Development of an Instantaneous Loading Impact Test System for Containment of a Nuclear Power Plant during Aircraft Impact on Steel Bar Joints.

As major projects such as nuclear power plants continuously increase, it is inevitable that loopholes will arise in safety precautions. Airplane anchoring structures, comprising steel joints and acting as a key component of such a major project, directly affect the safety of the project due to their resistance to the instant impact of an airplane. Existing impact testing machines have the limitations of being unable to balance impact velocity and impact force, as well as having inadequate control of impact velocity; they cannot meet the requirements of impact testing for steel mechanical connections in nuclear power plants. This paper discusses the hydraulic-based principle of the impact test system, adopts the hydraulic control mode, and uses the accumulator as the power source to develop an instant loading test system suitable for the entire series of steel joints and small-scale cable impact tests. The system is equipped with a 2000 kN static-pressure-supported high-speed servo linear actuator, a 2 × 22 kW oil pump motor group, a 2.2 kW high-pressure oil pump motor group, and a 9000 L/min nitrogen-charging accumulator group, which can test the impact of large-tonnage instant tensile loading. The maximum impact force of the system is 2000 kN, and the maximum impact rate is 1.5 m/s. Through the impact testing of mechanical connecting components using the developed impact test system, it was found that the strain rate of the specimen before failure was not less than 1 s-1, meeting the requirements of the technical specifications for nuclear power plants. By adjusting the working pressure of the accumulator group, the impact rate could be controlled effectively, thus providing a strong experimental platform for research in the field of engineering for preventing emergencies.

Dynamic Tensile Behaviors of HRB500E Connected with Extrusion Sleeves at Different Strain Rates.

In this paper, the connection performance of extrusion sleeves and the strain rate effect on 500 MPa-grade hot-rolled ribbed bar(HRB500E) connected with extrusion sleeves under a range of testing strain rates from 1.079/sto1.395/s, similar to what would be caused by an impact, were explored. The test results showed that, under strain rates likely caused by aircraft impact, the specimens mostly failed due to breaking outside the joint length. Furthermore, there was no relative slip between the rebar and the extrusion sleeve, indicating that the connection was stable and reliable in the used experimental parameter field. The percentage total elongation at maximum force (Agt) of HRB500E spliced by the extrusion sleeve showed an exponential decline with the increase in the strain rate, indicating a clear strain-rate sensitivity. The average deviation between the dynamic increase factors (DIF) calculated using the modified Cowper-Symonds formulas and the experimental values was within 5.4%, which can better reflect the strain rate effect on the strength of the spliced connection. The DIFy of sleeve-spliced rebars was higher than that of unspliced rebars, and the ratio of the DIFy of sleeve-spliced rebars to the DIFy of unspliced rebars increased with the strain rate. The experimental results can provide a basis for an optimized design of the aircraft impact-resistant extrusion sleeve rebar connections.

A Study on Correlation between Contrast-Enhanced Ultrasound Parameters and Pathological Features of Diabetic Nephropathy.

The objective of this study was to evaluate the correlation between contrast-enhanced ultrasound (CEUS) parameters and histopathological features in patients with diabetic nephropathy (DN). Sixty-two patients with DN (44 men, mean age: 52.61 ± 10.63 y) were enrolled. They underwent renal biopsy for DN at the Department of Ultrasound, PLA Hospital, between May 2017 and February 2020. Renal tissue was obtained by ultrasound-guided percutaneous needle biopsy. CEUS was performed, and time-intensity curves (TICs) and renal perfusion parameters were analyzed. Differences in CEUS parameters were analyzed according to the glomerular classification and interstitial fibrosis-tubular atrophy (IFTA) score. Continuous variables were evaluated using the analysis of variance or Mann-Whitney U-test. Discontinuous variables were compared with the χ2-test. Spearman correlation analyses evaluated associations among quantitative ultrasound perfusion parameters and histopathological characteristics. Peak enhancement (PE), wash-in rate (WiR), wash-in perfusion index (WiPI) and wash-out rate (WoR) of the cortex, and their cortex/medulla ratios, decreased with increasing glomerular classification grade (p < 0.05). The fall time (FT) of the cortex, and their cortex/medulla ratios, increased with increasing glomerular classification grade (p < 0.05). There were no significant differences in the CEUS parameters for different IFTA scores. The perfusion volume-relevant parameters (such as PE, WiR and WiPI) had a negative correlation (p < 0.05), while the perfusion time-relevant parameters (such as RT and FT) had a positive correlation (p < 0.05), with the severity of glomerular lesions, glomerulosclerosis rate and number of Kimmelstiel-Wilson lesions. The CEUS parameters of the cortex could reflect pathological characteristics, especially changes in glomerular lesions.