• Korean Journal of Biological Psychiatry
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• v.15 no.2
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• pp.83-91
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• 2008

Objectives : Neurological soft signs have been regarded as endophenotypes associated with the genetic basis of schizophrenia. This study was to investigate the intra-familial correlations of the neurological soft signs according to their genetic loading. Methods : Schizophrenic patients(N=14) were included, who had one parent with a family history of schizophrenia and the other without it. Genetic loading was determined by the patient's family history of schizophrenia using the Family Interview for Genetic Studies(FIGS). These parents were subdivided into two groups. The first group was designated as 'presumed carriers'(N=9) of genetic loading, who had one or more schizophreic firstor second-degree relatives. The second group was designated as 'presumed non-carriers'(N=11) of genetic loading, who had no schizophrenic first- or second-degree relatives. Normal controls(N=12) consisted of people without schizophrenic relatives. NSS were evaluated using the Neurological Evaluation Scale-Korean Version (NES-K), and the intra-familial correlations of NSS were tested using the Intra-Class Coefficients(ICC) method. Results : The scores of Motor Coordination subdimension of NES-K were significantly correlated between the patients and their presumed carriers(ICC=.804, p=.016), but not significantly correlated between the patients and their presumed noncarriers. In other subdimensions of NES-K, no significant correlation were found between the patients and their parents regardless of the genetic loading. But, there were no statistically significant differences in the scores of Motor Coordination subdimension of NES-K between the patients and controls. Conclusion : This study did not prove that the neurological soft signs might be an endophenotype of schizophrenia that cosegregate with the genetic loading. The future study using more subjects than this would be needed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.703-710
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• 1994

A nonlinear FEM analysis of steel members under very-low-cycle loading has been performed in conjunction with experimental works. This analysis is an FEM tracing toward cracking of steel members under cyclic loads such as a strong earthquake. After verifying the procedure by comparing global hysteretic behaviors from the analytical and experimental results, the local stress-strain hysteresis at critical sections for large cyclic deformations was traced by the numerical analysis. Local strain history was discussed in relation to cracking. Based on the experimental and analytical results, a new approach to seismic safety assessment for steel members was proposed in this paper.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.58-65
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• 2004

Thermal and structural finite element analyses were performed for the turbopump turbine bladed disk model with shroud of a liquid rocket engine. The only 1/80 part model was analyzed which consists of 3D eight node isoparametric solid elements. The applied loading history consists of a startup condition with a thermal spike and a steady state. Heat transfer coefficient on the blade was predicted using the commercial Navier-Stokes solver, Fluent. Transient thermal responses during startup and steady states were calculated using a 3D finite element code developed. Maximum stress and shroud tip displacement under the influence of centrifugal and thermal loading were also determined.

• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.96-104
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• 1992

Aircraft structures and engineering structures are always subject to variable amplitude loads. Variable amplitude loads include some kind of loading history; for example, constant amplitude load, single peak overload and block overload etc. Crack growth under variable amplitude loading exhibits retardation effect. In this study, the 4 point bending fatigue test was performed by hydrolic servo fatigue testing machine on 7075-T6 Al-alloy. The retardation effect of overload ratio and numbers of overload cycle was quantitatively studied. 1) Change of retardation effect against increment of overload ratio is more evident when the multiple overload is applied than single overload is done. 2) The number of overload cycle is very important factor about the crack growth retardation effect when the overload ratio is more than 1.75; that is not when the overload ratio is less than 1.75. 3) Overload affected zone size increased gradually by increment of crack growth retardation effect. 4) Crack driving force is more greatly reduced when the crack tip branched off two direction than it sloped to one direction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.43-54
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• 1987

Cumulative damage characteristics of concrete, on which rapetitive loads are applied, are investigated. Preliminarily, a series of uniaxial compression tests on cylindrical specimens of plain concrete is carried out to find out that, among various factors, stress levels of repetitive loadings and loading order are the most governing factors of cumulative damage of concrete. Based on this preliminary study, fatigue tests are carried out applying two levels of stresses, stepwisely. As a result, it is found that characteristics of cumulative damage of concrete are governed by nonlinear relationships and do not follow Miner's linear theory. It is also observed that cumulative damage characteristics and static strengths of concrete vary with loading history of stresses. Empirical equations which may be useful in predicting fatigue characteristics and remaining life of concrete stuctures are proposed for concrete subjected two stress levels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.194-202
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• 1996

An approach to increase the seismic resistance of large structures is to reduce the seismic forces, to which structures are subjected by base isolation systems. The anti-seismic performance of base-isolated beatings has been verified experimentally by shaking table tests. However, it may be difficult to perform the tests for the full-scale beatings of base-isolated structures. Therefore, the test program was designed to evaluate the reliability and properties of the beatings under a range of loading conditions including axial stress, loading frequency and direction, and temperature. The effects of scale were also evaluated by comparing the results of the 1/4-scale beatings with those from the full-scale bearings, and the ultimate behavior of both types of bearings with evaluated through a series of roll-out tests. This report draws comparisons among the different tests and bearings to determine the importance of various factors including load history, axial stress, and frequency. Comparisons between the 1/4-scale bearings were difficult because of the scaling effects in manufacturing and thermal radiation, but qualitative results from the 1/4-scale bearings can certainly be extrapolated the full-scale bearings.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.92-100
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• 2001

It is very important to determine the coefficient of earth pressure at rest accurately in order to estimate the behavior of soil structure. For estimation of K/sub 0/-value depending upon the stress history of dry sand, a new type of K/sub 0/-oedeometer apparatus is devised, and the horizontal earth pressure is accurately measured. For this study, 2 types of one-cyclic K/sub 0/-Loading/unloading models have been studied experimentally using four relative densities of the sand. The results obtained in this test are as follows : K/sub on'/ the coefficient of earth pressure at - rest for virgin loading is a function of the angle of internal friction Φ' of the sand and is determined as K/sub on/=1 - 0.914 sin Φ', K/sub ou'/ the coefficient of earth pressure at rest for virgin unloading is a function of K/sub on/ and over consolidation ratio(OCR), and is determined as K/sub ou/=K/sub on/(OCR)K/sup a/. The exponent α, increases as the relative density increases. K/sub or'/ the coefficient of earth pressure at rest for virgin reloading decreases in hyperbola type as the vertical stress, σ/sub v/’, increases. And, the stress path at virgin reloading leads to the maximum prestress point, independent upon the value of the minimum unloading stress. The gradient of this curve, m/sub r/ increases as OCR increases.

• Smart Structures and Systems
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• v.4 no.5
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• pp.583-603
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• 2008

In this study, a real-time damage detection method using output-only acceleration signals and artificial neural networks (ANN) is developed to monitor the occurrence of damage and the location of damage in structures. A theoretical approach of an ANN algorithm that uses acceleration signals to detect changes in structural parameters in real-time is newly designed. Cross-covariance functions of two acceleration responses measured before and after damage at two different sensor locations are selected as the features representing the structural conditions. By means of the acceleration features, multiple neural networks are trained for a series of potential loading patterns and damage scenarios of the target structure for which its actual loading history and structural conditions are unknown. The feasibility of the proposed method is evaluated using a numerical beam model under the effect of model uncertainty due to the variability of impulse excitation patterns used for training neural networks. The practicality of the method is also evaluated from laboratory-model tests on free-free beams for which acceleration responses were measured for several damage cases.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.2
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• pp.127-144
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• 2002

There is an increasing appreciation of the vital role that biomechanics play in the performance of oral implant. The aim of this article is to provide some basic principles that will allow a clinician to formulate a biomechanically valid treatment plan. However, at this point in the history of oral implantology, the clinician should realize that we do not know enough to provide absolute biomechanical rules that will guarantee success of all implants in all situations. To examine the biomechanical questions, one must begin with an analysis of the distribution of biting forcess to implants. Related topics, such as stress transfer to surrounding tissues and interrelationships between bone biology and mechanical loading are major subjects, deserving a separate discussion. Once rigid fixation, angulation, crestal bone level, contour, and gingival health are achieved, stress beyond physiologic limits is the primary cause of initial bone loss around implants. The restoring dentist has specific responsibilities to reduce overload to the bone-implant interface. These include proper diagnosis, leading to a treatment plan designed with adequate retention and form, and progressive loading to improve the amount and density of bone and further reduce the risk of stress beyond physiologic limits. The major remaining factor is the development of occlusal concept in harmony with the rest of the stomagnetic system.

• Earthquakes and Structures
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• v.7 no.6
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• pp.1141-1169
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• 2014

This study is aimed to investigate the seismic performance of low-rise precast wall system with base isolation. Three types of High Damping Rubber Bearing (HDRB) were designed to provide effective isolation period of 2.5 s for three different kinds of structure in terms of vertical loading. The real size HDRB was manufactured and tested to obtain the characteristic stiffness as well as damping ratio. In the vertical stiffness test, it was revealed that the HDRB was not an ideal selection to be used in isolating lightweight structure. Time history analysis using 33 real earthquake records classified with respective peak ground acceleration-to-velocity (a/v) ratio was performed for the remaining two types of HDRB with relatively higher vertical loading. HDRB was observed to show significant reduction in terms of base shear and floor acceleration demand in ground excitations having a/v ratio above $0.5g/ms^{-1}$, very much lower than the current classification of $0.8g/ms^{-1}$. In addition, this study also revealed that increasing the damping ratio of base isolation system did not guarantee better seismic performance particularly in isolation of lightweight structure or when the ground excitation was having lower a/v ratio.