Microwave NDT of cement-based materials using far-field reflection coefficients

Periodic assessment of ageing civil structures is important for structural integrity and public safety. Numerous destructive and non-destructive techniques employing different energy sources have been proposed for structural health monitoring. Amongst the non-destructive evaluation techniques proposed for monitoring material strength and contents of concrete structures, techniques employing microwaves offer distinct advantages in that they are non-radioactive and provide good penetration, excellent contrast between steel reinforcement bar and concrete, and insensitivity to ambient temperature. In this paper, the feasibility of a far-field microwave NDE technique for concrete imaging is investigated via numerical simulations and experiments on cement based samples using far-field microwave reflection coefficients.     

Optimization of squeeze casting process parameters using Taguchi analysis

Squeeze casting is a hybrid metal forming process combining features of both casting and forging in one operation. This paper reports a research in which an attempt was made to prepare solid cylindrical components of LM24 aluminum alloy through squeeze casting. The primary objective was to investigate the effect of process parameters on the mechanical properties exhibited by the castings produced though squeeze casting process. A set of trials were conducted based on parameters settings suggested in Taguchi’s offline quality control concept. The experimental results indicate that the squeeze pressure and the die-preheating temperature were the parameters making significant contribution toward improvement in mechanical properties of squeeze cast LM24 aluminum alloy.     

Determination of boron in Zr–Nb alloys by glow discharge quadrupole mass spectrometry

Direct determination of boron in Zr–2.5%Nb, Zr–1%Nb alloys and zirconium metals which are extensively used as structural materials in nuclear reactors has been carried out by glow discharge quadrupole mass spectrometer (GD-QMS). Relative sensitive factor (RSF) values for boron were determined using different solid standard reference materials (Zircaloy and steel). A comparison of the GD-QMS results obtained using these RSF values, with DC–Arc-AES (direct current arc atomic emission spectrometry)/certified values showed reasonably good agreement in all the Zr-based materials analysed for boron in the range of 0.1–7 mg kg⁻¹. Quantitation of boron in Zr matrix is possible even with a steel standard when certified for Zr and B. Internal precision (intra-sample precision) was found to be typically ±4% RSD (relative standard deviation) and the inter-sample precision was ±10% RSD for boron at 0.1 mg kg⁻¹ levels. The overall accuracy of the procedure was found to be ±8% at 0.5 mg kg⁻¹ levels of boron using Zircaloy and steel standards. Under optimised experimental conditions the detection limit for boron was found to be ±13 μg kg⁻¹.     

Taguchi-Controlled Knowledge-Based Assistant for Improving Quality of Hollow Cylindrical Sections

Abrasive reaming has been successfully applied for internal finishing of cylindrical sections to produce highly accurate bore characteristics, i.e. diameter, cylindricity, surface finish, straightness and roundness. The process is an alternative to honing and cylindrical grinding whose mechanics are more complex and expensive. This success has, however, been manually orientated with little use of computer aids. To achieve a given bore geometry and maintain low scrap rates, a knowledge- based system may be used to optimise the reaming process. This paper proposes a generic knowledge-based system, called SAR using parameters which significantly influence the reaming process, identified from Taguchi-based experimental analysis. The main objective of the system is to determine process limits, detect uncontrollable situations, identify causes and suggest corrective actions, in order to achieve a better overall bore profile.     

Schematic-Driven Substrate Noise Coupling Analysis in Mixed-Signal IC Designs

This paper presents an approach to reduce substrate cross-talk noise between noisy and sensitive circuitry in mixed-signal integrated circuits at different stages of design and layout development. Silencer! a new, fully automated, schematic-driven substrate noise coupling analysis tool is introduced to accomplish this task. The tool seamlessly enables substrate noise coupling analysis in a standard mixed-signal design flow. Two different methods, fast scalable macro-models and a boundary element solver are integrated into Silencer!. These methods allow extractions of a substrate network from geometric layout information. Simulation results obtained with Silencer! are accurate to within 10% of measured integrated circuits     

Interfacing geometric model data with rapid prototyping systems

The direct slicing of CAD models created in CADDS V to generate geometric data for rapid prototyping using fused feposition modeling technique (FDM) is presented in this paper. The report file from an explicit model is accessed for obtaining model data. Algorithms have been developed for determining the volumes of model material as well as support materials. New algorithms have been developed for filling the sheet solid. A simulation module has been developed to verify whether the filling is correctly done. Example of a model is manufactured using this approach is also presented in this paper.     

Impact of the shape of electrode-tool on radical overcut of micro-hole in electrochemical micromachining

To make use of the full capability of electrochemical micro-machining (EMM), a meticulous research is needed to improve the material removal, surface quality and accuracy by optimizing various EMM process parameters. Keeping this in view, an indigenous development of an EMM machine set-up has been considered to carry out a systematic research for achieving a satisfactory control on the EMM process parameters to meet the micromachining requirements. In this study an EMM machine has been developed and experiments were conducted to study the influence of some of the major process parameters such as the machining voltage, electrolyte concentrations, the pulse-on-time and the machining current on the machining rate and accuracy. The effect of the shape of the tool electrode tips on EMM has been investigated experimentally with 304 stainless steel sheets. The machining rate and the overcut are significantly influenced by the shape of the tool electrode tip.     

Residual stress and surface roughness when facing age hardened Inconel 718 with CBN and ceramic cutting tools

The demand for increasing productivity when machining heat resistant super alloys has resulted in the use of advanced cutting tools such as ceramics and cubic boron nitride (CBN). However, the effects of these tools on the surface integrity, especially the residual stresses created, in the high speed facing operation of Inconel 718 has not been dealt with. In this paper, the residual stresses and the surface roughness when facing age hardened Inconel 718 using CBN and mixed ceramic cutting tools at their respective optimum performance based on productivity has been investigated. The residual stress and surface finish generated during facing with CBN cutting tools have been investigated as a function of speed, depth of cut, coolant, tool geometry and nature of the tool coating. In addition, mixed ceramic cutting tools have been investigated for comparison. The results show that mixed ceramic cutting tools induce tensile residual stresses with a much higher magnitude than CBN cutting tools. The residual stresses and the surface roughness generated by CBN cutting tools are more sensitive to cutting speeds than depth of cut. The use of coolant results in either compressive residual stresses or lowers the magnitude of the tensile residual stresses, whereas dry cutting always resulted in tensile residual stresses. From this investigation, it is suggested that round CBN cutting tools should be used at slow cutting speeds (150 m/min) and small depths of cut (0.05 mm) and with the use of coolant to achieve compressive or minimal tensile residual stresses and good surface finish.     

Design of hemocompatible poly(DMAEMA‐co‐PEGMA) hydrogels for controlled release of insulin

This works aims at (i) studying the antiadhesive properties and the hemocompatibility of poly[2‐(dimethylamino)ethyl methacrylate]‐co‐poly[(ethylene glycol)methacrylate] [poly(DMAEMA‐co‐PEGMA)] copolymers and (ii) investigating the insulin delivery kinetics through hydrogels at physiological pH. A series of poly(DMAEMA‐co‐PEGMA) hydrogels have been synthesized, and their controlled composition was confirmed by X‐ray photoelectron spectroscopy. Then, antibiofouling properties of hydrogels—fibrinogen, erythrocytes, and thrombocytes adhesion—are correlated to their molecular compositions through their hydrophilic properties. As DMAEMA/PEGMA ratio of 70/30 (D70) offers the best compromise between pH sensitivity and hemocompatibility, it is selected for investigating the kinetic rate of insulin release at physiological pH, and the diffusion coefficient of insulin in gel is found to be 0.64 × 10^?7 cm² s^?1. Overall, this study unveils that poly(DMAEMA‐co‐PEGMA) copolymers are promising hemocompatible materials for drug delivery systems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42365.     

International collaboration in science: Participation by the Asian giants

Science in the last few years has become increasingly global and collaborative. The number of internationally coauthored papers has been increasing steadily. We have counted internationally jointly authored papers involving authors from the advanced countries and the Third World countries, usingSCI 1991. We have looked at the number of papers resulting from collaboration among authors residing in the countries of the North (e.g. EC and OECD countries), authors residing in the South (e.g. India and Bangladesh, Mexico and Brazil, China and Pakistan) and papers resulting from collaboration between authors residing in the countries of the South and the North (e.g. India and UK, China and USA). Despite its late start, China has published many more collaborative papers with most Asian countries and the advanced countries of the West except the UK than India — confirming the effectiveness of the open door policy of post-Mao China. Both India and China collaborate with USA much more often in physics than in other areas, followed by clinical medicine. However, India collaborates more with USA in chemistry than China. In Indo-US and Sino-US collaborations, collaborating institutions are mostly universities and institutes of higher learning in India and USA, whereas in China several institutions under the Academies also take part. The percentage of collaborative papers involving authors from India is even smaller than the percentage of journal articles originating from India. In general, papers resulting from international collaboration appear in better journals and are cited more often than papers that are the outcome of local research.Paper presented at the Fourth International Conference on Bibliometrics, Informetrics and Scientometrics in Berlin (Germany), September 11–15, 1993.