利用分层聚合进行高分辨率遥感影像多尺度分割

针对高分辨率遥感影像的特点,提出了一种基于分层聚合的多尺度分割算法。该算法首先对遥感影像进行分水岭变换,然后对初始分割区域构建底层加权无向图,利用代数多重网格解法(AMG)在尺度空间求解最优的图割测度,整个分割过程自动得到了多尺度的分割结果。实验表明,该方法能够得到满意的分割结果,并具有较高的自动化程度。     

灰色聚类分析在地质灾害综合区划中的应用

地质灾害作为一种主要的自然灾害,其综合区划研究成为当前学术界重要的前沿课题。利用灰色聚类分析的相关理论,在确立评价指标体系原则及要求的基础上,建立基于区域多源信息融合的地质灾害综合评价指标体系和评价模型,对陕西铜川地区的区域灾害程度进行了定量评价并得到地质灾害的聚类区划图谱。该地区可划分为极重灾、重灾和中灾3大片区,所得结果与区域实际灾情基本吻合。研究表明,灰色聚类分析的数学模型可以实现区域地质灾害的定量区划研究。     

水化学性质对蒙脱石悬浮液膨胀性的影响

实验研究了NaOH、HCl、NaCl和CaCl2等电解质加入量对蒙脱石悬浮液膨胀性的影响,并通过离子色谱、体视显微镜和激光粒度分析技术,研究了蒙脱石粒度变化与体积膨胀之间的关系。实验结果表明,NaOH、HCl对蒙脱石悬浮液膨胀性影响不明显,而NaCl和CaCl2对蒙脱石悬浮液的膨胀有明显的抑制作用;而且CaCl2对蒙脱石膨胀的抑制作用明显强于NaCl,CaCl2浓度比NaCl少了1个数量级时即可达到相同的膨胀抑制效果。离子色谱分析显示,CaCl2溶液与蒙脱石混合后,悬浮液上清液中的Ca2+浓度减少,而Na+浓度增加,分析存在离子交换过程。经激光粒度分析仪和体视显微镜观察,电解质的加入使颗粒之间产生了团聚作用,改变了颗粒的粒径,从而在宏观上表现为蒙脱石悬浮液体积的减少。     

地球剖分网格的地形量化模型

针对目前地形量化方法中,量化承载网格层级受限,且量化数据组织管理复杂的问题,提出了一种基于地球剖分网格的四边形网格的地形量化模型。该模型以GeoSOT地球剖分网格为支撑,通过GeoSOT网格编码实现了多层地形量化数据的关联、检索,为矢量数据和规则格网数据的量化处理、组织与存储以及量化数据聚合问题提供了方法。     

共沸蒸馏法制备电气石超细粉末

分别以水和正丁醇为研磨介质，得到电气石超细粉末的液相悬浮体，利用水和正丁醇可以形成共沸物的特点，分别采用直接加热和共沸蒸馏法脱分散介质干燥悬浮体制备电气石超细粉末。透射电镜分析结果表明，直接加热脱去水或正丁醇会使电气石超细颗粒发生硬团聚，而共沸蒸馏法则可有效防止硬团聚的产生；拉曼光谱结果表明，共沸蒸馏法制备的电气石粉末表面存在O—H和C—H键，说明正丁醇在颗粒表面为化学吸附，而直接干燥法得到的电气石粉末表面则没有；X射线粉晶衍射结果表明，研磨过程降低了粉末衍射峰的强度，但直接加热干燥和共沸蒸馏干燥均未破坏电气石的晶格结构。正丁醇中的丁氧基在共沸蒸馏过程中在电气石颗粒表面可取代羟基，产生化学吸附，能有效防止液桥的产生，阻止干燥过程中超细粉末的硬团聚。     

冠瘤海鞘同种群聚的化学诱因初步研究

研究了不同浓度的冠瘤海鞘成体被囊萃取物和幼体萃取物及不同的幼体密度对冠瘤海鞘(Styela canopus)幼体附着和变态的影响.结果表明,冠瘤海鞘被囊萃取物和幼体萃取物在5%和10%的浓度下均促进冠瘤海鞘幼体的附着和变态,但被囊萃取物的诱导效果明显强于幼体萃取物;幼体密度高于25只/cm3时,促进冠瘤海鞘幼体的附着和变态;幼体密度低于10只/cm3时,幼体的附着和变态不受密度影响.这些结果提示海区中冠瘤海鞘的同种群聚可能与其被囊或幼体内含诱导幼体附着和变态的化学因子有关.     

Effect of soil properties on erosion by wash and splash

This paper describes laboratory testing of 148 samples collected from Southern Alberta for erosion by wash and splash. Rainfall intensity was held constant during these tests. Soil aggregation was the most significant variable explaining soil loss. The significance of other soil properties, such as organic carbon and clay content is variable, depending on the interrelationships among aggregate stability, organic content, and clay content of particular soils. Variations in erodibility of the major soils examined are explained by the resistance of aggregates to compaction and dispersion. Splash detachment and wash transport are the dominant erosion mechanisms in inter-rill areas.     

Update of a Footprint-Based Approach for the Characterisation of Complex Measurement Sites

Horizontal heterogeneity can significantly affect the flux data quality at monitoring sites in complex terrain. In heterogeneous conditions, the adoption of the eddy-covariance technique is contraindicated by the lack of horizontal homogeneity and presence of advective conditions. In addition, uncertainty concerning the sources or sinks influencing a measurement compromises the data interpretation. The consideration of the spatial context of a measurement, defined by a footprint analysis, can therefore provide an important tool for data quality assessment. This study presents an update of an existing footprint-based quality evaluation concept for flux measurement sites in complex terrain. The most significant modifications in the present version are the use of a forward Lagrangian stochastic trajectory model for the determination of the spatial context of the measurements, and the determination of effective roughness lengths with a flux aggregation model in a pre-processing step. Detailed terrain data gathered by remote sensing methods are included. This approach determines spatial structures in the quality of flux data for varying meteorological conditions. The results help to identify terrain influences affecting the quality of flux data, such as dominating obstacles upwind of the site, or slopes biasing the wind field, so that the most suitable footprint regions for the collection of high-quality datasets can be identified. Additionally, the approach can be used to evaluate the performance of a coordinate rotation procedure, and to check to what extent the measured fluxes are representative for a target land-use type.     

The formation of high-grade ignimbrites, I: Experiments on high- and low-concentration transport systems containing sticky particles

 High-grade ignimbrites are thought to be deposited by pyroclastic flows at temperatures exceeding minimum welding temperature or even solidus temperature. Corresponding pyroclastic-flow particles range from plastic to partially liquid and are able to aggregate or coalesce. This contrasts with particles in pyroclastic flows producing unwelded ignimbrite, which are capable of elastic grain interactions. The low aspect ratio and great areal extent of high-grade ignimbrites requires transport in a particulate state either by (a) high-concentration mass flow facilitated by fluidizing gas reducing internal friction, or by (b) expanded turbulent flow of low but downward increasing concentration. This paper presents experiments designed to investigate the effects of plastic to liquid particles on these two contrasting transport mechanisms. Gas fluidization experiments using polyethyleneglycole (PEG) powders heated above minimum sintering (T_ms) and melting (T_m) temperatures cover a wide range of fluidization velocities (U_mf>U_a>0.6·U_t) but are always in the bubbly fluidization regime similar to fluidized ignimbrite ash, where particle volume concentration outside the bubbles is high (≈10^–1). When the powders reach a critical temperature T_m≥T≥T_ms, defluidization by catastrophic particle aggregation immediately commences in both stationary and laterally moving fluidized beds as well as in experiments using mixtures of high- and low-T_m (≥30 wt.%) PEG powders, when T≥T_ms of the lower-T_m powder. This indicates that extended particulate transport at T≥T_ms is not possible at such high particle concentrations. In the turbulent flow experiments, liquid sprays of molten PEG or water, vertically injected into a high-Re (>10⁴) horizontal air flow, form a low-concentration (10^–5 to 10^–4) turbulent suspension current. Proximal formation of partially coalesced aggregates, which settle faster than individual particles, causes the measured downstream decay of sedimentation rate to be steeper than predicted by theory of single solid-particle sedimentation from turbulent suspensions. As particles become finer downstream and coalescence efficiency decreases in response to cooling, more distally formed aggregates become too small and rare to modify sedimentation-rate decay from that of suspension flows containing solid particles. The key difference between the two transport systems is particle concentration, C. Since particle collision rate R_coll∝C², collision rates in fluidized beds are so high that all particles immediately aggregate when coalescence efficiency (1≥E_coal≥0) is larger than 10^-3. Low-concentration suspensions, on the other hand, require much higher values of E_coal for significant aggregation to occur. Dilute pyroclastic flows will have higher particle volume fractions (≈10^–3) than the experimental currents, but then viscous pyroclasts should have lower coalescence efficiencies than PEG droplets. Experimental results thus support an expanded turbulent transport mechanism of pyroclastic flows generating extensive high-grade ignimbrite sheets. Received: 28 August 1996 / Accepted: 3 December 1997     

“多元聚合分类”在预报上的初步应用

“多元聚合分类”是作者提出的旨在解决‘“相对最优分类”的一种可行的客观分类方案[1]。作者通过对南昌1990－1994年6月份资料的分析，说明该分类方法应用于预报有较好的效果。