• Smart Structures and Systems
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• 제12권1호
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• pp.55-71
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• 2013

Structural health monitoring (SHM) is vital for detecting the onset of damage and for preventing catastrophic failure of civil infrastructure systems. In particular, piezoelectric transducers have the ability to excite and actively interrogate structures (e.g., using surface waves) while measuring their response for sensing and damage detection. In fact, piezoelectric transducers such as lead zirconate titanate (PZT) and poly(vinylidene fluoride) (PVDF) have been used for various laboratory/field tests and possess significant advantages as compared to visual inspection and vibration-based methods, to name a few. However, PZTs are inherently brittle, and PVDF films do not possess high piezoelectricity, thereby limiting each of these devices to certain specific applications. The objective of this study is to design, characterize, and validate piezoelectric nanocomposites consisting of zinc oxide (ZnO) nanoparticles assembled in a PVDF copolymer matrix for sensing and SHM applications. These films provide greater mechanical flexibility as compared to PZTs, yet possess enhanced piezoelectricity as compared to pristine PVDF copolymers. This study started with spin coating dispersed ZnO- and PVDF-TrFE-based solutions to fabricate the piezoelectric nanocomposites. The concentration of ZnO nanoparticles was varied from 0 to 20 wt.% (in 5 % increments) to determine their influence on bulk film piezoelectricity. Second, their electric polarization responses were obtained for quantifying thin film remnant polarization, which is directly correlated to piezoelectricity. Based on these results, the films were poled (at 50 $MV-m^{-1}$) to permanently align their electrical domains and to enhance their bulk film piezoelectricity. Then, a series of hammer impact tests were conducted, and the voltage generated by poled ZnO-based thin films was compared to commercially poled PVDF copolymer thin films. The hammer impact tests showed comparable results between the prototype and commercial samples, and increasing ZnO content provided enhanced piezoelectric performance. Lastly, the films were further validated for sensing using different energy levels of hammer impact, different distances between the impact locations and the film electrodes, and cantilever free vibration testing for dynamic strain sensing.

• 정보보호학회논문지
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• 제28권3호
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• pp.563-577
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• 2018

VANET(Vehicular Ad hoc Network)에서 안전한 통신을 지원하기 위해 차량 간 또는 차량과 기반 구조 사이에서 교환되는 메시지는 인증이 반드시 수행되어야 한다. 본 논문에서는 VANET 환경을 위한 계층적 구조의 익명 인증 시스템을 제안한다. 제안하는 시스템 모델은 계층적으로 비밀키를 발급하여 기존 시스템의 문제점인 PKG의 오버헤드를 줄여 실용성을 높인다. 또한 페어링을 사용하지 않고 설계된 효율적인 2레벨 계층적 ID 기반 서명(Two-Level Hierarchical Identity-Based Signature, TLHIBS) 기법을 제안한다. 제안하는 기법은 조건부 익명성을 만족하여 차량의 프라이버시를 보호하고, 일괄검증(batch verification)을 지원하여 다수의 서명을 효율적으로 검증할 수 있다. 마지막으로 기존의 VAENT 환경에서 ID 기반 서명 기법들의 안전성 증명이 잘못된 것과는 다르게 제안한 기법의 안전성은 이산 대수 문제(Discrete Logarithm Problem, DLP)에 리덕션되어 랜덤 오라클 모델(random oracle model)에서 증명된다.

• 한국BIM학회 논문집
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• 제8권2호
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• pp.41-50
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• 2018

The current study focused on the utilization of building information modeling (BIM) data in steel-frame structures, which help to reduce project durations because they employ prefabricated structural members that are assembled on-site. In addition, a business process model was proposed using BIM data collected during the preconstruction, structural steel fabrication, and on-site construction phases of an actual steel-frame project. The ultimate expectation is that BIM data support at each phase, as well as the increased understanding among project participants, will result in an increase in project management productivity. The results from the current study are summarized as follows: To implement a BIM capable of application to steel-frame projects and data utilization, existing theories were studied to develop the construction project steps, both generally into the preconstruction (A1), steel fabrication (A2), and on-site construction phases, (A3) and specifically into 19 BIM-applicable phases. Based on the derived BIM-applicable phases, the model elements of the BIM object were identified, and the shortcomings of existing steel-frame projects were ameliorated, resulting in an improved data flow model. Moreover, for the proposed BIM data flow to progress efficiently, the BIM specialist needs to be well-acquainted with the phase-specific three-dimensional (3D) model output, and the infrastructure to construct an error-free 3D model must be provided. Based on the actual construction example, the BIM data utilized steel-frame projects - via production reports, clash checks, two-dimensional (2D) drawings, four-dimensional (4D) simulations, and 3D scanning - to make cooperation and communication among participants easier.

• 한국항해항만학회지
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• 제40권6호
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• pp.477-484
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• 2016

국제 교역에 있어서 항만은 중심 거점기능을 수행하지만 FTA가 해상물동량과 항만물동량에 미치는 영향을 실증적으로 분석한 연구는 드물다. 해운항만 분야의 경우 물동량은 항만시설 확충, 항만처리능력 산정 및 선박확충, 항로추가로 인한 선대구성의 중요한 자료임에도 불구하고 선행연구에서 실증분석이 대부분 교역금액 기준으로 이루어져 왔다. 향후 체결될 FTA의 경제적 기대효과 분석도 중요하지만, 현재 체결된 FTA의 효과를 파악하는 것도 실증적으로 의미가 크다. 따라서 본 연구에서는 2010년 체결된 한-인도 FTA를 대상으로 하여 FTA가 한국 물동량에 미치는 영향을 FTA의 경제적 파급효과를 파악하는데 네트워크 모형을 적용하여 실증 분석하였다.

• 한국실내디자인학회논문집
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• 제26권4호
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• pp.75-83
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• 2017

The cultural tendency based on sharing and cooperation, which has recently been a hot issue, accelerates throughout the world. This study began with a perception that a sharing culture is inherent in urban public spaces. This study aims to conduct a theoretical study of the sharing culture and to analyze the characteristics of the design composition of public spaces. This study selected squares in 16 European cities as cases for analysis. The results are summarized as follows:1)To analyze the design characteristics of public spaces in which a sharing culture is inherent, this study drew the shape and type of planes and sharing elements such as accessibility, symbolism and activity with the squares in the cases. 2)The shape of planes in the squares in the cases has been formed in close relations with the historic meaning and events of the area and the process of the construction of buildings surrounding the square. The squares in the cases were classified into seven plane types, and these squares have developmentally contributed to the formation of a sharing culture as a place for free participation and communication concerning social issues. 3)In the squares in the cases, the weight of road-centered access appears high, and in terms of the construction of human-friendly / environment-friendly infrastructure in the city or judging from the trend of the recent increase of pedestrian-centered plans for public space, it is judged that approaches with a high utilization rate of sidewalk or public transportation would be desirable. 4)Symbolic elements of the square become a device by which citizens can share the historic symbolism, along with artistic inspiration. In addition, by serving as an observatory from which people can take a view of the landscape of the city, it allows visual sharing of the entire city as well as the square. 5)A square is common pool resources in the community, and it is necessary to vitalize that in a direction of increasing the possibility of sharing, through the characteristics and methods of the composition of public design.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.923-928
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• 2014

수중통신은 통신채널로서의 물이 가시광 영역을 제외한 전자파 영역에는 본질적으로 전도성이 매우 떨어지므로 공기 중 통신에 비하여 성능이 심각하게 제한된다. 음파통신은 장거리 전송이 가능하지만 전자파에 비하여 음속이 수중에서 매우 느리므로 통신 속도에 제한이 있다. 한편 광무선 통신은 수중 관측이나 해중 모니터링을 위한 요구조건을 충족시킬 수 있는 대안 중의 하나로 제안되었다. 본 연구에서는 블루투스를 이용하여 모선의 통신시스템과 결합할 수 있는 수중 가시광 통신 시스템을 개발하였다. LED 조명통신 시스템과 블루투스의 인터페이스로 수중-수상 통신시스템을 연동할 수 있으며, 수중 3 m 거리에서 230.4 kbps 전송속도로 이미지와 문자를 에러 없이 전송할 수 있음을 보였다. 이러한 노력은 수중 무선 시스템과 수상에서 모니터링을 위한 모선과의 통신을 효과적으로 상호 연결하는 인프라를 강화하는데 기여할 것이다.

• 대한전자공학회논문지TC
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• 제44권4호
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• pp.40-48
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• 2007

MANET(Mobile Ad-Hoc Network) 환경의 센서 네트워크는 고정된 기반 없이 센서 노드간의 자율적이고 독립적인 네트워크를 구성한다. 또한, 네트워크를 구성하는 센서 노드의 이동으로 인한 토폴로지의 변화로 인해 데이터 처리, 제어 등을 효율적으로 관리하는데 많은 어려움이 있다. 특히, 각 센서 노드는 반드시 이동성을 고려해야 하기 때문에 에너지 사용에 대한 문제점이 발생한다. 이러한 문제를 해결하기 위해 클러스터 헤더와 멤버간 계층적 구조의 클러스터를 구성하는 기법들이 제안되었다. 하지만, 센서 노드의 센싱 파워 레벨이 일정하여 비효율적인 에너지 소비를 수반해 센서 네트워크의 에너지 불균형 및 생존 시간의 단축을 가져온다. 본 논문에서는 기존의 클러스터링 기법이 갖는 이러한 문제를 해결하기 위해 효율적 에너지 관리를 위한 지능형 클러스터링 기법을 제안하였다. 제안한 기법은 센서 노드의 이동에 따른 네트워크 토폴로지 변화에 빠르게 대응하고, 연속된 센싱을 요구하는 상황에서 기존의 기법에 비교하여 센서 노드의 생존 시간 향상을 가져온다.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.59-68
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• 2017

This paper aims at finding some lessons applicable to successful implementation of 'The 3D Printing R/D Project' through both examining the process of adopting overseas industrialized housing production technological knowhow by home builders during the 1970's~1980's period and thereafter until now the various efforts to adjust the technologies efficiently to the Korea's unique situation. Some meaningful lessons can be summarized as follows; I) Deep understanding of 3DP technological know-why along with its inheritance, II) Readjusting of R/D period and goals(cf. Global leader Winsun's 15 years experiment), III) Restructuring for more collaborative R/D B&E system among participating researchers IV) Fostering 3DP expert-engineers and technicians from the early stage, V) Clearing legal barriers in users' adopting 3DP methods necessary, VI) Development of appropriate building material besides concrete. Therefore, it is highly recommended that the above-mentioned 6 lessons positively accepted and applied to the Research Implementation Plan in due course, especially by KICT consortium and KAIA under the guidance of Ministry of Land, Infrastructure and Transport.

• Asian Pacific Journal of Cancer Prevention
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• 제15권13호
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• pp.5343-5348
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• 2014

Background: A meta-analysis was performed to examine the benefit/risk ratio for the addition of anti- HER MoAbs to chemotherapy in patients with advanced gastric and gastroesophageal cancer from six randomized phase II/III trials. Materials and Methods: We searched relative trials from Pubmed, EMBASE, Cochrane library databases, China National Knowledge Infrastructure databases, Google Scholar and the NIH ClinicalTrials. Primary outcomes were overall response rate (ORR), progression-free survival (PFS), overall survival (OS). Secondary outcomes were toxicities. All analyses were performed using STATA 12.0. Results: This meta-analysis included six randomized controlled trials (RCTs) with 2, 297 patients and we demonstrated that the anti-HER MoAbs arm did have a positive effect on ORR in the anti-HER MoAbs arm (OR 1.28, 95% CI 1.00-1.64, p=0.01). There was an increasing benefit regarding OS (HR 0.74, 95% CI 0.60-0.88, p<0.05) and PFS (HR 0.72, 95% CI 0.60-0.84, p<0.05) in the anti-HER2 subgroup, but a reduction of OS (HR 1.11, 95% CI 0.87-1.36, p<0.05) and PFS (HR 1.13, 95% CI 0.98 -1.28, P<0.05) in anti-EGFR subgroup. Some grade 3-4 toxicity had a significantly higher incidence in the anti-HER MoAbs arm. There was no significant publication bias for all endpoints. Conclusions: The addition of trstuzumab MoAb to chemotherapy for gastric and gastroesophageal cancer significantly improved outcome of OS and PFS endpoints, while other MoAbs led to no improvement in results. Some adverse events were increased in anti-HER MoAbs arm compared with the control.

• 한국도서관정보학회지
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• 제41권4호
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• pp.191-209
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• 2010

본 연구는 작은도서관의 설치와 운영을 지원하는 조례의 내용을 분석하여 문제점을 제시한 후, 바람직한 개선 방안을 제안하고자 하였다. 이를 위하여 지방자치단체가 제정한 조례 25건을 대상으로 조례를 구성하는 항목을 분석하였다. 분석의 대상은 조례의 명칭, 구성 항목, 작은도서관 기능, 설치 기준, 지방자치단체의 책무, 운영인력, 도서관 운영 규정, 운영위원회 등이다. 그 결과 조례의 구성항목들은 크게 다르지 않았으며, 지역의 특색을 반영한 조례도 거의 찾아보기 어려웠다. 또한 항목에 있어서도 강제조항보다는 임의조항이 많았기 때문에 지방자치단체장의 의지에 따라 설치와 지원의 규모가 달라질 수 있다는 것이 한계로 지적되었다. 따라서 작은도서관 조례는 지역의 도서관 인프라를 반드시 고려해야 하며, 공공성을 담보하기 위한 노력과 함께 지원기준을 명확하게 밝혀야 한다.