• 산업경영시스템학회지
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• 제43권4호
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• pp.208-216
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• 2020

With the spread of smart manufacturing, one of the key topics of the 4th industrial revolution, manufacturing systems are moving beyond automation to smartization using artificial intelligence. In particular, in the existing automatic machining, a number of machining defects and non-processing occur due to tool damage or severe wear, resulting in a decrease in productivity and an increase in quality defect rates. Therefore, it is important to measure and predict tool life. In this paper, ν-ASVR (ν-Asymmetric Support Vector Regression), which considers the asymmetry of ⲉ-tube and the asymmetry of penalties for data out of ⲉ-tube, was proposed and applied to the tool wear prediction problem. In the case of tool wear, if the predicted value of the tool wear amount is smaller than the actual value (under-estimation), product failure may occur due to tool damage or wear. Therefore, it can be said that ν-ASVR is suitable because it is necessary to overestimate. It is shown that even when adjusting the asymmetry of ⲉ-tube and the asymmetry of penalties for data out of ⲉ-tube, the ratio of the number of data belonging to ⲉ-tube can be adjusted with ν. Experiments are performed to compare the accuracy of various kernel functions such as linear, polynomial. RBF (radialbasis function), sigmoid, The best result isthe use of the RBF kernel in all cases

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.135-138
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• 1995

This paper presents a method to calculate the escape frequency factor and its verification from TSC(Thermally Stimulated Current) equation and cures. To apply calculation method of ν using asymptotic estimation, it utilized two sets of TSC data with 1K interval. This method enables one to get the exact value of ν and activation energy at the same time by using computer programming. So, it regards their calculation method as a useful process to obtain the value of physical behavior.

• 한국멀티미디어학회논문지
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• 제7권11호
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• pp.1550-1555
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• 2004

그림자는 화상의 사실성을 높이며 물체들 사이의 공간적 관계를 유추할 수 있도록 해준다. 기존의 그림자 텍스처 생성 방법에서는 한 물체의 텍스처를 생성하기 위해서 다른 모든 물체들을 렌더링 해야만 하므로 Ν개의 물체가 있을 때 모든 물체들의 그림자 텍스처를 만들기 위해서는 Ο(Ν$^2$)의 시간이 필요했다. 이 논문에서는 깊이버퍼를 그림자 텍스처 생성에 사용하여 각 물체들에 대해서 상수 시간에 그림자 텍스처를 생성하는 알고리즘을 제안한다. 또한 시간 일관성을 이용해서 속도를 더욱 향상시키는 방법을 제안한다. 정적인 물체의 깊이 값은 시간이 지나도 변화가 없다. 이 값들을 재사용하여 정적인 물체들은 되도록 그리지 않고 동적인 물체들만 렌더링 함으로써 깊이버퍼와 그림자 텍스처를 효율적으로 생성할 수 있다. 이 방법의 비용은 움직이는 물체의 개수에만 비례한다.

• Geomechanics and Engineering
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• 제24권1호
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• pp.57-65
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• 2021

The effects of initial soil fabric and aspect ratio (AR) on the small-strain stiffness (G0) of granular soils are studied by employing discrete element method (DEM) numerical analysis. Elongated clumps composed of subspheres were adopted, and the G0 values were obtained by DEM simulations of drained triaxial tests under different densities and initial confining pressure (p0). The DEM simulations indicate that the initial soil fabric has an insignificant effect on G0. The effect of the AR on G0 is related to the initial density. Namely, for dense specimens, G0 first increases with increasing AR, reaching a plateau value when the AR ≥ 1.5. However, for loose specimens, G0 gradually increases as the AR increases. Microscopic examination reveals that G0 uniquely depends on the coordination number of the particles (CN-particle) rather than the subspheres (CN-sphere) at the particulate level for the effects of initial soil fabric and AR. Finally, Poisson's ratio ν0 is also determined by CN-particle. In addition, based on data in literature and this study, ν0 can be fitted as ν0 = 5.920(G0/(p0)1/3)-0.99, which can be used to predict ν0 of granular soils based on the measured G0.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1767-1774
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• 2003

The objective of this paper is to present the performance comparison of the impulse turbines for different diameters. In the study, the investigation has been performed experimentally by model testing for some diameters, especially 0.3 m and 0.6 m. The experiment was performed for Reynolds number range of 0.17 ${\times}$ 10$\^$5/ -1.09 ${\times}$ 10$\^$5/ and for different values of hub-to-tip ratio ν ranging from 0.6 to 0.85. As a result, it was found that the critical Reynolds number is to be around 0.5 ${\times}$ 10$\^$5/ for ν=0.6 and 0.4 ${\times}$ 10$\^$5/ for ν=0.7. For the hub-to-tip ratio, the optimum value is 0.7 when the turbine is operated at lower Reynolds number. However, its value seems to be 0.6 at higher Reynolds number in the tested range.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.469-476
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• 2001

The Ν-value in the standard penetration test(SPT) is affected by the magnitude of the rod penetration energy transmitted from the falling hammer as well as the geotechnical characteristics of the ground. Understanding of the striking energy efficiency in the SPT equipment is getting important for that reason. The energy efficiencies of the doughnut hammer with the hydraulic lift system and the automatic trip hammer system were investigated through field tests using the instrumented rod and wave-signal acquisition systems including the pile driving analyzer(PDA) . The rod energy ratio, ΕR$\_$r/ was defined as the ratio of the energy delivered to the drilling rod to the potential free-fall energy of the hammer. It appears that the type of the hammer and lift/drop system had a strong influence on the energy transfer mechanism and ΕR$\_$r/ also varies according to the energy instrumentation system and the analysis methods.

• 대한조선학회논문집
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• 제41권2호
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• pp.70-78
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• 2004

The present study numerically investigates two-dimensional laminar flow past a circular cylinder in an aligned magnetic field using the spectral method. Numerical simulations are performed for flow fields with Re=100 and 200 in the range of 0$\leq$N$\leq$10, where Ν is the Stuart number that is the ratio of electromagnetic force to inertial force. The present study reports the detailed information of flow quantities on the cylinder surface at different Stuart numbers. It is shown that the vortex shedding can be controlled by the magnetic force representing the Stuart number. As Ν increases, the vortex shedding becomes weaker, resulting in drag reduction whose magnitude is the largest at a critical value. In addition, as the magnetic force increases, the lift amplitude decreases, reaching zero at the critical number.

• 에너지공학
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• 제2권1호
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• pp.95-103
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• 1993

열전반도체를 이용한 소형열펌프의 개념 설계를 시도하고, 열역학적인 해석을 통하여 시스템의 성능을 예측하였으며 각 변수들이 시스템에 미치는 영향을 조사하였다. 일정한 조건 즉, $\mu$(=nν), J(=nI) 및 물의 유입 온도(Twi)가 주어졌을 때 대기의 온도 T$_{a}$ 가 증가할수록 성능계수와 냉방용량은 감소한다. 일정 냉방용량의 시스템을 설계하는 문제는 대기 온도와 물의 입구온도가 주어지면 $\mu$, J를 결정하는 문제로 귀결되며 기 제작된 열전소자를 사용한다면 v는 제작할 때 정해지므로 결국 n, ν, I의 최적 조합을 구하는 문제가 된다. 냉방용량 및 물의 온도가 주어졌을 때 $\mu$가 증가할수록 J가 증가하는 경향을 보인다. $\mu$-J 곡선과 최적 $\mu$값으로부터 최적 전류를 계산한다. 냉방 용량이 일정할 때 유량이 증가함에 따라 성능계수가 증가하며 COP$_{R}$ 증가의 경향은 대기온도가 낮을 수록 뚜렷하다. 흡열부보다 방열부의 열전달 계수가 시스템의 성능에 미치는 영항이 크다.

• Bulletin of the Korean Chemical Society
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• 제9권6호
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• pp.345-349
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• 1988

The polycrystalline powder of (CaLa) (MgMo)$O_6$ has been prepared at $1350^{\circ}C$ in $H_2/H_2O$ and $N_2$ flowing atmosphere. The powder X-ray diffraction pattern indicates that (CaLa) (MgMo)$O_6$ has a monoclinic perovskite structure with the lattice constants $a_0=b_0=7.901(1){\AA}$, $c =7.875(1){\AA}\;and\;{\gamma}=89^{\circ}$16'(1'), which can be reduced to orthorhombic unit cell, a = 5.551(1) ${\AA}$, b = 5.622(1) ${\AA}$ and c = 7.875(1) ${\AA}$. The infrared spectrum shows two strong absorption bands with their maxima at 590($ν_3$) and 380($ν_4$) cm, which are attributed to $2T_{1u}$ modes indicating the existence of highly charged molybdenum octahedron $MoO_6$ in the crystal lattice. According to the magnetic susceptibility measurement, the compound follows the Curie-Weiss law below room temperature with the effective magnetic moment 1.83(1)$_{{\mu}B}$, which is well consistent with that of spin only value (1.73 $_{\mu}_B$) for $Mo^{5+}$ with $4d^1$-electronic configuration within the limit of experimental error. From the thermogravimetric analysis, it has been confirmed that (CaLa) (MgMo)$O_6$ decomposes gradually into $CaMoO_4,\;MoO_3,\;MgO,\;La_2O_3$ and unidentified phases due to the oxidation of $Mo^{5+}$ to $Mo^{6+}$.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.3-46
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• 1999

A new method called SRICOS is proposed to predict the scour depth z versus time t around a cylindrical bridge pier of diameter D founded in clay. The steps involved are ; 1. taking samples at the bridge pier site, 2. testing them in an Erosion Function Apparatus called the EFA to obtain the scour rate z versus the hydraulic shear stress applied $\tau$, 3. predicting the maximum shear stress r max which will be induced around the pier by the water flowing at ν Ο before the scour hole starts to develop, 4. using the measured z versus r curve to obtain the initial scour rate zi corresponding to r max , 5. predicting the maximum depth of scour zmax for the pier, 6. using zi and zmarx to develop the hyperbolic function describing the scour depth z versus time t curve, and 7. reading the z vs. t curve at a time corresponding to the duration of the flood to find the scour depth which will develop around the pier. A new apparatus is developed to measure the z vs t curve of step 2, a series of advanced numerical simulations are performed to develop an equation for the $\tau$ max value of step 3, and a series of flume tests are performed to develop an equation for the zmax value of step 5. The method is evaluated by comparing predictions and measurements in 42 flume experiments.