160,648 research outputs found
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
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
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
A novel reduced-order model method for characterization of acoustic response of laminar premixed flames
No full textThis study presents a general, predictive and cost-efficient reduced-order modeling (ROM) technique for characterization of laminar premixed flame response under acoustic modulation. The model is built upon the kinematic flame model-G-equation to describe the flame topology and dynamics, and the novelties of the ROM lie in i) a procedure to create the compatible base flow that can reproduce the correct flame geometry and i i ) the use of a physically-consistent acoustic modulation field for the characterization of flame response. This ROM addresses the significant limitations of the classical kinematic model, which is only applicable to simple flame configurations and relies on ad-hoc models for the modulation field. The ROM is validated by considering the acoustically-excited laminar premixed methane/air flames in conical and M-shape configurations, experimentally study by Durox et al. Proc. Combust. Inst. , 32 (2009). To test the model availability to practical burners, a confined flame configuration Cuquel et al., Proc. Combust. Inst. , 34 (2013) is also employed for model evaluation. The model accuracy is evaluated concerning flame geometrical features and flame describing function, and assessed by comparing the ROM results with both the experimental measurements and the direct-numerical-simulation results. It is found that the flame describing/transfer functions predicted by the ROM compare well with reference data, and are more accurate than those obtained from the conventional kinematic model built upon heuristically-presumed modulation fields. & COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.</p
On the understanding of a cryogenic two phase LOX/GH2 flame: Parametric sensitivity, characteristic scaling and phase instability
No full textThis study concerns the cryogenic hydrogen combustion in subcritical pressure conditions, with practical relevance to rocket engine applications. A cryogenic two phase flame in the counterflow configuration is calculated and analyzed with the consideration of real fluid effects and heat/mass transfer across the liquid gas interface. The effects of pressure, strain rate, fuel inlet temperature, and heat loss on the flame characteristic behaviors are examined. It is found that the vaporization rate of liquid oxidizer scales with the square root of pressure (p) times strain rate (ast), and is not a limiting factor for combustion. The total heat release scales withffiffiffiffiffiffiffiffip at lower strain rates while with p4=5a1=3 past st at higher strain rates. The significant results on the phase stability of cryogenic flame are also established. It is found that the unstable phase, in terms of vapor liquid equilibrium, arises in the vi cinity of the liquid gas interface; however, all unstable phase states still stay in the metastable region of the phase diagram. For all the flame solutions considered in this study, no thermochemical state enters the spinodal region.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</p
Data for: Towards high-efficient industrial p-type mono-like Si PERC solar cells
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Development and validation of a combustion large-eddy-simulation solver based on fully compressible formulation and tabulated chemistry
No full textThis study concerns the development and validation of a high-fidelity CFD solver for large-eddy simulations (LES) of combustion and reacting flows. The solver is built upon a high-resolution numerical scheme and leverages a compressible flamelet formulation, so that it can capture both the turbulent combustion and thermoacoustic effects simultaneously. The validation study is first performed by considering a scalar-mixing case in homogeneous turbulence, and then extended to LES of a non-premixed jet flame. The solver accuracy is assessed by comparing the numerical solutions with the available experimental data. It is found that the newly developed solver is able to accurately predict the time-averaged combustion fields as well as the fluctuation quantities. The predictive accuracy is comparable to that of the state-of-the-art low-Mach solvers in literature. (C) 2022 Elsevier Masson SAS. All rights reserved.</p
Boron-mediated directed aromatic C–H hydroxylation
No full textTransition metal-catalysed C–H hydroxylation is one of the most notable advances in synthetic chemistry during the past few decades and it has been widely employed in the preparation of alcohols and phenols. The site-selective hydroxylation of aromatic C–H bonds under mild conditions, especially in the context of substituted (hetero)arenes with diverse functional groups, remains a challenge. Here, we report a general and mild chelation-assisted C–H hydroxylation of (hetero)arenes mediated by boron species without the use of any transition metals. Diverse (hetero)arenes bearing amide directing groups can be utilized for ortho C–H hydroxylation under mild reaction conditions and with broad functional group compatibility. Additionally, this transition metal-free strategy can be extended to synthesize C7 and C4-hydroxylated indoles. By utilizing the present method, the formal synthesis of several phenol intermediates to bioactive molecules is demonstrated
Metal-free cascade boron–heteroatom addition and alkylation with diazo compounds
No full textTransition metal-catalyzed carbene transfer reaction is one of the most notable advances for C−C bond formation reactionsduring the past decade, which has been widely employed in the preparation of C3-substituted indoles. Here, we described an efficient example of catalyst- and metal-free aminoboration of alkynes and C[sbnd]C bond formation with diazo compounds to produce C3-substituted indoles. Diverse alkynylanilines and diazo compounds can be utilized for this tandem transformation under mild reaction conditions, resulting in broad functional group compatibility. Additionally, this metal-free strategy can be extended to construct substituted benzofurans
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