• 한국지반환경공학회 논문집
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• 제2권1호
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• pp.31-35
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• 2001

여과지속시간에 영향을 미지는 여과지의 유효경과 규조류 크기 사이의 관계를 기 보고된 데이터와 몇몇 정수장의 실 운영 데이터를 이용하여 평가하였다. 단일여재를 사용하는 정수장의 경우에 여과지속시간이 15시간 이하일 확률이 10~60%, 이중여재를 사용하는 정수장의 경우, 여과지속시간이 30시간 이하일 확률이 10~20%로 나타났다. 여과 폐색 발생 기간중 Synedra의 점유율은 64~92%인 것으로 나타났다. 이중여재의 유효경은 0.71~1.40mm이고 균등계수는 125~167이었다. 단일여재의 유효경은 0.52~0.65mm이고 균등계수는 0.25~1.40이었다. 계산된 이중여재의 침투깊이는 2.58~15.4cm이었으며, 단일여재의 경우에는 1.29~2.17cm이었다. 그리고 평균 여과지속시간은 이중여재가 40.1~83.3 시간, 단일여재가 13.9~34.9 시간으로 나타났다. 단일여재에서 Synedra의 수가 400cells/ml을 초과하면 여과지속시간은 5시간 이하로 나타났으며, 이중여재의 경우에는 70시간 이상으로 나타났다.

• 상하수도학회지
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• 제21권2호
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• pp.203-214
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• 2007

This study aimed at researching the process selection for two-stage and dual media filtration system, as a technology substituting the existing sand filter without expanding the site when retrofitting an old filter bed or designing a new one. In order to select the process for optimum complex filtration system, three running conditions have been tested. Test results demonstrated that Run 3 in which the 1st stage was filled with anthracite and coarse sand, and the 2nd stage was filled up with activated carbon and fine sand reduced the head loss and the load of turbidity substances. Also, Run 3 showed better performance in removing TOC, particle counts, THMFP and HAAFP, compared to other two conditions. 99 % of Cryptosporidium was removed. Bisphenol-A was rarely removed from the 1st stage of coarse sand and 2nd stage of fine sand, but 99 % of it was removed from the 2nd stage of activated carbon. In conclusion, when it is required to retrofit an old rapid filter bed or design a new one for the purpose of improving filtration performance, the following two-stage and dual media filtration system is suggested: the 1st stage of filter bed needs to be filled up with coarse sand to remove turbidity as the pretreatment for extending duration of filtering, the top part of 2nd stage needs to be filled up with granular activated caron to remove dissolved organic matters and others as the main process, and finally the bottom part of 2nd stage needs to be filled up with fine sand as the finishing process.

• 대한환경공학회지
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• 제22권5호
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• pp.919-926
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• 2000

정수장 여과지 모형실험장치를 이용하여 수중입자입도분석에 의한 모래 및 이중여재 여과지에 대한 여과특성 및 효율 평가를 탁도분석과 비교하여 실시하였다. 수중입자입도분석은 여과지의 효율 평가를 위한 훌륭한 평가방법으로 탁도분석에 비해 민감도가 뛰어나 여과유출수의 탁질누출 현상을 뚜렷이 관찰할 수 있었다. 모래여과지의 경우는 여과지속시간 내내 비교적 양호한 수질을 보여, 허용수두하에서는 초기탁질누출보다는 여과말기의 수위상승에 대한 주위가 필요하다. 반면에 이중여재 여과지의 경우는 내부여과에 의한 탁질의 침투가 이루어지므로 최적운영을 위해서는 적절한 여재구성과 각 여과지별로 연속적인 수질모니터링에 의한 탁질누출제어가 요구된다. 또한 보다 안정적이고 효율적인 수질의 확보를 위해서는 여과보조제의 사용도 고려되어야 할 것이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.888-893
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• 2004

This paper proposed a dual actuator using bimorph PZT for information storage device based on prove array NSOM(Near-field Scanning Optical Microscopy). The gap between the media and the optical head should be maintained within the optical tolerance. Therefore, a new actuator having high sensitivity is required. Bimorph PZT, which has fast access time and high sensitivity characteristic, is suitable for this precise actuating system. This paper is focused on derivation of mathematical model of dual bimorph PZT actuator and control algorithm. Hamilton's principle was used for mathematical model. The model is verified by FEA(Finite Element Analysis), and compared with experimental results. Different control algorithms were used f3r two bimorph PZT actuating same direction and opposite direction. The gap between recording media and optical head was controlled within 20nm in experiment.

• 방송과미디어
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• 제11권1호
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• pp.78-85
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• 2006

Cognitive radio is a paradigm for wireless communication in which either network of wireless node itself changes particular transmission or reception parameters to execute its tasks efficiently without interfering with the licensed users. This paper represents a performance of the cognitive radio technology on dual polarized MIMO system using six-port receiver. Six-port technology is well known direct conversion receiver. In this paper, a six-port phase discriminator based polarization signal separation is shown. That is, the SER(Symbol Error Rate) performance is improved using polarization separator and simple receiver architecture is proposed applying six-port receiver. The six-port technology has priority to adapt changeable frequency system and variable environments for cognitive radio. In general, dual polarized MIMO system has good capacity and quality using polarization separator [1].

• Journal of electromagnetic engineering and science
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• 제16권3호
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• pp.164-168
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• 2016

A dual-band through-the-wall imaging radar receiver for a frequency-modulated continuous-wave radar system was designed and fabricated. The operating frequency bands of the receiver are S-band (2-4 GHz) and X-band (8-12 GHz). If the target is behind a wall, wall-reflected waves are rejected by a reconfigurable $G_m-C$ high-pass filter. The filter is designed using a high-order admittance synthesis method, and consists of transconductor circuits and capacitors. The cutoff frequency of the filter can be tuned by changing the reference current. The receiver system is fabricated on a printed circuit board using commercial devices. Measurements show 44.3 dB gain and 3.7 dB noise figure for the S-band input, and 58 dB gain and 3.02 dB noise figure for the X-band input. The cutoff frequency of the filter can be tuned from 0.7 MHz to 2.4 MHz.

• 환경위생공학
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• 제17권4호
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• pp.47-52
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• 2002

This study was carried out to examine the characteristics of dual media filter with BAC and sand on a pilot scale which was installed in T Water Treatment Plant of Seoul. The conclusions drawn from experimental results are as follows : For the BAC-Sand filter, the preceded gravity sand filter did not largely affect the removal of organics and turbidity causing matters, tut the frequency of backwashing was explicitly reduced to two times with the stable growth of microorganisms. The biomass on media in case of existence of preceded sand filter was 1.4 times higher than that of nonexistence. In case of backwashing with water, the time needed to comply with below 10NTU took 22, 10, and 5 minutes respectively with the expansion ration of 1.2, 1.5 and 1.8. The higher the expansion ration was, the shorter the backwashing time was.

• Journal of Communications and Networks
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• 제7권1호
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• pp.76-86
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• 2005

Today's wireless access networks consist of several tiers that overlap each other. Provisioning of real time undisrupted communication to mobile users, anywhere and anytime through these heterogeneous overlay networks, is a challenging task. We extend the end-to-end approach for the handoff management in hybrid wireless data network by designing a fully mobile-controlled handoff for mobile devices equipped with dual mode interfaces. By handoff, we mean switching the communication between interfaces connected to different subnets. This mobile-controlled handoff scheme reduces the service disruption time during both horizontal and vertical handoffs and does not require any modification in the access networks. We exploit the IP diversity created by the dual interfaces in the overlapping area by simultaneously connecting to different subnets and networks. Power saving is achieved by activating both interfaces only during the handoff period. The performance evaluation of the handoff is carried out by a simple mathematical analysis. The analysis shows that with proper network engineering, exploiting the speed of mobile node and overlapping area between subnets can reduce service disruption and power consumption during handoff significantly. We believe that with more powerful network interfaces our proposal of dual interfaces can be realized.

• 대한지리학회지
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• 제41권2호
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• pp.227-243
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• 2006

이 글은 전자 미디어 기술이 기하 공간에서 시공간 차원을 어떻게 수반하고 생산하는지를 네 가지 이론적 관점에 초점을 두면서 고찰한다: 반 딕의 규모의 확장과 수축으로서 네트워크의 이중구조; 라투어의 유동적이고 혼종적 네트워크로서 행위자-네트워크; 비릴리오의 지구적 미디어 벡터로서 속도권 시간; 그리고 카스텔의 비순차적 흐름으로서 초월적 시간. 이들 네 가지 이론적 관점에서, 우리는 전자 미디어 기술이 기하 미디어 공간에서 상이하고 다중적인 시공간 차원을 수반한다는 것을 알 수 있다: 동심원의 이차원 공간 (면), 행위자-네트워크의 일차원 공간 (선), 속도권 시간의 영차원 공간 (점), 그리고 초월적 시간의 다중차원 공간 (하이퍼텍스트). 전자 미디어 공간이 지리적 공간에서 탈/토착화되는 방식을 이해하기 위해서는 우리는 전자 미디어 공간을 기하 미디어공간뿐만 아니라 지리 미디어 공간에서 설명할 필요가 있음을 제시하면서 이 글은 끝맺는다.

• 한국의류학회지
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• 제45권3호
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• pp.510-524
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• 2021

Selfie practices on social media can result in negative body image for men. The current study investigated the dual body image pathway model for the relationship between selfie practices on social media and body satisfaction, with internalization as a mediator. Structural equation modeling analyses supported our research model when studying 446 young Korean male Instagram users. The results indicated that selfie editing behavior, but not selfie browsing behavior, significantly predicted an increased internalization of a body ideal. The positive associations between internalization, muscularity dissatisfaction, and body fat dissatisfaction were confirmed. Additionally, the indirect effects of selfie editing behavior on muscularity and body fat dissatisfaction due to internalization were significant. The study confirmed the detrimental effects of selfie behavior on body satisfaction for male social media users. The results provided valuable information that selfie editing may be a risky behavior since it can result in developing muscularity and body fat dissatisfaction. Theoretical contributions and practical implications were discussed. Future research should address the age and cultural differences that may elucidate the impacts of selfie practices on men's body image concerns.