Screening of polymers on selected Hawaii soils for erosion reduction and particle settling

In recent years, high‐molecular‐weight anionic polyacrylamides (PAMs) have been tested on a variety of soils, primarily in temperate climates. However, little information is available regarding the effectiveness of PAM for preventing soil loss through runoff in tropical settings. Screening tests were performed using three negatively charged PAMs and one positively charged PAM on five Hawaii soils (two Oxisols, one Vertisol, and two Aridisols) to determine erosion loss, sediment settling, and aggregate stability. A laboratory‐scale rainfall simulator was used to apply erosive rainfall at intensities from 5 to 8·5 cm h^?1 at various PAM doses applied in both dry and solution forms. Soil detachment due to splash and runoff, as well as the runoff and percolate water volumes, were measured for initial and successive storms. The impact of PAM on particle settling and aggregate stability was also evaluated for selected soil‐treatment combinations. Among the PAMs, Superfloc A‐836 was most effective, and significantly reduced runoff and splash sediment loss for the Wahiawa Oxisol and Pakini Andisol at rates varying between 10 and 50 kg ha^?1. Reduced runoff and splash sediment loss were also noted for PAM Aerotil‐D when applied in solution form to the Wahiawa Oxisol. Significant reductions in soil loss were not noted for either the Lualualei Vertisol or the Holomua Oxisol. It is believed that the high montmorillonite content of the Lualualei Vertisol and the low cation‐exchange capacity of the Holomua Oxisol diminished the effectiveness of the various PAMs tested. The polymers were also found to enhance sediment settling of all soils and helped improve their aggregate stability. This screening study shows the potential use of PAM for tropical soils for applications such as infiltration enhancement, runoff reduction, and enhanced sedimentation of detention ponds. Copyright © 2005 John Wiley & Sons, Ltd.     

模拟退火机制下优化离散粒子群的端元提取算法

针对离散粒子群优化(Discrete Particle Swarm Optimization,DPSO)端元提取算法初始种群质量差、收敛性能低且易于陷入局部最优,本文将模拟退火算法引入到DPSO的不同阶段,模拟退火算法能以一定的概率接受和舍弃新状态,使种群内粒子渐趋有序、达到平衡,收敛到全局最优,有效避免了搜索陷入局部最优。因此,该算法不仅保持了DPSO的全局组合优化特点,克服了初始种群质量差、易陷入局部最优等缺点,而且还提高了收敛速度和端元提取精度。     

视景仿真中实体云的建模与渲染技术

在视景仿真中对云的建模和实时渲染是一项十分重要的工作.全面研究了视景仿真中3维实体云的建模与绘制技术,并根据视景仿真对云景仿真的需求,采用分形技术和粒子系统技术实现了一种既能获得良好的视觉效果,又能实时绘制的实体云建模与仿真技术.通过视点相关技术、层次细节技术、动态视点替用等技术大大提高了实体云仿真的实时性,使其在一般的微机平台上可以流畅运行.     

Indoor localization for pedestrians with real-time capability using multi-sensor smartphones

ABSTRACT

The localization of persons or objects usually refers to a position determined in a spatial reference system. Outdoors, this is usually accomplished with Global Navigation Satellite Systems (GNSS). However, the automatic positioning of people in GNSS-free environments, especially inside of buildings (indoors) poses a huge challenge. Indoors, satellite signals are attenuated, shielded or reflected by building components (e.g. walls or ceilings). For selected applications, the automatic indoor positioning is possible based on different technologies (e.g. WiFi, RFID, or UWB). However, a standard solution is still not available. Many indoor positioning systems are only suitable for specific applications or are deployed under certain conditions, e.g. additional infrastructures or sensor technologies. Smartphones, as popular cost-effective multi-sensor systems, is a promising indoor localization platform for the mass-market and is increasingly coming into focus. Today’s devices are equipped with a variety of sensors that can be used for indoor positioning. In this contribution, an approach to smartphone-based pedestrian indoor localization is presented. The novelty of this approach refers to a holistic, real-time pedestrian localization inside of buildings based on multi-sensor smartphones and easy-to-install local positioning systems. For this purpose, the barometric altitude is estimated in order to derive the floor on which the user is located. The 2D position is determined subsequently using the principle of pedestrian dead reckoning based on user's movements extracted from the smartphone sensors. In order to minimize the strong error accumulation in the localization caused by various sensor errors, additional information is integrated into the position estimation. The building model is used to identify permissible (e.g. rooms, passageways) and impermissible (e.g. walls) building areas for the pedestrian. Several technologies contributing to higher precision and robustness are also included. For the fusion of different linear and non-linear data, an advanced algorithm based on the Sequential Monte Carlo method is presented.     

改进分数阶达尔文粒子群的多Renyi熵图像分割算法

针对智能优化图像分割算法易陷入局部最优、分割精度不高等问题,本文融合改进的分数阶达尔文粒子群算法和二维Renyi熵多阈值,提出了一种新的多阈值遥感图像分割算法。算法利用粒子自身进化信息来定义进化因子,结合进化因子并利用高斯图函数调整分数阶次a系数以实现精确计算和快速收敛;根据局部最优概率因子对局部最优位置进行Levy飞行随机扰动以提高算法跳出局部最优的能力;同时将二维Renyi熵单阈值扩展到多阈值分割上,并结合改进的分数阶达尔文粒子群算法,将二维Renyi熵多阈值应用于遥感图像分割中仿真结果表明,与其他2种智能优化分割算法相比,本文分割算法在细节处理和分割精度上均有明显优势,在PRI上至少提升7.27%、VOI至少降低6.5%、GCE至少降低10.4%.     

引入退火机制的智能单粒子算法在复杂边坡最危险滑动面搜索中的应用

复杂边坡的安全系数可能存在多个局部极小值点,如何确定边坡的最小安全系数是复杂边坡稳定性分析中的一个关键问题.本文结合简化Bishop法,采用一种新的启发式全局优化算法--智能单粒子算法(ISP0)来搜索复杂边坡的最危险滑动面.为帮助该算法快速跳出局部极值点,本文将模拟退火(SA)机制引入到智能单粒子算法中,结合了两种算...     

Variation in the sediment deposition behind check‐dams under different soil erosion conditions on the Loess Plateau,China

To maintain a reasonable sediment regulation system in the middle reaches of the Yellow River, it is critical to determine the variation in sediment deposition behind check‐dams for different soil erosion conditions. Sediment samples were collected by using a drilling machine in the Fangta watershed of the loess hilly–gully region and the Manhonggou watershed of the weathered sandstone hilly–gully (pisha) region. On the basis of the check‐dam capacity curves, the soil bulk densities and the couplet thickness in these two small watersheds, the sediment yields were deduced at the watershed scale. The annual average sediment deposition rate in the Manhonggou watershed (702.0 mm/(km²·a)) from 1976 to 2009 was much higher than that in the Fangta watershed (171.6 mm/(km²·a)) from 1975 to 2013. The soil particle size distributions in these two small watersheds were generally centred on the silt and sand fractions, which were 42.4% and 50.7% in the Fangta watershed and 60.6% and 32.9% in the Manhonggou watershed, respectively. The annual sediment deposition yield exhibited a decreasing trend; the transition years were 1991 in the Fangta watershed and 1996 in the Manhonggou watershed (P < 0.05). In contrast, the annual average sediment deposition yield was much higher in the Manhonggou watershed (14011.1 t/(km²·a)) than in the Fangta watershed (3149.6 t/(km²·a)). In addition, the rainfalls that induced sediment deposition at the check‐dams were greater than 30 mm in the Fangta watershed and 20 mm in the Manhonggou watershed. The rainfall was not the main reason for the difference in the sediment yield between the two small watersheds. The conversion of farmland to forestland or grassland was the main reason for the decrease in the soil erosion in the Fangta watershed, while the weathered sandstone and bare land were the main factors driving the high sediment yield in the Manhonggou watershed. Knowledge of the sediment deposition process of check‐dams and the variation in the catchment sediment yield under different soil erosion conditions can serve as a basis for the implementation of improved soil erosion and sediment control strategies, particularly in semi‐arid hilly–gully regions. Copyright © 2018 John Wiley & Sons, Ltd.     

苏州澄湖湖底硬粘土粒度特征及成因初探

澄湖是太湖平原上的一个浅水湖泊,湖底十分平坦,主要由硬粘土组成,同时发育有NW—SE横穿澄湖的古河道和泥沼洼地。在接近湖泊中心部位的古河道中打钻获得了4 m长的岩芯,并进行了详细的粒度分析。结果表明,该岩芯下部的硬粘土主要由细粉砂、中粉砂和粘土组成,分别占26.7%~38.1%,26.9%~34.3%和19.7%~26.2%,可命名为粘土质粉砂;众数粒径为10~50 μm,平均占57.9%;平均粒径为6.3~6.9。将其与上部的湖泊沉积、镇江下蜀黄土和中国北方各地黄土的粒度比较表明,苏州澄湖湖底的硬粘土原本也是风尘沉积。     

海底爆破振动强度衰减规律及中华白海豚保护措施研究

为确保海底爆破施工所诱发的振动不对中华白海豚造成危害,基于量纲分析法对萨道夫斯基经验公式进行修正,建立适用于预测海底爆破质点峰值振动速度的相似准数方程。在此基础上根据现场试验数据进行非线性回归运算,得到相关参数并分析了海底爆破振动强度衰减规律。分析表明:海底爆破质点峰值振速主要由单段装药量、监测点距爆心水平距离、覆盖层厚度及海水深度等因素决定。将参数值分别代入萨氏公式及新建公式计算预测值并进行误差估计,其平均误差分别为20.3%和10.0%,新建公式提高了对质点振速预测的准确性。利用新建公式及超压内安全振速估算保护中华白海豚的安全距离并提出相应的保护措施,为同类工程施工提供理论参考依据。     

鄱阳湖沙地沉积物粒度特征及其影响因素北大核心CSCD

鄱阳湖沙地是亚热带湿润区典型风沙化土地,土地沙化问题严峻。鄱阳湖沙地研究多在小范围开展,研究意义有限,应在多处进行沙地粒度比对研究。选取庐山市、都昌县、永修县和南昌市新建区等沙地样品57个,分析其粒度特征。结果表明:(1)鄱阳湖沙地主要由中沙、细沙和粗沙组成,三者总含量超90%;Mz均值为1.79Φ,分选较差,呈正偏和尖锐分布;(2)鄱阳湖沙地不同土地类型沉积物表层(0-5 cm)与20-40 cm深度粒度特征存在一定差异,固定沙丘、半固定沙丘、流动沙丘和河滩表层比20-40 cm深度粒径大,但流动沙丘和湿地草滩表层分选优于20-40 cm深度;湿地草滩和河滩优势粒级含量和粒度参数有别于沙丘;(3)鄱阳湖沙地固定沙丘、半固定沙丘和流动沙丘为风成沉积;河滩以河流作用为主,风蚀为辅;湿地草滩是在风力和水动力共同作用下形成的。鄱阳湖沙地沿盛行风向从南到北S、SK、K依次减小,风沙运动多以两跳一悬式为主,以就地起沙为主,河滩湖滩作为补充。