• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.85-92
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• 2003

This paper presents an electric power generating system for stand-alone health monitoring sensor unit of bridge structure based on ambient vibration of bridge. In this paper, a novel electric power generator which has minimum effect of armature reaction is proposed. The related mechanical and electrical design equations are obtained, and a pilot generator has been implemented. In addition, the charging system for extremely low generator current is discussed, and some improvements are identified for the system. This investigation reveals that diode characteristics of rectifier is dominant factor in the charging process. Finally, both the simulation, which uses real measurement data of the Namhae bridge as input of the pilot generator, and indoor test are carried out. The results showed the applicability and effectiveness of the stand-alone vibration powered generator.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.6
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• pp.43-48
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• 2002

This study was carried out to clarify the change characteristics of stream water quality by land-use of forest from July to September, 2000 in three stands(Pinus densiflora, Castanea crenata (I), Castanea crenata (II) stand) of Jeongpyeong-ri, Jinju-si, Gyeongnam. The mean pH of rainfall results in acid rain of 5.3. The pH of stream water in three stands was high in order of Pinus densiflora (pH 6.59), Castanea crenata (II)(pH 6.53) and Castanea crenata (I) stand(pH 6.47). The electrical conductivity of stream water was high in order of Castanea crenata (I), Pinus densiflora and Castanea crenata (II) stand. Cations contents of three stands in stream water were high in order of $Ca^{2+}$, $Na^{2+}$, $Mg^{2+}$, $K^+$ and ${NH_4}^+$. But anions of stream water in Pinus densiflora stand and Castanea crenata (II) stand were high in order of ${SO_4}^{2-}$, $Cl^-$ and ${NO_3}^-$. In Castanea crenata (I) stand cations of stream water were high in order of ${NO_3}^-$, ${SO_4}^{2-}$ and $Cl^-$. The level of pH, ${NH_4}^+$, ${NO_3}^-$, $Cl^-$ and ${SO_4}^{2-}$ of stream water in Pinus densiflora stand and Castanea crenata (II) stand reached within the level of domestic use standard for drinking water But the level of ${NO_3}^-$ of stream water in Castanea crenata (I) stand was higher than that of domestic use standard. Therefore, non-point sources like forest watersheds which are fertilizer application lands should be taken to the appropriate mitigation measures.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.11 no.3
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• pp.20-27
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• 2008

This study was conducted to investigate the influence of thinning and pruning on characteristics of forest stand, mesopore ratio and soil water content at the Pinus koraiensis stands in Gwangneung, Gyeonggido. The Pinus koraiensis had been planted in 1976 and thinning and pruning were carried out in 1996. A sample area survey was conducted at experimental plots (thinned and unthinned) in 1998 and 2005, and mesopore ratio and soil water content have been monitored from 2000 to present. Average tree height of the thinned plot increased from 10.9m to 13.2m and from 10.3m to 12.8m for the unthinned plot. Average D.B.H of the thinned plot increased from 15.9cm to 21.1cm and from 14.5cm to 16.7cm for the unthinned plot during the period 1998-2005. Crown density at the thinned plot increased from 81.5% to 95.0% and from 89.5% to 95.0% for the unthinned plot during the period 1998-2005. Mesopore ratio (pF2.7) of A layer soil at the thinned plot was 40.1% while that of the unthinned plot was 37.3%. Changes of mesopore ratio at unthinned plot were not associated with stand age, but those at thinned plot had increased and then decreased, showing declining of the practice effect. Average soil water content at the thinned plot were 23.7% and 22.4% for the unthinned plot. Soil watercontents at both plots have been increased with increase in stand age. But the difference of soil watercontent at each plot has been decreased, especially at the depth of 10cm.

• Journal of agriculture & life science
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• v.45 no.2
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• pp.51-59
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• 2011

This study was conducted to analysis the growth characteristics and the diameter at breast height (10 cm) reached ages in natural stand and platation for the optimal planting density and planting timing of Acer mono for. rubripes. There was high correlation between the DBH and crown diameter (E-W: r=0.82, S-N: r=0.76) in natural stand, and between the DBH and crown diameter (E-W: r=0.76, S-N: r=0.90) in plantation. In natural stand, average reached age on DBH 10 cm was $21.1{\pm}7.0$, and was $9.2{\pm}1.3$ in plantation. Therefore, the collectable timing of sap in artificial planting short approximately 2.3 times over the natural regeneration.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.659-665
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• 2014

Wood properties are affected by environmental factors such as soil and climate change. There were close relationships between mechanical properties and stand characteristics for Quercus serrata stands in Gyeongsangnam-do Province, Jeollanam-do Province and Je-ju island. Both compression and shear strengths of woods showed a negative correlation with diameter at breast height (DBH) and the number of tree per hector, while they are positively related with with tree age, altitude, and drainage. The annual ring width was also negatively correlated with tree age, altitude, drainage, DBH, and tree height. However, anatomical characteristics of wood did not show much variation depending on the provincial regions. These results brought a conclusion that Quercus serrata in southern region could be useful forest resources for the utilization of wood.

• Fire Science and Engineering
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• v.21 no.4
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• pp.52-58
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• 2007

The effect of stand-growing-stock characteristics of thinning area and non-thinning area on forest fire was studied in this work. 14 spots were selected from 3 counties such as Yangyang, Injae, and Gapyeong and on-the-spot investigations were performed to evaluate the effect of forest fire. The stand-growing-stock characteristics on the spots were analyzed through the height of tree, breast height diameter, clear length, mortality of branch, forest tree standing crop density, degree of closure, and shrub and grass cover degree. The relation between forest fire and the risk of spread of forest fire were analyzed from the analysis of the stand-growing-stock characteristics. It is considered from this work that the possibility of forest fire is decreased on the thinning area compared to the non-thinning area because of higher clearlength, lower number of tree, lower mortality of branch and higher shrub and grass cover degree.

• Journal of Korean Society of Forest Science
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• v.113 no.1
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• pp.131-142
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• 2024

The purpose of this study was to estimate the optimal stand density criteria for each growth stage of Chamaecyparis obtusa (Siebold & Zucc.) Endl. to achieve the timber production goal for cypress forests and develop an optimal silvicultural system for forest thinning. A relative yield index (Ry) value of 0.75, presented as a stand density management criterion index, was estimated by analyzing the relationship characteristics between the composition ratio and stand density of slender trees from 216 sample plots of the recruited cypress forests. The analysis of the feasibility of achieving each production target in the existing silvicultural system for C. obtusa revealed that the growth rate according to the parameters of forest land productivity, such as site index and thinning intensity according to the increase in age, was not properly reflected. In the thinning system for each timber production target analyzed in this study, 353 high-quality large hardwoods from 498.1 m³/ha, 703 high-quality medium hardwoods from 376.2 m³/ha, and 1,758 small-diameter hardwoods from 249.5 m³/ha could be harvested. Although the silvicultural system prepared on the basis of the results of this study cannot be uniformly applied according to various management goals, this study is meaningful in that it presents empirical reference standards based on the stand density management diagram that reflects the growth characteristics of cypress forests in South Korea.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2280-2285
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• 1993

Many items, as internal pressure, thrust, temperature, strain, etc. are measured in Ground Firing Test (GFT) of rocket motors. But these items are influenced by various phenomena occurred during propellant combustion. In this study, natural frequencies of motor itself and system(motor+loadcell) on Stand were measured. Also motor responses were measured during burning and analyzed so that the vibration characteristics occurred during GFT and the causes and characteristics of vibration signal appearing on thrust curve were identified.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.303-308
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• 1990

The stand alone induction generator has been excited by capacitor bank or voltage source inverters. The conventional excitation methods offer several restrictions on the operation of the induction generator in various operating conditions. To overcome the restrictions, this paper presents the induction generator system excited by the current controlled inverter which operates on the principle of vector control. The proposed control scheme is based on the rotor flux oriented indirect vector control. The steady state characteristics are investigated to yield control ranges under various operating conditions. Through the simulation, it is confirmed that the system has good dynamic characteristics wi thin the controllable ranges given by the steady state analysis.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.2
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• pp.121-128
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• 2000

To identify the effects of air pollution on several physiological characteristics of Styrax japonica in Yeochon industrial comples soil properties photosynthetic capacity and chorophyll contents were investigated. All of these measurements were taken on Styrax japonica stand at 1. 3 and 7km from an industrial complex which is an air pollution source. In addition a Styrax japonica stand in Sang-ju city was selected as a control Each physiological measurement was in leaves of east-, west- south- and north-facing branches. The results obtained were as follows: 1) Al contents of soil in Yeochon industrial complex were higher than those of Sang-ju city a non-polluted area. higheral contents contributed to decrease in soil pH. 2) Chlorophyll contents of leaves at 1km from the industrial complex closest from the air pollution source were lower than those of 3 and 7km/ 3) Photosynthetic capacity of Styrax japonica at 1km from the air pollution source was lower than those at 3 and 7km.