• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.631-638
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• 2003

The wind turbine blade is the equipment converted wind into electric energy. The effect of the blade has influence of the output power and efficiency of wind turbine. The design of blade is considered of lift-to-drag ratio, structure, a condition of process of manufacture and stable maximum lift coefficient, etc. This study is used the simplified method for design of the aerodynamic blade and aerodynamic analysis used blade element method. This process is programed by delphi-language. The program has any input values such as tip speed ratio, blade length, hub length, a section of shape and max lift-to-drag ratio. The program displays chord length and twist angle by input value and analyzes performance of the blade.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.59.3-60
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• 2021

An investigation of flare-producing magnetic structure is important for studying an initiation of eruptive events. In this study we select two different eruptive events, M5.3 and X1.2 flares in active region (AR) 11283. Both events occur in the same AR, but brightenings of flare ribbons, seen in EUV images, are different shapes. In order to understand triggering process of eruptive flares, we reconstruct coronal magnetic fields using two observation-based models: a nonlinear force-free field (NLFFF) extrapolation model and a magnetohydodynamic (MHD) one. The NLFFFs show that sheared arcades and overlying fan-spine configurations are found in both cases, but the distributions of magnetic twist are weaker before the M5.3 flare than before the X1.2 flare. The MHD model is to explore the temporal evolution of coronal magnetic structures by considering the NLFFF with an anomalous resistivity as an initial condition. We discuss possible processes of two eruptive events using the MHD as well as the NLFFF model results.

• Korean Journal of Weed Science
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• v.15 no.1
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• pp.30-38
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• 1995

Soil-applied pre-emergence herbicide, pyrazolate(4-(2, 4-dichlorobenzoyl)-1, 3-dimethyl pyrazol-5-yl-p-toluene sulphonate) induced, twist effect of shoots of barnyardgrass under dry conditions, and etiolated leaf and stem of that under water condition. Plant height and root length of rice broadcast on soil surface were similar to the untreated control, but plant height of rice drilled in soil was more inhibited than root length as compared with the untreated control, while development of barnyardgrass seedling was severely inhibited at 20 days after application. The inhibition rate was much higher under water condition than under dry condition, but difference in rice and barnyardgrass did not abserve. However, growth of transplanted rice shown to increase to the untreated control. Shoot and root fresh weight of rice broadcast on soil surface was increase as compared with the untreated control, and that of rice drilled in soil was not affected whereas that of barnyardgrass was severely inhibited by 42% and 41%, respectively. Under dry condition at 20 days after pyrazolate application while root growth of rice broadcast on soil surface under water condition was deadly inhibited and development of barnyardgrass was almost completely inhibited. On the other hand, microscopic studies showed that constriction of mesophyll cell by destruction of chloroplast of barnyardgrass were occurred only under dry condition, whereas damage of rice and barnyardgrass under water and transplanting condition were not observed. Anatomical change in the meristernatic region of rice and barnyardgrass was not occurred, and similar to intact plant regardless of cropping patterns.

• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.677-684
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• 2016

This study was carried out to confirm the effects of the knife-incising and longitudinal kerfing treatment on high-temperature drying characteristics of red pine square timber with dimensions of thickness 15 cm. The range of final moisture content was investigated 5.6% to 7.5% after drying. The differences did not exist in the moisture content and distribution according to the pretreatment condition. In the case of longitudinal kerfing treatment, the surface check occurrence was reduced than the control. In addition, the twist had a tendency to decrease due to the longitudinal kerfing treatment. The knife-incising and longitudinal kerfing treatment were investigated to be ineffective on internal checks and drying shrinkage.

• Progress in Superconductivity and Cryogenics
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• v.19 no.4
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• pp.31-39
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• 2017

European R&D on designing their version of a DEMO fusion tokamak has recently resulted in the testing of a prototype $Nb_3Sn$ Cable-in-Conduit Conductor (CICC) for the DEMO TF coil. The characteristics and reported results of low temperature performance tests with the prototype CICC sample are compared with those from CICC samples incorporating other recent $Nb_3Sn$ cable designs. The EU-DEMO TF CICC prototype shows performance characteristics similar to that of the ITER CS CICC with short twist pitch. This is a first for a CICC sample that does not have a circular cross section. Assessment of its internal magnetostatic self-field suggests that a reduction in the internal self-field due to the rectangular geometry of the EU-DEMO TF CICC prototype compared to one with a circular geometry may have contributed to the performance characteristics showing current sharing temperature ($T_{cs}$) initially increase then stabilize with repeated electromagnetic loading, similarly to ITER CS CICC results. However, constraints on the internal self-field are not a sufficient condition for this $T_{cs}$ characteristic to occur.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.25-32
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• 2005

The aerodynamic loads at the blade hub and the drive shaft for 1MW horizontal axis wind turbine are calculated numerically. The geometric shape of the blade such as chord length and twist angle can be obtained fran the aerodynamic optimization procedure. Various airfoil data, that is thick airfoils at hub side and thin airfoils at tip side, are distributed along the spanwise direction of the rotor blade. Under the wind data fulfilling design load cases based on the IEC61400-1, all of the shear forces, bending moments at the hub and the low speed shaft of the drive train are obtained by using the FAST code. It shows that shear forces and bending moments have a periodic. trend. These oscillating aerodynamic loads will lead to the fatigue problem at both of the hub and drive train From the load analysis the maximum shear forces and bending moments are generated when wind turbine generator system operates in the case of the extreme speed wind condition.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.2
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• pp.43-59
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• 1985

In relation to the machinability of drilling operation, experiments were made to investigate the effect of cutting condition on static as well as dynamic cutting resistances in cutting plane carbon steel (SM 45 C) with H.S.S. twist drills. The results were as follows. 1) The static cutting resistances on carbon steel can practically be calculated by the following equations which were derived from experimental result. The deviation from the experimental values was less than 8% and 13% for cutting torque and thrust respectively. For cutting torque M: M=0.019 $H_B\;{f^{0.68}d^{1.68}$ For thrust T: T=0.400406 $r^{0.6}d^{0.68}$ + 0.1835 $H_BC^2$(where $H_B$: Brinnel hardness) 2) The static components of cutting resistance are increased exponentially with increasing drill diameter and feed rate. On the effect of drill diameter, the dynamic components of torque are decreased with increasing dirll diameter because of rigidity, the dynamic components of thrust being not effected with the changes. 3) As feed rates increase, the dynamic components of torque rather decrease although its changes on thrust components are unstable. 4) The static components of cutting resistance and dynamic component of torque are slightly decreased in accordance with the increase of spindle speed although its dynamic thrust components are not effected by the spindle speed.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.80-92
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• 1997

This research focuses onan efficient control method of temperature for multiple points using only one processor. For a yarn production system, the surface temperature control of heaters are very important for quality control. Therefore, we designed a temperature controller for a draw and twist machine and applied Fuzzy-PWM algorithm to the controller. If we use a processor for the temperature control of multiple points with the conventional ON/OFF control, the control performance of the system becomes poor. To overcome these problems, we developed a new Fuzzy-PWM algorithm for the adjustment of power rate to the heaters in the conventional ON/OFF control. It is shown that this algorithm has the same effects as the PID algorithm for the temperature control of each point. The proposed algorithm is robust against the production condition and environment such as the reference temperature and the thickness of yarn, since the power rate to the heater is adjusted by Fuzzy Rules derived from the values of the reference termperatureand the thickness of yarn. To obtain optimal Fuzzy rulees, the control simulations are perfodrmed through the modelling of the heater and simulation of Fuzzy rules. This algorithm is applied for the multiple pont temperature controller and showed satisfactory performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.10
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• pp.2586-2594
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• 1995

Two phase flow phenomena are observed in many industrial facilities and make much importance of optimum design for nuclear power plant and various heat exchangers. This experimental study has been investigated the classification of the flow pattern, the local void distribution and convective heat transfer in swirl and non-swirl two phase flow under the isothermal and nonisothermal conditions. The convective heat transfer coefficients in the single phase water flow were measured and compared with the calculated results from the Sieder-Tate correlation. These coefficients were used for comparisons with the two-phase heat transfer coefficients in the flow orientations. The experimental results indicate, that the void probe signal and probability density function of void distribution can used into classify the flow patterns, no significant difference in voidage distribution was observed between isothermal and non-isothermal condition in non-swirl flow, the values of two phase heat transfer coefficients increase when superficial air velocities increase, and the enhancement of the values is observed to be most pronounced at the highest superficial water velocity in non-swirl flow. Also two phase heat transfer coefficients in swirl flow are increased when the twist ratios are decreased.

• Structural Engineering and Mechanics
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• v.71 no.5
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• pp.469-483
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• 2019

In this paper, an improved mathematical model is presented for the bending analysis of doubly curved functionally graded material (FGM) sandwich rhombic conoids. The mathematical model includes expansion of Taylor's series up to the third degree in thickness coordinate and normal curvatures in in-plane displacement fields. The condition of zero-transverse shear strain at upper and lower surface of rhombic conoids is implemented in the present model. The newly introduced feature in the present mathematical model is the simultaneous inclusion of normal curvatures in deformation field and twist curvature in strain-displacement equations. This unique introduction permits the new 2D mathematical model to solve problems of moderately thick and deep doubly curved FGM sandwich rhombic conoids. The distinguishing feature of present shell from the other shells is that maximum transverse deflection does not occur at its center. The proposed new mathematical model is implemented in finite element code written in FORTRAN. The obtained numerical results are compared with the results available in the literature. Once validated, the current model was employed to solve numerous bending problems by varying different parameters like volume fraction indices, skew angles, boundary conditions, thickness scheme, and several geometric parameters.