Objective and subjective evaluation of static 3D mesh compression

3D mesh compression is essential in the context of network-based virtual worlds, but so are objective and subjective fidelity of the reconstructed mesh to the original one. Unfortunately, it is difficult to establish a fair way to compare objectively two textured, triangular 3D meshes meant to approximate the surface of the same 3D object. We explain why by elaborating on how the geometric distance between two meshes can be estimated, after introducing some basic concepts related to mesh shape and a brief taxonomy of static 3D mesh coding techniques. We review a selection of such coding techniques, almost all of which deal only with the shape of the surface, and then focus on surface appearance, usually described separately with a texture to be mapped onto the 3D mesh at rendering time, and we also review existing techniques specifically devised to compress textures meant for 3D models. Finally, we discuss the even larger complexity of establishing any reasonable way to compare the subjective quality of the experience produced by two versions of the same 3D object, especially if different rendering methods may be used.     

Connection Admission Control in the UTRAN Transport Network

In this paper we propose a Connection Admission Control (CAC) algorithm to provide Quality of Service (QoS) in UMTS Terrestrial Radio Access Networks (UTRAN). In UTRAN, the main QoS requirement is to ensure low packet delays. The CAC algorithm works with priority scheduling, which is used for QoS differentiation. We give a detailed investigation on the performance implications of applying priority scheduler. We provide novel closed-form formulae which are fast, simple and accurate enough for practical implementation of the CAC. A comprehensive performance evaluation study with illustrative numerical examples is also presented. The results are validated by simulations.     

A Time-Domain Digital-Intensive Built-In Tester for Analog Circuits

To solve test challenges in nanometer CMOS technologies, a time-domain digital-intensive built-in tester for analog circuits is proposed. The compact tester allows characterizations of AC response and DC gain for various analog circuits which have a low-pass frequency characteristic. By applying ramp signals to stimulate the circuit under test and measuring slopes and time delays of its responses, the testing can be simple and robust over process-voltage-temperature variations. Also, it is well suited for nanometer technologies because of its digital-intensive implementation. The tester was fabricated in 65 nm standard CMOS process and occupies 0.026 mm².     

Analysis of delay mean and variance of collision-free WDM rings with segment recirculation of blocked traffic

In Tunable-Transmitter Fixed-Receiver (TT-FR)-based Wavelength Division Multiplexed (WDM) ring topologies, each node is provided with a dedicated wavelength (home channel) for reception, which must be shared by the upstream nodes willing to communicate with it. Thus, to avoid channel collisions, it is necessary to define a Medium Access Control (MAC) mechanism that arbitrates access to a given destination wavelength. This work proposes and analyses a simple MAC mechanism that avoids channel collisions by recirculating traffic on the upstream ring segment where congestion was detected. Essentially, whenever a given node has got any traffic to transmit, it must first block access to in-transit traffic, which is reflected back to the upstream node over a second optical fibre. Such blocked traffic is given a second chance to pass through the congested node after a round segment delay, thus making use of the ring topology as buffering units. This work analyses the performance operation of such a MAC protocol under two policies applied to recirculated traffic: (1) recirculation bypass and (2) recirculation store-and-forward.     

On the Influence of the Propagation Channel in the Performance of Energy-Efficient Geographic Routing Algorithms for Wireless Sensor Networks (WSN)

In this paper, the influence of the features of the propagation channel in the performance of energy-efficient routing algorithms for wireless sensor networks is studied. Although there are a lot of works regarding energy-efficient routing protocols, almost no reference to realistic propagation channel models and influence is made in the literature. Considering that the propagation channel may affect the efficiency of the different energy-efficient routing algorithms, different propagation scenarios are proposed in this work, from the most simplistic free-space propagation model to more complex ones. The latter includes the effects of multipath propagation, shadowing, fading, etc. In addition, spatial diversity transmission/reception models are considered to mitigate the effects of hard propagation fading. Some results are provided comparing the performance of several energy-efficient routing algorithms in different scenarios.     

Improved Thermal Behavior of Multiple Linked Arrays of Silicon Nanowires Integrated into Planar Thermoelectric Microgenerators

Low-dimensional structures have been shown to be promising candidates for enhancing the thermoelectric properties of semiconductors, paving the way for integration of thermoelectric generators into silicon microtechnology. With this aim, dense arrays of well-oriented and size-controlled silicon nanowires (Si NWs) obtained by the chemical vapor deposition (CVD)-vapor–liquid–solid (VLS) mechanism have been implemented into microfabricated structures to develop planar unileg thermoelectric microgenerators (μTEGs). Different low-thermal-mass suspended structures have been designed and microfabricated on silicon-on-insulator (SOI) substrates to operate as microthermoelements using p-type Si NW arrays as the thermoelectric material. To obtain nanowire arrays with effective lengths larger than normally attained by the VLS technique, structures composed of multiple ordered arrays consecutively bridged by transversal microspacers have been fabricated. The successive linkage of multiple Si NW arrays enabled the development of larger temperature differences while preserving good electrical contact. This gives rise to small internal thermoelement resistances, enhancing the performance of the devices as energy harvesters.     

Behavioural models for distributed Fractal components

This paper presents a formal behavioural specification framework for specifying and verifying the correct behaviour of distributed Fractal components. The first contribution is a parameterised and hierarchical behavioural model called pNets that serves as a low-level semantic framework for expressing the behaviour of various classes of distributed languages and as a common internal format for our tools. Then, we use this model to define the generation of behavioural models for applications ranging from sequential Fractal components, to distributed objects, and finally to distributed components. Our models are able to characterise both functional and non-functional behaviours and the interaction between the two concerns. Finally, this work has resulted in the development of tools allowing the non-expert programmer to specify the behaviour of his components and (semi)automatically verify properties of his application.     

Joint optimization of delay and congestion in wavelength-routed optical networks using genetic algorithms

A new multipurpose genetic algorithm, based on Pareto optimality, is proposed to design logical topologies for wavelength-routed optical networks with the aim of minimizing both the congestion and the end-to-end delay. Simulation results show its efficiency when compared with other previously proposed algorithms, achieving in most cases optimal or near-optimal solutions, and in less time than other methods. Moreover, since the algorithm relies on Pareto optimality, not only does it obtain a single logical topology but a set of them, so that the network designer can easily select the most appropriate one according to the current network requirements.     

A behavioral-based multi-agent optimization algorithm for system level radio design

This paper introduces a multi-agent behavioral-based optimization algorithm for system level radio design. Making multi-standard wireless communication receivers that meet their specs while keeping the requirements of the individual blocks as relaxed as possible is the goal of this algorithm. In order to achieve this goal a “divide and conquer” approach is proposed. Different agents focus on different objectives that are pursued in parallel. Agents adopt different behaviors depending on the status of the environment and their interaction with other agents. Agents are cooperative by default as they try to meet their spec without making changes that affect other agents. However, more aggressive behaviors that lead to global changes can be adopted when needed. The interaction between these simple entities yields an emergent behavior able to deal smoothly with the complexity of the problem at hand.     

Study of copper drift during TDDB of intermetal dielectrics by using fully passivated MOS capacitors as test vehicle

A fully passivated Metal-Oxide-Semiconductor (MOS) capacitor [T?kei Zs. Barrier integrity and reliability in copper low-k interconnects. ISTC 2005; 386–95] is used to study the intrinsic properties of a barrier between copper and dielectric in Back-End-Of-Line interconnects. Several barriers are studied and compared to each other. The test vehicle is also used to thoroughly investigate the role of thermal diffusion or field assisted ionic copper drift during Time-Dependent-Dielectric Breakdown (TDDB) by investigating the breakdown of dielectrics without a barrier at very low voltages.Comparing different barriers revealed that a “standard” PVD-based Ta barrier has a significantly better TDDB-performance compared to an 8 nm SiCN-barrier.For samples without barrier, it was found that long thermal anneals without the application of a stress voltage changes the distribution of failure times. Furthermore, the possibility of a bimodal distribution was argued when stressing these devices at a wide range of fields. A corollary is that, in presence of copper, both the E-model and the root-E-model do not apply for describing the experimental data obtained on these samples without barrier.