DC-Link Voltage Coordinated-Proportional Control for Cascaded Converter with Zero Steady-State Error and Reduced System Type

copyright 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Cascaded converter is formed by connecting two sub-converters together, sharing a common intermediate DC-link voltage. Regulation of this DC-link voltage is frequently realized with a Proportional-Integral (PI) controller, whose high gain at DC helps to force a zero steady-state tracking error. Such precise tracking is however at the expense of increasing the system type, caused by the extra pole at the origin introduced by the PI controller. The overall system may hence be tougher to control. To reduce the system type while preserving precise DC-link voltage tracking, this paper proposes a coordinated control scheme for the cascaded converter, which uses only a proportional DC-link voltage regulator. The resulting converter is thus dynamically faster, and when compared with the conventional PI-controlled converter, it is less affected by impedance interaction between its two sub-converters. The proposed scheme can be used with either unidirectional or bidirectional power flow, and has been verified by simulation and experimental results presented in the paper

‘High risk’ clinical and inflammatory clusters in COPD of Chinese descent

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordIntroduction COPD is a heterogeneous disease demonstrating inter-individual variation. A high COPD prevalence in Chinese populations is described but little is known about disease clusters and prognostic outcomes in the Chinese population across South-East Asia. We aim to determine if clusters of Chinese patients with COPD exist and their association with systemic inflammation and clinical outcomes. Methods Chinese patients with stable COPD were prospectively recruited into two cohorts (derivation and validation) from six hospitals across three South-East Asian countries (Singapore, Malaysia and Hong Kong; n=1,480). Each patient was followed over two-years. Clinical data (including co-morbidities) were employed in unsupervised hierarchical clustering (followed by validation) to determine the existence of patient clusters and their prognostic outcome. Accompanying systemic cytokine assessments were performed in a subset (n=336) of COPD patients to determine if inflammatory patterns and associated networks characterised the derived clusters. Results Five patient clusters were identified including (1) Ex-tuberculosis (2) Diabetic (3) Low co-morbidity: low-risk (4) Low co-morbidity: high-risk and (5) cardiovascular. The ‘cardiovascular’ and ‘ex-tuberculosis’ clusters demonstrate highest mortality (independent of GOLD assessment) and illustrate diverse cytokine patterns with complex inflammatory networks. Conclusions We describe novel ‘clusters’ of Chinese COPD patients, two of which represent ‘high-risk’ clusters. The ‘cardiovascular’ and ‘ex-tuberculosis’ patient clusters exhibit high mortality, significant inflammation and complex cytokine networks. Clinical and inflammatory risk stratification of Chinese patients with COPD should be considered for targeted intervention to improve disease outcomes.Singapore Ministry of Health - National Medical Research CouncilSingapore Ministry of EducationNanyang Technological University, SingaporeEngineering and Physical Sciences Research Council (EPSRC

Genetic relationships among Neisseria gonorrhoeae serovars analysed by multilocus enzyme electrophoresis.

Multilocus enzyme electrophoretic analysis was employed to assess the genetic relatedness of Neisseria gonorrhoeae. Based on the diversity of electromorphs at 9 enzyme loci, 16 electrophoretic types (ETs) were established amongst the 65 isolates. The average number of alleles per enzyme locus was 1.7 and the mean genetic diversity per locus was 0.212. The majority of isolates belonged to either ET1 (32.3%) or ET2 (16.9%). No specific correlation of ETs was seen with serovars as the major types, ETs 1 and 2, were found distributed amongst the various serovars. Major serovars such as Bacjk (IB-1/2) and Bajk (IB-3/6) were each represented by 6 or 8 ETs respectively. Analysis of the genetic relationships of ETs to each other showed some clustering of subgroups that were more closely related than others

Resolution of clonal subgroups among Neisseria gonorrhoeae IB-2 and IB-6 serovars by pulsed-field gel electrophoresis.

OBJECTIVE--Analysis of macrorestriction patterns by PFGE to resolve the relatedness of clonal subgroups amongst N gonorrhoeae IB-2 and IB-6 serovar strains. MATERIALS AND METHODS--Nineteen IB-2 and eight IB-6 serovar strains that differed in either auxotype or penicillin sensitivity were isolated over a two and a half-year period from patients attending several STD clinics in Sydney. During this period, a major clone, Wt/IB-2 (FS), established on epidemiological grounds, was circulating amongst homosexual males. The genetic relation of this major clone to the other strains present in the community was determined by pulsed-field gel electrophoretic (PFGE) analysis of DNA restriction fragments. Genomic DNA from the 27 isolates were prepared, digested with SpeI and BglII and the restriction patterns were analysed by contour-clamped homogeneous electric field electrophoresis (CHEF) in a CHEF DRIII equipment. RESULTS--Phenotypic characterisation of the 27 isolates by the combined use of auxotype, serological characterisation and penicillin sensitivity indicated the presence of subgroups within each of the two serovars. In the present study, PFGE analysis of SPeI and BglII-generated genomic DNA restriction patterns from six of the ten Wt/IB-2 (FS) correlated well with phenotypic characterisation of this major clone. Four of the ten Wt/IB-2 (FS) were found to be clonally-derived variants of this major clone as minor genome variations (less than 3 DNA fragments) were observed. Distinct clones were represented by three Wt/IB-2 (LS) isolates as the DNA fingerprints generated from these were unrelated to the major clone. Analysis of PFGE patterns of 6 Pro/IB-2 isolates showed that one was genotypically identical to the major clone, two were clonal variants and three had significantly different patterns to indicate that they were genotypically unrelated. Wt/IB-6 isolates had heterogenous PFGE patterns that were clearly unrelated to the Wt/IB-2 serovar strains. Within the IB-6 serovar, there were three isolates with the Wt/IB-6 (FS) phenotype that could be considered as clonal variants whilst the rest were genotypically distinct. CONCLUSIONS--PFGE analysis of macrorestriction patterns generated from SpeI- and BglII-cleavage of genomic DNA has enabled the establishment of clonal origins of strains present in the Sydney community during the period of study. The delineation of strains belonging to major A/S groups by PFGE analysis presents a clearer epidemiological picture than phenotypic characterisation alone

The diagnostic accuracy of telegeriatrics for the diagnosis of dementia via video conferencing

Introduction The suitability of video conferencing (VC) technology for clinical purposes relevant to geriatric medicine is still being established. This project aimed to determine the validity of the diagnosis of dementia via VC. Methods This was a multisite, noninferiority, prospective cohort study. Patients, aged 50 years and older, referred by their primary care physician for cognitive assessment, were assessed at 4 memory disorder clinics. All patients were assessed independently by 2 specialist physicians. They were allocated one face-to-face (FTF) assessment (Reference standard – usual clinical practice) and an additional assessment (either usual FTF assessment or a VC assessment) on the same day. Each specialist physician had access to the patient chart and the results of a battery of standardized cognitive assessments administered FTF by the clinic nurse. Percentage agreement (P0) and the weighted kappa statistic with linear weight (Kw) were used to assess inter-rater reliability across the 2 study groups on the diagnosis of dementia (cognition normal, impaired, or demented). Results The 205 patients were allocated to group: Videoconference (n = 100) or Standard practice (n = 105); 106 were men. The average age was 76 (SD 9, 51–95) and the average Standardized Mini-Mental State Examination Score was 23.9 (SD 4.7, 9–30). Agreement for the Videoconference group (P0= 0.71; Kw = 0.52; P < .0001) and agreement for the Standard Practice group (P0= 0.70; Kw = 0.50; P < .0001) were both statistically significant (P < .05). The summary kappa statistic of 0.51 (P = .84) indicated that VC was not inferior to FTF assessment. Conclusions Previous studies have shown that preliminary standardized assessment tools can be reliably administered and scored via VC. This study focused on the geriatric assessment component of the interview (interpretation of standardized assessments, taking a history and formulating a diagnosis by medical specialist) and identified high levels of agreement for diagnosing dementia. A model of service incorporating either local or remote administered standardized assessments, and remote specialist assessment, is a reliable process for enabling the diagnosis of dementia for isolated older adults

Molecular typing of Neisseria gonorrhoeae by restriction fragment length polymorphisms.

OBJECTIVE--To characterise Neisseria gonorrhoeae isolates by restriction fragment length polymorphisms (RFLPs) in ribosomal RNA genes. DESIGN--Generation of RFLP patterns by HincII restriction of rRNA genes followed by hybridisation with a non-radioactive labelled broad spectrum 16 + 23S rRNA gene probe. This typing method was developed and compared with MAb based serotyping. SPECIMENS--Forty three randomly collected isolates from Bangkok (27 isolates) and Singapore (16 isolates) were studied. RESULTS--The RFLP patterns generated were reproducible and highly discriminatory between strains. Analysis of RFLPs produced by HincII restriction of rRNA genes established 9 patterns amongst the 43 isolates examined. Strains present within a common serovar could be further subdivided by RFLP typing. Identical RFLP patterns were found in some strains that belonged to various serovars. CONCLUSION--RFLP typing based on heterogeneities of rRNA gene restriction patterns could be advantageously used to complement monoclonal antibody based serotyping for further subdivision of serovars. Higher sensitivity of this combined approach would enable better differentiation of strains in epidemiological studies