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Hermetic digital scroll compressor has been widely used as a small-scale organic Rankine cycle application in the heating, ventilation, and air conditioning systems. A clunking noise issue is recently found in an air conditioning outdoor unit, and the main cause of the noise is experimentally identified to be the impact of the scrolls in the compressor unit during the switching process. The semi-active control methods are thus designed to greatly reduce the noise level by using additional valves to adjust the pressure changing rate within the modulation chamber. The response time for the impact of the scrolls can then be controlled by the added valves. The additional release valve with a smaller diameter pipe parallel to the main valve is tested firstly for its performance. Slower flow rate is produced and the pipe can extend the response time and decrease the speed of the impact process by reducing the pressure changing rate. The use of a discharge valve is also tested for controlling the pressure changing rate inside the chamber. The discharge valve with an opposite effect to the release valve is found useful for solving the noise issue. Both noise and vibration results confirm that the impact noise in the frequency range of interest can be reduced by using the proposed semi-active control methods.

While maternal exposure to high metal levels during pregnancy is an established risk factor for birth defects, the role of paternal exposure remains largely unknown. We aimed to assess the associations of prenatal paternal and maternal metal exposure and parental coexposure with birth defects in singletons. This study conducted within the Jiangsu Birth Cohort recruited couples in early pregnancy. We measured their urinary concentrations for 25 metals. A total of 1675 parent–offspring trios were included. The prevalence of any birth defects among infants by one year of age was 7.82%. Paternal-specific gravity-corrected urinary concentrations of titanium, vanadium, chromium, manganese, cobalt, nickel, copper, and selenium and maternal vanadium, chromium, nickel, copper, selenium, and antimony were associated with a 21–91% increased risk of birth defects after adjusting for covariates. These effects persisted after mutual adjustment for the spouse’s exposure. Notably, when assessing the parental mixture effect by Bayesian kernel machine regression, paternal and maternal chromium exposure ranked the highest in relative importance. Parental coexposure to metal mixture showed a pronounced joint effect on the risk of overall birth defects, as well as for some specific subtypes. Our findings suggested a couple-based prevention strategy for metal exposure to reduce birth defects in offspring.

Direct-drive wind turbines, different from the standard geared wind turbines, widely use a direct-drive permanent-magnet generator to avoid the gearbox failures. In the absence of a gearbox in the drive-train system, the direct-drive generator operates at low rotating speeds. Thus direct-drive wind turbines require a larger sized generator (higher weight) to transfer the kinetic energy into electrical energy. The inherent unbalanced magnetic pull force of the generator can have impact on the vibration behaviour of the drive-train system. This paper studies the effect of rotor position and weight adjustment on the vibration behaviour of the drive-train system within a 5 MW direct-drive wind turbine by considering the unbalanced magnetic pull force. The adjustment of rotor position and weight changes the location of the centre of gravity of the drive-train system. The drive-train system which consists of the main shaft, rotor, hub and blades is modelled as a four degree-of-freedom nonlinear system. Both rotor displacement and bearing forces are obtained for a wide range of rotor position and weight under different rotating speeds. The obtained results would provide useful information on the optimized rotor position and mass ratio to improve the performance of the drive-train system.

For a standard propeller system, the thrust output and the energy dissipation are proportionally dependent on its rotating speed, as its physical characteristics and working conditions are normally fixed during its operation. In order to improve the system performance and meet special application requirements, this paper presents the design of a novel two-stage propeller system with a morphing blade structure for higher thrust output and energy efficiency in operations. Based on the stacked Miura-ori (SMO) pattern, an origami-based structure is designed to enable a change in blade length for a propeller system and thus improve the system performance. The unique snap-through feature of the proposed origami structure is utilized to provide a two-stage working condition according to its rotating speed. The geometric parameter analysis of the SMO structure is first investigated, specifically focusing on the operating mechanism due to the snap-through behavior. Then, the implementation of the SMO structure into a rotating system is studied. The effects of design parameters on the critical transition points, which correspond to two operating states of the proposed propeller system, are numerically discussed. The simulation results confirm the performance improvement in the thrust output and energy-saving. The feasibility of using origami-based structures provides valuable insights into more applications in similar domains, such as fan system and wind turbine blades.

Resveratrol, a member of a class of polyphenolic compounds known as flavonols, has been extensively studied for its anticancer, antiviral, anti-inflammatory, and neuroprotective roles. Caenorhabidits elegans is a well-established animal for investigating responses to radiation. We found that resveratrol may provide protection against hazardous radiation. Pre-treatment with resveratrol extended both the maximum and mean life span of irradiated C. elegans. Resveratrol acted as a strong radical scavenger and regulated superoxide dismutase (SOD) expression. In addition, resveratrol was shown to be capable of alleviating gamma-ray radiation exposure-induced reduction in mitochondrial SOD expression. Ultimately, a correlation may exist between dietary intake of trace amounts of resveratrol and anti-aging effects. A specific response mechanism may be activated after the administration of resveratrol in irradiated animals. Our results suggest the protective effect of resveratrol is due to its strong ability to protect from oxidative stress and protective effects in mitochondria. Therefore, resveratrol is potentially an effective protecting agent against irradiative damage.