梯形明渠共轭水深计算方法

一方面,通过对共轭水深方程进行数学变换,并根据共轭水深的水流特点,得到计算其水深的迭代公式;另一方面,通过求解一元二、三次方程得到共轭水深的初值近似计算式,并以此为初值,用迭代公式进行一次迭代得到梯形明渠共轭水深的直接计算公式。计算数据表明,该法不依赖图表,计算便捷且精度很高,可供工程实际参考应用。     

双线浅埋隧道远近距离界定及地表沉降机理研究

利用Peck公式计算双线隧道开挖引起的地表沉降时,有多个参数会影响到计算结果的大小与沉降曲线的形状。从数学角度对隧道轴线埋深h和两隧道间距L的比率及沉降槽宽度参数K对地表沉降曲线的影响进行研究,得到以下结论在h/L比率逐渐增大的过程中,地表沉降曲线变化过程为较陡峭的W型—较平缓的W型—∪型—U型—V型;相同比率下的地表沉降曲线都呈现相同的型式,与隧道埋深无关;在K=0.600的情况下,沉降曲线由W型向U型转变,h/L的临界值为0.825,而后发现在不同K值下,存在h/L临界值使得不同埋深下的沉降曲线都呈现U型,得到了沉降槽宽度参数K与其对应h/L临界值的最优拟合方程。基于h/L临界值的分析结果,提出了双线隧道远近界线的判别公式,并与现有方法及规范进行对比,结果表明判别公式能较好地界定双线隧道远近距离。同时,对Peck公式预测隧道开挖引起地表沉降的机理进行了推测,并利用颗粒流软件对隧道开挖进行模拟,结果表明压力拱曲线符合高斯曲线。研究成果可为双线浅埋隧道设计、施工提供依据。     

水工钢闸门主梁的最优梁高

对水工钢闸门主梁高度的确定多以经验公式为主,理论不完善,未全面考虑截面形式与支座位置对梁高影响的问题,依据现行钢闸门设计规范,以满足强度、刚度、稳定性和几何构造要求为约束条件,以主梁和竖向隔板总用钢量最小为目标函数,分别建立单轴、双轴对称截面下的简支式和双悬臂式主梁梁高的优化模型。采用半解析法推导出简支式和双悬臂式主梁的最优梁高理论公式。通过与已建工程对比,结果表明:推导的最优梁高公式计算的梁高均与实际工程中的梁高接近,且公式有进一步优化的空间;通过减小隔板高厚比与主梁腹板高厚比可达到降低梁高的目的。该理论公式一方面可应用于工程实践,另一方面也可为完善规范提供理论基础。     

Cost-effectiveness of partially-hydrolyzed formula for prevention of atopic dermatitis in Australia

Abstract

Objective:

To perform an economic evaluation of a specific brand of partially hydrolyzed infant formula (PHF-W) in the prevention of atopic dermatitis (AD) among Australian infants.

Methods:

A cost-effectiveness analysis was undertaken from the perspectives of the Department of Health and Aging (DHA), of the family of the affected subject and of society as a whole in Australia, based on a decision-analytic model following a hypothetical representative cohort of Australian newborns who are not exclusively breastfed and who have a familial history of allergic disease (i.e., are deemed ‘at risk’). Costs, consequences, and incremental cost-effectiveness ratios (ICER) were calculated for PHF-W vs standard cow’s milk based infant formula (SF), and, in a secondary analysis, vs extensively hydrolyzed infant formula (EHF-Whey), when the latter was used for the prevention of AD.

Results:

From a representative starting cohort of 87,724 ‘at risk’ newborns in Australia in 2009, the expected ICERs for PHF-W vs SF were AU$496 from the perspective of the DHA and savings of AUD1739 and AU$1243 from the family and societal perspectives, respectively. When compared to EHF-Whey, PHF-W was associated with savings for the cohort of AU$5,183,474 and AU$6,736,513 from the DHA and societal perspectives.

Limitations:

The generalizability and transferability of results to other settings, populations, or brands of infant formula should be made with caution. Whenever possible, a conservative approach directing bias against PHF-W rather than its comparators was applied in the base case analysis. Assumptions were verified in one-way and probabilistic sensitivity analyses, which confirmed the robustness of the model.

Conclusions:

PHF-W appears to be cost-effective when compared to SF from the DHA perspective, dominant over SF from the other perspectives, and dominant over EHF-Whey from all perspectives, in the prevention of AD in ‘at risk’ infants not exclusively breastfed, in Australia.     

The density of the time to ruin for a Sparre Andersen process with Erlang arrivals and exponential claims

We derive expressions for the density of the time to ruin given that ruin occurs in a Sparre Andersen model in which individual claim amounts are exponentially distributed and inter-arrival times are distributed as Erlang(n,?β). We provide numerical illustrations of finite time ruin probabilities, as well as illustrating features of the density functions.     

基于实验与数学的匀速圆周运动向心力公式推导方法

本文运用观察实验和数学方法,给出了匀速圆周运动向心力公式的几种推导方法,以促进人们更加深刻地认识、理解和应用匀速圆周运动向心力。     

任意空间位置两多边形多匝线圈的互感计算

根据聂以曼公式推导出任意空间位置两多边形线圈互感的一般表达式,应用旋转矩阵实现了线圈位置的变化,通过MATLAB软件编程计算,绘出了互感的变化曲线,并对计算结果进行进行了分析验证。     

出口段收缩式有压泄水洞流量系数的试验分析

有压泄水洞的泄流能力是一个涉及其规模、尺寸的关键问题,是设计中必须解决的水力学问题。从有压恒定流的伯诺里方程出发,对有压泄水洞的流量计算进行了理论分析,并以已建工程试验数据为基础,提出了流量系数的经验计算式。     

水电工程价格指数发布情况回顾与展望

对2002～2008年水电建筑、安装工程价格指数的发布情况进行了总结回顾,并对今后价格指数变化趋势进行了走势分析.分坝型、分地区对几十个典型工程实例的设计概算进行了权数测算,并对近80种典型工艺进行了单价权数测算;从而确定了各调价因子的权数.分析认为,水电工程价格指数在将来的至少两年内不会再出现类似于2006～2007年猛烈上涨的情势,会维持在一个较平稳的位置,预计同比综合价格指数的涨幅将回落至2%左右.     

对国内外砂土地震液化评价介绍及比较

本文通过应用国内外不同的勘察规范对同一个工程场地的地震液化等级划分的计算及评价介绍,得出了一个采用不同规范,可取得比较一致的地震砂土液化等级的结论。