Numerical simulation and performance analysis of the radiofrequency inductive cathode

The radiofrequency(RF) inductive cathode has great prospects in space missions with long mission cycles, large speed increments, and rapid response requirements as the main electron source and neutralizer in Hall thrusters and ion thrusters. This paper proposes a comprehensive multi-physics RF inductive cathode model in which the RF electromagnetic field, electrostatic field for extracting electrons, flow field, plasma transport and electrochemical reaction process are all accounted for. Each physical field mentioned above can form a closed partial differential equation. The two-dimensional finite element code COMSOL is used to solve the multi-physics model. With this model, the formation process of the anode spot is exhibited and demonstrates the non-bipolar flow theory in practice. The simulation results demonstrate that the current jump in the RF inductive cathode is caused by the anode spot. Furthermore, the influences of preset discharge parameters such as RF power, bias voltage and actuating gas flow as well as structural parameters like the coil structure, discharge chamber size and ion collector area, emission hole size, distance between the anode target and the emission hole etc on the cathode performance are investigated, and some important optimal parameters are proposed.

Active dry yeast supplementation benefits ruminal fermentation,bacterial community,blood immunoglobulins,and growth performance in young dairy goats,but not for intermittent supplementation

This study evaluated the effects of active dry yeast(ADY)supplementation and supplementation stra-tegies on ruminal fermentation,bacterial community,blood metabolites,and growth performance in young dairy goats.Sixty young female Guanzhong dairy goats of similar age(4.00±0.50 months)and BW(19.65±0.41 kg)were randomly divided into 3 groups(n=20):(1)basal diet group(CON);(2)basal diet continuously supplemented with 3.0 g/goat per day commercial ADY(a proprietary strain of Saccharomyces cerevisiae with 5.0×10^(9)cfu/g)group(CSY);(3)basal diet with intermittently supple-mented ADY group(ISY;5 d supplementation with ADY at 4.5 g/goat per day following 5 d of no sup-plementation).The experiment lasted 67 d with the first 7 d as an adaptive period.Rumen fluid and blood samples were collected bi-weekly.Data were analyzed using the MIXED procedure combined with the SLICE option in SAS.Specific orthogonal contrasts of ADY vs.CON and CSY vs.ISY were also analyzed.During the experimental period,ADY supplementation resulted in greater DMI(P=0.03),ruminal ac-etate proportion(P<0.01)and acetylesterase activity(P=0.01),and blood contents of glucose(P=0.01)and IgM(P=0.02)and tended to have greater ADG(P=0.05)and paunch girth(P=0.06)than the CON,despite the propionate proportion(P=0.03)and contents of total protein(P=0.04)and IgA(P=0.03)being lower.The lower ruminal NH_(3)-N(P<0.01)and blood urea nitrogen(P=0.07)contents indicated greater nitrogen utilization with ADY supplementation.ADY supplementation showed persistent effects after it was stopped because the BW at 12 months of age(P=0.03)and birth weight of lambs(P=0.02)were greater than the CON.However,the ISY did not show those benefits and had significantly lower relative abundances of fiber-degrading related bacteria than the CSY.In conclusion,ADY supplementa-tion,especially continuously supplemented,may enhance ADG and ADG:DMI ratio by improving DMI,ruminal cellulolytic bacteria abundance and enzyme activity,nitrogen utilization,and immune status.These findings provide a theoretical basis for the rational application of ADY and have important practical implications for the design of nutritional strategies in growing dairy goats.

Protonic recognition and assembly for the creation of porous Bronsted acid catalysts with enhanced catalytic efficiency

Due to the high local concentration of substrates in confined space, porous solid Bronsted acids have been extensively explored for efficient acid-catalyzed reaction. However, the porous structures with strong Bronsted acids lack long-term stability due to chemical hydrolysis. Moreover, the products inhibition effect in confined rigid cavities severely obstructs subsequent catalysis. Here, tubular Bronsted acid catalyst with unique recognition of protons was presented by self-assembly of p H-responsive aromatic amphiphiles. The responsive assembly could mechanically transfer hydrogen ions from low-concentration acidic solution into tubular defined pores, thereby producing effective catalytic activity for Mannich reactions in mildly acidic solution. Notably, the tubular catalyst unfolded into flat sheets upon addition of triethylamine for efficient release of products, which could be recovered by subsequent acidification and the catalytic activity still remained. Therefore, the porous Bronsted acid with reversible assembly provides a new strategy for mass synthesis through increasing conversion times.