• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1025-1031
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• 2023

We aimed to evaluate the radiation dose and image quality by changing the Scout view voltage in low-dose chest CT (LDCT) and applying scan parameters such as AEC (auto exposure control) and ASIR (adaptive statistical iterative reconstruction) to find the optimal protocol. Scout view voltage was varied at 80, 100, 120, 140 kV and after measuring the dose 5 times using the existing low-dose chest CT protocol, the appropriate kV was selected for the study using the Dose report provided by the equipment. After taking a basic LDCT shot at 120 kV, 30 mAs, ASIR 50% was applied to this condition. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed by measuring Background noise (B/N). For dose comparison, CTDI_vol and DLP provided by the equipment were compared and analyzed using the formulas. The results indicated that the protocol of scout 140 + LDCT + ASIR 50 + AEC reduced radiation exposure and improved image quality compared to traditional LDCT, providing an optimal protocol. As demonstrated in the experiment, LDCT screenings for asymptomatic normal individuals are crucial, as they involve concerns over excessive radiation exposure per examination. Therefore, applying appropriate parameters is important, and it is expected to contribute positively to the public health in future LDCT based health screenings.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1177-1184
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• 2011

One of the main objectives of noise control act is to define and ensure application and respect of noise exposure limits. Most advanced countries have prepared a legal framework for noise limits either by national laws, ordinances or municipal by-laws. A large number of advaced countries have adopted the Leq index for the main sources of noise(road, railway, industry). The exception is aircraft noise for which regulatory practice is highly disparate. These differences in the indices adopted, the periods and areas to which regulations apply, definitions of measurement conditions and ways in which noise levels are calculated make it difficult to compare the current advanced countries standards. This study presents the current noise abatement policy of the advanced countries and proposes the improvement of the current noise abatement policy of Korea to catch up with it of the advanced countries.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.264-267
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• 2008

Relationship between exposure to combined noise sources and community annoyance have been investigated. Social surveys were conducted in urban spaces near the construction site with road traffics. The question relating to noise annoyance was answered on an 11-point numerical scale and 5-point verbal scale according to ISO 15666. The questionnaire also contained demographic factors, interference with daily activities, health-related symptoms, and noise sensitivity. Noise levels were measured in terms of A-weighted equivalent level ($L_{Aeq}$), and noise mapping technique was applied to predict the noise levels of urban spaces. Synthesis curves for the relationship between noise levels and percentage highly annoyed for combined noise sources were derived, and compared to the curves from a single noise source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.558-567
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• 2011

One of the main objectives of noise control act is to define and ensure application and respect of noise exposure limits. Most advanced countries have prepared a legal framework for noise limits either by national laws, ordinances or municipal by-laws. A large number of advaced countries have adopted the $L_{eq}$ index for the main sources of noise (road, railway, industry). The exception is aircraft noise for which regulatory practice is highly disparate. These differences in the indices adopted, the periods and areas to which regulations apply, definitions of measurement conditions and ways in which noise levels are calculated make it difficult to compare the current advanced countries standards. This study presents the current noise abatement policy of the advanced countries and proposes the improvement of the current noise abatement policy of Korea to catch up with it of the advanced countries.

• Journal of the Korea Society of Computer and Information
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• v.22 no.6
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• pp.149-156
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• 2017

In this paper, we propose to enhance a Physical working conditions to decrease absence from work. we demonstrated the correlation of worker's absence with various environmental factors in workplace by surveying 6,962 workers. As result, first, concerning exposure to physical work factors, most of them complained of vibration, and concerning exposure to improper working posture, most of them complained of repetitive arm and hand motions. Second, the absence experience had correlations with age, monthly income, smoking, number of employees, long term working, and shift work, and of the physical factors, hand vibration, noise, high temperature, low temperature and improper working posture had correlations with physical pain posture, movement of people and carrying heavy materials. Third, experience of exposure to hand vibration, noise and low temperature of the physical factors had impact on absence, and of the improper working posture, physical pain posture and carrying heavy stuff had impacts on absence. Through this study, it was found that of the work factors of Korean workers, physical factors and improper working posture had impacts on absence. The results of this study confirmed that physical factors and inappropriate working posture among work factors influenced the absenteeism. Therefore, it is required to improve the work environment regarding physical risk factors and prepare a systematic management plan.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.139-148
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• 2020

The purpose of this study is to propose a method to optimize the performance of Digital Radiography (DR) by analyzing the effect of exposure time change on the stability of radiation output and image quality. The experimental method was used to change the exposure time to 50 msec, 100 msec, 200 msec, and 400 msec so that the Percentage Average Error (PAE), Time-to-Radiation Dose Curve, Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR) and theses analysis were performed to evaluate the normal operation of parameters, radiation output and image quality. As a result, all the parameters used in the experiment showed the Percentage Average Error in the normal range, and the shorter the exposure time, the stability of radiation output and image quality decrease. In conclusion, it was found that the performance of Digital Radiography can be optimized when stable radiation output and image quality are applied by applying 100 msec ~ 200 msec exposure time.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.1
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• pp.51-70
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• 1995

The purpose of this investigation was to compare the direct digital radiographic system with film-based digital imaging system using Ektaspeed and Ektaspeed Plus film with respect to image characteristics and detectability and evaluate the sensor noise with the use of subtraction method. Direct digital radiographic system which used was Sens-A-Ray system(Regam Medical Systems, Sundsvall, Sweden) and film-based digital imaging system was composed of Macintosh II ci computer, high resolution Sony XC-77 CCD camera and intraoral x-ray film(Kodak Ektaspeed film, Kodak Ektaspeed Plus film). Images were taken by using CCD sensor of Sens-A-Ray system, Ektaspeed film and Ektaspeed Plus film with variable exposure time(0.06s, 0.1s, 0.16s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, O.8s, LOs), 5 times at each exposure time. And then ektaspeed films and ektaspeed plus films were digitized using CCD camera. Image groups were divided into 3 groups; Sens-A-Ray group(direct digital radiographic system), Ektaspeed group and Ektaspeed Plus group (film-based digital imaging system) They were assessed by the following three aspects; image density, image contrast and detectability and sensor noise of Sens-A-Ray system was also evaluated. The results were as follow : 1. S group showed higher density than E , EP group except at the low exposure time(p<0.01). 2. S group showed higher contrast than E,EP group except at the high exposure time(p<0.01). 3. All groups showed good detectability at the each proper exposure time. Lowest exposure time which shows maximum detectability in S,EP group(0.5s) was lower than that in E group(0.6s). 4. Sensor noise of Sens-A-Ray system generally increased according to exposure time. On the basis of the above results, it was considered that Sens-A-Ray system could show higher speed, higher contrast than Ektaspeed, Ektaspeed Plus film except at too high and low exposure time and the same detectability as the conventional intraoral film.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.765-771
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• 2019

Noise in skull X-ray imaging is inevitable, which reduces imaging quality and diagnostic accuracy and increases errors due to the nature of digital imaging devices. Increasing the dose can attenuate noise, but that could lead to big problems with higher exposure dose received by patients. Thus, noise reduction algorithms are actively being studied at low doses to solve dose problems and reduce noise at the same time. Wiener filter and median filter have been widely used, with the disadvantages of poor noise reduction efficiency and loss of much information about imaging boundary. The purpose of this study is to apply total variation (TV) algorithm to skull X-ray imaging that can compensate for the problems of previous noise reduction efficiency to assess quantitatively and compare them. For this study, skull X-ray imaging is obtained using various kVp and mAs using the skull phantom using the X-ray device of Siemens. In addition, contrast to noise ratio (CNR) and coefficient of variation (COV) are compared and measured when noisy image, median filter, Wiener filter and TV algorithm were applied to each phantom imaging. Experiments showed that when TV algorithms were applied, CNR and COV characteristics were excellent under all conditions. In conclusion, we've been able to see if we can use TV algorithm to improve image quality and CNR could be seen to increase due to the decrease in noise as the amount of increased mAs. On the other hand, COV decreased as the amount of increased mAs, and when kVp increased, noise was reduced and the transmittance was increased, so COV was reduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.900-904
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• 2005

Studies of community annoyance caused by civil aircraft noise exposure were carried out in fifteen areas near Gimpo and Gimhae international airports, Korea, to accumulate social survey data in Korea and to assess the relationship between aircraft noise level and degree of annoyance. Aircraft noise levels were measured automatically by airport noise monitoring system, B&K type 3597. A social survey was carried out people living within In meters of noise measurement points, as a rule. Questionnaires were only aggregated face-to-face interviews using various questions which concerned with demographic, degree of noise annoyance, interference with daily activities and health-related symptoms. The questions of noise annoyance were answered on an 11-point numerical scale. The respondents, from 18 to 70 years of age, were randomly selected and completed the questionnaire themselves. The total number of respondents for the questionnaires was 554.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.1 no.2
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• pp.173-191
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• 1994

This descriptive-correlational study was conducted to exam if there were relation between noise level and reaction to noise of inpatient. The purpose of this study was to provide a basic data for comfort of patient hospitalized. The hypotheses of the study are : 1. The higher perceived noise level of inpatient, the higher reaction level to noise. 2. The higher perceived noise level of inpatient, physiological reaction level to noise. 3. The higher perceived noise level of inpatient, the higher emotional reaction level to noise. The participant were 153 patients hospitalized in one general hospital. The research instruments used for this study were noise scale and reaction of patient scale developed by the author. Data was collected over a period of 10 days from the 9th of July to the 18th of July, 1994. Statistical analysis of the data included percentage, t-test, ANOVA and Scheffe test. Examination of the hypotheses was done by use of pearson correlation coefficient. The results are summarized as follows ; 1. The mean score of noise level was 2.24. Among noise factors reported by the subjects, that which ranked highest was 'Conversation of Visitors'(2.82). Next were 'noise of handling receptacle'(2.73), 'the others noise from outside'(2.73) and 'Conversation of supporter'(2.71). 2. The mean score of reaction level to noise was 2.19, physiological reaction level 2.04 and emotional reaction level 2.37. Among Physiological reaction to noise reported by the subjects, that which ranked highest was 'tired'(2.39). Next were 'sweating'(2.22) and 'headache'(2.20). Among emotional reaction to noise reported by the subjects, that which ranked highest was 'to irritate nerve'(2.53). Next were 'disturbing rest'(2.51) and 'to disturb sleep'(2.46). 3. The relationship between perceived noise level of inpatient and reaction to noise was statically significant (r=0.599, p=.0001). The relationship between perceived noise level of inpatient and physiological reaction to noise was statically significant (r=0.554, p=.0001). The relationship between perceived noise level of inpatient and emotional reaction to noise was statically significant(r=0.535, p=.0001). Thus hypothese 1, 2, 3 were supported. 4. There were significant differences between noise level of inpatient, admission periods, mobility of physical condition and exposure level to noise. 5. There were significant differences between physiological reaction level to noise, admission periods, mobility of physical condition and operation Yes or No. 6. There were significant difference between emotional reaction level to noise, admission periods, mobility of physical condition and exposure level to noise.