A Mathematical Model of Heat Transfer in Partially Insulated Airways in Deep, Frozen Ground Placer Mines

Large seasonal variations in the temperature of the ventilating air in mines in the arctic cause changes in the original thermal field through heat and mass exchanges between the air and the surrounding medium. These thermal interactions have major influence on climatic quality as well as on the stability of the mine openings. Thawing of walls and roof in mine airways can be reduced by various types of thermal-insulation. Application of thermal-insulation prevents deep thawing of the rockmass surrounding an airway. In this case, the mechanism of heat transfer around a frozen, underground airway would be much different. A model of heat transfer in a deep, partially insulated airway has been developed and analyzed using finite element methods. Results of the analysis show that without any thermal control, there will be stable change in temperature around the mine airway. With different insulations on the walls of the airway, roof thawing can be reduced and in certain cases, completely eliminated

CFD Simulations of Hydrogen Tank Fuelling: Sensitivity to Turbulence Model and Grid Resolution

CFD modelling of compressed hydrogen fuelling provides information on the hydrogen and tank structure temperature dynamics required for onboard storage tank design and fuelling protocol development. This study compares five turbulence models to develop a strategy for cost-effective CFD simulations of hydrogen fuelling while maintaining a simulation accuracy acceptable for engineering analysis: RANS models k-ε and RSM; hybrid models SAS and DES; and LES model. Simulations were validated against the fuelling experiment of a Type IV 29 L tank available in the literature. For RANS with wall functions and blended models with near-wall treatment, the simulated average hydrogen temperatures deviated from the experiment by 1–3% with CFL ≈ 1–3 and dimensionless wall distance y+ ≈ 50–500 in the tank. To provide a similar simulation accuracy, the LES modelling approach with near-wall treatment requires mesh with wall distance y+ ≈ 2–10 and demonstrates the best-resolved flow field with larger velocity and temperature gradients. LES simulation on this mesh, however, implies a ca. 60 times longer CPU time compared to the RANS modelling approach and 9 times longer compared to the hybrid models due to the time step limit enforced by the CFL ≈ 1.0 criteria. In all cases, the simulated pressure histories and inlet mass flow rates have a difference within 1% while the average heat fluxes and maximum hydrogen temperature show a difference within 10%. Compared to LES, the k-ε model tends to underestimate and DES tends to overestimate the temperature gradient inside the tank. The results of RSM and SAS are close to those of LES albeit of 8–9 times faster simulations

Accelerated Cavitation Damage of Steels in Liquid Metal Environments

Cavitation can be described as a hydrodynamic phenomenon which involves in the formation and collapse of vapor bubbles in a liquid medium. It always accelerates the cavitation damage and brings about multi-scale interactions of cavitation erosion between materials and fluids. For example, corrosion by dissolution/reaction can accelerate cavitation erosion under different liquid temperatures and velocities to alter interface films, and multiphase interface structure can also in turn affect the interfacial flow regime to induce cavitation in various fluids. In this chapter, interfacial characteristics and erosion-corrosion mechanism of directionally solidified (DS) Fe-B alloy with various Fe2B lamellar spacing in flowing zinc were investigated. The results indicate that the formation of adhesive interfacial film not only depends on erosion time and Fe2B lamellar spacing, but also relies on epitaxial ζ accumulation determined by zinc flow effect. Meanwhile, microturbulence of flowing zinc can result in the formation of slip bands and erosion pits on the ζ-FeZn13 surface. The flow-induced localized corrosion appears to accelerate the erosion-corrosion damage of interfacial adhesive film structure and morphology, which reveals underlying erosion mechanism of liquid metal

Rutin prevents retinal ganglion cell death and exerts protective effects by regulating transforming growth factor-β2/Smad2/3Akt/PTEN signaling in experimental rat glaucoma

Purpose: To investigate the protective effect of rutin against glaucoma in a rat model, and the mechanisms involved. Methods: Sprague-Dawley rats were injected hypertonic saline in the limbal vein for elevation of intraocular pressure (IOP). Rats in the treatment group were administered rutin at doses of 12.5, 25 or 50 mg/kg orally and daily for 21 days. Results: Rutin markedly (p < 0.05) reduced IOP and prevented loss of retinal ganglion cells (RGCs). The expression of apoptotic pathway proteins, i.e., Bcl-xL, Bcl-2, Bad and Bax were significantly (p < 0.05) regulated by rutin. Moreover, rutin caused a substantial decrease in TGF-β2 expression, and also down-regulated p-Smad2 and p-Smad3 dose-dependently (p < 0.05). Raised levels of collagen I, fibronectin and elastin were effectively down-regulated. Rutin substantially up-regulated the Akt pathway involved in cell survival, and markedly improved the survival of RGCs subjected to hypoxia in vitro (p < 0.05). Conclusion: These results reveal that rutin exerts protective effect against glaucoma in a rat model via a mechanism involving regulation of the TGF-β2/Smad2/3Akt/PTEN signaling pathways. Thus, rutin has potentials for use in the management of glaucoma

Solitary pulmonary mass in a patient with a history of lymphoma: a case report

INTRODUCTION: With the progress made in treatments, the survival rate for patients with malignant lymphoma in the last 30 years has significantly improved. However, the risk of experiencing a second primary malignancy or other disease has increased significantly. CASE PRESENTATION: A 44-year-old Mongolian man with a large mass in his right lower abdomen was admitted to our hospital 15 years previously. The mass was removed, and confirmed via pathological examination to be a malignant B-cell lymphoma in the appendix and distal small bowel. Post-operative chemotherapy with standard cyclophosphamide, hydroxydaunomycin, vincristine (Oncovin®) and prednisolone regimen was given for six cycles. No obvious recurrence was detected over the following 12 years. Subsequently, a mass in the right lung was found on a regular X-ray follow-up; our patient did not report chills, fever or cough. Chest computed tomography and positron emission tomography scans confirmed the mass. A primary lung carcinoma was considered to be the most likely diagnosis. However, after an exploratory thoracotomy and right upper lobectomy was performed a pathological examination of tissue samples demonstrated a lung cryptococcal granuloma, with positive staining for periodic acid Schiff and periodic acid-silver metheramine. CONCLUSIONS: Compared to the normal population, second primary malignancy (in particular leukaemia and lung cancer) in patients with malignant lymphoma during their long-term survival has been seen occasionally. However, other diagnoses should also be considered such as pulmonary cryptococcosis. Other than computed-tomography-guided needle biopsy, surgery for some patients is a much more appropriate choice, which could also help attain correct diagnosis and treatment

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.open0

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.open0

A fully-printed 3D antenna with 92% quasi-isotropic and 85% CP coverage

Internet of things (IoT) applications require orientation insensitive wireless devices to maintain stable and reliable communication. For those reasons, antennas providing a wide quasi-isotropic and circular polarization (CP) coverage are very attractive. However, achieving a wide quasi-isotropic and CP coverage simultaneously is challenging. In this work, we show that properly designed sloped dipoles on a 3D structure can maximize the CP coverage (theoretically up to 100%) even with equal-phased feed to the dipole elements. We derive the conditions and present the design graphs for the optimum slope angle for the dipole elements on a 3D hexagonal-shaped package to achieve a wide quasi-isotropic and CP coverage simultaneously. Based on the proposed theory, a practical antenna has been designed and fabricated using additive manufacturing. The measured results demonstrate a 7dB-isotropy of 92% and a CP coverage of 85%, which matches well with the predicted results from the theoretical analysis and full-wave simulations