冰水二相流渠道流冰输移演变规律及其安全运行措施研究

针对我国新疆、青海地区为数众多且无法采用冰盖下输水的宽浅式渠道工程,开展冰水二相流输运机理及运行调控技术研究,对于解决这些地区冬季用水矛盾、节省工程改造投资具有重要意义。以新疆北部地区某电站引水渠为例,通过构建一维渠道冰水力学数学模型,研究渠道流冰输移和发展规律,分析气温、出库水温、输水流量等关键因素对渠道冰情的影响,并提出冰水二相流渠道的安全运行措施,对实现冰水二相流安全水力调控、解决我国西北地区冬季缺水问题具有一定参考价值。     

管道水锤方程的Crank2Nicolson 离散格式及其工程应用

为了模拟输水管道的水力过渡过程, 建立了一种新型的有压管水力计算模型。采用有限体积法对一维有压管 道水锤方程在空间和时间上进行积分, 同时应用时间中心差分的Cr ank2Nico lson 隐式格式对偏微分项进行处理, 得 到具有二阶精度且无条件稳定的水锤方程离散格式, 并运用带有解析解的算例验证方法的准确性。通过模拟北京 市南水北调惠南庄泵站开、关过程, 可以提前预测出现的压力波动, 及早采取应对措施, 降低有害水锤出现的概率, 减少压力波动带来的不利影响, 使瞬变状态安全过渡到正常运行状态。结果表明此方法具有良好的工程应用性。     

Measurement of electrical conductivity of Pb-Bi alloys in the melting-solidification region

The electrical conductivity, σ(T), of Pb-Bi alloys of eutectic and near eutectic compositions was investigated in the melting-solidification temperature region. The revealed discrepancies between the heating and cooling σ(T) curves as well as a hysteresis observed in course of heating-cooling cycles suggest a metastable microheterogeneous structure of the Pb-Bi melts.     

硫酸铵改性Al_2O_3负载Ni基催化剂的异丁烷脱氢性能

采用浸渍法制备了含NiO质量分数为20%的NiO/(SO2-4)w-Al2O3(w为SO2-4质量分数)催化剂,借助X射线衍射仪、热重分析仪等对催化剂的性能进行了表征,同时考察了催化剂在560℃时的异丁烷脱氢反应性能。结果表明,NiO/Al2O3催化异丁烷脱氢时,异丁烷几乎全部转化为CH4和积炭,目的产物异丁烯收率为零。以硫酸铵改性NiO/Al2O3作为催化剂,不仅能明显改善异丁烷脱氢产物分布,大幅度提高异丁烯的选择性,还能抑制积炭生成;NiO/(SO2-4)32-Al2O3催化异丁烷脱氢反应性能为最佳,在反应7 h时,异丁烷转化率和异丁烯收率可分别达到34.5%,23.8%。     

Impact of corneal collagen cross-linking on vision-related quality of life measured with the keratoconus outcomes research questionnaire (KORQ) in patients with keratoconus

PurposeTo assess the impact of corneal collagen cross-linking on self-reported vision-related quality of life (VR-QoL) in keratoconus patients by means of the Keratoconus Outcomes Research Questionnaire (KORQ), a new disease-specific patient reported outcomes measures (PROMs) tool.MethodsPatients with progressive keratoconus undergoing corneal collagen cross-linking were consecutively enrolled. Patients completed the KORQ before and after the treatment, at 1, 3 and 6 months. Data were collected regarding the visual acuity and the topographic, aberrometric and pachymetric parameters of both eyes. Patients were also asked to quantify their eye rubbing behavior on a Visual Analogue Scale (VAS) from 0 to 10, before and 6 months after treatment.The KORQ scores were associated with the visual acuity, topographic, aberrometric and pachymetric data by means of the Spearman correlation coefficient.ResultsThe Activity Limitation (AL) subscale score was higher after surgery. Preoperatively, negative correlations were observed between the KORQ AL score and Best Corrected Visual Acuity (logMAR), maximum keratometry, flattest keratometry, steepest keratometry, symmetry index front and higher order aberrations (HOA) of the treatment eye. Postoperatively, we observed a shift toward the fellow eye, with stronger correlation of the KORQ scores with the fellow eye parameters. The Symptoms subscale score correlated with the aberrometric parameters of both eyes at various time points. Statistically significant correlations were observed between the change in KORQ scores and the change in aberrometric parameters. A statistically significant reduction in the eye rubbing behavior was detected (p < 0,0001).ConclusionsThese results suggest that the corneal cross-linking treatment is effective both in improving the subjective perception of the disease by the patient and in stabilizing the objective indicators of disease progression. Keratometric, aberrometric and visual acuity values showed a significant impact on self-reported VR-QoL. Corneal cross-linking, by halting the worsening of these parameters, may bear a beneficial effect on VR-QoL.     

长距离多泵联合运行输水系统停泵水锤防护措施

运用水锤理论和特征线法,结合工程实例,对采用缓闭式蝶阀、空气阀和单向调压塔等防护措施的长距离多泵联合运行输水系统停泵水锤进行计算和分析,得到了管道沿程的水头包络线以及泵端性能参数相对值的变化曲线。计算结果表明,无防护措施下最小水锤水头较低,泵端性能参数变化较大;泵端蝶阀防护可以有效地控制泵端性能参数流量和转速变化幅度,但水头的变化出现了振荡,最小水锤水头值降低;采用空气阀+泵端蝶阀防护可以有效地增加最小水锤水头值,只在管道局部出现负压,但与泵端蝶阀防护相比性能参数变化有所增大;单向调压塔+泵端蝶阀对停泵水锤防护效果最为明显。为了减小单向调压塔数目,最终选择单向调压塔+空气阀+泵端蝶阀的组合作为最终的防护措施,与无防护措施相比,组合防护下整个管道不出现负压,泵端水头虽出现了振荡,但幅度不大,流量最大变化幅度下降0.15,转速最大变化幅度下降0.7,转矩振荡时间变短。     

GPT2w模型在中国大陆地区的精度分析

全球气温气压(GPT)系列模型可用于计算全球任意位置的气温、气压和水汽压等各种气象参数,目前国内外广泛使用且精度较高的全球气温气压模型主要为GPT2w模型.本文利用2012—2016年中国大陆地区102个国家气象站实测的气温、气压和水汽压数据对GPT2w模型进行精度分析.结果表明:GPT2w模型的气温误差均值为-0.4...