Torque and bending moment acting on a flexible shaft agitated by disk turbines in a gas–liquid stirred vessel

The torque and bending moment acting on a flexible overhung shaft in a gas–liquid stirred vessel agitated by a Rushton turbine and three different curved-blade disk turbines(half circular blades disk turbine, half elliptical blades disk turbine, and parabolic blades disk turbine) were experimentally measured by a customized moment sensor. The results show that the amplitude distribution of torque can be fitted by a symmetric bimodal distribution for disk turbines, and generally the distribution is more dispersive as the blade curvature or the gas flow rate increases. The amplitude distribution of shaft bending moment can be fitted by an asymmetric Weibull distribution for disk turbines. The relative shaft bending moment manifests a "rising-falling-rising" trend over the gas flow number, which is a corporate contribution of the unstable gas–liquid flow around the impeller, the gas cavities behind the blades, and the direct impact of gas on the impeller. And the "falling" stage is greater and lasts wider over the gas flow number for Rushton turbine than for the curved-blade disk turbines.

Coupling simulation of fluid structure interaction in the stirred vessel with a pitched blade turbine

The interaction between fluid and a down-pumping pitched blade turbine fixed with a flexible shaft in the stirred vessel, as a typical fluid structure interaction phenomenon, was simulated by coupling the Computational Fluid Dynamics and Computational Structural Dynamics. Based on the verification of the simulated impeller torque and dimensionless shaft bending moment with experimental result, the dimensionless shaft bending moment and various loads acting on impeller(including lateral force, axial force and bending moment) were discussed in detail. By separating and extracting the fluid and structural components from those loads, the results show that the shaft bending moment mainly results from the lateral force on impeller although the axial force on impeller is much larger. The impeller mass imbalance increases the shaft bending moment and the lateral force on impeller, but has little influence on the axial force and bending moment acting on impeller. The dominant frequencies of impeller forces are macro-frequency, speed frequency and blade passing frequency, and are associated with the impeller mass imbalance.

14.1 W continuous-wave dual-end diode-pumped Er:Lu_(2)O_(3)laser at 2.85μm

We present our efforts towards power scaling of Er:Lu_(2)O_(3)lasers at 2.85μm.By applying a dual-end diode-pumped resonator scheme,we achieve an output power of 14.1 W at an absorbed pump power of 59.7 W with a slope efficiency of 26%.In a single-end pumped resonator scheme,an output power of 10.1 W is reached under 41.9 W of absorbed pump power.To the best of our knowledge,this is the first single crystalline mid-infrared rare-earth-based solid-state laser with an output power exceeding 10 W at room temperature.

Repercussions of COVID-19 pandemic on solid waste generation and management strategies

It has been over ten months since the beginning of the 2019 coronavirus disease(COVID-2019),and its impact on solid waste management,especially medical waste,is becoming clearer.This study systematically reviews the potential influences of the COVID-19 pandemic on medical waste,personal protection equipment waste and municipal solid waste(MSW),and discusses the corresponding measures and policies of solid waste management in typical countries.The results show that the generation of medical waste from the pandemic increased significantly,with 18%‒425%growth.It is estimated that the daily output of COVID-19 medical waste increased from 200 t/d on Feb.22 to over 29000 t/d at the end of September 2020 throughout the world.The use of personal protective equipment will continue to grow in the long-term,while the blockade and isolation measures greatly reduced the volume of commercial waste,especially for tourist cities,and part of this waste was transferred to household waste.Residents’attitudes and behavior toward food waste have changed due to the COVID-19 pandemic.In response to the pandemic,international organizations and several countries have issued new policies and guidelines and adjusted their management strategies for medical waste and MSW treatment.The pandemic has brought specific challenges to the disposal capacity of medical waste worldwide.It has also brought about the stagnation of policies related to the reduction of plastic products and waste recycling.This study will provide some useful information for managers and governmental officials on effective solid waste management during and after the COVID-19 pandemic.

Engineering immune-responsive biomaterials for skin regeneration

The progress of biomaterials and tissue engineering has led to significant advances in wound healing,but the clinical therapy to regenerate perfect skin remains a great challenge.The implantation of biomaterial scaffolds to heal wounds inevitably leads to a host immune response.Many recent studies revealed that the immune system plays a significant role in both the healing process and the outcome.Immunomodulation or immuno-engineering has thus become a promising approach to develop pro-regenerative scaffolds for perfect skin regeneration.In this paper,we will review recent advancements in immunomodulating biomaterials in the field of skin repair and regeneration,and discuss strategies to modulate the immune response by tailoring the chemical,physical and biological properties of the biomaterials.Understanding the important role of immune responses and manipulating the inherent properties of biomaterials to regulate the immune reaction are approaches to overcome the current bottleneck of skin repair and regeneration.

Mid-infrared Q-switch performance of ZrC

Zirconium carbide(ZrC)with layered structure and nanoparticle morphology was prepared by sonication in an ethyl alcohol solvent.The morphology and saturable absorption properties of the ZrC were systematically analyzed.By using ZrC nanoparticle coated substrates as saturable absorbers,stable Q-switched 3μm Er:Lu_(2)O_(3) lasers were realized.Pulse durations of 50 ns with pulse energies of 20μJ and peak power of 0.4 kW are the shortest obtained with novel-material-based Q-switched lasers in the 3μm wavelength range.