• Korean Journal of Human Ecology
• /
• v.16 no.3
• /
• pp.563-576
• /
• 2007

The purpose of this study is to analyze the financial performance according to the economic environment change. The data of 4,577 households in 2003 and 3994 households in 2000 is from the Korean Labor and Income Panel Study. The data were analyzed by various statistical methods such as frequency, mean-test, Duncan's multiple range test, k-mean cluster analysis. Findings were as follows; First, the classified household financial strategy types were Residual(44.3%), Financial Assets(24.0%), Informal Institutional(19.7%), Diversified Portfolio(7.6%), Real Estate(4.5%). Second, the criteria of classification of the financial strategies were relative, not absolute. Third, the rate of economic growth was high and the index of the current money was low in 2000. Fourth, households that employed a diversified portfolio strategy had the greatest net wealth.

• Korean Journal of Human Ecology
• /
• v.16 no.1
• /
• pp.75-87
• /
• 2007

The purpose of this study was to classify the financial strategies in elderly households. The data of 4,577 households with all ages and 1255 elderly households is from the Korean Labor and Income Panel Study(2000, 2003). The data were analyzed by various statistical methods such as frequency, mean-test, Duncan's multiple range test, k-mean cluster analysis and logistic regression. Findings were as follows; First, the classified household financial strategy types were Residual(44.3%), Financial Assets(24.0%), Informal Institutional(19.7%), Diversified Portfolio(7.6%), Real Estate(4.5%). Second, the criteria of classification of the financial strategies were relative, not absolute. Third, households(both elderly households and all households) that employed a diversified portfolio strategy had the greatest net wealth.

• Journal of Families and Better Life
• /
• v.25 no.3 s.87
• /
• pp.25-44
• /
• 2007

The purpose of this study was to classify the financial strategies and investigate major determinants of the financial performance in elderly households. This study used the data of 4,577households with all ages and 1,255 elderly households were from the Korean Labor and Income Panel Study(2000, 2003). The data were analyzed by various statistical methods such as frequency, mean-test, Duncan's multiple range test, k-mean cluster analysis and regression. The major findings were as follows: First, the classified household financial strategy types were Residual(44.3%), Financial Assets(24.0%), Informal Institutional(19.7%), Diversified Portfolio(7.6%), Real Estate(4.5%). Second, the criteria of classification of the financial strategies were relative, not absolute. Third, elderly households that employed a financial assets had the greatest financial performance (62,320,000 won net gain). Households with all ages that employed a diversified portfolio strategy had the greatest financial performance (98,360,000 won net gain). Forth, the determinants of the financial performance were significantly different according to the types of financial strategy.

• Structural Engineering and Mechanics
• /
• v.29 no.6
• /
• pp.603-622
• /
• 2008

This work deals with the design optimization of tuned mass damper (TMD) devices used for mitigating vibrations in high-rise towers subjected to seismic accelerations. A stochastic approach is developed and the excitation is represented by a stationary filtered stochastic process. The effectiveness of the vibration control strategy is evaluated by expressing the objective function as the reduction factor of the structural response in terms of displacement and absolute acceleration. The mechanical characteristics of the tuned mass damper represent the design variables. Analyses of sensitivities are carried out by varying the input and structural parameters in order to assess the efficiency of the TMD strategy. Variations between two different criteria are also evaluated.

• Journal of the Ergonomics Society of Korea
• /
• v.10 no.1
• /
• pp.11-22
• /
• 1991

This paper aims to examine experimentally the difference of subjectively measured degree of depth between two dimensional (2D) and three dimensional (3D) images. For this paper, two experiments were conducted; in the first experiment, the subjects were asked to estimate the distance between two objects presented with different depths, while in the second experiment, the subjects' role was to rank three objects in the order of distance from the screen. In both experiments, the objects were presented either in 2D or 3D images. The results of the experiments show that the use of 3D images can induce more accurate and more stable estimates of distance than the use of 2D images. However, it is also noted that the absolute degree of depth is not the unique criteria utilized by the subjects for the distinction of small differences of depth.

• Journal of Fisheries and Marine Sciences Education
• /
• v.18 no.2
• /
• pp.194-207
• /
• 2006

The purpose of this study was to examine the current student assessment plan of subject domain and to propose ways to improve it. This study analyzed the history of our student assessment plan of subject domain and overviewed the student assessment cases of several countries. And then researchers discussed the improvement plans of student assessment of subject domain. The results of this study are as follows. First, we need to enlarge the use of detailed subject-ability record space or to assess student's subject-related ability according to subordinate perspectives of subject. Second, we need to establish the desirable evaluation-perspective and to develop absolute evaluation criteria of each subject and unit. Third, we need to diffentiate the scores of differentiated test items or equate the scores of differentiated groups.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.1026-1031
• /
• 2003

A vibration isolation system fur a large reverberation chamber (1,228㎥, 1,000ton) has been installed. The reverberation chamber generates loud noise and induces high level of vibration to perform spacecraft acoustic environmental tests. The isolation system prevents vibration transfer from the chamber to enclosure buildings. This paper describes logical design process and commissioning experiments of the system. Design criteria have been induced from rigid body model of the chamber. Finite element model has been employed to select the characteristics of rubber pads. A total of 21 rubber pads have been installed between the chamber and supporting pedestals. A sand bag of 800kg was dropped on the chamber floor to measure the natural frequency of the isolation system. Absolute transmissibility has been measured while generating 145㏈ in the chamber. The natural frequency of the chamber is 10.5㎐, which is 80% of estimated value. Overall transmissibility at working frequency range (25㎐-10,000㎐) is less than -6㏈.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2003.03a
• /
• pp.238-246
• /
• 2003

By using simulated ground motions, which is sum of earthquake signals and noise, we measured the distortion of response spectra due to noise. We found that the distortion is more closely related to the signal-to-noise (S/N) ratio of root-mean-square (RMS) measurement than that of conventional peak measurement. Given a S/M ratio, the distortion of absolute acceleration response spectra is independent on the earthquake magnitude, while that of relative displacement response spectra has a strong dependence on the earthquake magnitude. This means that, when we calculate response spectra from time histories, we can efficiently predict the distortion of acceleration response spectra simply by measuring the RMS SJN ratios, or the distortion of displacement response spectra by combining the RMS S/N ratios and the earthquake magnitudes.

• Structural Engineering and Mechanics
• /
• v.70 no.3
• /
• pp.367-380
• /
• 2019

The paper concerns topology and geometry optimization of statically determinate beams with arbitrary number of supports. The optimization problem is treated as a bi-criteria one, with the objectives of minimizing the absolute maximum bending moment and the maximum deflection for a uniform gravity load. The problem is formulated and solved using the Pareto optimality concept and the lexicographic ordering of the objectives. The non-dominated sorting genetic algorithm NSGA-II and the local search method are used for the optimization in the Pareto sense, whereas the genetic algorithm and the exhaustive search method for the lexicographic optimization. Trade-offs between objectives are examined and sets of Pareto-optimal solutions are provided for different topologies. Lexicographically optimal beams are found assuming that the maximum moment is a more important criterion. Exact formulas for locations and values of the maximum deflection are given for all lexicographically optimal beams of any topology and any number of supports. Topologies with lexicographically optimal geometries are classified into equivalence classes, and specific features of these classes are discussed. A qualitative principle of the division of topologies equivalent in terms of the maximum moment into topologies better and worse in terms of the maximum deflection is found.

• Smart Structures and Systems
• /
• v.29 no.4
• /
• pp.549-560
• /
• 2022

The optimum damping and tuning frequency ratio of the tuned mass damper-inerter (TMDI) for the base-isolated structure is obtained using the numerical searching technique under stationary white-noise and filtered white-noise earthquake excitation. The minimization of the isolated structure's mean-square relative displacement and absolute acceleration, as well as the maximization of the energy dissipation index, were chosen as the criteria for optimality. Using a curve-fitting technique, explicit formulae for TMDI damping and tuning frequency for white-noise excitation are then derived. The proposed empirical expressions for TMDI parameters are found to have a negligible error, making them useful for the effective design of base-isolated structures. The effectiveness of TMDI and its optimum parameters are influenced by the soil condition and isolation frequency, according to the comparison made of the optimized parameters and response with different soil profiles. The effectiveness of an optimally designed TMDI in controlling the displacement and acceleration response of the flexible isolated structure under real and pulse-type earthquakes is also observed and found to be increased as the inertance mass ratio increases.