Wyniki wyszukiwania - BazTech

1

Investigation of the Influence of Stretch on the Air Permeability of Knitted Fabric: Effect of Loop Length

Kumar V., Prakash C., Manigandan G., Sampath V. R.

Fibres & Textiles in Eastern Europe

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2021

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Vol. 29, no. 1 (145)

53--56

EN

Most of the time, a certain degree of stretch prominently and incrementally occurs in intimate wear, leisure wear, sportswear, medical textiles etc., during their action. Variations in the stretch gradient would definitely cause changes in the air permeability of knitted fabrics. The influence of variables such as loop length, the presence of an elastomeric component and fabric structure on the air permeability of cotton single jersey and pique knitted fabrics in a stretched state was critically analysed. In this work, changes in the air permeability of cotton jersey samples with and without elastomer were investigated and reported by keeping the samples in static up to an incremental stretch of 40% at a rate of 10% of the stretch gradient, in a dry relaxed state, wet relaxed state and fully relaxed state.

PL

W większości przypadków, podczas użytkowania odzieży rekreacyjnej, sportowej, medycznej itp. występuje pewien stopień rozciągnięcia. Wahania gradientu rozciągliwości powodują zmiany przepuszczalności powietrza dzianin. W pracy przeanalizowano wpływ zmiennych, takich jak: długość pętli, obecność składnika elastomerowego i rodzaju struktury na przepuszczalność powietrza dzianin bawełnianych typu single jersey i typu pique w stanie rozciągniętym. W pracy zbadano i odnotowano zmiany przepuszczalności powietrza w przypadku próbek dżerseju bawełnianego z elastomerem i bez elastomeru, utrzymując próbki w stanie statycznym do przyrostowego rozciągnięcia 40% z 10% gradientem rozciągania w stanie mokrym i suchym.

2

Flow behavior in weakly permeable micro-tube with varying viscosity near the wall

Gupta R. R., Kumar V., Chand S.

Polish Journal of Chemical Technology

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2017

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Vol. 19, nr 4

16--21

EN

Weakly permeable micro-tubes are employed in many applications involving heat and/or mass transfer. During these processes, either solute concentration builds up (mass transfer) or steep change in temperature (heat transfer) takes place near the permeable wall causing a change in the viscosity of the fluid. Results of the present work suggest that such change in viscosity leads to a considerable alteration in the flow behavior, and the commonly assumed parabolic velocity profile no longer exists. To solve the problem numerically, the equation of motion was simplified to represent permeation of incompressible, Newtonian fluid with changing viscosity through a micro-tube. Even after considerable simplification, the accuracy of the results was the same as that obtained by previously reported results for some specific cases using rigorous formulation. The algorithm developed in the present work is found to be numerically robust and simple so that it can be easily integrated with other simulations.

3

Ferrofluid flow due to a rotating disk in the presence of a non-uniform magnetic field

Bhandari A., Kumar V.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 2

273--283

EN

The flow of a ferrofluid due to a rotating disk in the presence of a non-uniform magnetic field in the axial direction is studied through mathematical modeling of the problem. Contour and surface plots in the presence of 10 kilo-ampere/meter, 100 kilo-ampere/meter magnetization force are presented here for radial, tangential and axial velocity profiles, and results are also drawn for the magnetic field intensity. These results are compared with the ordinary case where magnetization force is absent.

4

Eigen value approach to two dimensional problem in generalized magneto micropolar thermoelastic medium with rotation effect

Singh R., Kumar V.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 1

205--219

EN

In this study an eigen value approach has been employed to examine the mechanical force applied along with a transverse magnetic field in a two dimensional generalized magneto micropolar thermoelastic infinite space. Results have been obtained by treating rotational velocity to be invariant. Integral transforms have been applied to solve the system of partial differential equations. Components of displacement, normal stress, tangential couple stress, temperature distribution, electric field and magnetic field have been obtained in the transformed domain. Finally numerical inversion technique has been used to invert the result in the physical domain. Graphical analysis has been done to described the study.

5

Design and performance analysis of InP/InGaAsP-MMI based 1310/1550-nm wavelength division demultiplexer with tapered waveguide geometry

Chack D., Kumar V., Raghuwanshi S. K.

Opto-Electronics Review

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2015

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Vol. 23, No. 4

271-277

EN

The design and performance analysis of a 1310/1550-nm wavelength division demultiplexer with tapered geometry based on InP/InGaAsP multimode interference (MMI) coupler has been carried out. Wavelength response of demultiplexer of conventional MMI and tapered input and tapered output (tapered I/O) waveguides geometry of the MMI have been discussed. The demultiplexing function has been first performed by choosing a suitable refractive index of the guiding region and geometrical parameters such as the width and length of MMI structure have been achieved. Access width of tapered I/O waveguides have been adjusted to give a low insertion loss (IL) and high extinction ratio (ER) for the considered wavelengths of 1310 nm and 1550 nm. The total size of the demultiplexer has been significantly reduced over the existing MMI devices. Numerical simulations with finite difference beam propagation method are applied to design and optimize the operation of the proposed demultiplexer.

6

Response due to impulsive force in generalized thermomicrostretch elastic solid

Kumar V., Singh R.

International Journal of Applied Mechanics and Engineering

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2015

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Vol. 20, no. 3

487--502

EN

A two dimensional Cartesian model of a generalized thermo-microstretch elastic solid subjected to impulsive force has been studied. The eigen value approach is employed after applying the Laplace and Fourier transforms on the field equations for L-S and G-L model of the plain strain problem. The integral transforms have been inverted into physical domain numerically and components of normal displacement, normal force stress, couple stress and microstress have been illustrated graphically.

7

Studies on carcinogenic PAHs emission generated by vehicles and its correlation to fuel and engine types

Kumar V., Kothiyal N. C., Saruchi

Polish Journal of Chemical Technology

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2014

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Vol. 16, nr 1

48--58

EN

The objective of this study was to find major PAHs produced in ambient air from the automobile exhaust as a function of fuels (diesel, petrol, and biodiesel) and engine type qualitatively and quantitatively. The recovery range was found between 30% and 70%. The study was carried out on two, three, and four wheelers. Biodiesel samples tested in the study were synthesized indigenously from different starting raw materials and analyzed for PAHs concentration in the exhaust on a Honda genset (EBK 2000AC Model). Biodiesel samples were blended with diesel in different ratio (25:75, 35:65 and 45:55) to investigate the exhaust behavior. Biodiesel was blended with Diesel the concentration of almost all PAHs reduces in comparison to pure Diesel exhaust. B(a)A and B(a) P was the common PAH found in higher concentration in almost all fuels. FTIR results indicate esterification of vegetable oil and NMR results indicate a complete conversion of oils into biodiesel.

8

Interaction due to mechanical source in generalized thermo microstretch elastic medium

Singh R., Kumar V.

International Journal of Applied Mechanics and Engineering

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2014

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Vol. 19, no. 2

347--363

EN

The eigen value approach, following the Laplace and Hankel transformation has been employed to find a general solution of the field equations in a generalized thermo microstretch elastic medium for an axisymmetric problem. An infinite space with the mechanical source has been applied to illustrate the utility of the approach. The integral transformations have been inverted by using a numerical inversion technique to obtain normal displacement, normal force stress, couple stress and microstress in the physical domain. Numerical results are shown graphically.

9

A robust computational technique for a system of singularly perturbed reaction–diffusion equations

Kumar V., Bawa R. K., Lal A. K.

International Journal of Applied Mathematics and Computer Science

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2014

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Vol. 24, no. 2

387--395

EN

In this paper, a singularly perturbed system of reaction–diffusion Boundary Value Problems (BVPs) is examined. To solve such a type of problems, a Modified Initial Value Technique (MIVT) is proposed on an appropriate piecewise uniform Shishkin mesh. The MIVT is shown to be of second order convergent (up to a logarithmic factor). Numerical results are presented which are in agreement with the theoretical results.

10

E-Braille Documents: Novel Method For Error Free Generation

Wajid M., Kumar V.

Image Processing & Communications

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2014

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Vol. 19, no. 4

21--26

EN

Present manuscript proposes a technique for estimating the angle of rotation for a Braille document image which in turn will be used for aiding its automatic character recognition. The technique is based on maximizing number of null projection of the derived image vector. Results show that any amount of rotation transformed distortion can be nullified and thus leading to proper reading of imprinted Braille character pattern. The proposed methods have been successfully tested on manually written as well as computer generated Braille with rotation distortion.

11

Study of combined effects of sediment rheology and basement focusing in an unbounded viscoelastic medium using P-SV-wave finite-difference modelling

Narayan J.P., Kumar V.

Acta Geophysica

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2014

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Vol. 62, no. 6

1214--1245

EN

This paper consists of two parts. First, a fourth-order-accurate staggeredgrid finite-difference (FD) program for simulation of P-SV-wave in viscoelastic medium is presented. The incorporated realistic damping is based on GMB-EK-model. The accuracy of program is validated by comparing computed phase-velocity and quality-factors with same based on GMB-EK-model and Futterman’s relations. The second part of paper presents the combined effects of sediment damping and synclinal basement focusing (SBT) on ground motion. The results reveal SBT focusing, mode conversion and diffraction of incident waves. The response of elastic SBT model reveals an increase of spectral amplification with increasing frequency. The viscoelastic response of SBT model reveals that a particular frequency may get largest amplification for a particular set of values for damping, focal-length and distance from tip of the SBT. This frequency-dependent amplification may explain mysterious damage reported in some past earthquakes if predominantly amplified frequency matches natural frequency of damaged structures.

12

Computation of ground motion amplification in Kolkata megacity (India) using finite-difference method for seismic microzonation

Shiuly A, Kumar V, Narayan J.P.

Acta Geophysica

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2014

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Vol. 62, no. 3

425--450

EN

This paper presents the ground motion amplification scenario along with fundamental frequency (F0) of sedimentary deposit for the seismic microzonation of Kolkata City, situated on the world’s largest delta island with very soft soil deposit. A 4th order accurate SH-wave viscoelastic finite-difference algorithm is used for computation of response of 1D model for each borehole location. Different maps, such as for F0, amplification at F0, average spectral amplification (ASA) in the different frequency bandwidth of earthquake engineering interest are developed for a variety of end-users communities. The obtained ASA of the order of 3-6 at most of the borehole locations in a frequency range of 0.2510.0 Hz reveals that Kolkata City may suffer severe damage even during a moderate earthquake. Further, unexpected severe damage to collapse of multi-storey buildings may occur in localities near Hoogly River and Salt Lake area due to double resonance effects during distant large earthquakes.

13

Investigation on the Physical and Dimensional Properties of Single Jersey Fabrics made from Cotton Sheath - Elastomeric Core Spun

Kumar V., Sampath V. R.

Fibres & Textiles in Eastern Europe

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2013

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Vol. 21, no. 3 (99)

73--75

EN

In this study, the physical and dimensional properties of single jersey fabrics made from cotton / elastomeric core spun yarn were investigated. The main purpose of this paper was to investigate the suitability of cotton - spandex core spun yarn for circular knitting as an alternative for bare spandex feeding and the effect of stitch length variables on knitted fabric geometric quality attributes such as wale density, course density, stitch density and areal density under different states of relaxation. The results clearly indicate that the resulting yarn is highly suitable for circular knitting and change in stitch length values does not have any significant impact on wale density values. At the same time, the remaining geometric properties of the samples were found to be inversely proportional to the stitch length values uniformly at all the states of relaxation. Along with this, the ability of the samples to reach the dimensional equilibrium state after repeated cycles of washing and drying was also studied. It is evident from the results that all the three samples produced with ascending stitch length orders attained a perfect state of dimensional stability before five cycles of washing and drying, and also the sample knitted with the smallest stitch length value reached its equilibrium state in a quick time.

PL

Głównym celem badań była ocena możliwości zastosowania przy produkcji dzianin na maszynach cylindrycznych bawełnianych przędz rdzeniowych elastomerowych jako alternatywę dla stosowania gołych przędz elastomerowych. Badano również wpływ długości splotu na geometrie i jakość dzianin, w tym na gęstość rządków i kolumienek, gęstość splotów i gęstość powierzchniową przy rożnych stanach relaksacji. Uzyskane wyniki wyraźnie wskazują, że proponowana przędza nadaje się jak najbardziej do projektowanego zastosowania. Stwierdzono również, że zmiany długości splotu nie mają wyraźnego wpływu na gęstość kolumienkową. Jednocześnie stwierdzono, że geometryczne właściwości próbek są odwrotnie proporcjonalne do długości splotu. Badano również zdolność próbek do osiągnięcia geometrycznej równowagi po kolejnych powtarzanych cyklach prania i suszenia. Stwierdzono, że wszystkie wyprodukowane próbki uzyskiwały stabilność wymiarową przed piątym cyklem prania i suszenia, w tym również te, które miały najmniejszą długość splotu.

14

Thermo-mechanical deformation in magneto micropolar thermoelastic medium with modified Fourier and Ohm's law

Singh R., Kumar V.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 1

83-105

EN

The present investigation is concerned with a two dimensional problem in a magnetic micropolar thermoelastic half space, whose surface is subjected to thermo-mechanical sources in the presence of transverse magnetic field with modified Ohm's and Fourier's law. The Laplace and Fourier transforms are used to solve the problem. As an application, concentrated normal force and thermal source are taken to illustrate the utility of the approach. The transformed components of displacement, stress, couple stress, electric field and current density vector are derived. Some special cases of interest are also deduced from the present investigation.

15

Thermal convection in a compressible Walters' (model b') elastico-viscous dusty fluid with hall currents

Vikrant, Kumar V., Jaimala

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 4

1189-1203

EN

A compressible Walters' (Model B') elastico-viscous dusty fluid layer heated from below in the presence of a vertical magnetic field to include the effect of Hall currents is considered. For the case of stationary convection, Walters' (Model B') elastico-viscous fluid behaves like an ordinary Newtonian fluid. The Hall currents and dust particles are found to have a destabilizing effect on the thermal convection, whereas compressibility and the magnetic field are found to have a stabilizing effect on the thermal convection. The viscoelasticity and magnetic field (and hence the Hall currents) introduce oscillatory modes in the system, which were non-existent in their absence. Graphs are also plotted for the critical Rayleigh number and various parameters by giving some numerical values to the parameters

16

Response due to mechanical and thermal sources in micropolar generalized thermoelastic medium

Singh R., Singh K., Kumar V.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 1

107-128

EN

The eigen value approach, following the Laplace and Fourier transformation, is employed to find the general solution of the field equation in a micropolar generalized thermoelastic medium for a plane strain problem. An application of an infinite space with an impulsive mechanical source and thermal source is taken to illustrate the utility of the approach. The integral transformation is inverted by using a numerical inversion technique to get a result in the physical domain. The result in the form of normal displacement, normal force stress, tangential force stress, tangential couple stress and temperature field components is obtained numerically and illustrated graphically. A special case of a thermoelastic solid also deduced.

17

Thermal convection in a Walters' (model B') elastico-viscous dusty fluid in hydromagnetics with the effect of compressibility and rotation

Kumar V., Aggarwal A. K., Kumar S.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 1

51-62

EN

A compressible, electrically conducting Walters'B' elastico-viscous fluid heated from below in the presence of a magnetic field and rotation is considered. At stationary convection, Walters' (Model B') elastico-viscous fluid behaves like a Newtonian fluid and compressibility, rotation are found to have a stabilizing effect whereas the suspended particles have a destabilizing effect on the thermal convection and magnetic field has a stabilizing effect under certain conditions. The presence of magnetic field and rotation introduces oscillatory modes in the system which were non-existent in their absence. Graphs have also been plotted by giving some numerical values to the parameters.

18

Synthesis, Characterization and Antibacterial Activity of Triorganotin(IV) Complexes of 4-Methylphenol

Sharma N., Kumar V., Thakur M., Kumari M., Chaudhry S. C.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 12

2051--2065

EN

The triorganotin(IV) com plex of com po si tion Ph3Sn(OArMe-4) has been synthesized in good yields by the reaction of Ph3SnCl with Me3SiOArMe-4/NaOArMe-4, while complexes of composition Me3Sn(OArMe-4) and n-Bu3Sn(OArMe-4) (where -OArMe-4 = -OC6H4CH3-4) have been obtained from the reaction of Me3SnCl and n-Bu3SnCl with 4-methylphenol in the presence of triethylamine in carbon tetrachloride. The complexes have been characterized by elemental analyses, molar conductance measurements, molecular weight determin tion and IR, 1H and 13C NMR and mass spectral studies. Thermal behaviour of the complexes has been studied by TG and DTA techniques. The organotin(IV) complexes have also been screened for their antibacterial properties and are found to exhibit appreciable activity. The reactions of the complexes with 2-, 3-, 4-cyanopyridines yielded 1:1 adducts as confirmed by physicochemical and IR spectral data.

19

Synthesis and application of new chiral variants of Marfey's reagent for liquid chromatographic separation of the enantiomers of α -amino acids

Bhushan R., Kumar V.

Acta Chromatographica

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2008

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Vol. 20, no. 3

329-347

EN

Two new structural variants of Marfey's reagent (1-fluoro-2,4-dinitrophenyl-5-L -alaninamide, FDNP-L -Ala-NH 2 ) were synthesized by nucleophilic substitution of one fluorine atom in 1,5-difluoro-2,4-dinitrobenzene (DFDNB) by L -methioninamide or D -phenylglycinamide. The new variants FDNP-L -Met-NH 2 and FDNP-D -Phg-NH 2 were characterized and used for derivatization of twenty-six α-amino acids. The resulting diastereomeric derivatives were separated on a reversed-phase C 18 HPLC column using a linear gradient of acetonitrile and aqueous trifluoroacetic acid (TFA) and the results were compared with those obtained by use of Marfey's reagent. To determine and establish the efficiency of both the new variants, separation results were compared for diastereomers of five representative amino acids (Ala, Phe, Ser, Asp, and Asn) prepared with MR, FDNP-L-Phe-NH 2 , FDNP-L -Val-NH 2 , FDNP-L -Leu-NH 2 , and FDNP-L -Pro-NH 2 , experiments being performed under identical conditions. Both the new chiral reagents enabled better separation of the diastereomers than Marfey's reagent for most of the amino acids. The reagent FDNP-D -Phg-NH 2 enabled excellent separation for serine and asparagine whereas other reagents failed or provided poor results.

20

Komunikacja bezprzewodowa - spojrzenie poza 3G

Kumar V.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2001

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nr 7

471-475

PL

Przedyskutowano aspekty związane z wprowadzeniem systemów komunikacji nowej generacji - Beyond 3G. Przedstawiono różne problemy związane z opracowywaniem tych systemów.

EN

Aspects concerning introduction of new generation communication systems Beyond 3G are discussed. Problems connected with new generation communication systems' development are presented.