Analytical and statistical study on the effects of porosity level on weld joint performance Progress report

Correlation between porosity defects and mechanical behavior of weld joint

Time-asymptotic solutions of the Navier-Stokes equation for free shear flows using an alternating-direction implicit method

An uncoupled time asymptotic alternating direction implicit method for solving the Navier-Stokes equations was tested on two laminar parallel mixing flows. A constant total temperature was assumed in order to eliminate the need to solve the full energy equation; consequently, static temperature was evaluated by using algebraic relationship. For the mixing of two supersonic streams at a Reynolds number of 1,000, convergent solutions were obtained for a time step 5 times the maximum allowable size for an explicit method. The solution diverged for a time step 10 times the explicit limit. Improved convergence was obtained when upwind differencing was used for convective terms. Larger time steps were not possible with either upwind differencing or the diagonally dominant scheme. Artificial viscosity was added to the continuity equation in order to eliminate divergence for the mixing of a subsonic stream with a supersonic stream at a Reynolds number of 1,000

Proposed CTV design reference missions in support of Space Station Freedom

Use of design reference missions (DRM's) for the cargo transfer vehicle (CTV) in support of Space Station Freedom (SSF) can provide a common baseline for the design and assessment of CTV systems and mission operations. These DRM's may also provide baseline operations scenarios for integrated CTV, Shuttle, and SSF operations. Proposed DRM's for CTV, SSF, and Shuttle operations envisioned during the early post-PMC time frame and continuing through mature, SSF evolutionary operations are described. These proposed DRM's are outlines for detailed mission definition; by treating these DRM's as top-level input for mission design studies, a range of parametric studies for systems/operations may be performed. Shuttle flight design experience, particularly rendezvous flight design, provides an excellent basis for DRM operations studies. To begin analysis of the DRM's, shuttle trajectory design tools were used in single case analysis to define CTV performance requirements. A summary of these results is presented

Star formation in Seyfert galaxies

An analysis of the IRAS data for a sample of classical (optically selected) Seyfert galaxies is presented. The IRAS fluxes at 25 micron, 60 micron, and 100 micron are found to be uncorrelated or only very weakly correlated with the UV/Optical continuum flux and the near and mid IR flux at 3.5 and 10 microns. To investigate the possibility that star formation accounts for the far IR flux, the IRAS measurements for the Seyfert galaxies are compared to IRAS observations of a sample of normal spiral galaxies, and a sample of Starburst galaxies. It is shown that the far IR luminosities and far IR colors of Seyfert galaxies are indistinguishable from those of the Starburst galaxies. Besides, normal galaxies are an order of magnitude less luminous than both the Seyfert and the Starburst galaxies. This indicates that star formation produces the bulk of the far infrared emission in Seyfert galaxies

Assessment and evaluation of noise controls on roof bolting equipment and a method for predicting sound pressure levels in underground coal mining

Over-exposure to noise remains a widespread and serious health hazard in the U.S. mining industries despite 25 years of regulation. Every day, 80% of the nation\u27s miners go to work in an environment where the time weighted average (TWA) noise level exceeds 85 dBA and more than 25% of the miners are exposed to a TWA noise level that exceeds 90 dBA, the permissible exposure limit (PEL). Additionally, MSHA coal noise sample data collected from 2000 to 2002 show that 65% of the equipment whose operators exceeded 100% noise dosage comprise only seven different types of machines; auger miners, bulldozers, continuous miners, front end loaders, roof bolters, shuttle cars (electric), and trucks. In addition, the MSHA data indicate that the roof bolter is third among all the equipment and second among equipment in underground coal whose operators exceed 100% dosage.;A research program was implemented to: (1) determine, characterize and to measure sound power levels radiated by a roof bolting machine during differing drilling configurations (thrust, rotational speed, penetration rate, etc.) and utilizing differing types of drilling methods in high compressive strength rock media (\u3e20,000 psi). The research approach characterized the sound power level results from laboratory testing and provided the mining industry with empirical data relative to utilizing differing noise control technologies (drilling configurations and types of drilling methods) in reducing sound power level emissions on a roof bolting machine; (2) distinguish and correlate the empirical data into one, statistically valid, equation, in which, provided the mining industry with a tool to predict overall sound power levels of a roof bolting machine given any type of drilling configuration and drilling method utilized in industry; (3) provided the mining industry with several approaches to predict or determine sound pressure levels in an underground coal mine utilizing laboratory test results from a roof bolting machine and (4) described a method for determining an operators\u27 noise dosage of a roof bolting machine utilizing predicted or determined sound pressure levels

The development of test beds to support the definition and evolution of the Space Station Freedom power system

Since the beginning of the Space Station Freedom Program (SSFP), the Lewis Research Center (LeRC) and the Rocketdyne Division of Rockwell International have had extensive efforts underway to develop test beds to support the definition of the detailed electrical power system design. Because of the extensive redirections that have taken place in the Space Station Freedom Program in the past several years, the test bed effort was forced to accommodate a large number of changes. A short history of these program changes and their impact on the LeRC test beds is presented to understand how the current test bed configuration has evolved. The current test objectives and the development approach for the current DC Test Bed are discussed. A description of the test bed configuration, along with its power and controller hardware and its software components, is presented. Next, the uses of the test bed during the mature design and verification phase of SSFP are examined. Finally, the uses of the test bed in operation and evolution of the SSF are addressed

Data-driven PDE discovery with evolutionary approach

The data-driven models allow one to define the model structure in cases when a priori information is not sufficient to build other types of models. The possible way to obtain physical interpretation is the data-driven differential equation discovery techniques. The existing methods of PDE (partial derivative equations) discovery are bound with the sparse regression. However, sparse regression is restricting the resulting model form, since the terms for PDE are defined before regression. The evolutionary approach described in the article has a symbolic regression as the background instead and thus has fewer restrictions on the PDE form. The evolutionary method of PDE discovery (EPDE) is described and tested on several canonical PDEs. The question of robustness is examined on a noised data example

The influence of body composition and physical activity on inflamm-aging, fatigue and function in older adults

Persistent feelings of fatigue are a widespread complaint reported by older adults, and are associated with detriments in health and quality of life. Aging is also accompanied by gains in adiposity, reductions in physical activity, and loss of lean mass and physical function. This study assessed the influences of body composition [adiposity (%Fat) and mineral-free lean mass (MFLM)] and physical activity (total and moderate-to-vigorous; MVPA) on fatigue and function in older adults. Furthermore, we sought to determine the mediating role of systemic inflammation on these health outcomes. One-hundred eighty-two community-dwelling older adults were recruited to participate in this study (age = 69.2±6.7 years, 98 men, 84 women) Body composition [adiposity (%Fat) and relative muscle mass (Skeletal Muscle Index (SMI); appendicular MFLM/ht2] was quantified via dual-energy X-ray absorptiometry (DXA). Physical activity (PA) was assessed by the Physical Activity Scale for the Elderly (PASE), and accelerometers were worn to determine total and MVPA. Fasting blood samples were obtained for measurement of serum C-reactive protein (CRP), Interleukin-6 (IL-6), the soluble IL-6 receptor (sIL-6R) and WBC count. Fatigue was assessed by the Multidimensional Fatigue Inventory (MFI), to determine levels of general, physical and mental fatigue as well as reduced activity and motivation. Lower-extremity physical function (LEPF) was evaluated by 7-m walk tests, a Timed Up and Go (Up&Go), a 30-second chair stand test (30-Chair), a 6-min walk, the Short Physical Performance Battery (SPPB) and the Star-Excursion Balance Test (STAR). It was hypothesized that 1) women would report higher levels of fatigue and have poorer performance of physical function than men, 2) adiposity would be an independent predictor of fatigue and LEPF, 3) PA would be inversely related to fatigue and positively with LEPF, and 4) inflammation would be positively associated with fatigue. Understanding the biological and behavioral influences on fatigue and function is imperative for combating health detriments in older adults. Men and women reported similar levels of fatigue in all dimensions (p > 0.05) with the exception of women reporting higher levels of mental fatigue than men (p = 0.05). Adiposity was positively correlated with several measures of fatigue (r range = 0.20 to 0.42), whereas PA was inversely associated with the same measures of fatigue (r range = 0.18 to 0.37), both of which were not related to mental fatigue. CRP, IL-6 and WBC were also related to several dimensions of fatigue (r range = 0.15 to 0.26). Compared across PA-adiposity groups, in the absence of an interaction, there was a main effect of PA and adiposity on general and physical fatigue (p < 0.05). Regression analyses revealed that the psychosocial variables depression and sleep quality and adiposity independently explained variance in general and physical fatigue. Adiposity and inflammation are positively related to general and physical fatigue, with adiposity remaining a predictor of both dimensions, independent of other associated factors. In addition, PA is inversely associated with these same dimensions of fatigue, and is an independent predictor of mental fatigue. Adiposity, physical activity and inflammation are identified as potential targets for reducing fatigue in older adults. Men performed better on all LEPF tests than women (all p < 0.05). Unlike all other independent variables, MFLM and SMI were not related to any LEPF outcomes. In the absence of a significant interaction, main effects for adiposity were found for mobility tests of LEPF, including WALK, Up&Go, 30-Chair and 6-min walk. There was a main effect of PA on 6-min walk only with greater PA corresponding to better performance. On STAR balance tests, an interaction existed for medial, posterior and composite reaches (p < 0.05). After accounting for influences of sex, age and number of co-morbidities, %Fat remained a significant predictor of all mobility measures and the STAR composite, as did PA for Up&Go and 6-min walk (all p < 0.05). Our results suggest that adiposity is a major determinant of fatigue and both balance and gait-related physical function in relatively healthy older adults. Physical activity may help to prevent age-associated fatigue and loss of mobility; however there does not seem to be an added benefit of MVPA. Given the high prevalence and associated health detriments of fatigue in older adults, longitudinal studies involving reductions in adiposity and increasing physical activity as possible prevention and treatment strategies for both fatigue and mobility impairments are warranted. Due to the complexity of these relationships, future work should simultaneously assess body composition components, physical activity and inflammation to further our understanding the disablement process. Uncovering the key influential factors contributing to fatigue and disability is essential for development and implementation of effective prevention and treatment strategies