A supercritical (SC) fluid technology coupled with power cogeneration is proposed to produce biodiesel fuels without the conventional complex separation/purification steps. The core of the integrated system consists of the transesterification (TE) of various triglyceride sources (i.e., vegetable oils and animal fats) with SC methanol/ethanol. Part of the reaction products can be combusted by a diesel engine integrated in the system, which, in turn, provides the power needed to pressurize the system and the heat of the exhaust gases for the TE process. This article reports laboratory-scale investigations directed to system optimum performance (i.e., near complete conversion in short processing time) in connection with the effects of process operating conditions. TE experiments have been conducted at 100-300 bar, 250-425 °C, and 0.73-8.2 min residence time with soybean/sunflower oils as triglycerides and SC methanol/ethanol at ratios of alcohol to oil from 3 (stoichiometric) to 24. Special emphasis was on reactant phase transitions from liquid to SC states. These transitions were monitored with a high-pressure, high-temperature view cell connected to the reactor outlet for the continuous TE experiments and also serving as a batch reactor. Under selected parameters, near complete oil conversion to biodiesel has been achieved with the glycerol decomposition products included in the fuel. Commercial biodiesel production by this method estimated processing costs as low as $0.26/gal for a plant capacity of 5 million gal/year, significantly lower than the current processing costs of ∼$0.51/gal for biodiesel produced by conventional catalytic methods. The retail cost of biodiesel produced by the proposed method is likely to be competitive with diesel fuel prices.
Software development is undergoing a major change away from a fully closed software process towards a process that incorporates open source software in products and services. Just how significant is that change? To answer this question we need to look at the overall growth of open source as well as its growth rate. In this paper, we quantitatively analyze the growth of more than 5000 active and popular open source software projects. We show that the total amount of source code as well as the total number of open source projects is growing at an exponential rate. Previous research showed linear and quadratic growth in lines of source code of individual open source projects. Our work shows that open source is expanding into new domains and applications at an exponential rate.
Abstract. Commercial software firms are increasingly using and contributing to open source software. Thus, they need to understand and work with open source software development processes. This paper investigates whether the practice of continuous integration of agile software development methods has had an impact on open source software projects. Using fine-granular data from more than 5000 active open source software projects we analyze the size of code contributions over a project's life-span. Code contribution size has stayed flat. We interpret this to mean that open source software development has not changed its code integration practices. In particular, within the limits of this study, we claim that the practice of continuous integration has not yet significantly influenced the behavior of open source software developers.
A typical manufacturing job shop comprises of legacy machine tools, new (modern) machine tools, material handling devices, and peripheral manufacturing equipments. Automated monitoring of legacy machine tools has been a long-standing issue for the manufacturing industry primarily because of the computer numeric controller (CNC) closed architecture and limited external communication functionality. This paper describes a non-invasive methodology and development of a software application to monitor real-time machine status, energy usage, and other machining parameters for a legacy machine tool using power signal analysis. State machine algorithm is implemented to detect tool changes and part count. The system architecture, implementation, benefits, limitations, and future work needed for the legacy machine tool monitoring application is explained in detail.
Statistical Process Control (SPC) techniques are used widely in the manufacturing industry. However, it is sometimes observed that a deviation that is within the acceptable range of inherent process variation does not necessarily conform to specifications. This is especially true in the case of low volume; high precision manufacturing that is customary in aerospace and defense industries. In order to study the limitations posed by conventional SPC techniques in such manufacturing environments, a study was undertaken at TechSolve Inc., Cincinnati to develop a standalone SPC tool. The SPC tool so developed effectively communicates with an on-machine probe and analyzes the collected data to carry out a statistical analysis. MTConnect, a new-generation machine tool communications protocol, was used in developing the communication interfaces with the on-machine probe on a Computer Numerical Control (CNC) machine. The XML (eXtensible Markup Language) code used to extend the MTConnect schema to include the data obtained from the probing routines is also presented. The statistical analysis was developed as a Graphical User Interface (GUI) in LabVIEW. The statistical analysis was carried out as a case study by producing a widget. Real machining was carried out to produce 48 of these widgets using a combination of end mills and face mills. The data obtained during the subsequent quality testing was used to carry out the statistical analysis. The limitations of conventional SPC techniques during the developmental and analytical phases of the study are discussed. The presence of a chip during an on machine probing routine, the variations due to disparities in tool macro geometry, and the demand for conformance to requirements are studied in the view of a statistical process monitoring standpoint. Various alternatives are also discussed that aim to correct and improve the quality of machined parts in these scenarios.
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