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71.
The photografting of methacrylic acid (MAA) on a linear low‐density polyethylene film (thickness = 30 μm) under air and nitrogen atmospheres was investigated at 60°C in mixed solvents consisting of water and an organic solvent, with xanthone as a photoinitiator. The organic solvents used were acetone, methanol, tetrahydrofuran, and dioxane. A maximum percentage of grafting occurred at a certain concentration of the organic solvent in the mixed solvent. This was observed for the systems under both air and nitrogen. The grafting reaction under air exhibited an induction period, but the rate of grafting after the period was greater than that under nitrogen. The formation of poly(ethylene peroxide)s by photoirradiation seemed to be a factor for the accelerated photografting under air. On the basis of attenuated total reflection infrared spectroscopy and scanning electron microscopy of the grafted film, the MAA‐grafted chains of the sample prepared under air tended to penetrate more deeply inside the film than those of the sample prepared under nitrogen. The resulting grafted films exhibited a pH‐responsive character: the grafted films shrank in an acidic medium but swelled in alkaline medium. This was evaluated from measurements of dimensional changes in the grafted films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 992–998, 2003 相似文献
72.
A wireless/mobile network supporting multilevel quality of service (QoS) is considered. In such a network, users or applications can tolerate a certain degree of QoS degradation. Bandwidth allocation to users can, therefore, be adjusted dynamically according to the underlying network condition so as to increase bandwidth utilization and service provider's revenue. However, arbitrary QoS degradation may be unsatisfactory or unacceptable to the users, hence resulting in their subsequent defection. Instead of only focusing on bandwidth utilization or blocking/dropping probability, two new user-perceived QoS metrics, degradation ratio and upgrade/degrade frequency, are proposed. A Markov model is then provided to derive these QoS metrics. Using this model, we evaluate the effects of adaptive bandwidth allocation on user-perceived QoS and show the existence of trade offs between system performance and user-perceived QoS. We also show how to exploit adaptive bandwidth allocation to increase system utilization (for the system administrator) with controlled QoS degradation (for the users). By considering various mobility patterns, the simulation results are shown to match our analytical results, demonstrating the applicability of our analytical model to more general cases. 相似文献
73.
We propose an asymmetric integral imaging method to adjust the resolution and depth of a three‐dimensional image. Our method is obtained by use of two lenticular sheets with different pitches fabricated under the same F/#. The asymmetric integral imaging is the generalized version of integral imaging, including both conventional integral imaging and one‐dimensional integral imaging. We present experimental results to test and verify the performance of our method computationally. 相似文献
74.
75.
The growth of carbide particles in TiC-XC-2 vol.% Ni and TiC-XC-30 vol.% Ni alloys, where X=Zr, Cr, W, Ta and Mo, was fitted
to an equation of the form d3-do
3=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with the addition of Mo2C or WC, changed little for TaC, and increased with the addition of ZrC or Cr3C2. The grain contiguity decreased with increasing Ni content in the TiC−Mo2C−Ni alloy and was greater in the alloys with smaller growth rate constant. Consequently, the effect of carbide addition on
the grain growth of 2 vol.% Ni alloys was found to be similar to that of 30 vol.% Ni alloys. The grain growth mechanism could
be explained by the effect of contiguous carbide grain boundaries in restricting the overall grain growth, as well as the
area of the solid/liquid interfaces in the alloy by the usual solution/reprecipitation model. 相似文献
76.
Woo-Seog Song Seungbae Lee Dong-Shin Shin Yang Na 《Journal of Mechanical Science and Technology》2006,20(6):905-913
The instability curve of a Rijke tube system was obtained accurately by following different paths of heat power and flow-rate
for three regions and by defining its locus from the criterion based on the measured sound pressure levels. The unstable limits
in the region of flow-rate lower than that at the minimal power are compared with previous data. To observe the effect of
turbulence on the unstable limits, inflow turbulence was introduced by placing a bundle of circular cylinders upstream of
the heating part (50< Red< 700). The large-amplitude inflow fluctuation may delay the transition of the chamber acoustic mode to the unstable zone
even at a sufficient power. 相似文献
77.
Shin S.-C. Ming-Da Tsai Ren-Chieh Liu Lin K.-Y. Huei Wang 《Microwave and Wireless Components Letters, IEEE》2005,15(7):448-450
A 24-GHz low-noise amplifier (LNA) was designed and fabricated in a standard 0.18-/spl mu/m CMOS technology. The LNA chip achieves a peak gain of 13.1 dB at 24 GHz and a minimum noise figure of 3.9 dB at 24.3 GHz. The supply voltage and supply current are 1 V and 14 mA, respectively. To the author's knowledge, this LNA demonstrates the lowest noise figure among the reported LNAs in standard CMOS processes above 20 GHz. 相似文献
78.
HA Mook DM Paul BC Sales LA Boatner L Cussen 《Canadian Metallurgical Quarterly》1988,38(16):12008-12010
79.
80.
Shafeeque G. Ansari Mushtaq Ahmad Dar Young-Soon Kim Hyung-Kee Seo Gil-Sung Kim Rizwan Wahab Zubaida A. Ansari Jae-Myung Seo Hyung-Shik Shin 《Korean Journal of Chemical Engineering》2008,25(3):593-598
A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with
1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force
microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma
etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance
of angular shaped grains corresponding to 〈100〉 and 〈110〉 crystallite surfaces for the scratched as well as plasma etched
substrate. Surface etching at 150 W plasma power results in a better growth in comparison with 50 and 100 W plasma powers.
Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332
cm−1 and a peak at ∼1,580 cm−1 for both samples. 相似文献