A Two-Layer Framework for Mitigating the Congestion of Urban Power Grids Based on Flexible Topology with Dynamic Thermal Rating

The urban power grid (UPG) combines transmission and distribution networks. Past studies on UPG congestion mitigation have primarily focused on relieving local congestion while ignoring large-scale energy transfer with safety margins and load balancing. This situation is expected to worsen with the proliferation of renewable energy and electric vehicles. In this paper, a two-layer congestion mitigation framework is proposed, one which considers the congestion of the UPG with flexible topologies. In the upper-layer, the particle swarm optimization algorithm is employed to optimize the power supply distribution (PSD) of substation transformers. This is known as the upper-layer PSD. The lower-layer model recalculates the new PSD, known as the lower-layer PSD, based on the topology candidates. A candidate topology is at an optimum when the Euclidean distance mismatch between the upper-and lower-layer PSDs is the smallest. This optimum topology is tested by standard power flow to ascertain its feasibility. The optimum transitioning sequence between the initial and optimum topologies is also determined by the two-layer framework to minimize voltage deviation and line overloading of the UPG considering dynamic thermal rating. The proposed framework is tested on a 56-node test system. Results show that the proposed framework can significantly reduce congestion, maintain safety margins, and determine the optimum transitioning sequence.     

Effects of chemical modification of epoxy‐(ethylene diamine) on water hyacinth fibers (Eichhornia crassiper)‐filled (low‐density polyethylene)/(natural rubber) blends

The effects of modification by epoxy‐(ethylene diamine) (EED) on (water hyacinth fiber)‐filled (low‐density polyethylene)/(natural rubber) (LDPE/NR/WHF_‐EED) composites were studied. The LDPE/NR/WHF and LDPE/NR/WHF_‐EED composites were prepared by using a Brabender Plasticorder. LDPE/NR/WHF_‐EED showed higher tensile strength, Young's modulus, and elongation at break but lower molar sorption of toluene compared with LDPE/NR/WHF composites. The Fourier‐transform infrared radiation analysis indicated that the absorption peak at 1,648 cm^?1 exhibited the C? N band. This C? N band was formed from the bond of the epoxy group and the amine group in the WHF‐g‐epoxy‐(ethylene diamine) (WHF_‐EED). The scanning electron microscopic morphology of LDPE/NR/WHF_‐EED composites displayed rougher surfaces and less fiber pull, which improved the interfacial adhesion among the fiber/matrix. J. VINYL ADDIT. TECHNOL., 20:201–209, 2014. © 2014 Society of Plastics Engineers     

Performance and diversity analysis of decode‐and‐forward cooperative system over Nakagami‐m fading channels

In this paper, we derive the upper bound of bit‐error rate (BER) performance and diversity gain for a decode‐and‐forward (DF) cooperative system. Either maximal‐ratio combining (MRC) or cooperative MRC (C‐MRC) is employed at the receiver in the presence of independent, non‐identical Nakagami‐m fading. Both analytical and simulation results show that C‐MRC takes advantage of spatial diversity more efficiently and thus achieves the same or better performance and diversity order as compared to MRC. Copyright © 2009 John Wiley & Sons, Ltd.     

Enhanced gettering of iron impurities in bulk silicon by using external direct current electric field

Iron impurities in bulk silicon are found to getter efficiently at the polysilicon layer by an electric field during isothermal annealing. Experimental results show that iron concentration at the polysilicon layer increases to the level that becomes detectable by total reflection x-ray fluorescence (TXRF) spectroscopy. The improved gettering efficiency for iron is attributed mainly to the directional drift of ionic iron interstitials toward the polysilicon gettering sites, under the influence of the applied potential gradient, thus presenting a more effective method for reducing the iron content in silicon.     

Maximum-likelihood receiver with side information for asynchronous FFH-MA/MFSK systems over Rayleigh fading channels

The maximum-likelihood (ML) receiver structure and the corresponding analytical bit-error rate (BER) expressions for a fast-frequency hopped multiple-access (FFH-MA) M-ary frequency-shift-keying (MFSK) system over Rayleigh-fading channels are derived. Numerical results are also presented to illustrate the superiority of the proposed ML receiver in terms of BER. However, the proposed ML receiver requires some side information of the noise and interfering users.     

Performance Analysis of a Maximum-Likelihood FFH/MFSK Receiver with Partial-Band-Noise Jamming over Frequency-Selective Fading Channels

A maximum-likelihood (ML) receiver is proposed for a fast frequency-hopping M-ary frequency-shift-keying system. The effects of frequency-selective Rayleigh-fading channels, partial-band-noise jamming, and additive white Gaussian noise are considered. It is shown that side information on the noise variance, the jamming variance, as well as the power levels of the correlated paths, is required to implement the ML receiver. Analytical bit-error rate expressions are derived for the ML receiver. Our analysis also shows that there exists an optimum diversity order under certain channel conditions.     

Rational bicubic simple quadrilateral mesh surfaces

In free-form modeling a closed smooth piecewise surface is highly desirable when the smoothness across the boundaries of patches can be represented within the formulation. Closed, smooth, piecewise bicubic surfaces, defined on simple quadrilateral mesh. (SQM), may be defined as SQM surfaces. We have extended previous work on SQM surfaces and described the surface representation in rational form. The global constraint of the control parameters associated with each control vertex is relaxed. The new local shape-control parameters with their larger range of usability further enhance the power of this free-form surface design scheme. We have also provided more B-spline functions. A complete set of B-spline functions for various topologies of the SQM is now available. Examples demonstrate that editing of shapes for reasonably complex objects can be carried out on an SGI Personal Iris machine at an interactive rate.