No abstract

No abstract

Cu-containing Mg alloys are a novel type of antibacterial biomaterial based on biodegradation of Mg and antibacterial functions of Cu. However, fast degradation limits their clinical application. For the first time, this work utilizes the synergistic effects of biodegradation of ZK30, antibacterial function of Cu and grain refinement by selective laser melting (SLM) to prepare high-performance antibacterial ZK30-Cu alloys. The obtained alloys have an improved biodegradation resistance, which is attributed to remarkable grain refinement by SLM. Furthermore, the alloys exhibit good antibacterial ability and cytocompatibility.

The paper reports an experimental investigation of a newly proposed solar collector that integrates a closed-end pulsating heat pipe (PHP) and a compound parabolic concentrator (CPC).The PHP is used as an absorber due to its simple structure and high heat transfer capacity. The CPC has a concentration ratio of 3.4 and can be readily manufactured by three-dimensional printing. The CPC can significantly increase the incident solar irradiation intensity to the PHP absorber and also reduce the heat loss due to the decrease in the area of the hot surface. A prototype of the solar collector has been built, consisting of a PHP absorber bent by 4 mm diameter copper tube, CPC arrayed by 10×2 CPC units with the collection area of 300×427.6 mm 2 , a hot water tank and a glass cover. HFE7100 was utilized as the working fluid at a filling ratio of 40%. The operating characteristics and thermal efficiency of the solar collector were experimentally studied. The steady and periodic temperature fluctuations of the evaporation and condensation sections of the PHP absorber indicate that the absorber works well with a thermal resistance of about 0.26 ℃/W. It is also found that, as the main factor, the thermal performance of the collector decreases with increasing evaporation temperature. The collector apparently shows start-up, operational and shutdown stages at the starting and ending temperatures of 75 °C. When the direct normal irradiance is 800 W/m 2 , the instantaneous thermal efficiency of the solar collector can reach up to 50%.