4-二苯胺基苯甲醇功能化石墨烯的制备、电子传递及光催化性能

在碱性条件下由氧化石墨(GO)还原获得还原石墨烯(RGO). RGO与4-二苯胺基苯甲醇(TPACH₂OH)混合后发生相互作用, 得到功能化石墨烯复合物(TPACH₂OH-RGO). 采用密度泛函理论(DFT)对TPACH₂OH-RGO模拟计算结果表明, TPACH₂OH和RGO之间主要通过氢键作用形成复合物. 利用紫外-可见光谱(UV-vis)、拉曼光谱(Raman)、荧光光谱(Fluorescence)、原子力显微镜(AFM)、透射电子显微镜(TEM)和电化学等方法研究了TPACH₂OH-RGO结构和光电性质, 并研究了以TPACH₂OH-RGO为催化剂在光照射下光催化分解水制氢性能. 实验结果表明: 光照下复合物中激发态TPACH₂OH向RGO转移电子. 在TPACH₂OH和RGO的质量比为4/3, 体系pH＝6条件下, 光照6 h, TPACH₂OH-RGO的产氢总量达到35.0 μmol, 比RGO的产氢总量(20.4 mmol)有明显的提高.     

Bright‐Dark Rogue Waves

During the last two decades, revealing mechanisms of origin waves with anomalous amplitude (rogue waves) have been in the focus of researchers from different fields ranging from oceanography to laser physics. Mode‐locked lasers, as a test bed system, provide a unique opportunity to collect more data on rogue waves in the form of random pulses (soliton rain) and to clarify the mechanisms of rogue‐wave emergence caused by soliton–soliton and soliton–dispersive wave interactions. Here, for the first time, for an Er‐doped mode‐locked laser, a new type of vector rogue waves is demonstrated experimentally and theoretically, which is driven by desynchronization of the orthogonal linear states of polarization, so leading to output power oscillations in the form of anomalous spikes‐dips (bright‐dark rogue waves). The results can pave the way to unlocking the universal nature of the origin of rogue waves and thus can be of interest to the broad scientific community.     

Dynamic conductivity modified by impurity resonant states in doping three-dimensional Dirac semimetals

The impurity effect is studied in three-dimensional Dirac semimetals in the framework of a T-matrix method to consider the multiple scattering events of Dirac electrons off impurities. It has been found that a strong impurity potential can significantly restructure the energy dispersion and the density of states of Dirac electrons. An impurity-induced resonant state emerges and significantly modifies the pristine optical response. It is shown that the impurity state disturbs the common longitudinal optical conductivity by creating either an optical conductivity peak or double absorption jumps, depending on the relative position of the impurity band and the Fermi level. More importantly, these conductivity features appear in the forbidden region between the Drude and interband transition, completely or partially filling the Pauli block region of optical response. The underlying physics is that the appearance of resonance states as well as the broadening of the bands leads to a more complicated selection rule for the optical transitions, making it possible to excite new electron-hole pairs in the forbidden region. These features in optical conductivity provide valuable information to understand the impurity behaviors in 3D Dirac materials.     

An innovative model for the transient response of a spherical thin-shell transducer and an experimental confirmation

正A unique characteristic of piezoelectric materials is their ability of electric-mechanical transduction and converting mechanical energy to electrical energy or vice versa. This remarkable property, embedded in piezoelectric materials,has been exploited to construct a wide variety of acoustic     

Synthesis of 1,3,4‐Oxadiazole‐Based Aromatic and Heterocyclic/Phenylpyrazole Derivatives

A new series of 1,3,4‐oxadiazole‐based aromatic and heterocyclic/phenylpyrazole derivatives 6a–c , 7a–d , and 8 were synthesized via sequential 1,3‐dipolar cyclization, hydrazidation, benzoylation, dehydrative cyclization, and the Suzuki coupling reaction. Among the derivatives, compounds 7a and 7c with the corresponding 2‐thienyl and 2‐benzo[b]thienyl (Ar) at the phenyl group located at the N‐1 position of pyrazole showed a better conjugation range.      

Wormhole Propagation Behavior and Its Effect on Acid Leakoff under In Situ Conditions in Acid Fracturing

In acid fracturing, excessive acid leakoff is thought to be the main reason that limits fracture propagation and live acid penetration distance. Although acid leakoff has been studied under experimental conditions, the acid leakoff theory developed under experimental conditions cannot be extended to in situ conditions because the injection rate or pressure drop across a core plug is fixed in the experiments. In this paper, we used a model that couples a two-scale continuum model simulating wormholing in the invaded zone and a reservoir flow model for the compressed zone to simulate acid leakoff process under in situ conditions. Based on this model, we investigated wormhole propagation behavior and its effect on acid leakoff under in situ conditions. The study shows different wormhole propagation behavior under in situ conditions from that under experimental conditions. Wormholes grow fast at the beginning and slow down at later time due to the rise of reservoir pressure caused by the leakoff and the growth of the invaded zone. In oil reservoirs, wormholing has minor effect on acid leakoff because of small compressibility and relatively high reservoir fluid viscosity, but in gas reservoirs, the influence of wormholing on acid leakoff becomes significant due to large compressibility and low reservoir fluid viscosity. Acid viscosity has more notable influence on acid leakoff in gas reservoirs than in oil reservoirs.     

分子构象聚类中的K-means密度峰值搜索算法

分子构象的聚类是搜索分子动力学模拟轨迹中代表构象的主要方法。 它是分析复杂构象改变或分子间相互作用机制的关键步骤. 作为一种基于密度的聚类算法,密度峰值搜索算法因其聚类的准确度而被应用于分子聚类过程中. 但随着模拟时长的增长,密度峰值搜索算法较低的计算效率限制了其应用的可能. 本文提出K-means密度峰值搜索算法的聚类算法,它是密度峰值搜索算法在计算效率方面的一个扩展版本,用于解决密度峰值搜索算法中巨大的资源消耗问题. 在K-means密度峰值搜索算法中,首先,通过高效的聚类算法(例如K-means)进行初始聚类,得到的聚类中心被定义为具有权重的典型点. 然后,对加权的典型点通过密度峰值搜索算法实现二次聚类,并细化点为核心点、边界点、加细光晕点. 在与密度峰值搜索算法具有相似的精度的同时,计算复杂度由O(n²)降至O(n). 通过二面角,二级结构,关联图描述的分子构象,将KFDP用于多个模拟轨迹的聚类过程中. 并通过与K-means聚类算法,DBSCAN聚类算法的比较结果,验证了K-means密度峰值搜索算法的优势.     

Effect of cyclic oxidation on electrochemical corrosion of type 409 stainless steel in the simulated muffler condensates

The electrochemical corrosion behavior of 409 stainless steel after cyclic oxidation below 400 °C was investigated in the simulated muffler condensates by using surface analysis and electrochemical measurement techniques. In the cyclic processes of condensate-dipping and oxidation, specimens may form defective oxide films and weak Cr depletion underlying the oxide films. Sulfate from the condensate-dipping will give rise to sulfidation during the cyclic oxidation, being detrimental to both the oxidation and corrosion properties of stainless steel. The oxidation above 300 °C deteriorates the corrosion resistance, even leading to active corrosion in the acidic condensate solutions. Comparatively, specimens oxidized cyclically without condensate-dipping show much higher condensate corrosion resistance. It is suggested that the acidic condensate corrosion is accelerated by the synergetic effect of oxidation and condensation in the mufflers, and then may result in perforation through the defects such as cracks and nodules in oxide films on the stainless steel surface.     

Dipole Field Guided Orientated Attachment of Nanocrystals to Twin‐Brush ZnO Mesocrystals

Mesocrystals of ZnO were synthesized hydrothermally by using gum arabic as a structure‐directing agent. Their hierarchical structure has a unique twin‐brush form consisting of vertically aligned nanorods in a single‐crystal‐like porous form. The formation mechanism of the twin‐brush ZnO was investigated by quenching a series of samples at different times and examining them by TEM, SEM, and XRD. The alignment of ZnO crystal units can be modulated by adding simple salts such as KCl to change the units from nanorods to nanoplates. This can be explained by screening the dipolar force of the polar crystal. Local cathodoluminescence of twin‐brush ZnO was used to follow the local structure changes.     

Combined effect of demagnetizing field and induced magnetic anisotropy on the magnetic properties of manganese-zinc ferrite composites

This work is devoted to the analysis of factors responsible for the high-frequency shift of the complex permeability (μ^?) dispersion region in polymer composites of manganese-zinc (MnZn) ferrite, as well as to the increase in their thermomagnetic stability. The magnetic spectra of the ferrite and its composites with polyurethane (MnZn-PU) and polyaniline (MnZn-PANI) are measured in the frequency range from 1 MHz to 3 GHz in a longitudinal magnetization field of up to 700 Ое and in the temperature interval from −20 °С to +150 °С. The approximation of the magnetic spectra by a model, which takes into account the role of domain wall motion and magnetization rotation, allows one to determine the specific contribution of resonance processes associated with domain wall motion and the natural ferromagnetic resonance to the μ^?. It is established that, at high frequencies, the μ^? of the MnZn ferrite is determined solely by magnetization rotation, which occurs in the region of natural ferromagnetic resonance when the ferrite is in the “single domain” state. In the polymer composites of the MnZn ferrite, the high-frequency permeability is also determined mainly by the magnetization rotation; however, up to high values of magnetizing fields, there is a contribution of domain wall motion, thus the “single domain” state in ferrite is not reached. The frequency and temperature dependence of μ^? in polymer composites are governed by demagnetizing field and the induced magnetic anisotropy. The contribution of the induced magnetic anisotropy is crucial for MnZn-PANI. It is attributed to the elastic stresses that arise due to the domain wall pinning by a polyaniline film adsorbed on the surface of the ferrite during in-situ polymerization.