A Dynamic Model of Induction Generators for Wind Power Studies

This paper presents an induction generator model that can be used for simulations to investigate and evaluate the control strategies for variable speed operation of doubly fed induction generators driven by wind turbines in transient conditions. The model makes use of rotor reference frame

Modelling of Bicycle Activity on Midsized City Road Segments in Indian Context

Bicycle comfort level rating (BCLR) is a qualitative measure that characterizes operational conditions of bicyclists and their level of comfort within the geometric and traffic flow conditions of a road. Most of the widely accepted international BLOS models are proposed for homogeneous traffic and cannot be adopted to measure the service quality of roads under the influence of heterogeneous traffic flow. Due attention was paid in this research on heterogeneous traffic flow conditions and a Bicycle Comfort Level Rating (BCLR) model was developed which can be adopted in Indian midsized cities. Several factors (based on road features, traffic flow characteristics, on-street parking, driveways and land use of adjoining area etc.) affecting the comfort level of cyclists were considered while developing the model. Required data set were collected form 60 segments of three Indian midsize cities namely; Bhubaneswar, Rourkela and Kottayam. In perception survey participants with a good cross-section of age, experience level, sex and education were participated. Relationship was established between the factors which contribute to the comfort level of bicyclists and perceived comfort level of users in the modeling process. The model was developed by stepwise multiple linear regression in SPSS V20.0 satisfied the significance criteria with correlation coefficient (R square = 0.757). The t-tests of the predictors are highly significant (p < 0.05). Four clustering techniques namely; FCM, HAC, K-Means and K-Medoid were applied to classify the BCLR model output into six categories (A-F) and K-medoid clustering was found to be the most applicable one in the present context. The model was compared with HCM BLOS model (for link) and two other widely accepted models namely, Bicycle Compatibility Index (BCI) model and FDOT BLOS model; and BCLR model was found to provide far better results than other models in Indian condition

Numerical Simulations of a High-Resolution RANS-FVDM Scheme for the Design of a Gas Turbine Centrifugal Compressor

The aero-thermodynamic design and performance of a compressor need to conquer many vital challenges like it is a gas-driven turbo-machinery component, involvement of extensive iterative process for the convergence of the design, enormous design complexity due to three-dimensional flow phenomena, and multiflow physics embedded within a dynamic state-of-the-art. In this chapter, a strong attempt is made to address the above-cited technical issues to achieve an optimized design and performance of a centrifugal compressor with backward swept blade profile producing total pressure ratio of 5.4 with an ingested mass flow rate of 5.73 kg/s. A mean-line design methodology was implemented to configure sizing of the compressor. An optimum grid size was well validated by carrying out computational analysis with three different mesh sizes within the same framework. Finally, a detailed three-dimensional numerical simulation was performed using Reynolds-averaged Navier-Stokes equations based on finite volume discretization method (RANS-FVDM) scheme. Consequently, the polytropic efficiency, total-to-total efficiency, stagnation pressure ratio at a fixed rotational speed, and the overall design and aero-thermodynamic performance of the centrifugal compressor are validated

Analysis of Pleated Discrete Pore Non Woven Layer Type Filter Element for Naval Applications

&nbsp; &nbsp; In naval applications generally, the pleated discrete pore non-woven layer filter element is used. Filters used for such applications require maximized filtration rate, lower pressure drop, higher permeability, effective pore size distribution and good filtration efficiency. In other most common wire mesh filter element types, the geometric parameters are well defined and can easily be modelled. In the case of non-woven layer filter elements the pores are arranged in a randomly distributed manner and the modelling becomes difficult. In this present study a new approach was contemplated for modelling the same. The fluid flow through the filter element is by percolation phenomenon. Using Darcy’s law approach, the pressure drop across the filter element for different flow rates, were found analytically by considering the flow resistance in axial, radial and circumferential directions. The theoretical prediction made by CFD analysis is correlated with actual model behaviour and a good degree of correlation is obtained which shows the efficacy of this method for wider use in similar application.&nbsp; &nbsp; &nbsp

Evaluating dimensionality reduction for genomic prediction

The development of genomic selection (GS) methods has allowed plant breeding programs to select favorable lines using genomic data before performing field trials. Improvements in genotyping technology have yielded high-dimensional genomic marker data which can be difficult to incorporate into statistical models. In this paper, we investigated the utility of applying dimensionality reduction (DR) methods as a pre-processing step for GS methods. We compared five DR methods and studied the trend in the prediction accuracies of each method as a function of the number of features retained. The effect of DR methods was studied using three models that involved the main effects of line, environment, marker, and the genotype by environment interactions. The methods were applied on a real data set containing 315 lines phenotyped in nine environments with 26,817 markers each. Regardless of the DR method and prediction model used, only a fraction of features was sufficient to achieve maximum correlation. Our results underline the usefulness of DR methods as a key pre-processing step in GS models to improve computational efficiency in the face of ever-increasing size of genomic data

A security analysis of automated Chinese turing tests

Text-based Captchas have been widely used to deter misuse of services on the Internet. However, many designs have been broken. It is intellectually interesting and practically relevant to look for alternative designs, which are currently a topic of active research. We motivate the study of Chinese Captchas as an interesting alternative design - counterintuitively, it is possible to design Chinese Captchas that are universally usable, even to those who have never studied Chinese language. More importantly, we ask a fundamental question: is the segmentation-resistance principle established for Roman-character based Captchas applicable to Chinese based designs? With deep learning techniques, we offer the first evidence that computers do recognize individual Chinese characters well, regardless of distortion levels. This suggests that many real-world Chinese schemes are insecure, in contrast to common beliefs. Our result offers an essential guideline to the design of secure Chinese Captchas, and it is also applicable to Captchas using other large-alphabet languages such as Japanese