Density and Young׳s Modulus of ternary glasses close to the eutectic composition in the CaO–Al2O3–SiO2-system

The elastic properties and the density of ternary glass forming systems within the CaO–SiO₂–Al₂O₃-system (CAS) were evaluated. Different glass compositions near the lowest eutectic (1170 °C) composition within the CaO–Al₂O₃–SiO₂-system have been melted from pure raw materials. Their target compositions differed not more than 4 wt% for each component. Exact chemical compositions were measured by x-ray fluorescence. The density, and acoustic properties were determined and the Young׳s Moduli were derived herefrom. It was of special interest to obtain information on these properties and their dependencies upon small variations in the composition. The density values were between 2.600 and 2.667 g cm⁻³ and the packing density factors V_p of the oxides glasses using the ionic radii of Pauling were in the range from 0.559 to 0.571. The determined data were compared to different model calculations. Density model calculations show relative deviations between 2 and 6%. The values calculated from the model for Young׳s Modulus by Makishima and Mackenzie (1973) [1] were somewhat smaller than the measured ones. The correction by Rocherulle et al. (1989) [3] of the Makishima model showed better agreement with the measured values.     

Structural explanation on natural draw ratio of metallocene-catalyzed high density polyethylene

The natural draw ratio of metallocen catalyzed high density polyethylenes was investigated with different crosshead speeds, molecular weights, and the cross-section shapes of sample specimens where the elastic components included in the conventional natural draw ratio such as residual strain and elastic aftereffect were eliminated. The perfect plastic deformation took place below a critical crosshead speed, whereas void formation occurred above the critical one. The natural draw ratio without elastic components and void formation was found to be dependent on the molecular weight of samples and the dimension of their specimens. On the basis of the SEM images, we proposed a simple structural model for explaining the necking formation in addition to the molecular weight and the cross-sectional shape dependences of the natural draw ratio.     

PREDICTING THE EFFECTS OF LOAD RATIO ON THE FATIGUE CRACK GROWTH RATE AND FATIGUE THRESHOLD

The effect of the load ratio, R, on fatigue crack growth behaviour is analysed on the basis of the recently proposed inelastic discrete asperities model. A wide range of load ratios, both positive and negative, are examined. Particular emphasis is placed on compressive excursions, i.e. negative R loadings. The inelastic discrete asperities model is a micro-mechanical analysis based on the plastic crushing of a single asperity (or multiple asperities) located on the crack face close to the crack tip and under dominantly plane strain conditions. Experimental data have indicated that the primary crack face contacts which obstruct closure are immediately adjacent to the crack tip, although segments of the crack face more distant from the crack tip are not neglected. However, the more distant asperities are a part of the past crack advance history which does not influence current behaviour. By use of this model, it is shown that the effect of the load ratio can be adequately predicted once some baseline information on mechanical material properties and surface roughness is provided. The model also provides useful trend information and explains many of the observed phenomena, e.g. the ‘saturation’ of the compressive underload effects. For a constant applied nominal stress intensity factor range, ΔK_nom , it is shown that the effective stress intensity factor range, ΔK_eff , initially decreases as the positive R decreases (corresponding to the increasing influence of closure), reaches a minimum around R = 0, and then starts increasing with negative R (corresponding to the plastic crushing of the asperities which reduces closure), eventually reaching a saturation level below ΔK_nom . Conversely, for an assumption of a constant ΔK_eff , the applied ΔK_nom increases as the positive load ratio decreases, reaching a maximum around R = 0, and then decreases with more negative R values, eventually reaching again a saturation level (above ΔK_eff ). It is also shown that the effect of material hardness can be directly analysed based on this model.     

A Review of the Potential for CO2 Sequestration and Enhanced Gas Recovery in an Iranian Gas Condensate Reservoir From a Fluid Properties Point of View

The use of carbon dioxide (CO₂) in enhanced oil recovery is a mature well-practiced technology; however, enhancing gas recovery (EGR) through the injection of CO₂ is yet to be tested in the field. Depleted natural gas or gas condensate reservoirs are becoming important targets for CO₂ injection. The study of injection of CO₂ for EGR needs accurate fluid modeling of CO₂ behavior in the gas reservoir conditions; especially the interaction of CO₂ and reservoir fluid should be taken into account to obtain the best conditions for injection (Oldenburg and Benson, 2001 Oldenburg, C. M. and Benson, S. M. Carbon sequestration with enhanced gas recovery. First National Conference. May14–17, Washington, DC.  [Google Scholar]). The purpose of this study is to evaluate the efficiency of CO₂ injection in one of Iranian gas condensate reservoirs by modeling of reservoir fluid properties and different behaviors of its mixture with CO₂ to have a proper estimation of injection condition and possibility of problems such as gravity segregation, viscous fingering, and liquid drop out at reservoir conditions. PVTi module of Eclipse software was used to perform modeling based on laboratory pressure-volume-temperature analysis of well number X of one of Iranian gas condensate reservoirs.     

Modeling Continuous Powder Mixing by Means of the Theory of Markov Chains

This article demonstrates the efficiency of the application of the theory of Markov chains as a tool to model and simulate continuous powder mixing to aid in better design of such equipment. Markov chain models allow calculating practically all parameters of the process necessary for its characterization, and in particular those related to particle residence time distribution (RTD). Some numerical examples from the model, which are important for better understanding the process, are also included. It is shown that the main factor defining the efficiency of continuous mixing, through the variance reduction ratio (VRR), is the ratio of the mean residence time and the period of inflows fluctuation, rather than the variance of the RTD. Also, the influence of the dimensions of the mixer outlet on the mean residence time, and in turn on the VRR, is examined as another way of improving the design.     

北京市工业用水节水分析及工业产业结构调整对节水的贡献

在分析20世纪90年代北京市工业及主要耗水行业节水特点的基础上,重点研究了产业结构调整对节水的作用,并以定量的形式计算出在不同时间段工业产业结构调整对节水的贡献率。1990—1994年间工业产业结构调整对节水的贡献率为29.5%,1994年以后比重逐渐上升,1998—2000年间比重已达到46.1%,表明1990—2000年间产业结构调整对北京市工业节水的贡献率呈上升趋势。     

Synthetic Effects of Frequency and Duty Ratio on Growth Characteristics,Energy Consumption and Corrosion Properties of Microarc Oxidized Coating Formed on Ti6Al4V

The synthetic effects of frequency and duty ratio on growth characteristics and corrosion properties of coating on Ti6 Al4 V fabricated by microarc oxidation are investigated comprehensively. Under the condition of uniform cumulating time of positive impulse width, the essence of altering frequency and duty ratio to determine the formation of coating is to vary the duration and interval time of positive pulse. The growth of coating is mainly controlled by duration time of positive pulse and hardly correlated to the interval time of positive pulse, while both duration and interval time of positive pulse have few influences on the morphology and phase structures of coating. The dynamic current is related to positive impulse width and the ratio of positive pulse on-time to pulse off-time. Regardless of uniform duration or interval time of positive pulse, the energy dissipation presents a descending tendency. The relationship between energy consumption and anticorrosion performance is contradictory, and obtaining excellent corrosion resistance is bound to sacrifice lots of energy. The duty ratio and frequency can be designed purposefully to realize the optimal process.     

氯氢压差控制系统的可靠性、稳定性探讨

介绍了离子膜法烧碱生产装置中氯氢压差控制系统的控制方案,并对仪表的选型、安装提出了建议和要求。     

聚丙烯纤维网混凝土桥面抗冻性探讨

以聚丙烯纤维网水泥混凝土替代普通水泥混凝土作为桥面铺装材料,可以改善混凝土抗冻性能,并能够利用聚丙烯纤维网良好的性能减轻桥面铺装混凝土在低温作用下的破坏,增加行车的舒适性,延长铺装及桥梁主体的使用寿命。本文对聚丙烯纤维网水泥混凝土桥面铺装的抗冻耐久性进行了试验研究,并对试验结果加以分析。     

数码涡旋多联式空调系统冬季运行特性实测

研究了数码涡旋多联式空调系统的冬季运行状况和节能性能,分析了影响系统小时平均供热性能系数HHPF的主要因素,得到了系统HHPF随室内机开机率、室外环境温度和室内设定温度的变化规律以及数码涡旋多联式空调系统部分负荷运行特性。通过计算每个工况点压缩机运行容量百分比,分析了室内机开机率和室外环境温度对压缩机运行容量百分比的影响。