Groundwater-surface water interactions and agricultural nutrient transport in a Great Lakes clay plain system

Nutrient export from agricultural land to surface waters is a significant environmental concern within the Great Lakes Basin (GLB). A field-based watershed-scale study was completed to investigate spatial and temporal variations of phosphorus and nitrate to assess nutrient transport pathways and groundwater-surface water interactions in an agriculturally dominated clay plain system. This was conducted in the 127 km² Upper Parkhill Watershed, near Lake Huron in southwestern Ontario, Canada. Data collection occurred from June 2018 to May 2019 via continuous sensor deployment and discrete sampling of stream water, groundwater, hyporheic zone, and tile drainage water. Samples were analyzed for various nutrient species (total, total dissolved, soluble reactive, and particulate phosphorus, and nitrate-N) to examine the hydrological dynamics of principal transport pathways of agriculturally-derived nutrients. Total phosphorus and nitrate concentrations in stream water ranged from 0.007 to 0.324 mg/L and 0.32 to 13.13 mg NO₃^?-N/L, respectively. Tile drainage water total phosphorous concentrations varied from 0.006 to 0.066 mg/L. Groundwater total dissolved phosphorus concentrations ranged from <0.003 to 0.085 mg/L. Transport of phosphorus through tile drainage was observed to be greater than through groundwater over the study period. No distinct relationship was observed between nutrient concentrations in the hyporheic zone and the vertical hydraulic gradient within this zone in the studied stream reach. Preliminary correlations were discerned between water quality observations and recognized land management practices. Given the elevated stream nutrient concentrations, these results are consequential for the continual improvement of strategies and programs devised to conserve water resources within the GLB.     

长江上游高洪水期泥沙输移特性

长江上游高洪水期(汛期)泥沙输移特性是决定三峡库区泥沙淤积的关键因素,直接关乎三峡水库使用寿命及综合效益的发挥。借助干、支流长系列水沙资料,分析了长江三峡水库入库寸滩站高洪水期泥沙输移特性,结果表明:近40 a来,寸滩站场次洪水中7 d洪量未出现趋势性变化,而7 d沙量显著减少,高洪水期输沙经历了“涨水输沙占优—涨、落水基本持平—落水输沙占优”的变化过程。2013年以前,寸滩站高洪水期径流及泥沙均主要来自于金沙江,而向家坝、溪洛渡水电站陆续投运后,2013—2019年寸滩站洪水场次(洪峰流量30 000 m³/s以上)共计14场。从径流来源来看,仅4场主要来自于金沙江,其余9场主要来自于嘉陵江,1场来自岷江;从泥沙来源来看,9场主要来自于嘉陵江,其余5场分别来自于沱江、岷江、横江,金沙江已不是寸滩站高洪水期过程中泥沙的主要来源区。研究成果可为三峡水库沙峰排沙调度、库尾减淤调度提供理论支撑,为长江泥沙治理提供保障。     

老挝南欧江梯级水电站二期厂房生活给水系统设计

水电站厂房生活给水系统应能够可靠、高效地为厂内工作人员提供满足要求的生活用水。老挝南欧江梯级水电站二期厂区附近均无可用的市政供水管,无法依靠市政供水系统为厂区提供生活用水。以老挝南欧江梯级水电站二期厂房生活给水系统设计为例,提出了针对远离城镇,无市政供水情况下,水电站厂房生活给水系统的设计思路、设计方案、设计的要点及难点。     

Transport properties of critical dilute solutions

On the basis of the isomorphism of critical phenomena, the behavior of transport properties of binary mixtures in the vicinity of the vapor-liquid critical line is considered. In particular, the renormalization of the singularity of the thermal conductivity in dilute critical solutions has been analyzed in detail. It is shown that the behavior of the thermal conductivity is determined by the critical background, i.e., the fluctuation-induced regular part, which diverges at the critical point of a solvent.     

一种高效的同尺寸长方体的装箱算法

针对应用广泛的同尺寸长方体货品的装箱问题,本文运用分层装载方案,根据货品的长宽高采用三种不同的层高,利用动态规划算法分别计算三种层的最大装载量,再通过背包算法对层进行组合,得出装箱的最优方案。该算法复杂度低,装载方案简单。     

浅谈GPS导航系统在油田运输管理中的应用

我油田地处华北东部,随着油田不断发展,对外承包业务愈来愈多。道路营运车辆也日益增多,营运范围也逐渐扩大,给道路运输经营管理与车辆合理调度工作提出了新的要求,而全球卫星定位系统的发展为道路运输管理的有效指挥、协调控制和管理提供了技术支持。本文结合GPS系统的原理,探讨GPS系统在油田运输管理中的应用。     

Directions for improving manual fire suppression using a physically based computer simulation

The Swedish Fire Research Board and the U.S. Federal Emergency Management Agency are sponsoring a project to further the understanding of the basic mechanisms involved, as well as to support the development of standards for and to seek ways of improving the performance of portable fire suppression systems used by fire departments.This paper describes a physically based computer model developed to simulate one aspect of the problem: the manual suppression of postflashover fires. This includes: (1) an overview of the physical basis behind the model; (2) a comparison of model predictions with available experimental data, and (3) an analysis of fire suppression effectiveness using the model.The analysis concludes that, when direct access and extinguishment of the burning fuel is not possible, improved fire control occurs with water sprays having a Rosin-Rammler distribution of droplet sizes with volume-median-drop diameters in the 0.15 to 0.35 mm range. This agrees with available experimental data. It is also shown that fire fighting venting and standoff distance requirements may lead to more severe fires requiring more water for control; although venting and water spray induced air/gas flow also serve to channel hot steam and gases away from the fire fighter adding to his safety. The analysis also shows that allowing higher gas and surface temperatures at fire control through improved fire fighter protective clothing and equipment design reduces water flow rate requirements. Additional experimental work is recommended before all these conclusions are considered definitive. Reference: L. M. Pietrzak and G. A. Johanson, Directions for Improving Manual Fire Suppression Using a Physically Based Computer Simulation,Fire Technology, Vol. 22, No. 3, August, 1986, p. 184.     

X-ray spectroscopy and local structures in glasses

X-ray spectroscopy which is a combination of two techniques, namely x-ray absorption near edge structure (xanes) and extended x-ray absorption fine structure (EXAFS) analyses, is a unique technique for the study of local structures in glasses. Availability of synchrotron radiation sources has made the technique quite attractive and useful because the photon flux from synchrotrons is very intense and polarized. In this article, a brief summary ofxanes andEXAFS techniques is given along with a few applications to the study of local structures in glasses. Communication No. 323 from Solid State and Structural Chemistry Unit.     

Photovoltaic effect and carrier transport mechanisms in Hg1-Mnxtdiodes

Hg_1-xMn_xTe semiconducting semimagnetic alloy has been examined in the context of its possible applications in infrared detectors. For analysis of detector properties the intrinsic carrier concentration has been calculated as a function of temperature and crystal composition. The starting material was In-doped Hg_1-xMn_xTe grown by the modified Bridgman method. The as-grown crystals with manganese content of 12-19% were p-type with carrier concentration and mobility of 100 cm²/ Vs at 77 K. An-type layer was formed on the surface by the annealing process in saturated Hg-vapour at 270-320° for 2 hrs. Capacitance-voltage curves have C^-3 dependence on applied voltage indicating that the junction is linearly graded. From standard electrical measurements and spectral characteristics the main detector parameters were determined and compared to those of Hg_1-xCd_xTe devices. The influence of material properties on detector parameters was analyzed. In order to estimate the carrier transport mechanisms, differential resistivities and current-voltage curves were measured over a wide range of temperaturesi.e. 25 to 300 K. From the temperature dependence of the R₀A product, it was established that at high temperatures (150-300 K) the carrier transport is dominated by a recombination-generation mechanism. In low temperature region the excess current at forward bias is probably attributed to carrier tunneling via energy states distributed randomly within the forbidden gap. At reverse bias the leakage surface or volume currents dominate in the carrier transport.