Tunable Optical Dispersion Compensator With Increased Bandwidth via Connection of a Mach–Zehnder Interferometer to an Arrayed-Waveguide Grating

We propose and demonstrate a novel colorless tunable optical dispersion compensator (TODC) consisting of a Mach-Zehnder interferometer (MZI) connected to an ar- rayed-waveguide grating with a thermooptic lens. The MZI approximately doubles the magnitude bandwidth at large dispersion settings. We demonstrate compensation of a 43-Gb/s nonreturn-to-zero signal dispersed over a range of -844 to + 1700 ps/nm. To our knowledge, +1700 ps/nm is the largest demonstrated dispersion compensation amount of a 40-Gb/s signal with a single TODC.     

A tunable interferometrically stable three-section higher order PMD emulator

We have developed a technique for emulating higher order polarization mode dispersion (PMD) that utilizes a three-section interferometrically stable configuration. Using this approach, we are able to study the impact of higher order PMD on 10-Gb/s nonreturn-to-zero and carrier-suppressed return-to-zero signals when first-order PMD is zero, which is a typical condition that occurs in one-stage optical PMD compensators.     

Accurate RF electrical characterization of CSPs using MCM-D thin film technology

The thin film multilayer multichip module-deposited (MCM-D) technology of IMEC is used for characterising the RF electrical performance of two types of chip scale packages (CSPs). The measurement technique called MCM-on-package-on-MCM (MoPoM) enables accurate measurements and de-embedding in the gigahertz (GHz) range of frequencies. Wafer processing of the MCM-D technology allows for several design structures to be integrated on a single mask. The packages chosen are a 120-pin plastic ball grid array (PBGA) and an 80-pin polymer stud grid array (PSGA). Lumped element models extracted from measurements and three-dimensional simulations show good agreement with the measurements up to 6 GHz for the BGA and the PSGA. The electrical performance of the packages is compared at 1.8 GHz (GSM), 2.4 GHz (Bluetooth), and 5.2 GHz (HiperLAN) and at 5.2 GHz both the packages exhibit a return loss of lower than -10 dB and hence cannot be used in most cases without design improvement. We also show that the influence of encapsulant is significant while transmission line detuning due to the package is not significant at microwave frequencies. We also briefly mention about the crosstalk effects. We demonstrate the significant degradation in the performance of a 5.2 GHz MCM-D low noise amplifier (LNA) after packaging. A significant improvement in package performance is observed by conjugate matching the package interconnects.     

Multiple and unsteady solutions for buoyancy driven flows in spherical annuli

Results from the analysis of buoyancy driven flows and heat transfer in concentric spherical annuli heated by the inner surface are presented. Crescent eddy flows obtained at low Grashof numbers, Gr, are consistent with published results. Multicellular flows, ranging from steady bicellular to oscillating five-cell flows, are calculated for Gr_c < Gr < Gr_r, the specific nature of the flows depending on γ and Gr. For Gr > Gr_r, the solution reverts to steady unicellular flows for the radial aspect ratios γ = 0.2 and 0.25, but with hysteresis for γ = 0.25. Heat transfer results, given in terms of the local and global Nusselt numbers, illustrate the effect of the flow structures on the heat transfer.     

The key to communicating at light speed-high-speed optoelectronicreceivers for fiber-optic communications

In this article, we will discuss the development and state-of-the-art results for an essential component in any fiber telecommunications system: the photoreceiver. The device technologies used in monolithically integrated receivers, the techniques for integration of the various devices required to realize a fully-functional OEIC, and the performance thus far achieved using these technologies will be described. In addition, some of the advantages of monolithic integration, as well as the promise of this technology for future network generations, will be presented     

Superscalar RISC machines,straight-line programs,and graphics

Implementors of graphics application programming interfaces (APIs) and algorithms are often required to support a plethora of options for several stages at the back end of the geometry and rasterization pipeline. Implementing these options in high-level programming languages such as C leads to code with many branches and large object modules due to indiscriminate duplication of very similar code. This reduces the speed of execution of the program. This paper examines the problems of branches and code size in detail and presents techniques for transforming typical code sequences in graphics programs to reduce the number of branches and to reduce to the size of the program. A set of branch-free basis functions is defined first. The application of these functions to common geometric queries, geometry pipeline computations, rasterization, and pixel processing algorithms is then discussed.     

Nontraditional Participation in Disaster Recovery Planning: Cases From China,India, and the United States

Problem, research strategy, and findings: Stakeholder participation facilitates efficient identification of recovery needs, dynamic exchange of information, and consolidation of diverse perspectives as well as builds long-term trust and social capital between stakeholders. Yet, planners often fail to use the full potential of participatory planning when they are caught in the fast-paced, uncertain, and complex post-disaster environment. We draw lessons from case studies on recovery planning after three major disasters: the Indian Ocean tsunami (2004), Hurricane Katrina (2005), and the Wenchuan earthquake (2008) in China. We collected qualitative data about participatory planning using key informant interviews with stakeholders, supplemented by field observations, records of planning meetings, and government documents. We find that stakeholder participation in disaster recovery planning can happen in nontraditional yet effective ways, including indirect representation and active opposition. Disasters can rebalance power relationships and create more opportunities for participation by marginalized groups. Stakeholders’ participatory behaviors evolve over the course of recovery due to shifting priorities, intensified resource competition, and the difficulty of using “normal” participatory mechanisms.

Takeaway for practice: Stakeholder participation, a time-consuming process, can actually speed up recovery in the long run. Planners must critically examine the local community's social and power structures, identify potential for nontraditional participation, tap into networks of indirect representation, and adapt to the changing landscape of actors and local interests to contend with the challenges of participation in disaster recovery and make use of new opportunities as they arise.     

Fully developed hydrodynamic and thermal transport in combined pressure and electrokinetically driven flow in a microchannel with asymmetric boundary conditions

Thermally and hydrodynamically fully developed combined pressure-driven and electroosmotic flow through a channel has been simulated for isoflux wall boundary conditions. Effects of asymmetries in wall zeta potential and heat flux have been considered and closed form expressions have been obtained for transverse distribution of electric potential, velocity and temperature. The results indicate that both flow and heat transfer characteristics are significantly affected by the asymmetries in wall boundary conditions for both purely electroosmotic and combined pressure-driven and electroosmotic flow. These findings have important implications for flow and heat transfer control in microfluidics through alteration of surface conditions.