• Journal of Korean Society of Forest Science
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• v.65 no.1
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• pp.68-73
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• 1984

The purpose of this paper was to figure out the efficiencies of two sampling techniques, a simple random sampling and a two-stage P.P.S. (probability proportional to size) sampling, in estimating the volume of the mature coniferous stands near Salzburg, Austria. With black-and-white infrared photographs at a scale 1:10,000, the following four classes were considered; non-forest, young stands less than 40 years, mature beech and mature coniferous stands. After the classification, a field survey was carried out using a relascope with a BAF (basal area factor) 4. For the simple random sampling, 99 points were sampled, while for the P.P.S. sampling, 75 points were sampled in the mature coniferous stands. The following results were obtained. 1) The mean standing coniferous volume estimate was $422.0m^3/ha$ for the simple random sampling and $433.5m^3/ha$ for the P.P.S. sampling method. However, the difference was not statistically significant. 2) The required number of sampling points for a 5% sampling error were 170 for the two stage P.P.S. sampling, but 237 for the simple random sampling. 3) The two stage P.P.S. method reduced field survey time by 17% as compared to the simple random sampling.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.3
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• pp.324-333
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• 2016

Objectives: We aimed to compare the sampling performance of different flow-based impactor samplers for collecting fungal spores and bacteria and to explore the association of the level of bioaerosols with activity patterns of occupants in daycare center settings. Methods: For comparison of sampling performance, two different flow-based samplers (greater than 100 L/min or not) were selected; a low flow-based sampler (one-stage Andersen sampler) and two high flow-based samplers (DUO SAS SUPER 360 sampler, BUCK bio-culture sampler). We collected airborne mold and bacteria in 30 daycare centers with various levels of contaminated air. Three repeat samplings per each sampler were performed. Mold and bacteria were grown for 96 hours at $25{\pm}1^{\circ}C$ and 48 hours at $35{\pm}1^{\circ}C$, respectively. The Andersen and SAS samplers were used for investigating the association between the level of bioaerosols and the activity patterns of occupants in daycares. Particular matters 10($PM_{10}$), temperature, and relative humidity were monitored as well. Samplings were carried out with one-hour interval from 9 to 5 O'clock. For statistical comparisons, Kruskal-Wallis test, Wilcoxon's signed rank test, and multiple regression analysis were carried out. Results: The airborne level of molds by the low flow-based sampler were significantly higher than that of high flow-based samplers (indoor, P=0.037; outdoor, P=0.041). However, no statistical difference was observed in the airborne level of bacteria by each sampler. Also the level of bioaerosols varied by the time, particularly with different activity patterns in daycare centers. The higher level of mold and bacteria were observed in play time in indoor. Similarly, the concentrations of $PM_{10}$ were significantly associated with the level of bioaerosols (P<0.05). Conclusions: Our findings indicate that the flow rate of sampler, rather than total air volume, could be able to affect the results of sampling. Also, the level of airborne mold and bacteria vary behavior patterns of occupants in indoor of daycare settings. Therefore, different samplers with other flow rate may be selected for mold or bacteria sampling, and activity patterns should be considered for bioaerosol sampling as well.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.70-79
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• 2016

This paper proposes a low-power range-scaled 14b 30 MS/s pipeline-SAR composite ADC for high-performance CIS applications. The SAR ADC is employed in the first stage to alleviate a sampling-time mismatch as observed in the conventional SHA-free architecture. A range-scaling technique processes a wide input range of 3.0VP-P without thick-gate-oxide transistors under a 1.8 V supply voltage. The first- and second-stage MDACs share a single amplifier to reduce power consumption and chip area. Moreover, two separate reference voltage drivers for the first-stage SAR ADC and the remaining pipeline stages reduce a reference voltage disturbance caused by the high-speed switching noise from the SAR ADC. The measured DNL and INL of the prototype ADC in a $0.18{\mu}m$ CMOS are within 0.88 LSB and 3.28 LSB, respectively. The ADC shows a maximum SNDR of 65.4 dB and SFDR of 78.9 dB at 30 MS/s, respectively. The ADC with an active die area of $1.43mm^2$ consumes 20.5 mW at a 1.8 V supply voltage and 30 MS/s, which corresponds to a figure-of-merit (FOM) of 0.45 pJ/conversion-step.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.75-85
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• 2009

This work proposes a 13b 100MS/s 0.13um CMOS ADC for 3G communication systems such as two-carrier W-CDMA applications simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs a four-step pipeline architecture to optimize power consumption and chip area at the target resolution and sampling rate. Area-efficient high-speed high-resolution gate-bootstrapping circuits are implemented at the sampling switches of the input SHA to maintain signal linearity over the Nyquist rate even at a 1.0V supply operation. The cascode compensation technique on a low-impedance path implemented in the two-stage amplifiers of the SHA and MDAC simultaneously achieves the required operation speed and phase margin with more reduced power consumption than the Miller compensation technique. Low-glitch dynamic latches in sub-ranging flash ADCs reduce kickback-noise referred to the differential input stage of the comparator by isolating the input stage from output nodes to improve system accuracy. The proposed low-noise current and voltage references based on triple negative T.C. circuits are employed on chip with optional off-chip reference voltages. The prototype ADC in a 0.13um 1P8M CMOS technology demonstrates the measured DNL and INL within 0.70LSB and 1.79LSB, respectively. The ADC shows a maximum SNDR of 64.5dB and a maximum SFDR of 78.0dB at 100MS/s, respectively. The ABC with an active die area of $1.22mm^2$ consumes 42.0mW at 100MS/s and a 1.2V supply, corresponding to a FOM of 0.31pJ/conv-step.

• Nutrition Research and Practice
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• v.8 no.6
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• pp.679-687
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• 2014

BACKGROUND/OBJECTIVES: Recently, there has been an increased interest in the importance of family meals on children's health and nutrition. This study aims to examine if the eating habits and eating behaviors of children are different according to the frequency of family dinners. SUBJECTS/METHODS: The subjects were third-grade students from 70 elementary schools in 17 cities nationwide. A two-stage stratified cluster sampling was employed. The survey questionnaire was composed of items that examined the general characteristics, family meals, eating habits, eating behaviors, and environmental influence on children's eating. The subjects responded to a self-reported questionnaire. Excluding the incomplete responses, the data (n = 3,435) were analyzed using ${\chi}^2$-test or t-test. RESULTS: The group that had more frequent family dinners (${\geq}$ 5 days/week, 63.4%), compared to those that had less (${\leq}$ 4 days/week, 36.6%), showed better eating habits, such as eating meals regularly, performing desirable behaviors during meals, having breakfast frequently, having breakfast with family members (P < 0.001), and not eating only what he or she likes (P < 0.05). Those who had more frequent family dinners also consumed healthy foods with more frequency, including protein foods, dairy products, grains, vegetables, seaweeds (P < 0.001), and fruits (P < 0.01). However, unhealthy eating behaviors (e.g., eating fatty foods, salty foods, sweets, etc.) were not significantly different by the frequency of family dinners. CONCLUSIONS: Having dinner frequently with family members was associated with more desirable eating habits and with healthy eating behaviors in young children. Thus nutrition education might be planned to promote family dinners, by emphasizing the benefits of having family meals on children's health and nutrition and making more opportunities for family meals.

• Nutrition Research and Practice
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• v.10 no.6
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• pp.597-605
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• 2016

BACKGROUND/OBJECTIVES: Childhood obesity has increased in recent decades in Korea. This study was designed to examine differences in the eating habits, physical activity (PA), nutrition knowledge, and self-efficacy of children by obesity status. SUBJECTS/METHODS: Subjects were 5th-grade children from 70 elementary schools in 17 cities nationwide. Two-stage stratified cluster sampling was employed. Survey questionnaire included items related to general characteristics, eating habits, PA, nutrition knowledge and self-efficacy. Excluding incomplete responses, 3,531 data were analyzed using SPSS. Subjects were categorized into overweight obesity (OW) and normal weight (NW) groups based on body mass index percentiles for age by sex. RESULTS: A total of 21.5% of subjects was overweight or obese. There were significant differences in gender, perceived stress, perception of body shape, body satisfaction, and interest in weight control between the OW and NW groups (P < 0.001). With respect to eating habits, the OW group ate breakfast (P < 0.05) and snacks (P < 0.01) less frequently, ate bigger meals (P < 0.001), and demonstrated less desirable behaviors during meals (P < 0.05 in boys) compared to the NW group. The OW group participated in less PA than the NW group, especially boys. OW boys spent less time walking during weekdays (P < 0.05) or the weekend (P < 0.001), spent more time being sedentary during weekdays or the weekend (P < 0.001), and exercised a fewer number of days (P < 0.01). For girls, the OW group spent more time being sedentary during the weekend (P < 0.01) and exercised a fewer number of days by walking or bicycle riding (P < 0.05) than the NW group. Nutrition knowledge was not significantly different between the OW and NW groups. Self-efficacy (P < 0.01 in boys), especially PA self-efficacy (P < 0.01), was significantly lower in the OW than NW group. CONCLUSIONS: This study revealed differences in eating habits, PA, and self-efficacy between OW and NW children. Obesity management programs for children need to focus on increasing self-efficacy, modifying eating habits, and increasing PA.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.3
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• pp.160-165
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• 2009

A 12b 2 MS/s cyclic ADC processing 3.3 Vpp single-ended rail-to-rail input signals is presented. The proposed ADC demonstrates an offset voltage less than 1 mV without well-known calibration and trimming techniques although power supplies are directly employed as voltage references. The SHA-free input sampling scheme and the two-stage switched op-amp discussed in this work reduce power dissipation, while the comparators based on capacitor-divided voltage references show a matched full-scale performance between two flash sub ADCs. The prototype ADC in a $0.18{\mu}m$ 1P6M CMOS demonstrates the effective number of bits of 11.48 for a 100 kHz full-scale input at 2 MS/s. The ADC with an active die area of $0.12\;mm^2$ consumes 3.6 m W at 2 MS/s and 3.3 V (analog)/1.8 V (digital).

• Korean Journal of Psychosomatic Medicine
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• v.7 no.1
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• pp.87-102
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• 1999

Objectives : The purposes of this study were to estimate the prevalence rate of eating disorders in Korean males and to clarify their characteristics in sociodemograhic data, the eating traits, and general psychopathology through the comparison with those of female high scored group on the Korean version of Eating Attitudes Test-26(KEAT-26). Methods : Using a multi-stage questionnaire sampling method including area sampling, proportionated stratified sampling, and quota sampling, we surveyed a total of 4,400 Korean adults over 18 in a nationwide area(9 kus, 10 middle or small cities, and 17 kuns), obtaining usable responses on 3,896. Of the 3,062 subjects(1249 males and 1813 females) who were available for analysis, we ascertained 52 males and 208 females who had high score($\geq$ cutoff point 21) on the KEAT-26. Results : 1) The proportion of this high score group was 1.7% in male and 6.8% in female with a sex ratio(male versus female) of 1 : 4. 2) The mean age was higher in the male group than in the female group, although it was not statistically significant(p=0.0514). Mean Body Mass Index(BMI) of the male group was significantly higher than that of female group, and the number of male subjects with below 20 of BMI was also significantly lower than in the female group. 3) There were no significant difference in past history of physical illness between two groups. However, frequency of smoking and alcohol use, and mean amount of alcohol consumption per month were significantly higher in the male group than in the female group. There were no significant differences between the two groups on various socio-demographic correlates such as economic status, total duration of education, number of family, marital status, religious status, and area of residence, but the exception of being occupational status. 4) The 'Eating Habits Scale' score and score of 'preference for vegetables and fish, and dislike for sweet-tasting food' of the male group were significantly lower than those of the female group. Although there was no significant difference between the two groups in total scores of the KEAT-26, the mean score on 'pursuit of thinness' subscale was higher in the female group than in the male group, while scores of 'food preoccupation' and 'self-control' subscales were higher in the male group than in the female group. 5) Scores on 'psychoticism' was significantly higher in the male group than in the female group, although there were no significant differences between the two groups on 'locus of control for weight', 'depression' and 'hypochondriasis'. Conclusion : These results support a possibility of a high prevalence of eating disorders in Korean males. These results suggest that eating related characteristics of high scorer on the EAT are different by sex in spite of the same high score on the EAT, and also suggest that male patients with eating disorders have more serious personality pathology than female patients with eating disorders.

• Korean Journal of Community Nutrition
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• v.21 no.2
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• pp.152-164
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• 2016

Objectives: This study was conducted to investigate the status and need for nutrition and dietary life education among nutrition teachers at schools. These characteristics were analyzed if they were different between elementary schools and middle-high schools. Methods: Subjects were 151 nutrition teachers from 70 elementary schools, 41 middle schools and 40 high schools in 17 cities nationwide selected by two-stage stratified cluster sampling process. Survey questionnaires included the items on general characteristics, status and need assessment for nutrition and dietary life education. Chi-square test or t-test was used for data analysis by school groups. Results: Nutrition education was implemented at 65.7% of elementary schools and 51.9% of middle-high schools. Nutrition education was mainly performed in 'discretionary activities extracurricular activities' at elementary school and through 'newsletters, school homepage, foodservice bulletin board' at middle-high school (p<0.001). The most needed topic for nutrition education in nutrition teachers was 'healthy dietary habits and table manners' and this was not significantly different by school groups. Responses on adequate frequency (p<0.01), methods used for nutrition education (p<001), materials for nutrition education (p<0.001), information sources for nutrition education (p<0.001) were significantly different by school groups. Major tasks for activating nutrition education included 'securing the time for implementing nutrition education by reducing work loads' and 'developing standardized nutrition education materials' in schools. Conclusions: Nutrition education at schools might be activated by improving working conditions of nutrition teachers and developing the practical programs that reflect the needs of nutrition teachers.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.53-60
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• 2005

This work proposes a 10b 100 MS/s $1.4\;mm^2$ CMOS ADC for low-power multimedia applications. The proposed two-step pipeline ADC minimizes chip area and power dissipation at the target resolution and sampling rate. The wide-band SHA employs a gate-bootstrapping circuit to handle both single-ended and differential inputs with 1.2 Vp-p at 10b accuracy while the second-stage flash ADC employs open-loop offset sampling techniques to achieve 6b resolution. A 3-D fully symmetrical layout reduces the capacitor and device mismatch of the first-stage MDAC. The low-noise references are integrated on chip with optional off-chip voltage references. The prototype 10b ADC implemented in a 0.18 um CMOS shows the maximum measured DNL and INL of 0.59 LSB and 0.77 LSB, respectively. The ADC demonstrates the SNDR of 54 dB, the SFDR of 62 dB, and the power dissipation of 56 mW at 100 MS/s.