Water quality data for Fall Creek,New York,USA: 1972–1995

The 33 086 ha mixed land use Fall Creek watershed in upstate New York is part of the Great Lakes drainage system. Results from more than 3500 water samples are available in a data set that compiles flow data and measurements of various water quality analytes collected between 1972 and 1995 in all seasons and under all flow regimes in Fall Creek and its tributaries. Data is freely accessible at https://ecommons.cornell.edu/handle/1813/8148 and includes measurements of suspended solids, pH, alkalinity, calcium, magnesium, potassium, sodium, chloride, nitrate nitrogen (NO3-N), sulphate sulphur (SO4-S), phosphorus (P) fractions molybdate reactive P (MRP) and total dissolved P (TDP), percent P in sediment, and ammonium nitrogen (NH4-N). Methods, sub-watershed areas, and coordinates for sampling sites are also included. The work represented in this data set has made important scientific contributions to understanding of hydrological and biogeochemical processes that influence loading in mixed use watersheds and that have an impact on algal productivity in receiving water bodies. In addition, the work has been foundational for important regulatory and management decisions in the region.     

SETTLING PROPERTIES OF COHESIVE AND NON-COHESIVE PARTICULATE MIXTURES IN WATER

1. INTRODUCTIONAs a wide range of size distirbution including usually a certain POrtion of cohesive material is thecommon feature of the sediment constituting hyperconcentrated flows. it is desirable to study the settling properties of mixtures of cohesive and non--cohesjve sediment particles at high concentrations.Past studies on the settling of discrete particles in a suspension of fine cohesjve sediment is scarcein the literature. The Sediment Research Laboratory of Tsinghua Universi…     

格运算的扩张定理与落影函数定理

讨论了格上可测结构的封闭性以及此结构上落影函数的有关问题。指出并证明了逐次扩张与同时扩张的充要条件 ,以及落影函数与模糊集的关系     

霰粒子下落速度对云系及降水发展影响的数值研究

云和降水的形成是动力过程与微物理过程相瓦作用的产物,云数值模式中的微物理过程参数化方案对云和降水发展过程有直接影响.在云数值模式中,粒子群体的下落速度都足用质量加权下落末速度公式来表达,而且不同的模式采用的公式存在差异,质量加权下落末速度中参数取值不同,引起的粒子下落末速度不同.为了了解粒子下落末速度变化对云系和降水发展的影响,对2004年8月12日一次冷锋降水过程,利用中尺度ARPS模式做模拟研究.在分析降水机制的基础上,对霰这一下落末速度较大的降水粒子,做下落末速度(Vg)的敏感性试验,从动力、热力、微物理的角度,通过数值模拟对比分析了霰下落末速度减小对降水分布和强度、云系的移动、云系的宏观热力和动力场的影响,并给出了影响的途径和机理.结果表明:Vg变化对云的厚度和含水量有影响,下落末速度减小对冰晶、雪、霰的含水量垂直分布及分布随时间变化影响较大,其中,霰的含水量显著减少,雪的含水量增加,并调整了云中水质粒的空间分布;Vg减小对地面累积总降水量的分布影响较小,但对降水强度的分布影响较大.Vg减小时,降水强度减小,降水时间延迟,因此,霰下落末速度变化将调整底层降水分布;对于云系的移动情况基本上没有影响,但对云中水质粒的空间分布有影响;霰下落末速度变化影响云中霰的融化和撞冻增长从而影响热力场.末速度减小时,霰和雪的融化罱明显减小,导致非绝热冷却率的减小,引起下沉气流的减小.     

EXPERIMENTAL STUDY ON FALL VELOCITY OF NON-UNIFORM SEDIMENT IN FLOWING WATER

I INTRODUCTIONThe settlement of particles in fluid has been studied in many fields such as hydraulics, metallurgy andchemistry since the middle of 19 century because of its great importance. Although the settlement ofsingle particle and group settling velocity of uniform particles in still water are relatively well-studied, yetthe settlement of non-uniform particles in flowing water lacks understanding. For instance, Cunningham(1910), Richardson (1954) and Batchelor (1972), have obtained…     

多波束测量系统在长江潜坝工程中的应用

通过叙述多波束测量系统在长江水下工程中的应用实践和体会，说明多波束测量系统和单波束等常规测量仪器相比，具有测深点多、测量迅速快捷、全覆盖等优点。     

黄河壶口瀑布国家地质公园开发建设构想

地质公园是地质遗迹景观和生态环境的重点保护区,是地质科学研究与普及的基地。黄河壶口瀑布的形成经历了一个复杂而漫长的演化过程。显露在河床及河谷两岸的地质遗迹,揭示着黄河壶口瀑布演化进程,对研究黄河发育史、晋陕峡谷的形成、瀑布成因、演化等问题,具有重要的科学理论价值。因此对黄河壶口瀑布国家地质公园的地质旅游资源进行了科学的综合评价,提出了开发构想。使黄河壶口瀑布地质地貌能得以科学的保护与合理的开发利用,不仅要将壶口瀑布建成我国著名的地质公园,更要将其建成我国的瀑布科学研究中心和科普教育基地。     

Hindered settling velocity of cohesive/non-cohesive sediment mixtures

New methods are proposed for predicting the hindered settling conditions encountered by concentrated suspensions containing mixtures of sand particles and mud flocs. These methods, based on two-fraction formulations, are developed by consideration of the settling characteristics of monodisperse and polydisperse solid particle suspensions applied to cohesive/non-cohesive mixtures of mud flocs and sand particles. The behaviour of these predictive methods is evaluated over a wide range of mixture conditions and compared with existing formulations, with their parametric dependence on the relative volumetric concentrations and floc/particle sizes for the mud and sand constituents established. The results indicate that consideration of the full return flow effects generated by both fractions provides the best modelling framework for predicting the hindered settling conditions over a wide range of sand–mud mixtures.     

The Braunschweig meteorite − a recent L6 chondrite fall in Germany

On April 23rd 2013 at 2:07 a.m., a 1.3 kg meteorite fell in the Braunschweig suburb Melverode (52° 13′ 32.19″ N. 10° 31′ 11.60″ E). Its estimated velocity was 250 km/h and it formed an impact pit in the concrete fall site with a diameter of 7 cm and a depth of 3 cm. Radial dust striae are present around the impact pit. As a result of the impact, the meteorite disintegrated into several hundred fragments with masses up to 214 g. The meteorite is a typical L6 chondrite, moderately shocked (S4) – but with a remarkably high porosity (up to 20 vol%). The meteorite was ejected from its parent body as an object with a radius of about 10–15 cm (15–50 kg). The U,Th-He gas retention age of ∼550 Ma overlaps with the main impact event on the L-chondrite parent body ∼470 Ma ago that is recorded by many shocked L chondrites. The preferred cosmic-ray exposure age derived from production of radionuclides and noble gas isotopes is (6.0 ± 1.3) Ma.