Conceptual Design of an Energy System for High Altitude Airships Considering Thermal Effect

High altitude airships possess tremendous potential for long-endurance spot hovering platforms for both commercial and strategic applications. The energy system, which is mainly made up of solar array and regenerative fuel cell, is the key component of a high altitude airship. The thermal effect is a major factor that affects the performance of the energy system of long endurance stratospheric vehicles. In this paper, a conceptual design method focusing on the thermal and power characteristics of an energy system for stratospheric airships is proposed. The effect of thermal behavior of solar array on the energy system is analyzed. An optimized case is obtained on the consideration of power supply, thermal behaviors of helium and solar array. Results show that the maximum temperature difference of the solar array may be reduced by about 20 K and the mass of payload can be improved by up to 5%

Numerical Investigation of a Novel Plate-Fin Indirect Evaporative Cooling System Considering Condensation

An indirect evaporative cooling system combining with thermoelectric cooling technology (i.e., TIEC system) is proposed, in which a counter-flow plate-fin indirect evaporative cooler is inserted with thermoelectric cooling (i.e., TEC) modules. In hot and humid climate, condensation may occur on the dry channel surface of the cooler. For the TIEC system, with the aid of TEC technology, the surface temperature of the dry channel can be much lower than that of a traditional indirect evaporative cooler, thus, the condensation from the primary air is more likely to take place. A numerical model of this novel TIEC system is developed with specifically taking condensation from primary air into account. Detailed performance analysis of the TIEC system is carried out. Analytical results found that the condensation from primary air reduces the dew point effectiveness by up to 45.0% by weakening the sensible heat transfer but increases the coefficient of performance by up to 62.2% by increasing the latent heat transfer, under given conditions. The effects of main operating conditions, such as the electrical current I and number n of TEC modules, inlet temperature Tp,i, humidity ratio RHp and velocity Vp of the primary air, and the mass flow rate ratio x of secondary to primary air, are investigated under non-condensation and condensation states. It is shown that condensate is more easily produced under higher I, n, Tp,i, RHp, x and lower Vp

Gut microbiome alterations in pulmonary hypertension in highlanders and lowlanders

Background Alterations in the gut microbiota have been observed in patients with pulmonary hypertension (PH), though whether the roles of the gut microbiota in PH at different altitudes are the same is unknown. This study aims to evaluate the associations of the gut microbiome with PH in highlanders and lowlanders. Methods PH patients and controls were recruited from those who permanently live on the Tibetan plateau (highlanders) or the plains (lowlanders), and underwent transthoracic echocardiography close to their altitude of residence (at 5070 m for highlanders versus6 m for lowlanders). The gut microbiome was profiled using metagenomic shotgun sequencing. Results In total, 13 PH patients (46% highlanders) and 88 controls (70% highlanders) were included. The overall microbial composition was different in PH patients compared to controls (p=0.003). Notably, among lowlanders, a composite microbial score of pro-atherosclerotic trimethylamine-producing species was increased in PH patients compared with that in controls (p=0.028), while among highlanders no such difference was observed (p=0.087). Another composite gut microbial score including eight species of Lactobacillus, which has shown beneficial effects on cardiovascular functions, was higher in highlanders than lowlanders (p<0.01). Furthermore, this score tended to be lower in PH patients than controls among highlanders (p=0.056) but not among lowlanders (p=0.840). In addition, the gut microbiome showed a good performance in distinguishing PH patients from controls in both lowlanders and highlanders. Conclusions Our study reported differently altered gut microbiome profiles between highland and lowland PH patients, highlighting the distinct microbial mechanism in PH in highlanders compared with lowlanders

Pressure Induced Amorphization of Pb²⁺ and Pb⁴⁺ in Perovskite PbFeO₃

Perovskite-type oxides have been the subject of intense research due to their various fascinating physical properties stemming from their charge degree of freedom. PbFeO3 has an unusual Pb2+0.5Pb4+0.5Fe3+O3 charge distribution with a long-ranged ordering of Pb2+ and Pb4+ and two inequivalent Fe3+ sites in a perovskite structure. Combined synchrotron X-ray diffraction and Mössbauer spectroscopy revealed a change to an orthorhombic GdFeO3 structure with a unique Fe3+ site and randomly distributed Pb2+ and Pb4+ at 29.0 GPa, namely, pressure-induced amorphization of Pb2+ and Pb4+. The absence of a charge transfer transition to the Pb2+Fe4+O3 phase, which was expected from the comparison with PbCrO3 and PbCoO3, was verified using ab initio density functional theory calculations in the range of 0–70 GPa