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To further explore the damage characteristics and impact response of the shaped charge to the solid rocket engine (SRE) in storage or transportation, protective armor was designed and the shelled charges model (SCM)/SRE with protective armor impacting by shaped charge tests were conducted. Air overpressures at 5 locations and axial acceleration caused by the explosion were measured, and the experimental results were compared with two air overpressure curves of propellant detonation obtained by related scholars. Afterwards, the finite element software AUTODYN was used to simulate the SCM impacted process and SRE detonation results. The penetration process and the formation cause of damage were analyzed. The detonation performance of TNT, reference propellant, and the propellant used in this experiment was compared. The axial acceleration caused by the explosion was also analyzed. By comprehensive comparison, the energy released by the detonation of this propellant is larger, and the HMX or Al particles contained in this propellant are more than the reference propellant, with a TNT equivalent of 1.168–1.196. Finally, advanced protection armor suggestions were proposed based on the theory of woven fabric rubber composite armor (WFRCA).

This study aimed to examine the changes in the blood fatigue indicators, inflammatory markers, and stress hormones following an 8-week intensity interval training in sprinters, and to investigate the effects on changes in the 100-m sprint records. Twenty sprinters from a boys’ high school were equally assigned to high-intensity and medium-intensity interval training groups, and three 60-min interval training sessions were performed per week for 8 weeks, for a total of 24 sessions. Exercise intensity was defined as 85%–95% and 75%–85% of heart rate reserve for high- and medium-intensity training, respectively. At rest, both groups had an exercise intensity of 60% of the heart rate reserve. Our results showed decreased fatigue indicators, inflammatory markers, and stress hormone levels after high-intensity and medium-intensity interval training, with no difference between the training levels. In addition, the 100-m sprint records were different in high- and medium-intensity interval training groups, based on the lactate dehydrogenase and adrenocorticotropic hormone levels. In conclusion, medium-intensity interval training with a reserve heart rate of ≥ 75% can have a positive effect on blood fatigue indicators, inflammatory markers, and stress hormones in sprinters. Specifically, the changes in adrenocorticotropic hormone level seen in the high-intensity interval training group were found to have a significant effect on the 100-m sprinting records.

The purpose of this study was to investigate the effects of physical activity on changes in lower limb muscle tone and body balance ability in people with developmental disabilities. In this study, subjects with developmental disabilities who showed voluntary participation as those diagnosed as developmental disabilities through medical examination were selected as subjects. These subjects were randomly assigned to the trampoline group (n=10) and the yoga group (n=10) as those who did not participate in the recent regular exercise program. The trampoline and yoga were performed twice a week for a total of 20 times for 10 weeks with 60 minutes each. The intensity of exercise was divided into 3 steps, and rating of perceived exertion(RPE) of 8-9, 10-11, and 12-13 were performed, respectively. Muscle tone was measured at rest in a total of three muscle groups of the quadriceps muscle, hamstring, and calf. Also, one leg standing test was used to test the static balance ability, and linear gait test was performed to test dynamic balance ability. Based on the results of the study, the following results were obtained. First, in the trampoline and yoga group, the quadriceps muscle tone increased(p

Experimental and theoretical studies on the erosion of silica phenolic nozzles with graphite inserts in solid rocket motors were carried out. Two identical segmented nozzles, consisting of graphite inserts and silica phenolic insulation in the convergent and divergent sections, were tested at same operating condition. Due to the different thermal resistance ability, steps are formed at the interface of two materials. The erosion rates, following the distribution of Reynolds number, exhibit an upward trend in the convergent section and decrease in the divergent section for both silicon phenolic and graphite. At high temperature, the graphite erosion rate is limited by the diffusion rate of the oxidizing species,while the erosion rate is limited by the chemical kinetics at low temperature. For the graphite nozzle insert, a switch from kinetics mechanism to diffusion mechanism occurs in the convergent section during the firing test.

To investigate the characteristics of genesis and development of peritoneal adhesion by different causes.236 rats underwent laparotomy with their vermiform processes lifted up and were randomly divided into 5 groups: Group A (control group), with the vermiform process exposed to air for 5 min, Group B, with the vermiform process smeared with talcum powder; Group C, with the vermiform process scraped by scalpel; Group D, with the tip of vermiform process stabbed by needle so as to squeeze the contents of intestine to cause infection; and Group E, with the artery of vermiform process ligated. Then the abdominal incision was sutured. 1, 2, 4, and 6 weeks after the treatment 11-12 rats from each group were randomly to undergo laparotomy. The degree of adhesion was graded blindly by Bhatia's method. The vermiform process was resected to undergo pathological examination and examination of the level of organ hydroxyproline (OHP) was detected.(1) At different time points the adhesive grades of Groups B-E were all significantly higher than that of Group A (all P0.05) and the adhesive grades of Groups B and D were both significantly higher than those of Groups C and E (both P0.05). There were no significant differences in the adhesive degree 1, 2, and 4 weeks after the treatment between Groups C and E, however, the adhesive degree of Group E was significantly lower than that of Group C (P0.05). (2) There were not significant differences in the OHP levels at any time points in Group A (all P0.05). There were not significant differences in the OHP levels 1, 2, and 4 weeks after the treatment (all P0.05), and the levels 8 weeks after the treatment were all significantly lower than those 1, 2, and 4 weeks after the treatment (all P0.05) in Groups B, D, and E. In Group C the OHP level 2 weeks after the treatment was 0.275 +/- 0.031 microg/mg protein, significantly lower than that 1 week after (0.221 +/- 0.036 microg/mg protein, P0.05), and the OHP level 8 weeks after the treatment was 0.254 +/- 0.039 microg/mg protein, significantly lower than those 1, 2, and 4 weeks after (all P0.05). The OH levels 1, 2, and 4 weeks after the treatment of the 4 experimental groups were all significantly higher than that of the control group (all P0.05). 8 weeks after the treatment the level of OHP of Groups B was significantly higher than that of Group A (P0.05), however, the OHP levels of Group C, D, and E had all decreased to almost similar to that of Group A (all P0.05). (3) The adhesive degrees of Groups C and E were significantly positively correlated with the OHP level (both P0.05), however, the adhesive degrees of Groups B and D were not significantly correlated with the OHP level (both P0.05). The adhesive degrees 1, 2, and 4 weeks after the treatment of the 5 groups were all significantly positively correlated with the OHP levels (all P0.05, however, the adhesive degrees 8 weeks after the treatment of the 5 groups were all not significantly correlated with the OHP levels (all P0.05). (4) The main pathological changes of Group B were foreign body granuloma reaction and fibroplasia in Group B and unspecific inflammatory reaction and fibroplasia in Groups C, D, and E.Abdominal adhesions resulting from different causes show different characteristics. The abdominal adhesion caused by foreign bodies and that caused by infection are relatively severe and more difficult to recover than those caused by injury and ischemia. It is more reliable to use OHP level as a marker of abdominal adhesion in the early stage.

To investigate the clinical characteristics and significance of thrombocytopenia after therapeutic hypothermia in severe traumatic brain injury (TBI).Ninety-six inpatients with severe brain injury were randomized into three groups: SBC (selective brain cooling) group (n=24), MSH (mild systemic hypothermia) group (n=30), and control (normothermia) group (n=42). The platelet counts and prognosis were retrospectively analyzed.Thrombocytopenia was present in 18 (75%), 23 (77%) and 15 (36%) patients in SBC group, MSH group and control group, respectively (P0.01). Thrombocytopenia, in which the minimum platelet count was seen 3 days after hypothermia, showed no significant difference between SBC and MSH group (P0.05). Most platelet counts (37 cases, 90%) in hypothermia group were returned to normal level after 1 to 2 days of natural rewarming. The platelet count in SBC group reduced by 16%, 27% and 29% at day 1, 3 and 5 respectively compared with the baseline value. Good recovery (GOS score 4-5) rate of thrombocytopenia 1 year after injury for hypothermia group (17 cases, 37%) was significantly lower than that of control group (P0.01).Therapeutic hypothermia increases the incidence of thrombocytopenia in severe TBI, and patients with thrombocytopenia after therapeutic hypothermia are associated with unfavorable neurological prognosis.

Hafnium carbide (HfC) modified carbon/carbon (HfC-C/C) composites were prepared by impregnating carbon felts with a saturated HfOCl2 · 8H2O ethanol solution and heat treating at 600 °C to form HfO2/C composites that were then densified with pyrocarbon by chemical vapor infiltration and graphitized at 2100 °C to convert HfO2 into HfC. The HfC-C/C composites as rocket throats were ablated at 7 MPa and around 3200 °C for 3 s by an experimental solid rocket motor. Results showed that the HfC-C/C composites with HfC contents more than 5.7 wt.% had a stable period with a constant ablation rate and the duration of this period increased with HfC content. The overall ablation rate was decreased by 25.2% and 49.6% for the composites having 5.7 and 8.7 wt.% HfC respectively as compared with the composite with 2.5 wt.% HfC.