Short Flight Times Research Articles

30 MeV X-band Electron Linac Neutron Source for Nuclear Data Study for Fukushima Accident Analysis

X-band (11.424GHz) electron linac as a neutron source for nuclear data study for the Fukushima nuclear plant accident is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident is established. For the purpose, we should now accumulate more precise nuclear data of U, Pu, TRU and MA (Cm, Am, etc.) especially in epithermal (0.1-10eV) neutrons. Therefore, we have decided to suspend the Compton scattering X-ray experiment and move the linac in the core space of the experimental nuclear reactor “Yayoi” which is now under the decommission procedure. Due to the compactness of the X-band linac, the electron gun and accelerating tube and other components can be installed in a small space in the core. First we plan to perform the TOF (Time Of Flight) transmission measurement for study of the total cross sections of the nuclei for 0.1-10eV neutrons. Therefore, if we adopt a TOF line of less than 10 m, the macro-pulse length of generated neutrons should be shorter than 100ns. Electron energy, macro-pulse length, power and neutron yield are ∼30 MeV, 100ns - 1μs, ∼0.4kW and ∼1012 n/s, ∼103 n/cm2/s at samples, respectively. Optimization of the design of a neutron target (Ta, W, 238U), TOF line and neutron detector (Ce:LiCAF) of high sensitivity and fast response is underway. For the purpose, we are upgrading the electron gun and buncher to realize higher current and beam power with a reasonable beam size in order to avoid damage of the neutron target. Although the neutron flux is limited in case of X-band electron linac based source, we take advantage of its short pulse aspect and availability for nuclear data measurement with a short TOF system. We plan to perform the two phased development and measurement. First, we form a tentative configuration in the current experimental room for Compton scattering in 2014. Then, after the decommissioning has been finished, we move it the “Yayoi” room and perform the operation and measurement.

T-Rex: Bare Electro-Dynamic Tape-Tether Technology Experiment on Sounding Rocket S520

The project to verify the performance of space tether technology was successfully demonstrated by the launch of the sounding rocket S520 the 25tu. The project is the space demonstration of science and engineering technologies of a bare tape electrodynamic tether (EDT) in the international campaign between Japan, USA, Europe and Australia. Method of Inverse ORIGAMI (Tape tether folding) was employed in order to deploy the bare tape EDT in a short period time of the suborbital flight. The deployment of tape tether was tested in a various experimental schemes on ground to show high reliability of tape tether deployment. The rocket was launched on the summer of 2010 and deployed a bare electro-dynamic tape tether with length 132.6 m, which is the world record of the length deployment of tape tether. The verification of tether technology has found a variety kind of science and technology results as the first in the humankind and will lead a large number of applications of space tether technologies

Transfer Trajectory Design for Mars Exploration

With regard to the human exploration of Mars, low energy transfer trajectory is designed for Mars exploration based on the combination of invariant manifolds, differential correction and aerobraking methods. The whole transfer trajectory is composed of four stages: 1) from the Earth parking orbit to the Lyapunov orbit around Lagrange point L2 in the Sun-Earth system; 2) from the Lyapunov orbit around L2 to the Lyapunov orbit around L1 in the Sun-Mars system; 3) from the Lyapunov orbit around L1 in the Sun-Mars system to the large elliptical orbit around Mars; and 4) from the large elliptical orbit around Mars to the near-Mars parking orbit. In the first three stages, the circular restricted three-body problem is considered, and the trajectory is designed by using invariant manifolds and the differential correction method. The simulation results show that the transfer trajectory designed by means of the invariant manifolds of the Lyapunov orbit costs lower energy and shorter time of flight than that designed by means of the invariant manifold of the Halo orbit. In the fourth stage, the two-body problem is considered, and the aerobraking method is applied. A comparative performance analysis of static and rotating atmospheric models is carried out by using the details of duration, aerodynamic loading of the Mars vehicle, and other orbital parameters. It is shown that, on the low periareon where the influence of the atmospheric density increases, the changes of orbit parameters between rotating and static atmospheric environments are in large difference, such as orbital semimajor axis, orbital eccentricity, and so on. The influence of Martian rotating atmospheric environment should be considered.

Three-dimensional Route Planning for Unmanned Aerial Vehicles in a Risk Environment

This paper introduces a new approach for three-dimensional flight path optimization for unmanned aerial vehicles. It considers the performance of the air vehicle as well as mission specific requirements including the avoidance of no-fly areas, risk reduction in threat environments by terrain following flight or terrain masking low-level flight, and other regulations such as fixed release and approach vectors at the start and destination locations. The focus of the approach is on a proper discretization of the airspace by a network which allows the application of standard algorithms of combinatorial optimization. In contrast to conventional discretizations by grids or grid-like graphs, our network is non-regular since created by some random process. Moreover, each path in the network corresponds to a twice continuously differentiable trajectory which obeys the kinematic restrictions of the air vehicle and which is feasible with respect to the operational requirements of the mission. With suitable costs defined on the edges of the network, a minimum-cost path calculation allows to identify a trajectory of shortest length, shortest flight time, minimum flight height, or minimum visibility from the ground. The latter objectives aim to minimize the probability of being detected by hostile forces, hence increasing the survivability of the air vehicle.

Effects of Fuel-Side Nitrogen Dilution on Structure and NOx Formation of Turbulent Syngas Non-premixed Jet Flames

In the present study, we have numerically investigated the effects of the fuel-side nitrogen dilution on the precise structure and NOx formation characteristics of the turbulent syngas non-premixed flames. The turbulence-chemistry interaction is represented by the Lagrangian flamelet model. In context with the Lagrangian flamelet model, the NO concentration is obtained directly from the flamelet calculation based on the full NOx chemistry, and the radiative heat loss is taken into account through the flamelet energy equation. Computations are made for three fuel-side nitrogen-diluted syngas non-premixed flames. Numerical results indicate that, for the highly nitrogen-diluted case with the higher scalar dissipate rate and the shorter flight time, the flame structure is dominantly influenced by the turbulence-chemistry interaction and marginally modified by the radiation effect. On the other hand, the flame structure for the no-dilution case with the longer flight time and the relatively intermediate scalar...

Diamond detectors for fast neutron measurements at pulsed spallation sources

The performance of a single crystal diamond (4.7x4.7x0.5mm3 active volume) detector was tested in the ISIS pulsed neutron beam using biparametric (time of flight and pulse height) data acquisition. Three characteristic regions in the biparametric spectra are observed: i) low pulse height events with very short time of flight induced by γ-rays; ii) low pulse height events at longer flight times (i.e. neutron energies En > 3.5–6 MeV), possibly due to neutron elastic scattering off 12C; iii) events with large pulse height and flight times corresponding to En > 6 MeV mainly due to inelastic reactions such as 12C(n,α)9Be and 12C(n,n')3α. The potential use of this detector is discussed in relation to the ChipIr neutron beam line for fast neutron irradiation of electronic components at the ISIS spallation source.

Real-Time Trajectory Optimization for Noise Abatement of Helicopter Landings

In this study, an optimization method is developed to reduce the ground noise impact of helicopter approach flights, and flight experiments are conducted to confirm the effectiveness of this optimization. First, we build a noise model of the JAXA (Japan Aerospace Exploration Agency) experimental helicopter based on measurement results. Then, we define optimal control problems to minimize the noise levels measured at points on the ground surface. The main objective of this paper is to propose a real-time flight trajectory optimization method for solving the optimization problems using actual flight conditions with an on-board computer. To validate the effect of the proposed method, some numerical simulations are conducted under real flight experiment scenarios. The obtained optimal solutions are characterized by steep flight path angles so as to avoid the flight conditions that generate large noise, avoidance of the measurement points, and short flight times; these optimal flights are different from conventional flight trajectories. Finally, the validity of the proposed optimization method is examined by means of flight experiments with the experimental JAXA helicopter. The actual flight experiments result in noise reduction, and prove the effectiveness of the optimization.

Optical Imaging: A New Window to the Adult Brain

Noninvasive optical imaging is an emerging method of functional neuroimaging that has major advantages that make it particularly suited to both basic and clinical neuroscience research as well as to clinical practice.2–7 It has great promise for contributing to neuropsychiatry.2 The required equipment is compact and portable, it is relatively easy to use, and the method is relatively tolerant of subject movement. Studies can be performed in almost any location including at the bedside and in natural settings. Patients who are not good candidates for more traditional functional imaging methods (e.g., functional MRI [fMRI] and positron emission tomography [PET]) often do well with optical imaging, as it does not require absolute stillness or confinement and has no associated loud noises. It is also safe to use in the presence of metal (e.g., plates, pins, pacemakers), an important consideration for some populations of interest. It has much faster time resolution than most other functional imaging techniques and can easily provide repeated within-subject measures. Other major advantages are low cost and high safety. Like surface electroencephalography (EEG), optical imaging captures activation-related changes only from the cerebral cortex. Historically, the major disadvantages of optical imaging have been its lower spatial resolution and smaller regions of coverage, areas of major improvement over the last decade. Use of optical imaging for monitoring of cerebral state in high-risk situations (e.g., neurosurgery, intensive care unit), while an important clinical application, is outside the scope of this review.8–10

Small‐Scale Remotely Piloted Vehicles in Environmental Research

AbstractSmall‐scale remotely piloted vehicles (RPVs) have been experimentally used in environmental fieldwork. They have found employment in range management, forestry, wildlife studies, crop monitoring, marine investigations, and aerobiological sampling. The advantages of small‐scale RPVs include pilot safety, fast data turnaround time, low capital and per‐flight costs, ease in flight planning, quick response for targets of opportunity, and the potential to gather ultrahigh resolution pictures in situations where in situ data gathering is impossible. Significant limitations of small‐scale RPVs include their low stability as photographic platforms; short flight times, airframe fragility, the paucity of sensor packages available, and the difficulties involved integrating pilot‐assist flight navigation systems. Further development is required before small‐scale RPVs will be accepted as mainstream tools for environmental monitoring. Besides discovering and validating environmental applications of the technology, this work includes the design of inexpensive lightweight sensor packages for environmental tasks and the improvement of image processing algorithms to interpret, rectify, and manage RPV imagery.

A dense plasma focus-based neutron source for a single-shot detection of illicit materials and explosives by a nanosecond neutron pulse

Recent progress in a single-pulse Nanosecond Impulse Neutron Investigation System (NINIS) intended for interrogation of hidden objects by means of measuring elastically scattered neutrons is presented in this paper. The method uses very bright neutron pulses having duration of the order of 10 ns only, which are generated by dense plasma focus (DPF) devices filled with pure deuterium or DT mixture as a working gas. The small size occupied by the neutron bunch in space, number of neutrons per pulse and mono-chromaticity (ΔE/E∼1%) of the neutron spectrum provides the opportunity to use a time-of-flight (TOF) technique with flying bases of about a few metres. In our researches we used DPF devices having bank energy in the range 2–7 kJ. The devices generate a neutron yield of the level of 108–109 2.45 MeV and 1010–1011 14 MeV neutrons per pulse with pulse duration ∼10–20 ns. TOF base in the tests was 2.2–18.5 m. We have demonstrated the possibility of registering of neutrons scattered by the substances under investigation—1 litre bottles with methanol (CH3OH), phosphoric (H2PO4) and nitric (HNO3) acids as well as a long object—a 1 m gas tank filled with deuterium at high pressure. It is shown that the above mentioned short TOF bases and relatively low neutron yields are enough to distinguish different elements’ nuclei composing the substance under interrogation and to characterize the geometry of lengthy objects in some cases. The wavelet technique was employed to ‘clean’ the experimental data registered. The advantages and restrictions of the proposed and tested NINIS technique in comparison with other methods are discussed.

Numerical Simulation of Real-Time Trajectory Optimization for Helicopter Noise Abatement

This study was an attempt to obtain optimal landing approaches for helicopters to reduce ground noise impact. Simulations and real flight tests in our previous study confirmed that flights along pre-calculated optimal trajectories resulted in lower noise levels than flights along conventional approach paths. However, some experiments did not show the expected optimization effects because of unforeseen disturbances. This paper therefore improves the algorithms in order to realize practical real-time optimization, which can involve external disturbances. To validate the effect of the new method, various computer simulations were conducted under real flight experimental scenarios. The obtained optimal solutions were characterized by steep flight path angles, which can avoid the generation of loud noise, the avoidance of noise sensitive points, and short flight times. These are different from conventional landing approaches. The optimal trajectories resulted in noise reduction on the ground, which shows the effectiveness and potential of the proposed real-time trajectory optimization method.

Impulsive lunar Halo transfers using the stable manifolds and lunar flybys

Since the stable manifolds of lunar Halo orbits could not approach the Earth, direct transfers from the Earth parking orbit to the stable manifolds is impossible. Three-impulse lunar Halo transfer using the stable manifolds and lunar flybys is studied in this paper. With an escape maneuver velocity about 3.1 km/s, the spacecraft departs from the Earth parking orbit. About 3–10 days later the spacecraft arrives at the vicinity of periselenium from where the spacecraft is injected into the stable manifolds of lunar Halo orbits with a second maneuver velocity about 180–220 m/s. After about 3–20 days, the spacecraft is captured into lunar Halo orbits with a third maneuver velocity about 0–160 m/s according to the size of the objective Halo orbit. The proposed transfer to lunar Halo orbit requires much lower maneuver velocity than that of direct fast transfer, and requires much shorter flight time than that of WSB transfer to lunar Halo orbit.

Arterial blood gas and electrolyte measurement on air ambulances

Arterial blood gas and electrolyte analyses are routinely conducted for critically unwell patients in the hospital setting. Modern and portable point-of care analysers now allow these tests to be performed in the pre-hospital setting. A small number of studies have looked at the potential for performing these tests in the prehospital setting and identified that on-scene testing can alter management of these critical patients. Aims To look at the feasibility of introducing a point-of-care arterial blood gas and electrolyte analyser onto a medically-led air ambulance service. Methods A retrospective review of the mission data for Warwickshire and Northamptonshire Air Ambulance (WNAA) for all missions between 1st January 2007 and 31st December 2007 was conducted. Patients who could potentially benefit from pointof- care analysis were identified. The physical properties of the i-STAT machine were analysed, specifically the operating temperature range. Air ambulance crew members were asked for their opinions on the potential of point-of-care analysers. Results The i-STAT machine could potentially have been used in 174 out of 414 patients (42%) transferred by the air ambulance. The most common indication for use would have been head-injured patients. The operating temperature range of the point-of-care analyser (16–30°C) and the associated temperature drop when the aircraft is flying at 1000 feet means that the machine would only be functional between June and late August (assuming normal seasonal maximum temperatures). Crew members felt that due to the short flight time for primary transfer to hospital, the impact on patient outcome would not be significant for the majority of patients. Conclusions The benefit of performing point-of-care analysis on air ambulance patients remains uncertain. The operating temperature range will also limit the i-STAT machine use on air ambulances.

The Change in Structure of Taiwan's Domestic Air Market before and after Deregulation

This paper investigates the influences of deregulation on Taiwan's domestic air market, which took place in 1987. The Herfindahl-Hirschman Index, the number of effective competitors, and the concentration ratio of a defined market are used to measure the associated market structure. The market structures of three selected flight routes and the entire domestic air market of Taiwan are analysed using a time-series data set spanning 21 years. Research results indicate that the market structure indicators of all defined markets were volatile after deregulation and then became stable again, with the recent market competition being greater than it was before. This reveals that market competition increased due to deregulation – in both the entire market and the markets of specific flight routes. While the domestic air market of Taiwan is unique – with relatively short flight times and fewer numbers of airlines in the market as compared with markets that are investigated in the literature using the same indicators – the results are promising in that those indices capture the variation of Taiwan's domestic air market due to the implementation of the deregulation policy. It implies that those measures are also suitable for markets with a relatively low degree of competition or which are relatively small scale.

Monitoring of trabecular bone induced microdamage using a nonlinear wave‐coupling technique

Bone tissue contains microcracks which may affect its mechanical properties as well as the whole trabecular structure. The relationship between crack density and bone strength is nevertheless poorly understood. Efficient nonlinear (NL) ultrasound methods have been widely developed for nondestructive testing and geophysical applications to detect microdamage. Moreover it has been reported that elastic nonlinearities increase with induced damage. We propose to monitor trabecular bone microdamage using a NL wave coupling technique. Ultrasonic short bursts times of flight (TOF) are modulated as result of NL interaction with a low‐frequency (LF) wave in the medium. TOF modulation (TOFM), or propagation velocity variations, are directly related to NL elasticity variations. This technique allows measuring the instantaneous TOFM as a function of the LF pressure. It is thus possible to analyze separately elasticity variations in tension and in compression, and to distinguish the tension to compression phase from the compression to tension phase (hysteresis). In several trabecular bone samples, different TOFM amplitudes in tension and in compression are observed, probably due to microdamage. For increasing damage levels progressively induced by quasi‐static compression testing, linear and nonlinear ultrasound parameters are compared to biomechanical parameters.

Flexibility in daily travel routines causes regional variation in bird migration speed

We used novel Global Positioning System-based satellite telemetry to reconstruct daily time budgets on travelling days of a long-distance migrant, the Osprey Pandion haliaetus, to reveal how landscape affects migratory performance. We compared daily travel routines between the Ospreys' passage of Europe and the Sahara. In Europe, where feeding habitat is abundant, Ospreys fed both before-after flights and during interruptions, thus, combining migration with foraging. This resulted in a 2.7-h shorter daily flight period in Europe than in the Sahara. A calculated energy budget indicated that a 'fly-and-forage migration strategy' is favourable in Europe because associated benefits (energy intake) more than outweigh costs (reduced flight time). The much shorter flight time in Europe was the main explanation why Ospreys covered on average 78 km less distance on a travelling day in Europe than in the Sahara. In addition, there were regional differences in hourly flight speeds that are most probably the result of variation in thermal soaring conditions. We conclude that landscape properties have a profound effect on migration through regional variation in daily routines.

Effects of carotenoid supply on escape flight responses in zebra finches, Taeniopygia guttata

Dietary carotenoids perform several important roles in animals including as antioxidants, immunostimulants and pigments responsible for sexual signals. However, carotenoids may be in limited supply because of foraging constraints and/or physiological trade-offs in their utilization. Studies of birds and fish have shown that females frequently prefer to mate with carotenoid-rich males, which may serve to ensure the acquisition of a healthier mate. Evidence suggests that antioxidant and immune defences can be constrained by carotenoid availability, but we still lack information about the functional consequences of such carotenoid limitation for health, or any measure of physiological performance at the behavioural level. We tested whether carotenoid availability influenced escape flight responses in captive male zebra finches. Birds were fed a control or carotenoid-supplemented diet for 8 weeks, before measurements of escape flight responses from a release chamber after a startle stimulus. Carotenoid supplementation enhanced flight performance: carotenoid-supplemented birds had shorter flight times than controls. In addition, compared to controls, carotenoid-supplemented birds less often required a repeat startle stimulus to elicit escape flight, and emerged sooner from the release chamber after a startle stimulus. Such effects of carotenoids could be ecologically important, since flight take-off performance is thought to be an important determinant of predator evasion and foraging, and thus of survival probability and the capacity to provide parental care. We discuss various putative physiological mechanisms to explain how carotenoids may influence flight behaviour and performance.

An Investigation of Diffusion in Droplets and of Evaporation of Volatile Components into Vacuum

A numerical investigation is performed of the dynamics of diffusion in droplets and of free-molecule evaporation into vacuum of volatile components of magnesium (Mg) and zinc (Zn) from aluminum alloys. The calculations are performed in application to the conditions of my experiments in high-frequency droplet formation under conditions of centrifugal dispersion in vacuum of rotating (overloads of 70–4000) blanks by the melting method under the effect of a concentrated energy source. In view of analogy between mass transfer and heat transfer, available solutions are used in heat transfer under convection cooling of bodies with boundary conditions of the third kind. It is demonstrated that the numerical values of Biot diffusion criteria (Bi) are functions of the properties of alloy components and do not depend on the initial content of volatile components. At the droplet temperature T = 1000 K and radius R = 0.25× 10−3 m, the Biot number is Bi = 14.8 for alloying systems Al-Mg and Bi = 74.4 for Al-Zn. The solution demonstrates that the diffusion resistance within droplets causes a several-fold decrease (compared to the initial value) in the transfer of the mass of volatile component to the droplet surface (with a decrease in the flow of vapors) even for the given short time of droplet flight τ = 0.01 s corresponding to the value of the Fourier criterion Fo = Dτ/R2 = = 1.2×10−3. The final depletion of the composition of droplets of magnesium, which is estimated relative to its permissible content in the alloy according to GOST (State Standard), is about 0.07% for a D16 alloy with a wide range of variation of Mg content from 1.2 to 1.8% by mass, which may be regarded as insignificant. For an AMg6 alloy with a smaller range of variation of Mg content from 5.8 to 6.8%, the depletion is about 0.2%, which may be regarded as appreciable.

Computation of low energy Earth-to-Moon transfers with moderate flight time

We consider a problem of constructing a spacecraft transfer trajectory with low cost and moderate flight time from the Earth to the Moon. We adopt the planar circular restricted three-body problem (PCR3BP) as the spacecraft model, and reduce computation of optimal transfers to a nonlinear boundary value problem (BVP). Using a computer software called AUTO, we numerically solve the nonlinear BVP and continue its solutions to obtain optimal transfers. Especially, we find a transfer trajectory having the same cost but 22% shorter flight time or having 7.5% lower cost, compared to the traditional Hohmann type transfer. Moreover, we show that these transfers are unstable in an appropriate meaning and closely relate to chaotic dynamics of the PCR3BP.

A comparison of molecular dynamic simulations and experimental observations: the sputtering of gold {1 0 0} by 20 keV argon

In order to further illuminate the sputtering process, the bombardment of Au {1 0 0} by 20 keV Ar is investigated using molecular dynamics (MD) simulations. The MD results are compared to experimental observations discussed by M.W. Thompson in his recent review of the atomic collision cascade process [Vacuum 66 (2) (2002) 99]. In his review, Thompson explains characteristics of experimental time-of-flight (ToF) and polar distributions using ejection mechanisms. Using mechanisms deduced from the MD results the ToF distributions are divided at 70 μs with atoms sputtered by direct recoil at shorter ToF and atoms sputtered by focused collision sequences at longer ToF. Surface lens assisted focusing arises from impacts along crystal symmetry lines (slice impact points) and results in a peak at surface normal in the polar distribution. These conclusions help to clarify the experimental observations made by Thompson and contribute to the overall description of sputtering.