Estimation of anisotropic properties of nano-structured arrays by modal vibration control at microscale

Nano-structured arrays are engineered to meet the requirements of a variety of applications such as microfilters, sensors, and structural interface due to their unique mechanical characteristics, which cannot be achieved by conventional solid materials. However, it is hard to evaluate the elastic properties of nano-structured arrays owing to the discrete structure, sample size, and availability of suitable techniques. To facilitate this, we develop an advanced three-dimensional microscale vibration testing process. In the test, a specially designed three-dimensional microspecimen with tuned mass is excited by a piezoelectric actuator, and the resonance frequencies are detected by a laser device successfully. The anisotropic elastic moduli of nano-structured array composed of helical nano-springs are identified from a single spectrum. This array shows so strong characteristic anisotropy that the solid one hardly can attain. The microscale testing technique can be extended to other materials and microstructures.     

Stress field near interface edge of elastic-creep bi-material

Stress fields on elastic-creep bi-material interfaces with different geometry of the interface edge are analyzed by finite element method. The results reveal that the stress highly concentrates near the interface edge at the loading instant and it gradually decreases as the creep-dominated zone expands from the small-scale creep to the large-scale creep. The stress singularity due to creep which resembles the HRR stress singularity appears near the interface edge in all cases. The stress intensity near the interface edge time-dependently decreases and becomes constant when the transition reaches the steady state. The magnitude is scarcely influenced by the edge shape of elastic material, though it depends on the edge shape of creep material. The stress intensity during the transition can be approximately predicted by the J-integral at the loading instant.     

PLL-based BiCMOS on-chip clock generator for very high-speedmicroprocessor

Described is a phase-locked loop (PLL)-based BiCMOS on-chip clock generator (PCG), which is used to generate an internal clock synchronized to a reference clock from outside the chip. In order to obtain a very wide operation bandwidth, it is proposed that the PCG include a compensation circuit for voltage-controlled oscillator (VCO) operation. The compensation circuit varies the oscillation bandwidth of the VCO according to the reference clock frequency, preventing the expected oscillation frequency from being outside the oscillation bandwidth. The PCG is designed and fabricated with 1.0 μm BiCMOS technology, and it achieves an operation bandwidth of 3 to 90 MHz     

Dissolution Behavior of Mg from Magnesia-Chromite Refractory into Al-killed Molten Steel

Magnesia-chromite refractory materials are widely employed in steel production, and are considered a potential MgO source for the generation of MgO·Al₂O₃ spinel inclusions in steel melts. In this study, a square magnesia-chromite refractory rod was immersed into molten steel of various compositions held in an Al₂O₃ crucibles. As the immersion time was extended, Mg and Cr gradually dissolved from the magnesia-chromite refractory, and the Mg and Cr contents of the steel melts increased. However, it was found that the inclusions in the steel melts remained as almost pure Al₂O₃ because the Mg content of the steel melts was low, approximately 1 ppm. On the surface of the magnesia-chromite refractory, an MgO·Al₂O₃ spinel layer with a variable composition was formed, and the thickness of the MgO·Al₂O₃ spinel layer increased with the immersion time and the Al content of the steel melts. At the rod interface, the formed layer consisted of MgO-saturated MgO·Al₂O₃ spinel. The MgO content decreased along the thickness direction of the layer, and at the steel melts interface, the formed layer consisted of Al₂O₃-saturated MgO·Al₂O₃ spinel. Therefore, the low content of Mg in steel melts and the unchanged inclusions were because of the equilibrium between Al₂O₃-saturated MgO·Al₂O₃ layer and Al₂O₃. In addition, the effects of the Al and Cr contents of the steel melts on the dissolution of Mg from the magnesia-chromite refractory are insignificant.     

Breakup of non-newtonian emulsion jets

The breakup of non-Newtonian emulsion jets into drops was experimentally studied by ejecting both O/W and W/O emulsions vertically downward into stagnant air through nozzles. Breakup lengths of non-Newtonian emulsion jets were found to be almost equivalent to those of Newtonian jets. Experimental breakup data establish that the static surface tension of the oil phase can be used as the surface tension of W/O emulsion jets, whereas the dynamic surface tension of aqueous surfactant solutions is used as that of O/W emulsion jets. Diameters of drops formed from non-Newtonian emulsion jets are in good agreement with the prediction from the stability theory previously developed by the authors. When the rheological index in a power law model is appreciably smaller than unity and the Ohnesorge number is significantly large, however, drop sizes are larger than the prediction because of the profile relaxation in jets. The critical velocity of emulsion jets, either O/W or W/O emulsion, is significantly lower than that of homogeneous Newtonian jets.     

Effects of hydrophilicity of crosslinker on membrane properties of poly(N-hydroxyethyl-L-glutamine) hydrogels

Summary Poly(N-hydroxyethyl-L-glutamine) (PHEG) hydrogels were prepared by aminolysis of poly( -benzyl L-glutamate) with 2-aminoethanol and hydrophobic or hydrophilic crosslinkers, and the effect of the hydrophobicity of the crosslinkers was evaluated. The swelling properties, tensile properties and enzymatic degradation behavior were studied in phosphate buffered saline (PBS). The swelling ratio and degradation rate of these hydrogels were highly dependent on the hydrophobicity of the crosslinkers, while tensile properties were dependent on the swelling ratio, but not on the hydrophobicity of the crosskinkers.     

Peel Test Using Nonstationary Peel Method

The cohesive peel spectra of pressure-sensitive adhesive (PSA) tapes have been measured using a non-stationary peel tester. The experimental evidence and a viscoelastic analysis based on a peel model indicate that there are no significant effects of acceleration in the normal rate region. The nonstationary peel tester can be regarded as a useful tool for testing and evaluating PSA tapes.     

DISTRIBUTION OF N- AND ISO- BUTYRALDEHYDES BETWEEN TRI-N-BUTYL PHOSPHATE/ N-DODECANE AND NITRIC ACID

ABSTRACT

The distribution of n- and iso-butyraldehydes between tri-n-butyl phosphate(TBP) n-dodecane(nDD) and HNO₃ were measured. The distribution ratio of n-butyraldehyde in the TBP/nDD and HNO₃ system was nearly the same as that of iso-butyraldehyde. The distribution ratios of n- and iso-butyraldehydes increased with TBP concentration in the organic phase. The equilibrium constant of the extraction reaction was about 2. In a uranium, neptunium and plutonium separation process, most of the n- and iso-butyra1dehydes fed into theNp separation stepor into thePu/U partition will be left with the TBP solvent. The two compounds will be partly back-extracted to the aqueous phase in the U purification and in the solvent washing steps of the PUREX process.     

AUGMENTATION OF PHOTOCATALYTIC ACTIVITY OF TiO2 THIN FILMS PREPARED BY A SOL-GEL TECHNIQUE

In order to increase the photocatalytic activity on TiO₂ thin film per its external surface area, the structure of flat thin film was modified by adding a small amount of polyethylene glycol (PEG) to TiO₂ sol solution. By firing PEG contained in a TiO₂ gel film, a porous structure was developed. The photocatalytic activities of the thin films prepared thus were evaluated by the degradation of 2-propanol in the aqueous solutions under black light illumination. The photocatalytic activity of TiO₂ thin film prepared with added PEG 400 by 2.6 wt% or PEG 2000 by 9.5 wt% was increased by about 30% as compared to that prepared without added PEG.     

铽-聚N-乙烯基乙酰胺-1,10-菲罗啉三元配合物的光学性能

以N乙烯基乙酰胺(NVA)为原料通过自由基聚合反应合成了N乙烯基乙酰胺(PNVA),在乙醇溶液中合成了铽聚N乙烯基乙酰胺1,10菲罗啉(TbPNVAphen)的三元稀土高分子配合物。利用FTIR、UV-vis和荧光光谱对三元配合物进行了结构表征。荧光光谱表明,配合物的最佳激发波长为304nm;在此波长激发下,配合物在490nm和546nm处发出较强铽的特征荧光,荧光强度分别为846.853和2086.798,分别比TbPNVA配合物增强了1310%和1290%。