007621   Biradar R C;Bhagyashree P R;Manvi S S (ECE Dep, SDM Coll of Engng and Technol, Dharwad-580 002, Email: rajashekharbiradar@yahoo.com) : Agent-based adaptive bandwidth allocation in wireless networks. IETE J Res 2007, 53(2), 127-36.

Services provided over wireless networks are growing at a rapid pace with the increasing number of users and their demands. Some of the services demand real-time multimedia communication and stringent bandwidth requirements owing to their varied service characteristics. Thus, there is a requirement for developing efficient bandwidth allocation schemes to achieve acceptable Quality of Service (QoS) and meet these challenges. Bandwidth is the most critical resource in wireless networks, which should be managed efficiently. This paper proposes an agent based adaptive bandwidth allocation scheme that allocates the bandwidth by using an interference bandwidth allocation algorithm in cellular system. Proposed scheme claims an agent based bandwidth allocation delay of 24.5 microseconds as opposed to 78 microseconds with non-agent based approach.

8 illus, 16 ref

007620   Bhunia C T (Haldia Inst of Technol, , P.O. Hit, Haldia, Purba, Medinipur-721 657, Email: ctbhunia@vsnl.com) : Performance analysis of IP header compression. IETE J Res 2007, 53(2), 113-18.

Several prior studies reported that the Header Compression (HC) achieves several gains like bandwidth savings, faster response time and better reliability. A few other studies reported about loss due to HC. Introduces a single parameter named "power" to measure the gains of HC. Authors introduce another single parameter as "effective power" to measure both the gains and the loss of HC. It has been find that the performance measurement by such single parameters gives more intuitive analysis and understanding of functions of HC.

4 illus, 18 ref

007619   Bhim Singh;Singh B P;Dwivedi S (Electrical Engineering Dep, Indian Institute of Technology, Hauz Khas, New Delhi-110 016, Email: bsingh@ee.iitd.ac.in) : DSP based implementation of vector control scheme for permanent magnet synchronous motor drive. IETE J Res 2007, 53(2), 153-64.

Presents an analysis and hardware implementation of a Vector Control (VC) scheme for Permanent Magnet Synchronous Motor (PMSM) drive using a motion control digital signal processor. The vector controlled PMSM drive system is implemented using minimum number of hardware components. The developed PMSM drive system consists of power circuit, control hardware and software. Power circuit consists of insulated gate bipolar transistor (IGBT) based voltage source inverter (VSI) and gate driver circuit. The control hardware consists of power supplies, resolver demodulation circuit, current sensors and interfacing circuits. The reference speed, rotor speed estimation using sensed position signals, speed controller, reference frame transformation, vector controller and PWM current controller for gating pulse generation of VSI are implemented in assembly language of DSP-ADMC401. The simulation model of the drive system is developed in MATLAB environment with simulink and PSB toolboxes to analyze the performance of the proposed drive system. The simulated performance alongwith test results of the PMSM drive are studied for starting, steady-state condition, speed reversal and load perturbation.

7 illus, 18 ref

007618   Bhattacharya D (NO, Consulting Engineering Services (India) Private Limited, New Delhi, Email: bdhrubajyoti@yahoo.co.in) : Analysis of tremie technique in concreting of bottom plug of wells. Indian Highw 2006, 34(5), 33-42.

"Tremie Technology" for pouring of concrete under water depends on the area of the dredge hole. Concept of the technology varies based on the concrete flow character vis-a-vis shape and size of the hole, where concrete is to be poured. Conventional "Tremie Technology", applied in cast-in-situ bored piles, is pouring of concrete under water through tremie pipe from bottom to top of the dredge hole in a continuous process. Upward flow of concrete is very important in conventional tremie technology. In case of concreting in well bottom plug, the "Tremie Technology" applied is not exactly similar to the conventional method. Due to large diameter of well, upward flow of concrete does not occur from bottom to top of the dredge hole. Concrete, during well bottom plug, spills down over the old concrete. First poured concrete does not come up. The technical analysis of the tremie technology in well bottom plug and flow character of the concrete during bottom plug operation in wells have been discussed in comparison with the conventional tremie technology, applied in cast-insitu bored piles.

7 illus, 5 ref

007617   Bhagwan Singh;Rao B S (RDM Div, Central Road Research Institute, New Delhi-110 020, Email: bhagwan.crri@nic.in) : Prioritizing maintenance of rural roads for Narsapur division of Andhra Pradesh state. Indian Highw 2006, 34(10), 45-53.

In view of the budgetary constraints and low priority for road maintenance in the rural setup, a need was indicated to develop Pavement Maintenance Management System (PMMS). Parameters used for developing PMMS are based on the relative importance of basic priorities like pavement condition, population distribution, age of pavement, economic development, traffic growth, tourism potential, religious places, political considerations etc. Based on these parameters a PMMS model comprising Pavement Condition Index (PCI) and Overall Priority Index (OPI) was developed to prioritize and maintain the rural road. The PMMS model will help to evaluate and prioritize the existing roads for up-gradation based on priorities. The model developed will assess and help to allocate the available funds, which will lead to overall development of the rural areas. It will be a very useful tool for decision-making authorities in allocation of funds for maintenance. This model has been applied for total 110.8 Ian (where 25.5 Ian are with paved surface and remaining 85.3 Ian are unpaved) road length for Narsapur division of West Godavari District (Andhra Pradesh).

3 illus, 11 tables, 11 ref

007616   Baskar R;Meera Sheriffa Begum K M;Sundaram S (Chem Engng Dep, Kongu Engng Coll, Perundural, Erode-638 052) : Reuse of tannery sludge in manufacture of bricks. Process Pl Engng 2006, 24(2), 48-51.

Managing the soild waste in one of the tughest tasks facing the process industry today. Untilization of wastes to get useful product is preferred in the view of disposal and economy. The technical characteristics of bricks made using tannery industry effluent treatment plant sludge were examined. The clay in the conventional brick making process was partially replaced with wates sludge up to 30% (w/w). Physio-Chemical properties of the sludge have been studied and reported. The tests on the brick specimens are conducted as per Bureau of Indian standards (BIS) specification codes. The percentage sludge addition and firing temperature were found to be the two key factors deciding the quality of the bricks formed. All the brick samples satisfied the requirements interms of shrinkage and weight loss characteristics, However bricks with more than 6% sludge were found not to satisfy the prescribed norms for compressive strenght at the maximum range of temperature condition studied. Thus tannery sludge up to 6%(w/w) can be effectively added to make first class brick material, satisfying all the norms specified.

7 illus, 3 tables, 9 ref

007615   Badal R (SMEC India Pvt Ltd, , New Delhi, Email: dr.badal@smeccig.com) : Mechanical excavation for tunneling works. Indian Highw 2006, 34(9), 39-47.

A brief description about the mechanical excavation methods for underground construction, evaluation, selection criteria for excavation equipment for the varied ground conditions or geo-environments and their effect on the project techno-economics. This paper also informs about an influence of rock formations on production consumables' and performance prediction. The performance of the mechanical excavation methods in some of the tunneling projects in the country have been critically analyzed, so that the resultant can serve as guidance and can also be optimally applied to the future projects.

6 illus, 1 table, 17 ref

007614   Anil Kumar (C.D.O. R.C.D., , Jharkhand) : Development of road infrastructure-retrospective and prospective - with special reference to Jharkhand state. Indian Highw 2006, 34(6), 27-31.

007613   Amalraj A J;Rajendran S;Sundaravadivelu M; Regis A P P;Sahayaraj J W (Chem Dep, St. Joseph's College, Tiruchirapalli-620 002, Email: srmjoany@sify.com) : The influence of pH on 2-chloroethylphosphonic acid-Zn<. Bull Electrochem 2006, 22(7), 311-16.

The inhibition effect of 2-chloroethylphosphonic acid (2 Cl EPA) and Zn²⁺ in controlling corrosion of carbon steel immersed in an aqueous solution containing 60 ppm of Cl- has been evaluated in the present study. The fonnulation consisting of 50 ppm of Zn²⁺ and 50 ppm of 2 Cl EPA has 74% inhibition efficiency (IE). The influence of pH 5, 7, 9 and 11 on the inhibition efficiency of the 2 Cl EPA-Zn²⁺ system has also been investigated. Polarization study reveals that the 2 Cl EP A-Zn²⁺ system functions as a mixed inhibitor system. AC imf..edance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Fe -2 Cl EPA complex and Zn(OH)₂.

3 illus, 8 tables, 23 ref

007612   Agarwal G (Molecular Biophysics Unit, Indian Inst of Sci, Bangalore-560 012, Email: garima@mbu.iisc.ernet.in) : Towards logical designs in biology. Resonance 2007, 12(2), 29-38.

Rreview gives an insight into the creation of gene circuits and discusses the potential applications in the field of biotechnology, medicine and environmental sciences.

10 ref

007611   Adeyemi O O;Oluwafemi S O (Chem Sci Dep, Olabisi Onabanjo Univ, P.O. Box 364, Ago-Iwoye, Ogun State, Nigeria, Email: OO_adeyemi@yahoo.co.uk) : 2-Aminopyridine as an effective inhibitor for the corrosion of mild steel in acidic solutions. Bull Electrochem 2006, 22(7), 317-19.

The inhibition action of 2-aminopyridine (2-AP) on acid corrosion of mild steel was studied by weight loss and potentiostatic polarisation measurements. 2-aminopyridine (2-AP) has a very good activity as mild steel corrosion inhibitor under different conditions. The inhibitive performance of 2-AP is due to multiple interaction model involving two coordinate bondings and a further hydrogen bonding interaction between 2-AP molecule and the metal surface. It behaves predominantly as cathodic inhibitor in HCl and mixed inhibitor in H₂SO₄. The inhibitor brings down the permeation current more effectively in acid solutions. The adsorption of 2-AP on mild steel from acid solutions is found to obey Langmuir's adsorption isotherm.

2 illus, 3 tables, 18 ref

006831   Yanmaz A M;Kose O (Civil Engineering Dep, Middle East Technical Univ, 06531, Ankara-Turkey, Email: myanz@metu.edu.tr ) : Time-wise variation of scouring at bridge abutments. Sadhana 2007, 32(3), 199-213.

Accurate estimation of the maximum possible depth of scour at bridge abutments is important in decision-making for the safe depth of burial of footings. Besides, investigation of the geometric features of scour holes around abutments provides useful information for the degree of scour counter-measure to be implemented against excessive scouring. Experiments have been performed to investigate time-dependent characteristics of scour holes around vertical wall abutments under clear water conditions with uniform bed materials. Temporal variations of scour depth and scour contours were measured. Using this information, an empirical relation was developed for temporal variation of scour depth. Additional relations were also derived for time-dependent volume and surface area of the scour holes around abutments. The findings of this study may provide useful information for preliminary design of abutment footings and placement details of armoring counter-measures, such as riprap.

10 illus, 1 table, 18 ref

006830   Vishal Singh (NO, Classified Specialist (Medicine) Institute of Aerospace Medicine, IAF, Bangalore) : Teaching series : aviation medicine electrocardiographic abnormalities in aircrew-I. Indian J Aerospace Med 2007, 51(1), 44-5.

ref

006829   Tripathy N K;Prasad G K G (NO, , Graded Specialist (Aviation Medicine) Air Force Station, Sirsa, Haryana) : Phacoemulsification and foldable posterior chamber intraocular lenses in aircrew: clinical behaviour and aeromedical implications. Indian J Aerospace Med 2007, 51(1), 25-31.

The advent of phacoemulsification and foldable lOL for surgical treatment of cataract, has drastically shortened the time period to return back to flying in aircrew. However this is not devoid of complications. Hence a follow up of these cases became imperative. 14 experienced aircrew from both civil and military flying, who had undergone phacoemulsification with foldable PC-IOL implants were assessed by an extensive questionnaire study and a detailed objective clinical examination. Among 14 pseudophakic aircrew, 3 had unilateral and 11 bilateral implants. Minor aeromedical problems such as haloes around lights, problems with fixed focal length, discomfort, problems due to dust and fumes and distortion of images, did not interfere with their flying. Out of 25 operated eyes reviewed, subluxation of the lens implant occurred in one eye. Opacification of the posterior capsule developed in one eye, requiring YAG laser capsulotomy. Postoperatively, there were 15 emmetropic, 6 hyperopic and 4 myopic eyes and all aircrew attained 6/6 best-corrected visual acuity. The mean absolute spherical refractive error was 0.22 dioptres and astigmatic error was 0.64 dioptres. The mean bifocal add was+1.63 dioptres. Mean intraocular pressure was 153 ± 2.08 mm Hg. Detailed ophthalmological examination did not show significant clinical abnormality in any of the eyes. Most of the aeromedical problems related to older generation lOLs could be eliminated to a significant level by implanting latest foldable PC-IOLs. Phacoemulsification enables the aircrew for an early return to flying by enhancing rapid visual rehabilitation and reducing postoperative complications. Thus the preferred recommended cataract procedure in an aircrew is phacoemulsification with implantation of an ideal-sized highly biocompatible foldable PC-IOL.

1 table, 21 ref

006828   Thiemsorn W;Keowkamnerd K;Suwannathada P; Hessenkemper H;Phanichaphant S (Faculty of Science, Chiang Mai Univ, Chaing Mai-50202, Thailand, Email: worapong@chiangmai.ac.th) : Redox ratio and optical absorption of polyvalent ions in industrial glasses. Bull Mater Sci 2007, 30(5), 487-95.

The changes in glass structure and redox ratio, R (reduced ion to oxidized ion) of Mn² Mn³⁺, Cu⁺-Cu²⁺, Cr³⁺-Cr⁶⁺, Ni²⁺-Ni³⁺ and Co²⁺-Co³⁺ couples and optical absorption due to Mn³⁺, Cu²⁺, Cr³⁺, Ni²⁺ and Co²⁺ ions in industrial soda-lime-silica glass were investigated as a function of Na₂O concentration in the range 11-19 mol%. With increasing Na₂O concentration in the experimental glasses, the basicity, expressed as calculated basicity, Λ_cal, increased. ²⁹Si NMR and X-ray diffraction were used to investigate the structural change in glasses. The NMR spectra showed high non-bridging oxygens (NBOs) when the basicity of glass was increased. The results were interpreted to be due to the tetrahedral networks; Q⁴ species were depolymerized by replacing the bridging oxygens (BOs) with NBOs to Q³ species. These results confirmed the shift of broadening peaks of ,XRD patterns. The redox reactions of the Mn²⁺-Mn³⁺, Cu₊-Cu²⁺ and Cr³⁺-Cr⁶⁺ couples shifted more toward their oxidized ions due to the oxygen partial pressure, p(O₂), during melting and the oxide ion activity, α_{o2-, increased with increasing glass basicity. These changes caused the redox ratio of these ion couples to decrease. The Ni²⁺-Ni³⁺ and Co²⁺-Co³⁺ couples were assumed to be present only in the Ni²⁺ and Co²⁺ ions in these glasses, respectively. The optical absorption bands due to Mn³⁺, Cu²⁺, Cr³⁺, Ni²⁺ and Co²⁺ ions were also investigated. Their spectra occurred at constant wavelengths with different optical densities or intensities as a function of glass basicity. The increase in the intensities of the absorption bands of these absorbing ions, except for Cr³⁺ ion, at the maximum wavelength, depends not only on the ion concentration but also on the increase of polarizability of oxide (-II) species, αoxide(-II), surrounding the ions. This value affected directly the extinction coefficients of the ions, ξion. The increase of ξion caused the colour of glasses appearing in high intensity. In the case of Cr³⁺ ion, the results were reversed such that the lower the concentration, the higher the intensities of colour.}

9 illus, 4 tables, 24 ref

006827   Simsek M;Kocaturk T (Civil Engineering Dep, Yildiz Technical Univ, Yildiz 34349, Istanbul, Turkey, Email: kocaturk@yildiz.edu.tr) : Free vibration analysis of beams by using a third-order shear deformation theory. Sadhana 2007, 32(3), 167-9.

In this study, free vibration of beams with different boundary conditions is analysed within the framework of the third-order shear deformation theory. The boundary conditions of beams are satisfied using Lagrange multipliers. To apply the Lagrange's equations, trial functions denoting the deflections and the rotations of the cross-section of the beam are expressed in polynomial form. Using Lagrange's equations, the problem is reduced to the solution of a system of algebraic equations. The first six eigenvalues of the considered beams are calculated for different thickness-to-length ratios. The results are compared with the previous results based on Timoshenko and Euler-Bemoulli beam theories.

5 tables, 19 ref

006826   Sharma D;Gupta V K;Brahmachari G;Mondal S; Gangopadhyay A (Physics Post Graduate Dep, Jammu Univ, Jammu Tawi-180 006, Email: vivek_gupta2k5@yahoo.co.in) : X-ray study of weak interactions in two flavonoids. Bull Mater Sci 2007, 30(5), 469-75.

X-ray diffraction studies were carried out on single crystals of two flavonoids, viz. 5-hydroxy-6,7,4'-trimethoxyflavone, C_18H16O6, (I) and 5-hydroxy-3,7,4'-trimethoxyfIavone, C₁₈II₁₆O₆, (II). Crystal structures of both the flavonoids were solved by direct methods and refined by full-matrix least-squares, procedures. In both the molecules, the benzopyran moiety is planar. The dihedral angle between the phenyl ring and the benzopyran portion is 5.50(4)° in (I) and 29.11(5)° in (II). In (I), the crystal packing is influenced by O-H...O hydrogen bonds, and weak C-H...O and π...π interactions whereas in (II) the crystal structure is stabilized by the presence of four intermolecular short contacts of the type C-H...O. There is also one C-H...π hydrogen bond with H... centroid distance of <60>2.7 A. The molecules are further stabilized by π-π interactions.

8 illus, 5 tables, 44 ref

006825   Sharma A K;Mishra K K;Raghuramaiah M;Naik P A;Gupta P D (Laser Plasma Div, Raja Ramanna Centre for Advanced Technology (RRCAT), Indore-452 013, Email: aksharma@cat.ernet.in) : Design and performance characteristics of an electromagnetic interference shielded enclosure for high voltage pockels cell switching system. Sadhana 2007, 32(3), 235-42.

An electro-magnetic interference noise shielding enclosure for Pockels cells for high speed synchronized switching has been set-up and tested. The shield-ing effectiveness of the aluminum enclosures housing the Pockels cells and the electronic circuitry has been measured using a high impedance probe and is found to be <126>50 dB. This ensures a noise-free and synchronized electro-optic switching in an Nd:glass re-generative amplifier of chirped pulse amplification based table top terawatt laser system.

3 illus, 16 ref

006824   Sasibhushana Rao G (Electronics and Communication Engineering Dep, Andhra Univ Engineering College, Visakhapatnam-530 003, Email: sasi_gps@yahoo.co.in) : Error analysis of satellite-based global navigation system over the low-latitude region. Curr Sci 2007, 93(7), 927-31.

Total electron content variations have been analysed for several years in the low-latitude region. GPS signal structure, various errors affecting the positional accuracy of GPS and the techniques used to mitigate their affects are presented.

3 illus, 1 table, 10 ref

006823   Sangwan N S;Sangwan R S (Central Institute of Medicinal and Aromatic Plants, , PO CIMAP, Lucknow-226 015) : Metabolic engineering for flavour enhancement in tomato - path setting for opportunities and strategies. Curr Sci 2007, 93(7), 899-901.

1 illus, 13 ref

006822   Saikia B K;Boruah R K;Gogoi P K (Chemical Sciences Dep, Tezpur Univ, Tezpur-784 028, Email: binoyrrl@yahoo.com) : XRD and FT-IR investigations of sub-bituminous Assam coals. Bull Mater Sci 2007, 30(4), 421-6.

Indicates that the coals are lignite in type and there is no evidence of graphite-like structures. The maximum in the G(r) plots of function of radial distribution of atoms (FRDA) relates to different distances between carbon atoms of aliphatic chains. The first significant maximum relates to the C-C bond (type C-CH=CH-C), the second maximum relates to the distance between carbon atoms of aliphatic chains that are located across one carbon atom. The curve intensity profiles obtained from FRDA show quite regular molecular packets for this coal. The coals were found to be lignite in nature. FT-IR study shows the presence of aliphatic carbon, C=O and C-O stretching associated with -OH and -NR stretching vibrations. Kaolinite and quartz were also found to be major minerals in Assam coals by FTIR spectroscopy. The, difference in intensities of carbonyl groups of the coal samples is likely to relate with the rank.

4 illus, 3 tables, 41 ref

006821   Ravi K R;Pillai R M;Paik B C;Chakraborty M (Materials and Minerals Div, Regional Research Laboratory (CSIR), , Thiruvananthapuram-695 019, Email: rmpillai_rrl@yahoo.com) : Separation of matrix alloy and reinforcement for aluminum metal matrix composites scarp by salt flux addition. Bull Mater Sci 2007, 30(4), 393-8.

Separation of matrix alloy and reinforcements from pure Al-SiC_p composite scrap by salt flux addition has been theoretically predicted using interface free energies. Experiments performed confirm the theoretical prediction. Complete separation of matrix "aluminum and reinforcement from metal matrix composites (MMCs) scrap has been achieved by addition of 2.05 wt% of equimolar mixture of NaCl-KCl salt flux with a metal and particle yield of 84 and 50%, respectively. By adding 5 wt% of NaF to equimolar mixture of NaCl-KC1, metal and particle yield improved to 91 and 73%, respectively. Reusability of both the matrix aluminum and the SiC separated from Al-SiC_p scraps has been analysed using XRD, SEM and DTA techniques. The matrix alloy separated from Al-SiC_p scraps can be used possibly as a low Si content AI-Si alloy. However, the inter-facial reaction that occurred during the fabrication of the composites had degraded the SiC particles.

9 illus, 15 ref

006820   Rajasankar J;Iyer Nagesh R;Yerraya Swamy B; Gopalakrishnan N;Chellapandi P (NO, Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai-600 113, Email: sankar@sercm.org) : SSI analysis of a massive concrete structure based on a novel convolution/deconvolution technique. Sadhana 2007, 32(3), 215-34.

Investigations conducted based on seismic soil-structure interaction analysis of a massive concrete structure supported on a raft foundation are presented in this paper. Linear transient dynamic analysis is carried out using finite element method and imposing transmitting boundary conditions at far field of layered elastic half-space. Analysis is conducted in two phases, namely: (i) free-field analysis of the layered half-space and (ii) seismic analysis of the structure by including soil-structure interaction effects. In the first phase, a simple and novel technique is used to establish free-field excitation at a depth in the half-space. In the second phase, seismic soil-structure interaction analysis of the structure is carried out for the free-field excitation determined in phase-I. Stress resultants experienced by the raft and the stresses at the interface between the rock and raft are evaluated. Critical examination of the results indicates tensile stresses of considerable magnitude at few locations in the rock-raft interface. Typical stress responses at the interface are presented and discussed in the paper.

6 tables, 15 ref

006819   Omkar S N;Manoj Kumar M;Mudigere D (Aerospace Engineering Dep, Indian Institute of Science, Bangalore) : Posture assessment using imageJ. Indian J Aerospace Med 2007, 51(1), 38-43.

Recurrent low back pain is common among pilots, aircrew and frequent fliers due to various vagaries of flight. The lower back pain manifests as a change in the posture. This change in posture can be used as an index to determine the health of the lower back. In this paper the authors propose a generic methodology to compare and quantify the changes in the posture without any dependence on the keen subjective observation of an expert. It is illustrated by taking two examples. ImageJ, a versatile public domain image processing tool, has been employed to carry out the postural analysis. The portrait and profile photographs of the subjects are considered to quantify the changes in the posture.

^ssc3 illus, 2 tables, 9 ref

006818   Narulkar V V;Prakash S;Chandra K (Mettallurgical and Materials Engineering Dep, Indian Institute of Technology, Roorkee-247 667, Email: vinaynarulkar@gmail.com) : Ceramic coated Y1 magnesium alloy surfaces by microarc oxidation process for marine applications. Bull Mater Sci 2007, 30(4), 399-402.

Property of corrosion resistance of ceramic coating was studied by CS300P electrochemistry-corrosion workstation, and the main impact factor of the corrosion resistance was also analysed. Microstructure and phase composition were analysed by SEM and XRD. The microhardness of the coating was also measured. The basic mechanism of microarc coating formation is explained in brief. The results show that the corrosion resistance properly of microarc oxidation coating on the Y1 magnesium surface is superior to the original samples in the 3.5 wt% NaCl solutions. The microarc oxidation coating is relatively dense and uniform, mainly composed of MgO, MgAl₂O₄ and MgSiO₃. The microhardness of the Y1 magnesium alloy surface attained 410 HV, which was much larger than that of the original Y1 magnesium alloy without microarc oxidation.

5 illus, 1 table, 16 ref

006817   Narulkar V V;Prakash S;Chandra K (Metallurgical and Materials Engineering Dep, Indian Institute of Technology, Roorkee-247 667, Email: vinaynarulkar@gmail.com) : Characteristics of porous zirconia coated with hydroxyapatite as human bones. Bull Mater Sci 2007, 30(4), 309-14.

Porous zirconia and alumina added zirconia ceramics were prepared by ceramic slurry infiltration of expanded polystyrene bead compacts, followed by firing at 1500°C. Then slurry of hydroxyapatite-borosilicate glass mixed powder was used to coat the porous ceramics, followed by firing at 1200°C. The porous structures without the coating had high porosities of 51-69%, high pore interconnectivity, and sufficiently large pore window sizes (300-500 μm). The porous ceramics had compressive strengths of 5-3<126>36.8 MPa, favourably comparable to the mechanical properties of cancellous bones. In addition, porous hydroxyapatite surface was formed on the top of the composite coating, whereas a borosilicate glass layer was found on the interface. Thus, porous zirconia-based ceramics were modified with a bioactive composite coating for biomedical applications.

7 illus, 11 ref

006816   Kothyari U C (Civil Engineering Dep, Indian Institute of Technology, Roorkee-247 667, Email: umeshfce@iitr.ernet.in) : Indian practice on estimation of scour around bridge piers- a comment. Sadhana 2007, 32(3), 187-97.

Well-laid foundation is mostly provided in road and railway bridges in India over large and medium-sized rivers. The age-old Lacey-Inglis method is used for estimation of the design scour depth around bridge elements such as pier, abutment, guide bank, spur and groyene. Codal provisions are seen to produce too large a scour depth around bridge elements resulting in bridge sub-structures that lead to increased construction costs. Limitations that exist in the codes of practice are illustrated in this paper using examples. The methods recently developed for estimation of the scour are described. New railway and road bridges are required to be built in large numbers in the near future across several rivers to strengthen such infrastructure in the country. It is strongly felt that provisions in the existing codes of practice for determination of design scour depth require immediate review. The present paper provides a critical note on the practices followed in India for estimating the design scour depth.

4 illus, 28 ref

006815   Kashyap K T;Yamdagni S (Mechanical Engineering Dep, PES Institute of Technology, 100 ft Ring Road, Bangalore-560 085, Email: ktkashyap@yahoo.com) : Modelling of soft impingement during solidification. Bull Mater Sci 2007, 30(4), 403-6.

Vogel and Doherty model is pursued by quantitative modeling of soft impingement problem and related to shape instability by constitutional supercooling theory. This analysis correctly predicts the spheroidal grain formation during stir casting or rheocasting. This model can also be used to explain the grain refinement of magnesium alloys by zirconium addition wherein spheroidal grains are formed.

4 illus, 2 tables, 8 ref

006814   Juan W;Yajiang L;Gerasimov S A (Key Lab of Liquid Structure and Heredity of Materials, School of Mater, Shandong Univ (South Campus), Jing Shi Road 73, Jinan-250 061, P.R. China, Email: jwang@sdu.edu.cn) : Interfacial microstructure and strength of diffusion brazed joint between Al₂O₃-TiC and 9Cr1Mo V steel. Bull Mater Sci 2007, 30(4), 415-19.

Joining of composite, Al₂O₃-TiC, with heat-resistant 9Cr1MoV steel, was carried out by diffusion brazing technology, using a combination of Ti, Cu and Ti as multi-interlayer. The interfacial strength was measured by shear testing and the result was explained by the fracture morphology. Microstruetural characterization of the Al₂O3-TiC/9CrlMoV joint was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy-dispersion spectroscopy (EDS). The results indicate that a Al₂O₃-TiC/ 9CrlMoV joint with a shear strength of 122 MPa can be obtained by controlling heating temperature at 1130øC for 60 min with a pressure of 12 MPa. Multi-interlayer Ti/Cu/Ti was fused fully and diffusion occurred to produce interfacial layer between Al₂O₃-TiC and 9CrlMoV steel. The total thickness of the interfacial layer is. about 100 μm and Ti₃AlC₂, TiC, Cu and Fe₂Ti are found to occur in the interface layer.

5 illus, 12 ref

006813   Joshi V V;Agarwal A;Rajesh Kumar (NO, , Air India & Classified specialist (Aviation Medicine). [Formerly Senior Medical Officer, IAF Contingent to United Nation) : Aeromedical experiences in Indian peace keeping missions under united nations in Sierra Leone (UNAMSIL) and Democratic Republic of Congo (MONUC). Indian J Aerospace Med 2007, 51(1), 32-7.

Indian Air Force helicopter contingents participated in the United Nations peace keeping missions in Sierra Leone (UNAMSIL) in the year 2000 and in Congo (MONUC) from 2003 till date. The paper discusses various aeromedical experiences in the year 2000 in UNAMSIL and June 2003 to Aug 2005 in MONUC. The difficult aviation environment in the mission areas and the resultant immense aeromedical challenges are discussed. The data of high aircrew fitness rates despite the difficult conditions is discussed. Large numbers of casuality evacuations were carried out where the contingent's medical personnel provided the in-flight medical cover. The details of the casuality evacuations data are discussed. In the three years under consideration, there was one human error accident and four major incidents attributable to technical reasons or battlefield damage and the paper discusses these in brief. The paper also discusses the dilemma of Malaria prophylaxis in aircrew deployed for prolonged periods in highly endemic and drug resistant areas. The reported side effects of Mefloquine, our Mefloquine administration strategies and precautions adopted are discussed. The observed side effects are elaborated and attempt is made to explain the variance of our experiences with Mefloquine vis-a-vis those reported in the Western literature.

6 ref

006812   Husem M;Pul S (Civil Engineering Dep, Karadeniz Technical Univ, 61080 Trabzon, Turkey, Email: mhusem@ktu.edu.tr ) : Investigation of stress-strain models for confined high strength concrete. Sadhana 2007, 32(3), 243-52.

The effects of confinement reinforcement on the behaviour of high strength concrete columns are investigated for which prismatic experimental specimens were prepared. In the experiment specimens, four longitude reinforcement and confinement reinforcement were used. For each experiment, stress-strain relationship of concrete was obtained and compared with models proposed earlier. The results show that confinement reinforcement improved the ductility of high strength concrete. The ascending branch of stress-strain curves depended on the ratio of confinement reinforcement was similar to the modified Kent-Park model and the descending branch similar to the Nagashima model.

4 illus, 7 tables, 31 ref

006811   Gupta P K;Kuri J (Centre for Electronics Design and Technology, Indian Institute of Science, Bangalore-560 012, Email: pawankumargupta@hotmail.com) : TCP with header checksum option for wireless links: an analytical approach towards performance evaluation. Sadhana 2007, 32(3), 253-75.

TCP performs poorly in wireless mobile networks due to large bit error rates. Basically, the TCP sender responds to these losses as if they were due to congestion in the network, and reduces the congestion window unnecessarily. In earlier work, it has been shown that adding a TCP header checksum is very useful in differentiating between congestion loss and corruption loss. With the modified TCP, receivers can explicitly indicate corruption of received packets by generating "Explicit Loss Notifications (ELNs)." This paper focuses on an analytical study of this modified TCP protocol. Derive a an expression for the probability of a receiver generating successful ELN, assuming a generic link layer protocol for data transfer over wireless links. Next, develop an analytical approach for TCP throughput evaluation under the modified scheme. Compared the throughput results obtained by analysis and simulation, and find very close agreement between the two sets. Also compare the performance of the modified scheme with the standard NewReno TCP, and find considerable improvement in data throughput over wireless links.

19 ref

006810   Goswami P;Sharma S (Graded Specialist (Physiology), Institute of Aerospace Medicine, IAF Bangalore) : In-flight evaluation of cooling efficiency of a modified environmental control system in a fighter upgrade aircraft. Indian J Aerospace Med 2007, 51(1), 15-24.

The Environmental Control System (ECS) of a fighter aircraft is designed on the principle of ram air cooling. This limits the capacity of on-board cooling facility especially during low level high speed flying,'in turn aggravating the cockpit heat load. An attempt to improve the cooling efficiency of the ECS of a fighter upgrade aircraft was made with some structural and design modifications of the fan and turbo-cooler assembly. This modified fan and turbo-cooler assembly (ModTC) required in-flight evaluation prior to its acceptance by the user. This study presents the findings of the flight trials of the ModTC fitted ac, and its comparison with unmodified fan and turbo-cooler assembly (UnmodTC) fitted aircraft. Wet Bulb Globe Temperature (WBGT) and dry bulb temperature (Tdb) were recorded to evaluate ModTC fitted ECS. A digital Heat Stress Monitor (HSM), for online computation and recording of the cockpit temperature, was installed at the gyro-gun sight inside the cockpit of the aircraft. Cockpit temperature recordings were averaged from 5 minutes of take-off till demist point, i.e. 7 minutes prior to landing, in low level sorties (200m, 0.6 M) with one aircraft fitted with ModTC and another with UnmodTC. The cockpit WBGT and Tdb recorded for ModTC were 29.58°C ± 0.42 and 27.44°C ± 0.94, respectively. In comparison, WBGT and Tdb for UnmodTC were 33.78°C ± 0.82 and 29.59°C ± 1.51, respectively. During the trials, the prevailing ambient conditions were 32.6° ± C/33.4°C Tdb and 29.26°C/30.66°C WBGT for ModTC/UnmodTC sorties, respectively. Comparative analysis of the modified fan and turbo-cooler assembly (ModTC) with the unmodified (UnmodTC) revealed that the modification did not improve the cockpit cooling efficiency. The deterioration in cockpit cooling efficiency was within acceptable limits for the fighter pilot for low level high speed sorties during the prevalent ambient conditions of the flight trials. The reduction in cooling power of the tested ECS, as compared to the unmodified one, could be attributed to the shortcomings in the modification of the design.

5 illus, 4 tables, 24 ref

006809   Gopinath U;Chandran D;Ansari S;Krishnan B; Panicker R;Natarajan R (NO, Centre for Materials for Electronics Technology, Thrissur-680 771, Email: rkg124@rediffmail.com) : Re-look at critical factors influencing single-phase formation of Ba₂ Ti₉O₂₀ microwave dielectrics. Bull Mater Sci 2007, 30(4), 333-8.

Focuses on critical factors limiting single-phase formation of Ba₂Ti₉O₂₀ (2:9). Apart from 2:9, other polytitanates that are richer in Ti or Ba could also be prepared as single-phase material without any stabilizing agent through chemical co-precipitation. 2:9 is found to be a stoichiometric compound and even 0.5% excess Ti or Ba leads to multiphase formation. Single-phase 2:9 could be achieved even through solid-state route without the addition of stabilizing agents using high purity raw materials. The results do not agree with existing hypotheses viz. diffusion, high surface and nucleation energy, potential barrier, nonstoichiometry etc as critical factors limiting formation of 2:9 as single-phase material.

6 illus, 3 tables, 23 ref

006808   Ghosh J;Chattopadhyay S K;Meikap A K; Chatterjee S K;Chatterjee P (Physics Dep, National Insitute of Technology, Durgapur-713 209, Email: jiten@cgcri.res.in) : Microstructure in vanadium-palladium alloys by X-ray diffraction technique. Bull Mater Sci 2007, 30(5), 447-54.

Present study considers microstructural characterization of vanadium-based palladium (V-Pd) alloys, which are widely used in marine environment due to their high corrosion resistance. The X-ray diffraction line profile analysis (XRDLPA) have been used to assess the microstructure in body centred cubic-(bcc) V-Pd alloys having four different nominal compositions in wt.%. X-ray diffraction line broadening analysis on V-Pd alloys has been performed by using different methods like the Warren-Averbach, double-Voigt and Rietveld methods. Finally microstructural defect parameters such as domain size (D), r.m.s. microstrain (ξ²)¹/2, twin fault (β), spacing fault (αξ) and deformation stacking fault (α) were evaluated in these alloys by Fourier line shape analysis using Rietveld method in which the X-ray diffraction profiles of these alloys were described by the pseudo-Voigt function to fit the experimental data. From analysis it has been observed that twin fault, β, and the spacing fault, αξ, are totally absent in these bcc alloy systems because the twin fault, β, has been observed to be either negative or very small (within experimental error limit) for these alloy systems and the spacing fault, αξ, appears to be negative. This analysis also revealed that the deformation stacking fault, α, is significantly present in this alloy system and increases with Pd content.

4 illus, 7 tables, 21 ref

006807   Gaur D;Bharati T;Dubey K K (Chief Research Officer & Senior Advisor (Aviation Medicine), Institute of Aerospace Medicine, IAF, Bangalore) : Semi-closed capsular ejection revisited: is it too late to modify an old aircraft?. Indian J Aerospace Med 2007, 51(1), 1-9.

In the IAF, MiG 21 T-77 is the only fighter aircraft that has a semi-closed ejection. The Original Equipment Manufacturer (OEM) laid down 94.0 cm as the maximum acceptable sitting height compatible with the aircraft, since the canopy slides over a metallic plate that may come in contact with the pilot's helmet when simulating the ejection sequence in encapsulation trials on ground and could be expected during actual ejection, as well. Therefore this study was carried out to re-define the sitting height limitations for aircrew to fly this aircraft. This was done specially in view of the new Light Weight Integrated Helmets (LWIH) currently in use by the fleet; and was thought to add more to the sitting height of the aircrew vis-a-vis the old ZSH-3 Helmet. Sitting height measurements of 11 subjects were taken with three different helmet types: LWIH of two different makes and ZSH-3. This was followed by cockpit and encapsulation trials, simulating the ejection sequence on ground. Trials were also conducted for an aircrew who had recently made a successful ejection from the aircraft. Encapsulation trials were repeated after removal of seat headrest cushion when it was noticed that this was contributing to worsening of posture and jeopardising safe encapsulation for aircrew with borderline sitting heights. The results of this study are discussed in detail. It was concluded that minor variations in sitting height on account of different helmets do not appear to worsen safe encapsulation on ground. Replacing the existing thick seat headrest cushion with a thinner one appears to be a logical modification to improve aircrew-aircraft compatibility. Aircrew with borderline sitting heights should be made aware of dynamics of the ejection process that ensures safe encapsulation during actual ejection.

6 tables, 7 ref

006806   Garg N K;Hassan Q (Civil Engineering Dep, Indian Institute of Technology Delhi, New Delhi-110 016, Email: nkgarg123@yahoo.com) : Alarming scarcity of water in India. Curr Sci 2007, 93(7), 932-41.

In this article the assessment of utilizable water resources of India, based on various studies by the government, has been reviewed and analysed. The analysis yields that the utilizable water resources are overestimated in various studies, ranging from 66% to 88%. Authors have estimated the utilizable water resources as 668 billion cubic metre (BCM) against 1110 BCM of CWC, 1209 to 1255 BCM of NCIWRDP and 1122 BCM of the National Water Policy of India. The consequence will be alarming as the projected demand of even 897 BCM, corresponding to low demand scenario, cannot be met even after full development of utilizable water resources. The analysis also revealed that almost all the basins would become water-deficit, and raises a big question about the availability of water through inter-basin transfer. It is also shown that the groundwater has already been overexploited as far back as 1997-98. Therefore, contrary to the previous studies like those of NCIWRDP, CWC, etc., water scarcity is alarming and calls for urgent action before it becomes unmanageable.

4 tables, 10 ref

006805   Erdem Imrak C;Gerdemeli I (Mechanical Engineering Dep, Istanbul Technical Univ, Gumussuyu, TR-34437, Istanbul, Turkey, Email: imrak@itu.edu.tr) : Problem of isotropic rectangular plate with four clamped edges. Sadhana 2007, 32(3), 181-6.

The examination of the exact solution of the governing equation of the rectangular plate is important for many reasons. This report discusses an exact solution of the governing equation of an isotropic rectangular plate with four clamped edges. A numerical method for clamped isotropic rectangular plate under distributed loads and an exact solution of the governing equation in terms of trigonometric and hyperbolic function are given. Finally, an illustrative example is given and the results are compared with those reported earlier. This method is found to be easier and effective. The results show reasonable agreement with other available results, but with a simpler and practical approach.

1 illus, 1 table, 14 ref

006804   Deshpande S K;Shrikhande V K;Jogad M S;Goyal P S;Kothiyal G P (Technical Physics & Prototype Engineering Div, UGC-DAE Consortium for Scientific Research, Mumbai Centre, R5 Shed, Bhabha Atomic Research Centre, Mumbai-400 085, Email: skdesh@barc.gov.in) : Conductivity of lithium zinc silicate glasses with varying lithium contents. Bull Mater Sci 2007, 30(5), 497-502.

The electrical conductivity of lithium zinc silicate (LZS) glasses with composition, (SiO₂)_0.527 (Na₂O)_0.054(B₂O₃)_0.05(P₂O₅)< v>0.029(ZnO)_0.34-x(Li₂O)_x (x = 0.05, 0.08, 0.11, 0.18, 0.21, 0.24 and 0.27), was studied as a function of frequency in the range 100 Hz-15 MHz, over a temperature range from 546-637-K.The a.c. conductivity is found to obey Jonscher's relation. The d.c. conductivity (σ_d.c) and the hopping frequency (ω_n), inferred from the a.c. conductivity data, exhibit Arrhenius-type behaviour with temperature. The electrical modulus spectra show a single peak, indicating a single electrical relaxation time, T, which also exhibits Arrhenius-type behaviour. Values of activation energy derived from σ_d.c, ω_n, and τ are almost equal within the experimental error. It is seen that σ_d.c. and ω_n, increase systematically with Li₂O content up to 21 mol% and then decrease for higher Li₂O content, indicating a mixed alkali effect caused by mobile Li⁺ and Na⁺ ions. The scaling behaviour of the modulus suggests that the relaxation process is independent of temperature but depends upon Li⁺ concentration.

16 illus, 3 tables, 34 ref

006803   Chen Z H;Chang Z C;Lin C B (Mechanical and Electro-mechanical Engineering Dep, Tamkang Univ, Tamsui, Taipei County, Republic of China, Email: cblin@mail.tku.edu.tw) : Macrovoids formation and light scattering of PMMA. Bull Mater Sci 2007, 30(4), 365-78.

After desorption of PMMA with saturated methanol and ethanol and then desorption by distilled water, the macrovoids are formed because of the phase inversion. The macrovoids on the surface of the specimens are larger and more numerous than those in the bulk. The macrovoids are likely to be closed type, if the hydrolysis temperature is lower. On the other hand, if the hydrolysis temperature is higher, the macrovoids are likely to be open-type. Due to the formation of macrovoids, smaller than visible wavelengths, the light will disperse, and therefore, reduces the transmittance of the specimens. The transmittance is decreased when the hydrolysis temperature and hydrolysis time are increased. Furthermore, it is much clearer when ethanol is used as solvent than methanol. The scattered intensity of the specimens after hydrolysis is inversely proportional to the visible wavelength with an exponent, n, in the range 0.04-2.83 for methanol and 0.02-0.21 for ethanol.

18 illus, 3 tables, 9 ref

006802   Bhat R V;Madhyastha M N (NO, Centre for Science, Society and Culture, M11, Kakateeyanagar, Habshiguda, Hyderabad-500 007, Email: mattu@dataone.in) : Preserving the heritage of mattu gulla - a variety of brinjal unique to Udupi District. Curr Sci 2007, 93(7), 906.

006801   Basavakumar K G;Mukunda P G;Chakraborty M (Mechanical Engineering Dep, Sri Bhagwan Mahavir Jain College of Engineering, Bangalore-562 112, Email: ganukb@rediffmail.com) : Effect of melt treatment on microstructure and impact properties of Al-7Si and Al-7Si-2.5 Cu cast alloys. Bull Mater Sci 2007, 30(5), 439-45.

The microstructures and impact toughness of Al-7Si and AI-7Si-2.5Cu cast alloys were studied after various melt treatments like grain refinement and modification. The results indicate that combined grain refined and modified Al-7Si-2.5Cu alloys have microstructures consisting of uniformly distributed α-Al grains, interdendritic network of fine eutectic silicon and fine CuAl₂ particles in the interdendritic region. These alloys exhibited improved impact toughness in as cast condition when compared to those treated by individual addition of grain refiner or modifier. The improved impact toughness of Al-7Si-2.5Cu alloys are related to breakage of the large aluminum grains and uniform distribution of eutectic silicon and fine CuAl₂ particles in the interdendritic region resulting from combined refinement and modification. This paper attempts to investigate the influence of microstructural changes in the Al-7Si and Al-7Si-2.5Cu cast alloys by grain refinement, modification and combined action of both on the impact toughness.

3 illus, 2 tables, 13 ref

006800   Basavakumar K G;Mukunda P G;Chakraborty M (Mechanical Engineering Dep, Sri Bhagwan Mahavir Jain College of Engineering, Bangalore-562 112, Email: ganukb@rediffmail.com) : Influence of melt treatments and polished CVD diamond coated insert on cuting force and surface integrity in turning of Al-7Si and Al-7Si-2.5 Cu cast alloys. Bull Mater Sci 2007, 30(5), 427-37.

The microstructures, machinability and surface characteristics of Al-7Si and Al-7Si-2.5Cu cast alloys were studied after various melt treatments like grain refinement and modification. The results indicate that combined grain refined and modified Al-7Si-2.5Cu cast alloys have microstructures consisting of uniformly distributed α-Al grains, eutectic AI-silicon and fine CuAl₂ particles in the interdendritic region. These alloys exhibited better machinability and surface characteristics in the cast condition compared with the same alloy subjected to only grain refinement or modification. Performances of the turning inserts (uncoated and polished CVD diamond coated) were evaluated in machining AI-7Si and Al-7Si-2-5Cu cast alloys under dry environment using a lathe. The polished CVD diamond coated insert outperformed the uncoated cutting insert which suffered from sizeable edge buildup leading to higher cutting force and poor surface finish. The polished CVD diamond coated insert shows a very small steady wear without flaking of the diamond film during cutting. This paper attempts to investigate the influence of grain refinement, modification and combined action of both on the microstructural changes in the AI-7Si and Al-7Si-2-5Cu cast alloys and their machinability and surface finish when different turning inserts are used.

9 illus, 3 tables, 12 ref

005622   Vasudevan R;Saravanavel S;Rajasekaran S; Thirunakkarasu D (Chemistry Dep, Thiagarajar College of Engineering, Madurai) : Utilisation of waste plastics in construction of flexible pavement. Indian Highw 2006, 34(7), 5-20.

The studies on the use of polymer-modefied bitumen (PMB) for flexible pavement are being carried out by different schools. Virgin & recycled polymers are being used for these studies. Use of desposed plastic waste is the need of the hour. The studies on the thermal behaviour and binding property of the molten plastic blend and its properties to find the suitability of the blend for road construction. The blend is almost to PMB. But when higher percentage of plastic waste was used, the polymer got separated from the blend. A modified technique was developed and the stone aggregate was coated with molten plastics and the plastic waste coated aggregate (PCA) was used as the raw material for flexible construction. PCA showed better binding property. It had less wetting property. Its voids were much less. The sample showed higher Marshall Stability value. The roads laid using PCA are performing well. A detailed study is presented below.

19 tables, 21 ref

005621   Uppal R (NO, , M/s Suvirs (Sales) Pvt. Ltd., Chandigarh) : Role of adhesion agents in road construction. Indian Highw 2006, 34(11), 39-41.

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005620   Tare V;Nrupesh K M (Civil Engg. & App. Mech. Dep, , SGSITS, Indore) : Overlay alternatives of flexible pavements. Indian Highw 2006, 34(12), 41-7.

Pavements are subjected to severe conditions of stresses and weathering effects from the day they are constructed and opened to traffic. Due to heavy loads and environmental factors all the components of the pavements structure get disturbed, thus causing deterioration which accumulated with the passage of time, causing failure to the pavement. To make the pavements ready to serve the traffic safely, comfortably and efficiently at a reasonable cost, there is every need to maintain the pavements periodically. Here comes the question when, where and what kind of the improvements are needed to extend the life of the pavement. A variety of rehabilitation techniques have been developed for the distressed pavements which are dealt

1 illus, 8 tables, 12 ref

005619   Stalin V K;Murugesan R;Babu P A (Civil Engineering, Anna Univ, Chennai) : Crushed sand in cement concrete pavement construction. Indian Highw 2006, 34(12), 49-55.

The studies available on the use of crushed sand in large quantity for engineering applications like roads, embankments, reclamation of coastal regions etc., are very limited. In this paper, an attempt made in the completed project "Mumbai - Pune Expressway package-1 The Ghat Portion" to replace conventional sand with crushed sand is discussed and conclusions are drawn.

3 illus, 3 tables, 17 ref

005618   Srikant Varma P;Narayanan G (Electrical Engineering Dep, Indian Institute of Science, Bangalore-560 012, Email: contact_verma@rediffmail.com) : Space vector PWM as a modified from of sine-triangle PWM for simple analog or digital implementation. IETE J Res 2006, 52(6), 435-49.

Conventional space vector PWM (CSVPWM) has the advantages of yielding up to 15% higher fundamental line-side voltage for a given DC bus voltage and also less harmonic distortion in line currents over sine-triangle PWM (SPWM). However, no analog implementation of CSVPWM is possible in its traditional form. Digital implementation of CSVPWM is also more complex than that of SPWM. Analyses the two techniques. The analysis establishes that CSVPWM can be viewed as a modified form of SPWM, and leads to a simple method to implement CSVPWM. The simplified method does not require evaluation of trigonometric functions, look-up tables, sector identification etc. An existing line of products employing SPWM can easily be upgraded to exploit the benefits of CSVPWM. The work serves to unify the understanding of triangle-comparison based PWM and space vector based PWM techniques. The work is of tutorial value to students and engineers.

11 illus, 5 tables, 13 ref

005617   Sinha V K (NO, , Mosrt&H on deputation, Indian Roads Congress, New Delhi) : Need to induct new materials, techniques in construction, maintenance and operation of highways. Indian Highw 2006, 34(11), 19-22.

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005616   Singla B S (NO, , Superintending Engineer (Roads), Haryana PWD (B&R)) : Quality control in bituminous works by computerisation. Indian Highw 2006, 34(11), 43-5.

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