Speed Control Analysis of Brushless DC Motor Based on Maximum Amplitude DC Current Feedback

This paper describes an approach to develop accurate and simple current controlled modulation technique for brushless DC (BLDC) motor drive. The approach is applied to control phase current based on generation of quasi-square wave current by using only one current controller for the three phases. Unlike the vector control method which is complicated to be implemented, this simple current modulation technique presents advantages such as phase currents are kept in balance and the current is controlled through only one dc signal which represent maximum amplitude value of trapezoidal current (Imax). This technique is performed with Proportional Integral (PI) control algorithm and triangular carrier comparison method to generate Pulse Width Modulation (PWM) signal. In addition, the PI speed controller is incorporated with the current controller to perform desirable speed operation of non-overshoot response. The performance and functionality of the BLDC motor driver are verified via simulation by using MATLAB/SIMULINK. The simulation results show the developed control system performs desirable speed operation of non-overshoot and good current waveforms

Efficiency comparison of trapezoidal and sinusoidal method for brushless DC motor drive

This paper compares overall efficiency of trapezoidal BLDC motor which is excited by trapezoidal drive and sinusoidal drive. The different characteristics and performance of trapezoidal brushless DC (BLDC) motor is formed by driving methods. Sinusoidal drive that excites trapezoidal BLDC motor generates greater maximum torque than trapezoidal drive. However, with regard to high frequency loss caused by a pulse width modulation (PWM) carrier and switching loss, the trapezoidal drive has potential to achieve higher efficiency than the sinusoidal drive. Thus, these two drive methods excite trapezoidal BLDC motor are compared to study the performance of efficiencies. The motors drives are simulated by using MATLAB and their efficiencies are measured. The results show that the trapezoidal BLDC motor with trapezoidal drive has higher efficiency compared to trapezoidal BLDC motor with sinusoidal drive

Switched Faults Analysis of Voltage Source Inverter (VSI) using Short Time Fourier Transform (STFT)

Three-phase voltage source inverter (VSI) play a very important role in the present industrial life. The knowledge and information about faults characteristic of the VSI is important to prevent failure of equipment, data losses, high maintenance and economic losses. Therefore, to insure a continuous and safety operation of the VSI, switches faults analysis implemented to prevent further damages and the commonly open and short circuit faults are happened within the VSI. This paper present the analysis of switches faults VSI by using linear time-frequency distribution (TFD) which is short time Fourier transform (STFT) by simulation using MATLAB. STFT are appropriate technique to analyze non-stationary that consist of multi-frequency component and magnitude that represent signal in time-frequency representation (TFR). From the TFR obtained, parameters of the signals are estimated such as instantaneous average current, instantaneous of root means square (RMS) current, fundamental RMS current, total harmonics distortion (THD), total nonHarmonics distortion (TnHD) and total waveform distortion (TWD). According the analysis of switches faults parameters VSI is presented. Based on the signal parameters, characteristic of signal are calculated. The end of research, various characteristics of parameter VSI faults are clearly differentiate between open and short switches faults. The information of analysis switches faults is usefull to industrial application in the process for identifying fault detection and can fault can be identify early

One Stop Cafe / Tajul Arif Mohd Shukor ... [et al.]

Our natured of business is in food Services. One Shop Cafe represents a cafe with the motoring sports concept. Our restaurant will be serving varieties of food especially western style for the customer

The effect of graphite flakes (GFs) and hybrid graphene nanoplatelets (GNPs) particles to the mechanical properties of epoxy composites

This paper reports the effects of epoxy when reinforced with graphite flakes (GFs) and was compared to epoxy reinforced by hybrid reinforcements consisted of graphite flakes (GFs) and grapheme nanoplatelets (GNPs). DGEBA, the type of epoxy which has been used in this work was added with 2, 4 and 6 wt.% of reinforcement respectively, relative to the total weight of the mixture. Nanocomposites was prepared using mechanical stirrer, stirred at 2000 rpm for 30 minutes followed by curing in the oven. The flexural testing shows that the epoxy/GFs composites has higher modulus compared to epoxy/GFs+GNPs. At 4wt.% filler loading, epoxy containing GFs exhibited 132% enhancement of modulus relative to neat epoxy. At the same filler amount, epoxy containing GFs+GNPs demonstrated slightly lower magnitude than system containing GFs with only 27% increase in modulus. However, addition of higher filler loading to the epoxy resin caused the modulus to decrease in magnitude speculated due to agglomeration of particles within the host matrix. The Charpy impact testing indicated similar pattern with epoxy/GFs system exhibited higher capability in absorbing energy than epoxy/GFs+GNPs where the peak was obtained at 4wt.% filler loading. At this amount of filler, 18.36 J/m increase in energy absorbed was recorded for epoxy/GFs compared to 2.13 J/m increased for epoxy/GFs+GNPs composite. Higher amount of filler loading added into epoxy only deteriorate the impact energy absorb by the sample. The hardness test show similar pattern of result with epoxy/GFs shows higher resistance in scratching compared to epoxy/GFs+GNPs

Academic Career In Malaysian Higher Education: The Identities Of Malaysian Professors

This paper describes the identities of Malaysia professors contextualized within the agenda of Malaysia higher education to become the hub higher education in the Asian Pacific region by 2020. in response to the challenges of global higher education, the Malaysian higher education has introduced a systematic strategic plan to develop a culture of academic excellence. However, little has been written about the changes in the academic career in response to this agenda. Future , there are claims that the academic's responsibilities are becoming more diversified and complex as the landscape of higher education changes is emphasis to massification, internationalization and accountability. Draw from this context, this paper aims to explore the roles of academics, particularly the professors and critical analysis of the Malaysian Higher Education policy documents, this paper describes a profile of Malaysian Professors. It also puts forth an argument that the identities of Malaysian professors are characterized by the local and global imperatives as they are shaped by not only the specific agenda of the country but also the global trend. Thus, this paper serves as awareness and guidance for young academics pursuing for professorship to strategize their career pathway in higher education sector

Effect Of Different Cooking Temperature And Alkalinity On Mechanical And Morphological Properties Of Composite Sheet From Durian Shell

Temperature and alkalinity are the critical factors that contribute to the successful of soda pulping. These factors influence the length size and interfibre bonding of the fibre. In this paper, durian (Durio zibethinus Murray) shell composite sheet were prepared by conducting chemical pulping through soda method to study the effect of different pulping temperature and % of NaOH on the mechanical and morphological characteristics of durian shell composite sheet. Six sets of composite sheet were produced from six sets of pulping. The pulping processes were conducted at 140, 160 and 170°C with 17, 19 and 21% of active alkali. The mechanical properties of the durian shell composite sheet were analyzed through few standard TAPPI analyses which are tensile, tear, burst, folding endurance and paper bulk thickness. The results show that the highest reading of paper bulk thickness, tensile, tear and burst index, and also folding endurance were achieved at the pulping condition of 170°C with 21% of NaOH with the value of 1.3366 g/cm3, 54.151 NM/g, 6.648 m.Nm2/g, 2.517 k.Pam2/g and 170 no. of fold, respectively. Scanning electron microscopic analysis showed that morphological changes took place depending on the size and arrangement of the fibres in the composites sheet

Factors associated with nonalcoholic fatty liver disease grades detected by ultrasound at a screening center in Klang Valley, Malaysia

Background: Non-alcoholic fatty liver disease (NAFLD) is a very common liver disease in the world, particularly in Western and developed countries. It is rapidly growing in the Asia- Pacific region. Objectives: This study was designed to determine the association between risk factors and non-alcoholic fatty liver disease grades among Malaysian adults. Patients and Methods: A cross-sectional observational study design was prospectively carried out in this study. Consecutive 628 respondents who attended for a medical checkup at urban health center had been recruited for the study. All respondents had the physical examination, blood tests, clinical assessments, and abdominal ultrasound. A structured self-administered questionnaire has been also used in this study in this survey. Results: From a total of 628 “health screened” subjects, 235 subjects (37.4%) were diagnosed to have non-alcoholic fatty liver disease. Female gender and Chinese race were predominant in our study population. Of those with NAFLD, more than half subjects (63.4) had a moderate grade of non-alcoholic fatty liver disease. The mean age of the study population was 54.54 ±6.69 years. Differences of the mean body mass index (BMI) and waist to hip ratio (WHR) were found to be significant among non-alcoholic fatty liver disease grades (P< 0.001). Similarly, mean triglycerides (TG) and high-densiy lipoprotein-cholesterol (HDL-C) levels had significant differences among non-alcoholic fatty liver disease grades (P< 0.001 and P= 0.016, respectively). Conclusion: the non-alcoholic fatty liver disease is common among urban Malaysian adult population. Anthropometric measurements were closely correlated with non-alcoholic fatty liver disease grades

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication