Displaying publications 61 - 80 of 411 in total

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  1. Integrated modeling and design for realizing a two-wheeled wheelchair for disabled
    Altalmas T, Aula A, Ahmad S, Tokhi MO, Akmeliawati R
    Assist Technol, 2016;28(3):159-74.
    PMID: 27187763 DOI: 10.1080/10400435.2016.1140688
    Two-wheeled wheelchairs are considered highly nonlinear and complex systems. The systems mimic a double-inverted pendulum scenario and will provide better maneuverability in confined spaces and also to reach higher level of height for pick and place tasks. The challenge resides in modeling and control of the two-wheeled wheelchair to perform comparably to a normal four-wheeled wheelchair. Most common modeling techniques have been accomplished by researchers utilizing the basic Newton's Laws of motion and some have used 3D tools to model the system where the models are much more theoretical and quite far from the practical implementation. This article is aimed at closing the gap between the conventional mathematical modeling approaches where the integrated 3D modeling approach with validation on the actual hardware implementation was conducted. To achieve this, both nonlinear and a linearized model in terms of state space model were obtained from the mathematical model of the system for analysis and, thereafter, a 3D virtual prototype of the wheelchair was developed, simulated, and analyzed. This has increased the confidence level for the proposed platform and facilitated the actual hardware implementation of the two-wheeled wheelchair. Results show that the prototype developed and tested has successfully worked within the specific requirements established.
    Matched MeSH terms: Equipment Design/methods*
  2. Fulltext Compact circularly polarized truncated square ring slot antenna with suppressed higher resonances
    Sabran MI, Abdul Rahim SK, Leow CY, Soh PJ, Chew BW, Vandenbosch GA
    PLoS One, 2017;12(2):e0172162.
    PMID: 28192504 DOI: 10.1371/journal.pone.0172162
    This paper presents a compact circularly polarized (CP) antenna with an integrated higher order harmonic rejection filter. The proposed design operates within the ISM band of 2.32 GHz- 2.63 GHz and is suitable for example for wireless power transfer applications. Asymmetrical truncated edges on a square ring create a defected ground structure to excite the CP property, simultaneously realizing compactness. It offers a 50.5% reduced patch area compared to a conventional design. Novel stubs and slot shapes are integrated in the transmission line to reduce higher (up to the third) order harmonics. The proposed prototype yields a -10 dB reflection coefficient (S11) impedance bandwidth of 12.53%, a 3 dB axial ratio bandwidth of 3.27%, and a gain of 5.64 dBi. Measurements also show good agreement with simulations.
    Matched MeSH terms: Equipment Design/methods*
  3. Fulltext An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions
    Naderipour A, Asuhaimi Mohd Zin A, Bin Habibuddin MH, Miveh MR, Guerrero JM
    PLoS One, 2017;12(2):e0164856.
    PMID: 28192436 DOI: 10.1371/journal.pone.0164856
    In recent years, renewable energy sources have been considered the most encouraging resources for grid and off-grid power generation. This paper presents an improved current control strategy for a three-phase photovoltaic grid-connected inverter (GCI) under unbalanced and nonlinear load conditions. It is challenging to suppress the harmonic content in the output current below a pre-set value in the GCI. It is also difficult to compensate for unbalanced loads even when the grid is under disruption due to total harmonic distortion (THD) and unbalanced loads. The primary advantage and objective of this method is to effectively compensate for the harmonic current content of the grid current and microgrid without the use of any compensation devices, such as active and passive filters. This method leads to a very low THD in both the GCI currents and the current exchanged with the grid. The control approach is designed to control the active and reactive power and harmonic current compensation, and it also corrects the system unbalance. The proposed control method features the synchronous reference frame (SRF) method. Simulation results are presented to demonstrate the effective performance of the proposed method.
    Matched MeSH terms: Equipment Design/instrumentation*
  4. Fulltext A low power and low ripple CMOS high voltage generator for RFID transponder EEPROM
    Rahman LF, Marufuzzaman M, Alam L, Sidek LM, Reaz MBI
    PLoS One, 2020;15(2):e0225408.
    PMID: 32023244 DOI: 10.1371/journal.pone.0225408
    A high-voltage generator (HVG) is an essential part of a radio frequency identification electrically erasable programmable read-only memory (RFID-EEPROM). An HVG circuit is used to generate a regulated output voltage that is higher than the power supply voltage. However, the performance of the HVG is affected owing to the high-power dissipation, high-ripple voltage and low-pumping efficiency. Therefore, a regulator circuit consists of a voltage divider, comparator and a voltage reference, which are respectively required to reduce the ripple voltage, increase pumping efficiency and decrease the power dissipation of the HVG. Conversely, a clock driving circuit consists of the current-starved ring oscillator (CSRO), and the non- overlapping clock generator is required to drive the clock signals of the HVG circuit. In this study, the Mentor Graphics EldoSpice software package is used to design and simulate the HVG circuitry. The results showed that the designed CSRO dissipated only 4.9 μW at 10.2 MHz and that the phase noise was only -119.38 dBc/Hz at 1 MHz. Moreover, the proposed charge pump circuit was able to generate a maximum VPP of 13.53 V and it dissipated a power of only 31.01 μW for an input voltage VDD of 1.8 V. After integrating all the HVG modules, the results showed that the regulated HVG circuit was also able to generate a higher VPP of 14.59 V, while the total power dissipated was only 0.12 mW with a chip area of 0.044 mm2. Moreover, the HVG circuit produced a pumping efficiency of 90% and reduced the ripple voltage to <4 mV. Therefore, the integration of all the proposed modules in HVG ensured low-ripple programming voltages, higher pumping efficiency, and EEPROMs with lower power dissipation, and can be extensively used in low-power applications, such as in non-volatile memory, radiofrequency identification transponders, on-chip direct current DC-DC converters.
    Matched MeSH terms: Equipment Design/methods*
  5. Novel Multipin Electrode Cap System for Dry Electroencephalography
    Fiedler P, Pedrosa P, Griebel S, Fonseca C, Vaz F, Supriyanto E, et al.
    Brain Topogr, 2015 Sep;28(5):647-656.
    PMID: 25998854 DOI: 10.1007/s10548-015-0435-5
    Current usage of electroencephalography (EEG) is limited to laboratory environments. Self-application of a multichannel wet EEG caps is practically impossible, since the application of state-of-the-art wet EEG sensors requires trained laboratory staff. We propose a novel EEG cap system with multipin dry electrodes overcoming this problem. We describe the design of a novel 24-pin dry electrode made from polyurethane and coated with Ag/AgCl. A textile cap system holds 97 of these dry electrodes. An EEG study with 20 volunteers compares the 97-channel dry EEG cap with a conventional 128-channel wet EEG cap for resting state EEG, alpha activity, eye blink artifacts and checkerboard pattern reversal visual evoked potentials. All volunteers report a good cap fit and good wearing comfort. Average impedances are below 150 kΩ for 92 out of 97 dry electrodes, enabling recording with standard EEG amplifiers. No significant differences are observed between wet and dry power spectral densities for all EEG bands. No significant differences are observed between the wet and dry global field power time courses of visual evoked potentials. The 2D interpolated topographic maps show significant differences of 3.52 and 0.44% of the map areas for the N75 and N145 VEP components, respectively. For the P100 component, no significant differences are observed. Dry multipin electrodes integrated in a textile EEG cap overcome the principle limitations of wet electrodes, allow rapid application of EEG multichannel caps by non-trained persons, and thus enable new fields of application for multichannel EEG acquisition.
    Matched MeSH terms: Equipment Design/instrumentation*
  6. Effect of different stent configurations using Lattice Boltzmann method and particles image velocimetry on artery bifurcation aneurysm problem
    Mokhtar NH, Abas A, Razak NA, Hamid MNA, Teong SL
    J Theor Biol, 2017 11 21;433:73-84.
    PMID: 28844907 DOI: 10.1016/j.jtbi.2017.08.016
    Proper design of stent for application at specific aneurysm effect arteries could help to reduce the issues with thrombosis and aneurysm. In this paper, four types of stent configuration namely half-Y (6 mm), half-Y (4 mm), cross-bar, and full-Y configuration will implanted on real 3D artery bifurcation aneurysm effected arteries. Comparisons were then conducted based on the flow patterns after stent placement using both LBM-based solver and PIV experimental findings. According to the data obtained from all 4 stent designs, the flow profiles and the computed velocity from both methods were in agreement with each other. Both methods found that half-Y (6 mm) stent configuration is by far the best configuration in reducing the blood velocity at the vicinity of the aneurysm sac. The analysis also show that the half-Y (6 mm) stent configuration recorded the highest percentage of velocity reduction and managed to substantially reduce the pressure at the bifurcation region. This high flow velocity reduction through the use of half-Y stent could consequently promote the formation of thrombus thereby reducing the risk of rupture in the aneurysm sac.
    Matched MeSH terms: Equipment Design/methods*
  7. Fulltext Reconfigurable ring filter with controllable frequency response
    Ab Wahab N, Mohd Salleh MK, Ismail Khan Z, Abd Rashid NE
    ScientificWorldJournal, 2014;2014:671369.
    PMID: 25121132 DOI: 10.1155/2014/671369
    Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GHz to 1.38 GHz spreading over 280 MHz frequency range. Both designs are found to be compact with acceptable insertion loss and high selectivity.
    Matched MeSH terms: Equipment Design
  8. Fulltext Experimental and numerical investigation of the effect of different shapes of collars on the reduction of scour around a single bridge pier
    Jahangirzadeh A, Basser H, Akib S, Karami H, Naji S, Shamshirband S
    PLoS One, 2014;9(2):e98592.
    PMID: 24919065 DOI: 10.1371/journal.pone.0098592
    The scour phenomenon around bridge piers causes great quantities of damages annually all over the world. Collars are considered as one of the substantial methods for reducing the depth and volume of scour around bridge piers. In this study, the experimental and numerical methods are used to investigate two different shapes of collars, i.e, rectangular and circular, in terms of reducing scour around a single bridge pier. The experiments were conducted in hydraulic laboratory at university of Malaya. The scour around the bridge pier and collars was simulated numerically using a three-dimensional, CFD model namely SSIIM 2.0, to verify the application of the model. The results indicated that although, both types of collars provides a considerable decrease in the depth of the scour, the rectangular collar, decreases scour depth around the pier by 79 percent, and has better performance compared to the circular collar. Furthermore, it was observed that using collars under the stream's bed, resulted in the most reduction in the scour depth around the pier. The results also show the SSIIM 2.0 model could simulate the scour phenomenon around a single bridge pier and collars with sufficient accuracy. Using the experimental and numerical results, two new equations were developed to predict the scour depth around a bridge pier exposed to circular and rectangular collars.
    Matched MeSH terms: Equipment Design
  9. An improved instrument mounting arm
    Gendeh BS, Khalid BA, Alberti PW
    J Laryngol Otol, 2001 Feb;115(2):126-7.
    PMID: 11320829
    Although some form of commercial instrument mounting arm is available, a paucity of information in the literature may cause problems in selecting the most appropriate model for an ENT department wishing to trial their invention for use in the clinic or operating theatre. The instrument mounting arm described here is based on existing designs used by hobbyists and model makers for many years but the main benefit of this innovation is its multi-purpose use in the operating theatre and cost effectiveness since it is made of aluminum alloy. It is compact, stable and easily adjustable and can incorporate an endoscope holder or an operating end piece to mount various ENT instruments that offers considerable advantages to the unassisted operator.
    Matched MeSH terms: Equipment Design
  10. Fulltext Effect of temperature and concentration on rheological properties pomelo juice concentrates
    Luqman Chuah, A., Russly A.R., Keshani, S.
    International Food Research Journal, 2012;19(2):553-562.
    MyJurnal
    Rheology is the science of deformation and flow behavior of fluid. Knowledge of rheological properties of fluid foods and their variation with temperature and concentration have been globally important for industrialization of food technology for quality, understanding the texture, process engineering application, correlation with sensory evaluation, designing of transport system , equipment design (heat exchanger and evaporator ), deciding pump capacity and power requirement for mixing. The aim of this study was to determine the rheological behavior of pomelo juice at different concentrations (20-60.4%) and temperatures (23-60°C) by using a rotational rotational Haake Rheostress 600 rheometer. Pomelo juice was found to exhibit both Newtonian and Non-Newtonian behavior. For lower concentration the Newtonian behavior is observed while at higher concentration Non-Newtonian behavior was observed. Standard error (SE) method was selected on the basis to carry out the error analysis due to the best fit model. For the four models the values of SE show that the Herschel-Bulkley and Power Law models perform better than the Bingham and Casson models but Herschel-Bulkley model is true at higher concentration. The rheological model of pomelo juice, incorporating the effects of concentration and temperature was developed. The master-curve was investigated for comparing data from different products at a reference temperature of 40°C. Multiple regression analysis indicated Master-Curve presents good agreement for pomelo juice at all concentrations studied with R2>0.8.
    Matched MeSH terms: Equipment Design
  11. Fulltext Karman Vortex Creation Using Cylinder for Flutter Energy Harvester Device
    Atrah AB, Ab-Rahman MS, Salleh H, Nuawi MZ, Mohd Nor MJ, Jamaludin NB
    Micromachines (Basel), 2017 Jul 21;8(7).
    PMID: 30400418 DOI: 10.3390/mi8070227
    This study presents the creation of a Karman vortex for a fluttering electromagnetic energy harvester device using a cylinder. The effects of two parameters, which are the diameter and the position of the cylinder, were investigated on the Karman vortex profile and the amplitude of the fluttering belt, respectively. A simulation was conducted to determine the effect of the creation of the Karman vortex, and an experiment was performed to identify influence of the position of the cylinder on the fluttering belt amplitude. The results demonstrated that vortex-induced vibration occurred at the frequency of the first natural mode for the belt at 3 cm and 10 cm for the diameter and position of the cylinder, respectively. Under such configuration, an electromagnetic energy harvester was attached and vibrated via the fluttering belt inside the turbulent boundary layers. This vibration provides a measured output voltage and can be used in wireless sensors.
    Matched MeSH terms: Equipment Design
  12. Design and development of a wheelchair seating pressure relief reminder system for pressure ulcer prevention among paraplegics
    Md Nadzri N, Hamzaid NA, Chung TY
    J Med Eng Technol, 2021 Oct;45(7):574-581.
    PMID: 34184592 DOI: 10.1080/03091902.2021.1936238
    Individuals with paraplegia spend their time on the wheelchair for life. Adapting to prolonged wheelchair seating for almost all activities of daily living is challenging. The loss of abilities to sense any pain or excessive seating pressure cause them to remain seated on the wheelchair without any pressure relief activities. This situation leads to secondary complications including pressure ulcer which further degrades the individual's health. To overcome this, a wheelchair seating pressure relief training system (WSETs) was developed. Optimal placement of the force sensitive resistors (FSR) as seating pressure sensors on the cushion were determined, and their responses were investigated with 5 paraplegics. Two different FSR orientations, A and B, were compared. Each paraplegic sat in resting position and then performed pressure relief activities (PRA) which included whole body push-up, left and right lean and forward lean, before returning to resting position. Orientation B, with more forward positioned FSRs, showed higher sensitivity, implying better capture of high-risk area of pressure ulcer development. The FSR sensor readings were significantly different among pressure relief activities in all subjects (p 
    Matched MeSH terms: Equipment Design
  13. Optimising hearing aid output to paediatric prescriptive targets improves outcomes in children
    Amri NA, Quar TK, Chong FY, Bagatto M
    Int J Audiol, 2022 11;61(11):924-931.
    PMID: 34859745 DOI: 10.1080/14992027.2021.2005832
    OBJECTIVE: This study examined the accuracy of hearing aid output to DSL v5.0 Child targets in a group of children who wear hearing aids, and the impact on their auditory outcomes.

    DESIGN: For each participant, the output of the initial hearing aid fitting was compared to DSL v5.0 Child prescriptive targets and again after the fitting was adjusted using coupler-based verification and RECD measures. Outcomes for initial and adjusted fittings were examined using the Speech Intelligibility Index (SII), Parent's Evaluation of Aural/Oral Performance of Children (PEACH) rating scale, and speech perception tests in quiet and noise.

    STUDY SAMPLE: Sixty-eight children aged 3 months to 17 years with moderate to profound hearing loss participated in the study.

    RESULTS: Fit-to-targets improved significantly after hearing aids were adjusted to match targets to within 5 dB RMSE. Adjusted hearing aids provided increased aided audibility compared to initial fittings and resulted in improved speech perception scores and parent-reported hearing performance. Fifty percent of the children aged 6 to 17 years preferred their adjusted fitting compared to 10% who preferred their initial fitting.

    CONCLUSIONS: Improvement in fit-to-target to a validated paediatric prescriptive formula using best practice procedures can result in improved auditory outcomes and possible self-reported satisfaction.

    Matched MeSH terms: Equipment Design
  14. Fulltext Optimal coordinated voltage control in active distribution networks using backtracking search algorithm
    Tengku Hashim TJ, Mohamed A
    PLoS One, 2017;12(10):e0177507.
    PMID: 28991919 DOI: 10.1371/journal.pone.0177507
    The growing interest in distributed generation (DG) in recent years has led to a number of generators connected to a distribution system. The integration of DGs in a distribution system has resulted in a network known as active distribution network due to the existence of bidirectional power flow in the system. Voltage rise issue is one of the predominantly important technical issues to be addressed when DGs exist in an active distribution network. This paper presents the application of the backtracking search algorithm (BSA), which is relatively new optimisation technique to determine the optimal settings of coordinated voltage control in a distribution system. The coordinated voltage control considers power factor, on-load tap-changer and generation curtailment control to manage voltage rise issue. A multi-objective function is formulated to minimise total losses and voltage deviation in a distribution system. The proposed BSA is compared with that of particle swarm optimisation (PSO) so as to evaluate its effectiveness in determining the optimal settings of power factor, tap-changer and percentage active power generation to be curtailed. The load flow algorithm from MATPOWER is integrated in the MATLAB environment to solve the multi-objective optimisation problem. Both the BSA and PSO optimisation techniques have been tested on a radial 13-bus distribution system and the results show that the BSA performs better than PSO by providing better fitness value and convergence rate.
    Matched MeSH terms: Equipment Design
  15. Fulltext A New Compact Double-Negative Miniaturized Metamaterial for Wideband Operation
    Hasan MM, Faruque MRI, Islam SS, Islam MT
    Materials (Basel), 2016 Oct 13;9(10).
    PMID: 28773951 DOI: 10.3390/ma9100830
    The aim of this paper is to introduce a compact double-negative (DNG) metamaterial that exhibits a negative refractive index (NRI) bandwidth of more than 3.6 GHz considering the frequency from 2 to 14 GHz. In this framework, two arms of the designed unit cell are split in a way that forms a Modified-Z-shape structure of the FR-4 substrate material. The finite integration technique (FIT)-based Computer Simulation Technology (CST) Microwave Studio is applied for computation, and the experimental setup for measuring the performance is performed inside two waveguide ports. Therefore, the measured data complies well with the simulated data of the unit cell at 0-degree and 90-degree rotation angles. The designed unit cell shows a negative refractive index from 3.482 to 7.096 GHz (bandwidth of 3.61 GHz), 7.876 to 10.047 GHz (bandwidth of 2.171 GHz), and 11.594 to 14 GHz (bandwidth of 2.406 GHz) in the microwave spectra. The design also exhibits almost the same wide negative refractive index bandwidth in the major region of the C-band and X-band if it is rotated 90 degrees. However, the novelty of the proposed structure lies in its effective medium ratio of more than 4, wide bandwidth, and compact size.
    Matched MeSH terms: Equipment Design
  16. Fulltext Time-resolved characteristics of deuteron-beam generated by plasma focus discharge
    Lim LK, Yap SL, Bradley DA
    PLoS One, 2018;13(1):e0188009.
    PMID: 29309425 DOI: 10.1371/journal.pone.0188009
    The plasma focus device discussed herein is a Z-pinch pulsed-plasma arrangement. In this, the plasma is heated and compressed into a cylindrical column, producing a typical density of > 1025 particles/m3 and a temperature of (1-3) × 107 oC. The plasma focus has been widely investigated as a radiation source, including as ion-beams, electron-beams and as a source of x-ray and neutron production, providing considerable scope for use in a variety of technological situations. Thus said, the nature of the radiation emission depends on the dynamics of the plasma pinch. In this study of the characteristics of deuteron-beam emission, in terms of energy, fluence and angular distribution were analyzed. The 2.7 kJ plasma focus discharge has been made to operate at a pressure of less than 1 mbar rather than at its more conventional operating pressure of a few mbar. Faraday cup were used to determine deuteron-beam energy and deuteron-beam fluence per shot while CR-39 solid-state nuclear track detectors were employed in studying the angular distribution of deuteron emission. Beam energy and deuteron-beam fluence per shot have been found to be pressure dependent. The largest value of average deuteron energy measured for present conditions was found to be (52 ± 7) keV, while the deuteron-beam fluence per shot was of the order of 1015 ions/m2 when operated at a pressure of 0.2 mbar. The deuteron-beam emission is in the forward direction and is observed to be highly anisotropic.
    Matched MeSH terms: Equipment Design
  17. Fulltext Single-fed broadband CPW-fed circularly polarized implantable antenna for sensing medical applications
    Butt AD, Khan J, Ahmad S, Ghaffar A, Abdullah Al-Gburi AJ, Hussein M
    PLoS One, 2023;18(4):e0280042.
    PMID: 37053176 DOI: 10.1371/journal.pone.0280042
    Biomedical telemetry relies heavily on implantable antennas. Due to this, we have designed and tested a compact, a circularly polarized, a low-profile biomedical implantable antenna that operate in the 2.45 GHz ISM band. In order to keep the antenna compact, modified co-planar waveguide (CPW) technology is used. Slotted rectangular patch with one 45-degree angle slot and truncated little patch on the left end of the ground plane generate a frequency-range antenna with circular polarization. Using a 0.25-millimeter-thick Roger Duroid-RT5880 substrate with a thickness of εr = 2.2, tanδ = 0.0009 provides flexibility. The volume of the antenna is 21 mm x 13.5 mm x 0.254 mm (0.25λg × 0.16λg × 0.003λg). The antenna covers 2.35-2.55 GHz (200 MHz) in free space and 1.63-1.17 GHz (1.17 GHz) in epidermal tissue. With skin tissue that has more bandwidth, the (x and y)-axis bends of the antenna are also simulated via the simulation. Bended antenna simulations and measurements show excellent agreement. At 2.45 GHz, the skin-like gel had -10dB impedance and 3dB axial ratio (AR) bandwidths of 47.7 and 53.8%, respectively. The ultimate result is that the SAR values are 0.78 W/kg in skin over 1 g of bulk tissue, as determined by simulations. The suggested SAR values are lower than the FCC's maximum allowable limit (FCC). This antenna is small enough to be implanted in the body, making it perfect for biomedical applications.
    Matched MeSH terms: Equipment Design
  18. Fulltext COVID-19 face mask valve for nasal and laryngeal endoscopy
    Gendeh HS, Husain S
    Ann R Coll Surg Engl, 2021 Jul;103(7):536-537.
    PMID: 33913780 DOI: 10.1308/rcsann.2021.0009
    Matched MeSH terms: Equipment Design
  19. Fulltext Particle swarm optimization algorithm-based PI inverter controller for a grid-connected PV system
    Roslan MF, Al-Shetwi AQ, Hannan MA, Ker PJ, Zuhdi AWM
    PLoS One, 2020;15(12):e0243581.
    PMID: 33362200 DOI: 10.1371/journal.pone.0243581
    The lack of control in voltage overshoot, transient response, and steady state error are major issues that are frequently encountered in a grid-connected photovoltaic (PV) system, resulting in poor power quality performance and damages to the overall power system. This paper presents the performance of a control strategy for an inverter in a three-phase grid-connected PV system. The system consists of a PV panel, a boost converter, a DC link, an inverter, and a resistor-inductor (RL) filter and is connected to the utility grid through a voltage source inverter. The main objective of the proposed strategy is to improve the power quality performance of the three-phase grid-connected inverter system by optimising the proportional-integral (PI) controller. Such a strategy aims to reduce the DC link input voltage fluctuation, decrease the harmonics, and stabilise the output current, voltage, frequency, and power flow. The particle swarm optimisation (PSO) technique was implemented to tune the PI controller parameters by minimising the error of the voltage regulator and current controller schemes in the inverter system. The system model and control strategies were implemented using MATLAB/Simulink environment (Version 2020A) Simscape-Power system toolbox. Results show that the proposed strategy outperformed other reported research works with total harmonic distortion (THD) at a grid voltage and current of 0.29% and 2.72%, respectively, and a transient response time of 0.1853s. Compared to conventional systems, the PI controller with PSO-based optimization provides less voltage overshoot by 11.1% while reducing the time to reach equilibrium state by 32.6%. The consideration of additional input parameters and the optimization of input parameters were identified to be the two main factors that contribute to the significant improvements in power quality control. Therefore, the proposed strategy effectively enhances the power quality of the utility grid, and such an enhancement contributes to the efficient and smooth integration of the PV system.
    Matched MeSH terms: Equipment Design
  20. A comparative study on the influence of equipment design on the efficiency of dynamic maceration of Azadirachta excelsa leaves
    Letchumanan K, Abdullah NH, Abdul-Aziz A
    Prep Biochem Biotechnol, 2024 Jul;54(6):749-763.
    PMID: 37990367 DOI: 10.1080/10826068.2023.2282529
    Dynamic maceration facilitates diffusion in solid-liquid extraction through controlling temperature and providing agitation. However, equipment design for dynamic maceration in previous investigations resulted in inadequate homogeneity of temperature and solid dispersion. A laboratory scale extractor was designed to aid the heat and mass transfer process while preventing solvent vaporization when performing dynamic maceration in a controlled environment. This study aimed to evaluate the efficiency of dynamic maceration using the laboratory scale extractor compared to a shaker incubator to extract triterpenoid saponins from Azadirachta excelsa leaves. The dynamic maceration of A. excelsa leaves was optimized using a Face-centered central composite design (FCCCD) with response surface methodology (RSM). Independent variables analyzed include ethanol-to-chloroform ratio, extraction temperature, extraction time, and sample-to-solvent ratio, while responses include yield of extract and triterpenoid saponins content (TSC). Optimum conditions were ethanol-to-chloroform ratio of 90:10, extraction temperature of 45 °C, extraction time of 60 minutes, and sample-to-solvent ratio of 1:50 g/ml. There was a significant percentage of increase in yield of extract and TSC by 41.1% and 13.3%, respectively, for the laboratory scale extractor compared to the shaker incubator. This study showed the importance of equipment design in enhancing triterpenoid saponins extraction through elevating the efficiency of the dynamic maceration process.
    Matched MeSH terms: Equipment Design
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