148 research outputs found
Multi-physics continuum modelling approaches for metal powder additive manufacturing: a review
No full textThis paper aims to present a systematic approach in the literature survey related to metal additive manufacturing (AM) processes and its multi-physics continuum modelling approach for its better understanding.
Design/methodology/approach
A systematic review of the literature available in the area of continuum modelling practices adopted for the powder bed fusion (PBF) AM processes for the deposition of powder layer over the substrate along with quantification of residual stress and distortion. Discrete element method (DEM) and finite element method (FEM) approaches have been reviewed for the deposition of powder layer and thermo-mechanical modelling, respectively. Further, thermo-mechanical modelling adopted for the PBF AM process have been discussed in detail with its constituents. Finally, on the basis of prediction through thermo-mechanical models and experimental validation, distortion mitigation/minimisation techniques applied in PBF AM processes have been reviewed to provide a future direction in the field.
Findings
The findings of this paper are the future directions for the implementation and modification of the continuum modelling approaches applied to PBF AM processes. On the basis of the extensive review in the domain, gaps are recommended for future work for the betterment of modelling approach.
Research limitations/implications
This paper is limited to review only the modelling approach adopted by the PBF AM processes, i.e. modelling techniques (DEM approach) used for the deposition of powder layer and macro-models at process scale for the prediction of residual stress and distortion in the component. Modelling of microstructure and grain growth has not been included in this paper.
Originality/value
This paper presents an extensive review of the FEM approach adopted for the prediction of residual stress and distortion in the PBF AM processes which sets the platform for the development of distortion mitigation techniques. An extensive review of distortion mitigation techniques has been presented in the last section of the paper, which has not been reviewed yet
Metal Organic Frameworks for Gas-phase Capacitive Sensing
No full textOLD ChemE/Organic Materials and Interface
Petri Nets Modelling and Analysis of the Veneer Layup System of Plywood Manufacturing Plant
Get PDFIn this paper performance behaviour is analysed in respect of the availability of the Veneer layup system of a plywood manufacturing plant. Generalized Stochastic Petri Nets (GSPN) technique is applied for modelling interactions among various components as well as the subsystems. The effects of the failure and repair rates, as well as availability of repair facilities on the behaviour of the system is investigated using a licensed software package. The outcomes will provide guidelines for the effective maintenance priorities to the practitioners and help in selecting appropriate maintenance strategies
Agricultural trade liberalization in the Uruguay Round : one step forward, one step back?
Get PDFAfter evaluating the Uruguay Round's impact on agriculture and border protection in the next decade, the author concludes that while there was significant reform of the rules - particularly the conversion of nontariff barriers into tariffs and the reduction and binding of all tariffs - in practice, trade will probably be liberalized less than expected. The objective of the Round was to reverse protectionism and remove trade distortions. This may not be achieved in practice, at least not until further reductions are carried out in future rounds of negotiations. The major exception to this conclusion is in high-income Asian countries, where protection for major commodities will be significantly reduced. The tariffication and binding of all tariffs on agricultural products represents a significant step forward. Liberalization is implicit because countries are prohhibited from arbitrarily raising tariffs to new higher levels. But many of the newly established tariffs are so high in many countries as to effectively prohibit trade. Patterns of liberalization vary considerably by commodity and by country. Generally, the extent of liberalization was diminished by binding tariffs to the base period of 1986-88, when border protection was at a high point. In most OECD countries, this was worsened by"dirty tariffication:"the new base tariffs offered even greater protection than the nontariff barriers they replaced. Even after the commitments to tariff reductions in the Round, the ad valorem measure of the final binding tariffs will remain higher than the average rate of protection in 1982-93. A number of developing countries in East Asia, Latin America, and the Middle East chose to lock in prior liberalization efforts on some products. But for most commodities, there will be little actual liberalization, since most developing countries chose to bind their tariffs at a maximum level. Even when countries reduced already-bound rates, bound tariffs remained significantly higher than current applied rates, giving countries the flexibility to raise tariffs later. The high level of bound tariffs may allow countries to apply variable tariffs below the bound level, thus failing to stabilize tariffs and improve market access. Moreover, the Round did not touch many of the worst distortions in developing countries, such as import subsidies, export taxes, state-trading monopolies, and domestic policies that implicitly tax agriculture.Trade Policy,Environmental Economics&Policies,Economic Theory&Research,Export Competitiveness,Rules of Origin,Trade Policy,Rules of Origin,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Theory&Research
Barriers analysis for green supply chain management implementation in power industry using ISM
No full textTime-based assessment of thermal performance of flat plate solar collector using magnesium oxide nanofluid
No full textThe effect of 0.1 and 0.3 volume% magnesium oxide nanofluid at a flow rate of 0.5, 1 and 1.5 litres per minute (lit/min) was analyzed on the flat plate solar collector in a gap of ten days. The 1.5 and 0.5 lit/min was not recommended due to lower outlet temperature and higher heat losses, respectively. At 1 lit/min, thermal efficiency declined by 61.2% for 0.3 volume% after ten days, while it dropped insignificantly for 0.1 volume%. The absorbed energy parameter, FR(τα) increased by 9.7%, and heat losses decreased by 50.5% for 0.1 volume%. The FR(τα) was about 17.7% and 4.8% for 1st and 10th day, respectively with 0.3 volume%. It purports that merely the optimum concentration of nanoparticles maximises the benefits
Design of Low-Threshold Comparator for Improved Timing-Resolution Analog/Digital SiPM
No full textCoincidence time resolution (CTR) in time-of-flight (TOF) positron emission tomography (PET) determines the signal-to-noise ratio (SNR) in iterative image reconstruction algorithms. In PET detectors, the photodetector's single-photon timing resolution (SPTR) influences the CTR by adding uncertainty to the single photoelectron time-of-arrivals. This effect can be modelled as the convolution of the scintillation pulse shape function and the total photodetector jitter at single-photon level, before following an order statistics process. Particularly in Cherenkov-based PET detectors, SPTR has a direct impacton the CTR due to the low number of detected photons. In this thesis, the research is focussed on the design of low thresh-old comparators for two specific purposes in PET. Firstly, the design of in-pixel (SPAD-cell) low-threshold comparator that improves SPAD jitter at the pixel level, since it allows the detection of photo-electron triggered avalanche at the earliest possible time, thus minimizing statistical fluctuations. The design is targeted for Cherenkov-based PET, where improvement in SPTR directly results in improvement of CTR. Secondly, for the integration of analog silicon photomultiplier (A-SiPM) on-chip. Such integration helps in realizing a high Photon Detection Effciency (PDE) and low Dark Count Rate (DCR) A-SiPM with integrated readout electronics. A high speed comparator with a direct connection to the fast terminal of A-SiPM has been realized.Electrical Engineering | Microelectronic
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