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Three Degree of Freedom Acoustic Energy Harvester Using Improved Helmholtz Resonator
Izhar,Farid Ullah Khan 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.1
This paper presents the development of a broadband, multi-frequency acoustic energy harvester. The devised energy harvester contains an optimized Helmholtz resonator with conical cavity and a piezoelectric composite plate. The shape and dimensions of the resonator are selected based on the 3D pressure acoustics analysis in COMSOL Multiphysics®. In addition, a cantilever beam, made up of a brass base, a copper rod and a steel sheet, is integrated with the harvester’s piezoelectric plate to add an extra degree of freedom to the device. The developed harvester exhibited three peaks at 1501, 1766 and 1890 Hz frequencies, which correspond to the three resonant frequencies of the harvester. Furthermore, the harvester, when subjected to 130 dB sinusoidal SPL and 1501 Hz resonant frequency, generated a maximum power of 214.23 μW. However, when the harvester is operated under random (real) SPL in the vicinity of household electric generated, it produced about 250 and 265 mV output AC and DC voltage levels respectively.
A NEW ITERATION SCHEME FOR A HYBRID PAIR OF NONEXPANSIVE MAPPINGS
( Izhar Uddin ),( Mohammad Imdad ) 호남수학회 2016 호남수학학술지 Vol.38 No.1
In this paper, we construct an iteration scheme involving a hybrid pair of nonexpansive mappings and utilize the same to prove some convergence theorems. In process, we remove a restricted condition (called end-point condition) in Sokhuma and Kaewkhao`s results [Sokhuma and Kaewkhao, Fixed Point Theory Appl. 2010, Art. ID 618767, 9 pp.].
Syed Izhar Haider Abdi,Sing Muk Ng,최정연,서지민,임정옥 한국고분자학회 2010 Macromolecular Research Vol.18 No.7
This paper reports a novel, simple, repeatable and cost-effective protocol for producing Ca-alginate beads with controlled sizes ranging from 50-250 μm with a narrow size distribution. The characteristics of the beads depend on the emulsion droplets formed, and the size of the beads can be controlled by manipulating the coalescence factor and the applied mechanical energy, which will also reduce the cost and overall time of the procedure. These results suggest that beads with diameters of 58±5, 69±7, 80±8, 145±11, 195±12 and 225±15 μm (mean diameter ±standard deviation) were easily produced. This was achieved simply by adding a minor amount of Pluronic F-127(i.e., 0.03%) and controlling the coalescence effect to reduce the stabilization of the emulsion. Therefore, the method has strong potential for mass production on an industrial scale. Furthermore, the solvent evaporation technique successfully evaporated the volatile organic solvent used for emulsification. The beads were proven to be safe via a cell culture study and might be suitable for use in the medical, pharmaceutical and bioengineering field.
Syed Izhar Haider Abdi,최정연,Hui Chong Lau,임정옥 한국조직공학과 재생의학회 2013 조직공학과 재생의학 Vol.10 No.3
Coagulative necrosis often occurs under hypoxic conditions, causing major limitation in the field of tissue engineering especially those dealing with larger tissues and organs. In this study, a comprehensive work has been performed in developing a tailor made design of a dual layered matrix that can produce oxygen to be utilized in tissue engineering application. Optimizations of protocol, ingredient and condition of the system were carried out specifically based on the responses observed from in vitro studies using L6 rat skeletal muscle cell as a candidate. Oxygen was generated from decomposition of encapsulated hydrogen peroxide. Poly (D,L)-lactide-co-glycolide (PLGA)with molecular weights of 90,000 and 110,000 gmol-1 managed to secure good encapsulation of hydrogen peroxide for this application, while the best stirring time during the encapsulation was found to be 8 hours. The PLGA microspheres were coated with a secondary layer of alginate that was pre-grafted with calatase to form the dual layer system. This dual layered architecture has successfully controlled the release rate of oxygen at an optimum level for the survival of muscle cells under hypoxia condition. It was found that muscle cells have low tolerance limit towards the direct contact with hydrogen peroxide, however the cells maintained high viability within encapsulated hydrogen peroxide in the matrix system. It was observed that 4% of encapsulated hydrogen peroxide in the matrix system can produce efficient amount of oxygen at a controlled release manner to sustain the survival of muscle cells under hypoxic condition.
Syed Izhar Haider Abdi,최정연,이지선,임현주,이창호,김지현,정호윤,임정옥 한국조직공학과 재생의학회 2012 조직공학과 재생의학 Vol.9 No.1
The epitome that cell carrier serves solely as passive vehicles has become outdated. It is now evident that the carrier microenvironment also contributes in the regeneration process. In this study, a combination of alginate,pluronic F127 and extracellular matrix (ECM) component, hyaluronic acid (HA) based scaffold has been prepared for in situ gelling vehicles for muscle cells. ECM incorporated blended hydrogel showed enhanced uniform distribution of muscle cells in a nude mouse model forming the scaffold in situ allowed the muscle cells to proliferate efficiently, indicating that a pluronic F127/alginate/HA matrix provided a beneficial environment for cellular growth and expansion. The formation of gel beneath the skin of nude mice was confirmed using optical coherence tomography (OCT). OCT has been used to visualize the in situ localization of cells as well. This in situ gelation is found to be advantageous for regenerative applications due to the absence of toxic solvents or co-polymerization agents;besides the handling process is simple. This study demonstrates that an in situ blended hydrogels enables the favorable settlement of cells and satisfactory cell delivery for muscle regeneration applications.
A NEW ITERATION SCHEME FOR A HYBRID PAIR OF NONEXPANSIVE MAPPINGS
Uddin, Izhar,Imdad, Mohammad The Honam Mathematical Society 2016 호남수학학술지 Vol.38 No.1
In this paper, we construct an iteration scheme involving a hybrid pair of nonexpansive mappings and utilize the same to prove some convergence theorems. In process, we remove a restricted condition (called end-point condition) in Sokhuma and Kaewkhao's results [Sokhuma and Kaewkhao, Fixed Point Theory Appl. 2010, Art. ID 618767, 9 pp.].
Regional sustainability assessment using emergy accounting approach: The case of Nepal in South Asia
Keshab Shrestha,Izhar Hussain Shah,Zhe Liu,Hung-Suck Park 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.5
Emergy accounting is an environmental assessment tool that accounts for all the energy pathways in production systems. In this regard, the System Thinking Experimental Learning Laboratory Animation (STELLA) with emergy model are used for a retrospective and prospective assessments. Nepal, a country having a relatively small economy but with faster recent growth as well as its geographical position and potentially high vulnerability to climate change was analyzed as a case study using data for 1998–2015 (retrospective) and 2015–2040 (prospective). As per our results, the rising use of non-renewable resources and decreasing use of locally extracted materials caused higher environmental load and reduced emergy sustainability scores. In addition, the effect of natural disasters, such as the Gorkha earthquake, on environmental performance of Nepal was analyzed by emergy accounting. Futuristic emergy analysis for 2015–2040 showed that total and non-renewable emergy would rise considerably, and the emergy sustainability index could further decrease by 33%. Based on these findings, small yet rapidly growing economies, such as Nepal, could improve their environmental management by reducing the material trade deficit (i.e., by increasing domestic material extraction and reducing imports of non-renewable resources), minimizing the use of non-renewables, improving soil fertility, and promoting renewable resource consumption.
Sajan Aggarwal,Izhar Uddin,Nuttapol Pakkaranang,Nopparat Wairojjana,Prasit Cholamjiak 경남대학교 기초과학연구소 2021 Nonlinear Functional Analysis and Applications Vol.26 No.1
In this paper we study the weak and strong convergence to minimizers of convex function of proximal point algorithm SP-iteration of three multivalued nonexpansive mappings in a Hilbert space.
CONVERGENCE THEOREMS FOR SP -ITERATION SCHEME IN A ORDERED HYPERBOLIC METRIC SPACE
Sajan Aggarwal,Izhar Uddin,Samad Mujahid 경남대학교 기초과학연구소 2021 Nonlinear Functional Analysis and Applications Vol.26 No.5
In this paper, we study the $Delta$-convergence and strong convergence of SP-iteration scheme involving a nonexpansive mapping in partially ordered hyperbolic metric spaces. Also, we give an example to support our main result and compare SP-iteration scheme with the Mann iteration and Ishikawa iteration scheme. Thus, we generalize many previous results.
ROBUST SEMI-INFINITE INTERVAL-VALUED OPTIMIZATION PROBLEM WITH UNCERTAIN INEQUALITY CONSTRAINTS
Jaichander, Rekha R.,Ahmad, Izhar,Kummari, Krishna The Kangwon-Kyungki Mathematical Society 2022 한국수학논문집 Vol.30 No.3
This paper focuses on a robust semi-infinite interval-valued optimization problem with uncertain inequality constraints (RSIIVP). By employing the concept of LU-optimal solution and Extended Mangasarian-Fromovitz Constraint Qualification (EMFCQ), necessary optimality conditions are established for (RSIIVP) and then sufficient optimality conditions for (RSIIVP) are derived, by using the tools of convexity. Moreover, a Wolfe type dual problem for (RSIIVP) is formulated and usual duality results are discussed between the primal (RSIIVP) and its dual (RSIWD) problem. The presented results are demonstrated by non-trivial examples.