An Archival Analysis of Stall Warning System Effectiveness During Airborne Icing Encounters

An archival study was conducted to determine the influence of stall warning system performance on aircrew decision-making outcomes during airborne icing encounters. A Conservative Icing Response Bias (CIRB) model was developed to explain the historical variability in aircrew performance in the face of airframe icing. The model combined Bayes’ Theorem with Signal Detection Theory (SDT) concepts to yield testable predictions that were evaluated using a Binary Logistic Regression (BLR) multivariate technique applied to two archives: the NASA Aviation Safety Reporting System (ASRS) incident database, and the National Transportation Safety Board (NTSB) accident databases, both covering the period January 1, 1988 to October 2, 2015. The CIRB model predicted that aircrew would experience more incorrect response outcomes in the face of missed stall warnings than with stall warning False Alarms. These predicted outcomes were observed at high significance levels in the final sample of 132 NASA/NTSB cases. The CIRB model had high sensitivity and specificity and explained 71.5% (Nagelkerke R2) of the variance of aircrew decision-making outcomes during the icing encounters. The reliability and validity metrics derived from this study suggest indicate that the findings are generalizable to the population of U.S. registered turbine-powered aircraft. These findings suggest that icing-related stall events could be reduced if the incidence of stall warning misses could be minimized. Observed stall warning misses stemmed from three principal causes: aerodynamic icing effects, which reduced the stall angle-of-attack (AoA) to below the stall warning calibration threshold; tail stalls, which are not monitored by contemporary protection systems; and icing-induced system issues (such as frozen pitot tubes), which compromised stall warning system effectiveness and airframe envelope protections. Each of these sources of missed stall warnings could be addressed by Aerodynamic Performance Monitoring (APM) systems that directly measure the boundary layer airflow adjacent to the affected aerodynamic surfaces, independent of other aircraft stall protection, air data, and AoA systems. In addition to investigating APM systems, measures should also be taken to include the CIRB phenomenon in aircrew training to better prepare crews to cope with airborne icing encounters. The SDT/BLR technique would allow the forecast gains from these improved systems and training processes to be evaluated objectively and quantitatively. The SDT/BLR model developed for this study has broad application outside the realm of airborne icing. The SDT technique has been extensively validated by prior research, and the BLR is a very robust multivariate technique. Combined, they could be applied to evaluate high order constructs (such as stall awareness for this study), in complex and dynamic environments. The union of SDT and BLR reduces the modeling complexities for each variable into the four binary SDT categories of Hit, Miss, False Alarm, and Correct Rejection, which is the optimum format for the BLR. Despite this reductionist approach to complex situations, the method has demonstrated very high statistical and practical significance, as well as excellent predictive power, when applied to the airborne icing scenario

Critical dislocation speed in helium-4 crystals

Our experiments show that in $^4$He crystals, the binding of $^3$He impurities to dislocations does not necessarily imply their pinning. Indeed, in these crystals, there are two different regimes of the motion of dislocations when impurities bind to them. At lowdriving strain $\epsilon$ and frequency $\omega$, where the dislocation speed is less than a critical value (45 $\mu$m/s), dislocations and impurities apparently move together. Impurities really pin the dislocations only at higher values of $\omega$. The critical speed separating the two regimes is two orders of magnitude smaller than the average speed of free $^3$He impurities in the bulk crystal lattice.We obtained this result by studying the dissipation of dislocation motion as a function of the frequency and amplitude of a driving strain applied to a crystal at low temperature. Our results solve an apparent contradiction between some experiments, which showed a frequency-dependent transition temperature from a soft to a stiff state, and other experiments or models where this temperature was assumed to be independent of frequency. The impurity pinning mechanism for dislocations appears to be more complicated than previously assumed

The application of Signal Detection Theory principles to aircraft certification

This paper presents the application of Signal Detection Theory (SDT) concepts to the certification of optional systems that provide operational or system safety benefits. The method and analysis yield quantitative requirements for the system performance that account for the risks and benefits of the potential system. This is in contrast to the standard certification approach which only focuses on Failure Conditions, and does not examine potential system benefits. A case study of an aircraft spotter on an electronic moving map illustrates that substantial safety improvements may be achieved even with the relatively low levels of software reliability associated with Commercial Off-the-shelf Software (COTS). The method makes few domain assumptions, and is based on the underpinnings of SDT and Bayesian probability theory, with well-established validity and reliability. Accordingly, the technique should have broad application to the certification of all optional aircraft systems

False Discovery Rate Control for High Dimensional Dependent Data with an Application to Large-Scale Genetic Association Studies

Large-scale genetic association studies are increasingly utilized for identifying novel susceptible genetic variants for complex traits, but there is little consensus on analysis methods for such data. Most commonly used methods include single SNP analysis or haplotype analysis with Bonferroni correction for multiple comparisons. Since the SNPs in typical GWAS are often in linkage disequilibrium (LD), at least locally, Bonferonni correction of multiple comparisons often leads to conservative error control and therefore lower statistical power. Motivated by an application for analysis of data from the genetic association studies, we consider the problem of false discovery rate (FDR) control under the high dimensional multivariate normal model. Using the compound decision rule framework, we develop an optimal joint oracle procedure and propose to use a marginal procedure to approximate the optimal joint optimal procedure. We show that the marginal plug-in procedure is asymptotically optimal under mild conditions. Our results indicate that the multiple testing procedure developed under the independent model is not only valid but also asymptotically optimal for the high dimensional multivariate normal data under some weak dependency. We evaluate various procedures using simulation studies and demonstrate its application to a genome-wide association study of neuroblastoma (NB). The proposed procedure identified a few more genetic variants that are potentially associated with NB than the standard p-value-based FDR controlling procedure

The role of interaction vertices in bound state calculations

In recent studies of the one and two-body Greens' function for scalar interactions it was shown that crossed ladder and ``crossed rainbow'' (for the one-body case) exchanges play a crucial role in nonperturbative dynamics. In this letter we use exact analytical and numerical results to show that the contribution of vertex dressings to the two-body bound state mass for scalar QED are cancelled by the self-energy and wavefunction normalization. This proves, for the first time, that the mass of a two-body bound state given by the full theory can in a very good approximation be obtained by summing only ladder and crossed ladder diagrams using a bare vertex and a constant dressed mass. We also discuss the implications of the remarkable cancellation between rainbow and crossed rainbow diagrams that is a feature of one-body calculations.Comment: 9 pages, 5 figure

Systems Engineering Management Plan NASA Traffic Aware Planner Integration Into P-180 Airborne Test-Bed

NASA's Traffic Aware Planner (TAP) is a cockpit decision support tool that provides aircrew with vertical and lateral flight-path optimizations with the intent of achieving significant fuel and time savings, while automatically avoiding traffic, weather, and restricted airspace conflicts. A key step towards the maturation and deployment of TAP concerned its operational evaluation in a representative flight environment. This Systems Engineering Management Plan (SEMP) addresses the test-vehicle design, systems integration, and flight-test planning for the first TAP operational flight evaluations, which were successfully completed in November 2013. The trial outcomes are documented in the Traffic Aware Planner (TAP) flight evaluation paper presented at the 14th AIAA Aviation Technology, Integration, and Operations Conference, Atlanta, GA. (AIAA-2014-2166, Maris, J. M., Haynes, M. A., Wing, D. J., Burke, K. A., Henderson, J., & Woods, S. E., 2014)

Decoquinato, lasalocida e monensina em concentrado inicial e desempenho de bezerros holandeses até 20 semanas de idade

A larga utilização de coccidiostaticos em rebanhos leiteiros tem levantado questões relacionadas à escolha do melhor produto baseada no suposto melhor desempenho de bezerros leiteiros. Este trabalho avaliou o desempenho de bezerros leiteiros recebendo 3 diferentes coccidiostaticos em fazenda no estado do Arizona, EUA. Sessenta e quatro bezerros holandêses foram distribuidos ao acaso em quatro tratamentos com 10 ± 4 dias de vida. Os bezerros receberam concentrado inicial sem (controle) ou com a adição de um dos seguintes coccidiostáticos: lasalocida, 30 mg kg-1; decoquinato, 19 mg kg-1; e monensina, 30 mg kg-1. Os bezerros receberam 3,6 kg d-1 de substituto de leite até 6 semanas de vida. O concentrado inicial foi oferecido "ad libitum" até o consumo de 2 kg d-1. Os animais tiveram acesso livre a água durante todo o período. Após a desmama foi fornecido feno de alfafa "ad libitum". O desempenho animal e o consumo de matéria seca (CMS) foram monitorados durante 20 semanas de tratamento, sendo este dividido em diferentes períodos (0-6, 7-12 e 13-20 semanas). Apesar do menor consumo de matéria seca e menor ganho de peso de fêmeas recebendo monensina durante todo o período experimental, não foram observadas diferenças entre os produtos nas condições deste experimento na maior parte das fases de monitoramento. Bom manejo e o clima quente e seco no Arizona reduziram as chances de aparecimento de cocidiose e portanto de diferenças no desempenho de bezerros leiteiros.The large utilization of coccidiostats in dairy herds has raised the question regards the best product to use, based on better animal performance. Sixty-four Holstein calves were randomly assigned to four treatments at 10 (±4) d of age to evaluate calf performance when fed approved coccidiostats available on the market in Arizona, USA. Calves received a dry calf starter without (control) or with one of the following coccidiostats: lasalocid, 30 mg kg-1; decoquinate, 19 mg kg-1; and monensin, 30 mg kg-1. Calves received 3.6 kg d-1 of a commercial 22% CP:20% fat milk replacer until 6 wk of age. Calves were offered starter "ad libitum" up to 2 kg d-1, and calves had free access to water throughout the trial. Alfalfa hay was offered "ad libitum" after weaning. Performance and dry matter intake (DMI) were monitored for 20 weeks and broken down in different periods of measurement (0-6, 7-12 and 13-20 weeks, respectively). Despite the lower dry matter intake and weight gain for females on monensin treatment during the whole period, differences among coccidiostats were seldom observed under the conditions of this study. Good calf management and the dry, hot climate of Arizona perhaps diminished the chances for subclinical and chronic disease appearance which negated potential differences and differences in calf performances

The effectiveness of the antegrade reamed technique: the experience and complications from 415 traumatic femoral shaft fractures

This retrospective study presents the experience gained through use of reamed femoral nails and reports results and respective complications. This study included 415 femur fractures (312 men and 101 women with a mean age of 27.8 years) that were treated from 1993 to 2004. The fractures were classified according to AO, and 74 open fractures were included and typed according to the Gustilo classification. Dynamic nailing was performed for nearly all type A fractures and static nailing for types B and C. After a mean follow-up of 1.5 years, union rate was 97.8%. The complications were: 9 non-unions, 14 delayed-unions, 4 torsional malunions, 6 limb length discrepancies (shortening) and 30 nerve pareses due to traction. Deep venous thrombosis (DVT) occurred below the knee in 4 patients, while there were recorded 3 pulmonary and 2 fat embolisms, 1 superficial and 1 deep infection. There were 28 broken screws identified postoperatively. Logistic regression analysis revealed that type B and C were associated with increased risk of complications, with respective odds ratios of 3.1 (95% CI = 1.3–7.2, P = 0.011) and 4.3 (95% CI = 1.8–10.3, P = 0.001) when compared to type A patterns. All patients returned to their activities in a mean time of 10 months. Intramedullary nailing is still the treatment of choice for femoral shaft fractures, but knowledge of potential complications and their association with certain fracture patterns is needed

Surgery As a Trigger for Incident Venous Thromboembolism: Results from a Population-Based Case-Crossover Study

Background Surgery is a major transient risk factor for venous thromboembolism (VTE). However, the impact of major surgery as a VTE trigger has been scarcely investigated using a case-crossover design. Aim To investigate the role of major surgery as a trigger for incident VTE in a population-based case-crossover study while adjusting for other concomitant VTE triggers. Methods We conducted a case-crossover study with 531 cancer-free VTE cases derived from the Tromsø Study cohort. Triggers were registered during the 90 days before a VTE event (hazard period) and in four preceding 90-day control periods. Conditional logistic regression was used to estimate odds ratios (ORs) with 95% confidence intervals (CIs) for VTE according to major surgery and after adjustment for other VTE triggers. Results Surgery was registered in 85 of the 531 (16.0%) hazard periods and in 38 of the 2,124 (1.8%) control periods, yielding an OR for VTE of 11.40 (95% CI: 7.42–17.51). The OR decreased to 4.10 (95% CI: 2.40–6.94) after adjustment for immobilization and infection and was further attenuated to 3.31 (95% CI: 1.83–5.96) when additionally adjusted for trauma, blood transfusion, and central venous catheter. In a mediation analysis, 51.4% (95% CI: 35.5–79.7%) of the effect of surgery on VTE risk could be mediated through immobilization and infection. Conclusions Major surgery was a trigger for VTE, but the association between surgery and VTE risk was in part explained by other VTE triggers often coexisting with surgery, particularly immobilization and infection