117 research outputs found
Robust statistics over Riemannian manifolds for computer vision
No full textThe nonlinear nature of many compute vision tasks involves analysis over curved nonlinear spaces embedded in higher dimensional Euclidean spaces. Such spaces are known as manifolds and can be studied using the theory of differential geometry. In this thesis we develop two algorithms which can be applied over manifolds.
The nonlinear mean shift algorithm is a generalization of the original mean shift, a popular feature space analysis method for vector spaces. Nonlinear mean shift can be applied to any Riemannian manifold and is provably convergent to the local maxima of an appropriate kernel density. This algorithm is used for motion segmentation with different motion models and for the filtering of complex image data.
The projection based M-estimator is a robust regression algorithm which does not require a user supplied estimate of the scale, the level of noise corrupting the inliers. We build on the connections between kernel density estimation and robust M-estimators and develop data driven rules for scale estimation. The method can be generalized to handle heteroscedastic data and subspace estimation. The results of using pbM for affine motion estimation, fundamental matrix estimation and multibody factorization are presented.
A new sensor fusion method which can handle heteroscedastic data and incomplete estimates of parameters is also discussed. The method is used to combine image based pose estimates with inertial sensors.Ph.D.Includes bibliographical references (p. 137-144)
The impact of two tier producer and consumer food pricing in India
No full textIndia's government procures agricultural products such as rice, wheat, and sugar at below-market prices and sells them in both urban and rural ration shops. The rest of such crops is sold in the open market. This creates a two-tier price system for consumers and producers. Many (including Dantwala, Mellor, and Hayami, Subbarao, and Otsuka) claim that such a policy raises the open-market price so much that it ultimately increases the average price received by farmers. Iftrue, the gainers would be the farm sector as a whole and low-income urban consumers with access to the ration shops. Losers would be the high-income urban consumers who buy at the open-market price. This view has provided an intellectual basis for the policy. The author examines a variety of cases: with and without rationing, with rationing by ration cards or by queuing, with and without the urban rich having access to the ration shops, with and without free trade, and with a marketable surplus with positive, negative, or zero price elasticity. He finds that in most cases the policy's impact on the average price is either negative or ambiguous, and it is negative in the more realistic cases. A negative impact implies that farmers on the whole lose from the procurement policy. But small farmers who are net buyers of the procured crops, and landless laborers, gain from a lower average price in the short run (especially if they have easy access to the rural ration shops). The long-run effect depends on the impact of the lower average price on rural employment and wages.Markets and Market Access,Economic Theory&Research,Environmental Economics&Policies,Consumption,Access to Markets
How to make public works work : a review of the experiences
No full textThis paper reviews the experience with public works programs (PWPs) in several countries over the past 20 years to delineate use patterns and to determine the factors contributing to its use as a successful safety net program. The analysis shows that PWP have been used extensively in response to either a one-time large covariate shock, or repeated shocks. In low income countries, PWPs also have an antipoverty or poverty reduction objective. Our review shows that well designed and implemented PWPs can help mitigating income shocks; the program can also be used as an effective anti-poverty instrument. The paper examines the factors behind the observed wide variation in the effectiveness of the program in accomplishing its goals and identifies prerequisites for making PWPs successful safety net interventions capable of protecting the poor from income shocks, thus reducing both temporal and seasonal poverty, while creating useful public goods or services for the communities. For public works programs to be successful, it is important firstly to: a) have clear objectives; b) select projects that can create valuable public goods; and c) ensure predictable funding. Secondly, the success of the program depends critically on careful design and incorporation of all the key design features. Finally, a credible monitoring and evaluation system designed right upfront, prior to launching of theprogram can allow for mid course corrections and to respond to sudden changes which can inhibit effective implementation. The potential of the PWP program is enormous both in countries that have experiences with these programs and especially in countries that never used them. However, more research is needed investigation is needed to better understand the impact of PWPs, such as second round effects from the created assets, the impacts on the labor market, and their cost-effectiveness after factoring in both the immediate and second round benefits from its program.Safety Nets and Transfers,Rural Poverty Reduction,Labor Markets,Labor Policies,Public Sector Economics
Subspace estimation using projection based M-estimators over Grassmann manifolds
No full textAbstract. We propose a solution to the problem of robust subspace estimation using the projection based M-estimator. The new method handles more outliers than inliers, does not require a user defined scale of the noise affecting the inliers, handles noncentered data and nonorthogonal subspaces. Other robust methods like RANSAC, use an input for the scale, while methods for subspace segmentation, like GPCA, are not robust. Synthetic data and three real cases of multibody factorization show the superiority of our method, in spite of user independence.
Effect of Surface Active Agents in Boiling Heat Transfer
No full textTitle: Effect of Surface Active Agents in Boiling Heat Transfer, Author: Subbarao N. Rao, Location: ThodeThe boiling heat transfer phenomenon has presented a state o ambiguity regarding the role of solid-liquid-vapour interface in the mechanisms of heat transfer. Recent studies (S1, M1) have given an indication to the possibility of the vaporization of a micro layer at the boiling surface as a alternative to the well known theories based purely on the hydrodynamic factors. This study is an attempt to understand the boiling heat transfer mechanism at solid-liquid-vapour interface and to study the effect of interfacial properties like surface tension and contact angle on the maximum (critical) heat flux. The present studies use the technique of changing the solid-liquid-vapour interface characteristics of water through the use of surface-active agent as additive, to study the boiling heat transfer under changed interface conditions. Four different surfactants were used at three levels of concentration in water. Surface tension and contact angle measurements were carried out using the shadow photographs of pendant cops and sessile drops. Boiling heat flux measurements of these surfactant solutions in water were carried out using heat transfer surface. Experiments involving pool boiling and the boiling of thin liquid films were carried out over the transition and nucleate boiling regimes. It has been observed that the solid-liquid-vapour interface characteristics play a cry important role in the boiling heat transfer mechanism. By a suitable choice type of surfactant and concentration, the critical heat flux and heat transfer coefficients can be improved markedly. It is suggested that the spreading wetting characteristic improves the heat transfer rate whereas the increased viscosity and decreased thermal conductivity of the liquid microlayer under the vapour masses may cause the heat flux to decrease. The present study shows significant possibilities for future studies in the nucleate boiling, transition boiling and film boiling regimes using surfactant solutions.ThesisMaster of Engineering (ME
Does corruption relieve foreign investors of the burden of taxes and capital controls?
No full textIn a sample of fourteen source countries making bilateral investments in forty five countries, the author finds that taxes, capital controls, and corruption, all have large, statistically significant negative effects on foreign investment. Moreover, there is no robust support in the data for the"efficient grease"hypothesis - that corruption helps attract foreign investment by reducing firms'tax burden and the irritant of capital controls.International Terrorism&Counterterrorism,Capital Markets and Capital Flows,Decentralization,Fiscal&Monetary Policy,Economic Theory&Research,Economic Theory&Research,International Terrorism&Counterterrorism,Governance Indicators,National Governance,Capital Flows
Nonlinear Mean Shift for Robust Pose Estimation
No full textWe propose a new robust estimator for camera pose estimation based on a recently developed nonlinear mean shift algorithm. This allows us to treat pose estimation as a clustering problem in the presence of outliers. We compare our method to RANSAC, which is the standard robust estimator for computer vision problems. We also show that under fairly general assumptions our method is provably better than RANSAC. Synthetic and real examples to support our claims are provided. 1
- …
