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Journal of Natural Gas Chemistry 2008年第3期17卷 256-263页

作者： B.Ravi kumar rajeev kumar Department of Chemical Engineering Indian Institute of Technology

The oxidative dehydrogenation （ODH） of propane was conducted on gallium, aluminum, and chromium doped Si30VMgO catalysts. On doping, the concentrations of the phases responsible for the activity and selectivity increased in their concentrations. The reaction studies were conducted in a tubular steel reactor at temperatures of 753, 783, 813, and 843 K and atmospheric pressure. The total flow rates of the feed were chosen as 30, 40, 50, and 60 ml/min. The propane to oxygen ratios were chosen at 1 ： 1, 2 ： 1, and 3 ： 1, respectively. The effect of various dopants on the activity and selectivity of the catalysts was studied. Deactivation studies were conducted over all the catalysts. The kinetic data were analyzed in terms of power law models and Langmuir-Hinshelwood （LH） models. The kinetic data results were analyzed by comparing the effect of dopants. Statistical model discrimination was done for the proposed models. AIC and BIC criteria were used for discrimination of the models.

关键词： oxidative dehydrogenation propane gallium aluminum chromium kinetic

Propagation of wave at the boundary surface of transversely isotropic thermoelastic material with voids and isotropic elastic half-space

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Applied Mathematics and Mechanics(English Edition) 2010年第9期31卷 1153-1172页

作者： Rajneesh kumar rajeev kumar Department of Mathematics Kurukshetra UniversityKurukshetra 136119India

The purpose of this research is to study the effect of voids on the surface wave propagation in a layer of a transversely isotropic thermoelastic material with voids lying over an isotropic elastic half-space. The frequency equation is derived after developing a mathematical model for welded and smooth contact boundary conditions. The dispersion curves giving the phase velocity and attenuation coefficient via wave number are plotted graphically to depict the effects of voids and anisotropy for welded contact boundary conditions. The specific loss and amplitudes of the volume fraction field, the normal stress, and the temperature change for welded contact are obtained and shown graphically for a particular model to depict the voids and anisotropy effects. Some special cases are also deduced from the present investigation.

关键词： propagation of wave transverse isotropy thermoelastic with voids isotropic elastic half-spaze phase velocity attenuation coefficient

Solution and Thermodynamic Studies on Binary and Ternary Complexes of Lanthanides

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Journal of Rare Earths 2005年第4期23卷 389-396页

作者： rajeev kumar Udai P Singh Department of Chemistry Indian Institute of Technology Roorkee Roorkee-247667 IndiaDepartment of Chemistry Indian Institute of Technology Roorkee Roorkee-247667 India

The interactions of La（ Ⅲ ）, Pr（ Ⅲ ）, Nd（ Ⅲ ）, Sm（ Ⅲ ）, Eu（Ⅲ）, Gd（ Ⅲ ）, Dy（ Ⅲ ）, and Yb（ Ⅲ ） with cytosine, 5-bromocytosine, 5-azacytosine and 5-flurocytosine as primary ligands （L） and guanine （A） as secondary ligand for both binary （ 1 ： 1 ） as well as ternary （ 1 ： 1 ： 1 ） systems were investigated by potentiometric equilibrium measurements at 25, 35 and 45 ℃ in aqueous solution （ionic strength, μ = 0.1 mol·dm^-3 NaNO3）. The stability constants of the binary （ 1 ： 1 ） and ternary （ 1 ： 1 ： 1 ） metal-ligand complexes follow the following order La 〈 Pr 〈 Nd 〈 Sm 〈 Eu 〉 Gd 〈 Dy 〉 Yb. Results also indicate that the ternary lanthanide complexes of La（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, Gd（Ⅲ）, Dy（Ⅲ）, and Yb（ Ⅲ ） are more stable than corresponding binary lanthanide complexes. The enthalpy （△Hf^o） and entropy （△Sf^o） changes for the formation of binary and ternary complexes were calculated from temperature coefficient data. The △△Sf^o values are positive for all the metal ligand systems. The negative △△Hf^o values indicate the extra stability of the ternary complexes by the exothermic enthalpy changes （△△Sf^o = △TSf^o - △BSf^o and △△Hf^o = △THf^o - △BHf^o where △TSf^o, △THf^o and △BSf^o, △BHf^o are the entropy and enthalpy values associated with the ternary and binary complexes, respectively）. It was also proposed that the guanine is bonded to metal ions through N1/C6 = O and N7 whereas cytosine and its derivatives are bonded through N3 atoms in ternary complexes.

关键词： lanthanide solution studies cytosine thermodynamic properties rare earths

An update on the role of medical treatment including antioxidant therapy in varicocele

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Asian Journal of Andrology 2016年第2期18卷 222-228,J0004页

作者： Harshit Garg rajeev kumar Department of Urology All india Institute of Medical Sciences New Delhi India

Varicocele-associated male infertility has classically been managed using surgery or assisted reproductive techniques. With increasing evidence of oxidative stress as a pathophysiological factor in varicocele-associated infertility, medical therapy especially antioxidants might become a treatment option with lower risks. We reviewed the existing literature on the role of various medical agents in the management of male infertility attributed to varicoceles. Medical therapy is typically evaluated in three different situations such as （a） comparison of two drugs or one drug with placebo, （b） comparison of drugs versus surgery, and （c） comparison of drugs as adjuvant therapy with surgery versus drug therapy alone. Due to heterogeneity of data and lack of well-conducted studies, there is insufficient data to recommend routine use of medical therapy for men with varicocele-associated infertility and surgery remains the treatment of choice. Pregnancy and live birth rates are usually not reported in most studies and mere improvement in sperm parameters or antioxidant capacity is insufficient to support its routine use. Antioxidant therapy is a potential option due to its theoretical benefit, data from preclinical studies, and lack of major side effects. Adjuvant therapy with antioxidants after surgical repair of varicocele may improve the outcome and is a potential area for further research.

关键词： antioxidant therapy drug therapy male infertility varicocele

Effect of processing parameters on the electromagnetic radiation emission during plastic deformation and crack propagation in copper-zinc alloys

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第11期7卷 1800-1809页

作者： kumar rajeev MISRA Ashok Department of Mechanical Engineering Birla Institute of Technology Mesra 835215 Ranchi India

This paper presents some investigations on the effect of processing parameters on the emission of electromagnetic radiation （EMR） during plastic deformation and crack propagation in copper-zinc alloys. Timing of the EMR emissions, maximum stress during crack instability, stress-intensity factor, elastic strain energy release rate, maximum EMR amplitude, RMS value of EMR amplitude, EMR frequency and electromagnetic energy release rate were analysed for the effect of rolling directions at different percentage of zinc content in Cu-Zn alloy specimens. The same parameters were also analysed for 68-32 Cu-Zn alloy specimens at different annealing temperatures and at different angles 0, to the rolling direction. EMR emissions are observed to be highly anisotropic in nature. At θ=45° to 60°, marked changes in mechanical and electromagnetic parameters were observed. Specimens annealed at 500℃, just above the recrystallization temperature, and at 700℃, when grain-size growth is rapid, EMR responses have been found to have well-defined patterns.

关键词： Radiation Plastic deformation Rolling direction Annealing Fracture

Battery energy storage-based system damping controller for alleviating sub-synchronous oscillations in a DFIG-based wind power plant

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Protection and Control of Modern Power Systems 2023年第2期8卷 260-277页

作者： Neevatika Verma Narendra kumar rajeev kumar Department of Electrical Engineering Delhi Technological UniversityNew DelhiIndia Electrical Engineering Department Jamia Millia IslamiaNew DelhiIndia Electrical and Electronics Engineering Department KIET Group of InstitutionsGhaziabadIndia

This paper presents the issue of the Sub-synchronous resonance(SSR)phenomenon in a series compensated DFIG-based wind power plant and its alleviation using a Battery Energy Storage-based Damping Controller(BESSDCL).A supplementary damping signal is developed considering the angular speed deviation and is incorporated into the BESS control ***-area Measurement System data is used to determine the angular speed deviation.A lin-earized system model is developed to perform eigenvalue analysis,and to detect and examine unstable SSR *** variation of wind speed and three-phase fault are also taken into consideration to validate the robustness of the *** further verify the efficacy of the proposed damping controller,time-domain simulations are performed using MATLAB/*** application of the proposed BESSDCL stabilizes all the unstable system modes effectively at wind speeds of 7 m/s,9 m/s,and 11 m/s,and at 40%,50%,and 60%series compensation levels,as well three-phase fault conditions.

关键词： Battery energy storage system Damping controller Doubly-fed induction generator(DFIG) Series

Grid Tied Solar PV System with Power Quality Enhancement Using Adaptive Generalized Maximum Versoria Criterion

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CSEE Journal of Power and Energy Systems 2023年第2期9卷 722-732页

作者： Manoj Badoni Alka Singh Ankit kumar Singh Hemant Saxena rajeev kumar Delhi Technological University Delhi 110042India.A.K.Singh is with Netaji Subhas University of TechnologyDelhi 110078India Netaji Subhas University of Technology Delhi 110078India Electrical and Electronics Engineering Department KIET Group of InstitutionsGhaziabadIndia Electrical Engineering Department Jamia Millia IslamiaNew DelhiIndia

A three phase grid tied solar photovoltaic(PV)system with power quality compensation features is presented in this *** system is used to transfer power generated from a solar PV array to feed linear and nonlinear loads along with compensation for several power quality(PQ)issues,such as harmonics,redundant reactive power and load *** generated DC power from the PV array is converted into AC by implementing a three-phase voltage source converter(VSC).In order to transfer active power and mitigate PQ problems,an efficient control technique is required for the grid tied solar PV *** study presents the use of an adaptive generalized maximum Versoria criterion(AGMVC)controller for VSC used in a solar PV energy conversion *** utilization of the solar PV array is accomplished by using the Perturb and Observe based maximum power point tracking(MPPT)*** experimental setup of the grid integrated PV system is implemented in the laboratory using an IGBT based VSC and DSP(dSPACE DS-1202).The performance of the AGMVC control technique is verified experimentally using laboratory *** control technique is compared with different conventional controllers,such as synchronous reference frame theory(SRFT)and instantaneous reactive power theory(IRPT)along with recently developed weight-based controllers viz.,least mean square(LMS),least mean mixed norm(LMMN)and normalized kernel least mean fourth-neural network(NKLMFNN).Numerous terms,such as fundamental weight convergence,steady state error,computational complexity,phase lock loop(PLL)requirement and harmonic compensation capability,are considered for comparison purposes of AGMVC with the above listed control *** system performance is verified according to the IEEE-519 standard.

关键词： Harmonics maximum versoria criterion power factor corection(PFC) solar photovoltaic

Universal converse flexoelectricity in dielectric materials via varying electric field direction

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International Journal of Smart and Nano Materials 2021年第1期12卷 107-128页

作者： Saurav Sharma rajeev kumar Rahul Vaish School of Engineering Indian Institute of Technology MandiMandiIndia

Flexoelectricity is a symmetry independent electromechanical cou-pling phenomenon that outperforms piezoelectricity at micro and nanoscales due to its size-dependent behavior arising from gradi-ent terms in its constitutive ***,due to this gradient term flexoelectricity,to exhibit itself,requires specially designed geometry or material composition of the dielectric *** of its kind,the present study put forward a novel strategy of achieving electric field gradient and thereby converse flexoelectri-city,independent of geometry and material composition of the *** spatial variation of the electric field is established inside the dielectric material,Ba_(0.67)Sr_(0.33)TiO_(3)(BST),by manipulating electrical boundary *** unique patterns of electrode placement are suggested to achieve this spatial *** varying direction of electric field gives rise to electric field gradient,the prerequisite of converse flexoelectricity.A multi-physics cou-pling based theoretical framework is established to solve the flexo-electric actuation by employing isogeometric analysis(IGA).Electromechanically coupled equations of flexoelectricity are solved to obtain the electric field distribution and the resulting displace-ments *** maximum displacements of 0.2 nm and 2.36 nm are obtained with patterns I and II,respectively,while pattern III can yield up to 85 nm of maximum displacement.

关键词： Converse flexoelectricity electrical boundary conditions electric field direction isogeometric analysis

Solar-PV inverter for the overall stability of power systems with intelligent MPPT control of DC-link capacitor voltage

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Protection and Control of Modern Power Systems 2023年第1期8卷 245-264页

作者： Sheetal Singh Sanju Saini SKGupta rajeev kumar Electrical Engineering Department Deenbandhu Chhotu Ram University of Science and Technology MurthalMurthalIndia Electrical and Electronics Engineering Department KIET Group of InstitutionsGhaziabadIndia

This paper demonstrates the controlling abilities of a large PV-farm as a Solar-PV inverter for mitigating the chaotic electrical,electromechanical,and torsional oscillations including Subsynchronous resonance in a turbogenerator-based power *** oscillations include deviations in the machine speed,rotor angle,voltage fluctuations(lead-ing to voltage collapse),and torsional *** the night with no solar power generation,the PV-plant switches to PV-STATCOM mode and works as a Solar-PV inverter at its full capacity to attenuate the *** full sun in the daytime,on any fault detection,the PV-plant responds instantly and stops generating power to work as a Solar-PV *** PV-farm operates in the same mode until the oscillations are fully *** paper mani-fests the control of the DC-link capacitor voltage of the Solar-PV inverter with a bacterial foraging optimization-based intelligent maximum power point tracking controller for the optimal control of active and reactive ***’s multi-machine model aggregated with PV-plant is modeled in the Matlab/Simulink environment to examine the rotor swing deviations with associated shaft *** results for different test cases of interest demonstrate the posi-tive outcomes of deploying large PV-farms as a smart PV-STATCOM for controlling power system oscillations.

关键词： PV-STATCOM Power oscillations Grid-connected system BFO algorithm Rotor dynamics

A comprehensive review of rectangular duct solar air heaters featuring artificial roughness

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Clean Energy 2024年第5期8卷 186-217页

作者： Ravi Shankar rajeev kumar Arun kumar Pandey Deep Singh Thakur Department of Mechanical Engineering Rajkiya Engineering College BandaUttar Pradesh 210201India Department of Mechanical Engineering Institute of Engineering&TechnologyLucknowUttar Pradesh 226021India Department of Mechanical Engineering Bundelkhand Institute of Engineering&TechnologyJhansiUttar Pradesh 284128India

Solar air heaters(SAHs)are widely used solar thermal systems with applications in diverse ***,its effectiveness is re-strained by low convective heat transfer(HT)coefficients at the absorber plate,leading to inefficient HT,and the elevated temperature of the absorber plate causes significant heat losses,reducing thermal *** study addresses these challenges by introducing ribs or roughness on the absorber plate creating turbulence in the airflow,resulting in significant *** research inves-tigates various rib configurations,the influence of rib parameters,performance methods,and arrangements to evaluate their HT and friction *** these rib configurations,a comparative analysis is done on various factors such as the Nusselt number ratio,thermal enhancement factor,friction factor ratio,and thermal efficiency to optimize distinct roughness parameters and rib ar-rangement *** study also provides valuable recommendations from existing literature,offering insights into the effective design,prospects,and implementation of SAH systems.

关键词： solar air heater artificial roughness low heat transfer heating solar energy