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Optimal Policies for Batch Control Operations in Information Systems
Kim, Kisu 한국경영과학회 1994 經營 科學 Vol.11 No.1
For an Information System to be successful the continual control of the database system(DBS) is very important. In general, such control operations are performed periodically in batches, even in real time systems. We explain DBS related such control operations and describe the decision problem in each of them. Specifically, backup, checkpointing, reorganization, and batch update operations are considered. Then we develop a general model of the batch backup situation to determine the optimal backup timing. Other operations are considered as special cases of the general batch backup operation. Under two common control policies, the optimal timings of the batch backup operation are derived and compared. We show that, in general, the control limit policy is superior to the fixed time interval policy in terms of the long-run average cost per unit time. Some practical considerations about the implementation of optimal policies are also mentioned.
Kim, Yong Seung,Joo, Kisu,Jerng, Sahng-Kyoon,Lee, Jae Hong,Moon, Daeyoung,Kim, Jonghak,Yoon, Euijoon,Chun, Seung-Hyun American Chemical Society 2014 ACS NANO Vol.8 No.3
<P>The integration of graphene into devices is a challenging task because the preparation of a graphene-based device usually includes graphene growth on a metal surface at elevated temperatures (∼1000 °C) and a complicated postgrowth transfer process of graphene from the metal catalyst. Here we report a direct integration approach for incorporating polycrystalline graphene into light emitting diodes (LEDs) at low temperature by plasma-assisted metal-catalyst-free synthesis. Thermal degradation of the active layer in LEDs is negligible at our growth temperature, and LEDs could be fabricated without a transfer process. Moreover, <I>in situ</I> ohmic contact formation is observed between DG and p-GaN resulting from carbon diffusion into the p-GaN surface during the growth process. As a result, the contact resistance is reduced and the electrical properties of directly integrated LEDs outperform those of LEDs with transferred graphene electrodes. This relatively simple method of graphene integration will be easily adoptable in the industrialization of graphene-based devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-3/nn405477f/production/images/medium/nn-2013-05477f_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn405477f'>ACS Electronic Supporting Info</A></P>
The Limit of Detection of Giant Magnetoresistive (GMR) Sensors for Bio-applications
Kisu Lee,Seungkyo Lee,Kwang-Seok Kim,Byungchul Kim,조병기 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
For the detection of specific bio-molecules, such as cells, proteins and DNA, it is necessary to verify the limit of detection (LOD) of an investigated giant magnetoresistive (GMR) sensor. We measured voltage drops across a GMR sensor before and after spreading magnetic particles on the surface of the GMR sensor and compared them to find the LOD of the GMR sensor. Magnetic particles (DynabeadsR) of 2.8 μm in diameter were used. The threshold for the detection was approximately 6 beads. This result indicates that the GMR sensor studied in this study can be used to detect bio-molecules, such as micron-sized cells.
KiSu Kim,Youngho Ko,Doyeon Hwang,Seong Young Ko,Jong-oh Park,Sukho Park 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
As demands of microrobots in medical applications increases, micro-actuators for the microrobots are actively studied. However, miniaturized motors cannot be easily applied to microrobots owing to the limitations of their sizes and generating forces. Therefore, a new functional smart material for microrobots should be developed. Among various smart materials, we focused on a ferro-actuator using ferrofluid. The ferro-actuator is regarded as a smart material and can show large displacements, excellent repetition performances, and relative small actuation forces. In this paper, a cellulose is used to make a paper backbone membrane because it has superior properties compared with any others conventional papers. The cellulose paper backbone membrane is easily fabricated as complex shapes and shows a large displacement in a magnetic field. In detail, patterned ferropaper actuator is made of cellulose acetate using general MEMS procedure and PDMS molding method. Finally, through bending experiments and alignment experiments of the fabricated ferropaper actuator using an electromagnetic actuation (EMA) system, the patterned ferropaper actuator was characterized.
A New Single-Phase Switched-Coupled-Inductor DC–AC Inverter for Photovoltaic Systems
Kim, Kisu,Cha, Honnyong,Kim, Heung-Geun Institute of Electrical and Electronics Engineers 2017 IEEE transactions on power electronics Vol. No.
<P>This paper presents a new single-phase switched-coupled- inductor dc-ac inverter featuring higher voltage gain than the existing single-phase qZ-source and semi-Z-source inverters. Similar to the single-phase qZ-source and semi-Z-source inverters, the proposed inverter also has common grounds between the dc input and ac output voltages, which is beneficial especially for photovoltaic inverter systems. The inverter volume and maximum current flowing can be reduced significantly through the coupling of all inductors. A theoretical analysis of the proposed inverter is described and a 280-W experimental prototype is built to verify the performance of the inverter.</P>
A Novel Voltage Balancing Strategy using LC for Dual Output Dual-Active-Bridge Converter
Kisu Kim,Jeonghun Kim,Viet C. Nguyen,Honnyong Cha 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this paper, a novel voltage balancing strategy (VBS) using one inductor and capacitor (LC) is proposed. The proposed VBS can be applied to dual output dual-active-bridge (DAB) converters such as half-bridge and neutral-point-clamped DAB converters. The dual output DAB converters with the proposed VBS achieve output voltage balancing regardless of output load conditions without additional voltage balancing circuit. Although LC is added between transformer and neutral-point of output capacitors, a conventional pulse-width-modulation scheme can be used and the LC has no significant effect on the operation of the converters. Therefore, the dual output DAB converters using the proposed VBS retain most of the characteristics of the conventional dual output DAB converters and achieve voltage balancing effectively. A 3-kW prototype converter was built and tested to verify the performances of the proposed VBS.