最新刊期
卷 56 ， 期 1 ， 2017
- 摘要：The ［OSSO］-type bis(phenolate) titanium complex (［OSSO］TiCl2) was supported by MgCl2/AlEtn(OEt)3-nand then used to efficiently promote the polymerization of ethylene under the activation of the cheap diethylaluminum chloride (AlEt2Cl). The resulted polymer was a long chain branched polyethylene. The influences of the preparation technology of support, triethyl aluminum modifying the adduct of MgCl2and ethyl alcohol (EtOH) (MgCl2/AlEtn(OEt)3-n), and the polymerization conditions including polymerization temperature, ethylene press and Al（in AlEt2Cl）∶Ti on the polymerization behavior and the polymer structure were explored. The result indicated that the supported catalyst could more actively promote the polymerization of ethylene than the homogeneous catalyst with the highest activity of 106g(PE)/(mol(Ti)·h), which was hundredfold of the homogeneous catalyst. The analysis of the13C nuclear magnetic resonance spectroscopy confirmed that the obtained polyethylene catalyzed by the supported catalyst was the long chain branched polyethylene with a branch number of 15 and a long branched chain content of 60.2%. The analysis of differential scanning calorimetry shows that the melting temperature of the branched polyethylene was 126 ℃. The kinetics of the ethylene polymerization was steady.关键词：［OSSO］-type bis(phenolate) titanium catalyst;supported catalyst;branched polyethylene
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发布时间：2023-12-11 - 摘要：Ultrasonic-assisted extraction (UAE) was used to extract proanthocyanidins (PC) from Spatholobus suberectus Dunn. Response surface methodology (RSM), based on a three-factor, three-level Box-Behnken central composite design (BBD), was employed to obtain the optimal extraction parameters, in which the extraction yields of PC was maximum. Three important factors, including extraction time, solidliquid ratio and acetone concentration, were selected by single-factor tests. Optimized extraction conditions for PC were a ratio of liquid to solid of 1∶45 mL/g, 25 ℃, 30 min, and acetone concentration as 70%, one-time extraction, 500 W ultrasonic power. Under these conditions，the extraction yield of PC was 25.58%. In DPPH· and ABTS· scavenging assays, the IC50of PC from S. suberectus were 8.42 μg/mL and 10.55 μg/mL, respectively.关键词：Spatholobus suberectus Dunn;proanthocyanidins;response surface methodology;antioxidant activity
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发布时间：2023-12-11 - 摘要：The chiral transition of lysine molecules confined in water and MOR zeolite combined environment was studied in the paper by introducing the ONIOM methods using combination of quantum mechanics and molecular mechanics. The molecular structure researches show that hydrogen bond angle of the transition state molecules in the hydrogen transfer reactions with the help of two water molecules is significantly larger than that with the help of one water molecule. The study of reaction channels shows there are three channels a, b and c in the title reaction where lysine is confined in MOR zeolite, protons transfer with the help of water molecules from one side to the other of the chiral C with amino, carbonyl and hydroxyl as a bridge, and at last the chiral transition is achieved. Calculations of potential energy surface show that channel a is the dominant reaction path and protons transfer the chiral C to amino is the stepdetermining where gibbs free energy barrier of two water-assisted proton transfers reaction is reduced to the minimum value 101.9 kJ·mol-1that is significantly lower than the gibbs free energy barrier 252.6, 229.7 and 123.9 kJ·mol-1respectively corresponding to the bare reaction, confined in MOR zeolite and confined in water environment. The results show that water and MOR zeolite combined environment has a good co-catalysis on the chiral transition of lysine molecules, and SLys in vivo can be slowly optical isomerism.关键词：MOR zeolite;lysine;chiral transition;our own n-layered integrated molecule orbit and molecule mechanics methods;density functional;transition state
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发布时间：2023-12-11 - 摘要：A novel and sensitive method was established for the determination of Vitamin C and Paracetamol in Vitamin C Yinqiao Tablets using Capillary Electrophoresis (CE) equipped with a photo-diodearray detector. The running buffer solution was 30 mmol·L-1sodium hydrogen phosphate solution containing 30 mmol·L-1 sodium deoxycholate (pH＝8.89). The capillary column efficient length was 40 cm (i. d 75 μm) with the separation voltage ＋20 kV. The result indicated that the peak area of Paracetamol and Vitamin C had a good linear relationship with their concentrations in a certain concentration range. The recoveries of both were more than 97.6% with RSDs less than 3.2%. CE method was simple and rapid in operation, sensitive and reliable in determination results with very little sample consumption, which can be used for the determination of Paracetamol and Vitamin C in Vitamin C Yinqiao Tablets.关键词：capillary electrophoresis (CE);Vitamin C Yinqiao Tablet;Vitamin C;Paracetamo
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发布时间：2023-12-11 - 摘要：Based on support structure project of the railway from Dali to Ruili, dynamic characteristics of retaining structures against bedding slopes are studied by numerical analysis and shaking table experiment. It mainly contains acceleration response on retaining structure under Wen-chuan earthquake XZ-excitation. Both of the numerical simulation and the shaking table experiment prove that the results are generally similar to each other. It is found that horizontal /vertical acceleration amplification factor is decreased with the increase of input field vibrations. The shaking table model test conforms well to the numerical simulations, validating that the results of shaking table model test are reasonable and the numerical simulation method is reliable.关键词：bedding slopes;FLAC3Dnumerical analysis;a shaking table test;combination retaining structures;acceleration
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发布时间：2023-12-11 - 摘要：Video sampling and reconstruction need to process a huge amount of data. In order to solve the problem, a novel video distributed compressive sensing based-BP (VDCS-BP) is proposed in the paper. Based on correlation model established by sparse filter, VDCS-BP can achieve distributed video sensing at encoder-decoder, and reduce numbers of measurement by DCS. Experimental results show that the VDCS-BP is effective.关键词：distributed compressive sensing;video;correlation;recovery
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发布时间：2023-12-11 - 摘要：This study aims to develop a sensitivity-based approach to identify the local damages in axially functionally graded beams. An objective function is established by minimizing the differences between the calculated and measured natural frequencies, and acceleration responses of the beam. An iterative optimization procedure is conducted by linearizing the objective function based on the penalty function method. A hybrid sensitivity matrix is constructed and used in the finite element model updating. The advantage of the present method lies in only the first several natural frequencies, and a few number of acceleration responses are needed in the identification. A single span simply supported beam and a multi-span beam are studied as two numerical examples to illustrate the correctness and efficiency of the proposed method. Good identified results can be obtained from the short time histories of a few number of measurement points and the first several natural frequencies.关键词：damage identification;axially functionally graded beam;hybrid sensitivity matrix;model updating
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发布时间：2023-12-11 - 摘要：BP neural network has been successfully applied in many fields, such as license plate recognition, however the general method of BP neural network is likely to fall into local optimum rather than converge to the global optimum, so its performance of recognition is not very satisfied. In order to avoid this situation, a license plate number recognition technology method is proposed based on PSO-BP neural network. The key of this method is to build an 8-25-1 BP neural network with 8 pixel rate features as its input vector firstly, and then use particle swarm optimization (PSO) algorithm to optimize the weights and thresholds of the BP neural network to get the best fitness value of global searching. By using 300 pair license plate images some with the different illumination and the stained parts, the simulation result indicates that the algorithm we mentioned comparing with the traditional template matching algorithm and general BP algorithm has the certain application value with the advantage of less output errors, global fast convergence, and high recognition rate.关键词：BP neural network;PSO;PSO-BP neural network;vehicle license plate recognition
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发布时间：2023-12-11 - 摘要：This work firstly analyzes the differences between DynasTIM road network and lane-level basic road network from three aspects including components, levels and the relationship of the road network components. The lane-level basic road network can be divided into three layers and it mainly includes Roadsegment, Roadsegmentnode, Node and Arc. While DynasTIM road network can be divided into two layers and mainly includes Node, Link, Segment and LeftCurb. So the corresponding relationship of the two road network components, integrated and extract method can be easily found. Finally, it realizes intelligently modeling from lane-level basic road network to DynasTIM road network. It not only greatly simplifies modeling effort but also provides an effective way for transformation among different road network models.关键词：simulation software;DynasTIM;lane-level basic road network;intelligently modeling
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发布时间：2023-12-11 - 摘要：The Noether theorem for nonholonomic mechanical systems of Nabla variational problem on time scales is studied. Firstly, based on the relationship between the Delta calculus and the Nabla calculus on time scales and the theory of time scale, the nonholonomic Lagrange equation for Nabla variational problem on time scales is established. Secondly, according to invariance of the Hamilton action under the infinitesimal transformation of Nabla variational problem on time scales, the Noether identity for nonholonomic mechanical systems is established, and the corresponding Noether conserved quantity is obtained. Finally, an example is presented to illustrate the application of the results.关键词：time scales;Nabla variation;nonholonomic systems;Noether identity;conserved quantity
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发布时间：2023-12-11 - 摘要：The discrete Φ-Laplacian boundary problem 〖JB({〗〖HL(1〗Δ((Δu(k－1)))+λp(k)f(u(k))=0,k∈{1,2,…,T},u(0)=u(T+1)=0〓〓〓〓〓〓〓〓〖HL)〗〖JB)〗 is studied, where T>5 is a given positive integer, λ is a nonnegative parameter and Φ is an odd and increasing homeomorphism from 〖WTHZ〗R〖WTBZ〗 onto 〖WTHZ〗R〖WTBZ〗. Applying the fixed point theorem in cones, it is proved under the weakened condition liminf〖DD(X〗u→∞〖DD)〗〖SX(〗f(u)〖〗(u)〖SX)〗∈(0,∞］ that the problem has at least one positive solution for λ belonging to an explicit open interval.关键词：discrete Φ-Laplacian problem;positive solution;semipositone problem
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发布时间：2023-12-11 - 摘要：The isentropic compressible Euler-Poisson equations, addressed to describe the motion of ideal gaseous stars, consist of the Euler-Poisson equations for the conservation of mass and momentum, and Poisson equation induced by the potential function of the self-gravitational force. Using the separation method, self-similar solution are presented for the isentropic compressible Euler-Poisson equations in three dimension.
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发布时间：2023-12-11 - 摘要：Aggregate signature becomes a hot topic in the digital signature technology researches because of its wide application in the Internet of Things. Ming et al. (2014) proposed an efficient certificateless aggregate signature scheme. But Zhang et al. (2015) showed the scheme is not secure against a Type II adversary, and then they proposed an improvement of Ming's scheme. However, it is pointed out that the improved scheme is still insecure against a Type II adversary by giving specific attacks. Then, based on Ming's scheme, a new certificateless aggregate signature scheme is constructed. The new scheme is provablysecure in the random oracle model and the length of aggregate signature is constant so that it is suitable for the Internet of Things.关键词：certificateless public key cryptography;aggregate signature;unforgeability
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发布时间：2023-12-11 - 摘要：Based on the “classic” scale-free network model, the network growth principle(preferential attachment mechanism) is extended. Starting from a more general situation, some vertex-preferential attachment probability in different constraint conditions are established, and then the partial differential equation satisfied a more general network dynamic system is set up, and also another important topological property of scale-free network is found. Then a much realistic preferential attachment probability is presented. Finally, a more general network model is generated. By discussing its scale-free property, that scale-free parameter γ ranges from 1 to 4 is captured.关键词：scale-free network model;dynamic evolution;partial differential equation;the six degrees of separation
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发布时间：2023-12-11 - 摘要：SD oscillator is a smooth and discontinuous nonlinear model, which has extensively applications in physics. For periodic orbits of a class of SD oscillator, the monotonic problem of the period is studied. It is proven that the period function of the SD oscillator is monotone.关键词：SD oscillator;period function;isochronous center
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发布时间：2023-12-11 - 摘要：Using the compactness theorem, the regularity of NavierStokes equations in fivedimensional space is studied. It is proven that if u∈L4,∞(Ω×(－T10))is a Leray-Hopf weak solution and ∫Ω×(－T1,0)u3+p3/2<ε, then u is Holder continuous.关键词：five dimensional space;Navier-Stokes;compact theorem;Holder continuous
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发布时间：2023-12-11 - 摘要：Continuous collection of shrimp-breeding pond water samples was respectively done and detected in 6 ponds(H1-H6) in aquaculture base located in Dongfang,Hainan from May to July 2014, as well as 9 ponds(Z1-Z9) in Zhuhai, Guangdong. Detect the concentration of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen as well as other physical and chemical factors were also detected in these shrimp farming ponds. The weather, feeding management, the outbreak of hepatic pancreas necrosis syndrome(HPNS) and its response management were recorded during the period of aquaculture. Result of the statistical analysis showed that ammonia and HPNS was significantly correlated. Three different forms of nitrogen had a significant change in the aquaculture period. With the increase of time and amount of feeding, ammonia and nitrogen in the aquaculture water showed an upward trend. In the first 70~85 days of aquaculture, HPNS successively occurred in varying degrees in H1-H6. The H1-H6 ammonia nitrogen ranged 0.29~0.74 mg/L when the HPNS occurred. The highest value of ammonia ranged 0.42~1.02 mg/L during the onset. After the feeding control taken in H1-H6 when the HPNS outbreak, the ammonia nitrogen concentration in five days was 60.03%~84.89% lower than its highest concentration during onset, respectively. HPNS was effectively controlled. The ammonia nitrogen of H1-H6 were less than 0.2 mg/L at the two days before raining days and the ammonia nitrogen increased dramatically after rain. The ammonia nitrogen in H5 which has increased least was 0.477 mg/L and the ammonia nitrogen in H3 which has increased most was 1.35 mg/L. Z1-Z9 experiment results showed that the average concentration of ammonia at the day before the typhoon was 0.2 mg/L whereas the average concentration of ammonia at the third day after the typhoon reached 0.66 mg/L. After typhoons, vannamei appeared jejunogastric and inappetence which are obvious symptoms of HPNS. The concentration of ammonia rose significantly and was accompanied with the occurrence of HPNS when the ponds were over-feeded or when typhoon or rain came.关键词：physical and chemical factors;Litopenaeus vannamei;ammonia nitrogen;pancreatic necrosis liver disease
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发布时间：2023-12-11 - 摘要：Alsophila gigantean is a large frond tree fern in family Cyatheaceae. The plant is a vulnerable species that prefers specific subtropical montane climate. Little work has been done so far to access the population genetic variation in A. gigantean. In this study, we developed 15 SSR markers using FIASCO protocol and evaluated these markers in four natural populations from Hainan Island, China. Seven loci proved to be polymorphic. The actual number of alleles ranged from one to nine, and the observed and expected heterozygosity varied from 0 to 0.769, and from 0 to 0.805, respectively. Loci AG-12 and AG-23 were found to significantly deviate from the Hardy-Weinberg equilibrium in populations HNjfl and HNbwl, respectively. Four null alleles were identified. Linkage disequilibrium was further detected at three pairs of loci. Moreover, four SSR markers were verified to be successfully transferred in Alsophila spinulosa.The novel polymorphic SSR markers characterized here will be used to survey population genetic variation and local adaptation in A. gigantean, which helps design effective conservation strategies.关键词：大叶黑桫椤;SSR标记;跨种扩增;遗传变异;局部适应性
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发布时间：2023-12-11 - 摘要：The long wing female adults of Sogatella furcifera were selected to extract their genomic DNA. According to the complete 18S rDNA gene sequence from Hemiptera, the unknown 18S rDNA sequence of S. furcifera was amplified by PCR. The complete 18S rDNA gene sequence of S. furcifera was obtained for the first time by splicing the unknown and known 18S rDNA sequences, whole sequence length was 1 891 bp. Comparing 18S rDNA sequence from S. furcifera and those from other insects, four conserved regions were found and the second region had the least insertion or deletion. Based on the second region, phylogenetic analysis was made and the results showed that most Homoptera insects used in this study had a close relatives with Eurydema maracandica (Hemiptera) except Delphacida.关键词：Key words：ribosome;18S rDNA;Sogatella furcifera
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发布时间：2023-12-11 - 摘要：The aim of the study was to establish an HPLC-MS/MS method for simultaneous determination of naringin and naringenin in human plasma. Naringin and naringenin were extracted from plasma by ethyl acetate, then determined by HPLC-MS/MS taking isoquercitrin as internal standard (IS). Chromatographic separation was carried out on a Agilent Poroshell 120 EC-C18column (3.0 mm×30 mm，2.7 μm). The mobile phase was composed of solvent A (0.1% formic acid, V/V) and B (methanol with 0.1% formic acid, V/V). The flow rate was 0.4 mL·min-1. Electrospray ionization (ESI) source was applied and operated in multiple reaction monitoring (MRM) mode with the transitions of m/z 579.1/270.8, m/z 270.9/150.7, m/z 463.1/2998 for naringin, naringenin and IS, respectively. The method was validated over the concentration range of 0.251 0~100.4 ng·mL-1for naringin, and 0.503 0~201.2 ng·mL-1for naringenin, respectively. The intra- and inter-run precisions were within the acceptable range, and the extraction recoveries were satisfactory. The established method is highly sensitive, accurate and reproducible, which can be applied for the simultaneous determination of naringin and naringenin in human plasma.关键词：human plasma;naringin;naringenin;HPLC-MS/MS
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发布时间：2023-12-11 - 摘要：In order to better understand the roles of cysteine proteinase gene and develop a novel molecular target for insect pest control, we obtained the full-length cDNA sequence of Bdcyp (GenBank accession no. KU904503) from the oriental fruit fly, Bactrocera dorsalis (Hende) by using RT-PCR and RACE methods. The deduced amino acid sequence analysis of Bdcyp was performed by using bioinformatics methods. The expression patterns of Bdcyp in different stages and tissues were investigated using quantitative real-time PCR (qPCR). The Bdcyp was 1 955 bp in lenght, containing an open reading frame of 1 653 bp which encodes 551 amino acid residues with a predicated molecular weight of 62 900 and isoelectric point of 6.11. Bdcyp had typical features of cysteine proteinase, including signal peptide, three catalytic active regions (Cys-His-Asn), and two conserved motifs (ERFNIN and GNFD). Phylogenetic analysis showed that Bdcyp has the closest genetic relationship with the cysteine proteinase of B. oleae. Bdcyp was constitutively expressed in the tested stages, including third-instar larvae, pupae and adults. The highest expression level was observed at the middle of pupal stage. Tissuespecific expression showed that the highest expression was in the fat body, followed by trachea and integument, and the expression in midgut was the lowest. The results provide the basis for further studying the function of Bdcyp.关键词：Bactrocera dorsalis;cysteine proteinase;cloning;sequence analysis;expression pattern
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发布时间：2023-12-11 - 摘要：Variability of the low-frequency climate change is the principle driver for the annual and interannual streamflow changes. The influences of lowfrequency climate indices such as El Nino/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO), on annual mean discharge (Qann) and annual peak discharge (Qmax) of the Pearl River basin have been quantitatively analyzed. The results show that: ① Qannand Qmaxwere significantly affected by different climate indices in different regions with distinctly different spatial patterns in terms of correlation degrees and sensitivity and also the trends of impact strength. ENSO and IOD at the same year exerted a persistent significant impact on the Qannat the regions covering most of the West River basin, and the strength of the correlation increased significantly, which can be taken as the predictor for Qann. For the same reason, PDO at the same year can be taken as the predictor for Qannin the eastern parts of the Pearl River basin and the North River basin, and NAO, IOD a year earlier and NAO at the same year can be taken as the predictor for Qmaxin the middle Pearl River basin; ② As for the entire Pearl River basin, negativephase ENSO, NAO and PDO tend to cause Qannat lower levels with an increasing risk of droughts. However, positivephase ENSO, IOD and negative phase NAO and PDO tend to cause Qmaxat higher levels with an increasing risk of extreme floods; ③ Qmaxwas more sensitive to variability of atmospheric circulation than Qann. Qannvaried between 03% and 24%, while Qmaxvaried between 0.5% and 31% per unit index change. The NAO and IOD both at the same year and a year earlier show a higher sensitivity in most area of the Pearl River basin, but the sensitivity difference between Qannand Qmaxwas significant, the latter had an area ratio of 56%, 59%, 71% and 36% sensitivity higher than the former.关键词：low-frequency climate indices;annual mean discharge;annual peak discharge;sensitivity
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发布时间：2023-12-11 - 摘要：Most seismic noise attenuation methods will reduce the data fidelity. A kind of adaptive noise attenuation scheme based on feedback mechanism is introduced in this paper. Noises in seismic data are classified into two categories: unbalanced and balanced noises. Two-step strategy is taken. The unbalanced noises are attenuated first and then the balanced noises. Two indicators NCR and SCR are established to denote the reliability of noise and signal section aiming at the two kinds of noises. The meanings of NCR and SCR are analyzed, adaptive noise feedback coefficient is designed based on the two indicators, the simultaneous enhancement of signal-to-noise ratio and fidelity is achieved. Tests demonstrate that the method is effective.关键词：noise attenuation;fidelity;signal-to-noise ratio;self-adaption;feedback
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发布时间：2023-12-11 - 摘要：Hyperspectral image-based target detection makes good use of the advantage of continuous spectral information of hyperspectral image, distinguishing the target and background mainly by spectral difference. However, fully considering the spatial relationship between image pixels in some spectra analysis algorithms can overcome the shortcomings of these algorithms, such as the lack of constrained energy minimization (CEM) algorithm estimating the background information with the information of full map and orthogonal subspace projection (OSP) algorithm being difficult to accurately construct background subspace. In this paper, spatial dimension information of targets are introduced and possible targets are filtered out by means of morphological opening operation to construct an accurate background, based on which OSP and CEM algorithms are implemented respectively for target detection. The 3D ROC curve is used to evaluate the accuracy of the detection results to overcome the shortcomings of traditional 2D ROC curve. The experimental results show that morphology-based CEM and OSP algorithms can effectively reduce the false alarm rate and improve detection efficiency.关键词：hyperspectral target detection;morphology;constrained energy minimization;orthogonal subspace projection;three dimensional receiver operating characteristics
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发布时间：2023-12-11
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