PVDF Hollow Fiber Formation via Modified NIPS Method: Evolution Elucidation of Phase Separation Mechanism, Structure and Properties of Membrane with Coagulation Strength Varied

Yu Zhu,Zhaocai Zhang 한국고분자학회 2014 Macromolecular Research Vol.22 No.12

In this work, hollow fiber membrane was prepared from poly(vinylidene fluoride) (PVDF)/triethyl phosphate(TEP)/water systems by modified non-solvent induced phase separation technique (mNIPS), which was characterizedin the process with relative high polymer content of 30 wt% in spinning dope. The ternary phase diagramand precipitation rate were determined to elucidate the various membrane formation mechanisms, and the membranesmorphologies were observed by field emission scanning electronic microscopy (FESEM). It was indicatedthat the phase separation mechanism was found to heavily depend on the bath strength. Although the solid-liquiddemixing process initiated the precipitation process, by changing the bath gradually from pure water to 40% TEP,the liquid-liquid demixing occurred earlier and earlier. Accordingly the top surface morphologies evolved from adense skin (asymmetric membrane) to a totally porous morphology (symmetric membrane). In addition, the permeability,maximum stress at break, medium pore size and porosity of hollow fiber membranes were also investigated. In conclusion, the successful application of modified non-solvent induced phase separation (mNIPS) may providean effective route to improve the membrane structure modulation.

자동화를 위한 네트워크 구현에 관한 연구

김형중,이준성,Yu Zhu 강원대학교 석재복합신소재제품연구센터 1997 석재연 논문집 Vol.2 No.-

본 연구에서는 Fieldbus의 한 종류인 CAN (Controller Area Network) 프로토콜에 대한 전반적인 고찰과 CAN의 리얼타임 스케줄링에 관해 서술하고, 리얼타임이 가능하도록 스케줄링을 구현하는 방법에 대해 소개한다. DM (Deadline Monotonic)이 CAN에 적용되기 위해 필요한 요건이 논의된다. CAN에서 리얼타임 스케쥴링의 효율을 높이기 위해 CAN 식별자를 조정하여 EDF (earliest-deadline first) 스케쥴링이 가능하게 구현하는 방법을 제안한다. Overview of CAN is addressed. Scheduling message on the CAN corresponds to assigning identifier to message. If fixed-priority scheduling such as deadline monotonic is used, it will result in low schedulability. Requirements for deadline monotonic application to CAN bus is addressed. Dynamic priority scheduling schemes such as earliest-deadline first can give greater schedulability. An implementation scheme of the earliest-deadline first is presented.

An Improved Density-Based Design Method of Additive Manufacturing Fabricated Inhomogeneous Cellular-Solid Structures

Yu Zhu,Jiaqi Zhao,Ming Zhang,Xin Li,Leijie Wang,Chuxiong Hu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.1

Benefited from the rapid development of additive manufacturing (AM), inhomogeneous cellular structures have attracted many interests for their superior structural and functional performance. Recently proposed density-based design methods have been shown to provide great computational efficiency and obtain structures with excellent performance. To achieve better structural performance while considering AM constraints, an improved density-based design method which introduces solid and void units into the design domain is proposed in this paper. First, based on homogenization theory and solid-body analysis, unit parameters of different preset unit relative densities are determined. And a unit effective property interpolation model is constructed. Then, the macro relative density layout is optimized with density methods. In the optimization process, an efficient density filter is proposed to increase the optimization domain and satisfy minimal feature size constraint. Finally, the structure reconstruction algorithm automatically constructs the optimized cellular structure based on the unit and density information obtained in the first two processes. Numerical examples show that the proposed method efficiently obtains inhomogeneous cellular structures with better performance, compared with existing density-based methods.

Extinction and non-extinction of solutions to a fast diffusive $p$-Laplace equation with a nonlocal source

Yuzhu Han,Wenjie Gao,Haixia Li 대한수학회 2014 대한수학회보 Vol.51 No.1

In this paper, the authors establish the conditions for the extinction of solutions, in finite time, of the fast diffusive $p$-Laplace equation $u_t=\mathrm{div}(|\nabla u|^{p-2}\nabla u)+a\int_\Omega u^q(y,t)dy$, $1<p<2$, in a bounded domain $\Omega\subset R^N$ with $N\geq1$. More precisely, it is shown that if $q>p-1$, any solution vanishes in finite time when the initial datum or the coefficient $a$ or the Lebesgue measure of the domain is small, and if $0<q<p-1$, there exists a solution which is positive in $\Omega$ for all $t>0$. For the critical case $q=p-1$, whether the solutions vanish in finite time or not depends crucially on the value of $a\mu$, where $\mu=\int_{\Omega}\phi^{p-1}(x)\mathrm{d}x$ and $\phi$ is the unique positive solution of the elliptic problem $-\mathrm{div}(|\nabla \phi|^{p-2}\nabla \phi)=1$, $x\in \Omega$; $\phi(x)=0$, $x\in\partial\Omega$. This is a main difference between equations with local and nonlocal sources.

Some types of reaction-diffusion systems with nonlocal boundary conditions

Yuzhu Han,Wenjie Gao 대한수학회 2013 대한수학회보 Vol.50 No.6

This paper deals with some types of semilinear parabolic systems with localized or nonlocal sources and nonlocal boundary conditions. The authors first derive some global existence and blow-up criteria. And then, for blow-up solutions, they study the global blow-up property as well as the precise blow-up rate estimates, which has been seldom studied until now.

Heteroatom‑doped porous carbon derived from covalent organic framework for high performance supercapacitor applications

Yuzhu Xing,Yan Dong,Jifan Zhao,Zhiqiang Zhang,Yue Wang 한국탄소학회 2023 Carbon Letters Vol.33 No.6

In recent years, supercapacitors have attracted extensive attention due to their advantages such as fast charge and discharge rate, high power density and long cycle life. Because of its unique porous structure and excellent electrochemical properties, heteroatom-doped porous carbon (HPC) is deemed as a promising electrode material for supercapacitors. However, it is a great challenge to synthesize electrode materials with large surface area, ultra-high porosity and good electrochemical performance. In this work, two-dimensional conjugated microporous polymers (CMPs) containing ketones were synthesized by a simple one-step coupling reaction and used as carbon precursors. A series of samples (CMP-Ts) were prepared with the procedures of coupling reaction and carbonization. The optimized carbon material has high specific surface area (up to 2229.85 m2 g? 1), porous structure, high specific capacitance (375 F g? 1 at 0.5 A g? 1), and good cycling stability (capacitance retention of 98.8% after 1000 cycles at 5 A g? 1). Further, the supercapacitor has an energy density of 28.8 Wh kg? 1 at a power density of 5000 W kg? 1. This work lays a foundation for the preparation of carbon materials using microporous polymer as a precursor system, provides a new way of thinking, and demonstrates a great potential of high-performance supercapacitors.

Finite-time Stability and Stabilization of Markovian Jump Linear Systems Subject to Incomplete Transition Descriptions

Yuzhu Bai,Hui-Jie Sun,Ai-Guo Wu 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.9

In this paper, the problems of finite-time stability analysis and finite-time stabilization are investigated for Markovian jump linear systems with incomplete transition descriptions. Two sufficient conditions are proposed to guarantee that the system states do not exceed a certain threshold in mean-square sense during a specified time interval for the continuous-time Markovian jump linear systems with partly unknown transition rates and the discretetime Markovian jump linear systems with partly unknown transition probabilities, respectively. On the basis of the above results, two state feedback controllers are developed to solve the finite-time stochastic stabilization problems of the considered systems in continuous-time domain and discrete-time domain, respectively. For the sake of computational convenience, all the conditions are cast in the format of linear matrix inequalities (LMIs). The main feature of the proposed methods is that the total number of LMIs is much less than that in some existing results. Thus, the solution of the finite-time controllers is more concise both in theory and in engineering. In the end, the validity of the developed theoretical results are demonstrated by two illustrative examples.

Self-Cleaning and Antifouling Properties of Silica/Octadecylamine-Coated Cotton Fabrics

Yuzhu Jin,Ying Liu,Xinru Li,Tian Zhong 한국섬유공학회 2023 Fibers and polymers Vol.24 No.11

Due to the multifaceted application potential, hydrophobically modified cotton fabrics have gathered a lot of attention in recent years. This study developed a self-cleaning and antibacterial cotton fabric that combines self-cleaning and antifouling properties. Dopamine was oxidized and self-polymerized on the surface of cotton fabric, and the polydopamine layer has adhesion properties and reactive activity. Therefore, it can adhere to hydrophobic silica microspheres while reacting with octadecylamine. As a consequence of the modification of the cotton fabric, excellent hydrophobicity (with a contact angle of 145°) as well as excellent stability in acid and alkali solutions and washing stability were developed. There is not much loss in the mechanical properties of the modified cotton fabric, and the higher contact angle gives the cotton fabric self-cleaning properties while resisting bacterial adhesion, with the bacteria adhesion number reduced by 50% and 90% for E. coli and S. aureus, respectively.

Polar poly(n‑butyl acrylate)‑g‑polyacrylonitrile elastomer with high temperature elasticity and healability as flexible electronic substrate

Yuzhu Zheng,Deli Xu,Shiyou Tian,Manli Li,Wenwen Wang,Ke Liu 한국의류학회 2021 Fashion and Textiles Vol.8 No.1

In this work, graft copolymer poly (n-butyl acrylate)-g-polyacrylonitrile with poly (n-butyl acrylate) as backbones and polyacrylonitrile as side chains (PnBA-g-PAN) was synthesized by macromonomer method and emulsion polymerization. The macromonomer was synthesized by atom transfer radical polymerization and end-group modification. The chemical structures and thermal properties of macromonomer and graft copolymer were investigated by FTIR, GPC, NMR and TGA, etc. The mechanical properties of graft copolymer elastomer was also measured by uniaxial tensile test. Rheological properties at different temperature and mechanical property demonstrated that graft copolymer elastomer possessed elasticity until 180 oC because of cyclization of cyano groups. Ag nanowires@PnBA-g-PAN composite elastomer was developed, and the resulted material exhibited autonomic healing property on account of segments’ flexibility and dynamic interaction between Ag nanowires (AgNWs) and cyano groups. This is a general method for generation of elastomer with high temperature elasticity and fast self-healing. The composite elastomer has potential application in flexible electronic conductor.

An optimized procedure for detection of genetically modified DNA in refined vegetable oils

Yuzhu Duan,Yan Pi,Changwen Li,Keji Jiang 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.1

In this study, the amplifiable DNA from refinedvegetable oils was isolated by using commercial DNAextraction kits based on the CTAB method in combinationwith nucleic acid enrichment, and then the presence ofgenetically modified (GM) soybean and maize DNA in theoils was traced by PCR. The results showed that theduration and intensity of heating had no significant effecton the DNA stability and concentration in oils for a shortperiod, suggesting that DNA in oils could be stablyreserved for a certain time, thus making it possible to tracedown refined vegetable oils reliably and effectively. Theresults provided a set of primers suitable for systematicGM oil detection. More importantly, this study made animportant contribution to the economical and reliabledetection of GM vegetable oils regarding food authenticityissues.