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排序方式: 共有150条查询结果,搜索用时 140 毫秒
71.
Biju K. Thapalia Stein W. Wallace Michal Kaut Teodor Gabriel Crainic 《Computational Management Science》2012,9(1):139-160
Stochastics affects the optimal design of a network. This paper examines the single-source single-commodity stochastic network
design problem. We characterize the optimal designs under demand uncertainty and compare with the deterministic counterparts
to outline the basic structural differences. We do this partly as a basis for developing better algorithms than are available
today, partly to simply understand what constitutes robust network designs. 相似文献
72.
Cletus B Olds W Izake EL Sundarajoo S Fredericks PM Jaatinen E 《Analytical and bioanalytical chemistry》2012,403(1):255-263
A time-resolved inverse spatially offset Raman spectrometer was constructed for depth profiling of Raman-active substances
under both the lab and the field environments. The system operating principles and performance are discussed along with its
advantages relative to traditional continuous wave spatially offset Raman spectrometer. The developed spectrometer uses a
combination of space- and time-resolved detection in order to obtain high-quality Raman spectra from substances hidden behind
coloured opaque surface layers, such as plastic and garments, with a single measurement. The time-gated spatially offset Raman
spectrometer was successfully used to detect concealed explosives and drug precursors under incandescent and fluorescent background
light as well as under daylight. The average screening time was 50 s per measurement. The excitation energy requirements were
relatively low (20 mW) which makes the probe safe for screening hazardous substances. The unit has been designed with nanosecond
laser excitation and gated detection, making it of lower cost and complexity than previous picosecond-based systems, to provide
a functional platform for in-line or in-field sensing of chemical substances. 相似文献
73.
R. Biju C. P. Reghunadhan Nair C. Gouri K. N. Ninan 《Journal of Thermal Analysis and Calorimetry》2012,107(2):693-702
An epoxy resin capable of exhibiting shape memory property was derived by curing diglycidyl ether of bisphenol A (DGEBA) with
a blend of carboxy telechelic poly(tetramethyleneoxide) (PTAC) and pyromellitic dianhydride (PMDA). The cure kinetics of DGEBA/PTAC/PMDA
blend of varying compositions was investigated using isothermal rheological analysis. The overall reaction conformed to a
second-order autocatalytic model. The kinetic parameters including reaction order, kinetic constants and activation energy
were determined. The results showed that increase of PTAC decreased the overall activation energy and frequency factor of
the cure reaction. This effect resulted in a diminution of the overall rate of curing. The catalysis by PTAC has its origin
from the activation of epoxy groups by the protons of the COOH groups. The autocatalysis was caused by the COOH groups generated
by the reaction of alcohol groups with anhydride. The activation energy for the autocatalysis was more than that for the primary
reaction as the COOH groups responsible for autocatalysis were generated on a sterically hindered polymer backbone. The kinetics
helped generate a master equation conforming to second-order autocatalytic model that could predict the cure profile of a
specified resin system at a given temperature, leading to cure optimization. 相似文献
74.
75.
A shape memory thermoset comprising of a co‐reacted system of epoxy resin (diglycidylether of bisphenol A), cyanate ester (bisphenol A dicyanate ester) and phenol telechelic poly(tetramethylene oxide) (PTOH) was investigated for its morphology, viscoelasticity and shape memory characteristics at the transition temperature regime. The system exhibited a switching temperature (Tswitch) centered at about 105°C. Atomic force microscopy analyses at different temperatures provided evidences for the existence of a discrete phase at Tswitch regime. Polarized light microscope images gave evidence for the birefringence and tubular crystal formation due to PTOH segments in the shape memory thermoset. It is concluded that the Tswitch has its origin from melting transition of PTOH and Tg of the thermoset matrix, the latter being lowered through plasticization by PTMO segments. Reversibility of Tswitch, and stress relaxation behavior of the blend were investigated by dynamic mechanical analysis (DMA). The reversibility of transition temperature was ascertained by cyclic DMA. Temperature dependency of shape memory properties implied fast recovery of original shape above the Tswitch. The cured system manifests shape memory properties even below Tswitch though it is a slow process. The extent of shape recovery increased with temperature and became faster in league with the trend in temperature dependency of stress relaxation of the polymer. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
76.
Biju AT Padmanaban M Wurz NE Glorius F 《Angewandte Chemie (International ed. in English)》2011,50(36):8412-8415
leahciM! The N-heterocyclic carbene catalyzed umpolung of Michael acceptors proceeds through the formation of a deoxy-Breslow intermediate (see scheme; EWG=electron-withdrawing group). This nucleophilic species can react with other Michael acceptors in an intermolecular fashion, thereby resulting in the formation of homo- or heterodimeric olefins. This "Michael umpolung" should become a valuable method for the formation of densely functionalized olefins. 相似文献
77.
Loewer Y Weiss C Biju AT Fröhlich R Glorius F 《The Journal of organic chemistry》2011,76(7):2324-2327
A chiral diborate with different counterions is reported whose structure was unambiguously confirmed by X-ray analysis. This chiral dianion was used in the resolution of trans-1,2-diamines and also as a chiral shift reagent for NMR analysis of triphenylphosphonium salts. 相似文献
78.
Nair V Menon RS Biju AT Sinu CR Paul RR Jose A Sreekumar V 《Chemical Society reviews》2011,40(11):5336-5346
Homoenolate is a reactive intermediate that possesses an anionic or nucleophilic carbon β to a carbonyl group or its synthetic equivalent. The recent discovery that homoenolates can be generated from α,β-unsaturated aldehydes via N-Heterocyclic Carbene (NHC) catalysis has led to the development of a number of new reactions. A majority of such reactions include the use of carbon-based electrophiles, such as aldehydes, imines, enones, dienones etc. resulting in the formation of a variety of annulated as well as acyclic products. The easy availability of chiral NHCs has allowed the development of very efficient enantioselective variants of these reactions also. The tolerance showed by NHCs towards magnesium and titanium based Lewis acids has been exploited in the invention of cooperative catalytic processes. This tutorial review focuses on these and other types of homoenolate reactions reported recently, and in the process, updates the previous account published in 2008 in this journal. 相似文献
79.
Mukundan Shilpaa Bell Jordan Teryek Matthew Hernandez Charles Love Andrea C. Parekkadan Biju Chan Leo Li-Ying 《Journal of fluorescence》2022,32(2):521-531
Journal of Fluorescence - Tumor spheroid models have proven useful in the study of cancer cell responses to chemotherapeutic compounds by more closely mimicking the 3-dimensional nature of tumors... 相似文献
80.
Dr. Biju Basumatary Ikuho Hashiguchi Dr. Shigeki Mori Prof. Dr. Soji Shimizu Dr. Masatoshi Ishida Prof. Dr. Hiroyuki Furuta 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16031-16035
A copper complex of a heterocorrole analogue with an N–N linkage, 1,19-diaza-21,24-dicarbadibenzocorrole ( Cu-5 ), was successfully synthesized via oxidative metalation–cyclization of a tetrapyrrolic precursor. The N–N linkage in the skeleton of Cu-5 , which serves as a mediator of π-electron delocalization, features an 18π aromatic system. The electronic structure of Cu-5 is best described as a ground-state singlet species stabilized by the distinct NNCC coordination core. This finding shows how the ligand's design can be used to modulate the Cu orbital energy, thereby making such compounds invaluable for copper-based catalytic applications. 相似文献