DQ型卷筒联轴器外套加工工艺研究

分析了DQ型卷筒联轴器的结构特点，对这种联轴器的重要部件一外套的加工工艺做了详细的分析，对加工中出现的问题也做了简要的说明，并编制了在数控车床上加工这种联轴器的数控程序。     

Creative Destruction, Investment Volatility, and the Average Age of Capital

In this article, a new numerical procedure is used to compute the equilibrium of a vintage capital growth model with nonlinear utility, where the scrapping time is nonconstant. We show that equilibrium investment and output converge nonmonotonically to the balanced growth path due to replacement echoes. We find that the average age of capital is inversely related to output, which is consistent with recent micro evidence reinforcing the importance of the embodied question. We also find that an unanticipated permanent increase in the rate of embodied technological progress causes labor productivity to slowdown in the short run.     

The effectiveness of information interventions to improve domestic food safety among rural consumers

Consumer education on food handling behavior is regarded as an effective method to improve domestic food safety and prevent foodborne illness, but is usually overlooked in rural areas. Using a presurvey and two rounds of postsurveys targeted at rural consumers from China included in a randomized controlled trial, this study investigated the effectiveness of two information interventions—a leaflet with tips for best practices and the leaflet plus consumer education sessions conveyed by phone—and compared them with a control group. Cloth use behavior was the target in the trial and five specific aspects were evaluated: (1) whether the cloth was made of old clothes, (2) whether the one used to clean kitchen tables was also used to wash dishes, (3) whether it was hung to dry, (4) how it was disinfected, and (5) how long the cloth was used before being discarded. Firstly, consumers' behavior was scored by summing the above-mentioned five behaviors. The results estimated using the difference-in-difference model showed that respondents in the leaflet-only group improved to a greater extent than those in the control group, but their difference in progress was not statistically significant until the second round of the postsurvey. Respondents in the leaflet-plus-phone group were quicker to adopt suggested practices and made discernible improvements compared with those in the leaflet-only group in the first round of the postsurvey, but the gap between these groups narrowed to statistically insignificant in the second round of the postsurvey. It was concluded that one consumer education session was effective and made a difference in the long term, whereas more education sessions produced normative behavior at faster rates, showing a significant improvement in the short term. Then, the study estimated the effectiveness of interventions on the five specific behaviors separately. The results were estimated using a probit difference-in-difference model and showed that the suggested behaviors with lower costs or a greater difference from past behaviors were more likely to be adopted by consumers. Consumer education facilitates proper food handling practices among rural households, which should be considered by policy makers.     

新型活塞式套筒阀在长距离重力输水系统中的应用

为预防DN1200多功能活塞式套筒阀在实际应用过程中因阀门关闭产生关阀水锤对输水管道造成破坏,通过数值模拟手段开展DN1200阀门的流量特性研究。基于水锤的特征线方程,通过编写代码将阀门的流量特性代入,对阀门关闭后管道中的压力变化特征进行分析,并据此制定合理的关阀策略。结果表明,该阀门具有良好的流量调节特性,且合理的关阀规律及关阀时间能够防止因阀门关闭在管道中产生过大的水锤压力,保障输水系统安全。     

厚煤层大倾角煤顶下掘进围岩控制数值模拟研究

为研究大倾角煤层开采过程中巷道围岩的稳定状况,以青东矿837机、风巷为工程背景,进行煤层顶底板岩石力学参数实验室测试,利用FLAC3D软件建立不同掘进工艺条件下的数值计算模型,分析软弱特厚煤层巷道分别在跟顶板掘进、全煤层掘进、破底掘进(不同破底深度)条件下巷道围岩破坏范围和变形特征。结果表明：跟顶板掘进方式下,围岩的塑性破坏主要发生在巷道底板下方,需要特别注意加强对底板的支护;跟底板掘进时,底板中部靠近帮脚处产生严重底鼓,应当加强对帮脚和巷帮的支护;在全煤层掘进时,巷道主要变形为底鼓与顶板下沉,顶底板破坏严重。研究成果对于指导大倾角厚煤层开采围岩控制具有一定的理论与工程意义。     

袁店一井煤矿深部复杂构造区失修岩巷综合控制技术研究

为了解决煤矿深部复杂构造区岩巷冒顶、底鼓等支护失效问题,以袁店一井煤矿深部复杂构造区失修岩巷为工程背景,提出高强锚注综合控制系统来保持围岩的完整性和稳定性。利用FLAC3D软件建立典型岩巷高强锚注综合控制技术方案的数值计算模型,分析强力锚固约束支护技术方案以及锚注一体化补强支护技术方案对围岩稳定性的影响。提出具体“高强锚注”主动支护技术方案,并且在103大巷进行现场试验。后续监测表明支护效果良好,切实解决深部大规模复杂构造区岩巷长期稳定性控制难题。研究成果对于指导深部复杂构造区岩巷围岩控制具有一定的理论与工程意义。     

显示设备固定结构在高铁既有站的应用研究

研究一种高铁既有车站站台层的L ED显示设备安装固定结构的应用.这种抱柱式站台显示屏固定结构通过将L ED显示屏固定于站台层两支撑立柱之间,解决了高铁线路中一些老式铁路既有车站运行班次多、运营状态不允许长时间站台施工和不能破坏站台钢筋混凝土结构的问题.基于三维建模和数值仿真对这种设备固定结构进行一系列静力学结构分析,包括在极端工况环境下的静态应力、应变和位移分析,结果安全有效,安装作业符合现场施工要求,实现了此类高铁既有站站台结构上L ED显示设备的安装和使用.为了研究这种抱柱式站台显示屏固定结构的工作可靠性,应用数值分析软件对结构模型进行预应力模态分析,在风荷载作用下分析各阶频率下结构的变形程度以及对地震灾害的预防影响,从而验证了这种L ED显示设备固定结构在铁路信息显示技术上,特别是在高铁既有车站上应用的有效性及其应用价值.     

双离合自动变速器电控电动换挡执行机构仿真优化与试验对比

为了提高双离合变速器在车辆上的换挡品质,提升电气化换挡执行机构的工作效率,给出执行机构性能与换挡品质评价准则;通过两种不同双离合变速器电控电动执行机构的工作原理与性能分析,基于MATLAB数值仿真方法优化出最高效率进行试验.基于车辆6个维度的换挡工况对二者所搭载的变速器分别进行试验与CAN线数据采集,对比研究两种机构优缺点,通过雷达图的方式进行优劣说明.结果表明,两种执行机构传动效率可达70％且换挡品质相当.可见Tip in tip out工况对二者要求最为严格.     

离心式血液泵水力特性设计及其试验研究

借助商业软件NREC开展离心式血液泵的水力特性设计,其设计流量为5 L/min,设计转速为5000 r/min,得到离心叶轮和蜗壳的三维结构设计方案,并针对其全通道网格进行设计工况下三维流场的定常数值模拟研究.对其溶血性指标进行分析,发现离心式血液泵中95％ 区域切应力小于150 Pa,最大切应力小于500 Pa,满足人体对血液泵溶血性的要求.搭建离心式血液泵流量-压升特性试验测试平台,以质量分数为0.06％ 的黄原胶溶液为流动介质进行试验研究,试验结果显示在设计转速下的实际体积流量偏大于设计流量,整体压升在6550 Pa左右.     

Do not swipe the small stuff: A randomized evaluation of rules of thumb-based financial education

We perform the first rigorous test of a rules of thumb-based approach to financial education on consumer behavior and outcomes. We test two rules of thumb that are targeted at reducing credit card revolving and deliver them in a randomized fashion via e-mail, online banner, and physical mailer. Using monthly administrative data and pre and postintervention credit data on almost 14,000 consumers, we find that the “Do not swipe the small stuff” rule of thumb reduces participants' targeted credit card balance by an average of 2% at a cost of around $0.50 per person. The “Credit keeps charging” rule shows a decline as well but the impact is not significant.