9,863 research outputs found
Elaborator reflection : extending Idris in Idris
Many programming languages and proof assistants are defined by elaboration from a high-level language with a great deal of implicit information to a highly explicit core language. In many advanced languages, these elaboration facilities contain powerful tools for program construction, but these tools are rarely designed to be repurposed by users. We describe elaborator reflection, a paradigm for metaprogramming in which the elaboration machinery is made directly available to metaprograms, as well as a concrete realization of elaborator reflection in Idris, a functional language with full dependent types. We demonstrate the applicability of Idris’s reflected elaboration framework to a number of realistic problems, we discuss the motivation for the specific features of its design, and we explore the broader meaning of elaborator reflection as it can relate to other languages.Postprin
Reliability Testing of AlGaN/GaN HEMTs Under Multiple Stressors
We performed an experiment on AlGaN/GaN HEMTs with high voltage and high power as stressors. We found that devices tested under high power generally degraded more than those tested under high voltage. In particular, the high-voltage-tested devices did not degrade significantly as suggested by some papers in the literature. The same papers in the literature also suggest that high voltages cause cracks and pits. However, the high-voltage-tested devices in this study do not exhibit cracks or pits in TEM images, while the high-power-tested devices exhibit pits
Linear response functions for a vibrational configuration interaction state
Linear response functions are implemented for a vibrational configuration interaction state allowing accurate analytical calculations of pure vibrational contributions to dynamical polarizabilities. Sample calculations are presented for the pure vibrational contributions to the polarizabilities of water and formaldehyde. We discuss the convergence of the results with respect to various details of the vibrational wave function description as well as the potential and property surfaces. We also analyze the frequency dependence of the linear response function and the effect of accounting phenomenologically for the finite lifetime of the excited vibrational states. Finally, we compare the analytical response approach to a sum-over-states approac
Scaling K2. I. Revised Parameters for 222,088 K2 Stars and a K2 Planet Radius Valley at 1.9 R_⊕
Previous measurements of stellar properties for K2 stars in the Ecliptic Plane Input Catalog largely relied on photometry and proper motion measurements, with some added information from available spectra and parallaxes. Combining Gaia DR2 distances with spectroscopic measurements of effective temperatures, surface gravities, and metallicities from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) DR5, we computed updated stellar radii and masses for 26,838 K2 stars. For 195,250 targets without a LAMOST spectrum, we derived stellar parameters using random forest regression on photometric colors trained on the LAMOST sample. In total, we measured spectral types, effective temperatures, surface gravities, metallicities, radii, and masses for 222,088 A, F, G, K, and M-type K2 stars. With these new stellar radii, we performed a simple reanalysis of 299 confirmed and 517 candidate K2 planet radii from Campaigns 1–13, elucidating a distinct planet radius valley around 1.9 R_⊕, a feature thus far only conclusively identified with Kepler planets, and tentatively identified with K2 planets. These updated stellar parameters are a crucial step in the process toward computing K2 planet occurrence rates
An Experimental Study of the Effects of Modularity on Resource Consumption in Software Development
Many authors have encouraged the use of modular programming techniques in software development. In fact, there is almost total agreement within industrial and academic circles that modularity is a desirable feature of any software package. Unfortunately, the desirability of modular design is almost always voiced without support from experimental evidence.
This paper consists of an experiment comparing the resource consumption of programmers based on the modularity practices employed during the design and programming phases of software development. The experiment tests the effectiveness of modularity in reducing psychological complexity of software.
The results of the research show that in some cases there is indeed a difference in resource consumption between the modularity practices tested. However, the stated benefits of modularity did not carry over to the design and programming phases of software development. The use of modularity seemed, in fact, to increase development costs in some cases
Toward a Better Understanding of the Effects of Hindrance and Challenge Stressors on Work Behavior
This study investigated the processes whereby hindrance and challenge stressors may affect work behavior. Three mechanisms were examined to explain the differential effects these stressors have demonstrated: job satisfaction, strains, and work self-efficacy. A model is proposed in which both types of stressors will result in increases in strains, but that job satisfaction is primarily involved in the relationship between hindrance stressors and citizenship behavior, and efficacy is involved in the relationship between challenge stressors and job performance. Although the results generally supported the dual-stressor framework showing meaningful relationships to the work outcomes through the proposed processes, the link between work self-efficacy and job performance was not significant. This model was analyzed using multi-source data collected from 143 employees from a variety of organizational settings. Implications for the conceptualization of stressors and the development of interventions are discussed
Nonlinear ac conductivity of one-dimensional Mott insulators
We discuss a semiclassical calculation of low energy charge transport in
one-dimensional (1d) insulators with a focus on Mott insulators, whose charge
degrees of freedom are gapped due to the combination of short range
interactions and a periodic lattice potential. Combining RG and instanton
methods, we calculate the nonlinear ac conductivity and interpret the result in
terms of multi-photon absorption. We compare the result of the semiclassical
calculation for interacting systems to a perturbative, fully quantum mechanical
calculation of multi-photon absorption in a 1d band insulator and find good
agreement when the number of simultaneously absorbed photons is large.Comment: Dedicated to Thomas Nattermann on the occasion of his 60th birthday.
To appear in JSTAT. 5 pages, 2 figure
Free charges versus excitons: photoluminescence investigation of InGaN/GaN multiple quantum well nanorods and their planar counterparts
InGaN/GaN multiple quantum well (MQW) nanorods have demonstrated significantly improved optical and electronic properties compared to their planar counterparts. However, the exact nature of the processes whereby nanorod structures impact the optical properties of quantum wells is not well understood, even though a variety of mechanisms have been proposed. We performed nanoscale spatially resolved, steady-state, and time-resolved photoluminescence (PL) experiments confirming that photoexcited electrons and holes are strongly bound by Coulomb interactions (i.e., excitons) in planar MQWs due to the large exciton binding energy in InGaN quantum wells. In contrast, free electron–hole recombination becomes the dominant mechanism in nanorods, which is ascribed to efficient exciton dissociation. The nanorod sidewall provides an effective pathway for exciton dissociation that significantly improves the optical performance of InGaN/GaN MQWs. We also confirm that surface treatment of nanorod sidewalls has an impact on exciton dissociation. Our results provide new insights into excitonic and charge carrier dynamics of quantum confined materials as well as the influence of surface states
Strangelet dwarfs
If the surface tension of quark matter is low enough, quark matter is not
self bound. At sufficiently low pressure and temperature, it will take the form
of a crystal of positively charged strangelets in a neutralizing background of
electrons. In this case there will exist, in addition to the usual family of
strange stars, a family of low-mass large-radius objects analogous to white
dwarfs, which we call "strangelet dwarfs". Using a generic parametrization of
the equation of state of quark matter, we calculate the mass-radius
relationship of these objects.Comment: 10 pages, LaTeX, added discussion of CFL phase and strangelet
pollution, version to appear in journal. arXiv admin note: text overlap with
arXiv:0808.067
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