Simulation of Relay modes in IEEE 802.16j Mobile Multi-hop Relay (MMR) WIMAX Networks

Two different relay modes are defined in IEEE 802.16j WIMAX standard: transparent mode and non-transparent mode. The non transparent mode is used to extend the coverage area of base stations, where low cost relay station of equal capacity as that of base station is placed at suitable position. Time taken to accept mobile stations and Bandwidth allocation are main problems in non transparent mode. In this we have studied the IEEE 802.16j standard multi hop relay WIMAX networks. We have used relay stations to extend the coverage of base stations. We have also analyzed the throughput between mobile stations with in the coverage area and outside coverage area of base stations. We have simulated the IEEE 802.16j transparent and non transparent mode multi hop WIMAX relay networks using NCTUns Too

Lattice expansion and non-collinear to collinear ferrimagnetic order in MnCr2_2O4_4 nanoparticle

We report magnetic behaviour of MnCr$_2$O$_4$, which belongs to a special class of spinel, known as chromite. Bulk MnCr$_2$O$_4$ shows a sequence of magnetic states, which follows paramagnetic (PM) to collinear ferrimagnetic (FM) state below T$_C$ $\sim$ 45 K and collinear FM state to non-collinear FM state below T$_S$ $\sim$ 18 K. The non-collinear spin structure has been modified on decreasing the particle size, and magnetic transition at T$_S$ decreases in nanoparticle samples. However, ferrimagnetic order is still dominating in nanoparticles, except the observation of superparamagnetic like blocking and decrease of spontaneous magnetization for nanoparticle. This may, according to the core-shell model of ferrimagnetic nanoparticle, be the surface disorder effect of nanoparticle. The system also show the increase of T$_C$ in nanoparticle samples, which is not consistent with the core-shell model. The analysis of the M(T) data, applying spin wave theory, has shown an unusual Bloch exponent value 3.35 for bulk MnCr$_2$O$_4$, which decreases and approaches to 1.5, a typical value for any standard ferromagnet, with decreasing the particle size. MnCr$_2$O$_4$ has shown a few more unusual behaviour. For example, lattice expansion in nanoparticle samples. The present work demonstrates the correlation between a systematic increase of lattice parameter and the gradual decrease of B site non-collinear spin structure in the light of magnetism of MnCr$_2$O$_4$ nanoparticles

Simulation and Implementation of Soft-Switched Interleaved DC-DC Boost Converter for Fuel Cell Systems

In this paper, a soft-switched Interleaved DC-DC Boost Converter (IBC) for fuel cell is simulated and implemented. The proposed two-phase IBC circuit consists of two identical boost converter connected in parallel and are controlled by interleaved switching signals. But in the conventional IBC switching loss increases with the number of switching devices. To solve this problem, this paper has proposed a soft switched IBC. Detailed analysis has been done to investigate the benefits of soft-switched IBC compared to that of conventional uncoupled and directly coupled IBC. The converter circuit is constructed using power MOSFET as power switch. The PWM is generated by PIC18F4450 microcontroller. In this paper, the analysis of the converter is presented which is verified by the results of simulation and experimentation

Impact of Tandem Repeats on the Scaling of Nucleotide Sequences

Techniques such as detrended fluctuation analysis (DFA) and its extensions have been widely used to determine the nature of scaling in nucleotide sequences. In this brief communication we show that tandem repeats which are ubiquitous in nucleotide sequences can prevent reliable estimation of possible long-range correlations. Therefore, it is important to investigate the presence of tandem repeats prior to scaling exponent estimation.Comment: 14 Pages, 3 Figure

On The Estimation of Parameters of Thick Current Shell Model of Equatorial Electrojet Using Optimisation Method

Equatorial electrojet, an intense current flowing eastward in the low latitude ionosphere within the narrow region flanking the dip equator, is a major phenomenon of interest in geomagnetic field studies. For the first time the five parameters required to fully describe the Onwumechili\'s composite thick current shell model format of equatorial electrojet have been evaluated from a single autonomous set of ground data at solar minimum. The non-linear model was applied to four data points, each with a pair of simultaneously measured horizontal H and vertical Z variation field components. The resultant system of eight non-linear equations with five unknown model parameters were subjected to non-linear least square optimisation method taking advantage of the robust Levenberg-Madquart optimisation subroutine of licensed MATLAB 6.0 version. The thick current shell format model parameters estimated for Indian sector are shown to be within the appropriate limits and in excellent agreement with literature and physical expectation. Keywords: Equatorial electrojet; Numerical models; Optimisation Journal of Science & Technology (Ghana) Vol. 28 (3) 2008: pp. 1-

STUDY OF INTERNAL ROLLER BURNISHING OPERATION ON EN8 MATERIAL

Burnishing is a cold working, a surface treatment process in which plastic deformation of surface irregularities occurs by exerting pressure through a very hard and smooth roller on a surface to generate a uniform and work-hardened surface. In this work, a simple internal roller burnishing tool is used to perform roller burnishing process on the holes drilled in EN8 material by varying the spindle speeds of drilling machine. The speed which produces maximum smoothness or minimum roughness on the surface is considered to be an optimal speed for carrying out burnishing operation in the drilled holes

FABRICATION OF COCONUT HUSK REMOVER WITH SHELL CUTTER

This project is to fabricate a coconut husk remover with shell cutter. At present coconut husk is being removed manually, which employs more time and more manpower. This coconut husk remover peels off the coconut husk from coconut fruit to obtain de-husked coconut fruit via pneumatic controlled de-husking device. An operator is required to handle the machine during the de-husking process. It can be used to de-husk both matured coconut and young coconut. This project consists of pneumatic cylinder, solenoid valve, linkages, husk remover and base frame.In this there are two main parts are there. One part is for removing the husk from the coconut and the other is cutting part. In both parts, pneumatic systems are used. The husk is removed with the help of hinge joint which connects to the pneumatic actuator. By connecting these two parts we fabricated as "coconut husk remover with shell cutter"

Miniaturization of photonic waveguides by the use of left-handed materials

We propose the use of a left-handed material in an optical waveguide structure to reduce its thickness well below the wavelength of light. We demonstrate that a layer of left-handed material, added to the cladding of a planar waveguide rather than to its core, allows for good light confinement in a subwavelength thin waveguide. We attribute the observed behavior to the change in phase evolution of electromagnetic waves in the guide. This technique can be used for the miniaturization of photonic integrated circuits.Comment: 4 pages, 4 figure

Weekly rainfall analysis using the Markov chain model in the Dharmapuri region of Tamil Nadu

During a rainy season, dry and wet spells tend to persist and can be represented using a Markov process. Knowing the succession of dry and wet periods is necessary to plant crops and carry out agricultural operations. This study aimed to analyze the probability of dry/wet spell rainfall using the Markov chain model in the Dharmapuri district of Tamil Nadu, India. In estimating the chance of dry and wet spells, the model used rainfall of below 20 mm in a week as a dry calendar week and rainfall of 20 mm or more as a wet calendar week from the years 1980 to 2019. From the 1st through the 32nd Standard Meteorological Week (SMW), a continuous dry week probability was 75-100%. The likelihood of a dry week trailed by another dry week was more up to the 32nd standard week, while the chance of a dry week followed by a wet week was more up to the 31st standard week, ranging from 75 to 100%. During the 37th to 45th weeks, the conditional likelihood of a rainy week followed by another rainy week ranged from 43.8 to 68%. According to a review of consecutive dry and wet spells, two consecutive dry weeks had a 55 to 97.5% chance of occurring within the first 32 weeks of the year. In the first 32nd week of the year, the chance of three successive dry weeks ranged from 32.6 to 92.6%. Consecutive dry weeks suggest the need for additional irrigation and proper moisture management practices. In contrast, consecutive wet calendar weeks indicate an abundance of extra water available for rainwater collection and the necessity for proper soil erosion control measures