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1.
Controlledradicalpolymerizationhasrapidlypro gressedsinceitsintroduction,andseveralnewmeth odshavebeendevisedforitspractice.Thesenewtechniquesincludeiniferterpolymerization,radical polymerizationwith2,2,6,6tetramethyl1piperidiny loxyl(TEMPO),atomtransferradicalpolymerization(ATRP)andreversibleadditionfragmentationchain transfer(RAFT)polymerization[1—4].Inallcasescontrolledradicalpolymerizationprocessescanbeachievedbyintroducingareversiblereactionbetween livinganddormantspecies.Especially…  相似文献   

2.
Xia  Fengshun  Li  Wenpeng  Guo  Junheng  Han  You  Zhang  Minqing  Wang  Baoguo  Li  Wei  Zhang  Jinli 《天津大学学报(英文版)》2021,27(5):409-421

A pore-array intensified tube-in-tube microchannel (PA-TMC), which is characterized by high throughput and low pressure drop, was developed as a gas–liquid contactor. The sulfite oxidation method was used to determine the oxygen efficiency (φ) and volumetric mass transfer coefficient (kLa) of PA-TMC, and the mass transfer amount per unit energy (ε) was calculated by using the pressure drop. The effects of structural and operating parameters were investigated systematically, and the two-phase flow behavior was monitored by using a charge-coupled device imaging system. The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number, flow rate, and number of helical coil turns and decreasing pore size, row number, annular size, annular length, and surface tension. The φ, ε and kLa of PA-TMC could reach 31.3%, 1.73 × 10−4 mol/J, and 7.0 s−1, respectively. The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.

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3.
(K0.47Na0.47Li0.06)NbO3 (KNLN) lead-free ceramics were prepared by molten salt synthesis (MSS) method using k2CO3-Na2CO3 eutectic mixtures as the flux. The microstructure and piezoelectric properties when sintered at 980-1 030 ℃ were investigated. The calcined powders were examined by X-ray diffraction. The microstructure of the calcined powders and sintered bodies was observed using a scanning electron microscope (SEM).The piezoelectric constant d33 was measured using a quasi-static piezoelectric d33 meter. The planar coupling coefficient Kp was calculated by resonance-antiresonance method. The experimental data for each sample's performance indicators were the average values of 8 specimens. The relative densities of sintered specimens are above 97%, and the dielectric loss is below 0.03. It was found that (K0.47Na0.47Li0.06)NbO3 prepared by MSS is compact and lead-free. The piezoelectric constant d33 is 216 pC·N-1 and the planar electromechanical coupling factor Kp is 0.352.  相似文献   

4.
With the straification theory we have proved the transversal layer s03,k(D) of complete equations for mixed fluid is not an empty set: s03,k(D)≠φfor all k(k≥1). Based on this conclusion and the "secondary equation" of s03,k(D), this paper fully presents the expressions of coefficients in all local analytic solutions of the equations. Therefore we provide the calculation formulas by which we can get the numerical solutions to any desired accuracy.  相似文献   

5.
The adsorption characteristics of Pb on sediments of the Dianshan Lake in Shanghai was studied. The results show that (1)the relationship between the amount q of apparent equilibrium adsorption and the equilibrium concentration C conforms to the Freundlich isothermal adsorption equation; (2) the adsorption and desorption of Pb on sediments are not reversible, that is, adsorption/desorption of Pb exhibits hysteresis; (3) Pb adsorption behavior is initially fast, followed by a slow reaction, and the slow reaction conforms to a reversible first-order reaction; (4) by deducing the Pb adsorption kinetics, four kinetics parameters n, k1, k2, qmax independent of C could be worked out; (5) the equilibrium parameter (K) and the free energy change (ΔG) could also be determined,and the negative values of free energy change (ΔG) indicate the spontaneous nature of the adsorption.  相似文献   

6.
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   

7.
Sweetpotato starch thermal properties and its noodle quality were analyzed using a rapid predictive method based on near-infrared spectroscopy （NIRS）. This method was established based on a total of 93 sweetpotato genotypes with diverse genetic background. Starch samples were scanned by NIRS and analyzed for quality properties by reference methods. Results of statistical modelling indicated that NIRS was reasonably accurate in predicting gelatinization onset temperature （To） （standard error of prediction SEP=2.014 ℃, coefficient of determination RSQ=0.85）, gelatinization peak temperature （Tp） （SEP=-1.371 ℃, RSQ=0.89）, gelatinization temperature range （Tr） （SEP=2.234 ℃, RSQ=0.86）, and cooling resistance （CR） （SEP=0.528, RSQ=0.89）. Gelatinization completion temperature （To）, enthalpy of gelatinization （△H）, cooling loss （CL） and swelling degree （SWD）, were modelled less well with RSQ between 0.63 and 0.84. The present results suggested that the NIRS based method was sufficiently accurate and practical for routine analysis of sweetpotato starch and its noodle quality.  相似文献   

8.
Comparison of MMA polymerization results with samarocene chloride, titanocene chloride and the title heterodinuclear (Sm−Ti) catalyst, respectively, showed synergism in the Sm-Ligand-Ti system, which obviously influenced the polymerization behaviors, for example, of yeilding higher activity and higher molecular weight polymer. Kinetic studies on polymerization of MMA with ethylene bridged samarocene and titanocene chloride/Al(i-Bu)3 showed that the polymerization rate was first-order on the catalyst concentration, and 1.9-order on the monomer. The overall activation energy measured was 52.8 kJ/mol. Project supported by NSFC (No. 20074028), and SINOPEC(X598037).  相似文献   

9.
1 Introduction We consider the finite digraphs that do not havemultiple arcs or loops , but pairs of opposite arcs areallowed.LetD=(V,A) be a digraph , whereVisthe set of vertices andAis the set of arcs .If there isan arc (x,y) fromxtoy,thenthe vertexxis …  相似文献   

10.
A comparative study on the photosynthetic parameters among intergeneric progenies derived fromOryza sativa L.×Sorghum vulgare L., its maternal parent Gui 630 and commercial 3-line hybrid rice Shanyou 63 in pot experiment in greenhouse was conducted. The morphological and photosynthetic characters of canopy leaves and chlorophyll fluorescence kinetic parameters includingF v/F m,F v/F 0, photochemical quenching coefficient and non-photochemical coefficient of canopy leaves of 3 varieties were measured. The results showed the progeny, Yanyou 1, derived from an intergeneric cross of rice and sorghum possesses better canopy spatial architecture with thicker, heavier and bigger canopy leaf than its maternal parent Gui 630. Higher photosynthetic rate due to higher chlorophyll content, higher primary energy transformation efficiency, potential of PSII and non-photochemical quenching coefficient (q E) were also measured in Yuanyou 1. These explain partly why the intergeneric progeny has higher biomass production, and better tolerance to adverse conditions and higher field yields even under stress conditions.  相似文献   

11.
The structural properties, mechanical behavior, and electronic structure of the newly developed diamondlike BC5 (d-BC5) was investigated using density functional theory (DFT) calculations. The results indicate that d-BC5 has great bulk modulus of 393 GPa, large shear modulus of 398 GPa, and high hardness of 62 Pa, and thus support the fact that d-BC5 is an ultra-incompressible and superhard material. Remarkably, the superhard d-BC5 exhibits metallic features. Furthermore, the trend that the mechanical behavior falls with the increase of boron content was revealed. The combination of huge stiffness, high hardness, and good metallicity makes series of diamondlike BC x (d-BC x ) valid for wider applications in comparison with pure diamond.  相似文献   

12.
To test the hypothesis that the etiology of reading difficulties may differ for males and females in more severely impaired samples, reading performance data from monozygotic (MZ), same-sex dizygotic (DZss), and opposite-sex dizygotic (DZos) twin pairs were analyzed using a model-fitting implementation of the DeFries-Fulker (DF) model (Purcell & Sham, 2003, Behavior genetics, 33, 271–278). Five non-independent samples were selected using cut-offs of −1 (N = 737 pairs), −1.5 (N = 654), −2 (N = 468), −2.5 (N = 335), and −3 (N = 198) standard deviations (s) below the mean composite reading score of control twins. Male/female gender ratios for children with reading difficulties were significantly higher than 1.0 for all five samples and increased as a function of severity (viz., 1.15, 1.17, 1.40, 1.61, and 1.88, respectively). When the DF model was fit to the data, estimates of heritability (h g2) and shared environmental influences (c g2) were not significantly different for males and females in any of the groups. Consequently, the most parsimonious model that provided a good fit to the data at all five levels of severity equated the heritabilities and shared environmental influences for males and females, and fixed the DZos coefficient of genetic relatedness at 0.5. Thus, these results provide no evidence for a differential etiology of reading difficulties as a function of gender in more severely impaired samples, and suggest that the same genetic and environmental influences contribute to reading difficulties in males and females, irrespective of severity.  相似文献   

13.
The effectiveness of various analytical formulas for estimating R 2 shrinkage in multiple regression analysis was investigated. Two categories of formulas were identified: estimators of the squared population multiple correlation coefficient (ρ2) and those of the squared population cross-validity coefficient (ρc 2). The authors conducted a Monte Carlo experiment to investigate the effectiveness of the analytical formulas for estimating R 2 shrinkage, with 4 fully crossed factors (squared population multiple correlation coefficient, number of predictors, sample size, and degree of multicollinearity) and 500 replications in each cell. The results indicated that the most widely used Wherry formula (in both SAS and SPSS) is probably not the most effective analytical formula for estimating ρ2. Instead, the Pratt formula and the Browne formula outperformed other analytical formulas in estimating ρ2 and ρc 2, respectively.  相似文献   

14.
研究目的：研究方法：重要结论：确定氢氧化钠溶液化学吸收硫酰氟的传质反应动力学区域,建立增强因子模型。研究气液传质测定设备双搅拌釜中氢氧化钠溶液化学吸收硫酰氟的过程,并结合实验研究与理论分析建立了增强因子模型。基于氢氧化钠溶液化学吸收硫酰氟过程的实验研究,确定了氢氧化钠溶液化学吸收硫酰氟的传质反应动力学区域为快速拟一级反应。得到了298K下其二级反应速率常数为1．44m3／（mol·s）,并建立了增强因子模型E=68．08CBL1/2,为脱除熏蒸后残留硫酰氟的工业化应用提供了理论依据。  相似文献   

15.
Fitting a large structural equation modeling (SEM) model with moderate to small sample sizes results in an inflated Type I error rate for the likelihood ratio test statistic under the chi-square reference distribution, known as the model size effect. In this article, we show that the number of observed variables (p) and the number of free parameters (q) have unique effects on the Type I error rate of the likelihood ratio test statistic. In addition, the effects of p and q cannot be fully explained using degrees of freedom (df). We also evaluated the performance of 4 correctional methods for the model size effect, including Bartlett’s (1950), Swain’s (1975), and Yuan’s (2005) corrected statistics, and Yuan, Tian, and Yanagihara’s (2015) empirically corrected statistic. We found that Yuan et al.’s (2015) empirically corrected statistic generally yields the best performance in controlling the Type I error rate when fitting large SEM models.  相似文献   

16.
Abstract

The purpose of this investigation was to determine the nature of the relationship among three variables: diadocho‐kinetic rate, speaking rate, and reading rate. A group of 40 individuals, 20 males and 20 females, performed three experimental tasks: (1) three repetitions at maximumt speed of each of the following: /p?//t?//k?/, and /p? t? k?/; (2) 10 readings of a standard prose passage; and (3) the presentation of a two‐minute impromptu speech based on the content of stimulus pictures. Results of subjects’ performances indicate that: (1) reading rate is highly related to speaking rate; (2) there is no strong relationship between diadochokinetic rate and speaking rate; and (3) diadochokinetic rate is not highly related to reading rate.  相似文献   

17.
In order to develop a model for screening the agonists of human β2-adrenoceptor from Chinese medicinal herbs extracts, we used a cell-based functional assay based on a common G protein-coupled receptor (GPCR) regulation mechanism and destabilized enhanced green fluorescent protein (d2EGFP) reporter gene technique. The positive cell clone was confirmed by real-time polymerase chain reaction (PCR) and imaging analysis. To assess the value of this model, we screened over 2000 high performance liquid chromatography (HPLC)-fractionated samples from the ethanol extracts of Chinese medicinal herbs. Six fractions (isolated from Panax japonicus, Veratrum nigrum, Phellodendron amurense, Fructus Aurantii Immaturus, Chaenomeles speciosa, and Dictamnus dasycarpus) showed significant effects on active reporter gene expression, three of which (isolated from Phellodendron amurense, Fructus Aurantii Immaturus, and Chaenomeles speciosa) were selected for further concentration response analysis and the half maximal effective concentration (EC1/2 max) values were 4.2, 2.7, and 4.8 μg/ml, respectively. Therefore, this reporter gene assay was suitable for screening β2-adrenoceptor agonists. The results suggest that the six herbal extracts are the possible agonists of β2-adrenoceptor. Project (No. 30873103) supported by the National Natural Science Foundation of China  相似文献   

18.
Acrylonitrile(AN)/1-vinyl-3-ethylimidazolium bromide(VIMB) copolymer was prepared via solution polymerization using dimethyl sulfoxide(DMSO) as a solvent and azodiisobutyronitrile as an initiator. The effects of comonomer VIMB on the polymerization, rheological properties of the polymer solution and thermal properties of the copolymer were investigated. The ionic liquid VIMB resulted in higher polymerization conversion ratio and higher average molecular weight when copolymerized with AN than itaconic acid(ITA). Rheological measurements indicated that the transition shear rate increased linearly with increasing temperature for P(AN/ITA)/DMSO solution, while an exponential growth with temperature was observed for P(AN/VIMB)/DMSO solution. The exothermic peaks of DSC curves in N_2 appeared at 276.67 and 257.34 °C for P(AN/VIMB) and P(AN/ITA), respectively. As a potential comonomer of AN for PAN carbon fibers, the VIMB resulted in about 7% higher char yield in N_2, and 23.7% less weight loss at 600 °C in air than ITA copolymer.  相似文献   

19.
The failure mode and adhesion of thermal barrier coating (TBC) 8YSZ (ZrO2+8% (w/w) Y2O3) deposited on NiCoCrAlTaY bond coat by atmospheric plasma spraying were investigated. A grooved modified three-point bending specimen that can generate a single interface crack to facilitate the control of crack growth was adopted for testing, which was conducted at the ambient temperature of 100 °C. The morphology and composition of fractured surfaces were examined by means of a scanning electron microscopy (SEM) and an energy disperse spectroscopy (EDS). Images and spectrum show that cracks are initiated and propagated exclusively within YSZ layer adjacent to top/bond coat interface. The load-displacement curves obtained exhibit similar shapes that indicate two distinct stages in crack initiation and stable crack growth. Finite element analyses were performed to extract the adhesion strength of the TBCs. The delamination toughness of the plasma-sprayed 8YSZ coatings at 100 °C, in terms of critical strain energy release rate Gc, can be reliably obtained from an analytical solution.  相似文献   

20.
We extend a results presented by Y.F.Hu and C.Storey(1991)^[1] on the global convergence rsult for conjugate gradient methods with different choices for the parameter βk.In this note,the conditions given on βk are milder than that used by Y.F.Huang C.Storey.  相似文献   

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