中波台电磁辐射叠加影响估算及与实测对比分析

以某中波电台为例,对多个不同频率的中波发射台同时运行时复合场强进行理论估算,对电磁辐射叠加影响进行分析,并将理论估算值与该台电磁辐射环境现状监测数据进行比对,得出距离发射塔近,复合场强理论估算值高于实测值,距离较远理论估算值与实测值较接近等结论。     

Experimental and theoretical studies on physico-chemical parameters affecting the solubility of phosphogypsum

Phosphogypsum is a waste by-product of the phosphate fertilizer industry, which is usually disposed in the environment because of its restricted use in industrial applications. Physico-chemical conditions existing in stack fluids and leachates are of major importance and determine solubility and redox stability of phosphogypsum, as well as radionuclide release from stacks to terrestrial environments. The aim of this study is to assess the effect of key parameters (e.g. ionic strength, temperature, pH) on the solubility of phosphogypsum. Phosphogypsum sampling and in-situ measurements were carried out at a coastal stack in Cyprus, solubility experiments were performed in simulated laboratory systems and thermodynamic calculations by means of MINTEQA2, an equilibrium speciation model. Generally, increasing ionic strength and temperature leads to increased phosphogypsum solubility, with the former being much more effective. The increased solubility of phosphogypsum in saline solutions is attributed solely to ionic strength effects on the activity of ionic species in solution and no solid phase transformations could be observed. The effect of pH on phosphogypsum solubility seems to be insignificant at least in a pH range between 4 and 8. Regarding uranium levels, there is a strong correlation between salinity and uranium concentration and linear correlation between phosphogypsum solubility and uranium levels in stack solutions, indicating the incorporation of uranium into the gypsum lattice and the formation of a solid solution.     

CHANGING RAINFALL-RUNOFF RELATIONSHIPS IN THE URBANIZING PEACHTREE CREEK WATERSHED,ATLANTA, GEORGIA1

ABSTRACT: Peachtree Creek is a gaged watershed that has experienced a substantial increase in urbanization. The relationships of runoff to rainfall were studied for total annual flows, low flows, and peak flows. For each type of flow the relationship in the later, more urbanized period was compared to that in the earlier, less urbanized period. An increase in total runoff in wet years was observed as urbanization increased, but a decrease occurred during dry years. For low flows a similar decrease of runoff in dry years was found. An increase in peak runoff was observed over most of the range of precipitation. Increasing peak flows and declining low flows can be adequately explained by urban hydrologic theoryshed. which focuses on the effects of urban impervious surfaces upon direct runoff and infiltration. However, a decline of total runoff in dry years can be explained only by taking into account evapotranspiration as well. The concept of advectively assisted urban evapotranspiration, previously discovered by climatologists, is needed to explain such a loss of total runoff. Urban hydrologic theory must take into account vegetation and evapotranspiration, as well as impervious surfaces and their direct runoff, to explain the magnitude of total annual flows and low flows. Urban stormwater management should address the restoration of low flows, as well as the control of floods.     

JUSTIFICATION FOR A REDUCTION IN THE CREST-STAGE GAGE PROGRAM IN LOUISIANA1

The crest-stage gage program in Louisiana was evaluated to determine if the data were adequate for use in developing regional flood-frequency equations and to determine if any crest-stage gage stations could be discontinued. An abundance of data at many crest-stage gage stations and a lack of data for urban areas and flat-slope areas indicated a need for a shift in the number, type, and locations of gages. Correlations and comparisons of annual peak discharges and watershed characteristics of 96 existing stations resulted in the elimination of 72 stations and the addition of one new station, reducing the total network to 25 stations that could be used for future flood-frequency analyses. The adequacy of the reduced network for development and verification of regional flood-frequency equations was tested by comparing a set of regional flood-frequency equations developed using data from the full network with a set developed using data from the reduced network. The results indicate that the crest-stage gage network can be reduced to 25 stations and still provide adequate information for future flood-frequency analyses.     

CAUSES OF PEAK FLOWS IN NORTHWESTERN MONTANA AND NORTHEASTERN IDAHO1

ABSTRACT: Both catchment experiments and a review of hydrologic processes suggest a varying effect of forest harvest on the magnitude of peak flows according to the cause of those peak flows. In northwestern Montana and Northeastern Idaho, annual maximum flows can result from spring snowmelt, rain, mid-winter rain-on-snow, or rain-on-spring-snowmelt. Meteorologic and physical data were used to determine the cause of annual maximum flows in six basins which had the necessary data and were smaller than 150 mi². Rain-on-spring-snowmelt was the most frequent cause of annual maximum flows in all six basins, although there was a strong gradient in the magnitude and cause of peak flows from southwest to northeast. Less frequent mid-winter rain-on-snow events caused the largest flows on record in four basins. Mid-winter rain-on-snow should be distinguished from rain-on-spring-snowmelt because of differences in seasonal timing, the relative contributions of rain vs. snowmelt, and the projected effects of forest harvest. The effects of mixed flood populations on the flood-frequency curve varied from basin to basin. Annual maximum daily flows could not be reliably predicted from rainfall and snowmelt data.     

FLOOD FREQUENCY ANALYSIS FOR SMALL WATERSHEDS IN SOUTHERN ILLINOIS1

ABSTRACT: Twenty-two gaging stations were selected for developing a regional flood frequency curve for small (area less than 2 square miles) watersheds in southern Illinois. Five probability functions were compared, and the extreme value type I function was selected to develop the regional flood curve. The curve was generated with the index flood method and also another empirical method that related the function parameters to the watershed area. Estimated peak discharges with various return periods were compared with the results obtained from multiple regression analysis.     

用固体力学化学理论研究岩土的力学化学行为——以成都龙泉紫色土为例

根据固体力学化学理论 ,提出用化学动力学方法研究岩土破坏及滑坡形成的机理 ,并以成都龙泉紫色土为例研究了在力与水协同作用下易滑土层的力学化学行为。实验表明 ,土长期抗剪强度降低的幅度与溶液的pH值有关 ,土的溶解速度与易溶盐含量有关 ,且溶解曲线略呈“S”型。这初步证明了龙泉紫色土破坏的力学 化学效应及其可能存在的自催化趋势。通过实验了解了力与水协同作用导致土破坏的力学化学规律 ,并将定量求解滑面长期抗剪强度与反应机理研究结合起来 ,为定量评价地下水和应力对岩土破坏机理这一滑坡学关键问题打下基础。     

提高节理面c和φ对岩坡开挖变形的影响

为了反映岩质边坡在节理面注浆后的变形效应,首先,通过室内试验,分析注浆前后岩体变形和破坏的全过程,以探讨其抗剪性能(粘结力c和内摩擦角φ)的变化;然后,基于理想弹塑性本构模型的Mohr-Cou-lomb准则,运用拉格朗日元数值方法(FLAC3D),对岩坡注浆前后变形效应(水平位移、垂直位移、剪应变增量)进行模拟。结果表明:注浆加固后,岩体的位移场变得均匀和连续,节理面处的较大位移受到抑制,边坡的整体性得到提高,有利于边坡的稳定性。     

饱和软土刚性长短桩复合地基——强度及变形实用计算公式

刚性长短桩复合地基有许多特点，如桩体均为刚性、短桩及长桩桩端为低压缩或中压缩性土等。长短桩复合地基的设计理论目前仍处于研究阶段，现行规范中尚无有关其强度及变形的具体计算方法。重点探讨了饱和软粘土体上采用刚性长短桩复合地基的强度及变形理论，并提出了适用于工程应用的实用计算方法。     

混凝土结构施工中人因差错的模拟

以施工现场人因差错真实准确的调查实测数据为依据,笔者采用人的可靠性分析方法建立了混凝土结构施工中人因差错发生及其对混凝土强度影响规律的数学模型,并编制了相应的模拟计算程序。将该模拟计算程序所得的考虑人因差错的混凝土强度模拟计算结果与实测的混凝土强度调查结果进行比较,二者具有很好的一致性,说明该数学模型和模拟计算程序是比较符合实际的,也是比较合理的。上述模拟计算结果为考虑人因差错的结构安全性分析以及人因差错的有效控制措施研究提供了参考依据。