• Fisheries and Aquatic Sciences
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• 제7권2호
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• pp.76-83
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• 2004

To supply fresh and quality quarantined seafood in live seafood specialty restaurants, facilities for short-term culture or holding of live marine fish and shellfish are a necessity. In this study, the performance of a simple recirculating aquarium system for the culture and holding of marine fish was evaluated. The aquarium system consisted of a culture tank, a foam fractionator for solids removal, and a Styrofoam bead filter for nitrification and solids trapping. In the first trial, the aquarium was stocked with a total of 12 kg Korean rockfish, which were fed approximately $0.5\%$ of the total fish body weight daily. During the 2-month culture period, total ammonia nitrogen (TAN) and nitrite nitrogen $(NO_2-N)$ concentrations remained below 1mg/L and 2mg/L, respectively. The chemical oxygen demand (COD) fluctuated between 13.6 and 31.2 mg/L on selected sampling days. The total suspended solids (TSS) removed by the foam fractionator was between 2.7 and 4.6g daily. The Styrofoam bead filter not only reduced TAN and $NO_2-N$ in the culture tank water, but also trapped solids equivalent to 8.3-26.7\% of the weight of feed supplied. In Trial 2, 30kg of live fish were held in the aquarium without feeding for a 24-hour period and the water quality parameters were monitored. TAN and $NO_2-N$ concentrations first increased and then decreased to around 0.3mg/L. These results demonstrate that the recirculating aquarium system is a functional option for the short-term culture or holding of marine fish.

• 한국초등과학교육학회지:초등과학교육
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• 제26권2호
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• pp.149-160
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• 2007

This study was conducted to investigate the relationships between the patterns of elementary school teachers' explanations and the patterns of students' questions types on scientific phenomena. for the purposes of this study, we collected questions related to scientific phenomena from 255 $3rd{\sim}6th$ students in 2 elementary schools. Classifying the students' questions collected, 20 representative questions for each type were selected. Data regarding teachers' scientific explanation from 62 teachers of 3 elementary schools were also collected. The results of the analysis of the questions for each science field show that the students in the 3rd, 4th, and 5th grades have the most questions regarding biology, and those in the 6th grade have more questions regarding earth science. Regarding question types, object exploration questions and explican exploration questions formed the majority. Moreover, the higher the students' grades, a decrease in the number of conjectural questions and an increase in the number of causal questions were observed. As a result of the analysis of the teachers' explanation, the following explanation types could be discerned; conjecture, hypothesis, prediction, teleological explanation, information given to feed exploration questions, as well as verification and information supply fer verification purposes. There were 4 kinds of relationships between question types and explanation types. One was the explanation fitting to each question type, a second was the explanation with additional content than the question required, a third was where the explanation was inappropriate to the question, and a forth was where the teacher responded that they "don't know." This study, investigating the relationships between questioning as a scientific inquiry process and explanation, will help to promote discussion regarding science classes in elementary school.

• Ocean and Polar Research
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• 제35권4호
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• pp.323-349
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• 2013

The mud shrimp Upogebia major (Upogebiidae: Decapoda: Crustacea) is a common species on muddy and sandy mud tidal flats in the west coast of Korea. They reside in Y-shaped burrows that can extend up to more than 2 meters below the sediment surface. They feed on suspended detritus carried into their burrow by the beating of their pleopods and captured by their hairy first two pairs of thoracic legs. Mud shrimp burrows provide a habitat for a variety of small organisms such as crabs, shrimps, polychaetes, and mollusks. Ovigerous females are observed from December to May. Females deposit eggs only once per breeding season. They start hatching in March and the pelagic larvae of first zoea appear in March and April, followed by benthic settlement in May. Growth over the first year is rapid, and females deposit their first eggs in the third breeding season, 31 months after their settlement. Adult shrimps live for 4~5 years. Depth of the burrow increases with body length. The deep burrows provide refuge from predators and physical stress, allowing the shrimps to survive for a long time. The mud shrimps supply oxygen-rich water to their deep burrows, and exert a great influence on the structure and metabolism of the tidal flat benthic community. However, recently this type of mud shrimp has posed a serious threat to the Korean clam industry along the west coast of Korea. The extensive burrowing shrimp populations suddenly invaded the tidal flats from 2010 where the clams (Ruditapes philippinarum) are raised. As a consequence, clam production has decreased by about 10% over the past three years in some Korean clam beds. Therefore, the objective of this study is to review the biology of this mud shrimp in order to seek solutions to control the burrowing of these shrimps.

• 대한전자공학회논문지SD
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• 제46권3호
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• pp.51-59
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• 2009

본 논문에서는 어쿠스틱 센서 IC 용 연속 시간 시그마-델타 모듈레이터를 구현하였다. 모듈레이터의 전력 소모를 최소화하기 위해 summing 단의 필요성을 제거한 피드-포워드 (feed-forward) 구조로 설계 하였으며, 해상도를 높이기 위해 선형성이 우수한 active-RC 필터를 사용하여 설계 하였다. 또한 초과 루프 지연 시간 (excess loop delay)에 의한 성능 저하를 방지하기 위한 회로 기법을 제안 하였다. 저 전압, 고 해상도의 4차 단일 비트 연속 시간 시그마-델타 모듈레이터는 $0.13{\mu}m$ 1 poly 8 metal CMOS 표준 공정으로 제작하였으며 코어 크기는 $0.58\;mm^2$ 이다 시뮬레이션 결과 25 kHz 의 신호 대역 내에서 91.3 dB의 SNR(signal to noise ratio)을 얻었고 전체 전력 소모는 $290{\mu}W$ 임을 확인하였다.

• Journal of Plant Biotechnology
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• 제36권3호
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• pp.197-201
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• 2009

The food self-support rate on the basis of cereals in Korea is approximately 27%, which will threaten the national food security. The dramatic increase in population accompanied by rapid industrialization in developing countries has caused imbalances in the supply of food and energy. To cope with these global crises over food and energy supplies as well as environmental problems, it is urgently required to develop new environmentally friendly industrial crop varieties to be grown on marginal lands including desertification areas for sustainable development. Sweetpotato (Ipomoea batatas (L.) Lam.) ranks seventh in annual production among food crops in the world. Its wide adaptability on marginal lands and rich nutritional content provide a high potential for preventing malnutrition and enhancing food security in the developing countries. In addition, sweetpotato can be developed as a bioreactor to produce valuable industrial materials including bio-ethanol, functional feed and antioxidants by molecular breeding. In this respect, we focus on the molecular breeding of sweetpotato with multi-function on marginal lands. The strategies for development of environmentally friendly industrial sweetpotato will be introduced and discussed.

• 한국동물위생학회지
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• 제42권4호
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• pp.275-278
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• 2019

Blindness was observed in five calves born from cattle fed only a commercial feed of growing stage and dried rice straws for about two years in a farm in Gyeongsangbuk-do province. Three of them died within a month after birth, and a body and sera of his mother and other 19 cattle were submitted for diagnosis. At necropsy, the calf was very weak and filled with cerebrospinal fluid in the cerebrum. Any histopathological lesion including atrophy of death of optic nerve cells was not observed, but the irregular proliferation such as lace pattern of choroidal cells and lymphocytic infiltration just below choroid was observed. No pathogen was detected as a result of the etiological tests on the internal organs of calves and bloods. In addition, the levels of serum vitamin A in different affected and his mother cattle were all lower than normal. Finally, we determined this case as an encephalopathy caused by maternal vitamin A deficiency in a calf. This report is an extreme example of how important it is to supply adequate s diets and a good quality of hay for each stage of growth in cattle.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.79-79
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• 1999

The varous techniques for fabrication of si or metal tip as a field emission electron source have been reported due to great potential capabilities of flat panel display application. In this report, 240nm thermal oxide was initially grown at the p-type (100) (5-25 ohm-cm) 4 inch Si wafer and 310nm Si3N4 thin layer was deposited using low pressure chemical vapor deposition technique(LPCVD). The 2 micron size dot array was photolithographically patterned. The KOH anisotropic etching of the silicon substrate was utilized to provide V-groove formation. After formation of the V-groove shape, dry oxidation at 100$0^{\circ}C$ for 600 minutes was followed. In this procedure, the orientation dependent oxide growth was performed to have a etch-mask for dry etching. The thicknesses of the grown oxides on the (111) surface and on the (100) etch stop surface were found to be ~330nm and ~90nm, respectively. The reactive ion etching by 100 watt, 9 mtorr, 40 sccm Cl2 feed gas using inductively coupled plasma (ICP) system was performed in order to etch ~90nm SiO layer on the bottom of the etch stop and to etch the Si layer on the bottom. The 300 watt RF power was connected to the substrate in order to supply ~(-500)eV. The negative ion energy would enhance the directional anisotropic etching of the Cl2 RIE. After etching, remaining thickness of the oxide on the (111) was measured to be ~130nm by scanning electron microscopy.

• 전기전자학회논문지
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• 제19권1호
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• pp.87-93
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• 2015

본 논문에서는 디지털 패스가 없는 연산증폭기 공유 기법을 이용한 $145{\mu}W$, 87dB SNR을 갖는 저전력 3차 Sigma-Delta 변조기를 제안한다. 기존 구조는 아날로그와 디지털 패스를 사용한 구조로 첫 번째 적분기의 계수가 작다는 단점을 지연된 피드포워드 패스를 추가하여 개선하였다. 제안한 구조는 디지털 패스를 제거하여 첫 번째 적분기의 계수를 크게 하였고 연상증폭기 공유 기법을 이용하여 전력소모가 기준 구조보다 적다. 전원전압 1.8V, 신호대역폭 20KHz, 샘플링 주파수 2.8224MHz 조건에서 $0.18{\mu}m$ CMOS 공정을 이용하여 제안한 구조의 시뮬레이션한 결과, SNR(Signal to Noise Ratio)은 87dB, 전력소비는 $145{\mu}W$이다.

• Journal of Ecology and Environment
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• 제41권7호
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• pp.191-201
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• 2017

Background: Limited availability of corn stover due to the competing uses (organic manure, animal feed, bio-materials, and bioenergy) presents a major concern for its future in the bio-economy. Furthermore, biomass research has exhibited different results due to the differences in the supply of enzymes and dissimilar analytical methods. The effect of the two leading pretreatment techniques (dilute acid and alkaline) on glucose yield from three corn stover fractions (cob, stalk, and leaf) sourced from a single harvest in Uganda were studied at temperatures 100, 120, 140, and $160^{\circ}C$ over reaction times of 5, 10, 30, and 60 min. Results: From this study, the highest glucose concentrations obtained from the dilute acid (DA) pretreated cobs, stalks, and leaves were 18.4 g/L (66.8% glucose yield), 16.2 g/L (64.1% glucose yield), and 11.0 g/L (49.5% glucose yield), respectively. The optimal pretreatment settings needed to obtain these yields from the DA pretreated samples were at a temperature of $160^{\circ}C$ over an incubation time of 30 min. The highest glucose concentrations obtained from the alkaline (AL) pretreated cobs, stalks, and leaves were 24.7 g/L (81.73% glucose yield), 21.3 g/L (81.23% glucose yield), and 15.0 g/L (51.92% glucose yield), respectively. To be able to achieve these yields, the optimal pretreatment settings for the cobs and stalks were $140^{\circ}C$ and for a retention time of 30 min, while the leaves require optimal conditions of $140^{\circ}C$ and for a retention time of 60 min. Conclusions: The study recommends that the leaves could be left on the field during harvesting since the recovery of glucose from the pretreated cobs and stalks is higher.

• Asian-Australasian Journal of Animal Sciences
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• 제15권6호
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• pp.878-883
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• 2002

Due to rising trend of beef demand in Asia in the next two decades it is necessary to find additional sources of beef supply. In most Southeast Asian countries, male dairy and swamp buffalo have not yet been raised for a primary purpose of quality beef production. This study was aimed to compare growth and feeding performances as well as economic returns from feeding male dairy, beef cattle and swamp buffalo for quality beef. Thirty-six animals, 12 of each breed group, were used in feeding trial to compare the cost of beef production. Two levels of concentrate feeding, 1.75% of body weight (BW) and 1.00% of BW, were used for each breed group in order to compare feeding methods i.e. high and low levels. Within each breed group two animals of similar initial BW were randomly assigned to the two levels of feeding. The animals were fed from about 150 kg BW until reaching the final weight of about 400 kg. The results from this study showed that under the prevailing economic conditions in Thailand the cost of beef production from buffalo was lowest due to very low cost of feeder stocks, followed by dairy and beef. However, the cost of feeding per kg of BW gain was lowest in beef and highest in buffalo i.e. when disregarding the differences in cost of feeder stocks. Beef calves grew faster than dairy and buffalo, with better feed efficiencies. The results indicated that beef cattle could be more suitable for beef production for high-quality beef market, while buffalo could be more suitable for small farms where high roughage feeding is common. Male dairy calves appeared to require higher level of concentrate feeding than 1% BW in order to maintain good body conditions.