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.

Synthesis and Properties of Biodegradable Polyurethane Crosslinkers from Methyl Ethyl Ketoxime-Blocked Diisocyanate

Tengfei Shen,Mangeng Lu,Liyan Liang 한국고분자학회 2012 Macromolecular Research Vol.20 No.8

A series of novel biodegradable blocked polyurethane crosslinkers (BPUCs) were synthesized from the reaction of toluene 2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI), polycaprolactone (PCL), 1,1,1-trimethylolpropane (TMP), and methyl ethyl ketoxime (MEKO). Synthesis of the accurate kind of BPUCs was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the deblocking temperatures of the BPUCs. The thermal analysis revealed that both TDI- and IPDI-based BPUC had the proper initial deblocking temperature (<160 oC) and the maximum deblocking temperature (<200 oC) for practical applications. Compared to IPDI-based BPUC, the TDI-based BPUC had a lower thermal dissociation temperature and a faster deblocking rate. Hydroxyl polyurethane (HPU) was introduced to study the crosslinking effect of prepared BPUCs. The reaction proceeded at various deblocking temperatures in different curing times. It was noticed that the elastic modulus and tensile strength of the HPU sample increased whereas elongation at break decreased with the addition of BPUC in comparison with pure HPU, which suggested better interfacial adhesion due to the strong chemical reaction between the released NCO groups from BPUC and hydroxyl groups from HPU. In addition, improvement on water resistance of the BPUC modified HPU samples compared to pure HPU samples also demonstrated the good crosslinking effect of prepared BPUCs.

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.

Water and Ink Mutually Beget Each Other

Tengfei Liu 한국콘텐츠학회 2016 ICCC International Digital Design Invitation Exhib Vol.2016 No.5

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.

A Youla-parameterized Gap Control for Next Generation of Optical Storage Systems

Tengfei Yue,Zhizheng Wu,Feng Li,Tao Wang,Lu Wang,Dziki Mbemba 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.6

With the development of ultra-high-density optical storage technology, the density of storage media is getting higher and higher, but the increase of the capacity of the optical disk leads to the reduce of the lens-disk interface gap and the tolerance of the focus error dramatically. In the case of extremely small spacing, various external disturbances are highly likely to cause a collision between the optical lens and the disc. In order to avoid the collision between the optical lens and disk, effectively eliminate the deterministic disturbance and suppress the unknown random disturbance, in this paper a multi-objective optimal output feedback controller design approach is proposed within the Q (Youla)-parameterized regulator scheme. The optimal Q parameter in the controller is obtained by solving the properly formulated linear matrix inequalities (LMIs). The experimental results show that the designed Q-parameterized controller can eliminate the influence of various disturbances and suppress the occurrence of collisions effectively.

Nonlinear finite element analysis of circular concrete-filled steel tube structures

Tengfei Xu,Tianyu Xiang,Renda Zhao,Yulin Zhan 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.3

The structural behaviors of circular concrete filled steel tube (CFT) structures are investigated by nonlinear finite element method. An efficient three-dimensional (3D) degenerated beam element is adopted. Based on those previous studies, a modified stress-strain relationship for confined concrete which introduces the influence of eccentricity on confining stress is presented. Updated Lagrange formulation is used to consider the geometrical nonlinearity induced by large deformation effect. The nonlinear behaviors of CFT structures are investigated, and the accuracy of the proposed constitutive model for confined concrete is mainly concerned. The results demonstrate that the confining effect in CFT elements subjected to combining action of axial force and bending moment is far sophisticated than that in axial loaded columns, and an appropriate evaluation about this effect may be important for nonlinear numerical simulation of CFT structures.

Hybrid simulation tests of high-strength steel composite K-eccentrically braced frames with spatial substructure

Tengfei Li,Mingzhou Su,Jiangran Guo 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.4

Based on the spatial substructure hybrid simulation test (SHST) method, the seismic performance of a high-strength steel composite K-eccentrically braced frame (K-HSS-EBF) structure system is studied. First, on the basis of the existing pseudostatic experiments, a numerical model corresponding to the experimental model was established using OpenSees, which mainly simulated the shear effect of the shear links. A three-story and five-span spatial K-HSS-EBF was taken as the prototype, and SHST was performed with a half-scale SHST model. According to the test results, the validity of the SHST model was verified, and the main seismic performance indexes of the experimental substructure under different seismic waves were studied. The results show that the hybrid simulation results are basically consistent with the numerical simulation results of the global structure. The deformation of each story is mainly concentrated in the web of the shear link owing to shear deformation. The maximum interstory drifts of the model structure during Strength Level Earthquake (SLE) and Maximum Considered Earthquake (MCE) meet the demands of interstory limitations in the Chinese seismic design code of buildings. In conclusion, the seismic response characteristics of the K-HSS-EBFs are successfully simulated using the spatial SHST, which shows that the K-HSS-EBFs have good seismic performance.

Spatial substructure hybrid simulation tests of high-strength steel composite Y-eccentrically braced frames

Tengfei Li,Mingzhou Su,Yan Sui 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.5

High-strength steel composite Y-eccentrically braced frame (Y-HSS-EBF) is a novel structural system. In this study, the spatial substructure hybrid simulation test (SHST) method is used to further study the seismic performance of Y-HSS-EBF. Firstly, based on the cyclic loading tests of two single-story single-span Y-HSS-EBF planar specimens, a finite element model in OpenSees was verified to provide a reference for the numerical substructure analysis model for the later SHST. Then, the SHST was carried out on the OpenFresco test platform. A three-story spatial Y-HSS-EBF model was taken as the prototype, the top story was taken as the experimental substructure, and the remaining two stories were taken as the numerical substructure to be simulated in OpenSees. According to the test results, the validity of the SHST was verified, and the main seismic performance indexes of the SHST model were analyzed. The results show that, the SHST based on the OpenFresco platform has good stability and accuracy, and the results of the SHST agree well with the global numerical model of the structure. Under strong seismic action, the plastic deformation of Y-HSS-EBF mainly occurs in the shear link, and the beam, beam-columns and braces can basically remain in the elastic state, which is conducive to post-earthquake repair.

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.