A Comparative Study on the Insulation Ageing of 10 kV XLPE Cable via Accelerated Electrical Test and Accelerated Water Tree Test

Li Weiwei,Zheng Wenyue,Ren Lulu,Li Huan,Zhao Xuetong,Wang Can,Li Jianying 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1

Medium and high voltage XLPE cables were widely used in urban distribution network. The electric-thermal eff ect of the cable conductor and water in the running environment are two important factors that cause ageing of cable insulating material. In this work, accelerated electrical test (AET) and accelerated water tree test (AWTT) on 10 kV XLPE cable were carried out for 1440 h, 2880 h and 4320 h, respectively. The physicochemical and dielectric properties of both aged and unaged XLPE samples were tested. Physicochemical investigation of Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diff raction (XRD) show that higher carbonyl groups index, and lower crystallinity of the XLPE insulating materials were generated in AWTT process than that in AET process. The thermal decomposition process of the AWTT XLPE are complicated, presenting a multi-peak phenomenon in the diff erential thermogravimetry (DTG) curve. The insulating strength of the samples after AWTT is monotonically decreased from 23.03 kV to 21.74 kV with ageing time. The dielectric properties show that the permittivity and dielectric loss of AWTT samples increased more severely than that of AET samples, with a new dielectric relaxation peak appearing at around 100 Hz. The combination of physicochemical and dielectric results reveals that AWTT process leads to more serious degradation for XLPE insulating materials. A schematic illustration is given to elucidate the development of micro defects in XLPE during the AET and AWTT processes.

Preparation and deposition mechanism of pyrolytic carbon by CVI using 3D Ni/wood-carbon catalyst

Lulu Han,Xiaohong Shi,Xu Han,Li Yang,Kun Li,Tian Xinfa,Mu Jierui,Wang Guoqing 한국탄소학회 2022 Carbon Letters Vol.32 No.1

To improve the pyrolytic carbon (PyC) deposition rate of Carbon/Carbon (C/C) composites prepared by the traditional chemical vapor infiltration (CVI) method, the 3D Ni/wood-carbon (3D Ni/C) catalyst was introduced into the CVI process. The effects of catalyst on the density of C/C composites were studied, and the deposition rate and morphologies of PyC were investigated after catalytic CVI. The morphologies of catalyst and PyC were characterized by scanning electron microscope and polarized light microscopy. The catalytic deposition mechanism of PyC was studied by density functional theory. The experimental results show that the initial carbon deposition efficiency of the catalytic pyrolysis process was 3–4 times that of the noncatalytic process. The catalyst reduced the energy barrier in the first step of deposition reaction from 382.55 to 171.67 kJ/mol according to simulation results. The pyrolysis reaction energy with Ni catalyst is reduced by 54% than that without the catalyst.

Study on Hot Deformation Behavior and Bending Forging Process of 7075 Aluminum Alloy

Lulu Li,Rui Ma,Jun Zhao,Ruixue Zhai 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.5

7075 aluminum alloy forged elbow has a wide range of application, but its deformation law is very complex. Its forging process parameters are difficult to control, so it is becoming a difficulty in practical production. In this paper, aiming at the forging parameters of 7075 aluminum alloy, the thermal simulation compression tests with different deformation parameters were cleverly designed, and the optimal forming range of 7075 aluminum alloy was obtained by combining theoretical calculation, microstructure and simulation. The results showed that: 7075 aluminum alloy forming process parameters range was 350∘C≤T≤450∘C+0.01/s≤ε˙≤0.78/s, T = 400 °C + 0.78/s≤ε˙≤1.0/s(except 400 °C + 0.1/s). The optimum forging parameters were: forging temperature 420 °C, forging speed 10 mm/s.

Facile Synthesis of Flower-Like AgI/BiOBr Z-Scheme Nanocomposite with Enhanced Photocatalytic Activity for Degradation of 17α-Estradiol (EE2)

Lingxin Li,Han Li,Yanju Long,Shan Wang,Yu Chen,Sifeng Zhang,Lulu Wang,Lijun Luo,Fengzhi Jiang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.1

In the present work, a direct Z-scheme AgI/BiOBr heterojunction displaying improved photocatalytic activity was designed by a chemical bath deposition method. The obtained photocatalysts were systematically characterized through XRD, SEM, XPS, BET and UV-Vis diffuse reflectance spectroscopy. The synthesized AgI/BiOBr photocatalyst displayed superior photocatalytic performance in the case of 17α-ethinylestradiol (EE2), where 97.0% compound has been removed within 9 min of irradiation. The rate constant using AgI/BiOBr photo-catalyst was 16.0 and 138.7 times more than that of pure AgI and BiOBr, respectively. Furthermore, the photocatalytic mechanism was investigated. The results of this study indicated that AgI/BiOBr was a stable and efficient photocatalyst, with promising practical applications.

Investigating the Shear Strength Characteristics of Slip Zone Soil Based on In-situ Multiple Shear Tests

Zhe Li,Juqiang Li,Meng Han,Lulu Liu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

Investigating the shear strength characteristics of sliding zone soil is crucial for evaluating slope safety and stability. This paper discusses the shear strength characteristics of Lishi loess and N2laterite in the sliding zone under different influencing factors based on in-suit multiple shear tests, and the shear strength characteristics of Lishi loess were contrasted and analyzed based on field and laboratory tests. The results indicated a favorable correlation between the shear strength of soil samples and normal stress. The shear strength attenuation of clay-rich N2laterite was much larger than that of sand-rich Lishi loess with the increase of the shear stage. Importantly, the mutation points of the shear rate corresponding to the peak stress of soil samples were obtained, which can be used as a symbol to judge the transfixion of the shear plane. Moreover, the stress-strain characteristics of Lishi loess under the same normal load were diverse as a result of the different experimental methods, and the residual strength characteristics for the two tests also varied substantially. Notably, the Lishi loess in the field test has a more stable residual strength than the laboratory direct shear test conducted. The findings can aid in the comprehension of the mechanical behavior of loess and laterite on the Loess Plateau.

Does matching relation exist between the length and the tilting angle of terminal implants in the all-on-four protocol? stress distributions by 3D finite element analysis

Li, Xiaomei,Cao, Zhizhong,Qiu, Xiaoqian,Tang, Zhen,Gong, Lulu,Wang, Dalin The Korean Academy of Prosthodonitics 2015 The Journal of Advanced Prosthodontics Vol.7 No.3

PURPOSE. To explore whether there is matching relation between the length and the tilting angle of terminal implants in the All-on-Four protocol by studying the effects of different implant configurations on stress distributions of implant, bone, and framework. MATERIALS AND METHODS. Four implants were employed to support a full-arch fixed prosthesis and five three-dimensional finite element models were established with CT images, based on the length (S and L) and distal tilt angle ($0^{\circ}$, $30^{\circ}$ and $45^{\circ}$) of terminal implants for an edentulous mandible, which named: Tilt0-S, Tilt30-S, Tilt30-L, Tilt45-S and Tilt45-L. An oblique 240 N was loaded at second molar. The von Mises Stresses were analyzed. The implants were consecutively named #1 to #4 from the loading point. RESULTS. 1) Tilt0-S had the greatest stress on the implants, with the other groups exhibiting variable reductions; the four implants of Tilt45-L demonstrated the greatest reduction in stress. 2) Tilt0-S had the greatest stress at bone around #1 implant neck, and Tilt45-L exhibited the least stress, which was a 36.3% reduction compared to Tilt0-S. 3) The greatest stress in the framework was found on the cantilevers distal to #1 implant. Tilt45-S exhibited the least stress. CONCLUSION. Matching different length and tilting angle of the terminal implants led to variable stress reductions on implants, bone and the superstructure. By optimizing implant configuration, the reduction of stress on implants and surrounding bone could be maximized. Under the present condition, Tilt45-L was the preferred configuration. Further clinical testings are required.

In situ Cross-linked Chitosan Composite Superfine Fiber via Electrospinning and Thermal Treatment for Supporting Palladium Catalyst

Li Nie,Lulu Liang,Minjuan Jiang,Linjun Shao,Chenze Qi 한국섬유공학회 2018 Fibers and polymers Vol.19 No.7

Uniform chitosan fibers (CS/PEO) with diameter of 398±76 nm were prepared by electrospinning with merely 5 wt.% of poly(ethylene oxide) (PEO) loading, and then annealed at elevated temperature without the use of additional crosslinker to improve the thermostability and solvent resistance. Swelling test shows that the CS/PEO composite fibers annealed at 200 oC were stable in 50 wt.% acetic acid aqueous solution. The mechanical strength test shows that the annealing temperature can affect the tensile strength of CS/PEO composite fiber mat. The cross-linked CS/PEO composite fibers provide a useful platform for the immobilization of palladium catalyst to catalyze the Mizoroki-Heck reactions of aromatic halides with olefins. Moreover, these CS/PEO composite fibers could be post modified with special ligands to chelate palladium species efficiently to further improve the catalytic activity and stability.

Weather Features in the Coastal Area of the Northern Yellow Sea under the Influence of Sea-Land Breeze

Li Huilin,Sun Lianqiang,Xu Lulu 한국기상학회 2011 한국기상학회 학술대회 논문집 Vol.2011 No.10-1

Qualitative and quantitative analysis of furosine in fresh and processed ginsengs

Li, Yali,Liu, Xiaoxu,Meng, Lulu,Wang, Yingping The Korean Society of Ginseng 2018 Journal of Ginseng Research Vol.42 No.1

Background: Furosine (${\varepsilon}$-N-2-furoylmethyl-L-lysine, FML) is an amino acid derivative, which is considered to be an important indicator of the extent of damage (deteriorating the quality of amino acid and proteins due to a blockage of lysine and a decrease in the digestibility of proteins) during the early stages of the Maillard reaction. In addition, FML has been proven to be harmful because it is closely related to a variety of diseases such as diabetes. The qualitative analysis of FML in fresh and processed ginsengs was confirmed using HPLC-MS. Methods: An ion-pair reversed-phase LC method was used for the quantitative analysis of FML in various ginseng samples. Results: The contents of FML in the ginseng samples were 3.35-42.28 g/kg protein. The lowest value was observed in the freshly collected ginseng samples, and the highest value was found in the black ginseng concentrate. Heat treatment and honey addition significantly increased the FML content from 3.35 g/kg protein to 42.28 g/kg protein. Conclusion: These results indicate that FML is a promising indicator to estimate the heat treatment degree and honey addition level during the manufacture of ginseng products. The FML content is also an important parameter to identity the quality of ginseng products. In addition, the generation and regulation of potentially harmful Maillard reaction products-FML in ginseng processing was also investigated, providing a solid theoretical foundation and valuable reference for safe ginseng processing.

Improving Translation of Organization Names Combining Translation Model and Web Mining

Bin Li,Yin Zhou,Ning Ma,Wuqi Liang,Lulu Dong 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.1

Named entity (NE) translation is a fundamental task in machine translation (MT) and cross-language information retrieval (CLIR). Furthermore, Organization name (ON) translation is the most complex among all the NEs. A novel system for translating ONs from Chinese to English, with a translation model and web resources, is proposed. Firstly, we built a translation model with Chunk. Then query expansion was adopted with the translation model and term-subject co-occurrence. Thirdly, we extracted the Chinese Organization names with English sentences using the method of frequency shifting and adjacency information to find English fragments as translation candidates. Finally, we found the best translation by computing the trustworthiness of all candidates. The experimental results showed that the approach returned a better performance than machine translation-based systems.