Characterization of Two Novel Machining Processes for Difficult to Machine Materials

New materials with superior mechanical properties, such as increased strength and hardness, have been developed to allow for new and improved products. However, the mechanical properties that make these materials useful also makes them difficult to process using conventional methods. New machining processes need to be developed to generate products from these materials. Thus, such processes need to be characterized better understand the process effects on the workpiece. Characterization of manufacturing processes can be done empirically or mechanistically. In this research, two machining process were investigated to compare the advantages and drawbacks of each characterization method. The first involved electrically-assisted grinding (EAG) of tool steel. In EAG, an electrical spark is generated between a metal-bonded grinding wheel and a workpiece to aid in material removal. An EAG prototype was successfully developed to empirically investigate the effects of current and electricity on hardness, surface roughness, cutting force, and tool wear. Applied current and voltage were found to cause deleterious tool wear, but were found to have no measurable effect on other process attributes. The second machining process investigated was laser ablation of a technical ceramic. A mechanistic model based on conservation of energy was developed to characterize the process. The model was used to predict depth of cut when fabricating microchannels in silicon carbide. Experiments were conducted to further refine the model, by examining the variance between the model and experimental results. Variance was found to be based on scan speed, with larger variance at low scan speeds and little variance at higher scan speeds. A variance correction term was empirically derived and used to refine the model. Over scan speeds from 100 to 1500 mm/sec and a 100-1000 W power range, the refined model predicted average variation of 9% from experimental data

Multi criteria risk analysis of a subsea BOP system

The Subsea blowout preventer (BOP) which is latched to a subsea wellhead is one of several barriers in the well to prevent kicks and blowouts and it is the most important and critical equipment, as it becomes the last line of protection against blowout. The BOP system used in Subsea drilling operations is considered a Safety – Critical System, with a high severity consequence following its failure. Following past offshore blowout incidents such as the most recent Macondo in the Gulf of Mexico, there have been investigations, research, and improvements sought for improved understanding of the BOP system and its operation. This informs the need for a systematic re-evaluation of the Subsea BOP system to understand its associated risk and reliability and identify critical areas/aspects/components. Different risk analysis techniques were surveyed and the Failure modes effect and criticality analysis (FMECA) selected to be used to drive the study in this thesis. This is due to it being a simple proven cost effective process that can add value to the understanding of the behaviours and properties of a system, component, software, function or other. The output of the FMECA can be used to inform or support other key engineering tasks such as redesigning, enhanced qualification and testing activity or maintenance for greater inherent reliability and reduced risk potential. This thesis underscores the application of the FMECA technique to critique associated risk of the Subsea BOP system. System Functional diagrams was developed with boundaries defined, a FMECA were carried out and an initial select list of critical component failure modes identified. The limitations surrounding the confidence of the FMECA failure modes ranking outcome based on Risk priority number (RPN) is presented and potential variations in risk interpretation are discussed. The main contribution in this thesis is an innovative framework utilising Multicriteria decision making (MCDA) analysis techniques with consideration of fuzzy interval data is applied to the Subsea BOP system critical failure modes from the FMECA analysis. It utilised nine criticality assessment criteria deduced from expert consultation to obtain a more reliable ranking of failure modes. The MCDA techniques applied includes the technique for order of Preference for similarity to the Ideal Solution (TOPSIS), Fuzzy TOPSIS, TOPSIS with interval data, and Preference Ranking Organization Method for Enrichment of Evaluations (PROMETHEE). The outcome of the Multi-criteria analysis of the BOP system clearly shows failures of the Wellhead connector, LMRP hydraulic connector and Control system related failure as the Top 3 most critical failure with respect to a well control. The critical failure mode and components outcome from the analysis in this thesis is validated using failure data from industry database and a sensitivity analysis carried out. The importance of maintenance, testing and redundancy to the BOP system criticality was established by the sensitivity analysis. The potential for MCDA to be used for more specific analysis of criteria for a technology was demonstrated. Improper maintenance, inspection, testing (functional and pressure) are critical to the BOP system performance and sustenance of a high reliability level. Material selection and performance of components (seals, flanges, packers, bolts, mechanical body housings) relative to use environment and operational conditions is fundamental to avoiding failure mechanisms occurrence. Also worthy of notice is the contribution of personnel and organisations (by way of procedures to robustness and verification structure to ensure standard expected practices/rules are followed) to failures as seen in the root cause discussion. OEMs, operators and drilling contractors to periodically review operation scenarios relative to BOP system product design through the use of a Failure reporting analysis and corrective action system. This can improve design of monitoring systems, informs requirement for re-qualification of technology and/or next generation designs. Operations personnel are to correctly log in failures in these systems, and responsible Authority to ensure root cause analysis is done to uncover underlying issue initiating and driving failures

Single-Phase Inverter and Rectifier for High-Reliability Applications

With the depletion of fossil fuels and skyrocketed levels of CO_(2) in our atmosphere, Renewable Energy Resources, generated from natural, sustained, clean, and domestic resources, have caught the eye in recent years of both the industries and governments worldwide. In addition to finding these energy resources, new technologies are being sought to improve the efficiency of consuming the generated energy. Power Electronics is the key technology for both generation and the efficient consumption of energy. The recent trend in power electronics is to integrate the electronics into the source (Photovoltaic (PV)) or the load (light). For PV and outdoor lighting applications, this imposes a harsh, wide-range operating environment on the power electronics. Thus, the reliability of power electronics converters becomes a very crucial issue. It is required that the power electronics, used in such environments, have reliability indices, such as lifetime, which match with the source or load one. This eliminates the reoccurring cost of power electronics replacement. Relatively high efficiencies have been reported in the literature, and standards have been developed to measure it. However, the reliability aspect has not received the same level of scrutiny. In this study, two main aspects have been investigated: (1) A new methodology to evaluate the integrated power electronics that becomes more involved task; and (2) new topology and control schemes, for the single-phase DC/AC and AC/DC converters, which will improve the reliability. The proposed methodology has been applied for different PV Module-Integrated-Inverter (MII) that employs different power decoupling techniques. The results showed that the decoupling capacitor is the limiting lifetime component in all the studied topologies. Moreover, topologies use film capacitor instead of electrolytic capacitor showed an order of magnitude improvement in the lifetime. This clearly suggests that replacing the electrolytic capacitor by a high-reliability film capacitor will enhance the reliability of the PV MII. In the second part of this study, the ripple-port concept is applied for the single-phase DC/AC inverter and AC/DC rectifier, which allows for the usage of the minimum required decoupling capacitance. In conclusion, film capacitor can be used, which led to the improvement of the overall reliability and lifetime

Mu2e Technical Design Report

The Mu2e experiment at Fermilab will search for charged lepton flavor violation via the coherent conversion process mu- N --> e- N with a sensitivity approximately four orders of magnitude better than the current world's best limits for this process. The experiment's sensitivity offers discovery potential over a wide array of new physics models and probes mass scales well beyond the reach of the LHC. We describe herein the preliminary design of the proposed Mu2e experiment. This document was created in partial fulfillment of the requirements necessary to obtain DOE CD-2 approval.Comment: compressed file, 888 pages, 621 figures, 126 tables; full resolution available at http://mu2e.fnal.gov; corrected typo in background summary, Table 3.

Proceedings of the Seventh Italian Conference on Computational Linguistics CLiC-it 2020

On behalf of the Program Committee, a very warm welcome to the Seventh Italian Conference on Computational Linguistics (CLiC-it 2020). This edition of the conference is held in Bologna and organised by the University of Bologna. The CLiC-it conference series is an initiative of the Italian Association for Computational Linguistics (AILC) which, after six years of activity, has clearly established itself as the premier national forum for research and development in the fields of Computational Linguistics and Natural Language Processing, where leading researchers and practitioners from academia and industry meet to share their research results, experiences, and challenges

1995 BRAC Commission

Navy Installations - China Lake, CA. Special Facilities and Equipment, Facilities/Equipment Capabilities Form. Box 176, L-108