Pathlistings applied to data flow analysis

Summary In this paper the pathlisting mechanism is developed as a new tool useful in performing efficient data flow analysis of programs for a wide variety of problems. An algorithm using this tool for forward flow, code improvement problems is presented. It is shown that for all practical purposes this algorithm is linear in the size of the input which is, generally speaking, a reducible flow graph modeling the given program. Pathlistings generalize the nodelisting approach, introduced by Kennedy, for solving data flow problems. The efficiency of the pathlisting algorithm is due to the reuse of intermediate values and due to the fact that the cycles of a reducible flow graph can be ordered. Other advantages of the approach are also discussed.Work supported by National Science Foundation grant DCR73-00365-AO     

A heuristic approach for designing hybrid PONs employing WDM and OCDMA with asymmetric traffic distribution

In this paper we examine the resource provisioning aspects in a passive optical network (PON) employing wavelength-division multiplexing (WDM) and optical code-division multiple access (OCDMA) techniques. A judicious resource allocation scheme is proposed for a given set of optical codes and wavelengths with due consideration to the traffic asymmetry between upstream and downstream transmissions. The proposed scheme employs some initial heuristic estimates, followed by a subsequent open search mode towards reaching an optimal solution. The search mechanism in the provisioning scheme is carried out by employing some network performance metrics and evaluated using the appropriate analytical models.     

Naturally-occurring folates in foods: Method development and analysis using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

An accurate method for detecting and quantifying both synthetic (folic acid) and naturally-occurring folates in foods is described. A system capable of analysing the five most commonly occurring folates (pteroylglutamic acid, 5-methyltetrahydrofolate, tetrahydrofolate, 10-formylfolate and 5-formyltetrahydrofolate) in 20 min using liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. Quantification of folates was performed using ¹³C labelled internal standards. This paper outlines the development of a comparatively fast LC–MS/MS method, method validation using commercially available folate standards and establishment of the method’s suitability for quantification using selected reaction monitoring (SRM) mass spectrometry. The application of the system was verified by analysing several certified reference materials and comparing results with certified values as determined by microbiological assay. LC–MS/MS promises to be an ideal tool for the quantitative analysis of folates in food.     

Load Balancing Technique for Congestion Control Multipath Routing Protocol in MANETs

A mobile ad hoc network (MANET) is a collection of wireless mobile nodes that can communicate without a central controller or fixed infrastructure. Due to node mobility, designing a routing protocol to provide an efficient and suitable method to route the data with less energy consumption, packet drop and to prolong the network lifetime has become a challenging issue in MANETs. In MANETs, reducing energy consumption and packet loss involves congestion control and load balancing techniques. Thus, this paper introduces an efficient routing technique called the multipath load balancing technique for congestion control (MLBCC) in MANETs to efficiently balance the load among multiple paths by reducing the congestion. MLBCC introduces a congestion control mechanism and a load balancing mechanism during the data transmission process. The congestion control mechanism detects the congestion by using an arrival rate and an outgoing rate at a particular time interval T. The load balancing mechanism selects a gateway node by using the link cost and the path cost to efficiently distribute the load by selecting the most desirable paths. For an efficient flow of distribution, a node availability degree standard deviation parameter is introduced. Simulation results of MLBCC show the performance improvements in terms of the control overhead, packet delivery ratio, average delay and packet drop ratio in comparison with Fibonacci sequence multipath load balancing, stable backbone-based multipath routing protocol and ad hoc on demand multipath distance vector routing. In addition, the results show that MLBCC efficiently balances the load of the nodes in the network.

     

Effect of solid lubricant and fibrous reinforcement on the abrasive wear of polyamides

Short glass fibre‐reinforced polyamide 6 and polyamide 11 (PA 6 and PA 11) with and without a solid lubricant of polytetrafluoroethylene and metal powders (e.g., bronze) and copper as fillers were formulated and characterised for their compositional and mechanical properties. A tribological evaluation of these composites' abrasive wear was carried out by abrading a polymer pin against 80 grade (175 um) silicon carbide (SiC) paper under single‐pass conditions at various loads. It was observed that the fibre reinforcement reduced the abrasive wear resistance of virgin polymers. A combination of fibre and particulate fillers was further detrimental in this respect. Efforts were made to correlate the wear performance with the ductility factor, fracture toughness, and fracture energy in the case of PA 6 and its composites.     

Composites as friction materials: Recent developments in non-asbestos fiber reinforced friction materials—a review

Replacement of conventional asbestos based friction materials has been called for because of bans on the use of asbestos. Research in this direction in the last decade has led to the development of more efficient asbestos-free friction materials for automobiles. Fiber reinforced polymers show great promise for applications in modern vehicles. This review article focuses on the recent developments in the application of composites as friction materials. The first part of the article contains brief information about brakes, their action, brake materials, their desired properties, etc. The second part deals with the recent developments in non-asbestos fiber reinforced friction materials.     

Nano-abrasives in friction materials-influence on tribological properties

It was aimed to explore the potential of abrasives in nanometer size in friction materials (FMs). Hence six FMs were developed using micro and nano-abrasives of three types viz. alumina, SiC and silica (2%). The nano and micro composites were developed and characterized for various physical and chemical properties. The tribological performance was evaluated on a reduced scale prototype under various operating parameters and output parameters such as wear, μ_avg as a function of speed and pressure, load-speed sensitivity of μ and friction stability were considered to compare the performance of nano and micro-composites (NCs and MCs). It was concluded that all performance parameters were significantly and beneficially affected due to nano-fillers. Nano-silica proved to impart highest wear resistance followed by SiC and then alumina while best combination of friction properties was exhibited by composites with SiC followed by Alumina and then silica. SEM on worn surfaces of pads and discs was done to understand wear mechanism and it was clearly observed that thin coherent film on both the surfaces in case of NCs was responsible for enhanced performance.     

Fish science research in China: How does it compare with fish research in India?

Fish and aquaculture research in the People's Republic of China over the six years 1994-1999 has been mapped using data from six databases– three abstracting services and three citation indexes. The results are compared with fish science research in India. During the six years China has published 2035 papers (roughly 4.5 –5% of the world output) and India 2454. More than 95% of China's papers are journal articles, compared to 82.8% of Indian papers. About 78% of China's journal paper output has appeared in 143 domestic journals compared to 70% from India in 113 Indian journals. Less than one-eighth of the journal articles published by Chinese researchers are published in journals indexed in SCI, compared to 30% of journal articles by Indian researchers. Less than a dozen papers from each of these countries have appeared in journals of impact factor greater than 3.0. Fish research institutes and fishery colleges are the major contributors of the Chinese research output in this area. In India academic institutions are the leading contributors (61%), followed by central government institutions (>25%). Qingdao, Wuhan, Beijing and Shanghai are the cities and Shandong, Hubei and Fujian are the provinces contributing a large number of papers. As we do not have addresses of all authors in most of the papers, we are unable to estimate the extent of international collaboration. Although China's research output and its citation impact are less than those of India, China's fish production and export earnings are far higher than those of India. Probably China is better at bridging the gap between knowhow (research) and do-how (technology and creation of employment and wealth). China is pretty strong in extension. This revised version was published online in June 2006 with corrections to the Cover Date.