Alex,A V; Jacob, Philip(Cochin University of Science and Technology, May , 2001)
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Abstract:
Ultrasonic is a good tool to investigate the elastic properties of crystals. It enables one to determine all the elastic constants, Poisson’s ratios, volume compressibility and bulk modulus of crystals from velocity measurements. It also enables one to demonstrate the anisotropy of elastic properties by plotting sections of the surfaces of phase velocity, slowness, group velocity, Young’s modulus and linear compressibility along the a-b, b-c and a-c planes. They also help one to understand more about phonon amplification and help to interpret various phenomena associated with ultrasonic wave propagation, thermal conductivity, phonon transport etc. Study of nonlinear optical crystals is very important from an application point of view. Hundreds of new NLO materials are synthesized to meet the requirements for various applications. Inorganic, organic and organometallic or semiorganic classes of compounds have been studied for several reasons. Semiorganic compounds have some advantages over their inorganic and inorganic counterparts with regard to their mechanical properties. High damage resistance, high melting point, good transparency and non-hygroscopy are some of the basic requirements for a material to be suitable for device fabrication. New NLO materials are being synthesized and investigation of the mechanical and elastic properties of these crystals is very important to test the suitability of these materials for technological applications
Jacob, Philip; Alex,A V(Indian Academy of Sciences, January , 2004)
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Abstract:
Certain organic crystals are found to possess high non- linear optical coefficients,often one to two orders of magnitude higher than those of the well known inorganic non-linear optical materials.Benzoyl glycine is one such crystal whose optical second-harmonic generation efficiency is much higher than that of potassium dihydrogen phosphate. Single crystals of benzoyl glycine are grown by solvent evaporation technique using N,N-dimethyl formamide as the solvent.All the nine second-order elastic stiffness constants of this orthorhombic crystal are determined from ultrasonic wave velocity measurements employing the pulse echo overlap technique.The anisotropy of elastic wave propagation in this crystal is demonstrated by plotting the phase velocity, slowness,Young's modulus and linear compressibility surfaces along symmetry planes.The volume compressibility, bulk modulus and relevant Poisson's ratios are also determined. Variation of the diagonal elastic stiffness constants with temperature over a limited range are measured and reported.
Godfrey,Louis; Jacob, Philip(Department of Physics, 1994)
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Abstract:
The thesis investigated the elastic properties and phase transitions in selected mixed sulphate crystals – Lithium Hydrazinium Sulphate [LiN2H2SO4], Lithium Ammonium Sulphate [LiNH4SO4] and Lithium Potassium Sulphate [LiKSO4] – using ultrasonic technique. The pulse echo overlap technique has been used for measuring ultrasonic velocity and its dependence on temperature along different directions with waves of longitudinal and transverse polarizations. Two major numerical techniques and the corresponding computer programs developed as part of present work are presented in this thesis. All the 9 elastic constants of LHS are determined accurately from ultrasonic measurements and applying misorientation correction refines the constants. Ultrasonic measurements are performed in LAS to determine the elastic constants and to study the low temperature phase transitions. Temperature variation studies of elastic constant of LAS are performed for 6 different modes of propagation for heating and cooling at low temperatures. All the 5 independent elastic constants of LPS is determined using ultrasonic measurements. It is concluded that LPS crystal does not undergo a phase transition near this temperature. A comparison of the three crystals studied shows that LPS has maximum number of phase transitions and LHS has the least number. It is interesting to note that LPS has the simplest formula unit among the three. There is considerable scope for the future work on these crystals and others belonging to the sulphate family.
Kannan, Balakrishnan; Simily, Joseph; Balachandran Nair, M R; Reji, Rajan Varghese(MECS, May , 2013)
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Abstract:
Speckle noise formed as a result of the coherent nature of ultrasound imaging affects the lesion detectability. We have proposed a new weighted linear filtering approach using Local Binary Patterns (LBP) for reducing the speckle noise in ultrasound images. The new filter achieves good results in reducing the noise without affecting the image content. The performance of the proposed filter has been compared with some of the commonly used denoising filters. The proposed filter outperforms the existing filters in terms of quantitative analysis and in edge preservation. The experimental analysis is done using various ultrasound images
Description:
I.J. Information Technology and Computer Science, 2013, 06, 1-9
Deepti Das, Krishna; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(Electronics Letters, August , 2008)
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Abstract:
An ultra-wideband (UWB) printed slot antenna, suitable for integration with the printed circuit board (PCB) of a wireless universal serial-bus (WUSB) dongle is presented. The design comprises a near-rectangular slot fed by a coplanar waveguide printed on a PCB of width 20 mm. The proposed design has a large bandwidth covering the 3.1-10.6 GHz UWB band, unaffected by the ground length, and omnidirectional radiation patterns. A linear phase response throughout the band further confirms its suitability for high-speed wireless connectivity.
Deepti Das, Krishna; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(Wiley InterScience, June , 2009)
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Abstract:
A compact ultra-wideband (UWB) printed slot antenna is described, suitable for integration with the printed circuit board (PCB) of a wireless, universal, serial-bus dongle. The design comprises of a near-rectangular slot fed by a coplanar waveguide (CPW) printed on a PCB of size 20 × 30 mm2. It has a large bandwidth covering the 3.1–10.6 GHz UWB band, with omnidirectional radiation patterns. Further, a notched band centered at 5.45 GHz wireless local area network bands is obtained within the wide bandwidth by inserting a narrow slot inside the tuning stub. Details of the antenna design are described, and the experimental results of the constructed prototype are presented. The time domain studies on the antenna shows a linear phase response throughout the band except at the notched frequency. The transient analysis of the antenna indicates very little pulse distortion confirming its suitability for high speed wireless connectivity.
Kannan, Balakrishnan; Jomy, John; Pramod, K V(Elsevier, December 31, 2012)
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Abstract:
This paper presents the application of wavelet processing in the domain of handwritten character recognition. To
attain high recognition rate, robust feature extractors and powerful classifiers that are invariant to degree of variability
of human writing are needed. The proposed scheme consists of two stages: a feature extraction stage, which is based
on Haar wavelet transform and a classification stage that uses support vector machine classifier. Experimental results
show that the proposed method is effective
Prabha, C; Dr.Pillai, P R S(Cochin University of Science And Technology, July 24, 2013)
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Abstract:
Underwater target localization and tracking attracts tremendous research interest due to various impediments to the estimation task caused by the noisy ocean environment. This thesis envisages the implementation of a prototype automated system for underwater target localization, tracking and classification using passive listening buoy systems and target identification techniques. An autonomous three buoy system has been developed and field trials have been conducted successfully. Inaccuracies in the localization results, due to changes in the environmental parameters, measurement errors and theoretical approximations are refined using the Kalman filter approach. Simulation studies have been conducted for the tracking of targets with different scenarios even under maneuvering situations. This system can as well be used for classifying the unknown targets by extracting the features of the noise emanations from the targets.
Description:
Department of Electronics, Cochin University of Science and Technology.
Harikrishnan, K P; Nandakumaran, V M(Elsevier, December 7, 1987)
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We study the period-doubling bifurcations to chaos in a logistic map with a nonlinearly modulated parameter and show that the bifurcation structure is modified significantly. Using the renormalisation method due to Derrida et al. we establish the universal behaviour of the system at the onset of chaos.
Nify, Benny; Dr.Sujatha, C H(Cochin University of Science and Technology, June , 2009)
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Abstract:
The thesis deals with a benchmark study of dissolved and sedimentary sulphur
compounds which play prominent roles in the prevailing redox conditions in the
selected sites of Cochin estuarine system. Sulphur and its analogues play prominent
roles in estuarine biochemical processes. A complete knowledge on the sulphur
involvement in these processes is restricted due to the lacking of data on the organic
sulphur compounds. Sulphate and sulphide in surface and bottom water and
Sulphate, acid volatile sulphide and total sulphur in sediments were studied and
correlated to know their interrelations in determining the redox condition of the
environment. It also characterises the sediments of the sites on the basis of total
organic carbon: total sulphur ratio. The study had attempted to decrease the
concentration levels of sulphur in the sedimentary environment by the application of
a remedial measure. Knowledge of sulphur uptake by plants from prior literatures
has prompted to use phytoremediation for decreasing the sulphur concentration.
Phytoremediation is an emerging technology that uses plants to clean up or remediate
contaminated soil, sludges, sediments, and ground water through contaminant
removal, degradation or containment. The plant selected was wheat grass since
earlier studies have shown that wheat grass is effective in remediating pollutants
particularly trace metals. So reduction in the concentration of selected trace metals
was also focussed.
Description:
Department of Chemical Oceanography, Cochin University of Science and Technology
Louis, Godfrey; Santhosh Kumar, A(Society of Photo-Optical Instrumentation Engineers, 2008)
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Abstract:
The red cells found in the red rain in Kerala, India are now considered as a possible case of extraterrestrial life form.
These cells can undergo rapid replication even at an extreme high temperature of 300 deg C. They can also be cultured in
diverse unconventional chemical substrates. The molecular composition of these cells is yet to be identified. This paper
reports the unusual autofluorescence characteristic of the cultured red rain cells. A spectrofluorimetric study has been
performed to investigate this, which shows a systematic shift of the fluorescence emission peak wavelength as the
excitation wavelength is increased. Conventional biomolecules are not known to have this property. Details of this
investigation and the results are discussed.
Anantharaman, M R; Al-Harthi, S H; Mohammed, Elzain; Muataz, Al-Barwani; Amal, Kora'a; Thomas, Hysen; Myo, Tay Zar Myint(Springer, 2012)
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Abstract:
Roughness and defects induced on few-layer graphene (FLG) irradiated by Ar+ ions at different energies were
investigated using X-ray photoemission spectroscopy (XPS) and atomic force microscopy techniques. The results
provide direct experimental evidence of ripple formation, sp2 to sp3 hybridized carbon transformation, electronic
damage, Ar+ implantation, unusual defects and edge reconstructions in FLG, which depend on the irradiation
energy. In addition, shadowing effects similar to those found in oblique-angle growth of thin films were seen.
Reliable quantification of the transition from the sp2-bonding to sp3-hybridized state as a result of Ar+ ion irradiation
is achieved from the deconvolution of the XPS C (1s) peak. Although the ion irradiation effect is demonstrated
through the shape of the derivative of the Auger transition C KVV spectra, we show that the D parameter values
obtained from these spectra which are normally used in the literature fail to account for the sp2 to sp3 hybridization
transition. In contrast to what is known, it is revealed that using ion irradiation at large FLG sample tilt angles can
lead to edge reconstructions. Furthermore, FLG irradiation by low energy of 0.25 keV can be a plausible way of
peeling graphene layers without the need of Joule heating reported previously
Description:
Al-Harthi et al. Nanoscale Research Letters 2012, 7:466
Radhakrishnan, N; Dr.Meera Bai,M(Cochin University of Science and Technology, November 20, 2003)
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Abstract:
Studies in urban water supply system are few in the state of Kerala.
It is a little researched area. In the case of water pricing a number of studies are
available. In Kerala state, exception to Jacob John’s study on “Economics of
Public Water Supply System”, which is a case study of Trivandrum Water Supply
System in 1997, no exhaustive research work has so far come out in this field.
loreover no indepth research study has come up, so far, relating to household
ater demand analysis and the distribution system of urban piped water supply.
he proposed study is first of its kind, which focuses on the distributional and
Iailability problems of piped water supply in an urban centre in Kerala state.
Hence there is a felt need for enquiring into the sufficiency of
)table water supplied to people in urban areas and the efficiency maintained in
roviding the scarce resource and preventing its misuse by the consumers. It is in
llS backdrop that this study was undertaken and its empirical part was conducted
|Calicut city in the state of Kerala. Study is confined to the water supply system
ithe city of Calicut
Description:
Department of Applied Economics,
Cochin University of Science and Technology
Rani, Joseph(OPA (Overseas Publishers Association), May 28, 1995)
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Abstract:
Amine Terminated Liquid Natural Rubber (ATNR) was used as a plasticiser in filled NR and NBR
compounds replacing oil/DOP. The scorch time and cure time were found to be lowered when ATNR
was used as the plasticiser. ATNR was found to improve the mechanical properties like tensile strength,
tear strength and modulus of the vulcanizates . The ageing resistance of the vulcanizates containing ATNR
was superior compared to the vulcanizates containing oil/DOP.