• 대한전자공학회논문지SD
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• 제38권8호
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• pp.34-42
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• 2001

본 논문에서는 다중모드 간섭이론(MMI : multimode interference)을 $Ag^+-Na^+$ 이온교환 방식에 적용하여 BK7 유리에 1${\times}$2, 1${\times}$4, 1${\times}$8 MMI 광파워 분리기를 설계 제작하였다. 소자를 제작하기 전에 채널형 도파로의 굴절률 분포와 MMI 광파워 분리기의 다중모드 영역의 폭과 다중모드 영역의 길이를 결정하였다. 다중모드 영역의 길이는 1${\times}$2 MMI : 887${\mu}m$, 1${\times}$4 MMI: 1666${\times}$, 1${\times}$8 MMI : 1834${\mu}m$이고, 다중모드 영역의 폭은 1${\times}$2 MMI : 40${\mu}m$, 1${\times}$4 MMI : 80${\mu}m$, 1${\times}$8 MMI : 120${\mu}m$였다. 제작된 소자들은 1.50~1.58${\mu}m$파장 범위 내에서 1${\times}$2 MMI의 경우 1.4dB, 1${\times}$4 MMI의 경우 1.7dB, 1${\times}$8 MMI의 경우 약 2dB의 광파워 불균형비를, 그리고 손실은 1${\times}$2 MMI의 경우 0.96[dB}, 1${\times}$4 MMI의 경우 2.29[dB], 1${\times}$8 MMI의 경우 1.67[dB]였다.

• Journal of Biosystems Engineering
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• 제26권4호
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• pp.323-330
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• 2001

The regular maintenance and repair status of major farm machinery such as power tiller, farm tractor, rice transplanter and combine harvester etc., were surveyed and analyzed for the full-time farmers in order to get basic information for promoting farm machinery productivity. The survey was carried out through 209 farmers from 9 provinces. The results of this study can be summarized as follows; 1. The regular maintenance of farm machinery was conducted at repair shop(49.5%) or dealer agency(12.0%), and also conducted by farmers at their house(34.9%). 2. For the status on the cleanness or exchange times of engine oil, fuel filter and air cleaner, most farmers conducted fewer times than the necessary times. And, 5.3%, 7.7%, and 2.9% of surveyed farmers experienced breakdowns due to the insufficient cleanness or exchange oil, fuel filer, and air cleaner, respectively. 3. Most farmers(76.1%) recognized the necessity of farm machinery training or education, and they preferred one week for the training period, simple or easy maintenance for the training level, agricultural technical center or farm machinery manufacturer for the training agency. 4. Complete recognition of operation manual and sufficient maintenance before-, during-, and after-operation for the farm machinery can minimize the breakdowns, enlarge the endurance prevent the safety accidents, and promote productivity of farm machinery. And, these can be accomplished by the thorough training or education for agricultural machinery.

• 한국자기학회지
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• 제12권1호
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• pp.24-29
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• 2002

반강자성 FeMn과 강자성 Co를 이용한 기판/Co/Cu/Co/FeMn 구조의 스핀밸브를 제조하여 자기저항 특성을 조사하였다. Cu를 하지층으로 하여 FeMn 반강자성층을 형성시킨 결과 ${\gamma}$y-FeMn과 고착층 Co와의 교환이방성 결합이 향상되었다. FeMn증착시 Ar 압력과 power를 달리해가며 최적의 FeMn 증착조건을 고찰하였다. 이로부터 FeMn과 Co간의 계면이 평탄해질수록 교환결합의 세기가 증가함을 알 수 있었다. AES 분석으로부터 열처리에 의해 Co와 Cu간 계면고용층이 소멸됨을 확인하였다. 기판/Co/Cu/Co/FeMn 스핀밸브를 열처리함으로써 교환이방성 결합과 자기저항비를 각각 3배와 1.4배 이상 향상시켰다.

• 대한가정학회지
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• 제17권1호
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• pp.22-28
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• 1979

The phyio-chemical properties of Ion exchange salt, crude salt, particaly refined salt, and Isoized salt were determined. The basic amount of salt used in cooking were standardized . Acceptabilities as to the taste and saltiness of food prepared with the standard amounts of various kinds of salt were compared. Whereupon, the following conclusion was obtained. 1) Crude salt showed 12.23 per cent water content, the highest among the kinds of salt examined, while particaly refined salt had 2.53% water content. Refined salt, Ion exchange salt, and Iodized salt showed 0.36%, and 0.28%, respectively. 2) Where the same amount of salt was dissolved in the same amount of water, crude salt and partialy refined salt were dissolved twice as Ion exchange salt of fine-grain form, refined salt, and Iodized salt. In actual cooking, Ion exchanges salt and refined salt are used only half as much as raw salt, and it can be said that the time required for dissolving salt is the same. 3) The comparison between content and weight of various kinds of salt showed that the weights of Ion exchange salt, Iodized salt, and refined salt were two times as heavy as crude salt and partialy refined condition of same content. 40 The threshold concentration of salt is the sensed degree of saltiness. Different concentrations were recorded for various for various kinds of salt, the threshold concentration of Ion exchanges salt showed the lowest degree of 0.05, while that of partialy refined salt was 0.09 equivalent to 1.8 times that of the former. 5) Experimental cooking involving various kinds of salt indicated that where salt was used accurately, soup, vegetables, kimchi, and soybean sauce which were prepared with Ion exchanges salt showed the best acceptability , but no statistical differences could be noted among sarious kinds of salt used in preparing those foods.

• 멤브레인
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• 제20권3호
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• pp.217-221
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• 2010

기존 고분자전해질연료전지(PEMFC)의 단점을 극복하기 위해 고체전해질 알카라인연료전지(SAMFC)가 근래에 많이 연구되고 있다. 본 논문에서는 술폰화 폴리벤지이미다졸(PBI) 유도체를 이용하여 SAMFC용 막을 제조하였다. 술폰화 폴리벤지이미다졸 유도체는 KOH에 의해 쉽게 도핑되고 도핑된 막은 높은 $OH^-$의 전도도와 기계적 강도를 보였다. 특히 sPBI-co-PBI (술폰화 PBI : 비술폰화 PBI = 75 : 25)의 경우, $90^{\circ}C$ 100% 상대습도 하에서 $2.98{\times}10^{-2}\;S/cm$의 높은 $OH^-$의 전도도를 보였다.

• 멤브레인
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• 제20권4호
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• pp.335-341
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• 2010

본 연구에서는 음이온교환막 개발에 관한 것으로 poly(ethylenimine) (PEI) / poly(vinyl alcohol) (PVA)의 혼합비율에 따라 막을 제조하였다. 제조된 막의 특성화를 평가하기 위하여 함수율, 접촉각, FT-IR, 이온교환용량, 이온전도도, 열 중량분석, 탄성계수 측정을 실시하였다. 이온전도도 측정 결과 PVA/PEI의 함량이 90 : 10으로 제조된 막의 경우 $5.16{\times}10^{-2}S/cm$의 값을 나타내어 우수한 음이온전도도를 나타내었으며 접촉각 측정 결과 PEI의 함량이 증가함에 따라 막표면의 소수성이 $78.3^{\circ}$까지 함께 증가하는 결과를 나타내었다. 또한 열에 대한 안정성은 PVA의 우수한 성질을 변화시키지 않았으며 탄성계수 측정을 통해 고강도 기계적 물성을 확인할 수 있었다.

• 천문학회지
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• 제10권1호
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• pp.23-30
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• 1977

식변광성 WZ And에 대한 지금까지 관측 발표된 극심시각을 수집하여 이 별의 수기 변화를 분석하였다. 0-C도에 의한 이 별의 주변화는 JD2418000과 JD243500근처에서 각각 dp/p=$+4.24{\times}10^{-6}$과 dp/p=$-2.46{\times}10^{-6}$의 돌발적인 주기 변화를 보였다. WZ And의 주기변화의 모습을 분석하기 위하여 Biermann and Hall(1973)이 제시한 접촉 연섬계로부터 $7.42{\times}10^6M_0$가 온도가 높은 별(hotter component)로 교환됨을 산출하였다. 이러한 량의 질량교환으로 인한 주기감소를 계산하였다. 질량교환 모델에 의한 JD243500이후의 이론적인 주기로 $0^d.69565848$를 얻었으며, 관측에 의한 0-C도로부터 얻은 주기 $0^d.69566034$과 매우 잘 일치하고 있다. 한편, WZ And의 질량비에 의하면 이 별은 온도가 더 높은 별이 Roche lobe를 채우고 있음을 보여주며 이러한 WZ And는 Paczynski(1970)의 접촉연성계의 접화단계에서 Stage II에 있는 별이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.21-24
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• 2008

Proton Exchange Membrane Fuel Cell (PEMFC) is an attractive candidate for residential power generator due to fast start-up and stop, high efficiency, low emission, and high power density. In this study, we employ short module stack to understand the performance of the unit cell of the stack in terms of operating temperatures. To simulate the practical fuel cell stack of residential power generator, the structure and active area of the short module stack is kept the same as that of the practical fuel cell. The results shows that the electric potential of short module stack is different from the number of cells times the potential of unit cell because of cell-to-cell variation.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1993년도 춘계공동학술대회 발표논문 및 초록집; 계명대학교, 대구; 30 Apr.-1 May 1993
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• pp.343-352
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• 1993

In this study, a modified algorithm for the exchange heuristic is developed and applied to a resource-constrained scheduling problem. The problem involves multiple projects and multiple resource categories and allows flexible resource allocation to each activity. The objective is to minimize the maximum completion time. The exchange heuristkc is a multiple pass algorithm which makes improvements upon a given initial feasible schedule. Four different modified algorithms are proposed. The original algorithm and the new algorithms were compared through an experimental investigation. All the proposed algorithms reduce the maximum completion time much more effectively than the original algorithm. Especially, one of four proposed algorithms obviously outperforms the other three algorithms. The algorithm of the best performance produces significantly shorter schedules than the original algorithm, though it requires up to three times more computation time. However, in most situations, a reduction in schedule length means a significant reduction in the total cost.

• Macromolecular Research
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• 제15권4호
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• pp.379-384
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• 2007

Sulfonation of polyetheretherketones (PEEK) was carried out in order to fabricate commercial perfluorosulfonic acid membrane alternatives, which were characterized in terms of their ion exchange capacity, ionic conductivity, water swelling, methanol crossover and electrochemical performance in their direct application as a methanol fuel cell. A high ion exchange capacity, 1.88, was achieved with a sulfonation reaction time of 8 h, with a significantly low methanol crossover low compared to that of Nafion. However, the morphological stability was found to deteriorate for membranes with sulfonation reaction times exceeding 8 h. Electrochemical cell tests suggested that the fabrication parameters of the membrane electrode assembly based on the sulfonated PEEK membranes should be optimized with respect to the physicochemical properties of the newly prepared membranes.