Tunable transport characteristics of graphene field-effect transistors by surface doping

Tingting FENG,Mengqiang WU 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Thermal transport phenomena in graphene aerogels

Feng GONG,Dimitrios PAPAVASSILIOU,Tingting FENG,Menqiang WU 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Hydrothermal Synthesis of Hierarchical Hollow Li(Ni0.8Co0.15Al0.05)O2 Microspheres for Lithium Ion Batteries

Liu Wenlong,Jiang Weiwei,Yan Chenran,Feng Wei,Wang Dongxia,Zhao Liming,Feng Tingting,Gong Feng 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.11

Li(Ni0.8Co0.15Al0.05)O2 (NCA) cathode material for lithium ion batteries is synthesized by calcining Ni–Co–Al hydroxide or carbonate hydroxide hydrate precursor, which is obtained by hydrothermal method, and the NCA cathode material is hierarchical hollow microspheres with the diameter in the range of 3–5 µm and composed of nanoflakes and/or nanowires. The effect of hydrothermal reaction time on the morphologies and the crystalline quality of the NCA cathode material is investigated on the basis of scanning electron microscopy, X-ray diffraction, and tunneling electron microscopy. The NCA cathode material shows smooth and monotonous charge/discharge characteristics, delivers a reversible capacity as 144.4 mAh/g and retains 90.4% after 50 cycles at a current density of 0.1 C between 2.5 and 4.3 V.

Reynolds number and scale effects on aerodynamic properties of streamlined bridge decks

Tingting Ma,Chaotian Feng 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.4

Section model test, as the most commonly used method to evaluate the aerostatic and aeroelastic performances of long-span bridges, may be carried out under different conditions of incoming wind speed, geometric scale and wind tunnel facilities, which may lead to potential Reynolds number (Re) effect, model scaling effect and wind tunnel scale effect, respectively. The Re effect and scale effect on aerostatic force coefficients and aeroelastic characteristics of streamlined bridge decks were investigated via 1:100 and 1:60 scale section model tests. The influence of auxiliary facilities was further investigated by comparative tests between a bare deck section and the deck section with auxiliary facilities. The force measurement results over a Re region from about 1×105 to 4×105 indicate that the drag coefficients of both deck sections show obvious Re effect, while the pitching moment coefficients have weak Re dependence. The lift coefficients of the smaller scale models have more significant Re effect. Comparative tests of different scale models under the same Re number indicate that the static force coefficients have obvious scale effect, which is even more prominent than the Re effect. Additionally, the scale effect induced by lower model length to wind tunnel height ratio may produce static force coefficients with smaller absolute values, which may be less conservative for structural design. The results with respect to flutter stability indicate that the aerodynamic-dampingrelated flutter derivatives 2 ∗ and 1 ∗ 3 ∗ have opposite scale effect, which makes the overall scale effect on critical flutter wind speed greatly weakened. The most significant scale effect on critical flutter wind speed occurs at +3° wind angle of attack, which makes the smallscale section models give conservative predictions.

Seasonal Variation and Sources of Heavy Metals in Urban Street Dusts and River Sediments of Dongluo River Watershed in Ji’nan City, China

Tingting Duan,Shanjun Liu,Dongying Wang,Jiashen Feng,Ningning Song,Yanxin Yu,Yingxia Li 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.5

Due to intense human activities, urban street dusts and river sediments are usually polluted by heavy metals. This study investigated the seasonal variations (summer and winter) of pollution level, spatial distribution and potential sources of heavy metals in street dusts (SD) and river sediments (RS) of Dongluo River watershed, Ji’nan, China. Results showed cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) contents were 3.5 (8.6), 3.0 (1.4), 4.9 (2.6), 4.1 (1.1) and 3.9 (4.0)-fold of their geochemical soil background values (BGV) of Shandong Province, China in summer (winter). Mercury (Hg) and arsenic (As) contents were lower than their background values in both summer and winter. The differences of Cd, Cr, Cu, Pb, Zn, Mn and As contents in river sediments between winter and summer were not statistically significant. The correlation coefficients between metal contents and the distance between sampling sites and the east-west boundary of study area were higher in summer than those in winter. Based on principal component analysis (PCA) and multivariate linear regression (MLR), coal combustion and traffic-related sources were the main sources in winter, and agricultural activities and traffic-related sources were the main sources in summer.

Construction of GPT-Vanishing Structures Using Shape Derivative

Global Science Press 2017 Journal of computational mathematics Vol.35 No.5

<P>The Generalized Polarization Tensors (GPT) is a series of tensors which contain informations on the shape of a domain and its material parameters. The aim of this paper is to provide a method of constructing GPT-vanishing structures using shape derivative for two-dimensional conductivity or anti-plane elasticity problem. We assume a multi-coating geometry as a candidate of GPT-vanishing structure. We define a cost functional to minimize GPT and compute the shape derivative of this functional deriving an asymptotic expansion of the perturbations of the GPTs due to a small deformation of interfaces of the structure. We present some numerical examples of GPT-vanishing structures for several different shaped inclusions.</P>

Osteogenic effect of magnesium oxychloride cement modified with phytic acid and loaded with strontium ranelate

Tingting Ma,Yijia Guan,Jinlun Feng,Yue Yang,Junying Chen,Wenjie Guo,Jianguo Liao,Yanru Zhang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Magnesium oxychloride cement has good mechanical properties, but poor water resistance. Methods Phytic acid, which can form chelate with Mg2+, was used to modify magnesium oxychloride cement, and the effects of phytic acid on the strength, in vitro degradation and biological activity of magnesium oxychloride cement were studied. Based on the preparation of phytic acid modified magnesium oxychloride cement with good water resistance and biological activity, osteoporosis treatment strontium ranelate was loaded on phytic acidmagnesium oxychloride cement, strontium ranelate/phytic acid-magnesium oxychloride cement was prepared. Results It was found that the compressive strength of 1.25 wt% phytic acid-magnesium oxychloride cement after soaking in SBF for 28 d could reach 40.5 ± 2.0 MPa, 13.33% higher than that of the control group (when phytic acid was 0 wt%), and the mass loss rate of all ages was lower than that of the control group. The water resistance of magnesium oxychloride cement was effectively improved by phytic acid. After loading with strontium ranelate, the water resistance of 1.25 wt% phytic acid-magnesium oxychloride cement was improved. Cell experiments showed that strontium ranelate could effectively promote cell proliferation and improve the expression of osteoblastrelated proteins. When strontium ranelate/phytic acid-magnesium oxychloride cement samples were implanted subcutaneously in rats for 4 w, no obvious inflammatory response was observed, and the material was tightly bound to the surrounding tissues. When bone cement was implanted into rat femur for 4 w, the bone cement was gradually wrapped and absorbed by new bone tissue, which grew from the outside to the inside, indicating that the bone cement containing strontium ranelate/phytic acid-magnesium oxychloride cement had excellent bone-forming ability. Conclusions In conclusion, the results indicated that strontium ranelate/phytic acid-magnesium oxychloride cement composite bone cement had a potential application prospect in clinical bone repair.

Nitrogen self‑doped porous carbon nanosheets derived from azo dye flocs for efficient supercapacitor electrodes

Tingting Wei,Liang Wu,Feng Yu,Yin Lv,Long Chen,Yulin Shi,Bin Dai 한국탄소학회 2019 Carbon Letters Vol.29 No.5

The present work introduces a new method for the recycling of waste flocculation sludge to prepare electrode materials for supercapacitor. Hazardous azo dye was removal from textile dying wastewater by a new chitosan-based flocculant, and the generated dye sludge flocs was used as a nitrogen-containing precursor for the fabrication of N-doped carbon materials. The influence of azo dye on specific surface areas, nitrogen content, pore evolution of the resulting products and their electrochemical performance were investigated in detail. The results demonstrated a dual role of azo dye worked as both a nitrogen resource and pore-forming agent. The resulting N-doped carbon nanosheets derived from azo dye flocs demonstrated high electrochemical capacitance and good stability for supercapacitor electrode, which is attributed to the unique nitrogen doping, higher specific surface area and efficient charge transfer ability.

Molecular cloning, characterization, and functional analysis of a gene encoding 3-hydroxy-3-methylglutaryl-coenzyme A synthase from Matricaria chamomilla

Feng Xu,Tingting Tao,Qiangwen Chen,Xiangxiang Meng,Jiaping Yan,Jie Chang 한국유전학회 2016 Genes & Genomics Vol.38 No.12

3-Hydroxy-3-methylglutaryl-CoA synthase (HMGS) catalyzes the condensation of acetyl-CoA and acetoacetyl- CoA to form 3-hydroxy-3-methylglutaryl-CoA as the first committed enzyme in the mevalonate (MVA) pathway. HMGS plays an important role in the biosynthesis of the sesquiterpene, which is the main constituent of essential oil in Matricaria chamomilla. In this paper, a HMGS gene designated as McHMGS (GenBank Accession No. KU529970) was successfully cloned from M. chamomilla. The full-length cDNA of McHMGS was 1495-bp and contained a 1374-bp open reading frame. It encoded a 458-amino-acid protein with a calculated molecular weight of about 50.7 kDa and isoelectric point of 5.69. Sequence comparison revealed that McHMGS showed extensive homology with HMGSs from other plant species. Phylogenetic tree analysis indicated that McHMGS is clustered with the HMGS of Asteraceae in the dicotyledoneae clade. Further functional complementation of McHMGS in hmgsdeficient mutant yeast strain YSC6274 demonstrated that cloned McHMGS cDNA encodes a functional HMGS and mediates the MVA biosynthesis in yeasts. The tissue expression pattern analysis revealed that McHMGS expression level is highest in the flowers and lowest in the stems. Quantitative real-time PCR analysis showed that the expression of McHMGS was induced by MeJA, and the expression level is highest 24 h after induction. The characterization and expression of McHMGS can help in further studying the role of McHMGS gene in the biosynthesis of sesquiterpene in M. chamomilla.

Nitrogen self-doped porous carbon nanosheets derived from azo dye flocs for efficient supercapacitor electrodes

Wei Tingting,Wu Liang,Yu Feng,Lv Yin,Chen Long,Shi Yulin,Dai Bin 한국탄소학회 2019 Carbon Letters Vol.29 No.5

The present work introduces a new method for the recycling of waste flocculation sludge to prepare electrode materials for supercapacitor. Hazardous azo dye was removal from textile dying wastewater by a new chitosan-based flocculant, and the generated dye sludge flocs was used as a nitrogen-containing precursor for the fabrication of N-doped carbon materials. The influence of azo dye on specific surface areas, nitrogen content, pore evolution of the resulting products and their electrochemical performance were investigated in detail. The results demonstrated a dual role of azo dye worked as both a nitrogen resource and pore-forming agent. The resulting N-doped carbon nanosheets derived from azo dye flocs demonstrated high electrochemical capacitance and good stability for supercapacitor electrode, which is attributed to the unique nitrogen doping, higher specific surface area and efficient charge transfer ability.