Rapid prototyping and manufacturing benchmarking

Ph.DDOCTOR OF PHILOSOPH

Development of Fe-50Co alloy and its composites by spark plasma sintering

Composite strengthening was attempted to improve the mechanical strength and toughness of the brittle near equiatomic Fe-Co alloy. The matrix alloy chosen for this research falls in the Fe-(30-50) Co group, which are known for their highest saturation induction (B-sat) and Curie temperature among the commercial soft magnetic alloys. The reinforcements, which exhibited a wide range of aspect ratios, included SiC particulates, SiC whiskers and carbon nanotubes (CNTs). In order to minimize the interfacial reaction between the reinforcements and the Fe-50Co alloy (matrix) and to realise higher compact density, spark plasma sintering (SPS) was selected for rapid compaction of materials. Reinforcements were coated using electroless deposition with Ni-P, copper and cobalt to modify the interfacial chemistry and thickness, and hence the final properties of the composites. A comprehensive study on the sintering variables found, within the range of examination and under constant heating and cooling rates, the optimum maximum temperature, soaking time and mechanical pressure of 900oC, 2-5 minutes and 80 MPa to rapidly consolidate the Fe- 50Co alloy to near-theoretical density. The volume fraction and size of the ordered regions in the monolithic alloy and hence the magnetic properties, were sensitive to the heating rate, cooling rate, temperature at which the mechanical pressure was applied and removed and post heat treatments. The influence of reinforcement coatings on the wetting characteristics, and in turn the properties, was compared using SiC particulate Fe-50Co composites. The introduction of bare and coarse (20 μm) SiC particulates negatively affected both magnetic and mechanical properties. Electroless Co coating of particulates improved both the flexural properties and magnetic characteristics such as permeability and coercivity by promoting the formation of narrower interfaces and better bonding. The addition of bare and coated whiskers in Fe-Co alloys enhanced densification and grain growth of the matrix. Copper coating over whiskers was found to be not helpful in realising uniform dispersion, whereas Co and Ni-P coating aided to achieve uniform dispersion of whiskers in the matrix. The amorphous Ni-P coating on whiskers was nanocrystallised during the rapid sintering process and resulted in a material with highly improved mechanical strength and ductility in comparison to the monolithic and other whisker reinforced composite materials. A novel attempt to prepare bulk Fe based alloy composites reinforced with CNTs was also undertaken. Both soft magnetic and mechanical property enhancements were observed in composites with lower vol% of CNTs (i.e. < 1.5%, in the range of examination up to 10%) due to the improvement of compact density by CNTs. An increase in the CNT vol% produced a negative effect on saturation induction and mechanical properties due to the agglomeration of CNTs and reduction in compact density. SPS helped to retain the structural integrity of CNTs during processing. Electroless Ni-P coating over the CNTs helped to reduce the structural damage of CNTs during processing and to improve the mechanical strength and ductility at a marginal cost of saturation induction, in comparison to the monolithic compacts and bare CNT reinforced composites. To date accurate temperature assessment of the compact in the SPS die has been difficult due to the remote position of the pyrometer within the body of the die. It has been found that the ferromagnetic Curie transition can be successfully employed to calibrate SPS pyrometer during processing

Local Values in Governance: Legacy of Choho in Forest and School Management in a Tamang Community in Nepal

The political modernization in Nepal accelerated since 1951 when the country changed its course owing to a popular movement that was acclaimed as the beginning of democracy in the country. However, the governments continued cultural and political homogenization.&nbsp; This has been so in the case of local governance practices as well. Modern governing structures/institutions are guided by the state formed policies and elite-based power structures despite the fact that different ethnic groups in Nepal have their own traditional self-governance systems. In this context, this article unfolds the inheritance of traditional practices of the Tamang community (one of the major ethnic groups of Nepal), in a village, in the district adjoining Kathmandu valley, within the modern structures of governance of forest and school management systems. The paper argues that there is a legacy of the traditional institution, the Choho, though the system of Choho itself has now largely disappeared. This paper, based on ethnographic fieldwork, presents the accounts of Choho and examples of how the particular norms, values, beliefs, and practices are still in practice challenging and denying the modern/state formed mechanisms of governing the forests and schools in the village. The paper further argues that given the modern governance system, the traditional souvenir exchange practice that was rooted in the notion of honour and respect has now shifted towards the practice of giving and receiving gifts based upon the principle of reciprocal benefits that could be described as a bribe

Understanding sustainability data through unit manufacturing process representations: a case study on stone production

Efficiency of natural stone production processes in quarries directly affects the economic output and environmental performances, such as production lead times and energy consumptions. Knowledge on stone production processes is crucial in making responsible decisions in this business. Having a structured representation of information characterizing the stone production processes will support stakeholders in better assessing production resources in terms of sustainability and productivity. Value stream mapping can provide an overview and guidance for sustainability performance evaluation, but its application is limited. The challenges arise when trying to specifically map and relate sustainability data between processes e.g., variability in lead time and CO2 emissions. Manufacturing process characterization standards currently being developed by ASTM International manifest the potential to not only fill this gap but also to provide opportunities to characterize and compose manufacturing processes with relevant environmental information and description. This paper shows the application and lessons learned from deploying once such effort towards standardization

Sustaining Engineering Informatics: Toward Methods and Metrics for Digital Curation

Ensuring the long-term usability of engineering informatics (EI) artifacts is a challenge, particularly for products with longer lifecycles than the computing hardware and software used for their design and manufacture. Addressing this challenge requires characterizing the nature of EI, defining metrics for EI sustainability, and developing methods for long-term EI curation. In this paper we highlight various issues related to long-term archival of EI and describe the work towards methods and metrics for sustaining EI. We propose an approach to enhance the Open Archival Information System (OAIS) functional model to incorporate EI sustainability criteria, Digital Object Prototypes (DOPs), and end user access requirements. We discuss the end user’s requirements from the point of view of reference, reuse and rationale – the “3Rs” – to better understand the level of granularity and abstractions required in the definition of engineering digital objects. Finally we present a proposed case study and experiment

Synthesis, antimicrobial, anticancer, antiviral evaluation and QSAR studies of 4-(1-aryl-2-oxo-1,2-dihydro-indol-3-ylideneamino)-N-substituted benzene sulfonamides

AbstractA series of 4-(1-aryl-2-oxo-1,2-dihydro-indol-3-ylideneamino)-N-substituted benzenesulfonamide derivatives (1–32) was synthesized and evaluated for its in vitro antimicrobial, antiviral and cytotoxic activities. Antimicrobial results indicated that compounds (11) and (18) were found to be the most effective ones. In general, the synthesized compounds were bacteriostatic and fungistatic in their action. The cytotoxic screening results indicated that the compounds were less active than the standard drug 5-fluorouracil (5-FU). None of the compounds inhibited viral replication at subtoxic concentrations. In general, the presence of a pyrimidine ring with electron releasing groups and an ortho- and para-substituted benzoyl moiety favored antimicrobial activities. The results of QSAR studies demonstrated the importance of topological parameters, valence zero order molecular connectivity index (0χv) and valence first order molecular connectivity index (1χv) in describing the antimicrobial activity of synthesized compounds

Angle-Closure Detection in Anterior Segment OCT based on Multi-Level Deep Network

Irreversible visual impairment is often caused by primary angle-closure glaucoma, which could be detected via Anterior Segment Optical Coherence Tomography (AS-OCT). In this paper, an automated system based on deep learning is presented for angle-closure detection in AS-OCT images. Our system learns a discriminative representation from training data that captures subtle visual cues not modeled by handcrafted features. A Multi-Level Deep Network (MLDN) is proposed to formulate this learning, which utilizes three particular AS-OCT regions based on clinical priors: the global anterior segment structure, local iris region, and anterior chamber angle (ACA) patch. In our method, a sliding window based detector is designed to localize the ACA region, which addresses ACA detection as a regression task. Then, three parallel sub-networks are applied to extract AS-OCT representations for the global image and at clinically-relevant local regions. Finally, the extracted deep features of these sub-networks are concatenated into one fully connected layer to predict the angle-closure detection result. In the experiments, our system is shown to surpass previous detection methods and other deep learning systems on two clinical AS-OCT datasets.Comment: 9 pages, accepted by IEEE Transactions on Cybernetic

Synthesis, in vitro antimicrobial, anticancer evaluation and QSAR studies of N′-(substituted)-4-(butan-2-lideneamino)benzohydrazides

AbstractA series of N′-(substituted)-4-(butan-2-ylideneamino)benzohydrazides (1–21) was synthesized and characterized by physicochemical as well as spectral means. The synthesized compounds were screened for their in vitro antimicrobial and anticancer potentials. The synthesized compounds displayed higher antifungal potential as compared to antibacterial potential. Besides having good antifungal potential, the synthesized compounds were having appreciable anticancer potential and a number of compounds displayed higher anticancer potential than the standard drug, carboplatin. The results of QSAR studies demonstrated the importance of steric parameter, molar refractivity (MR), topological parameters, third order molecular connectivity index (3χ), Kier’s first order shape index (κ1) in describing the antimicrobial activity of N′-(substituted)-4-(butan-2-ylideneamino)benzohydrazides

A systematic study on material properties of water retted Sterculia and Bauhinia fiber

Lignocellulose biomass forms an important component of traditional and next generation composite materials. To obtain desired properties, the biomass needs to be chemo‒mechanically processed at different levels. The raw lignocellulose fiber obtained from Sterculia villosa (Roxb.) and Bauhinia vahlii is traditionally believed to have high water stability; and therefore used in rural areas of South Asian regions to secure objects submerged under water. In this research, we systematically studied several material properties of raw Sterculia and Bauhinia fiber samples retted for 0, 20, 30 and 55 days (n=8). Water retting resulted in significant decrease in lignin and extractives content (p0.05). Interestingly, water retting resulted in increased thermal stability in both fiber types. These findings suggested that the fiber studied have excellent water stability. The observed trend in mechanical and thermal properties could have resulted from crystallinity change and/or nominal fiber damage as supported by XRD and SEM imaging data; respectively. These findings suggested that Sterculia and Bauhinia fiber biomass could be an important component of biodegradable composite materials which are intended for high wetting and/or humid conditions