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Han, Jusung,Kim, Kihyun,Kim, Junghwan,Kim, Sungjun,Choi, So-Won,Lee, Hyunhee,Kim, Jin-joo,Kim, Tae-Ho,Sung, Yung-Eun,Lee, Jong-Chan Elsevier 2019 Journal of membrane science Vol.579 No.-
<P><B>Abstract</B></P> <P>End-group cross-linked sulfonated poly(arylene ether sulfone) (SPAES) membranes were prepared using thiol capped SPAES (SH-SPAES) with different amounts of vinyl polysulfone (VPSf) as a polymeric cross-linker. The cross-linked membranes showed remarkably improved physicochemical stabilities compared to the corresponding linear SPAES membrane. Although the proton conductivity of the SPAES membrane composed of SPAES with the degree of sulfonation (DS) as 70 mol% could not be measured due to its low physical stability under the measurement condition, those of the cross-linked membranes were repeatedly evaluated due to the enhanced stability through the formation of cross-linked structures. The obtained proton conductivity values from cross-linked membranes are larger than those of the linear SPAES membrane which composed of SPAES with DS of 50 mol% having the ion exchange capacity (IEC) similar to that of the cross-linked membranes, especially at relative low humidity conditions. Furthermore, the fuel cell performance of the membrane electrode assembly (MEA) prepared with the cross-linked membrane, showing the optimized physicochemical stabilities and proton conductivity exhibited a maximum power density of 692 mW cm<SUP>−2</SUP>, which was larger than that with Nafion 212 (603 mW cm<SUP>−2</SUP>) at 80 °C under fully humidified H<SUB>2</SUB>/Air condition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thiol group capped highly sulfonated poly(arylene ether sulfone) and vinyl group containing poly sulfone were synthesized. </LI> <LI> End group cross-linked membranes were prepared by thiol-ene click reaction using polymeric cross-linker. </LI> <LI> Excellent physicochemical stability of end group cross-linked membranes. </LI> <LI> High proton conductivity of end group cross-linked membranes in low humidity condition. </LI> <LI> Outstanding cell performance of MEA prepared with end group cross-linked membrane. </LI> </UL> </P>
A Low-Complexity I/Q Imbalance Calibration Method for Quadrature Modulator
Kim, Jusung,Jo, Han-Shin,Lee, Kyoung-Jae,Lee, Dong-Ho,Choi, Dae-Hyun,Kim, Sangkil IEEE 2019 IEEE transactions on very large scale integration Vol.27 No.4
<P>This brief presents a low-complexity I/Q (in-phase and quadrature components) imbalance calibration method for the transmitter using quadrature modulation. Impairments in analog quadrature modulator have a deleterious effect on the signal fidelity. Among the critical impairments, I/Q imbalance (gain and phase mismatches) deteriorates the residual sideband performance of the analog quadrature modulator degrading the error vector magnitude. Based on the theoretical mismatch analysis of the quadrature modulator, we propose a low-complexity I/Q imbalance extraction algorithm. After the parameter extraction, the transmitter is calibrated by imposing the counter imbalanced mismatch of the transmitter through the digital baseband. In comparison with existing I/Q imbalance calibration methods, the novelty of the proposed method lies in that: 1) only three spectrum measurements of the device-under-test are needed for extraction and calibration of gain and phase mismatches; 2) due to the blind nature of the calibration algorithm, the proposed approach can be readily applicable to an existing I/Q transmitter; 3) no extra hardware that degrades the calibration accuracy is required; and 4) due to the noniterative nature, the proposed method is faster and computationally more efficient than previously published methods.</P>
Lee, Hyunhee,Han, Jusung,Kim, Kihyun,Kim, Junghwan,Kim, Eunki,Shin, Huiseob,Lee, Jong-Chan THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2019 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.74 No.-
<P><B>Abstract</B></P> <P>Sulfonated poly(arylene ether sulfone) (SPAES) composite membranes were prepared using graphene oxide (GO) and sulfonated poly(arylene thioether sulfone)-grafted graphene oxide (SATS-GO) as fillers for proton exchange membrane fuel cell (PEMFC) applications. When GO and SATS-GO were mixed with SPAES to form the composite membranes, dimensional stability, chemical stability, and mechanical strength were improved. The composite membranes containing SATS-GO especially showed higher proton conductivity than the pristine SPAES and the composite membrane containing GO because of highly sulfonated polymer (SATS) introduced on GO surface. Furthermore, the sulfonic acid groups in SATS-GO can increase the compatibility between the filler and matrix polymer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SPAES composite membranes were prepared using highly sulfonated polymer-grafted graphene oxide as a filler. </LI> <LI> The filler was synthesized by grafting highly sulfonated polymer on GO surface using a mild reaction condition. </LI> <LI> Outstanding compatibility between the filler and matrix polymer. </LI> <LI> Physicochemical stability of the composite membranes was highly improved. </LI> <LI> Excellent proton conductivity of the composite membranes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Concurrent Food Localization and Recognition using Deep Convolution Neural Network
Rohit Thakur(로힛 타쿠르),Jusung Kang(강주성),Hyunjun Han(한현준),Heung-No Lee(이흥노) 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.6
The analysis of food quality is considered as an important task because of the people’s nutrition habits that affect the global population. For this, it is very important to keep track of our eating habits by making automatic nutrition diaries. Keeping this in mind, we demonstrate how a deep learning technique is used to the tasks of localizing and recognizing various types of foods present in given images. Firstly, the Grad-CAM algorithm (a class-discriminative localization technique) along with data processing is used for generating discriminative image regions which helps in obtaining object proposals for detection purpose. Secondly, a classifier for object recognition is employed over it. Further, we compare our result with best state of art work and show our proposed method to be well equipped in terms of precision and accuracy. Through experiments we have verified that proposed approach is a convincing solution for concurrent food localization and recognition.
Kim, Kihyun,Heo, Pilwon,Han, Jusung,Kim, Junghwan,Lee, Jong-Chan Elsevier 2018 Journal of Power Sources Vol.401 No.-
<P><B>Abstract</B></P> <P>End-group cross-linked sulfonated poly (arylene ether sulfone) (C-SPAES) membranes with varying degree of cross-linking density are prepared by <I>in-situ</I> casting and heating of thiol-terminated SPAES (SH-SPAES) solutions containing different amounts of multifunctional cross-linker such as acrylo-polyhedral oligomeric silsesquioxane (A-POSS) <I>via</I> thiol-ene click reaction. SH-SPAES is prepared by stepwise substitution reactions between phenoxide-terminated SPAES and end capping reagents such as decafluorobiphenyl followed by thiobisbenzethiol. The C-SPAES membranes exhibit vastly improved chemical and physical stability and mechanical strength compared with linear SPAES membrane due to effective cross-linked structure, and their proton conductivity values are higher than Nafion-212 in relative humidity range of 50–95% (at 90 °C) due to high degree of sulfonation (70 mol%) and ion exchange capacity (2.48 mequiv. g<SUP>−1</SUP>) of SH-SPAES. Under various operating conditions of proton exchange membrane fuel cell including intermediate temperature and low humidity conditions, membrane electrode assemblies employing the C-SPAES membranes with optimized cross-linker contents show outstanding cell performances (e.g., 1.08 W cm<SUP>-2</SUP> at 0.5 V under 90 °C and 50% RH with 150 kPa).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thiol terminated sulfonated poly (arylene ether sulfone) (SH-SPAES) is synthesized. </LI> <LI> SH-SPAES has high degree of sulfonation and ion exchange capacity. </LI> <LI> End-group cross-linked SPAES membranes are prepared by thiol-ene click reaction. </LI> <LI> Excellent physicochemical stability of cross-linked SPAES membranes. </LI> <LI> Outstanding cell performances of MEAs prepared with cross-linked SPAES membranes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>