Characterization of Hot Deformation Behavior and Processing Map of As‑Cast H13 Hot Work Die Steel

Yahui Han,Changsheng Li,Jinyi Ren,Chunlin Qiu,En LI,Shuaishuai Chen 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

The hot-working behavior of as-cast H13 hot work die steel was investigated in the method of isothermal compression testinvolving the wide deformation temperatures of 900–1150 °C and strain rates of 0.01–10 s−1, with the true strain to 0.8, onthe MMS-200 thermo-mechanical simulator. Two characteristic parameters involving the critical strain for DRX initiation(c ) and the strain for peak stress (p ) were identified. The ratio of critical strain to peak strain ranged from 0.26 to 0.6, whichdecreased with the increase in temperature and decrease in strain rate. Processing maps were established using dynamicmaterial model at strains of 0.2, 0.4, 0.6, 0.8. The power dissipation maps were not significantly affected by the strain, whilethe instability maps were sensitivity with the strain when it was over 0.4. The area of instability domain at strain of 0.8 wasthe largest. The instable characteristics contained the mixed grain structure, adiabatic shear band, intense deformation inserious deformation area and brittle elemental segregation area. The chief effect on the power dissipation was the strain rate,the optimum hot working parameters at strain of 0.8 (910–985 °C, 1010–1150 °C and 0.01–0.05 s−1) were determined. Inthis filed, the original coarse as-cast grains were gradually refined by dynamic recrystallization mechanism and the DRXgrain numbers had a significant increase with the increase of power dissipation efficiency.

Fault diagnosis method of belt conveyor idler based on sound signal

Yahui Zhang,Siyan Li,Aimin Li,Gaoxiang Zhang,Mingzhuang Wu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

Damage to a belt conveyor idler will increase the downtime and maintenance cost, so it is very important to diagnose its fault. At present, the fault diagnosis of the idler of a belt conveyor is mostly based on vibration and temperature signal. However, contact fault diagnosis approaches are severely limited when sensors are inconvenient to install or when vibration and temperature signals cannot be returned. In this special case, the non-contact fault diagnosis method, represented by measuring acoustic signals, becomes a necessary means. To effectively extract mechanical state information from sound signals of belt conveyors and identify typical mechanical faults, we propose a fault detection method based on sample center distance weighted (support vector data description (SVDD)) and multi-frame fusion (Melfrequency cepstral coefficient (MFCC)) features. Aiming at the disadvantage that single frame MFCC features and traditional SVDD are susceptible to noise, multi-frame fusion MFCC optimization features are used as samples, and the weighted SVDD model based on sample center distance is used for fault detection. Finally, the overall recognition accuracy of the experiment is greatly improved. It is proved that MFCC features of multi-frame fusion sound signal and weighted SVDD fault detection based on sample center distance can effectively determine whether there is a fault in the of belt conveyor idler.

Effect of Homogenisation Temperature on the Microstructure and Microhardness of As-Cast H13 Steel

Yahui Han,Changsheng Li,Shuai He,Cairu Gao,Shuaishuai Chen,En Li 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.3

This study determined that the homogenisation temperature range of experimental as-cast H13 steel was from 1150 to1230 °C, whilst the effect of homogenisation temperature range on the microstructural evolution and microhardness wastested. The enrichment of alloying elements in the dendrite segregation region decreased the solidus temperature of matrix,whose total content determined the maximum homogenisation temperature. The secondary dendrite branches were mostdissolved at 1150 °C, and overheating appeared at 1230 °C in the segregation region. Moreover, the primary carbidesunderwent shrinking, passivation, fragmentation and dissolution. The secondary carbides M23C6and M6Cwere formed atthe interfaces of MC/γ and M7C3/γ, respectively. As the homogenisation temperature increased from 1150 to 1230 °C, thevalue of microhardness gradually decreased from 771 to 740 HV. Nevertheless, the standard deviation value decreased firstand then increased, which reached the minimum 32 HV at 1200 °C, indicating that the hardness homogeneity was the best.

Achieving High Yield of Lactic Acid for Antimicrobial Characterization in Cephalosporin-Resistant Lactobacillus by the Co-Expression of the Phosphofructokinase and Glucokinase

( Yahui Gong ),( Tiyuan Li ),( Shiyu Li ),( Zhenyou Jiang ),( Yan Yang ),( Junli Huang ),( Zhaobing Liu ),( Hanxiao Sun ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.6

Lactobacilli are universally recognized as probiotics that are widely used in the adjuvant treatment of inflammatory diseases, such as vaginitis and enteritis. With the overuse of antibiotics in recent years, the lactobacilli in the human body are killed, which could disrupt the microecological balance in the human body and affect health adversely. In this work, cephalosporin-resistant Lactobacillus casei RL20 was obtained successfully from the feces of healthy volunteers, which possessed a stable genetic set. However, the shortage of lactic acid (72.0 g/l at 48 h) by fermentation did not meet the requirement for its use in medicine. To increase the production of lactic acid, the functional genes pfk and glk were introduced into the wild strain. A yield of 144.2 g/l lactic acid was obtained in the transgenic L. casei RL20-2 after fermentation for 48 h in 1 L of basic fermentation medium with an initial glucose concentration of 100 g/l and increasing antibacterial activity. These data suggested that L. casei RL20-2 that exhibited a high yield of lactic acid may be a potential probiotic to inhibit the spread of bacterial infectious diseases and may be used for vaginitis therapy.

Secure Message Distribution Scheme with Configurable Privacy in Heterogeneous Wireless Sensor Networks

LI, YaHui,MA, JianFeng,MOON, SangJae The Institute of Electronics, Information and Comm 2010 IEICE transactions on information and systems Vol.93 No.3

<P>Security and privacy of wireless sensor networks are key research issues recently. Most existing researches regarding wireless sensor networks security consider homogenous sensor networks. To achieve better security and performance, we adopt a heterogeneous wireless sensor network (HWSN) model that consists of physically different types of sensor nodes. This paper presents a secure message distribution scheme with configurable privacy for HWSNs, which takes advantage of powerful high-end sensor nodes. The scheme establishes a message distribution topology in an efficient and secure manner. The sensor node only need generate one signature for all the messages for all the users, which can greatly save the communication and computation cost of the sensor node. On the other hand, the user can only know the messages that let him know based on a pre-set policy, which can meet the requirement of the privacy. We show that the scheme has small bandwidth requirements and it is resilient against the node compromise attack.</P>

Entity Relationship Modeling Approach Based on Micro- Blog Tag

Junjiang Li,Chunlin Li,Youlong Luo,Yahui Zhao,Xijun Mao 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.7

Due to the huge information, short length and noise data, the traditional method has poor effect on micro-blog entity relationship modeling. In this paper, a new micro-blog user interests discovering approach based on tag is presented to improve the entity relationship modeling. First the matrix of user tag built by traditional way may generate the problem of sparse matrix in tag recommendation, so we introduce the information of micro-blog and establish the bipartite graph of User-Tag and Tag-Word respectively, then use them to recommend tag to micro-blog users. Meanwhile interactive relationship between users also show their interests, we establish a graph of tag relation by users’ relationship and propose a method called Tag Rank on the basis of this graph to improve the precision of the model. Finally, we combine the two methods to discover user interests. In the experiment, we use several measurement metrics: F-value, precision and the recall rate. It is proven that the new approach in the paper have a perfect performance.

PLAGL2 increases adriamycin resistance and EMT in breast cancer cells by activating the Wnt pathway

Li Yuxiao,Liu Ruolin,Han Xingzhao,Xu Wei,Liu Yahui 한국유전학회 2023 Genes & Genomics Vol.45 No.1

Background Adriamycin (ADR) is an effective treatment for breast cancer; nevertheless, it is often linked with acquired resistance in breast cancer cells, reducing ADR’s therapeutic efficacy and increasing the risk of recurrence and poor prognosis. It has been revealed that the zinc-finger transcription factor pleomorphic adenoma gene like-2 (PLAGL2) is required for epithelial to mesenchymal transition (EMT) in cancer cells. Recent data indicates that PLAGL2 is also involved in regulating chemotherapeutic drug resistance, albeit the exact mechanism by which this happens remains unknown. Objective This study examines the effect of PLAGL2 on adriamycin resistance and EMT in breast cancer cells. Methods The small interfering RNA (siRNA) targeting PLAGL2 was transfected to breast cancer cells to alter PLAGL2 expression. Cell counting kit-8 (CCK-8) and colony formation assay detected cell growth and proliferation rate. Moreover, wound-healing and transwell assays were conducted to evaluate migration and invasion. Western blot (WB) checked the apoptosis and EMT-associated proteins. Results PLAGL2 expression is associated with breast cancer cells’ acquired resistance to ADR in this investigation. Additionally, deletion of PLAGL2 was associated with enhanced sensitivity to ADR, reduced proliferation, migration, and invasion capabilities, increased E-cadherin levels, and reduced Wnt6, β-catenin, and DVL1 levels in ADR-resistant breast cancer cells (MCF-7/ADR and MDA-MB-231/ADR cells). PLAGL2 could bind to the promoter region of Wnt6 and promote its expression. Additionally, the results of this research established that Wnt signaling is implicated in breast cancer cells’ resistance to ADR since BML-284, a Wnt signaling activator partly restored the sensitivity of MCF-7/ADR and MDA-MB-231/ADR cells to ADR. Conclusion PLAGL2 promotes adriamycin resistance and cell aggressiveness in breast cancer cells via activating the Wnt signaling pathway.

Photoelectrochemical Properties and Photocatalytic Activity of Fluorine-Doped Plate-Like WO3 from Hydrothermal Radio-Frequency (RF) Sputtered Tungsten Thin Films

Yahui Yang,GuanHua Jin,Hang Li 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.4

Fluorine-doped tungsten oxide (WO3) plate-like films were synthesized by hydrothermal radiofrequency (RF) sputtered tungsten (W) thin films in HF solution. The crystal structure, composition and morphology of nitrogen fluorine (F) doped WO3 were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectra (DRS) techniques. The results indicate that fluorine can be doped successfully into WO3 plate-like films by hydrothermal synthesis in hydrofluoric acid (HF) solution. The F-doped WO3 samples show stronger absorption in the UVVis range and a red shift in the band gap transition. Incident photon to current efficiency (IPCE) measurements carried out on photoelectrochemical cell with F-doped WO3 plate-like films as anodes demonstrate a significant increase of photoresponse in the visible region compared with undoped WO3. The photocatalytic activity under visible light irradiation for newly synthesized F-doped WO3 plate-like films was investigated by degradation of methyl orange. The photocatalytic activity of F-doped WO3 plate-like films was 3-fold enhancement compared with pure WO3 samples.

One-pot Process of 2'-Deoxyguanylic Acid Catalyzed by a Multi-enzyme System

Yanyu Li,Qingbao Ding,Ling Ou,Yahui Qian,Jiao Zhang 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.1

2'-Deoxyguanylic acid (deoxyguanosine-5'-monophosphate, dGMP) is a substance required by livingcells that is used extensively in reagents, fine chemicalsand other industrial fields. Traditionally, dGMP is separatedfrom DNA degradation products, which is low-yieldingand time-consuming. Herein, we investigated a novel, onepotmulti-enzymatic cascade reaction to produce dGMP. This reaction involved purine nucleoside phosphorylase(PNPase) and acetate kinase (ACKase) from Escherichiacoli, N-deoxyribosytransferase II (NDT-II) from Lactobacillusdelbrueckii and deoxyguanosine kinase (dGKase) fromBacillus subtilis. During the reaction, the initial guanosinesubstrate was cleaved into guanine and ribose-1-phosphateby PNPase. Then, deoxyguanosine (dGR) was subsequentlyproduced from a reaction between guanine and thymidinecatalysed by NDT-II. Finally, the intermediate dGR wasphosphorylated to dGMP by dGKase and a cytidinetriphosphate (CTP) regeneration system that utilised acetylphosphate via ACKase. A very small amount of CTP wasadded because CTP regeneration was efficient to transfer aphosphate group from acetyl phosphate to dGR. After 12 hof incubation, a maximal dGMP yield of up to 76% wasobtained based on the addition of 5 mM guanosine and 5mM thymidine.

Enhancement of Mechanical and Thermal Properties of SU‑8 Photoresist with Multilayer Woven Glass Fabric Based on Micromachining Technology

Wenwen Zhou,Yahui Li,Yunna Sun,Jinyuan Yao,Xutong Song,Guifu Ding 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.6

SU-8 photoresist has been more and more widely used as a structural material in micro electromechanical system (MEMS) because of its low cost and excellent biocompatibility. However, the inferior mechanical and thermal performances immensely impinge the reliability of the MEMS device based SU-8 and accordingly restrict its application. Here we report the mechanicaland thermal performance of SU-8 reinforced by the multilayer glass fabric with the MEMS technology. The finite element simulation and specific experiment are conducted, which confirm that the reinforced SU-8 composites have a 281% increase in Young’s modulus and a 64% decrease in coefficient of thermal expansion (CTE) compared with pure SU-8. Additionally,the improved mechanism has also been analyzed, including the excellent interface bonding between the SU-8 and glass fabric, and the high-bond energy of Si–O-Si chain structures in glass fabric. Furthermore, the glass fabric reinforced SU-8 could still possess a high light transmittance to maintain the ability of lithography patterning. Therefore, it is believed thatthe strategy proposed here may satisfy higher requirements of MEMS devices, which guarantees its practical applications in the functional microstructures.