考虑混凝土损伤的双面组合连续梁挠度和裂缝宽度研究

钢-混凝土双面组合连续梁负弯矩区上混凝土板受拉会产生裂缝。利用ANSYS有限元软件,考虑了混凝土的拉应变软化特性,对钢-混凝土双面组合2跨连续梁模型进行数值模拟分析,得到了上混凝土板裂缝分布和宽度。将计算结果与实测结果进行比较,验证了该模型的有效性。通过变换下混凝土板厚度和混凝土极限拉应变值,分析其对双面组合梁挠度和裂缝的影响;采用最小二乘法,对荷载-挠度;荷载-最大裂缝宽度曲线进行拟合,得出相应的计算公式。     

Multi-element ultrasound phased array applicator for the ablation of deep-seated tissue

High-intensity focused ultrasound (HIFU) has attracted increasing interests as a promising noninvasive modality for the treatment of deep tumors in the thoracic and abdominal cavity. A 90-element HIFU spherical phased array applicator operated at 1MHz has been developed for deep tissue ablation. The spherical array with a 5 cm wide central hole has a 21 cm diameter and an 18 cm radius of curvature. Annular element distribution with unequal element spacing is used to reduce the number of elements. The array is constructed with piezoelectric lead zirconate titanate (PZT-8) circular elements that are 1.4 cm in diameter and have a wall with thickness of 0.2 cm. The array offers an effective ablating depth of at least 8 cm in the tissue for both simulations and ex vivo experiments. The simulations demonstrate that the developed array can steer the focus with good quality of intensity distributions up to 6mm off center over ranges from 17 to 21 cm when the water depth is set at 11 cm. We also present the beam focusing capability in deep tissue through a series of ex vivo experiments by measuring discoloration areas after sonications. These results indicate that the developed array is ideal for the ablation of deep-seated tissue.     

船舶海上风险管理浅议

文章从ISM规则已明确要求航运公司建立风险管理机制,提高船舶安全管理水平这一基点出发,简要地介绍了风险管理的基本概念,即风险分析、风险评价和风险控制,并通过具体实例表述了风险管理的实际应用。     

脑电双频指数调控下的全凭静脉麻醉在小儿腹腔镜手术中的应用

目的探讨脑电双频指数(BIS)调控丙泊酚静脉麻醉在小儿腹腔镜手术中应用的可行性。方法择期行腹腔镜手术的男性患儿40例,随机分为BIS调控丙泊酚静脉麻醉组(Ⅰ组)和丙泊酚持续泵入组(Ⅱ组),比较两组术中麻醉药用量、血流动力学、血气变化及拔管时间;检测两组术中不同时点血浆皮质醇(Cor)、去甲肾上腺素(NE)、肾上腺素(E)、促肾上腺皮质激素(ACTH)的水平。结果Ⅰ组丙泊酚用量明显低于Ⅱ组[(110.0±7.2)μg/(kg.min)vs.(131.0±8.5)μg/(kg.min),P<0.05],拔管时间短于Ⅱ组[8.2±2.1]minvs.(13.4±4.3)min,P<0.05];Ⅰ组心率(HR)、平均动脉压(MAP)在插管时、气腹前两个时点低于Ⅱ组(P<0.05),余各时点血流动力学差异无统计学意义;血气变化各时点差异无统计学意义;Ⅰ组Cor、NE、E、ACTH水平在插管时、气腹前两个时点低于Ⅱ组(P<0.05),余各时点上述各指标差异无统计学意义。结论 BIS监测可减少丙泊酚用量并缩短患儿拔管时间,维持血流动力学稳定,降低应激反应,在小儿腹腔镜手术中的应用是可行的。     

胰岛素分泌囊泡双层脂膜中胆固醇的可视化与定量研究

目的通过菲律宾菌素III染色和脂质测定法,对胰岛素分泌囊泡双层脂膜中胆固醇的分布进行可视化与定量研究。方法利用胆固醇荧光探针菲律宾菌素Ⅲ标记稳定表达phogrin-GFP的MIN6细胞,对比细胞内游离胆固醇与胰岛素分泌囊泡的分布情况。通过连续蔗糖密度梯度离心法分离MIN6细胞中的胰岛素分泌囊泡,应用钼酸铵分光光度法和薄层分析法分别测定生物脂膜中磷脂和游离胆固醇含量,从而得到胆固醇所占比例。结果 MIN6细胞内菲律宾菌素III标记的游离胆固醇与胰岛素分泌囊泡在胞浆中的分布一致,主要聚集在核周及细胞膜下。此外,连续蔗糖密度梯度离心法分离胰岛素分泌囊泡层中富含胆固醇,该层游离胆固醇摩尔百分比为(48.62±3.28)mol%,高于其余各层的细胞器。结论本研究首次进行了胰岛素分泌囊泡双层脂膜中胆固醇的可视化与定量测定,发现胰岛素分泌囊泡富含胆固醇,为进一步研究胆固醇对胰岛素分泌囊泡形成的影响提供了理论基础和方法学依据。     

钢箱拱肋吊杆锚固结构受力分析

以重庆市江津区滨州路一号桥为研究对象,采用大型通用有限元软件ANSYS,分别建立了4种不同构造形式的吊杆锚固结构模型,进行计算分析.结果表明:吊杆与拱肋中心线夹角的变化对锚固结构的极限承载力、刚度变化影响微小,而圆管与拱肋底板连接形式对其影响较大.     

圆形钢筋混凝土桥墩抗震性能(Ⅱ):试验结果评估

根据桥墩拟静力正交试验现象及数据结果,研究了圆形钢筋混凝土桥墩的变形特征及弯曲强度特性;并对低周反复荷载作用下桥墩的位移延性、等效刚度和刚度退化性能以及极限位移状态下累积耗能能力进行了评估,综合考察了剪跨比、轴压比、纵筋率、配箍率等因素对桥墩延性性能的影响.可为桥梁的延性抗震设计提供参考.     

Controlled installation of spudcan foundations on loose sand overlying weak clay

Offshore jack-up rigs are often used for site exploration and oil well drilling. The footings of jack-up rigs are known as spudcan foundations. The risk of rapid uncontrolled penetration of spudcan in seabed (“punch-through”) exposes jack-ups to significant risk during installation in strong over weak layered seabeds. An example for this is a thin loose sand layer overlying a weaker stratum of clay. To prevent spudcans from “punch-through”, an in-situ measurement concept is suggested in this paper to control the installation process of spudcan foundations. First, three-dimensional finite element studies using a Coupled Eulerian–Lagrangian method are carried out to simulate the penetration process. The numerical results have been validated with existing analytical solutions and centrifuge model test data. Furthermore, parametric studies are carried out to quantify the influences of the sand thickness and shear strength of the clay on the bearing capacity of spudcans. Based on the numerical studies an idea for the development of an in-situ measurement concept is suggested to control the spudcan penetration process in-situ.     

促进民营经济投资上海航运产业

为调动民营经济投资上海航运产业的积极性,从民营经济在上海地方经济中的作用出发,分析上海民营企业投资上海航运业的现状和存在的主要问题,并提出相应的对策：缩小与国外的税收差异;改善船舶登记工作;提升对航运总部经济的高端服务能力;鼓励民营经济进入航运高端领域;在上海成立中国中小船舶所有人保赔协会总部;发展单项租赁业务;出台吸引航运人才的政策。     

超能力运行下港区内集装箱码头的博弈*

以上海外高桥港区集装箱码头为背景,构建超能力运行下同一港区内不同集装箱码头之间的博弈模型,通过逆向归纳法分析求解均衡收费和联盟利润,研究发现:与竞争博弈相比,集装箱码头联盟方都能收取相同并且较高的码头费用,其中部分联盟时联盟方的市场份额均为下降,而非联盟方的均衡收费、市场份额和利润均呈增加趋势。与完全联盟相比,部分联盟时联盟方收取的码头费用、市场份额和联盟利润皆为下降;非联盟方的均衡收费和利润也大幅降低,但市场份额却大幅增加,即同一港区集装箱码头博弈中真正的赢家是非联盟集装箱码头。