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201.
Hamed Jalali Raïsa Carmen Inneke Van Nieuwenhuyse Robert Boute 《European Journal of Operational Research》2019,272(1):195-206
In this article, we consider the impact of finite production capacity on the optimal quality and pricing decisions of a make-to-stock manufacturer. Products are differentiated along a quality index; depending on the price and quality levels of the products offered, customers decide to either buy a given product, or not to buy at all. We show that, assuming fixed exogenous lead times and normally distributed product demands, the optimal solution has a simple structure (this is referred to as the load-independent system). Using numerical experiments, we show that with limited production capacity (which implies load-dependent lead times) the manufacturer may have an incentive to limit the quality offered to customers, and to decrease market coverage, especially in settings where higher product quality leads to higher congestion in production. Our findings reveal that the simple solution assuming load-independent lead times is suboptimal, resulting in a profit loss; yet, this profit loss can be mitigated by constraining the system utilization when deciding on quality and price levels. Our results highlight the importance of the relationship between marketing decisions and load-dependent production lead times. 相似文献
202.
Russell P. Newton Andrea M. Evans Hamed G. Hassan Terence J. Walton A. Gareth Brenton Frank M. Harris 《Journal of mass spectrometry : JMS》1993,28(8):899-906
The syntheses of 2′-O-succinyl, 2′-O-succinyltyrosinyl methyl ester and 2′-O-succinyliodotyrosinyl methyl ester derivatives of a cyclic nucleotide, derivatives necessary for the successful development of a specific radioimmuno-assay, are described. Fast atom bombardment with collision-induced dissociation and mass-analysed ion kinetic energy spectroscopy were used to verify the positions of substitution and the retention of the 3′,5′-cyclic phosphate moiety. Comparison of spectra produced after different iodination times permitted the optimization of the reaction conditions. 相似文献
203.
C.L. Chakrabarti C.C. Wan R.J. Teskey S.B. Chang H.A. Hamed P.C. Bertels 《Spectrochimica Acta Part B: Atomic Spectroscopy》1981,36(5):427-438
At constant temperature (isothermal) maintained throughout in the capacitive discharge technique, the measured absorbance at any time t due to concentration of analyte atoms can be given by: absorbance = p[A]0{k1/(k1?k2)}[exp(?k2t)-exp(?k1t)], where p is a function of the oscillator strength (a constant) and the efficiency with which the analyte atoms are produced, [A]0 is the initial concentration of the analyte atoms, k1 and k2 are first-order rate constants for formation and decay of analyte atoms, respectively. This technique yields k1?k2 and k1t?k2t; and so the above equation reduces to: absorbance ?p[A]0, resulting in large enhancement in sensitivity. In the case of lead, the immediate precursor of the gaseous lead monomer is the gaseous lead dimer, which is partly lost by diffusion of the lead dimer with a first-order rate constant, k3. The kinetic parameters k1, k2 and k3 have been evaluated, and the values of k1 at different temperatures used to draw the Arrhenius plots, from which activation energies of the rate-determining steps have been determined. The activation energies have been used to elucidate atomization mechanisms by extensive correlation of the experimental energy values with the literature values. 相似文献
204.
Atef A. Hamed Ibrahim F. Zeid Hussein H. El-Ganzory Mohamed T. Abdel Aal 《Monatshefte für Chemie / Chemical Monthly》2008,139(7):809-820
A series of substituted thieno[2,3-d]pyrimidines was synthesized starting from ethyl-2-amino-4-isopropylthiophene-3-carboxlate. Reaction of 2-hydrazino-5-isopropyl-thieno[2,3-d]pyrimidin-4(3H)-one and its 3-methyl analogue with different reagents afforded thieno[2,3-d]triazolo[4,3-a]pyrimidines and thieno[3,2-e]triazolo[4,3-a]pyrimidines, beside open chain derivatives.
Correspondence: Atef A. Hamed, Department of Chemistry, Faculty of Science, Menoufia University, Shebin El Koam, Egypt. 相似文献
205.
Abdolhosseinzadeh Sina Asgharzadeh Hamed Sadighikia Sina Khataee Alireza 《Research on Chemical Intermediates》2016,42(5):4479-4496
Research on Chemical Intermediates - ZnO nanorods were hydrothermally grown on Zn foil in an alkaline solution and the immobilized nanorods were subsequently hybridized with reduced graphene oxide... 相似文献
206.
Yuval Filmus Hamed Hatami Nathan Keller Noam Lifshitz 《Israel Journal of Mathematics》2016,214(1):167-192
Let f: {-1, 1}n → [-1, 1] have degree d as a multilinear polynomial. It is well-known that the total influence of f is at most d. Aaronson and Ambainis asked whether the total L1 influence of f can also be bounded as a function of d. Ba?kurs and Bavarian answered this question in the affirmative, providing a bound of O(d3) for general functions and O(d2) for homogeneous functions. We improve on their results by providing a bound of d2 for general functions and O(d log d) for homogeneous functions. In addition, we prove a bound of d/(2p) + o(d) for monotone functions, and provide a matching example. 相似文献
207.
Hammad SF Mabrouk MM Habib A Elfatatry H Kishikawa N Nakashima K Kuroda N 《Biomedical chromatography : BMC》2007,21(10):1030-1035
A highly selective and sensitive method was developed for simultaneous determination of the antihistaminic drug hydroxyzine (HZ) and its pharmacologically active metabolite cetirizine (CZ) in human serum using haloperidol as internal standard. The method was based on fluorescence labeling of both drugs with a fluorescent arylboronic acid 4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl boronic acid followed by separation on silica column using a mobile phase consisting of acetonitrile and water (90:10, v/v%) containing triethylamine and acetic acid. The labeling reaction conditions were optimized and the liquid-liquid extraction method was successfully applied to extract the both drugs from serum. The linearity range was 0.025-2.00 microg/mL for HZ and CZ. The limit of detection (S/N = 3) was 10 and 5 ng/mL for HZ and CZ, respectively. 相似文献
208.
Khalid A. M. Salih Mohammed F. Hamza Hamed Mira Yuezhou Wei Feng Gao Ayman M. Atta Toyohisa Fujita Eric Guibal 《Molecules (Basel, Switzerland)》2021,26(4)
The strong demand for rare-earth elements (REEs) is driven by their wide use in high-tech devices. New processes have to be developed for valorizing low-grade ores or alternative metal sources (such as wastes and spent materials). The present work contributed to the development of new sorbents for the recovery of rare earth ions from aqueous solutions. Functionalized mesoporous silica composite was synthesized by grafting diethylenetriamine onto composite support. The physical and chemical properties of the new sorbent are characterized using BET, TGA, elemental analysis, titration, FTIR, and XPS spectroscopies to identify the reactive groups (amine groups: 3.25 mmol N g−1 and 3.41 by EA and titration, respectively) and their mode of interaction with Nd(III) and Gd(III). The sorption capacity at the optimum pH (i.e., 4) reaches 0.9 mmol Nd g−1 and 1 mmol Gd g−1. Uptake kinetics are modeled by the pseudo-first-order rate equation (equilibrium time: 30–40 min). At pH close to 4–5, the sorbent shows high selectivity for rare-earth elements against alkali-earth elements. This selectivity is confirmed by the efficient recovery of REEs from acidic leachates of gibbsite ore. After elution (using 0.5 M HCl solutions), selective precipitation (using oxalate solutions), and calcination, pure rare earth oxides were obtained. The sorbent shows promising perspective due to its high and fast sorption properties for REEs, good recycling, and high selectivity. 相似文献
209.
Mahmoud EL-Morshedy Fahad Sameer Alshammari Abhishek Tyagi Iberahim Elbatal Yasser S. Hamed Mohamed S. Eliwa 《Entropy (Basel, Switzerland)》2021,23(4)
In this article, we have proposed a new generalization of the odd Weibull-G family by consolidating two notable families of distributions. We have derived various mathematical properties of the proposed family, including quantile function, skewness, kurtosis, moments, incomplete moments, mean deviation, Bonferroni and Lorenz curves, probability weighted moments, moments of (reversed) residual lifetime, entropy and order statistics. After producing the general class, two of the corresponding parametric statistical models are outlined. The hazard rate function of the sub-models can take a variety of shapes such as increasing, decreasing, unimodal, and Bathtub shaped, for different values of the parameters. Furthermore, the sub-models of the introduced family are also capable of modelling symmetric and skewed data. The parameter estimation of the special models are discussed by numerous methods, namely, the maximum likelihood, simple least squares, weighted least squares, Cramér-von Mises, and Bayesian estimation. Under the Bayesian framework, we have used informative and non-informative priors to obtain Bayes estimates of unknown parameters with the squared error and generalized entropy loss functions. An extensive Monte Carlo simulation is conducted to assess the effectiveness of these estimation techniques. The applicability of two sub-models of the proposed family is illustrated by means of two real data sets. 相似文献
210.
Zeinab Sadat Sheikholeslami Mohammad Atai Azizollah Nodehi Hamed Salimi-Kenari 《高分子科学杂志,A辑:纯化学与应用化学》2017,54(9):605-611
Carboxymethyl Chitosan (CMCh) is a semi-synthetic derivative of chitosan (a natural biopolymer) with increasing biomedical applications as a matrix or scaffold material for tissue engineering applications. Since, the presence of impurities can cause immunological reactions in vivo where ultimately pure materials are needed. To this end, purity of commercial-grade CMCh samples was investigated here along with their purification by a solvent/nonsolvent technique. The resulting polymer was characterized by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDX) to confirm the validity of the purification process. 相似文献