• Journal of Wetlands Research
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• v.17 no.1
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• pp.19-25
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• 2015

The purpose of this study is to reveal the effect of plant life cycle to plant settlement by 1 year monitoring. The subjects of monitoring are the plants (3 plant life cycle, 9 taxa) well established in the mesocosm. 18 mesocosms were divided into 3 sets and water levels were maintained at 0, 20 and 60 cm during 16 weeks from mid-May, respectively and at 0 cm except these 16 weeks. Height and population size of transplanted perennial plants (Scirpus tabernaemontani, Zizania caduciflora, Typha (Typha angustifolia and Typha orientalis)) at 1st year were not affected by diverse water level, though any more seedlings of these species were not settled at this condition. In contrast, water level condition strong influenced annual and biennial plant, relatively. As a result, timing and duration of flooding have great effect on successful settlement of annual and biennial plant without rhizome.

• Applied Biological Chemistry
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• v.10
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• pp.101-105
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• 1968

The effect of concentration of carbon and nitrogen sources on the sporulation and the life cycles of three strains of Zygosaccharomyces was investigated. The results are as follows: 1) The good sporulation of Zygosaccharomyces bisporus, delbruekii, and Z. steineri was obtained on solid medium containing 0 to 0.001% of nitrogen and 10 to 20% of glucose. The high content of nitrogen was detrimental to sporulation and asci were formed under 0.01% of nitrogen. 2) It is widely accepted that the life cycle of Zygosaccharomyces proceeds in the following way: Ascospore...Vegetative cells...Conjugation of vegetative cells...Sporulation...Ascopores But zygotes of Z. bisporus proceeded to vegetative cells when transfered to the suitable medium for vegetative reproduction, and then formed asci.

• International Journal of Highway Engineering
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• v.18 no.3
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• pp.33-45
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• 2016

PURPOSES : Concrete pavement has been used in the construction of the Jungbu expressway in 1987. More than 60% of the pavement on the expressway is currently made of concrete, but most has been used far beyond their design life. Pavement life has been extended through routine maintenance or overlay. However, the structural capacity of the pavement has reached its limit, and extensive rehabilitation/reconstruction with long time traffic blocking should be considered. The three following issues on concrete rehabilitation/reconstruction will be discussed: (1) economic comparison of asphalt inlay and asphalt overlay, (2) economic comparison preventive overlay on a section which is currently good and routine overlay on the section which will be poor, and (3) economic analysis of early-strength concrete when it is used in concrete reconstruction. METHODS : First, various life cycle cost analysis tools were compared, and the proper tool for the extensive rehabilitation/reconstruction was selected. Second, a sensitivity analysis of the selected tool was performed to find the influential input variables, which should be carefully selected in the analysis. Third, three case studies, which can be issues in the rehabilitation/reconstruction of the expressway concrete pavement in Korea, were performed. RESULTS : Asphalt overlay without milling the deteriorated concrete showed 18~25% lower life cycle cost than the current asphalt inlay with milling. The good current preventive overlay on the section was economically justified within the scope of this study. The construction cost limit of the early strength concrete was suggested to be economical for 1, 3, and 7 days of construction alternative opening. CONCLUSIONS : CA4PRS was a viable tool for comparing various rehabilitation/reconstruction issue alternatives. Several concrete issues associated with the rehabilitation/reconstruction of the deteriorated concrete pavement were discussed as mentioned above.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.103-112
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• 2017

PURPOSES : In this study, field performance evaluation of crack treatment of pavement and the feasibility of surface treatment of pavement are presented. The performance and cost of preventive maintenance methods have been previously verified, and the methods are being used in many developed countries and cities. However, the performance and cost of the system have not been verified in domestic, field applications. Therefore, in order to improve performance, the field performance is evaluated, and a reasonable cost is proposed. METHODS : Visual Inspection was conducted to evaluate the field application and performance of the preventive maintenance method. In addition, the PCI index was calculated from the results of visual inspection of the application area of the surface treatment method, and the performance life of each method was predicted. For the economic evaluation, life cycle cost analysis was performed using the life cycle cost analysis program. RESULTS :In order to evaluate and quantify the field performance of crack repair material, the residue condition of the pavement surface after crack treatment, rather than the performance of the material, is evaluated. In addition, the crack resistance and performance life of surface treatment methods are evaluated. The cost of currently available treatment methods are compared to the common pavement cut and overlay method, and it is determined that the preventive method is not economical based on life cycle cost analysis. CONCLUSIONS :Because of the characteristics of cracking, it is necessary to conduct the evaluation of currently applied methods and the analysis of the cause of damage, by visual inspection. Moreover, in order to evaluate the performance and economic suitability of the currently applied surface treatment methods, it is necessary to acquire information on application sections by monitoring their long-term conditions and performance.

• Structural Engineering and Mechanics
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• v.28 no.4
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• pp.387-410
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• 2008

The fatigue damage accumulation rates of horizontally curved thin walled box-girder bridge have been estimated from vehicle-induced dynamic stress history using rain flow cycle counting method in the time domain approach. The curved box-girder bridge has been numerically modeled using computationally efficient thin walled box-beam finite elements, which take into account the important structural actions like torsional warping, distortion and distortional warping in addition to the conventional displacement and rotational degrees of freedom. Vehicle model includes heave-pitch-roll degrees of freedom with longitudinal and transverse input to the wheels. The bridge deck unevenness, which is taken as inputs to the vehicle wheels, has been assumed to be a realization of homogeneous random process specified by a power spectral density (PSD) function. The linear damage accumulation theory has been applied to calculate fatigue life. The fatigue life estimated by cycle counting method in time domain has been compared with those found by estimating the PSD of response in frequency domain. The frequency domain method uses an analytical expression involving spectral moment characteristics of stress process. The effects of some of the important parameters on fatigue life of the curved box bridge have been studied.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.149-154
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• 2008

Service life of bridges should be evaluated by physical life considering damage/deterioration. But it is difficult to identify optimal maintenance scenario due to insufficient research related to that. To identify optimal maintenance scenario, it is needed to develope life cycle profile model of condition state variation by deterioration factor. The LCP model has been developed in consideration of regression analysis and survey in this study. It is expected that the LCP model could help to achieve HBMS system improvement.

• Journal of the Korean housing association
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• v.9 no.1
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• pp.33-42
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• 1998

This study has been designed to analyze longterm trend of home-ownership probability over the family life cycle. In this study, 633 female household heads were interviewed on their critical life event such as pregnancy, birth or death of households, marriage, and residential movement between 1987 and 1990 in Oxaca, Mexico. The raw data composed of 100,000 lines were transformed into yearly segmented observation data, proposed by Allison. The results are drawn as follws: 1) There is significant effect of marriage cohort on residential mobility and home ownership: couples who married in 1960s are likely to change their residence at early stage of family life than those who married in 1940s. They also have lower probability of home ownership for 10 years after marriage than the other cohorts. 2) Over all the cohorts, it is consistent tendency that probability of home ownership continuously increases over the entire family life cycle for 40 years. 3) Of the logistic regression analysis of home ownership on household socioeconomic variables, the homeownership was positively related with age of marriage and time since marriage, and was negatively related with education of female head. Over in this study, it is proven that home owenership is ultimate goal of most families, and it is a function of family event variables.

• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.541-548
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• 2011

Thermomechanical fatigue (TMF) behavior of heat resistant austenitic stainless steel was evaluated in the temperature range from 100$^{\circ}C$ to peak temperatures of 600 to 800$^{\circ}C$; The fatigue lives under TMF conditions were plotted against the plastic strain range and the dissipated energy per cycle. In the expression of the inelastic strain range versus fatigue life, the TMF data obtained at different temperature ranges were located close to a single line with a small deviation; however, when the dissipated energy per cycle, calculated from the area of the stress-strain hysteresis loops at the half of the fatigue life, was plotted against the fatigue life, the data showed greater scattering than the TMF life against the inelastic strain range. A noticeable stress relaxation in the stress-strain hysteresis curve took place at the peak temperatures higher than 700$^{\circ}C$, but all specimens in this study exhibited cyclic hardening behavior with TMF cycles. Recrystallization occurred during the TMF cycle concurrent with the formation of fine subgrains in the recrystallized region, which is considered to cause the cyclic hardening of the steel.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.1-10
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• 2022

For Cu-Cr alloy developed for rocket engines, estimated fatigue lives were calculated using various fatigue life prediction methods and compared with fatigue life acquired from low-cycle fatigue tests. The utilized methods for fatigue life prediction are as follows: Coffin-Manson relation, plastic/total strain energy density relations, Smith-Watson-Topper relation, Tomkins relation, and Jahed-Varvani relation. As results of estimation of fatigue lives, it satisfied within scatter band two compared to the test fatigue lives in all methods. The quantitative calculation of the deviation of predicted fatigue lives gives that the total strain energy density relation presents the best result.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.13 no.1
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• pp.29-73
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• 1983

The age related changes in the life cycle of the progenitor cell population of murine oral epithelia was studied. Using radioautographic methods which have been adopted in previous cell cycle studies, the age-related changes of different phases in renewing cells of the palatal, buccal and lingual mucosae were determined. The results confirm published findings on cell cycle changes of epithelia with aging and illustrated further that mitotic phase which has hither to been considered stationary, also changes with aging. The major parts revealed by this study are as follows: 1) The basal progenitor cells in different regions of oral mucosa have different generation times. 2) The basal cell cycle time increases as a function of aging and the region most affected by aging appears to be the epithelium of the cheek. 3) The phases of the cell cycle affected by the process of aging are in increasing order of magnitude: M-, S- and G₁-phase. 4) The age elated change in the number of DNA synthesizing basal progenitor cells occurs at two age periods. Between 1 and 12 months of life it decreases, while from 12 to 20 months it increases.