An Improved Algorithm of Rough K-Means Clustering Based on Variable Weighted Distance Measure

Tengfei Zhang,Long Chen,Fumin Ma 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.6

Rough K-means algorithm has shown that it can provides a reasonable set of lower and upper bounds for a given dataset. With the conceptions of the lower and upper approximate sets, rough k-means clustering and its emerging derivatives become valid algorithms in vague information clustering. However, the most available algorithms ignore the difference of the distances between data objects and cluster centers when computing new mean for each cluster. To solve this issue, an improved algorithm of rough k-means clustering based on variable weighted distance measure is presented in this article. Comparative experimental results of real world data from UCI demonstrate the validity of the proposed algorithm.

Variational nodal methods for neutron transport: 40 years in review

Zhang Tengfei,Li Zhipeng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9

The variational nodal method for solving the neutron transport equation has evolved over 40 years. Based on a functional form of the Boltzmann neutron transport equation, the method now comprises a complete set of variants that can be employed for different problems. This paper presents an extensive review of the development of the variational nodal method. The emphasis is on summarizing the whole theoretical system rather than validating the methodologies. The paper covers the variational nodal formulation of the Boltzmann neutron transport equation, the Ritz procedure for various application purposes, the derivation of boundary conditions, the extension for adjoint and perturbation calculations, and treatments for anisotropic scattering sources. Acceleration approaches for constructing response matrices and solving the resulting system of algebraic equations are also presented

Syntheses and properties of Ti2AlN MAX-phase films

Tengfei Zhang 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.S1

Ti2AlN MAX-phase films were synthesized through the post-annealing process of as-deposited Ti-Al-N films. Near amorphous or quasi-crystalline ternary Ti-Al-N films were deposited on Si and Al2O3 substrates by sputtering a Ti2AlN MAX-phase target at room temperature, 300 ο C and 450 ο C, respectively. A vacuum annealing of those films at 800 ο C for 1 hour changed those films to crystalline Ti2AlN MAX-phase. The polycrystalline Ti2AlN MAX-phase films exhibited very excellent oxidation resistance due to its characteristics microstructure (nanolaminates), which has potential applications for high-temperature protective coatings. The microstructure and composition of Ti2AlN MAX-phase films were investigated using with a variety of characterization tools.

Dry reforming of methane over Ni/SBA-15 catalysts prepared by homogeneous precipitation method

Qiulin Zhang,Jing Wang,Ping Ning,Tengfei Zhang,Mingzhi Wang,Kaixian Long,Jianhong Huang 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.11

Ni/SBA-15 catalyst was prepared by homogeneous precipitation method (Ni-HP) and used for dry reforming of methane (DRM). The related characterization results indicated that the Ni particles were highly dispersed with a size range of 2-5 nm. Compared with Ni/SBA-15 catalyst prepared by impregnation (Ni-IM), the reduction temperature of Ni-HP obtained from H2-TPR was greatly improved, suggesting the stronger metal-support interaction. After reacting at 700 oC for 100 h, the CH4 conversion of DRM over Ni-HP catalyst slightly decreased from 74.5% to 73.8%. While, for the Ni-IM catalyst, the CH4 conversion dropped from 61.7% to 37.3%. Furthermore, the average particle size of Ni-HP was 3.7 nm and 4.7 nm before and after the long-time stability test, respectively, ascribed to the good antisintering property. Although a certain amount of coke was produced, mainly with disorder filamentous carbon of basegrowth, the Ni/SBA-15 prepared by homogeneous precipitation exhibited excellent catalytic activity and stability.

Carbon dioxide reforming of methane over MgO promoted Ni/CNT catalyst

Dehua Zhang,Guangcheng Wei,Yiru Wang,Jing Wang,Ping Ning,Qiulin Zhang,Mingzhi Wang,Tengfei Zhang,Kaixian Long 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.10

Carbon dioxide reforming of methane to syngas was investigated over a series of MgO promoted Ni/CNT catalysts. MgO played a critical role in improving the catalytic performance of Ni/CNT. The results showed that the addition of MgO strengthened the interaction of Ni and interior surface of CNT. Highly dispersed nickel particles with small size (less than 4.5nm) were also observed in MgO modified CNT. Otherwise, the NiO nanoparticles were facilely reduced over the catalyst prepared with a narrow size of CNT, as shown in H2-TPR. The reaction tests demonstrated that the Ni-based catalyst with an addition of MgO and narrow size of CNT exhibited better catalytic activity. Furthermore, the lifetime of Ni-based catalyst was prolonged effectively after adding MgO, attributed to the stabilization and dispersion of Ni particles and the effective restraint on the gasification of CNT.

Flatbands and Emergent Ferromagnetic Ordering in Fe3Sn2 Kagome Lattices

Lin, Zhiyong,Choi, Jin-Ho,Zhang, Qiang,Qin, Wei,Yi, Seho,Wang, Pengdong,Li, Lin,Wang, Yifan,Zhang, Hui,Sun, Zhe,Wei, Laiming,Zhang, Shengbai,Guo, Tengfei,Lu, Qingyou,Cho, Jun-Hyung,Zeng, Changgan,Zhan American Physical Society 2018 Physical Review Letters Vol.121 No.9

Evidences and magnitude of nighttime transpiration derived from Populus euphratica in the extreme arid region of China

Tengfei Yu,Qi Feng,Jianhua Si,Xiaoyou Zhang,Downey Alec,Chunyan Zhao 한국식물학회 2016 Journal of Plant Biology Vol.59 No.6

Extensive research has found that nighttime transpiration (E n) is positively correlated to the vapour pressure deficit (VPD), that suggested E n was highest during the night under high temperatures and low humidity along with high soil water availability, typically for the riparian forest in the extreme arid region of China. This study used the heat ratio method to measure sap velocity (V s) for mature and saplings Populus euphratica Oliv., and then E n was conservatively calculated as total nocturnal sap flow (F s, the product of V s and sapwood area A s) between 01:00 to 06:00. A gas exchange system was used to measure the leaf transpiration rate (T r) and stomatal conductance (g s) of saplings. For mature trees, nighttime V s was extensive and logarithmic correlated to VPD (similar to daytime). For saplings, g s and T r was extensive in different months, and also a strong logarithmic relationship was found between V s and VPD for both daytime and nighttime periods. Both of stem sap flow and leaf gas exchange suggusted the occurrence of E n, whether mature or sapling trees. E n contribution to daily transpiration (E d) was high just as expected for P. euphratica, which was confirmed by proportional E n to E d (E n/E d) means taken in 2012 (24.99%) and 2013 (34.08%). Compared to mature trees, E n/E d of saplings in 2013 was lower with means of 12.06%, that supported further by the shorter duration times and less T r,n (16.64%) and g s,n (26.45%) of leaf, suggesting that E n magnitude is associated to individual the tree size, that effect to stored water of individual trees, although this hypothesis requires further research.

Preparation of highly efficient self-healing anticorrosion epoxy coating by integration of benzotriazole corrosion inhibitor loaded 2D-COF

Tengfei Liu,Wen Li,Chenyang Zhang,Wei Wang,Wenwen Dou,Shougang Chen 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.97 No.-

In this work, multi-layer stacked two-dimensional (2D) covalent organic framework of TpPa-1 wassynthesized as nanocontainer to fabricate self-healing epoxy coating. The corrosion inhibitor ofbenzotriazole (BTA) was loaded into porous TpPa-1 (Tp: 1,3,5-Triformylphrogroglucinol, Pa-1: 1,4-phenylenediamine), and the load capacity was further improved by electrostatic adsorption. Then, 0.5 wt. % BTA/TpPa-1 and 0.5 wt.% TpPa-1 were added to the epoxy coating, respectively. The electrochemicalImpedance Spectroscopy (EIS) test shown that after 60 days of immersion, the impedance of the BTA/TpPa-1/EP in low-frequency region was 6.45108V cm2, while the impedance corresponding to theTpPa-1/EP coating was 9.04107V cm2. In addition, in the localized electrochemical impedancespectroscopy (LEIS) test, as the immersion time was extended, the impedance of TpPa-1/EP coating at thedefect continued to decrease, while the impedance at the defect of the BTA/TpPa-1/EP coating shown anupward trend, showing self-healing performance. This was due to the pH change when the metal at thedefect is corroded, which caused the BTA to be released from the nanocontainer and adhered to the metalsurface to form a protectivefilm. The improvement of the anti-corrosion performance of BTA/TpPa-1/EPcoating mainly comes from two aspects: (1) The good dispersion of TpPa-1 in EP coating improves thephysical shielding effect of the coating; (2) The controlled release of BTA can Realize the continuousformation of the bare metal surface protective layer.

Coupling conversion of methanol and 1-butylene to propylene on HZSM-5 molecular sieve catalysts prepared by different methods

Xin Zhang,Ting Bai,Xiling Liu,Tengfei Chen,Wentao Fan 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.7

A series of HZSM-5 catalysts were synthesized by different methods. The physicochemical properties of the HZSM-5 catalysts were characterized by XRD, SEM, N2 isothermal adsorption-desorption, NH3-TPD, Py-IR and TGA, respectively. The results indicated that different preparation conditions lead to different morphologies, textures and the distribution of acid sites. The nanosized HZSM-5 catalysts exhibited better catalytic reactivity and coke capacity than the micro-sized HZSM-5 because nanosized HZSM-5 had larger specific surface area, higher pore volume, more exposed channels and more accessible acid sites. The large particles of NZ-3 in a reasonable range and the smooth surface were conducive to product diffusion; therefore, NZ-3 exhibited higher specific propylene yield and stability than the other nanosized catalysts. The moderate density and distribution of acid sites on NZ-3 also favored the formation of propylene.

Rolling bearing fault convolutional neural network diagnosis method based on casing signal

Xiangyang Zhang,Guo Chen,Tengfei Hao,Zhiyuan He 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6

Affected by the transmission path, it is very difficult to diagnose the vibration signal of the rolling bearing on the aircraft engine casing. A fault diagnosis method based on convolutional neural network is proposed for the weak vibration signal of the casing under the excitation of rolling bearing fault. Firstly, the processing method of vibration signal is studied. Through comparison and analysis, it is found that the fault characteristics of rolling bearing are more easily expressed by continuous wavelet scale spectrum, and a better recognition rate is obtained. Finally, the experiment was carried out with an aero-engine rotor tester with a casing, and the method based on wavelet scale spectrum and convolutional neural network was used for diagnosis. The results were compared with the support vector machine method. The results show that the method has a high recognition rate for the weak fault signals of different fault types collected on the aero engine case, and its fault recognition rate reaches 95.82 %, which verifies the superiority and potential of the method for rolling bearing fault diagnosis.