• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.390-396
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• 2007

In the present study, we have developed a flapping wing using a smart material to mimic the nature's flyers, birds. The wing consists of composite frames, a flexible PVC film and a surface actuator, and the main wing motions are flapping, twisting and camber motions. To change the camber, a Macro-Fiber Composite(MFC) is used as the surface actuator, and it's structural response is analyzed by the use of piezoelectric-thermal analogy. To measure the lift and thrust simultaneously, a test stand consisting of two load cells is manufactured. Some aerodynamic tests are performed for the wing in a subsonic wind tunnel to evaluate the dynamic characteristics. Experimental results show that the main lift is mostly affected by the forward velocity and the pitch angle, but the thrust is mostly affected by the flapping frequency. The effect of the camber generated by the MFC actuator can produce the sufficient lift increment of up to 24.4% in static condition and 20.8% in dynamic condition.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.583-590
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• 2004

The autofocus is one of the important processes in the automated vision inspection or measurements using optical microscopes, because it influences the measuring accuracy. In this paper, we used the confocal microscope configuration based on not a pinhole but a single-mode optical fiber. A single mode fiber has the functions of source and detector by applying the reciprocal scheme. As a result, we acquired a simple system configuration and easy alignment of the optical axis. Also, we embodied a fast autofocus system by acquiring the focus error signal through a source modulation technique. The source modulation technique can effectively reduce physical disturbances compared with objective lens modulation, and it is easily applicable to general optical microscopes. The focus error signal was measured with respect to the modulation amplitude, reflectance of the specimen and inclination angle of the measuring surface. The performance of the proposed autofocus system was verified through autofocusing flat mirror surface. In addition, we confirmed that source modulation rarely degrades the depth resolution by the comparison between the FWHMs of axial response curves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.3 s.246
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• pp.318-327
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• 2006

Due to the diversified use of recent Piezoelectric Zirconate Titanate Composite Actuate. (PZTCA), various PZTCAs with the different ply orientation of the fiber layer have been applied. For this reason, the applicable bending moment equation is necessary even though the fiber layer ply orientation and the laminate configuration are changed. The aim of this research is to evaluate the relationship between the total effective moment $(M^E)$ and Bernoulli-Euler bending moment (M) when the ply orientations of UD CFRP are changed. In conclusions, firstly, as the performance test results by the CFRP ply orientation, the performance of [0] and [90] were stable. However, while the performance of [+45] was suddenly decreased after 5 hours. Secondly, the change of $(M^E)$ by the CFRP ply orientation was evaluated. As the CFRP ply orientation was increased from [0] to [+60], the $(M^E)$ were gradually decreased. However, they became a little bit increased from [+60] to [90]. Finally, after the change of M by the CFRP ply orientation was evaluated, it was found that $M^E=2.2M$ was valid for just [0] and that there was a relationship between $M^E$ and M according to the ply orientation.

• Applied Microscopy
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• v.37 no.3
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• pp.175-183
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• 2007

The Drosophila retinal cell is widely used to study cell development and cell signaling processes. In the past decades, conventional chemical fixation had been used to study the structure of retinal cells in Droscphila. Rapid freezing methods are superior to chemical fixation methods due to their fixation speed. Some Drosophila tissues, such as the eyes, should not be freezed due to their surrounding cuticle layer. Therefore, in the case of the Drosophila retina, the benefits of high pressure freezing and freeze substitution (HPF-FS) had not been verified. In this study, a retinal cell from Drosophila melanogaster had been studied by using the HPF-FS method. Compared to chemical fixation, the preservation of the cytoplasm in the HPF-FS sample was improved on the whole. The HPF-FS cell membranes were smoother than that of chemical fixation. In addition, HPF-FS preserved the mitochondria structures very well. These results of the present study suggest that HPF-FS is superior to other fixation methods for the preservation of the retinal cell structure.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.521-529
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• 2002

We have recently proposed the new concept of a phase-measuring volumetric interferometer that enables us to accurately measure the xyz-coordinates of the probe without metrology frames. The interferometer is composed of a movable target and a fixed photo-detector array. The target is made of point diffraction sources to emit two spherical wavefronts, whose interference is monitored by an array of photo-detectors. Phase shifting is applied to obtain the precise phase values of the photo-detectors. Then the measured phases are fitted to a geometric model of multilateration so as to determine the xyz-location of the target by minimizing least square errors. The proposed interferometer has been designed and built with a volumetric uncertainty of less than 1.0 $\mu\textrm{m}$ within a cubic working volume of side 120 mm. Here, in this paper, we also present error sources, an evaluated uncertainty, and test results from the prototype system. The self-calibration of two-dimensional precision metrology stages is applied to test the performance of the interferometer.

• Journal of Nutrition and Health
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• v.41 no.8
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• pp.742-753
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• 2008

The purpose of this study is to investigate risk factors of pre-hypertension and hypertension in rural residents. Nine hundred and ninety four subjects aged 40-70 yrs in Chungnam-do participated in this study. The subjects (n = 824) were classified into three groups of hypertensive, pre-hypertensive, and normotensive according to the Joint National Committee (JNC)-7 criteria. The weight, body mass index (BMI), waist-hip ratio (WHR), and serum total protein, albumin, BUN, and triglyceride (TG) were positively correlated with SBP and DBP. After adjusted by age, sex and BMI, the total protein, albumin and TG were significantly correlated with SBP and DBP (p < 0.01). There was no significant difference in eating habits according to the level of blood pressure. The serum albumin, creatinine, Glu-FBS, Glu-PP l20, and triglyceride were higher in both prehypertensive and hypertensive group than in the normotensive group. However, mean serum cholesterol was not different among three blood pressure groups. In this study, the common risk factors of pre-hypertension and hyper-tension were male, age of fifties, lower education level, ex-smoking, higher drinking frequency, higher BMI, body fat %, waist circumference, WHR, serum albumin and diabetes, even though the degree of risks in these variables were higher in the hypertensive group. The higher BUN was a risk factor of prehypertension, while the family history, prediabetes, serum total protein, Glu-PP l20 and higher alcohol drinking amount were the risk factors of hypertension. This result suggests that maintaining good health habit and normal range of blood parameters as well as controlling body weight have to be paid attention in order to prevent hypertention, and further reseasch on the relationship of blood pressure and BUN are needed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5A
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• pp.351-360
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• 2011

Jacket-type offshore structures are always exposed to severe environmental conditions such as salt, high speed of current, wave, and wind compared with other onshore structures. In spite of the importance of maintaining the structural integrity for offshore structure, there are few cases to apply structural health monitoring (SHM) system in practice. The impedance-based SHM is a kind of local SHM techniques and to date, numerous techniques and algorithms have been proposed for local SHM of real-scale structures. However, it still requires a significant challenge for practical applications to compensate unknown environmental effects and to extract only damage features from impedance signals. In this study, the impedance-based SHM was carried out on a 1/20-scaled model of an Uldolmok current power plant structure under changes in temperature and transverse loadings. Principal component analysis (PCA) was applied using conventional damage index to eliminate principal components sensitive to environmental change. It was found that the proposed PCA-base approach is an effective tool for long-term SHM under significant environmental changes.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.52-58
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• 2005

To establish low-cost and high efficiency water treatment process, feasibility of applying ultrasonic spray nozzle for chemical injection was evaluated. Ultrasonic spray nozzle was manufactured using piezoelectric ceramics. Treatment efficiencies of contaminants by ultrasonic spray nozzle were compared with conventional chemical mixing such as back-mixing. It was found out that the rate of chemical diffusion rate by ultrasonic spray nozzle was faster than by back-mixing method. Removal efficiencies of various contaminants, such as turbidity, organics and microorganism by ultrasonic spray nozzle were also higher than by back-mixing method. By adapting ultrasonic spray nozzle in coagulant injection process, it can be prevented that the decline of treatment efficiency by coagulant overdose. The amount of coagulant can be reduced by applying ultrasonic spray nozzle in water treatment. Along with these advantages chemical mixing chamber is not required if ultrasonic spray nozzle is adapted. From these results, it can be concluded that chemical injection by ultrasonic spray nozzle is an economical and highly efficient device for coagulant mixing.

• Journal of agricultural medicine and community health
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• v.31 no.3
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• pp.237-244
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• 2006

Objectives: DASH (dietary approaches to stop hypertension) diet are recommended as first-line therapy for prevention of hypertension individuals with high normal blood pressure. We studied the effects of DASH program on blood pressure among the pre-hypertension group. Methods: To determine the impact of dietary patterns on the control of hypertension we studied the subgroup of 141 participants with systolic blood pressure of 120 to 139 mm Hg or diastolic BP of 80 to 89mmHg, body mass index(BMI) ${\geq}25kg/m^3$ or waist to hip ratio(WHR) ${\geq}0.95$(for man). 0.85(for woman) enrolled in DASH program. Participants were received of education and consulting about DASH every week for 8 weeks. Results: The level of diet to prevention of hypertension and compliance of DASH increased after education. Also, The DASH program significantly reduced systolic BP (from $136.03{\pm}12.40mmHg$ to $126.09{\pm}11.25mmHg$, p< .01) and diastolic BP (from $81.80{\pm}6.32mmHg$ to $76.44{\pm}10.61mmHg$, p< .01). Conclusion: The DASH program effectively lowers BP and may be useful in achieving prevention of hypertension.

• Journal of agricultural medicine and community health
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• v.34 no.3
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• pp.375-385
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• 2009

Objectives: The objective of this study was to identify the association of food intake with bio-physiological indicators: blood pressure, body mass index (BMI), waist/hip ratio (WHR), cholesterol and urine sugar among rural people. Methods: The subjects were 890 inhabitants from 14 towns of G County in Honam province. Data were collected by interview and self-reported with structured questionnaires from April 6th to 30th 2005. Data were analyzed with the frequency, percentage, t-test, $x^2$-test, ANOVA, Scheffe test and ANCOVA using SPSS 12.0 program. Results: Pre-hypertensive and hypertensive group was 27.0%, overweight and obese 27.1%, more than 0.90 in WHR 42.0%, more than 201 mg/dl of cholesterol 23.9%, and positive urine sugar was 8.7% in general. Among eleven food groups, fruit intakes were more effective in normotensive group than in the others. Vegetables, liquors, and milk products were 0.90 WHR more effective than the others. Milk products and liquors in BMI, and grains, beans and seaweed in low cholesterol group were more effective than the others. Conclusions: Bio-physiological indicators are related significantly only with fruits, milk products, meats, cereal and liquors among eleven food categories. Further study on the relationship between food intake, physical activities, smoking, drinking and lifestyle with bio-physiological indicators are suggested.