质子交换MgO:LiNbO3波导的双层结构

本文报导MgO:LiN_bO₃质子交换波导X射线双晶衍射和红外吸收的实验结果。这些结果表明质子交换波导由浅表面层和深表面层构成。浅表面层是一个连续应变层,有着大量随机排列的O—H—O形式的缔合OH^-基团。深表面层是一个均匀应变层,其内H⁺以自由OH^-基团形式出现。质子交换波导折射串不稳定性与双层结构中的结构驰豫密切相关。通过对质子交换过程的分析,提出两条避免双层结构的途径,其一为降低交换剂中的H⁺浓度,另一条是采用有限源工艺。     

Status Set Sequential Pattern Mining Considering Time Windows and Periodic Analysis of Patterns

The traditional sequential pattern mining method is carried out considering the whole time period and often ignores the sequential patterns that only occur in local time windows, as well as possible periodicity. Therefore, in order to overcome the limitations of traditional methods, this paper proposes status set sequential pattern mining with time windows (SSPMTW). In contrast to traditional methods, the item status is considered, and time windows, minimum confidence, minimum coverage, minimum factor set ratios and other constraints are added to mine more valuable rules in local time windows. The periodicity of these rules is also analyzed. According to the proposed method, this paper improves the Apriori algorithm, proposes the TW-Apriori algorithm, and explains the basic idea of the algorithm. Then, the feasibility, validity and efficiency of the proposed method and algorithm are verified by small-scale and large-scale examples. In a large-scale numerical example solution, the influence of various constraints on the mining results is analyzed. Finally, the solution results of SSPM and SSPMTW are compared and analyzed, and it is suggested that SSPMTW can excavate the laws existing in local time windows and analyze the periodicity of the laws, which solves the problem of SSPM ignoring the laws existing in local time windows and overcomes the limitations of traditional sequential pattern mining algorithms. In addition, the rules mined by SSPMTW reduce the entropy of the system.     

Amorphous Cobalt Boride Alloy Synthesized by Liquid Phase Methods as Electrode Materials for Electrochemical Capacitors

An amorphous cobalt boride alloy with high electronic conductivity is fabricated through the liquid-phase reduction method. Benefiting from large specific surface area and hierarchical pore structure, the as-synthesized Co-B nanoflakes expose substantial electrochemical active sites, promote the transfer of electrons and ions, and accelerate the redox kinetic process. The as-obtained amorphous Co-B alloy sample displays a specific capacitance of 411 F g⁻¹ at 0.5 A g⁻¹, and with the current density increased to 10 A g⁻¹, it maintains 69% of the initial capacitance. The as-assembled asymmetric supercapacitor device reveals electrochemical properties comprising an excellent specific capacitance of 64.3 F g⁻¹ at 0.25 A g⁻¹, superior cyclical stability of 105% after 20,000 cycles at 3 A g⁻¹, and maximum energy density of 22.9 Wh kg⁻¹ at a power density of 200.3 W kg⁻¹. This study demonstrates great potential in developing high-conductivity materials for an asymmetric supercapacitor through utilizing an amorphous cobalt boride alloy as a promising electrode material.     

Temperature Dependent In-Plane Anisotropic Magnetoresistance in HfTe_5 Thin Layers

We report the observation of in-plane anisotropic magnetoresistance and planar Hall effect in non-magnetic HfTe₅ thin layers.The observed anisotropic magnetoresistance as well as its sign is strongly dependent on the critical resistivity anomaly temperature T_p.Below T_p,the anisotropic magnetoresistance is negative with large negative magnetoresistance.When the in-plane magnetic field is perpendicular to the current,the negative longitudinal magnetoresistance reaches its maximum.The negative longitudinal magnetoresistance effect in HfTe₅ thin layers is dramatically different from that induced by the chiral anomaly as observed in Weyl and Dirac semimetals.One potential underlying origin may be attributed to the reduced spin scattering,which arises from the in-plane magnetic field driven coupling between the top and bottom surface states.Our findings provide valuable insights for the anisotropic magnetoresistance effect in topological electronic systems and the device potential of HfTe5 in spintronics and quantum sensing.     

Unraveling the Mechanism for the Sharp‐Tip Enhanced Electrocatalytic Carbon Dioxide Reduction: The Kinetics Decide

The electrocatalytic reduction reaction of carbon dioxide can be significantly enhanced by the use of a sharp‐tip electrode. However, the experimentally observed rate enhancement is many orders of magnitudes smaller than what would be expected from an energetic point of view. The kinetics of this tip‐enhanced reaction are shown to play a decisive role, and a novel reaction‐diffusion kinetic model is proposed. The experimentally observed sharp‐tip enhanced reaction and the maximal producing rate of carbon monoxide under different electrode potentials are well‐reproduced. Moreover, the optimal performance shows a strong dependence on the interaction between CO₂ and the local electric field, on the adsorption rate of CO₂, but not on the reaction barrier. Two new strategies to further enhance the reaction rate have also been proposed. The findings highlight the importance of kinetics in modeling electrocatalytic reactions.     

Novel simple fluorescent sensor for nickel ions

A novel pyrazoline with benzimidazole substituent was conveniently synthesized, starting from a chalcone and 2-hydrazinylpyridine. The addition of Ni²⁺ to ethanol solution of the synthesized pyrazoline resulted in a rapid color change from blue to green which allows the selective detection of Ni²⁺ ion over a great number of other metal ions. The association constant for the 1:1 complex was determined to be 2.72 × 10⁷ M^?1.     

Palladium-catalyzed regio-, diastereo-, and enantioselective allylic alkylation of acylsilanes with monosubstituted allyl substrates

Acylsilanes as a new type of "hard" carbon prenucleophile reacted with monosubstituted allyl reagents under Pd-catalyzed asymmetric allylic alkylation reaction conditions to provide products with high regio-, diastereo-, and enantioselectivities. The usefulness of the protocol has been demonstrated by the ready conversion of the allylated products into the corresponding alcohols, esters, and ketones with retention of stereochemistry as well as by the enantioselective synthesis of cis-3-ethyl-4-phenylpiperidine and cinnamomumolide.