Evaluation of on-board hydrogen storage methods for hypersonic vehicles

Hydrogen is the foremost candidate as a fuel for use in high speed transport. Since any aircraft moving at hypersonic speeds must have a very slender body, means of decreasing the storage volume requirements below that for liquid hydrogen are needed. The total performance of the hypersonic plane needs to be considered for the evaluation of candidate fuel and storage systems. To accomplish this, a simple model for the performance of a hypersonic plane is presented. To allow for the use of different engines and fuels during different phases of flight, the total trajectory is divided into three phases: subsonic-supersonic, hypersonic and rocket propulsion phase. The fuel fraction for the first phase is found be a simple energy balance using an average thrust to drag ratio for this phase. The hypersonic flight phase is investigated in more detail by taking small altitude increments. This approach allowed the use of flight profiles other than the constant dynamic pressure flight. The effect of fuel volume on drag, structural mass and tankage mass was introduced through simplified equations involving the characteristic dimension of the plane. The propellant requirement for the last phase is found by employing the basic rocket equations. The candidate fuel systems such as the cryogenic fuel combinations and solid and liquid endothermic hydrogen generators are first screened thermodynamically with respect to their energy densities and cooling capacities and then evaluated using the above model

The Relationship between Event-Based Prospective Memory and Ongoing Task Performance in Chimpanzees (Pan troglodytes)

Prospective memory is remembering to do something at a future time. A growing body of research supports that prospective memory may exist in nonhuman animals, but the methods used to test nonhuman prospective memory differ from those used with humans. The current work tests prospective memory in chimpanzees using a method that closely approximates a typical human paradigm. In these experiments, the prospective memory cue was embedded within an ongoing task. Tokens representing food items could be used in one of two ways: in a matching task with pictures of items (the ongoing task) or to request a food item hidden in a different location at the beginning of the trial. Chimpanzees had to disengage from the ongoing task in order to use the appropriate token to obtain a higher preference food item. In Experiment 1, chimpanzees effectively matched tokens to pictures, when appropriate, and disengaged from the ongoing task when the token matched the hidden item. In Experiment 2, performance did not differ when the target item was either hidden or visible. This suggested no effect of cognitive load on either the prospective memory task or the ongoing task, but performance was near ceiling, which may have contributed to this outcome. In Experiment 3, we created a more challenging version of the task. More errors on the matching task occurred before the prospective memory had been carried out, and this difference seemed to be limited to the hidden condition. This finding parallels results from human studies and suggests that working memory load and prospective memory may have a similar relationship in nonhuman primates

Do Social Conditions Affect Capuchin Monkeys’ (Cebus apella) Choices in a Quantity Judgment Task?

Beran et al. (2012) reported that capuchin monkeys closely matched the performance of humans in a quantity judgment test in which information was incomplete but a judgment still had to be made. In each test session, subjects first made quantity judgments between two known options. Then, they made choices where only one option was visible. Both humans and capuchin monkeyswere guided by past outcomes, as they shifted from selecting a known option to selecting an unknown option at the point at which the known option went from being more than the average rate of return to less than the average rate of return from earlier choices in the test session. Here, we expanded this assessment of what guides quantity judgment choice behavior in the face of incomplete information to include manipulations to the unselected quantity.We manipulated the unchosen set in two ways: first, we showed the monkeys what they did not get (the unchosen set), anticipating that “losses” would weigh heavily on subsequent trials in which the same known quantity was presented. Second, we sometimes gave the unchosen set to another monkey, anticipating that this social manipulation might influence the risk-taking responses of the focal monkey when faced with incomplete information. However, neither manipulation caused difficulty for the monkeys who instead continued to use the rational strategy of choosing known sets when they were as large as or larger than the average rate of return in the session, and choosing the unknown (riskier) set when the known set was not sufficiently large. As in past experiments, this was true across a variety of daily ranges of quantities, indicating that monkeys were not using some absolute quantity as a threshold for selecting (or not) the known set, but instead continued to use the daily average rate of return to determine when to choose the known versus the unknown quantity

How Is Chimpanzee Self-Control Influenced by Social Setting?

Self-control is often required in natural situations involving interactions with other individuals, and personal self-control can be compromised if other individuals act impulsively. In this study, we tested self-control in pairs of chimpanzees in a variety of settings where at least one chimpanzee of each pair performed an established test for self-control in which candies accumulated one at time as long as the chimpanzee did not eat any of them. When tested alone, some chimpanzees exhibited greater self-control as compared to when tested alongside a chimpanzee that independently performed the same type of test. However, when the nonfocal animal freely consumed rewards while the focal chimpanzee performed the accumulation task, the self-control of some focal chimpanzees was elevated as compared to when working alone. Finally, when the focal and nonfocal animals worked jointly on the same test and the number of rewards accumulated was dependent on both animals’ continued ability to inhibit eating the items, chimpanzees performed the same when housed together or in adjacent enclosures. On the whole, the effects of social setting were modest, but these results may relate to the literature on vicarious depletion of self-control, and they present interesting avenues for future research

Biobanking, consent, and commercialization in international genetics research: the Type 1 Diabetes Genetics Consortium

Background and Purpose This article describes several ethical, legal, and social issues typical of international genetics biobanking, as encountered in the Type 1 Diabetes Genetics Consortium (T1DGC)

Single neutral pion production by charged-current νˉμ\bar{\nu}_\mu interactions on hydrocarbon at ⟨Eν⟩=\langle E_\nu \rangle = 3.6 GeV

Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the \minerva detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for $\bar{\nu}_e$ appearance oscillation experiments. The differential cross sections for $\pi^0$ momentum and production angle, for events with a single observed $\pi^0$ and no charged pions, are presented and compared to model predictions. These results comprise the first measurement of the $\pi^0$ kinematics for this process.Comment: 6 pages, 5 figures, submitted to Physics Letters

Direct Measurement of Nuclear Dependence of Charged Current Quasielastic-like Neutrino Interactions using MINERvA

Charged-current $\nu_{\mu}$ interactions on carbon, iron, and lead with a final state hadronic system of one or more protons with zero mesons are used to investigate the influence of the nuclear environment on quasielastic-like interactions. The transfered four-momentum squared to the target nucleus, $Q^2$, is reconstructed based on the kinematics of the leading proton, and differential cross sections versus $Q^2$ and the cross-section ratios of iron, lead and carbon to scintillator are measured for the first time in a single experiment. The measurements show a dependence on atomic number. While the quasielastic-like scattering on carbon is compatible with predictions, the trends exhibited by scattering on iron and lead favor a prediction with intranuclear rescattering of hadrons accounted for by a conventional particle cascade treatment. These measurements help discriminate between different models of both initial state nucleons and final state interactions used in the neutrino oscillation experiments

Reducing model bias in a deep learning classifier using domain adversarial neural networks in the MINERvA experiment

We present a simulation-based study using deep convolutional neural networks (DCNNs) to identify neutrino interaction vertices in the MINERvA passive targets region, and illustrate the application of domain adversarial neural networks (DANNs) in this context. DANNs are designed to be trained in one domain (simulated data) but tested in a second domain (physics data) and utilize unlabeled data from the second domain so that during training only features which are unable to discriminate between the domains are promoted. MINERvA is a neutrino-nucleus scattering experiment using the NuMI beamline at Fermilab. $A$-dependent cross sections are an important part of the physics program, and these measurements require vertex finding in complicated events. To illustrate the impact of the DANN we used a modified set of simulation in place of physics data during the training of the DANN and then used the label of the modified simulation during the evaluation of the DANN. We find that deep learning based methods offer significant advantages over our prior track-based reconstruction for the task of vertex finding, and that DANNs are able to improve the performance of deep networks by leveraging available unlabeled data and by mitigating network performance degradation rooted in biases in the physics models used for training.Comment: 41 page