Polaronic discontinuities induced by off-diagonal coupling

In this paper, we study a form of the Holstein molecular crystal model in which the influence of lattice vibrations on the transfers of electronic excitations between neighboring sites (off-diagonal coupling) is taken into account. Using the Toyozawa Ansatz and the Lanczos algorithm, the Holstein Hamiltonian with two types of off-diagonal coupling is studied focusing on a number of analyticity issues in the ground state. For finite-sized lattices and antisymmetric coupling, a sequence of discontinuities are found in the polaron energy dispersion, the size of the ground-state phonon cloud, and the linearized von Neumann entropy used to quantify the quantum entanglement between the exciton and the phonons in the ground state. Such behavior is accompanied by a shift of the ground-state crystal momentum from zero to nonzero values as the coupling strength is increased. In the thermodynamic limit, all discontinuities associated with antisymmetric coupling vanish except the one corresponding to the initial departure of the ground-state wavevector from the Brillouin zone center. For the case of symmetric off-diagonal coupling, a smooth crossover is found to exist in all parameters regimes.     

Dynamic Spectrum for noninvasive blood component analysis and its advances

Noninvasive blood component analysis by spectroscopy has broad prospects that based on Dynamic Spectrum (DS) can effectively suppress the influences of individual differences (such as skin, muscle, fat) and the variations of measurement conditions, which shows its potential in the clinical applications. The purpose of this article is to review the starting point and the advances of DS, to assess the current situation of the field and to explore future directions. The principle of DS and the error sources of noninvasive blood component analysis were introduced. An overview of the six stages of noninvasive blood component analysis, including sensing principle, acquisition methods of spectral photoplethysmography (photoplethysmography signal at multiple wavelengths) signals, spectral photoplethysmography (SPPG) preprocessing, DS extraction methods from SPPG, the quality evaluation for DS and modeling methods, was presented. Finally, the existing issues of DS are discussed and the future directions are predicted.     

Controlled Synthesis of a High-Mobility Bi3O2.5Se2 Semiconductor by Oxidation of Bi2Se3 for Fast and Highly Sensitive Photodetectors

The search of new high-mobility two-dimensional (2D) semiconductors is crucial for the development of next-generation photodetectors, since current photodetectors based on single 2D semiconductors usually cannot simultaneously own ultrafast response rate and ultrahigh sensitivity. Here, using a facial method of sequentially oxidizing Bi₂Se₃ at optimal O content, a series of bismuth oxyselenide semiconductors (Bi₃O_2.5Se₂, Bi₂O₂Se, Bi₂SeO₅) with appealing electronic applications are successfully synthesized. The crystal and band structures of a superlattice-free Bi₃O_2.5Se₂ phase are resolved by 3D electron diffraction and density functional theory calculations, showing a unique non-neutral layered structure, moderate band gap, and small effective mass. More importantly, the concept of Bi₂Se₃ + O₂ can be extended to synthesize the superlattice-free Bi₃O_2.5Se₂ ultrathin films by chemical vapor deposition, whose room-temperature mobility can be as high as ≈150 cm² V⁻¹ s⁻¹ based on Hall measurements. The ultrathin Bi₃O_2.5Se₂ photodetectors with a simple device configuration simultaneously own ultrafast response time (≈31 µs), ultrahigh responsivity (≈8 × 10⁴ A/W), and large detectivity (≈8 × 10¹³ Jones). This work not only introduces a facile way to regulate the phase in the bismuth oxyselenide family, but also provides an alternative candidate for ultrafast and ultrasensitive photodetectors.     

Vanadium-Catalyzed Synthesis of 4(3H)-Quinazolinones from Anthranilamides and Aryl Aldehydes

An efficient synthesis of 2-substituted and 2,3-disubstituted quinazolin-4(3H)-ones via tandem reaction of anthranilamides and aromatic aldehydes catalyzed by vanadyl acetylacetonate with 1 mol% loading under an air atmosphere is described. This new method is associated with several advantages such as low catalyst loading (only 1 mol%), use of green oxidant in the form of air, high atom economy, and good to excellent yields. A mechanism of vanadium-catalyzed synthesis of 4(3H)-quinazolinones has also been proposed.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

单级和两级脉冲管制冷机的设计和实验研究

介绍了一单级脉冲管制冷机的实验研究 ,并利用其作为一级进行了两级脉冲管制冷机的设计和实验研究。获得了2 1K的最低温度和两级脉冲管制冷机尺寸设计的经验     

一种新的基于弧段提取的椭圆检测方法

为了克服椭圆检测过程中对椭圆完整性和边缘梯度信息依赖性较强的缺点,实现椭圆目标的快速有效检测,提出了一种新的基于弧段提取的椭圆拟合方法。首先将梯度方向符号相同的相邻边缘点连接成弧段,然后根据弧段的凸性和象限分类组成包含三段弧的弧组,定义了新的弧选择策略,利用位置约束和弧对的椭圆中心估计提取候选椭圆,最后采用改进的拟合算法拟合椭圆。实验结果表明,基于弧段提取的椭圆拟合方法相对于LMEDS算法和RHT3具有更好的准确性、鲁棒性和稳定性,实时性也有一定的提高。     

Mode analysis of trilaminar bender bar transducers using an approximation method

Based on the vibration theory of a thin plate, an analytical treatment of the trilaminar bender bar with piezoelectric elements and inert substrate of various lengths is presented for mode analysis. Resonance frequency and effective electromechanical coupling coefficient are calculated by this method. The impacts of the geometries of the bender bar on the performance of its fundamental and third-order flexural mode are investigated in detail under rigid boundary conditions. It is shown that resonance frequency is extremely sensitive to the thickness of inert substrate. Moreover, the effective electromechanical coupling coefficient has peaks as the length of piezoelectric elements varies. The peaks are achieved when the length of piezoelectric elements equals the length between two nodes having zero strains in the x-direction. The trilaminar bender bar will be effectively excited when the strains on the piezoelectric element are in the same phase, which is important to disclose the vibration mechanisms of this kind of transducer. Also, analytical results are compared with the ones of numerical simulation. The results suggest that effective electromechanical coupling coefficient shares similar patterns with electrical conductance, which can be used to characterize transducer performance to a certain extent. It also demonstrates that the analytical treatment provides an efficient alternative way for optimizing the bender bar transducer design.     

Charging Quantum Batteries with a General Harmonic Driving Field

A general harmonic driving field was considered for improving the charging efficiency of the quantum battery system. Charge saturation was used to describe the charging efficiency, where the charging mode is divided into saturated and unsaturated. The relationships between the time-dependent charge saturation and parameters of the general driving field were evaluated both analytically and numerically. The Floquet theorem was used to express time-dependent charge saturation with the quasienergy and Floquet states of the system. The analytical and numerical results were used to identify the best parameter values for optimizing the charging efficiency.