• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.77-85
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• 2009

A two-dimensional cross-section analysis program based on the finite element method has been developed for composite blades with arbitrary cross-section profiles and material distributions. The modulus weighted approach is used to take into account the non-homogeneous material characteristics of advanced blades. The CLPT (Classical Lamination Plate Theory) is applied to obtain the effective moduli of the composite laminate. The location of shear center for any given cross-sections are determined according to the Trefftz' definition while the torsion constants are obtained using the St. Venant torsion theory. A series of benchmark examples for beams with various cross-sections are illustrated to show the accuracy of the developed cross-section analysis program. The cross section cases include thin-walled C-channel, I-beam, single-cell box, NACA0012 airfoil, and KARI small-scale blades. Overall, a reasonable correlation is obtained in comparison with experiments or finite element analysis results.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1486-1494
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• 2018

Based on the semiclassical theory of chaotic scattering, Tanner et al. [J. Phys. B 40, F157 (2007)] proposed the fluctuation in the partial photoionization cross section of helium below the double-ionization threshold would show the same characteristics as in the total cross section, predicting that the Fourier spectrum of the fluctuation reveals peaks at the classical actions of closed triple collision orbits and the amplitude of the fluctuation decreases algebraically as the energy approaches the double-ionization threshold. In that paper, however, the predictions were not clearly confirmed due to the lack of experimental data with sufficient accuracy. So instead, we calculate the partial photoionization cross sections of collinear eZe helium for the energy range from the single-ionization threshold $I_{20}$ to $I_{32}$ in order to numerically confirm the predictions. Analysis of the fluctuation in the partial cross section shows that the predictions are indeed valid. Our findings mean that the fluctuation in the partial photoionization cross section can be described by classical triple collision orbits in the semiclassical limit. Thus it explains in a natural way the mirroring and mimicking structures observed in cross section signals for different ionization channels.

• Journal of ILASS-Korea
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• v.13 no.2
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• pp.79-84
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• 2008

The correlations for cross-flow have not been well established, because of the complexity of breakup and atomization mechanism. A study was performed to investigate the characteristics of spray behaviour of liquid jet in the bag breakup regime injected into low-speed cross-flow with the pressure single-hole nozzle. The shadow-graphy method was used for the cross-flow jet visualization. The experimental variables of liquid jet were nozzle diameter $(0.3mm{\sim}1.0mm)$, injection pressure $(50kPa{\sim}150kPa)$, and the velocity of cross-flow $(27m/s{\sim}42m/s)$. The highest penetration trajectories of liquid jet are governed by the momentum ratio $({\rho}_{\iota}U_{\iota}^2/{\rho}_aU_{cross}^2)$ rather than the Weber number and the new empirical equations of the highest penetration trajectory and breakup point at low-speed corss-flow are established.

• Korean journal of applied entomology
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• v.33 no.4
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• pp.242-249
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• 1994

These studles were conducted to investigate the development of chem~cal resistance and cross.resista. nce m dlarnondback moth (Piuteiia xylostella L). The resistance development of diamondback moth greatly vaned under single selection of five insectlades. The tnflumuron and lambda cyhalothnn strains at 8th selected generation showed 374- and 29.l.fold resistant levels. respectively, as compared with the susceptible strain. However, the Baciilus thuringiensis-seleded at 8th selected generatLon exhibited 240-fold resistant level. and the prothiophos-selected at 8th generation revealed 14.3-fold resistant !eve1 while the cartap hydrochloride-selected at 8th generailon showed 9.1-fold resistant level Prothiophos- selected strain showed low cross-resistance level to cartap hydrochloride, while this strain exhibited no cross-resistance of 1.3 to 2.8-fold to other msectlcides. Cartap hydrochlonde- seleded strain showed 19.9-fold. a high cross-resistance to lambda cyhalothrin, but this strain showed 2.2-34 fold, no cross resistance to other insecticide. Lambda cyhalothnn-selected strain exhibited cross-resistance to cartap hydrochlolide and prothiophas. Triflumuron-seleded strain showed 1.3-4.9 fold. no cross-resistance to other ~nsectic~dTe he B. ihuring~ensis-selededs train showed no cross-resistance to other insecticides.

• The Journal of the Acoustical Society of Korea
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• v.39 no.3
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• pp.207-215
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• 2020

There are several methods for the time delay estimation between signals to two receivers. Among these methods, Generalized Cross Correlation (GCC), which estimates the relative delay from the cross-correlation between the different signals at the two receivers, is a traditionally well-known method. However, when using a narrow band Continuous Wave (CW) signal, the GCC method degrades the estimation performance from relatively higher signal-to-noise ratio than when using a wideband signal. To improve this phenomenon, this paper examines four different pre-processors for GCC using narrow band single frequency signals. Simulation shows that the performance gain of the preprocessed GCC is up to 9 dB for a 100 msec CW signal as well as up to 4 dB for a 1 s CW signal.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.699-709
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• 2014

This paper proposes a new method for predicting the derailment of a running train under cross-wind conditions, using the single wheelset derailment theory. The conventional theories used for predicting the derailment due to cross-winds were developed under the assumption that derailment will always be of the roll-over type, thus neglecting other possible types such as wheel-climbing, which may occur under special driving conditions. In addition, these theories do not consider running conditions such as dynamic wheel-rail interactions and friction effects. The new method considers the effects of dynamic wheel-rail interaction as well as those of lateral acceleration, rail cant, and cross-winds. The results of this method were compared and verified with those of the conventional methods and numerical simulations.

• Journal of IKEEE
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• v.20 no.4
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• pp.432-434
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• 2016

In conventional SIDO(Single Inductor Dual Output) boost converter, charging time is changed by load power consumption. In this case, if the power consumption of one load is changed to such a degree that switching frequency of the boost converter must be changed, another load charge time is also changed, which this causes cross regulation. In this paper, the charge copy technique is proposed to reduce cross regulation. When the switching frequency is changed to an integer ratio, another load charge time is also changed to integer ratio. Simulation result shows that proposed method reduces the 10.24mV cross regulation and 39.118us recover-time compared with conventional method.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.211-216
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• 2001

The components with the circular cross section have the symmetric combination parts for rotating balance and the crack emanates from the symmetric combination parts. The symmetric cracks from symmetric combination parts make a decrease in the component fatigue life more than single crack. In this study, to estimate the behavior of symmetric cracks, the fatigue test was performed using rotary bending tester on the specimen with a symmetric defects in circular cross section. The material used in this study is Ni-Cr-Mo steel alloy. Under the same stress, the result from the rotary bending fatigue test turned out that the symmetric cracks made a decrease in the fatigue life by 35% more than single crack and the relation between log a and cycle ratio $N/N_f$ obtained linearly.

• Journal of Korean Association for Spatial Structures
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• v.1 no.1 s.1
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• pp.117-124
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• 2001

In Single-layer latticed domes with rectangular network which is composed of ring of circumferential direction and rafter of longitudinal direction, that is, rib domes, if we use the cross-membered junction's method for the advantage in fabrication and construction, the eccentricity is occurred in the nodal point of crossing members. This paper is aimed at investigating the buckling characteristics for the effect of eccentricity according to rise-span ratios and distance of eccentricity. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems. The conclusion were given as follows: 1. The maximum decreasing ratio of buckling strength due to the junction's eccentricity is about 60% in models of this paper. 2. In the increasing ratio of buckling strength for rise-span ratio, that of Type 3 models is larger than that of type 2 models. On the other hand, that of Type 2 mode is larger than that of Type 3 for eccentricity-distance. 3. In the viewpoint of the value of buckling strength, that of Type 2 models is larger than that of type 3 models. The effect of the junction's rigidity on buckling strength is not great for overall models. Therefore if we use the cross-membered junction's method for the advantage in fabrication and construction, the method of Type 2 will have the great advantage of that of Type 3.

• International Journal of Fluid Machinery and Systems
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• v.9 no.4
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• pp.370-381
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• 2016

As a single-channel pump is used for wastewater treatment, this particular pump type can prevent performance reduction or damage caused by foreign substances. However, the design methods for single-channel pumps are different and more difficult than those for general pumps. In this study, a design optimization method to improve the hydrodynamic performance of a single-channel pump impeller is implemented. Numerical analysis was carried out by solving three-dimensional steady-state incompressible Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. As a state-of-the-art impeller design method, two design variables related to controlling the internal cross-sectional flow area of a single-channel pump impeller were selected for optimization. Efficiency was used as the objective function and was numerically assessed at twelve design points selected by Latin hypercube sampling in the design space. An optimization process based on a radial basis neural network model was conducted systematically, and the performance of the optimum model was finally evaluated through an experimental test. Consequently, the optimum model showed improved performance compared with the base model, and the unstable flow components previously observed in the base model were suppressed remarkably well.