Filters








48 Hits in 0.38 sec

Microbial desalination cells for energy production and desalination

Younggy Kim, Bruce E. Logan
2013 Desalination  
(Reprinted with Permission from Kim and Logan [19] . Copyright (2011) American Chemical Society.) Fig. 2 . 2 Salinity removal in MDCs from initial NaCl concentration of 20 g/L or higher.  ... 
doi:10.1016/j.desal.2012.07.022 fatcat:eypxryk4rbdq3fum2ecn43j56a

PhantomFS-v2: Dare You To Avoid This Trap

Jione Choi, Hwiwon Lee, Younggi Park, Huy Kang Kim, Junghee Lee, Youngjae Kim, Gyuho Lee, Shin-Woo Shim, Taekyu Kim
2020 IEEE Access  
doi:10.1109/access.2020.3034443 fatcat:32lwkruykzbxrh7sx3pzkpnu7a

Increasing phosphorus recovery from dewatering centrate in microbial electrolysis cells

Pengyi Yuan, Younggy Kim
2017 Biotechnology for Biofuels  
Microbial electrolysis cells (MECs) use bioelectrochemical reactions to remove organic contaminants at the bioanode and produce hydrogen gas at the cathode. High local pH conditions near the cathode can also be utilized to produce struvite from nutrient-rich wastewater. This beneficial aspect was investigated using lab-scale MECs fed with dewatering centrate collected at a local wastewater treatment plant. The main objective was to improve phosphorus recovery by examining various cathode
more » ... rations and electric current conditions. Results: The stainless steel mesh (SSM) cathode was relatively inefficient to achieve complete phosphorus recovery because struvite crystals were smaller (a few to tens of micrometers) than the open space between mesh wires (80 µm). As a result, the use of multiple pieces of SSM also showed a limited improvement in the phosphorus recovery up to only 68% with 5 SSM pieces. Readily available organic substrates were not sufficient in the dewatering centrate, resulting in relatively low electric current density (mostly below 0.2 A/m 2 ). The slow electrode reaction did not provide sufficiently high pH conditions near the cathode for complete recovery of phosphorus as struvite. Based on these findings, additional experiments were conducted using stainless steel foil (SSF) as the cathode and acetate (12 mM) as an additional organic substrate for exoelectrogens at the bioanode. With the high electric current (>2 A/m 2 ), a thick layer of struvite crystals was formed on the SSF cathode. The phosphorus recovery increased to 96% with the increasing MEC operation time from 1 to 7 days. With the high phosphorus recovery, estimated energy requirement was relatively low at 13.8 kWh (with acetate) and 0.30 kWh (without acetate) to produce 1 kg struvite from dewatering centrate. Conclusions: For efficient phosphorus recovery from real wastewater, a foil-type cathode is recommended to avoid potential losses of small struvite crystals. Also, presence of readily available organic substrates is important to maintain high electric current and establish high local pH conditions near the cathode. Struvite precipitation was relatively slow, requiring 7 days for nearly complete removal (92%) and recovery (96%). Future studies need to focus on shortening the time requirement.
doi:10.1186/s13068-017-0754-8 pmid:28331546 pmcid:PMC5359864 fatcat:kwpcmzcstng2rprvy2aoly4zkq

Methanogenesis control by electrolytic oxygen production in microbial electrolysis cells

Ryan C. Tice, Younggy Kim
2014 International journal of hydrogen energy  
C. and Kim, Y., Int. J. Hydrogen Energy 39 (2014) 3079-3086, doi:10.1016/j.ijhydene.2013.12.103.  ...  C. and Kim, Y., Int. J. Hydrogen Energy 39 (2014) 3079-3086, doi:10.1016/j.ijhydene.2013.12.103.  ...  C. and Kim, Y., Int. J. Hydrogen Energy 39 (2014) 3079-3086, doi:10.1016/j.ijhydene.2013.12.103.  ... 
doi:10.1016/j.ijhydene.2013.12.103 fatcat:e5cvzzeevvbf7eegupysyskcgq

Simultaneous removal of organic matter and salt ions from saline wastewater in bioelectrochemical systems

Younggy Kim, Bruce E. Logan
2013 Desalination  
► Microbial salinity-reduction electrolysis cells (MSCs) can treat saline wastewater. ► In MSCs, organic matter and salt ions were removed simultaneously. ► Ion-exchange membranes were not damaged for three months in MSCs. ► Exoelectrogens can generate high currents with salinities up to 36 g/L TDS. A new bioelectrochemical system is proposed for simultaneous removal of salinity and organic matter. In this process, exoelectrogenic microorganisms oxidize organic matter and transfer electrons to
more » ... he anode, hydrogen is evolved at the cathode by supplying additional voltage, and salt is removed from the wastewater due to the electric potential generated and the use of two ion-exchange membranes. Salinity removal (initial conductivity~40 mS/cm) increased from 21 to 84% by increasing the substrate (sodium acetate) from 2 to 8 g/L. A total of 72-94% of the chemical oxygen demand was degraded in the anode and cathode chambers, with 1-4% left in the anode chamber and the balance lost through the anion-exchange membrane into the concentrate waste chamber. The maximum hydrogen production rate was 3.6 m 3 -H 2 /m 3 -electrolyte per day at an applied potential of 1.2 V. The Coulombic efficiency was~100%, while the cathode recovery varied from 57 to 100%, depending on the extent of methanogenesis. Exoelectrogenic microbes generated high current densities (7.8 mA/cm 2 ) at ≤36 g/L of total dissolved solids, but >41 g/L eliminated current. These results provide a new method for achieving simultaneous removal of salinity and organic matter from a saline wastewater with H 2 production.
doi:10.1016/j.desal.2012.07.031 fatcat:fee6nvzenvd47eidtv2abvjucu

Contextual Relationship-based Activity Segmentation on an Event Stream in the IoT Environment with Multi-user Activities [article]

Minkyoung Cho, Younggi Kim, Younghee Lee
2016 arXiv   pre-print
The human activity recognition in the IoT environment plays the central role in the ambient assisted living, where the human activities can be represented as a concatenated event stream generated from various smart objects. From the concatenated event stream, each activity should be distinguished separately for the human activity recognition to provide services that users may need. In this regard, accurately segmenting the entire stream at the precise boundary of each activity is indispensable
more » ... igh priority task to realize the activity recognition. Multiple human activities in an IoT environment generate varying event stream patterns, and the unpredictability of these patterns makes them include redundant or missing events. In dealing with this complex segmentation problem, we figured out that the dynamic and confusing patterns cause major problems due to: inclusive event stream, redundant events, and shared events. To address these problems, we exploited the contextual relationships associated with the activity status about either ongoing or terminated/started. To discover the intrinsic relationships between the events in a stream, we utilized the LSTM model by rendering it for the activity segmentation. Then, the inferred boundaries were revised by our validation algorithm for a bit shifted boundaries. Our experiments show the surprising result of high accuracy above 95%, on our own testbed with various smart objects. This is superior to the prior works that even do not assume the environment with multi-user activities, where their accuracies are slightly above 80% in their test environment. It proves that our work is feasible enough to be applied in the IoT environment.
arXiv:1609.06024v1 fatcat:o53ri6bzzjfwxoxo5pt24toyja

Energy efficient reconcentration of diluted human urine using ion exchange membranes in bioelectrochemical systems

Ryan C. Tice, Younggy Kim
2014 Water Research  
., 2011; Kim and Logan, 2011) .  ...  and Logan, 2011; Kim and Logan, 2013) .  ... 
doi:10.1016/j.watres.2014.06.037 pmid:25046373 fatcat:vdlzwprgofenblguhav376trnm

OUTER AUTOMORPHISM GROUPS OF CERTAIN TREE PRODUCTS OF ABELIAN GROUPS

Y. D. CHAI, YOUNGGI CHOI, GOANSU KIM, C. Y. TANG
2008 Bulletin of the Australian Mathematical Society  
We prove that certain tree products of finitely generated Abelian groups have Property E. Using this fact, we show that the outer automorphism groups of those tree products of Abelian groups and Brauner's groups are residually finite. 2000 Mathematics subject classification: primary 20E26, 20E06; secondary 20F34, 57M05.
doi:10.1017/s0004972708000099 fatcat:arvapviuvffoji2yjejfborjpm

Powering microbial electrolysis cells by capacitor circuits charged using microbial fuel cell

Marta C. Hatzell, Younggy Kim, Bruce E. Logan
2013 Journal of Power Sources  
h i g h l i g h t s < MFCeMEC coupled systems enhanced with parallel aligned MFCs and capacitor circuit. < Hydrogen production rates and energy recoveries increased by as much as 212% and 77%. < Capacitor energy storage based circuit transferred charge with 90% efficiency.
doi:10.1016/j.jpowsour.2012.12.006 fatcat:2c7xa7m4dzf6vfx6rndzmruw7u

Design of aircraft on-glass antennas for FM radio communications

Gangil Byun, Woojoon Kang, Younggi Kim, Hosung Choo
2011 Microwave and optical technology letters (Print)  
isolations greater that 35 dB and 49 dB, respectively, have been achieved in simulation. Simulated VSWR at all ports are better than 2.0. The measured conversion loss is 6-8 dB for þ10 dBm LO power in whole RF band. The measured LO-IF and LO-RF isolations are greater than 40 dB and 45 dB, respectively. Simulated and measured conversion losses are shown in Figure 4 . The agreement of the simulated and measured results is fairly good. Table 2 summarizes the simulated and measured results. The
more » ... icated prototype mixer shown in Figure 5 , used for demonstration of the design, was precision machined from aluminum and measures 30 Â 25 Â 22 mm 3 . CONCLUSIONS A broadband single balanced waveguide mixer at K-band has been developed. The mixer configuration is of crossbar type and is implemented in suspended stripline circuit integrated with RF and LO waveguides. The mixer has wide IF bandwidth with fixed LO frequency. The Mixer has been simulated, fabricated, and measured. Simulation and measured results agrees well. The measured conversion loss across the whole band is 6-8 dB, and LO-IF and LO-RF port isolations are greater than 40 dB and 45 dB, respectively. This mixer design approach can also be applied to design broadband mixer at higher frequency bands. This mixer will be used in broadband communication systems. ACKNOWLEDGMENTS
doi:10.1002/mop.25779 fatcat:ytyjd7c5fvby7cpcs2vrcd73wa

Thoracoscopic anterior mediastinal mass removal using an articulating laparoscopic instrument

Younggi Jung, Jeong In Hong, Kook Nam Han, Hyun Koo Kim
2021 Interactive Cardiovascular and Thoracic Surgery  
Interactive CardioVascular and Thoracic Surgery thanks Kamran Ali, Wentao Fang, Dominique Gossot and the other, anonymous reviewer(s) for their contribution to the peer review process of this article. Video 1: Technological advancement in thoracic surgery has transformed surgical approaches from open to minimally invasive surgery such as video-or robotic-assisted thoracoscopic surgery. However, conventional video-assisted thoracoscopic surgery has a limited range of motion and is therefore an
more » ... pediment when performing complicated cases. A novel articulating wristed endoscopic instrument provides an experience similar to that of robotic-assisted thoracoscopic surgery, while also maintaining tactile sensitivity. We present a case of the successful removal of a bimanually performed thoracoscopic anterior mediastinal mass, with no major postoperative morbidity. This instrument might be an alternative to robotic-assisted thoracoscopic surgery, although a learning curve is needed for its handling.
doi:10.1093/icvts/ivab110 pmid:33880541 pmcid:PMC8759515 fatcat:wsqbkn7crvcknlyy47fdj4quua

Development of a Renewable Energy Facility Design and Its Simulation Case Study
신재생에너지 설비 설계방안 개발 및 시뮬레이션 사례 연구

Younggy Shin, Eun Joo Kim, Tae Hyung Kim
2013 Korean Journal of Air-Conditioning and Refrigeration Engineering  
Economic feasibility was conducted regarding the regulation that dictates obligatory installation of renewable energy facilities in small proportion. A concern is how to allocate the capacities of candidate facilities (solar collectors, PV cells and geothermal heat pumps) with minimum cost, and meet the obligatory energy supply proportion. A design rule has been developed, with which a designer can tune his or her design strategy between installation cost and LCC. This was derived mainly from
more » ... cuments regarding the KEMCO installation guide. It was concluded that PV was the cheapest, with respect to installation cost, but a geothermal heat pump was the most recommended, when LCC was also taken into account. The proposed design result was also confirmed, by simulation results obtained from Energy Plus.
doi:10.6110/kjacr.2013.25.8.464 fatcat:ocdddcklxncn5obtfxiv3gwy5m

Electrochemical analysis of separators used in single-chamber, air-cathode microbial fuel cells

Bin Wei, Justin C. Tokash, Fang Zhang, Younggy Kim, Bruce E. Logan
2013 Electrochimica Acta  
Polarization, solution-separator, charge transfer, and diffusion resistances of clean and used separator electrode assemblies were examined in microbial fuel cells using current-voltage curves and electrochemical impedance spectroscopy (EIS). Current-voltage curves showed the total resistance was reduced at low cathode potentials. EIS results revealed that at a set cathode potential of 0.3 V diffusion resistance was predominant, and it substantially increased when adding separators. However, at
more » ... a lower cathode potential of 0.1 V all resistances showed only slight differences with and without separators. Used separator electrode assemblies with biofilms had increased charge transfer and diffusion resistances (0.1 V) when one separator was used; however, charge transfer resistance increased, and diffusion resistance did not appreciably change with four separators. Adding a plastic mesh to compress the separators improved maximum power densities. These results show the importance of pressing separators against the cathode, and the adverse impacts of biofilm formation on electrochemical performance.
doi:10.1016/j.electacta.2012.11.004 fatcat:6ojlvpg6eje5habuaj74xiqsyi

Influence of substrate concentration and feed frequency on ammonia inhibition in microbial fuel cells

Ryan C. Tice, Younggy Kim
2014 Journal of Power Sources  
C. and Kim, Y., J. Power Sources 271 (2014) 360-365, doi:10.1016/j.jpowsour.2014.08.016.  ... 
doi:10.1016/j.jpowsour.2014.08.016 fatcat:df3zfyk6xzhvtifadtsx2ygarm

Topology Optimization of Compliant Mechanism with Geometrical Advantage

Seungjae MIN, Younggi KIM
2004 JSME international journal. Series C, Mechanical systems, machine elements and manufacturing  
A compliant mechanism is a mechanism that produces its motion by the flexibility of some or all of its members when the input forces are applied. Because of its mobility resulted from flexibility, it is difficult to expect the configuration in prioi. In this work, the design method of a compliant mechanism with the specified geometrical advantage is proposed to control the motion. The multiobjective optimization problem is formulated to minimize the deviation of the specified geometrical
more » ... ge and structural compliance of a mechanism and topology optimization is applied to determine the configuration of a mechanism. The results of example problems including a displacement converter design and a gripper design are compared with a multi-criteria model and show that the design of an accurate compliant mechanism with specified geometrical advantage can be obtained.
doi:10.1299/jsmec.47.610 fatcat:5r3ahbcxuzaqvngipcnlm5k3ye
« Previous Showing results 1 — 15 out of 48 results