城市绿地空间供需评价与布局优化——以徐州中心城区为例

以徐州市为例,基于0.25 m空间分辨率的Google影像与网络爬虫技术获取空间绿地与居住小区人口;采用两步移动搜索法评价小区尺度的绿地供给情况,结合相关标准分析其空间供需状况;为最大限度减少绿地供给不达标小区数量,用空间启发式算法搜索合适的低效工业地块转换为绿地得到优化的绿地布局。研究发现：徐州中心城区绿地供需存在空间不公平,39%的小区绿地供给小于20.1 m ²的需求标准,供给饱和区主要在云龙湖与泉山森林公园片区,不足区则主要在老城与金山桥片区;绿地空间配置应与人口空间分布保持一致,因此要在高层住宅集聚区配置大中型公园绿地;在空间上选取合适数量与位置的低效工业地块转换为绿地,转换431 hm ²的工业地块可使绿地不达标小区数目减少37个,而得到优化的绿地空间布局。     

GPS数据实时通讯中数据解码问题的算法研究

在GPS测量工作中,经常需将测量数据进行实时的传输和处理。然而,GPS测量数据的实时处理是以其正确解码为前提的。在分析串口通讯中数据传统解码算法的基础上,提出了一种直接基于字节数据的实用算法。通过对Ashtech UZ-12型GPS接收机实时传输数据解码试验,证明此算法是一种简单、高效、易于通过编程实现的GPS数据解码算法。     

基于多平台训练的海洋平台极短期运动预报研究

在风浪流等环境条件的共同作用下,浮式海洋平台会在六自由度方向上进行摇荡运动,进而对海上作业安全构成了严峻的威胁。准确的运动极短期预报,可以作为输入条件,提高运动补偿装置的性能;另一方面也可以提供及时的实时预警信息,指导安全作业。深度学习算法是指模型通过对现有的数据进行学习,在大量的训练后使得其能够提取到数据的特征,进而能够根据输入数据对未来进行预测。通过对若干海洋平台的模型试验数据进行学习,建立了基于长短期记忆神经网络（LSTM）的深度学习模型。模型实现了对未来20~40 s内的垂荡和纵荡运动的精确预报,预报精度总体可达到80%~90%以上,并以此对模型的输入、输出窗口长度以及波浪相位差开展了敏感性研究。通过多平台混合训练得到了输入、输出窗口长度以及波浪相位差三者间的合适比例关系,并以此为基础拓展了预报时间长度,为深度神经网络模型给出了推荐的构型参考。     

Development of Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Drop for the Determination of Trace Lead in Water

A new method for determining lead (Pb) content was developed by dispersive liquid–liquid microextraction based on the solidification of floating organic droplets followed by flame atomic absorption spectrometry. Under optimum conditions, the calibration graph was linear within the Pb content range of 8.43–400 µg L^?1 with a detection limit of 2.53 µg L^?1. The relative standard deviation for 10 replicate measurements of 20 and 400 µg L^?1 of Pb were 3.41 and 2.78%, respectively. The proposed method was assessed through the analysis of certified reference water and recovery experiments.     

Wave-induced drift of small floating objects in regular waves

Water waves induce a slow drift of an object floating on the water surface. In this study, we examined, by a series of laboratory experiments, the drift motion of small rigid floating objects driven by regular waves in deep water. Different shapes of planar objects, including square, circular and elliptical, were investigated for two different submergences, and their drift motions in waves were determined using an infrared motion monitoring system. The corresponding measurements enabled the quantification of the drift characteristics with respect to the wave characteristics and object shapes. Numerical simulations based on an existing theory were presented and comparisons between the experimental data and the predictions by the existing theory were performed.     

Rafting rocks reveal marine biological dispersal: A case study using clasts from beach-cast macroalgal holdfasts

Tracking and quantifying biological dispersal presents a major challenge in marine systems. Most existing methods for measuring dispersal are limited by poor resolution and/or high cost. Here we use geological data to quantify the frequency of long-distance dispersal in detached bull-kelp (Phaeophyceae: Durvillaea) in southern New Zealand. Geological resolution in this region is enhanced by the presence of a number of distinct and readily-identifiable geological terranes. We sampled 13,815 beach-cast bull-kelp plants across 130 km of coastline. Rocks were found attached to 2639 of the rafted plants, and were assigned to specific geological terranes (source regions) to quantify dispersal frequencies and distances. Although the majority of kelp-associated rock specimens were found to be locally-derived, a substantial number (4%) showed clear geological evidence of long-distance dispersal, several having travelled over 200 km from their original source regions. The proportion of local versus foreign clasts varied considerably between regions. While short-range dispersal clearly predominates, long-distance travel of detached bull-kelp plants is shown to be a common and ongoing process that has potential to connect isolated coastal populations. Geological analyses represent a cost-effective and powerful method for assigning large numbers of drifted macroalgae to their original source regions.     

Floating mucus aggregates derived from benthic microorganisms on rocky intertidal reefs: Potential as food sources for benthic animals

Mucus films, flocs or foams consisting of fine sand, algae and detritus frequently occur in the surface waters of rocky intertidal reef flats during incoming tide. These masses are referred to as mucus aggregates. We examined the developmental process of mucus aggregates and their abundance, distribution, migration and trophic composition. The trophic composition of mucus aggregates was then compared to those of sediments to evaluate their potential nutritional value for benthic animals. The organic matter content, chlorophyll a concentration, microalgal density and bacteria-derived fatty acid contents of mucus aggregates were higher than those observed in sediment, suggesting that mucus aggregates contain not only high levels of organic matter but also dense concentrations of microalgae and bacteria; therefore, mucus aggregates may serve as a qualitatively more energetic food source for benthic fauna compared to sediments. Benthic diatoms were the most abundant organisms in mucus aggregates. Large numbers of diatoms were trapped in fine mineral particles and mucilage-like strings, suggesting that a portion of the mucus is secreted by these benthic microalgae.Mucus aggregate accounted for only 0.01-3.9% of the daily feeding requirements of the dominant detritivore, Ophiocoma scolopendrina (Echinodermata: Ophiuroidea) over the entire sampling area. In contrast, for the species population on the back reef, where mucus aggregates ultimately accumulate, mucus aggregates provided from 0.4 to 113.3% of food for this species. These results suggest that mucus aggregate availability varies spatiotemporally and that they do not always provide adequate food sources for O. scolopendrina populations.     

岩溶区漓江河流阶地建筑场地地下水抗浮设防水位的确定

地下抗浮设防水位是勘察报告中的一项重要参数,影响抗浮设防水位的因素较多。该文结合工程实例,通过对河流阶地建筑场地内可能影响抗浮设防水位的因素进行综合分析,得出：抗浮设防水位要综合考虑场地不同的工程水文地质条件、建筑条件和地形地貌条件等因素,采用最不利组合综合确定。     

Nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion

A hybrid analytical and FEM is proposed to investigate the nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion. The tank is composed of a rigid cylindrical wall and a flat bottom, whereas the floating roof is treated as an elastic plate undergoing large deflection. The contained liquid is assumed to be inviscid and incompressible, and the flow is assumed to be irrotational. The method of analysis is based on representation of the liquid motion by superposing the analytical modes that satisfy the Laplace equation and the rigid wall and bottom boundary conditions. The FEM is then applied to solve the remaining kinematic and dynamic boundary conditions at the moving liquid surface coupled with the nonlinear equation of motion of the floating roof. This requires only the discretization of the liquid surface and the floating roof into finite elements, thus leading to a computationally efficient and accurate method compared with full numerical analysis. As numerical examples to illustrate the applicability of the proposed method, two oil storage tanks with single‐deck type floating roofs damaged during the 2003 Tokachioki earthquake are studied. It is shown that the nonlinear oscillation modes with the circumferential wave numbers 0, 2 and 3 caused by the finite liquid surface elevation as well as the membrane action due to large deflection of the deck produce excessively large stresses in the pontoon, which may cause the catastrophic failure of pontoon followed by the submergence of the roof. Copyright © 2012 John Wiley & Sons, Ltd.     

Spatial and Temporal Changes of Floating Population in China Between 1990 and 2000

By studying the county-level census data of 1990 and 2000, we analyzed the spatial and temporal changes in the floating population in China between 1990 and 2000. The results of the analysis revealed the following characteris- tics. First, the spatial distribution of the migrants (referred to as 'floaters' in this paper) became increasingly concentrated in the cities during the 1990s. Second, the number of floaters increased rapidly during this period, and the area in which the floaters settled expanded quickly into four population explosion belts: the coast, the Changjiang River Delta, the Beijing-Guangzhou Railway and national border belts. Third, the number of inter-province floaters increased rapidly and exceeded that of intra-province floaters in the 1990s. In addition, to obtain a quantitative relationship between the number of floaters and 10 socio-economic variables by using statistical methods and also to find the chiefly important pulling factors of the migration destination, the authors selected approximately 100 cities with the largest population of floaters. Consequently, we found that four factors-GDP, passenger trips per 10,000 persons, per capita GDP and foreign direct investment-could provide an explanation for 83.7% of the number of floaters in 2000. The GDP showed the highest correlation with the number of floaters, suggesting that a highly developed economy is the most important factor that attracts floaters. Furthermore, a fairly close relationship between the number of floaters and the GDP was also found in 2000 for all the counties.