Structure and Magnetic Characterization of Core-Shell Fe@ZrO2Nanoparticles Synthesized by Sol-Gel Process

Girija S. Chaubey,Jinkwon Kim* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.12

Highly crystalline, uniform Fe nanoparticles were successfully synthesized and encapsulated in zirconia shell using sol-gel process. Two different approaches have been employed for the coating of Fe nanoparticle with zirconia. The thickness of zirconia shell can be readily controlled by altering molar ratio of Fe nanoparticle core to zirconia precursor in the first case where as reaction time was found to be most effective parameter to controlled the shell thickness in the second method. The structure and magnetic properties of the ZrO2-coated Fe nanoparticles were studied. TEM and HRTEM images show a typical core/shell structure in which spherical a-iron crystal sized of ~25 nm is surrounded by amorphous ZrO2 coating layer. TGA study showed an evidence of weight loss of less than 2% over the temperature range of 50-500 C. The nanoparticles are basically in ferromagnetic state and their magnetic properties depend strongly on annealing temperature. The thermal treatment carried out in as-prepared sample resulted in reduction of coercivity and an increase in saturation magnetization. X-ray diffraction experiments on the samples after annealing at 400-600 C indicate that the size of the Fe@ZrO2 particles is increased slightly with increasing annealing temperature, indicating the ZrO2 coating layer is effective to interrupt growing of iron particle according to heat treatment.

Feature Selection Using Submodular Approach for Financial Big Data

Girija Attigeri,Manohara Pai M. M.,Radhika M. Pai 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.6

As the world is moving towards digitization, data is generated from various sources at a faster rate. It is gettinghumungous and is termed as big data. The financial sector is one domain which needs to leverage the big databeing generated to identify financial risks, fraudulent activities, and so on. The design of predictive models forsuch financial big data is imperative for maintaining the health of the country’s economics. Financial data hasmany features such as transaction history, repayment data, purchase data, investment data, and so on. The mainproblem in predictive algorithm is finding the right subset of representative features from which the predictivemodel can be constructed for a particular task. This paper proposes a correlation-based method usingsubmodular optimization for selecting the optimum number of features and thereby, reducing the dimensionsof the data for faster and better prediction. The important proposition is that the optimal feature subset shouldcontain features having high correlation with the class label, but should not correlate with each other in thesubset. Experiments are conducted to understand the effect of the various subsets on different classificationalgorithms for loan data. The IBM Bluemix Big Data platform is used for experimentation along with the Sparknotebook. The results indicate that the proposed approach achieves considerable accuracy with optimal subsetsin significantly less execution time. The algorithm is also compared with the existing feature selection andextraction algorithms.

Demystification of Bureaucracy-Life Events Approach in e-Government Portals

Girija Krishnaswamy 한국전자거래학회 2004 한국전자거래학회 학술대회 발표집 Vol.2004 No.-

Design and Optimization of Piezoresistive Materials Based Microbridge for Electro-osmosis Pressure Sensor

K. Girija Sravani,G. Sai Lakshmi,K. Srinivasa Rao 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.3

Diabetes is a metabolic disorder which is due to high sugar levels. Symptoms of diabetes are frequent urination, increased hungry and increased thirst. Here we are using electro-osmotic pressure sensor to measure the change in glucose concentration levels. Silicon dioxide, aluminium nitride and silicon nitride are suitable for microbridge membrane, among them SiO 2 is considered as membrane material due to minimum young’s modulus. Silicon, liquid crystal polymer and glass (quartz) are used for substrate materials, owing to its high cost LCP and glass (quartz) is not much preferable for substrate materials. By using FEM tool, the mechanical behavior of microbridge and electrical response of the Piezo resistors are analyzed based on the non-linearity and sensitivity.

Design and Analysis of a Serpentine Type RF MEMS Shunt Switch with Low Pull-in-Voltage

K. Girija Sravani,Ch. Gopichand,K. Srinivasa Rao 한국전기전자재료학회 2022 Transactions on Electrical and Electronic Material Vol.23 No.4

This paper presents the design and simulation of the RF MEMS capacitive shunt switch, using FEM and HFSS tools. Here, we have done electromechanical and electromagnetic analysis by varying the materials, thickness, of the beam, gap between the membrane and the dielectric. The Meanders are used to vary the spring constant, which supports changes in pull-in voltage, which is obtained as 6.92 V for gold beam material and the thickness is taken as 0.5 μm, and the switch has a good switching time as 4.9 μs. The up capacitance and stress analysis are obtained as 9.16 fF, 2.69 MPa. The RF performance analysis such as return, insertion loss are analyzed using HFSS software and are obtained as -26.48 dB and -0.60 dB at 60 GHz frequency. The maximum isolation of switch is -41.88 dB at 54.1 GHz, the overall proposed design shows good RF-performance at 45-70 GHz frequency range. Finally, the proposed switch is applicable for high-frequency applications.

환원된 산화그래핀기반 탄소 도핑된 다공성 ZnO 복합물의 합성 및 광촉매 특성

Edugulla Girija Shankar,유재수 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2

수역에서 제약화합물의 존재는 심각한 환경문제로 부상하고 있으며 환경 생물 다양성과 인간 건강을 위협하고 있다. 많은 수질정화기술이 개발되었으며 그 중에서 태양광 활성 광촉매 정수가 가장 유망한 후보로 관심을 받고 있다. 광촉매 효율은 에너지 밴드갭과 morphology를 제어하고 도핑을 통한 이종접합 나노구조의 형성을 통한 재결합시간을 늘림으로써 향상될 수 있다. 본 발표에서는 자연 태양광을 사용하여 상업적으로 이용 가능한 항생제 아목시실린 및 클라불라네이트 칼륨의 광촉매 분해를 강화하기 위해 환원된 산화그래핀 및 폴리아닐리기반의 탄소 도핑 다공성 ZnO 이종접합 나노 복합물을 합성하였고 광촉매 특성을 조사하였다.

Design and Analysis of Serpentine Flexure Based RF MEMS Switch for High Isolation with Low Pull-in voltage

K. Girija Sravani,Koushik Guha,K. Srinivasa Rao 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.2

This paper presents the design and performance analysis of radio frequency micro electro mechanical system switches having serpentine fl exure designs. In this paper, we have done, behavioral analysis by changing material, gap and thickness, increase in the actuation area using menders, impact of holes on eff ective working of the switch, stress analysis for low spring constant, electromechanical analysis for low pull-in voltage and high capacitance ratio, time dependent analysis for faster switching time, scattering parameter analysis for reducing RF losses are simulated and compared with the theoretical analysis. The signifi cant improvements in this work are lesser air gap and beam thickness reduced the pull-in voltage to 2.75 V for 1.66 μm displacement, a rapid switching time of 0.9 μs obtained through simulation, an improved capacitance ratio of 157.25, isolation is 49.59 dB, insertion loss is 0.005 dB. Actuation area is increased, and switch area is reduced to achieve the optimum performance of the switch.

Structure and Magnetic Characterization of Core-Shell Fe@ZrO₂ Nanoparticles Synthesized by Sol-Gel Process

Chaubey, Girija S.,Kim, Jin-Kwon Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.12

Highly crystalline, uniform Fe nanoparticles were successfully synthesized and encapsulated in zirconia shell using sol-gel process. Two different approaches have been employed for the coating of Fe nanoparticle with zirconia. The thickness of zirconia shell can be readily controlled by altering molar ratio of Fe nanoparticle core to zirconia precursor in the first case where as reaction time was found to be most effective parameter to controlled the shell thickness in the second method. The structure and magnetic properties of the ZrO2-coated Fe nanoparticles were studied. TEM and HRTEM images show a typical core/shell structure in which spherical α-iron crystal sized of ~25 nm is surrounded by amorphous ZrO2 coating layer. TGA study showed an evidence of weight loss of less than 2% over the temperature range of 50-500 °C. The nanoparticles are basically in ferromagnetic state and their magnetic properties depend strongly on annealing temperature. The thermal treatment carried out in as-prepared sample resulted in reduction of coercivity and an increase in saturation magnetization. X-ray diffraction experiments on the samples after annealing at 400-600 °C indicate that the size of the Fe@ZrO2 particles is increased slightly with increasing annealing temperature, indicating the ZrO2 coating layer is effective to interrupt growing of iron particle according to heat treatment.

Enhanced photocatalytic performance of novel self-assembled floral β-Ga2O3 nanorods

K. Girija,S. Thirumalairajan,Astam K. Patra,D. Mangalaraj,N. Ponpandian,C. Viswanathan 한국물리학회 2013 Current Applied Physics Vol.13 No.4

Self-assembled monoclinic phase of novel floral b-Ga2O3 nanorods were prepared using reflux condensation method by controlled precipitation of metal cations with urea. The structural and morphological properties were investigated by X-ray powder diffraction, Raman spectroscopy and Scanning electron microscope. Single-crystalline nanorods with size 100 nm involved in the selfassembly process to form flowery pattern have diameter w1 mm with surface area 40.8 m2/g confirmed from transmission electron microscope and BrunauereEmmetteTeller analysis. The band gap energy of 4.59 eV was evaluated from the UVevis diffuse reflectance spectrum and the photoluminescence spectrum displayed the characteristic luminescence and blue-light emission peaks. Further, the photocatalytic activity of novel b-Ga2O3 floral nanorods towards the photodegradation of Rhodamine B in aqueous solution under ultra violet light irradiation showed better photocatalytic activity than the commercial photocatalyst Degussa P25 TiO2.

Design and Optimization of Piezoresistive Materials Based Microbridge for Electro-osmosis Pressure Sensor

K. Girija Sravani,G. Sai Lakshmi,K. Srinivasa Rao 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.2

Diabetes is a metabolic disorder which is due to high sugar levels. Symptoms of diabetes are frequent urination, increased hungry and increased thirst. Here we are using electro-osmotic pressure sensor to measure the change in glucose concentration levels. Silicon dioxide, aluminium nitride and silicon nitride are suitable for microbridge membrane, among them SiO 2 is considered as membrane material due to minimum young’s modulus. Silicon, liquid crystal polymer and glass (quartz) are used for substrate materials, owing to its high cost LCP and glass (quartz) is not much preferable for substrate materials. By using FEM tool, the mechanical behavior of microbridge and electrical response of the Piezo resistors are analyzed based on the non-linearity and sensitivity.