销孔间隙与孔壁承压容许应力取值研究

销连接是现代钢结构连接常用的形式,然而销孔与销轴之间不可避免地存在间隙。利用ANSYS软件研究销孔间隙对耳板孔壁承压容许应力的影响。在弹塑性阶段,通过详细的数值分析以塑性区面积为“桥梁”研究了销孔间隙对耳板孔壁承压建议容许应力的影响。将得到的离散数据进行解析拟合,给出了耳板承压建议容许应力随销孔间隙变化的公式。     

Cystatin C as a predictor of mortality in elderly patients with chronic kidney disease

Background: The prevalence of chronic kidney disease (CKD) in the elderly is high. Serum cystatin C is an accurate marker of kidney function and it also has prognostic utility in CKD patients. The aim of our study was to determine the prediction of serum cystatin C and other markers of kidney function on long-term survival in elderly CKD patients.

Methods: Fifty eight adult Caucasian patients, older than 65 years, without known malignancy, thyroid disease and/or not on steroid therapy were enrolled in the study. In each patient, ⁵¹CrEDTA clearance, serum creatinine, serum cystatin C, and estimated glomerular filtration rate using different equations were determined on the same day and patients were then followed for 11 years or until their death.

Results: The means are as follows: ⁵¹CrEDTA clearance 53.3?±?17.4?ml/min/1.73?m², serum creatinine 1.62?±?0.5?mg/dl, serum cystatin C 1.79?±?0.5?mg/l, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation 40.1?±?14?ml/min/1.73?m², Berlin Initiative Study 2 (BIS2) equation 38.9?±?10.7?ml/min/1.73?m², full age spectrum (FAS) creatinine equation 43.8?±?13.8?ml/min/1.73?m², FAS cystatin C equation 40.1?±?11.7?ml/min/1.73?m². In the follow up period, 47 (81%) patients died. Cox regression analysis showed different hazard ratios (HRs) for death: for ⁵¹CrEDTA clearance HR 1.022 (95% CI 1.004–1.042; p?=?.015), serum creatinine HR 1.013 (95% CI 1.006–1.019; p?=?.001), serum cystatin C HR 2.028 (95% CI 1.267–3.241; p?=?.003), CKD-EPI creatinine equation HR 1.048 (95% CI 1.019–1.076; p?=?.001), BIS2 equation HR 1.055 (95% CI 1.021–1.088; p?=?.001), FAS creatinine equation HR 1.046 (95% CI 1.017–1.074; p?=?.001), FAS cystatin C equation HR 1.039 (95% CI 1.010–1.071; p?=?.009).

Conclusions: Our results showed the highest HR for serum cystatin C among kidney function markers for prediction of outcome in elderly CKD patients.     

Confidence Intervals for the Weighted Sum of Two Independent Binomial Proportions

Confidence intervals for the difference of two binomial proportions are well known, however, confidence intervals for the weighted sum of two binomial proportions are less studied. We develop and compare seven methods for constructing confidence intervals for the weighted sum of two independent binomial proportions. The interval estimates are constructed by inverting the Wald test, the score test and the Likelihood ratio test. The weights can be negative, so our results generalize those for the difference between two independent proportions. We provide a numerical study that shows that these confidence intervals based on large‐sample approximations perform very well, even when a relatively small amount of data is available. The intervals based on the inversion of the score test showed the best performance. Finally, we show that as for the difference of two binomial proportions, adding four pseudo‐outcomes to the Wald interval for the weighted sum of two binomial proportions improves its coverage significantly, and we provide a justification for this correction.     

A simple in-host model for Mycobacterium tuberculosis that captures all infection outcomes

ABSTRACT

Tuberculosis infection can result in clearance, latent infection, or active disease, with slow or fast progression. A four-dimensional model of in-host tuberculosis infection includes macrophages, T lymphocytes, tuberculosis bacteria, and their interactions. Changes in the infection rate, cell-mediated immunity rate, macrophage loss rate, and bacteria killing rate most affect disease outcomes. Simulations show that a periodic solution can occur. When the infected macrophage killing rate is constant, a backward bifurcation exists and the system is globally stable.     

四通换向阀内泄漏分析研究

内泄漏量是衡量四通换向阀性能的重要指标之一,本文建立了四通换向阀的气体试验中的泄漏模型,并通过试验方法研究了坟差、气体温度对泄漏量的影响,理论和试验结果表明,在同一个换向阀上,压差的增加会明显地增加泄漏量,而气体温度的上升会使泄漏量降低。     

浅谈楼板灌缝开裂的原因和预防措施

解决楼板灌缝开裂是砖混结构房屋常见的质量通病 ,多层住宅工程建设中表现更为突出。分析了楼板灌缝开裂的原因 ,提出了相应的解决办法     

管道冬季泄漏土壤热波动及原油渗流数值计算

采用有限容积法建立埋地管道泄漏多孔介质流固耦合相变数学模型,对冬季热油管道不同位置泄漏前后大地温度场的变化及原油在土壤中的分布规律进行数值模拟。研究表明：管道泄漏后,一定时间内管道周围土壤温度波动剧烈,由于受环境温度的影响,泄漏前锋原油温降较快,很快达到凝点,并出现不同形态的动态凝油层,致使原油渗流速率降低,热影响区范围变化逐渐趋于平稳。且随泄漏位置的不同,地表温度变化及土壤中原油分布差异较大。应用分布式光纤温度传感技术检测管道泄漏是可行的。     

齿轮副侧隙的概率分布

将齿轮副侧隙划分为随机变量侧隙和随机相位侧隙两部分。利用简化模型重点讨论了随机相位侧隙，它是一个平稳随机过程。验证了小模数齿轮国家标准侧隙基本计算式，依概率包容了任一时刻的概率极限侧隙，理论分析和实验证明了它的正确性和实用性。     

调整直列式多缸发动机气门间隙的简易方法

本文对直列式多缸发动机气门调整方法进行探讨，推荐一种新的方法。与传统法相比具有简单、科学、准确、适用范围广等特性。     

论进口避税行为及对策

进口避税的价格效应使进口商获得了额外的利润。为此 ,进口商利用完税价格确定的复杂性、进口关税税率的差异性等进行避税。对此 ,海关应在如下几方面加强反避税措施 :建立科学严密的关税征收管理体系 ;简化关税制度 ,弱化刺激避税因素 ;对跨国公司转移定价进行限制 ;建立以企业为主、商品为辅的风险机制 ;提高征管队伍的素质 ;创新税收征管手段 ;借助社会力量实现综合治理