The impact of a post-OTDM-demultiplexing optical filter on the performance of dense on-off keying (OOK) optical time division multiplexing (OTDM)—wavelength division multiplexing (WDM) systems was studied. For return-to-zero (RZ) modulation, it was found that the additional filter working in a double-tier filter configuration did not offer any significant improvements to performance when the signal pulse width is optimized. Improvements generally increase only when the signal pulse width deviates from its optimal value and only for low spectral densities. For ideal non-return-to-zero (NRZ) modulation, however, significant improvements of around 1 dB are obtained using the double-tier configuration over a large range of spectral densities. 相似文献
Bamboo-/kenaf-reinforced epoxy hybrid composites were prepared by hand layup method. The aim of this study is to look into the hybridization effect of bamboo and kenaf fibers at different ratios on thermal and thermo-oxidative (TOD) stabilities of hybrid composites. Three types of hybrid composites were fabricated with different mass ratios of bamboo fiber mat (B) to kenaf fiber mat (K), namely B/K 70:30, B/K 50:50 and B/K 70:30 while maintaining total fiber loading of 40% by mass. The thermal stability and thermo-oxidative (TOD) stability were analyzed by thermogravimetric analyzer. Differential scanning calorimetry (DSC) was used to investigate the oxidation onset temperature (OOT) of all the composites. The results reveal that bamboo composite shows higher thermal stability than kenaf composite in both inert and oxidative atmospheres. An increase in bamboo fibers mass ratio in the hybrid composite improved the thermal and TOD stability. The thermal and TOD stabilities of the hybrid composites follow the sequence of B/K 70: 30?>?B/K 50:50?>?B/K 30:70. Pure epoxy composite recorded the highest OOT at 197.50 °C. The results show that the addition of natural fiber in the epoxy matrix has significantly reduced the OOT compared to the pure epoxy. Data obtained from this work will help us to fabricate a sustainable and biodegradable component for automotive or building materials.
In the last few years, wide-area data services over North American digital (TDMA and CDMA) cellular networks have been standardized.
The standards were developed under three primary constraints: (i) compatibility with existing land-line standards and systems,
(ii) compatibility with existing cellular physical layer standards that are optimized for voice, and (iii) market demands
for quick solutions. In particular, the IS-95 CDMA air interface standard permits multiplexing of primary traffic (e.g., voice or circuit data) and secondary traffic (e.g., packet data) or in-band signaling within the
same physical layer burst. In this paper, we describe two radio link protocols for circuit-mode data over IS-95. The first
protocol, Protocol S, relies on a single level of recovery and uses a flexible segmentation and recovery (FSAR) sublayer to efficiently pack data frames into multiplexed physical layer bursts. We next describe Protocol T, that consists of two levels of recovery. Protocol T has been standardized
for CDMA circuit-mode data as IS-99 (Telecommunications Industry Association, 1994). We provide performance comparisons of
the two protocols in terms of throughput, delay and recovery from fades. We find that the complexity of the two level recovery
mechanism can buy higher throughput through the reduced retransmission data unit size. However, the choice of TCP (and its
associated congestion control mechanism) as the upper layer of recovery on the link layer, leads to long fade recovery times
for Protocol T. The two approaches also have significant differences with respect to procedures and performance at handoff
and connection establishment.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
Let be the Iwasawa decomposition of a complex connected semi-simple Lie group . Let be a parabolic subgroup containing , and let be its commutator subgroup. In this paper, we characterize the -invariant Kähler structures on , and study the holomorphic sections of their corresponding pre-quantum line bundles.
The rate of dye adsorption from aqueous effluents onto palm kernel shell (PKS) activated carbon has been studied experimentally using the batch adsorption method. The adsorption rates of methylene blue on PKS for systems of different initial dye concentrations are modeled using a film-pore-concentration dependent surface diffusion (FPCDSD) model. The FPCDSD model is sufficiently general and can be reduced easily to describe other simplified models. Using the FPCDSD model, only a single set of mass transfer parameters is required to describe the methylene blue/PKS system for different initial concentrations. A different set of mass transfer parameters are needed to obtain the best fitting if the pore diffusion is not included in the model. 相似文献