Power quality analysis of variable speed drives

A study was conducted to evaluate the effects of harmonics generated by Variable Speed Drives (VSDs). A VSD with a technology known as Reduced Harmonics Technology (RHT) was considered and benchmarked against existing solutions in industry in terms of cost and effectiveness. The RHT VSD, like the standard VSD, uses a three phase rectifier but with significantly lower DC bus capacitor banks and an advanced motor control processor. Simulation results reveal that the RHT VSD model produced current harmonics of approximately 30% when compared to a standard VSD, without any additional mitigation solutions, produced current harmonics above 100%. The RHT VSD was also found to be less expensive than the equivalent rated standard VSD. Laboratory experiments reveal that the input current of the RHT VSD and the standard VSD are similar to the input current waveforms from the simulation of the RHT VSD and the standard VSD respectively. Simulation of the DC bus capacitance and the source impedance reveal that in a lower range of DC capacitance values (below C1 = 600μF), the size of the DC bus capacitance has more effect on the input harmonics than the source impedance. An increase in source impedance does not reduce input harmonics. In the above mentioned range of capacitance values, it was noted that, the DC bus capacitance dominate the source impedance in its ability to reduce input harmonics. When the DC capacitance was increased above C1 = 600μF, the source impedance has more effect on the input harmonics than the size of the DC bus capacitance. The simulation and experimental results show that there are higher order (above 13th order) harmonic frequency components appearing at the input of the RHT VSD when compared to a standard VSD. It is clear that there is a trade off, due to the effect of the motor control processor, between there being reduced harmonics at the lower orders (below 13th order) and there being an increase in harmonics at higher orders (above 13th order). It was also noted from the experiment that there is no notable difference in the harmonic content at the outputs of the two VSDs

The role of mental imagery in Parkinson\u27s disease rehabilitation

Parkinson\u27s disease (PD) is a disabling neurodegenerative disease whose manifestations span motor, sensorimotor, and sensory domains. While current therapies for PD include pharmacological, invasive, and physical interventions, there is a constant need for developing additional approaches for optimizing rehabilitation gains. Mental imagery is an emerging field in neurorehabilitation and has the potential to serve as an adjunct therapy to enhance patient function. Yet, the literature on this topic is sparse. The current paper reviews the motor, sensorimotor, and sensory domains impacted by PD using gait, balance, and pain as examples, respectively. Then, mental imagery and its potential for PD motor and non-motor rehabilitation is discussed, with an emphasis on its suitability for addressing gait, balance, and pain deficits in people with PD. Lastly, future research directions are suggested

Pandemic, informality, and vulnerability : impact of COVID-19 on livelihoods in India

We analyze findings from a large-scale survey of around 5000 respondents across 12 states of India to study the impact of COVID-19 pandemic containment measures (lockdown) on employment, livelihoods, food security and access to relief measures. We find a massive increase in unemployment, an equally dramatic fall in earnings among informal workers, large increases in food insecurity, depletion of savings and patchy coverage of relief measures. Two-thirds of our respondents lost work. The few informal workers who were still employed during the lockdown experienced more than a fifty percent drop in their earnings. Even among regular wage workers, half received either no salary or reduced salary during the lockdown. Almost eighty percent of surveyed households experienced a reduction in their food intake and a similar percentage of urban households did not have enough money to pay next month's rent. We also use a set of logistic regressions to identify how employment loss and food intake varies with individual and household level characteristics. We find that migrants and urban Muslims are significantly worse off with respect to employment and food security. Among employment categories, self-employed workers were more food secure. The Public Distribution System (PDS) system was seen to have the widest reach among social security measures. However, even under PDS, 16 percent of vulnerable urban households did not have access to government rations. Further, half of the respondents reported not receiving any cash transfers (state or central). We conclude that much more is needed in the way of direct fiscal support that has been announced thus far by state and central governments in India

The Sine Gordon Model: Perturbation Theory and Cluster Monte Carlo

We study the expansion of the surface thickness in the 2-dimensional lattice Sine Gordon model in powers of the fugacity z. Using the expansion to order z**2, we derive lines of constant physics in the rough phase. We describe and test a VMR cluster algorithm for the Monte Carlo simulation of the model. The algorithm shows nearly no critical slowing down. We apply the algorithm in a comparison of our perturbative results with Monte Carlo data.Comment: compressed and uuencoded PostScript file, 25 pages, preprints CERN TH.7374/94, MS-TPI-94-

The Solid-on-Solid Surface Width Around the Roughening Transition

We investigate the surface width $W$ of solid-on-solid surfaces in the vicinity of the roughening temperature $T_r$. Above $T_r$, $W^2$ is expected to diverge with the system size $L$ like $\ln L$. However, close to $T_r$ a clean $\ln{L}$ behavior can only be seen on extremely large lattices. Starting from the Kosterlitz-Thouless renormalization group, we derive an improved formula that describes the small $L$ behavior on both sides of $T_r$. For the Discrete Gaussian model, we used the valleys-to-mountains-reflections cluster algorithm in order to simulate the fluctuating solid-on-solid surface. The base plane above which the surface is defined is an $L \times L$ square lattice. In the simulation we took $8\leq L\leq 256$. The improved formula fits the numerical results very well. {}From the analysis, we estimate the roughening temperature to be $T_r = 0.755(3)$.Comment: 9 pages, LaTeX (no figures), FSU-SCRI-93-67, CERN-TH.6893/9

Systematic Overview of Hepatitis C Infection in the Middle East and North Africa

AIM: To assess the quality of and to critically synthesize the available data on hepatitis C infections in the Middle East and North Africa (MENA) region to map evidence gaps. METHODS: We conducted an overview of systematic reviews (SRs) following an a priori developed protocol (CRD42017076736). Our overview followed the preferred reporting items for systematic reviews and meta-analyses guidelines for reporting SRs and abstracts and did not receive any funding. Two independent reviewers systematically searched MEDLINE and conducted a multistage screening of the identified articles. Out of 5758 identified articles, 37 SRs of hepatitis C virus (HCV) infection in populations living in 20 countries in the MENA region published between 2008 and 2016 were included in our overview. The nine primary outcomes of interest were HCV antibody (anti-) prevalences and incidences in different at-risk populations; the HCV viremic (RNA positive) rate in HCV-positive individuals; HCV viremic prevalence in the general population (GP); the prevalence of HCV co-infection with the hepatitis B virus, human immunodeficiency virus, or schistosomiasis; the HCV genotype/subtype distribution; and the risk factors for HCV transmission. The conflicts of interest declared by the authors of the SRs were also extracted. Good quality outcomes reported by the SRs were defined as having the population, outcome, study time and setting defined as recommended by the PICOTS framework and a sample size \u3e 100. RESULTS: We included SRs reporting HCV outcomes with different levels of quality and precision. A substantial proportion of them synthesized data from mixed populations at differing levels of risk for acquiring HCV or at different HCV infection stages (recent and prior HCV transmissions). They also synthesized the data over long periods of time (e.g., two decades). Anti-HCV prevalence in the GP varied widely in the MENA region from 0.1% (study dates not reported) in the United Arab Emirates to 2.1%-13.5% (2003-2006) in Pakistan and 14.7% (2008) in Egypt. Data were not identified for Bahrain, Jordan, or Palestine. Good quality estimates of anti-HCV prevalence in the GP were reported for Algeria, Djibouti, Egypt, Iraq, Morocco, Pakistan, Syria, Sudan, Tunisia, and Yemen. Anti-HCV incidence estimates in the GP were reported only for Egypt (0.8-6.8 per 1000 person-year, 1997-2003). In Egypt, Morocco, and the United Arab Emirates, viremic rates in anti-HCV-positive individuals from the GP were approximately 70%. In the GP, the viremic prevalence varied from 0.7% (2011) in Saudi Arabia to 5.8% (2007-2008) in Pakistan and 10.0% (2008) in Egypt. Anti-HCV prevalence was lower in blood donors than in the GP, ranging from 0.2% (1992-1993) in Algeria to 1.7% (2005) in Yemen. The reporting quality of the outcomes in blood donors was good in the MENA countries, except in Qatar where no time framework was reported for the outcome. Some countries had anti-HCV prevalence estimates for children, transfused patients, contacts of HCV-infected patients, prisoners, sex workers, and men who have sex with men. CONCLUSION: A substantial proportion of the reported outcomes may not help policymakers to develop micro-elimination strategies with precise HCV infection prevention and treatment programs in the region, as nowcasting HCV epidemiology using these data is potentially difficult. In addition to providing accurate information on HCV epidemiology, outcomes should also demonstrate practical and clinical significance and relevance. Based on the available data, most countries in the region have low to moderate anti-HCV prevalence. To achieve HCV elimination by 2030, up-to-date, good quality data on HCV epidemiology are required for the GP and key populations such as people who inject drugs and men who have sex with men

Knowledge and Perceptions about Zika Virus in a Middle East Country

BACKGROUND: Zika virus, an emerging serious infectious disease, is a threat to persons living or travelling to regions where it is currently endemic, and also to contacts of infected individuals. The aim of this study was to assess knowledge about this new public health threat to persons residing in a Middle Eastern country. METHODS: We conducted a survey at several international universities in Qatar to assess knowledge and awareness about this disease. An adapted version of the survey was also conducted using online channels from Qatar. RESULTS: The median age of the 446 participants, was 25 years, 280 (63%) were females, and 32% were from Gulf Cooperation Council (GCC) or other Middle East countries. Based upon their knowledge about availability of a vaccine, role of mosquitoes and other modes of transmission, and disease complications, we classified respondent\u27s knowledge as poor (66%), basic (27%) or broad (7%). Forty-five (16%) persons with poor knowledge considered themselves to be well-informed. CONCLUSIONS: This report from a sample of persons associated with Middle East educational complex, reveals inadequate knowledge about Zika virus, a serious emerging infectious disease. Although few cases have been reported from the region, future cases are possible, since this area is a transit hub connecting currently infected regions to North America, Europe and Asia. As a preventive measure, an educational program about Zika virus would be valuable, especially for individuals or family members travelling to afflicted regions