• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.181-188
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• 2001

The flow past a circular cylinder forced to vibrate transversely is numerically simulated by solving the two-dimensional Wavier-Stokes equations modified by the vibration velocity of a circular cylinder at a Reynolds number of 164. The higher-order finite difference scheme is employed for the spatial discretization along with the second order Adams-Bashforth and the first order backward-Euler time integration. The calculated cylinder vibration frequency is between 0.60 and 1.30 times of the natural vortex-shedding frequency. The calculated oscillation amplitude extends to $25\%$ of the cylinder diameter and in the case of the lock-in region it is $60\%$. It is made clear that the cylinder oscillation has influence on the wake pattern, the time histories of the drag and lift forces, power spectral density and phase diagrams, etc. It is found that these results include both the periodic (lock-in) and the quasi-periodic (non-lock-in) state. The vortex shedding frequency equals the driving frequency in the lock-in region but is independent in the non-lock-in region. The mean drag and the maximum lift coefficient increase with the increase of the forcing amplitude in the lock-in state. The lock-in boundaries are also established from the present direct numerical simulation.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.600-605
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• 2002

The keyhole formed by high energy density laser-material interaction periodically collapses due to surface tension of the molten metal in partial penetration welds. The collapse sometimes traps a void at the bottom of the keyhole, and it remains as welding defects. This phenomenon is seen as one cause of the instability of the keyhole during laser beam welding. Thus, it seems likely that improving the stability of the keyhole can reduce voids and uniform the penetration depth. The goal of this work is to develop techniques for controlling laser weld keyhole dynamics to reduce weld defects such as voids and inconsistent penetration. Statistical analysis of the penetration depth signals in glycerin determined that keyhole dynamics are chaotic. The chaotic nature of keyhole fluctuations and the ability of laser power modulation to control them have been demonstrated by high-speed video images of laser welds in glycerin. Additionally, an incident leading beam angle is applied to enhance the stability of the keyhole. The quasi-sinusoidal laser beam power of 400Hz frequency and 15$^{\circ}$ incident leading beam angle were determined to be the optimum parameters for the reduction of voids. Finally, chaos analyses of uncontrolled signals and controlled signals were done to show the effectiveness of modulation on the keyhole dynamics. Three-dimensional phase plots for uncontrolled system and controlled system are produced to demonstrate that the chaotic keyhole dynamics is converted to regular periodic behavior by control methods: power modulation and incident leading beam angle.

• Journal of East-West Nursing Research
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• v.20 no.2
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• pp.73-80
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• 2014

Purpose: This research aims to identify the physio-psychological effects of applying a qi massage program as an independent complementary intervention for employees with hypertension in a workplace. Methods: A quasi-experimental design was employed using a nonequivalent control group with pre- and post-tests. The study was performed from August 18 to October 10, 2008 on hypertensive employees being treated with a qi massage program in a company. The control group was recruited first to prevent treatment diffusion. The experimental group was subsequently recruited and received individual treatment for 30 minutes. Collected data was analyzed using SPSS16.0 version. ${\chi}^2$-test, Mann-Whitney U test, Wilcoxon signed ranks test, Fisher's exact test and paired t-test were implemented in order to examine the effects of individual intervention on patients who are treated with the qi massage program. Results: The experimental group showed a greater improvement in systolic blood pressure, diastolic pressure, stress, and quality of life than did the control group. Conclusion: A qi massage program may be implemented as a complementary intervention to effectively treat hypertensive persons.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.13 no.1
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• pp.42-49
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• 2006

Purpose: This study was done to evaluate the effectiveness of cardiac rehabilitation education individualized to PCI patients in order to improve their knowledge of these diseases and to lessen their anxiety. Method: A Quasi experimental design with non-equivalent control group non-synchronized design was used. The experimental group had the PCI operation for ischemic heart disease and individualized cardiac rehabilitation education and counseling twice for 25 minutes each time using an educational booklet developed by the authors. The effects of the education were analyzed using a knowledge assessment tool, state anxiety inventory and anxiety visual analogue scale. Results: The experimental group who received the individualized cardiac rehabilitation education showed a high level of knowledge about diseases compared to the control group and particularly showed a significant difference in knowledge about the drugs used for treatment. However, no significant difference was observed between the two groups in the level of state anxiety and anxiety visual analogue scale. Conclusion: Individualized cardiac rehabilitation education did not reduce anxiety but it was effective in enhancing the participants' knowledge about the diseases. Thus, it can be utilized effectively in addressing risk factors in ischemic heart diseases by providing education individualized according to patients' demands and knowledge levels.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.37.1-37.1
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• 2017

Since the seminal work of Perrin, physicists have understood in the context of kinetic theory how ink slowly diffuses in a glass of water. The fluctuations of the stochastic forces acting on water molecules drive the diffusion of the ink in the fluid. This is the archetype of a process described by the so-called fluctuation-dissipation theorem, which universally relates the rate of diffusion to the power spectrum of the fluctuating forces. For stars in galaxies, a similar process occurs but with two significant differences, due to the long-range nature of the gravitational interaction: (i) for the diffusion to be effective, stars need to resonate, i.e. present commensurable frequencies, otherwise they only follow the orbit imposed by their mean field; (ii) the amplitudes of the induced fluctuating forces are significantly boosted by collective effects, i.e. by the fact that, because of self-gravity, each star generates a wake in its neighbours. In the expanding universe, an overdense perturbation passing a critical threshold will collapse onto itself and, through violent relaxation and mergers, rapidly converge towards a stationary, phase-mixed and highly symmetric state, with a partially frozen orbital structure. The object is then locked in a quasi-stationary state imposed by its mean gravitational field. Of particular interests are strongly responsive colder systems which, given time and kicks, find the opportunity to significantly reshuffle their orbital structure towards more likely configurations. This presentation aims to explain this long-term reshuffling called gravity-driven secular evolution on cosmic timescales, described by extended kinetic theory. I will illustrate this with radial migration, disc thickening and the stellar cluster in the galactic centre.

• Korean Journal of Adult Nursing
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• v.18 no.3
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• pp.416-425
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• 2006

Purpose: To evaluate the effects of a follow-up program for breast cancer patients after surgery. Method: A quasi-experimental design was used. The subjects were 56 breast cancer patients (experimental group: 27, control group: 29). The subjects of the experimental group participated in the Follow-up program of 7 sessions once a week, during 4 weeks including one telephone visit. The program consisted of health education of breast cancer, exercise, lymph edema prevention, diet education, theraband rehabilitation exercise, laugh therapy, and breast self examination. The obtained data were analysed by using the ANCOVA of SPSS. Results: There was a significant difference in the scores of physical wellbeing, symptom distress and mood state between the two groups. Conclusion: Considering these research results, short-term intervention could improve physical and emotional functioning abilities by helping better health. Nurses should establish and manage a proper program to provide multipurpose support and it must apply the program after surgery as soon as possible for breast cancer women.

• Wind and Structures
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• v.11 no.3
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• pp.209-220
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• 2008

Flutter derivatives provide the basis of predicting the critical wind speed in flutter and buffeting analysis of long-span cable-supported bridges. Many studies have been performed on the methods and applications of identification of flutter derivatives of bridge decks under wind action. In fact, strong wind, especially typhoon, is always accompanied by heavy rain. Then, what is the effect of rain on flutter derivatives and flutter critical wind speed of bridges? Unfortunately, there have been no studies on this subject. This paper makes an initial study on this problem. Covariance-driven Stochastic Subspace Identification (SSI in short) which is capable of estimating the flutter derivatives of bridge decks from their steady random responses is presented first. An experimental set-up is specially designed and manufactured to produce the conditions of rain and wind. Wind tunnel tests of a quasi-streamlined thin plate model are conducted under conditions of only wind action and simultaneous wind-rain action, respectively. The flutter derivatives are then extracted by the SSI method, and comparisons are made between the flutter derivatives under the two different conditions. The comparison results tentatively indicate that rain has non-trivial effects on flutter derivatives, especially on and $H_2$ and $A_2$thus the flutter critical wind speeds of bridges.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.1
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• pp.217-220
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• 2015

Background: Breast cancer is the second most common cancer in the world and by far the most frequent cancer among women. Objective: This study was conducted to observe the effect of progressive relaxation exercises on anxiety and comfort level of breast cancer patients receiving chemotherapy. Materials and Methods: A control group pre-test/post-test quasi-experimental model was applied with experimental (30) and control (30) groups, who agreed to participate in this study. Data collection was with the "Personnel Information Form, State-Trait Anxiety Inventory and General Comfort Scale". Results: The average age of the patients that participated in the study was $49.1{\pm}7.96$ years. Eighty-three point three percent (n=25) of the patients in the experiment group and 86.7 (n=26) percent of patients in control group were married. Patient state of anxiety post-test mean scores were $36.2{\pm}8.21$ in the experimental group and $43.4{\pm}7.96$ in the control group, the difference being statistically significant (p<0.05). The general comfort scale post-test mean scores were $149.5{\pm}13.9$ in the experimental group and $137.7{\pm}15.0$ in the control group, again statistically significant (p<0.05). Conclusions: Progressive relaxation exercises positively affect patient comfort and anxiety levels in Turkey.

• Korean Journal of Adult Nursing
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• v.19 no.5
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• pp.115-126
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• 2007

Purpose: The present study is a quasi-experimental research for examining the effects of imagery on stress, anxiety and immune cells in acute leukemia patients receiving chemotherapy and utilizing the therapy for their self control and stress management. Methods: The subjects were 60 patients who were diagnosed with acute leukemia and scheduled to receive chemotherapy at A hospital in Seoul during the period from November 2006 to March 2007. After the start of chemotherapy, the experimental group received imagery for 4 weeks, three sessions a week, so a total of 12 sessions and 156 minutes. Results: The decrease of stress was larger in the experimental group than in the control group. Systolic blood pressure decreased significantly more in the experimental group than in the control group. In the experimental group, state anxiety decreased significantly in the 2nd week of the experiment and after the final stage of the experiment. The total number of white blood cells, and the absolute number of neutrophils and lymphocytes were showing significant differences between the time points. Conclusion: Imagery is an effective intervention for reducing stress and state anxiety and stabilizing blood pressure in acute leukemia patients receiving chemotherapy.

• Journal of Korean Academy of Nursing
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• v.30 no.2
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• pp.282-292
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• 2000

A meta-analysis of 14 quasi-experimental studies was conducted to compare the effect of size on various relaxation therapies applied to patients and health volunteer students. These studies were selected from theses, dissertations and papers that have been done between 1982 to 1993. Also They have a randomized or nonequivalent control group in a pre test-post test design. The studies were evaluated in different ways; 1) types of relaxation therapy, 2) total amount of time of relaxation therapy, and 3) types of outcome variables. For a group of homogenious studies, the weighted mean effect size and standard error were estimated. Some findings are summarized as follows : 1. Jacobson relaxation therapy had a larger effect on systolic and diastolic blood pressures than on state anxiety. 2. For the total time of relaxation therapy, (longer than 60 minutes) had a much larger effect in decreasing systolic and diastolic blood pressures than in the case of a time period shorter than 60 minutes. 3. Relaxation therapy applied to surgery patients also had a larger effect in decreasing state anxiety than when applied to other patients.