基于预见控制功能的直线伺服电机冲击振动故障分析与对策研究

以直线伺服电机的冲击振动故障现象为研究对象,分析了混联结构下的直线伺服电机运动控制原理,从运动控制的角度解释了电机振动的原因。并提出了基于Turbo PMAC控制卡中预见控制功能的电机冲击振动抑制策略。通过实验证明,此振动抑制方案可以较好地抑制电机的冲击与振动,从而提高系统的控制性能。     

Effect of short polyethylene terephthalate fibers on properties of ethylene-propylene diene rubber composites

The alteration in some properties of electron beam (EB) cured ethylene-propylene diene rubber (EPDM) reinforced by polyethylene terephthalate (PET) fiber was investigated in this study. Bonding system Resorcinol/Hexamethylenetetramine/Silica (RHS) was used to enhance the fiber/EPDM adhesion and to maintain optimum composite strength properties. Mechanical properties of composites namely; tensile strength, hardness and modulus at 100 % elongation have been enhanced by adding PET fibers and increasing irradiation dose. Moreover, the effect of fiber loading and irradiation dose on the soluble fraction behavior of the composite in benzene was also investigated. The soluble fraction of the composites decreased with increasing the fiber loading and irradiation dose. The extent of fiber alignment and strength of fiber-rubber interface adhesion were analyzed from the anisotropic swelling measurements. In addition, thermal stability of the composites was increased. Besides, the mechanical properties like tensile strength and stiffness were improved by thermal ageing. Scanning electron microscopy (SEM) for the fractured surfaces and Wide- angle X- ray diffraction (WAXD) of the investigated samples confirmed that the adhesion occurred between fibers and EPDM.     

Microhydrogel-Mediated Synthesis of Sintered Hydroxyapatite Granules

Synthesis of macroporous hydroxyapatite (HA) granules with a controlled microarchitecture has been demonstrated by following a polymer microhydrogel mediated synthesis process coupled with sintering. The process is basically based on in situ nucleation and growth of HA nanoparticles in polymer (polyvinyl alcohol) microhydrogels. A systematic variation of polymer concentration has manifested a controlled evolution of a hierarchical macroporous granular structure after sintering.     

维吾尔语三音节词中元音和谐的声学特征分析

该文从提高语音合成自然度的实际需求出发,首次从实验语音学的角度从《维吾尔语语音声学参数库》中统计出了333个三音节词,其中再筛选了93个全和谐词和半和谐词,并对其元音的宽带共振峰模式、共振峰值、音高、时长和音强等韵律参数进行了统计分析,归纳了其共振峰、音高、时长和音强分布特点来考察元音和谐的基本声学特征,总结出了一些重要的规则和结论,为参数式或波形拼接式语音合成系统中调整合成前的元音和谐问题提供了重要的参考依据。     

维吾尔语单音节词复辅音声学分析

为了提高语音合成的自然度该文从文本分析模块入手,利用“维吾尔语语音声学参数库”,选择了带复辅音的63 个单音节词的声学参数,包括辅音时长和辅音强度,通过语音分析软件研究了维吾尔语复辅音的组合规律和声学规律,复辅音中两个辅音声学特征之间的声学区别等问题。从语言类型学的角度看,在现代维吾尔语带复辅音的单音节词中前辅音比后辅音短且前辅音比后辅音强是固定声学特征。可是复辅音的组合不是固定的,因为组成复辅音的音素有可能再增加。     

Modeling of thermal radiation in a participating media with conjugate heat transfer

Modeling a combination of thermal radiation and conjugate heat transfer in a three-dimensional rectangular domain which has a participating media CO₂ flowing through is done numerically in OpenFOAM. The rectangular duct has a vertical step (facing forward to the inlet) which is located at a distance from the inlet (the distance is same as the height of the inlet section). The domain is divided into two regions (namely solid and fluid). Carbon dioxide, a highly absorbing fluid with extinction, is used here as the participating medium. The ability of the code is verified to analyze the thermal radiation in a participating media with conjugate heat transfer. The study was carried out for a constant Reynolds number 250 and a contraction ratio of 0.5. The study focused primarily on the importance of adding thermal radiation on to thermal analysis and the reason behind the Nusselt number variation on different regions of solid–fluid interface. It also discussed the effect of radiative properties, such as optical thickness and linear scattering albedo, on the average convective Nusselt Number.     

Host-Assisted Delivery of a Model Drug to Genomic DNA: Key Information from Ultrafast Spectroscopy and in silico Study

Drug delivery to a target without adverse effects is one of the major criteria for clinical use. Herein, we have made an attempt to explore the delivery efficacy of SDS surfactant in a monomer and micellar stage during the delivery of the model drug, Toluidine Blue (TB) from the micellar cavity to DNA. Molecular recognition of pre-micellar SDS encapsulated TB with DNA occurs at a rate constant of k₁ ∼652 s⁻¹. However, no significant release of encapsulated TB at micellar concentration was observed within the experimental time frame. This originated from the higher binding affinity of TB towards the nano-cavity of SDS at micellar concentration which does not allow the delivery of TB from the nano-cavity of SDS micelles to DNA. Thus, molecular recognition controls the extent of DNA recognition by TB which in turn modulates the rate of delivery of TB from SDS in a concentration-dependent manner.     

Controlling Degree of Inversion in MgFe2O4 Spinel Films Grown in External Magnetic Fields

Single-phase magnesium ferrite spinel films (MgFe₂O₄) were grown by magnetic field-assisted chemical vapor deposition (mfCVD) of a mixed-metal precursor compound, [MgFe₂(O^tBu)₈]. The formation of monophasic MgFe₂O₄ deposits as a function of the applied magnetic field strength (B = 0.0, 0.5, and 1.0 T) was investigated and confirmed by X-ray diffraction and photoelectron spectroscopy analyses. Thin film cross-sectional electron microscopic analysis (FIB-SEM) exhibited higher grain growth and densification in MgFe₂O₄ films obtained under the magnetic field influence when compared to spinel samples grown under zero-field conditions. Application of an external magnetic field of varying strengths during the chemical vapor deposition process resulted in a change in the light absorption properties and crystal orientation in the MgFe₂O₄ films, evident in the decreased photoabsorbance analyzed by the UV-Vis spectra and the decrease of intensity of the (400) peak in MgFe₂O₄ films grown under magnetic field. A comprehensive analysis of X-ray diffraction and X-ray magnetic circular dichroism (XMCD) results indicated a higher degree of inversion in MgFe₂O₄ deposits grown in an external magnetic field corroborated by a larger contribution of ligand field transitions of tetrahedrally coordinated Fe(III) centers affecting the visible light absorption of MgFe₂O₄ films.