• Journal of Korean Academy of Oral Health
• /
• v.43 no.3
• /
• pp.118-123
• /
• 2019

Objectives: The purpose of this study was to investigate changes in the composition of artificial cariogenic biofilms using a Streptococcus mutans biofilm model over a period of time. Methods: We analyzed the dry weight, colony forming unit (CFU) number, extracellular polysaccharide (EPS) biovolume, and acid production rate of S. mutans biofilms formed on saliva-coated hydroxyapatite discs after 26 h, 50 h, 74 h, 98 h, 171 h, and 195 h. In addition, we performed a laser scanning confocal fluorescence microscopy to determine the bacterial volume, EPS biovolume, and biofilm thickness. We calculated the biofilm density using dry weight and EPS biovolume. Results: Over a period of time, there was no change in the CFU number and acid production rate of S. mutans biofilms, but there was an increase in the dry weight and EPS biovolume of S. mutans biofilms. The bacterial volume, EPS biovolume, and biofilm thickness only increased in the 50-h-old biofilm; however, no change was observed in 50-195-h-old biofilms. In addition, an increase in the biofilm density was observed over time. Conclusions: These results suggest that the acid production ability of cariogenic biofilms does not change, but the biofilm density increases over time. However, due to scientific information, further research needs to be conducted in the field of dentistry to get further insights on the progression of cariogenic biofilms over time.

• Journal of the Korean Home Economics Association
• /
• v.43 no.9 s.211
• /
• pp.41-57
• /
• 2005

The purpose of this study was to examine the change of couple relationship factors predicting marital satisfaction and divorce intention over time tv comparing the couples' first year with their present year of marriage. The couple relationship factors consisted of affection, ambivalence, affectional expression, the expression of negativity. The study subjects 355 married women having preschool children aged 7 years old and elementary school students in the 6th grade. Data were analyzed by SPSSWIN with the method of MANOVA. The results of this study showed that couples in happy groups without divorce intention became less affectionate and demonstrated less affectional expression, and more ambivalence and expression of negativity over time. However, the amount of change was not as large as that of the unhappy groups. The findings of this research indicated that the decline of affection and affectional expression and the increase of ambivalence and expression of negativity were probably, as normative, a natural consequence of the transition from the first year of marriage to a more mature relationship. Therefore, the change over time was not important. However, the amount and aspects of change were the main points which researchers and practitioners should pal attention to in the future.

• Journal of the Korean Wood Science and Technology
• /
• v.44 no.2
• /
• pp.231-240
• /
• 2016

The change in chemical compositions of leachate and medium density fiberboard (MDF) from a laboratory-scale simulated landfill which constructed in a plastic container containing alternating layers of soil and MDF was investigated to evaluate decomposing of MDF in soil. Four treatments were conducted: 1) MDF in soil, 2) MDF only, 3) cured UF resin in soil, and 4) soil only. Molecular weight (MW) distribution of compounds in leachate from soil only treatment did not change over time. In UF resin in soil treatment, the MW distribution shifted to a lower MW distribution over time, while the peak shifted to the left indicated changing to higher MW distribution in leachate from treatment 1 and 2 contained MDF. Higher percent nitrogen in leachate was observed in MDF containing treatments due to the UF resin in the MDF. The percent carbon slightly increased in MDF only while that greatly decreased in MDF in soil treatment maybe due to bacterial activity. The percent of extractable materials from the MDF decreased greatly on day 35 compare to day 0, and subsequently did not change much on day 77. In contrast, percent holocellulose and lignin did not change much over time. No structural change of the wood fiber in MDF occurs during the study. Water-soluble materials from MDF in soil contributed the change in chemical composition of leachate.

• Journal of the Architectural Institute of Korea Planning & Design
• /
• v.34 no.10
• /
• pp.107-118
• /
• 2018

Cedric price is an architect and educator who have had an influence on architectural thinking through teaching and projects, rather than completed buildings. The purpose of this study was to analyze the architecture of Cedric Price in terms of time. Time was an important factor to understand his architecture along with his interest in technology, so most of his architectural thinking and methodology - anti-architecture, programmatic indeterminacy, a philosophy of enabling and so on, could be explained under the consideration of time. Depending on how he considered and used the concept of time, his projects could be categorized into two groups; The first group was related to the change over time, and this group again divided into three sub categories; change of user's preference, change of external environment, and change over building lifetime. The second group was related to planning of time, which could be divided again into two categories; programmatic planning and the usage planning during the period. This categorization could provide a frame to look into his architecture, through which his projects showed the limitation in modern architecture and the possibility for contemporary architecture.

• Atmosphere
• /
• v.18 no.3
• /
• pp.199-206
• /
• 2008

This study employs a structural time series method in order to model and estimate stochastic trend of surface temperatures of the globe, Northern Hemisphere, and Northeast Asia ($20^{\circ}N{\sim}60^{\circ}N$, $100^{\circ}E{\sim}150^{\circ}E$). For this study the reanalysis data CRUTEM3 (CRU/Hadley Centre gridded land-surface air temperature Version 3) is used. The results show that in these three regions range from $0.268^{\circ}C$ to $0.336^{\circ}C$ in 1997, whereas these vary from $0.423^{\circ}C$ to $0.583^{\circ}C$ in 2007. The annual mean temperature over Northeast Asia has increased by $0.031^{\circ}C$ in 2007 compared to 1997. The climate change in surface temperatures over Northeast Asia is slightly higher than that over the Northern Hemisphere.

• The Journal of the Korea Contents Association
• /
• v.11 no.9
• /
• pp.453-458
• /
• 2011

This study aimed to figure out the change of exposure dose to the radiologist according to the C-arm angle change. For the exam it was fixed with 101 kvp and 4.9mA for the exposure time with 3 seconds and 5 seconds respectively. C-arm Tube was located both under and over, then the average was taken after performing for 5 times with the change of angle from -30 degree to 0, 30, 60 and 90 degree. The detector measured in 160cm high from the position of the radiologist who operates the C-arm. The measurement was shown its highest result at -30 degree followed by 0, 30, 60, 90 from the highest order. Over tube method is higher than under tube method. Therefore, to reduce the exposure dose of the radiologist, it is required for using under tube method instead of over tube method. When the angle change is made, it is recommended to use the angle that tube is growing further apart from the radiologist. And it is also necessary to shorten exposed time as much as possible to create the same quality image and also to reduce the exposure dose.

• Geophysics and Geophysical Exploration
• /
• v.2 no.3
• /
• pp.154-158
• /
• 1999

This paper introduces a partial edge detection technique, that improves the processing time of an automatic change tracking system for multi-temporal images. In the conventional change tracking systems for multi-temporal images, the edge detection is performed over the whole image. In the proposed method, however, the necessary portions for the edge detection is selected first and the edge detection is performed over the selected parts only. As a consequence, the improvement in the processing time could be achieved. The proposed change tracking system is expected to be utilized as a very efficient tool to configure changes in large data set such as remotely sensed satellite imagery or geophysical time laps images.

• Journal of Food Hygiene and Safety
• /
• v.10 no.2
• /
• pp.111-131
• /
• 1995

Quality changes of sausages in refrierated storage for 60 days were investigated. Nine types of sausages produced in Korea were stored at 4$^{\circ}C$(3~5$^{\circ}C$), and then chemical, microbiological, and sensory characteristics were evaluated on every 10 days. The proximate analysis showed considerable variation in fat (23.97%, 17.10~30.20%) with less variation in moisture (51.96%, 48.10~56.30%) and protein (12.96%, 11.40~13.95%), pH value decreased over time averaging from 6.31 to 6.22 with no significant difference. Water activity was consistent over refrigerated storage averaging 0.95. Volatile basic nitrogen (VBN) values were still within 20 mg% though VBN for all types significantly increased over time (p<0.05). Thiobarbituric acid (TBA) values were well below 1.0 though TBA showed significant differences among storage periods (p<0.05). Standard plate counts (SPCs) significantly increased during storage (p<0.05) while coliform group was not counted in all cases. SPCs reached 104 CFU/g in two types after 50 days' storage and were below 105 CFU/g in all types after 60 days' storage. Instrumental texture analysis showed that springiness, adhesiveness, and hardness signficantly decreased over time (p<0.05) while no change was observed in external color. significantly decreased over time the 60-day storage period (p<0.05) while cohesiveness, chewiness and gumminess did not change. Lightness, redness and yellowness of the internal Hunter color significantly decreased over time (p<0.05) while no change was observed in external color. Sensory profile showed that flavor, taste, texture and overall acceptable after 60 days' storage at 4$^{\circ}C$. However, the shelf-life of the samples should be decided in the consideration of the growth rate other spoilage flora coupled with the bacterial growth after 50 days' storage.

• Korean Journal of Community Nutrition
• /
• v.28 no.5
• /
• pp.363-375
• /
• 2023

Objectives: The objective of this study was to identify factors associated with adolescent obesity, as well as any new factors that correlated with a change in the rate of obesity over time. Methods: The study used 5-yearly data collected by the Korea Youth Risk Behavior Survey starting from the year 2006 up until 2021 (data from 2nd, 7th, 11th, and 17th surveys were analyzed). Factors such as demographics, dietary factors, health behavioral factors, and mental health factors were studied. All data were analyzed using IBM SPSS 27.0, employing chi-square tests and multiple logistic regression analysis. Results: This study included data from a total of 255,200 participants. Factors contributing to obesity varied with time. Over the survey duration of 15 years, low academic achievement, parents with low levels of education, low frequency of fruit consumption, low frequency of fast food intake, long periods of being seated, and high levels of stress were significantly associated with a high rate of obesity. Factors that showed a new correlation with an increase in obesity rates included living with single parents, low frequency of muscle strengthening exercises, and experiencing intense sadness and despair in the past year. Factors that were correlated with a change in obesity rates over time included household economic status, frequency of carbonated beverage consumption, frequency of intense physical activity, and frequency of alcohol consumption. Breakfast intake and smoking were not significantly associated with obesity rates in the 15-year period. Conclusions: While several factors associated with obesity remained consistent over time, several new factors have emerged in response to social, economic, and environmental changes contributed to a change in obesity rate over time. Therefore, to prevent and manage adolescent obesity, continuous research into the new emergent factors contributing to obesity is needed.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.26 no.4
• /
• pp.426-435
• /
• 2016

Objectives: The major objective of this study was to analyze stress response after a change to consecutive day shifts from day and night shifts in a motor assembly factory. Methods: Using a survey conducted by a labor union, we collected data on stress response index(SRI), lifestyle factors, work-family conflict and job stress before and after a shift system change. We analyzed the transition on the SRI among 222 workers. The cut-off point for the SRI was a T-score over 60. Results: The high risk stress response group was 20.3% of the population before the shift system change. After the shift system change it decreased to 11.3%. After the shift system change, social support improved, leisure time became more sufficient, work-family conflict declined, and sleep quality in the night shift week improved. In multivariable linear regression, among workers under 40 years old sleep quality on night shift, leisure time sufficiency, social support and work-family conflict contributed to the improvement of stress response. Among workers over 40, work-family conflict contributed to the improvement of stress response. Conclusions: The change to consecutive day shifts improved stress response and mediated with improved nighttime sleep, decreased work-family conflict, increased leisure time and improved work-family conflict.