Computational simulation of intermingled-fiber hybrid composite behavior

Three-dimensional finite-element analysis and a micromechanics based computer code ICAN (Integrated Composite Analyzer) are used to predict the composite properties and microstresses of a unidirectional graphite/epoxy primary composite with varying percentages of S-glass fibers used as hydridizing fibers at a total fiber volume of 0.54. The three-dimensional finite-element model used in the analyses consists of a group of nine fibers, all unidirectional, in a three-by-three unit cell array. There is generally good agreement between the composite properties and microstresses obtained from both methods. The results indicate that the finite-element methods and the micromechanics equations embedded in the ICAN computer code can be used to obtain the properties of intermingled fiber hybrid composites needed for the analysis/design of hybrid composite structures. However, the finite-element model should be big enough to be able to simulate the conditions assumed in the micromechanics equations

Evolutionary Optimization of Electronic Circuitry Cooling Using Nanofluid

Liquid cooling electronics using microchannels integrated in the chips is an attractive alternative to bulky aluminum heat sinks. Cooling can be further enhanced using nanofluids. The goals of this study are to evaluate heat transfer in a nanofluid heat sink with developing laminar flow forced convection, taking into account the pumping power penalty. The proposed model uses semi-empirical correlations to calculate effective nanofluid thermophysical properties, which are then incorporated into heat transfer and friction factor correlations in literature for single-phase flows. The model predicts the thermal resistance and pumping power as a function of four design variables that include the channel diameter, velocity, number of channels, and nanoparticle fraction. The parameters are optimized with minimum thermal resistance as the objective function and fixed specified value of pumping power as the constraint. For a given value of pumping power, the benefit of nanoparticle addition is evaluated by independently optimizing the heat sink, first with nanofluid and then with water. Comparing the minimized thermal resistances revealed only a small benefit since nanoparticle addition increases the pumping power that can alternately be diverted towards an increased velocity in a pure water heat sink. The benefit further diminishes with increase in available pumping power

Polysialic acids: A tool for the optimisation of peptide and protein therapeutics.

Colominic acid (CA) is a low molecular weight derivative of polysialic acid (PSA), which is a naturally occurring biodegradable, highly hydrophilic polymer of N-acetylneuraminic acid. CA was proposed as an alternative to non-biodegradable mPEG for the delivery of proteins with short plasma half-lives, poor stability and high immunogenicity, thus facilitating their therapeutic potential. Here we add to the repertoire of proteins modified and introduce three 'new' smaller therapeutic peptides for polysialylation with a view to improving their in vitro stability, biological potency and in vivo pharmacokinetic properties. The biotherapeutics employed included, bovine polyclonal IgG and monoclonal IgG2a antibodies, which were chosen to model therapeutic Mabs which have the potential in treating cancers, autoimmune diseases and infections. The serine protease inhibitor, aprotinin chosen for the potential treatment of pancreatitis and haematological problems, insulin for treating diabetes and somatostatin (SS) for the treatment of growth disorders i.e. acromegaly. In addition, a novel strategy was developed in an attempt to further improve the efficiency and therapeutic value of the established method of polysialylation. Periodate oxidised CA was first coupled via Schiff base reductive amination to IgG (4.43%), aprotinin (29.20%), and insulin (63.33%) and yielded neoglycoproteins with a poor to moderate degree of modification based on the percentage of available amine residues modified with CA. Only SS obtained a quantitative yield of polysialylation. Introduction of the anionic detergent sodium dodecyl sulphate (SDS) into the coupling reaction seemed to enhance polysialylation and afforded bioconjugates with 1.5-3.0 fold increase in CA content. Size exclusion chromatography and electrophoresis were used to characterise and indicate the emergence of the neoglycoproteins. In vitro biological potency was mostly preserved for catalase (63-66%), IgG2a (82-94%) and aprotinin (59-87%) modified by either method of polysialylation. Furthermore, in vivo mean residence times of polysialylated and SDS-modified polysialylated IgG (45.46- 51.81h), aprotinin (22.23-24.73h) and insulin (22.81-23.26h) were significantly increased in comparison with their native counterparts. Polysialylation appears to confer stability to the biotherapeutics, maintain potency, delay plasma clearance, thereby improving their therapeutic potential in vivo

Speech Enhancement for Automatic Analysis of Child-Centered Audio Recordings

Analysis of child-centred daylong naturalist audio recordings has become a de-facto research protocol in the scientific study of child language development. The researchers are increasingly using these recordings to understand linguistic environment a child encounters in her routine interactions with the world. These audio recordings are captured by a microphone that a child wears throughout a day. The audio recordings, being naturalistic, contain a lot of unwanted sounds from everyday life which degrades the performance of speech analysis tasks. The purpose of this thesis is to investigate the utility of speech enhancement (SE) algorithms in the automatic analysis of such recordings. To this effect, several classical signal processing and modern machine learning-based SE methods were employed 1) as a denoiser for speech corrupted with additive noise sampled from real-life child-centred daylong recordings and 2) as front-end for downstream speech processing tasks of addressee classification (infant vs. adult-directed speech) and automatic syllable count estimation from the speech. The downstream tasks were conducted on data derived from a set of geographically, culturally, and linguistically diverse child-centred daylong audio recordings. The performance of denoising was evaluated through objective quality metrics (spectral distortion and instrumental intelligibility) and through the downstream task performance. Finally, the objective evaluation results were compared with downstream task performance results to find whether objective metrics can be used as a reasonable proxy to select SE front-end for a downstream task. The results obtained show that a recently proposed Long Short-Term Memory (LSTM)-based progressive learning architecture provides maximum performance gains in the downstream tasks in comparison with the other SE methods and baseline results. Classical signal processing-based SE methods also lead to competitive performance. From the comparison of objective assessment and downstream task performance results, no predictive relationship between task-independent objective metrics and performance of downstream tasks was found

Public awareness of the impacts of the Emerald Ash Borer and its management in New York State

The Emerald Ash Borer (EAB) (Agrilus planipennis fairmaire) is a major threat to the American Ash Tree (Fraxinus sp.). It is a native beetle of China and was first discovered in North America in 2002. It originally infested Canada and quickly spread to the Unites States (Kovacs at al, 2010). Though it cannot be confirmed, it is suspected that the insect arrived in Canada in wood packing materials commonly used to stabilize cargo ships or ship consumer products (www.nyis.info). Since its discovery ten years ago near Detroit, Michigan, infestations have been confirmed in 14 different states across the U.S.A (www.dec.ny.gov). The EAB is a phloem-feeding bug, which has the potential to eradicate ash trees across North America. Though it is only possible to detect an infestation once the EAB reaches the adult stage, it is the larvae that live inside the bark of the tree and feed on the phloem, slowly starving and killing the host tree over a two to three year time period. Because of this time delay in detection, once an EAB is found in a region, it is very likely that the beetle has already done significant amount damage (MacFarlene and Meyer, 2003). Already, the EAB is responsible for the death of over 53 million ash trees across the United States alone. Because of the low genetic diversity across species of ash trees, this non-native specie has the potential to spread and kill all ash trees (BenDor et al 2006)

Microfracture in high temperature metal matrix laminates

Computational simulation procedures are described to evaluate the composite microfracture behavior, establish the hierarchy/sequence of fracture modes, and the influence of compliant layers and partial debonding on composite properties and microfracture initiation. These procedures are based upon three-dimensional finite element analysis and composite micromechanics equations. Typical results for the effects of compliant layers and partial debonding, microfracture initiation, and propagation and the thermomechanical cyclic loading on a SiC/Ti15 composite system are presented and discussed. The results show that interfacial debonding follows fiber or matrix fracture, and the thermomechanical cyclic loading severely degrades the composite integrity