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In today’s competitive landscape, a growing number of enterprises are embarking on cyber-physical digitalization journeys to fulfil customer expectations and vitalize manufacturing processes in a cost-effective manner. Developing on top of Industry 4.0 paradigms, advanced robotics, predictive analytics, and process flow automation benefit from the use of digital replicas known as digital twins (DT). DT is a prevailing technology in manufacturing industries and leverages real-time monitoring, simulation, and decision-aid systems to generate feasible solutions to assist production operations, which can range from predictive maintenance to strategic planning. As a trending technology, many digital twin-driven approaches are formulated to achieve mass customization and implement smart product service systems. Hence, this chapter aims to provide insights into the various digital twin architectures and development trends in manufacturing environments. It also proposes the integration of other emerging technologies to allow stakeholders who are capitalizing on this technology to gain a significant competitive edge in the present competitive environment. With consideration to both business innovation and engineering product lifecycle management, this work serves as a guide to highlight the status of digital twin development trends and benefits with innovative use cases aiming at setting a consistent standard for digital twin creation throughout academia and industry.

Phase measurement techniques using a single-shot carrier fringe pattern play an important role in optical science and technology and have been widely used for various applications. In this paper, we focus on the comparative study of two major fringe analysis techniques, the sampling moire (SM) and the windowed Fourier transform (WFT). While SM converts a single-fringe pattern to multiple phase-shifted moire fringe patterns to extract the phase information in the spatial domain, WFT obtains the phase information in the windowed Fourier domain; thus, the two methods look entirely different. We evaluate the phase extraction errors of SM and windowed Fourier ridges (WFRs) as a typical WFT method for both linear and nonlinear phases with/without noise against the reference Fourier transform (FT) technique. For the simulated fringe patterns with linear or nonlinear phase and different random noise level, all the methods have high phase extraction accuracies. For a real experiment with more complicated phase and discontinuities, SM and WFR, both local methods, yield quite similar results and outperform FT.

Accurately extracting phase or phase derivative is the most important requirement in optical metrology. However, in practice, there are many error sources, among which nonlinear distortion in fringe patterns is often encountered. Several techniques have been proposed over time to remove the nonlinearity error. Among these techniques, the windowed Fourier ridges (WFR) algorithm has been shown to be an effective solution insensitive to nonlinearity, but it lacks a theoretical justification. In this paper, we theoretically analyze the local frequency estimation error and phase extraction error, which not only proves the mentioned insensitivity, but also supports the performance prediction and error control, and thus is very important and useful in optical measurement. The theoretical results have been verified by computer simulations. Other error sources such as model error and noise are also compared and discussed.

In recent times, both the windowed Fourier ridges (WFR) and sampling moiré (SM) algorithms have been extensively used due to their high effectiveness in the demodulation of carrier fringe patterns. As they are developed independently, they are mostly recognized as completely different techniques, but we theoretically prove that SM is a special WFR with a specific window shape and a preset local frequency. This unifies the two different algorithms and enhances the understanding of their theoretical aspects, which helps to simplify the selection of these algorithms in real applications. Published version

The windowed Fourier ridges (WFR) algorithm is shown to be a phase-shifting algorithm for phase extraction from a carrier fringe pattern. However, the former only provides a phase estimation with a controllable phase error, whereas the latter pursues exact phase extraction. This link not only is interesting but also enhances the understanding of different phase extraction techniques. Advantages and disadvantages of the WFRs algorithm are discussed. NRF (Natl Research Foundation, S’pore) Published version

The future of agriculture in India will be affected by substantial changes in the environment, although not uniformly across the country. These changes, as projected by the well-known General Circulation Model will grossly impact the food-cropping system. While developing adaptation strategies, it would be useful to understand the current climatic and farming regimes in similar or analogue sites, which have already experienced future conditions. The data used in this paper are from a study using the Climate Analogues tool, a web-based tool developed by the Research Programme on Climate Change, Agriculture and Food Security, which uses spatial and temporal variability in climate projections for different climatic scenarios using the General Circulation Model. Sites with statistically similar climates were thus identified and mapped; these include two sites from four different agro-ecological regions of wheat cropping in India. Comparisons were made specifically for the year 2030, keeping in mind changes in agricultural techniques and mechanisms that could potentially occur over a span of one and a half decades. Temperature was prioritized over other climatic variables in this study, which was conducted using the ECHAM models for the .:42 scenario. A comparison of the current yields of the selected sites with those of the future' analogue sites revealed the former to be at low, moderate or high risk, in accordance with the projected future climatic conditions for wheat cultivation. Most sites appeared to be at moderate risk due to temperature increase at these sites by the year 2030, and except for two sites, had significantly reduced yields.

The article describes the effect of structure of vinyl ester resins (VE) on the mechanical properties of neat sheets as well as glass fabric-reinforced composites. Different samples of VE were prepared by reacting ester of hexahydrophthalic anhydride (ER) and methacrylic acid (MAA) (1 : 1 molar ratio) followed by reaction of monomethacrylate terminated epoxy resin with glutaric (E) or adipic (F) or sebacic acid (G) (2 : 1 molar ratio). The neat VE were diluted with styrene and sheets were fabricated by using a glass mold. A significant reduction in the mechanical properties was observed by increasing the methylene content of resin backbone (i.e., sample E to G). Glass fabric-reinforced composites were fabricated by vacuum assisted resin transfer molding (VARTM) technique. Resin content in the laminates was 50 ± 5 wt %. Increase in the number of methylene groups in the vinyl ester resin (i.e., increasing the bridge length) did not show any significant effect on limiting oxygen index (LOI) value (21 ± 1) of the laminates but tensile strength, tensile modulus, flexural strength, and flexural modulus all increased though these values are significantly lower than observed in laminates based on resin B. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The paper describes the effect of backbone flexibility on the coating performance of vinyl ester resin. For this purpose four resins of varying flexibility were prepared. Bisacrylate terminated epoxy resin (D) was prepared by reacting 2 mol of acrylic acid with 1 mol of diglycidyl ester of hexahydrophthalic anhydride. The flexibility of the backbone was increased by chain extension of mono acryloxy derivative of diglycidyl ester of hexahydrophthalic anhydride with sebacic acid (resin G′). Partial cross-linking of resin D containing pendant hydroxyl group was also done by reacting with small amounts of isophorone diisocyanate (D2I10, D2I4). Fifteen resin formulations were used to evaluate the coating performance in terms of hardness, scratch, adhesion, abrasion resistance and weatherability. Nanosilica and nano-ZnO were used as additives in few formulations for stabilizing transparent coated metallic substrates. The flexibility of the resin backbone (G′) improved adhesion performance of coatings. The increase in the cross-linking improved thermal stability (D2I10 and D2I4) of the resin. Weatherability was only marginally affected by the backbone structure.

Mono- or di(meth)acrylate-terminated derivatives of diglycidyl hexahydrophthalate (ER) were prepared by reacting 1 : 1 or 1 : 2M ratio of ER and methacrylic acid or acrylic acid. These vinyl ester (VE) resins were characterized by determining epoxy equivalent weight, acid number, and molecular weight by gel permeation chromatography. Structural characterization was done by FTIR and 1H NMR spectroscopy. In the 1H NMR spectra of acrylate-terminated VE resins, three proton resonance signals were observed in the region 5.8–6.4 ppm due to vinyl group while in methacrylate-terminated VE resins only two proton resonance signals due to vinylidene protons were observed at 5.6–6.1 ppm. The Brookfield viscosity (room temperature (25 ± 2)°C) of these resins diluted with varying amounts of MMA was determined at 20 rpm. Curing behavior was monitored by determination of gel time and differential scanning calorimetry. An exothermic transition was observed in the DSC scans in the temperature range of (81–150)°C. Isothermal curing of MMA-diluted VE resins containing AIBN as an initiator was done at 60°C for 2 h in N2 atmosphere, and then heating for another 2 h in static air atmosphere. Thermal stability of isothermally cured resins in N2 atmosphere was evaluated by thermogravimetric analysis. All cured resins decomposed above 310°C in single step. Thermal stability of the cured resins having acrylate end caps was marginally higher than the resins having methacrylate end groups. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

In view of high data embedding capacity and many real time applications, we have proposed a reversible invisible watermarking algorithm. The technique is used to embed a set of watermark data in an image using a one pass embedding process and later recovering the original image without any loss, after the extraction of watermark. Main motivation behind this work is the usage of two different prediction schemes-Weighted Causal Average and Context Based Image Compression Algorithm, to obtain two images similar to the original image, and using the error pattern resulted from the two predicted images to embed data depending upon the nature of image. Based on this error pattern, binary data is embedded in an image using two different embedding schemes- Bijective Mirror Mapping technique and Histogram Shifting Algorithm, resulting in better embedding capacity or payload capacity and better PSNR than other reversible one-pass watermarking algorithms mentioned in literature.

Print Request Permissions Save to Project This paper proposes an efficient procedure for removal of salt and pepper noises from the noisy images on the basis of their local edge preserving filters. This algorithm consists of two major stages. In the first stage, the maximum and minimum pixel value in the the corrupted image is used to select noisy pixels or noise free pixels and then in second stage, local edge preserving filters are used on the basis of noisy pixel detected and the nature of its neighboring pixels in the selected window. Comparing the obtained results with other computationally simple noise removal techniques, our proposed algorithm gives much better qualitative and quantitative performance. Due to its simplicity and low computational cost, our method is suitable for its application in many real time situations.

In this paper, we propose a new adaptive image interpolation algorithm for enhancement of natural images. The proposed method uses different algorithms namely SAI, SPIA and Context-Based Image Interpolation Algorithm (CBIA) techniques, for both edgy and smooth type of images. The detailed part of smooth type image is interpolated by SAI, while we propose to use SPIA method for detailed part of edgy image. The rest of the pixels for either type of images are interpolated by CBIA. From the simulation results, we found that our adaptive interpolation technique results in better subjective and objective (PSNR) quality in comparision to some of the recent works in literature.