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Single-Phase Bridgeless Zeta PFC Converter with Reduced Conduction Losses
Shakil Ahamed Khan,Nasrudin Abd. Rahim,Ab Halim Abu Bakar,Tan Chia Kwang 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.2
This paper presents a new single phase front-end ac?dc bridgeless power factor correction (PFC) rectifier topology. The proposed converter achieves a high efficiency over a wide range of input and output voltages, a high power factor, low line current harmonics and both step up and step down voltage conversions. This topology is based on a non-inverting buck-boost (Zeta) converter. In this approach, the input diode bridge is removed and a maximum of one diode conducts in a complete switching period. This reduces the conduction losses and the thermal stresses on the switches when compare to existing PFC topologies. Inherent power factor correction is achieved by operating the converter in the discontinuous conduction mode (DCM) which leads to a simplified control circuit. The characteristics of the proposed design, principles of operation, steady state operation analysis, and control structure are described in this paper. An experimental prototype has been built to demonstrate the feasibility of the new converter. Simulation and experimental results are provided to verify the improved power quality at the AC mains and the lower conduction losses of the converter.
Single-Phase Bridgeless Zeta PFC Converter with Reduced Conduction Losses
Khan, Shakil Ahamed,Rahim, Nasrudin Abd.,Bakar, Ab Halim Abu,Kwang, Tan Chia The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.2
This paper presents a new single phase front-end ac-dc bridgeless power factor correction (PFC) rectifier topology. The proposed converter achieves a high efficiency over a wide range of input and output voltages, a high power factor, low line current harmonics and both step up and step down voltage conversions. This topology is based on a non-inverting buck-boost (Zeta) converter. In this approach, the input diode bridge is removed and a maximum of one diode conducts in a complete switching period. This reduces the conduction losses and the thermal stresses on the switches when compare to existing PFC topologies. Inherent power factor correction is achieved by operating the converter in the discontinuous conduction mode (DCM) which leads to a simplified control circuit. The characteristics of the proposed design, principles of operation, steady state operation analysis, and control structure are described in this paper. An experimental prototype has been built to demonstrate the feasibility of the new converter. Simulation and experimental results are provided to verify the improved power quality at the AC mains and the lower conduction losses of the converter.
Patel Mohammed Shakil,Lee Kwang Chear,Dhake Rakesh Padmakar,Longworth Stephen,Sell Philip 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.2
Study Design: Prospective study.Purpose: Yellow flags are psychosocial associated with a greater likelihood of progression to persistent pain and disability. These are referred to as obstacles to recovery. Despite their recognized importance, it is unknown how effective clinicians are in detecting them. The primary objective of this study was thus to determine the effectiveness of spine specialist clinicians in detecting the presence of yellow flags in patients presenting to an orthopedic outpatient clinic with low back-related disorders.Overview of Literature: Psychosocial factors have been previously studied as important predictors of prognosis in patients with low back pain. However, the ability of spinal specialist to identify them remains unknown.Methods: A prospective, single-center, consecutive cohort study was conducted over a period of 30 months. All new patients with low back-related disorders regardless of pathology completed a Yellow Flag Questionnaire that was adapted from the psychosocial flags framework. Clinicians assessing these patients completed a standardized form to determine which and how many yellow flags they had identified during the consultation.Results: A total of 130 patients were included in the analysis, and the clinicians reported an average of 5 flags (range, 0–9). Fear of movement or injury was the most frequently reported yellow flag, reported by 87.7% (n=114) of patients. Clinician sensitivity in detecting yellow flags was poor, correctly identifying only 2 flags, on average, of the 5 reported by patients, with an overall sensitivity of only 39%.Conclusions: The ability of spine specialists to identify yellow flags is poor and can be improved by asking patients to complete a simple screening questionnaire.
Malik, Saima Shakil,Kazmi, Zehra,Fatima, Iffat,Shabbir, Riffat,Perveen, Shagufta,Masood, Nosheen Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.5
Genetic polymorphisms constitute one of the reasons behind the racial variation in prostate cancer occurrence. Published studies regarding genetic associations of glutathione S-transferase mu 1 (GSTM1) and glutathione S-transferase theta 1 (GSTT1) null deletion polymorphisms with prostatic carcinoma have generated inconsistent results among different populations. To date, even a single meta-analysis is not available representing the association of these genes with prostate cancer in different ethnic groups. Therefore, the aim of the current study was to provide a clear picture of GSTM1 and GSTT1 null deletion and risk of prostate cancer among different ethnic groups (i.e. Asians, Europeans, Americans, Africans and Eurasians). A systematic search was performed with the help of various search engines to find out the all the recent studies (2004 to 2015) evaluating the role of GSTM1 and GSTT1 deletion in prostate cancer development. Odds ratios (ORs) with 95% confidence interval (CI) of a total of 34 studies with 7,281 cases and 9,082 controls was analyzed using STATA and MedCalc software. Overall, GSTM1 deletion (OR 3.67; CI 1.39-9.85; P= 0.001) was strongly associated with prostatic cancer. In the sub group analysis GSTM1 null deletion was also significantly associated with prostate cancer among Asians (OR 4.84; CI 1.08-21.5; P= 0.03), Eurasians (OR 17.69; CI 9.87-31.70; P< 0.001) and Americans (OR 0.11; CI 0.01-1.06; P= 0.05). No association was observed among Europeans (P=0.42) and Africans (P= 0.40). As a whole GSTT1 null deletion (OR 0.85; CI 0.28-2.58; P= 0.77) did not show anyt significant association with prostate cancer risk among different populations. When the data were stratified into different groups, however, Africans demonstrated a significant association of GSTT1 null deletion (OR 1.95; CI 1.57-2.39; P<0.001) with prostate cancer, whereas no association was found among Asians (P= 0.90), Americans (P= 0.50), Europeans (P= 0.89) and Eurasians (P= 1.0). In conclusion, both GSTM1 and GSTT1 may contribute to prostate cancer development but GSTM1 may prove to be a stronger candidate risk factor.
Visible Light Communication Based Wide Range Indoor Fine Particulate Matter Monitoring System
SEJAN MOHAMMAD ABRAR SHAKIL,안진영,한대현,정완영 한국융합신호처리학회 2019 융합신호처리학회 논문지 (JISPS) Vol.20 No.1
Fine particulate matter known as PM 2.5 refers to the atmospheric particulate matter that has a diameter less than 2.5 micrometer identified as dangerous element for human health and its concentration can provide us a clear picture about air dust concentration. Humans stay indoor almost 90% of their life time and also there is no official indoor dust concentration data, so our study is focused on measuring the indoor air quality. Indoor dust data monitoring is very important in hospital environments beside that other places can also be considered for monitoring like classrooms, cements factories, computer server rooms, petrochemical storage etc. In this paper, visible light communication system is proposed by Manchester encoding technique for electromagnetic interference (EMI)-free indoor dust monitoring. Important indoor environment information like dust concentration is transferred by visible light channel in wide range. An average voltage-tracking technique is utilized for robust light detection to eliminate ambient light and low-frequency noise. The incoming light is recognized by a photo diode and are simultaneously processed by a receiver micro-controller. We can monitor indoor air quality in real-time and can take necessary action according to the result.
A NOTE ON THE CHARACTERIZATIONS OF PARETO DISTRIBUTION BY UPPER RECORD VALUES
Ahsanullah, Mohammad,Shakil, Mohammad Korean Mathematical Society 2012 대한수학회논문집 Vol.27 No.4
Many researchers have studied the characterizations of probability distributions based on record values. It appears from literature that not much attention has been paid to the characterizations of the Pareto distribution. In this note, some new results on the characterizations of the Pareto distribution by upper record values have been established.