• Toxicological Research
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• 제23권3호
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• pp.207-214
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• 2007

Chronic oxidative stress produced by exposure to environmental chemicals or pathophysiological states can lead animals to aging, carcinogenesis and degenerative diseases. Indirect antioxidative mechanisms, in which natural or synthetic agents are used to coordinately induce the expression of cellular antioxidant capacity, have been shown to protect cells and organisms from oxidative damages. Electrophile and free radical detoxifying enzymes, which were originally identified as the products of genes induced by cancer chemopreventive agents, are members of this protective system. The NFE2 family transcription factor Nrf2 was found to govern expression of these detoxifying enzymes, and screening for Nrf2-regulated genes has identified many gene categories involved in maintaining cellular redox potential and protection from oxidative damage as Nrf2 downstream genes. Further, studies using Nrf2-deficient mice revealed that these mutant mice showed more susceptible phenotypes towards exposure to environmental chemicals/carcinogens and in oxidative stress related disease models. With the finding that cancer chemopreventive efficacy of indirect antioxidants (enzyme inducers) is lost in the absence of Nrf2, a central role of Nrf2 in the antioxidative protective system has been firmly established. Promising results from cancer prevention clinical trials using enzyme inducers propose that pharmacological interventions that modulate Nrf2 can be an effective strategy to protect tissues from oxidative damage.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5253-5270
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• 2016

With device-to-device (D2D) communications, an inactive user terminal can be utilized as a relay node to support multi-hop communication so that connective experience of the cell-edge user as well as the capacity of the whole system can be significantly improved. In this paper, we investigate the spectrum sharing for a cooperative relay assisted D2D communication underlying a cellular network. We formulate a joint relay selection and channel assignment problem to maximize the throughput of the system while guaranteeing the quality of service (QoS) requirements of cellular users (CUs) and D2D users (DUs). By exploiting coalition formation game theory, we propose two algorithms to solve the problem. The first algorithm is designed based on merge and split rules while the second one is developed based on single user's movement. Both of them are proved to be stable and convergent. Simulation results are presented to show the effectiveness of the proposed algorithms.

• 한국통신학회논문지
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• 제34권9B호
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• pp.892-899
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• 2009

주파수 분할 재사용 기법은 셀룰러 시스템의 성능을 향상시키기 위한 기술이다. 주파수 분할 재사용 기반시스템에 대한 기존 연구에서는 호의 발생과 채널 선택 과정을 설명하고 있지 않다. 따라서 본 논문에서는 단말의 채널 선택 과정을 설명하고 주파수 분할 재사용 기반 시스템의 성능을 분석한다. 성능은 채널 사용률과 호 차단 확률로 나타낸다. 본 논문의 결과는 차후 주파수 분할 재사용 기반 시스템의 성능 분석에 추가되어 실제적인 시스템의 성능 분석을 가능하게 할 것이다.

• ETRI Journal
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• 제28권3호
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• pp.282-290
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• 2006

In vertically overlaid cellular systems, a temporary traffic concentration can occur in a hot-spot area, and this adversely affects overall system capacity. In this paper, we develop an adaptive hot-spot operating scheme (AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in orthogonal frequency division multiple access downlink systems. Here, the base station in a macrocell can control the operation of picocells within the cell, and turns them on or off according to the system overload estimation function. In order to determine whether the set of picocells is turned on or off, we define an AHOS gain index that describes the number of subcarriers saved to the macrocell by turning a specific picocell on. For initiating the picocell OFF procedure, we utilize the changes in traffic concentration and co-channel interference to the neighboring cells. According to computer simulation, the AHOS has been proved to have maximize system throughput while maintaining a very low QoS outage probability under various system scenarios in both a single-cell and multi-cell environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4724-4747
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• 2016

To efficiently reduce on-grid energy consumption, the admission control algorithm in the hybrid energy powered cellular network (HybE-Net) with base stations (BSs) powered by on-grid energy and solar energy is studied. In HybE-Net, the fluctuation of solar energy harvesting and energy consumption may result in the imbalance of solar energy utilization among BSs, i.e., some BSs may be surplus in solar energy, while others may maintain operation with on-grid energy supply. Obviously, it makes solar energy not completely useable, and on-grid energy cannot be reduced at capacity. Thus, how to control user admission to improve solar energy utilization and to reduce on-grid energy consumption is a great challenge. Motivated by this, we first model the energy flow behavior by using stochastic queue model, and dynamic energy characteristics are analyzed mathematically. Then, fuzzy logic based admission control algorithm is proposed, which comprehensively considers admission judgment parameters, e.g., transmission rate, bandwidth, energy state of BSs. Moreover, the index of solar energy utilization balancing is proposed to improve the balance of energy utilization among different BSs in the proposed algorithm. Finally, simulation results demonstrate that the proposed algorithm performs excellently in improving solar energy utilization and reducing on-grid energy consumption of the HybE-Net.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권5호
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• pp.2258-2276
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• 2019

Resource sharing is one of the main goals achieved by network virtualization technology to enhance network resource utilization and enable resource customization. Though resource sharing can improve network efficiency by accommodating various users in a network, limited infrastructure capacity is still a challenge to ultra-low latency service operators. In this paper, we propose an inter-slice resource borrowing schema based on the device-to-device (D2D) potentiality especially for ultra-low latency transmission in cellular networks. An extended and modified Kuhn-Munkres bipartite matching algorithm is developed to optimally achieve inter-slice resource borrowing. Simulation results show that, proper D2D user matching can be achieved, satisfying ultra-low latency (ULL) users' quality of service (QoS) requirements and resource utilization in various scenarios.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.146-147
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• 2021

An increase in carbon emissions leads to the problem of global warming and is an issue to be solved in other countries. The problem of carbon dioxide has many effects not only on global warming but also on people. According to the World Health Organization (WHO), 4.3 million people have died because harmful substances generated indoors cannot be discharged to the outside and accumulate in the human body through the respiratory tract. In response to this situation, in order to reduce the generation of pollutants in the building itself, soak into lightweight bubble concrete to adsorb and purify indoor pollutants, mix charcoal, investigate the appropriate amount and physical characteristics, and check carbon dioxide This is an experiment for grasping the adsorption capacity, and the results are as follows. As the replacement rate of rice husk charcoal increased, the compressive strength tended to decrease, and the carbon dioxide reduction rate tended to increase. It is judged that the charcoal of rice husks shows a low density and the physical adsorption is smooth due to the porous structure. Since it is excellent in the basic physical properties and carbon dioxide adsorption surface of this experiment, it is judged that it has sufficient potential for use as an indoor finishing material.

• Steel and Composite Structures
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• 제49권4호
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• pp.393-405
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• 2023

In this paper, the energy absorption capability of a novel cruciform composite lattice structure was evaluated through the simulation of compression tests. For this purpose, several test samples of Polylactic acid cellular reinforced with continuous glass fibers were prepared for compression testing using the additive manufacturing method of material extrusion. Using a conventional path design for material extrusion, multiple debonding is probable to be occurred at the joint regions of adjacent cells. Therefore, an innovative printing path design was proposed for the cruciform lattice structure. Afterwards, quasistatic compression tests were performed to evaluate the energy absorption behaviour of this structure. A finite element model based on local material property degradation was then developed to verify the experimental test and extend the virtual test method. Accordingly, different combinations of unit cells' dimensions using the design of the experiment were numerically proposed to obtain the optimal configuration in terms of the total absorbed energy. Having brilliant energy absorption properties, the studied cruciform lattice with its optimized unit cell dimensions can be used as an energy absorber in crashworthiness applications. Finally, a cellular structure will be suitable with optimal behavior in crush load efficiency and high energy absorption.

• 전기전자학회논문지
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• 제13권4호
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• pp.75-81
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• 2009

차세대 셀룰러 시스템은 중계기를 이용한 다중 홉 전송을 사용함으로써 신호의 전달 거리가 감소하고 이를 통한 전송률을 증대시킨다. 그러나 다중 홉 전송을 이용한 전달 거리 감소는 외부 셀 입장에서 간섭량의 증가를 의미하기 때문에 중계기의 위치는 셀룰러 시스템 성능에 영향을 줄 수 있다. 본 논문에서는 중계기의 전송 전력과 위치에 따른 간섭량의 변화를 고려하여 최대의 전송률을 내기 위한 중계기 위치를 결정한다. 중계기 위치 결정을 위한 조건은 수학적인 모델로 분석되었고 모의실험 결과를 통해서 그 성능을 검증하였다. 본 논문의 분석에 따르면 하나의 셀의 평균 오수신 확률을 최소화 시킬 수 있는 중계기 설치 지점과 중계기 전송 전력이 존재하며, 주파수 재사용에 따른 셀들 간 간섭이 심각하지 않은 상황에서 중계기는 평균 오수신 확률을 감소시켜줌으로써 셀 용량 증대에 기여하였다. 반면 셀간 간섭이 심각한 경우 중계기의 사용은 오히려 해당 셀의 오수신 확률을 증가시키므로 지양해야 한다는 결론에 도달하였다.

• 한국전자파학회지:전자파기술
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• 제5권1호
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• pp.22-30
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• 1994

CCI Canceller와 MRC 다이버시티 수신 기볍을 채용하는 DS-CDMA /DPSK 셀룰라 이동통신 시스댐의 오율을, 가산성 가우스 잡음과 다중접속간섭(MUI) 및 m-분포 페이딩에 의해 특정지워지는 셀룰라 무선채널에서 해석하였다. 셀당의 사용자수를 나타내는 시스댐의 용량을 유도하여 수치 계산한 결과를, PN 코드의 길이, 페 이딩 지수, BER, 다이버시티 가지수, $E_b/N_o$, 동을 함수로 하여 그림으로 나타내었다. 본논문에서는 음성구동계 수를 3/8으로 가정하였고 셀은 3개의 섹터로 나뉘어져 있다고 가정하였으며 다중접속간섭은 가우시안 랜덤과 정으로 가정하였다. 얻은 결과로부터, 가산성 가우스 잡음과 다중접속간섭의 존재하에서 PN 코드의 길이에 따 른, CCI Canceller를 채용하는 DS-CDMA /DPSK 셀룰라 이동통신 시스댐의 용량을 구할 수 있었고,m-분포 페이딩 환경에서 페이딩 지수와 다이버시티 가지수의 변화에 따른 시스댐 용량의 증가를 구할 수 있었다.