3-D computational model of poly (lactic acid)/halloysite nanocomposites: Predicting elastic properties and stress analysis

A real-structure based 3-D micromechanical computational model of poly (lactic acid) nanocomposites reinforced by randomly oriented halloysite nanotubes (HNTs) was developed and compared with an idealized model (conventional model) and experimental results. The developed idealized model consists of nanotubes with fixed aspect ratio and the proposed alternative real-structure based model takes the experimentally observed variations of HNTs sizes, impurities and aspect ratios into account. The requirements of the 3-D HNTs nanocomposite models have been explored by testing idealized, real structure based models, as well as models with hollow and solid cylinder-like reinforcements with varied amounts of HNTs. A unit cell model with cylindrical reinforcements (representing HNTs) and at least 30 inclusions gave promising results, provided the model includes actual information about HNT's size ranges and aspect ratios. Numerical studies were validated with experimental investigations and the developed real-structure based model gave more accurate results than idealized and analytical models.     

A new analytical solar cell I–V curve model

A simple mathematical equation that can represent empirical I–V curves of individual solar cells, systems of solar cells and modules has been found. The basic model is determined by four parameters: the open circuit voltage, the short circuit current and two shape parameters. With the four parameters determined, the complete current–voltage curve, the fill factor and the maximum power point are given by simple analytical functions. The model is valid both in the positive and the negative (dark condition) voltage range. Several simple examples demonstrate some of the potential of the model. Due to its mathematical simplicity, it is suggested that the model will be suitable for analytical modeling of complex systems.     

Wood Enhancement Treatments I. Impregnation of Southern Yellow Pine with Melamine-Formaldehyde and Melamine-Ammeline-Formaldehyde Resins

Southern yellow pine (SYP) was impregnated with melamine-formaldehyde (MF) or melamine-ammeline-formaldehyde (MAF) resins. The dimensional stability, strength properties, weathering, fire resistance and chemical resistance of the impregnated wood were examined. The wood treated with two commercial MF resins or with a synthesized MAF resin exhibited greatly enhanced dimensional stability, fire resistance and resistance to weathering. The chemical resistance increased moderately.     

Influence of gas stunning and halal slaughter (no stunning) on rabbits welfare indicators and meat quality

This study assessed the effect of gas stunning which has not been conducted until now in comparison with slaughter without stunning on the welfare and meat quality of rabbits. Eighty male New Zealand White rabbits were divided into two groups of 40 animals and subjected to either halal slaughter without stunning (HS) or gas stunning using 61.4% CO₂, 20.3% oxygen and 18.3 % nitrogen (GS). Analysis of the sticking blood revealed that both slaughter procedures caused a substantial increase in the levels of catecholamines, hypercalcemia, hyperglycemia, lactic acidemia and an increase in enzyme activities. The ultimate pH of the Longissimus lumborum muscle did not differ between treatments. GS exhibited higher lightness and cooking loss, and lower glycogen and MFI than HS. This indicates that both GS and HS can be significant stressors although the amount of stress may be below the threshold to negatively affect rabbit meat quality.     

Stressed state of bodies with thermal cylindrical inclusions and cracks (plane deformation)

The thermoelastic potential of displacements and Airy stress function are used to determine stresses in infinite and semiinfinite planes with circular thermal inclusions (whose coefficients of linear thermal expansion differ from the corresponding coefficients of the matrix) subjected to uniform heating. The stress concentration is investigated in the case where inclusions are located near the boundary of the half plane. Analytic expressions are deduced for the stress intensity factors in the vicinity of a rectilinear crack located between two identical inclusions.     

Thermal analysis of vectra B950 liquid crystal polymer

The melting and crystallization behavior of Vectra^tm B950, a random liquid crystalline copoly(ester amide), was studied by differential scanning calorimetry (DSC). Nonisothermal experiments showed the existence of some interesting and peculiar transition behavior, which may depend on the crystallization conditions (cooling rate). In isothermal experiments, both the thermal and crystallization behavior have been studied as functions of annealing temperature and annealing time. Different thermal behaviors were observed, indicating the possibility of multiple states of mesophase aggregation In addition, the thermal decomposition of Vectra B950 was also studied by TGA-FTIR in both nitrogen and air environments. A single-stage decomposition process was found when heating in nitrogen atmosphere, and the decomposition is due to the easter linkage rupture. A double-stage decomposition process was found when heating in air, and the decompositions are mainly due to the ester linkage rupture for the first decomposition step and the oxidative reaction for the second decomposition step. Annealing slightly changes the decomposition composition occuring in the early stage of thermal degradation.     

Data quality and practical challenges of thyroid volume assessment by ultrasound under field conditions - observer errors may affect prevalence estimates of goitre

Background  

The ultrasonographic estimation of thyroid size has been advocated as being more precise than palpation to diagnose goitre. However, ultrasound also requires technical proficiency. This study was conducted among Saharawi refugees, where goitre is highly prevalent. The objectives were to assess the overall data quality of ultrasound measurements of thyroid volume (Tvol), including the intra- and inter-observer agreement, under field conditions, and to describe some of the practical challenges encountered.