A 90 nm CMOS 16 Gb/s Transceiver for Optical Interconnects

Interconnect architectures which leverage high-bandwidth optical channels offer a promising solution to address the increasing chip-to-chip I/O bandwidth demands. This paper describes a dense, high-speed, and low-power CMOS optical interconnect transceiver architecture. Vertical-cavity surface-emitting laser (VCSEL) data rate is extended for a given average current and corresponding reliability level with a four-tap current summing FIR transmitter. A low-voltage integrating and double-sampling optical receiver front-end provides adequate sensitivity in a power efficient manner by avoiding linear high-gain elements common in conventional transimpedance-amplifier (TIA) receivers. Clock recovery is performed with a dual-loop architecture which employs baud-rate phase detection and feedback interpolation to achieve reduced power consumption, while high-precision phase spacing is ensured at both the transmitter and receiver through adjustable delay clock buffers. A prototype chip fabricated in 1 V 90 nm CMOS achieves 16 Gb/s operation while consuming 129 mW and occupying 0.105 mm^2

CMOS transceiver with baud rate clock recovery for optical interconnects

An efficient baud rate clock and data recovery architecture is applied to a double sampling/integrating front-end receiver for optical interconnects. Receiver performance is analyzed and projected for future technologies. This front-end allows use of a 1:5 demux architecture to achieve 5Gb/s in a 0.25 μm CMOS process. A 5:1 multiplexing transmitter is used to drive VCSELs for optical transmission. The transceiver chip consumes 145mW per link at 5Gb/s with a 2.5V supply

Impact of solar panels on runoff generation process

Because of the benefits of solar energy, solar photovoltaic (PV) technology is being deployed at an unprecedented rate and the number of photovoltaic panels is sharply increasing. Agrophotovoltaic systems (solar farms) seem to be the most sustainable tools to create renewable energy without compromising agricultural production. However, utility-scale solar energy development is land intensive and its large-scale installation can have negative impacts on the environment. Moreover, its impacts on soil and on relative hydrological processes have been poorly studied. This article aims to evaluate the impact of solar panels on the runoff generation process, which is directly linked to the soil erosion process. Using a rainfall simulator, runoff measurements for a rainfall intensity equal to 56 mm/h were carried out by assuming different panel arrangements with respect to the maximum slope direction of the field (cross slope and aligned slope). Results were compared to a control reference of the same plot, with no panels (bare soil). Physical models found in the literature were then applied and calibrated, to upscale the models to a much higher hillslope length. Results showed that solar panels increase the peak discharge by about 11 times compared to the reference hillslope. A moderate effect of PV panel arrangement was observed on the peak discharges (11.7 and 11.5 times higher, for cross slope and aligned slope panels, respectively), whereas the time to runoff was the lowest for aligned slope panels (0.3 h), higher for cross slope panels (0.62 h), and the highest (1.2 h), for the bare soil hillslope. As it would be expected, upscaling the models to longer hillslopes resulted in increases in outlet discharges, and in the time to runoff, with an exception for aligned slope panels

Associations of cardiac structure with obesity, blood pressure, inflammation, and insulin resistance in African-American adolescents.

To determine if obesity, blood pressure (BP), markers of inflammation, and insulin resistance are associated with cardiac structure in African-American adolescents, a cross-sectional study was performed on a cohort oversampled for high BP and obesity. Measurements included the following: anthropometrics, BP, homeostasis model assessment (HOMA) to assess insulin resistance, high-sensitivity C-reactive protein, and plasma adipokines (adiponectin, interleukin-6, plasminogen activator inhibitor-1). Echocardiogram measurements were left-ventricular mass index (LVMI) (g/m(2.7)), LV relative wall thickness (LVRWT), left-atrial diameter index [LADI (mm/m)], and LV diastolic time intervals. LADI (r (2) = 0.25) was associated with body mass index (BMI) systolic BP (SBP) and female sex. LVMI (r (2) = 0.35) variation was associated with BMI SBP, heart rate, age, and male sex. LVRWT (r (2) = 0.05) was associated with HOMA. Tissue diastolic intervals were not associated with any risk factor. Inflammatory markers and adipokines were associated with BMI but were not independently associated with any echocardiographic measures. In African-American adolescents, BMI and SBP, but not inflammatory markers or adipokines, are important correlates of LA size and LVM

Spectral Ranking in Complex Networks Using Memristor Crossbars

Various centrality measures have been proposed to identify the influence of each node in a complex network. Among the most popular ranking metrics, spectral measures stand out from the crowd. They rely on the computation of the dominant eigenvector of suitable matrices related to the graph: EigenCentrality, PageRank, Hyperlink Induced Topic Search (HITS) and Stochastic Approach for Link-Structure Analysis (SALSA). The simplest algorithm used to solve this linear algebra computation is the Power Method. It consists of multiple Matrix-Vector Multiplications (MVMs) and a normalization step to avoid divergent behaviours. In this work, we present an analog circuit used to accelerate the Power Iteration algorithm including current-mode termination for the memristor crossbars and a normalization circuit. The normalization step together with the feedback loop of the complete circuit ensure stability and convergence of the dominant eigenvector. We implement a transistor level peripheral circuitry around the memristor crossbar and take non-idealities such as wire parasitics, source driver resistance and finite memristor precision into account. We compute the different spectral centralities to demonstrate the performance of the system. We compare our results to the ones coming from the conventional digital computers and observe significant energy savings while maintaining a competitive accuracy

Mesoscopic 3D Charge Transport in Solution-Processed Graphene-Based Thin Films: A Multiscale Analysis

Graphene and related 2D material (GRM) thin films consist of 3D assembly of billions of 2D nanosheets randomly distributed and interacting via van der Waals forces. Their complexity and the multiscale nature yield a wide variety of electrical characteristics ranging from doped semiconductor to glassy metals depending on the crystalline quality of the nanosheets, their specific structural organization ant the operating temperature. Here, the charge transport (CT) mechanisms are studied that are occurring in GRM thin films near the metal-insulator transition (MIT) highlighting the role of defect density and local arrangement of the nanosheets. Two prototypical nanosheet types are compared, i.e., 2D reduced graphene oxide and few-layer-thick electrochemically exfoliated graphene flakes, forming thin films with comparable composition, morphology and room temperature conductivity, but different defect density and crystallinity. By investigating their structure, morphology, and the dependence of their electrical conductivity on temperature, noise and magnetic-field, a general model is developed describing the multiscale nature of CT in GRM thin films in terms of hopping among mesoscopic bricks, i.e., grains. The results suggest a general approach to describe disordered van der Waals thin films

Properties of Neon, Magnesium, and Silicon Primary Cosmic Rays Results from the Alpha Magnetic Spectrometer

We report the observation of new properties of primary cosmic rays, neon (Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range 2.15 GV to 3.0 TV with 1.8 × 10$^{6}$ Ne, 2.2 × 10$^{6}$ Mg, and 1.6 × 10$^{6}$ Si nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The Ne and Mg spectra have identical rigidity dependence above 3.65 GV. The three spectra have identical rigidity dependence above 86.5 GV, deviate from a single power law above 200 GV, and harden in an identical way. Unexpectedly, above 86.5 GV the rigidity dependence of primary cosmic rays Ne, Mg, and Si spectra is different from the rigidity dependence of primary cosmic rays He, C, and O. This shows that the Ne, Mg, and Si and He, C, and O are two different classes of primary cosmic rays