• 한국도로학회논문집
• /
• 제19권6호
• /
• pp.97-103
• /
• 2017

PURPOSES : In this study, the pavement condition of non-mill-and-overlay and mill-and-overlay on deteriorated concrete pavement was compared. In addition, the suitable time to perform the initial overlay was investigated. METHODS : The condition of the pavement sections that were not additionally overlaid on non-mill-and-overlay or mill-and-overlay on deteriorated concrete pavements was investigated according to overlay pavement age. The condition of non-mill-and-overlay and mill-and-overlay sections of expressway route 25, which has more information on overlay history than other routes, was compared according to the number of times of overlay. The relation between the concrete pavement condition just before the overlay and the number of times of overlay was investigated for the non-mill-and-overlay and mill-and-overlay sections for which the first overlay was performed in the same year. RESULTS : The pavement condition of the non-mill-and-overlay sections was better than that of the mill-and-overlay sections, showing higher Highway Pavement Condition Index(HPCI) regardless of overlay pavement age. The number of reflection crackings of the non-mill-and-overlay sections was smaller than that of the mill-and-overlay sections. As a result of observing the cores obtained from the overlay sections, the proportion of the deteriorated non-mill-and-overlay sections was smaller than that of the mill-and-overlay sections. The SD measured just before the overlay on the concrete pavement for which additional overlay was not performed was smaller than that for which additional overlay was performed regardless of the milling of the concrete slab surface. The HPCI of the concrete pavement for which overlay was performed just once was higher than that for which overlay was performed more than one time. CONCLUSIONS : Accordingly, it was concluded that the condition of the non-mill-and-overlay sections was better than that of the mill-and-overlay sections. In addition, the better the condition of concrete pavement just before the initial overlay, the longer the duration of the overlay effect.

• 한국도로학회논문집
• /
• 제15권4호
• /
• pp.1-9
• /
• 2013

PURPOSES : Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance since the overlay layer and the existing pavement perform as a monolithic layer. It is important to have suitable bond strength criteria to secure the performance of bonded concrete overlay. This study aimed to investigate the factors influencing bond strength characteristics between existing concrete pavement and overlay material. METHODS: Bond strength between overlay and existing pavement are measured and analyzed for various conditions such as the type of overlay materials, compressive and flexure strength of overlay and existing pavement, and deterioration status of existing pavement. RESULTS: The strength of overlay material does not significantly influence the bond strength. The overlay of ultra-rapid hardening cement generally gives low bond strength. However, ultra rapid hardening polymer modified concrete gives robust bond strength. The deterioration of existing concrete significantly decrease the bond strength. CONCLUSIONS: Bond strength of bonded concrete overlay highly depends on condition of existing concrete pavement rather than overlay material.

• 한국도로학회논문집
• /
• 제16권1호
• /
• pp.1-10
• /
• 2014

PURPOSES : This study aimed to evaluate the long-term performance of bonded concrete overlay in Korean Highway, and factors influencing the performances. METHODS : The evaluation for long-term performance of bonded concrete overlay is investigated based on the following study : i) The pavement distress of number of bonded concrete overlay sections in Korean highway are collected through field measurement, and PCI for each section is calculated. ii) Performance of LTPP data of bonded concrete overlay sections in U.S.A is analysed. And it is compared with bonded concrete overlay of Korean highway. iii) An analysis of the factors influencing to long-term performance of bonded concrete overlay is investigated. RESULTS : Performance analysis was confirmed that the overlay thickness was affecting significantly on the Bonded Concrete Overlay life. The comparison of LTPP data(U.S.A) and field measurement data(Korean) was showed. CONCLUSIONS : It was showed that the performance of Korean bonded concrete overlay is relatively lower than that of the bonded concrete overlay in U.S.A. The cause of lower performance can be explained by the lack of overlay thickness.

• 한국도로학회논문집
• /
• 제15권2호
• /
• pp.47-55
• /
• 2013

PURPOSES : This study aimed to evaluate the feasibility of AASHTO86 design method for Bonded Concrete Overlay. METHODS : The Feasibility of AASHTO86 design method for Bonded Concrete Overlay is investigated based on the following study : i) Sensitivity analysis of designed service life of Bonded Concrete Overlay by major design input for AASHTO86 guide. ii) Comparison of actual Bonded Concrete Overlay life and predicted Bonded Concrete Overlay life by AASHTO86. iii) Finding the stress component influence the potential distress of Bonded Concrete Overlay based on 3-d FEM analysis. iv) Exploring the limitation of AASHTO86 in the aspect of design input. RESULTS : Sensitivity analysis showed that the condition of existing pavement significantly on the Bonded Concrete Overlay life. Also the overlay thickness affect the Bonded Concrete Overlay life. The comparison of actual Bonded Concrete Overlay life and predicted Bonded Concrete Overlay life showed relatively good agreement when the early distress sections are excluded in comparison. Bonding stress occurred at the interface may be larger than the bond strength used in the specification of Bonded Concrete Overlay construction. CONCLUSIONS : Bonded Concrete Overlay life predicted by the AASHTO86 may not be reliable. Number of points to improve the reliability in the design of Bonded Concrete Overlay are suggested in this study.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
• /
• pp.345-348
• /
• 2003

Overlay multicast is proposed as an alternative approach for providing muticast services. A logical infrastructure is built to form an overlay network on top of the physical layer. In this paper, we propose an efficient overlay multicast in wireless ad hoc networks. The overlay multicast tree adapts to the changes in underlying networks. The multicast tree adjusted according to the local member information.

• 한국도로학회논문집
• /
• 제14권4호
• /
• pp.19-28
• /
• 2012

PURPOSES : Recently, the mechanistic-empirical overlay pavement design program that is linked with Korea Pavement Research Program (KPRP) has been developed. This paper focused on establishing the framework and developing the program for the asphalt overlay design over the existing asphalt concrete pavement. METHODS : The overlay pavement design program developed in this study was investigated to assess the sensitivity to various pavement conditions, such as the damage level and thickness of existing layers. In addition, the actual overlay design on currently performing pavement was carried out as a practical example. RESULTS : From the sensitivity analysis, it was found that the thickness and damage level of existing asphalt layer mostly affect the overlay design results. In addition, under the same condition, the overlay pavement would better perform in cold region. From the overlay design with the actual condition, it is noted that the overlay thickness varies depending on the given condition. CONCLUSIONS : Based on various evaluations, it was concluded that the overlay design program developed in this study is a reliable and reasonable tool to be used in the actual pavement design.

• 한국정보통신학회논문지
• /
• 제25권10호
• /
• pp.1397-1402
• /
• 2021

Overlay2 파일 시스템은 다수의 directory를 하나로 통합하여 mount 하는 union 파일 시스템 중의 하나이다. 이 overlay2 일 시스템 마운트에 생성되는 write-able layer는 source directory에 독립적으로 동작하는 특징이 있어 application 배포를 위한 컨테이너 플랫폼 등에 많이 사용되고 있다. 그러나 overlay2 파일 시스템은 mount에 사용되는 source directory에 있는 파일을 임의 변조할 경우, 그 변조 내용이 write-able layer에 적용되는 보안 취약점이 있다. 본 연구에서는 보안 취약점을 제거하기 위한 overlay2 파일 시스템의 source directory 보호 기술을 제안하였다. 제안하는 아키텍처에 따라 실증 구현 후 source directory 보호 기능을 검증한 결과, 본 연구에서 제안하는 보호 기술은 실효적이라고 판단되었다. 다만 본 연구에서 제안하는 방법은 수동적인 보호 방식이므로, 이를 운영체제 레벨에서 자동 보호하기 위한 후속 연구가 필요하다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제6권12호
• /
• pp.3117-3132
• /
• 2012

The tree topology in multicast systems has high transmission efficiency, low latency, but poor resilience to node failures. In our work, some nodes are selected as backbone nodes to construct a tree-like core overlay. Backbone nodes are reliable enough and have strong upload capacity as well, which is helpful to overcome the shortcomings of tree topology. The core overlay is organized into a spanning tree while the whole overlay is of mesh-like topology. This paper focuses on improving the performance of the application-layer multicast overlay by optimizing the core overlay which is periodically adjusted with the proposed optimization algorithm. Our approach is to construct the overlay tree based on the out-degree weighted reliability where the reliability of a node is weighted by its upload bandwidth (out-degree). There is no illegal solution during the evolution which ensures the evolution efficiency. Simulation results show that the proposed approach greatly enhances the reliability of the tree-like core overlay systems and achieves shorter delay simultaneously. Its reliability performance is better than the reliability-first algorithm and its delay is very close to that of the degree-first algorithm. The complexity of the proposed algorithm is acceptable for application. Therefore the proposed approach is efficient for the topology optimization of a real multicast overlay.

• 한국산학기술학회:학술대회논문집
• /
• 한국산학기술학회 2002년도 춘계학술발표논문집
• /
• pp.106-108
• /
• 2002

반도체 physical layout design rule이 작아짐에 따라 Proximity effect와 overlay가 Pattern 구현에 크게 영향을 미치고 있다. Metal layer와 contact의 부족한 overlay margin으로 overlay 불량이 발생하고, 감소한 space margin으로 인해 bridge와 같은 문제가 나타난다. 따라서, resolution을 향상시키고, 최소한의 overlay margin을 확보함으로써 미세 pattern의 구현을 가능하게 한다. 이를 위해 OPC와 attPSM 같은 분해능향상기술이 사용된다. 그러나 attPSM의 사용은 원하지 않는 pattern이 생성되는 sidelobe와 같은 문제가 발생한다. 따라서 serial image simulation올 통해 추출한 rule을 rule-based correction에 적용하여 sidelobe현상을 방지한다. 그리고 overlay margin 부족으로 나타나는 문제는 metal layer와 contact overlap되는 영역의 line edge를 확장하고, rule checking을 통해 최소한의 space margin을 확보하여 해결한다 따라서 overlay error를 rule-based correction을 사용하여 효과적으로 방지한다.

• Journal of Welding and Joining
• /
• 제27권3호
• /
• pp.80-84
• /
• 2009

The Plasma Transferred Arc (PTA) overlay welding method is lately introduced as one of the most useful surface overlay method of the engine component. In this paper, the overlay welding on the SNCrW heat resisting alloy was conducted by the PTA overlay welding process using the super alloy powder. The characteristics of the overlay layers were investigated through the metallurgical and abrasive test. Experimental results showed that the overlay on the SNCrW heat resisting alloy surface was successfully made without hot cracking. The friction wear characteristics of the Co-base Stellite 6 overlayer were most superior. However the abrasive wear characteristics were most inferior in the Co-base Stellite 6 overlayer.