• Restorative Dentistry and Endodontics
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• 제26권4호
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• pp.341-349
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• 2001

Dental caries is the most common oral disease. There are many factors contributing to its development, but complete understanding and prevention are not fully known. However, it is possible to remineralize the early enamel curious lesion by fluoride containing remineralization solution. Recently the pH-cycling model has been used to examine the effect of fluoride solution on remineralization of artificial caries in vitro as it can closely simulate the conditions encountered in vivo within a carefully controlled environment. The aim of this study was to evaluate the remineralizing effects of supersaturated buffer solutions under pH-cycling model. The specimen with 3mm-diameter was made using mature bovine incisors which has no caries and has sound enamel surface. Early curious lesions were produced by suspending each specimens into demineralization solution at pH 5.0 for 33 hours and the specimen whose surface hardness value ranged from 25 to 45 VHN were used. The pH cycling treatment regimen consisted of 5 min soaks of three treatment solutions four times per days for 15 days and the continuous cycling of demineralization and remineralization were carried out for 15 days. Following the pH-cycling treatment regimen, the specimens' surface microhardness were measured by the Vickers hardness test (VHN) and analyzed by ANOVA and Duncan's multiple-range test. 1. The surface microhardness value of supersaturated solution, Senstime, and Gagline groups were increased after pH cycling, and that of supersaturated solution was significantly Increased compared to saline group(P<0.05). 2. The surface remineralization effect of fluoride containing solutions was accelerated by saliva under pH-cycling mode 3. The pH cycling model was considered appropriate to mimic the intra-oral pH changes when evaluating demineralization and remineralization in vitro. Under the results of above study, salivary remineralization effect can be improved by fluoride containing remineralization solution. The pH-cycling model was considered appropriate to mimic the intra-oral pH changes when evaluating demineralization and remineralization in vitro.

• 기본간호학회지
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• 제3권1호
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• pp.81-95
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• 1996

The purpose of this study was to investigate the effects of breast self-examination teaching methods which are printed material, videotape, demonstration used BSE model on women. The subjects for this study were non-medical professional 88 women in Kwangju. The data was collected from October 16 to November 24, 1995 by means of a structured questionnaire. For measuring BSE knowledge, Kim's(1994) instrument was used ard modified by researcher. For measuring BSE attitude based on health belief, Lee's(1982) & Kim's(1994) instrument was used and modified by researcher. Printed material from literature were reviewed by researcher, 'A woman's guide to breast self-examination' videotape by Nurse Practitioner Creation and BSE simulator by Narco were used 21 attitude scale and 13 knowledge scale were checked before and after teaching methods. The data was analyzed by frequency, paired t-test, ANOVA using the SAS program. The results were as follows : 1. The BSE total knowledge score after having teaching was higher than before, different significantly(t=-14.05, p=0.000). The most effective teaching method on BSE knowledge change was demonstration used BSE model in three teaching methods and was different significantly(F=8.44, p=0.000). 2. The BSE total attitude score after having teaching was changed to more positively, different significantly(t=4.59, p=0.000). The most effective teaching method on positive BSE attitude change was demonstration used BSE model in three teaching methods and was different significantly(F=3.21, p=0.045). 3. The HB score after having teaching was higher than before, and benefits, barriers and health concerns were different significantly(t=-2.51, p=0.014 ; t=-4.53, p=0.000 ; t=-3.71, p=0.000). Susceptibility and seriousness were not different significantly. 4. There were different significantly among knowledge, religion(F=3.92, p=0.013) and child (F=3.08, p=0.08). There were different significantly among attitude, age(F=4.65, p=0.05), mansturation state(F=4.39, p=0.016), and artificial abortion experience(F=5.18, p=0.026). There were different significantly among health concern, age(F=2.50, p=0.068), delivary experience(F=3.22, p=0.076), artificial abortion experience(F=5.46, p=0.023), and feeding(F=6.24, p=0.003). Printed material, videotape, and demonstration used BSE model may be valuable for changing positively knowledge and attitude related to BSE. Demonstration used BSE model was most effective teaching method in this study. Therefore, this study revealed that BSE teaching methods were a useful nursing intervention for promoting practice regularily and exactly on women.

• 산업경영시스템학회지
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• 제3권3호
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• pp.55-58
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• 1980

Today, L.P. model has often been used in solving economic and managemental phenomena. But in case of adopting L.P. model in dealing with practical economic and managemental problems there is a possibility that we have difficulties in solving these problems because of greatness of model size, cost for collecting data, cost for adjusting matrix, and etc. In this respect "Decomposition Algorithm for L.P." has been used in overcoming the difficulties above stated. In this paper therefore, I will try to introduce and them criticize Dantzig -Wolfe's "Decomposition Method" and Kornai - Liptak's "Two - Level Planning".ot;Two - Level Planning".uot;.

• 환경위생공학
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• 제22권4호
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• pp.11-21
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• 2007

The recent investigation indicates that the kinetic constants for anionic ions were merely the result of ion exchange between the algae cell wall surface and the anionic ion. In this study, Zygnema sterile and Lepocinclism textra, floating flagellate alga as the dominant algae strains, were cultivated using HRABR(High Rate Algae Biomass Reactor) and the cultivation conditions were 24 hrs. and 12 hrs. irradiation and it was studied how this algal biomass acts on the biosorption mechanism of anionic N and P. Results are as follows : 1. Calculating the specific chl.-a growth rate using Michaelis-Menten model, the one of 24hrs. irradiation was about 55 times higher than the one of 12 hrs. irradiation 2. Calculating the specific chl.-a growth rate using Kuo model, the one of 24 hrs. irradiation was about 2.26 times higher than the one of 12 hrs. irradiation 3. Langmuir model can apply to the biosorption mechanism of anionic N and P in HRABP. 4. Regarding the chlorophyll-a concentration as unit weight of sorbent, the ion selectivity coefficients for N and P are as follows : $(NH_3-N)+(NO_3-N)$ in 24 hrs. irradiation ; 44.984 $PO_4-P$ in 24 hrs. irradiation ; 24.237 $(NH_3-N)+(NO_3-N)$ in 12 hrs. irradiation ; 1432.851 $PO_4-P$ in 12 hrs. irradiation ; 599.076

• 한국물환경학회지
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• 제27권4호
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• pp.516-522
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• 2011

This study was performed to investigate the removal characteristics of phosphate by adsorption on olivine, which is generated as industrial by-products from quarry. The adsorption of phosphate on olivine was significantly achieved within 1 hour and equilibrated after 3 hours. The adsorption capacity of phosphate was enhanced with decreasing pH. The maximum adsorption capacity was observed to be 0.463 mg/g in the condition of pH 3. The $Ca^{2+}$ and $Mg^{2+}$ ion amount per adsorbent eluted from olivine was increased with decreasing pH. The precipitation test showed that phosphate in aqueous phase under the condition of pH 3 ~ 9 could be eliminated largely by adsorption on olivine, not precipitation. Freundlich adsorption model were successfully applied to describe the adsorption behavior of phosphate on olivine. The $q_m$ of Langmuir adsorption model were 1.3369 mg/g, 1.0544 mg/g, 1.0288 mg/g at pH 3, 6 and 9, respectively. The $K_F$ of Freundlich adsorption model were 0.4247 mg/g, 0.3399 mg/g, 0.2942 mg/g at pH 3, 6 and 9, respectively. The olivine showed high feasibility as a adsorbent for the removal of $PO_4$-P.

• 한국방사선학회논문지
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• 제14권5호
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• pp.651-660
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• 2020

본 연구에서는 보급형 3D 프린터를 이용하여 인체 Femur와 유사한 HU 값을 가진 팬텀을 제작하여 기존 돼지 뼈를 대체할 수 있는지 분석하고자 하였다. 인체 Femur의 HU 값을 알아보기 위해 연령별 총 372명의 데이터를 분석하였다. 보급형 3D 프린터를 이용하여 PLA-Cu 20%를 이용하여 인체 뼈 모형 팬텀을 제작하여 CT 검사하였다. 돼지 뼈는 생후 6개월 된 돼지로 도축된 지 2일이 지난 뼈를 이용하였다. 검사결과 내부채움 80%로 제작한 3D 프린팅 팬텀이 인체의 모든 데이터와 유사한 값이 나타났고(p<0.05) 돼지뼈와는 차이가 있었다(p>0.05). 또한 연령대별 Femur의 HU 값의 경우 연령대가 증가할수록 HU의 값은 줄어드는 것으로 확인 되었다(p<0.05). 3D 프린팅과 HU 값은 적층 높이에 대해서는 약한 음의 상관성을 확인 하였지만 내부 채움에서는 182.13±1.290으로 강한 양의 상관성(R²=0.996)을 확인하였다(p<0.05). 결론적으로 3D 프린팅을 이용한 인체 모형 팬텀이 기존 돼지뼈 팬텀에 비해 인체와 유사한 정도의 HU 값을 나타낼 수 있음을 확인할 수 있었으며 이에 본 연구가 3D 프린터를 이용한 인체 모형 팬텀의 제작에 기초자료를 제공할 수 있을 것이라 사료된다.

• 산업경영시스템학회지
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• 제30권2호
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• pp.15-22
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• 2007

By the early 20 century, "workman" introduced by SONY was the leading portable analog sounder. However, at the same century, workman was pushed out from the portable sounder by iRiver developed by MPMAN.COM. This portable digital sounder is called MP3-Player (MP3P), and has become the most popular portable digital sounder in the current market. This study combined two customer satisfaction models, mobile internet customer satisfaction model (Yu, 2002), and portable communication customer satisfaction model (Bae, 2003), in order to empirically test consumption of MP3P and its satisfaction. The proposed model tested four constructs, company's image, product price, product design and product function, influencing customer satisfaction, which leads to affect customer loyalty. 267 survey responses were analyzed by using structural equation modeling (SEM). The results show that all constructs had significant impact. This study suggests a good understanding of consumer satisfaction and loyalty of MP3P and the future direction of MP3P research regarding to consumer satisfaction.

• Geomechanics and Engineering
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• 제32권3호
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• pp.335-346
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• 2023

For structures with underground basement walls, the soil-structure-interaction between the side soil and the walls affects the response of the system. There is interest in quantifying the relationship between the lateral earth pressure and the wall displacement using p-y curves. To date, passive p-y curves in available limited studies were assumed elastic-perfectly plastic. In reality, the relationship between earth pressure and wall displacement is complex. This paper focuses on studying the development of passive p-y curves behind rigid walls supporting granular soils. The study aims at identifying the different components of the passive p-y relationship and proposing a rigorous non-linear p-y model in place of simplified elastic-plastic models. The results of the study show that (1) the p-y relationship that models the stress-displacement response behind a rigid basement wall is highly non-linear, (2) passive p-y curves are affected by the height of the wall, relative density, and depth below the ground surface, and (3) passive p-y curves can be expressed using a truncated hyperbolic model that is defined by a limit state passive pressure that is determined using available logarithmic spiral methods and an initial slope that is expressed using a depth-dependent soil stiffness model.

• Membrane and Water Treatment
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• 제9권3호
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• pp.173-179
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• 2018

Microcystin-LR, one of algal toxins induced by the eutrophication of a reservoir, is known to be harmful to human by adversely affecting our liver and brain. Hypochlorous acid is very efficient to remove Microcystin-LR in a clear well. The previous researches showed that CT, pH and temperature affected removal rate in batch tests. It was noted that hydrodynamic properties of clear well could also influence its removal rate. A mathematical model was built using an axial dispersion reactor model and software was used to simulate the removal rate. The model consisted of the second order differential equations including dispersion, convection, Microcystin-LR reaction with chlorine. Kinetic constants were obtained through batch tests with chlorine. They were $0.430{\times}10^{-3}L/mg/sec$ and $0.143{\times}10^{-3}L/mg/sec$ for pH 7.0 and 8.1, respectively. The axial dispersion reactor model was shown to be useful for the numerical model through conservative tracer tests. The numerical model successfully estimated the removal rate of Microcyctin-LR in a clear well. Numerical simulations showed that a small dispersion number, low pH and long hydraulic retention time were critical for higher removal rate with same chlorine dosage. This model could be used to optimize the operation of a clear well during an eutrophication season.

• 한국환경보건학회지
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• 제44권6호
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• pp.539-547
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• 2018

Objectives: Ozone ($O_3$) advisories are issued by provincial/prefectural and city governments in Korea and Japan when oxidant concentrations exceed the criteria of the related country. Advisories issued only after exposure to high $O_3$ concentrations cannot be considered ideal measures. Forecasts of $O_3$ would be more beneficial to citizens' health and daily life than real-time advisories. The present study was undertaken to present a simplified forecasting model that can predict surface $O_3$ concentrations for the afternoon of the day of the forecast. Methods: For the construction of a simple and practical model, a multivariate regression model was applied. The monitored data on gases and climate variables from Japan's air quality networks that were recorded over nearly one year starting from April 2016 were applied as the subject for our model. Results: A well-known inverse correlation between $NO_2$ and $O_3$ was confirmed by the monitored data for Iksan, Korea and Fukuoka, Japan. Typical time fluctuations for $O_3$ and $NO_x$ were also found. Our model suggests that insolation is the most influential factor in determining the concentration of $O_3$. $CH_4$ also plays a major role in our model. It was possible to visually check for the fit of a theoretical distribution to the observed data by examining the probability-probability (P-P) scatter plot. The goodness of fit of the model in this study was also successfully validated through a comparison (r=0.8, p<0.05) of the measured and predicted $O_3$ concentrations. Conclusions: The advantage of our model is that it is capable of immediate forecasting of surface $O_3$ for the afternoon of the day from the routinely measured values of the precursor and meteorological parameters. Although a comparison to other approaches for $O_3$ forecasting was not carried out, the model suggested in this study would be very helpful for the citizens of Korea and Japan, especially during the $O_3$ season from May to June.