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311.
Chandrasekhar Das 《The Journal of the Operational Research Society》1983,34(5):401-412
This paper attempts to show that the iterative methods that are used to solve a class of reorder point inventory models can be replaced by some non-iterative method. The method is described in general terms and two sufficient conditions are derived to check if the method applies to a model. As illustrations, two time-weighted backorder models are considered and they are solved for Normal and Gamma leadtime demand by the proposed method. It is observed that some of the computational advantages of the method also carry over to a class of multi-item models. 相似文献
312.
Loi MA Mura A Bongiovanni G Cai Q Martin C Chandrasekhar HR Chandrasekhar M Graupner W Garnier F 《Physical review letters》2001,86(4):732-735
We investigate the influence of interchain interactions on the photoluminescence processes in a sexithiophene single crystal by applying hydrostatic pressure. We perform transient photoluminescence spectroscopy in the time domain of 100 fs for pressures up to 60 kbar. The combined use of steady-state and time-resolved optical spectroscopies allows us to show that the pressure-induced quenching of the photoluminescence is caused by an ultrafast (approximately 100 fs) formation of intermolecular species. 相似文献
313.
The thermal conductivity of a series of lead/indium alloys was measured in the normal, superconducting and mixed states. The electronic part of the thermal conductivity near the upper critical field was compared with the theory of Caroli and Cyrot. There is good agreement in the dirty limit but large deviations are observed as the indium concentration is reduced. 相似文献
314.
Roesky HW Anantharaman G Chandrasekhar V Jancik V Singh S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(17):4106-4114
Lipophilic N-bonded silanetriol RSi(OH)(3) (R=(2,6-iPr(2)C(6)H(3))N(SiMe(3))) can be utilized as an effective synthon for building a variety of multimetallic assemblies containing the Si-O-M motif. The type of metallosiloxane synthesized-its nuclearity and its molecular topology-can be readily modulated by the choice of the metal substrate, reaction stoichiometry, and reaction conditions. It is anticipated that the synthetic principles elaborated here will allow the design of many other multifunctional synthons. 相似文献
315.
P.K. Mehrotra J. Chandrasekhar S. Subramanian P.T. Manoharan 《Chemical physics letters》1974,28(3):402-406
Molecular orbital calculations were performed using the LCAO MO iterative extended Hückel procedure on the 27 valence electron species AsF3? and AsC3?. It was found that theory predicts the shape and unpaired spin-density distribution fairly well. The method is potentially useful especially since optimally parametrised CNDO and INDO techniques have not been developed to include the III or IV row elements of the periodic Table. 相似文献
316.
A double-beam multiplex spectrometer is described which is specially suited for measuring small variations in absorptivity or reflectivity, or narrow spectral lines, against a strong and varying background. By a modification of the conventional Fourier spectrometer, the interferogram beam and the radiation normally going back to the source — the anti-interferogram beam — are combined in the sensitive area of a single detector. If a sample and a reference standard are placed in the interferogram and the anti-interferogram paths respectively, the Fourier transform of the interferogram of the combined intensity directly yields the difference between the spectra of the sample and the reference standard with the optical cancellation of the common features. The advantages and possible applications of this technique are discussed. 相似文献
317.
H.R. Chandrasekhar G. Bhattacharya R. Migoni H. Bilz 《Solid State Communications》1977,22(11):681-684
Lithium nitride, Li3N, belongs to the hexagonal structure with the symmetry point group D6h. The structure is ionic with four atoms per unit cell and N3- coordinated in a regular way with eight Li+ ions. Polarized Raman scattering and infrared reflectivity spectra are reported. The frequencies of zone center phonons are determined from a Kramers-Kronig analysis and the oscillator fits to the reflectivity data. A rigid shell model with eight parameters, including the anisotropic polarizability of nitrogen ions, yields an excellent fit to the observed phonon frequencies. 相似文献
318.
Cho H Baugh J Ryan CA Cory DG Ramanathan C 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,187(2):242-250
Here, we describe the design and performance characteristics of a low temperature probe for dynamic nuclear polarization (DNP) experiments, which is compatible with demanding multiple-pulse experiments. The competing goals of a high-Q microwave cavity to achieve large DNP enhancements and a high efficiency NMR circuit for multiple-pulse control lead to inevitable engineering tradeoffs. We have designed two probes-one with a single-resonance RF circuit and a horn-mirror cavity configuration for the microwaves and a second with a double-resonance RF circuit and a double-horn cavity configuration. The advantage of the design is that the sample is in vacuum, the RF circuits are locally tuned, and the microwave resonator has a large internal volume that is compatible with the use of RF and gradient coils. 相似文献
319.
B. Chandrasekhar 《Tetrahedron》2007,63(36):8746-8751
A stereo selective approach for the azasugars 1,4-dideoxy-1,4-imino-d-allitol, l-allitol, and 1,4-dideoxy-1,4-imino-d-talitol is described for different olefin compounds I derived from (R)-2,3-O-isopropylidine glyceraldehyde, l-ascorbic acid, and d-isoascorbic acid by using vinyl Grignard addition, allylation, RCM, and dihydroxylation as the key steps. 相似文献
320.
A linear trinuclear mixed-metal Co(2)Gd complex supported by two phosphorus-based multisite coordination ligands has been shown to be a single-molecule magnet. 相似文献