19672 research outputs found
Sort by
Smart Semi-active PID-ACO control strategy for tower vibration reduction in Wind Turbines with MR damper
No full textWind turbine technology is well known around the globe as an eco-friendly and effective renewable power source. However, this technology often faces reliability problems due to structural vibration. This study proposes a smart semi-active vibration control system using Magnetorheological (MR) dampers where feedback controllers are optimized with nature-inspired algorithms. Proportional integral derivative (PID) and Proportional integral (PI) controllers are designed to achieve the optimal desired force and current input for MR the damper. PID control parameters are optimized using an Ant colony optimization (ACO) algorithm. The effectiveness of the ACO algorithm is validated by comparing its performance with Ziegler-Nichols (Z-N) and particle swarm optimization (PSO). The placement of the MR damper on the tower is also investigated to ensure structural balance and optimal desired force from the MR damper. The simulation results show that the proposed semi-active PID-ACO control strategy can significantly reduce vibration on the wind turbine tower under different frequencies (i.e., 67%, 73%, 79% and 34.4% at 2 Hz, 3 Hz, 4.6 Hz and 6 Hz, respectively) and amplitudes (i.e. 50%, 58% and 67% for 50 N, 80 N, and 100 N, respectively). In this study, the simulation model is validated with an experimental study in terms of natural frequency, mode shape and uncontrolled response at the 1st mode. The proposed PID-ACO control strategy and optimal MR damper position is also implemented on a lab-scaled wind turbine tower model. The results show that the vibration reduction rate is 66% and 73% in the experimental and simulation study, respectively, at the 1st mode. © 2019, Institute of Engineering Mechanics, China Earthquake Administration
Effect of hot extrusion parameters on microhardness and microstructure in direct recycling of aluminium chips [Einfluss von Warmstrangpress-Parametern auf die Mikrohärte und das Gefüge beim Wiederverwerten von Aluminiumspänen]
No full textDirect hot extrusion is an alternative process for recycling aluminium without melting the scrap. It utilizes low energy and is environmental friendly. This paper reports the microhardness and microstructure of aluminium alloy chips when subjected to various settings of preheating temperature and preheating time in hot extrusion process. Three values of preheating temperature are taken as 450 °C, 500 °C, and 550 °C. On the other hand, three values of preheating time were chosen (1 h, 2 h, 3 h). The influences of the process parameters (preheating temperature and time) are analyzed using design of experiments approach whereby full factorial design with center point analysis are adopted. The total runs are 11 and they comprise of two factors of full factorial design with 3 center points. The responses are microhardness and microstructure. The results show that microhardness increases with the decrease of the preheating temperature. The results also show that the preheating temperature is more important to be controlled rather than the preheating time in microhardness analyses. The profile extrudes at 450 °C and 1 hour has gained the optimum microhardness and it can be concluded that setting temperature at 550 °C for 3 hours results in the highest responses for average grain sizes in analysis of microstructure. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei
Predicting the risk of chronic kidney disease among type 2 diabetes mellitus patients in a primary care setting: An evaluation of the QKidney model
No full textIntroduction: Diabetes mellitus is a major risk factor for chronic kidney disease (CKD). Thus, making routine screening among the diabetic group is necessary in order to reduce the burden of the disease. As such, various risk prediction models including QKidney model have been developed for early detection of CKD. However, the Qkidney model has not been validated in Malaysia. This study aimed to evaluate the performance of QKidney model in predicting a 5-year risk of developing CKD in a cohort of type 2 diabetes mellitus (T2DM) patients in the primary care setting. Methods: A total of 377 T2DM patients attended the primary care clinic at the town of Rawang, aged 30-74 years old, and free of CKD outcomes at baseline were recruited and followed-up for 5 years. Their CKD risk was calculated using the QKidney model. The predictive performance of QKidney model was assessed through discrimination and calibration analyses. Results: At the end of the 5-year follow-up, a total median QKidney score was 3.9% (IQR: 5.9). The median QKidney score of male participants (7.3%) was significantly higher than that of the females (3.0%) (p < 0.001). The QKidney model has a moderate discrimination in which the area under the receiver operating characteristic curve was 0.748, with good calibration (χ2 = 13.039, p = 0.111). Conclusion: It was found that the QKidney model had a moderate discriminative ability with good calibration. When taken together, it was suggested that the QKidney model could be utilized to predict a moderate-to-severe CKD risk in Malaysians with T2DM. © 2019 UPM Press. All rights reserved
A comparative study of patients’ perceptions of genetic and genomic medicine services in California and Malaysia
No full textIn the era of personalized and genomic medicine, awareness of patients with rare diseases is increasing as new approaches to diagnosis and treatment are developed. This study examined perceived barriers experienced by families with rare diseases and explored possible differences between participants in Malaysia and California, USA. The study involved N = 108 participants recruited in genetics clinic appointments at the University of Malaya Medical Center and three sites in Southern California. Participants completed a survey involving multiple choice and Likert scale items pertaining to perceived barriers to access genetics-related healthcare. Results from this study provide evidence of similar perceived barriers, despite differences in the two populations. Participants selected the expansion of healthcare provider knowledge of rare diseases to be the most beneficial approach to overcome perceived barriers. In both locations, it was also noted that travel distance to clinic was not perceived as a large stress factor. Taking these observations together, a healthcare model with a central location of providers well-versed in medical genetics may be considered if further data support our findings. The data from this study support a need for improving healthcare provider knowledge of genetics. Future studies exploring how these perceived stress factors are impacting families as well as different methods of educating providers are suggested by findings from the study, as well as studies querying the opinions of those who are unable to access genetics services. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature
Investigation of QoS performance evaluation over 5G network for indoor environment at millimeter wave bands
No full textOne of the crucial advancements in next-generation 5G wireless networks is the use of high-frequency signals specifically those are in the millimeter wave (mm-wave) bands. Using mm-wave frequency will allow more bandwidth resulting higher user data rates in comparison to the currently available network. However, several challenges are emerging (such as fading, scattering, propagation loss etc.), whenever we utilize mm-wave frequency wave bands for signal propagation. Optimizing propagation parameters of the mm-wave channels system are much essential for implementing in the real-world scenario. To keep this in mind, this paper presents the potential abilities of high frequencies signals by characterizing the indoor small cell propagation channel for 28, 38, 60 and 73 GHz frequency band, which is considered as the ultimate frequency choice for many of the researchers. The most potential Close-In (CI) propagation model for mm-wave frequencies is used as a Large-scale path loss model. Results and outcomes directly affecting the user experience based on fairness index, average cell throughput, spectral efficiency, cell-edge user’s throughput and average user throughput. The statistical results proved that these mm-wave spectrum gives a sufficiently greater overall performance and are available for use in the next generation 5G mobile communication network. © 2019 Polish Academy of Sciences. All Rights Reserved
Crop Acreage and Crop Yield Estimation using Remote Sensing and GIS Techniques, Bulandshahr District
No full textPresent study was conducted in the Bulandshahr district, Uttar Pradesh, India, for land use land cover changes, density of vegetation, difference vegetation index and estimation of crop yield for the year of 2000 and 2014. Remote sensing and geographical information system techniques were used in this study. Five land use land cover classes were identified such as built-up land, open land, crop land, and natural vegetation and water bodies through supervised classification with an accuracy of 97.9 and 99.5 per cent for the year 2000 and 2014, respectively. Increment in built-up land, open land and crop land were observed while natural vegetation was decline up to 15.6 per cent in fourteen years. Highest NDVI values for 2000 and 2014 were 0.4141 and 0.4166 while lowest were -0.4127 and -0.4166. In the crop yield estimation, an average of 3.7 x 106 ton ha-1 crop production was estimated. Overall, the study showed that the use of remote sensing and GIS in crop yield estimation was better as compared to traditional techniques. © 2019 Ecological Society of India. All rights reserved
Trust and loyalty among Islamic and conventional bank customers in Malaysia
No full textThe purpose of this study is to explore the dimensions of service quality and test an integrative model to study the influence of service quality, image, and trust on customer loyalty in the Malaysian banking sector. In this study, the service quality model is enhanced to improve the bank’s image. Structural Equation Modelling (SEM) was used to test the proposed research model. The proposed model indicates that delivering high-quality service can result in achieving the well-known image; the result also shows a positive relationship between image and trust, and trust and customer loyalty in both Islamic and conventional banks. Therefore, based on the findings, service quality, bank image and trust are considered to be antecedents of customer loyalty. Bank image is indirectly related to customer loyalty through trust. © Universiti Putra Malaysia Pres
Environmental goods and services sector in Malaysia: Regulatory shortcomings and policy constraints
No full textEnvironmental regulation is a key driver for the growth of environmental goods and services (EGS), while trade facilitates the diffusion of these goods and services. There has been no shortage of initiatives to develop the EGS sector in Malaysia. However, some policy (non-market) failures are already observed in the governance of this sector. This paper identifies the inadequacies in the regulatory framework (environmental institutions and laws) for creating an enabling environment for the EGS sector. The paper also reviews the trade direction for EGS and delineates concerns related to the sectoral approach of policy making for the sector. The findings from the documentary analyses suggest that the laws and policies related to the EGS are fragmented as they come under the purview of different agencies. As a result of this regulatory incoherence, the coordination and enforcement are weak leading to low uptake of EGS. The absence of a national policy for EGS also obscures the trade direction for this sector. The policy priority and generous support accorded to the renewable energy segment, more specifically, are also a concern given the limited and uncertain role that this segment is expected to play in global energy use. © 2019, Faculty of Economics and Administration. All rights reserved
“The best interest of the adolescent“: Exploring doctors’ decision to proceed with treatment of sexual reproductive health without parental consent
No full textIntroduction: Adolescents below the age of majority require parental consent for treatment or else the treating doctor may be liable for trespass and assault. This creates a dilemma for frontline doctors, as involving parents in the discussion could add yet another barrier to the existing barriers for adolescents in terms of access to healthcare services. Aim: This paper seeks to explore doctors’ treatment decisions made without parental consent when managing adolescents presenting with sexual and reproductive health issues. Methods: Based on a qualitative approach, in-depth interviews with 25 doctors throughout Malaysia were conducted. All audio-recorded interviews were transcribed verbatim and analyzed using a thematic approach. Results: Generally, doctors weigh any decision by examining the health risks and benefits involved. While fear of litigation influences treatment decisions, a strong adherence to the ethical duty of ‘do no harm’ outweighs other considerations. When all options are risky, choosing what is considered ‘the lesser of two evils,’ i.e., what is perceived to be in the best interest of the adolescent, is adopted. Conclusions: The complexity of a medical decision related to adolescent SRH issues is increased further when legal requirements are not in synch with the ethical and personal values of doctors. The laws relating to parental consent should be promulgated with a provision allowing doctors to exercise discretion in terms of treating specific SRH issues without parental consent. © 2019 Malaysian Family Physician. All rights reserved
Design optimization of the graded AlGaN/GaN HEMT device performance based on material and physical dimensions
No full textPurpose: To design and optimize the traditional aluminum gallium nitride/gallium nitride high electron mobility transistor (HEMT) device in achieving improved performance and current handling capability using the Synopsys’ Sentaurus TCAD tool. Design/methodology/approach: Varying material and physical considerations, specifically investigating the effects of graded barriers, spacer interlayer, material selection for the channel, as well as study of the effects in the physical dimensions of the HEMT, have been extensively carried out. Findings: Critical figure-of-merits, specifically the DC characteristics, 2DEG concentrations and mobility of the heterostructure device, have been evaluated. Significant observations include enhancement of maximum current density by 63 per cent, whereas the electron concentration was found to propagate by 1,020 cm−3 in the channel. Practical implications: This work aims to provide tactical optimization to traditional heterostructure field effect transistors, rendering its application as power amplifiers, Monolithic Microwave Integrated Circuit (MMICs) and Radar, which requires low noise performance and very high radio frequency design operations. Originality/value: Analysis in covering the breadth and complexity of heterostructure devices has been carefully executed through extensive TCAD modeling, and the end structure obtained has been optimized to provide best performance. © 2019, Emerald Publishing Limited