• The Korean Journal of Ecology
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• 제17권4호
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• pp.453-461
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• 1994

Size class structure and vegetative growth of a perennial herb of the temperate deciduous forests, Symplocarpus renifolius Schott, were studied from 1991 to 1994 in Namhansansung, Kyonggi Province, Korea. The size class structures of leaf number and leaf area per individual followed bell-shape curve, i.e. frequency of middle class was relatively high. The leaf area increased from the late-March to mid-May. At the end of the growing season, leaf area(length X breadth) was proportional to biomass, especially aboveground biomass. The leaf number and leaf area per individual increased at the rate of 0.08 leaf/year and 9.7 $cm^2/year$, respectively. The size of the individuals in large-sized classes, in leaf number and leaf area, decreased in next year, while the size of the individuals in small-sized classes increased. Therefore, it was concluded that the size class structure of S. renifolius population was largely determined by the growth form.

• Journal of Forest and Environmental Science
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• 제31권3호
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• pp.164-176
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• 2015

Cyathea gigantea is a tree fern distributed throughout humid tropical regions of northeast India and other parts of the country. However, wild populations of this species are largely affected by various natural and anthropogenic activities. Therefore, an attempt was made to study the population structure and regeneration status of C. gigantea in and around greater Itanagar area of Papum Pare district, Arunachal Pradesh. Altogether 45 patches, ranging from 19.63 to $260m^2$ of area, were randomly sampled to study population structure and regeneration status of the species. Population study showed highest number of youngs in the height class of 0.50-0.75 m while, immatures were recorded highest in the height class of 2.0 to 2.5 m. Majority of the matures belonged to 6-9 m height class while it was recorded maximum in the diameter class of 10-15 cm. Average density of C. gigantea was $0.07individuals\;ha^{-1}$ which varied greatly among different patches with a range of 2 to 14. Significant correlations were found between patch size and density of youngs, immatures, matures and total density. Maximum concentration of youngs was observed in patch size $60-140m^2$, while for immatures, it was highest in patch size $20-160m^2$. Similarly, highest concentration of matures was observed in patch size $20-80m^2$ and $80-180m^2$. Population structure of the total population exhibited inverted pyramid shaped distribution. Population structure consisting of youngs, immatures, matures showed that around 60% patches lack of regenerating individuals which depict very poor natural regeneration of the species. Effective conservation strategies are therefore to be formulated to save C. gigantea from the threat of extinction in near future.

• 헤리티지:역사와 과학
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• 제47권3호
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• pp.60-85
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• 2014

본 연구의 목적은 경주지역 목곽묘 축조집단의 위계분석을 통한 사회적 신분구조를 파악하는데 있다. 경주지역 목곽묘의 위계는 목곽묘 면적과 부장된 유물의 구성에 따라 다음과 같이 분류된다. 상형토기, 갑주 등이 매납되고 목곽의 면적이 $15.0m^2$ 이상인 '가'등급에서 토기류만 매납되고 목곽의 면적이 $4.9m^2$ 이하인 '차' 등급까지 총 10등급의 구조로 구성된다. 이러한 위계구조는 각 등급이 축조할 수 있는 목곽의 규모나 매납품의 종류와 재질, 수량에 있어서 일정한 제한이 있었음을 알 수 있다. 다시 말해 고분의 내 외적 규모나 구조 그리고 매납품의 수량 종류 재질 등의 내용은 피장자의 출생 신분과 생시의 사회적 신분(지위) 등에 따라 차등을 주는 엄격한 사회적 규제가 적용되었다는 것을 뜻한다. 이러한 위계등급을 신라(사로) 신분 사회에 실질적으로 적용해 보면 '가'등급은 목곽의 규모나 매납 유물의 종류와 재질 등으로 볼 때 신라(사로)를 대표하는 최상위 지배층으로 추정된다. 그리고 '나', '다'등급은 상위 지배층, '라', '마'등급은 중위 지배층, '바', '사'등급은 하위 지배층으로 추정된다. 또한 '아', '자'등급은 상위 일반민, '차'등급은 하위 일반민의 신분(평민)으로 상정해 볼 수 있다. 이와 같이 본다면 '가'~'사'등급이 신라(사로)사회를 이끌어가는 실질적인 지배계층이라고 할 수 있다.

• 대한전자공학회논문지TC
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• 제44권7호통권361호
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• pp.12-16
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• 2007

본 논문은 일반적으로 고효율 특성을 가지고 있는 class-F 전력 증폭기의 출력 단에서 기생되는 2차 고조파 성분을 제거함으로 3차 IMD (Intermodulation distortion) 특성을 개선하였다. class-F 전력 증폭기의 경우 과부동 특성으로 인해 고효율을 얻을 수 있으나 선형성 측면에서는 많은 단점을 가지고 있다. 따라서 본 논문은 특별한 선형화 기술을 적용하지 않고 CMRC 구조를 적용하여 2차 고조파를 제거하여 선형성을 나타내는 U 특성을 개선하였다. CMRC 구조의 경우 광대역 저지대역 특성을 가지고 있으며 PBG 구조 보다 작은 크기로 더 좋은 특성을 얻을 수 있다.

• 한국전자파학회논문지
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• 제21권1호
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• pp.61-68
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• 2010

본 논문에서는 접지 결함 구조(Defected Ground Structure: DGS)를 이용하여 기지국용 고효율 E급 전력 증폭기의 성능을 유지하면서 크기를 소형화 할 수 있는 방안을 제안하였다. E급 전력 증폭기에서 요구되는 고조파 임피던스는 아령형 DGS와 나선형 DGS를 사용함으로써 만족시켜 주었다. 제안하는 유사 E급 전력 증폭기의 DGS 부하 회로는 가장 큰 고조파 성분인 2차 고조파 대역에서 개방, 나머지 고차 고조파 임피던스는 단락에 가까운 고조파 임피던스를 갖는다. 제안하는 구조를 통하여 제작된 전력 증폭기는 출력 전력이 43.1 dBm, 포화전력 이득이 12.7 dB일 때 70.2 %의 전력 부가 효율(Power Added Efficiency: PAE)을 가지며, 이는 비교 대상인 E급 증폭기와 거의 유사한 값이다. 회로 크기의 관점에서 보면 각각의 고조파 성분 정합을 위해 여러 개의 스터브가 장착되어 있는 비교 대상인 E급 증폭기에 비해 전체 크기를 50 %로 소형화시킬 수 있었다.

• 한국환경과학회지
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• 제21권3호
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• pp.313-326
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• 2012

Three embankments, namely Changpo, Bokkil and Guil, in Chunggye Bay were investigated to assess the influence of environmental changes to phytoplankton size structure, distribution of species and standing crops. Three stations was sampled near at each embankment in Nov. 2006, Feb. 2007, May 2007 and Aug. Phytoplankton were classified into net-size (>20${\mu}m$) and nano-size (<20${\mu}m$). In summer, the freshwater discharge seemed to have influence in the decrease of salinity and in the increase of turbidity, ammonium and phosphorus concentrations. Chl a concentration and phytoplankton abundance in Feb. 2007 were observed to be generally higher in all stations compared to other periods. Net-size phytoplankton was observed to be higher in Feb. 2007 and May 2007 compared to nano-sized phytoplankton. However, there was shift in phytoplankton composition in Nov. 2006 and Aug. 2007. Phytoplankton under seven class (Bacillariophyceae, Chlorophyceae, Chrysophyceae, Cryptophyceae, Cyanophyceae, Dinophyceae, Euglenophyceae) was identified during the study period. It was found out that the major phytoplankton class was Bacillariophyceae. Phytoplankton was more diverse in autumn compared to any other season. Cyanophyceae was increased in summer. In rainy season, change in physical factors (salinity, transparency) seemed to have more influence on phytoplankton growth compared to inorganic nutrients.

• 제어로봇시스템학회논문지
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• 제13권4호
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• pp.385-391
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• 2007

A class D digital audio amplifier with small size, low cost, and high quality is positively necessary in the multimedia era. Since the digital audio amplifier is based on the PWM signal processing, it is improper to analyze the principle of signal generation using linear system theories. In this paper, a class D digital audio amplifier based ADSM (Advanced Delta-Sigma Modulation) is considered. We first model the digital audio amplifier and then explain the operation principle using variable structure control algorithm. Moreover, the ripple signal generated by the hysteresis in the comparator has a significant effect on the system performance. Thus, we present a method to find the magnitude and the frequency of the ripple signal using describing function. Finally, simulations and experiments are provided to show the validity of the proposed methods.

• 한국수산과학회지
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• 제46권4호
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• pp.445-453
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• 2013

Walleye pollock Theragra chalcogramma fisheries in Korean waters have changed dramatically during the last three decades: the highest catches occurred in 1981, followed by continuous decreases through the 1990s, ending with a complete collapse of the population in the 2000s. The major spawning ground of walleye pollock is located in North Korean waters, and some juveniles (called nogari in Korean, <300 mm) migrate to the south for feeding and growth. Since the 1960s, Korean fishermen have often caught juveniles, and the weight (metric tons) of juvenile catch was recorded from 1975-1997. However, because the walleye pollock were not aged, the population age structure was not delineated. We developed a model to estimate the number of walleye pollock of each size class based on catch statistics of adults and juveniles, the catch proportion of each size class, and length and weight information on specimens collected by Danish-seine and drift-gill-net fisheries. The model results demonstrated that the recruitment size of walleye pollock was consistently within the 200-250mm size class, and the highest number of this size class occurred in 1981, although values greatly fluctuated interannually. The number of juvenile pollock was 10.4 times higher than that of adult pollock during 1975-1997. The total yield of juvenile pollock was 0.95 million tons, which was equivalent to about 68.2% of total pollock production. The number of juvenile pollock caught during the same period, however, was 16 billion, comprising about 91.2% of the total number caught. Such high fishing pressure on juvenile pollock is considered one of the main factors causing the collapse of the pollock population.

• ALGAE
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• 제28권4호
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• pp.365-369
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• 2013

The objective of this study was to determine the optimal blade size and timing to transplant seed-stock of Ecklonia cava Kjellman onto the reef structure. We used the modified artificial stepped reef structure. A total of 14 units (3.0 m length ${\times}$ 3.5 m width ${\times}$ 1.1 m height) were deployed 7-8 m deep under the water to examine the optimal blade size and timing to transplant seed-stock of E. cava onto the structures. Sporophytes of E. cava <1 cm in length were all died within 1 month of transplantation. The blades of 5-10 cm in length which were transplanted in March 2007 survived and grew well on the artificial reefs. Growth rates of 5-10 cm size class were higher than those of longer blade sporophytes (20-30 cm size class, transplanted in April) while the survival rates showed no difference between the classes of blade size. Both classes of 5-10 and 20-30 cm in length grew until July, and a reduction in size had occurred in September. These results indicate the importance of the blade size of E. cava and timing for successful transplantation of the seaweed on artificial reef structures.

• 대한조선학회 특별논문집
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• 대한조선학회 2006년도 특별논문집
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• pp.97-105
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• 2006

Until now, we are designing the breakwater of container vessel as cantilever structure ypically. Recently, we have designed "side shell touch type breakwater" for the first time to 6,200TEU Class Container Carrier registered on Lloyd Classification. The Lloyd Rule does not provide requirements for breakwater scantling but only recommend breakwater wave load and Lloyd Class requests for submitting the calculation results. At early design step, we had reviewed the breakwater structure through the calculation of simple beam theory with wave load recommended by Lloyd and referring to already built same size of container vessel. At the same time we had carried out F.E.M analysis of breakwater structure and had updated design, so we could verify the strength of side shell touch type breakwater at final step.