Estimation of consistent wet period characteristics for further improvement of water resources studies

This study presents an analysis of consistent wet periods for further improvement of water resources studies. While previous studies have focused on characterizing dry periods, this study uses tree‐ring reconstructed precipitation to detect the occurrence of wet periods of magnitude larger than what can be achieved from the analysis of the historical precipitation records. Tree‐ring reconstructed precipitation for Madaba region in Jordan that began in 1743 was used. The analysis of the historical precipitation indicated the occurrence of short wet periods (1–4 years). The analysis of the 239 years of the reconstructed precipitation indicated the occurrence of long wet periods (7 years), and wet period magnitude of 551 mm, that is 20% larger than the observed from the analysis of historical precipitation. Furthermore, this study presents theoretical formulation that can be used to estimate the expected number of wet events of desired length that could emerge during the operation period of surface resources.     

Transport and deposition of sediment-associated Escherichia coli in natural streams

The association of microorganisms with sediment particles is one of the primary complicating factors in assessing microbial fate in aquatic systems. The literature indicates that the majority of enteric bacteria in aquatic systems are associated with sediments and that these associations influence their survival and transport characteristics. Yet, the nature of these associations has not been fully characterized. In this study, a combination of field experiments and mathematical modeling were used to better understand the processes which control the fate and transport of enteric bacteria in alluvial streams. An experimental procedure, involving the use of a tracer-bacteria, was developed to simulate the transport and deposition of bacteria-laden bed sediments in a small alluvial stream during steady flow conditions. The experimental data and mathematical model were used to determine dispersion coefficients, deposition rates, and partitioning coefficients for sediment-associated bacteria in two natural streams. The results provided evidence that bacterial adsorption can be modeled as an irreversible process in freshwater environments. Net settling velocities of fine sediments and associated bacteria were typically two orders of magnitude lower than those predicted from Stokes equation, due to re-entrainment of settled particles. The information presented in this study will further the development of representative microbial water quality models.     

干、湿喷混凝土和湿喷仿钢纤维混凝土强度性能比较分析

针对干、湿喷混凝土支护强度低、黏结强度低与韧性差等问题,对干、湿喷混凝土与湿喷仿钢纤维进行强度试验及柔韧性分析,并将其与干、湿喷混凝土强度与柔韧性进行对比。采用试验的方法,利用RMT力学试验机对干喷、湿喷混凝土及湿喷仿钢纤维混凝土从抗压强度、抗拉强度及抗折强度三方面力学性能进行试验,通过对试验数据的分析,可以得出湿喷仿钢纤维混凝土力学性能优于湿喷混凝土、湿喷混凝土优于干喷混凝土;其中仿钢纤维的掺入使得混凝土的力学性能大幅增强,相较于干喷混凝土抗压强度提升86.3%、抗拉强度提升85.9%、抗折强度提升132.9%;相较于湿喷混凝土抗压强度提升25.8%、抗拉强度提升24.5%、抗折强度提升45.8%;其柔韧性与抗裂性经折压比比较可知有所提高。     

Investigation of dry and wet deposition of air pollution in a rural area

The inorganic composition of dry and wet atmospheric depositions is reported from a rural sampling site near the city of Rome. Cellulose filter paper impregnated with an alkaline solution, and acetate cellulose pre-filters were used for the collection of SO₂ and suspended particulate matter, respectively. A rain-activated wet/dry precipitation collector was utilized.A seasonal trend of SO₂ was observed and analysis of particulate for H⁺, SO₄²⁻, NO₃⁻ and NH₄⁺ revealed that a significant amount of free strong acidity was present on particles. Fifty percent of precipitation pH values were below 5.6.On an annual basis the data show that dry acid deposition is more important for the area investigated.     

Potential acidifying capacity of deposition experiences from regions with high NH4+ and dry deposition in China

Acid rain may cause soil acidification possibly leading to indirect forest damage. Assessment of acidification potential of atmospheric deposition is problematic where dry and occult deposition is significant. Furthermore, uncertainty is enhanced where a substantial part of the potential acidity is represented by deposition of ammonium (NH(4)(+)) since the degree of assimilation and nitrification is not readily available. Estimates of dry deposition based on deposition velocity are highly uncertain and the models need to be verified or calibrated by field measurements of total deposition. Total deposition may be monitored under the forest canopy. The main problem with this approach is the unknown influence of internal bio-cycling. Moreover, bio-cycling may neutralize much of the acidity by leaching of mainly K(+). When the water percolates down into the rooting zone this K(+) is assimilated again and acidity is regenerated. Most monitoring stations only measure deposition. Lacking measurements of output flux of both NH(4)(+) and NO(3)(-) from the soil one cannot assess current net N transformation rates. Assumptions regarding the fate of ammonium in the soil have strong influence on the estimated acid load. Assuming that all the NH(4)(+) is nitrified may lead to an overestimation of the acidifying potential. In parts of the world where dry deposition and ammonium are important special consideration of these factors must be made when assessing the acidification potential of total atmospheric loading. In China dry and occult deposition is considerable and often greater than wet deposition. Furthermore, the main part of the deposited N is in its reduced state (NH(4)(+)). The IMPACTS project has monitored the water chemistry as it moves through watersheds at 5 sites in China. This paper dwells at two important findings in this study. 1) Potassium leached from the canopy by acid rain is assimilated again upon entering the mineral soil. 2) Nitrification apparently mainly takes place in forest floor (H- and O-) horizon as NH(4)(+) that escapes this horizon is efficiently assimilated in the A-horizon. This suggests that the potential acidification capacity of the deposition may be found in the throughfall and forest floor solution by treating K(+) and NH(4)(+), respectively, as acid cations in a base neutralization capacity (BNC) calculation.     

干湿混纺地毯燃烧性能研究

为研究火灾初期自动喷水灭火系统作用时对铺地材料燃烧性能的影响,利用火焰传播量热仪,以混纺地毯为例,分别研究了干态、含水率50%、全浸泡3 种状态下水对其燃烧性能的影响。试验结果表明：随着含水率的升高,混纺地毯的引燃时间增长,含水率高的混纺地毯不易被引燃;含水条件下峰值热释放速率比干态条件下大,火灾规模较大,火焰燃烧持续时间内总热值较小;含水条件下,总烟气生成量及组成成分峰值出现时间后移。     

干湿交替环境中CFRP加固预裂RC梁耐久性试验

对干湿交替环境中CFRP加固预裂RC梁的耐久性能进行了试验研究,重点分析了干湿交替环境对RC梁的界面破坏特征、刚度、跨中截面混凝土应变和CFRP应变变化的影响,结果表明：干湿交替环境弱化了CFRP与混凝土界面的粘结性能,对加固效果有一定的不利影响。     

不同类型盐渍土固化体的干缩与湿胀特性

采用三种固化剂对高含盐量的氯盐盐渍土和硫酸盐盐渍土进行固化,研究了它们的干缩和湿胀特性。结果表明,用矿渣和粉煤灰取代部分水泥,随后又增加粉煤灰的比例,可以连续降低固化土的干缩应变和干缩系数。矿渣和粉煤灰取代水泥后,水化活性减弱,产物减少,同时,体系内Ca2+的浓度降低,盐渍土中所含NaCl和Na2SO4对化学反应的促进作用减弱,化学反应程度以及由此引起的自由水到结合水的转化、孔隙特征的变化的差别缩小,因此,盐分引起的固化土的干缩应变和干缩系数的差别缩小。Na2SO4对固化土干缩应变和干缩系数的提高作用比NaCl明显。在低钙体系中,NaCl的物理作用比化学作用更突出。含NaCl的固化土试件在吸湿阶段具有明显的吸潮特性,但并不引起较大的膨胀。残存在土体中的Na2SO4在吸湿阶段可能发生剧烈膨胀而导致土体发生严重开裂。     

雾化湿法与过滤吸附相结合的净化试验研究

为解决餐饮业和家庭厨房产生的油烟问题，在分析已有净化方式的基础上，提出雾化湿法与过滤吸附相结合的方法，并分别对雾化法、吸附法及二者相结合的方法作了试验，结果表明二者相结合的方法油烟去除效率最高，达92％以上，且净化后油烟排放的浓度符合国家标准。     

A survey of heavy metals in municipal wastewater in combined sewer systems during wet and dry weather periods

During wet weather, combined sewer system overflows affect the quality of water in watercourses. For planning overflows, the lowest possible load of priority substances according to Directive 2008/105/EC is crucial and the knowledge of variability in concentrations of elements in the sewer system is necessary. The behaviour of heavy metals in a sewer system was observed in the course of dry weather flow (DWF) and wet weather flow (WWF). We found, from the comparison of concentration medians for the WWF and DWF that during wet weather periods, an increase in the concentrations of As, Cr, Cd, Pb, Mn and Fe occurs in the sewer system and the effect of nonpoint sources manifests itself. Zn, Cu and Ni concentrations decreased during wet weather periods, and Hg concentrations did not significantly change. During the WWF period, a considerable nonhomogeneity of the sewage system was demonstrated.     

水冷式表冷器传热研究（3）：半干半湿工况热力计算

将已较成熟的水冷式表冷器干工况和湿工况热力计算理论与干、湿工况的分界是点“表冷器空气初状态的露点温度”结合起来,建立了半干半湿工况热力计算公式。其特点在于把湿工况段转换为等价干工况处理。     

应用二灰改善潮湿土基试验分析及施工控制

对二灰在改善潮湿高液限黏土的降水性能,提高CBR值,改善水稳定性等方面进行了相关试验研究,并对二灰改善土大规模应用于路基填筑的施工特点进行了总结,阐述了二灰土的施工质量控制要点.     

湿喷射混凝土技术在抢险加固工程中的应用

结合具体工程实例,介绍了湿喷射混凝土技术在抢险加固工程中的应用,分别阐述了湿喷射混凝土施工的相关技术要求和施工难题及解决措施,为今后类似抢险加固工程提供了经验。     

土工布在湿软地基中的应用研究

结合工程概述,介绍了土工布对软土路基的作用原理,从物理、力学、水力、环境等方面分析了土工布的特性,阐述了土工布施工应注意的问题,并对沉降量进行监测,实践证明,用土工布处理湿软地基是一个较好的方法,值行推广。     

湿法烟气脱硫除尘设备应用中存在的问题

在中小型锅炉烟气处理技术领域，湿法脱硫除尘设备以及其净化效率高，初次投资省、运行费用低等特点发展最为成熟，然而在湿式脱硫除尘技术的设备中尚存在着一些问题。通过对湿法脱硫除尘设备工作原理的简要叙述，结合设计应用实践，分析并提出了在技术开发及应用中存在的问题，以引起重视。     

400×800的全瓷砖在公共部位湿贴的研究与应用

以晋中市第二人民医院儿科门诊住院综合楼工程为例,对400×800的全瓷砖在公共部位湿贴的施工工艺、材料要求、施工机具、操作要点进行了阐述,并提出了墙面砖质量验收标准及控制要点,解决了平整度、垂直度及空鼓现象的质量问题。     

Modeling of cooking-emitted particle dispersion and deposition in a residential flat: A real room application

Maintenance of good indoor air quality for residences could be very challenging. Episodic event such as cooking emits a large amount of ultrafine and supermicron particles. A numerical model is used to simulate a 10-min cooking process in a real room, followed by a few more minutes to allow the decay and removal of particles. Particle dispersion and deposition in the kitchen and the living room are simulated by a new drift-flux model. Strong buoyancy flow is observed and particle concentration is significantly affected by the thermal plume. Results show that for supermicron particles strong non-uniformity of concentration is observed in the kitchen but the non-uniformity is less obvious in the living room. Exposure analysis must take into account the influence of the particle sizes.     

湿砂场地爆炸成坑效应的现场试验与数值模拟研究

 蓄水土坝坝顶、地基浅层等部位的含水土体受到爆炸作用时会形成爆坑,从而对岩土工程构筑物造成严重灾害。为了研究含水土中爆炸成坑效应的影响因素,开展一系列湿砂中的爆炸现场试验,同时利用光滑粒子流体动力学和有限元耦合方法(SPH-FEM)对爆坑试验进行评价。研究结果表明：根据药包的比例埋深,湿砂中的爆坑形态分为封闭爆炸、塌陷型漏斗坑和抛掷型爆坑。当比例埋深小于1.5 m/kg1/3时,易形成抛掷型爆坑,而发生封闭爆炸的临界比例埋深为2.3 m/kg1/3。对于抛掷型爆坑,可见直径试验值和数值计算的真实直径均与相应的ConWep预测值表现出很好的一致性。通过SPH粒子的运动实现的爆炸鼓包过程与试验中抛掷物运动规律一致,发现利用数值计算的真实爆坑尺寸预测可见爆坑直径的方法满足工程应用要求。爆坑直径受土体的密度和强度参数的影响偏差都在10%以内,在试验基础上结合量纲分析法,推导了关于药量与埋深的爆坑直径经验公式。     

厨房空气中NOx和CO浓度的测试

介绍使用燃气用具厨房内空气中NOx和CO浓度的实测数据,并对厨房空气质量进行评价。     

微生物诱导沉积碳酸钙机理及其在混凝土裂缝修复中的应用

对光合生物诱导沉积、硫酸盐还原菌诱导沉积、氮循环菌诱导沉积等微生物诱导沉积碳酸钙(MICP)机制进行了回顾,分别阐述了不同机制的作用机理,并探讨了不同机制在混凝土裂缝修复中的应用研究进展。此外,还分析了目前MICP修复技术存在的问题和局限性,对未来的进一步研究提出了思路和建议。