Determining link weight system under various objectives for OSPF networks using a Lagrangian relaxation-based approach

An important traffic engineering problem for OSPF networks is the determination of optimal link weights. Certainly, this depends on the traffic engineering objective. Regardless, often a variety of performance measures may be of interest to a network provider due to their impact on the network. In this paper, we consider different objectives and discuss how they impact the determination of the link weights and different performance measures. In particular, we propose a composite objective function; furthermore, we present a Lagrangian relaxation-based dual approach to determine the link weight system. We then consider different performance measures and discuss the effectiveness of different objectives through computational studies of a variety of network topologies. We find that our proposed composite objective function with Lagrangian relaxation-based dual approach is very effective in meeting different performance measures and is computationally very fast.     

CFD analysis of low temperature water gas shift reactor

In the design of water gas shift reactors, the performance of catalysts is not known a priori and hence having a general kinetic expression will be of much help. Computational Fluid Dynamic study was carried out to investigate the performance of a packed bed reactor for different feed compositions using five commonly used types of macro kinetic models. User Defined Functions were developed for the reaction rate to predict the CO conversion in the reactor. The effects of temperature and time factor on CO conversion were studied. The Langmuir-Hinshelwood model gave the best prediction for H₂ rich mixtures. The Temkin model was better for higher CO concentrations, whereas the other models gave large deviations for the fixed bed reactor.     

Benchmarking temporal database models with interval-based and temporal element-based timestamping

Starting from mid 1980s, there has been a debate about what data model is most appropriate for temporal databases. A fundamental choice one has to make is whether to use intervals of time or temporal elements to timestamp objects and events with the periods of validity. The advantage of using interval timestamps is that Start and End columns can be added to relations for treating them within the framework of classical databases, leading to quick implementation. Temporal elements are finite unions of intervals. The advantage of temporal elements is that timestamps become implicitly associated with values, tuples, and relations. Furthermore, since temporal elements, by design, are closed under set theoretical operations such as union, intersection and complementation, they lead to query languages that are natural. Here, we investigate the ease of use as well as system performance for the two approaches to help settle the debate.     

Hydrogen production by partial oxidation of methane: Modeling and simulation

A one-dimensional non-isothermal model for oxygen permeable membrane reactor has been developed to simulate the partial oxidation of methane to produce hydrogen. The performance of two fixed bed reactors (FBRs) viz. one with pure O₂ in feed (FBR1), other with air in feed (FBR2), and a membrane reactor (MR) having air in non-reaction side have been studied at various feed conditions and inlet temperatures in order to investigate the effect of these parameters on conversion of methane and yield of hydrogen. The fixed bed reactor with pure O₂ in feed has been found to provide better performance as compared to fixed bed reactor with air and membrane reactor.     

Thousand-Core Chips [Roundtable]

The 2007 Design Automation Conference (DAC) had a special session entitled "1000 Core Chips," which was organized by Radu Marculescu (Carnegie Mellon University) and Li-Shiuan Peh (Princeton University). This session examined some of the ramifications of multicore chip design from four perspectives: technology, architecture, programming, and design automation. In this roundtable, held immediately following the conference session, the presenters expounded on the future of multicore chips with respect to education, programming languages, operating systems, and design automation.     

Energy use in the rural areas of India: setting up a rural energy data base

Aggregating and forecasting demand are crucial parts of energy planning. While a large number of energy consumption surveys have been conducted in the past in the rural energy sector of India, the lack of sufficient data and its compilation, coupled with doubt about the quality of data, has made the task extremely difficult. This paper summarizes our recent effort to compile, computerize and analyze data from 638 village energy consumption surveys covering over 39,000 households, carried out by different organisations between 1985 and 1989. The details of the level of information provided in the survey reports, area of survey, land use pattern, asset ownership, etc., of the collated studies are presented. Results based on the analysis of the energy consumption data compiled are then discussed. The national average for rural domestic thermal energy consumption (excluding water and space heating) estimated through this work (629 kcal or 2.63 MJ per capita daily) is much similar to the rural domestic thermal energy requirement assumed in most energy planning exercises in India in the past. The useful thermal energy consumption varies from 325 to 1065 kcal/cap/d (1.36-4.46 MJ/cap/d) in the East Coast Plain and Hills and the Eastern Himalayan Regions, respectively. Reconfirming the predominance of firewood, the data reveals that the contribution of firewood to the domestic thermal energy consumption has remained at about 58% over the last three decades; dungcake and agricultural residues contribute almost equally in the remaining share. At the national level, our estimates indicate that at least 180 million tonnes of firewood, 40 million tonnes of dungcakes and 30 million tonnes of agricultural residues were consumed in the rural sector for meeting the domestic thermal energy requirement in 1991. The paper also compares the estimates with those based on other surveys in India.     

Solubility enhancement of electrolyzed coal residues

Coal slurries were electrolyzed in acidic as well as basic electrolytes at different oxidizing potentials. The partially reacted coal residues were subjected to Soxhlet extraction with an equivolumetric mixture of benzene and ethanol for a period of 24 hours. The solvent-soluble organic part of coal was analyzed by GC-MS. Coal electrolyzed in acidic electrolytes became more accessible to extraction by the solvents used in the study. Electrolysis at 3.1 V vs. SCE (saturated calomel electrode) of a North Dakota lignite enhanced the solubility of coal in the benzene-ethanol mixture by a significant amount of 33%. Coal electrolysis in basic electrolytes at lower electrode potentials resulted in enhanced solubility of coal; however, at relatively large electrode potentials the yield of organic chemicals obtained by Soxhlet extraction declined.