Efficient visualization of large routing topologies

As the Internet grows in size and complexity, network managers face a significant challenge in trying to understand the behaviour of routing protocols in large networks. In this paper, we present a tool called VLNT (visualizing large network topologies), which helps network managers to analyse complex routing topologies. A key contribution of our system is a novel hybrid layout algorithm, which significantly reduces the computation time required to layout large network topologies in comparison to conventional layout approaches. In addition our algorithm includes a novel termination criterion that avoids unnecessary iterations when optimizing the network layout. We demonstrate how the visualization features of VLNT can be used to analyse and improve BGP routing topologies, and provide examples using real‐life routing data. Copyright © 2004 John Wiley & Sons, Ltd.     

Higher education for the information age

The new generation of engineering professionals needs to know not only the scientific and engineering principles, but also have extensive knowledge about arts, literature, and social sciences. They need far-reaching vision for the future in order to understand grand challenges on the technical-level, the system-level, and the social aspects of topics that are of importance to the modern society. One solution is to emphasize fundamental courses such as mathematics and physics with new interpretation to correlate with real-world applications. It is important to include system-oriented topics in the curriculum so that students know how to apply the basic principles, The key focus should be placed on analysis and design skills, and effective communication is essential to address any large-scale problems     

Polarisation insensitive semiconductor optical amplifier withintegrated electroabsorption modulators

The authors demonstrate a 1.55 μm wavelength multiquantum well semiconductor optical amplifier, integrated with bulk layer electroabsorption modulators and passive waveguide beam expanders at the input and output ports. The device has a fibre to fibre gain of 9 dB, an extinction ratio of 15 dB per modulator, a spectral range >35 nm, and polarisation sensitivity <1 dB     

Enhancement of the photoelectric performance of dye-sensitized solar cells by using a CaCO3-coated TiO2 nanoparticle film as an electrode

Core-shell-type nanoparticles with TiO₂ cores and CaCO₃ shells were applied as the electrode of dye-sensitized solar cells. The performance of the cell was significantly improved (as high as 26.7%) compared to the case when un-coated TiO₂ particle film was used as electrode. The improved energy conversion efficiency has been ascribed to (i) enhanced dye adsorption due to the high isoelectric point of the overlayer, and (ii) the prevention of the back electron transfer by the insulating nature of the overlayer.     

Development of a Highly Selective,Sensitive, and Fast Response Upconversion Luminescent Platform for Hydrogen Sulfide Detection

Hydrogen sulfide (H₂S) has been recognized as one of most important gaseous signaling molecules mediated by a variety of physiological and pathological processes. Yet, its functions remain largely elusive due to the lack of potent monitoring methods. Hereby this issue is addressed with a powerful new platform—dye‐assembled upconversion nanoparticles (UCNPs). A series of chromophores with different absorption bands and fast responses towards H₂S is combined with UCNPs and results in a library of H₂S sensors with responsive emission signals ranging from the visible to the near‐infrared (NIR) region. These nanoprobes demonstrate highly selective and rapid responses to H₂S in vitro and in cells. Furthermore, H₂S levels in blood can be detected using the developed nanoprobes. Hence the reported H₂S sensing platform can serve as a powerful diagnostic tool to research H₂S functions and to investigate H₂S‐related diseases.     

High-Gain Chemically Gated Organic Electrochemical Transistor

Organic electrochemical transistors (OECTs) have exhibited promising performance as transducers and amplifiers of low potentials due to their exceptional transconductance, enabled by the volumetric charging of organic mixed ionic/electronic conductors (OMIECs) employed as the channel material. OECT performance in aqueous electrolytes as well as the OMIECs’ redox activity has spurred a myriad of studies employing OECTs as chemical transducers. However, the OECT's large (potentiometrically derived) transconductance is not fully leveraged in common approaches that directly conduct chemical reactions amperometrically within the OECT electrolyte with direct charge transfer between the analyte and the OMIEC, which results in sub-unity transduction of gate to drain current. Hence, amperometric OECTs do not truly display current gains in the traditional sense, falling short of the expected transistor performance. This study demonstrates an alternative device architecture that separates chemical transduction and amplification processes on two different electrochemical cells. This approach fully utilizes the OECT's large transconductance to achieve current gains of 10³ and current modulations of four orders of magnitude. This transduction mechanism represents a general approach enabling high-gain chemical OECT transducers.     

Progressive NO2 Sensors with Rapid Alarm and Persistent Memory-Type Responses for Wide-Range Sensing Using Antimony Triselenide Nanoflakes

Antimony triselenide (Sb₂Se₃) nanoflake-based nitrogen dioxide (NO₂) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb₂Se₃ nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO₂ gas concentrations from 0.1 to 100 ppm. These Sb₂Se₃ nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb₂Se₃ nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO₂ gas flow of only 1 ppm. As a result, the Sb₂Se₃ nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations.     

2/spl times/4 optical add-drop module with no difference in propagation length

We developed a micromachined X-type 2/spl times/4 optical add-drop module (OADM) featuring no difference in propagation length. Four pairs of lensed fibers are aligned in "X" position, and four micromirrors are located between the pairs of optical fibers. The OADM was fabricated utilizing a silicon-on-insulator process. Electrostatic comb actuators can be driven up to 90 /spl mu/m to change the light path within 1 ms. The insertion loss and the on-off ratio were less than 3 and 70 dB, respectively. The loss uniformity in every channel was 1.5 dB.     

Probing stress effects in HfO2 gate stacks with time dependent measurements

Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO₂ dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (V_t) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on V_t.