• Journal of the Economic Geographical Society of Korea
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• v.17 no.1
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• pp.129-146
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• 2014

This paper investigates how industrial diversity affects unemployment and employment instability from the perspective of the regional economy. Through this analysis, we examine how the industry-specific policy to promote some industry strategically in most of areas affects the stability of the regional economy. We measure Herfindahl indexes using the 1993-2010 data of 16 regions in Korea, and use panel regression model for empirical analysis. The main results from this empirical analysis are summarized as follows. First, we confirm that the industrial structure of most regions has been changed to the direction of specialization in 1990s and to the direction of diversification in 2000s through analyzing the changes in the values of Herfindahl indexes during the given period. Second, we find from the estimation results of panel regression model that the higher industrial diversity in most of regions is, the lower the unemployment rate is. However, a statistically significant relationship between industrial diversity and employment instability only partially confirmed. Third, there exist high unemployment rate and employment instability in most metropolitan areas, but it is hard to say that this relationship is highly statistically significant. From the results of the empirical analysis, it is likely that the industry-specific policies such as the regional strategic industry development policies unlike policy goals make the unemployment rate to rise and economic instability to increase. From the viewpoint of employment aspects, the strategies to increase industrial diversity would be desirable rather than those to specialize in the industrial structure.

• Journal of KSNVE
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• v.11 no.1
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• pp.118-124
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• 2001

The effect of a concentrated mass on the regions of dynamic instability of an axially oscillating cantilever beam is investigated in this paper. The equations of motion are derived using Kane's method and the assumed mode method. It is found that the bending stiffness is harmonically varied by axial inertia forces due to oscillating motion. Under the certain conditions between oscillating frequency and the natural frequencies, dynamic instability may occur and the magnitude of the bending vibration increase without bound. By using the multiple time scales method, the regions of dynamic instability are obtained. The regions of dynamic instability are found to be depend on the magnitude of a concentrated mass or its location.

• Steel and Composite Structures
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• v.15 no.1
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• pp.57-79
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• 2013

This paper studies the dynamic instability of laminated composite plates under thermal and arbitrary in-plane periodic loads using first-order shear deformation plate theory. The governing partial differential equations of motion are established by a perturbation technique. Then, the Galerkin method is applied to reduce the partial differential equations to ordinary differential equations. Based on Bolotin's method, the system equations of Mathieu-type are formulated and used to determine dynamic instability regions of laminated plates in the thermal environment. The effects of temperature, layer number, modulus ratio and load parameters on the dynamic instability of laminated plates are investigated. The results reveal that static and dynamic load, layer number, modulus ratio and uniform temperature rise have a significant influence on the thermal dynamic behavior of laminated plates.

• Journal of ILASS-Korea
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• v.2 no.1
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• pp.8-17
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• 1997

A study has been carried out on the instability of a conical liquid sheet by using the linear instability theory. Various analytical methods using the Kelvin-Helmholtz instability theory were tried to examine the wave growth on cylindrical liquid sheets. Cylinderical liquid sheets were extended to the case with the conical sheets. Perturbations due to tangential motion as well as longitudinal one were taken into account. And it was assumed the the breakup occurs when amplitude ratio exceeds exp(12), drop sizes were predicted only by theoretical approach. The predicted drop size agreed well with the measured Sauter mean diameter, $D_{32}$.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.288-295
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• 2004

Concentrically braced steel frames are considered as being quite pone to soft-story response due to the degradation in brace compressive resistance after buckling under severe ground motions. When combined with the system P-Delta effects, collapse of the concentrically brsced frames by dynamic instability becomes highly probable. In this stidy, a new, relatively simple dynamic instability coefficient was proposed for diagonally braced steel flames by explicitly considering the strength degradation of the brace after buckling. Nonlinear dynamic analysis results showed that the dynamic instability coefficient proposed in this study predicted collapse limit state more consistently than the conventional one which ignores the strength degradation of the brace.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.683-686
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• 2002

The hydrodynamic instability of the three-dimensional boundary-layer over a rotating disk has been numerically investigated for three cases flows using linear stability theory (i.e. Rossby number, Ro = -1, 0, and 1). Detailed numerical values of the disturbance wave number, wave frequency, azimuth angle, radius (Reynolds number, Re) and other characteristics have been calculated for $K{\acute{a}}rm{\acute{a}}n$, Ekman and $B{\"{o}}ewadt$ boundary-layer flows. Neutral curves for these flows are presented. Presented are the neutral stability results concerning the two instability modes (Type I and Type II) by using a two-point boundary value problem code COLUEW that was based upon the adaptive orthogonal collocation method using B-spline. The prediction from the present results on both instability modes among the three cases agrees with the previously known numerical and experimental data well.

• Wind and Structures
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• v.14 no.3
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• pp.209-220
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• 2011

The cable system is generally considered to be a structural solution to increase the spanning capacity of suspension bridges. In this work, based on the Runyang Bridge over the Yangtze River, three case suspension bridges with different 3D cable systems are designed, structural dynamic characteristics, the aerostatic and aerodynamic stability are investigated numerically by 3D nonlinear aerostatic and aerodynamic analysis, and the cable system favorable to improve the wind-induced instability of long-span suspension bridges is also proposed. The results show that as compared to the example bridge with parallel cable system, the suspension bridge with inward-inclined cable system has greater lateral bending and tensional frequencies, and also better aerodynamic stability; as for the suspension bridge with outward-inclined cable system, it has less lateral bending and tensional frequencies, and but better aerostatic stability; however the suspension bridge is more prone to aerodynamic instability, and therefore considering the whole wind-induced instability, the parallel and inward-inclined cable systems are both favorable for long-span suspension bridges.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1774-1783
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• 1998

The transition from steady laminar to chaotic convection in a glass melting furnace specified by upper surface temperature distribution has been studied by the direct numerical analysis of the two and three-dimensional time dependent Navier-Stokes equations. The thermal instability of convection roll may take place when modified Rayleigh number($Ra_m$) is larger than $9.71{\times}10^4$. It is shown that the basic flows in a glass melting furnace are steady laminar, unsteady periodic, quasi-periodic or chaotic flow. The dimensionless time scale of unsteady period is about the viscous diffusion time, ${\tau}_d=H^2/{\nu}_0$. Through primary and secondary instability analyses the fundamental unsteady feature in a glass melting furnace is well defined as the unsteady periodic or weak chaotic flow.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.41-46
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• 2017

This study has numerically investigated the flame-acoustics interactions in the turbulent partially premixed flame field. In the present approach, in order to analyze the combustion instability, the present approach has employed the LES-based combustion model as well as the Helmholtz solver. Computations are made for the validation case of the partially premixed LIMOUSINE burner. In terms of the FFT data, numerical results are compared with experimental data. Moreover, Helmholtz equation in frequency domain is solved by combining CFD field data including the flight time from a nozzle to the flame zone. Based on numerical results, the detailed discussions are made for the essential features of the combustion instability encountered in the partially premixed burner.

• Clinics in Shoulder and Elbow
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• v.1 no.2
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• pp.236-241
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• 1998

Recurrent dislocation of elbow joint occurs relatively rarely by the injury of the collateral ligament which contributes elbow joint stability. Among them, posterolateral rotatory instability occurs by the injury to the lateral ulnar collateral ligament. We experienced a case of recurrent dislocation of elbow joint due to posterolateral rotatory instability. We treated operatively with lateral ulnar collateral ligament reconstruction using the palmaris longus tendon by technique of Nestor et al. We report it with literature analysis.