Showing papers by "Cochin University of Science and Technology published in 2007"
TL;DR: In this paper, the authors presented the results from an experimental program and an analytical assessment of the influence of addition of fibers on mechanical properties of concrete, which is at variance with both existing models and formulations based on the law of mixtures.
Abstract: This paper presents the results from an experimental program and an analytical assessment of the influence of addition of fibers on mechanical properties of concrete. Models derived based on the regression analysis of 60 test data for various mechanical properties of steel fiber-reinforced concrete have been presented. The various strength properties studied are cube and cylinder compres- sive strength, split tensile strength, modulus of rupture and postcracking performance, modulus of elasticity, Poisson's ratio, and strain corresponding to peak compressive stress. The variables considered are grade of concrete, namely, normal strength 35 MPa, moderately high strength 65 MPa, and high-strength concrete 85 MPa, and the volume fraction of the fiber Vf=0.0, 0.5, 1.0, and 1.5%. The strength of steel fiber-reinforced concrete predicted using the proposed models have been compared with the test data from the present study and with various other test data reported in the literature. The proposed model predicted the test data quite accurately. The study indicates that the fiber matrix interaction contributes significantly to enhancement of mechanical properties caused by the introduction of fibers, which is at variance with both existing models and formulations based on the law of mixtures. 85 MPa with various fiber dosages Vf=0, 0.5, 1.0, and 1.5%. An empirical relationship for various mechanical properties of SFRC has been proposed. The proposed model attempts to bring out the significance of fiber matrix interaction in all the strength properties. This study reports the experimental results of the strength properties of SFRC, namely, cube and cylinder compressive strength, split tensile strength, modulus of rupture, modulus of elasticity, Poisson's ratio, and strain corresponding to peak com- pressive stress. Empirical relationships were developed for vari- ous strength properties based on the regression analysis of the 60 test data. It is expected that these proposed models would be helpful in assessing the strength properties of fiber-reinforced concrete based on the matrix strength and fiber-RI.
410 citations
TL;DR: In this article, the influence of an antiwear/extreme pressure (AW/EP) additive on the tribological performance of coconut oil was also evaluated experimentally, which brought about considerable reduction in wear with coconut oil as 2T oil.
210 citations
17 Sep 2007
TL;DR: In this article, stable, OH free zinc oxide (ZnO) nanoparticles were synthesized by hydrothermal method by varying the growth temperature and concentration of the precursors.
Abstract: Stable, OH free zinc oxide (ZnO) nanoparticles were synthesized by hydrothermal method by varying the growth temperature and concentration of the precursors. The formation of ZnO nanoparticles were confirmed by x-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) studies. The average particle size have been found to be about 7-24 nm and the compositional analysis is done with inductively coupled plasma atomic emission spectroscopy (ICP-AES). Diffuse reflectance spectroscopy (DRS) results shows that the band gap of ZnO nanoparticles is blue shifted with decrease in particle size. Photoluminescence properties of ZnO nanoparticles at room temperature were studied and the green photoluminescent emission from ZnO nanoparticles can originate from the oxygen vacancy or ZnO interstitial related defects.
196 citations
TL;DR: In this article, an integrated hydrogeological investigation has been made to delineate the groundwater-potential zones of the Muvattupuzha river basin, Kerala, along the southwest coast of India.
Abstract: An integrated hydrogeological investigation has been made to delineate the groundwater-potential zones of the Muvattupuzha river basin, Kerala, along the southwest coast of India. The basin is characterized by charnockites and gneisses of Archean age covering more than 80% of the area and the remaining by Pleistocene laterites and Miocene formation. The basin receives high rainfall, measuring 3100 mm/year. However, acute water shortage occurs during the premonsoon season and hence, a number of dug wells are made to tap the groundwater. Seasonal rainfall during NE and SW monsoons is the major source of groundwater recharge. Further, hydrogeomorphology, geology, fracture systems and the slope of the terrain also play a significant role on the movement and behaviour of the groundwater of this basin. The integration of conventional and remote sensing data has been made through geographic information system (GIS) and it is found that about 50% of the area can be identified as very good or good potential zones, whereas the remaining area falls under moderate and poor categories. Most of the Muvattupuzha sub-basin and the western part of the Kothamangalam and Kaliyar sub-basins are classified as good groundwater-potential zones, although the eastern upstream part of the basin has poor groundwater potential.
170 citations
TL;DR: In this article, fine particles of cobalt ferrite were synthesized by the sol?gel method and X-ray diffraction studies were carried out to elucidate the structure of all the samples.
Abstract: Fine particles of cobalt ferrite were synthesized by the sol?gel method. Subsequent heat treatment at different temperatures yielded cobalt ferrites having different grain sizes. X-ray diffraction studies were carried out to elucidate the structure of all the samples. Dielectric permittivity and ac conductivity of all the samples were evaluated as a function of frequency, temperature and grain size. The variation of permittivity and ac conductivity with frequency reveals that the dispersion is due to Maxwell?Wagner type interfacial polarization in general, with a noted variation from the expected behaviour for the cold synthesized samples. High permittivity and conductivity for small grains were explained on the basis of the correlated barrier-hopping model.
161 citations
TL;DR: In this article, the effects of sodium acetate dip treatment, followed by vacuum-packaging, on the shelf life of beheaded, scaled and gutted Pearlspot (Etroplus suratensis) during chill storage were examined.
149 citations
TL;DR: A lot of effort is being carried out to reduce the use of lubricants in metal machining operations from the viewpoint of cost, ecology and human health issues as discussed by the authors, where Minimal Quantity Lubrication (MQL) is used.
Abstract: A lot of effort is being carried out to reduce the use of lubricants in metal machining operations from the viewpoint of cost, ecology and human health issues. Minimal quantity lubrication (MQL) is...
132 citations
TL;DR: The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.
130 citations
TL;DR: In this paper, a coplanar strip fed monopole antenna for multiband applications is presented, which exhibits three resonances around 1.8, 2.4, and 5.6 GHz covering the DCS/PCS/UMTS/IEEE 802.11a/HIPERLAN2 bands.
Abstract: A compact asymmetric coplanar strip fed monopole antenna for multiband applications is presented. The antenna exhibits three resonances around 1.8, 2.4, and 5.6 GHz covering the DCS/PCS/UMTS/IEEE 802.11b/g/IEEE802.11a/HIPERLAN2 bands. The multiband characteristic of the antenna is due to the various meandered current paths excited in the radiating structure. The antenna has an overall dimension of only 2830 when printed on a substrate of dielectric constant 4.4. The uniplanar design, simple feeding technique and compactness make it easy for the integration of the antenna into circuit boards. Details of the antenna design, experimental and simulated results are presented and discussed.
119 citations
TL;DR: In this paper, the enzymes α-amylase, glucoamylases and invertase were applied to acid activated montmorillonite (K 10) via adsorption and grafting using glutaraldehyde as spacer.
119 citations
TL;DR: In this article, α-Amylase was immobilized on zirconia via adsorption, and the support and the immobilized enzymes were characterized using XRD, IR spectra and N2 adaption studies.
TL;DR: Impact of acute salinity stress on the immunological and physiological response of Penaeus monodon to white spot syndrome virus (WSSV) infection was analysed.
TL;DR: In this article, the effect of the ceramic content (0.6 volume fraction) of TeO2 on the dielectric properties of the composites was studied at 1 MHz and 7 GHz.
Abstract: TeO2 particle-filled PTFE composites were prepared by the powder processing technique. The structure and microstructure of the composites were investigated by X-ray diffraction and scanning electron microscopic methods. The effect of the ceramic content (0–0.6 volume fraction) of TeO2 on the dielectric properties of the composites was studied at 1 MHz and 7 GHz. The dielectric constant and dielectric loss increased with an increase in the TeO2 content. For 60 vol% of TeO2, the composite has a dielectric constant of 5.4 and a loss tangent of 0.006 at 7 GHz. The measured dielectric constant (er) is compared with the effective dielectric constant calculated using different theoretical models. The observed dielectric constants are in agreement with that calculated using effective medium theory. The coefficient of thermal expansion of the composites decreases with the TeO2 content, reaching a minimum of 32 ppm/1C for 60 vol% loading.
TL;DR: In this article, the fluorescence behavior of nano colloids of ZnO has been studied as a function of the excitation wavelength, and it was shown that the existence of a distribution of energetically different molecules in the ground state coupled with a low rate of the excited state relaxation processes, namely, solvation and energy transfer, are responsible for the exciting wavelength dependent fluorescence behaviour of the systems.
Abstract: In this paper, the fluorescence behaviour of nano colloids of ZnO has been studied as a function of the excitation wavelength. We have found that excitation at the tail of the absorption band gives rise to an emission that shifts with the change of the excitation wavelength. The excitation wavelength dependent shift of the fluorescence maximum is measured to be between 60 and 100 nm. This kind of excitation wavelength dependent fluorescence behaviour, which may appear to be in violation of Kasha's rule of excitation wavelength independence of the emission spectrum, has been observed for nano ZnO colloids prepared by two different chemical routes and different capping agents. It is shown that the existence of a distribution of energetically different molecules in the ground state coupled with a low rate of the excited state relaxation processes, namely, solvation and energy transfer, are responsible for the excitation wavelength dependent fluorescence behaviour of the systems.
TL;DR: While most of the isolates were capable of producing hydrolytic enzymes such as amylase and gelatinase, lipolytic activity was low and Class 2 HDPE suffered the greatest biodegradation.
Abstract: The diversity and load of heterotrophic bacteria and fungi associated with the mangrove soil from Suva, Fiji Islands, was determined by using the plate count method. The ability of the bacterial isolates to produce various hydrolytic enzymes such as amylase, gelatinase and lipase were determined using the plate assay. The heterotrophic bacterial load was considerably higher than the fungal load. There was a predominance of the gram positive genus, Bacillus. Other genera encountered included Staphylococcus, Micrococcus, Listeria and Vibrio. Their effectiveness on the degradation of commercial polythene carry bags made of high density polyethylene (HDPE) and low density polyethylene (LDPE) was studied over a period of eight weeks in the laboratory. Biodegradation was measured in terms of mean weight loss, which was nearly 5 % after a period of eight weeks. There was a significant increase in the bacterial load of the soil attached to class 2 (HDPE) polythene. After eight weeks of submergence in mangrove soil, soil attached to class 1 and class 3 polythene mostly had Bacillus (Staphylococcus predominated in class 2 polythene). While most of the isolates were capable of producing hydrolytic enzymes such as amylase and gelatinase, lipolytic activity was low. Class 2 HDPE suffered the greatest biodegradation.
TL;DR: In this paper, three copper(II) complexes of salicylaldehyde N(4)-phenyl thiosemicarbazone (H2L1) and two copper-cyclohexyl THIOSEMICAZONE (H 2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies.
TL;DR: A series of short-isora-fiber-reinforced natural rubber composites were prepared by the incorporation of fibers of different lengths (6, 10, and 14 mm) at 15 phr loading and at different concentrations (10, 20, 30, and 40 phr) with a 10 mm fiber length.
Abstract: A series of short-isora-fiber-reinforced natural rubber composites were prepared by the incorporation of fibers of different lengths (6, 10, and 14 mm) at 15 phr loading and at different concentrations (10, 20, 30, and 40 phr) with a 10 mm fiber length. Mixes were also prepared with 10 mm long fibers treated with a 5% NaOH solution. The vulcanization parameters, processability, and stress–strain properties of these composites were analyzed. Properties such as tensile strength, tear strength, and tensile modulus were found to be at maximum for composites containing longitudinally oriented fibers 10 mm in length. Mixes containing fiber loadings of 30 phr with bonding agent (resorcinol-formaldehyde [RF] resin) showed mechanical properties superior to all other composites. Scanning electron microscopy (SEM) studies were carried out to investigate the fiber surface morphology, fiber pullout, and fiber–rubber interface. SEM studies showed that the bonding between the fiber and rubber was improved with treated fibers and with the use of bonding agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1640–1650, 2007
TL;DR: Functional results after extended myotomy for DOS are assessed to assess the role of surgery in the management of patients with diffuse oesophageal spasm.
Abstract: Background:
The role of surgery in the management of patients with diffuse oesophageal spasm (DOS) remains controversial. The aim of this study was to assess functional results after extended myotomy for DOS.
Methods:
This prospective study evaluated 20 patients who had extended myotomy (14 cm on the oesophagus and 2 cm below the oesophagogastric junction) with anterior fundoplication via a laparotomy for severe DOS. Median follow-up was 50 (range 6–84) months. Functional data were assessed by means of dysphagia (range 0–3), chest pain (range 0–3) and overall clinical (range 0–12, including dysphagia, chest pain, regurgitation, gastro-oesophageal reflux) scores.
Results:
All patients had severe DOS. The median preoperative overall clinical score was 6 (range 3–8) with a dysphagia score of at least 2. Median postoperative functional scores were significantly lower than preoperative values (overall clinical score 1 versus 6, dysphagia score 0 versus 3, chest pain score 0 versus 2). At final follow-up, good or excellent results were obtained for overall clinical score in 16 patients, for dysphagia score in 18 and for chest pain score in all 20 patients. Postoperative gastro-oesophageal reflux was noted in two of the 20 patients.
Conclusion:
Extended myotomy with anterior fundoplication is an effective treatment for severe DOS. Medium-term postoperative functional results were excellent, especially in terms of dysphagia and chest pain. Copyright © 2007 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.
TL;DR: In this paper, the effect of Sr2Ce2Ti5O16 ceramics filled PTFE composites were investigated by X-ray diffraction and scanning electron microscopic methods.
Abstract: Sr2Ce2Ti5O16 ceramics filled PTFE composites were prepared by powder processing technique. The structure and microstructure of the composites were investigated by X-ray diffraction and scanning electron microscopic methods. The effect of Sr2Ce2Ti5O16 ceramic content (0–0.6 volume fraction) on the dielectric properties of the composites was studied at 1 MHz and 7 GHz. The dielectric constant and dielectric loss increased with the increase of Sr2Ce2Ti5O16 content. The measured dielectric constant (ɛr) is compared with the effective dielectric constant calculated by Lichtenecker, Maxwell-Garnet, Jayasundere, Poon-Shin formulae and Effective Medium Theory. The observed dielectric constants are reasonably in good agreement with that calculated using Effective Medium Theory.
TL;DR: In this paper, hybrid polymer networks (HPNs) based on unsaturated polyester resin (UPR) and epoxy resins were synthesized by reactive blending, and the physical, mechanical, and thermal properties of the cured blends were compared with those of the control resin.
TL;DR: In this article, the tridentate character of the semicarbazone is inferred from IR spectra based on EPR studies, the spin Hamiltonian and bonding parameters have been calculated.
TL;DR: In this article, a simple melt compounding method was used to obtain poly(ethylene terephthalate) (PET) nanocomposites with single-walled carbon nanotubes (SWNTs).
Abstract: Poly(ethylene terephthalate) (PET) nanocomposites with single-walled carbon nanotubes (SWNTs) have been prepared by a simple melt compounding method. With increasing concentration (0–3 wt %) of SWNTs, the mechanical and dynamic mechanical properties improved, corresponding to effective reinforcement. Melt rheological characterization indicated the effective entanglements provided by SWNTs in the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical conductivity measurements on the composite films pointed out that the melt compounded SWNTs can result in electrical percolation albeit at concentrations exceeding 2 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
TL;DR: In this article, the effect of swift heavy ions on the structural and optical properties of polyaniline thin film is investigated, which is attributed to the rearrangement in the ring structure and the formation of Ctriple bond; length of mdash C \equiv C terminals.
TL;DR: In this paper, a transparent diode heterojunction on ITO coated glass substrates was fabricated using p-type AgCoO 2 and n-type ZnO films by pulsed laser deposition (PLD).
TL;DR: In this paper, the onset of convection over the central Bay of Bengal (88-92°E, 14-18°N) during the core summer monsoon (mid-May to September) is linked to the meridional gradient of SST in the bay.
Abstract: We use daily satellite estimates of sea surface temperature (SST) and rainfall during 1998–2005 to show that onset of convection over the central Bay of Bengal (88–92°E, 14–18°N) during the core summer monsoon (mid-May to September) is linked to the meridional gradient of SST in the bay. The SST gradient was computed between two boxes in the northern (88–92°E, 18–22°N) and southern (82–88°E, 4–8°N) bay; the latter is the area of the cold tongue in the bay linked to the Summer Monsoon Current. Convection over central bay followed the SST difference between the northern and southern bay (ΔT) exceeding 0.75°C in 28 cases. There was no instance of ΔT exceeding this threshold without a burst in convection. There were, however, five instances of convection occurring without this SST gradient. Long rainfall events (events lasting more than a week) were associated with an SST event (ΔT ≥ 0.75°C); rainfall events tended to be short when not associated with an SST event. The SST gradient was important for the onset of convection, but not for its persistence: convection often persisted for several days even after the SST gradient weakened. The lag between ΔT exceeding 0.75°C and the onset of convection was 0–18 days, but the lag histogram peaked at one week. In 75% of the 28 cases, convection occurred within a week of ΔT exceeding the threshold of 0.75°C. The northern bay SST, TN, contributed more to ΔT, but it was a weaker criterion for convection than the SST gradient. A sensitivity analysis showed that the corresponding threshold for TN was 29°C. We hypothesise that the excess heating (∼1°C above the threshold for deep convection) required in the northern bay to trigger convection is because this excess in SST is what is required to establish the critical SST gradient.
TL;DR: In this paper, a comparison of the luminance emission spectra of Zn 0.98 Ga 2 O 4 :Dy 0.02 and Ga 1.98 O 3 :DY 0.04 phosphors was performed.
Abstract: Dysprosium-doped zinc gallate phosphors with the nominal formulas ZnGa 2(1-x) O 4 :Dy 2x were prepared by the high-temperature conventional solid-state reaction technique, the dopant concentration being varied in the range 0 ≤ x ≤ 0.025. Zn 1-x Ga 2 O 4 :Dy x and Ga 2(1-x) O 3 :Dy 2x samples were also prepared for comparison for a dopant concentration of x = 0.02. Only the intrinsic self-activated emission of the ZnGa 2 O 4 host is observed in the photoluminescence emission spectra of Zn 0.98 Ga 2 O 4 :Dy 0.02, while both the host emission band and characteristic emission lines ( 4 F 9/2 → 6 H J ) of Dy 3+ are observed for ZnGa 2(1-x) O 4 :Dy 2x and Ga 1.98 O 3 :Dy 0.04 phosphors. The luminescent intensity differs in the phosphors due to the different energy-transfer rates from the respective hosts to the luminescent centers. Photoluminescent studies reveal the fact that Dy 3+ ions replace Ga 3+ ions in the host lattice at their octahedral sites. The source of white luminescence in the doped samples is the nonradiative resonant energy transfer via exchange interaction between the host and the activator. The CIE coordinates of the 2.5 atom % Dy 3+ -doped sample (0.32, 0.33) matches well with achromatic white (0.33, 0.33) on the chromaticity diagram.
TL;DR: In this paper, a model called Maintenance Quality Function Deployment (MQFD) has been developed to nourish the synergic power of QFD and total quality management (TPM) for converting customers' vague language into technical languages.
Abstract: Quality Function Deployment (QFD) is a technique used in the Total Quality Management (TQM) field for converting customers' vague language into technical languages. Total Productive Maintenance (TPM) is an approach being followed to achieve quality in maintenance engineering activities. In order to nourish the synergic power of QFD and TPM, a model called Maintenance Quality Function Deployment (MQFD) has been developed. One of the hallmarks of MQFD implementation is the consideration of factors such as customers, technology, competitors, etc. If MQFD implementation is to be successful among organisations with heterogeneous cultures, their critical factors have to be compared thoroughly. The technique 'Analytic Hierarchy Process' (AHP) helps to achieve this task. AHP carry out pairwise comparison and sensitivity analysis of various critical factors and subfactors considered in MQFD projects. A sample application study of implementing AHP in MQFD programme in a maintenance-intensive Indian automobile service station was carried out. The details are illustrated in the subsequent sections of the article.
TL;DR: In this paper, a printed square monopole antenna for UWB communication applications is presented, where slits are introduced to reject the IEEE 802.11a and HIPERLAN/2 bands used for WLAN applications.
Abstract: In this paper, we present a detailed study of a printed square monopole antenna for Ultra Wide Band (UWB) communication applications. The 2:1 VSWR bandwidth of the proposed antenna is from 2.87–14 GHz. The antenna can be made to reject particular frequency bands by introducing narrow slits on the patch. In addition, the rejection band can be easily tuned for centre frequency, VSWR and rejection bandwidth by adjusting the slit parameters. In the proposed antenna, slits are introduced to reject the IEEE802.11a and HIPERLAN/2 bands used for WLAN applications. The antenna is analyzed in both frequency and time domains. Radiation patterns of the antenna are omnidirectional with appreciable gain throughout the band. Transient analysis indicates linear phase response and minimum pulse distortion.
TL;DR: In this paper, a modified Weibull distribution is proposed for maximum wave height simulation and parametric relations are derived there from to estimate various wave height statistics including extreme wave heights.
TL;DR: A transient solution is obtained analytically using continued fractions for the system size in an M/M/1 queueing system with catastrophes, server failures and non-zero repair time.
Abstract: A transient solution is obtained analytically using continued fractions for the system size in an M/M/1 queueing system with catastrophes, server failures and non-zero repair time. The steady state probability of the system size is present. Some key performance measures, namely, throughput, loss probability and response time for the system under consideration are investigated. Further, reliability and availability of the system are analysed. Finally, numerical illustrations are used to discuss the system performance measures.