Effects of transport and insertion of radio frequency identification (RFID) transponders on resistance and shape of natural and synthetic pebbles: applications for riverine and coastal bedload tracking

RFID transponders, especially low‐frequency Passive Integrated Transponders (PIT tags), are now commonly used for assessing bedload mobility in gravel‐bed rivers. Early studies reported high PIT tag recovery rates in small streams, but recovery rates in larger systems remain low. Explanatory factors for low recovery rates have been identified, but only antenna detection ranges and clustering effects have been precisely characterized. Burial below detection limit and dispersion beyond the study site have been indirectly estimated, and PIT tag destruction is assumed to be negligible. In this study, we quantified the resistance of natural limestone pebbles equipped with PIT tags as related to tag insertion methods and distance travelled in an annular flume. We then compared the performance of these natural pebbles with synthetic pebbles made of polyurethane resin and corundum. Creation of synthetic pebbles makes it possible to test bigger transponders with a greater detection range and no clustering effects, bypassing the existing constraints of RFID tracking. We found that breakage of limestone particles leading to PIT tag destruction is far too rare to explain low recovery rates in situ. Further, breakage is more affected by initial pebble characteristics than by PIT tag insertion method. Synthetic pebbles are more sensitive to attrition, but less likely to break. Natural and synthetic pebbles show slight differences in mobility patterns, transport distances, and abrasion resistances. One of the two synthetic pebbles travelled faster than the other three indicating that mobility is not only related to density but also potentially to shape. To address clustering and detection range issues, we equipped synthetic pebbles with AIT‐tags (Active Integrated Transponders). These were tested for integrity and transponder endurance and show great promise for future applications. Copyright © 2016 John Wiley & Sons, Ltd.     

近场水平地震动选取原则及脉冲型水平地震动弹性谱特性研究

以近40年来世界范围内发生的20次地震总计800条水平地震记录为基础,从加速度反应谱入手,研究震中距、PGV/PGA比值及震级对水平加速度反应谱特性的影响,提出了一种同时考虑震中距、PGV/PGA比值及震级3个指标的近场地震动选取方法。然后对选取的脉冲型水平地震记录作加速度反应谱研究场地类别、震级、PGV/PGA比值等因素对脉冲型水平地震动反应谱特性的影响。研究表明:(1)PGV/PGA>0.2、震中距D<20 km、6.50.2、震中距207.0作为中远场脉冲型地震动的选择原则需要进一步研究。(3)震级M_w>7.0时脉冲型地震动反应谱谱值在中长周期范围内明显增大。(4)PGV/PGA>0.2时脉冲型地震动平均谱谱值在中长周期范围内明显增大。     

通勤距离对职住分离的统计验证

职住分离和通勤距离关系的定量测度,对公共政策、城市规划的制定具有指导作用。长期以来,该领域的计算方法及验证的可靠性、精确性存在多方面的制约,用得最普及的单元平衡法存在单元尺度多大合适、单元边界隔离2个局限性。本研究以上海市为例,以人口普查、经济普查、手机信令数据为基础,多角度开展方法探索。先对中心城区划定职住基本平衡范围,用考虑通勤距离的密度估计函数,按工作地估计职工的居住密度,和从业居民的实际密度相比较,使职住分离和通勤距离对应起来,同时缓解单元尺度问题、消解边界隔离问题。继而使用职住分离零壹指数代替传统职住比,用平均通勤距离验证职住分离,获得了很强的线性相关。尽管统计结果有效,依然会有样本偏离线性回归方程,利用置信区间,筛选出异常点,凭经验解释原因,可从定性角度进一步提高分析结果的可信,还可以探测职住失配的原因。基于上述分析方法,验证了：职大于住的地区,职工通勤距离偏长,居民通勤距离偏短;住大于职的地区,居民通勤距离偏长,职工通勤距离偏短,职住关系越平衡,通勤交通总量越小,越分离,交通总量越大。上述方法以上海为例得到验证,也能适用于其他大城市的中心城区。     

A comparative analysis of accessibility measures by the two-step floating catchment area (2SFCA) method

The recent decade has witnessed a new wave of development in the place-based accessibility theory, revolving around the two-step floating catchment area (2SFCA) method. The 2SFCA method, initially serving to evaluate the spatial inequity of health care services, has been further applied to other urban planning and facility access issues. Among these applications, different distance decay functions have been incorporated in the thread of model development, but their applicability and limitations have not been thoroughly examined. To this end, the paper has employed a place-based accessibility framework to compare the performance of twenty-four 2SFCA models in a comprehensive manner. Two important conclusions are drawn from this analysis: on a small analysis scale (e.g., community level), the catchment size is the most critical model component; on a large analysis scale (e.g., statewide), the distance decay function is of elevated importance. In sum, this comparative analysis provides the theoretical support necessary to the choice of the catchment size and the distance decay function in the 2SFCA method. Justification of model parameters through empirical evidence (e.g., field surveys about local travel activities) and model validation through sensitivity analysis are needed in future 2SFCA applications for various urban planning, service delivery, and spatial equity scenarios.     

广州老年人小病慢病“旁路”就医行为及其影响因素

基于广州13个社区问卷调查数据,运用多元线性回归模型探讨老年人“旁路”就医距离特征及其影响因素,结果发现：1）广州老年人小病及慢性病旁路就医距离以1 km为“就地—旁路”临界点,以5 km为“近旁路—远旁路”临界点,形成核心—边缘旁路就医圈层;2）男性老年人比女性老年人旁路就医距离更远;3）居住社区类型是影响旁路就医距离的关键因素,医疗级配不均对旁路就医距离远近影响较大,也是城乡社区老年人旁路就医距离差异化的重要原因;4）对社区越满意的老年人更倾向选择社区内就地就医。倾向特征、使能资源和医疗需求共同影响老年人旁路就医行为的距离远近,进而影响老年人健康公平结果。     

应用测距三角高程法进行跨河水准测量

为将三角高程法跨河水准测量的技术规范要求对应到工程案例中,有效指导技术人员实际操作,本文通过工程实例,按测距三角高程法跨河水准测量的作业流程、计算公式、各未知数据求值展开,逐层解构分析,细致阐述跨河水准测量中测距三角高程法的要点,实例验证了利用测距三角高程测量实现二等跨河水准测量的可行性。同时对“跨河垂直角观测时视线长”的简易计算公式进行了推导,探讨了计算结果的准确性和有效性,对跨河二等水准测量具有较好的推广价值。     

大规模数据集Spark并行优化谱聚类

针对已有大规模数据集并行谱聚类算法的计算耗时和资源占用巨大等问题,基于当前批处理和图计算兼顾的Spark并行技术,提出了大规模数据集谱聚类的并行优化改进算法,算法通过并行单向迭代避免了相似矩阵计算时的数据重复计算,通过并行位置变换、标量乘法替换及距离缩放优化算法的资源占用,通过近似特征向量替代进一步优化算法的计算量。试验结果验证了算法近特征向量的有效性及在大规模数据集下良好聚类性能和扩展性。     

An Analytical Solution for the Run-Out of Submarine Debris Flows

Submarine debris flows have a significant impact on offshore and coastal facilities. The unique characteristics of submarine debris flows involve large mass movements and long travel distances over very gentle slopes. To improve our insight and knowledge of the basic mechanism behind submarine debris flows, an analytical model was derived for the mobility of submarine debris flows. This model takes into account the mass change of debris flows induced by deposition, stagnation pressure, and the topography of the depositional area. One case study on the Palos Verdes debris flow proves its ability to predict the run-out distance of a submarine debris flow to a reasonable level of accuracy. On the gentle slopes, the submarine debris flow progressively loses mass due to deposition, which in turn influences the flow velocity. In addition, the results show that the slope angle and spreading angle of the debris depositional zone play important roles in the sliding process.     

生物集群相似性系数分析的适用性探讨

相似性系数的选择可能会影响生物集群间的β多样性分析。Bray-Curtis相似性系数是目前使用最广的系数之一,还有一些研究使用了欧氏距离等系数。通过非度量多维标度的结果直观对比了两个相似性系数在处理生物数据时的结果,以便了解两个系数的差异。分析结果表明,Bray-Curtis相似性系数比欧氏距离更适合处理包含很多零值的生物数据。生物数据中的零值与环境数据中的不同,不应该影响集群间相似性的计算。如果遇到完全没有生物的集群,可以选用零调整的Bray-Curtis系数,或者剔除此类集群后再计算Bray-Curtis相似性系数。一些研究忽略了相似性系数的差异,在比较和分析多元分析结果时应该慎重,以免在生态环境评价时被误导。     

北部湾涠洲岛红色赤潮藻的分子鉴定

为了弄清北部湾涠洲岛6株疑似红色赤潮藻（Akashiwo sanguinea）株的种类,作者采用光学显微镜和荧光显微镜对其进行形态学初步鉴定;并对藻株SSU rDNA、LSU rDNA和ITS序列测序,利用最大似然法构建系统发育树。结果表明,北部湾涠洲岛6株藻与红色赤潮藻形态特征基本符合;3种序列系统发育树分析均发现北部湾涠洲岛6株藻与不同海域来源的红色赤潮藻聚在同一大分支上,自展值高达99、100、100;与来自亚洲海域的韩国安山株、新加坡株、中国厦门港株序列差异最小,亲缘关系最近,而与其他地理来源的红色赤潮藻序列差异大,亲缘关系较远。红色赤潮藻SSU、LSU、ITS种内遗传距离分别为0.001~0.008、0.003~0.025和0.045~0.406,明显小于该藻与其他裸甲藻科（Gymnodiniaceae）藻属下的种间遗传距离0.032~0.072、0.165~0.222和0.589~1.559,因此可确定北部湾涠洲岛6株藻均为红色赤潮藻。研究结果将为北部湾海域赤潮生物来源与组成、赤潮的发生与管理提供基础信息。