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"XIAOJUN LI"
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Monitoring and modeling of global changes : a geomatics perspective
The chapters in this book present state-of-the-art geomatics technologies applied in global environmental studies. This text provides the latest research findings and delivers complete references to related publications. This book will motivate the undergraduate and graduate students, researchers and practitioners to better understand the environmental changes with informed solutions. Global change studies are increasingly considered a vital source of information to understand the Earth Environment, especially in the framework of human-induced, climate change and land use transformation. 'Satellite Earth Observing systems' and geomatics technologies provide a unique tool to monitor and model the changes, respectively. While the range of applications and innovative techniques are always increasing, this book provides a summary of key study cases where satellite data offers critical information to understand the usefulness of the geomatics technologies and global environmental issues. Geomatics technologies provide powerful tools to model and analyze the effects of those global environmental changes towards minimizing their adverse impacts on human health and the environment.
Book
Effect of Acetone Extract of Salvia miltiorrhiza Bunge on Feeding Selection Behavior of Diamondback Moth Larvae
ABSTRACT Diamondback moth (Plutella xylostella) is the most destructive pest on Brassicaceae plants family around the world. The present study investigated the feeding selection behavior of diamondback moth larvae with an approach to the acetone extract effects of Salvia Miltiorrhiza Bunge (SMB). It was found that acetone extracts of Salviami ltiorrhiza Bunge (SIB) represented by cryptotanshinone and dihydrotanshinone had lethal effect on diamondback moth larvae, and the correlation coefficient was 0.972. Through further antifeedant test, it was found that diamondback moth larvae had obvious antifeedant behavior to acetone extracts of SIB represented by cryptotanshinone and dihydrotanshinone, and the correlation coefficient was-0.915. By further observing the influence of acetone extract of SIB on the feeding selection behavior of diamondback moth larvae, it was found that diamondback moth larvae had obvious avoidance behavior towards acetone extract of SIB. Therefore, it can be considered that acetone extract of SIB can affect the feeding behavior of diamondback moth insects because of its biological effects such as dihydrotanshinone and cryptotanshinone. This effect is firstly fatal to diamondback moth larvae after feeding, and may also cause antifeedant and aversion of diamondback moth larvae.
Journal Article
Public opinion, international reputation, and audience costs in an authoritarian regime
Does the public in authoritarian regimes disapprove of their leaders' backing down from public threats and commitments? Answers to this question provide a critical micro-foundation for the emerging scholarship on authoritarian audience costs. We investigate this question by implementing a series of survey experiments in China, a single-party authoritarian state. Findings based on responses from 5375 Chinese adults show that empty threats and commitments expose the Chinese government to substantial disapproval from citizens concerned about potential damage to China's international reputation. Additional qualitative evidence reveals that Chinese citizens are willing to express their discontent of leaders' foreign policy blunders through various channels. These findings contribute to the ongoing debate over whether and how domestic audiences can make commitments credible in authoritarian states.
Journal Article
Precise synthesis and photovoltaic properties of giant molecule acceptors
Series of giant molecule acceptors DY, TY and QY with two, three and four small molecule acceptor subunits are synthesized by a stepwise synthetic method and used for systematically investigating the influence of subunit numbers on the structure-property relationship from small molecule acceptor YDT to giant molecule acceptors and to polymerized small molecule acceptor PY-IT. Among these acceptors-based devices, the TY-based film shows proper donor/acceptor phase separation, higher charge transfer state yield and longer charge transfer state lifetime. Combining with the highest electron mobility, more efficient exciton dissociation and lower charge carrier recombination properties, the TY-based device exhibits the highest power conversion efficiency of 16.32%. These results indicate that the subunit number in these acceptors has significant influence on their photovoltaic properties. This stepwise synthetic method of giant molecule acceptors will be beneficial to diversify their structures and promote their applications in high-efficiency and stable organic solar cells.
The synthesis of giant molecule acceptors with more than two subunits was challenging. Here, the authors present a stepwise precise synthetic method for acceptors of this type, explore and compare their photovoltaic performance to those of polymerized small molecule acceptor for organic solar cells.
Journal Article
Historical Ownership and Territorial Disputes
Some of the most enduring and dangerous territorial disputes often involve claims of historical ownership by at least one side of a dispute. Why does historical ownership lead to more hardened bargaining stances than in other territorial disputes? Do such uncompromising positions lead to more military conflict? We investigate these questions in this study. After developing a theoretical argument for how historical ownership may lead to a perception of territorial indivisibility, we test the hypotheses derived from the theory with a survey experiment implemented in China.We find that a historical ownership treatment increases the number of respondents who view the indivisible outcome of a hypothetical dispute as the only acceptable outcome. Furthermore, those who perceive a territory to be indivisible are more likely to favor economic sanctions and military solutions to the dispute and are much less likely to support bilateral negotiation or arbitration by an international organization.
Journal Article
Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells
Reducing the energy loss of sub-cells is critical for high performance tandem organic solar cells, while it is limited by the severe non-radiative voltage loss via the formation of non-emissive triplet excitons. Herein, we develop an ultra-narrow bandgap acceptor BTPSeV-4F through replacement of terminal thiophene by selenophene in the central fused ring of BTPSV-4F, for constructing efficient tandem organic solar cells. The selenophene substitution further decrease the optical bandgap of BTPSV-4F to 1.17 eV and suppress the formation of triplet exciton in the BTPSV-4F-based devices. The organic solar cells with BTPSeV-4F as acceptor demonstrate a higher power conversion efficiency of 14.2% with a record high short-circuit current density of 30.1 mA cm
−2
and low energy loss of 0.55 eV benefitted from the low non-radiative energy loss due to the suppression of triplet exciton formation. We also develop a high-performance medium bandgap acceptor O1-Br for front cells. By integrating the PM6:O1-Br based front cells with the PTB7-Th:BTPSeV-4F based rear cells, the tandem organic solar cell demonstrates a power conversion efficiency of 19%. The results indicate that the suppression of triplet excitons formation in the near-infrared-absorbing acceptor by molecular design is an effective way to improve the photovoltaic performance of the tandem organic solar cells.
Reducing energy loss of sub-cells is critical for high performance tandem organic solar cells. Here, the authors design and synthesize an ultra-narrow bandgap acceptor through replacement of terminal thiophene by selenophene in the central fused ring, achieving efficiency of 19% for tandem cells.
Journal Article
High performance polymerized small molecule acceptor by synergistic optimization on π-bridge linker and side chain
The polymerized small-molecule acceptors have attracted great attention for application as polymer acceptor in all-polymer solar cells recently. The modification of small molecule acceptor building block and the π-bridge linker is an effective strategy to improve the photovoltaic performance of the polymer acceptors. In this work, we synthesized a new polymer acceptor PG-IT2F which is a modification of the representative polymer acceptor PY-IT by replacing its upper linear alkyl side chains on the small molecule building block with branched alkyl chains and attaching difluorene substituents on its thiophene π-bridge linker. Through this synergistic optimization, PG-IT2F possesses more suitable phase separation, increased charge transportation, better exciton dissociation, lower bimolecular recombination, and longer charge transfer state lifetime than PY-IT in their polymer solar cells with PM6 as polymer donor. Therefore, the devices based on PM6:PG-IT2F demonstrated a high power conversion efficiency of 17.24%, which is one of the highest efficiency reported for the binary all polymer solar cells to date. This work indicates that the synergistic regulation of small molecule acceptor building block and π-bridge linker plays a key role in designing and developing highly efficient polymer acceptors.
The modification of small molecule acceptor building block and π−bridge linker is effective to improve photovoltaic performance. Here, the authors replace linear with branched alkyl chains and introduce difluorene-substituted linker to realise all-polymer solar cells with efficiency of 17.24%.
Journal Article
High performance tandem organic solar cells via a strongly infrared-absorbing narrow bandgap acceptor
Tandem organic solar cells are based on the device structure monolithically connecting two solar cells to broaden overall absorption spectrum and utilize the photon energy more efficiently. Herein, we demonstrate a simple strategy of inserting a double bond between the central core and end groups of the small molecule acceptor Y6 to extend its conjugation length and absorption range. As a result, a new narrow bandgap acceptor BTPV-4F was synthesized with an optical bandgap of 1.21 eV. The single-junction devices based on BTPV-4F as acceptor achieved a power conversion efficiency of over 13.4% with a high short-circuit current density of 28.9 mA cm
−2
. With adopting BTPV-4F as the rear cell acceptor material, the resulting tandem devices reached a high power conversion efficiency of over 16.4% with good photostability. The results indicate that BTPV-4F is an efficient infrared-absorbing narrow bandgap acceptor and has great potential to be applied into tandem organic solar cells.
Development of tandem organic solar cells has been limited by the choice of near-infrared absorbing materials for the rear cell. Here, the authors report a simple strategy to extend the conjugation length of acceptor Y6 and broaden its absorption range to near-infrared region. A tandem organic solar cell with efficiency of 16.4% was achieved.
Journal Article
Object detection algorithm based on improved YOLOv8 for drill pipe on coal mines
Gas extraction is an important measure for coal mine gas disaster control. Its effect is closely correlated to the drilling depth. The existing methods usually determine the drilling depth by manually counting the number of drill pipes, and the number of drill pipes can be automatically counted by object detection and real-time tracking algorithms. An improved object detection model was proposed for the problem of the poor performance of the object detection algorithm due to such interference factors as bright light, low illuminance and heavy dust and mist in coal mines. In terms of data augmentation, the ACE dehazing algorithm is introduced to improve image quality. In order to solve the problem of leak detection caused by the irregular shape that appears due to the interference of bright light, the deformable convolution DCNv2 module was integrated in the C2f module to make the sampling points of the convolution kernel diffuse irregularly, so as to fully extract the shape features of the drill pipe and then improve the detection rate of the model. For the problem of too low confidence of the model in detecting drill pipes due to uneven illumination, the attention paid by the model to the features of the drill pipe could be improved by embedding the SimAM non-parametric attention mechanism module in the backbone network, which can further improve the confidence of the drill pipe. For the problem of low average category detection accuracy caused by the changeable environment of the underground drilling site, the dynamic head was used to improve the ability of the model to extract the features of the drill pipe in scale, space, and channel, and improve the average category detection accuracy of the drill pipe. To address the issue of diverse angle differences between predicted and real boxes, CIoU loss function is replaced with the SIoU loss function. Finally, the improved detection algorithm was verified with the homemade drill pipe dataset. The experimental results showed that: the improved model effectively alleviated the problem of partial leak detection of the original network for scenes such as heavy dust and mist and uneven illumination; the recall rate increased by 4.9%; the mean average precision was improved by 5.3%. At the same time, it maintains a high real-time performance (the FPS is 117), providing the basis of the drill pipe detection model for the application of real-time tracking of the number of drill pipes.
Journal Article