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71.
Momina Moetesum Fazle Hadi Muhammad Imran Abid Ali Minhas Athanasios V. Vasilakos 《Wireless Networks》2016,22(7):2189-2201
Provisioning buffer management mechanism is especially crucial in resource-constrained delay tolerant networks (DTNs) as maximum data delivery ratio with minimum overhead is expected in highly congested environments. However, most DTN protocols do not consider resource limitations (e.g., buffer, bandwidth) and hence, results in performance degradation. To strangle and mitigate the impact of frequent buffer overflows, this paper presents an adaptive and efficient buffer management scheme called size-aware drop (SAD) that strives to improve buffer utilization and avoid unnecessary message drops. To improve data delivery ratio, SAD exactly determines the requirement based on differential of newly arrived message(s) and available space. To vacate inevitable space from a congested buffer, SAD strives to avoid redundant message drops and deliberate to pick and discard most appropriate message(s) to minimize overhead. The performance of SAD is validated through extensive simulations in realistic environments (i.e., resource-constrained and congested) with different mobility models (i.e., Random Waypoint and disaster). Simulation results demonstrate the performance supremacy of SAD in terms of delivery probability and overhead ratio besides other metrics when compared to contemporary schemes based on Epidemic (DOA and DLA) and PRoPHET (SHLI and MOFO). 相似文献
72.
Muhammad N.S. Hadi 《Construction and Building Materials》2009,23(2):1102-1108
This paper presents results of testing 16 specimens, 12 of which as columns under different eccentricities and four as beams under four point loading regime. All 16 specimens were circular in cross section and were made of reinforced concrete. Four specimens served as reference specimens and were just made of reinforced concrete. The next four specimens were wrapped with carbon fibre reinforced polymers (CFRP). The next four specimens had steel fibres added to the concrete. The final four specimens were reinforced with steel fibres and wrapped with CFRP. From each group of specimens, one specimen was tested as a column under a concentric load, the second specimen was tested as a column under 25 mm eccentricity, the third specimen was tested as a column under 50 mm eccentricity, and the final specimen was tested as a beam under four point loading regime. The experimental programme proved that the introduction of fibres as well as wrapping the specimens with FRP improve the properties of concrete, especially its ductility. 相似文献
73.
M. Hadi A. R. Kamali J. Khalil-Allafi A. R. Ebrahimi M. Hadavi 《Russian Journal of Non-Ferrous Metals》2009,50(1):24-29
Titanium aluminide intermetallic compounds have an excellent capability for use in engineering structures at high temperatures.
In the present work the formation of Nb rich inclusions in microstructure and evaporation of Al during melting of γ-TiAl based
alloy (Ti-48Al-2Cr-2Nb-1B (at %)) was studied. The results show that the inclusions cannot be removed even with a four-stage
melting process, when elemental Nb is used as raw material. However, by replacing Nb with NbAl3 and using a three-stage melting process, the inclusions were removed from microstructure and also evaporation of Al was reduced
remarkably. Otherwise, with removing elemental Al from raw material by using TiAl compound, evaporation of Al will be very
low. Increasing vessel pressure from 400 to 600 mbar will not influence evaporation of Al.
The article is published in the original. 相似文献
74.
High-penetration renewable energy-based generators (REGs) in distribution systems have increased the importance of impact assessment involving these systems. This assessment focuses on power quality (PQ) and compatibility between REGs and existing system components. Electric vehicle (EV) technology has also recently achieved a substantial market share. This technology requires the development of charging stations similar to current petroleum fuelling stations in the near future. Thus, the effect of EV stations (EVSs) on PQ must also be considered. This study presents a PQ analysis on the effects of high-penetration EVS and REG systems, including wind turbines, grid-connected photovoltaics (PVs), and fuel cell (FC) power generation units on a modified 16-bus distribution system under different loading and weather conditions. All data on EVS, wind farm, PV, and FC units as well as weather conditions presented in this paper were collected from different power companies and the Malaysian Meteorological Department. The system is modelled and simulated using the MATLAB/Simulink software to study the effects of these technologies on system performances at various penetration levels. Simulation results indicated that the presence of high-penetration EVSs and REGs can cause severe PQ problems such as frequency and voltage fluctuations, voltage drop, harmonic distortion and power factor reduction. 相似文献
75.
M.N.S. Hadi 《Construction and Building Materials》2011,25(2):851-858
The aim of this paper is to present results of testing a full scale reinforced concrete T connection by static loading. The connection represents a beam–column connection. The beam and column had a square cross section with a 300 mm dimension. The height of the column was 2.9 m and the clear beam length was 1.4 m. The connection was initially tested to failure. Galvanised steel straps were used to rehabilitate the connection. Epoxy resin was used to fix the steel straps to the concrete surface. The connection was tested after the rehabilitation. Results of testing the rehabilitated connection show that the yield and ultimate loads were 65 kN and 95 kN, respectively, compared with the original test results of 75 kN and 84 kN, respectively. Based on results of the tests, it can be concluded that the rehabilitating method used in this study was effective in increasing the ultimate strength of the T connection. 相似文献
76.
77.
78.
The influence of fuel type used to bake bread on the spectrum and concentrations of some polycyclic aromatic hydrocarbons and heavy metals in baked bread was assessed. Bread samples were collected from different bakeries operated by either electricity, solar, mazot or solid waste and their residue content of PAHs and heavy metals was assessed. The total concentration of PAHs detected in mazot, solar, solid waste and electricity operated bakeries had an average of 320.6, 158.4, 317.3 and 25.5 μg kg−1, respectively. Samples collected from mazot, solar and solid waste operated bakeries have had a wide spectrum of PAHs, in comparison to that detected in bread samples collected from electricity operated bakeries. Lead had the highest concentrations in the four group of bread samples, followed by nickel, while the concentrations of zinc and cadmium were the least. The concentration of lead detected in bread samples produced from mazot, solar, solid waste and electricity fueled bakeries were 1375.5, 1114, 1234, and 257.3 μg kg−1, respectively. Estimated daily intake of PAHs based on bread consumption were 48.2, 28.5, 80.1, and 4.8 μg per person per day for bread produced in bakeries using mazot, solar, solid waste and electricity, respectively. Meanwhile, the estimated daily intake of benzo (a) pyrene were 3.69, 2.65, 8.1, and 0.81 μg per person per day for bread sample baked with mazot, solar, solid waste and electricity, respectively. The daily intake of lead, based on bread consumption was 291, 200.5, 222, and 46.31 μg per person per day for bread sample baked with mazot, solar, solid waste and electricity, respectively. The present work has indicated the comparatively high level of daily intake of benzo (a) pyrene and lead in comparison to levels reported from many other countries and those recommended by international regulatory bodies. It is probable that residues detected in bread samples are partially cereal-borne but there is strong evidence that the process of baking and the gases emitted are responsible for most of the contamination load. 相似文献
79.
This paper addresses the problem of developing cyclic schedules for nurses while taking into account the quality of individual
rosters. In this context, quality is gauged by the absence of certain undesirable shift patterns. The problem is formulated
as an integer program (IP) and then decomposed using Lagrangian relaxation. Two approaches were explored, the first based
on the relaxation of the preference constraints and the second based on the relaxation of the demand constraints. A theoretical
examination of the first approach indicated that it was not likely to yield good bounds. The second approach showed more promise
and was subsequently used to develop a solution methodology that combined subgradient optimization, the bundle method, heuristics,
and variable fixing. After the Lagrangian dual problem was solved, though, there was no obvious way to perform branch and
bound when a duality gap existed between the lower bound and the best objective function value provided by an IP-based feasibility
heuristic. This led to the introduction of a variable fixing scheme to speed convergence. The full algorithm was tested on
data provided by a medium-size U.S. hospital. Computational results showed that in most cases, problem instances with up to
100 nurses and 20 rotational profiles could be solved to near-optimality in less than 20 min. 相似文献
80.
An algorithm extension to three dimensions is developed and presented for the highly phase-coherent modified second-order in time, fourth-order in space (or M24) finite-difference time-domain (FDTD) algorithm. A finite-volumes approach in conjunction with Yee's standard FDTD lattice is used for algorithm development. The corresponding dispersion relation is also developed, analyzed and compared to both the standard second-order and fourth-order FDTD algorithms as well as to two closely related high-order phase-coherent algorithms. Wideband algorithm attributes are also presented as well as sets of ready to use optimized algorithm coefficients. 相似文献