Reduction In Maximum Value Research Articles

Experimental and numerical analysis of blood flow in roughness impact-R test

Purpose The present study covers simulation of blood flow in a roughness impact R test model to anticipate the hemodynamic conditions of adhesion of blood elements to the modified surface. It was performed using numerical modelling of this process. The aim of these simulations is to create a surface morphology that stimulates the adhesion of blood elements to the surface of base plate of impact R test. Methods The morphology of base plate of impact R test was developed using a vacuum powder sintering of commercial purity titanium powder (CP-Ti) on Ti6Al7Nb substrate. The finite volume method (FVM) and disperse particle method (DPM) were applied to develop the target model of a roughness impact R test. The morphology of modified surfaces was documented with digital microscope and SEM (scanning electron microscopy). Results The impact R test developed using the two phase blood model performed on regularly structured base plate resulted in shear stress values higher than the analogous for the model lacking such modification. The most significant reduction in maximum values of shear stress occurred in case of the DPM model and especially in the model with regular structures. Conclusions The proposed models are very effective in modeling of the analysis of blood flow in roughness impact-R test.

Moisture Resistance, Thermal Stability and Fire Behavior of Unsaturated Polyester Resin Modified with L-histidinium Dihydrogen Phosphate-Phosphoric Acid.

In this paper, the fire behavior of unsaturated polyester resin (UP) modified with L-histidinium dihydrogen phosphate-phosphoric acid (LHP), being a novel intumescent fire retardant (IFR), was investigated. Thermal and thermomechanical properties of the UP with different amounts of LHP (from 10 to 30 wt. %) were determined by thermogravimetric analysis (TG) as well as dynamic mechanical thermal analysis (DMTA). Reaction to small flames was studied by horizontal burning (HB) test, while fire behavior and smoke emission were investigated with the cone calorimeter (CC) and smoke density chamber. Further, the analysis of volatile products was conducted (TGA/FT-IR). It was observed that the addition of LHP resulted in the formation of carbonaceous char inhibiting the thermal decomposition, burning rate and smoke emission. The most promising results were obtained for the UP containing 30 wt. % of LHP, for which the highest reduction in maximum values of heat release rate (200 kW/m2) and total smoke release (3535 m2/m2) compared to unmodified polymer (792 kW/m2 and 6895 m2/m2) were recorded. However, some important disadvantage with respect to water resistance was observed.

Fire behavior of flame retarded unsaturated polyester resin with high nitrogen content additives

The novel flame retarded unsaturated polyester resins have been developed and prepared by introduction of high nitrogen content additives into the polymer matrix in order to verify their effectiveness in the formation of swollen carbonaceous char inhibiting the burning process of the polymer. The intumescent flame retardants (IFRs) based on mixture or metal complex were developed and characterized by particle size distribution, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD), elemental analysis (CHN) and thermogravimetric analysis (TGA). The evaluation of the efficiency of IFRs addition on the flammability and smoke emission of the unsaturated polyester resins (UP) was carried out using the fire hazard (UL-94), limiting oxygen index (LOI) and cone calorimeter (CC) tests, as well as smoke density chamber tests. The volatile compounds evolved during the burning of materials were determined using a steady state tube furnace and a gas chromatograph with mass spectrometer. Furthermore, the prepared materials were subjected to differential scanning calorimetry (DSC), thermogravimetric analysis and water resistance tests. The mechanical properties of the materials were investigated using Shore D hardness and dynamic mechanical thermal analysis (DMA). The structural evaluation of the manufactured materials and samples after the cone calorimetry tests was carried out using scanning electron microscopy (SEM). It was found that the incorporation of new intumescent flame retardants led to the formation of carbonaceous char layers’ inhibiting the decomposition process and limiting the smoke emission. The most promising results were obtained for the resin containing complex designated as ZN3AT, for which the highest reduction in maximum values of heat release rate (419 kW/m2) compared to unmodified polymer (792 kW/m2) were recorded. Apart from that, the prepared intumescent flame retardants affect the cross-linking process as well as the thermal and mechanical properties of the UP.

Heat wave hinders green wave: The impact of climate extreme on the phenology of a mountain grassland

Climate extremes can have tremendous impacts on the terrestrial biosphere and their frequency is very likely going to increase in the coming years. In this study we examine the impact of the 2015 summer heat wave on a mountain grassland in the Western European Alps by jointly analyzing phenocam greenness (GCC) trajectories, proximal sensing, CO2 flux data and structural canopy traits. Phenocam effectively tracked the impact of the heat wave, showing 39% of reduction in maximum canopy greenness and a senescence advance of 32 days compared to mean values. The same patterns (i.e. reduction of maximum values and senescence advance) were observed for all considered canopy traits and photosynthetic ecosystem functional properties, in particular the maximum light-saturated rate of CO2 uptake (Amax), LAI and PRI. Pixel-level analysis of phenocam images allowed us to further highlight that forbs were more heavily impacted than grasses. Moreover the effect of the extreme event on greenness seasonal course was evaluated testing new formulations of the Growing Season Index (GSI) model. Results demonstrate that a combination of water and high temperature stress was responsible for the observed reduction of canopy greenness during the heat wave.

Evaluation of Design Parameters of Dental Implant Shape, Diameter and Length on Stress Distribution: A Finite Element Analysis

The aim was to evaluate the design parameters of dental implants shape, diameter and length on stress distribution by finite element analysis (FEA).The objectives of the study was to compare the influence of stress distribution in the implants of screw-vent tapered and parallel design by varying the implant diameter with a standard implant length. Six dental implant models have been simulated three-dimensionally. The influence of diameter and length on stress distribution was evaluated by Group I: for screw-vent tapered design (Zimmer Dental Implant Carlsbad, CA, USA) (1) Dental implant model with diameter 3.7mm and length 13mm. (2) Dental implant model with diameter 4.1mm and length 13mm. (3) Dental implant model with diameter 4.7mm and length 13mm. Group II: for parallel design (Zimmer Dental Implant Carlsbad, CA, USA) (4) Dental implant model with diameter 3.7mm and length 13mm. (5) Dental implant model with diameter 4.1mm and length 13mm. (6) Dental implant model with diameter 4.7mm and length 13mm. The 3-D model of the implant was created in the pro-e wildfire 4.0 software by giving various commands. This model was imported to the ANSYS software through IGES (initial graphic exchange specification) file for further analysis. All six models were loaded with a force of 17.1, 114.6 and 23.4N in a lingual, an axial and disto-mesial direction respectively, simulating average masticatory force in a natural oblique direction, to analyze the stress distribution on these implants. The increase in implant diameter in Group I and Group II from 3.7 to 4.1mm and from 4.1 to 4.7mm with constant 13mm length for screw-vent tapered and parallel design implant resulted in a reduction in maximum value of Von Mises stress in the bone surrounding the implant was statistically significant at 5% level done by student "t" test. The overall maximum value of Von Mises stress was decreased in parallel design implant diameter of 4.7mm with constant length of 13mm when compared to screw-vent tapered design implant samples. The results of the FEA computation depend on many individual factors including material properties, boundary conditions interface definition and also on the overall approach to the model. The results depicted that the tapered shape implant design exhibited higher stress levels in bone than the parallel shaped implant design which seemed to be distributing stresses more evenly. The application of a 3-D model simulation with the non-symmetric loading by the masticatory force on a dental implant resulted in a more satisfactory modeling of "clinical reality" than that achieved with 2-D models used in other studies.

Development of Insulation Technology in Compact SF6 Gas-filled Bushings-Development of Compact 800kV SF6 Gas-filled Bushings-

As for gas insulated switchgear (GIS), small space requirement and economical efficiency have been demanded. Circuit breakers (CB), disconnecting switches (DS) and earthing switches (ES) have been designed toward compactness. Compact & light bushings have been also required. As for bushings of GIS, there are roughly three types; capacitor, gas-filled and molding bushings. Since gas-filled bushings have the feature which is both of the lightness and the economical efficiency, it is important to develop compact and light gas-filled bushings by improvement of insulation technology. The main subject for compact design is reduction of electric field strength on the outside hollow insulator around the inside grounded electrode tip. We devised a new inner grounded electrode structure which consists of some column electrodes. This paper describes the effect of reduction of maximum value of electric field strength on the outside hollow insulator by a new inner grounded electrode. Then, improvement of insulation performance for electrodes with insulation coating in SF6 gas is described as composite insulation technology. Finally, the efficacy of these insulation technologies is described by fundamental insulation test results of prototype compact 800kV SF6 gas-filled bushing.