CO_2激光边带光谱仪用于SF_6分子v_3带Q支吸收谱的研究

用绝对频率精度优于1.2MHz的CO_2激光边带光谱仪记录了SF_6分子v_3带Q支的多普勒受限吸收谱,光谱范围在CO_2激光10P(16)支线中心两侧,距支线中心8.0～12.4 GHz。用内插法以<6MHz的均方误差测量了百余条跃迁谱线的频率,并标识出Q_Z、Q_R、Q_X、Q_W、Q_A等亚支的谱线,量子数J从26到83。用最小二乘法拟合实验数据得到了v_3带的部分光谱常数。     

Simultaneous estimation and variable selection in median regression using Lasso-type penalty

We consider the median regression with a LASSO-type penalty term for variable selection. With the fixed number of variables in regression model, a two-stage method is proposed for simultaneous estimation and variable selection where the degree of penalty is adaptively chosen. A Bayesian information criterion type approach is proposed and used to obtain a data-driven procedure which is proved to automatically select asymptotically optimal tuning parameters. It is shown that the resultant estimator achieves the so-called oracle property. The combination of the median regression and LASSO penalty is computationally easy to implement via the standard linear programming. A random perturbation scheme can be made use of to get simple estimator of the standard error. Simulation studies are conducted to assess the finite-sample performance of the proposed method. We illustrate the methodology with a real example.     

Vertically aligned γ-AlOOH nanosheets on Al foils as flexible and reusable substrates for NH<Subscript>3</Subscript> adsorption

Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH₃ adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH₃ adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH₃ molecules and the edge groups (-OH) further improve the capture ability of the nanosheets.     

Phenanthrene derivatives combined charge transport properties and strong solid-state emission

Science China Chemistry - As bifunctional materials, phenanthrene derivatives 2,7-diphenylphenanthrene and 2,7-di(styryl)phenanthrene (DPPa and DSPa) were designed and studied. Both materials show...     

Acceptor-Doping Accelerated Charge Separation in Cu2O Photocathode for Photoelectrochemical Water Splitting: Theoretical and Experimental Studies

Cu₂O is a typical photoelectrocatalyst for sustainable hydrogen production, while the fast charge recombination hinders its further development. Herein, Ni²⁺ cations have been doped into a Cu₂O lattice (named as Ni-Cu₂O) by a simple hydrothermal method and act as electron traps. Theoretical results predict that the Ni dopants produce an acceptor impurity level and lower the energy barrier of hydrogen evolution. Photoelectrochemical (PEC) measurements demonstrate that Ni-Cu₂O exhibits a photocurrent density of 0.83 mA cm⁻², which is 1.34 times higher than that of Cu₂O. And the photostability has been enhanced by 7.81 times. Moreover, characterizations confirm the enhanced light-harvesting, facilitated charge separation and transfer, prolonged charge lifetime, and increased carrier concentration of Ni-Cu₂O. This work provides deep insight into how acceptor-doping modifies the electronic structure and optimizes the PEC process.     

R410A在水平内螺纹管中沸腾换热实验研究

对于非共沸混合制冷剂R410A在外径9.52mm、5mm的两种不同的几何参数的内螺纹的流动沸腾换热进行了实验研究,分析讨论了制冷剂质量流速、管外水流量变化、强化管的参数、强化管的压降对换热系数影响以及其机理。试验的结果表明:换热系数随着流量的增大而增大,管径的大小对换热系数的影响较大,在相同的流量下,9.52mm的换热系数比5mm的大到110%~230%,5mm管的压降比9.52mm的大200%~300%。     

基于光导开关的Blumlein型PFN能量转换效率

为了驱动低能重复频率高阻抗X光管,采用低感陶瓷电容构建了一套电长度约33.5 ns、阻抗约8 的Blumlein型脉冲形成网络（BPFN）,在匹配负载条件下研究了采用GaAs光导开关（PCSS）作为脉冲输出开关时PCSS工作场强、激光触发能量与能量转换效率的关系。实验表明:PCSS截止场强为3.21～4.94 kV/cm,在工作场强高于20 kV/cm时,截止场强引起的能量损失对能量转换效率的影响不大;PCSS较高的导通电阻是影响PFN能量转换效率的主要因素,随着工作场强、激光触发能量的上升,能量转换效率呈指数上升趋势。     

Transition probabilities of the X1Σ+, A1Π, B1Δ, C1Σ+, and D1Π states of the AlO+ cation

ABSTRACT

This study computes the potential energy curves of the X¹Σ⁺, A¹Π, B¹Δ, C¹Σ⁺, and D¹Π states of AlO⁺ cation and the transition dipole moments between them. The orders of the rotationless radiative lifetimes are 10–100?μs for the A¹Π state, 1–1000?ms for the B¹Δ state, 10?ns for the first well and 100?ns for the second well of the C¹Σ⁺ state, and 1?μs for the D¹Π state. Emissions of the B¹Δ–A¹Π and D¹Π–C¹Σ⁺ systems are so weak that they are hardly measured via spectroscopy, the emissions of the C¹Σ⁺–X¹Σ⁺, C¹Σ⁺–A¹Π, and D¹Π–X¹Σ⁺ systems are so strong that they can be detected readily, and emissions of the A¹Π–X¹Σ⁺ and D¹Π–A¹Π systems can be observed through spectroscopy only by a significant effort. There is a strong great similarity between spontaneous emissions of the A¹Π–X¹Σ⁺ system of the AlO⁺ cation and the A²Π–X²Σ⁺ system of the AlO radical. The emissions of the A²Π–X²Σ⁺ system of the AlO radical have been measured in outer space Therefore, it is highly possible that the emissions of the A¹Π–X¹Σ⁺ system of the AlO⁺ cation can be detected in the astrophysical media.     

The Effect of OMMT on the Morphology and Mechanical Properties of PVC/ABS Blends

Poly(vinyl chloride) (PVC)/acrylonitrile-butadiene-styrene (ABS) blends containing organically modified montmorillonite (OMMT) were prepared using a twin-screw extruder followed by injection molding. The OMMT dispersion was evaluated by X-ray diffraction and transmission electron microscopy. The clay was preferentially situated in the PVC phase and across the interfaces of PVC/ABS. The effect of the addition of OMMT on the morphology and mechanical properties was also evaluated. Scanning electron microscopy revealed a large reduction in domain size when OMMT was used. The mechanical properties were studied through tensile and impact tests. The yield stress increased when an appropriate amount of OMMT was used without impairing the impact strength.     

Dynamics and pattern formations in diffusive predator‐prey models with two prey‐taxis

A reaction‐diffusion two‐predator‐one‐prey system with prey‐taxis describes the spatial interaction and random movement of predator and prey species, as well as the spatial movement of predators pursuing preys. The global existence and boundedness of solutions of the system in bounded domains of arbitrary spatial dimension and any small prey‐taxis sensitivity coefficient are investigated by the semigroup theory. The spatial pattern formation induced by the prey‐taxis is characterized by the Turing type linear instability of homogeneous state; it is shown that prey‐taxis can both compress and prompt the spatial patterns produced through diffusion‐induced instability in two‐predator‐one‐prey systems.