Timing analysis of network on chip architectures for MP-SoC platforms

Recently, the use of multiprocessor system-on-chip (MP-SoC) platforms has emerged as an important integrated circuit design trend for high-performance computing applications. As the number of reusable intellectual property (IP) blocks on such platforms continues to increase, many have argued that monolithic bus-based interconnect architectures will not be able to support the clock cycle requirements of these leading-edge SoCs. While hierarchical system integration using multiple smaller buses connected through repeaters or bridges offer possible solutions, such approaches tend to be ad hoc in nature, and therefore, lack generality and scalability. Instead, many different forms of network on chip (NoC) architectures have been proposed in the past few years to specifically address this problem. We believe that the NoC approach will ultimately be the preferred communication fabric for next generation designs. To support this conjecture, this paper demonstrates, through detailed circuit design and timing analysis that different proposed NoC architectures to date are guaranteed to achieve the minimum possible clock cycle times in a given CMOS technology, usually specified in normalized units as 10-15 FO4 delays. This is contrasted with the bus-based approach, which may require several design iterations to deliver the same performance when the number of IP blocks connected to the bus exceeds certain limits.     

Incompleteness,Complexity, Randomness and Beyond

Gödel's Incompleteness Theorems have the same scientific status as Einstein's principle of relativity, Heisenberg's uncertainty principle, and Watson and Crick's double helix model of DNA. Our aim is to discuss some new faces of the incompleteness phenomenon unveiled by an information-theoretic approach to randomness and recent developments in quantum computing.     

Polyurethane doped with low‐concentration erbium

Polyurethane (PU) with lactate structures in its conformation can be used as a biological and biodegradable polymer. Polyurethane lactate (PUL) was doped with small quantities of an erbium (Er³⁺) complex, which hindered the N?N group. 2,2′‐Dihydroxyazobenzene was used as a ligand for the Er³⁺ complex. PUL in the presence of the used Er³⁺ complex caused water from the complex to be replaced by the polar structures from the polymer. These structures acted as crystallization germs for the structuration of the PU matrix. As a consequence, both the mechanical and thermal properties of the polymer were improved. The sample with the highest mechanical properties contained only 0.064 μmol of Er³⁺ complex/g of sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 659–669, 2007     

Schottky barrier versus surface ferroelectric depolarization at Cu/Pb(Zr,Ti)O3 interfaces

The band bending at Cu/PZT(001) interfaces is investigated by X-ray photoelectron spectroscopy (XPS) for a PZT(001) layer which exhibits initial outwards ferroelectric polarization. Two competitive processes are identified: (a) formation of the Schottky barrier between the ferroelectric and unconnected Cu islands, and (b) coalescence of the Cu islands, realisation of an electrical contact to the ground of the system, inducing the apparent loss of the component of the ferroelectric polarization perpendicular to the sample surface, at least as it manifests in band bending. Three mechanisms are proposed to explain this loss of band bending when a full metal layer connected to ground is formed on the surface: (i) over-compensation of depolarization field in the sub-surface region, (ii) formation of domains with in-plane orientation of the polarization vector and (iii) loss of polarization in the near-surface layers of the ferroelectric due to electrons provided by the metal. These result in a non-monotonous variation of binding energies with the amount of Cu deposited. High resolution transmission electron microscopy and piezoresponse force microscopy confirmed these hypotheses. The XPS data allowed also to derive the surface PZT composition, its evolution with the deposition of copper and the formation of surface compounds.     

Charge Photogeneration in Few‐Layer MoS2

The 2D semiconductor MoS₂ in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS₂. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS₂ photovoltaic and photodetector devices are made.     

Potential for free-cooling by ventilation

Natural ventilation is one of the most effective techniques for cooling. Its potential for cooling may be assessed by using a method based on the indoor–outdoor temperature difference of the free-running building, the adaptive comfort criteria and the outdoor temperature. It is demonstrated that the free-running temperature may be used instead of the balance temperature in energy estimation methods. The indoor–outdoor temperature difference of the free-running building becomes a characteristic of the thermal behavior of the building which is decoupled from comfort range and outdoor temperature. A measure related to the energy saved and the applicability of free-cooling is given by the probabilistic distribution of the degree-hours as a function of the outdoor temperature and time. Weather data for this method are available in public domain from satellite investigation. The method can be applied when buildings similar to existing ones are constructed in a new location, when existing buildings are retrofitted or when completely new buildings are designed. The method may be used to interpret the results of building simulation software or of the field measurements.     

Experimentation with a water tank including a PCM module

Storage of heat is seen as a major issue for the development of solar energy for house heating and cooling under all climates. Most of the storage systems available on the market use water as the storage medium. The idea studied here was to add a phase change material (PCM) module at the top of a hot-water storage tank with stratification. An experimental solar pilot plant was constructed to test the PCM behaviour in real conditions. The PCM module geometry adopted was to use several cylinders. A granular PCM–graphite compound was chosen as the PCM for the experiments presented here.     

Effectiveness of nitrogen incorporation to enhance the photoelectrochemical activity of nanostructured TiO2:NH3 versus H2-N2 annealing

Highly ordered TiO(2) nanohole layers were synthesized by anodic oxidation of titanium foils using ethylene glycol and ammonium fluoride as the electrolyte. The effectiveness of different methods, namely annealing at 500?°C in NH(3) and in H(2) diluted in N(2), to incorporate nitrogen into TiO(2) and thus extend its photoelectrochemical (PEC) activity to the visible range was studied. The intra-gap levels introduced by both processes were identified by means of XPS and PL measurements. Water splitting experiments demonstrated that annealing in H(2) improved the photocatalytic activity of pure TiO(2), while annealing in ammonia led to a decrease in the PEC performance.     

Image Analysis of Representative Food Structures: Application of the Bootstrap Method

ABSTRACT:  Images (for example, photomicrographs) are routinely used as qualitative evidence of the microstructure of foods. In quantitative image analysis it is important to estimate the area (or volume) to be sampled, the field of view, and the resolution. The bootstrap method is proposed to estimate the size of the sampling area as a function of the coefficient of variation (CV _Bn ) and standard error (SE _Bn ) of the bootstrap taking sub-areas of different sizes. The bootstrap method was applied to simulated and real structures (apple tissue). For simulated structures, 10 computer-generated images were constructed containing 225 black circles (elements) and different coefficient of variation (CV _image ). For apple tissue, 8 images of apple tissue containing cellular cavities with different CV _image  were analyzed. Results confirmed that for simulated and real structures, increasing the size of the sampling area decreased the CV _Bn  and SE _Bn . Furthermore, there was a linear relationship between the CV _image  and CV _{Bn .} For example, to obtain a CV _Bn  = 0.10 in an image with CV _image  = 0.60, a sampling area of 400 × 400 pixels (11% of whole image) was required, whereas if CV _image  = 1.46, a sampling area of 1000 × 100 pixels (69% of whole image) became necessary. This suggests that a large-size dispersion of element sizes in an image requires increasingly larger sampling areas or a larger number of images.