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      • KCI등재

        Effect of Microstructure on Thermal Conductivity of Polymer Composites

        Yue Yang,Junjie Shu,Peng Chen,Ru Xia,Jiasheng Qian,Bin Yang,JIBIN MIAO,LIFEN SU,Zhengzhi Zheng,Ming Cao 한국고분자학회 2017 Macromolecular Research Vol.25 No.4

        Thermal conductivity (TC) of polymer composites is strongly depended on thermal conductive fillers as well as heat conduction pathways formed by these fillers. In this work, we examined effects of morphology, size and arrangement of fillers on TC of polymer composites by using energy-conserving dissipative particle dynamic (e-DPD) simulation. Theoretically, we explored effects of ideal and “pseudo” thermal conductive pathways on composites’ TC and investigated heat conduction of filler particles with cubic-center and lamellar morphology. To confirm orientation and size effects of lamellar filler particles on composites’ TC, we prepared a series of Boron Nitride/Silicon rubber composites (BN/SiR). Being same with those observed in e-DPD simulation, orientation could efficiently improve TC of BN/SiR composites. The TC of composites with filled diameters about 10 micrometer of BN flats is 11 times higher than that of SiR matrix. Our researching results show that heat conduction pathways are essential to transportation of heat flux in polymer composites and even “pseudo” pathways by disconnected filler particles along temperature gradient can accelerate heat conduction.

      • KCI등재

        In Situ Fabrication of TiO2/Bi3.64Mo0.36O6.55 Nanocomposite with High Visible-Light-Driven Photocatalytic Efficiency

        Zhiyuan Yang,Junjie Wang,Lu Chen,Mengjun Liang,Yulin Xu,Chentao Zou,Xiaoxia Liu,Shuijin Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5

        In this work, we developed a simple hydrothermal method toward the fabrication of TiO2/ Bi3.64Mo0.36O6.55 heterostructure, which had superior photocatalytic performance for degrading of RhB under visible light irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), UV-Vis diffuse reflectance spectroscopy (DRS) and photoelectrochemical measurements. The optimal composite with 15 wt.% TiO2/Bi3.64Mo0.36O6.55 (TBMO3) exhibits a much higher photocatalytic activity than that of Bi3.64Mo0.36O6.55 and P25 by degradation of RhB under visible light irradiation within 20 min. The enhanced performance of TBMO3 is predominantly attributed to the synergistic effect both in the higher surface area and the improved separation of photogenerated charge carriers between the two semiconductors. Recycling experiments indicated that TiO2/Bi3.64Mo0.36O6.55 photocatalysts had excellent cycle performance and stability. The photocatalytic mechanism of nanocomposite photocatalysts was proposed, which is confirmed by the active species trapping experiments and photoluminescence tests.

      • KCI등재

        Preintervention risk stratification of renal pelvic cancer and ureteral cancer should differ

        Tao Yang,Nan Zhang,Bo Yang,Dalin He,Junjie Fan,Jinhai Fan 대한비뇨의학회 2020 Investigative and Clinical Urology Vol.61 No.4

        Purpose: To identify different preintervention prognostic factors between renal pelvic cancer (RPc) and ureteral cancer (Uc) and to develop different preintervention risk stratifications for each cancer type. Materials and Methods: A total of 1,768 patients with organ-confined upper urinary tract urothelial carcinoma (1,067 patients with RPc and 701 with Uc) who presented between 2004 and 2015 were selected from the Surveillance, Epidemiology, and End Results database. Clinicopathologic characteristics were compared between RPc and Uc. Univariable and multivariable Cox regression models were used to examine the prognostic ability of the clinicopathologic characteristics with respect to oncology outcomes. Results: Age greater than 75 years was significantly associated with cancer-specific survival (CSS) in RPc patients but not in Uc patients. Tumor size had a significant influence on CSS in Uc patients but not in RPc patients; in contrast, age had an influence in RPc but not in Uc. Unlike CSS, age was significantly associated with overall survival (OS) in both RPc and Uc. Tumor size had an effect on OS in Uc patients but not in RPc patients. Conclusions: The preintervention prognostic factors differed between RPc and Uc. Thus, we should develop separate preintervention risk stratification standards for RPc and Uc. Using these specific preintervention risk stratifications, we may be able to select the most appropriate surgical options for patients in the clinic.

      • KCI등재

        Research on the vibration characteristics and performance optimization of the rotor-shaft system of an unbalanced permanent magnet synchronous motor

        Dongwen Wang,Wei Yang,Jiafeng Yang,Kongming Jiang,Junjie Zhang,Yang Fu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

        Research on the vibration characteristics of the permanent magnet synchronous motor (PMSM) is hindered by the harmonic characteristics of the unbalanced magnetic pull force when air-gap eccentricity is neglected. Thus, the effects of both air-gap eccentricity and mass eccentricity on the rotor vibration have not yet been fully elucidated. To address this, a unified expression for the unbalanced magnetic pull force of the motor was derived under various pole pairs and air-gap eccentricities. The distribution of the radial electromagnetic force under different eccentricities is revealed. An electromagnetic simulation model of the fan motor was established for three eccentric cases and the effect of the unbalanced magnetic pull distribution and harmonic frequency characteristics on the rotor were analyzed. Furthermore, the influence of the gyroscopic effects on the modal frequency of the rotor structure was studied. The harmonic response of the rotor shaft system was first established using multi-physical field coupling, then the vibration amplitude-frequency laws of the rotor-shaft system under the influence of air-gap eccentricity and mass eccentricity were investigated. To reduce the vibration of the unbalanced PMSM rotor-shaft system, a multi-objective optimization was performed using the genetic algorithm in ANSYS Workbench. Research on the vibration characteristics of the permanent magnet synchronous motor (PMSM) is hindered by the harmonic characteristics of the unbalanced magnetic pull force when air-gap eccentricity is neglected. Thus, the effects of both air-gap eccentricity and mass eccentricity on the rotor vibration have not yet been fully elucidated. To address this, a unified expression for the unbalanced magnetic pull force of the motor was derived under various pole pairs and air-gap eccentricities. The distribution of the radial electromagnetic force under different eccentricities is revealed. An electromagnetic simulation model of the fan motor was established for three eccentric cases and the effect of the unbalanced magnetic pull distribution and harmonic frequency characteristics on the rotor were analyzed. Furthermore, the influence of the gyroscopic effects on the modal frequency of the rotor structure was studied. The harmonic response of the rotor shaft system was first established using multi-physical field coupling, then the vibration amplitude-frequency laws of the rotor-shaft system under the influence of air-gap eccentricity and mass eccentricity were investigated. To reduce the vibration of the unbalanced PMSM rotor-shaft system, a multi-objective optimization was performed using the genetic algorithm in ANSYS Workbench. The optimization results show that when the motor rotor core is shifted 2 mm in the positive X direction and the distance between the double-row bearing and rotor core is 7 mm, the vibration acceleration amplitude is reduced by 54.9 % compared with the original model.

      • KCI등재

        Deadbeat and Hierarchical Predictive Control with Space-Vector Modulation for Three-Phase Five-Level Nested Neutral Point Piloted Converters

        Junjie Li,Xiangyu Chang,Dirui Yang,Yunlong Liu,Jianguo Jiang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

        To achieve a fast dynamic response and to solve the multi-objective control problems of the output currents, capacitor voltages and system constraints, this paper proposes a deadbeat and hierarchical predictive control with space-vector modulation (DB-HPC-SVM) for five-level nested neutral point piloted (NNPP) converters. First, deadbeat control (DBC) is adopted to track the reference currents by calculating the deadbeat reference voltage vector (DB-RVV). After that, all of the candidate switching sequences that synthesize the DB-RVV are obtained by using the fast SVM principle. Furthermore, according to the redundancies of the switch combination and switching sequence, a hierarchical model predictive control (MPC) is presented to select the optimal switch combination (OSC) and optimal switching sequence (OSS). The proposed DB-HPC-SVM maintains the advantages of DBC and SVM, such as fast dynamic response, zero steady-state error and fixed switching frequency, and combines the characteristics of MPC, such as multi-objective control and simple inclusion of constraints. Finally, comparative simulation and experimental results of a five-level NNPP converter verify the correctness of the proposed DB-HPC-SVM.

      • KCI등재

        Flow field characteristics of an agitator system of a large diameter slurry-water shield machine

        Junjie Liao,Kun Bai,Yi-Min Xia,Haizhen Li,Xianqiong Zhao,Xuemeng Xiao,Yang Wang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4

        A numerical model was established for calculation in this study on the basis of the standard k-epsilon turbulence model and the discrete phase model of the Euler-Lagrange equation. Results of the particle image velocimetry experiment were used to verify the reliability of the numerical model. The effects of the rotation speeds, slurry densities, and impeller structures on the flow field characteristics, including velocity distribution, ballast fluidity, and power loss, were also investigated. The results indicate that the increase of rotation speed has little influence on the flow field near the wall and bottom of the agitator, and the agitator performs well when the speed is set between 30 rpm and 40 rpm. The increase of the slurry density will increase the pressure loss between the inlet and the outlet, and it will also increase the load of the agitator. Hence, the slurry density must be less than 1400 kg/m 3 . The baffle can improve the velocity distribution of the flow field and the slag discharge capacity of the agitator.

      • KCI등재

        Development and Application of Polymorphic SSR Markers in Luffa cylindrica

        Junjie Cui,Zhen Lv,Tianwen Yang,Jing Wang,Yu Hong 한국원예학회 2022 원예과학기술지 Vol.40 No.5

        Two published genomes of Luffa cylindrica, ‘SG2019’ and ‘SO3’, were used to develop polymorphic SSR markers for L. cylindrica by searching and comparing the SSR motifs at the same site in the two genomes. Based on the SSR search conditions and primer design criteria, 2130 polymorphic SSR markers for L. cylindrica were developed. The main motif type was dinucleotide, accounting for 80.28% of the total; the main motif units were AT/AT and AAT/ATT, accounting for 87.80% of the total. Furthermore, 40 polymorphic SSR markers developed in this study were randomly selected and amplified in 24 Luffa samples. According to the results, the 40 polymorphic SSR markers showed an amplification rate of 100% and a polymorphism rate of 80%. Cluster analysis classified the 24 Luffa samples into two main groups, L. cylindrica and L. acutangula. Overall, the polymorphic SSR markers developed in this study display a high polymorphic rate and reliable utilization value.

      • First Larvae of Lebbeus comanthi and Thor amboinensis(Decapoda: Hippolytidae) Hatched in the Laboratory

        Yang, Hoi Jeong,Okuno, Junji The Korean Society for Integrative Biology 2004 Korean journal of biological sciences Vol.8 No.1

        The decapodid stage of Lebbeus comanthi Hayashi and Okuno and the first zoea of Thor amboinensis (De Man) are described based on laboratory-hatched eggs from females collected from Japan. The decapodid stage of L. comanthi is readily distinguished from that of L. groenlandicus by the carapace without anteroventral denticle and tooth behind rostrum, the absence of the antennal spine, the four-segmented outer flagellum of the antennule, the absence of the palp of the mandible, and the telson with posterior margin con caved medially and without dorsolateral spine. The carapace with anteroventral denticle and the third abdominal somite distinctly curved in lateral view distinguish the first zoea of T. amboinensis from that of T. dobkini Chace and T. floridanus Kingsley. Larval characters of the genus Thor are summarized.

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