• Journal of Korean Society of Forest Science
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• v.109 no.2
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• pp.202-210
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• 2020

This study investigated the optimal levels of stand density control considering the stability of Larix kaempferi stands. A stand density management diagram was developed from 259 sample plots. Based on these data, we determined an optimal level of the stand density control by identifying the relationship between the relative yield index (Ry) and height-to-diameter ratio. The estimated r-square (R²) of the stand density management diagram is 0.600. The analysis of the relationship between Ry and the slender tree incidence showed that when the stand density exceeded a certain threshold and the ratio of slender trees rapidly increased. The critical value of Ry was 0.63. The results of this study are expected to contribute to the establishment of stand management strategies that can reduce damage from natural causes, such as wind and snow, and to develop stand practice systems for the improved productivity of commercial forests.

• Journal of Ecology and Environment
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• v.31 no.4
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• pp.333-339
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• 2008

We investigated death rates, growth rates and recruitment of culms in two neighboring bamboo (Phyllostachys bamboosoides) stands nested in by two different bird species to analyze stand structure and to design conservation strategies. A third bamboo grove not used by birds, the Taewha stand, was included as a control stand. The bamboo stand occupied by birds in the family Ardeidae (the Ardeidae stand) had an approximately 1.5 times higher culm density than the stand occupied by birds in the family Corvidae (the Corvidae stand). The crude death rate and the number of newly emerged shoots were also higher in the Ardeidae stand than the Corvidae stand. The death rate for bamboo in the Ardeidae stand was not dependent on diameter at breast height (DBH) and was almost 40% for culms of all sizes, whereas most dead culms in the Corvidae stand were < 4 cm DBH. Consequently, we conclude that in the Ardeidae stand, density-independent causes of death are operating, while density-dependent factor are more important in the Corvidae site. The results of soil analysis in these stands suggest that the density-independent death pattern observed in the Ardeidae stand may be due to soil acidification resulting from wastes produced by the birds during breeding. On the other hand, the culm distribution and death patterns in the Corvidae stand suggest that the stand characteristics were not affected by the nesting birds. These results suggest that different conservation strategies must be applied to conserve bamboo groves used by ardeids and corvids for nesting.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.411-420
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• 2015

This study examined methods for stand density control by using shape ratio (tree height/DBH) and its application for effective management of Pinus thunbergii coastal disaster prevention forests. We analyzed the present conditions (height, DBH, and density) of P. thunbergii coastal disaster prevention forests at 123 study sites on Jeju Island and west, south, and east coasts of South Korea and compared them with results from previous studies. The average shape ratio for P. thunbergii showed positive correlations with stand density and was significantly higher on the west coast (66.32) than on the south (49.57) and east (48.19) coasts and Jeju Island (48.29). Stands with shape ratio higher than 70 accounted for 50% of the total study sites on the west coast, indicating a decrease in their disaster prevention function compared to that of other previous studies. The stand density in most coastal areas, except the east coast, was significantly higher than the standards recommended by the Korea Forest Service and the Forestry and Forest Products Research Institute of Japan, indicating the need for stand density control. According to the growth estimation equation for P. thunbergii in the coastal area of South Korea, density control is required for young stands less than 14 years old, which show drastic increase in the shape ratio, to conserve their disaster prevention function. Particularly, the first thinning of P. thunbergii forests should be implemented before the stand age of 8 years that a shape ratio exceeds 70. For disaster-prone young stands (${\leq}20cm$ DBH) of P. thunbergii, the stand density was higher in the standard of Japan considering shape ratio than in that of Korea aiming timber production. Hence, the standard guidelines employed in Japan, which assign higher importance to disaster prevention function based on field surveys, can be applied effectively for controlling the stand density of P. thunbergii coastal forests in South Korea, to improve their disaster prevention function.

• Journal of Korean Society of Forest Science
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• v.106 no.4
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• pp.457-464
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• 2017

This study has utilized the stand density management diagram to devise an efficient management standard for the stand density for Pinus densiflora that secures the health of the stands and predicted the harvest goals. The appropriate stand control level was estimated by modeling the relationship of the relative yield index (Ry) to the ratio of slender trees within the stand through an exponential function; the coefficient of determination ($R^2$) was found to be 0.424 according to the estimation. The ratio of slender trees within the stand showed a tendency of rapid increase at a certain relative yield index; with this relational function, the appropriate Ry value of 0.84 was obtained. By estimating the curve of the Ry value 0.84, which was the appropriate stand density management level, as well as the height of dominant trees in the central region of Korea, the production objective for each site index was set. Assuming that the final age by the site indices ranged from 10 to 16 for the P. densiflora in central region of Korea, the number of production was estimated to be between 426 to 1,311 trees per ha. It was predicted that the production of medium-diameter logs larger than 30 cm in diameter is possible for the target DBH at a site index of more than 16; small-diameter logs larger than 20 cm in diameter for site indices 12 and 14 enabled, and small-diameter logs of less than 20 cm for site index 10.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.430-436
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• 2004

This paper presents an advanced control technique for power density maximization of the Brushless DC (BLDC) generator by using the linear tracking method. In a generator of given rating, the weight and size of the system affect the fuel consumption directly. Therefore, power density is one of the most important issues in a stand-alone generator. BLDC generator has high power density in the machine point of view and additional increases of power density by control means can be expected. Conventional rectification methods cannot achieve the maximum power possible because of hon-optimal current waveforms. The optimal current waveform to maximize power density and minimize machine size and weight in a nonsinusoidal power supply system has been derived, incorporated in a control system, and verified by simulation and experimental work. A new simple algebraic method has been proposed to accomplish the proposed control without an FFT which is time consuming and complicated.

• Korean Journal of Environment and Ecology
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• v.35 no.4
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• pp.398-407
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• 2021

This study intended to identify causes of poor tree vigor in the Hanbando coastal forest by investigating its geographical environment, climate condition, soil physicochemical characteristics, and growth condition of Pinus thunbergii. It divided the forest into an area with poor tree vigor or dead standing trees and a control area with good tree vigor and examined them separately. The survey showed that stand density was significantly higher in the area with poor tree vigor. In contrast, the crown width in the area with good tree vigor was wider. The number of dead standing trees and the stand density showed a negative correlation. The stand density and diameter at breast height (DBH), tree height, crown height, and crown width also showed a negative correlation. The result indicated that, as the tree's stand density increases, the crowns of individual trees overlapped and the lower branches died. Then crown height and crown width decreased, and the number of leaves and photosynthesis was reduced, leading to lower tree height and weaker growth of breast diameter. As a result, tree vigor weakened, and combined with environmental pressures from the lack of moisture and nutrients in coastal soil and salty wind, P. thunbergii in coastal areas is expected to die massively. Although the causes of dead standing trees and poor tree vigor of P. thunbergii in the Hanbando coastal forest are complicated, poor management of adequate tree density in response to the growth of P. thunbergii is the primary cause. The secondary cause is external environmental pressures, including unfavorable soil conditions and salty and strong wind that obstruct the growth of P. thunbergii.

• Journal of Korean Society of Forest Science
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• v.99 no.1
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• pp.136-143
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• 2010

This study was conducted to provide basic information on the management of natural deciduous forests by presenting suitable stand density over time for natural deciduous forests in Pyungchang Area. The stand density index(SDI) for the sampling point was also computed. The cutting scenarios were adopted by considering the SDI estimated in the sampling point. And then, simulation cutting was enforced to the stand. Cutting scenarios consisted of three cutting levels, with the period of 5 years where each suitable cutting level of selection system will not have the SDI over the maximum SDI throughout 30 years and consider harvest after 30 years. As a result of the simulation cutting, it was found that removing 12% and 14% of basal area per each time kept proper stand density while removing 10% exceed to the adequate basis. From an economic point of view, it was concluded that removal 12% of basal area would be the most suit cutting level in selection system.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.600-609
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• 2019

This study was conducted to highlight the necessity for a stand density control management plan in consideration of the shape ratio of Pinus densiflora and Larix kaempferi in Korea. A total of 2,112 Pinus densiflora samples and 2,030 Larix kaempferi samples were cut, and their diameter at breast height (DBH), height, and clear length were measured for regional shape ratio (height/DBH) comparison and analysis.The shape ratio of Pinus densiflora was 72.3% in the Gangwon district, 64.0% in the central district, and 70.8% on average, indicating a higher percentage of Pinus densiflora in Gangwon than in the central area. Regionally, Yeongju had the highest percentage at 78.4%, with Yeongwol indicating 77.5%. Measured by diameter, results showed a presence of 90.4% for small diameter trees (6-16 cm), 71.7% for medium diameter trees (18-28 cm), and 56.1% for large diameter trees (30 cm). As density increased, the shape ratio of height to tree trunk diameter also increased; below 70% indicated a more stable trunk, while a result above 80% indicated trunks prone to wind hazards and snowstorms, and, therefore, the need for density control in partial areas. The overall shape ratio of Larix kaempferi was 90.6%. Pyeongchang indicated a 108.5% ratio, Yeongju 105.4%, and Danyang 100.5%, respectively.According to diameter class, small diameter trees showed 104.9% occurrence, medium diameter trees 92.7%, and large diameter trees 73.4%. The shape ratio of Larix kaempferi was higher than 80% overall, indicating vulnerability to wind hazards and snowstorms. Therefore, appropriate stand density management is required.

• The Journal of Korean Physical Therapy
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• v.24 no.5
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• pp.313-318
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• 2012

Purpose: This study examined the effects of an exercise program involving the Proprioceptive Neuromuscular Facilitation (PNF) lower-extremity patterns on the Bone Mineral Density (BMD), balance and lower muscular strength in patients with osteoporosis. Methods: The participants were allocated randomly to 2 groups: experimental group and control group. To evaluate the effects of exercise, the subjects were evaluated using the BMD and Time Up & Go Test and One Leg Stance Test for balance, and the Sit To Stand for lower muscular strength. Results: After the 8 week study, the experimental group showed a significant difference in all items compared to the control groups. Conclusion: These results suggest that a PNF exercise program is effective in patients with osteoporosis. Furthermore, an exercise program involving these patterns can be used in a follow-up program for patients with osteoporosis. Overall, more study will be needed to develop and apply more efficient exercise programs for such patients.

• Journal of IKEEE
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• v.23 no.3
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• pp.826-831
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• 2019

The stand-alone photovoltaic power systems are widely used for lighting equipment and CCTV. In order for these devices to be competitive, the life of power storage devices such as batteries is very important. The characteristic Hybrid supercapacitor is the high power density and long life. We have proposed a stand-alone photovoltaic power system that uses hybrid supercapacitor. The charge and discharge characteristics and the internal resistance of the hybrid capacitor were measured to configure the power converter. A stable maximum output point tracking control algorithm is proposed even with the change in solar radiation. In order to verify the validity of the proposed system, a prototype was fabricated and tested using a 18W hybrid capacitor and a 10W solar cell.