A new computer-aided approach to the analysis of CuK converter byusing the alternator equations

A novel approach to the computation of the transient and steady-state response of power electronic switching converters is presented. The solution exhibits precision and reflects the continuous character of the converter waveforms. The key to the approach is the extraction of the switching elements (transistors, or transistor and diode, operated as synchronous switches) in a time-varying two-port called an alternator. The remaining part of the converter is linear and time-invariant; it can be described, in the complex frequency domain, by a system of modified nodal equations. The constitutive equations of the alternator are added, providing a global model of the cyclically switching circuit in the s-domain. The converter is analyzed using the Laplace transform. The modified nodal equations of the converter are solved, and the inverse Laplace transform of their solutions is found. The time-domain solutions together with boundary conditions for cyclical operation of the converter are used for the computer-aided calculation of the transient and steady-state response. The method is applied to a coupled-inductor Cuk converter operating in a continuous conduction mode in which the transient state is due to a step-in-line input voltage     

Respiratory health, effects of ambient air pollution and its modification by air humidity in Drobeta-Turnu Severin, Romania

Background

Associations between ambient air pollution and respiratory health have been mainly reported for Western Europe and Northern America.

Objectives

Our goal was to investigate such associations among the population of Drobeta-Turnu Severin, Romania, a city in Central Eastern Europe (CEE), and to quantify their modification by air humidity. The latter is of increased interest for the current discussion about the potential effects of climate change on human health.

Methods

We investigated (study period: 23.01.2001-31.08.2002) the associations between chronic obstructive pulmonary disease (COPD), asthma and chronic bronchitis (CB) and total suspended particles (TSP), sulphur dioxide (SO₂) and nitrogen dioxide (NO₂). Generalized additive models (GAM) controlling for time patterns and weather effects were applied. Delayed effects up to seven days were analysed in single lag and polynomial distributed lag models (PDLMs).

Results

An increase of 10 µg/m³ TSP was related to a 3.3% (95% CI: 0.3%-6.4%) and a 2.8% (95% CI: 0.1%-5.7%) increase for hospital admissions for chronic bronchitis with a lag of one and four days, respectively. The adverse effect of TSP on chronic bronchitis was reduced by higher humidity. An increase of 10 µg/m³ SO₂ was related to a 6% (95% CI: 7%-25%) increase, with a two days lag, for hospital admissions for chronic bronchitis. We have not been able to identify a threshold, below which ambient TSP and SO₂ concentrations have no effect on hospital admissions for chronic bronchitis. We found adverse but nonsignificant influences of TSP, SO₂ and NO₂ on total respiratory hospital admissions, COPD and asthma and NO₂ on chronic bronchitis.

Conclusions

We conclude that in Drobeta-Turnu Severin CB is associated with TSP and mainly SO₂. Dry air aggravates the adverse effect of TSP.