• 제목/요약/키워드: Boiling absorption

검색결과 62건 처리시간 0.03초

쌀 품질 고급화 및 고부가가치화를 위한 육종현황과 전망 (Current Status and Perspectives in Varietal Improvement of Rice Cultivars for High-Quality and Value-Added Products)

  • 최해춘
    • 한국작물학회지
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    • 제47권
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    • pp.15-32
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    • 2002
  • 1980-'90년대에 쌀의 자급생산이 지속되고 생활수준 향상에 따른 양질미 수요가 점증되면서 자포니카 다수성 품종의 미질 개선에 힘을 크게 기울이게 되었고 식미향상을 위한 육종연구 와 효율적 평가 기술개발 연구에 박차를 가하게 되어 쌀의 이화학적 특성과 식미 및 밥 물리성간 상관과 식미의 객관적 평가방법 개발, 양식미 쌀 및 가공적성 특수미 개발 등 그 동안 많은 연구성과를 올리게 되었다. 1990년대에 밥맛이 매우 좋은 고품질 자포니카 품종과 대립, 심백미, 향미, 유색미 등 가공용 특수미 품종을 개발 보급하였고 식미와 용도에 대하여 식미검정계, 신속점도측정계 및 texture 분석계 등을 이용하여 검토하였다. 최근에는 아밀로스 함량이 9%로 찹쌀과 맵쌀의 중간 성질을 가진 중간찰 품종인 '백진주벼'와 배유가 보얀 멥쌀인 '설갱 벼'를 비롯하여 라이신 함량이 높은 '영안벼' 육성하여 쌀의 가공 이용성과 기능성을 한층 높혀 놓았다. 식미와 여러 가지 미질 특성간 관련성에 관한 연구 결과를 요약해 보면 다음과 같다. 쌀의 상온흡수율 및 최대흡수율은 K/Mg율 및 알칼리 붕괴도와 유의한 부의 상관성을 나타내었으며 가열흡수율이 높은 품종일수록 밥의 용적팽창률이 컸다. 수분함량이 낮은 경질인 쌀일수록 침지 20분 후의 상온흡수율과 최대흡수율이 더 높은 경향이었으며 이러한 흡수 특성은 쌀 단백질 함량이나 아밀로스 함량 및 식미와는 유의한 상관성이 없었다 취반 적정가수량은 품종에 따라 마른 쌀 무게의 1.45-l.61배의 변이를 나타내었고 평균은 1.52배였으며 알맞게 취사된 밥의 부피는 평균 쌀 부피의 2.63배가되었다. 쌀 형태, 알칼리붕괴도, 호응집성, 아밀로스 및 단백질 함량은 거의 비슷하지만 식미에 차이가 있는 자포니카 품종들을 사용하여 식미와 관련된 쌀의 이화학적 특성을 검토한 결과, 밥의 윤기와 식미 총평은 생산 연도에 따라 호화점도 특성 중 최고점도, 최저점도 및 응집점도와 밀접한 관계를 나타내었다. 밥맛이 가장 좋은 일품 벼는 쌀의 외층에 아밀로스 함량 분포가 낮고 쌀을 열탕에 담근 20분간 우러난 용출액의 요드 정색도가 낮고 증가정도도 완만하였다. 일품 벼는 밥맛이 떨어지는 동해 벼에 비해 밥알 횡단면의 주사형 전자현미경 사진에서 밥알 외층의 호화전분의 그 물망이 매우 치밀하고 속층의 전분립의 호화정도가 양호하였다. 식미총평은 식미관련 이화학적 특성과의 관계를 이용한 중회귀식에 의해 매우 높은 결정계수로 추정이 가능하였다. 밥노화의 품종간 차이는 α-amylase-iodine 법으로 비교할 수 있었는데 노화정도가 적었던 품종은 일품벼, 추청벼, 사사니시끼, 진부벼 및 고시히까리였다. 통일형 품종인 태백벼와 자포니카 품종 중 섬진벼가 비교적 밥노화가 빨랐다 일반적으로 밥맛이 좋은 품종이 밥의 노화정도가 느렸으며 찬밥의 탄력성이 큰 경향이었다. 또한 밥노화가 느렸던 품종은 최저점도가 높았고 최종점도가 낮았다 찬밥의 탄력성은 쌀의 마그네슘함량과 밥의 용적팽창률과 밀접한 관계를 나타내었다. 식은밥의 더운밥 대비 경도 변화율은 취반용출액의 고형물량과 취반용적 팽창률과 부의 상관을 나타내었다. 식미관련 주요 이화학적 특성은 밥의 노화와도 직접 간접으로 상관이 있는 것으로 평가되었다. 쌀의 여러 가지 식품 가공적성과 관련된 형태 및 이화학적 특성은 가공식품 종류에 따라 매우 다르다. 쌀 튀김성은 호응집성이 연질이거나 아밀로스 함량이 낮을수록 양호하며 지질함량이나 단백질 함량이 높으면 좋지 않은 경향이다. 심복백정도가 심할수록 튀김현미 정립률이 떨어지며 현미 강도가 높을수록 튀김률은 높은 경향이었다 쌀국수는 밀가루와 50% 혼합시에 쌀의 칼륨 및 마그네슘 함량이 높은 품종일수록 제면 총평이 낮은 경향이었고 제면이 양호한 것이 국수물의 용출고형 물량이 적은 경향이었다. 쌀빵 가공적성은 품종에 따라서 현미와 백미간에 현저한 차이를 나타내는 것이 있는데 현미에서 반죽의 부피 증가율이 큰 쌀일수록 푹신한 감이 있는 쌀방 제조가 가능하였으며 백미에서 단백질 함량이 높은 품종일수록 쌀빵이 더욱 촉촉한 느낌이 있는 경향이었다. 아밀로스 함량이 높고 호응집성이 경질인 쌀일수록 쌀빵의 탄력성이 더 높은 경향이었다. 쌀의 발효 및 양조적성은 심복백이 심한 쌀이나 새로운 돌연변이인 뽀얀 멥쌀이 홍국균이나 홍국균의 균사활착 밀도가 높고 당화 효소 역가도 높은 경향이었으며 쌀알이 대립이면서 단백질 함량이 낮은 쪽이 양조에 유리한 것으로 알려져 있다. 찰벼 품종도 여러 가지 이화학적 특성과 전분구조 특성의 차이에 따라 9개의 품종군으로 나누어 볼 수 있을 만큼 품종적 변이가 크며 이들 이화학적 및 구조적 특성간에 상호 밀접한 연관성을 나타내었으며 유과·인절미·식혜ㆍ미숫가루 등에 상당한 가공적성의 차이를 보였다. WTO 체제 출범이후 생산비와 가격 면에서 경쟁력이 약한 우리 쌀이 살아남기 위해서는 품질의 고급화와 쌀 가공식품의 다양화 및 고기능성 개발을 추구할 수밖에 없다. 따라서 이와 같은 노력은 벼 품종개발만으로 소기의 성과를 올리기 어렵고 쌀 식품의 고급화 및 다양화를 위한 여러 분야의 긴밀한 연구협력이 수반되지 않으면 안 된다.

공기조화, 냉동 분야의 최근 연구 동향 -2002년 및 2003년 학회지 논문에 대한 종합적 고찰 - (Recent Progress in Air Conditioning and Refrigeration Research - A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2002 and 2003 -)

  • 정광섭;김민수;김용찬;박경근;박병윤;조금남
    • 설비공학논문집
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    • 제16권12호
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    • pp.1234-1268
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    • 2004
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2002 and 2003 has been carried out. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment/design. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation in diverse facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat transfer, humidity was also interesting to promote comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing research topics. Well developed CFD technologies were widely applied for analysis and design of various facilities and their systems. (2) Heat transfer characteristics of enhanced finned tube heat exchangers and heat sinks were extensively investigated. Experimental studies on the boiling heat transfer, vortex generators, fluidized bed heat exchangers, and frosting and defrosting characteristics were also conducted. In addition, the numerical simulations on various heat exchangers were performed and reported to show heat transfer characteristics and performance of the heat exchanger. (3) A review of the recent studies shows that the performance analysis of heat pump have been made by various simulations and experiments. Progresses have been made specifically on the multi-type heat pump systems and other heat pump systems in which exhaust energy is utilized. The performance characteristics of heat pipe have been studied numerically and experimentally, which proves the validity of the developed simulation programs. The effect of various factors on the heat pipe performance has also been examined. Studies of the ice storage system have been focused on the operational characteristics of the system and on the basics of thermal storage materials. Researches into the phase change have been carried out steadily. Several papers deal with the cycle analysis of a few thermodynamic systems which are very useful in the field of air-conditioning and refrigeration. (4) Recent studies on refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement when new alternative refrigerants are applied. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and new alternative refrigerants including natural refrigerants. Efficiency of various compressors and performance of new expansion devices are also dealt with for better design of refrigeration/air conditioning system. In addition to the studies related with thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out. It should be noted that the researches on two-phase flow are constantly carried out. (5) A review of the recent studies on absorption refrigeration system indicates that heat and mass transfer enhancement is the key factor in improving the system performance. Various experiments have been carried out and diverse simulation models have been presented. Study on the small scale absorption refrigeration system draws a new attention. Cooling tower was also the research object in the respect of enhancement its efficiency, and performance analysis and optimization was carried out. (6) Based on a review of recent studies on indoor thermal environment and building service systems, it is noticed that research issues have mainly focused on several innovative systems such as personal environmental modules, air-barrier type perimeterless system with UFAC, radiant floor cooling system, etc. New approaches are highlighted for improving indoor environmental conditions and minimizing energy consumption, various activities of building energy management and cost-benefit analysis for economic evaluation.

설비공학 분야의 최근 연구 동향 : 2010년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2010)

  • 한화택;이대영;김서영;최종민;김수민;권영철;백용규
    • 설비공학논문집
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    • 제23권6호
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    • pp.449-469
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    • 2011
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

공기조화, 냉동 분야의 최근 연구 동향: 2006년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2006)

  • 한화택;신동신;최창호;이대영;김서영;권용일
    • 설비공학논문집
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    • 제20권6호
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    • pp.427-446
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    • 2008
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2006 has been accomplished. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro heat exchanger and siphon cooling device using nano-fluid. Traditional CFD and flow visualization methods were still popular and widely used in research and development. Studies about diffusers and compressors were performed in fluid machinery. Characteristics of flow and heat transfer and piping optimization were studied in piping systems. (2) The papers on heat transfer have been categorized into heat transfer characteristics, heat exchangers, heat pipes, and two-phase heat transfer. The topics on heat transfer characteristics in general include thermal transport in a cryo-chamber, a LCD panel, a dryer, and heat generating electronics. Heat exchangers investigated include pin-tube type, plate type, ventilation air-to-air type, and heat transfer enhancing tubes. The research on a reversible loop heat pipe, the influence of NCG charging mass on heat transport capacity, and the chilling start-up characteristics in a heat pipe were reported. In two-phase heat transfer area, the studies on frost growth, ice slurry formation and liquid spray cooling were presented. The studies on the boiling of R-290 and the application of carbon nanotubes to enhance boiling were noticeable in this research area. (3) Many studies on refrigeration and air conditioning systems were presented on the practical issues of the performance and reliability enhancement. The air conditioning system with multi indoor units caught attention in several research works. The issues on the refrigerant charge and the control algorithm were treated. The systems with alternative refrigerants were also studied. Carbon dioxide, hydrocarbons and their mixtures were considered and the heat transfer correlations were proposed. (4) Due to high oil prices, energy consumption have been attentioned in mechanical building systems. Research works have been reviewed in this field by grouping into the research on heat and cold sources, air conditioning and cleaning research, ventilation and fire research including tunnel ventilation, and piping system research. The papers involve the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies on indoor air quality took a great portion in the field of building environments. Various other subjects such as indoor thermal comfort were also investigated through computer simulation, case study, and field experiment. Studies on energy include not only optimization study and economic analysis of building equipments but also usability of renewable energy in geothermal and solar systems.

분리대두단백 두부의 제조를 위한 가열시간 및 혼합응고제의 영향 (Effect of Heating Time and Mixed Coagulants for Prepared SPI Tofu)

  • 구경형;김우정
    • 한국식품과학회지
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    • 제26권1호
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    • pp.26-30
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    • 1994
  • 분리대두단백(SPI)을 주원료로 마쇄와 여과, 압착 과정을 생략한 두부의 연속적 제조 방법을 위한 기초자료로서 분리대두단백의 보수력과 보유력, 가열시간, 단일응고제 소요량, 혼합응고제에 따른 두부의 텍스쳐 및 수율변화 그리고 관능적 특성을 조사하였다. SPI 분산액의 $100^{\circ}C$에서 가열시간이 길어짐에 따라 $CaCl_{2}$와 GDL응고제 양은 감소하다가 증가하였고, $MgCl_2$는 감소하는 경향이었으며, $CaSO_{4}$는 대조구를 제외하고 큰 차이가 없었다. 응고에 필요한 응고제의 양은 $CaSO_{4}>GDL>MgCl_{2}>CaCl_{2}>$순이었다. 압착두부 제조방법에 의한 두부의 수율은 $CaSO_{4}$로 응고한 두부로 가열시간 6분일 때 가장 높았으며, GDL로 응고한 두부의 수율은 다른 응고제에 비하여 낮았으나 6분에서 약간 높은 수율을 보였고, 이외의 응고제에 의한 두부수율은 가열시간에 큰 영향을 받지 않았다. SPI의 보수력은 $100^{\circ}C$에서 가열시간이 증가함에 따라 크게 감소하였고, 보유력은 9분까지 증가하다가 감소하였다. 또 혼합응고제$(CaSO_{4}-GDL,\;CaSO_{4}-CaCl_{2},\;CaCl_{2}-GDL)$로 응고한 압착두부의 물리적 특성은 $CaCl_{2}$와 GDL 비율이 많아짐에 따라 경두부의 특성을 나타내었다. 최고의 수율은 $CaSO_{4}$ 100% 응고두부였으며, 최소의 수율은 GDL로 응고한 두부였다. 관능검사 결과 $CaSO_{4}$ 비율이 증가함에 따라 부드럽고, 균일한 조직을 얻었으며, GDL과 $CaCl_{2}$의 비율이 많은 혼합응고제로 제조한 두부는 신맛과 쓴맛의 강도가 컸다.

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토양질소(土壤窒素)의 유효도(有效度) 검정방법(檢定方法)에 의한 황색종연초(黃色種煙草)의 적정시비량(適正施肥量) 추정(推定) (Prediction of Optimum Fertilizer Rate for Flue-Cured Tobacco by Nitrogen Availability in Soils)

  • 정훈채;조성진;홍순달;이윤환
    • 한국토양비료학회지
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    • 제18권2호
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    • pp.169-176
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    • 1985
  • 토양질소(土壤窒素)의 공급능력(供給能力)(유효도(有效度)) 검정방법(檢定方法)에 의한 밭토양의 비옥도(肥沃度) 평가(評價) 및 황색종연초(黃色種煙草)의 정적시비량(定適施肥量)을 추정(推定)하기 위하여 1982~1983년(年)에 23개소(個所)의 재배전(栽培前) 공시토양(供試土壤) 시료(試料)를 재료(材料)로 몇가지 토양검정치(土壤檢定値)에 의한 실내실험(室內實驗)과 이미 얻어진 무비구(無肥區) 건엽중(乾葉重)과의 상호관계(相互關係)를 검토(檢討)하였다. 토양(土壤)의 유효태질소(有效態窒素) 검정방법(檢定方法)으로서 본연구(本硏究)에서 사용(使用)된 a) 2주(週), b) 4주(週)동안의 항온(恒溫) 항습처리(恒濕處理)로 무기화(無機化)된 $NO_3-N$값, c) 0.01M-$NaHCO_3$ 침출물(浸出物)의 자외선(紫外線)(260nm) 흡광도(吸光度)값과 d) 동침출액(同浸出液)의 산분해(酸分解) 질소(窒素)값, e) 0.01M-$CaCl_2$ 용액(溶液)으로 자비(煮沸)하여 침출(浸出)한 질소(窒素)값과 f) 동용액(同溶液)으로 고온가압(高溫加壓) 침출(浸出)한 질소(窒素)값등의 모든 검정방법(檢定方法)이 무비구(無肥區)에서의 건엽중(乾葉中) 및 질소흡수량(窒素吸收量)과 밀접(密接)한 관계(關係)가 있었다. 따라서 유효태질소(有效態窒素) 토양검정결과(土壤檢定結果)로서 황색종연초(黃色種煙草)의 무비구(無肥區) 건엽중(乾葉中)의 추정(推定)은 물론, 토양비옥도(土壤肥沃度) 등급구분(等級區分) 및 적정시비량(適正施肥量) 추천범위(推薦範圍)의 산출(算出)도 가능(可能)하였다.

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New Boron Compound, Silicon Boride Ceramics for Capturing Thermal Neutrons (Possibility of the material application for nuclear power generation)

  • Matsushita, Jun-ichi
    • 한국재료학회:학술대회논문집
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    • 한국재료학회 2011년도 춘계학술발표대회
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    • pp.15-15
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    • 2011
  • As you know, boron compounds, borax ($Na_2B_4O_5(OH)_4{\cdot}8H_2O$) etc. were known thousands of years ago. As for natural boron, it has two naturally occurring and stable isotopes, boron 11 ($^{11}B$) and boron 10 ($^{10}B$). The neutron absorption $^{10}B$ is included about 19~20% with 80~81% $^{11}B$. Boron is similar to carbon in its capability to form stable covalently bonded molecular networks. The mass difference results in a wide range of ${\beta}$ values between the $^{11}B$ and $^{10}B$. The $^{10}B$ isotope, stable with 5 neutrons is excellent at capturing thermal neutrons. For example, it is possible to decrease a thermal neutron required for the nuclear reaction of uranium 235 ($^{235}U$). If $^{10}B$ absorbs a neutron ($^1n$), it will change to $^7Li+^1{\alpha}$ (${\alpha}$ ray, like $^4He$) with prompt ${\gamma}$ ray from $^{11}B$ $^{11}B$ (equation 1). $$^{10}B+^1n\;{\rightarrow}\;^{11}B\;{\rightarrow}\; prompt \;{\gamma}\;ray (478 keV), \;^7Li+4{\alpha}\;(4He)\;\;\;\;{\cdots}\; (1)$$ If about 1% boron is added to stainless steel, it is known that a neutron shielding effect will be 3 times the boron free steel. Enriched boron or $^{10}B$ is used in both radiation shielding and in boron neutron capture therapy. Then, $^{10}B$ is used for reactivity control and in emergency shutdown systems in nuclear reactors. Furthermore, boron carbide, $B_4C$, is used as the charge of a nuclear fission reaction control rod material and neutron cover material for nuclear reactors. The $B_4C$ powder of natural B composition is used as a charge of a control material of a boiling water reactor (BWR) which occupies commercial power reactors in nuclear power generation. The $B_4C$ sintered body which adjusted $^{10}B$ concentration is used as a charge of a control material of the fast breeder reactor (FBR) currently developed aiming at establishment of a nuclear fuel cycle. In this study for new boron compound, silicon boride ceramics for capturing thermal neutrons, preparation and characterization of both silicon tetraboride ($SiB_4$) and silicon hexaboride ($SiB_6$) and ceramics produced by sintering were investigated in order to determine the suitability of this material for nuclear power generation. The relative density increased with increasing sintering temperature. With a sintering temperature of 1,923 K, a sintered body having a relative density of more than 99% was obtained. The Vickers hardness increased with increasing sintering temperature. The best result was a Vickers hardness of 28 GPa for the $SiB_6$ sintered at 1,923K for 1 h. The high temperature Vickers hardness of the $SiB_6$ sintered body changed from 28 to 12 GPa in the temperature range of room temperature to 1,273 K. The thermal conductivity of the SiB6 sintered body changed from 9.1 to 2.4 W/mK in the range of room temperature to 1,273 K.

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Adhesion of Model Molecules to Metallic Surfaces, the Implications for Corrosion Protection

  • de Wit, J.H.W.;van den Brand, J.;de Wit, F.M.;Mol, J.M.C.
    • Corrosion Science and Technology
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    • 제7권1호
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    • pp.50-60
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    • 2008
  • The majority of the described experimental results deal with relatively pure aluminium. Variations were made in the pretreatment of the aluminum substrates and an investigation was performed on the resulting changes in oxide layer composition and chemistry. Subsequently, the bonding behavior of the surfaces was investigated by using model adhesion molecules. These molecules were chosen to represent the bonding functionality of an organic polymer. They were applied onto the pretreated surfaces as a monolayer and the bonding behavior was studied using infrared reflection absorption spectroscopy. A direct and clear relation was found between the hydroxyl fraction on the oxide surfaces and the amount of molecules that subsequently bonded to the surface. Moreover, it was found that most bonds between the oxide surface and organic functional groups are not stable in the presence of water. The best performance was obtained using molecules, which are capable of chemisorption with the oxide surface. Finally, it was found that freshly prepared relatively pure aluminum substrates, which are left in air, rapidly lose their bonding capacity towards organic functional groups. This can be attributed to the adsorption of contamination and water to the oxide surface. In addition the adhesion of a typical epoxy-coated aluminum system was investigated during exposure to water at different temperatures. The coating was found to quite rapidly lose its adhesion upon exposure to water. This rapid loss of adhesion corresponds well with the data where it was demonstrated that the studied epoxy coating only bonds through physisorptive hydrogen bonding, these bonds not being stable in the presence of water. After the initial loss the adhesion of the coating was however found to recover again and even exceeded the adhesion prior to exposure. The improvement could be ascribed to the growth of a thin oxyhydroxide layer on the aluminum substrate, which forms a new, water-stable and stronger bond with the epoxy coating. Two routes for improvement of adhesion are finally decribed including an interphasial polymeric thin layer and a treatment in boiling water of the substrate before coating takes place. The adhesion properties were finely also studied as a function of the Mg content of the alloys. It was shown that an enrichment of Mg in the oxide could take place when Mg containing alloys are heat-treated. It is expected that for these alloys the (hydr)oxide fraction also depends on the pre-treatment and on the distribution of magnesium as compared to the aluminium hydroxides, with a direct impact on adhesive properties.

식품 중 무기비소의 위해 분석 (Risk Analysis of Inorganic Arsenic in Foods)

  • 양승현;박지수;조민자;최훈
    • 한국식품위생안전성학회지
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    • 제31권4호
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    • pp.227-249
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    • 2016
  • 비소는 화학적 형태에 따라 독성이 상이하며 무기비소의 독성이 강하며 피부병변이나 피부암을 유발시키는 발암물질로 알려져 있다. 무기비소의 인체섭취한계량으로, JECFA에서는 기존의 무기비소의 주간잠정섭취허용량 $15{\mu}g/kg$ b.w./week을 철회하였으며, EFSA에서는 폐, 피부암, 피부병변 등에 대한 $BMDL_{0.1}$ $0.3{\sim}8{\mu}g/kg$ b.w./day를 제시하였다. 식품 중 쌀, 해조류 및 음료류은 무기비소 함량이 높은 식품으로 알려져 있다. 식품 중 쌀, 해조류 및 음료류은 무기비소 함량이 높은 식품으로 알려져 있다. 쌀을 재배하는 논 토양은 혐기성으로 주요 무기비소 화학종이 As(III)이기 때문에 쌀에서도 주요 무기비소 화학종이 As(III)인 반면, 수계에서는 주로 As(V)로 존재하기에 해조류에서의 주요 무기비소 화학종은 As(V)이다. 식품 중 무기비소 분석은 증류수, 메탄올, 질산용액 등을 이용해 가온 또는 상온조건에서 추출한 후 이온교환크로마토그래피과 액체크로마토그래피를 활용하여 비소화학종을 분리하고 원자흡광광도계, 유도결합플라즈마 질량분석기를 통하여 정량 및 정성분석이 이루어지고 있으나, 국제적으로 통용되는 보편화된 방법은 아직 제시되지 않고 있다. 유럽, 미국인 등의 무기비소 노출수준은 $0.13{\sim}0.7{\mu}g/kg$ bw/day인 반면, 우리나라를 포함한 아시아인의 무기비소 노출수준은 $0.22{\sim}5{\mu}g/kg$ bw/day인 것으로 추정되고 있다. 각 국가에서는 식품 중 무기비소 기준을 설정하고 있으며 국내에서도 관련 기준 설정을 준비 중에 있다. 현재까지 식품 중무기비소 저감화를 위해 많은 연구가 이루어지고 있으며, 쌀의 경우 도정도를 높이거나 세척을 많이 할수록, 해조류는 끓이는 과정을 통해 무기비소 함량을 크게 줄일 수 있다. 식품 중 무기비소 안전관리 강화를 위해서는 관련 시험법의 국제적 조화, 실태조사를 통한 무기비소 노출에 관한 지속적인 연구가 요구된다.