Onset of slugging criterion based on characteristics and stability analyses of transient one-dimensional two-phase flow equations of two-fluid model

A two-step approach has been used to obtain a new criterion for the onset of slug formation: (1) In the first step, a more general expression than the existing models for the onset of slug flow criterion has been derived from the analysis of singular points and neutral stability conditions of the transient one-dimensional two-phase flow equations of two-fluid model. (2) In the second step, introducing simplifications and incorporating a parameter into the general expression obtained in the first step to satisfy a number of physical conditions a priori specified, a new simple criterion for the onset of slug flow has been derived. Comparisons of the present model with existing models and experimental data show that the present model agrees very closely with Taitel & Dukler's model and experimental data in horizontal pipes. In an inclined pipe (θ = 50°), however, the difference between the predictions of the present model and those of existing models is appreciably large and the present model gives the best agreement with Ohnuki et al.'s data.     

Polycyclic Aromatic Hydrocarbons in Sediments of the Southern Basin of Lake Michigan

The southern basin of Lake Michigan is receiving polycyclic aromatic hydrocarbon (PAH) inputs from many sources. An investigation of parent PAH compounds in sediments from different depositional zones revealed concentrations ranging from 0.2–6.2 μg/g dry sediment weight. The distribution of the parent PAH is distinctive of high temperature combustion sources. PAH alkyl homolog analyses showed the presence of several highly alkylated PAHs, such as retene, indicating possible inputs from paper industries, and alkylated naphthalenes, which may indicate contributions from municipal/industrial effluents and petroleum shipping activities. A subsurface concentration maximum of total parent PAHs observed in depositional zone sediments may be due to either a physical process (resuspension) or decreased anthropogenic input.     

MOR/MCM-41复合分子筛的制备及其催化性能的研究

以十六烷基三甲基溴化铵(CTAB)为模板剂,将一定浓度的NaOH碱溶液处理后的微孔MOR分子筛溶液作为硅铝源,采用水热晶化合成法制备了MOR/MCM-41微孔-介孔复合分子筛。利用XRD、SEM、N2吸附-脱附等技术对其进行了表征,考察了碱浓度、碱溶解时间、晶化温度、晶化时间等因素对制备MOR/MCM-41复合分子筛影响。结果表明,较优的MOR/MCM-41复合分子筛制备工艺条件为:NaOH浓度为2.0mol/L,碱溶解时间为0.5h,晶化温度为120℃,晶化时间为24h,晶化体系pH为8.5。将合成的MOR/MCM-41复合分子筛作为催化剂,在微型固定床反应装置上考察了萘异丙基化反应的催化性能,实验结果表明,MOR/MCM-41复合分子筛与MOR分子筛相比,具有较好的催化性能。     

A dialogue computer model as an aid to the operator for taking decisions

A method for constructing computer program for algorithmic and high level language is considered. It is built-up for editing and processing of documents recorder of a two dimensional array. The method enables such a program to be written easily and faster than other known approaches. It may be applied for information activities, for example, in railway, motor or air transport, place reservations, time-tables and other domestic information processes.     

City size and energy conservation: Do large cities in China consume more energy?

Although the nexus between urbanization and energy consumption has been widely discussed at the macro level or in specific areas such as in relation to residents and transport, how the expansion of city size affects energy consumption in the process of urbanization is still unknown. Clarifying this impact mechanism is necessary for China to achieve its energy conservation goals. In this context, based on a systematic theoretical elaboration, this study constructs an econometric model of the nexus between city size and energy use and performs a series of robust empirical analyses through the endogenous control of instrumental variables. The results show that the current expansion of China's city size tends to positively affect energy consumption; however, as city size continues to expand, energy consumption will exceed the critical value and change from increasing to decreasing. In this process, it is easier to achieve a decline in energy intensity than a decline in per capita energy consumption. Cities with a population exceeding 1 million in their urban districts are more conducive to reducing energy use. Compared with the expansion of urban built-up areas, an increasing population agglomeration can more effectively promote the decline of urban energy consumption. This study provides policy makers with new ideas about urban planning and energy conservation.     

Nanostructure development in refractory metals: ECAP processing of Niobium and Tantalum using indirect-extrusion technique

A modified ECAP die by implementing the principles of indirect extrusion was fabricated to process refractory metals of Niobium and Tantalum. The main advantage of this modified technique over conventional method of ECAP is the reduction of frictional force during extrusion. Finite Element Method was utilized to demonstrate the difference between the extruding loads during the process. Several samples of Niobium and Tantalum were subjected to ECAP in different passes. Analysis of experimental results demonstrated a dramatic improvement in mechanical properties. Similarly, microstructure and XRD analyses of the samples showed noticeable enhancement in grain refinement of metals towards nanoscale.     

The effect of high-energy methods of forming on the sintering behaviour and properties of Si3N4-based materials

In the study, Si₃N₄-Al₂O₃-Y₂O₃ samples were obtained in two stages. In the first stage, the materials were compacted using different methods: Isostatic Pressing, UHP (Ultra High Pressure), and SC (Shock Compaction). In the second stage, the green body samples obtained were sintered using the free sintering method.Powder mixtures, in wt%, 88 Si₃N₄ - 6 Al₂O₃ - 6Y₂O₃, were based on commercial nano - and micropowders. The parameters of green bodies compaction and sintering processes were optimised using the criteria of highest density, hardness, and Young's modulus. When compared to theoretical density values, the density of green body samples was 58% for the Isostatic Pressing and 82% for UHP and Shock Compaction. The Vickers hardness was measured only for Shock Compacted green body samples and was ~10.8–14 GPa depending on the applied load during the measurement. The largest changes in lattice constant parameters were measured for the Y₂O₃ phase for the dynamic compaction method (a = 0.02% - 2.26%).The highest relative density was measured for materials which were compacted by UHP method and subsequently free sintered (95%). Young's modulus for UHP and Isostatic green body free sintered samples was 284 GPa and 241 GPa, respectively. The hardness values of samples after free sintering were as follows: 11.7GPa for Isostatic, 14.8 GPa for UHP, and 17.6 GPa for Shock Compaction samples.     

Risk and resilience in the Nigerian oil sector: The economic effects of pipeline sabotage and theft

Political unrest in the Niger Delta has long been viewed as a hurdle for extracting maximum value from Nigeria's oil resources. Recently, investors and policymakers have laid blame for sector under-performance on pipeline sabotage and theft, and sounded the alarm for an impending ‘oil crisis’. However, our understanding of the economic effects of social action against oil companies is incomplete. Rigorous analysis has not heretofore been offered as evidence for such dire futures. Despite the obvious risk of pipeline interdiction, price dynamics and aggregate production respond minimally to pipeline interdiction. Based on quantitative analysis of the relationship among price, production and pipeline interdiction from multiple data sources covering different time intervals (monthly data from 2005 to 2014 and annual data from 1999 to 2013), we find no evidence of significant effects of pipeline interdiction on production and a weak relationship between pipeline interdiction and Bonny light crude prices. Reported losses in product are substantial, but there is no evidence of statistically significant impacts on price or production in the aggregate. Explanations for this counterintuitive result are cast in terms of sector resilience. The implications of this finding for producer risk and the likelihood of an impending ‘oil crisis’ are discussed.