Showing papers by "Indian Institute of Technology Guwahati published in 2006"
TL;DR: A survey of the literature related to dynamic analyses of flexible robotic manipulators has been carried out in this article, where both link and joint flexibility are considered in this work and an effort has been made to critically examine the methods used in these analyses, their advantages and shortcomings and possible extension of these methods to be applied to a general class of problems.
791 citations
TL;DR: Observations indicated that Ag NPs, above a certain concentration, not only were bactericidal but also were found to reduce the sizes of treated bacteria in comparison to untreated ones.
Abstract: Recombinant Escherichia coli (E. coli) bacteria expressing green fluorescent protein (GFP) was used as a model system to investigate the antimicrobial activities of Ag nanoparticles (NPs). A convenient in situ method of Ag NP synthesis using sodium borohydride, in the bacterial growth medium, was developed to produce preformed NPs for the study. Fluorescence spectroscopic and microscopic techniques allowed rapid detection of time-dependent changes in bacterial growth as well as fluorescence characteristics in the presence of Ag NPs. In addition, X-ray diffraction, UV-vis spectroscopic, and transmission electron microscopic measurements were carried out to understand the effect of Ag NPs on the bacteria. Our observations indicated that Ag NPs, above a certain concentration, not only were bactericidal but also were found to reduce the sizes of treated bacteria in comparison to untreated ones. Cell lysis of Ag NP-treated bacteria was suggested by the increased GFP fluorescence obtained in the medium. In vitro DNA-Ag NP interaction was detected by spectrophotometric analysis. However, electrophoresis studies indicated no direct effect of Ag NPs on DNA or protein profiles.
416 citations
TL;DR: In this paper, a three-bladed rotor system has been tested in a low speed wind tunnel, and its performance has been compared with conventional semicircular blades (with twist angle of 0°) on the basis of starting characteristics, static torque and rotational speed.
248 citations
TL;DR: The medicinal plants used by the people of Assam for curing different skin ailments and for cosmetics ranges from the enhancement of skin colour, hair care, removal of ugly spots, colouring of nails, palms, and teeth, but many of the plant preparations used for enhancing beauty were also applied for therapeutic use.
236 citations
TL;DR: The proposed method for prosody (pitch and duration) modification using the instants of significant excitation of the vocal tract system during the production of speech is compared with linear prediction pitch synchronous overlap and add (LP-PSOLA) method.
Abstract: Prosody modification involves changing the pitch and duration of speech without affecting the message and naturalness. This paper proposes a method for prosody (pitch and duration) modification using the instants of significant excitation of the vocal tract system during the production of speech. The instants of significant excitation correspond to the instants of glottal closure (epochs) in the case of voiced speech, and to some random excitations like onset of burst in the case of nonvoiced speech. Instants of significant excitation are computed from the linear prediction (LP) residual of speech signals by using the property of average group-delay of minimum phase signals. The modification of pitch and duration is achieved by manipulating the LP residual with the help of the knowledge of the instants of significant excitation. The modified residual is used to excite the time-varying filter, whose parameters are derived from the original speech signal. Perceptual quality of the synthesized speech is good and is without any significant distortion. The proposed method is evaluated using waveforms, spectrograms, and listening tests. The performance of the method is compared with linear prediction pitch synchronous overlap and add (LP-PSOLA) method, which is another method for prosody manipulation based on the modification of the LP residual. The original and the synthesized speech signals obtained by the proposed method and by the LP-PSOLA method are available for listening at http://speech.cs.iitm.ernet.in/Main/result/prosody.html.
188 citations
TL;DR: The speaker recognition studies on NIST 2002 database demonstrates that even though, the recognition performance from the excitation information alone is poor, when combined with evidence from vocal tract information, there is significant improvement in the performance.
170 citations
TL;DR: In this paper, an investigation of CO 2 absorption into aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA) is presented.
158 citations
TL;DR: These methods include minimization or elimination of viral genes, retargeting of vector to the tissue of interest, and generation of immunocompromised recombinant vectors that lead to safer use of Ad vector systems that improve persistence of transgene expression.
Abstract: Gene therapy is a promising tool for treatment of the human diseases that cannot be cured by rational therapies, and its primary success depends on suitable vectors to deliver therapeutic genes. Adenoviruses (Ads) are among the most commonly used vectors for gene therapy, second only to retroviruses. During the last decade, remarkable progress has been made in the development of Ad vectors and in the understanding of the toxicity related to the Ad vector system. Ad vector has certain advantages such as high transduction efficiency for different quiescent and dividing cell types and high levels of short-term expression to provide therapeutic benefits. However, researchers are facing the challenges associated with tissue-specific targeting of vectors and the vector-mediated immunogenicity. This review mainly focuses on the studies that have employed methods to improve Ad vectors and reduce viral toxicity for different applications. These methods include minimization or elimination of viral genes, retargeting of vector to the tissue of interest, and generation of immunocompromised recombinant vectors that lead to safer use of Ad vector systems that improve persistence of transgene expression. Moreover, the therapeutic applications of Ad vectors for liver-targeted gene therapy, suicide gene therapy, delivery of small interfering RNA, and production of recombinant vaccine under regulated conditions used in clinical trials are discussed.
134 citations
TL;DR: A knowledge-based system is developed for the prediction of surface roughness in turning process using neural networks and fuzzy set theory, which helps the user in understanding the behavior of the cutting process and to assess the effectiveness of the model.
Abstract: In the present work, a knowledge-based system is developed for the prediction of surface roughness in turning process. Neural networks and fuzzy set theory are used for this purpose. Knowledge acquired from the shop floor is used to train the neural network. The trained network provides a number of data sets, which are fed to a fuzzy-set-based rule generation module. A large number of IF–THEN rules are generated, which can be reduced to a smaller set of rules by using Boolean operations. The developed rule base may be used for predicting surface roughness for given process variables as well as for the prediction of process variables for a given surface roughness. The concise set of rules helps the user in understanding the behavior of the cutting process and to assess the effectiveness of the model. The performance of the developed knowledge-based system is studied with the experimental data of dry and wet turning of mild steel with HSS and carbide tools.
132 citations
TL;DR: A laboratory-scale study was conducted in batch mode to investigate the feasibility of using zero-valent magnesium (Mg(0), for removal of nitrate from aqueous solution, and reaction pH increased rapidly above ten and insignificant nitrate removal (7-16%) was achieved.
132 citations
TL;DR: In this paper, the authors have proposed a method for the computation of natural convection flow in a square enclosure with a centered internal conducting square block both of which are given an inclination angle.
TL;DR: In this article, a general formulation of the governing transient radiative transfer equation applicable to a 3-D Cartesian enclosure has been presented, and formulations have been presented for the three commonly used methods in the study of radiative heat transfer, viz., the discrete transfer method, the discrete ordinate method and the finite volume method.
TL;DR: A new, erbium-doped tellurite glass that has high glass transition temperature and channels show waveguiding at 1310 nm which is promising for the fabrication of integrated lasers and broadband amplifiers is made.
Abstract: We have made and characterized a new, erbium-doped tellurite glass that has high glass transition temperature. Addition of phosphate is found to increase the phonon energy. The peak emission cross section is 6 × 10-21 cm2 at 1537 nm and the fluorescence lifetime of the 4I13/2-4I15/2 transition is 4.1 ms. We have written 2-D channel waveguides in this glass using focused, 45-fs pulses from an amplified Ti:sapphire laser at different laser energies and writing speeds. Migration of atoms towards the periphery of the waveguides occurs, leading to refractive index changes. Channels show waveguiding at 1310 nm which is promising for the fabrication of integrated lasers and broadband amplifiers.
TL;DR: In this paper, the Vyazovkin model-free approach is applied to study non-isothermal decomposition kinetics of waste PET samples using various temperature integral approximations such as Coats and Redfern, Gorbachev, and Agrawal and Sivasubramanian approximation and direct integration.
TL;DR: Copper(II) complex 1 selectively catalyzes the oxidation of primary alcohols to aldehydes in high yields by atmospheric oxygen in the presence of TEMPO.
TL;DR: In this article, a two-degree-of-freedom (2dof) model comprising nonlinear delay differential equations (DDEs) is analyzed for self-excited oscillations during orthogonal turning.
TL;DR: The proposed Wavelet threshold based ECG signal compression technique using uniform scalar zero zone quantizer (USZZQ) and Huffman coding on differencing significance map (DSM) achieves the required compression ratio with less reconstruction error for GSM-based cellular telemedicine system.
TL;DR: In this paper, the authors presented explicit forms of nonadiabatic coupling (NAC) elements of nuclear Schrodinger equation (SE) for a coupled three-state electronic manifold in terms of mixing angles of real electronic basis functions.
Abstract: We present explicit forms of nonadiabatic coupling (NAC) elements of nuclear Schrodinger equation (SE) for a coupled three-state electronic manifold in terms of mixing angles of real electronic basis functions. If the adiabatic-diabatic transformation (ADT) angles are the mixing angles of electronic bases, ADT matrix transforms away the NAC terms and brings diabatic form of SE. ADT and NAC matrices are shown to satisfy a curl condition with nonzero divergence. We have demonstrated that the formulation of extended Born-Oppenheimer (EBO) equation from any three-state BO system is possible only when there exists a coordinate-independent ratio of the gradients for each pair of mixing angles. On the contrary, since such relations among the mixing angles lead to zero curl, we explore its validity analytically around conical intersection(s) and support numerically considering two nuclear-coordinate-dependent three surface BO models. Numerical calculations are performed by using newly derived diabatic and EBO equations and expected transition probabilities are obtained.
TL;DR: Sinusoidal features perform better compared to the linear prediction and cepstral features in recognizing the emotions in a speech signal.
Abstract: In this paper, a sinusoidal model has been proposed for characterization and classification of different stress classes (emotions) in a speech signal. Frequency, amplitude and phase features of the sinusoidal model are analyzed and used as input features to a stressed speech recognition system. The performances of sinusoidal model features are evaluated for recognition of different stress classes with a vector-quantization classifier and a hidden Markov model classifier. To find the effectiveness of these features for recognition of different emotions in different languages, speech signals are recorded and tested in two languages, Telugu (an Indian language) and English. Average stressed speech index values are proposed for comparing differences between stress classes in a speech signal. Results show that sinusoidal model features are successful in characterizing different stress classes in a speech signal. Sinusoidal features perform better compared to the linear prediction and cepstral features in recognizing the emotions in a speech signal.
TL;DR: A simple identification method based on relay feedback test for stable and unstable first order plus time delay (FOPDT) processes and a two degree of freedom proportional-integral–proportional-derivative (PI–PD) controller based on the loop phase margin and gain margin criteria is proposed.
TL;DR: A new quadrature scheme has been suggested that is a simple one and does not involve complicated mathematics for determination of direction cosines and weights and satisfies all the required moments.
Abstract: Evaluation of the radiative component in heat-transfer problems is often difficult and expensive. To address this problem, in the recent past, attention has been focused on improving the performance of various approximate methods. Computational efficiency of any method depends to a great extent on the quadrature schemes that are used to compute the source term and heat flux. The discrete ordinate method (DOM) is one of the oldest and still the most widely used methods. To make this method computationally more attractive, various types of quadrature schemes have been suggested over the years. In the present work, a new quadrature scheme has been suggested. The new scheme is a simple one and does not involve complicated mathematics for determination of direction cosines and weights. It satisfies all the required moments. To test the suitability of the new scheme, four benchmark problems were considered. In all cases, the proposed quadrature scheme was found to give accurate results.
TL;DR: Various design parameters of a CPE process have been estimated by developing correlations for dye solubilization and fractional coacervate phase volume with the operating conditions by studying the effects of different operating parameters on extraction of both dye and surfactant.
TL;DR: In this paper, the authors extended the discrete transfer method (DTM) to the analysis of radiative heat transfer in a variable refractive index participating medium, where the participating medium was assumed to be in radiative equilibrium.
Abstract: Application of the discrete transfer method (DTM) has been extended to the analysis of radiative heat transfer in a variable refractive index participating medium. To validate the DTM formulation, radiative heat transfer in an absorbing, emitting and isotropically scattering planar medium was considered. The participating medium was assumed to be in radiative equilibrium. For both constant and variable refractive indices of the medium, the DTM results were compared with those available in the literature. The DTM was found to provide accurate results.
TL;DR: This work mimics the cytosolic crowding in vitro, using dextrans and Ficolls, for the first time in a variety of sizes ranging from 15 to 500 kDa, in a concentration range 0-30% w/w and indicates that larger dextran apparently reduce the frequency of enzyme substrate encounter.
Abstract: The cell cytosol is crowded with macromolecules such as proteins, nucleic acids, and membranes. The consequences of such crowding remain unclear. How is the rate of a typical enzy- matic reaction, involving a freely diffusing enzyme and substrate, affected by the presence of macro- molecules of different sizes, shapes, and concentrations? Here, we mimic the cytosolic crowding in vitro, using dextrans and Ficolls, for the first time in a variety of sizes ranging from 15 to 500 kDa, in a concentration range 0-30% w/w. Alkaline phosphatase-catalyzed hydrolysis of p-nitrophenyl phosphate (PNPP) was chosen as the model reaction. A pronounced decrease in the rate with increase in fractional volume occupancy of dextran is observed for larger dextrans (200 and 500 kDa) in contrast to smaller dextrans (15-70 kDa). Our results indicate that, at 20% w/w, smaller dextrans (15-70 kDa) reduce the initial rate moderately (1.4- to 2.4-fold slowing), while larger dextrans (>200 kDa) slow the reaction considerably (>5-fold). Ficolls (70 and 400 kDa) slow the reaction moderately (1.3- to 2.3-fold). The influence of smaller dextrans was accounted by a combination of increase in viscosity as sensed by PNPP and a minor offsetting increase in enzyme activity due to crowding. Larger dextrans apparently reduce the frequency of enzyme substrate en- counter. The reduced influence of Ficolls is attributed to their compact and quasispherical shape, much unlike the dextrans. # 2006 Wiley Periodicals, Inc. Biopolymers 83: 477-486, 2006 This article was originally published online as an accepted preprint. The ''Published Online'' date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
TL;DR: Bromodimethylsulfonium bromide has been found to be an effective and regioselective reagent for α-monobromination of β-keto esters and 1,3-diketones.
Abstract: Bromodimethylsulfonium bromide has been found to be an effective and regioselective reagent for α-monobromination of β-keto esters and 1,3-diketones. A wide variety of β-keto esters and 1,3-diketones undergo chemoselective α-monobromination with excellent yields at 0−5 °C or room temperature. The notable advantages of this protocol are no need of chromatographic separation, use of less hazardous reagent than molecular bromine, and no added base, Lewis acid, or other catalyst.
TL;DR: In this article, a back propagation neural network (BPNN) was used to predict the flank wear of a drill bit in mild steel work-piece by high speed steel (HSS) drill bits over a wide range of cutting conditions.
TL;DR: The densities and viscosities of aqueous blends of piperazine (PZ) with N-methyldiethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) have been measured at (288, 293, 298, 303, 308, 313, 318, 323, 328, and 333) K.
Abstract: The densities and viscosities of aqueous blends of piperazine (PZ) with N-methyldiethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) have been measured at (288, 293, 298, 303, 308, 313, 318, 323, 328, and 333) K. The total amine mass fraction in all solutions was kept at 30 % in view of recent interest in using concentrated amine solutions in gas treating. Correlations for the density and viscosity of the ternary mixtures are presented as a function of temperature and amine concentration.
TL;DR: In this paper, a coupled tuned mass dampers (CTMD) was proposed to control the asymmetric buildings with respect to their lateral and torsional vibrations. But, the authors did not consider the effect of asymmetry in both plan and elevation.
Abstract: An arrangement of tuned mass dampers, termed coupled tuned mass dampers (CTMDs) has been introduced, where a mass is connected by translational springs and viscous dampers in an eccentric manner. The CTMD has coupled modes of lateral and rotational vibration, which have been utilized to control coupled lateral and torsional vibrations of asymmetric buildings. An efficient control strategy has been presented in this context to control displacements as well as acceleration responses of asymmetric buildings having asymmetry in both plan and elevation. The building is idealized as a simplified three-dimensional model with two translational and a rotational degrees of freedom for each floor. The principles of rigid body transformation have been incorporated to account for eccentricity between center of mass and center of rigidity. A nondominated sorting genetic algorithm (GA) has been used for solving the multi-objective optimization problem. Tuning of optimum locations of TMDs and their parameters have been done from the multiple pareto-optimal solutions obtained simultaneously. Comparative studies of performance of CTMD with conventional TMDs and bi-directional TMDs have been presented. It has been observed that CTMDs are more effective and robust in controlling coupled lateral and torsional vibrations of asymmetric buildings. The optimal locations have been observed to be reasonably compact and practically implementable for CTMDs. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: Surfactant-based separation of toxic eosin dye is studied to estimate the potential of micellar enhanced ultrafiltration (MEUF) using cetyl(hexadecyl) pyridinium chloride (CPC) as the cationic surfactant.
TL;DR: In this article, a combined system consisting of three sequentially arranged suspended growth reactors under anaerobic, anoxic and aerobic environments were used to treat a synthetic wastewater containing phenol, cyanide, thiocyanate and ammonia.