Parametric resonance of composite skew plate under non-uniform in-plane loading

Rajesh Kumar,Abhinav Kumar,Sarat Kumar Panda 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.2

Parametric resonance of shear deformable composite skew plates subjected to non-uniform (parabolic) and linearly varying periodic edge loading is studied for different boundary conditions. The skew plate structural model is based on higher order shear deformation theory (HSDT), which accurately predicts the numerical results for thick skew plate. The total energy functional is derived for the skew plates from total potential energy and kinetic energy of the plate. The strain energy which is the part of total potential energy contains membrane energy, bending energy, additional bending energy due to additional change in curvature and shear energy due to shear deformation, respectively. The total energy functional is solved using Rayleigh-Ritz method in conjunction with boundary characteristics orthonormal polynomials (BCOPs) functions. The orthonormal polynomials are generated for unit square domain using Gram- Schmidt orthogonalization process. Bolotin method is followed to obtain the boundaries of parametric resonance region with higher order approximation. These boundaries are traced by the periodic solution of Mathieu-Hill equations with period T and 2T. Effect of various parameters like skew angle, span-tothickness ratio, aspect ratio, boundary conditions, static load factor on parametric resonance of skew plate have been investigated. The investigation also includes influence of different types of linearly varying loading and parabolically varying bi-axial loading.

A high efficiency on‐chip reconfigurable Doherty power amplifier for LTE communication cells

Kumar, Rajesh,Kanuajia, Binod Kumar,Dwari, Santanu,Kumar, Sandeep,song, Hanjung John Wiley Sons, Inc. 2018 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.60 No.10

<P><B>Abstract</B></P><P>In this paper, a high efficiency on‐chip reconfigurable Doherty power amplifier (DPA) with proposed topology is proposed for LTE or 4G communication cells. The proposed DPA consists of input driver topology, hybrid coupler, asymmetric amplifiers, and 1:1 balun filtered network. The proposed input driver circuit provides wide amplified signal operation within range of 2.3GHz to 6GHz with flat gain of 33 dB. The amplified signal is unsteadily divided into two paths toward the carrier and the power amplifier by 90<SUP>0</SUP> hybrid couplers and demonstrates 27.6 dB and 28.3 dB of gain along with 83.2% and 84.5% of power added efficiency at average output power of 40 dBm. The high efficiency and almost flatness in gain stability of proposed DPA providing better solution in order to overcome the interference and the broadband issues for LTE communication cells. The balun‐filtered network is employed for combined the two outputs of carrier and peak amplifiers that provides more uniform desired band of operation in the frequency responses. The proposed DPA circuit are implemented and optimized by using advanced design RF simulator platform. The fabricated chip is made by using 0.13 μm GaN HEMT on Si‐Nitride monolithic microwave integrated circuit die process. The fabricated chip of DPA provides 85% of PAE with 28 dB gain which are made close agreement with simulation results. The size of chip is 2.8*1.2mm<SUP>2</SUP> which occupies less die area as compared to existing DPAs.</P>

Investigation of Ionic Transport Through Track-Etched Conical Nanopores of PET Membrane

Sushil Kumar,Rajesh Kumar,Sushil Kumar,Narinder Kumar,S. K. Chakarvarti 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.1

The control of ionic transportation inside the multi asymmetric conical nanopores in polyethylene terephthalate (PET) membrane was investigated. The conical nanopores were prepared by chemical etching in irradiated PET foil using etchant (9 M NaOH) and stopping solution (1 M NaCl + 1 M HCOOH). The behavior of ionic current was recorded under stepping voltage - 2 V to +2 V at different molar concentrations of potassium halides (KCl, KBr and KI) under symmetric bathing condition in electrochemical cell. It is found that the presence of multiple ionic species and the occurrence of counterion condensation of charge regulated polyelectrolyte play an effective role in ionic current rectification (ICR). The electrical conductance of conical nanopores may be estimated by measuring the ionic current rectification properties of track-etched nanopores. The charge transport properties vary with molar concentration and pH of electrolyte. Moreover, ICR may be used as a voltage gating phenomena with wide technological applications.

Determinants of COVID-19 Vaccination Willingness among Health Care Workers: A Quick Online Survey in India

Rajesh Kumar,Kalpana Beniwal,Yogesh Bahurupi,Ravi Kant,Mukesh Bairwa 대한가정의학회 2021 Korean Journal of Family Medicine Vol.42 No.6

Background: The coronavirus disease 2019 (COVID-19) pandemic has caused a large number of deaths along with severe socio-economic effects. The vaccine is considered to be the last hope to control viral transmission. This study aimed to explore the determinants of health care workers’ (HCWs) willingness to take the COVID-19 vaccina-tion.Methods: A structured, pre-validated, and pre-tested questionnaire was administered online to 599 HCWs includ-ing physicians, residents, and nurses from different types of healthcare set-ups across India. Information was col-lected regarding vaccine acceptability, attitude toward vaccination, and reasons for hesitancy. The chi-square test, followed by multinomial regression analysis, was applied to determine the factors associated with HCWs’ vaccina-tion willingness.Results: It was found that 73 % (n=437) of HCWs were willing to accept the vaccines, while 10.85% (n=65) refused and 16.2% (n=96) needed more time to decide. Gender (P<0.001), occupation (P=0.040), working as front-line workers (P=0.008), vaccine manufacturing country preferences (P<0.001), and perceived risk of catching COVID-19 in the next 6 months (P=0.005) had a significant association with intent to receive vaccination (the response were “yes” vs. “no” and “not sure”). The reasons for vaccine hesitancy were vaccine safety and efficacy concerns, antivac-cine attitude and beliefs, personal choice, and not wanting to take a vaccine before others.Conclusion: The majority of HCWs agreed to take COVID-19 vaccines once available. Nevertheless, providing sup-port to manage evolving vaccine environments will help change the perception of HCWs who refuse or are reluc-tant to take the vaccines.

Solvent extraction of uranium(VI) and separation of vanadium(V) from sulfate solutions using Alamine 336

Kumar, Jyothi Rajesh,Kim, Joon-Soo,Lee, Jin-Young,Yoon, Ho-Sung Springer-Verlag 2010 JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY Vol.285 No.2

In vitro Bionics of Face Centered Cubic Lattice Crystal Nanoparticles by Saccharomyces cerevisiae and Its Microbicidal Screening

Kumar, Ramasamy Rajesh,Cho, Jae Young The Korean Society for Applied Biological Chemistr 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.3

Extracellular synthesis of nanoparticles has received attention due to its more advantageous form of synthesis in large quantities and also easy for downstream processing. In the present investigation, we report in vitro extracellular synthesis of silver nanoparticles (AgNPs) using Saccharomyces cerevisiae with silver nitrate solution. The AgNPs were produced in 72 h of incubation time. The AgNPs formed were further characterized by means of UV-Vis spectrophotometry, Fourier Transform Infra-Red (FTIR), X-Ray Diffraction (XRD), and Scanning Electron Microscope (SEM). The synthesized AgNPs had maximum absorbance at ~420 nm in the UV- visible region. FTIR bands were observed at 3353.40, 2075.09, 1637.71 and $1397.30cm^{-1}$. XRD patterns of the AgNPs confirmed the formation of face centered cubic (fcc) lattice crystal silver particles. The SEM analysis revealed that the size of the AgNPs were of 30-60 nm. The synthesized AgNPs inhibited the growth of the test microorganisms at the concentration of $100{\mu}L$. The present study highlights the possibility of using the common baker's yeast S. cerevisiae to synthesize AgNPs and as a microbicidal agent.

Instability and vibration analyses of FG cylindrical panels under parabolic axial compressions

Rajesh Kumar,Tanish Dey,Sarat K. Panda 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.2

This paper presents the semi-analytical development of the dynamic instability behavior and the dynamic response of functionally graded (FG) cylindrical shallow shell panel subjected to different type of periodic axial compression. First, in prebuckling analysis, the stresses distribution within the panels are determined for respective loading type and these stresses are used to study the dynamic instability behavior and the dynamic response. The prebuckling stresses within the shell panel are the same as applied in-plane edge loading for the case of uniform and linearly varying loadings. However, this is not true for the case of parabolic loadings. The parabolic edge loading produces all the stresses (σxx, σyy and τxy) within the FG cylindrical panel. These stresses are evaluated by minimizing the membrane energy via Ritz method. Using these stresses the partial differential equations of FG cylindrical panel are formulated by applying Hamilton‟s principal assuming higher order shear deformation theory (HSDT) and von-Kármán non-linearity. The non-linear governing partial differential equations are converted into a set of Mathieu-Hill equations via Galerkin‟s method. Bolotin method is adopted to trace the boundaries of instability regions. The linear and non-linear dynamic responses in stable and unstable region are plotted to know the characteristics of instability regions of FG cylindrical panel. Moreover, the non-linear frequency-amplitude responses are obtained using Incremental Harmonic Balance (IHB) method.

The Effect of Early Intervention and Rehabilitation in the Expression of Aquaporin-4; and Ultrastructure Changes on Rat’s Offspring’s Damaged Brain Caused by Intrauterine Infection

Kumar Rajesh,Li Xiaojie,Kong Xiangying 대한신경외과학회 2015 Journal of Korean neurosurgical society Vol.58 No.1

Objective : To study the effect of early intervention and rehabilitation in the expression of aquaporin-4 and ultrastructure changes on cerebral palsy pups model induced by intrauterine infection. Methods : 20 pregnant Wistar rats were consecutively injected with lipopolysaccharide intraperitoneally. 60 Pups born from lipopolysaccharide group were randomly divided into intervention group (n=30) and non-intervention group (n=30); intervention group further divided into early intervention and rehabilitation group (n=10), acupuncture group (n=10) and consolidate group (n=10). Another 5 pregnant rats were injected with normal saline intraperitoneally; 30 pups born from the normal saline group were taken as control group. The intervention group received early intervention, rehabilitation and acupuncture treatment. The motor functions of all pups were assessed via suspension test and modified BBB locomotor score. Aquaporin-4 expression in brain tissue was studied through immunohistochemical and western-blot analysis. Ultrastructure changes in damaged brain and control group were studied electron-microscopically. Results : The scores of suspension test and modified BBB locomotor test were significantly higher in the control group than the intervention and non intervention group (p<0.01); higher in the intervention group than the non-intervention group (p<0.01). The expression of Aquaporin-4 was lower in intervention and non intervention group than in the control group (p<0.01); also lower in non-intervention group than the intervention group (p<0.01). Marked changes were observed in ultrastructure of cortex and hippocampus CAI in brain damaged group. Conclusion : Early intervention and rehabilitation training can improve the motor function in offspring with brain injury and reduce the expression of aquaporin-4 in damaged brain.

Supersonic Mach Disk Characteristics in a Plasma Wind Tunnel

Rajesh Kumar Chinnaraj(친나라즈라제쉬쿠마),Philyong Oh(오필용),Seongman Choi(최성만) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5

0.4 MW 급 고 엔탈피 초음속 아크 가열 플라즈마 풍동에서 발생된 팽창 유동에 대한 기초연구를 실험적으로 완료하였다. 노즐 출구로부터의 마하 디스크의 직경과 위치는 전체 압력비가 200에서 30까지 측정되었다. 마하 디스크 직경과 위치에 대한 경험적인 상관관계는 실험결과와 매우 일치하는 결과를 얻었다. A primary investigation on the underexpanded flow generated in a 0.4 MW class high enthalpy supersonic arc-heated plasma wind tunnel is conducted experimentally. The diameter and the position of the Mach disk from the nozzle exit is measured for overall pressure ratios ranging from 200 to 30. The empirical correlations for Mach disk diameter and position are determined which show very good agreement with experimental results.

Production of Recombinant Human Asparaginase from Escherichia coli under Optimized Fermentation Conditions: Effect of Physicochemical Properties on Enzyme Activity

Rajesh Kumar Kante,Silpa Somavarapu,Sandeep Vemula,Chandrika Kethineni,Maheshwara Reddy Mallu,Srinivasa Reddy Ronda 한국생물공학회 2019 Biotechnology and Bioprocess Engineering Vol.24 No.5

The recombinant human asparaginase (rhASP) plays an important role in the treatment of acute lymphoblastic leukemia. In the present work, volumetric mass transfer coefficient (kLa) values are derived from the E. coli cultivation under different agitation and aeration conditions, in order to improve the rhASP productivity. The aeration and agitation conditions were systematically optimized by the kLa. The maximum biomass (2.4 g/L) and rhASP (1.68 g/L) are achieved with the kLa of 0.024 s-1 at 1.5 lpm and 700 rpm process conditions. The kinetic properties of purified rhASP are also extensively studied and optimized for the maximal enzyme activity. The optimal pH, temperature and incubation duration conditions for accomplishing maximum enzyme activity are found to be 9.0, 40°C, and 30 min, respectively. The optimum substrate concentration and substrate specificity for the highest enzyme activity are of 0.07 M and L-asparagine, respectively. The enzyme activity (204 IU/mL) is significantly improved in the presence of sodium metal (Na+) ions and the inhibitors 2- mercaptoethanol, bromoacetic acid and urea have presented the highest inhibition rate on rhASP activity. The enzyme kinetic parameters Km and Vmax of the purified rhASP are recorded as 2.25 mM and 250 IU/mL, respectively. This work provides the extensive characteristic properties of rhASP enzyme, which enables us to place in a competition for the development of oncology drugs.