Dynamic mechanical behavior of LLDPE composites reinforced with kevlar fibers/short glass fibers

Kevlar fibers (DuPont) and glass fibers have been used to reinforce linear lowdensity polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different compositions is compared and has been explained on the basis of volume fraction of fibers. The addition of glass fibers decreases the Izod impact strength of LLDPE. The Izod impact strength of the composite increses when glass fibers are replaced by Kevlar fibers. Dynamic mechanical α‐relaxation is studied and the effect of variation of fiber composition on the relaxation is reported in the temperature range from −50°C to 150°C at 1 Hz frequency. The α‐relaxation shifts towards the higher temperature side on addition of fibers in LLDPE. The addition of fibers increases the storage modulus, E′, of LLDPE. The hybridization of Kevlar and glass fibers helps in desiging composites with a desirable combination of impact strength and modulus. At the low temperature region, E′ increases significantly with glass fibers as compared to that noted with the addition of Kevlar fibers. The α‐transition temperature of composites increases significantly with Kevlar fibers as compared to that observed with addition of glass fibers.     

Multifold stiffness and fracture toughness enhancement in W-doped VO2 microcrystals

Vanadium dioxide is popular for the metal-insulator phase transition at 68°C. Chemical doping is one of the effective ways adopted to tune the phase transition temperature, where tungsten is known to reduce the transition temperature of VO₂. This work investigates the effect of tungsten doping on the mechanical properties of VO₂ microcrystals and their polymer composites. Doping of VO₂ with W shows a systematic reduction in phase transition temperature up to 33°C for 4 wt% W-doped VO₂. For 3 wt% W-doped VO₂, the elastic modulus values enhance by 50%. The fracture toughness of 3 wt% W-doped VO₂ shows an enhancement of fourfold compared to the undoped VO₂. The dynamic compressive strength of 3 wt% W-doped VO₂–UHMWPE polymer composite at room temperature is found to be 7% higher than the undoped VO₂—composite.     

Video Frame Prediction by Joint Optimization of Direct Frame Synthesis and Optical-Flow Estimation

Video prediction is the problem of generating future frames by exploiting the spatiotemporal correlation from the past frame sequence. It is one of the crucial issues in computer vision and has many real-world applications, mainly focused on predicting future scenarios to avoid undesirable outcomes. However, modeling future image content and object is challenging due to the dynamic evolution and complexity of the scene, such as occlusions, camera movements, delay and illumination. Direct frame synthesis or optical-flow estimation are common approaches used by researchers. However, researchers mainly focused on video prediction using one of the approaches. Both methods have limitations, such as direct frame synthesis, usually face blurry prediction due to complex pixel distributions in the scene, and optical-flow estimation, usually produce artifacts due to large object displacements or obstructions in the clip. In this paper, we constructed a deep neural network Frame Prediction Network (FPNet-OF) with multiple-branch inputs (optical flow and original frame) to predict the future video frame by adaptively fusing the future object-motion with the future frame generator. The key idea is to jointly optimize direct RGB frame synthesis and dense optical flow estimation to generate a superior video prediction network. Using various real-world datasets, we experimentally verify that our proposed framework can produce high-level video frame compared to other state-of-the-art framework.     

Physician knowledge,attitudes, and practices regarding physical activity restrictions in pediatric hemodialysis patients

Introduction

Epidemiologic studies of physical activity among pediatric hemodialysis (HD) patients are lacking. A sedentary lifestyle in End-Stage Kidney Disease is associated with a higher cardiovascular mortality risk. In those patients receiving HD, time spent on dialysis and restrictions on physical activity due to access also contribute. No consensus exists regarding physical activity restrictions based on vascular access type. The aim of this study was to describe the patterns of physical activity restrictions imposed by pediatric nephrologists on pediatric HD patients and to understand the basis for these restrictions.

Methods

We conducted a cross-sectional study involving US pediatric nephrologists using an anonymized survey through Pediatric Nephrology Research Consortium. The survey consisted of 19 items, 6 questions detailed physician characteristics with the subsequent 13 addressing physical activity restrictions.

Findings

A total of 35 responses (35% response rate) were received. The average years in practice after fellowship was 11.5 years. Significant restrictions were placed on physical activity and water exposure. None of the participants reported accesses damage or loss that was attributed to physical activity and sport participation. Physicians practice is based on their personal experience, standard practice at their HD center, and clinical practices they were taught.

Discussion

There is no consensus among pediatric nephrologists about allowable physical activity in children receiving HD. Due to the lack of objective data, individual physician beliefs have been utilized to restrict activities in the absence of any deleterious effects to accesses. This survey clearly demonstrates the need for more prospective and detailed studies to develop guidelines regarding physical activity and dialysis access in order to optimize quality of care in these children.     

CFD analysis of a flat tube with semi-circular fins using graphene nanofluid and to compare performance with square type of fins

CFD analysis on a flat tube with semi-circular fins under laminar flow conditions was performed with graphene-based nanofluids considering the nanofluids as incompressible. Different simulations were performed at four different concentrations of nanofluids (0.01%, 0.1%, 0.2%, and 0.4%) and at different volume flow rates (4, 6, 8, and 10 LPM) and at four different forced convective heat transfer coefficients at different wind velocities at 300 K (50, 100, 150, and 200 W/m² K). It was observed that with an increase in the concentration of nanoparticles in nanofluids, the thermal conductivity of base fluid water was increased (at 353 K the nanofluid of 0.4% volume concentration, the thermal conductivity of nanofluid increased by 200% with respect to base fluid). Graphene-based nanofluids have higher effectiveness than most nanofluids hence it is considered for the analysis, at 0.4% concentration of nanofluid the effectiveness observed was 36.84% at 4 LPM, and for water, the effectiveness was 28.22% under similar conditions. The effect of flow rate on temperature drop was significant. At 4 LPM and at 0.4% of nanofluid, an outlet coolant temperature of 333 K was observed whereas the water outlet temperature at 10 LPM is 346.13 K. The effect of forced convective air heat transfer coefficient was significantly high. At h = 50 W/m² K the outlet temperature of 0.4% nanofluid at 4 LPM was 345.25 K and at h = 200 W/m² K, the outlet coolant temperature was 333.47 K. A single tube of the radiator was considered for the analysis whereas the original radiator consists of 50 tubes due to problems of Ansys in meshing.