Viking Orbiter 1975 thrust vector control system accuracy

The thrust vector control (TVC) system of the Viking Orbiter 1975 is discussed. The purpose of the TVC system is to point the engine thrust at the vehicle center of mass and to maintain attitude stability during propulsive maneuvers. This is accomplished by mounting the engine in a two-axis gimbal system. The TVC system then controls the pointing of the engine by closed loop control of two linear actuators which extend or retract and rotate the engine in its gimbal system. The effect of the TVC on the velocity vector pointing error incurred during a propulsive maneuver is analyzed. Models for predicting the magnitude of the error for various propulsive maneuvers are developed

Bayesian analysis of coefficient instability in dynamic regressions

This paper proposes a Bayesian regression model with time-varying coefficients (TVC) that makes it possible to estimate jointly the degree of instability and the time-path of regression coefficients. Thanks to its computational tractability, the model proves suitable to perform the first (to our knowledge) Monte Carlo study of the finite-sample properties of a TVC model. Under several specifications of the data generating process, the proposed model’s estimation precision and forecasting accuracy compare favourably with those of other methods commonly used to deal with parameter instability. Furthermore, the TVC model leads to small losses of efficiency under the null of stability and it is robust to mis-specification, providing a satisfactory performance also when regression coefficients experience discrete structural breaks. As a demonstrative application, we use our TVC model to estimate the exposures of S&P 500 stocks to market-wide risk factors: we find that a vast majority of stocks have time-varying risk exposures and that the TVC model helps to forecast these exposures more accurately.time-varying regression, coefficient instability

Study of solid rocket motor for a space shuttle booster. Appendix B: Typical component recertification test procedures

Flexseal assemblies, TVC actuators, hydraulic supply system, TVC electronic control unit, flight instrumentation system, ordnance system electronics, and hydrotest of SRM case segments are discussed, applied to typical component recertification test procedures

Religion and Leadership in Nation-Building

This write-up looks at the contributions of religion to nation building and the impact of leadership towards the growth of nation building. Hence, bringing out religious and leadership focus towards the upliftment of the nation. Thus, this writings are broken down into different stage and steps to allow understanding. It touches topics like the concept of religion: meaning and definition of religion. It also touches the contribution of Islamic and Christian religion in nation-building. This study anchored on the overview and definition of leadership. In the same vein, the contributions of leadership in nation-building are well outlined and expanciated for easy understanding. Nation-building in question are fairly treated and explained for a clearer  comprehension. Finally, recommendations and conclusion was made to give insight for further research and criticism

Verification test results of Apollo stabilization and control systems during undocked operations

The results are presented of analysis and simulation testing of both the Skylark 1 reaction control system digital autopilot (RCS DAP) and the thrust vector control (TVC) autopilot for use during the undocked portions of the Apollo/Soyuz Test Project Mission. The RCS DAP testing was performed using the Skylab Functional Simulator (SLFS), a digital computer program capable of simulating the Apollo and Skylab autopilots along with vehicle dynamics including bending and sloshing. The model is used to simulate three-axis automatic maneuvers along with pilot controlled manual maneuvers using the RCS DAP. The TVC autopilot was tested in two parts. A classical stability analysis was performed on the vehicle considering the effects of structural bending and sloshing when under control of the TVC autopilot. The time response of the TVC autopilot was tested using the SLFS. Results indicate that adequate performance stability margins can be expected for the CSM/DM configuration when under the control of the Apollo control systems tested

Re-admissions to hospital and patient satisfaction among patients with chronic obstructive pulmonary disease after telemedicine video consultation - a retrospective pilot study

Background: Chronic obstructive pulmonary disease (COPD) is a major cause of acute hospital admissions. The main object of our study was to evaluate the effects of telemedicine video-consultation (TVC) on the frequency of hospital re-admissions due to COPD exacerbations. Our secondary aim was to assess the impact of TVC on the length of re-admission stays within 6 and 12 months follow up after TVC. Patient satisfaction was also evaluated. Methods: The study was a retrospective observational study of COPD patients who after hospital discharge or during outpatient treatment for acute COPD exacerbations, were monitored for 2 weeks by TVC at home by a specialist nurse at the hospital during a pilot project period. Retrospectively, we compared the frequencies (chi-square test) and durations of hospital re-admissions (paired t-test) due to COPD exacerbations within 6 and 12 months follow up after TVC to comparable events 6 and 12 months prior to TVC. Results: Among 99 patients followed for 6 months after TVC, 56 were followed for totally 12 months. The number of patients re-admitted and the number of re-admissions due to COPD exacerbations were not reduced within 6 or 12 months post-TVC, as compared to 6 and 12 months pre-TVC. The mean length of re-admission stays within 12 months post-TVC was markedly reduced as compared to pre-TVC. Patients hospitalised the last 6 and 12 months pre-TVC, had significantly shorter re-admission stays, p = 0.033 and p = 0.001, respectively. Patient satisfaction was high. Conclusion: Despite the failure to demonstrate reduced frequency of re-admissions within 6 and 12 months post-TVC, the re-admission length within 12 months post-TVC was markedly reduced as compared to pre-TVC. The patient satisfaction was high. Future prospective, randomised, controlled trials must be performed before TVC can be recommended in COPD management.publishedVersio