• Title/Summary/Keyword: Former channel

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Fish Community Structure of the Former Channel Isolated by Channelization in the Mangyeong River, Korea: Implications for Connectivity Restoration (만경강에서 하천정비에 의하여 격리된 구하도의 어류 군집 구조: 연결성 복원을 위한 제안)

  • Kim, Seog Hyun;Cheon, Hyoung Tae;Cho, Kang-Hyun
    • Ecology and Resilient Infrastructure
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    • v.2 no.1
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    • pp.22-32
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    • 2015
  • This study investigated the difference in fish community structures in a main channel and an isolated former channel, considering the environmental factors in the Mangyeong River, Korea. Principal component analysis (PCA) with environmental factors showed that former channels were composed of a fine substrate covered by in-stream vegetation, whereas the main channel was covered by a wide range of substrates with a higher dissolved oxygen and conductivity. The result of the hierarchical cluster analysis with species abundance delineated to the four main groups; three abandoned channel groups and one main channel group. Non-metric multidimensional scaling (NMDS) showed that fish community structures of each study site differed from environmental factors: former channel fish communities were positively related to in-stream vegetation cover, whereas main channel fish communities were positively associated with dissolved oxygen and conductivity. The results indicated that channelization, where there was a separation between the former channel and the main channel, had detrimental effects on fish community structures of both the main channel and the abandoned channel in the Mangyeong River. In conclusion, this study suggested that the connectivity between the main channel and abandoned channel were required to enhance both habitat structural diversity and species diversity of the Mangyeong River.

Characterization of Pore Structures for Porous Sintered Reaction-Bonded Silicon Nitrides with Varied Pore-Former Content

  • Park, Young-Jo;Song, In-Hyuck;Kim, Hai-Doo
    • Journal of the Korean Ceramic Society
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    • v.45 no.11
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    • pp.675-680
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    • 2008
  • The effect of pore former content on both porosity and pore structure was investigated for porous sintered reaction-bonded silicon nitrides (SRBSNs). A spherical PMMA with $d_{50}=8{\mu}m$ was employed as a pore-former. Its amount ranged from 0 to 30 part. Porous SRBSNs were fabricated by post-sintering at various temperatures where the porosity was controlled at $12{\sim}52%$. The strong tendency of increasing porosity with PMMA content and decreasing porosity with sintering temperature was observed. Measured pore-channel diameter increased $(0.3{\rightarrow}1.1{\mu}m)$ with both PMMA content and sintering temperature.

Evaluation of Habitat Improvement Using Two-Dimensional Fish Habitat Modeling after the Connectivity Restoration in an Isolated Former Channel (2차원 어류 서식처 모의를 이용한 격리된 구하도의 연결성 복원에 따른 서식지 개선 평가)

  • Kim, Seog Hyun;Kim, Dana;Cho, Kang-Hyun
    • Ecology and Resilient Infrastructure
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    • v.2 no.2
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    • pp.137-146
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    • 2015
  • Lateral connectivity between a main channel and a former channel plays an integral role in maintaining ecological functions of stream-floodplain ecosystems. This study virtually restored the connectivity of the former channel, which is currently isolated by channelization, in the Mangyeong River, Korea. Fish habitat improvement after the connectivity restoration was evaluated using River2D, two-dimensional depth-averaged hydraulic modeling, depending on normal and flood flow conditions. Target fish species were crucian carp (Carassius auratus), which are known as lentic species, and pale chub (Zacco platypus), known as lotic species. The weighted usable area (WUA) of the two species was increased after the connectivity restoration: the two-way connection between the main and formal channels was more effective than the one-way connection. The result of the physical habitat simulation at a flood flow condition demonstrated an increased rate of the WUA than during a normal flow condition. In particular, the WUA of pale chub increased about four times on the two-way connectivity restoration. This result suggests that habitat availability of both lentic and lotic fish species will increase after a connectivity restoration, and a two-way connectivity restoration may be more effective. In addition, the restored formal channel would function as a shelter for fish during the flood season.

Comparison of Hole Mobility Characteristics of Single Channel and Dual Channel Si/SiGe Structure (단일채널 Strained Si/SiGe 구조와 이중채널 Strained Si/SiGe 구조의 이동도 특성 비교)

  • Jung, Jong-Wan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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    • pp.113-114
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    • 2007
  • Hole mobility characteristics of single surface channel and dual channel Si/SiGe structure are compared, where the former one consists of a relaxed SiGe buffer layer and a tensile strained Si layer on top, and for dual channel structure a compressively strained SiGe layer is inserted between them. Due to the difference of hole mobility enhancement factors of layers between them, hole mobility characteristics with respect to the Si cap thickness shows the opposite tend. Hole mobility increases with thicker Si cap for single channel structure, whereas it decreases with thicker Si cap for dual channel structure.

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Impact of Energy Relaxation of Channel Electrons on Drain-Induced Barrier Lowering in Nano-Scale Si-Based MOSFETs

  • Mao, Ling-Feng
    • ETRI Journal
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    • v.39 no.2
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    • pp.284-291
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    • 2017
  • Drain-induced barrier lowering (DIBL) is one of the main parameters employed to indicate the short-channel effect for nano metal-oxide semiconductor field-effect transistors (MOSFETs). We propose a new physical model of the DIBL effect under two-dimensional approximations based on the energy-conservation equation for channel electrons in FETs, which is different from the former field-penetration model. The DIBL is caused by lowering of the effective potential barrier height seen by the channel electrons because a lateral channel electric field results in an increase in the average kinetic energy of the channel electrons. The channel length, temperature, and doping concentration-dependent DIBL effects predicted by the proposed physical model agree well with the experimental data and simulation results reported in Nature and other journals.

Pilot Assisted Channel Frequency Response Estimation for an OFDM System with a Comb-Type Pilot Pattern (빗 형태 패턴을 가지는 OFDM 시스템을 위한 파일럿 심볼 기반 채널 주파수 응답의 추정)

  • Kim, Youngwoong;Kim, Namhoon;Yoon, Eunchul
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39A no.6
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    • pp.333-342
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    • 2014
  • The pilot assisted channel frequency response (CFR) estimation schemes for an OFDM-based system with virtual subcarriers are analyzed under the assumption that pilot symbols are located according to a comb-type pattern in the OFDM block. In particular, as the minimum mean square error (MMSE) based scheme aiming to directly predict the channel impulse response and the MMSE based scheme aiming to suppress the leakage have not been clearly compared, by proving that the mean square errors (MSEs) of the latter scheme is always larger than that of the former scheme, this paper shows that the former scheme is superior to the latter scheme. Moreover, the impact of the number of pilots on the performances of the MMSE and least-square based channel estimation schemes are investigated. The performance analyses of the presented schemes are confirmed by computer simulation.

Improvement and Performance Evaluation of the Traffic Channel Management of the Radio Network Controller in IMT-2000 Network (IMT-2000 망에서 제어국의 트래픽 채널 관리 방식의 개선 및 성능 평가)

  • Ryu, Byung-Han;Ahn, Jee-Hwan;Baek, Jang-Hyun
    • IE interfaces
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    • v.16 no.3
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    • pp.311-321
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    • 2003
  • We propose the improved channel assignment and management methods for an efficient use of traffic channel resource for supporting 12.2 Kbps, 64 Kbps, and 384 Kbps traffic with the different quality of service(QoS) in the radio network controller(RNC) in asynchronous IMT-2000 system. We consider two types of traffic channel block assignments for utilizing the traffic channel efficiently; the Completely Shared(CS) channel assignment and the Partially Dedicated and Partially Shared(PDPS) channel assignment. The former is that all traffic channel blocks are completely shared with all traffic types. The latter is that some traffic channel block is independently assigned to each traffic type and the other blocks are completely shared with some traffic type. We also propose the traffic channel management method which consists of the block and task management step, for efficiently assigning, releasing, and managing the channel resource. Finally, we evaluate the performance through various numerical examples when applying our proposed channel block assignment and resource management methods.

CONFUTER-AIDED CASTING DESIGN FOR IMPLANT TITANIUM SUPERSTRUCTURES (컴퓨터 시뮬레이션을 이용한 임플란트 상부 티타늄 구조물의 주조방안)

  • Oh Se-Wook;Lee Ho-Yong;Lee Keun-Woo;Shim Jun-Sung
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.4
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    • pp.421-439
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    • 2003
  • Statement of problem : It is difficult to obtain a good titanium casting body using the traditional sprue design because of high melting point of Ti, and the low fluidity and high reactivity of molten Ti. Purpose : A new sprue design for titanium casting bodies needs more trial and error. In order to decrease the number of trial and error, computer simulation(MAGMASOFT, Magmasoft Giessereitechnologie GmbH, Achen, Germany) was used to optimize sprue design in U-shaped implant superstructures. Material and method : Five kinds of sprue were examined for the design of the sprue former for titanium casting: Sprue design A(sprue length 4 mm, rectangular shape, 4 sprues), Sprue design B(sprue length 4 mm. round shape. radius 2 mm, 7 sprues), Sprue design C (sprue length 2 mm, round shape, radius 2 mm, 7 sprues). Sprue design D (sprue length 2 mm, cone shape, large radius 3mm. small radius 2mm, 7 sprues), and Sprue design E( sprue length 2 mm. one unit channel shape). Sprue design F(sprue length 2mm, one unit channel shape) was also examined for the design of the customized sprue former in the Biotan system(Schutz Dental Gmbh, Germany). The casting bodies were taken in Sprue design A, Sprue design D, Sprue design E, and Sprue design F in the Biotan casting system. The numerically predicted defects were compared with the experimental dental castings by the radiographic and sectional view observations. Results : 1. According to the result of computer simulation, turbulence during mold filling was decreased in the sequence of Sprue design F, Sprue design E, Sprue design D, Sprue design C, Sprue design B, and Sprue design A. 2. The calculated solidification time contours indicate that hot spot was moved from the casting body to the sprue button in the sequence of Sprue design A, Sprue design B, Sprue design C, Sprue design D, and Sprue design E. The filling pattern of Sprue design F was similar to that of Sprue design E. 3 The predicted filling pattern shows that less turbulence was found in the customized sprue former than in the standard sprue former. 4. According to the results of the radiographic and cross sectional observations, casting defects less than 1mm were found at the center of a casting body with Sprue design E and Sprue design F. However, larger casting defects of 4mm were found in a casting with Sprue design A. 5. The predicted casting porosity was similar to that of the real casting. Conclusion : One unit channel-type and customized sprue former can be recommended. Further research and developement of various sprue designs using computer simulation in necessary to optimize casting design, in order to reduce the formation of casting defects in implant titanuim super-structures.

소비자파워에 의한 갈등이 경로관리에 미치는 영향

  • 서봉철
    • Journal of Distribution Research
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    • v.1 no.1
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    • pp.83-107
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    • 1996
  • The concern of external environment is growing up in the field of channel distribution. In the former channel distribution, the channel distribution environment is little bit unmoveable owing to a powerful manufacture control against poor distributor. Therefore intra-efficiency is channel member's core interest. The structure of channel governance, however, come to be changable because of the mature distributor power against manufacturer such as a Price Break, JIT of channel governance, and a serial of change. Accordingly, it is acceptable that the interest of external-environment of channel members' is more and more enlarged, and external-environment change in the channel distribution make the serious problems in intraorganizational system. Thus, it is meaningful that this study try to discover the consumer power as external environment factor and to find the best strategy to overcome this consumer power. Resource dependence theory, Transaction cost theory, Political Economic Approach, and Working partnership Approach are the theory foundation of the reasearch. Apparel franchise is a sample to analyse the hypothesis and correlation and multi-regression are a chief tools to estimate the hypothesis. Thus, the above results imply that a flexible governance is appropriate to consumer power, conflict is not intervening value between consumer power and channel governance, and the channel member's satisfaction can be confirmed in the flexible governance better than control governance.

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Hole Mobility Characteristics of Biaxially Strained SiGe/Si Channel Structure with High Ge Content (고농도의 Ge 함량을 가진 Biaxially Strained SiGe/Si Channel Structure의 정공 이동도 특성)

  • Jung, Jong-Wan
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.1
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    • pp.44-48
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    • 2008
  • Hole mobility characteristics of two representative biaxially strained SiGe/Si structures with high Ge contents are studied, They are single channel ($Si/Si_{1-x}Ge_x/Si$ substrate) and dual channel ($Si/Si_{1-y}Ge_y/Si_{1-x}Ge_x/Si$ substrate), where the former consists of a relaxed SiGe buffer layer with 60 % Ge content and a tensile-strained Si layer on top, and for the latter, a compressively strained SiGe layer is inserted between two layers, Owing to the hole mobility performance between a relaxed SiGe film and a compressive-strained SiGe film in the single channel and the dual channel, the hole mobility behaviors of two structures with respect to the Si cap layer thickness shows the opposite trend, Hole mobility increases with thicker Si cap layer for single channel structure, whereas it decreases with thicker Si cap layer for dual channel. This hole mobility characteristics could be easily explained by a simple capacitance model.