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991.
Kitty W. Lee De-Jun Li Yip-Wah Chung 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(9):49-52
Coating properties and performance can be tailor-designed by proper control of nano structure andprocess conditions. This
paper presents two examples: first, the synthesis and optimization of 1 nm thick nitrogenated carbon (CNx) nano-layers as protective overcoats in extremely highdensity harddisksystems, and, second, the development of multilayer
coatings for wear protection at elevated temperatures. Synthesis of these coatings was done by magnetron sputtering. These
studies demonstrate that one canproduce atomically smooth 1 nmthickCNxovercoatswith acceptable corrosionperformance. In addition, this paper shows that, with the proper choice of nanolayer thickness
and process conditions, superhard coatings based on TiN/SiNx and TiB2/TiC multilayers with high thermal stability, low internal stress, and high wear resistance can be synthesized. 相似文献
992.
993.
J. R. Woods J. Kung J. Adjaye L. S. Kotlyar B. D. Sparks K. H. Chung 《Petroleum Science and Technology》2004,22(3):347-365
In this work we explore the chemistry of a gas oil fraction in the mid-boiling range (433-483°C) and its products after hydrotreating at 375, 385, and 400°C. Each sample was fractionated by high performance liquid chromatography (HPLC) based on the elution times for saturate, mono-, di-, and poly-aromatic standards. The HPLC saturate fraction is practically free of aromatic components. The nominal mono- and di-aromatics fractions differ in that the former has a higher molecular weight and H/C ratio cbut lower aromaticity and heteroatom content. The H/C atomic ratios, aromaticities, and average structural parameters of the HPLC poly-aromatic subfractions are virtually the same. Regardless of their structural resemblances they differ substantially in their HPLC elution behavior. This can be attributed to the differences in their oxygen and, especially, nitrogen contents. Hydrogenation produced a significantly greater amount of saturate material having a higher H/C ratio than the original feed. A large part of this increase must result from dealkylation, saturation, or opening of aromatic molecules. This mechanism also produced nominally mono-aromatic compounds from the poly-aromatic species originally present. The effect of hydrogenation on heteroatoms was mixed. While the overall amount of nitrogen was reduced, its concentration in the poly-aromatic fractions actually increased. Overall, oxygen concentration in the product was not much affected by hydrogenation, except that its distribution became skewed towards the more easily eluted HPLC front-fractions. Both thiophenic and sulphide sulphur were significantly reduced in all of the separated fractions. 相似文献
994.
用溶胶—凝胶法将不同浓度的罗丹明6G(Rhodamine 6G,R6G)染料掺入硅凝胶块和涂层薄膜中,用倍频 YAG 激光(0.53μm)做激发光源研究其荧光性质。对凝胶块、凝胶薄膜和乙醇溶液中 R6G 的荧光光谱进行了比较,研究了温度和 R6G 浓度对荧光性质的影响。实验结果表明,当R6G/SiO_2摩尔比高达 10~(-4)时,凝胶薄膜中的 R6G 分子仍不发生聚集现象;在475K 以下,积分荧光强度随温度的变化表现出很好的重现性;当温度高于600K 时,荧光消失,表明染料 R6G 已完全分解。 相似文献
995.
HR Yeom YJ Park SJ Lee IC Rhyu CP Chung RJ Nisengard 《Canadian Metallurgical Quarterly》1997,68(11):1102-1109
Clinical and microbiological effects of subgingival delivery of 10% minocycline-loaded (MC), bioabsorbable microcapsules were examined in 15 adult periodontitis patients. Patients received oral hygiene instruction 2 weeks prior to the study. At baseline (day 0) all teeth received supragingival scaling (SC); 2 quadrants received no further treatment and 1 quadrant received subgingival scaling and root planning (SRP). In the fourth quadrant, the tooth with the deepest probing sites (at least 1 site > or = 5 mm) was treated with minocycline microcapsules. The sites were evaluated at baseline and weeks 1, 2, 4, and 6. Clinical indices included bleeding on probing (BOP), probing depths (PD), and attachment loss (AL). Microbiological evaluations included percent morphotypes by phase-contrast microscopy; cultivable anaerobic, aerobic, and black-pigmented Bacteroides (BPB); and percent Porphyromonas gingivalis, Prevotella intermedia, Eikenella corrodens, and Actinomyces viscosus by indirect immunofluorescence. In the SC + MC group, BOP, PD, and AL were significantly reduced from baseline for weeks 1 to 6. BOP in the SC + MC group was significantly reduced compared to the SRP group from weeks 2 to 6. In the SC + MC group the percent of spirochetes and motile rods decreased and the percent of cocci increased after 1 week. The increased cocci and decreased motile rods were statistically greater at weeks 4 and 6 in the SC + MC group compared to the SRP group. This study demonstrates that local subgingival delivery of 10% minocycline-loaded microcapsules as an adjunct to scaling results in reduction in the percent sites bleeding on probing greater than scaling and root planning alone and induces a microbial response more favorable for periodontal health than scaling and root planing. 相似文献
996.
Y J Tseng H H Chang C Y Shiau W Y Chung D H Pan W C Chu 《IEEE engineering in medicine and biology magazine》2003,22(5):92-107
The PC-based dose-calculation system designed for gamma knife radiosurgery introduced in this article delivers desired accuracy and is equipped with a friendly graphical user interface to allow foolproof operations. With the ongoing advancement in PC technology, the performance/cost ratio is expected to continue to rise to render more incentive in developing a PC-based dose-calculation system. 相似文献
997.
Who Kee Chung 《Microelectronics Reliability》1980,20(4):517-519
This paper presents a k-out-of-N:G three-state unit redundant system availability model including common-caue failures. The steady-state probability and system availability equations are developed. Further, the frequency of encountering a state and the average duration of residence in a state are also derived. 相似文献
998.
The total scattered electric field of a periodic dielectric optical waveguide is derived in terms of the Green's functions of the unperturbed structure. A condition for self-excitation that takes into account the coupling between radiation and guided modes is obtained in a very general manner and, therefore, is valid for arbitrary periods of the grating structure. Results show that the effect of the coupling between the oscillating guided field and radiation modes is to change the dependence of the threshold gain on the amplitude of the periodic perturbation: increasing the depth of the grating beyond an optimum value causes an increase in threshold due to larger coupling to radiation modes. 相似文献
999.
Fourteen adult cats were exercised on a motor-driven treadmill 5 days each week for 6 weeks to determine the effect of exercise conditioning on the intrinsic contractile state of the myocardium. The exercise program was sufficient to produce a cardiovascular training effect manifested by slower exercising heart rates and resting heart rates after atropine by the end of the 6th week. The mechanical function of the isolated right ventricular papillary muscle from exercised cats was compared with that of 17 sedentary adult cats. There were no significant differences between exercised and control cats in in heart weight-body weight ratios, resting and active lenght - tension relations, maximal rate of isometric force development at the peak of the length-tension curve (Lmax), time to peak force at Lmax, maximal force development with paired stimulation and norepinephrine, or force-velocity relations. These results indicate that the intrinsic state of feline myocardium is unaffected by exercise conditioning. 相似文献
1000.
By using droplet combustion in oxidizer-rich environments as a model problem, the present investigation demonstrates both experimentally and theoretically that variable transport properties and flame dissociation are important factors which influence the bulk combustion charateristics, such as the fuel consumption rate and the flame temperature and location. A simplified, internally consistent methodology is proposed for the evaluation of these properties by analyzing the transport aspects of the problem and separately determining the characteristics of the flame in dissociation equilibrium through adiabatic flame temperature calculation, with allowance for the falsification of the oxidizer concentration due to diffusional stratification. 相似文献