• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.137-145
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• 2008

An experimental study was performed in order to investigate the influence of Reynolds number on the drag coefficient variations of an oscillating airfoil. A NACA 0012 airfoil was sinusoidally pitched at the quarter chord point with an oscillating amplitude of ${\pm}6^{\circ}$. The free-stream velocities were 1.98, 2.83 and 4.03 m/s and the corresponding chord Reynolds numbers were $2.3{\times}10^4$, $3.3{\times}10^4$ and $4.8{\times}10^4$, respectively. The drag coefficient was calculated from the ensemble average velocity measured by an X-type hot-wire probe(X-type, 55R51) in the near-wakes region. In the case of Re=$2.3{\times}10^4$, variation of drag coefficient shows a negative damping (counter-clockwise variation), which implies an unstable state which could be excited by aerodynamic force, whereas the drag coefficient represents the positive damping (clockwise variation) as the Reynolds number increases from Re=$3.3{\times}10^4$ to $4.8{\times}10^4$. Hence, the drag coefficient variations show significant differences between Re=$2.3{\times}10^4$ and $4.8{\times}10^4$이다.

• Journal of Advanced Navigation Technology
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• v.22 no.1
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• pp.31-36
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• 2018

In this paper, we designed and implemented an ultra wideband(UWB) antenna with band rejection characteristics. The proposed antenna consists of a planar radiation patch with slots and ground planes on both sides. Due to the slots in the radiation patch, the antenna shows band rejection characteristics. U-type slot contributes for wireless local area network(WLAN, 5.15~5.825 GHz) band rejection and n-type slot contributes for X-Band(7.25~8.395 GHz) band rejection. To make voltage standing wave ratio(VSWR) less than 2.0 for UWB frequency band except rejection bands, the shapes of planar radiation patch and ground plane was modified. The Ansoft 's high frequency structure simulator(HFSS) was used for the design process and simulations of the proposed antenna. The simulated antenna showed VSWR less than 2.0 for all UWB band excepts for dual rejection bands of 5.15 ~ 5.94 GHz and 7.02 ~ 8.45 GHz. And measured VSWR for the implemented antenna is less than 2.0 for all UWB band of 3.10~10.60 GHz excluding dual rejection bands of 5.12~5.95 GHz and 7.20~8.58 GHz.

• Journal of agriculture & life science
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• v.45 no.6
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• pp.151-162
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• 2011

Methanol and hexane extracts from 35 species in 27 families of herbal plants were evaluated for their acaricidal activities against two-spotted spider mite, Tetranychus urticae by leaf-dipping and spraying methods in laboratory, pot and field, respectively. Acaricidal activities were different depending on herbal plants. When T. urticae was released on leaves of Phaseolus vulgaris var. humilis that were dipped in the 1,000 ppm hexane extracts from fruits of Torreya nucifer and Daphan genkwa, seeds of Xanthium strumarium and Pharbitis nil at one minute they experienced 56.8, 47.8, 47.7, and 47.7% mortalities, respectively. Dipping time influenced acaricidal activity, that is, one minute dipping was more effective than 30 second dipping of Phaseolus vulgaris var. humilis leaves. However, extracts of X. strumarium and P. nil seeds had comparatively high activities. Concentration of hexane extract of X. strumarium and P. nil seeds revealing LC50 were 1,824 and 1,899 ppm, respectively. Extracts of both plants from hot and cold water were not effective representing <20% mortality at 1,000 ppm. However, hexane extracts of X. strumarium and P. nil seeds were effective against T. urticae on P. vulgaris var. humilis representing 76.3 and 71.3% mortalities in pot, respectively. Control effects of hexane extract of P. nil seed were 50.8 and 35.1% at 2,000 and 1,000 ppm against T. urticae on Chrysanthemum morifolium in greenhouse, respectively.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.895-905
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• 1994

The solid phase crystallization behavior of undoped amorphous $Si_{1-x}Ge_{x}$ (X=O to 0.53) alloyfilms was studied by X-ray diffractometry(XRD) and transmission electron microscopy(TEM). Thefilms were deposited on thermally oxidized 5" (100) Si wafer by MBE(Mo1ecular Beam Epitaxy) at 300'C and annealed in the temperature range of $500^{\circ}C$ ~ $625^{\circ}C$. From XRD results, it was found that the thermal budget for full crystallization of the film is significantly reduced as the Ge concentration in thefilm is increased. In addition, the results also shows that pure amorphous Si film crystallizes with astrong (111) texture while the $Si_{1-x}Ge_{x}$ alloy film crystallzes with a (311) texture suggesting that the solidphase crystallization mechanism is changed by the incorporation of Ge. TEM analysis of the crystallized filmshow that the grain morphology of the pure Si is an elliptical and/or a dendrite shape with high density ofcrystalline defects in the grains while that of the $Si_{0.47}Ge_{0.53}$ alloy is more or less equiaxed shape with muchlower density of defects. From these results, we conclude that the crystallization mechanism changes fromtwin-assisted growth mode to random growth mode as the Ge cocentration is increased.ocentration is increased.

• Journal of radiological science and technology
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• v.29 no.3
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• pp.167-175
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• 2006

With the recent prevalence of helical CT and multi-slice CT, which deliver higher radiation dose than conventional CT due to overbeaming effect in X-ray exposure and interpolation technique in image reconstruction. Although multi-detector and helical CT scanner provide a variety of opportunities for patient dose reduction, the potential risk for high radiation levels in CT examination can't be overemphasized in spite of acquiring more diagnostic information. So much more concerns is necessary about dose characteristics of CT scanner, especially dose efficient design as well as dose modulation software, because dose efficiency built into the scanner's design is probably the most important aspect of successful low dose clinical performance. This study was conducted to evaluate z-axis geometric dose efficiency in single detector CT and each level multi-detector CT, as well as to compare z-axis dose efficiency with change of technical scan parameters such as focal spot size of tube, beam collimation, detector combination, scan mode, pitch size, slice width and interval. The results obtained were as follows ; 1. SDCT was most highest and 4 MDCT was most lowest in z-axis geometric dose efficiency among SDCT, 4, 8, 16, 64 slice MDCT made by GE manufacture. 2. Small focal spot was 0.67-13.62% higher than large focal spot in z-axis geometric dose efficiency at MDCT. 3. Large beam collimation was 3.13-51.52% higher than small beam collimation in z-axis geometric dose efficiency at MDCT. 4. Z-axis geometric dose efficiency was same at 4 slice MDCT in all condition and 8 slice MDCT of large beam collimation with change of detector combination, but was changed irregularly at 8 slice MDCT of small beam collimation and 16 slice MDCT in all condition with change of detector combination. 5. There was no significant difference for z-axis geometric dose efficiency between conventional scan and helical scan, and with change of pitch factor, as well as change of slice width or interval for image reconstruction. As a conclusion, for reduction of patient radiation dose delivered from CT examination we are particularly concerned with dose efficiency of equipment and have to select proper scanning parameters which increase z-axis geometric dose efficiency within the range of preserving optimum clinical information in MDCT examination.

• Tuberculosis and Respiratory Diseases
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• v.51 no.4
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• pp.346-353
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• 2001

Background : Pulmonary Langerhans cell histiocytosis forms part of a spectrum of diseases that are characterized by a monoclonal proliferation and infiltration of organs by Langerhans cells. Several organ systems may be involved in Langerhans cell histiocytosis, including the lungs, bone, skin, pituitary gland, liver, lymph nodes and thyroid. Pulmonary histiocytosis X represents 2.8% of interstitial lung disease. Here we present the clinical, radiological, therapeutic aspects of pulmonary histiocytosis X. Method : Fourteen cases of biopsy-proven pulmonary histiocytosis X patients who were diagnosed in Seoul National University Hospital during the period from January 1990 to December 1998 were analyzed retrospectively. Result : There were 12 men and 2 women in this study. The initial presenting symptoms were dyspnea, cough, chest pain, which was associated with the pneumothorax, and chest radiography abnormalities. Only 8 patients (57%) were smokers. There were 5 patients with extra-pulmonary histiocytosis (pituitary, bone, skin). Eight patients had received the chemotherapy. There were no mortalities and only one patient experienced an aggravation of symptom during the follow-up period. Conclusion : In contrast to previous reports from other countries, the patients with pulmonary histiocytosis X in this study presented with several different clinical characteristics, such as a male predominance, relatively low smoker's rate, and a better prognosis.

• Korean Journal of Hospice Care
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• v.2 no.2
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• pp.28-48
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• 2002

The advances of medical technologies have not only prolonged human life span, but also extended suffering period for the patients with incurable medical diseases. Hospice movement was developed to help these patients keep dignity and lives peaceful at the end of their life. Since many patients prefer to spend the last moment of life at home with their family, hospice home care has become very popular worldwide. The purpose of this study for a promotion and development of hospice home care in Korea, and features basic research on medical profession's knowledge and attitudes to hospice home care. This study which was used for the research questionnaires developed by the researcher that were answered by 100 physicians and 127 nurses in a general hospital. Data were collected from April 22, 2002 to May 10, 2002. The SPSS was used to make a comparative analysis of the frequency, percentile, ANOVA, and x2-test. The results of the study were as follows; 1.The medical profession showed high level of knowledge of the definition and philosophy of hospice. However, the physician group of the examinees showed insufficient knowledge of the fact that hospice care includes bereavement care, while the nurse group's response to the same question showed a significant difference(x2=10.752, p=.001). 2.For whom the hospice home care is provided, 95.6% of the respondents showed very high level of knowledge as answering that the incurable terminal illness patients and their families are the beneficiaries of hospice care. The respondents counted nurses, volunteers, pastors, physicians and social workers, consecutively, as hospice care providers. More nurse were positive toward pastors than physicians in regarding as a hospice care provider by a significant difference(x2=11.634, p=.001). 3.For when to referral hospice home care to the patients, only 34.2% answered that patients with less than 6 months of survival time are advised to receive hospice care, reflecting very low level of knowledge. 23.0% of the physicians and 48.0% of the nurses answered that hospice care should be provided when death is imminent, making a significant difference between the two groups(x2=6.413, p=.000). 4.To promote hospice activities, 87.2% pointed out that it is crucial to make general people, including those engaging in the medical field, more aware of hospice. 79.7% answered that a national hospice management should be developed, marking a significant difference between the physician group and nurse group(x2=10.485, p=.001). 5.Advantages of hospice home care are 87.2% responded that patients can have better rest at home receiving hospice home care. Economical merit was brought forward as one of the advantages also, where there was a significant difference between the physicians group and nurse group(x2=7.009, p=.008). 6.The medical professions' attitude to hospice home care are 92.8% of the physicians answered that they would advise incurable terminally ill patients to be discharged from hospital, with 44.3% of them advising the patients to receive hospice home care after leaving the hospital. From the nurses' point of view, 20.9% of the terminally ill patients are being referred to hospice home care after discharge, which makes a significant difference from the physicians' response(x2=19.121, p=.001). 7. 30.6% of physicians have referred terminally ill patients to hospice home care, 75.9% of whom were satisfied with their decision. Those physicians who have never referred their patients to hospice home care either did not know how to do it(66.7%) or were afraid of losing trust by giving the patients an impression of giving up(27.3%). 94.9% of the physicians responded that they would refer their last stage patients to a doctor who is involving palliative care. 8.Only 36.2% of nurses have suggested to physicians that refer the terminally ill patients discharged from the hospital to hospice home care. Once suggested, 95.8% of the physicians have accepted the suggestion. Nurses were reluctant to suggest hospice home care to the physicians, as 48.8% of the nurses said they did not want to. From the result of this study the following conclusion can be drawn, the medical profession's awareness of general hospice care has been increased greatly compared to the results of the previously performed studies. However, this study result also shows that their knowledge of hospice home care is not good enough yet. There is a need for high recommended that medical education institute and develop regular courses on various types of hospice care. Medical field training courses for physicians and nurses will be very helpful as well. It is also important to train hospice experts such as palliative physicians and develop a national hospice management urgently in order to improve the hospice care in Korea.

• Korean Journal of Environmental Agriculture
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• v.6 no.1
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• pp.67-75
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• 1987

The major objectives of this study were to find out the growth and yield of two ecotypes of Korean garlic in main garlic producing districts in Korea. The data were collected by the field survey which had been conducted at 270 township in 58 major garlic production countries throughout the country on 10th, 20th, and 30th day of every month from 1982 to 1984. The results of this study were as follow: 1) Sowing period of garlic of southern and northern ecotype were around September 20 and October 20, respectively. 2) Average number of plants per $3.3m^2$ of the southern and northern ecotype were 123 and 100, respectively. 3) Leaf emergence time of southern ecotype was before the beginning of winter (November) and that of northern ecotype was from early February till April. 4) Stepwise multiple regression analysis showed that the plant heights measured on November 30 for southern ecotype and on June 30 for northern ecotype most adequately predicted the yield of garlic. The relationship between yield and plant height were as follows: Southern ecotype; Y=571.56+5.34X Northern ecotype; Y=251.81+5.45X where Y is yield expressed in Kg/l0a and X is height in cm at the respective date. 5) The number of leaves increased until harvest in both ecotypes. At harvest, the number of leaves in southern and northern ecotype were 10 and 8, respectively. Number of leaves counted on January 20 for southern ecotype and on June 20 for northern ecotype correlated best with the yield of the ecotypes. 6) The highest senescent portion of southern ecotype and northern ecotype were seen on January 30 and May 30, respectively. Stepwise multiple regression analysis showed that the senescent portion of southern ecotype counted on January 30 and that of northern ecotype on June 20 mostly affected the yield. 7) Average yield of southern and northern ecotype at the main garlic producing districts were 771 and 652Kg/10a, respectively.

• Tuberculosis and Respiratory Diseases
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• v.50 no.4
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• pp.484-492
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• 2001

Background : Pulmonary tuberculosis with a remaining cavitary lesion is considered to be a problem with the course of treatment. In particular, re-treatment cases tend to respond poorly to current anti-tuberculosis agents. Therefore the factors that are related with the poor closure of a cavitary lesion in pulmonary tuberculosis during treatment were evaluated. Methods : A retrospective review of the medical records and chest X -ray films of 68 patients who had chemotherapy for the pulmonary tuberculosis with cavitary lesions was made. All the patients had been followed up for more than 12 months at National Masan Tuberculosis Hospital as of Aug. 2000. Results : The male to female ratio was 3.9:1.72.4% of the patients were between 20 to 50 years of age. 66.2% of the cavitary lesions on the chest X-ray films were confined to the upper lung fields : 36.8% in the right upper lung field and 29.4% in the left upper lung field. 82.4% of the cavities were less than 40 mm in their size, and 83.8% were less than 6 mm thick. The cavitary lesions were closed in 48 cases and remained in 20 cases during a follow-up period of more than 12 months. The factors that are thought to affect to the outcomes of the cavities were age, past medication history, the number of unused drugs, and the number of sensitive drugs. Conclusion : In the treatment courses of pulmonary tuberculosis with cavitary lesions, the following factors are associated with less desirable outcome:an age over 45, a past medication history of more than 2 courses of treatment, The number of unused drugs not exceeding average 6 and the number of sensitive drugs not exceeding average 7.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.171-177
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• 2001

The thermal and mechanical properties of amorphous Z $r_{62-x}$N $i_{10}$C $u_{20}$A $l_{8}$ $Ti_{x}$ (x=3, 6, 9at%) alloys were investigated. The crystallization process was confirmed as amorphous longrightarrow amorphous + Z $r_2$A $l_3$+ Zr + (Ni,Ti) longrightarrow Z $r_2$Cu + Al + (Ni,Ti) for 3at%Ti, amorphous longrightarrow amorphous + Al longrightarrow $Al_2$Ti + NiZr + CuTi for 6at%Ti and amorphous longrightarrow amorphous + Zr + Al longrightarrow Zr + $Al_2$Zr + Al $Ti_3$+ CuTi for 9at%Ti. lickers hardness ( $H_{v}$ ) increased with increasing volume fraction( $V_{f}$ ) of pricipitates for all concerned compositions. Tensile fracture strength ($\sigma_{f}$ ) showed a maximum value 1219MPa at $V_{f}$ = 38% for 3at%Ti, 1203MPa at $V_{f}$ = 2% for 6at%Ti and 1350MPa at $V_{f}$ = 5% for 9at%Ti. The $\sigma_{f}$ was rapidly decreased after showing the maximum value. The $V_{f}$ corresponding to rapidly decreased $\sigma_{f}$ coincided with the $V_{f}$ transited from ductile to brittle fracture surface.ace.