Thermal simulation of the consolidation process of textile-reinforced thermoplastic components using homogenized parameters

The optimum mold tool design for the consolidation of textile reinforced thermoplastic components requires the calculation of process times in development stage. A reduction of modeling effort can be achieved by homogenization of the thermal model parameters heat conductivity, specific heat capacity and density. On the example of braided hollow sections, consisting of glass-polypropylene-hybrid yarn, which includes reinforcement fibers and matrix material, the homogenization of these thermal model parameters is described. The comparison of simulated and measured temperature profiles of the consolidation process shows the applicability of this homogenization technique.     

Porous asymmetric microfiltration membranes shaped by combined alumina freeze and tape casting

An assembled asymmetric alumina microfiltration membrane with high performance was prepared by combining freeze and tape casting techniques followed by two sintering steps. Freeze casting was used for manufacturing of the porous support layer with a highly interconnected pore network. Tape casting was applied on the top layer to form a pre-membrane with smaller pore size and controlled thickness, which was set on the sintered support. Morphology influences were investigated for different solid loadings, additives content and the assembled layer membrane structures. No delamination among the layers was observed. The assembled ceramic membrane had an average pore size between 30 and 50 μm together with a top surface layer around 0.35 μm, which is suitable to the microfiltration separation process. Porosity in the range of 26–50 % and water flux of 11–32 m³ m^?2 h^?1 bar^?1 were reached for samples prepared with two sintering steps at 1600 and 1300 °C for 2 h.     

Strategic,tactical and operational decisions in multi-national logistics networks: A review and discussion of modelling issues

The rapidly developing worldwide marketplace is leading to the geographical dispersion of production, assembly and distribution operations. This paper deals with three aspects of international logistics networks: strategic, tactical and operational. The strategic level designs the logistics network, including prescribing facility locations, production technologies and plant capacities. The tactical level prescribes material flow management policies, including production levels at all plants, assembly policy, inventory levels, and lot sizes. The operational level schedules operations to assure in-time delivery of final products to customers. This paper reviews the literature that deals with strategic, tactical and operational levels and discusses relevant modelling issues.     

Preparation of CAD infrastructure for ITER procurement packages allocated to Korea

It is necessary to use the same CAD platform for standardization and efficient design collaboration between project partners. ITER has selected CATIA with ENOVIA as the primary CAD and integration tool. During the preparation of the CAD infrastructure, there were several difficulties with respect to information technology (IT). ITER design is classified as mechanical and plant. The procurement arrangement is divided into three types; functional specification, detailed design, and build to print. Therefore, it is important to prepare the suitable prerequisites according to the design type, and to comply with CAD methodologies to avoid trial and error. This paper presents how to overcome the difficulties and how to perform the CAD activities for ITER Korea procurement packages including important matters on a CAD infrastructure in a big project.     

Development and characterization of a coronary polylactic acid stent prototype generated by selective laser melting

In-stent restenosis is still an important issue and stent thrombosis is an unresolved risk after coronary intervention. Biodegradable stents would provide initial scaffolding of the stenosed segment and disappear subsequently. The additive manufacturing technology Selective Laser Melting (SLM) enables rapid, parallel, and raw material saving generation of complex 3- dimensional structures with extensive geometric freedom and is currently in use in orthopedic or dental applications. Here, SLM process parameters were adapted for poly-l-lactid acid (PLLA) and PLLA-co-poly-ε-caprolactone (PCL) powders to generate degradable coronary stent prototypes. Biocompatibility of both polymers was evidenced by assessment of cell morphology and of metabolic and adhesive activity at direct and indirect contact with human coronary artery smooth muscle cells, umbilical vein endothelial cells, and endothelial progenitor cells. γ-sterilization was demonstrated to guarantee safety of SLM-processed parts. From PLLA and PCL, stent prototypes were successfully generated and post-processing by spray- and dip-coating proved to thoroughly smoothen stent surfaces. In conclusion, for the first time, biodegradable polymers and the SLM technique were combined for the manufacturing of customized biodegradable coronary artery stent prototypes. SLM is advocated for the development of biodegradable coronary PLLA and PCL stents, potentially optimized for future bifurcation applications.     

Two-dimensional Fourier transform rheological study on thermosensitivity of poly(N,N-diethylacrylamide) in aqueous solutions

The phase transition of a thermo-responsive polymer, poly(N,N-diethylacrylamide) (PDEA) above its critical overlap concentration (c*) has been studied by two-dimensional Fourier transform (FT) rheology using Large Amplitude Step Shear Oscillation (LASSO). This technique allows the separation of the linear and nonlinear contributions to different relaxation processes and the determination of their time scale and amplitude through the time response of the shear stress after step strain experiments. The interchain interactions increase at the onset of the phase transition at 29 °C, indicated by an increased non-linear contribution at short relaxation times as compared to the single phase condition. During the phase separation of a concentrated solution above the phase transition temperature, the polymer-rich phase can form a transient network created by the hydrophobic interactions between the collapsed polymer chains. The non-linear behavior of a phase-separated system well above the transition temperature (at 33 °C) reflects the stretching of the bridging chain segments between larger aggregated domains and the coalescence of aggregates broken during the step in strain. Relaxation time distributions have been fitted in the LASSO spectra by the nonlinear regularization (NLREG) technique and the relaxation times have been attributed with various linear and non-linear processes below and above the phase transition temperature.     

Solar cell efficiency tables (version 42)

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2013 are reviewed. Copyright © 2013 John Wiley & Sons, Ltd.     

Solar cell efficiency tables (version 41)

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since June 2012 are reviewed. Copyright © 2012 John Wiley & Sons, Ltd.     

Magnetic Electrospun Fibers for Cancer Therapy

Iron oxide nanoparticles (IONPs) for magnetic hyperthermia in cancer treatment have recently gained substantial interest. Unfortunately, the use of free IONPs still faces major challenges such as poor tumor targetability, high variability in the amount of IONPs taken up by the tumor and the IONP leakage from dead cancer cells into the surrounding healthy tissues. The present work reports on electrospun fiber webs, heavily loaded with 50 nm sized IONPs. The high loading capacity of the fibers enables significant heating of the environment upon applying an alternating magnetic field. Furthermore, magnetic fibers can be repeatedly heated without loss of heating capacity or release of IONPs. Upon functionalization of the fiber surface with collagen, human SKOV‐3 ovarian cancer cells attached well to the fibers. Applying an alternating magnetic field during 10 minutes to the fiber webs killed all fiber‐associated cancer cells. Killing the cells using this method seemed more efficient compared to the use of a warm water bath. As the fiber webs can be i) loaded with a well‐controlled amount of IONPs and ii) localized in the body by Magnetic Resonance Imaging, magnetic electrospun fibers may become promising materials for a highly reproducible (repeated) heating of cancer tissues in vivo.     

Regulatory challenges for the transition of public telephony to the Internet

Fixed and mobile telephony with other telecommunication services are moving to a fundamentally different infrastructure as the transition proceeds from the public telephone network to the Internet. There are many opportunities to make significant progress on major developments such as separation of operator independent functions, modular design, and the integration of other desirable features of sustainable Internet solutions. This progress also means that the impacts of some shortcomings of currently competitive telephony services will decline??another benefit of the transition. However, because telephony services are essentially being ??emulated?? over the Internet infrastructure, other aspects of these services will be changed in ways that could affect the public good. In particular, trust-related issues such as authentication and validation, along with their business implications, present significant challenges. This paper explores these issues, including the opportunity that industry and the regulators now have to address them, and suggests approaches to sustainable solutions that can benefit all the stakeholders in this transition.