Sediment storage and shallow groundwater response to beaver dam analogues in the Colorado Front Range,USA

Enthusiasm for using beaver dam analogues (BDAs) to restore incised channels and riparian corridors has been increasing. BDAs are expected to create a similar channel response to natural beaver dams by causing channel bed aggradation and overbank flow, which subsequently raise water tables and support vegetation growth. However, lack of funding for monitoring projects post‐restoration has limited research on whether BDAs actually cause expected channel change in the Front Range and elsewhere. Geomorphic and hydrologic response to BDAs was monitored in two watersheds 1 year post‐restoration. BDAs were studied at Fish Creek, a steep mountainous catchment, and Campbell Creek, a lower gradient piedmont catchment from May to October 2018. At each restoration site, the upstream‐ and downstream‐most BDAs were chosen for intensive study in comparison with unrestored reference reaches. Monitoring focused on quantifying sediment volumes in BDA ponds and recording changes to stream stage and riparian groundwater. Despite differences in physical basin characteristics, BDA pools at both sites stored similar volumes of sediment and stored more sediment than reference pools. Sediment storage is positively correlated to BDA height and pool surface area. However, BDAs did not have a significant influence on shallow groundwater. The lack of groundwater response proximal to BDAs could indicate that local watershed factors have a stronger influence on groundwater response than restoration design 1 year post‐restoration. Systematic, long‐term studies of channel and floodplain response to BDAs are needed to better understand how BDAs will influence geomorphology and hydrology.     

三河口水利枢纽泄洪消能工体型优化试验研究

通过水力学模型对三河口水利枢纽泄洪消能工体型进行了试验研究。结果表明:两底孔出口采用矩形不对称宽尾墩形成的窄缝体型,三表孔采用左、右表孔差动式齿坎与中表孔舌型鼻坎组合的优化方案具有表孔、底孔出口水舌上下分层、前后拉开、横向扩散的特点,从而改善了水垫塘内的水流流态,提高了消能效率,水垫塘底板所受动水冲击压力及脉动压力达到了设计要求。     

磁场和活性剂联合作用下TIG焊热源模型的确定

为了确定磁场和活性剂联合作用下TIG焊热源模型,分别采用双椭圆面热源模型和双椭球体热源模型对焊接熔池的温度场分布进行了数值模拟,根据模拟结果的等值线分布情况可以获得熔池形状.通过将试验值和模拟值进行对比可以发现,利用双椭球体热源模型得到的熔池形状与实际熔池尺寸相吻合,而双椭圆面热源模型不能很好地反应厚度方向上的温度分布.结果表明,双椭球体热源模型可以更加准确地表征磁场和活性剂联合作用下TIG焊的实际焊接过程,打破了以往依照焊接方法选取热源模型的传统.     

库坝池窖联合高效利用水资源技术推广成效与经验

宁南山区降水主要集中在7—9月,而旱灾一般发生在春夏之交的3—5月,降水的时空分布与作物需水不匹配.为了解决宁南山区水资源利用率低等现状问题,利用彭阳县陈沟村已建成的蓄水池等水土保持拦蓄工程,开展水利部科技推广项目"库坝池窖联合高效利用水资源技术引进与示范",通过合理调节水资源的时空分布,制订适用的水资源管理分配制度,发展节水高效灌溉技术,实现"秋水春用、低水高用".2013年共调蓄水量6 100 m3,水分生产效率提高0.34~30.04元/m3,增加示范户农民纯收入5.0%~16.9%,带动更多群众致富.     

环境水样中挥发酚测定方法研究

采用LWCC超长比色池的连续流动分析仪分析环境水样中的挥发酚,检出限为0.056μg/L,检测下限为0.17μg/L,对1μg/L 样品,相对标准偏差为1.3%,相对误差3.9%,与《水质挥发酚的测定4-氨基安替比林分光光度法》（ HJ503-2009）相比具有检出限低、精密性好、准确度高、分析速度快,适宜于大批量样品分析,对地表水和地下水中挥发酚类预警监测作用明显,同时省去了萃取分光光度计法繁琐的操作步骤,避免了三氯甲烷对实验人员的危害。     

水基淬火介质量化淬火循环冷却系统的设计

根据量化控制淬火原理，针对水基淬火介质，选用三个量化控制参数：K、Ts和Q，设计了符合量化淬火要求的循环冷却系统。     

熔池表面变形对电弧行为特征的影响

在电弧与熔池统一模型的基础上研究熔池上表面变形对电弧行为特征的影响。用本模型计算出的平坦熔池表面电流密度和热流密度的分布与试验结果显示了很好的一致性。而变形熔池表面的电流密度和热流密度分布则不再符合近似的高斯分布。这就为下一步研究电弧和熔池的工作提供了基础。     

双丝MAG焊工艺

双丝MAG焊接具有良好的发展前景，正广泛应用于各项工程领域之中，从其焊接设备的要求、保护气体以及其熔滴过渡控制、焊接过程等几个方面，详细介绍双丝MAG焊的工艺及其特点。     

Molten pool and temperature field in CO_2 laser welding

0IntroductionCompared with conventional welding methods,laserwelding has many advantages,such as large penetrationratio,small HAZ,small welding deformation.Another ad-vantage of laser welding is easy to weld complicated com-ponents because laser can be transferred by mirrors andoptical fiber.The laser welding will find wide applicationswith the laser system developing.Induced-plasma,molten pool and keyhole are mainphenomena in study of laser welding process.The varietiesof them indicate the …     

Prediction and verification of melting front in GTA weld pool of full-penetration

A thermal conduction model is applied to speed up the numerical analysis of the temperature distribution and the weld pool geometry of full penetration in gas tungsten arc （GTA） welding. With considering both top and bottom flee surface deformation of full-penetrated weld pool, three-dimensional weld pool with melting front and solidification front is predicted. Welding experiments are conducted to measure the melting front curves at the top surface and the longitudinal section of the weld. It shows that the predicted and measured results are in good agreement.