1,871 research outputs found
Geometric approach to Fletcher's ideal penalty function
Original article can be found at: www.springerlink.com Copyright Springer. [Originally produced as UH Technical Report 280, 1993]In this note, we derive a geometric formulation of an ideal penalty function for equality constrained problems. This differentiable penalty function requires no parameter estimation or adjustment, has numerical conditioning similar to that of the target function from which it is constructed, and also has the desirable property that the strict second-order constrained minima of the target function are precisely those strict second-order unconstrained minima of the penalty function which satisfy the constraints. Such a penalty function can be used to establish termination properties for algorithms which avoid ill-conditioned steps. Numerical values for the penalty function and its derivatives can be calculated efficiently using automatic differentiation techniques.Peer reviewe
Antiferromagnetic ordering and dipolar interactions of YbAlO
In this paper we report low-temperature magnetic properties of the rare-earth
perovskite material YbAlO. Results of elastic and inelastic neutron
scattering experiment, magnetization measurements along with the crystalline
electrical field (CEF) calculations suggest that the ground state of Yb moments
is a strongly anisotropic Kramers doublet, and the moments are confined in the
-plane, pointing at an angle of to the
-axis. With temperature decreasing below K, Yb moments
order into the coplanar, but non-collinear antiferromagnetic (AFM) structure
, where the moments are pointed along their easy-axes. In addition, we
highlight the importance of the dipole-dipole interaction, which selects the
type of magnetic ordering and may be crucial for understanding magnetic
properties of other rare-earth orthorhombic perovskites. Further analysis of
the broad diffuse neutron scattering shows that one-dimensional interaction
along the -axis is dominant, and suggests YbAlO as a new member of one
dimensional quantum magnets.Comment: 8 pages, 6 figure
Near Sharp Strichartz estimates with loss in the presence of degenerate hyperbolic trapping
We consider an -dimensional spherically symmetric, asymptotically
Euclidean manifold with two ends and a codimension 1 trapped set which is
degenerately hyperbolic. By separating variables and constructing a
semiclassical parametrix for a time scale polynomially beyond Ehrenfest time,
we show that solutions to the linear Schr\"odiner equation with initial
conditions localized on a spherical harmonic satisfy Strichartz estimates with
a loss depending only on the dimension and independent of the degeneracy.
The Strichartz estimates are sharp up to an arbitrary loss. This is
in contrast to \cite{ChWu-lsm}, where it is shown that solutions satisfy a
sharp local smoothing estimate with loss depending only on the degeneracy of
the trapped set, independent of the dimension
Conflicting discourses of church youths on masculinity and sexuality in the context of HIV in Kinshasa, Democratic Republic of Congo
Masculinity studies are fairly new and young churchgoers are an under-researched group in the current Congolese church context. In response to this knowledge gap, this paper attempts to explore discourses of youngĀ churchgoers from deprived areas of Kinshasa regarding masculinity and sexuality in the era of HIV. A series of 16 semi-structured interviews were conducted with unmarried young churchgoers from the Salvation Army, Protestant and Revival churches. The interviews were tape-recorded, transcribed verbatim and analysed using discourse analysis. Five main discourses emerged: āwe are aware of the church message on sexā, āyoung men need sexā, āyoung women need moneyā, āto use or not to use condomsā and āwe trust in the church messageā. Although all informants knew and heard church messages against premarital sex, many of them were sexually active. The perception was that young men were engaged in sexual activities with multiple partners as a result of sexual motivations surrounding masculinity and sexual potency, while young women sought multiple partners through transactional and intergenerational sex for economic reasons. These sexual practices of young people conflicted with church messages on sexual abstinence and faithfulness. However, a small number of participants challenged current gender norms and suggested alternative ways of being a man or a woman. To elucidate theseĀ alternatives, we suggest that church youths and church leaders might take concrete actions to deconstruct misconceptions about being men. In this way, they can possibly enhance a frank and fruitful dialogue on sex, sexuality and gender to promote positive masculinities and constructive partnerships to prevent HIV.Keywords: masculinity, sexuality, young churchgoers, HIV prevention, gender equality, DR CongoDans le contexte actuel des eĀ“glises Congolaises, les eĀ“tudes relatives a` la masculiniteĀ“ sont presque reĀ“centes et les jeunes chreĀ“tiens constituent un groupe dāindividus qui ne font pas lāobjet des recherches scientifiquesĀ approfondies. En reĀ“ponse a` cette insuffisance de connaissances dans le contexte a` VIH, le preĀ“sent article tente dāexplorer les discours relatifs a` la masculiniteĀ“ et a` la sexualiteĀ“ des jeunes chreĀ“tiens issus desĀ quartiers deĀ“favoriseĀ“s de Kinshasa. Une seĀ“rie de 16 interviews semi-structureĀ“es ont eĀ“teĀ“ meneĀ“s aupre`s des jeunes chreĀ“tiens ceĀ“libataires appartenant a` lāArmeĀ“e du Salut, aux eĀ“glises Protestantes et a` celles du ReĀ“veil du Congo. Les interviews ont eĀ“teĀ“ enregistreĀ“es et analyseĀ“es en utilisant la meĀ“thode du discours. Cinq discours ont eĀ“mergeĀ“ notamment: Ā« Nous connaissons le message des eĀ“glises au sujet du sexe Ā», Ā« les garcĀøons ont besoin des rapports sexuels Ā», Ā« les filles ont besoin dāargent Ā», Ā« faudrait-il utiliser ou ne pas utiliser les condoms Ā» et Ā« nous croyons dans le message des eĀ“glises Ā». Alors que tous les participantsĀ connaissaient le message des eĀ“glises qui interdisent les rapports sexuels preĀ“maritaux, beaucoup dāentre eux eĀ“taient deĀ“ja` sexuellement actifs. Les garcĀøons ont eĀ“teĀ“ percĀøus comme des personnes qui ont des rapports sexuels avec plusieurs partenaires concomitants pour prouver leur masculiniteĀ“ et leur puissance sexuelle. Les filles chercheraient a` avoir des rapports sexuels mercantiles et intergeĀ“neĀ“rationnels avec des partenairesĀ multiples a` des fins eĀ“conomiques. Ces pratiquesĀ sexuelles des jeunes sāopposent aux discours des eĀ“glisesĀ qui promeuvent lāabstinence sexuelle et la fideĀ“liteĀ“. Cependant, quelques participants ont remis en cause les normes courantes du genre et ont suggeĀ“reĀ“ des alternatives en ce qui concerne lāidentiteĀ“ des hommes et des femmes. Pour les eĀ“lucider, nous proposons que les jeunes chreĀ“tiens et les leaders des eĀ“glises puissent mener des actions concre`tes dans le but de deĀ“construire les conceptions erroneĀ“es de ce que veut dire eĖtre homme. Ce faisant, ils peuvent probablement maximiser les chances dāun dialogue franc et productif en ce qui concerne le sexe, la sexualiteĀ“ et le genre afin de promouvoir la masculiniteĀ“ positive et le partenariatĀ constructif, susceptibles de preĀ“venir lāinfection a` VIH.Mots cleĀ“s: masculiniteĀ“, sexualiteĀ“, jeunes chreĀ“tiens, preĀ“vention du VIH, eĀ“galiteĀ“ du genre, RD Cong
Quantum ergodicity for restrictions to hypersurfaces
Quantum ergodicity theorem states that for quantum systems with ergodic
classical flows, eigenstates are, in average, uniformly distributed on energy
surfaces. We show that if N is a hypersurface in the position space satisfying
a simple dynamical condition, the restrictions of eigenstates to N are also
quantum ergodic.Comment: 22 pages, 1 figure; revised according to referee's comments. To
appear in Nonlinearit
Ytterbium divalency and lattice disorder in near-zero thermal expansion YbGaGe
While near-zero thermal expansion (NZTE) in YbGaGe is sensitive to
stoichiometry and defect concentration, the NZTE mechanism remains elusive. We
present x-ray absorption spectra that show unequivocally that Yb is nearly
divalent in YbGaGe and the valence does not change with temperature or with
nominally 1% B or 5% C impurities, ruling out a valence-fluctuation mechanism.
Moreover, substantial changes occur in the local structure around Yb with B and
C inclusion. Together with inelastic neutron scattering measurements, these
data indicate a strong tendency for the lattice to disorder, providing a
possible explanation for NZTE in YbGaGe.Comment: 4 pages, 4 figure, supplementary inf
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