Impacts of climate and land‐cover changes on water resources in a humid subtropical watershed: a case study from East Texas,USA

This study investigates the response of water resources regarding the climate and land‐cover changes in a humid subtropical watershed during the period 1970–2009. A 0.7°C increase in temperature and a 16.3% increase in precipitation were observed. Temperature had a lower increase trend, and precipitation showed definite increasing trend compared to previous studies. The main trend of land‐cover change was conversion of vegetation and barren lands to developed and crop lands affected by human intervention, and forest and grass to bush/shrub which considered to be caused by natural climate system. Hydrologic responses to climate and land‐cover changes resulted in increases of surface run‐off (15.0%), soil water content (2.7%), evapotranspiration (20.1%) and a decrease in groundwater discharge (9.2%). We found that surface run‐off is relatively stable with precipitation, whereas groundwater discharge and soil water content are sensitive to changes in land cover, especially land cover brought about by human intervention.     

岩体软弱夹层的弹性模量动力测试方法

 针对岩体软弱夹层的力学参数具有渐变性,假设软弱夹层的损伤度按照二次曲线规律变化,建立应力波在软弱夹层的传播模型,研究应力波的波形变化规律,提出软弱夹层弹性模量的动力测试方法。现场试验研究表明：当采用波形变化系数量化入射侧的计算波形和实测波形差异时,随着软弱夹层峰值损伤度增加,波形变化系数先减小后再增加,波形变化系数为最小值时,入射侧的计算波形和实测波形非常接近;随着子波主频增加,软弱夹层的动态弹性模量近似成线性增加,通过线性拟合求得了软弱夹层的静态峰值弹性模量为0.74 GPa;基于变形相等原则计算得本次试验的软弱夹层的等效动态弹性模量为4.24 GPa,采用波速法测试得夹层动态弹性模量为4.70 GPa,波速法测试结果与等效动态弹性模量相近,表明该方法测试结果合理。     

螺旋管式相变蓄冰装置的结构优化

对冰蓄冷系统中,螺旋管式蓄冰装置相变蓄冰过程进行研究。采用第三类边界条件建立传热方程式,可以较好地描述相变传热过程。建立可靠的模拟模型,对螺旋管相变蓄冰过程进行数值模拟,模拟结果表明,螺旋管中心容易产生相变死区,蓄冷材料利用率不高;采用螺旋管中间加装直管段的方式进行优化,模拟结果表明,同等蓄冰条件,溶液出口温度同比提高1.5℃;相变蓄冷4 h,结冰质量由9.07 kg同比提高到10.45 kg,相变死区问题得到解决,蓄冷材料利用率提高。综合表明采用加装直管段优化方式具有合理性。     

Development and numerical validation of a new model for walls with phase change materials implemented in TRNSYS

This paper presents a model of a wall with variable properties dedicated to modelling phase change materials (PCMs) in building envelopes. The model is implemented in the TRNSYS simulation tool and referred to as Type 3258. The 1-D conduction heat transfer equation is solved using an explicit finite-difference method coupled with an enthalpy method to consider the variable PCM thermal capacity. This model includes temperature-dependent thermal conductivity and PCM-specific effects like hysteresis and supercooling. The stability conditions are discussed and the algorithm implemented in TRNSYS is described. A numerical validation performed on wall test cases proposed by the International Energy Agency is presented, showing that the developed model is in agreement with reference models. The paper also discusses the impact of temporal and spatial discretization on the model performance. Modelling problems encountered when using an effective heat capacity method (compared to an enthalpy method) and when representing supercooling are also discussed.     

Estimation of greenhouse gas emissions from municipal wastewater treatment systems in India

Greenhouse gas (GHG) emissions generated from municipal wastewater treatment plants in India is estimated in this study. The emissions from the wastewater treatment process as well as from the electricity used during the treatment process are estimated by using the methodology of Intergovernmental Panel on Climate Change. The present treatment plants of capacity 15 997 million litres per day (MLD) contributes towards GHG emissions of 7.3 Mt of CO₂‐eq/year. The future GHG emissions would depend upon the treatment technology used for treating 34 109 MLD of untreated wastewater. The highest GHG emissions would occur if all new wastewater treatment plants are based on upflow anaerobic sludge blanket technology, 19.66 Mt CO₂‐eq/year and lowest if sequential batch reactor technology is adopted, 2.93 MtCO₂‐eq/year.     

多雨炎热地区膨胀土观测站的选址

膨胀土的工程性质对气候的变化十分敏感。在分析广西膨胀土分布情况、基本性质以及地区气候的基础上,充分考虑了气象因素与研究基础的影响,解决了1个膨胀土野外观测站的选址问题,为研究膨胀土力学性质-气候的作用机理提供良好的工作平台。     

探析工程建设项目成本控制的几个要点

指出工程项目建设成本控制贯穿于项目建设的整个过程,在此基础上,从确定科学合理的设计方案、制定严密的合同条款、加强施工过程中的成本控制等方面论述了项目成本控制的几个要点,从而更好的指导实践,以期以最低的成本创造出最大的效益。     

相变储能材料在建筑节能中的应用研究

阐述了相变储能材料用于建筑节能的优势,介绍了相变储能材料在建筑中的应用研究进展与现阶段研究特点,探讨了相变储能材料在建筑节能应用方面存在的主要问题,并展望了相变储能材料在建筑节能中的应用前景。     

储热领域的微胶囊相变材料

介绍了微胶囊相变材料的特点、相变机理及在储热领域的应用,展望了微胶囊相变材料的发展前景。     

Transient thermal response of a PCS heat storage system

Over the last years the use of phase change slurries (PCSs) based on microencapsulated phase change material (MEPCM) increased considerably due to their capacity of adaptation to various heat storage systems. PCSs are obtained by dispersing a microencapsulated PCM (particle diameter 5-20 μm) into a heat carrier fluid (e.g. water). Heat storage systems are used in applications where the available energy supply is not synchronous with the demand, such as solar thermal and waste heat recovery systems. The theoretical study conducted here - based on heat transfer and energy conservation equations - is intended to developing a theoretical model of the heat storage properties of phase change slurries capable of predicting the transient thermal response of a thermal energy storage system (TES). Most of the research work was focused on investigating the enthalpy-temperature curves resulting from a heating-cooling cycle around the melting point of the PCM. The influence of other parameters such as mico-particles diameter was assessed.