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  • 2020-2022  (4)
  • 1985-1989  (8)
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  • 1
    Publication Date: 2020-08-20
    Description: We evaluated pain status change and associations with subsequent opioid/marijuana use among 1,208 adult survivors of childhood cancer. Pain status and opioid/marijuana were self-reported at baseline and follow-up evaluation (mean interval: 4.2 years). Over time, 18.7% of survivors endorsed persistent/increasing significant pain; 4.8% and 9.0% reported having used opioids and marijuana at follow-up. Persistent/increased (vs. none/decreased) pain, persistent/increased (vs. none/decreased) anxiety, and lack of health insurance increased odds of subsequent opioid use by 7.69-fold (95% CI = 3.71 to 15.95), 2.55-fold (95% CI = 1.04 to 6.24), and 2.50-fold (95% CI = 1.07 to 5.82), respectively. Persistent/increased (vs. none/decreased) depression increased odds of subsequent marijuana use by 2.64-fold (95% CI = 1.10 to 6.33).
    Electronic ISSN: 2515-5091
    Topics: Chemistry and Pharmacology , Medicine
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  • 2
    Publication Date: 2020-07-12
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 3
    Publication Date: 2021-04-28
    Description: To prevent discrimination, the U.S. Navy enlisted-personnel promotion process relies primarily on objective measures. However, it also uses the subjective opinion of a sailor’s superior. The Navy’s promotion and retention process involves two successive decisions: The Navy decides whether to promote an individual, and conditional on that decision, the sailor decides whether to stay. Using estimates of these correlated decision-making processes, we find that during 1997–2008, Blacks and Hispanics were less likely to be promoted than Whites, especially during wartime. The Navy’s decision-making affects Blacks’ differential promotion rates by twice as much as differences in the groups’ characteristics. However, Nonwhite retention probabilities, even when not promoted, are higher than for Whites, in part because they have fewer opportunities in the civilian market. Females have lower promotion rates than males and slightly lower retention rates during wartime.
    Electronic ISSN: 1932-6203
    Topics: Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2021-05-01
    Print ISSN: 0966-6923
    Electronic ISSN: 1873-1236
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Elsevier
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  • 5
    Publication Date: 2011-08-19
    Description: A key step in the application of formal automated design techniques to structures under transient loading is the calculation of sensitivities of response quantities to the design parameters. This paper considers response quantities to the design parameters. This paper considers structures with general forms of damping acted on by general transient loading and addresses issues of computational errors and computational efficiency. The equations of motion are reduced using the traditional basis of vibration modes and then integrated using a highly accurate, explicit integration technique. A critical point constraint formulation is used to place constraints on the magnitude of each response quantity as a function of time. Three different techniques for calculating sensitivities of the critical point constraints are presented. The first two are based on the straightforward application of the forward and central difference operators, respectively. The third is based on explicit differentiation of the equations of motion. Condition errors, finite difference truncation errors, and modal convergence errors for the three techniques are compared by applying them to a simple five-span-beam problem. Sensitivity results are presented for two different transient loading conditions and for both damped and undamped cases.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 32; 2, 19; 433-443
    Format: text
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  • 6
    Publication Date: 2011-08-19
    Description: The space shuttle Challenger accident investigation focused on the failure of a tang-clevis joint on the right solid rocket motor. The existence of relative motion between the inner arm of the clevis and the O-ring sealing surface on the tang has been identified as a potential contributor to this failure. This motion can cause the O-rings to become unseated and therefore lose their sealing capability. Finite element structural analyses have been performed to predict both deflections and stresses in the joint under the primary, pressure loading condition. These analyses have demonstrated the difficulty of accurately predicting the structural behavior of the tang-clevis joint. Stresses in the vicinity of the connecting pins, obtained from elastic analyses, considerably exceed the material yield allowables indicating that inelastic analyses are probably necessary. Two modifications have been proposed to control the relative motion between the inner clevis arm and the tang at the O-ring sealing surface. One modification, referred to as the capture feature, uses additional material on the inside of the tang to restrict motion of the inner clevis arm. The other modification uses external stiffening rings above and below the joint to control the local bending in the shell near the joint. Both of these modifications are shown to be effective in controlling the relative motion in the joint.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 4; 317-327
    Format: text
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  • 7
    Publication Date: 2013-08-31
    Description: A study has been performed focusing on the calculation of sensitivities of displacements, velocities, accelerations, and stresses in linear, structural, transient response problems. One significant goal was to develop and evaluate sensitivity calculation techniques suitable for large-order finite element analyses. Accordingly, approximation vectors such as vibration mode shapes are used to reduce the dimensionality of the finite element model. Much of the research focused on the accuracy of both response quantities and sensitivities as a function of number of vectors used. Two types of sensitivity calculation techniques were developed and evaluated. The first type of technique is an overall finite difference method where the analysis is repeated for perturbed designs. The second type of technique is termed semianalytical because it involves direct, analytical differentiation of the equations of motion with finite difference approximation of the coefficient matrices. To be computationally practical in large-order problems, the overall finite difference methods must use the approximation vectors from the original design in the analyses of the perturbed models.
    Keywords: STRUCTURAL MECHANICS
    Format: application/pdf
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  • 8
    Publication Date: 2013-08-31
    Description: The problem of calculating detailed stress distributions around discontinuities in buckled, composite structural components for use with the various analytical failure prediction techniques has not been thoroughly explored. The purpose here is the application of computational methods to the detailed stress analysis problem which is the focus of this session of the workshop. One approach to uncovering the difficulties of this type of analysis and to providing specific directions for future research in this area is a direct attack on the problem using currently available analysis tools. A candidate problem has been selected and experiences from calculating its structural response are described.
    Keywords: STRUCTURAL MECHANICS
    Type: Computational Methods for Structural Mechanics and Dynamics, Part 1; p 51-65
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-28
    Description: Future in-space construction and assembly facilities will require the use of space cranes capable of supporting and manipulating large and massive loads. The large size of the space components being considered for construction will require that these cranes have a reach on the order of 100 meters. A space crane constructed from an erectable four-longeron truss beam with 19 5-sq-m truss bays is considered. This concept was selected to be compatible with the Space Station truss. This truss is hinged at three locations along its bottom edge and attached at one end to a rotary joint cantilevered to the assembly depot's main truss structure. The crane's boom sections are rotated by extensible longeron actuators located along the top edge of the beam. To achieve maximum position maneuvering capability for the crane requires that the individual sections be capable of rotating 180 degrees about the hinge point. This can only be accomplished by offsetting the hinges from the longeron axes. Since offset hinges introduce bending moments in the truss members, an analysis of the effect of hinge offsets on the load-carrying capacity of the structure is required. The objective of the static finite element analysis described is to determine the effect of various offset lengths on the overall bending stiffness of the crane and on the maximum stresses.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-101498 , NAS 1.15:101498
    Format: application/pdf
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  • 10
    Publication Date: 2019-06-28
    Description: A key step in the application of formal automated design techniques to structures under transient loading is the calculation of sensitivities of response quantities to the design parameters. This paper considers structures with general forms of damping acted on by general transient loading and addresses issues of computational errors and computational efficiency. The equations of motion are reduced using the traditional basis of vibration modes and then integrated using a highly accurate, explicit integration technique. A critical point constraint formulation is used to place constraints on the magnitude of each response quantity as a function of time. Three different techniques for calculating sensitivities of the critical point constraints are presented. The first two are based on the straightforward application of the forward and central difference operators, respectively. The third is based on explicit differentiation of the equations of motion. Condition errors, finite difference truncation errors, and modal convergence errors for the three techniques are compared by applying them to a simple five-span-beam problem. Sensitivity results are presented for two different transient loading conditions and for both damped and undamped cases.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-100589 , NAS 1.15:100589
    Format: application/pdf
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