Theoretical modeling of the effects of temperature and moisture content on the acoustic velocity of Pinus resinosa wood

To investigate the effects of temperature and moisture content(MC) on acoustic wave velocity(AWV)in wood,the relationships between wood temperature,MC,and AWV were theoretically analyzed.According to the theoretical propagation characteristics of the acoustic waves in the wood mixture and the differences in velocity among various media(including ice,water,pure wood or oven-dried wood),theoretical relationships of temperature,MC,and AWV were established,assuming that the samples in question were composed of a simple mixture of wood and water or of wood and ice.Using the theoretical model,the phase transition of AWV in green wood near the freezing point(as derived from previous experimental results) was plausibly described.By comparative analysis between theoretical and experimental models for American red pine(Pinus resinosa) samples,it was established that the theoretically predicted AWV values matched the experiment results when the temperature of the wood was below the freezing point of water,with an averageprediction error of 1.66%.The theoretically predicted AWV increased quickly in green wood as temperature decreased and changed suddenly near 0 °C,consistent with the experimental observations.The prediction error of the model was relatively large when the temperature of the wood was above the freezing point,probably due to an overestimation of the effect of the liquid water content on the acoustic velocity and the limited variables of the model.The high correlation between the predicted and measured acoustic velocity values in frozen wood samples revealed the mechanisms of temperature,MC,and water status and how these affected the wood(particularly its acoustic velocity below freezing point of water).This result also verified the reliability of a previous experimental model used to adjust for the effect of temperature during field testing of trees.

Low-temperature alteration of oceanic island basalts and their contribution to transition metal circulation of the ocean

The major elements, rare earth elements （REE） and trace elements of four basalt samples from central and western Pacific ferro- manganese crust provinces have been analyzed using chemical methods and ICP - MS, respectively. The results indicate that the samples have been extensively altered and that the contents of their major elements have changed significantly. However, the similarity of REE partition patterns and trace element contents of basalt samples to those of fresh oceanic island basalts （OIB） indicate that the basalt samples originated as OIB. Because of low-temperature alteration, the contents of A1203 , Fe203 , MnO, K20 and P205 increased, while MgO and FeO decreased. Active components, such as magnesium and iron, were leached from OIB resulting in the relative enrichment of SiO2. The leaching of active components can cause the relative enrichment of REE, while the precipitation of LREE-rich ferromanganese oxides in vesicles and fissures not only causes an increase of REE contents, but also induces ＂fractionation＂ of LREE and HREE. Based on the enrichment mechanism of REE contents, the theoretical quantities of precipitated ferromanganese oxides and the depleted quantities of active components are calculated ： the depleted quantities of active components for the unit mass of fresh basalts vary in the range of 0.15 ～ 0. 657, and the precipitated quantities of ferromanganese oxides for the unit mass of fresh basahs vary in the range of 0. 006 ～ 0. 042. Of the major elements, the two most depleted are iron, and magnesium, with 18.28% ～ 70.95% of iron and 44.50% ～ 93.94% of magnesium in the fresh basalts was leached out. Theoretical calculation and geochemistry results both indicate that low-temperature alteration of basalts can supply abundant amount of metals to seawater, and may play an important role in ocean metal circulation.

Theory and Application of Numerical Simulation of Chemical Flooding in High Temperature and High Salt Reservoirs

Applications, theoretical analysis and numerical methods are introduced for the simulation of mechanical models and principles of the porous flow in high temperature, high salt, complicated geology and large-scale reservoirs in this paper. Considering petroleum geology, geochemistry, computational permeation fluid mechanics and computer technology, we state the models of permeation fluid mechanics and put forward a sequence of implicit upwind difference iteration schemes based on refined fractional steps of the upstream, which can compute the pressures, the saturation and the concentrations of different chemistry components. A type of software applicable in major industries has been completed and carried out in numerical analysis and simulations of oil extraction in Shengli Oil-field, which brings huge economic benefits and social benefits. This software gives many characters: spatial steps are taken as ten meters, the number of nodes is up to hundreds of thousands and simulation time period can be tens of years and the high-order accuracy can be promised in numerical data. Precise analysis is present for simplified models of this type and that provides a tool to solve the international famous problem.

Improvements on Calculation Model of Theoretical Combustion Temperature in a Blast Furnace

On the basis of the existing originally modified calculation models of theoretical combustion temperature（TCT）,some factors,such as the combustion ratio of pulverized coal injection（PCI）,the decomposition heat of PCI and the heat consumption of SiO2 in ash reduced in high temperature environment,were amended and improved to put forward a more comprehensive model for calculating TCT.The influences of each improvement on TCT were studied and the results were analyzed compared with those of traditional model and originally modified model,which showed that the present model could reflect the thermal state of a hearth more effectively.

A Modified Model for Calculating Theoretical Flame Temperature in Blast Furnace and Its Application

The theoretical flame temperature （TFT） before tuyere, always highly concerned by blast furnace （BF） operators, is one of the most important parameters for evaluating the thermal state of hearth. However, some influ- encing parameters, for example, the SiO2 reduction by carbon, were always neglected or inaccurate when calculating the TFT. According to the definition of TFT, the temperature of coke into raceway and the reduction rate of SiO2 in ash of coke and pulverized coal were obtained by analyzing the samples before tuyere in blast furnace. Taking full ac- count of different factors, a modified model for calculating the TFT in blast furnace was established. The effects of the oxygen enrichment rate, the reduction rate of SiO2 in raceway, the ash content in coke and pulverized coal and the pulverized coal injection （PCI） rate on TFT were determined quantitatively. The modified model was applied to selecting the used coal for PCI in blast furnace. Considering the different SiO2 contents of mixed coal, the calculated TFT remained a stable level. This showed that the selected coal could be suitable for PCI in blast furnace.

Prediction of the theoretical and semi-empirical model of ambient temperature

It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowl- edge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during mea- surement. The ambient temperature over time is modeled based on the previous Train and Tmax data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.

Sampling efficiency of a polyurethane foam air sampler:Effect of temperature

Effective monitoring of atmospheric concentrations is vital for assessing the Stockholm Convention's effectiveness on persistent organic pollutants(POPs).This task,particularly challenging in polar regions due to low air concentrations and temperature fluctuations,requires robust sampling techniques.Furthermore,the influence of temperature on the sampling efficiency of polyurethane foam discs remains unclear.Here we employ a flow-through sampling(FTS)column coupled with an active pump to collect air samples at varying temperatures.We delved into breakthrough profiles of key pollutants,such as polycyclic aromatic hydrocarbons(PAHs),polychlorobiphenyls(PCBs),and organochlorine pesticides(OCPs),and examined the temperature-dependent behaviors of the theoretical plate number(N)and breakthrough volume(VB)using frontal chromatography theory.Our findings reveal a significant relationship between temperature dependence coefficients(K_(TN),K_(TV))and compound volatility,with decreasing values as volatility increases.While distinct trends are noted for PAHs,PCBs,and OCPs in KTN,KTV values exhibit similar patterns across all chemicals.Moreover,we establish a binary linear correlation between log(V_(B)/m^(3)),1/(T/K),and N,simplifying breakthrough level estimation by enabling easy conversion between N and VB.Finally,an empirical linear solvation energy relationship incorporating a temperature term is developed,yielding satisfactory results for N at various temperatures.This approach holds the potential to rectify temperature-related effects and loss rates in historical data from long-term monitoring networks,benefiting polar and remote regions.

氟金云母陶瓷材料铣削温度预测模型及试验研究

为了研究铣削的主要工艺参数中铣削速度、每齿进给量、铣削宽度和铣削深度对氟金云母陶瓷材料铣削过程中的温度影响,对铣削过程中热量的来源进行分析。通过热源法建立铣削面热源对已加工表面传热的温度数学模型,并优化热量分配比例系数,使数学模型的计算误差减小;设计单因素试验分析主要工艺参数对氟金云母陶瓷的铣削温度影响规律,发现在参数范围内铣削温度均随着加工参数的增大而增大。最后将温度数学模型计算的理论值与试验值进行对比以验证结果的一致性,并发现两者之间的误差在1~11℃之间,均在合理误差范围内。

基于理论域框架的麻醉复苏期体温管理实施障碍因素分析

目的:基于理论域框架探讨麻醉复苏期医护人员体温管理行为的障碍因素,旨在为探索术后体温管理策略提供依据。方法:采用现象学方法,依据理论域框架设计访谈提纲,对13名医护人员进行访谈,采用类属分析法对访谈资料进行整理和分析。结果:影响麻醉复苏期体温管理行为的理论域有知识、社会/职业角色及认同、环境和资源、社会影响、行为规范5项,主要表现为医护人员对体温管理了解不全面、体温管理意识薄弱、麻醉复苏室人力及设备紧缺、组织氛围不良导向、流程及具体措施不具象。结论:影响麻醉复苏期体温管理实施的障碍因素多样,本研究归纳的5项内容可作为改进目标,管理者应探索术后体温管理策略和实施方案以促进体温管理质量改进。

寒区隧道洞口空气幕温度场理论分析

为研究寒区隧道洞口空气幕保温技术的可行性,采用流体力学原理、叠加原理和贝塞尔特征函数等方法,构建完整的寒区隧道洞口空气幕温度场的理论体系。通过数值模拟,验证该保温技术的可行性,总结该保温技术的保温原则。结果表明:理论计算结果和数值计算结果较为接近,空气幕保温技术可有效防止隧道冻害;空气幕保温技术的保温原则可总结为加热为主,隔风为辅。研究成果可为今后的工程实践提供理论基础。

R134a制冷机组中压缩机和回热器性能的试验研究

为研究R134a制冷机组中压缩机和回热器运转性能,以制冷机组运行压比为调节变量,使用压缩机排气温度、功耗、等熵效率、机组制冷量及系统能效比COP为评价指标,采用单一变量法对两元件运转性能进行测试。试验运行中,主要通过控制制冷机组蒸发温度、冷凝温度实现压缩机压比的调节。结果表明:压缩机排气温度、功耗随压缩机压比的增加而增大,机组制冷量、COP及压缩机等熵效率随压缩机压比的增加而减小;压缩机功耗与蒸发温度呈负相关,而其他性能指标与蒸发温度呈正相关。根据试验数据揭示压缩机等熵效率与压缩机压比之间的内在联系,所获取模型可实现压缩机等熵效率的高精度预测,预测平均误差约为0.45%。基于试验数据对比分析了回热器应用前后压缩机功耗、机组性能的变化趋势,除回热器在低压比工况下可明显提升机组制冷量外,在大部分工况下回热器可通过降低压缩机功耗提升机组整体性能。

复叠式空气源高温热泵蒸汽系统性能的理论研究

通过复叠式空气源高温热泵和机械蒸汽压缩系统耦合,构建一种可以供应高温高压蒸汽并实现制冷效果的热泵蒸汽系统。该系统以R410A、R245fa和R718分别作为系统低温、高温和机械蒸汽压缩循环的工质,并在系统中采用补液和喷水降温的方式提升系统性能。理论研究表明:随着R410A冷凝温度的升高,系统的制热量、制冷量和功耗都降低,而制热性能系数(COP)、制冷COP和总COP先升高后降低。当蒸发温度为20℃,饱和蒸汽温度为160℃时,系统的制热COP为1.49,总COP达到2.35。这表明该系统同时供应蒸汽和制冷时,性能优于采用电锅炉供热和空调制冷,可以助力工业领域的节能降碳。

考虑温度变化下三层复合衬垫中重金属污染物一维运移理论模型

针对考虑温度变化下由土工膜(geomembrane,简称GM)+土工复合膨润土衬垫(geosynthetic clay liner,简称GCL)+压实黏土衬垫(compacted clay liner,简称CCL)组成的3层复合衬垫中重金属污染物一维运移问题,基于相关假定发展得到了热传导与重金属污染物运移的控制方程,并建立了相应理论模型。通过有限差分,对所建理论模型进行了数值求解。随后,开展了与试验结果、解析解计算结果以及其他数值解计算结果的对比分析,验证了该模型的合理性。最后,以Cd^(2+)为例,分析和讨论了不同因素对运移规律的影响。结果表明,上部温度升高会使复合衬垫中Cd^(2+)的运移通量和底部浓度增大,但会使其上部浓度降低。热扩散效应对运移行为的影响会随Soret系数ST的增大而变显著,当ST为0.001、0.005、0.01、0.05、0.1 K^(-1)时,所定义的击穿时间tb依次为37.9、37.2、36.4、31.2、26.5 a。GCL和CCL最大吸附量的增大均会使t_(b)近似线性增加,且在一定渗沥液水头h_(b)下,t_(b)随GCL和CCL厚度的增大呈线性增大趋势。此外,当h_(b)从0.5m增大到1.0m时,t_(b)平均降低了8.33 a。在工程实践中,可结合GCL和CCL的吸附性能和厚度来设计复合衬垫,同时应考虑温度变化对阻隔效果的影响。

首钢股份3号高炉高富氧冶炼实践

对首钢股份3号高炉高富氧冶炼实践进行了总结。3号高炉富氧率由4.74%逐步提高到6.73%,对理论燃烧温度、炉腹煤气量、煤气流分布、煤气利用率等参数的影响较大。为此,操作上进行了相应调整,通过采取管控原燃料质量、调整装料制度、优化送风制度、调控热制度及改善出铁操作等措施,理论燃烧温度维持在2100℃左右,炉腹煤气量指数控制在60.5~62.5m/min,煤气利用率提高至50.7%左右。3号高炉主要技术经济指标稳步改善,利用系数最高达到2.54V(m^(3)·d),焦比降至320kg/t。

催化裂解装置液化石油气分离系统脱丙烷方案优化

随着催化裂解装置裂解深度的增加,液化石油气中二烯烃含量增加。液化石油气分离常规流程中脱丙烷塔底温度约108℃,较高的温度增加了二烯烃聚合的可能性,影响装置运行周期和经济效益,国内几家催化裂解液化石油气分离装置的脱丙烷塔普遍存在塔釜和重沸器结焦堵塞的情况。在实际生产中为了缓解脱丙烷塔底结焦引起的停工等问题,通常在进料和塔底物料中加入阻聚剂,以降低物料聚合速率。文中分析了压力对脱丙烷体系相对挥发度和塔底温度的影响,得出较低的塔压有利于降低塔釜温度、提高轻重关键组分的相对挥发度,使分离更容易。塔压在0.9~1.1 MPa范围内较为合适,可将塔釜温度控制在80℃以下,在满足脱丙烷塔分离要求的前提下,减少因塔釜结焦造成的装置非计划停工。另外,文中从能耗和设备投资两方面对优化方案和常规方案进行了对比,优化方案能耗比常规方案降低约37%,主要设备投资也比常规方案低。

基于热阻法的多层热障涂层叶片隔热预测模型研究

为实现有热障涂层(TBCs)的叶片表面温度预测,开展基于热阻法的热障涂层隔热理论分析,建立了TBCs隔热理论模型,模型包括有热障涂层叶片表面温度预测式(VT-TBCs)和热障涂层隔热温度预测式(IT-TBCs),并分别基于IT-TBCs和仿真分析了陶瓷层(TC)、粘结层(BC)的厚度、导热系数对隔热温度的影响。结果表明:与数值仿真结果相比,VT-TBCs的计算结果最大误差不超过3%,平均误差为0.65%。通过IT-TBCs分析可知,导热系数小于0.5 W(/m·K)时,热障涂层厚度与隔热温度趋近对数关系,当导热系数大于0.5 W(/m·K)时,热障涂层厚度与隔热温度趋近线性关系,BC层的导热系数与厚度对隔热温度基本无影响。仿真分析结果与IT-TBCs分析结果一致。

催化材料调控室温钠硫电池性能的进展与挑战

室温钠硫电池因理论能量密度高(1274 Wh/kg,基于硫的质量)、资源丰富、价格低廉等优势,在大规模储能、动力电池领域备受青睐。然而,要实现Na-S电池中良好的可逆性、可循环性、活性物质高利用率,最终实现钠硫电池的商业化仍然极具挑战性。不仅需要解决多硫化物溶解和循环过程中的多硫化物“穿梭效应”问题,还要解决因S_(8)和Na_(2)S的低电导率和固体Na_(2)S_(2)/Na_(2)S沉积带来的高极化所导致的循环性能差和存在的安全隐患等问题。因此合理引入催化材料促进多硫化物的快速转化,加快反应动力学至关重要,也是实现室温钠硫电池商业化应用的关键所在。本文详细综述了室温钠硫电池的基本原理、存在的主要问题,并阐述了催化作用在室温钠硫电池中的重要意义;归纳了室温钠硫电池中常用的催化材料种类;总结了各种催化材料与多硫化物之间的相互作用机理。最后,对室温钠硫电池中催化材料相关研究可能面临的挑战和未来发展方向进行了预测。

富氧率提升下的钒钛矿高炉冶炼

对承德钒钛某2500 m3高炉提高富氧率的生产实践进行了总结,系统地分析了富氧率提高对钒钛矿高炉冶炼生产的影响。高炉提富氧后,在相同的w[Si+Ti]条件下,理论燃烧温度有所提高,降低w[Si+Ti]仍能保证铁水有充足的物理热;通过合理配煤,炉况更容易稳定,在铁水温度不变的前提下,更适合于低w[Si+Ti]冶炼。根据研究结果,从高炉工艺操作制度、理论燃烧温度控制、高富氧条件下生产组织优化以及提高富氧对炉缸活跃程度的影响等方面入手,研究了钒钛矿冶炼高炉长期保持高富氧率的工艺操作方法。通过对装料制度、送风制度以及喷煤工艺的优化调整以及加强炉前管理等一系列措施,实现了钒钛矿高炉冶炼在高富氧条件下的长周期稳定生产,钒回收率与以往相比显著提高。

钒钛矿冶炼高炉鼓风加湿系统

针对钒钛磁铁矿高炉冶炼以及所处北方高炉的生产环境特点,分析了冷风中湿分对高炉风口前理论燃烧温度的影响,以及控制理论燃烧温度在钒钛磁铁矿高炉冶炼过程中的重要性,确定了高炉冷风恒湿的冶炼手段,并对风口前理论燃烧温度的传统经验计算公式进行了优化。根据优化后的理论燃烧温度计算公式,在实际生产中通过对高炉冷风湿度、大气湿度及其他相关参数的跟踪统计,研究了鼓风湿分与理论燃烧温度及各鼓风参数的对应关系,在此基础上对1250 m^(3)钒钛矿高炉风口前理论燃烧温度以及高炉鼓风加湿量做出正确调剂控制,并且在冷风恒湿的基础上,通过对风口前理论燃烧温度的灵活控制,使炉内温度分布区间更加合理、稳定,达到优化炉缸煤气流初始分布和调整、稳定炉身煤气流通道的目的,使钒钛矿高炉在对待生产外围条件的变化上有了更强的抗风险能力,为提高钒钛磁铁矿高炉冶炼强度、稳定炉况趋势、确保高炉长周期稳定顺行增加了调节手段。

高温高压下CO_2在水中溶解度实验及理论模型

利用自行研制的高温高压反应釜,在不同温度、压力和矿化度条件下测试CO2在地层水中的溶解度。实验结果表明:温度一定的条件下,CO2在水中的溶解度随压力的增加而增加;压力一定的条件下,CO2在水中溶解度的主要变化趋势为随温度的增加而降低,当温度大于100℃、压力在22 MPa左右时,CO2在地层水中的溶解度将发生异常,出现低压(小于22 MPa)时随温度的增加而降低,高压(大于22MPa)时随温度的增加而略微升高;在温度压力都一定的条件下,CO2在水中的溶解度随矿化度的增加而降低。并且,在新测得的实验数据和已有的实验数据的基础上,通过修正PR-HV状态方程中的参数,建立了一个能够精确计算CO2在水中溶解度的模型;并将该模型与其他模型对比。对比结果表明,该模型计算精度最高,平均相对误差仅为2.69%。