• Corrosion Science and Technology
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• v.4 no.3
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• pp.100-107
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• 2005

Reinforcing steel bars in reinforced concrete structures are protected from corrosion by passive film on the steel surface inside concrete with high alkalinity. However, when the passive film breaks down due to chloride ion ingressed into the RC structures, a corrosion initiates at the surface of steel bars. Then, internal pressure by volume expansion of corrosion products in reinforcing bars induces cracking and spalling of cover concrete, which reduces not only durability performance but also structural performance in RC structures. In this paper, a service life prediction of RC structures is carried out by using a micro-mechanics based corrosion model. The corrosion model is composed of a chloride penetration model to evaluate the initiation of corrosion and an electric corrosion cell model and an oxygen diffusion model to evaluate the rate and the accumulated amounts of corrosion. Then, a corrosion cracking model is combined to the models to evaluate critical amount of corrosion product for initiation cracking in cover concrete. By implementing the models into a finite element analysis program, a time and space dependent corrosion analysis and a service life prediction of RC structures due to chloride attack are simulated and the results of the analysis are compared with test results. The effect of crack width on the corrosion and the service life of the RC structures are analyzed and discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.743-746
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• 1999

One of the main deteriorating factors that affect the service life of concrete structures is the corrosion of reinforcement. The chlorides penetrate the concrete, destroy the passive layer surrounding the steel, and help initiate the steel corrosion. A Corrosion Prediction System(CPS) has been developed to assist the engineer in analyzing the service life of existing sea-shore structures and future concrete repairs by calculate the chloride diffusion in concrete. The CPS calculates mixing design, physical properties or recent chloride profiles. The CPS can be used to evaluate changes in concrete cover, chloride loads, and environmental conditions in different structural designs.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.773-778
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• 2002

The variance characteristics of the calcium carbonate contents along to the concrete cover depth takes the prediction method of remaining service life of concrete. Calcium carbonate contents were measured by the Thermo Gravimetric/Differential Thermal Analysis method at three point, depth of 0.25cm, 0.75cm, 1.25cm from the surface of concrete. This prediction method contain some assumption that the chemical protection conferred on steel is through a passive protective oxide film which forms on steel in an environment at or above a pH of 10.5$^{4)}$ .

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.29-36
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• 2016

A wireless passive sensor network is a network which, by letting separate RF sources supply energy to sensor nodes, is able to live an eternal life without batteries. Against expectations about an eternal life, however, a wireless passive sensor network still has many problems; scarcity of energy, non-simultaneity of energy reception and data transmission and inefficiency in resource allocation. In this paper, we focus on a wireless passive sensor network providing a packet service which is tolerable to packet losses but requires timely delivery of packets. Perceiving the practical constraints, we then consider a contending-type MAC scheme, rooted in framed and slotted ALOHA, for supporting many sensor nodes to deliver packets to a sink node. Next, we investigate the network-wide throughput achieved by the MAC scheme when the packets transmitted by geographically scattered sensor nodes experience path losses hence capture phenomena. Especially, we derive an exact formula of network-wide throughput in a closed form when 2 sensor nodes reside in the network. By controlling design parameters, we finally optimize the contending-type MAC scheme as to attain the maximum network-wide throughput.

• Architectural research
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• v.22 no.2
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• pp.41-52
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• 2020

Laboratory buildings with specialized equipment and ventilation systems pose challenges in terms of efficient energy use and initial construction costs. Additionally, lab spaces should have flexible and efficient layouts and provide a comfortable indoor research environment. Therefore, this study aims to identify the correlation between the facade of a building and its interior layout from case studies of energy-efficient research labs and to propose passive energy design strategies for the establishment of an optimal research environment. The case studies in this paper were selected from the American Institute of Architects Committee on the Environment Top Ten Projects and Leadership in Energy and Environmental Design (LEED) certified research lab projects. In this paper, the passive design strategies of space zoning, façade design devices to control heating and cooling loads were analyzed. Additionally, the relationships between these strategies and the interior lab layouts, lab support spaces, offices, and circulation areas were examined. The following four conclusions were drawn from the analysis of various cases: 1) space zoning for grouping areas with similar energy requirements is performed to concentrate similar heating and cooling demands to simplify the HVAC loads. 2) Public areas such as corridor, atrium, or courtyard can serve as buffer zones that employ passive solar design to minimize the mechanical energy load. 3) A balanced window-to-wall ratio (WWR), exterior shading devices, and natural ventilation systems are applied according to the space programming energy requirements to minimize the dependence on mechanical service. 4) Lastly, typical laboratory space zoning categories can be revised, reversed, and even reconfigured to minimize the energy load and adjust to the site context. This study can provide deep insights into various design strategies employed for construction of green laboratories along with intuitive arrangement of various building components such as laboratory spaces, lab support spaces, office spaces, and common public areas. The key findings of this study can contribute towards creating improved designs of laboratory facilities with reduced carbon footprint and greenhouse emissions.

• Korean System Dynamics Review
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• v.12 no.4
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• pp.125-156
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• 2011

The information service management models developed thus far have put their focuses mostly on technical dimensions of information systems (IS), finding their rationale from the goods-dominant logic (GDL) that IS as goods has value in itself. Information systems, however, is nothing more than a mechanism by which value is delivered to the users. According to the service-dominant logic (SDL), value is created and determined not at the time serve is made by the providers but at the time it is consumed by the users. The users therefore should be regarded as active value creators not as passive consumers of the value delivered by the providers. Based on the service-dominant logic, DISQM (Dynamic Information Service Quality Model) is developed. DISQM's backbone is designed in causal loop diagrams referring to and reinterpreting in systems thinking the 'Parasuraman, Zeithaml & Berry's GAP Model' and 'SERVQUAL' as an operational tool for the GAP Model, and the main IS success constructs are mapped onto the model exploiting the 'DeLone & MacLean's IS Success Model'. With VENSIM simulation software, this paper also shows how DISQM works in computer-simulation settings. After confirming DISQM's validity with the base simulation run, two scenarios are developed for the exemplary purpose and tested in terms of IS quality, service quality, and net benefits from the service for the public information service. Implications from the simulation runs are also discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.125-128
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• 2001

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. PON architecture is very simple but it requires MAC protocol for control of upstream traffic. This paper proposes a MAC protocol for a broadband access network using an ATM Passive Optical Network supporting CBR/rtVBR, nrtVBR, ABR aild UBR traffic. For the proposed MAC scheme, we present grant field format, minislot format, and bandwidth allocation algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7B
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• pp.620-627
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• 2003

Ethernet passive optical networks (EPONs) are an emerging access network technology that provide a low-cost method of deploying optical access lines between a carrier's central office and customer sites. Dynamic bandwidth allocation (DBA) provides statistical multiplexing between the optical network units for efficient upstream channel utilization. To support dynamic bandwidth distribution, 1 propose an cyclic polling-based DBA algorithm for differentiated classes of service in EPONs. And, I show that an interleaved polling scheme severely decreases downstream channel capacity for user traffics when the upstream network load is low. To obtain realistic simulation results, I used synthetic traffic that exhibits the properties of self-similarity and long-range dependence I then analyzed the network performance under various loads, specifically focusing on packet delays for different classes of traffic.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.441-446
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• 2003

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. The PON architecture is very simple but it requires a MAC protocol for control of upstream traffic. The MAC protocol must support QoS (Quality of Service) administration function by various traffic class, efficient dynamic bandwidth assignment function, CDV (Ceil Delay Variation) minimization function etc. This paper proposes a dynamic bandwidth assignment algorithm of the MAC protocol for a broadband access network using an Ethernet Passive Optical Network supporting various traffic class. We compare our proposed with MDRR algorithm using simulation, and confirmed that our proposed Request-Counter algorithm produces shorter average cell delay.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1354-1358
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• 2007

Nowaday, the wideband multimedia service, high speed and great capacity internet service etc. are increasing, so the network construction with the base of optical subscriber network is necessary. As efficient and economic optical subscriber networks are developed, so efficient network construction is possible. The most technology of them is WDM(Wavelength Division Multiplexing)-PON technology of ONU(Optical Network Unit) jointing method using PON(Passive Optical Network). In this paper, we have studied on a method for automatic optimization of data modulation current as optical power when the data is transmitted.