Showing papers by "Delhi Technological University published in 2005"

Dispersion Properties of Photonic Crystal Fiber: Comparison by Scalar and Fully Vectorial Effective Index Methods

Abstract: The development of analysis and simulation of propagation characteristics of photonic crystal fiber (PCF) using scalar and fully vectorial effective index methods are described. As a result, we report how the fundamental space filling mode, guided mode and dispersion of the PCF depends on its structural parameters like its normalized air hole spacing, center-to-center spacing of the air holes in the photonic crystal or pitch and radius of the unit cell. Normalized frequency parameter Veff as a function of normalized wavelength for various relative air hole sizes is obtained to estimate the dispersion characteristics of PCF. It is observed that wavelength of zero dispersion, ultraflattened dispersion response and high negative dispersion remarkably differ from two different effective index methods.

A novel current controlled current mode universal filter: SITO approach

Abstract: A novel electronically tunable single-input three-output (SITO) universal filter employing three current controlled conveyors and two grounded capacitors is presented. The proposed filter offers the following advantageous features: low input impedance and high output impedance- a desirable property of current mode filters, realization of low pass, band pass, high pass, notch and all pass signals from the same configuration, no matching constraint, low sensitivity performance and use of grounded capacitors ideal for integration. The validity of the proposed filter is verified through PSPICE simulations.

Mixed dopant conducting polyaniline reusable blend for the detection of aqueous ammonia

Abstract: The present paper reports about the conducting polyaniline-poly(acrylonitrile–butadiene–styrene) blend films as a sensor material for aqueous ammonia. The change in resistance value of these blend films on exposure to different concentrations of aqueous ammonia shows its utility as a sensor material. The conducting blend films on exposure to 10−4, 10−5 and 10−6N aqueous ammonia show a well-defined response behaviour and this aspect has been utilized in designing the ammonia sensor.

Design of ultra compact polarization splitter based on the complete photonic band gap

Abstract: A novel design of polarization splitter based on the complete photonic band gap has been proposed in this paper. The proposed Photonic Band Gap (PBG) polarization splitter is formed by two photonic crystal waveguides composed of dielectric rods in air in honeycomb structure for which complete photonic band gap is obtained using the plane wave expansion (PWE) method. The splitting properties (i.e. coupling length, extinction ratio and insertion loss) of PBG polarization splitter have numerically been investigated using the finite difference time domain (FDTD) method. It has been shown that polarization splitter of length as small as 32 μm can be designed at λ=1.55 μm. The proposed polarization splitter offers a large bandwidth of 120 nm.

Ultimate bearing capacity of footings on coal ash

Abstract: Coal ash is recognized as an alternative fill material to the conventional natural soils near a coal fired thermal power station where its large deposits are available. This paper presents experimental investigations on footings on coal ash subjected to loads. A series of laboratory model tests on varying sizes of footings were conducted. The conventional bearing capacity evaluation methods applied for natural soils do not consider progressive failure. These effects are explained based on the non-linear strength behavior of the granular soil and occurrence of progressive failure. The classical bearing capacity theory was applied in relation to the relative dilatancy of coal ash to describe this phenomenon. Few novel observations presented here show that the extent of progressive failure of ash fills is a compressed function of material characteristics of the ash, size and depth of footing and the settlement ratio.

Effect of nano‐barium titanate on the mechanical, electrical and solubility performance of ferrite‐filled poly(ether ether ketone) composites

Abstract: Ferrite and nano-barium titanate reinforced poly(ether ether ketone) (PEEK) composites were made by compression moulding technology. The effects of reinforcement of the ferrite and nano-barium titanate on the PEEK matrix were studied with the aim assessing its potential as a radar-absorbing structural material (RASM). With an increase in the percentage filling of ferrite in the PEEK matrix, the specific gravity, hardness, tensile and flexural moduli, brittleness, dielectric constant, loss tangent and reflection losses were increased, while the tensile and flexural strengths, and elongation at break, were decreased. With increasing nano-barium titanate reinforcement in the ferrite-filled PEEK composites, the specific gravity, hardness, tensile and flexural strengths, tensile modulus and dielectric constant were comparatively increased, while the elongation at break, flexural modulus and loss tangent (marginally) were decreased. Reinforcement of the nano-barium titanate caused a comparatively marginal reduction in the loss tangent, although no effect on reflection losses was observed. The solubility resistance of the ferrite-filled PEEK composites was improved with reinforcement by the nano-barium titanate. Copyright © 2004 Society of Chemical Industry

A model of the static synchronous series compensator for the real time digital simulator

Abstract: This paper presents a detailed simulation model of the static synchronous series compensator for the real time digital simulator. The RTDS is a fully digital electromagnetic transients power system simulator that operates in real time and replaces the previous generation of network analyzers which were based on analog technology. It has been created specifically for real time power system simulation, utilizing advanced custom hardware and software technologies. The SSSC is a FACTS device which is based on the voltage source converter technology employing gate turn-off thyristors in the 2 level inverter which is coupled to a DC capacitor on one end and to the transmission line through a series transformer on the other. The model is verified for standard operational characteristics of the device in a simple 2 bus network and is prepared for further implementation in bigger and more complex networks

Graceful signed graphs: II. The case of signed cycles with connected negative sections

Abstract: In our earlier paper [9], generalizing the well known notion of graceful graphs, a (p, m, n)-signed graph S of order p, with m positive edges and n negative edges, is called graceful if there exists an injective function f that assigns to its p vertices integers 0, 1,,q = m + n such that when to each edge uv of S one assigns the absolute difference |f(u)-f(v)| the set of integers received by the positive edges of S is {1,2,,m} and the set of integers received by the negative edges of S is {1,2,,n} Considering the conjecture therein that all signed cycles Z k , of admissible length k ≥ 3 and signed structures, are graceful, we establish in this paper its truth for all possible signed cycles of lengths 0, 2 or 3 (mod 4) in which the set of negative edges forms a connected subsigraph

Interrelation of Scanning Electron Micrographs with Flexural Behavior of Ferrite and Nano-Barium Titanate Reinforced Poly-Ether-Ether-Ketone (PEEK) Composites

Abstract: The flexural behavior of ferrite filled poly-ether-ether-ketone (PEEK) composites, with and without reinforcement of nano-barium titanate, was studied and was corroborated through scanning electron microscopy (SEM). In this study, ferrite filled PEEK, and ferrite and nano-barium titanate reinforced PEEK composites were prepared. Ferrite filled PEEK composites showed reduction in flexural strength and increase in flexural modulus with the increase in ferrite content, whereas, with the reinforcement of nano-barium titanate, flexural strength increased and flexural modulus decreased at similar ferrite content. The SEM micrographs corroborated well with flexural behavior, as ferrite particles and smooth topographic surfaces of brittle fracture were evident in the samples having higher ferrite content in ferrite filled PEEK composites, whereas, typical yield pattern of crust and trough on fractured topographic surfaces of ferrite and nano-barium titanate, reinforced PEEK composites, was visible.

Regret analysis of sequential goal programming for multiobjective optimal power flows

Abstract: The ideal power system operation is achieved when various objectives like cost of generation, system transmission losses, environmental pollution etc. are simultaneously attained with minimum values. These cannot be handled by single objective techniques as the above three objectives may be conflicting in nature in certain domain. Therefore, multiobjective programming techniques have to be employed as these are capable of minimizing more than one objective simultaneously. In this paper, three objectives of multiobjective optimal power flow (MOPF) problem - cost of generation, system transmission losses, environmental pollution are considered and MOPF problem is attempted sequentially using sequential goal programming (SGP). Six strategies have been developed for IEEE 5, 14 and 30 bus systems. The optimal strategy has been identified by the power systems operator using regret analysis

Discussion of “Impact Stops on Vehicle Fuel Consumption and Emissions” by Hesham Rakha and Yonglian Ding

Abstract: A discussion of an article with the aforementioned title, published in this journal (Vol. 129, No. 1, January/February 2003), is presented. The discusser recognizes the effort of the author to systematically quantify the impact of vehicle stops and their associated levels of acceleration and deceleration on vehicle fuel consumption and emission rates. However, the discusser argues that a study using only instantaneous speed and acceleration levels as the input parameters has very limited field application. The discusser suggests several points that would have made the study more useful, including the consideration of: engine speed, feasible acceleration rate, differences between emissions from diesel and gasoline engines, roadway-related factors, and the variability of time spent on accelerating and decelerating.

Charge storage mechanism in vacuum deposited PVF films

Abstract: Thermally stimulated discharge current (TSD) behavior of vacuum deposited polyvinyl fluoride (PVF) films has been studied as a function of various polarization parameters such as field (1.0 × 103–14.0 × 103 V/cm), temperature (313–453 K), time (3.6 × 103–6.0 × 103 sec), electrode work function (copper, silver, aluminum and indium) and thickness (2000–10000 A). In a field dependent case the TSD spectra of PVF films show a single relaxation peak centered around 430 ± 1 K. The peak current, charge, peak position and activation energy associated with the peak depend strongly on the polarization parameters. The mechanism of origin of the relaxation peak has been attributed to the space charge polarization where the charge carriers injected at the electrode-polymer interface barrier are displaced at macroscopic distances and get subsequently trapped at trapping levels that are distributed in their activation energies and relaxation times.

A novel design of dispersion compensating Raman/two stage EDFA hybrid for amplification in L-band and U-band

Abstract: Dispersion compensating discrete Raman amplifier are known to open up new wavelength bands. However there is also the issue of wastage of Raman pump power. The length of dispersion compensating discrete Raman amplifier is decided to minimize the dispersion. Hence significant pump power is wasted. In this paper, a novel design of dispersion compensating Raman/ Two stage EDFA hybrid is reported which recycles the residual pump power from the dispersion compensating Raman and feeds this pump to the second stage of two stage EDFA. The first stage is remotely pumped from another laser source. Using this configuration, we have achieved an extremely large gain bandwidth of 117.5nm from 1582.5-1700nm with a 3dB ripple, has been achieved This amplifier topology while using minimum no of pump sources solves the twin problem of wastage of Raman pump power and providing amplification in U-band. We also performed the simulations of another topology in which a 5m long unpumped EDF was inserted between the first stage and second stage of the EDFA. The backward traveling Amplified Spontaneous Emission (ASE) from the second stage caused the pumping in the unpumped EDF thereby causing signal gain instead of loss. This topology further showed an enhancement in gain of 1-2 dB in the wavelength band of interest (1600-1700nm). The design issue in these topologies is the length of the EDF's. By suitably modeling these lengths, we can obtain appropriate gain profile.

Performance Analysis and Comparison of Trellis-coded and Turbo-coded Optical CDMA Systems

Abstract: In this paper, we have compared the performance of a Turbo coded and a Trellis coded optical code division multiple access (OCDMA) system. The comparison of the two codes has been accomplished by employing optical orthogonal codes (OOCs). The Bit Error Rate (BER) performances have been compared by varying the code weights of address codes employed by the system. We have considered the effects of optical multiple access interference (OMAI), thermal noise and avalanche photodiode (APD) detector noise. Analysis has been carried out for the system with and without double optical hard limiter (DHL). From the simulation results it is observed that a better and distinct comparison can be drawn between the performance of Trellis and Turbo coded systems, at lower code weights of optical orthogonal codes for a fixed number of users. The BER performance of the Turbo coded system is found to be better than the Trellis coded system for all code weights that have been considered for the simulation. Nevertheless, the Trellis coded OCDMA system is found to be better than the uncoded OCDMA system. We can thus conclude that Trellis coded OCDMA can be used in systems where decoding time has to be kept low, bandwidth is limited and high reliability is not a crucial factor as in local area networks. Also the system hardware is less complex in comparison to the Turbo coded system. Trellis coded OCDMA can be used without significant modification of the existing chipsets. Turbo coded OCDMA should however be employed in systems where high reliability is needed and bandwidth is not a limiting factor.

National water grid-its objectives and challenges

Abstract: (2005). NATIONAL WATER GRID-ITS OBJECTIVES AND CHALLENGES. ISH Journal of Hydraulic Engineering: Vol. 11, No. 2, pp. 158-161.

Generation of Excitation Signal in Voice Excited Linear Predictive Coding using Discrete Cosine Transform

Abstract: Methods involved to generate the excitation parameters and gain have been proposed that provide improvement over plain linear predictive coding (LPC) in terms of better speech reconstruction. DCT computation to transmit the excitation signal energy in initial few coefficients gives a better reconstruction of innovation signal at the receiver as compared to the primitive method of pitch estimation. Gain computation in terms of the root mean square (RMS) value of the voltage levels for each frame reduces the complexity involved as compared to plain LPC, where gain was calculated in terms of mean square error.

Modelling of local scour around rectangular submerged vanes

Abstract: In Eq. (7), it is seen that only Froudes' number of approach flow govern the maximum scour depth which appear to be independent of other parameters like bed sediments, vane inclination (used 40\" by authors), vane shape, size etc. Such equation developed for a particular vane inclination (40\") and a particular bed material should not be generalised. It is now almost universally accepted that the principal parameters governing local scour is the size of obstruction. Authors could have used the projected width of the vanes (size not indicated) normal to the flow as the etfective size of obstruction for computing scour, as in the case of local scour around piers developed by researchers like Breussers and Raudkivi ( 1991 ), Melville and Coleman (2000), Richardson and Davis ( 1995), Kothyari-Garde-Rangaraju ( 1991) etc., all of which clearly demonstrate that various parameters governing the local scour are

Discussion of “Reconstruction of the Building Infrastructure: Two Performance Prediction Models” by Mohamed Attalla, Tarek Hegazy, and Ralph Haas

Abstract: The discusser responds to an earlier article addressing the use of regression analysis and artificial neural networks to identify critical success factors in reconstruction projects. The discusser enumerates his reservations about the applicability of the methodology used to compare predictive performance.