离子束增强沉积氮化硅膜及TiAl抗高温氧化性能的改善

用离子束增强沉积（ＩＢＥＤ）方法在金属间化合物ＴｉＡｌ上合成厚度为０．５，１，和２μｍ的氮化硅薄膜。所形成的薄膜为非晶态，膜与基底间存在混合的过渡区，膜与基底结合紧密用ＡＥＳ，ＸＲＤ和ＸＰＳ研究薄膜的组成和结构，高温循环氧化结果表明，经沉积膜的ＴｉＡｌ试样的抗氧化性能显著提高其中沉积０．５μｍ薄膜的试样表现出极好的抗循环氧化性能由ＳＥＭ及ＥＤＳ分析得出，良好的高温稳定性能、高的膜／基底结合力和形成富Ａｌ２Ｏ３和硅化物的保护层是提高ＴｉＡｌ抗高温氧化性能的主要因素．     

EXTRACTION OF METAL IONS WITH DZEHPA FROM MIXED AQUEOUS-ORGANIC MEDIA

Extraction of metal ions from the aqueous-organic solution containing dimethyl formamide(DMF), dimethyl sulfoxide(DMSO) and acetonitrile(AN) was investigated by using di-2-ethylhexyl-phosphoric acid(D2EHPA) as an extractant. The organic phase was a binary solution of D2EHPA and n-hexane, or D2EHPA and toluene, while the polar phase was a three component solution of metal salt, non-aqueous solvent and water. The extracted metal ions were Cr(III), Fe(III), Al, Cu, Ni, Co(II), Mg and Ag.

The extraction behaviors may be explained by the solvation ability of non-aqueous solvents, the decrease in distribution of the extractant and extract into the organic phase, and the interaction between the extractant and non-aqueous solvents due to the dissolution of non-aqueous solvents in the organic phase.     

L2-bounded stability for a stochastic system†

Both types of linear and non-linear systems with random coefficients are treated in this paper. Four theorems are proved by using the stochastic Liapunov functional, which give the sufficient condition in matrix form for exponential asymptotic stability in the largo with probability one and L₂-bounded stability with probability one.     

Window functions obtained by convolution integrals of rectangular windows

The rectangular, triangular, and Parzen windows, which have been defined independently of each other, are obtained by repeating convolution integrals of the rectangular window with itself. They are extended to make a series of window functions. This series has the advantage that the sidelobe fall-off is variable though it has the disadvantage that the mainlobe band-width for the same highest sidelobe level is 1–1·3 times those of the gaussian, Kaiser, Dolph–Chebyshev or Blackman–Harris windows. Moreover, this series has a desirable mainlobe bandwidth of 0·85–1 times that of cos^x x windows for the same highest sidelobe level and sidelobe fall-off. Thus, this series is useful in designing window functions whose mainlobe bandwidth is in between that of the gaussian or Kaiser windows and that of cos^x x windows and whose sidelobe fall-off is as good as that of the cos^x x windows.     

High-pressure synthesis of diamond from phenolic resin

Two kinds of phenolic resin, novolak and resols, have been studied with an addition of cobalt at pressures between 2 and 4 GPa and at temperatures from 1300 to 1900 °C, all under thermodynamically graphite-stable conditions. Diamond was synthesized from these resins which had been pre-fired at 500–1000 °C. From such resins, carbon precursors carrying a great number of radicals, being nearly free of hydrogen and oxygen, and turbostratic in structure, can be constructed. The pressure–temperature conditions suitable for the diamond synthesis were dependent on the pre-firing temperatures. The cobalt served as a catalyst–solvent, similar to the case of conventional diamond synthesis from graphite under diamond-stable conditions. Well-defined single crystals cubo-octahedral in shape, measuring 0.3–0.7 mm across and classified as type Ib were obtained. This revised version was published online in November 2006 with corrections to the Cover Date.     

Debittering Mechanism in Bitter Peptides of Enzymatic Hydrolysates from Milk Casein by Aminopeptidase T

The bitter peptide fraction present in casein hydrolysates obtained by using three proteases (subtilisin, papain and trypsin) was treated with aminopeptidase T from Thermus aquaticus YT-1. The bitterness of the bitter peptide fraction could be decreased, and it sometimes disappeared completely, with an increase in free amino acids. The percentages of total free amino acids released from each bitter peptide fraction (subtilisin, papain and trypsin) by aminopeptidase digestion for 20 hr were approximately 11%, 8.7%, and 6.5%, respectively. Bitter peptide (α_s1-CN f91-100) was isolated from a tryptic hydrolysate of casein by HPLC, its threshold value of bitterness being 2.9 ppm (w/v). The peptide (α_s1-CN f96-100) obtained from the amino peptidase digestion of this bitter peptide showed no bitterness.     

Transmission electron microscopy study of martensites in laser-clad ni-ai bronze on aluminum alloy AA333

The microstructure and crystal structure of laser-clad Ni-Al bronze on Al alloy AA333 were investigated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX). The SEM and TEM revealed two kinds of martensites in the clad region: sheet martensite and lath martensite. Selected area diffraction (SAD) analysis showed that the sheet martensite had a close-packed structure with different stacking modulations. Two crystal structure analysis procedures based on a hexagonal unit cell were applied to identify the stacking periods and orders of the sheet martensite. The analysis showed that a nine-layer stacking mode specified as ABCBCACAB was predominant and that an 1 1-layer stacking mode specified as ABCBCACABAB was also locally present. The crystal structure of the lath martensite was identified as face-centered cubic (fcc) by SAD. No ordering of alloying elements was detected in the sheet and lath martensites.     

Electrical and mechanical properties of ZrO2(2Y)/TiN composites and laminates made from these materials

High density composites with the compositions of ZrO₂(2Y):TiN=40:60 and 70:30 mol% have been fabricated by hot isostatic pressing for 2 h at 1500°C and 196 MPa. The electrical resistivities (ρ) of the two composites are very different; showing metallic behaviour in the first case and insulating behaviour in the latter case. These properties are highly dependent on the sample texture. Laminated materials with compositions of ZrO₂(2Y)/TiN=(40:60)/(70:30)/(40:60) mol% have been prepared by hot isostatic pressing. The electrical resistivities in the perpendicular and parallel to the interface directions have been determined to be ρ⊥≈1×109 and ρ∥≈ 1×10^-6 Ωm, respectively. A residual stress of as much as ≈ 150 MPa is induced in the interfaces. The fracture toughness is greatly affected by the residual stress. This revised version was published online in November 2006 with corrections to the Cover Date.     

COMPARISON OF PHYSICAL PROPERTIES OF AGAR, LOW GEL STRENGTH AGAR AND GELATIN, AS SUPPLEMENTARY FOOD FOR PEOPLE WITH SWALLOWING DIFFICULTY

Low gel strength agar (LGSA), recently developed as a supplementary food for swallowing was compared with ordinary agar and gelatin. LGSA was developed to have physical properties close to that of gelatin, while keeping one property of agar, i. e. its setting temperature which can be controlled comparatively easier than gelatin. Each specimen was prepared with and without orange flavor. After determination of their basic properties, i. e. hardness, adhesiveness, cohesiveness and gumminess, three samples of two flavors, six in all, were studied for ease of swallowing using electromyography and sensory evaluation, on middle age (40 to 60 years old) and senior age (60 to 70 years old) subjects. Those experiments revealed nearly the same results with all samples, except for a slight difference in gumminess in LGSA and gelatin. No significant difference in electromyograms were noted in six samples or with age of subjects. It is feasible to employ agar materials together with gelatin in institutions whose members have swallowing disorders.     

Determination of Hypoxanthine in Fish Meat with an Enzyme Sensor

An enzyme sensor specific for hypoxanthine (Hx) was developed using immobilized xanthine oxidase-membrane and an oxygen probe. Xanthine oxidase (E.C. 1.2.3.2.) was covalently immobilized on a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane, and glutaraldehyde. Hx is oxidized to uric acid by the immobilized enzyme, the output current of the oxygen probe decreasing due to oxygen consumption. A linear relationship was obtained between current decrease and Hx concentration in the range 0.06–1.5 mM. The enzyme sensor could be used for more than 100 assays without decrease of output current After 30-day-storage at 5°C, no remarkable decrease of output current was observed. The enzyme sensor system was applicable to the simple, rapid, and economical determination of Hx in several fish meats including sea bass, saurel, mackerel, yellowfish, and flounder.