Apollo experience report: Lunar module environmental control subsystem

A functional description of the environmental control subsystem is presented. Development, tests, checkout, and flight experiences of the subsystem are discussed; and the design fabrication, and operational difficulties associated with the various components and subassemblies are recorded. Detailed information is related concerning design changes made to, and problems encountered with, the various elements of the subsystem, such as the thermal control water sublimator, the carbon dioxide sensing and control units, and the water section. The problems associated with water sterilization, water/glycol formulation, and materials compatibility are discussed. The corrective actions taken are described with the expection that this information may be of value for future subsystems. Although the main experiences described are problem oriented, the subsystem has generally performed satisfactorily in flight

Study of CeO2 and its native defects by density functional theory with repulsive potential

We investigated the native point defects in CeO2 by the density functional (DFT) +U method, and using a non-linear core-corrected norm-conserving Ce pseudopotential. We find the neutral oxygen vacancy (VO 0) in CeO2 to have a very low formation energy of only 0.39eV in the Opoor limit. It is a deep donor with negative U behavior, only stable in its neutral and doubly positive states. The anion Frenkel defect is found to be the lowest energy disorder defect, with a formation energy of only 2.08eV per defect site. These low formation energies arise from the improved transferability of our Ce pseudopotential for its +3 and +4 valence states. The negative U behavior of VO leads to excellent photo-catalytic behavior, while the low formation energy of the anion Frenkel defect leads to a superior oxygen storage-and-release capability.All computing facilities and calculation resources receive funding from the Research Grant Council, University Grants Committee of the HKSAR government. BH would like to thank the fund support and calculations resources all supplied by the Department of Physics and Materials Science, City University of Hong Kong.This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/jp506625h, under the title 'Study of CeO2 and Its Native Defects by Density Functional Theory with Repulsive Potential'

The screening effects of the screened exchange hybrid functional in surface systems: A case study on the CO/Pt(111) problem

The screened exchange (sX) hybrid functional has been widely used in computational material science. Although it has widely been studied in bulk systems, less is known about its functional behavior in surface systems which are crucial to many technologies such as materials synthesis and nano-electronic devices. Assessing the screening dependent functional behaviors in the surface systems is therefore important for its application in such systems. In this work, we investigate the screening effects of the sX in CO adsorption on Pt(111) surface. The differences between the sX and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functionals, and the effects of screening parameters are studied. The screening has two effects: first, the HOMO-LUMO gap is screening dependent. This affects the site preference most significantly. In this work, atop adsorption of CO/Pt(111) is predicted by the hybrid functionals with screened exchange potential. The sX(1.44) gives the largest HOMO-LUMO gap for the isolated CO molecule. The adsorption energy difference between the atop and fcc site is also the largest by the sX(1.44) which is explained by the reduced metal d states to the CO 2π* state back-donation, with stronger effect for the fcc adsorption than for the atop adsorption; second, the adsorption energy is screening dependent. This can be seen by comparing the sX(2.38) and HSE06 which have different screening strengths. They show similar surface band structures for the CO adsorption but different adsorption energies, which is explained by the stronger CO 5σ state to the metal d states donation or the effectively screened Pauli repulsion. This work underlines the screening strength as a main difference between sX and HSE06, as well as an important hybrid functional parameter for surface calculation.The author J.R. and H.L. thank EC project GRAFOL, CP-IP 285275 and EPSRC (grant reference no. EP/M009297), and Chinese Postdoctoral Science Foundation, respectively, for financial support. This work was supported by the Darwin Supercomputer of the University of Cambridge High Performance Computing Service and Tsinghua National Laboratory for Information Science and Technology.This is the final version of the article. It first appeared from the American Institute of Physics via http://dx.doi.org/10.1063/1.495403

A Parimutuel-like Mechanism from Information Aggregation: A Field Test Inside Intel

Field tests of a new Information Aggregation Mechanism (IAM) developed via laboratory experimental methods were implemented inside Intel Corporation for sales forecasting. The IAM, which incorporates selected features of parimutuel betting, is uniquely designed to collect and quantize as probability distributions any dispersed, subjectively held information that might exist. The tests demonstrate the robustness of experimental results and the practical usefulness of the IAM. The IAM yields predicted distributions of future sales that are very accurate at short horizons; indeed, more accurate than Intel's official in-house forecast 59% of the time. A symmetric game model suggests why the IAM works

Investigating Varied Pedagogical Approaches for Problem-Based Learning in a Fire Safety Engineering Course

Fire safety engineering is a critical component of a well-rounded engineering undergraduate curriculum but is understudied in the context of engineering education literature. Guided by previous work in problem-based learning, we conducted a multiple case study structured around three sections of a fire safety engineering course for students across engineering programmes. Our goal was to develop a better understanding of the impact of different pedagogical approaches on students. These approaches were chosen for study because they align with predominating approaches to industry practice in fire safety engineering. Classroom observations and student coursework from each of the three sections were used to evaluate the different approaches: (A) controlling (the specialist approach), (B) student autonomy (the generalist approach), and (C) combination strategy (autonomous/generalist and controlling/specialist). Findings confirm more autonomous/generalist approaches foster positive student experiences and outcomes, but a balance of instructional techniques is still needed. It is clear that more work needs to be done to explore engineering education in the context of fire safety engineering, and this study provides preliminary results that suggest areas for future scholarship

Two Information Aggregation Mechanisms for Predicting the Opening Weekend Box Office Revenues of Films: Boxoffice Prophecy and Guess of Guesses

Successful field tests were conducted on two new Information Aggregation Mechanisms (IAMs). The mechanisms collected information held as intuitions about opening weekend box office revenues for movies in Australia. Participants were film school students. One mechanism is similar to parimutuel betting that produces a probability distribution over box office amounts. Except for “art house films”, the predicted distribution is indistinguishable from the actual revenues. The second mechanism is based on guesses of the guesses of others and applied when incentives for accuracy could not be used. It tested well against data and contains information not encompassed by the first mechanism

Divergence and Convergence in Scarf Cycle Environments: Experiments and Predictability in the Dynamics of General Equilibrium Systems

Previous experimental work demonstrates the power of classical theories of economic dynamics to accurately characterize equilibration in multiple market systems. Building on the literature, this study examines the behavior of experimental continuous double auction markets in convergence-challenging environments identified by Scarf (1960) and Hirota (1981). The experiments provide insight into two important economic questions: (a) do markets necessarily converge to a unique interior equilibrium? and (b) which model, among a set of classical specifications, most accurately characterizes observed price dynamics? We observe excess demand driven prices spiraling outwardly away from the interior equilibrium prices as predicted by the theory of disequilibrium price dynamics. We estimate a structural model establishing that partial equilibrium dynamics characterize price changes even in an unstable general equilibrium environment. We observe linkages between excess demand in one market and price changes in another market but the sign of expected price change in a market does not depend on the magnitude of excess demand in other markets unless disequilibrium is severe

Single-particle-sensitive imaging of freely propagating ultracold atoms

We present a novel imaging system for ultracold quantum gases in expansion. After release from a confining potential, atoms fall through a sheet of resonant excitation laser light and the emitted fluorescence photons are imaged onto an amplified CCD camera using a high numerical aperture optical system. The imaging system reaches an extraordinary dynamic range, not attainable with conventional absorption imaging. We demonstrate single-atom detection for dilute atomic clouds with high efficiency where at the same time dense Bose-Einstein condensates can be imaged without saturation or distortion. The spatial resolution can reach the sampling limit as given by the 8 \mu m pixel size in object space. Pulsed operation of the detector allows for slice images, a first step toward a 3D tomography of the measured object. The scheme can easily be implemented for any atomic species and all optical components are situated outside the vacuum system. As a first application we perform thermometry on rubidium Bose-Einstein condensates created on an atom chip.Comment: 24 pages, 10 figures. v2: as publishe