Al-doped ZnS layers synthesized by solution growth method

K. Nagamani,N. Revathi,P. Prathap,Y. Lingappa,K.T. Ramakrishna Reddy 한국물리학회 2012 Current Applied Physics Vol.12 No.2

ZnS is one of the potential candidates as a window/buffer layer for solar photovoltaic applications. Aldoped ZnS nanocrystalline films were grown by a simple and economic process, chemical solution growth method. The layers were prepared for different Al-dopant concentrations that vary in the range, 0e10 at. %. The effect of Al-doping on the composition, structure, optical, electrical and photoluminescence properties of the synthesized layers was determined using appropriate techniques. The elemental composition of a typical sample with 6 at. % ‘Al’ in ZnS was Zn ¼ 44.9 at. %, S ¼ 49.8 at. % and Al ¼ 5.3 at. %. The films were nanocrystalline in nature and showed (111) plane of ZnS as the preferred orientation for all the doping concentrations. The layers with 6 at. % of Al showed a crystallite size of w9 nm. The FTIR studies confirmed the presence of ZnS in the layers. The layers showed an average transmittance of w75% in the visible region. The change of photoluminescence behaviour with dopant concentration was also studied. The electrical resistivity was considerably decreased from 107 Ucm to 103 Ucm with Al-doping. The detailed analysis of results will be presented and discussed.

On the Development of Lofts for Doubly Curved Sheet Metal Components

Prasad, K.S.R.K.,Selvaraj, P.,Ayachit, Praveen V.,Nagamani, B.V. Society for Computational Design and Engineering 2006 International Journal of CAD/CAM Vol.6 No.1

Practical automated flat pattern generation with inbuilt production features for doubly curved sheet metal components (SMCs) is addressed here utilizing a new and unique Point Transformation Algorithm (PTA). This is the third in the series of papers on practical Flat Pattern Development (FPD) [8] and Production Loft Generation Systems (PLGS) [9] complementing the pioneering work [6,7]. In the first two publications, automated loft generation programs have addressed sheet metal components having a Principal Flat Surface (PFS) only. The flat pattern development of 3-D components that do not have the flat surface(termed as Non-PFS components) having complex features of double curvature in addition to cutouts and nibbled holes typical of aircraft components were so far not addressed due to lack of relevant published algorithms. This paper traces the evolution of developments and provides the record of fully illustrated, automated loft generation scheme for aircraft SMCs including the Non-PFS components which underwent validation through production tests by sponsors. Details of some of the unique features of the system like simplified surface model generation, termed as topological model and powerful algorithms deployed with potential for CAD/CAM applications are included.

Spatial data integration for disaster/emergency management: an Indian experience

V. Bhanumurthy,K. Ram Mohan Rao,G. Jai Sankar,P. V. Nagamani 대한공간정보학회 2017 Spatial Information Research Vol.25 No.2

Disaster/emergency management needs rapid sharing of essential database for effective decision making. It requires comprehensive and structured database elements for handling emergency situations. The essential database includes variety of multi-scale information covering core, disaster specific and non-spatial information for effective decision making. Every disaster is unique and requires specific information for effective handling of the situation in all the phases of emergency management. Spatial technologies enable effective disaster risk management to assess and map extent of natural events such as floods, cyclones, tsunami, landslide, earthquake, forest fire etc. These disaster products derived from space based inputs generated in near/real time are extremely useful for planning and decision making. However, building spatial database system is a complex task because of key challenges. In this article the concept of spatial data integration is defined for effective integration procedures, storage methods, analysis, and dissemination of these inputs as web services for decision support tools for effective disaster/ emergency management.

Stress-strain behavior and toughness of high-performance steel fiber reinforced concrete in compression

P. Ramadoss,K. Nagamani 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.2

The complete stress-strain behavior of steel fiber reinforced concrete in compression is needed for the analysis and design of structures. An experimental investigation was carried out to generate the complete stress-strain curve of high-performance steel fiber reinforced concrete (HPSFRC) with a strength range of 52–80 MPa. The variation in concrete strength was achieved by varying the water-to-cementitious materials ratio of 0.40-0.25 and steel fiber content (Vf = 0.5, 1.0 and 1.5% with l/d = 80 and 55) in terms of fiber reinforcing parameter, at 10% silica fume replacement. The effects of these parameters on the shape of stress-strain curves are presented. Based on the test data, a simple model is proposed to generate the complete stress-strain relationship for HPSFRC. The proposed model has been found to give good correlation with the stress-strain curves generated experimentally. Inclusion of fibers into HPC improved the ductility considerably. Equations to quantify the effect of fibers on compressive strength, strain at peak stress and toughness of concrete in terms of fiber reinforcing index are also proposed, which predicted the test data quite accurately. Compressive strength prediction model was validated with the strength data of earlier researchers with an absolute variation of 2.1%.

Behavior of high-strength fiber reinforced concrete plates under in-plane and transverse loads

Ramadoss, P.,Nagamani, K. 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.4

The concrete plates are most widely used structural elements in the hulls of floating concrete structures such as concrete barges and pontoons, bridge decks, basement floors and liquid storage tanks. The study on the behavior of high-strength fiber reinforced concrete (HSFRC) plates was carried out to evaluate the performance of plates under in-plane and transverse loads. The plates were tested in simply supported along all the four edges and subjected to in-plane and traverse loads. In this experimental program, twenty four 150 mm diameter cylinders and twelve plate elements of size 600 × 600 × 30 mm were prepared and tested. Water-to-cementitious materials ratios of 0.3 and 0.4 with 10% and 15% silica fume replacements were used in the concrete mixes. The fiber volume fractions, Vf = 0%, 1% and 1.5% with an aspect ratio of 80 were used in this study. The HSFRC mixes had the concrete ompressive strengths in the range of 52.5 to 70 MPa, flexural strengths ranging from 6.21 to 11.08 MPa and static modulus of elasticity ranging from 29.68 to 36.79 GPa. In this study, the behavior of HSFRC plate elements subjected to combined uniaxial in-plane and transverse loads was investigated.

A new strength model for the high-performance fiber reinforced concrete

P. Ramadoss,K. Nagamani 사단법인 한국계산역학회 2008 Computers and Concrete, An International Journal Vol.5 No.1

Steel fiber reinforced concrete is increasingly used day by day in various structural applications. An extensive experimentation was carried out with w/cm ratio ranging from 0.25 to 0.40, and fiber content ranging from zero to1.5 percent by volume with an aspect ratio of 80 and silica fume replacement at 5%, 10% and 15%. The influence of steel fiber content in terms of fiber reinforcing index on the compressive strength of high-performance fiber reinforced concrete (HPFRC) with strength ranging from 45 85 MPa is presented. Based on the test results, equations are proposed using statistical methods to predict 28-day strength of HPFRC effecting the fiber addition in terms of fiber reinforcing index. A strength model proposed by modifying the mix design procedure, can utilize the optimum water content and efficiency factor of pozzolan. To examine the validity of the proposed strength model, the experimental results were compared with the values predicted by the model and the absolute variation obtained was within 5 percent.

Statistical methods of investigation on the compressive strength of high–performance steel fiber reinforced concrete

P. Ramadoss,K. Nagamani 사단법인 한국계산역학회 2012 Computers and Concrete, An International Journal Vol.9 No.2

The contribution of steel fibers on the 28-day compressive strength of high-performance steel fiber reinforced concrete was investigated, is presented. An extensive experimentation was carried out over water-cementitious materials (w/cm) ratios ranging from 0.25 to 0.40, with silica fume- cementitious materials ratios from 0.05 to 0.15, and fiber volume fractions (Vf = 0.0, 0.5, 1.0 and 1.5%) with the aspect ratios of 80 and 53. Based on the test results of 44 concrete mixes, mathematical model was developed using statistical methods to quantify the effect of fiber content on compressive strength of HPSFRC in terms of fiber reinforcing index. The expression, being developed with strength ratios and not with absolute values of strengths, is independent of specimen parameters and is applicable to wide range of w/cm ratios, and used in the mix design of steel fiber reinforced concrete. The estimated strengths are within ±3.2% of the actual values. The model was tested for the strength results of 14 mixes having fiber aspect ratio of 53. On examining the validity of the proposed model, there exists a good correlation between the predicted values and the experimental values of different researchers. Equation is also proposed for the size effect of the concrete specimens.

Investigations on the tensile strength of high-performance fiber reinforced concrete using statistical methods

P. Ramadoss,K. Nagamani 한국계산역학회 2006 Computers and Concrete, An International Journal Vol.3 No.6

This paper presents the investigations towards developing a better understanding on the contribution of steel fibers on the tensile strength of high-performance fiber reinforced concrete (HPFRC). An extensive experimentation was carried out with w/cm ratios ranging from 0.25 to 0.40 and fiber content ranging from zero to 1.5 percent with an aspect ratio of 80. For 32 concrete mixes, flexural and splitting tensile strengths were determined at 28 days. The influence of fiber content in terms of fiber reinforcing index on the flexural and splitting tensile strengths of HPFRC is presented. Based on the test results, mathematical models were developed using statistical methods to predict 28-day flexural and splitting tensile strengths of HPFRC for a wide range of w/cm ratios. The expressions, being developed with strength ratios and not with absolute values of strengths and are applicable to wide range of w/cm ratio and different sizes/shapes of specimens. Relationship between flexural and splitting tensile strengths has been developed using regression analysis and absolute variation of strength values obtained was within 3.85 percent. To examine the validity of the proposed model, the experimental results of previous researchers were compared with the values predicted by the model.