Development and evaluation of transfer functions for a variable speed compressor

In this study, transfer functions of electronic expansion valve and variable speed scroll compressor in a chiller system are developed based on an experimental analysis. Dynamic behaviours of water temperature at chiller output and refrigerant superheat at evaporator outlet have either the first- or the second-order linear models, respectively. Different from the existing modelling studies in literature novel models are presented for variable speed refrigeration system with scroll compressor and liquid type evaporator. The scroll compressor used in the current study is not produced for variable speed operation however it is operated with some limitations in the range of 30 to 50 Hz through an inverter. Similar restrictions are presented for the electronic expansion valve as 10 per cent to 35 per cent opening range because of operational limitations. To validate transfer functions of the variable speed scroll compressor and electronic expansion valve, mean square error values for all transfer functions are calculated. The mean square error values vary between 0.0126 and 0.3116. In addition, all transfer functions are designed and tested using corresponding proportional-integral-derivative controllers in order to see their applicability. The results indicate that energy savings are a consequence of operating the chiller at smaller frequencies than the basic 50 Hz while partial load occurred. © Authors 2011

A microcontroller based test platform for controller design

The Institute of Electrical and Electronics Engineers (IEEE);IEEE Industrial Electronics Society (IES);IEEE Control Systems Society (CSS);Society of Instrument and Control Engineers (SICE-Japan);Politecnico di Bari2010 IEEE International Symposium on Industrial Electronics, ISIE 2010 -- 4 July 2010 through 7 July 2010 -- Bari -- 83019This paper presents a microcontroller based emulator which is developed for the design-test-and-redesign of controllers through examining the controller candidates on the emulated plants operating under the created real-time and real environmental conditions. The analog and digital peripheral units of the plant emulator provide the recreation of the real environmental conditions such that the whole emulator runs as if the real plant whenever the model implemented in the microcontroller is a right model for the plant. The emulator has the flexibility of changing the plant model and/or its parameters manually and it also enables to apply, in an automatic way, analog disturbances and analog parameter perturbations to the plant model. The developed plant emulator communicated with the simulator of the controller part both managed by a graphical user interface implemented in the computer constitutes a controller design-test-redesign platform which has the advantages of using simulated plants in the controller design providing a test-flexibility and also of testing the controller candidates on the emulated plants operating under the conditions very close to the real situations, so assuring the desired controller performances. © 2010 IEEE

The diagnostic value of quantitative texture analysis of conventional MRI sequences using artificial neural networks in grading gliomas

AIM: To explore the value of quantitative texture analysis of conventional magnetic resonance imaging (MRI) sequences using artificial neural networks (ANN) for the differentiation of high-grade gliomas (HGG) and low-grade gliomas (LGG)

Introduction to complex systems analysis with wavelets

In this chapter the authors deal with a few methods of nonlinear wavelet analysis for the characterization of nonstationary signals. The methods herein described can be used in a wide variety of biological signals including ECG, HRV, pressure waves and heart sounds. The reader can find both conventional methods of wavelet analysis such as linear and nonlinear denoising, as well as more sophisticated methods based on fractal analysis and entropy. Applications of such algorithms to the analysis of the heartbeat dynamics are also described

Surgical site infection after gastrointestinal surgery in children : an international, multicentre, prospective cohort study

Introduction Surgical site infection (SSI) is one of the most common healthcare-associated infections (HAIs). However, there is a lack of data available about SSI in children worldwide, especially from low-income and middle-income countries. This study aimed to estimate the incidence of SSI in children and associations between SSI and morbidity across human development settings. Methods A multicentre, international, prospective, validated cohort study of children aged under 16 years undergoing clean-contaminated, contaminated or dirty gastrointestinal surgery. Any hospital in the world providing paediatric surgery was eligible to contribute data between January and July 2016. The primary outcome was the incidence of SSI by 30 days. Relationships between explanatory variables and SSI were examined using multilevel logistic regression. Countries were stratified into high development, middle development and low development groups using the United Nations Human Development Index (HDI). Results Of 1159 children across 181 hospitals in 51 countries, 523 (45 center dot 1%) children were from high HDI, 397 (34 center dot 2%) from middle HDI and 239 (20 center dot 6%) from low HDI countries. The 30-day SSI rate was 6.3% (33/523) in high HDI, 12 center dot 8% (51/397) in middle HDI and 24 center dot 7% (59/239) in low HDI countries. SSI was associated with higher incidence of 30-day mortality, intervention, organ-space infection and other HAIs, with the highest rates seen in low HDI countries. Median length of stay in patients who had an SSI was longer (7.0 days), compared with 3.0 days in patients who did not have an SSI. Use of laparoscopy was associated with significantly lower SSI rates, even after accounting for HDI. Conclusion The odds of SSI in children is nearly four times greater in low HDI compared with high HDI countries. Policies to reduce SSI should be prioritised as part of the wider global agenda.Peer reviewe