Separation Minima Research Articles

Метод багатокритеріального розв’язання конфліктної ситуації між двома повітряними суднами у тривимірному просторі на основі динамічного програмування

Мета: Глобальні тенденції зростання інтенсивності повітряного руху обумовлюють збільшення кількості конфліктних ситуацій між повітряними судами. Актуальною проблемою є розробка нових методів розв’язання конфліктних ситуацій, які повинні забезпечувати синтез безконфліктних траєкторій у тривимірному просторі у відповідності до різних критеріїв ефективності польотів. Методи: Розроблено метод багатокритеріального розв’язання конфліктної ситуації між двома повітряними суднами із застосуванням маневрування зміною курсу, швидкості та висоти польоту. Описаний метод на основі динамічного програмування забезпечує синтез оптимальної безконфліктної траєкторії відповідно до критеріїв регулярності, економічності польотів та складності маневрування. Наведено рівняння багатокритеріального динамічного програмування для визначення множини Парето-оптимальних оцінок безконфліктних траєкторій у неперервній та дискретній формі. Синтез Парето-оптимальних безконфліктних траєкторій здійснюється із застосуванням прямої процедури дискретного багатокритеріального динамічного програмування. Моделювання траєкторій польоту виконується із використанням спеціальної моделі керованого руху повітряного судна. Вибір оптимальної безконфліктної траєкторії з множини Парето-оптимальних виконується із застосуванням згортки критеріїв оптимальності. В рамках методу визначено наступні процедури: прогнозування порушень мінімумів ешелонування; дискретизації станів та керувань, інтерполяції оцінок ефективності траєкторій за встановленими критеріями оптимальності. Результати: Дослідження запропонованого методу виконано шляхом комп’ютерного моделювання, результати якого показали, що розрахована оптимальна безконфліктна траєкторія забезпечує усунення конфліктної ситуації та відповідає встановленим критеріям оптимальності. Обговорення: Основними перевагами методу є: застосування маневрів по зміні курсу, швидкості та висоти польоту для усунення конфлікту; багатокритеріальна оптимізація безконфліктних траєкторій; застосування динамічного програмування, що підвищує обчислювальну ефективність. Запропонований метод може бути використаний при розробці засобів розв’язання конфліктних ситуацій для автоматизованих систем управління повітряним рухом.

Extending Required Navigation Performance to Include Time Based Operations and the Vertical Dimension

Extending Required Navigation Performance to Include Time Based Operations and the Vertical Dimension

Angle isomerism, as exemplified in a five-coordinate, dimeric copper(ii) Schiff base complex. Observation of Ostwald ripening

All bonding parameters in the X-ray structures of two forms of a Cu(ii) complex are found to be the same except for two angles. Correspondingly, two separate minima are located in DFT calculations.

Performance Evaluation on Several Exchange-correlation Functional Ap-proximations in Calculations of Alkali-metals and IB Group Metals Pair Potentials

In the present paper, inter-atomic pair potentials in alkali-metals and IB group metals, in crystal state and dia- tomic system, respectively, are systematically calculated by means of electronic density functional theory with several ex- change-correlation (EC) functional approximations. In the absence of experimental potential function information, exper- imentally available bonding length and binding energy of crystal lattice structure, and equilibrium separation and potential minimum of diatomic systems, are used for the first time in the context of potential energy as a function of atom separa- tion, to evaluate the performance of the EC approximations considered in calculating the main properties of neutral atom potential energy curve. Comparison between the experiment measures and first-principle calculations indicates that (i) all EC functional approximations show great changes in their performances for different systems, and the performances of a given EC functional approximation are variable even for the same element but different structures. (ii) The EC functional approximations considered show relatively stronger adaptability in calculations for the crystal lattice structures of both al- kali-metals and IB metals, but the performances for the IB metals Cu, Ag, Au diatomic systems degrade somewhat; more than that, the alkali-metal Li, Na, K, Rb, and Cs diatomic systems are inexorably the most difficult to be dealt with by all EC approximations considered. (iii) Although the calculated inter-atomic pair potentials in the diatomic system comprised of the IB metals and alkali-metals, respectively, display unmistakable deviations from the experimental measures, they still constitute specific empirical materials on which effective inter-atomic pair potentials are constructed to take into ac- count the three-body interactions in the statistical mechanics theory considering only two-body interactions.

Sense and Avoid

This study explored the ability of operators to provide separation between three unmanned aircraft using basic cockpit traffic displays. Four groups of three general aviation, instrument-rated pilots flew cross-country flights controlling simulated twin-engine unmanned aircraft systems (UAS). They were required to maintain 2 nautical miles (nmi) horizontal and 500 ft vertical separation from all other aircraft. To examine the effect of two important safety factors, the flights were conducted with and without communication among the operators and with and without variable accuracy in the displayed traffic location due to degraded sensor quality. Twenty four different three-dimensional traffic conflict trajectories with three UASs, were repeated randomly for each of the four experimental conditions for each group. Of the 1152 aircraft encounters 12.8% were in violation of separation minimums. Eighteen of these were closer than 400 ft vertically or 1.6 nmi horizontally. The minimum separation of all aircraft pairs was 293 ft and 0.13 nmi. No difference in minimum separations was found due to the presence of communications, the variable accuracy of traffic position, or the participant group. The type and time of evasive maneuvers showed no effect when displayed horizontal position accuracy was variable. When operators were able to communicate and coordinate their maneuvers, the time to resolve the conflict was reduced. Participant groups varied significantly in: time of conflict resolution, frequency and type of maneuvers, control activity, reported amount of threat, confidence, satisfaction, and appraisal of the efficacy of their communications. The findings of this study serve as a benchmark for the development of sense and avoid procedures and minimum equipage standards for operating UASs in the airspace over the United States.

Fuel Burn Model Development on Implementation of Reduced Vertical Separation Minimum (RVSM)

Much work has already been done with this end in mind; however, given the high degree of complexity associated with a large system such as this, there is opportunity for improvements in modeling capability. The FAA system for assessing Aviation’s Global Emissions (SAGE) is a well-established model for the creation of global inventories of aviation fuel use and emissions. The first is the way in which the specific fuel consumption (SFC) is calculated. Previous to this study, SFC was calculated through the methods put forward in EUROCONTROL’s Base of Aircraft Data (BADA). The results of this analysis provide insight into not only the benefits of RVSM, but also the effects of these model improvements and the efficacy of the different efficiency metrics used.

Evidence for distinct modes of solar activity

Aims. The Sun shows strong variability in its magnetic activity, from Grand minima to Grand maxima, but the nature of the variability is not fully understood, mostly because of the insufficient length of the directly observed solar activity records and of uncertainties related to long-term reconstructions. Here we present a new adjustment-free reconstruction of solar activity over three millennia and study its different modes. Methods. We present a new adjustment-free, physical reconstruction of solar activity over the past three millennia, using the latest verified carbon cycle, 14C production, and archeomagnetic field models. This great improvement allowed us to study different modes of solar activity at an unprecedented level of details. Results. The distribution of solar activity is clearly bi-modal, implying the existence of distinct modes of activity. The main regular activity mode corresponds to moderate activity that varies in a relatively narrow band between sunspot numbers about 20 and 67. The existence of a separate Grand minimum mode with reduced solar activity, which cannot be explained by random fluctuations of the regular mode, is confirmed at a high confidence level. The possible existence of a separate Grand maximum mode is also suggested, but the statistics is too low to reach a confident conclusion. Conclusions. The Sun is shown to operate in distinct modes - a main general mode, a Grand minimum mode corresponding to an inactive Sun, and a possible Grand maximum mode corresponding to an unusually active Sun. These results provide important constraints for both dynamo models of Sun-like stars and investigations of possible solar influence on Earth's climate.

Optical Research on Delivery of Departure Aircraft in Airspace Class D

In order to ensure flight safety and efficiently sequence departure aircraft in airspace class D, a sequencing model for scheduling the sequence of departure aircraft in airspace class D was discussed. Model's objective is minimizing the loss of delays under the premise separation minima which is used to keep the safety between proceeding aircraft and following aircraft must be satisfied. Then the model is transferred to pure integer nonlinear program model so that it can be solved by some program software like Lingo. At last, a numerical example is used to illustrate the process of solving the model. The numerical example shows that the model proposed in this paper is extremely efficient and model used for the aircraft sequencing in the airspace class D is feasible.

A Novel Probability Density Estimating Method for Relative Altitudes of Civil

With the rapid development of civil aviation, the shortage of airspace resource is becoming one of the main limiting factors for air traffic transportation. Inspired by the ideas of reduced vertical separation minimum and reducing aircraft separation standard, this paper analyzes the distributing characteristics of civil aircraft tracks in cruising level space and presents a novel method for probability density estimation of civil aircraft tracks' relative altitudes in their cruising flight level spaces, and analyzes the distributing characteristics at their cruising altitude direction.The method is based on QAR data of enough random civil aircraft tracks from a domestic airline. First, we choose altitude data of each track's main cruise phase and calculate altitude values relative to the standard cruise altitude of respective cruising flight level, we call these processes as spatial alignment and the relative altitudes as relative-cruising altitudes or relative-cruise altitudes. Secondly, we do temporal alignment and figure out the relative altitude values of these tracks in panel data form. Then, we estimate the probability density of the relative altitude values using kernel density estimate method, with the least square cross-validation method choosing asymptotically optimal smoothing parameters. Finally, we figure out different confidence track bands, namely confidence interval limits, and do analysis.All the analysis results show that there is a great deal of airspace margin and space resource potential in each cruising levels. Hence there are a great possibility and expectation that the vertical separation minimum can be reduced again and add flight levels, which is beneficial to increase air traffic capacity and relieve traffic jams.

Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone

Abstract. The replenishment of consumed oxygen in the open ocean oxygen minimum zone (OMZ) off northwest Africa is accomplished by oxygen transport across and along density surfaces, i.e. diapycnal and isopycnal oxygen supply. Here the diapycnal oxygen supply is investigated using a large observational set of oxygen profiles and diapycnal mixing data from years 2008 to 2010. Diapycnal mixing is inferred from different sources: (i) a large-scale tracer release experiment, (ii) microstructure profiles, and (iii) shipboard acoustic current measurements plus density profiles. From these measurements, the average diapycnal diffusivity in the studied depth interval from 150 to 500 m is estimated to be 1 × 10−5 m2 s−1, with lower and upper 95% confidence limits of 0.8 × 10−5 m2 s−1 and 1.4 × 10−5 m2 s−1. Diapycnal diffusivity in this depth range is predominantly caused by turbulence, and shows no significant vertical gradient. Diapycnal mixing is found to contribute substantially to the oxygen supply of the OMZ. Within the OMZ core, 1.5 μmol kg−1 yr−1 of oxygen is supplied via diapycnal mixing, contributing about one-third of the total demand. This oxygen which is supplied via diapycnal mixing originates from oxygen that has been laterally supplied within the upper Central Water layer above the OMZ, and within the Antarctic Intermediate Water layer below the OMZ. Due to the existence of a separate shallow oxygen minimum at about 100 m depth throughout most of the study area, there is no net vertical oxygen flux from the surface layer into the Central Water layer. Thus all oxygen supply of the OMZ is associated with remote pathways.

Hazard Analysis Methodology and Derivation of Performance Criteria for ADS-B and Alternate Surveillance Means

Recent standards work has derived minimum performance criteria for ADS-B surveillance using radar-like separation standards and operational methods in en route and terminal airspace. This paper introduces an alternative methodology for deriving ADS-B, radar and other surveillance system performance requirements based on generic hazard analysis methodology summarized by the FAA in recent Safety Management System (SMS) documents. The methodology is illustrated by first principles derivation of ADS-B performance criteria such as containment integrity (NIC, SIL) and position accuracy (NACp) for specified separation standards using GPS and alternate position sources. The level of the analysis is consistent with preliminary hazard analysis (PHA), to identify candidate surveillance sensors and initial performance criteria to meet desired target level of safety (TLS) criteria for specified separation minima. A simplified separation error probability (SEP) methodology is introduced that enables direct derivation of accuracy and integrity criteria for ADS-B systems, and provides a generic methodology for other positioning sensors, such as radar. The SEP methodology is extendable for end-to-end analysis, i.e., from generation of aircraft position and velocity reports to display of aircraft traffic for air traffic control and separation management.

Benefits on Implementation of Reduced Vertical Separation Minimum (RVSM) in Uzbekistan

Much work has already been done with this end in mind; however, given the high degree of complexity associated with a large system such as this, there is opportunity for improvements in modeling capability. The FAA system for assessing Aviation’s Global Emissions (SAGE) is a well-established model for the creation of global inventories of aviation fuel use and emissions. The first is the way in which the specific fuel consumption (SFC) is calculated. Previous to this study, SFC was calculated through the methods put forward in EUROCONTROL’s Base of Aircraft Data (BADA). The results of this analysis provide insight into not only the benefits of RVSM, but also the effects of these model improvements and the efficacy of the different efficiency metrics used.

On the Safety Assessment of the Airspace under Reduced Vertical Separation Minimum Operation(<Special Survey>Safety and Reliability of Aerospace Systems)

On the Safety Assessment of the Airspace under Reduced Vertical Separation Minimum Operation(<Special Survey>Safety and Reliability of Aerospace Systems)

Theoretical and Experimental Studies of the Rigidity Spectrum of the 27-Day Variation of the Galactic Cosmic Ray Intensity in Different Epochs of Solar Activity

We consider the recent, very exceptional, 11-year cycle (2003 – 2009) of solar activity and confirm that the relative amplitude in rigidity spectrum, δD(R)/D(R), which can be approximated by a power law in rigidity R, of the first three harmonics of the 27-day variation of the galactic cosmic ray (GCR) intensity is hard in the maximum and soft in the minimum epochs of solar activity, as was found by neutron monitor data for the period of 1965 – 2002. This property is seen not only in separate minimum and maximum epochs but in individual intervals of a solar Carrington rotation as well: There exist many individual intervals of solar rotation when the expected rigidity spectrum of the 27-day variation of the GCR intensity indeed is hard in the maximum epoch of solar activity and is soft in the minimum epoch. We then construct a three-dimensional model of the 27-day variation of the GCR intensity based on Parker’s transport equation, by implementing in situ measurements of the changes in heliographic longitude of the solar wind velocity and interplanetary magnetic field for different epochs of solar activity.

RVSM Implementation in Malaysia

This paper addresses the current scenario of air traffic over Malaysian airspace and its impact on existing routes and capacity. In dealing with the increase of capacity, ICAO has embarked on implementing several new measures that would accommodate more aircrafts and the same time maintaining the highest level of safety. Those measures are outlined in ICAO’s Doc 9574 and 9937. Instead of introducing more routes, which up to one point could reach its maximum saturation point, ICAO has introduced Reduced Vertical Separation Minima (RVSM). RVSM increases the number of aircraft that can be accommodated on the given route. The Malaysian airspace is strategically located in the middle of the Westbound and Eastbound routes over the Asia Pacific region. This is an added advantage for the installation the Height Monitoring Unit for RVSM performance of aircraft. Generally, almost all of the aircraft overflying Malaysian airspace are already at their optimum flight levels. This paper uses the trend for year 2010 and 2011 data provided by the Department of Civil Aviation of Malaysia in the analysis. The paper analyses the current scenario of air traffic safety over Malaysian airspace and identifies suggestions to develop a system that could extract information from ADS-B for height monitoring purposes.

Associations Among Indicators of Depression in Medicaid-Eligible Community-Dwelling Older Adults

The purpose of this research was to examine associations among 2 separate Minimum Data Set-Home Care (MDS-HC) depression measures (the Depression Rating Scale [DRS] and medical diagnosis of depression) with billed antidepressant medications in Medicaid paid claim files. The sample for this cross-sectional research included 3,041 Medicaid-eligible older adult participants in a Home and Community Based Waiver Program and used data from the MDS-HC, Version 1 and Medicaid Paid Claim Files. Sensitivity and specificity analyses, receiver operating characteristic (ROC) curve analysis, and t tests were utilized. DRS scoring indicated that 15.4% of participants had behaviors indicative of depression, whereas 42% had a medical diagnosis of depression noted in the MDS-HC. Of those with a medical diagnosis of depression, 51% had a prescribed antidepressant medication. ROC analysis suggested that the DRS was a poor distinguisher of participants with and without a medical diagnosis of depression or prescribed antidepressant medications. Approximately half of Medicaid-eligible older adults medically diagnosed with depression were treated pharmacologically. Longitudinal research is recommended to assess responsiveness of the DRS over time to pharmacological and psychotherapeutic interventions for depression.

The effect of pressure on the hydration structure around hydrophobic solute: A molecular dynamics simulation study

Molecular dynamics simulations are performed to study the effects of pressure on the hydrophobic interactions between neopentane molecules immersed in water. Simulations are carried out for five different pressure values ranging from 1 atm to 8000 atm. From potential of mean force calculations, we find that with enhancement of pressure, there is decrease in the well depth of contact minimum (CM) and the relative stability of solvent separated minimum over CM increases. Lower clustering of neopentane at high pressure is also observed in association constant and cluster-structure analysis. Selected site-site radial distribution functions suggest efficient packing of water molecules around neopentane molecules at elevated pressure. The orientational profile calculations of water molecules show that the orientation of water molecules in the vicinity of solute molecule is anisotropic and this distribution becomes flatter as we move away from the solute. Increasing pressure slightly changes the water distribution. Our hydrogen bond properties and dynamics calculations reveal pressure-induced formation of more and more number of water molecules with five and four hydrogen bond at the expense of breaking of two and three hydrogen bonded water molecules. We also find lowering of water-water continuous hydrogen bond lifetime on application of pressure. Implication of these results for relative dispersion of hydrophobic molecules at high pressure are discussed.

A time-optimal aircraft-following model based on Pontryagin’s minimum principle

A time-optimal aircraft-following model is introduced to address air traffic flow interference by velocity reduction. The objective function is set up as minimizing the recovery time during which the separation minima are not infringed and the separation of the air traffic flow returns to the initial separation at the terminal time. Pontryagin’s minimum principle is used to solve the optimum aircraft-following velocity control law. An analytical minimum safe following separation is also provided under the time-optimal control law. The simulation results show that the precision first-order tracking accuracy is achieved without losing the separation.

Air Traffic Control Separation Minima: Part 2 – Transition to a Trajectory-based System

Current strategic plans for Air Traffic Management (ATM) envisage a transition from radar control to a trajectory-based system. Part 1 sketched the historical origins of separation minima and then analysed the safety thinking behind current minima and the issues involved in risk modelling. Part 2 examines the future situation. This focuses on the intermediate steps to the final system – upgraded capabilities in a mixed-equipage system. Future traffic mixes two categories of traffic: V aircraft, i.e. vectored traditional ATC-handled, and 4D aircraft, i.e. flying on 4D trajectories. Conflict probe and other decision support tools will need to be in place, inter alia to prevent controller workload from increasing. Conceptually, future risks in the transition period will be the sum of three types of aircraft encounter risk: V/V, 4D/4D and 4D/V. These pose different kinds of problem for ATC, appropriate conflict alerting systems and risk assessment. The numbers of 4D/V encounters increase rapidly with growth in the proportion of 4D aircraft. With reduced minima, airborne collision avoidance systems would be unlikely to resolve higher relative velocity encounters were the ATC system to fail. It would be a difficult decision to reduce markedly ATC separation minima for any category of aircraft encounters during the transition period.

RNAV平行経路の最小経路間隔の一推定方法

An area navigation (RNAV) road map was prepared by the Japan Civil Aviation Bureau for effective aircraft operation and effective utilization of air space. Following the road map, RNAV routes have been implemented in Japan. RNAV is a method of navigation which permits aircraft operation on any desired flight path within the coverage of station-referenced navigation aids or within the limits of the capability of self-contained aids, or a combination of these. This paper describes a methodology for estimating safe minimum route spacing for RNAV-approved aircraft. Radar track data of aircraft which flew on a Kagoshima RNAV standard terminal arrival route (STAR) were collected for six months for the purpose of analyzing the cross-track deviations for RNAV-approved aircraft. The distribution of cross-track deviations was estimated using this data set. A probability distribution model of it was then found. The lateral overlap probability was estimated using the empirical distribution and its deformation. Collision risk was estimated using the estimate of lateral overlap probability together with other given parameters. Comparing the estimated collision risk with the target level of safety (TLS) for the lateral dimension separation minimum, safe minimum route spacing was obtained. As a result, in the case that the population of aircraft with poor navigation performance, i.e., barely meeting the 95% containment requirement for RNAV approved aircraft, is assumed to be 10 percent, estimates of safe minimum route spacing are 8 nautical miles (NM) for RNAV1-approved aircraft and 32NM for RNAV5-approved aircraft, respectively. Additionally, safe minimum route spacing which takes into account of the fluctuation of data is estimated using the Bootstrap method. The result shows that the estimated ranges of minimum route spacing are 7NM-9NM for RNAV1-approved aircraft and 29NM-38NM for RNAV5-approved aircraft, respectively.