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As the three-dimensional (3D) finite element model (FEM) has become the de facto standard for ship structural design, interest in accurately transferring seakeeping loads to panel-based structural models has increased dramatically in recent years. In today's design practices, panel-based hydrodynamic analyses are often used for mapping seakeeping loads to 3D FEM structural models. However, 3D panel-based hydrodynamic analyses are computationally expensive. For monohull ships, methods based on strip theories have been successfully used in the industry for many years. They are computationally efficient, and provide good predictions for motions and hull girder loads. However, many strip theory methods provide only hull girder sectional forces and moments, such as vertical bending moment and vertical shear force, which are difficult to apply to 3D finite element structural models. Previously, the authors have proposed a hybrid strip theory method to transfer 2D strip theory-based seakeeping loads to 3D FEM. In the hybrid approach, the velocity potentials of strip sections are first calculated based on the ordinary 2D strip theories. The velocity potentials of a finite element panel are obtained from the interpolation of the velocity potentials of the strip sections. The panel pressures are then computed based on Bernoulli's equation. Integration of the pressure over the FEM wetted panels yields the hydrodynamic forces and moments. The equations of motion are then formulated based on the FEM. The method not only produces excellent ship motion results, but also results in a perfectly balanced structural model. In this article, the hybrid approach is extended to the 2.5D high-speed strip theory. The simple Rankine source function is used to compute velocity potentials. The original linearized free surface condition, where the forward speed term is not ignored, is used to formulate boundary integral equations. A model based on the Series-64 hull form was used for validating the proposed hybrid method. The motion response amplitude operators are in good agreement with VERES's 2.5D strip theory and with experimental results. Finally, an example is provided for transferring seakeeping loads obtained by the 2.5D hybrid strip theory to a 3D FEM. [ABSTRACT FROM AUTHOR]

Purpose: Atherosclerosis causes plaque to build-up in arteries. Effect of the specific local hemodynamic environment around an atherosclerotic plaque on the thrombosis formation does not remain quite clear but is believed to be crucial. The aim of this study is to uncover the flow effects on plaques formation. Methods: To study the mechanically regulated plaque formation, the flow fields in artery blood vessels with different stenosis rates at various Reynolds numbers were simulated numerically with the two-dimensional axisymmetric models, and the hemodynamic characteristics around the plaque were scaled with stenosis rate and Reynolds number. Results: The results showed that increases of both Reynolds number and stenosis rate facilitated the occurrence of flow separation phenomenon, extended recirculation zone, and upregulated the maximum normalized wall shear stress near the plaque throat section while downregulated the minimal normalized wall shear stress at the front shoulder of plaque, as it should be; in the atherosclerotic plaque leeside of the recirculation zone, an obvious catch bond region of wall shear stress might exist especially under low Reynolds number with stenosis rate smaller than 30%. This catch bond region in the plaque leeside might be responsible for the LBF (low blood flow)-enhanced formation of the atherosclerotic plaque. Conclusions: This work may provide a novel insight into understanding the biomechanical effects behind the formation and damage of atherosclerotic plaques and propose a new strategy for preventing atherosclerotic diseases. [ABSTRACT FROM AUTHOR]

Small amounts of organoclays of different sizes and concentrations were added into thermotropic liquid crystalline polymer (TLCP) forming four types of organoclay-modified TLCPs (TC3 white, TC3 dark, TC3 FS, and TC3 UP), which had different rheological behaviors in the nematic temperature region of TLCP. Acting as viscosity reduction agents, 1.0 wt% of each organoclay-modified TLCPs were blended with high molecular mass polyethylene (HMMPE), respectively. The organoclay-modified TLCP/HMMPE blends displayed different rheological properties from each other or compared with HMMPE and 1.0 wt% TLCP/HMMPE blend [PT1]. The organoclay-modified TLCPs had greater viscosity reduction efficiency than the original TLCP in HMMPE, a lower yielding stress and yielding start shear rate, and a narrower yielding transition region than those of PT1. The rheological performance of the blends, 1.0 wt% TC3 white/HMMPE, 1.0 wt% TC3 FS/HMMPE, and PT1, could be successfully described by a binary flow pattern model. [ABSTRACT FROM AUTHOR]

Experimental studies on a kind of thermotropic liquid crystalline polymer (TLCP) containing 30% p-hydroxybenzoic acid (HBA), 35% hydroquinone (HQ), and 35% sebacic acid (SA) in mole fractions and its nanocomposite (TC3) containing 3.0 wt% organoclay are reported. The structures and dynamics of shear-induced phase separation and the effects of these structures on the macroscopic rheological properties of the nanocomposite are characterized under different shear conditions at 190 °C, which is in the nematic transition region of TLCP. The molecular level interactions between organoclay and TLCP molecules form a percolated-network structure in the composite, causing the composite to display complex viscosity with more than two orders of magnitude greater than that of TLCP in linear regions. However, such a network structure is easily destroyed in steady shear deformation, and it does not recover. Polarized optical microscopy (POM) equipped with a Cambridge shear system and transmission electron microscopy (TEM) confirm a shear-induced phase separation phenomenon during steady shear deformation. Two phases are observed in POM and TEM, with TLCP-rich and organoclay-rich phases. Steady shear at a small shear rate is effective to separate the two phases for characterizations. [ABSTRACT FROM AUTHOR]

Organoclay with a size of 100–200 nm was successfully prepared by a combination of wet ball milling and ultrasonication methods without changing its physico-chemical properties. A nanocomposite (TC3 FS) of 3.0 wt% treated organoclay in thermotropic liquid crystalline polymer (TLCP) was prepared. The treated organoclay was of comparable size to the fully extended TLCP molecules and it formed weak interactions with them. The liquid crystallinity of the TLCP was not greatly affected by the treated organoclay at the nematic temperature of the TLCP. Rheological characterization demonstrated that the viscosity of the TC3 FS was less than one order of magnitude higher than that of the TLCP in the linear viscoelastic region, and the steady shear viscosity of the two materials was comparable in steady shear experiments. Thus, TC3 FS is a promising viscosity reduction agent for high molecular mass polyethylene (HMMPE), functioning similarly to TLCP. The 1.0 wt% TC3 FS in HMMPE has more efficient viscosity reduction ability than the 1.0 wt% TLCP in HMMPE, with lower yielding stress and yield-starting shear rate, as well as a narrower yield shear rate region. The viscosity reduction ability of the TLCP was enhanced by the treated organoclay. [ABSTRACT FROM AUTHOR]

Small amounts of organoclays in different sizes and concentrations were added into thermotropic liquid crystalline polymer (TLCP) by a combination method of ultrasonication, centrifugation, and solution casting (and shear-induced phase separation). Four kinds of organoclay-modified TLCP composites were obtained. TC3 UP was a kind of organoclay which displayed a marked shear-induced phase separation phenomenon at 190 °C and higher temperatures. TC3 UP could be separated into a TLCP-rich part, TC3 white, and an organoclay-rich part, TC3 dark. TC3 white was an organoclay-modified TLCP with fully exfoliated organoclay of a uniform size of 15–25 nm well dispersed in the TLCP. TC3 dark had a typical intercalated model structure with some TLCP molecules confined in organoclay galleries. TC3 FS was an organoclay-modified TLCP with organoclay of comparable size to that of the fully extended TLCP molecule, i.e., 85 nm. The organoclay layers dispersed into the polymeric matrix as a few randomly organized organoclay layers or stacks of layers in the quiescent condition in organoclay-modified TLCPs. The larger organoclay size or higher concentration of organoclay in the composites (such as, TC3 UP and TC3 dark) caused a greater proportion of the layers or stacks be hydro-dynamically impeded in the quiescent state, resulting in the filler–filler interaction becoming important and in fact dominating the long-term viscoelasticity of the composites. Additionally, the ease with which the organoclay structure could be altered by flow was considerably enhanced, primarily because of filler–filler interactions. Organoclay size has primary effect on the liquid crystallinity of TLCP. Small or comparable organoclay size with the fully extended TLCP molecule in TC3 white and TC3 FS has weak or negligible negative influence on the liquid crystallinity of TLCP, while larger organoclay size totally damages the liquid crystallinity of TLCP. The morphologies, liquid crystallinity as well as the linear and non-linear viscoelastic behaviors of organoclay-modified TLCPs have been characterized in detail. [ABSTRACT FROM AUTHOR]