An Improved `DC-DC Type' High Frequency Transformer-Link Inverter by Employing Regenerative Snubber Circuit

This work proposes a bidirectional high frequency (HF) link inverter using center-tapped high frequency transformer. The main advantage of this topology is the reduced size of the converter. However the utilization of the high frequency transformer results in the occurrence of high voltage spike at its secondary. To solve this problem, we incorporate a regenerative snubber to clamp the spike and subsequently feed the energy back to the power circuit. The inverter also utilizes less number of switches, which results in lower conduction and switching losses. This paper describes some of the important aspects of the snubber design. It is verified with a 1 kW inverter prototyp

Mechanical and Thermal Evaluation of Carrageenan/Hydroxypropyl Methyl Cellulose Biocomposite Incorporated with Modified Starch Corroborated by Molecular Interaction Recognition

Vegetarian hard capsule has attracted surging demand as an alternative to gelatin; however, only few have been commercialized. Carrageenan extracted from seaweed has the potential to be utilized as a hard capsule material. Improving the mechanical and thermal properties of carrageenan biocomposite is therefore of great importance for future use in the drug delivery system. Hence, carboxymethyl sago starch (CMSS) was incorporated to strengthen the carrageenan biocomposite in a concentration range from 0 to 1.0% w/v. The intermolecular hydrogen bonding formed between carrageenan and CMSS was revealed via density functional theory (DFT) calculations and substantiated by 1H NMR and FTIR spectra. The result showed that the hydrogen bond is established between hydroxyl (carrageenan)–carbonyl (CMSS) groups at a distance of 1.87 Å. The bond formation subsequently increased the tensile strength of the biocomposite film and the loop strength of the hard capsule by 20.6 and 7.7%, respectively. The glass transition temperature of the film was increased from 37.8 to 47.8 °C, increasing the thermal stability. The activation energy upon decomposition of the film is 74.4 kJ·mol–1, representing a 26.2% increase over the control carrageenan. These findings demonstrate that incorporation of CMSS increases the properties of carrageenan biocomposite and provides a promising alternative to animal-based hard capsules

Control of an underactuated double-pendulum overhead crane using improved model reference command shaping: Design, simulation and experiment

This paper presents a new control scheme based on model reference command shaping (MRCS) for an overhead crane, with double-pendulum mechanism effects. The approach has an advantage in achieving an accurate trolley positioning, with low hook and payload oscillations, under various desired trolley positions and parameter uncertainties, without the requirement for measurement or estimation of system parameters. These are challenging in practice. The previously developed MRCS algorithm is improved in order to reduce its design complexity, as well as to ensure that it can be augmented with a feedback controller so that a concurrent controller tuning can be realised. The combined MRCS and feedback controller is used to achieve both, precise trolley positioning, and low hook and payload oscillations. To evaluate the effectiveness and the robustness of the approach, simulations and experiments using a nonlinear model and a laboratory double-pendulum crane are carried out. Under various desired positions and parameter uncertainties that involve varying the cable lengths (payload hoisting) and the payload mass variations, the superiority of the proposed approach is confirmed by achieving higher hook and payload oscillation reductions when compared with a recently proposed feedback controller. In addition, the desired trolley positions are achieved with smoother responses

Waste segregation through recycle and composting activities in urban and suburban areas

The number of wastes generated in Malaysia is increasing every year. Eighty per cent of solid waste in landfills comes from recycled material, and food waste production has risen to around 15 000 tons per day. Recyclable waste and food waste are the highest waste produced in landfills. Recycling and food composting are two solutions that can reduce waste and slow down the rate of garbage received at the landfill. This research aims to determine the knowledge and awareness of waste segregation through recycling and composting. This paper also identifies the constraint of respondents on performing waste segregation. Here, an online questionnaire has been distributed to the community in urban and suburban areas in Selangor and Johor. A total of 125 respondents participated in this study. Analysis from the survey found no significant difference in the knowledge of waste segregation through recycling and composting between urban and suburban areas. It can be denoted that the respondents have a basic understanding of awareness on waste segregation, although only a few have not practised recycling due to several highlighted constraints. Therefore, some recommendation has been emphasized based on this finding, such as installing reverse vending machines (RVM), organizing campaigns, and providing more information on waste segregation. These suggestions have been the top choices to encourage waste segregation in the community. Moreover, further study needs to be extended to the household group in other states and assessing the effectiveness of RVM will elucidate the segregation behaviours among the community

Performance of Kaolin Clay on the concrete pavement

This paper investigates the performance of concrete pavement containing kaolin clay with their engineering properties and to determine the optimum kaolin clay content. The concrete used throughout the study was designed as grade 30 MPa strength with constant water to cement ratio of 0.49. The compressive strength, flexural strength and water absorption test was conducted in this research. The concrete mix designed with kaolin clay as cement replacement comprises at 0%, 5%, 10% and 15% by the total weight of cement. The results indicate that the strength of pavement concrete decreases as the percentage of kaolin clay increases. It also shows that the water absorption increases with the percentage of cement replacement. However, 5% kaolin clay is found to be the optimum level to replace cement in a pavement concrete

Effect of black rice husk ash on asphaltic concrete properties under aging condition

The scarcities of natural resources and increment in waste production rates have promoted efforts to investigate the potential incorporation of various by-products in roads construction. Reusing of waste materials such as black rice husk ash (BRHA) in asphaltic concrete was considered as one of the proper management of the waste, which ensures economic and environmental benefits. Hence, this study investigates the effect of black rice husk ash on asphalt mixtures properties under different aging condition. BRHA was added in the asphalt mix in a proportion of 0%, 2%, 4% and 6% by weight of bitumen. 5% optimum bitumen content with 60/70 penetration grade binder was selected for this study. The asphalt mixtures for each fraction was prepared in three different aging conditions i.e. un-aging (UA), short term aging (STA) and long term aging (LTA). The properties of asphalt mixtures were evaluated by voids, stiffness and dynamic creep tests. The results indicate that asphalt mixtures consisting of BRHA have exhibited better performance in term of voids, stiffness and creep modulus when compared to the conventional asphalt mixtures. The STA and LTA mixtures modified with BRHA produced higher performance than the unmodified mixtures. It can be concluded that the optimum additional percentage of BRHA was in the range of 4% to 6%

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Supported ionic liquid membranes (SILMs) as a contactor for selective absorption of CO2/O2 by aqueous monoethanolamine (MEA)

Application of membrane contactors in a combination of monoethanolamine as a solvent system for post-combustion CO2 capture has been extensively studied in the last decades. Due to the better performance to capture CO2 at low concentration, the potentialities of novel technology of supported ionic liquids membranes (SILMs) for absorption process in gas-liquid membrane contactor system are currently being explored to improve and compliment previous technology. In this study, a modified hydrophobic gas-liquid membrane contactor system was prepared using Liqui-Cel® parallel flow module as a membrane support and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [emim] [NTf2] ionic liquid as a supporting phase. Under moderate operating conditions, parallel flow mode and use of monoethanolamine (MEA) as an absorbent, the effects of absorbent temperature and gas velocity on the CO2 absorption efficiency and CO2/O2 selectivity were determined using this modified module. Further investigation to compare the performances of blank and modified membrane module was implemented at different temperatures (303–348 K) and gas velocities (4.63 × 10−6 to 3.70 × 10−5 m s−1). Results revealed that efficiency of the CO2 absorption process of the modified module is almost doubled with an average selectivity factor of CO2/O2 around 5 times compared to blank contactor system. Thus, this modified membrane contactor system had shown a great potential for further used in the real industrial CO2 capture and beneficial to bottleneck the issue of MEA oxidation that usually occurred in previous gas-liquid membrane contactor system

Productivity growth in Malaysian manufacturing sector: A two stage analyses of the malmquist luenberger productivity index

Productivity growth must reflect the realities of production activities. In the manufacturing sector, emissions from fossil fuel combustion, which are acknowledged as being undesirable outputs, should be taken into account in productivity change measurement. The main purpose of this study is to calculate productivity change using the Malmquist Luenberger Productivity Index (MLPI) on the 15 states in Malaysia. Two stage analyses with a three year ‘window’ of data is employed to overcome the infeasibility problem that may occur in the MLPI calculated by Directional distance function (DDF). It was found that the main source of the productivity deterioration when taking carbon dioxide (CO2) emissions into account is eco-efficiency change

Horizontal Axis Wind Turbine Performance Analysis

The present work uses the method of Blade Element Momentum Theory as suggested by Hansen. The method applied to three blade models adopted from Rahgozar S. with the airfoil data used the data provided by Wood D. The wind turbine performance described in term of the thrust coefficient , torque coefficient  and the power coefficient  . These three coefficient can be deduced from the Momentum theory or from the Blade element Theory(BET).  The present work found the performance coefficient derived from the Momentum theory tent to over estimate. It is suggested to used the BET formulation in presenting these three coefficients. In overall the Blade Element Momentum Theory follows the step by step as described by Hansen  work well for these three blade models. However  a little adjustment on the blade data is needed. To the case of two bladed horizontal axis wind turbine, Hansen’s approach works well over if the blade radius is  the calculation should start from r = 0.1 &nbsp