J. -O. Hansen - NASA Goddard Institute for Space Studies and Columbia University Earth Institute

J. -O. Hansen
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J. -O. Hansen
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NASA Goddard Institute for Space Studies and Columbia University Earth Institute
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Physics - Chemical Physics (7)
 
Nuclear Experiment (7)
 
Mathematics - Information Theory (6)
 
Computer Science - Information Theory (6)
 
Physics - Soft Condensed Matter (5)
 
Physics - Mesoscopic Systems and Quantum Hall Effect (4)
 
General Relativity and Quantum Cosmology (4)
 
Physics - Computational Physics (4)
 
Mathematics - Algebraic Geometry (4)
 
Computer Science - Sound (4)
 
Physics - Materials Science (3)
 
High Energy Physics - Theory (3)
 
Computer Science - Computation and Language (3)
 
High Energy Physics - Experiment (3)
 
Physics - Atmospheric and Oceanic Physics (3)
 
Mathematics - Numerical Analysis (3)
 
Physics - Plasma Physics (2)
 
High Energy Physics - Phenomenology (2)
 
Physics - Accelerator Physics (2)
 
Physics - Instrumentation and Detectors (1)
 
Physics - Fluid Dynamics (1)
 
Physics - Atomic and Molecular Clusters (1)
 
Physics - Biological Physics (1)
 
Mathematics - Optimization and Control (1)
 
Quantum Physics (1)
 
Computer Science - Learning (1)
 
Statistics - Machine Learning (1)
 
Quantitative Biology - Biomolecules (1)
 
Physics - Data Analysis; Statistics and Probability (1)

Publications Authored By J. -O. Hansen

Peer-Led Team Learning (PLTL) is a learning methodology where a peer-leader co-ordinate a small-group of students to collaboratively solve technical problems. PLTL have been adopted for various science, engineering, technology and maths courses in several US universities. This paper proposed and evaluated a speech system for behavioral analysis of PLTL groups. Read More

$[Background]$ Measurements of the neutron charge distribution are made difficult by the fact that, with no net charge, the neutron electric form factor, $G^n_E$, is generally much smaller than the magnetic form factor, $G^n_M$. In addition, measurements of these form factors must use nuclear targets which requires accurately accounting for nuclear effects. $[Method]$ The inclusive quasi-elastic reaction $^3\overrightarrow{\rm{He}}(\overrightarrow{e},e')$ was measured at Jefferson Lab. Read More

Long linear codes constructed from toric varieties over finite fields, their multiplicative structure and decoding. The main theme is the inherent multiplicative structure on toric codes. The multiplicative structure allows for \emph{decoding}, resembling the decoding of Reed-Solomon codes and aligns with decoding by error correcting pairs. Read More

Demand response represents a significant but largely untapped resource that can greatly enhance the flexibility and reliability of power systems. This paper proposes a hierarchical control framework to facilitate the integrated coordination between distributed energy resources and demand response. The proposed framework consists of coordination and device layers. Read More

The gravitational radiation capture between unequal mass black holes without spins has been investigated with numerical relativistic simulations, and the results are compared with the Post-Newtonian (PN) approximations. We adopt the parabolic approximation which assumes that the gravitational wave radiation from a weakly hyperbolic orbit is the same as that from the parabolic orbit having the same pericenter distance. Using the radiated energies from the parabolic orbit simulations, we have obtained the impact parameters ($b$) of the gravitational radiation captures for weakly hyperbolic orbits as a function of initial energy. Read More

In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration gradient is modelled through Fick's law, and a new constitutive relation for the mass flux due to the potential gradient is proposed. Read More

The charge and magnetic form factors, FC and FM, of 3He have been extracted in the kinematic range 25 fm-2 < Q2 < 61 fm-2 from elastic electron scattering by detecting 3He recoil nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility at Jefferson Lab. The measurements are indicative of a second diffraction minimum for the magnetic form factor, which was predicted in the Q2 range of this experiment, and of a continuing diffractive structure for the charge form factor. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the three-body nuclear problem. Read More

This document briefly describes the systems submitted by the Center for Robust Speech Systems (CRSS) from The University of Texas at Dallas (UTD) to the 2016 National Institute of Standards and Technology (NIST) Speaker Recognition Evaluation (SRE). We developed several UBM and DNN i-Vector based speaker recognition systems with different data sets and feature representations. Given that the emphasis of the NIST SRE 2016 is on language mismatch between training and enrollment/test data, so-called domain mismatch, in our system development we focused on: (1) using unlabeled in-domain data for centralizing data to alleviate the domain mismatch problem, (2) finding the best data set for training LDA/PLDA, (3) using newly proposed dimension reduction technique incorporating unlabeled in-domain data before PLDA training, (4) unsupervised speaker clustering of unlabeled data and using them alone or with previous SREs for PLDA training, (5) score calibration using only unlabeled data and combination of unlabeled and development (Dev) data as separate experiments. Read More

Most existing Neural Machine Translation models use groups of characters or whole words as their unit of input and output. We propose a model with a hierarchical char2word encoder, that takes individual characters both as input and output. We first argue that this hierarchical representation of the character encoder reduces computational complexity, and show that it improves translation performance. Read More

Peer-Led Team Learning (PLTL) is a structured learning model where a team leader is appointed to facilitate collaborative problem solving among students for Science, Technology, Engineering and Mathematics (STEM) courses. This paper presents an informed HMM-based speaker diarization system. The minimum duration of short conversationalturns and number of participating students were fed as side information to the HMM system. Read More

In language recognition, the task of rejecting/differentiating closely spaced versus acoustically far spaced languages remains a major challenge. For confusable closely spaced languages, the system needs longer input test duration material to obtain sufficient information to distinguish between languages. Alternatively, if languages are distinct and not acoustically/linguistically similar to others, duration is not a sufficient remedy. Read More

Global temperature is a useful metric for global climate that helps define the potential amplitude of slow climate feedbacks, such as ice sheet melt and sea level rise. Annual temperature in 2016, enhanced by the 2015-2016 El Nino, was +1.3 degC relative to 1880-1920. Read More

We examine overlapping clustering schemes with functorial constraints, in the spirit of Carlsson--Memoli. This avoids issues arising from the chaining required by partition-based methods. Our principal result shows that any clustering functor is naturally constrained to refine single-linkage clusters and be refined by maximal-linkage clusters. Read More

We characterize the equation of state for a simple three-dimensional DNA hairpin model using a Metropolis Monte Carlo algorithm. This algorithm was run at constant temperature and fixed separation between the terminal ends of the strand. From the equation of state, we compute the compressibility, thermal expansion coefficient, and specific heat along with adiabatic path. Read More

Peer-led team learning (PLTL) is a model for teaching STEM courses where small student groups meet periodically to collaboratively discuss coursework. Automatic analysis of PLTL sessions would help education researchers to get insight into how learning outcomes are impacted by individual participation, group behavior, team dynamics, etc.. Read More

Superregular matrices have the property that all of their submatrices, which can be full rank are so. Lower triangular superregular matrices are useful for e.g. Read More

In 2006, a novel cobalt-based superalloy was discovered [1] with mechanical properties better than some conventional nickel-based superalloys. As with conventional superalloys, its high performance arises from the precipitate-hardening effect of a coherent L1$_2$ phase, which is in two-phase equilibrium with the fcc matrix. Inspired by this unexpected discovery of an L1$_2$ ternary phase, we performed a first-principles search through 2224 ternary metallic systems for analogous precipitate-hardening phases of the form $X_{3}$[$A_{0. Read More

One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in mono-alcohols. Read More

We use numerical climate simulations, paleoclimate data, and modern observations to study the effect of growing ice melt from Antarctica and Greenland. Meltwater tends to stabilize the ocean column, inducing amplifying feedbacks that increase subsurface ocean warming and ice shelf melting. Cold meltwater and induced dynamical effects cause ocean surface cooling in the Southern Ocean and North Atlantic, thus increasing Earth's energy imbalance and heat flux into most of the global ocean's surface. Read More

Systems of Cooee bitumen and water up to 4 mass % are studied by molecular dynamics simula- tions. The cohesive energy density of the system is shown to decrease with an increasing water content. This decrease is due mainly to an increase in potential energy which is not high enough to counterbalance the increase in volume due to the addition of water. Read More

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the world's first proton driven plasma wakefield acceleration experiment. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV/c proton beam bunches from the SPS. Read More

2015Nov

This report describes the conceptual steps in reaching the design of the AWAKE experiment currently under construction at CERN. We start with an introduction to plasma wakefield acceleration and the motivation for using proton drivers. We then describe the self-modulation instability --- a key to an early realization of the concept. Read More

We discuss the plastic behavior of an amorphous matrix reinforced by hard particles. A mesoscopic depinning-like model accounting for Eshelby elastic interactions is implemented. Only the effect of a plastic disorder is considered. Read More

The original frequentist approach for computing confidence intervals involves the construction of the confidence belt which provides a mapping of the observation in data into a subset of values for the parameter. There are different prescriptions for constructing the confidence belt, here we use the one provided by Feldman and Cousins. Alternative methods based on the frequentist idea exist, including the delta likelihood method, the $CL_s$ method and a method here referred to as the $p$-value method, which have all been commonly used in high energy experiments. Read More

We investigate the relation between the existence of mass inflation and model parameters of string-inspired gravity models. In order to cover various models, we investigate a Brans-Dicke theory that is coupled to a U(1) gauge field. By tuning a model parameter that decides the coupling between the Brans-Dicke field and the electromagnetic field, we can make both of models such that the Brans-Dicke field is biased toward strong or weak coupling directions after gravitational collapses. Read More

RUMD is a general purpose, high-performance molecular dynamics (MD) simulation package running on graphical processing units (GPU's). RUMD addresses the challenge of utilizing the many-core nature of modern GPU hardware when simulating small to medium system sizes (roughly from a few thousand up to hundred thousand particles). It has a performance that is comparable to other GPU-MD codes at large system sizes and substantially better at smaller sizes. Read More

This paper introduces the fundamental continuum theory governing momentum transport in isotropic nanofluidic flows. The theory is an extension to the classical Navier-Stokes equation, which includes coupling between translational and rotational degrees of freedom, as well as non-local response functions that incorporates spatial correlations. The continuum theory is compared with molecular dynamics simulation data for both relaxation processes and fluid flows showing excellent agreement on the nanometer length scale. Read More

Tin-containing nanocrystals, embedded in silicon, have been fabricated by growing an epitaxial layer of Si_{1-x-y}Sn_{x}C_{y}, where x = 1.6 % and y = 0.04 %, followed by annealing at various temperatures ranging from 650 to 900 degrees C. Read More

We construct linear network codes utilizing algebraic curves over finite fields and certain associated Riemann-Roch spaces and present methods to obtain their parameters. In particular we treat the Hermitian curve and the curves associated with the Suzuki and Ree groups all having the maximal number of points for curves of their respective genera. Linear network coding transmits information in terms of a basis of a vector space and the information is received as a basis of a possibly altered vector space. Read More

Freestanding graphene membranes were functionalized with SnO2 nanoparticles. A detailed procedure providing uniform coverage and chemical synthesis is presented. Elemental composition was determined using scanning electron microscopy combined with energy dispersive X-ray analysis. Read More

New results are reported from a measurement of $\pi^0$ electroproduction near threshold using the $p(e,e^{\prime} p)\pi^0$ reaction. The experiment was designed to determine precisely the energy dependence of $s-$ and $p-$wave electromagnetic multipoles as a stringent test of the predictions of Chiral Perturbation Theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. Read More

The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences and pressure of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. Read More

The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. Read More

A general theory for constructing linear secret sharing schemes over a finite field $\Fq$ from toric varieties is introduced. The number of players can be as large as $(q-1)^r-1$ for $r\geq 1$. We present general methods for obtaining the reconstruction and privacy thresholds as well as conditions for multiplication on the associated secret sharing schemes. Read More

Asphaltene and smaller aromatic molecules tend to form linear nanoaggregates in bitumen.Over the years bitumen undergoes chemical aging and during this process, the size of the nanoaggregate increases. This increase is associated with an increase in viscosity and brittleness of the bitumen, eventually leading to road deterioration. Read More

We investigate gravitational collapses of charged black holes in string-inspired gravity models, including dilaton gravity and braneworld model, as well as f(R) gravity and the ghost limit. If we turn on gauge coupling, the causal structures and the responses of the Brans-Dicke field depend on the coupling between the charged matter and the Brans-Dicke field. For Type IIA inspired models, a Cauchy horizon exists, while there is no Cauchy horizon for Type I or Heterotic inspired models. Read More

2014May
Affiliations: 1Jefferson Lab Hall A Collaboration, 2Jefferson Lab Hall A Collaboration, 3Jefferson Lab Hall A Collaboration, 4Jefferson Lab Hall A Collaboration, 5Jefferson Lab Hall A Collaboration, 6Jefferson Lab Hall A Collaboration, 7Jefferson Lab Hall A Collaboration, 8Jefferson Lab Hall A Collaboration, 9Jefferson Lab Hall A Collaboration, 10Jefferson Lab Hall A Collaboration, 11Jefferson Lab Hall A Collaboration, 12Jefferson Lab Hall A Collaboration, 13Jefferson Lab Hall A Collaboration, 14Jefferson Lab Hall A Collaboration, 15Jefferson Lab Hall A Collaboration, 16Jefferson Lab Hall A Collaboration, 17Jefferson Lab Hall A Collaboration, 18Jefferson Lab Hall A Collaboration, 19Jefferson Lab Hall A Collaboration, 20Jefferson Lab Hall A Collaboration, 21Jefferson Lab Hall A Collaboration, 22Jefferson Lab Hall A Collaboration, 23Jefferson Lab Hall A Collaboration, 24Jefferson Lab Hall A Collaboration, 25Jefferson Lab Hall A Collaboration, 26Jefferson Lab Hall A Collaboration, 27Jefferson Lab Hall A Collaboration, 28Jefferson Lab Hall A Collaboration, 29Jefferson Lab Hall A Collaboration, 30Jefferson Lab Hall A Collaboration, 31Jefferson Lab Hall A Collaboration, 32Jefferson Lab Hall A Collaboration, 33Jefferson Lab Hall A Collaboration, 34Jefferson Lab Hall A Collaboration, 35Jefferson Lab Hall A Collaboration, 36Jefferson Lab Hall A Collaboration, 37Jefferson Lab Hall A Collaboration, 38Jefferson Lab Hall A Collaboration, 39Jefferson Lab Hall A Collaboration, 40Jefferson Lab Hall A Collaboration, 41Jefferson Lab Hall A Collaboration, 42Jefferson Lab Hall A Collaboration, 43Jefferson Lab Hall A Collaboration, 44Jefferson Lab Hall A Collaboration, 45Jefferson Lab Hall A Collaboration, 46Jefferson Lab Hall A Collaboration, 47Jefferson Lab Hall A Collaboration, 48Jefferson Lab Hall A Collaboration, 49Jefferson Lab Hall A Collaboration, 50Jefferson Lab Hall A Collaboration, 51Jefferson Lab Hall A Collaboration, 52Jefferson Lab Hall A Collaboration, 53Jefferson Lab Hall A Collaboration, 54Jefferson Lab Hall A Collaboration, 55Jefferson Lab Hall A Collaboration, 56Jefferson Lab Hall A Collaboration, 57Jefferson Lab Hall A Collaboration, 58Jefferson Lab Hall A Collaboration, 59Jefferson Lab Hall A Collaboration, 60Jefferson Lab Hall A Collaboration, 61Jefferson Lab Hall A Collaboration, 62Jefferson Lab Hall A Collaboration, 63Jefferson Lab Hall A Collaboration, 64Jefferson Lab Hall A Collaboration, 65Jefferson Lab Hall A Collaboration, 66Jefferson Lab Hall A Collaboration, 67Jefferson Lab Hall A Collaboration, 68Jefferson Lab Hall A Collaboration, 69Jefferson Lab Hall A Collaboration, 70Jefferson Lab Hall A Collaboration, 71Jefferson Lab Hall A Collaboration, 72Jefferson Lab Hall A Collaboration, 73Jefferson Lab Hall A Collaboration, 74Jefferson Lab Hall A Collaboration, 75Jefferson Lab Hall A Collaboration, 76Jefferson Lab Hall A Collaboration, 77Jefferson Lab Hall A Collaboration, 78Jefferson Lab Hall A Collaboration, 79Jefferson Lab Hall A Collaboration, 80Jefferson Lab Hall A Collaboration, 81Jefferson Lab Hall A Collaboration, 82Jefferson Lab Hall A Collaboration, 83Jefferson Lab Hall A Collaboration, 84Jefferson Lab Hall A Collaboration, 85Jefferson Lab Hall A Collaboration, 86Jefferson Lab Hall A Collaboration, 87Jefferson Lab Hall A Collaboration, 88Jefferson Lab Hall A Collaboration, 89Jefferson Lab Hall A Collaboration, 90Jefferson Lab Hall A Collaboration, 91Jefferson Lab Hall A Collaboration, 92Jefferson Lab Hall A Collaboration, 93Jefferson Lab Hall A Collaboration, 94Jefferson Lab Hall A Collaboration, 95Jefferson Lab Hall A Collaboration, 96Jefferson Lab Hall A Collaboration, 97Jefferson Lab Hall A Collaboration, 98Jefferson Lab Hall A Collaboration

In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei can provide information on the details of the effective hyperon-nucleon interaction. Electroproduction of the hypernucleus Lambda-9Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a 9Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. Read More

The solution, $x$, of the linear system of equations $A x\approx b$ arising from the discretization of an ill-posed integral equation with a square integrable kernel $H(s,t)$ is considered. The Tikhonov regularized solution $ x(\lambda)$ is found as the minimizer of $J( x)=\{ \|A x - b\|_2^2 + \lambda^2 \|L x\|_2^2\}$. $ x(\lambda)$ depends on regularization parameter $\lambda$ that trades off the data fidelity, and on the smoothing norm determined by $L$. Read More

The charge form factor of $^$4He has been extracted in the range 29 fm$^{-2}$ $\le Q^2 \le 77$ fm$^{-2}$ from elastic electron scattering, detecting $^4$He nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility of Jefferson Lab. The results are in qualitative agreement with realistic meson-nucleon theoretical calculations. The data have uncovered a second diffraction minimum, which was predicted in the $Q^2$ range of this experiment, and rule out conclusively long-standing predictions of dimensional scaling of high-energy amplitudes using quark counting. Read More

The inverse problem associated with electrochemical impedance spectroscopy requiring the solution of a Fredholm integral equation of the first kind is considered. If the underlying physical model is not clearly determined, the inverse problem needs to be solved using a regularized linear least squares problem that is obtained from the discretization of the integral equation. For this system, it is shown that the model error can be made negligible by a change of variables and by extending the effective range of quadrature. Read More

This document contains supplementary derivations and discussions not provided in the submitted paper arXiv:1309.4498 with the same title. Additional results for the NCP and L-Curve comparisons with higher noise levels are given. Read More

The mixed-field orientation of an asymmetric-rotor molecule with its permanent dipole moment non-parallel to the principal axes of polarizability is investigated experimentally and theoretically. We find that for the typical case of a strong, nonresonant laser field and a weak static electric field complete 3D orientation is induced if the laser field is elliptically polarized and if its major and minor polarization axes are not parallel to the static field. For a linearly polarized laser field solely the dipole moment component along the most polarizable axis of the molecule is relevant resulting in 1D orientation even when the laser polarization and the static field are non parallel. Read More

We study chemical aging in "COOEE bitumen" using molecular dynamic simulations. This model bitumen is composed of four realistic molecule types: saturated hydrocarbon, resinous oil, resin, and asphaltene. The aging reaction is modelled by the chemical reaction: "2 resins $\rightarrow$ 1 asphaltene". Read More

We propose a four-component molecular model of bitumen. The model includes realistic chemical constituents and introduces a coarse-graining level that suppresses the highest frequency modes. Molecular dynamics simulations of the model are being carried out using Graphic-Processor-Units based software in time spans in order of microseconds, and this enables the study of slow relaxation processes characterizing bitumen. Read More

In this paper, we investigate the dynamics inside and outside of black-branes in anti de Sitter space by numerical simulations using double-null formalism. We prepare a charged planar matter shell which, due to a negative cosmological constant, collapses and dynamically forms a black-brane with an apparent horizon, a singularity and a Cauchy horizon. The gravitational collapse cannot form a naked overcharged black-brane and hence weak cosmic censorship is safe. Read More

We present a general theory to obtain linear network codes utilizing forms and obtain explicit families of equidimensional vector spaces, in which any pair of distinct vector spaces intersect in the same small dimension. The theory is inspired by the methods of the author utilizing the osculating spaces of Veronese varieties. Linear network coding transmits information in terms of a basis of a vector space and the information is received as a basis of a possibly altered vector space. Read More

2012Nov
Affiliations: 1NASA Goddard Institute for Space Studies and Columbia University Earth Institute, 2NASA Goddard Institute for Space Studies and Columbia University Earth Institute, 3NASA Goddard Institute for Space Studies and Columbia University Earth Institute, 4NASA Goddard Institute for Space Studies and Columbia University Earth Institute

Cenozoic temperature, sea level and CO2 co-variations provide insights into climate sensitivity to external forcings and sea level sensitivity to climate change. Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise paleoclimate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity 3 +/- 1{\deg}C for 4 W/m2 CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Read More

We present a general theory to obtain good linear network codes utilizing the osculating nature of algebraic varieties. In particular, we obtain from the osculating spaces of Veronese varieties explicit families of equidimensional vector spaces, in which any pair of distinct vector spaces intersects in the same dimension. Linear network coding transmits information in terms of a basis of a vector space and the information is received as a basis of a possible altered vector space. Read More

Linear network coding transmits information in terms of a basis of a vector space and the information is received as a basis of a possible altered vectorspace. Ralf Koetter and Frank R. Kschischang in Coding for errors and erasures in random network coding (IEEE Transactions on Information Theory, vol. Read More