• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.42-47
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• 2017

This paper proposes a new series-coupled voltage-controlled oscillator (VCO). The proposed VCO consists of four current-reuse Armstrong VCOs (CRA-VCOs) coupled by four transformers. The series-coupling, current-reuse, and Armstrong topologies improve the phase noise performance by increasing the negative-Gm of the VCO core with half the current consumption of a conventional differential VCO. The proposed VCO consumes 6.54 mW at 9.78 GHz from a 1-V supply voltage. The measured phase noise is -115.1 dBc/Hz at an offset frequency of 1 MHz, and the FoM is -186.5 dBc/Hz. The frequency tuning range is from 9.38-10.52 GHz. The core area is $0.49mm^2$ in a $0.13-{\mu}m$ CMOS process.

• 정보처리학회논문지D
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• 제13D권2호
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• pp.271-278
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• 2006

본 논문은 CE(Consumer Electronics) 제품을 개발하는 기업에서 소프트웨어 재사용의 향상을 위하여 기업 내에서 추진한 여러 사례들을 기반으로 소프트웨어 재사용에 대한 기반을 구축하고, 이를 개발 조직에 적용하면서 발생한 문제점의 도출과 개선점의 반영에 대해 논한다. 기업내에서의 재사용 기반을 구축하기 위해서는 기술적, 관리적, 개발환경의 측면이 모두 고려된 종합적인 접근 방법이 필요하다. 본 논문에서는 기술적 측면에서 개발 방법론을, 관리적 측면에서 재사용 메트릭을, 그리고 개발환경의 측면에서 재사용 저장소를 개발하고 운영한 사례를 논하며, 각각을 적용하면서 발생한 문제점을 분석하여 기업에서 보다 효과적인 재사용 기반을 구축하는 개선사례를 제시한다. 본 논문에서 다루는 재사용 활동의 대상은 개발대상 측면에서 내장 소프트웨어라는 특성, 조직적 측면에서 다앙한 제품을 다루는 수십 개의 각기 다른 개발영역과 조직구조를 가진 대규모 조직이라는 특성, 그리고 제품 개발 주기가 매우 짧으며 동일 제품에 대한 파생 제품이 동시에 다량으로 개발된다는 개발 환경의 특성에 기반하고 있다. 본 논문은 상기 분야에 대한 소프트웨어 재사용 현황에 대한 보고서로, 또한 이로부터 기업 내 재사용 기반을 개선하는 사례와 그 방안을 제시한다는 측면에서의 활용도가 있겠다.

• 대한환경공학회지
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• 제39권7호
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• pp.377-384
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• 2017

본 연구는 환경부 시범사업으로 진행된 수원시 물 재이용(중수도)시설물 설치사업으로 설치된 물재이용시설을 통하여 건축물 단위의 물재이용을 통한 물 부족 문제 해결 가능성을 살펴보았다. 개별 건축물 단위의 물재이용이 이루어지며 도시의 물 수요를 최대 25%까지 줄일 수 있다. 이는 우리나라의 수자원 부족 문제를 해결할 수 있는 수준이다. 하지만 개별 건축물 단위의 물 재이용 시설을 활성화하려면 사용자의 중수도 거부감 해소와 경제성 문제를 해결하여야 한다. 중수도 거부감 해소는 MBR 공정과 AOP 공정을 연계 하였을 경우 해결 가능하다. MBR 공정과 AOP 공정을 연계하여 운영할 시 사용자들은 상수도와 중수도의 수질 차이를 느끼지 못하는 것으로 나타났다. 경제성 문제는 건설비와 운영비를 고려할 경우 시설용량 100톤/일 이상, 운영비만 고려할 경우 15톤/일 이상일 경우 상 하수도요금 수준에서 해결이 가능하다. 더 나아가 사회적 편익비용까지 고려할 시 150톤/일 이상부터는 수익이 창출되는 것으로 나타났다.

• Journal of Communications and Networks
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• 제12권2호
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• pp.103-113
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• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• 상하수도학회지
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• 제24권5호
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• pp.595-601
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• 2010

It is evident that Korea will continue its battle with water shortage and alternative program are being taken into action. One of the main actions is reusing 1,800 tons of effluent of 357 sewage treatment plant located nationwide. Therefore this study supplemented ozone oxidation methods that would increase the efficiency of organic oxidation and coagulation. Through this method, fouling will be controled sufficiently by preventing membrane process in the system for advanced sewage treatment. In this study, ozone-coagulation-microfiltration membrane were used. The final removal efficiency of the pretreated water from the result of the ozone-coagulation were 50% of CODcr, 38% of TP and 11% of TOC respectively. Water quality treatment has decreased about 80% for TP. Ozone-coagulation-microfiltration membrane maintains the high flux while decreasing the number of organic matter and the membrane fouling, and reducing the TP. As a result, in order to reuse the water from the sewage, the ozone-coagulation-microfiltration membrane type must be considered in order to achieve the best efficiency.

• 상하수도학회지
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• 제27권3호
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• pp.339-349
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• 2013

Biological treatment of RO concentrate from wastewater reuse process is known to be very difficult due to its high concentration of non-degradable organics and salt ions such as chloride, nitrate and phosphate. In this research, the treatment performance of MBR was examined using RO concentrate mixed with raw wastewater as the influent of MBR. Addition of PAC (powdered activated carbon) to MBR was also evaluated in order to enhance the treatment performance and stability. The performance of MBR for treating only RO concentrate decreased gradually although external carbon source was added. The average removal performance of MBR with and without PAC decreased from 99.1 %(98.8 %) to 94.9 %(91.4 %) for COD, 81.3 %(80.3 %) to 42.0 %(41.9 %) for T-N and 57.3(55.0 %) to 30.0 %(21.0 %) for T-P with the increase of RO concentrate mixing rate of 0 % to 20 % in the feed water. Addition of PAC showed positive effect on the performance of MBR for the removal of COD and phosphorus in case that the ratio of RO concentrate to feed water increased.

• Membrane and Water Treatment
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• 제12권1호
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• pp.1-9
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• 2021

This study optimized the chemical cleaning process of discarded RO membranes for reuse in less demanding separation processes. The effect of physicochemical parameters, including the temperature, cleaning time, pH of the cleaning solution, and addition of additives, on the cleaning process was investigated. The membrane performance was evaluated by testing the flux recovery rate and salt rejection before and after the cleaning process. High temperatures (45-50 ℃) resulted in a better flux recovery rate of 71% with more than 80% salt rejection. Equal time for acid and base cleaning 3-3 h presented a 72.43% flux recovery rate with salt rejection above 85%. During acid and base cleaning, the best results were achieved at pH values of 3.0 and 12.0, respectively. Moreover, 0.05% concentration of ethylenediaminetetraacetic acid presented 72.3% flux recovery, while 69.2% flux was achieved using sodium dodecyl sulfate with a concentration of 0.5%; both showed >80% salt rejection, indicating no damage to the active layer of the membrane. Conversely, 0.5% concentration of sodium percarbonate showed 83.1% flux recovery and 0.005% concentration of sodium hypochlorite presented 85.2% flux recovery, while a high concentration of these chemicals resulted in oxidation of the membrane that caused a reduction in salt rejection.

• 디지털산업정보학회논문지
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• 제10권1호
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• pp.7-15
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• 2014

The accuracy of global navigation satellite system(GNSS) positioning has been studied during the last decades. Early GPS software was developed as monolithic tool in which all functions packed in the same software. But, these GPS software have the problems of the high cost of constructing system. close system architecture and the reusability. And there is a lack of interoperability between them because most of them have their own unique data format according to their application fields. In this paper, we have introduced requirements for design and specifications based on business process for the GPS system. commonly used to extract components from the requirements of the GPS business-based development process is presented. These components extracted by the process can be used to assemble components only. In particular, applications for developers to add features specific case without affecting the other components that can be modify the component.

• 해양환경안전학회지
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• 제4권1호
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• pp.41-48
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• 1998

There are several serious problems in treating shipboard wastewater due to special environmental conditions of ship, such as confined space, rolling and pitching, change of temperature and so on. It was suggested that Sequence Batch Reator (SBR) process might be suitable for overcoming above problems in terms of small size, high capacity of treating wastewater and full automation. In this study the SBR process was used for the secondary treatment of shipboard wastewater. The average removal efficiency of DOC, nitrogen, phosphorus and surfactants(MBAS) were studied and the effects of various C/N ration on the efficiency of treatment were investgated. From the experimental results it was convinced that the SBR process would be able to be used as a suitable process for removing organic matters and nitrogen in reuse system of shipboard wastewater.

• 한국환경과학회지
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• 제7권1호
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• pp.81-88
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• 1998

This study was conducted to assess the characteristics of plgment wastewater and the removal rates of appropriate treatment by physical, chemical and biological Process, and the possibility of reuse for effluent. Based on the results, the wastewater qualities of pigment were pH 5.1$\pm$3.4, temperature 43.0$\pm$ 15.$0^{\circ}C$, BOD 1,431.4$\pm$589.6mg/l, COD 2,282.8$\pm$466.5mg/l, turbidity 1,340$\pm$820NTU, color 243.0$\pm$147.0unit, Pb 36.5$\pm$9.5mg/l and $Cr^+6$ 10.3$\pm$ 1.3mg/l, respectively. The removal rates of adsorption by activated carbon and filter process were BOD 40.6% , COD 57.0% , turbidity 89.6%, color 87.2%, Pb 86.0% and $Cr^+6$ 10.6%, respectively. And the removal rates of reduction, neutralization, coagulation and aP floatation process were BOD 18.2%, COD 24.3%, turbidity 74.3%, color 56.7%, Pb 68.6% and $Cr^+6$ 97.8%, respectively. The removal rates of activated sludge process were BOD 95.9%, COD 86.0%, turbidity 27.8%, color 25. 2%. Pb 26.9% and $Cr^+6$ 50.0% , respectively. The total removal rates of treatment by physical, chemical and biological process were BOD 98.0% , COD 95.4%, turbidity 98.1%, color 95.8%, Pb 97.0% and $Cr^+6$ 99.0%, respectively. According to the test results for possibility of reuse with coagulation-adsorption by activated carbon process of effluent, COD was higher than that of raw water and others were similar to that of raw water thus, it Is considered to be reused.