• 한국기계가공학회지
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• 제11권3호
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• pp.80-85
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• 2012

The ultrasonic cutting method is which cutting by applying high frequency vibrational energy into specific area at constant pressure. Ultrasonic cutting is consisted of power supply, transducer, booster and cutting tool. Precise designing is required since each part's shape, length and mass can affect driving frequency and vibration mode. This paper focused to cutting tool design, its length L was set by calculating vibration equation. And the value of the shape parameter a was diversified as the integral multiple and the result of 40,189Hz the analysis of Modal was shown in the length 30mm of the result of performance b in the 11th mode Also by performing harmonic response analysis, the frequency response result was 40,189Hz, which was similar to modal analysis result.

• 한국기계가공학회지
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• 제9권4호
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• pp.1-7
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• 2010

Recently optical and electric and electronic forms in the field of ultra fine patterns has been used extensively, and techniques of the optical parts are required that can precision-machine this micro-patterns such as V or R-shaped micro-groove patterns. In this study, V and R type, shaping the way micro groove brass machining process to characterize the material feed rate and cutting depth and the V and R as a variable brother, using two kinds of diamond tools for each picture shape and surface roughness caused by conditions such as chips, processed through the analysis of effects of geometry and analysis such as precision machining.

• 한국생산제조학회지
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• 제20권5호
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• pp.570-575
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• 2011

Ultrasonic metal welder is consisted of power supply, transducer, booster, and horn. Precise designing is required since each parts' shape, length and mass can affect driving frequency and vibration mode. This paper analyzed Cu sheet deposition characteristics using ultrasonic metal welder and tension tester. A horn suitable for 40,000Hz was attached to the ultrasonic metal welder in order to weld Cu plates. The Cu sheet welding was done with different amplitude, pressure, and welding time, and its maximum tension was measured with tension tester. Maximum tension of 153.87N was obtained when the pressure was 2.0bar, amplitude was 80%, and welding time was 0.30s. Therefore, excessive welding condition negatively influences maximum tension measurement result.

• 한국생산제조학회지
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• 제23권2호
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• pp.173-177
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• 2014

In this study, a 20,000Hz ultrasonic horn was designed and fabricated using a finite element analysis. The horn's resonate frequency was 19,991Hz, and the harmonic response frequency was 20,000Hz. In order to observe the developed horn's performance, 4,000 pieces of displacement data were obtained using an optical sensor and were analyzed using a fast Fourier transform. Finally, the developed horn's resonate frequency was found to be 19,992Hz. The effect of the tip area of the developed horn on the weldability of a Cu sheet was experimentally investigated. It was found that the welding strengths of specimens welded using a small tip area were generally higherthan those of specimens welded using a large tip area.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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• pp.96-102
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• 2004

This study presents an effective stiffness-based optimal technique to control quantitatively lateral drift for 3-D steel frameworks subject to lateral loads. To this end, the displacement sensitivity depending on behavior characteristics of 3-D steel frameworks is established. Also, approximation concept that can preserve the generality of the mathematical programming and can efficiently solve large scale problems is introduced. Resizing sections in the stiffness-based optimal design are assumed to be uniformly varying in size. Two types of 30-story frames are presented to illustrate the features of the Quantitative lateral drift control technique proposed in this study.

• 생태와환경
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• 제47권4호
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• pp.302-311
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• 2014

Global climate change is significant issue in marine ecosystem and fishery market. According to rising of both seawater temperature and sea-level, global fishery environment and marine ecosystem are changing drastically. Moreover, over-exploitation in fishery areas is the most important issue in the marine ecosystem conservation. In analysis and statistics of global network, major fish populations are decreasing very fastly, but fish catch are increasing annually. It means balance between product and consume is not appropriate in the global market. China as emerging new fish consumer in the world is strongly developing fishery industry and technology. In this paper, I try to review a relationship between marine ecosystem and climate change in global scale according to references. I also suggested possibility of sustainable global fishery in changing marine ecosystem by analysis of some related reports of international global fishery.

• 생태와환경
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• 제40권4호
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• pp.581-585
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• 2007

Swarm formation of Scapholeberis kingi Sars 1903 was observed in a shallow reservoir on 27 May 2007 (Dongpan Reservoir) for the first time. Dense swarms composed of asexual females, only occurred during daytime (13:00-17:00, local time) at the littoral zone. Correlation between density of S. kingi and environmental factors such as water temperature and density of juvenile fish were positively significant. Therefore, it is suggested that the swarming of S. kingi seems to be induced for predator avoidance than increase of mating chance, and water temperature may affect their swarming behavior.

• 생태와환경
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• 제40권4호
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• pp.511-519
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• 2007

It is known that phytoplankton biomass or turbidity are lower in waters with submerged macrophytes than those without submerged plants at a given nutrient level. We hypothesize that presence of submerged macrophytes would lower phytoplankton biomass below levels expected by total phosphorus levels through various mechanisms and that phytoplankton biomass would decrease more as the biomass increase of the submerged macrophytes. To find submerged macrophytes effectively lowering phytoplankton growth, we conducted spatial field surveys at 21 water bodies and a temporal monitoring at Seung-un 1 Reservoir, Anmyyeondo Island. We measured chlorophyll ${\alpha}$ concentrations and total phosphorus (TP) concentrations from waters in patches of submerged macrophytes with measurements of submerged plant biomass. Majority of our sites with submerged macrophytes showed much less chlorophyll a concentrations than the predicted ones from literature. Among submerged macrophytes studied, Myriophyllum spicatum and Hydrilla verticillata showed patterns of lowering chlorophyll ${\alpha}/TP$ ratios with increase of their biomass in both spatial and temporal surveys.

• 생태와환경
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• 제40권4호
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• pp.520-526
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• 2007

To select submerged macrophytes to suppress growth of Microcystis aeruginosa through releasing allelochemicals, we conducted growth experiments with water from patches of submerged macrophytes and with aqueous extracts of those submerged macrophytes. In the first experiment, growth rates of M. aeruginosa decreased as biomass of Myriophyllum spicatum and Hydrilla verticillata increased. In the second experiment, M. aeruginosa showed approximately 50% growth reduction with extracts from M. spicatum and 24% reduction with extracts from Ottelia alismoides. Both M. aeruginosa growth experiments with water and plant extracts suggest that M. spicatum would be the best candidate to reduce M. aeruginosa growth.

• 생태와환경
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• 제46권4호
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• pp.507-512
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• 2013

Aquatic oligochaetes were investigated from a small amount of sediment sampled from the Jungnang Stream, an urban stream in Seoul, Korea, in November 2012. Sorted oligochaetes were observed under a light microscope in a drop of carbonated water, and then preserved in 70% ethanol. Some specimens were slide mounted using glycerin and Eupharal. As a result, the following 12 species were identified including 8 new Korean records, Bothrioneurum vejdoskyanum Stolc, Branchiodrilus hortensis (Stephenson), Chaetogaster cristalinus Vejdosky, Nais communis Piguet, Nais pardalis Piguet, Dero obtusa d'Udekem, Piguetiella denticulata Liang, and Haemonais waldvogeli Brescher and 4 additional known species, Limnodrilus hoffmeisteri Cleparede, Branchiura sowerbyi Beddard, Chaetogaster diastrophus (Gruithuisen), and Stylaria fossularis Leidy. This study shows how freshwater oligochaetes are diverse even in urban streams in Korea, if a proper sampling and examining method is employed.