• Journal of Forest and Environmental Science
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• v.34 no.2
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• pp.119-125
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• 2018

The tropical forests in developing countries are faced with the problem of illegal exploitation of trees. However, dearth of empirical means of expressing the dimensions, structure, quality and quantity of a removed tree has imped conviction of offenders. This study aimed at developing a model that can effectively estimate individual tree basal area (BA) from stump diameter (Ds) for Tectona grandis stands in Omo Forest Reserve, Nigeria, for timber valuation in case of illegal felling. Thirty-six $25m{\times}25m$ temporary sample plots (TSPs) were laid randomly in six age strata; 26, 23, 22, 16, 14, and 12 years specifically. BA, Ds and diameter at breast height were measured in all living T. grandis trees within the 36 TSPs. Least square method was used to convert the counted stumps into harvested stem cross-sectional areas. Six basal area models were fitted and evaluated. The BA-Ds relationship was best described by power model which gave least values of Root mean square error (0.0048), prediction error sum of squares (0.0325) and Akaike information criterion (-15391) with a high adjusted coefficient of determination (0.921). This study revealed that basal area estimation was realistic even when the only information available was stump diameter. The power model was validated using independent data obtained from additional plots and was found to be appropriate for estimating the basal area of Tectona grandis stands in Omo Forest Reserve, Nigeria.

• Journal of Korean Society of Forest Science
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• v.107 no.4
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• pp.336-343
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• 2018

This study was carried out to provide the technology of silvicultural practices and management for regeneration by sprouts in the oak forests distributed on the slope. A total of 1,451 stumps were examined for the following factors relative to the occurrence and growth of the sprouts: stump height & diameter; location & quantity and root collar diameter & height of arisen sprouts. The amount of sprouts deceased or increased as the stump diameter increased. However, it tended to increase with stump height. The difference in the stump height between direction of the upwards (DUS) and downward slopes (DDS) was occurred, because oak trees were felled lower based on direction of the upward for convenience of regeneration works on the slope. The number of sprouts was higher relatively in the stumps of DDS. The rate of arisen side and root sprouts was higher in the stumps of DDS and DUS, respectively. The stump height difference was found to affect the arisen part of sprouts. As a result of comparing the sprouts growth according to the arisen part, there was no difference in the stump of DUS, but the growth of side sprouts in the stump of DDS was higher than that of the root. In order to improve the quality of oak sprouts considering the distribution characteristics of the oak forests in South Korea, it is necessary to apply the silvicultural technique, making the cutting surface parallel with the slope to reduce the stump height difference, to suppress arising side sprouts.

• The Korean Journal of Ecology
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• v.17 no.2
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• pp.203-211
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• 1994

The establishment by seeds and the maintenance by ramets of the autumn olive (Elaeagnus umbellata) population were investigated in the Namhansansung Provincial Park, Jungbu-myun, Kwangju-gun, Kyunggi-do. Seed production and germination rate were 3, 300 $seeds{\cdot}m^{-2}{\cdot}yr^{-1}$ and 52%, respectively. The ramet formation in the population was classified into 4 types: stump type, creeping root type, lateral root type and secondary creeping root type. The subterranean creeping roots were 0.1~1.0 m in length, 4.5~14.0 mm in diameter and 0.06~0.2 m in soil depth. The number of ramets formed from a node was 1~21. The subterranean roots spread $5~509cm^2{\cdot}plant^{-1}{\cdot}yr^{-1}$, which began to be produced from 7~9 year-old individuals. The number of stems was 1~67 per stump, which was reduced by self-thinning from 2 to 14 year-old trees. The frequency distribution of stem diameter$(D_{30})$ showed a reverse J-shaped curve, suggesting that this population be maintained perpetually by their own ramets.

• Journal of Chest Surgery
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• v.56 no.6
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• pp.387-393
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• 2023

Background: The aim of this study was to evaluate the clinical efficacy of a modified surgical procedure for the treatment of varicose veins. Methods: This retrospective analysis was conducted on lower extremities with symptomatic great saphenous vein (GSV) incompetence that underwent stripping from the groin to the knee, with preservation of the superficial epigastric vein (SEV), between January 2015 and April 2022. Follow-up assessments were performed using Doppler ultrasound, Venous Clinical Severity Score (VCSS), and the Aberdeen Varicose Vein Questionnaire (AVVQ) at 6 and 12 months after surgery. Results: The study included 179 limbs from 120 patients (47 men and 73 women). The mean patient age was 56.5 years (range, 20-78 years), and the distribution of preoperative Clinical-Etiology-Anatomy-Pathophysiology clinical classes was 8% C0-C1, 88% C2, and 4% C3-C6. The preoperative diameter of the saphenofemoral confluence averaged 6.9 mm (range, 2.7-15.8 mm). After a mean postoperative follow-up period of 24 months, evidence of neovascularization around the stump of the saphenofemoral junction (SFJ) was observed in 2 limbs (1.1%). Additionally, varicose vein recurrence was found in 1 limb (0.6%) and was associated with an incompetent thigh perforator. At postoperative follow-up, both VCSS and AVVQ scores were significantly lower than the preoperative scores. Conclusion: Modified surgical treatment of GSV incompetence, involving preservation of the SEV and stripping of a short segment up to the knee, demonstrated favorable clinical results in terms of postoperative complication rate, neovascularization rate around the SFJ stump, varicose vein recurrence rate, and improvement in lower extremity symptoms.

• Journal of Korean Society of Forest Science
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• v.88 no.2
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• pp.169-178
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• 1999

The natural regeneration pattern was evaluated for 11 useful hardwood species in the natural deciduous forest where three different silvicultural practices (two-storied system, shelterwood system, and selection system) were applied and passed by three growing seasons. The study forest was presently dominated by Quercus mongolica in the upper canopy. However, since the analysis indicated that the number of regenerated seedlings of Acer mono and Fraxinus rhynchophylla was fairly abundant enough, these two species were anticipated to have the possibility to be among dominant species along with Quercus mongolica. The results of seedling occurrence after regenerating cutting showed that the number of seedlings was estimated for 3,145/ha(10 times of overstory) in the two-storied system, 6,885/ha(9 times of overstory) in the shelterwood system, and 2,275/ha(4 times of overstory) in the selection system. The estimation was varied by species, and the number of stump sprout was more abundant. The proportion of seedlings was high in 60~80% of overstory density and 60~70% of understory coverage, and high in the site of less than $25^{\circ}$ of slope and from southwest to northwest of aspect. These results were still varied by species. Stump diameter and height had little influence on the occurrence of sprout.

• Journal of Korean Society of Forest Science
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• v.105 no.1
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• pp.103-107
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• 2016

This study aims to select the most appropriate poplar clones for planting on short rotation coppice poplar plantations in a riparian area. The research investigated biomass production, nitrogen and carbon absorption with 2-year-old poplar (Populus spp.) clones including P. euramericana clone Eco28, P. deltoides hybrid clone 97-18, and P. alba ${\times}$ P. glandulosa hybrid clone 72-30. The average number of stems per stump was five and P. euramericana clone Eco28 had the greatest average number of live stems per stump with 5.9. The average stem diameter was 23.2 mm, and P. deltoides hybrid clone 97-18 achieved the largest average diameter with 25.4 mm. The average annual above-ground biomass production of Populus deltoides hybrid clone 97-18 was 16.1 ton/ha/year, followed by P. alba ${\times}$ P. glandulosa hybrid clone 72-30 and P. euramericana clone Eco28, 12.3 and 5.4 ton/ha/year, respectively. The average annual nitrogen uptake of poplar clones was 46.5 kg/ha/year. P. alba ${\times}$ P. glandulosa hybrid clone 72-30 had the highest average, 63.1 kg/ha/year. The average of annual carbon absorption was estimated 5.3 ton/ha/year and Populus deltoides hybrid clone 97-18 showed the best results with 7.7 ton/ha/year. Based on the results given above, P. deltoides hybrid aspen clone 97-18 is considered as the most suitable poplar clones for wood biomass production on riparian areas.

• Journal of Korea Foresty Energy
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• v.19 no.2
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• pp.61-68
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• 2000

This study was carried ou to compare sprouting and sprout growth after the stumps of four Quercus species(Q. mongolica, Q. variabilis, Q. acutissima and Q. dentata) were cut at 20cm from the soil surface in 1996 and 2000 at Mt. Taehwa, Kwangju-Gun, Kyounggi-Do, Korea. The results obtained were as follows: ⑴ Q. mongolica showed most vigorous sprouting, followed by Q. variabilis, Q. dentata, and Q. acutissima. ⑵ The sprouting ability was more vigorous when cut in winter to earl spring than that in summer. ⑶ The initial diameter growth of the sprouts for 2 year after cutting was the highest in Q. acutissima, followed by Q. dentata, Q. mongolica and Q.variabilis, but the growth for 5years after cutting was Q. variabilis > Q. mongolica > Q. dentata > Q. acutissima. ⑷ The height growth of sprouts for 2 years after cutting was the highest in Q. acutissima and followed by Q. mongolica, Q. dentata and Q. variabilis, but the growth for 5 years after cutting was Q. variabilis > Q. mongolica > Q. dentata > Q. acutissima. ⑸ Tending is needed for the stands of Q. variabilis and Q. acutissima to be regenerated successully by sprouting. ⑹ The sprouting ability of Quercus species decreased with incerasing stump diameter, while its diameter growth seemed to increase.

• Journal of Korean Society of Forest Science
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• v.102 no.3
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• pp.355-364
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• 2013

This study was conducted to investigate the population structure and dynamics of the Picea jezoensis stands which are located in Mt. Gyebangsan and surveyed from March to October 2012. Results showed that the diameter class distribution of P. jezoensis presented a reverse J-shaped distribution pattern with 32 trees less than 10 cm DBH, 20 trees in 10~30 cm DBH, and 11 trees more than 30 cm DBH. It showed seedlings and saplings of P. jezoensis seem to prefer areas with more sun light or with open upper layer. It was also observed that P. jezoensis preferes areas with organic soils and abundant water such as areas around stumps. Also, occurrences of P. jezoensis stands were analyzed through annual mean radial growth of the trees. And the results showed that the growth naturally or artificially occurred approximately on the years 1854, 1915, 1918, 1993 and 2002 years. Most of the gap-makers were classified as standing dead type with 23 individuals (45.1%).

• The Korean Journal of Ecology
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• v.27 no.2
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• pp.115-120
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• 2004

Coarse woody debris (CWD, $\ge$ 5 cm in maximum diameter) is an important functional component, especially to nutrient cycling in forest ecosystems. To compare mass and nutrient dynamics of CWD in natural oak forests, a two-year study was conducted at Quercus serrata and Q. variabilis stands in Yangpyeong, Kyonggi Province. Total CWD (snag, stump, log and large branch) and annual decomposition mass (Mg/ha) were 1.9 and 0.4 for the Q. serrata stand and 7.5 and 0.5 for the Q. variabilis stand, respectively. Snags covered 72% of total CWD mass for the Q. variabilis stand and 42% for the Q. serrata stand. Most of CWD was classified into decay class 1 for both stands. CWD N and P concentrations for the Q. variabilis stand significantly increased along decay class and sampling time, except for P concentration in 2002. There were no differences in CWD N concentration for the Q. serrata stand along decay class and sampling time. However, CWD P concentration decreased along sampling time. CWD N and P contents (kg/ha) ranged from 3.5∼4.7 and 0.8∼1.3 for the Q. serrata stand to 22.8∼23.6 and 3.7∼4.7 for the Q. variabilis stand. Nitrogen and P inputs (kg/ha/yr) into mineral soil through the CWD decomposition were 0.7 and 0.3 for the Q. serrata stand and 1.6 and 0.3 for the Q. variabilis stand, respectively. The number of CWD and decay rate were main factors influencing the difference in CWD mass and nutrient dynamics between both stands.

• Computers and Concrete
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• v.21 no.4
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• pp.407-417
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• 2018

Concrete which is a composite material is one of the most important construction materials. Compressive strength is a commonly used parameter for the assessment of concrete quality. Accurate prediction of concrete compressive strength is an important issue. In this study, we utilized an experimental procedure for the assessment of concrete quality. Firstly, the concrete mix was prepared according to C 20 type concrete, and slump of fresh concrete was about 20 cm. After the placement of fresh concrete to formworks, compaction was achieved using a vibrating screed. After 28 day period, a total of 100 core samples having 75 mm diameter were extracted. On the core samples pulse velocity determination tests and compressive strength tests were performed. Besides, Windsor probe penetration tests and Schmidt hammer tests were also performed. After setting up the data set, twelve artificial intelligence (AI) models compared for predicting the concrete compressive strength. These models can be divided into three categories (i) Functions (i.e., Linear Regression, Simple Linear Regression, Multilayer Perceptron, Support Vector Regression), (ii) Lazy-Learning Algorithms (i.e., IBk Linear NN Search, KStar, Locally Weighted Learning) (iii) Tree-Based Learning Algorithms (i.e., Decision Stump, Model Trees Regression, Random Forest, Random Tree, Reduced Error Pruning Tree). Four evaluation processes, four validation implements (i.e., 10-fold cross validation, 5-fold cross validation, 10% split sample validation & 20% split sample validation) are used to examine the performance of predictive models. This study shows that machine learning regression techniques are promising tools for predicting compressive strength of concrete.