• Journal of Industrial Technology
• /
• v.26 no.B
• /
• pp.73-81
• /
• 2006

A sensitivity analysis about effects of influencing factors on the stability of Soil cut slope was performed. Slope stability analyses were carried out under dry, rainy and seismic conditions. Dominant factors controlling the slope stability were chosen such as cohesion and internal friction angle, unit weight of soil, water table and seismic horizontal coefficient used for the slope stability during earthquake. Parametric stability analysis with those factors was performed for sensitivity analysis. As results of analyzing the sensitivity of factors under dry and rainy conditions, effects of cohesion, internal friction angle and unit weight of soil on the stability of slope are more critical in the dry condition than in the rainy condition. Cohesion and internal friction angle are more dominant factors influencing the slope stability irrespective of dry or rainy conditions than unit weight of soil and the horizontal seismic coefficient. The unit weight and the horizontal seismic coefficient affects crucially the stability according to conditions of slope formation and dry or rainy seasons. For the effect of horizontal seismic coefficient on stability of slope, safety factor of slope is not affected significantly by dry or rainy conditions. However, increase of the horizontal seismic coefficient under the rainy condition floes reduce the safety factor significantly rather than the dry condition. Therefore, it is needed that the location of the water table is assigned appropriately to satisfy the required safety factor of stability in the case of checking slope stability for the rainy and seismic conditions.

• Smart Structures and Systems
• /
• v.25 no.3
• /
• pp.311-322
• /
• 2020

This paper studies the influence of parameters of a novel SMA helical spring energy dissipation brace on the seismic resistance of a frame structure. The force-displacement relationship of the SMA springs is established mathematically based on a multilinear constitutive model of the SMA material. Four SMA helical springs are fabricated, and the force-displacement relationship curves of the SMA springs are obtained via tension tests. A numerical dynamic model of a two-floor frame with spring energy dissipation braces is constructed and evaluated via vibration table tests. Then, two spring parameters, namely, the ratio of the helical spring diameter to the wire diameter and the pre-stretch length, are selected to investigate their influences on the seismic responses of the frame structure. The simulation results demonstrate that the optimal ratio of the helical spring diameter to the wire diameter can be found to minimize the absolute acceleration and the relative displacement of the frame structure. Meanwhile, if the pre-stretch length is assigned a suitable value, excellent vibration reduction performance can be realized. Compared with the frame structure without braces, the frames with spring braces exhibit highly satisfactory seismic resistance performance under various earthquake waves. However, it is necessary to select an SMA spring with optimal parameters for realizing optimal vibration reduction performance.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.8
• /
• pp.123-133
• /
• 2004

The magnitudes of wall thrust acting on quay walls can easily vary due to the development of excess pore pressure in backfill. In this research, a new displacement model was proposed to predict the displacement of the wall considering such magnitude variations of the wall thrust. This model is based on Newmark sliding block concept. The magnitude variation of the wall thrust is modelled by varying the magnitude of yield acceleration. The parametric study was performed to analyze the effects of input parameters on the seismic displacement of the wall, and the validity of this model was verified by comparing its predicted displacements with those of Is shaking table tests.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.1441-1446
• /
• 2009

Numerical analysis is a powerful method in evaluating the soil-pile-structure interaction under the dynamic loading, and this approach has been applied to the practical area due to the development of computer technology. Finite Difference Method, one of the most popular numerical methods, is sensitive to the shape and the number of mesh. However, the trial and error approach is conducted to obtain the accurate results and the reasonable simulation time because of the lack of researches about mesh size and the number. In this study, FLAC 3D v3.1 program(FDM) is used to simulate the dynamic pile model tests, and the numerical results are compared with the 1G shaking table tests results. With the different size and shape of mesh, the responses of pile behavior and the simulation time are estimated, and the optimum mesh sizes in dynamic analysis of single pile is studied.

• Korean Journal of Community Nutrition
• /
• v.2 no.3
• /
• pp.294-304
• /
• 1997

The purpose of this study was to explore the relationship between dietary behavior and the nutrient intake status in the youth of rural areas, based on their personal characters such as their sex, age, family type, number of family members, mother's age, occupation, and school career. This study was made by use of a self-administrated questionnaire with a 24-hour recall for 5days as an instrument with 439 randomly selected students. Statistical methods applied to analyze the data were frequency, percent, Willcoxon Rank-sum test, Kruskal-wallis test, x2-test by contingence table, and Spearman's correlation coefficient in non parametric statistical cases. Some of the interesting results are as follows : 1) The correlation between sex and breakfast is highly significant. That is, over 80% of male students had breakfast every day, whereas only about 60% of female students had breakfast every day. Bad table manners and some other problems are insignificant with respect to the personal characters in the relations between the personal characters and eating behaviors. However, the regularity of every meal, the frequency of having meals with other family members, and the frequency of meals eaten out and snacks show significant differences. 2) The mother's occupation does not have any influence on the nutrient intake of their students when the relationship between personal characters and nutrient intake was analysed. On the other hand sex, the mother's school career, the numbers of family members, the type of family, and the income of the family showed significant differences nutrient intakes. 3) The regularity and the frequency of having meals, meals eaten out with their family members, and the table manners during meals showed significant differences in the intake of nutrient elements such as calorie, protein, fat, fiber, calcium, iron, phosphorus, vitamin B1, vitamin B2, niacin and vitamin C. However some consideration during meals and problems in eating habit are insignificant with regard to nutrient intake.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.8
• /
• pp.46-59
• /
• 1998

This paper presents shape design, surface construction, and cutting path generation for the surface of marine ship propeller blades. A propeller blade should be designed to satisfy performance constraints that include operational speed which impacts rotations per minutes, stresses related to deliverable horst power, and the major length of the marine ship which impacts the blade size and shape characteristics. Primary decision variables that affect efficiency in the design of a marine ship propeller blade are the blade diameter and the expanded area ratio. The blade design resulting from these performance constraints typically consists of sculptured surfaces requiring four or five axis contoured machining. In this approach a standard blade geometry description consisting of blade sections with offset nominal points recorded in an offset table is used. From this table the composite Bezier surface geometry of the blade is created. The control vertices of the Hazier surface patches are determined using a chord length fitting procedure from tile offset table data. Cutter contact points and path intervals are calculated to minimize travel distance and production time while maintaining a cusp height within tolerance limits. Long path intervals typically generate short tool paths at the expense of increased however cusp height. Likewise, a minimal tool path results in a shorter production time. Cutting errors including gouging and under-cut, which are common errors in machining sculptured surfaces, are also identified for both convex and concave surfaces. Propeller blade geometry is conducive to gouging. The result is a minimal error free cutting path for machining propeller blades for marine ships.

• International Journal of Fluid Machinery and Systems
• /
• v.9 no.3
• /
• pp.213-221
• /
• 2016

Due to the nature of cavitation numerical analyses, computational optimization of a pump with respect to the cavitation properties is extremely demanding. In this paper it is shown how a combination of Transient Blade Row (TBR) method and some simplifications can be used for making the optimization process more efficient and thus possible on current generation of hardware. The aim of the paper is not the theory of hydraulic design. Instead, the practical aspects of numerical optimization are shown. This is done on an example of a radial pump and a combination of ANSYS CFX, ANSYS software tools and custom scripts is used. First, a comparison of TBR and fully-transient simulation is made. Based on the results, the TBR method is chosen and a parametric model assembled. Design of Experiment (DOE) table is computed and the results are used for sensitivity analysis. As the last step, the final design is created and computed as fully-transient. In conclusion, the results are discussed.

• Communications for Statistical Applications and Methods
• /
• v.16 no.4
• /
• pp.697-705
• /
• 2009

The Pearson chi-squared statistic or the deviance statistic is widely used in assessing the goodness-of-fit of the generalized linear models. But these statistics are not proper in the situation of continuous explanatory variables which results in the sparseness of cell frequencies. We propose a goodness-of-fit test statistic for the cumulative logit models with ordinal responses. We consider the grouping of a dataset based on the ordinal scores obtained by fitting the assumed model. We propose the Pearson chi-squared type test statistic, which is obtained from the cross-classified table formed by the subgroups of ordinal scores and the response categories. Because the limiting distribution of the chi-squared type statistic is intractable we suggest the parametric bootstrap testing procedure to approximate the distribution of the proposed test statistic.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.11 no.2
• /
• pp.71-76
• /
• 2011

The problem of decision making under imprecise environments are widely spread in real life decision situations. We present a method of object recognition from imprecise multi observer data, which extends the work of Roy and Maji [J Compu. Appl. Math. 203(2007) 412-418] to generalized intuitionistic fuzzy soft set theory. The method involves the construction of a comparison table from a generalized intuitionistic fuzzy soft set in a parametric sense for decision making.

• Earthquakes and Structures
• /
• v.16 no.4
• /
• pp.391-399
• /
• 2019

Residual deformation of high-speed railway bridge piers is cumulative under repeated earthquakes, and influences the safety and ride comfort of high-speed trains. This paper investigates the effects of the peak ground acceleration, longitudinal reinforcement ratio, and axial compression ratio on the cumulative deformation through finite element analysis. A simply-supported beam bridge pier model is established using nonlinear beam-column elements in OpenSees, and validated against a shaking table test. Repeated earthquakes were input in the model. The results show that the cumulative deformation of the bridge piers under repeated earthquakes increases with the peak ground acceleration and the axial compression ratio, and decreases with the longitudinal reinforcement ratio.