GaAs-AlGaAs quantum cascade lasers: physics, technology, andprospects

In recent years, the performance of GaAs-AlGaAs-based quantum cascade (QC) lasers has improved markedly. These devices are capable of pulsed room temperature operation and can deliver respectable average powers (11 mW at λ~9 μm) operating on a Peltier cooler. This performance has been achieved by the suppression of thermally activated carrier leakage through increases in the heterobarrier band offset. We demonstrate that QC lasers, with wavelengths λ⩾9 μm, can operate using heterostructures encompassing the entire composition range of Al_xGa_1-xAs, without encountering potential problems-of the satellite X-minima for x>45%. Furthermore, we present particular characteristics of these devices, such as a phonon-limited temperature dependence, electrical and optical self-oscillations, and novel design concepts that exploit this closely lattice matched material system. Finally, we discuss improvements in device fabrication to lower the operating current through a reduction of the area of current injection. Using this technology, devices can be designed to selectively pump the fundamental lateral mode. We, therefore, observe single spatial-mode operation over the entire current range of operation     

Empirical study on Game Transfer Phenomena in a location-based augmented reality game

Research on Game Transfer Phenomena (GTP) has demonstrated that playing video games can lead to re-experiencing images, sounds, tactile sensations, spontaneous thoughts and actions, sometimes triggered by physical objects/events associated with the game. Location-based augmented reality games posit interesting questions regarding GTP, particularly because they use physical locations, they overlay digital images in physical contexts and the gameplay shifts between the virtual and the physical world. This study aims to investigate the prevalence of GTP and the role of immersion, augmented reality and sound in a sample of English- (EnS) and Spanish- (SpS) speaking gamers of the game Pokémon Go (PoGo). A total of 1313 gamers (M_age?=?31.47) were recruited online. GTP was less common than in previous studies; however, 82.4% had experienced GTP at least once. The SpS showed higher prevalence of GTP and played more intensively. Automatic mental processes predominated in the EnS, while behaviours and actions were more common in the SpS. The absence or presence of video game features seems important for the way GTP manifests. For instance, tactile hallucinations were more prevalent, while sensations of self-motion were less reported. Playing with augmented reality (AR) and sounds showed significant correlations with various GTP types, but not with re-experiencing images from the game. More gamers who reported the sensation that Pokémon were physically present or looked for Pokémon outside the screen while playing, as connotations of immersion, had experienced GTP. Experiencing GTP while playing may be more common in location-based augmented reality games, compared to other games.     

Fabrication and characterization of PEDOT nanowires based on self-assembled peptide nanotube lithography

In this article we demonstrate the use of self-assembled peptide nanotube structures as masking material in a rapid, mild and low cost fabrication of polymerized p-toluenesulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT:TsO) nanowire device. In this new fabrication approach the PEDOT:TsO nanowire avoids all contact with any organic solvents otherwise traditionally used in clean room fabrication. This can be achieved due to the intriguing properties of the self-assembled peptide nanotubes utilized as a dry etching mask for the patterning of the PEDOT:TsO nanowire. The peptide nanotubes, despite remaining stable during the reactive ion etching procedure, can be dissolved rapidly in water afterwards. The fabricated PEDOT:TsO nanowire devices exhibit excellent electrical characteristics. Finally, the potential of PEDOT:TsO nanowires as temperature sensors has been demonstrated and the high resolution of the sensor was illustrated.     

Output feedback and dynamical sliding-mode control of power converters

Using the underlying idea of the most widely accepted controller for power converters, the current-mode control, a new dynamical and sliding-mode control for dc–dc power converters, is proposed. The controller requires only voltage measurements; is easy to design; is robust under load and input voltage variations, exhibits fast response and does not depend on the load (although a knowledge of the load range is necessary to tune the controller). In spite of these features, it can be easily implemented using standard electronics components. The stability analysis is carried out using the discontinuous (large signal) nonlinear model. This analysis provides a set of controller admissible parameters to keep closed-loop system stability.     

Very Low Voltage MOS Translinear Loops Based on Flipped Voltage Followers

A novel technique for operating MOS Translinear loops at very low supply voltages is described, based on the use of Flipped Voltage Followers for biasing the loops. The resulting topologies, suited to standard CMOS processes, can be successfully applied to a varied repertory of low-voltage analog circuits, such as squarers, multipliers, filters, oscillators, and RMS-DC converters. Measurement results for a geometric-mean and a squarer/divider circuit demonstrate on silicon the usefulness of this technique.     

Exploring Social Networks and Improving Hypertext Results for Cloud Solutions

Internet technologies are constantly evolving as well as the way people use them. Search engines help users to find higher and better relevant results to their searches. Cloud Computing is an evolution of the Internet services and provides a step further ecosystem that can be used to improve the search of more relevant results. Each search engine is based on different modules in order to retrieve the results expected by users using specific keywords. Social networks appear as a reliable Web technology that can directly support a content search. Several studies have been performed showing the growth of social networks in people lives. Using the cloud computing paradigm it is possible to propose a more scalable and efficient way to explore public information available on online social networks. This paper includes the analyses of several social networks services, available contents, cloud-crawlers, and information extraction. In order to collect relevant data from social networks, a social crawler on cloud is proposed. The new approach provides a cloud-based crawler for low-cost, effective, and personalized search models. Moreover, a new algorithm to rank Web documents is proposed and demonstrated. The proposed system is evaluated in comparison with the top Internet search engine, Google, its behavior is very promising, and it is ready for use.     

License Plate Recognition for Parking Control System by Mathematical Morphology

Nowadays, license plate recognition for parking systems is a critical task to provide automatic control of customers and payment. This paper introduces a new method for automatic recognition of license plates of vehicles by mathematical morphology.The proposed method can provide the license plate number of the plates in different light conditions, colors,sizes, and inclination(angles). The algorithm can recognize the license plates of European Union vehicles quickly and correctly. The pattern learning of mathematical skeletons has high efficiency in the process. The performance of the algorithm is demonstrated well by the test in a parking control system.     

Highly linear micropower class AB current mirrors using Quasi-Floating Gate transistors

A design approach to achieve low-voltage micropower class AB CMOS cascode current mirrors is presented. Both class AB operation and dynamic cascode biasing are based on the use of Quasi-Floating Gate transistors. They allow high linearity for large signal currents and accurately set quiescent currents without requiring extra power consumption or supply voltage requirements. Measurement results show that dynamic cascode biasing allows a wider input range and a linearity improvement of more than 23 dB with respect to the use of conventional biasing. A THD value better than −35 dB is measured for input amplitudes up to 100 times the bias currents. Two class AB current mirror topologies are proposed, with slightly different ways to achieve class AB operation and dynamic biasing. The proposed current mirrors, fabricated in a 0.5 µm CMOS technology, are able to operate with a supply voltage of 1.2 V and a quiescent power consumption of only 36 µW, using a silicon area <0.025 mm².     

Scheduling Combined Unicast and Multicast Traffic in Broadcast WDM Networks

This paper studies the performance of various strategies for scheduling a combined load of unicast and multicast traffic in a broadcast WDM network. The performance measure of interest is schedule length, which directly affects both aggregate network throughput and average packet delay. Three different scheduling strategies are presented, namely: separate scheduling of unicast and multicast traffic, treating multicast traffic as a number of unicast messages, and treating unicast traffic as multicasts of size one. A lower bound on the schedule length for each strategy is first obtained. Subsequently, the strategies are compared against each other using extensive simulation experiments in order to establish the regions of operation, in terms of a number of relevant system parameters, for which each strategy performs best. Our main conclusions are as follows. Multicast traffic can be treated as unicast traffic, by replicating all multicast packets, under very limited circumstances. On the other hand, treating unicast traffic as a special case of multicast traffic with a group of size 1, produces short schedules in most cases. Alternatively, scheduling and transmitting each traffic component separately is also a good choice.     

Ku-band high-power lowpass filter with spurious rejection

A Ku-band high-power lowpass filter with spurious passband suppression up to 40 GHz is proposed in rectangular waveguide technology. The new design consists of a conventional E-plane corrugated lowpass filter cascaded with a quasi-periodic structure tuned to reject the undesired spurious passbands. This new design technique allows the minimum gap of the original corrugated filter to be kept wide enough to permit high-power operation