Effects of Holding Time on Thermomechanical Fatigue Properties of Compacted Graphite Iron Through Tests with Notched Specimens

In cylinder heads of compacted graphite iron (CGI), the heating and cooling cycles can lead to localized cracking due to thermomechanical fatigue (TMF). Traditionally, TMF behavior is studied by thermal cycling of smooth specimens. The resulting number of cycles to failure (N _f) constitutes a single parameter that can be used to predict actual service failures. Nevertheless, there are also some drawbacks of the conventional testing procedures, most noticeably the prolonged testing times and a considerable scatter in test results. To address these drawbacks, TMF tests were performed using notched specimens, resulting in shorter testing times with less scatter. In the case of cast iron, artificial notches do not necessarily change the TMF behavior since the inherent graphite particles behave as internal notches. Using a notch depth of 0.2 mm, the effect of prolonged holding times (HT) on TMF lifetime was studied and a clear effect was found. Extended holding times were also found to be accompanied by relaxation of compressive stresses, causing higher tensile stresses to develop in the subsequent low temperature stages of the TMF cycles. The lifetimes in notched CGI specimens can be predicted by the Paris’ fatigue crack growth model. This model was used to differentiate between the individual effects of stress level and holding times on TMF lifetime. Microstructural changes were evaluated by analyzing quantitative data sets obtained by orientation contrast microscopy based on electron backscattered diffraction (EBSD).     

An alternative to traditional iron-ore sinter phase classification

An alternative to the traditional quantification of iron ore sinter mineralogy is presented through the use of QEMSCAN instrumentation. The classification of minerals by QEMSCAN is based on chemical composition whilst the traditional classification of iron ore sinter mineralogy, through point counting, is based on morphology. The classification of iron ore sinter minerals through XRD is based on crystal structure. Advantages of the QEMSCAN technique include the ability to distinguish magnesio ferrites from calcio magnetites and the fact that calcium ferrite and silico-ferrite of calcium and aluminium (SFCA) distinction is not dependant on the sectioning of the sample mount.     

Empowering Smallholder Farmers in Markets: strengthening the advocacy capacities of national farmer organisations through collaborative research

The Empowering Smallholder Farmers in Markets programme (ESFIM) supported the advocacy capacities of national farmer organisations (NFOs) for improving smallholder market access. The programme gave NFOs in 11 countries the opportunity to contract local experts to strengthen the evidence-base of their advocacy proposals. By means of a participative process, each NFO analysed the key advocacy issues for which research support was most needed. This resulted in a diversity of themes and advocacy processes. These ranged from research and advocacy on the role of cooperatives in Uruguayan innovation policies to a simulation game on market dynamics in a commodity exchange in the Philippines, and from the review of various seed multiplication programmes in Malawi to the legal and administrative hurdles preventing smallholders from selling to government procurement programmes in Peru and Bolivia. We describe the dynamics surrounding research partnerships in each of the 11 countries and reflect on results of this research-for-advocacy. We also assess the impact of the ESFIM programme on the advocacy capacity of the NFOs. We used a self-evaluation technique, in which board members considered a list of statements covering five capacities that are deemed necessary for effective advocacy. We compared their scores with the observations of external stakeholders who were active in the agricultural sector and knowledgeable about the NFOs’ activities. We conclude that ESFIM has helped to increase coherence in advocacy priorities and has influenced decision making on key policy issues, with encouraging results. In most organisations, ESFIM contributed to the advocacy process, together with many other actors and factors defining advocacy. Based on these experiences, we suggest earmarking funds for NFO-led research support, in order to facilitate the participation of smallholders in the design and monitoring of development policies.     

Effect of melting and crystallization on the conductive network in conductive polymer composites

Investigation on the effect of melting and crystallization of polypropylene (PP) on the conductive network of multi-wall carbon nanotubes (MWNTs) and carbon black (CB) in MWNT/PP and CB/PP composites is performed. The conductive networks formed by fillers with different aspect ratios (MWNTs and CB) are compared during melting and cooling experiments. The network is found to be deformed during melting and re-constructed again due to the re-agglomeration of fillers during isothermal annealing of the melt. Both deformation and re-construction of the network result in a substantial increase/decrease of the thermal resistivity of MWNT/PP and CB/PP composites. For the modelling of the dynamic network reformation three different approaches are tested: classic percolation theory, general effective medium theory (GEM) and Fournier equation.     

A Novel Concept for Highly Oriented Carbon Nanotube Composite Tapes or Fibres with High Strength and Electrical Conductivity

A new concept is described for the creation of multifunctional polymer nanocomposite tapes (or fibres) that combines high stiffness and strength with good electrical properties and a low percolation threshold of carbon nanotubes (CNTs). The concept is based on a bicomponent tape (or fibre) construction consisting of a highly oriented polymer core and a conductive polymer composite (CPC) skin based on a polymer with a lower melting temperature than the core, enabling thermal annealing of these skins to improve conductivity through a dynamic percolation process while retaining the properties of the core and hence those of the tape (or fibre). The percolation threshold in the CPC skins of the highly drawn conductive bicomponent tapes could be decreased from 5.3 to 1.1 wt.‐% after annealing.

     

Investigations on double-diffused MOS transistors under ESD zap conditions

In this paper we analyzed, through experiments and 2-D simulations, the behavior under high reverse voltages of a double-diffused MOS transistor. It turned out that the drift diffusion region (resistor) between the drain contact and p-diffusion region (PI) plays an important role both in the switching on of the parasitic bipolar structure and in the failure mechanism.     

Knowledge-based segmentation of Landsat images

A knowledge-based approach for Landsat image segmentation is proposed. The image segmentation problem is solved by extracting kernel information from the input image to provide an initial interpretation of the image and by using a knowledge-based hierarchical classifier to discriminate between major land-cover types in the study area. The proposed method is designed in such a way that a Landsat image can be segmented and interpreted without any prior image-dependent information. The general spectral land-cover knowledge is constructed from the training land-cover data, and the road information of an image is obtained through a road-detection program