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IMPROVEMENT OF FUEL CELL DURABILITY PERFORMANCE BY AVOIDING HIGH VOLTAGE
Seungki Yang,Sungbum Choi,Youngmin Kim,Jongjin Yoon,SeJoon Im,Hyunsuk Choo 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.6
In order to increase the durability of fuel cell stack, various operating technologies such as voltage cut-off and lean air operation was verified. With an application of upper voltage cut-off, cell performance loss was effectively diminished, which suggests that a formation of surface oxide layer on Pt was suppressed resulting in less irreversible catalyst deterioration such as Pt dissolution. In addition, it was found that voltage sweeping to lower reductive potential with a lean air supply was beneficial in preventing a power loss. With a simulated vehicle driving mode, it was confirmed that performance durability was 3 times improved with an application of both voltage cut-off and lean air supply which might be ascribed to the maintaining the electrochemical acive area of Pt catalyst. The suggested operating conditions based on Pt degradation mechanism will contribute the durability enhancement of fuel cell stack for FCEVs.
Sensor Fusion Algorithm Design in Detecting Vehicles Using Laser Scanner and Stereo Vision
Seungki Kim,Hyunkyu Kim,Wonseok Yoo,Kunsoo Huh IEEE 2016 IEEE transactions on intelligent transportation sy Vol.17 No.4
<P>It is well known that laser scanner has better accuracy than stereo vision in detecting the distance and velocity of the obstacles, whereas stereo vision can distinguish the objects better than the laser scanner. These advantages of each sensor can be maximized by sensor fusion approach so that the obstacles in front can be detected accurately. In this paper, high-level sensor fusion for the laser scanner and stereo vision is developed for object matching between the sensors. Time synchronization, object age, and reordering algorithms are designed for robust tracking of the objects. A time-delay update algorithm is also developed to determine the process time delay of the laser scanner. The expanded laser scanner data at every 1 ms is predicted by Kalman filter and is matched with the stereo vision data at every 66 ms. A cost function is formulated to describe the object matching similarity between the sensors, and the best matching candidate is selected for theminimumcost function. The proposedmatching algorithms are verified experimentally in field tests of various maneuvering cases.</P>
Changes in Pharyngeal Width Over Time as an Indicator of Dysphagia in Stroke Patients
Seungki Baek,Il Hwan Jung,Ho Young Lee,Jimin Song,Eunsil Cha,Kwang-Ik Jung,Woo-Kyoung Yoo,Suk Hoon Ohn 대한재활의학회 2020 Annals of Rehabilitation Medicine Vol.44 No.3
Objective To verify the pharyngeal width at rest as a measurement that could be used to assess changes in the degree of dysphagia over time in stroke patients. Methods In a cohort of stroke patients, we performed serial measurements of the pharyngeal width at the midpoints of the second (C2) and third (C3) cervical vertebral bodies using lateral neck X-rays while the patients were at rest. The JOSCYL width, a parameter named after the first initial of each developers’ surname and defined as the average value of the upper and lower pharyngeal widths, was used to formulate the JOSCYL scale, which was calculated as the JOSCYL width × 100/neck circumference. All patients also underwent serial videofluoroscopic swallowing studies (VFSSs). The Spearman correlation analysis was used to detect correlations between the serial VFSS results, JOSCYL widths, and JOSCYL scale values. Results Over time, we observed significant positive and negative correlations of change in the JOSCYL width and scale with changes in the Penetration-Aspiration Scale and the Dysphagia Outcome and Severity Scale scores, respectively. Conclusion The JOSCYL width and JOSCYL scale clearly reflected changes in dysphagia in stroke patients over time. These parameters may provide an easier method for evaluating whether post-stroke dysphagia has been alleviated.
Sorting of MSW incineration bottom ash according to size and density by applying Air Table separator
( Seungki Back ),( Hirofumi Sakanakura ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 심포지움 Vol.2019 No.1
Various types of metal could be contained in a municipal solid waste (MSW) incineration bottom ash ranging from a large size of scrap metal to trace of valuable metal in small size particles. Recently, interest in physical separation of metals from MSW incineration bottom ash is growing up in order to move towards a material cycles society. Separation and characterization of MSW incineration bottom ash could derive two effects: recovery of metals as resources and excluding toxic metals before recycling the bottom ash in construction as a secondary raw material. The present research examined the Air table separator as a dry method for physical sorting according to size and density of bottom ash particles. Recycling of scrap metal such as iron and aluminum have been widely carried out in commercial MSW incineration plants. Also, ferrous and non-ferrous metals were separated from incineration bottom ash using conventional magnetic and eddy current separation. However, efficiency for small particles of a commercial eddy current separator is known to be unsatisfactory. A technique for separating small size particle containing metal compounds is needed to be applied in order to more aggressive metal recovery from incineration bottom ash. Air Table is an effective method for sorting mixtures of various particles with different density. Air Table has advantages; low capital and operating costs and less possibility secondary contamination because Air table is a dry type physical separator without chemicals. Particles with different density could be separated by changing of variables: air injection rate, vibration intensity, end slope, and side slope. Introduced target sample could be separated depends on density of particles by controlling the variables of Air Table. In this study, Air Table separation was applied to classification of MSW incineration bottom ash depends on particle density. And, bulk density and dry density of separated bottom ash were measured. MSW incineration bottom ash with 4-8, 2-4, 1-2, and 0.5-1 mm was applied to Air Table to identify particle movement on Air Table by various operating conditions as a performance test. The outlet of Air Table was divided into 4 parts to collect separated bottom ash particles according to its density. Based on data from the performance test, the effect of each variable (air injection rate (1.0-2.9 m/sec), vibration intensity (5.5-8.0 Hz), and end slope (3-14.5˚)) on particle movement was evaluated. Then, the bottom ash with 4 size ranges was classified into 6 bulk density ranges from < 0.7 g/cm3 to >1.1 g/cm3 at intervals of 1 g/cm3. Measuring cylinder and balance were used for the measurement of bulk density of particles. And, the dry density meter (AccuPyc Ⅱ 1340, Micromeritics) was applied to measure the dry density in a series of experiments. The dry density of the separated bottom ash was measured ranging from 2.19 g/cm3 to 3.63 g/cm3. The fractions which contain a high proportion of the specific elements could be separated according to particle size and its density. XRF analysis was conducted to identify the element composition of the separated particles. Heavy metals (Pb, Cu, Zn) of the higher density fractions showed high concentration compared to the lighter density fractions. On the other hand, the concentration of certain elements (Ca, Cl, etc.) showed a negative correlation with the density of the particles. The results of this study could be utilized for the sorting of MSW incineration bottom ash in terms of recycling of metal, and reducing of environmental hazard.
Seungki Nam,이재훈,Yonggyoo Kim,Kyun-Hyun Tchah,Jaeyong Jeong,정지채 한국물리학회 2005 Current Applied Physics Vol.5 No.3
To electrically characterize ball grid array (BGA) packages, one-portS-parameter measurements have been performed.Equivalent circuit parameters using theC and T models are extracted from measuredS-parameters for three dierent frequencyranges. The accuracy of two selected equivalent circuits is evaluated by comparison between the re-calculatedS11 using the extractedequivalent circuit parameters and measuredS-parameters. The results show that the T lumped model can be used to representS-parameters of BGA packages without distributed elements up to 2 GHz..
Light-Induced Molecular Delivery Using Plasmonic Hybrid Nanogels
Seungki LEE,Jieun YOU,Hakchun KIM,Doyun KIM,Inhee CHOI 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Light is a kind of intuitive, easily controllable, and spatiotemporal stimuli that is advantageous in controlled molecular delivery system. Gold nanoparticles (GNPs) are well known as optically active plasmonic materials and generate the local heat by photothermal conversion effect under the resonance condition. Taking this benefit, hybrid structures with plasmonic nanoparticles have been broadly suggested for developing advanced nanocarriers. Here, we present a simple single-step integration method to obtain plasmonic hybrid nanogels (PHNs) composed of thermo-responsive polymers and GNPs. Under the resonant light illumination, PHN generates local heat enough to induce structural change of the polymeric networks and sequentially release the loaded molecules. To maximize this effect, we systematically tune the number of GNPs integrated in the PHNs by changing the co-building blocks. Then, we evaluate their capability to control the molecular delivery via intracellular behaviors of the PHNs stimulated by light. We envision that the proposed light responsive PHNs would be beneficial nanocarriers to improve and understand the controlled drug delivery system more precisely.