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171.
Orthogonal wavelets enclose more potential of dropping the ISI- and ICI-sway amid the carriers due to multipath propagation over the free-space fading channels. Moreover, wavelet-OFDM is more bandwidth efficient as compared to conventional OFDM and is less affected by Doppler shift. Accordingly, a BER estimation of discrete Fourier transform (DFT) based OFDM system and discrete wavelet transform (DWT) based OFDM system is carried out in this work. The assessment is demonstrated by means of diverse modulation schemes explicitly BPSK, QPSK, 8-PSK, QAM, 8-QAM, 16-QAM for both conventional- and wavelet-OFDM wireless system over AWGN channels. Higher orders of PSK schemes involve more SNR requirement to target an acceptable BER of 10−5 over AWGN channels in both the cases. Furthermore, the efficiency of W-OFDM increases with decreasing the required value of BER. 相似文献
172.
173.
A hybrid OFDM–IsOWC system incorporating diverse modulation schemes like optical double side band (ODSB), optical tandem side band (OTSB) and optical single side band (OSSB) is carried out to optimize a long reach high speed inter-satellite link (ISL) with acceptable SNR and BER. The proposed system is also reported under the influence of antenna efficiency and pointing error at varied values of power levels. Simulations point toward that the proposed hybrid OFDM–OSSB–IsOWC transmission system promises significantly enhanced ISL link compared to conventional IsOWC systems. 相似文献
174.
175.
Lagrangian heuristics for scheduling new product development projects in the pharmaceutical industry
To stay ahead of their competition, pharmaceutical firms must make effective use of their new product development (NPD) capabilities
by efficiently allocating its analytical, clinical testing and manufacturing resources across various drug development projects.
The resulting project scheduling problems involve coordinating hundreds of testing and manufacturing activities over a period
of several quarters. Most conventional integer programming approaches are computationally impractical for problems of this
size, while priority rule-driven heuristics seldom provide consistent solution quality. We propose a Lagrangian decomposition
(LD) heuristic that exploits the special structure of these problems. Some resources (typically manpower) are shared across
all on-going projects while others (typically equipment) are specific to individual project categories. Our objective function
is a weighted discounted cost expressed in terms of activity completion times. The LD heuristics were subjected to a comprehensive
experimental study based on typical operational instances. While the conventional “Reward–Risk” priority rule heuristic generates
duality gaps between 47–58%, the best LD heuristic achieves duality gaps between 10–20%. The LD heuristics also yield makespan
reductions of over 30% over the Reward–Risk priority rule. 相似文献
176.
In this article, the powerful, easy-to-use and effective approximate analytical mathematical tool like homotopy analysis method (HAM) is used to solve the telegraph equation with fractional time derivative α (1 < α ? 2). By using initial values, the explicit solutions of telegraph equation for different particular cases have been derived. The numerical solutions show that only a few iterations are needed to obtain accurate approximate solutions. The method performs extremely well in terms of efficiency and simplicity to solve this historical model. 相似文献
177.
The article presents the approximate analytical solutions of general nonlinear diffusion equation with fractional time derivative in the presence of an absorbent term and a linear external force obtained with the help of powerful mathematical tool like Homotopy Perturbation Method. By using initial value, the approximate analytical solutions of the equation are derived. The fractional derivatives are described in the Caputo sense. Numerical results for different particular cases are presented graphically. The anomalous behavior of nonlinear diffusivity in the presence or absence of external force and reaction term are calculated numerically and presented graphically. 相似文献
178.
A one dimensional mathematical model is developed to optimize the design parameters of desiccant wheel. The result shows that after some value of design parameters, change in moisture removal is negligible. The optimum isotherm shape should be R = 0.1. At this isotherm optimum value of wheel length, and channel pitch should be in the range of 0.2–0.25 and 0.003–0.004 m respectively. 相似文献
179.
S. V. Bara Vishal Arora S. Chinnaesakki S. J. Sartandel B. S. Bajwa R. M. Tripathi V. D. Puranik 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):769-776
This paper presents the results of measurement of natural and fallout radioactivity in soil samples of Chamba and Dharamshala
areas in Himachal Pradesh, India. Spatial distribution of 238U, 226Ra, 232Th, 40K, 137Cs was determined using High resolution gamma-ray spectrometry. The mean activity concentration in Chamba region due to 238U, 232Th, 40K and 137Cs was 32.3, 58.4, 588.3, and 10.9 Bq kg−1, respectively, whereas in Dharamshala it was 35.7, 61.3, 594.9, 10.0 Bq kg−1, respectively. Absorbed gamma dose rate (D) in air was calculated using appropriate dose conversion factors, which was varying
from 45 to 103 nGy h−1. To control the radiation exposure due to natural radioactivity in soil, if it is used as building materials, radium equivalent
activity (Raeq) and activity index were also evaluated. Radium equivalent activity calculated for the soil ranged from 95.5 to 234.2 Bq kg−1 with average of 171.0 Bq kg−1.The calculated Activity concentration index was ranged from 0.34 to 0.85 with an average value of 0.64. The natural and fallout
radioactivity in soil of this region is comparable with Indian average and other parts of the world. The percentage contribution
of 238U, 232Th and 40K and 137Cs to the average external gamma dose rate was 22, 46, 32, 2%, respectively. This shows that the dose contribution due to
fallout radioactivity is negligible as compared to the natural radioactivity. 相似文献
180.
Vishal SharmaVivek Gupta Sumati AnthalAjit K. Saxena Mohan Paul S. Ishar 《Tetrahedron letters》2012,53(42):5649-5651
Irradiation of (E,E)-arylidene-β-ionones in the presence of oxygen leads to the formation of 8-[β-arylethenyl]-2,2,6-trimethyl-7,9,10-trioxa-tricyclo[6.2.2.01,6]dodec-11-enes (3). However, prolonged irradiation in the presence of oxygen leads to their conversion to 6-hydroxy-1,7,7-trimethyl-2-oxa-bicyclo[4.4.0]dec-4-en-3-one (4), apparently proceeding through addition of oxygen to the side chain π-bond in 3. 相似文献