Urban waterlogs control in China: more effective strategies and actions are needed

Natural Hazards - Urban flooding and waterlogging is becoming one of the foremost challenges in the process of rapid urbanization expansion in China. With a huge investment, the Chinese government...     

Investigation of three-dimensional active earth pressure and load transfer according to aspect ratio

ABSTRACT

Although there is a noticeable difference between two-dimensional and three-dimensional earth pressures, most researchers have suggested various earth pressure theories under the two-dimensional condition. Only a few studies have been conducted on the three-dimensional load transfer to the adjacent ground, whereas most studies in literature on the three-dimensional active earth pressure have been conducted by focusing on the stability of active wall. For accurate prediction of the three-dimensional active earth pressure, it is required to study not only the three-dimensional earth pressure distribution but also the three-dimensional load transfer to the adjacent ground. In this paper, size and distribution of the three-dimensional active earth pressure as well as the load transfer according to aspect ratio of retaining wall are investigated through a series of model tests. As a results, the three-dimensional active earth pressure distribution showed the highest value at the wall height of 0.5–0.55h when the aspect ratio of equal to 1.2 or higher. The load transfer showed higher values in vertical direction than horizontal direction. The load transfer distribution can be evaluated by applying the size and effect range of the loads transferred to the adjacent soil of the retaining wall.     

LPS-induced NO inhibition and antioxidant activities of ethanol extracts and their solvent partitioned fractions from four brown seaweeds

The nitric oxide inhibitory (NOI) and antioxidant (ABTS and DPPH radical scavenging effects with reducing power) activities of the ethanol (EtOH) extracts and solvent partitioned fractions from Scytosiphon lomentaria, Chorda filum, Agarum cribrosum, and Desmarestia viridis were investigated, and the correlation between biological activity and total phenolic (TP) and phlorotannin (TPT) content was determined by PCA analysis. The yield of EtOH extracts from four brown seaweeds ranged from 2.6 to 6.6% with the highest yield from D. viridis, and the predominant compounds in their solvent partitioned fractions had medium and/or less polarity. The TP and TPT content of the EtOH extracts were in the ranges of 25.0–44.1 mg GAE/g sample and 0.2–4.6 mg PG/g sample, respectively, which were mostly included in the organic solvent partitioned fractions. Strong NOI activity was observed in the EtOH extracts and their solvent partitioned fractions from D. viridis and C. filum. In addition, the EtOH extract and its solvent partitioned fractions of D. viridis exhibited little cytotoxicity to Raw 264.7 cells. The most potent ABTS and DPPH radical scavenging capacity was shown in the EtOH extracts and their solvent partitioned fractions from S. lomentaria and C. filum, and both also exhibited strong reducing ability. In the PCA analysis the content of TPT had a good correlation with DPPH (r = 0.62), ABTS (r = 0.69) and reducing power (r = 0.65), however, an unfair correlation was observed between the contents of TP and TPT and NOI, suggesting that the phlorotannins might be responsible for the DPPH and ABTS radical scavenging activities.     

A simple method of correction for profile-length water-column height variations in high-resolution,shallow-water seismic data

In high-resolution, shallow-water seismic surveys, correction for water-column height variations caused by tides, weather, and currents is an important part of data processing. In this study, we present a very simple method of correction for profile-length (i.e., long-wavelength) water-column height variations for high-resolution seismic data using a reference bathymetric grid. First, the difference between the depth of the seafloor picked from seismic data and the bathymetry from the bathymetric grid is computed at the locations where the shot points of seismic profiles and the bathymetric grid points are collocated or closest. Then, the results are gridded and smoothed to obtain the profile-length water-column height variations for the survey area. Next, the water-column height variations for each seismic profile are extracted from the smoothed grid and converted to two-way traveltimes. The corrections for the remaining mis-ties at the intersections, computed within a circular region around each tie shot point, are added to the corrections for the water-column height variations. The final, mistie corrected water-column height corrections are loaded to the SEGY trace header of seismic data as a total static. We applied this method to the sparker data acquired from the shallow-water area off the western-central part of Korea where the tidal range is over 7 m. The corrections for water-column height variations range from -10 to 4 m with a median value of about -2 m. Large corrections occur locally between and near the islands probably due to the amplification and shortening in tidal wavelength caused by rapid shoaling toward the islands.     

Validation of Sea Level Data in the East Asian Marginal Seas： Comparison between TOPEX／POSEIDON Altimeter and In-Situ Tide Gauges

In an effort to assess the reliability of satellite altimeter systems, the authors conduct a comparative analysis of sea level data that were collected from the TOPEX/POSEIDON (T/P) altimeter and 10 tide gauges (TG) near the satellite passing ground tracks. The analysis is made using datasets collected from marginal sea regions surrounding the Korean Peninsula at T/P cycles of 2 to 230, which correspond to October 1992 to December 1998. Proper treatment of tidal errors is a very critical step in data processing because the study area has very strong tide. When the T/P data are processed, the procedures of Park and Gamberoni (1995) are adapted to reduce errors associated with the tide. When the T/P data are processed in this way, the alias periods of M2, $2, and K1 constituents are found to be 62.1, 58.7, and 173 days repectively. The compatibility of the T/P and TG datasets are examined at various filtering periods.The results indicate that the low-frequency signals of the T/P data can be interpreted more safely with longer filtering periods (such as up to the maximum selected value of 200 days). When RMS errors for the 200-day low-pass filter period are compared with all 10 tidal stations, the values span the range of 2.8 to 6.7 cm. The results of a correlation analysis for this filtering period also show a strong agreement between the T/P and TG datasets across all stations investigated (e.g., p-values consistently less than 0.001). Hence according to the analysis, the conclusion is made that the analysis of surface sea level using satellite altimeter data can be made safely with reasonably extended filtering periods such as 200 days.     

应力控制技术及其应用综述

概述了应力控制技术的基本原理及其在国内外的应用状况，指出了应力控制技术对于解决深井高地应力岩层的开采与支护问题有独特的作用，及它在我国深井矿山开采中的应用前景，并对其力学机理作了初步探讨。     

新疆气候对地表水资源影响的区域差异性初探

利用单相关、典型相关及逐步回归方法, 分析了新疆气候对地表水资源影响的区域差异性, 得到以下几点新认识:(1) 新疆气候对地表水资源时空变化的影响, 以北疆为最大, 东疆最小, 南疆居中。(2) 揭示了北疆、东疆、南疆气候场对其地表水资源场空间分布特征的主要影响形式。(3) 发现在北疆及东疆, 水文年降水是决定其地表水资源场时空分布特征的主导气候因子, 5~9月平均温度是辅助气候因子, 它通过影响蒸发对地表水资源起减少作用, 但在东疆5~9月平均温度对其地表水资源的影响要比北疆大些。南疆5~9月平均温度是决定其地表水资源场时空分布特征的主导气候因子, 高山区前2年的水文年降水为辅助气候因子, 它通过冰川融水的形式对当年的地表水资源起增加作用。     

建筑物对城市通风自净能力影响的数值试验

应用城市气候数值模式，分别计算了三栋6层住宅楼和一栋20层住宅楼两类建筑形式影响下的风场，以及在此风场中街道汽车尾气的浓度分布。计算结果表明在总建筑面积基本相同的情况下，高层建筑周围环境的通风自净能力要优于多层建筑。     

坡度阀值与坡面泥石流--以重庆市北碚区为例

通过对重庆市北碚区的 2 1个坡面泥石流的实地调查表明 ,坡度对坡面泥石流发生具有重要控制性作用。在对坡面泥石流流域大量原始坡度进行统计分析后发现 ,各坡面泥石流的坡度分布具有明显的正态分布特征 ,且平均坡度分布具有显著的规律。根据这一分布规律 ,将本区坡面泥石流发生的坡度阀值确定为三类 :第一类的坡面泥石流植被覆盖率高 ,远离居民区 ,人类影响活动微弱 ,坡度阀值为 32 4° ;第二类坡面泥石流无一例外均位于林地结合部 ,森林覆盖率很低 ,人类活动影响十分剧烈 ,坡度阀值为 2 7 3° ;第三类的两条坡面泥石流相邻 ,均位于观音峡峡谷地带 ,它们的发生完全受地形条件的控制 ,坡度阀值为 36 8°。本文从定量的角度阐述了坡度阀值与坡面泥石流发生的关系 ,为生态脆弱区的划分、工程建设、防灾减灾和政府决策提供服务