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        검색결과 167

        81.
        2013.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Physically and chemically activated carbons (ACs) exhibited high adsorption capacities for organic and inorganic pollutants compared with other adsorbents due to their expanded sur-face areas and wide pore volume distribution. In this work, seven steam-ACs with different burn-off have been prepared from cotton stalks. The textural properties of these sorbents were determined using nitrogen adsorption at -196°C .The chemistry of the surface of the present sorbents was characterized by determining the surface functional C-O groups using Fourier transform infrared spectroscopy, surface pH, pHpzc, and Boehm’s acid-base neutral-ization method. The textural properties and the morphology of the sorbent surface depend on the percentage of burn-off. The surface acidity and surface basicity are related to the burn-off percentage. A theoretical model was developed to finda mathematical expression that relates the % burn-off to ash content, surface area, and mean pore radius. Also, the chemistry of the carbon surface is related to the % burn-off. A mathematical expression was proposed where % burn-off was taken as an independent factor and the other variable as a dependent factor. This expression allows the choice of the value of % burn-off with required steam-AC properties.
        4,000원
        82.
        2012.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구에서는 CVD법으로 세라믹 막을 제조하였다. 튜브의 α-Al2O3 지지체 위에 Ga 염이 첨가된 γ-Al2O3를 코팅하였고, 실란화합물인 tetramethylorthosilane (TMOS) 를 650℃에서 화학적 기상 증착법으로 막에 증착하였다. 제조된 세라믹 막을 사용하여 수소, 질소, 이산화탄소, 메탄의 단일조성 기체투과 실험을 600℃에서 시행하였다. Ga 염 비첨가 시, 600℃ 수분 처리 실험의 H2/N2 선택도가 926에서 829로 감소한 반면, Ga 염 첨가 시에는 910에서 904로 안정하였다. 이 결과를 통해, 막에 금속염을 첨가하여 제조한 막이 수분 안정성을 향상시킴을 확인하였다.
        4,200원
        83.
        2012.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper examines the effects of various methods of soft steaming(i.e., forced convection-boiler, forced convection-fan, and natural convection) on the quality of potatoes. In particular, the paper investigates the effects of cooking conditions (the steaming method, the treatment time, and the temperature) on the color(L, a, b), moisture content, texture profile, and ascorbic acid of potatoes. The results indicate that not only the cooking method, the treatment time, and the temperature but also the heat transfer mechanism had considerable influence on potato quality. In addition, natural convection steaming was superior to other treatment methods in terms of nutrient retention and texture maintenance. The results of this study should be useful for establishing commercial standards for processing potatoes and improving the quality of thermally processed foods.
        4,000원
        84.
        2011.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        고온수증기전기분해(HTSE) 장치의 수소생산 및 열 화학적 특성을 파악하고자 COMSOL Multiphysics®를 사용해 2차원 정상상태 수치해석을 실시하였다. 계산을 위한 주요 파라메터로는 작동전압, ASR(Area-specific Resistance) 및 유입가스의 온도와 압력 등이다. 해석결과 1.2454 V에서 Thermal-neutral Voltage가 나타나고, 작동 전압이 증가함에 따라 Cell의 내부 온도가 단조 증가하는 것이 아니라 Thermal-neutral Voltage를 기준으로 낮은 전압에서는 Cell의 온도가 감소하고, 높은 전압에서는 Cell의 온도가 증가하였다. 또한, ASR 값이 증가함에 따라 Cell 내부의 온도는 하강하고, 수소생산율도 낮아지는 경향을 보였다.
        4,000원
        86.
        2010.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Activated carbons are well known as adsorbents for gases and vapors. Micro porous carbons are used for the sorption/separation of light gases, whereas, carbon with bigger pore size are applied for removal of large molecules. Therefore, the control of pore size of activated carbon plays a vital role for their use in specific applications. In the present work, steam activation parameters have been varied to control pore size of the resulting activated carbon. It was found that flow rate of steam has profound effect on both surface characteristic and surface morphology. The flow rate of steam was optimized to retain monolith structure as well as higher surface area.
        4,000원
        87.
        2010.05 구독 인증기관·개인회원 무료
        Electroantennogram techniques (EAGs) were employed to record olfactory responses in the antennae of the adult female stable fly, Stomoxys calcitrans (Diptera: Muscidae), to Zanthoxylum piperitum pericarp steam distillate (ZP-SD), Z. armatum seed oil (ZA-SO) and their 29 volatile constituents alone as well as binary mixture of the ZP-SD and ZA-SO with 1-octen-3-ol. The electrophysiological responses of the test materials were compared with those of DEET and 1-octen-3-ol. At concentration of 10-1 (v/v) in mineral oil, ZP-SD, ZA-SO, and all volatiles elicited EAG responses in the fly antennae except for DEET, which is extremely low volatile. ZP-SD, ZA-SO, and some of the test volatiles elicited EAG responses rather lower than 1-octen-3-ol, which showed vapor phase repellency and toxicity to the fly in our previous behavioral research. This suggests that the stable fly possesses olfactory receptor neurons responding to given repellent compounds per se. In binary mixture with 1-octen-3-ol at concentration of 10-1, ZP-SD and ZA-SO elicited 16±0.55 and 18±0.63 mV while ZP-SD, ZA-SO, and 1-octen-3-ol alone elicited responses of 14±0.45, 15.8±0.37 and 16.2±0.58 mV, respectively. Among the volatile compounds, terpinen- 4-ol, β-myrcene, α-phellanderene, citronellal, and limonene oxide elicited 80 – 96% relative EAG amplitude compared to 1-octen-3-ol as a reference (100%). Based on structure-activity relationships, constituents having aldehyde moiety elicited bigger EAG responses than those of alcohol or ether one. The perception in the fly antenna to plant volatile compounds exhibited complicated patterns of olfactory responses. Current and future directions of this study on sensory processing mechanisms underlying repellent behaviors will be discussed.
        88.
        2010.05 구독 인증기관·개인회원 무료
        The vapor phase repellency and toxicity of Zanthoxylum piperitum pericarp steam distillate (ZP-SD), Z. armatum seed oil (ZA-SO), and their 29 constituents to the adult female stable fly, Stomoxys calcitrans (Diptera: Muscidae), were examined using filter paper fumigation bioassay. Results were compared with those of the currently used repellent: DEET. Both of ZP-SD and ZA-SO exhibited vapor phase repellency and toxicity to female flies at 5 to 40 mg/filter paper (0.23 to 1.82 mg/cm3 air) during a 120-min exposure, whereas DEET exhibited neither repellency nor toxicity to the stable fly. At 5 mg/filter paper, vapor phase of ZP-SD and ZA-SO repelled 50 to 67% and 61 to 51% flies, respectively, to control area during 30 to 120 min. At 40 mg/filter paper, vapor phase of ZP-SD and ZA-SO caused 100% and 81% mortality, respectively, after 120 min of exposure. Among the tested volatile constituents, cuminaldehyde was the strongest repellent and toxic compound to the fly and was four times more toxic than ZP-SD and ZA-SO. Cuminaldehyde vapor phase repelled 62% flies to control area after 30 min at 2.5 mg/filter paper and caused 100% mortality after 120 min at 10 mg/filter paper. Based on the structure-activity relationships, the toxicity and repellency of constituents having aldehyde moiety were better than those of alcohol or ether one. Overall, ZP-SD, ZA-SO, and their bioactive constituents could be useful as potential vapor repellents to control stable fly population.
        89.
        2009.10 구독 인증기관·개인회원 무료
        The toxicity of Cyperus rotundus rhizome steam distillate constituents and their related compounds to adult females and males of the susceptible KS-BG strain and field-collected SR-BG and DR-BG colonies of Blattella germanica (L.) was examined using residual contact + fumigant and vapor-phase mortality bioassays. Results were compared with those of three organophosphorus (chlorpyrifos, dichlorvos, and fenitrothion), three carbamate (bendiocarb, dioxacarb, and propoxur), and three pyrethroid insecticides (bifenthrin, cypermethrin, and deltamethrin). In contact + fumigant mortality bioassay, p-cymene (LC50, 0.33 mg/cm2) was the most toxic terpenoid, followed by o-cymene, m-cymene, β-pinene, 1,8-cineole, and α-pinene, (LC50, 0.44–0.92 mg/cm2) against female B. germanica. These terpenoids were less toxic than the insecticides tested. Females were 3.1–3.6 times more tolerant than males to three cymene compounds. The toxicity of these monoterpenoids were almost identical against females from either of the three strains, even though the SR-BG and DR-BG females exhibited resistance to bifenthrin [resistance ratio (RR), 96 and 17], cypermethrin (RR, 67), deltamethrin (97 and 66), dioxacarb (19 and 22), and propoxur (24 and 32). In vapor-phase mortality bioassay, these monoterpenoids were effective in closed but not in open containers, indicating that the effect of these compounds was largely a result of vapor action. C. rotundus rhizome steam distillate and its constituents merit further study as potential insecticides for the control of insecticide-resistant B. germanica populations as fumigants with contact action.
        90.
        2009.05 구독 인증기관·개인회원 무료
        The toxicity of Asarum heterotropoides root steam distillate compounds to third instar larvae of Culex pipiens pallens, Aedes aegypti, and Ochlerotatus togoi (formerly Aedes togoi) was examined using a direct contact mortality bioassay. Results were compared with those following the treatment with fenthion and temephos. A. heterotropoides root steam distillate exhibited good larvicidal activity (21.07-27.64 ppm), based on LC50 values. Potent activity was produced by safrole (LC50, 8.22-16.10 ppm), terpinolene (11.85-15.32 ppm), -terpinene (12.64-17.11 ppm), (–)-β-pinene (12.87-18.03 ppm), (+)-limonene (13.26-24.47 ppm), 3-carene (13.83-19.19 ppm), and α-phellandrene (13.84-23.08 ppm), although the larvicidal activity of these compounds was less toxic than either fenthion (LC50, 0.023-0.029) or temephos (0.016-0.020). A. heterotropoides root steam distillate and its constituents described merit further study as potential mosquito larvicides for protection from humans and domestic animals from vector-borne diseases and nuisance caused by mosquitoes.
        91.
        2009.03 구독 인증기관 무료, 개인회원 유료
        Precast concrete produced in the industry is advantageous in a sense that it meets certain requiring standards and thus is easy to manage, and it saves construction period by shortening concrete curing time in the field. Nevertheless, studies on the strength evaluation of PC material by steam curing have rarely been done. In addition,as concrete becomes of high strength, it is speculated that relevant steam curing temperature history is also required. Therefore this study is on the steam curing method in manufacturing precast concrete products, and cement mortar has been used for experiments to exclude the possibility that concrete aggregate granularity and aggregate shape change may affect on strength development by cement hydration. In addition, this research is to provide the fundamental information of industrial manufacture of PC member by suggesting the optimal steam curing condition. The optimal steam curing condition has been investigated from the relations between temperature history condition and strength development, via modifying temperature patterns in various ways such as pre-tirne, curing maximaI temperature, maximaI temperature maintenance time which are factors that affect on high strength concrete product in steam curing.
        4,000원
        92.
        2009.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        수소에너지는 풍부한 자원으로부터 얻을 수 있는 2차 청정에너지로서 연소 및 반응 생성물이 환경을 오염시키지 않을 뿐만 아니라 에너지의 수송 및 저장이 용이한 화학적 매체이다. 물의 전기분해를 이용한 수소제조는 오염을 유발시기지 않으면서도 영구적인 재생에너지 시스템으로 이용할 수 있다. 고온 수증기전해의 핵심기술은 분해된 산소 또는 프로톤 이온이 전해질을 통해 신속하게 전달될 수 있는 전해질의 개발이 제1 핵심요건이며, 이어서 전류효율에 큰 영향을 미치는 전해질막과 전극재료의 접합기술의 확보가 중요한 핵심 요소기술이다.
        4,000원
        93.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The objective of this work is to study the feasibility of the preparation of the activated carbon (AC) from coconut tree flowers using high temperature fluidized bed reactor (HTFBR). The activating agent used in this work is steam. The reactor was operated at various activation temperature (650, 700, 750, 800 and 850℃) and activation time (30, 60, 120 and 240 min) for the production of AC from coconut tree flowers. Effect of activation time and activation temperature on the quality of the AC preparation was observed. Prepared AC was characterized in-terms of iodine number, methylene blue number, methyl violet number, ethylene glycol mono ethyl ether (EGME) surface area and SEM photographs. The best quality of AC from coconut tree flowers (CFC) was obtained at an activation temperature and time of 850℃ and 1 hr restectively. The effectiveness of carbon prepared from coconut tree flowers in adsorbing crystal violet from aqueous solution has been studied as a function of agitation time, carbon dosage, and pH. The adsorption of crystal violet onto AC followed second order kinetic model. Adsorption data were modeled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacity qm was 277.78 mg/g., equilibrium time was found to be 180 min. This adsorbent from coconut tree flowers was found to be effective for the removal of CV dye.
        4,000원
        94.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        에너지원으로서 수소를 생산하기 위하여 하니컴 구조를 갖는 모노리스에 10 wt% Ni/CeO2-ZrO2 촉매를 담지한 후 메탄의 수증기 개질 실험을 수행하였다. 다른 CeO2/ZrO2 몰비를 갖는 촉매들 중에서, Ni/CeO2-ZrO2(CeO2/ZrO2=4/1)촉매가 700-800℃에서 높은 메탄의 전환율을 보여 주었다. 10wt% Ni/CeO2-ZrO2 촉매가 담지된 금속 모노리스 촉매체는 높은 열전도도와 비표면적들로 인하여 좋은 촉매 특성을 보여줌을 확인할 수 있었다. 또한, 금속모노리스 촉매체는 반응물에서 과다의 수증기에 의한 수소 수율에서 크게 영향을 받지 않음을 알 수 있었다. GHSV=30,000h-1, 반응물 비(H2O/CH4=3.0) 반응온도 800℃에서 금속모노리스 촉매체는 98%이상의 메탄의 전환율을 보여주었다. 생성물 가스에서 CO2/CO의 비는 수증기/메탄의 반응물비가 증가할수록 수성가스화 반응에 의하여 증가됨을 알 수 있었다.
        4,000원
        95.
        2006.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        원자력 발전소의 증기발생기 슬러지 중에서는 이온교환수지가 발견되어서는 안 된다. 원자력 발전소의 증기발생기 슬러지 시료 중에서 발견되어 이온교환수지 입자로 의심되는 구형 입자들의 특성을 측정하였다. 미세조작기술을 이용하여 광학현미경으로 입자 크기 분포를, EPMA로 구형입자의 성분을, 그리고 IR 분광 스펙트럼 비교에 의하여 이온교환수지 여부를 조사하였다. 슬러지의 입자 크기는 1 내지 이었으나 구형 입자는 이었다. 슬러지의 주요 불순원소가 Si, Al, Mn, Cr, Ni, Zn, 그리고 Ti이었으나 구형 입자는 Si, Cu, Zn 이었다. 주성분은 두 경우 모두 철이었다. 구형 입자의 IR 분광스펙트럼은 증기발생기 취출수 정화계통에서 사용하는 이온교환수지의 스펙트럼과 비교했을 때 서로 일치하지 않음을 보여주었다. 이 결과들은 증기발생기 슬러지 시료 중에서 발견된 구형 입자가 이온교환수지는 아니며 일반적인 슬러지가 생성되는 과정에서 작은 슬러지 입자들이 크게 뭉쳐서 생성된 것임을 나타내고 있다.
        4,000원
        99.
        2002.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Short pitch fibers were prepared from petroleum based isotropic precursor pitch by melt-blown technology. The pitch fibers were stabilized in oxidizing condition, followed by steam activations at various conditions. The fiber surface and pore structures of the activated carbon fibers (ACFs) were respectively characterized by using SEM and applying BET theory from nitrogen adsorption at 77 K. The weight loss of the oxidized fiber was proportional to activation temperature and activation time, independently. The adsorption isotherms of the nitrogen on the ACFs were constructed and analyzed to be as Type I consisting of micropores mainly. The specific surface area of the ACFs proportionally increased with the weight loss at a given activation temperature. The specific surface area was ranged 850~1900 m2/g with pores of narrow distribution in sizes. The average pore size was ranged 5.8~14.1 a with the larger value from the more severe activation condition.
        4,000원
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