天生桥一级水电厂AGC振动区处理策略

一般情况下,自动发电控制(AGC)对于振动区的处理原则是避免机组运行在振动区.由于天生桥一级机组的振动区极为特殊,过大的振动区范围导致其可调范围较小,因此南方电网允许天生桥一级水电厂AGC可以短时间内运行在振动区.文中根据机组在振动区运行的累积时间或机组进入振动区运行的优先级,采取机组轮流进入振动区运行的策略,不仅可以有效避免对南方电网稳定断面潮流的影响,而且有利于电网的稳定运行.     

Sources and temporal dynamics of arsenic in a New Jersey watershed, USA

We examined potential sources and the temporal dynamics of arsenic (As) in the slightly alkaline waters of the Wallkill River, northwestern New Jersey, where violations of water-quality standards have occurred. The study design included synoptic sampling of stream water and bed sediments in tributaries and the mainstem, hyporheic-zone/ground water on the mainstem, and seasonal and diurnal sampling of water at selected mainstem sites. The river valley is bordered by gneiss and granite highlands and shale lowlands and underlain by glacial deposits over faulted dolomites and the Franklin Marble. Ore bodies in the Marble, which have been mined for rare Zn ore minerals, also contain As minerals. Tributaries, which drain predominantly forested and agricultural land, contributed relatively little As to the river. The highest concentrations of As (up to 34 mug/L) emanated from the outlet of man-made Lake Mohawk at the river's headwaters; these inputs varied substantially with season--high during warm months, low during cold months, apparently because of biological activity in the lake. Dissolved As concentrations were lower (3.3 microg/L) in river water than those in ground water discharging into the riverbed (22 microg/L) near the now-closed Franklin Mine. High total As concentrations (100-190 mg/kg) on the <0.63 microm fraction of bed sediments near the mine apparently result from sorption of the As in the ground-water discharge as well as from the As minerals in the streambed. As concentrations in river water were diluted during high stream flow in fall, winter and spring, and concentrated during low flow in summer. In unfiltered samples from a wetlands site, diurnal cycles in trace-element concentrations occurred; As concentrations appeared to peak during late afternoon as pH increased, but Fe, Mn, and Zn concentrations peaked shortly after midnight. The temporal variability of As and its presence at elevated concentrations in ground water and sediments as well as streamwater demonstrate the importance of (1) sampling a variety of media and (2) determining the time scales of As variability to fully characterize its passage through a river system.     

新疆大石峡水利枢纽混凝土碱-硅酸反应抑制研究

新疆大石峡水利枢纽混凝土选用的骨料存在碱活性,可能导致工程产生碱骨料破坏问题,本文研究了当地粉煤灰和矿粉对碱-硅酸反应(ASR)的影响,并采用XRD和SEM-EDS测试分析了水化产物和界面过渡区的形态。结果表明：粉煤灰掺量≥20%(质量分数)或矿粉掺量≥40%(质量分数)都能显著抑制碱-硅酸反应;在纯水泥样品界面过渡区可以观察到无定形相,在含有粉煤灰或矿粉的样品中未观察到无定形相,这意味着碱-硅酸反应发生在纯水泥样品中;添加粉煤灰或矿粉降低了界面过渡区物相的Ca/Si摩尔比,抑制了碱-硅酸反应。     

平砧压薄坯件死区边界滑移线函数的积分

本文通过在死区边界滑移线中引入参变量t,建立滑移线转角O和座标x的可积函数,通过积分求得死区接触表面总压力及平均单位压力分布的精确值。因此,这种换元积分法在理论上可以替代常用的数值积分计算法。     

螺旋榨油机喂料段的理论与实践

基于单螺杆挤压机固体输送段的非塞流理论,将榨油机的喂料段螺槽中的油料简化为上、中、下3层,通过应力-速度方程,推导出产量与压力降的三次方程.详细讨论了摩擦因数和喂料螺旋的几何参数对最大产量和系统压力的影响.结果表明,适当增加喂料螺旋的覆盖长度和榨笼内壁的摩擦因数是提高喂料段末端压力和输送能力的有效途径.实践证明,在榨油机的喂料段附加一个带阻转槽的衬套是实现高油分、低粗纤维含量的软油料在榨油机中顺畅喂料的行之有效的方法.并给出了带阻转槽的衬套的结构和设计方法.     

米糠油不饱和脂肪酸对肝癌细胞HepG_2克隆及迁移能力的影响

本研究采用软琼脂克隆形成和Transwell小室迁移实验观察分析了米糠油不饱和脂肪酸(RBO-UFA)在体外对HepG_2的影响,并通过Western blot检测了凋亡相关因子NF-κB在用RBO-UFA处理前后其表达的变化。Heochst染色结果显示HepG_2经RBO-UFA处理后细胞数量明显减少,胞质浓缩,细胞核内染色质凝集;软琼脂克隆形成检测结果显示HepG_2经RBO-UFA处理后克隆团明显减少,甚至无克隆团出现;迁移检测结果显示亚麻酸和亚油酸抑制HepG_2细胞迁移能力的抑制率分别为47.45±4.60%、41.61±4.08%,其次是米糠油32.85±3.24%,油酸25.55±2.56%(P0.05)。Western Blot结果显示,RBO-UFA处理后HepG_2细胞全蛋白中NF-κB表达水平显著低于正常对照组,米糠油、油酸、亚油酸、亚麻酸处理组与正常对照组相比,其相对表达量分别降低了0.46±0.017、0.058±0.018、0.25±0.005、0.47±0.011;而在核蛋白中NF-κB表达水平均高于正常对照组,相对表达量分别增加了0.59±0.036、0.053±0.040、0.28±0.043、0.59±0.007(P0.05)。结果表明米糠油不饱和脂肪酸(RBO-UFA)对肝癌细胞HepG_2的克隆形成及迁移具有一定的抑制作用。     

防止电网大面积停电的电源自投系统母差保护新闭锁逻辑技术研究

通过对现场备自投装置的放电及动作逻辑过程的分析,以及备自投装置对母线故障区域特点进行识别进行研究,发现目前的备自投逻辑导致未发生故障的母线也失压,损失大量的负荷,导致电网大面积停电,为此特提出一种防止电网大面积停电的备用电源自投系统新闭锁逻辑技术,能识别母线相继故障;能识别母联死区故障;解决未故障段母线恢复供电问题;能够实现故障段母线的隔离。在恢复无故障设备的供电,对用户供电的连续性和可靠性提供保证．防止电网大面积停电。     

降低高度不饱和脂肪酸乙酯中的过氧化值方法的研究

以LiAlH_4为还原剂,试图降低富含高度不饱和脂肪酸乙酯(主要是5、8、11、14、17、——廿碳五烯酸乙酯,5、8、11、14、17、20——廿二碳六烯酸乙酯。分别简称为EPA乙酯,DHA乙酯)的鱼油酸乙酯的过氧化值。其中,以乙醚为溶剂,LiAlH_4的用量为3％,反应时间为60～90min,去过氧化值的效果显著,方法较简便。     

反射环对区熔炉温度场的影响

针对悬浮区熔法生长较大直径的单晶硅时,单晶硅外部的轴向温度梯度比内部温度梯度大很多,从而导致硅单晶径向电阻率不均匀及生长裂纹的问题。通过有限元法对生长区熔硅单晶的温度场进行了数值模拟,建立了有反射环和无反射环的两种模型,得到了两种模型下的单晶温度分布图,并对比分析了两种模型下的单晶外表面温度分布及纵向温度梯度分布。研究结果表明,反射环可改善温度场分布,降低单晶硅外表面轴向温度梯度,使晶体径向温度趋于一致,提高硅单晶径向电阻率均匀性,并有效解决了生长过程中单晶硅易出现裂纹的问题。     

Prediction of flashback limits for laminar premixed hydrogen-air flames using flamelet generated manifolds

Development of models that can help predict flashback limits of premixed flames at an affordable computational cost is essential for the safe and efficient design of combustion chambers. For flames with strong preferential diffusion effects, usually the focus has been on the development of at least a three dimensional flamelet database that can predict the enthalpy and mixture fraction mapped on to the reaction progress variable. However, in this study, we show that a 3D FGM table is sufficient to predict flashback limits for lean laminar methane-air flames but is not sufficient to predict the same for lean hydrogen flames and an over-prediction of 100% could occur in the calculation of the flashback limits. We trace the root cause of this over-prediction to be related to the thickness of the reaction zone in the progress variable for hydrogen flames. This results in the development of a novel correction factor for the progress variable source term using 1D flame simulations where the flame experiences strong enthalpy gradients. In the end, we successfully show for the first time that the flashback limits for hydrogen flames can be predicted accurately using flamelet generated manifolds with a source term corrector function.