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Jungmoon Kim,Mok, Philip K. T.,Chulwoo Kim IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.2
<P>A charge pump using 0.13- μm CMOS process for low-voltage energy harvesting is presented. A low-power adaptive dead-time (AD) circuit is used which automatically optimizes the dead-time according to the input voltage. A negative charge pump is also utilized for high efficiency at low input voltages (V<SUB>IN</SUB>). The AD circuit improves efficiency by 17% at V<SUB>IN</SUB> of 0.2 V compared to the fixed dead time circuit as well as enables the charge pump to work at V<SUB>IN</SUB> down to 0.15 V. Dynamic body bias (DBB) and switch-conductance enhancement techniques are applied to a unit stage of the three-stage charge pump. The reverse current flowing through the cross-coupled NMOS switches is prevented and the current transfer is also maximized. Together with the AD circuit and the DBB technique, the maximum output current was improved by 240% as compared to the conventional charge pump design using only the forward body bias.</P>
Jungmoon Kim,Chulwoo Kim IEEE 2013 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.28 No.8
<P>This paper presents a dc-dc boost converter with the maximum power point tracking (MPPT) technique for thermoelectric energy harvesting applications. The technique realizes variation tolerance by adjusting the switching frequency of the converter. A finely controlled zero-current switching (ZCS) scheme together with the accurate MPPT technique enhances the overall efficiency of the converter because of an optimal turn-on time generated by a one-shot pulse generator that is proposed. Moreover, the ZCS technique can deal with low- and high-temperature differences applied to the thermoelectric generator. This allows a wider range of conversion ratios compared to those of conventional converters used for thermal energy harvesting. Experimentally, the converter implemented in a 0.35-μm BCDMOS process had a peak efficiency of 72% at the input voltage of 500 mV while supplying a 5.62-V output.</P>
Calling site preferences in four cicada species in central Korea
Dong-Youn Kim,Jungmoon Ha,Yikweon Jang 한국응용곤충학회 2010 한국응용곤충학회 학술대회논문집 Vol.2010 No.10
Male cicadas produced species-specific calling songs to attract conspecific receptive females. Male cicadas typically occupy tree trunks or tree branches during calling song production. We studied calling site preference in four species of cicada: Cryptotympana dubia, Meimuna opalifera, Oncotympana fuscata, and Meimuna mongolica. Several males were observed to sing together in a tree in C. dubia, but males of other species tended to sing singly in trees. There were also cases in which two or three individuals of different species sang together in a tree. Species differed significantly in height of and distance to trunk from calling site. Both tree height and tree crown were significant factors for calling site preference. The height of calling site was the highest in C. dubia, followed by M. opalifera, M. mongolica, and O. fuscata. The distance to trunk from calling site in M. opalifera was the farthest and was significantly different from those of other species. Males of other species tended to sing close to tree trunks. Males of M. opalifera were mobile when they produced calling songs, whereas males of other species were stationary. That is, males of M. opalifera sang only for short periods of time and moved around adjacent trees. Segregation of calling sites suggests that these four cicada species occupy different sections of trees, thereby avoiding competition for calling sites.
Calling site preference of four cicada species in central Korea
Dong-Youn Kim,Jungmoon Ha,Yikweon Jang 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.10
Male cicadas produce species-specific calling songs to attract conspecific receptive females, and they typically occupy tree trunks or branches during calling. We studied calling site preference in the natural environment for four species of cicada: Cryptotympana dubia, Meimuna opalifera, Oncotympana fuscata, and Meimuna mongolica. Males of M. opalifera tended to sing singly in trees, whereas other species were often observed singing together in one tree. In some cases, two or three individuals of different species sang together in one tree; the only possible pairwise combination not observed was M. mongolica with O. fuscata. Calling sites of the four species differed significantly in distance to the ground and distance to trunk, and both tree height and tree crown were significant factors for calling site preference in multivariate analysis of variance (MANOVA). Distance from calling site to the ground was highest in C. dubia, followed by M. opalifera, M. mongolica, and O. fuscata. The distance from calling site to the trunk was greatest in M. opalifera and differed significantly from those of other species, which tended to sing close to tree trunks. Males of M. opalifera were mobile when they produced calling songs, whereas males of other species were stationary. That is, males of M. opalifera sang only for short periods of time and moved around adjacent trees. Segregation of calling sites suggests that these four cicada species occupy different niches, thereby avoiding competition for calling sites as much as possible.
A Self-Calibrated DLL-Based Clock Generator for an Energy-Aware EISC Processor
Sewook Hwang,Kyeong-Min Kim,Jungmoon Kim,Seon Wook Kim,Chulwoo Kim IEEE 2013 IEEE transactions on very large scale integration Vol.21 No.3
<P>This paper describes a low-jitter delay-locked loop (DLL)-based clock generator for dynamic frequency scaling in the extendable instruction set computing (EISC) processor. The DLL-based clock generator provides the system clock with frequencies of 0.5× to 8× of the reference clock, according to the workload of the EISC processor. The proposed analog self-calibration method and a phase detector with an auxiliary charge pump can effectively reduce the delay mismatch between delay cells in the voltage-controlled delay line and the static phase offset due to the current mismatch in the charge pump, respectively. The self-calibrated output waveform exhibits 9.7 ps of RMS jitter and 73.7 ps of peak-to-peak jitter at 120 MHz. The prototype clock generator implemented in a 0.18-μm CMOS process occupies an active area of 0.27 mm<SUP>2</SUP> and consumes 15.56 mA.</P>
Kim, Kihyun,Bae, Jungmoon,Lim, Min-Young,Heo, Pilwon,Choi, So-Won,Kwon, Heock-Hoi,Lee, Jong-Chan Elsevier 2017 Journal of membrane science Vol.525 No.-
<P><B>Abstract</B></P> <P>Sulfonated poly(arylene ether sulfone) (SPAES) composite membranes were prepared using antioxidant grafted graphene oxide as a filler for polymer electrolyte membrane fuel cell (PEMFC) applications. SPAES was synthesized <I>via</I> condensation polymerization of 4,4′-dihydroxybiphenyl, 4,4′-dichlorodiphenylsulfone and 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone. The antioxidant grafted graphene oxide was prepared by grafting hindered amine, 4-amino-2,2,6,6-tetramethylpiperidine, onto the surface of graphene oxide (GO). The SPAES composite membrane containing the antioxidant grafted GO showed improved physicochemical properties such as mechanical strength, chemical and thermal stabilities, and proton conductivity compared to pristine SPAES membrane. In particular, the antioxidant grafted GO was much more effective in enhancing the chemical stability of SPAES than GO without the antioxidant. For example after Fenton's test, the SPAES composite membrane with grafted antioxidant showed smaller decrease of both the weight and proton conductivity values than the pristine SPAES and SPAES composite membrane with GO. The enhanced chemical stability of SPAES composite membrane with antioxidant grafted GO can be explained by the combined antioxidant effect of both grafted antioxidant functional groups and GO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SPAES composite membranes were prepared using antioxidant grafted GO as filler. </LI> <LI> Excellent chemical and physical stabilities of SPAES composite membranes. </LI> <LI> Proton conductivity of the composite membranes was highly increased. </LI> <LI> Proton conductivity of the composite membranes after Fenton's test was enhanced. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
지속적인 디지털 전환을 위한 소상공인 디지털 리터러시 측정지표 개발 연구: 3차 산업(숙박 및 음식점업, 도·소매업, 서비스업)을 중심으로
최정문(Jungmoon Choi),이정훈(Junghoon Lee),김지원(Jiwon Kim) 한국데이터전략학회 2023 Journal of information technology applications & m Vol.30 No.1
As the DT of micro businesses emerges as an important task, the government is also promoting support projects such as policy establishment and micro business education. This study aims to develop a new index (checklist) that can objectively measure the level of digital literacy required for DT in the tertiary industry, which accounts for the largest share of micro business owners. In this study, indicators were derived through review of existing studies and FGI, and the validity and reliability of Likert 5 were measured for decision makers in the tertiary industry. In the field of digital literacy for micro business owners, a total of 22 indicators were developed, largely composed of basic technology environment competency, information utilization competency, information dissemination and production capability, and mind recognition capability. This study has academic significance in that it can contribute to accurately understanding the digital capabilities of micro business owners by developing a digital literacy index for micro business owners, a specific group lacking in research.
Minseob Shim,Jungmoon Kim,Junwon Jeong,Sejin Park,Chulwoo Kim IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.10
<P>A piezoelectric (PE) energy harvesting system with one-cycle maximum power point (MPP) sensing is presented. The one-cycle MPP sensing method uses a very small size sensing capacitor and it can make the transducer output voltage reach the open circuit voltage within one cycle. The proposed MPP sensing block can sense the open circuit voltage with a proposed peak detector and stores the MPP voltage using charge sharing blocks. The one-cycle MPP sensing approach simplifies the design of an MPP tracking algorithm and greatly reduces the tracking time. All control blocks are self-biased and choose the higher voltage between the input or output voltages of the switching converter as a supply voltage (V DD). Therefore, a voltage multiplexer and a low-power ramp generator with V DD independence are also proposed to control the system without additional DC to DC converter. The entire system has been implemented in a 0.35 μm BCDMOS process. It operates at 90 kHz with a 10-mH inductor. The total power dissipation of the controller is 10 μW at a V DD of 2.7 V. The MPP tracking time is only 9.09 ms/V when the input voltage of the switching converter is changed from 3.4 V to 1.2 V.</P>