Shape optimization of microvascular composites used in active cooling applications

Inspired by microchannels networks in biological systems, microvascular composites are being used for various applications including active cooling, autonomic healing, and sensing. The recent development of a manufacturing technique for microvascular composites based on a sacrificial fiber approach has enabled the creation of complex networks of microchannels embedded in composite parts [1]. Motivated by these recent improvements in manufacturing of microvascular composites, we study design of an actively cooled composite plate. We examine the impact of microchannels configuration on the thermal response of the microvascular composite. Here, the composite plate is subjected to a heat flux that causes a high surface temperature in the absence of the active cooling by microchannels. The objective of this study is to determine the optimal configuration of the microchannels to maximize the thermal efficiency of microchannels to keep the domain temperature below a critical temperature value. We present a new gradient-based Isogeometric Interface-enriched Generalized Finite Element Method (IIGFEM) [2–4] optimization scheme that allows for the accurate and efficient extraction of the sensitivity of objective functions and constraints on the design parameters that define the geometry of the microchannels. At the heart of the modeling effort, the IIGFEM allows for the very accurate and efficient capture of the thermal impact of the embedded microchannel network on the thermal field in the composite part. Because the microchannels diameters are typically much smaller than other characteristic dimensions of the problem, we model microchannels as line (or curve) sinks. The IIGFEM solver allows for the capture of curved and branched microchannels over a mesh that does not conform to the geometry of the microchannels. One of the key challenges associated with the conventional finite element-based shape optimization of microvascular composites is the large mesh distortion that often takes place during the optimization process, as the finite element mesh must conform to the evolving microstructural elements. This mesh distortion may affect the accuracy of the optimum solution. Because of the stationary nature of the nonconforming mesh used by the IIGFEM, the issue of mesh distortion disappears. In this study, we adopt an isogeometric IGFEM-based adjoint shape sensitivity approach, which is simplified by the fact that only the enrichment (interface) nodes move, appear or disappear during the shape optimization process. To demonstrate the performance of the method, a set of microstructural shape optimization problems for the design of microvascular composites are presented

Learning together through international collaboration in teacher education in Malaysia. Report of a project to develop a Bachelor of Education (Honours) in Primary Mathematics

Copyright University of Hertfordshire, School of Education 2011Learning together through international collaboration in teacher education in Malaysia is the report of an enterprising partnership between the University of Hertfordshire, UK, the Ministry of Education Malaysia and two Institutes of Teacher Education in Malaysia. Working collaboratively with colleagues in Malaysia, the University of Hertfordshire School of Education designed, validated, supported and quality assured a Bachelor of Education (Honours) degree programme for initial teacher training for a single cohort of 120 students over four years. All the students graduated in 2010. Learning together through international collaboration in teacher education in Malaysia provides a record of the project itself. It also documents in-depth insights from contributors to the project in two main areas: the collaborative approach to working together and issues relating to learning and teaching, including the Action – Reflection – Modelling (ARM) pedagogical approach, which underpinned the degree programme. Senior managers, teacher educators and lecturers share some of their learning from working together to develop and implement the new degree programme. Student teachers voice some experiences from their school placements. They describe how they used ARM; highlight some of the benefits of the approach and identify some of the challenges associated with introducing a different pedagogy in schools as they were 'learning to teach'. There are glimpses of 'lively and attractive' classes in which 'pupils enjoy and feel comfortable to learn' and 'are eager to answer my questions'. School mentors provide additional insights into the student teachers' learning and teaching practice. The richness of the contributions is reflected in the many quotations included in the report. The successful completion of this project was due to the dedication and expertise of many contributors. The findings documented in this report are relevant for all those engaged in international collaboration and teacher education.Final Published versio

Nutrigenomic and nutritional analyses reveal the effects of pelleted feeds on Asian Seabass (Lates calcarifer)

As nutrition-related expenses constitute the majority of the costs for aquaculture farms, it is essential for them to use feeds that provide an ideal combination of nutrients for the species of choice. In this study, the relative effect of consuming three different pelleted feeds (B, C and D) in comparison to frozen baitfish (A; control) were compared on juvenile Asian seabass (77.3 ± 22.4g) that were selected for increased growth rate over two generations. Our objectives were: 1) to evaluate the effects of different pelleted feeds based on overall physiological changes and nutritional quality of fillets; 2) improve our understanding of the underlying mechanisms with transcriptomic analysis; 3) if possible, identify the feed type that supports the growth of these fishes without substantially reducing the nutritional quality of fillet. The growth performance, fatty acid composition of fillet, hepatic histology and transcriptome of the fishes (Groups A-D) were analyzed. The majority of fatty acids of the fillets, except γ-linolenic acid (GLA, C18:3n6), correlated significantly with the respective diets. Asian seabass fed Feed C showed highest specific growth rate (SGR) and feed conversion efficiency (FCE) with closest histology and transcriptomic profile to control, but their fillet contained the highest n6/n3 ratio. When the liver-based transcriptomes were analyzed, a complex set of differentially expressed genes were detected between groups fed pelleted feeds and controls as well as among the pellet-fed groups themselves. Significant enrichment of genes with growth-related function tallied with the morphological data measured. When compared with control (Group A), ‘Biosynthesis of unsaturated fatty acids’ and ‘Steroid biosynthesis’ pathways were significantly enriched in pellet-fed groups. Reduced goblet cell numbers were observed in the gut of pellet-fed fish compared to controls and fads6 was found to be a suitable candidate gene to separate wild-caught Asian seabass, from pellet-fed ones. These results provide insights for researchers on the various effects of feeds on the biochemistry and global gene expression of the fish and potentially for seabass farms to make more informed feed choices

Finite element analysis of tibia with osteogenesis imperfecta: the influence of considering cancellous bone in model reconstruction

The paper aims to develop the finite element (FE) models of tibia with Osteogenesis Imperfecta (OI) based on a patient-specific computed tomography (CT)-images. Two types of FE model have been developed. The first model was set the tibia bone as a single solid model whereas the second model consists of cortical bone and cancellous bone. The developed FE models were used for FE analysis using Voxelcon under various loadings, and then the results of the different models were compared. It was found that the single model yields relatively in agreement to piecewise model, with percentage different of below than 2% for all loading conditions. It seems that the reconstructed FE model considering the cancellous bone did not give significant effect compared to the solid model that neglecting the microstructure of cancellous bone. Hence, we can conclude that the single solid FE model with OI has predicted well, at least for the present boundary conditions, although the cancellous bone was neglected in the model reconstruction

The energy spectrum of all-particle cosmic rays around the knee region observed with the Tibet-III air-shower array

We have already reported the first result on the all-particle spectrum around the knee region based on data from 2000 November to 2001 October observed by the Tibet-III air-shower array. In this paper, we present an updated result using data set collected in the period from 2000 November through 2004 October in a wide range over 3 decades between $10^{14}$ eV and $10^{17}$ eV, in which the position of the knee is clearly seen at around 4 PeV. The spectral index is -2.68 $\pm$ 0.02(stat.) below 1PeV, while it is -3.12 $\pm$ 0.01(stat.) above 4 PeV in the case of QGSJET+HD model, and various systematic errors are under study now.Comment: 12 pages, 7 figures, accepted by Advances in space researc

Moon Shadow by Cosmic Rays under the Influence of Geomagnetic Field and Search for Antiprotons at Multi-TeV Energies

We have observed the shadowing of galactic cosmic ray flux in the direction of the moon, the so-called moon shadow, using the Tibet-III air shower array operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic rays are positively charged; for that reason, they are bent by the geomagnetic field, thereby shifting the moon shadow westward. The cosmic rays will also produce an additional shadow in the eastward direction of the moon if cosmic rays contain negatively charged particles, such as antiprotons, with some fraction. We selected 1.5 x10^{10} air shower events with energy beyond about 3 TeV from the dataset observed by the Tibet-III air shower array and detected the moon shadow at $\sim 40 \sigma$ level. The center of the moon was detected in the direction away from the apparent center of the moon by 0.23$^\circ$ to the west. Based on these data and a full Monte Carlo simulation, we searched for the existence of the shadow produced by antiprotons at the multi-TeV energy region. No evidence of the existence of antiprotons was found in this energy region. We obtained the 90% confidence level upper limit of the flux ratio of antiprotons to protons as 7% at multi-TeV energies.Comment: 13pages,4figures; Accepted for publication in Astroparticle Physic

The ARGO-YBJ Experiment Progresses and Future Extension

Gamma ray source detection above 30TeV is an encouraging approach for finding galactic cosmic ray origins. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has been established. Significant progresses have been made in the experiment. A large air shower detector array in an area of 1km2 is proposed to boost the sensitivity. Hybrid detection with multi-techniques will allow a good discrimination between different types of primary particles, including photons and protons, thus enable an energy spectrum measurement for individual specie. Fluorescence light detector array will extend the spectrum measurement above 100PeV where the second knee is located. An energy scale determined by balloon experiments at 10TeV will be propagated to ultra high energy cosmic ray experiments

Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure