Consistent Approximations for the Optimal Control of Constrained Switched Systems

Though switched dynamical systems have shown great utility in modeling a variety of physical phenomena, the construction of an optimal control of such systems has proven difficult since it demands some type of optimal mode scheduling. In this paper, we devise an algorithm for the computation of an optimal control of constrained nonlinear switched dynamical systems. The control parameter for such systems include a continuous-valued input and discrete-valued input, where the latter corresponds to the mode of the switched system that is active at a particular instance in time. Our approach, which we prove converges to local minimizers of the constrained optimal control problem, first relaxes the discrete-valued input, then performs traditional optimal control, and then projects the constructed relaxed discrete-valued input back to a pure discrete-valued input by employing an extension to the classical Chattering Lemma that we prove. We extend this algorithm by formulating a computationally implementable algorithm which works by discretizing the time interval over which the switched dynamical system is defined. Importantly, we prove that this implementable algorithm constructs a sequence of points by recursive application that converge to the local minimizers of the original constrained optimal control problem. Four simulation experiments are included to validate the theoretical developments

Empowering girls, delaying marriage: Exploring the role of marital age and education on domestic violence in India

Domestic violence represents the most important component of violence against women. Whilst some literature report female empowerment as a protective factor against domestic violence, some literature find the opposite because the husband may attempt to compensate for the enhanced status of his wife. This paper aims to investigate the effects of female empowerment in the form of marital age and education on domestic violence in India, where intimate partner violence is amongst the highest in Asia. The analysis is based on the sample of eligible women aged 15-49 with valid response on domestic violence in the 2015- 2016 National Family Health Survey (NFHS-4) (n=9722). Upon estimating a series of instrumental variable (IV) regressions using age at menarche as an exogenous and strong instrument, we establish a causal relationship between empowerment and domestic violence taking into account the endogeneity of marital age and education. We further disentangle the relationships between domestic violence and age at marriage and education, separately. In addition, we investigate how maritage age and education influence domestic violence through labour market participation and spouse quality channels. We find that: i) empowered women do experience less domestic violence; ii) marital age and education are partially complementary; iii) labour market participation and spousal quality are relevant mediators of these relationships. Policies aiming at reducing domestic violence in India hence should be holistic, focussing on investing in education both for women and men and improving the conditions of the women’ labour market

DoA estimation in EM lens assisted massive antenna system using subsets based antenna selection and high resolution algorithms

In recent times, massive antenna array technology has captured significant attention among wireless communication researchers. This is a field with strong potential to increase rates of data transfer; mitigate interference and serve a large number of users simultaneously. To contribute further to this emerging technology, this paper presents an approach for the line-of-sight (LoS) based direction of arrival (DoA) estimation using the electromagnetic (EM) lens-focusing antenna concept. The EM lens focuses the received signal energy as a function of the angle of arrival (AoA) to a small subset/area of the antenna array. This is advantageous, as it helps to reduce both hardware implementation (RF chains) and the complexity of signal processing in the large number of antennas system. Furthermore, this focusing capability of the EM lens provides additional interference rejection gain which leads to estimate the DoA of user terminals precisely. Hence, in this work, subsets based antenna selection approach and subspace-based high resolution DoA estimation algorithms have been considered in combination with the EM lens assisted massive antenna system. In simulations where the DoA is estimated with the EM lens, the results are comparable with conventional methods of DoA estimation without an EM lens, despite the significantly reduced overall system complexity

Performance analysis of 180\ub0 HRR coupler used for direction finding with an antenna array

This paper presents the performance analysis of  hybrid rat race coupler, widely used in radio frequency (RF)/wireless communication systems to couple the power in the desired way. The  hybrid ring coupler consists of 4 ports, two for the input signals and two for the output signals, where sum and difference patterns of the applied two signals can be obtained at two output ports and usually called sum and difference ports. In this work, the couplers have been designed and simulated at central frequencies (fo) of 2.4 and 10 GHz using different types of substrates such as RT Duroid 5880 and FR4.  Furthermore, the coupler has been used for direction finding (angle-of-arrival estimation) application, where we combine the designed  hybrid rat race coupler with a simple two antenna elements array  (at fo=10GHz and RT Duroid =2.2) and fabricate the circuit in order to validate the performance of the coupler by measuring the direction of arrival (DoA) from  and  ports. The obtained results show that good performance can be achieved with the designs considered in this paper.

An Improved Algorithm to Solve Transportation Problems for Optimal Solution

In this paper, we have developed an algorithm to obtain initial basic feasible solution of transportation problems where the object is to minimize the transportation cost. The proposed method is compared with well-known existing methods including Least-Cost Method and North-West Corner Method and is found to yield better results. Feasible solution from the proposed method leads to solution closest to the optimal solution; and in some numerical examples same as the optimal solution. Key words: Transportation problem, Initial Basic Feasible Solution, Optimal Solutio

Flow induced vibration of a square cylinder with high scruton number

Flow over a square cylinder is numerically studied to understand the effect of reduced velocity to the transverse oscillation under the influence of high Scruton number elastic system of 4.316. For low reduced velocities, the transverse oscillation behavior can be grouped in the initial branch region. In this region, the motion is mainly controlled by the lift fluctuation. For intermediate reduced velocities, the transverse oscillation behavior is grouped in the lower branch region. In this region, its natural frequency slowly becomes significant. For high reduced velocities, the galloping region is observed. In this region, the natural frequency dominated the shape of the amplitude oscillation

Aerodynamics characteristics around simplified high speed train model under the effect of crosswinds

The aerodynamics problems of train commonly come when the flow pass through train body. The increasing speed of train to achieve highly technology demands has led to increase the forces and moments and increase sensitivity of train stability and may cause the train to overturn. In this paper, two prisms arranged in tandem represent a simplified model of high speed train are performed at different yaw angle ranging from 0° to 90° by using the unsteady Reynolds- Averaged Navier Stokes (URANS) equation combined with k-ω SST turbulence model. The Reynolds number is 3.14x105based on height of the train and the free stream velocity. The aerodynamic quantities such as the side force, lift force and drag force coefficient show a similar trend where the forces increase with the yaw angle until a certain critical yaw angle before start to decrease till the yaw angle of 90°. The flow structure around the train under the effect of crosswind is visualized. The vorticiticy start to form from the nose and slowly drifts away further towards the trailing edge. The two-dimensional mean streamlines on the cross-section of train at different yaw angle show that the size of vortex increase as the yaw angle increase. Time averaged pressure contour plotted on the cross section along x-axis show the variation of region between high pressure and low pressure region on the leeward and windward side of the train model that may cause train to overturn. © 2006-2017 Asian Research Publishing Network (ARPN)

Aerodynamics characteristics around simplified high speed train model under the effect of crosswinds

The aerodynamics problems of train commonly come when the flow pass through train body. The increasing speed of train to achieve highly technology demands has led to increase the forces and moments and increase sensitivity of train stability and may cause the train to overturn. In this paper, two prisms arranged in tandem represent a simplified model of high speed train are performed at different yaw angle ranging from 0° to 90° by using the unsteady Reynolds- Averaged Navier Stokes (URANS) equation combined with k-ω SST turbulence model. The Reynolds number is 3.14x105based on height of the train and the free stream velocity. The aerodynamic quantities such as the side force, lift force and drag force coefficient show a similar trend where the forces increase with the yaw angle until a certain critical yaw angle before start to decrease till the yaw angle of 90°. The flow structure around the train under the effect of crosswind is visualized. The vorticiticy start to form from the nose and slowly drifts away further towards the trailing edge. The two-dimensional mean streamlines on the cross-section of train at different yaw angle show that the size of vortex increase as the yaw angle increase. Time averaged pressure contour plotted on the cross section along x-axis show the variation of region between high pressure and low pressure region on the leeward and windward side of the train model that may cause train to overturn. © 2006-2017 Asian Research Publishing Network (ARPN)

Utilizing open source software running in inexpensive high performance computing system for cfd applications

The high cost of conducting research is a significant issue for the successfulness of any research project. For research activities involving flow simulation, the licensing fee for the numerical software and the cost to acquire powerful machine are the main factors contributing to the high cost. This paper reports our experiences in setting up a cost effective way of doing computational fluid dynamics (CFD). The actions involve two areas, i.e., software and hardware. For the software, open source softwares are utilized, particularly the OpenFOAM(r) as the CFD package. For the hardware, a parallel computer made from a cluster of inexpensive desktop computer is constructed. This architecture is found able to meet our requirement in investigating various flow problems that include aeroacoustics, vibration and wind engineering for ventilation