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Bifurcations in a Horizontally Driven Pendulum
Jaeyong JEONG,Sang-Yoon Kim 강원대학교 기초과학연구소 1999 기초과학연구 Vol.10 No.-
We consider a forced pendulum with a horizontally oscillating suspension point. Bifurcations associated with stability at the symmetric period-l orbit (SPO), arising from the "unforced" stationary point, are investigated in details by varying the two parameters A (the normalized driving amplitude) and Ω (the normalized natural frequency). We thus obtain the phase diagram showing the bifurcation curves or the SPO in the Ω-A plane through numerical calculations or the Floquet (stability) multipliers and winding numbers. We note that a specific substructure in the bifurcation set of the SPO recurs in the parameter plane.
Dynamic Erase Voltage and Time Scaling for Extending Lifetime of NAND Flash-Based SSDs
Jeong, Jaeyong,Song, Youngsun,Hahn, Sangwook Shane,Lee, Sungjin,Kim, Jihong IEEE 2017 IEEE TRANSACTIONS ON COMPUTERS - Vol.66 No.4
<P>The decreasing lifetime of NAND flash memory, as a side effect of recent advanced semiconductor process scaling, is emerging as one of major barriers to the wide adoption of SSDs in high-performance computing systems. In this paper, we propose Dynamic Erase Voltage and Time Scaling (DeVTS), an integrated approach to extend the lifetime (particularly, endurance) of NAND flash memory. DeVTS is motivated by our key observation that erasing a NAND block with a lower voltage or at a slower speed can significantly improve NAND endurance. However, using a lower erase voltage causes adverse side effects on the write performance and retention capability of NAND flash memory. In order to improve NAND endurance without affecting the other NAND requirements, we take advantage of idle times between write requests and variations of the retention requirement when writing data to a NAND block erased with a lower voltage. We have implemented a DeVTS-aware FTL, called dvsFTL, which exploits the tradeoff relationship between the endurance and erase voltages/times by accurately predicting the write performance and retention requirements. Our experimental results show that dvsFTL can improve NAND endurance by 94 percent, on average, over an existing DeVTS-unaware FTL while all the NAND requirements are preserved.</P>
Recent Trend of Residual Pesticides in Korean Feed
Jeong, Jin Young,Kim, Minseok,Baek, Youl-Chang,Song, Jaeyong,Lee, Seul,Kim, Ki Hyun,Ji, Sang Yun,Lee, Hyun-Jeong,Oh, Young Kyun,Lee, Sung Dae The Korean Society of Grassland and Forage Science 2018 한국초지조사료학회지 Vol.38 No.3
Pesticide application in agriculture provides significant benefits such as protection from disease, prevention of harmful insects, and increased crop yields. However, accurate toxicological tests and risk assessments are necessary because of many related adverse effects associated with pesticide use. In this review, we discuss and analyze residual pesticides contained in livestock feed in Korea. A pesticide residue tolerance standard for livestock feed has not been precisely established; so, risk assessments are required to ensure safety. Standards and approaches for animal criteria and appropriate methods for evaluating residual pesticides are discussed and analyzed based on technology related to animal product safety in Korea. The safety of livestock feed containing pesticides is assessed to establish maximum residue limits relative to pesticides. Analysis of residual pesticides in milk, muscle, brain, and fat was performed with a livestock residue test and safety evaluation of the detected pesticide was performed. Efficacy of organic solvent extraction and clean-up of feed was verified, and suitability of the instrument was examined to establish if they are effective, rapid, and safe. This review discussed extensively how pesticide residue tolerance in livestock feed and hazard evaluation may be applied in future studies.
정재용(JaeYong Jeong),노삼혁(Sam Hyuk Noh),민상렬(Sang Lyul Min),조유근(Yookun Cho) 한국정보과학회 2002 정보과학회 컴퓨팅의 실제 논문지 Vol.8 No.1
본 논문에서는 실제 플래시 메모리와 동일한 특성을 갖는 플래시 메모리 시뮬레이터를 설계 및 구현한 내용을 설명한다. 본 시뮬레이터는 생산 방식, 전체 용량, 블록 크기, 페이지 크기 등 플래시 메모리의 특성을 변화시키면서 실험할 수 있을 뿐만 아니라 정확한 수행 시간과 인자 검증 기능을 제공함으로써, 운영체제 입장에서는 실제 플래시 메모리 장치를 사용하는 효과를 얻을 수 있다. 또한, 내부 루틴의 수행 시간 로깅 기능을 제공함으로써 플래시 메모리 관리 소프트웨어의 병목 지점을 판단할 수 있도록 하였다. 마지막으로, Linux 운영체제 환경에 구현된 시뮬레이터와 실제 플래시 메모리를 장착한 테스트 보드에서 응용 프로그램의 성능 측정 결과를 비교함으로써 본 시뮬레이터가 실제 플래시 메모리 장치 대용으로 사용할 수 있음을 보였다. This paper introduces the design and implementation of a flash memory simulator to emulate a real flash memory. Since this simulator provides exact execution time information and parameter testing functions as well as the type, total capacity, block size, and page size of flash memory, it can be used as a real flash memory as viewed by the operating system. Furthermore, the simulator provides time logging functions of the internal routines of the flash memory management software allowing the monitoring of bottlenecks within the software. Finally, we show the performance measurements of applications under the Linux operating systems on both the simulator and a test board verifying the simulator's use as a replacement for real flash memory.
선박 프로펠러에 의해 발생하는 수중방사소음에 대한 수치 해석
정재용(Jaeyong Jeong),김인녕(Innyoung Kim),윤대근(Daegeun Yoon),김성훈(Sunghoon Kim),유동현(Donghyun You) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.1
Numerical simulations of turbulent flow, propeller cavitation, and induced underwater radiated noise over a marine propeller with a realistic ship geometry are conducted. Scaled ship geometries of the KVLCC2 hull and the KP458 propeller are considered in the present simulation. Turbulent flow past a marine propeller is investigated using incompressible large eddy simulation (LES) to accurately capture small scale turbulent fluctuations. In addition, to treat the propeller cavitation and track the cavity interface, a volume of fluid method (VOF) is used with the Schnerr-Sauer cavitation model. By using time series of fluid pressure and velocity field, acoustic pressure at the monitoring point is computed by the Ffowcs-Williams Hawkings (FW-H) acoustic analogy. The predicted acoustic pressure computed by integration on the cylindrical FW-H data surface are well matched with the experimental results measured at KRISO.