Simulation of a novel zero voltage transition technique based on boost power factor correction converter with EMI filter

P. Ram Mohan, M. Vijaya Kumar, O.V. Raghava Reddy and S. Rama Reddy

A novel Zero Voltage Transition (ZVT) technique based closed loop control of Boost Power Factor Correction (PFC) converter with Electro Magnetic Interference (EMI) Filter is presented in this paper. It operates at a fixed frequency while achieving zero voltage turn-on of the main switch and zero current turn-off of the boost diode. This is accomplished by employing resonant operation only during switch transitions. During the rest of the cycle, the resonant network is essentially removed from the circuit and converter operation is identical to its non-resonant counterpart. The principle of operation and simulation results of proposed converter is presented in this paper. The power factor is improved to near 0.99 using the proposed converter.

Earthquake-induced settlements in saturated sandy soils

C. Y. Lee

A simplified approach is proposed to estimate the earthquake-induced settlements in saturated sandy soils. The simplified approach consists of a set of equations that can be used to estimate directly the settlements of a saturated sandy soil layer subjected to earthquake loading. The proposed approach is based on Tokimatsu and Seed (1987) procedure, but does not require the use of charts, tables and diagrams and hence it can be conveniently implemented numerically and allows the expeditious analysis of complicated soil profiles. It is particularly useful for sensitivity analyses and for analyzing soil profile with multiple layers. The proposed approach may be able to characterize the liquefaction boundary line that separates liquefaction from non-liquefaction regions. The proposed approach has been used to predict the settlements observed at two sites subjected to different magnitude of earthquakes. The settlement predictions by the proposed method are in reasonably good agreement with those computed by other published approaches and field measurements.

Optical bistability in a trimodale laser containing a saturable absorber

S. Djabi, H. Boudoukha and M. Djabi

A simple mathematical model to describe the action of a saturable absorber in a laser cavity (LSA) was developed. The approach considered here takes in a phenomenological way into account the essential physical processes which makes it possible to determine the principal parameters in a LSA and their influences on the optical bistability. We will study theoretically optical bistability in a trimodale laser containing a saturable absorber in the case that the active medium and absorber show a homogeneous broadening. We determine the densities of photons as function of the pumping of the active medium and analyze the linear stability of the solutions obtained.

Buckling behavior of partially embedded reinforced concrete piles in sand

P. Senthil Kumar, K. Babu Karuppaiah and P. Parameswaran

This paper aims to unify the structural and geotechnical aspects of the partially embedded slender reinforced concrete pile-soil system together, specifically under eccentric loading, where eccentricity is inevitable in actual practice. Seven reinforced concrete specimens partially embedded in sand as foundation medium were tested with the various critical combinations of unsupported length, loading eccentricity and coefficient of horizontal subgrade modulus of the sand medium. In this study, a simple approach to predict the buckling capacity of an eccentrically loaded partially embedded reinforced concrete pile in sand is formulated using the conventional Davisson and Robinson method combined with the ACI’s flexural stiffness equation of the slender reinforced concrete column and also, introducing a reduction factor to account eccentricity. Comparison was also made between the theoretical predictions and the test results.

A simulation software development for performance analysis of DVS algorithm for low power embedded system

A. Chilambuchelvan, S. Saravanan and J. Raja Paul Perinbam

Energy efficiency is an important property of mobile and pervasive computing devices. Dynamic voltage scaling   (DVS) is an energy saving technique, achieve this property by reducing energy dissipation of the core by lowering the supply voltage and operating frequency. In this paper a simulation environment for testing of different DVS algorithms under EDF and RM have been discussed- as there are no standard simulators readily available in market. The simulator environment provides a framework for objective performance evaluations of different DVS algorithms. Several key DVS algorithms recently proposed for hard real-time periodic task sets have been compared; analyzed for their energy efficiency and discussed the performance differences quantitatively. It is shown through simulations that the real time DVS algorithms closely approach the theoretical lower bound on energy consumption and can easily reduce energy consumption (15-20%) in an embedded real-time system.

A novel topology of EMI filter to suppress common mode and differential mode noises of electro magnetic interference in switching power supplies

P. Ram Mohan, M. Vijaya Kumar and O.V. Raghava Reddy

Abstract:

This paper deals with Electro Magnetic Interference (EMI) in switching power supplies. The EMI consists of mainly common mode and differential mode noises. Due to interference, the efficiency of the equipment reduces and some times the equipment may be damaged. A procedure to design a novel topology of EMI filter to suppress these two noises is presented in this paper.

Settlement and load distribution analysis of underreamed piles

C. Y. Lee

This paper presents the elastic behaviour of underreamed piles in homogeneous soils. The modified boundary element method is used to obtain parametric solutions of underreamed piles under axial loading. Consideration is given to the effect of pile slenderness ratio, pile-soil relative stiffness, underreamed diameter and bearing stratum on response of underreamed piles. The characteristic of load distribution along the pile length is also studied.