Data-driven estimation of change-points with mean shift

Yang Wenzhi,Liu Huanshuo,Wang Yiwei,Wang Xuejun 한국통계학회 2023 Journal of the Korean Statistical Society Vol.52 No.1

Asymptotically linear negative quadrant dependent (ALNQD) sequence is more general than negatively associated (NA) sequence and \rho∗-mixing sequence. Based on ALNQD errors, the CUSUM estimator of mean change-point is studied with common conditions. We obtain a limiting distribution of CUSUM estimator, which can be used to judge the existence of mean change-point. Meanwhile, some weak and strong convergence rates are established for the CUSUM estimator of change-point. In addition, a data-driven algorithm of multiple change-point detection is given, which performs better than Lasso algorithm. Last, multiple change-point detection simulations and real data analysis illustrate the accuracy of our results.

A Novel Method for Pavement Transverse Crack Detection Based on 2D Reconstruction of Vehicle Vibration Signal

Wenzhi Yuan,Qun Yang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Pavement transverse cracks are associated with pavement performance. However, due to lowrecognition accuracy, the transverse cracking detection through vehicle’s vibration responsehas hardly been considered. This paper proposes a novel method for pavement transversecracking detection using reconstructed vehicle vibration signal. An accelerometer installed inthe vehicle collects the vibration response between the vehicle and the pavement transversecracks. A brand-new approach to data processing is suggested that transforms a onedimensionalvibration signal into a two-dimensional vibration image. The two-dimensionalvibration image generated can obtain different features effectively from the time domain. Based on Gray Level Concurrence Matrix (GLCM) algorithm, a characteristic index establishedfrom the vibration image’s contrast can distinguish transverse cracks from uncracked sections. Then its feasibility was investigated by 410 pavement sections, the accuracy of the index is93.84%. The transverse crack detection method proposed in this paper seems promising forprecisely identifying pavement transverse cracks.

Numerical simulation and analysis of the aerodynamic noise of a nautilus-inspired bionic multiblade centrifugal fan

Hongzhan Lv,Wenzhi Yang,W. J. Zhang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9

This paper proposes a nautilus-inspired bionic volute for a multiblade centrifugal fan. Analysis of the noises generated by the fan is presented. This is made possible by a model that integrates a steady-state equation using the Reynolds-averaged Navier-Stokes (RANS) model and an unsteady-state estimation using the large-eddy simulation (LES) model and the Ffowcs Williams-Hawkings aerodynamic noise model, and by numerical solution to the model. Our computational model is validated on the sound pressure level with the help of the measurements on a physical system. The validation suggests that the proposed bionic volute significantly increases the aerodynamic performance particularly in terms of transformation between the pressure and flow rate under the rated power. The noise associated to the bionic volute is found to be predominantly tonal noise, and this is the primary source of the noise of the fan. Another finding is that the large expansion profile of the proposed volute contributes to the attenuation of the tonal noise associated to the periodic jet impingement at the impeller outlet.

Exponential inequalities and complete convergence for a LNQD sequence

Wang Xuejun,Hu Shuhe,Yang Wenzhi,Li Xiaoqin 한국통계학회 2010 Journal of the Korean Statistical Society Vol.39 No.4

Some exponential inequalities for a linearly negative quadrant dependent sequence are obtained. By using the exponential inequalities, we give the complete convergence and almost sure convergence for a linearly negative quadrant dependent sequence. In addition,the asymptotic behavior of the probabilities for the partial sums of a linearly negative quadrant dependent sequence is studied.

Maximal inequalities for some dependent sequences and their applications

Shuhe Hu,Xiaoqin Li,Wenzhi Yang,Xuejun Wang 한국통계학회 2011 Journal of the Korean Statistical Society Vol.40 No.1

In this paper, we obtain the maximal inequalities for linear process, ϕ-mixing sequence and linearly negative quadrant dependent (LNQD) sequence when the rth moments of random variables are finite for r > 2. Applying these maximal inequalities above, we get the Hájek–Rényi-type inequality, strong law of large numbers, strong growth rate and integrability of supremum for these three sequences.

An Active Voltage Doubling Rectifier with Unbalanced-Biased Comparators for Piezoelectric Energy Harvesters

Lianxi Liu,Junchao Mu,Wenzhi Yuan,Wei Tu,Zhangming Zhu,Yintang Yang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

For wearable health monitoring systems, a fundamental problem is the limited space for storing energy, which can be translated into a short operational life. In this paper, a highly efficient active voltage doubling rectifier with a wide input range for micro-piezoelectric energy harvesting systems is proposed. To obtain a higher output voltage, the Dickson charge pump topology is chosen in this design. By replacing the passive diodes with unbalanced-biased comparator-controlled active counterparts, the proposed rectifier minimizes the voltage losses along the conduction path and solves the reverse leakage problem caused by conventional comparator-controlled active diodes. To improve the rectifier input voltage sensitivity and decrease the minimum operational input voltage, two low power common-gate comparators are introduced in the proposed design. To keep the comparator from oscillating, a positive feedback loop formed by the capacitor C is added to it. Based on the SMIC 0.18-μm standard CMOS process, the proposed rectifier is simulated and implemented. The area of the whole chip is 0.91×0.97 ㎟, while the rectifier core occupies only 13% of this area. The measured results show that the proposed rectifier can operate properly with input amplitudes ranging from 0.2 to 1.0V and with frequencies ranging from 20 to 3000 Hz. The proposed rectifier can achieve a 92.5% power conversion efficiency (PCE) with input amplitudes equal to 0.6 V at 200 Hz. The voltage conversion efficiency (VCE) is around 93% for input amplitudes greater than 0.3 V and load resistances larger than 20kΩ.

Discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins

Liu, Juan,Xu, Yangrong,Yang, Jingjing,Wang, Wenzhi,Zhang, Jianqiang,Zhang, Renmei,Meng, Qingguo The Korean Society of Ginseng 2017 Journal of Ginseng Research Vol.41 No.3

Ocotillol-type saponins are one kind of tetracyclic triterpenoids, sharing a tetrahydrofuran ring. Natural ocotillol-type saponins have been discovered in Panax quinquefolius L., Panax japonicus, Hana mina, and Vietnamese ginseng. In recent years, the semisynthesis of 20(S/R)-ocotillol-type saponins has been reported. The biological activities of ocotillol-type saponins include neuroprotective effect, antimyocardial ischemia, antiinflammatory, antibacterial, and antitumor activities. Owing to their chemical structure, pharmacological actions, and the stereoselective activity on antimyocardial ischemia, ocotillol-type saponins are subjected to extensive consideration. In this review, we sum up the discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins.

Discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins

Juan Liu,Yangrong Xu,Jingjing Yang,Wenzhi Wang,Jianqiang Zhang,Renmei Zhang,Qingguo Meng 고려인삼학회 2017 Journal of Ginseng Research Vol.41 No.3

Ocotillol-type saponins are one kind of tetracyclic triterpenoids, sharing a tetrahydrofuran ring. Natural ocotillol-type saponins have been discovered in Panax quinquefolius L., Panax japonicus, Hana mina, and Vietnamese ginseng. In recent years, the semisynthesis of 20(S/R)-ocotillol-type saponins has been reported. The biological activities of ocotillol-type saponins include neuroprotective effect, antimyocardial ischemia, antiinflammatory, antibacterial, and antitumor activities. Owing to their chemical structure, pharmacological actions, and the stereoselective activity on antimyocardial ischemia, ocotillol-type saponins are subjected to extensive consideration. In this review, we sum up the discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins.

MAXIMAL INEQUALITIES AND STRONG LAW OF LARGE NUMBERS FOR AANA SEQUENCES

Xuejun, Wang,Shuhe, Hu,Xiaoqin, Li,Wenzhi, Yang Korean Mathematical Society 2011 대한수학회논문집 Vol.26 No.1

Let {$X_n$, $n{\geq}1$} be a sequence of asymptotically almost negatively associated random variables and $S_n=\sum^n_{i=1}X_i$. In the paper, we get the precise results of H$\acute{a}$jek-R$\acute{e}$nyi type inequalities for the partial sums of asymptotically almost negatively associated sequence, which generalize and improve the results of Theorem 2.4-Theorem 2.6 in Ko et al. ([4]). In addition, the large deviation of $S_n$ for sequence of asymptotically almost negatively associated random variables is studied. At last, the Marcinkiewicz type strong law of large numbers is given.

An Active Voltage Doubling Rectifier with Unbalanced-Biased Comparators for Piezoelectric Energy Harvesters

Liu, Lianxi,Mu, Junchao,Yuan, Wenzhi,Tu, Wei,Zhu, Zhangming,Yang, Yintang The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

For wearable health monitoring systems, a fundamental problem is the limited space for storing energy, which can be translated into a short operational life. In this paper, a highly efficient active voltage doubling rectifier with a wide input range for micro-piezoelectric energy harvesting systems is proposed. To obtain a higher output voltage, the Dickson charge pump topology is chosen in this design. By replacing the passive diodes with unbalanced-biased comparator-controlled active counterparts, the proposed rectifier minimizes the voltage losses along the conduction path and solves the reverse leakage problem caused by conventional comparator-controlled active diodes. To improve the rectifier input voltage sensitivity and decrease the minimum operational input voltage, two low power common-gate comparators are introduced in the proposed design. To keep the comparator from oscillating, a positive feedback loop formed by the capacitor C is added to it. Based on the SMIC 0.18-μm standard CMOS process, the proposed rectifier is simulated and implemented. The area of the whole chip is 0.91×0.97 mm², while the rectifier core occupies only 13% of this area. The measured results show that the proposed rectifier can operate properly with input amplitudes ranging from 0.2 to 1.0V and with frequencies ranging from 20 to 3000 Hz. The proposed rectifier can achieve a 92.5% power conversion efficiency (PCE) with input amplitudes equal to 0.6 V at 200 Hz. The voltage conversion efficiency (VCE) is around 93% for input amplitudes greater than 0.3 V and load resistances larger than 20kΩ.