• 대한전자공학회논문지SD
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• 제46권9호
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• pp.68-73
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• 2009

본 논문은 CMOS RF 집적 회로 측정 시 측정 회로의 디지털 실시간 제어를 위한 직렬 주변 인터페이스 회로의 풀커스팀(Full Custom) 방식 CMOS 집적 회로 구현과 이의 구동 소프트웨어의 개발에 관하여 기술하였다. 개발된 SPI는 제어하고자 하는 회로의 복잡도에 따라 필요한 어드레스 (Address)의 크기를 쉽게 확장 또는 축소 할 수 있는 구조로 설계 되었고 이의 구동 소프트웨어도 이에 따라 쉽게 재구성할 수 있도록 설계되었다. 따라서, 본 SPI는 다양한 종류의 CMOS RF 집적회로 설계 시 요구되는 복잡도에 따라 최적의 구조로 효과적으로 변경할 수 있도록 구성되었으며 검증대상 RF회로를 효율적으로 검증할 수 있는 장점이 있다. 설계된 재구성형 SPI는 $0.13{\mu}m$ CMOS 공정으로 제작되었으며 동일 칩에 제작된 2.7GHz CMOS RF 분수형 주파수 합성기를 통하여 성공적 검증되었다.

• 산업기술연구
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• 제36권
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• pp.71-76
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• 2016

In this study, we determined the precise coordinates of TBMs (Tidal Bench Marks), which used as the national reference points in coastal area of Korea, using a GPS data analysis SW for the academic and scientific applications, GAMIT/GLOBK. For accurate 3-D positioning of TBM locations, we performed the GPS point surveying according to the national surveying policy and also acquired the GPS data for 48 TBMs located in the western and southern coastal part of Korea. Considering the results of baseline analysis to each observation session obtained from GAMIT module, the baseline analysis was realized to be done precisely because the values of Normalized RMS (NRMS) were mostly less than ${\pm}0.20mm$. Before the network adjustment using GLOBK module, we evaluated the suitability of observations for each session by applying the chi-squared test (${\chi}^2$ test) to the degree of freedom in observed session. An overall distributions of ${\chi}^2$ test were less than 1.0 for all sessions, and the statistical of ${\chi}^2$ test showed the average, 0.267 with minimum and maximum value, 0.063 and 0.653, respectively. Finally, we analyzed the network adjustment for 48 TBMs to reduce the residuals of baseline analysis on each point by connecting with 42 permanent GPS stations in Korea. In the network adjustment procedure, we set up the weighted values of each permanent station to be allocated between 0.9 and 1.14, and also removed the observed points having residual exceeds 4-times of standard deviation ($4{\sigma}$).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.293-296
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• 2001

The dynamic softening mechanisms of AISI 316, AISI 304 and AISI 430 stainless steels were studied with torsion test in the temperature range of $900 - 1200^{\circ}C$ and the strain rate range of $5.0x10^{-2}-5.0x10^0/sec$. The austenitic stainless steels, such as AISI 316 and AISI 304 were softened by dynamic recrystallization (DRX) during hot deformation. Also, the evolutions of flow stress and microstructure of AISI 430 ferritic stainless steel show the characteristics of continuous dynamic recrystallization (CDRX). To establish the quantitative equations for DRX of AISI 316 stainless steel, the evolution of flow stress curve with strain was analyzed. The critical strain (${\varepsilon}_c$) and strain for maximum softening rate (${\varepsilon}^{*}$) could be confirmed by the analysis of work hardening rate ($d{\sigma}/d{\varepsilon}={\theta}$). The volume fraction of dynamic recrystallization ($X_{DRX}$) as a function of processing variables, such as strain rate ( $\varepsilon$ ), temperature (T), and strain ( $\varepsilon$ ) were established using the ${\epsilon}_c$ and ${\varepsilon}^{*}$. For the exact prediction the ${\varepsilon}_c,\;{\varepsilon}^{*}$ and Avrami' exponent (m') were quantitatively expressed by dimensionless parameter, Z/A, respectively. It was found that the calculated results were agreed with the experimental data for the steels at my deformation conditions. Also, we can reasonably conclude that the DRX, CDRX and grain refinement of stainless steels can be achieved by large strain deformation at high Z parameter condition.

• 대한기계학회논문집
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• 제16권10호
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• pp.1890-1899
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• 1992

본 연구에서는 이종재료간의 Ⅴ-노치균열의 노치각도 및 재료의 종류에 따른 응력특이성지수와 응력강도 계수 해석에 각각 뉴톤-랍슨법(newtonraphson method), 뉴톤-랍슨법과 최소자승법을 이용한 선점법(collocation method)인 수치해석적 방법을 응용하고, 광탄성 등색선 무늬를 컴퓨터 그래픽하여 응력특이성지수와 응력강도계수가 모우드(mode)에 미치는 특성과 경계요소법(boundary element method)으로 응력해석한 결과로써 선점법을 이용하여 응력강도계수를 해석하고 기존의 결과등과 비교, 검토하 고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1116-1121
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• 2004

In this study, the effect of central fuel injection on a coaxial laminar $CH_{4}/air$ flame was experimented at the defined premixing condition(${\Phi}=1.90$, ${\sigma}=50/75/100%$, x/D=10). The partial premixing parameter are the equivalence ratio that total fuel is fixed at 200cc/min, the fuel split degree which means the percentage of fuel entering the outer tube to the total amount, and the mixing distance indicating the nonreactant mixture's homogeneity between inner tube top and burner exit. The object is to investigate the flame structure and chemiluminescence characteristics of laminar partial premixed flame as changing mixing parameters. The radical signal was acquired from ICCD camera and PMT. Each intensity was compared with Abel inverted value for measuring the effect of background light on the peak signal location and the intensity at central preheat zone. The results show that the peak location of each radical was broaden as the fuel split degree increasing because the mixing quality was enhanced. and $OH^{\ast}$ is a good indicator for flame front between reaction and preheat zone. At last $CH_{2}^{\ast}$ has the same tendency with $CH^{\ast}$ but a thinner reaction zone than $CH^{\ast}$ due to a rapid decay on the burned gas side.

• 지질공학
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• 제19권2호
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• pp.165-175
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• 2009

본 연구는 대구지역에 분포하는 함안층내 적색 셰일에 대하여 단일단계 크리프 시험과 다단계 크리프 시험을 수행하여 대상 암석의 크리프 특성을 규명한 것이다. 획득된 전체 데이터를 회귀분석하여 Griggs(1936)가 제시한 수식 ${\epsilon}_t$=a+$b{\cdot}log$ t +$c{\cdot}t$의 각 크리프 상수값을 도출하였다. 또한 1차, 2차 크리프의 전이시간(Tt)은 d/dt($b{\cdot}log$ t)=d/dt($c{\cdot}t$) 되는 시간으로 하였다. 세 번의 다단계 크리프 시험으로 재하하중과 크리프 상수간의 관계식을 도출하였으며, 획득된 크리프 상수값과 시료파괴시의 최대 변형률에 따라 각 재하하중에서의 시료파괴 예상시간(Ft)을 예상하였다.

• 한국식품조리과학회지
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• 제14권1호
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• pp.106-113
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• 1998

The purpose of this study is to investigate the antimicrobial effect of mugwort (Artemisia asiatica Nakai) on the rice cake and bread preservation, and to identify their antimicrobial compounds. The mugwort extracts showed complete inhibition on the growth of Bacillus subtilis and Staphylococcus aureus at 250 $\mu\textrm{g}$/ml level. Antimicrobial activi쇼 of mugwort extract were stronger than that of commercial antimicrobial agent. Five % of sodium propionate solution showed complete inhibition on the growth of B. subtilis, E. coli and S. aureus, but L. plantarum was inhibited 50.87% at the same concentration. When various amounts of freeze-dried mugwort powder were added in sulgis (steamed rice cake), 3% ssooksulgi (mugwort powder added sulgi) had quite lower level of total bacterial count (5.5$\times$$10^/5 CFU/g) compared with the control group (1.4$\times$$10^/7 CFU/g) at ambient temp. (30$\pm$1$^{\circ}C$) after 72 hr. Three % addition of mugwort showed 2 days extention of shelf-life of rice cake. The sensory qualities of ssooksulgi has no significant difference in moistness, consistency, cohesiveness, afterswallowing and overall quality compared with control group. Ssooksulgi with 3% of mugwort powder had the best overall quality in sensory test. The methanol extract of 500 $\mu\textrm{g}$/ml of mugwort could lead the successful retardation of the growth of putrefactive microorganism during the incubation of rice cake at 37$^{\circ}C$ for 24 hr. On the other hand, coumarin (Sigma) had 54% inhibitory effect at 500 $\mu\textrm{g}$/ml level, and (E,E)-2,4-decadienal completely inhibited the growth of putrefactive microorganism of whitesulgi at 100 $\mu\textrm{g}$/ml level during the incubation at 37$^{\circ}C$ for 48 hr.48 hr.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.259-268
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• 2007

A knock detection circuit that is based on the signal of an accelerometer installed on the engine block of a spark ignition automotive engine has a band-pass filter with a certain frequency as a parameter to be calibrated. A new statistical method for the determination of the frequency which is the most suitable for the knock detection in real-time applications is proposed. The method uses both the cylinder pressure and block vibration signals and is divided into two steps. In both steps, a new recursive trigonometric interpolation method that calculates the frequency contents of the signals is applied. The new trigonometric interpolation method developed in this paper improves the performance of the Discrete Fourier Transformation, allowing a flexible choice of the size of the moving window. In the first step, the frequency contents of the cylinder pressure signal are calculated. The knock is detected in the cylinder of the engine cycle for which at least one value of the maximal amplitudes calculated via the trigonometric interpolation method exceeds a threshold value indicating a considerable amount of oscillations in the pressure signal; this cycle is selected as a knocking cycle. In the second step, the frequency analysis is performed on the block vibration signal for the cycles selected in the previous step. The knock detectability, which is an individual cylinder attribute at a certain frequency, is verified via a statistical hypothesis test for testing the equality of two mean values, i.e. mean values of the amplitudes for knocking and non-knocking cycles. Signal-to-noise ratio is associated in this paper with the value of t-statistic. The frequency with the largest signal-to-noise ratio (the value of t-statistic) is chosen for implementation in the engine knock detection circuit.

• 분석과학
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• 제7권3호
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• pp.271-276
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• 1994

셀룰로스에 대한 +2와 +3가 금속이온들의 흡착성을 최적 조건에서 실험하였는데, +2가 금속이온으로 Cu(II), Zn(II), Pb(II) 및 Cd(II) 이온을 선택하였으며, +3가 금속이온으로 Cr(III)와 Fe(III) 이온을 선택하여 실험하였다. 셀룰로스에 대한 흡착능을 증대시키기 위하여 셀룰로스를 2M NaOH로 처리하여 Na-셀룰로스를 제소하였다. 셀룰로스에 대한 금속이온 흡착능은 매우 작아서 고분자 흡착제로서의 효과가 없었으나 Na-셀룰로스는 고분자 흡착제로서 매우 효과적이었다. Na-셀룰로스에 대한 금속이온들의 흡착은 뱃치법으로 실험하였다. 최적 조건에서 Na-셀룰로스에 대한 금속이온들의 흡착은 +2가 금속이온들은 1:2, +3가 금속이온들은 1:3의 흡착비로 흡착하는 이온교환 흡착이었다. Na-셀룰로스에 대한 금속이온들의 흡착엔탈피는 -18kcal/mol 정도였으며, carboxymethylcellulose(CMC)와 Dowex 50W-X8 수지와 비교 실험한 결과, Na-셀룰로스에 대한 금속이온들은 흡착은 이온교환흡착으로, 비슷한 작용기를 가지고 있는 CMC와 비슷한 흡착엔탈피를 보였다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권1호
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• pp.20-32
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• 2018

Purpose: The purpose of this study is to set up an anomaly detection criteria for sensor data coming from a motorcycle. Methods: Five sensor values for accelerator pedal, engine rpm, transmission rpm, gear and speed are obtained every 0.02 second from a motorcycle. Exploratory data analysis is used to find any pattern in the data. Traditional process control methods such as X control chart and time series models are fitted to find any anomaly behavior in the data. Finally unsupervised learning algorithm such as k-means clustering is used to find any anomaly spot in the sensor data. Results: According to exploratory data analysis, the distribution of accelerator pedal sensor values is very much skewed to the left. The motorcycle seemed to have been driven in a city at speed less than 45 kilometers per hour. Traditional process control charts such as X control chart fail due to severe autocorrelation in each sensor data. However, ARIMA model found three abnormal points where they are beyond 2 sigma limits in the control chart. We applied a copula based Markov chain to perform statistical process control for correlated observations. Copula based Markov model found anomaly behavior in the similar places as ARIMA model. In an unsupervised learning algorithm, large sensor values get subdivided into two, three, and four disjoint regions. So extreme sensor values are the ones that need to be tracked down for any sign of anomaly behavior in the sensor values. Conclusion: Exploratory data analysis is useful to find any pattern in the sensor data. Process control chart using ARIMA and Joe's copula based Markov model also give warnings near similar places in the data. Unsupervised learning algorithm shows us that the extreme sensor values are the ones that need to be tracked down for any sign of anomaly behavior.