• Tribology and Lubricants
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• v.36 no.2
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• pp.105-115
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• 2020

This paper presents a numerical study on the rotordynamic analysis of a dual-spool turbofan engine in the context of blade defect events. The blades of an axial-type aeroengine are typically well aligned during the compressor and turbine stages. However, they are sometimes exposed to damage, partially or entirely, for several operational reasons, such as cracks due to foreign objects, burns from the combustion gas, and corrosion due to oxygen in the air. Herein, we designed a dual-spool rotor using the commercial 3D modeling software CATIA to simulate blade defects in the turbofan engine. We utilized the rotordynamic parameters to create two finite element Euler-Bernoulli beam models connected by means of an inter-rotor bearing. We then applied the unbalanced forces induced by the mass eccentricities of the blades to the following selected scenarios: 1) fully balanced, 2) crack in the low-pressure compressor (LPC) and high pressure compressor (HPC), 3) burn on the high-pressure turbine (HPT) and low pressure compressor, 4) corrosion of the LPC, and 5) corrosion of the HPC. Additionally, we obtained the transient and steady-state responses of the overall rotor nodes using the Runge-Kutta numerical integration method, and employed model reduction techniques such as component mode synthesis to enhance the computational efficiency of the process. The simulation results indicate that the high-vibration status of the rotor commences beyond 10,000 rpm, which is identified as the first critical speed of the lower speed rotor. Moreover, we monitored the unbalanced stages near the inter-rotor bearing, which prominently influences the overall rotordynamic status, and the corrosion of the HPC to prevent further instability. The high-speed range operation (>13,000 rpm) coupled with HPC/HPT blade defects possibly presents a rotor-case contact problem that can lead to catastrophic failure.

• Korean Journal of Community Nutrition
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• v.14 no.1
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• pp.55-66
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• 2009

This study was aimed to examine nutrition knowledge, dietary attitudes, and eating habits of elementary school students and to examine if their characteristics differ by gender. Subjects were 5th and 6th graders of an elementary school (n = 317) in Seoul, and the survey was done during July 2007. Mean height, weight, BMI of subjects was 148.1 cm. 41.7 kg, 19.0, and 14.3% of subjects were categorized as the overweight/obese group. Anthropometric data were not significantly different by gender. Mean score of nutrition knowledge was 14.9 out of 20 showing moderate knowledge levels, and girls scored higher on nutrition knowledge than boys (p < 0.05). Subjects showed knowledge deficit in areas such as nutrients, food groups and specific weight control information. The percentages of correct answers regarding meals for brain function were significantly higher in girls than in boys (p < 0.05). They got nutrition information mainly from mass media and family/relatives. The mean score of dietary attitudes was 41.2 (possible score: 10-50) indicating somewhat positive attitudes, and the score of eating behaviors was 34.8 (possible score: 15-45). Subjects showed problems in eating habits such as having unbalanced diets and snack foods. 82.6% of subjects had unbalanced meals, and these percentages were higher in girls (87.2%) than in boys (78.1%, p < 0.05). Vegetables and fish/shellfish were the most disliked foods. Specific eating behaviors, such as eating slowly, eating grains and having processed foods less frequently, were better in girls than in boys (p < 0.05). Results also showed that majority of subjects need to improve specific behaviors including having diverse foods, eating meals slowly, having meals at regular times, having adequate foods in each food groups, and eating sweets or salty foods less frequently. Only 52.7% of subjects perceived their body images as normal, and 56.4% had experience of weight control. Reasons for weight control were different by gender (p < 0.05). Based on these findings, nutrition education for school children should focus on modifying eating habits or eating behaviors, by suggesting practically applicable methods and providing nutrition information that is interesting and suitable to school-aged children.

• Journal of Nutrition and Health
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• v.37 no.3
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• pp.193-201
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• 2004

The objective was to evaluate the factors influencing on the growth of children aged 3 - 6 years by mini dietary assessment and anthropometric indices in 556 children and by analyzing mineral contents of hair from 273 children by inductively coupled plasma mass spectrometry (ICP-MS). The mean concentration of zinc (Zn) in hair was 68.9 $\pm$ 31.1 ppm and the zinc level of 91 ％ children was less than 60％ of the reference value of 180 ppm. The mean content of lead (Pb) in hair was 1.76 $\pm$ 1.20 ppm, but only 67％ of 273 children was within the reference value of 2 ppm and the lead level of 33％ of children was 2 - 4 times higher than the reference value. The level of Zn was negatively correlated with Pb content (r = -0.305, p 〈 0.01). Hair Zn content, regardless of age, was significantly positively correlated with height (r = 0.214) and body weight (r = 0.159). The height of 95.3％ children was belonged to the normal range of 90 - 109.9％ of standard value and the body weight of 49.8％ children was in the range of 90 - 109.9％ of standard value. However, 8.1 ％ children was overweighted (110 - 119.9％ of standard) and 9.4％ children was obese (120 - 149.9％ of standard) and 0.9％ children was severe obese (〉 150％) which resulted in total 10.3％ obese. Contrary to our expectation, 32.8％ children was underweight (70 - 89.9％ of standard) and 36％ of the underweight children showed the low content of zinc (10 - 49 ppm) in hair. There was no significant correlation between dietary intake of Zn and hair Zn content. Hair Zn content was low even though children consumed greater than 75％ of their requirement for zinc. Regardless of dietary intake of Zn, hair Zn level was rather negatively correlated to the content of Pb in hair. 38.8％ children had an unbalanced diet which resulted in lower intake of calorie, Ca, Zn, vitamin B$_2$ compared with those consuming variety of foods. Therefore, it would be needed that new approach for nutrition education to improve eating habit having the unbalanced diet in preschool children. It might be also suggested to develop new food products to complement the nutrients of Zn, Ca, Fe as snacks or dietary supplement for Korean preschool children.

• Journal of Community Nutrition
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• v.1 no.1
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• pp.25-32
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• 1999

In this study, focus group interviews were used to investigate female university students' eating behavior, factors related to eating behavior, information sources for nutrition, and formats for nutrition education. Thirty-six students participated in one of five focus groups during December 1998 in Seoul. Focus group discussions were video, audio-taped, transcribed and analyzed by major themes. Results showed that subjects have undesirable eating behaviors, such s eating irregular meals and skipping meals. These behaviors are caused by a lack of time, habit, or for the purpose of losing weight. The students tended to have unbalanced diets and frequently ate out. They had a large amount for dinner and frequently snaked when stressed or had an empty stomach. Most of them were interested in weight control and had attempted to lose weight, but they did not participate in regular exercise. The most frequently used source for nutrition information was the mass media, but much nutrition information was based on what they learned from home economics class during middle to high school. They received more support from mothers, elder sisters, and friends for eating behaviors, such s lowering caloric intake and losing weight. In nutrition education, they wanted to learns behaviorla skills to adopt healthy behaviors, including meal planning, applying scientific weight control methods, exercise that fit into their lives, and stress management. They also mentioned that nutrition screening and assessment should be a part of nutrition education programs. As a method for nutrition education, subjects preferred an individualized approach to group education. These results provide the qualitative information for developing nutrition education programs which will be implemented for Korean University students.

• Journal of Microbiology and Biotechnology
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• v.25 no.12
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• pp.2090-2099
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• 2015

Recently, the cardiovascular disease has been widely problematic in humans probably due to fibrin formation via the unbalanced Western style diet. Although direct (human plasmin) and indirect methods (plasminogen activators) have been available, bacterial enzyme methods have been studied because of their cheap and mass production. To detect a novel bacterial fibrinolytic enzyme, 111 bacterial strains with fibrinolytic activity were selected from kimchi. Among them, 14 strains were selected because of their stronger activity than 0.02 U of plasmin. Their 16S rRNA sequence analysis revealed that they belong to Bacillus, Leuconostoc, Propionibacterium, Weissella, Staphylococcus, and Bifidobacterium. The strain B. subtilis ZA400, with the highest fibrinolytic activity, was selected and the gene encoding fibrinolytic enzyme (bsfA) was cloned and expressed in the E. coli overexpression system. The purified enzyme was analyzed with SDS-PAGE, western blot, and MALDI-TOF analyses, showing to be 28.4 kDa. Subsequently, the BsfA was characterized to be stable under various stress conditions such as temperature (4-40oC), metal ions (Mn²⁺, Ca²⁺, K²⁺, and Mg²⁺), and inhibitors (EDTA and SDS), suggesting that BsfA could be a good candidate for development of a novel fibrinolytic enzyme for thrombosis treatment and may even be useful as a new bacterial starter for manufacturing functional fermented foods.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.103-112
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• 1999

This is study to estimate the pump induced vibration in time and frequency domain by frequency response function between two points in case of 20Hp and 50Hp centrifugal pumps. The frequency response function has real and imaginary information of signals, and response function has also real and imaginary information. So the vibration force can be obtained from the response function and frequency response function by complex calculation. And it is compared with the theoretically estimated values and it is suggested that the amplitude of vibration with main frequency is about 10~25% of pump and motor weight, and the magnitude of unbalanced mass is about 30~60% of pump and motor weight to estimated vibration force in time domain. There are the other kinds of vibration components with different frequency values of 2~3 times of its main frequency, and these kinds of information are used to control the tuning ratio between operating frequency of pump and structural frequency of concrete slab.

• The Korean Journal of Food And Nutrition
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• v.24 no.2
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• pp.145-152
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• 2011

This study was conducted to investigate the meal quality and dietary behaviors of low-income family children by qualitative method. The subjects were 12 children(2 boys and 10 girls) aged 7 to 11, enrolled in an after-school care center in Kimpo, Gyeonggi province. Most of their mothers had jobs(83.3%) and 75% were the beneficiaries of a government assistance program. When compared using body mass index(BMI) percentile, 16.7% of the subjects were classified as being overweight. The food intake patterns and meal qualities were evaluated from dietary records for three non-consecutive days. The mean dietary diversity score(DDS) was 3.8, suggesting at least one food group was deficit. Only 8.3% of the records indicated a satisfactory intake of all five food groups, and fruit was the most deficit food group(58.3%). Also, the proportion of balanced of meals was low, especially breakfast(36%), in that main dish(the source of protein) was not included. The children had problematic eating behaviors, such as an unbalanced diet, eating meals in a hurry, skipping breakfast, and irregular meal times. They answered that they liked to eat simple meals and convenient foods. In conclusion, nutrition education should incorporate strategies to reach families and help with meal planning and management, as well as modifying the eating behaviors of children, in order to improve nutritional status.

• Journal of the East Asian Society of Dietary Life
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• v.14 no.2
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• pp.113-122
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• 2004

This study was conducted to examine the correlation among growth development, bone mineral density, and nutrient intakes in preschool children. A total of 62 preschool children measured the anthropometric characteristics and the bone mineral density of carpus using DEXA. The questionnaires categorized to determine health status, life style, dietary behaviors, and dietary intakes were filled out by children's mothers. The average ages of the study subjects were 62.4 months in boys and 62.1 months in girls. The birth height and weight of the subjects were 50.9 cm and 3.4 kg in boys and 50.3 cm and 3.3 kg in girls, respectively. The average height, weight, % body fat, and obesity index were 111.7 cm, 19.6 kg, 15.0%, -2.1% in boys and 109.4 cm, 18.7 kg, 17.5%, 0.2% in girls, respectively. The bone mineral density in carpus was 0.25 g/cm$^2$ in boys and 0.24 g/cm$^2$. In girls. Proportions of children having regular meals were 69.0%, 94.7%, and 69.0% for breakfast, lunch, and dinner, respectively. The major reasons for irregular meal were poor appetite and lack of time for breakfast and snacks for dinner. Most of the children(52.6%) had breakfast with the whole family together, and all the children had lunch and dinner with a part of the family. Most of the children answered they had snack more than once a day, and 64.3% had an unbalanced diet. The intakes of energy, calcium, iron, zinc, vitamin A, vitamin B$_1$, niacin, and vitamin C did not meet the Korean RDAs. Average bone mineral density in carpus was positively correlated to the body weight, the total body water, the lean body mass, and the obesity index, respectively(p＜0.01, p＜0.01, p＜0.01 and p＜0.01). The body weight, the total body water, and the lean body mass showed the significant negative correlations with the animal iron intake(p＜0.05, p＜0.01 and p＜0.01). The bone mineral density in the distal carpus was negatively correlated to the animal protein intake and the animal iron intake(p＜0.05 and p＜0.05). And the bone mineral density in the ultradis carpus and the average bone mineral density in the carpus were positively correlated to the plant calcium intake(p＜0.05 and p＜0.05). Therefore, more systematic studies to investigate the roles of protein, iron, and calcium in growth development of preschool children were required.

• Journal of Korean Academy of Nursing
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• v.3 no.3
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• pp.36-49
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• 1973

This study was carried out for the objectives to collect the basic informations on the health behaviors of the elementary school children in an urban area in Korea. Seven hundred students were drawn to fill in the designed questionnaire which carries variety of Questions on health re-lated behaviors in general, eating habits, disease history, mental health, and sex education. Questionnaire were filled in by their parents. Major findings are as follows: ① 55.7% had habits of washing the hands before eating whereas 59.8% trashing their hands after toilet. The others had no idea of washing hands before eating and after toilet. ② 26,5% had habits of brushing the teeth twice a day 54.7% only once in the morning, and 2.6% once only in the evening. Thus, the idea of prevention from decayed teeth seems to be lacking among the school children. ③ Bathing habits were also inquired to get 40.3% of bathing more than once a week, 43.1% once every two weeks, and the rest of 16.6% once every one to three months. ④ 41.7% keep the regular bedding time whereas 58.3% irregular. Physical exercises were con-ducted by 76.6% on the ground while 23.5% did not practice any physical exercises at all. Of those physical exercises, rope skipping occupied 37.5%, and the other 66.9% consisted of 14 different kinds of individual type physical exercises such as gymnastic exercise. The main reasons for not enjoying exercises were different by sex; boys largely complained the inadequacy and lack of gymnastic facilities and girls felt in short of friends who could join the exercises. ⑤ 31.9% of the school children had been taking not much of food while 28.3% had unbalanced diets. Of these unbalanced diets, meat occupied 33.2% to be the priority to have an order of the following items such as vegetables, bread or noodle, and fishes as next to each. For eating habits, 88.5% take simple snack such as bread (38.4%, cookies, fruits, and candies in order. 25.8% of the children were provided such snacks or their parents regularly. Breakfast was sufficiently taken by 45.0% whereas 8.4% had never sufficiently. As to the lunch, 63.6% had sufficiently while 16.8% insufficiently. 70.6% take breakfast with all family members together and 30.4% separately. Correlation of sufficient taking of breakfast and eating together of tile family member's seems to be significant when we compare 72.5% of sufficient takers who enjoy breakfast together with the family members with 55.6% of insufficient takers who enjoy it with the family. This finding allows the investigator to point out the importance of table circumstances for children's eating. ⑥ The most common disease was catching a cold (38.8%), and the second was stomach trouble to be followed by the frequency of car sickness, headache, and skin infection. Doctors are consulted only by 23.9% when they are sick whereas 59.7% resorted to the drug stores. The lower the educational attainment of the parents, the lower the rate of visiting clinics. ⑦ 36.7% of their parents pointed out the problems of personality guidance as the most difficult thing at home 71.3% of their parents worried about and unsatisfied with their children's personality traits. Of these complains of the parents, impatience stood at the top to be tabulated at 24.1%, and 21.1% indicated narrow-mindedness. In line with this primary socialization at home, the most crucial problem seems to be related with the lack or recognition of the parents'own role when we find only 43.1% of the parents understood the importance of their own role for the home education of children; the latter group attributed tile responsibility of personality formation to the children themselves. ⑧ As to the sex educational aspects, 30.9% of children have ever asked about the physiology of reproduction or sexual matters to their parents, of those parents only 17.0% could give the constructive responses to the inquiries of the children. In companies on with these data, 25.6% recognized their own role in sex education for their own children while the large segments of the parents (51.1%) attributed the responsibility of sex education to tile low level of 38.3% who recognized the importance of sex education in the school curriculum and 25.1% of the parents insisted to wait until they get to know naturally about sex. 38.1% of the parents said they had some knowledge on sex from books while 16.9% through mass media. The next groups had common senses of sex from their own parents, school friends and other sources.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.6
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• pp.926-933
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• 2014

The purpose of this study was to evaluate vegetable intakes according to body mass index (BMI) of adolescents. For this, 400 middle and high school adolescents living in Buyeogun, Chungnam were classified into underweight group, healthy weight group, and overweight group according to BMI, after which eating habits, daily intake levels of vegetables, perception of vegetables, and vegetable-related eating habits were compared and analyzed. As the reason for skipping breakfast, 'Lack of time (44.3%)' was the most frequently cited. In the case of unbalanced food intakes, the underweight group and overweight group showed the highest response for 'grain' while the healthy weight group showed the highest response for 'vegetables' with significant differences (P<0.001). Daily intakes of one serving size of vegetables was 3.3 in the underweight group, 3.8 servings in the healthy weight group, and 3.8 servings in the overweight group, but there was no significant difference. However, frequency of vegetable intake at lunch was once in the underweight group, which was significantly lower than 1.3 servings in the healthy weight group and 1.4 servings in the overweight group (P<0.05). Regarding perception of vegetables, perception of 'Vegetable consumption helps to get beautiful skin' (P<0.01) and 'I eat vegetables or don't eat depending on a cooking method' (P<0.05) were significantly higher in the underweight group. In the evaluation of vegetables-related eating habits, preference for vegetables in the underweight group was lower than that in the healthy weight and overweight groups (P<0.05). Summarizing the above results, vegetable intake by adolescents was generally low, and the frequency of vegetable intake at lunch as well as preference for vegetables were significantly lower in the underweight group. Studies to identify the relationships between adolescent body types and vegetable intakes are required.