• 대한기계학회논문집
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• 제18권11호
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• pp.2860-2870
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• 1994

When crack are detected in aged turbine rotors of power plants, information on fracture resistance of the aged material at operating temperature is needed for determination of critical loading condition and residual life of the turbine. In this study, fracture toughness (J$_lc$) and tearing modulus(T$_mat$) of virgin and thermally degraded 1Cr-1Mo-0.25V steel, which is one of the most widely used rotor steels, were measured at 538.deg. C according to ASTM E813 and ASTM E1152, respectively. Five kinds of specimen with different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C.$ It was observed that J$_lc$ and T$_mat$ value decreased as the degradation level increased. Analysis of microstructures using a scanning electron microscope showed that the decrement of J$_lc$ is related to segregation of impurities at grain boundaries. It was also verified that the DC electric potential drop method is accurate and reliable for crack length monitoring at elevated temperature.

• 한국환경과학회지
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• 제28권10호
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• pp.873-885
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• 2019

In this study, a load duration curve was applied to the Jangseongcheon, one of the tributaries of the Yeongsan River, to assess whether the target water quality was achieved. In addition, pollution of the water body was investigated to develop and suggest the optimal management time with respect to polluted flow sections and monthly conditions. The average flow rates of sections JS1 and JS2 were $0.25m^3/s$ and $1.08m^3/s$, respectively. The BOD and T-P for water-quality standards at JS1 were rated at II, whereas the COD and TOC were rated at III, thus indicating a fair level of water quality. By contrast, the BOD at JS2 was rated at III, the T-P at IV, and the TOC at V, indicating poor water quality in this section. The load duration curve was plotted using the actual flow data measured in eight-day intervals for eight years from 2011 to 2018 at locations JS1 and JS2 in the Jangsungcheon Basin. In an assessment using the load duration curve on whether the target water quality was met at location JS1, all of the water quality parameters (BOD, COD, TOC, T-N, T-P, and SS) satisfied the target water quality. By contrast, at location JS2, parameters COD, TOC, T-N, and T-P exceeded target values by more than 50%, indicating the target water quality was not met. The discharge loads of locations JS1 and JS2 were analyzed to identify the reasons the target water quality was exceeded. Results revealed that the land system contributed considerably. Furthermore, the discharge load of JS2 accounted for more than 80% of the load on the entire basin, excluding that of JS1. Therefore, the best method for restraining the inflow of pollutants into the stream near location JS2 must be applied to manage the water quality of the Jangsungcheon.

• 농업과학연구
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• 제11권1호
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• pp.160-175
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• 1984

로우터리 경운(耕耘)날의 회전속도(回轉速度) 및 작업속도(作業速度)가 경운소요(耕耘所要)토오크에 미치는 영향을 분석(分析)하기 위(爲)하여, 형상각(形狀角) ${\theta}=30^{\circ}$, $40^{\circ}$인 2종(種)의 경운(耕耘)날로 로우터리축(軸)을 204, 243, 285, 360rpm 4단계로, 전진속도(前進速度)는 29.40cm/s, 46.93cm/s로 변화(變化)시키면서 인공토양조(人工土壤槽)에서 dynamic strain gage system을 이용(利用)하여 경운소요(耕耘所要)토오크를 측정분석(測定分析)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 경운(耕耘)날의 회전속도(回轉速度) 및 전진속도(前進速度)는 경운소요(耕耘所要)토오크에 교호작용(交互作用)으로 영향(影響)을 미치는 것으로 분석(分析)되었으며, response surface analysis를 통(通)하여 분석(分析)한 수학적(數學的)인 모형(模型)은 다음과 같다. $$T=a_0+a_1V+a_2R+a_3VR+a_4VR^2$$ 여기서 T=경운소요(耕耘所要)토오크 (kg-m) $a_0$=당(當)수(數) $a_1,\;a_2,\;a_3,\;a_4$= 계(係)수(數) V=경운장치(耕耘裝置)의 전진속도(前進速度) (cm/s) R=경운(耕耘)날의 회전속도(回轉速度) (rpm) 2. 최대경운소요(最大耕耘所要)토오크는 로우터리날 회전속도(回轉速度)가 증가(增加)함에 따라 ${\frac{{\partial}T}{{\partial}V}}$는 증가(增加)하였으며, 200~220rpm에서 증가율(增加率)이 최저(最低)가 되었고, 같은 조건(條件)에서 ${\frac{{\partial}T}{{\partial}R}}$은 감소(減少)하는 경향(傾向)이었으며, 전진속도(前進速度)가 증가(增加)함에 따라 감소율(減少率)은 증가(增加)되었다. 3. 평균경운소요(平均耕耘所要)토오크는 회전속도(回轉速度)가 320~360rpm에서 ${\frac{{\partial}T}{{\partial}R}}$의 變化가 적었으며, ${\frac{{\partial}T}{{\partial}R}}$은 회전속도(回轉速度)가 증가(增加)함에 따라 감소율(減少率)이 증가(增加)되었다. 4. 전진속도(前進速度)에 대(對)한 토양(土壤)의 단위체적당(單位體積當) 평균경운소요(平均耕耘所要)토오크의 변화율(變化率)${\frac{{\partial}T}{{\partial}R}}$는 270~300rpm에서 최저(最低)가 되었으며, ${\frac{{\partial}T}{{\partial}R}}$은 V=29.40cm/s와 V=46.93cm/s일때 변화율(變化率)이 280~290rpm에서 교착(交錯)하였다. 5. 로우터리날의 형상각(形狀角)이 증가(增加)함에 따라 순경운소요동력(純耕耘所要動力)은 증가(增加)하였다. 그러나 실제(實際) 이용면(利用面)에서는 형상각(形狀角)이 작으면 로우터리날에 검불이 감기게 되므로 소요동력(所要動力)이 크게 증가(增加)함을 보여주는 연구결과도 있다. 그러므로 형상각(形狀角) 변화(變化)에 대(對)해서는 계속 연구(硏究)되어야 할 과제(課題)라 인정(認定)된다.

• 호남수학학술지
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• 제42권4호
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• pp.747-755
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• 2020

The mathematical proof for establishing some new inequalities involving arithmetic, geometric, harmonic means for the arguments lying on the paths of triangular wave function (linear) and new parabolic function (curved) over the interval (0, 1) are discussed. The results representing an extension as well as strengthening of Ky Fan Type inequalities.

• Journal of Magnetics
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• 제14권1호
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• pp.11-14
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• 2009

We investigated the I-V curves and differential tunneling conductance of two, CoFeB/MgO/CoFeB-based, magnetic tunnel junctions (MTJs): one with a low tunneling magnetoresistance (TMR; 22%) and the other with a high TMR (352%). This huge TMR difference was achieved by different MgO sputter conditions rather than by different annealing or deposition temperature. In addition to the TMR difference, the junction resistances were much higher in the low-TMR MTJ than in the high-TMR MTJ. The low-TMR MTJ showed a clear parabolic behavior in the dI/dV-V curve. This high resistance and parabolic behavior were well explained by the Simmons' simple barrier model. However, the tunneling properties of the high-TMR MTJ could not be explained by this model. The characteristic tunneling properties of the high-TMR MTJ were a relatively low junction resistance, a linear relation in the I-V curve, and conduction dips in the differential tunneling conductance. We explained these features by applying the coherent tunneling model.

• 천문학회지
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• 제27권2호
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• pp.133-146
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• 1994

We have detected a SiO maser line (v=1, J=2- 1) for 15 stars out of about 80 long period variables in the wide range of period. No new sources are detected; all detected sources are variables with period longer than 300 days; no evidence is found that the dust grains in the outer envelope have influenced on this line. The time variation of this maser line for 7 stars, T Cep, ${\mu} Cep$, U Her, R Leo, R Lmi, U Ori, and R Ser is observed and compared with optical light curve at the same epoch of maser observation. No universial relation between the time variation and the optical light curve is found. It implies that the radiation from a central star does not much play an important role for the direct pumping of the SiO maser line.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 추계학술대회
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• pp.101-103
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• 2022

타원곡선 암호 (elliptic curve cryptography; ECC)는 효율적인 하드웨어 구현이 가능하면서 높은 보안 강도를 가져 오늘날 IoT 기기나 V2X 통신의 공개키 보안 하드웨어 구현에 폭넓게 사용되고 있다. 그러나 ECC 기반의 공개키 보안 시스템은 부채널 공격 (side channel attacks; SCA)에 대한 일부 보안 취약점을 갖는 것으로 알려지고 있어 ECC 프로세서 설계 시 보안공격에 대한 대응 방법의 적용이 필요하다. 본 논문에서는 부채널 공격 유형과 ECC 프로세서 설계에 적용할 수 있는 부채널 공격 대응 방안에 대해 알아본다.

• Advances in Traditional Medicine
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• 제7권1호
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• pp.41-45
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• 2007

The roots of the plant Korean ginseng have been extensively used in the traditional Chinese herbal medicine. The effects of chronic administration of Korean ginseng extract (KGE) were investigated on two different anxiety models: the elevated T-maze (for inhibitory avoidance and escape measurements) and the open field test (OFT). Diazepam (1 mg/kg), KGE (10, 30 and 100 mg/kg) were administered orally for 15 days. On the 14th day, mice were previously exposed for 30 min to one of the open arms of the T-maze, 24 h before the test. On 15th day, mice had two exposures to the enclosed and open arm of the elevated T-maze followed by exposure to the open field apparatus. The number of line crossings in the apparatus was used to assess locomotor changes. Cumulative Concentration Response Curve of 5-HT was plotted using rat fundus which were pre-treated in a similar way. Treatment with Diazepam (1 mg/kg) and KGE (10, 30 and 100 mg/kg) significantly (P < 0.05) impaired inhibitory avoidance performance but did not impair escape latency. In OFT, diazepam facilitated locomotion as compared to vehicle and other treatment groups. KGE at any of the selected doses did not impair locomotion. Concentration response curve of 5-HT was shifted towards the right with suppression of maxima in rats treated with KGE. The results suggest that KGE exerts anxiolytic like behaviour in a specific subset of defensive behaviour, particularly those related to generalized anxiety disorder.

• 한국산업정보학회논문지
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• 제17권7호
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• pp.51-57
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• 2012

본 논문에서는 안전한 V2V 통신과 V2I 통신을 보장하는 ECDH(Elliptic Curve Diffie Hellman) 기반 그룹키를 제안하였다. 본 논문에서 제안하는 ECDH기반 그룹키는 AAA 서버를 사용하지 않고 차량과 차량사이의 그룹키인 VGK(Vehicular Group Key), 차량 그룹 사이의 그룹키인 GGK(Globak Group Key), 그리고 차량과 RSU사이의 그룹키인 VRGK(Vehicular and RSU Group Key)를 ECDH 알고리즘을 이용하여 생성한다. 차량과 RSU 사이의 그룹키인 VRGK는 현재 RSU에서 다음 RSU에게로 RGK(RSU Group Key)로 암호화하여 안전한 채널을 통하여 전달하기 때문에 완벽한 순방향 기밀(Perfect Forward Secrecy) 보안 서비스가 제공된다. 또한, 메시지를 전송한 차량이 해당 그룹의 구성원인지를 그룹키 이용하여 확인함으로써 Sybil공격을 탐지할 수 있다. 그리고 그룹간의 안전한 통신으로 불필요한 네트워크 트래픽이 발생하지 않으므로 메시지 전송 시간 및 서버의 오버헤드를 줄일 수 있다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.526-532
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• 2015

We quantitatively investigated instability mechanisms under simultaneous positive gate and drain bias stress (SPGDBS) in self-aligned top-gate amorphous indium-zinc-oxide thin-film transistors. After SPGDBS ($V_{GS}=13V$and $V_{DS}=13V$), the parallel shift of the transfer curve into a negative $V_{GS}$ direction and the increase of on current were observed. In order to quantitatively analyze mechanisms of the SPGDBS-induced negative shift of threshold voltage (${\Delta}V_T$), we experimentally extracted the density-of-state, and then analyzed by comparing and combining measurement data and TCAD simulation. As results, 19% and 81% of ${\Delta}V_T$ were taken to the donor-state creation and the hole trapping, respectively. This donor-state seems to be doubly ionized oxygen vacancy ($V{_O}^{2+}$). In addition, it was also confirmed that the wider channel width corresponds with more negative ${\Delta}V_T$. It means that both the donor-state creation and hole trapping can be enhanced due to the increase in self-heating as the width becomes wider. Lastly, all analyzed results were verified by reproducing transfer curves through TCAD simulation.