摘要 : Polycyclic aromatic hydrocarbons (PAHs) are widely employed in laser protection applications owing to their excellent nonlinear optical absorption (NLA) properties. Nevertheless, the underlying enhancement mechanisms governing their NLA performance, particularly concerning structure-property relationships, remain ambiguous. To study the influence of π-bridges on nonlinear optical absorption (NLA) performance and excited-state dynamics, we designed and synthesized three two-branched anthracene derivatives (ZN1, ZN2, and ZN3) in this work. By introducing different π-bridges, we modulate the dihedral angle θ between the anthracene core and side chains in these two-branched molecules from 90° to 0°, thereby governing their electron transition characteristics. Through an integrated computational-experimental framework, we elucidate the distinct excitation pathways in these systems—including intramolecular charge transfer (ICT) and local excitation (LE)—by employing hole-electron analysis and transient absorption spectroscopy. Reducing the dihedral angle θ facilitates orbital overlap between the conjugated core and side chains, which extends the π-conjugated system and significantly augments the molecule's reverse saturable absorption (RSA) performance. Based on the above molecular optimization strategy, we have successfully improved the ultrafast broadband optical limiting (OL) performance of these compounds (515–650 nm), with an OL threshold as low as 9.11 mJ/cm 2 .

摘要 : Merging proton relay ligands to metal catalysts has proven to be an effective route for regulating the proton transfer and enhancing efficiency in CO 2 reduction reactions (CO 2 RR). The structure-activity relationship for these synergistic ligands remains barely explored. We herein functionalized Si/ZnO/Au photocathodes with proton relay ligands and investigated their activity for CO 2 -to-CO transformations. A series of ligands with varied acid-base properties (pK a : ∼3–10) were selected and compared, which eventually found a volcano-shape dependence of CO 2 photoconversion on the ligands' pK a . The electrode functionalized with 2-mercaptoimidazole (pK a = 8) was optimal and effectively elevated the CO selectivity by ∼2 folds, furnishing 84 % CO Faradic efficiency (FE CO ) at 0 V (vs. RHE) with > 20 h operation stability. In the mechanistic investigations, we successed to link the protonation/deprotonation abilities (defined by pK a ) of the ligands to the kinetics of the crucial COO − /COOH formation steps. Ultimately, we found that achieving a balance between these two steps, facilitated by a ligand with a medium pK a, maximizes the CO 2 reduction selectivity.

摘要 : Traditional Simultaneous Localization and Mapping (SLAM) systems assume static environments, and their localization accuracy degrades significantly when encountering dynamic objects. Although dynamic SLAM based on semantic information can handle simple dynamic objects, it fails to address the impact of pseudo-dynamic objects and unrecognized dynamic objects on pose estimation. To address these issues, we propose a DC-SLAM system, comprehensively eliminating two types of dynamic features while preserving valid static features. The system implements a dual-category mechanism: for active dynamic features, it combines a dynamic object detection network with dense optical flow for detection and removal, preventing excessive elimination of static features' for passive dynamic features, the system first determines their attributes using multi-view geometry, then clusters all feature points based on depth information and object detection categories, and finally optimizes dynamic properties through Mahalanobis distance analysis of outlier similarity. This approach compensates for the limitations of multi-view geometry, enabling more effective suppression of passively dynamic objects. Additionally, an octree mapping module is developed to assist mobile robots in scene understanding for practical applications. Extensive experiments on the TUM dataset, Bonn dataset, and real-world dynamic scenes verify DC-SLAM's effectiveness. The results demonstrate significant improvements, compared with ORB-SLAM2, DC-SLAM reducing Absolute Trajectory Error (ATE) by 98.86 % and Relative Pose Error (RPE) by 97.28 %, while enabling the reliable construction of octree maps to enhance spatial understanding.

摘要 : Recently, Andrews and Paule introduced a partition function P D N 1 ( N ) which denotes the number of partition diamonds with ( n + 1 ) copies of n where summing the parts at the links gives N . They also presented the generating function for P D N 1 ( n ) and proved several congruences modulo 5, 7, 25, 49 for P D N 1 ( n ) . At the end of their paper, Andrews and Paule asked for determining infinite families of congruences similar to Ramanujan's classical p ( 5 k n + d k ) ≡ 0 ( mod 5 k ), where 24 d k ≡ 1 ( mod 5 k ) and k ≥ 1 . In this paper, we give an answer of Andrews and Paule's open problem by proving three congruences modulo arbitrary powers of 5 for P D N 1 ( n ) . In addition, we prove two congruences modulo arbitrary powers of 7 for P D N 1 ( n ), which are analogous to Watson's congruences for p ( n ) .

摘要 : Gallai's conjecture asserts that every connected graph on n vertices can be decomposed into n + 1 2 paths. For general graphs (possibly disconnected), it was proved that every graph on n vertices can be decomposed into 2 n 3 paths. This is also best possible (consider the graphs consisting of vertex-disjoint triangles). Lovász showed that every n -vertex graph with at most one vertex of even degree can be decomposed into n 2 paths. However, Gallai's conjecture is difficult for graphs with many vertices of even degrees. Favaron and Kouider verified Gallai's conjecture for all Eulerian graphs with maximum degree at most 4. In this paper, we show if G is an Eulerian graph on n ≥ 4 vertices and the distance between any two triangles in G is at least 3, then G can be decomposed into at most 3 n 5 paths.

摘要 : Let G be a graph with n vertices. A path decomposition of G is a set of edge-disjoint paths including all the edges of G . Let p ( G ) denote the minimum number of paths in a path decomposition of G . Gallai's Conjecture asserts that if G is connected, then p ( G ) ≤ ⌈ n 2 ⌉ . The E -subgraph of G is the subgraph induced by the vertices of even degree in G . A well-known result of Lovász is that if the E -subgraph of G is empty or isomorphic to K 1, then p ( G ) ≤ ⌊ n 2 ⌋ . In this paper, we prove that if the E -subgraph of G is isomorphic to K m with m ≤ 15, then p ( G ) ≤ ⌊ n 2 ⌋ + 1, which implies, under the condition, that Gallai's Conjecture holds when n is odd. A simple graph G on n vertices is called a semi-clique if | E ( G ) | > ⌊ n 2 ⌋ ( n − 1 ) . By the definition, if G is a semi-clique on n vertices, then n must be odd and p ( G ) ≥ ⌈ n 2 ⌉ . As a corollary of our main result, we obtain that if G is a semi-clique on n vertices, then p ( G ) ≤ 4 n + 6 7 .

摘要 : Mass lumping of flexure beams plays a critical role in the dynamic compliance matrix method (DCM) for both kinetostatic and vibration analyses of compliant mechanisms and structures. The primary objective of this study is to derive and compare various mass matrix formulations for use in the DCM. Continuous and diagonal lumped mass matrices of flexure hinges and beams as well as their local-to-global coordinate transformation formulations are derived, discussed and clarified. By virtue of mass lumping and grounding, the schemes of compliance matrix summation for serial beam chains and stiffness/mass matrix summation for parallel branches are developed considering damping effects. The performance of different mass matrices is evaluated through case studies, which highlight the variation in performance with different mass matrices. The established mass matrix library of general flexure hinges and beams enhances the robustness of the DCM, and thus offers a straightforward performance-oriented analysis tool for compliant mechanisms and beam structures in terms of dynamic compliance.

摘要 : This study aims to improve the applicability of green-synthesized nano zero-valent iron (GT-nZVI) for wastewater treatment under natural pH conditions by developing a novel -nZVI composite stabilized with polystyrene sulfonate (PSS) and green tea polyphenols (GT-nZVI@PSS) at different PSS/Fe mass ratios (0.01–0.5) for Pb(II) removal. Particular emphasis was placed on elucidating the influences of humic acid (HA) and sulfate ubiquitous constituents in wastewaters on Pb(II) removal performance, with the underlying mechanisms of their effects systematically clarified. Results demonstrated that GT-nZVI@PSS (PSS/Fe = 0.05) exhibited excellent Pb(II) removal at neutral pH, primarily driven by enhanced Pb(II) reduction and Pb 0 precipitation. This performance is mainly attributed to improved dispersibility resulting from the synergistic effects of PSS and tea polyphenols on the particle surface. HA and sulfate exerted opposing effects on Pb(II) removal by GT-nZVI@PSS. At low concentrations, HA enhanced Pb(II) uptake by increasing the surface negative charge, improving particle dispersion, and providing additional active sites for the formation of Fe–HA/Pb complexes. In contrast, sulfate inhibited Pb(II) removal by disrupting the polyphenol coating and forming surface sulfate–iron species and PbSO 4 precipitates, thereby accelerating passivation and reducing Fe release. However, at high concentrations, excessive HA molecules formed large aggregates that enveloped the particle surfaces, ultimately hindering Pb(II) access to the active sites of GT-nZVI@PSS. Conversely, high concentrations of sulfate promoted GT-nZVI@PSS corrosion, facilitating Fe 0 release and thereby enhancing Pb(II) removal. These findings highlight the crucial role of water matrix constituents in modulating the performance of GT-nZVI@PSS, as an eco-friendly and cost-effective material.

摘要 : The oxygen evolution reaction (OER), as the core half-reaction in water electrolysis (WE), plays a decisive role in determining the overall efficiency of hydrogen production. Cobalt carbonate hydroxide (CoCH) has recently emerged as a attractive material for alkaline OER due to its robust structural stability. In this study, urchin-like CoCH was employed as a precursor template to synthesize Fe and Mn co-modified CoCH catalyst on nickel foam (NF) through Mn-doping and surface Fe-modification strategies (recorded as Fe, Mn-CoCH/NF). This optimized hierarchical structure enhanced the exposure of active sites and facilitated faster electron/mass transport paths. The incorporation of Fe and Mn effectively regulated the position of d-band center and facilitated a more efficient lattice oxygen mechanism (LOM) for OER, thereby enhancing the intrinsic activity of the catalyst. Compared to the unmodified CoCH/NF, the Fe, Mn-CoCH/NF exhibited significantly improved OER catalytic activity, characterized by a substantially reduced overpotential (204 mV at 10 mA cm −2 ) in alkaline electrolyte, alongside remarkable stability. Utilizing this catalyst, an overall water splitting (OWS) system was further developed, capable of driving efficient OWS at a low cell voltage (1.49 V at 10 mA cm −2 ). Furthermore, the unique hierarchical structure of Fe, Mn-CoCH/NF contributed to mitigating electrochemical corrosion and the toxic effects of Cl − during seawater electrolysis, enabling the catalyst to maintain excellent catalytic activity and stability even in alkaline seawater system.

摘要 : SnS2 has emerged as a promising anode material for sodium-ion batteries (SIBs) due to its ultrahigh theoretical specific capacity (1136 mAh g −1 ) and large interlayer spacing (5.9 Å). However, its practical application is severely hindered by significant volume expansion and poor intrinsic conductivity. In this work, SnS2@GO was successfully synthesized via a reflux method. The integration of SnS2 with GO not only enhance the overall conductivity but also yield ultrasmall nanoparticles which shorten the diffusion pathways for Na + and electrons while mitigating volume expansion. As a result, SnS2@GO demonstrates exceptional electrochemical properties, including outstanding cycling performance (1120 mAh g −1 at 0.1 A g −1 ), remarkable rate capability (788 mAh g −1 at 5 A g −1 ), and superior long-term cycling stability (588 mAh g −1 at 5 A g −1 after 1200 cycles), highlighting its great potential for the applications of SIBs.