• Computers and Concrete
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• 제28권5호
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• pp.465-478
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• 2021

On the premise of ensuring that the static performance of the concrete spreader is met, the first-order natural frequency of the concrete spreader is increased, and the weight of the main beam is reduced. ANSYS is used as an analysis tool to perform modal analysis on the concrete spreader. The natural frequency, mode shape and modal test verification will be obtained to ensure the accuracy of finite element model analysis. Using the ANSYS designxplorer module, the size of the main beam is set, and the response surface model between the parameter variables and the optimization objective is established according to the experimental design points. Screening algorithm and MOGA algorithm are used to multi-optimize the stress, first-order natural frequency and girder weight, and the optimal solution is obtained by comparison. The results of modal analysis are consistent with those of the experiment, and a set of optimal solutions is obtained through the optimization algorithm. The optimal solution obtained can meet the purpose of increasing the first-order natural frequency of the concrete spreader and reducing the weight of the main beam under the premise of ensuring the overall dynamic and static performance of the concrete spreader.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.127-134
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• 1996

In this paper, the effect of neglecting the own weight of the composite plate on the natural frequency of vibration of the laminated plates is presented. The method used has been developed by the author since 1974. This method is very effective for the plates with arbitrary boundary conditions and irregular sections. When the attached mass is equal to the weight of the plate, the effect of neglecting the plate weight is 9.26 percent

• 대한인간공학회지
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• 제15권2호
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• pp.177-184
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• 1996

In light-weight hand tools, static posture may result in postural fatigue. Psotural tremor of the upper extremity in a static posture was measured to provide guidelines for hand tool weight. Postural tremor was measured on five levels of tool weitht : no weight, 400g, 800g, 1200g, and 1600g. Three types of camcorder recording postures were selected. For each condition, postural tremor was measured together with ENG of biceps, deltoid and pectoralis major, and Borg's CR-20 ratings of perceved exertion. Results of the experiment are as follows : frequency analysis of tremor revealed increased amplitude of frequency bands of 2-4Hz and 10-14Hz. Postural tremor of the upper extremeity maintained the initial level until fatigue developed. After the development of fatigue, the rate of change of postural tremor significantly increased. Different tool weights and hand postures showed different rates of tremor increase. Time tp fatigue and corresaponding endurance time were positively correlated with Borg's RPE scores.

• 한국음향학회지
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• 제27권5호
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• pp.252-255
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• 2008

본 논문에서는 성별 인식 시스템의 성능향상을 위해 변별적 가중치 학습 (discriminative weight training) 기반의 최적화된 SVM (support vector machine)을 제안한다. MCE (minimum classification error)방법을 도입하여, 각각의 MFCC (mel-frequency cepstral coefficients) 특징벡터 차수별로 다른 가중치를 가지는 SVM을 제안한다. 제안된 알고리즘은 기존의 동일 가중치를 가지는 SVM 기반의 성별인식 시스템과 비교하였으며, 우수한 성능을 보인다.

• 여성건강간호학회지
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• 제13권4호
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• pp.320-326
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• 2007

Purpose: This study was carried out in an attempt to find weight control behaviors (BMI, experiences of weight control, weight control related factors, etc.) of college female students. Method: The subjects were 596 female students in 104 universities and colleges in Korea. Data was collected by using a questionnaire developed through a pretest. Result: Seventy five percent of subjects were in the normal range in weight, but 63.8% have experienced weight control behaviors and 58.9% have worried about their weight. Middle and high school was the first time to have concerns about their weight/body image. In addition, the influence towards weight control was mainly by mass communication. Weight control frequency in the most recent most year correlated with concern about weight, first time of weight control, maximum maintaining period of losing weight and BMI. Conclusion: To ensure resonable body image and weight control behaviors in women, education has to begin in elementary schools. In the case of weight control, scientific and systematic weight reduction programs should be developed.

• 대한지역사회영양학회지
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• 제9권4호
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• pp.453-463
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• 2004

In order to investigate food purchase frequency of elementary school children and its related ecological factors, 431 4th, 5th and 6th grade elementary school children and their mothers, living in Seoul and Daejon, small city and rural area of Chungnam Province, were participated in this study. The subjects and their parents were surveyed by a self-recording questionnaire about food purchase frequency and some ecological factors. Average height and weight of the subjects by gender and grade were similar to or a little bit more than the 1998 Korean Growth Standard. According to relative body weight, 30.6% and 10.8% of the subjects belonged to under-weight and obesity categories, respectively. Of the subjects, 46.9% used PC telecommunication or internet, 53.8% of them used it for less than an hour per day, and 46.4% watched TV for 2 to 4 hours a day. About 42% of the subjects spent 500 Won or less daily to buy snacks. A half of the subjects took snacks once a day because of hunger. Mothers' nutrition knowledge score was averagely 8.16 out of 13 full score and the average attitude score was 43.22 out of 50 full score. Foods purchased more than once a week were milk and yoghurt, cookies, ice-cream, ramyun, and gum in order. Family income, parents' education level, mothers' nutrition knowledge and food attitude score, students' snacking frequency and TV watching time showed significant correlations with purchase frequencies of some individual food items. In conclusion, the elementary school children considered taste most important rather than nutrition in buying snacks and most frequently bought carbohydrate foods and concentrated sugars except milk. Ecological factors such as mothers' nutritional knowledge and food attitude, TV watching time and snacking frequency had influenced the children's food purchase frequency. Accordingly, it is necessary to educate both children and their mothers about good food purchase and the importance of snacking.

• 대한지역사회영양학회지
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• 제15권2호
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• pp.227-239
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• 2010

The purpose of this study was to compare weight control behaviour, eating habits and health-related life habits according to the obesity degree by body fat percentage (%Fat) among middle-aged women. The subjects were 170 middle-aged women who lived Gunsan City, and they were assigned to one of the following groups based on their %Fat; normal weight group (18% - < 28%), overweight group (28% - < 33%) and obesity group (over 33%). The height, body weight, %Fat, the circumference of waist and hip of them were measured. Eating habits and health-related life habits were evaluated based on questionnaires. The results were as follows. Their weight, %Fat, body mass index (BMI), relative body weight (RBW), waist, hip, and waist-hip ratio (WHR) were significantly higher in the obesity subjects when compared to the normal and overweight subjects. Self-perception for weight (p < 0.001), desire for weight control (p < 0.01), and reasons of weight control (p < 0.05) were different among three groups. The main skipped meal was breakfast (67.9%), reasons of skipping meals were different among three groups (p < 0.05), and main reasons were "lose one's appetite" and "have not enough time". Food habits score for each food was not significantly different among three groups, but eating the meal on thinking with food combination in normal group was higher than overweight and obesity group (p < 0.01). Correlation coefficients of food habits score and anthropometric measurements were that salty of food was negative and food habits scores were positive correlation for anthropometric measurements and obesity index (p < 0.05 - p < 0.001). Frequency of exercise and fitting exercise for body were different among three groups (p < 0.05). Obesity group was lower frequency of exercise than the other groups. Regular diet was positive correlation with food combination (p < 0.01), taking fish (p < 0.05), taking vegetables (p < 0.01), taking bean products (p < 0.01) and food habits score (p < 0.01), frequency of eating out and snacks were negative correlation with taking fruits and fishes. Therefore, proper nutritional education for middle-aged women in obesity group is recommended regular diet, good food habits and exercise. The middle-aged women must decrease the frequency of eating out, snack and the salty foods, and increase the fruits and vegetables. They must have healthy life styles for exercise, smoking, and drinking.

• Computers and Concrete
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• 제17권2호
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• pp.241-253
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• 2016

Depending on the researcher, the effect of prestressing on the natural frequency of a PSC (prestressed concrete) structure appear to have been interpreted differently. Most laboratory tests on PSC beams available showed that the natural frequency is increased appreciably by prestressing. On the other hand, some other references based on field experience argued that the dynamic response of a PSC structure does not change regardless of the prestressing applied. Therefore, the deduced conclusions are inconsistent. Because an experiment with and without prestressing is a difficult task on a full size PSC bridge, the change in natural frequency of a PSC bridge due to prestressing may not be examined through field measurements. The study examined analytically the effects of prestressing on the natural frequency of PSC bridges. A finite element program for an undamped dynamic motion of a beam-tendon system was developed with additional geometric stiffness. The analytical results confirm that a key parameter in changing the natural frequency due to prestressing is the relative ratio of prestressing to the total weight of the structure rather than the prestressing itself.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.155-162
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• 2019

It is very common to find an empirical formulation in an earthquake design code to calculate fundamental vibration period of a structural system. Fundamental vibration period or frequency is a key parameter to provide adequate information pertinent to dynamic characteristics and performance assessment of a structure. This parameter enables to assess seismic demand of a structure. It is possible to find an empirical formulation related to reinforced concrete structures, masonry towers and slender masonry structures. Calculated natural vibration frequencies suggested by empirical formulation in the literatures has not suits in a high accuracy to the case of rest of the historical masonry bridges due to different construction techniques and wide variety of material properties. For the listed reasons, estimation of fundamental frequency gets harder. This paper aims to present an empirical formulation through Mean Square Error study to find ambient vibration frequency of historical masonry bridges by using a non-linear regression model. For this purpose, a series of data collected from literature especially focused on the finite element models of historical masonry bridges modelled in a full scale to get first global natural frequency, unit weight and elasticity modulus of used dominant material based on homogenization approach, length, height and width of the masonry bridge and main span length were considered to predict natural vibration frequency. An empirical formulation is proposed with 81% accuracy. Also, this study draw attention that this accuracy decreases to 35%, if the modulus of elasticity and unit weight are ignored.

• 한국해양공학회지
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• 제24권6호
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• pp.109-113
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• 2010

We present the minimum weight optimum design of cross sectional for frame structures subject to natural frequency. The optimum design in this paper employ discrete and continuous design variables and Genetic Algorithms. In this paper, Genetic Algorithms is used in optimization process, and be used the method of Elitism and penalty parameters in order to improved fitness in the reproduction process. For 1-Bay 2-Story frame structure, in examples, continuous and discrete design variables are used, and W-section (No.1~No.64), from AISC, discrete data are used in discrete optimization. In this case, Exhaustive search are used for finding global optimum. Continuous variables are used for 1-Bay 7-Story frame structure. Two typical frame structure optimization examples are employed to demonstrate the availability of Genetic Algorithms for solving minimum weight optimum of frame structures with fundamental and multi frequency.