124,724 research outputs found
From nominal to true a posteriori probabilities: an exact Bayesian theorem based probabilistic data association approach for iterative MIMO detection and decoding
No full textIt was conventionally regarded that the existing probabilistic data association (PDA) algorithms output the estimated symbol-wise a posteriori probabilities (APPs) as soft information. In this paper, however, we demonstrate that these probabilities are not the true APPs in the rigorous mathematicasense, but a type of nominal APPs, which are unsuitable for the classic architecture of iterative detection and decoding (IDD) aided receivers. To circumvent this predicament, we propose an exact Bayesian theorem based logarithmic domain PDA (EB-Log-PDA) method, whose output has similar characteristics to the true APPs, and hence it is readily applicable to the classic IDD architecture of multiple-input multiple-output (MIMO) systems using the general M-ary modulation. Furthermore, we investigate the impact of the PDA algorithms' inner iteration on the design of PDA-aided IDD receivers. We demonstrate that introducing inner iterations into PDAs, which is common practice in PDA-aided uncoded MIMO systems, would actually degrade the IDD receiver's performance, despite significantly increasing the overall computational complexity of the IDD receiver. Finally, we investigate the relationship between the extrinsic log-likelihood ratio (LLRs) of the proposed EB-Log-PDA and of the approximate Bayesian theorem based logarithmic domain PDA (AB-Log-PDA) reported in our previous work. We also show that the IDD scheme employing the EB-Log-PDA without incorporating any inner PDA iterations has an achievable performance close to that of the optimal maximum a posteriori (MAP) detector based IDD receiver, while imposing a significantly lower computational complexity in the scenarios considered
Pharmacoeconomic analysis of adjuvant oral capecitabine vs intravenous 5-FU/LV in Dukes' C colon cancer: the X-ACT trial
No full textOral capecitabine (Xeloda<sup>®</sup>) is an effective drug with favourable safety in adjuvant and metastatic colorectal cancer. Oxaliplatin-based therapy is becoming standard for Dukes' C colon cancer in patients suitable for combination therapy, but is not yet approved by the UK National Institute for Health and Clinical Excellence (NICE) in the adjuvant setting. Adjuvant capecitabine is at least as effective as 5-fluorouracil/leucovorin (5-FU/LV), with significant superiority in relapse-free survival and a trend towards improved disease-free and overall survival. We assessed the cost-effectiveness of adjuvant capecitabine from payer (UK National Health Service (NHS)) and societal perspectives. We used clinical trial data and published sources to estimate incremental direct and societal costs and gains in quality-adjusted life months (QALMs). Acquisition costs were higher for capecitabine than 5-FU/LV, but higher 5-FU/LV administration costs resulted in 57% lower chemotherapy costs for capecitabine. Capecitabine vs 5-FU/LV-associated adverse events required fewer medications and hospitalisations (cost savings £3653). Societal costs, including patient travel/time costs, were reduced by >75% with capecitabine vs 5-FU/LV (cost savings £1318), with lifetime gain in QALMs of 9 months. Medical resource utilisation is significantly decreased with capecitabine vs 5-FU/LV, with cost savings to the NHS and society. Capecitabine is also projected to increase life expectancy vs 5-FU/LV. Cost savings and better outcomes make capecitabine a preferred adjuvant therapy for Dukes' C colon cancer. This pharmacoeconomic analysis strongly supports replacing 5-FU/LV with capecitabine in the adjuvant treatment of colon cancer in the UK
Voltage calculation on low voltage feeders with distributed generation
No full textIncludes bibliographical references.The increasing levels of greenhouse gas emission and the continued depletion of fossil fuels have been the driving factors for power utilities to utilize renewable energy sources for power generation. In South Africa, a target was set in 2008 to achieve 10000 GWh of renewable generation by 2013, which includes DG on LV feeders. This has seen the increase in small scale generators, close to load centres in low voltage distribution networks such as solar PV panels in residential houses, to supplement the energy needs of consumers. This has sparked much debate over the impacts, as well as benefits, of increasing the amount of generation on these low voltage (LV) feeders. However, the power utility holds the statutory role to preserve and maintain the quality of supply of electricity and must therefore assess any impact of increasing generation on LV distribution systems. This created the need for a planning tool to assess the impact of increasing DG on LV distribution networks. There has been a lot of work carried out by researchers to assess the impact of DG on the power system, using various indicators like frequency, power losses, current, voltage etc. Keeping the voltage of a DG-integrated feeder system within the pre-defined standards has been a major challenge for power utilities today. In this report, the voltage impact of DG in LV distribution systems is examined and analysed for increasing DG penetration, particularly solar PV panels in residential households. In South Africa, the recommended method for voltage calculation in feeders is the Herman-Beta algorithm, which is used in the design of passive LV feeders. In 2011, Gaunt experimented with modelling DG as negative loads in the HB algorithm to extend the voltage calculation to include the presence of DG on LV feeders. This work identifies and develops a tool(s) to enable power utility planners to analyse the voltage impact of DG on LV feeders. The work in this study adds onto the DG modelling approach, introduced by Gaunt in 2011, to produce an algorithm for voltage calculation in active LV feeders with DG. This involves three major steps. First step involves the thorough testing of the HB algorithm, written in Matlab, for passive LV feeders and validating it against voltage calculation through Monte Carlo Simulation (MCS). The second step involves ammending and extending the HB algorithm for voltage calculation in active LV feeders with DG, testing and validation against voltage calculation through Monte Carlo Simulation (MCS). With the HB algorithm fully tested and validated, the third step involves using the algorithm for voltage analysis of active feeders with increasing DG penetration. The third and final step, analysing the voltage rise constraints of active LV feeders, involves running the HB algorithm, analytical method, in a MCS to create various scenarios on the feeder. Simulations have been performed to assess the voltage impact of increasing DG penetration on LV feeders for various test cases to mimic practical LV feeder conditions. The outcome of this study presented an application tool for the design of active LV feeders, whose output/results are summarized into implications for voltage rise mitigation and providing useful information on the DG hosting capacity of LV feeders. The recommended DG penetration limit for LV feeders in this study has been DG capacity of 30 of the actual ADMD, used to design the passive feeder. It has been shown that after this limit, the feeder should be reinforced to avoid incidents of voltage violations. In addition, the work done in this project has set a foundation upon which a variety of similar studies can be done with active LV feeders such as the effect of solar water heating and the penetration of other DG technologies such as wind
IFI and ISI premitigation for block-code-modulated noncoherent UWB impulse radio: A code optimization approach
No full textCodeword matching and signal aggregation (CMSA) is a recently proposed low-complexity noncoherent receiver for block code modulated UWB Impulse Radio (UWB-IR) systems. As the frame/symbol duration is shortened to boost data rate, inter-frame interference (IFI) or inter-symbol interference (ISI) occurs and degrades detection performance of CMSA. In this paper, an effective IFI/ISI pre-mitigation scheme is proposed for CMSA by means of a code optimization approach. By employing a tailored interference model that highlights the codeword properties, the system performance in the presence of moderate IFI/ISI is evaluated and an average collected channel gain (CCG) is introduced as the metric for code optimization. With the primary focus on binary modulation, two IFI/ISI-robust code properties are generalized as Shifted-Orthogonality and Shifted-Repetition. Based on these properties, the optimal code is constructed. It is observed that, when the optimal code occurs, the leaked signal energy or the interference can be partially used to enhance the detection performance of CMSA in the presence of IFI/ISI. Unlike most of the existing IFI/ISI mitigation schemes for noncoherent UWB-IR that focus mainly on signal processing after the nonlinear detector, the optimized code is exploited to aggregate leaked signal energy along with the linear pre-detection operation already involved in CMSA receiver. Both analysis and simulation show that a distinct performance improvement is achieved
Overvoltage prevention in LV smart grid using customer resources coordination
No full textVoltage rise is one of the main factors which limits the capacity of Low Voltage (LV) network to accommodate more Renewable Energy (RE) sources. This paper proposes a robust and effective approach to coordinate customers' resources and manage voltage rise in residential LV networks. PV is considered as the customer RE source. The suggested coordination approach in this paper includes both localized control strategy, based on local measurement, and distributed control strategy based on consensus algorithm. This approach can completely avoid maximum permissible voltage limit violation. A typical residential LV network is used as the case study where the simulated results are shown to verify the effectiveness of the proposed approach
Distributed probabilistic-data-association-based soft reception employing base station cooperation in MIMO-aided multiuser multicell systems
No full textIntercell cochannel interference (CCI) mitigation is investigated in the context of cellular systems relying on dense frequency reuse (FR). A distributed base-station (BS)-cooperation-aided soft reception scheme using the probabilistic data association (PDA) algorithm and soft combining (SC) is proposed for the uplink of multiuser multicell MIMO systems. The realistic 19-cell hexagonal cellular model relying on unity FR is considered, where both the BSs and the mobile stations (MSs) are equipped with multiple antennas. Local-cooperation-based message passing is used, instead of a global message passing chain for the sake of reducing the backhaul traffic. The PDA algorithm is employed as a low-complexity solution for producing soft information, which facilitates the employment of SC at the individual BSs to generate the final soft decision metric. Our simulations and analysis demonstrate that, despite its low additional complexity and backhaul traffic, the proposed distributed PDA-aided SC (DPDA-SC) reception scheme significantly outperforms the conventional noncooperative benchmarkers. Furthermore, since only the index of the possible discrete value of the quantized converged soft information has to be exchanged for SC in practice, the proposed DPDA-SC scheme is relatively robust to the quantization errors of the soft information exchanged. As a beneficial result, the backhaul traffic is dramatically reduced at negligible performance degradation
Unified bit-based probabilistic data association aided MIMO detection for high-order QAM constellations
No full textA unified Bit-based Probabilistic Data Association (B-PDA) detection approach is proposed for Multiple-Input Multiple-Output (MIMO) systems employing high-order rectangular Quadrature Amplitude Modulation (QAM). The new approach transforms the symbol detection process of QAM to a bit-based process by introducing a Unified Matrix Representation (UMR) of QAM. Both linear natural and nonlinear binary reflected Gray bit-to-symbol mappings are considered. With the aid of simulation results, we demonstrate that the linear natural mapping based B-PDA approach typically attained an improved detection performance (measured in terms of both Bit Error Ratio (BER) and Symbol Error Ratio (SER)) in comparison to the conventional symbol-based PDA aided MIMO detector, despite its dramatically reduced computational complexity. The only exception is that at low SNRs, the linear natural mapping based B-PDA is slightly inferior in terms of its BER to the conventional symbol-based PDA using binary reflected Gray mapping. Furthermore, the simulation results show that the linear natural mapping based B-PDA MIMO detector may approach the best-case performance provided by the nonlinear binary reflected Gray mapping based B-PDA MIMO detector under ideal conditions. Additionally, the implementation of the B-PDA MIMO detector is shown to be much simpler in the case of the linear natural mapping. Based on these two points, we conclude that in the context of the uncoded B-PDA MIMO detector it is preferable to use the linear natural bit-to-symbol mapping, rather than the nonlinear Gray mapping
G-CSF for Extensive STEMI
No full textRationale: In the exploratory Phase II STEM-AMI (Stem Cells Mobilization in Acute Myocardial Infarction) trial, we reported that early administration of G-CSF (granulocyte colony-stimulating factor), in patients with anterior ST-segment-elevation myocardial infarction and left ventricular (LV) dysfunction after successful percutaneous coronary intervention, had the potential to significantly attenuate LV adverse remodeling in the long-Term. Objective: The STEM-AMI OUTCOME CMR (Stem Cells Mobilization in Acute Myocardial Infarction Outcome Cardiac Magnetic Resonance) Substudy was adequately powered to evaluate, in a population showing LV ejection fraction ≤45% after percutaneous coronary intervention for extensive ST-segment-elevation myocardial infarction, the effects of early administration of G-CSF in terms of LV remodeling and function, infarct size assessed by late gadolinium enhancement, and myocardial strain. Methods and Results: Within the Italian, multicenter, prospective, randomized, Phase III STEM-AMI OUTCOME trial, 161 ST-segment-elevation myocardial infarction patients were enrolled in the CMR Substudy and assigned to standard of care (SOC) plus G-CSF or SOC alone. In 119 patients (61 G-CSF and 58 SOC, respectively), CMR was available at baseline and 6-month follow-up. Paired imaging data were independently analyzed by 2 blinded experts in a core CMR lab. The 2 groups were similar for clinical characteristics, cardiovascular risk factors, and pharmacological treatment, except for a trend towards a larger infarct size and longer symptom-To-balloon time in G-CSF patients. ANCOVA showed that the improvement of LV ejection fraction from baseline to 6 months was 5.1% higher in G-CSF patients versus SOC (P=0.01); concurrently, there was a significant between-group difference of 6.7 mL/m2 in the change of indexed LV end-systolic volume in favor of G-CSF group (P=0.02). Indexed late gadolinium enhancement significantly decreased in G-CSF group only (P=0.04). Moreover, over time improvement of global longitudinal strain was 2.4% higher in G-CSF patients versus SOC (P=0.04). Global circumferential strain significantly improved in G-CSF group only (P=0.006). Conclusions: Early administration of G-CSF exerted a beneficial effect on top of SOC in patients with LV dysfunction after extensive ST-segment-elevation myocardial infarction in terms of global systolic function, adverse remodeling, scar size, and myocardial strain. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01969890
Technical Committees: Recent Activities of the DEIS Technical Committee on 'HVDC Cable Systems': Two New Study Groups for Novel IEEE Standards on Space Charge Measurement
No full textThe IEEE DEIS TC 'HVDC cable systems (cables, joints and terminations)' has been quite active since its formation in 2012 (for a summary, see the TC website [1]) and has issued the following two IEEE standards: (1) IEEE 1732-2017, 'Recommended Practice for Space Charge Measurements in HVDC Extruded Cables for Rated Voltages up to 550 kV' [2] and (2) IEEE 2862-2020, 'Recommended Practice for Partial Discharge Measurements under AC Voltage with VHF/UHF Sensors During Routine Tests on Factory and Pre-moulded Joints of HVDC Extruded Cable Systems up to 800 kV' [3]
Synthetic representation of flexibility from aggregated LV Distributed Energy Resources
No full textThe EU plan for the climate-friendly economy transition requires the increase of renewable generation and electrification of end uses of energy. High shares of new renewable generation are and will be even more connected to the distribution networks through the so-called Distributed Generation (DG). MV and LV networks are not designed and conceived for hosting significant shares of generation. Issues with generation are accrued because, at the distribution level, power generation is based on nonprogrammable renewable energy sources that make distribution planning and operation more challenging. The use of flexibility from distributed energy resources (DER) can help face new distribution issues but, conversely, it reduces the amount of flexibility available for the power system. In the paper, a methodology for assessing the share between the flexibility used by the LV system and the residual flexibility available for other uses is presented. It has been assumed that the LV networks are equipped with an energy management system to assess the flexibility needed and available. The energy management system is a multi-agent system capable of handling the small resources' flexibility with a master-client scheme that mimics a possible aggregator-client link. An exemplary Italian LV distribution network is used to test the procedure
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