Modeling and analysis of post ejection wall deflections in products made out of polypropylene

Dimensional control of injection molded products remains an important issue as applications require increasing precision. Accurate dimensions of a product result not only from well tuned manufacturing processes, but also from sound design and engineering analysis. This article introduces a model that predicts edge deformations of deep container walls. The model was developed using energy methods and predicts thermoelastic deformations caused by a drop in temperature once the part is released from the mold. The model was validated using results from FEA simulations as well as comparisons with field measurements of parts made of Polypropylene (PP). In general, good agreement was found. Material properties and process conditions were measured for the analyzed cases, which contributed to the accuracy of the results. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Improving minimum quantity lubrication in CBN grinding using compressed air wheel cleaning

The application of minimum quantity lubrication (MQL) in grinding has emerged as an alternative for reducing the abundant flow of cutting fluids, thus achieving cleaner production. Although considered an innovative technique in grinding operations, its widespread application is hindered due primarily to the high heat generation and wheel pore clogging caused by machined chips, harming the final product quality and increasing tool wear on the machine. This study sought to improve MQL use in grinding. In addition to the conventional MQL injected at the wheel/workpiece interface, a compressed air jet was used to clean the mixture of MQL oil and machined chips from clogged wheel pores. Experiments were conducted using external cylindrical plunge grinding on AISI 4340 quenched and tempered steel, and a vitrified cubic boron nitrite (CBN) wheel. The cooling-lubrication methods employed were the conventional flood coolant application, MQL (without cleaning), and MQL with a cleaning jet directed at the wheel surface at different angles of incidence. The main goal of these experiments was to verify the viability of replacing the traditional abundant flow of cutting fluid with MQL and wheel cleaning. The analyses were conducted by measuring the following output variables of the process: workpiece surface roughness and roundness errors, diametrical wheel wear, acoustic emission generated by the process, and metallographic images of the ground surface and subsurface. Results show the positive effects of implementing the cleaning jet technique as a technological improvement of minimum quantity lubrication in grinding in order to reduce the usage of cutting fluids. The MQL technique with cleaning compressed air jet, for a specific angle of incidence (30°), proved to be extremely efficient in the improvement of the surface quality and accurate workpiece shape; it also reduced wheel wear when compared to the other cooling-lubrication methods that were tested (without a cleaning jet).     

Comprehensive two-dimensional gas chromatography with time of flight mass spectrometry applied to biomarker analysis of oils from Colombia

In order to become GC × GC-TOFMS a useful tool in geochemical oil prospecting, it is mandatory to be able to calculate quantitative geochemical parameters. A suite of Colombian oils from Upper Magdalena Valley Basin was chosen to obtaining several thermal maturity and source parameters based on biomarker ratios showing that GC × GC-TOFMS is able to be used to provide relevant geochemical information.     

Users,Economics, Technology: Unavoidable Interdynamics

This paper briefly presents some conclusions of a brainstorming session on the way technology is evolving in ICT. Technology advances have overcome society ability to answer, both in economic and in human aspects. The current design paradigms, of agnostic technology development, need to be reconsidered, and the user needs to be repositioned at the center of future developments.     

Hydrogen production through steam electrolysis: Model-based dynamic behaviour of a cathode-supported intermediate temperature solid oxide electrolysis cell

Hydrogen production via steam electrolysis may involve less electrical energy consumption than conventional low temperature water electrolysis, reflecting the favourable thermodynamics and kinetics at elevated temperatures. In the present paper, a one-dimensional model of a cathode-supported planar intermediate temperature solid oxide electrolysis cell (SOEC) stack is employed to study the dynamic behaviour of such an electrolyser. The simulations found that step changes in the average current density cause the stack temperature to alter during both exothermic and endothermic operation. However, the temperature control, by the variation of the air flow through the stack, was predicted to be capable of returning the stack temperature to the initial value. Furthermore, the proposed control strategy is observed to reduce the interim temperature excursions between the initial and final steady states, suggesting that such a control strategy has a good potential to prevent the issues of cell component fracture, and transitions in stack operating mode, which are related to the temperature fluctuations during dynamic operation of an SOEC stack.     

Alkaline pretreatment and steam explosion process on coffee silverskin and incorporation of cellulose fibers in poly(butylene adipate-co-terephthalate)

In this work, coffee silverskin (CSS) fibers were subjected to alkali pretreatment (ALK-CSS) and alkali pretreatment, followed by a 4-bar steam explosion process (SEW4). Both treated fibers presented a higher degree of crystallinity, enhanced thermal resistance and also cleaner, rough, and defibrillated surface due to the removal of noncellulosic components, as was shown in scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectra, and x-ray diffraction (XRD) results. The SEW4 fibers were incorporated into the poly(butylene adipate-co-terephthalate) (PBAT) matrix in contents up to 5% wt. through melt processing. PBAT/SEW4 composites were evaluated by their microstructure, thermal properties, degree of crystallinity, and hydrophilic behavior. XRD results showed PBAT/SEW4 composites with higher degrees of crystallinity and contact angle tests revealed increased composite hydrophobicity with the increase of SEW4 content in the PBAT matrix. This work describes the importance of recovering coffee lignocellulosic waste and producing value-added by-products, especially in packaging manufacturing.     

Solid oxide fuel cell micro combined heat and power system operating strategy: Options for provision of residential space and water heating

Solid oxide fuel cell (SOFC) based micro combined heat and power (micro-CHP) systems exhibit fundamentally different characteristics from other common micro-CHP technologies. Of particular relevance to this article is that they have a low heat-to-power ratio and may benefit from avoidance of thermal cycling. Existing patterns of residential heat demand in the UK, often characterised by morning and evening heating periods, do not necessarily complement the characteristics of SOFC based micro-CHP in an economic and technical sense because of difficulties in responding to large rapid heat demands (low heat-to-power ratio) and preference for continuous operation (avoidance of thermal cycling). In order to investigate modes of heat delivery that complement SOFC based micro-CHP a number of different heat demand profiles for a typical UK residential dwelling are considered along with a detailed model of SOFC based micro-CHP technical characteristics. Economic and environmental outcomes are modelled for each heat demand profile. A thermal energy store is then added to the analysis and comment is made on changes in economic and environmental parameters, and on the constraints of this option. We find that SOFC-based micro-CHP is best suited to slow space heating demands, where the heating system is on constantly during virtually all of the winter period. Thermal energy storage is less useful where heat demands are slow, but is better suited to cases where decoupling of heat demand and heat supply can result in efficiencies.     

A study of encoding overhead in network management protocols

Next‐Generation Network (NGN) is a critical scenario in terms of network management because of its network dimension, its number of users and its heterogeneity. Since the introduction of the Simple Network Management Protocol (SNMP) at the beginning of the 1990s, much effort has been devoted to the development of new network management technologies. Both the Desktop Management Task Force (DMTF) and the Internet Engineering Task Force (IETF) have developed different network and system management protocols, such as Common Open Policy Service, Web‐Based Enterprise Management, Network Configuration and even adapted other protocols, such as Diameter and Web Services. A network management technology with poor scalability could compromise NGN management and ultimately NGN network behaviour. This paper analyses the network overhead of several management technologies developed by the DMTF and IETF, and goes on to compare their results with the usage of SNMP. Furthermore, some deployment recommendations are proposed for performance optimization in NGNs. Copyright © 2012 John Wiley & Sons, Ltd.