SUMMARY
It is essential to pick P-wave and S-wave arrival times rapidly and accurately for the microseismic monitoring systems. Meanwhile, it is not easy to identify the arrivals at a true phase ...automatically using traditional picking method. This is one of the reasons that many researchers are trying to introduce deep neural networks to solve these problems. Convolutional neural networks (CNNs) are very attractive for designing automatic phase pickers especially after introducing the fundamental network structure from semantic segmentation field, which can give the probability outputs for every labelled phase at every sample in the recordings. The typical segmentation architecture consists of two main parts: (1) an encoder part trained to extracting coarse semantic features; (2) a decoder part responsible not only for recovering the input resolution at the output but also for obtaining sparse representation of the objects. The fundamental segmentation structure performs well; however, the influence of the parameters in the structure on the pickers has not been investigated. It means that the structure design just depends on experience and tests. In this paper, we solve two main questions to give some guidance on network design. First, we show what sparse features will learn from the three-component microseismic recordings using CNNs. Second, the influence of two key parameters in the network on pickers, namely, the depth of decoder and activation functions, is analysed. Increasing the number of levels for a certain layer in the decoder will increase the burden of demand on trainable parameters, but it is beneficial to the accuracy of the model. Reasonable depth of the decoder can balance prediction accuracy and the demand of labelled data, which is important for microseismic systems because manual labelling process will decrease the real-time performance in monitoring tasks. Standard rectified linear unit (ReLU) and leaky rectified linear unit (Leaky ReLU) with different negative slopes are compared for the analysis. Leaky ReLU with a small negative slope can improve the performance of a given model than ReLU activation function by keeping some information about the negative parts.
The main production area of Camellia vietnamensis (C. vietnamensis) is in the low mountain and hilly areas of southern China. The low survival rate of seedlings caused by drought is one of the main ...obstacles restricting the development of the C. vietnamensis industry. An exploration of the key adaptation mechanism of C. vietnamensis to drought stress is important in order to improve its drought resistance. We conducted a study on the morphological, physiological, biochemical, and drought resistance-related genes of five C. vietnamensis cultivars grown in Hainan province under varying degrees of drought stress. The results indicate that drought stress can lead to a decrease in the relative water content and photosynthetic capacity of C. vietnamensis leaves. Compared with the control, the drought damage index, malondialdehyde, relative electrical conductivity, soluble protein, soluble sugar and proline contents of the five C. vietnamensis cultivars increased with drought-stress duration and degree. With increasing drought-stress intensity, the activity of antioxidant enzymes and the content of related metabolites (total polyphenols, total flavonoids, tea saponins) gradually increased, and the expression levels of phenylpropanoid pathway-related genes (Cv4CL1, CvCAD1, CvCAD2, CvPOX1, CvPOX2, CvPOX3) were upregulated. Based on the results of the drought tolerance coefficients, principal component analysis, and hierarchical cluster analysis, we classified five C. vietnamensis cultivars into drought-tolerant cultivars (‘Haida 1’); moderately drought-tolerant cultivars (‘Haida 4’ and ‘Wanhai 4’); and drought-sensitive cultivars (‘Wanhai 3’ and ‘Wanhai 1’). The results of this study provide a theoretical basis for the promotion and cultivation of C. vietnamensis and the selection of drought-resistant cultivars.
A series of tetrathiophene‐based fully non‐fused ring acceptors (4T‐1, 4T‐2, 4T‐3, and 4T‐4), which can be paired with the star donor polymer PBDB‐T to fabricate highly efficient organic solar cells ...are developed. Tailoring the size of lateral chains can tune the solubility and packing mode of acceptor molecules in neat and blend films. It is found that the incorporation of 2‐ethylhexyl chains can effectively change the compatibility with the donor polymer PBDB‐T, and an encouraging power conversion efficiency of 10.15% is accomplished by 4T‐3‐based organic solar cells. It also presents good compatibility with the other polymer donor and an even higher power conversion efficiency (PCE) of 12.04% is achieved based on D18:4T‐3 blend, which is the champion PCE for the fully non‐fused acceptors. Importantly, these inexpensive tetrathiophene fully non‐fused ring acceptors provide cost‐effective photovoltaic performance. The results demonstrate a high photovoltaic performance from synthetically inexpensive materials could be achieved by the rational design of non‐fused ring acceptor molecules.
Four tetrathiophene‐based fully non‐fused acceptors are obtained via simple syntheses. The side chain selection is crucially important to the corresponding solubility, absorption, packing mode etc. The four 2‐ethylhexyl functionalized 4T‐3 achieves a champion power conversion efficiency of 12.04% with an excellent figure‐of‐merit of 32.8, which is the highest value among the reported acceptors. Such cost‐effective strategy paves new way for future commercial applications.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Distributed acoustic sensing (DAS) is an innovative seismic data acquisition technology in the field of seismic monitoring. It has emerged as a highly attractive and promising fiber-optic sensing ...technology over the past decade. DAS uses Rayleigh scattering to localize and restore information about fiber vibrations. However, the response of optical fibers to seismic waves is primarily limited to the axial direction due to inherent characteristics of the glass fiber material. As a result, traditional DAS monitoring is restricted to capturing a single component of the seismic signal. To address this limitation and enable optical fibers to have a multicomponent response to seismic waves, this article proposes a DAS-based three-component fiber-optic geophone. Unlike conventional geophone, this proposed scheme does not include any electronic elements, relying solely on the optical fiber for sensing purposes. In this article, the equations of motion for the proposed scheme are derived in detail, and a physical prototype is successfully produced based on the theoretical derivation. We then performed active source excitation experiments in which the proposed three-component fiber-optic geophone captured the acceleration characteristics of the three-component vibration signal and successfully expressed it in phase form, which reflects the strain change in the optical fiber, and compared with the control group (traditional geophone), the signal-to-noise ratio (SNR) of this geophone has a slight improvement of about 1.87 dB, satisfying the requirements of high SNR and low power consumption. At the same time, the scheme maintains the time and spatial consistency with the traditional geophone.
Nonfused-ring electron acceptors have attracted much attention in recent years due to their advantages of simple synthetic routes, high yields, low costs, reasonable power conversion efficiencies ...(PCEs), and so on. Herein, three simple A-π-D-π-A-type acceptors (DTC-BO-4F, DTS-BO-4F, and DTP-BO-4F) comprising a tricyclic fused-ring core, two 2,5-bis(alkyloxy)phenylene spacers, and two difluorinated terminal groups (DF-IC) were developed. Compared with DTS-BO-4F, DTC-BO-4F and DTP-BO-4F exhibit higher molar extinction coefficients, stronger crystallinity, and more orderly stacking. The PBDB-T:DTC-BO-4F-based blend film shows suitable phase separation and higher and more balanced charge mobilities. Finally, the photovoltaic devices based on DTC-BO-4F give an outstanding PCE of 13.26% with a small nonradiative voltage loss of 0.23 eV.
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Non‐fullerene acceptors have shown great promise for organic solar cells (OSCs). However, challenges in achieving high efficiency molecular system with conformational unicity and effective molecular ...stacking remain. In this study, we present a new design of non‐fused tetrathiophene acceptor R4T‐1 via employing the encapsulation of tetrathiophene with macrocyclic ring. The single crystal structure analysis reveals that cyclic alkyl side chains can perfectly encapsulate the central part of molecule and generate a conformational stable and planar molecular backbone. Whereas, the control 4T‐5 without the encapsulation restriction displays cis‐ and twisted conformation. As a result, R4T‐1 based OSCs achieved an outstanding power conversion efficiency (PCE) exceeding 15.10 % with a high short‐circuit current density (Jsc) of 25.48 mA/cm2, which is significantly improved by ≈30 % in relative to that of the control. Our findings demonstrate that the macrocyclic encapsulation strategy could assist fully non‐fused electron acceptors (FNEAs) to achieve a high photovoltaic performance and pave a new way for FNEAs design.
A fully non‐fused acceptor R4T‐1 was designed via macrocyclic encapsulation on the simple tetrathiophene, which achieves conformational unicity, eliminates intermolecular electronic cross‐communication at the center and guarantees the formation of efficient charge transport channels. Thus, an impressive power conversion efficiency (PCE) of 15.10 % with a significantly enhanced short‐circuit current density (Jsc) of 25.48 mA/cm2 was accomplished.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We precisely design and synthesize two A−π–D−π–A type dipyran-cored nonfullerene acceptors (NFAs) Ph-DTDP o -OT and Ph-DTDP i -OT with oxygen atoms at the outer and inner positions, respectively. ...3-Hexyloxythiophene is used as the π-spacer to expand the effective conjugation length of the acceptors. These two NFAs possess similar optical band gaps and energy levels. However, the position of the oxygen atom at the dipyran core can markedly influence the molecular packing and aggregation behavior of the resulted acceptors. Ph-DTDP o -OT with a strong intermolecular affinity tends to form larger aggregates blending with PBDB-T, leading to a lower photovoltaic performance; Ph-DTDP i -OT presents good miscibility with PBDB-T and the blend films preferentially adopt a face-on orientation. Ph-DTDP i -OT-based devices display high and balanced hole and electron mobilities, leading to an optimal power conversion efficiency of 11.38%, which is much higher than those of Ph-DTDP o -OT-based ones (7.60%). Moreover, Ph-DTDP i -OT-based devices also exhibit a lower nonradiative recombination voltage loss of 0.268 eV. Our work demonstrates that the π-spacer and chemical structure of the core unit can greatly influence the molecular packing and the morphology of blend films, which are critical to the photovoltaic performance of devices.
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The electron transport layer (ETL) is a critical component in achieving high device performance and stability in organic solar cells. Conjugated polyelectrolytes (CPEs) have become an attractive ...alternative due to film‐forming properties and ease of preparation. However, p‐type CPEs generally exhibit poor charge mobility and conductivity, incorporation of electron‐withdrawing units forming alternated D‐A conjugated backbone can make up for these deficiencies. Herein, the ratio of electron withdrawing moieties are further increased and two poly(A1‐alt‐A2) typed PIIDNDI‐Br and PDPPNDI‐Br based on the combination of naphthalene diimide (NDI) with isoindigo (IID) or diketopyrrolopyrrole (DPP) via direct arylation polycondensation are synthesized. These CPEs possess excellent alcohol solubility, a suitable lowest unocuppied molecular orbital energy level, and work function tunability. Surprisingly, the incorporation of IID and DPP units generate distinct self‐doping behaviors, which are confirmed by UV–vis absorption and ESR spectra. However, no matter doped or undoped, both CPEs present better charge‐transporting properties and conductivity when utilized as ETLs. The PIIDNDI‐Br and PDPPNDI‐Br display good universal compatibility with the blend of PM6:Y6 and PM6:L8‐BO, and PCEs of 18.32% and 18.36% are obtained, respectively, which also present excellent storage stability. In short, the combination of two different acceptors demonstrates an efficient strategy to design highly efficient ETLs for high performance photovoltaic devices.
Two conjugated polyelectrolytes of PIIDNDI‐Br and PDPPNDI‐Br are designed via direct arylation polycondensation. The A1‐A2 conjugated backbone ensures good charge‐transporting properties and high conductivity, whereas distinct self‐doping effect are observed for different acceptor combination. The PDPPNDI‐Br and PIIDNDI‐Br‐based organic solar cells exhibit high power conversion efficiencies of 18.32% and 18.36%. Such dual‐acceptor strategy of electron transport layers is efficient for thickness‐insensitive and high‐performance photovoltaic devices.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The rapid advance of fused-ring electron acceptors (FREAs) has made them a potential substitute to fullerene-based acceptors and offered new avenues for the construction of organic solar cells ...(OSCs). Nonfused-ring acceptors (NFRAs) could significantly reduce the synthetic cost while achieving reasonable power conversion efficiencies (PCEs). Widely used fullerene acceptors have been applied as a second acceptor to regulate the morphology, absorption, and electron transport. To take full advantage of both nonfullerene and fullerene acceptors at the same time, we rationally designed and synthesized two novel NFRAs with phenyl-C
-butyric acid methyl ester (PCBM) as the lateral pendent. With the incorporation of fullerene pendent in
and
, varied UV-vis absorption and photoluminescence (PL) quenching behaviors were observed, and isotropic diffraction patterns were obtained via grazing incidence wide-angle X-ray scattering (GIWAXS) measurements. The bulky, spherical, and electronic isotropic fullerene pendent could effectively suppress severe molecular aggregation and form the preferred blend morphology. This strategy significantly improved the efficiencies for exciton separation and charge collection relative to the control acceptor
. Finally, the
,
, and fill factor (FF) of
-based devices were simultaneously improved and an enhanced PCE of 13.55% was accomplished.
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