Bayesian algorithm based on auxiliary variables for estimating item response theory models with non-ignorable missing response data

Zhang Jiwei,Zhang Zhaoyuan,Tao Jian 한국통계학회 2021 Journal of the Korean Statistical Society Vol.50 No.4

Missing responses generally exist in educational and psychological assessments. The statistical inference will lead to serious deviation if the missing responses are not properly modeled in the framework of non-ignorable missing mechanism. In this current study, it is studied whether the different missing mechanism (ignorable missing and non-ignorable missing) models are appropriate to analyze the missing response data from the perspective of parameter estimation and model assessment. In addition, a highly effective Bayesian sampling algorithm based on auxiliary variables is used to estimate the complex models. Compared with the traditional marginal likelihood method and other Bayesian algorithms, the advantages of the new algorithm are discussed in detail. Based on the Markov Chain Monte carlo samples from the posterior distributions, the deviance information criterion (DIC) and the logarithm of the pseudomarignal likelihood (LPML) are employed to compare the different missing mechanism models. Four simulation studies are conducted and a detailed analysis of PISA science data is carried out to further illustrate the proposed methodology.

Isolation, Identification, and Expression of Microbial Cellulases from the Gut of Odontotermes formosanus

( Jiwei Duan ),( Jun Liu ),( Xueling Ma ),( Yue Zhang ),( Xiaohua Wang ),( Kai Zhao ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.1

Termites are destructive to agriculture, forestry, and buildings, but they can also promote agro-ecosystem balance through the degradation of lignocellulose. Termite-triggered cellulose digestion may be clarified through microbial metabolism of cellulose products. In the present study, we characterized the activities of cellulase and its three components synthesized by the cellulase-producing fungal strain HDZK-BYTF620 isolated from the gut of Odontotermes formosanus. The protein components of cellulases were synthesized by strain HDZK-BYTF620, which were isolated and characterized using polyacrylamide gel electrophoresis, and the expression of the cellulases was studied at the proteome level.

Atomistic simulations of defect accumulation and evolution in heavily irradiated titanium for nuclear-powered spacecraft

Guopeng Zhang,Bin Cai,Hai Huang,Xiaoting Yuan,Longjingrui Ma,Jiwei Lin Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6

Titanium alloys are expected to become one of the candidate materials for nuclear-powered spacecraft due to their excellent overall performance. Nevertheless, atomistic mechanisms of the defect accumulation and evolution of the materials due to long-term exposure to irradiation remain scarcely understood by far. Here we investigate the heavy irradiation damage in a-titanium with a dose as high as 4.0 canonical displacements per atom (cDPA) using atomistic simulations of Frenkel pair accumulation. Results show that the content of surviving defects increases sharply before 0.04 cDPA and then decreases slowly to stabilize, exhibiting a strong correlation with the system energy. Under the current simulation conditions, the defect clustering fraction may be not directly dependent on the irradiation dose. Compared to vacancies, interstitials are more likely to form clusters, which may further cause the formation of 1/3<1210> interstitial-type dislocation loops extended along the (1010) plane. This study provides an important insight into the understanding of the irradiation damage behaviors for titanium.

Reliability analysis based on the principle of maximum entropy and Dempster–Shafer evidence theory

Qiu Jiwei,Zhang Jianguo,Ma Yupeng 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2

The Probability density functions (PDFs) of some uncertain parameters are difficult to determine precisely due to insufficient information. Only the varying intervals of such parameters can be obtained. A method of reliability analysis based on the principle of maximum entropy and evidence theory was proposed to address the reliability problems of random and interval parameters. First, the PDFs and cumulative distribution functions of interval parameters were obtained on the basis of the principle of maximum entropy and Dempster– Shafer evidence theory. Second, the normalized means and standard deviations of interval parameters were obtained using the equivalent normalization method. Third, two explicit iteration algorithms of reliability analysis were proposed on the basis of the advanced firstorder and second-moment method to avoid solving the limit state function and obtain the reliability index. Finally, the accuracy and efficiency of the proposed methods were verified through a numerical example and an engineering case.

A New Result on the Stability and Convergence of Self-tuning Adaptive Control

Weicun Zhang,Yuejin Song,Jiwei Liu 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10

Among various types of self-tuning control schemes, only one-step-ahead self-tuning control of deterministic plant and minimum variance self-tuning control of stochastic plant can guarantee the stability and convergence of closed-loop system without requiring the convergence of parameter estimation. This paper presents a new result that the convergence of parameter estimates is not necessary for the stability and convergence of a general self-tuning control system comprising of any admissible control strategy and any admissible parameter estimation algorithm. This breakthrough result is owing to the adoption of a new type of virtual equivalent system: slow switching control system, whose stability and tracking performance are guaranteed under mild conditions.

Study of temperature-induced structural evolution in (Na0.5Bi0.5)TiO3- (K0.5Bi0.5)TiO3-(K0.5Na0.5)NbO3 lead-free ceramics

Xing Liu,Jiwei Zhai,Bo Shen,Feng Li,Yang Zhang,Peng Li,Baihui Liu 한국물리학회 2017 Current Applied Physics Vol.17 No.5

In this work, the temperature-induced structural evolution in 0.79(Na0.5Bi0.5)TiO3-0.2(K0.5Bi0.5)TiO3- 0.01(K0.5Na0.5)NbO3 (NKBNT) lead-free ceramics was investigated by Raman microscopic spectroscopy combined with electrical macroscopic measurements. The NKBNT ceramics possess the local structure with the coexisted rhombohedral R3c and tetragonal P4bm polar-nano-regions (PNRs). The R3c and P4bm PNRs coexist in a wide temperature range, then the local structure transforms to the P4bm PNRs around the temperature of dielectric maximum (Tm) evidenced by the doublet splitting of Ti-O modes (peak B) and oxygen octahedral vibrational modes (peak C). The discontinuous changes of wavenumber and linewidth of peak B2 and peak C3 as well as the dielectric local maxima around the rhombohedral-tetragonal phase transition temperature (TRT) are considered to result from the thermal evolution of R3c and P4bm PNRs. The macroscopic changes of non-polar phase with electric field and temperature were investigated by the temperature-dependent polarization-electric field (P-E) loops, current-electric field (I-E) loops and bipolar strain (S-E) curves. The electric-field level necessary to form the long-range ferroelectric order from non-polar phase associated with the stability of the induced ferroelectric phase depends strongly on the temperature.

Prediction of Power Generation in China Using Process Neural Network

Jianghua Ge,Jiwei Wen,Chuntao Zhang,Yaping Wang,Gang Ding 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.5

The power generation prediction problem can be seen as a time series prediction problem in nature. The traditional time series prediction methods based on regression analysis do not take account into the time accumulation effect existed in the time series due to their discrete input values. This limitation causes the low prediction accuracy of the time series prediction methods based on regression analysis. To solve this problem, a power generation time series prediction model based on the process neural network is proposed. The inputs of the proposed prediction model can be continuous time-varying functions. The time accumulation effect existed in the power generation time series can be expressed and computed by the integration operator of the process neural network. The proposed prediction model is trained and the efficiency of the proposed prediction model is tested by the month power generation data form January 2001 to April 2012, and the comparison experiment results indicate that the process neural network performs better than the auto regression analysis.

Improved temperature stability of Ba0.5Sr0.5TiO3/ZnAl2O4 ceramics by controlling microstructure with sintering behavior

Yuze Xue,Mingwei Zhang,Le Xin,Luchao Ren,Panpan Lv,Hang Zhan,Jing He,Jiwei Zhai 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.2

0.2ZnAl2O4/0.8Ba0.5Sr0.5TiO3 ceramics with good dielectric temperature stability were synthesized by controlling sinteringbehavior. The relationship between sintering conditions, microstructure, and dielectric properties of ceramics was studied. Cubic structures were confirmed in all ceramics. Double sintering (DS) behavior can effectively improve the density, and thegrain size has no obvious change compared with non-repeated sintering. The maximum dielectric permittivity (220 at 10 kHz)and minimum leakage current (3.98×10-6 A/cm2 at 0.25 kV/cm) are obtained in the DS ceramics, which is superior to thoseof the single sintering ceramics. This can be ascribed to the higher relative density of the DS ceramics in contrast to the singlesintering ceramics. More importantly, the temperature stability of the DS sample in all samples is optimal due to the highsurface energy at grain boundaries and improved density. This work demonstrates a route to produce ceramics with weaktemperature sensitivity for microwave applications.

Blast vibration of a large-span high-speed railway tunnel based on microseismic monitoring

Li, Ao,Fang, Qian,Zhang, Dingli,Luo, Jiwei,Hong, Xuefei Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.5

Ground vibration is one of the most undesirable effects induced by blast operation in mountain tunnels, which could cause negative impacts on the residents living nearby and adjacent structures. The ground vibration effects can be well represented by peak particle velocity (PPV) and corner frequency ($f_c$) on the ground. In this research, the PPV and the corner frequency of the mountain surface above the large-span tunnel of the new Badaling tunnel are observed by using the microseismic monitoring technique. A total of 53 sets of monitoring results caused by the blast inside tunnel are recorded. It is found that the measured values of PPV are lower than the allowable value. The measured values of corner frequency are greater than the natural frequencies of the Great Wall, which will not produce resonant vibration of the Great Wall. The vibration effects of associated parameters on the PPV and corner frequency which include blast charge, rock mass condition, and distance from the blast point to mountain surface, are studied by regression analysis. Empirical formulas are proposed to predict the PPV and the corner frequency of the Great Wall and surface structures due to blast, which can be used to determine the suitable blast charge inside the tunnel.

miR-122 promotes diabetic retinopathy through targeting TIMP3

Wang Mingliang,Zheng Huifen,Zhou Xianbo,Zhang Jiwei,Shao Guanghui 한국통합생물학회 2020 Animal cells and systems Vol.24 No.5

Diabetic retinopathy (DR) is a primary complication of diabetes mellitus. DR can cause severe vision loss for patients. miR-122 is elevated in DR patients, while its role in DR is unclear. Hence, the purpose of this study was to analyze the effect of miR-122 on the function of high glucoseinduced REC cells and the underlying molecular mechanisms. In this study, our results revealed that miR-122 was up-regulated in high glucose-induced human retinal pigment epithelial cells (ARPE-19). High glucose decreased the cell viability of ARPE-19 cells, which was then restored by miR-122 knockdown. In addition, miR-122 knockdown suppressed apoptosis of high glucoseinduced ARPE-19 cells. High glucose also inhibited B-cell lymphoma-2 (Bcl-2) level and increased cleaved caspase-3 level in ARPE-19 cells, which were reversed by miR-122 knockdown. Tissue inhibitor of metalloproteinases-3 (TIMP3) was a direct target of miR-122. TIMP3 was decreased in high glucose-induced ARPE-19 cells, and the decrease was abrogated by miR-122 knockdown. In addition, the effects of miR-122 overexpression in cell viability and apoptosis of high glucoseinduced ARPE-19 were abolished by overexpression of TIMP3. In conclusion, the effect and mechanism of miR-122 on high glucose-induced ARPE-19 cells were demonstrated for the first time. miR-122 promoted diabetic retinopathy through targeting TIMP3, making miR-122 a promising target for diabetic retinopathy therapy.