• Smart Structures and Systems
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• v.10 no.1
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• pp.67-87
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• 2012

A dragonfly inspired flapping wing is investigated in this paper. The flapping wing is actuated from the root by a PZT-5H and PZN-7%PT single crystal unimorph in the piezofan configuration. The non-linear governing equations of motion of the smart flapping wing are obtained using the Hamilton's principle. These equations are then discretized using the Galerkin method and solved using the method of multiple scales. Dynamic characteristics of smart flapping wings having the same size as the actual wings of three different dragonfly species Aeshna Multicolor, Anax Parthenope Julius and Sympetrum Frequens are analyzed using numerical simulations. An unsteady aerodynamic model is used to obtain the aerodynamic forces. Finally, a comparative study of performances of three piezoelectrically actuated flapping wings is performed. The numerical results in this paper show that use of PZN-7%PT single crystal piezoceramic can lead to considerable amount of wing weight reduction and increase of lift and thrust force compared to PZT-5H material. It is also shown that dragonfly inspired smart flapping wings actuated by single crystal piezoceramic are a viable contender for insect scale flapping wing micro air vehicles.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.4
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• pp.3-14
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• 1990

For a moored body on the sea surface, incident waves with narrow-banded spectra excite the body oscillations of short and long periods. Since the period of slow oscillations can be as long as the natural period of the moored body in horizontal modes, resonance can occur and resulting large motions may cause significant strains in mooring cables. By using the perturbation method of multiple scales, the large slow motion can be analyzed without solving any second-order potentials explicitly. To the leading order, the flows associated with the fast and slow motions interact only parametrically and thus they can be studied separately. It is found that the slow motion strongly depends on the mooring stiffness. In particular, if the moring stiffness is considerably weak compared to the body inertia, the slow motion is highly amplified near resonance. It is also shown that the slow motion is associated with the generation of long waves.

• Steel and Composite Structures
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• v.51 no.4
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• pp.391-406
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• 2024

The present research investigates the combination resonance behaviors of porous FG shallow shells reinforced with oblique stiffeners and subjected to a two-term excitation. The oblique stiffeners considered in this research reinforce the shell internally and externally. To model the stiffeners, Lekhnitskii's smeared stiffeners technique is utilized. According to the first-order shear deformation theory (FSDT) and stress functions, a nonlinear model of the oblique stiffened shallow shell is established. With regard to the FSDT and von-Kármán nonlinear geometric assumptions, the stress-strain relationships for the present shell system are developed. Also, in order to discretize the nonlinear governing equations, the Galerkin method is implemented. To obtain the required relations for investigating the combination resonance theoretically, the method of multiple scales is applied. For verifying the results of the present research, generated results are compared with previous research. Additionally, a comparison with the P-T method is conducted to increase the validity of the generated results, as this method has illustrated advantages over other numerical methods in terms of accuracy and reliability. In this method, the piecewise constant argument is used jointly with the Taylor series expansion, which is why it is named the P-T method. The effects of stiffeners with different angles, and the effects of material parameters on the combination resonance behaviors of the present system are addressed. With the findings of this research, researchers and engineers in this field may use them as benchmarks for their design and research of porous FG shallow shells.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2002.04a
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• pp.25-33
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• 2002

Historical maps are precious materials, which show spatial distribution of land use, streets and so on at the time when the maps were produced. In analysis of historical maps, the most practical method is to compare them with the present ones, for instance by overlaying them. However, the low precision, in the geometrical sense, of the historical maps makes the task of comparison very difficult. This drawback brings us the idea to incorporate the historical maps into GIS after rubber-sheet transformation, i.e. geometric correction, of them. It makes comparing and overlaying multiple maps from different time periods. Furthermore, it gives map-scales to the historical maps, which are not in general represented on the old maps, and if we allow ourselves to ignore the changes in terrain from past to present, it will make overlaying of present contour lines on the historical maps. As a result, we can bring the points of view of quantitative consideration and three-dimensional visualization into analyses of historical map. We have addressed incorporating historical maps produced in Edo period (1603-1867) in Japan into our GIS for Tokyo. This article shows the outline of our procedures and some applications, e.g., overlaying different maps from Edo period to present, quantitative analyses of land use in Edo, and visualization of landscape of Edo.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.370-375
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• 2005

While the international standards bodies recommend the dual leaky buckets for the traffic specification for VBR service, video traffic shows burstiness in multiple time-scales. In order to fill this gap between the current standards and real traffic characteristics, we present a standard-compatible traffic parameter selection method based on the notion of a critical time scale (CTS). Since the defined algorithm minimizes the required link capacity under a maximum delay constraint, it could be used as a benchmark even when it can not be implemented easily. Simulation results with compressed video traces demonstrate the efficiency of the defined traffic parameter selection algorithm in resource allocation.

• Korean Journal of Adult Nursing
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• v.14 no.1
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• pp.125-134
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• 2002

Purpose: The objectives for this study were to identify the factors that correlate with appraisal of illness and to explore what variables are predictive of cancer patients primary caregivers' cognitive appraisal for stress. Method: The subjects were selected by convenient sampling and 130 caregivers who completed a questionnaire. Measures used in this study included the Family Inventory of Resources for Management, Social Support Index, Family Crisis Oriented Personal Evaluation Scales and Family Coping Coherence Index. Pearson correlation was used to identify the relationship among factors and multiple regression was used to determine the individual and cumulative effect of potential predictors on the caregivers' appraisal. Results: Patient's level of activity, severity of the disease, quality of relation between patient and caregiver, caregiver's subjective health status, economic status, family resources and coping were significantly correlated. Among the variables, coping, family resources, economic status and quality of relation between caregiver and patient predicted 49.2 percent of the variance in appraisal of caregivers' stress condition. Conclusion: These findings suggest that coping mechanisms and family resources are important for positive appraisal. Nurses should provide adequate nursing care for the primary caregiver about professional care information and supportive counseling.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.349-358
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• 1988

Natural convection velocity and temperature profiles are obtained approximately in the core at boundary layer flow regime for varying Prandtl number in a low aspect ratio rectangular Enclosure. Analysis is based on the formally obtained core flow equations using the multiple scales method. Results show good agreement with the existing works for $P_{r}$ ~ 1. No comparison, however, is possible yet for $P_{r}$ >> 1 and $P_{r}$ < 1 due to the lack of available date. It is shown here that boundary layer flow regimes are governed by two parameters, A $R_{a}$$^{1}$4/ and A( $P_{r}$ $R_{a}$)$^{1}$4 for $P_{R}$.geq. 1 and $P_{r}$ < 1 respectively.ely.ively.ely.y.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.15 no.4
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• pp.513-521
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• 2008

Purpose: The purpose of this study was to investigate the effect of stress, social support and self-efficacy on the mental health of female undergraduate students. Method: Three hundred ninety-nine undergraduate students were conveniently selected from a university in Seoul. The instruments used in this study were stress, social support, self-efficacy, and mental health scales. ANOVA, t-test, Pearson correlation coefficients, and stepwise multiple regression with SPSS Win 16.0 Version were used to analyze the data. Results: Mental health was significantly influenced by stress, social support, self-efficacy, and monthly expenditures. These variables accounted for 44.2% of the variance in mental health. Conclusion: The important factor that was found to affect the mental health of undergraduate female students was stress. Therefore, future studies need to be pursued to develop various strategies, such as stress relief programs, for mental health promotion of female undergraduate students.

• Journal of Pharmacopuncture
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• v.9 no.1
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• pp.59-67
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• 2006

Objectives : This study planed to evaluate effect of oriental medicine therapy treatment method of dyspnea that happen from cancer of the pancreas patient who accompany Multiple metasis Methods : Patient complained dyspnoea during admission into dept. Of internal medicine, college of oriental medicine, Dong-eui Univ, was appealed patient treated by Oriental medicine therapy that is of use Herb Medication and Herbal -acupuncture Treatment being diagnosed in lung asthenia including deficiency of Eum and insufficiency of Gi of the lung(肺虛), the fire due to deficiency(虛火), and loving warfare of symptoms evaluated through VAS (visual analog scales). Results & Conclusion : Patient's difficulty in breathing symptoms took a favorable turn after treatment. This study means that Oriental medicine therapy that is difficulty in breathing symptoms that happen from patient surely has effectiveness.

• Journal of Korean Public Health Nursing
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• v.21 no.2
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• pp.146-157
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• 2007

Purpose: To investigate the effect of self-efficacy and self-esteem on the mental health of the elderly in a rural area. Method: The subjects were 120 elderly aged 65 years or over. The instruments used in this study were the self-efficacy, self-esteem, and mental health scales. The data were analyzed by SPSS Win version 10.0, including mean, standard deviation, t-test, ANOVA, and stepwise multiple regression. Results: The means were 78.95$\pm$8.11 for self-efficacy, 25.07$\pm$4.79 for self-esteem, and 82.58$\pm$9.78 for mental health. Mental health was significantly influenced by age, spouse, family type, general self-efficacy, social self-efficacy, and self-esteem. These variables accounted for 21.5% of the variances of mental health. Conclusion: The important factors that affected the mental health of the elderly were self-efficacy and self-esteem. Therefore, these findings may provide useful data for constructing a geriatric mental health program of the elderly in a rural area.