Hydro resource management,risk aversion and equilibrium in an incomplete electricity market setting

Since the outset of power system reform, one of the main objectives of regulation has been to assess whether the market, of its own accord, can induce agents to adopt decisions that maximise social welfare.This paper analyses the effect of generating companies' risk aversion on their medium-term (typically 1 year) hydroelectric resource planning, along with its possible inducement of system operation that deviates from the centralised (maximum social welfare) solution.Forward markets may play a key role by making hedging instruments available to risk-averse agents. A stylised mathematical model is used in this study to prove the equivalence of centralised planning and market equilibrium in the presence of such agents under the following assumptions: 1) both the spot and forward markets are perfectly competitive; 2) it has at least one risk-neutral consumer or arbitrageur; 3) all agents share the same beliefs about uncertain parameters; 4) only one price is in place in each trading period (which can be perfectly hedged with a forward contract); and 5) a solution for the resulting market equilibrium problem exists.The findings show that such equivalence vanishes when forward markets are missing or inaccessible (attributable in some electricity markets to the absence of demand-side participation). This article consequently suggests that requiring demand-side agents to sign forward contracts with generators might constitute an effective regulatory measure where no fully functional forward market is already in place.     

Preparation and temperature-resistance characteristics of novel dense SiAlCN ceramics

The compact green bodies, prepared via a novel solid-liquid mixing method of precursors, were successfully pyrolyzed to obtain the dense bulk SiAlCN ceramics at 1000 °C. It can be seen from their SEM that they have uniform and dense microstructure, indicating that this method can be used to prepare bulk ceramics. In order to verify that they can be used as sensor heads, their temperature-resistance characteristics and repeatability were tested. The results show that the conductive mechanism belongs to Arrhenius's Tailed-State and Extended-State in the temperature range of 500–650 °C and 650–930 °C, respectively. And it shows that SiAlCN ceramics can be used as the sensor heads for high-temperature sensors.     

A call admission and rate control scheme for multimedia support over IEEE 802.11 wireless LANs

Quality of service (QoS) support for multimedia services in the IEEE 802.11 wireless LAN is an important issue for such WLANs to become a viable wireless access to the Internet. In this paper, we endeavor to propose a practical scheme to achieve this goal without changing the channel access mechanism. To this end, a novel call admission and rate control (CARC) scheme is proposed. The key idea of this scheme is to regulate the arriving traffic of the WLAN such that the network can work at an optimal point. We first show that the channel busyness ratio is a good indicator of the network status in the sense that it is easy to obtain and can accurately and timely represent channel utilization. Then we propose two algorithms based on the channel busyness ratio. The call admission control algorithm is used to regulate the admission of real-time or streaming traffic and the rate control algorithm to control the transmission rate of best effort traffic. As a result, the real-time or streaming traffic is supported with statistical QoS guarantees and the best effort traffic can fully utilize the residual channel capacity left by the real-time and streaming traffic. In addition, the rate control algorithm itself provides a solution that could be used above the media access mechanism to approach the maximal theoretical channel utilization. A comprehensive simulation study in ns-2 has verified the performance of our proposed CARC scheme, showing that the original 802.11 DCF protocol can statically support strict QoS requirements, such as those required by voice over IP or streaming video, and at the same time, achieve a high channel utilization. Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January 2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft Research Asia from January 2002 to July 2002. Currently he is pursuing the PhD degree in the Department of Electrical and Computer Engineering, University of Florida. He is a student member of IEEE. Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997 and 2000, respectively, and the Ph.D. degree in electrical and computer engineering from the University of Florida, Gainesville, in 2005. He is currently a Senior Research Engineer at Motorola Labs, Arlington Heights, IL. His research interests include resource management, medium access control, and quality of service (QoS) in wireless networks. He is a Member of Tau Beta Pi and a student member of IEEE. Yuguang Fang received a Ph.D degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D degree in Electrical Engineering from Boston University in May 1997. From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering at University of Florida where he got the early promotion with tenure in August 2003 and has been an Associate Professor since then. He has published over one hundred (100) papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications and Networking Conference (WCNC’2000).     

Mathematical framework for Bz-based MREIT model in electrical impedance imaging

Magnetic resonance electrical impedance tomography (MREIT) is a new medical imaging modality visualizing static conductivity images of a subject by injecting electrical currents (Neumann data) and measuring the induced internal magnetic flux density B using an MRI scanner. Taking advantage of the internal information B, MREIT can deal with the ill-posed characteristics of the inverse problem in electrical impedance tomography (EIT However, the MREIT model at its early stage has technical difficulties in clinical applications mainly due to the requirement of subject rotations for acquiring all of the three components of B = (B_z, B_y, B_z). Lately, a new model so called the B_z-based MREIT model has been proposed to eliminate the subject rotation procedure. In this new MREIT model, we need to measure only one component B_z when the z-axis is the direction of the main magnetic field of the MRI scanner. There have been significant advances in reconstruction algorithms based on the B_z-based MREIT model and experimental studies showed that an excellent contrast resolution can be achievable. Although these advance in B_z-based MREIT, we have not dealt with its rigorous mathematical theory yet.The primary purpose of this work is to provide the rigorous mathematical framework for the B_z-based MREIT model. With this mathematical framework, we obtain the uniqueness in a two-dimensional setting of the B_z-based MREIT model. After introducing an example of the B_z-based MREIT algorithm, we present typical numerical and also experimental results.     

Three-diemensional scanner software using a video camera

This paper presents a software development for the obtaining in an automatic way of three-dimensional models of objects (e.g. sculptures, mechanical pieces). Nowadays, there is available software which is able to create three-dimensional models of objects using laser systems, but they are pretty expensive (up to 120,000 €) due to the high technology used for data capture (laser scanner). On the other hand, the software depicted in this paper develops a new process that captures the data with a simple digital video camera and a motorized pedestal (about 1200 €). This way, more than 1300 images of the object are obtained. The later analysis of the edges of all these images will completely define the geometry of the object. So, this software is able to create accurate digital models with a resolution that varies from hundreds to one million of points. In order to export these three-dimensional models the software generates VRML, or ASCII files. These models are very useful in sciences like computer graphics, architecture, mechanics, automated mapping/facilities management, etc.     

Implementation of RNS-Based Distributed Arithmetic Discrete Wavelet Transform Architectures Using Field-Programmable Logic

Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength).     

Magnetic effects of direct ion implantation of Mn and Fe into p-GaN

In p-GaN implanted with Mn (3×10¹⁶ cm⁻² at 250 keV), the material after annealing shows ferromagnetic properties below 250 K. Cross-sectional transmission electron microscopy (TEM) revealed the presence of platelet structures with hexagonal symmetry. These regions are most likely Ga_xMn_1−xN, which produce the ferromagnetic contribution to the magnetization. In p-GaN implanted with Fe, the material after annealing showed ferromagnetic properties at temperatures that were dependent on the Fe dose, but were below 200 K in all cases. In these samples, TEM and diffraction analysis did not reveal any secondary phase formation. The results for the Fe implantation are similar to those reported for Fe doping during epitaxial growth of GaN.     

Mullite Formation by Endothermic Reaction of α-Alumina/Silica Microcomposite Particles

The formation of mullite was investigated using microcomposite powders which consist of α-alumina cores and amorphous silica coatings. Differential thermal analysis and X-ray diffraction showed that the mullitization reaction was endothermic. In contrast, mullite forms exothermically in samples prepared by sol-gel processing. The results are shown to be consistent with available thermodynamic data for mullite formation from different alumina and silica phases.     

Chronic wounds

Skin ulcers are the most common chronic wounds. Current management principles and theories of causation of the most common ulcers--pressure, diabetic, and venous--are described. Issues related to occlusive dressings, compression dressings, topical antimicrobials, debridement, growth factors, grafting, and bioengineered tissue therapy are discussed. Special emphasis is placed on regulatory concerns.