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81.
An expectation value approach to calculations of first-order properties using the non-iterative, triple-excitation amplitudes
in the coupled cluster wave function is exploited. Three methods are suggested and analysed using the many body perturbation
theory (MBPT) expansion arguments. The first method, in which non-iterative triple-excitation amplitudes are used in the expression
for the expectation values, makes the wave function accurate through the second order of MBPT. In the second method, which
is an extension of the first, effects of triple-excitation amplitudes are coupled with single- and double-excitation amplitudes.
The correlated density matrix equivalent through the fourth order to that obtained when CCSDT-la amplitudes are used is employed
in the third method. The suggested methods are tested on dipole moment and polarizability calculations for several diatomic
closed-shell molecules and are compared to other related approaches.
Received: 15 May 1997 / Accepted: 5 June 1997 相似文献
82.
Siu Kay Wong 《Accreditation and quality assurance》2005,10(8):409-414
Proficiency testing (PT) is an essential tool used by laboratory accreditation bodies to assess the competency of laboratories.
Because of limited resources of PT providers or for other reasons, the assigned reference value used in the calculation of
z-score values has usually been derived from some sort of consensus value obtained by central tendency estimators such as the
arithmetic mean or robust mean. However, if the assigned reference value deviates significantly from the ‘true value’ of the
analyte in the test material, laboratories’ performance will be evaluated incorrectly. This paper evaluates the use of consensus
values in proficiency testing programmes using the Monte Carlo simulation technique. The results indicated that the deviation
of the assigned value from the true value could be as large as 40%, depending on the parameters of the proficiency testing
programmes under investigation such as sample homogeneity, number of participant laboratories, concentration level, method
precision and laboratory bias. To study how these parameters affect the degree of discrepancy between the consensus value
and the true value, a fractional factorial design was also applied. The findings indicate that the number of participating
laboratories and the distribution of laboratory bias were the prime two factors affecting the deviation of the consensus value
from the true value. 相似文献
83.
David W. Schwenke Steven L. Mielke Donald G. Truhlar 《Theoretical chemistry accounts》1991,79(3-4):241-269
Summary We have developed efficient and accurate techniques for the calculation of quantum mechanical reaction probabilities of atom-diatom exchange reactions in the gas phase, and we have optimized a computer code employing these techniques and applied it sucessfully to several systems. In this paper we consider further strategies for improving the algorithm to allow even more demanding applications. In this context, improvement means that equivalent results can be obtained using fewer computational resources (computer time or storage) or that an equivalent expenditure of resources can yield higher accuracy. The new strategies discussed here lead to improvement in both of these areas. Two areas of special focus in the present paper are (i) the finite difference boundary value method used for calculating distorted wave Green's functions and regular solutions for scattering by the distortion potential and (ii) the choice of the distortion potential itself. Among other results included here is the first application of the outgoing wave or scattered wave variational principle to reactive scattering. 相似文献
84.
With some applications in view, the following problem is solved in some special case which is not too special. LetF(s) =Σ
n
∞
=1an
λ
n
−s
be a generalized Dirichlet series with 1 =λ
1 <λ
2 < …,λ
n≤Dn, andλ
n+1 -λ
n ≥D
− 1
λ
n+1
− a
where α>0 andD(≥ 1) are constants. Then subject to analytic continuation and some growth conditions, a lower bound is obtained for
. These results will be applied in other papers to appear later. 相似文献
85.
86.
在很多实际应用中需要计算大规模矩阵的若干个最小奇异组.调和投影方法是计算内部特征对的常用方法,其原理可用于求解大规模奇异值分解问题.本文证明了,当投影空间足够好时,该方法得到的近似奇异值收敛,但近似奇异向量可能收敛很慢甚至不收敛.根据第二作者近年来提出的精化投影方法的原理,本文提出一种精化的调和Lanczos双对角化方法,证明了它的收敛性.然后将该方法与Sorensen提出的隐式重新启动技术相结合,开发出隐式重新启动的调和Lanczos双对角化算法(IRHLB)和隐式重新启动的精化调和Lanczos双对角化算法(IRRHLB).位移的合理选取是算法成功的关键之一,本文对精化算法提出了一种新的位移策略,称之为"精化调和位移".理论分析表明,精化调和位移比IRHLB中所用的调和位移要好,且可以廉价可靠地计算出来.数值实验表明,IRRHLB比IRHLB要显著优越,而且比目前常用的隐式重新启动的Lanczos双对角化方法(IRLB)和精化算法IRRLB更有效. 相似文献
87.
Nawal K. Z. AlFadhly Nawfal Alhelfi Ammar B. Altemimi Deepak Kumar Verma Francesco Cacciola Arunaksharan Narayanankutty 《Molecules (Basel, Switzerland)》2022,27(17)
Spirulina is a kind of blue-green algae (BGA) that is multicellular, filamentous, and prokaryotic. It is also known as a cyanobacterium. It is classified within the phylum known as blue-green algae. Despite the fact that it includes a high concentration of nutrients, such as proteins, vitamins, minerals, and fatty acids—in particular, the necessary omega-3 fatty acids and omega-6 fatty acids—the percentage of total fat and cholesterol that can be found in these algae is substantially lower when compared to other food sources. This is the case even if the percentage of total fat that can be found in these algae is also significantly lower. In addition to this, spirulina has a high concentration of bioactive compounds, such as phenols, phycocyanin pigment, and polysaccharides, which all take part in a number of biological activities, such as antioxidant and anti-inflammatory activity. As a result of this, spirulina has found its way into the formulation of a great number of medicinal foods, functional foods, and nutritional supplements. Therefore, this article makes an effort to shed light on spirulina, its nutritional value as a result of its chemical composition, and its applications to some food product formulations, such as dairy products, snacks, cookies, and pasta, that are necessary at an industrial level in the food industry all over the world. In addition, this article supports the idea of incorporating it into the food sector, both from a nutritional and health perspective, as it offers numerous advantages. 相似文献
88.
目的:检测与分析实验动物血液RBC(RBC·O2,RBC·CO2),Hb(HbO2,HbCO2)和人体皮肤表面流动血液氧化·还原状态的成像与未成像可见光谱领域OD值特征,并为该技术对白癜风病表皮黑色素颗粒检测中的应用尊定基础。方法:利用不同光谱技术和invitro和invivo检测手段,统计分析血液不同状态下波长与位置的OD值信息。结果:invitro检测:动物血液Hb·O2和RBC·O2两者在可见领域均有367,414(Soret带)nm与541,576(Q带)nm的吸收峰位;血液Hb·CO2和RBC·CO2均有432(Soret带)与和553(Q带)nm的波长吸收峰位;血液RBC状态和Hb溶血状态波长吸收峰位无改变,只是在氧化与还原状态下有完全独立的吸收峰位,血液RBC状态和Hb溶血状态波长吸光度OD值之间,有显著性差异(p<0·01)。浓度为1·5×107cell·mL-1的RBC·O2和Hb·O2在576nm的吸收峰位吸光度(y)与红细胞浓度(x)做成两条回归曲线:既,Hb·O2(b1)^y=0·05 0·983x;RBC·O2(b2)y^=0·127 1·934x,两者之间差异有显著性(p<0·01)。invivo检测:在人手背皮肤表面ImSpector图像中RBC·O2状态在540,576nm,RBC·CO2状态在555和755nm处有吸收峰。选择(a:指甲,b:指,c:手背)三个点位分别进行波长检测,每点(n=10)545nm吸收峰的平均OD值,依次为0·83±0·001,0·73±0·001和0·62±0·001,其三处测定点的OD值之间有显著性差异(p<0·01)。结论:invitro检测的RBC与Hb两者波长吸收峰位不变,但吸光度OD值不同,认为RBC状态测定结果更接近于活体组织血管内原始状态。invivo检测对人体无任何侵袭与损伤,灵敏度高,测试时间短,并且同时获得被测样品的波长与位置信息画面等优势,有望表皮中黑素等有色颗粒的直接检测。 相似文献
89.
90.
由于场景中目标与背景的温差相对较小,红外图像会存在对比度低、视觉效果差的问题,针对这一问题,提出一种基于奇异值非线性修正的红外图像对比度实时增强方法。该方法首先对红外图像进行奇异值分解得到其原始奇异值,然后采用一个对数型非线性变换对图像奇异值进行优化,最后根据修正的奇异值重构出对比度增强的红外图像。利用对数型非线性变换修正图像奇异值不仅能够有效拉伸奇异值的动态范围,同时可优化奇异值的变化梯度,使图像的能量信息得到更充分地表达,改善红外图像不良的视觉效果。实验结果表明,该方法较几种对比方法在视觉效果和客观评价方面均具有更优的增强性能;同时体现出良好的实时性,为实现红外图像的实时增强提供了新途径。 相似文献