The modal decomposition study of the non-reactive flow field in a dual-swirl combustor is investigated through the large eddy simulation. The formation mechanism and function of various recirculation ...zones are elaborated by analyzing the time-averaged and instantaneous velocity contours of the center section. The precessing vortex core (PVC) is first visualized by the pressure iso-surface, and the evolution process is presented. Different dimensionality reduction methods are adopted to identify the coherent structures from the flow field. The most energetic spatial structure corresponding to the PVC and its second-order harmonic structure is extracted by the classical proper orthogonal decomposition (POD). The coherent structures with high frequency have relatively low energy content. In addition, a spectral proper orthogonal decomposition (SPOD) method, which can implement spatial-temporal decomposition simultaneously, is introduced to obtain the energy-based spatial structures at all characteristic frequencies. A triple-helix with azimuth wave number m = 3 and a quadruple-helix with azimuth wave number m = 4 are discovered as the third-order and the fourth-order harmonics of single-helix, respectively.
Abstract
Background
Premature ventricular complexes (PVCs) originating in the ventricular outflow tracts are mostly of benign character.
Case Summary
We describe a rare case of pulmonary hypertension ...with severe hypoxaemia and confusion caused by a significant mitral regurgitation (MR) during PVC originating in the left ventricle summit. After successful PVC ablation, all above-mentioned clinical parameters had normalized.
Discussion
Premature ventricular complexes originating in the outflow tracts should be considered as a potential though rare cause of severe MR and pulmonary hypertension.
This study describes the synthesis of new nonmigrating PVC plasticizers based on oleic acid as the main raw material. Their structures and production routes were planned to ensure that the resulting ...synthesis by‐products could also act as PVC plasticizers. All received Esters 1, 2, and 3 revealed plasticizing effect on PVC. Achieved results of elongation at break (260%) for PVC composites with Ester 2 (C11) and Ester 3 (C14) were comparable to those recorded for diisononyl phthalate (DINP) and dioctyl terephthalate (DOTP) (C2 and C5), and only 15% lower for Ester 1 (C8). As intended, the developed plasticizers showed high resistance to migration. The Ester 3 proved to be an extremely migration‐resistant bio‐based plasticizer, due to its high oxirane ring content and large molecule size. After 28 days of survey, the loss of this plasticizer from the PVC sample with 50 PHR of plasticizer was 4.7%, which is nearly 80% lower compared to DINP. Ester 2 was slightly less resistant to migration—with 14.1% mass loss observed after 28 days, which can be attributed to the smaller size of its molecules. Additionally, PVC composites containing Esters 1, 2, and 3 exhibited higher thermal stability compared to composites with DINP or DOTP. T10% for PVC composites with 60 PHR of Esters 1, 2, and 3 was recorded at 286.2°C, 282.8°C, and 286.4°C, respectively. Thus, the developed esters can act not only as PVC plasticizers, but also as thermal stabilizers.
New bio‐based nonmigrating PVC plasticizers.
Since cadmium is a hazardous material for environment, various techniques have been developed for safe removal of cadmium. Among these techniques, ionic polymer inclusion membranes (IPIMs) have a ...higher membrane structural stability that can be used to separate and recover cadmium ions with a higher selectivity. Also, the ion transport capacity of IPIMs can be further increased by selecting suitable ion carriers and plasticizers. In this study, preparation of IPIMs was accomplished by selecting newly synthesized symmetric and having different alkyl chain room temperature ionic liquids as ion carriers for selective the separation of cadmium from iodide-containing acidic solutions. The highest mass transport was determined as 0.958 μmol s−1 cm−2 from 25 mg L−1 and 2.02 μmol s−1 m−2 from 75 mg L−1 Cd(II) solution, respectively, when using the optimized IPIM containing 24.97% (w/w) 2-nitrophenyl octyl ether as plasticizer and 35.12% (w/w) 1,3-decyl-1 H-imidazol-3-ium bromide as carrier. The mass transport of cadmium was determined as 0.567 μmol s−1 m−2 in the presence of Cr3+, Fe2+, Co2+, Ni2+ and Zn2+. Surface analyses were explored by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), while the structural analysis was carried on by Fourier infrared spectroscopy (FTIR) before/after Cd transport experiments.
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•Synthesis of PVC based IPIMs with symterical RTILs.•Removal of Cd2+ from industrial wastes.•Selective extraction of Cd2+.
The present study was aimed to investigate the effect of PVC on reproductive competence in adult male Wistar rats. Further, the study also encompasses the protective effect of trans-resveratrol on ...PVC-induced reproductive toxicity in rats. Adult male rats weighing 210–240 g were administered with either PVC at two different doses 100 and 500 mg/kg body weight, orally, daily for 60 days or resveratrol (20 mg/kg body weight/day) through gavage for 60 days on alternate days or both PVC (500 mg/kg body weight) and resveratrol. The results revealed significant reduction in the weights of reproductive organs, epididymal sperm count, viable-, motile-, and HOS-tail coiled sperm and testicular daily sperm production, steroidogenic enzyme activities, serum testosterone levels in PVC treated rats. Conversely the levels of lipid peroxidation increased significantly with a decrease in activity levels of antioxidant enzymes in the testis of PVC exposed rats. Exposure to PVC resulted in reduction in epithelial thickness and seminiferous tubule diameter. No significant changes in the selected reproductive variables were observed in the resveratrol alone treated control rats, whereas, co-administration of resveratrol and PVC resulted in a significant improvement in steroidogenesis and spermatogenesis and mitigated oxidative stress over PVC exposed rats.
•Exposure to PVC reduced reproductive organ weights and spermatogenesis in rats.•Serum testosterone levels decreased significantly in PVC exposed rats.•The testicular oxidative toxicity increased in rats exposed to PVC.•Co-administration of resveratrol ameliorated PVC-induced suppressed reproduction.
The objective of this paper is to study the thermal characteristic of low-voltage alternating current (AC) arc faults. Two series of experiments were designed, including polyvinyl chloride (PVC) wire ...ignitions experiments and electrode arcing experiments (non-ignitions) subjected to arc faults at different effective currents. The ignition time of the wire and the temperature of the electrode were investigated to characterize the arcing hazard. Results show that the ignition time of the wire decreases with the increasing arc current, and the wire with a larger cross-section area requires more time to be ignited at the same current. For non-ignition experiments, the electrode temperature increases first and then varies little. A heat equilibrium stage can be reached, where the heat transfer of the arc to the electrode is equal to the heat dissipation of the electrode. Furthermore, a heat transfer model for the arc fault is established to obtain the electrode temperature. The temperature of the arc-electrode interface is used to characterize the arc energy, and it is found the temperature showed a logarithmic increase with the current. The results of this study may be useful in the safety design of electrical wires, and can be exploited as hazard indicators for the risk assessment of electrical fires.
Polyvinyl chloride (PVC) is a common thermoplastic polymer with limited optical applications due to its large optical band gap. In this study, organic soluble nitrogen-doped carbon dots (ONCDs) were ...synthesized from 4-aminoantipyrine (4AA) as the precursor through a solvent-free method and employed to reduce the optical band gap of PVC polymer considerably. The formation of ONCDs was investigated through spectroscopic analysis. The synthesized ONCDs were characterized using various techniques, including FTIR, XPS, 13C NMR, 1H NMR, UV–Vis spectroscopy, PL spectroscopy, HR-TEM, and XRD. FTIR and XPS analyses identified the existence of amine, imine, and hydroxy groups on the surface of ONCDs. Furthermore, XPS analysis revealed the presence of carbon, nitrogen, and oxygen via distinguished peaks. 13C NMR and 1H NMR spectra supported the formation of ONCDs. UV–Vis, PLE, and PL spectroscopy techniques provided insights into the light absorption and emission properties of ONCDs. HR-TEM analysis showed uniform ONCDs with a mean particle size of 9 nm. XRD analysis confirmed an amorphous nanostructure of ONCDs with 0.42 nm interlayer spacing. The results illustrate that the absorption of photons by the PVC/ONCDs films covers the entire range of UV to near-infrared. The refractive index was tuned from 1.72 to 2.16 upon adding ONCDs. The increase of the optical dielectric constant (ɛ1) is attributed to the increase in the localized density of states (N/m*). Based on quantum concepts, the optical dielectric loss (ɛ2) was examined to determine the exact value of energy gaps. Taucs model along ɛ2 results was utilized to determine the type of electron transition. The PVC/ONCDs films display a low band gap within the range of 1.52–1.78 eV. These findings demonstrate that the PVC/ONCDs films have improved optical properties and potential for various optoelectronic applications.
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•We investigated the formation mechanism of nitrogen-doped carbon dots.•Enhanced optical properties of polyvinyl chloride using nitrogen-doped carbon dots.•Taucs Model and Optical dielectric loss was used to obtain band gap values.•Band gap shrinkage of PVA from 4.76 eV to 1.52 eV were achieved.•Optical dielectric functions used to determine fundamental parameters.
The present study describes the electromagnetic interference shielding effectiveness (EMI SE) of poly (vinyl chloride) (PVC)/MWCNT nanocomposites prepared by solution blending in the presence of PVC ...beads and their corresponding electrically conductivity. Commercial PVC beads were added to the high viscous media of solution blended PVC-MWCNT during solvent evaporation of the prepared PVC/MWCNT nanocomposite. Addition of PVC beads increased the EMI SE and electrical conductivity values of the nanocomposite compared to the PVC/MWCNT nanocomposite without any PVC beads. Additionally, both EMI SE and electrical conductivity were also increased with increasing content of PVC bead at constant MWCNT loading in the nanocomposite. The insulating PVC bead regions are free from any MWCNT and acts as dispersed domains (excluded volume) which enhances effective concentration of MWCNT in the continuous PVC phase of the nanocomposites, and thus, play the key role to lower the percolation threshold, enhance the EMI SE and electrical conductivity values of the nanocomposite. The nonconductive PVC bead region in the nanocomposite acts as excluded volume that attenuates the microwave energy through multiple internal reflections by creating an impedance mismatch in the nanocomposites.
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This study evaluated the effects of temperature and speed screw rotation of rigid recycled PVC pipe extrusion process on mechanical properties and dimensional variation. In developing the experiments ...were used the factorial design method type 2k. Were studied the influence of process variables on the properties of impact resistance, dimensional change and tensile strength of PVC pipe. From this study, it was possible to define the best extrusion process conditions with a point of view on the best properties of PVC pipes. The results indicated that the screw rotation has a significant influence on the impact property. For the dimensional variation, the extrusion temperature had a significant influence. There is no significant statistical values for the tensile strength in the studied variables.
This study provided a geographic and technical matching approach supporting low-carbon style recycling systems, demonstrated using polyvinyl chloride waste (PVCW) generated in 2018 in Mie Prefecture, ...Japan. From a carbon dioxide (CO
) emission basis, mechanical/material recycling (MR) and energy recovery facilities were all allocated full capacity; however, parts of chemical recycling facilities were excluded in the optimal solutions. From the spatial distribution of the allocated result, we confirmed a trend that to achieve the minimum total emissions, the matchings from pretreatment to recycling facilities were done based on a nearby priority rule. From an emission reduction basis, MR accounted for the major proportion of total reductions which was similar to that accessed from an emission basis. Thus, the promotion of MR should be prioritized at the current technical level when optimizing emissions of the whole lifecycle. The number of facilities allocated were substantially reduced; meanwhile, the averaged emission reductions per ton of PVCW disposed were increased from the current level (2.93) to the near-future level (4.99 t-CO
t
). Thus, we concluded that this optimization under a higher technical level was effective to make the current recycling system with more emission reductions (low-carbon environmental effect) and require fewer disposal facilities (cost-saving economic effect). Meanwhile, certain long-distance routes found in solutions implied that technical parameters were more important than geolocation parameters to achieve maximum emission reductions.
