1/f噪声源与其在半导体器件可靠性评估中的应用

1／f噪声,由于其能够反映器件的质量与可靠性参数,其研究受到重视。本文首先较为系统地介绍了1／f噪声源两种较为成熟的理论：迁移率涨落模型和载流子涨落模型,最后介绍了几个1／f噪声与半导体器件参数漂移相关的实例。     

三峡库区消落带农用坡地磷素径流流失特征

消落带是三峡库区重要的生态交错带,但自发农用和无序开发可能会造成更多的氮磷流失,进而加剧三峡库区水体富营养化。通过对库区连续3 a的定位监测（2011~2013年）,研究了三峡库区消落带农用坡地的磷素流失特征。结果表明：次降雨事件中常规施肥处理的地表径流、壤中流总磷平均浓度分别为0.848±0.153、0.140±0.006 mg/L,其中地表径流中磷的形态以颗粒态为主,壤中流以溶解态的生物可利用磷为主。常规施肥下,地表径流、壤中流磷素年均流失通量分别为0.236±0.004、0.100±0.003 kg·hm 2,地表径流、壤中流磷素流失通量分别占总流失通量的70.2%、29.8%,地表径流是坡地磷素流失的主要途径,但壤中流也是不可忽视的重要途径。与常规施肥处理相比,减量施肥处理地表径流、壤中流磷素流失量分别降低了45.3%、40.0%。建议采取减量施肥的方式,以降低营养盐负荷,保护水环境。     

降低超高压输电线路电晕噪声的对策研究

从电力金具的选型、设计、生产、运输、安装和优化改造等环节提出了降低超高压输电线路电晕噪声的对策措施。同时,通过对超高压输电线路铁塔可听噪声和金具电晕放电情况的检测,验证优化改造金具的降噪效果,查找金具安装的缺陷和漏洞,为金具制造和设计、预防电晕措施的选择及电力金具的改良、安装和运行等方面提供决策和参考依据。     

高加速应力试验装置技术参数的测量

气锤驱动的高加速应力试验装置,能产生温度和非高斯随机振动应力,其中振动应力是由多个气锤作六自由度运动产生的。一般用来进行高温步进、低温步进、快速温度变化、振动、快速温变和振动复合试验。目前国家标准和校准规程中均无关于该试验装置的技术参数的校准方法。本文结合试验装置的技术特点,提出了几个关于温度和振动技术参数的测量方法,如:温度偏差、温度波动度、温度均匀度、温度过冲量、温度变化速率、均方根加速度、横向振动比、功率谱密度等。     

水位波动带氮素迁移转化规律

为考察水位波动对非饱和-饱和土层中氮素迁移转化的影响,设计土柱实验装置Ⅰ和Ⅱ分别模拟水位稳定与波动两种情景,测定一个水位波动周期内地下水中NO₃^--N、NO₂^--N和NH₄⁺-N浓度变化情况。结果表明,柱Ⅱ水位第1次下降柱内1^#,2^#,3^#,4^#采样点NO₃^--N浓度均增大,增幅分别为6.5%、14.9%、15.33%和19.8%。水位上升时结果相反,分别降低17.3%、26.15%、50.29%和44.61%。第2次水位下降至初始位置4个采样点NO₃^--N浓度再次增大,幅度分别为7.1%、10.6%、13.89%和7.76%。铵态氮呈相反趋势不同程度的变化。水位波动柱Ⅱ连通水槽内总氮量增加显著高于柱I水槽,即水位波动有利于波动带地下水中氮素垂向迁移,加重波动带以下地下水硝酸盐污染。因此,水位波动对氮素迁移转化的影响不容忽视。     

基于DFA法的江苏省极端降水时空分布特征研究

为进一步掌握江苏省极端降水的时空分布特征,基于该省1961-2010年均一性较好的逐日降水数据,利用去趋势波动分析法确定了全省13个站点的极端降水阈值,并通过Morlet小波及Mann-Kendall法分析了江苏省极端降水频数的振荡周期及其突变。结果表明,江苏省极端降水年频数和夏季极端降水均呈现8～10 a的变化周期,且1998年和2006年分别为其突变增加年,而秋季极端降水主要呈2～3 a与5～7 a的变化周期;极端降水与降水总量的空间分布具有较好的一致性,均呈南部大、北部小的特征。     

太阳活动与四川盆地气候资源波动

本文应用四川省气象局提供的气候资料,借助于电子计算机,统计分析了太阳黑子位相与四川盆地热量资源、降水资源波动的关系;采用文献[2]的公式,计算了太阳黑子相对数年均值与热量、降水资源的同期及延后相关系数,并进行了周期分析,进而分析其演变趋势及其对农业生产的影响和应采取的对策。     

THE INFLUENCE OF DRAW-DOWN ON RECREATION ON THE TRENT CANAL RESERVOIR-LAKES1

ABSTRACT: Water-based outdoor recreation constitutes an important benefit in many multiple-use projects. One problem frequently encountered, however, is the fluctuation of the water-level in a reservoir, especially if draw-downs occur during the summer recreation season. The Trent Canal in Ontario, Canada, forms a unique recreation waterway of some 240 miles of canal and navigable lakes and rivers. For the control of the water in the canal, the Canadian Federal government manages 44 reservoir-lakes as water-storage sites to augment the flows in the canal. While most disputes in water allocation for recreation generally involve recreation uses versus other, non-recreation uses, in the case of the Trent Canal and its reservoir-lakes the dispute in water allocation exists between two competing recreation-uses: for recreation boating on the Canal and its waterway, and for recreation use of the reservoir-lakes. Each use has its own duty-of-water in terms of requirements, or water conditions, for its optimum use. On the reservoir-lakes, by far the largest recreation user-group, is made up of the owners of private shoreline summer cottages (cabins). Draw-downs on the reservoir-lakes, in some cases as much as 13 feet, hence constitute a negative externality imposed by the canal, especially since water-level lowering takes place continuously throughout the summer. In-depth interviews conducted with over 100 cottage-owners indicate four main conclusions. First, the previous user assumptions of the extent of the negative effect of water-level fluctuation on recreation had been exaggerated. Only in extreme draw-downs during infrequent dry years would draw-down constitute a serious imposition. Second, water-level fluctuation does constitute a form of inconvenience to the private riparian recreation property owners, but it does not generally reduce the quantity of recreation use of the reservoir-lakes. Third, there is evidence that reservoir-lake users have learned to adapt successfully to water-level draw-downs. Fourth, the shoreline physiography of the location of a riparian owner strongly influences the way in which draw-down affects attitudes and opinions. The complex jurisdictional split of the land and water resources of the region points to the need to establish a Trent Canal Authority, to oversee the proper use and development of the canal, its waterway, and the reservoir-lakes.     

中国热带近百年气候波动与自然灾害

20世纪，中国热带气温呈波动上升趋势。在气温波动过程中有2个冷期和2个暖期。最暖的时期为80年代后，这与全球变化相一致，但是昆明最暖的时期为40年代。气候型大多为暖湿同期，这与全国其它区域的状况不同。自然灾害有加剧的趋势：台风次数增多，多台风年洪水多发，旱灾和冷害次数增多，广州曾降微雪，海口和崖县曾见霜，昆明曾有4年强降雪。     

三峡库区支流库湾消落带土壤磷形态赋存特征及其释放风险

三峡库区消落带经历反复的淹水-落干循环影响,消落带土壤磷迁移转化过程加快,可能加剧支流库湾水体富营养化.采集了三峡库区腹心支流库湾典型消落带土壤,测定磷赋存形态与磷素饱和度(DPS)等,分析磷释放风险.结果表明,(1)消落带土壤ω[总磷(TP)]、ω[无机磷(IP)]和ω[有机磷(OP)]均值分别为771.80、485.33和166.30 mg·kg^-1,IP和OP均以非活性形态磷为主.(2)消落带土壤形态磷的赋存格局受落干-淹水方式影响,Ex-P和NaHCO₃-Po含量显著高于对照土壤,Fe-P、HCl-Po和Fulvic-Po含量沿高程下降而显著降低(P<0.05),反复的干湿交替促进了消落带土壤活性磷的生成和中等活性磷的释放和积累.(3)消落带土壤生物ω[有效磷(Bio-P)]为49.19～148.78 mg·kg^-1,占TP的质量分数为7.71%～24.78%,磷素饱和度(DPS)为5.85%～22.00%.目前,支流库湾消落带土壤整体磷释放风险较低,170 m高程土壤需要重点关注.Fe-P、HCl-Po和...