• Steel and Composite Structures
• /
• v.22 no.6
• /
• pp.1391-1415
• /
• 2016

Limit load of pressure bearing structures was reviewed in this article. By means of the finite element analysis, limit load of pressurized cylinder with nozzle was taken as an example. Stress classification method and Elastic-plastic finite element analysis combining with limit load determination methods were used to determine limit load of cylinder with nozzle. Comparison of limit load determined by different methods, the results indicated that limit load determined by linearization method was the smallest. Limit load determined by twice elastic slope criterion was the nearest than experimental results. Elastic-plastic finite element analysis had comparably computational precision, but required time consuming. And then the requirements of computer processing and storage capacity by power system became higher and higher. Most of criteria for limit load estimation included any human factors based on a certain substantive characteristics of experimental results. The reasonable criterion should be objective and operational.

• IE interfaces
• /
• v.16 no.1
• /
• pp.85-93
• /
• 2003

The purposes of this study are to investigate perceived discomfort for static joint motions, and to propose rankings for the joint motions based on the perceived discomfort. The perceived discomfort was measured through an experiment using the free modulus method of the magnitude estimation, in which ten healthy college-age female students participated. The results showed that joints, joint motions and their levels significantly affected the perceived discomfort at $\alpha$=0.01, and that the interaction of joints and joint motion levels was also significant. Based on the experimental results, three rankings were proposed by joint and joint motions, by joints and by joint motions, which were very different from the existing ones. Especially, the proposed rankings were different from the males' published before in their order and magnitude. These rankings can be used as a valuable tool for better understanding potentially adverse effects of poor working postures in industrial sites, and as basic data for developing the postural classification scheme.

• Journal of Microbiology and Biotechnology
• /
• v.22 no.12
• /
• pp.1597-1604
• /
• 2012

Genus Bacillus is a spore-forming bacterium that has unique properties in cell differentiation, allowing the forming of spores in stress conditions and activated in the vegetative cell, with suitable environments occurring during the life cycle acting as a trigger. Their habitat is mainly in soil; thus, many species of Bacillus are associated with plants as well as rhizosphere bacteria and endophytic bacteria. Signal transduction is the principal mechanism of interactions, both within the cell community and with the external environment, which provides the subsequent functions or properties for the cell. The antimicrobial compounds of Bacillus sp. are potentially useful products, which have been used in agriculture for the inhibition of phytopathogens, for the stimulation of plant growth, and in the food industry as probiotics. There are two systems for the synthesis of these substances: nonribosomal synthesis of cyclic lipopeptides (NRPS) and polyketides (PKS). For each group, the structures, properties, and genes of the main products are described. The different compounds described and the way in which they co-exist exhibit the relationship of Bacillus substances to plants, humans, and animals.

• Tunnel and Underground Space
• /
• v.4 no.2
• /
• pp.170-185
• /
• 1994

Surface subsidence is one of the problems caused by mined out caverns. Depending on the geologic conditions and mining methods, subsidence can occur in various forms. This report describes the ground stability assessment for the mining induced subsidence area where unfilled caverns still exist abandoned. Geologic features which could affect the stability of the ground were investigated and all the possible geophysical methods were employed to obtain data that could explain the state of the ground in question. Basic rock tests were conducted from the drill cores and rock mass classification was performed by core logging and borehole camera investigation. Numerical analyses were carried out to predict the ground stability using data obtained by various investigations. The result could have been more reliable if in-situ stress were measure and reflected in the numerical analysis.

• Korean Journal of Social Welfare
• /
• v.68 no.2
• /
• pp.213-232
• /
• 2016

The purpose of this study is to explore the stress profile that adolescent perceives by using Latent Profile Analysis (LPA), and to examine the effect of characteristics variable per groups that appeared in profile. By using the cross-section data of 'A survey on the human right of Korean children and adolescent in 2013' issued by National Youth Policy Institute, the LPA concerning the stress type was conducted and surveyed 9,521 adolescents from fourth grade in elementary school to seniors in high school nationwide. The result of this study shows that two class types were selected according to the goodness-of-fit index and latent class classification rate. Type 1 is named low-risk group as they show low level, whereas type 2 is named relative risk group as they show high level. In order to predict the characteristics of adolescent stress, the study conducted Binary Logistic Regression analysis on the basis of low-risk group. There is higher probability to belong to relative risk group, the more they are female students than male students, the less their subjective health condition and happiness, the more runaway experience, the less school grades and the less economic affluence in their household. The implication of this research, its limitation and direction of follow-up research were suggested.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.9
• /
• pp.482-491
• /
• 2018

This study intended to identify different level of teacher-efficacy, perception of principals' leadership and peer collaboration as it pertains to a teachers' job stress and job satisfaction in Elementary school. Samples include 1,031 teachers in elementary school from Korean Children & Youth Panel Survey(KCYPS) and data were analyzed using Latent Class Analysis(LCA) to identify different patterns of teacher-efficacy and perception of principals' leadership and peer collaboration. Multivariate analysis of variance were employed to identify the influence of predictors for classification of teachers' job stress and job satisfaction among latent classes. The study found three latent classes at risk class, middle-level adaptive class, and adaptive class and results showed that each distinctive class can be identified by some of predictors. Teachers at adaptive class showed higher teacher-efficacy and positive perception of principals' leadership and peer collaboration than teachers at risk and middle-level adaptive class. Also, teachers at adaptive class showed lower job stress and higher job satisfaction than teachers at two other classes. The study suggests that help teachers based on personal profile are effective rather teacher-efficacy and perception of principals' leadership and peer collaboration.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.3
• /
• pp.47-58
• /
• 2014

To investigate the unsaturated characteristics of the tailings obtained from the waste dump at Imgi mine, matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. Based on the measured result, Soil Water Characteristic Curves (SWCC) were estimated by van Genuchten model. According to the unsaturated soil classification method, the tailings of the waste dump correspond to clayey sand. As a result of Suction Stress Characteristic Curve (SSCC) by Lu and Likos model, SSCC has a shape of S which is similar to SWCC. The hysteresis phenomenon occurred in SSCCs, which means the suction stress of drying path is larger than that of wetting path in the same effective degree of saturation. The effective stress of unsaturated soil is equal to that of saturated soil when matric suction is less than Air Entry Value (AEV). However, the effective stress of unsaturated soil is larger than that of saturated soil when matic suction is more than AEV. Meanwhile, unsaturated hydraulic conductivity by van Genuchten model decreased with increasing matric suction, and the hydraulic conductivity of drying path is larger than that of wetting path.

• Tunnel and Underground Space
• /
• v.32 no.6
• /
• pp.530-548
• /
• 2022

The site selection process for deep geological disposal of high-level radioactive waste will be conducted in stages, and 103 evaluation parameters related to site selection have been proposed. In the field of rock mechanics and rock engineering, there are 33 evaluation parameters for intact rock, joint and rock mass, and they are applied in the basic and detailed investigation stages. In this report, uniaxial compressive strength, in-situ stress, joint distribution, and rock mass classification were selected as the main evaluation parameters, and among them, uniaxial compressive strength and in situ stress were selected as key evaluation parameters. Statistical techniques or regression analysis were performed for granite in Wonju and Chuncheon to evaluate the distribution range for the selected key evaluation parameters. The average of the uniaxial compressive strength in the Wonju area estimated through the posterior distribution is about 171 MPa, and about 123 MPa in the Chuncheon area. The maximum in situ stress acting in the Wonju area was less than 30 MPa and less than 40 MPa in the Chuncheon area. The direction of the maximum horizontal stress calculated by regression analysis was 101° in Wonju, and in the case of Chuncheon, it was 95°, respectiviely.

• Korean Journal of Culture and Social Issue
• /
• v.28 no.3
• /
• pp.483-512
• /
• 2022

This study examined the patterns of coping strategies among Koreans during the early stage of the COVID-19 pandemic, explored the influence of demographic information (gender, age, economic level, household type), along with the unusual experiences due to COVID-19 (fear, stress of COVID, constraints of routine, income risk) on the classification of subclasses, and analyzed the latent profile differences in psychological wellbeing (life satisfaction, depression, and anxiety). An online survey was conducted among Korean Adults(n=600) between April 13, 2020 and 21, when WHO declared COVID-19 a global pandemic and Daegu as well as Gyeongsangbuk-do was nominated as a special disaster zone. First, Latent Profile Analysis (LPA) was used to identify subclasses of coping strategies and results suggested that the 4-class model had the best fit. Second, Class memberships were predicted by gender, age, economic level, as well as fear, stress, constraints of routine, and income risk, among the unusual experiences due to COVID-19. Finally, there are differences in psychological wellbeing among latent profiles. 'High level of adaptive coping group 3' showed the highest level of life satisfaction, 'Adaptive-maladaptive coping group 4' showed the highest level of depression, anxiety. Implications and suggestions are discussed based on the study results.

• Journal of the Korean Wood Science and Technology
• /
• v.43 no.4
• /
• pp.446-455
• /
• 2015

Based on comparative studies on standards and grading procedures of machine graded lumber in Korea and other countries, this study proposed a procedure of determining the grade classification and design strengths of domestic machine graded lumber. Differences between machine stress rated lumber and E-rated laminations were detailed in order to clarify the need for the procedure improvement. To this improvement the use of average MOE requirement for grading was introduced instead of the fixed minimum MOE requirement which is currently used in the Korean standards. It was found that the fixed minimum MOE requirement method was easier for an inspector to grade but, less efficient as a strength predictor than the average MOE requirement method. The advantage of average MOE requirement method is statistically MOR-MOE regression-based MOR prediction and highly efficient in quality control though it requires a computer-aided operation system in an initial setup. A major weakness of the current Korean grading system was found that different strength characteristics depending on wood species were not reflected on the grade classification and the tabulated allowable design stress. The proposed procedures were developed taking advantages of respective merits of both methods and based on MOR-MOE regression analysis. Through this procedure, the grades of machine stress rated lumber should be revised to become interchangeable with E-rated lamination, which would be beneficial to the cost competitiveness of domestic machine graded lumber and glued laminated timber industry.