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Journal Article

A Bayesian Approach to Cross-Validation in Pedestrian Accident Reconstruction

In statistical modeling, cross-validation refers to the practice of fitting a model with part of the available data, and then using predictions of the unused data to test and improve the fitted model. In accident reconstruction, cross-validation is possible when two different measurements can be used to estimate the same accident feature, such as when measured skidmark length and pedestrian throw distance each provide an estimate of impact speed. In this case a Bayesian cross-validation can be carried out by (1) using one measurement and Bayes theorem to compute a posterior distribution for the impact speed, (2) using this posterior distribution to compute a predictive distribution for the second measurement, and then (3) comparing the actual second measurement to this predictive distribution. An actual measurement falling in an extreme tail of the predictive distribution suggests a weakness in the assumptions governing the reconstruction.
Technical Paper

Informativeness of the Finger Temperature/Heat Flux as an Index of Human Thermal Status Under Local Cold Influences

Introduction Human thermoregulation during EVA remains a challenge. The establishment of a high correlation between the thermal status of the fingers and the heat surplus/deficit in the body provides an index with potential to more effectively monitor and control the astronaut’s thermal status. This series of studies evaluated the changes in finger temperature (Tfing) trajectories in conditions relevant to EVA. Methods In different experiments, subjects were donned in a liquid cooling/warming garment (LCWG) that covered the full body surface except for the face and hands; they wore either a physiologically designed warming glove or the Phase VI glove. The experimental protocols were as follows: imposition of temperature differences in the left and right gloves; different thermal insulation levels of the gloves; sequential grasping of a highly cold rail in different glove conditions; placement of the finger thermistor on different sites of the finger.
Technical Paper

Subjective Perception of Thermal and Physical Comfort in Three Liquid Cooling Garments

The subjective aspects of comfort in three different cooling garments, the MACS-Delphi, Russian Orlan, and LCVG were evaluated. Six subjects (4 males and 2 females) were tested in separate sessions in each garment and in one of two environmental chamber conditions: 24°C and 35°C. Subjects followed a staged exercise/rest protocol with different levels of physical exertion at different stages. Thermal comfort and heat perception were assessed by ratings on visual analog scales. Ratings of physical comfort of the garment and also garment flexibility in positions simulating movements during planetary exploration were also obtained. The findings indicated that both overall thermal comfort and head thermal comfort were rated highest in the MACS-Delphi at 24°C. The Orlan was rated lowest on physical comfort and less flexible in different body positions.
Technical Paper

The Advanced Design of a Liquid Cooling Garment Through Long-Term Research: Implications of the Test Results on Three Different Garments

The most recent goal of our research program was to identify the optimal features of each of three garments to maintain core temperature and comfort under intensive physical exertion. Four males and 2 females between the ages of 22 and 46 participated in this study. The garments evaluated were the MACS-Delphi, Russian Orlan, and NASA LCVG. Subjects were tested on different days in 2 different environmental chamber temperature/humidity conditions (24°C/H∼28%; 35°C/H∼20%). Each session consisted of stages of treadmill walking/running (250W to 700W at different stages) and rest. In general, the findings showed few consistent differences among the garments. The MACS-Delphi was better able to maintain subjects within a skin and core temperature comfort zone than was evident in the other garments as indicated by a lesser fluctuation in temperatures across physical exertion levels.
Technical Paper

Effect of Local Hand Thermal Insulation on Total and Local Comfort Under Different Levels of Body Heat Deficit

Introduction: There are contradictory opinions regarding the contribution of local hand thermal insulation to support local and total comfort during extravehicular activity (EVA). Instead of a local correction by means of thermal insulation on the periphery of the body to prevent heat dissipation, it may be optimal to prevent heat dissipation from the body core. To examine such a concept, the effects of different insulation levels on the left and right hands on the heat flux and temperature mosaic on the hands was measured. These variables were assessed in relation to the level of heat deficit forming in the core organs and tissues. Methods: Six subjects (4 males, 2 females) were donned in a liquid cooling/warming garment (LCWG) that totally covered the body surface except for the face. Participants wore the Phase VI space gloves including the entire micrometeoroid garment (TMG) on the left hand, and the glove without the TMG on the right hand.
Technical Paper

Cooling and Thermal Control Strategies in the Space Suit for Routine and Emergency Situations

A series of demonstration studies were conducted with the aim of better understanding how to regulate body heat and thus enhance thermal comfort of astronauts during EVA requiring intensive physical exertion. The first study evaluated body zone heat transfer under different cooling temperatures in a liquid cooling garment (LCG), confirming the effectiveness of areas with high density tissue. The second study evaluated different configurations of hoods and neck scarves to maximize heat extraction from these key areas for heat release. The third study explored the possibility of regulating body heat by control of the water temperature circulating through selected body zones in the LCG, or blocking heat dissipation from particular body areas. The potential of heat insertion/removal from the head, hands, and feet to stabilize body comfort was evaluated in terms of the ability to advance this heat current “highway” from the core.
Technical Paper

Trade Study of an Exploration Cooling Garment

A trade study was conducted with a goal to develop relatively high TRL design concepts for an Exploration Cooling Garment (ExCG) that can accommodate larger metabolic loads and maintain physiological limits of the crewmembers health and work efficiency during all phases of exploration missions without hindering mobility. Effective personal cooling through use of an ExCG is critical in achieving safe and efficient missions. Crew thermoregulation not only impacts comfort during suited operations but also directly affects human performance. Since the ExCG is intimately worn and interfaces with comfort items, it is also critical to overall crewmember physical comfort. Both thermal and physical comfort are essential for the long term, continuous wear expected of the ExCG.
Technical Paper

Person to Person Biological Heat Bypass During EVA Emergencies

During EVA and other extreme environments, mutual human support is sometimes the last way to survive when there is a failure of the life support equipment. The possibility to transfer a warming fluid from one individual to another to increase heat and support the thermal balance of the individual with system failure was assessed. The following analog scenarios were considered: 1. one subject has a cooling system that is not working well and already has a body heat deficit equal to 100-120 kcal and a finger temperature decline to 26-27ºC, the other subject is at comfort level; 2. one subject is overcooled due to system failure and the other is mildly overheated. Preliminary findings showed promise in using such thermal sharing tactics to extend the time duration of survival in extreme situations when there is an increased metabolic rate in the donor.
Journal Article

Late Intake Valve Closing as an Emissions Control Strategy at Tier 2 Bin 5 Engine-Out NOx Level

A fully flexible valve actuation (FFVA) system was developed for a single cylinder research engine to investigate high efficiency clean combustion (HECC) in a diesel engine. The main objectives of the study were to examine the emissions, performance, and combustion characteristics of the engine using late intake valve closing (LIVC) to determine the benefits and limitations of this strategy to meet Tier 2 Bin 5 NOx requirements without after-treatment. The most significant benefit of LIVC is a reduction in particulates due to the longer ignition delay time and a subsequent reduction in local fuel rich combustion zones. More than a 95% reduction in particulates was observed at some operating conditions. Combustion noise was also reduced at low and medium loads due to slower heat release. Although it is difficult to assess the fuel economy benefits of LIVC using a single cylinder engine, LIVC shows the potential to improve the fuel economy through several approaches.
Technical Paper

Comparison of Shortened and Standard Liquid Cooling Garments to Provide Physiological and Subjective Comfort During EVA

The shortened liquid cooling/warming garment (SLCWG) developed by the University of Minnesota group was compared with the standard NASA liquid cooling/ventilating garment (LCVG) garment during physical exertion in comfort (24°C) and hot (35°C) chamber environments. In both environmental conditions, the SLCWG was just as effective as the LCVG in maintaining rectal temperature (Tre) in a thermal comfort range; sweat production on the face was less; and subjective perception of overall and local body comfort was higher. The findings indicate that the SLCWG produces the same or greater comfort level as that achieved with the LCVG's total coverage of the body surface.
Technical Paper

An Advanced Physiological Based Shortened Liquid Cooling/Warming Garment for Comfort Management in Routine and Emergency EVA

The focus of this research is on the development of a more energy efficient shortened liquid cooling/warming garment (LCWG) based on physiological principles comparing the efficacy of heat transfer of different body zones; the capability of blood to deliver heat; individual muscle and fat body composition as a basis for individual thermal profiles to customize the zonal involvement of the garment; and the development of shunts to minimize or redirect the cooling/warming loop for different environmental conditions, physical activity levels, and emergency situations. The total length of tubing in the LCWG is approximately 35% less, and the weight decreased by 45% compared to the LCVG currently used in space.
Technical Paper

Comfort Management in Rest and Exercise Conditions in an Innovative Shortened Liquid Cooling/Warming Garment

Comfort management in extreme environments is complex, requiring temperature stabilization of the body core and distal parts of the extremities. Examination of the capability of body zones to absorb and release heat can facilitate a solution to this problem. Using an experimental shortened liquid cooling/warming garment (LCWG), heat transfer effectiveness of different body zone combinations was assessed in rest and exercise conditions, at different levels of body heat deficit and intensities of physical exertion. Comfort stabilization in terms of minimum changes in core (Tc) and finger (Tfing) temperatures was achieved in exercise (200-400 W) at 18-22°C inlet water temperature in the following zonal combination: a portion of the torso, the internal thigh area covering the femoral artery, the forearm, neck, and part of the head.
Technical Paper

Forced and Directed Heat Exchange for Providing Human Body Comfort in Extreme Environments

A new methodological tool was developed consisting of a patchwork thermal cool/warm grid with great flexibility to manipulate the temperature on different areas of the body. Through conflicting temperatures on the body surface, it is possible to direct heat current to different distal or proximal areas. The effectiveness of the use of a cooled hood, gloves, socks on the overheated body was evaluated as countermeasures for balancing heat exchange. Temperature in the magistral vessels was the main source of information for understanding the mechanism of the relationship between core and shell, and shell and distal parts of the limb.
Technical Paper

Maximal Conductive Heat Exchange through Different Body Zones in a Liquid Cooling/Warming Space Garment

The maximal capability of several body areas to absorb/release heat by varying the circulating water temperature in different zones of a multi-compartment liquid cooling/warming garment (LCWG) was explored. The goal was to identify the areas that are highly effective to stabilize body comfort, and to use this information for developing a more physiologically-based design of the space suit. The results showed a high capability of the upper compared to the lower body in the conductive heat exchange process. The involvement of the head in this process is still problematic, because there was not a high level of direct heat absorption/release through the cooling/warming hood in the LCWG. Exclusion of the legs but with involvement of the feet in heat exchange had no effect on comfort of the distal parts of the extremities and core body status.
Technical Paper

Augmentation of Blood Circulation to the Fingers through Wrist Warming to Enhance Finger Comfort during Long-Duration EVA

This pilot study explored the effectiveness of local wrist warming as a potential countermeasure for providing finger comfort during extended duration EVA. Four subjects (3 males and 1 female) were evaluated in three different experimental conditions. Two additional body surface and wrist thermal conditions were evaluated on a smaller number of subjects. Wrist warming significantly increased finger temperature in ambient temperature. A clear positive effect to the fingers was evident when total body heat deficit was 30% of basal metabolic heat production in resting conditions. These initial findings indicate that wrist warming has considerable potential for increasing astronaut comfort during EVA while decreasing power requirements.
Technical Paper

An Exhaust Ionization Sensor for Detection of Late Combustion with EGR

In many operating regimes, exhaust gas recirculation (EGR) while maintaining MBT spark timing improves cycle efficiency in SI engines. As the level of exhaust dilution is increased, the flame speed is reduced and the combustion rate is impaired. This leads to a drop in fuel economy as EGR rates are increased beyond the optimal level. To take advantage of the efficiency benefit of EGR without incurring the penalties of late combustion, a sensor which detects late combustion is tested. The signal from an ionization sensor placed near the exhaust port has been found to correlate to combustion which continues late into the expansion stroke. It may be possible to use the output from the ion sensor to maintain the EGR at the the optimum for fuel economy.
Technical Paper

Comfort and Heat Control During Extended Space Flights

The inability to adequately assess overall temperature in contradictory thermal conditions is problematic for monitoring the safety and comfort of the astronaut during extended EVA. A nonuniform heating/cooling system applied to the surface of the body provides a paradigm for identifying the most sensitive areas for measuring overall heat status. Manipulating warming /cooling tube patterns in the space suit during EVA has potential in providing a normal heat topography. Systematically varying astronaut's heat exchange onboard can enhance comfort and performance and prevent health problems that accompany living in a closely-controlled, constant environmental habitat.
Technical Paper

Applications of U.S.-Russian Expedition Research to Aerospace Settings

Psychological, group interaction, and task performance characteristics were evaluated in four polar expedition teams varying in national and gender composition. Leaders played a crucial role in promoting strong group cohesiveness and morale. North American members were more highly focused on achievement strivings, Russians on avoidance of failure. Gender differences in behavior were also evident. An all women's team demonstrated a high level of cooperativeness and social support of other team members. Across teams, anxiety, tension, and health concerns increased in the early stages of the expedition and decreased significantly at later stages. The overall findings indicate the need to focus on the interaction of personality, cultural, gender, and task performance demands in personnel selection and during long duration missions. Implications for the optimal design of space vehicles and habitats are discussed.
Technical Paper

Body Surface Temperature Tuning as a Comfort Support System in Space and Other Extreme Environments

The potential of controlling human body thermal status through monitoring temperature and heat flux indices of the fingers was evaluated. A cooling/warming suit was used that provided a range of uniform and nonuniform temperature regimes on the body surface. Temperature changes on the skin surface changed body comfort significantly but did not affect core temperature. However, under different imposed thermal conditions, peripheral temperature, particularly the fingers, closely followed the thermal conditions either within or on the surface of the body. The fingers appear to have considerable potential as a key site in developing an automatic thermal feedback system in the EVA suit.
Technical Paper

Modifications of a Quad 4 Engine to Permit Late Intake Valve Closure

Previous studies have shown Late Intake Valve Closure (LIVC) through Variable Valve Timing (VVT) to offer reduced fuel consumption through reduced pumping work. Load modulation through the controlled phasing of one of two intake valves/cylinder is one means of accomplishing the LIVC strategy on a multi-valve engine. Experimental studies of LIVC show that cycle-to-cycle variations and reduced flame velocity in single or synchronized multiple intake valve engines are associated with performance which, though superior to throttled engine performance, falls short of its promised fuel economy. To examine if the higher mixture velocity promised by valve phasing relative to single or synchronized LIVC mitigates cycle-to-cycle variations and flame velocity defects, a modification of the Quad 4 engine has been designed and built and is, at the present writing, being tested. The design employs a third camshaft placed above the original intake valve camshaft.