A two-dimensional air streamer discharge modified model based on artificial stability term under non-uniform electric field at low temperature and sub-atmospheric pressure

In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate. Based on the modified model, the characteristics of low temperature subatmospheric air discharge under 13 kV direct current voltage are discussed, including needle-plate and needle-needle electrode structures. Firstly, in order to verify the reliability of the model, a numerical example and an experimental verification were carried out for the modified model respectively. Both verification results show that the model can ensure the accuracy and repeatability of the calculation. Secondly, according to the calculation results of the modified model, under the same voltage and spacing, the reduced electric field under low temperature subatmosphere pressure is larger than that under normal temperature and atmospheric pressure. The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier, and has a faster propagation speed in the streamer development stage, which shortens the overall discharge time. Finally, the discharge characteristics of the two electrode structures are compared, and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure. When the pre-ionization level reaches 1013 cm-3, the propagation speed of the positive streamer remains unchanged throughout the discharge process, and is no longer affected by the negative streamer. The peak value of electric field decreases with the increase of pre-ionization level, and tends to be constant during streamer propagation. Based on the previous paper, this paper constructs the air discharge model under non-uniform electric field, complements with the previous paper, and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure, which provides a certain reference for future research.

21G细针穿刺致肝包膜下血肿伴休克1例

出血是经皮经肝胆道引流术(percutaneous transhepatic biliary drainage,PTBD)的并发症之一,尽管发生率不高(2%~2.5%)[1],但可导致严重后果[2,3]。无论胆道出血、腹腔出血、胸腔出血,都多由加硬套管或引流管损伤所致。单纯21G细针穿刺所致的出血十分罕见。我科室遇到1例仅21G细针穿刺3次致肝动脉损伤,引起肝包膜下巨大血肿,进而导致休克的病例。现将诊疗过程及经验教训报道如下。

Growth performance, nutrient digestibility, and slaughter traits of male fattening lambs under different feeding standards

This study compared the growth performance, nutrient utilization, and slaughter traits of Dorper crossbred male lambs fed as per the established nutrition recommendations for sheep, with an aim to verify the efficacy of different feeding standards. A total of 576 lambs(4 months of age, 28.3 ± 0.86 kg BW) were randomly allotted to 3 treatments with 12 replicates per treatment(16 lambs per replicate).The lambs were fed diets formulated according to the following 3 nutritional systems: the nutrient requirements of Dorper crossbred lambs established by Chinese Academy of Agricultural Sciences(CAAS),NRC(National Research Council),(2007), and AFRC(Agricultural and Food Research Council)(1993). The experiment lasted for 81 d. Feed intake was recorded every 3 days, and lambs were weighed every 20 days. Digestibility trials were conducted with 6 lambs each group from d 42 to 53 and d 70 to 81. At the end of the experiment, 10 lambs randomly chosen from each group were sacrificed to determine the carcass traits and meat quality. The results indicated that the lambs in the NRC group had the highest dry matter intake(DMI), followed by those in the AFRC and CAAS groups(P < 0.05). The average daily gain,carcass weight, and dressing percentage were higher for lambs in the CAAS group than those in the NRC group(P < 0.05). The lambs in the CAAS group had the lowest feed conversion ratio, followed by those in the AFRC and NRC groups(P < 0.05). The apparent digestibility of DM was higher for the lambs in the CAAS group than those in the NRC group(P < 0.05). Water losing rate, as well as the lightness(L*),redness(a*), and yellowness(b*) values of the longissimus thoracis were not different among groups(P > 0.05). In conclusion, Dorper crossbred lambs fed diets formulated according to the CAAS recommendations exhibited superior growth performance than those fed diets formulated according to the American or British feeding standards.