STRATIFIED THREE PHASE FLOW IN PIPES - STABILITY AND TRANSITION

The stability of stratified three phase flow (water-oil-gas) was analyzed using two approaches: A straight forward Kelvin-Helmholtz stability analysis on the two interfaces termed here the “exact” approach and a simplified approach. 1 n the “exact” approach the two interfaces (water-oil and oil-gas) are perturbed, while in the simplified approach the perturbed interface is only the upper oil-gas interface. Both approaches include the viscous Kelvin-Helmholtz analysis in which the shear stresses are laken into account and the inviscid K H analysis where the shear stresses are neglected.

Comparison with some experimental results suggests that the simplified method is a better predictor of the transition from stratified flow than the “exact” approach, suggesting, perhaps, that the stability analysis on the upper interface alone is preferred.     

Knowledge and Know‐How in Emission Control for Mobile Applications

Abstract

Concerns about emissions of carbon dioxide have created a need to develop more fuel‐efficient vehicles. Diesel engines are generally more efficient than gasoline engines but improvements in the latter can be achieved by operating under lean‐burn conditions. With both diesel and lean‐burn gasoline engines, the nitrogen oxides are emissted under oxidising conditions. It is scientifically very challenging to reduce nitrogen oxides under oxidising conditions. After a short survey of conventional three‐way catalysts, and the associated fundamental aspects of NO_x reduction under stoichoimetric conditions, this review focuses on the knowledge and know‐how that has been developed for lean engine emission control. Early research on hydrocarbon selective catalytic reduction on zeolite, oxide, and metal‐based systems is examined, and some of the key mechanistic models are described. Since none of these systems are of sufficient activity and stability to satisfy current legislation attention has turned to NO_x storage and reduction systems. The basic principles of these are described, and the present state of knowledge regarding the mechanisms of storage and regeneration are discussed. The many apparent discrepancies are highlighted and an attempt is made to rationalise the current state of knowledge by taking into account the varying experimental conditions reported nit he literature. For diesel engines, NO_x storage and reduction is not an ideal solution and so the final section of this review is concerned with silver‐based catalysts and especially with the dramatic effect of small amounts of hydrogen on the efficiency of these catalysts for hydrocarbons selective catalytic reduction.     

Continuity and change in interorganizational project practices: The Dutch shipbuilding industry, 1950–2010

The Dutch shipbuilding industry has a longstanding tradition in project-based production. Recently, industry actors have acknowledged a serious misfit between interorganizational project practices, defined as behaviors related to collaboration, and interorganizational project demands, defined as environmental conditions. This misfit leads to a weaker competitive position due to higher communication and production costs, and longer production times. However, the causes of this misfit remain unclear. Among project researchers there is a growing awareness that history has a major influence on contemporary practices in interorganizational projects, suggesting that some of the causes of the present-day misfit may be rooted in the past. This paper studies historical developments of interorganizational project practices in Dutch shipbuilding projects, in order to understand to what extent contemporary misfit in project practices is rooted in the past and results from path dependencies and lock-ins. We answer the following research question: How did interorganizational project practices and demands in the Dutch shipbuilding industry develop between 1950 and 2010 and to what extent do these developments help us understand the current misfit between project practices and demands? Our results show that a web of self-reinforcing mechanisms at least partially explains the current misfit in the Dutch shipbuilding industry. This paper answers to the conceptual call by Sydow et al. (2009) and supplements path dependence literature by showing that self-reinforcing mechanisms causing path dependence can be separated analytically, but are intertwined empirically.     

城市居住小区停车方式的选择

私家车的膨胀发展使城市居住小区停车问题日益突出,由于国内尚未出台相应的停车规划导则,在实际建设项目中,对停车方式的选择有很大的随意性。本文简述了城市住区的几种停车方式,分析了住宅容积率、工程造价等因素对城市居住小区停车方式选择的影响,提出了可行的设计建议与方法,以使居住小区停车方式能根据具体情况,选择不同的建设模式。     

Project finance risk evaluation of the Electric power industry of Serbia

From the aspect of the development of a country, the energy sector represents a domain of strategic interest. Generation and use of energy resources most often belongs to the public sector, and are most often under the influence of the government in most countries. This paper analyzes the risks that are characteristic to the business of the public enterprise, Electric Power Industry of Serbia (EPS). EPS has started its restructuring and is adjusting to changes and challenges imposed by the launched reforms in the energy sector. However, due to certain limitations, it is still not possible to implement its complete restructuring and modernization. The paper aims to point at the risks a potential strategic partner faces. The risks have been identified as commercial, financial and political, classification immanent for project finance, and their evaluation was done using Failure Mode and Effects Analysis (FMEA). Risk analysis was performed based on current conditions for two potential scenarios that predict different types of changes in the analyzed period. The results of the analysis show that the potential strategic partner should pay special attention to price risks, estimation, investments, project activity neglect, quasi-risks and debt collection.     

Social cost-benefit analysis of electricity interconnector investment: A critical appraisal

This paper examines the economic analysis (social cost-benefit analysis) underlying two decisions to build an interconnector (NorNed and the East–West interconnector) in Europe. The main conclusion is that current interconnector and transmission investment decisions in Europe are unlikely to maximize social welfare. The arguments are as follows. (i) It is unclear how much demand for transmission capacity and interconnectors actually exists, and thus the benefits of investment are unclear. (ii) Both analyses underlying the investments studied are incorrect, to the point where, in one case, even the sign may be wrong. (iii) The main criticism concerns the fact that they do not take the resulting changes in generator investment plans into account and ignore the (potential) benefits of increased competition. (iv) Several smaller issues can be improved, such as the discount rate used. (v) Decisions at the European level are taken very differently, and approval may depend on which authority grants approval. (vi) Interconnector decisions receive the most attention, although most money goes to transmission investments. Two research recommendations for future improvements are formulated.     

Predicting completed project cost using bidding data

Neural network and regression models have been developed to predict the completed cost of competitively bid highway projects constructed by the New Jersey Department of Transportation. Bid information was studied for inclusion as inputs to the models. Data studied included the low bid, median bid, standard devi9 ation of the bids, expected project duration and the number of bids. A natural log transformation of the data was found to improve the linear relationship between the low bid and completed cost. The stepwise regression procedure was applied, and yielded the best performing predictive model. This regression model used only the natural log of the low bid as independent variable to predict the natural log of the completed cost. Radial basis neural networks were also constructed to predict the final cost. The best performing regres4 sion model produced superior predictions to the best performing neural network model. Hybrid models that used a regression model prediction as an input to a neural network were also studied and were found to also produce reasonable predictions. The calculated models produced good predictions of the completed project cost, but were found to be deficient in predicting very large cost increases. Simple models using the natural log of the low bid as input produced the best results. From the analysis it may be concluded that additional information about the variability of the bids submitted does not provide useful information for predicting the final project outcome.     

Project Network Interdependency Alignment: New Approach to Assessing Project Effectiveness

The engineering and construction industry has evolved to a task-centric approach to evaluating the effectiveness of projects. However, a narrow task-based view of project network logic neglects the coordination of communication and knowledge exchanges across the project organizational network. This paper departs from traditional approaches to introduce a new approach to assessing project effectiveness that focuses on alignment of actual knowledge exchanges with knowledge exchange requirements across task-organization network dyads. A new modeling approach is introduced, called Project Network Interdependency Alignment. Project Network Interdependency Alignment identifies potentially excessive or insufficient communication and knowledge exchanges that can make projects ineffective. The modeling approach is introduced and retrospectively validated by using a building renovation construction project. The case study demonstrates that the approach can provide project managers with the capacity to analyze task and organizational network interdependence on projects and the critical capability to identify misalignments that impede project effectiveness.     

The impact of the Internet on the social lives of users: A representative sample from 13 countries

One of the most vociferous criticisms of the Internet has always been that it contributes to loneliness among its users. This study analyses results from the World Internet Project, comprised of representative samples from 13 countries (22,002 participants). Thus creating an exceptional international representative sample. In analyzing those results, we argue that in order to achieve a comprehensive understanding of the Internet’s influence over individuals’ social lives; it is essential to consider the different types of social connections that might be influenced by the Internet. We assess the influence of Internet use over social interactions in separate life domains (e.g. with family members; friends; colleagues). Our analysis confirms that Internet usage can actually enhance the social lives of its users. Qualifications to the research are discussed while highlighting the different life domains in which we found significant correlations between Internet usage and increased social interactions.     

Model‐Aided Design of a Three‐Phase Gas‐Lift Reactor for Oxidation Accompanied by Catalyst Reversible Deactivation

A mathematical model of a three‐phase gas‐lift reactor (GLR) is developed to aid the design of a target reactor for simultaneous substrate catalytic oxidation in riser and a deactivated reactivation catalyst in the downcomer section of the multifunctional reactor. In the GLR model, the hydrodynamics of a real GLR and the kinetics of glucose oxidation by air over a palladium catalyst are incorporated. The GLR model searches for the optimal geometry of the target reactor. With regard to the GLR optimal geometry, the reactor productivity is maximal for given input operational conditions. An algorithm of the GLR model is presented together with simulation results of the target GLR and with insight into the parametric sensitivity of the model. Effects of the reaction components concentrations and the gas‐phase superficial velocity on the location of the target reactor optimal geometry and on the reactor productivity are discussed.