• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.4
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• pp.573-583
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• 2015

Objectives: This study was carried out to evaluate the effect of noise exposure and aging on changes in hearing threshold level and the relationship between age and noise. Materials: The author selected 274 male shipyard and assembly line workers as the noise exposed group and 582 males not exposed to noise as the general population group. Data were collected from five years of consecutive annual audiometric tests performed from 2008 to 2012. Results: In the general population and noise exposed groups, there was a reverse phenomenon that hearing threshold level for 2009 was lower than that of 2008, which seemed to be due to the learning effect, but from 2010 hearing threshold level increased. In the noise exposed group, the mean hearing threshold level in the left ear was significantly higher than that for right ear. In the general population group, the older was the age, the higher was the hearing threshold level, especially at 4000 Hz. In the general population and noise exposed groups, frequency, age group and noise exposure independently affected hearing threshold level, and there was no relationship between age and noise exposure. Over all frequencies, the change of hearing threshold level was larger in the noise exposed group than in the general population group. In the noise exposed group below thirty years old, the change at 4000 Hz was remarkable. Conclusions: Age and noise exposure seem to affect hearing threshold level independently and contribute to an additive effect on hearing threshold level.

• Journal of Oral Medicine and Pain
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• v.23 no.4
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• pp.327-341
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• 1998

Aims : The purpose of this study was to investigate whether there are any changes in taste sensitivity with advancing age and to see if smoking or oral hygiene can affect the taste sensitivity. Method : Nine hundred and thirty four subjects(458 male and 476 females) were included for the study and they were categorized into 4 age groups( under 20, 20 to 39, 40 to 59, and over 60 age group ). The electrical taste thresholds were measured using an electrogustometer for the 4 different sites in the oral cavity, I.e., tongue tip, tougue alteral, circumvallate papilla, and soft palate. Results : The elctrical taste thresholds were significantly incresed with advancing age in both gender, but the pattern of change is moere abrupt in female after 40. There were not significant differences in electrical taste threshold between smoking and non-smoking people. Taste thresholds were significantly lower in the groups with higher frequency of daily toothbrushing than the groups with lower frequency Conclusion : The electrical taste threshold is increased with aging. It is not influenced by smoking but by toothbrushing.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.71-78
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• 2008

This study aims to identity the age group where driving performance significantly decreases based on the data collected from the Korea Transportation Safety Authority's driver aptitude tests in 2006. The test includes following six driving simulator-based tests: estimation of moving objects' speed, estimation of stopping distance, three tests for drivers' multi-task ability, and kinetic depth perception. These six test results were utilized for the identification of the age threshold applying the CART technique, suggesting driving ability significantly be decreased over 50s. This finding was confirmed by two analyses using the accident history data containing the information of accident and non-accident drivers and the degree of accident severity. The results of this study imply that accident prevention efforts should be enhanced over a wider range of age group than the current practice where the age of 65 is generally applied for the threshold dividing senior and non-senior driver groups.

• Speech Sciences
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• v.8 no.2
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• pp.7-22
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• 2001

This research with 40 hearing impaired children was performed to find out the characteristics of the phonological processes for each age, hearing loss degree and aided threshold degree through the transcriptions. The phonological processes of hearing impaired children are similar to those of normal children with a peculiar type of patterns in phonological processes. The results show that: (1) Between 5 and 6 year old groups the phonological processes were significantly different in palatal backing, glottal replacement and frication; between 6 and 7 year old groups the phonological processes were significantly different in velar fronting, labialization, alveolization and labial assimilation; between 7 and 8 year old groups the phonological processes, labialization, alveolization and alveolar assimilation, however 8 year old group showed more phonological processes than 7 year old group. (2) Between moderately-severe and severe hearing impaired groups, phonological processes were significantly different in the omissions of postvocalic, nasal and velar, stopping and stop assimilation. The differences of severe and profound groups were not found at all. (3) Aided hearing thresholds did not show any significant difference.

• International Journal of Highway Engineering
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• v.17 no.1
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• pp.129-142
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• 2015

PURPOSES : The purpose of this study is to suggest a basis for setting appropriate safety goals specifically related to the threshold zone luminance in a vehicular traffic tunnel. METHODS : In the test, drivers were divided into two groups. One group consisted of all drivers (average drivers) group with an age ratio of drivers holding domestic driver's license and driver group by age to produce threshold zone luminance in the tunnel. The threshold zone luminance produced as a result was used to analyze how it affects the safety level of each driver group and provide a basis for setting an appropriate safety criterion that can be used to determine threshold zone luminance. We used test equipment, test conditions, and ananalysis of threshold zone luminance identical to that reported by ChoandJung(2014) but the values of adaptation luminance in our analys is were expanded to range from100 to $10,000cd/m^2$. RESULTS : Adaptation luminance and threshold zone luminance are found to be related by a quadratic function. The threshold zone luminance needed by older drivers to ensure a certain safety level is significantly higher than that for drivers of other age brackets when adaptation luminance increases. 56% of older drivers are at an increased risk of an accident at the same luminance for which the safety level of average drivers is 75%. The safety level that can be achieved for older drivers increases to above 60% when threshold zone luminance level is set with the goal of attaining a safety level of more than 85% for average drivers. The safety level that can be attained for average drivers is above 90% when the threshold zone luminance is high enough to ensure over 75% in the safety level of older drivers. Results of this study are applicable to highways and others whose designed speed is 100 km/h. CONCLUSIONS : Threshold zone luminance determined on the basis of drivers having average visual ability is of limited value as a performance standard for ensuring the safety of older drivers. Hence, safety level for older drivers should be considered separately from safety levels for drivers with an average ability to avoid risk. Upward adjustment of older drivers' safety level in the process of determining appropriate threshold zone luminance in a vehicular traffic tunnel may bring both tangible and intangible benefit as a result of reducing accidents. However, there is an associated dollar cost arising from installing and operating lights. As a result, the economic impact of these trade-offs should also be considered.

• Journal of Applied Reliability
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• v.17 no.3
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• pp.246-255
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• 2017

Purpose: This study proposes the optimal PM (preventive maintenance) policy of leased equipment for lessee's decision-making using two types of reliability condition. Methods: We consider reliability threshold based PM model. Equipment reliability is estimated and used as condition variable. The effect of repair for maintenance is imperfect and represented by age reduction factor. Results: We provide two PM policies. Policy 1 is focused on minimized total cost. This policy guarantees reliability threshold until last maintenance action. Policy 2 focus on maintaining reliability threshold during leased period. The proposed approach provides optimal reliability threshold under number of PM. Through result, we finally construct decision-making process for lessee using reliability threshold and end of reliability. Conclusion: This study provides two PM policy for lessee's decision-making. Through numerical example, we get a result of optimal reliability threshold, number of PM, optimum alternative under lessee's reliability condition.

• Imaging Science in Dentistry
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• v.50 no.3
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• pp.209-216
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• 2020

Purpose: In India, the age of 14 years is the legal age threshold for child labour. Therefore, in suspected instances of child labour, age assessment plays a crucial role in determining whether a violation of the law on the employment of children has occurred. The aim of this retrospective cross-sectional study was to assess the discriminatory ability of stages of cervical vertebral maturation (CVM) in predicting the legal age threshold of 14 years. Materials and Methods: Routinely taken lateral cephalograms from 408 subjects aged 10 to 18 years were evaluated retrospectively using the CVM stages described by Baccetti et al. Descriptive statistics, accuracy, sensitivity, specificity, positive and negative predictive values, and likelihood ratios were calculated for stages 2, 3, and 4 of CVM. Results: Real age increased as the CVM stage gradually increased. The results of 2×2 contingency tables showed that CVM stage 4 produced an accuracy of 71% and 73%, a false positive rate of 7% and 18%, and a post-test probability of 59% and 68% for boys and girls, respectively. Conclusion: Based on these findings, it can be concluded that the stages of CVM are of limited use for predicting the attainment of the legal age threshold of 14 years. Future studies should investigate whether combinations of skeletal and dental methods could achieve better accuracy and post-test probability.

• Journal of Preventive Medicine and Public Health
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• v.24 no.1 s.33
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• pp.86-92
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• 1991

To test if exposure history to rifle fire or cannonade training during military duty can induce hearing loss, history of personal military service and histroy of gunshot exposure were asked to 228 male college students with self -administrative questionnaire. Otoscopic examination and Rinne's test were performed if any abnormal finding was detected by pure-tone audiometry. Average hearing threshold levels of 500 Hz, 1,000 Hz, 2,000 Hz, 4,000 Hz and threshold levels at 4,000 Hz were calculated for 112 students who were remained after exclusion of cases with history of ear disease, of ototoxic drug administration, and of neuropsychiatric disease, and mean of those were compared between group of students who have completed military duty (completed group) and group of those who have not (not-completed group), and between group exposed (exposed group) and group unexposed to gunshot sound (unexposed group). Mean of average hearing threshold level and mean of threshold levels at 4,000 Hz of completed group and those of exposed group were higher than those of not-completed group and unexposed group, respectively. Proportion of cases that average threshold level was greater than 40 dB or threshold levels at 4,000 Hz was greater than 50 dB were higher also in completed group and exposed group than in duty not-completed group and unexposed group, respectively Multiple linear regression analysis including age, duration of military service, degree of gunshot sound exposure as independant variables and average hearing threshold level as dependant variable, was performed in order to estimate the effect of age on hearing, and any considerable effect of age on hearing could not be found. In conclusion, hearing impairment can be induced by rifle fire or cannonade training.

• Korean Journal of Community Nutrition
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• v.18 no.3
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• pp.223-232
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• 2013

The purpose of the study was to investigate the influence of salt (NaCl) recognition threshold and pleasant salt concentrations of Korean rural elderly subjects on preference of salty food as well as food group consumption patterns. The subjects were 213 elderly people (male 71 and female 142) over 65 and under 90 yr of age from Sunchang area. The higher values were found with male subjects in the areas of basic taste recognition threshold and pleasant concentration level of salt. The taste sensitivity scores of male subjects did not decrease with the increasing age, but female subjects exhibited a significant decrease with the age. The major determinant factor of salt preference of the elderly subjects in this study appeared to be personal pleasant concentration of salt rather than salt recognition threshold level and this trend was more evident in males than in females. The subject group of lower salt pleasant concentration i.e. consuming less salt showed the higher number of fruit and fruit juice intakes per week, and higher MNA (define this) scores were implying that they display more desirable nutritional status. Therefore, nutritional education focused on not only a variety of food consumption but also lowering pleasant salt concentration levels is advised to improve the quality of nutrition in the elderly.

• Journal of Oral Medicine and Pain
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• v.41 no.3
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• pp.85-90
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• 2016

Purpose: The aim of this study was to develop an automated software to extract tooth and pulpal area from sectional cone-beam computed tomography (CBCT) images, which can guarantee more reproducible, objective and time-saving way to measure pulp/tooth volume ratio. Methods: The software program was developed using MATLAB (MathWorks). To determine the optimal threshold for the region of interest (ROI) extraction, user interface to adjust the threshold for extraction algorithm was added. Default threshold was determined after several trials to make the outline of extracted ROI fitting to the tooth and pulpal outlines. To test the effect of starting point location selected initially in the pulpal area on the final result, pulp/tooth volume ratio was calculated 5 times with different 5 starting points. Results: Navigation interface is composed of image loading, zoom-in, zoom-out, and move tool. ROI extraction process can be shown by check in the option box. Default threshold is adjusted for the extracted tooth area to cover whole tooth including dentin, cementum, and enamel. Of course, the result can be corrected, if necessary, by the examiner as well as by changing the threshold of density of hard tissue. Extracted tooth and pulp area are reconstructed three-dimensional (3D) and pulp/tooth volume ratio is calculated by voxel counting on reconstructed model. The difference between the pulp/tooth volume ratio results from the 5 different extraction starting points was not significant. Conclusions: In further studies based on a large-scale sample, the most proper threshold to present the most significant relationship between age and pulp/tooth volume ratio and the tooth correlated with age the most will be explored. If the software can be improved to use whole CBCT data set rather than just sectional images and to detect pulp canal in the original 3D images generated by CBCT software itself, it will be more promising in practical uses.