Oxychloridoselenites( iv ) with cubane-derived anions and stepwise chlorine-to-oxygen exchange

The novel oxychloridoselenites(IV) [BMIm][Se$_3$Cl$_{13}$] (1), [BMIm][Se$_4$Cl$_{15}$O] (2), [BMIm]$_2$[Se$_4$Cl$_{14}$O$_2$] (3), [BMPyr]$_2$[Se$_4$Cl$_{14}$O$_2$] (4), [BMPyr]$_2$[Se$_6$Cl$_{18}$O$_4$] (5), [BMIm]$_2$[SeCl$_4$O] (6), [BMPyr]$_2$[Se$_2$Cl$_6$O$_2$] (7), and [BMPyr]$_2$[Se$_6$Cl$_{14}$O$_6$] (8) are prepared by ionic-liquid-based synthesis. Accordingly, SeCl$_4$, SeO$_2$ (1–6), and/or SeOCl$_2$ (7,8) as the starting materials are reacted in [BMIm]Cl or [BMPyr]Cl as ionic liquid (BMIm: 1-butyl-3-methylimidazolium, BMPyr: 1-butyl-1-methylpyrrolidinium; partially with AlCl$_3$ in addition). Generally, the composition and structure of title compounds can be derived from the tetrameric, heterocubane-type (SeCl$_4$)$_4$ as the initial building unit. Thus, chlorine is successively exchanged by oxygen from 1 to 8. Moreover, the four edge-sharing (SeCl$_6$) octahedra in (SeCl$_4$)$_4$ are increasingly dismantled, ending with a [SeCl$_4$O]$^{2−}$ anion as a single pseudo-octahedron in 6. Based on the weakly coordinating ionic liquid, it is possible to selectively obtain the different species via synthesis near room temperature (20–80 °C). The oxychloridoselenite anions [Se$_4$Cl$_{15}$O]$^−$, [Se$_4$Cl$_{14}$O$_2$]$^{2−}$, [Se$_6$Cl$_{18}$O$_4$]$^{2−}$, and [Se$_6$Cl$_{14}$O$_6$]$^{2−}$ are obtained for the first time. The title compounds are characterized by X-ray structure analysis based on single crystals and powders as well as by infrared spectroscopy and thermal analysis

Mean and Random Errors of Visual Roll Rate Perception from Central and Peripheral Visual Displays

A large number of roll rate stimuli, covering rates from zero to plus or minus 25 deg/sec, were presented to subjects in random order at 2 sec intervals. Subjects were to make estimates of magnitude of perceived roll rate stimuli presented on either a central display, on displays in the peripheral ield of vision, or on all displays simultaneously. Response was by way of a digital keyboard device, stimulus exposition times were varied. The present experiment differs from earlier perception tasks by the same authors in that mean rate perception error (and standard deviation) was obtained as a function of rate stimulus magnitude, whereas the earlier experiments only yielded mean absolute error magnitude. Moreover, in the present experiment, all stimulus rates had an equal probability of occurrence, whereas the earlier tests featured a Gaussian stimulus probability density function. Results yield a ood illustration of the nonlinear functions relating rate presented to rate perceived by human observers or operators

Information Management to Mitigate Loss of Control Airline Accidents

Loss of control inflight continues to be the leading contributor to airline accidents worldwide and unreliable airspeed has been a contributing factor in many of these accidents. Airlines and the FAA developed training programs for pilot recognition of these airspeed events and many checklists have been designed to help pilots troubleshoot. In addition, new aircraft designs incorporate features to detect and respond in such situations. NASA has been using unreliable airspeed events while conducting research recommended by the Commercial Aviation Safety Team. Even after significant industry focus on unreliable airspeed, research and other evidence shows that highly skilled and trained pilots can still be confused by the condition and there is a lack of understanding of what the associated checklist(s) attempts to uncover. Common mode failures of analog sensors designed for measuring airspeed continue to confound both humans and automation when determining which indicators are correct. This paper describes failures that have occurred in the past and where/how pilots may still struggle in determining reliable airspeed when confronted with conflicting information. Two latest generation aircraft architectures will be discussed and contrasted. This information will be used to describe why more sensors used in classic control theory will not solve the problem. Technology concepts are suggested for utilizing existing synoptic pages and a new synoptic page called System Interactive Synoptic (SIS). SIS details the flow of flight critical data through the avionics system and how it is used by the automation. This new synoptic page as well as existing synoptics can be designed to be used in concert with a simplified electronic checklist (sECL) to significantly reduce the time to configure the flight deck avionics in the event of a system or sensor failure

An optimal control approach to pilot/vehicle analysis and Neal-Smith criteria

The approach of Neal and Smith was merged with the advances in pilot modeling by means of optimal control techniques. While confirming the findings of Neal and Smith, a methodology that explicitly includes the pilot's objective in attitude tracking was developed. More importantly, the method yields the required system bandwidth along with a better pilot model directly applicable to closed-loop analysis of systems in any order

Evaluation of Technology Concepts for Energy, Automation, and System State Awareness in Commercial Airline Flight Decks

A pilot-in-the-loop flight simulation study was conducted at NASA Langley Research Center to evaluate flight deck systems that (1) provide guidance for recovery from low energy states and stalls, (2) present the current state and expected future state of automated systems, and/or (3) show the state of flight-critical data systems in use by automated systems and primary flight instruments. The study was conducted using 13 commercial airline crews from multiple airlines, paired by airline to minimize procedural effects. Scenarios spanned a range of complex conditions and several emulated causal and contributing factors found in recent accidents involving loss of state awareness by pilots (e.g., energy state, automation state, and/or system state). Three new technology concepts were evaluated while used in concert with current state-of-the-art flight deck systems and indicators. The technologies include a stall recovery guidance algorithm and display concept, an enhanced airspeed control indicator that shows when automation is no longer actively controlling airspeed, and enhanced synoptic pages designed to work with simplified interactive electronic checklists. An additional synoptic was developed to provide the flight crew with information about the effects of loss of flight critical data. Data was collected via questionnaires administered at the completion of flight scenarios, audio/video recordings, flight data, head and eye tracking data, pilot control inputs, and researcher observations. This paper presents findings derived from the questionnaire responses and subjective data measures including workload, situation awareness, usability, and acceptability as well as analyses of two low-energy flight events that resulted in near-stall conditions

Regarding Pilot Usage of Display Technologies for Improving Awareness of Aircraft System States

ed systems and the procedures for ng in complexity. This interacting trend places a larger burden on pilots to manage increasing amounts of information and to understand system interactions. The result is an increase in the likelihood of loss of airplane state awareness (ASA). One way to gain more insight into this issue is through experimentation using objective measures of visual behavior. This study summarizes an analysis of oculometer data obtained during a high-fidelity flight simulation study that included a variety of complex pilot-system interactions that occur in current flight decks, as well as several planned for the next generation air transportation system. The study was comprised of various scenarios designed to induce low and high energy aircraft states coupled with other emulated causal factors in recent accidents. Three different display technologies were evaluated in this recent pilot-in-the-loop study conducted at NASA Langley Research Center. These technologies include a stall recovery guidance algorithm and display concept, an enhanced airspeed control indication of when the automation is no longer actively controlling airspeed, and enhanced synoptic diagrams with corresponding simplified electronic interactive checklists. Multiple data analyses were performed to understand how the 26 participating airline pilots were observing ASA-related information provided during different stag specific events within these stages

Low Temperature Raman Spectra of Dichlorosulfane (SC12), Tetrachlorosulfurane (SC14), Dichlorodisulfane (S2C12) and Dichlorodiselane (Se2Cl2) [1]

The Raman spectrum of commercial "sulfur dichloride" shows strong lines due to SCl2 and S2Cl2 and weak Cl2 lines at 25 °C, but strong SCl2 and SCl4 signals at -100 °C (the latter are superimposed on the S2Cl2 lines). Thus, the intense Raman effect of SCl4 can be used to detect small amounts of chlorine in SCl2 . Mixtures of SCl2 and Cl2 (1:15) yield the Raman spectrum of SCl4 at -140 °C, while at 25 °C not trace of this compound can be detected. The spectra of SCl4 and α-SeCl4 are quite different, indicating different molecular and/or crystal structures, although ECl3 + ions (E = S, Se) are present in both cases. While Se2Cl2 dimerizes reversibly below -50 °C, S2Cl2 neither dimerizes nor isomerizes on cooling. The S2Cl2 dimer is characterized by a Raman line at 215 cm-1 the intensity of which was used to calculate an enthalpy of dimerization as of -17 kJ/mol

State transition matrix for inertial navigation systems

Error equation for inertial navigation systems formulated and solved in state space notatio