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1.
1 Introduction Interior-point methods (IPMs) for semidefinite opti-mization (SDO) have been studied intensively,due totheir polynomial complexity and practical efficiency.In the past decade , SDO has become a popular re-search area in mathematical programming when it be-came clear that the algorithm for linear opti mization(LO) can often be extended to the more general SDOcase. Other two factors are also responsible for thisincreasing interest in SDO. Firstly, SDO has a wideapplication…  相似文献   

2.
INTRODUCTION To compute the minimum distance between two convex polygons or polyhedrons is often a main step of many applications, such as collision detection (Choi et al., 2006; Li et al., 2003), path planning. In order to reduce the time complexity of the algorithm as much as possible, the convex property must be applied fully. Edelsbrunner (1985) proposed an algorithm for computing the minimum distance between two dis- joint convex polygons. The algorithm takes O(logm logn) time, and …  相似文献   

3.
SO4^2- / TiO2-La2O3, a novel solid superacid, was prepared and its catalytic activities at different synthetic conditions are discussed with esterification of n-butanoic acid and n-butyl alcohol as probing reaction. The optimum conditions have also been found, mole ratio of n（La^3＋）：n（Ti^4＋） is 1：34, the soaked consistency of H2SO4 is 0.8 tool/L, the soaked time of HESO4 is 24 h, the calcining temperature is 480 ℃, the calcining time is 3 h. Then it was applied in the catalytic synthesis often important ketals and acetals as catalyst and revealed high catalytic activity. Under these conditions on which the molar ratio of aldehyde/ketone to glycol is l： 1.5, the mass ratio of the catalyst used in the reactants is 0.5%, and the reaction time is 1.0 h, the yields of ketals and acetals can reach 41.4%-95.8%.  相似文献   

4.
Elsholtzia splendens (Lamiaceae) is a copper-tolerant plant species growing on copper deposits in the south of China. Chromatographic separation of n-BuOH extracts from the flowering aerial biomass afforded apigenin-7-O-β-d-glycoside, using macroporous resin, Sephadex? LH-20 gel, polyamide resin as well as preparative high-performance liquid chromatography (P-HPLC) columns. Chemical structure was elucidated using HPLC/ESI-MS (electrospray ionization-mass spectrometry), Fourier transform infrared (FTIR), and 1D- and 2D-nuclear magnetic resonance (NMR). Apigenin-7-O-β-d-glycoside could be the post-harvesting product from E. splendens biomass.  相似文献   

5.
Epistemological beliefs and self-regulated learning with hypertext   总被引：3，自引：0，他引：3  
This study investigated the relationship between epistemological beliefs, prior domain knowledge and self-regulated learning. Biology students (n?=?25) and humanities students (n?=?26) who varied in their epistemological beliefs learned with a hierarchical hypertext about the topic of genetic fingerprinting. During their learning processes, logfiles and questionnaire data were collected. Results indicate that students do metacognitively calibrate their learning process to the complexity of the presented learning material, e.g. by processing more complex deeper-level nodes longer. Furthermore, these calibration processes were significantly related to epistemological beliefs. For example, more ‘sophisticated’ epistemological beliefs were associated with processing more nodes, whereas more ‘naïve’ beliefs were related to spending more time on single nodes. Both effects were especially pronounced on deeper hierarchical hypertext levels. Prior domain knowledge also had an impact, especially on comprehensibility ratings: biology students considered all nodes more comprehensible than humanities students. Additionally, epistemological beliefs as well as prior domain knowledge were also significantly associated with the learning outcome: for example, more prior domain knowledge led to significantly higher learning outcome.  相似文献   

6.
The aim of this article is to explicitly compute the number of generalized magic squares of order 3. Counting functions for (generalized) magic squares of order n with fixed line sum r is known to be a polynomial function in r over ? of degree (n?1)2. For higher values of n, it is quite difficult to explicitly write down such counting functions.  相似文献   

7.
In this paper we study the scaling behavior of nucleotide cluster in 11 chromosomes of Encephalitozoon cuniculi Genome. The statistical distribution of nucleotide clusters for 11 chromosomes is characterized by the scaling behavior of P（S） ∝ e^-αs＇ where S represents nucleotide cluster size. The cluster-size distribution P（S1＋S2） with the total size of sequential C-G cluster and A-T cluster S1＋S2 were also studied. P（S1＋S2） follows exponential decay. There does not exist the case of large C-G cluster following large A-T cluster or large A-T cluster following large C-G cluster. We also discuss the relatively random walk length function L（n） and the local compositional complexity of nucleotide sequences based on a new model. These investigations may provide some insight into nucleotide cluster of DNA sequence.  相似文献   

8.
Theories of self-regulated learning assume that learners flexibly adapt their learning process to external task demands and that this is positively related to performance. In this study, university students (n = 119) solved three tasks that greatly differed in complexity. Their learning processes were captured in detail by task-specific questionnaires and computer-generated log files. Results indicate that students adapted almost all learning processes significantly to task complexity. For example, students accessed more hypertext pages for complex tasks than for simple tasks. However, this kind of adaptation was not consistently related to performance. For variables capturing learners’ self-regulation, such as the number of accessed hypertext pages, more pronounced adaptation was significantly and positively related to performance even when learners’ general processing depth was statistically controlled. Results were less consistent for variables capturing learners’ self-monitoring, such as their judged task complexity.  相似文献   

9.
For non-negative integers k, n, let P k (n) denote the sum {fx27-1}. We show by two different means that if k ≥ 3 and odd, then n 2(n+1)2 iss a factor of the polynomial P k (n); and if k ≥ 2 and even, then n (n+1) (2n+1) is a factor of the polynomial P k (n). We also derive a relatively unknown result first obtained by Johann Faulhaber in the 17th century. Shailesh Shirali has been at Rishi Valley School, Andhra Pradesh (Krishnamurti Foundation India) since the 1980’s. He has a deep interest in teaching and writing about mathematics at the high school/post school levels, with particular emphasis on problem solving and on historical aspects of the subject. He has been involved in the Mathematics Olympiad movement at the national and international level for the past two decades. He is the author of several expository books and articles aimed at interested high school students.  相似文献   

10.
The copolymerization of CO and styrene catalyzed by Pd/C toward the formation of polyketones(PK)was studied in the N-valeronitrile-N'-methylimidazolium hexafluorophosphate([C4CNmim]+PF-6) medium. The synthesized PK was characterized by Fourier transform infrared(FTIR), elemental analysis, 13C-nuclear magnetic resonance(13C-NMR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and gel permeation chromatography(GPC). The supported ionic liquid film on the surface of Pd/C catalyst can prevent the products from covering the hole of active carbon due to its chemical stability and weak coordination ability with metal ions, and thus efficiently improve the catalytic activity. The effects of different amounts of ionic liquid on the catalytic activity and reusability of the catalyst and the molecular weight of PK were discussed. When the usage of ionic liquid is 10wt%(0.1 g ionic liquid / 1 g active carbon carrier) and the theoretical content of Pd2+ is 5wt%(0.05 g Pd2+/ 1 g active carbon carrier), the highest catalytic activity 2 963.64 gSTCO/(gPd·h) is achieved with the molecular weight and polydispersity index of PK as Mn=9 684, Mw=13 452 and Mw /Mn=1.389.  相似文献   

11.
The log-odds ratio (ln[OR]) is commonly used to quantify treatments' effects on dichotomous outcomes and then pooled across studies using inverse-variance (1/v) weights. Calculation of the ln[OR]'s variance requires four cell frequencies for two groups crossed with values for dichotomous outcomes. While primary studies report the total sample size (n..), many do not report all four frequencies. Using real data, we demonstrated pooling of ln[OR]s using n.. versus 1/v weights. In a simulation study we compared two weighting approaches under several conditions. Efficiency and Type I error rates for 1/v versus n.. weights used to pool ln[OR] estimates depended on sample size and the percent of studies missing cell frequencies. Results are discussed and guidelines for applied meta-analysts are provided.  相似文献   

12.
Ritavan 《Resonance》2014,19(5):466-470
Taylor’s theorem in analysis provides a way of approximating an n+1-times differentiable real function by an nth degree polynomial in a neighbourhood of a point x 0. The usefulness of the theorem lies in the fact that if the bounds on |f (n+1)(x)| are known, then the error introduced by the polynomial approximation can be estimated. So while Taylor’s theorem provides an extremely useful manner of approximating the given function to a desired degree of precision in a neighbourhood of a given point, it says nothing about the nature of the polynomial approximation itself, and intuitive arguments are often offered to explain why the derivatives of f must figure in the coefficients of such a polynomial. In what follows, we shall attempt a rigorous explanation of the sense in which such a polynomial is the ‘best’ approximation of the given function.  相似文献   

13.
Let k,m,n be positive integers,and k≥2,α∈(0,1],0＜r＜min {m,n} an integer,d=r (m-r)/(k α),and iff∈ Ck,α(Rm,R″),A =Cr(f)= {x ∈ Rm ,rank(Df(x))≤r},thenf(A)is d-null.Thus the statement posed by Arthur Sard in 1965 can be completely solved when k≥2.  相似文献   

14.
INTRODUCTION Along with the great progress in 3D data meas- urement device and the popularization of complex solid modelling, recursive subdivision has been a research focus in CAGD and CG (Wang et al., 2001). However, most interpolating subdivision schemes are Lagrange-type schemes whose smoothness is not easily verified. The geometric features of this kind of subdivided curves and surfaces are difficult to be generated, which restricts the application of subdivi- sion methods. From a…  相似文献   

15.
The study investigates the preschool readiness of moderately preterm children and, in particular, the likely presence of learning disabilities at preschool age. Its theoretical model detects linguistic comprehension and expression; memory-related metacognition and cognition skills; orientation and motor coordination skills; premathematics and preliteracy ones. The research project involved an experimental group made up of 55 moderately preterm children (mean age?=?62 months, mean gestational age?=?34.6 weeks), without any clinical neonatal complications, and low birth weight (M?=?2,100 g, SD?=?350 g); a control group made up of 55 full-term children without pre- and perinatal complications. The children’s primary school reference teachers were given a questionnaire (Observative Questionnaire for Early Identification of Learning Disabilities), which was aimed at identifying any likely social and cognitive skill deficits at preschool age. The data, submitted to nonparametric univariate variance, show how scores of moderately preterm children in the metacognition [U (n1 e?n2?=?55)?=?35, p?=?0.04, r?=?0.49] are statistically lower, other cognitive skills (memory, orientation, and visual–motor coordination) [U (n1?e?n2?=?55)?=?32, p?=?0.02, r?=?0.45], premathematics [U (n1?e?n2?=?55)?=?32, p?=?0.02, r?=?0.44], and the total score [U (n1?e?n2?=?55)?=?31, p?=?0.02, r?=?0.12]. Such data would seem to suggest the need for hypothesizing preventive training and educational paths as a prerequisite for the development of the school abilities.  相似文献   

16.
Chemically processed Nb-doped SrTiO3 films and properties   总被引：1，自引：0，他引：1  
Homogeneous, crack-free SrNbxTi1−x O3 thin films on (110) silicon substrates were successfully fabricated by sol-gel processing. The optimum route and conditions were systematically investigated. Sr(OAc)2 glacial acctic acid solution, after being refluxed and reacted with tartrate, formed Sr(OAc)2(C4H6O6)2; Ti(OBu)4 formed Ti(OAc)4−x (AcAc)x after having the ligand partially exchanged with AcAc, while Nb(OC2H5)5 formed (OAc)2Nb(AcAc) (C4H6O6) by exchanging of ligand in glacial acetic acid with (CH3CO)2O. All the metal species after undergoing partial hydrolysis and polymerization with hydroxyl or oxygen, formed SrNbxTi1−x O13 cluster sol. Methyl cellulose (MCL) caused SrNbxTi1−x O3 sol to have polymeric structure and easily form films. SrNbxTi1−x O3 films with perovskite were subsequently formed after being annealed at 650∼750 °C for 60 min in 25% N2+75% H2 (volume ratio) atmosphere. Resistivity of the SrNb0.1Ti0.9O3 films at room temperature was 64 μω·cm, a particular T 2 temperature dependence of the resistivity, from 25 K up to room temperature, was observed. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China  相似文献   

17.
BackgroundAcquiring more complex coping strategies despite a history of childhood adversity may transpire in settings outside the family home.ObjectivesThe objectives of this cross-sectional study included investigating coping strategies under stressful situations in a non-clinical sample of active athletes and performing artists. Participants and Setting: In this community and university sample (n = 577), 40.4% had no ACEs, 43.4% had 1–3 ACEs, and 16.3% had ≥4 ACEs.MethodsA series of multivariate analyses (gender and age included as covariates) were conducted to examine differences between the three ACE groups.ResultsResults indicated no between-subject differences between the three ACE groups for flow-like experiences during preferred activities, although gender differences were significant (p < .001). Individuals in the ≥4 ACEs group endorsed more intense creative experiences compared to the no-ACE and 1–3 ACEs groups (p = .006, η2 = .048); however, in the third MANCOVA they had heightened anxiety, internalized shame, dissociative processing, emotion-oriented coping, and cumulative trauma (p < .001, η2 = .132). There were no group differences for task-oriented and avoidant-oriented coping, a finding that highlights the ability of active individuals to engage in effective coping strategies under stressful situations.ConclusionRegardless of past childhood adversity history, this non-clinical high achieving sample was able to engage in a range of coping strategies under stress.  相似文献   

18.
This research aims to promote our understanding of feedback engagement processes in writing tasks using a combination of online and offline measures, including eye-tracking, thinking-aloud, and text-analyses. Study 1 explored how sixteen students read, evaluate, and use feedback for revision. Results revealed three feedback processing strategies: (1) superficial processing (n = 6), which is characterized by reading feedback in a linear way, without critically rereading or revising the text, (2) local processing (n = 6) in which students switched between reading the comments and the commented text, and (3) deep processing (n = 4) in which students integrated the feedback with both commented and uncommented parts of the text and made more substantial revisions. In Study 2, we investigated the local and deep feedback reading strategy in more detail with 41 students using a within-subject design with different types of feedback. Results demonstrated the same strategies among students, but also that the focus of feedback affected students' revision behavior, above and beyond an individual feedback processing strategy. This finding is in line with previous research that emphasized the effects of feedback characteristics on students’ use of feedback. By triangulating various process measures, this research is one of the first that provides empirical evidence for different feedback processing strategies among students. These novel insights in individual feedback engagement processing can be used to extend and refine current theories on how, when, and why feedback works and for whom.  相似文献   

19.
This work investigated the microwave dielectric properties of A-site substitution by rare earth La3+in(Pb0.5Ca0.5)(Fe0.5Ta0.5)O3(PCFT) system.A single perovskite phase was obtained only when the doping content was 2%.Suitable La3+ doping improved microwave dielectric performances.Excessive La3+doping caused the formation of secondary phase,which resulted in the decreasing of permittivity εrand quality factor Qfvalues.Especially,when the doping content is 2%-5%,permittivity εrwas above 75 and Qfvalues were 6...  相似文献   

20.
In this study, we used a simple impregnation method to prepare Fe–Ce–O x catalysts and tested them regarding their low-temperature (200–300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94–99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h?1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80–98% between 200 and 300 °C at a space velocity of 204,000 h?1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200–300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance.  相似文献   

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