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Search Results: 1 - 10 of 224150 matches for " R Bhargava "
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A study of ocular findings in vitiligo patients treated with PUVASOL
Doria R,Bhargava Rishi
Indian Journal of Dermatology, Venereology and Leprology , 1991,
Abstract: Ocular changes were studied in sixty patients treated with PUVASOL at six months interval. Trioxelen, psoralen and 8 MOP in 3 groups of twenty patients each were given for eighteen months. Photo adduct formation of cornea and lens were noticed after six months of therapy. Reversible visual acuity changes were seen at each visit. Fundus showed dull macular degeneration with psorelens and 8 MOP in patients above thirty years of age.
Model for a piezoelectric strip of crack arrest subjected to Mode-I loadings
R.R. Bhargava,A. Setia
Archives of Computational Materials Science and Surface Engineering , 2009,
Abstract: Purpose: In the present paper a crack arrest model is proposed for an infinitely long narrow poled piezoelectric strip embedded with a centrally situated finite hairline straight crack.Design/methodology/approach: The ceramic of the strip is assumed to be mechanically brittle and electrically ductile. Combined mechanical and electrical loads applied at the edge of the strip open the rims of the crack in mode-I deformations. Consequently a yield zone protrudes ahead of each tip of the crack. Under small scale yielding the yield zone are assumed to lie on the line segment along the axis of the crack. To arrest the crack from further opening the rims of the yield zones are subjected to normal, cohesive quadratically varying yield point stress. Two cases are considered: Case-I the edges of the strip are subjected to in-plane normal and in-plane electrical displacement and in Case-II the in-plane stresses and in-plane electrical field are applied on the edges of the strip. In each case problem is solved using Fourier transform method which finally reduces to the solution of integral equation.Findings: Analytic expressions are derived for stress intensity factor, yield zone, crack opening displacement, crack growth rate, variation of these quantities with respect to affecting parameters viz. width of the strip, yield zone length, crack length, material constants for different ceramics have been plotted.Research limitations/implications: The material of the strip is assumed mechanically brittle and electrically ductile consequently mechanically singularity is encountered first. The investigations in this paper are carried at this level. Also the crack yielding under the loads is considered small scale hence the yield zone is assumed to be lying on the line segment ahead of the crack.Practical implications: Piezoelectric ceramics are widely used as sensors and actuators, this necessity prompts the fracture study on such ceramics under different loading conditions.Originality/value: The paper gives an assessment of the quadratically varying load required to be prescribed on yield zones so as to arrest the opening of the crack. The investigations are useful to smart material design technology where sensors and actuators are manufactured.
Modified strip saturation model for a cracked piezoelectric strip
R.R. Bhargava,A. Setia
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The investigations aim to propose a model for arresting an electrical opening of a crack which weakensa narrow, poled and infinite piezoelectric strip. The edges of the strip are subjected to uniform, constant anti-planestresses and in-plane electrical displacements.Design/methodology/approach: The loads applied at the edges of the strip open the crack in a self-similar fashion.Consequently at each tip of the crack a saturation zone protrudes. To stop the crack from further opening the rims ofdeveloped saturation zones are subjected to normal, cohesive linearly varying saturation limit electric displacement. Theedges of the strip are subjected to anti-plane deformation and in-plane electrical displacement. Fourier integral transformmethod employed reduces the problem to the solution of a Fredholm integral equation of second kind.Findings: The electrical displacement, stress intensity factor, the saturation zone length, crack opening displacementand crack growth rate have been calculated. The results obtained presented graphically, analysed and concluded.Research limitations/implications: The ceramic used for strip is being assumed to be electrically morebrittle. The investigations are carried at this level in the present paper. Also the small scale electrical yielding isconsidered. Consequently the developed saturation zone is proposed to lie in a line segment ahead of crack.Practical implications: Piezoelectric ceramics being widely used as transducers. Their wide utility hasprompted to study many attires of such ceramic and one such attire is fracture mechanics of these ceramics.Originality/value: The paper gives an assessment of the electrical load necessary to arrest the electrical crack opening.The investigations are useful to smart material design technology where sensors and actuators are manufactured.
Crack arrest model for a piezoelectric strip subjected to Model loadings
R.R. Bhargava,A. Setia
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The present paper aims at proposing a crack arrest model for an infinitely long narrow, poled ceramic strip weakened by a finite hairline straight crack when the edges of the strip are subjected to combined mechanical and electrical loads.Design/methodology/approach: (Model) As a consequence of loads the rims of crack open forming a yield zone ahead of each tip of the crack. To arrest the crack from further opening the rims of the yield zones are subjected to normal cohesive quadratically varying yield point stress. Two cases are presented when edges of the strip are subjected to: Case-I~in-plane stresses and electrical displacement or Case-II~in-plane stresses and in-plane electric field. Problems are solved using Fourier integral transform method.Findings: The stress intensity factor, yield zone length, crack opening displacement, crack growth rate have been calculated. Their variation with respect to affecting parameters viz. yield zone length, width of the strip, material constant, electrical and mechanical loads has been depicted graphically.Research limitations/implications: The material of the strip is assumed mechanically brittle and electrically ductile consequently mechanically singularity is encountered first. The investigations in this paper are carried at this level. Also the crack yielding under the loads is considered small scale hence the yield zone is assumed to be lying on the line segment ahead of the crack.Practical implications: Piezoelectric ceramics are widely used as sensors and actuators, this necessity prompts the fracture study on such ceramics under different loading conditions.Originality/value: The paper gives an assessment of the quadratically varying load required to be prescribed on yield zones so as to arrest the opening of the crack. The investigations are useful to smart material design technology where sensors and actuators are manufactured.
Crack arrest saturation model under combined electrical and mechanical loadings
R.R. Bhargava,A. Setia
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The investigation aims at proposing a model for cracked piezoelectric strip which is capable to arrest the crack.Design/methodology/approach: Under the combined effect of electrical and mechanical loadings applied at the edges of the strip, the developed saturation zone is produced at each tip of the crack. To arrest further opening of the crack, the rims of the developed saturation zones are subjected to in-plane cohesive, normal uniform constant saturation point electrical displacement. The problem is solved using Fourier integral transform method which reduces the problem to the solution of Fredholm integral equation of the second kind. This integral equation in turn is solved numerically.Findings: The expressions are derived for different intensity factors and energy release rate. A qualitative analysis of the parameters affecting the arrest of opening of the crack and fatigue crack growth with respect to strip thickness and material constants are presented graphically.Research limitations/implications: The investigations are carried out by considering the material electrical brittle. Consequently, the zones protrude along the straight lines ahead of the crack tips. And further, the small scale electrical yielding conditions are used.Practical implications: Piezoelectric materials are widely getting used nowadays, even in day to day life like piezoelectric cigarette lighter, children toys etc. And, its advance used in technology like transducers, actuators has been already in progress. So, the aspect of cracking of piezoelectric materials are of great practical importance.Originality/value: The piezoelectric material under the combined effect of electrical and mechanical loadings gives the assessment of electrical displacement which is required to arrest the crack. The various useful interpretations are also drawn from the graphs.
Crack arrest model for a piezoelectric strip subjected to Mode-I loadings
R.R. Bhargava,Amit Setia
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The present paper aims at proposing a crack arrest model for an infinitely long narrow, poledceramic strip weakened by a finite hairline straight crack when the edges of the strip are subjected to combinedmechanical and electrical loads.Design/methodology/approach: (Model) As a consequence of loads the rims of crack open forming a yieldzone ahead of each tip of the crack. To arrest the crack from further opening the rims of the yield zones aresubjected to normal cohesive quadratically varying yield point stress. Two cases are presented when edges ofthe strip are subjected to: Case-I~in-plane stresses and electrical displacement or Case-II~in-plane stresses andin-plane electric field. Problems are solved using Fourier integral transform method.Findings: The stress intensity factor, yield zone length, crack opening displacement, crack growth rate havebeen calculated. Their variation with respect to affecting parameters viz. yield zone length, width of the strip,material constant, electrical and mechanical loads has been depicted graphically.Research limitations/implications: The material of the strip is assumed mechanically brittle and electricallyductile consequently mechanically singularity is encountered first. The investigations in this paper are carried atthis level. Also the crack yielding under the loads is considered small scale hence the yield zone is assumed tobe lying on the line segment ahead of the crack.Practical implications: Piezoelectric ceramics are widely used as sensors and actuators, this necessity promptsthe fracture study on such ceramics under different loading conditions.Originality/value: The paper gives an assessment of the quadratically varying load required to be prescribedon yield zones so as to arrest the opening of the crack. The investigations are useful to smart material designtechnology where sensors and actuators are manufactured.
A Modified Strip-Yield-Saturation-Induction Model Solution for Cracked Piezoelectromagnetic Plate
R. R. Bhargava,Pooja Raj Verma
International Journal of Engineering Mathematics , 2014, DOI: 10.1155/2014/892576
Abstract: A strip-yield-saturation-induction model is proposed for an impermeable crack embedded in piezoelectromagnetic plate. The developed slide-yield, saturation, and induction zones are arrested by distributing, respectively, mechanical, electrical, and magnetic loads over their rims. Two cases are considered: when saturation zone exceeds induction zone and vice-versa. It is assumed that developed slide-yield zone is the smallest because of the brittle nature of piezoelectromagnetic material. Fourier integral transform technique is employed to obtain the solution. Closed form analytic expressions are derived for developed zones lengths, crack sliding displacement, crack opening potential drop, crack opening induction drop, and energy release rate. Case study presented for BaTiO3–CoFe2O4 shows that crack arrest is possible under small-scale mechanical, electrical, and magnetic yielding. 1. Introduction The work on magnetoelectroelastic (MEE) fracture problem was started late back in the last century. The field is a natural extension of piezoelectric media since electricity and magnetism go in hand. Due to coupling effect of magneto-, electro-, and elastic fields, MEE materials become more popular than piezoelectric materials and serve as the excellent sensor, actuator, and transducer. Wang and Shen [1] obtained energy release rate for a mode-III magnetoelectroelastic media based on the concept of energy-momentum tensor. Based on the extended Stroh formalism combined with complex variable technique, Green’s function is obtained for an infinite two-dimensional anisotropic MEE media containing an elliptic cavity which degenerates into a slit crack, by Jinxi et al. [2]. Sih and Song [3] proposed a model which showed that crack growth in a magnetoelectroelastic material could be suppressed by increasing the magnitude of piezomagnetic constants in relation to these for piezoelectricity. They [4] further derived energy density function for cracked MEE medium and studied the additional magnetic strictive effect which could influence crack initiation as applied field direction is altered. Wang and Mai [5] addressed the problem of a crack in a MEE medium possessing coupled piezoelectric, piezomagnetic, and magnetoelastic effects. Wang and Mai [6] further extended above problem to calculate a conservative integral based on governing equations for MEE media. Gao et al. [7] investigated the fracture mechanics for an elliptic cavity in a MEE solid under remotely applied uniform in-plane electromagnetic and/or antiplane mechanical loadings. Reducing cavity into a crack they
A Finite Element Study of the Transport Phenomena in MHD Micropolar Flow in a Darcy-Forchheimer Porous Medium
S. Rawat,R. Bhargava,O. Anwar Beg
Lecture Notes in Engineering and Computer Science , 2007,
Abstract:
Prevalence of aspergillosis in chronic lung diseases
Shahid M,Malik A,Bhargava R
Indian Journal of Medical Microbiology , 2001,
Abstract: Eighty eight patients of chronic lung diseases (CLD) attending TB and Chest department of J.N. Medical college Hospital were studied to find out the prevalence of Aspergillus in Broncho-alveolar Lavage (BAL) and anti- aspergillus antibodies in their sera. Direct microscopy and fungal culture of BAL was done. Antibodies were studied by immunodiffusion (ID) and Enzyme linked immunosorbent assay (ELISA). Dot blot assay for anti-aspergillus antibodies was also performed in sera of patients which were either positive by ID or by ELISA. Aspergillus was isolated in culture from 13(14.7%) cases of CLD, while, 30.6% cases showed anti-aspergillus antibodies by serological methods. Aspergillus fumigatus was the predominant species isolated. 17(19.3%) cases of CLD showed antibody against Aspergillus by ID, 22(25%) by ELISA, while 19 of 27 seropositive cases also showed positive results by Dot Blot assay. In cases of bronchogenic carcinoma and pulmonary tuberculosis, anti-aspergillus antibodies were detected equally by ID and ELISA in 21.42% and 21.05% cases respectively. In bronchial asthma, the antibodies could be detected in 60% cases by ELISA, while, in only 10% cases by ID. ELISA was found more sensitive than ID for detection of anti-aspergillus antibodies. The sensitivity of Dot Blot lies some what between ID and ELISA. It is concluded that prevalence of Aspergillosis is quite high in chronic lung diseases, culture and serological test should be performed in conjunction and more than one type of serological tests should be performed to establish the diagnosis.
Pharmaceutical Study of Kanta Lauha and Teekshna Lauha Bhasma
Reddy K R C,Subash Chandra Bhargava
International Journal of Ayurvedic Medicine , 2012,
Abstract: The Ayurvedic medicines are formulated by using plant, animal, metal and minerals. Conversion of metals and minerals into acceptable form i.e. bhasma is a unique technology of Ayurveda. Certain technical procedures like Sodhana, Marana (Incineration process) etc. will play a greater role in converting the material into acceptable form. GMP provides certain directions for processing these medicines in present day. Standard operative procedure, particularly for bhasma preparation has become mandatory for the standardization and quality control of bhasmas. By considering these views in present research work the different samples of lauha bhasma were prepared by using different raw materials viz. Magnetite iron ore, iron turnings. As per the description of Ayurveda, Kanta lauha (Magnetite iron ore) is considered as best raw material for lauha bhasma preparation. After this next best raw material for lauha bhasma preparation is Teekshna lauha (iron turnings). The availability of Kanta lauha (magnetite iron ore) is rare, hence in many Ayurvedic pharmaceutical industries, lauha bhasma is prepared by Teekshna lauha. In the present work a step is made to find out the best quality of lauha bhasma by preparing various samples of lauha bhasma.
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