ISSN 0253-2778

CN 34-1054/N

2020 Vol. 50, No. 4

Display Method:
Original Paper
Limit properties of weighted cumulative sum estimator of change-point in variance
FANG Weijie, JIN Baisuo
2020, 50(4): 389-395. doi: 10.3969/j.issn.0253-2778.2020.04.001
Some limit properties of the weighted cumulative sum(WCS) estimator for the change-point in variance was studied. The consistency and convergence rate of the estimator were proved. In addition, the asymptotic distribution of the change-point estimator under local alternative hypothesis, which was a two-side Brownian motion with a drift, was developed. By the numerical solution of asymmetric distribution, an asymptotic confidence interval was constructed. Simulation results and a real data example show that the proposed estimator has a good performance in the application.
Weyl type theorem and hypercyclic property for bounded linear operators
WANG Jing, CAO Xiaohong
2020, 50(4): 396-401. doi: 10.3969/j.issn.0253-2778.2020.04.002
Let H be an infinite dimensional separable complex Hilbert space and B(H) be the algebra of all bounded linear operators on H. T∈B(H)satisfies Browder’s theorem if σ(T)\σw(T)π00(T) or σw(T)=σb(T). If σ(T)\σw(T)=π00(T), Weyl’s theorem holds for T, where σ(T), σw(T), σb(T) denote the spectrum set, Weyl spectrum, and Browder spectrum respectively, and π00(T)={λ∈iso σ(T):0<dim N (T-λI)<∞}. Using the newly defined spectrum, the sufficient and necessary conditions for operator functions satisfying Weyl type theorem were studied if T is a hypercyclic operator. In addition, the spectrum mapping theorem for some new spectrums was discussed.
The maximum signless Laplacian separator of tricyclic and quadricyclic graphs
JU Hongjuan, LEI Yingjie
2020, 50(4): 402-408. doi: 10.3969/j.issn.0253-2778.2020.04.003
Let G be a graphs of order n and q1(G)≥q2(G)≥…≥qn(G) be its Q-eigenvalues. The signless Laplacian separator SQ(G) of G is defined as SQ(G)=q1(G)-q2(G). The maximum signless Laplacian separator of tricyclic and quadricyclic graphs was studied, and the corresponding extremal graphs were characterized.
The product of two σ-supersoluble groups
毛月梅, 马小箭
2020, 50(4): 409-417. doi: 10.3969/j.issn.0253-2778.2020.04.004
Let Nσ denote the classes of all σ-nilpotent groups and GNσ be the σ-nilpotent residual of G. We say that G is σ-supersoluble if each chief factor of G below GNσ is cyclic. A subgroup H of G is said to be completely c-permutable with a subgroup T of G if there exists an element x∈〈H,T〉 such that HTx=TxH.
A modified coherent diffraction algorithm based on the total variation algorithm for insufficient data
JIANG Qi, LIU Jianhong, GUAN Yong, BAI Haobo, LIU Gang, TIAN Yangchao
2020, 50(4): 418-427. doi: 10.3969/j.issn.0253-2778.2020.04.005
X-ray coherent diffraction imaging (CDI) is a lensless imaging technology. Its basic principle is to illuminate an isolated sample with a highly coherent X-ray beam, then collect the information of the coherent diffraction pattern in the far field, and last restore the real structure information of the sample from the diffraction pattern by using the the CDI algorithm. Due to the limitation of experimental technology experimental data are usually defective, thus tolerance to noise and missing data is an important indicator for the CDI algorithm. Here a modified coherent diffraction algorithm by adding the total variation (TV) constraint into the CDI reconstruction algorithm was developed to improve the tolerance to noise and missing data. Then the performance of the modified coherent diffraction algorithm based on the total variation algorithm was verified using simulation data and experimental data. The results show the modified algorithm can accelerate convergence and improve the tolerance to noise and missing data.
Simulating method of sodium-water reaction accident in steam generator of sodium-cooled fast reactor
XIANG Yang, TAN Chao, CHEN Yunlong, ZHU Jiayin, YU Shuwen, ZHAO Pinghui
2020, 50(4): 428-435. doi: 10.3969/j.issn.0253-2778.2020.04.006
The simulation of sodium-water reaction accident is the difficulty in the development of the simulating system of sodium cooled reactor. In order to solve this problem, a simulation program of sodium-water reaction accident was designed based on the mathematical physical equation of sodium-water reaction accident caused by water leakage in heat transfer tube of sodium-cooled fast reactor steam generator. Based on SimTherm thermal-hydraulic simulation program and the structure of sodium-cooled fast reactor, a second-circuit model of sodium-cooled fast reactor was designed for the study of sodium-water reaction accidents. By coupling the simulation program of sodium-water reaction accident with SimTherm, the simulation of sodium-water reaction accident was realized, which provides a new idea for the development of sodium-cooled fast reactor simulator.
Fabrication of dispersion ceramic nuclear fuel pellets with a highly uniform distribution of nuclide by 3D printing
LIAN Chao, GUO Lin, CHANG Zhenqi
2020, 50(4): 436-441. doi: 10.3969/j.issn.0253-2778.2020.04.007
The distribution of nuclear particles in dispersion-type nuclear fuel pellets is a crucial property since it strongly influences in-pile fuel behaviors. A way of improving the distribution of the fissile elements in the dispersion-type nuclear fuel pellets was presented. In this study, the selective laser sintering (SLS) was introduced to the fabrication of the dispersion nuclear fuel pellets to ensure a highly uniform distribution of the nuclear fuel microspheres in the pellet. A detailed technical route and fabrication processes was described. The effect of the size of MgO particle, scanning parameters and the post-processing of green nuclear fuel pellets were also investigated. The cross-sectional views of the final pellet showed that the distribution of nuclear fuel microspheres in the pellet was very homogeneity.
Study on the influence of radiation of particle groups on arc volt-ampere characteristics
QIN Peng, LIAO Mengran, XIA Weidong, WANG Cheng
2020, 50(4): 442-449. doi: 10.3969/j.issn.0253-2778.2020.04.008
When particle groups are injected directly into a plasma torch, the influence of the particle groups on the arc plasma is an important factor in the design of the plasma torch. This paper introduces the P-1 radiation model, which is used to describe the radiation between particle groups. Combined with the P-1 radiation model, the Elenbass-Heller equation is modified and then solved to probe into the radiation influence of the graphite particle groups on the volt-ampere characteristics of the arc plasma. The results show that the radiation of the graphite particle groups increases the heat conductivity of the arc, the arc is compressed by cooling down, and the intensity of the electric field of the arc increases. At the same time, the effect of particle group radiation on the intensity of the electric field is more evident along with the larger arc channel radius. Moreover, the effect on the argon arc plasma is much larger than its effect on the hydrogen arc plasma. It is recognized by the calculation of the particle radiation that the particle group radiation mainly plays an important role in the location near the wall. At the edge of the cold wall, the particle group radiation functions as net absorption, and the heat transferred to the cold wall is reduced.
Interface passivation by Al2O3 and SnO2 at the CdTe solar cell front contact
ZHENG Genhua, WANG Dongming, WU Lingling, WANG Guangwei, CAI Yanbo, WANG Deliang
2020, 50(4): 450-456. doi: 10.3969/j.issn.0253-2778.2020.04.009
Al2O3 and SnO2 thin layers employed as the passivation layer for MgxZn1-xO(MZO)/CdTe thin-film solar cells were grown by RF magnetron sputtering. Time-resolved photoluminescence (TRPL)spectroscopy spectra show that the minority carrier lifetime of the MZO/Al2O3/CdTe structure is much longer than that of the MZO/CdTe structure, indicating that Al2O3 has a strong passivation effect on CdTe. However, the CdTe solar cells with Al2O3 as the passivation layer demonstrate serious “S-kink” in the light current density-voltage curves. The band alignment of solar cells with different passivation layer were analyzed by X-ray photoelectron spectroscopy (XPS). The large conduction band offset between Al2O3 and CdTe was found to be responsible for the “S-kink” for the solar cells with Al2O3. By controlling the thickness of the SnO2 layer, quantum size effect can be used to adjust the conduction band offset between SnO2 and CdTe, thus reducing the “S-kink” phenomenon, improving the filling factor and short-circuit current density. A solar cell with an efficiency of 9.7% has been fabricated. This study demonstrates that large conduction band offset is the main reason for the “S-kink” in the J-V curves, and that reducing the conduction band offset can effectively decrease the “S-kink” phenomenon and increase the solar cell efficiency.
Verification and characterization of circRNAs in two holophilic archaea
LUO Wenqi, WANG Xiaolin, YANG Yan, SHAN Ge, CHEN Liang
2020, 50(4): 457-466. doi: 10.3969/j.issn.0253-2778.2020.04.010
Circular RNA (circRNA) is a special type of RNA, which forms covalent-closed continuous loop in most cases through 5’ to 3’ ends via back-splicing. CircRNAs demonstrate a certain degree of conservation and show some tissue specificity in multicellular animals. Archaea is one of the three domains of life, and archaeal organisms often live in high temperature, high salt, low oxygen, or other extreme environments.
Study on factors associated with urinary albumin-to-creatinine ratio among adults with type 1 diabetes mellitus
DING Yu, ZHENG Xueying, YANG Daizhi, LING Ping, WEI Xueying, LIU Ziyu, LIN Qiongyan, YAN Jinhua, WENG Jianping, LUO Sihui
2020, 50(4): 467-473. doi: 10.3969/j.issn.0253-2778.2020.04.011
Objective Diabetic kidney disease (DKD) is closely related to end-stage renal failure and increased risk of cardiovascular disease in type 1 diabetes mellitus (T1DM). To investigate factors associated with urinary albumin-to-creatinine ratio (UACR) and establish the prediction model for elevation of UACR among adults with T1DM. Methods Eligible adults with T1DM from Guangdong Type 1 Diabetes Translational Study who were enrolled between January, 2016 and December, 2017. Basic characteristics and clinical information were collected. All patients were divided into two groups: normal UACR group (UACR < 30 mg/g) and elevated UACR group (UACR ≥ 30 mg/g) according to their UACR level. To screen factors that were potentially associated with UACR, comparison of clinical variables between the two groups were performed. Logistic regression analysis and Nomogram model were used to explore major factors associated with UACR and to predict the probability of UACR elevation. Results A total of 495 patients were enrolled, with a mean age of (34.44±11.65) years and diabetes duration of (7.83±6.22) years. Among them, 296 patients (59.8%) were women. 385 patients (77.8%) were assigned to the normal UACR group and 110 patients (22.2%) to the elevated UACR group. Findings from the comparisons between the two groups demonstrated that diabetes duration, systolic blood pressure(SBP), diastolic blood pressure(DBP), resting heart rate, glycosylated hemoglobin A1c(HbA1c), estimated glucose disposal rate (lneGDR), hypertension were associated with UACR. The results of logistic regression showed that lneGDR [OR=0.33 (95%CI,0.17~0.60), P<0.05] was a protective factor from UACR elevation, while resting heart rate [OR=1.03 (95% CI, 1.00~1.05), P<0.05] and presence of hypertension [OR=2.17 (95% CI, 1.29~3.63), P<0.05] were risk factors. The Nomogram model suggested that a higher probability of UACR elevation was associated with lower lneGDR (i.e., greater insulin resistance), higher resting heart rate, longer diabetes duration and the presence of hypertension. Conclusion Many factors were associated with UACR among adult T1DM patients in China. It is possible to reduce the incidence of UACR by improving insulin resistance, controlling resting heart rate and blood pressure, so as to provide ideas for the prevention and control of DKD among adults with type 1 diabetes mellitus.
The value of coagulation molecular markers TAT, PIC, TM and t-PAIC in early diagnosis of DIC
JIANG Dongxue, ZHAI Zhimin
2020, 50(4): 474-478. doi: 10.3969/j.issn.0253-2778.2020.04.012
Objective To explore the clinical significance of thrombin molecular marker in disseminated intrascular coagulation (DIC), which include thrombin-antithrombin complex (TAT), thrombomodulin (TM), plasmin-antiplasmin inhibitor complex (α2-plamininhibitor-plasmin complex,PIC) and tissue plasminogen activator inhibitor complex (t-PAIC) .Methods This study included 233 patients with bleeding tendency or thrombosis, according to the 2017 edition of the Chinese disseminated intravascular coagulation diagnostic score system (CDSS),who were divided into the dominant DIC group, pre-DIC group and non-DIC group. The differences in laboratory indicators between groups were compared, and its value in the early diagnosis of DIC was evaluated.The molecular markers were measured by qualitative chemiluminescence enzyme immunoassay performed on HISCL automated analyzers.All patients with suspected DIC were followed for 7 days to screen for development of overt-DIC.Results In patients with overt-DIC, TAT, TM, PIC were significantly higher than those in non-DIC patients, and t-PAIC was statistically insignificant between the overt-DIC and non-DIC groups. TAT, TM, PIC, t-PAIC levels were significantly higher in patients with pre-DIC than in non-DIC patients.The AUC shows that the combined diagnostic curve of TAT, TM, PIC, and t-PAIC is 0.887,and AUC combined PT, APTT, and D-D is 0.933.Conclusions The combination of TAT, TM, PIC and t-PAIC can improve the early diagnosis rate of DIC and provide optimal timing for early clinical intervention and treatment.
Vocational aptitude: An empirical study of its assessment validity and effects
WENG Qingxiong, LI Yanfei
2020, 50(4): 479-496. doi: 10.3969/j.issn.0253-2778.2020.04.013
Based on the Holland occupational classification and situational judgment tests, taking Holland’s enterprising jobs as an example, a new vocational aptitude assessment tool was developed. A mediation model was developed and tested, which demonstrates the indirect effects of vocational aptitude on task performance via person-job fit and work engagement, and the moderating effects of person-group fit. Data from 471 effective samples was used to conduct an empirical analysis. The results revealed that: ①vocational aptitude exerts a significantly positive effect on task performance; ②vocational aptitude has an indirect effect on task performance through person-job fit and work engagement, respectively; ③person-job fit and work engagement play significantly as serial mediators between vocational aptitude and task performance;④the examined mediating effects are moderated by person-group fit.
Product strategy and pricing research of the luxury companies: Considering the characteristics of consumers in the new era
ZHANG Jialei, WANG Manman
2020, 50(4): 497-515. doi: 10.3969/j.issn.0253-2778.2020.04.014
Based on the research background of the oligopoly market, status utility was applied to luxury goods customization and the pricing of different products (standard and customization) in the luxury market was studied and a comparative analysis of four different product strategies was given. Four product strategies was proposed: ①product strategy with only pure-standard products, ②product strategy with customized products, ③multi product strategy that consumers can not freely choose the customization, ④multi product strategy that consumers can freely choose the customization. For these four strategies, the optimal pricing of different product strategies and the optimal decision of the company’s different production costs were explored, which led to the following conclusions: first, the effect of status utility on the pricing of customized products is more important than that of standard products; second, based on the comparative analysis of profits, the optimal choice of product strategy is given, and the choice of the company’s product strategy depends on the flexibility of production. In the expansion research, some profit analysis under the competitive market was discussed for the pure standard product strategy.
Exchange rate prediction method based on ARIMA-HPSO-Elman combined model with SSA: Based on the central parity rate data of USD/CNY
YANG Jie, WANG Xiangning
2020, 50(4): 516-527. doi: 10.3969/j.issn.0253-2778.2020.04.015
Exchange rate has the characteristics of both linear and non-linear mixed behavior. Single linear model and non-linear model are not perfect for forecasting exchange rate.Here the central parity rate series of USD/CNY exchange rate was studied. Firstly, the SSA method was used to denoise the exchange rate series, and ARIMA model was established to fit and predict the reconstructed exchange rate series to extract the linear components of the original exchange rate series. Secondly, the residual part was modeled and predicted by Elman neural network optimized by hybrid particle swarm optimization algorithm based on crossover and mutation. The sum of the results was the predicted value of the original exchange rate series. Empirical results show that CNY exchange rate fluctuation has the characteristics of periodic oscillation. On the 30-day forecast outside the sample of exchange rate series, the performance of the combination model based on SSA method is better than that of the single model and the combination model without SSA method in the short term.
Analysis of the characteristics of satellite-derived multiple channel microwave emissivity difference vegetation index (EDVI) over different vegetation types
HU Jiheng, LI Rui, WANG Yu, WANG Yipu, FU Yuyun
2020, 50(4): 528-541. doi: 10.3969/j.issn.0253-2778.2020.04.016
The satellite-derived microwave land surface Emissivity Difference Vegetation Index (EDVI) is a good indicator of vegetation water content (VWC). And it can be used under a cloudy sky and over dense vegetation areas where satellite optical vegetation index can be easily saturated. Previous studies on EDVI used the two frequencies of 19 and 37 GHz only. The associated EDVI can only represent VWC in one single layer of the canopy. Measurements from Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) onboard NASA’s Aqua satellite provided multiple choices of satellite remote sensing VWC with EDVI. In this study, multiple source measurements, including microwave brightness temperature from AMSR-E, cloud parameters from Moderate-resolution Imaging Spectroradiometer (MODIS), and reanalysis of atmosphere states from ECMWF were synergized, to retrieve the microwave land surface emissivity at 6.925, 10.65, 18.7 and 36.5 GHz in eastern and southeastern Asia from 2003 to 2010. The retrievals were then used to define multiple channel EDVIs of EDVI(6v, 37v),EDVI(10v, 37v) and EDVI(18v, 37v) and the characteristics of those EDVIs over forest and cropland areas were studied. The results showed that, EDVI(6v, 37v) and EDVI(10v, 37v) are greater than EDVI(18v, 37v) in forest dominated areas. This is most likely due to the fact that the penetration depth of EDVI(6v, 37v) and EDVI(10v, 37v) are deeper than that of EDVI(18v, 37v), thus indicating relatively more VWC in thicker canopy layer of the forest. The differences among the three EDVIs can be used to represent the vertical distribution of VWC in upper, middle and lower layers of high and dense vegetation. However, for the shallow and sparse vegetation without significant vertical variation of VWC, the differences among the three EDVIs are too small to be used.
Phase field simulation of an extended dislocation passing through void and inclusion under shear stress
GUO Wenhui, NI Yong
2020, 50(4): 542-550. doi: 10.3969/j.issn.0253-2778.2020.04.017
The dynamics of the extended dislocation passing through the void and inclusion in the face-centered cubic (FCC) crystals of aluminum (Al) and copper (Cu) under shear stress were simulated by phase-field method combined with the phase-field microelasticity (PFM) theory and the Peierls-Nabarro (PN) model, respectively. The PFM theory was employed to calculate the long-range elastic interaction between the dislocation and the void (or the inclusion phase), the PN model was used to describe the structure of the extended dislocation based on the one-dimensional crystal energy function, and the Ginzburg-Landau dynamic equation was used to describe the movement of the dislocation. The simulated results showed that when the dislocation slips to the void, the dislocation is attracted to the edge of the void first and then pinned and finally depinned. When the dislocation slips to the inclusion phase, the dislocation is first bent by the inclusion and then passes through the inclusion with a dislocation loop left. Moreover, in the case that the stacking fault (SF) energy is relatively low, it was found that the SF narrows when the extended dislocation approaches the void (or the inclusion phase). While an extended dislocation passes through the void (or the inclusion phase), the leading partial dislocation passes through the void first, and then the trailing partial dislocation passes through the void, which is also accompanied by the phenomenon of SF broadening. Our simulation results are not only consistent with the previous atomic simulated results, but also further reveal the effects of stress amplitude and SF energy parameters on the dynamics of the extended dislocation passing through the void (or the inclusion) at a longer time scale.