Confined photo-catalytic oxidation: a fast surface hydrophilic modification method for polymeric materials

When a very thin persulfate salt aqueous solution layer (μm) was sandwiched between two polymer films and strong UV light irradiated the assembly from the side transparent to UV light, a fast surface hydrophilic modification method for most of commercial polymeric materials was developed. For example, irradiating for 90 s and using 30 wt% ammonium persulfate, the static surface water contact angles of polymeric substrates decreased from 100 to 44° for LDPE, from 107 to 34° for HDPE, and from 73 to 15° for PET. The increases in surface hydrophilicity came from the formation of a sulfate salt group (SO₄⁻NH₄⁺)-ionized surface, which was characterized by XPS and ATR-FTIR. The surface topography of the modified polymer substrates were observed by SEM and AFM, and no visible etching effect to original surface were found. A possible reaction model named by ‘confined photo-catalytic oxidation’ was put forward to interpret the above results.     

Crack initiation condition in the specimens of ductile materials

In this paper, the elasto-plastic Finite Element Method was used to simulate the ductile fracture initiation of four kinds of specimens made of low-carbon steel No. 20 (Chinese steel), and the damage parameter V_D was calculated for these specimens. The results showed that the damage mechanics criterion V_D proposed by the author and B. X. Yang [Engng Fracture Mech. 27, 371–386 (1987)], could be applied to predict the crack initiation. Also, the relationship between the damage parameter V_Dc and the crack tip opening displacement was discussed in this study.     

A study of the electromagnetic vibration of a capacitor induction motor caused by time-harmonic voltages

In recent years, power source voltage waveform distortion has become noticeable, as electrical appliances with rectifier circuits have become widely used. Connecting capacitor inductor motor (CRM) to such distorted supply, or controlling CRM by simple controller with a switching device (such as triacs), harmonic voltage is supplied to CRM. In that case, CRM produces electromagnetic vibrations caused by not only the fundamental voltage but also time-harmonic voltages in the distorted voltage. In addition, CRM produces electromagnetic vibration due to backward magnetic fields. Thus, it is difficult to clarify a relationship between electromagnetic vibration of CRM and harmonic voltages. In this paper, the causes of the electromagnetic vibration of CRM operating under distorted wave supply voltage are discussed. First, a general equation of dominant electromagnetic force waves is shown considering not only forward magnetic fields but also backward magnetic fields. Using a general equation, causes of dominant electromagnetic vibration can be clarified. Next, by discussing in detail some examples of the dominant vibration, the relationship between the vibration and harmonic voltages becomes evident. Furthermore, the relationship between the vibration and backward magnetic field is clarified.     

The effects of accumulated experience on radiofrequency ablation of accessory pathways

Increasing experience in radiofrequency ablation for accessory pathways appears to reduce the procedure time, radiation time and radiofrequency pulse number, and results in a higher success rate. However, the effect of a learning curve on this procedure from the perspective of location and conduction direction of accessory pathways has not been reported before. The purpose of this study was to determine the effect of accumulated experience on the outcomes of radiofrequency ablation for accessory pathways and on the duration of the procedure parameters by analyzing the results of a dedicated ablation team. The first 512 patients with a single accessory pathway treated in this laboratory were included for analysis of the procedure parameters with respect to locations and conduction directions of accessory pathways. The results showed that the average procedure time, radiation time, and radiofrequency pulse number differed significantly among the different subgroups (left free wall, right free wall, posteroseptal and anteromidseptal location; manifest or concealed conduction). All subgroups except the anteromidseptal pathways showed a significant improvement of the procedure parameters with increased ablation experience. Although the initial rate of improvement was similar among the different subgroups, the rate of improvement in left free wall pathways nearly reached a plateau after 120 ablation procedures. Thus it was concluded that a certain number of ablation procedures was necessary before achievement of a high success rate with shorter procedure and radiation times and a lower radiofrequency pulse number.     

A computer method for formal linearization of nonlinear systems by the discrete fourier expansion and its applications

This paper proposes a numerical computer method for formal linearization of nonlinear systems by using the discrete Fourier expansion. A nonlinear system is described by a system of nonlinear ordinary differential equations. A linearizing function is given by a sequence of trigonometric functions. The nonlinear terms of the differential equations are expanded into finite sums of trigonometric functions by the method of the discrete Fourier expansion. As a result, a formal linear system is derived from the given nonlinear system. A computer algorithm of the linearization is acquired and numerical computation is easily carried out with the aid of computers. Further, as the application of the linearization, both a nonlinear observer and a nonlinear filter are synthesized in this paper. Examples show that the accuracy of the method is improved as the order of the trigonometric functions increases.     

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大张坨地下储气库是以凝析油气藏的砂岩作为储层的，该储层具有压力亏空和孔隙度、渗透率高的特点。因此，钻井时必须根据储层岩性的特点和物性特征，找出对储层造成伤害的因素，有针对性地优化钻井液体系、性能参数和保护措施。实践证明，聚合物、有机硅钻井液体系满足了大张坨地下储气库各个阶段的施工要求，保证了安全快速钻井；钻井液性能稳定、抑制能力强、井壁稳定；采用双项屏蔽保护剂及保护措施，能较好地保护好储层。     

Properties of syndiotactic-rich poly(vinyl alcohol) thin film in water. III. Contraction and extension of drawn and annealed thin film in water

Contraction and extension behaviors in water for drawn (four times original length) and annealed (at 60–215°C) thin films of poly(vinyl alcohol) (PVA_VTFA) derived from vinyl trifluoroacetate have been examined. At a constant temperature of 25°C, drawn films annealed at 60–190°C contracted after a certain standing time. Length of films annealed at 200°C did not change after standing of 20 min and film annealed at 215°C extended very little. As the temperature was raised, the drawn films annealed at 60–190°C contracted further until a certain temperature and then extended. The drawn film annealed at 200°C first started contraction at 70°C. The drawn film annealed at 215°C extended further very little until 75°C and then contracted very little until 99°C (in boiling water). In standing at 99°C, it contracted very little with standing and resisted without breaking for 300 min.     

Coal liquefaction using indene-tetralin and indene-decalin mixtures as solvent

Indene-tetralin and indene-decalin mixtures were used as the solvent for coal liquefaction. The effect of mixing on conversion for Yallourn coal was observed under nitrogen pressure at 400 and 440 °C. Conversion to benzene-soluble material in an indene-decalin mixture (50:50, wt) at 440 °C for 1 h was 73.0% and was only 9% lower than that in 100% tetralin. The reaction of indene with tetralin or decalin may provide the active species for coal dissolution. Simultaneously, coal radicals may be scavenged by indene.     

Optical and structural properties of implanted silicon nanocrystals

A novel method for the fabrication of Si nanocrystals in an amorphous SiO₂ matrix by ion implantation is reported. Transmission electron microscopy indicates the formation and growth of Si nanocrystals on annealing at 1100°C which were not observed before annealing. After annealing, a photoluminescence band around 1.7 eV is observed. The shape of the emission spectrum of the photoluminescence is found to be independent of annealing time, while the intensity of the luminescence increases and then decreases as the annealing time increases. We also show direct evidence of widening of the band-gap energy of a few nanometer-sized Si particles by employing photoacoustic spectroscopy. These results indicate that the photons are absorbed by Si nanocrystals, for which the band-gap energy is modified by the quantum confinement effects, and the emission is not simply due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and SiO₂.