• Journal of the Korean Institute of Gas
• /
• v.5 no.1
• /
• pp.1-6
• /
• 2001

The main objective of this study is to determine if the sources of AE in corroded specimens of aluminum could be identified iron the characteristics of the waveform signals recorded during fatigue loading. Coupons of notched 2024-T3 aluminum with or without corrosion (at the notch) were subjected to fatigue loading and the AE signals were recorded using non-resonant, flat, wide-band transducers. The time history and power spectrum of each individual wave signal recorded during fatigue crack growth were examined and classified according to their special characteristics. Five distinct types of signals were observed regardless of specimen condition. The waveform and power spectra were shown to be dependent on specimen condition. During the initial phase of crack growth, the signals obtained in the as-received specimens are most probably due to transgranular cleavage caused by extrusion and intrusion under fatigue loading. In the corroded specimen the signal are probably generated by intergranular cleavage due to embrittlement of grain boundary neat the pitting tip. The need for additional research to further validate these findings is indicated.

• Geotechnical Engineering
• /
• v.5 no.4
• /
• pp.37-46
• /
• 1989

The object of this paper is to study the general characteristics of overconsolidated silty clays subjected to repeated loading. The samples are first remolded. overconsolidated and a series of strain - controlled triaxial repeated tests are carried out. Generally the relationship of deviator stress - axial strain of overconsolidated clay is similar in pattern to the normally consolidated clay under single load. But the behavior of the pore water pressure build up in the sample subjected to repeated loading is dependent upon the consolidation history and the level of repeated stress. Therefore through the series of the tests, the characteristics of stress -strain relationship of soils which are differentlly overconsolidated are investigated, analysed and then compared with each soils. And also, from the relationship of test results, the strength and strain characteristics of soils are obierved. The equilibrium lines which presents the critical repeated stress and equilibrium state in the sample under repeated loading, are often straight, but may be curved. And the tendency of the equilibrium lines is observed as to the variation of overconsolidation ratio.

• Steel and Composite Structures
• /
• v.46 no.6
• /
• pp.793-804
• /
• 2023

In this study, cyclic loading tests were conducted to assess the seismic performance of cast-in-place (CIP) concrete-filled hollow core precast concrete columns (HPCC) constructed using steel ducts and rubber tubes. The outer shells of HPCC, with a hollow ratio of 47%, were fabricated using steel ducts and rubber tubes, respectively. Two combinations of shear studs & long threaded bars or cross-deformed bars & V-ties were employed to ensure the structural integrity of the old concrete (outer shell) and new CIP concrete. Up to a drift ratio of 3.8%, the hysteresis loop, yielding stiffness, dissipated energy, and equivalent damping ratio of the HPCC specimens were largely comparable to those of the solid columns. Besides the similarities in cyclic load-displacement responses, the strain history of the longitudinal bars and the transverse confinement of the three specimens also exhibited similar patterns. The measured maximum moment exceeded the predicted moment according to ACI 318 by more than 1.03 times. However, the load reduction of the HPCC specimen after reaching peak strength was marginally greater than that of the solid specimen. The energy dissipation and equivalent damping ratios of the HPCC specimens were 20% and 25% lower than those of the solid specimen, respectively. Taking into account the overall results, the structural behavior of HPCC specimens fabricated using steel ducts and rubber tubes is deemed comparable to that of solid columns. Furthermore, it was confirmed that the two combinations for securing structural integrity functioned as expected, and that rubber air-tubes can be effectively used to create well-shaped hollow sections.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.2A
• /
• pp.261-271
• /
• 2006

Many uncertainties affecting to the structural behavior of prestressed concrete (PSC) bridges reinforced with the un bonded external tendons are analyzed on the basis of the analytical method introduced in the companion paper. Many design parameters, which must be considered in design procedure, such as friction slip at the deviators, number of deviators, time-dependent deformations of concrete, relaxation of tendon and influence of loading history in PSC bridges are reviewed, and a lot of valuable results are obtained through this parametric study. In advance, the structural responses according to the external tendon profiles are analyzed to grasp if an optimum tendon profile depends on the applied loading type, and the obtained results show that the most stable structural response is revealed when the locations of deviators are coincident with the loading points.

• Korean Journal of Biological Psychiatry
• /
• v.2 no.2
• /
• pp.218-236
• /
• 1995

The author studied prognostic indicators of sixty Korean male alcoholics in psychological, social and biological aspects who were divided into abstinent and drinking groups. Thirty patients were assigned to each group. They were controlled in age and sex. Both groups were compared in terms of the demographic characteristics, past drinking history, treatment history, famaily history, ego strength and personality factors differences and distribution of dopamine $D_2$ receptor gene Al allele. Also the author studied relation of clinical course, alcoholic family history and dopamine $D_2$ receptor gene Al allele in both groups. The results were as follows; 1) The abstinent group had higher rate of married state, higher economic status, longer education years and maintained more stable job than the drinking group. But made no differences in occupation and religion. 2) The abstinent group showed higher rate of living with family members than the drinking group, and wives and fellows of the alcoholics anonymous were important factors for maintenance of abstinence. Family loading and parent's characters were not different. 3) The abstinent group had longer maximal length of abstinence but mean amount of alcohol consumption per day were larger than the drinking group. But there were no differences in duration of past drinking, drinking pattern, main drinking time, first drinking age and preference of the kind of alcoholic beverage in the past drinking history. 4) The abstinent group showed stronger treatment motivation, absolute abstinence in treatment goal, more voluntary adimission and maintained longer therapeutic relationship otter discharge than the drinking group. But both groups showed negative attitude toward antabuse therapy. 5) The abstinent group had higher mean score in ego strength scale than the drinking group. 6) In the personality factor questionnaire, the abstinent group showed strong laugh poise and the trait of praxernia, conservatism personality but the drinking group showed tough poise, the trait of weak ego strength(unstableness) and tough mindedness personality. 7) In comparision of dopamine $D_2$ receptor gene A1 allele, the prevalence of A1 allele was seventy percent and the frequency was 0.38 in the abstinent group. The prevalence of A1 allele was sixty percent and the frequency was 0.42 in the drinking group. Both groups were not significantly different in A1 allele prevalence and frequency. 8) In comparision of dopamine $D_2$ receptor gene A1 allele according to alcoholic family history, the prevalence of A1 allele was seventy percent and the frequency was 0.43 in the family history positive group. The prevalence of A1 allele was sixty-one percent and the frequency was 0.38 in the family history negative group. Both groups were not significantly different in A1 allele prevalence and frequency. In comparision of past drinking history according to alcoholic family history, the family history positive group showed earlier first drinking and problem drinking, but the family history negative group hod longer duration of past drinking. The mean amount of alcohol consumption per day, the longest duration of abstinence and Alcoholism Screening Test of Seoul Natoinal Mental Hospital(NAST) results were not significant. In conclusion, the results suggest that successful prognostic indicators of Korean alcoholics are married state, higher economic status, longer education years, stable job, living with family members, longer abstinence during past drinking history, strong treatment motivation, absolute abstinence in treatment goal, voluntary adimission, maintained therapeufic relationship, strong ego strength and the trait of praxernia, conservatism personality. But occupation, religion, alcoholic family history, parent's characters, duration of past drinking, drinking pattern, main drinking time, first drinking age, preference of the kind of alcoholic beverage, attitude to antabuse therapy and distribution of dopamine $D_2$ receptor A1 allele were not significantly related to the prognostic indicators of Korean alcoholics.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.5
• /
• pp.623-628
• /
• 2007

The accurate peak response estimation of a seismically excited structure with frictional damping system(FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated that by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In the case that an earthquake load is defined with probabilistic characteristics, the corresponding response of the structure with FDS has probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake loads generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Finally, coefficients of the proposed PDF are obtained by regression analysis of the statistical distribution of the time history responses. Finally the correlation between PDFs and statistical response distribution is presented.

• Journal of Preventive Medicine and Public Health
• /
• v.29 no.3 s.54
• /
• pp.483-494
• /
• 1996

The objectives of this study are to estimate the prevalence of diabetes mellitus (DM) and to identify risk factors associated with fasting blood sugar in a rural adult population. We carried out a cross - sectional study on the residents over 30-year old. Among the 1077 eligible subjects, 725 persons responded to the study;the study consisted of interview on family and past history of DM, anthropometry, blood pressure, and blood sugar level in each subjects. Only 707 subjects of 725 participants had fasting blood sugar(FBS) examined and the rest, 18 subjects were had casual blood sugar examined due to failure of fasting over 8 - hour. When subjects had $FBS\geq140mg/dl$, 2 hours postprandial blood sugar level was checked after 75g oral glucose loading. The prevalence of DM was 8.9%, and age standarized prevalence rate adjusted to Korean population of 1995 was 5.8%. Mean and SD of fasting blood sugar in men was $99.8{\pm}22.6$, and in women was $111.5{\pm}29.9$. Mean levels of fasting blood sugar were significantly higher in women than in man and as their ages advanced the prevalences increased in both sexes. PP2 blood sugar levels were significantly higher in elder age and in persons with higher FBS levels than others. The risk factors associated with FBS were past history of diabetes, sex, socioeconomic status and waist - to - hip circumference ratio;the risk of diabetes was increased in female, people with past DM history, central obesity and low socioeconomic state. The low socioeconomic status associated with DM in this study, which is different from other study results, should be pursued in further studies.

• Tuberculosis and Respiratory Diseases
• /
• v.66 no.6
• /
• pp.477-481
• /
• 2009

Leflunomide, a disease-modifying antirheumatic drug (DMARD) for the treatment of rheumatoid arthritis has been available in Korea since 2003. Leflunomide-associated interstitial pneumonitis has been appearing recently. A 25-year-old woman with a 12-month history of seronegative rheumatoid arthritis (RA) presented with acute respiratory insufficiency. She developed fever, dyspnea, and non-productive cough. Her medication history included methotrexate (15 mg/week. commencing 1 year prior) and leflunomide (20 mg/day, no loading dose, commencing 4 months prior). She was diagnosed with leflunomide-associated interstitial pneumonitis based on history, physical examination, laboratory and radiologic findings. She recovered quickly after leflunomide was withdrawn and steroids and cholestyramine were initiated quickly. We report a case of leflunomide-associated interstitial pneumonitis treated successfully with intravenous high-dose steroid and cholestyramine.

• Journal of Korean Society of societal Security
• /
• v.3 no.1
• /
• pp.33-42
• /
• 2010

This study predicts the stress history for truss bridge with local damages by using global-local model combination method. For this end, the global structure is modeled by 3D frame elements and the selected local details are modeled by shell elements. Then superposition principle enable the global-local model to be combined interactively. Because the frame model cannot consider the rigidity of gusset plate and the interation of structural members due to the complexity of stress distribution in truss connection. The section modification factors are proposed to calibrate the stiffness of global frame element. The global-local model combination is verified by comparing the numerical results with experimental data obtained from the proof loading test to the operating truss bridge. Furthermore, stress histrories of the truss bridge are generated in the consideration of the rigidity of truss connection with local damage by using the combination method.

• Computers and Concrete
• /
• v.20 no.4
• /
• pp.369-380
• /
• 2017

The effects of the vertical component of a ground motion on the earthquake performances of semi-ductile high-rise R/C structures were investigated in the present study. Linear and non-linear time-history analyses were conducted on an existing in-service R/C building for the loading scenarios including and excluding the vertical component of the ground motion. The ratio of the vertical peak acceleration to the horizontal peak acceleration (V/H) of the ground motion was adopted as the main parameter of the study. Three different near-source earthquake records with varying V/H ratio were used in the analyses. The linear time-history analyses indicated that the incorporation of the vertical component of a ground motion into analyses greatly influences the vertical deflections of a structure and the overturning moments at its base. The lateral deflections, the angles of rotation and the base shear forces were influenced to a lesser extent. Considering the key indicators of vertical deflection and overturning moments determined from the linear time-history analysis, the non-linear analyses revealed that the changes in the forces and deformations of the structure with the inclusion of the vertical ground motion are resisted by the shear-walls. The performances and damage states of the beams were not affected by the vertical ground motion. The vertical ground motion component of earthquakes is markedly concluded to be considered for design and damage estimation of the vertical load-bearing elements of the shear-walls and columns.