Calculation of Influence on Longitudinal Deformation of Adjacent Tunnels Due to Excavation

Unloading of excavation of foundation pit has influence on adjacent tunnels, therefore it is important to predict the deformation of metro tunnels to ensure the operation of tunnel. The displacement effect due to the surrounding wall soil unloading of adjacent excavation was not considered by the theoretical analysis method, and the analysis procedure of FEM was usually too complicated to get a satisfied result, so the horizontal and vertical additional stress were calculated by the Mindlin solutions. Furthermore, the tunnel structure was considered as the beam with infinite length. The additional stress was imposed on the Winkler model and the governing equation was built up on the adjacent tunnel structure. Finally, displacements and internal forces of existing tunnels were obtained. Compared with the numerical simulation and an engineering case, the results of the presented formula are in good agreement. It can provide certain theoretical and calculation basis for metro tunnels influenced by adjacent excavation.     

Seismic Characteristics of Widened Beam Flange Joints

In order to analyze the seismic behavior of widened beam flange joints, 16 specimens were derived from finite element models base on experiments. The effects of some parameters, such as the increased width and length, on ultimate load and ductility performance of joints were further discussed with ANSYS finite element method. According to specimen failure phenomenon of both experiment and finite element method, the weak link of the joints was found and the cracking possibility was evaluated. A theoretical analysis of the fracture mechanism of widened beam flange connection was conducted. In addition, design method of widened beam flange parameters was introduced, which will offer valuable information and reference for seismic design in steel frame joints.     

由“中梁刚度放大”到“强柱弱梁”

通过对“中梁刚度放大”系数取值的不同观点的辩驳,分析楼板在框架体系中的作用,阐述“柱铰机制”形成的机理并提出如何实现“强柱弱梁”的建议和方法。     

离子束注入后大豆M2农艺性状的遗传变异分析

采用2种剂量的C+离子束和2种剂量的Al+离子束处理5个北方夏大豆品种,研究其M2主要农艺性状的遗传变异。结果表明:(1)C+4MeV 8×1012ions/cm2处理的品种冀豆15M2的各农艺性状均明显高于对照;(2)两种离子束4种剂量均使品种楚秀M2的株高降低30%以上,结荚高度降低35%;Al+8×1011ions/cm2处理使品种中黄44M2的结荚高度增加了38.1%;(3)C+4MeV 8×1012ions/cm2与Al+4MeV8×1011ions/cm2处理使各品种M2的单株荚数增加、单株粒数比对照高出50%以上;(4)两种离子束处理对大豆品种百粒重的变异均影响不大。     

氮离子注入对同源四倍体水稻的诱变效应

选用不同倍性的水稻进行低能氮离子束注入试验,研究离子注入后的效果与染色体组倍性之间的关系,结果表明,同源四倍体水稻比二倍体水稻对低能氮离子束注入处理更敏感;在同源四倍体水稻群体中所出现的变异频率比在二倍体水稻群体中出现的变异频率高;在经过低能氮离子束注入处理的同源四倍体后代群体中,分别筛选到结实率高达90.16%的单株和具有双胚苗性状的单株,同源四倍体水稻的高结实率特性和双胚苗特性表现出一定的可遗传性。     

Important anatomical variations of the superior posterior alveolar artery: Studied by cone beam computed tomography

The knowledge of anatomical variations of the posterior superior alveolar artery (PSAA) is very important in surgeries for maxillary sinus (MS) elevation and subsequent insertion of dental implants, avoiding common and serious surgical complications. The main objective of this study was to analyse important anatomical variations of the PSAA by means of cone beam computed tomography (CBCT) examinations. 180 tomographic CBCT were analysed, and MS was divided into three equal regions: (I) anterior, (II) intermediate and (III) posterior. Variables evaluated were the visualisation of the artery, distance from the artery to the ridge crest, distance from the artery to the sinus floor, alveolar ridge height and arterial diameter. The PSAA visualisation was more prevalent in males and region III (76.7%). The distance from the artery to the sinus floor presented no significant difference between regions II and III, with both regions showing significantly lower values than region I. A significant difference was observed in the diameter of the arteries with higher prevalence of diameters >1.0 mm in males and <1.0 mm in females. The PSAA can be well visualised frequently with a CBCT, and differences in artery diameter were observed in relation to gender (males > females). Additional care is recommended when it is necessary to extend surgeries to the posterior MS region, avoiding haemorrhages that are associated with failures in these procedures.     

低能离子束介导外源基因进入水稻细胞的研究

用离子束介导法将编码β－葡萄糖苷酸酶的ｇｕｅ基因引入受体植物细胞,并实现瞬间表达。水稻悬浮细胞经离子束辐照后,电镜下能观察到细胞表面留下的溅射和刻蚀痕迹,细胞存活率随辐照剂量的增加而显著降低。将离子束（３０ｋｅＶ,２×ｌ０１５Ｎ＋／ｃｍ２）处理后的水稻悬浮细胞,浸入含有ｇｕｓ基因外源ＤＮＡ的ＳＳＣ温育介质,两天后,观察到受离子束直接作用的细胞团的一面有外源ｇｕｓ基因的导入和表达。ｇｕｓ基因瞬间表达的最佳处理剂量悬浮细胞为２×ｌ０１５Ｎ＋／ｃｍ２,成熟胚为２０×ｌ０１５Ｎ＋／ｃｍ２,而且３０ｋｅＶ能量的离子束处理明显较２０ｋｅＶ优越。ＳＳＣ缓冲导入介质最为理想,而添加ＤＭＳＯ（一种细胞促渗透剂）的ＳＳＣ和富含ｃａ２＋的ｋｒｅｎ’ｓＦ溶液（ｃａ２＋对促进质膜稳定性有好处）对离子束介导外源基因进入水稻细胞均不理想。     

离子注入诱变的广亲和新品系在籼粳亚种杂种优势中的应用

经离子束诱变处理的新广亲和系,影响其产量的主要因素是有效穗数、每穗实粒数和千粒重,三者对产量具有均等的贡献。亲子代性状之间相关分析表明:通过选用千粒重大,每穗实粒数多、株高较矮、全生育期适中的亲本,能达到改善杂优组合的目的。遗传力高的较为稳定的性状,诱变后变异幅度不大,育种上最好选择杂合体进行离子束诱变处理。     

离子束辐照对pUC18质粒DNA结构和功能影响的初步研究

离子束辐照ｐＵＣ１８质粒ＤＮＡ，可以造成其ＤＮＡ链的断裂。在剂量较低的情况下（５～１５×１０１５Ｎ＋／ｃｍ２），以单链断裂为主，电镜下主要呈开环结构；在相对较高的剂量下（２５×１０１５Ｎ＋／ｃｍ２），由于相对部位双链的断裂出现，电镜下可观察到线性质粒结构。经离子束辐照的质粒ＤＮＡ，其转化活性（即存活率）随处理剂量的增加而降低，且ＬａｃＺ基因也能发生较高频率的突变，与６０Ｃｏ—ｒ射线相比，在存活率相近的情况下，突变率较高。     

基于高阶理论的高精度层合梁单元

提出一种在于高阶理论的高精度层合梁单元，该高阶理论满足层间位移、应力连续条件，由此建立的梁单元具有列式简单、计算效率和精度高的优点。