Synthesis of Novel Poly(aryl ether sulfone)s Bearing Bulky Pendants for Gas Separation Membranes

Zhuang Liu,Baijun Liu,Long Li,Yinan Zhang,Zhenhua Jiang 한국고분자학회 2013 Macromolecular Research Vol.21 No.6

A hydroxylated poly(aryl ether sulfone) (PES-OH) was synthesized by a demethylation reaction of a methoxy-functionalized PES (PES-OCH3) using the HCl/pyridine system. Derived from this hydroxylated PES precursor,bulky (2-trifluoromethyl-4-nitro) phenyl (TFN) and benzophenone (BZP) were introduced to the PES backbones as side groups via aromatic nucleophilic substitution reactions. A direct property comparison of PES-OH,PES-OCH3, PES-TFN and PES-BZP has been made, and these analogues exhibited different solubility, thermal properties and gas permeability. PES grafted with the trifluoromethyl side group (PES-TFN) demonstrated more attractive permeabilities and permselectivities for O2/N2 separation compared to the others, and it exhibited the best P(O2)/P(N2) value of 8.44.

Synthesis of Sulfonated Fluorenyl-Containing Poly(ether ether ketone ketone)s and Their Blends with an Amino-Functionalized Poly(ether ether ketone) for Fuel Cell Applications

Long Li,Baijun Liu,Siyuan Liu,Zhuang Liu,Yunwu Yu,Liwei Jing,Zhenhua Jiang 한국고분자학회 2013 Macromolecular Research Vol.21 No.7

A new family of sulfonated fluorenyl-containing poly(ether ether ketone ketone)s (SFPEEKKs) were successfully synthesized through a mild postsulfonation in concentrated sulfuric acid at room temperature. Further, a series of “molecule-enhanced” blend membranes were prepared based on SFPEEKKs and an amino-functionalized poly(ether ether ketone) by the solution casting method. These blend membranes generally showed higher thermal stability, lower swelling ratio and methanol permeability and superior mechanical properties in comparison with pristine SFPEEKK membranes. The results showed that some blend membranes may be promising proton exchange membranes for fuel cell applications.

Tuning Molecular Composition for Better Cross-section Homogeneity of Thermal Oxidative Stabilized Polyacrylonitrile for Carbon Materials

Shiyu Liu,Yuan Ge,Baijun Liu,Zhongyu Fu,Xiaoyu Yu,Ming Yao Zhang,Hui Xuan Zhang 한국섬유공학회 2022 Fibers and polymers Vol.23 No.6

A strategy to improve the cross-section homogeneity of thermal oxidative stabilized polyacrylonitrile for carbonmaterials was provided in the present work. A kind of comonomer, dimethyl itaconate (DMI), which possesses two bulkyside groups was introduced into poly(acrylonitrile-co-itaconic acid). The efficiency of DMI in improving the cross-sectionhomogeneity of polyacrylonitrile films during thermal oxidative stabilization (TOS) processes and the properties of resultedPAN-based carbon materials were investigated in detail. It was found that DMI facilitated the formation of longer cyclicstructures, higher oxygen content, more homogeneous cross-section fracture morphology and denser structure during TOSprocess. DMI was also benefit for easing heat release. The presence of DMI also facilitated a smaller ID/IG value of thecarbonized PAN film and a bigger in-plane size of graphite crystals La.

Evidence of the Recent Decade Change in Global Fresh Water Discharge and Evapotranspiration Revealed by Reanalysis and Satellite Observations

서기원,Duane E. Waliser,Baijun Tian,김백민,박성찬,Steve Cocke,손병주,Masayoshi Ishii 한국기상학회 2012 Asia-Pacific Journal of Atmospheric Sciences Vol.48 No.2

Variations of global evapotranspiration (ET) and fresh water discharge from land to oceans (D) are important components of global climate change, but have not been well monitored. In this study, we present an estimate of twenty years (1989 to 2008) variations of global D and ET derived from satellite remote-sensed measurements and recent reanalysis products, ERA-Interim and CFSR, by using a novel application of the water balance equations separately over land and over oceans. Time series of annual mean global D and ET from both satellite observations and reanalyses show clear positive and negative trends, respectively, as a result of modest increase of oceanic evaporation (Eo). The inter-annual variations of D are similar to the in-situ-based observations, and the negative trend of ET supports the previous result that relative humidity has decreased while temperature has increased on land. The results suggest considerable sensitivity of the terrestrial hydrological cycles (e.g., D and ET) to small changes in precipitation and oceanic evaporation.

A tunable dynamic vibration absorber for unbalanced rotor system

Hongliang Yao,Tongzhao Wang,Bang-chun Wen,Baijun Qiu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4

A tunable dynamic vibration absorber for unbalanced rotor system which is made up of coil springs and magnetic spring is presented. The structure of the absorber is introduced and the stiffness tuning mechanism of the magnetic spring is explained. A finite element model of the rotor-absorber system was built and the influencing factors to the appearance of the absorber were studied numerically. Finally, experiments were carried out to verify the numerical results, and PID control strategy was tested. The numerical and experimental results show that the present absorber is effective for vibration suppression of an unbalanced rotor system, and the control strategy is effective.

Fluorinated/Non-Fluorinated Sulfonated Polynaphthalimides as Proton Exchange Membranes

Yang Song,Chang Liu,Dianfu Ren,Liwei Jing,Zhenhua Jiang,Baijun Liu 한국고분자학회 2013 Macromolecular Research Vol.21 No.5

Two -SO3H containing diamine monomers, 2,5-bis(4-amino-2-trifluoromethylphenoxy)benzenesulfonic acid and 2,5-bis(4-aminophenoxy)benzenesulfonic acid were successfully synthesized through a typical aromatic nucleophilic substitution reaction followed by a reduction reaction, respectively. Derived from the diamine monomers,two series of sulfonated naphthalic polyimides (polynaphthalimides) containing ether and ketone linkages were synthesized through a “one pot” polymerization reaction. Some properties including thermal stability, mechanical properties, water uptake, swelling dimensional ratio, methanol permeability, and proton conductivity were thoroughly investigated. Some exhibited attractive properties as proton exchange membranes. It was found that the fluorinated series (CF3-SPI-X) exhibited higher dimensional stability and lower methanol permeability in comparison with non-fluorinated ones (SPI-X) at the same -SO3H group content.

Lignin Based Flexible Electromagnetic Shielding PU Synergized with Graphite

Jia Zhang,Yunxia Qi,Yumei Zhang,Jinchi Duan,Bairun Liu,Baijun Liu,Zhaoyan Sun,Yiquan Xu,Wei Hu,Niaona Zhang 한국섬유공학회 2021 Fibers and polymers Vol.22 No.1

In this paper, lignin (L)-based polyurethane (FeGLPU) with excellent electromagnetic shielding properties wasprepared and studied. The modified reduced iron powder was modified with KH550, and then the obtained modified reducediron powder (Fe) was mixed with lignin, polyethylene glycol 200 (PEG200), hexamethylene diisocyanate (HDI) and graphite(G) to in-situ synthesize the FeGLPU. The thermal stability, mechanical properties, electronic conductivity, and morphologyof the composite FeGLPU were characterized in detail. The electromagnetic interference shielding effectiveness (EMI SE) ofFeGLPU was tested in the frequency range of 8.2-26.5 GHz. When the content of Fe and G was fixed at 10 % and the lignincontent was 5 %, the maximum EMI SE was 21.6 dB, and the frequency width of EMI SE greater than 10 dB was 18.3 GHz. The conductivity was 4.27×10-4 S/m, and the tensile strength of Fe10G10L5PU reached 11.7 MPa. When the lignin contentincreased to be 20 %, the maximum EMI SE was 22.5 dB, and the frequency width of EMI SE greater than 10 dB was18.3 GHz. The conductivity was 1.06×10-2 S/m, and the thermal decomposition temperature T5 (5 % weight loss) reached234 °C. The obtained excellent EMI SE should be due to the synergistic effect of Fe, G and lignin. It can be observed fromthe SEM observation that the G and Fe are uniformly dispersed in PU matrix with strong interfacial interaction. It wasillustrated that the prepared FeGLPU was with efficient electromagnetic shielding properties, good mechanical properties,and high thermal stability. This lignin based electromagnetic shielding PU was proposed to have broad application prospectsdue to its low expenses and ecology friendliness.

Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013

Seo, Ki-Weon,Wilson, Clark R.,Scambos, Ted,Kim, Baek-Min,Waliser, Duane E.,Tian, Baijun,Kim, Byeong-Hoon,Eom, Jooyoung American Geophysical Union 2015 Journal of geophysical research. JGR. Earth surfac Vol.120 No.5

<P> Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr<SUP>2</SUP>. Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr<SUP>2</SUP>. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr<SUP>2</SUP>. Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr<SUP>2</SUP>. </P>

Representation of tropical subseasonal variability of precipitation in global reanalyses

Kim, Daehyun,Lee, Myong-In,Kim, Dongmin,Schubert, Siegfried D.,Waliser, Duane E.,Tian, Baijun Springer-Verlag 2014 Climate dynamics Vol.43 No.1

Epidemiological Characteristics of Norovirus Outbreaks in Shenyang from 2017 to 2021

Qi Ying,Dong Xinxin,Cheng Xiaowei,Xu Han,Wang Jin,Wang Bing,Chen Ye,Sun Baijun,Zhang Linlin,Yao Yan 한국미생물학회 2023 The journal of microbiology Vol.61 No.4

Norovirus is one of the leading causes of acute gastroenteritis outbreaks worldwide. This study aimed to identify the epidemiological characteristics of norovirus outbreaks and to provide evidence for public health entities. Specimens and epidemiological survey data were collected to determine if there were differences in the attack rate of norovirus in terms of the year, season, transmission route, exposure setting, and region and to determine whether there were relationships between the reporting interval, the number of illnesses in a single outbreak and the duration of the outbreak. Norovirus outbreaks were reported throughout the year, with seasonal characteristics (i.e., high rates in spring and winter). Among all regions in Shenyang with the exception of Huanggu and Liaozhong, norovirus outbreaks had been reported, and the primary genotype was GII.2[P16]. Vomiting was the most common symptom. The main places of occurrence were childcare institutions and schools. The person-to-person route was the main transmission route. The median duration of norovirus was 3 days (IQR [interquartile range]: 2–6 days), the median reporting interval was 2 days (IQR: 1–4 days), the median number of illnesses in a single outbreak was 16 (IQR: 10–25); there was a positive correlation between these parameters. Norovirus surveillance and genotyping studies still need to be further strengthened to increase knowledge regarding the pathogens and their variant characteristics, to better characterize the patterns of norovirus outbreaks and to provide information for outbreak prevention. Norovirus outbreaks should be detected, reported and handled early. Public health entities and the government should develop corresponding measures for different seasons, transmission routes, exposure settings, and regions.