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Novel Water-Air Circulation Quenching Process for AISI 4140 Steel
Liyun Zheng,Dawei Zheng1,Lixin Zhao,Lihui Wang,Kai Zhang 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
AISI 4140 steel is usually used after quenching and tempering. During the heat treatment process in industry production, there are some problems, such as quenching cracks, related to water-cooling and low hardness due to oil quenching. A water-air circulation quenching process can solve the problems of quenching cracks with water and the high cost quenching with oil, which is flammable, unsafe and not enough to obtain the required hardness. The control of the water-cooling and air-cooling time is a key factor in the process. This paper focuses on the quenching temperature, water-air cycle time and cycle index to prevent cracking for AISI 4140 steel. The optimum heat treatment parameters to achieve a good match of the strength and toughness of AISI 4140 steel were obtained by repeated adjustment of the water-air circulation quenching process parameters. The tensile strength, Charpy impact energy at -10 °C and hardness of the heat treated AISI 4140 steel after quenching and tempering were approximately 1098 MPa, 67.5 J and 316 HB, respectively.
Historical Long-term Exposure to Pentachlorophenol Causing Risk of Cancer - A Community Study
Zheng, Rui-Zhi,Zhang, Qing-He,He, Yi-Xin,Zhang, Qian,Yang, Lin-Shen,Zhang, Zhi-Hua,Zhang, Xiu-Jun,Hu, Jing-Ting,Huang, Fen Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.2
Background: Pervious studies suggested occupational workers exposure to pentachlorophenol (PCP) might contribute to increased risk of cancer. However, few studies have focused on associations between PCP and cancer risk at the community level. Objective: The present study was to explore the cancer risk for the community population living long-term in a PCP contaminated area. Methods: All the cancer cases diagnosed in 2009-2011 in Tongling City were collected. The cancer patients' residencies were geo-referenced in each district. The historical PCP usage for each district of Tongling was calculated as the PCP pollution index, which was further used to divide into PCP exposure categories. Standardized rate ratios (SRRs) of cancer incidence were applied to detect the cancer risk as exposure grade elevated. Correlation analysis was performed to analyze the relationship between PCP pollution and cancer incidence. Results: A total of 5,288 cancer cases (3,451 male and 1,837 female) were identified. PCP usage was correlated with the incidence of leukemia (r=0.88, P=0.002) for males, and with cancer of the esophagus for males (r=0.83, P=0.008) and females (r=0.71, P=0.020). Compared with the low exposure category, significant SRRs for total cancer sites was obtained for high PCP exposure category (SRR=1.61, 95%CI=1.59-1.62). Most SRR values of the cancer sites were significantly increased as exposure grade elevated and exposure time extended. Conclusion: The present study found that community residents living in the PCP contaminated area had increased risk of cancers. Leukemias, lymphomas and nasopharyngeal and esophageal cancers are most possibly associated with PCP exposure.
Zhang Wentao,Zheng Zongtai,Wang Keyi,Mao Weipu,Li Xue,Wang Guangchun,Zhang Yuanyuan,Huang Jianhua,Zhang Ning,Wu Pengfei,Liu Ji,Zhang Haimin,Che Jianping,Peng Bo,Zheng Junhua,Li Wei,Yao Xudong 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-
Accumulating studies have confirmed that PIWI-interacting RNAs (piRNAs) are considered epigenetic effectors in cancer. We performed piRNA microarray expression analysis on renal cell carcinoma (RCC) tumor tissues and paired normal tissues and performed a series of in vivo and in vitro experiments to explore piRNAs associated with RCC progression and investigate their functional mechanisms. We found that piR-1742 was highly expressed in RCC tumors and that patients with high piR-1742 expression had a poor prognosis. Inhibition of piR-1742 significantly reduced tumor growth in RCC xenograft and organoid models. Mechanistically, piRNA-1742 regulates the stability of USP8 mRNA by binding directly to hnRNPU, which acts as a deubiquitinating enzyme that inhibits the ubiquitination of MUC12 and promotes the development of malignant RCC. Subsequently, nanotherapeutic systems loaded with piRNA-1742 inhibitors were found to effectively inhibit the metastasis and growth of RCC in vivo. Therefore, this study highlights the functional importance of piRNA-related ubiquitination in RCC and demonstrates the development of a related nanotherapeutic system, possibly contributing to the development of therapeutic approaches for RCC.
Time Discretization of Nonlinear Time-delay System using Matrix Exponential Method
Zheng Zhang,Yuanliang Zhang,장영원,정길도 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.6
A time discretization method for nonlinear time-delay systems is proposed in this paper. The proposed method is based on the matrix exponential method and includes the automatic correction of rounding errors. It is robust to ill-conditioned problems and suitable for any nonlinear system. In the proposed algorithm, each sampling time interval is divided into two subintervals to be considered separately according to the time delay and the sampling period. The performance of the proposed discretization procedure is evaluated by two case studies.
An Improved Wavelet PWM Technique with Output Voltage Amplitude Control for Single-phase Inverters
Zheng, Chun-Fang,Zhang, Bo,Qiu, Dong-Yuan,Zhang, Xiao-Hui,Li, Rui The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4
Unlike existing pulse-width modulation (PWM) techniques, such as sinusoidal PWM and random PWM, the wavelet PWM (WPWM) technique based on a Harr wavelet function can achieve a high fundamental component for the output voltage, low total harmonic distortion, and simple digital implementation. However, the original WPWM method lacks output voltage control. Thus, the practical application of the WPWM technique is limited. This study proposes an improved WPWM technique that can regulate output voltage amplitude with the addition of a parameter. The relationship between the additional parameter and the output voltage amplitude is analyzed in detail. Experimental results verify that the improved WPWM exhibits output voltage control in addition to all the merits of the WPWM technique.
Zheng, Tao,Zhang, Tian-biao,Wang, Chao-liang,Zhang, Wei-xing,Jia, Dong-hui,Yang, Fan,Sun, Yang-yang,Ding, Xiao-ju,Wang, Rui Korean Society for Molecular and Cellular Biology 2018 Molecules and cells Vol.41 No.6
Icariside II (ICA II) is used in erectile dysfunction treatment. Adipose tissue-derived stem cells (ADSCs) are efficient at improving erectile function. This study aimed to explore the action mechanism of ADSCs in improving erectile function. ADSCs were isolated from the adipose tissues of rats. Cell proliferation was determined using the Cell Counting Kit-8 (CCK-8) assay. The expressions of mRNA and protein were determined separately through qRT-PCR and western blot. The endogenous expressions of related genes were regulated using recombinant plasmids and cell transfection. A Dual-Luciferase Reporter Assay was performed to determine the interaction between miR-34a and STAT3. Rat models with bilateral cavernous nerve injuries (BCNIs) were used to assess erectile function through the detection of mean arterial pressure (MAP) and intracavernosal pressure (ICP). ICA II promoted ADSCs' proliferation and differentiation to Schwann cells (SCs) through the inhibition of miR-34a. Suppressed miR-34a promoted the differentiation of ADSCs to SCs by upregulating STAT3. ICA II promoted the differentiation of ADSCs to SCs through the miR-34a/STAT3 pathway. The combination of ICA II and ADSCs preserved the erectile function of the BCNI model rats. ADSCs treated with ICA II markedly preserved the erectile function of the BCNI model rats, which was reversed through miR-34a overexpression. ICA II promotes the differentiation of ADSCs to SCs through the miR34a/STAT3 pathway, contributing to erectile function preservation after the occurrence of a cavernous nerve injury.
Canonical Projector Techniques for Analyzing Descriptor System
Zheng Zhang,Ngai Wong 제어·로봇·시스템학회 2014 International Journal of Control, Automation, and Vol.12 No.1
Physical systems are often naturally formulated as descriptor systems (DSs) which form a superset of the more restrictive standard state spaces. The analysis of a DS, however, is complicated by the algebraic coupling between its proper and improper subsystems. The recently emerging canonical projector technique, stemming from iterative matrix chain construction, provides a theoretically sound and numerically effective way to completely decouple these subsystems and largely facilitates the re-use or adaptation of standard state space techniques for DS analysis. Nonetheless, results concerning canonical projectors are scattered and their potential use is currently less appreciated. The objectives of this paper are twofold: i) It serves as a tutorial that collects distributed results about canonical projectors and presents them in a coherent manner; and more than just a tutorial, it elaborates and provides new/elegant/corrected proofs to some fundamental properties of canonical projectors. An iterative procedure for canonical projector construction, lacking in the literature, is also described. ii) Obvious applications, including some latest development, of projector techniques in practical circuit design problems are succinctly illustrated. By creating a self-contained repository of important canonical projector theories, it is hoped that more interest will be drawn and efficient numerical implementations will follow.
Hybrid discretization method for time-delay nonlinear systems
Zhang, Zheng,Kostyukova, Olga,Zhang, Yuanliang,Chong, Kil-To 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3
A hybrid discretization scheme that combines the virtues of the Taylor series and Matrix exponential integration methods is proposed. In the algorithm, each sampling time interval is divided into two subintervals to be considered according to the time delay and sampling period. The algorithm is not too expensive computationally and lends itself to be easily inserted into large simulation packages. The mathematical structure of the new discretization scheme is explored and described in detail. The performance of the proposed discretization procedure is evaluated by employing case studies. Various input signals, sampling rates, and time-delay values are considered to test the proposed method. The results demonstrate that the proposed discretization scheme is better than previous Taylor series method for nonlinear time-delay systems, especially when a large sampling period is inevitable.
Zheng, Chao,Zhang, Kai,Sheng, Canhui,Lin, Junjie,Xue, Jinying,Chen, Dezhi,Zhang, Zhiqiang,Luo, Bangyun 대한전기학회 2014 The Journal of International Council on Electrical Vol.4 No.1
Aiming at the three UHVDC controller model in the electromechanical simulation software BPA which widely used in China, the structural features were analyzed. By the time-domain simulation, the influence of different simulation models and the key controller parameters on the recovery characteristics of the receiving end power system were studied. Simulation results show that the commutation failure simulated method impacts the recovery characteristic significantly for weak power grids, increasing the voltage measurement time constant of constant dc power control module and enhancing the start voltage threshold of voltage dependent current order limit (VDCOL) can decrease the reactive power consumption of inverter during the disturbance, and can help to improve the recovery characteristic of receiving end power grid.