Design and Construction of a Tesla Transformer by using Microwave Oven Transfer for Experimentation

This paper has focused on the step-by-step design of a high frequency medium size (1-3 kW) air-cored resonance transformer commonly called tesla coil, that can be easily used for measurements and general research. Therefore, the task is to minimize the number of stochastic and unknown parameters influencing the device functionality and pointing out pros and cons of each solution. The physical dimension of the tesla transformer has been chosen due to cost effectiveness and availability of the regarding components. This design has mainly two units’ viz., a power supply and tesla coil. The power supply which fed the Tesla coil having voltage rating 12kV and current rating 120mA has been designed by using three microwave oven components. These components are assembled as dual MOTs voltage doubler circuit and necessary simulation has been carried out by using MicroSim Schematics for the verification of performance. Keywords:Microwave Oven , Transformer, Multi mini Capacitors, MicroSim Schematics, Toroid, Tesla Coil CAD

Bifurcation analysis and chaos control in a discrete-time predator-prey system with Crowley-Martin functional response

In this paper, the dynamics of a discrete-time predator-prey system with Crowley-Martin functional response is examined. Via application of the center manifold theorem and bifurcation theorems, we algebraically show that the system undergoes a bifurcation (flip or Neimark-Sacker) in the interior of R2+. Numerical simulations are presented not only to validate analytical results but also to reveal new dynamical behaviors which include bifurcations, phase portraits, period- 5, 6, 7, 10, 11, 15, 16, 17, 21, 28, and period- 51 orbits, invariant closed cycle, sudden disappearance of chaotic dynamics and abrupt emergence of chaos, and attracting chaotic sets. Furthermore, maximum Lyapunov exponents and fractal dimension are computed numerically to justify the chaotic behaviors of the system. Finally, we apply a strategy of feedback control to control chaos exists in the system

A novel approach of developing micro crystalline cellulose reinforced cementitious composites with enhanced microstructure and mechanical performance

This paper reports a novel approach of preparing aqueous suspensions of microcrystalline cellulose (MCC) for fabrication of cementitious composites. MCC was dispersed homogeneously in water using Pluronic F-127 as a surfactant with the help of ultrasonication process and the aqueous suspensions were added to cement/sand mixture to prepare cementitious composites. A commonly used stabilizing agent for MCC, carboxy methyl cellulose (CMC) was also used for the comparison purpose. The prepared suspensions were characterized through visual inspection, UV-Vis spectroscopy and optical microscopy. The developed composites were characterized for their bulk density, flexural and compressive properties as well as microstructure. The influence of Pluronic and CMC concentration, superplasticizer, dispersion technique and dispersion temperature on mortar's mechanical performance was thoroughly studied to find out the optimum conditions. Overall, Pluronic (with Pluronic: MCC ratio of 1:5) led to better MCC dispersion as well as dispersion stability as compared to CMC. The best mechanical performance was achieved with Pluronic in combination with superplasticizer using ultrasonication process, resulting in improvement of 106%, 31% and 66% in flexural modulus, flexural strength and compressive strengths, respectively (highest values reported till date). The bulk density and hydration of cementitious composites also improved significantly with the addition of MCC.The authors acknowledge the Portuguese Fundação para a Ciência e a Technologia (FCT) for financial support through project PEst-C/CTM/LA0025/2013 (Strategic Project - LA 25 - 2013-2014). The authors also acknowledge the financial support from Portuguese National Funding, through, on the framework of project UID/CTM/00264/2013 and national funds through FCT, I.P., within the research unit C-MADE, Centre of Materials and Building Technologies (CIVE-Centro-Covilhã-4082), Universidade da Beira Interior, Portugal.info:eu-repo/semantics/publishedVersio

Two-step robust estimator in heteroscedastic regression model in the presence of outliers

Although the ordinary least squares (OLS) estimates are unbiased in the presence of heteroscedasticity, these are no longer efficient. This problem becomes more complicated when the violation of constant error variances comes together with the existence of outliers. The weighted least squares (WLS) procedure is often used to estimate the regression parameters when heteroscedasticity occurs in the data. But there is evidence that the WLS estimators suffer a huge set back in the presence of outliers. Moreover, the use of the WLS requires a known form of the heteroscedastic errors structures. To rectify this problem, we proposed a new method that we call two step robust weighted least squares (TSRWLS) method where prior information on the structure of the heteroscedastic errors is not required. In the proposed procedure, the robust technique is used twice. Firstly, the robust weights are used for solving the heteroscedasic error and secondly, the robust weighting function is used for eliminating the effect of outliers. The performance of the newly proposed estimator is investigated extensively by real data sets and Monte Carlo simulations

DETERMINANTS OF SUPPLY CHAIN PERFORMANCE: A STRATEGIC POINT OF VIEW.

With the application of supply chain strategy, retailers can make a wise decision to increase supply chain performance. This study is one of the novelties in supply chain management research because it aimed at empirically analyzing the influence of supply chain strategies as the determinants of retail supply chain performance. For the purpose of the study, data were collected with a structured questionnaire from 115 mangers of some selected retail chain stores in Bangladesh. Collected data were analyzed using Partial Least Squares method with smart PLS software version 2.0M3. The present study has shown some meaningful findings regarding the determinants of retail supply chain performance. Firstly, it is found in the study that agile supply chain strategy is the most pivotal factor influencing retail supply chain performance. The lean strategy was also found to be a contributor to the retail supply chain performance while hybrid strategy was found to exhort very weak influence in increasing the performance of retail supply chain. The findings of this study can benefit the supply chain managers involved in retailing. From this study retail managers can know which strategy they should adopt to bring forth substantial advantage for the companies by maintaining their supply chain in a better way

Bifurcation Analysis and Chaos Control in a Discrete-Time Predator-Prey System of Leslie Type with Simplified Holling Type IV Functional Response

The dynamic behavior of a discrete-time predator-prey system of Leslie type with simplified Holling type IV functional response is examined. We algebraically show that the system undergoes a bifurcation (flip or Neimark-Sacker) in the interior of R+2. Numerical simulations are presented not only to validate analytical results but also to show chaotic behaviors which include bifurcations, phase portraits, period 2, 4, 6, 8, 10, and 20 orbits, invariant closed cycle, and attracting chaotic sets. Furthermore, we compute numerically maximum Lyapunov exponents and fractal dimension to justify the chaotic behaviors of the system. Finally, a strategy of feedback control is applied to stabilize chaos existing in the system

Modeling Bangladesh's gross domestic product using regression approach

This study finds the factors that affect Bangladesh’s Gross Domestic Product (GDP) through regression approach. Stepwise and Ridge regression techniques have been applied to build the suitable regression model. Model adequacy also has been checked and multicollinearity problem is addressed for a plausible model using appropriate remedial measures for each of the model one after another that yields stepwise regression. The multicollinearity problem has also been tried to combat by ridge regression. Finally, the model which is adequate and free from multicollinearity problem after applying the ridge regression has been considered as the credible model for predicting the GDP of Bangladesh. The final model shows that the factors population, imports of goods and services, agriculture value added, manufacturing value added and labor force are positively affecting the GDP of Bangladesh

Robust Wild Bootstrap for Stabilizing the Variance of Parameter Estimates in Heteroscedastic Regression Models in the Presence of Outliers

Nowadays bootstrap techniques are used for data analysis in many other fields like engineering, physics, meteorology, medicine, biology, and chemistry. In this paper, the robustness of Wu (1986) and Liu (1988)'s Wild Bootstrap techniques is examined. The empirical evidences indicate that these techniques yield efficient estimates in the presence of heteroscedasticity problem. However, in the presence of outliers, these estimates are no longer efficient. To remedy this problem, we propose a Robust Wild Bootstrap for stabilizing the variance of the regression estimates where heteroscedasticity and outliers occur at the same time. The proposed method is based on the weighted residuals which incorporate the MM estimator, robust location and scale, and the bootstrap sampling scheme of Wu (1986) and Liu (1988). The results of this study show that the proposed method outperforms the existing ones in every respect