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Search Results: 1 - 10 of 775342 matches for " O. M. A. Dardeer "
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Design of Compact Dual Notched Self-Complementary UWB Antenna  [PDF]
K. S. Sultan, O. M. A. Dardeer, H. A. Mohamed
Open Journal of Antennas and Propagation (OJAPr) , 2017, DOI: 10.4236/ojapr.2017.53008
Abstract: In this paper, a novel double notched UWB antenna is introduced. The proposed antenna is Quasi Self-Complementary (QSC) with wide impedance bandwidth from 2.2 GHz to more than 12 GHz. The antenna consists of semi-ring with rectangular tapered section for more matching and it is designed on FR-4 substrate with thickness 1.5 mm and has compact size of 11.5 × 14.5 × 1.5 mm3. The dual notched bands are achieved by using a T-shaped slit etched in the radiating patch to reject interference with WIMAX band and two C-shaped are placed close to the microstrip feed line to reject the interference with the WLAN band. The proposed antenna is designed, simulated and measured. All simulation results are performed using the CST software. Good agreement is presented between the experimental and the simulated results.
Dual Band BPF Based on Parallel Coupled Lines Loaded by Open Stubs for Ku-Band Satellite Applications  [PDF]
Ahmed S. I. Amar, Osama M. A. Dardeer, Abdelhaleem A. Zekry
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2019, DOI: 10.4236/jemaa.2019.119010
Abstract: This paper presents a dual band Band Pass Filter (BPF) operating at both the downlink and uplink frequency bands for Ku-band satellite applications. The commonly used frequency band in mobile communications satellites is the Ku-band. These mobile satellite systems help connect remote regions, vehicles, ships, people and aircraft to other parts of the world and/or other mobile or stationary communications units, in addition to serving as navigation systems. The structure of the proposed filter is based on parallel coupled microstrip lines and four sections are used. Tuning the two operational bands can be achieved using two open-circuited stubs at the first and last sections of the parallel coupled microstrip lines. The proposed filter is adjusted to operate at 12.54 GHz and 14.14 GHz for downlink and uplink bands, respectively. The proposed dual band BPF is fabricated, measured, and good agreement is obtained between simulated and measured results.
Compact UWB Power Divider, Analysis and Design  [PDF]
Osama Dardeer, Tamer Abouelnaga, Ashraf Mohra, Hadia Elhennawy
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2017, DOI: 10.4236/jemaa.2017.92002
Abstract: In this paper, two ultra-wide band power dividers are introduced. Compact equal power divider is considered firstly where an extended transmission lines and double open stubs are used in order to increase the bandwidth. Secondly, an unequal UWB power divider is introduced where multi-stage impedance is used. The proposed power dividers are fabricated and measured. The overall sizes of the proposed power dividers are 11.37 × 17.87 mm2 for the equal one and 12.13 × 29.03 mm2 for the unequal power divider. The simulated results are compared with the measured results and good agreement is obtained.
Acidity/Rancidity Levels, Chemical Studies, Bacterial Count/Flora of Fermented and Unfermented Silver Catfish (Chrysichthys nigrodigitatus)  [PDF]
O. A. Oyelese, O. M. Sao, M. A. Adeuya, J. O. Oyedokun
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.411149
Abstract:

The keeping quality and shelf life of fermented and unfermented Chrysichthys nigrodigitatus were monitored in this study. Four kilograms of fresh Chrysichthys nigrodigitatus was minced into fine particles (with an initial pH of 7.2 before distribution into 8 samples). Samples 1-4 are unfermented cooked while Samples 5-8 were fermented, not cooked. All the 8 prepared samples barely lasted for two weeks, while samples 1, 3 and 7 lasted for six weeks. Total Volatile Base (TVB) ranged higher (24.12 - 29.43) mg/100gm in Samples 1-4 than (14.23 - 18.09) mg/100gm recorded in Samples 5-8. In Samples 1-4, FFA values were not significantly (P > 0.05) different; also followed a narrow range of (6.14 - 6.45)% while higher range of (6.42 - 12.27)% recorded in samples (5-8). Peroxide values (PV) increased in all the 8 samples in the second, fourth and sixth week, however higher values were recorded in Samples 5-8. Acidity generally increased with length (weeks) of fermentation with a gradual drop in pH from 7.2 (in the fresh fish) to pH 4.5 (sample 7), the worst sample at six weeks. Sample 4 with bacteria load of 5.05 × 105 at second week and sample 7 (8.2 × 105) at sixth week became unfit for consumption having exceeded the 5.0 × 105 ICMSF standard for safe fish product. Five bacteria species (Lactobacillus sp, Proteus spp, Staphylococcus aureus, Staphylococcus epidermis, Bacillus sp) with the exception of Proteus spwere not represented in sample 1 (due to salt content). Strong positive correlation (r = 0.97, P < 0.01) exists between PV and FFA. Acidityof the fermented products increased over the weeks with strong negative correlation (r = -0.121, P < 0.01) exists between pH and FFA. Acidity (i.e drop in PH) with increasing rancidity since (r = -0.313, P < 0.05) exists between PV and pH.

Evaluation of Variations in Seed Vigour Characters of West African Rice (Oryza sativa L.) Genotypes Using Multivariate Technique  [PDF]
M. A. Adebisi, F. S. Okelola, M. O. Ajala, T. O. Kehinde, I. O. Daniel, O. O. Ajani
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.42047
Abstract: Seeds of 24 West African rice (Oryza sativa L.) genotypes were evaluated for seed vigour traits in the laboratory and field in two cropping seasons at the Research Farm of Federal University of Agriculture, Abeokuta, Nigeria. Seed yields of these genotypes were also determined in the field during the two seasons. Data collected on seed vigour traits were subjected to multivariate analysis including principal component analysis (PCA) and cluster analysis. The first three axes of the principal component analysis across the two seasons captured 86.34% of the total variation among the entries and identified seedling vigour index-I, seedling vigour index-II, speed of germination index, percentage germination, seedling establishment, emergence percentage and seed yield per plant as the characters contributing most to the variation. Cluster analysis classified these genotypes into four distinct groups based on germination and emergence percentages. Fifteen of the genotypes with mean values of between 60.43% and 65.18%, clustered in group 1, two genotypes each with mean values of 65.71% and 58.81% and 20.11% and 29.49% clustered in groups II and IV respectively while the remaining five genotypes with mean values of between 55.19% and 55.88% clustered in group III. Hybridization of genotypes across dusters could lead to increase in heterosis in cross progenies. Those characters identified by PCA could be included in the crop improvement programme for improved seed quality within West African low land rice germplasm.
Prevalence of oral lesions and the effects of HAART in adult HIV patients attending a tertiary hospital in Lagos, Nigeria  [PDF]
O. M. Eweka, G. A. Agbelusi, O. Odukoya
Open Journal of Stomatology (OJST) , 2012, DOI: 10.4236/ojst.2012.23036
Abstract: Background: Oral lesions have been reported to be early clinical features of HIV infection. The objective of this study was to establish the prevalence of oral lesions and the management outcome using HAART in HIV Seropositive patients attending a tertiary hos- pital in Lagos, Nigeria. Methods: This was a prospective study in 114 newly diagnosed adult HIV infected patients (not on antiretroviral therapy), who attended the PEPFAR clinic at Lagos University Teaching Hospital. They were assessed for oral lesions which were evaluated using EEC/WHO—Classification on the diagnostic criteria for oral lesions in HIV. Data were collected using an interviewer administered questionnaire. Oral examination was carried out and oral lesions detected were recorded. Presence or absence of oral lesions was evaluated following 3 months use of HAART. Results: 114 patients were enrolled into the study, 49(43.0%) males and 65(57.0%) females, with age range of 18-63 years. 42 (36.8%) presented with oral lesions, 19 (45.2%) of which had multiple lesions. Oral Candidiasis which accounted for 47.7% was the most common oral lesion observed followed by Oral Hairy Leukoplakia (21.6%) and oral hyperpigmentation (10.8%). Pseudomembraneous Candidiasis was the most common variant of oral Candidiasis seen. Prevalence of oral lesions was significantly associated with low CD4 count and high viral load. Eighty four percent (84%) of oral lesions disappeared following 3 months of HAART treatment. Conclusion: Oral lesions are common features of HIV and a marker for progression of the disease to AIDS. There was significant reduction in oral lesions following 3 months treatment with HAART.
Optimum Calcium Carbonate Filler Concentration for Flexible Polyurethane Foam Composite  [PDF]
M. A. Usman, S. O. Adeosun, G. O. Osifeso
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2012, DOI: 10.4236/jmmce.2012.113023
Abstract: The production cost of flexible polyurethane foam is significantly dependent on the cost of polyol, which constitute the largest percentage of materials used in foam production with the characteracterics to induce superior mechanical properties. Suitable fillers that are relatively cheap can be introduced in the foam matrix as replacement for polyol. However, certain compositions of filler have deleterious effect on some relevant mechanical properties of the foam. This paper investigates the effect of CaCO3 filler in flexible polyurethane foam matrix for the dual purposes of achieving sustained mechanical properties and reduction in production cost. The optimum CaCO3 composition was found to be 20 wt % representing a concomitant 18.54% reduction in cost of production.
A Simulation Study on the Performances of Classical Var and Sims-Zha Bayesian Var Models in the Presence of Autocorrelated Errors  [PDF]
M. O. Adenomon, V. A. Michael, O. P. Evans
Open Journal of Modelling and Simulation (OJMSi) , 2015, DOI: 10.4236/ojmsi.2015.34016
Abstract: It is well known that a high degree of positive dependency among the errors generally leads to 1) serious underestimation of standard errors for regression coefficients; 2) prediction intervals that are excessively wide. This paper set out to study the performances of classical VAR and Sims-Zha Bayesian VAR models in the presence of autocorrelated errors. Autocorrelation levels of (-0.99, -0.95, -0.9, -0.85, -0.8, 0.8, 0.85, 0.9, 0.95, 0.99) were considered for short term (T = 8, 16); medium term (T = 32, 64) and long term (T = 128, 256). The results from 10,000 simulation revealed that BVAR model with loose prior is suitable for negative autocorrelations and BVAR model with tight prior is suitable for positive autocorrelations in the short term. While for medium term, the BVAR model with loose prior is suitable for the autocorrelation levels considered except in few cases. Lastly, for long term, the classical VAR is suitable for all the autocorrelation levels considered except in some cases where the BVAR models are preferred. This work therefore concludes that the performance of the classical VAR and Sims-Zha Bayesian VAR varies in terms of the autocorrelation levels and the time series lengths.
Short Term Forecasting Performances of Classical VAR and Sims-Zha Bayesian VAR Models for Time Series with Collinear Variables and Correlated Error Terms  [PDF]
M. O. Adenomon, V. A. Michael, O. P. Evans
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.57074
Abstract:

Forecasts can either be short term, medium term or long term. In this work we considered short term forecast because of the problem of limited data or time series data that is often encounter in time series analysis. This simulation study considered the performances of the classical VAR and Sims-Zha Bayesian VAR for short term series at different levels of collinearity and correlated error terms. The results from 10,000 iteration revealed that the BVAR models are excellent for time series length of T=8 for all levels of collinearity while the classical VAR is effective for time series length of T=16 for all collinearity levels except when ρ = -0.9 and ρ = -0.95. We therefore recommended that for effective short term forecasting, the time series length, forecasting horizon and the collinearity level should be considered.

On the Performances of Classical VAR and Sims-Zha Bayesian VAR Models in the Presence of Collinearity and Autocorrelated Error Terms  [PDF]
M. O. Adenomon, V. A. Michael, O. P. Evans
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.61012
Abstract: In time series literature, many authors have found out that multicollinearity and autocorrelation usually afflict time series data. In this paper, we compare the performances of classical VAR and Sims-Zha Bayesian VAR models with quadratic decay on bivariate time series data jointly influenced by collinearity and autocorrelation. We simulate bivariate time series data for different collinearity levels (0.99, 0.95, 0.9, 0.85, 0.8, 0.8, 0.85, 0.9, 0.95, 0.99) and autocorrelation levels (0.99, 0.95, 0.9, 0.85, 0.8, 0.8, 0.85, 0.9, 0.95, 0.99) for time series length of 8, 16, 32, 64, 128, 256 respectively. The results from 10,000 simulations reveal that the models performance varies with the collinearity and autocorrelation levels, and with the time series lengths. In addition, the results reveal that the BVAR4 model is a viable model for forecasting. Therefore, we recommend that the levels of collinearity and autocorrelation, and the time series length should be considered in using an appropriate model for forecasting.
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