Phosphorus Inputs to Lake Simcoe from 1990 to 2003: Declines in Tributary Loads and Observations on Lake Water Quality

Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue.     

Variations in Spectral Slope in Lake Taihu,a Large Subtropical Shallow Lake in China

Spectral slope (S), describing the exponential decrease of the absorption spectrum over a given wavelength range, is an important parameter in the study of of chromophoric dissolved organic matter (CDOM) dynamics, and also an essential input parameter in remote sensing models. Furthermore, S is often used as a proxy for CDOM composition, including the ratio of fulvic to humic acids and molecular weight. The relative broad range in S values reported in the literature can be explained by the different spectral ranges and fitting methods used. A single exponential model is used to fit the S values for 17 investigations involving 458 samples in Lake Taihu from January to October in 2004. The average S value was 15.18 ± 1.39 μm⁻¹ for the range of 280–500 nm, which fell within the range reported in the literature. The frequency distribution of S value basically obeyed a normal distribution. Significant differences in S values between summer and other seasons showed that phytoplankton degradation was one of the important sources of CDOM in summer, whereas CDOM mainly came from the river input in other seasons. Furthermore, the estimated S value decreased with increasing wavelength range used in regression. The maximum and minimum values derived from the regression were 17.89 ± 1.25 μm⁻¹ and 13.62 ± 2.11 μm⁻¹ for the wavelength ranges of 280–380 nm and 400–500 nm, respectively, a decrease of 23.9%. S values significantly decreased with the increase of CDOM absorption coefficients. CDOM absorption coefficients could be more appropriately estimated from exponential model introducing the variation of S with absorption coefficients, making them useful for a remote sensing bio-optical model of Lake Taihu. DOC-specific absorption coefficient a*(λ) and the parameter M describing molecular size of the humic molecules could also be used as a proxy for the sources and types of CDOM. A general relationship was found between S and a*(λ), and M values. S increased with the decrease of DOC-specific absorption coefficient and the increase of M corresponding to the decrease of molecular weight.     

Most-Favored Treatment Provisions as Nondiscrimination Guarantees

A firm employs suppliers who make specific investments. Because output demand is uncertain and the cost of enumerating contingencies high, the firm retains some unilateral control over the input quantities it purchases. To allay suppliers’ concerns over potential opportunism the firm must commit not to pit them against one another ex post by threatening to buy less from those who refuse to discount their prices. By extending most-favored treatment guarantees the firm commits not to discriminate. In some circumstances this generates efficient and opportunism-free outcomes. In others it is less effective but may remain attractive relative to other options. Evidence from field market contracts for natural gas corroborates this nondiscrimination hypothesis.     

浅谈水库总磷监测的质量控制

质量控制是监测分析全过程中质量保证的一个重要环节,为此,通过对大王滩水库总磷监测质量控制的实验资料进行分析总结,对较为理想的质量控制方法进行探讨。     

罗马法所有权及对我国所有权制度完善的影响

罗马法的物权概念是现代民法物权概念的基础,罗马法中的所有权更是具备了现代民法中所有权的主要内容.我们应借鉴罗马法所有权并结合我国所有权的立法和实践,对社会主义市场经济条件下的所有权制度进行理论创新和实践改革.     

湖南服务业全要素生产率变动的实证研究

本文使用基于DEA的非参数Malmquist指数方法研究了1996-2005年湖南服务业中的9个行业的全要素生产率的变动状况,并将其分解为技术效率和技术进步.结果表明,在这期间,湖南服务业全要素生产率的平均增长率为5.8%,其增长的主要动力是技术效率的提高;服务业大部分行业的全要素生产率水平都有一定程度的提高,但是增长、降低交替,而非持续增长;10年间除了1998年几乎所有各行业的生产率水平都在下降,而其他年份则各有改善.     

基于SWMM模型的LID措施年SS总量去除率计算

由于SWMM(storm water management model)模型在进行污染物模拟时并未考虑LID(low impact development)措施的净化作用,致使计算年SS总量去除率时存在较大误差,为弥补该误差,本研究提出了一种基于SWMM模型并考虑LID措施净化作用的年SS总量去除率值计算方法。以深圳市玉田河流域为例,构建SWMM模型,结果表明,年SS总量去除率值不考虑LID措施净化作用时为23. 2%,考虑LID措施净化作用时为30. 1%,后者为前者的1. 3倍。同时论述了年径流总量控制率和年SS总量去除率的概念差异,指出两者之间并无确定比例关系。因为LID主要截留初期中小降雨,在考虑初期雨水冲刷效应的情况下,典型地块年SS总量去除率值可能大于年径流总量控制率值。     

有偏技术进步对全要素生产率的解释——来自中国省际的经验证据

有偏技术进步对传统全要素生产率方法不能较好说明的生产函数斜率变动提供了一重较好的解释,利用有偏技术进步指数能够在一定程度上说明等产量曲线斜率的变化如何作用于产出的增长。本文在Antonelli和Quatraro（2010）提出的有偏技术进步测度方法框架下,利用中国29个省市的数据进行了有偏技术进步的计算和比较,发现尽管不同省份的传统全要素生产率和总的全要素生产率都呈现出各异的变动趋势,但是绝大多数地区的增长趋势说明自改革开放以来,技术进步对产出的增加有显著作用,导致生产函数位置的移动及斜率的变化,证明技术进步正在改变生产函数的斜率,即在推动增长向更加高级和先进的阶段发展。     

中国种植业碳全要素生产率增长核算、动态演进与空间溢出

[目的]种植业碳全要素生产率增长是促进种植业可持续发展和实现“双碳”目标的重要抓手。[方法]文章将种植业碳排放与碳汇分别作为非期望与期望产出,运用非径向非角度的SBM-GML指数模型对2000—2020年中国30个省（市、区,不含港澳台和西藏）的种植业碳全要素生产率增长进行核算与分解,接着利用核密度估计方法考察其动态演进趋势,最后运用空间杜宾模型分析其影响因素及空间效应。[结果]（1）考察期内中国种植业碳全要素生产率年均增长1.76%,前沿技术进步年均增长1.97%,技术效率年均下降0.21%;(2)中国种植业碳全要素生产率增长的核密度曲线由“尖窄型”逐渐变为“宽扁型”,省际差距逐步扩大;（3）农业经济发展水平、农业结构调整与农村居民人均纯收入对种植业碳全要素生产率增长有显著的正向影响,财政支持水平和城镇化水平显著抑制了种植业碳全要素生产率增长,农业经济发展水平和农业结构调整具有显著的正向空间溢出效应。[结论]重点关注落后地区和省份的种植业低碳生产与发展,积极倡导地区间与省份间合作,通过提升农村居民收入水平、科学合理调整农业财政支持资金投入方向与比重,有效推动种植业低碳转型,促进我国种植业可持续发展。     

可视化仿真技术在管输油气领域的应用

可视化仿真技术是一种重要的计算机技术,在管输油气领域中有着广阔的应用,在管道设计、运行调度、生产管理等工作中产生了巨大的应用价值,降低了管输油气的生产成本,提升了企业效益。随着计算机各种技术的研究应用水平的不断提高,可视化仿真技术出现了从数值仿真到虚拟可视化仿真的跨越。根据中石油天然气管道公司的实际生产和业务需要,应用可视化技术和仿真技术对输油气场站可视化仿真信息系统进行分析、设计和开发。其成果将为该输油气场站站内施工维护、动火改造及应急指挥等提供方便快捷的查询、分析平台,为生产运行、设备管理和领导决策提供形象直观的可靠管理手段。