• Proceedings of the Korea Information Processing Society Conference
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• 2021.05a
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• pp.22-24
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• 2021

본 논문은 원격 서버에 저장 내용을 백업하는 RAM 기반 디스크 시스템인 NBRD의 프로토타입 구현을 위한 블록 장치 구동기와 이를 이용한 디스크 입출력 성능을 평가한다. 또, SSD의 성능 평가를 실시하여 향후 NBRD의 이점 및 향후 성능 향상 목표값을 설정한다.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.77-84
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• 1999

Numerical design optimization techniques are implemented for the improvement of the ram accelerator performance. The design object is to find the minimum ram tube length required to accelerate projectile from initial velocity $V_0$ to target velocity $V_e$. The premixture is composed of $H_2,\;O_2,\;N_2$ and the mole numbers of these species are selected as design variables. The objective function and the constraints are linearized during the optimization process and gradient-based Simplex method and SLP(Sequential Linear Programming) have been employed. With the assumption of two dimensional inviscid flow for internal flow field, the analyses of the nonequilibrium chemical reactions for 8 steps 7 species lave been performed. To determined the tube length, ram tube internal flow field is assumed to be in a quasi-steady state and the flow velocity is divided into several subregions with equal interval. Hence the thrust coefficients and accelerations for corresponding subregions are obtained and integrated for the whole velocity region. With the proposed design optimization techniques, the total ram tube length had been reduced $19\%$ within 7 design iterations. This optimization procedure can be directly applied to the multi-stage, multi-premixture ram accelerator design optimization problems.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.81-84
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• 2014

The bipolar resistive switching characteristics of resistive random access memory (ReRAM) based on $HfO_2$ thin films have been demonstrated by using Ag/$HfO_2$/Pt structured ReRAM device. MIcrowave irradiation (MWI) treatment at low temperature was employed in device fabrication with $HfO_2$ thin films as a transition layer. Compared to the as-deposited Ag/$HfO_2$/Pt device, highly improved uniformity characteristics of resistance values and operating voltages were obtained from the MWI treatment Ag/$HfO_2$/Pt ReRAM device. In addition, a stable DC endurance (> 100 cycles) and a high data retention (> $10^4$ sec) were achieved.

• Journal of the Korean Society of Systems Engineering
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• v.15 no.1
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• pp.16-24
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• 2019

In this study, an improved method of setting the RAM goals for surveillance system using OMS/MP and field operations data of similar systems is suggested and a case study of surveillance system A is given. Newly suggested methods for setting the RAM goals consist of the procedures such as On/Off time analysis of configuration equipment based on OMS/MP, field operations data analysis of similar systems, adjustment of preventive maintenance time, the number of corrective maintenances, and TALDT in wartime, introducing new subsystem to reliability structure of surveillance system, and reflecting expert's opinion. A case study of surveillance system A shows that newly suggested method in this study for setting the RAM goals is reasonably acceptable and practically applicable to other similar systems.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.55-61
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• 2019

Motor pumps cannot be used in those areas where electricity is not accessible such as remote rural areas in many African countries. Hydraulic ram pump is one of the solutions for supplying water for irrigation or domestic uses. The hydraulic ram pumps are working based on the water hammer effect for pumping without external power or electricity. This study was conducted to investigate the effect of air chamber volume and operation parameters on the performance of the hydraulic ram pump which was assembled with common plumbing parts. The experimental results showed the volume of the air chamber did not affect the performance such as discharge rate and head. When drive heights were 1.7 and 2.35 m, the maximum discharge heads were up to 7 m and 10 m, respectively. When the air chamber volume was 1 L, discharge rates were 0.23 and 2.12 L/min under the drive heights of 1.7 and 2.35 m, respectively. The average energy efficiency of the hydraulic ram pump assembled in this study was about 60% for all the experimental conditions.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.77.1-77.1
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• 2019

It has been proposed by Gunn & Gott (1972) that galaxies may lose their interstellar gas by ram pressure due to the dense intra-cluster medium while falling to the cluster potential. The observational evidence for this process, which is known as ram pressure stripping, is increasing, and it is believed to be one of the key environmental effects that can dramatically change the star formation activity of galaxies and hence their evolution. Intriguingly however, some cases with clear signs of ram pressure stripping are found in the environment which betrays our expectations (e.g. large clustercentric distances), and our understandings to the detailed working principle behind ram pressure stripping seem to be still lacking. As one of the ways to gain more theoretical insights into the conditions for ram pressure stripping process, we have been comparing the gas truncation radius which is predicted based on the simple Gunn & Gott's prescription with what is actually observed in a sample of carefully selected Virgo galaxies. In this work, we present the results of our comparisons between the theoretically predicted truncation radius and the observationally measured truncation radius for individual galaxies in the sample and discuss which additional conditions are needed in order to fully understand the observations.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.326-326
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• 2014

It has been known since the mid 1960s that Ag can be photodissolved in chalcogenide glasses to form materials with interesting technological properties. In the 40 years since, this effect has been used in diverse applications such as the fabrication of relief images in optical elements, micro photolithographic schemes, and for direct imaging by photoinduced Ag surface deposition. ReRAM, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of a conductive filament in a solid electrolyte. Especially, Ag-doped chalcogenide glasses and thin films have become attractive materials for fundamental research of their structure, properties, and preparation. Ag-doped chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in ReRAM devices. In this paper, we investigated the nature of thin films formed by the photo-dissolution of Ag into Ge-Se glasses for use in ReRAM devices. These devices rely on ion transport in the film so produced to create electrically programmable resistance states [1-3]. We have demonstrated functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of Ag+ ions photo-induced diffusion in thin chalcogenide films is considered. The influence of Ag+ ions is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Saturated Ag+ ions have been used in the formation of conductive filaments at the solid electrolyte which is the active medium in ReRAM devices. Following fabrication, the cell displays a metal-insulator-metal structure. We measured the I-V characteristics of a cell, similar results were obtained with different via sizes, due to the filamentary nature of resistance switching in ReRAM cell. As the voltage is swept from 0 V to a positive top electrode voltage, the device switches from a high resistive to a low resistive, or set. The low conducting, or reset, state can be restored by means of a negative voltage sweep where the switch-off of the device usually occurs.

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.675-696
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• 2023

Terpenoids, also referred to as terpenes, are a large family of naturally occurring chemical compounds present in the essential oils extracted from medicinal plants. In this study, a nondestructive methodology was created by combining ATR-FT-IR (attenuated total reflectance-Fourier transform infrared), and Raman spectroscopy for the terpenoids assessment in medicinal plants essential oils from ten different geographical locations. Partial least squares regression (PLSR) and support vector regression (SVR) were used as machine learning methodologies. However, a deep learning based model called as one-dimensional convolutional neural network (1D CNN) were also developed for models comparison. With a correlation coefficient (R²) of 0.999 and a lowest RMSEP (root mean squared error of prediction) of 0.006% for the prediction datasets, the SVR model created for FT-IR spectral data outperformed both the PLSR and 1 D CNN models. On the other hand, for the classification of essential oils derived from plants collected from various geographical regions, the created SVM (support vector machine) classification model for Raman spectroscopic data obtained an overall classification accuracy of 0.997% which was superior than the FT-IR (0.986%) data. Based on the results we propose that FT-IR spectroscopy, when coupled with the SVR model, has a significant potential for the non-destructive identification of terpenoids in essential oils compared with destructive chemical analysis methods.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.181.1-181.1
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• 2015

용액 공정을 이용한 Resistive random access memory (ReRAM)은 간단한 공정 과정, 대면적화, 저렴한 가격 등의 장점으로 인해 큰 관심을 받고 있으며, HfOx, TiOx, AlOx 등의 산화물이 ReRAM 절연 막으로 주로 연구되고 있다. 더 나아가 최근에는 organic 물질을 메모리 소자로 사용한 연구가 보고되고 있다. 이는 경제적이며, wearable 또는 flexible system에 적용이 용이하다. 그럼에도 불구하고, organic 물질을 갖는 메모리 소자는 기존의 산화물 소자에 비해 열에 취약하며 전기적인 특성과 신뢰성이 우수하지 못하다는 단점을 가지고 있다. 이를 위한 방안으로 본 연구에서는 AlOx - polymethylmethacrylate (PMMA) blended thin film ReRAM을 제안하였다. 이는 organic물질의 전기적 특성을 개선시킬 뿐 아니라, inorganic 물질을 wearable 소자에 적용했을 때 발생하는 crack과 같은 기계적 물리적 결함을 해결할 수 있는 새로운 방법이다. 먼저, P-type Si 위에 습식산화를 통하여 SiO2 300 nm 성장시킨 기판을 사용하여 electron beam evaporation으로 10 nm의 Ti, 100 nm의 Pt 층을 차례로 증착하였다. 그리고 PMMA 용액과 AlOx 용액을 초음파를 이용하여 혼합한 뒤, 이 용액을 Pt 하부 전극 상에서 spin coating방법으로 1000 rpm 10초, 5000 rpm 30초의 조건으로 증착하였다. Solvent 및 불순물 제거를 위하여 150, 180, $210^{\circ}C$의 온도로 30 분 동안 열처리를 진행하였고, shadow mask를 이용하여 상부 전극인 Ti를 sputtering 방식으로 100 nm 증착하였다. 150, 180, $210^{\circ}C$로 각각 열처리한 AlOx - PMMA blended ReRAM의 전기적 특성은 HP 4156B semiconductor parameter analyzer를 이용하여 측정하였다. 측정 결과 제작된 소자 전부에서 2 V이하의 낮은 동작전압, 안정된 DC endurance (>150cycles), 102 이상의 높은 on/off ratio를 확인하였고, 그 중 $180^{\circ}C$에서 열처리한 ReRAM은 더 높은 on/off ratio를 갖는 것을 확인하였다. 결론적으로 baking 온도를 최적화하였으며 AlOx - PMMA blended film ReRAM의 우수한 메모리 특성을 확인하였다. AlOx-PMMA blended film ReRAM은 organic과 inorganic의 장점을 갖는 wearable 및 system용 비휘발성 메모리소자에 적용이 가능한 경제적인 기술로 판단된다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.1-7
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• 2010

In this paper, we suggested a sensing method of PoRAM with the multilevel cell When a specific voltage is applied between top and bottom electrodes of PoRAM unit cell, we can distinguish cell states by changing resistance values of the cell. Especially, we can use the PoRAM as the multilevel cell due to have four stable resistance values per cell. Therefore, we proposed an address decoding method, sense amplifier and control signal for sensing of a multilevel cell. The sense amplifier is designed based on a current comparator that compared a cell current the cell with a reference current, and have a low input impedance for a amplification of the current. The proposed circuit was designed in a $0.13{\mu}m$ CMOS technology, we verified to sense each data "00", "01", "10", "10" by four states of a cell current.