• Proceedings of the KIEE Conference
• /
• 1990.11a
• /
• pp.125-128
• /
• 1990

The growth of water trees was measured using CNRS Laboratory Models in laboratory polyethylene specimens. The effect of deaerating the specimens, and annealing them under different gaseous atmospheres was investigated. These factors were found to be secondary in the growth of water trees. The gas in contact with the material during the growth of water trees is considered not to influence the intiation stage but the propagation stage.

• Proceedings of the Korean Society of Computational and Applied Mathematics Conference
• /
• 2003.09a
• /
• pp.16.1-16
• /
• 2003

A subset S of vertices of a graph G is independent if no two vertices of S are adjacent by an edge in G. Also we say that S is maximal independent if it is contained In no larger independent set in G. A planted plane tree is a tree that is embedded in the plane and rooted at an end-vertex. A (k＋1) -valent tree is a planted plane tree in which each vertex has degree one or (k＋1). We classify maximal independent sets of (k＋1) -valent trees into two groups, namely, type A and type B maximal independent sets and consider specific independent sets of these trees. We study relations among these three types of independent sets. Using the relations, we count the number of all maximal independent sets of (k＋1) -valent trees with n vertices of degree (k＋1).

• Korean Journal of Weed Science
• /
• v.8 no.2
• /
• pp.141-155
• /
• 1988

We have large areas of forests in our country where various types of trees can grow. Since Japan geographically locates on a wide region with the extention of 3,000 km south and north, the climate varies from subtropical to subarctical one. Many mountains additionally make the climatic condition more complicated. Thus, we are able to see many kinds of trees in our forest areas. We have also frequent rainfalls through whole season and the precipitation reaches approximately 1,500 mm per year in many forests areas. In some rainy regions, it sometimes account for more than 2,000 mm. The condition is so advantageous for the growth of weeds and shrubs that it makes them very strong competitors with plantation trees in our forestries. It, therefore, may be said that the most important problem in Japanese forestries is to combat with undesirable vegetations continuously and to keep trees from weeds.

• Journal of Korean Society of Forest Science
• /
• v.95 no.2
• /
• pp.183-187
• /
• 2006

This study investigated concentrations of the several air pollutants and compared antioxidative enzyme activities on Platanus occidentalis because this tree species is one of the widespread street trees in Korea. This species has been emerging the ambient air pollutants during its growing periods. The purpose of this study was to identify the relationship between air pollution on the tree species and antioxidant enzyme activities on the trees. $O_3$, $NO_2$, CO and $SO_2$ concentrations of several cities in Korea were compared for last decades. Among the air pollutants, $O_3$ and $NO_2$ concentrations in six big cities in Korea showed similar increasing trends during this period. In contrast, $SO_2$ and CO concentrations in the same cities dramatically decreased between 1994 and 2005. Platanus occidentalis trees were controlled to investigate, ascorbate peroxidase (APX) and glutathione reductase (GR) activity. Ozone exposure generally increased APX and GR activities of tree seedlings. It is a typical compensatory strategy of stressed trees.

• The Korean Journal of Ecology
• /
• v.13 no.4
• /
• pp.331-342
• /
• 1990

Analysis of vegetation on the pavements and under the trees of streets in Seoul city were investigated from July to November 1989. All of the vascular herbs were 9 orders, 13 families, 30 genera, 37 species and 1 forma. Species diversity and evenness index were higher on the pavements than under the trees of streets. Eragrostis multicaulis with C-4 pathway was a dominant species, and next orders of importace values were Eleusine indica(C-4), Digitaria sanguinalis(C-4), Taraxacum officinale(C-3) and Erigeron annus(C-3). On the pavements and under the trees of streets, light intensity and surface temperature were very high, Also, these sites were affected by many kinds of human interferences. Therefore, it was an example of adaptation to specific ecological environments that C-4 plats were more dominant than C-3, growth forms of C-3 plants were rosette or prostrate, and annual or biennial plants were distributed in these studied sites. Generally, fruits types were grains, achens and capsules. Seeds were very small and some had appendages such as pappus.

• Journal of Ecology and Environment
• /
• v.37 no.2
• /
• pp.105-111
• /
• 2014

To elucidate whether small diameter at breast height correlates with tree death in an overcrowded tree population, we analyzed self-thinning occurring over the course of 37 years in naturally established Pinus densiflora populations in Sugadaira, central Japan. As trees grew, their diameters at breast height increased and the number of trees consequently decreased. Spatial distribution, which was initially clumped, changed accordingly, first becoming random and finally uniform. We calculated the "available area" of individual trees to elucidate the contribution of this parameter to tree mortality. Small diameter at breast height was strongly correlated with tree death, with a slight correlation observed between tree death and small available area of individual trees.

• Proceedings of the Korean Society of Plant Biotechnology Conference
• /
• 2005.11a
• /
• pp.120-125
• /
• 2005

Continuous degradation of forest in both quality and quantity threatens wood security in the future. Thus in the future, most wood and pulp will be expected to be produced from plantation forests. We attempt to produce superior trees suitable for such plantations with maximum productivity in limited land area. Tree productivity could be enhanced either by promoting growth and wood quality or by reducing loss caused by abiotic and biotic stresses. Genetic transformation techniques may offer ways to improve the productivity by enabling trees to tolerate the stresses or to covert limited resources into big biomass. With the availability of information on various functional genes and gene transfer techniques, it should be possible to develop such trees. In this presentation, our work to produce such trees at Korea Forest Research Institute is briefly introduced.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.11 no.1
• /
• pp.47-51
• /
• 1974

In this paper, we have tried to study topological method for generating trees and Co-trees of a given circuit which is required in the first step of analysis of networks, and also illustrative examples that compare with other available methods in aspect of the efficiency are given. It is believed that the proposed method is more efficient than other methods already available and that it will play a fundamental role in the topological analysis of electrical networks.

• Journal of Environmental Science International
• /
• v.11 no.12
• /
• pp.1189-1193
• /
• 2002

This study was conducted to determine the contents of heavy metals in leaves of roadside trees according to different growth stages in Daegu city. The orders of heavy metal contents in leaves of roadside tree and soil were Fe>Mn>Zn>Pb>Cu>Cr>Cd and Fe>Mn>Zn>Cu>Pb>Cr>Cd, respectively. The contents of heavy metals in leaves of roadside trees and soil showed an increasing tendency as the levels of traffic volume increased. The contents of heavy metals in loaves on October were higher than those on May. Zelkova serrate and Ginkgo biloba showed high contents of Cr, Cd and Pb.

• KSBB Journal
• /
• v.8 no.2
• /
• pp.122-125
• /
• 1993

Taxol is the promising diterpene alkaloid with antineoplastic activities. The taxol content in various parts of yew trees in Korea, Mt. Deokyu, Mt. Sobaek, Mt. Taebaek and Suwon area, have been determined. The highest taxol content was observed in yew trees of Mt. Soback. In various parts of trees the taxol content in bark was highest and the taxol content in twig was higher than that in leaves.