Control of hole distribution in quantum-dot/organic light-emitting diodes and its applications

Song, Sukho Sungkyunkwan university 2021 국내박사

Both quantum-dot light-emitting diodes (QD-LEDs) and organic light-emitting diodes (OLEDs) are self-emissive devices and attracting attention as display light sources because of their advantages such as high color purity, fast response time, and high contrast ratio. However, the QD-LED has a structure wherein hole injection is difficult because of the high ionization potential of the QD, whereas the OLED has a structure wherein electron injection is difficult because of the shallow lowest unoccupied molecular orbital (LUMO) level of the organic electroluminescent materials. The charge imbalance in QD-LEDs and OLEDs results in Auger recombination and triplet-triplet annihilation, respectively, which are non-radiative recombination processes that degrade the device efficiency. Thus, to improve the charge balance, structural approaches were conducted in this thesis. In the case of QD-LEDs, studies on a bi-layered hole injection layer (HIL) structure to enhance the hole injection ability are discussed. The hole current density was significantly improved by applying the bi-layered HIL structure, which was verified to result from the lowered effective hole injection barrier by designing a step-wise energy level. In the case of OLEDs, an OLED structure with a hole modulation layer (HML) inserted in the middle of the emission layer to improve the charge balance was demonstrated. The HML insertion effectively delayed the hole flow and mitigated the charge imbalance, which was confirmed by charge distribution analysis. Improvements in the charge balance in both QD-LED and OLED devices have led to an improvement in the device efficiency, a 65% improvement in the maximum power efficiency (PE) for the QD-LED device, and a 58% improvement in the maximum PE for the OLED device. The device structures introduced in this thesis are expected to effectively reduce the power consumption for actual displays and can be applied in the implementation of ultra-high-resolution displays. In addition, the ‘side-by-side’ geometry method is currently the most widely used technology to reproduce various mixed colors. However, it has limitations in implementing ultra-high-resolution displays because of the inherent low fill factor. In this thesis, we introduce a unique tandem QD-LED structure wherein hole injection from the electrodes is suppressed and only electrons can be injected into the device. Tandem QD-LEDs with configurations where two LED units face each other, with different emission colors stacked in series, are designed. Based on the polarity of the applied voltage, the operating LED unit differs such that the emission color changes within a pixel. Moreover, mixed colors can be reproduced through pulse-width modulation (PWM). Precise and broad color tuning is achieved by simply adjusting the duty cycle of the PWM operation. We expect that the color-tunable tandem QD-LED introduced in this thesis has the potential to be applied to ultra-high-resolution displays in the future. 양자점 발광 다이오드 (quantum-dot light-emitting diode, QD-LED)와 유기 발광 다이오드 (organic light-emitting diode, OLED)는 높은 색 순도, 빠른 응답 속도, 높은 명암비 등의 장점이 있어 디스플레이 광원으로 각광받고 있다. 그러나, QD-LED는 QD의 높은 이온화 에너지로 인하여 정공 주입이 어려운 구조를 지니며, OLED는 유기 발광 재료의 가장 낮은 비점유된 분자궤도함수 (lowest unoccupied molecular orbital, LUMO) 준위가 얕아 전자 주입이 어려운 구조를 지닌다. 이와 같이 불균일하게 전하가 소자에 주입되면 비발광 재결합인 Auger recombination와 triplet-triplet annihilation이 QD-LED와 OLED에서 발생하여 소자의 효율을 저하시킨다. 따라서, 소자의 효율을 향상시키고자 본 논문에서는 구조적인 접근 방법들을 통해 전하 균형을 개선하였다. QD-LED 소자의 경우, bi-layered HIL 구조를 적용하여 hole injection ability를 향상시키는 연구를 진행하였다. Bi-layered HIL 구조를 적용한 경우 정공 전류 밀도가 크게 개선되었는데, 이는 소자의 에너지 레벨을 계단식으로 설계하는 것을 통해 정공 주입 에너지 장벽을 낮출 수 있었기 때문이다. OLED 소자의 경우, hole modulation layer (HML)을 발광층 중간에 삽입하여 전하 균형을 개선하는 연구를 진행하였다. HML 삽입은 정공 흐름을 효과적으로 지연시켜 전하 불균형을 완화하였으며, 이는 전하 분포 분석을 통해 규명하였다. QD-LED 및 OLED 소자의 전하 균형 개선은 소자의 효율 향상으로 이어졌으며, QD-LED의 최대 전력 효율은 65% 개선되었고, OLED의 최대 전력 효율은 58% 개선되었다. 본 논문에서 제시한 소자 구조는 실제 디스플레이의 전력 소모를 효과적으로 감소시키고 초고해상 디스플레이 구현에 적용될 수 있을 것으로 기대한다. 또한, 다양한 혼합색을 구현하는데 있어, 현재 가장 널리 사용되는 방식인 ‘side-by-side’ geometry 기법으로는 한 화소 내에서의 발광 면적을 개선하는데 본질적으로 제한이 있기 때문에 초고해상도 디스플레이를 구현하는데 한계가 있다. 본 논문에서는 전극으로부터의 정공 주입이 억제되어 소자 외부에서는 전자만 주입될 수 있는 tandem QD-LED 구조를 소개한다. Tandem QD-LED의 소자 구조를 서로 다른 색을 발광하는 두 발광 다이오드 유닛이 마주보는 형태로 적층되도록 설계하였다. 이를 통해 인가 전압의 극성에 따라 작동하는 발광 다이오드 유닛이 달라 하나의 화소에서 발광하는 색이 변하는 소자를 구현할 수 있었다. 그리고 펄스 폭 변조 (pulse-width-modulation, PWM) 구동을 통해 두 색상 사이의 다양한 혼합색을 재현할 수 있었다. 단순히 PWM 구동의 duty cycle을 조정하는 것을 통해 정확하고 광범위한 색상 조정이 가능하였다. 본 논문에서 소개하는 색 변조 tandem QD-LED는 향후 초고해상도 디스플레이에 적용 가능하리라 기대한다.

Quantum dot light emitting diode using graphene oxide as hole injection layer

Song, Daeho Sungkyunkwan university 2018 국내박사

In this dissertation, we discuss the performance improvement of quantum dot light-emitting diode (QLED) using graphene oxide (GO) and reduced graphene oxide (rGO) as the hole injection layer (HIL). Graphene oxide is synthesized by Hummers' method and dispersed in DI water with 0.5 wt%. Since GO has an inherent insulating property, we have confirmed the hole injection capability of GO. First, we compared two types of QLEDs with and without GO HIL. The device without GO-QLED exhibited extremely low luminance and efficiency. However, the device with GO-QLED improved all electro-optical performance of the device. These results imply that the GO can work properly as an HIL layer in QLED, although GO is an insulation layer. Furthermore, we optimized the thickness of the GO to be 2 nm in QLED. Then, we fabricated a QLED device with a GO/PEDOT:PSS bilayer HIL and compared it to counterpart QLED devices with PEDOT:PSS or GO HILs. The QLED with a GO/PEDOT:PSS bilayer HIL exhibited dramatically improved luminance, external quantum efficiency, current efficiency, and turn-on voltage compared to the QLED with GO and PEDOT:PSS HIL. Finally, we used reduced graphene oxide (rGO) instead of GO as the HIL in the QLEDs, where the degree of reduction of rGO was controllable by UV exposure. Interestingly, the electric conductivity of rGO increased with the decrease in oxygen concentration, and the work function of rGO was tunable. As a result of using rGO as the HIL, the QLED device exhibited a high luminance of more than 10,000 cd/m2, a current efficiency of 14.99 cd/A and an external quantum efficiency of 4.23%. These results indicate that GO and rGO can be good alternative materials to replace PEDOT:PSS or transition metal oxide, which are commonly used hole injection layers, and can be used as an HIL of a QLED.

(The) impact of psychological distance on user experience on the C2C online shopping platform

Song, Yeosol Sungkyunkwan University 2023 국내석사

Users should feel a sense of belonging and establish a trustworthy environment through social networks on the C2C shopping platform. Reducing the psychological distance among users can help increase trust towards users and reduce uncertainty in the seller on a C2C shopping platform. The study explored the effect of psychological distance on user experience by dividing the psychological distance into physical and social aspects felt among users on an online shopping platform. Study 1 conducted a survey of 506 participants to investigate how physical distance affects trust, attitude and intention for continued use, and Study 2 conducted a 2 (geographical distance: near versus far) × 2 (personal profile: absence versus presence) between-subjects experiment (N = 98) to examine whether they can affect psychological distance and user experience. The results showed that a reduced psychological distance had a positive effect on user experience (Study 1). Moreover, a personal profile affected social-psychological distance and user experience, while geographical proximity did not have a significant impact on user experience (Study 2). Analyzing users’ trust and behavioral intentions in online shopping according to psychological distance has practical implications in that specific service designs were verified through experiments. C2C 쇼핑 플랫폼에서는 사용자들이 소속감을 느끼며, 사회적인 관계망을 통해 신뢰할 만한 환경을 구축하는 것이 중요하다. 거래 상대방에 대한 심리적 거리감을 감소시키는 것은 기존 중고 거래시장의 문제점으로 인식되는 판매자에 대한 신뢰 부족과 불확실성 문제를 해결하는데 도움이 될 수 있으며, 신뢰 이전 이론에 따르면 플랫폼에 대한 신뢰가 형성됨으로써 긍정적인 온라인 거래 환경을 갖출 수 있다. 본 연구는 온라인 쇼핑 플랫폼에서 상대방에 대해 느끼는 심리적 거리감을 물리적, 사회적 측면으로 나누어 사용자 경험에 미치는 영향을 연구했다. 연구 1은 당근마켓 사용자 506명을 대상으로 설문조사를 실시하여 심리적 거리감이 신뢰, 태도, 지속 사용의도에 어떠한 영향을 미치는지를 조사했으며, 연구 2에서는 98명의 참여자들을 대상으로 온라인 거래를 수행하는 실험을 진행하여 지리적 근접성과 개인 프로필의 존재 여부가 심리적 거리감과 사용자 경험에 영향을 줄 수 있는지를 살펴보았다. 결과적으로, 연구 1에서 심리적 거리감의 두 가지 차원 모두 신뢰와 사용자 경험에 긍정적인 영향을 미쳤다. 연구 2에서 개인 프로필의 존재가 심리적 거리감에 영향을 주어 신뢰와 사용자 경험을 증가시키는 것으로 나타났지만, 이와 달리 지리적 근접성에서는 차이가 나타나지 않았다. 온라인 쇼핑에서의 사용자들의 신뢰와 행동의도를 심리적 거리감에 따라 분석함으로써 해석 수준 이론의 범위를 확장하였으며, 실험을 통해 구체적인 서비스 디자인을 검증했다는 실증적 함의를 지닌다.

Design and synthesis of polymer-based nanocomposites for bio, sensory and catalytic applications

Song, Sungu Sungkyunkwan university 2021 국내박사

In the modern industry, the increasing demands of higher mechanical, chemical properties and novel characteristics of materials such as bio-compatibility, green synthesis are hard to satisfy with monolithic materials. For this reason, many researchers have focused on the polymer matrix nanocomposites (PNC) due to the synergistic effects of composites inducing enhanced physical and chemical properties and adapting novel characteristics for the applications such as catalyst, bio-medicine, and sensors easily. However, PNC still has limitations in the precise size and morphology control of nanoparticles and polymers, destabilization on disperses, the uneasy orientation of the dispersed phase, and agglomeration problems. Herein, I proposed novel molecules, methods, and mechanisms to develop the novel nanocomposites based on polymers, supramolecules, carbon-nanotubes for bio-, sensory and catalytic applications. I proposed imidazoliums with thiophene groups coordinated with a gold precursor, which can be converted to N-heterocyclic carbene (NHC) polymers with gold nanoparticles (AuNPs) with disproportionation and in-situ polymerization in chapter 2. In chapter 3, a binaphthyl group was introduced for precise control of the size and shape of PNC by solvents types and molecular weights of polymers. I also proposed supramolecular nanocomposite structures using cucurbit[7]uril in chapter 4 to synthesize the various metal nanoparticles (Au, Ag, Pt, Pd, Cu, and Fe) but adopt bio-compatible properties with green synthesis. In chapter 5, I proposed a solid-state synthesis method to synthesize size-controlled dextran/metal nanoparticle PNC to solve the problems of large-scale synthesis, green synthesis, and nanoparticle storage, and test anti-cancer activity. Finally, in chapter 6, I proposed single-walled carbon nanotube-based nanocomposites aligned with a the dielectrophoresis method in portable and selective chemical warfare agent sensors. 고분자 나노복합체는 고분자에 나노사이즈의 분리된 상의 물질이 복합된 형태의 물질로서, 기존 물질의 물리적, 화학적, 전기적 성질을 향상시키는 특성과 더불어, 목표하는 복합체의 물성뿐 아니라, 바이오적합성, 환경친화적인 성질등을 고분자 구조의 설계를 통해서 쉽게 달성할 수 있는 물질로서 큰 관심을 가지고 연구가 되고 있다. 본 연구에서는 고분자 나노복합체는 분류 중 고분자 기반 금속 나노입자의 합성과 응용, 초분자 기반 금속 나노입자의 합성과 응용, 탄소나노튜브 기반 고분자 복합체를 이용한 화학 센서로의 응용에 대하여 연구하였다. 우선, 이미다졸리윰 기반 물질에 금속 전구체가 결합된 형태의 단분자에서, 싸이오펜 그룹을 도입하여 단분자내에서 불균등화반응에 의해 생성된 금나노입자가 이미다졸리윰 물질에 단단히 결합하여 금속나노입자의 위치를 특정할수 있음과 동시에, 전기적 특성을 보이는 싸이오펜 그룹이 금나노입자에 의해 고분자화 반응이 진행되어서, 2TNHC-AuCl 단분자 하나로 고분자 금 나노입자 복합체를 형성하는데 성공하였다. 이에 이에서 바이나프틸 단분자 구조를 도입하여, 금 전구체를 이용해 금속나노입자의 합성과 고분자 합성을 동시에 진행하였으며, 용매에 따른 나노복합체의 크기 조절의 메커니즘 연구를 진행하였다. 이에, 보다 구체적인 복합체의 성질을 도입하고 응용하기 위하여 Cucurbit[7]uril 초분자를 도입하여 NaOH를 통하여 다양한 금속의 나노입자를 합성하고, 생체친화적인 성질을 보이는 CB7의 성질이 도입되었음을 확인하였고 4-나이트로페놀의 촉매 작용 및 항암성질에 응용하였다. 이어서, 초분자가 아닌 덱스트란을 고분자 이용하여 덱스트란의 분자량, 비율등에 의해 고분자 나노복합체의 크기 및 모양이 조절되는 것을 확인하였으며, 고체합성 반응을 도입하여 대량합성 및 나노복합체의 보관에 있어서 높은 안정성을 보이는 물질을 합성하였다. 또한, 보다 다양한 분야에의 응용을 위하여 탄소나노튜브를 도입하여, 유전영동을 통해 고정된 탄소나노튜브에 공유결합과 비공유결합 형태의 탄소나노튜브 기반 나노복합체를 형성하여 정전용량센서에 응용하여 화학작용제를 탐지할 수 있는 센서를 개발하였으며, 유사작용제 및 실작용제를 탐지하는데 성공하였으며, PCA 분석을 통하여 선택성을 보이는 센서를 개발하였다.

Childhood and adolescence in the United States and Korea

Song UMI 1990 국내박사

The tax system of the Republic of Korea

Song UMI 1990 국내박사

The Impact of Expected and Unexpected Socio-economic Change on Air Pollutants and Carbon

Seyeong Song Ulsan National Institute of Science and Technology 2022 국내석사

This study investigates the impact of unexpected and expected socio-economic changes on air pollutants and carbon. For the impact of socio-economic changes on air pollutants, the analysis used the air quality, thermal power generation, and macroeconomic indices data to identify the effect of thermal power generation and COVID-19 on air quality. The findings are that thermal power generation had worsened the level of CO from 2015 to 2019 and that the impact of COVID-19 improves the air quality in China and South Korea. For the impact of socio-economic changes on carbon, the analysis used firm-level emissions and corporate variables to identify how ETS implementation has influenced carbon productivity (a firm-level revenue created per unit of carbon emission). The findings are that the firms increased carbon productivity after participating in the national-level Emission Trading Scheme (ETS) of South Korea, especially for high-emitting industries, and firms that are profitable, innovative, and managed by CEOs with environment-related educational or working experience successfully increase their carbon productivity. These findings suggest that to improve air pollution and global warming, governments have to establish appropriate air quality control measures on each air pollutant and assist green-minded firms and firms have to increase profitability and invest in eco-friendly technologies by green-minded executives with regulations on high-emitting firms.

American protestant missionary perceptions of the Korean independence movement of 1919 and its effects upon the churches of Korea

Song UMI 1990 국내박사

Assessment of Artificial Pollination Factors Related to Fruit Set, Fruit Quality, and Seed Formation in Yellow-fleshed Kiwifruits

Oh, Eun Ui 제주대학교 2020 국내박사

키위는 자웅이주 식물로 상업적 재배를 위해서는 인공수분이 매우 중요하다. 키위는 유효수분기간이 짧기 때문에 안정적인 착과를 위해서는 짧은 기간에 인공수분 할 수 있는 재배기술이 필요하다. 또한 화분친의 배수성이 국내 육성 키위 품종의 과실 품질에 미치는 영향에 대한 연구는 아직 보고된 바가 없다. 따라서 본 연구는 황색 계통으로 제주지역에서 많이 재배하고 있는 ‘Halla Gold’와 ‘Sweet Gold’ 품종에 대해 효과적인 인공 수분 시기 및 수분 시간을 제시하고, 인공 수분 방법 및 배수성이 다른 화분친이 과실 품질 및 종자 형성에 미치는 영향을 알아보고자 수행되었다. 제주지역 무가온 플라스틱 하우스에서 재배되고 있는 ‘Halla Gold’와 ‘Sweet Gold’ 품종에 인공 수분 시기와 수분 시간에 따른 과실 품질 및 종자 형성에 미치는 영향을 알아보고자 수행하였다. ‘Halla Gold’와 ‘Sweet Gold’ 모두 개화 후 3일차에 수분하였을 때 착과율과 생체중, 건물률이 감소하기 시작하였다. 반면 당도, 산도, 건물율, H값은 유의적 차이가 나타나지 않았다. 종자무게와 백립중은 개화 후 3일차에 감소하는 경향을 확인 할 수 있었고, 효과적인 수분 기간은 생체중과 종자 충실도에 영향을 미치는 것을 확인할 수 있었다. 인공 수분 시간에 따른 ‘Halla Gold’와 ‘Sweet Gold’의 착과율은 모두 90% 이상으로 나타났다. 생체중은 오전 7시와 10시에 수분하였을 때 높게 나타났고, 16시 수분할 때에는 낮게 나타났다. ‘Halla Gold’에서 건물률은 오전 7시와 10시에 수분했을 때 높게 나타났고 16시 수분했을 때 낮게 나타났지만, ‘Sweet Gold’에서는 유의적 차이가 없었다. ‘Halla Gold’와 ‘Sweet Gold’ 모두에서 당도, 산도, 경도, H값, 종자수, 백립중의 통계적 유의성은 없었다. 따라서 제주지역의 무가온 플라스틱 하우스에서 재배되는 ‘Halla Gold’와 ‘Sweet Gold’의 수분 가능한 기간은 개화 후 3일 이내로 판단되었고, 수분 시간은 과실 품질 및 종자형성에 큰 영향을 주지 않는 것을 확인하였다. ‘Halla Gold’와 ‘Sweet Gold’ 품종에 인공 수분 방법에 따른 과실 품질 및 종자 형성에 미치는 영향을 알아보고자 수행하였다. 중복적으로 인공 수분 했을 때가 생체중, 건물율, 종자 수와 백립중이 높게 나타났다. 당도와 산도는 모든 처리에서 유의적 차이가 없었다. 3번 중복 인공 수분한 처리에서 경도는 낮게, H값은 높게 나오는 경향을 나타냈지만, ‘Halla Gold’에서는 유의적 차이가 없었다. 또한 암꽃의 물 처리 후 바로 수분하였을 때 ‘Halla Gold’와 ‘Sweet Gold’ 모두 생체중 및 건물률, 경도, 종자수, 백립중이 가장 낮게 나타났다. 중복 인공 수분에서는 암술 내 화분관 신장은 인공 수분 3일 후에 밑씨에 도달하여 결합하는데, 그 양상은 인공 수분 횟수에 따라 차이가 있었다. ‘Halla Gold’와 ‘Sweet Gold’는 화분관의 수는 한번 인공 수분할 때보다 중복적으로 인공 수분하였을 때 확연하게 많이 관찰되었다. 물을 뿌린 직후에 인공 수분하였을 때 ‘Halla Gold’와 ‘Sweet Gold’ 은 모두 생체중, 건물중, 경도, 종자수, 백립중이 가장 낮은 반면, 물을 뿌린 1시간 후, 화분현탁액을 뿌린 직후, 화분현탁액을 뿌린 1시간 후에는 과실 품질 및 종자 형성에 유의한 차이가 나타나지 않았다. 화분 현탁액을 이용한 물수분은 ‘Halla Gold’와 ‘Sweet Gold’에서 생체중이 기존 dry pollen pollination보다는 낮게 나타났지만 ‘Halla Gold’에서는 유의적 차이가 없었다. 또한 화분증량제를 수용액 형태의 화분현탁액을 이용한 물수분과 분말 형태의 석송자를 이용한 수분은 생체중을 제외한 과실 품질 및 종자 형성도에서 크게 차이를 나타내지 않았다. 따라서 화분 현탁액을 이용한 물수분은 인공수분 노동력과 꽃가루의 소요량이 작기 때문에 효율적인 수분방법이 될 수 있을 것이다. 4배체 ‘Halla Gold’와 ‘Sweet Gold’ 품종에 배수성이 다른 ‘CK3’ (diploid), ‘T’ line (tetraploid), ‘Bowha’ (hexaploid), and ‘Chieftain’ (hexaploid) 품종이 과실 품질 및 종자 형성에 미치는 영향을 알아보고자 수행하였다. 암술 내 화분관 신장은 인공수분 3일 후에 밑씨에 도달하여 결합하는데, 그 양상은 배수성이 다른 화분친에 따라 차이가 있었다. ‘Halla Gold’와 ‘Sweet Gold’는 화분관의 수는 ‘CK3’으로 수분하였을 때 다른 꽃가루에 비해 확연하게 적게 관찰되었다. ‘Halla Gold’와 ‘Sweet Gold’의 모든 화분 처리에서 착과률이 90%을 나타냈다. ‘Halla Gold’와 ‘Sweet Gold’의 과실 무게에서는 'Chieftain'과 'Bowha'의 수분에서 높게 나타났다. 당도는 ‘Sweet Gold’에서는 ‘Chieftain’에서 높게 나타났으나 ‘Halla Gold’에서는 큰 차이가 없었다. 건물률과 산도는 모든 처리에서 유의적 차이가 없었다. 경도는 ‘Halla Gold’에서는 ‘Chieftain’에서 높게 나타났고, ‘Sweet Gold’에서는 ‘Bowha’에서 높게 나타났다. 색차계 h˚ 은 ‘Halla Gold’와 ‘Sweet Gold’ 모두 ‘CK3’에서 낮게 나타났다. ‘Halla Gold’와 ‘Sweet Gold’의 종자 수는 과중과 비슷한 경향을 보였으나, 백립중은 ‘T’ line에서 가장 높게 나타났다. 화분의 배수성 수준이 착과율보다 과일 품질에 더 많은 영향을 준다는 것을 확인할 수 있었다. 또한 ‘Halla Gold’와 ‘Sweet Gold’ 재배에 적합한 꽃가루는 생체중과 과실 경도, 종자수, 종자무게에서 높은 경향을 나타낸 4배체 ‘T’ line과 6배체 ‘Bohwa’와 ‘Chieftain’으로 판단된다. Kiwifruit is a dioecious plant, and artificial pollination is very important for commercial cultivation. Since the effective pollination period of kiwifruits is short, cultivation techniques that allow artificial pollination in a short period of time are needed for stable fruit set. Also, there have been few studies on the correlation between the ploidy of the pollen donor and the quality characteristics of fruit for Korean kiwifruit cultivars. This study was conducted to suggest the effective artificial pollination period and time for yellow-flesh type ‘Halla Gold’ and ‘Sweet Gold’ widely cultivated in the Jeju region, and to investigate the effects of different artificial pollination methods and pollen donors with different polyploidy on fruit quality and seed formation. This study was conducted to evaluate the effect of artificial pollination period and pollination time on fruit quality and seed formation in 'Halla Gold' and 'Sweet Gold' kiwifruits grown in a non-heated plastic film house in Jeju, Korea. When both ‘Halla Gold’ and ‘Sweet Gold’ cultivars were pollinated on the third day after blooming, the fruit set rates, fresh weight and dry matter percentage started to decrease. On the other hand, the dry matter percentage, soluble solids content (SSC), acidity and h value did not show any significant difference. It could be seen that the seed number and 100-seed weight decreased on the third day after blooming, and the effective pollination period affected the fruit weight and seed development. The fruit set rates of both ‘Halla Gold’ and ‘Sweet Gold’ cultivars with the different artificial pollination time were over 90%. The fruit weight and dry matter showed the tendency of similar level in pollination at 7 and 10 AM and 1 PM and of low level at 4 PM. In both 'Halla Gold' and 'Sweet Gold' cultivars, there was no statistical significance in the SSC, acidity, firmness, h value, seed number and 100-seed weight. The results indicates that the efficient pollination period of 'Halla Gold' and 'Sweet Gold' cultivars grown in the non-heated plastic film house in Jeju is within 3 days after blooming, and the pollination time of the day has a minor effect on fruit quality and seed formation. This study was conducted to investigate the effect of pollen application methods for artificial pollination on such as pretreatment before pollination, repeated pollination and application types on fruit quality and seed formation. As for repeated pollination, it was observed that the pollen tube in pistil reached and penetrated into the ovule at 3 days after artificial pollination although the patterns varied depending on the number of dry pollen application. In ‘Halla Gold’ and ‘Sweet Gold’ cultivars, the number of pollen tubes was clearly higher in repeated pollination than when in single pollination. Furthermore, when pollen application was repeated, the fruit weight, dry matter percentage, number of seeds and 100-seed weight were higher. The firmness was low and the h value was high in pollination repeated three times. The soluble solids content and acidity showed no significant difference in all treatments. When pistillate flowers were pollinated with dry pollen immediately after water sprinkle, both ‘Halla Gold’ and ‘Sweet Gold’ cultivars showed the lowest fruit weight, dry matter percentage, firmness, number of seeds, and 100-seed weight, whereas dry pollen application 1 h after water sprinkle, immediate or 1 h after suspension medium sprinkle didn’t show significant differences on the fruit quality and seed formation. In wet application using pollen suspension, the fruit weight was lower in both 'Halla Gold' and 'Sweet Gold' cultivars than in conventional dry pollen application, but there was no significant difference in 'Halla Gold' cultivar. Application types with dry pollen and pollen suspension did not show a significant difference in fruit quality and seed formation except the fruit weight of ‘Halla Gold’ cultivar. The results indicate that raindrops or dewdrops on stigma might reduce an efficiency of artificial pollination with dry pollen, but repeated pollination and application types with dry pollen and pollen suspension have a minor influence. This investigated how the ploidy level of the kiwifruit pollinizer cultivars ‘CK3’ (diploid), ‘T’ line (tetraploid), ‘Bohwa’ (hexaploid) and ‘Chieftain’ (hexaploid) affected fruit set, fruit quality, and seed formation in the tetraploid kiwifruit cultivars ‘Halla Gold’ and ‘Sweet Gold’ cultivated. Pollen tubes growing in the pistil reached and combined with the ovule 3 days after artificial pollination, and their patterns differed depending on the ploidy level of the pollen parent. The number of pollen tubes observed in ‘Halla Gold’ and ‘Sweet Gold’ pistils was significantly lower following pollination by ‘CK3’ than with the other pollen donors. In all pollen treatments, the fruit set rates were >90%. The fruit weight of both ‘Halla Gold’ and ‘Sweet Gold’ were high following pollination with ‘Chieftain’ and ‘Bohwa’. The dry matter content, soluble solids, and acidity were not significantly different among all pollination treatments. Fruit firmness was higher following pollination with ‘Chieftain’ and ‘Bowha.’ Colorimeter h˚ values for flesh of ‘Halla Gold’ was low following pollination with ‘CK3’, but there were no differences for ‘Sweet Gold’ among all pollinations. The number of seeds showed a similar trend to fruit weight, but the 100-seed weight was highest with ‘T’ line as the pollinizer. The results indicate that the ploidy level of the pollen donor affects fruit quality more than fruit set. Also, the pollen most suitable for cultivation of ‘Halla Gold’ and ‘Sweet Gold’ is considered to be tetraploid ‘T’ line and hexaploid ‘Bohwa’ and ‘Chieftain’, which showed favorable effects on the weight and firmness of fruits, and the number and weight of seeds without adversely influencing fruit set and dry matter content.

Effect of the Tibetan plateau on the Asian summer monsoon circulations : a regional climate model study

송지혜 Graduate School, Yonsei University 2008 국내석사

In order to understand impacts of the Tibetan Plateau (TP) upon the Asian summer monsoon (ASM), a series of numerical experiments using a regional climate model are conducted with the various TP heights ranging from the flat surface (1.2 km) to the 140% of the real height. Compared to what was observed, the control experiment with a realistic TP height reproduces the precipitation and large-scale features properly.From the experiment using flat topography over the TP region, it is found that the presence of the TP leads to the increased (decreased) precipitation over northern (southern) India through both dynamical and thermal effects. The major causes to bring these changes are lower-atmospheric thermal low developed south to the TP and upper-atmospheric Tibetan high north to the TP, which results in consequent rising motion over the Indian summer monsoon (ISM) region. From a series of sensitivity experiments to the various TP height, the dynamical effects are consistently confirmed with somewhat reduced magnitudes; however, the resulting seasonal precipitation is not as robust as revealed in the flat topography run. It indicates that dynamical effects mixed with the weak thermal effects due to the small differences in TP height are not strong enough to bring out sufficient changes in the lower atmospheric circulation that is able to overcome nonlinear diabatic physical processes, so that changes in the ISM precipitation in response to the TP height are not linear.It is found that the presence of the TP intensifies the cyclonic circulation in the lower troposphere over East Asia, which is associated with positive (negative) height anomalies over the TP (east of the TP) in the upper troposphere. These dynamical circulation features due to the TP induce a weakening of the thermal and pressure gradient between land and ocean in the lower atmosphere toward what was observed. A series of sensitivity experiments reveals that both the lower- and higher-TP result in northwestward displacement of the East Asian summer monsoon (EASM) due to the enhanced subtropical northwestern Pacific high. It is concluded that a dominant factor for the EASM due to the TP is the dynamical effect caused by changes in the upper-atmospheric circulation, whereas the role of dynamically driven thermal effect is significant for the Indian summer monsoon.