• Journal of Plant Biology
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• v.36 no.1
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• pp.35-42
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• 1993

This study deals with the effect of dwarf growth for the wood and the structural changes of cambium in Pinus koraiensis subjected to water stress. The length and wall thickness of tracheary elements in dwarf trees was shorter and thicker than that in normal trees. The redial width and cell number of the annual rings are narrower and smaller in dwarf trees than those in normal trees. In serial tangential sections, the frequency of anticlinal division is low and loss of cambial initials is small in dwarf trees. The length of cambial initials in water deficit, trees are slightly shorter than that in normal trees, and the instructive growth of cambial initials during differentiation of xylem mother cells is inactive in dwarf trees. Thus, it is interpreted that the shortening of tracheary elements in dwarf trees is due to the fact that the length of cambial initials are shortened and the intrusive growth of those during differentiation of xylem mother cells is inactive. The structural variations in the wood of naturally occurring dwarf trees are similar to those of trees subjected to artificial water stress. Therefore, it is suggested that the variation of xylem element in dwarf trees are related to water conditions.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.1395-1403
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• 2021

The COVID-19 pandemic is having an adverse impact on Bangladesh's economy by affecting millions of people's life and hampering their income sources. The outbreak of COVID-19 has created more pressure on the labor market. The pandemic reduces employment opportunities as most of the companies have stopped their recruitment process to cut their operational costs, which increases the rate of graduate unemployment in Bangladesh. Hence, this study aims to investigate the impact of COVID-19 on graduate employability in Bangladesh that adversely affects the income of families and eventually the nation's economy. A literature review has been conducted from secondary sources to evaluate the impact, which shows that the rate of graduate unemployment increased from 47% to 58% in 2020 with an expected annual loss estimated at $53 million. Findings also reveal that the prime reasons for graduate employability are low demand and huge supply of graduates in the labor market, lack of professional skills of graduates, ineffective education system, etc. The study suggests that the government of Bangladesh should develop some policies to overcome this problem such as ensuring employment subsidies, implementing skills development programs, improving labor market flexibility, initiating credit programs for generating employment, and developing entrepreneurial ecosystems in Bangladesh.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.7
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• pp.195-201
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• 2021

This study aims to assess the impact of ownership structure of commercial banks on bank credit risk in Vietnam. The authors used the unbalanced table data of 28 commercial banks in the period from 2004 to 2020 with 439 observations. The ratio of loan loss provisioning to loans (CR) is selected as a dependent variable representing credit risk at commercial banks. The regression methods used include: least squares method (OLS), fixed-effect model (FEM), random-effect model (REM) and general least squares method (GLS). The results reveal that, with interaction variable between the ratio of equity to total assets and foreign ownership, the national GDP annual growth rate is negatively associated with credit risk. With the ratio of equity to total assets, the interaction variable between equity and state ownership, and bank size have a significant positive impact on credit risk. In addition, inflation has negligible impact on the credit risk of commercial banks in Vietnam over the research period. The findings of this study suggest that, if foreign-owned banks increase equity capital, there will be a stronger impact on reducing credit risk than other banks. On the other hand, when state-owned commercial banks in Vietnam increase equity, they will have higher credit risk.

• Annual Conference on Human and Language Technology
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• 2022.10a
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• pp.251-256
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• 2022

범주 불균형은 분류 모델이 다수 범주에 편향되게 학습되어 소수 범주에 대한 분류 성능을 떨어뜨리는 문제를 야기한다. 언더 샘플링 기법은 다수 범주 데이터의 수를 줄여 소수 범주와 균형을 이루게하는 대표적인 불균형 해결 방법으로, 텍스트 도메인에서의 기존 언더 샘플링 연구에서는 단어 임베딩과 랜덤 샘플링과 같은 비교적 간단한 기법만이 적용되었다. 본 논문에서는 트랜스포머 기반 문장 임베딩과 군집화 기반 샘플링 방법을 통해 텍스트 데이터의 정보 손실을 최소화하는 언더샘플링 방법을 제안한다. 제안 방법의 검증을 위해, 감성 분석 실험에서 제안 방법과 랜덤 샘플링으로 추출한 훈련 세트로 모델을 학습하고 성능을 비교 평가하였다. 제안 방법을 활용한 모델이 랜덤 샘플링을 활용한 모델에 비해 적게는 0.2%, 많게는 2.0% 높은 분류 정확도를 보였고, 이를 통해 제안하는 군집화 기반 언더 샘플링 기법의 효과를 확인하였다.

• Annual Conference on Human and Language Technology
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• 2019.10a
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• pp.18-22
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• 2019

FAQ 분류는 자주 묻는 질문을 범주화하고 사용자 질의에 대해 가장 유사한 클래스를 추론하는 방식으로 진행된다. FAQ 데이터셋은 클래스가 다수 존재하기 때문에 클래스 간 포함 및 연관 관계가 존재하고 특정 데이터가 서로 다른 클래스에 동시에 속할 수 있다는 특징이 있다. 그러나 최근 FAQ 분류는 다중 클래스 분류 방법론을 적용하는 데 그쳤고 FAQ 데이터셋의 특징을 모델에 반영하는 연구는 미미했다. 현 분류 방법론은 이러한 FAQ 데이터셋의 특징을 고려하지 못하기 때문에 정답으로 해석될 수 있는 예측도 오답으로 여기는 경우가 발생한다. 본 논문에서는 신뢰성이 부족한 FAQ 데이터셋에서도 분류를 잘 하기 위해 손실 함수를 조정하는 정규화 기법을 소개한다. 이 정규화 기법은 클래스 간 포함 및 연관 관계를 반영할 수 있도록 오답을 예측한 경우에도 예측 강도에 비례하여 손실을 줄인다. 이는 오답을 높은 확률로 예측할수록 데이터의 신뢰성이 낮을 가능성이 크다고 판단하여 학습을 강하게 하지 않게 하기 위함이다. 실험을 위해서는 다중 클래스 분류에서 가장 좋은 성능을 보이고 있는 모형인 BERT를 이용했으며, 비교 실험을 위한 정규화 방법으로는 통상적으로 사용되는 라벨 스무딩을 채택했다. 실험 결과, 본 연구에서 제안한 방법은 기존 방법보다 성능이 개선되고 보다 안정적으로 학습이 된다는 것을 확인했으며, 데이터의 신뢰성이 부족한 상황에서 효과적으로 분류를 수행함을 알 수 있었다.

• Annual Conference on Human and Language Technology
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• 2023.10a
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• pp.491-496
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• 2023

사전학습 언어모델을 개선하여 고품질의 문장 표현(sentence representation)을 도출하기 위한 다양한 대조 학습 방법에 대한 연구가 진행되고 있다. 그러나, 대부분의 대조학습 방법들은 문장 쌍의 관계만을 고려하며, 문장 간의 유사 정도를 파악하는데는 한계가 있어서 근본적인 대조 학습 목표를 저해하였다. 이에 최근 삼중항 손실 (triplet loss) 함수를 도입하여 문장의 상대적 유사성을 파악하여 대조학습의 성능을 개선한 연구들이 제안되었다. 그러나 많은 연구들이 영어를 기반으로한 사전학습 언어모델을 대상으로 하였으며, 한국어 기반의 비지도 대조학습에 대한 삼중항 손실 함수의 실효성 검증 및 분석은 여전히 부족한 실정이다. 본 논문에서는 이러한 방법론이 한국어 비지도 대조학습에서도 유효한지 면밀히 검증하였으며, 다양한 평가 지표를 통해 해당 방법론의 타당성을 확인하였다. 본 논문의 결과가 향후 한국어 문장 표현 연구 발전에 기여하기를 기대한다.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.3
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• pp.127-133
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• 2005

The measurement technique using laser distometer to estimate soil erosion on sloped upland was assessed for its possibility for application. This technique was practiced in lysimeter installed in Chuncheon and Pyeongchang in 2001. The lysimeter installed at Chuncheon has 12% slope, 10 m slope length, 2 m width, and soil texture was sandy loam, while the lysimeter installed at Pyeongchang showed 23% slope, 15 m slope length, 5 m width, and sandy loam soil. Change of surface soil height was monitored using laser distance meter before and after rainy season on same spots. The Investigated periods in Chuncheon and Pyeongchang were from 22 June to 22 September and from July to October, respectively. Precipitation in Chuncheon and Pyeongchang in this period was 892.2 and 931.9 mm, respectively. Rainfall over 60% of annual precipitation was concentrated on July and August in Chuncheon and September and October in Pyeongchang, respectively. By monitoring the change of surface soil height using laser distance meter before and after rainy season, eroded soil surface in up-down fallow field in Chuncheon was 0.874 cm, while eroded soil surface in slant furrow field in Pyeongchang was 1.127 cm, which correspond to 79.5 and $98.0MT\;ha^{-1}$. Soil erosion increased as furrow length increased. Amounts of estimated soil loss using laser distance meter was 0.98-1.18 times higher compared to the estimated values through Iysimeter experiment, which implies possibility for application to monitor soil loss particularly in up-down and slant furrowed field. However, in the lysimeter with contoured tillage, amount of estimated soil loss using laser distance meter was approximately a half compared to that from lysimeter experiment, which implies inadequacy of distance meter application in contour- tillage field. The great soil loss difference between distance meter and lysimeter might be caused by disruption of some of the contoured furrows in lysimeter. The measurement technique using distometer in this study could be useful to estimate soil loss especially in up-down and slant-tillage fields.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.3
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• pp.119-126
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• 2005

Soil erosion at Jawoon-Ri in Hongcheon highland is one of serious problems since saprolite piling on farmland has been typically practiced at 2-3 year's intervals. The objective of the case study was to survey management practices such as tillage, application of saprolite, and cultivating crops and to propose best management practices (BMP) to reduce soil loss in Jawoon-Ri, Hongcheon-Gun. Jawoon-Ri is located in the upper stream of Naerinchun. Upland areas of Jawoon 2 and 4Ri were 206.9 and 142.3 hectare, respectively. Estimation of soil loss in this study was based on USLE (Universal soil loss equation). Annual averaged soil losses were 15.6 MT per hectare in Jawoon-2Ri and 9.0 MT per hectare in Jawoon-4Ri, respectively. This case study tried to find methods to reduce soil erosion below tolerant soil loss level which is $11MT\;ha^{-1}\;yr^{-1}$. Estimated soil losses in more than 40% of uplands in Jawoon-2Ri and 4Ri were higher than tolerant soil loss level. Especially, edge of uplands undergone excessive soil erosion by concentrated runoff water. Therefore consolidation of upland edge was included as one of the proposed Best management practices BMP). The proposed BMP in this area were buffer strips, contour and mulching, diversion drain channel, grassed water-way, detour watet-way and cover crops and so on. Amounts for BMP requirements were 7,680 m for buffer strips, 123 ha (35%) for contour and mulching, 201 ha (57%) for diversion drain channel, 13,880 m for grassed water-way, 3,860 m for detour drainage, 8,365 m for sloping side consolidation and 3,492 ha for cover crops, respectively. Application of BMP are urgently needed in uplands which is direct conjunction with stream.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.2
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• pp.59-65
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• 2005

This study was performed to estimate the soil loss on a national scale and grade regions with the potential risk of soil erosion. Universal soil loss equation (USLE) for rainfall and runoff erosivity factors (R), cover management factors (C) and support practice factors (P) and revised USLE for soil erodibility factors (K) and topographic factors (LS) were used. To estimate the soil loss, the whole nation was divided into 21,337 groups according to city county, soil phase and land use type. The R factors were high in the southern coast of Gyeongnam and Jeonnam and part of the western coast of Gyeonggi and low in the inland and eastern coast of Gyeongbuk. The K factors were higher in the regions located on the lower streams of rivers and the plain lands of the western coast of Chungnam and Jeonbuk. The average slope of upland areas in Pyeongchang-gun was the steepest of 30.1%. The foot-slope areas from the Taebaek Mountains to the Sobaek Mountains had steep uplands. Total soil loss of Korea was estimated as $50{\times}10^6Mg$ in 2004. The potential risk of soil erosion in upland was the severest in Gyeongnam and the amount of soil erosion was the greatest in Jeonnam. The regions in which annual soil loss was estimated over $50Mg\;ha^{-1}$ were graded as "the very severe" and their acreage was $168{\times}10^3ha$ in 2004. The soil erosion maps of city/county of Korea were made based on digital soil maps with 1:25,000 scale.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.1
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• pp.56-65
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• 2006

In the past, flooding is commonly occurred in the Bockha stream watershed area with inundation by the water and eroded sediments. The purpose of this study is to find the relationship between area under cultivation and amount of soil erosion in each watershed areas using geographic information system(GIS) for decreasing the damages of flooding. The soil erosion amounts were computed on GIS using by universal soil loss equation(USLE). Small catchment areas was divided by topography and computed soil erosion amounts. The mean amount of soil erosion is 0.03 $ton/ha{\cdot}yr$ on the condition of the 1,329 mm/yr annual precipitation. The high erosion area(0.05 $ton/ha{\cdot}yr$) is shown in farm areas of the Sangyong-ri in Baeksa-myeon. The high erosion watershed area is related on the slopes of the farm lands and bare soil areas adjoining between the mountain slope and fluvial streams show much amount of soil erosion.