Smart applications for energy harvested WSNs

A Wireless Sensor Network (WSN) powered using harvested energies is limited in its operation by instantaneous power. Since energy availability can be different across nodes in the network, network setup and collaboration is a non trivial task. At the same time, in the event of excess energy, exciting node collaboration possibilities exist; often not feasible with battery driven sensor networks. Operations such as sensing, computation, storage and communication are required to achieve the common goal for any sensor network. In this paper, we design and implement a smart application that uses a Decision Engine, and morphs itself into an energy matched application. The results are based on measurements using IRIS motes running on solar energy. We have done away with batteries; instead used low leakage super capacitors to store harvested energy. The Decision Engine utilizes two pieces of data to provide its recommendations. Firstly, a history based energy prediction model assists the engine with information about in-coming energy. The second input is the energy cost database for operations. The energy driven Decision Engine calculates the energy budgets and recommends the best possible set of operations. Under excess energy condition, the Decision Engine, promiscuously sniffs the neighborhood looking for all possible data from neighbors. This data includes neighbor's energy level and sensor data. Equipped with this data, nodes establish detailed data correlation and thus enhance collaboration such as filling up data gaps on behalf of nodes hibernating under low energy conditions. The results are encouraging. Node and network life time of the sensor nodes running the smart application is found to be significantly higher compared to the base application.

Electrical transport and magnetic properties of La0.5Ca0.5MnO3-y with varying oxygen content

We report the tuning of oxygen content of La0.5Ca0.5MnO3-y and its effect on electrical transport and magnetic properties. A small reduction of oxygen content leads to a decrease in sample resistivity, which is more dramatic at low temperatures. No significant change is seen to occur in the magnetic properties for this case. Further reduction in the oxygen content increases the resistivity remarkably, as compared to the as-prepared sample. The amplitude of the ferromagnetic (FM) transition at 225 K decreases, and the antiferromagnetic (AFM) transition at 130 K disappears. For samples with y=0.17, insulator-metal transition and paramagnetic-ferromagnetic transition occur around 167 K. The results are explained in terms of the effect of oxygen vacancies on the coexistence of the metallic FM phase and the insulating charge ordered AFM phase.

Insulator-metal transition and magnetoresistance of La0.5Ca0.5MnOy induced by tuning the oxygen content

The oxygen content of La0.5Ca0.5MnOy was tuned by annealing the samples at high temperatures in flowing nitrogen with graphite powder nearby. The reduction of oxygen content has dramatic effect on the electrical transport and magnetic properties. The samples with y=2.983, 2.83, and 2.803 show an insulator-metal transition, and an unusual temperature and magnetic-field dependence of the magnetoresistance. The paramagnetic-ferromagnetic transition also shifts to lower temperatures and the antiferromagnetic transition at lower temperature is suppressed. The results are discussed in terms of the effect of oxygen vacancies on the various properties of La0.5Ca0.5MnOy. (C) 2002 American Institute of Physics.

A chemical approach to understand fragilities of glass-forming liquids

Fragility is viewed as a measure of the loss of rigidity of a glass structure above its glass transition temperature. It is attributed to the weakness of directional bonding and to the presence of a high density of low-energy configurational states. An a priori fragility function of electronegativities and bond distances is proposed which quite remarkably reproduces the entire range of reported fragilities and demonstrates that the fragility of a melt is indeed encrypted in the chemistry of the parent material. It has also been shown that the use of fragility-modified activation barriers in the Arrhenius function account for the whole gamut of viscosity behavior of liquids. It is shown that fragility can be a universal scaling parameter to collapse all viscosity curves on to a master plot.

An appraisal of electric automobile power sources

Road transportation, as an important requirement of modern society, is presently hindered by restrictions in emission legislations as well as the availability of petroleum fuels, and as a consequence, the fuel cost. For nearly 270 years, we burned our fossil cache and have come to within a generation of exhausting the liquid part of it. Besides, to reduce the greenhouse gases, and to obey the environmental laws of most countries, it would be necessary to replace a significant number of the petroleum-fueled internal-combustion-engine vehicles (ICEVs) with electric cars in the near future. In this article, we briefly describe the merits and demerits of various proposed electrochemical systems for electric cars, namely the storage batteries, fuel cells and electrochemical supercapacitors, and determine the power and energy requirements of a modern car. We conclude that a viable electric car could be operated with a 50 kW polymer-electrolyte fuel cell stack to provide power for cruising and climbing, coupled in parallel with a 30 kW supercapacitor and/or battery bank to deliver additional short-term burst-power during acceleration.

A self-supported 40W direct methanol fuel cell system

A self-supported 40W Direct Methanol Fuel Cell (DMFC) system has been developed and performance tested. The auxiliaries in the DMFC system comprise a methanol sensor, a liquid-level indicator, and fuel and air pumps that consume a total power of about 5W. The system has a 15-cell DMFC stack with active electrode-area of 45 cm(2). The self-supported DMFC system addresses issues related to water recovery from the cathode exhaust, and maintains a constant methanol-feed concentration with thermal management in the system. Pure methanol and water from cathode exhaust are pumped to the methanol-mixing tank where the liquid level is monitored and controlled with the help of a liquid-level indicator. During the operation, methanol concentration in the feed solution at the stack outlet is monitored using a methanol sensor, and pure methanol is added to restore the desired methanol concentration in the feed tank by adding the product water from the cathode exhaust. The feed-rate requirements of fuel and oxidant are designed for the stack capacity of 40W. The self-supported DMFC system is ideally suited for various defense and civil applications and, in particular, for charging the storage batteries.

Role of Management Decision Variables in Determining Technology Progress and Technical Efficiency in Indian Electronic Industry

This paper analyses the influence of management on Technical Efficiency Change (TEC) and Technological Progress (TP) in the communication equipment and consumer electronics sub-sectors of Indian hardware electronics industry. Each sub-sector comprises 13 sample firms for two time periods.The primary objective is to determine the relative contribution of TP and TEC to TFP Growth (TFPG) and to establish the influence of firm specific operational management decision variables on these two components. The study finds that both the sub-sectors have strived and achieved steady TP but not TEC in the period of economic liberalisation to cope with the intensifying competition. The management decisions with respect to asset and profit utilization, vertical integration, among others, improved TP and TE in the sub-sectors. However, R&D investments and technology imports proved costly for TFP indicating inadequate efforts and/or poor resource utilisation by the management. Management was found to be complacent in terms of improving or developing their own technology as indicated by their higher dependence on import of raw materials and no influence of R&D on TP.

New Ventures’ influence on the Growth of SME Employment, Production and Exports in India: Does Institutional Credit matter?

New ventures are considered to be a major source of small firm growth. In Indian context the contribution of new ventures in terms of new employment, production and exports has largely remained unexplored. It is equally important and unexplored, the significance of the contribution of bank credit to the growth of new ventures in India. This paper is an attempt to throw light on these two aspects. The research is based on secondary data of the liberalized period provided by Ministry of Micro, Small and Medium Enterprises, Government of India and Reserve Bank of India. To analyze the influence of bank credit growth on new ventures and the influence of new ventures on growth of additional employment, additional production and additional exports, we used a Bi-Variate Vector Auto Regression. Based on the model generated, Granger causality tests are conducted to obtain the results. The study found that rate of growth of bank credit causes the number of new ventures, implying any increase in the rate of growth of bank credit will be beneficial to the growth of new ventures. The study also concluded that new ventures are not causing the growth of additional employment or additional production. However new ventures cause the growth of additional exports. This is reasonable as entrepreneurs start their new ventures with minimum possible employment and relatively low rate of capacity utilization and they come up to take advantage of the process of globalization by catering to the international market.

Total Factor Productivity Growth and Output Growth in Indian Electronics Industry in the Liberalization Era: An Empirical Examination

This paper analyses the efficiency and productivity growth of Electronics industry, which is considered one of the vibrant and rapidly growing manufacturing industry sub-sectors of India in the liberalization era since 1991. The main objective of the paper is to examine the extent and growth of Total Factor Productivity (TFP) and its components namely, Technical Efficiency Change (TEC) and Technological Progress (TP) and its contribution to total output growth. In this study, the electronics industry is broadly classified into communication equipments, computer hardware, consumer electronics and other electronics, with the purpose of performing a comparative analysis of productivity growth for each of these sub-sectors for the time period 1993-2004. The paper found that the sub-sectors have improved in terms of economies of scale and contribution of capital.The change in technical efficiency and technological progress moved in reverse directions. Three of the four industry witnessed growth in the output primarily due to TFPG and the contribution of input growth to output growth had been negative/negligible, except for Computer hardware where contribution from both input growth and TFPG to output growth were prominent. The paper explored the possible reasons that addressed the issue of low technical efficiency and technological progress in the industry.

Subcontracting Relationship of Indian SMEs with a Global TNC: Do SMEs Gain and How?

TNCs having their production bases in developing countries provide increasing opportunity for local SMEs to have subcontracting relationships with these TNCs.Even though some theoretical and a few empirical studies throw light on the nature of assistance provided by TNCs to local SMEs through subcontracting relationships,none of the studies so far analysed the diversity of assistance that subcontracting SMEs of India would be able to obtain from a TNC using quantitative measurement.This paper probes the extent of linkages and diversity of assistance that Indian subcontracting SMEs would be able to obtain from a TNC customer based on primary data from SME subcontractors of a major TNC automobile manufacturer. Statistical analysis of direct assistance revealed that SMEs receive more of product and purchase process assistance. The extent of assistance for their process related,marketing, human resource and financial requirements is low whereas the assistance for their organisational know-how requirements is moderate. The major indirect benefits these SMEs could achieve are knowledge transfer, business volume, superior work culture, reputation and quality improvement.