• Journal of Embryo Transfer
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• v.24 no.4
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• pp.281-287
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• 2009

As a simple and economical method for in vitro produced embryos, we have used BSA instead of serum for the production and embryo transfer of Hanwoo in vitro fertilized (IVF) embryos and obtained the following results: 1) When using serum (FBS; fetal bovine serum) or BSA-containing culture media as the initial culture media for immature oocytes, it is regarded as inappropriate to add only BSA to the culture solutions from maturation of the immature oocytes to development stage culture, but serum still needs be added though there is no significant difference in the concentration, with a change from 5% to 10%. 2) The results of culturing IVF embryos after development (4 cell stage) in the Medium199 solutions containing BSA instead of serum (FBS) showed that 0.3% BSA concentration is not optimal and 0.5% or higher BSA concentration has no significant difference among 0.5%, 0.7%, 1% and 2% (p > 0.05). 3) The post-freezing survival ratio after development in 5% FBS-Medium199 showed that 1% BSA concentration of the culture solution is the most suitable in the BSA concentrations of 0.3% (51%), 0.5% (67%), 0.7% (69%), 1% (77%) and 2% (75%). 4) The pregnancy rates of the transplanted fresh(not frozen) blastocyst had no significant concentration dependency (p > 0.5), and the average pregnancy rate was 63.8%. 14% of overweight calves were found among the calves given birth to by the transfer of IVF blastocysts cultured in the serum-added culture solution, but none was found in the experimental groups in which BSA was added instead of serum.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.111-117
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• 2008

The effect of characteristics of ground and circular foundation on the dynamic behavior of the foundation in vertical motion are considered using an approximated analytical solution and a finite element analysis with absorbing (consistent transmitting) boundary. The shear wave velocity of homogeneous ground affects the resonant frequency of the foundation much but has nothing to do with the maximum response amplitude at resonant frequency. The density in this case affects both the resonant frequency and the maximum response. The size and the mass of the circular foundation are related both to the resonant frequency and the maximum response. However, Poisson's ratio has very little effect on dynamic behavior of the foundation. When the ground is not homogeneous but has the layers, different formations of shear wave velocities would also change the maximum response at resonant frequency.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.37-45
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• 1998

The relational database system on fatigue strength was constructed, and the properties of fatigue life distribution were examined to analyze reliability and safety of metallic materials. Data manipulations were efficiently performed in relational fatigue strength database system using dependency diagram. Regardless of the distribution of fatigue strength, the proposed method, the Robust method and the complementary error function method using probability distribution, successfully estimated parameters of the 3-parameter Weibull distribution. The proposed criterion for estimating non-failure probability showed good results regardless of censoring time. The fatigue life distribution function described as a function of parameters of the Weibull distribution and applied stress ratio produced P-S-N characteristics reasonably.

• Polymer(Korea)
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• v.26 no.5
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• pp.607-614
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• 2002

Polyorganosiloxane(HBPS) modified polyurethane (UMPS) was synthesized to improve weatherability in the polyurethane (ITPU) sealant and its rheological propoerty was investigated. It was found that the viscosity increased with increasing HBPS content in polyurethane and maximum viscosity was observed in UMPS having 70/30 ITPU/HBPS ratio. This was understood that the segregation of HBPS segment in UMPS chain has been developed. Further increasing of the content of HBPS resulted in the lowering of viscosity because of the flexibility of HBPS block segment in UMPS chain. It was also found that UMPS has more sensitive environmental dependency of viscosity than ITPU such as shear rate, humidity and temperature. In additions, UMPS having Si(O$CH_3$)$_3$ end group (TUMPS) by adding coupling agent up to 0.3 wt% resulted in the increase of viscosity by the acceleration of curing. But introducing more than 0.5wt% curing agent to TUMPS caused the lowering of viscosity because of less NCO group in TUMPS for the curing.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.11
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• pp.561-572
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• 2001

Since energy consumption of CMOS circuits has a quadratic dependency on the supply voltage, lowering the supply voltage is the most effective way of reducing energy consumption. We propose an intra-task voltage scheduling algorithm for low-energy hard real-time applications. Based on a static timing analysis technique, the proposed algorithm controls the supply voltage within an individual task boundary. By fully exploiting all the slack times, as scheduled program by the proposed algorithm always complete its execution near the deadline, thus achieving a high energy reduction ratio. In order to validate the effectiveness of the proposed algorithm, we built a software tool that automatically converts a DVS-unaware program into an equivalent low-energy program. Experimental results show that the low-energy version of an MPEG-4 encoder/decoder (converted by the software tool) consumes less than 7~25% of the original program running on a fixed-voltage system with a power-down mode.

• Korea journal of population studies
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• v.9 no.2
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• pp.79-92
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• 1986

Death is one of the population movement phenomena used as an important health index in most society. Especially it is regarded as group phenomenon in a specific group rather than individual one and considered important in public health field because the level and cause of death is related to health of public. The auther examined the changes of the Korean mortality pattern to evaluate the status of the Korean public health by studying mortality indicator using the population census and other materials from 1930 to 1980. The results are as follows: First, the Korean crude death rate was reduced to one third in 1980 compared to that in 1930, but the crude birth rate was constant from 1930 to 1960 causing the increase of population. So the population pattern is changing from the classic pyramic shape to bell shape and the dependency ratio was reduced from 78 in 1930 to 61 in 1980. Second, the infant mortality rate decrease rapidly. In 1980 it was one seventh of that in 1930 which was proved by the change of the age-specific death rate curve from U to J shape. Third, the male mortality reduction after the age of forty was much less than that of female, which explained the specific death pattern of high mortality in Korean middle and oldaged males. Fourth, the main cause of death was changed from infectious, parasitic, respiratory and digestive system disease to circulatory of tumorous diseases. Considering the above results, Korean health problem is now changing from the infant infection to geriatric chronic regressive disease. That naturally the direction of health service should be turned from the infant stage maternal and child health to the health problems of old people.

• Korea journal of population studies
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• v.3 no.1
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• pp.62-77
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• 1979

The purpose of this study is to explain the increasing trend of the aged population and its demographic characteristics. This study is based on the data for the aged population above 65 years old published by the Bureau of Statistics, Economic Planning Board. The increasing trend of the aged population has been analyzed and projected from 1955 to the year 2000. Some demographic charicteristics of the aged population including marital status, educational status and status of economic activities have also been analyzed in order to identify the problems associated with aging of population in Korea. The study offers the following conclusion. 1. The aged population index, the proportion of aged population to total population was 3.6 in 1975 and projected to be 6.6 in 2000. There has been steady increase of the aged population is reflected in changes of population structure. The proportional change of the aged population index was 100.0 in 1955, 109.0 in 1975 and 200.0 in 2000 respectively. 2. As for marital status of the aged population 77.6 per cent of male were married while 24.3 per cent of female were married in 1975. 22 per cent of male were widowed while it spouses died declined remarkable the mortality rate declined. 3. As the educational status of the aged, 77 per cent never attended school and 18 per cent attended from a primary school. This is very low and the number of educated men is higher than that of educated women. The rank ordering of schooling is city, Eub and Myeon in that aged. 4. The dependency ratio of the aged population was 5.9 in 1955, 6.1 in 1975 and will be 9.8 in 2000. It is gradually increasing as indicated above 20 per cent of aged population was economically active of these, they are employed in the following occupations as listed in order of the magnitude of the aged population employed. The employment status of the aged workers shows that a greater number of persons are self-employed than workers for another employer. In particular, temporary employees comprise 56.0 per cent of those employed.

• Journal of Korea Planning Association
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• v.54 no.2
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• pp.93-108
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• 2019

This study examines the relationship between three-dimensional urban built environment and urban surface temperature using LANDSAT 8 satellite image data in Seoul city. The image was divided into 600m×600m grid units as an unit of analysis. Due to the high level of spatial dependency in surface temperature, this study uses spatial statistics to take into account spatial auto-correlation. The spatial error model shows the best goodness of fit. The analysis results show that the three-dimensional built environment and transport environment as well as natural environment have statistically significant associations with surface temperature. First, natural environment variables such as green space, streams and river, and average elevation show statistically significant negative association with surface temperature. Second, the building area shows a positive association with surface temperature. In addition, while sky view factor (SVF) has a positive association with surface temperature, surface roughness (SR) shows a negative association with it. Third, transportation related variables such as road density, railway density, and traffic volume show positive associations with surface temperature. Moreover, this study finds that SVF and SR have different effects on surface temperature in regard to the levels of total floor areas in built environment. The results indicate that interactions between floor area ratio (FAR) and three-dimensional built environmental variables such as SVF and SR should be considered to reduce urban surface temperature.

• Journal of the Korea Convergence Society
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• v.13 no.4
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• pp.155-161
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• 2022

The outbreak of the Covid 19 increased the interest on the 'Virtual Tourism. In this research the key word related to "Virtual Tourism" was collected through the search engine and was analyzed through the data mining method such as Log-odds ratio, Frequency, and network analysis. It is clear that the information and communication dependency increased in the field of "Virtual Tourism" after Covid 19 and also the trend have changed from "securement of the contents diversity" to "project related to economic recovery." Since the demands for the "Virtual Reality" such as metaverse is increasing, there should be an economic and circular structure in which the government establishing a related policy and the funding plan based on the research, local government and the private companies planning and producing discriminate contents focusing on AISAS(Attension, Interest, Search, Action, Share) aand the research institutions and universities developing, applying, assessing and commercializing the technology.

• Computers and Concrete
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• v.33 no.4
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• pp.399-407
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• 2024

This study nondestructively examined the evolution of crack density in ultra-high performance concrete (UHPC) upon cyclic loading. Uniaxial compression was repeatedly applied to the cylindrical specimens at levels corresponding to 32% and 53% of the maximum load-bearing capacity, each at a steady strain rate. At each stage, both P-wave and S-wave velocities were measured in the absence of the applied load. In particular, the continuous monitoring of P-wave velocity from the first loading prior to the second loading allowed real-time observation of the strengthening effect during loading and the recovery effect afterwards. Increasing the number of cycles resulted in the reduction of both elastic wave velocities and Young's modulus, along with a slight rise in Poisson's ratio in both tested cases. The computed crack density showed a monotonically increasing trend with repeated loading, more significant at 53% than at 32% loading. Furthermore, the spatial distribution of the crack density along the height was achieved, validating the directional dependency of microcracking development. This study demonstrated the capability of the crack density to capture the evolution of microcracks in UHPC under cyclic loading condition, as an early-stage damage indicator.