等温容器放气过程FLUENT仿真及其温度变化模型建立

作为国际标准ISO/DIS 6358-3所界定的气动元件流量特性参数的测试仪器,等温容器及其内部的换热过程还需要进一步研究。假设等温容器内部换热介质为多孔介质,应用FLUENT软件对等温容器放气过程进行了仿真。通过仿真和实验的对比,掌握了等温容器放气过程中容器内部的压力、流速和温度变化趋势。通过电模拟的方法,初步建立了等温容器内部压缩气体在压力不断变化时的温度变化模型。

极轨卫星热红外地表温度日变化模拟

针对极轨卫星热红外数据不能提供地表温度日变化信息的问题,从热传导方程出发,提出了一个三参数地表温度日变化模型。该模型利用中分辨成像光谱仪MODIS获取的一天4次观测数据,通过最小二乘拟合方法,实现了地表温度日变化的模拟。研究结果表明,该模型应用于MODIS数据时,可以很好地模拟一天中地表温度随时间的变化。为了评估地表温度日变化模型的模拟精度,进一步将该模型应用于可旋转增强的可见光和红外成像光谱仪SEVIRI数据。结果表明,模型模拟精度的直方图峰值位于1.2K左右,大部分像元的模型模拟精度都优于3K。

黄河源区不同植被类型覆盖下季节冻土冻融过程中的土壤温湿空间变化

在对不同植被覆盖度(95%,70%～80%,40%～50%和10%)下的土壤水分(θ_V)和土壤温度(T_s)进行日观测的基础上,研究了冻融过程中植被覆盖变化对土壤水分分布和温度的影响.土壤温度与水分关系的回归分析表明:土壤冻融过程明显受植被覆盖变化的影响,植被覆盖变化还导致土壤水分和温度的耦合变化.使用了一个土壤水分和温度的耦合模型来研究植被覆盖的影响,结果证明了这一方法的有效性.结果表明:土壤水分对土壤温度的变化范围和幅度都有影响,高盖度下的土壤比低盖度土壤持水性强.此外,在冻结过程中,由于水的热容量大于土壤的,高盖度土壤能够抑制土壤温度的降低幅度,高盖度土壤具有较好的绝热功能.对于黄河源区不同植被类型覆盖下季节冻土冻融过程中的土壤温湿空间变化研究有利于为高寒冻土地区冻土和生态环境的保护及合理利用提供科学依据.

基于微分方程的回焊炉焊接区域温度分析

为确保电子集成产品的自动焊接质量,通过机理分析,建立相关数学模型对回焊炉焊接区域温度进行研究。首先确立一维热传导方程,据此给出回焊炉的稳态温度分布函数;再由热传导方程,配设初始条件和边界条件,建立焊接区域的偏微分方程模型,并利用有限差分法将其转化为差分格式,从而可用追赶法求出炉温曲线;为了对差分格式的参数进行估计,引入最小二乘法思想,采用变步长穷举搜索确定参数;当发现误差较大时,对模型进行修正,并得到满意结果。

地表温度日变化模型偏差系数解算的地表温度降尺度

地表温度LST(Land Surface Temperature)是全球气候变化研究的关键参数,遥感是获取全球和区域尺度地表温度的一种切实可行手段,但现有的单一传感器无法提供高时空分辨率的LST数据,限制了遥感地表温度数据的深入广泛应用。现有的降尺度方法难以生成无缝高时空分辨率的地表温度数据,且降尺度效果易受高空间分辨率LST数据缺失及有效时刻分布影响。本文提出了一种基于地表温度日变化模型DTC(DiurnalTemperature Cycle)偏差系数解算的地表温度降尺度方法,采用FY-4A、MODIS和Landsat 8的LST数据生成晴空及多云条件下逐小时100 m的无缝LST数据。方法主要包含4部分:(1)利用空值重建方法获取无缝的FY-4A的LST数据;(2)建立FY-4A LST数据的DTC模型;(3)采用时空融合模型对MODIS的LST数据进行空间降尺度;(4)解算DTC模型偏差系数,获取逐小时100 m分辨率的无缝LST数据。实验结果表明,本文提出的方法具有较高的降尺度精度,可获得晴空及多云条件下无缝高时空地表温度数据,且高空间分辨率的地表温度数据缺失和有效时刻分布对本文方法降尺度结果影响较小。

Coupled effect of cement hydration and temperature on rheological properties of fresh cemented tailings backfill slurry

The fluidity of fresh cemented tailings backfill（CTB） slurry depends on its rheological properties. Hence, it is crucial to understand the rheology of fresh CTB slurry, which is related to the cement hydration progress and temperature evolution within CTB mixtures. For this reason, a numerical model was developed to predict the evolution of the rheological properties of fresh CTB slurry under the coupled effect of cement hydration and temperature. Experiments were conducted to investigate the rheological behaviours of the fresh CTB slurry. By comparing the simulated results with the experimental ones, the availability of this developed model was validated. Thereafter, the model was used to demonstrate the coupled effect of cement hydration and temperature on the evolution of fresh CTB slurry＇s rheological properties, under various conditions（initial CTB temperature, cement to tailings ratio, and water to cement ratio）. The obtained results are helpful to better understanding the rheology of CTB slurry.

隔热专用服装相关问题研究

隔热专用服装通常由三层特殊材料制成,将服装与人体时间的间隙看做第四层,即假设此类服装共有四层。它可以有效避免被高温工作环境灼伤。因此,研究高温条件温度的分布对设计隔热专用服装具有重要意义。建立高温作业专用服装在热传导过程中多层温度变化模型,并利用此模型设计最优的织物材料厚度。

Changes in surface air temperature over China under the 1.5 and 2.0 ℃ global warming targets

This study investigated the projected changes in the annual mean surface air temperature （SAT） over China under the 1.5 and 2.0 ℃ targets, by analyzing the outputs from 22 models of the Coupled Model Intercomparison Project Phase 5. Under the 1.5 ℃ target, the scope of changes in the average SAT over China is quite narrow and has the largest probability to increase by 1.7-2.0 ℃ under the various RCP pathways, although the time of occurrence of the 1.5 ℃ target has a large spread of 40-60 years. Similarly, the models consistently show that the average SAT over China would most likely increase by 2.4-2.7 ℃ under the 2.0 ℃ target. Furthermore, the warming shows a clear spatial distinction over China： being stronger in the northwest part and weaker in the southeast part. Under all RCP pathways, the SAT over the northwest part would increase by 1.9-2.1 ℃ for the 1.5℃ target, which is much stronger than the SAT increase over the southeast part （1.3-1.5 ℃）. A similar spatial pattern appears for the 2.0 ℃ target.

Health monitoring and comparative analysis of time-dependent effect using different prediction models for self-anchored suspension bridge with extra-wide concrete girder

The structural health status of Hunan Road Bridge during its two-year service period from April 2015 to April 2017 was studied based on monitored data.The Hunan Road Bridge is the widest concrete self-anchored suspension bridge in China at present.Its structural changes and safety were evaluated using the health monitoring data,which included deformations,detailed stresses,and vibration characteristics.The influences of the single and dual effects comprising the ambient temperature changes and concrete shrinkage and creep(S&C)were analyzed based on the measured data.The ANSYS beam finite element model was established and validated by the measured bridge completion state.The comparative analyses of the prediction results of long-term concrete S&C effects were conducted using CEB-FIP 90 and B3 prediction models.The age-adjusted effective modulus method was adopted to simulate the aging behavior of concrete.Prestress relaxation was considered in the stepwise calculation.The results show that the transverse deviations of the towers are noteworthy.The spatial effect of the extra-wide girder is significant,as the compressive stress variations at the girder were uneven along the transverse direction.General increase and decrease in the girder compressive stresses were caused by seasonal ambient warming and cooling,respectively.The temperature gradient effects in the main girder were significant.Comparisons with the measured data showed that more accurate prediction results were obtained with the B3 prediction model,which can consider the concrete material parameters,than with the CEB-FIP 90 model.Significant deflection of the midspan girder in the middle region will be caused by the deviations of the cable anchoring positions at the girder ends and tower tops toward the midspan due to concrete S&C.The increase in the compressive stresses at the top plate and decrease in the stresses at the bottom plate at the middle midspan will be significant.The pre-deviations of the towers toward the sidespan and pre-lift of the midspan girder can reduce the adverse influences of concrete S&C on the structural health of the self-anchored suspension bridge with extra-wide concrete girder.

Design and control of a p-xylene oxidation process

The p-xylene(PX) oxidation process is of great industrial importance because of the strong demand of the global polyester fiber.A steady-state model of the PX oxidation has been studied by many researchers.In our previous work,a novel industrial p-xylene oxidation reactor model using the free radical mechanism based kinetics has been developed.However,the disturbances such as production rate change,feed composition variability and reactor temperature changes widely exist in the industry process.In this paper,dynamic simulation of the PX oxidation reactor was designed by Aspen Dynamics and used to develop an effective plantwide control structure,which was capable of effectively handling the disturbances in the load and the temperature of the reactor.Step responses of the control structure to the disturbances were shown and served as the foundation of the smooth operation and advanced control strategy of this process in our future work.

风云静止卫星地表温度产品空值数据稳健修复

静止卫星地表温度数据是研究昼夜气候和环境变化的重要参数。但现有发布的静止卫星地表温度数据由于受到云等大气因素的影响,往往出现数值缺失现象。针对该问题,提出基于昼夜变化模型的风云静止卫星地表温度空值数据的稳健修复方法。由多项式、傅里叶函数和高斯函数构建新的昼夜变化模型,并利用LevenbergMarquardt算法进行模型参数的求解与优化,进而实现空值修复。以风云2号F星数据(FY-2F)为例,模拟不同类型的像元缺失情况进行修复,并将不同模型修复结果与真实温度值比较,同时也对真实数据进行了测试。结果表明:本文提出的修复方法能有效对温度空值数据修复,且优于传统方法。

航空遥感地表温度时间归一化

航空热红外遥感影像的航带宽度一般较为有限,通常需要进行连续飞行获得多个航带才能覆盖一个较大的研究区;由于地表温度随时间变化迅速,不同航带间地表温度存在差异。因此,进行不同航带影像拼接之前,需要对不同航带的地表温度进行时间归一化。本文基于温度日变化模型,构建了航空遥感地表温度时间归一化方法;结合Hi WATER试验区高密度的气象观测数据,分析了天气晴朗条件下,风速的大小和波动剧烈程度对地表温度日变化模型的影响,在此基础上发展了一种考虑风速影响的改进温度日变化模型。验证结果表明:两种模型均能够减小观测时间不同导致的地表温度瞬时波动差异;考虑风速影响的改进模型比未改进模型的精度提高0.3—0.6 K,且其提供的地表温度在时间尺度变化上更加符合实际情况。本研究建立的相关模型对于卫星遥感地表温度的时间归一化也具有借鉴意义。

Transport properties,upper critical field and anisotropy of Ba(Fe_(0.75)Ru_(0.25))_2As_2 single crystals

The temperature and angle dependent resistivity of Ba(Fe 0.75 Ru 0.25) 2 As 2 single crystals were measured in magnetic fields up to 14 T.The temperature dependent resistivity with the magnetic field aligned parallel to c-axis and ab-planes allow us to derive the slope of dH ab c2 /dT and dH c c2 /dT near T c yielding an anisotropy ratio Γ = dH ab c2 /dT/dH c c2 /dT ≈ 2.By scaling the curves of resistivity vs.angle measured at a fixed temperature but different magnetic fields within the framework of the anisotropic Ginzburg-Landau theory,we obtained the anisotropy in an alternative way.Again we found that the anisotropy(m c /m ab) 1/2 was close to 2.This value is similar to that in Ba0.6K0.4Fe2As2(K-doped Ba122) and Ba(Fe 0.92 Co 0.08) 2 As 2(Co-doped Ba122).This suggests that the 3D warping effect of the Fermi surface in Ru-doped samples may not be stronger than that in the K-doped or Co-doped Ba122 samples,therefore the possible nodes appearing in Ru-doped samples cannot be ascribed to the 3D warping effect of the Fermi surface.

Modeling of growth stress gradient effect on the oxidation rate at high temperature

A new oxidation kinetics model is established for high-temperature oxidation. We assume that the interface reaction is fast enough and the oxidation rate is controlled by diffusion process at high temperature. By introducing the growth stress gradient we modify the classical oxidation parabolic law. The modified factor of the oxidation rate constant is a function of growth strain, environment oxygen concentration, and temperature. The modeling results show that the stress gradient effect on the oxidation rate cannot be ignored. Growth strain will dominate whether the stress gradient effect promotes or slows down the oxidation process. The stress gradient effect becomes weaker at higher temperature. This effect is amplified at higher concentrations of environmental oxygen. Applied mechanical loads do not affect the oxidation rate. This model is available for high temperature oxidation of metals and alloys.

Reducing the climate shift in a new coupled model

Climate drift refers to spurious long-term changes that may be inherent in coupled models when external forcing factors are fixed. Understanding the sources of this drift and tuning the drift are crucial for obtaining reasonable simulations from coupled models. To prepare for the upcoming Coupled Model Intercomparison Project Phase 6, a new coupled model has been constructed based on the Community Earth System Model and the Grid-point Atmospheric Model of IAP LASG version 2. However, the surface temperature predicted by the new model is too underestimated, and this underestimation is caused by a type of climate drift, i.e., ‘‘initial shock.'' This study analyzes the source of the cold surface temperature from the perspective of energy balance and attempts to reduce the surface temperature drift by tuning the relative humidity threshold for low cloud.