Thermal and mechanical properties of diamond/SiC substrate reinforced by bimodal diamond particles

Pengfei Liu,Xulei Wang,Xinbo He,Xuanhui Qu 한국탄소학회 2022 Carbon Letters Vol.32 No.3

Diamond reinforced silicon carbide matrix composites (diamond/SiC) with high thermal conductivity were prepared by tape casting combined with Si vapor infiltration for thermal management application. The effects of the mixing mode of bimodal diamond particles on the microstructure, thermal and mechanical properties of the composites were analyzed. The results reveal that the thermal conductivity of composites is affected significantly by mixing mode of diamond. In general, when the content of large diamond remains constant, adding a slight amount of small diamond was found to be effective in improving the thermal conductivity of the composite. However, excess small diamonds added will decrease thermal conductivity due to its high interfacial thermal resistance. The maximum thermal conductivity of obtained diamond/SiC is 469 W/(m K) when 38 vol% large diamond and 4 vol% small diamond were added. Such a result can be attributed to the formation of efficient heat transfer channels within the composite and sound interfacial bonding between diamond and SiC phase. Diamond/SiC with high thermal conductivity are expected to be the next generation of electronic packaging substrate.

플라즈마 하이브리드를 통한 Xylene의 부산물 제어특성

LIU PENGFEI,김조천,Dinh Trieu Vuong,최인영,박성룡 한국대기환경학회 2014 한국대기환경학회 학술대회논문집 Vol.2014 No.10

The thermal and dielectric properties of diamond/SiC composites prepared by polymer impregnation and pyrolysis

Liu Pengfei,He Xinbo,Qu Xuanhui 한국탄소학회 2023 Carbon Letters Vol.33 No.2

This article reported a simple method for preparing diamond/SiC composites by polymer impregnation and pyrolysis (PIP) process, and the advantages of this method were discussed. Only diamond and SiC were contained in the diamond/SiC composite prepared by PIP process, and the diamond particles remained thermally stable up until the pyrolysis temperature was increased to 1600 °C. The pyrolysis temperature has a significant impact on the thermal conductivity and dielectric properties of composites. The thermal conductivity of the composite reaches a maximum value of 63.9 W/mK when the pyrolysis temperature is 1600 °C, and the minimum values of the real and imaginary part of the complex permittivity are 19.5 and 0.77, respectively. The PIP process is a quick and easy method to prepare diamond/SiC composites without needing expensive equipment, and it is of importance for promoting its application in the field of electric packaging substrate.

Comparison between laparoscopic and abdominal radical hysterectomy for stage IB1 and tumor size <2 cm cervical cancer with visible or invisible tumors: a multicentre retrospective study

Pengfei Li,Lan Chen,Yan Ni,Jiaqi Liu,Donglin Li,Jianxin Guo,Zhihua Liu,Shuangling Jin,Yan Xu,Zhiqiang Li,Lu Wang,Xiaonong Bin,Jinghe Lang,Ping Liu,Chunlin Chen 대한부인종양학회 2021 Journal of Gynecologic Oncology Vol.32 No.2

Objective: To compare 5-year disease-free survival (DFS) and overall survival (OS) rates oflaparoscopic radical hysterectomy (LRH) and abdominal radical hysterectomy (ARH) forstage IB1 and tumor size <2 cm with visible or invisible tumors. Methods: We retrospectively compared the oncological outcomes of 1,484 cervical cancerpatients with IB1 and tumor size <2 cm on final pathology, who received ARH (n=899) or LRH(n=585) between January 2004 and December 2016. Patients were divided into visible tumorsubgroup (ARH: n=668, LRH: n=444) and invisible tumor subgroup (ARH: n=231, LRH:n=141) according to tumor type. Results: LRH and ARH showed similar 5-year DFS and OS rates (93.3% vs. 93.1%, p=0.997;96.2% vs. 97.5%, p=0.351) in total study population. LRH was not associated with worse5-year DFS rate (hazard ratio [HR]=0.96; 95% confidence interval [CI]=0.58–1.58; p=0.871)or OS rate (HR=1.37; 95% CI=0.65–2.89; p=0.409) by multivariable analysis. In the visibletumor subgroups, LRH and ARH showed similar 5-year DFS and OS rates (91.9% vs. 91.9%,p=0.933; 95.0% vs. 96.9%, p=0.276), and LRH was not associated with worse 5-year DFS orOS rate (p=0.804, p=0.324). In the invisible tumor subgroups, LRH and ARH also showedsimilar 5-year DFS and OS rates (97.3% vs. 97.1%, p=0.815; 100% vs. 99.5%, p=0.449), andLRH was not associated with worse 5-year DFS rate (p=0.723). Conclusions: Among patients with stage IB1 and tumor size <2 cm, whether the tumor isvisible or not, the oncological outcomes of LRH and ARH among cervical cancer patients arecomparable. This suggests that LRH may be suitable for stage IB1 and tumor size <2 cm withvisible or invisible tumors.Trial Registration: International Clinical Trials Registry Platform Identifier: CHiCTR180017778

A simple method of correcting the parallel plate rim shear stress for non-Newtonian behavior

Pengfei Liu,Yang Wang,Yee-Kwong Leong,Seung Hyuk Kwon,최형진 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.2

In the rheological characterization of non-Newtonian fluids in a steady torsional shear flow using a parallelplate geometry, there is a need to correct the shear stress at the rim for non-Newtonian behavior. Solving the governing torsional flow equation inversely by Tikhonov regularization using experimental torque vs. rim shear rate data is the most scientific method for obtaining the model independent shear stress. In this short communication, a simple empirical method based on using the derivative of the polynomial fit to torque vs. rim shear rate to correct for the shear stress is presented. This method can be applied to any fluid behavior. The accuracy of this method was confirmed by the outstanding agreement of between the shear stress results of the two methods of polynomial and the inverse problem for magnetorheological fluids. The performance of other correction methods was also discussed.

Preparation and investigation of Dy³⁺-doped Ca₉LiGd_2/3(PO₄)₇ single-phase full-color phosphor

Liu, Shihua,Liu, Simei,Wang, Jingjing,Sun, Pengfei,Zhong, Yifan,Jeong, Jung Hyun,Deng, Bin,Yu, Ruijin Elsevier 2018 Materials research bulletin Vol.108 No.-

<P><B>Abstract</B></P> <P>Novel single-phased white-light-emitting Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:<I>x</I>Dy<SUP>3+</SUP> (<I>x</I> = 0.02, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30) β-Ca<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>-type phosphate phosphors were synthesized. The phase structure, luminescence, and thermal stability of the phosphors were characterized by X-ray powder diffraction analysis, photoluminescence excitation and emission spectra, thermal quenching, and decay curves. XRD analysis confirmed the phase formation of Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:Dy<SUP>3+</SUP> materials. Under the excitation of 352 nm, the emission of the Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:0.20Dy<SUP>3+</SUP> sample centered at blue (488 nm) and yellow (580 nm), which corresponded to <SUP>4</SUP>F<SUB>9/2</SUB>–<SUP>6</SUP>H<SUB>15/2</SUB> transition and <SUP>4</SUP>F<SUB>9/2</SUB>–<SUP>6</SUP>H<SUB>13/2</SUB> transition. The optimum dopant concentration of Dy<SUP>3+</SUP> ions was around 20 mol%, and the critical transfer distance of Dy<SUP>3+</SUP> was calculated as 18 Å. The thermal-quenching temperature was above 500 K for Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:0.20Dy<SUP>3+</SUP>. The developed phosphor has a great potential as a single-component white-light-emitting phosphor for UV-light-emitting diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel single-phased Ca<SUB>9</SUB>LiGd<SUB>2/3</SUB>(PO<SUB>4</SUB>)<SUB>7</SUB>:<I>x</I>Dy<SUP>3+</SUP> phosphor was firstly synthesized. </LI> <LI> Its structure, luminescent properties are well studied and characterized. </LI> <LI> It was promising as a single-component white-light-emitting phosphor for w-LEDs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Financial and Economic Risk Prevention and Countermeasures Based on Big Data and Internet of Things

Songyan Liu,Pengfei Liu,Hecheng Wang 한국정보처리학회 2024 Journal of information processing systems Vol.20 No.3

Given the further promotion of economic globalization, China's financial market has also expanded. However,at present, this market faces substantial risks. The main financial and economic risks in China are in the areasof policy, credit, exchange rates, accounting, and interest rates. The current status of China's financial marketis as follows: insufficient attention from upper management; insufficient innovation in the development of thefinancial economy; and lack of a sound financial and economic risk protection system. To further understandthe current situation of China's financial market, we conducted a questionnaire survey on the financial marketand reached the following conclusions. A comprehensive enterprise questionnaire from the government'sperspective, the enterprise's perspective and the individual's perspective showed that the following problemsexist in the financial and economic risk prevention aspects of big data and Internet of Things in China. Thepolitical system at the country’s grassroots level is not comprehensive enough. The legal regulatory system isnot comprehensive enough, leading to serious incidents of loan fraud. The top management of enterprises doesnot pay enough attention to financial risk prevention. Therefore, we constructed a financial and economic riskprevention model based on big data and Internet of Things that has effective preventive capabilities for bothenterprises and individuals. The concept reflected in the model is to obtain data through Internet of Things, usebig data for screening, and then pass these data to the big data analysis system at the grassroots level for analysis. The data initially screened as big data are analyzed in depth, and we obtain the original data that can be used tomake decisions. Finally, we put forward the corresponding opinions, and their main contents represent thefollowing points: the key is to build a sound national financial and economic risk prevention and assessmentsystem, the guarantee is to strengthen the supervision of national financial risks, and the purpose is to promotethe marketization of financial interest rates.

Exploration of the Glycosyltransferase BmmGT1 from a Marine-Derived Bacillus Strain as a Potential Enzyme Tool for Compound Glycol-Diversification

( Quanquan Liu ),( Pengfei Ren ),( Yang Liu ),( Wen Qin ),( Huayue Li ),( Wenli Li ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.6

Glycosyltransferases (GTs) from microbes are an emerging and rich source for efficient glycol-transformation of natural/unnatural compounds. Here, we probed the catalytic capability and substrate promiscuity of BmmGT1 from marine-derived Bacillus methylotrophicus B-9987. The regioselectivity of BmmGT1 on macrolactin A (1) was explored by optimization of the reaction conditions, in which a series of O-glycosylated macrolactins (1a-1e) were generated, including two new di/tri-O-glucosyl analogs (1b and 1e). Furthermore, BmmGT1 was able to catalyze the glycosylation of the thiol (S-) or amine (N-) sites of phenolic compounds (2 and 3), leading to the generation of N- (2a) or S-glycosides (3a and 3b). The present study demonstrates that BmmGT1 could serve as a potential enzyme tool for O-, N-, or S-glycosyl structural diversification of compounds for drug discovery.

Three birds with one stone: Nitrilotriacetic acid interface anchoring helps prepare efficient and stable perovskite solar cells

Chen Ting,Liu Pengfei,Liu Tianxiao,Li Xueyuan,Wang Huihui,He Tingwei,Liu Zhiyong 한국물리학회 2024 Current Applied Physics Vol.58 No.-

Electron transport layer (ETL) plays an important role in perovskite solar cells (PSCs). In this paper, a stable and cheap metal chelating agent, subnitrotriacetic acid (NTA), was used to modify SnO2 ETL in two ways:1) By incorporating NTA into SnO2 colloidal dispersion, the oxygen vacancy causing charge recombination was greatly reduced, and the recombination of psc was reduced by reducing the introduction of surface Ovs, 2) Spin-coating NTA at the SnO2/perovskite interface not only manages a large number of oxygen vacancies generated by high-temperature annealing, but also interacts with the unpaired Pb2+ in the perovskite absorption layer by interface modification of the C=O bond in NTA, passivates the surface of the perovskite layer, inhibits ion migration, stabilize the perovskite structure, and avoid its collapse, while significantly reducing the defect state density. By inhibiting the shallow interface trap and reducing the non-radiative recombination, efficient and stable perovskite solar cells were prepared. Under the condition of relative humidity greater than 40 % (RH), the efficiency of perovskite solar cells prepared by interface-anchored NTA was increased to 22.6 %, and the stability was significantly enhanced.

A Hardware-in-the-loop Platform for Modular Multilevel Converter Simulations

Liu, Chongru,Tian, Pengfei,Wang, Yu,Guo, Qi,Lin, Xuehua,Wang, Jiayu The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

In this paper, a hardware-in-the-loop simulation platform for MMCs is established, which connects a real time digital simulator (RTDS) and a designed MMC controller with optical fiber. In this platform, the converter valves are simulated with a small time step of 2.5 microsecond in the RTDS, and multicore technology is implemented for the controller so that the parallel valve control is distributed between different cores. Therefore, the designed controller can satisfy the requirements of real-time control. The functions of the designed platform and the rationality for the designed controller are verified through experimental tests. The results show that different modulation modes and various control strategies can be implemented in the simulation platform and that each control objective can been tracked accurately and with a fast dynamic response.