Search Results

Extended range electric vehicles (EREVs) are a potential solution for fossil fuel usage mitigation and on-road emissions reduction. The use of EREVs can be shown to yield significant fuel economy improvements when proper energy management strategies (EMSs) are employed. However, many in-use EREVs achieve only moderate fuel reduction compared to conventional vehicles due to the fact that their EMS is far from optimal. This paper focuses on in-use rule-based EMSs to improve the fuel efficiency of EREV last-mile delivery vehicles equipped with two-way Vehicle-to-Could (V2C) connectivity. The method uses previous vehicle data collected on actual delivery routes and machine learning methods to improve the fuel economy of future routes. The paper first introduces the main challenges of the project, such as inherent uncertainty in human driver behavior and in the roadway environment. Then, the framework of our practical physics-model guided data-driven approach is introduced.

Diesel particulate filter (DPF) technology has proven performance and reliability. However, the addition of a DPF adds significant cost and packaging constraints leading some manufacturers to design engines that reduce particulate matter in-cylinder. Such engines utilize high fuel injection pressure, moderate exhaust gas recirculation and modified injection timing to mitigate soot formation. This study examines such an engine designed to meet US EPA Interim Tier 4 standards for off-highway applications without a DPF. The engine was operated at four steady state modes and aerosol measurements were made using a two-stage, ejector dilution system with a scanning mobility particle sizer (SMPS) equipped with a catalytic stripper (CS) to differentiate semi-volatile versus solid components in the exhaust. Gaseous emissions were measured using an FTIR analyzer and particulate matter mass emissions were estimated using SMPS data and an assumed particle density function.

The critical speed method uses measurements of the radii of yawmarks left by vehicles, together with values for centripetal acceleration, to estimate the speeds of the vehicles when the yawmarks were made. Several field studies have indicated that equating the centripetal force with braking friction produced biased estimates, but that the biases tended to be small (e.g. within 10%-15% on average) and led to underestimates, suggesting that the method can be useful for forensic purposes. Other studies, however, have challenged this conclusion. The critical speed method has also seen use in safety-related research, where it is important to have a reliable assessment of the uncertainty associated with a speed estimate. This paper describes a variant of the critical speed method, where data from field tests lead to an informative prior probability distribution for the centripetal acceleration.

Diesel fuel injection systems are operating at increasingly higher pressure (up to 250 MPa) with smaller clearances, making them more sensitive to diesel fuel contaminants. Most liquid particle counters have difficulty detecting particles <4 μm in diameter and are unable to distinguish between solid and semi-solid materials. The low conductivity of diesel fuel limits the use of the Coulter counter. This raises the need for a new method to characterize small (<4 μm) fuel contaminants. We propose and evaluate an aerosolization method for characterizing solid particulate matter in diesel fuel that can detect particles as small as 0.5 μm. The particle sizing and concentration performance of the method were calibrated and validated by the use of seed particles added to filtered diesel fuel. A size dependent correction method was developed to account for the preferential atomization and subsequent aerosol conditioning processes to obtain the liquid-borne particle concentration.

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.

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.

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.

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.

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.

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.

Many engine exhaust emissions measurements require exhaust dilution. With low-emission engines, there is the possibility for contaminants in the dilution air to contribute artifacts to the emissions measurement. The objectives of this work are to discuss common methods used to clean the dilution air, to present the detailed analysis of a pressure swing adsorption (PSA) system and to compare the performance of the PSA with 2 other systems commonly used to provide dilution air for engine exhaust nanoparticle measurements. The results of the comparison are discussed in context with some emissions measurements that require exhaust dilution.

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.

This paper focuses on modeling of torque-biasing devices of a four-wheel-drive system used for improving vehicle stability and handling performance. The proposed driveline system is based on nominal front-wheel-drive operation with on-demand transfer of torque to the rear. The torque biasing components of the system are an electronically controlled center coupler and a rear electronically controlled limited slip differential. Kinematic modeling of the torque biasing devices is introduced including stage transitions during the locking stage and the unlocking/slipping stage. Analytical proofs of how torque biasing could be used to influence vehicle yaw dynamics are also included in the paper. A yaw control methodology utilizing the biasing devices is proposed. Finally, co-simulation results with Matlab®/Simulink® and CarSim® show the effectiveness of the torque biasing system in achieving yaw stability control.

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.

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.

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.

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.

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.

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.

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.