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111.
Some authors claim that reporting the best result obtained by a stochastic algorithm in a number of runs is more meaningful
than reporting some central statistic. In this short note, we analyze and refute the main argument brought in favor of this
statement. 相似文献
112.
In this paper,we consider a class of quadratic maximization problems.For a subclass of the problems,we show that the SDP relaxation approach yields an approximation solution with the ratio is dependent on the data of the problem with α being a uniform lower bound.In light of this new bound,we show that the actual worst-case performance ratio of the SDP relaxation approach (with the triangle inequalities added) is at least α δd if every weight is strictly positive,where δd > 0 is a constant depending on the problem dimension and data. 相似文献
113.
《Magnetic resonance in chemistry : MRC》2003,41(9):660-670
Reduced forms of iso‐α‐acids (isohumulones), used in modern beer brewing were separated and characterized by 1H and 13C NMR spectroscopy. Components from mixtures of rho‐iso‐α‐acids, tetrahydro‐iso‐α‐acids, and hexahydro‐iso‐α‐acids were isolated using high‐performance liquid chromatography (HPLC) and analyzed by use of one‐ and two‐dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso‐α‐acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso‐α‐acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C‐4 side‐chain of the rho‐ and hexahydro‐iso‐α‐acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
114.
115.
In this paper,the concept of the infinitesimal realization factor is extended to the parameter-dependent performance functions in closed queueing networks. Then the concepts of realization matrix (its elements are called realization factors) and performance potential are introduced,and the relations between infinitesimal realization factors and these two quantities are discussed. This provides a united framework for both IPA and non IPA approaches. Finally,another physical meaning of the service rate is given. 相似文献
116.
Summary Hydroxypropyl methyl cellulose (HPMC) and polyethylene glycol 400 (PEG 400) content in HypoTears™ Daily Dose ophthalmic solution
are determined simultaneously by size exclusion chromatography. The retention times of HPMC and PEG 400 are 10.6 and 15.4
minutes, respectively. The method requires minimal sample pretreatment and is accurate and reproducible. The peak area response
from a refractive index detector versus HPMC and PEG 400 concentration is linear over the range of 50–150 % of their label
claims of 2.5 mg/mL and 10 mg/mL, respectively. The mean absolute recoveries of HPMC and PEG 400 at their label claim using
the described method are 98.9±1.3 % and 100.4±1.2 % (mean±SD, n=12), respectively. 相似文献
117.
本文研究并比较了分别以8-羟基喹啉和巯基苯骈噻唑为萃取剂,以活性硅胶为载体的柱式萃取色谱法对环境水中Zn、Cu、Pb、Cd、Fe、Co、Ni和Mn的最佳富集和洗脱条件。实验证明,后者明显优于前者。以巯基苯骈噻唑为萃取剂的色谱柱对金属元素的吸附具有快速、完全、寿命长和重现性好等特点。在pH=7~8之间回收率可达98%以上,富集倍数为200倍。 相似文献
118.
119.
Polyethyleneimine (PEIM) samples crosslinked by a commercial epoxy resin (Epon 828) were prepared, and their adsorption capacity for acidic gases was studied. The swelling and deswelling characteristics of the crosslinked samples were also examined as part of this program. Reactivation of these adsorbents could be carried out by heat, or by a combination of heat and treatment in dilute alkalies. 相似文献
120.
用电子顺磁共振方法研究了一些高温超导氧化物样品的零场非共振吸收信号和正常的ESR共振信号。认为这种方法可以作为鉴别样品进入超导态的实验判据之一。利用零场非共振吸收实验给出的下临界磁场Hc1(T)很好地遵多Hc1(T)=Hc1(0)(1-T&^2/Tc^2)。 相似文献