Finite Element Analysis of Elastoplastic Elements in the Iwan Model of Bolted Joints

The Iwan model is composed of elastoplastic elements and is widely used to represent the stiffness degradation of bolted joints under mixed-mode loading (normal and tangential loading). The latest static methods of parameter identification established the relationship between the elastoplastic elements and the contact pressure under normal loading. Under mixed-mode loading, the parameters of the Iwan model are dynamic for the evolution of contact conditions. Therefore, static parameter identification methods are not suitable for the dynamic Iwan model. A new technique was proposed to identify the parameters of the elastoplastic elements in this paper. Firstly, several different finite element models were established. The influence of the contact method and the thread structure were analyzed, and a reliable and efficient bolted-joint modeling method was proposed. Secondly, the evolution of contact conditions was studied. The dynamic elliptical contact model and the ellipticity discrete method were proposed. Finally, the residual stiffness of the Iwan model was analyzed to establish the mapping between the residual stiffness and the bending of the screw. The results can provide a technique for identifying the parameters of the dynamic Iwan model.     

The Discrepancy between Coal Ash from Muffle,Circulating Fluidized Bed (CFB), and Pulverized Coal (PC) Furnaces,with a Focus on the Recovery of Iron and Rare Earth Elements

Coal ash (CA) is not only one of the most solid wastes from combustion, easily resulting in a series of concerns, but it is also an artificial deposit with considerable metals, such as iron and rare earth. The variation in the coal ash characteristics due to the origins, combustion process, and even storage environment has been hindering the metal utilization from coal ash. In this study, three ash sample from lab muffle, circulating fluidized bed (CFB), and pulverized coal (PC) furnace was derived for the discrepancy study from the combustion furnace, including properties, iron, and rare earth recovery. The origins of the coal feed samples have more of an effect on their properties than combustion furnaces. Magnetic separation is suitable for coal ash from PC because of the magnetite product, and the iron content is 58% in the Mag-1 fraction, with a yield of 3%. The particles in CA from CFB appear irregular and fragmental, while those from PC appear spherical with a smooth surface. The results of sequential chemical extraction and observation both indicated that the aluminosilicate phase plays an essential role in rare earth occurrences. Rare earth in CA from muffling and CFB is facilely leached, with a recovery of approximately 50%, which is higher than that from PC ash. This paper aims to offer a reference to easily understand the difference in metal recovery from coal ash.     

用原核增强子提高hTERT启动子介导的基因表达

目的:探讨原核增强子能否提高hTERT启动子的转录活性及对其肿瘤特异性的影响。方法:将增强子SV40、CMV分别或组合构建一系列GFP和荧光素酶报告基因载体,转染人肝癌、鼻咽癌、宫颈癌、结直肠癌细胞、成纤维肉瘤和正常成纤维细胞,流式细胞仪计数和双荧光酶分析系统检测基因的表达效率。结果:在正常成纤维细胞中这些载体均不能有效表达;而在肿瘤细胞中hTERT启动子能介导基因表达但效率不高,增强子能使基因表达增强3~26倍,特别是单独CMV增强子和SV40-CMV双增强子使荧光素酶表达提高20~26倍,是常用的CMV增强子/启动子的2~7倍;完整CMV增强子/启动子对hTERT启动子的活性影响因不同细胞而异。结论:增强子能显著增强hTERT启动子的转录活性并对其肿瘤特异性没有影响,CMV增强子或SV40-CMV双增强子/hTERT启动子是高效特异的通用调控元件,用于靶向性肿瘤基因治疗具有巨大潜力。     

无机活性元素组织工程支架材料重建修复山羊颌骨缺损的扫描电镜观察

目的:用扫描电镜观察无机活性元素组织工程支架材料构建的组织工程骨及其修复羊大面积颌骨缺损的体内成骨状况.方法:实验组对15只山羊下颌角缺损(30 mm×25 mm×10 mm大小)以支架材料修复,左侧为实验组,右侧为空白对照组,术后分别于1、3、6个月处死5只动物行扫描电镜及生物化学检查,观察无机活性元素组织工程支架材料体内成骨情况.结果:实验组骨缺损新生骨在1、3、6个月显著优于对照组,空白对照组6个月骨缺损区均无明显骨修复现象.结论:应用扫描电镜观察到无机活性元素组织工程支架材料具有优良的成骨效果.     

金昌市学龄前儿童血铅水平与8种微量元素的相关性研究

目的探讨甘肃省金昌市学龄前儿童高铅血症现状及血铅水平与微量元素铜、锌、钒、铬、锰、钴、镓、锗间的相互关系。方法随机抽取金昌市部分幼儿园的256名儿童,用石墨炉原子吸收分光光度仪进行血铅、铜、锌、钒、铬、锰、钴、镓、锗含量的测定。结果①256名儿童血铅含量为28.30～268.00μg/L,平均（126.19±52.91）μg/L,其中〉100μg/L者160名（占62.54%）。②钒、铜元素水平男高于女,差异有统计学意义（P〈0.05、0.01）;不同年龄组间锌、锗元素在6～7岁较2岁组降低,差异有统计学意义（P〈0.01）。③铜元素在高血铅组较低血铅组增高,锌、锰、钴元素在高血铅组较低血铅组降低,差异均有统计学意义（P均〈0.05）。④多元线性回归分析显示血铅与血锌、钴元素呈负相关。结论金昌市学龄前儿童高铅血症发生率高,应加强环境污染的治理,儿童应定期复查血铅水平,给予针对性的健康教育和营养指导。儿童高铅血症可导致血锌、锰、钴元素水平下降,血铜元素升高。     

微量接触类生物检材的游离 DNA 问题分析

目的探究接触类生物检材的游离DNA问题,游离DNA和细胞内DNA含量的比例问题,以及游离DNA在法医检验中的影响。方法对手部、面部和足部的皮肤及口腔粘膜进行模拟微量接触类检材的制备,对模拟检材进行浸泡,对游离DNA进行定量和STR扩增,对剩余检材使用常规程序进行DNA提取、定量和STR扩增,并对结果进行分析和讨论。结果实验观察到,78.55%的样品检测到了游离DNA,其中,手部模拟检材的游离DNA检测率为82.1%,脸部模拟检材的游离DNA检测率为82.1%,口腔模拟检材的游离DNA检测率为96.4%,足部模拟检材的游离DNA检测率为53.6%,微量接触类检材中游离DNA量占DNA总量的12.9%。结论接触类生物检材中提取到的DNA,除了包括细胞内DNA,还存在一定比例的细胞外游离DNA,这为微量接触类检材的DNA有效提取和检验提供了新的理论依据。     

五音经络疗法思想探析

《黄帝内经》首将“五音疗疾”引入中医学,五音经络疗法是以阴阳五行学说和中医经络腧穴理论为基础,把五音阶中宫、商、角、徵、羽以音作药,与中医闻诊、针灸等及其他方法相互协调补充,综合预防、诊断和治疗身心疾病的中国传统医疗方式。这种疗法,将五音与五脏经络连属起来,是对音乐与情感及脏腑脏气之间的声音频率和共鸣互动关系的深刻体验和总结。医者根据音变辨病变,取相对应的经络、腧穴来调节,从而达到治疗的目的。     

环境香烟烟雾和缺碘对大鼠微量元素代谢的联合作用

采用析因实验设计,以尿碘含量显着减低(P<0.05)为标志的环境香烟烟雾(ETS)和碘缺乏(ID)双因素大鼠模型观察对微量元素的影响.结果发现:产生协同效应有Se、I和Zn含量在甲状腺降低,Se和Zn含量在肝脏降低,而I和Cu含量增加,血中I含量下降.ETS因素使甲状腺I、Se和Zn含量均降低,肝脏Se和Cu含量下降,I含量增高,大脑Se和Zn含量降低;ID因素使甲状腺I、Se和Zn含量降低,肝Se和Li含量降低.Cu和Zn含量增加.提示:ETS和ID联合作用,可引起多种微量元素代谢障碍,以Se和I贮备下降和利用异常变化为主.因此,补碘效果不明显时,应究其原因     

教育数据挖掘对教育要素的影响研究

大数据时代,通过教育数据挖掘技术能够对教育教学过程中产生的海量数据进行有效地分析,且运用数据分析的结果,发现教育过程中的问题,提供指导性的建议,促成行之有效的解决策略。文章从教育者、受教育者、教育管理者、教育资源四个要素探究教育数据挖掘对教育产生的影响,剖析教育数据挖掘技术精进对教育各要素带来的影响,阐释个中不足,旨在顺应智慧时代发展,使教育数据挖掘技术更好地促进教育发展。     

山东黄芪及其江苏引种品活性成分的比较

通过测定黄芪中的活性成分黄芪甲甙、总多糖、γ-氨基丁酸(GABA)等19种氨基酸及硒等13种微量金属元素的含量,分析比较了山东黄芪及其江苏引种品的质量。结果表明生药外观木质化与上述活性成分含量多少并无内在联系,徐州黄芪质量并不亚于山东黄芪。