A preliminary modeling analysis of water quality in Lake Okeechobee, Florida: Calibration results

To gain understanding of nutrient and phytoplankton dynamics in Lake Okeechobee, Florida, we developed and applied a deterministic, mass balance, water quality model at the whole-lake spatial scale. The model was calibrated to a comprehensive set of field data for 1985–1986, and then used to simulate the period 1973–1992. The model represented the mean behavior of in-lake total phosphorus, dissolved available phosphorus, total nitrogen and chlorophyll a concentrations reasonably well during the calibration period. The model did not represent dissolved available nitrogen concentrations very well, nor did it capture much of the observed temporal variability during the calibration period. The model results identified important information needs to improve our understanding of the nitrogen cycle including, sediment-water nitrogen fluxes, denitrification and nitrogen fixation. Results from the 1973–1992 simulation indicated that model assumptions and/or calibration parameters were not uniformly applicable over this period. Total phosphorus concentration results from this model were compared with results from two site-specific, empirical loading models for the lake. None of these models represented annual average concentrations uniformly well over the entire 20-year period, and none captured much of the observed inter-annual variability. External total phosphorus loadings and lake hydrology are not sufficient to fully describe total phosphorus dynamics in Lake Okeechobee. Other important factors are diffusive sediment-water fluxes, wind-induced sediment resuspension, and the spatial heterogeneity in the lake.     

Driving factors of the flushing time of bays formed where tributaries enter a reservoir

Flushing time is an integrative parameter that can represent water exchange capacity and sensitivity to pollution threats. As bays formed where tributaries enter the Three Gorges Reservoir of China have experienced frequent algal blooms over the past decade, we examine the spatially variable flushing time of a typical tributary bay (Xiangxi Bay) by numerical tracer experiments. First, the tracer concentration reduction could be approximated well by a double exponential decay curve, and the local flushing time of Xiangxi Bay is determined using key flushing coefficients. Second, a sensitivity analysis is performed to examine the influence of upstream inflow, temperature difference, wind, water level of the reservoir, and daily water level fluctuation on the spatial variation in local flushing time. Finally, according to local flushing time values and the sensitivity analysis results, the bay can be generally characterized by three zones: riverine, transitional, and mainstream‐influenced zones. In particular, the local flushing times in the riverine zone are mainly affected by the upstream inflow. The difference in temperature between the reservoir mainstream and Xiangxi Bay is the main forcing in the transitional and mainstream‐influenced zones. This study is the first to investigate different driving factors for flushing time in a typical reservoir tributary bay. The findings provide insights on the transport processes in such water bodies, suggesting the possibility of using the longitudinal zonation of flushing time for reservoir management.     

SHOVELNOSE STURGEON SPAWNING IN RELATION TO VARYING DISCHARGE TREATMENTS IN A MISSOURI RIVER TRIBUTARY

Many lotic fish species use natural patterns of variation in discharge and temperature as spawning cues, and these natural patterns are often altered by river regulation. The effects of spring discharge and water temperature variation on the spawning of shovelnose sturgeon Scaphirhynchus platorynchus have not been well documented. From 2006 through 2009, we had the opportunity to study the effects of experimental discharge levels on shovelnose sturgeon spawning in the lower Marias River, a regulated tributary to the Missouri River in Montana. In 2006, shovelnose sturgeon spawned in the Marias River in conjunction with the ascending, peak (134 m³/s) and descending portions of the spring hydrograph and water temperatures from 16 °C to 19 °C. In 2008, shovelnose sturgeon spawned in conjunction with the peak (118 m³/s) and descending portions of the spring hydrograph and during a prolonged period of increased discharge (28–39 m³/s), coupled with water temperatures from 11 °C to 23 °C in the lower Marias River. No evidence of shovelnose sturgeon spawning was documented in the lower Marias River in 2007 or 2009 when discharge remained low (14 and 20 m³/s) despite water temperatures suitable and optimal (12 °C?24 °C) for shovelnose sturgeon embryo development. A similar relationship between shovelnose sturgeon spawning and discharge was observed in the Teton River. These data suggest that discharge must reach a threshold level (28 m³/s) and should be coupled with water temperatures suitable (12 °C?24 °C) or optimal (16 °C?20 °C) for shovelnose sturgeon embryo development to provide a spawning cue for shovelnose sturgeon in the lower Marias River. Copyright © 2012 John Wiley & Sons, Ltd.     

三峡库区低水位运行期库尾支流筑坝对其水体CO2分压及排放的影响

为探究三峡库区低水位运行期间库尾支流河坝对其上下游水体CO₂分压、水气界面扩散通量的影响,于2019年8月对三峡库区库尾典型筑坝支流御临河进行采样研究。原位测定关键理化环境因子,采用顶空平衡法,结合亨利定律和薄边界层理论计算水体CO₂分压（p_CO2）及水气界面扩散通量（Flux（CO₂））。结果表明,库区低水位运行期御临河水体表层p_CO2为54.55~336.73 Pa,均值为206.68 Pa,Flux（CO₂）为1.65~67.84 mmol/（m²·d）,均值为39.01 mmol/（m²·d）,表现为大气CO₂排放源排放水平显著高于三峡库区中下游支流。御临河受其下游筑坝影响,河坝上游较近河段表现为湖泊型水体（流速v<0.05 m/s）,上游较远河段和下游表现为过渡型水体（v=0.05~0.2 m/s）。湖泊型水体p_CO2和Flux（CO₂）显著低于过渡型水体,且p_CO2随水深增加迅速增大。相关性分析及多元逐步回归分析表明,库区低水位运行期御临河p_CO2及Flux（CO₂）受水温、pH、DO、Chl-a等理化环境指标影响显著,Chl-a是影响p_CO2的最主要因素,p_CO2是影响Flux（CO₂）的最主要因素。     

三峡库区梅溪河河口干支流界面水流特征

通过对三峡库区中部典型支流梅溪河库湾水动力参数及水体温度、浊度数据进行分析,研究水库运行各时期梅溪河河口干支流界面水流特性,探讨其影响因素以及水交换对库湾的影响。结果表明:梅溪河河口双向水流特征明显,在温差异重流、干流惯性作用以及库区水位变动等因素影响下,干支流界面水流强度、进出水体间界面结构及形态在不同运行期有显著差异;由于双向水流结构的存在,尽管梅溪河河口干支流界面净流量较小(多小于100 m~3/s),但是干支流水体的交换量相对显著,介于314.17~535.26 m~3/s之间,可达净流量的4~40倍;在净流量最小的低水位运行期,干流倒灌水体基本能到达支流库湾常年回水区的末端。     

北京电信网155 Mbit/s信号时隙编号统一规则

介绍了北京电信网155Mbit/s信号时隙编号统一问题产生的原因，探讨了北京电信网155Mbit/s信号时隙编号统一原则，并论述了北京电信传输网、交换网155Mbit/s信号时隙编号统一策略。     

补赔奖融合机制下流域干支流治污减排策略演化博弈分析

流域是由干流和多个、多级支流组成的相互影响的复杂系统,为了解决流域水污染和水生态环境问题,需要干流和支流各地区的共同治理。然而,现有的研究大多关注上下游水污染治理机制的研究,对于干流与多个支流间治污协作机制的研究较少,因此水污染协同治理机制很难在全流域实施。论文为系统性解决流域跨界水污染问题,形成覆盖整个流域的水污染治理机制,将上下游跨界水污染治理研究拓展到干流和两个支流,研究干流政府和两支流政府决策行为的变化规律和影响因素。基于演化博弈模型,通过构建三方政府博弈收益矩阵并求解复制动态方程,探讨补偿赔偿奖励融合机制下三方政府策略选择的演化稳定路径,并讨论了博弈均衡点策略演化的稳定条件。基于数值仿真分析了污染转移系数、干流政府对支流政府的奖励以及初始治污意愿等参数对三方策略选择的影响规律。研究结果表明：1）支流政府之间的主要影响因素是污染转移系数和初始治污意愿,某一支流污染转移系数越大,其他支流治理意愿越低,当污染转移系数超过某一临界值时,其他支流会选择不治理的策略,同时支流政府的初始治污意愿越高,其稳定于治理策略的速度越快,污染转移系数的临界值越大;2）干支流政府之间的主要影响因素是干流政府对支流政府的补偿和奖励以及支流政府对干流政府的生态赔偿,干流政府对支流政府额外治污减排的奖励越多,越能激励支流政府治污减排。研究结论可为干流和多个支流间形成生态补偿、赔偿和奖励机制以达到治污减排目标提供参考。     

全数字化PDH复接系统的设计

为了便于ＰＤＨ复接系统的集成和设备的小型化，以及改善系统的性能，本文介绍了复接系统的几个主要部分（定时提取，码速调整，收端支路时钟恢复等）的数字化实现方法，还介绍了采用这些数字化方法的多功能复接专用集成电路－ＭＸＺＷ６８２３１。     

晚清中国在巨文岛事件中的外交斡旋(1885-1886)

朝鲜问题一直是甲午战争前夕东北亚地区国际斗争的焦点之一,在中日双方就中朝宗藩关系体制的存废争执不休的同时,英国和俄国也为争夺对远东的控制而进行了明争暗斗。中国清廷在英俄两国之间展开外交斡旋,中国清廷本着维护中国对朝鲜的宗主权为出发点利用英俄两国的矛盾,使两国的争端得以缓和,最终以俄国允诺不侵占朝鲜领土和英国撤出巨文岛为结束。巨文岛事件的解决是晚清中国政府利用外交斡旋手段处理大国矛盾的比较成功的特例,但也使得清廷滋长了对未来朝鲜问题再度尖锐化的麻痹,盲目自信的态度也为日后甲午战争的外交失败埋下了伏笔。     

80×40 Gbit/s DWDM系统及800 km传输实验

介绍了烽火通信研制的国内首套、具有完全知识产权的80 ×40Gbit/s密集波分复用(DWDM)系统,该系统采用了低成本的非归零(NRZ)码,开发了分布拉曼放大、超强前向纠错(FEC)、子速率复用等多项技术,并在G.652光纤上进行了10×80 km的无电再生中继传输实验.实验结果表明,经过800km传输后,光通道代价＜2dB,连续观察60 h无误码.