• 한국군사과학기술학회지
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• 제16권3호
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• pp.304-313
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• 2013

Wireless Sensor Networks, especially supporting for surveillance service, are one of the core properties of network-centric warfare(NCW) that is a key factor of victory in future battlefields. Such a tactical surveillance sensor network must be designed not just for energy efficiency but for real-time requirements of emergency data transmission towards a control center. This paper proposes efficient clustering-based methods for supporting mobile sinks so that the network lifetime can be extended while emergency data can be served as well. We analyze the performance of the proposed scheme and compare it with other existing schemes through simulation via Qualnet 5.0.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.31-37
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• 2002

Rail cars are subject to vibration, impact and wear which can cause severe defects leading to a fatal accident. Thus, they are designed and manufactured in consideration of such factors influencing their service lifetime. Under-frames are composed of steel and support most of load imposed on the car. Steel is very sensitive to corrosive environment and corroded even in a normal service condition. Regular maintenance can Protect steel Parts from corrosion by painting. However, an exposure of defect point to corrosive agents can make corrosion proceed to a considerable depth, which may cause the structure to remain under safety standard. It is necessary to understand corrosion behavior of rail cars in order to estimate unexpected accidents by corrosion.

• Structural Monitoring and Maintenance
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• 제2권2호
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• pp.133-143
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• 2015

Civil engineering infrastructure is aging and requires cost-effective maintenance strategies to enable infrastructure systems operate reliably and sustainably. This paper presents an approach for determining risk-cost balanced repair strategy of corrosion damaged reinforced concrete structures with consideration of uncertainty in structural resistance deterioration. On the basis of analytical models of cover concrete cracking evolution and bond strength degradation due to reinforcement corrosion, the effect of reinforcement corrosion on residual load carrying capacity of corroded reinforced concrete structures is investigated. A stochastic deterioration model based on gamma process is adopted to evaluate the probability of failure of structural bearing capacity over the lifetime. Optimal repair planning and maintenance strategies during the service life are determined by balancing the cost for maintenance and the risk of structural failure. The method proposed in this study is then demonstrated by numerical investigations for a concrete structure subjected to reinforcement corrosion. The obtained results show that the proposed method can provide a risk cost optimised repair schedule during the service life of corroded concrete structures.

• 한국동물위생학회지
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• 제46권4호
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• pp.363-368
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• 2023

Patent ductus arteriosus (PDA) in monkeys is very rare. A 9-year-old male Japanese macaque (Macaca fuscata) had an hourglass-shaped PDA with a large luminal diameter. Morphological analysis of the vessel cast and heart revealed cardiovascular pathological changes including pulmonary artery hypertension and right ventricular hypertrophy. However, left ventricle hypertrophy or left atrial enlargement were not observed. This macaque had showed no clinical signs of PDA during its lifetime. We present the first documented case of solitary PDA in a male macaque.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권7호
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• pp.1547-1568
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• 2013

Wireless body area network (WBAN) is an emerging short-range wireless communication network with sensor nodes located on, in or around the human body for healthcare, entertainment and ubiquitous computing. In WBANs, energy is severely constrained which is the prime consideration in the medium access control (MAC) protocol design. In this paper, we propose a novel MAC protocol named Energy-efficient Relay MAC with dynamic Power Control (ERPC-MAC) to save energy consumption. Without relying on the additional devices, ERPC-MAC employs relaying nodes to provide relay service for nodes which consume energy fast. Accordingly the superframe adjustment is performed and then the network topology can be smoothly switched from single-hop to multi-hop. Moreover, for further energy saving and reliability improvement, the dynamic power control is introduced to adjust the power level whenever a node transmits its packets to the coordinator or the relaying node. To the best of the authors' knowledge, this is the first effort to integrate relay, topology adjustment and power control to improve the network performance in a WBAN. Comprehensive simulations are conducted to evaluate the performance. The results show that the ERPC-MAC is more superior to the existing standard and significantly prolongs the network lifetime.

• 한국통신학회논문지
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• 제34권4B호
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• pp.329-337
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• 2009

무선 네트워크에서 수율(throughput) 최대화와 에너지 소모 최소화는 상충되는 두 목표이다. 탄력적 트래픽(elastic traffic)을 수신할 때에 사용자의 QoS(Quality-of-Service)는 수율에 의해 결정되므로 이를 최대화하는 것이 중요하다. 뿐만 아니라, 제한된 에너지로 동작하는 단말의 수명을 늘리기 위해서는 에너지 소모를 최소화해야 한다. 본 논문은 수율과 에너지 절약을 동시에 고려하는 에너지 효율적인 휴면 기법을 제안한다. 제안된 기법은 탄력적 트래픽을 수신할 때 수율과 에너지 절약 사이에서 적절히 동작하도록 설계되었다. 다양한 모의실험을 통해 기존 방식과 제안한 기법들의 성능을 비교하였는데, 가중 총 전송시간과 이 때 소모되는 에너지의 곱에 반비례하는 효용 측면에서 제안된 기법이 우수한 성능을 보임을 알 수 있었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.20-21
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• 2008

In the IEEE 802.16 Wireless MAN standard, the best effort service class is ranked on the lowest position in priority so that only scarce resource may be available for it. Also, the best effort service is usually assisted by a MAC scheme based on reservation ALOHA without explicit acknowledgement. However, the standard only specifies the skeleton of the MAC scheme. In this paper, we propose some rules to specify the indefinite part of the MAC scheme as well as to improve the throughput and delay performance of the MAC scheme. As generic rules for demanding and granting resource, we first propose non-gated exhaustive, gated exhaustive, non-gated limited, and gated limited demand rules, and deficient and full grant rules. Secondly, we propose grant regulation rules, identified as replacement and lifetime rules, to avoid excessive grant incurred by not giving acknowledgement. Noting the residual resource is inflated by adopting a grant regulation rule, we finally propose a rule for investing the residual resource to a subscriber station. Simulation results confirm that a combination of proposed rules improves the performance of the MAC scheme.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.441-447
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• 2003

Recently there is a growing Interest In mobile cellula r network providing multimedia service. However, the link bandwidth of mobile cellular network is not sufficient enough to provide satisfactory services to use rs. To overcome this problem, an adaptive framework has been proposed in this study, we propose a new method of estimating DPR(degradation period ratio) in an adaptive multimedia network where the bandwidth of ongoing call can be dynamically adjusted during its lifetime. DPR is a QoS(quality of service) parameter which represents the ratio of allocated bandwidth below a pre-defined target to the whole service time of a call. We improve estimation method of DPR using DTMC(discrete time Markov chain) model. We also calculate mean degradation period and degradation probability more precisely than in existing studies. Under Threshold CAC(call admission control) algorithm, we present analytically how to guarantee QoS to users and illustrate the method by numerical examples. The proposed method is expected to be used as one of CAC schemes in guaranteeing predefined QoS level of DPR

• 방사성폐기물학회지
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• 제14권1호
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• pp.11-19
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• 2016

This paper focuses on the estimation of durability and service-life of reinforced concrete structures in Wolsong Low- and intermediate-level wastes Disposal Center (WLDC) in Korea. There are six disposal silos located in the saturated environment. The silo concrete is degraded due to reactions with groundwater and chemical attacks, and finally it will lose its properties as a transport barrier. The infiltration of sulfate and magnesium, leaching of potassium hydroxide, and chlorine induced corrosion are the most significant factors for degradation of reinforced concrete structure in underground environment. From the result of evaluation of the degradation time for each factor, the degradation rate of the reinforced concrete due to sulfate and magnesium is $1.308{\times}10^{-3}cm/yr$, and it is estimated to take 48,000 years for full degradation while potassium hydroxide is leached in depth of less than 1.5 cm at 1,000 years after the initiation of degradation. In case of chlorine induced corrosion, it takes 1,648 years to initiate corrosion in the main reinforced bar and 2,288 years to reach the lifetime limit of the structural integrity, and thus it is evaluated as the most significant factor.

• 한국전자통신학회논문지
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• 제14권4호
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• pp.657-662
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• 2019

웨어러블 센서, 심전도조정기의 전력 소비는 네트워크 수명을 늘리기 위해 매우 낮아야 하며 WBAN노드에서 처리하는 데이터의 에러교정 및 인증등의 예상되는 서비스품질 제어는 중요하다. 따라서 서비스품질제어는 건강모니터링규정에서 WBAN을 구현하는 데 있어 가장 긴급한 관심사이다. 최적의 QoS제어를 위해 에너지 효율을 고려한 에러교정기법과 IEEE 802.15.6과 성능을 에너지효율 및 평균전송갯수면에서 비교평가 한다. 제안된 에러교정기법의 성능은 채널 추정을 이용하여 부호화율을 적절히 조절함으로써 에너지 효율 및 전송율이 향상됨을 보인다.