激光热弹激励流-固界面波声场的数值模拟

利用热弹体运动方程和热传导方程耦合问题的变换域解,求解其极点留数的解析表达式.通过数值求根方法,得出铁-水、铝-水、铁-空气、铝-空气这4种流-固界面波的速度值,从而得到4种界面各界波相应的极点留数值.用快速傅立叶变换(FFT)技术得到脉冲激光线源热弹激励时流-固界面波瞬态位移波形.计算结果表明,这2种界面波不但存在于液-固界面,而且存在于气-固界面,但这2种流-固界面上波成分的相对幅度、脉冲持续时间不同.

用现代CAD方法设计一种气固两相激波管系统

介绍了现代CAD方法的应用,并通过一种气固两相激波管的设计过程加以说明,最后比较了传统CAD设计方法与现代CAD设计方法。

用现代CAD方法设计一种气固两相激波管系统

介绍了现代CAD方法的应用,并通过一种气固两相激波管的设计过程加以说明,最后比较了传统CAD设计方法与现代CAD设计方法。

Experimental investigation of vibration pretreatment-microwave curing process for carbon fiber reinforced resin matrix composites

The vibration pretreatment-microwave curing process is an efficient,low energy consumption,and high-quality out-of-autoclave curing process for carbon fiber resin matrix composites.This study aims to investigate the impact of vibration pretreatment temperature on the fiber weight content,microscopic morphology and mechanical properties of the composite laminates by using optical digital microscopy,universal tensile testing machine and thermo-gravimetric analyzer.Additionally,the combined mode of Bragg fiber grating sensor and temperature measurement fiber was employed to explore the effect of vibration pretreatment on the strain process during microwave curing.The study results revealed that the change in vibration pretreatment temperature had a slight impact on the fiber weight content when the vibration acceleration remained constant.The metallographic and interlaminar strength of the specimen formed at a vibration pretreatment temperature of 80℃ demonstrated a porosity of 0.414% and a 10.69% decrease in interlaminar shear strength compared to autoclave curing.Moreover,the introduction of the vibration energy field during the microwave curing process led to a significant reduction in residual strain in both the 0°and 90°fiber directions,when the laminate was cooled to 60℃.

靠泊趸船固泊结构强度分析

针对趸船固泊强度问题,以某海事趸船固泊为例,就较为关心的潮汐水位变化和上下游水体流速以及靠泊时对系固设备强度的影响为分析对象,进行了定位桩系固方式强度的准静力学剖析,从趸船系固牛腿的布置、结构强度和其他船靠泊时的受力分析和载荷特点等方面出发,阐述定位桩系固的计算要点和注意点。分析表明,在完成靠泊后,趸船受风载荷、水力以及横浪作用下的撞击载荷影响比较大,尤其对多艘船舶非对称停靠比较敏感。

流-固多层结构中软层介质参数反演研究

建立了固体层内含软层介质的多层流-固界面模型。使用传递矩阵法,导出固体层内含软层介质的流-固界面波的频散方程。根据频散方程计算频散曲线,改变软层介质的深度、厚度及横波波速,观察频散曲线的变化。使用有限元软件建立仿真模型,引入遗传反向传播(Back Propagation, BP)神经网络,对模型参数进行了反演。反演结果表明,使用遗传BP神经网络,能有效地反演出软层介质的深度、厚度与横波波速参数。

α-甲基乙酰乙酸乙酯的合成

以乙酰乙酸乙酯为原料,硫酸二甲酯为甲基化试剂,固体氢氧化钠为碱,PEG-800为相转移催化剂,采用固/液相转移催化法合成α—甲基乙酰乙酸乙酯,粗品含量92.2％,折纯收率为70％。

Effect of travelling magnetic field on interface morphology in directionally solidified Sn-Cd alloy

The diversity of interface morphologies is observed for directionally solidified Sn-0.65%Cd alloy under a travelling magnetic field （TMF） in the 4 mm-diameter sample. Under an upward TMF, planar and cellular interface morphologies transform alternately with increasing magnetic flux density （B≤10.3 mT）. The interface morphology transforms from shallow cellular to deep cellular morphology under a weak downward TMF （B=3.2 mT）. When the magnetic flux density increases further, both sides of the interface morphology appear to be slightly inconsistent, but they roughly tend to be planar under a strong downward TMF （BS10.3 mT）. The interface instability may be attributed to the flow driven by the TMF. Moreover, the shape of interface appears to be almost flat under an upward TMF, but deflective under a downward TMF.

Structure design and simulation of MEMS vibrating ring gyroscope

MEMS gyroscope is a new inertial navigation sensor,which can measure the input angular rate of sensitive axis using Coriolis effect.Compared to the conventional gyroscope,it owns many unique advantages.A novel structure of vibrating ring gyroscope is proposed and the finite element model of the oscillator is established based on MEMS technology.Through the modal analysis,the natural frequency and mode shapes of the oscillator are obtained.By analyzing the effects of the structural parameters on the mode shapes and frequency of the harmonic oscillator,the optimal design parameters are got.The frequency difference between the operating mode and the other modes is greater than 1kHz after optimization,which can avoid the frequency coupling of the operating mode and other vibrating modes of the oscillator.The simulation results show that the performance parameters of the ring structure meet the design requirements and have obvious advantages.

Microwave direct synthesis and thermoelectric properties of Mg_(2)Si by solid-state reaction

In order to reduce the oxidation and volatilization caused by Mg element in the traditional methods for synthesizing Mg2Si compounds,Mg2Si thermoelectric materials were prepared by solid state reaction and microwave radiation techniques.Structure and phase composition of the materials were investigated by X-ray diffraction.The electrical conductivity,Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 700 K.It is found that high purity Mg2Si powders can be obtained with excessive content of 8% Mg from the stoichiometric Mg2Si at 853 K and 2.5 kW for 30 min.A maximum dimensionless figure of merit,ZT,of about 0.13 was obtained for Mg2Si at 600 K.

激光在气-固界面激励泄漏Lamb波的数值模拟与实验检测

以激光超声的热弹激发机理为基础,采用有限元技术求解热传导和热弹体运动的流-固耦合问题,得到了脉冲激光线源激励下气-铝界面上的瞬态泄漏Lamb波波形.在实验上,建立了基于光偏转原理的泄漏Lamb波探测装置,探测了脉冲激光在气-铝界面上激励泄漏Lamb波的实验波形.以数值计算和实验数据为基础,通过波形的相位谱和振幅谱分析了泄漏Lamb波的色散特性和衰减特性.

Microwave Attenuation of Solid Propellant Exhaust Plume in Oblique Orientation

Aim To investigate the effects of the incident orientation on the microwave attenuation. Methods Attenuation allowing microwave signal transmitting in an oblique or vertical direction through the solid propellant exhaust plume was computed, and the experiments were performed utilizing a lab scale solid rocket motor with a fully expanded nozzle. Results The predicted results accord well with the experimental results. Conclusion The microwave attenuation in the oblique path is greater than that in the vertical path.

The filtering characteristics of HHT and its application in acoustic log waveform signal processing

Array acoustic logging plays an important role in formation evaluation. Its data is a non-linear and non-stationary signal and array acoustic logging signals have time-varying spectrum characteristics. Traditional filtering methods are inadequate. We introduce a Hilbert- Huang transform （HHT） which makes full preservation of the non-linear and non-stationary characteristics and has great advantages in the acoustic signal filtering. Using the empirical mode decomposition （EMD） method, the acoustic log waveforms can be decomposed into a finite and often small number of intrinsic mode functions （IMF）. The results of applying HHT to real array acoustic logging signal filtering and de-noising are presented to illustrate the efficiency and power of this new method.

Effect of traveling magnetic field on dendrite growth of Pb-Sn alloy during directional solidification

The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated.The melt convection was modulated by traveling magnetic field.When the direction of traveling magnetic field was changed from upward to downward,the primary dendrite spacing gradually increased,and the distribution peak of the primary dendrite spacing shifted to the field of narrower spacing.These result from the different intensities of melt convection,which are controlled by the traveling magnetic field.The effects of the traveling magnetic field on melt convection are similar to those of adjustment in the gravity level,thus,the primary dendrite spacing varies.When the intensity of the traveling magnetic field was 1 mT,and the drawing speed was 50 μm/s,the gravity acceleration reached 0.22g for the downward-traveling magnetic field and 3.07g for the upward-traveling magnetic field.

磷钼酸铋光催化降解亚甲基蓝

采用微波固相法,以硝酸铋、钼酸铵、磷酸二氢铵为原料合成了磷钼酸铋,用FT-IR、XRD、PL等对磷钼酸铋的结构和电子-空穴对的复合性能进行表征。在紫外光下降解亚甲基蓝为研究对象,考查磷钼酸铋光催化剂的光照时间、催化剂用量、亚甲基蓝初始浓度、亚甲基蓝初始酸度等因素对亚甲基蓝降解的影响。实验结果表明:合成的磷钼酸铋具有Keggin结构,通过降低光生电子和空穴的复合几率,提高催化剂的光催化活性。在紫外光照射时间60min,催化剂用量为0.6g,亚甲基蓝溶液初始浓度为20mg/L,溶液的pH值为5时,亚甲基蓝降解率可达98.4%。

Characteristics and Transdermal Drug Delivery of Triamcinolone-Acetonide-Acetate-Loaded Solid Lipid Nanoparticles Carbomer Gel

Aim To prepare triamcinolone-acetonide-acetate (TAA)-loaded solid lipidnanoparticles (SLN) carbomer gel with tripalmitin glyceride (TPG), and investigate theircharacteristics and transdermal drug delivery. Methods SLN suspension was prepared by high-pressurehomogenization technique, and then mixed with carbomer gel matrix to get SLN gel. The morphology,particle size with polydispersi-ty index (PI) and zeta potential were examined by atomic forcemicroscopy (AFM) and photon correlation spectroscopy (PCS). The entrapment efficiency, stability andin vitro drug release were also studied. The transdermal drug delivery through porcine ear skin wasevaluated using modified Franz diffusion cells. Results The SLN had a spherical shape with theaverage size of (95.5 - 186.2) nm, the zeta potential of (-26.3- -15.7) mV and the entrapmentefficiency of 67.4%-90.3% for different TAA encapsulated compounds. TAA-SLN carbomer gel had goodstability, the release profile in vitro fitted Higuchi equation. In comparison with conventionalhydrogels, TAA-SLN carbomer gel resulted in higher drug permeation amount and drug deposition withinporcine ear skin after 24 h penetration experiment. Conclusion TAA-SLN carbomer gel is preparedwith stable physicochemical properties. The release profile and improved drug permeation into skinmake it be a promising vehicle for transdermal drug delivery.

A unique method for curing composite materials by introducing vibration treatment into the hybrid heating process

Carbon fiber reinforced plastics provide many excellent properties and are widely used in the aerospace industry.However,the existing composites autoclave process still faces difficulties such as high-energy consumption,uneven distribution of temperature field,complications of pressure transmission,and high cost,which limit their application in manufacturing of large complex composites components.In this study,the vibration treatment was introduced into the composites microwave curing process innovatively.On the basis of giving full play to the uniform heating characteristics of the microwave,the problems of a large number of internal defects and poor molding quality caused by the insufficient curing pressure have been solved.The results showed that the samples cured by the improved microwave process without external pressure had a few internal voids,excellent interface bonding conditions,and lower residual stress.Their properties were almost consistent with the samples prepared by the standard autoclave process,which provided a new method for the high-performance,efficient,safe,and low-cost manufacturing of large complex composites components.

Numerical simulation of stress for the blasting of foundation pit

Through the simulation of explicit dynamic analysis software LS-DYNA,made an analysis to the particle velocity and the stress distribution of surrounding rock when the explosives blasting.Explicated the mechanical character of surrounding rock in the foun- dation pit blasting,provided a basis to set of blasting parameters and optimized the blast- ing construction.

An All-Solid-State Tunable Dual-Wavelength Ti：Sapphire Laser with Quasi-Continuous-Wave Outputs

A high power dual-wavelength Ti：sapphire laser system with wide turning range and high efficiency is described, which consists of two prism-dispersed resonators pumped by an a11-solid-state frequency-doubled Nd：YAG laser. Tunable dual-wavelength outputs, with one wavelength range from 750nm to 795nm and the other from 80Ohm to 850nm, have been demonstrated. With a pump power of 23 W at 532nm, a repetition rate of 6.5kHz and a pulse width of 67.6ns, the maximum dual-wavelength output power of 5.6 W at 785.3nm and 812.1 run, with a pulse width of 17.2ns and a line width of 2nm, has been achieved, leading to an optical-to-optical conversion efficiency of 24.4%.

Wavelet analysis of pressure fluctuation signals in a gas-solid fluidized bed

It has been shown that much dynamic information is hidden in the pressure fluctuation signals of a gas-solid fluidized bed. Unfortunately, due to the random and capricious nature of this signal, it is hard to realize reliable analysis using traditional signal processing methods such as statistical analysis or spectral analysis, which is done in Fourier domain. Information in different frequency band can be extracted by using wavelet analysis. On the evidence of the composition of the pressure fluctuation signals, energy of low frequency (ELF) is proposed to show the transition of fluidized regimes from bubbling fluidization to turbulent fluidization. Plots are presented to describe the fluidized bed's evolution to help identify the state of different flow regimes and provide a characteristic curve to identify the fluidized status effectively and reliably.