Lévy flight artificial bee colony algorithm

Artificial bee colony (ABC) optimisation algorithm is a relatively simple and recent population-based probabilistic approach for global optimisation. The solution search equation of ABC is significantly influenced by a random quantity which helps in exploration at the cost of exploitation of the search space. In the ABC, there is a high chance to skip the true solution due to its large step sizes. In order to balance between diversity and convergence in the ABC, a Lévy flight inspired search strategy is proposed and integrated with ABC. The proposed strategy is named as Lévy Flight ABC (LFABC) has both the local and global search capability simultaneously and can be achieved by tuning the Lévy flight parameters and thus automatically tuning the step sizes. In the LFABC, new solutions are generated around the best solution and it helps to enhance the exploitation capability of ABC. Furthermore, to improve the exploration capability, the numbers of scout bees are increased. The experiments on 20 test problems of different complexities and five real-world engineering optimisation problems show that the proposed strategy outperforms the basic ABC and recent variants of ABC, namely, Gbest-guided ABC, best-so-far ABC and modified ABC in most of the experiments.     

Through a glass darkly [Internet]

This article discussed some important historical success of the Internet. Kevin Kelly of Wired Magazine reckons that the Internet got properly underway in 1995 with Netscape's wildly successful IPO.     

Secretion of cardiac plasminogen activator during hypoxia-induced right ventricular hypertrophy

In the circulation, fibrinolytic activity is determined to a large degree by the relative levels of tissue plasminogen activator (tPA) and its major inhibitor (PAI-1). Vascular beds in different organs secrete tPA and PAI-1 into the circulation, and the total secretory rate of each protein is balanced by its half-life in the bloodstream. We are testing the hypothesis that in the heart, ventricular hypertrophy will alter the rates of formation of tPA and/or PAI-1 and the rates of their release into the cardiac vasculature. In this study, we have examined the effects of continuous hypoxia on PA activity in extracts of rat heart ventricles, on the activity secreted into the cardiac vasculature of perfused hearts, and on the levels of mRNAs for tPA and PAI-1. Rats were subjected to hypobaric hypoxia at 0.5 atm for 1-21 days. The treatment caused polycythemia within 1-3 days, and right ventricular hypertrophy by 3 days. PA activity in extracts of both right and left ventricles was significantly elevated after 3 days of hypoxia, continued to increase for 4 additional days, and remained elevated for 3 weeks. The actions of inhibitors of urokinase and tPA indicated that the PA activity in heart extracts was exclusively tPA. Fibrin zymography confirmed that result. The mRNAs for tPA and for PAI-1 were elevated after 1 day of hypoxia and then returned to near control levels on days 2 and 3. After 7 days, hearts from hypoxic rats secreted more tPA activity into perfusates than did hearts from controls. The difference in secretory rates was proportional to the differences in the levels of tPA in the corresponding heart extracts.     

Decentralized energy planning model for optimum resource allocation with a case study of the domestic sector of rurals in Nepal

The paper is concerned with the development of a simplified linear model which attempts to optimize the cost function of an energy supply system consisting of a mix of energy resources and conversion devices, each of which may have a constraint with respect to availability, efficiency and cost. The model has been applied in three villages, from three different physiographic zones of Nepal, for which detailed data were collected and analysed. The results of the study show that the optimized use of different energy sources in different regions is strongly dependent on demographic and climatic parameters. For hill villages, hydropower could become the cheapest source of energy if technical options were provided, but until then more efficient use of wood is the only viable solution. Commercial sources like kerosene and LPG are not likely to play any significant role in hill and mountain villages. On the other hand, the use of biogas is economically most feasible in Terai village. The availability of kerosene rules out wood or agriculture waste as feasible solutions for cooking energy needs, as this village is closer to the Indian border and has good road access.     

Hyperbolic decline-curve analysis using linear regression

Two rigorous techniques for hyperbolic decline-curve analysis based on the fundamental equations are investigated. The parameter estimation is made more accurate and repeatable than type curve matching if linear regression is used to extract the unknowns D_iq_i and n from the data. Maximizing the regression coefficient is the criterion used to select the correct parameter values. In application to six field examples, it is seen that the two methods do not always give identical results if there is a lot of scatter in the data.