• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.4
• /
• pp.9-18
• /
• 2016

In this research, the modeling of erosive burning and analysis of effective parameters were carried out for the application of fluid-structure integration analysis. The manufacture, test, and analysis of erosive burning motors were carried out to estimate the erosive burning applying Lenoir & Robillard model considering effective parameters. The erosive burning phenomenon was detected from experimental results. Erosive burning model and its effective parameters were evaluated and analyzed considering existence of aluminum in propellant, relationship among erosive burning coefficients according to characteristic length, effect of grain initial temperature. The erosive burning model was applied to the fluid-structure integration analysis, and the estimated results were close to the experimental results.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.3
• /
• pp.69-76
• /
• 2012

An achieving method of highly progressive pressure gradient is presented to enhance the missile ejection system's performance by using a gas generator in the condition of preventing erosive burning. To obtain and confirm a stable burning, a ground burning test was performed to evaluate the new methods of a radial-hole and a multi-row propellant grain. The test results show that a radial-hole grain takes good effect on erosive burning and not on ejection performance. On the other hand, a multi-row grain which reduces the length-to-diameter ratio(L/D) of grain is very effective to prevent the erosive burning and to enhance the ejection performance simultaneously.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.432-439
• /
• 2011

An achieving method of highly progressive pressure gradient is presented to enhance the missile ejection system's performance by using a gas generator in the condition of preventing erosive burning. To obtain and confirm a stable burning, a ground burning test was performed to evaluate the new methods of a radial-hole and a multi-row propellant grain. The test results show that a radial-hole grain takes good effect on erosive burning and not on ejection performance. On the other hand, a multi-row grain which reduces the legnth-to-diameter ratio(L/D) of grain is very effective to prevent the erosive burning and to enhance the ejection performance simultaneously.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.2
• /
• pp.312-322
• /
• 1998

There are many concerns about the erosive effect of acidic beverage. In this study, the erosive effect of bovine enamel caused by $Pepsi-Cola^{(R)}$(pH 2.41) and rehardening effect by intraoral exposure were determined by microhardness test and SEM. The bovine enamel specimen was imbedded in 100ml $Pepsi-Cola^{(R)}$ during 5 minutes and exposed to the intraoral environment with removable resin plate. The microhardness test was performed after 1 hr, 24 hrs, and 48 hrs. The results obtained from this study can be summarized as follows ; 1. The microhardness value was significantly (p<0.05) reduced by cola beverage, and significantly (p<0.05) increased after 1 hr and 24 hrs respectively. 2. The difference in the microhardness between 24 hrs group and 48 hrs group was not significant (p>0.05) and microhardness value of 48 hrs group was significantly less than that of initial group (p<0.05). 3. The erosive effect of cola beverage and remineralization effect by intraoral exposure were visualized by the SEM photo. But, the enamel surfaces did not return to their original state.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.1
• /
• pp.739-744
• /
• 2020

This study evaluates the erosive potential and effects of mixed alcohols by analyzing the pH, titratable acidity, and fluorescence loss degree (△F). Following alcohol groups were investigated: Soju, Calamansi+soju, Yakult+soju, Cola+soju, and Energy drink+soju. The ratio of soju:beverage in the alcohol mixtures was 7:3. Ed. Notes: The sentence lacks clarity. Please review if the edit correctly portrays the meaning. If not, please revise appropriately. Measurement of the pH and titratable acidity (the amount of 1M NaoH solution required to raise to pH 5.5 (TA5.5) and 7.0 (TA7.0)) of alcohols was achieved by stirring with pH meter. The erosive effect of the alcohol mixtures on bovine tooth (△F) after 1, 2, 4, and 6 hours exposure were analyzed by quantitative light-induced fluorescence (QLF-D). All the mixed alcohols in this study showed an acidic pH, lower than 4.5. The average pH of mixed alcohols was 3.17 ± 0.50 whereas the pH of Soju was 8.6 ± 0.01. The TA5.5 and TA7.0 values of the mixed alcohols were 0.5~18 and 0.5~23.5, respectively. △F of the three tested mixed alcohol groups (except yakult+soju group) were observed to increase in a time-dependent manner. The calamansi mixed alcohol had the highest acidity potential and erosive effect among the tested groups. Taken together, the results indicate that the mixed alcohols have a strong erosive effect and potential on dental enamel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.1115-1121
• /
• 2017

In order to obtain high thrust at the beginning of the flight, the solid rocket motor with large initial burning surface area was designed and tested. From the static firing test, lower initial thrust was obtained compared with the expected thrust based on the internal ballistic prediction due to the negative erosive burning effect which reduced the burning rate estimated by APN Law. In addition, the radial mode combustion instability was observed with 8 fins grain configuration. This instability was removed after the odd number of fins were used.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.8
• /
• pp.774-779
• /
• 2009

A numerical modelling was performed to predict unsteady combustion processes for the AP/HTPB/Al propellant in a solid rocket motor. Its results were compared with the experimental data. Temporal pressure development was found to match quite well with measured data. A change in propellant surface was traced using the moving grid. The propellant thickness change was also observed to confirm the erosive burning effect.

• Restorative Dentistry and Endodontics
• /
• v.47 no.3
• /
• pp.29.1-29.10
• /
• 2022

Objectives: This study aimed to investigate the anti-erosive/abrasive effect of resin infiltration of previous deproteinized dentin. Materials and Methods: Dentin slabs were randomly assigned to 3 groups (n = 15): Control (no deproteinization; no resin infiltrant applied), RI (no deproteinization; resin infiltrant applied), and DRI (deproteinization; resin infiltrant applied). After undergoing the assigned treatment, all slabs were subjected to an in vitro cycling model for 5 days. The specimens were immersed in citric acid (0.05 M, pH = 3.75; 60 seconds; 3 times/day) and brushed (150 strokes). Between the challenges, the specimens were exposed to a remineralizing solution (60 minutes). The morphological alterations were analyzed by mechanical profilometry (㎛) and scanning electron microscopy (SEM). Data were submitted to one-way analysis of variance (ANOVA) and Tukey tests (p < 0.05). Results: Control and RI groups presented mineral wear and did not significantly differ from each other (p = 0.063). DRI maintained a protective layer preserving the dentin (p < 0.001). After erosive/abrasive cycles, it was observed that in group RI, only 25% of the slabs partially evidenced the presence of the infiltrating, while, in the DRI group, 80% of the slabs presented the treated surface entirely covered by a resin-component layer protecting the dentin surface as observed in SEM images. Conclusions: The removal of the organic content allows the resin infiltrant to efficiently protect the dentin surface against erosive/abrasive lesions.

• Gut and Liver
• /
• v.12 no.6
• /
• pp.633-640
• /
• 2018

Background/Aims: Obesity is a risk factor for gastroesophageal reflux disease (GERD), with several studies demonstrating positive associations between body mass index (BMI) and GERD symptoms. However, little is known about the effect of BMI changes on erosive esophagitis (EE). In this study, we investigated whether BMI reduction could resolve EE. Methods: A retrospective cohort study was performed to assess the natural course of EE according to changes in BMI. Participants undergoing health check-ups from 2006 to 2012 were enrolled, and 1,126 subjects with EE were included. The degree of esophagitis was measured by upper endoscopy and serially checked over a 5-year follow-up. Logistic regression and Cox proportional hazards models were used to investigate the association between BMI reduction and EE resolution. Results: Substantial weight loss is associated with EE resolution. The adjusted odds ratio for EE resolution was 1.44 (95% confidence interval [CI], 1.09 to 1.92) among participants with a decrease in BMI compared to those with no decrease in BMI. The EE resolution rate was related to the degree of BMI reduction. The effect of weight loss on EE resolution was higher among subjects who lost more weight. Compared with subjects with no decrease in BMI, the hazard ratios for EE resolution were 1.09 (95% CI, 0.89 to 1.35), 1.31 (95% CI, 1.01 to 1.72) and 2.12 (95% CI, 1.44 to 3.12) in subjects with BMI reductions of ${\leq}1$, 1-2, and >$2kg/m^2$, respectively. Conclusions: EE resolution is associated with a decrease in BMI, and weight loss is potentially an effective GERD treatment.

• Journal of Korean society of Dental Hygiene
• /
• v.22 no.5
• /
• pp.461-468
• /
• 2022

Objectives: To investigate the effect of several elder-friendly foods on oral health and suggest guidelines for proper food intake. Methods: Six elderly-friendly foods (liquid type) and two control groups (mineral water and mixed coffee) were selected for this study. The pH of the food was measured using a calibrated pH meter, and the titratable acidity was determined using 1 M NaOH until 7.0 (TA 7.0). The screening method suggested by the International Organization for Standards was performed using an undersaturated hydroxyapatite solution to determine the difference between the initial and final pH of the screening solution (△pH). In addition, the sugar content was measured and expressed as Brix (%). Results: All the elder-friendly foods tested in this study showed a neutral pH (6.68-7.35), similar to mineral water (pH 7.84). The range of TA 7.0 values was 0.00-0.54 ㎖. The changes in pH determined using the screening solution confirmed that the largest change in pH was found in Careon (△pH 1.14±0.02), which has no erosive potential. Nevertheless, all elder-friendly foods had higher sugar content than the negative control group. Conclusions: Low tooth erosive potential was found in elder-friendly foods, but these foods showed high sugar content.