Semi-theoretical analyses of the concrete plate perforated by a rigid projectile

Based on the three-stage perforation model, a semi-theoretical analysis is conducted for the ballistic per- formances of a rigid kinetic projectile impacting on concrete plates. By introducing the projectile resistance coefficients, dimensionless formulae are proposed for depth of penetra- tion （DOP）, perforation limit thickness, ballistic limit veloc- ity, residual velocity and perforation ratio, with the projec- tile nosed geometries and projectile-target interfacial fric- tion taken into account. Based on the proposed formula for DOP and lots of penetration tests data of normal and high strength concrete targets, a new expression is obtained for target strength parameter. By comparisons between the re- sults of the proposed formulae and existing empirical formu- lae and large amount of projectile penetration or perforation tests data for monolithic and segmented concrete targets, the validations of the proposed formulae are verified. It is found that the projectile-target interfacial friction can be neglected in the predictions of characteristic ballistic parameters. The dimensionless DOP for low-to-mid speed impacts of non-flat nosed projectiles increases almost linearly with the impact factor by a coefficient of 2/（nS）. The anti-perforation ability of the multilayered concrete plates is dependent on both the target plate thickness and the projectile impact velocity. The variation range of the perforation ratio is 1-3.5 for concrete targets.

Key design parameters and optimum method of medium- and high-velocity synchronous induction coilgun based on orthogonal experimental design

The energy conversion efficiency of a multistage synchronous induction coilgun(MSSICG) has become one of the key factors that restricts its industrialization. To improve the launch efficiency of medium-and high-velocity MSSICG,we propose an optimization design scheme combining orthogonal experimental design(OED) and self-consistent design method in this paper. The OED is introduced to reduce the number of iterations and improve the identification accuracy and efficiency. A self-consistent design model is established to overcome a defect that the parameters that need to be optimized will multiply as the number of coil stages increases. The influence of six factors(radial thickness of armature, axial length of armature, axial length of coil, capacitance, wire diameter, and slip speed) on the launch efficiency are then evaluated by range analysis. This work presents a valuable reference for optimizing medium-and high-velocity MSSICG.

Damage of a large-scale reinforced concrete wall caused by an explosively formed projectile(EFP)

To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building,the combined damage characteristics of the reinforced concrete wall caused by EFP penetration and explosion shock wave were studied.Based on LS-DYNA finite element software and RHT model with modified parameters,a 3D large-scale numerical model was established for simulation analysis,and the rationality of the material model parameters and numerical simulation algorithm were verified.On this basis,the combined damage effect of EFP penetration and explosion shock wave on reinforced concrete wall was studied,the effect of steel bars on the penetration of EFP was highlighted,and the effect of impact positions on the damage of the reinforced concrete wall was also examined.The results reveal that the designed shaped charge can form a crater with a large diameter and high depth on the reinforced concrete wall.The average crater diameter is greater than 67 cm(5.58 times of charge diameter),and crater depth is greater than 22 cm(1.83 times of charge diameter).The failure of the reinforced concrete wall is mainly caused by EFP penetration.When only EFP penetration is considered,the average diameter and depth of the crater are 54.0 cm(4.50 times of charge diameter)and 23.7 cm(1.98 times of charge diameter),respectively.The effect of explosion shock wave on crater depth is not significant,resulting in a slight increase in crater depth.The average crater depth is 24.5 cm(2.04 times of charge diameter)when the explosion shock wave is considered.The effect of explosion shock wave on the crater diameter is obvious,which can aggravate the damage range of the crater,and the effect gradually decreases with the increase of standoff distance.Compared with the results for a plain concrete wall,the crater diameter and crater depth of the reinforced concrete wall are reduced by 5.94%and 9.96%,respectively.Compared to the case in which the steel bar is not hit,when the EFP hit one steel bar and the intersection of two steel bars,the crater diameter decreases by 1.36%and 5.45%respectively,the crater depth decreases by 4.92%and 14.02%respectively.The EFP will be split by steel bar during the penetration process,resulting in an irregular trajectory.

Association between heat and upper urinary tract stones morbidity and medical costs: A study in the subtropical humid climate zone

Urolithiasis is a heat-specific disease.Exploring heat-related urolithiasis susceptibility subtypes,economic burden,and modifying factors could assist governments in targeting interventions to reduce the heat-related health risks of urolithiasis morbidity.We collected data on 23,492 patients with upper urinary tract stones(main subtypes of urolithiasis)from 2013 to 2017 in Nanjing,China.We adopted generalized additive quasi-Poisson models to examine the associations between daily mean temperatures and morbidity of upper urinary tract stones,while generalized additive Gaussian models were used to explore the relationships between temperatures and log-transformed medical costs.We examined the modification effects of disease subtypes(kidney and ureteral calculus),sex,and age through stratified analyses and the modif-cation effects of other meteorological factors by introducing interaction terms in the models.We found that short-term summer heat exposure has a statistically significant effect on ureteral calculus morbidity but not on kidney calculus morbidity.For ureter calculus,a 1℃ temperature increase was associated with a 4.36%(95%confidence interval[CI]:1.94%,6.83%)increase in daily hospitalization and a 5.44%(95%CI:2.71%,8.25%)increase in daily medical costs.The attributable fraction associated with heat(greater than the median value of daily mean temperature,26.8℃)was 7.85%(95%empirical confidence interval[eCI]:3.64%,11.44%)for hospitalization and 9.36%(95%eCI:4.91%,13.14%)for medical costs.The effects of heat on ureter calculus morbidity were significantly higher among the males and those with high sunshine duration than females and those with low sunshine duration.Short-term summer heat exposure was associated with increased morbidity and medical costs of ureteral calculus.Relevant government organizations should take effective intervention measures,including community health education,to reduce the health hazards and economic losses caused by heat.

A novel experience of deferential vessel-sparing microsurgical vasoepididymostomy

Microsurgical longitudinal intussusception vasoepididymostomy （LIVE） has been widely used to treat epididymal obstructive azoospermia since 2004. Although the deferential vasculature plays an important role in supplying blood to the testis and epididymis, little attention has been paid to the potential benefits of sparing the deferential vessels during the anastomosis in LIVE. This study aimed to evaluate the efficacy and safety of deferential vessel-sparing LIVE in humans. From December 2013 to December 2015, 69 azoospermic men with epididymal obstruction due to a genital infection, trauma, or idiopathic factors underwent deferential vessel-sparing LIVE in the First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China. The outcomes of these patients were analyzed retrospectively. The mean age was 31.1 years for men and 28.3 years for their partners. Fifty-nine （85.5%, 59/69） men were followed up after surgery for approximately 16 months. Patency was noted and confirmed by semen analysis （〉10 000 sperm/ml） in 83.1% （49159） of men. The natural pregnancy rate was 40.7% （24/59） by the end of the study, with 87.5% （21124） of these natural pregnancies achieved within 12 months after surgery. No severe adverse events or complications were observed. In this study, we present a novel technique for sparing the deferential vessels during LIVE. The preliminary outcomes show this technique to be safe with favorable patency and pregnancy rates.

高速列车头部外形多目标气动优化设计（英文）

目的:为改善高速列车明线运行时的气动性能,提出一种基于近似模型的高速列车头部外形多目标气动优化设计方法。创新点:1.建立包含转向架区域的高速列车参数化模型;2.基于近似模型并结合遗传算法,对高速列车头部外形及转向架区域进行多目标气动优化设计。方法:1.建立包含转向架区域的原始头型高速列车模型(图2和3),并基于CATIA脚本文件和MATLAB自编程序对列车头部外形进行参数化处理;2.通过最优拉丁超立方设计方法在设计空间内对优化设计变量进行采样,并采用计算流体动力学方法对样本点中新头型列车气动性能进行计算;3.基于样本点的列车头型优化设计变量及优化目标(表4),建立优化目标与设计变量之间的近似模型;4.基于近似模型和多目标遗传算法,对高速列车头部外形进行多目标优化设计,选取其中的一个优化头型与原始头型进行比较,并验证横风下优化头型的可行性。结论:1.相较于原始头型列车,无横风时,优化头型列车的整车气动阻力减小2.61%,尾车气动升力减小9.90%;2.横风下,优化头型列车的整车气动阻力减小2.98%,头车气动侧力减小0.24%;3.横风下,优化头型列车的头车气动载荷波动幅值有所减小。

Erectile dysfunction is associated with subclinical carotid vascular disease in young men lacking widely-known risk factors

This study aimed to gain insight into the underlying pathogenesis of erectile dysfunction in young men under the age of 40 years without widely-known risk factors. Compared with normal controls, patients with erectile dysfunction had increased carotid intima- media thickness, fasting levels of blood glucose and insulin, and homeostatic model assessment index, as well as lower flow-mediated vasodilation and testosterone levels （P 〈 0.05）, though all of these values were within their respective normal range. Multivariate logistic regression analysis identified carotid intima-media thickness, flow-mediated vasodilation, insulin level, and homeostatic model assessment index as significant predictors of erectile dysfunction. Young men with flow-mediated vasodilation 〈10.65% were 11.645 times more likely to have erectile dysfunction, young men with carotid intima-media thickness 〉0.623 mm had a 4.16-fold, and young men with homeostatic model assessment index 〉1.614 had a 5.993-fold greater risk of having erectile dysfunction. In conclusions, in young men with normal results from general clinical screening, an increased carotid intima-media thickness and homeostatic model assessment index and reduced flow-mediated vasodilation were associated with a higher incidence of erectile dysfunction. Erectile dysfunction may appear before the detection of traditional cardiovascular risk factors and may be the earliest clinical sign of subclinical cardiovascular disease.