Geometric, Variational Integrators for Computer Animation

We present a general-purpose numerical scheme for time integration of Lagrangian dynamical systems—an important computational tool at the core of most physics-based animation techniques. Several features make this particular time integrator highly desirable for computer animation: it numerically preserves important invariants, such as linear and angular momenta; the symplectic nature of the integrator also guarantees a correct energy behavior, even when dissipation and external forces are added; holonomic constraints can also be enforced quite simply; finally, our simple methodology allows for the design of high-order accurate schemes if needed. Two key properties set the method apart from earlier approaches. First, the nonlinear equations that must be solved during an update step are replaced by a minimization of a novel functional, speeding up time stepping by more than a factor of two in practice. Second, the formulation introduces additional variables that provide key flexibility in the implementation of the method. These properties are achieved using a discrete form of a general variational principle called the Pontryagin-Hamilton principle, expressing time integration in a geometric manner. We demonstrate the applicability of our integrators to the simulation of non-linear elasticity with implementation details

Spin-polarized Quantum Transport in Mesoscopic Conductors: Computational Concepts and Physical Phenomena

Mesoscopic conductors are electronic systems of sizes in between nano- and micrometers, and often of reduced dimensionality. In the phase-coherent regime at low temperatures, the conductance of these devices is governed by quantum interference effects, such as the Aharonov-Bohm effect and conductance fluctuations as prominent examples. While first measurements of quantum charge transport date back to the 1980s, spin phenomena in mesoscopic transport have moved only recently into the focus of attention, as one branch of the field of spintronics. The interplay between quantum coherence with confinement-, disorder- or interaction-effects gives rise to a variety of unexpected spin phenomena in mesoscopic conductors and allows moreover to control and engineer the spin of the charge carriers: spin interference is often the basis for spin-valves, -filters, -switches or -pumps. Their underlying mechanisms may gain relevance on the way to possible future semiconductor-based spin devices. A quantitative theoretical understanding of spin-dependent mesoscopic transport calls for developing efficient and flexible numerical algorithms, including matrix-reordering techniques within Green function approaches, which we will explain, review and employ.Comment: To appear in the Encyclopedia of Complexity and System Scienc

Intelligent Agents: A Physics Education Opportunity in Latin-America

Intelligent Agents are being applied in a wide range of processes and everyday applications. Their development is not new, in recent years they have had an increased attention and design in learning and as mentoring tools. In this paper we discuss the definition of what an intelligent agent is; how they are applied; how thy look like; recent implementations of agents; agents as support in learning process; their state in Latin-American countries and future developments and trends that will permit a better communication between people and agents.Comment: 6 page

Humidity control in different building applications; restaurant and operation theatre

Air conditioning (AC) in tropical climate required dehumidification of air at a low dew point temperature to meet humidity standard. This increase the required cooling energy and heating energy is needed to raise the supply air temperature to meet the room’s design temperature. This research was carried out to study energy efficiency and indoor environment factor in two different applications that is restaurant and operation theatre (OT). A method was proposed to enhance the humidity control and energy efficiency in the AC system by applying psychrometric analysis based on actual measurement. Three (3) different systems were used in this study that consists of economizer damper, desiccant wheel and heat pipe heat exchanger (HPHX).The economizer damper analysed base on fresh air intake requirement for ventilation purposes on standard ASHRAE 55 (2010). Manufacturing software by Novelaire and HPC were used to perform the psychorometric analysis for desiccant wheel and HPHX. At the restaurant, the grand total loads (Qt) of the existing AC system were 296.1 kW as to meet temperature and humidity level requirement. The Qt was reduced to 153.8 kW for economizer damper, 170 kW with heating 60.38 kW for desiccant wheel and 178.3 kW with heating 4.1 kW for HPHX. In actual measurement for the OT, the existing AC system had a grand total load Qt of 90.1 kW with heating 5.6 kW and it did not meet the humidity level requirement. However, the AC system required Qt 95.9 kW with heating 12.2 kW as to meet the humidity level requirement for an OT. By using the HPHX in the system, a reduced Qt of 81.6 kW with heating 17.7 kW was achieved, where as a Qt of 100.8 kW with heating 39.9 kW was attained by utilizing the desiccant wheel, whilst maintaining the humidity level requirement. The economizer damper was not applicable for the OT because the OT requires 100% fresh air intake. As a conclusion, damper economizer was beneficial for energy efficiency in restaurants with reducing of 48% energy used and HPHX was beneficial for energy efficiency with reduced 9.4% in OT compared with existing AC system