Typical Mission Research Articles

Media functions: evolution and interpretation of concepts

The article is devoted to a comparative analysis of the approaches of various humanities and social sciences to the definition and interpretation of the concepts of "journalism functions", "media functions", "media discourse functions", as well as consideration of the factors of their transformation in different historical periods. An activity-based approach is used in order to correlate the concepts of the type of activity, type of creativity, purpose, mission, and functions of modern mass media. In this paper, we propose to identify the following key approaches in the analysis of modern media that do not have spatial boundaries (philosophical, cultural, political, psychological, sociological and philological), allowing a multifaceted approach to the characterization of media as an integral object, complex in its structure and functionality, to expand understanding of the role of the media in a multipolar world and the values split. In this study, in addition to the comparison method, structural-functional, sociological, cultural and philological approaches were used. The scientific novelty of the article is the identification of the expanded functions of the media in modern society, where traditional roles are complemented by cognitive, adaptive and semantic aspects. The research focuses on the changing importance of the media in the context of digital transformation, globalization and information wars, emphasizing their role in the formation of meanings, social values and management of social processes. The media, in turn, perform many functions, including informational, ideological, cultural, communicative and cognitive. Their role varies depending on socio-historical conditions, having both positive and negative effects on society. In the context of modern challenges, it is of particular importance not only to combat "fakes" and disinformation, but also to form new social values.

Autonomous numerical predictor-corrector guidance for human Mars landing missions

The numerical predictor-corrector guidance method with a linear bank angle parameterization has been widely applied to various atmospheric entry guidance problems. However, it has been found that the linear bank angle approach has limitations in satisfying the final state requirement of a specific type of atmospheric entry mission. In response, this paper proposes a novel bank angle parameterization based on a logistic function, which improves the energy preservation capability and increases the potential final altitude at the end of the entry phase. The paper also suggests a guideline to determine a guidance law activation point for better entry performance. Numerical simulations demonstrate that the proposed guidance scheme outperforms the linear bank profile approach and is suitable for future human Mars landing missions.

Deterministic Trajectory Design and Attitude Maneuvers of Gradient-Index Solar Sail in Interplanetary Transfers

A refractive sail is a special type of solar sail concept, whose membrane exposed to the Sun’s rays is covered with an advanced engineered film made of micro-prisms. Unlike the well-known reflective solar sail, an ideally flat refractive sail is able to generate a nonzero thrust component along the sail’s nominal plane even when the Sun’s rays strike that plane perpendicularly, that is, when the solar sail attitude is Sun-facing. This particular property of the refractive sail allows heliocentric orbital transfers between orbits with different values of the semilatus rectum while maintaining a Sun-facing attitude throughout the duration of the flight. In this case, the sail control is achieved by rotating the structure around the Sun–spacecraft line, thus reducing the size of the control vector to a single (scalar) parameter. A gradient-index solar sail (GIS) is a special type of refractive sail, in which the membrane film design is optimized though a transformation optics-based method. In this case, the membrane film is designed to achieve a desired refractive index distribution with the aid of a waveguide array to increase the sail efficiency. This paper analyzes the optimal transfer performance of a GIS with a Sun-facing attitude (SFGIS) in a series of typical heliocentric mission scenarios. In addition, this paper studies the attitude control of the Sun-facing GIS using a simplified mathematical model, in order to investigate the effective ability of the solar sail to follow the (optimal) variation law of the rotation angle around the radial direction.

Techno-economic analysis of diesel, natural gas, electric and hydrogen buses

Abstract Many regions and cities are implementing Electric (BEB – Battery Electric Bus) and hydrogen (FCB – Fuel Cell Bus) buses instead of the diesel (Diesel) and natural gas (CNG – Compressed Natural Gas) traditional ones. Many papers and reports compare the different Total Cost of Ownership of these buses but not always clarify mission, powertrain and context data. This study, starting from literature analysis, referring to a specific typical urban bus mission (17 km/h average speed per 12 h daily service), quotes techno-economic-environmental buses (purchase, maintenance, energy consumption and CO2 emissions costs), powertrains (combustion engine, battery, fuel cells, hydrogen storage) and context (diesel, CNG, electricity, hydrogen costs) data. Furthermore, a comparative analysis is carried out considering different operational scenarios based on high or low consumptions, high or low electricity costs, three hydrogen production ways and current (current, batteries and hydrogen technologies costs) and future (15% increase of diesel and CNG costs and decrease of batteries and hydrogen technologies costs) so evaluating 24 scenarios. The results shows that TCO is mainly constituted by every year costs (i.e. maintenance plus emissions and energy consumption,) respect to the one-time cost (so divided by the lifetime, i.e. purchase costs) except in the more competitive hydrogen scenarios where these 3 costs correspond equally to a 30% of the overall TCO. Thus, the bus choice, have to be made on the specific technologies and energies context costs instead on the international buses purchase cost. In fact, it is not possible to define a best technology for any scenario, especially for the future scenarios (so with a variation of diesel, CNG, battery, fuel cells, electricity and hydrogen costs). The best technology will depend on the specific context, and so specific analysis have to be made before to choose the technology to be applied. Indeed, CNG in the current scenarios is always the best technology followed by diesel, but CNG and diesel have emission costs and fossil fuel cost are expected to increase. BEB in the current and future scenarios are never the best technologies but it can be the best technology in scenarios with lower autonomy. FCB in the future scenarios are the best technology for 10 of the 12 scenarios analysed, that it is possible to say that FCB, taking into account the great possibilities of hydrogen production and the flexibility in power and energy respect the electric, even with the lower powertrain efficiencies respect to electric, is a technology that can be applied in many different contexts.

Professionalism and Self-Evaluation: Diverging Perspectives Among Physicians and Nurses.

Professionalism among healthcare professionals is often defined in terms such as altruism, humanism, and excellence. The integration of such professionalism ideals to healthcare professionals' practice poses a challenge to medical tutors. We examined the assessment of professionalism among physicians and nurses by their peers and evaluated the significance of each professional role component within each sector. We also performed a cross-sector assessment whereby physicians assessed nurses' professionalism and vice versa. A survey among physicians, interns, and nurses. The participants were asked to rate the extent that each of the 12 characteristics contributes to physicians' and nurses' professionalism of on a scale of 1 (does not contribute at all) to 10 (highly contributes). Each participant rated the contribution of each component to the professionalism of their own occupation (direct scoring) and to the professionalism of the other occupation (cross scoring). In total, 300healthcare professionals (mean age 36.6, 46% males) responded to the survey. The most highly contributing characteristics to physicians' professionalism were knowledge, responsibility, decision-making and leadership, clustered as "strategic judgment". The most highly contributing characteristics to nurses' professionalism were responsibility, personal attention, empathy, and skills, clustered as "bedside approach" and "performance abilities". Cross-assessment among professionals was different: Nurses assigned higher ratings in general, interns assigned higher ratings to physicians' characteristics, whereas physicians assigned lower ratings to professionalism characteristics, and especially to those of nurses. Nurses emphasized patient centeredness and communication skills more than physicians. Nurses and interns appreciated teamwork compared to physicians. Major differences in how physicians and nurses perceive professionalism revealed physicians' emphasis on "strategic judgment" while nurses emphasis on "bedside approach". Physicians and nurses hold differing viewpoints on many topics, including the objectives of their mission, expected performance, and activity types. Medical professionals can assess their colleagues and partners, recognizing both strengths and weaknesses in themselves and others.

Radiation exposure of astronauts following an intense solar particle event: analysis and comparison of doses in male and female voxel phantoms.

According to NASA's plans, a human travel to the Moon is planned by the end of 2025 with the Artemis II mission, and humans should land on the Moon again in 2026. Exposure to space radiation is one of the main risks for the crew members; while for these short missions the doses from galactic cosmic rays would be relatively low, the possible occurrence of an intense solar particle event (SPE) represents a major concern, especially considering that in 2025 the Sun activity will be at its peak. Quantifying the amount and the effects of such exposure is therefore crucial, to identify shielding conditions that allow respecting the dose limits established by the various space agencies. By exploiting an interface between the BIANCA biophysical model and the FLUKA Monte Carlo radiation transport code, in this work we implemented a male and a female voxel phantom and we calculated absorbed doses and Gy-Eq doses in the various tissues/organs, as well as effective doses, following exposure to the August 1972 SPE, the most intense event of the modern era. The calculations were performed respect the organ dose limits for 30 d missions. A detailed comparison between male and female doses was then carried out, also considering that the Artemis II crew will include a woman. The results showed that female doses tend to be higher than male doses, especially with light shielding. This should be taken into account in mission design, also considering that, in a typical lunar mission, up to 15% of time may be spent in extra-vehicular activities, and thus with light shielding. More generally, this work outlines the importance of performing separate calculations for male and female astronauts when dealing with radiation doses and effects.

Identification and analysis of interior and exterior resonant orbits in the Sun–Venus system

With Venus being Earth’s nearest neighbor and it being similar in size to Earth, it is the ideal candidate for certain mission types. These missions range from scientific, such as helio-physics and space weather monitoring, to defense focused, such as monitoring Earth’s orbital path for meteoroid threats. Limited research has been done on the periodic orbits in the Sun–Venus system. The first step to understanding which orbits could be useful for such a mission is to identify families of resonant periodic orbits in the Sun–Venus system and conduct a stability analysis on these orbits. This research work identifies 90 periodic, resonant orbits in the Sun–Venus system and their associated families of orbits. The orbits are found within the Circular Restricted 3 Body Problem (CR3BP) dynamical model with solar radiation pressure included as a perturbation. The periodic orbits are found using Poincaré maps, and the families are generated using a continuation method that steps through different Jacobi constants. The stability for each orbit in the family is calculated and the structure of the eigenvalues for each is assessed to determine when the family has crossed a bifurcation point. This research work seeks to generate a catalog of resonant orbits within the Sun–Venus system while providing stability and bifurcation information for each resonant orbit family.

A timeliness analysis of emergency services and cardiovascular outcomes in cardiac patients referred through prehospital emergency services between 2020 and 2023: a cross-sectional study in Iran

ObjectiveEffective time management is crucial for the survival of all patients, particularly those with cardiovascular conditions. This is especially true in the context of pre-hospital emergency services, where prompt intervention can significantly impact outcomes. This study delves into the timeliness of emergency services and the subsequent outcomes for hospitalized cardiovascular patients in EMS center in Fasa University of Medical Sciences, southern Iran.ResultsA total of 4972 emergency calls related to cardiac diagnoses were received between 2020 and 2023. The transport time was significantly correlated with age, location of the mission, and type of mission. Of the total, 86 underwent angioplasty within the standard time of less than 90 min, of which 81 were discharged and 5 died. 51 patients underwent angioplasty after more than 90 min, of which 47 were discharged and 4 died. In addition, 124 of these patients experienced cardiopulmonary resuscitation, of which 63 were successful and 61 were unsuccessful.

Resilience-oriented adaptive predictive maintenance optimization for continuous process manufacturing systems considering mission profile variation

Continuous process manufacturing systems (CPMSs) are typical phased mission systems that require high standards of operational stability, reliability, and safety. With the variation of production mission profiles, CPMSs are required to run in diverse modes or conditions in different phases; therefore, to meet these standards, maintenance decisions applied to CPMSs should be adapted to such variations. Considering that the concept of “resilience” provides a systematic solution to evaluate system adaptability via “disruption absorption” and “recoverability,” this paper proposes a CPMS resilience evaluation model and utilizes it as guidance for the optimization of CPMS predictive maintenance (PdM). The proposed method consists of the following steps: (1) applying a customized Seasonal Trend Decomposition model to predict the future trend of production mission profile variations, (2) assessing the production mission accomplishment capability of CPMS based on a Gamma process model of equipment performance degradation, (3) using disruption response ratio to evaluate CPMS resilience based on mission accomplishment capability, and (4) proposing a Simulated Annealing Q-Learning algorithm for adaptive PdM optimization, which keeps resilience above a threshold level while minimizing maintenance costs. The applicability and effectiveness of the proposed method are validated by an industrial case study of a nuclear fuel rod shielding component CPMS.

Integrated Power and Thermal Management System for a Hybrid-Electric Aircraft: Integrated Modelling and Passive Cooling Analysis

Abstract Aircraft electrification introduces challenges in power and thermal management. In a hybrid-electric aircraft (HEA), the additional heat loads generated by the high-power electrical components in the propulsion system can negate the benefits of the HEA. Consequently, an integrated energy management system is required for the HEA to reject the additional heat loads while minimizing energy consumption. This paper presents the integrated modelling method for an integrated power and thermal management system (IPTMS) for HEA. With this method, a platform can be developed to assess the varying efficiencies of the components in the electrical propulsion system (EPS), and the performance of the thermal management system (TMS), such as passive cooling, during a flight mission. This makes it applicable to modular designs and optimizations of the IPTMS. A small/medium range (SMR) aircraft similar to ATR72 is studied. In this study, the EPS operates only during take-off and climb. Therefore, the platform assesses the heat and power loads of the IPTMS for a typical flight mission (take-off and climb) in this study. The performance of passive cooling is also analysed across this typical flight mission and under normal, hot-day, and cold-day conditions. It was found that passive cooling is sufficient under these three conditions, and the active temperature control is requried to ensure the components' temperatures are above the minimum temperatures. These findings imply the potential to minimize TMS weight and energy consumption, providing an insight for further research on IPTMS.

Toward a mission-oriented framework for funding public research institutions: a multi-case study approach

Abstract This study proposes a mission-oriented framework for funding public research institutions (PRIs). Using a multi-case study approach and focus group interviews, a comprehensive framework was developed and refined. The framework encompasses three main dimensions: funding mechanisms, the amount of government funding, and organizational arrangements for resource allocation. It introduces diversified funding mechanisms for PRIs, including block grants, performance-based contracts, competitive funding, targeted allocations for specific missions, and excellence budgets. The proportion of each mechanism in the funding portfolio can vary depending on the mission types of PRIs. The framework recommends estimating government funding amounts using per capita formulas based on relevant input/output indicators tailored to the mission types of PRIs. Clear organizational arrangements are essential, including establishing a national research agency to oversee the estimation, steering, and monitoring of financial resource allocation and utilization.

Cooperative Mission Planning Using Rollout Policy Optimization

This paper proposes a novel cooperative mission planning for uncrewed aerial systems (UAS), using roll-out policy optimization and a blend of straight and double-Archimedean-spiral (DAS) paths. Typical mission tasks using UAS, possibly multiple, include visiting distinct locations/waypoints and covering specific areas of interest (AOIs). For the UAS, to guarantee the coverage of the AOI, the algorithm generates a DAS path that even accounts for the sensor’s field-of-view constraints. A scalar spiral density parameter in the algorithm effectively provides customized adjustments to the length of the DAS over an AOI while developing mission plans. A lower and upper bound value for the spiral density parameter and the dependency of the parameter on the coverage of an AOI are derived. This scalar parameter gives the users potential flexibility in the design of mission plans. Roll-out policy optimization minimizes the overall path length for the cooperative UAS mission and, as a direct consequence, minimizes time and fuel. This method leads to finding a near-optimal path in that the computation time does not grow exponentially with the number of UAS. Results from the simulation studies with several cooperative mission scenarios, including multiple UASs visiting several waypoints and AOIs starting from identical and distinct initial locations, demonstrate the efficacy of the proposed concept. The results from a data-based complex test case using the LiDAR data set further demonstrate the adaptability of the proposed mission planning approach in a real-world setting.

Development and Support of Ukrainian Domestic Entrepreneurship in the Knowledge Economy

This paper explores the elements of support and development of entrepreneurship in Ukraine. It suggests that digitalization is an important organizational component in the development of the business sector in the knowledge economy. The authors present a comprehensive study of the most advanced domestic business ecosystems (Diia, UNIT.CITY, Genesis) and highlight their key characteristics, i.e., type of ownership, structure, mission and vision, services for entrepreneurs, investment fund availability, and areas and types of investment. The paper concludes that support for entrepreneurship in Ukraine is based on the principles of efficiency, accessibility, social security, openness, and transparency. Entrepreneurship support is considered as a set of measures of the state-funded and private institutions and organizations aimed at ensuring the sustainable functioning of small and medium-sized business entities and stimulating their development by creating the following favorable conditions: building a competitive environment and increasing competitiveness; fostering investment and innovation efforts; promoting manufactured goods (works, services) or knowledge-based products in domestic and foreign markets; ensuring employment by supporting the citizens’ entrepreneurial initiatives. Areas of public and private support of domestic entrepreneurship include provision of information, consultancy, and special services. Moreover, the paper pays special attention to the forms and methods of supporting businesses and entrepreneurship under martial law in Ukraine in 2022.

MissionML: A Mission Architecture Modeling Language based on Unified Architecture Framework

AbstractThe missions of complex systems, organizations, or groups can be identified through careful requirements and domain analysis. Mission architecture modeling is a crucial step for enterprise modeling and design. However, mission modeling is lacking from the Unified Architecture Framework (UAF), which system engineers must specify and model from sketch. This paper proposes a Mission Architecture Modeling Language (MissionML). This two‐layer architecture language generalizes the general common and special knowledge from four typical missions as a core layer and mission layer. The elements of the core layer are obtained through slight extensions of the operational layer elements in UAFML, and the elements of the mission layer are derived from the elements in the core layer. Moreover, MissionML is implemented as a UAF profile, incorporating numerous domain concepts in its syntax and semantics for mission modeling. Finally, we use five public case studies to demonstrate learnability and extensibility from the viewpoint of system engineers.

A study on dual quaternion based cooperative relative navigation of multiple UAVs with monocular vision-inertial integration

This paper addresses a cooperative relative navigation problem for multiple aerial agents, relying on visual tracking information between vehicles. The research aims to investigate a sensor fusion architecture and algorithm that leverages partially available absolute navigation knowledge while exploiting collaborative visual interaction between vehicles in mission flight areas, where satellite navigation-denied regions are irregularly located. To achieve this, the paper introduces a new approach to defining the relative poses of cameras and develops a corresponding process to secure the relative pose information. This contrasts with previous research, which simply linearized the relative pose information of aircraft cameras into navigation states defined in an absolute coordinate system. Specifically, the target pose in relative navigation is defined, and the pose of the camera and feature points are directly derived using dual quaternion representation, which compactly represents both translation and rotation. Furthermore, a mathematical model for the relative pose of the camera is derived through the dual quaternion framework, enabling an explicit pose formulation of relative navigation. The study investigates navigation performance in typical mission flight scenarios using an in-house high-fidelity simulator and quantitatively highlights the contributions of the proposed scheme by comparing the navigation error performance. Consequently, the proposed method demonstrates to have navigation accuracy in decimeter level even in GNSS-denied environments and an improved 3D Root Mean Square (RMS) error by 30% smaller than the conventional absolute navigation framework.

Interstellar exploration: From science fiction to actual technology

The technology for even the most advanced missions in the solar system doesn't need advances in basic science. Traveling through the solar system can be described through what is called ‵hard science fiction’, i.e. science fiction strictly based on scientific knowledge. Interstellar exploration is a completely different matter. Robotic flyby missions to the nearest stars using nanoprobes can be performed using technologies based on known science, while anything beyond this requires advances which we don't know how to implement, or even we are not sure whether they are possible at all. The point applies not only to the technological aspects but even the scientific bases on which the relevant technologies may rest. The missions requiring less scientific-technological advances, are slow missions, like space arks (generation ships) or missions based on hibernation with travel times up to hundred years. To implement both, the uncertainties are more related to the advances in space medicine and biology than in propulsion and physics. The fastest travels allowed by the current interpretations of the relativity theory are relativistic missions in which the time contraction at speeds closing the speed of light is exploited to decrease the travel time for the astronauts, although the travel time seen by those who remain on Earth is close, in years, to the distance traveled expressed in light years. However, the energy required for this type of missions is large and grows drastically with the increase of time contraction.Faster than light travel, which seems to be possible following some interpretations of relativity involving either wormholes or some sort of warp drive, requires substantial advances in fundamental physics. A symptom of this is that the novels dealing with interstellar travels belong more to the space opera – which doesn't follow strict scientific credibility – than to the hard science fiction subgenre. No novel of this kind explains details about how the relevant machinery works, and even less scientifically realistic are the movies, TV series, and videogames of this kind. Moreover, to achieve a travel time allowing to reach distant star systems in reasonable times using warp drives, the authors of Star Trek had to resort to the Warp Factor which is essentially a nonlinear scale. This makes the requirements for FTL travel even more difficult to achieve.

Conceptual Design of an Unmanned Electrical Amphibious Vehicle for Ocean and Land Surveillance

Unmanned vehicles (UVs) have become increasingly important in various scenarios of civil and military operations. The present work aims at the conceptual design of a modular Amphibious Unmanned Ground Vehicle (A-UGV) that can be easily adapted for different types of land and/or water missions with low monetary cost (EUR < 5 k, without sensors). Basing the design on the needs highlighted in the 2021 review of the Strategic Directive of the Portuguese Navy, the necessary specifications and requirements are established for two mission scenarios. Then, a market research analysis focused on vehicles currently available and their technological advances is conducted to identify existing UV solutions and respective characteristics/capabilities of interest to the current work. To study and define the geometry of the hull and the configuration of the A-UGV itself, preliminary computational structural and fluid analyses are carried out to ensure it complies with the specifications initially established. As a result, one obtains a fully electric vehicle with approximate dimensions of 1050 × 670 × 450 mm (length–width–height), enabled with 6 × 6 traction capable of reaching 20 km/h on land, which possesses amphibious capabilities of independent propulsion in water up to 8 kts and an estimated autonomy of over 60 min.

A Sensemaking Framework for Defensive Cyber Operations: Filling the Void in Leadership Discourse

In the realm of contemporary warfare dominated by cyber threats, Defensive Cyber Operations (DCO) serve as a linchpin for mitigating risks and ensuring mission assurance. This article delves into the intricate landscape of DCO, focusing on the critical role played by Defensive Cyberspace Forces (DCFs). Despite their significance, the absence of a unified sensemaking framework poses a challenge for leaders responsible for the nuanced development and strategic employment of DCFs. The lacuna in the existing literature revolves around the lack of a comprehensive sensemaking framework tailored for operational and DCF leaders. The inadequacies of current frameworks, either overly broad or excessively specific, hinder effective dialogue and understanding. This deficiency not only obstructs the planning efforts and operational tempo of DCO but also restrains the maturation of DCFs, amplifying residual risks faced by commanders. This paper endeavours to present a purpose-built sensemaking framework crafted for leaders engaged in the dynamic realms of DCF development. Integrating well-established risk mitigation principles with the unique organizational structures and missions of DCFs, the framework fills a crucial void in the literature. Beyond being a decision-support tool, it strives to foster a shared mental model, providing a nuanced lens for leaders to contextualize and prioritize their efforts in the complex landscape of DCO. Through a meticulous critique of existing frameworks, this article introduces a tailored model designed to address identified shortcomings. Emphasizing the practical utility of the proposed framework, the discussion unfolds to elucidate how it not only facilitates the development and employment of DCF but also contributes to organizational resilience and risk mitigation. This article contributes a novel sensemaking framework to the academic discourse on DCO. While acknowledging limitations imposed by an unclassified context, the framework provides valuable insights into the strategic dimensions of DCF development and employment, DCO planning intricacies, and organizational analyses. Future avenues for research include the integration of classified information to refine the framework, ensuring its applicability across diverse DCO mission types and aligning DCF core functions with specific threats, thereby enhancing the efficacy of defensive cyber strategies.

Developing a Three-Dimensional Bubble Dynamics Model for Centrifugal Nuclear Thermal Propulsion

Nuclear thermal propulsion (NTP) is a highly efficient type of propulsion system that could yield a specific impulse up to 800 s. High-performance NTP allows for possibilities of various mission types from flyby to interplanetary flight, manned or unmanned. Centrifugal nuclear thermal propulsion (CNTP) is a type of NTP that uses liquid fissile material instead of a solid core in a standard reactor configuration. CNTP requires an interaction between liquid fissile fuel and gaseous propellant to perform heat transfer and generate thrust in a spinning enclosure. Because of the liquid state of the fissile fuel, it is essential to monitor bubble behavior and trajectory. For example, the bubble dwell time within the liquid and hydrogen flow rates can influence the liquid volume fraction and volume, which in turn can affect reactivity. A model is developed and presented that, as it matures, will predict the bubbles’ behavior based on the various types of liquid and gas and their corresponding properties as well as assist in cross-validation with the concurring experiment. The model primarily utilizes the smooth particle hydrodynamics (SPH) approach to simulate the liquid and gas interaction within the design space. The physics include buoyancy and drag on the bubbles. The pressure field within the liquid is modeled using hydrostatics, in which centrifugal motion introduces a radial gradient. Boundary conditions are devised to confine the liquid and gas within the enclosure. In this paper, we present the progress to date in two centrifugal fuel element–relevant subscale devices, the so-called “Antfarm” and “Blender II.” Antfarm is a static stage in a rectangular enclosure where buoyancy is purely gravity driven. Blender II refers to a rectangular enclosure that spins at up to 7000 rpm. Both Antfarm and Blender II are experiments that provide important data for validation against our SPH model. Two liquid and gas combinations are modeled in the present study using the Antfarm setup: water-air, and Galinstan-Nitrogen. The bubbles’ behavior was comparable to the experiment, and the velocity was at the same order of magnitude. The liquid simulation performed for the Blender II model shows that the pressure gradient within the liquid in the radial direction matches that predicted analytically from the centrifugal acceleration. The Blender II liquid model awaits experimental data for validation and verification.

Structured replacement policies for a system subject to random mission types

AbstractThis paper optimizes condition‐based replacement policies for a mission‐oriented system. The key challenge in our problem is that the system does not work under a fixed mission type but is subject to an infinite sequence of random types of missions assigned in a Markovian manner, which is realistic in many practical situations. The mission process modulates the deterioration process. Taking advantage of the opportunities when missions are switched, condition monitoring is conducted to support replacement decision‐making. This paper considers two practical scenarios in which the type of the next mission is either available or unavailable at each decision epoch. The objective is to determine the optimal replacement decisions for both scenarios that minimize their long‐run expected average cost rates. The optimization problems are analyzed in the framework of the Markov decision process. The optimal decisions of both scenarios are proven to be of partially monotone control‐limit forms. Near‐optimal policies with multilevel thresholds are provided for more convenient decision‐making. The policy iteration algorithm is modified for efficient optimization. A numerical example is used to demonstrate the feasibility of the proposed approach.