Learning Economic Parameters from Revealed Preferences

A recent line of work, starting with Beigman and Vohra (2006) and Zadimoghaddam and Roth (2012), has addressed the problem of {\em learning} a utility function from revealed preference data. The goal here is to make use of past data describing the purchases of a utility maximizing agent when faced with certain prices and budget constraints in order to produce a hypothesis function that can accurately forecast the {\em future} behavior of the agent. In this work we advance this line of work by providing sample complexity guarantees and efficient algorithms for a number of important classes. By drawing a connection to recent advances in multi-class learning, we provide a computationally efficient algorithm with tight sample complexity guarantees ($\Theta(d/\epsilon)$ for the case of $d$ goods) for learning linear utility functions under a linear price model. This solves an open question in Zadimoghaddam and Roth (2012). Our technique yields numerous generalizations including the ability to learn other well-studied classes of utility functions, to deal with a misspecified model, and with non-linear prices

Functional linear regression with derivatives

We introduce a new model of linear regression for random functional inputs taking into account the first-order derivative of the data. We propose an estimation method that comes down to solving a special linear inverse problem. Our procedure tackles the problem through a double and synchronised penalisation. An asymptotic expansion of the mean square prevision error is given. The model and the method are applied to a benchmark dataset of spectrometric curves and compared with other functional models

Desain Sistem Pendingin Ruang Muat Kapal Ikan Tradisional Dengan Menggunakan Campuran Es Kering Dan Cold Ice Yang Berbahan Dasar Propylene Glycol

Penanganan ikan hasil perikanan supaya tetap segar biasanya menggunakan es basah, terutama oleh nelayan tradisional. Penggunaan es basah hanya bertahan dalam waktu singkat. Propylene glycol merupakan salah satu bahan yang mampu menjaga kestabilan suhu rendah. Sehingga sangat efektif dan efisien apabila digunakan sebagai bahan pendingin ikan. Selain tidak membutuhkan tempat yang luas dalam penyimpanannya, propylene glycol mampu mempertahankan suhu rendah dalam waktu yang lama, tidak beracun dan mudah didegradasi oleh lingkungan (ramah lingkungan). Penelitian ini dilakukan untuk mengetahui lama waktu yang dicapai alat pendingin dengan penambahan uap es kering dan propylene glycol. Serta mengetahui mutu ikan dengan menggunakan sistem pendingin yang dirancang dengan bahan dasar propylene glycol. Sistem pendingin ini dirancang dengan menggunakan cool box yang terdiri dari dua box yang terpisah. Coolbox yang pertama sebagai tempat ikan dengan es basah. Coolbox yang ke dua (yang lebih kecil) sebagai tempat es kering dan propylene glycol. Uap dingin dari es kering dan propylene glycol dialirkan ke kotak yang pertama dengan menggunakan blower. Sistem pendingin yang dirancang ini akan mampu mempertahankan suhu rendah dan menjaga kualitas ikan hasil tangkapan tetap segar. Sehingga sistem pendingin yang berbahan dasar propylene glycol akan lebih efektif, efisien dan ramah lingkungan

Designing virtual communities of practice for informal caregivers of Alzheimer’s patients : an integrative review

Caring for a person with dementia burdens family caregivers, and there is a close negative relationship between this burden and their quality of life (QoL). Research suggests that caregivers’ main needs are information and training about the disease, and support from others experiencing the same situation, and Internet interventions hold considerable promise for meeting these needs. Virtual Communities of Practice (VCoP) are Internet frameworks to share knowledge where members collaborate and achieve a sense of trust in the community. This paper seeks to evaluate the impact of participating in a VCoP (developed through an App) on the QoL of caregivers to people with Alzheimer`s. Results show QoL before and after the intervention changed significantly. The impact of VCoP on caregivers’ overall QoL is moderated by age and relation with the person with Alzheimer’s, specifically those over 65 (66.3 to 74.64), and spouses (69.75 to 75.68). VCoPs allow interaction and knowledge sharing among caregivers which provide them mainly with information and support from peers helping them to meet their needs. Furthermore, caregivers’ QoL did not decrease when their relative deteriorated functionally, which could be due to the participation in VCoP. Although we found significant pre and post differences in caregivers’ health literacy, we must report the ambiguous result that this variable only impacts on QoL’s physical domain. Participants also reported that they had a positive experience because the App was perceived to be another useful tool, because they could manage their own participation, they met peers and felt less lonely

Ultraviolet and Infrared Divergences in Implicit Regularization: a Consistent Approach

Implicit Regularization is a 4-dimensional regularization initially conceived to treat ultraviolet divergences. It has been successfully tested in several instances in the literature, more specifically in those where Dimensional Regularization does not apply. In the present contribution we extend the method to handle infrared divergences as well. We show that the essential steps which rendered Implicit Regularization adequate in the case of ultraviolet divergences have their counterpart for infrared ones. Moreover we show that a new scale appears, typically an infrared scale which is completely independent of the ultraviolet one. Examples are given.Comment: 9 pages, version to appear in Mod. Phys. Lett.

Two-Connection Renormalization and Nonholonomic Gauge Models of Einstein Gravity

A new framework to perturbative quantum gravity is proposed following the geometry of nonholonomic distributions on (pseudo) Riemannian manifolds. There are considered such distributions and adapted connections, also completely defined by a metric structure, when gravitational models with infinite many couplings reduce to two--loop renormalizable effective actions. We use a key result from our partner work arXiv:0902.0911 that the classical Einstein gravity theory can be reformulated equivalently as a nonholonomic gauge model in the bundle of affine/de Sitter frames on pseudo-Riemannian spacetime. It is proven that (for a class of nonholonomic constraints and splitting of the Levi-Civita connection into a "renormalizable" distinguished connection, on a base background manifold, and a gauge like distortion tensor, in total space) a nonholonomic differential renormalization procedure for quantum gravitational fields can be elaborated. Calculation labor is reduced to one- and two-loop levels and renormalization group equations for nonholonomic configurations.Comment: latex2e, 40 pages, v4, accepted for Int. J. Geom. Meth. Mod. Phys. 7 (2010

The effect of collisional enhancement of Balmer lines on the determination of the primordial helium abundance

This paper describes a new determination of the primordial helium abundance (Y_P), based on the abundance analysis of five metal-poor extragalactic HII regions. For three regions of the sample (SBS 0335-052, I Zw 18, and H29) we present tailored photoionization models based on improved calculations with respect to previous models. In particular, we use the photoionization models to study quantitatively the effect of collisional excitation of Balmer lines on the determination of the helium abundance (Y) in the individual regions. This effect is twofold: first, the intensities of the Balmer lines are enhanced with respect to the pure recombination value, mimicking a higher hydrogen abundance; second, the observed reddening is larger than the true extinction, due to the differential effect of collisions on different Balmer lines. In addition to these effects, our analysis takes into account the following features of HII regions: (i) the temperature structure, (ii) the density structure, (iii) the presence of neutral helium, (iv) the collisional excitation of the HeI lines, (v) the underlying absorption of the HeI lines, and (vi) the optical thickness of the HeI lines. The object that shows the highest increase in Y after the inclusion of collisional effects in the analysis is SBS 0335-052, whose helium abundance has been revised by Delta Y = +0.0107. The revised Y values for the five objects in our sample yield an increase of +0.0035 in Y_P, giving Y_P = 0.2391 +/- 0.0020.Comment: 59 pages, 8 figures. AAS Latex. Accepted for publication in the Astrophysical Journa

Dispersionful analogues of Benney's equations and NN-wave systems

We recall Krichever's construction of additional flows to Benney's hierarchy, attached to poles at finite distance of the Lax operator. Then we construct a ``dispersionful'' analogue of this hierarchy, in which the role of poles at finite distance is played by Miura fields. We connect this hierarchy with $N$-wave systems, and prove several facts about the latter (Lax representation, Chern-Simons-type Lagrangian, connection with Liouville equation, $\tau$-functions).Comment: 12 pages, latex, no figure