Microstructure, Mechanical Properties and Fracture Behavior of Magnesium/Steel Bimetal Using Compound Casting Assisted with Hot-Dip Aluminizing

Wenming Jiang,Haixiao Jiang,Guangyu Li,Feng Guan,Junwen Zhu,Zitian Fan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

In this work, microstructure, mechanical properties and fracture behavior of the magnesium/steel bimetal using compoundcasting assisted with hot-dip aluminizing were investigated, and the interface bonding mechanism of the magnesium/steelbimetal were also analyzed. The results indicate that the magnesium/steel bimetal obtained without hot-dip aluminizing hadlarger gaps through the whole interface without reaction layers between magnesium and steel, leading to a poor mechanicalbonding. After the steel substrate was hot-dip aluminized, an intermetallic layer along with an Al topcoat layer wereformed on the surface of the steel substrate, and the intermetallic layer was constituted by Fe2Al5,τ10-Al9Fe4Si3, FeAl3andτ6-Al4.5FeSi phases. In the case of the magnesium/steel bimetal obtained with hot-dip aluminizing, a compact and uniforminterface layer with an average thickness of about 17 μm that consisted of Fe2Al5,τ10-Al9Fe4Si3, FeAl3and Al12Mg17intermetalliccompounds was formed between the magnesium and the steel, obtaining a superior metallurgical bonding. The interfacelayer had much higher nano-hardnesses compared to the magnesium and steel matrixes, and its average nano-hardness wasup to 11.1 GPa, while there were respectively 1.1 and 4.2 GPa for the magnesium and steel matrixes. The shear strength ofthe magnesium/steel bimetal with hot-dip aluminizing reached to 23.3 MPa, which increased by 8.59 times than that of thecomposites without hot-dip aluminizing. The fracture of the magnesium/steel bimetal with hot-dip aluminizing representeda brittle fracture nature, initiating from the interface layer.

Preparation of Al2O3/AZ91D Mg Interpenetrating Composites Using Lost Foam Casting Combined with Layered Extrusion Forming

Wenming Jiang,Guangyu Li,Feng Guan,Junwen Zhu,Dongping Zhang,Zitian Fan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

A novel method named lost foam casting (LFC) process combined with layered extrusion forming (LEF) technology wasproposed to prepare the Al2O3/AZ91D Mg interpenetrating composites, and the microstructural characteristics, thermalexpansion performance and wear resistance of the Al2O3/AZ91D interpenetrating composites were investigated in this work. The results indicated that a superior bonding between AZ91D magnesium alloy and Al2O3porous ceramic was achieved. The Al2O3/AZ91D interpenetrating composites exhibited obvious improvements in the thermal expansion performance andthe wear resistance compared to the AZ91D alloy. Therefore, the LFC process combined with the LEF technology providesa promising method for the preparation of the Al2O3/AZ91D interpenetrating composites.

A Duplex PCR Assay for Rapid Detection of Phytophthora nicotianae and Thielaviopsis basicola

Liu, Na,Jiang, Shijun,Feng, Songli,Shang, Wenyan,Xing, Guozhen,Qiu, Rui,Li, Chengjun,Li, Shujun,Zheng, Wenming The Korean Society of Plant Pathology 2019 Plant Pathology Journal Vol.35 No.2

A duplex PCR method was developed for simultaneous detection and identification of tobacco root rot pathogens Phytophthora nicotianae and Thielaviopsis basicola. The specific primers for P. nicotianae were developed based on its internal transcribed spacer (ITS) regions of ribosomal gene, ras gene and hgd gene, while the specific primers for T. basicola were designed based on its ITS regions and ${\beta}$-tubulin gene. The specificity of the primers was determined using isolates of P. nicotianae, T. basicola and control samples. The results showed that the target pathogens could be detected from diseased tobacco plants by a combination of the specific primers. The sensitivity limitation was $100fg/{\mu}l$ of pure genomic DNA of the pathogens. This new assay can be applied to screen out target pathogens rapidly and reliably in one PCR and will be an important tool for the identification and precise early prediction of these two destructive diseases of tobacco.

Performance and Mechanism Analysis of Succinate Production under Different Transporters in Escherichia coli

Xiaozhan Li,Wenming Zhang,Mingke Wu,Fengxue Xin,Weiliang Dong,Hao Wu,Min Zhang,Jiangfeng Ma,Min Jiang 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.5

Succinic acid is a platform chemical with potential for bio-based synthesis. However, the production of bio-based succinate is limited because of insufficient succinate efflux capacity in the late stage of fermentation. In the present study, three different transporters, which have been reported to be responsible for C4-dicarboxylates transport, were employed for investigation of the transport capacity of succinate in Escherichia coli. After engineered strains were constructed, the fermentative production of succinic acid was studied in serum bottles and 3 L of fermentor. The results demonstrated that engineered strain showed better efflux capacity than control strain under high concentration of succinate. The highest production of succinate was 68.66 g/L, while the NCgl2130 transporter may be the best candidate for succinate export in E. coli. Further research showed that the expression levels and relative enzyme activities involved in the metabolic pathway all increased markedly, and the maximum activities of PPC, PCK, PYK, and MDH increased by 1.50, 1.38, 1.28, and 1.27-fold in recombinant E. coli AFP111/pTrc99a- NCgl2130, respectively. Moreover, the maximum level of intracellular ATP increased by 23.79% in E. coli AFP111/ pTrc99a-NCgl2130. Taken together, these findings indicated that engineered transporters can improve succinate production by increasing key enzyme activities and intracellular ATP levels. To the best of thew authors’ knowledge, this is the first report on a mechanism to improve succinate production by engineered transporters. This strategy set up a foundation for improving the biosynthesis of other C4-dicarboxylates, such as fumaric acid and malic acid.

Design-oriented acceleration response spectrum for ground vibrations caused by collapse of large – scale cooling towers in NPPs

Feng Lin,Wenming Jiang 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.8

Nuclear-related facilities can be detrimentally affected by ground vibrations due to the collapse ofadjacent cooling towers in nuclear power plants. To reduce this hazard risk, a design-oriented accelerationresponse spectrum (ARS) was proposed to predict the dynamic responses of nuclear-related facilitiessubjected to ground vibrations. For this purpose, 20 computational cases were performed basedon cooling tower-soil numerical models developed in previous studies. This resulted in about 2664ground vibration records to build a basic database and five complementary databases with considerationof primary factors that influence ground vibrations. Afterwards, these databases were applied to generatethe design-oriented ARS using a response spectrum analysis approach. The proposed design-orientedARS covers a wide range of natural periods up to 6 s and consists of an ascending portion, a plateau,and two connected descending portions. Spectral parameters were formulated based on statisticalanalysis. The spectrum was verified by comparing the representative acceleration magnitudes obtainedfrom the design-oriented ARS with those from computational cases using cooling tower-soil numericalmodels with reasonable consistency.

Effects of Cu²⁺ on alkaline phosphatase from <i>Macrobrachium rosenbergii</i>

Wang, Zhi-Jiang,Ma, Wenming,Yang, Jun-Mo,Kang, Yani,Park, Yong-Doo Elsevier 2018 INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES Vol.117 No.-

<P><B>Abstract</B></P> <P>To gain insight into the effect of Cu<SUP>2+</SUP> on the activity and structure of alkaline phosphatase (ALP) from <I>Macrobrachium rosenbergii</I>, the enzyme was purified using ammonium sulfate fractionation, Sephacryl S-200, and DEAE anion exchange chromatography. We studied Cu<SUP>2+</SUP>-mediated inhibition and aggregation of ALP, and found that Cu<SUP>2+</SUP> significantly inactivated ALP activity with an <I>IC</I> <SUB>50</SUB> of 1.47 ± 0.02 mM. We further revealed that Cu<SUP>2+</SUP> reversibly inhibited ALP in a mixed-type manner with <I>K</I> <SUB>i</SUB> = 0.41 ± 0.02 mM. Time-interval kinetics showed that the inhibition followed first-order reaction kinetics. This process was associated with conformational changes and significant transient free-energy change. Spectrofluorometry results showed that Cu<SUP>2+</SUP> induced ALP tertiary structural changes, including the exposure of hydrophobic surfaces that directly induced ALP aggregation. The results provide new information regarding ALP from <I>M. rosenbergii</I>.</P>

A Duplex PCR Assay for Rapid Detection of Phytophthora nicotianae and Thielaviopsis basicola

Na Liu,Shijun Jiang,Songli Feng,Wenyan Shang,Guozhen Xing,Rui Qiu,Chengjun Li,Shujun Li,Wenming Zheng 한국식물병리학회 2019 Plant Pathology Journal Vol.35 No.2

A duplex PCR method was developed for simultaneous detection and identification of tobacco root rot pathogens Phytophthora nicotianae and Thielaviopsis basicola. The specific primers for P. nicotianae were developed based on its internal transcribed spacer (ITS) regions of ribosomal gene, ras gene and hgd gene, while the specific primers for T. basicola were designed based on its ITS regions and β-tubulin gene. The specificity of the primers was determined using isolates of P. nicotianae, T. basicola and control samples. The results showed that the target pathogens could be detected from diseased tobacco plants by a combination of the specific primers. The sensitivity limitation was 100 fg/μl of pure genomic DNA of the pathogens. This new assay can be applied to screen out target pathogens rapidly and reliably in one PCR and will be an important tool for the identification and precise early prediction of these two destructive diseases of tobacco.