• Title/Summary/Keyword: Guard cell

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A Study for the Application of Ammonia Propulsion Model: Focusing on the Training Ship (암모니아 추진 모델 적용을 위한 연구: 실습선을 중심으로)

  • GA-YOUNG YANG;JAE-WOO AHN;SUNG-BIN HONG;KANG-HYEON KIM;JAE-MIN PARK;BO RIM RYU;HO KEUN KANG
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2022.11a
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    • pp.156-157
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    • 2022
  • Currently, due to the increase in GHG emissions, the global weather phenomenon is constantly occurring, and each international organization is trying to reduce 온실가스 through various regulations to reduce GHG. To comply with the regulations, eco-friendly ships are currently being studied to reduce GHG. This paper models the fuel propulsion system of NH3 sofc fuel cell propulsion ship through the case study of eco-friendly ships, especially NH3 fuel cells, and provides information on how NH3 sofc fuel cell propulsion ships can benefit energy efficiency and decarbonization compared to existing FO vessels.

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Development of Fruit Structure in 'Fuji' Apples (사과 '후지' 과실의 조직 발달)

  • Park, Hee-Seung;Park, Ji-Young
    • Horticultural Science & Technology
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    • v.18 no.3
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    • pp.368-372
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    • 2000
  • The fruit structure of 'Fuji' apples from full bloom to maturing was observed from 1997 to 1998. Cell division period of the fruit was found to be 4 to 5 weeks after full bloom. Vascular bundles in the inner part of the fruit skin which were not described in the books illustrating apple fruit structure was observed, as they were tentatively named as outer vascular bundles (OVB), and another vascular bundles were also observed newly in periphery of locules, as they were tentatively named as inner vascular bundles (IVB). In the observation of the inner epidermis (IE) in the inner part of the locules on 2 days prior to full bloom, the guard cells were observed and these were disappeared in the observation made 2 days later, i.e. on full bloom. The formation of fruit skin was observed at the microscope 65 days after full bloom and the number of cell which organized the fruit skin did not change from this time to maturation period. Tannin which is mainly in the fruit skin changing from continuously during fruit growth, specially the tannin of epidermis disappeared completely 100 days after full bloom stage, and then constituted again. Starch was not almost found out in cell division period of fruit from full bloom stage after this time it constituted much at flesh part and decreased at maturation period. Epidermis was developed by uniform cells of a layer the cell of epidermis constituted irregularity after pigmentation stage, the organization of fruit was not close because the very big intercellular space constituted at hypodermis and flesh structure.

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Enhanced Spatial Covariance Matrix Estimation for Asynchronous Inter-Cell Interference Mitigation in MIMO-OFDMA System (3GPP LTE MIMO-OFDMA 시스템의 인접 셀 간섭 완화를 위한 개선된 Spatial Covariance Matrix 추정 기법)

  • Moon, Jong-Gun;Jang, Jun-Hee;Han, Jung-Su;Kim, Sung-Soo;Kim, Yong-Serk;Choi, Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.5C
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    • pp.527-539
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    • 2009
  • In this paper, we propose an asynchonous ICI (Inter-Cell Interference) mitigation techniques for 3GPP LTE MIMO-OFDMA down-link receiver. An increasing in symbol timing misalignments may occur relative to sychronous network as the result of BS (Base Station) timing differences. Such symbol synchronization errors that exceed the guard interval or the cyclic prefix duration may result in MAI (Multiple Access Interference) for other carriers. In particular, at the cell boundary, this MAI becomes a critical factor, leading to degraded channel throughput and severe asynchronous ICI. Hence, many researchers have investigated the interference mitigation method in the presence of asynchronous ICI and it appears that the knowledge of the SCM (Spatial Covariance Matrix) of the asynchronous ICI plus background noise is an important issue. Generally, it is assumed that the SCM estimated by using training symbols. However, it is difficult to measure the interference statistics for a long time and training symbol is also not appropriate for MIMO-OFDMA system such as LTE. Therefore, a noise reduction method is required to improve the estimation accuracy. Although the conventional time-domain low-pass type weighting method can be effective for noise reduction, it causes significant estimation error due to the spectral leakage in practical OFDM system. Therefore, we propose a time-domain sinc type weighing method which can not only reduce the noise effectively minimizing estimation error caused by the spectral leakage but also implement frequency-domain moving average filter easily. By using computer simulation, we show that the proposed method can provide up to 3dB SIR gain compared with the conventional method.

Characteristics of the Carbon Capture and Utilization System in Methanol Fuel Propulsion Ships Based on the Hydrogen Fuel Cell Hybrid System (수소 연료전지 하이브리드 시스템 기반 메탄올 연료추진 선박에서 CCU 적용에 따른 시스템 특성 분석)

  • YoonHo Lee;JunHo Kim
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.30 no.2
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    • pp.239-251
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    • 2024
  • In this study, a hydrogen fuel cell process based on methanol was developed to reduce greenhouse gas emissions. In Case1, the methanol fuel engine system was designed to investigate the emission of exhaust gas when methanol was supplied as fuel instead of gasoline to the engine. In Case2, a hydrogen fuel cell system was designed by adding a methanol reforming system to Case1. This hybrid system produced gray hydrogen and combined the output of the engine and fuel cell to drive the ship. However, gray hydrogen emits carbon in the process of producing hydrogen. To address this problem, a carbon capture and utilization (CCU) system was added to Case3. The CO2 of the flue gas discharged from Case2 was synthesized with gray hydrogen to produce blue methanol. The results of the case studies revealed that the optimal operating conditions were 220 ℃, 500 kPa, SCR = 1.0, and flow ratio = 0.7. The system of Case3 reduced carbon emissions by 42% compared with that Case1. Thus, the hybrid system of Case3 could considerably reduce the ship's CO2 emissions.

Material Tests for Module Type Crash Cushion (모듈타입 충격흡수장치를 위한 재료실험)

  • Ko, Man-Gi;Kim, Kee-Dong;Sung, Jung-Gon;Kim, Jin-Man
    • International Journal of Highway Engineering
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    • v.10 no.1
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    • pp.87-95
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    • 2008
  • One way to shield an atypical structure to secure the occupant safety of an impact vehicle is to stack energy absorbing material modules around the structure. To be applicable to a cushion module, material must have enough energy absorbing capabilities while satisfying the safety requirements of the vehicle occupant. Static compression test of the potential materials gives a good indication which material is good for a slacking module. This paper presents the mechanical properties that a cushion material must have to satisfy the safety requirements. Static tests are performed for Quard-Guard system module, sand bag, recycled tires, Geo-Container, Geo-Cell and Expanded Polystyren (EPS) Blocks. Static test results are discussed and EPS block of $30kg/m^{3}$ density showed good potential for a cushion module. To check the dynamic effect of EPS block, drop tests have been made up to 35.6km/h impact speed. Drop test results are compared with static test results and no appreciable difference was found. To improve the EPS module property, making holes to the block is suggested and drop test are performed for the modified blocks. From the drop test results, design values are suggested.

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The Effect of working hours on fatigue and immune function in private security (시큐리티 종사자들의 근무시간이 피로도 및 면역기능에 미치는 영향)

  • Jung, Sung-Sook;Park, Jun-Seok;Jeon, Hee-Cheol;Lee, Young-Seok
    • Korean Security Journal
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    • no.21
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    • pp.121-134
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    • 2009
  • The purpose of present study was to examine the effects of working time on fatigue and immune function in private security. The number of private guard on which this study has been conducted in 153, who work at large companies, medium or small companies and the like as located in Seoul and kyonggi. In this study blood T-lympocyte, Natural T-Killer cell and immunoglobulin(IgG, IgA and IgM) were measured to see the level of working hours. There was significant difference in Natural T-Killer cell and immunoglobulin(IgG, IgA and IgM) and fatigue between working hours(P<0.05). in view of the results of this study, it can be thought that fatigue and immune function is more affected by working hours In summary, these results are interpreted to mean that fatigue levels and immune function (Natural T-Killer cell, and immunoglobulin) decrease due to a rise in working hours.

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A 10-bit 100 MSPS CMOS D/A Converter with a Self Calibration Current Bias Circuit (Self Calibration Current Bias 회로에 의한 10-bit 100 MSPS CMOS D/A 변환기의 설계)

  • 이한수;송원철;송민규
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.40 no.11
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    • pp.83-94
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    • 2003
  • In this paper. a highly linear and low glitch CMOS current mode digital-to-analog converter (DAC) by self calibration bias circuit is proposed. The architecture of the DAC is based on a current steering 6+4 segmented type and new switching scheme for the current cell matrix, which reduced non-linearity error and graded error. In order to achieve a high performance DAC . novel current cell with a low spurious deglitching circuit and a new inverse thermometer decoder are proposed. The prototype DAC was implemented in a 0.35${\mu}{\textrm}{m}$ n-well CMOS technology. Experimental result show that SFDR is 60 ㏈ when sampling frequency is 32MHz and DAC output frequency is 7.92MHz. The DAC dissipates 46 mW at a 3.3 Volt single power supply and occupies a chip area of 1350${\mu}{\textrm}{m}$ ${\times}$750${\mu}{\textrm}{m}$.

Analysis of the Characteristics of Reformer for the Application of Hydrogen Fuel Cell Systems to LNG Fueled Ships (LNG 추진선박에 수소 연료전지 시스템 적용을 위한 개질기의 특성 분석)

  • Lee, Yoon-Ho
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.1
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    • pp.135-144
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    • 2021
  • In this study, we investigated the characteristics of the process of hydrogen production using boil-of gas (BOG) generated from an LNG-fueled ship and the application of hydrogen fuel cell systems as auxiliary engines. In this study, the BOG steam reformer process was designed using the UniSim R410 program, and the reformer outlet temperature, pressure, and the fraction and consumption of the product according to the steam/carbon ratio (SCR) were calculated. According to the study, the conversion rate of methane was 100 % when the temperature of the reformer was 890 ℃, and maximum hydrogen production was observed. In addition, the lower the pressure, the higher is the reaction activity. However, higher temperatures have led to a decrease in hydrogen production owing to the preponderance of adverse reactions and increased amounts of water and carbon dioxide. As SCR increased, hydrogen production increased, but the required energy consumption also increased proportionally. Although the hydrogen fraction was the highest when the SCR was 1.8, it was confirmed that the optimal operation range was for SCR to operate at 3 to prevent cocking. In addition, the lower the pressure, the higher is the amount of carbon dioxide generated. Furthermore, 42.5 % of the LNG cold energy based on carbon dioxide generation was required for cooling and liquefaction.

Leaf epidermal structure of the Allium L. and its taxonomic significance (부추속(Allium L.) 잎 표피의 구조와 이의 분류학적 중요성)

  • Choi, Hyeok-Jae;Jang, Chang-Gee;Ko, Sung-Chul;Oh, Byoung-Un
    • Korean Journal of Plant Taxonomy
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    • v.34 no.2
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    • pp.97-118
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    • 2004
  • A comparative anatomical and ultrastructural study was undertaken to investigare on the leaf epidermis by light microscopy (LM) and scanning electron microscopy (SEM). On the basis of results from this study, it was grasped major characters of taxa and variation range of each character on the level of species, section and subgenus respectively. The shape of leaf epidermal cell was oblong to linear, which was varied by each taxon. Epidermal cell of taxa in sects. Microscordum, Anguinum, and Rhizirideum, which had wide leaf blade, oblong instead of linear shape in others examined taxa in this study. The leaf of taxa in sect. Anguinum was hypostomatic, while the rest of taxa had amphistomatic leaf. This was also one of characters which could discriminate taxa of sect. Anguinum from others. The guard cell in investigated taxa had not so much variation in the respect of its size. The number of stomata per unit area reduced by increasing size of epidermal cell, the fewest number of stomata per unit area was found in the taxa of sect. Anguinum. The type of stomatal apparatus of observed all taxa was anomocytic. It was found to know ultrastructural variation in the epidermal cell, like as patterns of sculpture on the cell wall, and features of deposition of wax by SEM. There were no depositions of wax in the taxa of sect. Microscordum and Anguinum, but fine thread-like structures which were parallel or cross to axis was found on the surface of epidermal cell respectively. The patterns of sculpture on the cell were prominent straight in sects. Recticulato-bulbosa and Rhizirideum, discontinuous line in the sect. Oreiprason. The epicuticular wax had been deposited on the surface of its epidermal cell in all taxa except sects. Microscordum and Anguinum.

Studies on a Tetraploid of Robinia pseudoacacia L. Selected in the Planted Forest (조림지(造林地)에서 선발(選拔)한 자연(自然) 4배체(倍體) 아까시나무(Robinia pseudoacacia L.)에 관(關)한 연구(硏究))

  • Kim, Chung Suk;Lee, Suk Koo
    • Journal of Korean Society of Forest Science
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    • v.14 no.1
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    • pp.39-44
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    • 1972
  • Cytological investigation was done on a tetraploid tree of Robinia pseudoacacia L. selected in the planted forest in Chilbo Mountain. From the results of observation of chromosomes on mitotic metaphase in leaves, it was confirmed that the mutant is tetraploid plant (2n=40). The external form of leaves of the spontaneous tetraploid was gigantic and dark green one in comparison with diploid. There was no difference in the size of guard cell and the number of stomata per unit area between the mutant and the diploid plant, however, length and thickness of wood fiber were increased as compared with that of diploid. The spontaneous gigas tetraploid showed growth performance as much as the colchicine induced gigas tetraploid.

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