The need for operational reasoning in data‐driven rating curve prediction of suspended sediment

The use of data‐driven modelling techniques to deliver improved suspended sediment rating curves has received considerable interest in recent years. Studies indicate an increased level of performance over traditional approaches when such techniques are adopted. However, closer scrutiny reveals that, unlike their traditional counterparts, data‐driven solutions commonly include lagged sediment data as model inputs, and this seriously limits their operational application. In this paper, we argue the need for a greater degree of operational reasoning underpinning data‐driven rating curve solutions and demonstrate how incorrect conclusions about the performance of a data‐driven modelling technique can be reached when the model solution is based upon operationally invalid input combinations. We exemplify the problem through the re‐analysis and augmentation of a recent and typical published study, which uses gene expression programming to model the rating curve. We compare and contrast the previously published solutions, whose inputs negate their operational application, with a range of newly developed and directly comparable traditional and data‐driven solutions, which do have operational value. Results clearly demonstrate that the performance benefits of the published gene expression programming solutions are dependent on the inclusion of operationally limiting, lagged data inputs. Indeed, when operationally inapplicable input combinations are discounted from the models and the analysis is repeated, gene expression programming fails to perform as well as many simpler, more standard multiple linear regression, piecewise linear regression and neural network counterparts. The potential for overstatement of the benefits of the data‐driven paradigm in rating curve studies is thus highlighted. Copyright © 2011 John Wiley & Sons, Ltd.     

Vulnerability of ordinary moment resistant concrete frames

The effects of structural modeling (bar slip in lap splice), ground motion selection process (epsilon effect) and size of a structure (number of bays and stories) on the fragility of reinforced concrete ordinary moment resisting frames are investigated. An analytical model is developed to account for bar slip in lap splice, which exhibits good correlation with existing experimental data. Then, incremental dynamic analysis is used to derive the fragility curves for four model structures. The model structures simulate frames with a different number of bays and stories. Finally, the fragility curves are corrected for the epsilon effect. The results show that slip in the lap splice can significantly increase the failure probability, especially for the collapse prevention limit state. At the same time, it is found that spectral shape has a significant impact on the fragility curves. It is also found that accounting for or ignoring bar slip or epsilon effects increases the probability of failure for larger structures. This indicates an unconservative bias in the safety of larger structures.     

元分维曲线滑动窗口尺寸自动判定方法与应用

基于地图目标在空间形态上存在的内部差异性和邻近趋同性,在其分形分析中引入了元分维模型的思想。该模型是对传统分形分析的方法扩展,在其建立过程中滑动窗口决定着空间单元的局部影响范围,因此该窗口尺寸成为元分维模型构建的重要参数之一。在前期基于地图目标元分维模型的研究中,滑动窗口大小主要通过人为判断选取,没有考虑地图目标本身的形态结构特点,缺乏科学的定量化指标判定原则,因此存在随意性和执行效率低等问题。本文以地图线目标的元分维模型,即元分维曲线为主要研究对象,通过对其分维扩展的尺度分析,在倒置的Logistic模型函数拟合的基础上提出了一种自动确定滑动窗口尺寸的定量方法,并将该方法应用到对长江河道形态特征的分析研究中,验证了其可行性和合理性。     

地震滑坡灾害下输电杆塔灾损评估研究

为快速评估地震与滑坡灾害对输电杆塔的损毁作用,辅助风险防控措施制定与应急指挥人员决策,研究输电杆塔在地震与滑坡灾害中的损失概率模型。使用蒙特卡洛方法模拟地震震级与震源点坐标,结合峰值地面加速度与脆弱性曲线构建输电杆塔震损概率模型。基于Newmark理论与材料力学原理,构建地震诱发滑坡概率模型及杆塔滑坡冲击损毁概率模型。对我国西南部某区域输电杆塔进行地震与滑坡灾损分析,得到研究区域内各输电杆塔震损概率及滑坡冲击损毁概率。研究结果表明,输电杆塔损毁概率随震级的增大而增大,震级相同时输电杆塔损毁概率主要取决于震中距。滑坡体高度及杆塔与坡脚距离是影响杆塔损毁概率的主要因素,较高处的滑坡体下落时将重力势能转化为动能,进而冲击作用于杆塔,而较小的杆塔与坡脚距离将导致摩擦损耗较小。对于损毁概率较高的杆塔,应采取避让、迁移等措施,降低滑坡灾害的影响。     

Study of photoelectric observations of the eclipsing binary system FZ-Delphinus

Photoelectric observations in B and V for the FZ Del system are presented and its light curves are analyzed. Absolute parameters are obtained. The system shows a near contact subgaint secondary component with a likely K1 spectral type. The O-C curve is presented and probably a secular orbital period variations is detected on a timescale of about 6.9×10⁶ yrs, suggesting thermal timescale mass transfer. A new light elements for the system have been obtained. The system can be considered as an early stage of conservative case of mass transfer. This revised version was published online in August 2006 with corrections to the Cover Date.     

紧致的Hilbert曲线Gray码索引算法

Hilbert曲线具有良好的聚簇性,使其成为设计全球立体网格多维数据索引的重要工具。但当数据集在不同维度上的分布密度存在较大差异时,常规Hilbert曲线索引会出现大量的冗余。对此,本文基于Gray码推导分析了Hilbert曲线索引的构造特点,进而设计实现了紧致Hilbert曲线索引算法,在保持Hilbert曲线良好聚簇性的同时,避免了数据维度分布差异带来的索引冗余问题。试验结果表明,相比常规Hilbert索引,紧致Hilbert曲线索引计算复杂度相当,在实例数据测试中编码耗时减少约40%,索引存储空间减少约46%,排序速度约为Hilbert排序的4.3倍。     

西南印度洋构造地貌与构造过程

基于高精度地形数据,将西南印度洋中脊（11.88°E—66.75°E）分为6个区域,按不同区域分析洋脊轴部形态及其两侧基底沉降曲线的变化,由此探讨西南印度洋中脊的岩浆活动及其受热点影响的机制。结果显示：① 对于整个西南印度洋中脊,轴部隆起占13.38%,轴部裂谷占82.8%,平坦过渡形占3.82%,其中19°E,36°E,41.2°E,43.7°E,50.4°E和64.5°E等处为较集中的洋脊轴部隆起;② 埃里克辛普森—英多姆转换断层之间的区域（39.4°E—45.77°E）显示出异常浅的轴部裂谷和异常小且南北不对称的基底沉降速率,这表明埃里克辛普森—英多姆转换断层之间的区域是热点对洋中脊影响较为明显的区域,南侧较北侧异常小的基底沉降速率表明热点与洋中脊的相互作用主要表现为热点岩浆从洋中脊南部向上流动到岩石圈底部,然后与岩石圈发生相互作用。     

Temporal variation of codaQ during Hualien earthquake of 1986 in eastern Taiwan

The May 20, 1986, Hualien earthquake sequence occurred on the northeastern coast of Taiwan. TheM=6.1 (GS mb) mainshock was followed by a large number of closely-clustered aftershocks with the largest being anM=5.5 event. One seismic station, TWD of the Taiwan Telemetered Seismographic Network, is located in the surface projection of the source region and provides excellent recordings of the entire earthquake sequence. These recordings, plus events occurring in the same source area preceding the mainshock, offer a unique opportunity to study the spatial and temporal variations of codaQ in a region of active subduction. A simple technique is devised that uses the envelope of the coda waveform to enable a quick determination of the codaQ from drum records. For recordings with a peak power at about 8 Hz, the following findings have been obtained: 1. The ambient codaQ near an active subduction region was as low as 145; 2. There was no significant decrease in codaQ within the period beginning one year and four months prior to the mainshock; 3. There was a significant drop of codaQ immediately after the mainshock; this drop lasted approximately two days before returning to the ambient level; 4. CodaQ values varied with focal depth.     

Removal of Fluoride from Aqueous Solutions by Adsorption Using a Siliceous Mineral of a Kenyan Origin

The problem of high fluoride in water sources in Africa and the rest of the developing world has exacerbated in the latest past due to increasing shortage of water. More people are being exposed to high water fluoride resulting in elevated levels of fluorosis in the societies. Fluoride (F) adsorption from solutions using a siliceous mineral from Kenya (M1) was studied on batch basis and results verified on high fluoride water using fixed‐bed column experiments. About 100% batch F adsorption was achieved at 200 mg/L F concentration, 0.5 g/mL adsorbent dosage, 303–333 K, and pH 3.4 ± 0.2. Based on Giles classifications, F adsorption isotherm was found to be an H3 type isotherm. The equilibrium data was correlated to Freundlich and Langmuir models and the maximum Langmuir adsorption capacity was found to be 12.4 mg/g. Column experiments were conducted for different fluoride concentrations, bed depths, and flow rates. The F breakthrough curves were analyzed using the Thomas model and efficient F adsorption was found to occur at low flow rates and low influent concentrations. The Thomas F adsorption capacity (11.7 mg/g) was consistent with the Langmuir isotherm capacity showing that M1 could be applied as an inexpensive medium for water defluoridation.     

基于向量代数的点与多边形拓扑关系的推理

在分析向量代数的几何意义的基础上,提出了利用向量叉积的几何性质来判断点与多边形的拓扑关系,通过判断点生成一个水平向量,通过该向量和多边形各边的向量叉乘运算,利用k分量的符号来判断两向量的位置关系,并对各种位置关系赋予相应的权重值,最后根据权重值之和的奇偶性来判断点与多边形的位置关系。该算法无需计算出实际的交点,同时,还对某些特殊位置关系作了几何等价处理。从程序运行效果来看,该算法具有稳定性高、运行速度快等优点。