Harmonic evaluation of traction system by Monte Carlo simulation

This paper presents a method to predict the harmonic current level of traction system with phase-controlled DC Drives by Monte Carlo simulation. Based on Behavioral Modeling Technique (BMT), a model for electrical unit of traction is proposed. The probability density functions (pdf) of speed and notch numbers are obtained from longtime field measurement. The mean and variance of harmonic current of single electrical unit is obtained based on the speed pdf and traction electrical unit model. The results of Monte Carlo simulation are in good accordance with the experimental and analytic conclusions. The harmonics of a different number of trains are systematically investigated. It is shown the Total Harmonic Distortion (THD) decreases with the increase of the number of trains and the harmonic current per train decreases with the train number because of the harmonic cancellation.published_or_final_versio

Modeling of electric railway vehicle for harmonic analysis of traction power-supply system using spline interpolation in frequency domain

It is essential to model nonlinear traction converter loads for harmonic analysis of traction systems. A behavioral model in frequency domain to represent electric railway vehicle based on testing and measurement is proposed for harmonic analysis. The harmonic current characteristics are represented by a set of polynomials generated from cubic smoothing spline interpolation. The purpose of this paper is to report and discuss the development of an electric railway model for harmonic analysis and demonstrate results from the simulation with this train load model. System simulation based on this model is performed and the results match satisfactorily with field measurement.published_or_final_versio

Probabilistic characterization of current harmonics of electrical traction power supply system by analytic method

Current harmonics of an urban railway traction system in Hong Kong are investigated by analytic approach. With the statistic knowledge of speed and notch number of the trains in the system, the mean and variance of harmonic current of individual trains are computed based on a behavior oriented model of the traction electrical unit. According to the Large Number Law and Central Limit Theorem, current harmonics at a substation, which is a vectorial summation of harmonics of random number of trains electrically connected to it, are normally distributed provided that the number of trains is large enough. A set of equations are established by which probability density functions (pdfs) of current harmonics at a substation are calculated and found to be in good accordance with results obtained by Monte Carlo simulation. This approach of harmonics evaluation for traction system with random loading has evident advantages of cheap, fast and convenience and with no compromise of accuracy.published_or_final_versio

Traction system scheduling to minimize harmonic current level at substation by genetic algorithm

Harmonics of individual trains are closely related to its loading, speed and operation mode. The harmonic current at substations is the sum of the individual components from all the trains electrically connected to the substation. There will be cancellation of the harmonics if the harmonics are not of the same phase angles. It is possible to schedule the traction system so as to minimize the harmonic distortion, improve the power factor and reduce the harmonic currents at substations. In this study genetic algorithm (GA) is used to find out the optimal schedule of the system with minimum harmonic levels. The optimized solution can be integrated into automatic train operation (ATO) controller to control the departure, speed regulation of each train of the system. Mathematical description of the problem is first presented and the genetic algorithm is introduced. The optimal solution is given at the end of this paper. It is demonstrated that the scheduling of traction system is applicable to harmonic reduction and GA is fit for such kinds of optimization problems. Such method of harmonics reduction can bring about considerable saving in filtering equipment.published_or_final_versio

The clinical course of polymyalgia rheumatica in Chinese

Polymyalgia rheumatica (PMR) is diagnosed based on clinical features that may overlap with other rheumatic conditions like rheumatoid arthritis (RA). Furthermore, a proportion of PMR patients may subsequently evolve into RA. The aim of this study was to examine the clinical characteristics of PMR patients in a Chinese cohort compared to a Caucasian series. Patients diagnosed to have PMR during 1997-2008 were reviewed for clinical features and compared to a reported Caucasian series. Rheumatoid factor (RF) and anticyclic citrullinated peptide (CCP) antibodies were determined by immunonephelometry and enzyme-linked immunosorbent assay, respectively. Forty-four patients of southern Chinese origin were diagnosed to have PMR according to specialist opinion. Seventy-five percent of patients (n = 33) were >65 years of age at diagnosis (mean ± standard deviation, 75.8 ± 9.6 years). The commonest feature at disease onset was elevated erythrocyte sedimentation rate >40 mm/h (100% vs. 95.7%; p = 0.17) and bilateral shoulder pain or stiffness (95.5% vs. 90.8%; p = 0.31), comparable in frequency to the Caucasian cohort. However, Chinese patients had significantly longer duration of symptoms before diagnosis (p < 0.001) but less bilateral upper arm tenderness (p < 0.001) and generalized stiffness (p = 0.01). Twelve (27.3%) patients evolved into RA after a median duration of 2 months from onset of PMR. RF and anti-CCP antibodies were positive in 66.7% and 60% of these patients compared to 9.4% and 6.2%, respectively, among those who did not evolve into RA during the period observed. Chinese patients with PMR have modestly different clinical profile compared to the Caucasian counterpart. RF and anti-CCP antibodies were more likely to be present in those who subsequently developed into RA. © 2009 Clinical Rheumatology.postprin

Platinum binding preferences dominate the binding of novel polyamide amidine anthraquinone platinum(II) complexes to DNA

Complexes incorporating a threading anthraquinone intercalator with pyrrole lexitropsin and platinum(II) moieties attached were developed with the goal of generating novel DNA binding modes, including the targeting of AT-rich regions in order to have high cytotoxicities. The binding of the complexes to DNA has been investigated and profiles surprisingly similar to that for cisplatin were observed; the profiles were different to those for a complex lacking the pyrrole lexitropsin component. The lack of selective binding to AT-rich regions suggests the platinum binding was dominating the sequence selectivity, and is consistent with the pyrrole lexitropsin slowing intercalation. The DNA unwinding profiles following platinum binding were evaluated by gel electrophoresis and suggested that intercalation and platinum binding were both occurring

Novel polyamide amidine anthraquinone platinum(II) complexes: cytotoxicity, cellular accumulation, and fluorescence distributions in 2D and 3D cell culture models

1- and 1,5-Aminoalkylamine substituted anthraquinones (AAQs, 1C3 and 1,5C3) were peptide coupled to 1-, 2-, and 3-pyrrole lexitropsins to generate compounds that incorporated both DNA minor groove and intercalating moieties. The corresponding platinum(II) amidine complexes were synthesized through a synthetically facile amine-to-platinum mediated nitrile 'Click' reaction. The precursors as well as the corresponding platinum(II) complexes were biologically evaluated in 2D monolayer cells and 3D tumour cell models. Despite having cellular accumulation levels that were up to five-fold lower than that of cisplatin, the platinum complexes had cytotoxicities that were only three-fold lower. Accumulation was lowest for the complexes with two or three pyrrole groups, but the latter was the most active of the complexes exceeding the activity of cisplatin in the MDA-MB-231 cell line. All compounds showed moderate to good penetration into spheroids of DLD-1 cells with the distributions being consistent with active uptake of the pyrrole containing complexes in regions of the spheroids starved of nutrients

Use of smartphones by art and design students for accessing library services and learning

Purpose – The purpose of this paper is to explore art and design students’ use of smartphones for accessing library services and learning at the Hong Kong Design Institute (HKDI). Design/methodology/approach – A questionnaire survey involving 51 HKDI students was conducted to examine the students’ utilization of apps and the internet on mobile devices to find information for the purpose of academic learning, social networking, and collaborative learning. Findings – Survey results showed that while the HKDI students were all smartphone owners and active users of such mobile communication devices, only a minority of them “frequently” use these mobile devices for formal learning purposes. They demonstrated a keen preference to use search engines, social communications, and other diverse use of smartphones. Except for research and image/audio-visual needs, the rest of their needs and usage behaviour is similar to mainstream university students. Practical implications – The results suggest opportunities for the libraries to develop services and facilities that could better fulfil students’ information needs, and to improve the network coverage outside the library. Originality/value – This is probably the first study of its kind to explore art and design students’ use of smartphones for learning needs. In particular, the recent capability of smartphones and mobile internet speed are comparable with desktops, it is vital to re-examine the much changed environment and user needs.postprin

Cost-Effective Use of Silver Dressings for the Treatment of Hard-to-Heal Chronic Venous Leg Ulcers

Aim To estimate the cost-effectiveness of silver dressings using a health economic model based on time-to-wound-healing in hard-to-heal chronic venous leg ulcers (VLUs). Background Chronic venous ulceration affects 1–3% of the adult population and typically has a protracted course of healing, resulting in considerable costs to the healthcare system. The pathogenesis of VLUs includes excessive and prolonged inflammation which is often related to critical colonisation and early infection. The use of silver dressings to control this bioburden and improve wound healing rates remains controversial. Methods A decision tree was constructed to evaluate the cost-effectiveness of treatment with silver compared with non-silver dressings for four weeks in a primary care setting. The outcomes: ‘Healed ulcer’, ‘Healing ulcer’ or ‘No improvement’ were developed, reflecting the relative reduction in ulcer area from baseline to four weeks of treatment. A data set from a recent meta-analysis, based on four RCTs, was applied to the model. Results Treatment with silver dressings for an initial four weeks was found to give a total cost saving (£141.57) compared with treatment with non-silver dressings. In addition, patients treated with silver dressings had a faster wound closure compared with those who had been treated with non-silver dressings. Conclusion The use of silver dressings improves healing time and can lead to overall cost savings. These results can be used to guide healthcare decision makers in evaluating the economic aspects of treatment with silver dressings in hard-to-heal chronic VLUs