薄板坯连铸连轧技术在我国的确大有可为

对我国薄板坯连铸连轧技术2002年以后的发展进行了分析，认为今后将有更大的发展前景，并提出开发新一代薄板坯连铸连轧生产线的设想。     

目前云南钢铁工业发展的对策

分析了促进我国钢铁工业持续、高速发展的因素,借鉴世界主要产钢国过去100年发展的历程,对我国今后20年钢铁需求量进行了预测,讨论了云南钢铁工业发展的有利条件和主要制约因素,提出了加快云南钢铁工业发展的对策。     

从迁徙自由权的剖析入手——试论我国户籍法规与国际人权公约的冲突及其调整

迁徙自由是《公民权利与政治权利国际公约》所规定的一项基本人权,我国于1998年签署了该公约。一旦我国人大批准,该公约将对我国产生法律拘束力,而我国现行法律制度的规定与该公约的差距是明显的。本文从迁徙自由权出发,剖析我国户籍制度与该公约的法律冲突,并提出法律调整的途径。     

Numerical Solution of Boussinesq Equations to Simulate Dam-Break Flows

To investigate the effect of nonhydrostatic pressure distribution, dam-break flows are simulated by numerically solving the one-dimensional Boussinesq equations by using a fourth-order explicit finite-difference scheme. The computed water surface profiles for different depth ratios have undulations near the bore front for depth ratios greater than 0.4. The results obtained by using the Saint Venant equations and the Boussinesq equations are compared to determine the contribution of individual Boussinesq terms in the simulation of dam-break flow. It is found that, for typical engineering applications, the Saint Venant equations give sufficiently accurate results for the maximum flow depth and the time to reach this value at a location downstream of the dam.     

Experimental Investigation on Influence of Aeration on Plane Jet Scour

A series of experiments was conducted to investigate the influence of aeration on plane jet scour. The scour holes caused by the aerated and the nonaerated jets were compared under the same conditions of jet velocity, water discharge per unit width, and tailwater depth. A quantitative relationship between the air concentration of jet and the relative scour depth was established, which is not affected by jet velocity and water discharge per unit width. The profile of the scour hole was found to mainly depend on the scour depth under the same conditions of bed material and tailwater depth and affected very little by the air concentration itself in the test range. The aeration influences the shape of the scour hole mainly through decreasing the scour depth. The scour holes formed under aerated and nonaerated conditions are self-similar.     

Comparative Analysis of Chlorine Dioxide, Free Chlorine and Chloramines on Bacterial Water Quality in Model Distribution Systems

Drinking water utilities may be required to change disinfectant to improve water quality and meet more stringent disinfection regulations. This research was conducted to assess and compares chlorine dioxide to free chlorine and chloramines on bacterial water quality monitored within model distribution systems (i.e., annular reactors). Following colonization with nondisinfected water, annular reactors containing either polycarbonate or cast iron coupons were treated with free chlorine, chlorine dioxide or chloramines. Two disinfectant doses (low/high) were tested for each disinfectant. Under specific environmental conditions, bacterial inactivation varied as a function of the disinfectant type and dose, sample type (bulk water versus biofilm bacteria) and coupon material. The ranking by efficiency was as follows: chlorine dioxide > chlorine > chloramines. On preformed biofilms of 106–107?cfu/cm2, the continuous application of a disinfectant led to a log removal of heterotrophic bacteria concentrations for suspended and biofilm bacteria ranging from 1.1 to 4.0, and from 0.2 to 2.5, respectively. Doubling the amount of disinfectant doses led to an additional log inactivation of 1–2.5 of heterotrophic bacteria levels. This study demonstrates that bacterial inactivation in distribution systems is governed by various inter-related parameters. The data indicate that chlorine dioxide represents a viable alternative for secondary disinfection in distribution systems.     

Confounding Effect of Flow on Estuarine Response to Nitrogen Loading

The total maximum daily load (TMDL) concept provides the basis for regulating pollution load from riverine sources to impaired water bodies. However, load is comprised of two components: flow and concentration. These two components may have confounding, or even conflicting, effects on waterbody attributes of concern. This is particularly the case for dynamic, advective systems, such as estuaries. Resolving these components is critical for properly predicting the response of impaired systems to watershed management actions. The Neuse River Estuary in North Carolina is an example of such an impaired system. Nitrogen has been identified as the pollutant of concern, and the process of developing a TMDL for nitrogen is underway. We, therefore, analyze the extensive data that have been collected for the Neuse River and estuary to investigate spatiotemporal relationships between river flow, riverine total nitrogen (TN) inputs, water temperature, dissolved inorganic nitrogen concentration, algal density, and primary productivity. Results support the belief that phytoplankton in the estuary are under substantial riverine control. However, the riverine TN concentration alone has only a minor role in determining estuarine chlorophyll concentration. River flow has a stronger influence, likely through its effects on down-estuary nitrogen delivery, residence time, salinity, and turbidity. These results imply that using riverine nitrogen load as the metric to evaluate watershed nutrient management may not be appropriate. While nitrogen controls should reduce loads in the long term, in the short term, river flow is the dominant component of load and has the opposite effect of nitrogen on algae at the up-estuary locations.     

Soil Water Content and Dry Density by Time Domain Reflectometry

Soil water content and dry density are two important properties for compaction quality control. This paper presents a new method for determining soil water content and dry density using a single time domain reflectometry test, which is an improvement over that designated by ASTM D6780. This new method is based on simultaneous measurement of apparent dielectric constant and bulk electrical conductivity on the same soil sample. Calibration equations correlate these two parameters with soil gravimetric water content and dry density, which are simultaneously solved after adjusting field-measured conductivity to a standard conductivity. The method compensates for temperature effects. The test process takes about 3 min and all calculations are automated. Testing may be done in situ using a special probe that provides sufficient sampling volume or in a compaction mold adapted to form a probe. Laboratory and field tests results show this one-step method is a fast, accurate, and safe method for construction quality control.     

土壤中氮磷浸出对水库水质影响的模拟实验研究

水库建成蓄水后,库底土壤中氮、磷的浸出会对库水水质会产生一定影响。本文以南水北调中线工程的调蓄水库———瀑河水库为例,在现场调查基础上,使用蒸馏水和模拟水分别进行模拟实验,分析研究了土壤中氮、磷浸出对库水中总氮、总磷浓度的影响。实验结果表明,总氮、总磷的浓度均发生一定程度的变化,且模拟水中的浓度变化小于蒸馏水中的变化;但从整体趋势看,源于土壤的含量较低,对库水水质未产生明显不良影响。     

环境因素对蔬菜累积硝酸盐影响的研究进展

蔬菜中的硝酸盐是一种对人体有害的化学物质,其含量比其它植物都高,人体摄入它会引起多种疾病。对近年来国内外有关光照、温度、气体、土壤中的水分和养分等对蔬菜硝酸盐积累的影响进行了综述。