不同粒度颗粒在非恒定管流中跟随性试验

管道中固液两相流水击对管道和输送系统可能产生严重的破坏,而固液两相在这种非恒定流中的运动特性是计算最大水击压力变化的重要依据。采用粒子图像测速技术（Particle Image Velocimetry,PIV）,通过试验研究水击发生时,水平圆管中不同平均流速、颗粒粒径条件下,流体介质和粗颗粒在管道断面的速度分布以及粗颗粒跟随性的变化规律。研究结果表明:①在水击发生的不同时刻,圆管流中粗颗粒的流速在管道断面分布呈不规则的抛物线型分布,主要表现为靠近管道壁面底部的颗粒流速略小于靠近管道顶部流速,当颗粒粒径大于1.5 mm,平均流速小于2.5 m/s时,粗颗粒表现出明显的沉降特性;②粗颗粒的跟随性与颗粒受力有密切关系,其中颗粒速度与流体速度的变化量是影响颗粒受力的重要参数;③基于试验数据拟合得到了水击条件下粗颗粒跟随性系数k的经验公式,并分析了颗粒粒径、管道直径、两相流平均流速以及水击发生时间等不同参数对粗颗粒跟随性系数的影响,公式计算值与实测值之间的误差在5%以内。     

附加GIM约束的全球电离层建模

针对目前地基GNSS台站在全球分布不均匀,导致南半球海洋和中高纬地区出现与实际不符的VTEC为负值的问题,利用IGS前1 d的最终GIM作为虚拟观测值对TEC可能为负值的地区进行约束,结合GNSS数据建立全球电离层模型(称为SGG模型),并用2014年200多个IGS台站数据对模型进行验证。结果表明,各台站VTEC的RMS优于3 TECu(赤道异常区域RMS在5~7 TECu)。同时SGG能有效消除南半球海洋(40°~90°S)VTEC为负的情况,且对原有非负VTEC几乎没有影响(其变化小于2 TECu)。SGG的卫星DCB与CODE 相比,RMS和MEAN分别优于0.2 ns和0.04 ns,不同纬度带SGG与CODE的接收机DCB估值变化基本一致,两者之差基本在1 ns以内。     

Antifouling biocides in discarded marine paint particles

Antifouling paint fragments collected from marinas and leisure boat maintenance facilities and in the vicinity of abandoned boats have been chemically characterised. High concentrations of Cu (23-380 mg g⁻¹) and Zn (14-160 mg g⁻¹) in the samples (n = 14) are consistent with the use of these metals in the principal biocidal and non-biocidal pigments in contemporary antifouling formulations. Up to about 2% and 7% of the respective metals were solvent-extractable, suggesting that organo-forms of Cu and Zn (e.g. pyrithiones) were also present. Of the organic biocides, dichlofluanid was present in most samples and at concentrations up to about 20 mg g⁻¹. Chlorothalonil and Irgarol 1051® were only detected in one and four cases, respectively, and Sea Nine 211® was not detected in any sample. Results are discussed in terms of UK legislation regarding biocide usage and the likely effects and fate of discarded paint particles in coastal environments where boats are repaired or moored.     

Barriers to movement: Modelling energetic costs of avoiding marine wind farms amongst breeding seabirds

Proposals for wind farms in areas of known importance for breeding seabirds highlight the need to understand the impacts of these structures. Using an energetic modelling approach, we examine the effects of wind farms as barriers to movement on seabirds of differing morphology. Additional costs, expressed in relation to typical daily energetic expenditures, were highest per unit flight for seabirds with high wing loadings, such as cormorants. Taking species-specific differences into account, costs were relatively higher in terns, due to the high daily frequency of foraging flights. For all species, costs of extra flight to avoid a wind farm appear much less than those imposed by low food abundance or adverse weather, although such costs will be additive to these. We conclude that adopting a species-specific approach is essential when assessing the impacts of wind farms on breeding seabird populations, to fully anticipate the effects of avoidance flights.     

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不同频率循环荷载作用下岩石阻尼比试验与变形破坏机制细观分析

通过对取自海南昌江核电厂一期工程主厂区的黑云母花岗岩,在RMT－150B多功能全自动刚性岩石伺服试验机进行单轴不同频率的循环加卸载试验,研究花岗岩动应变-应力滞回曲线、动弹性模量和阻尼比同循环频率之间的规律,然后对破坏断裂断口进行细观电镜扫描试验,分析了不同频率下花岗岩断口细观形貌与结构特征。结果表明,花岗岩在循环荷载作用下的加卸应力-应变曲线并不重合,而是形成一个封闭的滞回环;当循环频率在0.01～1.0 Hz范围内变化时,随着频率增大,花岗岩滞回环面积、动弹模和阻尼比都增大;通过细观数字图像试验分析发现,循环荷载作用下,随着频率的增大,岩石断口细观裂纹总的数目、面积、分形维数均变大。文中给出不同频率循环荷载作用下岩石破裂的细观损伤力学机制,研究成果对海南昌江核电厂的地震反应分析和场地安全性评价有着重要参考价值。     

橡胶颗粒改良粉煤灰土的动力特性试验研究

对橡胶颗粒改良粉煤灰土的动强度、动模量、黏聚力和内摩擦角进行了动三轴试验研究,并将试验结果与粉煤灰土的动力特性加以对比,分析表明：粉煤灰土及橡胶颗粒改良粉煤灰土在同一围压下动强度均随破坏周数的增加而减小;在同一破坏周数下动强度随着围压的增加而增加;粉煤灰土的黏聚力为203.73 kPa,内摩擦角为11°;橡胶颗粒改良粉煤灰土的黏聚力为227.26 kPa,内摩擦角为17°,橡胶颗粒改良粉煤灰土的黏聚力增大了23.53 kPa,提高了11.55%;粉煤灰土的初始切线模量及平均动模量高于橡胶颗粒改良粉煤灰土的初始切线模量及平均动模量。研究表明,橡胶颗粒改良后的粉煤灰土具有动强度高、黏聚力和内摩擦角大的特点,从而说明橡胶颗粒改良后的粉煤灰土可以作为季冻区路基冷阻层材料     

两种pH水环境干、湿循环作用对泥质砂岩的侵蚀研究

选取三峡库区某边坡的泥质砂岩为研究对象,分别对pH=3和pH=7溶液下干、湿循环作用的泥质砂岩进行电镜扫描试验（SEM）、4种围压下的三轴压缩试验,通过MATLAB软件处理得到不同pH值和干、湿循环次数下SEM图像的骨架面积比和分形维数。研究表明：在相同的干、湿循环次数下,pH=3酸性环境下的分形维数比pH=7的要大;分形维数与吸水率成正比例相关;与骨架面积、凝聚力成反比例相关;泥质砂岩在干、湿循环作用下的临界骨架面积比为0.55左右;提出了泥质砂岩在干、湿循环作用下的侵蚀度概念,计算并拟合了泥质砂岩的侵蚀度随干、湿循环次数变化的关系曲线;推导出凝聚力的损伤变量公式,为研究不同pH水环境对岩石的侵蚀作用提供参考依据。