Modelling and multi mode control of thermoacoustic instabilities

This research study focuses on modelling, simulating, and multi mode control of the thermoacoustic instabilities in combustion chambers of modern gas turbines. The chamber is excited acoustically by a loudspeaker mounted underneath the flame zone. The chamber is identified in cold flow condition as well as both steady and unsteady combustion. The stability analysis based on the identification results shows that premixed flame becomes unstable at fuel to air ratio larger than 0.8. The frequency response obtained from the identification results shows that the Helmholtz mode is the dominant unstable mode of the chamber which couples with the flame and forms thermoacoustic instability. The analytical model is developed in Matlab based on the 1D acoustic equations and the resulting wave equation with the nonlinear flame transfer function. The loudspeaker is identified experimentally and modelled by Multi Microphone Method (MMM) approach. The main purpose of modelling the combustion chamber is to predict the onset of the thermoacoustic instabilities when a control parameter such as equivalence ratio or fuel flow is altered. In the analytical model developed in this work, the delay factor in the flame transfer function influences the interaction between the incoming acoustic wave and the flame heat release, affects the thermoacoustic stability. The loudspeaker is an electromechanical system coupled with the pressure acoustic inside the tube in which each subsystem is governed by different sets of differential equations. Hence, multiphysics modelling is required to model this system. For further stability analysis, a finite element model (FEM) is developed in Comsol environment and the results are compared to the results obtained from the analytical model developed in Matlab. The reason for using FEM is its high accuracy and convenience in modelling bulk resonance such as Helmholtz mode. On the other hand, the analytical model developed in Matlab is linearised and used in model based control and for control prototyping. Based on the obtained reduced order model, several model based control approaches are developed and compared. The experimental results show that the dual mode controller with a Pade approximation as local stabilizer, is the most robust controller and works in a wider range of OPs. Finally, two different model based constrained approaches are developed to stabilize a Rijke tube with repetitively pulsing plasma discharge: a dual mode controller and a dynamic matrix controller. The two concepts are evaluated by using both simulation and the real setup

Quality of Life in Patients with Bipolar I Disorder: Is It Related to Disorder Outcome?

Bipolar I disorder (BID) and its treatments have shown to be associated with deep impacts on patients' subjective feelings and quality of life (QOL). There are also some comments about impact of these feelings on course and outcome of patients with BID. This study was aimed to evaluate quality of life in patients with BID and to assess its relationship with course of disorder. Fifty patients with BID were recruited based on the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) from May 2008 and followed for 12 months. Quality of life and mood disorder recurrence were assessed through World Health Organization Quality of Life and SCID-I tools respectively at baseline and after 6 and 12 months. Repeated measures analysis and logistic regression were used to analyze the independent effect of QOL and demographic factors on BID recurrence. Fifty patients (66% male; 48% never married; 48% in primary school level) with mean ± SE age and age of BID onset 33.8±1.5 and 26.6±1.1 years were studied. They had 3.4±0.6 episodes already. Twenty eight percent suffered from recurrences during the follow-up. The QOL scores at baseline, after 6 and 12 months were 70±1.8, 69.6±1.1 and 73±1.3 respectively. There were no significant change in QOL and its sub-domains during the follow-up (P=0.37). QOL showed no independent relationship with BID recurrences (P>0.1). No change in the QOL during the follow-up could denote lack of effectiveness of routine interventions on this factor. Also, short-term follow-up might be concerned as the possible reason. Of prime importance is to consider quality of life independently in treating patients with bipolar disorder

The Iranian blood pressure measurement campaign, 2019: study protocol and preliminary results

Purpose Hypertension is one of the most important risk factors for premature mortality and morbidity in Iran. The objective of the Iranian blood pressure (BP) measurement campaign was to identify individuals with raised blood pressure and providing appropriate care and increase the awareness among the public and policymakers of the importance of tackling hypertension. Methods The campaign was conducted in two phases. The first (communication) phase started on May 17th (International Hypertension Day). The second phase started on June 8th, 2019, and lasted up to July 7th during which, blood pressures were measured. The target population was Iranians aged >= 30 years. Participants voluntarily referred to health houses in rural and health posts and comprehensive health centers in urban areas in the setting of the Primary Health Care network. Additionally, over 13,700 temporary stations were set up in highly visited places in urban areas. Volunteer healthcare staff interviewed the participants, measured their BP, and provided them with lifestyle advice and knowledge of the risks and consequences of high blood pressure. They referred participants to physicians in case their BP was high. Participants immediately received a text message containing the relevant advice based on their measured BP and their past history. Results Blood pressure was measured for a total of 26,678,394 participants in the campaign. A total of 13,722,148 participants (51.4%) were female. The mean age was 46 +/- 14.1 years. Among total participants, 15,012,693 adults (56.3%) with no past history of hypertension had normal BP, 7,959,288 participants had BP in the prehypertension range (29.8%), and finally, 3,706,413 participants (13.9%) had either past medical history of hypertension, used medications, or had high BP measured in the campaign. Conclusion The campaign was feasible with the objective to increase the awareness among the public and policymakers of the importance of tackling hypertension in Iran