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991.
从水资源对社会经济发展的作用出发,采用向量模法对恩施州近5年的水环境承载力进行分析评价.研究结果表明,2007-2011年恩施州水环境承载力呈增加趋势,其值由2007年的0.302增加到2011年的0.6056,年平均增长率为19%,说明恩施州的水环境承载力能够满足社会经济发展的需要. 相似文献
992.
This paper reports a simple and highly selective method for preconcentrating and separating of trace Pd(II) and Pt(IV) with silica gel bonded by aminopropyl-benzoylazo-4-(2-pyridy-lazo)-resorcinol (ABPR-SG). ABPR-SG is stable in solution from 6 mol/L HCl to pH 7.0 and in common organic solvents. The maximum adsorptive capacity of Pd(n) on ABPR-SG is 362 μmol/g. After preconcentration and separation by using ABPR-SG column, Pd(II) and Pt(IV) of μg/L level in artificial water samples can be measured reliably by common spedrophotometry. The maximum concentration factors of Pd(II) and Pt(IV) on ABPR-SG column are 143 and 125 respectively. The chromatographic column packed with ABPR-SG can be reused. The method is simple and efficient. 相似文献
993.
In previous papers1,2, we reported our recent findings that chalcone (l,3-dipheny1-2-propen-1-one) derivatives are novel potential antimalarials that are active against chloroquine-resistant strains of Plasmodium falciparum. According to our structure-activity relationships (SAR) and computer modeling data1,2, we expect the chalcone derivatives with hydroxyl functionality on one of the aromatic rings and with some other appropriate substitutions on the other ring will be even more potent as a… 相似文献
994.
Li Feng Zhi‐Ming Li Zhen‐Xia Chen Yong‐Sheng Tan Lin‐Hong Weng Feng‐Gang Tao 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o680-o681
The title compound, C38H32BrNO6, is a new photochromic tetrahydroazepinoisoquinoline (THAI). The longest spiro bond [1.589 (4) Å] can be broken very easily by UV light, leading to ring opening. This explains the photochromic behaviour. 相似文献
995.
996.
Evaluation for the performance of learning algorithm has been the main thread of theoretical research of machine learning.
The performance of the regularized regression algorithm based on independent and identically distributed(i.i.d.) samples has
been researched by a large number of references. In the present paper we provide the convergence rates for the performance
of regularized regression based on the inputs of p-order Markov chains. 相似文献
997.
GaN thin films grown on sapphire were implanted by Eu~3+ with three different fluences (5.0×10~14 , 2.5×10~15 and 5.0×10~15cm~-2 ). The photoluminescence (PL) spectra show that, after annealing, the samples exhibit strong emission at around 622.0 nm under 325 nm laser excitation. The intensity of this emission increases by one order of magnitude after annealing at from 600 ℃ to 900 ℃. Moreover, it increases less than 2 times when the fluence increases from 5×10~14 cm~-2 to 5×10~15 cm~-2 for the sample annealing at 900 ℃. The PL emission peaks around 622 nm of samples annealing at 900 ℃ can be well clarified by Gaussian fitting into 620.2, 622.0 and 625.0 nm, which are due to the Eu~3+ related with defects, Eu~3+ occupied at substitutional positions of Ga, and that located at interstitial sites, respectively. It shows that the different microenvironments and positions of Eu~3+ are responsible for these peaks, and especially the defects introduced by implantation play an important role in the behavior of the PL because they set up an energy transmission bridge from exotic photons to Eu~3+ . 相似文献
998.
In this study, we detail a method for estimating the flux-averaged solid fraction of a steady granular flows moving down an
inclined rectangular chute using velocity measurements from along the perimeter cross section, combined with knowledge of
the mass flow rate through the cross section. The chute is 5 cm wide and 150 cm long with an adjustable inclination angle.
Four inclination angles, from 27° to 36° at 3° intervals, are tested. This angle range overlaps the internal friction angle
of the glass beads, which are 4 mm nominal in diameter. Two slender mirrors are installed at the top and the bottom of the
transparent chute to reflect images of the flow down the chute of the two surfaces. This allows photographic recording of
the flow with a PIV imaging system and measurement of the flow depth. The mass flow rate can be calibrated simultaneously
by collecting the accumulated mass at the chute exit. A linear interpolation scheme is proposed to interpolate the volume
flow rate in each section of the chute. Sensitivity analysis suggests that the relative standard deviation of this scheme
is about ±6%, i.e., the resultant solid volume fraction is only moderately dependent on the interpolation scheme for the tested
cases. This is further confirmed by a direct intercepting method. Compared to the sophisticated magnetic resonance imaging
(MRI) or the radioactive positron emission particle tracking (PEPT) methods, the present method is verified as a cost-effective
and nonhazardous alternative for ordinary laboratories. Two distinct groups of streamwise dependence of the solid fractions
are found. They are separated by the inclination angle of the chute and agreed with the internal friction angle. In the experiments
using the two smaller inclination angles, the solid fraction ratios are found to be linear functions of the streamwise distance,
while for the two larger inclination angles, the ratios have a nonlinear concave shape. All decrease with growing downstream
distance. 相似文献
999.
1000.
蔡圣义 《温州大学学报(自然科学版)》2001,22(6):4-7
对大多数排序问题来说,机器集往往是事先给定的,而且在算法进行过程中,机器集是不变的。Imreh和Noga第一次提出了在排序中考虑机器费用的模型。他们研究了所谓的List Model problem,并给出了竞争比为(1+5的平方根)/2≈1.618的在线算法,同时证明了该模型的任意在线算法的竞争比至少是4/3。本文研究List Model problem的一个半在线情形,我们假设工件的最大加工时间预先知道,我们将给出一个竞争比为19/12≈1.583的半在线算法,同时证明对该问题的这一半在线情形,任意半在线算法的竞争比至少是4/3。这表明部分信息有利于设计更好的算法。 相似文献