Search

Automated conflict detection in terminal airspace is a challenging problem, in part because key information regarding flight intent is not available. Unlike en route controllers, terminal controlle...

Skin aging is characterized by color and wrinkle caused by degeneration of collagen and elastin in the dermis. Recently, the volume, diameter and branching of the micro vessels in the skin are proved to affect these biomechanical changes. Thus, high resolution imaging for both micro structure and micro vessels of the skin is desired. In the present study, dual-wavelength photoacoustic microscope (PAM) combined with high frequency ultrasound (HFUS) is developed to visualize both the morphology and microcirculation of the skin. Two Nd:YAG laser light sources with the wavelength of 532/556 nm, pulse width of 1.2/3.6 ns, pulse energy of 16 μJ/pulse and repetition rate of 1 kHz were equipped in the HFUS-PAM system. The optical fiber for laser delivery was inserted through the center hole of the concave ultrasound transducer with the central frequency of 75 MHz. Both HFUS and PA signals were acquired at the sampling rate of 500 MHz and the resolution of 12 bits. The transducer was scanned by voice coil actuators to obtain 3D dataset of HFUS and PA signals. Oxygen saturation of the micro circulation was calculated by the PA signals alternately obtained at 532 nm and 556 nm. 3D image of the layered structure and the micro vessels representing oxygen saturation in the 6 mm x 6 mm x 3 mm volume of the skin was successfully obtained with the system. HFUS-PAM will provide important information of skin morphology and microcirculation for assessment of skin aging.

Arrival air traffic operations in the presence of convective weather are subject to uncertainty in aircraft routing and subsequently in flight trajectory predictability. Current management of arrival operations in weather-impacted airspace results in significant flight delay and suspension of arrival metering operations. The Dynamic Routing for Arrivals in Weather (DRAW) concept provides flight route amendment advisories to Traffic Management Coordinators to mitigate the impacts of convective weather on arrival operations. DRAW provides both weather conflict and schedule information for proposed route amendments, allowing air traffic managers to simultaneously evaluate weather avoidance routing and potential schedule and delay impacts. Subject matter experts consisting of retired Traffic Management Coordinators and retired Sector Controllers with arrival metering experience participated in a simulation study of Fort Worth Air Route Traffic Control Center arrival operations. Data were collected for Traffic Management Coordinator and Sector Controller participants over three weeks of simulation activities in October, 2017. Traffic Management Coordinators reported acceptable workload levels, a positive impact on their ability to manage arrival traffic while using DRAW, and initiated weather mitigation reroutes earlier while using DRAW. Sector Controllers also reported acceptable workload levels while using DRAW.

In conventional pulsed laser deposition (PLD) technique, plume deflection and composition distribution change with the laser incident direction and pulse energy, then causing uneven film thickness and composition distribution for a multicomponent film and eventually leading to low device quality and low rate of final products. We present a novel method based on PLD for depositing large CIGS films with uniform thickness and stoichiometry. By oscillating a mirror placed coaxially with the incident laser beam, the laser's focus is scanned across the rotating target surface. This arrangement maintains a constant reflectance and optical distance, ensuring that a consistent energy density is delivered to the target surface by each laser pulse. Scanning the laser spot across the target suppresses the formation of micro-columns, and thus the plume deflection effect that reduces film uniformity in conventional PLD technique is eliminated. This coaxial scanning PLD method is used to deposit a CIGS film, 500 nm thick, with thickness uniformity exceeding ±3% within a 5 cm diameter, and exhibiting a highly homogeneous elemental distribution.

It is common for aircraft to conduct visual and instrument final approaches to a single runway or multiple parallel runways. Useful, nonexcessive safety alerts on aircraft conducting visual approaches are helpful to air traffic controllers, though pilots are responsible for separation with the preceding aircraft. A variety of visual approaches to various runway configurations are studied, and a set of safety alert thresholds is proposed. Fast-time simulations with recorded real-world air traffic data of mostly visual approach flights are performed on a prototype tactical separation assurance system for terminal airspace. Alerts are generated -- with both the standard separation thresholds and the proposed safety alert thresholds -- and compared with those from the Conflict Alert (CA) functionality in the Standard Terminal Automation Replacement System (STARS). The results show that the number of Mode-C Intruder alerts generated was reduced 76% as compared to STARS CA. The nuisance alerts generated by assuming visual to be instrument approaches was reduced by 92% when the proposed safety alert thresholds were used and visual approaches were assumed.A set of safety alert thresholds, which allow safety alerts to be provided to the controllers for aircraft conductingvisual approaches to a single runway or multiple parallel runways, has been proposed based on input from SubjectMatter Experts as well as visual approach procedures and common practices. The goal is to maximize the thresholdswithin the guidance of the procedures and common practices and to minimize the number of nuisance alerts and totalnumber of alerts with the support of flight intent information. Tests have been performed using a recently developedprototype tactical separation assurance system for terminal airspace, called Terminal Tactical Separation-AssuredFlight Environment (T-TSAFE). The input was a full day of air traffic data from Dallas/Fort Worth (DFW) TRACONwith most arriving flights conducting visual approaches. The results compare favorably with those of the ConflictAlert (CA) functionality of the Standard Terminal Automation Replacement System (STARS).When fast-time simulation experiment was performed using T-TSAFE with all arriving flights assumed to conductinstrument approaches, the expected large number of separation alerts were observed. When compared with STARSCA, the conflict pairs common to both T-TSAFE and STARS CA was only 21% of the total STARS CA alerts. As aresult, the nuisance-alert rate for STARS CA was estimated to be about 70%, which is comparable to a similar previously estimation of 80% nuisance-alert rate for CARTS (Common Automated Radar Terminal System) CA. The Mode-CIntruder (MCI) alerts were also reduced by 76% as compared to STARS CA.Examination of the common conflict pairs between T-TSAFE and STARS CA shows that they are valid separationconflicts with good alert lead times for T-TSAFE. However, many of them would still be considered nuisance alertsif the aircraft were conducting visual approaches. This was confirmed by another visual approach fast-time simulationT-TSAFE experiment, in which all DFW arriving flights were assumed to be on visual approaches and our proposedsafety alert thresholds were used and tested. The result of the experiment showed that the number of non-MCI alertswas less by 92% as compared to the number when all DFW arrivals were assumed to be conducting instrumentapproaches. The common conflict pairs involving aircraft conducting visual approaches to parallel runways werereduced by 93% as well. Thus, the flight intent information and the safety alert thresholds are effective in reducingnuisance alerts.T-TSAFE can thus provide separation and safety conflict alerts seamlessly in the real-world environment of mixedterminal operations with arriving flights of both visual and instrument approaches. Compared with STARS CA, TTSAFEhas fewer false alerts, larger alert lead time, and larger alert thresholds. While the nuisance alerts are reducedsignificantly with the safety alert thresholds, further work is needed to study if the alert lead time for safety alerts issufficient.

A tactical separation assurance prototype system is evaluated for its fitness to support the Standard Terminal Automation Replacement System (STARS) in a complex terminal airspace environment that includes a mix of visual- and instrument-approach aircraft, Mode C intruders, and limited trajectory-intent data. Fast-time simulation experiments using air traffic data from human-in-the-loop simulations and live Terminal Radar Control (TRACON) operations featuring a mix of visual and instrument approaches and Mode C intruders are performed to assess the performance and benefits of the system in a near-term national airspace system (NAS). It is found that nuisance alerts attributable to aircraft on visual approach are eliminated with a high-severity alerting option. With a normal lowseverity alerting option, Mode C intruder alerts are reduced more than 50% as compared to the Conflict Alert system, a legacy function in STARS. The trajectory intent information that is most effective in reducing false alerts is identified and found to be available in STARS or easily adapted from existing NAS automation.

A conflict detection and resolution tool, Terminal Tactical Separation Assurance Flight Environment (T-TSAFE), is being developed to improve the accuracy and reduce the false alert rate beyond currently deployed technology. The legacy system in use today, Conflict Alert, relies primarily on a dead reckoning algorithm. By adding altitude intent information for conflict detection and resolution, T-TSAFE may improve conflict detection accuracy. In addition to verifying T-TSAFE's efficacy over Conflict Alert, an initial human-in-the-loop study suggested possible avenues of tool improvement through heuristic analysis. Results of this analysis were then used to guide a follow-up T-TSAFE investigation, which is described in this paper. This follow-up study tested four experimental conditions. The first two conditions varied conflict detection with and without altitude clearances entered into the tool by the controllers via keyboard. The other two conditions varied the presence of Automatic Terminal Proximity Alert (ATPA), an FAA tool used for monitoring final approach [1]. One of these final approach conditions used regular alerts in the data block without cones and the others used ATPA cones between different aircraft (i.e., a cone graphic shown in the flight display) as a warning for possible compression errors in the final approach. Entering altitude clearances into T-TSAFE was expected to reduce false alerts but did not, possibly due to the short duration of the runs, which did not allow for a large enough frequency of altitude entries to study the issue adequately. Also, the test conditions did not significantly impact the duration of the alert or the controller's response time to the alert. The subjective data showed that controllers favored the ATPA cones over the T-TSAFE alerts in the data blocks on final approach. Results also indicate manageable levels of workload and situation awareness, which combined with other results, seem to indicate promise for T-TSAFE as a viable air traffic control tool, pending further research and adaptation.

• Altitude entries did not impact false alerts • The user interface of the ATPA cones preferred over T-TSAFE alerts in the data block • Higher potential for complacency in the ATPA cones condition as compared to the T-TSAFE alerts in final approach • Overall there is enough trust in the tool to stay engaged

A method for determining the severity of impending losses of separation (LOSs) is proposed. It is based on the FAA (Federal Aviation Administration) separation conformance category for classification of operational errors. A recently proposed short-term conflict detection algorithm for terminal airspace is enhanced with this severity concept. The alerts from the resulting algorithm are compared with the Conflict Alert (CA) currently in the field, which is a legacy system for automated short-term conflict detection. Three complementary sets of aircraft track data are employed. The first set is real-world data with documented LOSs due to operational errors. It allows determination of average alert lead time while providing regression testing of the algorithm. The second set is realistic data from human-in-the-loop experiments with no visual approaches allowed and with known intervention from controllers or pilots available. As a result more objective determination of false alert rate is possible. The third set is real-world data with unknown mixed operations of Instrument Landing System (ILS) and visual approaches but with CA alerting data available from the FAA. The comparison with CA indicates that the algorithm produces a similar total number of alerts but with a much larger safety buffer and a much lower false alert rate. The study also suggests that a high-severity conflict prediction option may be used for aircraft performing visual approaches to satisfy the controller’s moral responsibility for those aircraft.

Despite the recent economic recession and its adverse impact on air travel, the Federal Aviation Administration (FAA) continues to forecast an increase in air traffic demand that may see traffic double or triple by the year 2025. Increases in air traffic will burden the air traffic management system, and higher levels of safety and efficiency will be required. The air traffic controllers primary task is to ensure separation between aircraft in their airspace and keep the skies safe. As air traffic is forecasted to increase in volume and complexity [1], there is an increased likelihood of conflicts between aircraft, which adds risk and inefficiency to air traffic management and increases controller workload. To attenuate these factors, recent ATM research has shown that air and ground-based automation tools could reduce controller workload, especially if the automation is focused on conflict detection and resolution. Conflict Alert is a short time horizon conflict detection tool deployed in the Terminal Radar Approach Control (TRACON), which has limited utility due to the high number of false alerts generated and its use of dead reckoning to predict loss of separation between aircraft. Terminal Tactical Separation Assurance Flight Environment (T-TSAFE) is a short time horizon conflict detection tool that uses both flight intent and dead reckoning to detect conflicts. Results of a fast time simulation experiment indicated that TTSAFE provided a more effective alert lead-time and generated less false alerts than Conflict Alert [2]. TSAFE was previously tested in a Human-In-The-Loop (HITL) simulation study that focused on the en route phase of flight [3]. The current study tested the T-TSAFE tool in an HITL simulation study, focusing on the terminal environment with current day operations. The study identified procedures, roles, responsibilities, information requirements and usability, with the help of TRACON controllers who participated in the experiment. Metrics such as lead alert time, alert response time, workload, situation awareness and other measures were statistically analyzed. These metrics were examined from an overall perspective and comparisons between conditions (altitude resolutions via keyboard entry vs. ADS-B entry) and controller positions (two final approach sectors and two feeder sectors) were also examined. Results of these analyses and controller feedback provided evidence of T-TSAFE s potential promise as a useful air traffic controller tool. Heuristic analysis also provided information on ways in which the T-TSAFE tool can be improved. Details of analyses results will be presented in the full paper.

Air traffic systems have long relied on automated short-term conflict prediction algorithms to warn controllers of impending conflicts (losses of separation). The complexity of terminal airspace has proven difficult for such systems as it often leads to excessive false alerts. Thus, the legacy system, called Conflict Alert, which provides short-term alerts in both en-route and terminal airspace currently, is often inhibited or degraded in areas where frequent false alerts occur, even though the alerts are provided only when an aircraft is in dangerous proximity of other aircraft. This research investigates how a minimal level of flight intent information may be used to improve short-term conflict detection in terminal airspace such that it can be used by the controller to maintain legal aircraft separation. The flight intent information includes a site-specific nominal arrival route and inferred altitude clearances in addition to the flight plan that includes the RNAV (Area Navigation) departure route. A new tactical conflict detection algorithm is proposed, which uses a single analytic trajectory, determined by the flight intent and the current state information of the aircraft, and includes a complex set of current, dynamic separation standards for terminal airspace to define losses of separation. The new algorithm is compared with an algorithm that imitates a known en-route algorithm and another that imitates Conflict Alert by analysis of false-alert rate and alert lead time with recent real-world data of arrival and departure operations and a large set of operational error cases from Dallas/Fort Worth TRACON (Terminal Radar Approach Control). The new algorithm yielded a false-alert rate of two per hour and an average alert lead time of 38 seconds.

The nation’s air transportation system is currently unable to support the forecasted demand for air travel. New airborne and ground-based capabilities are being investigated to address the myriad of challenges that pilots, operators, and air navigation service providers will face. One approach being studied considers a layered architecture involving a strategic and a tactical system to provide automated separation assurance. Because the tactical system will operate in a time horizon that may overlap with on-board collision-avoidance systems, it must be designed not to interfere with these systems. This paper presents a new set of vertical conflict resolutions for a conflict aircraft pair. Heuristics are presented which govern the use of the new vertical and recently-developed horizontal conflict resolution algorithms to minimize interference with an on-board collision-avoidance system. To address the expected increase in traffic density, an algorithm for globally resolving conflicts involving multiple aircraft is also presented. Evaluation using real-world encounters in both en route and terminal airspace demonstrates the effectiveness of both the vertical algorithm and the heuristics used to reduce the interference.

Superconductivities in the 90K range as measured by resistance and magnetic susceptibility are reported for RBa2Cu3O9-y (R=Y, Nd, Sm, Eu, Gd, Dy, Er, Tm, Yb) having the orthorhombic perovskite structure. Unstable resistance drop above 100K has been found in ErBCO, probably associated with interfacial superconductivity.