Coherency Conditions In Simultaneous Linear Equation Models With Endogenous Switching Regimes

In modeling disequilibrium macroeconomic systems which one would want to subject to econometric estimation one typically faces the problem of whether the structural model can determine a unique equilibrium. The problem inherits a special form because the regimes in which the equilibria can lie are each linear. By placing restrictions on the parameters that insure the uniqueness of such a solution for each value of the exogenous and random variables, we can improve the estimation procedure. This paper provides necessary and sufficient conditions for uniqueness -- or "coherency." These conditions are applied to a variety of models that have been prominent in the literature on econometrics with 'switching regimes' such as those of self-selectivity (Maddala), simultaneous equation tobit and probit (Amemiya, Schmidt) and multi-market macroeconomic disequilibrium (Gourieroux, Laffont and Nonfort).

Opting out and topping up reconsidered: Informal care under uncertain altruism

National audienceWe study the design of public long-term care (LTC) insurance when the altruism of informal caregivers is uncertain. We consider non-linear policies where the LTC transfer depends on the level of informal care, which is assumed to be observable, while children's altruism is not. Our policy encompasses two policies traditionally considered in the literature: topping up policies consisting of a transfer independent of informal care, and opting out policies entailing a positive transfer only if children fail to provide care. We show that both total and informal care should increase with the children's level of altruism. This is obtained under full and asymmetric information. Public LTC transfers, on the other hand, may be non-monotonic. Under asymmetric information, public LTC transfers are lower than their full information level for the parents whose children are the least altruistic, while it is distorted upward for the highest level of altruism. This is explained by the need to provide incentives to highly altruistic children. In contrast to both topping up and opting out policies, the implementing contract is always such that social care increases with informal care.Repenser les polices exclusives et non-exclusives : les soins informels dans un contexte de devouement aleatoire. Dans cet article, nous etudions le modele public d'assurance de soins de longue duree lorsque le devouement des aidants naturels est aleatoire. Nous nous interessons aux polices non-lineaires ou le transfert des soins de longue duree depend du niveau de soins informels, lequel etant supposement observable, a l'inverse du devouement des enfants, qui ne l'est pas. Notre police s'appuie sur les deux polices traditionnellement etudiees dans la litterature : les polices non-exclusives ( topping up policies ) consistant en un transfert independant des soins informels, et les polices exclusives ( opting out policies ) impliquant un transfert positif uniquement lorsque les enfants sont dans l'incapacite de fournir de l'aide. Nous montrons que l'ensemble des soins ainsi que les soins informels devraient augmenter proportionnellement au devouement des enfants, que l'information soit complete ou asymetrique. Les transferts publics de soins de longue duree, en revanche, peuvent s'averer non monotones. Dans un contexte d'information asymetrique, et pour les parents dont les enfants sont les moins devoues, les transferts publics de soins de longue duree sont inferieurs a ceux observes dans un contexte d'information complete; pour les parents dont les enfants sont les plus devoues, on observe une distorsion a la hausse. Ceci s'explique par la necessite de fournir des mesures incitatives aux enfants hautement devoues. Et contrairement aux polices exclusives et non-exclusives, le contrat d'execution est toujours tel que les soins sociaux augmentent proportionnellement aux soins informels

Incentivizing High Quality Crowdwork

We study the causal effects of financial incentives on the quality of crowdwork. We focus on performance-based payments (PBPs), bonus payments awarded to workers for producing high quality work. We design and run randomized behavioral experiments on the popular crowdsourcing platform Amazon Mechanical Turk with the goal of understanding when, where, and why PBPs help, identifying properties of the payment, payment structure, and the task itself that make them most effective. We provide examples of tasks for which PBPs do improve quality. For such tasks, the effectiveness of PBPs is not too sensitive to the threshold for quality required to receive the bonus, while the magnitude of the bonus must be large enough to make the reward salient. We also present examples of tasks for which PBPs do not improve quality. Our results suggest that for PBPs to improve quality, the task must be effort-responsive: the task must allow workers to produce higher quality work by exerting more effort. We also give a simple method to determine if a task is effort-responsive a priori. Furthermore, our experiments suggest that all payments on Mechanical Turk are, to some degree, implicitly performance-based in that workers believe their work may be rejected if their performance is sufficiently poor. Finally, we propose a new model of worker behavior that extends the standard principal-agent model from economics to include a worker's subjective beliefs about his likelihood of being paid, and show that the predictions of this model are in line with our experimental findings. This model may be useful as a foundation for theoretical studies of incentives in crowdsourcing markets.Comment: This is a preprint of an Article accepted for publication in WWW \c{opyright} 2015 International World Wide Web Conference Committe

Isokinetic muscle strengthening after acquired cerebral damage: A literature review

AbstractObjectiveIsokinetic strengthening is a rehabilitation technique rarely used in stroke patients. However, the potential benefits of force and endurance training in this population are strongly suspected.MethodThis literature review synthesizes the results of clinical trials on this topic. The research was conducted on PubMed, using “Stroke”, “rehabilitation”, “isokinetic”, “upper limb” and “training” as keywords.ResultsSeventeen studies focusing on the use of isokinetics in assessment or rehabilitation (six studies) following stroke were reviewed. For the lower limb, muscle strength and walking ability improved after isokinetic rehabilitation programs. For the upper limb, the only two studies found in the literature suggest improvement in the strength of the trained muscles, of grip force, of the Fugl-Meyer motor score and of global functional capacities. This review does not reveal any consensus on the protocols to be implemented: type of muscle contraction, velocities….ConclusionWhile isokinetic strengthening has not proven its efficiency in rehabilitation of the upper limb following stroke, its interest with regard to rehabilitation of the lower limbs has been recognized. Randomized controlled trials in this field are necessary to confirm its efficiency, especially concerning upper arm rehabilitation

Microstructural Characterization of Graphite Spheroids in Ductile Iron

The present work brings new insights by transmission electron microscopy allowing disregarding or supporting some of the models proposed for spheroidal growth of graphite in cast irons. Nodules consist of sectors made of graphite plates elongated along a hai direction and stack on each other with their c axis aligned with the radial direction. These plates are the elementary units for spheroidal growth and a calculation supports the idea that new units continuously nucleate at the ledge between sectors

Inner Space Preserving Generative Pose Machine

Image-based generative methods, such as generative adversarial networks (GANs) have already been able to generate realistic images with much context control, specially when they are conditioned. However, most successful frameworks share a common procedure which performs an image-to-image translation with pose of figures in the image untouched. When the objective is reposing a figure in an image while preserving the rest of the image, the state-of-the-art mainly assumes a single rigid body with simple background and limited pose shift, which can hardly be extended to the images under normal settings. In this paper, we introduce an image "inner space" preserving model that assigns an interpretable low-dimensional pose descriptor (LDPD) to an articulated figure in the image. Figure reposing is then generated by passing the LDPD and the original image through multi-stage augmented hourglass networks in a conditional GAN structure, called inner space preserving generative pose machine (ISP-GPM). We evaluated ISP-GPM on reposing human figures, which are highly articulated with versatile variations. Test of a state-of-the-art pose estimator on our reposed dataset gave an accuracy over 80% on PCK0.5 metric. The results also elucidated that our ISP-GPM is able to preserve the background with high accuracy while reasonably recovering the area blocked by the figure to be reposed.Comment: http://www.northeastern.edu/ostadabbas/2018/07/23/inner-space-preserving-generative-pose-machine

Size-dependent spinodal and miscibility gaps for intercalation in nano-particles

Using a recently-proposed mathematical model for intercalation dynamics in phase-separating materials [Singh, Ceder, Bazant, Electrochimica Acta 53, 7599 (2008)], we show that the spinodal and miscibility gaps generally shrink as the host particle size decreases to the nano-scale. Our work is motivated by recent experiments on the high-rate Li-ion battery material LiFePO4; this serves as the basis for our examples, but our analysis and conclusions apply to any intercalation material. We describe two general mechanisms for the suppression of phase separation in nano-particles: (i) a classical bulk effect, predicted by the Cahn-Hilliard equation, in which the diffuse phase boundary becomes confined by the particle geometry; and (ii) a novel surface effect, predicted by chemical-potential-dependent reaction kinetics, in which insertion/extraction reactions stabilize composition gradients near surfaces in equilibrium with the local environment. Composition-dependent surface energy and (especially) elastic strain can contribute to these effects but are not required to predict decreased spinodal and miscibility gaps at the nano-scale