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Search Results: 1 - 10 of 467554 matches for " Mustafa A Rahman "
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The Effect of Packaging Shape on the Distribution of Electric and Magnetic Fields and SAR Induced in 3D Models of Water Containers  [PDF]
Maher A. A. Abdelsamie, Russly B. Abdul Rahman, Shuhaimi Mustafa, Dzulkifly Hashim
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2014, DOI: 10.4236/jemaa.2014.69022

In this study, two software packages using different numerical techniques—FEKO 6.3 with Finite-Element Method (FEM) and XFDTD 7 with Finite Difference Time Domain Method (FDTD)—were used to assess exposure of 3D models of square-, rectangular-, spherical- and pyramidal-shaped water containers to electromagnetic waves at 300, 900, and 2400 MHz frequencies. Using the FEM simulation technique, the peak electric field of 25, 4.5, 3, and 2 V/m at 300 MHz and 15.75, 1.5, 1.8 and 1.75 V/m at 900 MHz were observed in pyramidal-, rectangular-, spherical-, and squareshaped 3D container models, respectively. The FDTD simulation method confirmed a peak electric field of 12.782, 10.907, 0.81867 and 10.625 V/m at 2400 MHz in the pyramidal-, square-, spherical-, and rectangular-shaped 3D models, respectively. The study demonstrated an exceptionally high level of electric field in the water in the two identical pyramid-shaped 3D models analyzed using the two different simulation techniques. Both FEM and FDTD simulation techniques indicated variations in the distribution of electric, magnetic fields, and specific absorption rate of water stored inside the 3D container models. The study successfully demonstrated that shape and dimensions of 3D models significantly influence the electric and magnetic fields inside packaged materials; thus, specific absorption rates in the stored water vary according to the shape and dimensions of the packaging materials.

Quality Traps in Localized Competition
Partha Gangopadhyay,Mustafa A Rahman,Nasser Elkanj
Modern Applied Science , 2011, DOI: 10.5539/mas.v5n5p3
Abstract: A wide spectrum of technologies, producing a vast array of product qualities, coexists in modern markets today. Many of these markets are also characterised by what is commonly known as localized competition that refers to a special industrial structure in which different firms compete directly with different groups of rivals. We explore the endogenous choice of product quality in localized competition such that the choice of product quality by a seller has effects only on those rivals who share the common market segment. In the proposed model multiple equilibria may occur and the present analysis may be seen as a rationalization for the idea that a market segment may become trapped in a “low-quality” equilibrium. In the presence of multiple equilibria and the quality trap, the industrial policy may have a welfare-enhancing role in coordinating expectations. We then extend the model to highlight the conditions that can preclude the possibility of the quality trap in localised competition.
RF-to-DC Direct Power Conversion of AlGaAs/GaAs Schottky Diode for On-Chip Rectenna Device Application in Nanosystems
F. Mustafa,S.F.A. Rahman,A.M. Hashim,N. Parimon
Journal of Applied Sciences , 2010,
Abstract: The Schottky diodes enjoined with coplanar waveguides are investigated for applications in on-chip rectenna device application without insertion of a matching circuit. The design, fabrication, DC characteristics and RF-to-DC conversion of the AlGaAs/GaAs HEMT Schottky diode is presented. The RF signals are well converted by the fabricated Schottky diodes with cut-off frequency up to 25 GHz estimated in direct injection experiments. The mW output power can be achieved by optimizing the material structure and ohmic metals so that lower series resistance is realized. Proper circuitry also should lead to maximum power conversion, for example the ground lines of the system are connected to the same point. Direct integration of the planar dipole antenna to the Schottky diode via coplanar waveguide transmission line may allow omission of any matching impedance circuit. The outcomes of these results provide conduit for breakthrough designs for ultra-low power on-chip rectenna device technology to be integrated in nanosystems.
Effects of Packaging Shape with Sharp Edges on Electromagnetic Energy Distribution: a Possible Mechanism for Non-thermal Effects of Microwaves
Maher A. A. Abdelsamie,Russly b Abdul Rahman,Shuhaimi Mustafa,Dzulkifly Hashim
Physics , 2014,
Abstract: The research works on the biological effects of electromagnetic (EM) radiation have increased globally. Computer simulation models were developed to assess exposure of square, rectangular, pyramidal, and cylindrical water containers to microwave radiation at 300, 900, and 2,400 MHz. The development of the models included determination of EM field distribution and the resulting specific absorption rate (SAR) in the stored water. These models employed CST STUDIO SUITE 2014 package to solve EM field equations by applying the finite-difference time-domain (FDTD) method. The effect of frequency, packaging shape, and polarization on SAR induced in water was determined. High electric field and point SAR were obtained over the whole azimuth and elevation angles range in the pyramidal container model. The highest values of SAR were induced in water at the sharp edges of the four water container models. The order of the effect on total SAR and maximum point SAR is cylindrical < square < rectangular < pyramidal model at 300, 900, and 2,400 MHz for both vertical and horizontal polarizations. It can be concluded that the variation in the packaging shape of the containers, polarization, irradiation geometry, and frequency. In addition, the sharp edges of the container models significantly affect the calculation and distribution of electric and magnetic fields and SAR values induced in the stored water, which in turn could cause variations in the non-thermal effects of the electromagnetic fields in the stored water.
Fabrication of Pt-Circular Schottky Diode on Undoped AlGaN/GaN HEMT
M. Mohamad,F. Mustafa,A.M. Hashim,S.F. Abd Rahman
Journal of Applied Sciences , 2010,
Abstract: In this study, Pt-circular Schottky diode is successfully fabricated for gas sensor application. The fabricated Schottky diode shows good rectification characteristics. The device which shows improvement in term of wiring connection for electrical characterization is fabricated. The DC I-V curves of fabricated Schottky diodes show low series resistance of 210 Ω and 330 Ω. The Schottky barrier height (SBH) in the range of 0.458-0.708 eV are experimentally obtained and the discrepancy with the calculated SBH is discussed. A measurement setup that has a capability to allow measurement at high temperature, high hydrogen gas density and low vacuum pressure is also presented. The fabricated device is expected to be suitable for gas sensing application.
Matiur Rahman,Muhammad Mustafa
International Journal of Economics and Research , 2010,
Abstract: This paper is an exploration of the primary reasons for current U.S. great recession, its global transmission, major economic and financial programs, future challenges, and exit strategies. The root cause lies in the U.S. real estate market debacle due to massive subprime lending and proliferation of mortgage-backed securities. The real estate market trouble spilled over into U.S. major banks and other financial intermediaries as well as financial markets. Due to rapid financial globalization, the U.S. financial meltdown and deep recession caused damages to other major economies in the world. Worldwide major economic and financial programs saved the world economy from further deterioration, and set a stage for uncharted nascent recovery. There are dangers of high global inflation in the future with chance of double-dip recession if exit strategies are applied untimely to withdraw excess liquidity in inappropriate doses.
Open-Gate Liquid-Phase Sensor Fabricated on Undoped-AlGaN/GaN HEMT Structure
M.S.Z. Abidin,M.E. Sharifabad,S.F.A. Rahman,F. Mustafa
Journal of Applied Sciences , 2010,
Abstract: Sensing responses of an open-gate liquid-phase sensor fabricated on undoped-AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated in aqueous solution. In air-exposed ambient, the open-gate undoped AlGaN/GaN HEMT shows the only presence of linear region of currents while Si-doped AlGaN/GaN shows linear and saturation regions of currents, very similar to those of gated devices. This seems to show that very low Fermi level pinning by surface states exists in undoped AlGaN/GaN sample compared to Si-doped sample. In aqueous solution, the typical current-voltage (I-V) characteristics of HEMTs with reasonably good gate controllability are observed. The potential of the AlGaN surface at the open-gate area is effectively controlled via aqueous solution by Ag/AgCl gate electrode. The open-gate undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to large leakage current where it increases with the negative gate voltage, the Nernstian’s like sensitivity cannot be determined as what commonly reported in literatures. This large leakage current may be caused by the technical factors rather than the characteristics of the devices themselves. Suprisingly, although there is imperfection in the device preparation, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage is likely to improve the device performance. The fabricated open-gate undoped-AlGaN/GaN structure is expected to be suitable for pH sensing application.
Frequency of Malignancy in Solitary Thyroid Nodule in a Tertiary Level Hospital of Bangladesh  [PDF]
Md Shazibur Rashid, Najnin Akhter, Md Shafiqur Rahman, Jahangir Alam Majumder, A. H. M. Delwar, Md Golam Mustafa
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2019, DOI: 10.4236/ijohns.2019.84015
Abstract: Objectives: To determine the frequency of thyroid malignancy in clinically and sonographically solitary thyroid nodule in patients undergoing thyroidectomy in Comilla Medical College Hospital. Methods: A cross sectional study was carried out at the Department of Otolaryngology and Head Neck Surgery of Comilla Medical College Hospital during the period from January 2016 to January 2019. This study includes all patients admitted and undergoing surgery with solitary thyroid nodule. Results: Out of 188 patients 146 patients were female and 42 patients were male with female:male ratio of 3.4:1. Out of 188 patients 24 patients were found histologically thyroid malignancy. Among them 14 patients were male and 10 patients were female. Papillary carcinoma was found in all cases. Conclusions: Follicular carcinoma is rare in our country. Histopathological examiners may not efficiently be doing their job to differentiate carcinoma from adenoma.
The Effect of Queuing Mechanisms First in First out (FIFO), Priority Queuing (PQ) and Weighted Fair Queuing (WFQ) on Network’s Routers and Applications  [PDF]
Mustafa El Gili Mustafa, Samani A. Talab
Wireless Sensor Network (WSN) , 2016, DOI: 10.4236/wsn.2016.85008
Abstract: The paper presents the simulation results of the comparison of three Queuing Mechanisms, First in First out (FIFO), Priority Queuing (PQ), and Weighted Fair Queuing (WFQ). Depending on their effects on the network’s Routers, the load of any algorithm of them over Router’s CPUs and memory usage, the delay occurred between routers when any algorithm has been used and the network application throughput. This comparison explains that, PQ doesn’t need high specification hardware (memory and CPU) but when used it is not fair, because it serves one application and ignore the other application and FIFO mechanism has smaller queuing delay, otherwise PQ has bigger delay.
Determination of the Metastable Zone Width, Nucleation Kinetics, Structural and Optical Properties of KCl Doped KAP Crystal  [PDF]
M. A. Rahman, M. M. Rahman
Journal of Crystallization Process and Technology (JCPT) , 2015, DOI: 10.4236/jcpt.2015.52005
Abstract: Slow evaporation method was used to grow pure and KCl (10 mol%) doped KAP single crystal. The solubility and metastable zone width of aqueous solutions of pure and KCl (10 mol%) doped KAP crystal were evaluated to analyze the crystallization process. Measuring the induction period τ, the critical nucleation parameters like interfacial energy (σ), energy of formation of the critical nucleus (ΔG*) were determined using the classical theory of nucleation. The structural properties and optical constants of the grown crystals have been put to test and observed that the addition of KCl results in an enhancement of properties of the crystal. Grown crystals were characterized by powder X-ray diffraction. FTIR spectra confirmed the presence of KCl in pure KAP crystal. UV- Visible spectroscopic studies revealed that addition of KCl in pure KAP crystal increased transparency from 75% to 80%. The analysis of the optical absorption data revealed the presence of both indirect and direct transitions and both of these band gaps increased with the addition of KCl. The transmittance data was analyzed to calculate the refractive index, oscillator energy, dispersion energy, electric susceptibility, zero-frequency dielectric constant and both the real and imaginary parts of the dielectric permittivity as a function of photon energy. The moments of ε(E) were also determined. The dispersion i.e. spectral dependence of the refractive index was discussed according to the single-effective oscillator model proposed by Wemple and DiDomenico.
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