| Abstract: | This paper presents the design and analysis of a novel machine family—the enclosed-rotor Halbach-array permanentmagnet brushless dcmotors for spacecraft applications. The initial design, selection of major parameters, and air-gap magnetic flux density are estimated using the analytical model of the machine. The proportion of the Halbach array in the machine is optimized using finite element analysis to obtain a near-trapezoidal flux pattern. The machine is found to provide uniform air-gap flux density along the radius, thus avoiding circulating currents in stator conductors and thereby reducing torque ripple. Furthermore, the design is validated with experimental results on a fabricated machine and is found to suit the design requirements of critical spacecraft applications |
| Description: | IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 59, NO. 9, SEPTEMBER 2012 |
| URI: | http://dyuthi.cusat.ac.in/purl/4481 |
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| A Novel Slotles ... pacecraft Applications.pdf | (752.8Kb) |
| Abstract: | This paper presents the design and analysis of a novel machine family of Siotiess Permanent Magnet Brushless DC motors (PMBLDC) for precise positioning applications of spacecrafts. Initial design, selection of major parameters and air gap magnetic flux density are estimated using the analytical model of the machine. The proportion of the halbach array in the machine was optimized using FE to obtain near trapezoidal flux pattern. The novel machine topology is found to deliver high torque density, high efficiency, zero cogging torque, better positional stability, high torque to inertia ratio and zero magnetic stiction suiting space requirements. The machine provides uniform air gap flux density along the radius thus avoiding circulating currents in stator conductors and hence reducing torque ripple |
| Description: | Communication Control and Computing Technologies (ICCCCT), 2010 IEEE International Conference on |
| URI: | http://dyuthi.cusat.ac.in/purl/4501 |
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| A Novel Slotles ... ositioningApplications.pdf | (1.450Mb) |
| Abstract: | Design, development and experimental observations of a L: band printed dipole antenna is presented.Bandwidth enhancement is achieved by end-loading or the dipole arms. Using the present technique Impedance bandwidth van be enhanced up to 50% without degrading the efficiency of the antenna. |
| URI: | http://dyuthi.cusat.ac.in/purl/1435 |
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| Novel wide band printed dipole antenna.PDF | (1.287Mb) |
| Abstract: | Coded OFDM is a transmission technique that is used in many practical communication systems. In a coded OFDM system, source data are coded, interleaved and multiplexed for transmission over many frequency sub-channels. In a conventional coded OFDM system, the transmission power of each subcarrier is the same regardless of the channel condition. However, some subcarrier can suffer deep fading with multi-paths and the power allocated to the faded subcarrier is likely to be wasted. In this paper, we compute the FER and BER bounds of a coded OFDM system given as convex functions for a given channel coder, inter-leaver and channel response. The power optimization is shown to be a convex optimization problem that can be solved numerically with great efficiency. With the proposed power optimization scheme, near-optimum power allocation for a given coded OFDM system and channel response to minimize FER or BER under a constant transmission power constraint is obtained |
| Description: | International Journal of Scientific and Research Publications, Volume 4, Issue 1, January 2014 |
| URI: | http://dyuthi.cusat.ac.in/purl/4186 |
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| A Numerically e ... nimum frame error rate.pdf | (208.4Kb) |
| Abstract: | Results of a numerical study of synchronisation of two directly modulated semiconductor lasers, using bi-directional coupling, are presented. The effect of stepwise increase in the coupling strength (C) on the synchronisation of the chaotic outputs of two such lasers is studied, with the help of parameter space plots, synchronisation error plots, phase diagrams and time series outputs. Numerical results indicate that as C increases, the system achieves synchronisation as well as stability together with an increase in the output power. The stability of the synchronised states is checked by applying a perturbation to the system after it becomes synchronised and then noting the time it takes to regain synchronisation. For lower values of C the system does not regain synchronisation. But, with higher values synchronisation is regained within a very short time. |
| URI: | http://dyuthi.cusat.ac.in/purl/2557 |
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| Dyuthi-P0116.pdf | (729.4Kb) |
| Abstract: | We have numerically studied the behavior of a two-mode Nd-YAG laser with an intracavity KTP crystal. It is found that when the parameter, which is a measure of the relative orientations of the KTP crystal with respect to the Nd-YAG crystal, is varied continuously, the output intensity fluctuations change from chaotic to stable behavior through a sequence of reverse period doubling bifurcations. The graph of the intensity in the X-polarized mode against that in the Y-polarized mode shows a complex pattern in the chaotic regime. The Lyapunov exponent is calculated for the chaotic and periodic regions. |
| URI: | http://dyuthi.cusat.ac.in/purl/2533 |
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| Dyuthi-P0108.pdf | (743.1Kb) |
| Abstract: | Kerala is one of the smallest states in India which is situated in the south west coast of the country. Sediment samples from four prominent areas of Kerala Coast were collected and analyzed for nutrients. Variation of nutrients was highlighted according to the distributional characteristics of the designated sites. Nutrient trend in Cape, Trivandrum, Kollam was in the order as Ammonia > Nitrite >Nitrate, where as Cochin showed the trend as Ammonia > Nitrate > Nitrite. Greater concentration of ammonia in the entire sediments showed the ammonification of nitrogen compounds |
| Description: | INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 3, No 5, 2013 |
| URI: | http://dyuthi.cusat.ac.in/purl/4617 |
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| Nutrient dynami ... iments of Kerala coast.pdf | (289.1Kb) |
| Abstract: | Distribution and chemistry of major inorganic forms of nutrients along with physico-chemical parameters were investigated. Surface sediments and overlying waters of the Ashtamudi and Vembanad Lakes were taken for the study, which is situated in the southwest coast of India. High concentrations of dissolved nitrogen and phosphorus compounds carried by the river leads to oxygen depletion in the water column. A concurrent increase in the bottom waters along with decrease in dissolved oxygen was noticed. This support to nitrification process operating in the sediment-water interface of the Ashtamudi and Vembanad Lake. Estuarine sediments are clayey sand to silty sand both in Ashtamudi and Vembanad in January and May. Present study indicates that the sediment texture is the major controlling factor in the distribution of these nutrient forms. For water samples nitrite, inorganic phosphate was high in Vembanad in January and May compared to Ashtamudi. For sediments, enhanced level of inorganic phosphate and nitrite was found in Vembanad during January and May. It had been observed that the level of N and P is more in sediments. A comparative assessment of the Ashtamudi and Vembanad Lake reveals that the Vembanad wetland is more deteriorated compared to the Ashtamudi wetland system |
| Description: | Indian Journal of Marine Sciences Vol. 38(4), December 2009, pp 451-456 |
| URI: | http://dyuthi.cusat.ac.in/purl/4615 |
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| Nutrient dynami ... lakes of Kerala, India.pdf | (1.039Mb) |
| Abstract: | Pulsed photoacoustic measurements have been carried out in liquid CS2 using 532 nm radiation from a frequency doubled Nd:YAG laser. Variation of signal amplitude with laser fluence clearly indicates the role of multiphoton processes in the generation of photoacoustic effect. It is also shown that four photon induced dissociation and five photon induced ionization are likely processes in CS2 and 532 nm radiation. |
| URI: | http://dyuthi.cusat.ac.in/purl/2634 |
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| Dyuthi-P0193.pdf | (264.3Kb) |
| Abstract: | Two-photon absorption in Rhodamine 6G using the second harmonic of a pulsed Q-switched Nd:YAG laser has been studied by photoacoustic technique. It is observed that there is a competition between one-photon and two-photon absorption processes. At lower concentration the two-photon process is predominant over the one-photon process. |
| URI: | http://dyuthi.cusat.ac.in/purl/2493 |
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| Dyuthi-P0291.pdf | (252.6Kb) |
| Abstract: | Observation of laser induced two-photon photoemission optogalvanic (TPPOG) effect from tungsten electrode in a discharge cell using 564 nm radiation obtained from a pulsed dye laser is described. The magnitude of the POG signal is studied as a function of laser energy under various discharge parameters. Competition between one-photon and two-photon processes has been observed when nitrogen gas is used in the discharge cell. |
| URI: | http://dyuthi.cusat.ac.in/purl/2492 |
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| Dyuthi-P0296.pdf | (201.4Kb) |
| Abstract: | Symbiotic diatom-diazotrophic cyanobacteria association (DDA) of Rhizosolenia hebetata and Rhizosolenia formosa with endosymbiotic cyanobacteria Richelia intracellularis was noticed and documented for the first time during a bloom of the cyanobacterium Trichodesmium erythraeum in the oligotrophic shelf waters along Kochi and Mangalore transects, southeastern Arabian Sea (SEAS), during spring intermonsoon (April 2012). Although the host is frequently seen, the symbiont is rarely reported in the Indian EEZ. The presence of nitrogen-fixing symbiotic association of Rhizosolenia-Richelia along with Trichodesmium erythraeum highlights the significance of DDAs on the nutrient and energy budgets of phytoplankton in the oligotrophic environments of the Arabian Sea during spring intermonsoon |
| Description: | International Journal of Oceanography Volume 2013, Article ID 350594, 6 pages |
| URI: | http://dyuthi.cusat.ac.in/purl/3933 |
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| Occurrence and ... a Diatom-Diazotrophic.pdf | (2.738Mb) |
| Abstract: | A dual port dual polarized octagonal microstrip patch antenna suitable for dual band applications is discussed theoretically and experimentally. The antenna exhibits good impedance bandwidth, gain and broad radiation patterns. Parameters predicted by the Conformal Finite Difference Time Domain algorithm show good agreement with the simulated results and experimental observations |
| Description: | Proc. XXVIII URSI General Assembly |
| URI: | http://dyuthi.cusat.ac.in/purl/4337 |
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| Octagonal Micro ... Dual Band Applications.pdf | (878.3Kb) |
| Abstract: | The paper proposes an octagon shaped Microstrip Patch Antenna suitable for dual band applications. The striking features of this compact, planar antenna are sufficient isolation between the two operating bands and an area reduction of - 29% in comparison to a conventional circular patch antenna operating in the same band |
| Description: | Antennas and Propagation Society International Symposium, 2002. IEEE |
| URI: | http://dyuthi.cusat.ac.in/purl/4328 |
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| Octagon Shaped ... Dual Band Applications.pdf | (161.2Kb) |
| Abstract: | Optical Character Recognition plays an important role in Digital Image Processing and Pattern Recognition. Even though ambient study had been performed on foreign languages like Chinese and Japanese, effort on Indian script is still immature. OCR in Malayalam language is more complex as it is enriched with largest number of characters among all Indian languages. The challenge of recognition of characters is even high in handwritten domain, due to the varying writing style of each individual. In this paper we propose a system for recognition of offline handwritten Malayalam vowels. The proposed method uses Chain code and Image Centroid for the purpose of extracting features and a two layer feed forward network with scaled conjugate gradient for classification |
| Description: | Emerging Trends in Electrical and Computer Technology (ICETECT), 2011 International Conference on |
| URI: | http://dyuthi.cusat.ac.in/purl/4196 |
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| Offline Handwri ... n Chain Code Histogram.pdf | (1.324Mb) |
| Abstract: | Materials belonging to the family of manganites are technologically important since they exhibit colossal magneto resistance. A proper understanding of the transport properties is very vital in tailoring the properties. A heavy rare earth doped manganite like Gd0·7Sr0·3MnO3 is purported to be exhibiting unusual properties because of smaller ionic radius of Gd. Gd0·7Sr0·3MnO3 is prepared by a wet solid state reaction method. The conduction mechanism in such a compound has been elucidated by subjecting the material to low temperature d.c. conductivity measurement. It has been found that the low band width material follows a variable range hopping (VRH) model followed by a small polaron hopping (SPH) model. The results are presented here |
| Description: | Bull. Mater. Sci., Vol. 35, No. 1, February 2012, pp. 41–45. |
| URI: | http://dyuthi.cusat.ac.in/purl/4432 |
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| On conduction m ... of Gd basedmanganites.pdf | (148.3Kb) |
| Abstract: | The D-eigenvalues of a graph G are the eigenvalues of its distance matrix D, and the D-energy ED(G) is the sum of the absolute values of its D-eigenvalues. Two graphs are said to be D-equienergetic if they have the same D-energy. In this note we obtain bounds for the distance spectral radius and D-energy of graphs of diameter 2. Pairs of equiregular D-equienergetic graphs of diameter 2, on p = 3t + 1 vertices are also constructed. |
| URI: | http://dyuthi.cusat.ac.in/purl/1537 |
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| On distance energy of graphs.PDF | (2.514Mb) |
| Abstract: | The D-eigenvalues of a graph G are the eigenvalues of its distance matrix D, and the D-energy ED(G) is the sum of the absolute values of its D-eigenvalues. Two graphs are said to be D-equienergetic if they have the same D-energy. In this note we obtain bounds for the distance spectral radius and D-energy of graphs of diameter 2. Pairs of equiregular D-equienergetic graphs of diameter 2, on p = 3t + 1 vertices are also constructed. |
| URI: | http://dyuthi.cusat.ac.in/purl/626 |
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| 7) ON DISTANCE ENERGY OF GRAPHS.pdf | (2.976Mb) |
| Abstract: | A feasible way of implementing a temporal database is by mapping temporal data model onto a conventional data model followed by a commercial database management system. Even though extensions were proposed to standard SQL for supporting temporal databases, such proposals have not yet come across standardization processes. This paper attempts to implement database operators such as aggregates and universal quantifier for temporal databases, implemented on top of relational database systems, using currently available SQL standards. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2006 |
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| On Implementing Joins....pdf | (261.1Kb) |
| Abstract: | This paper presents a novel approach to recognize Grantha, an ancient script in South India and converting it to Malayalam, a prevalent language in South India using online character recognition mechanism. The motivation behind this work owes its credit to (i) developing a mechanism to recognize Grantha script in this modern world and (ii) affirming the strong connection among Grantha and Malayalam. A framework for the recognition of Grantha script using online character recognition is designed and implemented. The features extracted from the Grantha script comprises mainly of time-domain features based on writing direction and curvature. The recognized characters are mapped to corresponding Malayalam characters. The framework was tested on a bed of medium length manuscripts containing 9-12 sample lines and printed pages of a book titled Soundarya Lahari writtenin Grantha by Sri Adi Shankara to recognize the words and sentences. The manuscript recognition rates with the system are for Grantha as 92.11%, Old Malayalam 90.82% and for new Malayalam script 89.56%. The recognition rates of pages of the printed book are for Grantha as 96.16%, Old Malayalam script 95.22% and new Malayalam script as 92.32% respectively. These results show the efficiency of the developed system |
| Description: | (IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 3, No. 7, 2012 |
| URI: | http://dyuthi.cusat.ac.in/purl/4106 |
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| An Online Chara ... ha Script to Malayalam.pdf | (548.4Kb) |
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