叶片组轴向模态共振失效的理论与实验研究

为了找出叶片的失效机理及解决的办法，利用金相、扫描电镜等分析手段，从宏观和微观的角度对叶片及断口进行了观察和分析；用三维有限元法和实验方法对其振动特性进行了研究。分析得出：造成叶片开裂是由于叶片组第2类轴向振动模态和喷嘴叶栅出口气流不均匀引起的激振力频率发生共振，导致叶片高周疲劳造成的。叶根齿表面加工粗糙是裂纹起裂的一个重要诱发因素。采用不改变叶型，仅调整叶片组中的叶片数，成功地实现了叶片的改型设计。该研究表明：叶片组的第2类轴向振动模态同喷嘴激振力共振是危险的，应该避免。调整叶片组中的叶片数是调整叶片组轴向固有振动模态的一个有效方法。图6表3参5     

EFFECT of PLASTICIZER LEVEL and TEMPERATURE ON WATER VAPOR TRANSMISSION of CELLULOSE-BASED EDIBLE FILMS1

This study was conducted to determine water sorption isotherms of cellulose-based films made from methyl cellulose (MC) and hydroxypropyl cellulose (HPC), and to evaluate the effect of plasticizer concentration and temperature on water vapor permeability coefficient in those films. the equilibrium moisture contents of MC film and HPC film increased slowly with an increase in water activity (a_w) up to 0.75, but increased greatly after 0.75 a_w. the water vapor permeability coefficient of HPC film increased as the concentration of polyethylene glycol (PEG) increased; however, the water vapor permeability coefficient of MC film which contained 0.22 ml PEG/g cellulose was lower than of films which contained no or higher PEG. an Arrhenius-type relationship was fitted to examine temperature dependence of water vapor permeability coefficients of cellulose films. the edible films studied exhibited relatively low activation energies (14.56–16.43 kJ/mol) compared with typical food packaging materials.     

White luminescence of Ho3+/Tm3+/Yb3+-codoped CaWO4 synthesized via citrate complex route assisted by microwave irradiation

The nanocrystalline Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ upconversion (UC) phosphors were successfully synthesized by a modified citrate complex method using microwave irradiation. The citrate complex precursors were heat-treated at temperature ranging from 300 to 700 °C for 3 h. Crystallization of the Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ was detected at 400 °C, and entirely completed at 600 °C. The Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ heat-treated at 600 °C showed primarily spherical and homogeneous morphology. Under the laser excitation of 980 nm, Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ shows the bright white upconversion (UC) emission visible to the naked eye, which is composed of a blue emission at 475 nm from Tm³⁺, and green and red emissions at 543 and 651 nm respectively from Ho³⁺. The coordinates of Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ in the Commission International De'eclairage (CIE) chromaticity diagram could be controlled from a cool to a warm white color depending on the Tm³⁺ and Ho³⁺ concentrations. The UC luminescent properties on Tm³⁺ and Ho³⁺ concentrations and related mechanism based on laser pump power were discussed in detail.     

生物植入用碳纳米管增强混合功能梯度材料的力学性能(英文)

利用羟基磷灰石(HA)、不锈钢316L(SS316L)和碳纳米管(CNT)制备生物医学植入体用混合功能梯度材料(FGM)。加入SS316L和CNT增强功能梯度材料离散层的HA制成三种不同类型的功能梯度材料。第一种功能梯度材料加入10%~40%(质量分数)的SS316L强化微米HA,浓度梯度为10%。第二种功能梯度材料,在第一种功能梯度材料的基础上加入0.5%(质量分数)的功能化碳纳米管。第三种功能梯度材料在第二种功能梯度材料的基础上加入微米HA和纳米HA(1:1)的混合物。所有类型的功能梯度材料在相似的压缩参数和烧结参数下,进行单轴压缩实验,并采用无压烧结技术进行烧结。结果表明,加入碳纳米管和纳米晶体HA提高了功能梯度材料的致密度。碳纳米管增强的功能梯度材料的硬度和断裂韧性增加,但是微米和纳米晶体HA增强的功能梯度材料的硬度和断裂韧性的增加更明显。     

AN ANALYTICAL SOLUTION FOR A TUBULAR REACTOR MODEL WITH DISPERSION IN BOTH RADIAL AND AXIAL DIRECTIONS

An analytical solution for an unsteady-state tubular reactor model with dispersion in the radial as well as in the axial direction is presented. An arbitrary initial concentration profile and an arbitrary time-varying feed concentration are allowed; and the reaction occurs also on the interior surface wall of the reactor. The problem is recast into a more tractable form by an exponential transformation and then the method of Green's function combined with the orthonormal eigenfunction expansions based on the solution of the associated Helmholtz equation is used to arrive at the solution.     

Selective recovery of Sn from copper alloy dross and its heat-treatment for synthesis of SnO2

Preliminary study on concentration and separation of tin (Sn) from copper alloy dross by selective dissolution method was conducted. The tin in the copper alloy dross did not dissolve in an aqueous nitric acid solution which could allow separation of tin from the copper alloy dross. The tin as H₂SnO₃ (metastannic acid) phase was precipitated in the solution with centrifuging process and transformed to tin dioxide (SnO₂) after drying process. The dried sample was heat-treated at low temperature and its phase characteristics, surface morphology and chemical composition were investigated.     

Laser Surface Hardening of 9CrSi Steel

The effects of laser hardening parameters such as beam power,beam diameter and scanning rate on microstructure and mardness of 9CrSi steel were investigated.The microstructure of the surface layer of 9CiSi steel was changed from pearlite to martensite,retained austenite and carbide by laser hardening .The depth of the hardened layer increased with increasing laser energy density and the surface hardeness increased by 3-5times as high as the untreated steel.The laser hardened surface had good wear resistance due to martensite and carbide in the surface layer.The wear mode at low speed was abrasive,while the wear mode at high speed was adhesive.     

Cobalt chloride stimulates phosphoinositide 3-kinase/Akt signaling through the epidermal growth factor receptor in oral squamous cell carcinoma

Tumor cells are often found under hypoxic conditions due to the rapid outgrowth of their vascular supply, and, in order to survive hypoxia, these cells induce numerous signaling factors. Akt is an important kinase in cell survival, and its activity is regulated by the upstream phosphoinositide 3-kinase (PI3K) and receptor tyrosine kinases (RTKs). In this study, we examined Akt activation and RTKs/PI3K/Akt signaling using the hypoxia-mimetic cobalt chloride in oral squamous carcinoma cells. Cobalt chloride increases Akt phosphorylation in both a dose- and time-dependent manner. Blocking the activation of the PI3K/Akt pathway using LY294002 abolished Akt activation in response to cobalt chloride, suggesting that Akt phosphorylation by cobalt chloride is dependent on PI3K. In addition, activation of the PI3K/Akt pathway seems to rely on the epidermal growth factor receptor (EGFR), since the inhibition of EGFR attenuated cobalt chloride-induced Akt activation. The results in this study also demonstrate that cobalt chloride increases EGFR protein levels and induces oral squamous cell carcinoma cells to enter S phase.     

Comparative studies on the binding site of anesthetics to GABA a receptors using <i>in silico</i> docking methods

Background: Although the GABAA receptor (GABAAR) has been proposed as the main action site for sevoflurane, isoflurane, halothane, enflurane, propofol, and benzodiazepines (BZDs), binding of these anesthetics with high-resolution structures of the GABAAR have been rarely examined by comparative docking analyses. Moreover, various combinations of ligands on more GABAARs with various subtypes need to be analyzed to understand the elaborate action mechanism of GABAARs better because some GABAA ligands showed specificity toward the distinct subtypes of the GABAAR. Methods: We performed in silico docking analysis to compare the binding modes of sevoflurane, isoflurane, halothane, enflurane, propofol, and BZDs to the GABAAR based on one of the most recently provided 3D structures. We performed the docking analysis and the affinity-based ranking of the binding sites. Results: Our docking studies revealed that isoflurane, halothane, and enflurane docked in an extracellular domain (ECD) on GABAARs, in contrast to sevoflurane. Conclusion: Our results supported a multi-site mechanism for the allosteric modulation of propofol. Propofol was bound to the pore or favored various subsites in the transmembrane domain (TMD). Our result confirmed that different chemically related BZD ligands interact via distinct binding modes rather than by using a common binding mode, as previously suggested.