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The design, simulation and testing of an omni-direction deflector for vertical axis wind turbine
Get PDFResearch have shown a growing interest in vertical axis wind turbines (VAWTs) due to their numerous benefits especially the omni-direction feature. However, VAWTs exhibit lower efficiency and difficult to selfstart. In this research, an omni-direction deflector (ODD) has been proposed to enhance the performance of a straight-bladed VAWT. Three-dimensional numerical simulations have been performed to analyze the
aerodynamic characteristics of a straight-bladed NACA 0021 VAWT and the effects of a flat plate deflector. Sliding mesh method was employed to simulate the rotational motion of the VAWT using ANSYS Fluent at tip speed ratio (TSR) of 2.58. The unsteady flow CFD simulation was validated with the wind tunnel experiment data available in the literature. A few parameters including the position, the inclination angle and the length of the flat plate deflector were investigated. The simulations showed that the augmented flow occurred at the near wake region of the flat plate deflector. This flow was directed and accelerated by the deflector about 25% higher than the oncoming wind flow before impinging with the turbine; hence the coefficient of power (CP) of the VAWT
improved significantly. From the simulation results, the optimum parameters for the flat plate deflector were
placed at the horizontal distance of 2R from the rotor axis, a vertical distance of 0.66H from the lower edge of the
VAWT, no inclination angle, and 1.5H for the plate length. With these parameters, the average coefficient of
torque increases about 46.95% compared to the VAWT without the deflector. The research was extended for the
development the ODD where it comprises six flat plate deflectors evenly surround the VAWT with a distance of
0.66H from the lower edge of the VAWT rotor blade. Simulations with the same setup were performed with the
ODD. In order to simulate wind flow from all direction, the ODD was oriented at 0° and 30° with the oncoming wind. The simulation shows a higher average CP of 35.48% and 37.63% were achieved for the ODD place at 0° and 30° respectively. In addition, lab tests were conducted to verify the effects of the ODD on a five-bladed VAWT with the oncoming wind speed at 6 m/s. From the result, both the simulation and experiment results showed a good agreement on the performance enhancement with the presence of the ODD. The ODD accelerates and directs the oncoming wind towards the VAWT, hence, improve the CP of the VAWT significantly. From the lab tests, the maximum CP achieved was 0.051 and 0.049 at TSR 0.9 when the ODD oriented at 0° and 30° with the oncoming wind, compared to the bare turbine of 0.0413 at TSR 0.8, it was about 23.5% and 18.6% increased respectively. Furthermore, a higher rotational speed, wider TSR range, and better self-start ability were achieved with the employment of the ODD in the lab tests. The design of the ODD has a good potential as it can be easily retrofitted to the existing VAWT system hence enhance the performance
Water-based graphene quantum dots dispersion as a high-performance long-term stable nanofluid for two-phased closed thermosyphons
No full textWater-based graphene quantum dots (GQD) suspension has great potential for different heat transfer applications as a novel coolant due to their unique colloidal stability, high thermal conductivity and low penalty for rheological properties once loading GQD. To this end, graphene quantum dots were firstly prepared through a new and cost-effective exfoliation procedure. Based on the morphological characterization, the average thickness and diameter of the synthesized amine treated-GQD (AGQD) were determined as mostly less than 1 nm and in the range of 5–20 nm, respectively. Case studies show that water-based AGQD nanofluid at very low weight fractions shows a considerably higher thermal conductivity than that of base fluid. In a detailed rheological investigation of the water-based AGQD nanofluid, no noteworthy increase was observed in comparison with the base fluid, which is considered as a major benefit for this novel generation of coolants. The water-based AGQD nanofluids were also found to be especially more effective in the thermosyphon in terms of overall thermal properties such as net heat transfer, and thermal efficiency, and rheological property such as effective viscosity, as well as, total pressure drop in comparison to the distilled water. Since the water-based AGQD nanofluids show no sedimentation, high thermal conductivity and fairly no effect on rheological properties, it would provide an economical approach for enhancing the performance of industrial heat pipes and thermosyphons
Ceftaroline fosamil laden allograft: A new modality in reducing infection?
No full textPurpose: Allograft infection remains the greatest challenge in orthopaedic reconstructive surgery especially methicillin-resistant Staphylococcus aureus (MRSA). This risk can be minimized with the use of antibiotic laden allograft (ALA) via iontophoresis. Ceftaroline fosamil (CF) is an advanced-generation cephalosporin, an alternative treatment for MRSA infections. Its antibacterial activity and safety profile are better than vancomycin. CF iontophoresed bone has not been used before. This study was conducted to establish the feasibility of creating a CF ALA and establish the prime conditions for its expenditure. Method: We created an iontophoresis cell; 3% CF was inserted within medullary segment of goat bone and sealed from external saline solution. The cell operated at the following voltages 30, 60 and 90 V and at the following durations 5, 10, 15, 20, 25 and 30 min. Information regarding optimal conditions for its application was then obtained. After which, correlation between voltages and time with CF concentration in the bone was analysed. A bioavailability test was also conducted to observe the optimal rate of CF elution from the graft. Result: The optimal condition for the impregnation process is 3% CF at 90 V for 10 min. Bone graft impregnated with CF at optimal conditions can elute above minimum inhibitory concentration of the CF against MRSA for 21 days. Conclusion: CF iontophoresis was found feasible for allograft impregnation. The technique is simple, inexpensive and reproducible clinically. Iontophoresis offers a novel solution to reduce the rate of perioperative infection in reconstructive surgery involving use of bone graft
Zero-inflated Conway-Maxwell Poisson Distribution to Analyze Discrete Data
No full textIn this paper, we study the zero-inflated Conway-Maxwell Poisson (ZICMP) distribution and develop a regression model. Score and likelihood ratio tests are also implemented for testing the inflation/deflation parameter. Simulation studies are carried out to examine the performance of these tests. A data example is presented to illustrate the concepts. In this example, the proposed model is compared to the well-known zero-inflated Poisson (ZIP) and the zero-inflated generalized Poisson (ZIGP) regression models. It is shown that the fit by ZICMP is comparable or better than these models
On the minimum order of 4-lazy cops-win graphs
No full textWe consider the minimum order of a graph G with a given lazy cop number c L (G). Sullivan, Townsend and Werzanski [7] showed that the minimum order of a connected graph with lazy cop number 3 is 9 and K 3 □K 3 is the unique graph on nine vertices which requires three lazy cops. They conjectured that for a graph G on n vertices with ∆(G) ≥ n − k 2 , c L (G) ≤ k. We proved that the conjecture is true for k = 4. Furthermore, we showed that the Petersen graph is the unique connected graph G on 10 vertices with ∆(G) ≤ 3 having lazy cop number 3 and the minimum order of a connected graph with lazy cop number 4 is 16
Psychometric Properties of the Simplified Chinese Version of the Malaysian Medication Adherence Scale (C-MALMAS) on Elderly Patients
No full textBackground: Poor medication adherence is a concern among elderly patients. One of the convenient measures of medication adherence is by using a validated instrument. Therefore, this study aimed to examine the psychometric properties of the Simplified Chinese version of the Malaysian Medication Adherence Scale (C-MALMAS) for assessing medication adherence of elderly patients. Methods: The C-MALMAS consists of 8 items which measure one domain. It was translated into the Simplified Chinese version and validated on a convenience sample of 100 elderly outpatients in Malaysia. Internal consistency of the C-MALMAS was evaluated based on Cronbach's alpha value. A retest was conducted a month later to assess its stable reliability. Validity was assessed using convergent validity by comparing C-MALMAS to the Simplified Chinese translation of the 8-item Morisky Medication Adherence Scale (MMAS-8) and concurrent validity was confirmed by comparing the medication adherence determined using C-MALMAS with that using pill count. Results: The C-MALMAS has an acceptable internal consistency, with Cronbach's alpha of 0.586 and a test-retest correlation of 0.405 (p < 0.001), indicating fair correlation. A good correlation between the C-MALMAS and MMAS-8 was found (Spearman's rho = 0.717; p < 0.001). A significant association between medication adherence based on the C-MALMAS and pill count was observed. The C-MALMAS has a sensitivity and specificity of 94.4% and 33.3%, respectively, with positive and negative predictive values of 67.3% and 80.0%, respectively. Conclusion: C-MALMAS is a reliable and valid instrument for measuring medication adherence of elderly patients, especially when a specific recall period is required
Evaluation on stability and thermophysical performances of covalently functionalized graphene nanoplatelets with xylitol and citric acid
No full textAn economical and environmentally friendly approach has been introduced to synthesize highly stable graphene nanoplatelets (GNPs) dispersions with different solvents e.g. water, ethylene glycol, methanol, ethanol, and 1-hexanol. The strategy involved with the introduction of hydroxyl groups through mild oxidation of GNPs which was then grafted with citric acid and xylitol that polymerized together, improving the solubility of GNPs. The functionalization of GNPs was proved by Fourier transform infrared (FTIR), Raman spectroscopy and high resolution-transmission electron microscope (HRTEM). Further study was carried out by using xylitol and citric acid (XC)-treated GNPs as an additive in base fluid to check their thermophysical properties. Great stability for water-, methanol-, ethanol-, 1-hexanol- and ethylene glycol-based XC-treated GNPs dispersions at 0.01 wt% was achieved, representing stable weight concentrations of 89%, 75%, 72%, 64% and 82% after 15 days, respectively. In addition, the XC-treated GNPs show remarkable enhancement in the thermal conductivity up to 34% at 60 °C. Furthermore, water-based XC-treated GNPs dispersions with different concentrations show Newtonian behaviour
Linking consumer confidence index and social media sentiment analysis
No full textThis study aims to analyse the link (correlation) between and the official CCI and social media big data (via sentiment analysis) on consumer purchasing behaviour for two types of products over the course of two years (24 months, from January 2015 to December 2016). The CCI data was obtained from the Malaysian Institute of Economic Research (MIER) while the sentiment analysis was obtained from twitter. The results indicate that there is a significant but very small relationship between CCI and social media sentiment analysis. On the basis of the results we conclude that social media can offer huge a huge volume of data on consumer confidence, the analysis of which can be conducted at a more rapid time and integrated with existing methods in a synergistic way to refine the accuracy of the CCI using data from far larger populations
Graphene coated silica microfiber for highly sensitive magnesium sensor
No full textA high sensitivity and simple magnesium sensor based on an silica optical microfiber coated with graphene for the detection of different concentrations of magnesium in de-ionized water is developed and demonstrated. The silica microfiber probe is fabricated by flame brushing technique and it has a waist diameter of 6 μm with tapering length of 3 cm. The microfiber is coated with graphene, which functions as a sensing layer using drop coating method. It is observed that the output power from the probe decreases as the magnesium concentration increases. Without the graphene coating, the sensor has a sensitivity of 12.1 dB/% with slope linearity of more than 98.31% and resolution of 0.0102%. However, the sensitivity of the sensor is significantly improved to 19.63 dBm/% with better slope linearity of 99.25% and resolution of 0.0038% as the graphene is coated onto the silica microfiber probe. The resonant peak also shifts to a longer wavelength as the concentration of magnesium solution increased
Leadership behaviour on job satisfaction in Malaysian national secondary schools: Motivation and hygiene satisfaction
No full textInter-relationship between the principal and his/her teachers is vital in ensuring the success in school performance. Principal leadership behaviour is attributed to teachers’ job satisfaction thus may directly or indirectly, influence the achievement of school when striving for a goal or vision. The present study aims to determine the influence of principals’ leadership behaviour on teachers’ job satisfaction from the perception of a group of selected secondary schools teacher. Quantitative approach was used and questionnaires were distributed to 301 teachers for data collection. Descriptive and inferential analyses were used to analyse the data collected. Two instruments were utilized namely, (1) Leadership Behaviour Questionnaire and; (2) Teacher Job Satisfaction Questionnaire. The findings indicate that there is a significant correlation between principal leadership with teacher job satisfaction. This study also reports that the supportive and achievement-oriented leadership style influence teachers’ job statisfaction and contributed it to 30.7%. Our findings indicate that supportive leadership contributed more to the teachers’ job satisfaction compared to the achievement-oriented leadership style. This study confirms the importance of leadership behaviour on teachers’ job satisfaction. Generally, supportive and achievement-oriented leadership are the primary contributors to the satisfaction of the subordinate