A NEW CLUSTERING METHOD FOR PARTITIONING PRICE ZONE IN POWER MARKET ENVIRONMENT

In order to reduce the difficulties in using nodal pricing, the notion of price zone is widely adopted in actual pricing scheme. The key for establishing simple and efficient zonal pricing scheme is to accurately partition transmission network in the presence of congestion. Unfortunately, in actual power market operation, operators usually establish price zones based on their experience, considering the locations of congested lines, without mathematical analysis. In order to achieve accurate price zone partition without any a priori partition knowledge, this paper firstly extracts the sensitivities of nodal power injections to power flows on all congested lines as cluster features of nodal price. Secondly, the scale-space theory simulating human visual system is introduced, and further a scale-space-based hierarchical clustering method for price zone partition is proposed. Finally, test results on IEEE 118-node system show the validity and feasibility of this proposed method

Illumination sensing in LED lighting systems based on frequency-division multiplexing

Recently, light emitting diode (LED) based illumination systems have attracted considerable research interest. Such systems normally consist of a large number of LEDs. In order to facilitate the control of such high-complexity system, a novel signal processing application, namely illumination sensing, is thus studied. In this paper, the system concept and research challenges of illumination sensing are presented. Thereafter, we investigate a frequency-division multiplexing (FDM) scheme to distinguish the signals from different LEDs, such that we are able to estimate the illuminances of all the LEDs simultaneously. Moreover, a filter bank sensor structure is proposed to study the key properties of the FDM scheme. Conditions on the design of the filter response are imposed for the ideal case without the existence of any frequency inaccuracy, as well as for the case with frequency inaccuracies. The maximum number of LEDs that can be supported for each case is also derived. In particular, it is shown that, among all the other considered functions, the use of the triangular function is able to give a better tradeoff between the number of LEDs that can be supported and the allowable clock inaccuracies within a practical range. Moreover, through numerical investigations, we show that many tens of LEDs can be supported for the considered system parameters. Remark on the low-cost implementations of the proposed sensor structure is also provided

Signal detection for high-density magnetic recording systems

Master'sMASTER OF ENGINEERIN

Piecewise companding transform assisted optical-OFDM systems for indoor visible light communications

In visible light communications (VLCs) relying on intensity-modulation and direct detection (IM/DD), the conversion from electrical signals to optical signals and the limited dynamic range of the light-emitting diodes (LEDs) constitute the fundamental impediments in the way of high-integrity communications, especially when orthogonal frequency-division multiplexing (OFDM) is employed. In IM/DD VLCs, only real-valued positive signals are used for signal transmission. However, the Fourier transform of OFDM systems is operated in the complex domain. In order to meet the requirements of the IM/DD VLCs, the complex-to-real conversion is achieved at the cost of reducing the bandwidth efficiency. Moreover, OFDM signals experience a high peak-to-average power ratio; hence, typically clipping is used for confining the positive-valued signals within the LED's dynamic range. However, hard clipping leads to the loss of orthogonality for optical OFDM (O-OFDM) signals, generating inter-carrier interference. As a result, the performance of the clipping-based O-OFDM systems may be severely degraded. In this paper, the concept of piecewise companding transform (CT) is introduced into the O-OFDM system advocated, forming the CTO-OFDM arrangement. We first investigate the general principles and design criteria of the piecewise CTO-OFDM. Based on our studies, three types of piecewise companders, namely, the constant probability sub-distribution function, linear PsDF (LPsDF), and the non-LPsDF-based CT, are designed. Furthermore, we investigate the nonlinear effect of hard clipping and of our CT on O-OFDM systems in the context of different scenarios by both analytical and simulation techniques. Our investigations show that the CTO-OFDM constitutes a promising signaling scheme conceived for VLCs, which exhibits a high bandwidth efficiency, high flexibility, high reliability, as well as a high data-rate, despite experiencing nonlinear distortions

Performance analysis of orthogonal frequency division multiplexing systems in dispersive indoor power line channels inflicting asynchronous impulsive noise

Hidden semi-Markov modelling of the asynchronous impulsive noise (IN) encountered in indoor broadband power line communications (PLCs) is investigated by considering the statistical distributions of both the inter-arrival time and the duration of asynchronous IN components. Then, the bit error ratio (BER) of orthogonal frequency division multiplexing systems using Q-ary quadrature amplitude modulation is analysed with the aid of the proposed noise model, when communicating over dispersive indoor power line channels inflicting asynchronous IN in addition to the background noise. The authors’ simulation results confirm the accuracy of the analysis and quantify the impact of various factors on the achievable BER performance. The grave impact of asynchronous IN on indoor broadband PLCs suggests that efficient techniques have to be designed for mitigating its effect

EC-Conf: An Ultra-fast Diffusion Model for Molecular Conformation Generation with Equivariant Consistency

Despite recent advancement in 3D molecule conformation generation driven by diffusion models, its high computational cost in iterative diffusion/denoising process limits its application. In this paper, an equivariant consistency model (EC-Conf) was proposed as a fast diffusion method for low-energy conformation generation. In EC-Conf, a modified SE (3)-equivariant transformer model was directly used to encode the Cartesian molecular conformations and a highly efficient consistency diffusion process was carried out to generate molecular conformations. It was demonstrated that, with only one sampling step, it can already achieve comparable quality to other diffusion-based models running with thousands denoising steps. Its performance can be further improved with a few more sampling iterations. The performance of EC-Conf is evaluated on both GEOM-QM9 and GEOM-Drugs sets. Our results demonstrate that the efficiency of EC-Conf for learning the distribution of low energy molecular conformation is at least two magnitudes higher than current SOTA diffusion models and could potentially become a useful tool for conformation generation and sampling.Comment: 10 pages, 3 figure

Compressed sensing improves the performance of subcarrier index-modulation assisted OFDM

In orthogonal frequency division multiplexing relying on subcarrier index modulation (OFDM-SIM), the information is conveyed by both the indices of the activated subcarriers and the conventional amplitude-phase modulated (APM) symbols. It has been shown that OFDM-SIM is capable of striking a tradeoff between the attainable spectral efficiency (SE) and energy efficiency (EE). In order to further increase the EE of the OFDM-SIM system, while potentially increasing its SE, we propose a compressed sensing (CS) assisted signalling strategy for the family of OFDM-SIM systems. Correspondingly, we first consider the joint maximum likelihood (JML) detection of the CS assisted index-modulated (CSIM) and of the classic APM symbols, despite its high complexity. Then, we propose a low complexity detection algorithm, which is termed as the iterative residual check (IRC) based detector. This is based on the Greedy Pursuit concept of CS, which makes locally optimal choices at each step. Finally, both analytical and simulation results are provided for characterizing the attainable system performance of our proposed OFDM-CSIM system. We demonstrate that in comparison to the conventional OFDM-SIM system, the proposed OFDM-CSIM arrangement is capable of achieving both a higher SE as well as an increased EE. We also show that the diversity gain provided by the OFDM-CSIM system is much higher than that of the OFDM-SIM system. Furthermore, our investigation of the detection performance shows that the proposed IRC detector is capable of providing an attractive detection performance at a low complexity