掺木质素花岗岩残积土的单轴抗压强度特性

将木质素掺入花岗岩残积土,通过击实和单轴压缩试验,对比研究了木质素掺量和含水率变化对土样压实性和单轴抗压强度特性的影响。结果表明:在试验范围内,掺入木质素后,花岗岩残积土土样干密度对含水率的敏感性增大;随着木质素掺量的增加,各土样的最优含水率先降低后升高,最大干密度先增大后减小。随着含水率的减小,花岗岩残积土土样的单轴抗压强度逐渐增大;随着木质素掺量的增加,在较高含水率下,各土样单轴抗压强度总体上呈下降的趋势,在较低含水率下土样的强度得到有效提高。     

福建省典型花岗岩残积土路堤温度场特征研究

采用有限差分法对福建典型花岗岩残积土路堤温度场进行模拟研究。结果表明:路堤浅层温度呈现日周期变化,且滞后于气温,温度最值随深度呈滞后性;福建省四季典型路堤的平均温度分别为33.5℃、44℃、23.5℃、12.5℃,夏季在路堤浅层范围内产生的温度梯度最大,应考虑温度梯度对湿度迁移的影响;压实度越大,温度变化的速率越大;热导率越大,传递速度越快;体积比热容越大,温度变化越慢。     

基于神经网络集成的作物需水量预测

应用神经网络集成模型,以空气湿度、温度、太阳辐射以及风速为输入,利用交叉验证方法确定网络隐层节点数,建立作物需水量的预测模型。实验结果表明,与单个神经网络与随机森林模型相比,神经网络集成模型能获得更好的预测精度,可用于节水灌溉。     

梅州大埔某残积土滑坡力学性质与稳定性评价

梅州地区花岗岩残积土分布广泛,花岗岩残积土滑坡是威胁建筑安全的主要地质灾害,滑坡稳定性评价方法历来是工程地质领域的研究热点.针对这一问题,以梅州大埔某残积土滑坡为例,对该滑坡的土体进行了直接快速剪切试验,获得其强度指标,残积土试样浸水后抗剪强度降低,主要是粘聚力的减小,内摩擦角降幅很小.利用Slide滑坡稳定性计算软件对天然工况、降雨条件、地震条件下的稳定性进行评价.稳定性结果分别为1.101、1.040和1.039,稳定性差.     

容易错解的物态变化七例

1、把0℃的水放在0℃的房间里一定不会结冰吗?分析:我们知道在任何温度下,水都能进行蒸发,如果空气中的水蒸气未达到饱和状态时,单位时间内从水面逸出的分子数多于从空气中回到液面的分子数,由于水的温度又和空气的温度相等(均匀0℃),蒸发时无法从空气中吸热,现在水又处在冰点,温度不可降,只有通过部分水的凝固释放的热量来满足蒸发的需要,所以在一个标准大气压下空气湿度又较小,0℃的水放在0℃的房间里也能够结冰。     

土质文物的风蚀模型

在西北地区寒旱环境条件下,受干湿、冻融、风蚀等自然条件以及人为因素的影响,土质文物逐渐剥落坍塌.在众多破坏因素中,风蚀危害是最严重的因素之一.土质文物本体具有一定的内聚力,表现出不同于散体土壤颗粒的风蚀行为.通过对土壤风蚀影响因素和已有风蚀预测模型的分析,提出了适用于土质文物的风蚀预测模型,研究将土质文物风蚀影响因素分为营力子系统(风力)和响应子系统(粒度、含水率、强度).通过对土质文物风蚀营力子系统和响应子系统的分析,土质文物的风蚀模型应包括风速(V)、土体含水率(W)、粒径(d)和土体强度(F)四个影响因子,根据分析,其甬数形式为E=f(eA0VW1/2d-2F-1).土质文物不同于土壤,在不被植被覆盖、灌溉翻耕的情况下,能够比较客观地反映土质文物受到风蚀的情况.且在对前人风蚀实验数据总结的基础上,提出了风蚀量与风速、风蚀时间、风蚀面积之间的定量关系,可以用于预报一次风蚀事件的风蚀量.     

为什么自来水管会“出汗”？

夏季气温高,大量的水分蒸发为水汽进入空气中,空气的湿度增大。水管中水很凉,使水管本身的温度比环境温度要低。当空气中的水汽接触到温度低的物体时,就会在物体表面冷凝成水珠。水汽的冷凝也叫做液化,是物质从气态转化为液态的过程。烧水的热锅中蒸发出来的水汽,在锅盖上凝结成密集的水珠,也是因为温度较高的水汽接触到了温度较低的锅盖后发生了液化。     

冻融循环作用下冻结冰碛土剪切特性

针对中国西南某高速铁路昌林段沿线冰碛土的特殊环境,通过相似级配法对冻结冰碛土进行固结排水直剪试验,研究冻融循环次数与初始含水率对冻结冰碛土力学性能的影响。结果表明：冻融循环次数是影响冻结冰碛土抗剪强度的重要因素,而初始含水率影响不大;该土样的抗剪强度与冰饱和度密切相关,在初始含水率为8%～12%时存在最大值;冻融循环致使土体强度持续降低,较低初始含水率时的强度损失与冻融次数基本呈线性关系,高初始含水率时前期冻融循环对土体的破坏作用更为明显;2个因素对土体内摩擦角的影响不大,对黏聚力的影响显著。引入综合性参数(K),建立了黏聚力与K值的指数函数模型,回归分析结果表明,该模型能够较好地描述K值与黏聚力之间的关系。     

砂土冻融特性试验研究

为探究外界条件对砂土在冻融过程中的温度及水分迁移的影响,分别控制水分补给状态、冷端温度以及土体的初始含水率进行单因素研究。以顶端单向冻结的方式,对冻融过程中土体不同高度处的温度及含水率进行监测。试验结果表明:随着冻结锋面的下移,温度影响范围内各高度处的温度均有所降低,含水率也呈现出不同程度的减少;高冷端温度冻结下,不同系统状态土样各高度的温度及含水率变化基本一致,水分补给对砂土的水分重分布影响不大;温度对土体的冻深及水分迁移量有显著影响,温度低冻深大,相同高度处的含水率存在差异,温度低水分迁移量大;不同初始含水率冻融后土体温度变化趋势相同,初始含水率本身对土体的水分迁移量不存在影响,但从客观上减缓冻结锋面的推进速度,增大了水分迁移量。     

基于物联网的农业环境数据收集系统设计

设计了基于物联网的农业环境数据收集系统,该系统使用支持向量机回归(SVMR)算法来处理原始数据,并预测日常空气温度、相对空气湿度和风速值,以帮助预测有害病菌在农田的传播。结果表明:预测的平均空气温度值和实际测量值平均绝对误差为1℃;预测的平均相对空气湿度值和实际测量值平均绝对误差为5%;预测的平均风速值和实际测量值平均绝对误差为1 km/h。该系统通过物联网访问环境数据,有助于田间作物管理人员更好地管理和预防病菌蔓延。     

Simplification and Experimental Verification for Temperature and Humidity Field Coupling Model of Conservatory Soil

Based on the surface energy balance model which is widely used abroad, a temperature and humidity field coupling model of conservatory soil without crop vegetation in full illumination was established. Considering the relatively closed environment in conservatory, weak solar radiation and little surface evaporation of soil, the daily variation of water content in different soil layers may be neglected, then the temperature and humidity field coupling model was simplified to a one-dimensional thermal diffusion model. The simplified model and the temperature and humidity field coupling model adopted the same computational method of soil physical parameters and discrete format of heat diffusion differential equations, and were applied to the continuous simulation of temperature field in conservatory soil without crop vegetation in full illumination. Through the comparison between simulation results and experimental data, the precision of the simplified model was verified. The typical rule of soil heat flux variation in a 24 h cycle was also obtained.     

Thermal analyses of combined utilization process of seawater by solar chimney

It is promising to simultaneously develop multiple products through the combined utilization of sea-water by solar chimney technology. A small scale experimental system was set up. The collector temperature, the seawater temperature, and the temperature and humidity of the airflow under the collector were measured. Thermal network analysis of the system was carried out. The results show that the airflow is nearly saturated at the entrance of the chimney, and the mean dry-bulb and wet-bulb temperatures of the airflow have increased by 8.4℃ and 9.6℃ respectively. The radiation heat transfer between the collector and the sky is the biggest heat loss in the system, which is up to 29.1% on average of the solar energy. However, the water evaporation heat is about 23.6% on average of the solar energy. To reduce the heat loss and enhance the water evaporation, it is necessary to reduce the emissivity and thermal conductivity of the collector and increase the evaporation areas.     

Analysis of urban heat island effect using an improved CTTC and STTC model

An improved cluster thermal time constant (CTTC) and surface thermal time constant (STTC) numerical model was introduced,which took into account the effect of vegetation coverage and modified the expression of net longwave radiation of the canyon layer.In the case study the model was used to calculate the air temperature variation at downtown of Tianjin City.The relative error between the calculated and measured air temperatures was less than 3%.The tendency of air temperature variation was predicted when the building aspect ratio,vegetation rate,and wind speed changed respectively.It is demonstrated that when the aspect ratio of a building with south-north orientation increased,the heat island intensity at day time was mitigated; however,it became worse after sunset.The vegetation coverage rate and wind speed both had negative relationship with the urban heat island intensity.     

热气候风洞实验台环境测控系统动态工况误差分析与不确定度评定

探讨了热气候风洞实验台环境测控系统动态工况的误差,对系统各环境参数(温度、湿度、辐射照度和风速)的测量不确定度进行评定。通过分析影响系统控制不稳定的因素,找出其规律性,并给出改善建议。     

Field investigation on effects of wheat-straw/corn-stalk mulch on ecological environment of upland crop farmland

This work systematically investigates the effects of wheat-straw/corn-stalk mulch on the ecological environment in upland crops (winter wheat, summer corn) field from 1997 to 1998. With and without mulch soil moisture distribution, water demand, day and night variation of soil temperature, weeds control, crop yields, water and soil conservation, as well as improvement of soil texture were experimentally investigated. The optimal mulch rate for both water saving and yield-increase was determined. Ineffective interplant evaporation can be turned into effective transpiration of leaf by application of wheat-straw/corn-stalk mulch, which enhances the utility factor of soil moisture and reduces irrigation norm, and may also regulate soil temperature, increase soil fertility, and improve soil texture after being returned to the field. Wheat-straw/corn-stalk mulch inhibits evaporation of moisture so that accumulation of salinity near the soil surface is prevented, and thus ameliorates salinization of land. In the region of severe soil erosion, mulch is used to cover land so as to forestall hydraulic and wind erosion of the soil.     

Study on the Mathematical Model of Hydraulic Jump Atomization

An equation of atomization quantity from energy dissipation by hydraulic jump was derived from the dimensional analysis. By applying Gauss diffusion equation, the spray diffusion rule in valley was studied under the condition of continuous linear source and random wind direction. By considering the spray-rain switching process, coagulation, condensation and evaporation of droplets, the air temperature, air relative humidity,spray density and the rainfall intensity in the lower reaches of the linear source were calculated. The 3-D numerical simulation fitted well with prototype monitoring. Finally, the prediction of atomization influence on environments for Xiangjiaba Hydropower Station was conducted.     

校园不同绿地类型对温湿效应的影响

选择宜春学院校园内的草坪,灌草和乔灌草等绿地类型,利用温湿度表,测量分析各绿地内的温湿度变化和对温湿度影响的差异。乔灌草绿地日温变化较缓,且其日温最高值出现于16点,其它绿地日温变化较大,其日温最高值出现于14点,与大气的日气温高点一致。湿度是由高到低再升高的过程。对于温度,与水泥地相比,乔灌草类的绿地最高温度平均下降了9.4℃,灌草类下降了7.4℃,草坪下降了3℃。对于湿度,与水泥地相比,乔灌草的最低湿度平均增加了24.8%RH,灌草的湿度增加了17.6%RH,草坪增加了10.4%RH。结果表明,草坪型、灌草型和乔灌草型的绿地都有降温增湿的作用,乔灌草类的绿地降温增湿效果最明显。     

基于间接蒸发冷却技术新风换气机的实验

针对室内排风的热回收效率不高的问题,设计了一种基于间接蒸发冷却技术的新回风换气机,采取微雾喷淋方式的水蒸发冷却技术和亲水高分子纤维的芯体,可实现高效热回收。通过建立实验平台,对该新换热气机的换热过程进行了测试分析,结果表明热回收效率高达141%,节能效果显著。     

基于MATLAB和SPSS的空气质量数据建模及分析校准

利用Excel对空气质量国控点与自建点的"两尘四气"浓度日平均数据进行透视分析,得到二者相对应的变化趋势,发现大部分数据波动比较大;再利用SPSS对"两尘四气"数据与风速、压强、降水量、温度、湿度的相关性进行分析,结果表明,PM2.5、PM10与湿度呈中度相关,SO₂与风速、湿度基本不相关;最后以自建点整点时刻"两尘四气"的平均数据与国控点数据的差值为因变量,风速、压强、降水量、温度、湿度为自变量,用MATLAB进行多元线性回归,建立自建点数据的矫正模型,模型校验效果达到预期。