Fluorinated halon replacement agents in explosion inerting

The US Federal Aviation Administration (FAA) observed during explosion tests that at a low concentration of agent, some candidate halon replacement agents increased the explosion severity instead of mitigating the event. At UTC Aerospace Systems a test program was developed to assess the behaviour of alternative agents at values below inerting concentration. Two agents were selected, C2HF5 (Penta- fluoroethane, HFC-125) and C6F12O (FK-5-1-12, Novec™1230). Baseline tests were performed with unsuppressed C3H8 (propane)/air mixtures and C3H8/air mixtures with CF3Br (Halon 1301) and N2 (nitrogen). Using CF3Br or N2 at below inerting concentrations mitigated the explosion. C2HF5 was tested against C3H8 at stoichiometric (4 vol%) and lower explosion limit (LEL) (2 vol%). Against 4 vol% C3H8 the combustion was mitigated, proportional to agent concentration; however, low concentrations of C2HF5 with 2 vol% C3H8 enhanced the explosion. Tests with N2 against a volatile mixture of C3H8 with C2HF5 showed that N2 mitigated the events. Final tests were performed with low concentrations of C6F12O against C3H8/air mixtures. This showed similar behaviour to that observed with the C2HF5 tests. Normally during qualification tests for new agents the stoichiometric concentration of a fuel is deemed to be the worst case scenario and the baseline against which agents are tested. The above described test results show that this assumption may need to be reconsidered. This work shows that contrary to common assumption the agents investigated are unlikely to have acted chemically at the flame front, but most likely, mainly cooled the flame and changed the stoichiometry, i.e. the ratio of components of the flammable mixture

Mutual Information for the Detection of Crush

Fatal crush conditions occur in crowds with tragic frequency. Event organizers and architects are often criticised for failing to consider the causes and implications of crush, but the reality is that both the prediction and prevention of such conditions offer a significant technical challenge. Full treatment of physical force within crowd simulations is precise but often computationally expensive; the more common method of human interpretation of results is computationally “cheap” but subjective and time-consuming. This paper describes an alternative method for the analysis of crowd behaviour, which uses information theory to measure crowd disorder. We show how this technique may be easily incorporated into an existing simulation framework, and validate it against an historical event. Our results show that this method offers an effective and efficient route towards automatic detection of the onset of crush

Prediction of the radiative heat transfer in small and large scale oxy-coal furnaces

Predicting thermal radiation for oxy-coal combustion highlights the importance of the radiation models for the spectral properties of gases and particles. This study numerically investigates radiation behaviours in small and large scale furnaces through refined radiative property models, using the full-spectrum correlated k (FSCK) model and Mie theory based data, compared with the conventional use of the weighted sum of grey gases (WSGG) model and the constant values of the particle radiation properties. Both oxy-coal combustion and air-fired combustion have been investigated numerically and compared with combustion plant experimental data. Reasonable agreements are obtained between the predicted results and the measured data. Employing the refined radiative property models achieves closer predicted heat transfer properties to the measured data from both furnaces. The gas-phase component of the radiation energy source term obtained from the FSCK property model is higher within the flame region than the values obtained by using the conventional methods. The impact of using non-grey radiation behaviour of gases through the FSCK is enhanced in the large scale furnace as the predicted gas radiation source term is approximately 2-3 times that obtained when using the WSGG, while the same term is in much closer agreement between the FSCK and the WSGG for the pilot-scale furnace. The predicted total radiation source term (from both gases and particles) is lower in the flame region after using the refined models, which results in a hotter flame (approximately 50-150 K higher in this study) compared with results obtained from conventional methods. In addition, the predicted surface incident radiation reduces by using the refined radiative property models for both furnaces, in which the difference is relevant with the difference in the predicted radiation properties between the two modelling techniques. Numerical uncertainties resulting from the influences of combustion model, turbulent particle dispersion and turbulence modelling on the radiation behaviours are discussed

Measurement and Modeling of Particle Radiation in Coal Flames

This work aims at developing a methodology that can provide information of in-flame particle radiation in industrial-scale flames. The method is based on a combination of experimental and modeling work. The experiments have been performed in the high-temperature zone of a 77 kWth swirling lignite flame. Spectral radiation, total radiative intensity, gas temperature, and gas composition were measured, and the radiative intensity in the furnace was modeled with an axisymmetric cylindrical radiation model using Mie theory for the particle properties and a statistical narrow-band model for the gas properties. The in-flame particle radiation was measured with a Fourier transform infrared (FTIR) spectrometer connected to a water-cooled probe via fiber optics. In the cross-section of the flame investigated, the particles were found to be the dominating source of radiation. Apart from giving information about particle radiation and temperature, the methodology can also provide estimates of the amount of soot radiation and the maximum contribution from soot radiation compared to the total particle radiation. In the center position in the flame, the maximum contribution from soot radiation was estimated to be less than 40% of the particle radiation. As a validation of the methodology, the modeled total radiative intensity was compared to the total intensity measured with a narrow angle radiometer and the agreement in the results was good, supporting the validity of the used approach

Treatment of myofascial trigger points in common shoulder disorders by physical therapy: A randomized controlled trial [ISRCTN75722066]

Contains fulltext : 52454.pdf (publisher's version ) (Open Access

Exploring Technology Usage By School Counselors: A Mixed Methods Study

School counseling is progressing from the tradition of responsive services to a proactive system linked to school mission (Dahir, 2009, p 4.). This paradigm shift within the profession has drastically increased the responsibility required of school counselors. This study explored data drawn from a population of school counselors at Recognized American School Counselor Association (ASCA) Model Programs (RAMP). A multi-phase, sequential explanatory mixed methods design was used for this study. The study focused on nine specific technologies: website, e-mail, Internet, Microsoft Word, Microsoft Excel, Microsoft PowerPoint, student database system, social networking platforms, and EZ Analyze. Mean scores, frequency distribution tables, and rankings regarding usage frequencies and purposes were determined and framed within the four quadrants of the ASCA National Model. In the second qualitative phase of the study, school counselors identified three emerging themes relative to the use of technology in school counseling: communication, inappropriate technology usage, and data collection and anaylsis. The following five conclusions emerged: 1) Social networking platforms have not been widely accepted by school counselors at RAMP schools. 2) The findings of this study support previous findings which demonstrate increases in the use of technology within the profession of school counseling over time. 3) The types of technologies used by school counselors at RAMP schools in a are consistent from school counselor to school counselor. 4) School counselors at RAMP schools have similar concerns regarding technology integration within the profession. 5) A need exists for increased preparation and professional development for school counselors in regards to technology usage for the purpose of data collection and analysis. Recommendations for future studies include: 1) Repeat this study with a much larger, multifarious population. 2) Identify the influence age has on the technology usage frequency of school counselors. 3) Research the role of school setting when analyzing technology usage frequencies in regards to school counselors. 4) Studies that examine the continued transition of school counseling programs from responsive to proactive practices. Adviser: Miles Bryan