• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.35 no.2
• /
• pp.255-264
• /
• 2015

Steel plate concrete (SC) structure has been developed as a new structural type. Rational damping value shall be determined for the seismic design of SC structure. This study evaluated damping ratio of SC structure through experiments. For the study, a SC shear wall specimen was constructed and dynamically tested on the shaking table. Acceleration time history responses measured from testing were converted to the transfer functions and analyzed by using experimental modal analysis technique. The structural damping ratio of the specimen was identified as 4% to critical. Considering the shaking table test was performed at the excitation level corresponding to the low stress level of the specimen, 4% could be suggested as a structural damping for design of SC structure for operating basis earthquake.

• Journal of Community Nutrition
• /
• v.8 no.4
• /
• pp.185-192
• /
• 2006

This study was performed to investigate factors affecting sensitivity and preference for salty tastes of Korean adult females. Sensitivity and preference for salty tastes were determined as detection threshold concentration of NaCl solution and the optimally-preferred NaCl concentration of the bean sprout soup, respectively. A self-administered questionnaire was used to obtain the information regarding general characteristics, self diagnosis of stress, health-related lifestyle practices, dietary habits and food preferences. Dietary intake using 24-hours recall and blood pressure were measured. Salty taste detection thresholds and optimally-preferred NaCl concentrations were 0.0197% and 0.357%, respectively. There was a significant positive correlation between the optimally-preferred salt concentration and age, despite no significant correlation between either sensitivity or preference for salty taste and sodium intake, which was 3,605mg/day. Those who had bread or cereal with milk as breakfast instead of a traditional Korean meal and those who preferred jjigae to soup had significantly higher NaCl preferences for bean sprout soup. Going to bed after midnight and skipping meals (${\geq}3/week$) decreased salty taste sensitivity without reaching statistical significance. Self awareness of one's own health, recent weight changes, family history of hypertension, sleep quality, getting-up time, rate of eating and other food preferences did not affect either perception. Stress level, TV watching, BMI and sodium intake did not have significant correlation to sensitivity or preference. Further research including a large number of well-controlled subjects and more accurate measurement of sodium intake should be directed to find other factors affecting salt preference and sensitivity in order to decrease Na intake and related diseases.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.19 no.4
• /
• pp.884-892
• /
• 2005

Seeing through the reference of literatures ${\ll}$Internal Classic${\gg}$, ${\ll}$Donguibogam${\gg}$ and Master Jisan's theory about Ki-Hyul and Hyul-Ki, the writer came to conclusions as follows. In ${\ll}$Internal Classic${\gg}$ Ki-Hyul is expressed into being orderly and ordinate, but Hyul-Ki is described differently into making Hyul-Ki or operating Hyul-Ki. In ${\ll}$Donguibogam${\gg}$ Ki-Hyul and Hyul-Ki are not distinguished between two things, but Ki-Hyul is mentioned as harmony of Ki-Hyul and Hyul-Ki, and Hyul-Ki as ascending and descending or as deficiency and excess. In Hyungsang medicine the special characters of Ki-Hyul is seized the essence of the meanings from the deflection between left and right, changes of skin, flesh, meridian, muscle and bones. And the distinctive marks of Hyul-Ki is got hold from changes of complexion, many or few hairs, ascending or descending spirits of ears, eyes, mouth and nose. Also Ki-Hyul is recognized by laying stress on rise and fall, after birth, breast, upper limbs, eight extra meridians. And Hyul-Ki is recognized by laying stress on going up and down, the inborn constitution, abdomen, lower limbs, and twelve meridians. Jisan distinguished Ki-Hyul from Hyul-Ki theoretically and he applied the theory to clinical examination proved the facts that the theory and the examination are in accord with each other. This attempts was for the first time in Oriental medicine history and the theory was set up. It is thought that the defects of the theory about Ki-Hyul and Hyul-Ki which Jisan insisted on need much more study from now on.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.2
• /
• pp.1-9
• /
• 2005

An end beam is one of the most important structural members supporting uncovered freight under in-service loading. In general, it needs to endure over 25 years. However fatigue fracture has occurred at dynamic stress concentration location of the end beam because user's specifications demanded high speed and vehicle manufacturer made the uncovered freight car with comparatively low strength and stiffness. For durability analysis, finite element analysis is performed to evaluate the problem of uncovered freight structure and local strain. The uncovered freight car was operated on actual problematic railroad line to measure dynamic stress versus time history on the critical part from which a crack is initiated often. Rainflow cycle counting method was used to estimate fatigue damage at dangerous area under operating condition. Therefore, this study shows that analytical fatigue life at the end beam can be predicted on the basis of S-N curve and structure analysis and has a fairly good correlation with experimental fatigue life.

• The Journal of Engineering Geology
• /
• v.1 no.1
• /
• pp.121-136
• /
• 1991

The focal mechanism of the Hongsung Earthquake (1978. Oct. 7, M$_L$=5.0, Latitude 36.62N, Longitude 1 26.67E) was evaulated using the polarity distribution of the P-Waveforms. Through the non-linear computer process, the compatibility of polarity distributions of the 9 P-Waveforms observed at teleseismic distances from the Hongsung Earthquake epicenter was investigated to those of the focal mechanism determined from the varying strike, dip and rake angles. The resultant values for the strike and dip angle of the principal fault plane, which apparently matches very well the sunface lineament of the Hongsung region, are determined to be about 247 degree and 78 degree with uncertainties, respectively. However, the rake angle of the focal mechanism has wide range of 40 degree to 160 degree, which is mainly due to the poor coverage of the azimuthal angle of the observed seismic stations. Due to the consistency of principal stress axes, the resultant focal mechanism could support the current stress regime of that region, which may be caused by subduction of the Pacific Plate under the Eurasia Plate along the Japan Trench. It also provides information of seismic source characteristics of the part of the Korean Peninsula for aseismic design criteria such as Site Specific Response Spectrum and Strong Ground Motion Time History for the nuclear power plants and related nuclear waste disposal facility sites.

• Women's Health Nursing
• /
• v.27 no.4
• /
• pp.326-336
• /
• 2021

Purpose: This study explored the prevalence of prenatal and postpartum depression in Korea and its influencing factors from 20 weeks of pregnancy to 12 weeks postpartum. Methods: Using a prospective cohort study design, data on women's depression and its influencing factors were collected at 20, 28, and 36 weeks of pregnancy and at 2, 6, and 12 weeks postpartum. The participants were 219 women and 181 spouses during pregnancy; and 183 mothers and 130 spouses after childbirth. Depressive symptoms were assessed by the Edinburgh Postnatal Depression Scale and influencing factors were measured by the Postpartum Depression Predictors Inventory-Revised, parity, and spousal depression. Results: The prevalence of maternal depression was 10.5% to 21.5% before birth, and it was 22.4% to 32.8% postpartum. The prevalence slightly decreased during the prenatal period but peaked at 2 weeks postpartum. Antenatal depression was influenced by low socioeconomic status, lower self-esteem, having experienced prenatal depression, having experienced prenatal anxiety, a previous history of depression, lower social support, lower marital satisfaction, and higher life stress. The factors influencing postpartum depression were lower self-esteem, having experienced prenatal depression, having experienced prenatal anxiety, lower social support, lower marital satisfaction, and higher life stress, as well as infant temperament and maternal blues. Parity and spousal depression had no impacts. Conclusion: The prevalence and influencing factors of maternal depression changed over time. Nurses need to screen women accordingly during the perinatal period and should provide education or counseling to prevent depression and promote adjustment to parenthood.

• Journal of Theoretical and Applied Mechanics
• /
• v.3 no.1
• /
• pp.45-65
• /
• 2002

A constitutive model on oorthotropic thermo-elasto-viscoplasticity for fiber-reinforced composite materials Is illustrated, and their thermomechanical responses are predicted with the fully-coupled finite element formulation. The unmixing-mixing scheme can be adopted with the multipartite matrix method as the constitutive model. Basic assumptions based upon the composite micromechanics are postulated, and the strain components of thermal expansion due to temperature change are included In the formulation. Also. more than two sets of mechanical variables, which represent the deformation states of multipartite matrix can be introduced arbitrarily. In particular, the unmixing-mixing scheme can be used with any well-known isotropic viscoplastic theory of the matrix material. The scheme unnecessitates the complex processes for developing an orthotropic viscoplastic theory. The governing equations based on fully-coupled thermomechanics are derived with constitutive arrangement by the unmixing-mixing concept. By considering some auxiliary conditions, the Initial-boundary value problem Is completely set up. As a tool of numerical analyses, the finite element method Is used with isoparametric Interpolation fer the displacement and the temperature fields. The equation of mutton and the energy conservation equation are spatially discretized, and then the time marching techniques such as the Newmark method and the Crank-Nicolson technique are applied. To solve the ultimate nonlinear simultaneous equations, a successive iteration algorithm is constructed with subincrementing technique. As a numerical study, a series of analyses are performed with the main focus on the thermomechanical coupling effect in composite materials. The progress of viscoplastic deformation, the stress-strain relation, and the temperature History are careful1y examined when composite laminates are subjected to repeated cyclic loading.

• Journal of the Korean Mathematical Society
• /
• v.38 no.5
• /
• pp.1069-1105
• /
• 2001

Regular maps and hypermaps are cellular decompositions of closed surfaces exhibiting the highest possible number of symmetries. The five Platonic solids present the most familar examples of regular maps. The gret dodecahedron, a 5-valent pentagonal regular map on the surface of genus 5 discovered by Kepler, is probably the first known non-spherical regular map. Modern history of regular maps goes back at least to Klein (1878) who described in [59] a regular map of type (3, 7) on the orientable surface of genus 3. In its early times, the study of regular maps was closely connected with group theory as one can see in Burnside’s famous monograph [19], and more recently in Coxeter’s and Moser’s book [25] (Chapter 8). The present-time interest in regular maps extends to their connection to Dyck\`s triangle groups, Riemann surfaces, algebraic curves, Galois groups and other areas, Many of these links are nicely surveyed in the recent papers of Jones [55] and Jones and Singerman [54]. The presented survey paper is based on the talk given by the author at the conference “Mathematics in the New Millenium”held in Seoul, October 2000. The idea was, on one hand side, to show the relationship of (regular) maps and hypermaps to the above mentioned fields of mathematics. On the other hand, we wanted to stress some ideas and results that are important for understanding of the nature of these interesting mathematical objects.

• Steel and Composite Structures
• /
• v.25 no.3
• /
• pp.315-326
• /
• 2017

In this work, thermoelastic dynamic behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) cylinders subjected to mechanical pressure loads, uniform temperature environment or thermal gradient loads is investigated by a mesh-free method. The material properties and thermal stress wave propagation of the nanocomposite cylinders are derived after solving of the transient thermal equation and obtaining of the time history of temperature field of the cylinders. The nanocomposite cylinders are made of a polymer matrix and wavy single-walled carbon nanotubes (SWCNTs). The volume fraction of carbon nanotubes (CNTs) are assumed variable along the radial direction of the axisymmetric cylinder. Also, material properties of the polymer and CNT are assumed temperature-dependent and mechanical properties of the nanocomposite are estimated by a micro mechanical model in volume fraction form. In the mesh-free analysis, moving least squares shape functions are used to approximate temperature and displacement fields in the weak form of motion equation and transient thermal equation, respectively. Also, transformation method is used to impose their essential boundary conditions. Effects of waviness, volume fraction and distribution pattern of CNT, temperature of environment and direction of thermal gradient loads are investigated on the thermoelastic dynamic behavior of FG-CNTRC cylinders.

• Smart Structures and Systems
• /
• v.20 no.1
• /
• pp.11-22
• /
• 2017

The long-term effect of ambient temperature on bridge strain is an important and challenging problem. To investigate this issue, one year data of strain and ambient temperature of a long-span cable-stayed bridge is studied in this paper. The measured strain-time history is decomposed into two parts to obtain the strains due to vehicle load and temperature alone. A linear regression model between the temperature and the strain due to temperature is established. It is shown that for every $1^{\circ}C$ increase in temperature, the stress is increased by 0.148 MPa. Furthmore, the extreme value distributions of the strains due to vehicle load, temperature and the combination effect of them during the remaining service period are estimated by the average conditional exceedance rate approach. This approach avoids the problem of declustering of data to ensure independence. The estimated results demonstrate that the 95% quantile of the extreme strain distribution due to temperature is up to $1.488{\times}10^{-4}$ which is 2.38 times larger than that due to vehicle load. The study also indicates that the estimated extreme strain can reflect the long-term effect of temperature on bridge strain state, which has reference significance for the reliability estimation and safety assessment.