The effect of nonlinearities on the dynamic response of a large shuttle payload

The STS Centaur was designed to be a high energy upper stage for use with the Space Shuttle. Two versions were designed under development when the program was cancelled. The first version, designated G-prime, was for planetary missions. The second version, designated G, was to place spacecraft in geosynchronous orbit. As a part of the STS Centaur finite-element model verification effort, test articles of both versions were subjected to a series of static tests. In addition the Centaur G-prime test article was subjected to a series of dynamic tests including a modal survey. Both the static and dynamic tests showed that nonlinearities existed in the Centaur and its support system. The support system included flight-like latches. The nonlinearities were particularly apparent in tests that loaded the forward support structure of the Centaur. These test results were used to aid in the development of two improved finite-element models. The first was a linear model, while the second contained nonlinear elements at the boundaries. Results from both models were compared with the transient response obtained from a step-relaxation or twang test. The linear model was able to accurately match the low frequency response found in the test data. However, only the nonlinear model was able to match higher frequency response that was present in some of the test data. In addition the nonlinear model was able to predict other nonlinear behavior such as the dynamic jump that occurs in systems with nonlinear stiffness

Teaching College Economics in a High School Setting: Lessons Learned and Implementation Strategies

Interest in exposing high school seniors to college level economics has risen in recent years. Under one delivery option, a dual-enrollment program, students are concurrently enrolled in college and high school, and receive credit at both institutions for the same course. These programs benefit high schools by increasing the academic rigor in the senior year, and may also aid colleges' external relations and recruitment. Colleges and universities considering such a program must recognize important administrative and student body differences between the university and high school settings. This paper summarizes the experiences of Southern Illinois University, where a dual-enrollment program was implemented in the mid 1990s, and uses this case to illustrate key differences between the two classroom environments. Suggested strategies for coping with these differences are described.

Moving Past Assumptions: Recognizing Parents as Allies in Promoting the Sexual Literacies of Adolescents through a University-Community Collaboration

This article recounts how a university-community collaborative challenged prevailing assumptions about parents as barriers to the provision of gender and sexuality information to their children, allowing for the recognition of parents as critical stakeholders and partners in sexual literacy work with youth. We provide evidence that parents’ support for inclusive sexuality education uniquely situates them to educate and advocate for young people around these issues, and in so doing we hope to disrupt the rhetoric that casts parents in the United States as solely gatekeepers when it comes to young people’s access to information about the broad spectrum of human sexuality

Benchmarking treewidth as a practical component of tensor-network--based quantum simulation

Tensor networks are powerful factorization techniques which reduce resource requirements for numerically simulating principal quantum many-body systems and algorithms. The computational complexity of a tensor network simulation depends on the tensor ranks and the order in which they are contracted. Unfortunately, computing optimal contraction sequences (orderings) in general is known to be a computationally difficult (NP-complete) task. In 2005, Markov and Shi showed that optimal contraction sequences correspond to optimal (minimum width) tree decompositions of a tensor network's line graph, relating the contraction sequence problem to a rich literature in structural graph theory. While treewidth-based methods have largely been ignored in favor of dataset-specific algorithms in the prior tensor networks literature, we demonstrate their practical relevance for problems arising from two distinct methods used in quantum simulation: multi-scale entanglement renormalization ansatz (MERA) datasets and quantum circuits generated by the quantum approximate optimization algorithm (QAOA). We exhibit multiple regimes where treewidth-based algorithms outperform domain-specific algorithms, while demonstrating that the optimal choice of algorithm has a complex dependence on the network density, expected contraction complexity, and user run time requirements. We further provide an open source software framework designed with an emphasis on accessibility and extendability, enabling replicable experimental evaluations and future exploration of competing methods by practitioners.Comment: Open source code availabl

Clinical outcomes in high-hypoglycaemia-risk patients with type 2 diabetes switching to insulin glargine 300 U/mL versus a first-generation basal insulin analogue in the United States: Results from the DELIVER High Risk real-world study

Aims: To compare 12-month clinical effectiveness of insulin glargine 300 units/mL (Gla-300) versus first-generation basal insulin analogues (BIAs) (insulin glargine 100 units/mL [Gla-100] or insulin detemir [IDet]) in patients with type 2 diabetes (T2D) who were at high risk of hypoglycaemia and switched from one BIA to a different one (Gla-300 or Gla-100/IDet) in a real-world setting. // Methods: DELIVER High Risk was a retrospective observational cohort study of 2550 patients with T2D who switched BIA to Gla-300 (Gla-300 switchers) and were propensity score-matched (1:1) to patients who switched to Gla-100 or IDet (Gla-100/IDet switchers). Outcomes were change in glycated haemoglobin A1c (HbA1c), attainment of HbA1c goals (<7% and <8%), and incidence and event rates of hypoglycaemia (all-hypoglycaemia and hypoglycaemia associated with an inpatient/emergency department [ED] contact). // Results: HbA1c reductions were similar following switching to Gla-300 or Gla-100/IDet (−0.51% vs. −0.53%; p = .67), and patients showed similar attainment of HbA1c goals. Patients in both cohorts had comparable all-hypoglycaemia incidence and event rates. However, the Gla-300 switcher cohort had a significantly lower risk of inpatient/ED-associated hypoglycaemia (adjusted odds ratio: 0.73, 95% confidence interval: 0.60–0.89; p = .002) and experienced significantly fewer inpatient/ED-associated hypoglycaemic events (0.21 vs. 0.33 events per patient per year; p < .001). // Conclusion: In patients with T2D at high risk of hypoglycaemia, switching to Gla-300 or Gla-100/IDet achieved similar HbA1c reductions and glycaemic goal attainment, but Gla-300 switchers had a significantly lower risk of hypoglycaemia associated with an inpatient/ED contact during 12 months after switching

ML-based Fault Injection for Autonomous Vehicles: A Case for Bayesian Fault Injection

The safety and resilience of fully autonomous vehicles (AVs) are of significant concern, as exemplified by several headline-making accidents. While AV development today involves verification, validation, and testing, end-to-end assessment of AV systems under accidental faults in realistic driving scenarios has been largely unexplored. This paper presents DriveFI, a machine learning-based fault injection engine, which can mine situations and faults that maximally impact AV safety, as demonstrated on two industry-grade AV technology stacks (from NVIDIA and Baidu). For example, DriveFI found 561 safety-critical faults in less than 4 hours. In comparison, random injection experiments executed over several weeks could not find any safety-critical faultsComment: Accepted at 2019 49th Annual IEEE/IFIP International Conference on Dependable Systems and Network

Multicolor Observations of a Planetary Transit of HD 209458

We present B, V, R, I and Z-band photometric observations of HD 209458 during the transit by its planetary companion on UT 1999 November 15 with the University of Hawaii 0.6m and 2.2m telescopes and the High Altitude Observatory STARE telescope. The detailed shape of the transit curve is predicted to vary with color due primarily to the color-dependent limb-darkening of the star, but potentially due as well to the effect of color-dependent opacity in the planetary atmosphere. We model the light curves and present refined values for the transit timing and orbital period, useful for planning future observations of the planetary transit. We also derive significantly improved measurements of the planetary radius, R_p = 1.55 +/- 0.10 R_Jup, stellar radius, R_s = 1.27 +/- 0.05 R_Sun, and orbital inclination, i = 85.9 +/- 0.5 deg. The derived planetary radius favors evolutionary models in which the planet has a low albedo.Comment: 6 pages, 3 figures, accepted for publication in ApJ Letter

Success Rate of Embolization for Type II Endoleaks at a Major Tertiary Referral Center

Objective: The rise of endovascular aneurysm repair (EVAR) as the preferred treatment for abdominal aortic aneurysm (AAA) has introduced endoleaks as a major complication following AAA repair. The objective of this study is to assess the outcomes associated with endovascular embolization of type II endoleaks after EVAR. Methods: The institutional Radiology database at our tertiary referral hospital was queried for type II endoleak during the period 2006-2018. A retrospective chart review was then carried out. Only patients who underwent intervention for isolated type 2 endoleaks were analyzed. The primary outcome was success of the endoleak repair as determined by cessation of growth (i.e., ≤5mm change in diameter over follow-up period) of the native aneurysm sac. Patient outcomes for each failure of the above criterion were also collected. Other data pertaining to the location of endoleak, type of occlusion performed, type of embolic agent used, type of endograft used for EVAR, and incidence of aneurysm rupture were collected as secondary outcomes.Results:During this period 41 patients were treated for type II endoleaks. Demographics are shown in table 1. Cessation of growth was achieved in 28/41 (68.3%) of the patients after one embolization procedure. In 13/41 (31.7%) of patients, growth of the native aneurysm sac continued. Of the patients whose aneurysms continued to grow, 61.5% (8/13) did not undergo a second embolization. The remaining 38.5% (5/13) underwent a second embolization.Patient outcomes for both of these groups are presented in table II. None of the patients were found to have ruptured their aneurysm sac during follow-up after embolization. None of gender, race, the embolization site, or method of embolization were associated with embolization failure. Conclusions: Embolization of type II endoleaks is associated with a cessation of growth in the majority of cases and seems to be protective regarding the risk of aneurysm sac rupture. Future studies and additional follow-up will be important to elucidate the most significant risk factors for expansion and/or rupture of the endovascularly repaired abdominal aneurysm.Table I: Demographics for patients with type II endoleaks who underwent endovascular embolizationVariableValue Age (years +/- sd)75.66 +/- yearsAverage follow-up (months)62.65 monthsSex (%)71.7% male28.3% femaleRace (%)77.7% white17.8% black4.4% otherInflow vessel (%)43.2% lumbar only36.4% IMA only20.5% mixEmbolization site (%)40.5% vessel only14.3% cavity only20.5% mixEmbolization type (%)66.7% coil9.5% glue23.8% mixTable II: Outcomes for patients with continued growth after embolizationThose that did no undergo further embolizationThose that underwent a second embolization 3 were found to have type III endoleak and were successfully repaired with lining of the graft.2 whose aneurysm sac ceased growing. 2 who declined further treatment. 2 whose aneurysm sac continued to grow with persistent evidence of endoleak.1 who died from non-vascular complications. 1 who was lost to follow-up. 1 who is scheduled future surgical repair. 1 who was lost to follow-up.https://scholarlycommons.henryford.com/merf2019clinres/1026/thumbnail.jp