ISSN 0253-2778

CN 34-1054/N

2018 Vol. 48, No. 5

Display Method:
Original Paper
A note on the eigenfunction in a relativistic closed Toda chain
WEN Xiaocheng
2018, 48(5): 347-356. doi: 10.3969/j.issn.0253-2778.2018.05.001
Recently, the eigenfunction for an N-particle relativistic closed Toda chain has been calculated by association with gauge theory. The results involve only the behavior of the eigenfunction of the energy level but do not include nonphysical energy. A conjecture was thus proposed to determine the eigenfunction of the nonphysical energy and a numerical calculation was conducted to prove that it is impossible to get an entire eigenfunction of the nonphysical energy. Because of the pole cancellation condition, the relation between the open and closed Bogomol’nyi-Prasad-Sommerfield (BPS) invariants could be derived.
The shock solution to a class of singularly perturbed time delay nonlinear boundary value problem
ZHU Hongbao
2018, 48(5): 357-360. doi: 10.3969/j.issn.0253-2778.2018.05.002
The shock solution to a class of singularly perturbed time delay nonlinear boundary value problem were considered. The solution was obtained by using the matching asymptotic expansion, and the uniform validity of the solution was proved by the theory of differential inequalities.
Optimal algebraic decay of solutions for 2D Navier-Stokes equations with partial dissipation
ZHANG Zhaoyun, XIE Qianqian, JIA Yan, DONG Boqing
2018, 48(5): 361-366. doi: 10.3969/j.issn.0253-2778.2018.05.003
The optimal algebraic decay of solutions for two-dimensional Navier-Stokes equation with partial dissipation was studied. By developing the classic Fourier splitting methods together with inductive methods, the higher-order derivatives of solutions in the optimal algebraic rates was obtained.
Short-bunch-length operating-mode design at HLS-Ⅱ storage ring for coherent terahertz radiation
GAO Weiwei, WANG Lin
2018, 48(5): 367-373. doi: 10.3969/j.issn.0253-2778.2018.05.004
Coherent THz radiation has become an important research tool in many basic science studies and applied research. A detailed simulation process for coherent THz (terahertz) radiation at the HLS-Ⅱ (Hefei Light Source-Ⅱ) storage ring with 2 mm bunch lengths was presented. The low-alpha mode and harmonic cavity mode were two methods applied here for coherent THz radiation. The related issues of short bunch length, including beam instability threshold current, radiation power, and longitudinal phase-space damping progress, were also discussed.
The source of diffusion equation and amplitude attenuation equation of density matrix by using coherent state representation
YU Zhisong, YU Ziyang, FAN Hongyi
2018, 48(5): 374-377. doi: 10.3969/j.issn.0253-2778.2018.05.005
Diffusion and amplitude dissipation are two major mechanisms of photon field’s evolution, which may be used in quantum controlling and in generating new photon fields. Here two time-evolution equations for diffusion and dissipation from the physical point of view were derived, i.e., the coherent state representation was employed to demonstrate that these two equations’ classical correspondence makes common sense in general. In this way the two equations are reasonable without any doubt. Consequently, it was shown that the dissipation of a binomial state is embodied in its paramenter r0→r0e-2χt,χ is the dissipation coefficient.
Corrosion behavior of T91 steel in liquid lead-bismuth eutectic at 550 ℃ under different tensile stresses
HU Yadong, LUO Lin, JIANG Zhizhong, LI Chunjing, CHEN Jianwei
2018, 48(5): 378-384. doi: 10.3969/j.issn.0253-2778.2018.05.006
To efficiently evaluate the corrosion behavior of T91 steel in lead-bismuth eutectic (LBE) under different stresses, a corrosion experiment of small tapered conical specimen of T91 in LBE with an oxygen concentration of 1×10-6 wt% at 550 ℃ under 0~180 MPa was carried out. The results showed that the (Fe,Cr)3O4 and internal oxidation zone always exist, but the Fe3O4 peels off severely under tensile stress, and its fragments become smaller with the increase of stress; (Fe,Cr)3O4 has two sub-layers, which is caused by different Cr enrichments; As the tensile stress increases, the cracks increase in number and size, extending continuously to the matrix direction, running through the whole (Fe,Cr)3O4 by the time the tensile stress reaches 180 MPa. Moreover, with the tensile stress increasing, the thickness of each oxide layer increases, but the rate of incrassation decreases constantly.
Numerical investigation on flapping of a flexible filament in a viscoelastic fluid flow
LU Yang, QUE Xia, LIU Nansheng
2018, 48(5): 385-391. doi: 10.3969/j.issn.0253-2778.2018.05.007
The flapping of a flexible filament in a uniform incoming flow of viscoelastic fluid of polymeric solution was numerically investigated. This paper aims at examining the effects of fluid elasticity on the filament flapping behavior by a comparison with its counterpart in the Newtonian flow. Specifically, the FENE-MCR model was used as the constitutive equation for the viscoelastic fluid. The simulations of fluid flow were based on the lattice Boltzmann method to solve the Navier-Stokes (N-S) equations, the finite difference method to solve the constitutive equation of the polymer stress, the finite element method to solve the motion equation of the filament, and a penalty immersed boundary method to deal with the fluid-structure interaction. From the numerical results obtained, it was found that for a relatively weak fluid elasticity of We<20, the critical mass ratio of the filament to the fluid increases dramatically for the transition from a steady state to a periodically flapping state. However, for a stronger elasticity of We>20, increasing We number leads to a tendency of the critical mass ratio to be an approximate value of ~0.43. Moreover, it was demonstrated that increasing We number is also commensurate with the decrease of the time-averaged drag coefficient, the flapping amplitude, and the flapping frequency of the flexible filament. The above-mentioned facts indicate that enhancing the fluid elasticity has the increasing suppressing effects on the filament flapping behaviors.
A new data inversion analysis method based on digital filtered pump-stop data of hydraulic fracturing
WEN Jiexiong, TIAN Wei, BI Quanfu, LI Xuebin, LU Detang
2018, 48(5): 392-399. doi: 10.3969/j.issn.0253-2778.2018.05.008
Hydraulic fracturing is currently the main method of exploiting tight gas and oil. The pump-stop pressure and flow-rate data measured during hydraulic fracturing process contains a great deal of important information, such as the formation pressure, permeability and fracture half-length. These parameters are significant judgment to decide post-fracturing mining system. A new method of pump-stop data-inversion analysis method based on digital filtered pump-stop flow-rate and density-changing pressure data of hydraulic fracturing was presented. Firstly, the ground pressure was converted to the well bottom pressure according to the vertical pipe flow theory. The obtained bottom pressure data, also known as pump-stop pressure data, was processed through the FIR filter to eliminate the interference of water hammer and other noise signals. Finally, the filtered data, which contains the information of formation permeability and initial pressure, was processed according to vertical fracture well test analysis. This new method has been proved reliable by comparing it with pressure build-up, making real-time evaluation of fracture and formation information possible.
Application of response surface method and BFGS algorithm in well test analysis
LI Daolun, CHEN Gang, ZHA Wenshu, XU Enhua
2018, 48(5): 400-408. doi: 10.3969/j.issn.0253-2778.2018.05.009
Well test analysis is a typical inverse problem that analyzes the formation and wellbore parameters using the time-varying data of the bottom hole pressure measured during shut-in. Based on the response surface method, a new method for automatically evaluating parameters was presented to solve the numerical well test interpretation. Select the uncertain parameters and their scope, the experimental examples were determined, and then the polynomial approximation function was obtained by matching method, that is, constructing the response surface model. Using the response surface model, the objective function of the deviation between the calculated value and the actual observation value was constructed. The minimum value of the objective function was obtained by using the BFGS algorithm and the Latin hypercube sampling to obtain the uncertain parameter value. The numerical examples show that the method can effectively match the bottom hole pressure and the pressure derivative, and thus has a good potential for application.
The impact of financial and fiscal decentralization on investment and consumption ratio
HE Jun, WANG Xuerong, CAO Su
2018, 48(5): 409-419. doi: 10.3969/j.issn.0253-2778.2018.05.010
Based on the analysis and testing of provincial panel data in China from 1998 to 2014, financial decentralization was taken as the threshold variable to investigate the nonlinear relationship between China’s financial decentralization and ratio of investment to consumption. The results show that: ① At different levels of financial decentralization, China’s financial decentralization has different effects on the ratio of investment to consumption, which is characterized by the nonlinear characteristics of “double threshold effect”. ② The nonlinear relationship varies with different level of financial decentralization. In provinces with low levels of financial decentralization, financial decentralization is positively related to the ratio of investment to consumption; in the provinces with medium levels of financial decentralization, the relationship between financial decentralization and the ratio of investment to consumption is uncertain; in the provinces with high levels of financial decentralization, financial decentralization is negatively related to the ratio of investment to consumption. ③ Fiscal decentralization has some influence on the nonlinear relationship between financial decentralization and the ratio of investment to consumption. The combined effect of financial and fiscal decentralization has expanded the ratio of investment to consumption. ④ The number of provinces with high levels of financial decentralization in China is quite small, with most of the provinces being still in the stage of medium and low financial decentralization. In order to reduce the ratio of investment to consumption, the financial decentralization process should be promoted vigorously in provinces with low or medium levels of financial decentralization.
Optimal investment of DC pension under the inflation and loss aversion
WANG Chuanyu, FU Chunyan, SHENG Guoxiang
2018, 48(5): 420-430. doi: 10.3969/j.issn.0253-2778.2018.05.011
The optimal investment problem of DC pension under the inflation and loss aversion was studied.First, the stochastic differential equation of the real stock price after inflation was discounted by the Ito formula. Then, in the framework of prospect theory, considering the problem of maximizing the expected utility of terminal wealth discounted by inflation at retirement, the explicit solution of the optimal investment strategy of DC pension at any time before retirement was derived by using the martingale method.In the end, the impact of the loss aversion on the optimal investment strategy of DC pension was analyzed using the Monte-Carlo method.