Weak Light Conditions Research Articles

Hybrid energy harvester based on dual band transparent dielectric resonator antenna

AbstractThis article presents a compact hybrid solar and radio frequency (RF) energy harvester based on dual‐band transparent dielectric resonator antenna (TDRA). It integrates with an amorphous silicon solar cell film, a TDRA and a rectifier circuit. The TDRA replaces the glass protective of the traditional solar cell to prevent the solar cell from being oxidized and damaged and also can efficiently harvest electromagnetic (EM) waves, which achieves harvesting solar and RF energy at the same time. The measured results show that the TDRA can reach impedance bandwidth (|S11| < −10 dB) of 2.37–3.03 GHz and 3.41–3.88 GHz and the realized gain of 4.9 dBi at 2.45 GHz and 5.95 dBi at 3.6 GHz. The efficiency of the rectifier can reach 60% and 40% at two resonance frequencies, respectively. The results prove that under weak lighting conditions, the hybrid harvester has a higher DC output power compared with the RF‐only or solar‐only energy harvester. Thus, it can be well applied to wireless sensors and Internet of Things devices.

RESEARCH ON VISUAL NAVIGATION PATH DETECTION METHOD FOR DENSE PLUM GROVE

Aiming at the field management of plum grove in Inner Mongolia of China, taking the dense planting plum groves in Bikeqi town of Hohhot City as the research object, this paper proposed a visual navigation path detection algorithm for plum grove. By processing the video image information of plum grove, comparing RGB and HSV color space model, HSV color model was selected to separate the plant and background in V channel. Homomorphic filtering was used to highlight the region of interest in the image, Otsu was selected to segment the image, the intersection of plum trunk and ground was extracted as feature points, and the least square method was used to fit the navigation path. Through the comparative analysis of detection rate under different detection conditions in one day, the verification test of route accuracy was carried out. The experimental results show that: for dense planting plum grove, the average path detection accuracy of the algorithm is 70% and 73.3% under the condition of front light and weak light, respectively. The detection accuracy and real-time meet the requirements of plum grove field management, and the navigation baseline can be generated more accurately, which provides a preliminary basis for the realization of mechanical vision navigation in plum grove field management.

Beet seedling and weed recognition based on convolutional neural network and multi-modality images

Difficulties in the recognition of beet seedlings and weeds can arise from a complex background in the natural environment and a lack of light at night. In the current study, a novel depth fusion algorithm was proposed based on visible and near-infrared imagery. In particular, visible (RGB) and near-infrared images were superimposed at the pixel-level via a depth fusion algorithm and were subsequently fused into three-channel multi-modality images in order to characterize the edge details of beets and weeds. Moreover, an improved region-based fully convolutional network (R-FCN) model was applied in order to overcome the geometric modeling restriction of traditional convolutional kernels. More specifically, for the convolutional feature extraction layers, deformable convolution was adopted to replace the traditional convolutional kernel, allowing for the entire network to extract more precise features. In addition, online hard example mining was introduced to excavate the hard negative samples in the detection process for the retraining of misidentified samples. A total of four models were established via the aforementioned improved methods. Results demonstrate that the average precision of the improved optimal model for beets and weeds were 84.8% and 93.2%, respectively, while the mean average precision was improved to 89.0%. Compared with the classical R-FCN model, the performance of the optimal model was not only greatly improved, but the parameters were also not significantly expanded. Our study can provide a theoretical basis for the subsequent development of intelligent weed control robots under weak light conditions.

REAL OBJECT DETECTION SYSTEM FOR IRAQ TRAFFIC SIGNS BASED ON MASK R-CNN

Traffic signs object detection has gained great interest in recent years, as one of the most important object detector applications. Traffic signs detection is based on deep learning, which gives it the benefit of high detection precision and timely response to condition changes of the traffic. Therefore, this paper shows an efficient method for detecting traffic signs in real-time. Hence, it implements a new Iraqi Traffic Sign Detection Benchmark (IQTSDB) dataset based on Mask Region-based Convolutional Neural Network (Mask R-CNN). The results show that the implementation of IQTSDB dataset with Mask R-CNN has a great efficiency in different conditions such as sunny, cloudy, weak light, and rainy conditions. In addition, the real video captured for traffic signs in Baghdad has been taken and compared to the German Traffic Signs Detection Benchmark (GTSDB) dataset. The IQTSDB dataset has a better performance than GTSDB dataset based on the performance parameters training loss and mean Average Precision (mAP).

Solar Radiation Effects on Dry Matter Accumulations and Transfer in Maize.

Solar radiation is the energy source for crop growth, as well as for the processes of accumulation, distribution, and transfer of photosynthetic products that determine maize yield. Therefore, learning the effects of different solar radiation amounts on maize growth is especially important. The present study focused on the quantitative relationships between solar radiation amounts and dry matter accumulations and transfers in maize. Over two continuous years (2017 and 2018) of field experiments, maize hybrids XY335 and ZD958 were grown at densities of 4.5 × 104 (D1), 7.5 × 104 (D2), 9 × 104 (D3), 10.5 × 104 (D4), and 12 × 104 (D5) plants/ha at Qitai Farm (89°34′E, 44°12′N), Xinjiang, China. Shading levels were 15% (S1), 30% (S2), and 50% (S3) of natural light and no shading (CK). The results showed that the yields of the commonly planted cultivars XY335 and ZD958 at S1, S2, and S3 (increasing shade treatments) were 7.3, 21.2, and 57.6% and 11.7, 31.0, and 61.8% lower than the control yields, respectively. Also, vegetative organ dry matter translocation (DMT) and its contribution to grain increased as shading levels increased under different densities. The dry matter assimilation amount after silking (AADMAS) increased as solar radiation and planting density increased. When solar radiation was <580.9 and 663.6 MJ/m2, for XY335 and ZD958, respectively, the increase in the AADMAS was primarily related to solar radiation amounts; and when solar radiation was higher than those amounts for those hybrids, an increase in the AADMAS was primarily related to planting density. Photosynthate accumulation is a key determinant of maize yield, and the contributions of the vegetative organs to the grain did not compensate for the reduced yield caused by insufficient light. Between the two cultivars, XY335 showed a better resistance to weak light than ZD958 did. To help guarantee a high maize yield under weak light conditions, it is imperative to select cultivars that have great stay-green and photosynthetic efficiency characteristics.

Effect of Light Regulation on the Quality of Sweetpotato Sprouts

Sweetpotato sprouts are buds or young shoots formed under dark or low-light conditions that can be eaten directly by people. This study was conducted to investigate the effects of light intensity and photoperiod on the quality and yield of sweetpotato sprouts and to identify the most suitable production conditions to provide a theoretical basis and technical parameters for the production of these vegetables. Four treatments involving different light intensities and photoperiods were set up: WL-1, WL-2, SL-1, and SL-2. The leaf color, nutritional quality, antioxidant capacity, texture characteristics, and yield of the sweetpotato sprouts were analyzed using Duncan’s new complex range method. The results demonstrated the following: 1) an increase in photoperiod improved leaf brightness and enhanced the appearance of the product, whereas light intensity had little effect on these parameters; and 2) low light intensity increased the yield of sweetpotato sprouts, whereas high light intensity reduced their yield. Under weak light conditions, the quality and yield of sweetpotato sprouts were improved, and their taste was unaffected. Therefore, the condition of 750 μmol·m−2·s−1 for 2 hours/day was chosen to produce crispy, high-quality, and high-yielding sweetpotato sprouts.

Structural Alteration of Rice Pectin Affects Cell Wall Mechanical Strength and Pathogenicity of the Rice Blast Fungus Under Weak Light Conditions.

Pectin, a component of the plant cell wall, is involved in cell adhesion and environmental adaptations. We generated OsPG-FOX rice lines with little pectin due to overexpression of the gene encoding a pectin-degrading enzyme [polygalacturonase (PG)]. Overexpression of OsPG2 in rice under weak light conditions increased the activity of PG, which increased the degradation of pectin in the cell wall, thereby reducing adhesion. Under weak light conditions, the overexpression of OsPG decreased the pectin content and cell adhesion, resulting in abnormally large intercellular gaps and facilitating invasion by the rice blast fungus. OsPG2-FOX plants had weaker mechanical properties and greater sensitivity to biotic stresses than wild-type (WT) plants. However, the expression levels of disease resistance genes in non-infected leaves of OsPG2-FOX were more than twice as high as those of the WT and the intensity of disease symptoms was reduced, compared with the WT. Under normal light conditions, overexpression of OsPG2 decreased the pectin content, but did not affect cell adhesion and sensitivity to biotic stresses. Therefore, PG plays a role in regulating intercellular adhesion and the response to biotic stresses in rice.

Research on Fast Recognition Method of Complex Sorting Images Based on Deep Learning

For the logistics sorting warehouse without much light is complex, and the difference between express packaging is not obvious, a fast recognition method of sorting images based on deep learning and dual tree complex wavelet transform was studied. Sorting images are not very clear due to factors such as the enclosed environment and the weak lighting conditions of the warehouse. First, the dual tree complex wavelet transform is used to preprocess the sorting image for noise reduction and other image preprocessing. Second, a convolutional neural network (CNN) was designed. On the basis of Alexnet neural network, parameters of convolutional layer, ReLU layer and pooling layer of CNN are redefined to accelerate the learning speed of neural network. Lastly, according to the new image classification task, the last three layers of the neural network, the full connection layer, the softmax layer and the classification output layer are defined to adapt to the new image recognition. The proposed fast sorting image recognition technology based on deep learning has higher training speed and recognition accuracy in the face of more complicated sorting image recognition, which can meet the experimental requirements. Rapid identification of sorting images is of great significance to improve the efficiency of logistics in unmanned warehouses.

Production of hydroxy fatty acids and its effects on photosynthesis in the cyanobacterium Synechocystis sp. PCC 6803

Microalgal lipids and fatty acids are important components for achieving biofuel because of their potential high productivity. Although fatty acids that have a hydroxy group adjacent to the end of the acyl chain might be an important chemical feedstock, most algae do not accumulate it. To produce (ω−1)-hydroxy fatty acids from 3-hydroxybutylyl-CoA, an intermediate for polyhydroxybutylate biosynthesis in the cyanobacterium Synechocystis sp. PCC 6803, we expressed a gene for the promiscuous 3-ketoacyl-ACP synthase III from Alicyclobacillus acidocalderius (aaKASIII) by the cpc560 promoter. To supply 3-hydroxybutyryl-CoAs for aaKASIII, the phaC gene for polyhydroxybutylate polymerase was deleted, and the phaAB genes for 3-hydroxybutyryl-CoA synthesis from Cupriavidus necator were overexpressed. The genetically modified strain synthesized 15-hydroxyhexadecanoic acid, 17-hydroxyoctadecanoic acid, and 17-hydroxyoctadec-9-enoic acid, and accumulated approximately 2.1 mol% of (ω−1)-hydroxy fatty acids in total fatty acids under illumination with 70 μmol photons m−2 s−1, although its growth was severely retarded. Under weak light (35 μmol photons m−2 s−1) conditions, the strain grew as well as the wild-type and showed lower hydroxy fatty acids (0.04 mol%) accumulation than that at higher illumination levels. The photosynthetic activity of this strain was lower than that of wild-type cells, suggesting that high light conditions enhanced hydroxy fatty acids production and inhibited photosynthesis. (ω−1)-Hydroxy fatty acids were not predominantly observed in the galactolipids from thin-layer chromatography, which are the major lipid classes in cyanobacteria. To the best of our knowledge, this is the first report on photoautotrophic production of fatty acids possessing a functional group near the end of the acyl chain in cyanobacteria.

Comprehensive comparison of single-pixel imaging methods

Single-pixel imaging is a novel computational imaging scheme. It allows one to use a spatially unresolvable photodetector to acquire the spatial information of objects and reconstruct images by a computational means. The core of single-pixel imaging is encoding the spatial information of objects into one-dimensional light signals by using spatial light modulation and subsequently decoding the information to reconstruct the image. Such a novel imaging scheme has a potential of tacking some challenges in conventional imaging, such as imaging with non-visible light, imaging under weak-light conditions, imaging through turbid media, etc. However, the practicality of single-pixel imaging is limited by its imaging quality and efficiency. Thus, how to improve the imaging quality and reduce the imaging time in single-pixel imaging is extensively explored in the field. In this paper, we comprehensively investigate five representative and widely used single-pixel imaging methods – computational ghost imaging, compressive sensing ghost imaging, Hadamard single-pixel imaging, Fourier single-pixel imaging, and binary Fourier single-pixel imaging. We review the principle of these methods and compare the performance of these methods by numerical simulations and experiments. The comparison not only reveals the connections and differences among these methods, but also shows the advantages and disadvantages of their own. This paper also discusses the problems that remain to be solved in single-pixel imaging and prospects for the future development.

The cold-induced switch in direction of chloroplast relocation occurs independently of changes in endogenous phototropin levels.

When exposed to fluctuating light intensity, chloroplasts move towards weak light (accumulation response), and away from strong light (avoidance response). In addition, cold treatment (5°C) induces the avoidance response even under weak-light conditions (cold-avoidance response). These three responses are mediated by the phototropin (phot), which is a blue-light photoreceptor and has also been reported to act as a thermosensory protein that perceives temperature variation. Our previous report indicated that cold-induced changes in phot biochemical activity initiate the cold-avoidance response. In this study, we further explored the induction mechanism of the cold-avoidance response in the liverwort Marchantia polymorpha and examined the relationship between changes in the amount of phot and the induction of the cold-avoidance response. The switch between the accumulation and avoidance responses occurs at a so-called ‘transitional’ light intensity. Our physiological experiments revealed that a cold-mediated decrease in the transitional light intensity leads to the induction of the cold-avoidance response. While artificial overexpression of phot decreased the transitional light intensity as much as cold treatment did, the amount of endogenous phot was not increased by cold treatment in wild-type M. polymorpha. Taken together, these findings show that the cold-avoidance response is initiated by a cold-mediated reduction of the transitional light intensity, independent of the amount of endogenous phot. This study provides a clue to understanding the mechanism underlying the switch in direction of chloroplast relocation in response to light and temperature.

Reducing current fluctuation of Cs3Bi2Br9 perovskite photodetectors for diffuse reflection imaging with wide dynamic range

Recently, the newly booming metal halide perovskites have attracted extensive attention worldwide due to their outstanding optoelectronic performance, and are expected to be ideal candidates for photodetectors (PDs). However, there is still lack of perovskite PDs-based imaging devices coming into commercialization stage, due to some practical reasons including toxicity brought by lead-based perovskites and the large light current fluctuations. In this paper, for the first time we fabricate a lead-free Cs3Bi2Br9 perovskite PD, and build a prototype of this perovskite PD-based imaging system with diffuse reflection imaging mode. Moreover, we propose a new parameter F related to light current fluctuation to evaluate imaging performance of a PD especially for weak diffuse light condition, and prove its usability by comparison of unoptimized lead-free Cs3Bi2Br9 perovskite PD and atomic layer deposition (ALD) optimized Cs3Bi2Br9 PD. ALD-optimization can improve the quality of perovskite film and suppress the dark current and current fluctuation. Finally, we obtain satisfactory diffuse reflection images of 2D and 3D objects with wide dynamic range. Therefore, the ALD-optimized Cs3Bi2Br9 PD has addressed two major concerns about perovskite PDs-based imaging devices, that may extend application of perovskite materials and improve imaging quality.

Gait Recognition for Co-Existing Multiple People Using Millimeter Wave Sensing

Gait recognition, i.e., recognizing persons from their walking postures, has found versatile applications in security check, health monitoring, and novel human-computer interaction. The millimeter-wave (mmWave) based gait recognition represents the most recent advance. Compared with traditional camera-based solutions, mmWave based gait recognition bears unique advantages of being still effective under non-line-of-sight scenarios, such as in black, weak light, or blockage conditions. Moreover, they are able to accomplish person identification while preserving privacy. Currently, there are only few works in mmWave gait recognition, since no public data set is available. In this paper, we build a first-of-its-kind mmWave gait data set, in which we collect gait of 95 volunteers 'seen' from two mmWave radars in two different scenarios, which together lasts about 30 hours. Using the data set, we propose a novel deep-learning driven mmWave gait recognition method called mmGaitNet, and compare it with five state-of-the-art algorithms. We find that mmGaitNet is able to achieve 90% accuracy for single-person scenarios, 88% accuracy for five co-existing persons, while the existing methods achieve less than 66% accuracy for both scenarios.

Phototropin2 Contributes to the Chloroplast Avoidance Response at the Chloroplast-Plasma Membrane Interface.

Blue-light-induced chloroplast movements play an important role in maximizing light utilization for photosynthesis in plants. Under a weak light condition, chloroplasts accumulate to the cell surface to capture light efficiently (chloroplast accumulation response). Conversely, chloroplasts escape from strong light and move to the side wall to reduce photodamage (chloroplast avoidance response). The blue light receptor phototropin (phot) regulates these chloroplast movements and optimizes leaf photosynthesis by controlling other responses in addition to chloroplast movements. Seed plants such as Arabidopsis (Arabidopsis thaliana) have phot1 and phot2. They redundantly mediate phototropism, stomatal opening, leaf flattening, and the chloroplast accumulation response. However, the chloroplast avoidance response is induced by strong blue light and regulated primarily by phot2. Phots are localized mainly on the plasma membrane. However, a substantial amount of phot2 resides on the chloroplast outer envelope. Therefore, differentially localized phot2 might have different functions. To determine the functions of plasma membrane- and chloroplast envelope-localized phot2, we tethered it to these structures with their respective targeting signals. Plasma membrane-localized phot2 regulated phototropism, leaf flattening, stomatal opening, and chloroplast movements. Chloroplast envelope-localized phot2 failed to mediate phototropism, leaf flattening, and the chloroplast accumulation response but partially regulated the chloroplast avoidance response and stomatal opening. Based on the present and previous findings, we propose that phot2 localized at the interface between the plasma membrane and the chloroplasts is required for the chloroplast avoidance response and possibly for stomatal opening as well.

Three-Dimensional Imaging via Time-Correlated Single-Photon Counting

Three-dimensional (3D) imaging under the condition of weak light and low signal-to-noise ratio is a challenging task. In this paper, a 3D imaging scheme based on time-correlated single-photon counting technology is proposed and demonstrated. The 3D imaging scheme, which is composed of a pulsed laser, a scanning mirror, single-photon detectors, and a time-correlated single-photon counting module, employs time-correlated single-photon counting technology for 3D LiDAR (Light Detection and Ranging). Aided by the range-gated technology, experiments show that the proposed scheme can image the object when the signal-to-noise ratio is decreased to −13 dB and improve the structural similarity index of imaging results by 10 times. Then we prove the proposed scheme can image the object in three dimensions with a lateral imaging resolution of 512 × 512 and an axial resolution of 4.2 mm in 6.7 s. At last, a high-resolution 3D reconstruction of an object is also achieved by using the photometric stereo algorithm.

High-precision laser spot center positioning method for weak light conditions.

In the acquisition stage of many space applications, such as the Taiji program, the spot center of weak laser light must be accurately determined. Under weak light conditions, the precision of most traditional positioning methods is greatly affected. In this paper, we present a high-precision laser spot center positioning method based on the theoretical analysis of influence factors of precision. It is shown through experimental study that the method's precision can fulfill the requirement of the Taiji program.

The influence of bilateral environment of dyed-TiO2/electrolyte interface on detailed recombination process during the “mature” period of sensitized solar cell

The complete dye-sensitized solar cell (DSC) life cycle includes three stages: “mature” period, stability period and degradation period. However, during the DSC performance adjustment period, considering the influence of both sides of the dyed-TiO2/electrolyte interface on the electron recombination process is still blank. In this paper, the effects of the environment on both sides of the interface between TiO2 and electrolyte during the DSC performance adjustment on the electron recombination process are studied. The results show that the performance adjustment of DSC is greatly influenced by the chemical environment of electrolyte. The film microstructures have a certain influence on the electron recombination process during the performance adjustment. During the performance adjustment period of DSC, the adjustment of quasi-Fermi level is more complicated under the condition of weak light than under the condition of strong light. The results of this paper are significant for studying complex systems of DSC, understanding the device working mechanism and improving the cell efficiency.

A Laser Interferometer Prototype with Pico-Meter Measurement Precision for Taiji Space Gravitational Wave Detection Missionin China

The laser interferometer is one of the most important key technologies for the space gravitational wave detection. A laser interferometer prototype with pico-meter measurement precision for Taiji mission in China is presented in the paper. The results showed that the path-length measurement precision reached 5 pm/√Hz within the frequency range of 10 mHz – 1 Hz by improving the temperature fluctuation noise and electronic readout noise of the laser interferometer, which meets the requirement of Taiji Pathfinder mission inside the frequency range of 1 mHz – 1 Hz under the weak-light condition. It would be a fine experimental platform for the key technologies demonstration including the laser pointing modulation and the laser phase-locking control to improve the precision for the low measurement noise.

Semiautomated Device for Plucking of Flower Buds

Indians are celebrating more number of festivals than any other country. In festival celebrations, flowers are used as a prime element. Without flowers we will not celebrate even single festival. Most popular flowers in south India is Nerium oleander, jasmine, rose, etc. These flowers are demanded high among the flowers due to its fragrance. Another added advantage is its less cost. Though it has many advantages, certain drawbacks limit the business. One major problem is plucking flower at the right time. It is very difficult task because the workers must pluck the flowers before its blossom. So, they have to pluck early morning around 4’o clock under weak light condition. At weak light condition workers may not able to identify the insects and snakes. Because of this workers efficiency is reduced as well as some of them died. To overcome this problem, we proposed a device for plucking and packing of flower buds. The proposed device can able to move forward, backward and rotate. Camera with light is used to capture the image of the flower bud. Image processing technique is used to match the image of the bud. Robot arm is used to pluck the bud. Container is used to pack the buds. The proposed device is a waterproof device.

Semiautomated Device for Plucking of Flower Buds

Indians are celebrating more number of festivals than any other country. In festival celebrations, flowers are used as a prime element. Without flowers we will not celebrate even single festival. Most popular flowers in south India is Nerium oleander, jasmine, rose, etc. These flowers are demanded high among the flowers due to its fragrance. Another added advantage is its less cost. Though it has many advantages, certain drawbacks limit the business. One major problem is plucking flower at the right time. It is very difficult task because the workers must pluck the flowers before its blossom. So, they have to pluck early morning around 4’o clock under weak light condition. At weak light condition workers may not able to identify the insects and snakes. Because of this workers efficiency is reduced as well as some of them died. To overcome this problem, we proposed a device for plucking and packing of flower buds. The proposed device can able to move forward, backward and rotate. Camera with light is used to capture the image of the flower bud. Image processing technique is used to match the image of the bud. Robot arm is used to pluck the bud. Container is used to pack the buds. The proposed device is a waterproof device.