热振子式Z轴MEMS角速度陀螺敏感机理的研究

揭示了一种热振子式Z轴MEMS角速度陀螺的敏感机理。在给出工作原理、热振子的振动模态和陀螺效应的基础上,对敏感结构内的温度场进行了计算。结果表明:(1)开机1.8 s后在敏感结构内形成一个稳定的温度场。(2)热振子在Y方向建立驱动模态,当沿着Z轴输入角速度时,在哥氏力的作用下热振子沿着X方向移动,造成温度场偏移,X方向上对称平行设置的两热线温差ΔT_(X)随着输入加速度az的加大呈现线性增长,温度灵敏度为125 mK/(°/s)。(3)根据输入-输出ω_(z)-V_(Xout)特性曲线,得到数学模型,揭示了该陀螺的敏感机理,陀螺灵敏度为0.095 mV/(°/s),非线性度为2.97%。本研究为优化结构奠定了实用理论基础。

热振子式双轴MEMS角速度陀螺敏感机理的研究

该文给出了一种热振子式双轴微机电系统(MEMS)角速度陀螺的敏感机理。在给出双轴敏感原理、热振子的振动模态和陀螺效应的基础上,对敏感结构内的温度场进行了计算。结果表明,开机1.8 s后在敏感结构内形成了一个稳定的温度场;当有角速度加载时,热振子随着输入角速度而移动,造成温度场偏移,两个正交Y(X)方向上对称设置的两热线温差ΔTY(ΔTX)随着输入角速度ax(ay)的加大呈现线性增长,x、y轴平均温度灵敏度为121 mK/(°)/s;根据输入-输出ω_(x)-V_(Yout)和ω_(y)-V_(Xout)特性曲线得到数学模型,从而揭示了敏感机理,x、y轴平均灵敏度为0.091 mV/(°)/s,平均非线性度为1.86%,平均交叉耦合为2.3%。该文为优化结构奠定了实用理论基础。

一种用于磁振热理疗仪的磁热振子设计与分析

提出一种新的结构简单、产热快、磁场参数多、振动效果好、方便使用的磁热振子结构。对该磁热振子的基本结构、工作机理、温度参数、磁场参数和振动参数进行了分析。该磁热振子可以产生磁、振、热三种物理因子,且可以通过改变工作电源进行控制,达到动态平衡,实现温度控制,使用不同表磁的永磁体改变磁场范围,修改供电电源频率和固定装置置留空间,产生不同振动频率和振幅。该磁热振子符合磁振热理疗仪需要,能够提供稳定的磁、振、热三种物理治疗因子。

用于康复治疗的磁振热理疗仪设计

开发一种用于康复治疗的磁振热理疗仪,该理疗仪包括磁热振子与控制系统两部分,磁热振子提供磁、振、热3种物理治疗因子,控制系统实现对时间设定与治疗温度实时监控,能够为患者提供磁场强度、治疗温度、振动按摩等参数多种选择。通过对该理疗仪的磁热振子进行实验,结果显示其含芯线圈的温度在通电5 min后可以达到稳定,且可以通过设置工作电源电压对温度进行精确控制。实验结果证明,该磁振热理疗仪具有多磁场强度、温度独立设置、两种按摩方式等特点,能够很好满足临床上不同患者的需求。

Effects of Thermal Lattice Vibration on the Effective Potential of Weak-Coupling Bipolaron in a Quantum Dot

Based on the Huybrechts' linear-combination operator,effects of thermal lattice vibration on the effective potential of weak-coupling bipolaron in semiconductor quantum dots are studied by using the LLP variational method and quantum statistical theory.The results show that the absolute value of the induced potential of the bipolaron increases with increasing the electron-phonon coupling strength,but decreases with increasing the temperature and the distance of electrons,respectively;the absolute value of the effective potential increases with increasing the radius of the quantum dot,electron-phonon coupling strength and the distance of electrons,respectively,but decreases with increasing the temperature;the temperature and electron-phonon interaction have the important influence on the formation and state properties of the bipolaron:the bipolarons in the bound state are closer and more stable when the electron-phonon coupling strength is larger or the temperature is lower;the confinement potential and coulomb repulsive potential between electrons are unfavorable to the formation of bipolarons in the bound state.

Quantum fluctuations of mesoscopic damped mutual capacitance coupled double resonance RLC circuit in thermal excitation state

Mesoscopic damped mutual capacitance coupled double resonance circuit is quantized by the method of damped harmonic oscillator quantization. Hamiltonian is diagonalized by the method of unitary transformation. The energy spectra of this circuit are given. The quantum fluctuations of the charge and current of each loop are investigated by the method of thermo- field dynamics (TFD) in thermal excitation state,thermal squeezed vacuum state, thermal vacuum state and vacuum state. It is shown that the quantum fluctuations of the charge and current are related to not only circuit inherent parameter and coupled magnitude, but also quantum number of excitation, squeezed coefficients, squeezed angle and environmental temperature. And the quantum fluctuations increase with the increase of temperature and decay with time.

Direct Observation of Electron-Vibration Coupling at MXene-Solvent Interface

MXenes,a new family of two-dimensional(2D)materials,have received extensive interest due to their fascinating physicochemical properties,such as outstandinglight-to-heat conversion efficiency.However,the photothermal conversion mechanism of MXenes is still poorly understood.Here,by using femtosecond visible and mid-infrared transient absorption spectroscopy,the electronic energy dissipation dynamics of MXene(Ti_(3)C_(2)T_(x))nanosheets dispersed in various solvents are carefully studied.Our results indicate that the lifetime of photoexcited MXene is strongly dependent on the surrounding environment.Especially,the interfacial electron-vibration coupling between the MXene nanosheets and the adjacent solvent molecules is directly observed following the ultrafast photoexcitation of MXene.It suggests that the interfacial interactions at the MXene-solvent interface play a critical role in the ultrafast energy transport dynamics of MXene,which offers a potentially feasible route for tailoring the light conversion properties of 2D systems.

Efficient Coherent Population Transfer of D2 Molecules by Stark-induced Adiabatic Raman Passage

Preparation of a high flux of hydrogen molecules in a specific vibrationally excited state is the major prerequisite and challenge in scattering experiments that use vibrationally excited hydrogen molecules as the target. The widely used scheme of stimulated Raman pumping suffers from coherent population return which severely limits the excitation efficiency. Re- cently we successfully transferred D2 molecules in the molecular beam from （v=0, J=0） to （v=1, J=0） level, with the scheme of Stark-induced adiabatic Raman passage. As high as 75% of the excitation efficiency was achieved. This excitation technique promise to be a unique tool for crossed beam and beam-surface scattering experiments which aim to reveal the role of vibrational excitation of hydrogen molecules in the chemical reaction.

Construction of an operando dual-beam fourier transform infrared spectrometer and its application in the observation of isobutene reactions over nano-sized HZSM-5 zeolite

An operando dual‐beam Fourier transform infrared (DB‐FTIR) spectrometer was successfully developed using a facile method. The DB‐FTIR spectrometer is suitable for the real‐time study of the dynamic surface processes involved in gas/solid heterogeneous catalysis under real reaction conditionsbecause it can simultaneously collect reference and sample spectra. The influence of gas‐phasemolecular vibration and heat irradiation at real reaction temperatures can therefore be eliminated.The DB‐FTIR spectrometer was successfully used to follow the transformation of isobutene over nano‐sized HZSM‐5 zeolite under real reaction conditions.

Effects of Intermolecular Interactions on Luminescence Property in Organic Molecules

The organic solid-state lightemitting materials have attracted more and more attention owing to their promising applications in displays,lasers and optical communications.In contrast to isolated molecule,there are various weak intermolecular interactions in organic solids that sometimes have a large impact on the excited-state properties and energy dissipation pathways,resulting in strong fluorescence/phosphorescence.It is increasingly necessary to reveal the luminescence mechanism of organic solids.Here,we briefly review how intermolecular interactions induce strong normal fluorescence,thermally activate delayed fluorescence and room-temperature phosphorescence in organic solids by examining changes in geometry,electronic structures,electron-vibration coupling and energy dissipation dynamics of the excited states from isolated to aggregated molecules.We hope that the review will contribute to an in-depth understanding of the excited state properties of organic solids and to the design of excellent solid-state light-emitting materials.

Aroma Profile of Myrrh and Its Thermal Variation

The authors examined the thermal change in the aroma profile of myrrh. The fresh odor of raw myrrh and its hexane extract depended on the amount of （E）-13-ocimene. Myrrh was extracted with hexane to avoid inducing changes in the constituents and odor. The main constituent, （E）-L3-ocimene （group A; low boiling point）, and the other constituents （group B; high boiling point） of the hexane extract were separated by bulb-to-bulb distillation. The constituents of groups A and B were analyzed over time by nuclear magnetic resonance analysis and the odors were evaluated. Myrrh＇s odor depended on both the amount of thermally unstable （E）-[3-ocimene, which contributed to the fresh odor, and the constituents of group B （thermally stable）, which contributed to the myrrh-like odor. Six compounds （c^-santalene, （Z）-a-bisabolene, c^-bergamotene, （E）-ct-santalal, c^-photosantalol and campherenol） were isolated from group B. No individual group B component had a myrrh-like odor, although the combined odor of group B was myrrh like. The authors demonstrated that the aroma profile of myrrh depends on the thermal instability of （E）-^-ocimene and a combination of six thermally stable terpenes with similar molecular structures.

Design of Anode HVPS of ECRH on HL-2A Tokamak

The ECRH is an effective way of plasma heating on tokamak. The gyrotrons with two high voltage power supplies （ HVPS ） are used in ECRH experiment on the HL-2A tokamak. This type of gyrotron is benefit to improve the output efficiency and HVPS design. So the anode HVPS with higher output power, reliable characteristic and controlling easily are necessary for the work of gyrotron normally.

Theoretical Study on Vibrational Spectra, Detonation Properties and Pyrolysis Mechanism for Cyclic 2-Diazo-4,6-dinitrophenol

Based on the full optimized molecular geometrical structures at the DFT-B3LYP/6- 311＋G^＊＊ level, there exists intramolecular hydrogen bond interaction for cyclic 2-diazo- 4,6-dinitrophenol. The assigned infrared spectrum is obtained and used to compute the thermodynamic properties. The results show that there are four main characteristic regions in the calculated IR spectra of the title compound. The detonation velocities and pressures are also evaluated by using Kamlet-Jacobs equations based on the calculated density and condensed phase heat of formation. Thermal stability and the pyrolysis mechanism of 2- diazo-4,6-dinitrophenol are investigated by calculating the bond dissociation energies at the B3LYP/6-311＋G^＊＊ level.

Stochastically driven vibrations of single-layered graphene sheets

Thermal vibration of single-layered graphene sheets (SLGSs) is investigated using plate model together with the law of equi-partition of energy and the molecular dynamics (MD) method based on the condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field.The in-plane stiffness and Poisson ratio of SLGSs are calculated by stretching SLGSs.The effective thickness of SLGSs is obtained by the MD simulations for the thermal vibration of SLGSs through the natural frequency.The root-mean-squared (RMS) amplitudes for SLGSs of differing temperatures and boundary conditions are calculated by the MD,and are compared with the results calculated by the thin plate model together with the law of equi-partition of energy.At the center of SLGSs,the thin plate theory can predict the MD results reasonably well.For the difference of bonding structure of the edge atoms,the deviation between the MD results and plate theory becomes more readily apparent near the edges of SLGSs.

Structure characterization,magnetic and photoluminescence properties of Mn doped ZnS nanocrystalline

Wurzite ZnS:Mn nanorods are synthesized via a solvothermal method by using ethylenediamine and water as mixed solvent.The diameters of the nanorods increase and the lengths decrease with the Mn concentration.High resolution transmission electron microscopic images illustrate that a few cubic ZnS:Mn nanoparticles arise along with hexagonal nanorods on high Mn concentration.The samples set off yellow-orange emission at 590 nm,characteristic of 4 T→ 6 A 1 transition of Mn 2+ at T d symmetry in ZnS.Electron spin resonance spectrum of the nanorods shows that high Mn concentrations produce a broad envelope,whereas six-line hyperfine appears for lower Mn concentrations.These results together with the magnetization curves indicate that all the ZnS:Mn samples are paramagnetic even down to 4 K,which suggests that the ZnS:Mn is not suitable for dilute magnetic semiconductor.

Heat Generation by Electrical Current in Quantum Dot System with Fano Resonance

We study the heat generation in quantum dot system with Fano resonance by nonequilibrium Green＇s functions method. The Fano resonance influences the heat generation significantly. As increases, the heat generation decreases gradually. From the study of Q-eV curves, we llnd that the linewidth function F has huge influence on the heat generation. The Q-eV curves display obvious steps when the linewidth function is small. However, these steps disappear with F increasing. As the source-drain bias eV increases, the Q-eVg curves also display interesting behaviors.

Ag nanoparticles preparation and their light trapping performance

Ag nanoparticles were fabricated on Si substrates by radio-frequency magnetron sputtering and thermal annealing treatments.It was found that Ag nanoparticles are ellipsoid at low annealing temperature,but the axis ratio decreases with the increase of annealing temperature,and a shape transformation from ellipsoid to sphere occurs when the temperature increases to a critical point.The experimental results showed that the surface plasmon resonances depend greatly on the nanoparticles'shape and size,which is in accordance with the theoretical calculation based on discrete dipole approximation.The results of forward-scattering efficiency(FSE) and light trapping spectrum(LTS) showed that Ag nanoparticles annealed at 400°C could strongly enhance the light harvest than those annealed at 300 and 500°C,and that the LTS peak intensity of the former is 1.7 and 1.5 times stronger than those of the later two samples,respectively.The conclusions obtained in this paper showed that Ag ellipsoid nanoparticles with appropriate size is more favorable for enhancing the light trapping.

Microwave-assisted hydrothermal synthesis of cube-like Ag-Ag_2MoO_4 with visible-light photocatalytic activity

Cube-like Ag-Ag2MoO4 composite has been successfully prepared in the presence of PVP （potyvinylpyrrolidone） via a facile microwave-assisted hydrothermal process. Studies of its photocatalytic performance in the decomposition of RhB indicate that the cube-like Ag-Ag2MoO4 composite exhibits good catalytic activities under visible-light irradiation. The face that Ag pro- motes the absorption of visible light may be attributed to the surface plasmon resonance. Further XRD characterization after recycle photocatalytic tests confirms that partial Ag~ ions in Ag2MoO4 have been reduced to metallic Ag. Reaction temperature, reaction time and the amount of PVP have also been studied and found to play crucial roles in the formation of the cube-like microstructures.