Current U.S. electricity markets select supply bids by using a bid cost minimization (BCM) auction mechanism but then settle the payments based on locational marginal prices (LMPs). The resulting payments can be signi...
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ISBN:
(纸本)9781467327275
Current U.S. electricity markets select supply bids by using a bid cost minimization (BCM) auction mechanism but then settle the payments based on locational marginal prices (LMPs). The resulting payments can be significantly higher than the minimized bid costs. An alternative payment cost minimization (PCM) mechanism aiming to minimize the total payments has been discussed. Studies on single product problems have shown that PCM leads to reduced payments, but few results have been reported for the co-optimization of energy and other products. In view that co-optimization leads to a more efficient capacity allocation than optimizing each product individually, it is important to investigate the PCM cooptimization problems, and solve them in standard MIP solvers for a fair comparison with BCM. In PCM, prices are decision variables and need to be appropriately defined. We characterized marginal price-setting units by using logical constraints and converted them to linear forms since linearity is required by the standard MIP solvers. The nonlinear crossproduct in PCM objective function, however, cannot be converted to linear forms. Based on our recent results on surrogate optimization, a method is developed to deal with nonlinearity. Prices are first fixed at their values at the previous iteration to obtain linear formulation, and are then updated using price definition if the surrogate condition is satisfied. Numerical testing results of small examples and a 24-bus example demonstrate the effectiveness and efficiency of the method.
An integrated variable temperature coefficient (TC) reference generator for multi-level cell phase change memory (PCM)/NAND flash memory hybrid three dimensional solidstate drive is proposed and demonstrated by 0.18μ...
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ISBN:
(纸本)9781467327701
An integrated variable temperature coefficient (TC) reference generator for multi-level cell phase change memory (PCM)/NAND flash memory hybrid three dimensional solidstate drive is proposed and demonstrated by 0.18μm CMOS process. The proposed generator outputs both positive and negative TC reference current and voltage for PCM and NAND, respectively. TC is programmable and it can be widely changed down to -5.47mV/K and up to 5.74mV/K. Output level is also variable and it is independently controlled from the TC control. The flexible TC and output level control also enable a compensation of characteristics changes due to the program/erase cycling as wells as the process variations of the memory devices. The size of the reference generator is 0.195mm 2 . The power consumption is 0.68mW at 120degC, 2.3V output.
Kernel based fuzzy clustering has been extensively used for pattern sets that have clusters that overlap and clusters of different volume. The kernel approach adds additional degree of freedom by implicitly mapping in...
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ISBN:
(纸本)9781467315074
Kernel based fuzzy clustering has been extensively used for pattern sets that have clusters that overlap and clusters of different volume. The kernel approach adds additional degree of freedom by implicitly mapping input patterns into higher dimensional space known as kernel space. Kernel based fuzzy clustering has shown to produce improved results over conventional fuzzy clustering algorithms such as fuzzy C-means (FCM), possibilistic c-means (PCM) and possibilistic fuzzy C-means (PFCM) not only for spherical data sets but also non spherical data sets. However, in the case of kernel possibilistic C-means (KPCM) as well as PCM, the cluster coincidence drawback still exist which results in poor locations of the prototypes. In this paper, we propose an interval type-2 (IT2) approach to KPCM to overcome the cluster coincidence problem in PCM and KPCM. Although the choice of kernel function can be data dependent, we use the Gaussian kernel for our experiments. Using the same value of variance for the Gaussian kernel our proposed method outperforms KPCM. Experimental results show the validity of our proposed method.
Phase Change RAM (PCM) is a promising candidate of emerging memory technology to complement or replace existing DRAM and NAND Flash memory. A key drawback of PCMs is limited write endurance. To address this problem, s...
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ISBN:
(纸本)9783981080186
Phase Change RAM (PCM) is a promising candidate of emerging memory technology to complement or replace existing DRAM and NAND Flash memory. A key drawback of PCMs is limited write endurance. To address this problem, several static wear-leveling methods that change logical to physical address mapping periodically have been proposed. Although these methods have low space overhead, they suffer from unnecessary data migrations thereby failing to exploit the full lifetime potential of PCMs. This paper proposes a new dynamic wear-leveling method that reduces unnecessary data migrations by adopting a hot/cold swapping-based dynamic method. Compared with the conventional hot/cold swapping-based dynamic method, the proposed method requires only a small amount of space overhead by applying Bloom filters to the identification of hot and cold data. We simulate our method using SPEC2000 benchmark traces and compare with previous methods. Simulation results show that the proposed method reduces unnecessary data migrations by 58～92% and extends the memory lifetime by 2.18～2.30 times over previous methods with a negligible area overhead of 0.3%.
We introduce an alternative to pulse width modulation (PWM) for LED intensity control called "Pseudorandom pulse code modulation." Rather than using a single pulse with a variable duty factor to control the ...
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ISBN:
(纸本)9780819468178
We introduce an alternative to pulse width modulation (PWM) for LED intensity control called "Pseudorandom pulse code modulation." Rather than using a single pulse with a variable duty factor to control the time-averaged LED drive current, we generate a pseudorandom pulsecode to perform the same function. The advantages of this technique include: 1) the ability to control multiple channels without the need for dedicated PWM hardware circuitry;2) drive current averaging;and 3) reduction of acoustic noise due to magnetostriction.
This study describes a novel version of digital pulse position modulation (PPM) called offset PPM, which operates at half the line rate of digital PPM and offers an increase in sensitivity. To demonstrate the effectiv...
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This study describes a novel version of digital pulse position modulation (PPM) called offset PPM, which operates at half the line rate of digital PPM and offers an increase in sensitivity. To demonstrate the effectiveness of the technique, theoretical results are presented for an offset PPM system coding 3 bits of pulse code modulation (PCM) data, at a rate of 1 Gbit/s. An optical channel with a Gaussian impulse response, such as that obtained from graded-index plastic optical fibre, was considered. The results are compared to those obtained for digital PPM, using a maximum likelihood sequence detector, and it is shown that offset PPM is more tolerant of pulse dispersion giving a 3.1 dB increase in sensitivity when operating with a channel bandwidth equal to half the PCM bit rate.
This paper focuses on the hysteresis effect of the polarization characteristics of a polymer electrolyte membrane fuel cell (PEMFC), mainly due to the compressor-air supply system dynamics. Indeed in PEMFC/ultracapaci...
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This paper focuses on the hysteresis effect of the polarization characteristics of a polymer electrolyte membrane fuel cell (PEMFC), mainly due to the compressor-air supply system dynamics. Indeed in PEMFC/ultracapacitor hybrid vehicles, fuel cells can be used to supply the low frequencies of the power demand only. First, the different parts of a FC system are described and modeled in order to analyze the transient stack performance decrease and to identify its main influential factors for automotive applications. Then, apart from humidity and temperature variations, each phenomenon is dynamically described, leading to a complete mathematical model based on macroscopic component parameters. Thus, an analytical model based on this set of equations enables us to draw the static voltage versus current FC characteristics. Furthermore, the hysteresis effect on the V-I curve, which still occurs during low dynamic responses, is shown while temperature and humidity are kept constant. Finally, dynamic responses of the Ballard PEMFC Nexa 1200 W generator are analyzed, and detailed experimentation and simulation are carried out for a large magnitude sinusoidal waveform at different frequencies.
With the approaching commercialization of PEM fuel cell technology, developing active, inexpensive non-precious metal ORR catalyst materials to replace currently used Pt-based catalysts is a necessary and essential re...
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With the approaching commercialization of PEM fuel cell technology, developing active, inexpensive non-precious metal ORR catalyst materials to replace currently used Pt-based catalysts is a necessary and essential requirement in order to reduce the overall system cost. This review paper highlights the progress made over the past 40 years with a detailed discussion of recent works in the area of non-precious metal electrocatalysts for oxygen reduction reaction, a necessary reaction at the PEM fuel cell cathode. Several important kinds of unsupported or carbon supported non-precious metal electrocatalysts for ORR are reviewed, including non-pyrolyzed and pyrolyzed transition metal nitrogen-containing complexes, conductive polymer-based catalysts, transition metal chalcogenides, metal oxides/carbides/nitrides/oxynitrides/carbonitrides, and enzymatic compounds. Among these candidates, pyrolyzed transition metal nitrogen-containing complexes supported on carbon materials (M N-x/C) are considered the most promising ORR catalysts because they have demonstrated some ORR activity and stability close to that of commercially available Pt/C catalysts. Although great progress has been achieved in this area of research and development, there are still some challenges in both their ORR activity and stability. Regarding the ORR activity, the actual volumetric activity of the most active non-precious metal catalyst is still well below the DOE 2015 target. Regarding the ORR stability, stability tests are generally run at low current densities or low power levels, and the lifetime is far shorter than targets set by DOE. Therefore, improving both the ORR activity and stability are the major short and long term focuses of non-precious metal catalyst research and development. Based on the results achieved in this area, several future research directions are also proposed and discussed in this paper.
It is shown that the dicodepulse position modulation (DiPPM) scheme, presented in this study, demonstrates several key advantages in comparison with other existing PPM schemes, because of the compact structure and ef...
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It is shown that the dicodepulse position modulation (DiPPM) scheme, presented in this study, demonstrates several key advantages in comparison with other existing PPM schemes, because of the compact structure and efficient recovery process of the clock signal. An error corrector for the DiPPM scheme is presented, where experimental results prove the theoretical expectations of a previous publication. Thus, it is demonstrated that DiPPM with the use of a maximum likelihood sequence detector (MLSD) error corrector, significantly reduces or eliminates errors incurred during the transmission. Comparison of and discussion on the outcomes of a DiPPM system with and without the error corrector are included.
A complete system of micro fuel cell with NaBH4 microreactor was developed for micro power sources. The micro fuel cell system consists of two main components;one is a micro PEM fuel cell and the other is a microreact...
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ISBN:
(纸本)9781424496341
A complete system of micro fuel cell with NaBH4 microreactor was developed for micro power sources. The micro fuel cell system consists of two main components;one is a micro PEM fuel cell and the other is a microreactor for hydrogen generation from NaBH4 alkaline solution. All of BOP such as a fuel cartridge, a micropump, and an auxiliary battery were integrated for a complete micro power device, and the performance of the micro fuel cell system was measured.
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