Iterative min-sum decoding of tail-biting codes

By invoking a form of the Perron-Frobenius theorem for the “min-sum” semi-ring, we obtain a union bound on the performance of iterative decoding of tail-biting codes. This bound shows that for the Gaussian channel, iterative decoding will be optimum, at least for high SNRs, if and only if the minimum “pseudo-distance” of the code is larger than the ordinary minimum distance

Analysis of First-Time Completion in the Field Service Environment

First-time completion is an important measure of service quality and efficiency in the field service industry. Customers call upon field service providers to repair their equipment in a timely manner so it can be put back into service for their business demands. Responsiveness can be measured through first-time completion and is defined as completing the repair on the first visit of a service call. This research is exploring the first-time completion in the forklift service industry. This research found the primary factors that impact first-time completion percentage in this industry include parts on hand, parts backorder process, technician experience, and anticipating service demands

The Effects of Fire Fighting and On-Scene Rehabilitation on Hemostatis

Fire fighting is a dangerous occupation – in part because firefighters are called upon to perform strenuous physical activity in hot, hostile environments. Each year, approximately 100 firefighters lose their lives in the line of duty and tens of thousands are injured. Over the past 15 years, approximately 45% of line of duty deaths have been attributed to heart attacks and another 650-1,000 firefighters suffer non-fatal heart attacks in the line of duty each year. From 1990 to 2004, the total number of fireground injuries has declined, yet during this same period, the number of cases related to the leading cause of injury - overexertion/strain – remained relatively constant. It is well recognized that fire fighting leads to increased cardiovascular and thermal strain. However, the time course of recovery from fire fighting is not well documented, despite the fact that a large percentage of fire fighting fatalities occur after fire fighting activity. Furthermore, on scene rehabilitation (OSR) has been broadly recommended to mitigate the cardiovascular and thermal strain associated with performing strenuous fire fighting activity, yet the efficacy of different rehabilitation interventions has not been documented. Twenty-five firefighters were recruited to participate in a “within-subjects, repeated measures” study designed to describe the acute effects of fire fighting on a broad array of physiological and psychological measures and several key cardiovascular variables. This study provided the first detailed documentation of the time course of recovery during 2½ hours post-fire fighting. Additionally, we compared two OSR strategies (standard and enhanced) to determine their effectiveness.published or submitted for publicationnot peer reviewe

Characterizing a Firefighter’s Immediate Thermal Environment in Live-Fire Training Scenarios

Detailed characterization of a firefighter’s typical thermal exposures during live-fire training and responses can provide important insights into the risks faced and the necessary protections, protocols, and standards required. In order to gather data on representative thermal conditions from a firefighter’s continually varying local environment in a live-fire training exercise, a portable heat flux and gas temperature measurement system was created, calibrated, and integrated into firefighter personal protective equipment (PPE). Data were collected from 25 live-fire training exposures during seven different types of scenarios. Based on the collected data, mild training environments generally exposed firefighters to temperatures around 50 degrees Celsius and heat fluxes around 1 kW/m2, while severe training conditions generally resulted in temperatures between 150 degrees Celsius and 200 degrees Celsius with heat fluxes between 3 kW/m2 and 6 kW/m2. For every scenario investigated, the heat flux data portrayed a more severe environment than the temperature data when interpreted using established thermal classes developed by the National Institute for Standards and Technology for electronic equipment used by first responders. Local temperatures from the portable measurement system were compared with temperatures measured by stationary thermocouples installed in the training structure for 14 different exposures. It was determined the stationary temperatures represented only a rough approximate bound of the actual temperature of the immediate training environment due to the typically coarse distribution of these sensors throughout the structure and their relative (fixed) distance from the fire sets. The portable thermal measurement system has provided new insights into the integration of electronic sensors with firefighter PPE and the conditions experienced by firefighters in live-fire training scenarios, which has promise to improve the safety and health of the fire service.Ope

Characterizing a Firefighter's Immediate Thermal Environment in Live-Fire Training

In 2013, over 7,500 firefighters were injured during training related activities, including highrisk, but necessary, live-fire training. Although a standard for live-fire training exists, little physical data have been collected from the thermal environment encountered in this type of training. Acquiring data from live-fire training scenarios would be extremely beneficial to the fire service; it would allow for the evaluation and improvement of live-fire training evolutions as well as testing standards for firefighter personal protective equipment (PPE). In order to gather data from a firefighters immediate thermal environment in a live-fire training exercise, a portable heat flux and gas temperature measurement system was created and integrated into firefighter PPE. The system was tested and calibrated in a laboratory setting at the National Institute of Standards and Technology and then used to measure the ambient temperature and incident heat flux of a firefighters immediate environment in live-fire scenarios. Data were collected from 28 live-fire training evolutions conducted during seven different training scenarios. It was discovered that a mild thermal environment generally contained temperatures between 50C and 75C and heat fluxes around 1 kW/m2, while a severe thermal environment generally contained temperatures between 150C and 225C and heat fluxes between 3 kW/m2 and 6 kW/m2. Additionally, heat flux proved to be a more effective metric than temperature in evaluating the severity of the thermal environment. The portable thermal measurement system has provided new insights into conditions experienced by firefighters, which will greatly improve the safety and health of the US fire service.Ope

Occupant Tenability in Single Family Homes: Part II: Impact of Door Control, Vertical Ventilation and Water Application

This paper describes experimental investigations of fire service ventilation and suppression practices in full-scale residential structures, including a one-story, 112 m2, 3 bedroom, 1 bathroom house with 8 total rooms and a two-story 297 m2, 4 bedroom, 2.5 bathroom house with 12 total rooms. The two-story house featured a modern open floor plan, two-story great room and open foyer. Seventeen experiments were conducted varying fire location, ventilation locations, the size of ventilation openings and suppression techniques. The experimental series was designed to examine the impact of several different tactics on tenability: door control, vertical ventilation size, and exterior suppression. The results of these experiments examine potential occupant and firefighter tenability and provide knowledge the fire service can use to examine their vertical ventilation and exterior suppression standard operating procedures and training content. It was observed that door control performed better at controlling the thermal exposure to occupants than did fully opening the door. Additionally, the impact of increased vertical ventilation area was minimal, and only slightly reduced the thermal exposure to occupants in a few non-fire rooms. In the two-story structure, the non-fire rooms on the second floor consistently had larger thermal fractional effective rate (FER) values (approximately 2.59 the thermal risk to oocupants) than did the non-fire rooms on the first floor. Water application was also shown to reduce the thermal risk to occupants 60 s after water application 1/3rd the original values on second floor rooms of the two-story structure and by at least 1/5th of the original values on the first floor rooms of both structures. Data also showed that the impact of front door ventilation on the toxic gases exposure was minimal, as the toxic gases FER actually increased after front door ventilation for several experiments. However, after vertical ventilation there was a 30% reduction in the toxic gases exposure rate in two of the one-story structure experiments.Funding was provided by the Department of Homeland Security (Grant No. EMW-2010-FP-00661).Ope

Occupant Tenability in Single Family Homes: Part I—Impact of Structure Type, Fire Location and Interior Doors Prior to Fire Department Arrival

This paper describes an experimental investigation of the impact of structure geometry, fire location, and closed interior doors on occupant tenability in typical single family house geometries using common fuels from twenty-first century fires. Two houses were constructed inside a large fire facility; a one-story, 112 m2, 3-bedroom, 1-bathroom house with 8 total rooms, and a two-story 297 m2, 4-bedroom, 2.5-bathroom house with 12 total rooms. Seventeen experiments were conducted with varying fire locations. In all scenarios, two bedrooms had doors remaining open while the door remained closed in a third bedroom immediately adjacent to the open door bedrooms. Temperature and gas measurement at the approximate location of a crawling or crouching trapped occupant (0.9 m from the floor) were utilized with the ISO 13571 fractional effective dose (FED) methodology to characterize occupant tenability up to the point of firefighter intervention. The FED values for the fire room were higher for heat exposure than for toxic gases, while target rooms reached highest FED due to CO/CO2 exposure. The closed interior door decreased FED significantly, with the worst case scenario resulting in a 2% probability of receiving an incapacitating dose compared to the worst case scenario for an open bedroom of 93% probability of receiving an incapacitating dose. In fact, in 7 of the 17 experiments, the closed interior door resulted in a less than 0.1% chance of an occupant receiving an incapacitating dose prior to firefighter ‘intervention.’Funding was provided by U.S. Department of Homeland Security (Grant No. EMW-2010-FP-00661).Ope

Accuracy of the VO2peak prediction equation in firefighters

Background: A leading contributing factor to firefighter injury and death is lack of fitness. Therefore, the Fire Service Joint Labor Management Wellness-Fitness Initiative (WFI) was established that includes a focus on providing fitness assessments to all fire service personnel. The current fitness assessment includes a submaximal exercise test protocol and associated prediction equation to predict individual VO2peak as a measure of fitness. There is limited information on the accuracy, precision, and sources of error of this prediction equation. This study replicated previous research by validating the accuracy of the WFI VO2peak prediction equation for a group of firefighters and further examining potential sources of error for an individual firefighters’ assessment. Methods: The sample consisted of 22 firefighters who completed a maximal exercise test protocol similar to the WFI submaximal protocol, but the test was terminated when firefighters reached a maximal level of exertion (i.e., measured VO2peak). We then calculated the predicted VO2peak based on the WFI prediction equation along with individual firefighters’ body mass index (BMI) and 85% of maximum heart rate. The data were analyzed using paired samples t-tests in SPSS v. 21.0. Results: The difference between predicted and measured VO2peak was -0.77 ± 8.35 mL•kg-1•min-1. However, there was a weak, statistically non-significant association between measured VO2peak and predicted VO2peak (R2 = 0.09, F(1,21) = 2.05, p = 0.17). The intraclass correlation coefficient (ICC = 0.215, p > 0.05) and Pearson (r = 0.31, p = 0.17) and Spearman (ρ = 0.28, p = 0.21) correlation coefficients were small. The standard error of the estimate (SEE) was 8.5 mL•kg-1•min-1. Further, both age and baseline fitness level were associated with increased inaccuracy of the prediction equation. Conclusions: We provide data on the inaccuracy and sources of error for the WFI VO2peak prediction equation for predicting fitness level in individual firefighters, despite apparently accurate predictions for a group of firefighters. These results suggest that the WFI prediction equation may need to be reevaluated as a means of precisely determining fitness for individual firefighters, which may affect employment status, duty assignment, and overall life safety of the firefighter.This study was supported by a research grant from the Department of Homeland Security through a Federal Emergency Management Agency Assistance to Firefighters Grant (FEMA-AFG) (EMW-2010-FP-01606).Ope

Feasibility of Knots to Reduce the Maximum Dynamic Arresting Load in Rope Systems

Impact loads to the human body due to falls from height can be mitigated by well-designed and characterized fall protection systems. While energy absorption methods using rope deformation and/or accessory components have previously been evaluated, the ability for simple knots tied in the system to alter impact loads has not been studied in detail. We quantify the effectiveness of various common knots to reduce dynamic loads in typical fall scenarios for which the systems are designed, and interpret this change in the context of rope strength reduction due to the knot. Knots are shown to significantly (45–60 %) reduce the quasistatic strength of rope when compared to a manufactured sewn-eye (40 %). A single exception to this outcome is with the quadruple overhand on a bite (30–35 %). Knots significantly reduce the maximum arresting load due to a dynamic impact event when compared to ropes without knots, providing significantly more energy absorption than the sewn-eye alone. In nearly all rope/knot combinations, the ratio of maximum arrest load (MAL) to breaking strength was lower with the knotted ropes when compared to the sewn-eye terminations. In particular, the quadruple overhand on a bite tied in the Technora–Technora rope resulted in MALs that were only 33 % of the minimum breaking strength (MBS). Ropes with sewn-eye terminations resulted in MALs that were 80 % of the MBS. From the scenarios investigated, the quadruple overhand on a bite provides a favorable reduction in arrest loads with the smallest associated loss of strength.This research was funded by the Department of Homeland Security’s Assistance to Firefighters Grant Program’s Fire Prevention and Safety Grants through Grant # EMW-2008-FP-02504.Ope

Isospin Fluctuations from a Thermally Equilibrated Hadron Gas

Partition functions, multiplicity distributions, and isospin fluctuations are calculated for canonical ensembles in which additive quantum numbers as well as total isospin are strictly conserved. When properly accounting for Bose-Einstein symmetrization, the multiplicity distributions of neutral pions in a pion gas are significantly broader as compared to the non-degenerate case. Inclusion of resonances compensates for this broadening effect. Recursion relations are derived which allow calculation of exact results with modest computer time.Comment: 10 pages, 5 figure