Papers by santiago acosta
Learning to operate a vehicle is generally accomplished by forming a new cognitive map between th... more Learning to operate a vehicle is generally accomplished by forming a new cognitive map between the body motions and extrapersonal space. Here, we consider the challenge of remapping movement-to-space representations in survivors of spinal cord injury, for the control of powered wheelchairs. Our goal is to facilitate this remapping by developing interfaces between residual body motions and navigational commands that exploit the degrees of freedom that disabled individuals are most capable to coordinate. We present a new framework for allowing spinal cord injured persons to control powered wheelchairs through signals derived from their residual mobility. The main novelty of this approach lies in substituting the more common joystick controllers of powered wheelchairs with a sensor shirt. This allows the whole upper body of the user to operate as an adaptive joystick. Considerations about learning and risks have lead us to develop a safe testing environment in 3D Virtual Reality. A Personal Augmented Reality Immersive System (PARIS) allows us to analyse learning skills and provide users with an adequate training to control a simulated wheelchair through the signals generated by body motions in a safe environment. We provide a description of the basic theory, of the development phases and of the operation of the complete system. We also present preliminary results illustrating the processing of the data and supporting of the feasibility of this approach.
Experimental Brain Research, 2010
Survivors of spinal cord injury need to reorganize their residual body movements for interacting ... more Survivors of spinal cord injury need to reorganize their residual body movements for interacting with assistive devices and performing activities that used to be easy and natural. To investigate movement reorganization, we asked subjects with high-level spinal cord injury (SCI) and unimpaired subjects to control a cursor on a screen by performing upper-body motions. While this task would be normally accomplished by operating a computer mouse, here shoulder motions were mapped into the cursor position. Both the control and the SCI subjects were rapidly able to reorganize their movements and to successfully control the cursor. The majority of the subjects in both groups were successful in reducing the movements that were not effective at producing cursor motions. This is inconsistent with the hypothesis that the control system is merely concerned with the accurate acquisition of the targets and is unconcerned with motions that are not relevant to this goal. In contrast, our findings suggest that subjects can learn to reorganize coordination so as to increase the correspondence between the subspace of their upper-body motions with the plane in which the controlled cursor moves. This is effectively equivalent to constructing an inverse internal model of the map from body motions to cursor motions, established by the experiment. These results are relevant to the development of interfaces for assistive devices that optimize the use of residual voluntary control and enhance the learning process in disabled users, searching for an easily learnable map between their body motor space and control space of the device.
The paper develops a fully-microfounded DGE model for a small open economy subject to frictions i... more The paper develops a fully-microfounded DGE model for a small open economy subject to frictions in the credit market. Agents in the economy face credit constraints in financing investment due to information asymmetries; in addition, the assets of these agents are denominated in the domestic cur- rency while their liabilities are denominated in the foreign currency. These credit-market frictions are
Fitoterapia, 2003
... Corresponding Author Contact Information , E-mail The Corresponding Author , LV Muro, AL Sace... more ... Corresponding Author Contact Information , E-mail The Corresponding Author , LV Muro, AL Sacerio, AR Peña and SN Okwei. Pharmacy Department, Chemical and Pharmacy School, Central University of Las Villas, Carretera a Camajuaní Km. 5.5, Santa Clara, Villa Clara ...
We develop a two-sectors small open economy model with imperfect competition, one-period nominal ... more We develop a two-sectors small open economy model with imperfect competition, one-period nominal price rigidities and a nancial accelerator mechanism. The latter assumes an asymmetric information problem between lenders and capital good producers (entrepreneurs). Studying the zero-in ation steady state, it is shown that the model with the nancial accelerator mechanism nests a fairly standard RBC model; case in which entrepreneurs \disappear" as a di erentiated sector from households. It is also explained that credit market imperfections essentially reduce the aggregate supply of capital relative to the RBC case. Turning to the dynamics, we study the e ects of an unanticipated and permanent increase in the level of the money supply. In this context the exchange rate jumps immediately to its new steady state level without showing any overshooting process as in . Analysing the case without credit market imperfections but with pre-set prices, it is demonstrated that money is not neutral in the long-run, that capital adds persistence to the initial shock, and that some traditional results of the Mundell-Fleming model still hold. JEL Classi cation: F3, F4. Acknowledgement: I would like to thank Neil Rankin for his supervision, guidance and support. Alejo Macaya, Marcus Miller, Atsuyoshi Morozumi, Marcelo Sanchez and the participants of the RES Easter School 2007 in Birmingham provided helpful comments. The conventional disclaimer applies.
We develop a two-sectors small open economy model with imperfect competition, one-period nominal ... more We develop a two-sectors small open economy model with imperfect competition, one-period nominal price rigidities and a nancial accelerator mechanism. The latter assumes an asymmetric information problem between lenders and capital good producers (entrepreneurs). Studying the zero-in ation steady state, it is shown that the model with the nancial accelerator mechanism nests a fairly standard RBC model; case in which entrepreneurs \disappear" as a di erentiated sector from households. It is also explained that credit market imperfections essentially reduce the aggregate supply of capital relative to the RBC case. Turning to the dynamics, we study the e ects of an unanticipated and permanent increase in the level of the money supply. In this context the exchange rate jumps immediately to its new steady state level without showing any overshooting process as in . Analysing the case without credit market imperfections but with pre-set prices, it is demonstrated that money is not neutral in the long-run, that capital adds persistence to the initial shock, and that some traditional results of the Mundell-Fleming model still hold. JEL Classi cation: F3, F4. Acknowledgement: I would like to thank Neil Rankin for his supervision, guidance and support. Alejo Macaya, Marcus Miller, Atsuyoshi Morozumi, Marcelo Sanchez and the participants of the RES Easter School 2007 in Birmingham provided helpful comments. The conventional disclaimer applies.
We develop a two-sectors small open economy model with imperfect competition, one-period nominal ... more We develop a two-sectors small open economy model with imperfect competition, one-period nominal price rigidities and anancial accelerator mechanism. The latter assumes an asymmetric information problem between lenders and capital good producers (entrepreneurs). Studying the zero-ination steady state, it is shown that the model with thenancial accelerator mechanism nests a fairly standard RBC model; case in which entrepreneurs \disappear" as
We develop a two-sectors small open economy model with imperfect competition, one-period nominal ... more We develop a two-sectors small open economy model with imperfect competition, one-period nominal price rigidities and anancial accelerator mechanism. The latter assumes an asymmetric information problem between lenders and capital good producers (entrepreneurs). Studying the zero-ination steady state, it is shown that the model with thenancial accelerator mechanism nests a fairly standard RBC model; case in which entrepreneurs \disappear" as
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Papers by santiago acosta