Modeling and Experimental Validation of 5-level Hybrid H-bridge Multilevel Inverter Fed DTC-IM Drive

Md. Didarul Islam,C.M.F.S. Reza,Saad Mekhilef 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.2

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

Comparative Study of Path Loss Models of WiMAX at 2.5 GHz Frequency Band

Md. Didarul Alam,Md. Rezaul Huque Khan 보안공학연구지원센터 2013 International Journal of Future Generation Communi Vol.6 No.2

Modeling and Experimental Validation of 5-level Hybrid H-bridge Multilevel Inverter Fed DTC-IM Drive

Islam, Md. Didarul,Reza, C.M.F.S.,Mekhilef, Saad The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.2

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

Solid organ fabrication: comparison of decellularization to 3D bioprinting

Jangwook P. Jung,Didarul B. Bhuiyan,Brenda M. Ogle 한국생체재료학회 2016 생체재료학회지 Vol.20 No.3

Solid organ fabrication is an ultimate goal of Regenerative Medicine. Since the introduction of Tissue Engineering in 1993, functional biomaterials, stem cells, tunable microenvironments, and high-resolution imaging technologies have significantly advanced efforts to regenerate in vitro culture or tissue platforms. Relatively simple flat or tubular organs are already in (pre)clinical trials and a few commercial products are in market. The road to more complex, high demand, solid organs including heart, kidney and lung will require substantive technical advancement. Here, we consider two emerging technologies for solid organ fabrication. One is decellularization of cadaveric organs followed by repopulation with terminally differentiated or progenitor cells. The other is 3D bioprinting to deposit cell-laden bio-inks to attain complex tissue architecture. We reviewed the development and evolution of the two technologies and evaluated relative strengths needed to produce solid organs, with special emphasis on the heart and other tissues of the cardiovascular system.

Modeling and Experimental Verification of ANN Based Online Stator Resistance Estimation in DTC-IM Drive

Reza, C.M.F.S.,Islam, Didarul,Mekhilef, Saad The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.2

Direct Torque controlled induction motor (DTC-IM) drives use stator resistance of the motor for stator flux estimation. So, stator resistance estimation properly is very important for a stable and effective operation of the induction motor. Stator resistance variations because of changing in temperature make DTC operation difficult mainly at low speed. A method based on artificial neural network (ANN) to estimate the stator resistance online of IM for DTC drive is modeled and verified in this paper. To train the neural network a back propagation algorithm is used. Weight adjustment of neural network is done by back propagating the error signal between measured and estimated stator current. An extensive simulation has been carried out in MATLAB/SIMULINK to prove the efficacy of the proposed stator resistance estimator. The simulation & experimental result reveals that proposed method is able to obtain precise torque and flux control at low speed.

Antioxidant and anti-inflammatory activity of Heritiera fomes (Buch.-Ham), a mangrove plant of the Sundarbans

Islam Md. Emdadul,Islam Kazi Mohammed Didarul,Billah Md. Morsaline,Biswas Rana,Sohrab Md. Hossain,Rahman S. M. Mahbubur 경희대학교 융합한의과학연구소 2020 Oriental Pharmacy and Experimental Medicine Vol.20 No.2

The antioxidant and anti-inflammatory potential of Heritiera fomes ethanolic extract was evaluated.Query Ethanolic extraction of dried and grinded plant leaves and bark was performed. Antioxidant activity was evaluated by 1, 1-diphenyl-2-picryl-hydrazil (DPPH) free radical scavenging assay, ferric reducing antioxidant power (FRAP) and β-carotene bleaching inhibition assay. Total phenolic and flavonoid content were also determined. Anti-inflammatory activity was evaluated by in vitro human RBC membrane stabilizing assay and in vivo mice paw edema test. Ethanolic bark and leaf extracts of H. fomes (S1 and S2, respectively) showed significant scavenging effect on DPPH scavenging 68.51 µg/ml for S1 and 108.64 µg/ml for S2. Potent reduction potential (FRAP) was observed in S1 (83.75 mM of ferrous equivalent) while the FRAP of standard ascorbic acid was found 86.66 μM of ferrous equivalent. S1 also exhibited 87.43% β-carotene bleaching inhibition as comparable to standard butylated hydroxytoluene with 98.85% inhibition. Substantial phenolic and flavonoid content was also observed in S1 (136.83 μg gallic acid equivalent/g of extract and 76.67 μg quercetin equivalent/g of extract, respectively). S1 could provide 61.73% and 53.27% protection of RBC membrane in hypotonicity and heat induced lysis of RBC, respectively while the standard diclofenac sodium provided 91.66% and 86.66% protection, respectively. Furthermore, 44.16% reduction in mice paw edema at 40 μg/kg bw concentration was observed in S1 as compared to standard indomethacine (53.54% in 10 μg/kg bw concentration). The results revealed that the bark extract (S1) of H. fomes possesses significant antioxidant and anti-inflammatory activity.

Modeling and Experimental Verification of ANN Based Online Stator Resistance Estimation in DTC-IM Drive

C.M.F.S. Reza,Md. Didarul Islam,Saad Mekhilef 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.2

Direct Torque controlled induction motor (DTC-IM) drives use stator resistance of the motor for stator flux estimation. So, stator resistance estimation properly is very important for a stable and effective operation of the induction motor. Stator resistance variations because of changing in temperature make DTC operation difficult mainly at low speed. A method based on artificial neural network (ANN) to estimate the stator resistance online of IM for DTC drive is modeled and verified in this paper. To train the neural network a back propagation algorithm is used. Weight adjustment of neural network is done by back propagating the error signal between measured and estimated stator current. An extensive simulation has been carried out in MATLAB/SIMULINK to prove the efficacy of the proposed stator resistance estimator. The simulation & experimental result reveals that proposed method is able to obtain precise torque and flux control at low speed.

Antioxidant and antibacterial activity of three herbs belonging to Zingiber genus of Bangladesh

Afiya Aunjum,Rana Biswas,Tauhidur Rahman Nurunnabi,S.M. Mahbubur Rahman,Md. Morsaline Billah,Md. Emdadul Islam,Kazi Mohammed Didarul Islam 경희대학교 융합한의과학연구소 2020 Oriental Pharmacy and Experimental Medicine Vol.20 No.3

Apart from boosting flavor, herbs and spices are also known for their preservative, antioxidant, antimicrobial and other medicinal properties. Bioactive metabolites with aspiring prospect have guided the present study to screen for antibacterial and antioxidant activity of three Zingiber plants available in Bangladesh. For that purpose, rhizomes of Zingiber officinale, Z. montanum and Z. zerumbet were extracted with ethanol as solvent system for bioactivity analysis. Antioxidant activity was assessed by employing DPPH free radical scavenging assay, reducing power assay and ferric reducing antioxidant power (FRAP) assay. Z. officinale extract demonstrated the highest free radical scavenging activity ( IC50: 43.65 μg/ml), reducing power ( EC50: 189.026 μg/ml) and FRAP value (137.18 ± 0.116 μM Fe(II)/100 μg dry weight of extract). Moreover, total phenolic, flavonoid and tannin content were determined which significantly correlated (Pearson correlation) with the antioxidant activities. For the evaluation of antibacterial activity, zone of inhibition (ZOI) was measured by disc diffusion bioassay against four Gram positive bacteria Bacillus megaterium, Staphylococcus aureus, Micrococcus spp., and S. epidermidis as well as ten Gram negative bacteria Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, S. paratyphi, Vibrio cholera, Shigella dysenteriae, S. flexneri, Proteus spp., Mycobacterium spp., and Campylobacter spp. Z. montanum extract exhibited significant activity against E. coli (13.67 ± 0.577 mm ZOI) and Micrococcus spp. (14.33 ± 0.763 mm ZOI) if compared to standard erythromycin with ZOI 15.33 ± 0.577 mm and 15.67 ± 0.577 mm, respectively. Furthermore, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Z. montanum extract were determined against B. megaterium, Micrococcus spp., E. coli and S. paratyphi. Thus, Z. officinale and Z. montanum extracts could be utilized as source and template for the synthesis of potential drugs and food supplements as well.