Enhanced activity and hydrothermal stability of Rh-based three-way catalyst for emission control from motorcycles with the assistance of monoethanolamine

Li Lan,Jinfeng Wang,Shanhu Chen,Dacheng Li,Hongmei Li,Dayu Liu,Wei Wang,Yaoqiang Chen 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.71 No.-

In this work, an advanced Rh/CeO2–ZrO2 (Rh/CZ) three-way catalyst was synthesized with the assistanceof monoethanolamine. Compared with conventional Rh/CZ, the dispersion and oxidation state of Rhspecies, as well as the hydrothermal aging resistance are remarkably modified. That is, upon agingtreatment, conventional Rh/CZ undergoes severe agglomeration of Rh species and formation of largeamount of reduction-resistive RhO2, resulting in serious catalyst deactivation. Fortunately, after theintroduction of monoethanolamine, the sintering of Rh species and transformation into inactive RhO2upon aging are effectively suppressed. Consequently, improved reducibility and advanced three-waycatalytic activity are achieved for the modified catalyst.

Controllable synthesis of zone-distributed Pd over CeO2–ZrO2/Al2O3 as advanced three-way catalyst

Li Lan,Shanhu Chen,Hongmei Li,Hanmei Li,Wanxia Wu,Jie Deng,Yaoqiang Chen 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.58 No.-

Two optimally designed catalysts (Ce0.7Zr0.3O2/Pd/Al2O3, Pd/Ce0.7Zr0.3O2/Pd/Al2O3) were synthesized and compared with conventional Pd/Ce0.7Zr0.3O2/Al2O3. The characterization results reveal that for Pd/Ce0.7Zr0.3O2/Al2O3, Pd species undergo severe agglomeration and encapsulation during thermal aging process, leading to dramatic catalyst deactivation. While for the two optimized catalysts, some Pd species initially distributed on Al2O3 would migrate to the surface of CexZr1−xO2(CZ) grains upon aging treatment, resulting in enhanced Pd–CZ interaction, thus the two aged samples possess higher dispersion, larger amount of oxidized Pd2+ species and more oxygen vacancies compared with conventional Pd/Ce0.7Zr0.3O2/Al2O3-a. Consequently, modified reducibility and improved three-way catalytic performance are obtained, especially for Pd/Ce0.7Zr0.3O2/Pd/Al2O3-a.

71% Common‑mode voltage suppression modulation strategy for indirect matrix converters

Shanhu Li,Zijing Lu,Sunpeng Cao,Xu Liu,Zhaoyang Jin,Weitao Deng 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.2

Common-mode voltage (CMV) with a high amplitude and frequency is generated when an indirect matrix converter (IMC) is operating, which damages the motor winding insulation and accelerates motor aging. Existing IMC modulation methods can only suppress the CMV by 42.3%. However, this paper proposes a modulation strategy with a 71% reduction in the peak CMV. The proposed method selects active vectors based on the characteristics of the CMV amplitude under each of the active vectors. The rectifier stage selects two active vectors within each modulation sector. According to the sector where the input reference current vector is located, the inverter stage chooses active-voltage vectors whose corresponding peak CMV is 1/3 the minimum peak line voltage for modulation. Moreover, the CMV spikes caused by the dead zone effect are eliminated by reasonably arranging the switching sequence of the voltage vectors in the inverter stage. The proposed approach considerably lowers the peak CMV and has a good suppression effect on the amplitude of high-frequency CMV. Finally, experimental results illustrate the CMV reduction efficiency of the modulation strategy.

Performance Degradation Model and Reliability Evaluation of Brush DC Motor for the Intelligent on–Off Valve

Yang Tianhao,Li Shanhu,Duan Shuyong,Tao Yourui,Han Xu 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

Application of the intelligent on–off valve reduces heat loss. As the critical control component of the intelligent on–off valve, the health state of the brush DC motor directly impacts whether the intelligent on–off valve can perform the regular operation. Therefore, the reliability evaluation of the brush DC motor is of great significance to the whole heat supply network. In this study, the failure mechanism of the brush DC motor is analyzed, and the absolute value of steady-state current variation is taken as the performance degradation characteristic parameter. According to the performance degradation characteristic parameter, the performance degradation model based on the Wiener process is established, and the inverse power rate acceleration model is introduced into the Wiener process to derive the reliability function of the motor. Based on the actual operating conditions that the motor in the intelligent on–off valve needs to start and stop frequently, an accelerated life test based on start-stop is designed. The error analysis result shows that the error between the expected start-stop times predicted by the proposed and the actual average failure start-stop times is only 2.14%. The proposed degradation model is more accurate than the motor's traditional performance degradation model.

Analysis and Research on Space Vector Over-modulation Strategy of Indirect Matrix Converter

Wenshen Wang,Shanhu Li,Xu Liu,Yongjian Li,Yiping Liu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

In this paper, based on the characteristics of six space vector modulation methods, a variety of Space Vector Over-modulation strategies with voltage transfer ratio of 1.05 for indirect matrix converter is proposed. Firstly, the six space vector modulation methods are combined by adjusting the phase of the input current vector and the amplitude and phase of the output voltage vector. Secondly, the limit input current and output voltage vector characteristics, the limit fundamental voltage amplitude and the main low-frequency harmonic components of the input and output under the six modulation methods are analyzed in detail. According to the limit characteristics of the six modulation methods and the principle of limit vector superposition, multiple space vector over-modulation strategies based on single-mode, doublemode and multi-mode are proposed. Finally, the characteristics of the six space vector modulation methods are verified by experiments.

Association of Perceived Stress With Depression Among Vaccinated Healthcare Workers During the SARS-CoV-2 Variant Outbreak: The Mediating Role of Compassion Fatigue

Cai Xue,Li Guohong,Feng Haixia,Wang Xiaoyan,He Lijun,Luo Dan,Xu Cuirong,Huang Yingzi,Qiu Shanhu 대한신경정신의학회 2023 PSYCHIATRY INVESTIGATION Vol.20 No.4

Objective Depression was common during coronavirus disease-2019 (COVID-19) pandemic, while the association of perceived stress with depression among vaccinated healthcare workers has not been investigated. This study aimed to address this issue.Methods We included a total of 898 fully vaccinated healthcare workers during the outbreak of severe acute respiratory syndrome coronavirus 2 Delta variant in Nanjing, 2021. Depression was ascertained by Patient Health Questionnaire-9, with a cut-off score of ≥5 indicative of mild-to-severe depression. Perceived stress, resilience, and compassion fatigue were assessed by Perceived Stress Scale-10, Resilience Scale-25, and Professional Quality of Life Scale version-5, respectively. Logistic regression analyses were used to estimate the odds ratio (OR) and 95% confidence interval (CI), along with subgroup and mediation analyses.Results The prevalence of mild-to-severe depression was 41.1% in vaccinated healthcare workers. The odd of mild-to-severe depression was increased with higher perceived stress. Compared with vaccinated healthcare workers with the lowest tertile of perceived stress, those with the highest tertile had increased odds of mild-to-severe depression by 120% (OR 2.20, 95% CI 1.46 to 3.31) after multivariable-adjustment. However, perceived stress was not associated with mild-to-severe depression in vaccinated healthcare workers with strong resilience, but was in those with weak resilience (p_interaction=0.004). Further analysis showed that compassion fatigue mediated the relationship between perceived stress and mild-to-severe depression, with a mediating effect of 49.7%.Conclusion Perceived stress was related to an increased odd of mild-to-severe depression in vaccinated healthcare workers during COVID-19 pandemic, and this relationship might be explained by compassion fatigue.

Four-year changes in central fatness, risk of diabetes, and metabolic control in older adults: a cohort study with mediation analysis

( Xue Cai ),( Dan Luo ),( Shuling Liu ),( Ruxue Li ),( Yanhui Lu ),( Mingzi Li ),( Shanhu Qiu ) 대한내과학회 2022 The Korean Journal of Internal Medicine Vol.37 No.1

Background/Aims: Older adults are vulnerable to central obesity, while the association of changes in central fatness with risk of diabetes and metabolic control has not been investigated among this particular population. This study was aimed to address these issues. Methods: A total of 1,815 adults aged ≥ 60 years without diabetes at baseline were followed for 4 years. Incident diabetes was ascertained based on plasma glucose, hemoglobin A1c, medical history, and/or the use of anti-diabetic drugs. Central fatness was assessed by waist circumference (WC), waist-height ratio (WHtR), and body roundness index (BRI). Logistic regression analyses were used to assess the association of changes in central fatness with risk of diabetes, along with dose-response and mediation analyses. Results: During the 4-year follow-up, 177 participants developed diabetes. The risk of diabetes was increased by 42%, 41%, and 40% per 1 standard deviation increases in WC, WHtR, and BRI, respectively, in multivariable-adjusted models (all p < 0.01). Moreover, these relationships were all linearly-shaped (all p_nonlinearity ≥ 0.11). Increases in WC, WHtR, and BRI correlated with increases in hemoglobin A1c, triglycerides-and-glucose index, triglycerides, white blood cell, and C-reactive protein (all p ≤ 0.04). Yet only changes in hemoglobin A1c and triglycerides-and-glucose index were identified as the possible mediators for risk of diabetes, with their mediating effect being about 35% and 21%, respectively. Conclusions: Increases in central fatness were related to elevated risk of diabetes, and this association might be partly explained by the worsening of glycemic control and insulin resistance in older adults.