZrNb0.5Y0.5O12 electrolyte can reach 8.29 × 10−4 S cm−1 at 30 °C when sintered at 1230 °C for only 15 h. Surprisingly, the conductivity of Li7La3ZrNb0.5Y0.5O12 can be maintained at 6.91 × 10−4 S cm−1 after exposure to air for 1.5 months, indicating excellent air stability. Furthermore, a LiFePO4/Li7La3ZrNb0.5Y0.5O12/Li cell displayed stable charge/discharge and cycling performance at ambient temperature, suggesting there is potential to use Li7La3ZrNb0.5Y0.5O12 electrolyte in Li-ion batteries. Additionally, the effects of varying the co-doping amount and dwelling time on the Li-ion conductivity of Li7La3Zr2-2xNbxYxO12 were investigated.

Although the anti-friction and wear resistant technology in dry condition between friction contacts has attracted widespread attention, it has limitations because of the challenges associated with the solid lubricant. A strategy is herein presented using a Cu@Graphite solid lubricant in the reduction of friction and wear in dry condition. The tribological tests were carried out at three sliding speeds (0.1 m/s, 0.3 m/s and 0.5 m/s) at room temperature with a ball-on-block contact. The graphite in the Cu@Graphite solid lubricant plays a key role in separating the contact pair to decrease the adhesion, which decreases the coefficient of friction (COF). Moreover, the copper in the Cu@Graphite solid lubricant can be transformed to the contact pair and then fill in the micro-defects and tiny scratches, which repairs the friction pair. The COF between the friction pair decreased >400% and the wear volume decreased sharply when the Cu@Graphite solid lubricant was introduced in the interface of the friction pair. In addition, the study develops a promising application prospect of the hybrid composite material, not only as a solid lubricant, but also as a repairing additive.

Advanced electronic technology makes mobile phone suitable for image processing technology on fruit yield estimation. A new method was proposed to estimate yield of kiwifruit orchard via image processing using an Android mobile phone. Image processing was used to select significant color channels and their threshold for segmentation, generate binarized image, and remove noise. A fruit-counting algorithm was developed to calculate the number of kiwifruit by identifying the number of fruit calyxes. Image area was estimated by the pixels proportion of a reference board hung under the canopy. Finally, yield was calculated by multiplying the proportion of the image in three-dimensional space with the number of kiwifruit in an image and the kiwifruit orchard area. Under natural conditions, the performance of the fruit counting algorithm software was validated with 100 kiwifruit images. The proposed method achieved a good precision and recognition ratio of 76.4%. Results showed the pixels area of the reference board could be correctly detected. It is reliable to estimate the yield of kiwifruit orchard by recognizing the number of kiwifruit and the area of the reference board. The results indicated that the approach could be utilized to estimate the fruit yield of a kiwifruit orchards, which is valuable information to forecast yield, and plan harvest schedules.

The energy loss (Eloss ), especially the nonradiative recombination loss and energetic disorder, needs to be minimized to improve the device performance with a small voltage (VOC ) loss. Urbach energy (EU ) of organic photovoltaic materials is related to energetic disorder, which can predict the Eloss of the corresponding device. Herein, a polymer donor (PBDS-TCl) with Si and Cl functional atoms for organic solar cells (OSCs) is synthesized. It can be found that the VOC and Eloss can be well manipulated by regulation of the energy level of the polymer donor and EU , which is dominated by the morphology. A low energetic disorder with an EU of 23.7 meV, a low driving force of 0.08 eV, and a low Eloss of 0.41 eV are achieved for the PBDS-TCl:Y6-based OSCs. Consequently, an impressive open circuit voltage (VOC ) of 0.92 V is obtained. To the best of knowledge, the VOC value and Eloss are both the record values for the Y6-based device. These results demonstrate that fine-tuning the polymer donor by functional atom modification on the side chain is a promising way to reduce EU and energy loss, as well as obtain small driving force and high VOC for highly efficient OSCs.

In this article, a review of the mechanisms that have been developed to improve the efficiency of Chinese jujube (Ziziphus Jujuba Mill) was made. This fruit is considered as an economic crop in the arid and semiarid regions especially in China, where the cultivation methods alternate between traditional and intensive. In the former the trees are large and planted with relatively wide space, whereas in the latter the trees are dwarfed with tight spacing among them. Mechanisms which were studied and tested, for each cultivation method, were summarized and compared in terms of fruit collecting efficiency and rate of damage. These mechanisms were branch beating, trunk shaking, air shaking for traditional cultivation and tree shaking, canopy shaking, and vacuum suction for intensive cultivation. The comparison indicated that as the efficiency increase for any single mechanism the rate of damage increases accordingly. Therefore, a combination of mechanism would maintain the efficiency and reduce damage. In particular, a combination of a mechanism of tree shaking, developed earlier for blueberry, and trunk shaking was thought to be with high potential of low rate of damage. This article also spots on the possibilities of fully automating the post-harvest operation of fruit grading by describing a number of previous articles that have tackled fruit sorting not only for fruit processing but also for fresh market. The hope is that this review will spark the renewal of research and development of the cultivation of Chinese jujube so as to meet the increasing demand.

Hydroponic lettuce has been planted in nutrient solution, and it was one of typical plant factory leaf vegetables. Nowadays, hydroponic lettuce was mainly manually harvested in China with low efficiency and high labor cost. In order to improve the harvesting efficiency of hydroponic lettuce, an automatic harvesting system was designed, which integrated the operation steps like multilayer conveying, lettuce gathering, stem cutting, lettuce unloading and packaging. Therefore, the automatic harvesting system was designed in T shape and consisted of a multilayer conveying device, a mechanism for lettuce gathering, stem cutting, and lettuce unloading (gathering-cutting-unloading mechanism), and a machine for lettuce packaging. The multilayer conveying device contained 2 layers, where every layer contained 3 planting boards. The gathering-cutting-unloading mechanism has two holding rods, a cutter bar, an unloading cylinder. The gathered and stem-cut lettuce was then put into packaging box automatically, which was sealed with film by the packaging machine. The overall size of harvester was 3530x3090x1845 mm. The harvesting system was manufactured and controlled by single chip microcomputers. Cylinders and stepper motors were employed as the execution component. For experiment, 108 lettuces were selected for the verification tests, which mainly aimed to measure the performance of the harvesting system like the working efficiency and success rate. Experimental results showed that the operating time, the mean operating time and working efficiency of the harvesting system were 44 – 81 s, 61 s, and 59 lettuces per hour, respectively. The success rate of the harvesting system was 92%.

Hydroponic lettuce was one of typical vegetables in plant factory, and its production scale is increasing rapidly. In order to extend the preservation time of for sale and thus increase the added value, effect of root lengths on preservation performance for hydroponic lettuce was studied. After that, a root cutting machine for hydroponic lettuce was developed. Four indexes (changes in relative chlorophyll content, changes in color of lettuce leaves, weight loss rate, and sensory quality) were employed to study the effects of different root lengths on hydroponic lettuce fresh-keeping performance, which concluded that keeping the lettuce root length 9 cm was good for lettuce preservation. The root cutting machine was then developed according to the preservation tests. The key components of the root cutting machine including a setting board conveying device, a root cutting device, and a lettuce pulling and carrying device, which were designed though preliminary tests and mechanical analysis. The root cutting machine was manufactured and tested by 90 lettuces which aimed to measure its success rate and operation efficiency. Experimental results showed that the success rate of root cutting was 82% and the operation efficiency for one lettuce was 7.7 s.

To design an automatic harvesting machine for hydroponic lettuce, the physical and mechanical properties of hydroponic lettuce were investigated and analyzed. Moisture content of stem, root and leaf, geometric characteristics, pulling force, and root cutting force were studied for harvesting hydroponic lettuce. The pulling force was examined by a tensile experiment, and the root cutting force was investigated by a shear experiment on the electronic universal testing machine. The moisture content of hydroponic lettuce was obtained by direct drying. The experiment data were processed using regression analysis and mathematical statistics method. A regression equation and the law of numerical distribution were obtained. The results showed that the geometrical characteristics of the hydroponic lettuce had little change, and the distribution of physical parameters was concentrated. Moisture content was found statistically similar in stem and root (around 91%), while the highest moisture content was found in the leaf of 95.73%. The root cutting force decrease with the increase of cutting speed and decrease with the cutting position move downward. The minimum average root cutting force in the experiment was 1.41 N. The average pulling force was 13 N. This study provides adequate theoretical support for the design of the automatic harvesting machine of hydroponic lettuce.

Monolithic microwave integrated circuit (MMIC) transit/receive (T/R) modules are widely used in radar and communication systems. The transmitter and receiver usually share the same antenna either by a high frequency switch or a magnetic circulator. Switches can be monolithically integrated in the same chip with the power amplifier (PA) and low noise amplifier (LNA) circuits. But signals are processed by the PA and LNA alternately. Circulator has an advantage over switches as it allows simultaneous signal transmission and reception. However, conventional circulators use ferrites which need external permanent magnets to bias ferrites [1]. This makes circulators bulky and limits or even prohibits monolithic implementation in T /R modules. In a self-biased (SB) circulator, ferrite possesses remnant magnetization and no external magnetic field is needed [2]–[4]. In this report, we have demonstrated the first monolithically integrated Ka-band SB circulator on a GaN/SiC wafer leveraging Qorvo's GaN technology and self-biased ferrite materials from Metamagnetics.

Two highly crystalline polymer donors (PBTz4T2C-a, PBTz4T2C-b) with isomers (4T2C-a, 4T2C-b) are synthesized and applied in polymer solar cells. The developed polymers possess proper energy levels and complementary absorption with an efficient electron acceptor IT2F. It is interesting that the photophysical properties, crystallinity, and active layer morphology characteristic can be significantly changed by just slightly regulating the substitution position of the carboxylate groups. A series of simulation calculations of the two isomers are conducted in the geometry and electronic properties to explore the difference induced by the position adjustment of carboxylate groups. The results decipher that 4T2C-b moiety features much stronger intramolecular noncovalent S⋯O interactions compared to that of 4T2C-a, implying a higher coplanarity and much stronger crystallinity, and leading to excessive phase separation in PBTz4T2C-b:IT2F blend film. In contrast, PBTz4T2C-a with 4T2C-a moiety exhibits suitable crystallinity with a lower the highest occupied molecular orbital level, higher film absorption coefficient, and charge mobilities, resulting in a much higher power conversion efficiency of 11.02%. This research demonstrates that the molecular conformation is of great importance to be considered for developing high-performance polymer donors.