A highly loaded NiΣiO₂ core-shell catalyst for CO methanation

Lakshmanan, P.,Kim, M.S.,Park, E.D. Elsevier 2016 Applied Catalysis A Vol.513 No.-

<P>The specific catalytic activity of a supported metal catalyst increases with an increase in the number of active sites per mass of catalyst, which can be accomplished by increasing the metal content and/or decreasing the particle size of the metal. However, this leads to sintering of metal particles during the reaction, especially in highly exothermic reactions such as CO methanation. In this study, we prepared different SiO2-supported Ni catalysts by wet impregnation and sol-gel methods, and applied them to CO methanation. The prepared catalysts were characterized with N-2 physisorption, X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction with H-2 (H-2-TPR), and transmission electron microscopy (TEM). Some problems associated with the wet impregnation method, such as sintering of Ni and the inability to load the silica with large amounts of Ni, were avoided by using the sol-gel method, in which size-controlled NiO was first synthesized using a polymer stabilizing agent, and then coated with a mesoporous silica shell through a polymerization approach. The prepared 55 wt% Ni@SiO2 catalyst exhibited the co-presence of Ni nanoparticles (mean size = 8.0 +/- 4.4 nm) and nanorods (mean length =15.5 +/- 13 nm, mean width = 8.1 +/- 4.4 nm). This catalyst was far superior for CO methanation than the conventional 33 wt% Ni/SiO2 catalyst prepared by wet impregnation, in which the Ni particle size was 24.5 nm. The 55 wt% Ni@SiO2 catalyst also exhibited excellent catalytic performance for selective CO methanation in the presence of an excessive amount of CO2. (C) 2015 Elsevier B.V. All rights reserved.</P>

Preferential oxidation of CO in a hydrogen-rich stream over Au/MO_x/Al₂O₃ (M=La, Ce, and Mg) catalysts

Lakshmanan, P.,Park, J.E.,Kim, B.,Park, E.D. Elsevier Science Publishers 2016 CATALYSIS TODAY - Vol.265 No.-

<P>The preferential oxidation of CO (CO-PROX) under excess hydrogen over Au/MOx/Al2O3 (M = La, Ce, and Mg) catalysts was investigated. All catalysts were prepared by a deposition-precipitation method with urea and characterized with inductively coupled plasma-atomic emission spectroscopy, N-2 physisorption, temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy. The catalytic activity of the supported gold catalysts was found to be dependent on the promoter, and decreased in the order: Au/La2O3/Al2O3 > Au/CeO2/Al2O3 > Au/MgO/Al2O3 > Au/Al2O3. The catalytic activity of the Au/La2O3/Al2O3 catalyst depended on the pretreatment conditions, i.e., reduction with aqueous NaBH4, thermal reduction with H-2, and calcination with O-2. This indicates that the oxidation state of gold is an important factor in the activity of the catalyst, and that metallic gold is more suitable than its oxidized form for this reaction. XPS results revealed that the treatment with aqueous NaBH4 resulted in more negative charge in gold particles than that of conventional thermal reduction under H-2. Smaller gold particles appeared to be favorable for the low-temperature CO-PROX activity of the Au/La2O3/Al2O3 catalysts, which showed stable CO-PROX performance, even in the presence of CO2. (C) 2015 Elsevier B.V. All rights reserved.</P>

State Estimation for Genetic Regulatory Networks With Mode-Dependent Leakage Delays, Time-Varying Delays, and Markovian Jumping Parameters

Lee, Tae H.,Lakshmanan, S.,Park, Ju H.,Balasubramaniam, P. IEEE 2013 IEEE transactions on nanobioscience Vol.12 No.4

<P>This paper considers the state estimation problem for Markovian jumping genetic regulatory networks (GRNs) with mode-dependent leakage and time-varying delays. In order to approximate the true concentrations of the mRNA and protein, the state estimator is designed using available measurement outputs. The GRNs are composed of N modes. The system switches from one mode to another according to a Markovian chain with known transition probabilities. Based on the Lyapunov functionals, including triple integral terms, some inequalities, and a time-varying delay partitioning approach, delay-dependent criteria which employ all upper bounds of time delays of each mode are obtained in terms of linear matrix inequalities (LMIs). This guarantees that the estimation error dynamics can be globally asymptotically stable from solutions of LMIs. Finally, a numerical example is presented to demonstrate the efficiency of the proposed estimation scheme.</P>

Mammalian Systems Biotechnology Reveals Global Cellular Adaptations in a Recombinant CHO Cell Line

Yusufi, F.N.K.,Lakshmanan, M.,Ho, Y.S.,Loo, B.L.W.,Ariyaratne, P.,Yang, Y.,Ng, S.K.,Tan, T.R.M.,Yeo, H.C.,Lim, H.L.,Ng, S.W.,Hiu, A.P.,Chow, C.P.,Wan, C.,Chen, S.,Teo, G.,Song, G.,Chin, J.X.,Ruan, X. Cell Press 2017 Cell systems Vol.4 No.5

Effective development of host cells for therapeutic protein production is hampered by the poor characterization of cellular transfection. Here, we employed a multi-omics-based systems biotechnology approach to elucidate the genotypic and phenotypic differences between a wild-type and recombinant antibody-producing Chinese hamster ovary (CHO) cell line. At the genomic level, we observed extensive rearrangements in specific targeted loci linked to transgene integration sites. Transcriptional re-wiring of DNA damage repair and cellular metabolism in the antibody producer, via changes in gene copy numbers, was also detected. Subsequent integration of transcriptomic data with a genome-scale metabolic model showed a substantial increase in energy metabolism in the antibody producer. Metabolomics, lipidomics, and glycomics analyses revealed an elevation in long-chain lipid species, potentially associated with protein transport and secretion requirements, and a surprising stability of N-glycosylation profiles between both cell lines. Overall, the proposed knowledge-based systems biotechnology framework can further accelerate mammalian cell-line engineering in a targeted manner.

Flexural Behaviour of Steel-Foam Concrete Composite Light-Weight Panels

Prabha, P.,Palani G. S.,Lakshmanan N.,Senthil R. 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

The present study explores the applicability of composite panel made of thin profiled steel sheets of thickness 0.8 mm as the outer skins with an infill Light-weight Foam Concrete (LFC) core of density 1200 kg/m3 for use as floor/roof panel in buildings by conducting experimental studies. This study was carried out in continuation with the previous studies reported by Prabha et al. (2013) on composite wall panels. Through-through mild steel connectors were used for the load transfer between sheet and concrete. Two types of concrete core, namely (a) Normal Foam Concrete (NFC) and (b) Fibre Reinforced Foam Concrete (FRFC) were investigated. The polypropylene fibres were used for improving the tensile strength of LFC. The composite panels exhibit gradual load-deflection response and ductile failure mode at higher deflections under four point bending test. The ultimate load of FRFC specimen is found to be 6% stronger than NFC panels, which implies that the use of polypropylene fibers marginally improved the flexural strength. The panels possess sufficient flexural capacity for spans upto 5 m and high ductility factor of 10 to be used as floor/ roof panels in residential buildings. Numerical parametric studies indicate that the configuration 24 nos. of studs used in the experiment is found to be optimal and the flexural capacity increases proportionally for the higher thickness of steel sheet. Simplified equation is proposed for the evaluation of flexural strength of the panel.

Facile, Morphology-Controlled and Mass Production of 0D-Ag/2D-g-C3N4/3D-TiO2 Nano-Composite Materials: Effect of Silver Morphology and Loading on the Electrochemical Performance

R. Ranjithkumar,P. Lakshmanan,N. Palanisami,P. Devendran,N. Nallamuthu,S. Sudhahar,M. Krishna Kumar 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.2

The 0D-Ag/2D-g-C3N4/3D-TiO2 nano-composite materials were fabricated by simple and mass production method. It involvesthe combination of incipient wetness impregnation and thermal spreading techniques. By changing the order of impregnationand thermal spreading, silver nanoparticles with “on-top” and “embedded” morphologies could be selectively controlled. Thethermal spreading followed by impregnation (TS-IM) leads to the “on-top” structure [Ag/g-C3N4/TiO2] while, the reverseorder (IM-TS) produces the embedded silver nanoparticles [g-C3N4/Ag/TiO2]. The 16%Ag/g-C3N4/TiO2 (TS-IM) sampleexhibited the best performance due to the presence of very small and highly dispersed silver nanoparticles over g-C3N4/TiO2 sample. The loading of silver not only doubled the specific capacitance but also stabilized the recycling performanceagainst deactivation. This study reveals easy and performance tunable synthesis of Ag/g-C3N4/TiO2 nano-composite materialstowards energy-storage applications.

Bi-modal spectral method for evaluation of along-wind induced fatigue damage

S. Gomathinayagam,P. Harikrishna,A. Abraham,N. Lakshmanan 한국풍공학회 2006 Wind and Structures, An International Journal (WAS Vol.9 No.4

Several analytical procedures available in literature, for the evaluation of wind induced fatigue damage of structures, either assume the wide band random stress variations as narrow band random process or use correction factors along with narrow band assumption. This paper compares the correction factors obtained using the Rainflow Cycle (RFC) counting of the measured stress time histories on a lamp mast and a lattice tower, with those evaluated using different frequency domain methods available in literature. A Bi-modal spectral method has been formulated by idealising the single spectral moment method into two modes of background and resonant components, as considered in the gust response factor, for the evaluation of fatigue of slender structures subjected to along-wind vibrations. A closed form approximation for the effective frequency of the background component has been developed. The simplicity and the accuracy of the new method have been illustrated through a case study by simulating stress time histories at the base of an urban light pole for different mean wind speeds. The correction factors obtained by the Bi-modal spectral method have been compared with those obtained from the simulated stress time histories using RFC counting method. The developed Bi-modal method is observed to be a simple and easy to use alternative to detailed time and frequency domain fatigue analyses without considerable computational and experimental efforts.

Change of Knowledge Intensive Service Sectors’ Employment in Two Highway Corridors on the U.S. East Coast

송예나,William P. Anderson,T. R. Lakshmanan 한국경제지리학회 2010 한국경제지리학회지 Vol.13 No.4

Aiming to reveal the employment evolution around interstate highway corridors,an extended shift-share analysis is conducted for metropolitan areas in two interstate highway corridors on the U.S. east coast: I-95 and I-85. Our focus is on knowledge service sectors, specifically finance, insurance, business services and health services for two time periods, 1977-1990 and 1990-2005. In the first period, the two corridors’ metropolitan areas have outperformed their regions in terms of both output and labor productivity. But this picture turned negative in later period with some variation by industries. Also variation in performance over time was found even in metropolitan areas in the same corridor or in geographically adjacent areas.

Evolution of Industrial Agglomeration and Its Causal Relation with Road Networks in the U.S.

Yena Song(송예나),William P. Anderson,T.R. Lakshmanan 대한지리학회 2013 대한지리학회지 Vol.48 No.1

산업집적은 경제지리학에서 오랫동안 연구되어온 주제 중의 하나이며 지금까지 다양한 방법을 통해 산업집적 현상을 설명하고 이의 영향을 평가해왔다. 하지만 시계열 데이터를 이용해 집적의 추이를 살펴본 연구는 아직 활발히 이루어지지 않고 있다. 본 연구는 지난 29년 간의 데이터를 이용해 사례로 선정된 산업들의 집적 정도를 평가하고 이러한 시계열 패턴과 도로 네트워크의 확장이 어떠한 인과관계를 맺고 있는 지 살펴보고 있다. 집적 정도를 측정한 결과 사례로 선정된 산업의 종사자들은 지리적으로 균등하게 분포되지 않고 있었다. 또한 사례 산업들 간에 공통된 시계열적 변화 특성은 나타나지 않았으나 각 산업의 발전 단계 및 비즈니스 환경 변화가 개별 산업의 집적 정도에 영향을 주고 있는 것으로 보이고 있다. 집적 정도와 도로교통망 사이의 관계를 살펴보기 위해 각 산업 별로 Granger causality test를 실시하였고 도로 교통망이 산업 집적에 영향을 주고 있음을 몇몇 사례를 통해 확인할 수 있었다. 그러나 이와 반대의 경우 혹은 상호 간에 영향을 주는 사례도 나타나 교통망과 산업집적이 보다 복잡한 관계를 맺고 있음을 보여준다. Industrial agglomeration is an old theme in economic geography and many studies have been devoted to this topic. But only few have empirically looked at the time trend of industrial agglomeration. This study measured agglomeration of U.S. industries over last 29 years and measurement results indicated that industrial clustering has occurred during the study period in all study industries without a common time trend shared amongst the study industries. The agglomeration levels then were plugged in to investigate causalities, i.e. causal relations, around industrial agglomeration. Three variables were selected to see causal relations with agglomeration levels based on literatures, and our focus was given to the causality between transport network and agglomeration. Causal relation from transport to agglomeration was found in various industries and this supports the argument that the development of transportation influences industrial agglomeration. At the same time inverse and bi-directional causalities were also revealed implying more complex relationship between these two.

Bi-modal spectral method for evaluation of along-wind induced fatigue damage

Gomathinayagam, S.,Harikrishna, P.,Abraham, A.,Lakshmanan, N. Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.4

Several analytical procedures available in literature, for the evaluation of wind induced fatigue damage of structures, either assume the wide band random stress variations as narrow band random process or use correction factors along with narrow band assumption. This paper compares the correction factors obtained using the Rainflow Cycle (RFC) counting of the measured stress time histories on a lamp mast and a lattice tower, with those evaluated using different frequency domain methods available in literature. A Bi-modal spectral method has been formulated by idealising the single spectral moment method into two modes of background and resonant components, as considered in the gust response factor, for the evaluation of fatigue of slender structures subjected to "along-wind vibrations". A closed form approximation for the effective frequency of the background component has been developed. The simplicity and the accuracy of the new method have been illustrated through a case study by simulating stress time histories at the base of an urban light pole for different mean wind speeds. The correction factors obtained by the Bi-modal spectral method have been compared with those obtained from the simulated stress time histories using RFC counting method. The developed Bi-modal method is observed to be a simple and easy to use alternative to detailed time and frequency domain fatigue analyses without considerable computational and experimental efforts.