• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.365-370
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• 2000

Sea dike construction for the tidal flat reclamation works in estuary and coast may change the characteristics of tidal motion and wave conditions in the region. In turn, a new hydraulic condition provides the impacts on sediment transport pattern and forms a new morphological environment. Also, morphological changes during the closure works of sea dike are closely related with a safy of sea dike. Therefore, the prediction of morphological changes is required secure the safe closure work and the economic design of sea dikes. To investigate morphological changes due to sea dike construction, hydrodynamic changes of tides and waves have to be evaluated, then sediment transport and sea bottom changes are computed. Mathematical modelling is required for representation of interrelation of tidal motion, wave and sediment transport. In this study, numerical model MORSYS is applied to compute the hydrodynamics and morphological changes around the closure gap for Saemankuem dike. This model allows a flexible integration of the module for waves, currents, sediment transport and bottom changes.

• Journal of Ecology and Environment
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• v.42 no.1
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• pp.20-29
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• 2018

Background: For various reasons such as agricultural and economical purposes, land-use changes are rapidly increasing not only in Korea but also in the world, leading to shifts in the characteristics of local carbon cycle. Therefore, in order to understand the large-scale ecosystem carbon cycle, it is necessary first to understand vegetation on this local scale. As a result, it is essential to comprehend change of the carbon balance attributed by the land-use changes. In this study, we attempt to understand accumulated soil carbon (ASC) and soil respiration (Rs) related to carbon cycle in two ecosystems, artificially turned forest into pastureland from forest and a native deciduous temperate forest, resulted from different land-use in the same area. Results: Rs were shown typical seasonal changes in the alpine pastureland (AP) and temperate deciduous forest (TDF). The annual average Rs was $160.5mg\;CO_2\;m^{-2}h^{-1}$ in the AP, but it was $405.1mg\;CO_2\;m^{-2}h^{-1}$ in the TDF, indicating that the Rs in the AP was lower about 54% than that in the TDF. Also, ASC in the AP was $124.49Mg\;C\;ha^{-1}$ from litter layer to 30-cm soil depth. The ASC was about $88.9Mg\;C\;ha^{-1}$, and it was 71.5% of that of the AP. The temperature factors in the AP was high about $4^{\circ}C$ on average compared to the TDF. In AP, it was observed high amount of sunlight entering near the soil surface which is related to high soil temperature is due to low canopy structure. This tendency is due to the smaller emission of organic carbon that is accumulated in the soil, which means a higher ASC in the AP compared to the TDF. Conclusions: The artificial transformation of natural ecosystems into different ecosystems is proceeding widely in the world as well as Korea. The change in land-use type is caused to make the different characteristics of carbon cycle and storage in same region. For evaluating and predicting the carbon cycle in the vegetation modified by the human activity, it is necessary to understand the carbon cycle and storage characteristics of natural ecosystems and converted ecosystems. In this study, we studied the characteristics of ecosystem carbon cycle using different forms in the same region. The land-use changes from a TDF to AP leads to changes in dominant vegetation. Removal of canopy increased light and temperature conditions and slightly decreased SMC during the growing season. Also, land-use change led to an increase of ASC and decrease of Rs in AP. In terms of ecosystem carbon sequestration, AP showed a greater amount of carbon stored in the soil due to sustained supply of above-ground liters and lower degradation rate (soil respiration) than TDF in the high mountains. This shows that TDF and AP do not have much difference in terms of storage and circulation of carbon because the amount of carbon in the forest biomass is stored in the soil in the AP.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.443-446
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• 2005

The Kaplan turbine model has been tested and analyzed. The blade angle and the guide vane opening of the turbine model were designed to be varied according to the best combination of guide vane and runner blade opening. When the changes in head and output were comparatively large, the efficiency drop were small, so the efficiency characteristics and stability of the entire operating condition were maintained in good condition. These results showed that the developed model in this study will be suitable for small hydro power stations with large changes in head and load.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.493-499
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• 1997

In this study, the changes in transmitting and receiving characteristics, especially resonance frequencies, of the underwater acoustic planar array transducer by the transformers used in the analog weighting circuit are investigated. Electrical equivalent circuit analysis shows that an ideal transformer does not change the resonance frequency of the transmitting mode, but the resonance frequency which gives the maximum receiving sensitivity can be designed by adjusting the magnitude of reactance of transformer.

• Korean Journal of Psychosomatic Medicine
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• v.7 no.1
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• pp.103-115
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• 1999

Objectives : A large of studies have found an association between premenstrual syndrome and affective disorder, in particular, depression. Some studies have reported that women with depressive disorders may experience menstrual cycle-associated changes in the severity of their symptoms. This study was designed to compare the characteristics of premenstrual changes between control group and affective patient group, and to assess possible risk factors for premenstrual changes in patients. Methods : Eighty normal controls and eighty outpatients given maintenance therapy with fixed dose for at least more than four weeks were asked to complete questionnaires on menstrual history, obstetric-gynecological history, and functional impairment. In addition, to compare the characteristics of premenstrual changes, 16 items based on DSM-IV criteria A for premenstrual dysphoric disorder were rated on the following scale : 0(no change), 1(mild), 2(moderate), 3(severe). Moderate or severe change in each item was considered as premenstrual change and the subjects who reported more than one premenstrual change were defined as premenstrual change group. Results : The results were as follows : 1) The percentage of premenstrual change group was 32.6% in patient group and 50% in control group. 2) Frequently reported premenstrual changes were as follows in control group : breast tenderness; anger ; affective liability ; lethargy, easy fatigability, or marked lack of energy ; abdominal pain or discomfort. In patients, the mood or behavioral changes were frequently reported. The changes were as follows : lethargy, easy fatigability, or marked lack of energy ; change in appetite; affective liability ; sense of difficulty in concentrating : hypersomnia or insomnia. 3) In the premenstrual change group, the patients with only mood or behavioral changes were significantly more than those with only physical changes or both changes. 4) The severity of functional impairment was significantly correlated with the frequency of mood or behavioral changes in patients. 5) There were no significant differences in menstrual characteristics between patients with premenstrual changes and patients without them except the severity of dysmenorrhea. And the severity of dysmenorrhea was correlated with the frequency of premenstrual change. Conclusion : The proportion of patients with affective disorder, who reported moderate-to-severe premenstrual changes, experiencing mood or behavioral changes larger than those experiencing physical changes during premenstrual period. It is possible that some patients with affective disorder, who reported premenstrual mood or behavioral changes, suffer from coexisting premenstrual syndrome with affective disorder or premenstrual exacerbation of affective disorder. Since the more premenstrual changes, the severer functional impairment, the patients reporting mood or behavioral disturbance in premenstrual period should be carefully evaluated, and appropriate therapeutic stategies might be considered.

• KIEAE Journal
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• v.17 no.4
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• pp.5-12
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• 2017

Purpose: Recently, a sudden increase in one household in Korea has become an important social problem. Changes in lifestyles such as population change, marriage, childbirth, and divorce are becoming increasing factors for single-family households. As a result of these changes, the government has implemented policies for one accredited state. However, the policy for one domestic applicant is insufficient compared to other countries. As a measure to cope with the increase in the number of applicants, Shared House has emerged and research on Shared House is necessary. Method: First, we analyze the overall characteristics of domestic share house. And it does a spatial analysis of domestic share house. Especially, it analyzes the relationship between private space and public space. Finally, the plan characteristics are derived based on the analysis results. Result: The results are as follows. First, the type of share house is classified according to the combination of the arrangement of private space and the public space. Second, the larger the scale, the more vertical arrangement than horizontal arrangement. Finally, the character of the share house changes according to the characteristics of the resident.

• The Korean Journal of Quaternary Research
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• v.21 no.2
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• pp.74-76
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• 2007

The modern foraminiferal distribution patterns and species diversity in surrounding seas of Korea are controlled by winter monsoon and characteristics of water masses. Abrupt climate change, Younger Dryas cold episode" is identified in Korea. The Younger Dryas is characterized by local extinctions of foraminifera. Several record-breaking climate phenomena observed in Korea, especially September, 2007.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2004.11a
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• pp.271-276
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• 2004

This study was intended to examine the changes of housing in the context of women's status since civilization in Korea. The purpose was accomplished by review of existing related literature. It was concluded that the changes of women's status due to social changes had meaningful influences on various characteristics of housing. The location of kitchen, housing service, there cognition of housing as a shared space for the family are those which were influenced by changes of women's status.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.2
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• pp.133-139
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• 2013

Morphing aircraft capable of varying their wing form can operate efficiently at various flight conditions. However, radical morphing of the aircraft leads to increased structural complexities, resulting in occurrence of dynamic instabilities such as flutter, which can lead to catastrophic events. Therefore, it is of utmost importance to investigate and understand the changes in flutter characteristics of morphing wings, to ensure uncompromised safety and maximum reliability. In this paper, a study on the flutter characteristics of the folding wing type morphing concept is conducted, to examine the effect of changes in folding angles on the flutter speed and flutter frequency. The subsonic aerodynamic theory Doublet Lattice Method (DLM) and p-k method are used, to perform the flutter analysis in MSC.NASTRAN. The present baseline flutter characteristics correspond well with the results from previous study. Furthermore, enhancement of the flutter characteristics of an aluminum folding wing is proposed, by varying the outboard wing folding angle independently of the inboard wing folding angle. It is clearly found that the flutter characteristics are strongly influenced by changes in the inboard/outboard folding angles, and significant improvement in the flutter characteristics of a folding wing can be achieved, by varying its outboard wing folding angle.

• Tribology and Lubricants
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• v.31 no.6
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• pp.245-250
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• 2015

This study investigates the lubrication characteristics of fuel injection pumps with reference to different fuel oils. Medium-speed diesel engines use fuel oils with various viscosities, such as heavy fuel oil (HFO, which is a high-viscosity fuel oil) and light diesel oil (LDO, which is a low-viscosity fuel oil). When fuel oil with a low viscosity is used, both fuel oil and lubricating oil lubricate the system. Thus, the lubrication of the fuel injection pump is in a multi-viscosity condition when the fuel oil in use changes. We suggest three cases of multi-viscosity models, and divide the fuel injection pump into three lubrication sections: a, the new oil section; b, the mixed oil section; and c, the used oil section. This study compares the lubrication characteristics with variation of the multi-viscosity model, clearance. The volume of Section b does not affect the lubrication characteristics. The lubrication characteristics of the fuel injection pump are poor when high-viscosity fuel oil transfers to low-viscosity fuel oil. This occurs because the viscosity in the new oil section (i.e., Section a) dominates the lubrication characteristics of the fuel injection pump. However, the lubricant oil supply in the used oil section (i.e., Section c) can improve the lubrication characteristics in this condition. Moreover, the clearances of the stem and head significantly influence the lubrication characteristics when the fuel oil changes.