장백낙엽송 ( Larix olgensis H . ) 인공림의 유교 수관형에 관한 연구

이봉일(Feng Ri Li),윤종화(Jong Wha Yun) 한국산림과학회 1996 한국산림과학회지 Vol.85 No.4

Based on stem analysis as well as branch analysis data of each tree from 8 plots of circle clear-cutting and 1 biomass plot in Changbai Mountain area, located in Northeast of China, the effective crown form of Changbai larch(Larix olgensis H. ) plantation were studied by using the approach of crown curve. The results indicated that the cross-section forms of effective crown were stable and showed approximate circle for different tree size. Because the effective crown was on upper position of the canopy and its form reflects crown architecture under non-competition condition, the architecture is mainly affected by species hereditary feature. Therefore, for the specified species the effective crown form was thought to be relatively stable. The effective crown form of tree was neither related to the tree size within stand nor to the stand condition for different stand. The total effective crown curve of larch plantation could be characterized by using mean effective crown taper.

중국 풍림자연보호구 산림경관 양상 분석

이봉일(Feng Ri Li),김광택(Guang Ze Jin),김지홍(Ji Hong Kim) 한국산림과학회 2002 한국산림과학회지 Vol.91 No.3

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장백낙엽송 ( Larix olgensis H. ) 인공림의 가지 직경생장과 신장생장에 관한 연구

이봉일(Feng Ri Li),양희문(Hee Moon Yang),김지홍(Ji Hong Kim) 한국산림과학회 2002 한국산림과학회지 Vol.91 No.2

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중국 동북부 지방 활엽수 - 잣나무 천연림의 생장 모델과 수확 모델 개발

이봉일(Feng Ri Li),김지홍(Ji Hong Kim),최정기(Jung Kee Choi) 한국산림과학회 2001 한국산림과학회지 Vol.90 No.5

The growth and yield models for five different kinds of natural forest types were systemically developed in the natural Broadleaved-Korean pine Forests in Northeast China. The data were collected from 359 temporary plots and 58 permanent plots with area ranged from 0.06 ha to 1.0 ha, ranging in stand age from 43 to 364 years. The Site Class Index (SCI) was introduced to evaluate site quality and the Crown Competition Factor (CCF) was selected as a measure of stand density for the mixed natural forest. The Chapman-Richards function was adopted to develop SCI equation and height-diameter curve. The Schumacher growth function was selected as base model to develop the DBH, basal area, and stand volume growth models by using re-parameterized method. In modeling mean DBH and basal area growth, it was found that the asymptotic parameter A of Schumacher function was exponentially related to site quality (SCI) and stand density (CCF). The rate parameter k was related to stand density and it was independent of SCI. Several validation measures for predicted stand variables were evaluated in the growth and yield models using independent data sets. The results indicated that relative mean errors (RME) in predicted stand attributes were less than ± 5% and the estimated precision values of the stand variables were all greater than 95%.

뇌임펄스전압에 대한 SF₆와 dry-air의 절연특성

이봉,유양우,김동규,이복희,Li, Feng,Yoo, Yang-Woo,Kim, Dong-Kyu,Lee, Bok-Hee 한국조명전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.8

본 논문은 준평등전계에서 뇌임펄스전압에 대한 $SF_6$와 dry-air의 절연파괴 특성에 대하여 기술하였다. 준평등전계로 사용된 구-평판전극계의 전계이용률은 71[%]이다. $SF_6$는 0.1~0.2[MPa] 범위에서, dry-air는 0.2~0.6[MPa]에서 $SF_6$와 dry-air의 절연파괴전압을 임펄스전압의 극성과 가스압력에 따라 측정 분석하였다. 그 결과 뇌임펄스전압에 대한 두 가스의 절연파괴전압은 정극성이 부극성보다 높았으며, $SF_6$의 절연파괴전압이 dry-air의 절연파괴전압보다 약 2.67배정도 높았다. 본 연구결과는 뇌서지에 대하여 우수한 성능을 가지는 배전기기에서 $SF_6$의 대체가스 성능 평가에 유용한 정보가 될 것이다. This paper describes dielectric characteristics of $SF_6$ and dry-air gases under lightning impulse voltages in a quasi-uniform electric field. In order to simulate to a quasi-uniform electric field, electric field utilization factor of the used sphere-plane electrode is 71[%]. The gas pressure of $SF_6$ ranges from 0.1 to 0.2[MPa] and that of dry-air ranges from 0.2 to 0.6[MPa]. Electrical breakdown voltages of $SF_6$ and dry-air gases are measured and analyzed as functions of the polarity of lightning impulse voltage and gas pressure. As a result, the electrical breakdown voltage of both gases under the positive lightning impulse voltage is higher than that under the negative one. The electrical breakdown voltage in $SF_6$ is almost higher than 2.67 times compared to dry-air. The results presented in this paper can be used as a useful information to evaluate the capability of alternative insulation gases for $SF_6$ in power distribution equipment with prominent ability against lightning surge.

뇌임펄스전압에 대한 SF₆와 dry-air의 절연특성

이봉(Feng Li),유양우(Yang-Woo Yoo),김동규(Dong-Kyu Kim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.8

본 논문은 준평등전계에서 뇌임펄스전압에 대한 SF?와 dry-air의 절연파괴 특성에 대하여 기술하였다. 준평등전계로 사용된 구-평판전극계의 전계이용률은 71[%]이다. SF6는 0.1∼0.2[㎫] 범위에서, dry-air는 0.2∼0.6[㎫]에서 SF6와 dry-air의 절연파괴전압을 임펄스전압의 극성과 가스압력에 따라 측정?분석하였다. 그 결과 뇌임펄스전압에 대한 두 가스의 절연파괴전압은 정극성이 부극성보다 높았으며, SF?의 절연파괴전압이 dry-air의 절연파괴전압보다 약 2.67배정도 높았다. 본 연구결과는 뇌서지에 대하여 우수한 성능을 가지는 배전기기에서 SF?의 대체가스 성능 평가에 유용한 정보가 될 것이다. This paper describes dielectric characteristics of SF? and dry-air gases under lightning impulse voltages in a quasi-uniform electric field. In order to simulate to a quasi-uniform electric field, electric field utilization factor of the used sphere-plane electrode is 71[%]. The gas pressure of SF6 ranges from 0.1 to 0.2[㎫] and that of dry-air ranges from 0.2 to 0.6[㎫]. Electrical breakdown voltages of SF? and dry-air gases are measured and analyzed as functions of the polarity of lightning impulse voltage and gas pressure. As a result, the electrical breakdown voltage of both gases under the positive lightning impulse voltage is higher than that under the negative one. The electrical breakdown voltage in SF? is almost higher than 2.67 times compared to dry-air. The results presented in this paper can be used as a useful information to evaluate the capability of alternative insulation gases for SF6 in power distribution equipment with prominent ability against lightning surge.

천연 갈색다이아몬드의 5.6 Gpa-10분 조건에서 처리온도에 따른 색 변화 연구

이봉 ( Feng Li ),송오성 ( Oh Sung Song ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.1

The color of a natural diamond that contains nitrogen impurities can be enhanced by a high pressure high temperature (HPHT) treatment. Type IaAB diamond samples containing nitrogen impurities were executed by HPHT process of 5.6 Gpa, 10 min by varying the annealing temperature at 1600, 1650, and 1700℃. Property characterization was carried out using an optical microscope, FT-IR spectrometer, lowtemperature PL spectrometer, and micro Raman spectrometer. By observing optical micrographs, it can be seen that diamond sample began to alter its color to vivid yellow at 1700℃. In the FT-IR spectrum, there were no Type changes of the diamond samples. However, amber centers leading to brown colors lessened after 1700℃ annealing. In the PL spectrum, all the H4 centers became extinct, while there were no changes of yellow color center H3 before or after treatment. In the Raman spectrum, no graphite spots were detected. Consequently, diamond color enhancement can be done by higher than 1700℃ HPHT annealing at 5.6 GPa- 10 min.

온도변화에 따른 SF<SUB>6</SUB>/N<SUB>2</SUB> 혼합가스의 임펄스 절연파괴특성

이봉(Feng Li),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2008 조명·전기설비학회논문지 Vol.22 No.12

본 논문은 온도변화에 따른 SF<SUB>6</SUB>/N<SUB>2</SUB> 혼합가스 중에서 높은 불평등전계의 임펄스절연파괴특성에 대한 실험적인 결과를 기술하였다. 온도범위는 -25~25[℃]로 정하여 실힘을 수행하였다. 임펄스 전구방전진전은 방전전류와 방전 광신호의 측정에 의해 분석되었다. 결과로써, 절연파괴전압은 정극성보다 부극성에서 온도변화에 대한 의존성이 강하게 나타났다. 온도가 상승함에 따라 부극성에서의 리더진전 스텝핑시간이 정극성보다 더 길게 나타났다. 본 연구 결과는 뇌서지에 대하여 우수한 성능을 가지는 가스절연선로의 섣계에 유용한 정보가 될 것이다. This paper presents the experimental results of impulse breakdown characteristics in SF<SUB>6</SUB>/N<SUB>2</SUB> gas mixtures under a highly non-uniform electric field with a change in tempreature. The test temperature ranges from -25[℃] to 25[℃J. The processes of impulse preliminary breakdown developments were analyzed by the measurements of current pulse and luminous signals. As a result, the temperature dependance of breakdown voltage for the negative polarity was much stronger than that for the positive polarity. When increasing the temperature, The leader stepping time for the negative polarity was shown to be longer than that for the positive polarity. The results presented in this paper can be used as a useful information in designing the gas insulation lines with prominent ability for lightning surge.

큐빅지르코니아의 색향상을 위한 저온열처리 공정 연구

이봉(Li, Feng),신운(Shen, Yun),송오성(Song Ohsung) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.4

스컬 용융법으로 제조된 유색 큐빅지르코니아의 색향상을 위해서 1200°C, 1400°C에서 10~60분으로 조건을 바꾸면서 진공열처리를 실시하였다. 진공 열처리 시간과 온도가 증가함에 따라 준비된 7가지의 큐빅지르코니아는 점 점 채도가 떨어지며 파스텔톤의 바디색을 유지하다가 궁극적으로 흑색으로 변화하였다. 흑색화가 완료된 시료는 다시 대기 중에서 산소토치를 이용하여 10분간 가열하면 원래의 색으로 환원되었다. 즉, 목표하는 색을 위해 진공 열처리 를 진행하거나, 일단 진공열처리로 흑색화를 진행하고, 대기중 열처리를 통하여 목표하는 색을 가진 큐빅지르코니아 의 색조정이 가능하였다. 이러한 신공정은 다이아몬드 보석재를 모사한 고부가가치 합성석으로 활용이 가능하였다. Colored cubic zirconia specimen made by skull melt process were annealed in vacuum at the temperature of 1200℃~1400℃ for 10~60 minutes to enhance the color. All the seven specimen become darker and eventually be black as annealing temperature and time increase. The black samples turned into original colors when we elevated the temperature with oxy-acetylene torch for around 10 minutes in the air. Finally, we could tune the colors of cubic zirconia either anneal in vacuum or the black samples in the air to obtain the proposed colors. Our proposed new process may be appropriate to fabricate the precious synthetic colored cubic zirconia to simulate the natural colored gem quality diamonds.

매설지선의 길이와 전류인가점에 따른 접지임피던스특성

이봉(Feng Li),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.6

본 논문은 임펄스전류가 인가된 매설지선의 과도접지임피던스특성에 관한 것으로 길이가 10, 30, 50 [m]인 3개의 매설지선에 대하여 임펄스전류의 인가점을 파라미터로 하여 과도접지임피던스와 규약접지임피던스를 측정하고 분석하였다. 임펄스전류의 상승시간에 대한 규약접지임피던스는 과도접지임피던스와 비슷한 경향이었다. 과도접지임피던스는 임펄스전류의 인가위치에 영향을 크게 받으며, 짧은 시간영역에서 과도접지임피던스는 매설지선의 길이에 매우 의존적이다. 임펄스전류가 인가된 10 [m]의 매설지선은 용량성 특성이었으나 30 [m]와 50 [m]의 매설지선은 유도성 특성을 나타내었다. 접지도선은 매설지선의 중앙점에 접속하는 것이 바람직한 것으로 밝혀졌다. This paper presents the grounding impedance behaviors of counterpoise exposed to impulse currents. The transient and conventional grounding impedances of three counterpoises having the length of 10, 30 and 50 [m] were measured and analyzed as a function of the injection point of impulse currents. As a result, the trend of the conventional grounding impedances measured as a function of risetime of impulse current is similar to the transient grounding impedance of counterpoise. The injection point of impulse current has great influence on the transient grounding impedance characteristics of counterpoise. The transient grounding impedance characteristics in a short time range are strongly dependent on the length of counterpoise. The transient characteristics of grounding impedance of 10 [m] counterpoise subjected to the impulse current was capacitive behavior, on the other hand, those of 30 [m] and 50 [m] counterpoises were inductive behavior. It is found that the grounding conductor should be connected to the central point of counterpoise.