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Increased Sensitivity of Carbon Nanotube Sensors by Forming Rigid CNT/metal Electrode

  • Park, Dae-Hyeon;Jeon, Dong-Ryeol
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.348-348
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    • 2011
  • Carbon nanotube (CNT) field effect transistors and sensors use CNT as a current channel, of which the resistance varies with the gate voltage or upon molecule adsorption. Since the performance of CNT devices depends very much on the CNT/metal contact resistance, the CNT/electrode contact must be stable and the contact resistance must be small. Depending on the geometry of CNT/electrode contact, it can be categorized into the end-contact, embedded-contact (top-contact), and side-contact (bottom-contact). Because of difficulties in the sample preparation, the end-contact CNT device is seldom practiced. The embedded-contact in which CNT is embedded inside the electrode is desirable due to its rigidness and the low contact resistance. Fabrication of this structure is complicated, however, because each CNT has to be located under a high-resolution microscope and then the electrode is patterned by electron beam lithography. The side-contact is done by depositing CNT electrophoretically or by precipitating on the patterned electrode. Although this contact is fragile and the contact resistance is relatively high, the side-contact by far has been widely practiced because of its simple fabrication process. Here we introduce a simple method to embed CNT inside the electrode while taking advantage of the bottom-contact process. The idea is to utilize a eutectic material as an electrode, which melts at low temperature so that CNT is not damaged while annealing to melt the electrode to embed CNT. The lowering of CNT/Au contact resistance upon annealing at mild temperature has been reported, but the electrode in these studies did not melt and CNT laid on the surface of electrode even after annealing. In our experiment, we used a eutectic Au/Al film that melts at 250$^{\circ}C$. After depositing CNT on the electrode made of an Au/Al thin film, we annealed the sample at 250$^{\circ}C$ in air to induce eutectic melting. As a result, Au-Al alloy grains formed, under which the CNT was embedded to produce a rigid and low resistance contact. The embedded CNT contact was as strong as to tolerate the ultrasonic agitation for 90 s and the current-voltage measurement indicated that the contact resistance was lowered by a factor of 4. By performing standard fabrication process on this CNT-deposited substrate to add another pair of electrodes bridged by CNT in perpendicular direction, we could fabricate a CNT cross junction. Finally, we could conclude that the eutectic alloy electrode is valid for CNT sensors by examine the detection of Au ion which is spontaneously reduced to CNT surface. The device sustatined strong washing process and maintained its detection ability.

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Bacterial Diseases in Flounder Farms of Cheju Island (제주도 양식넙치의 세균성질병 발생상황(1991년-1997년))

  • Oh, Sang-Pil;Kim, Dae-Hwan;Lee, Jung-Jae;Lee, Chang-Hoon
    • Journal of fish pathology
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    • v.11 no.1
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    • pp.23-27
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    • 1998
  • This research was carried out to know the trend in annual occurrence of bacterial disease. The diseased fish were collected from 147 flounder farms of Cheju Island from January, 1991 to December, 1997. Two types of diseases, that is "simple infection" and "mixed infection", were recognized. The simple infections were Vibriosis, Edwardsiellosis Streptococcal infection and Columnaris disease. The mixed infections were caused by a pair of pathogens mentioned above. During the whole period of this study, the highest number of annual occurrence of simple infection was 243 (26.8% of the total) in 1997 and the lowest one was 82 (9.1 %) in 1991. Monthly occurrence of simple infection was the highest number at 132 (14.6% of the total) in August and the lowest one was at 38 (4.2%) in January. Monthly occurrence of the mixed infected disease showed common pattern except November and December. The highest number of annual occurrence of the simple infected disease was 437 (48.2% of the total) in Vibriosis and the lowest one was 22 (2.4%) in Columnaris disease. The highest number of annual occurrence of the simple infected disease was 178 (53.1% of the total) in Vibriosis+Columnaris disease and the lowest one was 28 (8.4%) in Edwardsiellosis+Streptococcal infection.

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Construction of a Microsatellite DNA Profile Database for Pear Cultivars and Germplasm (배 품종 및 유전자원에 대한 Microsatellite DNA 프로파일 데이터베이스 구축)

  • Hong, Jee-Hwa;Shim, Eun-Jo;Kwon, Yong-Sham
    • Horticultural Science & Technology
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    • v.35 no.1
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    • pp.98-107
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    • 2017
  • A DNA profile database was constructed to investigate the genetic relatedness of 72 germplasm samples of Pyrus and related cultivars using microsatellite markers. Three P. pyrifolia, four P. commus, and one P. betulifolia cultivars with different morphological traits were screened using 387 pairs of microsatellite primers. A core set of 11 primer pairs was selected to obtain 133 polymorphic amplified fragments meeting three criteria: high polymorphism information contents (PIC), high repeatability, and distinct allele patterns. The number of alleles per locus ranged between 4 and 22. Average PIC was 0.743 (range: 0.557 - 0.879). Cluster analysis using the unweighted pair - group method with arithmetical average (UPGMA) separated the 72 pear cultivars and germplasm samples into four major groups: Chinese, European pears, and a cluster of 55 Asian pears that could be reclassify into two subcluster, I - $1^{st}$ and II - $2^{nd}$, according to pedigree information. Almost all of the cultivars were discriminated by 11 microsatellite marker genotypes. The microsatellite DNA profile database may be utilized as tool to verify distinctness, uniformity, and stability between candidate cultivar, and to verify in the distinctness of existing cultivars.

Detection of M:N corresponding class group pairs between two spatial datasets with agglomerative hierarchical clustering (응집 계층 군집화 기법을 이용한 이종 공간정보의 M:N 대응 클래스 군집 쌍 탐색)

  • Huh, Yong;Kim, Jung-Ok;Yu, Ki-Yun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.30 no.2
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    • pp.125-134
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    • 2012
  • In this paper, we propose a method to analyze M:N corresponding relations in semantic matching, especially focusing on feature class matching. Similarities between any class pairs are measured by spatial objects which coexist in the class pairs, and corresponding classes are obtained by clustering with these pairwise similarities. We applied a graph embedding method, which constructs a global configuration of each class in a low-dimensional Euclidean space while preserving the above pairwise similarities, so that the distances between the embedded classes are proportional to the overall degree of similarity on the edge paths in the graph. Thus, the clustering problem could be solved by employing a general clustering algorithm with the embedded coordinates. We applied the proposed method to polygon object layers in a topographic map and land parcel categories in a cadastral map of Suwon area and evaluated the results. F-measures of the detected class pairs were analyzed to validate the results. And some class pairs which would not detected by analysis on nominal class names were detected by the proposed method.

Distinguishing the Korean Silage Corn Varieties through Development of PCR-Based SNP Marker (SNP마커 개발을 통한 사료용 옥수수 품종판별)

  • Kim, Sang Gon;Lee, Jin-Seok;Bae, Hwan Hee;Kim, Jung-Tae;Son, Beom-Young;Baek, Seong-Bum
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.37 no.2
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    • pp.168-175
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    • 2017
  • Single nucleotide polymorphisms (SNP) markers allow rapid screening of crop varieties in early growth stages. We developed a modified SNP PCR procedure for assaying SNPs in maize. For SNP marker development, we chosen 200 SNP sites from MaizeGDB database, and designed two base pair mismatch primers based on putative SNP site of B73 genome sequence. PCR products size was from 200 to 500 bp or was not shown in the case of SNP site existing in Korean silage corns. Using previously discovered 16 primer sets, we investigated distinctness of 50 silage F1 hybrid corns including 10 Korean silage corns developed by RDA such as Gangdaok, Kwangpyeongok, Dapyeongok, Andaok, Yanganok, Singwangok, Jangdaok, Cheongdaok, Pyeonggangok, and Pyeonganok as well as 40 foreign commercial silage corns. From cluster analysis, we confirmed that 10 Korean silage F1 hybrid corns were clearly distinguished except for Singwangok, P1395, and several foreign commercial corns, and selected minimum SNP primer combination for Gangdaok, Jangdaok, Pyeonggangok, and Pyeonganok. Therefore, development of SNP marker sets might be faster, cheaper, and feasible breed discrimination method through simple PCR and agarose gel electrophoresis.

Silver nanowires and nanodendrites synthesized by plasma discharge in solution for the catalytic oxygen reduction in alkaline media

  • Kim, Hoe-Geun;Song, Myeon-Gyu;Kim, Dong-U;Lee, Sang-Yul
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.62-62
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    • 2018
  • Pt is still considered as one of the most active electrocatalysts for ORR in alkaline fuel cells. However, the high cost and scarcity of Pt hamper the widespread commercialization of fuel cells. As a strong candidate for the replacement of Pt catalyst, silver (Ag) has been extensively studied due to its high activity, abundance, and low cost. Ag is more stable than Pt in the pH range of 8~14 as the equilibrium potential of Ag/Ag+ being ${\approx}200mV$ higher than that of Pt/PtO. However, Ag is the overall catalytic activity of Ag for oxygen reduction reaction(ORR) is still not comparable to Pt catalyst since the surface Ag atoms are approximately 10 times less active than Pt atoms. Therefore, further enhancement in the ORR activity of Ag catalysts is necessary to be competitive with current cutting-edge Pt-based catalysts. We demonstrate the architectural design of Ag catalysts, synthesized using plasma discharge in liquid phase, for enhanced ORR kinetics in alkaline media. An attractive feature of this work is that the plasma status controlled via electric-field could form the Ag nanowires or dendrites without any chemical agents. The plasma reactor was made of a Teflon vessel with an inner diameter of 80 mm and a height of 80 mm, where a pair of tungsten(W) electrodes with a diameter of 2 mm was placed horizontally. The stock solutions were made by dissolving the 5-mM AgNO3 in DI water. For the synthesis of Agnanowires, the electricfield of 3.6kVcm-1 in a 200-ml AgNO3 aqueous solution was applied across the electrodes using a bipolar pulsed power supply(Kurita, Seisakusyo Co. Ltd). The repetition rate and pulse width were fixed at 30kHz and 2.0 us, respectively. The plasma discharge was carried out for a fixed reaction time of 60 min. In case of Ag nanodendrites, the electric field of 32kVcm-1 in a 200-ml AgNO3 aqueous solution was applied and other conditions were identical to the plasma discharge in water in terms of electrode configuration, repetition rate and discharge time. Using SEM and STEM, morphology of Ag nanowires and dendrites were investigated. With 3.6 kV/cm, Ag nanowire was obtained, while Ag dendrite was constructed with 32 kV/cm. The average diameter and legth of Ag nanowireses were 50 nm and 3.5 um, and thoes values of Ag dendrites were 40 nm and 3.0 um. As a results of XPS analysis, the surface defects in the Ag nanowires facilitated O2 incorporation into the surface region via the interaction between the oxygen and the electron cloud of the adjacent Ag atoms. The catalytic activity of Ag for oxygen reduction reaction(ORR) showed that the catalytic ORR activity of Ag nanowires are much better than Ag nanodendrites, and electron transfer number of Ag nanowires is similar to that of Pt (${\approx}4$).

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A Study on Driver's Perception over the Change of the Headlamp's Illuminance : 3. Driver's psychological property (전조등 조도변동에 대한 운전자의 인식연구 : 3. 운전자의 심리적 특성)

  • Kim, Huyn-Ji;Kim, Hyun-Jin;Kim, Gi-Hoon;Kim, Hoon;An, Ok-Hee
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.10
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    • pp.19-26
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    • 2006
  • In this study, psychological assessment was carried out to investigate the driver's psychological characteristics by the change of the headlight. The participants were 20 men and 20 women in their 20s and thirty-two different conditions in combinations of waveform of light, voltage, and alteration time were used. The questionnaire for the assessment was evaluated by 8 subjective item and 5-point SD criteria of 19 pair's adjective. The results were as follows : 1. The assessment results from SD method indicated 4 factors by factor analysis, and it was shown that A waveform had significances in a sense of security and impetus and B waveform had a significance in a sense of security. The levels of the limitations for the voltage change were 12[V] in the factor of a sense of security and 11[V] in the factor of a sense of impetus for A waveform, 12.6[V] in the factor of a sense of security for B waveform. 2. The results of the subjective assessment showed that the limitation of A waveform's brightness change was 12[V]. Moreover, the limitations of voltage changes were 12.67[V] for B waveform brightness change, 12.12[V] for discomfort, 12.71[V] for darkness. And the limitation of C waveform's brightness change was 12[V].

Ultrastructure of the Androgenic Gland of the Freshwater Prawn, Macrobrachium nipponense (징거미새우, Macrobrachium nipponense의 Androgenic Gland 미세구조)

  • 김대현;강정하;김대중;한창희
    • Development and Reproduction
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    • v.3 no.1
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    • pp.53-58
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    • 1999
  • The androgenic gland secretes a hormone, androgenic gland hormone, which is believed to act on the differentiation of the primary, secondary, and behavioral sex characteristics in most malacostracan crustaceans. This report presents the ultrastructural morphology of the androgenic gland in the freshwater prawn Macrobrachium nipponense. This gland, located in the coxopodite of the last pair of walking legs, was attached to the subterminal region of the sperm duct. The gland was composed of simple cellular strands, encased by a fibrous sheath. Microvilli were situated in the fibrous sheath, especially at the edge of each cellular strand. The androgenic gland cells had the large and round nucleus and rough endoplasmic reticulum arranged either in spirals or in concentric circles throughout the cytoplasm of the cell. They also had the well-developed Golgi complex and long mitochondria with flat and transverse cristae. The Golgi complex was similar to microvesicular cluster, but usually in the shape of typical dictyosomes, These features of androgenic gland cells coincides well with the protein/peptide secretion in their function. However, despite the apparent ultastructual equipment for protein/peptide secretion, no accumulation of materials secreted were noticed in the cytoplasm. Therefore it is strongly suggested that the transient transportation of the materials into the hemocoel has occurred just after synthesis.

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Histologic and Microstructural Analyses on Postembryonic Development in the Wolf Spider Arctosa kwangreungensis (Araneae: Lycosidae) (광릉늑대거미 (Arctosa kwangreungensis) 배후발생과정의 조직 미세구조 분석)

  • Yang, Sung-Chan;Moon, Myung-Jin
    • Applied Microscopy
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    • v.42 no.1
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    • pp.17-26
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    • 2012
  • Histologic and microstructural changes during the postembryonic development of the wolf spider Arctosa kwangreungensis were studied using light and scanning electron microscopy to examine the relationship between a morphological differentiation and behavioral properties. The postembryo with abdominal yolk sac was stayed inactive in the egg case because its muscular and visual systems were not fully developed to a functional level. The first instar spiderlings, developed from the postembryo by a first molting process, started to exhibit its pigmentation on their body cuticles. In particular, undifferentiated cell clusters of central nervous system (CNS) were densely distributed within the cephalothorax, and highly differentiated abdominal ganglion was observed. They had a characteristic visual system looks more like its adult counterpart, and had segmented appendages looks more like the tiny spiders containing well oriented muscular system. After 3rd instar, spiderlings grew more rapidly with accordance to their consistent growth and periodical molting processes. Thus, the relative area of CNS with respect to cephalothorax was gradually decreased, instead a pair of venom glands, musculature, and connectives occupied the residual area. It has been revealed that the early development of spider can be controled by the feeding condition of larval period, since histologic and microstructural differentiations in both appendages and optic system were completed at the second instar. In particular, behavioral properties of the wandering spiders that depend on vision and their running ability were deeply related to physiological differentiation of the microstructural development.

Morphological Study of the Suction Trap in Aquatic Utricularia japonica (수생형 통발(Utricularia japonica)의 흡입식 포충낭 형태 연구)

  • Kim, In-Sun
    • Applied Microscopy
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    • v.40 no.2
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    • pp.109-116
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    • 2010
  • Morphology and microstructure of the suction trap in aquatic Utricularia japonica were examined using scanning electron microscopy. Branched stems bear numerous suction traps without root formation. The traps are derived axillary from the node, and their antennae and appendages extend in a peculiar fashion. The trap walls are thin, two-celled, parenchyma tissue and simple, small glands are scattered in both internal and external surface of the trap. The entrance of the trap is surrounded by one pair of dorsal antennae and ventral appendages, where the former guides the prey to the entrance. Trap door is situated below the entrance and numerous sessile and stalked capitate trichomes cover the entrance and even on the door surface. The capitate trichomes are secretory, but four trigger hairs formed on the central areas of the door are not. They are believed to function in activating and tripping the trap door. A specialized region of the threshold come in contact with the lower portion of the door upon closing. The secretory capitate trichomes near this region are responsible for producing and secreting a mucilage-like substance which composes the velum. Two-armed bifid glands are located in the interior side of the threshold, while four-armed quadrifid glands are considerably numerous occurring over the entire inner trap wall. Bifid and quadrifid glands develop semi-spherical basal cells that connect them to the inner wall surface. Antennae, trigger hairs, capitate trichomes, bifid and quadrifid glands are more important structures in the carnivory of U. japonica.