Mission Characteristics Research Articles

Multi-Objective Optimization for Aircraft Power Systems Using a Network Graph Representation

Today, the electrification of flight is more popular than ever, creating a wide array of concept aircraft and associated power system topologies. In order to gain insights into benefits of these varying architectures, this article introduces the development of a framework for electric aircraft power system (EAPS) optimization. The proposed framework accepts inputs from a designer in the form of component parameters and desired flight mission characteristics. A collective graph representing many possible architectures is formed, from which subgraphs that describe power system topologies meeting the flight requirements are extracted and analyzed. Optimal EAPS architectures with respect to goals of minimizing mass while maximizing efficiency and reliability can be subsequently selected from these subgraphs. The framework is exemplified on a 500-kW rated aircraft using data collected from surveys of component parameters, such as power density and efficiency. The presented results show a comparative analysis of different EAPS types with respect to the competing performance metrics of mass, efficiency, and survivability.

Research on mission characteristics-based evaluation model of flight test workload

As a product of modern industrial cutting-edge technology, a large civil aircraft needs to undergo rigorous flight test before entering the aviation market, which fully ensures the safety of aircraft and its system. This makes the aircraft meet the airworthiness standards and requirements. The flight test of civil aircraft is a complex system project, which the top-level planning throughout the flight test period has an important influence on progress control and flight test efficiency of a new type aircraft. The core content of the top-level plan is the evaluation of flight test workload with consideration of test aircraft quantity. This paper proposes a flight test workload analysis and evaluation model based on the types of test missions through the analysis of the characteristics of civil aircraft flight test mission, which provides a feasible method for quantitative evaluation of flight test workload.

Direct tensile mechanical properties and acoustice mission characteristics of coal at different depths of Pingdingshan mining area

Uncertainties in the basic theory of shallow mining that continues to be used in deep mining result in frequent engineering disasters with deep characteristics. Thus, it is necessary to elucidate the mechanism of mechanical deformation and failure behavior of coal from shallow to deep depths. Coal samples from the same coal seam in the Pingdingshan mining area of Henan Province were obtained at depths of 300 m, 600 m, 700 m, 850 m, and 1050 m. Direct tensile tests were conducted on the coal samples obtained at different depths. The tensile strength exhibits as low decreasing trend with increasing depth, reaching a minimum at 1050 m. This variation trend is consistent with that of acoustic emission cumulative ring-down counts and the cumulative energy measured during tensile tests on coal samples obtained at different depths. These conclusions provide a reference for the differences between the mechanical behavior of shallow and deep coal, which has both theoretical and engineering significance.

Research progress of autonomous planetary landing site assessment and selection

<p indent=0mm>To address potential safety threats posed by various terrain conditions on the planetary surface, the recent development of autonomous planetary landing site assessment and selection methods is systematically reviewed in this paper. First, the mission characteristics and main technical challenges in landing site selection are summarized. Critical factors to be considered in landing site selection are introduced together with the selection process and applications of the Safety Index method. Then, an overview of the research progress of autonomous landing site assessment and selection methods is provided. Past missions and theoretical developments are analyzed from the aspects of hazard detection, terrain safety assessment, and comprehensive landing site selection. Lastly, based on the growing requirements of mission intelligence in future planetary exploration, several suggestions and recommendations with regard to landing site selection technology development trends are proposed.

Science merit function for the Kepler mission

The Kepler mission was a National Aeronautics and Space Agency (NASA) Discovery-class mission designed to continuously monitor the brightness of at least 100,000 stars to determine the frequency of Earth-size and larger planets orbiting other stars. Once the Kepler proposal was chosen for a flight opportunity, it was necessary to optimize the design to accomplish the ambitious goals specified in the proposal and still stay within the available resources. To maximize the science return from the mission, a merit function (MF) was constructed that relates the science value (as determined by the PI and the Science Team) to the chosen mission characteristics and to models of the planetary and stellar systems. This MF served several purposes; predicting possible science results of the proposed mission, evaluating the effects of varying the values of the mission parameters to increase the science return or to reduce the mission costs, and supporting quantitative risk assessments. The MF was also valuable for the purposes of advocating the mission by illustrating its expected capability. During later stages of implementation, it was used to keep management informed of the changing mission capability and support rapid design tradeoffs when mission down-sizing was necessary. The MF consisted of models of the stellar environment, assumed exoplanet characteristics and distributions, detection sensitivity to key design parameters, and equations that related the science value to the predicted number and distributions of detected exoplanet. A description of the MF model and representative results are presented. Examples of sensitivity analyses that supported design decisions and risk assessments are provided to illustrate the potential broader utility of this approach to other complex science-driven space missions.

Disparities between Rural and Urban Areas of the Central Region of Saudi Arabia in the Utilization and Time-Centeredness of Emergency Medical Services.

The purpose of this study was to explore differences in characteristics of missions dispatched by Emergency Medical Services (EMS) between rural and urban areas of Riyadh province in Saudi Arabia (SA). It also aimed at identifying weaknesses related to utilization and Response Time (RT). The study retrospectively evaluated 146,639 completed missions in 2018 by measuring the utilization rate in rural and urban areas. The study shows there are six times more ambulance crews available for rural areas compared to urban. There were 22.1 missions per 1000 urban inhabitants and 11.2 missions per 1000 in rural areas. The median RT for high urgent trauma cases was 20.2 min in rural compared to 15.2 min in urban areas (p < 0.001). In urban areas, the median RT for high urgent medical cases was 16.1 min, while it was 15.2 min for high urgent trauma cases. Around 62.3% of emergency cases in urban and 56.5% in rural areas were responded to within 20.00 min. Women utilized EMS less frequently. The RT was increased in urban areas compared to previous studies. The RT in the central region of SA has been identified as equal, or less than 20.00 min in 62.4% of all emergency cases. To further improve adherence to the 20′ target, reorganizing the lowest urgent cases in the rural areas seems necessary.

A multi-objective optimization framework of constellation design for emergency observation

To meet the urgent needs of emergency observation missions, a well-designed constellation is key to ensuring system performance. This paper presents a multi-objective optimization framework which is well suited for constellation designers to identify key trade-offs and make decisions. Firstly, this work investigates the metrics of responsiveness and coverage simultaneously to approximate to the actual conditions of emergencies, and a multi-objective mathematical model is constructed to explore solutions to enhance the overall system performance. Then, according to the characteristics of emergency missions, a hierarchical chromosome encoding method is proposed in the framework to encode a solution that explores different sized constellations without constraining its specific geometry. Finally, we propose the use of radial axes plots to help constellation designers to gain pragmatic insights for informed decision making. The simulation of disaster management verifies that the proposed chromosome encoding method effectively promotes the convergence of the algorithm, and the multi-objective optimization framework helps to generate a rapid and adequate observation satellite constellation to provide maximum coverage performance while ensuring timeliness.

The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager

Context.The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the “connection science” between solar activity and the heliosphere.Aims.With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.Methods.The EUI consists of three telescopes, the Full Sun Imager and two High Resolution Imagers, which are optimised to image in Lyman-αand EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. The EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, onboard image processing, and event selection. The imposed power limitations and potentially harsh radiation environment necessitate the use of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft’s heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimise the throughput of every optical element and the reduction of noise levels in the sensor.Results.In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the onboard software, the intended operations, the ground software, and the foreseen data products.Conclusions.The EUI will bring unique science opportunities thanks to its specific design, its viewpoint, and to the planned synergies with the other Solar Orbiter instruments. In particular, we highlight science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high-resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs.

The meaning of service questionnaire and its association with psychological growth among Veterans

ABSTRACT Few studies have investigated what soldiers find meaningful after being exposed to highly stressful events and what positive effects they might have in the aftermath. This study reports the psychometric properties of a newly developed questionnaire, Meaning of Service (MoS), and its application to the study of how strongly meaning-making processes are associated with psychological growth. One hundred eighty-four Norwegian Air Force Veterans who have participated in various missions abroad in different branches of the military completed the MoS questionnaire along with other scales reflecting psychological growth, hardiness, resilience, stress, and exposure, as well as personal and mission characteristics. The principal component analysis mainly identified three major meaning themes as expected from previous qualitative research (Confirmation of ability, Cohesion of peers, and Significance of effort). The hierarchical regression analysis showed that all three meaning themes and two coping strategies were associated with psychological growth, and that Confirmation of ability (coping and recognition of coping) seems particularly important to enhance Veterans’ prospects of psychological growth. Future research directions are proposed including suggestions for minor modifications of the questionnaire.

Using a Panchromatic Image to Improve Hyperspectral Unmixing

Hyperspectral unmixing is a widely studied field of research aiming at estimating the pure material signatures and their abundance fractions from hyperspectral images. Most spectral unmixing methods are based on prior knowledge and assumptions that induce limitations, such as the existence of at least one pure pixel for each material. This work presents a new approach aiming to overcome some of these limitations by introducing a co-registered panchromatic image in the unmixing process. Our method, called Heterogeneity-Based Endmember Extraction coupled with Local Constrained Non-negative Matrix Factorization (HBEE-LCNMF), has several steps: a first set of endmembers is estimated based on a heterogeneity criterion applied on the panchromatic image followed by a spectral clustering. Then, in order to complete this first endmember set, a local approach using a constrained non-negative matrix factorization strategy, is proposed. The performance of our method, in regards of several criteria, is compared to those of state-of-the-art methods obtained on synthetic and satellite data describing urban and periurban scenes, and considering the French HYPXIM/HYPEX2 mission characteristics. The synthetic images are built with real spectral reflectances and do not contain a pure pixel for each endmember. The satellite images are simulated from airborne acquisition with the spatial and spectral features of the mission. Our method demonstrates the benefit of a panchromatic image to reduce some well-known limitations in unmixing hyperspectral data. On synthetic data, our method reduces the spectral angle between the endmembers and the real material spectra by 46% compared to the Vertex Component Analysis (VCA) and N-finder (N-FINDR) methods. On real data, HBEE-LCNMF and other methods yield equivalent performance, but, the proposed method shows more robustness over the data sets compared to the tested state-of-the-art methods. Moreover, HBEE-LCNMF does not require one to know the number of endmembers.

Analysis of Vision and Mission Statements Characteristics and their Association with Organizational Performance: A Guide to Writing Effective Vision and Mission Statements

This paper empirically examines vision and mission statements of Fortune 500 firms for the purpose of identifying and examining specific characteristics and associating these attributes with organizational performance. Additionally, this paper provides a theoretical foundation for the inclusion of various characteristics of vision and mission documents, and thus provides guidance for organizations to develop and revise these important strategic planning documents.&#x0D; JEL CODE: M21, O21

Enhanced tailored durability test specification for multiaxial dynamically excited structures attached to a single input base under off-road loading environment

Tailored bench tests are vibration experiments specifically developed for a product to reproduce the severity of a customized application, generally within an accelerated timeframe.When structures are dynamically excited, the response is extremely sensitive to input(s). The tailored test parameters, (a) input degree of freedom, (b) magnitude, (c) frequency content and (d) exposure time, must be determined not only based on mission characteristics but also considering the component’s modal properties. Since inevitable deviations occur between the operational and test environments, a consistent tailoring method is essential to avoid uncorrelated failure modes and worthless tests. Herein, computational tools (FEA) were combined with traditional signal processing to enhance durability assessment and test specification. The studied case is a durability failure of a pneumatic brake chamber support, a typical unsprung structure attached to a vehicle’s axle. The crack occurred during an off-road application, a worldwide ordinary chaotic mission.The tailored input is given by PSD(s) for each DoF. They are inherently ergodic and stationary signals. Therefore, reproducing the off-road wide variable multiaxial events, whether deterministic or random, is challenging to start with. There are, however, other questionable assumptions during PSD computation according to the mission’s fatigue damage spectrum (FDS). The first is the election among SDoF responses, displacement or velocity, as the stress-proportional parameter. The second is the flat frequency, a white noise base-driven acceleration. Such a condition is only rarely empirically satisfied. Last, multiaxial loaded components are not properly addressed, since FDSs are calculated individually for each input DoF despite their simultaneous imposition on operational application.Two tailoring test approaches were compared in terms of life contour correlation, durability prediction, failure mode reproduction and acceleration factor. While the first assumes simultaneous application of each input DoF (x, y and z) and equalizes the overall damage level, the second adjusts the exposure time (and damage level) specifically for each input DoF, composing a successive test to match the mission total damage. Counterintuitively, the latter resulted in a superior correlated result.

Analysis of Vision and Mission Statements Characteristics and their Association with Organizational Performance: A Guide to Writing Effective Vision and Mission Statements

This paper empirically examines vision and mission statements of Fortune 500 firms for the purpose of identifying and examining specific characteristics and associating these attributes with organizational performance. Additionally, this paper provides a theoretical foundation for the inclusion of various characteristics of vision and mission documents, and thus provides guidance for organizations to develop and revise these important strategic planning documents. JEL CODE: M21, O21

Mission Capability Estimation of Multicopter UAV for Low-Altitude Remote Sensing

Restricted mission capability becomes one of the most important challenges facing multicopter UAVs with the increasing complexity of the low-altitude remote sensing mission. Mission capability estimation is the major precondition and the foundation of the mission planning, decomposition, and execution. It’s constrained by platform performance, payload characteristics, mission requirements, and environmental conditions. Flight energy consumption has become the main capability metric criterion of multicopter UAVs in coverage path planning based remote sensing missions. Modeling on flight energy consumption has been the principal subject of many pieces of research. However, current models have not established a connection between inflight performance and remote sensing mission characteristics. Therefore, a mechanistic model is proposed in this study to estimate a multicopter UAV’s mission capability during the mission planning procedure. This model is based on the combination of multicopter flight mechanics and remote sensing mission-oriented coverage path planning theories. The field wind condition is taken into consideration as well. The applicability and performance of the model were evaluated by combining simulation and 60 field mission sorties. The model estimated results are in accordance with the true values. The mean error in the total energy consumption is 5% of the battery used in the experiment. This model will ultimately provide a theoretical basis for mission decision making, help to reduce the low-battery risk and guarantee the safety and efficiency of mission operations prior.

Mission planning of multi base UAV Based on improved artificial bee colony algorithm

Aiming at the constraint that the take-off and landing position of Unmanned Aerial Vehicle (UAV) varies from time in maritime operations, a cooperative attack model of multi-base UAV is established. An improved artificial bee colony algorithm based on coding operation pool is proposed, which retains the basic idea of standard artificial bee colony algorithm, It draws lessons from RNA coding operation and introduces coding operation pool to ensure that the algorithm has better global search ability. The simulation results show that the cooperative attack model of multi-base and multi-UAV complies with the characteristics of modern maritime unmanned combat missions, and the proposed algorithm has strong optimization efficiency and optimization ability.

Dynamics and control for in-space assembly robots with large translational and rotational maneuvers

There are two major characteristics of in-space structure assembly missions. First, in order to improve the transport efficiency of assembly robot and reduce the number of structural modules, the size of each structural module is usually designed as large as possible. Second, it is necessary for autonomous assembly robot to quickly transport such large-sized flexible structural modules to the desired locations for integration. However, the coupling effect between the deformation of structural module and large-scale maneuver of robot is inevitably involved during transportation. In this paper, a dynamics modeling method for in-space assembly (ISA) robot with large translational and rotational maneuvers was proposed. The descriptions of dual quaternions were expanded, and a general expression for the dynamics model of rigid-flex system was derived to describe motion of the assembly robot. Innovation of this method is that it considered the complex coupling effect among deformation of structural modules, translational and rotational maneuvers of the assembly robot during transportation in ISA missions. On this basis, the proportional-derivative (PD) controllers were adopted as the in-space structural module assembly method. Finally, taking the ISA of antenna as an example, successful application of the proposed dynamics model and controller to the assembly mission was verified.

A Procedure for the Derivation of a Schedule-Based Energy-Equivalent Driving Cycle for Urban Buses

The present paper takes the lead from the long-lasting experience gained by the author on mathematical modeling of vehicle energy performances and on the calibration of those models based on real data acquired on buses in real operation. In particular, the paper focuses on a possible way to define a schedule-based energy-equivalent driving cycle which may have a number of applications (e.g., for buses’ performance prediction, propulsion systems choice and net optimization). Specific attention was given to energy-equivalency of the proposed driving cycles to the foreseeable real mission of the vehicles on their scheduled duty (e.g., mean inertial energy on play during vehicle Start and Stops, mean stops in between the arcs, mean vehicle speed and acceleration, etc.): The objective was in fact that of reproducing the same energy characteristics of the real vehicle mission in a simplified way. To this aim, the main energy characteristics of the expected mission were foreseen through a regressive interpolation of data coming from an extensive analysis of onboard measured data, based on independent variables (mean vehicle cruise speed and slope), which could be efficiently estimated by vehicle schedule. There could be a number of possible uses of the so-defined driving cycles (e.g., for buses’ performance prediction, propulsion systems choice and net optimization): All these applications will benefit from the precision of the cycles in predicting energy characteristics of the real vehicle use and will therefore be much more reliable than in usual practice (which normally makes reference to standardized bus cycles with very limited connection to expected vehicle use).

Між суспільством і владою: радянська школа в УРСР [Рец. на кн.: Лаврут О. «Радянська школа у другій половині ХХ ст.: вимір України». Слов’янськ: Друкарський двір, 2020

The aim of the article is to analyze the monograph of Olga Alexandrovna Lavrut, which is devoted to the characteristics of the school's mission in the Ukrainian SSR in the late 1940s–1980s. The paper clarifies the socio-economic conditions of institutions in the USSR; organization of the educational process, content of education; the personnel structure of teachers, dynamics and ways of its formation are analyzed. The author described the working conditions of teachers, specific features of everyday life of teachers; correlated the declarative and the real in the process of realization of the educational and social mission of the teacher. The place of school in the life of teachers, students and their parents is determined in the work; the specifics of school in Ukraine in comparison with the rest of the USSR in the second half of the XX century are investigated.

Modeling and verification of contingency resolution strategies for multi-robot missions using temporal logic

This article presents an approach for assessing contingency resolution strategies using temporal logic. We present a framework for nominal mission modeling, then specifying contingency resolution strategies and evaluating their effectiveness for the mission. Our approach focuses on leveraging the use of model checkers to the domain of multi-robot missions to assess the adequacy of contingency resolution strategies that minimize the adverse effects of contingencies on the mission execution. We consider missions with deterministic as well as probabilistic transitions. We demonstrate our approach using two case studies. We consider the escorting of a ship in a port where multiple contingencies may occur concurrently and assess the adequacy of the proposed contingency resolution strategies. We also consider a manufacturing scenario where multiple assembly stations collaborate to create a product. In this case, assembly operations may fail, and human intervention is needed to complete the assembly process. We investigate several different strategies and assess their effectiveness based on mission characteristics.

Three-Dimensional Displacement Fields from InSAR through Tikhonov Regularization and Least-Squares Variance Component Estimation

Synthetic aperture radar interferometry (InSAR) measures the projection of three-dimensional (3D) ground displacement in the range direction and in the azimuth direction through image processing. The incapability of InSAR in measuring the 3D displacements restricts its capability for assessing real Earth surface deformation. The near-polar orbiting characteristics of InSAR missions reduce the sensitivity of line-of-sight (LOS) displacements significantly to the north-south components of the real 3D displacement fields and weaken the geometric strength of a given configuration. Applying range measurements from various missions to address 3D displacement leads to an ill-posed inverse problem that needs to be regularized. Moreover, it needs appropriate weighting of the observations to give proper estimates of the parameters. In this study, we propose Tikhonov regularization (TR) and least-squares variance component estimation (LS-VCE) methods for retrieving 3D displacement vectors from range and azimuth displacements. Depending on the functional degree of freedom (DoF) of the inverse problem, the TR and LS-VCE methods are applied in determined and overdetermined equation systems, respectively, to stabilize the ill-conditioned models and estimate the variance components of observations. These methods were evaluated by two synthetic data sets and a real data set from the Sentinel-1 terrain observation by progressive scan (TOPS) and ALOS-2 phased array type L-band synthetic aperture radar (PALSAR-2) missions in 2015 of the MW = 8.3 Illapel earthquake in Chile. Results indicate more than 40% improvement in both the precision and accuracy of retrieving 3D deformation fields when the regularized LS-VCE (RLS-VCE) is adopted instead of the conventional method (CM) that considers primary weighting for observations. Applying the range and azimuth InSAR displacements together with adopting the LS-VCE method reveal a north-south convergent borderline near 31.2° S in the 2015 Illapel earthquake.