The Molecular Structure of SBR and Filler Type Effects on Thermal Diffusivity of SBR/BR Compounds Used in Tire Tread

This research work is devoted to the study of the thermal diffusivity of SBR/BR compounds used as the tread of radial tires. Three series of rubber compounds were prepared, in which two solution SBR grades (with and without extra oil) as well as an emulsion SBR were selected. Five compounds with different CB/silica ratios were designed for each of the three series. Moreover, three compounds without fillers were prepared as reference samples. Thermal diffusivities of the compounds were determined by a novel technique to solve an inverse heat transfer problem. Abaqus and Isight codes were used to carry out the finite element solution and optimization. It is shown that, in all the compounds the thermal diffusivities were reduced with increasing the temperature. In addition, the macro- and micro- structures of SBR as well as the CB/silica ratios greatly affected the variations in thermal diffusivities with temperature. The thermal diffusivity and its variabilities were studied and discussed by different structural and functional parameters such as intermolecular distance, molecular vibrational energy, difference between the thermal diffusivities of the polymer and filler, and the chemical bonds between the polymer and silica

Study on the Effectiveness of Some Multicomponent Material Models with Hyper-viscoelasticity and Stress Softening for SBR/Carbon Black Compounds under two Loading Modes

Hypothesis: Determination of the parameters of the material models for rubber compounds is usually carried out under simple modes such as uniaxial tension. These models are typically consisted of hyper-viscoelastic and stress-softening equations. However, due to the complicated behaviors of rubbery materials, the effectiveness and accuracy of such models under combined loads of tension, compression, and shear should be verified.Methods: Three rubber compounds were prepared based on SBR reinforced by three different amounts of carbon blacks and underwent uniaxial cyclic under two loading/unloading rates and volumetric tests. The experimental data were used for the determination of parameters of three complex material models using a nonlinear curve fitting method. These models were selected based on the results of our previous findings. We have verified the uniaxial condition of the chosen test method and sample size using finite element method. The computed parameters were employed to simulate cylindrical rubber samples prepared from the same compounds through the finite element method using Abaqus code under compressive-contact loads. The predicted results were next compared with their experimentally measured data.Findings: The results showed that the effectiveness of a material model in the prediction of stress-strain or stress-time behavior of a rubber compound under a simple load case does not necessarily guarantee that the same level of accuracy is obtained for the other loading modes, especially for highly filled compounds.  It is shown here that to obtain accurate results in such cases, in addition to hyper-viscoelastic and stress softening equations, the material model should include proper terms to consider the effect of the filler-filler interactions into account, especially for highly carbon black-loaded compounds. It is found that the best model is the one in which the viscoelastic behavior of the filler-filler structure is independently included

Effects of continuous sonication on laminar convective heat transfer inside a tube using water–TiO2 nanofluid

In this research, an experimental study is carried out to investigate the effect of adding TiO2 nanoparticles to the distilled water on convective heat transfer and pressure drop with and without continuous induced ultrasonic field in the nanofluid’s reservoir under constant heat flux. Experiments are done for laminar flow regime with volume concentration, up to 0.25%. It is observed that adding nanoparticles to the base liquid enhances Nusselt number, and more particle concentration leads to more enhancements in Nusselt number except for 0.25% volume concentration. Results also show that the Nusselt number of the nanofluids at the volume concentration of 0.25vol.% was approximately the same as base fluids for the given conditions. In addition, the achievements demonstrate that inducing ultrasonic field increases Nusselt numbers dramatically compared with those results obtained with no sonication. Finally, no significant increase occurs in pressure drop in the range of studied volume fractions

Primary hydatid cyst of the thyroid glands: two case reports and a review of the literature

Abstract Introduction Although hydatid cyst remains one of the prevalent parasitic infections in humans, hydatid cyst of the thyroid is extremely rare, even in endemic areas. Here we present two cases of thyroid hydatid cysts. Case presentation A 35 and a 50 year-old Iranian female with a positive history of animal contact were presented with a neck lump without any compressive symptoms. A physical exam revealed neck masses that elevated with swallowing. Thyroid gland ultrasonography showed cystic thyroid lesions, and fine needle aspiration (FNA) suggested a thyroid hydatic cyst. Thyroid lobectomy and isthmectomy were done for the first patient, and near-total thyroidectomy was done for the other. The pathology report confirmed the diagnosis of a hydatid cyst. None of the patients had hydatid cysts in other sites. Patients were discharged without an antiparasitic drug, and no recurrence was detected at the six-month follow-up. Conclusion It is necessary to consider hydatid cysts in the differential diagnosis of cystic lesions of the thyroid gland in endemic areas, especially in people with a positive history of animal contact

Establishment of a novel triage system for SARS-CoV-2 among trauma victims in trauma centers with limited facilities

Objectives The triage of trauma patients with potential COVID-19 remains a major challenge given that a significant number of patients may be asymptomatic or pre-symptomatic. This study aimed to compare the specificity and sensitivity of available triage systems for COVID-19 among trauma patients. Furthermore, it aimed to develop a novel triage system for SARS-CoV-2 detection among trauma patients in centers with limited resources.Methods All patients referred to our center from February to May 2020 were enrolled in this prospective study. We evaluated the SARS-CoV-2 triage protocols from the WHO, the Iranian Ministry of Health and Medical Education (MOHME), and the European Centre for Disease Control and Prevention (ECDC) for their effectiveness in finding COVID-19 infected individuals among trauma patients. We then used these data to design a stepwise triage protocol to detect COVID-19 positive patients among trauma patients.Results According to our findings, the WHO protocol showed 100% specificity and 13.3% sensitivity. The MOHME protocol had 99% specificity and 23.3% sensitivity. While the ECDC protocol showed 93.3% sensitivity and 89.5% specificity, it did not prioritize patients based on traumatic injuries and unstable conditions. Our stepwise triage protocol, which prioritizes traumatic injuries, had 93.3% sensitivity and 90.3% specificity.Conclusion Our study shows that the triage protocols from the WHO, MOHME and ECDC are not best equipped to diagnose SARS-CoV-2 infected individuals among trauma patients. In our proposed stepwise triage system, patients are triaged according to their hemodynamic conditions, COVID-19 related clinical states, and COVID-19 related laboratory findings. Our triage model can lead to more accurate and resource-effective management of trauma patients with potential COVID-19 infection.Level of evidence Level Ⅲ