• The Journal of the Acoustical Society of Korea
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• v.11 no.2
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• pp.59-67
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• 1992

Recently, the problem which actively control the unwanted noise propagated from the technical structure by the generated secondary sound has become considerable topic from the environmental preservation point of view. In most of these studies, active noise control deals with a plane wave propagation at low frequency using adaptive filtering techniques. On the other hand, in real acoustic systems are mostly short due to the limitation of geometric configuration. In this case, the acoustic properties such as reflections and resonances inside the acoustic system should be considered. In this paper, the acoustic modeling method for short length duct was introduced using the transfer matrix method, and the active noise control problem was investigated with \implementation of FIR filter for the transfer function of control system derived from this modeling method. The identification methods for the acoustic model of actual control system was proposed by numerical computation technique based on the estimation of optimal FIR filter coefficients. The acceptable attenuation on the real acoustic system and stability of the controller are predicted in this computational simulation.

• Journal of the Korean Home Economics Association
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• v.27 no.4
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• pp.85-103
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• 1989

The purpose of this study is to figure out the urban low-income consumers' present possesion condition of electric appliances, the way of purchasing, shopping scope of groceries and electric appliances, and the shopping scope and information seeking behavior of groceries and electric appliances according to the socioeconomic variables, and the shopping scope of electric appliances according to the way of paying price. For this purpose 129 low-income consumers living in Inchon were interviewed through questionnares. Finally 100 questionnares were analyzed. The first major of this study is that the possesion rates of color television set and refrigerator are comparativelyl high, while those of washing machine, record player and camera are low. In case of electric appliances, consumers usually purchase things on credit and as a shopping place, they usually go to a commercial agent. In case of groceries, they usually buy things for cash, and in case of one price labeled groceries they usually buy things at a supermarket. Second, according to the way of paying price, the shopping scope of some electric appliances is broader in case of purchase for cach than in case of purchase on credit. Third, the shopping scope and information seeking behavior classified by the socioeconomic variables according to the income, age and education. That is as the income and education become higher and the age becomes lower, the shopping scope becomes broader, mass media information source is much more uaed and the frequency of seeking becomes higher. Through this study, I would like to suggest the followings. (1) The problem of low-income consumers is closely connected with the low education level, so it can be solved a bit through consumer education. (2) Especially the consumers' problem is more serious in case of those who are aged and get very low income and education. Therefore special attention is needed to those consumers.

• Journal of the Korean Home Economics Association
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• v.51 no.2
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• pp.195-206
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• 2013

This study was conducted in order to investigate the variables that relate and affect the internalizing and externalizing problems of multicultural children. 159 multicultural children in the $3^{rd}{\sim}6^{th}$grade were selected from elementary schools in Gwangju and the Jeollanamdo area. The data was analyzed by using the frequency, Cronbach's ${\alpha}$, t-test, ANOVA, Pearson's correlation and hierarchical regression by SPSS 12.0 program. The results were as follows: first, the internalizing problems were different according to the socio-demographic variable: (gender, subjective economic level), multicultural characteristic variable: (mother's communication ability, likability of mother's nationality, etc.), parent-child relationship variable: (relationship with mother, relationship with father) and social support variable: (peer support, teacher support). Further, the externalizing problems were different according to the socio-demographic variable: (gender), multicultural characteristic variable: (mother's nationality, mother's communication ability, etc.), parent-child relationship variable: (relationship with mother, relationship with father) and social support variable: (peer support, teacher support). Second, the influential variables regarding the internalizing problems were children's stress from cultural adaptability and the likability of the mother's nationality of the multicultural characteristic variable group, peer support of the social support variable group and the subjective economic-level of the socio-demographic variable group. Moreover, the influential variable on the externalizing problems was children's stress from the cultural adaptability of the multicultural characteristic variable group. The most influential variable of such variables was children's stress from cultural adaptability of the multicultural characteristic variable group. The results of this study will provide information for the development of educational and therapeutic intervention program for multicultural children.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.219-225
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• 2019

There is a problem with the existing method of selecting the difficulty levels of Hanja characters. Some Hanja characters selected by the existing methods are different from Sino-Korean words used in real life and it is impossible to know how many times the Hanja characters are used. To solve this problem, we measure the difficulty of Hanja characters using the multiple regression analysis with the frequency as the features. Based on the elementary textbooks, FWS and FHU are counted. A questionnaire is written using the two frequencies and stroke together to answer the appropriate timing of learning the Hanja characters and use them as target variables for regression. Use stepwise regression to select the appropriate features and perform multiple linear regression. The R² score of the model was 0.1105 and the RMSE was 0.1105.

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.179-199
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• 2012

Purpose: This study was conducted to prepare the fundamental data on oral hygiene of the elderly and to assess the behavior of oral hygiene, subjective oral health, oral health problem among the elderly, and to contribute to successful enhancement of life in their declining years. Methods: The author surveyed the behavior of oral hygiene, subjective oral health, oral health problem to 192 elderly at a health center of Busan using structured self- administered questionnaire from Nov. 2nd 2009 to Feb. 10th 2010. Collected data were analysed by SPSS WIN 18.0 statistical program for frequency, percentage production, ${\chi}^2$ (Chi-square) verification, t-test, One-way ANOVA, Logistic Regression. Results: The distribution of total subjects by oral health behaviors were 56.8% for "have ever trained how to tooth brushing", 76.6% for "correctly performed tooth brushing by himself ", 71.8% for "tooth brushing a day is two times and less", 87.5% for "it doesn't tooth brushing in meals and after" and 53.6% for "it doesn't use the facility for oral health", respectively. The distribution of total subjects by the state of perceived oral health were 51.0% for "feel the oral discomfort", 51.6% for "feel the comfortable chewing on starchy food", respectively. The mean point of perceived oral health by general characteristics of total subjects were statistically significant difference in sex, type of medical insurance, smoke, exercise, and chronic disease. The mean point of perceived oral health by oral health behaviors of total subjects were statistically significant difference in educational experience on tooth brushing, recognition for tooth brushing by himself, tooth brushing a day, and tongue cleaning. The risk factors of perceived oral health were type of medical insurance and chronic disease in general characteristics, tooth brushing in meals and after and tooth brushing a day, and tongue cleaning in oral health behaviors. Conclusion: The author recommend to the prevention of chronic disease, carry out the tooth brushing in meals and after, three times and over tooth brushing a day and tongue cleaning for oral health. and the author consider that it need to prepare the active countermeasure to oral health such as reeducation for oral health and supply to the tongue cleaner.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.2
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• pp.159-164
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• 2016

A wireless communication system is required to be implemented with the low power circuits because it uses a battery having a limited energy. Therefore, the current mode circuit has been studied because it consumes constant power regardless of the frequency change. However, the clock-feedthrough problem is happened by leak of stored energy in memory operation. In this paper, we suggest the current memory circuit to minimize the clock-feedthrough problem and introduce a technique for ultra low power operation by inducing dynamic voltage scaling. The current memory circuit was designed with BSIM3 model of $0.35{\mu}m$ process and was operated in the near-threshold region. From the simulation result, the clock-feedthrough could be minimized when designing the memory MOS Width of $2{\mu}m$, the switch MOS Width of $0.3{\mu}m$ and dummy MOS Width of $13{\mu}m$ in 1MHz switching operation. The power consumption was calculated with $3.7{\mu}W$ at the supply voltage of 1.2 V, near-threshold voltage.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.7 no.4
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• pp.179-186
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• 2012

The purpose of this research is to analyze how the suicide prevention affects private soldiers' stress-coping method, problem-solving ability, depression, and idea of suicide. In order to achieve such research hypothesis, Air Force ${\bigcirc}{\bigcirc}$ Unit has previously classified 64 soldiers, who have signs of suicide, and are assorted to have suicidal symptoms by the Unit, and think that they have such symptoms and need our program. Following that, overall 16 times of suicide prevention program was carried out for them. For a statistical process of collected materials after testing the effectiveness of Korean Soldiers suicide prevention program, we practiced Frequency Analysis, Analysis of Variance, Correlation Analysis, and Paired t-test by using the statistical package program of SPSS 12.0 for Windows. In result, suicide prevention program shows positive effects upon improving stress-coping method and problem-solving ability as well as reducing depression and suicide thoughts.

• Journal of Preventive Medicine and Public Health
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• v.24 no.3 s.35
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• pp.328-338
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• 1991

To find out the state of illness, patterns of medical care utilization, and factors which determine medical care utilization for aged we surveyed 679 rural old persons who live in the Chungnam province from Jan. 10 1991 to Jan. 19. The major findings of this study were as follows : 1. The morbidity rate of chronic illness during last 3 months was 56.4% for all surveyed old persons ; 58.7% for female and 52.8% for male. 2. As expected, 80 years old or above group showed the highest morbidity rate, 60.2% and the 65-69 years age group was the lowest, 50.5%. 3. Old persons who are householder, whose family income is less than 290,000 won per month, and who receive benifits from the public medical assistance program had relative higher morbidity rate than other groups and the difference was statistically significant (p<0.05). 4. The most frequent chronic illness was musculoskeletal disease, 49.6% ; the disease from which the aged had suffered for the longest period was gastrointestinal, 11.6yrs : the cerebrovascular was the disease which inflicts the lowest level of physical ability. 5. 67.1% of 383 persons who were suffering from chronic illness were in need of medical care but unmet ; among the remaining 32.9% who utilized medical care, 19.2% utilized it in local clinics or hospital OPD and 15% in th health centers or subcenters. 6. Old person who are married, whose sons are householder and whose family income is 500,000 won or above per month showed relative higher utilization rate than other groups and the difference was statistically significant (p<0.05). 7. The most common reason why the aged did not utilize, in spite of, need medical care was economic problem, 35.4%. For the aged whose family income per month is 500,000 won or above, however the most common reason was tolerable symptom, 46.9% while persons who answered economic problem were 6.1% of them, the lowest frequency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.617-624
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• 2011

The two-dimensional sloshing problem in a rigid rectangular tank with a free surface is considered. The flow is generated by a container in harmonic motion in time along the horizontal axis, i.e., a container excited by u=Asin($2{\pi}ft$) where u denotes the container velocity imposed externally, A is the amplitude of the oscillation velocity, and f is the frequency of oscillation. Experimental apparatus is arranged to investigate the large-amplitude sloshing flows in off-resonant conditions, where the large amplitude means that A~O(1), and the distance, S, is comparable to the breadth, L, of the container, i.e., L/S~O(1). Comprehensive particle image velocimetry (PIV) data are obtained, which show that the flow physics of the nonlinear off-resonant sloshing problem can be characterized into three peculiar free surface motions: standing-wave motions similar to those of linear sloshing, a run-up phenomenon along the vertical sidewall at the moment of turn-over of the container, and gradually propagating bore motion from the sidewall to the interior fluid region, like a hydraulic jump.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.26-35
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• 2007

The vehicle of urban transit is a complex system that consists of various electric, electronic, and mechanical equipments, and the maintenance cost of this complex and large-scale system generally occupies sixty percent of the LCC (Life Cycle Cost). For reasonable establishing of maintenance strategies, safety security and cost limitation must be considered at the same time. The concept of system reliability has been introduced and optimized as the key of reasonable maintenance strategies. For optimization, three preceding studies were accomplished; standardizing a maintenance classification, constructing RBD (Reliability Block Diagram) of VVVF (Variable Voltage Variable Frequency) urban transit, and developing a web based reliability evaluation system. Historical maintenance data in terms of reliability index can be derived from the web based reliability evaluation system. In this paper, we propose applying inverse problem analysis method and hybrid neuro-genetic algorithm to system reliability optimization for using historical maintenance data in database of web based system. Feed-forward multi-layer neural networks trained by back propagation are used to find out the relationship between several component reliability (input) and system reliability (output) of structural system. The inverse problem can be formulated by using neural network. One of the neural network training algorithms, the back propagation algorithm, can attain stable and quick convergence during training process. Genetic algorithm is used to find the minimum square error.