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Tert‐butyl Peroxyacetate Initiated Semibatch Polymerization of 1, 1‐difluoroethylene in Supercritical Carbon Dioxide
No full textDue to its inertness and solubility in vinylidene fluoride, (VF2), supercritical carbon dioxide is used as a replacement solvent for producing polyvinylidene fluoride (PVDF). tert‐butyl peroxyacetate (TBPA) was evaluated for the first time as a free radical initiator for radical chain polymerization of VF2 producing PVDF without use of a dispersion agent in a semibatch reactor using supercritical carbon dioxide. Diethyl peroxydicarbonate (DEPDC) at 75°C has been evaluated in many publications as an initiator in batch and continuous reactors for polymerization of VF2 in supercritical carbon dioxide. The effects of monomer and initiator concentration, agitation, and reaction time upon average molecular weight and polydispersity were evaluated using TBPA as an initiator at 104°C and compared with DEPDC initiated polymerization. It was found that as agitation rate, monomer concentration, and reaction time increased, the average molecular weight of PVDF using TBPA as an initiator increased. Lower concentrations of TBPA were needed compared to DEPDC to produce comparable molecular weights of PVDF. Using TBPA as an initiator at the conditions investigated resulted in lower polydispersity at similar monomer concentrations compared to DEPDC. Average molecular weights using TBPA ranged from 49,900 g/mol to 1.3 million g/mol and polydispersity ranged from 1.3 to 5.4. POLYM
Developing Entrepreneurial Mindset in Industrial Engineering Classes: A Case Study
Get PDFInstilling entrepreneurial mindset among engineering students is one of the challenges in engineering education. This paper presents the efforts to improve a core undergraduate industrial engineering course, Designing Value in Supply Chain, to infuse entrepreneurial thinking among students using an internally funded grant by Kern Entrepreneurial Engineering Network (KEEN). For this purpose, three new course modules are designed and their effectiveness on student learning is evaluated. This course is ideal for establishing entrepreneurially minded learning (EML) as a systematic approach is required for managing the chain of supply, especially since the impacts of the decisions are not isolated and will be spread out through the entire chain. In addition, creative multidisciplinary knowledge is required to address most of the supply chain challenges. The proposed modules are expected to promote students’ creative thinking, curiosity, collaboration and communication skills, and enable them to identify the opportunities where they can apply their technical skills to create value in the community based on customers’ expectations. These factors are key pillars of EML as proposed by KEEN. In the first course module, students propose a new product to be released to the market (idea generation). They complete this module as the product moves toward the end user in the supply chain following the concepts they learn during the term. This module enables the students to observe the domino impact of the decisions they make in the initial stages of supply chain and enhances structured learning experience by linking different concepts. In the second module, in order to expose the students to real life applications of the course content, wireless consumption data provided by students is used to practice different demand forecasting methods. Students also need to provide some economic analysis to choose the best solution alternative regarding their forecasted values. This module makes the learning process more meaningful as the learners observe a real life application of the subject. In the third module, students practice energy management in order to minimize energy waste as one of the most important types of waste in lean production systems. In this module, they are expected to determine several sources of energy waste on campus and propose action plans, and estimate the economic impact of their solution. As a result of this project, students learn how to create value and communicate an engineering solution in terms of economic benefits. Students provide a report for each module which is graded based on designed rubrics. All these modules are performed in teams which in turn improves students’ team work and collaboration skills. This paper elaborates the details of each module and learning outcomes, and presents the student evaluation results, and at the end discusses the lessons learned
2016 Draft Statement Engineering
No full textA Draft Statement presenting the findings of the recent evaluation by the Engineering Accreditation Commission of ABET
Influence of AC voltage on the positive DC corona current pulses in a wire-cylinder gap View Document
Get PDFIn the development of hybrid HVDC and HVAC transmission lines, the study of radio interference is an important issue. Positive corona current pulses from high voltage transmission lines are the main source of radio interference. In this paper, the design of a wire-cylinder gap electrode system is presented to study the influence of AC voltage on the characteristics of positive corona current pulses. The study shows that the mode of the current pulses is different from that of either DC or AC corona discharge. Waveform parameters of the pulses, such as rise time, half wave time, duration time, repetition rates, average amplitude, and time intervals of secondary pulses are all statistically analyzed in this study. The empirical formulas for the repetition rates with different AC voltages are presented. A theoretical explanation based on an ion cloud model is given to reveal the mechanism behind the influence of AC voltage on positive corona discharge. The experimental results could provide some references for the prediction of radio interference from hybrid AC/DC transmission lines
Investigation and Thermal Analysis of Friction Stir Welding Process Parameters of AA6061 Plates
No full textFriction stir welding (FSW) is a solid state welding process in which a non-consumable rotating tool with a specially designed pin and shoulder is inserted into the abutting edges of sheets or plates to be joined and subsequently traversed along the joint line. In FSW, a pin tool with different shapes spins against the edges of two metal pieces of same or different thickness positioned next to each other. As the pin travels along, it creates friction that generates heat, mixes, and joins the alloys without melting them. To optimize the process, several researchers created pins of different shape, and geometry, and used them in FSW but varied the depth, rotational speed, and tilt angle of the pins. Statistical analysis has been used to identify the most optimum combination of tool and weld parameters that could support high-speed production. Many studies support that the faster FSW is carried out, the stronger (better weld quality) the resulting welds will be. The objective of this paper is to predict the effects of some of the process parameters on the performance of the aluminum alloy components joined using ANSYS simulation tool. Although not reported in this paper, the mechanical and metallurgical properties of the welded members have been measured in the laboratory. The goal is to gain an understanding of how FSW can be used to successfully join aluminum alloys and to study the effect of the various process parameters on the process. The material used is AA6061 as it is one of the popular choices for automotive applications. Experiments have been conducted to validate some of the simulation results from ANSYS software
Synthesis, Characterization and Performance Evaluation of an Advanced Solid Electrolyte and Air Cathode for Rechargeable Lithium-Air Batteries
No full textSynthesis and characterization of a tri-layered solid electrolyte and oxygen permeable solid air cathode for lithium-air battery cells were carried out in this investigation. Detailed fabrication procedures for solid electrolyte, air cathode and real-world lithium-air battery cell are described. Materials characterizations were performed through FTIR and TGA measurement. Based on the experimental four-probe conductivity measurement, it was found that the tri-layered solid electrolyte has a very high conductivity at room temperature, 23˚C, and it can be reached up to 6 times higher at 100˚C. Fabrication of real-world lithium-air button cells was performed using the synthesized tri-layered solid electrolyte, an oxygen permeable air cathode, and a metallic lithium anode. The lithium-air button cells were tested under dry air with 0.1 mA - 0.2 mA discharge/ charge current at elevated temperatures. Experimental results showed that the lithium-air cell performance is very sensitive to the oxygen concentration in the air cathode. The experimental results also revealed that the cell resistance was very large at room temperature but decreased rapidly with increasing temperatures. It was found that the cell resistance was the prime cause to show any significant discharge capacity at room temperature. Experimental results suggested that the lack of robust interfacial contact among solid electrolyte, air cathode and lithium metal anode were the primary factors for the cell’s high internal resistances. It was also found that once the cell internal resistance issues were resolved, the discharge curve of the battery cell was much smoother and the cell was able to discharge at above 2.0 V for up to 40 hours. It indicated that in order to have better performing lithium-air battery cell, interfacial contact resistances issue must have to be resolved very efficientl
Synthesis and Performance Evaluation of an S-POSS Based PBI Electrolyte for High Temperature PEM Fuel Cell Applications
No full textIn this paper, using patented nano-additive based polymer synthesis technology, a novel approach to the design and fabrication of high temperature proton exchange membrane (PEM) has been developed. The presence of sulfonated octaphenyl POSS (S-POSS) in a PBI-PA (polybenzimidazole-phosphoric acid) membrane results in a 40–50% increase in conductivity at 120–200$deg relative to non-sulfonated silica or POSS control fillers at comparable weight percent filler loadings and PBI molecular masses, and also relative to unfilled PBI-PA membranes. In addition, the presence of S-POSS and silica both result in physical reinforcement of the membrane and increased its modulus and mechanical integrity, but only S-POSS offers the benefits of both increased conductivity and increased modulus. Isophthalic acid and 3,3’-diaminobenzidine (DAB) were polymerized in the presence of polyphosphoric acid (PPA) and S-POSS nanoadditive, and the degree of polymerization was monitored by viscosity and torque change measurements. Molecular mass was determined by inherent viscosity measurements of samples removed from the reaction solution. Membranes were prepared by casting the reaction solution and allowing PPA to hydrolyze to PA under ambient conditions. The membranes were characterized for acid content, in-plane conductivity, tensile modulus and shear modulus, and were roll-milled to achieve the desired thickness for membrane electrode assembly (MEA) fabrication