• Journal of The Korean Association For Science Education
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• v.16 no.2
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• pp.134-145
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• 1996

The purpose of this study was to investigate effects of mental capacity and mental demand on problem solving. Two kinds of tests were used for this study. One was FIT 752 test which required general knowledge, the other was Ohm's law test which required domain specific knowledge. The items of each test had the same logical structure and content knowledge but had different sizes of mental demand. The results of the study were summarized as follows: As mental demand of the items increased, the success rates decreased. The analysis of the hierarchical relation among items was that items with large mental demand were higher than those with small demand or at least the same level. According to the results, mental of an item was a significant factor affecting solving the problem. Effect of mental capacity on problem solving was different according to the kind of required knowledge to solve. Mental capacity was a significant factor affecting solving the FIT 752 task which required general knowledge. On the contary, solving the task which required domain specific knowledge, the results were different depending on subjects' chunk size. The results of problem solving of the groups which had small chunk size were that mental capacity was appeared a significant factor. However, results of problem solving of groups which had large chunk size were that mental capacity was not.

• Atmosphere
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• v.16 no.4
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• pp.359-370
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• 2006

Terrain height variance spectra for the Korean mountain region are calculated in order to determine an adequate grid size required to resolve terrain forcing on mesoscale model simulation. One-dimensional spectral analysis is applied to specifically the central-eastern part of the Korean mountain region, where topographical-scale forcing has an important effect on mesoscale atmospheric flow. It is found that the terrain height variance spectra in this mountain region has a wavelength dependence with the power law exponents of 1.5 at the wavelength near 30 km, but this dependence is steeply changed to 2.5 at the wavelength less than 30 km. For the adequate horizontal grid size selection on mesoscale simulation two-dimensional terrain height spectral analysis is also performed. There is no directionality within 50% of spectral energy region, so one-dimensional spectral analysis can be reasonably applied to the Korea Peninsula. According to the spectral analysis of terrain height variance, the finer grid size which is higher than 6 km is required to resolve a 90% of terrain variance in this region. Numerical simulation using WRF (Weather Research and Forecasting Model) was performed to evaluate the effect of different terrain resolution in accordance with the result of spectral analysis. The simulated results were quantitatively compared to observations and there was a significant improvement in the wind prediction across the mountain region as the grid space decreased from 18 km to 2 km. The results will provide useful guidance of grid size selection on mesoscale topographical simulation over the Korean mountain region.

• The Korean Journal of Air & Space Law and Policy
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• v.1
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• pp.163-191
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• 1989

The accident of the midair collision, passengers' falling or goods' dropping occurs or supersonic aircraft make a sonic boom during their conveying passengers or goods to the destination. The accident in transmit damages the their parties on the surface or their properties. In these cases, the third parties who were harmed to their lives or properties have the right to claim damages against the air carrier who caused them. These matters have become one of the important things since aircraft conveyed passengers and goods. Therefore, it is a great concern to settle these matters by law. But the Safety of the present aircraft has been much increased and the aircraft have become larger in size. Its flight altitude became higher than before. So the relationship of the aircraft to the third parties is much different from that of the earlier aircraft. The air transport is now indispensable to our life. It is not so easy to control these matters. In the early part of 20th century, when the third parties suffered the damage, many European countries made laws on the basis of the principle of liability without fault. But each country had a variety of its own law, and different kinds of difficulties have been brought about. Accordingly, the Rome Convention on Surface Damage (1933, 1952, 1978) has been made and revised. In spite of being revised, it contains many problems, and is not carried into effect world-wide. On the other hand, there are no regulations about the compensation of the third parties damaged in Korean existing laws. In case the damage is brought about to them, it is obviously true that the settlement of the liability of compensation for damage should be made by the general principle on the tort in domestic laws. At this point, it is urgent that we make a special law though the domestic legislation as a preliminary measure before we sign the international convention to save third damaged. It is desirable that we should, for the responsibility of the air carriage for the demage of the third parties on the surface, bring in the theory of the absolute liability in view of the legislation of many conutries. As the aircraft fly in the sky, their flight always contains some danger. It is very difficult to prove the fault, and the operator should suffer the principle of liability without fault or the similiar one. In case the liability without fault will be imposed upon the operator for the damage of the third parties, it is necessary to bring in the liability protection system for the protection and up upbringing of the air carriage. The Burden of danger of the air carriage will be reduced by introducing the system. A domestic legislation measure should be necessarily taken as soon as possible as a legal security measure on these matters.

• Advances in nano research
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• v.8 no.3
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• pp.191-202
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• 2020

The article brings the study of nonlocal, surface and the couple stress together to apparent the frequency retaliation of FG nanobeams (Functionally graded). For the examination of frequency retaliation, the article considers the accurate spot of neutral axis. This article aims to enhance the coherence of proposed model to accurately encapsulate the significant effects of the nonlocal stress field, size effects together with material length scale parameters. These considered parameters are assimilated through what are referred to as modified couple stress as well as nonlocal elasticity theories, which encompasses the stiffness-hardening and softening influence on the nanobeams frequency characteristics. Power-law distribution is followed by the functional gradation of the material across the beam width in the considered structure of the article. Following the well-known Hamilton's principle, fundamental basic equations alongside their correlated boundary conditions are solved analytically. Validation of the study is also done with published result. Distinct parameters (such as surface energy, slenderness ratio, as nonlocal material length scale and power-law exponent) influence is depicted graphically following the boundary conditions on non-dimensional FG nanobeams frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.883-888
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• 2002

This study describes the limit and application of the two-microphone impedance tube method to the sound transmission loss measurement of several sound isolation materials with different physical properties. For the sound isolation materials having small flexural rigidity, it is shown that the two-microphone impedance tube method is validated to practically measure the sound transmission loss. For the sound isolation materials having large flexural rigidity, on the other hand, it is found that the two-microphone impedance tube method is no longer valid to measure the sound transmission loss because the regions of resonance and mass law are moved into the higher frequencies. In addition, in order to accurately measure the sound transmission loss of sound isolation materials, their size should be decided based on the consideration of the effect of acoustic excitation on their vibration response.

• Steel and Composite Structures
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• v.33 no.3
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• pp.463-472
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• 2019

Initial thermo-elastic and steady state creep deformation of a rotating functionally graded simple blade is studied using first-order shear deformation theory. A variable thickness model for cantilever beam has been considered. The blade geometry and loading are defined as functions of length so that one can define his own blade profile and loading using any arbitrary function. The blade is subjected to a transverse distributed load, an inertia body force due to rotation and a distributed temperature field due to a thermal gradient between the tip and the root. All mechanical and thermal properties except Poisson's ratio are assumed to be longitudinally variable based on the volume fraction of reinforcement. The creep behaviour is modelled by Norton's law. Considering creep strains in stress strain relation, Prandtl-Reuss relations, Norton' law and effective stress relation differential equation in term of effective creep strain is established. This differential equation is solved numerically. By effective creep strain, steady state stresses and deflections are obtained. It is concluded that reinforcement particle size and form of distribution of reinforcement has significant effect on the steady state creep behavior of the blade.

• Steel and Composite Structures
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• v.48 no.4
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• pp.443-459
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• 2023

This paper investigates the stability of a bi-directional functionally graded (BD-FG) cylindrical beam made of imperfect concrete, taking into account size-dependency and the effect of geometry on its stability behavior. Both buckling and dynamic behavior are analyzed using the modified coupled stress theory and the classical beam theory. The BD-FG structure is created by using porosity-dependent FG concrete, with changing porosity voids and material distributions along the pipe radius, as well as uniform and nonuniform radius functions that vary along the beam length. Energy principles are used to generate partial differential equations (PDE) for stability analysis, which are then solved numerically. This study sheds light on the complex behavior of BD-FG structures, and the results can be useful for the design of stable cylindrical microstructures.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.123-128
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• 2016

The effect of propeller surface roughness condition on ship performance is very significant even the influence of fouling on propeller performance is not well established compared to biofouling on the hull surface. In present study, predictions of open water efficiency of propeller are made for three different fouling conditions, and its application is given for the 7m full-scale propeller of a medium-size tanker in open water condition. The numerical predictions of propeller efficiency loss due to fouling are based on the results from laboratory-scale drag measurements and boundary layer similarity law analysis presented in Schultz (2007) together with an in-house unsteady lifting surface code which is an appropriate tool to predict the effect of propeller surface roughness on propeller performance. The results of this study indicate that the subject propeller with the small calcareous fouling ($k_s=0.001$) can lead to as high as 15 % loss at the propeller operating condition (J=0.5) and the loss of propeller efficiency due to fouling should be evaluated while the ship is operating.

• KDI Journal of Economic Policy
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• v.30 no.2
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• pp.1-26
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• 2008

This paper attempts to re-evaluate the size of housing wealth effect in Korea. Our focus is on the size of 'genuine' housing wealth effect, i.e., the response of consumption spending by home-owners to the changes in housing wealth. Two issues show up while we estimate the 'genuine' wealth effects using aggregate time series data: the issues around home ownership and proper measure of consumption. We first argue that it is more appropriate to use non-housing consumption, because housing consumption is in large part not of the choice of home owners but the imputed rents they do not actually choose to pay. We then proceed to address the issue of home ownership, by examining how much to revise the estimates of housing wealth effect obtained from aggregate non-housing consumption data. We construct two structural models and estimate the share of home-owners' consumption in those models' context. It is found that, if properly revised in light of the estimated consumption shares of home-owners, the magnitude of resulting housing wealth effects are larger than what simple time series regressions imply.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.77
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• pp.259-284
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• 2018

The purpose of this study is to identify the determinants of the export performance of the most preferred trade exhibitions for SMEs. And the results are as follow. First, it is analyzed that the challenging entrepreneurship, the global orientation toward the overseas market, the quality of the excellent trade show, and the support system of the trade exhibition of the export related organizations all have a very positive effect on the export performance of the SMEs participating in the trade show. Second, the number and size of participating trade shows has no influence on controlling export performance. Third, there is a difference in export performance depending on participation frequency, participation size, participation method, and participating region. The implication of this study is that SMEs, which have a strong sense of entrepreneurship and a strong commitment to the global market, need to actively participate in trade exhibitions with relatively low barriers to entry. The policy implication is that organizers and export-related organizations need to understand the internal capabilities of participating companies in order to maximize the performance of participating companies. And Korea should also create an environment that can attract and hold excellent trade exhibitions held overseas. Therefore, the government and export-related organizations should expand the infrastructure for hosting global trade exhibitions. As well as an urgent need to build a system for attracting overseas buyers that can dramatically boost overseas buyer visits.