Commentary on Space Propulsion Activities

Space propulsion systems required to launch large payloads - General commentar

Modular space station phase B extension period executive summary

A narrative summary is presented of technical, programmatic, and planning information developed during the space station definition study extension period. The modular space station is emphasized, but tasks pertaining to shuttle sorties missions and information management advanced development are included. A series of program options considering technical, schedule, and programmatic alternatives to the baseline program are defined and evaluated

Structural optimization of framed structures using generalized optimality criteria

The application of a generalized optimality criteria to framed structures is presented. The optimality conditions, Lagrangian multipliers, resizing algorithm, and scaling procedures are all represented as a function of the objective and constraint functions along with their respective gradients. The optimization of two plane frames under multiple loading conditions subject to stress, displacement, generalized stiffness, and side constraints is presented. These results are compared to those found by optimizing the frames using a nonlinear mathematical programming technique

Simultaneous structural and control optimization via linear quadratic regulator eigenstructure assignment

A method for simultaneous structural and control design of large flexible space structures (LFSS) to reduce vibration generated by disturbances is presented. Desired natural frequencies and damping ratios for the closed loop system are achieved by using a combination of linear quadratic regulator (LQR) synthesis and numerical optimization techniques. The state and control weighing matrices (Q and R) are expressed in terms of structural parameters such as mass and stiffness. The design parameters are selected by numerical optimization so as to minimize the weight of the structure and to achieve the desired closed-loop eigenvalues. An illustrative example of the design of a two bar truss is presented

Ariel - Volume 3 Number 2

Editors Richard J. Bonanno Robin A. Edwards Associate Editors Steven Ager Stephen Flynn Tom Williams Lay-out Editor Eugenia Miller Contributing Editors Paul Bialas Milton Packer Robert Breckenridge Lynne Porter Mark Pearlman Terry Burt Mike Leo Editors Emeritus Delvyn C. Case, Jr. Paul M. Fernhof

PTSD, depression, and anxiety among Palestinian women victims of domestic violence in the Gaza Strip

Background: Domestic violence is a universal phenomenon which affects all family members and specially children and women. Common reactions to domestic violence are post-traumatic stress disorder, depression, and anxiety. Aims: The aim of this study is to find type and severity of domestic violence against Palestinian women in the Gaza Strip, and to investigate whether it is associated with mental health problems such as post-traumatic stress disorder, depression, and anxiety. Methods: The study sample included 622 Palestinian women randomly selected from the five areas of the Gaza Strip aged from 18 to 50 years (mean age = 31.5 years). They were interviewed using questionnaires including Sociodemogrophic variables, Conflicts Tactics Scale, post-traumatic stress disorder scale, Beck Depression Inventory, Taylor manifestation Anxiety Scale. Results: The study showed that psychological assault was 56.91%, physical assault 37.3%, physical injury 12.06%, and sexual assault was 7.14%. The study showed that domestic violence was significantly higher in women living in villages than in cities or camps. Also, women living in villages experienced more psychological abuse than women living in cities or camps. The study showed that 71 women (11.4%) had been diagnosed as post-traumatic stress disorder, 15% had moderate to severe depression, and 29.9% had very severe anxiety. The study showed that psychological assault toward women was positively correlated to depression, anxiety, and posttraumatic stress disorder. Also, there were significant positive relationships between physical assault and depression, anxiety, and posttraumatic stress symptoms. Physical injury and sexual assault were significantly positively related to post traumatic stress disorder, depression, and anxiety. Conclusion: The study showed that one third Palestinian women exposed to physical violence and half of them exposed to psychological violence which lead to post-traumatic stress disorder depression, and anxiety. So, a great need for more programs for women victims of domestic violence in Palestinian society are needed with well trained professionals in the field of psychological support and therapy. More specific programs should be established in Gaza to enable women of using new coping strategies with difficulties. Also, training programs including primary health care professional such physicians, nurses, social service experts, and midwives should be provide to enable them of early detection of victims of violence and provide social support to these women

Eigenvalue routines in NASTRAN: A comparison with the Block Lanczos method

The NASA STRuctural ANalysis (NASTRAN) program is one of the most extensively used engineering applications software in the world. It contains a wealth of matrix operations and numerical solution techniques, and they were used to construct efficient eigenvalue routines. The purpose of this paper is to examine the current eigenvalue routines in NASTRAN and to make efficiency comparisons with a more recent implementation of the Block Lanczos algorithm by Boeing Computer Services (BCS). This eigenvalue routine is now available in the BCS mathematics library as well as in several commercial versions of NASTRAN. In addition, CRAY maintains a modified version of this routine on their network. Several example problems, with a varying number of degrees of freedom, were selected primarily for efficiency bench-marking. Accuracy is not an issue, because they all gave comparable results. The Block Lanczos algorithm was found to be extremely efficient, in particular, for very large size problems

Suppression of biodynamic interference in head-tracked teleoperation

The utility of helmet-tracked sights to provide pointing commands for teleoperation of cameras, lasers, or antennas in aircraft is degraded by the presence of uncommanded, involuntary heat motion, referred to as biodynamic interference. This interference limits the achievable precision required in pointing tasks. The noise contributions due to biodynamic interference consists of an additive component which is correlated with aircraft vibration and an uncorrelated, nonadditive component, referred to as remnant. An experimental simulation study is described which investigated the improvements achievable in pointing and tracking precision using dynamic display shifting in the helmet-mounted display. The experiment was conducted in a six degree of freedom motion base simulator with an emulated helmet-mounted display. Highly experienced pilot subjects performed precision head-pointing tasks while manually flying a visual flight-path tracking task. Four schemes using adaptive and low-pass filtering of the head motion were evaluated to determine their effects on task performance and pilot workload in the presence of whole-body vibration characteristic of helicopter flight. The results indicate that, for tracking tasks involving continuously moving targets, improvements of up to 70 percent can be achieved in percent on-target dwelling time and of up to 35 percent in rms tracking error, with the adaptive plus low-pass filter configuration. The results with the same filter configuration for the task of capturing randomly-positioned, stationary targets show an increase of up to 340 percent in the number of targets captured and an improvement of up to 24 percent in the average capture time. The adaptive plus low-pass filter combination was considered to exhibit the best overall display dynamics by each of the subjects