Aerospace Engineering

A cycling peloton is the main group of cyclists riding closely together to reduce aerodynamic drag and energy expenditure. Previous studies on small groups of in-line drafting cyclists showed reductions down to 70 to 50% the drag of an isolated rider at same speed and these values have also been used for pelotons. However, inside a tightly packed peloton with multiple rows of riders providing shelter, larger drag reductions can be expected. This paper systematically investigates the drag reductions in two pelotons of 121 cyclists. High-resolution CFD simulations are performed with the RANS equations and the Transition SST-k-ω model. The cyclist wall-adjacent cell size is 20 μm and the total cell count per peloton is nearly 3 billion. The simulations are validated by four windtunnel tests, including one with a peloton of 121 models. The results show that the drag of all cyclists in the peloton decreases compared to that of an isolated rider. In the mid rear of the peloton it reduces down to 5%-10% that of an isolated rider. This corresponds to an "equivalent cycling speed" that is 4.5 to 3.2 times less than the peloton speed. These results can be used to improve cycling strategies.

A cycling peloton is the main group of cyclists riding closely together to reduce aerodynamic drag and energy expenditure. Previous studies on small groups of in-line drafting cyclists showed reductions down to 70 to 50% the drag of an isolated rider at same speed and these values have also been used for pelotons. However, inside a tightly packed peloton with multiple rows of riders providing shelter, larger drag reductions can be expected. This paper systematically investigates the drag reductions in two pelotons of 121 cyclists. High-resolution CFD simulations are performed with the RANS equations and the Transition SST-k-ω model. The cyclist wall-adjacent cell size is 20 μm and the total cell count per peloton is nearly 3 billion. The simulations are validated by four windtunnel tests, including one with a peloton of 121 models. The results show that the drag of all cyclists in the peloton decreases compared to that of an isolated rider. In the mid rear of the peloton it reduces down to 5%-10% that of an isolated rider. This corresponds to an "equivalent cycling speed" that is 4.5 to 3.2 times less than the peloton speed. These results can be used to improve cycling strategies.

Two new interplanetary technologies have advanced in the past decade to the point where they may enable exciting, affordable missions that reach further and faster deep into the outer regions of our solar system: (i) small and capable interplanetary spacecraft and (ii) light-driven sails. Combination of these two technologies could drastically reduce travel times within the solar system. We discuss a new paradigm that involves small and fast moving sailcraft that could enable exploration of distant regions of the solar system much sooner and faster than previously considered. We present some of the exciting science objectives for these miniaturized intelligent space systems that could lead to transformational advancements in the space sciences in the coming decade.

This paper focuses on a topic that is frequently used nowadays namely 3D printing. The term 3D printing encompasses several manufacturing technologies that build parts layer-by-layer an inconvenience of this process is that the deposition of material takes place in the plane (2D space) then by applying a constant increment on the third axis it is moved to the next plane. The deposition of material is taking part in a 2D space. There are many types of 3D printing such as FDM (fused deposition modeling), SLA (stereolitography), SLS (selective laser sintering), DMLS (direct metal laser sintering), DLP (digital light process), EBM (electron beam melting). Typically these applications involve lowvolumes and complex geometries. Often, components for aerospace and medical applications are ideal candidates for production 3D printing. This paper proposes a new approach to the 3d printing process by using a robotic arm to ensure more than 3 degrees of freedom and deposition paths with spatial orientation. One propose two types of working: nonplanar with the tip normal to the working plane and nonplanar with the tip normal to the trajectory.

A parameter analysis is performed on an analytical penetration model which has been recently developed. Figures are plotted to show how the disturbed zone size, parameters of displacement and stress fields and dynamic section pressure are dependent on soil compressibility, shear strength and mass density. Main results are presented and discussed.

Multidimensional structure warp-knitted spacer fabrics (WKSFs) are integrated with polyurethane elastomers (PUEs) to fabricate shear-resistant reinforced composite materials, demonstrating a 58% enhancement in shear strength compared to pristine PUEs. We quantitatively evaluated the interface thickness and adhesion between WKSFs and PUEs to assess the influence of the physical and chemical properties of the interface on stress conduction and dispersion. The results demonstrate that the stress transfer efficiency and overall reinforcement are highly dependent on the interface quality and the mesh structure of the WKSFs. Finite-element analysis reveals a multidimensional stress dispersion mechanism within the structure, leading to a more effective stress distribution from a theoretical perspective. The findings provide insights into the stress dispersion in different directions of warp-knitted spacer fabric fibers and offer practical guidelines for designing advanced high-performance, energy absorbing, and shear-resistant materials for applications such as protective systems, structural reinforcement, and energy storage.

The standard formulation of the probability hypothesis density (PHD) and cardinalised PHD (CPHD) filters assumes that the target birth intensity is known a priori. In situations where the targets can appear anywhere in the surveillance volume this is clearly inefficient, since the target birth intensity needs to cover the entire state space. This paper presents a new extension of the PHD and CPHD filters, which distinguishes between the persistent and the newborn targets. This extension enables us to adaptively design the target birth intensity at each scan using the received measurements. Sequential Monte-Carlo (SMC) implementations of the resulting PHD and CPHD filters are presented and their performance studied numerically. The proposed measurement-driven birth intensity improves the estimation accuracy of both the number of targets and their spatial distribution.

The hot electron transport properties of the Cu/Si(001) interface have been studied using ballistic electron emission microscopy (BEEM). The Schottky barrier height was measured to be 0.64±0.02 eV. The scanning tunneling microscopy images provide evidence of Volmer–Weber growth of the metal, while Rutherford backscattering spectrometry data corroborated with Auger depth profiling indicate distinct Cu and Si regions with little intermixing. Comparison with Au/Si(001) BEEM data provides some insight into the hot electron transport and scattering properties of the Cu/Si(001) interface.

SummarySolutions of partial differential equations could exhibit a multiscale behavior. Standard discretization techniques are constraints to mesh up to the finest scale to predict accurately the response of the system. The proposed methodology is based on the standard proper generalized decomposition rationale; thus, the PDE is transformed into a nonlinear system that iterates between microscale and macroscale states, where the time coordinate could be viewed as a 2D time, representing the microtime and macrotime scales. The macroscale effects are taken into account because of an FEM‐based macrodiscretization, whereas the microscale effects are handled with unidimensional parent spaces that are replicated throughout the domain. The proposed methodology can be seen as an alternative route to circumvent prohibitive meshes arising from the necessity of capturing fine‐scale behaviors.

Sparse model identification by means of data is especially cumbersome if the sought dynamics live in a high dimensional space. This usually involves the need for large amount of data, unfeasible in such a high dimensional settings. This well-known phenomenon, coined as the curse of dimensionality, is here overcome by means of the use of separate representations. We present a technique based on the same principles of the Proper Generalized Decomposition that enables the identification of complex laws in the low-data limit. We provide examples on the performance of the technique in up to ten dimensions.

The influence of the anisotropy of the (5×n) reconstructed (100) face of gold on the generation of vacancy islands by sputtering with 600 eV Ar+ ions has been investigated by scanning tunneling microscopy. The shapes of these islands, bounded by monoatomic steps, are shown to be growth shapes, rather than equilibrium shapes. The growth mechanisms leading to these shapes are discussed.

phase and to progressively implement such demonstrations; The success of the third and last Ariane 5 qualification flight is a major milestone in the future of space transportation in Europe; the new launcher and its evolutions will now play the leading role in the next decades.

The UNOOSA Workshop presentation is covering the wide aspects of Academia-Industry partnership, using Silicon Valley as an example. In this presentation the partnership between International Space University, Stanford and SAP is highlited. The Workshop is to foster dialogue among a diverse group of stakeholders in the fieldof capacity building for space science, technology and its applications, and to take stock and discuss about various ideas and proposals for improving coordination and cooperation in the future. The outcomes and recommendations identified were provided inputs for the United Nations.

This paper presents and discusses Implicit Large Eddy Simulation (ILES) results of vitiation effects in ground tests of supersonic air/H 2 combustion. This work is useful for realistic extrapolation of ground test data to flight conditions. The high-enthalpy flow configuration retained, typical of scramjet engines, is the Mach 2 LAERTE combustion chamber of the French aerospace lab ONERA. The supersonic air co-flow is preheated by burning a small amount of hydrogen in oxygen-enriched air. Stable numerical simulations of such high-speed turbulent shocked flows require dissipative numerics that interact with molecular diffusion. The premature ignition in the case of vitiation by oxygen atom can be observed using reduced finite rate chemistry in the quasi-laminar approximation, i.e. without any subgrid combustion model, because the Damköhler number (ratio of turbulent to chemical time scale) is less than unity. Turbulent time scales are only moderately affected by vitiation, but chemical time scales are significantly reduced.

This paper presents and discusses Implicit Large Eddy Simulation (ILES) results of vitiation effects in ground tests of supersonic air/H 2 combustion. This work is useful for realistic extrapolation of ground test data to flight conditions. The high-enthalpy flow configuration retained, typical of scramjet engines, is the Mach 2 LAERTE combustion chamber of the French aerospace lab ONERA. The supersonic air co-flow is preheated by burning a small amount of hydrogen in oxygen-enriched air. Stable numerical simulations of such high-speed turbulent shocked flows require dissipative numerics that interact with molecular diffusion. The premature ignition in the case of vitiation by oxygen atom can be observed using reduced finite rate chemistry in the quasi-laminar approximation, i.e. without any subgrid combustion model, because the Damköhler number (ratio of turbulent to chemical time scale) is less than unity. Turbulent time scales are only moderately affected by vitiation, but chemical time scales are significantly reduced.

In order to predict the laminar/turbulent transition on a hypersonic vehicle forebody at Mach numbers 4 and 6, the three-dimensional (3D) modal linear stability analysis is applied, coupled with the e N method. Nevertheless, N factors are unknown for wind tunnel conditions. Experimental investigations have been carried out on a §at plate in the blowdown wind tunnel T-313 of ITAM RAS (Novosibirsk). At M ∞ = 2 to 6, the position of laminar/turbulent transition was measured by both Pitot tube and thermocouples. Then, stability analysis allows computing N factors at transition on the §at plate: they are about 3 ∼ 4, typical of conventional wind tunnels. These §at plate correlations can then be used to predict the transition on the forebody in the same wind tunnel. Experiments for the forebody are currently in progress and will allow checking the predicted transition location.

Venturing into the Fourth Industrial Revolution (4IR), being digital savvy is what makes a fresh graduate to be more employable than the others. Graduates with good digital skills will emerge as highly employable graduates as they are able to meet the industry's needs. Most companies nowadays are diverting towards digital content in promoting and informing their audiences about their product, as well as services. Being autonomous in creating meaningful content, such as marketing, as well as promotion videos, and even personal branding content that can help to attract targeted audiences can benefit the graduates not only as an employee, but also as an individual respectively. Having the skills of digital content creation not only helps to cater to the demand of industries, but also helpful in promoting autonomous employability skills within graduates to adapt to the workforce environment. In conjunction to this, employing a qualitative design of research with focus group discussion involving ten undergraduate students as the sampling of this study, this study will be discussing the relevance of a digital content creation course in tertiary education to prepare graduates' for autonomous skills in the workforce environment, also to accommodate the demand of industry in the Malaysian context. It is believed that, if planned accordingly, a digital content creation course could bring potential to assist undergraduate students to be more employable, alongside unleashing their English intercultural communication skills to cater to both themselves and the industry's needs.

A fully elliptic, control volume solution of the two-dimensional incompressible Navier-Stokes equations for the prediction of cascade performance over a wide incidence range is presented in this paper. The numerical technique is based on a new pressure substitution method. A Poisson equation is derived from the pressure weighted substitution of the full momentum equations into the continuity equation. The analysis of a double circular are compressor cascade is presented, and the results are compared with the available experimental data at various incidence angles. Good agreement is obtained for the blade pressure distribution, boundary layer and wake profiles, skin friction coefficient, losses and outlet angles.

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Cross-flow fan propulsion has not been seriously considered for aircraft use since an Vought Systems Division (VSD) study for the U.S. Navy in 1975. A recent conceptual design study of light-weight, single seat VTOL aircraft suggest that rotary-engine powered cross-flow fans may constitute a promising alternative to the conventional lift-fan vertical thrust augmentation systems for VTOL aircraft. The cross-flow fan performance data obtained by VSD supported the hypothesis that they could be improved to the point where their thrust augmentation could be used in a VTOL aircraft. In this paper we report results of a NASA Glenn supported experimental and computational cross-flow fan investigation which is currently in progress and we provide an assessment of the potential suitability of crossflow fans for VTOL aircraft propulsion. The tests are carried out in the Turbopropulsion Laboratory of the Naval Postgraduate School, using an existing Turbine Test Rig as a power source to drive the crossflow fan. A 0.305 m (12-inch) diameter, 38.1 mm (1.5-inch) span cross-flow fan test article was constructed to duplicate as closely as possible the VSD fan so that baseline comparison performance data could be obtained. Performance measurements were taken over a speed range of 1,000 to 7,000 RPM and results comparable to those measured by Vought Systems Division were obtained. At 3,000 RPM a 2:1 thrust-to-power ratio was measured which dropped to one as the speed was increased to 6,000 RPM. Performance maps were experimentally determined for the baseline configuration as well as one with both cavities blanked off, for the speed range from 2,000 to 6,000 rpm. Using Flo++, a commercial PC-based computational fluid dynamics software package by Softflo, 2-D numerical simulations of the flow through the cross-flow fan were also obtained. Based on the performance measurements it was concluded that the optimum speed range for this rotor configuration was in the 3,000 to 5,000 rpm range. The lower speed producing the best thrust-to-power ratio and the upper speed range producing the highest efficiency over sizeable throttling range.

Laser-Doppler velocimetry measurements through a one millimeter hole in the casing of an annular turbine cascade were performed in the endwall region downstream of the blade row. Complementary threehole pressure probe measurements were also taken downstream of the nozzle blades, as well as blade surface pressure measurements. The object of this study was to devise methods for the measurement close to an endwall and to overcome the problems associated with optical access window contamination. The eventual aim of the project was to perform laser anemometry measurements in the tip leakage region of an operating turbine of comparable size. Good comparisons with numerical predictions of the flowfield were also obtained. P static pressure Pt stagnation pressure Po reference stagnation pressure Prat inlet total -to-exit static (at the hub) pressure ratio U mean axial velocity u' fluctuating axial velocity V mean circumferential velocity Vexit maximum exit plane velocity v' fluctuating circumferential velocity X axial direction Y tangential direction * Associate Professor, Member AIAA ** Lt. US Navy *** LCDR. US Navy

A research program was carried out to explore the effects of nozzle trailing-edge modi cations on the ow structure, jet mixing with the ambient air, and jet noise of a rectangular supersonic jet. Nozzles with one modi ed trailing edge were used with the intention of enhancing mixing and reducing noise. The modi cations were simple cutouts in the plane of the nozzle wall and acted to induce large-scale streamwise vortices. A rectangular jet, with a design Mach number of 2 and with various trailing edges, was examined using optical diagnostics and noise measurements in ow regimes ranging from moderately overexpanded M j = 1:5 to moderately underexpanded M j = 2:5. The results indicated that in nonideally expanded ow regimes, one could generate pairs of streamwise vortices of various strength and sign and that the mixing could be signi cantly enhanced. The results also indicated that the modi cations could eliminate or at least substantially reduce screech noise and could signi cantly decrease the overall far-eld sound pressure level in the nonideally expanded ow regimes. In the ideally expanded ow regime, the trailing-edge modi cations did not seem to induce streamwise vortices and, thus, did not have a substantial effect on the jet mixing or noise.

This paper presents experimental results of fast intrinsic evolutionary design and evolutionary fault recovery of a 4-bit Digital to Analog Converter PAC) using the JPL stand-alone board-level evolvable system (SABLES). SABLES is part of an elport to achieve integrated evolvable systems and provides autonomous, fast (tens to hundreds of seconak), on-chp evolution involving about 100.000 circuit evaluations. Its main components are a JPL Field Programmable Tronsistor Array (FPTA) chip used ar transistor-level recontgurable hardware, and a TI DSP that implements the evolutionary algorithm controlling the FPTA reconfiguration. The paper describes an experiment consisting of the hierarchical evolution of a 4-bit DAC using 20 cells of the FPTA chip. Fault-recovery is demonstrated aper applying stuck-at 0 faults to all switches of one particular cell, and using evolution to recoverfunctionality. It has been veri$ed that thefunctionality can be recovered in less than one minute aBer the fmlt is detected while the evolutionary design of the 4-bit DACfrom scratch took about 3 minutes. ' lLSB =Vrefl16, forVref=453mV.

There are many smallsat missions now in progress or in development, and these are pushing smallsats into new realms of technology, compactness, and mission utility. Proposals for the near term will shrink smallsats further, couple them in new ways using constellations or fractionated architectures, and edge into new mission areas. What, though, is on the horizon looking out 10-25 years or more? While there have been some overly optimistic predictions about smallsats, the advances demonstrated or in development in computing, nanomaterials, microelectromechanical systems, and other areas indicate the future will include some smallsat applications only now being imagined, and others that have not yet been imagined. As once smallsat developers worked with no idea that carbon nanotubes and powerful computers on chips would be available to them, designers of tomorrow will have both evolutionary and revolutionary technologies at their disposal. Ideas that were deemed to push technology too far or cost too much may well be in the mainstream in 2020 or beyond. Some future smallsats will have dimensions measured in millimeters. Some will cooperate in swarms in ways not possible today. Some will be deployed around other celestial bodies or in deep space. Some will perform missions that today require huge spacecraft or cannot be done at all. This paper surveys the leading programs and thinkers in the smallsat realm about what may appear beyond commonly used planning horizons. We have seen 25 years of progress presented at Small Satellite Conferences so far. What might be presented 25 years from now?

The study deals with the flow resistance and heat transport properties of woven and knitted wire gauzes stacked in a tubular apparatus. The experimental programme included flow resistance and heat transfer experiments performed for air flow (Re = 2-300) using three woven gauzes and one knitted gauze. During the heat transfer experiments, the gauzes were heated by electric current flowing directly through them. The models describing the flow resistance and the heat transfer were put forward. Both the models base on the concept of the laminar flow developing in a short capillary channel (i.e. the gauze mesh). The model describing the flow resistance does not contain the experimentally derived parameters thus it may describe a number of wire gauzes offered on the market. The heat transfer results might be described using single empirical equation for all the gauzes studied if the concept of developing laminar flow is applied. The number of the gauze sheets stacked influences neither flow resistance (per single gauze sheet) nor the heat transfer coefficient.

The study deals with the flow resistance and heat transport properties of woven and knitted wire gauzes stacked in a tubular apparatus. The experimental programme included flow resistance and heat transfer experiments performed for air flow (Re = 2-300) using three woven gauzes and one knitted gauze. During the heat transfer experiments, the gauzes were heated by electric current flowing directly through them. The models describing the flow resistance and the heat transfer were put forward. Both the models base on the concept of the laminar flow developing in a short capillary channel (i.e. the gauze mesh). The model describing the flow resistance does not contain the experimentally derived parameters thus it may describe a number of wire gauzes offered on the market. The heat transfer results might be described using single empirical equation for all the gauzes studied if the concept of developing laminar flow is applied. The number of the gauze sheets stacked influences neither flow resistance (per single gauze sheet) nor the heat transfer coefficient.

Hot carrier injection (HCI) degradation is evaluated for n-metal oxide semiconductor (MOS) and pMOS high-κ-fin shaped field effect transistor with (100) and (110) sidewall surface orientations. It was found that impact ionization at the source, in addition to the traditional drain side enhances HCI degradation for the Vg=Vd condition. The degradation increases with decreasing fin length, with negligible dependence on substrate orientation.

Dynamic crushing behavior of elliptical aluminium foam-filled tube (EFT) under axial impact was analyzed thoroughly. First, the deformation mechanism of EFT is investigated. Based on this, a theoretical model to predict the mean crushing force is established under some specific assumption. The interaction work between the foam and tube are introduced in the model to improve the accuracy. Further numerical simulations of the EFT are conducted to validate the theoretical models which indicates the theoretical model is pretty accurate. Finally, the influence of the geometric parameters of EFT on the mean crushing force is also revealed. The study aims at quantifying the energy absorption of EFT under axial impact loading, for variations in the geometry parameters of the tube. This can guide the engineers to design great energy absorber more efficiently.

Propellants or combustion products can reach high pressures and temperatures in advanced or conventional propulsion systems. Variations in flow properties and the effects of real gases along a nozzle can become significant and influence the calculation of propulsion and thermodynamic parameters used in performance analysis and design of rockets. This work derives new analytical solutions for propulsion parameters, considering gases obeying the van der Waals equation of state with specific heats varying with pressure and temperature. Steady isentropic one-dimensional flows through a nozzle are assumed for the determination of specific impulse, characteristic velocity, thrust coefficient, critical flow constant, and exit and throat flow properties of He, H 2 , N 2 , H 2 O, and CO 2 gases. Errors of ideal gas solutions for calorically perfect and thermally perfect gases are determined with respect to van der Waals gases, for chamber temperatures varying from 1000 to 4000 K and chamber pressures from 5 to 35 MPa. The effects of covolumes and intermolecular attraction forces on flow and propulsion parameters are analyzed.

Propellants or combustion products can reach high pressures and temperatures in advanced or conventional propulsion systems. Variations in flow properties and the effects of real gases along a nozzle can become significant and influence the calculation of propulsion and thermodynamic parameters used in performance analysis and design of rockets. This work derives new analytical solutions for propulsion parameters, considering gases obeying the van der Waals equation of state with specific heats varying with pressure and temperature. Steady isentropic one-dimensional flows through a nozzle are assumed for the determination of specific impulse, characteristic velocity, thrust coefficient, critical flow constant, and exit and throat flow properties of He, H2, N2, H2O, and CO2 gases. Errors of ideal gas solutions for calorically perfect and thermally perfect gases are determined with respect to van der Waals gases, for chamber temperatures varying from 1000 to 4000 K and chamber pressur...

Background: Massive Open Online Courses (MOOCs) have emerged as an alternative educational platform for disseminating information globally. Universities are increasingly investing in the development of MOOCs addressing public health issues, such as menstrual disorders. These courses aim to raise awareness and provide up-to-date, evidence-based content to students and the public. In Egypt, where a high percentage of females experience menstrual disorders, creating an engaging MOOC on this topic for nursing students can empower them to manage their own symptoms and improve patient care and support. Objective: The study aimed to develop a MOOC on menstrual disorders for female nursing students and explore its effect on their knowledge and satisfaction. Setting: This pre-experimental study was conducted in the obstetrics and gynecological nursing department, faculty of Alexandria. Subjects: the study subjects included all (103 students) female nursing students who were enrolled in the Obstetric and Gynecological Nursing Department during the second semester of the academic year 2020-2021 and agreed to participate in the study. Tools: two tools were used for data collection: the Female Nursing Students' knowledge questionnaire about Menstrual Disorders and the Nursing Students' Satisfaction Scale about MOOC. Results: The data showed a highly significant improvement in the students' knowledge after the participation in the MOOC on menstrual disorder. A significant majority of the students expressed a high level of satisfaction with the MOOC. Conclusion: The MOOC had a significant positive effect on enhancing students' knowledge, thereby positively influencing their satisfaction with the course and their understanding of menstrual disorders. The MOOC's diverse features, including its flexibility, accessibility, interactive elements, visual and audio components, high-quality content, and interactive learning community likely contributed to its success in facilitating students' knowledge acquisition, and ultimately enhancing overall satisfaction. Recommendation: the study recommends that MOOCs can be integrated into the nursing curriculum in a way that complements and enhances the existing courses while fostering a culture of self-directed learning. Moreover. nurse educators should be provided access to necessary resources for developing MOOCs specific to their specialties and expertise.

This research aims to identify and analyze the contestation of identity political discourse has developed in society digital space ahead of the election for Governor of Southeast Sulawesi. In this research theory that used are framing theory, the concept of public space, and the identity politics concept to find out why the community selects Governor. Identity politics can arise based on a society's ethnicity, religion, and culture. This is significant since the rise in community political participation in Southeast Sulawesi is heavily influenced by tribal factors. Meanwhile, the data collection technique used literature study with data analysis techniques that include three stages Data reduction, data presentation and drawing conclusions. The research findings that the constestation of identity political discourse in the digital space ahead of the election for Governor of Southeast Sulawesi showed that there dynamics in the use of digital space, especially on social media facebook and instagram. The tribal phenomenon has become a hot topic of discussion in the digital space, as showed by the comments of supporters of the three gubernatorial candidates, namely Andi Sumangerukka (ASR), a Bugis tribe, Kery Saiful Konggoasa (KSK), and Lukman Abunawas (LA) a tolaki tribe. The tribal public mindset of Kendari city people can determine the map of political power, making them to select who is most ideal to be a leader in Southeast Sulawesi.

This paper describes a planar Doppler velocimetry (PDV) technique that is capable of measuring the three, instantaneous and time average components of velocity over two spatial dimensions using a single pair of signal and reference cameras. The three views required to obtain three-component velocity information are guided from the collection optics to a single imaging plane using flexible fibre imaging bundles. These are made up of a coherent array of single fibres and are combined at one end as the input plane to the measurement head. Measurements of the velocity field of a rotating disk are used in the development of the technique and initial results of the instantaneous velocity field of a jet are presented.

The objective of this research was to create a generic and flexible framework for the exploration, evaluation and side by side comparison of novel propulsion architectures. The intent for these evaluations was to account for varying operation strategies and to support architectural design space decisions, at the conceptual design stages, rather than single point design solutions. To this end, main propulsion subsystems were categorized into energy, power and thrust sources. Two types of matrices, namely the Property and Interdependency Matrices, were created to describe the relationships and power flows among these sources. These matrices were used to define various electrified propulsion architectures, including but not limited to turboelectric, series-parallel and distributed electric propulsion configurations. As a case study, the matrices were used to generate and operate a notional distributed electric propulsion architecture of NASA's X-57 Mod IV aircraft concept. The mission performance results were acceptably close to the data obtained from literature. Finally, the matrices were used to simulate the changes in operation strategy under two motor failure scenarios to demonstrate the ease of use, rapidness and automation. It was seen that this new framework enables rapid and analysis-based comparisons among unconventional propulsion architectures where solutions are driven by requirements.

In this work a technique for cloud detection and classification from MSG-SEVIRI (Meteosat Second Generation-Spinning Enhanced Visible and Infra-red Imager) imagery is presented. It is based on the segmentation of the multispectral images using order-invariant watershed algorithms, which are applied to the corresponding gradient images, computed by a multi-dimensional morphological operator. To reduce the over-segmentation produced by the watershed method, a RAG (Region Adjacency Graph) based region merging technique is applied, using region dissimilarity functions. Once the objects present in the image have been segmented, they are classified using a multi-threshold method based on physical considerations that takes into account the statistical parameters inside each region.

In recent years, hydrofoils have become ubiquitous and critical components of high-performance surface vehicles. Twenty-meter-long hydrofoil sailing craft are capable of reaching speeds in excess of 45 knots. Hydrofoil dinghies routinely travel faster than the wind and reach speeds up to 30 knots. Besides, in the quest for super-maneuverability, actuated hydrofoils could enable the efficient generation of large forces on demand. However, the control of hydrofoil systems remains challenging, especially in rough seas. With the intent to ultimately enable the design of versatile, small-scale, highspeed, and super-maneuverable surface vehicles, we investigate the problem of controlling the lift force generated by a flexible, surface-piercing hydrofoil traveling at high speed through a random wave field. We present a test platform composed of a rudder-like vertical hydrofoil actuated in pitch. The system is instrumented with velocity, force, and immersion depth sensors. We carry out high-speed field experiments in the presence of naturally occurring waves. The 2 cm chord hydrofoil is successfully controlled with a LTV/feedback linearization controller at speeds ranging from 4 to 10+ m/s.

In the decades since the advent of in situ plasma measurements on board spacecraft, the instrumentation has grown bigger, heavier, and more complex as our understanding of space plasmas improves, and our appetite for more information increases. The result is that current state-of-the art instruments may be up to several kg in mass. However, we can no longer afford either these larger instruments or the spacecraft which carry them. There has thus been a recent interest in the miniaturization of both spacecraft and the instrument payload. Traditionally, the design of a spacecraft and its payload proceed along relatively independent paths, with little anempt at producing an optimized "whole". The need for optimization becomes more critical as the spacecraft becomes smaller, since interactions between subsystems become more severe. However, to achieve such optimization, the spacecraft + instruments must be treated as a complete system. This paper describes the results and status of an ongoing design study to understand the problems and trade space of fully integrating an instrument into a micro-spacecraft. The example chosen for the study is a miniature ("chip" sized) magnetometer, under development at the Jet Propulsion Laboratory, using the electron tunneling effect in silicon. The micro-spacecraft is then built around the very specific needs of the sensor. The fully integrated electronics include circuits for the sensor, signal processing, and telemetry. As an application, a set of these autonomous, expendable "Free-flyer Magnetometers" would be ejected from a parent spacecraft to measure both temporal and spatial structure of the magnetic field in selected 1 regions of the magnetosphere during the approximately 1 hour life of the free-flyer's battery power.

We have examined simultaneous ULF activity in the Pi2 and Pc3 bands at the near-equatorial magnetic stations in South America from SAMBA and MAGDAS arrays and low-orbiting CHAMP satellite during its passage over this meridional network. At the nighttime, both Pi2 and Pc3 waves in the upper ionosphere and on the ground are nearly of the same magnitude and in-phase. At the same time, the daytime Pc3 pulsations on the ground and in space are nearly out-of-phase. Comparison of observational results with the theoretical notions on the MHD wave interaction with the system ionosphere-atmosphere-ground suggests that nighttime low-latitude Pi2 and Pc3 wave signatures are produced by magnetospheric fast compressional mode. The daytime near-equatorial Pc3 waves still resist a quantative interpretation. These waves may be produced by a combination of two mechanisms: compressional mode leakage through the ionosphere, and by oscillatory ionospheric current spreading towards equatorial latitudes.

The purpose of this study is to investigate the relationship between the angles of mental rotation when attempting to spatially orientate and the resulting response times and levels of accuracy. By means of a computer program, participants were presented with 64 mental rotational trials. The mental rotational trials consisted of a triangle placed in the center of the screen with a standard stick symbol of an aircraft appearing at various headings and orientations around the triangle. The participants were required to imagine themselves inside the flight deck of the aircraft, and then respond as quickly and accurately as possible to where the triangle is in relation to their orientation. Analysis of the data indicated that as the amount of angular displacement increased from the straight ahead and directly behind positions, the response times and accuracy rates increased and decreased respectively. Additionally, responses for the cardinal orientations were faster than the non-cardinal orientations.

emission is being investigated as a way to continuously monitor the space station Freedom for damage caused by space debris impact and seal failure. Experiments run to date focused on detecting and locating simulated and real impacts and leakage. These were performed both in the laboratory on a section of material similar to a space station shell panel and also on the full-scale common module prototype at Boeing's Huntsville facility. A neural network approach supplemented standard acoustic emission detection and analysis techniques.

This paper revisits trilateration in three-dimensional positioning. Specifically, range between a positioning target and the reference points through time-of-flight (ToF) measurements. In a ToF, range is yielded by multiplying the time required by a wave to travel between two points and its propagation speed. Position of the target can be then estimated once the number of references are adequate, i.e. at least three for two-dimensional positioning and four for threedimensional one. In this paper, the positioning is considered for navigation where the target moves following a trajectory whilst the ToFs take place in a certain period. The target position at the time is computed based on the ToFs through least square estimation. Through a numerical simulation, it is shown that the trilateration can track a target's trajectory despite the decreasing performance at the end of the course.

This communication deals with the optical characterization of droplets and fluids parameters that are relevant for liquid-liquid extraction processes, and notably, for nuclear fuel reprocessing. In immiscible liquid-liquid dispersions, i.e. droplets with a homogeneous but low value relative refractive index, the first order rainbow is localized in the near forward to sideways region. It exhibits also an unusual higher contrast for a parallel polarization illumination. Nevertheless, it is possible, considering appropriate light scattering models and inverse methods, to derive from its analysis the droplets' size and composition. When a mass transfer occurs, the refractive index of the droplets and the surrounding fluid become inhomogeneous. In a pure molecular diffusion regime, the rainbow patterns can still be interpreted as well, allowing the estimation of relevant properties for chemical engineering processes, like molecular diffusivities or the distribution constant.

The knowledge of reentry vehicles (RV) §ight characteristics regarding geometrical shape, dimensions, and mechanical properties is essential for precise prediction of their §ight trajectory, impact point, and possible deviations according to simulation uncertainties. The §ight characteristic estimations of existing RV require both body dimensions and mechanical properties of the objects. Due to comparatively simple and reliable methods of specifying the vehicle outer dimensions, e. g., photos and videomaterials, the estimation of mechanical properties is a subject of higher uncertainties. Within this study, a generic medium range ballistic missile (MRBM) RV was examined for several modi¦cations such as center of gravity (CoG) position, weight moment of inertia, and initial reentry §ight states. Combinations of these variables with constant aerodynamic properties for maximal lateral accelerations will be determined. Basing on these, potential evasion maneuver capabilities of the RV will be described.

An experimental investigation was conducted to study the effect of ambient pressure fluctuations on the dual-bell transition behavior. Ambient or back pressure fluctuations of different frequencies (1.0, 1.5, and 3Hz) were artificially introduced inside the high-altitude simulation chamber using three magnetic valves. The dual-bell transition behavior is found to be very sensitive to back pressure fluctuations of magnitude > 20% which triggers a flip-flop phenomenon that is observed to continue as long as the fluctuations prevail. Increasing the throttling up rate also does not seem to help much in achieving a stable dual-bell transition within the scope of the present tests. This too is not favorable as it can lead to a delay in transition. These test results suggest that the dual-bell nozzle can present

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This document outlines a proposal to raise the maturity of a monitoring and control system designed for hydrogen fuel cells with natural air cooling, advancing from TRL 5 to TRL 9 within the automotive sector. The primary goal is to guarantee optimal performance and efficiency during full operation, all while establishing a dependable supply chain for essential components. Moreover, dedicated efforts are aimed at enhancing the reliability and scalability of this technology, offering distinct advantages for streamlined series production that supports Full Cell Electric Vehicles (FCEVs). This, in turn, simplifies their seamless integration with electric powertrain systems in diverse urban and industrial transport environments.

We present the laboratory measurements of light scattering by rough surfaces, i.e. alumina plate with different degree of roughness, two layers of alumina particles with diameters of 2mm and 500pm, and a layer of alumina powder. It is found that a specular reflection disappears as the roughness of the plate or the size of particle layer increases. In addition, the anisotropic scattering observed in our measurements can be described by bidirectional reflectance models, Our measurements will be used to analyse the in situ photo-polarimetric data of asteroid NEREUS obtained by an asteroid sample return mission (MUSES-C in ISAS) in 2002.