Effect of Different Cooling Rates in High Rheological Rate Forming Process on Mechanical Properties of Zr57Cu20Al10Ni8Ag5 Bulk Metallic Glass

Xiao‑Bo Mei,Bao‑Chuan Liu,Wei Jiang,Quan Xu,Qi‑Dong Zhang,Yu‑Bai Ma,Fang‑Qiu Zu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9

The influence of cooling rates on the mechanical properties of a Zr-based bulk metallic glass prepared with high rheologicalrate forming (HRRF) was investigated and compared with traditional suction cast methods. Amorphous samples of Zr57Cu-20Ni8Al10Ag5 were prepared in copper molds with different sizes in order to obtain different cooling rates for both HRRFand traditional cast methods. These specimens were subjected to compression experiments, including microhardness testing,X-ray diffraction testing and differential scanning calorimetry analysis. The results indicate that the plasticity of the samplesformed by HRRF are higher than that of the as-cast ones at the same cooling rates, while the microhardness manifests theopposite principle. As the cooling rate increases further, the difference in plasticity further increases between two methods,indicating that the plasticity of metallic glasses is more sensitive to cooling rates during the HRRF process. At the core ofthis phenomenon is the fact that HRRF methods can introduce more free volume into glasses than traditional cast methodswith an elevated cooling rate are able to.

Axial Resistance of Bored Piles Socketed into Soft Rock

Xiao-yu Chen,Ming-yi Zhang,Xiao-yu Bai 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1

Three fully-instrumented full-scale static load tests were conducted on three 0.8-m-diameter bored piles socketed at 3.2 m deep into argillaceous siltstone (1.6 and 1.6 deep into strong and medium decomposed siltstones, respectively) in Qingdao, China. About 50% of head load was transmitted and supported by base resistance at the end of the tests. Totally 53 test piles socketed into soft rock with unconfined compressive strength less than 20 MPa in Qingdao were reviewed. The measured side resistance along shaft socked into rock was compared with prediction using empirical methods in literatures based on database from Qingdao projects.

Experimental and numerical investigation on post-earthquake fire behaviour of the circular concrete-filled steel tube columns

Yu-Hang Wang,Qi Tang,Mei-Ni Su,Ji-Ke Tan,Wei-Yong Wang,Yong-Sen Lan,Xiao-Wei Deng,Yong-Tao Bai,Wei Luo,Xiao-Hua Li,Jiu-Lin Bai 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.1

Post-earthquake fire is a common disaster which causes serious safety issues to infrastructures. This study aims to investigate the residual loading capacities of circular concrete-filled steel tube (CFST) columns under post-earthquake fire experimentally and numerically. The experimental programme contains two loading steps - pre-damage cyclic loading at room temperature and transient state tests with constant compression loads. Three finite element models are developed and validated against the test results. Upon validation, a total of 48 numerical results were generated in the parametric study to investigate the effects of thickness and strengths of steel tube, axial compression ratio and damage degree on the fire resistance of circular CFST columns. Based on the analysis on experimental and numerical results, the loading mechanism of circular CFST columns is discussed. A design method is proposed for the prediction of fire resistance time under different seismic pre-damage and compression loads. The predictions by the new method is compared with the newly generated experimental and numerical results and is found to be accurate and consistent with the mean value close to the unity and a coefficient of variation around 1%.

Effect of polymer and additive on the structure and property of porous stainless steel hollow fiber

Xiao-Hua Ma,Zhen-Liang Xu,Yu Bai,Yue Cao 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.8

Porous stainless steel hollow fiber has been widely used due to its high mechanical strength, excellentthermal conductivity and good sealing properties compared with other porous supports. We successfully prepared porousstainless steel hollow fibers using polyacrylonitrile (PAN) as polymer via dry-wet spinning followed by sintering throughtemperature programming method. The PAN concentration had an obvious impact on the structure and property ofporous stainless steel hollow fiber even if it would be burned off during sintering. The results showed that the morphologycould be tuned by adjusting the concentration of PAN. With increasing PAN concentration in casting solutionfor spinning, the viscosity was increased dramatically, resulting in much compact structures with high pure water flux(higher than 3×105 L·m−2·h−1·Pa−1). A more dense structure could be obtained by adding additive polyvinylpyrrolidone(PVP) as viscosity enhancer.

Design of a High-Voltage Piezoelectric Converter for Airbag Ignition Modules

Xiao, Hongbing,Du, Yu,Bai, Chunyu,Guo, Zerong,Yen, Kang K. The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

Due to the requirements for high reliability and accuracy, safety issues for airbag ignition systems need to be studied. In this paper, a high-voltage piezoelectric converter is designed to improve these requirements in airbag ignition systems. The proposed converter includes an inverter drive circuit, a Rosen piezoelectric transformer (PZT), an output circuit and a feedback control circuit. The key components of the high-voltage piezoelectric transformer are analyzed in detail. In addition, the proposed converter system is simulated and implemented for testing. The experimental results show that when the power supply is turned on, the charging time is less than 800ms. Furthermore, the output voltage of this converter can be kept between 2.9kV and 3.1kV, under high-efficiency constant current charging mode and zero-voltage switching conditions.

Distinctive Slow β Relaxation and Its Impact on Mechanical Property of LaCe Based Bulk Metallic Glasses

Xiao Cui,Jing Guo,Qi‑dong Zhang,Xiao‑jun Meng,Bing‑chuan Bian,Ren‑gao Zhao,Yu‑bai Ma,Fang‑qiu Zu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.10

The slow β relaxation which occurring at temperatures far below glass transition temperature, typically playing importantroles in the plastic deformation behavior of metallic glasses. Compared with polymer glasses, most of the metallic glasses donot exhibit obvious β relaxation based on dynamic mechanical analysis. In the current work, prominent β relaxation behaviorsof a series (LaxCe100−x) Al10Co25(x = 50, 60, 70, 80) bulk metallic glasses (BMGs) at low temperature are observed usingdynamic mechanical analysis. Compared with other BMGs, the LaCe based BMGs show a pronounced β relaxation peak andrelative low peak temperature, the activation energy of the β relaxation based on Arrhenius equation are calculated around79.3 kJ/mol to 86.4 kJ/mol, which obey an empirical rule that Eβ ≈ (26 ± 4) RTg, with the coefficient of 23. Experimentalresults from room temperature compression tests for the LaCe based BMGs indicate that low temperature activated β relaxationbehaviors facilitate the good plasticity of the LaCe based BMGs.

Integrated three-dimensional digital assessment of accuracy of anterior tooth movement using clear aligners

Xiao-Juan Zhang,Li He,Hong-Ming Guo,Jie Tian,Yu-Xing Bai,Song Li 대한치과교정학회 2015 대한치과교정학회지 Vol.45 No.6

Objective: To assess the accuracy of anterior tooth movement using clear aligners in integrated three-dimensional digital models. Methods: Cone-beam computed tomography was performed before and after treatment with clear aligners in 32 patients. Plaster casts were laser-scanned for virtual setup and aligner fabrication. Differences in predicted and achieved root and crown positions of anterior teeth were compared on superimposed maxillofacial digital images and virtual models and analyzed by Student’s t-test. Results: The mean discrepancies in maxillary and mandibular crown positions were 0.376 ± 0.041 mm and 0.398 ± 0.037 mm, respectively. Maxillary and mandibular root positions differed by 2.062 ± 0.128 mm and 1.941 ± 0.154 mm, respectively. Conclusions: Crowns but not roots of anterior teeth can be moved to designated positions using clear aligners, because these appliances cause tooth movement by tilting motion.

Transcriptional profiling of MED Bemisia tabaci exposed to thermal stress and verification of HSP70 expression

Bai Jing,Liu Xiao‐Na,Lu Ming‐Xing,Du Yu‐Zhou 한국곤충학회 2021 Entomological Research Vol.51 No.5

Temperature changes impact agricultural production and also influence the behavior and community structure of many insect species. Bemisia tabaci, is an invasive and destructive pest with at least 44 cryptic species and occurring in over 100 countries and regions. In this study, transcriptional profiling was used to evaluate the response of the Mediterranean (MED) cryptic species B. tabaci exposed to cold and hot temperature stress. In response to cold stress, 3,024 unigenes were differentially expressed and mapped to 39 Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathways. A total of 4,437 unigenes were differentially expressed during heat stress, and these represented 18 KEGG enrichment pathways. Quantitative RT-PCR was used to determine the relative expression level of the 11 HSP70 fragments; these were significantly up-regulated during high temperature stress relative to the control group that was maintained at 26°C. In conclusion, the transcriptome data indicated that B. tabaci responds to thermal stress via multiple genes and networks. Furthermore, HSP70 plays an important role in stress tolerance of the MED B. tabaci, especially during heat stress.

Characteristics and Impact Factors of Renal Threshold for Glucose Excretion in Patients with Type 2 Diabetes Mellitus

Xiao-Dan Yue,Jing-Yu Wang,Xin-Rong Zhang,Ju-Hong Yang,Chun-Yan Shan,Miao-Yan Zheng,Hui-Zhu Ren,Yi Zhang,Shao-Hua Yang,Zhen-Hong Guo,Bai Chang,Bao-Cheng Chang 대한의학회 2017 Journal of Korean medical science Vol.32 No.4

Sodium glucose co-transporter 2 (SGLT-2) inhibitors are newly developed but promising medicine for type 2 diabetes. However, patients with a different renal threshold for glucose excretion (RTG) may have a different reaction to this medicine. Therefore, the objective of this study was to investigate the characteristics of RTG and its impact factors in patients with type 2 diabetes mellitus (T2DM). The clinical and laboratory data of 36 healthy individuals and 168 in-hospital patients with T2DM were collected and analyzed, RTG was calculated using blood glucose (BG) measured by dynamic BG monitoring, urinary glucose excretion (UGE) and estimated glomerular filtration rate (eGFR). The characteristics of RTG were investigated. The risk factors for high RTG were analyzed using non-conditional logistic regression analysis. Our results found that RTG of the T2DM group was higher than that of the healthy individuals (P < 0.05); and 22.22% from the healthy individuals group but 58.33% from the T2DM group had high RTG. Age, duration of diabetes, body mass index (BMI), and homeostasis model assessment insulin resistance index (HOMA-IR) were independently associated with high RTG (P < 0.05). Further stratified analysis revealed that RTG in T2DM patients increased with age, duration of diabetes, and BMI. In conclusion, RTG is increased in patients with T2DM, especially in those with longer diabetic duration, higher BMI, and those who are older. Therefore, these patients may be more sensitive to SGLT-2 inhibitors.

Design of a High-Voltage Piezoelectric Converter for Airbag Ignition Modules

Hongbing Xiao,Yu Du,Chunyu Bai,Zerong Guo,Kang K. Yen 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

Due to the requirements for high reliability and accuracy, safety issues for airbag ignition systems need to be studied. In this paper, a high-voltage piezoelectric converter is designed to improve these requirements in airbag ignition systems. The proposed converter includes an inverter drive circuit, a Rosen piezoelectric transformer (PZT), an output circuit and a feedback control circuit. The key components of the high-voltage piezoelectric transformer are analyzed in detail. In addition, the proposed converter system is simulated and implemented for testing. The experimental results show that when the power supply is turned on, the charging time is less than 800ms. Furthermore, the output voltage of this converter can be kept between 2.9kV and 3.1kV, under high-efficiency constant current charging mode and zero-voltage switching conditions.