Accuracy comparison of gridded historical cultivated land data in Jiangsu and Anhui provinces

The spatial resolution of source data, the impact factor selection on the grid model and the size of the grid might be the main limitations of global land datasets applied on a regional scale. Quantitative studies of the impacts of rasterization on data accuracy can help improve data resolution and regional data accuracy. Through a case study of cropland data for Jiangsu and Anhui provinces in China, this research compared data accuracy with different data sources, rasterization methods, and grid sizes. First, we investigated the influence of different data sources on gridded data accuracy. The temporal trends of the History Database of the Global Environment(HYDE), Chinese Historical Cropland Data(CHCD), and Suwan Cropland Data(SWCD) datasets were more similar. However, different spatial resolutions of cropland source data in the CHCD and SWCD datasets revealed an average difference of 16.61% when provincial and county data were downscaled to a 10 × 10 km~2 grid for comparison. Second, the influence of selection of the potential arable land reclamation rate and temperature factors, as well as the different processing methods for water factors, on accuracy of gridded datasets was investigated. Applying the reclamation rate of potential cropland to grid-processing increased the diversity of spatial distribution but resulted in only a slightly greater standard deviation, which increased by 4.05. Temperature factors only produced relative disparities within 10% and absolute disparities within 2 km~2 over more than 90% of grid cells. For the different processing methods for water factors, the HYDE dataset distributed 70% more cropland in grid cells along riverbanks, at the abandoned Yellow River Estuary(located in Binhai County, Yancheng City, Jiangsu Province), and around Hongze Lake, than did the SWCD dataset. Finally, we explored the influence of different grid sizes. Absolute accuracy disparities by unit area for the year 2000 were within 0.1 km~2 at a 1 km~2 grid size, a 25% improvement over the 10 km~2 grid size. Compared to the outcomes of other similar studies, this demonstrates that some model hypotheses and grid-processing methods in international land datasets are truly incongruent with actual land reclamation processes, at least in China. Combining the model-based methods with historical empirical data may be a better way to improve the accuracy of regional scale datasets. Exploring methods for the above aspects improved the accuracy of historical cropland gridded datasets for finer regional scales.     

Barium uptake and adsorption in diatoms

Using trace metal-defined culture conditions, we measured the cellular barium concentration in cultures of the diatom Thalassiosira weissflogii. In cultures with low Fe concentration, at a typical surface seawater Ba concentration of 35 to 40 nmol/L, the cellular Ba was 0.5 μmol/mol P (∼0.04 μg/g dw), much below all previously published values for phytoplankton. When the Fe concentration in the growth medium was increased, the measured “cellular” Ba increased proportionally to the particulate Fe. Under conditions of ferric hydroxide precipitation, similar particulate Ba concentrations were measured in the absence and the presence of cells for a given concentration of particulate Fe. Thus, the bulk of the particulate Ba in such experiments was not truly intracellular but adsorbed on precipitated Fe hydroxides associated with the cell surface. A similar mechanism likely explains the high cellular Ba concentrations reported by previous investigators who utilized relatively high ratios of Fe to EDTA concentrations in the growth medium, resulting in Fe precipitation. On the basis of our results, it seems highly unlikely that intracellular uptake by living phytoplankton explains the vertical flux of Ba in oceanic waters. But the adsorption of Ba on Fe hydroxides that is seen in laboratory experiments must also occur in the oceans and contribute to Ba transport in the upper part of the water column. To be significant, however, such a mechanism would require that the particles that transport Ba out of the surface have a markedly lower Ba/Fe ratio than is measured in the average suspended material.     

气动或液动冲击回转双管正循环钻进工艺及MD-100型锚固工程钻机

针对岩土锚固成孔的难题，提出适合复杂地层链固钻进的新工艺-“双管钻进”工艺，并结合新工艺应用，研制了新型锚固工程钻机，详细介绍了“双管钻进“方法和钻机情况。     

混凝法用于污水处理的实验研究

用混凝法处理洗浴污水，并把处理后的水作为中水回用。影响污水处理效果的因素有混凝剂的种类，混凝剂投加量，水力条件等方面。混凝法处理洗浴废水的最佳条件是：选择比较便宜易得的混凝剂（硫酸铝）采用适宜混凝剂浓度（5％），强化混凝反应强度和时间（强搅拌 较长的反应时间），投加适量的混凝剂（90mg/L)。在最佳试验条件下，可以使处理后的洗浴废水达到中水回用标准和生活杂用水标准。     

海风发展对模式初始场依赖的敏感性试验

本文建立了一个二维的中尺度静力模式，考虑了长短波辐射，湿凝结和土壤等物理因子，用六种典型的初始风场对海风发展作了敏感性试验，发现至少有一部分中尺度系统发生发展的结构与性质可以不依赖于初始场的中尺度特征，而是由局地中尺度强迫作用决定的。但是，中尺度系统的强度与位置仍然受初始场的影响。     

Distinguishing between cellular and Fe-oxide-associated trace elements in phytoplankton

In cultures and in nature, ferric (oxyhydro-)oxides (FeO_x) precipitate and become associated with phytoplankton surfaces. Other trace elements adsorb on FeO_x and it is thus difficult to differentiate between cellular- and oxide-associated concentrations of both iron and these elements. Existing techniques to selectively dissolve the FeO_x associated with phytoplankton surfaces often contaminate the sample or necessitate elaborate pre-cleaning procedures and/or proceed by unknown and thus uncontrolled mechanisms.     

从增长到发展──罗马俱乐部可持续发展思想述评

系统地介绍和评论罗马俱乐部怀疑指数式增长,提出有机增长,进而形成发展概念的思想历程。扼要介绍了罗马俱乐部对可持续发展基础的认识。试图为正确理解可持续发展的内涵提供参考。     

粤东政区演变及其对惠州发展的启示

从历史地理学角度,分阶段地研究了广东东部行政区域及其中心的演变过程,认为演变的总趋势是行政系统与自然系统、交通系统、经济系统的耦合。据此,文中提出了历史结论对惠州规划、发展的四点启示。     

茂名30万吨级单点码头输油海管悬空段人工海草试验研究

2006年11月在茂名海底输油管线悬空路段成功完成人工海草的海底种植安装,2007年4月通过潜水人员水下检测、海流测量等工作,检查了海底人工海草的状态。检测发现,人工海草尚未被破坏时,确实具有明显降低海流流速和促进泥沙淤积的功能。1.0 m高的人工海草实际效果要好于0.5 m高的人工海草;尽管海草草体已吸附了大量悬浮泥沙,多数海草出现倒伏和部分掩埋的现象,但仍然可降低流速15%-20%;人工海草垫直接铺设于海底管线之上,比铺设于海底管线之一侧更有利于管线的保护。