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121.
Carbon nanotubes (CNT) have some highly desirable sorbent characteristics which make them attractive for a variety of analytical
applications. High adsorption capacity and rapid desorbability make CNT excellent candidates for micro-scale devices for gas
and liquid-phase analysis. In gas-phase analysis one can implement a micro-concentrator or a micro-sorbent trap, which have
been used in a variety of on-line chromatography and sensing applications. Interesting liquid-phase microtrapping applications
include micro-scale solid-phase extraction (μ-SPE) and solid-phase micro extraction (SPME). In addition, the ease of surface
functionalization, self assembly by chemical vapor deposition, and the formation of diverse polymer composites may well make
CNT the high-performance sorbent of the future. 相似文献
122.
Christine Gregory Ken Darby-DowmanGautam Mitra 《European Journal of Operational Research》2011,212(2):417-428
Robust optimization is a tractable alternative to stochastic programming particularly suited for problems in which parameter values are unknown, variable and their distributions are uncertain. We evaluate the cost of robustness for the robust counterpart to the maximum return portfolio optimization problem. The uncertainty of asset returns is modelled by polyhedral uncertainty sets as opposed to the earlier proposed ellipsoidal sets. We derive the robust model from a min-regret perspective and examine the properties of robust models with respect to portfolio composition. We investigate the effect of different definitions of the bounds on the uncertainty sets and show that robust models yield well diversified portfolios, in terms of the number of assets and asset weights. 相似文献
123.
Das A Hübner A Weber M Bolte M Lerner HW Wagner M 《Chemical communications (Cambridge, England)》2011,47(40):11339-11341
The dimethyl sulfide adduct 2(DMS) is a crystalline storage form of the unstable hydroboration reagent 9-H-9-borafluorene (2); 2(DMS) is available by the addition of DMS to either in situ generated [2](2) or 1,2-(2,2'-biphenylylene)diborane(6) (7). 相似文献
124.
A new anthracenyl-imino-glucosyl conjugate (L) selectively senses Hg(2+) by turn-on fluorescence with a 13 ± 1 fold enhancement by forming a 2?:?1 complex in pH 5 to 10 even in the presence of several biologically and ecologically relevant metal ions, with a 25 ± 2% fluorescence enhancement at the EPA limit of 2 ppb. L is equally sensitive towards Hg(2+) in the presence of albumin proteins and in blood serum and milk. 相似文献
125.
Tapas Mitra G. Sailakshmi A. Gnanamani A. B. Mandal 《Journal of Thermal Analysis and Calorimetry》2011,105(1):325-330
This study emphasizes, cross-linking potential of a simple di-carboxylic acid, namely, oxalic acid with type I collagen for
the preparation of collagen based biomaterial for clinical applications. Further the study discusses the characteristics features
of the cross-linked material in comparison with the standard cross-linker. In addition, the study also demonstrates the role
of ionic interactions in providing the thermal stability and tensile strength to the cross-linked biopolymer material. Type
I collagen from rat tail tendon treated with oxalic acid at optimized concentrations provided a biopolymer material without
changing the triple helical pattern of collagen (CD spectrum) and also with 6–7 fold increase in tensile strength than native
collagen. FTIR spectral details demonstrate the ionic interactions between collagen and oxalic acid. Thermal stability analyses
of oxalic acid cross-linked biopolymer revealed, high thermal stability compared to materials of glutaraldehyde cross-linked.
The results of the study suggest oxalic acid as a suitable cross-linker for collagen and it cross-link with collagen through
ionic interactions. 相似文献
126.
The jet axial velocity field exiting from a nozzle/chamber configuration with an expansion ratio of 5 is investigated using
Stereo-PIV for a range of chamber lengths and Reynolds (Re) numbers. The jet can exit the chamber in axial jet (AJ) mode with the maximum velocity near the chamber axis or precessing
jet (PJ) mode with the maximum velocity near the chamber wall and rotating or precessing about the chamber axis. Algorithms
were developed to determine the jet mode from exit conditions and allow conditional averaging of the velocity field in PJ
mode. The probability of the jet in PJ mode was found to be a strong function of chamber length, L/D and only a mild function of Re for Re > 10,000. High precession probability was found for chambers of length in the range 2 < L/D < 2.75 for all cases for Re > 10,000. An abrupt reduction in precession probability occurred for chamber lengths L/D~3. For increasing chamber lengths, an increase in precession probability was observed. The ratio of entrainment-into-the-chamber
of surrounding fluid to jet exit fluid was found not to be a function of Re or jet mode (AJ or PJ) but only a function of L/D. A maximum ratio entrainment-into-the-chamber was observed to occur in the range 2 < L/D < 2.5. Conditionally averaged velocity profiles also showed the exiting jet to be a strong function of L/D and with only a mild effect of Re for all cases of Re > 10,000. 相似文献
127.
From numerical and experimental investigations it has been recently established that convective heat transfer can be dramatically enhanced by the generation of longitudinal vortices in the flow. The phenomenological similarity between heat and mass transfer suggests that longitudinal vortices should increase also mass transfer. The mixing between two parallel streams of two components in a rectangular channel with and without a pair of rectangular winglets as vortex generators has been numerically investigated. The results show that one pair of vortex generators can increase the global mixing by more than 50 for laminar flow. This global mixing has been defined as the sum of the square of the differences of concentrations. 相似文献
128.
Indranil Chakraborty Debolina Mitra Satya P. Moulik 《Journal of nanoparticle research》2005,7(2):227-236
CdS is a large band gap material compared to HgS. Both are interesting from academic and technological points of view. The nanodispersions (colloids) of CdS and HgS as well their core-shell products and composites (co-colloids) were prepared by varied modes of precursor addition in micellar solution of cationic surfactant cetyltrimethylammonium bromide (CTAB). The prepared dispersions were studied by spectroscopic and electron microscopic techniques. 相似文献
129.
Konstantin Volosov Gautam Mitra Fabio Spagnolo Cormac Lucas 《Computational Optimization and Applications》2005,32(1-2):179-207
In this paper we formulate a model for foreign exchange exposure management and (international) cash management taking into consideration random fluctuations of exchange rates. A vector error correction model (VECM) is used to predict the random behaviour of the forward as well as spot rates connecting dollar and sterling. A two-stage stochastic programming (TWOSP) decision model is formulated using these random parameter values. This model computes currency hedging strategies, which provide rolling decisions of how much forward contracts should be bought and how much should be liquidated.The model decisions are investigated through ex post simulation and backtesting in which value at risk (VaR) for alternative decisions are computed. The investigation (a) shows that there is a considerable improvement to “spot only” strategy, (b) provides insight into how these decisions are made and (c) also validates the performance of this model. 相似文献
130.
A complex harmonic-oscillator basis is employed for the three-body problem obeying S
3-symmetry. Unlike a real basis it generates an additional quantum number (N
a
), in addition to the standard principal quantum number (N), and thus facilitates a more quantitative S
3-classification of the various states than is usually possible. It is shown that certain bilinear forms with definite S
3-symmetry properties, which can be constructed out of the linear harmonic-oscillator operators (a, a
†) satisfy several uncoupled sets of SO(2, 1) algebras with spectra bounded from below. It is also briefly indicated how this S
3-formalism can be adapted to the core structure of a more general relativistic three-particle system with unequal-mass kinematics
through an appropriate choice of internal variables.
Received May 11, 1994; revised November 3, 1994; accepted for publication November 23, 1994 相似文献