A modified Holzapfel-Ogden law for a residually stressed finite strain model of the human left ventricle in diastole

In this work, we introduce a modified Holzapfel-Ogden hyperelastic constitutive model for ventricular myocardium that accounts for residual stresses, and we investigate the effects of residual stresses in diastole using a magnetic resonance imaging–derived model of the human left ventricle (LV). We adopt an invariant-based constitutive modelling approach and treat the left ventricular myocardium as a non-homogeneous, fibre-reinforced, incompressible material. Because in vivo images provide the configuration of the LV in a loaded state even in diastole, an inverse analysis is used to determine the corresponding unloaded reference configuration. The residual stress in this unloaded state is estimated by two different methods. One is based on three-dimensional strain measurements in a local region of the canine LV, and the other uses the opening angle method for a cylindrical tube. We find that including residual stress in the model changes the stress distributions across the myocardium and that whereas both methods yield qualitatively similar changes, there are quantitative differences between the two approaches. Although the effects of residual stresses are relatively small in diastole, the model can be extended to explore the full impact of residual stress on LV mechanical behaviour for the whole cardiac cycle as more experimental data become available. In addition, although not considered here, residual stresses may also play a larger role in models that account for tissue growth and remodelling

Measuring the influence of concept detection on video retrieval

There is an increasing emphasis on including semantic concept detection as part of video retrieval. This represents a modality for retrieval quite different from metadata-based and keyframe similarity-based approaches. One of the premises on which the success of this is based, is that good quality detection is available in order to guarantee retrieval quality. But how good does the feature detection actually need to be? Is it possible to achieve good retrieval quality, even with poor quality concept detection and if so then what is the 'tipping point' below which detection accuracy proves not to be beneficial? In this paper we explore this question using a collection of rushes video where we artificially vary the quality of detection of semantic features and we study the impact on the resulting retrieval. Our results show that the impact of improving or degrading performance of concept detectors is not directly reflected as retrieval performance and this raises interesting questions about how accurate concept detection really needs to be

Numerical study on regular wave overtopping flows over sea dike

Based on the filtered Navier-Stokes equations and Smagorinsky turbulence model, a numerical wave flume is developed to investigate regular wave overtopping flow over trapezoidal smooth impermeable sea dike. Simulation of wave breaking is carried out to validate the numerical wave flume with wave generation and absorbing modules. With the in-house developed code, a series of test cases combined different crest heights and wave parameters are carried out. These results are compared with experimental results and numerical results available. The varying tendency of layer thickness and maximum velocity along dike crest is analyzed for both non-breaking and breaking regular waves. Then, the relationship between the magnitude of overtopping flow velocity and overtopping discharge is investigated

Flow Investigation on the Directional Instability of Aircraft with the Single Vertical Tail

AbstractAgeneric aircraft with the single vertical tail usually lose its directional stability at medium angle of attack (typically 20° to 30°). A model with moderate sweptwing of 47.5° and a conventional vertical tail is investigated in order to identify physical mechanisms responsible for directional stability. The results show that vertical tail and fuselage are the main components of the aircraft that generate yawing momentby the tests of model parts mounted and dismounted. The broken down vortex at windward side of vertical tail is the main reason for reducingstable yawing moment of vertical tail. Moreover, the middle part of the fuselage including air inlet and forepart of the wing is the main region of the fuselageenhancing unstable yawing moment

Degradation of Inorganic Nitrogen in Beiyun River of Beijing, China

AbstractNitrogen pollution characteristics of Beiyun River and the migration of inorganic nitrogen in sediment-water were studied using laboratory experiment. Extract NH4-N was the dominant pollutants in Beiyun River that caused the severe harm to aquatic system. NH4-N exchange in sediment-water system was observable at different sites. The calculating of NH4-N degradation coefficients showed there was little difference of NH4-N degradation rate at three sites of Beiyun River. Nitrification process was mainly occurred in 12 days and NH4-N can rapidly in the degradation without input

Behavior modeling for the spraying device in the layered manufacturing process

Published ArticleA component, which has a perfect combination of different materials (probably including homogeneous materials and three different types of heterogeneous materials) in its different portions for a specific application, is considered as the component made of a multiphase perfect material. To fabricate such components, a hybrid layered manufacturing process has been developed. In order to accurately spray different materials with their required volume fractions for every pixel during fabrication, it is important to investigate its spraying operation. This paper establishes the behavior model of the spraying device and proves its validity using digital simulations

Naringin supplementation affects performance, carcass traits, meat quality and oxidative stability of finishing pigs

Naringin is a major flavanone derivate that has many important biological functions in animals. However, its effect on pigs is unknown. The aim of this study was to investigate the effect of naringin supplementation on performance, carcass traits, meat quality and oxidative stability in finishing pigs. Ninety-six pigs, with an average initial body weight of 66.2 ± 0.63 kg, were randomly divided into four groups. One group was fed a basal diet without supplementation (control), and the three others were fed diets supplemented with 0.5, 1.0 or 1.5 g naringin /kg DM of feed for 50 days. Each treatment was replicated six times with four pigs per replicate. Feed and water were available ad libitum. The 0.5 g/kg naringin treatment group had an improved loin eye muscle area, reduced serum triglycerides and were leaner compared with the other groups. Pigs in the 1.5 g/kg naringin treatment had higher pH45min values and inosine monophosphate concentrations, and lower MyHC IIb mRNA expression in muscle than the other groups. MyHC IIa mRNA expression was significantly up-regulated in all naringin-supplemented diet groups. Naringin significantly increased superoxide dismutase (SOD) activity and total anti-oxidative capacity in meat, as well as SOD and glutathione peroxidase activity in the liver. These results indicate that the dietary addition of naringin at 0.5 g/kg improved carcass characteristics, while 1.5 g/kg improved the oxidative stability and pork quality in finishing pigs. Keywords: antioxidant capacity; carcass characteristics; naringin-supplemented diets; pork qualit

Understanding of hydrogel network formation and its application in the architecture of significantly enhanced hydrogel

An understanding of the physical hydrogel network formation has been obtained by dynamic rheological experiments. The evidence shows that the network formation turns out to be a nucleation-controlled process. It was found that there exists a critical temperature Tc; fiber branching is greatly enhanced when the network formation is performed in the regime of T&lt;Tc (T, the final setting temperature). This finding enables the authors to build significantly enhanced gel networks. So far G&prime; (elastic modulus) of the hydrogel network has been enhanced by 187% while the formation period can be greatly shortened to only 1/20 of the previous process.<br /