Optimization of annealing treatment parameters in a twin roll cast and warm rolled ZK60 alloy sheet

Chen, Hongmei,Yu, Huashun,Kang, Suk Bong,Cho, Jae Hyoung,Min, Guanghui Elsevier 2010 Materials science & engineering. properties, micro Vol.527 No.4

<P><B>Abstract</B></P><P>The microstructure of twin roll cast and warm rolled ZK60 alloy sheet was investigated using OM and TEM technique after annealing treatment at the temperature ranging from 300°C to 400°C. Tensile test at room temperature was performed to show the influence of annealing treatment on mechanical properties. Static recrystallization (SRX) was observed during annealing treatment of ZK60 alloy sheet at and above 300°C. Shear bands, dislocations and twins play an important role during static recrystallization and serve as nucleation sites. Disc-shaped precipitates could be found in annealed ZK60 alloy sheet. Higher temperature annealing treatment resulted in higher density precipitates, and at this condition the dispersion strengthening particles improved the ability of resistance to softening at elevated temperature. Annealing treatment at 375°C for 10<SUP>3</SUP>s can be considered to be the optimum annealing treatment, and under this condition the tensile strength, yield strength and elongation are 388MPa, 301MPa and 22.9%, respectively.</P>

Digital Post-processing Techniques for Time-interleaved ADCs

Hongmei Chen,Lanyu Wang,Jian Wang,Jiashen Li,Honghui Deng,Xu Meng,Yongsheng Yin 대한전자공학회 2022 IEIE Transactions on Smart Processing & Computing Vol.11 No.6

This paper presents an all-digital post-processing circuit for a high-speed and highprecision time-interleaved ADC (TIADC). By pre-inputting a test signal in the TIADC, channel mismatch errors are estimated and stored, and the stored values are extracted to compensate for errors when the input signal is at a special frequency. The frequency can be detected by a threshold judgement module. This solves the problem of the traditional modulation calibration algorithm, which cannot calibrate the signal at a special frequency. A high-speed low-complexity digital down converter (DDC) circuit with an optional decimation ratio of 1, 2, 4, or 8 times was designed to have different frequency outputs of the TIADC. We applied it to a four-channel 14-bit 360-MHz TIADC system with an input signal fin of 110 MHz. The FPGA verification results show that after calibration and decimation, the spurious-free dynamic range (SFDR) and signal-to-noise distortion ratio (SNDR) improve by about 40 dB and 30 dB, respectively.

Effects of a Death Education Intervention for Older People with Chronic Disease and Family Caregivers: A Quasi-Experimental Study

Weilin Chen,Hongmei Ma,Xiao Wang,Jiaojiao Chen 한국간호과학회 2020 Asian Nursing Research Vol.14 No.4

Purpose: To investigate the effectiveness of a structured death education program for older adults withchronic illness and their family caregivers. Methods: This study adopted two-group, nonrandomized quasi-experimental design. Patientecaregiverdyads in the intervention group (N ¼ 40 dyads) engaged in the death education program at the bedsideonce a week for 5 weeks, and were compared with participants (N ¼ 40 dyads) in the control group whoreceived usual health education. The program consisted of five sessions based on the Interaction Modelof Client Health Behavior. Death attitude, death competence, well-being, family function, and satisfactionwere measured at baseline (T0), immediately after the intervention (T1), and 1 month later (T2). Datacollection was conducted from July 30, 2019, to December 30, 2019. Results: The intention-to-treat analysis The intention-to-treat analysis of between groups at 1-monthfollow-up revealed that the intervention group had greater decreases in the fear of death (p=.002, 95% CI-2.53, -0.47; p<.001, 95% CI -3.61, -1.65) and death avoidance (p<.001, 95% CI -3.46, -1.84; p<.001, 95% CI-3.89, -2.43), had greater increases in the neutral acceptance (p=.032, 95% CI 0.05, 1.38; p<.001, 95% CI0.99, 2.56) and death competence (p<.001, 95% CI 4.10, 8.01; p<.001, 95% CI 7.80, 12.11) in patients andcaregivers, respectively. There were significant intergroup differences over time for patient well-being of(p<.001, 95% CI 3.06, 9.74) and satisfaction of (p<.001, 95% CI 2.01, 4.59). Results were consistent with theresults from the sensitivity analysis. Conclusion: This study demonstrated the feasibility and benefits of death education in hospitals andprovided an implementation plan for nursing professionals. Nurses should consider providing deatheducation for older adults with chronic diseases and their families to promote the development ofpalliative care and the quality of end-of-life.

β‑Sitosterol attenuates liver injury in a rat model of chronic alcohol intake

Zhenjuan Chen,Ancheng Wu,Hongmei Jin,Fuhui Liu 대한약학회 2020 Archives of Pharmacal Research Vol.43 No.11

Liver disease associated with long-term drinkingis one of the leading causes of death. There is an urgentneed for more effective drugs to reduce alcoholic liver damage. Yin Chen Hao, a traditional Chinese herbal medicine,is widely used for liver diseases. Here, we aimed to explorethe protective effect of β-sitosterol (the active ingredientof Artemisia spp.) on alcoholic liver injuries. We treatedthe rats with alcohol and different dosages of β-sitosterol todetect the expression levels of liver function indicators inserum. The functions of β-sitosterol were evaluated basedon variations in histology, liver function indicators and DNAoxidative damages. The underlying mechanism was investigatedby measuring lipid peroxidation, the antioxidant, theexpression of cytochrome P450 2E1 and the expression ofapoptosis related genes. The results showed that β-sitosterolcould improve liver histology and suppress biochemical indicatorscaused by alcohol in serum. In addition, β-sitosterolalleviates alcohol-induced oxidative stress, such as restoringerythrocyte membrane fluidity, reducing glutathione depletion,restoring antioxidant enzyme activity and reducingmalondialdehyde overproduction. Furthermore, β-sitosteroldownregulated the expression of apoptosis-related genesthrough the PI3K/Akt pathway. In conclusion, β-sitosterolhas a protective effect on chronic alcoholism and has broadclinical application prospects in the treatment of alcoholinducedliver damage.

Model-Free Adaptive Integral Backstepping Control for PMSM Drive Systems

Hongmei Li,Xinyu Li,Zhiwei Chen,Jingkui Mao,Jiandong Huang 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

A SMPMSM drive system is a typical nonlinear system with time-varying parameters and unmodeled dynamics. The speed outer loop and current inner loop control structures are coupled and coexist with various disturbances, which makes the speed control of SMPMSM drive systems challenging. First, an ultra-local model of a PMSM driving system is established online based on the algebraic estimation method of model-free control. Second, based on the backstepping control framework, modelfree adaptive integral backstepping (MF-AIB) control is proposed. This scheme is applied to the permanent magnet synchronous motor (PMSM) drive system of an electric vehicle for the first time. The validity of the proposed control scheme is verified by system simulations and experimental results obtained from a SMPMSM drive system bench test.

Catalytic combustion of volatile aromatic compounds over CuO-CeO2 catalyst

Hongmei Xie,Qinxiang Du,Hui Li,Guilin Zhou,Shengming Chen,Zhaojie Jiao,Jianmin Ren 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.7

Ce1−xCuxO2 oxide solid solution catalysts with different Ce/Cu mole ratios were synthesized by the one-pot complex method. The prepared Ce1−xCuxO2 catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). Their catalytic properties were also investigated by catalytic combustion of phenyl volatile organic compounds (PVOCs: benzene, toluene, xylene, and ethylbenzene) in air. XRD analysis confirmed that the CuO species can fully dissolve into the CeO2 lattice to form CeCu oxide solid solutions. XPS and H2-TPR results indicated that the prepared Ce1−xCuxO2 catalysts contain abundant reactive oxygen species and superior reducibility. Furthermore, the physicochemical properties of the prepared Ce1−xCuxO2 catalysts are affected by the Ce/Cu mole ratio. The CeCu3 catalyst with Ce/Cu mole ratio of 3.0 contains abundant reactive oxygen species and exhibits superior catalytic combustion activity of PVOCs. Moreover, the ignitability of PVOCs is also affected by the respective physicochemical properties. The catalytic combustion conversions of ethylbenzene, xylene, toluene, and benzene are 99%, 98.9%, 94.3%, and 62.8% at 205, 220, 225, and 225 oC, respectively.

Novel Asymptotic Synchronization Criteria on Riemann-Liouville Derivative Type Nonidentical Delayed Neural Networks

Hongmei Zhang,Hai Zhang,Weiwei Zhang,Chen Wang 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.4

This article focuses on investigating the asymptotic synchronization of two nonidentical RiemannLiouville (R-L) fractional-order delayed neural networks (FDNNs). Compared with the existing literature, the considered model is concerned with the nonidentical FDNNs rather than identical NNs. Under a novel feedback controller, two asymptotic synchronization criteria on FDNNs are established by utilizing the Lyapunov direct method. The derived criteria are concise and easy to test in actual applications. A numerical example is given to verify the availability of the presented results for nonidentical FDNNs.

Hysteretic model of isolator gap damper system and its equivalent linearization for random earthquake response analysis

Hongmei Zhang,Chen Gu 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.3

In near-fault earthquake prone areas, the velocity pulse-like seismic waves often results in excessive horizontal displacement for structures, which may result in severe structural failure during large or near-fault earthquakes. The recently developed isolator-gap damper (IGD) systems provide a solution for the large horizontal displacement of long period base-isolated structures. However, the hysteresis characteristics of the IGD system are significantly different from the traditional hysteretic behavior. At present, the hysteretic behavior is difficult to be reflected in the structural analysis and performance evaluation especially under random earthquake excitations for lacking of effective analysis models which prevent the application of this kind of IGD system. In this paper, we propose a mathematical hysteretic model for the IGD system that presents its nonlinear hysteretic characteristics. The equivalent linearization is conducted on this nonlinear model, which requires the variances of the IGD responses. The covariance matrix for the responses of the structure and the IGD system is obtained for random earthquake excitations represented by the Kanai-Tajimi spectrum by solving the Lyapunov equation. The responses obtained by the equivalent linearization are verified in comparison with the nonlinear responses by the Monte Carlo simulation (MCS) analysis for random earthquake excitations.

Enantioseparation and Determination of Sibutramine in Pharmaceutical Formulations by Capillary Electrophoresis

Hongmei Zhu,Enqi Wu,Jianbo Chen,Chuvan Men,장유선,Wonku Kang,Jung Kap Choi,이원재,강종성 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.6

Sibutramine enantiomers were separated successfully by capillary zone electrophoresis using substituted cyclodextrins as chiral selectors. The effects of cyclodextrin concentration, pH, voltage, buffer type, and electrolyte concentration on the migration time and resolution of enantiomers were examined. Separation of sibutramine enantiomers on an unmodified fused silica capillary (total length, 54 cm; effective length, 45 cm) was achieved using a mixed buffer of 20 mM phosphate/10 mM citrate containing either 5 mM methyl-β-cyclodextrin (pH 4.3) or 5 mM carboxymethyl-β-cyclodextrin (pH 6.5). Samples were injected with a pressure of 50 mbar for 5 s and were detected at a wavelength of 223 nm. The established method showed good precision and accuracy, with intra- and inter-day variations of less than 2.9 and 4.7%, respectively, and recoveries of 95.7 - 103.8%. The stability constants of (R)- and (S)-sibutramine demonstrated that the resolution of sibutramine enantiomers was attributable primarily to the difference in stability constants. When this optimized method was applied to the determination of sibutramine enantiomers in commercial drug formulations, it proved to be economical and convenient, affording sufficient accuracy, precision, and reproducibility as well as sensitivity and selectivity.

Genome Shuffling of Lactobacillus brevis for Enhanced Production of Thymidine Phosphorylase

Hongmei Li,Fang Xue,Weijie Wang,Baozhen Chen 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.2

Thymidine phosphorylase (TPase) plays a vital role in the biosynthesis of nucleosides and their analogs which have tremendous potential in antiviral and anticancer therapies. In this study, genome shuffling was applied to develop new strains of Lactobacillus brevis with an enhanced production of TPase. The parent organisms were mutated using ultraviolet (UV) irradiation and were shuffled by recursive pool-wise protoplast fusion. The parent protoplasts of each cycle were inactivated by UV irritation for 50 min or by heating at 60°C for 60 min. A rapid and efficient pre-screening method for determining L. brevis fusants with increased TPase production was established by adding appropriate concentrations of substrate thymidine and potassium phosphate to the culture broth based on significant differences in the absorption spectra of substrate thymidine and its product, thymine, in alkaline solution at 290 nm. Strains F3-19 and F3-36 showed high TPase activity and favorable hereditary stability and were screened out through three rounds of recursive protoplast fusion. The increase in the TPase activity of F3-19 and F3-36 was 252.6 and 260.5%, respectively, in comparison with the wild type.