Six model compounds have been synthesized and used for probing the structural features of the Mn cluster in oxygen_evolving complex (OEC) of photosystem Ⅱ (PSⅡ). The model compounds contain Mn 2(μ_O) 2 and μ_O_...Six model compounds have been synthesized and used for probing the structural features of the Mn cluster in oxygen_evolving complex (OEC) of photosystem Ⅱ (PSⅡ). The model compounds contain Mn 2(μ_O) 2 and μ_O_μ_carboxylato di_manganese structural units, which offer Mn—Mn, Mn……Mn, and Mn—O(N) structural parameters consistent with the corresponding data of the OEC in PSⅡ, implying that the Mn cluster in OEC may possess similar structural features. Two model compounds containing halide anion have been used for discussing the binding of Cl - to Mn in PSⅡ. It is suggested that in the five S states, ligand exchange would lead to the ligation of chloride to Mn in the S states with Mn of higher valence.展开更多
The photosynthetic oxygen-evolving center(OEC)is a unique Mn_(4)CaO_(5)cluster catalyzing the water oxidation into electrons,protons and O_(2)through a five-intermediate state cycle(Sn,n=0,1,2,3,4).The modeling of OEC...The photosynthetic oxygen-evolving center(OEC)is a unique Mn_(4)CaO_(5)cluster catalyzing the water oxidation into electrons,protons and O_(2)through a five-intermediate state cycle(Sn,n=0,1,2,3,4).The modeling of OEC is essential for understanding the water oxidation mechanism and developing high efficient water oxidation catalysts.Recently,a series of Mn_(4)CaO_(4)model complexes have been synthesized,which have very similar structures to OEC and also show reactivity of water oxidation.In this work,we employed DFT method to investigate the stability of Mn_(4)CaO_(4)model complex in oxidative conditions,aiming to figure out whether it decomposes itself to release O_(2)during the catalytic water oxidation process.We discovered that the barrier for the O−O bond formation is quite high in the S1 and S2 states,while decreases to 40.2 kcal/mol in the S3 state,indicating the good stability in all oxidation states under normal conditions.Acetonitrile and pyridine can effectively reduce the barrier to 36.5 kcal/mol and 29.9 kcal/mol,respectively.Therefore,strong Lewis base,such as pyridine,could be harmful to the stability of Mn_(4)CaO_(4)and shall be avoided when designing such a catalytic system.Once the O−O bond is formed,Mn_(4)CaO_(4)in the S3 state can readily decompose to O_(2),solvated Ca^(2+)and Mn_(4)O_(2)complex,with the assistance of acetonitrile or pyridine.As a comparison,the O_(2)decomposition in the S2 state is kinetically hindered and thermodynamically disfavored.The S4 state Mn_(4)CaO_(4)has a much lower barrier for O-O bond formation,and is unstable.However,the S4 state Mn_(4)CaO_(4)is difficult to achieve under water oxidation condition,as evidenced by the calculated redox potential of 2.3 V for S3→S4 transition.展开更多
Oxygen-evolving complex （OEC） protein is the original name for membrane-peripheral subunits of photosystem （PS） II. Recently, multiple isoforms and homologs for OEC proteins have been iden- tified in the chloropla...Oxygen-evolving complex （OEC） protein is the original name for membrane-peripheral subunits of photosystem （PS） II. Recently, multiple isoforms and homologs for OEC proteins have been iden- tified in the chloroplast thylakoid lumen, indicating that functional diversification has occurred in the OEC family. Gene expression profiles suggest that the Arabidopsis OEC proteins are roughly categorized into three groups： the authentic OEC group, the stressresponsive group, and the group including proteins related to the chloroplast NAD（P）H dehydrogenase （NDH） complex involved in cyclic electron transport around PSI. Based on the above gene expression profiles, molecular functions of the OEC family proteins are discussed together with our current knowledge about their functions.展开更多
Cytochrome b_559 in photosystem Ⅱ reaction center was purified from spinach ( Spinacia oleracea L.) and rice ( Oryza sativa L.) by a rapid and simple procedure. Their low temperature fluorescence emission and e...Cytochrome b_559 in photosystem Ⅱ reaction center was purified from spinach ( Spinacia oleracea L.) and rice ( Oryza sativa L.) by a rapid and simple procedure. Their low temperature fluorescence emission and excitation spectra, ultraviolet fluorescence spectra and absolute absorption spectra were presented. The author's purification methods, which enhanced the yield of pure protein and shorted the time for isolation, have several advantages: 1. use of oxygen_evolving PSⅡ core complexes as the starting material in order to avoid disturbing from other cytochromes; 2. isocratic elution of cytochrome b_559 from a DEAE_Sephacel column for eliminating the impurity and yielding the protein in pure state; 3. a simple column procedure for removal of excess Triton X_100. Purified cytochromes b_559 from these species have similar optical spectra and mobility during gel electrophoresis under native conditions. From the results of novel electrophoresis (Tricine_SDS_PAGE), cytochrome b_559 from both spinach and rice reveal two polypeptide bands (apparent molecular weight 9 kD and 4 kD, respectively). By measuring of 77 K fluorescence spectra, it was shown that for the purified cytochrome b_559 there were two excitation peaks at 439 nm and 413 nm, and two emission peaks at 563 nm and 668 nm. This is the first indication that Cyt b_559 is able to emit fluorescence and also transfer excited electrons to chlorophyll. By the use of ultraviolet fluorescence spectra, it was demonstrated for the first time that the location of Trp residue could be in the hydrophobic transmembrane region of cytochrome b_559.展开更多
Three copper(Ⅱ),nickel and cadmium(Ⅱ)complexes,namely[Cu_(2)(μ-H2dbda)2(phen)2]·2H_(2)O(1),[Ni(μ-H2dbda)(μ-bpb)(H_(2)O)2]n(2),and[Cd(μ-H2dbda)(μ-bpa)]n(3),have been constructed hydrothermally using H4dbda(...Three copper(Ⅱ),nickel and cadmium(Ⅱ)complexes,namely[Cu_(2)(μ-H2dbda)2(phen)2]·2H_(2)O(1),[Ni(μ-H2dbda)(μ-bpb)(H_(2)O)2]n(2),and[Cd(μ-H2dbda)(μ-bpa)]n(3),have been constructed hydrothermally using H4dbda(4,4'-dihydroxy-[1,1'-biphenyl]-3,3'-dicarboxylic acid),phen(1,10-phenanthroline),bpb(1,4-bis(pyrid-4-yl)benzene),bpa(bis(4-pyridyl)amine),and copper,nickel and cadmium chlorides at 160℃.The products were isolated as stable crystalline solids and were characterized by IR spectra,elemental analyses,thermogravimetric analyses,and singlecrystal X-ray diffraction analyses.Single-crystal X-ray diffraction analyses revealed that three complexes crystallize in the monoclinic P21/n,tetragonal I42d,and orthorhombic P21212 space groups.The complexes exhibit molecular dimers(1)or 2D metal-organic networks(2 and 3).The catalytic performances in the Knoevenagel reaction of these complexes were investigated.Complex 1 exhibits an effective catalytic activity and excellent reusability as a heterogeneous catalyst in the Knoevenagel reaction at room temperature.CCDC:2463800,1;2463801,2;2463802,3.展开更多
Six new lanthanide complexes:[Ln(3,4-DEOBA)3(4,4'-DM-2,2'-bipy)]2·2C_(2)H_(5)OH,[Ln=Dy(1),Eu(2),Tb(3),Sm(4),Ho(5),Gd(6);3,4-DEOBA-=3,4-diethoxybenzoate,4,4'-DM-2,2'-bipy=4,4'-dimethyl-2,2'...Six new lanthanide complexes:[Ln(3,4-DEOBA)3(4,4'-DM-2,2'-bipy)]2·2C_(2)H_(5)OH,[Ln=Dy(1),Eu(2),Tb(3),Sm(4),Ho(5),Gd(6);3,4-DEOBA-=3,4-diethoxybenzoate,4,4'-DM-2,2'-bipy=4,4'-dimethyl-2,2'-bipyridine]were successfully synthesized by the volatilization of the solution at room temperature.The crystal structures of six complexes were determined by single-crystal X-ray diffraction technology.The results showed that the complexes all have a binuclear structure,and the structures contain free ethanol molecules.Moreover,the coordination number of the central metal of each structural unit is eight.Adjacent structural units interact with each other through hydrogen bonds and further expand to form 1D chain-like and 2D planar structures.After conducting a systematic study on the luminescence properties of complexes 1-4,their emission and excitation spectra were obtained.Experimental results indicated that the fluorescence lifetimes of complexes 2 and 3 were 0.807 and 0.845 ms,respectively.The emission spectral data of complexes 1-4 were imported into the CIE chromaticity coordinate system,and their corre sponding luminescent regions cover the yellow light,red light,green light,and orange-red light bands,respectively.Within the temperature range of 299.15-1300 K,the thermal decomposition processes of the six complexes were comprehensively analyzed by using TG-DSC/FTIR/MS technology.The hypothesis of the gradual loss of ligand groups during the decomposition process was verified by detecting the escaped gas,3D infrared spectroscopy,and ion fragment information detected by mass spectrometry.The specific decomposition path is as follows:firstly,free ethanol molecules and neutral ligands are removed,and finally,acidic ligands are released;the final product is the corresponding metal oxide.CCDC:2430420,1;2430422,2;2430419,3;2430424,4;2430421,5;2430423,6.展开更多
Three zinc(Ⅱ),nickel(Ⅱ),and cadmium(Ⅱ)complexes,namely[Zn(μ-Htpta)(py)_(2)]n(1),[Ni(H_(2)biim)2(H_(2)O)2][Ni(tpta)(H_(2)biim)2(H_(2)O)]2·3H_(2)O(2),and[Cd_(3)(μ4-tpta)2(μ-dpe)_(3)]_(n)(3),have been construc...Three zinc(Ⅱ),nickel(Ⅱ),and cadmium(Ⅱ)complexes,namely[Zn(μ-Htpta)(py)_(2)]n(1),[Ni(H_(2)biim)2(H_(2)O)2][Ni(tpta)(H_(2)biim)2(H_(2)O)]2·3H_(2)O(2),and[Cd_(3)(μ4-tpta)2(μ-dpe)_(3)]_(n)(3),have been constructed hydrothermally at 160℃ using H_(3)tpta([1,1':3',1″-terphenyl]-4,4',5'-tricarboxylic acid),py(pyridine),H_(2)biim(2,2'-biimidazole),dpe(1,2-di(4-pyridyl)ethylene),and zinc,nickel and cadmium chlorides,resulting in the formation of stable crystalline solids which were subsequently analyzed using infrared spectroscopy,element analysis,thermogravimetric analysis,as well as structural analyses conducted via single-crystal X-ray diffraction.The findings from these single-crystal Xray diffraction studies indicate that complexes 1-3 form crystals within the monoclinic system P2_(1)/c space group(1)or triclinic system P1 space group(2 and 3),and possess 1D,0D,and 3D structures,respectively.Complex 1 demonstrated substantial catalytic efficiency and excellent reusability as a heterogeneous catalyst in the reaction of Knoevenagel condensation under ambient temperature conditions.In addition,complex 1 also showcased notable anti-wear performance when used in polyalphaolefin synthetic lubricants.CCDC:2449810,1;2449811,2;2449812,3.展开更多
This paper reports the preparation of three di‑iron complexes containing a thiazole moiety.Esterification of complex[Fe_(2)(CO)_(6)(μ‑SCH_(2)CH(CH_(2)OH)S)](1)with 4‑methylthiazole‑5‑carboxylic acid gave the correspo...This paper reports the preparation of three di‑iron complexes containing a thiazole moiety.Esterification of complex[Fe_(2)(CO)_(6)(μ‑SCH_(2)CH(CH_(2)OH)S)](1)with 4‑methylthiazole‑5‑carboxylic acid gave the corresponding ester[Fe_(2)(CO)_(6)(μ‑tedt)](2),where tedt=SCH_(2)CH(CH_(2)OOC(5‑C_(3)HNSCH_(3)))S.Further reactions of complex 2 with tri(ptolyl)phosphine(tp)or tris(4‑fluorophenyl)phosphine(fp)gave the phosphine‑substituted derivatives[Fe_(2)(CO)_(5)(tp)(μ‑tedt)](3)and[Fe_(2)(CO)_(5)(fp)(μ‑tedt)](4).The structures of the newly prepared complexes were elucidated by elemental analysis,NMR,IR,and X‑ray photoelectron spectroscopy.Moreover,single‑crystal X‑ray diffraction analysis confirmed their molecular structures,showing that they contain a di‑iron core ligated by a bridged dithiolate bearing a thiazole moiety and terminal carbonyls.The electrochemical and electrocatalytic proton reduction were probed by cyclic voltammetry,revealing that three complexes can catalyze the reduction of protons to H_(2) under the electrochemical conditions.For comparison,complex 4 possessed the best efficiency with a turnover frequency of 23.5 s^(-1)at 10 mmol·L^(-1)HOAc concentration.In addition,the fungicidal activity of these complexes was also investigated in this study.CCDC:2477511,2;2477512,3;2477513,4.展开更多
The hydrated tricyclohexyltin theophylline-7-acetic acid(tpH)complex[Sn(C_(6)H_(11))_(3)(tp)(H_(2)O)]was synthesized via an ethanol solvothermal method using tricyclohexyltin hydroxide and tpH in a 1∶1 molar ratio.Th...The hydrated tricyclohexyltin theophylline-7-acetic acid(tpH)complex[Sn(C_(6)H_(11))_(3)(tp)(H_(2)O)]was synthesized via an ethanol solvothermal method using tricyclohexyltin hydroxide and tpH in a 1∶1 molar ratio.The complex was characterized by IR,^(1)H(^(13)C)NMR,elemental analysis,and powder X-ray diffraction,and the crystal structure was determined by single-crystal X-ray diffraction.The crystal belongs to the orthorhombic system with space group Iba2,and the central tin atom is in a five-coordinated trigonal bipyramidal configuration.Quantum chemistry ab initio calculations were performed to investigate the stability,molecular orbital energy,and frontier molecular orbital characteristics of the complex.Additionally,its thermal stability,electrochemical properties,and in vitro anticancer activity were evaluated.CCDC:2380308.展开更多
Single-pixel imaging(SPI)receives widespread attention due to its superior anti-interference capabilities,and image segmentation technology can effectively facilitate its recognition and information extraction.However...Single-pixel imaging(SPI)receives widespread attention due to its superior anti-interference capabilities,and image segmentation technology can effectively facilitate its recognition and information extraction.However,the complexity of the target scene and plenty of imaging time in SPI make it challenging to achieve high-quality and concise segmentation.In this paper,we investigate the image-free intricate scene semantic segmentation in SPI.Using“learned”illumination patterns allows for the full extraction of the object's spatial information,thereby enabling pixel-level segmentation results through the decoding of the received measurements.Simulation and experimentation show that,in the absence of image reconstruction,the mean intersection over union(MIoU)of segmented image can reach higher than 85%,and the Dice coefficient(DICE)close to 90%even at the sampling ratio of 5%.Our approach may be favorable to applications in medical image segmentation and autonomous driving field.展开更多
Dear Editor,We present a case of acute zonal occult outer retinopathy(AZOOR)complex in a myopic patient with angioid streaks(ASs).A 19-year-old female has been experiencing visual field defects in her left eye for mor...Dear Editor,We present a case of acute zonal occult outer retinopathy(AZOOR)complex in a myopic patient with angioid streaks(ASs).A 19-year-old female has been experiencing visual field defects in her left eye for more than 3y.She was diagnosed with ASs and choroiditis at a local hospital.She has a seven-year history of bilateral high myopia.A fundus examination confirmed the presence of ASs and myopic fundus changes in both eyes.Multimodal imaging revealed an AZOOR complex in the left eye.展开更多
The complexes 1-4 of cyclobutanocucurbit[5]uril(CyB5Q[5])with Na^(+)/K^(+)have been synthesized and characterized by single-crystal X-ray diffraction.The results show that although the inorganic salts are used when th...The complexes 1-4 of cyclobutanocucurbit[5]uril(CyB5Q[5])with Na^(+)/K^(+)have been synthesized and characterized by single-crystal X-ray diffraction.The results show that although the inorganic salts are used when the cations are the same and the anions are different,in complex 1,Na^(+)closes one port of CyB5Q[5]through Na—O seven coordination bonds to form a molecular bowl;in complex 3,Na^(+)completely closes the two ports of CyB5Q[5]to form a molecular capsule with six Na—O coordination bonds;in complexes 2 and 4,the two ports of CyB5Q[5]are completely closed to form K—O coordinated molecular capsules,but the K^(+)of complex 2 is six-coordinated and that of complex 4 is eight-/nine-coordinated.and complex 4 are connected by three oxygen bridges to form a 1D molecular chain.CCDC:2457122,1;2457121,2;2457400,3;2457120,4.展开更多
Large-scale complex systems are integral to the functioning of various organizations within the national economy.Despite their significance,the lengthy construction cycles and the involvement of multiple entities ofte...Large-scale complex systems are integral to the functioning of various organizations within the national economy.Despite their significance,the lengthy construction cycles and the involvement of multiple entities often result in the deprioritization of standardized management practices,as they do not yield immediate benefits.The implementation of such systems typically encompasses the integrated phases of "development,construction,utiliz ation,and operation and maintenance".To enhance the overall delivery quality of these systems,it is imperative to dismantle the management barriers among these phases and adopt a holistic approach to standardized management.This paper takes a specific system project as a research object to identify common challenges,and proposes improvement strategies in the implementation of standar dized management.Empirical results indicate a substantial reduction in the system s full-lifecycle costs.展开更多
Cisplatin(CDDP)-based chemotherapy is an effective strategy for the treatment of advanced nasopharyngeal carcinoma(NPC).However,serious toxic side effects of CDDP limit patient tolerance and treatment compliance,which...Cisplatin(CDDP)-based chemotherapy is an effective strategy for the treatment of advanced nasopharyngeal carcinoma(NPC).However,serious toxic side effects of CDDP limit patient tolerance and treatment compliance,which urgently needs to be addressed in clinical application.Liposomes have been considered ideal vehicles for reducing CDDP toxicity due to their high biocompatibility,low toxicity and passive targeting ability.Nevertheless,CDDP's poor water/lipid solubility usually results in a low liposome druglipid ratio,limiting tumor delivery ability.Herein,a CDDP-polyphenol complex liposome was designed to increase the drug loading capacity of CDDP to realize the reduction of toxicity and effective antitumor effect simultaneously.The complex was prepared via complexation reaction of different stoichiometric ratios of CDDP and polyphenolic substances(gallic acid,epigallocatechin gallate and tannic acid),followed by encapsulation of complex in liposomes to improve tumor targeting.Notably,the molecular interaction forces between CDDP and polyphenolic substances were intensively investigated through a binding force disruption assay.In vitro studies demonstrated that the optimal formulation of CDDP-epigallocatechin gallate complex liposome(CDDP-EGCG Lips) showed the highest CDDP encapsulation efficiency,favorable stability,pH-sensitive release,enhanced cellular uptake and apoptosis effect.In vivo studies revealed that CDDP-EGCG Lips retarded the elimination of CDDP to prolong their circulation time,inhibited the growth of tumors,and significantly reduced the toxic side effects compared to CDDP monotherapy.This delivery strategy holds great promise for improving the clinical use of platinum-based drugs.展开更多
The Mechanism for Air pollution compleX version 1.0(MAX1),describing detailed tropospheric chemical processes,has been developed based on the latest knowledge.MAX1 contains 940 reactions,including photolysis,gaseous r...The Mechanism for Air pollution compleX version 1.0(MAX1),describing detailed tropospheric chemical processes,has been developed based on the latest knowledge.MAX1 contains 940 reactions,including photolysis,gaseous reactions,and heterogeneous reactions of 300 species,which is adequate for both box model and climate transport model(CTM)applications.Detailed chemical processes of chlorine chemistry,chemistry of Criegee intermediates,and heterogeneous uptake of HO_(2) and N_(2)O_(5) have been implemented and updated.With this level of explicitness,MAX1 can support investigations into the quantification of secondary pollutant productions and the chemical behavior of the crucial intermediates,such as organic peroxy radicals.Box model and CTM tests were conducted to evaluate the performance of MAX1 from different perspectives.Simulations of MAX1 successfully captured the variation of ozone in all cases tested.Meanwhile,significant improvement was made on predictions of radicals compared to other mechanisms,especially under the low NO_(x) environment,with good similarity to simulations of a nearly explicit chemical mechanism(i.e.,Master Chemical Mechanism)that contains over 17000 reactions.The computational expense of MAX1 is acceptable and it can be applied in atmospheric scientific research and air quality prediction.MAX1 introduces new dimensions in atmospheric chemistry modeling,and its potential application in policymaking is a promising yet exploratory step.It offers improved insights into air quality dynamics,which could assist policymakers in making more informed decisions.However,the translation of its detailed chemical understanding into practical strategies remains an area for further investigation.This model suggests a path towards more nuanced air pollution control methods,contributing to ongoing efforts in environmental management.展开更多
Ultra-high-strength aluminumalloy profile is an ideal choice for aerospace structuralmaterials due to its excellent specific strength and corrosion resistance.However,issues such as uneven metal flow,stress concentrat...Ultra-high-strength aluminumalloy profile is an ideal choice for aerospace structuralmaterials due to its excellent specific strength and corrosion resistance.However,issues such as uneven metal flow,stress concentration,and forming defects are prone to occur during their extrusion.This study focuses on an Al-Zn-Mg-Cu ultra-high-strength aluminum alloy profile with a double-U,multi-cavity thin-walled structure.Firstly,hot compression experiments were conducted at temperatures of 350○C,400○C,and 450○C,with strain rates of 0.01 and 1.0 s^(−1),to investigate the plastic deformation behavior of the material.Subsequently,a 3D coupled thermo-mechanical extrusion simulation model was established using Deform-3D to systematically analyze the influence of die structure and process parameters on metal flow velocity,effective stress/strain,and temperature distribution.The simulation revealed significant velocity differences,stress concentration,and uneven temperature distribution.Key parameters,including mesh density,extrusion ratio,die fillet,and bearing length,were optimized through full-factorial experiments.This optimization,combined with a stepped flow-guiding die design,effectively improved the metal flow pattern during extrusion.Trial production based on both the initial and optimized parameters were carried out.A comparative analysis demonstrates that the optimized scheme results in a final profile whose cross-section matches the target design closely,with complete filling of complex features and no obvious forming defects.This research provides a valuable reference for the extrusion process optimization and die design of complex-section profiles made from ultra-high-strength aluminum alloys.展开更多
Charge-transfer complexes(CTCs)have emerged as promising n-type organic thermoelectric(TE)materials due to their inherent high electrical conductivity and tunable transport polarities.In this study,we performed a comp...Charge-transfer complexes(CTCs)have emerged as promising n-type organic thermoelectric(TE)materials due to their inherent high electrical conductivity and tunable transport polarities.In this study,we performed a comprehensive first-principles investigation on the TE properties of nine CTCs comprised of 2,7-dialkyl[1]benzothieno[3,2-b][1]benzothiophenes(CnBTBT,n=4,8,12)as donors and fluorinated derivatives of tetracyanoquinodimethane(F_(m)TCNQ,m=0,2,4)as acceptors,aiming to identify high-performance n-type organic TE materials and elucidate the underlying structure-property relationships.Our calculation results,based on the Boltzmann transport equation and deformation potential theory,reveal that the length of the alkyl side chains and the number of fluorine substitutions significantly impact their electronic structures and TE properties.Notably,the CnBTBT-F_(m)TCNQ CTCs with shorter alkyl chains and more fluorine substitution demonstrate superior n-type characteristics,particularly C4BTBT-F4TCNQ,which achieves an excellent power factor of 671µW cm^(-1) K^(-2) at an optimal charge carrier concentration.Our findings not only clarify the critical role of molecular engineering in CTC-based TE materials but also provide valuable guidance for developing high-efficiency organic TE materials with versatile practical applications.展开更多
In modern industrial production,foreign object detection in complex environments is crucial to ensure product quality and production safety.Detection systems based on deep-learning image processing algorithms often fa...In modern industrial production,foreign object detection in complex environments is crucial to ensure product quality and production safety.Detection systems based on deep-learning image processing algorithms often face challenges with handling high-resolution images and achieving accurate detection against complex backgrounds.To address these issues,this study employs the PatchCore unsupervised anomaly detection algorithm combined with data augmentation techniques to enhance the system’s generalization capability across varying lighting conditions,viewing angles,and object scales.The proposed method is evaluated in a complex industrial detection scenario involving the bogie of an electric multiple unit(EMU).A dataset consisting of complex backgrounds,diverse lighting conditions,and multiple viewing angles is constructed to validate the performance of the detection system in real industrial environments.Experimental results show that the proposed model achieves an average area under the receiver operating characteristic curve(AUROC)of 0.92 and an average F1 score of 0.85.Combined with data augmentation,the proposed model exhibits improvements in AUROC by 0.06 and F1 score by 0.03,demonstrating enhanced accuracy and robustness for foreign object detection in complex industrial settings.In addition,the effects of key factors on detection performance are systematically analyzed,providing practical guidance for parameter selection in real industrial applications.展开更多
Unmanned aerial vehicles(UAVs)are widely utilized in area coverage tasks due to their flexibility and efficiency in geo-graphic information acquisition.However,complex boundary conditions in actual water area maps oft...Unmanned aerial vehicles(UAVs)are widely utilized in area coverage tasks due to their flexibility and efficiency in geo-graphic information acquisition.However,complex boundary conditions in actual water area maps often reduce coverage efficiency.To address this issue,this paper proposes a map preprocessing algorithm that linearizes boundary lines and processes concave areas into concave polygons,followed by gridding the map.Additionally,a collaborative area coverage method for UAV swarms is introduced based on region partitioning,which considers the comprehensive cost of energy consumption and time.An improved Hungarian algorithm is utilized for region partitioning,and a Dubins-A*-based plow-ing area full coverage path planning method is proposed to achieve path smoothing and collaborative coverage of each partition.Two sets of simulation experiments are conducted.The first experiment verifies the effectiveness of the map preprocessing algorithm,and the second compares the proposed collaborative area coverage algorithm with other methods,demonstrating its performance advantages.展开更多
Optical two-way time-frequency transfer(O-TWTFT),utilizing optical frequency comb carriers and linear optical sampling,effectively enables space-to-ground optical frequency standard comparisons.Previously reported det...Optical two-way time-frequency transfer(O-TWTFT),utilizing optical frequency comb carriers and linear optical sampling,effectively enables space-to-ground optical frequency standard comparisons.Previously reported detection sensitivities of O-TWTFTs were typically in the nanoWatt level,necessitating high-power optical frequency combs to compensate for significant losses in high-orbit satellite-to-ground passes.Such hardware-based solutions,while effective,tend to be costly.This paper presents a novel data post-processing algorithm to enhance sensitivity.Unlike previous timing methods,which depend solely on optical phase data and discard intensity information—resulting in elevated errors,especially under low-reception power,our approach employs complex least squares(CLS)estimation in the complex frequency domain.By preserving all intermediate data and avoiding noise from phase unwrapping,it achieves superior sensitivity and accuracy.Experiments over a 113-kilometer free-space link validate the algorithm's robustness,delivering a detection sensitivity of0.1 nanoWatts—over tenfold better than prior techniques—despite a 100-decibel link loss,comparable to Earth-Moon optical links.展开更多
基金The State Key Basic Research and Development Plan(G1998010100)the National Natural Science Foundation of China(29733090,29973047,39970177)
文摘Six model compounds have been synthesized and used for probing the structural features of the Mn cluster in oxygen_evolving complex (OEC) of photosystem Ⅱ (PSⅡ). The model compounds contain Mn 2(μ_O) 2 and μ_O_μ_carboxylato di_manganese structural units, which offer Mn—Mn, Mn……Mn, and Mn—O(N) structural parameters consistent with the corresponding data of the OEC in PSⅡ, implying that the Mn cluster in OEC may possess similar structural features. Two model compounds containing halide anion have been used for discussing the binding of Cl - to Mn in PSⅡ. It is suggested that in the five S states, ligand exchange would lead to the ligation of chloride to Mn in the S states with Mn of higher valence.
基金supported by the National Natural Science Foundation of China(No.92061114)Chinese Academy of Sciences(XDB17010000)。
文摘The photosynthetic oxygen-evolving center(OEC)is a unique Mn_(4)CaO_(5)cluster catalyzing the water oxidation into electrons,protons and O_(2)through a five-intermediate state cycle(Sn,n=0,1,2,3,4).The modeling of OEC is essential for understanding the water oxidation mechanism and developing high efficient water oxidation catalysts.Recently,a series of Mn_(4)CaO_(4)model complexes have been synthesized,which have very similar structures to OEC and also show reactivity of water oxidation.In this work,we employed DFT method to investigate the stability of Mn_(4)CaO_(4)model complex in oxidative conditions,aiming to figure out whether it decomposes itself to release O_(2)during the catalytic water oxidation process.We discovered that the barrier for the O−O bond formation is quite high in the S1 and S2 states,while decreases to 40.2 kcal/mol in the S3 state,indicating the good stability in all oxidation states under normal conditions.Acetonitrile and pyridine can effectively reduce the barrier to 36.5 kcal/mol and 29.9 kcal/mol,respectively.Therefore,strong Lewis base,such as pyridine,could be harmful to the stability of Mn_(4)CaO_(4)and shall be avoided when designing such a catalytic system.Once the O−O bond is formed,Mn_(4)CaO_(4)in the S3 state can readily decompose to O_(2),solvated Ca^(2+)and Mn_(4)O_(2)complex,with the assistance of acetonitrile or pyridine.As a comparison,the O_(2)decomposition in the S2 state is kinetically hindered and thermodynamically disfavored.The S4 state Mn_(4)CaO_(4)has a much lower barrier for O-O bond formation,and is unstable.However,the S4 state Mn_(4)CaO_(4)is difficult to achieve under water oxidation condition,as evidenced by the calculated redox potential of 2.3 V for S3→S4 transition.
基金supported by a Grant-in Aid for Scientific Research on Priority Areas(grant no.17051016 to K.I.and F.S.)for Young Scientists(B)(grant no.18770032to K.I.)
文摘Oxygen-evolving complex （OEC） protein is the original name for membrane-peripheral subunits of photosystem （PS） II. Recently, multiple isoforms and homologs for OEC proteins have been iden- tified in the chloroplast thylakoid lumen, indicating that functional diversification has occurred in the OEC family. Gene expression profiles suggest that the Arabidopsis OEC proteins are roughly categorized into three groups： the authentic OEC group, the stressresponsive group, and the group including proteins related to the chloroplast NAD（P）H dehydrogenase （NDH） complex involved in cyclic electron transport around PSI. Based on the above gene expression profiles, molecular functions of the OEC family proteins are discussed together with our current knowledge about their functions.
文摘Cytochrome b_559 in photosystem Ⅱ reaction center was purified from spinach ( Spinacia oleracea L.) and rice ( Oryza sativa L.) by a rapid and simple procedure. Their low temperature fluorescence emission and excitation spectra, ultraviolet fluorescence spectra and absolute absorption spectra were presented. The author's purification methods, which enhanced the yield of pure protein and shorted the time for isolation, have several advantages: 1. use of oxygen_evolving PSⅡ core complexes as the starting material in order to avoid disturbing from other cytochromes; 2. isocratic elution of cytochrome b_559 from a DEAE_Sephacel column for eliminating the impurity and yielding the protein in pure state; 3. a simple column procedure for removal of excess Triton X_100. Purified cytochromes b_559 from these species have similar optical spectra and mobility during gel electrophoresis under native conditions. From the results of novel electrophoresis (Tricine_SDS_PAGE), cytochrome b_559 from both spinach and rice reveal two polypeptide bands (apparent molecular weight 9 kD and 4 kD, respectively). By measuring of 77 K fluorescence spectra, it was shown that for the purified cytochrome b_559 there were two excitation peaks at 439 nm and 413 nm, and two emission peaks at 563 nm and 668 nm. This is the first indication that Cyt b_559 is able to emit fluorescence and also transfer excited electrons to chlorophyll. By the use of ultraviolet fluorescence spectra, it was demonstrated for the first time that the location of Trp residue could be in the hydrophobic transmembrane region of cytochrome b_559.
文摘Three copper(Ⅱ),nickel and cadmium(Ⅱ)complexes,namely[Cu_(2)(μ-H2dbda)2(phen)2]·2H_(2)O(1),[Ni(μ-H2dbda)(μ-bpb)(H_(2)O)2]n(2),and[Cd(μ-H2dbda)(μ-bpa)]n(3),have been constructed hydrothermally using H4dbda(4,4'-dihydroxy-[1,1'-biphenyl]-3,3'-dicarboxylic acid),phen(1,10-phenanthroline),bpb(1,4-bis(pyrid-4-yl)benzene),bpa(bis(4-pyridyl)amine),and copper,nickel and cadmium chlorides at 160℃.The products were isolated as stable crystalline solids and were characterized by IR spectra,elemental analyses,thermogravimetric analyses,and singlecrystal X-ray diffraction analyses.Single-crystal X-ray diffraction analyses revealed that three complexes crystallize in the monoclinic P21/n,tetragonal I42d,and orthorhombic P21212 space groups.The complexes exhibit molecular dimers(1)or 2D metal-organic networks(2 and 3).The catalytic performances in the Knoevenagel reaction of these complexes were investigated.Complex 1 exhibits an effective catalytic activity and excellent reusability as a heterogeneous catalyst in the Knoevenagel reaction at room temperature.CCDC:2463800,1;2463801,2;2463802,3.
文摘Six new lanthanide complexes:[Ln(3,4-DEOBA)3(4,4'-DM-2,2'-bipy)]2·2C_(2)H_(5)OH,[Ln=Dy(1),Eu(2),Tb(3),Sm(4),Ho(5),Gd(6);3,4-DEOBA-=3,4-diethoxybenzoate,4,4'-DM-2,2'-bipy=4,4'-dimethyl-2,2'-bipyridine]were successfully synthesized by the volatilization of the solution at room temperature.The crystal structures of six complexes were determined by single-crystal X-ray diffraction technology.The results showed that the complexes all have a binuclear structure,and the structures contain free ethanol molecules.Moreover,the coordination number of the central metal of each structural unit is eight.Adjacent structural units interact with each other through hydrogen bonds and further expand to form 1D chain-like and 2D planar structures.After conducting a systematic study on the luminescence properties of complexes 1-4,their emission and excitation spectra were obtained.Experimental results indicated that the fluorescence lifetimes of complexes 2 and 3 were 0.807 and 0.845 ms,respectively.The emission spectral data of complexes 1-4 were imported into the CIE chromaticity coordinate system,and their corre sponding luminescent regions cover the yellow light,red light,green light,and orange-red light bands,respectively.Within the temperature range of 299.15-1300 K,the thermal decomposition processes of the six complexes were comprehensively analyzed by using TG-DSC/FTIR/MS technology.The hypothesis of the gradual loss of ligand groups during the decomposition process was verified by detecting the escaped gas,3D infrared spectroscopy,and ion fragment information detected by mass spectrometry.The specific decomposition path is as follows:firstly,free ethanol molecules and neutral ligands are removed,and finally,acidic ligands are released;the final product is the corresponding metal oxide.CCDC:2430420,1;2430422,2;2430419,3;2430424,4;2430421,5;2430423,6.
文摘Three zinc(Ⅱ),nickel(Ⅱ),and cadmium(Ⅱ)complexes,namely[Zn(μ-Htpta)(py)_(2)]n(1),[Ni(H_(2)biim)2(H_(2)O)2][Ni(tpta)(H_(2)biim)2(H_(2)O)]2·3H_(2)O(2),and[Cd_(3)(μ4-tpta)2(μ-dpe)_(3)]_(n)(3),have been constructed hydrothermally at 160℃ using H_(3)tpta([1,1':3',1″-terphenyl]-4,4',5'-tricarboxylic acid),py(pyridine),H_(2)biim(2,2'-biimidazole),dpe(1,2-di(4-pyridyl)ethylene),and zinc,nickel and cadmium chlorides,resulting in the formation of stable crystalline solids which were subsequently analyzed using infrared spectroscopy,element analysis,thermogravimetric analysis,as well as structural analyses conducted via single-crystal X-ray diffraction.The findings from these single-crystal Xray diffraction studies indicate that complexes 1-3 form crystals within the monoclinic system P2_(1)/c space group(1)or triclinic system P1 space group(2 and 3),and possess 1D,0D,and 3D structures,respectively.Complex 1 demonstrated substantial catalytic efficiency and excellent reusability as a heterogeneous catalyst in the reaction of Knoevenagel condensation under ambient temperature conditions.In addition,complex 1 also showcased notable anti-wear performance when used in polyalphaolefin synthetic lubricants.CCDC:2449810,1;2449811,2;2449812,3.
文摘This paper reports the preparation of three di‑iron complexes containing a thiazole moiety.Esterification of complex[Fe_(2)(CO)_(6)(μ‑SCH_(2)CH(CH_(2)OH)S)](1)with 4‑methylthiazole‑5‑carboxylic acid gave the corresponding ester[Fe_(2)(CO)_(6)(μ‑tedt)](2),where tedt=SCH_(2)CH(CH_(2)OOC(5‑C_(3)HNSCH_(3)))S.Further reactions of complex 2 with tri(ptolyl)phosphine(tp)or tris(4‑fluorophenyl)phosphine(fp)gave the phosphine‑substituted derivatives[Fe_(2)(CO)_(5)(tp)(μ‑tedt)](3)and[Fe_(2)(CO)_(5)(fp)(μ‑tedt)](4).The structures of the newly prepared complexes were elucidated by elemental analysis,NMR,IR,and X‑ray photoelectron spectroscopy.Moreover,single‑crystal X‑ray diffraction analysis confirmed their molecular structures,showing that they contain a di‑iron core ligated by a bridged dithiolate bearing a thiazole moiety and terminal carbonyls.The electrochemical and electrocatalytic proton reduction were probed by cyclic voltammetry,revealing that three complexes can catalyze the reduction of protons to H_(2) under the electrochemical conditions.For comparison,complex 4 possessed the best efficiency with a turnover frequency of 23.5 s^(-1)at 10 mmol·L^(-1)HOAc concentration.In addition,the fungicidal activity of these complexes was also investigated in this study.CCDC:2477511,2;2477512,3;2477513,4.
文摘The hydrated tricyclohexyltin theophylline-7-acetic acid(tpH)complex[Sn(C_(6)H_(11))_(3)(tp)(H_(2)O)]was synthesized via an ethanol solvothermal method using tricyclohexyltin hydroxide and tpH in a 1∶1 molar ratio.The complex was characterized by IR,^(1)H(^(13)C)NMR,elemental analysis,and powder X-ray diffraction,and the crystal structure was determined by single-crystal X-ray diffraction.The crystal belongs to the orthorhombic system with space group Iba2,and the central tin atom is in a five-coordinated trigonal bipyramidal configuration.Quantum chemistry ab initio calculations were performed to investigate the stability,molecular orbital energy,and frontier molecular orbital characteristics of the complex.Additionally,its thermal stability,electrochemical properties,and in vitro anticancer activity were evaluated.CCDC:2380308.
基金Project supported by the Fundamental Research Funds for the Central Universities of China(Grant No.531118010757)。
文摘Single-pixel imaging(SPI)receives widespread attention due to its superior anti-interference capabilities,and image segmentation technology can effectively facilitate its recognition and information extraction.However,the complexity of the target scene and plenty of imaging time in SPI make it challenging to achieve high-quality and concise segmentation.In this paper,we investigate the image-free intricate scene semantic segmentation in SPI.Using“learned”illumination patterns allows for the full extraction of the object's spatial information,thereby enabling pixel-level segmentation results through the decoding of the received measurements.Simulation and experimentation show that,in the absence of image reconstruction,the mean intersection over union(MIoU)of segmented image can reach higher than 85%,and the Dice coefficient(DICE)close to 90%even at the sampling ratio of 5%.Our approach may be favorable to applications in medical image segmentation and autonomous driving field.
基金Supported by the National Natural Science Foundation of China(No.82171073).
文摘Dear Editor,We present a case of acute zonal occult outer retinopathy(AZOOR)complex in a myopic patient with angioid streaks(ASs).A 19-year-old female has been experiencing visual field defects in her left eye for more than 3y.She was diagnosed with ASs and choroiditis at a local hospital.She has a seven-year history of bilateral high myopia.A fundus examination confirmed the presence of ASs and myopic fundus changes in both eyes.Multimodal imaging revealed an AZOOR complex in the left eye.
文摘The complexes 1-4 of cyclobutanocucurbit[5]uril(CyB5Q[5])with Na^(+)/K^(+)have been synthesized and characterized by single-crystal X-ray diffraction.The results show that although the inorganic salts are used when the cations are the same and the anions are different,in complex 1,Na^(+)closes one port of CyB5Q[5]through Na—O seven coordination bonds to form a molecular bowl;in complex 3,Na^(+)completely closes the two ports of CyB5Q[5]to form a molecular capsule with six Na—O coordination bonds;in complexes 2 and 4,the two ports of CyB5Q[5]are completely closed to form K—O coordinated molecular capsules,but the K^(+)of complex 2 is six-coordinated and that of complex 4 is eight-/nine-coordinated.and complex 4 are connected by three oxygen bridges to form a 1D molecular chain.CCDC:2457122,1;2457121,2;2457400,3;2457120,4.
文摘Large-scale complex systems are integral to the functioning of various organizations within the national economy.Despite their significance,the lengthy construction cycles and the involvement of multiple entities often result in the deprioritization of standardized management practices,as they do not yield immediate benefits.The implementation of such systems typically encompasses the integrated phases of "development,construction,utiliz ation,and operation and maintenance".To enhance the overall delivery quality of these systems,it is imperative to dismantle the management barriers among these phases and adopt a holistic approach to standardized management.This paper takes a specific system project as a research object to identify common challenges,and proposes improvement strategies in the implementation of standar dized management.Empirical results indicate a substantial reduction in the system s full-lifecycle costs.
基金supported by the National Natural Science Foundation of China (Nos.81872823,82073782,and 82241002)the Key R&D Plan of Ganjiang New District of Jiangxi (No.2023010)。
文摘Cisplatin(CDDP)-based chemotherapy is an effective strategy for the treatment of advanced nasopharyngeal carcinoma(NPC).However,serious toxic side effects of CDDP limit patient tolerance and treatment compliance,which urgently needs to be addressed in clinical application.Liposomes have been considered ideal vehicles for reducing CDDP toxicity due to their high biocompatibility,low toxicity and passive targeting ability.Nevertheless,CDDP's poor water/lipid solubility usually results in a low liposome druglipid ratio,limiting tumor delivery ability.Herein,a CDDP-polyphenol complex liposome was designed to increase the drug loading capacity of CDDP to realize the reduction of toxicity and effective antitumor effect simultaneously.The complex was prepared via complexation reaction of different stoichiometric ratios of CDDP and polyphenolic substances(gallic acid,epigallocatechin gallate and tannic acid),followed by encapsulation of complex in liposomes to improve tumor targeting.Notably,the molecular interaction forces between CDDP and polyphenolic substances were intensively investigated through a binding force disruption assay.In vitro studies demonstrated that the optimal formulation of CDDP-epigallocatechin gallate complex liposome(CDDP-EGCG Lips) showed the highest CDDP encapsulation efficiency,favorable stability,pH-sensitive release,enhanced cellular uptake and apoptosis effect.In vivo studies revealed that CDDP-EGCG Lips retarded the elimination of CDDP to prolong their circulation time,inhibited the growth of tumors,and significantly reduced the toxic side effects compared to CDDP monotherapy.This delivery strategy holds great promise for improving the clinical use of platinum-based drugs.
基金supported by the National Natural Science Foundation of China(Grant Nos.22325601,92044302,42377105)the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”.
文摘The Mechanism for Air pollution compleX version 1.0(MAX1),describing detailed tropospheric chemical processes,has been developed based on the latest knowledge.MAX1 contains 940 reactions,including photolysis,gaseous reactions,and heterogeneous reactions of 300 species,which is adequate for both box model and climate transport model(CTM)applications.Detailed chemical processes of chlorine chemistry,chemistry of Criegee intermediates,and heterogeneous uptake of HO_(2) and N_(2)O_(5) have been implemented and updated.With this level of explicitness,MAX1 can support investigations into the quantification of secondary pollutant productions and the chemical behavior of the crucial intermediates,such as organic peroxy radicals.Box model and CTM tests were conducted to evaluate the performance of MAX1 from different perspectives.Simulations of MAX1 successfully captured the variation of ozone in all cases tested.Meanwhile,significant improvement was made on predictions of radicals compared to other mechanisms,especially under the low NO_(x) environment,with good similarity to simulations of a nearly explicit chemical mechanism(i.e.,Master Chemical Mechanism)that contains over 17000 reactions.The computational expense of MAX1 is acceptable and it can be applied in atmospheric scientific research and air quality prediction.MAX1 introduces new dimensions in atmospheric chemistry modeling,and its potential application in policymaking is a promising yet exploratory step.It offers improved insights into air quality dynamics,which could assist policymakers in making more informed decisions.However,the translation of its detailed chemical understanding into practical strategies remains an area for further investigation.This model suggests a path towards more nuanced air pollution control methods,contributing to ongoing efforts in environmental management.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB3710805).
文摘Ultra-high-strength aluminumalloy profile is an ideal choice for aerospace structuralmaterials due to its excellent specific strength and corrosion resistance.However,issues such as uneven metal flow,stress concentration,and forming defects are prone to occur during their extrusion.This study focuses on an Al-Zn-Mg-Cu ultra-high-strength aluminum alloy profile with a double-U,multi-cavity thin-walled structure.Firstly,hot compression experiments were conducted at temperatures of 350○C,400○C,and 450○C,with strain rates of 0.01 and 1.0 s^(−1),to investigate the plastic deformation behavior of the material.Subsequently,a 3D coupled thermo-mechanical extrusion simulation model was established using Deform-3D to systematically analyze the influence of die structure and process parameters on metal flow velocity,effective stress/strain,and temperature distribution.The simulation revealed significant velocity differences,stress concentration,and uneven temperature distribution.Key parameters,including mesh density,extrusion ratio,die fillet,and bearing length,were optimized through full-factorial experiments.This optimization,combined with a stepped flow-guiding die design,effectively improved the metal flow pattern during extrusion.Trial production based on both the initial and optimized parameters were carried out.A comparative analysis demonstrates that the optimized scheme results in a final profile whose cross-section matches the target design closely,with complete filling of complex features and no obvious forming defects.This research provides a valuable reference for the extrusion process optimization and die design of complex-section profiles made from ultra-high-strength aluminum alloys.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Science(No.XDB0520000)the National Natural Science Foundation of China(Nos.52273170 and 52394271)the National Key R&D Program of China(No.2022YFA1203200).
文摘Charge-transfer complexes(CTCs)have emerged as promising n-type organic thermoelectric(TE)materials due to their inherent high electrical conductivity and tunable transport polarities.In this study,we performed a comprehensive first-principles investigation on the TE properties of nine CTCs comprised of 2,7-dialkyl[1]benzothieno[3,2-b][1]benzothiophenes(CnBTBT,n=4,8,12)as donors and fluorinated derivatives of tetracyanoquinodimethane(F_(m)TCNQ,m=0,2,4)as acceptors,aiming to identify high-performance n-type organic TE materials and elucidate the underlying structure-property relationships.Our calculation results,based on the Boltzmann transport equation and deformation potential theory,reveal that the length of the alkyl side chains and the number of fluorine substitutions significantly impact their electronic structures and TE properties.Notably,the CnBTBT-F_(m)TCNQ CTCs with shorter alkyl chains and more fluorine substitution demonstrate superior n-type characteristics,particularly C4BTBT-F4TCNQ,which achieves an excellent power factor of 671µW cm^(-1) K^(-2) at an optimal charge carrier concentration.Our findings not only clarify the critical role of molecular engineering in CTC-based TE materials but also provide valuable guidance for developing high-efficiency organic TE materials with versatile practical applications.
文摘In modern industrial production,foreign object detection in complex environments is crucial to ensure product quality and production safety.Detection systems based on deep-learning image processing algorithms often face challenges with handling high-resolution images and achieving accurate detection against complex backgrounds.To address these issues,this study employs the PatchCore unsupervised anomaly detection algorithm combined with data augmentation techniques to enhance the system’s generalization capability across varying lighting conditions,viewing angles,and object scales.The proposed method is evaluated in a complex industrial detection scenario involving the bogie of an electric multiple unit(EMU).A dataset consisting of complex backgrounds,diverse lighting conditions,and multiple viewing angles is constructed to validate the performance of the detection system in real industrial environments.Experimental results show that the proposed model achieves an average area under the receiver operating characteristic curve(AUROC)of 0.92 and an average F1 score of 0.85.Combined with data augmentation,the proposed model exhibits improvements in AUROC by 0.06 and F1 score by 0.03,demonstrating enhanced accuracy and robustness for foreign object detection in complex industrial settings.In addition,the effects of key factors on detection performance are systematically analyzed,providing practical guidance for parameter selection in real industrial applications.
基金National Natural Science Foundation of China(62402020,62303022)Beijing Nova Program(20240484720)+1 种基金Project of Cultivation for Young Top-Notch Talents of Beijing Municipal Institutions(BPHR202203043)BTBU Digital Business Platform Project byBMEC.
文摘Unmanned aerial vehicles(UAVs)are widely utilized in area coverage tasks due to their flexibility and efficiency in geo-graphic information acquisition.However,complex boundary conditions in actual water area maps often reduce coverage efficiency.To address this issue,this paper proposes a map preprocessing algorithm that linearizes boundary lines and processes concave areas into concave polygons,followed by gridding the map.Additionally,a collaborative area coverage method for UAV swarms is introduced based on region partitioning,which considers the comprehensive cost of energy consumption and time.An improved Hungarian algorithm is utilized for region partitioning,and a Dubins-A*-based plow-ing area full coverage path planning method is proposed to achieve path smoothing and collaborative coverage of each partition.Two sets of simulation experiments are conducted.The first experiment verifies the effectiveness of the map preprocessing algorithm,and the second compares the proposed collaborative area coverage algorithm with other methods,demonstrating its performance advantages.
基金supported by the National Key Research and Development Programme of China(Grant Nos.2020YFC2200103 and 2020YFA0309800)the National Natural Science Foundation of China(Grant No.T2125010)+4 种基金Strategic Priority Research Programme of Chinese Academy of Sciences(Grant No.XDB35030000)Anhui Initiative in Quantum Information Technologies(Grant No.AHY010100)Key R&D Plan of Shandong Province(Grant No.2021ZDPT01)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Innovation Programme for Quantum Science and Technology(Grant Nos.2021ZD0300100,2021ZD0300300,and2021ZD0300903)。
文摘Optical two-way time-frequency transfer(O-TWTFT),utilizing optical frequency comb carriers and linear optical sampling,effectively enables space-to-ground optical frequency standard comparisons.Previously reported detection sensitivities of O-TWTFTs were typically in the nanoWatt level,necessitating high-power optical frequency combs to compensate for significant losses in high-orbit satellite-to-ground passes.Such hardware-based solutions,while effective,tend to be costly.This paper presents a novel data post-processing algorithm to enhance sensitivity.Unlike previous timing methods,which depend solely on optical phase data and discard intensity information—resulting in elevated errors,especially under low-reception power,our approach employs complex least squares(CLS)estimation in the complex frequency domain.By preserving all intermediate data and avoiding noise from phase unwrapping,it achieves superior sensitivity and accuracy.Experiments over a 113-kilometer free-space link validate the algorithm's robustness,delivering a detection sensitivity of0.1 nanoWatts—over tenfold better than prior techniques—despite a 100-decibel link loss,comparable to Earth-Moon optical links.
