Effects of thickness profile and inner/outer of localized thin area defects on the remaining strength of pressure equipment

When encountering pressure equipment with a structural defect such as a local thinning defect (LTA), a critical question often arises regarding the safety of continued operation. This is primarily determined by the strength at the LTA zone, as it represents the weakest point of the structure. The remaining strength factor (RSF) is proposed as an indicator to evaluate the remaining strength and life of pressure equipment when a severe LTA is identified. The API 579/ASME FFS standard offers a series of practical engineering approaches for field engineers to follow, which have achieved great success. However, it has been found that the simpler Level 1 and Level 2 approaches sometimes fail to differentiate between LTAs on the inner or outer surface of the pressure equipment, yielding identical numerical processes and results. Moreover, the use of critical thickness profiles to replace the actual thickness profile in analysis can lead to overly optimistic estimation of the RSF, posing a potential danger when the RSF is close to the allowable limit. Key issues investigated in this study include: (a) discrepancies caused by the use of simplified critical thickness profiles or parabolic profiles, as API 579 suggested, on the RSF; (b) differences in RSFs when the same LTA is on the inner and outer wall; and (c) comparisons of membrane stress and bending stress, as well as their influences on the RSF at the cross-section of the vessel wall. It can be concluded with certainty that all simplified geometries (CTP and PTP) tend to underestimate the RSF and should be used with caution. Additionally, the actual remaining strength of the outer LTA was found to be slightly lower than that of the inner LTA of identical size. Therefore, when remaining life and derating for prolonged operation are of interest, finite element analysis on pressure equipment with the LTA is recommended.     

高速铁路插板式声屏障抗弯能力有限元分析

声屏障作为噪声污染治理的主要措施之一,已广泛应用于公路、铁路、市政等多种领域。以往人们主要做了高速铁路声屏障风荷载等相关研究,本文在分析高速铁路声屏障风载荷构成的基础上,对北京士兴钢结构有限公司提供的声屏障装配体制作了有限元模型对其抗弯能力进行了仿真研究。通过仿真研究整理出一套声屏障抗弯承载力仿真分析的方法,并利用该方法对不同规格和结构的声屏障产品进行了分析研究,对声屏障开发及技术改进做出了理论上的支持。     

微量元素对黄孢原毛平革菌降解苯酚的影响

研究了氮源,铁、铜、锰等金属元素以及Tween 80等有机添加剂对黄孢原毛平革菌降解苯酚的影响。结果表明,氮源是黄孢原毛平革菌生长的必需元素,铜元素和锰元素对苯酚降解具有明显的促进作用,而铁元素的促进作用并不显著。各种微量元素的最佳浓度分别为:氮0.1 g/L、铁0.5 mmol/L、锰1.0 mmol/L、铜0.3 mmol/L、Tween 80 0.01 mmol/L。     

基于炭化痕迹的火灾数值重构及应用

利用试验方法建立了炭化痕迹的数学模型,与火灾流体动力学软件FDS相耦合,实现对炭化痕迹的再现,同时,进行了较为接近真实火灾的火灾场景试验,并用新编译的FDS软件对试验进行重构。结果表明:火势发展变化趋势基本一致;起火后,火场热释放速率迅速上升,100 s左右达到约2750 kW,随后开始下降,直至434 s降到700kW左右,与火势进程基本吻合;试验得到的密度板炭化痕迹未被烧损的区域(横向30.2~86.8 cm、纵向0~18.6 cm)略小于重构得到的密度板炭化痕迹未被烧损的区域(横向33.4~91.6 cm、纵向0~18.9cm),但分布规律基本一致,验证了新编译的FDS软件的有效性。将该软件应用于消防工作,不仅可以作为一种定量方法来描述炭化痕迹的形成过程,还可以通过火场中的炭化痕迹来反推起火点位置,辅助火灾调查工作。     

Effects of whole spine alignment patterns on neck responses in rear end impact

Objective: The aim of this study was to investigate the whole spine alignment in automotive seated postures for both genders and the effects of the spinal alignment patterns on cervical vertebral motion in rear impact using a human finite element (FE) model.

Methods: Image data for 8 female and 7 male subjects in a seated posture acquired by an upright open magnetic resonance imaging (MRI) system were utilized. Spinal alignment was determined from the centers of the vertebrae and average spinal alignment patterns for both genders were estimated by multidimensional scaling (MDS). An occupant FE model of female average size (162 cm, 62 kg; the AF 50 size model) was developed by scaling THUMS AF 05. The average spinal alignment pattern for females was implemented in the model, and model validation was made with respect to female volunteer sled test data from rear end impacts. Thereafter, the average spinal alignment pattern for males and representative spinal alignments for all subjects were implemented in the validated female model, and additional FE simulations of the sled test were conducted to investigate effects of spinal alignment patterns on cervical vertebral motion.

Results: The estimated average spinal alignment pattern was slight kyphotic, or almost straight cervical and less-kyphotic thoracic spine for the females and lordotic cervical and more pronounced kyphotic thoracic spine for the males. The AF 50 size model with the female average spinal alignment exhibited spine straightening from upper thoracic vertebra level and showed larger intervertebral angular displacements in the cervical spine than the one with the male average spinal alignment.

Conclusions: The cervical spine alignment is continuous with the thoracic spine, and a trend of the relationship between cervical spine and thoracic spinal alignment was shown in this study. Simulation results suggested that variations in thoracic spinal alignment had a potential impact on cervical spine motion as well as cervical spinal alignment in rear end impact condition.     

High starter phosphorus fertilization facilitates soil phosphorus turnover by romoting microbial functional interaction in an arable soil

Microbial phosphorus (P) turnover is critical in C utilization efficiency in agroecosystems. It is therefore necessary to understand the P mobilization processes occurring during P fertilization in order to ensure both crop yield and environmental quality. Here, we established a controlled pot experiment containing soil amended with three different levels of starter P fertilizer and collected soil samples after 30, 60, and 90 days of incubation. Quantitative microbial element cycling (QMEC) smart chip technology and 16S rRNA gene sequencing were used to investigate functional gene structures involved in carbon, nitrogen and P cycling and the bacterial community composition of the collected samples. Although P fertilization did not significantly affect the structure of the soil microbial community, some rare microbiota were changed in particular phosphorus-solubilizing bacteria were enriched at the high P fertilization level, suggesting that the rare taxa make an important contribution to P turnover. P fertilization also altered the functional gene structure, and high P concentrations enhanced the functional gene diversity and abundance. Partial redundancy analysis further revealed that changes in rare taxa and functional genes of soil microorganisms drive the alteration of soil P pools. These findings extend our understanding of the microbial mechanisms of P turnover.     

南四湖表层沉积物中铍、锑、铊的地球化学特征与环境风险

南水北调工程是世界规模最大,同时也是受益人口最多的调水工程之一.南四湖是南水北调东线工程中最大的调蓄湖库.本文研究了南四湖表层沉积物中铍(Be)、锑(Sb)、铊(Tl)的含量分布与赋存形态特征,并结合多种方法评估了其环境风险.结合前人已取得的成果,定义了Be、Sb、Tl的毒性系数.研究表明,南四湖表层沉积物中Be和Sb的平均含量略高于环境背景值,而Tl的含量低于环境背景值.赋存形态分析表明,残渣态Be、Sb、Tl的占比分别超过了65%、70%、84%,而酸可溶态百分含量非常低,可移动性与生物可利用性均不强.结合上述风险评价方法可知,Be、Sb、Tl在南四湖表层沉积物中富集程度较低,生态危害性较小.Be、Sb、Tl均以自然来源为主,人类活动来源为辅.Sb的人类活动来源明显不同于Be和Tl,可能主要为大气沉降.Be、Sb、Tl在沉积物中的分布状况不同程度地受到粒度、有机碳、铝及铁锰氧化物等的制约.     

气象要素对气溶胶光学厚度估算PM2.5的影响

地面监测得到的近地面细颗粒物PM_(2.5)浓度较为精确,但数据覆盖范围相对较小,卫星遥感反演的气溶胶光学厚度(AOD)数据可以反映污染物浓度分布,具有范围大且速度快的特点,因此,大多数学者通过建立PM_(2.5)-AOD模型来实现卫星遥感监测PM_(2.5)浓度,并通过引入气象要素来优化模型.然而,气象要素的选择与引入往往对模型的精度有较大的影响,如何有效地选择对PM_(2.5)浓度影响较大的气象要素一直是PM_(2.5)-AOD模型中的关键问题.因此,本文基于华东地区2014—2015年的MODIS AOD和地面监测站的PM_(2.5)浓度数据,结合再分析气象资料,利用多元逐步线性回归方法建立PM_(2.5)-AOD模型,从由特定时刻、高度上的气象要素与随时间、高度变化的气象要素组成的气象要素集中,筛选出对因变量PM_(2.5)浓度有显著影响的关键气象要素.结果表明:在地域与季节双重尺度下的PM_(2.5)-AOD模型精度更高;相较于特定时刻高度的气象要素,随时间和高度变化的气象要素对PM_(2.5)-AOD模型的影响更为显著;在地域与季节双重尺度下,1000～850 hPa经向风速差、世界时0:00—6:00近地面温度差、850～600 hPa温度差、6:00边界层高度、12:00—18:00近地面压强差、1000～850 hPa温度差对模型影响较大,但应依据不同季节和不同地区的具体影响程度作为选择标准.     

稻壳生物炭对污染土壤中稀土元素生物有效性的影响

利用农业秸秆制备了污染土壤修复材料稻壳生物炭和稻壳灰,在模拟稀土（REE）污染的酸性土壤中,添加0、5%和10%的稻壳灰（RHA）稻壳生物炭（RHB）,通过栽培实验考察RHA和RHB对REEs的形态和生物有效性的影响.春秋两季的盆栽实验结果表明,RHA和RHB的添加有效的降低了稀土的弱酸可提取态,随着添加量的增加效果越明显,10% RHA和10% RHB土壤中REEs的弱酸（乙酸）提取态较对照组分别降低了31.65%、19.915%,弱酸可提取态转化为了可还原态,与对照组相比,RHA和RHB的土壤中稀土元素的可还原态分别增加了26.367%、10.321%.两种修复材料显著降低了胡萝卜和茼蒿对稀土元素的富集,10% RHA处理组胡萝卜和茼蒿REEs含量分别较对照组降低了98.08%、93.41%,10% RHB胡萝卜和茼蒿REEs含量分别较对照组降低了68.61%、66.75%.研究结果表明,稻壳生物炭和稻壳灰的施用,能够有效的改善污染土壤的理化性质,降低稀土元素生物可利用态的含量,从而遏制植物对稀土元素的富集.     

国Ⅴ公交车燃用生物柴油的颗粒物碳质组分排放特性

以一辆国Ⅴ柴油公交车为研究对象,在重型底盘测功机上运行中国典型城市公交循环,研究了纯柴油（D100）,体积混合比例分别为5%,10%和20%餐厨废弃油脂制生物柴油-柴油混合燃料（即B5,B10,B20）的颗粒物（PM）碳质组分排放特性.结果表明：国Ⅴ柴油公交车尾气颗粒物碳质组分包括有机碳（OC）和元素碳（EC）,OC占73%~82%,OC的主要组分是OC2和OC3,生物柴油对车辆尾气颗粒物OC组成比例没有影响;随着生物柴油混合比例的增加,公交车尾气颗粒物OC和OC+EC排放呈降低的趋势,EC排放增加,且B10的OC排放较高;PM_0.05~0.1,PM_0.1~0.5,PM_0.5~2.5,PM_2.5~18 4个粒径段颗粒物中,PM_0.1~0.5的OC和EC排放最高,PM_2.5~18的EC排放几乎为零,生物柴油可改善公交车尾气超细颗粒（PM_0.05~0.1）的OC排放,对公交尾气颗粒物EC排放基本没有影响;公交使用生物柴油混合燃料尾气颗粒物OC/EC减小,且PM_0.05~0.1和PM_0.5~2.5OC/EC降低幅度明显,对大气二次气溶胶的影响减弱.