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.

A Corpus-based Study of Collocation in Chinese EFL Learners’ Oral Production

Lihui Zheng,Richard Zhonghua Xiao 한국코퍼스언어학회 2015 Corpus Linguistics Research Vol.1 No.-

This article provides a systematic account of collocational use in Chinese EFL learners’ oral production and explores some of the issues involved, by adopting a corpus-based error analysis approach. The distribution of six types of collocational errors extracted from two sizeable Chinese learner English corpora shows that verb-noun collocations pose the greatest difficulty for Chinese learners. An exploration of the correlation between the learners’ English proficiency and collocational performance finds that the learners’ knowledge of collocation has not developed alongside their knowledge of vocabulary in general. Our further descriptive and diagnostic analyses of verb-noun errors indicate that 1) Chinese EFL learners have the greatest difficulty with the verbs when using verb-noun collocations; 2) the learners’ use of nouns is also not satisfactory; 3) due attention should be paid to the inappropriate use of the non-lexical elements (prepositions and articles); and 4) the main causes of verb-noun collocational errors include L1 transfer, assumed synonyms, overgeneralization and misselection of the target word. It is suggested that university English teaching in China should attach more importance to the examination and diagnosis of collocational errors and also integrate learner-centered, corpus-based methods into vocabulary teaching.

Lactate exacerbates lung damage induced by nanomicroplastic through the gut microbiota–HIF1a/PTBP1 pathway

Xuan Lihui,Xu Zheng,Luo Jinhua,Yin Wang,Yan Yuhui,Qu Can,Xie Zuozhong,Skonieczna Magdalena,Zhou Ping-Kun,Huang Ruixue 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

Exposure to nanomicroplastics (nano-MPs) can induce lung damage. The gut microbiota is a critical modulator of the gut–lung axis. However, the mechanisms underlying these interactions have not been elucidated. This study explored the role of lactate, a key metabolite of the microbiota, in the development of lung damage induced by nano-MPs (LDMP). After 28 days of exposure to nano-MPs (50–100 nm), mice mainly exhibited damage to the lungs and intestinal mucosa and dysbiosis of the gut microbiota. Lactate accumulation was observed in the lungs, intestines and serum and was strongly associated with the imbalance in lactic acid bacteria in the gut. Furthermore, no lactate accumulation was observed in germ-free mice, while the depletion of the gut microbiota using a cocktail of antibiotics produced similar results, suggesting that lactate accumulation in the lungs may have been due to changes in the gut microbiota components. Mechanistically, elevated lactate triggers activation of the HIF1a/PTBP1 pathway, exacerbating nano-MP-induced lung damage through modulation of the epithelial–mesenchymal transition (EMT). Conversely, mice with conditional knockout of Ptbp1 in the lungs (Ptbp1flfl) and PTBP1-knockout (PTBP1-KO) human bronchial epithelial (HBE) cells showed reversal of the effects of lactate through modulation of the HIF1a/PTBP1 signaling pathway. These findings indicate that lactate is a potential target for preventing and treating LDMP.

Bearing fault diagnosis based on amplitude and phase map of Hermitian wavelet transform

Hui Li,Lihui Fu,Haiqi Zheng 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.11

The rolling element bearing characteristic frequencies contain very little energy and are usually overwhelmed by noise and higher level of structural vibrations. The continuous wavelet transform enables one to look at the evolution in the time scale joint representation plane. This makes it very suitable for the detection of singularity generated by localized defects in a mechanical system. However, most applications of the continuous wavelet transform have widely focused on the use of the Morlet wavelet transform. The complex Hermitian wavelet is constructed based on the first and the second derivatives of the Gaussian function to detect signal singularities. The Fourier spectrum of Hermitian wavelet is real, which the Fourier spectrum has no complex phase and the Hermitian wavelet does not affect the phase of a signal in complex domain. This gives the desirable ability to detect the singularity characteristic of a signal precisely. In this study, the Hermitian wavelet amplitude and phase map are used in conjunction to detect and diagnose the bearing fault. The Hermitian wavelet amplitude and phase map are found to show distinctive signatures in the presence of bearing inner race or outer race damage. The simulative and experimental results show that the Hermitian wavelet amplitude and phase map can extract the transients from strong noise signals and can effectively diagnose bearing faults.

NEW METHODOLOGY FOR DETERMINATION OF LOAD SPECTRA FOR THE VEHICLE ACCELERATED DURABILITY TESTING ASSOCIATED WITH THE TIME CORRELATED FATIGUE DAMAGE ANALYSIS METHOD

Jiawei Yu,Songlin Zheng,Jinzhi Feng,Lihui Zhao 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.3

The generation of valid and effective test spectra from proving ground recorded load spectra is critical for automotive durability testing. Traditional methods mostly based on spectrum damage were used to select load spectra. Statistical characteristics of load spectra were taken into account, and a new load spectra determination method based on a concatenation of a multi-section minimum standard deviation spectrum (CMSD) was proposed. The CMSD spectra were created and based on proving ground recorded load spectra. Fatigue damage analyses showed that the CMSD spectra approximated the mean damage spectra and were representative of proving ground load spectra. Subsequently, the CMSD spectra were edited by applying the time correlated fatigue damage (TCFD) analysis method to generate accelerated loading spectra. The spectra editing process of the TCFD was discussed in detail. Validation of the accelerated spectra was conducted from amplitude and frequency domains. The same fatigue damage and identical spectrum properties were retained in the accelerated spectra. A vehicle 4-post testing was finally conducted where the accelerated loading spectra were applied as the target spectra. Several fatigue fracture phenomena occurred during our test, which showed good agreement with the field test. Therefore, the load spectra determination method CMSD associated with the load spectra editing method TCFD were demonstrated reasonable and practical.

Ligandless palladium supported on SiO2–TiO2 as effective catalyst for Suzuki reaction

Guozhi Fan,Bing Zou,Siqing Cheng,Lihui Zheng 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.2

TiO2–SiO2 mixed oxides were prepared by the homogeneous precipitation method, and the supports were characterized by XRD, IR and BET. Ligandless palladium supported on SiO2–TiO2 was prepared by the deposition–precipitation method and used as recoverable catalyst for Suzuki reactions. The results revealed that the supported catalyst Pd/SiO2–TiO2 exhibited excellent catalytic activity for the coupling of aryl bromides with arylboronic acid, and also exhibitedmoderate catalytic activity for the coupling of aryl chlorides. The catalyst was recycled by simple filtration and reused without further disposal, no significant Pd leaching and loss of catalytic activity was observed except the first reuse.

Solution-processed WOx hole injection layer for efficient fluorescent blue organic light-emitting diode

Wanshu Li,Yan Zhang,Qinghong Zheng,Kai Xu,Xiuyun Zhang,Liming Liu,Bin Wei,Lihui Wang,Jiwen Xu,Xiaowen Zhang 한국물리학회 2018 Current Applied Physics Vol.18 No.5

Solution-processed tungsten oxide (s-WOx) interfacial layer for efficient hole injection in fluorescent blue organic light-emitting diode (OLED) is demonstrated. The OLED using 2-methyl-9,10-bis(naphthalen-2- yl)anthracene (MADN) as emitter shows luminous efficiency of 3.3 cd/A, power efficiency of 2.5 lm/W and external quantum efficiency of 4.6% with Commission Internationale d'Eclairage (CIE) color coordinates of (0.154, 0.102). Using MADN doped 1-4-di-[4-(N,N-diphenyl)amino]styryl-benzene as emitter, luminous efficiency of 10.8 cd/A, power efficiency of 6.4 lm/W and external quantum efficiency of 7.2% with CIE color coordinates of (0.167, 0.283) are achieved. Atomic force microscopy and X-ray photoelectron spectroscopy show that s-WOx features superior film morphology and non-stoichiometry with slight oxygen deficiency. Current-voltage characteristics and impedance spectroscopy analysis indicate that s-WOx behaves slightly enhanced hole injection and accordingly contributes to improved device performance in comparison with conventional vacuum thermal evaporation WOx. Our results pave an alternative way for broadeningWOx application with solution process and advancing fluorescent blue OLEDs.

Wear Detection in Gear System Using Hilbert-Huang Transform

Li, Hui,Zhang, Yuping,Zheng, Haiqi The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.11

Fourier methods are not generally an appropriate approach in the investigation of faults signals with transient components. This work presents the application of a new signal processing technique, the Hilbert-Huang transform and its marginal spectrum, in analysis of vibration signals and faults diagnosis of gear. The Empirical mode decomposition (EMD), Hilbert-Huang transform (HHT) and marginal spectrum are introduced. Firstly, the vibration signals are separated into several intrinsic mode functions (IMFs) using EMD. Then the marginal spectrum of each IMF can be obtained. According to the marginal spectrum, the wear fault of the gear can be detected and faults patterns can be identified. The results show that the proposed method may provide not only an increase in the spectral resolution but also reliability for the faults diagnosis of the gear.