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Understanding the fundamental details of drop/wall interactions is important to improving engine performance. Most of the drop-wall interactions studies are based on the impact of a single drop on the wall. To accurately mimic and model the real engine conditions, it is necessary to characterize spray/wall interactions with different impingement frequencies at a wide range of wall temperatures. In this study, a numerical method, based on Smoothed Particle Hydrodynamics (SPH), is used to simulate consecutive droplet impacts on a heated wall both below and above the Leidenfrost temperature. Impact regimes are identified for various impact conditions by analyzing the time evolution of the post-impingement process of n-heptane drops at different impingement frequencies and wall surface temperatures. For wall temperature below the Leidenfrost temperature, the recoiled film does not leave the surface.

In recent years, study on the ride comfort of vehicles has attracted wide attention. The vibration caused by the road is transmitted to the human body through the tire, suspension, vehicle body, and the seat. Since the human body is in contact with the seat and the vibration is transmitted directly to the human body through the seat, the seat pan angle plays an important role on the vibration response of the human body. Previous studies have explored the effects of different backrest designs on human vibration response, but ignored the effects of different seat pan angles. Therefore, this paper will use a human biodynamic model combined with a 6-DOF seat model to study the effect of seat pan angles and feet-floor interaction on human vibration response. Three cases are proposed: Case 1 has a seat pan angle 8°, Case 2 has a seat pan angle 13°, and Case 3 has a seat pan angle 17°.

Vehicle tire performance is an important consideration for vehicle handling, stability, mobility, and ride comfort as well as durability. Significant efforts have been dedicated to tire modeling in the past, but there is still room to improve its accuracy. In this study, a detailed in-plane flexible ring tire model is proposed, where the tire belt is discretized, and each discrete belt segment is considered as a rigid body attached to a number of parallel tread blocks. The mass of each belt segment is accumulated at its geometric center. To test the proposed in-plane tire model, a full-vehicle model is integrated with the tire model for simulation under a special driving scenario: acceleration from rest for a few seconds, then deceleration for a few seconds on a flat-level road, and finally constant velocity on a rough road. The simulation results indicate that the tire model is able to generate tire/road contact patch forces that yield reasonable vehicle dynamic responses.

A tire may be one of the most critical and complex components in vehicle dynamics and road loads analyses because it serves as the only interface between the road surface and the vehicle. Extensive research and development activities about vehicle dynamics and tire models have been published in the past decades, but it is still not clear about the applications and parameter identification associated with all of these tire models. In this literature review study, various published tire models used for vehicle dynamics and road loads analyses are compared in terms of their modeling approaches, applications and parameters identification process and methodologies. It is hoped that the summary of this literature review work can help clarify and guide the future research and development direction about tire modeling.

In vehicle driving environment, the driver is subjected to the vibrations in horizontal, vertical, and fore-aft directions. The human body is very much sensitive to whole body vibration and this vibration transmission to the body depends upon various factors including road irregularities, vehicle suspension, vehicle dynamics, tires, seat design and the human body's properties. The seat design plays a vital role in the vibration isolation as it is directly in contact with human body. Vibration isolation properties of a seat depend upon its dynamic parameters which include spring stiffness and damping of seat suspension and cushion. In this paper, an optimization-based method is used to determine the optimal seat dynamic parameters for seat suspension, and cushion based on minimizing occupant's body fatigue (occupant body absorbed power). A 14-degree of freedom (DOF) multibody biodynamic human model in 2D is selected from literature to assess three types of seat arrangements.

Digital human modeling and posture prediction can only be used as a design tool if the predicted postures are realistic. To date, the most realistic postures have been realized by simultaneously optimizing human performance measures (HPMs). These HPMs currently consist of joint discomfort, delta potential energy, and visual displacement. However these HPMs only consider the kinematics of human posture. Dynamic aspects of human posture such as external loads and mass of limbs have not yet been considered in conjunction with the current HPMs. This paper gives the formulation for a new human performance measure combination including the use of joint torque to account for the dynamics of human posture. Postures are then predicted using multi-objective optimization (MOO) techniques to optimize the combination of the new HPM and the current. The predicted postures are then compared with the benchmark postures which are those obtained from using the current HPMs only.

Biological pre-treatment of early planetary/lunar base wastewater has been extensively studied because of its predicted ability to offer equivalent system mass (ESM) savings for long term space habitation. Numerous biological systems and reactor types have been developed and tested for treatment of the generally unique waste streams associated with space exploration. In general, all systems have been designed to reduce organic carbon (OC) and convert organic nitrogen (ON) to nitrate and/or nitrite (NOx -). Some systems have also included removal of the oxidized N in order to reduce overall oxygen consumption and produce additional N2 gas for cabin use. Removal of organic carbon will generally reduce biofouling as well as reduce energy and consumable cost for physiochemical processors.

Comfort assessment of respirator fit plays an important role in the respirator design process and standard development. To reduce the cost and design time of respirators, the design, fit, and evaluation process can be performed in a virtual environment. Literature shows that respirator-induced discomfort relates to stress, area, and region of the face covered. In this work, we investigate the relationship between the strap tensions and the stress and deformation distribution on the interface between the respirator and the headform. This is the first step towards a comprehensive understanding of the contribution of contact stress to the mathematical comfort fit model. The 3D digital models for respirators and headforms have been developed based on 3D scanning point-cloud using a Cyberware® 3D digitizer. Five digital headform models have been generated: small, medium, large, long and short.

Microbial control in closed environmental systems, such as those of spacecraft or proposed base missions is typically limited to disinfection in the potable water system by a strong chemical agent such as iodine or chlorine. However, biofilm growth in the environmental system tubing threatens both the sterility of the potable water distribution as well as operational problems with wastewater systems. In terrestrial systems, biofilm has been recognized for its difficulty to control and eliminate as well as resulting operational problems. In order to maintain a potable water source for crew members as well as preventing operational problems in non-sterile systems, biofilm needs to be considered during system design. While biofilm controls can limit biofilm buildup, they are typically disruptive and cannot completely eliminate biofilm. Selenium coatings have shown to prevent initial biofilm attachment as well as limit attached growth on a variety of materials.

A modified membrane-aerated biofilm reactor (mMABR) was constructed by incorporating two distinct biofilm immobilization media: gas-permeable hollow fiber membranes and high surface area inert bio-media. In order to evaluate the mMABR for space flight applications, a synthetic ersatz early planetary base (EPB) waste stream was supplied as influent to the reactor, and a liquid loading study was conducted at three influent flow rates. On average, percent carbon removal ranged from 90.7% to 93.1% with volumetric conversion rates ranging from 25 ± 3.3 g / m3 d and 95 ± 13.4 g / m3 d. Simultaneous nitrification/denitrification (SND) was achieved in a single reactor. As the liquid loading rate increased from 0.15 mL/min to 0.45 mL/min, the volumetric denitrification rates elevated from 27 ± 3.3 g / m3 d to 65 ± 5.2 g / m3 d. Additionally, it was found that nitrification and denitrification were linearly related with respect to both percent efficiency and volumetric reaction rates.

Hollow fiber membrane reactors (HFMBRs) may be used for biological wastewater treatment, and may be integrated with NASA's current research developments. The goal of this paper is to (a) evaluate the effect of mass transfer and hydrodynamics in a microporous HFMBR and (b) appropriateness of HFMBRs for use in space applications. Even though bubble-less aeration was not achieved by the use of microporous membranes, mass transfer within the HFMBR was found to increase after biofilm formation. Conversely, convective flow dominated transport within the system. Despite the high treatment efficiency obtained by the HFMBR, due to the bioreactor size, configuration and membrane spacing within the HFMBR, the bioreactor was not a suitable option for application under microgravity conditions. Even though developing a system with more favorable system hydrodynamics would aid in treatment efficiency, the use of a microporous HFMBR is not a recommended option to meet NASA's needs.

The feasibility of a long-term space mission is partially reliant upon the ability to effectively recycle wastewater. Merged biological and physiochemical processes (integrated water recovery systems (IWRS)) are capable of producing potable water at lower equivalent system mass (ESM) than treatment systems composed of only physiochemical processes. Reducing the ESM of the water recycling units can increase the practicality of extended space missions by decreasing payload weight. In order to lower the ESM of the biological pre-treatment component, a single-stage biological reactor capable of simultaneous carbon and nitrogen removal was created by modifying the membrane-aerated biofilm reactor (MABR) design. Studies were performed in order to evaluate the water quality performance of this reactor.

Hollow fiber membranes aerate wastewater without bubble formation by separating the liquid and gases phases with a semi-permeable membrane. These membranes have shown to successfully create aerobic conditions within a biological reactor. This research investigated the effect of long term usage and biofilm growth on membrane's ability to transfer oxygen to solution. Results show that oxygen transfer across the membrane decreased significantly compared to unused membranes in areas of high biofilm growth while low biofilm growth showed only slight decreases.

The Advanced Integration Matrix (AIM) project at the Johnson Space Center (JSC) was chartered to study and solve systems-level integration issues for exploration missions. One of the first issues identified was an inability to conduct trade studies on control system architectures due to the absence of mature evaluation criteria. Such architectures are necessary to enable integration of regenerative life support systems. A team was formed to address issues concerning software and hardware architectures and system controls.. The team has investigated what is required to integrate controls for the types of non-linear dynamic systems encountered in advanced life support. To this end, a water processing bioreactor testbed is being developed which will enable prototyping and testing of integration strategies and technologies.

This research is based on the hypothesis that recycling biofilm can provide the required carbon to increase biological denitrification of the carbon limited early planetary base wastewater. Recycling biofilm may offer significant advantages including a reduction in solid waste from biological wastewater processors, increased N2 return to cabin air, a reduction in TDS loading to the RO system, and increased alkalinity to drive further nitrification. The results of the study indicate that denitrification rate did increase due to the addition of lysed biofilm derived from the nitrification reactor. However, there was a simultaneous large release of additional ammonium. Further work will be required to understand the magnitude of the ammonium release and overall benefits of the process.

NASA's mission statement includes the protection of the home planet and a goal to inspire the next generation of explorers. NASA's current vision also includes human exploration of the Moon and Mars. Typically, residents of low-income communities are not directly involved in the space exploration process. Parents of children in low-income communities are inclined to be more interested in the educational components of NASA's activities rather than the technological accomplishments. This paper describes the approach taken to start and support a space and science club in a colonia near the U.S. - Mexico border in South Texas. The club provided a new organizational structure for linking NASA's goals with a low-income community. The structure of the club evolved over the course of three years to reflect the interests and resources of the youth that lived in the colonia.

From 1997 to 2001, the third author worked with a team of engineers at JSC to develop the requirements and basic design for the Bioregenerative Planetary Life Support Systems Test Complex, or BIO-Plex. Under the Advanced Integration Matrix (AIM) Project, this earlier effort is extended to an investigation of methods and approaches for Advanced Systems Integration and Control. The intent is to understand and validate the use of software as an integrating function for complex heterogeneous systems, particularly for Advanced Life Support (ALS), in the context of support of mission operations. Preliminary investigations undertaken in the summer of 2004 indicate that integration of controls for the type of dynamic, non-linear, closed-loop biological systems under investigation for ALS systems require a different systems engineering approach than that required for traditional avionics systems.

Biological pre-treatment of liquid waste could potentially offer equivalent mass savings for long term space habitation. However, limited engineering studies have been performed to determine the optimum loading rates or to fully characterize (limiting reactants) the biochemical transformations occurring within the reactors. The objective of these studies was to provide loading rate data on a proposed and well studied reactor configuration. All studies were performed using a simulated early planetary base waste stream. Results indicate that the reactor’s efficiency is greater than typical terrestrial reactors and that transformation is limited by non-kinetic parameters.

Texas colonias are unincorporated subdivisions characterized by inadequate water and wastewater infrastructure, inadequate drainage and road infrastructure, substandard housing, and poverty. Since 1989 the Texas Legislature has implemented policies to halt further development of colonias and to address water and wastewater infrastructure needs in existing and new colonias along the border with Mexico. Government programs and non-government and private organization projects aim to address these infrastructure needs. Texas Tech University's Water Resources Center demonstrated the use of alternative on-site wastewater treatment in the Green Valley Farms colonia, San Benito, Texas. The work in Green Valley Farms was a component of a NASA-funded project entitled “Evaluation of NASA's Advanced Life Support Integrated Water Recovery System for Non-Optimal Conditions and Terrestrial Applications.” Two households within the colonia were demonstration sites for the constructed wetlands.

The objective of this study was to investigate the potential of membrane-aerated bioreactors as long term microgravity compatible nitrifying biological water processors (BWP). A small-scale (1/20th) replica of the water recovery system (WRS) at JSC has been operated and extensively analyzed at Texas Tech University (TTU) for the last 3 years. The current nitrifying tubular reactor at JSC and TTU has experienced difficulty in maintaining efficiency and low maintenance. In an attempt to increase the efficiency of the biological portion of the WRS, a membrane-aerated bioreactor (MABR) was constructed and operated using the same parameters as the TTU-WRS in August 2003. The MABR is downstream of an anaerobic packed bed and is designed to promote nitrification (NH4 → NOx). The MABR achieved a percent nitrification of 61% and 55% for recycle ratios of 10 and 20, respectively.