Abstract
The Linear inverted pendulum model is widely used in biped walking approaches. This model assumes that the hip height is fixed while the robot walks. In this paper, the hip height movement, or vertical Center of Mass (CoM) trajectory, is used by a robot to achieve a faster and more stable walk. For the first time, the hip height movement is modeled in a formal way and its parameters are learned. The inverted pendulum model and a numerical approach are used to control the Zero Moment Point (ZMP) for generating a balanced walk. Covariance Matrix Adaptation Evolution Strategy (CMA-ES) is applied to optimize the hip height trajectory and walking parameters with respect to walking speed and stability. Experimental results are achieved on a simulated NAO robot. A comparison of the results of the proposed gait model (and development approach) with those obtained using fixed hip height shows that fixed height walking is slower than variable height walking.

Abstract

Abstract
Hand gestures are a powerful way for human communication, with lots of potential applications in the area of human computer interaction. Vision-based hand gesture recognition techniques have many proven advantages compared with traditional devices, giving users a simpler and more natural way to communicate with electronic devices. This work proposes a generic system architecture based in computer vision and machine learning, able to be used with any interface for human-computer interaction. The proposed solution is mainly composed of three modules: a pre-processing and hand segmentation module, a static gesture interface module and a dynamic gesture interface module. The experiments showed that the core of vision-based interaction systems can be the same for all applications and thus facilitate the implementation. In order to test the proposed solutions, three prototypes were implemented. For hand posture recognition, a SVM model was trained and used, able to achieve a final accuracy of 99.4%. For dynamic gestures, an HMM model was trained for each gesture that the system could recognize with a final average accuracy of 93.7%. The proposed solution as the advantage of being generic enough with the trained models able to work in real-time, allowing its application in a wide range of human-machine applications.

Abstract
The kidney exchange problem (KEP) is an optimization problem arising in the framework of transplant programs that allow exchange of kidneys between two or more incompatible patient-donor pairs. In this paper an approach based on a new decomposition model and branch-and-price is proposed to solve large KEP instances. The optimization problem considers, hierarchically, the maximization of the number of transplants and the minimization of the size of exchange cycles. Computational comparison of different variants of branch-and-price for the standard and the proposed objective functions are presented. The results show the efficiency of the proposed approach for solving large instances.

Abstract
Wastewater and greywater have different scales of end-uses in irrigation in Portugal. Wastewater is treated in a central wastewater treatment plant and reused in public/private large areas of irrigation, like agriculture, public gardens and golf courses. On the contrary, greywater reuse is generally applied in in situ small scales, treated and used in the same place, generally in the production site. The main aim of this paper is to compare the two types of systems: a wastewater centralized reuse system (WWCRS) and a greywater decentralized reuse system (GWDRS) in terms of water quality, energy consumption and CO2 emissions. In this paper, the main characteristics of both streams are presented and the degree of treatment required in each stream is analyzed. The advantages and disadvantages of its reuse in different scales, in terms of water quality, energy consumption and CO2 emissions are discussed. A methodology to calculate the energy consumptions and CO2 emissions related to wastewater treatment that may be applied in different cases is presented. A hypothetical example of the two systems: one referring to a WWCRS and the other to a GWDRS is presented. The energy consumption and the CO2 emissions are analyzed and compared. The WWCRS needs a higher degree of treatment and so it spends more energy and leads to more CO2 emissions to the environment than the GWDRS that consumed between 11.8 and 37.5% of the energy consumed in the WWCRS considering the same number of inhabitants served.

Abstract