The Role of Intermixing in the Phase Determination of the Interlayer Exchange Coupling in Multilayers: Application to Fe-Cr Superlattices

The phase of the short-range interlayer exchange coupling oscillations in Fe n Cr m superlattices is expressed in terms of the intermixing at the Fe-Cr as well as at the Cr-Fe interfaces. The interdiffusion is modeled through stochastic algorithms, which presupposes floating of the atoms on the surface of the sample during the epitaxial growth. It automatically leads to the different chemical and magnetic structure of Fe on Cr and Cr on Fe interfaces. Self-consistent calculations of the magnetic moments are performed on the basis of the periodic Anderson model. Although short-range (2 monolayers (ML)) oscillations of exchange coupling were detected for all considered structures, its amplitude and phase strongly depend on the interface alloying. Introduction of the same intermixing at both interfaces does not change the phase as compared to the ideal superlattices with sharp interfaces. However different interdiffusion leads to the ~ -phase shift in accordance with experimental results for the Fe-Cr-Fe trilayers grown on an Fe whiskers. Distribution of magnetic moments on Fe atoms contains several distinct peaks but their position and relative area weakly depend on the alloying and interlayer exchange coupling in the superlattice. On the contrary, magnetic moments on Cr atoms are very sensitive to the intermixing and their behavior determines the strength and the phase of exchange coupling oscillations.     

Transient response of a rotor-AMBs system connected by a flexible mechanical coupling

In this paper, the effect of angular misalignment on the transient dynamics of a rotor-Active Magnetic Bearings (AMBs) system was examined with numerical analysis. A spatial model of a misaligned rotor mounted in two identical AMBs is setup to account angular misalignment with a flexible coupling having torsional and lateral flexibility. The driving rotor was powered by an electric motor in transient regime. Three models of AMBs were used with four; six and eight magnets. They were powered by bias and control current. The AMBs dynamics support parameters were modeled by stiffness and damping matrices. These were computed through an electromagnetic theory and derivation of the magnetic forces. The general equations of motion of the driven rotor were derived and solved using the Newmark time integration method. Simulation results were carried out to determine the frequency and transient responses in term of misalignment magnitude. Dynamic responses come to confirm a significant influence of the transient regime on the dynamic behavior of misaligned rotor. Simulated results also reveal that vibrations induced by angular misalignment were more important in the case of AMBs with four magnets. Spectral components of the system response were investigated, in sort to present diagnostic information about the signature of this kind of fault in transient regime.     

Q波段圆波导轴线弯曲TE01-TE11模式变换器设计

在模式耦合理论的基础上, 采用相位重匹配技术对圆波导轴线弯曲TE01-TE11模式变换器进行了数值优化计算和分析.在Q波段给出了两种不同周期数TE01-TE11模式变换器的优化设计参数.数值计算表明: 四周期模式变换器的最高转换效率为98.82%, 带宽为2.2 GHz, 六周期最高转换效率为99.89%, 带宽为1.7 GHz.研究了模式变换器关键几何尺寸在小范围内变化对转换效率的影响.并利用HFSS对给出的模式变换器进行了仿真, 仿真结果与数值模拟一致性较好.同时加工了六周期结构模式变换器并进行了小功率热测实验, 测试结果表明输出了模式纯度较高的TE11模式.     

The adaptive coupling scheme and the heterogeneity in intrinsic frequency and degree distributions of the complex networks

In the paper, we applied an adaptive principle to three kinds of complex networks as well as a random network within the context of the Kuramoto model. We found that the adaptive scheme could suppress the negative effect of the heterogeneity in the networks and the phase synchronization is enhanced obviously. The paper mainly investigates the adaptive coupling scheme in the small-world network, the scale-free network, and the modular network. Comparing with other weighted or unweighted static coupling schemes, the adaptive coupling scheme has a better performance in synchronization and communication efficiency, and provides a more realistic picture of synchronization in complex networks.     

CuCl catalyzed green and efficient one-pot synthesis of aminoindolizine frameworks via three-component reactions of aldehydes, secondary amines, and terminal alkynes in PEG

CuCl catalyzes efficient synthesis of aminoindolizine scaffolds by one-pot reactions in PEG of pyridine- or quinoline-2-carboxaldehydes with secondary amines and terminal alkynes via tandem C-H activation, coupling, and cyclization reactions. The reactions are easy to perform, atom-economic, environment friendly, broad in scope, and allow the generation of a number of biologically potent aminoindolizine frameworks from readily accessible starting materials.     

Effects of Ge/Ge preamorphization combined with sub-keV boron implantation in pMOSFET fabrication

The reduction of transient enhanced diffusion (TED) and suppression of short-channel effect (SCE) are very critical for the formation of ultra shallow junctions required for deep sub-micron devices. This article reports the nanoscale gate length of p-type metal-oxide-semiconductor field-effect transistor (pMOSFET) technology using ⁷²Ge/⁷⁴Ge germanium preamorphization implantation (Ge PAI) upon the (1 0 0)-oriented silicon substrates. It is demonstrated that the channeling can be eliminated by the formation of a Ge-implantation induced thin amorphous layer near the surface prior to boron implantation. Optimizing the amorphous layer thickness by controlling a high ⁷²Ge/⁷⁴Ge ratio, the device performance of pMOSFETs can be enhanced. In addition, the optimum conditions of Ge PAI would help the confinement of boron ions to avoid the channeling phenomenon. It is also found that the thin Ge PAI amorphous layer formed by a low ⁷²Ge/⁷⁴Ge ratio would cause the degradation of threshold voltage (V_th) roll-off characteristics, I_on/I_off ratio and the fluctuation of 62.14% in gain factor, as compared to that formed by a high ⁷²Ge/⁷⁴Ge ratio. It is attributed to a thinner Ge amorphous layer that has a weak ability to suppress the channeling tail of boron, as compared to a thicker Ge amorphous layer at the same implanted doses and acceleration energies among various ⁷²Ge/⁷⁴Ge ratios.     

Development of the radical C–O coupling reaction of phenols toward the synthesis of natural products comprising a diaryl ether skeleton

Compounds comprising a diaryl ether skeleton exist among natural phenols. The diaryl ether skeleton is thought to be biosynthesized through the coupling of two or more phenols. It is an important structural feature in medicines and agrochemicals, and it is imperative to develop methods for constructing such skeletons in organic synthesis. However, by the synthesis method through the coupling of phenols, coupling occurs preferentially at the ortho-substituted carbon atom of phenols. In this study, various radical-generating reagents and conditions were investigated with the aim of developing a short-step construction method of the diaryl ether skeleton by the radical homo-coupling of two phenol molecules. In addition, cross-coupling reactions between radicals of 2,4,6-tri-tert-butylphenol and p-substituted phenol were conducted to synthesize eight C (ortho)–O coupling products. Based on the results, a computational chemical approach was employed to verify the cause of C (ortho)–O bond formation.     

Partial Shift Mapping for PAPR Reduction with Low Complexity in OFDM Systems

The high peak‐to‐average power is one of the main drawbacks in OFDM systems. This letter proposes a partial shift mapping (PSM) method for peak power reduction in OFDM systems. By utilizing the properties of the discrete Fourier transform, the proposed method generates a set of candidate signals without additional complex multiplication and selects the one with minimum peak power for transmission. Analyses and simulations confirm that the PSM method achieves satisfactory peak power reduction performance and low complexity compared with other kindred methods, for example, selected mapping and partial transmit sequences.     

The all configuration mean energy multiconfiguration self-consistent-field method. I. Equal configuration weights

ABSTRACT

The All Configuration Mean Energy (ACME) conditions are a special case of state averaging for Multiconfigurational Self-Consistent-Field (MCSCF) orbital optimisation. The method is formulated using the Graphical Unitary Group Approach (GUGA) in which the Configuration State Function (CSF) basis is represented as walks within a Shavitt graph. This graphical formulation leads to efficient recursive algorithms for the energy and reduced density matrices (RDM) that are independent of the CSF dimension and that scale only as O(n²) where n is the number of occupied orbitals. The Hamiltonian matrix diagonalization step is obviated and the CSF expansion coefficients are neither referenced nor required during the orbital optimisation. This allows MCSCF orbital optimisation to be performed for essentially unlimited numbers of active orbitals and arbitrarily large CSF expansions. The discussion includes various types of CSF expansion spaces, the partitioning of the essential and redundant orbital optimisation parameters, the computation of the spin-density, and the formulation of state-specific analytic gradients and nonadiabatic coupling for high-level electronic structure methods that use the ACME MCSCF orbitals.     

Coupling analysis of screwing motion of double-walled carbon nanotubes

As the inner tube is excited from a rotation frequency at a separation distance, the inner tube will generate a reciprocating screwing motion. In this work, this coupling effect is investigated theoretically. The van der Waals force between two carbon nanotubes is expressed in a simple form of Fourier series so that the coupled nonlinear differential equations can be quickly solved. The proposed approach is thousands of times faster than the traditional method, which makes it possible to fit the coupling coefficients. As a result, expressions for the coefficients of the coupled equations are given. It is observed that a larger initial rotation frequency excitation will result in a higher dissipation rate of the axial oscillation, and vice versa.