• Proceedings of the KSME Conference
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• 2000.11b
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• pp.297-303
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• 2000

Natural convection heat transfer have been paid attention because it can be applied to various areas such as cooling of nuclear reactor, heat storing system and so on. Among such applications, the melting process of phase change material(PCM) has been actively studied. However most researches have focused on phase change heat transfer in natural melting. Therefore, In this paper, ultrasonic vibration was adopted to increase the melting rate. In addition, general relationship and corelationship between melting with ultrasonic vibration and melting without ultrasonic vibration have been established during the melting of PCM.

• Journal of Korean Society of Rural Planning
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• v.25 no.3
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• pp.129-139
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• 2019

The purpose of this study is to monitor the long-term vegetation change of the village complementary forest after restoration. Based on the monitoring in 2010, six years after the restoration project in 2004, the monitoring of the complementary forest in Dubang village in 2019 after 9 years was conducted. This study identifies the change of species diversity and structure, growth, vegetation coverage, structural quality etc. and succession through long-term monitoring. For this, field survey was conducted in 2003 and 2010, 2019. The results demonstrate significant increase of species diversity and multi-layer structure and progress of natural succession. Overall, Part I is considered to be a quasi-natural complementary village forest, which has a natural balance between natural vegetation that have remained in nature for a long time and anthropogenic vegetation, revealing the coexistence of nature and humanity. It means ecological structure and function have improved. Part II should be restored to the lost part and adaptive management rather than excessive management should be carried out to leave natural succession.

• Journal of Korean Society of Forest Science
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• v.94 no.4 s.161
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• pp.252-257
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• 2005

The study on long-term change of natural and sediment disasters such as landslides and debris flows is not thoroughgoing enough in spite of increasing of concern for disaster. Therefore, the change of natural and sediment disasters was investigated with the number of victims caused by both disasters and the ratio of sediment disasters for natural disasters was compared. The number of victims by sediment and natural disasters has apparently been decreasing despite of the change of rainfall pattern. The number of victims was changed to 140 persons/year in the late 1990s from 250 persons/year in the 1970s of natural disaster and that of sediment disaster to 20 persons/year in the late 1990s from 60 persons/year in the late 1970s. Furthermore, the ratio of sediment disaster victims to natural disaster victims has decreased from 2/7 in the 1970s to 2/15 after 1980s. But, the system of sediment disaster management and new soil erosion control works tough introduction of watershed management concept are requested because of increased landslide area in recent years (206ha in 1981 $\rightarrow$ 688ha in 1999).

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.58-64
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• 2016

Vibrational characteristics of curved pipe structures are investigated with respect to the change of inside flow velocities. Based upon the Hamilton's principle, the equations of motions are derived, and the finite element equation is constructed to solve the frequency equation for curved pipe structures. When the initial tension is neglected in cured pipes, the natural frequencies are reduced as flow velocity increases, and the rapid decreases of the natural frequencies take place. However, when the initial tension is taken into account, the natural frequencies are not changed with the change of the flow velocity. In free vibrational simulation of pipe systems, it is necessary to calculate the initial force due to the velocity and the pressure of the fluid flow from the equilibrium. The force should be included in the equation of motion of the systems to get more accurate natural frequencies. The mechanical properties like stiffness or the location of pipe support need to be changed to avoid resonance. The natural frequencies are to be isolated from the frequency range of dominant vibration modes. The angles of elbows do not affect the change of the fundamental natural frequency, but affect the change of the third or higher natural frequencies.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.323-326
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• 2007

Recently, occurrence frequency of natural disasters decrease but scale of damage increase remarkably by the Climate change due to global warming. Especially, extreme heat become more critical weather problem in the Korean Peninsula. But, we don't have exact threshold about extreme heat. Extreme heat does not classify into natural disaster. Therefore, we have compared death count of the natural disaster with the one of extreme heat at Seoul, Korea. As a result, the number of death by extreme heat don't smaller than one by the natural disasters and we knew extreme heat have also to consider as natural disaster.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.51-56
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• 2000

The Finite Element Solutions Is reported on solid-liquid phase change in porous media with natural convection including freezing. The model is based on volume averaged transport equations, while phase change is assumed to occur over a small temperature range. The FEM (Finite Element Method) algorithm used in this study is 3-step time-splitting method which requires much less execution time and computer storage the velocity-pressure integrated method and the penalty method. And the explicit Lax-Wendroff scheme is applied to nonlinear convective term in the energy equation. For natural convection including melting and solidification the numerical results show reasonable agreement with FDM (Finite Difference Method) results.

• Journal of Community Nutrition
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• v.7 no.1
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• pp.8-20
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• 2005

The study purpose was to examine which factors including health perceptions & behaviors, psychosocial factors, dietary intakes were different by stages of change to reduce fast food consumption among university students. Survey data(n = 341) were analyzed using X$^2$ test or analysis of variance. With respect to stages of change, $17\%$ were in the precontemplation ; $21.4\%$ for contemplation, $19.7\%$ for preparation, 11.7% for action, and $30.2\%$ for the maintenance stage. Frequency of fast food consumption (p < 0.001), health status, interest toward health, and exercising behavior (p < 0.05) differed significantly by stages of change. Demographics and nutrient intakes, however, had no association with stages of change. Those in precontemplation through preparation stages felt more strongly on the advantages such as taste, satiety, cleanness of restaurants (p < 0.001), and diverse menus (p < 0.05). Compared to maintainers or actors, pre-contemplators agreed less to the disadvantages of eating fast foods, including sanitary problems (p < 0.001), overeating, indigestion, decreased vegetable intakes (p < 0.01) and loss of freshness (p < 0.05). Influence of significant others (e.g., friends, siblings, parents) significantly differed by stages of change. Compared with maintainers, those in preaction stages felt less control over facilitators or situations for fast food consumption. These included 'others like fast foods', 'providing standard meals', 'when I don't have foods for meals'(p < 0.001), availability, advertisement, 'socially popular', 'when I feel hungry'(p < 0.01), and 'when I don't like to prepare meals' (p < 0.05). These results suggested that nutrition education be planned considering one's stages of change for fast food consumption. For those in preaction stages, it is desirable to use motivational strategies to increase benefits and remove barriers of change, and help to develop skills to deal with situations or factors for fast food consumption. The support from friends or families is also needed to move to further stages.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.978-980
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• 2003

This study explores the temporal and spatial features near 67years (1934 ?2001) and landcover change in last 14 years (1987-2001) in Shijiazhuang, China, based on 67-year time series data edited from historical maps, TM and ETM+ imageries by integrating GIS and remote sensing method. An index named Annual Growth Rate (AGR) is used to analyze the spatial features of urban sprawl, and Maximum Likelihood classification method is utilized to detect the land cover types change. At last, the relationship between urbanization and factors is analyzed.

• Journal of the Korean Wood Science and Technology
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• v.50 no.1
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• pp.31-45
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• 2022

After manufacturing the natural dyed actual size Hanji using 11 kinds of plant natural dyeing materials and 2 kinds of animal natural dyeing materials, the color characteristics and color change and color fastness after post-mordanting were compared and discussed. The hues of 13 types of natural dyed Hanji were black, PB, and RP, each with 1 type, YP with 3 types, and Y with 7 types. Among the natural dyeing materials, Chinese ink, indigo and Lac showed high color yield and color difference, and violet-root cromwell and gardenia seeds showed low color yield. The color fastness of Hanji dyed with turpentine diluted Ottchil, Pagoda tree seeds, Chinese ink and indigo was excellent, while that of gardenia seeds and violet-root cromwell were very poor. After post-mordanting of natural dyed Hanji with Al, Cu, and Fe mordants, the hue changes were show up the Alnus firma, clove, lac and cochineal. In addition, the color difference was very diverse and was overall the most biggest due to Fe mordant. After 72 hr. of UV irradiation on post-mordanting natural dyed Hanji, hue change was observed in 3 types and color fastness was improved in 8 types by post-mordanting. The Hue and color fastness are significantly different depending on the type of natural dying materials and post-mordants. Therefore, when dyeing Hanji with natural dyes, it is necessary to dye with sufficient knowledges and informations about the desired color and fastness.

• Elastomers and Composites
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• v.19 no.3
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• pp.163-177
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• 1984

The effect of curing temperature increase and sulfur amount added were studied with natural and synthetic rubbers. Also, the effects of TMTD, MBTS and mixture of zinc soaps of high molecular fatty acids added to natural rubber were investigated respectively. The experimental results showed that, in the case of the conventional curing ($145^{\circ}C$), natural rubber, compared with synthetic rubber, gave higher values in elongation, tensile strength, cure rate, and lower values in modulus change. But, at high temperature curing ($180^{\circ}C$), natural rubber showed faster reversion rate, and higher heat build-up compared to synthetic rubber, than in the conventional curing. Also, natural rubber produced at high temperature showed severe degradation in hardness and tensile strength before heat-aging as well as in hardness, modulus and tensile strength after heat-aging. Improved reversion effect was obtained with natural rubber either by blending mixture of zinc soaps of high molecular acids or by applying semi-efficient vulcanization system.