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981.
Routing for disruption tolerant networks: taxonomy and design 总被引:5,自引:0,他引:5
Thrasyvoulos Spyropoulos Rao Naveed Bin Rais Thierry Turletti Katia Obraczka Athanasios Vasilakos 《Wireless Networks》2010,16(8):2349-2370
Communication networks, whether they are wired or wireless, have traditionally been assumed to be connected at least most
of the time. However, emerging applications such as emergency response, special operations, smart environments, VANETs, etc.
coupled with node heterogeneity and volatile links (e.g. due to wireless propagation phenomena and node mobility) will likely
change the typical conditions under which networks operate. In fact, in such scenarios, networks may be mostly disconnected,
i.e., most of the time, end-to-end paths connecting every node pair do not exist. To cope with frequent, long-lived disconnections,
opportunistic routing techniques have been proposed in which, at every hop, a node decides whether it should forward or store-and-carry a message.
Despite a growing number of such proposals, there still exists little consensus on the most suitable routing algorithm(s)
in this context. One of the reasons is the large diversity of emerging wireless applications and networks exhibiting such
“episodic” connectivity. These networks often have very different characteristics and requirements, making it very difficult,
if not impossible, to design a routing solution that fits all. In this paper, we first break up existing routing strategies
into a small number of common and tunable routing modules (e.g. message replication, coding, etc.), and then show how and when a given routing module should be used, depending on the set of network characteristics exhibited by the wireless application. We further attempt to create a taxonomy for intermittently connected networks. We
try to identify generic network characteristics that are relevant to the routing process (e.g., network density, node heterogeneity, mobility patterns) and dissect different
“challenged” wireless networks or applications based on these characteristics. Our goal is to identify a set of useful design guidelines that will enable one to choose an appropriate routing protocol for the application or network in hand. Finally, to demonstrate
the utility of our approach, we take up some case studies of challenged wireless networks, and validate some of our routing
design principles using simulations. 相似文献
982.
Huang C.-Y. Huang T.-S. Cheng C.-Y. Chen Y.-C. Wan C.-T. Rao M. V. M. Su Y.-K. 《Photonics Technology Letters, IEEE》2010,22(5):305-307
983.
N.H. Al-Hardan M.J. Abdullah A. Abdul Aziz Z. Hassan 《Materials Science in Semiconductor Processing》2010,13(3):199-204
Ti/Pt as heating element for gas sensor applications was fabricated on silicon (Si) wafer substrate. The fabricated device was subjected to heat treatment at different prescribed time periods for thermal stability. The energy dispersion spectroscopy (EDS) results of the device indicated that there were no Ti traces on the Pt surface after heat treatment at 450 °C for 3 and 4 h in an argon (Ar) atmosphere. A maximum temperature coefficient of resistance (TCR) with a value of 2.88×10?3 K?1 was obtained for the device with 3 h heat treatment. 相似文献
984.
By heating H3BO3 with urea in 1 : 6 molar ratio, nanoparticles and nanotubes of BN are obtained. The urea–boric acid reaction can also be exploited to obtain graphene analogues of BN, with the number of layers depending on the relative proportions of the two reactants. Synthesis with a high proportion of urea yields a product containing graphene analogues of BN with an average of 2 layers. The surface area of BN increases with the decreasing number of layers, and the high-surface-area BN also exhibits high CO2 adsorption. Few-layer BN can be solubilized by interaction with Lewis bases. Nanopans and nanosheets formed by graphene-like BN are generated by the vapor phase reaction of NH3 and BBr3 at 1223 K. Nanopans of BN, being reported for the first time, have a bottom comprising single-layer BN and a wall of 0.7 nm height. The average inner volume of the nanopan is around 400 nm3. 相似文献
985.
Md. Forhad Mina Md. Akramul Haque Md. Khairul Hassan Bhuiyan Md. Abdul Gafur Yukihiro Tamba Tsutomu Asano 《应用聚合物科学杂志》2010,118(1):312-319
Nanocomposites of isotactic polypropylene (iPP) and multiwalled carbon nanotubes (MWCNTs) with various contents of MWCNTs were fabricated by double molding techniques. X‐ray diffraction measurements reveal a development of α‐crystal with lamellar stacks having a long period of 150 Å in the neat iPP that increases to 165 Å in 2 wt % MWCNTs‐loaded composites, indicating that MWCNTs enhance crystallization of iPP as a nucleating factor. Mechanical properties, such as tensile strength, flexural strength, Young's modulus, tangent modulus, and microhardness are found to increase with increasing MWCNTs content. Thermal analyses represent an increase of crystallization and melting temperatures and a decrease of thermal stability of the composites with increasing MWCNTs. Changes in structural, mechanical, and thermal properties of the composites due to the addition of MWCNTs are elaborately discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
986.
E. Muhammad Abdul Jamal P. A. Joy Philip Kurian M. R. Anantharaman 《Polymer Bulletin》2010,64(9):907-923
Rubber–nickel nanocomposites were synthesized by incorporating freshly prepared nanometric nickel particles in two different
matrices namely natural rubber and neoprene rubber according to specific recipes for various loadings of nano nickel and the
cure characteristics of these composites were evaluated. The maximum torque values register an increase with the increase
in loading of nickel in both composites and this is attributed to the non-interacting nature of nickel nanoparticles with
rubber matrices. The cure time of natural rubber composites decreases with increase in the content of nickel, and in neoprene
rubber cure, time increases with increase in filler content. In natural rubber, the curing reaction seems to be activated
by the presence of nickel particles. The magnetization studies of the composites reveal that the magnetic properties of nickel
are retained in the composite samples. The elastic modulus of natural rubber and neoprene rubber are largely improved by the
incorporation of nickel particles. 相似文献
987.
Sze-Mun Lam Jin-Chung Sin Abdul Rahman Mohamed 《Korean Journal of Chemical Engineering》2010,27(4):1109-1116
P25 powder embedded and TiO2 immobilized on activated carbon (TiO2-P25/AC) was prepared by P25 powder modified sol-gel and dip-coated method. The photocatalysts were characterized by XRD, BET, SEM and their photocatalytic activities were evaluated through phenol degradation in a fluidized bed photoreactor. The addition of P25 in the photocatalysts could significantly enhance the photocatalytic activity, and the optimum loading of P25 was 3 g L?1. The operating parameter results indicated that the optimum pH for phenol degradation was 5.2; the effect of air flow rate gave an optimal value of 2 L min?1; the increasing of UV light intensity led to an increase of degradation efficiency due to more photons absorbed on the surface of the photocatalyst. The kinetics of the phenol degradation fitted well with the Langmuir-Hinshelwood kinetics model. Finally, the photocatalytic ability of TiO2-P25/AC was reduced only 10% after five cycles for phenol degradation. 相似文献
988.
Anwesha Maity Dipul Kalita Tarun Kumar Kayal Tridip Goswami Omprakash Chakrabarti Himadri Sekhar Maiti Paruchuri Gangadhar Rao 《Ceramics International》2010,36(1):323-331
Synthesis of SiC ceramic from processed cellulosic bio-precursor was investigated. Bamboo (Bambusa tulda Roxb.) plants abundantly available in the Jorhat district of Assam, India, were selected for extraction of fibers following Kraft pulping method and bleached bamboo pulp fibers were suitably cast in the form of rectangular boards. Coir fibers available in the Alleppy district of Kerala, India, were initially digested with dilute alkali, mixed with cellulose acetate solution, air dried and then hot-pressed at 140 ± 5 °C under 2.0–2.5 MPa pressure to make rectangular boards. Well-characterized processed bio-precursors were pyrolysed at ~800 °C under flowing N2 atmosphere to prepare the bio-carbonaceous preforms (carbon templates) which showed nearly uniform shrinkages in all directions. Coir fiber composite board carbon showed lower pyrolytic weight loss (~66%), higher density (0.49 g cm?3), lower porosity (~58%) and narrower pore diameter (10 μm) compared to the cast bamboo pulp fiber board carbon. The carbon samples showed perfect retention of fibrous morphological features of hierarchically grown bio-structures. Ceramization of carbon templates could be done by reactive melt silicon infiltration into porous channels at ~1600 °C under vacuum. The final ceramics were adequately dense (%theoretical density > 99%), showed negligible linear dimensional changes (indicating net-dimension formation capability), presence of crystalline Si and SiC phases and duplex microstructure with complete preservation of fibrous architecture of plant bio-structure. The Si/SiC ceramic composite synthesized from coir fiber board gave room temperature 3-point flexural strength and Young's modulus values of 121 MPa and 276 GPa, respectively. Both the ceramic composites showed adequate oxidation resistance during heating at 1300 °C for 7 h in air. 相似文献
989.
Application of FTIR Spectroscopy for the Determination of Virgin Coconut Oil in Binary Mixtures with Olive Oil and Palm Oil 总被引:1,自引:0,他引:1
Abdul Rohman Yaakob B. Che Man Amin Ismail Puziah Hashim 《Journal of the American Oil Chemists' Society》2010,87(6):601-606
Rapid Fourier transform infrared (FTIR) spectroscopy combined with attenuated total reflectance (ATR) was applied for quantitative
analysis of virgin coconut oil (VCO) in binary mixtures with olive oil (OO) and palm oil (PO). The spectral bands correlated
with VCO, OO, PO; blends of VCO and OO; VCO and PO were scanned, interpreted, and identified. Two multivariate calibration
methods, partial least square (PLS) and principal component regression (PCR), were used to construct the calibration models
that correlate between actual and FTIR-predicted values of VCO contents in the mixtures at the FTIR spectral frequencies of
1,120–1,105 and 965–960 cm−1. The calibration models obtained were cross validated using the “leave one out” method. PLS at these frequencies showed the
best calibration model, in terms of the highest coefficient of determination (R
2) and the lowest of root mean standard error of calibration (RMSEC) with R
2 = 0.9992 and RMSEC = 0.756, respectively, for VCO in mixture with OO. Meanwhile, the R
2 and RMSEC values obtained for VCO in mixture with PO were 0.9996 and 0.494, respectively. In general, FTIR spectroscopy serves
as a suitable technique for determination of VCO in mixture with the other oils. 相似文献
990.
S. Uma M. Chidambaram A. Seshagiri Rao Chang Kyoo Yoo 《Chemical engineering science》2010,65(3):1065-1075
This paper presents a simple cascade controller in the enhanced modified Smith predictor structure for control of integrating processes. The proposed structure consists of two control loops, a secondary inner loop and a primary outer loop. The method has totally three controllers of which the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is designed using IMC technique. The primary loop set-point tracking and disturbance rejection controllers are designed using direct synthesis method. The primary set-point tracking controller is designed as a PID with lag filter and the primary disturbance rejection controller is designed as a PD with lead-lag filter. Simulation studies have been carried out on various cascade integrating processes with/without zero. The present method gives significant disturbance rejection both in the inner and outer loops and also shows significant improvement when compared to the recently reported methods. 相似文献