Development of a model-based optimal control strategy of Centrifugal Chiller System

2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Optimal control of multi-zone vav air-conditioning system

2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Development and present status of the research on optimal control of chilled water systems in central air-conditioning

2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Time constant of heart rate recovery after low level exercise as a useful measure of cardiovascular fitness

In this study we aimed to establish the usefulness of the time constant of heart rate recovery (Tr) in the evaluation of cardiovascular fitness. 15 male subjects exercised on recumbent bicycle at three different workloads (75W, 100W 125W) where R-R intervals were monitored to determine Tr. In order to find the maximal oxygen uptake (V̇O2max) of each subject, oxygen consumption rate (V̇O2) was recorded throughout the treadmill exercise (10km/h). Based on V̇O2max' we classified the subjects into two groups: the "fit" group and the "unfit" group. We found a significant difference in Tr between these two groups only existed when the workload was 75W (p ≤ 0.01) and only at this workload did the R-R intervals achieve stability during the 5 minutes of exercise. Furthermore, we found the cut-off value for predicting cardiovascular fitness at this workload was 55 seconds, with an associated sensitivity of 85.7% and specificity of 87.5%. © 2006 IEEE

Oxygen uptake estimation in humans during exercise using a Hammerstein model

This paper aims to establish a block-structured model to predict oxygen uptake in humans during moderate treadmill exercises. To model the steady state relationship between oxygen uptake (oxygen consumption) and walking speed, six healthy male subjects walked on a motor driven treadmill with constant speed from 2 to 7 km/h. The averaged oxygen uptake at steady state (VO 2) was measured by a mixing chamber based gas analysis and ventilation measurement system (AEI Moxus Metabolic Cart). Based on these reliable date, a nonlinear steady state relationship was successfully established using Support Vector Regression methods. In order to capture the dynamics of oxygen uptake, the treadmill velocity was modulated using a Pseudo Random Binary Signal (PRBS) input. Breath by breath analysis of all subjects was performed. An ARX model was developed to accurately reproduce the measured oxygen uptake dynamics within the aerobic range. Finally, a Hammerstein model was developed, which may be useful for implementing a control system for the regulation of oxygen uptake during treadmill exercises. © 2007 Biomedical Engineering Society

Analysis of orientation error of triaxial accelerometers on the assessment of energy expenditure

This paper investigates the effects of orientation error in the positioning of triaxial accelerometers on the assessment of energy expenditure. Four subjects walked on a treadmill at varying velocities ranging from 4km.h -1 to 5km.h-1. During each test, a triaxial accelerometer attached to the lower back at arbitrary orientations to record body accelerations. Energy expenditure was estimated by the sum of the integrals of the absolute value of accelerometer output from all the three measurement directions. Based on theoretical analysis and experimental observations, it is concluded that small orientation errors ( < 3° ) have no distinguishable effects on the estimation of energy expenditure. We propose an efficient method to compensate for larger orientation errors. The experimental results verified the effectiveness of this proposed compensation method. ©2005 IEEE

Heart rate control during treadmill exercise

A computer-controlled treadmill and related data collection and processing systems have been developed for the control of heart rate during treadmill exercise. Minimizing deviations of heart rate from a preset profile is achieved by controlling the speed and/or the gradient of the treadmill. A simple and practical heart rate measurement algorithm has been developed to robustly measure the variations of heart rate. Both conventional Proportional-Integral- Derivative (PID) control and fuzzy Proportional-Integral (PI) control approaches have been employed for the controller design. The fuzzy Proportional-Integral algorithm achieved better heart rate tracking performance. Finally, a heart rate based exercising protocol was successfully implemented on the newly designed exercise system. © 2005 IEEE

Estimation of oxygen consumption for moderate exercises by using a hammerstein model

This paper aims to establish block-structured nonlinear model (Hammerstein model) to predict oxygen uptake during moderate treadmill exercises. In order to model the steady state relationship between oxygen uptake (oxygen consumption) and walking speed, six healthy male subjects walked on a motor driven treadmill at six different speed (2,3,4,5,6, and 7 km/h). The averaged oxygen uptake of exercisers at steady state was measured by a mixing chamber based gas analyzer(AEI Moxus Metabolic Cart). Based on these reliable experiment data, a nonlinear static function was obtained by using Support Vector Regression. In order to capture the dynamics of oxygen uptake, a suitable Pseudo Random Binary Signal (PRBS) input was designed and implemented on a computer controlled treadmill. Breath by breath analysis of all exercisers' dynamic responses (PRBS responses) to treadmill walking was performed. A useful ARX model is identified to justify the measured oxygen uptake dynamics within the aerobic range. Finally, a Hammerstein is achieved, which is useful for the control system design of oxygen uptake regulation during treadmill exercises. © 2006 IEEE

State of Climate Change Adaptation and Mitigation Efforts in Agriculture for Bangladesh

In many countries including south Asia, Climate Change remains a high talk low implementation phenomenon, with highly media savvy workshops and beautiful documents marred by poor implementation on the grounds. On the contrary, Bangladesh, In spite of its reputation for being poverty and disaster stricken nation with high levels of corruption has made exceptional progress in recent times. In particular the government of Bangladesh s initiatives in response to climate change (BCCSAP), food security (CIP), establishment of funding mechanisms (CCTF & BCCRF), and the creation of institutions such as climate change unit and a climate cell in all government agencies to oversee the implementation of programs and projects prescribed in BCCSAP and CIP which are now aligned into the 6th five year plans are exemplary and commendable. It was a truly gratifying experience and I remain enthused and excited with anticipation of what will come out of Bangladesh at the end of their 6th five-year plan