预拌全轻混凝土导热系数影响因素分析

全轻混凝土的导热系数是一项重要的热工指标,其导热性能受多方面因素的影响,该文结合相关的标准规范、工作经验和相关书籍文献对影响全轻混凝土导热系数的多种因素进行了总结、分析和探讨,以期促进预拌全轻混凝土技术的进步。     

现代室内环境需要绿色建材

根据有关统计数据表明,人的活动大部分在室内进行,随着经济的发展和物质生活水平的提高,人们对室内环境的要求更严格.为此,在七十年代末发达国家的科学家就已着手研究建筑材料所释放的气体对室内空气的影响,及对人体健康的危害的程度.大量研究证明,除了人类活动的影响外,造成室内空气污染有两大因素:即通风和建筑材料(包括装饰材料、家具等),现代通风设备的使用,导致室内外空气交换量大量减少,建筑材料释放的VOC(挥发性有机化合物——Vola tile OrganicCompounds)被大量浓缩,造成更严重的室内空气的污染,对人体健康的威胁更大.从而选择释放VOC含量少的“健康型、环保型、安全型”的建筑材料——绿色建材,已成为国外建筑设计的基本要求.     

七天模拟失重对大鼠生理指标的影响

失重可一定程度抑制人体与周围环境的热交换,对人体生理、心理均有很大影响。为研究模拟失重对大鼠生理指标的影响,采用大鼠尾部悬吊法建立模拟失重模型,将28只健康SPF级雄性SD大鼠随机均分为模拟失重组(实验组)与参照组。实验环境温度23±1℃,历时7天,每日对大鼠体重、胸部温度、直肠温度进行监测,7天后同时取2组大鼠血样测定血常规、血生化、血液流变性中41项指标,并进行统计分析。实验结果表明:模拟失重可导致大鼠体重增长受抑制,胸部温度、直肠温度上升,会不同程度地影响血常规、血生化、血液流变性等指标。     

沥青混合料集料接触特性切片图像评价方法

为了评价沥青混合料集料的接触特性,提出了一种较能准确有效评价沥青混合料集料接触特性的新方法。研究中建立了表征集料接触特性的量化指标——接触对,以AC20型沥青混合料为例,对车辙板试件的72幅切片图像进行了分析,通过对所有切片的集料接触数据进行统计分析,得到了集料接触对数目的分布规律。在此基础上,还进行了集料接触特性的影响因素分析,并提出了影响集料接触特性的3个主要因子:4.75 mm以上集料含量C4.75、细度指数FI和离析指数SI。结果表明这3个因子与集料接触对之间有较好的关联度,集料接触特性变化受3个因子共同作用的影响,单因素或双因素都不能正确反映样本的接触对数目。     

含水量和孔结构对多孔建筑陶瓷砖导热系数影响的试验研究

多孔建筑陶瓷砖是一种多相复合材料,其导热性受温湿度和孔隙率等多个因素的综合影响。通过试验研究了不同孔结构、孔隙率和含水量等因素变化条件下多孔建筑陶瓷砖导热系数的变化规律。结果表明,以淀粉和碳粉为造孔剂制备的建筑陶瓷均以开口气孔为主,整体连通性强。淀粉造孔的孔径尺寸相对比较均匀,显气孔率高于碳粉。随着造孔剂含量的增加,显气孔率和吸水率线性增大,孔径分布趋于分散。多孔建筑陶瓷砖导热性的各影响因素之间具有明显的耦合作用特征,即含水率越高,温度变化对其导热性的影响越显著;显气孔率越高,导热系数对含水量的变化越敏感。     

粗骨料随机分布对混凝土导热性能的影响

采用COMSOL与MATLAB联合仿真的方法,基于混凝土二维细观几何模型,实现了混凝土稳态热传导的数值模拟.在利用试验结果验证数值模拟有效性的基础上,分析了骨料随机分布对混凝土导热性能的影响,并讨论了粗骨料粒径、形状及其体积分数,以及分散相导热系数对混凝土导热性能的影响规律.结果表明:粗骨料随机分布是造成混凝土导热性能产生随机性的重要因素;混凝土导热系数相对平均值随着粗骨料体积分数、分散相导热系数的增加而增大,但受粗骨料粒径和形状的影响不大;粗骨料体积分数越高,分散相与水泥砂浆导热系数相差越大,粗骨料粒径越大,轴长比越大,混凝土导热系数的变异性越显著,但当粗骨料体积分数超过35%后混凝土导热系数的变异性基本保持不变.     

严寒地区人体热适应性研究(3):散热器供暖环境下热反应实验研究

为了考察冬季供暖期间室外气温变化时不同室内温度对人体生理反应和心理热反应的影响,在散热器供暖的微气候室中,对受试者的皮肤温度、心率和血压等生理参数进行了测试,并对其热感觉和热舒适等主观热反应进行了问卷调查,研究供暖初期、中期和末期人体生理反应和心理热反应的变化规律。结果表明:随着冬季室外气温的下降,人们会更容易从心理上接受偏冷的环境,对室内温度期望不高,在相同的室内环境中感觉越来越热;相同的室外气温下,随着室内温度的降低,人体的皮肤温度会降低,心率下降;当室外气温下降而室内温度相同时,人体手臂皮肤温度显著升高,心率加快。说明随着冬季供暖期室外气温的逐渐降低,人们对偏冷环境的热适应性增强,这为严寒地区人体心理适应和生理习服提供了证据。     

珠三角区域城市房建工程扬尘排放特征研究

以广州市和佛山市11个房建施工项目为监测对象,以PM2.5和TSP为监测指标进行了为期9个月的监测,监测结果表明:珠三角区域城市房建施工活动所引起的扬尘超标率较低,主要超标部位为施工道路、室内装修和建筑材料堆放场;土方施工并不是房建施工活动的主要产尘源,其主要产尘源为施工道路和材料堆放场;施工区PM2.5和TSP均随空气湿度和地面含水率增加呈下降趋势,施工区PM2.5既受施工活动影响亦受城市大环境的影响,而TSP则主要受施工活动影响,故在评价洒水或喷雾措施的抑尘或降尘效果时宜选TSP。     

2024年3月建筑材料工业景气指数（MPI）

<正>3月份建筑材料工业景气指数2024年3月份建筑材料工业景气指数为128.2点,高于临界点,处于景气区间,比2月份明显回升,但回升幅度不及上年同期。1月、2月为建筑材料市场淡季,建筑材料工业景气指数在临界点以下波动,2月份受春节假期因素影响,出现小幅回落。3月份随着气候、假期等季节性因素变化,下游建筑业、制造业市场逐步启动,建材企业加快恢复生产,建筑材料工业景气指数回升至景气区间。     

水泥混凝土导热性能影响因素及预估模型研究

为提高融冰雪效率,研究具有良好导热性能的混凝土铺面材料,通过试验得出了普通、钢纤维、碳纤维混凝土的配合比,采用热传导仪测定了它们的导热系数λ.系统研究了骨料体积分数、砂率、水灰比、温度、纤维种类和掺量对混凝土导热系数的影响规律,并基于广义灰关联法对各因素进行排序,依据测试结果和影响规律建立了以上3类混凝土导热系数预估模型.结果表明:钢纤维混凝土最适宜作为融冰雪路面材料;纤维种类和掺量对混凝土导热性能起主导作用,骨料体积分数、温度和水灰比的影响次之,砂率的影响最小.     

高层建筑户外景观空间感知机制量化 研究

高层建筑群的兴起为人类景观感知带来了新问题——高层景观，主要是指城市高空的聚居者由建筑或场所之内向外部周围观看引发的景观空间感知。高层景观为人类身心健康带来了新的机遇与挑战，对于聚居者“一览众山晓”的积极作用与远离绿化、缺乏户外活动场地的负面影响并存。然而，迄今关于这种高层景观的人类身心影响研究尚未开展。作为起步性研究，尝试从揭示基本规律着手，选取上海地区相对120m高度上的高层景观，研究面对城市空间、绿地和水景的景观时，个体生理和心理的反应影响：基于阶段性视觉刺激，借助脑电图、心率变异性和皮肤电导测量了20名被试者的压力水平，并使用改进的语义差异问卷评估了其心理反应。结果显示，面对绿色空间和水景的高层景观，会引起α相对波活动增加，使副交感神经活动显著增加，相比面对城市建筑的高层景观，被试者的放松程度更高。此外，相比于面对城市建筑景观，被试者在高层观看绿色景观和水景图像时表现出了更大的舒适感和放松感。这些发现初步揭示了居聚于城市高层建筑中的人类个体关于高层景观感受的基本规律，凸显了为高层聚居个体提供自然景观视觉刺激的重要性。     

A model of human physiology and comfort for assessing complex thermal environments

The Berkeley Comfort Model is based on the Stolwijk model of human thermal regulation but includes several significant improvements. Our new model allows an unlimited body segments (compared to six in the Stolwijk model). Each segment is modeled as four body layers (core, muscle, fat, and skin tissues) and a clothing layer. Physiological mechanisms such as vasodilation, vasoconstriction, sweating, and metabolic heat production are explicitly considered. Convection, conduction (such as to a car seat or other surface in contact with any part of the body) and radiation between the body and the environment are treated independently. The model is capable of predicting human physiological response to transient, non-uniform thermal environments. This paper describes the physiological algorithms as well as the implementation of the model.     

Elevated airflow can maintain sleep quality and thermal comfort of the elderly in a hot environment

The effect of elevated airflow on sleep quality was investigated with 18 elderly. Three airflow conditions were set: ceiling fan/30°C/max.0.8 m/s and mean 0.7 m/s, task fan/30°C/max.0.8 m/s and mean 0.6 m/s, and thermally neutral /27°C/0.2 m/s. Sleep quality was evaluated objectively by analysis of electroencephalogram signals that were continuously monitored during the sleeping period. Urinary cortisol concentrations were analyzed to measure the activity of sympathetic nervous system. No significant difference in sleep quality, thermal comfort, or cortisol concentration was found between the ceiling fan and the neutral condition. The duration of total sleep time decreased by 35 minutes, the duration of REM sleep decreased by 15 minutes, and the cortisol concentration in the morning increased by 50 ng/mL in the task fan than the other two conditions. Compared with ceiling fan, less heat load was removed in the task fan condition, possibly due to the lower air speed. This study shows that even small heat load led to reduced sleep quality and overactive sympathetic nervous system of the elderly. By supplying an airflow of 0.8 m/s evenly over the human body, the elderly could maintain sleep quality and thermal comfort at an air temperature that was 3 K higher than the neutral temperature.     

Using electroencephalogram to continuously discriminate feelings of personal thermal comfort between uncomfortably hot and comfortable environments

Thermal comfort is an important factor for the design of buildings. Although it has been well recognized that many physiological parameters are linked to the state of thermal comfort or discomfort of humans, how to use physiological signal to judge the state of thermal comfort has not been well studied. In this paper, the feasibility of continuously determining feelings of personal thermal comfort was discussed by using electroencephalogram (EEG) signals in private space. In the study, 22 subjects were exposed to thermally comfortable and uncomfortably hot environments, and their EEG signals were recorded. Spectral power features of the EEG signals were extracted, and an ensemble learning method using linear discriminant analysis or support vector machine as a sub-classifier was used to build the discriminant model. The results show that an average discriminate accuracy of 87.9% can be obtained within a detection window of 60 seconds. This study indicates that it is feasible to distinguish whether a person feels comfortable or too hot in their private space by multi-channel EEG signals without interruption and suggests possibility for further applications in neuroergonomics.     

Conduction-corrected modified effective temperature as the indices of combined and separate effect of environmental factors on sensational temperature

In living spaces, people sit or lie on the floor and adopt a posture in which much of the surface of the body is in contact with the floor. When the temperature of the spatial structure or the surface temperature of an object in contact with the human body is not equivalent to the air temperature, these effects are non-negligible. Most research examining the physiological and psychological responses of the human body has involved subjects sitting in chairs. Research that takes into account body heat balance and assessments of thermal conduction into the environment is uncommon. Thus, in this study, conduction-corrected modified effective temperature (ETF), which is a new thermal environmental index incorporating heat conduction, is defined in order to make possible the evaluation of thermal environments that take into account different postures. This sensational temperature index converts the effects of the following parameters into a temperature equivalent: air velocity, thermal radiation, contact material surface temperature and humidity. This index has the features of a summation formula. Through the use of these parameters, it is possible to represent and quantify their composite influence on bodily sensation and the effects of discrete meteorological elements through an evaluation on an identical axis.     

Alpha and beta radioactivity in groundwater of the hickory,mid‐cambrian and ellenburger‐san saba aquifers,central texas,USA

Gross alpha and beta activity in sandstone and limestone aquifers of central Texas locally exceed drinking water standards. The Hickory (sandstone), Mid‐Cambrian (sandstone) and Ellenburger‐San Saba (ESS) (limestone) Aquifers registered median alpha levels of 13, 17 and 4 pCi/l, and median beta levels of 18, 17 and 4.5 pCi/l, respectively. Several observations, 46% (Hickory), 67% (Mid‐Cambrian) and 16% (ESS), exceeded the 15 pCi/l maximum contaminant level (MCL) for alpha activity. Fewer observations, 18% (Hickory), 0% (Mid‐Cambrian) and 10% (ESS), exceeded the 50 pCi/l level of concern for beta activity. There were significant positive correlations between alpha and beta activity in each aquifer, alpha activity and well depth in the ESS Aquifer, and beta activity and well depth in the Hickory and ESS Aquifers. Constituents of sandstone aquifers derived from underlying granite and groundwater moving through weathered zones in granite and overlying shale likely contribute to the radioactivity trends outlined above.     

Thermal and moisture parameters of a dry coarse-grained fill or drainage layer

The thermal conductivity, water vapour permeability, hygroscopic and capillary equilibrium water contents of dry coarse-grained fill and drainage materials are determined by a series of laboratory tests. Test results show that there is a significant difference between the hygroscopic equilibrium moisture contents of the materials and the volumes of water the same material can transport by capillary action. Yet the relative humidity (RH %) is the same in materials either in hygroscopic region or almost fully saturated by capillary action. Therefore the water content is the best indication variable when determining the moisture behaviour of drainage or fill layers next to the foundation or slab structures. In dry conditions the thermal conductivity of coarse-grained drainage materials is significantly lower than the conductivity of moist or wet subsoil layer. In structures where the slab-on-ground structure is built on top of a relatively thick fill or drainage layer, this difference in thermal conductivities between the subsoil and the drainage materials should be taken into consideration when determining the temperature distribution at the fill–slab interface or the heat loss via the ground slab structures.     

我国湿热地区人群基础热舒适反应研究(2):研究结果的对比分析

基于我国湿热地区人群的气候室实验结果,从心理热反应、生理热反应和生理-心理关系等多方面对国内外研究结果进行了系统对比与分析,发现现行国际标准不适用于我国湿热地区,生理热习服和心理热适应是其重要原因。考虑热习服和热适应的影响作用,建立我国湿热地区人群的生理热调节模型与心理-生理模型,是掌握其基础热舒适反应规律、合理制定热环境标准的重要途径。     

基于生理指标评价人体热舒适、工作效率和长期健康的研究路线探讨

分析了人体在热环境中的生理响应机制,综述了国内外基于生理指标的人体热舒适、工作效率和长期健康的研究现状,指出生理指标在评价工作效率和人体健康方面具有重要价值,但对于热舒适研究只能作为一个辅助评价指标,并提出了生理指标在评价热舒适、工作效率和人体健康方面的研究路线。     

局部热舒适性研究现状与展望

本文介绍了局部热舒适性的研究背景和主要进展,主要包括局部环境参数与局部热感觉的关系、局部环境参数与局部生理参数的关系、局部生理参数与局部热感觉的关系、不同部位的热感觉对整体热感觉的影响权重、局部热感觉对整体热反应的影响共5个方面,并且提出了今后的研究方向.