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Jun Peng,Qian Wang,Jin Wang,Jun Yang,Taijun Jiang,Guangsheng Zeng 한국고분자학회 2022 Macromolecular Research Vol.30 No.11
Cardo containing phenoxy and -CF3 derivate diamine was synthesized, and further it was polymerized with 3,3',4,4'-biphenyl tetracarboxylic dianhydride to prepare polyetherimide containing Cardo group. The transmittance of the prepared polymer increased from 82% to 88% and the dielectric constant decreased from 2.91 to 2.83 with a slight decline in thermal and mechanical performance when -CF3 was introduced. The molecular simulation in terms of charge distribution, electric potential energy, chain stiffness and aggregation state revealed that -CF3 could restrain charge transfer and decrease the unit dipole moment and polarization for its larger volume. The optical and dielectric performance was significantly enhanced, but the thermal and mechanical performance decreased slightly when the -CF3 group was introduced. The glass transition temperature of the polymer declined from 329℃ to 311℃. The investigation conducted in this paper can offer valuable reference to the optimization and development of synthesis and comprehensive performance of polyimide.
Junpeng Yang,Qi Cai,Yongchang Liu,Chong Li,Zongqing Ma,Huijun Li 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
The W-modifi ed Ti 2 AlNb-based alloys synthesized at 1100 °C by spark plasma sintering were solution treated at 1300 °Cfor 4 h and then aged at 800–1000 °C for 1 h. The phase composition, microstructure evolution, and microhardness of theaged alloys are investigated in this study. A signifi cant enhancement of hardness, ~ 750 HV, is obtained in the alloy aged at900 °C, while that of the one without W addition is only ~ 470 HV. The hardness is also higher than that of common β-Ti andTi–6Al–4V alloys. As the ageing temperature increases, the B2/O structure evolves from B2 + O colonies to Widmannstättenstructure, followed by a “disordering to ordering” procedure. This process also involves the variation of the angle betweenadjacent O phase from 90° to 60°. Specifi cally, a herringbone Widmannstätten B2 + O structure is constructed in the alloysaged in the α 2 + B2 + O phase region, which is related to the diff usion of W and the substitution of W for Nb in the latticeof B2 or O.
Junpeng Zhu,Wei Gu,Ping Jiang,Shan Song,Haitao Liu,Huishi Liang,Ming Wu 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.6
When a failure occurs in active distribution system, it will be isolated through the action of circuit breakers and sectionalizing switches. As a result, the network might be divided into several connected components, in which distributed generations could supply power for customers. Aimed at decreasing customer interruption cost, this paper proposes a theoretically optimal island partition model for such connected components, and a simplified but more practical model is also derived. The model aims to calculate a dynamic island partition schedule during the failure recovery time period, instead of a static islanding status. Fluctuation and stochastic characteristics of the renewable distributed generations and loads are considered, and the interruption cost functions of the loads are fitted. To solve the optimization model, a heuristic search algorithm based on the hill climbing method is proposed. The effectiveness of the proposed model and algorithm is evaluated by comparing with an existing static island partitioning model and intelligent algorithms, respectively.
Ding projective dimension of Gorenstein flat modules
Junpeng Wang 대한수학회 2017 대한수학회보 Vol.54 No.6
Let $R$ be a Ding-Chen ring. Yang \cite{Yang2012} and Zhang \cite{Zhang2015} asked whether or not every $R$-module has finite Ding projective or Ding injective dimension. In this paper, we give a new characterization of that all modul\-es have finite Ding projective and Ding injective dimension in terms of the relationship between Ding projective and Gorenstein flat modules. We also give an example to obtain negative answer to the above question.
Microstructural Topology Optimization for Minimizing Dynamic Response in the Time Domain
Junpeng Zhao(자오준펭),Heonjun Yoon(윤헌준),Byeng D. Youn(윤병동) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
This paper presents an efficient approach for topology optimization of microstructures for minimizing dynamic response of two-scale hierarchical structures in the time domain. The density-based approach is employed to perform microstructural topology optimization. The numerical homogenization method is used to compute the effective material properties of the porous materials. The differentiate-and-then-discrete approach and the decoupled sensitivity analysis method are combined to perform sensitivity analysis. The model reduction method is employed to efficiently solve the primal and adjoint equations. A modified Heaviside projection method is used to obtain black-and-white design for the microstructure, and the method of moving asymptotes (MMA) is employed to update design variables. Two numerical examples are presented to demonstrate the effectiveness of the proposed approach.
Zhu, Junpeng,Gu, Wei,Jiang, Ping,Song, Shan,Liu, Haitao,Liang, Huishi,Wu, Ming The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.6
When a failure occurs in active distribution system, it will be isolated through the action of circuit breakers and sectionalizing switches. As a result, the network might be divided into several connected components, in which distributed generations could supply power for customers. Aimed at decreasing customer interruption cost, this paper proposes a theoretically optimal island partition model for such connected components, and a simplified but more practical model is also derived. The model aims to calculate a dynamic island partition schedule during the failure recovery time period, instead of a static islanding status. Fluctuation and stochastic characteristics of the renewable distributed generations and loads are considered, and the interruption cost functions of the loads are fitted. To solve the optimization model, a heuristic search algorithm based on the hill climbing method is proposed. The effectiveness of the proposed model and algorithm is evaluated by comparing with an existing static island partitioning model and intelligent algorithms, respectively.