Analysis of switched capacitor DC-DC step down converter

A 5V/1 V Switched Capacitor (SC) dc-dc converter designed for a 0.18μm CMOS process is analysed in detail, in this paper. Analytical equations are derived for the voltages and currents through the main components of the SC converter. The model includes switches, capacitors, equivalent series resistances and the load. The switches in the converter are represented by MOSFETs in the UMC 0.18μm CMOS process. The impact of system parameters on output voltage ripple are studied using the analytical expressions.

1.55-μm VCSEL transmission performance up to 20 Gb/s for access networks

We experimentally demonstrate for the first time 1.55μm vertical-cavity surface-emitting laser (VCSEL) transmission over 6.5 km single mode fiber (SMF) at 20 Gb/s for optical access networks. Characterization of the device is also investigated. © 2009 IEEE.

Synapses with short-term plasticity are optimal estimators of presynaptic membrane potentials.

The trajectory of the somatic membrane potential of a cortical neuron exactly reflects the computations performed on its afferent inputs. However, the spikes of such a neuron are a very low-dimensional and discrete projection of this continually evolving signal. We explored the possibility that the neuron's efferent synapses perform the critical computational step of estimating the membrane potential trajectory from the spikes. We found that short-term changes in synaptic efficacy can be interpreted as implementing an optimal estimator of this trajectory. Short-term depression arose when presynaptic spiking was sufficiently intense as to reduce the uncertainty associated with the estimate; short-term facilitation reflected structural features of the statistics of the presynaptic neuron such as up and down states. Our analysis provides a unifying account of a powerful, but puzzling, form of plasticity.

Carbon dioxide from earthworks: A bottom-up approach

Concerns over climate change mean engineers need to understand the greenhouse gas emissions associated with infrastructure projects. Standard coefficients are increasingly used to calculate the embodied emissions of construction materials, but these are not generally appropriate to inherently variable earthworks. This paper describes a new tool that takes a bottom-up approach to calculating carbon dioxide emissions from earthworks operations. In the case of bulk earthworks this is predominantly from the fuel used by machinery moving materials already on site. Typical earthworks solutions are explored along with the impact of using manufactured materials such as lime.

Evidence of shark predation and scavenging on fishes equipped with pop-up satellite archival tags

Over the past few years, pop-up satellite archival tags (PSATs) have been used to investigate the behavior, movements, thermal biology, and postrelease mortality of a wide range of large, highly migratory species including bluefin tuna (Block et al., 2001), swordfish (Sedberry and Loefer, 2001), blue marlin (Graves et al., 2002), striped marlin (Domeier and Dewar, 2003), and white sharks (Boustany et al., 2002). PSAT tag technology has improved rapidly, and current tag models are capable of collecting, processing, and storing large amounts of information on light level, temperature, and pressure (depth) for a predetermined length of time before the release of these tags from animals. After release, the tags float to the surface, and transmit the stored data to passing satellites of the Argos system.