Study on the key factors allowing the PEM fuel cell systems large commercialization: fuel cell degradation and components integration

PEM Fuel Cells are expected to gradually substitute internal combustion engines as electrical and co-generation power sources thanks to high efficiency, low operating temperature, fast startup time and favourable power-to-weight ratio. However, while PEMFCs have achieved significant progresses in the last decade, their short lifetime and high cost still continue to impede large-scale commercialization. The first subject of the present work had been the study of the PEM fuel cells degradation mechanisms with the aim of: a) find out the most relevant phenomena concerning the fuel cell lifetime, b) testing some methods able to promptly detect the degradation mechanisms and, mostly, c) find out the mitigation strategies able to increase the fuel cells lifetime. At the end of the research three mitigation strategies had been developed and tested: cell voltage monitoring, the current modulation and the stack shunt. According to the tests results all these mitigation strategies, if adopted all together, can effectively led to doubling the fuel cells lifetime. In parallel to the fuel cell lifetime increase, a deep investigation on system components integration had been conducted. Following this principle, the system cost has been considerably reduced mostly thanks to the DC-DC converter integration with the stack and the coolant circuit simplification. The prototypes realized during this work has been taken as example for the production of new fuel cell power systems with increased lifetime at lower cos

Optimisation of Balçova-Narlıdere geothermal district heating system

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2003Includes bibliographical references (leaves: 118-121)Text in English; Abstract: Turkish and Englishxiv, 121 leavesThe main goal of this study is to determine optimum control strategy of Balçova-Narlıdere geothermal district heating system to minimise the energy consumption. First heat demand model of the system was constructed by using statistical method called time series analysis. This model provides the heat demand forecast of next day, by considering ambient temperature forecast of the next day. Then geothermal pipeline system and city distribution system have been modelled in the PIPELAB district heating simulation program. To model the system close to the actual case, database of Balçova geothermal company was used as an input, and the code of PIPELAB program was adapted to be used in geothermal pipeline system. Once the sysem was modelled in PIPELAB, it would be possible to obtain pressure and temperature distribution along the pipe networks in the system. To determine the optimum operation strategy of the wells according to the changing heat demand first the energy consumption of each well pump was defined as a function of their heat production rate. Then these functions were inserted into dynamic programming algorithm which selects the optimum well operation strategy among thousands of options. Also power consumption models of circulation pumps were built and calibrated with actual values. Finally optimum control strategy for the system was determined and the system model was operated by using optimum control strategy according to ambient temperature data of 2001 and 2002. The acual energy consumption values were compared with the optimum energy consumption values and decisive factors in efficient control and operation of the system have been defined

Stress Management Factors In Education

The high percentage of faculty and staff absenteeism due to significant stressful situations was addressed by the implementation of Stress Management Workshops in the target school. This occurred at a secondary institution where there were five different approaches to the program: Guest speakers, movies, after school activities, environmental improvements and positive sharing. The workshop consisted of four guest speakers in the topics of: Stress Management Awareness, Time Management and Organizational Skills, Nutritional Needs During Stress, and Physical Fitness Related to Stress. All the speakers gave their presentations during morning school hours and nutritional morning munchies were served. Inservice points were awarded to all participants. Environmental improvements were made in the lounges. Participants were provided with fruit weekly as a nutritional boost. A movie was shown on the value system of the nation, comparing the different age groups and the relationship with peoples\u27 values. Positive informational notes were distributed weekly for a morale booster. Results showed a significant decrease in staff absenteeism due to stress

Studies of community-associated meticillin resistant Staphylococcus aureus (caMRSA) carriage in people and animals

Meticillin resistant Staphylococcus aureus (MRSA) is a leading cause of bloodstream infections in Australia and is one of the top ten pathogens with an adverse impact on human health worldwide. Infections caused by this organism were originally associated with the healthcare setting, termed healthcare-associated MRSA (haMRSA). New strains of MRSA termed community-associated caMRSA (caMRSA), with different genetic characteristics to haMRSA strains, were first identified in patients residing in remote communities in Western Australia during the early 1990’s. Colonisation with caMRSA precedes and increases the risk of subsequent infection with this organism. Research on caMRSA carriage in community settings has mainly come from Europe and the US. Community specific data for caMRSA carriage in Australia is sparse. This study aimed to detail the prevalence of MRSA in community members (n=283), as well as in groups at risk for the acquisition of MRSA, comprising contact sports participants (n=199), dogs (n=108), dog handlers (n=94), horses (n=310), horse handlers (n=38), veterinary nurses (n=48) and veterinarians (n=60). The role of household contacts and the environment as sources of caMRSA was investigated in the veterinary cohort. Genotypic analyses were used to differentiate strains of caMRSA from haMRSA, and unique strain characteristics were detailed. Genotypic tests included multiplex real-time PCR (RT-PCR), macro-restriction pulsed field gel electrophoresis (PFGE), SCCmec typing, multilocus sequence typing (MLST) and DNA microarrays. The findings of the present study revealed caMRSA poses a greater risk to veterinarians (20%), veterinary nurses (6.25%) and horse handlers (5.26%) than to all other cohorts investigated in which prevalence of caMRSA was found to be low (<2%) or absent

Constraint-based Programming: A Survey

Report on constraint-based computer programming analyzing finite-domain and continuous-domain constraint satisfaction methods and existing systems which apply constraints to problem-solving, modeling, and simulation