ISSN 0253-2778

CN 34-1054/N

2020 Vol. 50, No. 5

Display Method:
Original Paper
Analysis of heat transfer characteristics of an air jet cooling a conical heat sink
LI Hai, TANG Zhiguo, GAO Qing, ZHANG Feng, SONG Anqi
2020, 50(5): 551-558. doi: 10.3969/j.issn.0253-2778.2020.05.001
The heat transfer characteristics of a single air jet to cool conical heat sinks with different conical angles were studied by numerical simulation. The Transition SST turbulence model was adopted to solve the Navier-Stokes equation. The difference of heat transfer between different locations was analyzed in combination with flow characteristics. The results show that introducing a conical protrusion greatly enhances the heat transfer near the stagnation point. The average heat transfer performances of cone heat sinks with small angles are better than that of flat heat sinks. And the smaller the angle, the better the heat transfer enhancement. At the bottom edge of the cone, the heat transfer has been weakened first and then enhanced, which is caused by flow separation and secondary jet respectively.
Spatial distributions of oceanic non-precipitating warm clouds and in-cloud vertical structures of liquid water content as revealed by CloudSat measurements
WEI Junbo, DING Yuhao, LAO Ping, LIU Qi
2020, 50(5): 559-569. doi: 10.3969/j.issn.0253-2778.2020.05.002
Using cloud profile radar (CPR/CloudSat) data from 2007 to 2009, the horizontal distributions of non-precipitating warm clouds over global oceans were examined and the vertical variation characteristics of LWC (liquid water content) were analyzed for four major warm cloud types, i.e., cumulus (Cu), stratus (St), stratocumulus (Sc) and altocumulus (Ac). It was found that among all oceanic non-precipitating warm clouds, the proportion of each type is stratocumulus (76.46%), stratus (12.48%), cumulus (7.45%) and altocumulus (3.61%). Stratocumulus plays a dominant role in the total coverage area of non-precipitating warm clouds over oceans. After the global normalization of the sample volume, there are also large differences in the spatial distribution patterns among the four types. Stratocumulus and stratus are mainly concentrated in coastal waters near the west of North and South American continents, while cumulus and altocumulus clouds are widely distributed on the Pacific Ocean, Atlantic Ocean and Indian Ocean, and high occurrences generally appear in the central part of each ocean. In spite of distinct formation regimes and morphologies, the vertical structures of LWC show similar patterns among the four types. From the cloud bottom up to cloud top, LWC was found to increase first and then decrease. The approximately linearly increasing structure in the lower and middle part of the cloud column reflects the quasi-adiabatic growth characteristics of LWC. The upward decreasing structure near the upper part and near cloud top clearly reflects that cloud top is generally strongly affected by the intrusion of overhead dry air. The resulting evaporation of cloud water attenuates heavily downward from the cloud top. The LWC vertical structure was found to be affected by cloud top height and cloud thickness. As cloud thickness increases, the upward increasing part becomes thicker, while the upward decreasing part becomes thinner. Clouds with the same thickness but different cloud top heights also have different LWC structures. This indicates that for a particular type of the clouds, there are differences in the LWC structures corresponding to different periods during the cloud’s generation and development process.
Energy and exergy analyses of seawater desalination system based on absorption heat transformer driven by solar energy
LU Dunfang, HU Peng
2020, 50(5): 570-575. doi: 10.3969/j.issn.0253-2778.2020.05.003
The absorption heat transformer (AHT) can raise the temperature of low-temperature thermal energy. In this study, a seawater desalination system was developed based on the AHT driven by solar energy, where AHT was used to raise the temperature of the solar collector heat source to heat and evaporate the seawater and then condense the steam to obtain fresh water while preheating the seawater. Through energy and exergy analyses of each component in the system, changes in system performance with time were obtained. Comparisons were conducted between the effects of condenser preheating or its absence on system performance. The results show that the seawater preheated by the condenser can increase the average thermal efficiency of the system by 12.9%, the average efficiency by 16.2%, and the average freshwater production by 29.2%.
Some characterizations for the exponential φ-expansiveness of linear skew-product semiflows
YUE Tian, SONG Xiaoqiu
2020, 50(5): 576-580. doi: 10.3969/j.issn.0253-2778.2020.05.004
The exponential φ-expansiveness of linear skew-product semiflows in Banach space was studied. Based on the definition of uniform exponential expansiveness, a linear skew-product semiflow with exponential φ-expansiveness was presented. Some characterizations for exponential φ-expansiveness were obtained via mathematical analysis and operator theory. The results extend some well-known conclusions in the exponential stability theory.
Optimal pricing and advertising strategy concern the bilateral spillover effect of advertising investment
XIA Tian, YANG Feng
2020, 50(5): 581-588. doi: 10.3969/j.issn.0253-2778.2020.05.005
Assuming the firm is highly responsive and has cost advantages and is thus capable of entering the market at the same time as the manufacturer by producing a similar version of the manufacturer’s new product. The impact of this mechanism on the two firms is studied through the bilateral spillover effect of advertisement. The main results are as follows. First, contrary to the traditional marketing concept——“good wine needs no bush”, the better quality the products, the more they need to be advertised. Second, our model explains why the quality of most copycats’ products is relatively poor. Finally, low quality products of copycat firms are expected by the manufacturer as well as the copycat firms. The advertising investment of a copycat firm will always increase its profits and reduce the manufacturer’s loss of profit caused by the copycat entering the market, which allows manufacturer and copycat to coexist in the market harmoniously.
Sparse-Lagrangian FDF simulation of Sandia flame E with modified density coupling
HUANG Lihang, ZHU Minming, YE Taohong
2020, 50(5): 589-595. doi: 10.3969/j.issn.0253-2778.2020.05.006
Sparse-Lagrangian filtered density function (FDF) simulation is performed for Sandia flame E. Sparse-Lagrangian Monte Carlo method is used to solve the scalar FDF transport equations, in which a generalized multiple mapping conditioning (MMC) model is implemented to enforce mixing localness. A modified density coupling method for Sparse-Lagrangian FDF is proposed, in which the conditional mean source term of equivalent enthalpy is fed back directly as the source term in the Eulerian equivalent enthalpy transport equation of large eddy simulation (LES). The results of Sparse-Lagrangian FDF simulation indicated that the new density coupling method is more reasonable than the previous ones in reducing the numerical errors in LES results, and that the simulation results agree well with the experimental data.
A multi-view based semi-supervised classifier with co-regularization for imbalanced data
CUI Wenquan, CHEN Wei, CHENG Haoyang
2020, 50(5): 596-604. doi: 10.3969/j.issn.0253-2778.2020.05.007
A method of constructing a multi-view semi-supervised learning classifier was presented for manifold learning and multi-puncture processing. The multi-view and semi-supervised learning of the data is achieved through recursive optimization, and appropriate labeling and equalization processing, until the efficiency of learning becomes stable. The properties of this multi-classifier were given, for instance, an upper bound of the generalization error, which showed a good capacity for generalization. Simulation and empirical analysis showed that the new method performs well with small samples.
Separation and purification to prepare N-acetylneuraminic acid after oxalic acid hydrolysis of polysialic acid
WU Zhibo, CHEN Xiangsong, WU Jinyong, SUN Lijie, YUAN Lixia, YAO Jianming
2020, 50(5): 605-611. doi: 10.3969/j.issn.0253-2778.2020.05.008
The polysialic acid was obtained from fermentation of escherichia coli, and hydrolyzed to separate, purify and prepare the N-acetylneuraminic acid. In order to study the process conditions of separation and purification to prepare high purity of n-acetylneuraminic acid from the polysialic acid which was hydrolyzed by the oxalic acid, so as to simplify the process and reduce the production cost, the authors investigated emphatically the hydrolysis of the polysialic acid by oxalic acid , contrasted firstly the effects on hydrolysis of polysialic acids between oxalic acids as other conventional hydrolytic acids and determined oxalic acids as hydrolytic acids. The best operating parameters of the oxalic acid hydrolysis of the polysialic acid was determined by the orthogonal experiment: hydrolysis temperature 90 ℃, hydrolysis time 3.5 h, hydrolysis acid concentration 0.1 mol/L and diluted multiples of polysialic acid 5 times. In these conditions, the hydrolyze rate of the polysialic acid was more than 94 %, and the hydrolyze yield was more than 97 %. The separation and purification conditions were optimized through experiments, and the separation and purification process for the preparation of high purity N-acetylneuraminic acid was obtained. In these process conditions, the analytic results of the infrared spectrum and HPLC showed that the purity of the N-acetylneuraminic acid product was 98.5 %, and the yield was 58.4 %.
Dynamic dependence of return and volatility between BRICS stock markets based on TV-Copula-X model
YE Wuyi, DING Yalin, JIAO Shoukun
2020, 50(5): 612-628. doi: 10.3969/j.issn.0253-2778.2020.05.009
The TV-Copula-X model was constructed with the addition of an exogenous variable the dynamic Copula function. Based on the definition of ‘volatility surprise’, the dependence structures of the BRICS were studied from the perspectives of mean spillover and volatility spillover, and whether the structures would be affected by the US stock market. The data of the BRICS and the US stock markets was selected for empirical research. The results show that the BRICS have significant dependence from the aspects of return and volatility. There are asymmetric dependent structures between the volatility of the BRICS but only some countries of BRICS have asymmetric dependent structures between their yields. The US stock market has a certain impact on the interdependence of some BRICS countries, and the correlation between the BRICS stock markets will increase when a financial crisis or positive events occurs.
Dissociative photoionization of dimethyl ether in the energy range of 13.3~14.3 eV
XU Lei, WU Xiangkun, YU Tongpo, ZHOU Xiaoguo, LIU Shilin
2020, 50(5): 629-636. doi: 10.3969/j.issn.0253-2778.2020.05.010
Dissociative photodissociation of dimethyl ether in the photon energy of 13.30~14.30 eV was studied using threshold photoelectron photoion coincidence mass spectrometry, combined with photoionization using a vacuum ultraviolet light source from synchrotron radiation. In this range, the dimethyl ether ions in B2B2 and C2A2 states were prepared, and the main fragment ions were m/z=45, 29 and 31. By subtracting the contribution of the m/z=29 fragment ions, the reliable time-of-flight profile of the m/z=31 fragment ions was obtained. Then the related kinetic energy distribution was derived from fitting the profile. Below 14.00 eV, a unique statistical dissociation was observed for the formation of the m/z=31 ions, while the dissociation mechanism was changed significantly to dual dissociation
The kinetic mechanism of H+ in lysozyme with increasing temperature
LI Mengna
2020, 50(5): 637-644. doi: 10.3969/j.issn.0253-2778.2020.05.011
In this study, Raman spectroscopy was employed to study the kinetic mechanism of lysozyme denaturation at high temperatures induced by
Thermal behavior analysis of 21700 type lithium ion battery during charge-discharge cycles based on electrochemical-thermal model
XU Wenjun, HU Peng
2020, 50(5): 645-653. doi: 10.3969/j.issn.0253-2778.2020.05.012
Lithium ion batteries have become a hotspot in the field of electric vehicles due to their excellent performance of high specific energy, long lifespan, high output power, and wide range of charge-discharge rates. The thermal behavior of the batteries during the charge-discharge cycle has a large impact on their performance, life cycle and safety. In this work, an electrochemical-thermal model is established based on a 21700 type cylindrical lithium ion battery, and corresponding experiments are conducted to validate the model. The thermal behavior during the charge process is analyzed, including the temperature and heat generation distribution. The results show that temperature rise in the charging process is mainly affected by the constant current charging process, the average temperature and heat generation of the battery both exhibit a trend of ascending first and descending later, and the irreversible heat shares a larger proportion of the total heat generation. The thermal behavior is contrasted between the charge and discharge process, and it is found that compared with the discharge process, the thermal behavior at the charge process has the characteristics of quick temperature change and high heat generation peaks.
Risk measurement and backtesting of financial market based on E-GAS-AST model
XIA Yimeng, CHEN Yu
2020, 50(5): 654-668. doi: 10.3969/j.issn.0253-2778.2020.05.013
Concerning financial data's fat-tail,volatility clustering and asymmetry, we raise two data-driven models: E-GAS-AST model and E-GAS-AST-GPD model,and proceed risk measuring and backtesting with real data. Based on generalized autoregressive score(GAS) model,combining asymmetric student-t (AST) distribution with heavy tail,we propose an new model denoted by E-GAS-AST referring to EGARCH model.Considering describing more of tail features,we propose another E-GAS-AST-GPD model with generalized pareto distribution (GPD).Afterwards,the paper computes VaR and ES by studying distributions of residuals,and backtests them separately.Introducing parameter-driven models,such as semi-parameter generalized autoregressive conditional heteroskedasticity(GARCH) model,EGARCH-t model and GJR-GARCH-t model to produce risk measurement we compare them with two above models proposed.Empirical analysis using Dow Jones Index and Shanghai Stock Exchange Composite Index concerning change point reveals E-GAS-AST model is proper to model financial market and measure risk.
Ore-type condition for loose Hamilton cycles in 3-uniform hypergraphs
YU Lei
2020, 50(5): 669-672. doi: 10.3969/j.issn.0253-2778.2020.05.014
A classic result of Ore in 1960 states that if the degree sum of any two independent vertices in an n-vertex graph is at least n, then the graph is Hamiltonian. Here a similar problem for 3-uniform hypergraph was studied and an approximate result was obtained.
Optimization model of correlation interval combination forecasting based on COWA operator and its approximate solutions
ZHOU Daidi, CHEN Huayou, ZHANG Qianyun, JIANG Lihui
2020, 50(5): 673-681. doi: 10.3969/j.issn.0253-2778.2020.05.015
On the basis of Holt exponential smoothing model, multi-layer perceptron (MLP) model and support vector machine (SVM) model, an interval optimal combination forecasting model was built by introducing the concept of COWA operator and correlation coefficient and some properties of the model were discussed. At the same time, the correlation coefficient was used as the contribution index of the single point forecasting method in the combined forecasting, and the Shapley value in the cooperative game was combined to give the approximate solution of the corresponding optimal combined forecasting model. The data of WTI spot price were used to demonstrate the feasibility and effectiveness of the model, and the attitude parameters on COWA operator was done with the sensitivity analysis.
Dynamic analysis of an SIQR model with saturation contact rate and hybrid strategies
MA Yanli, CHU Zhengqing, LI Hongju
2020, 50(5): 682-687. doi: 10.3969/j.issn.0253-2778.2020.05.016
Considering vaccination, quarantine and elimination hybrid strategies, an SIQR epidemic model with saturation contact rate was established. And the global stability of the model was studied by means of both theoretical and numerical ways. Firstly, the threshold-basic reproductive number R0 which determines whether the disease is extinct or not and the conditions for the existence of equilibriums were obtained by the calculation. Secondly, by Liapunov function, it was proved that the disease-free equilibrium P0 is globally asymptotically stable when R0<1. Thirdly, by constructing a suitable Dulac function, it was obtained that the unique endemic equilibrium P* is globally asymptotically stable when R0>1. Finally, some numerical simulations were presented to illustrate the analysis results.
Study on relation between wet deformation of Xuan paper and quality of mounted calligraphy and paintings
GONG Decai, ZHOU Yujun, ZHONG Jiarang, GONG Yuxuan
2020, 50(5): 688-694. doi: 10.3969/j.issn.0253-2778.2020.05.017
Most of the harm to the paintings and calligraphy is related to "the force". However, few studies have been reported on the research of the mechanical behavior. Xuan paper is a primary material of the mounting of Chinese paintings and calligraphy. Dimensional variation occurs upon changes in its moisture content during the drying process, and serious deformation may affect the stability of the paintings and the effects of the mounting. Digital image correlation was used to measure the wet deformation of single-layer Xuan paper and the sample of a mounted painting on two layers of Xuan paper, with considerations of dimensional changes caused by wetting and the influences on the deformation from Xuan paper's fiber orientation upon drying on the wall. The results show that the mechanical properties and wet deformation were related to the fiber orientation of Xuan paper, and that fiber orientation was the main contributing factor in the influence on deformation in drying. In addition, excessive shrinkage in both vertical and horizontal directions was observed in new Xuan paper due to the existence of internal stress. Suggestions are thus provided on improvement, which will help raise the quality of mounting and restoration of cultural relics such as calligraphy and paintings.
Solving multi-station refuse collection problem based on cooperative co-evolutionary algorithm
ZHANG Yuzhou, ZHANG Ziwei
2020, 50(5): 695-704. doi: 10.3969/j.issn.0253-2778.2020.05.018
With the continuous development of the economy and the rapid advancement of urbanization, the amount of refuse produced nationwide is rapidly increasing, and the cost for refuse processing is in turn on the rise, with refuse collection occupying an increasing proportion of it. A complex refuse collection problem is investigated, i.e., the multi-station refuse collection problem (MSRCP). The MSRCP is mapped to the multi-depot vehicle routing problem (MDVRP), and a model for MSRCP with the goal of minimum vehicle transportation cost is established. According to the characteristics of MSRCP, an approach based on Cooperative Co-evolutionary (CC) as external framework is designed for the problem. Firstly, the improved clustering algorithm is used to assign each collection point to the appropriate station. Then, a hybrid genetic algorithm (HGA) is designed for the vehicle routing problem (VRP) with the stations as the depots and MSRCP being divided into some VRPs. Finally, the refuse collection in Daguan District of Anqing City was taken as an example to verify the model and its algorithm, The results show that the proposed algorithm is effective in reducing transportation cost of complex refuse collection problems.
3D time-domain IP forward modeling using unstructured finite element method under uneven terrain
HUANG Du, WU Xiaoping
2020, 50(5): 705-714. doi: 10.3969/j.issn.0253-2778.2020.05.019
It is generally believed that the undulating terrain has little influence on the induced polarization (IP) exploration, because it has no influence under the relatively ideal condition of uniform polarization of the underground medium. However, for the complex medium model with ore body under the condition of undulating terrain, the terrain will certainly have an impact on the induced polarization method. Three have been very few studies on the quantitative characterization of terrain effect on the induced polarization method,mainly because the undulating terrain is not easy to simulate, especially for the three-dimensional model. In this paper, the three-dimensional unstructured finite element numerical simulation of induced polarization is developed. The unstructured mesh is particularly suitable for the numerical simulation of three-dimensional geoelectric model under arbitrary undulating terrain and the study of its influence on induced polarization. With the newly developed method, the three-dimensional induced polarization numerical simulation for plate-shaped and spherical anomaly bodies in rolling terrain is carried out, and the influence of rolling terrain on induced polarization response is discussed. The results show that the asymmetric topography will make the center position of IP anomaly deviate. The larger the slope gradient is, the larger the deviation will be, and the IP amplitude becomes smaller with increasing slope gradient. The asymmetry of polarization anomaly also plays an important role in the topography impact for its IP response.